investigation into the chemical processing and colorimetric

1

INVESTIGATION INTO THE CHEMICAL

PROCESSING AND COLORIMETRIC

PROPERTIES OF SULPHUR DYED

CELLULOSIC TEXTILES

A thesis submitted to the University of Manchester for the

degree of Doctor of Philosophy (PhD) in the

Faculty of Engineering and Physical Sciences

2015

QURATULAIN MOHTASHIM

SCHOOL OF MATERIALS/Textiles and Paper

2

Table of Contents

Table of contents .......................................................................................................... 2

List of tables ............................................................................................................... 11

List of figures ............................................................................................................. 18

List of abbreviations ................................................................................................... 25

Abstract ...................................................................................................................... 26

Declaration ................................................................................................................. 27

Copyright statement ................................................................................................... 28

Dedication .................................................................................................................. 29

Acknowledgements .................................................................................................... 30

1. Introduction ........................................................................................................ 32

1.1. Background of the study .............................................................................. 33

1.2. Research problem ........................................................................................ 34

1.3. Research aim and objectives ....................................................................... 35

1.4. Scope and significance of the research ........................................................ 36

1.5. Proposed research ........................................................................................ 36

1.6. Research methods and analysis ................................................................... 37

1.6.1. Colorimetric, fastness and tensile properties ....................................... 37

1.6.2. Surface chemistry, topography and bulk analysis ................................ 37

1.7. References ................................................................................................... 37

2. Literature review ................................................................................................ 40

2.1. History of sulphur dyes ............................................................................... 40

2.2. Constitution of sulphur dyes ........................................................................ 40

2.3. Methods of formation .................................................................................. 41

2.4. Classification of sulphur dyes ..................................................................... 42

2.4.1. CI Sulphur dyes .................................................................................... 43

3

2.4.2. CI Leuco Sulphur dyes ......................................................................... 43

2.4.3. CI Solubilised Sulphur dyes ................................................................. 44

2.4.4. CI Condensate Sulphur dyes ................................................................ 44

2.5. General application procedure of sulphur dyes ........................................... 44

2.6. Properties of sulphur dyes ........................................................................... 45

2.6.1. Fastness to light .................................................................................... 45

2.6.2. Colour fastness ..................................................................................... 46

2.6.3. Fastness to washing .............................................................................. 46

2.6.4. Fastness to bleaching............................................................................ 46

2.6.5. Fastness to rubbing ............................................................................... 46

2.6.6. Acid tendering of sulphur dyes ............................................................ 47

2.7. Reduction of sulphur dyes ........................................................................... 47

2.7.1. Conventional reducing systems ........................................................... 47

2.7.2. Green chemistry/non-sulphide reducing systems................................. 49

2.7.3. Nitrogen (nitro process) based reduction ............................................. 58

2.7.4. Natural/organic reduction..................................................................... 58

2.7.5. Alkaline protease reduction.................................................................. 59

2.7.6. Alkaline catalase reduction .................................................................. 61

2.7.7. Alkaline pectinase reduction ................................................................ 62

2.7.8. Electrochemical reduction .................................................................... 64

2.8. Redox chemistry .......................................................................................... 65

2.9. Oxidation of sulphur dyes ........................................................................... 65

2.9.1. Hydrogen peroxide ............................................................................... 65

2.9.2. Sodium dichromate .............................................................................. 66

2.9.3. Iodates .................................................................................................. 66

2.9.4. Sodium chlorite .................................................................................... 67

2.9.5. Enzymes (Laccase)............................................................................... 67

4

2.10. Fixation additives to enhance the fastness properties .............................. 70

2.10.1. Alkylating agents .............................................................................. 70

2.10.2. Cationic fixing agents ....................................................................... 71

2.10.3. Softeners ........................................................................................... 74

2.10.4. Lanthanum triacetate ........................................................................ 74

2.10.5. Crease resist finish ............................................................................ 76

2.11. Surface chemical analysis of sulphur dyed laundered fabric ................... 76

2.12. Application of sulphur dyes on non-cellulosic fibres .............................. 78

2.12.1. Dyeing of silk ................................................................................... 78

2.12.2. Dyeing of nylon ................................................................................ 78

2.12.3. Dyeing of wool ................................................................................. 80

2.13. References ................................................................................................ 82

3. Research methodology ....................................................................................... 88

3.1. Introduction ................................................................................................. 88

3.2. Materials ...................................................................................................... 88

3.2.1. Fabric.................................................................................................... 88

3.2.2. Sulphur dyes and auxiliaries ................................................................ 88

3.3. Finishing auxiliaries .................................................................................... 89

3.3.1. Bayprotect Cl ....................................................................................... 89

3.3.2. Fixapret CP .......................................................................................... 90

3.3.3. Choline chloride ................................................................................... 90

3.3.4. Cationic fixatives ................................................................................. 91

3.4. Experimental approach ................................................................................ 93

3.4.1. Dyeing with sodium sulphide............................................................... 93

3.4.2. Dyeing with Diresul Reducing agent D ............................................... 94

3.5. Physical testing ............................................................................................ 94

3.5.1. Colour fastness to domestic laundering ............................................... 94

5

3.5.2. Colour fastness to crocking (ISO 1O5- X12:2002).............................. 96

3.5.3. Colour fastness to light (ISO 1O5- BO2) ............................................. 97

3.5.4. Tensile properties of fabrics BS EN ISO 13934/1 1999 ...................... 98

3.6. Equipment ................................................................................................... 98

3.6.1. Padder ................................................................................................... 98

3.6.2. Tenter ................................................................................................... 98

3.6.3. Dyeing machine ................................................................................... 98

3.7. Analytical testing ......................................................................................... 99

3.7.1. Scanning electron microscopy (SEM) ................................................. 99

3.7.2. Fourier transform infrared spectroscopy (FTIR)................................ 100

3.7.3. X-Ray photoelectron spectroscopy (XPS) ......................................... 101

3.7.4. Elemental bulk analysis...................................................................... 103

3.8. References ................................................................................................. 103

4. Investigation into the effects of aftertreatments with Bayprotect Cl on the fastness

properties of sulphur dyed cotton fabric .................................................................. 105

4.1. Introduction ............................................................................................... 105

4.2. Application procedures for Bayprotect Cl on polyamide fabric ............... 108

4.3. Effects of application methods, presence/absence of electrolyte and varying

time….. ................................................................................................................. 108

4.3.1. Exhaust method of application ........................................................... 109

4.3.2. Continuous method of application ..................................................... 110

4.3.3. Results and discussion ....................................................................... 112

4.3.4. Summary ............................................................................................ 114

4.4. Effects of varying concentrations of Bayprotect Cl in the presence/absence of

sodium sulphate .................................................................................................... 114

4.4.1. Effect of the application of varying concentrations of Bayprotect Cl with

sodium sulphate on the ISO 1O5 CO9 wash fastness of the sulphur dyed cotton115

6

4.4.2. Effect of the application of varying concentrations of Bayprotect Cl

without sodium sulphate on the ISO 1O5 CO9 wash fastness of the sulphur dyed

cotton…… ........................................................................................................ 116

4.4.1. Summary ............................................................................................ 117

4.5. Effects of varying temperatures on the exhaust application of Bayprotect Cl

and sodium sulphate ............................................................................................. 118

4.5.1. Summary ............................................................................................ 121

4.6. Optimised parameters for the application of Bayprotect Cl on sulphur dyed

cotton fabric ......................................................................................................... 122

4.7. Aftertreatment of sulphur dyed cotton fabrics with Bayprotect Cl and sodium

sulphate (reduced with Diresul RAD) .................................................................. 122



sulphate (reduced with sodium sulphide) ............................................................. 129


4.9. Mechanism ................................................................................................ 132

4.10. Surface topography of the untreated and Bayprotect Cl aftertreated

fabrics…… ........................................................................................................... 134

4.11. Effects of reducing systems on the colour strength and fastness properties of

sulphur dyed cotton fabrics .................................................................................. 137

4.12. Conclusions ............................................................................................ 139

4.13. References .............................................................................................. 139

5. Investigation into the effects of aftertreatments with Bayprotect Cl, Fixapret CP

and choline chloride on the fastness properties of sulphur dyed cotton fabric ........ 141

5.1. Introduction ............................................................................................... 141

5.2. Effects of sequential application of Fixapret CP and Bayprotect Cl ......... 142

5.2.1. Summary ............................................................................................ 145

5.3. Effects of sequential application of Bayprotect Cl, Fixapret CP and choline

chloride ................................................................................................................. 148

7

5.3.1. Summary ............................................................................................ 151

5.4. Application of relative proportions of Bayprotect Cl, Fixapret CP and choline

chloride ................................................................................................................. 152

5.4.1. Summary ............................................................................................ 155

5.5. Application of reduced concentrations of choline chloride with Bayprotect Cl

and Fixapret CP .................................................................................................... 156

5.5.1. Summary ............................................................................................ 160

5.6. References ................................................................................................. 163

6. Investigation into the effects of aftertreatments with Bayprotect Cl and cationic

fixatives on the fastness properties of sulphur dyed cotton fabric ........................... 164

6.1. Introduction ............................................................................................... 164

6.2. Investigation into the application of different cationic fixatives ............... 168

6.2.1. Two bath sequential application of Bayprotect Cl and cationic

fixatives….. ...................................................................................................... 168

6.2.2. Summary ............................................................................................ 170

6.3. Determining a suitable sequence for two-bath application of Tinofix ECO and

Bayprotect Cl ....................................................................................................... 171

6.3.1. Summary ............................................................................................ 174

6.4. Surface topography of Tinofix ECO aftertreated fabric ............................ 175

6.5. Conclusions ............................................................................................... 177

6.6. References ................................................................................................. 177

7. Optimisation of process parameters for sequential application of Tinofix ECO and

Bayprotect Cl on sulphur dyed cotton fabric ........................................................... 179

7.1. Background ............................................................................................... 179

7.2. Introduction to experimental ..................................................................... 180

7.3. Aftertreatment sequence ............................................................................ 181

7.4. Effect of varying concentration of Tinofix ECO ....................................... 185

8

7.5. Effect of varying concentrations of Bayprotect Cl over 5% omf Tinofix ECO at

different temperatures .......................................................................................... 186

7.6. Application of protection system with one bath-two stage process .......... 195

7.7. Application of protection system (one bath-two stage process) at varying time

intervals ................................................................................................................ 196

7.7.1. Effect of aftertreatments with Tinofix ECO and Bayprotect Cl on rubbing

and light fastness of CI Leuco Sulphur Black 1 dyed cotton fabric ................ 198

7.8. Optimised parameters for one bath-two stage application of Tinofix ECO and

Bayprotect Cl on sulphur dyed cotton fabric ....................................................... 199

7.9. Aftertreatments of sulphur dyed cotton fabrics (reduced with Diresul RAD)

with Tinofix ECO and Bayprotect Cl .................................................................. 199


7.10. Aftertreatments of sulphur dyed cotton fabric (reduced with sodium

sulphide) with Tinofix ECO and Bayprotect Cl ................................................... 204

7.10.1. Results and discussion .................................................................... 208

7.11. Mechanism ............................................................................................. 210

7.12. Surface topography of Tinofix ECO and Bayprotect Cl aftertreated

fabrics….. ............................................................................................................. 212

7.13. Conclusions ............................................................................................ 212

7.14. References .............................................................................................. 216

8. Fourier transform infrared spectroscopic study of sulphur dyed and aftertreated

cotton fabrics ............................................................................................................ 218

8.1. Introduction ............................................................................................... 218

8.2. Fourier transform infrared spectroscopic analysis of the undyed cotton

fabric……. ........................................................................................................... 220

8.3. Fourier transform infrared spectroscopic analysis of cotton fabric dyed with CI

Leuco Sulphur Black 1 ......................................................................................... 222


Leuco Sulphur Black 1 and aftertreated with Bayprotect Cl ............................... 223

9


Leuco Sulphur Black 1 and aftertreated with Tinofix ECO ................................. 226


Leuco Sulphur Black 1 and aftertreated with Tinofix ECO and Bayprotect Cl ... 228

8.7. Conclusions ............................................................................................... 229

8.8. References ................................................................................................. 229

9. Surface and bulk chemical analysis of sulphur dyed and aftertreated cotton

fabrics….. ................................................................................................................. 232

9.1. Introduction ............................................................................................... 232

9.2. Investigation into the effects of aftertreatments with Bayprotect Cl on the

surface chemistry of CI Leuco Sulphur Black 1 dyed fabric subjected to ISO 105 C06

and ISO 105 C09 washing regimes ...................................................................... 233

9.2.1. Investigation into the effects of aftertreatments with Bayprotect Cl on

surface elemental compositions of CI Leuco Sulphur Black 1 dyed fabric ..... 234

9.2.2. Investigation into the effects of aftertreatments with Bayprotect Cl on S

(2p) spectra of CI Leuco Sulphur Black 1 dyed fabric .................................... 236

9.2.3. Investigation into the effects of aftertreatments with Bayprotect Cl on C

(1s) spectra of CI Leuco Sulphur Black 1 dyed fabric ..................................... 241

9.2.4. Investigation into the effects of aftertreatments with Bayprotect Cl on N

(1s) spectra of CI Leuco Sulphur Black 1 dyed fabric ..................................... 247

9.2.5. Conclusions ........................................................................................ 251

9.3. Investigation into the effects of aftertreatments with Tinofix ECO and

Bayprotect Cl (one bath–two stage process) on surface chemistry of CI Leuco

Sulphur Black 1 dyed fabric subjected to ISO 105 C09 washing regime ............ 251

9.3.1. Investigation into the effects of aftertreatments with Tinofix ECO and

Bayprotect Cl (one bath–two stage process) on surface elemental compositions of

CI Leuco Sulphur Black 1 dyed fabric ............................................................. 254


Bayprotect Cl (one bath–two stage process) on S (2p) spectra of CI Leuco Sulphur

Black 1 dyed fabric .......................................................................................... 256

10


Bayprotect Cl (one bath–two stage process) on C (1s) spectra of CI Leuco Sulphur



Bayprotect Cl (one bath–two stage process) on N (1s) spectra of CI Leuco Sulphur


9.4. Elemental bulk analysis of CI Leuco Sulphur Black 1 dyed fabric aftertreated

with Tinofix ECO and Bayprotect Cl (one bath–two stage process) following ISO 105

C09 washing regime ............................................................................................. 281

9.5. Conclusions ............................................................................................... 282

9.6. References ................................................................................................. 283

10. Conclusions and recommendations for future work ..................................... 285

10.1. Conclusions ............................................................................................ 285

10.2. Recommendations for future work ........................................................ 287

10.3. References .............................................................................................. 288

Counted words: 71,057

11

List of Tables

Table 3.1 Dyes used ................................................................................................... 89

Table 4.1 Composition and application parameters for aftertreatments with Bayprotect

Cl on CI Leuco Sulphur Black 1 dyed cotton .......................................................... 109

Table 4.2 Colorimetric data for CI Leuco Sulphur Black 1 dyed cotton fabric

aftertreated with Bayprotect Cl following different washing regimes ..................... 110

Table 4.3 Composition and application parameters for aftertreatments with varying

concentrations of Bayprotect Cl on CI Leuco Sulphur Black 1 dyed cotton fabric . 115

Table 4.4 Composition and application parameters for aftertreatments with Bayprotect

Cl (at varying temperatures) on CI Leuco Sulphur Black 1 dyed cotton fabric ...... 118


aftertreated with Bayprotect Cl and sodium sulphate at different temperatures (reduced

with Diresul RAD) ................................................................................................... 119


aftertreated with Bayprotect Cl and sodium sulphate at different temperatures (reduced

with sodium sulphide) .............................................................................................. 120

Table 4.7 Colorimetric data for ISO 1O5 CO6 and CO9 washed CI Leuco Sulphur Red

14 dyed fabric aftertreated with Bayprotect Cl and sodium sulphate (reduced with

Diresul RAD) ........................................................................................................... 123

Table 4.8 Colorimetric data for ISO 1O5 CO6 and CO9 washed CI Leuco Sulphur Blue

7 dyed fabric aftertreated with Bayprotect Cl and sodium sulphate (reduced with Diresul

RAD) ........................................................................................................................ 123

Table 4.9 Colorimetric data for ISO 1O5 CO6 and CO9 washed CI Leuco Sulphur

Black 1 dyed fabric aftertreated with Bayprotect Cl and sodium sulphate (reduced with

Diresul RAD) ........................................................................................................... 124


Yellow 22 dyed fabric aftertreated with Bayprotect Cl and sodium sulphate (reduced

with Diresul RAD) ................................................................................................... 124


Green 2 dyed fabric aftertreated with Bayprotect Cl and sodium sulphate (reduced with

Diresul RAD) ........................................................................................................... 125

Table 4.12 Light and crocking fastness data for sulphur dyed cotton fabrics aftertreated

with Bayprotect Cl and sodium sulphate (reduced with Diresul RAD) ................... 125

12

Table 4.13 Effects of aftertreatment with Bayprotect Cl and sodium sulphate on tensile

properties of CI Leuco Sulphur Black 1 dyed cotton fabrics ................................... 126

Table 4.14 Colorimetric data for ISO 1O5 CO6 and CO9 washed CI Leuco Sulphur Red

14 dyed fabric aftertreated with Bayprotect Cl and sodium sulphate (reduced with

sodium sulphide) ...................................................................................................... 129


Blue 7 dyed fabric aftertreated with Bayprotect Cl and sodium sulphate (reduced with

sodium sulphide) ...................................................................................................... 129


Black 1 dyed fabric aftertreated with Bayprotect Cl and sodium sulphate (reduced with

sodium sulphide) ...................................................................................................... 130


Yellow 22 dyed fabric aftertreated with Bayprotect Cl and sodium sulphate (reduced

with sodium sulphide) .............................................................................................. 130


Green 2 dyed fabric aftertreated with Bayprotect Cl and sodium sulphate (reduced with

sodium sulphide) ...................................................................................................... 131


with Bayprotect Cl and sodium sulphate (reduced with sodium sulphide) .............. 131

Table 4.20 Colour strength and fastness properties of untreated sulphur dyed cotton

fabrics reduced with sodium sulphide and Diresul Reducing agent D .................... 137

Table 5.1 Composition and application parameters for sequential application of

Bayprotect Cl and Fixapret CP on CI Leuco Sulphur Black 1 dyed cotton fabric .. 143

Table 5.2 Colorimetric data for ISO 1O5 CO6 and ISO 1O5 CO9 washed CI Leuco

Sulphur Black 1 dyed cotton fabric aftertreated with Bayprotect Cl and Fixapret CP…

.................................................................................................................................. 143


Bayprotect Cl, Fixapret CP and choline chloride on CI Leuco Sulphur Black 1 dyed

cotton fabric ............................................................................................................. 149


Sulphur Black 1 dyed cotton fabric aftertreated with Bayprotect Cl, Fixapret CP and

varying concentrations of choline chloride .............................................................. 150

Table 5.5 Composition and application parameters for Bayprotect Cl, Fixapret CP and

choline chloride on CI Leuco Sulphur Black 1 dyed cotton fabric .......................... 152

13


Sulphur Black 1 dyed cotton fabric aftertreated with Bayprotect Cl, Fixapret CP and

choline chloride ........................................................................................................ 153

Table 5.7 Composition and application parameters for reduced concentrations of

Bayprotect Cl, Fixapret CP and choline chloride on CI Leuco Sulphur Black 1 dyed

cotton fabric ............................................................................................................. 157


Sulphur Black 1 dyed cotton fabric aftertreated with reduced concentrations of

Bayprotect Cl, Fixapret CP and choline chloride .................................................... 157

Table 5.9 Light and crocking fastness data for CI Leuco Sulphur Black 1 dyed cotton

fabric aftertreated with reduced concentrations of Fixapret CP, Bayprotect Cl and

choline chloride ........................................................................................................ 159

Table 5.10 Effects of aftertreatments with Fixapret CP, Bayprotect Cl and choline

chloride on tensile properties of CI Leuco Sulphur Black 1 dyed cotton fabrics .... 159

Table 6.1 Composition and application parameters for different fixatives .............. 168

Table 6.2 Compositions and application parameters for sequential application of

Bayprotect Cl and cationic fixatives on CI Leuco Sulphur Black 1 dyed cotton fabric.

.................................................................................................................................. 169


Sulphur Black 1 dyed cotton fabric sequentially aftertreated with Bayprotect Cl and

cationic fixatives ...................................................................................................... 169

Table 6.4 Light and crocking fastness data for CI Leuco Sulphur Black 1 dyed cotton

fabric aftertreated with Bayprotect Cl and cationic fixatives ................................... 170


Bayprotect Cl and Tinofix ECO on CI Leuco Sulphur Black 1(Examining the effects of

an electrolyte) ........................................................................................................... 171


Sulphur Black 1 dyed cotton fabric sequentially aftertreated with Bayprotect Cl and

Tinofix ECO (Examining the effects of an electrolyte) ........................................... 172

Table 6.7 Compositions and application parameters for CI Leuco Sulphur Black 1 dyed

cotton fabric sequentially aftertreated with Bayprotect Cl and Tinofix ECO (Examining

the effects of varying concentrations) ...................................................................... 172

14


Sulphur Black 1 dyed cotton fabric sequentially aftertreated with Tinofix ECO and

Bayprotect Cl (Examining the effects of varying concentrations) ........................... 173

Table 7.1 Aftertreatment procedures for optimisation ............................................. 183

Table 7.2 Composition and application parameters for optimisation of sequential

application of Tinofix ECO and Bayprotect Cl on CI Leuco Sulphur Black 1 dyed cotton

fabric ........................................................................................................................ 184

Table 7.3 Colorimetric data for ISO 1O5 CO9 washed CI Leuco Sulphur Black 1 dyed

cotton fabric reduced with Diresul RAD and aftertreated with Tinofix ECO ......... 188


cotton fabric reduced with sodium sulphide and aftertreated with Tinofix ECO .... 188


cotton fabric (reduced with Diresul RAD) aftertreated with 5% omf Tinofix ECO and

x% omf Bayprotect Cl at 40oC for 20 minutes ........................................................ 190

Table 7.6 Colorimetric data for ISO 1O5 CO9 washed CI Leuco Sulphur Black 1dyed



Table 7.7 Colorimetric data for ISO 1O5 CO9 washed CI Leuco Sulphur Black 1dyed




cotton fabric (reduced with sodium sulphide) aftertreated with 5% omf Tinofix ECO and









cotton fabrics (reduced with Diresul RAD) aftertreated with with one bath–two stage

process (application of 5% TE and 5% BP at 40oC) ................................................ 195

15


cotton fabrics (reduced with sodium sulphide) aftertreated with one bath–two stage

process (application of 5% TE and 5% BP at 40oC) ................................................ 196

Table 7.13 Colorimetric data for one bath–two stage application of Tinofix ECO and

Bayprotect Cl, at different time intervals, following ISO 1O5 CO9 washing (CI Leuco

Sulphur Black 1 dyed cotton fabric reduced with RAD) ......................................... 197

Table 7.14 Colorimetric data for one bath–two stage application of Tinofix ECO and

Bayprotect Cl, at different time intervals, following ISO 1O5 CO9 washing (CI Leuco

Sulphur Black 1 dyed cotton fabric reduced with SS) ............................................. 197

Table 7.15 Rubbing and light fastness properties of CI Leuco Sulphur Black 1 dyed

cotton fabric aftertreated with Tinofix ECO and Bayprotect Cl (reduced with Diresul

RAD and sodium sulphide) ...................................................................................... 198


fabric aftertreated with Tinofix ECO and Bayprotect Cl (reduced with RAD) ....... 200

Table 7.17 Colorimetric data for ISO 1O5 CO9 washed CI Leuco Sulphur Blue 7 dyed


Table 7.18 Colorimetric data for ISO 1O5 CO9 washed CI Leuco Sulphur Yellow 22

dyed fabric aftertreated with Tinofix ECO and Bayprotect Cl (reduced with Diresul

RAD) ........................................................................................................................ 201

Table 7.19 Colorimetric data for ISO 1O5 CO9 washed CI Leuco Sulphur Red 14 dyed


Table 7.20 Colorimetric data for ISO 1O5 CO9 washed CI Leuco Sulphur Green 2 dyed



with Tinofix ECO and Bayprotect Cl (reduced with Diresul RAD) ........................ 202

Table 7.22 Colorimetric data for ISO 1O5 CO9 washed CI Leuco Sulphur Red 14 dyed

fabric aftertreated with Tinofix ECO and Bayprotect Cl (reduced with sodium sulphide)

.................................................................................................................................. 205

Table 7.23 Colorimetric data for ISO 1O5 CO9 washed CI Leuco Sulphur Green 2 dyed


.................................................................................................................................. 205



.................................................................................................................................. 205

16

Table 7.25 Colorimetric data for ISO 1O5 CO9 washed CI Leuco Sulphur Blue 7 dyed


.................................................................................................................................. 206

Table 7.26 Colorimetric data for ISO 1O5 CO9 washed CI Leuco Sulphur Yellow 22

dyed fabric aftertreated with Tinofix ECO and Bayprotect Cl (reduced with sodium

sulphide) ................................................................................................................... 206


with Tinofix ECO and Bayprotect Cl (reduced with sodium sulphide) ................... 207

Table 7.28 Effects of different aftertreatments on tensile properties of CI Leuco Sulphur

Black 1 dyed cotton fabrics ...................................................................................... 208

Table 8.1 Compositions for CI Leuco Sulphur Black 1 dyed fabric aftertreated with

Tinofix ECO and Bayprotect Cl ............................................................................... 219

Table 8.2 Regions of the infrared spectrum for preliminary analysis [2] ................ 219

Table 8.3 Vibrational absorption assignments in the FTIR spectrum of undyed cotton

fabric ........................................................................................................................ 221

Table 8.4 Vibrational absorption assignments in the FTIR spectrum of CI Leuco

Sulphur Black 1 dyed cotton fabric .......................................................................... 223

Table 8.5 Vibrational absorption assignments in the FTIR spectrum of Bayprotect Cl

................................................................................................................................. .224

Table 8.6 Vibrational absorption assignments in the FTIR spectrum of Tinofix ECO..

.................................................................................................................................. 226

Table 8.7 Vibrational absorption assignments in the FTIR spectrum of CI Leuco

Sulphur Black 1 dyed cotton fabric aftertreated with Tinofix ECO and Bayprotect Cl.

.................................................................................................................................. 228

Table 9.1 Application of Bayprotect Cl to CI Leuco Sulphur Black 1 dyed fabric . 233

Table 9.2 Colorimetric data for CI Leuco Sulphur Black 1 dyed fabric aftertreated with

Bayprotect Cl following ISO 1O5 CO6 and ISO 1O5 CO9 washing ...................... 233

Table 9.3 XPS surface elemental composition for CI Leuco Sulphur Black 1 dyed

fabric aftertreated with Bayprotect Cl following ISO 1O5 CO6 and ISO 1O5 CO9

washing .................................................................................................................... 234

Table 9.4 Relative intensity data of the deconvoluted S (2p) spectra for CI Leuco

Sulphur Black 1 dyed fabric aftertreated with Bayprotect Cl following ISO 1O5 CO6

and ISO 1O5 CO9 washing ...................................................................................... 237

17

Table 9.5 Relative intensity data of the deconvoluted C (1s) spectra for CI Leuco

Sulphur Black 1 dyed fabric aftertreated with Bayprotect Cl following ISO 1O5 CO6

and ISO 1O5 CO9 washing ...................................................................................... 242

Table 9.6 Application conditions for CI Leuco Sulphur Black 1 dyed fabric aftertreated

with Tinofix ECO and Bayprotect Cl ...................................................................... 252


aftertreated with Tinofix ECO and Bayprotect Cl following ISO 1O5 CO9 washing

.............................................................................................................................. …252

Table 9.8 XPS surface elemental composition for CI Leuco Sulphur Black 1 dyed

fabric aftertreated with Tinofix ECO and Bayprotect Cl following ISO 1O5 CO9

washing .................................................................................................................... 253

Table 9.9 Relative intensity data of the deconvoluted S (2p) spectra for CI Leuco

Sulphur Black 1 dyed fabric aftertreated with Tinofix ECO and Bayprotect Cl following

ISO 1O5 CO9 washing ............................................................................................ 258

Table 9.10 Relative intensity data of the deconvoluted C (1s) spectra for CI Leuco

Sulphur Black 1 dyed fabric aftertreated with Tinofix ECO and Bayprotect Cl following

ISO 1O5 CO9 washing ............................................................................................ 267

Table 9.11 Elemental analysis for CI Leuco Sulphur Black 1 dyed fabric aftertreated

with Tinofix ECO and Bayprotect Cl following ISO 1O5 CO9 washing ................ 282

18

List of Figures

Figure 1.1 Share of the world dye market for cellulosic fibres, reproduced from[2]…..33

Figure 2.1 Effect of temperature on reduction potential of reducing sugar and sodium

sulphide at pH of 12 from [5] ..................................................................................... 51

Figure 2.2 Influence of glucose concentration on colour strength of CI Sulphur Black 1

at 90oC, reproduced from [16] ................................................................................... 52

Figure 2.3 Effect of caustic soda concentration on pH of the three reducing systems,

from [18] .................................................................................................................... 54

Figure 2.4 Effect of caustic soda concentration on colour yield (K/S) of the three

reducing systems, from [18] ....................................................................................... 54

Figure 2.5 Comparison of dye receptivity (K/S) in catalase and sulphide reduction

system from [29] ........................................................................................................ 62

Figure 2.6 Comparison of colour strength of cotton dyed in sulphide and pectinase

systems from [30] ....................................................................................................... 64

Figure 2.7 Effect of laccase concentration on K/S of sulphur dyes from [34] ........... 69

Figure 2.8 Colour loss of dyeings with CI Leuco Sulphur Black 1 with and without

aftertreatment from [50] ............................................................................................. 73

Figure 2.9 Effect of lanthanum triacetate on resistance of sulphur dyes against oxidation

for one LOW cycle using NOBS detergent from [54] ............................................... 75

Figure 3.1 Application of Solfix E ............................................................................. 91

Figure 3.2 Application of Tinofix ECO ..................................................................... 92

Figure 3.3 Application of Indosol E-50 ..................................................................... 92

Figure 3.4 Sulphur dyeing method for cotton using sodium sulphide ....................... 93

Figure 3.5 Sulphur dyeing method for cotton using Diresul Reducing agent D ........ 94

Figure 3.6 Schematic of image formation by SEM from [7] ................................... 100

Figure 3.7 Initial (left) and final (right) states in the photoelectric effect in XPS, from

[13] ........................................................................................................................... 102

Figure 4.1 Structures of tannin components (a) gallic acid (b) hexahydroxydiphenic

acid, reproduced from [4] ......................................................................................... 107

Figure 4.2 Aftertreatments with Bayprotect Cl (exhaust application) ..................... 109

Figure 4.3 Effect of aftertreatments with Bayprotect Cl on wash fastness of CI Leuco

Sulphur Black 1 dyed cotton fabric .......................................................................... 112

19

Figure 4.4 Effect of aftertreatment with varying concentrations of Bayprotect Cl, in the

presence of sodium sulphate, on the ISO 1O5 CO9 wash fastness of CI Leuco Sulphur

Black 1 dyed cotton fabric ....................................................................................... 116

Figure 4.5 Effect of aftertreatment with varying concentrations of Bayprotect Cl, in the

absence of sodium sulphate, on the ISO 1O5 CO9 wash fastness of CI Leuco Sulphur

Black 1 dyed cotton fabric ....................................................................................... 117

Figure 4.6 Effects of varying application temperatures for exhaust application of

Bayprotect Cl and sodium sulphate on the wash fastness of CI Leuco Sulphur Black 1

dyed cotton fabric (reduced with Diresul RAD) ...................................................... 119

Figure 4.7 Effects of varying application temperatures for exhaust application of

Bayprotect Cl and sodium sulphate on the wash fastness of CI Leuco Sulphur Black 1

dyed cotton fabric (reduced with sodium sulphide) ................................................. 120

Figure 4.8 Effect of aftertreatments with Bayprotect Cl and sodium sulphate on fastness

to laundering (ISO 1O5 CO6) of sulphur dyed cotton fabrics (reduced with Diresul

RAD) ........................................................................................................................ 128

Figure 4.9 Effect of aftertreatments with Bayprotect Cl and sodium sulphate on fastness

to laundering (ISO 1O5 CO9) of sulphur dyed cotton fabrics (reduced with Diresul

RAD) ........................................................................................................................ 128

Figure 4.10 Effect of aftertreatments with Bayprotect Cl and sodium sulphate on

fastness to laundering (ISO 1O5 CO6) of sulphur dyed cotton fabrics (reduced with

sodium sulphide) ...................................................................................................... 133


fastness to laundering (ISO 1O5 CO9) of sulphur dyed cotton fabrics (reduced with

sodium sulphide) ...................................................................................................... 133

Figure 4.12 SEM micrograph of unlaundered untreated sulphur dyed cotton fabric

Magnification 1000x ................................................................................................ 135

Figure 4.13 SEM micrograph of unlaundered untreated sulphur dyed cotton fabric

Magnification 5000x ................................................................................................ 135

Figure 4.14 SEM micrograph of ISO 105 CO9 laundered untreated sulphur dyed cotton

fabric Magnification 1000x ...................................................................................... 135

Figure 4.15 SEM micrograph of ISO 105 CO9 laundered untreated sulphur dyed cotton

fabric Magnification 5000x ...................................................................................... 135

Figure 4.16 SEM micrograph of unlaundered 4% omf Bayprotect Cl treated sulphur

dyed cotton fabric Magnification 1000x .................................................................. 136

20

Figure 4.17 SEM micrograph of unlaundered 4% omf Bayprotect C treated sulphur

dyed cotton fabric Magnification 5000x…………………………………………..136

Figure 4.18 SEM micrograph of ISO 105 CO9 laundered 4% omf Bayprotect Cl treated

sulphur dyed cotton fabric Magnification 1000x ..................................................... 136

Figure 4.19 SEM micrograph of ISO 105 CO9 laundered 4% omf Bayprotect Cl treated


Figure 5.1 Effect of aftertreatments with Bayprotect Cl and Fixapret CP on wash

fastness of CI Leuco Sulphur Black 1 dyed cotton fabric ........................................ 147

Figure 5.2 Effect of aftertreatments with Bayprotect Cl, Fixapret CP and varying

concentrations of choline chloride on wash fastness of CI Leuco Sulphur Black 1 dyed

cotton fabric ............................................................................................................. 151

Figure 5.3 Effect of aftertreatments with relative proportions of Bayprotect Cl, Fixapret

CP and choline chloride on the fastness of CI Leuco Sulphur Black 1 dyed cotton 155

Figure 5.4 Effect of aftertreatments with reduced concentrations of Bayprotect Cl,

Fixapret CP and choline chloride on the wash fastness of CI Leuco Sulphur Black 1

dyed cotton fabric ..................................................................................................... 162

Figure 6.1 Effect of aftertreatments with sequential application of Tinofix ECO and

Bayprotect Cl on wash fastness (ISO 1O5 CO9) of CI Leuco Sulphur Black 1 dyed

cotton fabric ............................................................................................................. 174

Figure 6.2 SEM micrograph of unlaundered 5% omf Tinofix ECO treated sulphur dyed

cotton fabric Magnification 1000x ........................................................................... 176

Figure 6.3 SEM micrograph of unlaundered 5% omf Tinofix ECO treated sulphur dyed

cotton fabric Magnification 5000x ........................................................................... 176

Figure 6.4 SEM micrograph of ISO 1O5 CO9 laundered, 5% omf Tinofix ECO treated


Figure 6.5 SEM micrograph of ISO 1O5 CO9 laundered, 5% omf Tinofix ECO treated

sulphur dyed cotton fabric Magnification 10000x ................................................... 176

Figure 7.1 Cation aftertreatment .............................................................................. 182

Figure 7.2 Tannin aftertreatment ............................................................................. 182

Figure 7.3 One bath-two stage cation/tannin aftertreatment .................................... 182

Figure 7.4 Effect of varying concentrations of Tinofix ECO on ISO 1O5 CO9 wash

fastness CI Leuco Sulphur Black 1 dyed cotton fabric ............................................ 189

21

Figure 7.5 Effect of varying concentrations and application temperatures of Bayprotect

Cl on ISO 1O5 CO9 wash fastness of CI Leuco Sulphur Black 1 dyed cotton fabric

(reduced with Diresul RAD) .................................................................................... 193

Figure 7.6 Effect of varying concentrations and application temperatures of Bayprotect

Cl on ISO 1O5 CO9 wash fastness of CI Leuco Sulphur Black 1 dyed cotton fabric

(reduced with sodium sulphide) ............................................................................... 194

Figure 7.7 Effect of aftertreatment with Tinofix ECO and Bayprotect Cl on ISO 1O5

CO9 wash fastness of sulphur dyed cotton fabrics (reduced with Diresul RAD) .... 202

Figure 7.8 Effect of aftertreatment with Tinofix ECO and Bayprotect Cl on ISO 1O5

CO9 wash fastness of sulphur dyed cotton fabrics (reduced with sodium sulphide)…207

Figure 7.9 SEM micrograph of unlaundered, 5% omf Tinofix ECO + 5% omf BP Cl

treated cotton fabric Magnification 1000x ............................................................... 214

Figure 7.10 SEM micrograph of unlaundered, 5% omf Tinofix ECO + 5% omf BP Cl

treated cotton fabric Magnification 5000x ............................................................... 214

Figure 7.11 SEM micrograph of ISO 1O5 CO9 laundered, 5% omf Tinofix ECO + 5%

omf BP Cl treated cotton fabric Magnification 1000x ............................................. 214

Figure 7.12 SEM micrograph of ISO 1O5 CO9 laundered, 5% omf Tinofix ECO + 5%

omf BP Cl treated cotton fabric Magnification 5000x ............................................. 214

Figure 7.13 Formation of complexes between dye and cation................................. 215

Figure 7.14 Formation of complexes between dye/cation and tannin ..................... 215

Figure 8.1 FTIR spectrum of undyed cotton fabric.................................................. 221

Figure 8.2 FTIR spectrum of CI Leuco Sulphur Black 1 dyed cotton fabric........... 222

Figure 8.3 FTIR spectrum of Bayprotect Cl ........................................................... 223

Figure 8.4 FTIR spectra of CI Leuco Sulphur Black 1 dyed cotton fabric untreated and

aftertreated with Bayprotect Cl ................................................................................ 225

Figure 8.5 FTIR spectrum of Tinofix ECO .............................................................. 226


aftertreated with Tinofix ECO ................................................................................. 227


aftertreated with Tinofix ECO and Bayprotect Cl ................................................... 228

Figure 9.1 S (2p) spectrum of untreated CI Leuco Sulphur Black 1 dyed fabric

(unlaundered) ........................................................................................................... 238

Figure 9.2 S (2p) spectrum of untreated CI Leuco Sulphur Black 1 dyed fabric .... 238

Figure 9.3 S (2p) spectrum of untreated CI Leuco Sulphur Black 1 dyed fabric .... 239

22

Figure 9.4 S (2p) spectrum of CI Leuco Sulphur Black 1 dyed fabric aftertreated with

4% omf Bayprotect Cl (unlaundered) ...................................................................... 239


4% omf Bayprotect Cl (ISO 1O5 CO6 laundered) .................................................. 240



Figure 9.7 C (1s) spectrum of untreated CI Leuco Sulphur Black 1 dyed fabric

(unlaundered) ........................................................................................................... 243

Figure 9.8 C (1s) spectrum of untreated CI Leuco Sulphur Black 1 dyed fabric (ISO 1O5

CO6 laundered) ....................................................................................................... 243

Figure 9.9 C (1s) spectrum of untreated CI Leuco Sulphur Black 1 dyed fabric (ISO 1O5

CO9 laundered) ........................................................................................................ 244

Figure 9.10 C (1s) spectrum of CI Leuco Sulphur Black 1 dyed fabric aftertreated with






Figure 9.13 Concentration of carbon functionalities determined by curve fitting of the C

(1s) peaks from XPS spectra (fabric dyed with CI Leuco Sulphur Black 1 and

aftertreated with Bayprotect Cl) ............................................................................... 247

Figure 9.14 N (1s) spectrum of untreated CI Leuco Sulphur Black 1 dyed fabric

(unlaundered) ........................................................................................................... 248

Figure 9.15 N (1s) spectrum of untreated CI Leuco Sulphur Black 1 dyed fabric (ISO

1O5 CO6 laundered) ................................................................................................ 248


1O5 CO9 laundered) ................................................................................................ 249

Figure 9.17 N (1s) spectrum of CI Leuco Sulphur Black 1 dyed fabric aftertreated with






23

Figure 9.20 Wide scan XP spectra of CI Leuco Sulphur Black 1 dyed fabric aftertreated

with Tinofix ECO and Bayprotect Cl: ..................................................................... 254


(unlaundered) ........................................................................................................... 259

Figure 9.22 S (2p) spectrum of untreated CI Leuco Sulphur Black 1 dyed fabric (ISO

1O5 CO9 laundered) ................................................................................................ 259


TE1 (unlaundered) .................................................................................................... 260


TE1 (ISO 1O5 CO9 laundered) ................................................................................ 260


TE2 (unlaundered) .................................................................................................... 261




TE1, BP

3 (unlaundered) ............................................................................................ 262


TE1, BP

3 (ISO 1O5 CO9 laundered) ........................................................................ 262


TE1, BP

1 (unlaundered) ............................................................................................ 263


TE1, BP


Figure 9.31 C (1s) spectrum of undyed and unlaundered cotton fabric ................... 264


(unlaundered) ........................................................................................................... 268

Figure 9.33 C (1s) spectrum of untreated CI Leuco Sulphur Black 1 dyed fabric (ISO

1O5 CO9 laundered) ................................................................................................ 268


TE1 (unlaundered) .................................................................................................... 269




TE2 (unlaundered) .................................................................................................... 270

24




TE1, BP

3 (unlaundered) ............................................................................................ 271


TE1, BP



TE1, BP

1 (unlaundered) ............................................................................................ 272


TE1, BP


Figure 9.42 Concentration of carbon functionalities determined by curve fitting the C

(1s) peaks from XPS spectra (fabric dyed with CI Leuco Sulphur Black 1 and

aftertreated with Tinofix ECO and Bayprotect Cl) .................................................. 273


(unlaundered) ........................................................................................................... 276


1O5 CO9 laundered) ................................................................................................ 276


TE1 (unlaundered) .................................................................................................... 277




TE2 (unlaundered) .................................................................................................... 278



Figure 9.49 N(1s) spectrum of CI Leuco Sulphur Black 1 dyed fabric aftertreated with

TE1, BP

3 (unlaundered) ............................................................................................ 279


TE1, BP



TE1, BP

1 (unlaundered) ............................................................................................ 280


TE1, BP


25

List of abbreviations

Colour index CI

The international organisation for standardisation ISO

A color space defined by the Commission

Internationale de l'Eclairage

CIELab

X-Ray photoelectron spectroscopy XPS

Electron spectroscopy for chemical analysis ESCA

Fourier transform infrared spectroscopy FTIR

Attenuated total reflectance ATR

Scanning electron microscopy SEM

Tetraacetylethylenediamine TAED

Nonanoyloxybenzenesulphonate NOBS

Grams per square meter GSM

Ends per inch EPI

Picks per inch PPI

Dimethyldihydroxyethyleneurea DMDHEU

Relative humidity RH

Organisation for economic cooperation and development OECD

SIDS initial assessment meeting SIAM

Screening information dataset SIDS

Grey scale rating GS

On the mass of the fabric omf

Liquor to goods ratio L:R

26

Abstract

University of Manchester

Quratulain Mohtashim

Doctor of Philosophy (PhD)

Investigation into the chemical processing and colorimetric properties of sulphur

dyed cellulosic textiles

October 2015

This work documents the chemical processing, colorimetric properties and fastness

characteristics of sulphur dyed cellulosic textiles. It is well-known that cotton is the

most commonly used cellulosic fibre and the sulphur dye class is reported to have the

highest consumption among all other colorants applied to cotton. The most attractive

feature of sulphur dyes is their low cost which makes their application attractive for dark

shades including black, navy, brown and olive. They possess moderate to good fastness

which allows them to broadly satisfy the needs of industry, but with the increasing

performance demands of garment suppliers and customers, the use of these dyes is

gradually declining as they are getting replaced by other dye classes. A major reason for

their continuing unpopularity is the environmental impact that is created by the use of

the conventional reducing agent sodium sulphide, which is highly toxic for marine life

and sewerage systems. Secondly, cellulosic goods dyed with sulphur dyes are

particularly susceptible to perborate bleach-containing washing powders thus exhibiting

impaired washfastness against oxidative bleaching.

The aim of this research is to explore possible solutions for the aforementioned

problems. In order to address the environmental concerns related to dye application, a

comparative analysis for the conventional and alternative glucose-based biodegradable

reducing systems was made. The fastness properties and cross staining performance of

sulphur dyed fabric is usually characterised with the standard ISO 1O5 CO6 benchmark.

In recent times, a distinctive combination of standard detergent, a low temperature

tetraacetylethylenediamine (TAED) bleach activator has been developed which mimics

modern detergent formulation and laundering practices. This is the ISO 1O5 CO9

washing protocol, the effect of which has not been reported for sulphur dyes. The

purpose of this research is to determine the resistance of the sulphur dyes against such

formulations and crucially to identify aftertreatments to reduce the wash down of dyes

during repeated laundering cycles over the life time of a cellulosic textile material.

In order to produce dyed fabric with improved wash fastness against the aggressive ISO

1O5 CO9 washing regime, a protective system was developed involving the sequential

application of a cationic fixative and tannin-based product. The process parameters were

optimised to formulate a standard workable recipe. The optimised parameters were

evaluated for five different sulphur dyes for the colour strength (K/S), wash fastness,

light fastness and dry/wet crocking fastness of the treated fabric. The effects on surface

morphology of the untreated and treated fabrics were examined through Scanning

Electron Microscopy (SEM). In order to identify the presence of possible functional

groups produced as a result of the aftertreatments, Fourier Transform Infrared (FTIR)

and X-Ray Photoelectron Spectroscopy (XPS) techniques were utilised.

27

Declaration

No portion of the work referred to in this thesis has been submitted in support of an

application for another degree or qualification of this or any other university or other

institute of learning.

Quratulain Mohtashim

Introduction

28

Copyright statement

i. The author of this thesis (including any appendices and/or schedules to this thesis)

owns certain copyright or related rights in it (the “Copyright”) and she has given The

University of Manchester certain rights to use such Copyright, including for

administrative purposes.

ii. Copies of this thesis, either in full or in extracts and whether in hard or electronic

copy, may be made only in accordance with the Copyright, Designs and Patents Act

1988 (as amended) and regulations issued under it or, where appropriate, in accordance

with licensing agreements which the University has from time to time. This page must

form part of any such copies made.

iii. The ownership of certain Copyright, patents, designs, trademarks and other

intellectual property (the “Intellectual Property”) and any reproductions of copyright

works in the thesis, for example graphs and tables (“Reproductions”), which may be

described in this thesis, may not be owned by the author and may be owned by third

parties. Such Intellectual Property and Reproductions cannot and must not be made

available for use without the prior written permission of the owner(s) of the relevant

Intellectual Property and/or Reproductions.

iv. Further information on the conditions under which disclosure, publication and

commercialisation of this thesis, the Copyright and any Intellectual Property and/or

Reproductions described in it may take place is available in the University IP Policy

(see http://documents.manchester.ac.uk/DocuInfo.aspx?DocID=487), in any relevant

Thesis restriction declarations deposited in the University Library, The University

Library’s regulations (see http://www.manchester.ac.uk/library/aboutus/regulations) and

in The University’s policy on Presentation of Theses.

Introduction

29

This thesis is dedicated to my wonderful husband Mohtashim Shahid and my sons

Mahad Mohtashim and Ahmad Mohtashim.

Introduction

30

Acknowledgements

First of all, I am grateful to Almighty Allah for giving me strength and ability to

complete this study.

I would like to thank my supervisors Professor Franz Wortmann, Dr. Muriel Rigout and

Professor Christopher Carr for their valuable advice, guidance and encouragement during

my study. I am grateful to Professor Franz Wortmann, for his indefinite support and

boosting up my self-confidence in the final phase of my project. I would especially like to

express my sincere gratitude to Dr. Muriel Rigout for her kindness, understanding,

guidance and knowledgeable advice throughout the course of this project. I would also

like to appreciate Professor Christopher Carr, for his great help in offering a place at the

reputed, University of Manchester together with the proficient counselling and guidance

in the research work. I am also grateful to Mr. Phil Cohen, who provided guidance and

support in locating the auxiliaries, handling equipment and carrying out dyeing and

wash fastness testing. Mr. David Kenyon provided support in colorimetric data

collection in colour physics lab and Ms. Paula Crook guided on the use of FTIR

spectrometer. I cannot forget the sincere and kind efforts of Dr. Christopher Wilkins

who guided me through the use of SEM and the assistance given by Dr. John Walton for

XPS experimentations.

I would also like to thank NED University of Engineering & Technology, Pakistan, for

providing scholarship for PhD program and EPSRC (Engineering and Physical Sciences

Research Council, UK) for the financial support needed for completion of this project.

To all my friends in Mez 3, thank you for listening, offering me advice, and supporting

me through this entire process. Many thanks to Syed Naveed for helping me and my

family in the initial phase of settling in a new country. For making me smile when it

mattered the most my thanks and best wishes go to Allaa, Celina, Tahani, Kate, Ghada ,

Katie, Lizzy, Govi and Nazmul. I cannot forget the selfless help by my friends Allaa

and Abbas who helped me with the analysis softwares for FTIR and XPS.

I would like to thank my in-laws (Mushir, Almas, Aiman and Abdul Ahad in particular)

and siblings (Shagufta, Sobia, Azhar, Aamir and Saqib), who always supported me in

my decision for higher studies. In particular, I am grateful to my mother-in-law (Habiba

Introduction

31

Khanum) and parents (Altaf Siddiqui and Noor Jehan), as I would not have been able to

achieve this opportunity without their prayers.

Last but not the least, this journey would not have been possible without the support of

my family, that is my children Mahad and Ahmad and husband Mohtashim Shahid to

whom I dedicate this thesis.

To my husband, thank you for encouraging me in all of my pursuits and inspiring me to

follow my dreams. Thanks a lot for all the fun times and care through the tough times,

for making me feel comfortable by solving small issues related to everyday life. I

always knew that you believed in me and wanted the best for me. I would never be able

to thank you for whatever you have done for me. Thanks for sacrificing your work for

my higher studies and for guiding me as a person, a best friend, life partner and teacher

and for offering knowledgeable advices throughout my PhD study period.

I am especially grateful to my children, who supported me emotionally, cheered me in

times of stress and comforted me whenever I felt alone and helpless. They have always

been a great source of motivation and energy for me that pushed me to work harder.

Introduction

32

1. Introduction

Sulphur dyes are a major class of textile dyes that are applied to cellulosic textiles [1].

With the introduction of reactive dyes in the 1950’s, it was believed that these dyes

would replace a major market share of sulphur, direct and vat dyes [2]. At that time

world production for sulphur dyes was estimated at 110,000-120,000 tons per year

which was the highest production percentage of any group of dyes. In 2007, sulphur

dyes were the third-highest produced dyes in China at 8500 tons [3].

In the years between 1992 and 2000, the annual consumption of sulphur dyes for

cellulosic fibres was estimated at ca.70,000 tons [4, 5]. The level of consumption of

sulphur dyes against other dyes is clearly evident from the world consumption data

(Figure 1.1) [2] and half of the volume of all dyes produced for cellulosic fibres consists

of sulphur dyes [6].

The most attractive feature of sulphur dyes is their cost efficiency. This dye class is

relatively inexpensive when compared to other dye classes applied to cellulosic

material. They are well known for black, brown, navy, olive and green colour in

medium to heavy depths [2]. Another important reason for the popularity of this dye

class is the ease of application and the choice of availability for products like garments,

furnishings, linings and carpets [7].

The importance of sulphur dyes are realised due to the fact that they offer an economical

method of achieving dyeing of good colour strength and acceptable fastness dyeings on

cellulosic substrates [4].

Among the aforementioned colours, CI Sulphur Black 1 is one of the most popular dyes

in the world and comes in a range of forms i.e. CI Sulphur Black 1, CI Solubilised

Sulphur Black 1 and CI Leuco Sulphur Black, constituting around 10% by mass of all

dyes produced around the globe annually [8, 9].

Sulphur dyes have moderate to good fastness to light and wet treatments [2, 10, 11].

However, the main limitations associated with this class of dye are the lack of

availability of bright colours and it’s fading on exposure to laundering with detergent

and perborates/peroxides formulations. In order to meet the growing requirements of

Introduction

33

customers regarding the higher wash fastness, garment traders are in turn demanding

their suppliers to achieve these properties against single and multiple washes [8].

Figure 1.1 Share of the world dye market for cellulosic fibres, reproduced from

[2]

1.1. Background of the study

Historically sulphur dyes were the most widely consumed dyes for cotton and cotton

blends because of their low cost, availability of dark shades, good wet fastness and

moderate to good light fastness. However, with the passage of time, reactive dyes have

gradually replaced sulphur dyes due to the latter’s low resistance to oxidative laundering

and the considerable decrease in reactive dyes’ price [12].

In order to improve the wet fastness of sulphur dyes, a substantial body of work has

been contributed to by various researchers. The use of alkylating agents has been

reported to not only replace the conventional oxidation treatment but also to improve the

wash fastness of sulphur dyes against the severe washing condition with peroxide-

containing detergents [10, 13-15]. Other recommended compounds include quaternary

ammonium alkyl compounds [15, 16], dicyandiamide-formaldehyde condensates [13]

29%

27.40%

19.40%

9.70%

8.10%

6.40%

Sulphur dyes

Direct Dyes

Vat dyes

Reactive Dyes

Azoic dyes

Pigments

Introduction

34

and crease resist finishing agents [10, 17, 18]. Besides that, the exhaust and continuous

application treatments with several cationic fixing agents have also been explored by

Burkinshaw [8, 13, 18-20]. Moreover, the pad application of lanthanum triacetate for

reducing the colour loss of sulphur dyed cotton during laundering has also been

explored [12]. The method substantially improved the oxidative bleaching resistance of

sulphur dyed textiles which were durable to repeated launderings [12]. However, the

resistance of sulphur dyes against the action of oxidative bleaching formulations

including bleach activators has not been taken much into consideration.

1.2. Research problem

In spite of their extensive use, surprisingly little is known about the exact structure of

sulphur dyes. The main features that make them unique are the organic intermediates

from which they are derived and the method of sulphurisation involved in their

manufacturing [2]. Sulphurisation involves various reaction such as substitution, ring

formation, reduction and oxidation for which the starting materials are relatively

common aromatic compounds [1]. In order to understand the research problem,

chemistry of the sulphur dyes must be explained first. Sulphur dyes are considered as

polymeric in nature and the sulphur containing chromophores (thiazole, thiazone or

thianthrene) are linked together by disulphide bonds pendant to their ring structures [4].

The application of the dye to cellulose involves the reduction of the dye using a

reducing agent and an alkali. The reduced form (also called thiolate form) is reconverted

into the parent insoluble form with the aid of an oxidising agent, at the end of the dyeing

process. The dyed fabric is then rinsed to remove any surface dye, soaped and finally

washed. When this fabric is exposed to subsequent laundering with bleach containing

washing powder, the disulphide bonds within the sulphur dye may get further oxidised.

This over-oxidation of the dye causes the breaking of disulphide bonds thus converting

them into water soluble dye fragments which may easily be removed from the surface of

the fabric [8, 21].

Introduction

35

1.3. Research aim and objectives

The basic aim of the research is to develop a post treatment method for sulphur dyed

fabric which influences its chemistry in a way that it makes it resistant to home

laundering processes, in particular ISO 105 CO9. The dyed and aftertreated fabric on

reaching the consumer would then only fade after a long time thus improving the level

of customer satisfaction. Additionally, the protection system developed could be applied

on two systems of sulphur dyed cotton fabric reduced with conventional and

biodegradable reductant, which would enhance its resistance to washing regimes.

In order to achieve the aforementioned aim, the following research objectives were

outlined:

Study the effects of reducing agents (sodium sulphide, glucose based Diresul

Reducing agent D) on colour yield and fastness properties of sulphur dyed fabric;

Explore the colorimetric behaviour of sulphur dyed fabric (colour profiles, K/S and

CIELab);

Investigate the influence of various protective agents - Bayprotect Cl, alternative

tannins, resins and cationic reactants/polymers;

Examine the effects of protective agents against ISO 1O5 CO6 and ISO 1O5 CO9

wash fastness;

Examine the effects of protective agents against rub fastness, wet and dry;

Examine the effects of protective agents against light fastness;

Analyse the surface chemistry of dyed, after treated and laundered samples using

XPS to determine the relative levels of oxidation of sulphur at the fibre surface and

comparing to bulk analysis to characterise oxidised and unoxidised sulphur species;

Identify the chemical composition of the untreated and treated fabric and

accumulate relative intensity data of the deconvoluted C (1s), N (1s) and S (2p)

spectra for comparison;

Study the FTIR spectra to identify the functional groups on the untreated and treated

sulphur dyed cotton fabrics;

Evaluate the effects of aftertreatments on the tensile strength of the fabric.

Introduction

36

1.4. Scope and significance of the research

With the passage of time, the developments in household laundering detergents and

their impact on cellulosic fibres have been taken into consideration. The fastness

properties and cross staining performance of sulphur dyed fabric is usually characterised

with the help of standard ISO 1O5 CO6 benchmark. In recent times, a distinctive

combination of standard detergent, a low temperature tetraacetylethylenediamine

(TAED) bleach activator has been developed which resembles to modern detergent

formulation and laundering practice, this is the ISO 1O5 CO9 washing protocol [22].

Cellulosic goods dyed with sulphur dyes are particularly affected by bleach-containing

washing powders. The purpose of bleach (such as sodium perborate) is to help remove

the stains produced by tea, coffee, fruit juice etc. and the addition of a bleach activator

(such as TAED) facilitates the low temperature removal of these stains [8].

The purpose of this research is to determine the resistance of the sulphur dyes against

such formulations and the potential of aftertreatments to reduce the washdown of dyes

during repeated laundering cycles over the life time of a cellulosic textile material.

1.5. Proposed research

Although it will be seen (chapter 2) that various cationic polymers, lanthanides and

crease resistant finishes can be used to improve the wash fastness of sulphur dyes [8, 12,

13, 19, 23], the resistance of the dyes against aggressive ISO 105 CO9 has not been

taken into consideration. This limitation in dye fixation is overcome by the introduction

of a protection system on the fabric with the sequential application of a cationic fixative

and tannin. This involves the development of a novel route with the optimised process

parameters so that the potential time, energy, and other savings associated with such a

procedure are delivered.

Introduction

37

1.6. Research methods and analysis

The following methods were employed to analyse the sulphur dyed cotton fabric against

the oxidative action of various washing systems.

1.6.1. Colorimetric, fastness and tensile properties

Colour measurement with Datacolor Spectroflash ( L*, a*, b*,c , ho values)

Fastness to washing (ISO 1O5 CO6, ISO 1O5 CO9)

Fastness to rubbing (ISO 105–X12:2002)

Fastness to light (ISO 105–BO2)

Tensile strength (BS EN ISO 13934/1 1999)

1.6.2. Surface chemistry, topography and bulk analysis

Scanning electron microscopy

X-Ray photoelectron spectroscopy

Fourier transform infrared spectroscopy

Elemental analysis

1.7. References

[1] Nguyen TA and Juang RS. Treatment of waters and wastewaters containing sulfur

dyes: A review. Chemical Engineering Journal. 2013;219:109-17.

[2] Shore J. Cellulosics dyeing. Bradford: Society of Dyers and Colourists, 1995.

[3] Shankarling G, Paul R and Thampi J. Novel dyes and commercial forms. Colourage.

1997;44(4):71-4.

Introduction

38

[4] Blackburn RS and Harvey A. Green chemistry methods in sulfur dyeing:

Application of various reducing D-sugars and analysis of the importance of optimum

redox potential. Environmental Science and Technology. 2004;38(14):4034-9.

[5] Bechtold T, Berktold F and Turcanu A. The redox behaviour of CI Sulphur Black 1 -

a basis for improved understanding of sulphur dyeing. Journal of the Society of Dyers

and Colourists. 2000;116(7-8):215-21.

[6] Wang M, Yang J and Wang H. Optimisation of the synthesis of a water-soluble

sulfur black dye. Dyes and Pigments. 2001;50(3):243-6.

[7] Parvinzadeh M. The effects of softeners on the properties of sulfur-dyed cotton

fibers. Journal of Surfactants and Detergents. 2007;10(4):219-23.

[8] Burkinshaw SM and Collins GW. Aftertreatment to reduce the washdown of leuco

sulphur dyes on cotton during repeated washing. Journal of the Society of Dyers and

Colourists. 1998;114(5-6):165-8.

[9] Zollinger H and Rys P. Fundamentals of the chemistry and application of dyes:

University Microfilms, 1993.

[10] Preston C. The dyeing of cellulosic fibres: Dyers' Company Publications Trust,

1986.

[11] Burkinshaw S. Application of dyes. The chemistry and application of dyes:

Springer; 1990. p. 237-379.

[12] Zhou W and Yang Y. Improving the resistance of sulfur dyes to oxidation.

Industrial and Engineering Chemistry Research. 2010;49(10):4720-5.

[13] Burkinshaw SM and Collins GW. Aftertreatments to improve the wash fastness of

sulphur dyeings on cotton. Dyes and Pigments. 1995;29(4):323-44.

[14] Wood WE. Sulphur dyes–1966–1976. Review of Progress in Coloration and

Related Topics. 1976;7(1):80-4.

[15] Cook CC. Aftertreatments for improving the fastness of dyes on textile fibres.

Review of Progress in Coloration and Related Topics. 1982;12(1):73-89.

Introduction

39

[16] Heid C, Holoubek K and Klein R. One hundred years of sulfur dyes. Melliand

Textilberichte International. 1973;54(12):1314-27.

[17] Venkataraman K. The chemistry of synthetic dyes: Elsevier, 1974.

[18] Burkinshaw SM and Collins GW. Pad-dry and pad-flash cure aftertreatments to

improve the wash fastness of sulphur dyeings on cotton. Dyes and Pigments.

1997;33(1):1-9.

[19] Burkinshaw SM, Chaccour FE and Gotsopoulos A. The aftertreatment of sulphur

dyes on cotton. Dyes and Pigments. 1997;34(3):227-41.

[20] Burkinshaw SM and Collins GW. Continuous dyeing with sulphur dyes: After

treatments to improve the wash fastness. Book of Papers: 1996 International Conference

& Exhibition - American Association of Textile Chemists and Colorists. 1996:296-303.

[21] Carr CM. Chemistry of the textiles industry: Springer Science and Business Media,

1995.

[22] Soliman G, Carr CM, Jones CC and Rigout M. Surface chemical analysis of the

effect of extended laundering on C. I. Sulphur Black 1 dyed cotton fabric. Dyes and

Pigments. 2013;96(1):25-30.

[23] Shekarriz S. Effects of polycarboxylic acids on untreated cotton and solubilised

sulfur dyed cotton. Journal of Progress in Color, Colorants and Coatings. 2014;7(1):1-9.

Literature review

40

2. Literature review

2.1. History of sulphur dyes

Sulphur dyes were accidently discovered by Croissant and Bretonnière in 1873. They

heated lignin-containing organic waste (such as sawdust) with sodium polysulphide at

about 300oC to get the product which came to be known as Cachou de Laval. However,

the recognised inventor of sulphur dyes was a chemist named Vidal, who was able to

produce the dyes from specific organic compounds. The synthesis of Sulphur Black T

(CI Sulphur Black 1) was carried out from 2,4-dinitrophenol in 1899. From then

onwards, many of the intermediates were treated with sulphur, sodium sulphide or

sodium polysulphide to introduce sulphur linkages, the method so called sulphurisation

or thionation [1].

2.2. Constitution of sulphur dyes

In spite of their recognised use over a long period of time, surprisingly little is known

about the exact chemistry and detailed constitution of sulphur dyes. The structure of the

starting material can be taken from the Colour Index, which tends to be quite misleading

in some cases, as products with the same CI number and same starting material can have

different properties. The dyestuffs produced from the same starting material but through

different processes may have different dye contents, dyeing characteristics and

ecological influences. A number of structural units have been proposed for sulphur dyes

but they are generally believed to be polymeric consisting of sulphur containing

aromatic heterocyclic units (such as thiazines and thiazoles) linked by di or polysulphide

bonds as shown in Scheme 2.1 and Scheme 2.2 [2].

The substantivity of sulphur dyes for the cellulosic substrate is produced as a result of

hydrogen bonding, ion-dipole and dispersion forces between the dye anion and the

substrate. The extent of substantivity largely depends on the type of the dye and brands

of the same dye. Exhaustion rate is usually increased with the increasing temperature.

Addition of an electrolyte facilitates and increases the rate of exhaustion [3].

Literature review

41

Scheme 2.1 Sulphur dye in reduced form, redrawn from [2]

2.3. Methods of formation

The properties of sulphur dyes depend upon the starting material and the method of

sulphurisation, which involves various reactions such as substitution, ring formation,

reduction, and oxidation. The starting material generally comprises of common aromatic

compounds, including benzene, naphthalene, diphenyl, diphenylamine, azobenzene,

etc., which bear at least one nitro, nitroso, amino, substituted amino, or hydroxyl group

[4].

Sulphur dyes are known to be manufactured by two methods. The first one involves

heating organic materials like amines, nitro compounds, phenols and their derivatives

with sodium polysulphide in an aqueous or alcoholic solution; this method is carried out

under pressure at temperatures around 130oC. The second system encompasses the

baking of starting materials with sodium sulphide or sulphur alone at a temperature

between 180 and 350oC [1, 2].

The baking method leads to the formation of yellow, orange or brown sulphur dyes,

many of which are believed to contain benzothiazole groups. Certain intermediates

when treated with aqueous or alcoholic sodium polysulphide produces red, blue, green

Literature review

42

and black sulphur dyes. These compounds have the ability to form quinonimine ring

systems [1].

Scheme 2.2 Chromophoric systems in sulphur dyes, redrawn from [5]

2.4. Classification of sulphur dyes

The three commercially available ranges of sulphur dyes include CI Sulphur dyes, CI

Leuco Sulphur dyes and CI Solubilised Sulphur dyes. The typical application procedure

involves the reduction of an insoluble dye and application of the reduced or leuco

(thiolate) form to the cellulosic material. In the end, the thiol derivative is reconverted

into the parent insoluble form by oxidation [6].

The substantivity between the reduced dye and the substrate arises from hydrogen

bonding and ion-dipole and dispersion forces operating between the dye anion and the

fibre. The substantivity varies from dye to dye and between brands of the same dye [3].

Literature review

43

2.4.1. CI Sulphur dyes

In discussing sulphur dyes, it is initially important to distinguish between sulphur dyes

and sulphur vat dyes. They are not separately classified in the Colour Index which

consists of a collection of dyes from a range of categories (CI Sulphur and CI Vat), the

latter bearing superior wet fastness and resistance to bleaching as compared to

traditional sulphur dyes. CI Vat Blue 42 and 43, CI Vat Red 10, CI Vat Green 7 and 20,

CI Vat Brown 96 and CI Vat Black 11 belong to the Sulphur-Vat type class, which do

not possess polysulphide links between their chromophoric systems and require some

level of caustic soda/sodium dithionite reduction [2, 7].

CI Sulphur is a water insoluble form which is the oldest among all other classes. This

dye consists of sulphur not only as an integral part of the chromophore but is also

present in attached polysulphide chains. They are first dissolved by boiling them with a

reducing agent in an alkaline medium. After that, they are subsequently oxidised to an

insoluble form on the fibre. The reducing agents most commonly used are sodium

sulphide, sodium hydrogen sulphide and soda ash. Moreover, this dye has to be cooled

down to room temperature if applied through continuous process [2, 7, 8].

2.4.2. CI Leuco Sulphur dyes

This class of dye has the same constitution as CI Sulphur (parent sulphur dye), however,

the content of the actual dye ranges from 25% to 50% when compared to the parent dye.

It is a soluble leuco form of the parent dye and consists of the parent dye and a reducing

agent such as sodium sulphide or hydrosulphide so as to facilitate its application directly

or with an addition of small amount of extra reducing agent. Since both dyes behave in a

similar way when added into a dye bath, hence this dye can easily be applied [7, 8].

Literature review

44

2.4.3. CI Solubilised Sulphur dyes

This category of sulphur dye is a thiosulphate derivative (Bunte Salt) of the parent dye

and hence bears a different constitution number to that of the parent dye. The

thiosulphate ester of the thiol or Bunte salt is achieved by reacting disulphides with

sodium sulphite as shown in Scheme 2.3. This dye does not have affinity for cellulose in

the absence of a reducing agent. It is converted into substantive alkali soluble thiol form

during dyeing by boiling with a suitable reducing agent [2, 7].

Dye − S − S − Dye + Na2SO3 → Dye − S − SO3Na + Dye − SNa

2Dye − S − SO3Na + Na2S → Dye − S − S − S − Dye + 2Na2SO3

Dye − S − S − S − Dye + Na2SO3 → Dye − S − S − Dye + Na2S2O3

Scheme 2.3 Reaction of dye disulphide bond with sodium sulphite to produce

Bunte salt, from [2]

2.4.4. CI Condensate Sulphur dyes

The Condensate Sulphur dyes are now only of historical interest. They contain sulphur

and their method of manufacturing and constitution resembles that of the traditional

sulphur dyes. They are based on sodium S-alkyl or S-arylthiosulphates and cannot be

applied through conventional dyeing methods. They require reducing agents like sodium

sulphide or polysulphide for application [1, 7].

2.5. General application procedure of sulphur dyes

Sulphur, vat and indigo dyes accounting for about 31% of the world dyestuff

consumption market [9] have to be reduced before application to convert them into

water soluble leuco enolate form. Finally they are re-oxidised to convert them into their

insoluble form inside the fibre. This process can be summarised by Scheme 2.4. A

number of oxidation and reduction methods are applied to the textiles, dyes and

multitude of other important processing compounds to either synthesise or chemically

Literature review

45

modify them. This is done by changing the number of electrons assigned to atoms

undergoing the reaction. In the dye chemistry, oxidation is the ubiquitous chemical

reaction involving the combination of a substance with oxygen or removal of electrons.

In the same way, reduction corresponds to a decrease in the amount of oxygen or its

complete removal or the addition of electrons. In order to assure complete reduction, a

suitable reducing agent with a sufficiently low reduction potential is selected [10, 11].

Scheme 2.4 Application method for sulphur, vat and indigo dyes, reproduced

from [10]

2.6. Properties of sulphur dyes

2.6.1. Fastness to light

Sulphur dyes generally possess satisfactory to good fastness to light [12]. On

considering the test method BO2 Xenon arc (BS 1006:1990), fastness to light increases

from yellows and oranges being the lowest to blacks and navy blues, being the highest.

Nevertheless, there are some exceptions such as the yellow-browns: CI Sulphur Brown

10 fades quicker than CI Sulphur Brown 51 or 60. Pale shades of yellow, orange and

brown show quite low light fastness but CI Sulphur Black 1 gives a GS (grey scale)

rating of 5 even in pale depths. Medium to heavy colours in most brown and khaki hues

can also produce a light fastness of rating 5 [7].

Colour change can be measured with the help of grey scales which consists of five pairs

of grey coloured material numbered from 1 to 5. The tested specimen is compared with

the original untreated material and any loss in colour is graded with reference to the

Literature review

46

grey scale. Number 5 has two identical greys which show that there is no colour change

between the reference and the tested specimens. Number 1 shows the greatest contrast,

and number 2, 3 and 4 have intermediate contrasts.

2.6.2. Colour fastness

Colourfastness may be defined as the resistance of a material to change in any of its

colour characteristics. Fading refers to the change in colour or lightening of colour. On

the other hand, bleeding is the transfer of colour to adjacent or accompanying fibre

material, also called soiling or staining [13].

2.6.3. Fastness to washing

In general, sulphur dyes exhibit good fastness to washing tests, depending upon the

detergent formulation being used. However, they are less resistant to laundering with

detergent/perborate formulations which is a general requirement for domestic washing

powders. Even here, fastness to washing below 50oC is quite reasonable [7, 12].

2.6.4. Fastness to bleaching

Sulphur dyes exhibit poor fastness to bleaching; in particular to hypochlorite bleaching.

Likewise, they lose considerable depth when exposed to washing regimes containing

peroxide along with detergent [7].

2.6.5. Fastness to rubbing

The exact rubbing fastness ratings cannot be identified because it largely depends on the

fabric type, its preparation and dyeing process. Quality of rinsing after oxidation plays a

vital role in overall rubbing fastness ratings. The fastness to dry rubbing is normally

quite good, being 4-5 even for heavy depths. The wet rubbing for heavy depths like

black and navy tends to be in the stain ratings of 2-3 [7].

Literature review

47

In order to achieve better rub fastness properties, it is essential to wash the dyed fabric

thoroughly before the oxidation stage, and dye the fabric with the necessary amount of

sequestering agent and anti-oxidant [7].

2.6.6. Acid tendering of sulphur dyes

Sulphur dyes produce low level of sulphuric acid when exposed to humid and hot

storage conditions, leading to acid tendering of the dyed fabric. This problem may be

minimised or even removed by either a thorough rinsing of the dyed fabric before

oxidation or treating the dyed fabric with a final alkaline rinse. The use of resins and

cationic fibre protective agents has been reported to inhibit the tendering of sulphur dyes

[7].

2.7. Reduction of sulphur dyes

2.7.1. Conventional reducing systems

2.7.1.1. Sodium sulphide (Na2S)

Sulphide type reducing agents include sodium sulphide (Na2S), sodium hydrosulphide

(NaHS) and sodium polysulphide (Na2Sx) where x varies from 1 to 6. The sulphides and

hydrosulphides are available in solid as well as liquid forms but the polysulphide variety

is available as an aqueous solution. The polysulphides do not only act as a pH buffer but

also as an antioxidant [14]. The conventional method of application of sulphur dyes is

carried out by reduction with sodium sulphide. This traditional reducing agent is

available in the form of crystals and flakes. The specific class of the dye dictates the

amount of the reducing agent that needs to be used, and is usually directly proportional

to the dye weight [7].

Literature review

48

Sodium sulphide undergoes hydrolysis in water, which is shown below in Scheme 2.5:

Na2S + H2O ↔ NaHS + NaOH [14]

Scheme 2.5 Hydrolysis of sodium sulphide in water from [14]

The treatment of sodium sulphide with insoluble sulphur dye leads to the reduction of

sulphide links forming individual heteroaromatic units with thiol groups (Scheme 2.6).

Due to its toxicological and ecological issues, the replacement of this reducing agent

with environmentally friendlier systems is being preferred [15].

−S − Dye − S − S − Dye − S − S − Dye − S − S − Dye − S − +2ne̅ ↔ nS̅̅ ̅ − Dye − S ̅

Scheme 2.6 Reduction of sulphide links from [2]

2.7.1.2. Sodium hydrosulphide (NaHS)

Sodium hydrosulphide is now widely used in place of sodium sulphide; it is available in

solid as well as liquid form and in several different concentrations. It is available from

many sources, such as the manufacturers of paper and viscose fibres [7]. In particular,

the use of sodium hydrosulphide has little importance for sulphur dyeings with red,

brown, green and olives. This is because the dyes break down in the presence of sodium

hydrosulphide and exhibit the inherent drawback of poor colour yield and

reproducibility. However, the application of CI solubilised sulphur black dyes and

sodium hydrosulphides produce good results with the exhaustion mode of dyeing.

However the use of solubilised sulphur dyes tend to be more expensive than the ready-

to-use leuco sulphur dyes which already contain inbuilt sodium sulphide as the reducing

agent and is more compliant with continuous dyeing [14].

2.7.1.3. Sodium dithionite

Until recently this was the only sulphide free system for dyeing with sulphur dyes but

was not popular for commercial purpose because of lack of reproducibility and

Literature review

49

difficulty in controlling the process. The system tends to be quite useful when a mixed

system of sodium sulphide/caustic soda and sodium dithionite is used. This is preferred

in jig dyeing only. The warp dyeing of denim with traditional insoluble sulphur dyes has

used this system previously. The colour yield is however lower than that for the

sulphide system [7].

2.7.2. Green chemistry/non-sulphide reducing systems

2.7.2.1. Glucose and other alternatives

Glucose is a well-known reducing agent considered to be a biocompatible,

biodegradable, and non-toxic, naturally occurring molecule, which is being used for

reduction of sulphur dyes and bleaching of cotton [3]. It is a hexose monosaccharide

consisting of six carbon atoms, with an aldehyde bearing (–CHO) group. Five carbons

and an oxygen atom form a loop called a “pyranose ring” which is the most stable form

of six-carbon aldoses. Each carbon is linked to hydroxyl and hydrogen side groups in

this loop/ring, excluding the fifth atom which links to a 6th carbon atom outside the

ring, forming the CH2OH group. It exists in two forms (α and β) [10].

Sugar crystallises from aqueous solutions at temperatures below 50°C as α-D-glucose

monohydrate, which has the melting point of 80°C. At temperatures above 50°C but

below 115°C, the stable form is anhydrous α-glucose with the structure shown in

Scheme 2.7. Glucose experiences a complex degradation sequence in alkaline solutions

and the reducing effect of glucose is known to be connected with the degradation

intermediate. Glucose is highly sensitive to temperature and it acts as a very good

reducing agent at high temperatures. The supporting factors, which contribute to its

reducing ability, are high alkalinity and polysulphide addition [10]. The reduction of

sulphur dyes is achieved in alkaline solutions by the aldehyde group of the glucose [2].

The use of sulphur dyeing for cellulosic fibres and its advantages with respect to cost is

appreciated throughout the dyeing industry [3]. Sodium sulphide is the most common

reducing agent for sulphur dyes accounting about 90% of all sulphur dyes being reduced

by this auxiliary [16]. However, the popularity of this auxiliary is declining as a result of

Literature review

50

its adverse effects on the environment. Therefore, attempts have been made to replace

this hazardous component of dyeing by more eco-friendly alternatives. In this context, a

substantial body of work has been undertaken on the use of reducing sugars for the

dyeing of cellulose with sulphur dyes [3].

Scheme 2.7 Chemical structure of α-D-glucose, reproduced from [10]

Glucose in combination with caustic soda has considerable reducing potential to reduce

sulphur dyes into their cellulose substantive form at 90oC. However, when compared to

sulphide based reducing systems, it produces a lower colour yield and fastness.

Blackburn has investigated the use of various reducing sugars, such as hexose and

pentose monosaccharides and disaccharides as a replacement for sodium sulphide [3].

The optimum conditions and application concentrations have also been elucidated for

the scheme to be used commercially and to achieve comparable results to conventional

systems [3, 16].

An optimum redox potential of around -650 mV was found to give maximum colour

strength of the dyeings and minimum colour loss after washing. The work established

that an optimum redox potential for D-sugars would lead to dyeings with comparable or

better colour yield and fastness than the conventional systems based on sodium

polysulphide and sodium hydrosulphide [3].

Another important factor to be considered was the influence of the two reducing agents

on the environment. COD (Chemical Oxygen Demand) is defined as the amount of

oxygen consumed in the chemical oxidation of organic matter by potassium dichromate

Literature review

51

in the presence of sulphuric acid. It is well characterised that oxygen dissolves in water

and this oxygen is an essential source of growth for many organisms like fishes and

aerobic bacteria. This oxygen can easily be depleted by various sources, and one of

them is the biochemical oxidation of sulphur compounds. To keep the necessary amount

of oxygen maintained in water various natural and artificial means of aeration are in use

for example through the effect of waterfalls and turbulent flow in streams and by

pumping air in water at sewage treatment plants [17].

Figure 2.1 Effect of temperature on reduction potential of reducing sugar and

sodium sulphide at pH of 12 from [5]

The impact of using sugars on the environment was compared by evaluating the

theoretical COD of the starting dyebath. The reducing sugars produced a slight increase

in the theoretical COD compared to sodium sulphide but all of them had lower COD

than sodium hydrosulphide. The use of sugars like glucose, fructose and lactose are

much more competitive in terms of cost as well. They did not only produce dyeings with

high colour strength and wash fastness but also benefited in terms of cost. They would

also offer cheaper water treatment protocols than the one currently used for sulphide

based reduction. Hence, the use of reducing sugars could provide a sustainable,

nontoxic, biodegradable and cost-effective alternative with comparable properties of the

dyed goods [3].

Literature review

52

The effect of redox potential and concentration of the reducing agents are not the only

factors contributing the optimum conditions required to achieve sulphur dyeings with

comparable colour strength and wash fastness. Another vital factor is the temperature of

the dyeing procedure employed for a particular kind of sugar.

The effect of dyeing temperature on the reduction potential of reducing sugar and

sodium sulphide is shown in Figure 2.1.

The impact of the three variables, that is, the type of reducing agent, concentration,

temperature and their cumulative effects have been studied by Madhu [16]. The effect of

these variables was evaluated in terms of colour strength, wash fastness and tensile

strength of the fabric. CI Sulphur Black 1 and CI Sulphur Brown M dyes were

employed for the experiments with three reducing agents that are sodium sulphide,

glucose and fructose. They were applied at varying concentrations from 0.5 to 5 g/L at

three different temperatures 50, 70, and 90oC [16].

Figure 2.2 Influence of glucose concentration on colour strength of CI Sulphur

Black 1 at 90oC, reproduced from [16]

The comparison of glucose, fructose and sodium sulphide produced useful insights for

example, in the case of CI Sulphur Black 1, the use of glucose produced somewhat

better washing fastness than the conventional reducing agent. The colour strength and

tensile strength were also comparable. Even in the case of CI Sulphur Brown M, the

10.75

13.28

15.49

16.67 17.39

17.8 18.24

18.63 18.78 18.81

8

10

12

14

16

18

20

0.5 1 1.5 2 2.5 3 3.5 4 4.5 5

K/S

va

lue

Glucose concentration (g/L)

Literature review

53

wash fastness and colour strength were superior to sulphide based reducing agent.

Moreover, the wash fastness, colour strength and tensile strength were also comparable

in the case of fructose when tested for the two sulphur dyes. An increase in the amount

of the reducing sugar caused an increased level of colour strength, however, after a

certain optimum concentration; the colour strength became constant which is shown in

Figure 2.2 [16]. This phenomenon was explained by Blackburn and Harvey, according

to which the optimum concentration and redox potential caused the dye to produce best

wash fastness and colour yield as the dye molecule is either too large or fragmented

above or below that value. These optimum conditions support the maximum diffusion of

the dye within the substrate, thus resulting in premium effects [3]. The study of the

cumulative effects of concentration, temperature and reducing agent type indicated that

the reducing sugars have an optimum concentration related to their redox potential

which offers maximum colour strength and less colour loss upon washing when dyed

above a temperatures of 70oC [16].

Another significant study was carried out by Zouhaier, where three environmentally

friendly reducing agents were compared on the basis of reducing agent and caustic soda

concentrations [18]. The reducing agents were sodium sulphide, sodium dithionite and

glucose and their effects on reduction of a sulphur dyestuff (CI Leuco Sulphur Black 1),

redox potential, pH and the colour yield (K/S) were evaluated. A continuous mode of

application was adopted for the comparison. In the first instance, the stability of the

reducing systems with respect to time (10 minutes intervals) while keeping the

temperature constant was measured. The reduction potential of the three reducing

systems reduced with increasing time. The reducing agent representing the minimum

variations was assumed to be the most stable one. Therefore, the three systems were

classified as sodium sulphide being the most and sodium dithionite being the least stable

reductant [18].

Subsequently, the influence of temperature on the reduction potential of the reducing

agents at various dye bath temperatures (60, 70, 80, 90, 100oC) was evaluated and it was

found that the effect of temperature on the potential was to cause a slight increase with

increasing temperature. The effect of dye bath temperature on the reduction potential

can be explained as; the increase in temperature causes the increased reactivity hence

causing an increment in potential. Therefore, the stability of the reducing systems with

Literature review

54

respect to temperature can be classified the same way as time factor (sodium dithionite

< glucose < sodium sulphide) [18].

Similarly the effect of reducing agent concentration on the colour yield of the dyes was

studied and a quantity of 6 g/L was found to produce the maximum colour yield for

sodium dithionite and glucose while 7 g/L for sodium sulphide [18].

In addition, the effect of increasing concentrations of caustic soda on the pH and colour

yield can be explained by Figure 2.3 and Figure 2.4, respectively. The most effective

caustic soda concentration for sodium sulphide and glucose was found to be 15 g/L

while that for sodium dithionite was 20 g/L since the colour yield decreased beyond

these concentrations [18].

Figure 2.3 Effect of caustic soda concentration on pH of the three reducing

systems, from [18]

Figure 2.4 Effect of caustic soda concentration on colour yield (K/S) of the three

reducing systems, from [18]

Literature review

55

For dyeing cotton with sulphur dyes, sodium sulphide and sodium dithionite are

considered to be the most highly used and most effective reducing systems, respectively.

A comparative study has been undertaken by Baffoun, in which the two reducing agents

were compared with glucose in terms of colour yield and fastness properties. The effects

of varying concentrations of reducing agent, caustic soda and sodium carbonate on pH

and redox potential were measured [19].

The cotton fabric was dyed with CI Leuco Sulphur Black 1 using the three reducing

systems with their redox potentials being measured during dyeing in order to compare

the stability of the three reducing systems with respect to time. The redox potential of

the dye bath based on sodium sulphide was the lowest indicating that this was the most

stable reducing system while sodium dithionite was the least stable one but with the

maximum reducing power [19].

To study the effect of dyebath temperature on the reduction potential of each reducing

system, the temperature of the dyebath was varied between 85oC and 100

oC. Similarly,

the time was varied between 10 minutes and 70 minutes in order to study the effect of

time on dyebath stability of the systems. The reducing power was improved slightly as a

function of the temperature for sodium sulphide and glucose while the potential increase

was more pronounced for sodium dithionite. The temperature and time had the same

effects on the stability of the three reducing systems that is sodium sulphide being the

most and sodium dithionite least stable reducing system [19].

An increase in the concentration of the reducing agent did not significantly vary the

redox potential. However, the pH value increased with an increase in concentration of

reducing agent except for sodium dithionite where the pH increased up to a

concentration of 5 g/L, beyond which it decreased. Likewise, the colour yield improved

with an increase in reducing agent concentration to a certain value beyond which it

deteriorated. The highest colour yield was obtained at a concentration of 5 g/L for

sodium dithionite and glucose and at 6 g/L for sodium sulphide [19].

The effect of different caustic soda concentrations was also studied and demonstrated

that the redox potential remained stable at -862 mV for sodium dithionite, at -631 mV

for glucose and at -517 mV for sodium sulphide. The highest colour strength was

achieved for sodium dithionite which had the highest reducing power, followed by

glucose and then sodium sulphide. Optimum colour yield was obtained at a caustic soda

Literature review

56

concentration of 20 g/L using sodium dithionite as a reducing agent and at 15 g/L using

sodium sulphide or glucose to reduce the sulphur dye [19].

After optimising the concentrations of reducing agents and sodium hydroxide, dyeings

with different concentrations of sodium carbonate (5-50 g/L) were undertaken. It was

observed that with the increase in sodium carbonate concentration, the alkalinity of

dyeing bath increases accordingly. The pH value increases significantly for sodium

dithionite and sodium sulphide while the variation in pH for glucose was less

significant. At different sodium carbonate concentrations, the redox potential remains

stable at -852 mV for sodium dithionite, at -631 mV for glucose and at -525 mV for

sodium sulphide. The optimised concentration of sodium carbonate (15 g/L) was found

to improve colour exhaustion for the three reducing agents [19].

The optimised parameters obtained in terms of reducing agent, caustic soda and sodium

carbonate concentrations, indicated that the best colour yield was obtained using sodium

dithionite to reduce the sulphur dye. However, glucose and sodium sulphide gave

comparable colour exhaustion which was slightly better for glucose [19]. The wash

fastness values at 60oC and 90

oC of dyeings recognised with sodium dithionite were

better than those achieved with sodium sulphide or glucose as reducing agent. The

crocking and light fastness remained the same for the three reducing systems [19].

Hydrol, a by-product of the sugar industry and a molasses based material is another

product which is being used by a number of industries for the reduction of sulphur dyes.

This is yet another eco-friendly alternative available for sulphur dyes application [14].

2.7.2.2. Mercaptoethanol/ Thioglycol (2-mercaptoethanol)

2-Mercaptoethanol is an alternate substitute for environmentally friendly dyeing of

sulphur dyes, producing a sulphide-free effluent and absence of unpleasant smell

emission. It is marketed by BASF under the trade name of Molleskal SF and is suitable

for applying solubilised sulphur dyes by the exhaustion and one-bath pad-steam process

[8, 14].

The application of thioglycol with caustic soda on solubilised sulphur dyes has been

investigated for exhaust and one bath pad-steam processes, the colour yield however is

Literature review

57

lower than that achieved with sulphide dyeings. The advantage of using thioglycol is a

sulphide free and odourless effluent, but certain limitations make its use unacceptable. It

cannot be used for vat sulphur and the water-insoluble dyes do not completely dissolve

in it, the process is also more costly than other substitutions [7].

2.7.2.3. Hydroxyacetone

Similar to thioglycol, the effluent of this reducing agent is free from sulphide but it has a

characteristic odour of acetone. It can be applied to solubilised sulphur dyes, but the

colour yield is lower, the cost is higher and the product is highly flammable thus making

an overall process undesirable for industrial use [7].

2.7.2.4. Thiourea dioxide

A more environmentally friendly alternative to sodium sulphide consists of using of

thiourea dioxide. It was found out through a number of experiments that alkaline media

enhances the reducing properties of thiourea dioxide, so sodium hydroxide is added to

the dye bath. The dyeings were tested with and without Glauber’s salt (sodium

sulphate), which had little influence on the depth of shade. The dyeings of the latter

system and sodium sulphide were compared and it was established that the colour

strength and fastness properties were comparable [15]. A little change in shade was

observed in some cases. However, the dyeing produced from thiourea dioxide was

brighter in most of the cases except CI Sulphur Brown 12 and CI Sulphur Brown 14:1.

The latter dye produced deeper and bluer shade with thiourea dioxide while the former

dye produced dyeing with the diminished colour value when compared with the dyeings

produced by sodium sulphide. The dyeing with brown shades is problematic and needs

care to avoid over-reduction [15].

Thiourea dioxide was found to be less toxic than other reducing systems. The analysis

of residual liquors obtained from sulphide and thiourea dioxide indicated that there was

a considerable reduction in the quantity of oxidant required for chemical degradation of

Literature review

58

the effluent from thiourea dioxide liquor. In the case of CI Sulphur Yellow 1 and CI

Sulphur Blue 1, the permanganate and dichromate oxidation values (COD) were

reduced by half. Since there was no sodium sulphate in the dyebath, there was a

significant reduction in the sulphate ion content in the exhausted dyebath. The overall

evaluation indicated that thiourea dioxide could be a safer yet a more expensive

alternative to sulphide based dyeing of sulphur [15].

2.7.3. Nitrogen (nitro process) based reduction

A novel dyeing technique for sulphur dyes has been developed by Clariant that entails

the use of nitrogen gas for minimising the amount of reducing agent for dyeing.

Nitrogen, one of the nature’s most abundant and inert elements, is being purged into the

dyeing vessel during the process thus reducing the amount of reducing agent and overall

cost [14, 20].

2.7.4. Natural/organic reduction

The use of natural reducing agents for the reduction of sulphur dyes was tested for

shade, colour strength and fastnesses by Zahra [21]. The natural product used was the

burnt residue of plants with reducing properties. The comparison of this agent with

sodium dithionite was investigated where the latter was taken as standard. The natural

reducing agent named sheghar in Iran is the burnt ajveh plant. The plant contains some

capsules filled with liquid. On burning, the capsules burst and the inner water

evaporates. The inside substance of the capsules is dried and used for the purpose of

reduction [21].

The results of CI Sulphur Brown 10 dyed with sheghar showed good colour strength

indicating its good reducing ability. The wash fastness, light fastness and colour strength

produced by shegar were similar to those produced by sodium dithionite. On the other

hand, the rubbing fastness was half a unit inferior (on the grey scale for staining) to that

produced by the standard reducing agent [21].

The method for evaluating the dry and wet rub fastness is explained in section 3.5.2.

The rubbed samples are rated on the basis of grey scale for staining which consists of a

Literature review

59

set of five pairs of white and grey coloured material numbered from 1 to 5. Fastness

rating 5 is shown by two identical white samples (that is no staining) and rating 1 shows

a white and grey sample (that shows the maximum staining). The other numbers show

geometrical steps of contrast between white and a series of grey at 9 levels: 5, 4/5, 4,

3/4, 3, 2/3, 2, 1/2, 1. A piece of untreated, unstained, undyed cloth is compared with the

stained sample that has been in contact with the dyed sample during the rubbing test and

a numerical assessment of staining is given according to the grey scale for staining. Half

a unit inferior means that the sample rating is half a unit less than the reference sample.

2.7.5. Alkaline protease reduction

Due to the increasing environmental hazards caused by the use of sodium sulphide,

various alternatives such as glucose [3, 16, 22], hydroxyacetone [7, 23], electrochemical

reduction [24, 25] and reducing sugar have been introduced.

In order to make textile processes more eco-friendly and less toxic, the use of certain

enzymes particularly those based on oxidoreductase and hydrolase classes are gaining

much attention. The use of an alkaline protease belonging to the hydrolase class was

chosen for study which possesses a distinguishing feature of stability at high

temperature in alkaline pH and in association with chelating agents. The enzyme has got

a reducing power in alkaline medium and is commercially applied in bating of hides (i.e.

removal of hair) in the leather industry and is capable of reducing organohalogen

(AOX) content in effluents [26].

Alkaline protease has a characteristic property of cleaving bi- and polysulphide bonds

with greater ease, thus causing reduction under alkaline conditions similar to sodium

sulphide. This is because it belongs to the hydrolytic enzyme category; the hydrolytic

activity is synergised in the presence of alkali causing the splitting of molecule followed

by solubilisation similar to the reducing action of sodium sulphide for sulphur dyes.

Hence, the reduction potential, dye strength, dyebath stability and colour fastness were

evaluated for both systems [26].

Dyebath preparation, dyeing, oxidation, soaping were carried out in the same manner

for both systems, the only difference was the replacement of sodium sulphide with

Literature review

60

alkaline protease (0.05-1.5 times the amount of dye) along with the use of sodium

hydroxide to produce the same pH as that in the conventional system dyebath [26].

Cotton was dyed with 10 different sulphur dyes and the pH and the reduction potential

were studied. In case of sodium sulphide, the addition of dye dropped the pH and

reduction potential indicated reduction and solubilisation of the dye. This reduction

increased as the dyeing was completed. The optimum colour strength was achieved

when the quantity of sodium sulphide was twice that of the dye, thus endorsing that this

is the optimum concentration of reducing agent [26].

The optimisation of parameters like pH, temperature, concentration of alkaline protease,

concentration of salt and time of dyeing produced positive results which were

comparable to those produced by sodium sulphide system [26].

These optimised parameters are summarised below:

pH: nearer to 12 with sodium hydroxide;

Concentration of alkaline protease: 0.25T with respect to dye;

Dyeing temperature: 90oC;

Salt concentration: 20 g/L;

Dyeing time: 2 hours.

The optimised conditions were applied to 10 sulphur dyes; CI Sulphur Black 5, Green 1,

Green 12, and Brown 12 showed comparable dye strength in both systems, CI Sulphur

Blue 4, Blue 7, Green 22 and Green 8 showed a little less dye strength; CI Sulphur Red

10 and Yellow 9 showed higher dye strength in the enzyme system [26].

The dye bath stability was evaluated by measuring the pH and reduction potential of the

two systems at three stages namely:

1. Before reduction of dye;

2. After reduction of dye, and;

3. At the end of dyeing.

The dyeing of cotton with sulphur dyes showed comparable reduction potential for both

systems. The stability of dyebaths in the presence and absence of dye were found to be

the same that is fairly stable for two hours in the sulphide system and one hour in

alkaline protease system. The overall stability was better in the presence of dye [26].

Literature review

61

The wash fastness of sulphur dyes with both systems was excellent and comparable. As

a result of good fastness, stability and colour strength it can be said that the alkaline

protease based system can be used as a replacement of sulphide based system [26].

2.7.6. Alkaline catalase reduction

There are certain enzymes which are found to be reducing in nature and are potentially

useful to catalyse the reduction of dyes [27, 28]. Catalase is a type of enzyme belonging

to the class of oxido-reductase and having many industrial applications such as textile

bleaching, electronics, sterilisation of liquid food products and conversion of residual

hydrogen peroxide to oxygen and water. The use of this enzyme as an alternative for

sodium sulphide has been explored and evaluated for reduction potential of the dye bath,

dye receptivity of dyed cotton (K/S), stability of the bath and fastness properties. The

dyebath was prepared with varying concentrations of the reductants (0.05-1.5 times the

amount of dye) and sodium hydroxide was used for corresponding dyebath pH (around

12). The enzymatic dyeing was done exactly the same way as followed in sodium

sulphide procedure [29].

The comparison of the reduction potential of the two systems at different stages of

dyeing indicated comparable efficiency of catalase based dyebath (reduction potential

ranging from -500 mV to -550 mV). The dye receptivity (colour strength) of the

samples reduced with catalase confirms the reduction and solubilisation of the dye with

enzyme. However, the results were not comparable to the conventional system. In order

to achieve maximum benefits from the newly introduced system, the dyeing process

parameters were optimised in terms of concentration of catalase and electrolyte, pH,

temperature and time of dyeing. The optimum parameters using alkaline catalase for

dyeing of cotton with sulphur dyes were pH (12), catalase concentration (0.5 times

weight of the dye), salt (nil), temperature (90oC) and a dyeing time (2 hours). These

optimised conditions were applied for catalase based dyeing and dye receptivity was

compared with sulphide system, as shown in Figure 2.5 [29].

Literature review

62

Figure 2.5 Comparison of dye receptivity (K/S) in catalase and sulphide

reduction system from [29]

The two systems were also compared for reduction bath stability (in the absence of dye)

for which they were found to retain their reducing capability for 24 hour of storage in

terms of both the reduction potential and pH. To study the potential of stored dyebaths

towards successful dyeing, the stability of the bath with the dye was evaluated for which

the bath was stored for 24 hours. Likewise, the catalase based dyebath showed

comparable stability to the sulphide system. The comparison of fastness properties of

the cotton fabric dyed in catalase system to the sulphide one showed overall good

comparative performance [29].

2.7.7. Alkaline pectinase reduction

The application of enzyme for the reduction of sulphur dyes was also considered by

making use of pectinase. In this study, a comparison between the conventional sodium

sulphide and the enzyme system was carried out, in which sodium sulphide was

substituted with alkaline pectinase [30].

Pectinases or pectiolytic enzymes are a complex of at least six enzymes involved in the

degradation of pectic substances by means of splitting them at different sites [31]. These

Literature review

63

enzymes are chiefly produced in nature by saprophytes and plant pathogens that include

bacteria and fungi, for the degradation of plant cell walls. Pectinase is present in the

roots, stem, leaves and fruits of higher plants in the form of pectin methyl esterase [32].

In order to study the effect of the enzyme on the performance of the dyed fabric, the

preparation of dyebath, dyeing and oxidation were carried out in the same way as those

using the sulphide system. Sodium sulphide was replaced with pectinase (0.05-1.5 times

the amount of dye) along with sodium hydroxide for the corresponding dyebath pH. The

ability of the pectinase to reduce sulphur dyes was evaluated by preparing dyebaths with

five different sulphur dyes, namely CI Sulphur Blue 3, Black 5, Green 11, Red 10 and

Yellow 4, using sodium hydroxide and pectinase (1 T with respect to weight of dye)

followed by heating up at 90-95oC and dyeing. The colour receptivity indicated that the

application of alkaline pectinase resulted in reduction and solubilisation of sulphur dyes

[30].

The reduction potential and depth of dyeing (K/S) of dyed cotton was found to be

equivalent to those obtained in sulphide systems (Figure 2.6). However, stability of the

alkaline pectinase based reduction baths was found to be slightly inferior. The

colourfastness of the dyed cotton was also approximately equal to that of the sulphide

system. Therefore, it can be postulated that the use of enzymes can be a good

replacement to sodium sulphide which is highly toxic and can be substituted with

alkaline pectinase thus making the sulphur dyeing process increasingly more

environment friendly [30].

Literature review

64

Figure 2.6 Comparison of colour strength of cotton dyed in sulphide and

pectinase systems from [30]

2.7.8. Electrochemical reduction

An alternative route to the environmentally safe reduction of sulphur dyes has been

achieved by a direct cathodic reduction method. This was carried out by a multi-cathode

electrolyser and the redox potentials were varied as a function of charge flow. The

catholyte also acted as a dyebath for the cotton samples. The relationship between

colour yield, redox potential and charge flow was investigated and its understanding

thus facilitates the direct control of the dyeing process by the aforesaid method of

reduction [33].

It was found that the application of sulphur dyes could be achieved for exhaust as well

as continuous dyeing methods. The continuous method was undertaken in two steps,

firstly reducing the dyes cathodically then applying the dye through a pad steam (100oC,

saturated steam) method. The electrochemical reduction process could also be applied

for exhaust dyeing by direct coupling between the dyebath and electrolyser. The

application of dye by the exhaust method was investigated by Bechtold by direct

coupling of multi cathode electrolyser to a dyeing unit. The process not only enables the

piloting of dyeing conditions by the measurement of redox potential and the cell current

but also substitutes the non-regenerable reducing agents in the dyeing processes [33].

K/S

Literature review

65

Therefore, the technical application will need a careful measurement of the redox

potential which is the most important factor for the dye reduction. Moreover, the colour

depth prediction can be achieved by the charge flow applied to reduce the bath.

However, the cell efficiency and reoxidation of the dye on exposure to air needs to be

controlled and kept constant [33].

2.8. Redox chemistry

The redox behaviour and properties of CI Sulphur Black 1 was studied by Bechtold with

the aid of redox and potentiometric titration, and indicated the reduction of dyestuff at

the molecular level [33]. Fast reducing agents such as tin chloride and iron

triethanolamine were investigated and a redox potential of ca -600 mV related to the

maximum colour depth. The more negative redox potential ranging above -800 mV

produced lighter dyeings with surplus of reducing agent left in the dyebath. The study

indicated that the partially reduced dye at -600 mV had greater affinity for cellulose than

the fully reduced dye. The same parameters were also found to be equally important for

other reducing agents including glucose and sodium dithionite [33].

2.9. Oxidation of sulphur dyes

2.9.1. Hydrogen peroxide

Hydrogen peroxide acts as a very strong oxidising agent in an alkaline medium. It does

not produce harsh handle like dichromate [14]. Some leuco dyes (red-browns) are not

oxidised by peroxy compounds, on the other hand, some blues are over-oxidised. In

order to achieve brighter blues and blacks, the use of hydrogen peroxide and sodium

perborate at pH 9 and temperature around 40oC for 10-20 minutes is quite common.

Though, this reduces the wet fastness by one or more grey scale units when compared to

sodium dichromate oxidation. The reason of the impaired wet fastness may possibly be

due to the over-oxidation of the disulphide groups forming ionisable sulpho groups

caused by active peroxide. This over-oxidation increases the water solubility and

Literature review

66

decreases the wet fastness and results in staining of other goods during washing. The

usage of peroxide under slightly acidic conditions in the presence of acetic acid is

widely used for package dyeing and offers a somewhat slower rate of oxidation [2, 7].

2.9.2. Sodium dichromate

This is the preferred oxidising system as it produces sulphur dyeings with complete

oxidation of all reduced sulphur dyes by chromium (IV) compounds, good colour yield,

good fastness properties, repeatability of process and is comparatively cheaper than

other systems hence commercially attractive [14]. However, the use of this oxidising

agent is not environmentally safe and is being restricted by many water authorities. Its

use is also avoided in the case of yarn dyeing due to its adverse effects on handle and

sewability, especially for sulphur blacks. The application of dichromate produces

stiffness in dyed cotton due to the precipitation of chromium compounds, leading to an

intermittent change in tone, reduction in hydrophilicity and an increase in the solid

content of the discharged waste water [34]. In future the use of dichromate as an

oxidising agent will no more be permitted due to the increasingly strict legislations

relating to the permissible amount of chromium compounds in effluents [7].

2.9.3. Iodates

Sulphur dyes can also be oxidised with sodium or potassium iodate which can be a

substitute for dichromate. Advantages of using iodate instead of dichromate are that it

offers excellent colour and fastness reproducibility with softer handle. The drawbacks of

using iodates are high cost of the chemicals involved and iodine precipitation in washers

when used along with formic acid instead of acetic acid [8, 14].

Literature review

67

2.9.4. Sodium chlorite

The oxidation with sodium chlorite is usually carried out in an alkaline pH at near boil

temperatures. It is a relatively weak oxidising agent [8]. It has become an active

ingredient in some of the registered formulations which include stabiliser, detergent and

a sequestering agent together with the oxidising agent [7]. The advantages include very

good and reproducible results and the main disadvantage is the slow reaction which is

not comparable to dichromate oxidation [8, 35].

2.9.5. Enzymes (Laccase)

The use of enzymes particularly those belonging to the class of oxidoreductase have

been found to be a toxic free alternative to sodium and potassium dichromate. It is not

only suitable for the oxidation of reduced and solubilised sulphur dyes but also for

precipitation of dyes from unexhausted dyebaths. Laccases are ubiquitous glycoproteins

synthesised from fungi, plants, insects and a few bacteria [34, 36-39]. Using molecular

oxygen as an electron acceptor, it catalyses single-electron oxidation reaction of several

inorganic and organic compounds. This causes simultaneous reduction of molecular

oxygen to water and oxidation of substrates typically phenolic in nature [40-43].

Laccases are poorly water soluble [37]. It is problematic to oxidise too large substrates

because either it is difficult to penetrate into the enzyme active site or they possess high

redox potential. This drawback is overcome and their reactivity can be improved by

using redox mediators which are low molecular weight compounds that can easily be

oxidised by a laccase, producing very reactive radicals. They act as intermediate

substrates for laccases (Scheme 2.8). These reactive radicals have the capability of

attacking more complex substrate before returning to their original state [40, 42].

Commonly used mediators include 1-hydroxybenzotriazole (HBT), 2,2-azino-bis-3-

ethylbenzthiazoline-6-sulfonic acid (ABTS) [42], benzotriazole (BT), Remazol Brilliant

Blue (RBB), chlorpromazine (CPZ), promazine (PZ), 1-nitroso-2-naphthol-3,6-

disulfonic acid (NNDS), 4-hydroxy-3-nitroso-1-naphthalenesulfonic acid (HNNS) [40],

1,2,4,5-tetramethoxybenzene [41], etc

Literature review

68

Scheme 2.8 Schematic representation of laccase-catalysed redox cycles for

oxidation of substrates (a) in the absence of and (b) in the presence of chemical

mediators, reproduced from [34]

In order to study the effectiveness of laccase as an oxidising catalyst and precipitation of

unexhausted sulphur dyes, Chakraborty used a laccase of an acidic nature and ten

sulphur dyes which were applied 5% omf on mercerised cotton fabric with sodium

sulphide. He compared potassium dichromate based oxidised fabric with laccase based

system by varying its process parameters such as concentration, temperature and time

[34].

In the first instance, the solubility and colour of the laccase was evaluated at various pH

and temperatures. It was found that the laccase was fairly soluble in an acidic medium

and converted into a gel as the pH became alkaline. The colour change was from

orange-yellow in highly acidic pH to light yellow and to light pink to colourless at

increasingly alkaline pH. An increase in temperature from 30oC to 80

oC slightly reduces

the solubility of the laccase [34].

There was no effect of temperature on the redox potential of the laccase. However,

increasing the pH of 1% solution of laccase (at 30oC) from acidic (4) to alkaline (13)

was found to reduce its redox potential from 250 to -267 mV. The colour yield for three

dyes namely CI Sulphur Black 5, Brown 8 and Green 1 when applied to cotton were

found to be maximum at a laccase concentration of 2 g/L at 50-60oC for 10 minutes.

The change in colour strength of the dyes due to different concentrations of laccase is

shown in Figure 2.7. Similar conditions when extended to rest of the dyes tested,

Literature review

69

revealed that colour strength of the dyeings produced from dichromate and laccase

based oxidising systems were comparable and constituted a close match [34].

The handle of the dyed fabric oxidised with the laccase was better than the one oxidised

with dichromate, probably because of the deposition of chromium compounds on dyed

cotton. In addition to the latter process being used as an oxidising agent, the laccase also

proved to be a good option for the precipitation of unexhausted dye. The pH of the

exhausted dyebaths was neutralised with acetic acid and then precipitated with 1-5% of

laccase. It was found that 1% of laccase could precipitate almost all of the sulphur dye

from an unexhausted dyebath in the first hour. The acidic nature of the laccase could

also substitute the use of acetic acid but for that a large amount of laccase would be

needed [34].

The laccase recovered sulphur dyes were capable of reproducing the shades. Against 5%

omf shade for the control, 6% omf of the recovered dye was needed for CI Sulphur

Green 1 and Black 5, while CI Sulphur Brown 1 was not reproducible even with double

the amount of precipitated dye (that is 10% omf). The 6-10% omf shades represented a

good match with the control. The wash, light and rubbing fastness of laccase oxidised

sulphur dyed fabric to other oxidising systems (potassium dichromate, potassium iodate,

hydrogen peroxide, air oxidised) produced a comparable match [34].

Figure 2.7 Effect of laccase concentration on K/S of sulphur dyes from [34]

.

Literature review

70

2.10. Fixation additives to enhance the fastness properties

The function of oxidation for sulphur dyes is usually carried out with conventional

oxidants such as sodium dichromate/acetic acid, H2O2 or sodium chlorite. The use of

compounds like isocyanates, diazonium salts, metal salts and alkylating agents could

perform the same function by removing an electron from the leuco form of the sulphur

dye, but they considered to behave as fixing agents rather than oxidising agents by

Aspland [6].

2.10.1. Alkylating agents

The fastness of sulphur dyes to severe washing conditions, especially in the presence of

peroxide based detergents, has been found to be improved by the use of alkylating

agents [44-48]. These agents are cationic, fibre substantive, reactive compounds like

polyhalogenohydrins. Under alkaline conditions, these compounds react with

nucleophilic thiolate or amino groups in the dye thus causing simultaneous alkylation

and crosslinking [6, 46].

It has been known for quite some time that the use of alkylating agents is a good

replacement for the oxidation of leuco sulphur dyes. These agents can be used in place

of conventional oxidants in leuco dyeings except those containing quinoneimine groups

bearing a marked yellow leuco colour, e.g. CI Vat Blue 43 or CI Sulphur Blue 7 for

which a mild oxidation treatment is required before alkylation for them to achieve their

true colours. Generally, the colour and wet fastness of dyeing is much improved by the

alkylation process, and this is because the thiol (-SH) groups are converted to alkylated

(-SR) groups instead of reconverting into disulphide groups, as is normally achieved as

a result of oxidation [7, 8, 14, 49, 50].

There are certain drawbacks associated with aftertreatment with alkylating agents. First,

they tend to destroy the dye chromogen if stripping is attempted for a successive

correction in shade. Secondly, they produce dyeings with potential shade change and an

inferior light fastness causing about a one point decrease on the blue wool standard scale

[7, 8, 14, 50].

Literature review

71

2.10.2. Cationic fixing agents

Cationic fixing agents are used to improve washfastness of unoxidised sulphur dyeings.

However, some work has also been done to produce better resistance against oxidative

bleaching to oxidised dyeings such as the use of quaternary ammonium alkyl

compounds [46, 47], dicyandiamide-formaldehyde condensates and crease resist

finishes [6, 44].

Significant research has been done by Burkinshaw regarding the use of cationic fixing

agents to increase the wet fastness of sulphur dyeings [6, 12, 49-52]. The author used

five cationic agents namely Matexil FC-ER and Matexil FC-PN along with three other

development products (A, B and C) to assess the impact of their application on wet

fastness on CI Sulphur Black 1, Yellow 23, Green 2 and Blue 5 of the three commercial

forms of CI Solubilised Sulphur dyes, CI Leuco Sulphur dyes and CI Sulphur dyes. The

oxidised dyeings were treated with the abovementioned fixing agents by an exhaust

method and the wash fastness was evaluated with ISO CO6/C2S test method. All five

cationic agents noticeably improved the washfastness of all 12 dyes, but the commercial

products of Matexil were found to be less effective than the development products.

However, the aftertreatments caused a slight flattening of the shade while they had little

effect on the colour strength (K/S) of the dyeings.

The author proposed several possible reasons for the improved wet fastness. Firstly, the

adsorption of these polycationic agents may have been produced as a result of the

electrostatic forces of attraction between the cationic agent and the anionic dye

molecules. As in the case of direct dyes, the polycations form a large molecular size

dye-cationic agent complex with low aqueous solubility, these cationic agents and the

sulphur dye molecules might have formed large molecular size complexes which get

locked within the fabric. Another reason may perhaps be the formation of a peripheral

layer (as syntans used for nylons) of polycations molecules which might reduce the

diffusion of the dye out of the dyed and treated fabric during laundering. Finally, this

could be due to ion-ion interactions between the carboxylic groups on the fibre and the

polycations resulting in holding the fixative and dye molecules with the fabric [6].

The work discussed latter relates to the application of polycations by exhaust application

methods. Nonetheless, Burkinshaw has also been able to produce viable results using

Literature review

72

non-exhaust/continuous techniques including pad-dry and pad-flash cure. He applied

two cationic fixing agents namely Matexil FC-PN and Fixogene CXF on oxidised

dyeings of four CI Leuco Sulphur dyes which resulted in improved fastness to the ISO

1O5 CO6/C2 wash test. It was found that the aftertreatment imparted an improvement of

1 grey scale unit for CI Leuco Sulphur Black 1 and Blue 5. Similarly, an improvement

of 1.5 units was observed for CI Leuco Sulphur Yellow 23 and Green 2 [12].

The application of three cationic fixing agents as pre-treatments to the CI Solubilised

Sulphur dyes was also investigated by Burkinshaw [51]. Pretreatment with cationic

fixing agents once gained considerable attention to improve the dyeability of cotton with

direct and reactive dyes. The cationisation or amination of cotton and other cellulosic

fibres causes the introduction of cationic sites, based on nitrogen, within the fibre. The

main objective in pre-treating the fibre is to enhance the substantivity of the anionic dye

for the cationic fibre.

Solfix E is the reactive cationic fixing agent employed for aftertreatments of direct dyes

on cellulosic fibres. It has been applied (by exhaust method) to the oxidised and leuco

derivatives of the sulphur dye in place of the oxidation stage in the dyeing process. The

effect on wash fastness of aftertreated dyeings of six CI Solubilised Sulphur dyes on

cotton was evaluated with varying concentrations of Solfix E. The aftertreated samples

were subjected to ISO 1O5 CO6/C2 wash test and exhibited significant improvements in

terms of shade change and staining of adjacent multifibre fabric. The aftertreatment

caused an increase in the colour strength of the dyed fabric but caused a slight reddening

which was persisted even after washing. Hence, the findings suggested that Solfix E

could be used to replace the traditional oxidation stage in the dyeing process yet provide

dyeings with superior wash fastness thereby reducing the time and cost of processing

[49].

Three cationic fixing agents namely Fixogene CXF (polyquaternary amine), Matexil

FC-ER (aqueous solution of high molecular-weight-resin) and DPA (development

product by ICI for which no details were provided because of commercial

confidentiality) were also applied on sulphur dyeings and subjected to repeated wash

fastness testing. This time the dyed fabrics were laundered under the Marks & Spencer

C46 wash test for which a sequence of four wash cycles simulate a series of typical

customer washes. A significant reduction in washdown was perceived for CI Leuco

Literature review

73

Sulphur Black 1 (as shown in Figure 2.8) and CI Leuco Sulphur Blue 5. A slight change

in hue and chroma of the dyeings were observed, however, there was very little effect

on the colour strength [50].

Figure 2.8 Colour loss of dyeings with CI Leuco Sulphur Black 1 with and

without aftertreatment from [50]

The treatment of cotton fibre with Matexil FC-ER, Matexil FC-PN and Solfix E

contributed to an increased colour strength and wash fastness as compared to the

untreated dyed fabric. The details of the composition of the three cationic fixing agents

are not known but the public domain information describes them as either being

nitrogenous condensation products or resins of high Mr (molecular mass) or polyamines.

The proposed theory behind the improved characteristics and dye uptake might be the

increase in substantivity between the anionic dye and cationic substrate as a result of

ion-ion forces of attraction [6].

The efficiency of cationic fixing agents generally depends on the particular type of

fixative, method of application, the strength of the dye/fixative bond, aggressiveness of

the wash conditions and the detergent formulation. Since the exact chemistry of the used

fixing agents is unknown, hence no comparison could be made on the basis of the

fixative formulations.

No aftertreatment Fixogene CXF Matexil FC-ER DPA

Co

lour

loss

(%

)

Literature review

74

2.10.3. Softeners

Depending on the chemical nature, softeners have the property to impart smoothness,

soft handle, elasticity, hydrophilicity and soil release properties to the textile material.

The effects of various softeners including anionic, cationic, non-ionic, micro and macro

silicone softeners were evaluated on the wash fastness properties of four Sulphur dyes

namely CI Sulphur Yellow 2, CI Sulphur Black 1, CI Solubilised Sulphur Black 1 and

CI Solubilised Sulphur Blue 11 [53].

It has been observed that the lightness of all sulphur dyed fabric samples decreased

when treated with non-ionic micro and macro silicone softeners. However,

aftertreatment with cationic and anionic softeners only slightly altered the shade of the

dyed sample, with exception of CI Sulphur Yellow 2, for which the CIE a*, b*, c*

values remain unchanged. The main objective of the research was to find the impact of

softeners on the washing and light fastness of the sulphur dyeings. The washfastness and

light fastness were measured according to ISO 1O5 CO5 and Daylight ISO 1O5 BO1. It

was observed that there was no considerable change on the washfastness of aftertreated

samples, in fact aftertreatment with non-ionic softeners reduced the grey scale for fading

by half a unit for all four types of dyes. The light fastness showed more fading for

aftertreated samples after 2 days of exposure, while an extension of exposure to 7 days

produced no further change [53].

2.10.4. Lanthanum triacetate

The effect of lanthanum triacetate has been examined by Zhou to improve the anti-

oxidation and anti-aging ability of sulphur dyed fabrics [54]. The theory of oxidative

bleaching of sulphur dyes has already been discussed previously (sections 1.2 and 1.4).

While, the effect of ageing on sulphur dyeing relates to the prolong exposure of the dyed

cotton to hot and humid environment. This is because the oxidised sulphur linkages on

hydrolysis generate sulphur containing acids such as mild sulphuric acid. These acids

degrade the cellulose stored under conditions of high temperature and humidity [54].

The effect of lanthanum triacetate was examined on CI Leuco Sulphur dyed cotton

fabric. The accelerated Launder-Ometer washing method (LOW) was operated

Literature review

75

according to AATCC Test Method 190-2002, for testing colour fastness to home

laundering with detergent containing activated oxidative bleach. Both standard

Reference Detergent 1993 (without optical brightener) and NOBS (nonanoyloxy-

benzenesulphonate) detergent were used to evaluate the influence of the oxidative

bleacher in the detergent on colour changes after laundering [54].

Figure 2.9 Effect of lanthanum triacetate on resistance of sulphur dyes against

oxidation for one LOW cycle using NOBS detergent from [54]

Samples were subjected to single and triplicate wash cycles with both detergents and the

comparison of untreated and treated fabric was made with the help of ∆E (Lab)* values.

Aftertreated samples showed considerable resistance against both laundering regimes

especially against oxidative bleaching using NOBS detergent (shown in Figure 2.9). All

colours when washed with NOBS detergent exhibited large colour loss after just one

LOW (accelerated Launder-Ometer washing method) cycle. The percentage reduction in

colour loss for most of the dyes was approximately 50%, indicating the effectiveness of

lanthanum ions on all dyes. The treatment also lowered the staining on adjacent

mutifibre fabric and little shade changes were observed for the aftertreated fabric when

compared to untreated ones [54].

Where;

Control: Untreated

DB: Diresul Black RDT-4D

SB: Sodyesul Black 4GCF

SR: Sodyesul Red 2B

DN: Diresul Navy RDT-GF1

SN: Sodyesul Navy GFCF

SG: Sodyesul Green NYCF

DY: Diresul Yellow E

Literature review

76

2.10.5. Crease resist finish

The effect of crease-resist finishes on sulphur dyeing is quite appreciable in terms of

improvement in wet fastness. It produces about one grey-scale unit increase in wet

treatments while the light fastness is either unaffected or slightly improved.

Nevertheless, it inclines to a redder and duller tone as compared to untreated fabric. The

durable press (DP) finishing, plays a vital role in preventing aging and improving the

resistance of sulphur dyeing against oxidative bleaching but it severely damages the

mechanical properties of the fabric, leading to a lower tensile or tear strength of the

finished goods. This alternative is limited to the applications where easy care finish is

needed [7, 54].

The effect of crease resist finish has also been explored by Burkinshaw [12]. He applied

two commercial cationic fixing agents namely Matextil FC-PN® and Fixogene CXF

®

(ICI Chemicals) and a Crease-Resist Finish KKR (Clariant) to the oxidised CI Leuco

Sulphur dyes. The crease-resist finish is usually applied by pad-dry-cure or pad-flash

cure procedures. The researcher examined the application of cationic fixing agents with

these methods and compared it with the Finish KKR. The comparison of the latter finish

with cationic fixing agent showed that a harsher handle and a decrease in chroma was

produced, and the quantity of finish utilised was much higher as compared to the

cationic polymers thus making the overall process mere costly. However, the extents of

wash fastness imparted by the finish as well as cationic polymers were equivalent [12].

2.11. Surface chemical analysis of sulphur dyed laundered fabric

The effect of various washing regimes such as ISO 1O5 CO6 (single and triplicate wash

cycles) and ISO 1O5 CO9 have been evaluated on CI Sulphur Black 1 with the help of

surface sensitive X-Ray photoelectron spectroscopy (XPS). The study involved the

exposure of cotton fabric to the aforementioned washing practices, with and without

oxidant sodium perborate and with and without abrasive steel balls. The surface

functionalities and the elemental composition was then characterised using XPS and the

durability of the sulphur dyes against the oxidative bleaching was assessed. As a result

Literature review

77

of washing the modification in the surface sulphur was related to colour strength (K/S)

and lightness of the fabric using a Datacolor Spectroflash 600 [55].

On reviewing the elemental composition (XPS atomic % of carbon, nitrogen, oxygen

and sulphur) of the washed sulphur dyed cotton fabric it was observed that the loss in

sulphur content on the surface is minimum in the case of washing without perborate in

both cases. However, a slight reduction could be seen when the fabric was exposed to a

single wash of ISO 1O5 CO6 in the presence of perborate. The loss in surface sulphur

was much more severe when the fabric was treated with ISO 1O5 CO6 triplicate wash

cycles and ISO 1O5 CO9 in the presence of perborate. However, the presence of steel

balls did not have an influential effect on the surface sulphur content [55].

The S (2p) XP spectra were also analysed to differentiate the possible presence of three

main sulphur species namely unoxidised S2+

(-S-, -S-S-), over-oxidised S6+

(−SO3−,

−S − SO2 − or − S − SO3−) and partially or intermediate oxidised S

4+. The washing

with ISO 1O5 CO6 with perborate indicated the presence of S6+

dye species, its spectral

intensity was further increased with repeated washings with perborate. There was no

apparent increase in surface oxidation with or without the inclusion of steel balls which

indicated that the abrasive action does not contribute to the formation of oxidised

sulphur dyes at the fibre surface [55].

The oxidative effect of washing without perborate was insignificant compared to

perborate based washing, but when the two washing systems were compared it was

found that XP spectrum of the dyed fabric washed with ISO 1O5 CO9 without perborate

demonstrated less oxidation than CO6. However, a pronounced loss of sulphur from the

fibre surface was observed in the case of perborate based washing regime of ISO 1O5

CO9 which lead to the understanding that the oxidation of the disulphide bonds of the

sulphur dyes causes the formation of water-soluble sulphonated short chain dye

fragments which were finally lost in the solution. The investigation of ISO 1O5 CO9 S

(2p) XP spectrum demonstrated the presence of oxidised S6+

dye species, indicating that

the surface dye had been affected by the much more aggressive TAED catalysed

perborate treatment, which in turn reduced the surface sulphur concentration. This could

perhaps be because of the loss of sulphonated dye fragments into the solution [55].

Further study of colour strength and lightness supported the aforesaid information. The

two washing systems with perborate exhibited a significant reduction in colour strength

Literature review

78

and increase in lightness especially in case of CO9 and CO6 (repeated washing).

Laundering with CO9 resulted in higher surface oxidation, concomitant decrease in

colour strength and much greater dye loss as a result of the bleaching environment

generated with the catalysed TAED/perborate procedure. On the other hand, the tests

performed without perborate presented surface oxidation to a much lower extent [55].

2.12. Application of sulphur dyes on non-cellulosic fibres

2.12.1. Dyeing of silk

Silk displays substantivity towards every dye type due to its amphoteric properties and

hydrophilic character [56, 57]. A study has been carried out by Burkinshaw where CI

Solubilised Sulphur dyes were applied at low temperature using sodium thioglycolate as

a reducing agent [58]. Moderate to deep shades with good wet fastness were achieved

on cultivated silk. The dyeing was carried out at pH 7 for 30 min at 60oC in the absence

of an electrolyte. The dyed fabric displayed good to excellent fastness to washing at

40oC (ISO 1O5 CO6/A2C); little or no fading could be seen for oxygen bleaching that is

UK-TO (ISO 1O5 CO9) test method. The dry rub fastness varied from moderate to good

while the wet rub fastness appeared to vary from poor to moderate. The mild application

conditions that are dyeing at 60oC for 30 min had only a small effect on the tensile

strength of the silk fabric [58].

2.12.2. Dyeing of nylon

Nylon 6,6 can be dyed with a variety of dye classes such as acid, mordant, direct,

reactive, disperse, vat and basic dyes. For sulphur dyes, the influence of various

application parameters such as pH, temperature, liquor ratio, type of reducing agent as

well as the mechanism of dyeing has been explored by Burkinshaw [59-62]. It was

recognised that pH of the dye bath influence the colour strength and over a pH range of

6-12, the maximum colour strength is achieved at pH 7. The temperature range of 70-

98oC had only a minor effect on colour of the dyeings whereas lower (50 and 60

oC) and

higher (110 and 120oC) temperatures resulted in colour change. The dyeing temperature

Literature review

79

had no effect on the wash fastness and staining of adjacent mutifibre while it had a

limited effect on the light fastness. The dyeings displayed poor light fastness except for

the sulphur blacks [61].

The dyeings were also evaluated on the basis of different commercial reducing systems

and oxidation treatments (H2O2, air and Diresul Oxidation Liquid BRI). The reducing

systems did not only affect the colour strength but also changed the colour of the

dyeings which may be attributed to the state of reduction of the dyes and their

subsequent oxidative condensation. The oxidising systems did not much influence the

colour strength but altered the hue. However, the type of the oxidant hardly produced

any effect on the wash fastness of the dyed fabric. The dyeings, however, displayed

good wash fastness properties for five repeated wash tests. At the end of the dyeings, the

dyed fabrics were subjected to a wash-off process using four commercial reagents

(Formosul GR, Sandoclean PC, Diresul EW and Cyclanon ECO). The washed samples

were compared with the control sample in terms of wash fastness and colorimetric

properties. The control sample was a dyed fabric which was rinsed only in running tap

water for five minutes prior to drying. The wash-off improved the extent of staining on

the mutifibre fabric but did not improve the change in colour as a result of multiple

washes. However, each one of the washing compounds varied in terms of removal of the

dye and their efficiency on different dyes. All dyeings except black displayed poor light

fastness and overall this behaviour was merely influenced by the type of reductant,

oxidation system and wash-off methods employed [62].

The presence of amino end groups (AEG) in nylon fibres imparts substantivity of the

fibre towards anionic dyes. It is known that the forces of interaction between the anionic

dyes and nylon 6,6 are produced in acidic media and are mainly caused between anionic

(typically sulphonate) groups in the dye and the protonated amino end groups in the

fibre. Hence, the adsorption of anionic dyes on nylon 6,6 is site specific [63].

However, the nature of the interaction between sulphur dye and nylon fibre has also

been studied by Burkinshaw [60]. He applied solubilised sulphur and sulphur dyes onto

four different types of nylon 6,6 fabric. It was found that the adsorption of the dye on

nylon was least dependent on the AEG content of the fibre or the nature of the extracted

polymer, since variation in both properties did not influence the colour of the dyeings.

Hence it may be postulated that the adsorption of both solubilised sulphur dyes and

Literature review

80

sulphur dyes onto nylon 6,6 is principally non-site-specific. It can further be

hypothesised that dye-fibre substantivity occurs principally through hydrogen bonding,

dispersion forces and polar Van der Waals’ forces of interaction [60].

2.12.3. Dyeing of wool

Presently, deep black and navy shades on wool are achieved with metal based dyestuff

particularly chrome dyes that represent about 20% of the total wool dye market [64].

The use of sodium dichromate in chrome dyeing is not only hazardous to the workers in

the dye house but also to the environment as a result of the dyebaths discharged into the

water streams. Therefore, the woollen products containing such harmful compounds

may become increasingly unacceptable with time [65].

Wool can be dyed with metal free reactive dyes with high wet fastness but with some

shades light fastness can be a problem. It is sometimes difficult to achieve dark navy

and black shades with reactive dyes [7]. Vat dyes have also been used on wool and wool

blends [66]. However, the literature is not enough to explain the behaviour of sulphur

dyes on wool, due to the damaging effects of highly alkaline sodium sulphide on wool

[2, 7]. The reduction potential of sulphur dyes is lower than vat dyes; hence they are

easier to be converted into their leuco form by reduction [2].

The use of sodium sulphide and sodium hydrosulphide for the reduction of sulphur dyes

have been discussed in previous sections (2.7.1.1, 2.7.1.2). The use of organic reducing

agents like glucose requires higher temperatures, higher concentrations of sodium

hydroxide to achieve sufficient level of dyestuff reduction [2, 7].

Recently, Rohm and Raas have developed a reducing system by mixing sodium

borohydride and sodium bisulphite which produces hydrosulphite. The chemical

reaction is illustrated in Scheme 2.9 [67].

NaBH4 + 8NaHSO3 → 4Na2S2O4 + NaBO2 + 6H2O

Scheme 2.9 Production of hydrosulphite by reacting sodium borohydride and

sodium bisulphite from [67]

Literature review

81

The mixture of sodium bisulphite and sodium hydroxide solution (12%), in the ratio of

4:1 is found to be useful for application of vat dyes to cotton under alkaline conditions.

This reducing system has been more efficient than hydrosulphite alone and gives

approximately 15% dyestuff savings [68]. This reducing system has also been found

useful for the reductive bleaching of wool under acidic to neutral conditions [69].

Hence, this was considered to be an alternative solution to the dyeing of wool with

sulphur dyes. The method was tested with CI Sulphur Black 1, as this is the single most

highly consumed sulphur dye.

The wool fabric was dyed in dark shades with reactive and chrome dyes, to be used as

standards for comparison. The dyes used were Lanasol Black CE and Eriochrome Black

PV (CI Mordant Black 9). It was found that the pre-chlorination of the fabrics increased

the colour yield of both the reactive and chrome dyes on the fabric [67].

Dyeing of wool with the new reducing system was carried out at 60oC for 40 minutes.

After dyeing, the wool fabric was rinsed and oxidised as usual. The following

concentrations were found to be optimum for application of sulphur dyes on wool:

Sodium bisulphite: 4-8 g/L;

Sodium borohydride solution (12% SB-S): 1-2 g/L;

Sodium hydroxide solution (38oBe/320 g/l): 3-6 g/L [67].

Satisfactory results were achieved at 2 g/L SB-S and 8 g/L sodium bisulphite, under

which the dye was maintained in the leuco form until the exhaustion phase and the

colour yield of the fabric was improved. The colour yield was further increased by

increasing the concentration of sodium hydroxide from 3 to 6 mL/L. This increased the

pH of the bath from 7.3 to 8.9 [67].

Both untreated and chlorinated wool was dyed with sulphur dyes using the above

system of reduction. The results indicated that dyeing at 70oC produced better colour

yield than 60oC, which was higher than those achieved with chrome and reactive dyes.

However, the fabric handle at 70oC was harsher than 60

oC, reflecting the expected

greater level of fibre damage at higher temperatures [67].

The wash and alkaline fastness of the samples dyed with sulphur dyes using the new

reducing system were either identical to or superior to those achieved with chrome and

reactive dyes. The dry rubbing fastness was good but the wet rubbing fastness was

Literature review

82

lower than those achieved with chrome or reactive dyes due to the inherent properties of

these classes of dye. The light fastness rating obtained with sulphur dyes was similar to

chrome dyes and better than reactive dyes. Wool fibre damage was assessed by

comparing the wet burst strength of the dyed fabrics with the undyed wool. It was

observed that the level of damage of undyed fabric was lesser than the dyed samples.

The three dyes can be classified as reactive dyed fabric being the strongest and sulphur

dyed fabric being the weakest. The sulphur dyed samples showed the highest loss in

fabric strength, probably due to the alkaline nature of the dye bath [67].

2.13. References

[1] Shore J. Colorants and auxiliaries: organic chemistry and application properties.

Bradford: Society of Dyers and Colourists, 1990.

[2] Broadbent AD. Basic principles of textile coloration. Bradford: Society of Dyers and

Colorists, 2001.




[4] Nguyen TA and Juang RS. Treatment of waters and wastewaters containing sulfur

dyes: A review. Chemical Engineering Journal. 2013;219:109-17.

[5] Clark M. Handbook of textile and industrial dyeing. Cambridge: Woodhead

Publishing Limited, 2011.




[8] Klein R. Sulfur dyes today and tomorrow. Journal of the Society of Dyers and

Colourists. 1982;98(4):106-13.

[9] Roessler A and Jin X. State of the art technologies and new electrochemical methods

for the reduction of vat dyes. Dyes and Pigments. 2003;59(3):223-35.

Literature review

83

[10] Bozic M, Lipus LC and Kokol V. Magnetic field effects on the redox potential of

reduction and oxidation agents. Croatica Chemica Acta. 2008(81):413-21.

[11] Aspland JR. Textile Dyeing and Coloration: American Association of Textile

Chemists and Colorists, 1997.



1997;33(1):1-9.

[13] Schindler WD and Hauser PJ. Chemical finishing of textiles: Woodhead Publishing

Limited, 2004.

[14] Teli M, Paul R, Landage SM and Aich A. Ecofriendly processing of sulphur and

vat dyes-An overview. Indian Journal of Fibre and Textile Research. 2001;26(1/2):101-

7.

[15] Czajkowski W and Misztal J. The use of thiourea dioxide as reducing agent in the

application of sulfur dyes. Dyes and Pigments. 1994;26(2):77-81.

[16] Madhu and Amit. Sulfur dyeing with non-sulfide reducing agents. Journal of

Textile and Apparel, Technology and Management 2012;7(4):1-13.

[17] Tan KH. Principles of soil chemistry: CRC Press, 2011.

[18] Zouhaier R, Sofiène D and Faouzi S. The use of glucose as ecological reducing

agent for sulphur dyes: Optimization of experimental conditions. European Scientific

Journal. 2014;10(18):436-46.

[19] Baffoun A, Hamdaoui M and Romdhani Z. Use of glucose as an ecofriendly

reducing sugar in the application of sulphur dyes-Comparative study with traditional

reducing agent. Indian Journal of Fibre and Textile Research. 2015;40(1):57-61.

[20] Kubanik R. Reduction in the chemical required for sulfur dyeing. International

Textile Bulletin. 1998;44(3):85-86.

[21] Motaghi Z. The comparison between a natural reducing agent and sodium

dithionite in vat, indigo and sulphur dyeing on cotton fabric. Eco-Dyeing, Finishing and

Green Chemistry. 2012;441:207-11.

Literature review

84

[22] Choudhury AKR. Textile preparation and dyeing: Science Publishers, 2006.

[23] Shamey R and Hussein T. Critical solutions in the dyeing of cotton textile

materials. Textile Progress. 2005;37(1-2):1-84.

[24] Bechtold T, Burtscher E and Turcanu A. Continuous sulfur dyeing without

reducing agents: Fully reduced Sulfur Black 1 by cathodic reduction. Textile Chemist

and Colorist. 1998;30(8):72-7.

[25] Bechtold T, Turcanu A and Schrott W. Electrochemical reduction of CI Sulphur

Black 1 - Correlation between electrochemical parameters and colour depth in exhaust

dyeing. Journal of Applied Electrochemistry. 2008;38(1):25-30.

[26] Jaruhar P and Chakraborty J. Dyeing of cotton with sulfur dyes using alkaline

protease. Textile Research Journal. 2013;83(13):1345-55.

[27] Božič M, Pricelius S, Guebitz GM and Kokol V. Enzymatic reduction of complex

redox dyes using NADH-dependent reductase from Bacillus subtilis coupled with

cofactor regeneration. Applied Microbiology and Biotechnology. 2010;85(3):563-71.

[28] Cavaco-Paulo A and Gubitz G. Textile processing with enzymes: Elsevier, 2003.

[29] Chakrabortya J and Jaruhar P. Dyeing of cotton with sulphur dyes using alkaline

catalase as reduction catalyst. Indian Journal of Fibre and Textile Research.

2014;39:303-9.

[30] Jaruhar P and Chakraborty JN. Bio-reduction of sulphur dyes with alkaline

pectinase. Journal of Chemistry and Chemical Engineering. 2013;7:930-41.

[31] Polaina J and MacCabe AP. Industrial enzymes: Springer Science and Business

Media, 2007.

[32] Nierstrasz V and Cavaco-Paulo A. Advances in textile biotechnology: Elsevier,

2010.

[33] Bechtold T, Berktold F and Turcanu A. The redox behaviour of CI Sulphur Black 1

- a basis for improved understanding of sulphur dyeing. Journal of the Society of Dyers

and Colourists. 2000;116(7-8):215-21.

Literature review

85

[34] Chakraborty J and Dhiman G. Effectiveness of laccase in the oxidation and

recovery of sulfur dyes. Textile Research Journal. 2013;83(5):441-9.

[35] Aspland J. Oxidation and fixation of reduced sulfur dyes. Textile Chemist and

Colorist. 1970;2(13).

[36] Madhavi V and Lele S. Laccase: properties and applications. BioResources.

2009;4(4):1694-717.

[37] Riva S. Laccases: blue enzymes for green chemistry. Trends in Biotechnology.

2006;24(5):219-26.

[38] Sharma KK and Kuhad RC. Laccase: enzyme revisited and function redefined.

Indian Journal of Microbiology. 2008;48(3):309-16.

[39] Xu F and Salmon S. Potential applications of oxidoreductases for the re-oxidation

of leuco vat or sulfur dyes in textile dyeing. Engineering in Life Sciences.

2008;8(3):331-7.

[40] Guevara-González RG and Torres-Pacheco I. Advances in agricultural and food

biotechnology: Research Signpost, 2006.

[41] Thurston CF. The structure and function of fungal laccases. Microbiology.

1994;140(1):19-26.

[42] Cavaco-Paulo A and Gèubitz GM. Textile processing with enzymes: CRC Press,

2003.

[43] Abadulla E, Tzanov T, Costa S, Robra K-H, Cavaco-Paulo A and Gübitz GM.

Decolorization and detoxification of textile dyes with a laccase from Trametes hirsuta.

Applied and Environmental Microbiology. 2000;66(8):3357-62.

[44] Preston C. The dyeing of cellulosic fibres: Dyers Company Publications Trust,

1986.

[45] Wood WE. Sulphur dyes–1966–1976. Review of Progress in Coloration and

Related Topics. 1976;7(1):80-4.



Literature review

86

[47] Heid C, Holoubek K and Klein R. One hundred years of sulfur dyes. Melliand

Textilberichte International. 1973;54(12):1314-27.

[48] Baldwinson T and Shore J. Colorants and Auxiliaries. Bradford: Society of Dyers

and Colourists, 1990.





Colourists. 1998;114(5-6):165-8.

[51] Burkinshaw SM and Gotsopoulos A. The pre-treatment of cotton to enhance its

dyeability—I. Sulphur dyes. Dyes and Pigments. 1996;32(4):209-28.




[53] Parvinzadeh M. The effects of softeners on the properties of sulfur-dyed cotton

fibers. Journal of Surfactants and Detergents. 2007;10(4):219-23.

[54] Zhou W and Yang Y. Improving the resistance of sulfur dyes to

oxidation. Industrial and Engineering Chemistry Research. 2010;49(10):4720-5.


effect of extended laundering on CI Sulphur Black 1 dyed cotton fabric. Dyes and

Pigments. 2013;96(1):25-30.

[56] De Giorgi MR, Cerniani A, Colonna GM and Bianchi AS. Thermodynamic affinity

of acid dyes on silk. Dyes and Pigments. 1991;15(1):47-55.

[57] Blackburn R and Burkinshaw S. Aftertreatment of 1: 2 metal‐complex acid dyes on

conventional and microfibre nylon 6.6 with a commercial syntan/cation system. Part 2:

Repeated washing. Coloration Technology. 1999;115(3):102-5.

Literature review

87

[58] Burkinshaw SM and Paraskevas M. The dyeing of silk Part 1: Low temperature

application of solubilised sulphur dyes using sodium thioglycolate. Dyes and Pigments.

2010;87(3):225-33.

[59] Burkinshaw SM, Chevli SN and Marfell DJ. The dyeing of nylon 6,6 with sulphur

dyes. Dyes and Pigments. 2000;45(1):65-74.

[60] Burkinshaw SM and Lagonika K. Sulphur dyes on nylon 6,6. Part 3. Preliminary

studies of the nature of dye-fibre interaction. Dyes and Pigments. 2006;69(3):185-91.

[61] Burkinshaw SM, Lagonika K and Marfell DJ. Sulphur dyes on nylon 6,6 - part 1:

the effects of temperature and pH on dyeing. Dyes and Pigments. 2003;56(3):251-9.

[62] Burkinshaw SM, Lagonika K and Marfell DJ. Sulphur dyes on nylon 6,6 - part 2:

the effects of reductant, oxidant and wash-off. Dyes and Pigments. 2003;58(2):157-70.

[63] Burkinshaw S. Chemical principles of synthetic fibre dyeing: Springer Science and

Business Media, 1995.

[64] Lewis DM. The coloration of wool. In: Johnson NAG, Russell IM, editors.

Advances in wool technology: Woodhead Publishing; 2009. p.183-213.

[65] Johnson NA and Russell IM. Advances in wool technology: Woodhead Publishing

Limited and CRC Press, 2009.

[66] John A. Rippon, Cai JY and Smith SM. Dyeing wool with metal-free dyes – The

use of sodium borohydride for the application of vat dyes to wool: INTECH Open

Access Publisher, 2011.

[67] Cai JY, Rippon JA, McDonnell J and Parnell AE. Dyeing wool with a sulphur

black dye using a sodium borohydride/sodium bisulphite reducing system. Coloration

Technology. 2012;128(1):9-14.

[68] Schoots HP. Method for dyeing textiles. Google Patents; 2007, US5861045 A.

[69] Schoots HP and Stevens Jr LF. Methods for use in wool whitening and garment

washing. Google Patents; 2003, US6663677 B2.

Research methodology

88

3. Research methodology

3.1. Introduction

The project specifically considers the improvement of sulphur dyed cotton fabric’s

resistance to domestic laundering. In this section, an overview of the dyeing and

aftertreatments procedure, materials and methods utilised is provided.

Several experiments were conducted to establish the technical possibilities of improving

the overall fastness properties of sulphur dyed fabric in the light of literature findings,

the details of which are outlined in the following chapters. Optimal application

conditions were investigated by experimentation design. Standardised testing measures

were utilised, other methodologies were developed or replicated on the basis of previous

research work in the field.

3.2. Materials

3.2.1. Fabric

A plain woven, bleached, unmercerised, 100% cotton fabric having GSM 103 and

EPIxPPI-77x66 was used throughout the study. The fabric was generously provided by

Phoenix Calico Limited.

3.2.2. Sulphur dyes and auxiliaries

The range of sulphur dyes used during experiments was Diresul CI Leuco Sulphur dyes

manufactured by Clariant. Dyes with their CI numbers are listed below in Table 3.1.

.


89

Table 3.1 Dyes used

Trade name CI name

Diresul Black RDT-LS LIQ 200 Leuco Sulphur Black 1

Diresul Liquid Green RDT-N Leuco Sulphur Green 2

Diresul Liquid Blue RDT-G Leuco Sulphur Blue 7

Diresul Liquid Yellow RDT-E Leuco Sulphur Yellow 22

Diresul Liquid Red RDT-BG Leuco Sulphur Red 14

The reducing agents used were Diresul Reducing agent D which is a biodegradable

reducing agent by Clariant and the conventional sodium sulphide (Laboratory grade,

Aldrich Chemicals Ltd, UK.). The oxidation bath comprised of hydrogen peroxide and

sodium bicarbonate (Laboratory grade, Aldrich Chemicals Ltd, UK.). The fabric was

finally soaped with ALK-D (a non-ionic detergent, Clariant International Ltd.). The

ECE non-phosphate detergent, ECE phosphate detergent and tetraacetylethylenediamine

(92% active) were purchased from the Society of Dyers and Colourists (SDC),

Bradford, UK. Sodium perborate tetrahydrate (97% active, Laboratory grade, Aldrich

Chemicals Ltd, UK.) was purchased from Aldrich Chemicals Ltd., UK.

3.3. Finishing auxiliaries

In order to improve the wash fastness of sulphur dyes against domestic washing regimes

as replicated by ISO 1O5 CO6 (single and triplicate wash cycles) and ISO 1O5 CO9

(single wash) in the presence and absence of sodium perborate, the dyed fabric was post

treated with various finishing agents. A number of variations were prepared to identify

the optimal conditions, the details of which are discussed in chapter 4, 5, 6 and 7.

3.3.1. Bayprotect Cl

The application of tannin (or tannin based product) on sulphur dyed cotton fabric for

improving the wash fastness has been investigated for the first time. According to the

product information guide (received from Tanatex Chemicals, Netherlands) Bayprotect


90

Cl is an anionic stain-release agent for polyamide 6,6 and polyamide 6. It is a tannin

based product and acts as an anti-oxidant, providing pronounced protection against

sodium hypochlorite solutions (cleaning agents and bleaches), benzoyl peroxide (acne

cream) and other oxidative substances. It is a yellowish brown viscous liquid and can be

diluted with water at any ratio. Its general application is on polyamide and best results

are obtained on this fibre when tested against oxidative substances. It is stable to

substances causing hardness of water, dilute organic and inorganic acids but has only

limited stability to heavy metal salts and alkalis [1]. The application conditions

employed for aftertreatments with Bayprotect Cl on sulphur dyed cotton fabric are

discussed in chapter 4.

3.3.2. Fixapret CP

Sulphur dyed fabrics were aftertreated with the durable press finish Fixapret CP, based

on DMDHEU (Dimethyldihydroxyethyleneurea) in the presence of magnesium chloride

(reagent grade, Aldrich Chemicals Ltd, UK.) used as a catalyst. Sulphur dyed fabric

was padded with a wet pick-up of 70-80% in a solution containing 120 g/L of Fixapret

CP and 24g/L of magnesium chloride. The fabric was then dried at 100oC for 1 min and

cured at 150oC for 4 minutes.

3.3.3. Choline chloride

Aftertreatments with cationic reactant, choline chloride, obtained from Aldrich

Chemicals Limited were carried out by pad dry cure application. Choline chloride was

applied individually and also added in different concentrations to the liquor containing

Fixapret CP. The application method is the same as described above in section 3.3.2.


91

3.3.4. Cationic fixatives

3.3.4.1. Solfix E

Solfix E was supplied by Solophenyl, CIBA Geigy Company as an aqueous solution. It

is a polyaminochlorohydrin quaternary ammonium polymer with epoxide functionality

that can react with cellulose via ether formation in the presence of alkalis [2, 3]. It is

modified polyamine derivative, fibre-reactive, wet fastness improver and contains no

formaldehyde [4].

Sulphur dyed fabric was introduced into liquor containing 6% omf Solfix E at 20oC. The

L:R (liquor to goods ratio) was 10:1 and Mathis Labomat was used for the exhaust

application of the finish liquor. The liquor temperature was increased to 40oC at a

gradient of 4oC/minute, at this point 2mL/L of caustic soda was added to maintain an

alkaline pH and the process further continued for 30 minutes. The sample was then

rinsed in warm and cold water and finally air dried. The application method is shown in

Figure 3.1.

A=dyed fabric, 6% omf Solfix E

B= 2mL/L of caustic soda, pH 8-9

Figure 3.1 Application of Solfix E

3.3.4.2. Tinofix ECO

The product Tinofix ECO (Solophenyl, CIBA Geigy Company, Switzerland) is based

on polyethylene polyamine and contains no formaldehyde [5].

Sulphur dyed fabric was treated with liquor containing 3% omf Tinofix ECO in Mathis

Labomat with a L:R (liquor to goods ratio) of 10:1. The pH of the liquor was not

A

30 min

25oC

40oC

4oC/min

B

20oC


92

adjusted with an acid or alkali as it was already in the range of 6-7 (pH range prescribed

by the manufacturer). The fabric was treated at 40oC for 30 minutes, rinsed in cold

water and finally air dried. The method of application is represented in Figure 3.2.

A=dyed fabric, 3% omf Tinofix ECO, pH 6-7

Figure 3.2 Application of Tinofix ECO

3.3.4.3. Indosol E-50

The cationic fixing agent Indosol E-50 (Clariant) is intended for exhaust application.

With this fixation alternative the wet fastness properties of direct dyes, especially

domestic laundering up to 50oC, can be improved [6].

Sulphur dyed fabric was introduced into a finishing bath containing 4% omf Indosol

E-50 and 5 g/L Glauber’s salt (this counteracts any dye migration out of the fibre during

treatment). The L:R (liquor to goods ratio) was 10:1 and Mathis Labomat was used for

the exhaust application of the finish. The temperature of the liquor was increased to

60oC at a gradient of 4

oC/minute and maintained at this temperature for 20 minutes. The

sample was then rinsed in warm and cold water and finally air dried. The application

procedure is shown in Figure 3.3.

A=dyed fabric, 4% omf Indosol E-50 + 5 g/L Glauber’s salt, pH 6-7

Figure 3.3 Application of Indosol E-50

A

30 min

25oC

40oC

4oC/min

20oC

A

20 min

25oC

60oC

4oC/min

20oC


93

3.4. Experimental approach

3.4.1. Dyeing with sodium sulphide

All dyeings were carried out in sealed stainless steel dye pots of 1000 cm3 capacity,

housed in Mathis Labomat laboratory dyeing machine. The dyeing of cotton fabric with

conventional reducing agent is carried out with 5% omf dye, 5 g/L sodium sulphide, 5

g/L sodium carbonate and 15 g/L sodium chloride with liquor to goods ratio of 10:1.

The fabric is first heated to a temperature of 40-50oC in the presence of half of the

quantities of water, sodium sulphide and soda ash. The liquor is kept at this temperature

for 5 min and then the dyestuff and balance of water, sodium sulphide and soda ash are

added. The dye bath is further kept for 10 minutes at the same temperature and then salt

is added. The temperature is now increased to 90oC at a gradient of 2

oC/min then treated

for 30 minutes. The solution is then cooled to 50oC (Figure 3.4). The fabric is then

washed thoroughly with cold water to remove any unfixed surface dye. The fabric is

then oxidised with 5 g/L hydrogen peroxide and 1 g/L soda ash at 40-45oC for 15

minutes. It is then finally soaped with 1g/L of non-ionic detergent (ALD-K by Clariant)

at the boil for 20 minutes and then rinsed with cold and warm water. The L:R (liquor to

goods ratio) employed for oxidation and soaping was 10:1. The same method is

employed for all colours.

A=fabric, half quantities of water, sodium sulphide and soda ash

B=dyestuff and balance of water, sodium sulphide and soda ash

C=salt

Figure 3.4 Sulphur dyeing method for cotton using sodium sulphide

A

50o

10 min 5 min

90o

30 min

50o

C

B C

2oC/min

2oC/min


94

3.4.2. Dyeing with Diresul Reducing agent D

Dyeing of cotton with Diresul Reducing agent D is carried out by the method prescribed

by Clariant. The cotton fabric is introduced into a dye bath containing 5% omf dye, 25

g/L sodium chloride, 13 mL/L of sodium hydroxide (67oTw), 9 g/L Diresul Reducing

agent D with liquor to goods ratio of 10:1. The dyebath is raised to either 98oC or 70

oC

at a gradient of 4oC/min and maintained at the boil for 60 minutes. Dyeing of black is

carried out at 98oC while that of other colours at 70

oC (Figure 3.5). The post washing,

oxidation and soaping method is the same as that mentioned in section 3.4.1.

A= fabric, dyestuff, sodium chloride, sodium hydroxide, Diresul Reducing agent D and water

Figure 3.5 Sulphur dyeing method for cotton using Diresul Reducing agent D

3.5. Physical testing

Several wash fastness tests were conducted to assess the suitability of the

aftertreatments to achieve the maximum resistance against fading of the dyes. The

cotton fabric was exposed to domestic laundering, light fastness and crocking fastness

procedures which were executed in accordance to respective British standards

methodologies.

3.5.1. Colour fastness to domestic laundering

A common quality parameter of a sulphur dyed fabric from the consumer’s perspective

is colour fastness to washing. The tests enable to estimate the loss of colour and shade

change of the treated sample as well as any possible staining of other garments that may

A 60 min 50

oC

70/98oC

4oC/min


95

be washed with it. These tests are used to determine the performance of any dyed or

printed textile product to the common washing process using a detergent and additives.

The dyed fabric was exposed to ISO 1O5 CO6 standard washing procedures and the

more recently developed ISO 1O5 CO9 resembling the modern washing powders

formulation.

3.5.1.1. ISO 1O5-CO6

The laundering test was performed according to the methodologies employed in BS EN

ISO 1O5 CO6:2010. A specimen was cut in 10cmx4cm size and attached to a SDC

multi-fibre strip. The composite specimen and multi-fibre were placed in the wash

wheel pot containing wash liquor, with additives. The liquor consisted of 4 g/L ECE

phosphate based detergent and 1 g/L sodium perborate tetrahydrate, adjusted to pH 10.5

with sodium carbonate. The wash wheel was then run for 30 minutes at 60oC. The

specimens were then removed, rinsed and dried in still air. The same test was also

repeated without perborate. The effect of laundering on single and triplicate wash cycles

was evaluated. The triplicate wash cycles were executed in a similar way, as mentioned

above, just after each wash the sample along with a multi-fibre swatch was rinsed with

water and added into fresh liquor for the next cycle.

3.5.1.2. ISO 1O5-CO9

The dyed fabric was also washed in accordance with ISO 1O5 CO9 laundering regime.

The dyed fabric sample measuring 10cmx5cm was weighed and liquor:goods ratio of

1:100 was employed. It was introduced in a liquor containing 10 g/L ECE non-

phosphate detergent, 1.8 g/L TAED (tetraacetylethylenediamine) low temperature

bleach activator, with or without 12 g/L sodium perborate, at 25oC and raising the

temperature to 60oC at 2

oC/minute and maintaining at 60

oC for 30 minutes. The

specimens were then removed, rinsed and air dried.


96

3.5.1.3. Wash fastness sample evaluation

The colorimetric data of the dyed and aftertreated cotton fabrics were measured using a

Datacolor Spectroflash 600 spectrophotometer, with a 10o standard observer and D65

illuminant, and were the average of four measurements.

In order to evaluate the washdown of dyed fabrics, the samples were analysed using

colour strength (K/S) and grey scale rating (1-5, 1 being the worst and 5 best). The K/S

value indicated the shade depth on the fabric, the higher the K/S value, the deeper the

shade. The colour strength was evaluated using the Kubelka–Munk equation

(represented in Scheme 3.1).

(K

S)

λ=

(1 − Rλ )2

2Rλ

Scheme 3.1

Where K is the absorption coefficient, S is the scatter coefficient, R is the reflectance

expressed as a fractional value at wavelength of maximum absorption λ.

The % colour loss of the untreated and aftertreated dyed fabrics after laundering were

evaluated with the following equation (Scheme 3.2):

% colour loss =

K

S before washing −

K

S after washing

K

S before washing

X 100

Scheme 3.2

3.5.2. Colour fastness to crocking (ISO 1O5- X12:2002)

This test is designed to determine the resistance of the colour of textiles of all kinds to

rubbing off and staining other materials. It is applicable to textile made from all fibres in

the form of yarn or fabric whether dyed, printed or otherwise coloured.

In this study, rub fastness of the cotton fabric was performed in accordance with ISO

105-X12: 2002 standard. The crockmeter was used as the rubbing fastness tester. Prior


97

to testing, the crock squares and specimens were conditioned for at least 24 hours in an

atmosphere of 21±1oC and 65±2% RH. The specimen was then placed on the base of the

crockmeter resting flat and the crock square measuring 5cmx5cm covered the end of the

finger (16±0.1 mm). For the wet rub fastness, the crock squares need to be wetted at a

wet pick-up about 95-100%. The finger was lowered onto the test specimen and moved

10 complete turns in 10 seconds. The white crock squares were evaluated in comparison

to the grey scale for staining.

3.5.3. Colour fastness to light (ISO 1O5- BO2)

This method is intended for determining the resistance of the colour of textiles of all

kinds and in all forms to the action of an artificial light source representative of natural

daylight (D65).

A specimen of textiles was exposed to artificial light along with Blue Wool references

(8 reference samples). The colour fastness was assessed by comparing the change in

colour of the specimen with that of the references used. The specimen to be tested and

blue wool references were of equal size (approximately 4.5cmx1cm) and shape in order

to avoid errors in the assessment due to overrating the visual contrast between exposed

and unexposed parts. The samples and references were being pasted on the cards and

each exposed and unexposed area was not less than 10mmx8mm. The specimens and

references were arranged with a cover covering one-quarter of the total length of each

specimen and reference. They were exposed under the light and the effect of light was

followed by lifting the cover periodically and inspecting the references. When a change

in reference 3 was perceived equal to grey scale grade 4-5, the specimens were

inspected and their light fastness rated by comparing any change that occurred with the

changes that occurred in references 1, 2 and 3. The cover was again replaced in exactly

the same position and samples exposed until a change in reference 4 was perceived

equal to grey scale 4-5. At this point an additional cover was placed which overlapped

the first cover, the samples were further exposed until a change in reference 6 was

perceived equal to grey scale 4-5. All covers on references and specimens were removed

and changes in the specimens were compared with the relevant changes in the

references under suitable illumination.


98

3.5.4. Tensile properties of fabrics BS EN ISO 13934/1 1999

The protocol for tensile testing was adapted from BS EN ISO 13934/1:1999 for textile

strips. Tensile strength and elongation tests were performed in an Instron 3345

mechanical testing machine, using a 1 kN load cell. Test samples were cut into

300mm×50mm strips, with the warp and weft along the length. The crosshead rate used

in the test was 200 mm/min. Five replicates were analysed for each sample, and the

average values were calculated.

3.6. Equipment

3.6.1. Padder

A horizontal, vertical padder type from Werner Mathis AG at Oberhasli, Switzerland

was used for applying finishes to cotton fabric. The air pressure of the padder was set at

approximately 3 atms. for controlling fabric wet pick up at 70-80%. The padding fabric

speed was set for 1.2 m/min.

3.6.2. Tenter

A Werner Mathis AG lab dryer, at Oberhasli Switzerland was used for drying and

curing fabric samples. The oven operates by hot air circulation.

3.6.3. Dyeing machine

Mathis Labomat dyeing machine was used to dye the fabric via exhaust method.


99

3.7. Analytical testing

3.7.1. Scanning electron microscopy (SEM)

The technique of scanning electron microscopy (SEM) was employed to examine and

obtain the images of surface morphology of unlaundered/laundered, untreated and

aftertreated sulphur dyed cotton samples. Microscopy is the study of the fine structure

and morphology of the object with the help of a microscope, for which resolution and

contrast are the key factors to be considered. In scanning imaging microscopes some

local property of the specimen is analysed with the aid of passing a small probe over the

surface of the sample and generating some useful signals. The probe may be a sharp

point or a narrow beam of either electrons or photons while the types of the signals and

detectors are diverse [7-9].

In SEM, probe current means an electron beam focused on a specimen. When the

specimen is under analysis, probe current emits electrons containing information on the

specimen such as secondary electrons and backscattered electrons. The size of probe

current determines the number of secondary electrons and backscattered electrons

emitted [10].

The common feature of all the instruments is the detector output signal that varies with

time. It is displayed like a television image. The intensity of each pixel in the image is

controlled by the signals from the microscope. Linear size of the image divided by size

of the region scanned on the specimen (the field) is called the magnification. It can

easily be altered without affecting the other image conditions. Scanning in SEM is

digitally controlled so the position of the probe corresponds to the memory location as

shown Figure 3.6 [7-9].

3.7.1.1. SEM measurements

The observation of the surface topography of untreated and aftertreated sulphur dyed

cotton fabrics was made using a Philips XL30 Field Emission SEM. The samples were

mounted on a 2.1 cm Al specimen stub using double-sided conductive tape (silicon


100

release paper). A conductive silver paint was applied to the outer parameters of the

samples. The samples were then coated with platinum in a Gatan precision etching and

coating system (PECS), the samples were completely dried before loading into SEM

chamber.

The scanning electron microscope was operated at 6 kV accelerating voltage and 2 spot

size. In order to analyse the macroscopic and microscopic structure of the samples, two

different magnifications were used (1000x and 5000x).

Figure 3.6 Schematic of image formation by SEM from [7]

3.7.2. Fourier transform infrared spectroscopy (FTIR)

One of the most important analytical techniques available for the use of today’s

preparative as well as analytical chemist is undoubtedly infrared spectroscopy [11]. One

of the advantages of infrared spectroscopy is that it can be used to study virtually any

sample in any state whether it’s liquid, solution, paste, powder, film, gas or a surface. A

number of sampling techniques are judiciously selected to analyse any of these samples

[12]. Therefore, infrared spectroscopy provides a variety of possibilities for sample


101

measurement and substance preparation [11]. In spite of the availability of various

spectrometers, the popularity of Fourier transform infrared spectroscopy (FTIR)

spectrometers is increasing due to speed, accuracy and sensitivity they offer [13].

FTIR spectroscopy includes the absorption, emission, reflection, or photo acoustic

spectrum obtained by Fourier transform of an optical interferogram [13]. This technique

is based on the vibrations of the atoms of a molecule. When the radiations are passed

through a sample, an infrared spectrum is generated and the fraction of incident

radiation absorbed at a particular energy can be determined. The appearance of any peak

at certain energy in the absorption spectrum corresponds to the frequency of a vibration

of a part of a sample molecule [12].

Fourier spectroscopy is a general term that refers to the analysis of any varying signal

into its constituent frequency components. Fourier transforms can be applied to a variety

of spectroscopies including Fourier transform infrared (FTIR), nuclear magnetic

resonance (NMR), and electron spin resonance (ESR) spectroscopy [13].

3.7.2.1. FTIR measurements

FTIR-ATR (Attenuated total reflectance) requires no special sample preparation. ATR

spectra of untreated and aftertreated samples were obtained by using a Nicolet 5700

FTIR for an angle of incidence of 45o with a Diamond-ATR smart orbit accessory (IR

penetration 2 µm) to provide information about the surface of the sulphur dyed cotton

samples. Before collecting the sample spectrum, the background spectrum was obtained.

All FTIR spectra were collected at a spectrum resolution of 4 cm-1

, with 64 co-added

scans over the range from 4000 to 500 cm-1

. All spectrum manipulations were carried

out using the OMNIC software (Nicolet).

3.7.3. X-Ray photoelectron spectroscopy (XPS)

X-Ray photoelectron spectroscopy (XPS) is one of the common and most powerful

techniques utilised for surface chemical analysis. It is also known as electron

spectroscopy for chemical analysis (ESCA) [13].


102

The working principle of XPS is based on the photoelectric effect in which a core-level

electron is excited and ejected from the analyte. This occurs when the binding energy

(EB) of a core level electron of the analyte is exceeded by the energy (hv) of an

impinging soft X-Ray photon. An electron spectrometer, whose work function is Φ, is

used to measure the kinetic energies of the ejected photoelectrons, EK. Raising

conservation of energy, the following relationship is obtained (Scheme 3.3):

EB= hv−Ek − Φ

Scheme 3.3 [13]

The binding energy of the photoelectron is characteristic of the orbital from which the

photoelectron originates and it also depends on the final state configuration after

photoemission. The initial and final state configurations are represented in Figure 3.7

[13].

Figure 3.7 Initial (left) and final (right) states in the photoelectric effect in XPS

from [13]

A significant amount of information can be obtained by studying the ejected

photoelectrons. XPS can be utilised for the qualitative elemental identification for the

entire periodic table apart from H and He. Survey scans or low resolution spectra over a

broad binding energy range can be utilised for simple identification of the elements.

Likewise, in binding energy regions of interest, acquisition of high resolution spectra

followed by peak fitting can provide information concerning the chemical (oxidation)


103

state or region of the sample. Therefore, angle-resolved XPS and XPS imaging provide

the ability to learn about spatial atomic distribution within the sample and to understand

the surface and bulk chemistry of the sample [13].

3.7.3.1. XPS measurements

XPS analysis was performed using a Kratos Axis system spectrometer. The fabric

samples (5mmx5mm) were cut from the centre of the specimen and attached to the

sample holder using a double sided tape of the same size. The samples were irradiated

with monochromatic Al Kα X-rays (1486.6 eV) with a power of 150 W. The wide scan

spectra were recorded with pass energy of 160 eV from which the surface composition

(C, O, S and N) was determined. High resolution Carbon (1s), Nitrogen (1s) and

Sulphur (2p) spectra were recorded with pass energy of 40 eV and the binding energy

(BE) values were calculated relative to Carbon (1s) photoelectron peak at 285.0 eV.

Charge compensation for the samples was achieved using a 4-7 eV beam at a flood

current of approximately 0.1 mA, with an electrically ground 90% transmission nickel

mesh screen. All samples were analysed in duplicate and data analysed using the CASA

XPS software [14].

3.7.4. Elemental bulk analysis

Elemental analysis for the carbon, hydrogen, nitrogen and sulphur were achieved by

using the Flash 2000 organic elemental analyser made by Thermo Scientific.

3.8. References

[1] Tanatex Chemicals product datasheet. Tanatex Chemicals BV, Netherlands.

[2] Kamel M, El Zawahry M, Ahmed N and Abdelghaffar F. Ultrasonic dyeing of

cationized cotton fabric with natural dye. Part 1: Cationization of cotton using Solfix E.

Ultrasonics Sonochemistry. 2009;16(2):243-9.


104

[3] Nassar S. Cationic pretreatment of cotton fabric for anionic dye and pigment printing

with better fastness properties. Coloration Technology. 2002;118(3):115-20.

[4] Solfix E product datasheet. Solophenyl, CIBA Geigy Company.

[5] Tinofix ECO product datasheet. Solophenyl, CIBA Geigy Company.

[6] Indosol E-50 product datasheet. Clariant International Limited.

[7] Sawyer LC, Grubb DT and Meyers GF. Specimen Preparation Methods. Polymer

Microscopy: Springer New York; 2008. p.130-247.

[8] Goldstein JI, Newbury DE, Echlin P, Joy DC, Fiori C and Lifshin E. Scanning

electron microscopy and X-Ray microanalysis. A text for biologists, materials scientists,

and geologists: Plenum Publishing Corporation, 1981.

[9] Echlin P. Handbook of sample preparation for Scanning electron microscopy and X-

Ray microanalysis: Springer, 2009.

[10] Sun-Jong L and Chan-Hong L. Analysis of probe current in scanning electron

microscopy. International Conference on Control, Automation and Systems 2008.

p.1200-3.

[11] Günzler H and Gremlich HU. IR Spectroscopy: An Introduction: Wiley, 2002.

[12] Stuart B, George B and Mclntyre P. Modern infrared spectroscopy: Wiley India

Pvt. Limited, 2008.

[13] Vij DR. Handbook of applied solid state spectroscopy: Springer, 2007.

[14] Walton J, Wincott P, Fairley N and Carrick A. Peak fitting with CasaXPS: A Casa

pocket book. 2010.

Investigation into the effects of aftertreatments with Bayprotect Cl on the fastness properties of

sulphur dyed cotton fabric

105

4. Investigation into the effects of aftertreatments with Bayprotect

Cl on the fastness properties of sulphur dyed cotton fabric

4.1. Introduction

The word ‘tannin’ is derived from the French word ‘tanin’ which means tanning

substance and is used for a range of natural polyphenols [1]. The word is used to

describe the process of transforming animal hides into leather by making use of plant

extracts from different parts of various plant species [2]. Tannins are naturally occurring

water soluble polyphenolic compounds of high molecular weight consisting of phenolic

hydroxyl groups which enable them to crosslink with proteins and other

macromolecules. Tannins include a large class of organic substances having different

chemical compositions and reactions [2, 3].

Tannins are present in a number of families of higher plants such as in chestnut,

oakwood and pine. Tannins are present in a number of trees and shrubs. Various parts of

the plant consist of high concentrations of tannin such as bark, wood, fruits, leaves,

roots and seed [4]. For example, they can be extracted from black mimosa bark,

quebracho wood, oak bark, chestnut wood, mangrove wood, bark of several species of

pines and firs [5].

Tannic acid and tannins are polyphenolic compounds having the capability of building

complex chemical structures [6]. From a biological point of view, tannins are the

polyphenols that belong to a class of secondary metabolites found in many higher plants

having molecular weights between 800 and 3000 Dalton (gm/mol). They can be divided

into three major groups of compounds, the commonly available condensed tannins

which are formed by proanthocyanidins, and the hydrolysable tannins, which are

comparatively less abundant and are subdivided into gallotannins and ellagitannins [7].

The condensed tannins are oligomeric while the hydrolysable tannins are reported to be

non-polymeric. As a result of the suspected lack of polymeric nature of hydrolysable

tannins, they can form complex structures and they have covalently and intimately

linked carbohydrates with their phenolic moieties, which are considered to be the part of

the tannin [5].



106

The polyphenolic part in the molecules of the hydrolysable tannins is represented by

gallic acid and hexahydroxydephinic acid (HHDP) as shown in Figure 4.1. They

hydrolyse and condense in the presence of acid and enzyme. Those having the HDPP

group are called ellagitannins as they produce ellagic acid upon hydrolysis while those

having only the galloyl groups are known as gallotannins [8].

A large quantity of proanthocyanidins (condensed tannins), a group of phenolic

polymers, is distributed within woody growth. They are the most abundantly available

polyphenols in plants after lignins. They are present in leaves, fruit woods, roots or bark

and play a vital role in various nutritional and ecological applications [8].

Hydrolysable tannins are best suited to offer a high degree of activity, high purity and a

low influence on colour. Moreover the unique tannic acid chemistry provides a number

of unusual properties combined in one molecule:

Strong metal complexing properties;

Complex formation with proteins, alkaloids and certain polysaccharides;

Strong affinity towards polyamides;

Strong anti-oxidizing properties [7].

Tannins form the following types of bonds with proteins (such as wool and silk):

1. The phenolic hydroxyl group of tannin forms a hydrogen bond with both the

free amino and amido groups of proteins;

2. Ionic bonds between cationic group on protein and suitable charged anionic

group on tannin;

3. Covalent bonds produced as a result of an interaction of any quinine or semi

quinone groups in the tannins and any other suitable reactive groups in the

protein or other polymer [3].

http://www.natural-specialities.com/natural-specialities/en/8452-tannic-acid.html



107

Figure 4.1 Structures of tannin components (a) gallic acid (b)

hexahydroxydiphenic acid, reproduced from [4]

Cotton lacks affinity for natural dyes, however, these dyes can be fixed on cotton with

the help of natural or metallic mordants. The natural mordant also acts as a primary

mordant for metallic salts where treatment of cotton with tannic acid can absorb all

kinds of metallic mordants. Tannic acid is a common mordant used in the dyeing

process for cellulose fibres such as cotton especially when using natural dyes for dyeing,

since it is used in pretreatment or aftertreatment to improve dye fixation and wash

fastness properties. In this way, use of mordants facilitates the application of natural

dyes, acid and basic dyes on cotton [3].

Treatment of cotton fabrics with tannic acid is presumed to introduce additional

hydroxyl and carboxyl groups on the fibre matrix. The adsorption of tannic acid on

cotton fibres depend essentially on physical adsorption due to the formation of hydrogen

bonding between the aromatic hydroxyl groups of tannic acid and carboxylic acid

groups of cotton cellulose.



108

4.2. Application procedures for Bayprotect Cl on polyamide fabric

According to the manufacturers (Tanatex Chemicals), Bayprotect Cl can be applied by

exhaust or continuous (pad-steam) processes in a separate step after dyeing. The pH

value of the application liquor should not go above 3.5, in order to achieve the best

results. However, the temperature control as well as the qualities used is dependent on

the type of fibre and fibre processing. It cannot be applied in a one-bath process with

metal-complex dyes. In case of continuous application, the product is recommended to

be applied by a dosing method, rather than padding as it tends to cause frosting [9].

The general exhaust application procedure recommended for polyamide fabric is as

below:

1. 3-6% Bayprotect Cl on PA 6,6;

2. 4-9% Bayprotect Cl on PA 6;

3. pH<3.5 with citric acid;

4. 20 minutes at 65-98oC;

5. Rinse warm and cold.

4.3. Effects of application methods, presence/absence of electrolyte and varying time

Some initial experiments were performed with varying time and addition of Glauber’s

salt to confirm the anti-oxidation properties of Bayprotect Cl on sulphur dyed cotton

fabric. The fabric was dyed with CI Leuco Sulphur Black 1 dye using Diresul Reducing

agent D and four replicates were taken for each sample.

The exhaust and continuous methods of post treatment were explored to examine the

influence of the said treatment on sulphur dyed cotton fabric. As recommended by the

manufacturer, the maximum concentration of 10% omf was selected with the

application conditions (AC) outlined in Table 4.1. The colorimetric data of various

application conditions and their effects on different washing conditions (WC) are

represented in Table 4.2 and Figure 4.3, respectively.



109

Table 4.1 Composition and application parameters for aftertreatments with

Bayprotect Cl on CI Leuco Sulphur Black 1 dyed cotton

EXHAUST APPLICATION

Application

conditions Compositions

L:R/

Pick-

up

Temperature Time

pH

Bayprotect Cl sodium sulphate

AC 1 10% omf - 10:1 98oC 20

minutes <3.5

AC 2 10% omf 100 g/L 10:1 98oC 20

minutes <3.5

AC 3 10% omf - 10:1 98oC 60

minutes <3.5

AC 4 10% omf 100 g/L 10:1 98oC 60

minutes <3.5

CONTINUOUS APPLICATION (PAD-STEAM)

AC 5 100 g/L - 500% 102 oC 3 minutes <3.5 AC 6 100 g/L 100 g/L 500% 102 oC 3 minutes <3.5

20/60 minutes

A= dyed fabric, 10% omf Bayprotect Cl, x gm/L sodium sulphate, citric acid to pH<3.5

Figure 4.2 Aftertreatments with Bayprotect Cl (exhaust application)

4.3.1. Exhaust method of application

CI Leuco Sulphur Black 1 dyed fabrics (reduced with Diresul RAD) were treated with

liquor containing 10% omf Bayprotect Cl and a pH <3.5 was maintained with citric

acid. In order to determine the effect of electrolyte on the exhaustion properties of

anionic tannin, 100 g/L sodium sulphate was added. The effects of time were also

evaluated by treating the fabrics for two different time intervals that are 20 and 60

minutes. The samples along with the liquor were treated at 98oC for either 20/60

minutes with liquor to goods ratio of 10:1. The exhaust application method is shown in

Figure 4.2.

98oC

98oC

98oC

98oC

20oC

20oC

20oC

20oC

4oC/min

4oC/min

25oC

25oC

25oC

25oC

A

A



110

4.3.2. Continuous method of application

Bayprotect Cl was applied with a dosing method, as the pad application was not

recommended by the manufacturer as it tends to cause frosting. A solution containing

100 g/L Bayprotect Cl (with and without sodium sulphate), maintained at a pH <3.5

with citric acid, was dosed onto the samples (CI Leuco Sulphur Black 1 dyed fabrics

reduced with Diresul RAD) to achieve a 500% wet pick-up. It was then treated with

steam for 3 minutes at 102oC.

All aftertreated samples were rinsed in warm and cold water and finally air dried.


aftertreated with Bayprotect Cl following different washing regimes

Washing L* a* b* c* h K/S

% Colour

loss GS Rating

Treatment

Untreated 27.5 -0.7 -4.2 4.3 260.5 9.3

WF 1 29.0 -1.3 -4.6 4.8 254.4 8.6 8% 4

WF 2 28.1 -1.4 -4.6 4.8 253.3 9.2 1% 4/5

WF 3 30.6 -1.5 -4.7 4.9 252.8 7.7 17% 3

WF 4 29.0 -1.4 -4.6 4.8 253.1 8.6 8% 4

WF 5 40.7 -1.7 -4.0 4.4 24.8 3.7 60% 1

WF 6 28.9 -1.2 -4.5 4.7 255.4 8.6 8% 4

AC 1 10% omf Bayprotect Cl (98oC, 20 minutes)

Aftertreated 27.2 -0.7 -4.1 4.2 260.2 9.6

WF 1 28.7 -1.3 -4.6 4.8 254.9 8.8 8% 4

WF 2 28.3 -1.2 -4.6 4.7 255.0 9.0 6% 4/5

WF 3 29.8 -1.4 -4.7 4.9 253.3 8.1 16% 3/4

WF 4 28.4 -1.2 -4.5 4.6 254.6 9.0 6% 4

WF 5 28.3 -1.1 -4.6 4.7 256.6 4.1 57% 1

WF 6 39.4 -1.5 -4.3 4.5 250.9 9.0 6% 4/5

AC 2 10% omf Bayprotect Cl + 100 g/L sodium sulphate (98oC, 20 minutes)

Aftertreated 27.9 -0.7 -4.0 4.1 259.9 9.0

WF 1 28.4 -1.2 -4.4 4.6 254.2 8.9 1% 4/5

WF 2 28.2 -1.3 -4.2 4.4 253.4 9.0 0% 4/5

WF 3 29.5 -1.4 -4.6 4.8 252.7 8.3 8% 4

WF 4 28.6 -1.3 -4.4 4.6 254.2 8.8 2% 4/5

WF 5 40.3 -1.7 -4.1 4.5 147.0 3.9 57% 1

WF 6 28.2 -1.2 -4.3 4.5 254.1 9.1 -1% 4/5

AC 3 10% omf Bayprotect Cl (98oC, 60 minutes)

Aftertreated 28.3 -0.7 -3.6 3.7 258.7 8.7

WF 1 29.1 -1.3 -4.2 4.4 252.9 8.4 3% 4/5

WF 2 26.4 -1.1 -3.9 4.0 253.5 10.3 -18% 4

WF 3 31.3 -1.6 -4.5 4.7 250.9 7.3 16% 3

WF 4 27.5 -1.2 -4.1 4.3 253.0 9.5 -9% 4/5

WF 5 39.4 -1.5 -3.8 4.1 247.6 4.1 53% 1/2

WF 6 28.8 -1.1 -4.1 4.3 54.6 8.6 1% 4/5



111

AC 4 10% omf Bayprotect Cl + 100g/L sodium sulphate (98oC, 60 minutes)

Aftertreated 28.5 -0.7 -4.0 4.0 259.6 8.6

WF 1 28.5 -1.3 -4.4 4.6 253.7 8.9 -3% 4/5

WF 2 28.5 -1.2 -4.2 4.4 253.9 8.8 -2% 4/5

WF 3 29.4 -1.4 -4.5 4.7 252.5 8.4 2% 4/5

WF 4 27.8 -1.2 -4.2 4.3 254.2 9.3 -8% 4/5

WF 5 39.0 -1.7 -3.8 4.2 246.4 4.2 51% 1/2

WF 6 28.3 -1.3 -4.2 4.4 253.5 9.0 -5% 4/5

AC 5 100 gm/L Bayprotect Cl (102oC, 3 minutes)

Aftertreated 28.1 -0.8 -4.0 4.1 259.1 8.9

WF 1 27.9 -1.2 -4.6 4.8 254.8 9.3 -4% 4/5

WF 2 28.2 -1.4 -4.6 4.8 253.3 9.1 -2% 4/5

WF 3 28.5 -1.4 -4.8 5.0 254.3 9.0 -1% 4/5

WF 4 27.9 -1.3 -4.5 4.7 254.0 9.3 -4% 4/5

WF 5 40.8 -1.8 -4.1 4.5 246.5 3.7 58% 1

WF 6 29.2 -1.4 -4.5 4.7 252.6 8.5 4% 4

AC 6 100 gm/L Bayprotect Cl + 100g/L sodium sulphate (102oC, 3 minutes)

Aftertreated 29.0 -0.8 -4.0 4.0 259.0 8.3

WF 1 28.1 -1.3 -4.6 4.8 253.7 9.2 -11% 4/5

WF 2 27.9 -1.3 -4.5 4.7 254.3 9.3 -12% 4

WF 3 30.1 -1.4 -4.7 4.9 253.3 8.0 4% 4

WF 4 28.0 -1.3 -4.5 4.7 253.9 9.2 -11% 4

WF 5 39.5 -1.8 -3.9 4.3 2245.4 4.1 51% 1/2

WF 6 28.2 -1.3 -4.5 4.7 253.7 9.1 -10% 4/5

Where:

WF 1: ISO IO5 CO6 (with perborate) single wash

WF 2: ISO IO5 CO6 (without perborate) single wash

WF 3: ISO IO5 CO6 (with perborate) triplicate wash

WF 4: ISO IO5 CO6 (without perborate) triplicate wash


WF 6: ISO IO5 CO9 (without perborate) single wash



112

Figure 4.3 Effect of aftertreatments with Bayprotect Cl on wash fastness of

CI Leuco Sulphur Black 1 dyed cotton fabric

4.3.3. Results and discussion

The colorimetric data, colour strength and Grey scale rating for the untreated and

aftertreated dyed samples are shown in Table 4.2. Analysing the CIE L*, a*, b*, C*, and

ho coordinates of the treated samples illustrates that aftertreatment with tannin slightly

affected the hue and chroma of the dyeings. The change in hue was due to the inherent

colour of tannin which is slightly yellowish brown in colour.

The untreated sample when exposed to laundering regimes of ISO 1O5 CO6 and CO9

(with perborate) undergoes a considerable colour loss, especially in the case of CO9

(Figure 4.3). The grey scale (GS) rating varied from 4 to 3, from a single to triplicate

wash cycles for CO6, while it was 1 for CO9. This is because the washing liquor for

CO9 contains a significant amount of perborate that is 12 g/L while CO6 contains 1 g/L

of perborate. The samples were also exposed to the same washing tests in the absence of

sodium perborate to compare the effect of bleach on laundering conditions. It can be

seen from the GS rating as well as the colour difference highlighted the relatively small

impact of washings done without bleaching agent (sodium perborate).

8% 8%

1% 3%

-3% -4%

-11%

17% 16%

8%

16%

2%

-1%

4%

60% 57% 57%

53% 51%

58%

51%

-20%

-10%

0%

10%

20%

30%

40%

50%

60%

70%

Non-Treated AC1 AC2 AC3 AC4 AC5 AC6

% C

olo

ur

loss

ISO 1O5 CO6 with perboratex1 ISO 1O5 CO6 with perboratex3 ISO 1O5 CO9 with perborate



113

From the data it is apparent that the samples treated with sodium sulphate showed better

protecting effect of Bayprotect Cl than those without sodium sulphate as observed in

AC1 and AC2. It can be postulated that Na2SO4 would have dissociated into Na+ and

SO4−

ions in water. The negatively charged tannin ions might have been attracted into

the cellulosic fabric which was covered with positively charged sodium ions thus

facilitating the exhaustion of tannin into the fabric.

Comparison of AC 1 and AC 2, which were given the same conditions (treated at boil

for 20 minutes) except for the addition of sodium sulphate, shows that in the presence of

sodium sulphate (AC 2) there is less fading of the dyed fabric for the CO6 treatments for

both single and triplicate wash cycles. However, there is not a substantial change in case

of CO9 if the GS rating is considered, as it is “1” for both. The colour strength of the

dyed and aftertreated fabric for AC 1 is slightly increased while that for AC 2 was

reduced as compared to untreated sample. The reason for increased colour strength

could possibly be slight fibrillation of the surface, resulting in an exposure of the sub-

surface of the dyed fabric with higher content of the dye. However, the reduced colour

strength for AC 2 may possibly be due to the removal of surface dye with the finishing

liquor containing Bayprotect Cl and sodium sulphate. There is no considerable

difference in hue or chroma of the fabrics under these application conditions.

Examination of the AC 3 and AC 4 samples, for which the application duration of

aftertreatment has been increased from 20 to 60 minutes while the rest of the conditions

remained the same, it can be seen that AC 4 showed less colour loss than AC 3.

Nevertheless, when compared to AC 2 there was a slight improvement in CO9

performance which increased to a GS rating of 1-2. On the other hand, the extended

treatment had an influence on the hue and chroma of the treated sample which can be

viewed from the decreased c and h values.

Examination of the continuous pad-steam AC 5 and AC 6 samples shows that AC 5

seems to be more effective when considering CO6 treatment, as the GS rating is 4-5

even after 3 wash cycles but AC 6 showed an increased protective effect in terms of WF

5 giving a slight increase to GS rating from 1 to 1-2. However, AC 5 offers almost the

same reduction in percentage colour loss as AC 2 for WF 5. Further, slight changes in

hue and chroma of the aftertreated samples could be observed compared to the untreated

dyed fabric. As seen in Table 4.2, AC 5 and AC 6 samples tend to be greener and also



114

portray reduced chroma when compared to untreated sample, hence the use of exhaust

method of application was preferred over continuous method.

It can be observed that in some cases, the colour strength of the aftertreated samples is

increased after laundering resulting in negative colour loss. One reason for this

observation could possibly be the coating of aftertreated sample with the finishing agent

resulting in reduced colour strength. This aftertreated sample when exposed to

laundering caused the removal of the finish and leaving the fabric with increased colour

strength. The reason for increased colour strength after laundering could conceivably be

slight fibrillation of the surface, resulting in an exposure of the sub-surface of the dyed

and aftertreated fabric with higher content of the dye.

4.3.4. Summary

The results of the preliminary experiments indicate that the presence of sodium sulphate

is more important in the case of the exhaust process than that of the continuous process.

Aftertreatment with chemical exhaustion over 20 minutes produced better resistance to

washing with minor impact on hue and chroma while treatment for 60 minutes affects

the chroma and hue. Taking into consideration the conservation of energy, AC 2 is a

better option than AC 4 as the duration of treatment is reduced to one third. On the basis

of these observations, AC 2 with 10% omf Bayprotect Cl, 100 g/L sodium sulphate and

an exhaustion time over 20 minutes were taken as the basis for further work examining

the application of Bayprotect Cl as protective agent on cotton fabric dyed with sulphur

dyes.

4.4. Effects of varying concentrations of Bayprotect Cl in the presence/absence of

sodium sulphate

In order to determine the optimum conditions for the application of Bayprotect Cl on

sulphur dyed fabric, the samples were treated with various concentrations of tannin with

and without co-application of sodium sulphate to determine the optimum combination

capable of producing maximum resistance against oxidative bleaching.



115

The fabric was dyed with CI Leuco Sulphur Black 1 using Diresul Reducing agent D.

The application temperature (98oC), pH (<3.5 maintained with citric acid), time (20

minutes) and liquor to goods ratio (10:1) were kept the same for all application

conditions. The details of the process parameters are shown in Table 4.3.

The purpose of this set of experiments was to minimise the use of excessive amounts of

auxiliaries while maintaining the protective effect.


varying concentrations of Bayprotect Cl on CI Leuco Sulphur Black 1 dyed

cotton fabric

Application



AC 7 2% omf 100 g/L

AC 8 4% omf 100 g/L

AC 9 6% omf 100 g/L

AC 10 8% omf 100 g/L

AC 11 10% omf 100 g/L

AC 12 30% omf 100 g/L

AC 13 2% omf -

AC 14 4% omf -

AC 15 6% omf -

AC 16 8% omf -

AC 17 10% omf -

AC 18 30% omf -

4.4.1. Effect of the application of varying concentrations of Bayprotect Cl with sodium

sulphate on the ISO 1O5 CO9 wash fastness of the sulphur dyed cotton

The sulphur black dyed fabric was treated with varying concentrations of Bayprotect Cl

that are 2%, 4%, 6%, 8%, 10% and 30% omf. The method of aftertreatment involved

treating the dyed fabric at the boil for 20 minutes in the presence of 100 g/L sodium

sulphate. As seen in Figure 4.4, the results indicate that the retention of colour strength

of the samples increased up to 4% omf application level (AC 8). Increasing the

concentration above 4% omf did not significantly improve the resistance of dye to



116

oxidative bleaching. It can therefore be concluded that there are no benefits to

increasing the concentration of Bayprotect Cl above 4% omf in terms of protection

against oxidative bleaching in household laundering conditions.

Figure 4.4 Effect of aftertreatment with varying concentrations of Bayprotect

Cl, in the presence of sodium sulphate, on the ISO 1O5 CO9 wash fastness of CI

Leuco Sulphur Black 1 dyed cotton fabric

4.4.2. Effect of the application of varying concentrations of Bayprotect Cl without

sodium sulphate on the ISO 1O5 CO9 wash fastness of the sulphur dyed cotton

Varying concentrations of Bayprotect Cl was applied to sulphur dyed fabric in the

absence of an electrolyte (sodium sulphate) as shown in Figure 4.5. Once again the

percentage colour loss of the dyed sample decreased up to the concentration of 4% omf

(AC 14), after which the colour loss remained relatively constant. There were therefore

no benefits to employing higher concentrations of Bayprotect Cl for improving the ISO

1O5 CO9 wash fastness for sulphur dyed cotton.

60%

56%

53% 53% 53%

56% 56%

48%

50%

52%

54%

56%

58%

60%

62%


% C

olo

ur

loss

ISO 1O5 CO9 with perborate



117

Figure 4.5 Effect of aftertreatment with varying concentrations of Bayprotect

Cl, in the absence of sodium sulphate, on the ISO 1O5 CO9 wash fastness of CI

Leuco Sulphur Black 1 dyed cotton fabric

4.4.1. Summary

The preliminary experiments indicated that using 4% omf Bayprotect Cl rather than

10% omf offered similar levels of protection against oxidative bleaching in household

laundering environments as determined by percentage colour loss. Thus, the

concentration of 4% omf was used for the rest of the work. However, the impact of

using sodium sulphate with Bayprotect Cl for improving the wash fastness of the dye

against ISO 1O5 CO9 in particular was small. Nevertheless, keeping in mind the

effectiveness of the electrolyte in improving the wash fastness of the dye against ISO

1O5 CO6 washing regime (Table 4.2, AC 2), the rest of the experiments were carried

out with 100 g/L sodium sulphate.

60%

58%

55%

56% 56% 56%

53%

48%

50%

52%

54%

56%

58%

60%

62%


% C

olo

ur

loss




118

4.5. Effects of varying temperatures on the exhaust application of Bayprotect Cl and

sodium sulphate

Initial experiments lead to the observation that the combined application of Bayprotect

Cl and 100 g/L sodium sulphate produced an improvement in the wash fastness of

sulphur dyed cotton fabric. In order to further optimise the process, the effect of varying

application temperatures on the resistance of the colour against fading was assessed.

The compositions and the application parameters are outlined in Table 4.4.

The cotton fabric was dyed with CI Leuco Sulphur Black 1 using the biodegradable

(Diresul Reducing Agent D) and conventional (sodium sulphide) reducing systems. The

colorimetric data for the two systems are illustrated in Table 4.5 and Table 4.6,

respectively. The effects of varying application temperatures of Bayprotect Cl on

percentage colour loss of CI Leuco Sulphur Black 1 dyed cotton fabric are shown in

Figure 4.6 and Figure 4.7.


Bayprotect Cl (at varying temperatures) on CI Leuco Sulphur Black 1 dyed

cotton fabric

Exhaust application

Compositions

L:R

Temperature

Time

pH

Bayprotect Cl Sodium sulphate

AC 19 4% omf 100 g/L 10:1 40oC

20

minutes

<3.5

(citric acid)

AC 20 4% omf 100 g/L 10:1 60oC

20

minutes

<3.5

(citric acid)

AC 21 4% omf 100 g/L 10:1 80oC

20

minutes

<3.5

(citric acid)

AC 22 4% omf 100 g/L 10:1 98oC

20

minutes

<3.5

(citric acid)



119


aftertreated with Bayprotect Cl and sodium sulphate at different temperatures

(reduced with Diresul RAD)

Washing

treatment L* a* b* c* h K/S

%Colour

loss

GS

Rating DE

Untreated 29.6 -0.8 -4.6 4.7 260.3 8.0

WF 1 30.6 -1.2 -4.9 5.0 255.9 7.6 5% 4/5 1.1

WF 5 41.0 -1.5 -4.1 4.3 250.5 3.6 55% 1/2 11.4


Aftertreated 30.5 -0.3 -4.2 4.2 265.9 7.3

WF 1 30.2 -1.3 -4.7 4.9 254.8 7.8 -7% 4/5 1.1

WF 5 41.3 -1.4 -4.0 4.3 250.7 3.6 51% 1/2 10.8


Aftertreated 30.8 -0.4 -4.2 4.3 264.6 7.2

WF 1 30.4 -1.3 -4.7 4.8 255.0 7.7 -7% 4/5 1.1

WF 5 41.1 -1.4 -4.2 4.4 251.1 3.6 50% 1/2 10.3


Aftertreated 30.2 -0.3 -4.2 4.2 266.2 7.4

WF 1 30.3 -1.3 -4.6 4.8 254.4 7.8 -5% 4/5 1.1

WF 5 39.6 -1.4 -4.1 4.4 250.9 4.0 46% 2 9.5


Aftertreated 31.3 -0.3 -4.1 4.1 266.1 6.9

WF 1 30.3 -1.2 -4.5 4.7 255.1 7.8 -13% 4 1.5

WF 5 39.3 -1.2 -4.1 4.3 253.3 4.1 41% 2 8.0

Where:



Figure 4.6 Effects of varying application temperatures for exhaust application

of Bayprotect Cl and sodium sulphate on the wash fastness of CI Leuco Sulphur

Black 1 dyed cotton fabric (reduced with Diresul RAD)

5%

-7% -7% -5%

-13%

55% 51% 50%

46% 41%

-20%

-10%

0%

10%

20%

30%

40%

50%

60%

70%

Non-Treated AC19 AC20 AC21 AC22

% C

olo

ur

loss

ISO 1O5 CO6 with perboratex1 ISO 1O5 CO9 with perborate



120


aftertreated with Bayprotect Cl and sodium sulphate at different temperatures

(reduced with sodium sulphide)

Washing

treatment L* a* b* c* H K/S

%Colour

loss

GS

Rating DE

Untreated 27.5 -0.7 -4.9 5.0 262.3 9.5

WF 1 30.1 -1.1 -5.4 5.5 258.8 8.0 16% 3/4 2.7

WF 5 44.1 -1.5 -5.4 5.7 254.5 3.0 68% 1 16.6


Aftertreated 29.2 0.2 -4.7 4.7 271.9 8.0

WF 1 30.3 -1.1 -5.5 5.6 258.4 7.8 3% 4 1.9

WF 5 43.8 -1.5 -5.5 5.7 255.0 3.1 61% 1 14.7


Aftertreated 29.4 0.2 -4.7 4.7 272.1 7.9

WF 1 30.1 -1.0 -5.4 5.5 259.9 7.9 0% 4 1.5

WF 5 42.9 -1.4 -5.6 5.7 256.1 3.3 58% 1 13.6


Aftertreated 28.7 0.2 -4.6 4.6 272.7 8.3

WF 1 29.4 -1.0 -5.3 5.4 259.3 8.3 0% 4 1.6

WF 5 41.6 -1.3 -5.7 5.8 257.5 3.6 57% 1 13.1


Aftertreated 27.9 0.3 -4.4 4.4 273.7 8.8

WF 1 28.6 -0.9 -5.1 5.2 259.5 8.8 0% 4 1.6

WF 5 42.3 -1.2 -5.6 5.7 257.9 3.4 61% 1

Where:



Figure 4.7 Effects of varying application temperatures for exhaust application

of Bayprotect Cl and sodium sulphate on the wash fastness of CI Leuco Sulphur

Black 1 dyed cotton fabric (reduced with sodium sulphide)

16%

3% 0% 0% 0%

68% 61%

58% 57% 61%

-10%

0%

10%

20%

30%

40%

50%

60%

70%

80%

Non-Treated AC19 AC20 AC21 AC22

% C

olo

ur

loss

ISO 1O5 CO6 with perboratex1 ISO 1O5 CO9 with perborate



121

4.5.1. Summary

The colorimetric data presented in Table 4.5 and table 4.6 indicates that the protective

effect of Bayprotect Cl (in terms of percentage colour loss for ISO 1O5 CO9 washing

system) increases initially as the application temperature increases from 40oC to 60

oC.

In case of cotton fabric reduced with Diresul RAD, the colour loss of the dyed fabric is

concomitantly reduced with the increasing temperature (Figure 4.6). However, for

cotton fabric dyed with sodium sulphide, lower percentage colour loss may be achieved

when applying Bayprotect Cl at 80oC instead of at boil (98

oC). This is presumably due

to the fact that kinetic effects in the finish bath lead to increasing level of deposition of

Bayprotect Cl as the temperature increases from 40oC to 80

oC. At the boil however

dispersion rates are also increased leading to a lower level of application, as seen by a

reduction in protective effect (Figure 4.7).

This combination of kinetic and thermal effects has been well reported with direct dyes

and hence is presumed to also apply in the case of Bayprotect Cl. Generally, in exhaust

dyeing, the dyeing rate and the final exhaustion is influenced by the temperature and

chemicals such as salts and acids. Increasing temperature increases the rate of dyeing

and of dye migration. Taking an example of the application of direct dyes on cotton,

initially the exhaustion increases as the dyeing temperature increases. This is because

the increase in dyeing temperature causes the dye aggregates to breakup and more

individual molecules are available for penetration into the fibres. The exhaustion thus

increases with increasing temperature. Eventually, if there is no dye in its aggregated

form and the dyeing temperature increases further, then final exhaustion decreases with

increasing temperature [10].



122

4.6. Optimised parameters for the application of Bayprotect Cl on sulphur dyed

cotton fabric

According to the outcomes obtained from the investigations discussed above (sections

4.3, 4.4 and 4.5), the following parameters are achieved for improving the wash fastness

of CI Leuco Sulphur Black 1 dyed cotton fabric (reduced with Diresul Reducing agent

D) against ISO 1O5 CO6 and CO9 washing procedures:

Method of application: Exhaust;

Temperature: 80oC;

Time: 20 minutes;

Liquor to goods ratio: 10:1;

Concentration of electrolyte (sodium sulphate): 100 g/L;

Concentration of Bayprotect Cl: 4% omf;

pH (citric acid): less than 3.5.


sulphate (reduced with Diresul RAD)

The aforementioned parameters (section 4.6) found to offer significant protection

against oxidative household laundering condition were adopted for the application of

Bayprotect Cl on cotton fabrics dyed with various sulphur dyes (5% omf) namely

Diresul Black RDT-LS LIQ 200 (CI Leuco Sulphur Black 1), Diresul Liquid Green

RDT-N (CI Leuco Sulphur Green 2), Diresul Liquid Blue RDT-G (CI Leuco Sulphur

Blue 7), Diresul Liquid Yellow RDT-E (CI Leuco Sulphur Yellow 22) and Diresul

Liquid Red RDT-BG (CI Leuco Sulphur Red 14). These dyes were reduced with the

biodegradable Diresul Reducing agent D (dyeing procedure discussed in section 3.4)

and the effects of the aftertreatments were evaluated for ISO 1O5 CO6 and ISO 1O5

CO9 washing (Table 4.7 to Table 4.11), crocking and light fastness (Table 4.12).



123

Table 4.7 Colorimetric data for ISO 1O5 CO6 and CO9 washed CI Leuco

Sulphur Red 14 dyed fabric aftertreated with Bayprotect Cl and sodium


Washing


%Colour

loss

GS

Rating DE

Untreated 60.4 39.6 7.5 40.3 10.7 2.9

WF 1 61.1 38.9 7.0 39.5 10.2 2.7 7% 4/5 1.2

WF 5 62.5 37.9 6.3 38.5 9.5 2.3 21% 3/4 3.0

AC 21 59.4 38.4 3.9 38.6 5.8 2.5

WF 1 60.5 38.6 7.1 39.3 10.5 2.4 4% 3 3.5

WF 5 62.2 38.5 6.5 39.0 9.6 2.4 4% 3 3.8

Where:




Sulphur Blue 7 dyed fabric aftertreated with Bayprotect Cl and sodium


Washing


%Colour

loss

GS

Rating DE

Untreated 53.2 1.5 -21.0 21.1 273.9 2.0

WF 1 55.0 1.4 -22.2 22.3 273.6 1.8 10% 4 2.2

WF 5 58.9 -1.3 -22.2 22.2 266.6 1.5 25% 2 6.5

AC 21 53.3 0.9 -20.2 20.2 272.6 2.0

WF 1 54.6 1.0 -21.3 21.3 272.6 1.9 5% 4 1.7

WF 5 59.0 -1.2 -22.2 22.2 267.0 1.5 25% 2 6.4

Where:





124


Sulphur Black 1 dyed fabric aftertreated with Bayprotect Cl and sodium


Washing


%Colour

loss

GS

Rating DE

Untreated 29.6 -0.8 -4.6 4.7 260.3 8.0

WF 1 30.6 -1.2 -4.9 5.0 255.9 7.6 5% 4/5 1.1

WF 5 41.0 -1.5 -4.1 4.3 250.5 3.6 55% 1/2 11.4

AC 21 30.2 -0.3 -4.2 4.2 266.2 7.4

WF 1 30.3 -1.3 -4.6 4.8 254.4 7.8 -5% 4/5 1.1

WF 5 39.6 -1.4 -4.1 4.4 250.9 4.0 46% 2 9.5

Where:




Sulphur Yellow 22 dyed fabric aftertreated with Bayprotect Cl and sodium


Washing


%Colour

loss

GS

Rating DE

Untreated 86.7 -7.5 44.8 45.4 99.5 3.3

WF 1 88.4 -9.0 43.6 44.5 101.7 2.9 12% 3/4 2.5

WF 5 90.7 -10.7 43.8 45.1 103.8 2.6 21% 2/3 5.3

AC 21 84.5 -5.1 42.9 43.2 96.8 3.2

WF 1 86.6 -7.0 43.0 43.6 99.3 3.1 3% 3/4 2.8

WF 5 89.6 -9.4 44.4 45.4 101.9 2.8 13% 2 6.8

Where:





125


Sulphur Green 2 dyed fabric aftertreated with Bayprotect Cl and sodium


Washing


%Colour

loss

GS

Rating DE

Untreated 69.2 -14.2 -8.8 16.7 211.9 0.9

WF 1 70.0 -15.1 -9.0 17.6 211.0 0.9 0% 4/5 1.2

WF 5 75.3 -13.8 -9.8 16.9 215.4 0.7 22% 2 6.2

AC 21 69.0 -14.0 -8.2 16.2 210.3 1.0

WF 1 70.1 -15.4 -9.9 18.4 212.8 1.0 0% 2 2.6

WF 5 74.8 -13.2 -9.9 16.5 216.9 0.7 30% 2 6.1

Where:



Table 4.12 Light and crocking fastness data for sulphur dyed cotton fabrics

aftertreated with Bayprotect Cl and sodium sulphate


Treatments Light

fastness

Crocking fastness

Dry Wet

CI Leuco Sulphur Black 1

Untreated 4 4-5 3-4

4% omf Bayprotect Cl + 100 g/L sodium sulphate 4 4-5 3-4

CI Leuco Sulphur Green 2

Untreated 2-3 5 4-5

4% omf Bayprotect Cl + 100 g/L sodium sulphate 4 5 4-5

CI Leuco Sulphur Blue 7

Untreated 4 5 4

4% omf Bayprotect Cl + 100 g/L sodium sulphate 4-5 5 4-5

CI Leuco Sulphur Yellow 22

Untreated 2-3 5 3-4


CI Leuco Sulphur Red 14

Untreated 4 4-5 3




126

Table 4.13 Effects of aftertreatment with Bayprotect Cl and sodium sulphate

on tensile properties of CI Leuco Sulphur Black 1 dyed cotton fabrics

Samples

Warp direction Weft direction

Tensile

strength

(N/mm2)

Tensile

extension

at Break

(mm)

Tensile strength

(N/mm2)

Tensile

extension

at Break

(mm)

Untreated, undyed 4.6 19.3 3.1 15.8

Untreated, dyed 4.6 19.9 3.8 31.8

5% omf Bayprotect Cl 5.6 19.4 4.4 31.1



The influence of Bayprotect Cl on five CI Leuco Sulphur dyed cotton fabrics (reduced

with Diresul Reducing agent D) has been investigated through the colorimetric data

(Table 4.7 to Table 4.11). It can be seen that CI Leuco Sulphur Red 14, Black 1 and

Yellow 22 aftertreated with Bayprotect Cl showed noteworthy improvements in terms

of minimising the colour loss for ISO IO5 CO9 and CO6 washing. However, the impact

of aftertreatment on CI Leuco Sulphur Green 2 and Blue 7 for ISO IO5 CO9 washing

regime was insignificant. In the case of CI leuco Sulphur Black 1, being the most

important and commonly used sulphur dye, a substantial reduction in colour loss for

ISO IO5 CO9 can be perceived, that is from 55% (untreated) to 46% (aftertreated). The

comparative results of aftertreatments are shown in Figure 4.8 and Figure 4.9. Since the

exact chemistry and the dye structures for sulphur dyes are still unknown, so no

evidence or suggestion could be provided for an improved wash fastness of the cotton

fabric dyed with different sulphur dyes.

The effects of the aftertreatments on crocking and light fastness have also been

evaluated for the treated samples. As seen in Table 4.12, the light fastness of CI Leuco

Sulphur Green 2 and Yellow 22 treated samples has improved by 1.5 units while CI

Leuco Sulphur Blue 7 and Red 14 were also slightly improved. However, the light

fastness of CI Leuco Sulphur Black 1 dyed and aftertreated cotton fabric remained

unchanged, for which no specific reason could be identified. The wet crocking for CI



127

Leuco Sulphur Blue 7 and Red 14 has increased by half a unit, however, the treatment

did not greatly improve the dry crocking of the dyed fabrics.

The effect of aftertreatment with tannin on light fastness of sulphur dye cotton fabric

can be explained by the study done by Cristea [11]. The anti-oxidants also called

oxidation inhibitors are the organic compounds that are added to oxidisable organic

materials to inhibit auto-oxidation. Some examples of effective antioxidants include

hindered phenols, secondary aromatic amines and hindered amines. They can be broadly

classified into two classes depending upon the mechanism of function, namely radical

trapping (chain breaking) or peroxide decomposing. Gallic acid and its esters and

vegetal polyphenols can be categorised as radical trapping antioxidants while citric acid

can be cited as metal chelating antioxidant [11]. Some investigations into the effects of

aftertreatments with antioxidants on the light fastness of cotton fabric dyed with natural

dyes demonstrated some benefits. The objective of the study was to evaluate the effects

of commonly used antioxidants and UV absorbers on the light fastness of the dyed

fabrics. Aftertreatments with these reagents were found to improve the light fastness of

the dyes where gallic acid and vitamin C were the most effective of all [11]. This is

commensurate with the fact that Bayprotect Cl also belongs to a class of polyphenols

and antioxidants. It is expected to form some bonds either with the cotton substrate or

the dye which eventually leads to UV protection and an increased light fastness.

On treating CI Leuco Sulphur Black 1 dyed fabric with Bayprotect Cl, the tensile

strength of the aftertreated samples was slightly increased as listed in Table 4.13. This is

probably due to the higher physical interactions between the phenolic hydroxyl groups

of tannin based Bayprotect Cl and carboxylic acid groups of the cotton fabric.



128


fastness to laundering (ISO 1O5 CO6) of sulphur dyed cotton fabrics



fastness to laundering (ISO 1O5 CO9) of sulphur dyed cotton fabrics


10%

5%

7%

4%

0% 0%

12%

3%

5%

-5% -6%

-4%

-2%

0%

2%

4%

6%

8%

10%

12%

14%

Untreated Treated with Bayprotect Cl

% C

olo

ur

loss

ISO 1O5 CO6 (CI Leuco Sulphur Blue 7) ISO 1O5 CO6 (CI Leuco Sulphur Red 14)ISO 1O5 CO6 (CI Leuco Sulphur Green 2) ISO 1O5 CO6 (CI Leuco Sulphur Yellow 22)ISO 1O5 CO6 (CI Leuco Sulphur Black 1)

25% 25% 21%

4%

22%

30%

21%

13%

55%

46%

0%

10%

20%

30%

40%

50%

60%

70%


% C

olo

ur

loss




129


sulphate (reduced with sodium sulphide)

The optimised process parameters for aftertreatments achieved with Diresul RAD

reduced CI Leuco Sulphur Black 1 dyed cotton fabric, identified as leading to

significant improvements in the wash fastness were used to treat cotton fabrics dyed

with various sulphur dyes and reduced with the conventional sodium sulphide. The

effects of the aftertreatments were tested for ISO 1O5 CO6 and CO9 washing (Table

4.14 to Table 4.18), crocking and light fastness (Table 4.19).


Sulphur Red 14 dyed fabric aftertreated with Bayprotect Cl and sodium


Washing


%Colour

loss

GS

Rating DE

Untreated 62.8 36.4 7.0 37.1 10.8 2.2

WF 1 64.3 34.7 7.1 35.4 11.6 1.9 14% 4 2.3

WF 5 65.3 34.8 6.3 35.4 10.3 1.8 18% 3/4 3.1

AC 21 61.9 35.5 4.7 35.8 7.6 2.0

WF 1 64.2 33.9 7.4 34.7 12.3 1.9 5% 3 3.8

WF 5 65.9 34.5 6.5 35.1 10.6 1.7 15% 2/3 4.5


Sulphur Blue 7 dyed fabric aftertreated with Bayprotect Cl and sodium


Washing


%Colour

loss

GS

Rating DE

Untreated 47.3 2.1 -22.9 23.0 275.3 3.0

WF 1 49.5 2.9 -23.6 23.7 277.0 2.6 13% 3/4 2.4

WF 5 54.1 0.0 -23.8 23.8 269.9 2.1 30% 2 7.2

AC 21 46.8 2.0 -21.8 21.8 275.2 3.1

WF 1 48.3 2.5 -22.7 22.8 276.3 2.8 10% 4 1.8

WF 5 52.7 0.1 -23.8 23.8 270.2 2.3 26% 2 6.5

Where:





130


Sulphur Black 1 dyed fabric aftertreated with Bayprotect Cl and sodium


Washing


%Colour

loss

GS

Rating DE

Untreated 27.5 -0.7 -4.9 5.0 262.3 9.5

WF 1 30.1 -1.1 -5.4 5.5 258.8 8.0 16% 3/4 2.7

WF 5 44.1 -1.5 -5.4 5.7 254.5 3.0 68% 1 16.6

AC 21 28.7 0.2 -4.6 4.6 272.7 8.3

WF 1 29.4 -1.0 -5.3 5.4 259.3 8.3 0% 4 1.6

WF 5 41.6 -1.3 -5.7 5.8 257.5 3.6 57% 1 13.1

Where:




Sulphur Yellow 22 dyed fabric aftertreated with Bayprotect Cl and sodium


Washing


%Colour

loss

GS

Rating DE

Untreated 84.8 -6.7 49.2 49.7 97.8 4.2

WF 1 86.7 -8.1 49.4 50.0 99.3 3.6 14% 3/4 2.3

WF 5 88.8 -9.3 51.5 52.4 100.2 3.6 14% 2/3 5.3

AC 21 83.7 -4.5 47.5 47.7 95.4 3.8

WF 1 85.5 -6.4 48.7 49.1 97.5 3.8 0% 3/4 2.8

WF 5 89.1 -9.2 50.6 51.4 100.3 3.4 11% 2 7.8

Where:





131


Sulphur Green 2 dyed fabric aftertreated with Bayprotect Cl and sodium


Washing


%Colour

loss

GS

Rating DE

Untreated 67.5 -10.6 -9.4 14.2 221.6 0.9

WF 1 73.1 -10.7 -10.3 14.8 223.8 0.6 33% 2/3 5.7

WF 5 74.0 -9.9 -11.0 14.8 228.2 0.6 33% 2 6.7

AC 21 66.6 -10.0 -8.6 13.2 220.5 1.0

WF 1 68.6 -11.1 -9.8 14.8 221.4 0.9 10% 3/4 2.6

WF 5 73.1 -10.0 -11.2 15.0 228.1 0.7 30% 2 7.0

Where:




aftertreated with Bayprotect Cl and sodium sulphate


Treatments Light

fastness

Crocking fastness

Dry Wet


Untreated 4 4-5 3

4% omf Bayprotect Cl + 100 g/L sodium sulphate 4 4-5 3


Untreated 2-3 4-5 3-4

4% omf Bayprotect Cl + 100 g/L sodium sulphate 3-4 5 4


Untreated 3-4 4-5 3

4% omf Bayprotect Cl + 100 g/L sodium sulphate 4-5 5 3-4


Untreated 4 4-5 3

4% omf Bayprotect Cl + 100 g/L sodium sulphate 4-5 4-5 3


Untreated 3 4-5 3-4

4% omf Bayprotect Cl + 100 g/L sodium sulphate 4-5 4-5 4



132


The influence of Bayprotect Cl on the five leuco sulphur dyed cotton fabrics (reduced

with sodium sulphide) has been presented above in the form of colorimetric data (Table

4.14 to Table 4.18). It can be seen that CI Leuco Sulphur Red 14, Black 1 and Blue 7

show significant improvements in percentage colour loss for ISO IO5 CO6 and CO9

washing schemes (that are reflected in clear visual improvements). However, the impact

of aftertreatments on CI Leuco Sulphur Green 2 and Yellow 22 dyed fabrics for ISO

IO5 CO9 are small. In the case of CI Leuco Sulphur Black 1, a substantial reduction in

colour loss for ISO IO5 CO9 can be perceived, that is from 68% (untreated) to 57%

(aftertreated). The comparative results of aftertreatments are shown in Figure 4.10 and

Figure 4.11. The effects of aftertreatments on crocking and light fastness have also been

evaluated for the treated samples and as can be seen in Table 4.19, the light fastness of

treated samples has significantly improved in comparison to untreated samples for all

colours except CI Leuco Sulphur Black 1 which remained unchaged. The wet crocking

for CI Leuco Blue 7, Green 2 and Red 14 increased by half a unit, similar improvements

were seen for the dry crocking of CI Leuco Sulphur Green 2 and Blue 7.

On comparing the fastness properties of the leuco sulphur dyed fabrics reduced with the

two reducing systems, it can be concluded that the wash fastness of CI Leuco Sulphur

Black 1, Yellow 22 and Red 14 dyed fabrics (reduced with Diresul RAD) against

domestic laundering process of ISO 1O5 CO6 and ISO 1O5 CO9 can be improved by

the application of Bayprotect Cl and sodium sulphate. In the case of fabrics reduced

with sodium sulphide, significant improvements were observed for of CI Leuco Sulphur

Black 1, Blue 7 and Red 14. In general, significant improvements were observed for the

light fastness of all dyes (reduced with both the systems), while the dry and wet rub

fastness was either slightly improved (by ½ a unit) or remained unchanged.

4.9. Mechanism

The mechanism by which the wash fastness of sulphur dyed fabric is improved by

aftertreatments with tannin is probably related to the behaviour observed with the

application of tannic acid/tartar emetic (potassium antimonyl tartrate) combination and

syntans on dyed nylon fabric.



133

Figure 4.10 Effect of aftertreatments with Bayprotect Cl and sodium sulphate

on fastness to laundering (ISO 1O5 CO6) of sulphur dyed cotton fabrics


Figure 4.11 Effect of aftertreatments with Bayprotect Cl and sodium sulphate

on fastness to laundering (ISO 1O5 CO9) of sulphur dyed cotton fabrics


13%

10%

14%

5%

33%

10%

14%

0%

16%

0%

-5%

0%

5%

10%

15%

20%

25%

30%

35%

40%


% C

olo

ur

loss


30% 26%

18% 15%

33% 30%

14% 11%

68%

57%

0%

10%

20%

30%

40%

50%

60%

70%

80%


% C

olo

ur

loss




134

The wash fastness of acid dyes on nylon can be improved by back-tanning process in

which the dyed fabric is first treated with tannic acid and then tartar emetic. The anionic

tannic acid is adsorbed onto the surface of nylon by forces of attraction between the

anionic tannic acid and cationic ammonium ion groups at the ends of the polymer chains

of nylon. Further, on application of tartar emetic a film of the insoluble antimony salt of

tannic acid is produced that restricts desorption of the dyes. Hence, the insoluble anionic

tannic acid repels dye anions on a nylon surface after back tanning [10].

Syntans (synthetic tanning agents) are also used in place of tannins as they are less

expensive and environmentally friendly. The mechanism by which syntans improve the

wash fastness of acid dyes on nylon is slightly different. The anionic syntans do not

form a layer like the tannic acid/tartar emetic combination, instead they are substantive

to nylon. The syntan molecules adsorb on the surface by interaction with ammonium ion

sites but they cannot penetrate into the polymer because of their large molecular size.

The large sized adsorbed syntan on the nylon surface inhibits the dye leakage during

laundering [10]. Another theory favours the aromatic attraction of dyestuff and syntan,

thus hindering the dyestuff molecules from migrating out of the fibre [12].

Therefore, the improvement of wash fastness of sulphur dyed fabric by application of

tannin could presumably occur due to formation of a layer of tannin molecules on the

surface of the fabric thus limiting desorption of the dye. The other reason could possibly

be the adsorption of tannin molecules on the surface and the forces of repulsion between

the anionic tannin and anionic dye molecules, thus keeping the dye within the fabric.

4.10. Surface topography of the untreated and Bayprotect Cl aftertreated fabrics

The SEM micrographs of untreated CI Leuco Sulphur Black 1 dyed cotton fabric

(reduced with Diresul RAD) are shown in Figure 4.12 to Figure 4.15. The SEM images

of sulphur dyed cotton fabrics treated with 4% omf Bayprotect Cl (AC 21) do not

indicate the presence of any surface depositions or coatings (Figure 4.16 to Figure 4.19).

However, after ISO 1O5 CO9 laundering slight fibrillation with some protruding

fragments was observed which could probably be due to wet abrasion of the cotton

fibres. There was no observable difference between the untreated and Bayprotect Cl

treated samples.



135

Figure 4.12 SEM micrograph of

unlaundered untreated sulphur dyed

cotton fabric

Magnification 1000x


unlaundered untreated sulphur dyed

cotton fabric

Magnification 5000x

Figure 4.14 SEM micrograph of ISO 105

CO9 laundered untreated sulphur dyed

cotton fabric

Magnification 1000x


CO9 laundered untreated sulphur dyed

cotton fabric

Magnification 5000x



136


unlaundered 4% omf Bayprotect Cl

treated sulphur dyed cotton fabric

Magnification 1000x


unlaundered 4% omf Bayprotect Cl


Magnification 5000x


CO9 laundered 4% omf Bayprotect Cl


Magnification 1000x


CO9 laundered 4% omf Bayprotect Cl


Magnification 5000x



137

4.11. Effects of reducing systems on the colour strength and fastness properties of

sulphur dyed cotton fabrics

The physical state and the size of dye are generally more important than the chemical

structure [11]. The colour strength, wash fastness, rubbing fastness and light fastness

properties of the dyes are also dependent on the size of the dye molecule to some extent.

In the case of sulphur dyes, the size of the dye greatly depends on application conditions

such as the type of the reducing agent used and reduction potential of the dye bath. The

appropriate reduction potential offers the maximum colour strength and minimum

colour loss during laundering owing to the reduction of the polymeric dye molecule to

an optimum size for fibre affinity and diffusion into the fibre [13].

Table 4.20 Colour strength and fastness properties of untreated sulphur dyed

cotton fabrics reduced with sodium sulphide and Diresul Reducing agent D

Dyes

Colour strength

(K/S) % Colour loss

Diresul

RAD

Sodium

sulphide

Diresul RAD Sodium sulphide

ISO 1O5

CO6

ISO 1O5

CO9

ISO 1O5

CO6

ISO 1O5

CO9

CI Leuco Sulphur Black 1 8.0 9.5 5 55 16 68

CI Leuco Sulphur Yellow 22 3.3 4.2 12 21 14 14

CI Leuco Sulphur Blue 7 2.0 3.0 10 25 13 30

CI Leuco Sulphur Red 14 2.9 2.2 7 21 14 18

CI Leuco Sulphur Green 2 0.9 0.9 0 22 33 33

Dyes

Rubbing fastness Light fastness

Diresul RAD Sodium sulphide Diresul

RAD

Sodium

sulphide Dry Wet Dry Wet

CI Leuco Sulphur Black 1 4-5 3-4 4-5 3 4 4

CI Leuco Sulphur Yellow 22 5 3-4 4-5 3 2-3 4

CI Leuco Sulphur Blue 7 5 4 4-5 3 4 3-4

CI Leuco Sulphur Red 14 4-5 3 4-5 3-4 4 3

CI Leuco Sulphur Green 2 5 4-5 4-5 3-4 2-3 2-3

As shown in Table 4.20, on comparing the effects of reducing systems on untreated

sulphur dyed cotton fabrics, it was observed that the colour strength achieved for CI



138

Leuco Sulphur Black 1, Yellow 22 and Blue 7 dyeings reduced with sodium sulphide is

higher than Diresul RAD reduced samples. In the case of CI Leuco Sulphur Red 14,

sodium sulphide reduced fabric has lower colour strength while for CI Leuco Sulphur

Green 2 there was no change. In general, the percentage colour loss for sodium sulphide

reduced samples against ISO IO5 CO6 as well as ISO IO5 CO9 laundering systems was

higher than Diresul RAD reduced samples. Similar observations were made for dry and

wet crocking. The dry crocking for sodium sulphide reduced samples was either the

same or half unit inferior to Diresul RAD samples. Similarly, the wet crocking was also

half to 1 unit inferior to Diresul RAD samples except for CI Leuco Sulphur Red 14,

which was half unit superior. The colour strength and fastness properties of sulphur dyes

reduced with the two systems can be related to the dye molecular size. It can be

postulated that sulphur dyes reduced with sodium sulphide might have smaller

fragments than Diresul RAD reduced dyes resulting in higher colour strength and

increased colour loss during laundering. It is also expected that the small dye molecules

would have less affinity for cellulose resulting in poor rubbing fastness.

The reason for the smaller molecular size of the dye reduced with sodium sulphide

could possibly be related to the reduction potential of the reducing system. A reduction

potential of -650 mV is considered to be an optimum value for achieving the dyeings

with maximum colour strength and minimum colour loss as above and below which the

dye molecule is either too large or too fragmented for maximum adsorption and

subsequent diffusion [13]. It can be postulated that the reduction potentials of the two

systems were different from each other thus resulting in different molecular sizes of the

dye. The reduction potentials data of the two systems might prove the effect of varying

dye molecular sizes on the colour strength, wash fastness, crocking fastness and light

fastness properties.

In the case of light fastness, dyed fabric bearing more finely dispersed dye will fade

rapidly owing to the exposure of large surface area to light. In contrast fibres with large

aggregates of dye are more light fast, since a smaller surface area of the dye is exposed

to air and light [11]. However, sulphur dyes reduced with the two systems were found to

display variable performance. In this case, the light fastness of for CI Leuco Sulphur

Black 1 and Green 2 was the same for the two reducing systems. CI Leuco Sulphur Red

14 and Blue 7 reduced with sodium sulphide exhibited one and half unit lower light

fastness, respectively, while CI Leuco Sulphur Yellow 22 was 1.5 units superior to



139

Diresul RAD reduced sample. Hence, the light fastness of the samples dyed with the

two systems cannot be explained on the basis of the dye molecular size.

4.12. Conclusions

Aftertreatments with Bayprotect Cl on CI Leuco Sulphur Black 1 in particular and

multiple sulphur dyed cotton fabrics were shown to offer benefits in terms of

improvements of wash fastness of the dyes for both ISO IO5 CO6 and CO9 washing

procedures. Significant improvements were also observed for light and wet rub fastness

of the dyes. However, dry rub fastness was not significantly enhanced. Sequential

processing methods employed for the optimisation of parameters were useful for

achieving the best combination resulting in less processing cost and environmental

impact. SEM analyses did not demonstrate the presence of depositions or film on the

fibre surface. Hence, Bayprotect Cl was found to provide a “protective effect” against

oxidation on the sulphur dyed cotton fabric during laundering, without altering the

surface morphology of the fabric and with no noticeable effect on the tensile properties.

4.13. References

[1] Khanbabaee K and Van Ree T. Tannins: classification and definition. Natural

Product Reports. 2001;18(6):641-9.

[2] Ramakrishnan K, Selvi S and Shubha R. Tannin and its analytical techniques. Indian

Chemical Engineer. 2006;48(2):88-93.

[3] Prabhu K and Bhute AS. Plant based natural dyes and mordnats: A Review. Journal

of Natural Product & Plant Resources. 2012;2(6):649-64.

[4] Rahim AA and Kassim J. Recent development of vegetal tannins in corrosion

protection of iron and steel. Recent Patents on Materials Science. 2008;1(3):223-31.

[5] Pizzi A. Tannins: major sources, properties and applications. Monomers, polymers

and composites from renewable resources: Elsevier; 2008. p. 179-99.



140

[6] Pantoja-Castro MA and González-Rodríguez H. Study by infrared spectroscopy and

thermogravimetric analysis of tannins and tannic acid. Revista latinoamericana de

química. 2011;39(3):107-12.

[7] Textan 3 product datasheet. Ajinomoto OmniChem.

[8] Pinto B. Carbohydrates and their derivatives, including tannins, cellulose, and

related lignins. Elsevier: New York; 1999.

[9] Bayprotect Cl product datasheet. Tanatex Chemicals.

[10] Broadbent AD. Basic principles of textile coloration. Bradford: Society of Dyers

and Colorists, 2001.

[11] Cristea D and Vilarem G. Improving light fastness of natural dyes on cotton yarn.

Dyes and Pigments. 2006;70(3):238-45.


Limited, 2004.




Investigation into the effects of aftertreatments with Bayprotect Cl, Fixapret CP and choline chloride

on the fastness properties of sulphur dyed cotton fabric

141


Cl, Fixapret CP and choline chloride on the fastness properties of


5.1. Introduction

One of the most important aspects of this research work was to design an aftertreatment

formulation to improve the wash down of sulphur dyeings when exposed to aggressive

washing system of ISO 1O5 CO9. This system does not only include detergent and a

high concentration of perborate bleach but also includes a bleach activator TAED,

which helps to remove stains at lower temperatures. The work done so far has produced

potential solutions to improve the resistance of sulphur dyed cotton fabric against ISO

1O5 CO6 treatments. However, the effect of ISO 1O5 CO9 washing is far more

degradative to the colour, hence a further protective system is needed to be developed

which could safeguard the dyed material from the highly oxidative environment

produced by this washing regime. For this purpose, the use of crease resist finish

Fixapret CP, cationic reactant choline chloride and their combinations with Bayprotect

Cl have been explored.

The crease resist finish plays a vital role in improving the wet fastness of sulphur dyes.

The effect of aftertreatments with the said finishing agent on light fastness is less

significant. The light fastness is either unaffected or slightly improved. On the other

hand, it severely damages the mechanical properties of the fabric, leading to a lower

tensile or tear strength finished goods with a duller tone [1, 2].

In this study, sulphur dyed fabrics were treated with the durable press finish, Fixapret

CP, which is based on DMDHEU (Dimethyldihydroxyethyleneurea) in the presence of

magnesium chloride as a catalyst. The catalyst used for the reaction in resin finishing

includes acids or latent acid agents, the latter having the ability to produce acidity on

heating. The structure of DMDHEU is shown in Scheme 5.1. The most popular catalyst

for DMDHEU reactants is magnesium chloride which tends to be neutral in aqueous

solution at all temperatures and thus offers maximum bath stability [3, 4].



142

Scheme 5.1 Structure of DMDHEU from [3]

5.2. Effects of sequential application of Fixapret CP and Bayprotect Cl

DMDHEU based resins are produced as a result of the reaction between glyoxal, urea

and formaldehyde and react with the cellulose by etherifying the hydroxyl groups in the

amorphous phase. The N-methylol groups in DMDHEU react with the cellulose and a

crosslinking net is formed [3, 4]. This higher crosslinking between the fabric and an

easy care finish results in improved easy care properties and wash fastness. Since the

dyeings aftertreated with Bayprotect Cl could not produce significant improvements in

the case of ISO 1O5 CO9 laundering processes, hence, the sequential application of

Bayprotect Cl and DMDHEU based durable press finish was attempted to resist the

oxidation of the dyes during domestic laundering and achieve sulphur dyed cotton fabric

with improved wash fastness.

In order to determine the influence of Fixapret CP on the sulphur dyed fabric, some

preliminary experiments were conducted where the finish was applied on its own as

well as after Bayprotect Cl treatment. The cotton fabric was dyed with 5% omf CI

Leuco Sulphur Black 1 with biodegradable reducing agent (Diresul Reducing agent D)

and four replicates were taken for each application condition (AC). Fixapret CP was

applied at concentrations of 60 g/L and 120 g/L with 12 g/L and 24 g/L of catalyst

magnesium chloride respectively, while Bayprotect Cl was applied at 4% omf and 10%

omf, the application parameters are detailed in Table 5.1. Fixapret CP and choline

chloride were applied through pad-dry-cure (P-D-C) method while Bayprotect Cl was

applied through exhaust application procedure (application methods described in

sections 3.3.2 and 4.3.1 respectively). The colorimetric data of sulphur black dyed fabric

subjected to different wash fastness conditions (WF) is detailed in Table 5.2.



143

Bayprotect Cl was applied at the initial process parameters discussed in (Section 4.3,

AC 2). However the process parameters were not optimised, as the results obtained from

the sequential application of the two reagents were not fulfilling the research objectives

(which are discussed in section 5.5.1).


Bayprotect Cl and Fixapret CP on CI Leuco Sulphur Black 1 dyed cotton fabric

Application

conditions

Concentrations

Application

procedure Fixapret CP

(g/L)

Magnesium

chloride

(g/L)

Bayprotect Cl

(% omf)

Sodium

sulphate

(g/L)

AC 1 60 12 - - Pad-Dry-Cure

AC 2 120 24 - - Pad-Dry-Cure

AC 3 - - 4 100 98

oC, 20 minutes

60 12 - - Pad-Dry-Cure

AC 4 - - 4 100 98

oC, 20 minutes


AC 5 - - 10 100 98

oC, 20 minutes


AC 6 - - 10 100 98

oC, 20 minutes


AC 7 - - 4 100 98oC, 20 minutes

AC 8 - - 10 100 98oC, 20 minutes

Table 5.2 Colorimetric data for ISO 1O5 CO6 and ISO 1O5 CO9 washed CI

Leuco Sulphur Black 1 dyed cotton fabric aftertreated with Bayprotect Cl and

Fixapret CP

Washing

Treatment L* a* b* c* h K/S

%Colour

loss

GS

Rating DE

Untreated 30.9 -1.3 -4.5 4.6 254.0 7.4

WF 1 32.3 -1.5 -4.7 4.9 252.0 6.7 9% 4 1.5

WF 2 34.4 -1.7 -4.7 5.0 250.3 5.8 22% 3 3.5

WF 3 43.8 -2.0 -3.6 4.1 241.5 3.0 59% 1 12.9

AC 1 60 g/L Fixapret CP + 12 g/L magnesium chloride (Pad-Dry-Cure)

Aftertreated 33.7 -1.3 -3.4 3.7 248.8 5.9

WF 1 33.4 -1.6 -4.0 4.3 278.7 6.2 -5% 4/5 0.7

WF 2 34.0 -1.6 -4.0 4.3 248.0 5.9 0% 4/5 0.7

WF 3 38.2 -1.8 -2.3 2.9 233.2 4.3 27% 2/3 4.7



144

AC 2 120 g/L Fixapret CP + 24 g/L magnesium chloride (Pad-Dry-Cure)

Aftertreated 34.3 -1.3 -3.3 3.6 248.3 5.7

WF 1 34.0 -1.7 -3.9 4.2 247.1 5.9 -4% 4/5 0.7

WF 2 34.0 -1.6 -3.9 4.2 247.6 5.9 -4% 4/5 0.7

WF 3 37.1 -1.8 -2.7 3.2 237.0 4.7 18% 3/4 2.9

AC 3 4% omf Bayprotect Cl + 100 g/L sodium sulphate (98

oC, 20 minutes)

60 g/L Fixapret CP + 12 g/L magnesium chloride (Pad-Dry-Cure)

Aftertreated 33.7 -0.9 -2.9 3.1 252.4 5.8

WF 1 32.7 -2.0 -2.4 3.1 229.9 6.4 -10% 4 1.2

WF 2 33.4 -2.1 -2.5 3.3 230.8 6.1 -5% 4 1.5

WF 3 35.7 -1.9 -2.2 3.0 229.2 5.2 10% 3/4 2.4


oC, 20 minutes)


Aftertreated 33.2 -0.9 -2.7 2.9 251.5 6.0

WF 1 32.6 -2.0 -2.4 3.1 230.1 6.4 -7% 4 1.3

WF 2 33.3 -2.1 -2.2 3.0 227.0 6.1 -2% 4 1.3

WF 3 35.1 -1.9 -2.3 3.0 230.1 5.4 10% 3/4 2.2


oC, 20 minutes)


Aftertreated 33.2 -0.9 -2.9 3.0 252.1 6.0

WF 1 33.3 -2.2 -1.8 2.8 219.6 6.1 -2% 4 1.6

WF 2 33.7 -2.3 -1.6 2.8 214.4 6.0 0% 4 2.0

WF 3 35.0 -2.1 -2.2 3.1 225.9 5.4 10% 3/4 2.4


oC, 20 minutes)


Aftertreated 33.4 -1.0 -2.8 2.9 250.5 5.9

WF 1 32.9 -2.1 -1.8 2.8 221.3 6.3 -7% 4 1.6

WF 2 33.0 -2.3 -1.4 2.7 212.0 6.2 -5% 4 1.9

WF 3 35.4 -2.1 -2.1 3.0 224.5 5.3 10% 3/4 2.4


Aftertreated 31.5 -0.5 -4.0 4.0 262.7 6.8

WF 1 32.1 -1.5 -4.5 4.8 251.2 6.9 -1% 4/5 1.1

WF 2 33.4 -1.6 -4.6 4.9 250.9 6.2 9% 3/4 2.2

WF 3 43.3 -1.7 -3.6 4.0 244.2 3.1 54% 1 11.6


Aftertreated 31.2 -0.5 -4.0 4.0 263.1 6.9

WF 1 30.8 -1.6 -4.4 4.7 250.4 7.5 -9% 4/5 1.2

WF 2 34.2 -1.7 -4.6 4.9 250.3 5.9 14% 3/4 3.3

WF 3 43.3 -1.8 -3.8 4.2 244.8 3.1 55% 1 11.8

Where:






145

5.2.1. Summary

The untreated sulphur dyed cotton fabric exhibits low resistance to bleaching (Table

5.2) and this bleach sensitivity of sulphur dyes is usually attributed to the cleavage of

some of the S-S (disulphide) bonds within the complex heterocyclic macromolecules

and loss of the chromophores [5].

The results show that the application of the crease resist finish alone produces an

appreciable improvement in resistance of sulphur dyes against oxidative bleaching,

especially ISO 1O5 CO6 washing conditions (AC 1 and AC 2). However, the wash

fastness of the dyed fabric against the more aggressive ISO 1O5 CO9 treatment tends to

be better when a combination with the tannin is used. The improved wash fastness

achieved as a result of sequential application of Fixapret CP and Bayprotect Cl may be

attributed to the formation of low aqueous solubility tannin/finishing agent complex.

Application of crease resist finish to cotton involves padding the material with a

solution containing a condensation polymer precursor and a suitable polymerisation

catalyst followed by drying and curing. As a result of heating, the polymer precursor

either reacts with hydroxyl groups in the cellulose to form crosslinks between adjacent

polymer chains, or it polymerises in the amorphous regions of the fibres [5].Crease

resist finish treatment of sulphur dyed cotton produces crosslinked cellulose fabric and

the crosslinking treatment serves to “lock” the dye in the fabric, so increasing the wash

fastness [6]. In general, compared to the reference sample, Fixapret CP crosslinked

sulphur dyed fabric exhibited improved wash fastness (less colour change) against both

(ISO 1O5 CO6 and ISO 1O5 CO9) washing regimes. However, a significant loss in

colour strength was observed which could possibly be attributed to the removal of

surface dye as a result of aftertreatment with the finish. Further, the effect on the colour

of the dyeing is to produce a duller tone fabric [1]. On comparing the laundered

samples, it is observed that the colour strength of the finished fabric is higher than

untreated sample, hence the durable press finished fabric exhibits improved wash

fastness than untreated.

Application of different concentrations of Bayprotect Cl (4% omf and 10 % omf) and

Fixapret CP (60 g/L and 120 g/L) indicate that increasing the concentration of tannin



146

from 4% omf to 10% omf does not yield significant changes in percentage colour loss,

hence, lower concentration of Bayprotect Cl (4% omf ) was chosen for further work.

Although the combination of 4% omf Bayprotect Cl and 120 g/L Fixapret CP (AC 4)

may best be suited for protection against ISO 1O5 CO9, the shade appears to change

more than in the case of ISO 1O5 CO6 when compared to the independent application

of Fixapret CP (Figure 5.1). As seen in Table 5.2, application of Fixapret CP (AC 1) on

sulphur dyed fabric causes the fabric to become yellower and also reduces the chroma.

When the fabric is subjected to following Bayprotect Cl (AC 3) treatment, the dyed

fabric tends to be redder and yellower and the chroma is further reduced. These changes

in shade are more noticeable in ISO 1O5 CO6 washed samples than ISO 1O5 CO9,

presumably due to different detergent formulations. Hence, the GS rating as well as DE

values for the samples aftertreated with Fixapret CP and Bayprotect Cl and laundered

under ISO 1O5 CO6 washing regime are affected (Figure 5.1). Since the crease resist

finished fabric undergoes shade changes when exposed to bleaching environment, this

change is further enhanced due to Bayprotect Cl treatment. This is presumably due to

the characteristic yellowish brown colour of the anionic tannin based product.

Investigation into the effects of aftertreatments with Bayprotect Cl, Fixapret CP and choline chloride on the fastness properties of sulphur dyed cotton fabric

147

Figure 5.1 Effect of aftertreatments with Bayprotect Cl and Fixapret CP on wash fastness of CI Leuco Sulphur Black 1 dyed cotton

fabric (where BP refers to Bayprotect Cl and 100 g/L sodium sulphate, Fixapret CP also infers use of magnesium chloride as detailed in

Table 5.1)

1.5 0.7 0.7

1.2 1.3 1.6 1.6

1.1 1.2

3.5

0.7 0.7 1.5 1.3

2.0 1.9 2.2

3.3

12.9

4.7

2.9 2.4 2.2 2.4 2.4

11.6 11.8

0.00

2.00

4.00

6.00

8.00

10.00

12.00

14.00

Non-Treated 60g /LFixapret CP

120g/lFixapret CP

4% BP+60g/lFixapret CP



10%BP+120g/lFixapret CP

4% BP 10% BP

DE

ISO IO5 CO6 With perborate x1 ISO IO5 CO6 With perborate x3 ISO IO5 CO9 With perborate



148

5.3. Effects of sequential application of Bayprotect Cl, Fixapret CP and choline

chloride

A single finish containing crosslinker, acid catalyst and quaternary ammonium

compounds can be used for differential treatments of cotton fabric. The finished, dried

and cured fabric is partly crosslinked and cationic and partly untreated cotton. The

fabric is dyed under different pH conditions and using different dyes to produce two-

colour and contrasting tonal effects. The purpose of using a reactive additive in

crosslinking system is to produce additional properties in the crosslinked fabric other

than resiliency and shrinkage control [7].

Previous work on modification of electrical resistivity of durable press finishes showed

that cationic groups could possibly be introduced into the finished cotton by the

covalent attachment of choline along with the crosslinking agent. The combination of a

crosslinking agent and choline chloride applied through pad-dry-cure method was useful

in binding choline to the cotton fabric. This fabric was capable for higher uptake of CI

Reactive Red 2 under acidic conditions in the absence of salt. Thus CC-treated fabrics

were capable of increasing exhaustion of reactive dyes in the absence of salt and in fact

the addition of salt reduced the dye uptake. The dyeing of CC-grafted cotton fabric

under acidic conditions gave the highest colour yields and improved wash fastness [8].

In order to improve the wash fastness of sulphur dyed cotton fabric, a sequential

application of Bayprotect Cl followed by combination of Fixapret CP and choline

chloride (a cationic reactant) was also investigated. Choline chloride is a quaternary

amine salt, it dissociates in water into the corresponding positively charged quaternary

hydroxyl alkylammonium ion and the negatively charged chloride ion. According to

OECD-criteria (organisation for economic cooperation and development) it is readily

biodegradable [9]. It imparts cationic charge to cotton fabric and enhances the reactivity

of anionic dye when used in combination with resins [10].

The purpose of using choline chloride with Fixapret CP was to impart cationic charge to

the fabric so as to improve the wash fastness of the dyed fabric against both washing

regimes. While keeping the amount of Bayprotect Cl and Fixapret CP constant, three

combinations were investigated with increasing concentrations of choline chloride.



149

Choline chloride was added into the finish bath containing Fixapret CP and magnesium

chloride and applied through pad-dry-cure method of application. AC 9 contains 4%

omf Bayprotect Cl and 120 g/L Fixapret CP along with 24 g/L magnesium chloride.

This application condition was used as the base formulation owing to the observed

improved protection against oxidative bleaches in household laundering conditions (AC

4, Table 5.2). AC 10, AC 11 and AC 12 contains 1 g/L, 10 g/L and 60 g/L of choline

chloride respectively while the quantity of Bayprotect Cl (4% omf) and Fixapret CP

(120 g/L) were fixed. Application conditions (AC) for the investigations into the effect

of choline chloride for aftertreatments of CI Leuco Sulphur Black 1 dyed cotton fabric

(reduced with Diresul RAD) are detailed in Table 5.3. The colorimetric data of CI

Leuco Sulphur Black 1 dyed cotton fabric (reduced with Diresul RAD) subjected to

different wash fastness conditions (WF) is represented in Table 5.4.


Bayprotect Cl, Fixapret CP and choline chloride on CI Leuco Sulphur Black 1

dyed cotton fabric

Application

conditions

Concentrations

Application


(g/L)

Magnesium

chloride

(g/L)

Choline

chloride

(g/L)

Bayprotect Cl

(% omf)

Sodium

sulphate

(g/L)

AC 9 - - - 4 100 98

oC,

20 minutes

120 24 - - - Pad-Dry-Cure

AC 10 - - - 4 100 98

oC,

20 minutes

120 24 1 - - Pad-Dry-Cure

AC 11 - - - 4 100 98

oC,

20 minutes

120 24 10 - - Pad-Dry-Cure

AC 12 - - - 4 100 98

oC,

20 minutes

120 24 60 - - Pad-Dry-Cure



150


Leuco Sulphur Black 1 dyed cotton fabric aftertreated with Bayprotect Cl,

Fixapret CP and varying concentrations of choline chloride

Washing

Treatment L* a* b* c* h K/S

%Colour

loss

GS

Rating DE


oC, 20 minutes)

120 g/L Fixapret CP + 24 g/L magnesium chloride (P-D-C)

Aftertreated 33.1 -0.7 -3.1 3.2 256.9 6.1

WF 1 33.1 -1.8 -2.4 3.0 232.7 6.1 0% 4 1.3

WF 2 33.3 -1.9 -2.2 2.9 229.1 6.1 0% 4 1.5

WF 3 35.3 -1.7 -2.1 2.7 230.5 5.3 13% 3/4 2.7


oC, 20 minutes)

120 g/L Fixapret CP + 24 g/L magnesium chloride + 1 g/L choline chloride (P-D-C)

Aftertreated 33.0 -0.7 -3.1 3.2 257.4 6.0

WF 1 32.7 -1.9 -2.6 3.2 234.6 6.3 -5% 4 1.3

WF 2 32.6 -1.9 -2.4 3.0 232.3 6.4 -7% 4 1.4

WF 3 35.4 -1.8 -2.3 2.9 232.5 5.3 12% 3/4 2.7

AC 11 4% omf Bayprotect Cl + 100g/L sodium sulphate (98

oC, 20 minutes)

120g/L Fixapret CP + 24 g/L magnesium chloride + 10 g/L choline chloride (P-D-C)

Aftertreated 32.1 -0.6 -3.1 3.1 259.1 6.4

WF 1 31.8 -1.7 -2.8 3.2 238.4 6.8 -6% 4/5 1.2

WF 2 33.2 -2.0 -2.5 3.2 231.2 6.2 3% 4 1.9

WF 3 37.1 -1.8 -1.9 2.7 226.8 4.6 28% 2/3 5.3

AC 12 4% omf Bayprotect Cl + 100g/L sodium sulphate (98

oC, 20 minutes)

120g/L Fixapret CP + 24 g/L magnesium chloride + 60 g/L choline chloride (P-D-C)

Aftertreated 33.5 -0.7 -3.1 3.1 256.7 5.8

WF 1 32.9 -1.9 -2.9 3.4 236.3 6.3 -9% 4 1.3

WF 2 33.5 -2.0 -2.4 3.1 229.8 6.1 -5% 4 1.5

WF 3 38.6 -1.9 -0.9 2.1 205.1 4.2 28% 2/3 5.7

Where:






151

Figure 5.2 Effect of aftertreatments with Bayprotect Cl, Fixapret CP and

varying concentrations of choline chloride on wash fastness of CI Leuco

Sulphur Black 1 dyed cotton fabric (where BP and CC refers to Bayprotect Cl

and choline chloride, respectively)

5.3.1. Summary

Sequential application of a crosslinking agent after tannin treatment has produced

improved fastness for ISO 1O5 CO9; however it tends to reduce the chroma when

compared to the individual application of the crosslinking agent to the sulphur dyed

fabric. However, the co-application of choline chloride and Fixapret CP after tannin

treatment did not considerably enhance the washfastness of the dyed samples for either

test. In fact on increasing the concentration of choline chloride, the colour strength of

ISO 1O5 CO9 washed fabric was reduced which resulted in increased colour loss. The

possible reason for this could be desorption of the dye from the fabric surface as a result

of higher concentrations of choline chloride and Fixapret CP.

1.5 1.3 1.3 1.2 1.3

3.5

1.5 1.4 1.9

1.5

12.9

2.7 2.7

5.3 5.7

0.00

2.00

4.00

6.00

8.00

10.00

12.00

14.00

Non-Treated 4% omf BP + 120g/L Fixapret

4% omf BP + 120g/L Fixapret + 1

g/L CC


g/L CC


g/L CC

DE

ISO 1O5 CO6 with perborate x1 ISO IO5 CO6 With perborate x3 ISO IO5 CO9 With perborate



152

In order to make sure that similar experimental conditions are maintained every time,

AC 4 was repeated in this set of experiments with the title “AC 9”. On comparing AC 4

and AC 9, slight variations in the percentage colour loss can be observed which are

expected during the repetition of the experiments, however the grey scale rating is the

same for both samples. The summarised results are illustrated in Figure 5.2.

5.4. Application of relative proportions of Bayprotect Cl, Fixapret CP and choline

chloride

The crease resistant finish, Fixapret CP was found to produce deleterious effect on the

shade of the dyed fabric when used in high concentrations (AC 2, Table 5.2), therefore,

smaller quantities (10-30 g/L) were introduced in the finish bath with a range of choline

chloride and Fixapret CP concentrations tested to assess the effects of the fixatives on

both washing systems. The compositions are detailed in Table 5.5. The selected

concentration for Bayprotect Cl was 4% omf, which was found to be an optimum

quantity from previous work (section 5.2). The amount of Fixapret CP introduced was

10-30 g/L while various concentrations of choline chloride (20, 30 and 50 g/L) were

also added to investigate the comparative impact on the aftertreated fabrics. The

colorimetric data of the above said experiments is listed in Table 5.6.

Table 5.5 Composition and application parameters for Bayprotect Cl, Fixapret

CP and choline chloride on CI Leuco Sulphur Black 1 dyed cotton fabric

Application

conditions

Concentrations

Application


(g/L)

Magnesium

chloride

(g/L)

Choline

chloride

(g/L)

Bayprotect Cl

(% omf)

Sodium

sulphate

(g/L)

AC 13 - - 20 - - Pad-Dry-Cure

AC 14 - - - 4 100 98oC,

20 minutes

AC 15 - - - 4 100 98

oC,

20 minutes


AC 16 - - - 4 100 98

oC,

20 minutes




153

AC 17 - - - 4 100 98

oC,

20 minutes


AC 18 - - - 4 100 98

oC,

20 minutes


AC 19 - - - 4 100 98

oC,

20 minutes



Leuco Sulphur Black 1 dyed cotton fabric aftertreated with Bayprotect Cl,

Fixapret CP and choline chloride

Washing


%Colour

loss

GS

Rating DE

AC 13 20 g/L choline chloride (P-D-C)

Aftertreated 33.6 -0.9 -4.5 4.6 258.5 6.0

WF 1 34.6 -1.4 -4.7 4.9 253.1 5.7 5% 4/5 1.1

WF 2 36.4 -1.5 -4.7 4.9 252.6 5.0 17% 3/4 2.8

WF 3 46.7 -1.7 -3.5 3.9 244.1 2.5 58% 1 13.1


Aftertreated 32.2 -0.6 -3.9 3.9 261.7 6.5

WF 1 32.7 -1.5 -4.2 4.5 250.9 6.5 0% 4/5 1.1

WF 2 34.3 -1.4 -4.3 4.5 252.2 5.8 11% 3/4 2.4

WF 3 43.2 -1.7 -3.4 3.8 243.1 3.0 54% 1 11.9


oC, 20 minutes)

10 g/L Fixapret CP + 2 g/L magnesium chloride +20 g/L choline chloride (P-D-C)

Aftertreated 32.9 -0.5 -3.5 3.6 261.5 6.1

WF 1 33.4 -1.6 -3.7 4.0 246.6 6.2 -2% 4/5 1.2

WF 2 34.0 -1.7 -3.8 4.1 246.5 5.9 3% 4 1.6

WF 3 42.5 -1.7 -1.3 2.2 217.8 3.2 48% 1/2 9.9


oC, 20 minutes)


Aftertreated 34.4 -0.5 -3.4 3.5 262.0 5.4

WF 1 34.2 -1.6 -3.6 4.0 246.0 5.8 -7% 4/5 1.2

WF 2 34.9 -1.6 -3.8 4.1 246.5 5.5 -2% 4 1.3

WF 3 42.9 -1.7 -1.5 2.3 221.3 3.2 41% 1/2 8.8


oC, 20 minutes)


Aftertreated 33.5 -0.5 -3.5 3.6 261.6 5.8

WF 1 33.9 -1.7 -3.5 3.9 244.4 5.9 -2% 4/5 1.2

WF 2 33.8 -1.8 -3.4 3.9 242.8 6.0 -3% 4 1.3

WF 3 41.7 -1.7 -0.4 1.7 194.8 3.4 41% 1/2 8.8



154


oC, 20 minutes)


Aftertreated 33.5 -0.5 -3.4 3.4 262.0 5.8

WF 1 33.2 -1.6 -3.4 3.7 244.7 6.2 -7% 4/5 1.2

WF 2 34.2 -1.7 -3.5 3.9 243.7 5.8 0% 4 1.4

WF 3 41.8 -1.8 -0.9 2.0 206.4 3.4 41% 1/2 8.7


oC, 20 minutes)


Aftertreated 34.3 -0.6 -3.5 3.5 260.9 5.5

WF 1 34.5 -1.9 -3.3 3.8 240.0 5.7 -4% 4 1.4

WF 2 34.6 -1.8 -3.6 4.0 243.4 5.7 -4% 4 1.3

WF 3 43.2 -1.8 0.6 1.9 161.1 3.0 45% 1/2 9.9

Where:






155

Figure 5.3 Effect of aftertreatments with relative proportions of Bayprotect Cl,

Fixapret CP and choline chloride on the fastness of CI Leuco Sulphur Black 1

dyed cotton fabric (where BP and CC refers to Bayprotect Cl and choline

chloride)

5.4.1. Summary

As discussed previously (section 5.2.1), sequential application of Bayprotect Cl and

Fixapret CP produced notable improvements for ISO 1O5 CO9 but had a deleterious

effect on the shade when the fabric was exposed to ISO 1O5 CO6 washing protocol.

Application of choline chloride did not significantly alter the hue and chroma of the

dyed fabric but was found to improve the wash fastness of the dyed cotton fabric. Thus,

it can be concluded that the addition of choline chloride to the crease resist finish bath

does not affect the shade of the finished fabric and because of its cationic nature is

expected to form complexes with the dye molecules thus enhancing the overall wash

fastnesses.

1.5 1.1 1.1 1.2 1.2 1.2 1.2 1.4

3.5 2.8

2.4 1.6 1.3 1.3 1.4 1.3

12.9 13.1

11.9

9.9

8.8 8.8 8.7

9.9

0

2

4

6

8

10

12

14

Non-Treated 20 g/L CC 4% omf BP 4% omf BP,10 g/L

Fixapret CP +20 g/L CC

4% omf BP,20 g/L


4% omf BP,20 g/L


4% omf BP,30 g/L


4% omf BP,25 g/L


DE




156

Looking at the grey scale ratings, the sequential application of Bayprotect Cl and

reduced concentrations of Fixapret CP and choline chloride (AC 15-AC 18)

significantly improved the wash fastness of the dyed fabric for single ISO 1O5 CO6

washing but only slight improvements were observed for triplicate ISO 1O5 CO6 and

ISO 1O5 CO9 washing. In order to improve the effect of post-treatments on ISO 1O5

CO6 (triplicate cycles) and ISO 1O5 CO9 washing regime, choline chloride was applied

independently and together with Fixapret CP at lower concentrations (10-20 g/L) after

Bayprotect Cl treatment and evaluated for the fastnesses.

5.5. Application of reduced concentrations of choline chloride with Bayprotect Cl

and Fixapret CP

In order to reduce the hazardous environmental effects produced as a result of

formaldehyde present in higher concentrations (60 g/l and 120 g/l) of Fixapret CP and

adverse influence of the same on the chroma, handle and shade of the dyed fabric, lower

quantity of Fixapret CP (10 g/L) was co-applied with choline chloride (10-20 g/L) to the

finish bath. This combination as well as choline chloride on its own was found to offer

increased level of protection against oxidation from previous work (section 5.4).

While keeping the concentration of Bayprotect Cl and Fixapret CP constant that is 4%

omf and 10 g/L respectively, two application conditions (AC 25 and 26) were conducted

with different proportions of choline chloride (10 and 20 g/L) applied on dyed fabric

treated with Bayprotect Cl. Two different application conditions were also carried out

with the sequential application of Bayprotect Cl followed by choline chloride (AC 23

and 24). The details are outlined in Table 5.7, Table 5.8 and Figure 5.4.

.



157

Table 5.7 Composition and application parameters for reduced concentrations

of Bayprotect Cl, Fixapret CP and choline chloride on CI Leuco Sulphur Black

1 dyed cotton fabric

Application

conditions

Concentrations

Application


(g/L)

Magnesium

chloride

(g/L)

Choline

chloride

(g/L)

Bayprotect Cl

(% omf)

Sodium

sulphate

(g/L)

AC 20 10 2 - - - Pad-Dry-Cure

AC 21 - - - 4 100 98oC,

20 minutes

AC 22 - - - 4 100 98

oC,

20 minutes

10 2 - - - Pad-Dry-Cure

AC 23 - - - 4 100 98

oC,

20 minutes

- - 10 - - Pad-Dry-Cure

AC 24 - - - 4 100 98

oC,

20 minutes

- - 20 - - Pad-Dry-Cure

AC 25 - - - 4 100 98

oC,

20 minutes


AC 26 - - - 4 100 98

oC,

20 minutes



Leuco Sulphur Black 1 dyed cotton fabric aftertreated with reduced

concentrations of Bayprotect Cl, Fixapret CP and choline chloride

Washing


%Colour

loss

GS

Rating DE

AC 20 10 g/L Fixapret CP + 2 g/L magnesium chloride (P-D-C)

Aftertreated 29.8 -1.0 -3.8 3.9 255.8 7.9

WF 1 30.4 -1.3 -4.1 4.2 252.7 7.7 3% 4/5 0.7

WF 2 30.8 -1.3 -4.0 4.2 252.3 7.4 6% 4/5 1.1

WF 3 38.7 -1.6 -2.5 3.0 236.6 4.2 47% 1/2 9.1


Aftertreated 29.4 -0.4 -3.8 3.8 264.2 7.9

WF 1 29.8 -1.3 -4.2 4.4 252.7 8.0 -1% 4/5 1.1

WF 2 31.7 -1.4 -4.3 4.5 251.8 7.0 11% 3/4 2.6

WF 3 41.1 -1.5 -3.1 3.5 243.9 3.6 54% 1 11.8



158


oC, 20 minutes),

10 g/L Fixapret CP + 2 g/L magnesium chloride (P-D-C)

Aftertreated 29.9 -0.4 -3.5 3.6 263.4 7.6

WF 1 29.4 -1.3 -3.8 4.0 251.2 8.2 -8% 4/5 0.9

WF 2 30.0 -1.2 -3.9 4.1 252.6 7.8 -3% 4/5 1.0

WF 3 38.1 -1.5 -2.4 2.9 237.4 4.3 43% 1/2 8.4


oC, 20 minutes),

10 g/L choline chloride (P-D-C)

Aftertreated 29.8 -0.5 -3.7 3.8 263.2 7.7

WF 1 29.7 -1.2 -4.0 4.2 253.0 8.0 -4% 4/5 0.8

WF 2 30.6 -1.2 -4.1 4.3 253.3 7.5 3% 4/5 1.2

WF 3 39.0 -1.5 -2.9 3.3 243.5 4.1 47% 1/2 9.2


oC, 20 minutes),

20 g/L choline chloride (P-D-C)

Aftertreated 29.7 -0.4 -3.7 3.7 264.2 7.7

WF 1 29.3 -1.2 -4.1 4.2 253.2 8.3 -8% 4/5 1.0

WF 2 30.6 -1.2 -4.1 4.3 253.4 7.5 3% 4 1.3

WF 3 39.2 -1.5 -2.9 3.2 243.5 4.1 47% 1/2 9.6


oC, 20 minutes),


Aftertreated 30.1 -0.4 -3.5 3.5 263.4 7.5

WF 1 29.6 -1.3 -3.7 3.9 250.5 8.1 -8% 4/5 1.1

WF 2 31.1 -1.2 -3.9 4.1 252.6 7.2 4% 4 1.4

WF 3 38.2 -1.5 -2.5 2.9 238.3 4.3 43% 1/2 8.2


oC, 20 minutes),


Aftertreated 30.2 -0.5 -3.5 3.5 262.7 7.4

WF 1 30.1 -1.3 -3.8 4.0 250.5 7.8 -5% 4/5 0.9

WF 2 29.1 -1.2 -3.8 4.0 251.9 8.4 -14% 4 1.3

WF 3 38.4 -1.6 -2.5 2.9 237.3 4.3 42% 1/2 8.3

Where:






159

Table 5.9 Light and crocking fastness data for CI Leuco Sulphur Black 1 dyed

cotton fabric aftertreated with reduced concentrations of Fixapret CP,

Bayprotect Cl and choline chloride

Aftertreatments Light fastness Crocking fastness

Dry Wet

Untreated (No aftertreatment) 4 4-5 3-4

AC 7 4 4-5 3-4

AC 20 4 4-5 3

AC 22 4 4-5 3

AC 23 4 4-5 3-4

AC 24 4 4-5 3-4

AC 25 4 4-5 3

AC 26 4 4-5 3

Table 5.10 Effects of aftertreatments with Fixapret CP, Bayprotect Cl and

choline chloride on tensile properties of CI Leuco Sulphur Black 1 dyed cotton

fabrics

Samples


Tensile

strength

(N/mm2)

Tensile

extension

at Break

(mm)

Tensile

strength

(N/mm2)

Tensile

extension

at Break

(mm)

Untreated

(No aftertreatment) 4.6 19.9 3.8 31.8

AC 2 3.7 12.1 2.5 14.0

AC 4 3.3 8.6 2.4 16.5

AC 20 3.8 14.1 3.6 20.9

AC 22 3.5 13.6 3.4 22.9

AC 23 4.1 14.7 3.4 23.5



160

5.5.1. Summary

Investigation into the sequential application of 4% omf Bayprotect Cl and 10 g/L

Fixapret CP coupled with 10 and 20 g/L of choline chloride indicated that the combined

application of Fixapret CP and choline chloride following Bayprotect Cl treatment does

not yield any significant effect on the wash durability to the CO6 washing test. On the

other hand, when choline chloride was applied after Bayprotect Cl, it produced results

comparable to the individual application of Fixapret CP (AC 20 and 23). Two different

concentrations (10 and 20 g/L) of choline chloride in AC 23 and 24, respectively, were

applied after 4% omf Bayprotect Cl. It was established that sequential application of 4%

omf Bayprotect Cl and 10 g/L of choline chloride would produce improved results in

terms of increased fastness to laundering. The combination (AC 23) worked well for

both washing systems, that is, ISO 1O5 CO6 and CO9, offering 0.5 GS unit rises for the

dyed and treated fabric. It is presumed that this effect was due to the formation of

complexes between cationic reactant (choline chloride) and anionic dye or tannin

(Bayprotect Cl) resulting in the formation of large molecular sized complexes which are

locked in the fabric.

The impact of aftertreatments on the light and rub fastnesses of the treated fabrics was

also evaluated and the results indicated that these treatments did not affect the light

fastness and dry crocking of the dyed fabric (being 4 and 4-5 for all samples

respectively). However, it can clearly be seen that treatment with Fixapret CP induced

detrimental effects on the wet crocking of the dyed fabric, which is a typical

characteristic of the finish. The mechanical properties of the aftertreated samples

revealed that the application of crease resistant finish concomitantly reduced the tensile

strength of the fabric on increasing the concentrations of the finish from 10 g/L to 120

g/L. This effect was further increased with the sequential application of the tannin

followed by crease resistant finish. However, the treatment of dyed fabric with

Bayprotect Cl and choline chlorine did not significantly damage the tensile strength

(Table 5.10).

Aftertreatments with various combinations of Bayprotect Cl, Fixapret CP and choline

chloride indicated that sequential application of Bayprotect Cl and choline chloride



161

appears to be comparatively better option for improving the wash fastness of sulphur

dyed fabric against both washing systems.

The application conditions leading to improved wash fastness of sulphur dyed fabrics,

discussed in chapters 4 and 5 can be summarised as follows:

1. Application of Bayprotect Cl and sodium sulphate;

2. Sequential application of Bayprotect Cl and choline chloride;

3. Application of Fixapret CP;

4. Sequential application of Bayprotect Cl and Fixapret CP.

Methods 1 and 2 proved relatively effective in improving the wash down of sulphur

dyes against the oxidative bleaching action of standard ISO 1O5 CO6 washing system.

However, in order to reduce the fading of sulphur dyed fabrics against more aggressive

ISO 1O5 CO9 washing protocol, methods 3 and 4 proved to be better as they involved

the application of DMDHEU based crease resistant finish which possibly crosslinks the

dye with cellulosic fibre. Nevertheless, the introduction of choline chloride in the

Fixapret CP finish bath did not significantly improve the wash fastness of the dyed

fabric.

Although sequential application of Bayprotect Cl and Fixapret CP was beneficial in

terms of achieving an improved wash fastness against ISO 1O5 CO9 washing, but

Fixapret CP was found to have deleterious effects on the tensile strength, wet crocking

and chroma of the fabric. Furthermore, the aftertreatments with Fixapret CP would not

lead to an eco-friendly alternative due to the presence of formaldehyde. Since, the main

focus of research was to significantly enhance the wash fastness of sulphur dyed cotton

fabric against ISO 1O5 CO9 washing with minimum influence on the fabric properties

and the environment, hence further work was carried out to meet these requirements.

The treatment of the dyed fabric with Bayprotect Cl and choline chloride was found to

offer improved wash fastness with minimum effects on the shade of the finished fabric,

therefore aftertreatments with different cationic fixatives were carried out. The sulphur

dyed fabric was aftertreated with cationic fixatives on their own and after Bayprotect Cl

treatment, the details of which are described in chapter 6.

Investigation into the effects of aftertreatments with Bayprotect Cl, Fixapret CP and choline chloride on the fastness properties of sulphur dyed cotton fabric

162

Figure 5.4 Effect of aftertreatments with reduced concentrations of Bayprotect Cl, Fixapret CP and choline chloride on the wash

fastness of CI Leuco Sulphur Black 1 dyed cotton fabric

1.5 0.7

1.1 0.9 0.8 1.0 1.1 0.9

3.5

1.1

2.6

1.0 1.2 1.3 1.4 1.3

12.9

9.1

11.8

8.4

9.2 9.6

8.2 8.3

0.00

2.00

4.00

6.00

8.00

10.00

12.00

14.00

Non-Treated 10 g/L Fixapret 4% omf BP 4% omf BP, 10g/L Fixapret

4% omf BP, 10g/L CC

4% omf BP, 20g/L CC

4% omf BP,10 g/L Fixapret

+10 g/L CC

4% omf BP, 10g/l Fixapret +20

g/L CC

DE




163

5.6. References


[2] Zhou W and Yang Y. Improving the resistance of sulfur dyes to oxidation. Industrial

and Engineering Chemistry Research. 2010;49(10):4720-5.

[3] Heywood D. Textile finishing. Bradford: Society of Dyers and Colourists, 2003.

[4] Dehabadi VA, Buschmann H-J and Gutmann JS. Durable press finishing of cotton

fabrics: An overview. Textile Research Journal. 2013;83(18):1974-95.

[5] Broadbent AD. Basic principles of textile coloration. Bradford: Society of Dyers and

Colorists, 2001.

[6] Shekarriz S. Effects of polycarboxylic acids on untreated cotton and solubilised

sulfur dyed cotton. Journal of Progress in Color, Colorants and Coatings. 2014;7(1):1-9.

[7] Harper RJ. Crosslinking, grafting and dyeing: Finishing for added properties. Textile

Chemist and Colorist. 1991;23(11):15-20.

[8] Lewis DM and McIlroy KA. The chemical modification of cellulosic fibres to

enhance dyeability. Review of Progress in Coloration and Related Topics. 1997;27(1):5-

17.

[9] Choline Chloride -SIDS initial assessment report for SIAM 19. UNEP Publication.

[10] Cardamone JM and Turner J. Cationic applications for union dyeing wool/cotton

blends. Textile Chemist and Colorist and American Dyestuff Reporter. 2000;32(6):49-

53.

Investigation into the effects of aftertreatments with Bayprotect Cl and cationic fixatives on the

fastness properties of sulphur dyed cotton fabric

164


Cl and cationic fixatives on the fastness properties of sulphur dyed

cotton fabric

6.1. Introduction

It was concluded from investigations in chapter 5, that the sequential application of

Bayprotect Cl and choline chloride provides some protection to the sulphur dyed fabric

from the oxidative action of perborate in domestic laundering processes. However, to

enhance the protective effect, three cationic fixing agents were tested in place of choline

chloride. The cationic fixing agents were applied individually and following Bayprotect

Cl treatment with a view to evaluate the wash durability of theses fixatives under ISO

1O5 CO6 and CO9 test conditions. These cationic fixing agents have been used

previously to improve the wash fastness of direct dyes with a simple exhaust application

method [1].

It is known that many dye fixing agents are cationic, and are based on various

quaternised or otherwise cationically charged organic nitrogen compounds. Cationic

fixatives are available under various trade names from several suppliers.

The durability of these fixatives generally depends on the particular type of fixative,

method of application, the strength of the dye/fixative bond, aggressiveness of the wash

conditions and the detergent formulation [2].

Cationisation of cellulose can be carried out by introducing amine groups or quaternary

ammonium groups via its hydroxyl groups. A considerable body of studies on this

subject has been carried out since the late 1930s and it has been reported by Granacher

that the cationised cellulose having ether linkages could be synthesised by reacting the

hydroxyl groups with other compounds [3]. A wide variety of cationic fixing agents are

commercially available for post treatments of direct dyeings resulting in enhanced wash

fastness articles. The majority of the cationic fixing agents are polycations of high

molecular mass which are believed to form a large molecular size and low aqueous

solubility complex between the anionic dye and the cationic fixing agent [4].



165

However, a substantial quantity of work has also been conducted to establish the impact

of these fixing agents on the improved fastness of CI Solubilised Sulphur, CI Leuco

Sulphur and CI Sulphur dyes. These studies showed that the use of cationic

polymers/reactants produced improvements in the resistance of sulphur dyeing against

oxidative action of various wash tests such as ISO 1O5 CO6/C2 [1, 4, 5], ISO 4 [4] and

Marks and Spencer C46 [6]. The introduction of cationic sites has been carried out as

pretreatments [7] and aftertreatments [1, 4-6, 8] for leuco and oxidised sulphur dyeings

[4]. Further work revealed that in addition to exhaust application, pad-dry and pad-flash

cure methods of cationisation could also be used to improve the wash fastness of leuco

sulphur dyes [5].

A comprehensive study was carried out by Oakes [2], where cotton fabrics dyed with

three direct dyes (CI Direct Black 22, CI Direct Red 80 and CI Direct Green 26) were

fixed with a range of fixatives of varying efficacy and evaluated for the durability of dye

fixatives. Generally the fixatives were found to be effective in the following order (best

first): Indosol E-50=Tinofix ECO=Solfix E=Indosol CR>Alcofix R>Croscolor F3.

Since Indosol E-50, Tinofix ECO and Solfix E were found to be the most effective

fixatives for direct dyes and Solfix E was previously explored by Burkinshaw on

sulphur dyed cotton fabrics and found to offer significant resistance against oxidation

[4], so these fixatives were selected for CI Leuco Sulphur Black 1 dyed cotton fabric

(reduced with Diresul Reducing agent D) to be used as one of the components of the

protective system.

The use of Solfix E (Ciba-Geigy) for improving the wash fastness of sulphur dyes has

been evaluated by Burkinshaw [4, 7]. This is a proprietary reactive cationic fixing agent

which is believed to form an extensively polymerised and insoluble network of fixative

and dye. This is probably due to the reaction between tertiary amine and cationic groups

present in stoichiometric proportions. The structure of the fixative is still unknown but

the cationic polymer possibly contains a polyamine backbone. It is a fibre-reactive wet

fastness improver and is free of formaldehyde. The reactive groups are formed as a

result of reaction with epichlorohydrin to produce a reactive cationic chlorohydrin

derivative. A highly reactive epoxide is formed in alkaline media, which reacts with

nucleophiles by addition as shown in Scheme 6.1. The benefit of using tertiary amine in



166

a reactive fixative is the enhanced fastness produced as a result of formation of

additional cationic charges [2].

Scheme 6.1 Nucleophilic addition reaction of Solfix E in alkaline media,

reproduced from [2]

The pretreatments and aftertreatments of cotton fabric with Solfix E resulted in sulphur

dyeings with superior wash fastness to ISO 1O5 CO6 and ISO 4 and imparted

substantial enhancement in colour strength. The reason suggested for these findings was

conceivably the reaction of fixing agent with nucleophilic thiol group of reduced

sulphur dye and the formation of large molecular size, sulphur dye-Solfix E compound

retaining low diffusional power within the fibre [4, 7].

Tinofix ECO is an eco-friendly fixative of undisclosed structure and is thought to be a

product derived from reaction of a urea derivative, for example dicyandiamide, with a

guanidine derivative such as diethylenetriamine [2].

Indosol E-50 is believed to have a chemical structure resembling to the dye fixative

Sandofix SWE which is prepared from dicyandiamide. The Indosol E-50 structure is

particularly designed to interact with a number of different sulphonate groupings within

the dye but also to complex with the copper atom in the dye molecule resulting in a

more stable interaction between dye and fixative [2]. The proposed chemical structure

of Indosol E-50 and fixative Sandofix SWE are presented in Scheme 6.2 and Scheme

6.3, respectively.



167

Scheme 6.2 Proposed structural element of Indosol E-50, from [2]

Scheme 6.3 Chemical structure of fixative Sandofix SWE, from [2]

Cationic polymers have the ability to develop a strong electrostatic bond between the

positive charge on the fixative and sulphonate groups on the dye. In this case the bond

energy is of the order of 550–1000 kJ/mol, compared with 15–60 kJ/mol for normal

hydrogen bonding between dye and fabric [2]. There is probably the potential for the

formation of a large molecular size dye-cationic agent complex with low aqueous

solubility arising from the electrostatic forces of attraction between the anionic groups

in the dye and the polycations [1]. For this to occur, the dye must contain anionic group

similar to the sulphonated groups in direct dye. In spite of the fact that only little is

known about the exact chemistry of the sulphur dyes, it has been proposed that some

sulphur dyes may contain sulphonic acid groups [9]. Hence, the large surface area may

lead to maximising the cumulative effect of weak intermolecular forces and also the

physical entrapment.

Similarly, considering that the dyed fabric contains carboxylic acid group on its own

and these groups are further generated as a result of the oxidation achieved by hydrogen

peroxide in the final stage of dyeing, the better adsorption of the dye onto the fabric

might have arisen owing to the ion-ion interactions between the cationic fixing agent

and the anionic carboxylic acid groups on the substrate [1,10].



168

However, an alternative mechanism based on the use of syntans was also proposed

according to which the wet fastness of the sulphur dyes are improved in the same way as

the anionic dyes on nylon. It has been proposed that syntans when applied under acidic

conditions to the polyamide fibre dyed with non-metallised acid dyes develop a

peripheral layer of syntan molecules which inhibits the dye leakage form the fibre. It is

the ion-ion interaction which operates between the protonated amino group in the fibre

and sulphonated group in the syntan along with the hydrogen bonding which contributes

towards the syntan-fibre substantivity [1,11].

6.2. Investigation into the application of different cationic fixatives

Some initial investigations were made with different cationic fixing agents following

application procedures suggested by the manufacturers. The exhaust method of post

treatments was explored to examine the influence of fixatives on sulphur dyed cotton

fabric. Diresul Black RDT was applied at a concentration of 5% omf using

biodegradable Diresul Reducing agent D and four replicates were taken for each

application condition (AC). As recommended by the manufacturers, the maximum

concentrations were selected for the three fixatives outlined in Table 6.1. The details of

application methods have been discussed in chapter 3.

Table 6.1 Composition and application parameters for different fixatives

Fixing agents Concentration L:R Temperature Time pH

Tinofix ECO 3% omf 10:1 40oC 30 minutes 6-7

Solfix E, 2 mL/L NaOH 6% omf 10:1 40oC 30 minutes 8-9

Indosol E-50 + 5 g/L Glauber’s salt 4% omf 10:1 60oC 20 minutes 6-7

6.2.1. Two bath sequential application of Bayprotect Cl and cationic fixatives

In order to determine the effects of cationic fixatives and their combinations with

Bayprotect Cl, the dyed fabric was first treated with cationic fixatives on their own and

then followed by Bayprotect Cl treatments. The details of the application parameters

and colorimetric data are shown in Table 6.2 and Table 6.3, respectively.



169

Table 6.2 Compositions and application parameters for sequential application

of Bayprotect Cl and cationic fixatives on CI Leuco Sulphur Black 1 dyed

cotton fabric

Application


Application

procedure

AC 1 3% omf Tinofix ECO 40oC, 30 minutes

AC 2 6% omf Solfix E and 2 mL/L NaOH 40oC, 30 minutes

AC 3 4% omf Indosol E-50 + 5 g/L Glauber’s salt 60oC, 20 minutes

AC 4 4% omf Bayprotect Cl + 100 g/L sodium sulphate, 98

oC, 20 minutes

3% omf Tinofix ECO 40oC, 30 minutes


oC, 20 minutes

6% omf Solfix E and 2 mL/L NaOH 40oC, 30 minutes


oC, 20 minutes

4% omf Indosol E-50 + 5 g/L Glauber’s salt 60oC, 20 minutes


Leuco Sulphur Black 1 dyed cotton fabric sequentially aftertreated with

Bayprotect Cl and cationic fixatives

Washing


%Colour

loss

GS

Rating DE

Untreated 28.1 -0.9 -4.1 4.2 257.4 9.0

WF 1 29.8 -1.3 -4.3 4.5 253.9 8.0 11% 4 1.7

WF 2 31.5 -1.3 -4.4 4.6 253.4 7.1 21% 3 3.4

WF 3 42.7 -1.6 -3.3 3.6 243.5 3.2 64% 1 14.7

3% omf Tinofix ECO (40oC, 30 minutes)

AC 1 28.9 -1.2 -4.2 4.3 254.3 8.5

WF 1 28.7 -1.5 -4.3 4.5 250.3 8.8 -4% 4/5 0.4

WF 2 29.4 -1.5 -4.2 4.5 250.6 8.4 1% 4/5 0.6

WF 3 37.1 -1.8 -2.3 2.9 231.9 4.7 45% 1/2 8.5

6% omf Solfix E and 2 mL/L NaOH (40oC, 30 minutes)

AC 2 28.1 -1.5 -3.9 4.1 249.1 9.1

WF 1 29.0 -1.5 -3.9 4.1 249.5 8.5 7% 4/5 0.9

WF 2 29.4 -1.4 -3.6 3.9 248.2 8.3 9% 4 1.3

WF 3 35.1 -1.8 -0.1 1.8 181.7 5.2 43% 2 8.0

4% omf Indosol E-50 + 5 g/L Glauber’s salt (60oC, 20 minutes)

AC 3 29.0 -1.3 -4.0 4.2 252.4 8.5

WF 1 29.6 -1.7 -4.2 4.5 247.7 8.3 2% 4/5 0.7

WF 2 29.8 -1.7 -4.1 4.4 248.0 8.1 5% 4/5 0.9

WF 3 41.0 -1.8 -1.7 2.5 223.6 3.6 58% 1 12.2

4% omf Bayprotect Cl + 100 g/L sodium sulphate (98oC, 20 minutes)


AC 4 28.8 -0.7 -3.9 4.0 259.6 8.4

WF 1 27.9 -1.6 -3.6 4.0 246.8 9.2 -10% 4/5 0.9

WF 2 28.7 -1.6 -3.6 3.9 246.4 8.7 -4% 4/5 1.2

WF 3 36.1 -1.7 -2.1 2.7 231.7 5.0 40% 2 7.6



170


6% omf Solfix E and 2 mL/L NaOH (40oC, 30 minutes)

AC 5 27.3 -2.4 -1.9 3.0 219.2 9.7

WF 1 27.1 -1.7 -3.2 3.6 242.2 9.8 -1% 4 1.4

WF 2 28.2 -1.7 -2.9 3.4 239.4 9.0 7% 4 1.5

WF 3 35.5 -1.7 -0.1 1.8 202.3 5.1 44% 1/2 8.3


4% omf Indosol E-50 + 5 g/L Glauber’s salt (60oC, 20 minutes)

AC 6 29.1 -1.0 -3.9 4.0 256.0 8.3

WF 1 29.6 -1.7 -3.5 3.9 243.5 8.1 2% 4/5 1.0

WF 2 29.6 -1.7 -3.2 3.7 242.1 8.1 2% 4/5 1.1

WF 3 39.1 -1.7 -2.1 2.7 230.1 4.1 51% 1/2 10.2

Where:




Table 6.4 Light and crocking fastness data for CI Leuco Sulphur Black 1 dyed

cotton fabric aftertreated with Bayprotect Cl and cationic fixatives

Application conditions Light

fastness

Crocking fastness

Dry Wet

Untreated 4 4-5 3-4

3% omf Tinofix ECO 4 4-5 3-4

6% omf Solfix E and 2 mL/L NaOH 4 4-5 3-4

4% omf Indosol E-50 + 5 g/L Glauber’s salt 4-5 4-5 3-4

4% omf Bayprotect Cl + 100 g/L sodium sulphate,

3% omf Tinofix ECO 4 4-5 3-4


6% omf Solfix E and 2 mL/L NaOH 4 4-5 3-4


4% omf Indosol E-50 + 5 g/L Glauber’s salt 4-5 4-5 3

6.2.2. Summary

Three different kinds of cationic fixatives were applied to sulphur dyed fabric on their

own and followed by Bayprotect Cl treatment. As seen in Table 6.3 (AC 4), application

of Tinofix ECO after Bayprotect Cl produces the maximum improvements in reduction

of colour loss for ISO 1O5 CO9 washing (reducing percentage colour loss from 64% for



171

untreated fabric to 40% for treated fabric). In addition to this, the colour coordinates

(L*a*b*) do not vary as much as that of the dyed fabrics treated with other cationic

fixatives. No significant deleterious effects of this fixative on light and crocking fastness

were observed (Table 6.4). Hence, Tinofix ECO was selected for the development of a

tannin-cation sequential application process to achieve improved wash fastnesses for

sulphur dyed cotton fabrics.

6.3. Determining a suitable sequence for two-bath application of Tinofix ECO and

Bayprotect Cl

In order to investigate the characteristic effects of using Tinofix ECO with Bayprotect

Cl on the wash fastness of sulphur dyed cotton fabric, several initial experiments were

conducted with varying concentrations and application sequence of the two compounds.

Initially, Tinofix ECO and Bayprotect Cl were applied in a direct sequence as well as

reverse manner to identify the variation in the properties of the washed samples. With

the aim to evaluate the effect of electrolyte (sodium sulphate) in the application of

Bayprotect Cl, two application conditions (AC 8 and 9) were carried out with and

without sodium sulphate as shown in Table 6.5 and Table 6.6. The two finishing agents

were also utilised in two different concentrations with equal proportions that are 5% and

10% omf (Table 6.7 and Table 6.8).


Bayprotect Cl and Tinofix ECO on CI Leuco Sulphur Black 1

dyed cotton fabric (Examining the effects of an electrolyte)

Application

conditions Compositions Application procedure

AC 7 4% Bayprotect Cl + 100 g/L sodium sulphate 98

oC, 20 minutes


AC 8 3% omf Tinofix ECO 40oC, 30 minutes

4% omf Bayprotect Cl 98oC, 20 minutes

AC 9


4% omf Bayprotect Cl + 100 g/L sodium

sulphate 98

oC, 20 minutes



172

Table 6.6 Colorimetric data for ISO 1O5 CO6 and ISO 1O5 CO9 washed

CI Leuco Sulphur Black 1 dyed cotton fabric sequentially aftertreated with

Bayprotect Cl and Tinofix ECO (Examining the effects of an electrolyte)

Washing


%Colour

loss

GS

Rating DE

4% omf Bayprotect Cl + 100 g/L sodium sulphate (98

oC, 20 minutes),

3% omf Tinofix ECO (40

oC, 30 minutes)

AC 7 28.7 -0.5 -3.8 3.9 261.9 8.4

WF 1 28.8 -1.7 -3.6 3.9 245.0 8.6 -2% 4/5 1.2

WF 2 28.7 -1.6 -3.3 3.7 243.8 8.6 -2% 4/5 1.2

WF 3 35.4 -1.8 -2.1 2.7 229.9 5.3 37% 2 7.0


oC, 30 minutes),

4% omf Bayprotect Cl (98

oC, 20 minutes)

AC 8 29.6 -0.4 -3.8 3.9 264.2 7.8

WF 1 28.8 -1.5 -3.7 4.0 247.6 8.7 -12% 4 1.4

WF 2 29.4 -1.5 -3.5 3.8 246.5 8.2 -5% 4/5 1.2

WF 3 34.7 -1.8 -2.1 2.8 230.5 5.5 29% 2/3 5.5


oC, 30 minutes),

4% omf Bayprotect Cl + 100 g/L sodium sulphate (98

oC, 20 minutes)

AC 9 29.7 -0.5 -4.0 4.0 263.0 7.8

WF 1 28.5 -1.5 -3.5 3.9 246.5 8.8 -13% 4 1.7

WF 2 29.1 -1.6 -3.2 3.6 244.1 8.4 -8% 4 1.4

WF 3 35.0 -1.8 -2.1 2.8 229.4 5.4 31% 2 5.8

Where:




Table 6.7 Compositions and application parameters for CI Leuco Sulphur

Black 1 dyed cotton fabric sequentially aftertreated with Bayprotect Cl and

Tinofix ECO (Examining the effects of varying concentrations)

Application


Application

procedure

AC 10 5% Tinofix ECO 40oC, 30 minutes


oC, 20 minutes

5% Tinofix ECO 40oC, 30 minutes

AC 12 5% Tinofix ECO 40

oC, 30 minutes

5% Bayprotect Cl 98oC, 20 minutes


oC, 20 minutes

10% Tinofix ECO 40oC, 30 minutes

AC 14 10% Tinofix ECO 40

oC, 30 minutes

10% Bayprotect Cl 98oC, 20 minutes



173


Leuco Sulphur Black 1 dyed cotton fabric sequentially aftertreated with Tinofix

ECO and Bayprotect Cl (Examining the effects of varying concentrations)

Washing


%Colour

loss

GS

Rating DE


AC 10 28.8 -1.2 -4.2 4.3 255.8 8.6

WF 1 28.7 -1.5 -4.3 4.5 250.3 8.8 -2% 4/5 1.2

WF 2 29.4 -1.5 -4.2 4.5 250.6 8.4 2% 4/5 1.2

WF 3 36.4 -1.8 -2.5 3.1 234.1 5.0 42% 2 8.1

5% omf Bayprotect Cl + 100 g/L sodium sulphate (98oC, 20 minutes),


AC 11 29.2 -0.6 -3.8 3.8 260.5 8.1

WF 1 28.8 -1.8 -3.4 3.8 242.5 8.7 -7% 4/5 1.2

WF 2 29.4 -1.7 -3.4 3.8 243.9 8.3 -2% 4/5 1.1

WF 3 35.9 -1.9 -2.0 2.8 227.1 5.1 37% 2 7.4

5% omf Tinofix ECO (40oC, 30 minutes),

5% omf Bayprotect Cl (98oC, 20 minutes)

AC 12 29.8 -0.6 -3.9 3.9 260.9 7.7

WF 1 29.1 -1.6 -3.7 4.0 246.0 8.5 -10% 4 1.3

WF 2 29.2 -1.8 -3.1 3.6 240.7 8.4 -9% 4 1.5

WF 3 35.0 -1.8 -2.0 2.7 227.5 5.4 30% 2/3 5.6

10% omf Bayprotect Cl + 100 g/L sodium sulphate (98oC, 20 minutes),


AC 13 29.8 -0.7 -3.8 3.9 259.1 7.8

WF 1 28.4 -1.8 -3.3 3.7 241.8 8.9 -14% 4 1.9

WF 2 29.2 -1.9 -3.0 3.6 238.5 8.4 -8% 4 1.5

WF 3 35.9 -1.8 -1.9 2.7 226.1 5.1 35% 2 6.5

10% omf Tinofix ECO (40oC, 30 minutes),

10% omf Bayprotect Cl (98oC, 20 minutes)

AC 14 30.5 -0.6 -3.8 3.9 261.8 7.3

WF 1 28.5 -1.7 -3.5 3.9 244.3 8.9 -22% 3/4 2.3

WF 2 29.6 -1.9 -3.0 3.5 237.7 8.1 -11% 4 1.8

WF 3 34.3 -1.9 -2.0 2.7 226.7 5.7 22% 2/3 4.4

Where:






174

Figure 6.1 Effect of aftertreatments with sequential application of Tinofix ECO

and Bayprotect Cl on wash fastness (ISO 1O5 CO9) of


6.3.1. Summary

As seen in Table 6.6, the sequential application of Tinofix ECO first and then

Bayprotect Cl produces better improvements in wash fastness of the dyes against ISO

1O5 CO9, instead of the reverse application of the sequence. The GS rating for WF 3

for the dyed and treated fabric in AC 8 is 2/3, which exhibits half unit increase when

compared to AC 7. This was presumably due to the formation of a large molecular size

and low aqueous solubility dye-cation complex between the anionic dye and the cationic

fixing agent. On further application of Bayprotect Cl, which is anionic in nature, it is

expected that cation-tannin complexes are formed which keeps the dye molecules

locked within the fabric.

Furthermore, the presence of an electrolyte with Bayprotect Cl did not yield improved

results (AC 9) which could be explained by the salt free dyeing of reactive dyes with

choline chloride grafted cotton. Since cotton fabric aftertreated with choline chloride

produces cationic charges on the fabric, it facilitates the adsorption of reactive dye on

the fabric in the absence of electrolyte [12]. Here also when the anionic Bayprotect Cl

42%

37%

30%

35%

22%

0%

5%

10%

15%

20%

25%

30%

35%

40%

45%

50%

AC 10 AC 11 AC 12 AC 13 AC 14

% C

olo

ur

loss




175

was applied to cationic sulphur dyed fabric, it attracted the oppositely charged tannin

molecules thus avoiding the use of sodium sulphate.

Likewise increasing the concentrations of the fixatives from 5% to 10% omf did not

produce remarkable improvements in terms of Grey scale rating, as shown for AC 12

and AC 14 in Table 6.8. Hence, the two fixatives can provide equally good results with

5% omf concentrations.

6.4. Surface topography of Tinofix ECO aftertreated fabric

Figures 4.4-4.7 are SEM micrographs of the untreated unlaundered and laundered cotton

fabric which on comparison with the Tinofix ECO (AC 10) treated dyed fabrics (Figure

6.2-Figure 6.5) confirms that the surface of the cationised fibre did not show

considerable change. As the extent of cationisation was small under the selected

conditions, the physical structure of the cotton was little changed and the obtained

cationic cotton was suitable for further application in finishing process [13].

However, on observing the SEM micrographs of laundered cationic fabric, some distinct

crystals could be seen. These crystals seemingly appear to be either the protruded

constituent parts of the finish or any component of the laundering formulation.



176

Figure 6.2 SEM micrograph of unlaundered

5% omf Tinofix ECO


Magnification 1000x

Figure 6.3 SEM micrograph of unlaundered

5% omf Tinofix ECO


Magnification 5000x


ISO 105 CO9 laundered, 5% omf Tinofix

ECO treated sulphur dyed cotton fabric

Magnification 1000x


ISO 105 CO9 laundered, 5% omf Tinofix

ECO treated sulphur dyed cotton fabric

Magnification 10000x



177

6.5. Conclusions

The sequential application of three different commercial cationic fixing agents (Tinofix

ECO, Solfix E and Indosol E-50) after Bayprotect Cl treatment on CI leuco Sulphur

Black 1 dyed cotton fabric was evaluated in terms of oxidative bleach damage and it

was found that Tinofix ECO would be a better choice to develop a protective system for

the dye. Greater improvements in terms of percentage colour loss and minimum

damaging impact on colour coordinates and other fastness properties lead to the

selection of this fixative.

On comparing the results produced by the pre and post application of cationic fixative, it

was observed that Tinofix ECO should be applied first so as to get improved results for

ISO 1O5 CO9. However, applying the two auxiliaries in equal proportions with two

different concentrations (5% and 10% omf) did not create a sizable improvement in the

wash fastness of the samples. Hence the 5% omf application was found to be sufficient

for both the chemicals. In contrast, this application procedure surprisingly did not

produce significant improvements for ISO 1O5 CO6 (single and triplicate washes),

since deterioration in shade and GS rating was observed. The basic aim of the research

was to develop the protection system for improving the resistance of the dyes against the

aggressive ISO 1O5 CO9, hence, in order to make the overall process viable for

industrial purpose, optimisation of the process parameters needed to be carried out

which is outlined in the next chapter.

6.6. References



[2] Oakes J, Gratton P and Dixon S. Solubilisation of dyes by surfactant micelles. Part

5: Durability of dye fixatives. Coloration Technology. 2004;120(6):276-83.

[3] Seong H and Ko S. Synthesis, application and evaluation of cationising agents for

cellulosic fibres. Journal of the Society of Dyers and Colourists. 1998;114(4):124-9.



178





1997;33(1):1-9.



Colourists. 1998;114(5-6):165-8.

[7] Burkinshaw SM and Gotsopoulos A. The pre-treatment of cotton to enhance its

dyeability—I. Sulphur dyes. Dyes and Pigments. 1996;32(4):209-28.


treatments to improve the wash fastness. Book of Papers: International Conference &

Exhibition - American Association of Textile Chemists and Colorists. 1996:296-303.


Colorist. 1970;2(13):29-34.

[10] Peter R. Textile chemistry. Vol. III: The physical chemistry of dyeing. Elsevier:

New York, 1975.



[12] Lewis DM and McIlroy KA. The chemical modification of cellulosic fibres to

enhance dyeability. Review of Progress in Coloration and Related Topics. 1997;27(1):

5-17.

[13] Wang L, Ma W, Zhang S, Teng X and Yang J. Preparation of cationic cotton with

two-bath pad-bake process and its application in salt-free dyeing. Carbohydrate

Polymers. 2009;78(3):602-8.

Optimisation of process parameters for sequential application of Tinofix ECO and Bayprotect Cl on


179

7. Optimisation of process parameters for sequential application of

Tinofix ECO and Bayprotect Cl on sulphur dyed cotton fabric

7.1. Background

In the preceding chapter, a study was reported regarding enhancement of wash fastness

of sulphur dyed cotton fabric with the sequential application of a cationic fixative

(Tinofix ECO) and tannin (Bayprotect Cl). It was found that the extent of wash fastness

improvement imparted by the cation-tannin system was greater than that given by a

cationic fixative on its own. The present work continues this investigation for

optimising the process parameters of the two-bath system, which are application

temperature, time and concentrations of the two reagents.

In order to improve the wash fastness of various dyes, the application of two different

fixatives in one-bath or two-bath systems is a common practice. The effects of

sequential aftertreatments with tannin/tannic acid, metal salts, polymeric cationic agents

and syntan (synthetic tanning agents) on the fastness properties of various dyes had

already been investigated several times [1-8].

Few examples would be discussed before introducing the process parameters,

application conditions and possible mechanism of the cation-tannin protection system

developed in this study. In this context, starting with acid dyes, these dyes exhibit

characteristically poor fastness to repeated washing on polyamide fibres. Traditionally,

the aftertreatment of dyed polyamide is carried out with a two-stage (tannic acid and

potassium antimony tartrate), a full backtan process (nowadays rarely used owing to the

toxicity of tartar emetic and shade changes in dyeings) or a single-stage syntan

aftertreatment. In order to eliminate the use of toxic tartar emetic and produced dyeings

with improved fastnesses, a new full backtan method has been employed in which a tin

sulphate derived product (Gallofix) has been used. The tin salt forms a metal complex

with tannin acid (Floctan 1) and so enhanced wash fastness is achieved on polyamide 6,

6 with non-metallised and pre-metallised acid dyes. Similarly, a commercial syntan

(Fixogene AXF) and polymeric cationic agent (Fixogene CXF) were sequentially

applied to the acid dyed polyamide fibre resulting in the formation of a large molecular

size, low aqueous solubility complex between the anionic syntan and the cationic



180

compound within the fibre. These aftertreatments improved the fastness of the dyeing to

repeated wash testing at 40oC [6, 9].

Another example is the application of tannic acid and iron (II) sulphate to improve the

wet fastness and shade depth of black acid dye on nylon 6,6. Dyeings were aftertreated

with a single-stage and two stage method to improve the fastness to repeated washing at

60oC. The possible reason suggested by the author for improved wash fastness was the

formation of a low solubility, large molecular size iron tannate complex within the

periphery of the dyed fibre [4].

7.2. Introduction to experimental

According to observations from chapter 6, the sequential application of Tinofix ECO

(TE) and Bayprotect Cl (BP) on sulphur dyed fabric can be utilised to improve the wash

fastness of sulphur dyes against the oxidative bleaching action of

detergent/perborate/bleach activator formulations (ISO 1O5 CO9). Therefore, the above

mentioned method has been chosen for optimisation so that the overall process could be

made attractive for commercial purposes. The concentrations, application temperatures

and time for Tinofix ECO and Bayprotect Cl as well as the consumption of water have

been worked out for fulfilling the needs for optimisation and to formulate a standard

workable recipe (Table 7.1).

The cotton fabric was dyed with 5% omf Diresul Black RDT (CI Leuco Sulphur Black

1) and reduced with the aid of conventional sodium sulphide (SS) and Diresul Reducing

agent D (RAD). Four replicates were taken for each sample subjected to ISO 1O5 CO9

wash test in the presence of sodium perborate. The optimised parameters were applied

on cotton fabrics reduced with the two reducing systems and dyed with 5% omf Diresul

Liquid Green RDT-N (CI Leuco Sulphur Green 2), Diresul Liquid Blue RDT-G (CI

Leuco Sulphur Blue 7), Diresul Liquid Yellow RDT-E (CI Leuco Sulphur Yellow 22)

and Diresul Liquid Red RDT-BG (CI Leuco Sulphur Red 14) and the samples evaluated

for the wash, light and crocking fastnesses. The dyeing methods have been discussed

previously in section 3.4.



181

Overall optimisation steps are summarised as follows:

1. Application of 1, 2, 3, 4, 5, 8 and 10% omf Tinofix ECO at 40oC for 30 minutes;

2. Two bath sequential application of 5% omf Tinofix ECO and 1, 2, 3, 5 and 10% omf

Bayprotect Cl at 40oC, 60

oC and 98

oC;

3. One bath-two stage application of 5% omf Tinofix ECO (30 minutes) and 5% omf

Bayprotect Cl (at 40oC for 5, 10, 15 and 20 minutes);

4. One bath-two stage application of 5% omf Tinofix ECO (at 40oC for 15 and 20

minutes) and 5% omf Bayprotect Cl (at 40oC for 10 and 15 minutes).

7.3. Aftertreatment sequence

Rinsed sulphur dyeings were aftertreated using:

I. A single stage cationic fixing agent (Tinofix ECO) treatment as shown in Figure

7.1. Sulphur dyed and rinsed cotton fabric was aftertreated with liquor

containing 1, 2, 3, 4, 5, 8 and 10% omf Tinofix ECO with a liquor to goods ratio

of 10:1. The pH of the liquor was needed to be adjusted to 6-7 (the liquor was

already in the range). The fabric was treated at 40oC for 30 minutes, rinsed in

warm and cold water and finally air dried;

II. A two bath cation + tannin (Tinofix ECO + Bayprotect Cl) process in which

dyeings had been aftertreated with 5% omf Tinofix ECO using the method

described above, rinsed in water and subjected to tannin treatment depicted in

Figure 7.2. 1, 2, 3, 5 and 10% omf Bayprotect Cl was applied after cationic

treatment at 40, 60 and 98oC with a liquor to goods ratio of 10:1. The pH of the

treatment bath was adjusted to 3-3.5 with citric acid. The finished fabric was

rinsed in warm and cold water and finally air dried;

III. A single bath–two stage, cation + tannin (Tinofix ECO + Bayprotect Cl) process

in which dyeings had been aftertreated with 5% omf Tinofix ECO and 5% omf



182

Bayprotect Cl with a liquor to goods ratio of 10:1 for varying time intervals, as

shown in Figure 7.3.

A=dyed fabric, x% omf Tinofix ECO, pH 6-7

Figure 7.1 Cation aftertreatment

A=dyed fabric aftertreated with Tinofix ECO, x% omf Bayprotect Cl, pH 3-3.5

Figure 7.2 Tannin aftertreatment

A=dyed fabric, 5% omf Tinofix ECO, pH 6-7

B=5% omf Bayprotect Cl, pH 3-3.5

Figure 7.3 One bath-two stage cation/tannin aftertreatment

40oC, 30 min, pH 6-7

40oC, 60

oC and 98

oC, 20 min, pH 3-3.5

x min, pH 6-7 x min, pH 3-3.5 40

oC

A B

A

A

Optimisation of process parameters for sequential application of Tinofix ECO and Bayprotect Cl on sulphur dyed cotton fabric

183

Table 7.1 Aftertreatment procedures for optimisation

Aftertreatments method

Tinofix ECO

concentration

(% omf)

Bayprotect Cl

concentration

(% omf)

Application

temperature of

Tinofix ECO

(oC)

Application

temperature of

Bayprotect Cl

(oC)

Application

time of Tinofix

ECO

(minutes)

Application

time of

Bayprotect Cl

(minutes)

1. Two bath 1, 2, 3, 4, 5, 8 and 10 - 40 - 30 -

2. Two bath 5 1, 2, 3, 5 and 10 40 40, 60 and 98 30 20

3. One bath – two stage 5 5 40 40 30 20, 15, 10, 5

4. One bath – two stage 5 5 40 40 20,15 15,10

1. Test for determining optimum concentration of Tinofix ECO in two bath process

2. Test for determining optimum concentration and application temperature of Bayprotect Cl in two bath process

3. Test for determining optimum application time for Bayprotect Cl in one bath-two stage process

4. Test for determining optimum application time for Tinofix ECO in one bath-two stage process



184

Table 7.2 Composition and application parameters for optimisation of

sequential application of Tinofix ECO and Bayprotect Cl on


Application

conditions

Concentration

of

Tinofix ECO

( % omf)

Concentration

of

Bayprotect Cl

( % omf)

Application

temperature

of

Bayprotect Cl

(oC)

Application

time

of

Tinofix ECO

(min)

Application

time

of

Bayprotect Cl

(min)

Two bath application

AC 1 1 - - 30 -

AC 2 2 - - 30 -

AC 3 3 - - 30 -

AC 4 4 - - 30 -

AC 5 5 - - 30 -

AC 6 8 - - 30 -

AC 7 10 - - 30 -

AC 8 5 1 40 30 20

AC 9 5 2 40 30 20

AC 10 5 3 40 30 20

AC 11 5 5 40 30 20

AC 12 5 10 40 30 20

AC 13 5 1 60 30 20

AC 14 5 2 60 30 20

AC 15 5 3 60 30 20

AC 16 5 5 60 30 20

AC 17 5 10 60 30 20

AC 18 5 1 98 30 20

AC 19 5 2 98 30 20

AC 20 5 3 98 30 20

AC 21 5 5 98 30 20

AC 22 5 10 98 30 20

One bath–two stage application

AC 23 5 - - 30 -

AC 24 5 5 40 30 20

AC 25 5 5 40 30 15

AC 26 5 5 40 30 10

AC 27 5 5 40 30 05

AC 28 5 - - 20 -

AC 29 5 5 40 20 15

AC 30 5 5 40 20 10

AC 31 5 - - 15 -

AC 32 5 5 40 15 15

AC 33 5 5 40 15 10



185

7.4. Effect of varying concentration of Tinofix ECO

Table 7.3 and Table 7.4 detail the effect of increasing the concentration of the cationic

fixing agent Tinofix ECO on the colour loss of the fabric dyed with Diresul Black RDT

and reduced with Diresul reducing agent D and sodium sulphide respectively. It is clear

that within the range examined, increasing the concentration of Tinofix ECO up to 5%

omf brings about a sharp reduction in the colour loss, that is from 59% and 71% for the

untreated to 43% and 41% for treated samples respectively. This effect is presumably

due to the formation of large molecular size complexes between cationic fixative and

anionic dye molecules on cotton fabric. However, on exceeding concentration from 5%

to 10% omf, the fixative does not produce significant reduction in the amount of dye

loss from the fabric. For this reason, 5% omf concentration of the cationic fixative was

selected for further investigations.

The colour strength and percentage colour loss after laundering for sodium sulphide

reduced fabric was higher than for the comparable fabric reduced with Diresul Reducing

agent D. The Diresul Reducing agent D is a commercial product based on glucose and is

stated as a biodegradable reducing system. Glucose is expected to produce sulphur

dyeings with comparable colour strength and wash fastness to the conventional sulphide

system when applied under suitable temperature and concentrations of reducing agent

and alkali [10]. Dyeing of cellulosic fabric with sulphur dyes at optimum redox potential

(-650 mV) was found to offer the highest colour strength and lowest colour loss after

washing for sodium sulphide as well as reducing sugars. The fabric dyeings produced at

this reduction potential achieve maximum dye uptake, since above and below this value

the dye molecule is either too large or too fragmented for maximum adsorption and

subsequent diffusion [11].

It is proposed that large dye molecules have high affinity for cellulosic fibre owing to

extensive hydrophobic interactions and hydrogen bonding. However, the bigger size dye

molecules will have reduced penetration resulting in decreased adsorption, diffusion and

colour strength. On the other hand, smaller molecules can easily diffuse but their

affinity for cellulose would be lower due to lesser degree of dye-fibre interaction, hence

would display lower levels of wash fastness in relation to larger fragments [11, 12]. The

decrease in the wash fastness of fabric dyed with sodium sulphide may possibly be



186

attributed to aforementioned concept. It is anticipated that CI Leuco Sulphur Black 1

dye reduced with sodium sulphide might have produced smaller dye fragments in

comparison to Diresul RAD reduced dye molecules, resulting in higher colour strength

and reduced wash fastness.

On comparing the effects of Tinofix ECO on the two systems, it was observed that

treating Diresul RAD reduced fabric with 5% omf Tinofix ECO decreased the

percentage colour loss by 16%, while for sodium sulphide reduced sample it was 30%.

This shows that the cationic fixative is found to offer more protection to the sodium

sulphide reduced fabric against oxidation in domestic laundering. The protective effect

of varying concentrations of Tinofix ECO against the aggressive ISO 1O5 CO9 is

summarised in Figure 7.4.

7.5. Effect of varying concentrations of Bayprotect Cl over 5% omf Tinofix ECO at

different temperatures

As illustrated in section 7.4, 5% omf Tinofix ECO was found to be the optimum level

for reducing the colour loss of the sulphur dyed fabric. In order to achieve further

improvement in resistance of the dyes against oxidation, the cationised fabric was

treated with Bayprotect Cl. The reason for the two-bath sequential application of the two

reagents was that they require different pH conditions to effectively exhibit their

fixation properties. Bayprotect Cl requires an acidic pH (<3.5) while Tinofix ECO needs

a pH range of 6-7.

Table 7.5, Table 7.6 and Table 7.7 show the variation in percentage colour loss of CI

Leuco Sulphur Black 1 dyed cotton fabric (reduced with Diresul RAD) as a function of

concentration and application temperature of Bayprotect Cl. Five different add-on levels

of the Bayprotect Cl at three different temperatures were applied to each fabric,

resulting in fifteen finish combinations per fabric. It is evident that on increasing the

concentration of the tannin (Bayprotect Cl), a concomitant decrease in colour loss was

observed. However, as seen in Figure 7.5, the impact of application temperature of

Bayprotect Cl was insignificant and an increase in temperature does not reduce colour

loss to a great extent. Presumably, the exhaustion of the tannin at lower temperature was



187

enhanced by the cationic charge on the dyed fabric, which attracted the oppositely

charged tannin molecules.

As a result, the application of the protection system would be feasible to be used with

the concentration of 5% omf Bayprotect Cl at the preferred lowest temperature of 40oC.

This would not only help to reduce the overall process temperature but also the two

auxiliaries can be applied at the same temperature. Likewise, Table 7.8, Table 7.9 and

Table 7.10, present the data for CI Leuco Sulphur Black 1 dyed cotton fabric reduced

with the conventional reducing system (sodium sulphide). Similar parameters are

suggested to be selected for improving the resistance of the dye against oxidative action

of the laundering system (results summarised in Figure 7.6).



188

Table 7.3 Colorimetric data for ISO 1O5 CO9 washed CI Leuco Sulphur Black

1 dyed cotton fabric reduced with Diresul RAD and aftertreated with

Tinofix ECO

Application

conditions L* a* b* c* H K/S

%Colour

loss

GS DE

Rating

Untreated 28.2 -1.0 -4.5 5.6 257.2 9.0

Laundered 41.1 -1.9 -4.1 4.5 245.6 3.7 59% 1 13.0

AC 1 29.0 -1.1 -4.5 4.6 256.0 8.5

Laundered 39.0 -1.9 -3.4 3.9 241.0 4.2 51% 1/2 10.1

AC 2 29.2 -1.2 -4.6 4.7 255.8 8.4

Laundered 38.5 -1.9 -3.2 3.8 239.5 4.3 49% 1/2 9.4

AC 3 29.0 -1.1 -4.5 4.6 256.3 8.5

Laundered 38.2 -1.9 -2.9 3.5 237.7 4.4 48% 1/2 9.3

AC 4 28.4 -1.1 -4.3 4.5 256.1 8.9

Laundered 36.5 -1.8 -2.9 3.4 237.4 4.9 45% 1/2 8.3

AC 5 28.5 -1.1 -4.4 4.5 255.8 8.8

Laundered 36.4 -1.8 -2.5 3.1 234.1 5.0 43% 2 8.1

AC 6 28.6 -1.1 -4.4 4.5 255.6 8.8

Laundered 35.8 -1.9 -2.2 2.9 229.0 5.1 42% 2 7.6

AC 7 29.1 -1.2 -4.5 4.6 255.6 8.5

Laundered 36.3 -2.0 -2.3 3.0 228.9 5.0 41% 2 7.6


1 dyed cotton fabric reduced with sodium sulphide and aftertreated with

Tinofix ECO

Application

conditions L* a* b* c* H K/S

%Colour

loss

GS

Rating DE

Untreated 26.6 -0.4 -4.7 4.7 265.6 10.2

Laundered 44.1 -1.3 -5.0 5.1 255.2 3.0 71% 1 17.6

AC 1 27.3 -0.5 -4.8 4.8 264.0 9.5

Laundered 43.0 -1.6 -4.0 4.4 247.9 3.2 66% 1 15.8

AC 2 27.8 -0.6 -5.0 5.0 263.4 9.2

Laundered 38.1 -1.7 -3.9 4.2 246.7 4.5 51% 1/2 10.9

AC 3 27.7 -0.6 -4.9 4.9 263.3 9.3

Laundered 36.6 -1.8 -3.6 4.0 243.1 5.0 46% 1/2 9.0

AC 4 27.5 -0.6 -4.9 4.9 262.9 9.5

Laundered 35.7 -1.7 -3.6 4.0 244.5 5.3 44% 1/2 8.4

AC 5 27.4 -0.6 -4.9 4.9 263.4 9.5

Laundered 34.9 -1.9 -3.3 3.8 240.5 5.6 41% 2 7.8

AC 6 28.0 -0.6 -5.0 5.0 262.8 9.1

Laundered 35.0 -1.9 -3.4 3.9 240.2 5.6 38% 2 7.3

AC 7 28.2 -0.6 -5.0 5.0 262.7 9.0

Laundered 34.9 -2.0 -3.1 3.7 237.2 5.6 38% 2 7.1


189

Figure 7.4 Effect of varying concentrations of Tinofix ECO on ISO 1O5 CO9 wash fastness CI Leuco Sulphur Black 1 dyed cotton fabric

71%

66%

51%

46% 44%

41% 38% 38%

59%

51% 49% 48%

45% 43% 42% 41%

0%

10%

20%

30%

40%

50%

60%

70%

80%

Non-Treated 1% Tinofix ECO 2% Tinofix ECO 3% Tinofix ECO 4% Tinofix ECO 5% Tinofix ECO 8% Tinofix ECO 10% Tinofix ECO

% C

olo

ur

loss

ISO 1O5 CO9 (Reduced with sodium sulphide) ISI 1O5 CO9 (Reduced with Diresul Reducing agent D)



190


1 dyed cotton fabric (reduced with Diresul RAD) aftertreated with 5% omf

Tinofix ECO and x% omf Bayprotect Cl at 40oC for 20 minutes

Washing


%Colour

loss

GS

Rating DE

Untreated 28.3 -1.0 -4.6 4.7 258.1 9.0

Laundered 40.9 -1.9 -4.3 4.6 246.4 3.7 59% 1 12.7

AC 5 28.5 -1.1 -4.4 4.5 255.8 8.8

Laundered 36.4 -1.8 -2.5 3.1 234.1 5.0 43% 2 8.1

AC 8 29.0 -0.4 -4.4 4.4 265.3 8.2

Laundered 34.4 -2.0 -3.0 3.6 237.1 5.8 29% 2/3 5.8

AC 9 29.0 -0.4 -4.6 4.6 264.5 8.3

Laundered 33.9 -1.9 -3.1 3.6 238.6 6.0 28% 2/3 5.3

AC 10 29.3 -0.4 -4.6 4.6 264.8 8.1

Laundered 33.9 -1.9 -3.1 3.6 238.6 6.0 26% 2/3 5.1

AC 11 29.8 -0.4 -4.5 4.5 265.2 7.8

Laundered 33.9 -1.9 -3.2 3.7 239.7 6.0 23% 2/3 4.2

AC 12 29.8 -0.3 -4.4 4.4 265.6 7.8

Laundered 33.8 -1.9 -3.2 3.7 238.8 6.0 23% 2/3 4.5


1dyed cotton fabric (reduced with Diresul RAD) aftertreated with 5% omf


Washing


%Colour

loss

GS

Rating DE

Untreated 28.3 -1.0 -4.6 4.7 258.1 9.0

Laundered 40.9 -1.9 -4.3 4.6 246.4 3.7 59% 1 10.6

AC 5 28.5 -1.1 -4.4 4.5 255.8 8.8

Laundered 36.4 -1.8 -2.5 3.1 234.1 5.0 43% 2 8.1

AC 13 29.1 -1.1 -4.7 4.8 257.3 8.4

Laundered 34.6 -1.9 -3.1 3.6 238.7 5.7 32% 2/3 5.7

AC 14 29.0 -0.4 -4.4 4.4 265.3 8.2

Laundered 34.4 -2.0 -3.0 3.6 237.1 5.8 29% 2/3 5.8

AC 15 29.0 -0.4 -4.6 4.6 264.5 8.3

Laundered 33.9 -1.9 -3.1 3.6 238.6 6.0 28% 2/3 5.3

AC 16 29.3 -0.4 -4.6 4.6 264.8 8.1

Laundered 33.9 -1.9 -3.1 3.6 238.6 6.0 26% 2/3 5.1

AC 17 29.8 -0.3 -4.4 4.4 265.6 7.8

Laundered 33.8 -1.9 -3.2 3.7 238.8 6.0 23% 2/3 4.5



191


1dyed cotton fabric (reduced with Diresul RAD) aftertreated with 5% omf


Washing


%Colour

loss

GS DE

Rating

Untreated 28.3 -1.0 -4.6 4.7 258.1 9.0

Laundered 40.9 -1.9 -4.3 4.6 246.4 3.7 59% 1 12.7

AC 5 28.5 -1.1 -4.4 4.5 255.8 8.8

Laundered 36.4 -1.8 -2.5 3.1 234.1 5.0 43% 2 8.1

AC 18 29.4 -0.5 -4.3 4.4 263.2 8.4

Laundered 33.6 -1.8 -3.1 3.6 239.5 6.0 29% 2/3 5.1

AC 19 28.7 -0.5 -4.3 4.3 263.4 8.5

Laundered 33.5 -1.9 -2.8 3.4 236.4 6.1 28% 2/3 5.2

AC 20 29.2 -0.5 -4.4 4.4 263.8 8.1

Laundered 34.0 -2.0 -3.1 3.7 237.8 5.9 27% 2/3 5.1

AC 21 29.7 -0.5 -4.2 4.3 263.3 7.8

Laundered 34.0 -1.8 -3.2 3.7 240.7 5.9 24% 2/3 4.6

AC 22 28.8 -0.5 -4.0 4.1 263.1 8.3

Laundered 32.6 -1.9 -3.0 3.5 237.9 6.5 22% 2/3 4.2


1 dyed cotton fabric (reduced with sodium sulphide) aftertreated with 5% omf


Washing


%Colour

loss

GS

Rating DE

Untreated 27.0 -0.3 -4.6 4.7 266.1 9.8

Laundered 45.1 -1.3 -4.6 4.7 254.1 2.8 71% 1 18.1

AC 5 28.0 -0.5 -4.8 4.8 264.3 9.0

Laundered 35.6 -1.8 -2.9 3.4 237.6 5.3 41% 2 8.0

AC 8 28.0 0.2 -4.6 4.6 272.2 8.7

Laundered 35.7 -1.9 -3.1 3.6 238.6 5.3 39% 2 8.1

AC 9 28.1 0.1 -4.8 4.8 269.8 8.8

Laundered 35.1 -1.9 -3.0 3.5 237.5 5.5 38% 2 7.5

AC 10 27.9 0.1 -4.7 4.7 270.8 8.9

Laundered 34.5 -1.9 -3.0 3.5 237.8 5.7 36% 2 7.1

AC 11 28.4 0.1 -4.7 4.7 271.4 8.5

Laundered 34.1 -1.9 -3.0 3.5 238.0 5.9 31% 2 6.3

AC 12 28.5 0.1 -4.7 4.7 271.3 8.5

Laundered 33.9 -1.9 -3.0 3.5 237.5 6.0 29% 2 6.1



192


1 dyed cotton fabric (reduced with sodium sulphide) aftertreated with 5% omf


Washing


%Colour

loss

GS DE

Rating

Untreated 25.5 -0.2 -4.3 4.3 267.1 10.8

Laundered 43.7 -1.5 -4.6 4.9 251.7 3.1 71% 1 18.2

AC 5 27.3 -0.5 -4.7 4.7 264.2 9.5

Laundered 34.3 -1.8 -3.1 3.6 240.1 5.6 41% 2 7.3

AC 13 27.2 0.1 -4.6 4.6 271.4 9.3

Laundered 33.8 -1.7 -3.5 3.9 243.4 6.0 35% 2 7.0

AC 14 27.2 0.2 -4.6 4.6 272.0 9.4

Laundered 33.7 -1.8 -3.3 3.7 241.2 6.1 35% 2 6.9

AC 15 27.5 0.1 -4.6 4.6 271.7 9.1

Laundered 33.2 -1.7 -3.4 3.8 242.7 6.3 31% 2 6.1

AC 16 27.5 0.1 -4.6 4.6 271.7 9.1

Laundered 32.7 -1.8 -3.2 3.6 240.6 6.5 29% 2/3 5.7

AC 17 27.6 0.1 -4.5 4.5 271.3 9.0

Laundered 32.3 -1.7 -3.4 3.8 243.5 6.7 26% 2/3 5.1

Table 7.10 Colorimetric data for ISO 1O5 CO9 washed CI Leuco Sulphur

Black 1 dyed cotton fabric (reduced with sodium sulphide) aftertreated with

5% omf Tinofix ECO and x% omf Bayprotect Cl at 98oC for 20 minutes

Washing


%Colour

loss

GS

Rating DE

Untreated 26.7 -0.3 -4.8 4.8 266.4 10.0

Laundered 45.2 -1.5 -4.8 5.1 252.4 2.8 71% 1 18.5

AC 5 28.0 -0.5 -4.8 4.8 264.3 9.0

Laundered 35.6 -1.8 -2.9 3.4 237.6 5.3 41% 2 8.0

AC 18 27.7 0.1 -4.7 4.7 270.9 9.0

Laundered 35.1 -2.0 -2.9 3.5 236.1 5.3 41% 2 8.2

AC 19 28.0 0.1 -4.8 4.8 270.0 8.9

Laundered 35.8 -2.0 -3.1 3.6 237.4 5.2 41% 2 7.9

AC 20 28.0 0.1 -4.7 4.9 270.7 8.8

Laundered 35.1 -1.9 -3.0 3.6 237.3 5.5 38% 2 7.5

AC 21 27.7 0.1 -4.5 4.5 271.4 9.0

Laundered 34.0 -1.9 -2.7 3.3 235.5 5.9 34% 2 6.9

AC 22 27.9 0.1 -4.6 4.6 271.8 8.8

Laundered 34.0 -1.9 -3.3 3.8 240.7 5.9 33% 2 6.6


193

Figure 7.5 Effect of varying concentrations and application temperatures of Bayprotect Cl on ISO 1O5 CO9 wash fastness of CI Leuco

Sulphur Black 1 dyed cotton fabric (reduced with Diresul RAD)

59%

43%

29% 28% 26%

23% 23%

59%

43%

32% 29% 28%

26% 23%

59%

43%

29% 28% 27% 24%

22%

0%

10%

20%

30%

40%

50%

60%

70%

Non-Treated 0% Bayprotect Cl 1% Bayprotect Cl 2% Bayprotect Cl 3% Bayprotect Cl 5% Bayprotect Cl 10% Bayprotect Cl

% C

olo

ur

loss

Application of Bayprotect Cl at 40oC Application of Bayprotect Cl at 60oC Application of Bayprotect Cl at 98oCApplication of Bayprotect Cl at 40oC Application of Bayprotect Cl at 60oC Application of Bayprotect Cl at 98oC


194

Figure 7.6 Effect of varying concentrations and application temperatures of Bayprotect Cl on ISO 1O5 CO9 wash fastness of CI Leuco

Sulphur Black 1 dyed cotton fabric (reduced with sodium sulphide)

71%

41% 39% 38%

36%

31% 29%

71%

41%

35% 35%

31% 29%

26%

71%

41% 41% 41% 38%

34% 33%

0%

10%

20%

30%

40%

50%

60%

70%

80%

Non-Treated 0% Bayprotect Cl 1% Bayprotect Cl 2% Bayprotect Cl 3% Bayprotect Cl 5% Bayprotect Cl 10% Bayprotect Cl

% C

olo

ur

loss

Application of Bayprotect Cl at 40oC Application of Bayprotect Cl at 60oC Application of Bayprotect Cl at 98oCApplication of Bayprotect Cl at 40oC Application of Bayprotect Cl at 60oC Application of Bayprotect Cl at 98oC



195

7.6. Application of protection system with one bath-two stage process

As discussed in sections 7.4 and 7.5, the substantial loss in colour during ISO 1O5 CO9

laundering can be reduced by treating CI Leuco Sulphur Black 1 dyed cotton fabric with

5% omf Tinofix ECO and 5% omf Bayprotect Cl at 40oC for 30 and 20 minutes

respectively. Nevertheless, a one-bath process to apply both finishes has been

investigated which would help to reduce the consumption of water, which is the most

demanding feature in everyday textile industrial procedures.

Since Tinofix ECO is cationic and Bayprotect Cl is anionic in nature and both the

reagents require different pH conditions for their better performance as fixatives,

therefore their sequential application was mandatory. Hence, the fabric was first

aftertreated with Tinofix ECO so that it can cationise the dyed fabric and introduce

positively charged ions (cations) to the dyed fabric. The next step was to treat the

cationised fabric with the anionic tannin, which would attract the oppositely charged

ions resulting in the neutralisation of the two oppositely charged ions and forming

complexes. These complexes may possibly be accounted for an improved wash fastness

and an increased resistance of the dyed fabric against oxidation in domestic laundering.

Results show that both finishes are compatible for application in a one-bath process, and

the finishing properties of the two auxiliaries are adequate with this process (Table 7.11

and Table 7.12).


Black 1 dyed cotton fabrics (reduced with Diresul RAD) aftertreated with

one bath–two stage process (application of 5% TE and 5% BP at 40oC)

Washing


%Colour

loss

GS

Rating DE

AC 11 29.8 -0.4 -4.5 4.5 265.2 7.8

Laundered 33.9 -1.9 -3.2 3.7 239.7 6.0 23% 2/3 4.2

AC 24 29.7 -0.7 -4.6 4.6 261.5 7.9

Laundered 34.0 -1.8 -2.9 3.5 238.5 5.9 25% 2/3 4.7



196


Black 1 dyed cotton fabrics (reduced with sodium sulphide) aftertreated with

one bath–two stage process (application of 5% TE and 5% BP at 40oC)

Washing


%Colour

loss

GS

Rating DE

AC 11 28.4 0.1 -4.7 4.7 271.4 8.5

Laundered 34.1 -1.9 -3.0 3.5 238.0 5.9 31% 2 6.3

AC 24 28.7 -0.5 -4.9 4.9 264.3 8.6

Laundered 35.2 -2.0 -3.5 4.0 240.3 5.5 36% 2 6.8

7.7. Application of protection system (one bath-two stage process) at varying time

intervals

As discussed in sections 7.4, 7.5 and 7.6, 5% omf Tinofix ECO and 5% omf Bayprotect

Cl can sequentially be applied by two-bath as well as one bath-two stage systems to

significantly reduce the percentage colour loss of CI Leuco Sulphur Black 1 dyed cotton

fabric. The reduction in percentage colour loss for one bath-two stage aftertreated fabric

reduced with Diresul RAD was 59% (untreated) down to 25% (aftertreated), while for

sulphide reduced fabric the decrease was 71% (untreated) to 36% (aftertreated). Since

the concentrations and application temperatures of the two reagents have been

optimised, the next step was to identify the optimised duration of application. In order to

make the overall process economical and practical for industrial purposes, the

application interval of the two finishes (Tinofix ECO and Bayprotect Cl) were also

minimised (AC 23 to AC 33 in Table 7.2).

The colorimetric data represented in Table 7.13 and Table 7.14 demonstrate that on

treating the sulphur dyed fabric (reduced with Diresul RAD) for 15 minutes with each of

the two compounds would produce approximately 50% reduction in colour loss and

improves the Grey scale rating from 1 for the untreated fabric to 2-3 for the treated

fabric. On the other hand, cotton fabric reduced with sodium sulphide acquires

approximately 40% reduction in percentage colour loss and improves by 1 Grey scale

unit only.



197

Table 7.13 Colorimetric data for one bath–two stage application of Tinofix

ECO and Bayprotect Cl, at different time intervals, following ISO 1O5 CO9

washing (CI Leuco Sulphur Black 1 dyed cotton fabric reduced with RAD)

Application

conditions L* a* b* c* h K/S

%Colour

loss GS Rating DE

AC 23 30.2 -1.1 -4.7 4.8 256.7 7.8

Laundered 37.7 -1.8 -2.5 3.1 235.2 4.5 42% 2 7.8

AC 24 31.0 -0.6 -4.5 4.6 262.8 7.2

Laundered 35.0 -1.8 -2.8 3.4 237.8 5.3 26% 2/3 5.1

AC 25 31.1 -0.6 -4.5 4.5 262.5 7.1

Laundered 35.6 -1.8 -2.9 3.4 239.2 5.3 25% 2/3 4.9

AC 26 31.1 -0.6 -4.5 4.6 263.0 7.1

Laundered 36.9 -1.8 -2.8 3.3 237.5 4.8 32% 2 6.2

AC 27 30.7 -0.6 -4.6 4.6 262.3 7.4

Laundered 36.7 -1.8 -2.8 3.3 237.2 4.9 34% 2 6.4

AC 28 29.7 -1.0 -4.5 4.6 258.2 8.0

Laundered 38.5 -1.8 -2.8 3.3 237.7 4.3 46% 1/2 9.0

AC 29 30.7 -0.6 -4.6 4.6 263.0 7.3

Laundered 35.7 -1.8 -2.8 3.3 237.7 5.2 29% 2/3 5.4

AC 30 30.8 -0.5 -4.7 4.7 263.5 7.3

Laundered 36.9 -1.8 -2.9 3.5 238.3 4.8 34% 2 6.5

AC 31 29.2 -1.0 -4.5 4.7 257.8 8.4

Laundered 37.9 -1.8 -2.8 3.3 237.2 4.5 46% 1/2 9.0

AC 32 30.5 -0.6 -4.6 4.6 263.2 7.5

Laundered 35.8 -1.8 -3.0 3.5 239.6 5.2 31% 2/3 5.7

AC 33 30.3 -0.5 -4.6 4.7 263.4 7.5

Laundered 37.2 -1.8 -2.9 3.4 237.6 4.7 37% 2 7.2

Table 7.14 Colorimetric data for one bath–two stage application of Tinofix

ECO and Bayprotect Cl, at different time intervals, following ISO 1O5 CO9

washing (CI Leuco Sulphur Black 1 dyed cotton fabric reduced with SS)

Application


%Colour

loss

GS

Rating DE

AC 23 28.9 -0.9 -5.1 5.2 260.6 8.6

Laundered 35.4 -2.0 -3.7 4.2 241.6 5.5 36% 2 6.8

AC 24 28.4 -0.2 -4.9 4.9 267.2 8.7

Laundered 32.1 -1.9 -3.5 4.0 241.4 6.9 21% 2/3 4.3

AC 25 28.7 -0.3 -4.9 4.9 266.5 8.5

Laundered 32.8 -2.0 -3.4 4.0 239.7 6.6 22% 2/3 4.7

AC 26 28.8 -0.3 -5.0 5.0 266.6 8.5

Laundered 33.6 -2.0 -3.5 4.0 240.4 6.2 27% 2/3 5.3

AC 27 28.2 -0.3 -4.9 4.9 266.4 8.9

Laundered 33.8 -2.0 -3.7 4.2 241.9 6.1 31% 2 5.9

AC 28 26.8 -0.5 -4.7 4.7 263.8 9.9

Laundered 33.0 -1.7 -3.2 3.7 242.8 6.3 36% 2 6.5

AC 29 27.3 0.0 -4.8 4.8 269.5 9.4

Laundered 32.6 -1.7 -3.4 3.8 243.5 6.6 30% 2/3 5.8

AC 30 27.5 0.0 -4.8 4.8 270.2 9.2

Laundered 33.5 -1.8 -3.4 3.8 241.7 6.2 33% 2 6.4

AC 31 27.1 -0.5 -4.8 4.8 264.3 9.7

Laundered 33.3 -1.7 -3.1 3.5 241.1 6.2 36% 2 6.6

AC 32 27.6 0.0 -5.0 5.0 269.9 9.2

Laundered 33.3 -1.7 -3.5 3.9 244.6 6.3 32% 2 6.1

AC 33 27.5 0.0 -4.8 4.8 270.2 9.2

Laundered 33.5 -1.8 -3.4 3.8 241.7 6.2 33% 2 6.4



198

7.7.1. Effect of aftertreatments with Tinofix ECO and Bayprotect Cl on rubbing and

light fastness of CI Leuco Sulphur Black 1 dyed cotton fabric

The aftertreatments with the cationic fixing agent Tinofix ECO and the tannin based

product Bayprotect Cl did not produce any significant improvements on the rubbing and

light fastness of CI Leuco Sulphur Black 1 dyed and aftertreated cotton fabrics. These

properties remained unchanged for aftertreated fabrics dyed with both reducing systems

(Table 7.15).

Table 7.15 Rubbing and light fastness properties of CI Leuco Sulphur Black 1

dyed cotton fabric aftertreated with Tinofix ECO and Bayprotect Cl

(reduced with Diresul RAD and sodium sulphide)

Reducing agent Aftertreatments

Rub fastness

Light fastness

Dry

Wet

Diresul Reducing agent D

Nil 4/5 ¾ 4

AC1-AC33 4/5 ¾ 4

Sodium sulphide

Nil 4/5 3 4

AC1-AC33 4/5 3 4

As discussed in section 7.4, CI Leuco Sulphur Black 1 dyeings (untreated) reduced with

sodium sulphide showed lower wash fastness as compared to Diresul Reducing agent D

reduced fabric. This may possibly be due to the large molecular size of the dyeing

produced with Diresul RAD. It was observed that dyed fabric reduced with sodium

sulphide also exhibited a half unit reduction in wet crocking.

In the case of sulphur dyeing, the fastness to rubbing is greatly dependent on the fabric,

its preparation and the dyeing process, especially the efficiency of rinsing before

oxidation. The dyeing should be thoroughly rinsed to remove as much unfixed dye as

possible before the oxidation stage is reached [12]. If the dyestuff is water soluble and

not sufficiently fixed to the fibre, it can also contribute to the staining [13]. However, in

this study, the dyeings produced with the two reducing systems were given similar

rinsing and oxidation treatments so the reduced rub fastness of sulphide based dyeings

cannot be attributed to the inappropriate rinsing or oxidation. Nevertheless, better



199

fixation due to the higher affinity of large molecular size sulphur dye to cellulose

presumably is an important factor for the improved wet rubbing fastness of Diresul

RAD reduced fabric.

The effect of reducing system on the light fastness of CI leuco Sulphur Black 1 dye was

insignificant, as both dyeings had the same rating.

7.8. Optimised parameters for one bath-two stage application of Tinofix ECO and

Bayprotect Cl on sulphur dyed cotton fabric

According to the outcomes obtained from the investigations discussed above (sections

7.4, 7.5, 7.6 and 0), the following parameters lead to significant improvement in the

wash fastness of CI leuco Sulphur Black 1 dyed cotton fabric (reduced with Diresul

RAD and sodium sulphide) against ISO 1O5 CO9 washing while minimising

processing time, temperature and auxiliary use:

Method of application: Exhaust (one bath–two stage);

Application temperature of Tinofix ECO: 40oC;

Application temperature of Bayprotect Cl: 40oC;

Application time of Tinofix ECO: 15 minutes;

Application time of Bayprotect Cl: 15 minutes;

pH of Tinofix ECO: 6-7;

pH of Bayprotect Cl: 3-3.5;

Liquor to goods ratio: 10:1.

7.9. Aftertreatments of sulphur dyed cotton fabrics (reduced with Diresul RAD) with

Tinofix ECO and Bayprotect Cl

The aforementioned parameters found to offer significant protection against oxidative

household laundering condition were adopted for the application of 5% omf Tinofix

ECO on its own (AC 31) and one bath-two stage applications of Tinofix ECO and

Bayprotect Cl (AC 32). Cotton fabric dyed with multiple sulphur dyes (5% omf) namely

Diresul Black RDT-LS LIQ 200 (CI Leuco Sulphur Black 1), Diresul Liquid Green



200

RDT-N (CI Leuco Sulphur Green 2), Diresul Liquid Blue RDT-G (CI Leuco Sulphur

Blue 7), Diresul Liquid Yellow RDT-E (CI Leuco Sulphur Yellow 22) and Diresul

Liquid Red RDT-BG (CI Leuco Sulphur Red 14) were evaluated for the fastness

properties. These dyes were reduced with the biodegradable Diresul Reducing agent D

(dyeing procedure discussed in section 3.4) and the effects of the aftertreatments were

evaluated for ISO 1O5 CO9 washing (Table 7.16 to Table 7.20), crocking and light

fastness (Table 7.21).


Black 1 dyed fabric aftertreated with Tinofix ECO and Bayprotect Cl


Application


%Colour

loss

GS

Rating DE

Untreated 29.0 -0.8 -4.5 4.6 259.9 8.3

Laundered 41.9 -1.6 -4.1 4.4 248.2 3.4 59% 1 13.0

AC 31 29.2 -1.0 -4.5 4.7 257.8 8.4

Laundered 37.9 -1.8 -2.8 3.3 237.2 4.5 46% 1/2 9.0

AC 32 30.5 -0.6 -4.6 4.6 263.2 7.5

Laundered 35.8 -1.8 -3.0 3.5 239.6 5.2 31% 2/3 5.7

Table 7.17 Colorimetric data for ISO 1O5 CO9 washed CI Leuco Sulphur Blue

7 dyed fabric aftertreated with Tinofix ECO and Bayprotect Cl


Application


%Colour

loss

GS

Rating DE

Untreated 53.2 1.5 -21.0 21.1 273.9 2.0

Laundered 58.9 -1.3 -22.2 22.2 266.6 1.5 25% 2 6.5

AC 31 53.8 0.7 -21.4 21.5 271.8 2.0

Laundered 57.9 -2.4 -21.2 21.4 263.5 1.6 20% 2/3 5.2

AC 32 53.6 0.7 -20.9 20.9 271.9 2.0

Laundered 57.4 -2.5 -21.4 21.5 263.3 1.7 15% 2/3 5.0



201


Yellow 22 dyed fabric aftertreated with Tinofix ECO and Bayprotect Cl


Application


%Colour

loss

GS

Rating DE

Untreated 86.7 -7.5 44.8 45.4 99.5 3.3

Laundered 90.7 -10.7 43.8 45.1 103.8 2.6 21% 2/3 5.3

AC 31 86.8 -7.2 43.9 44.5 99.3 2.9

Laundered 89.1 -8.9 45.6 46.4 101.0 2.9 0% 3/4 3.3

AC 32 84.8 -5.2 43.7 44.0 96.8 3.2

Laundered 87.9 -7.8 46.1 46.8 99.6 3.2 0% 3 4.7

Table 7.19 Colorimetric data for ISO 1O5 CO9 washed CI Leuco Sulphur Red



Application


%Colour

loss

GS

Rating DE

Untreated 60.4 39.6 7.5 40.3 10.7 2.9

Laundered 62.5 37.9 6.3 38.5 9.5 2.3 21% 3/4 3.0

AC 31 60.4 38.0 6.4 38.5 9.5 2.7

Laundered 60.6 37.5 5.6 37.9 8.5 2.4 11% 4 1.8

AC 32 60.6 37.0 5.2 37.4 8.0 2.4

Laundered 61.5 37.5 6.0 38.0 9.1 2.4 0% 4/5 1.3


Green 2 dyed fabric aftertreated with Tinofix ECO and Bayprotect Cl


Application


%Colour

loss

GS

Rating DE

Untreated 69.2 -14.2 -8.8 16.7 211.9 0.9

Laundered 75.3 -13.8 -9.8 16.9 215.4 0.7 22% 2 6.2

AC 31 69.1 -15.3 -8.9 17.6 210.2 1.0

Laundered 73.1 -12.4 -9.4 15.5 217.2 0.8 20% 2/3 5.0

AC 32 69.1 -14.4 -8.9 16.9 211.6 1.0

Laundered 73.2 -11.9 -8.7 14.7 216.4 0.8 20% 3 3.7



202

Figure 7.7 Effect of aftertreatment with Tinofix ECO and Bayprotect Cl on ISO

1O5 CO9 wash fastness of sulphur dyed cotton fabrics



aftertreated with Tinofix ECO and Bayprotect Cl (reduced with Diresul RAD)

Treatments Light fastness Crocking fastness

Dry Wet


Non-Treated 4 4-5 3-4

Tinofix ECO 4 4-5 3-4

Tinofix ECO + Bayprotect Cl 4 4-5 3-4

CI Leuco Sulphur Liquid Green 2

Non-Treated 2-3 5 4-5

Tinofix ECO 2 5 4-5

Tinofix ECO + Bayprotect Cl 4 4-5 4

CI Leuco Sulphur Liquid Blue 7

Non-Treated 4 5 4

Tinofix ECO 2-3 4-5 4

Tinofix ECO + Bayprotect Cl 4 4 4

25%

20%

15%

21%

11%

22% 20% 20% 21%

0 0

59%

46%

31%

0%

10%

20%

30%

40%

50%

60%

70%

Untreated Treated with Tinofix ECO Treated with Tinofix ECO andBayprotect Cl

% C

olo

ur

loss

ISO 1O5 CO9 (CI Leuco Sulphur Blue 7) ISO 1O5 CO9 (CI Leuco Sulphur Red 14)

ISO 1O5 CO9 (CI Leuco Sulphur Green 2) ISO 1O5 CO9 (CI Leuco Sulphur Yellow 22)

ISO 1O5 CO9 (CI Leuco Sulphur Black 1)



203


Non-Treated 2-3 5 3-4

Tinofix ECO 2-3 4-5 3-4

Tinofix ECO + Bayprotect Cl 3-4 3-4 3


Non-Treated 4 4-5 3


Tinofix ECO+Bayprotect Cl 4-5 3-4 2-3


The influence of Tinofix ECO and Bayprotect Cl on the fastness of five sulphur dyed

cotton fabrics (reduced with Diresul Reducing agent D) has been presented in the form

of colorimetric data (Table 7.16 to Table 7.20). It can be seen that CI Leuco Sulphur

Red 14, Black 1 and Blue 7 showed notable improvements in terms of minimising the

colour loss from ISO IO5 CO9 washing. However, the impact of aftertreatments for CI

Leuco Sulphur Yellow 22 and Green 2 were insignificant in comparison to treatment

with Tinofix ECO alone. As shown in Table 7.18, the colour loss for cotton fabric dyed

with CI Leuco Sulphur Yellow 22 and aftertreated with AC 31 is 0% while the GS

rating is 3/4. This is because the GS rating is not only dependent on the colour strength

of the dyed fabric but it also takes the colour changes into consideration, so even if there

is no colour loss after laundering the change in colour coordinates may reduce the GS

rating.

In the case of CI Leuco Sulphur Black 1, being the most important and commonly used

sulphur dye, a substantial reduction in colour loss for ISO IO5 CO9 can be perceived

from 59% (untreated) to 31% (aftertreated). The comparative results of aftertreatments

on percentage colour loss of various sulphur dyed fabrics are shown in Figure 7.7.

The effects of the aftertreatment on crocking and light fastness have also been evaluated

for the treated samples. As seen in Table 7.21, the light fastness of Tinofix ECO treated

samples has reduced by half unit in the case of CI Leuco Sulphur Green 2 and Red 14,

while 1.5 units for CI Leuco Sulphur Blue 7. However, an improvement from 0.5-1.5

units was observed when the dyed fabrics were treated with Tinofix ECO following

Bayprotect Cl treatment. The light fastness of CI Leuco Sulphur Black 1 and Sulphur



204

Blue 7 remained unchanged. This is commensurate with the fact that Bayprotect Cl on

its own also can improve the light fastness of sulphur dyed cotton fabrics. Since the

reagent belongs to a class of polyphenols and antioxidants so it is expected to form

some bonds either with the cotton substrate or the dye which eventually leads to UV

protection and an increased light fastness [14]. Possibly free radical scavenging of the

excited intermediates leads to photostabilisation.

The crocking fastness for CI Leuco Sulphur Black 1 was unaffected. In general,

aftertreatments with Tinofix ECO did not affect either dry or wet crocking fastness of

rest of the colours. However, subsequent treatment with Bayprotect Cl decreased the dry

and wet crocking by half to 1 unit for all the colours except black. These findings can be

attributed to a difference in the extent to which Tinofix ECO and the cation-tannin

complex were able to diffuse within the dyed fibre. The cationic fixative and the dye

complex might have generated in situ within the fibre, thus maintaining the dry and wet

rub fastness of the fabric. In contrast, the large molecular size complex produced as a

result of the two-stage process deposited on the fabric surface can be anticipated to

display very low diffusional behaviour and, therefore, will have deposited mostly at the

periphery of the dyed fibre, resulting in low rub fastness.

7.10. Aftertreatments of sulphur dyed cotton fabric (reduced with sodium sulphide)

with Tinofix ECO and Bayprotect Cl

Similar to section 7.9 the process parameters identified as leading to significant

improvements in the wash fastness were used to treat cotton fabrics dyed with various

sulphur dyes and reduced with the conventional sodium sulphide. The effects of the

aftertreatments were tested for ISO 1O5 CO9 washing (Table 7.22 to 7.26), crocking

and light fastness (Table 7.27).



205

Table 7.22 Colorimetric data for ISO 1O5 CO9 washed CI Leuco Sulphur Red



Application


%Colour

loss

GS

Rating DE

Untreated 62.8 36.4 7.0 37.1 10.8 2.2

Laundered 65.3 34.8 6.3 35.4 10.3 1.8 18% 3/4 3.1

AC 31 64.2 34.7 7.1 35.4 11.5 1.9

Laundered 66.0 34.5 6.2 35.0 10.2 1.6 16% 4 2.0

AC 32 63.6 35.5 5.2 35.9 8.3 1.9

Laundered 65.9 34.4 6.2 35.0 10.2 1.7 11% 3/4 2.8


Green 2 dyed fabric aftertreated with Tinofix ECO and Bayprotect Cl


Application


%Colour

loss

GS

Rating DE

Untreated 67.5 -10.6 -9.4 14.2 221.6 0.9

Laundered 74.0 -9.9 -11.0 14.8 228.2 0.6 33% 2 6.7

AC 31 67.7 -10.4 -9.3 14.0 222.0 0.9

Laundered 73.3 -10.2 -11.4 15.3 228.3 0.7 22% 2 5.9

AC 32 69.7 -9.9 -8.8 13.3 221.5 0.8

Laundered 74.3 -9.9 -11.2 14.9 228.3 0.6 25% 2/3 5.3


Black 1 dyed fabric aftertreated with Tinofix ECO and Bayprotect Cl


Application


%Colour

loss

GS

Rating DE

Untreated 26.6 -0.4 -4.7 4.7 265.6 10.0

Laundered 44.3 -1.3 -5.0 5.2 255.2 2.9 71% 1 18.2

AC 31 27.1 -0.5 -4.8 4.8 264.3 9.7

Laundered 33.3 -1.7 -3.1 3.5 241.1 6.2 36% 2 6.6

AC 32 27.6 0.0 -5.0 5.0 269.9 9.2

Laundered 33.3 -1.7 -3.5 3.9 244.6 6.3 32% 2 6.1



206

Table 7.25 Colorimetric data for ISO 1O5 CO9 washed CI Leuco Sulphur Blue



Application


%Colour

loss

GS

Rating DE

Untreated 47.3 2.1 -22.9 23.0 275.3 3.0

Laundered 54.1 0.0 -23.8 23.8 269.9 2.1 30% 2 7.2

AC 31 47.2 2.4 -22.5 22.6 276.1 3.0

Laundered 53.2 0.0 -24.0 24.0 270.0 2.2 27% 2 6.7

AC 32 46.6 2.2 -21.4 21.5 275.8 3.1

Laundered 52.5 0.0 -23.9 23.9 270.0 2.3 26% 2 6.8


Yellow 22 dyed fabric aftertreated with Tinofix ECO and Bayprotect Cl


Application


%Colour

loss

GS

Rating DE

Untreated 84.8 -6.7 49.2 49.7 97.8 4.2

Laundered 88.8 -9.3 51.5 52.4 100.2 3.6 14% 2/3 5.3

AC 31 85.8 -7.2 48.5 49.1 98.4 3.5

Laundered 88.3 -8.6 50.6 51.3 99.7 3.5 0% 3/4 3.5

AC 32 85.1 -5.5 48.1 48.4 96.6 3.6

Laundered 89.1 -9.3 50.7 51.5 100.4 3.4 6% 2/3 6.0



207

Figure 7.8 Effect of aftertreatment with Tinofix ECO and Bayprotect Cl on ISO

1O5 CO9 wash fastness of sulphur dyed cotton fabrics



aftertreated with Tinofix ECO and Bayprotect Cl


Treatments Light fastness Crocking fastness

Dry Wet


Non-Treated 4 4-5 3

Tinofix ECO 4 4-5 3

Tinofix ECO + Bayprotect Cl 4 4-5 3


Non-Treated 2-3 4-5 3-4

Tinofix ECO 2-3 4-5 3-4



Non-Treated 3-4 4-5 3

Tinofix ECO 4 4-5 3

Tinofix ECO + Bayprotect Cl 4-5 5 3-4

30% 27% 26%

18% 16% 11%

33%

22% 25%

14%

0%

6%

71%

36% 32%

0%

10%

20%

30%

40%

50%

60%

70%

80%

Non-Treated Treated with Tinofix EcoTreated with Tinofix Eco and Bayprotect CL

% C

olo

ur

loss

ISO 1O5 CO9 (CI Leuco Sulphur Blue 7) ISO 1O5 CO9 (CI Leuco Sulphur Red 14)

ISO 1O5 CO9 (CI Leuco Sulphur Green 2) ISO 1O5 CO9 (CI Leuco Sulphur Yellow 22)

ISO 1O5 CO9 (CI Leuco Sulphur Black 1)



208


Non-Treated 4 4-5 3


Tinofix ECO + Bayprotect Cl 4 4-5 3-4


Non-Treated 3 4-5 3-4

Tinofix ECO 3 4-5 3-4


Table 7.28 Effects of different aftertreatments on tensile properties of CI Leuco

Sulphur Black 1 dyed cotton fabrics

Application conditions

on CI Leuco Sulphur

Black 1 dyed cotton fabric


Tensile

strength

(N)

Tensile

extension

at Break

(mm)

Tensile

strength

(N)

Tensile

extension

at Break

(mm)

Untreated 4.6 19.9 3.8 31.8

5% omf Tinofix ECO 5.6 20.5 3.7 27.6

10% omf Tinofix ECO 4.9 20.1 4.9 33.2

5% omf Tinofix ECO,


10% omf Tinofix ECO,



The influence of aftertreatments with Tinofix ECO and Bayprotect Cl on five leuco

sulphur dyed fabrics (reduced with sodium sulphide) has been presented in the form of

colorimetric data (Table 7.22 to Table 7.26). It can be seen that CI Leuco Sulphur Red

14 and Black 1 showed significant improvements in percentage colour loss for ISO IO5

CO9 washing system. However, the impact of aftertreatments in the case of CI Leuco

Sulphur Yellow 22, Blue 7 and Green 2 was insignificant. In the case of CI Leuco

Sulphur Black 1, a substantial reduction in colour loss for ISO IO5 CO9 can be

perceived, that is from 71% (untreated) to 32% (aftertreated). The comparative results of

aftertreatments on percentage colour loss of various sulphur dyed fabrics are shown in

Figure 7.8.

The effects of aftertreatments with Tinofix ECO and Bayprotect Cl on crocking and

light fastness have also been evaluated for the treated samples. As seen in



209

Table 7.27, the light fastness of treated samples has significantly improved in

comparison to untreated samples for all colours except CI Leuco Sulphur Black 1 and

Yellow 22 that remained unchanged. The wet crocking for CI Leuco Sulphur Blue 7,

Green 2, Yellow 22 and Red 14 has increased by half a unit, similar improvements were

seen for the dry crocking of CI Leuco Sulphur Blue 7. On analysing the dyed fabric

treated with Tinofix ECO and Bayprotect Cl, it is perceived that the aftertreatments did

not affect the tensile strength of the fabric, rather in fact a slight improvement was

observed as seen in Table 7.28. Effect of cationic fixatives on the tensile strength of

cotton fabric has also been studied by Molla [15], where four cationic fixatives namely

Tinofix ECO, Solfix E, Acramine Berfix K and CTMAB were applied on cotton and

nylon 6 fabrics. The exhaust application of Tinofix ECO was found to increase the

tensile strength of the cotton fabric similar to the observations made in Table 7.28.

However, no explanation was provided to support the given data.

On comparing the fastness properties of aftertreated leuco sulphur dyed fabrics reduced

with the two reducing systems, it can be concluded that the wash fastness of CI Leuco

Sulphur Black 1, Blue 7 and Red 14 dyed fabrics against domestic laundering process of

ISO 1O5 CO9 can be improved by the one bath-two stage sequential application of

Tinofix ECO and Bayprotect Cl. However, the influence of this aftertreatment on CI

Leuco Sulphur Green 2 and Yellow 22 was disappointingly low.

In general, significant improvements were observed for the light fastness of all dyes

(reduced with both the systems) except CI Leuco Sulphur Black 1 (reduced with both

systems), Blue 7 (reduced with RAD) and Yellow 22 (reduced with sodium sulphide)

that remained unchanged.

However, in case of leuco sulphur dyed fabrics reduced with Diresul Reducing agent D,

the dry and wet crocking was either reduced or remained unchanged. In contrast,

rubbing fastness of all dyed fabrics reduced with sodium sulphide showed half unit

improvements for wet crocking except CI Leuco Sulphur Black 1 that remained

unchanged and dry crocking of all the dyed fabrics remained unchanged except for CI

Leuco Sulphur Blue 7 which improved by half unit.

In general, one-bath two stage application of Tinofix ECO and Bayprotect Cl on cotton

fabrics dyed with sulphur dyes and reduced with Diresul RAD showed more resistance

to oxidation than the sodium sulphide samples.



210

7.11. Mechanism

There could be a number of possible reasons for the improvement of wash fastness of

sulphur dyed fabric as a result of aftertreatment with a cationic fixing agent and the

tannin. Initially, the role of cationic fixing agent for the improved wet fastness would be

discussed. In the first instance there is probably the potential for the formation of a large

molecular size dye-cationic agent complex with low aqueous solubility arising from the

electrostatic forces of attraction between the anionic groups in the dye and the

polycations [16]. For this to occur, the dye must contain anionic group similar to the

sulphonated groups in direct dye. In spite of the fact that only little is known about the

exact chemistry of the sulphur dyes, it has been proposed that some sulphur dyes may

contain sulphonic acid groups [17]. Hence, the large surface area may lead to

maximising the cumulative effect of weak intermolecular forces and also the physical

entrapment. The large molecules of these complexes would fix inside the fibrous

structure of the fabric and it would be difficult for them to get of the fabric during the

laundering process.

The effect of cationic fixatives on sulphur dyed cotton fabric can somehow be related to

the direct dyes. Firstly, sulphur dyes are proposed to bear sulphonic acid groups as

direct dyes so they might exhibit increased attractive forces between the anionic dye

molecules and cationic fixative, causing the formation of large molecular sized

complexes. Secondly, the molecular size of sulphur dye may vary depending upon the

type of reducing system used and the reduction potential during the dyeing process.

Hence, highly reduced dye would have smaller dye molecules with better capability of

reacting with the cationic polymeric molecules and causing the formation of bigger dye-

fixative complexes.

Similarly, considering that the dyed fabric contains carboxylic acid group on its own

and these groups are further generated as a result of the oxidation achieved by hydrogen

peroxide in the final stage of dyeing, the better adsorption of the dye onto the fabric

might have been arisen owing to the ion-ion interactions between the cationic fixing

agent and the anionic carboxylic acid groups on the substrate [16, 18].

However, an alternative mechanism based on the use of syntans was also proposed

according to which the wet fastness of the sulphur dyes are improved in the same way as



211

the anionic dyes on nylon. It has been proposed that syntans when applied under acidic

conditions to the polyamide fibre dyed with non-metallised acid dyes develop a

peripheral layer of syntan molecules which inhibits the dye leakage form the fibre. It is

the ion-ion interaction which operates between the protonated amino group in the fibre

and sulphonated group in the syntan along with the hydrogen bonding which contributes

towards the syntan-fibre substantivity [16, 19].

The further enhancement of the wash fastness of sulphur dyes by application of tannin

may again be related to the improved wash fastness of acid dyes on nylon produced by

an aftertreatment with either a synthetic or a natural tanning agent. In the case of full

backtan with natural tanning agent, it is believed that the high molecular weight

gallotannin component (tannic acid) binds to the protonated amino end groups in the

nylon fibre and following treatment with potassium antimony tartrate (tartar emetic)

results in the formation of a surface skin. However, due to the environmental concerns,

the use of the full backtan has been replaced by synthetic tanning agents (syntans) [9]. It

has been revealed that the efficiency of a commercial syntan in improving the wash

fastness of various premetallised acid dyes [1, 2] and also non-metallised acid dyes [6]

on nylon 6,6 can be enhanced by the subsequent application of a polymeric cationic

agent to the syntanned, dyed material. It is proposed [6, 9] that this two-stage

aftertreatment process, results in the formation of a large molecular size, low aqueous

solubility, complex between the anionic syntan and the cationic compound within the

dyed fabric.

Yet again, the possible reason for the improvement in the wet fastness could be the

formation of complexes between the cationic fixative (Tinofix ECO) and the anionic

tannin (Bayprotect Cl) forming a large molecule of cation-tannin, which would fix in the

fabric during washing. The other reason for the enhanced fastness could be the ion - ion

interaction between the sulphonated salt groups in the tannin and the cations forming a

peripheral layer over the dyed fabric and preventing the dye from coming out of the

substrate.

Likewise this effect can also be explained by the mordanting technique used for the

adsorption of cationic dyes on cotton. Since these dyes have very low substantivity for

cotton, therefore to dye cotton with cationic dyes, the substrate is usually mordanted

with tannic acid fixed with tartar emetic. The insoluble, anionic tannin attracts coloured



212

dye cations hence facilitating the fixation of the dye molecules [20]. However, in this

case the possible reason proposed for the improved wash fastness is the attraction

between anionic tannin and cationic fixative causing the formation of large molecular

sized complexes that inhibits the dye desorption.

7.12. Surface topography of Tinofix ECO and Bayprotect Cl aftertreated fabrics

The SEM micrographs of CI Leuco Sulphur Black 1 dyed cotton fabrics treated with 5%

omf Tinofix ECO showed appearance of crystals on the fabric surface which may be

attributed to the protruded constituent parts of the finish or the cationic ions. However,

on sequentially treating the fabric with 5% omf Tinofix ECO and 5% omf Bayprotect Cl

(AC 32) did not indicate the presence of any surface depositions or crystals, Figure 7.9

to Figure 7.12. This may be explained as the positive charge of the cationic fixing agent

would have been neutralised (to a given extent) by the anionic Bayprotect Cl resulting in

the removal of the crystals from the cationised fabric. However, after ISO 1O5 CO9

laundering slight fibrillation with some protruding fragments was observed which could

probably be due to wet abrasion of the cotton fibres.

7.13. Conclusions

In order to maximise the benefits for the sequential application of Tinofix ECO and

Bayprotect Cl for improving the wash fastness of sulphur dyes against oxidative

bleaching action of detergent/perborate formulation, the following process parameters

were found to produce the optimised results for the one bath - two stage application

method:

Concentration (omf) Temperature (oC) Time (minutes)

Tinofix ECO 5% 40 15

Bayprotect CL 5% 40 15

The optimised results indicate that aftertreatments with one bath-two stage application

of Tinofix ECO and Bayprotect Cl on CI Leuco Sulphur Black 1 in particular and



213

multiple dyes reported to offer benefits in terms of improvements of wash fastness of

sulphur dyed fabrics against ISO IO5 CO9 washing. The aftertreatments resulted in

approximately 50% reduction in colour loss of CI Leuco Sulphur Black 1 applied with

the conventional and biodegradable reducing systems.

Significant improvements were also observed for light and wet rub fastness properties of

the dyed fabrics; however, dry rub fastness was either reduced or remained unaffected.

Sequential processing methods employed for the optimisation of process parameters

were useful for achieving the best combination resulting in less processing cost and

environmental impact. Hence, the aftertreatment was found to provide a “protective

effect” on the sulphur dyed fabric although no visible signs of depositions or surface

film formation could be detected through SEM analysis indicating that the

aftertreatment did not affect the exterior of the fabric.

The possible suggested reason for the improved wash fastness is that, this combination

has a tendency to produce complexes between anionic tannin and cationic polymer

which inhibit the dissolution of dye molecules and protects the dye against ISO 1O5

CO9 washing regime based on modern detergent formulation.

Since the process involves sequential application of a cationic fixing agent and tannin,

it is postulated that the application of a formaldehyde free polyethylene polyamine

derivative (cationic fixing agent) introduces cationic sites on cellulose as depicted in

Figure 7.13



214


unlaundered, 5% omf Tinofix ECO +

5% omf BP Cl treated cotton fabric

Magnification 1000x


unlaundered, 5% omf Tinofix ECO +


Magnification 5000x


CO9 laundered, 5% omf Tinofix ECO +


Magnification 1000x


CO9 laundered, 5% omf Tinofix ECO +


Magnification 5000x



215

Figure 7.13 Formation of complexes between dye and cation

Sequential application of an aromatic carboxylic acid derivative (anionic tannin)

forms complexes with the cations as shown in Figure 7.14.

Figure 7.14 Formation of complexes between dye/cation and tannin

Therefore, the reasons for the improved wash fastness could presumably be any of the

following:

1) The electrostatic forces of attraction between the cationic agent and the anionic dye

molecules forming large molecular sized complexes;

2) The ion-ion interactions between the cationic agent and the anionic carboxyl groups

in the fibre resulting in the attachment of the cationic agent molecules to the fabric

and partially blocking pores/locking the polymeric structure;

3) Formation of a large molecular size cationic agent/tannin complex with low aqueous

solubility as a result of intermolecular forces of attraction also partially blocking

pores/locking the polymeric structure;

4) Formation of a peripheral layer of polycations molecules or anionic tannin which

might reduce the diffusion of the dye out of the dyed and treated fabric during the

laundering.

To further investigate the introduction of various functional groups and possible reasons

for reduction in the oxidation of the dye, the surface chemical analysis of the untreated

and aftertreated CI Leuco Sulphur Black 1 dyed fabric samples with the help of surface

Positive charges produced by Tinofix ECO

Negative charges produced by Bayprotect Cl



216

sensitive X-Ray photoelectron spectroscopy (XPS) were undertaken which is described

in chapter 9. This technique assisted to probe the nature of the outer 3-10 nm of the

cotton surface, characterise the surface functionalities and establish the reasons for

durability of the surface dye to different aftertreatments and washing regimes.

7.14. References

[1] Blackburn R and Burkinshaw S. Aftertreatment of 1:2 metal complex acid dyes on

conventional and microfibre nylon 6,6 with a commercial syntan/cation system. Journal

of the Society of Dyers and Colourists. 1998;114(3):96-100.

[2] Blackburn R and Burkinshaw S. Aftertreatment of 1:2 metal‐complex acid dyes on

conventional and microfibre nylon 6,6 with a commercial syntan/cation system. Part 2:


[3] Feiz M and Radfar Z. Improvement of wash fastness of direct and acid dyes applied

to silk by aftertreatment with syntan, syntan/cation, and full backtan processes. Iranian

Polymer Journal. 2006;15(4):299.

[4] Burkinshaw S and Kumar N. A tannic acid/ferrous sulfate aftertreatment for dyed

nylon 6,6. Dyes and Pigments. 2008;79(1):48-53.

[5] Burkinshaw S and Paraskevas M. The dyeing of silk part 2: Aftertreatment with

natural and synthetic tanning agents. Dyes and Pigments. 2011;88(2):156-65.

[6] Burkinshaw S and Maseka K. Improvement of the wash fastness of non-metallised

acid dyes on conventional and microfibre nylon 6,6. Dyes and Pigments. 1996;30(1):21-

42.



1997;33(1):1-9.

[8] Feiz M and Salimpour S. Improvement in wash fastness of dyed silk by

aftertreatment with commercial syntan/metal salts. Progress in Color, Colorants and

Coatings. 2008;1(1):27-36.



217

[9] Burkinshaw S. Chemical principles of synthetic fibre dyeing: Springer Science and

Business Media, 1995.

[10] Madhu and Amit. Sulfur dyeing with non-sulfide reducing agents. Journal of

Textile and Apparel, Technology and Management 2012;7(4):1-13.






Limited, 2004.

[14] Cristea D and Vilarem G. Improving light fastness of natural dyes on cotton yarn.

Dyes and Pigments. 2006;70(3):238-45.

[15] El-Molla M, Badawy N, Abdel-Aal A, El-Bayaa A and El-Shaimaa H. Dyeability

of cationised cotton and nylon 6 fabrics using acid dyes. Indian Journal of Fibre and

Textile Research. 2011;36(1):88-95.




Colorist. 1970;2(13):29-34.

[18] Peter R. Textile chemistry. Vol. III: The physical chemistry of dyeing. Elsevier:

New York, 1975.



[20] Broadbent AD. Basic principles of textile coloration. Bradford: Society of Dyers

and Colorists, 2001.

Fourier transform infrared spectroscopic study of sulphur dyed and aftertreated cotton fabrics

218

8. Fourier transform infrared spectroscopic study of sulphur dyed

and aftertreated cotton fabrics

8.1. Introduction

Infrared spectroscopy is an extremely powerful analytical technique utilised for the

qualitative and quantitative analysis of the samples. However, other analytical methods

may also provide useful complementary and/or confirmatory information regarding the

sample so this technique should not be used in isolation. Other analytical techniques

may include simple chemical tests and elemental analysis [1].

In this study, Fourier transform infrared (FTIR) attenuated total internal reflection

(ATR) technique has been used for the study of the undyed, dyed and aftertreated cotton

fabrics in order to gain some insight into the presence of possible functional groups

which were introduced to the fabric surface as a result of dyeing and aftertreatments.

The samples used were cotton fabrics dyed with 5% omf CI Leuco Sulphur Black 1 dye

(reduced with Diresul RAD) and aftertreated with Tinofix ECO and Bayprotect Cl. The

two finishing agents were analysed in isolation to characterise the materials and the

aftertreated fabrics were further analysed to investigate the effects of the finishing

agents on the surface chemistry of the dyed cellulosic fabric. However, in order to make

the quantitative analysis and determine the oxidation states of important elements, the

dyed and aftertreated fabrics were also examined with X-ray photoelectron

spectroscopic technique. XPS enables the measurement of the spectral peak areas which

leads to quantitative information about the surface composition of the fibres. Further,

elemental bulk analysis was done to support the information obtained from FTIR-ATR

and XPS data.

FTIR-ATR spectra were obtained for undyed, dyed, cationised and cation-tannin treated

cotton fabrics. The fixatives, Tinofix ECO and Bayprotect Cl which were applied as part

of the aftertreatment methods were analysed and the details are summarised in Table

8.1.

A plot of measured infrared radiation intensity versus wave number is known as an

infrared spectrum. Traditionally, an infrared spectrum is plotted with high wave number


219

on the left and low on the right. The absorbance lies on Y-axis while the wave number

on X-axis. Sometimes the Y-axis can also be plotted in transmittance. Irrespective of the

Y-axis units, it is the wavenumber (X-axis) positions of the peaks that correlate with

molecular structure [1].

Table 8.2 gives a broad overview of the expected functional groups and possible species

that exist in a particular region of FTIR spectra.

Table 8.1 Compositions for CI Leuco Sulphur Black 1 dyed fabric aftertreated

with Tinofix ECO and Bayprotect Cl

Exhaust application (L:R=10:1)

Aftertreatments

to sulphur dyed

cotton fabric

Concentration of

Tinofix ECO

Concentration of

Bayprotect Cl

Application

temperature

and time for

Tinofix ECO

Application

temperature

and time for

Bayprotect Cl

BP - 5% omf - 80oC, 20 minutes

TE 5% omf - 40oC, 30 minutes -

TE, BP 5% omf 5% omf 40oC, 30 minutes 40

oC, 20 minutes

Where:

TE: Tinofix ECO

BP: Bayprotect Cl

Table 8.2 Regions of the infrared spectrum for preliminary analysis [2]

Region (cm-1

) Group Possible functional species present

3700-3100 ─OH Alcohol, aldehyde, carboxylic acids

─NH Amides, amines

≡ C − H Alkynes

3100-3000 =C─H Aromatic compounds

─CH2 or ─CH=CH─ Alkenes or unsaturated rings

3000-2800 ─CH, ─CH2, ─CH3 Aliphatic groups

2800-2600 ─CHO Aldehydes

2700-2400 ─POH Phosphorous compounds

─SH Mercaptans and thiols

─PH Phosphine

2400-2000 −C ≡ N Nitriles

─N=N+=N

- Azides

−C ≡ C − Alkynes


220

1870-1650 C=O Acid halides, aldehydes, amides, amino

acids, anhydrides, carboxylic acids, esters,

ketones, lactans, lactones, quinines

1650-1550 C=C, C=N, NH Unsaturated aliphatics, aromatics,

unsaturated heterocycles, amides, amines,

amino acids

1550-1300 NO2 Nitro compound

CH3 and CH2 Alkanes, alkenes, etc.

1300-1000 C─O─C and C─OH Ethers, alcohols, sugars

S=O, P=O, C─F Sulphur, phosphorus, and fluorine

compounds

1100-800 Si─O and P─O Organosilicon and phosphorus compounds

1000-650 =C─H Alkenes and aromatic compounds

─NH Aliphatic amines

800-400 C─halogen Halogen compounds

Aromatic rings Aromatic compounds

8.2. Fourier transform infrared spectroscopic analysis of the undyed cotton fabric

FTIR has been commonly used to characterise natural fibres with various treatments

such as grafting, coupling and mercerisation. It is a useful tool for obtaining in-depth

knowledge of modified natural fibres [3].

In order to analyse the effect of various aftertreatments, a comparative study between

the untreated and treated CI Leuco Sulphur Black 1 dyed cotton fabrics was carried out.

However initially the FTIR spectrum of undyed cotton fabric was collected (Figure 8.1).

The frequency of the vibrational absorptions is identified in Table 8.3.


221

Figure 8.1 FTIR spectrum of undyed cotton fabric

Table 8.3 Vibrational absorption assignments in the FTIR spectrum of undyed

cotton fabric

Peak wave number

(cm-1

)

Absorbance

intensity Bending deformation, stretching or bending

660 strong Broad, C-OH out-of-plane bending (hydrogen

bonding)

893 medium Nonsymmetric out phase ring

1029 strong C-C, C-OH, C-H ring and side group vibrations

1053 strong C-O-C asymmetrical stretching

1105 strong Nonsymmetric in phase ring

1160 strong Nonsymmetric bridge C-O-C

1235 medium C-O stretching

1236 medium C=O stretching or NH2 deformation

1280 medium C-H and O-H vibrations

1314 medium C-OH and HCC vibrations

1426 weak CH2 symmetric bending

1627 medium OH deformation

2894 medium C-H

3285 medium Broad O-H stretching

The absorption region of 3200-3400 cm-1

is the major characteristic absorption peaks for

cellulosic fibres. The FTIR spectrum of undyed cotton fabric shows strong absorption

between 3000 and 3600 cm-1

(which is attributed to the O-H stretching vibration). This

absorption band is composed of two vibrations located at 3285 cm-1

(attributed to

0

0.01

0.02

0.03

0.04

0.05

0.06

0.07

0.08

0.09

0.1

400900140019002400290034003900

Ab

sorb

ance

Wave number cm-1

3285 cm-1 2894 cm-1

1627 cm-1

1314 cm-1

1029 cm-1

660 cm-1


222

intermolecular hydrogen bonds) and 3330 cm-1

(attributed to intra-molecular hydrogen

bonds) [4]. Nearly identical weak peak at 2894 cm-1

associated with C-H stretching and

1426 cm-1

associated with CH2 symmetric bending can also be observed in the spectrum

[5]. The appearance of absorption peaks at 1314 and 1280 cm-1

shows the existence of

C-H, O-H [6] and C-OH, HCC [7] vibrations respectively. Likewise, the peak located at

1235 cm-1

can be assigned to the C-O stretching [8]. In addition to O-H bending

vibration of physically adsorbed water molecules located at 1627 cm-1

[9], the vibrations

located at 1236 cm-1

is assigned to C=O stretching (originating from esters or amides) or

NH2 deformation (corresponding to proteins or amino acids) [10]. Examination of the

fingerprint region (600-1400 cm-1

) indicates the presence of numerous absorption bands

in the range of 1030-1320 cm-1

which can be attributed to cellulose hydroxyl functional

group [11]. The strong vibration band at 660 cm-1

is also attributed to the O-H out of

plane bending confirming the presence of hydrogen bonding [3, 11-13].


Leuco Sulphur Black 1

Figure 8.2 FTIR spectrum of CI Leuco Sulphur Black 1 dyed cotton fabric

0

0.01

0.02

0.03

0.04

0.05

0.06

0.07

0.08

0.09

0.1

400900140019002400290034003900

Ab

sorb

ance

Wave number cm-1

Undyed cotton fabric Sulphur Black dyed cotton fabric

498 cm-1 1024 cm-1

1144 cm-1

1072 cm-1


223

Table 8.4 Vibrational absorption assignments in the FTIR spectrum of


Peak wave

number (cm-1

)

Absorbance

intensity

Bending deformation, stretching or

bending

430-500 weak-medium S-S stretching (Aromatic disulphides)

1000-1150 weak-medium Oxidised sulphur species

Compared to the FTIR spectrum of undyed cotton fabric, the spectrum of fabric dyed

with CI Leuco Sulphur Black 1 exhibited additional vibrations between 430-500 cm-1

and 1000-1150 cm-1

as shown in Figure 8.2 and Table 8.4.

As seen in the spectrum above, an additional peak at 498 cm-1

is presumed to relate to

the S-S stretching vibration of aromatic disulphide [11, 14]. The presence of three peaks

in the range of 1000-1150 may possibly be attributed to oxidised sulphur species.


Leuco Sulphur Black 1 and aftertreated with Bayprotect Cl

Figure 8.3 FTIR spectrum of Bayprotect Cl

0.0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

400900140019002400290034003900

Ab

sorb

ance

Wave number cm-1

3286 cm-1

2869 cm-1

926 cm-1

1059 cm-1

1315 cm-1

1439 cm-1 1720 cm-1


224


Bayprotect Cl

Peak wave

number (cm-1

)

Absorbance


2500-3300 medium Broad OH stretching vibration, hydrogen

bonding present

2869 medium CH2 (symmetric -C-H- stretching vibration)

1700-1725 medium C=O stretching

1439 medium -C-C- aromatic groups

1395-1440 medium C-O stretching

1280-1320 medium O-H deformation

1059 strong -C-O-C- stretching

915-955 medium Out of plane deformation of OH...O group

As seen in Figure 8.3, the FTIR spectrum of Bayprotect Cl shows a distinctive, broad

and strong band at 3286 cm-1

which is assigned to the aromatic hydroxyl group (OH)

stretching vibration assuring the presence of hydrogen bonding. A sharp peak at

2869 cm-1

is associated with the asymmetric -C-H- stretching vibrations of CH2

(methylene) group [15]. The deformation vibration of the carbon-carbon bonds in the

phenolic groups absorbs in the region of 1400-1500 cm-1

, and the peak at 1439 cm-1

indicates the presence of CH2 vibration associated with the aromatic CH2-OH group.

Similarly the absorption at 1720 cm-1

corresponds to carbonyl stretching vibrations and

a strong absorption peak 1059 cm-1

can be attributed to -C-O-C- stretching vibration that

is a characteristic of a sulphonated salt absorption peak [11, 14, 15]. The presence of a

broad band due to O-H stretching vibration, a strong band of C=O stretching vibration

and intermolecular hydrogen bonding, Bayprotect Cl can be expected to be a tannin

based product possibly an aromatic carboxylic acid derivative. The details of the peak

wave numbers and functional groups are summarised in Table 8.5.


225

Figure 8.4 FTIR spectra of CI Leuco Sulphur Black 1 dyed cotton fabric

untreated and aftertreated with Bayprotect Cl

The comparison of the spectra of untreated CI Leuco Sulphur Black 1 dyed fabric with

Bayprotect Cl aftertreated fabric (Figure 8.4) showed additional peak located at 2922

cm-1

which possibly corresponds to asymmetric -C-H- stretching vibrations of CH2

(methylene) group [15]. The absorption peak in the range of 1700-1725 cm-1

is

attributed to carbonyl vibrations, whereas the peak at 1267 cm-1

indicates the presence

of OH deformation [11, 14]. A strong absorption peak 1059 cm-1

can be attributed to -C-

O-C- stretching vibration that is a characteristic of a sulphonated salt absorption peak

[11, 14, 15].

0

0.01

0.02

0.03

0.04

0.05

0.06

0.07

0.08

400900140019002400290034003900Wavenumber cm-1

Untreated Aftertreated with 5% omf Bayprotect Cl

1718 cm-1

1267 cm-1

1059 cm-1

2922 cm-1


226


Leuco Sulphur Black 1 and aftertreated with Tinofix ECO

Figure 8.5 FTIR spectrum of Tinofix ECO


Tinofix ECO

Peak wave

number (cm-1

)

Absorbance


3250-3550 medium N-H stretching

1580-1650 medium N-H deformation

1020-1090 medium C-N stretching

On analysing the FTIR absorption bands for Tinofix ECO, a strong and wide band

within 2900 and 3600 cm-1

corresponds to the N-H stretching vibrations. The absorption

peaks at 1590 cm

-1 indicates the presence of N-H deformation while that at 1053 cm

-1

attributes to C-N stretching [11]. This shows that Tinofix ECO possibly be a polyamine

derivative. The FTIR spectrum and bond stretching of Tinofix ECO are represented in

Figure 8.5 and Table 8.6, respectively.

0.0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

400900140019002400290034003900

Ab

sorb

ance

Wavenumber cm-1

3305 cm-1

1590 cm-1

1053 cm-1


227


untreated and aftertreated with Tinofix ECO

The FTIR spectrum of CI Leuco Sulphur Black 1 dyed fabric aftertreated with Tinofix

ECO shows an absorption peak at 1112 cm-1

range corresponding to C-N stretching

vibrations while an intensive distinct band at 1058 cm-1

is a characteristic of the primary

–C-O-H stretching deformation [11, 16, 17]. The IR spectra of untreated and Tinofix

ECO treated fabrics are shown in Figure 8.6.

0

0.01

0.02

0.03

0.04

0.05

0.06

0.07

0.08

0.09

400900140019002400290034003900

Ab

sorb

ance

Wavenumber cm-1

Untreated Aftertreated with 5% omf Tinofix ECO

1112 cm-1

1058 cm-1


228


Leuco Sulphur Black 1 and aftertreated with Tinofix ECO and Bayprotect Cl


untreated and aftertreated with Tinofix ECO and Bayprotect Cl


CI Leuco Sulphur Black 1 dyed cotton fabric aftertreated with Tinofix ECO

and Bayprotect Cl

Peak wave

number (cm-1

)

Absorbance

Intensity

Bending deformation, stretching or bending

940-1140 strong C-O-C stretching vibrations

On relating the absorbance spectra of untreated sulphur dyed cotton fabric with

Bayprotect Cl and Tinofix ECO aftertreated sample, a broad peak could be seen (Table

8.7 and Figure 8.7) between 900 and 1100 cm-1

which may possibly be assigned to the

C-O-C stretching vibrations [11].

0

0.01

0.02

0.03

0.04

0.05

0.06

0.07

0.08

0.09

0.1

400900140019002400290034003900

Ab

sorb

ance

wavenumber cm-1

Untreated Aftertreated with 5% omf Tinofix ECO + 5% omf Bayprotect Cl

989 cm-1


229

8.7. Conclusions

In this study we investigated the use of the FTIR-ATR spectroscopy to identify the

presence of various functional groups which are possibly generated as a result of three

different aftertreatments on cotton fabric dyed with CI Leuco Sulphur black 1 and

reduced with Diresul reducing agent D. It was observed that, the application of Tinofix

ECO introduces C-N and -C-O-H functional groups to the fibre surface and the product

is presumably a polyamine derivative. On the other hand, the treatment of the dyed

fabric with Bayprotect Cl indicates the presence of C-O-C stretching , -C-H stretching,

OH deformation and C=O stretching vibrations and it is presumably considered to be a

tannin based product. The sequential application of the two aforementioned auxiliaries

causes the formation of C-O-C stretching vibration.

8.8. References

[1] Smith BC. Fundamentals of Fourier transform infrared spectroscopy: Taylor &

Francis, 1995.

[2] Lambert JB, Shurvell HF, Lightner DA and Cooks RG. Organic structural

spectroscopy: Prentice Hall Upper Saddle River, NJ, 1998.

[3] Fan M, Dai D and Huang B. Fourier transform infrared spectroscopy for natural

fibres. Fourier Transforms-Materials Analysis: InTech. 2012. p.45-68.

[4] Liang C and Marchessault R. Infrared spectra of crystalline polysaccharides. II.

Native celluloses in the region from 640 to 1700 cm−1

. Journal of Polymer Science.

1959;39(135):269-78.

[5] Kavkler K and Demşar A. Application of FTIR and Raman spectroscopy to

qualitative analysis of structural changes in cellulosic fibres. Slovene Journal for Textile

and Clothing Technology, Design and Marketing. 2012;55(1):19-31.

[6] Oh SY, Yoo DI, Shin Y and Seo G. FTIR analysis of cellulose treated with sodium

hydroxide and carbon dioxide. Carbohydrate Research. 2005;340(3):417-28.


230

[7] Proniewicz LM, Paluszkiewicz C, Wesełucha-Birczyńska A, Majcherczyk H,

Barański A and Konieczna A. FT-IR and FT-Raman study of hydrothermally

degradated cellulose. Journal of Molecular Structure. 2001;596(1):163-9.

[8] Azadfallah M, Mirshokraei SA, Jahan Latibari A and Parsapajouh D. Analysis of

photodegraded lignin on cellulose matrix by means of FTIR spectroscopy and high

pressure size exclusion chromatography. Iranian Polymer Journal. 2008;17(1):73-80.

[9] Cao Q, Zhu S, Zhao H and Tu H. Application of Fourier transform attenuated total

reflection infrared spectroscopy to identifying archaeological fibres. Research Journal of

Textile and Apparel. 2010;14(1):38-41.

[10] Abidi N, Hequet E and Cabrales L. Applications of Fourier transform infrared

spectroscopy to study cotton fibers. Fourier Transforms-New Analytical Approaches

and FTIR Strategies: InTech. 2011. p.89-114.

[11] Socrates G. Infrared characteristic group frequencies: Tables and charts: Wiley,

1994.

[12] Chung C, Lee M and Choe EK. Characterization of cotton fabric scouring by FT-IR

ATR spectroscopy. Carbohydrate Polymers. 2004;58(4):417-20.

[13] Arain RA, Khatri Z, Memon MH and Kim I-S. Antibacterial property and

characterization of cotton fabric treated with chitosan/AgCl–TiO< sub> 2</sub>

colloid. Carbohydrate Polymers. 2013;96(1):326-31.

[14] Stuart B, George B and Mclntyre P. Modern infrared spectroscopy: Wiley India

Private Limited, 2008.

[15] Pantoja-Castro MA and González-Rodríguez H. Study by infrared spectroscopy

and thermogravimetric analysis of tannins and tannic acid. Revista latinoamericana de

química. 2011;39(3):107-12.


cationized cotton fabric with natural dye. Part 1: Cationization of cotton using Solfix E.

Ultrasonics Sonochemistry. 2009;16(2):243-9.


231


cationized cotton fabric with natural dye. Part 2: Cationization of cotton using Quat 188.

Industrial Crops and Products. 2011;34(3):1410-7.

Surface and bulk chemical analysis of sulphur dyed and aftertreated cotton fabrics

232

9. Surface and bulk chemical analysis of sulphur dyed and

aftertreated cotton fabrics

9.1. Introduction

The development of techniques for the surface selective modification of cotton fibres

and the need to understand the changes in the fibre chemistry and properties has

emphasised the necessity for the application of the XPS (X-Ray photoelectron

spectroscopy) technique in textiles. In order to study the chemistry of modified cotton,

the introduction of XPS method was pioneered by Soignet [1] and subsequently the

surface chemistry of cellulosic fibres has been investigated by a number of researchers

[1-9].

In this study the relative effect of aftertreatments with Tinofix ECO and Bayprotect Cl

on ISO 105 C06 and ISO 105 C09 washing of CI Sulphur Black 1 dyed cotton fabric

has been evaluated in order to compare visual change with surface chemical changes.

The chemical and physical effects on the outer surface of CI Leuco Sulphur Black 1

dyed fabrics aftertreated with the stated fixing agents has been investigated for the first

time. The surface sensitive X-Ray photoelectron spectroscopic technique was used to

probe the nature of the outer 3-10 nm of the cotton’s surface so as to characterise the

surface functionalities, establish the elemental composition and assess the durability of

the surface sulphur dye to different aftertreatments. This spectroscopic technique helped

in fully understanding the nature of the fibre surface interface of untreated and

aftertreated cotton fabric on exposure to chemically aggressive bleaching media and the

improvements produced as a result of aftertreatments.

This chapter is divided into two sections. The first section (section 9.2) explains the

surface chemistry of 5% omf CI Leuco Sulphur Black 1 dyed cotton fabric (reduced

with Diresul RAD) aftertreated with Bayprotect Cl and the effects of aftertreatments on

ISO 105 C06 and ISO 105 C09 washing regimes. The second section (section 9.3) is

based on the surface chemical analysis of the aforementioned dyed fabric aftertreated

with optimised one bath – two stage process with sequential application of Tinofix ECO

and Bayprotect Cl following ISO 105 C09 washing.


233

9.2. Investigation into the effects of aftertreatments with Bayprotect Cl on the surface

chemistry of CI Leuco Sulphur Black 1 dyed fabric subjected to ISO 105 C06 and ISO

105 C09 washing regimes

X-Ray photoelectron spectroscopic measurements of untreated sulphur black dyed

cotton fabric in comparison to Bayprotect Cl aftertreated samples were made to analyse

the surface chemistry of the untreated and aftertreated samples before and after

laundering. The sulphur dyed fabric was aftertreated with 4% omf Bayprotect Cl and

100 g/L sodium sulphate. The compositions, colorimetric data and elemental

composition of the samples are illustrated in Table 9.1, Table 9.2 and Table 9.3,

respectively.

Table 9.1 Application of Bayprotect Cl to CI Leuco Sulphur Black 1 dyed fabric

EXHAUST APPLICATION

Compositions

L:R

Temperature

Time

pH


4% omf 100 g/L 10:1 80

oC

20

minutes

<3.5

(citric acid)

Table 9.2 Colorimetric data for CI Leuco Sulphur Black 1 dyed fabric

aftertreated with Bayprotect Cl following ISO 1O5 CO6 and ISO 1O5 CO9

washing

Washing


%Colour

loss

GS

Rating DE

Untreated 29.6 -0.8 -4.6 4.7 260.3 8.0

WF 1 30.6 -1.2 -4.9 5.0 255.9 7.6 5% 4/5 1.1

WF 5 41.0 -1.5 -4.1 4.3 250.5 3.6 55% 1/2 11.4

Aftertreated 30.2 -0.3 -4.2 4.2 266.2 7.4

WF 1 30.3 -1.3 -4.6 4.8 254.4 7.8 -5% 4/5 1.1

WF 5 39.6 -1.4 -4.1 4.4 250.9 4.0 46% 2 9.5

Where:




234

Table 9.3 XPS surface elemental composition for CI Leuco Sulphur Black 1

dyed fabric aftertreated with Bayprotect Cl following ISO 1O5 CO6 and

ISO 1O5 CO9 washing

Sulphur dyed

samples

Washing treatment

% Atomic composition

Carbon

Nitrogen

Oxygen

Sulphur

O/C

Untreated

Sample 1 None 70.5 1.1 27.2 1.2 0.4

Sample 2 WF 1 70.6 1.1 27.5 0.8 0.4

Sample 3 WF 5 70.7 0.9 27.9 0.5 0.4

Aftertreated

Sample 4 None 70.1 1.1 27.7 1.1 0.4

Sample 5 WF 1 70.0 0.9 28.1 1.0 0.4

Sample 6 WF 5 69.3 0.7 29.4 0.6 0.4

Where:



9.2.1. Investigation into the effects of aftertreatments with Bayprotect Cl on surface

elemental compositions of CI Leuco Sulphur Black 1 dyed fabric

Table 9.3 details the elemental compositions of unlaundered and laundered samples of

dyed and Bayprotect Cl aftertreated fabrics subjected to ISO 105 C06 and ISO 105 C09

washing regimes. On analysing unlaundered samples (sample 1 and 4), treating the dyed

fabric with Bayprotect Cl shows a slight reduction in sulphur and carbon content, which

probably have arisen as a result of the removal of surface dye and slight fibrillation due

to aftertreatments. An increase in oxygen content presumably describes the

functionalisation of the surface with oxygen-containing groups, however, the nitrogen

content remains unchanged. The chemistry of Bayprotect Cl does not refer to the

presence of nitrogen, which is further supported by the XPS surface elemental

composition data above. Hence, this suggests that the tannin based product Bayprotect

Cl does not introduce any nitrogen species on the dyed fabric and that it is perhaps an

impurity from the original product.


235

Examining the laundered samples, the untreated sulphur dyed fabric undergoes a

concomitant reduction in sulphur content from 1.2% to 0.8% and 0.5% for ISO 105 C06

and ISO 105 C09 washing, respectively. This was presumably due to oxidation of the

dye disulphide bonds leading to the formation of water-soluble sulphonated short chain

dye fragments which are lost into solution [3]. As the amount of sulphur content in

sample 3 is less than sample 2, this means that the effect of ISO 105 C09 is far more

destructive than ISO 105 C06 washing owing to the presence of high concentration of

bleaching agent (sodium perborate) in the wash liquor.

However, Bayprotect Cl aftertreated samples laundered with ISO 105 C06 and ISO 105

C09 washing showed increased sulphur concentrations of 1% (sample 5) and 0.6%

(sample 6) respectively, which is much higher than the percentage content of surface

sulphur found on the untreated samples. This indicates that as a result of aftertreatments,

the sulphur species are bound to the fabric surface and retained there even after

laundering.

Inspecting the nitrogen contents, it was observed that untreated and ISO 1O5 CO9

laundered sample showed a relative decrease in surface nitrogen concentrations from

1.1% (sample 1) to 0.9% (sample 3) while ISO 1O5 CO6 washing does not affect the

surface nitrogen content (sample 2). However, a slight reduction in nitrogen content

might be expected due to the removal of dye but it was not observed for CO6 washing.

Sulphur dyed fabric aftertreated with Bayprotect Cl significantly loses surface nitrogen

on laundering (sample 5 and 6).

The O/C ratio of unlaundered and laundered samples remains unchanged while a

comparative increase in the oxygen content was observed for laundered samples, which

indicates surface oxidation of untreated and aftertreated samples as a result of oxidative

bleaching environment offered by sodium perborate/detergent washing.


236

9.2.2. Investigation into the effects of aftertreatments with Bayprotect Cl on S (2p)

spectra of CI Leuco Sulphur Black 1 dyed fabric

Examination of the S (2p) spectra of sulphur dyed cotton fabric indicates the presence of

sulphur at the surface of the cotton fibres and details the different oxidation states of

sulphur. As illustrated in the inset of Figure 9.1 to Figure 9.6, all samples show broad

sulphur signals in the range from 164 to 168 eV, which exhibit well-separated peak

structures at low (164 eV) and high (168 eV) binding energies. Additional information

regarding the presence and chemical binding state of sulphur is explained by

investigation of these S (2p) chemical shifts.

In case of untreated and unlaundered sample, a distinctive peak can be seen at 168 eV

contributing around 48% of the total sulphur content. This peak intensity proposes the

re-oxidation of the alkali reduced sulphur dye thiols to reform the insoluble disulphide

bond-based sulphur dye has resulted in over-oxidation to S6+

species [3]. The possible

reason for the presence of oxidised species could possibly be the slight over oxidation

caused by the use of hydrogen peroxide in the final dyeing stage for converting the thiol

derivative into the parent insoluble form of the dye (Figure 9.1), which is the over

oxidation of the disulphide groups forming ionisable sulpho groups caused by active

peroxide [10]. The effect of laundering with detergent, sodium perborate and TAED

was to increase the amount of higher binding energy spectral component at 168 eV

(Figure 9.2 and Figure 9.3). Most likely the precursor to the loss of the dye from the

fibre surface is S6+

oxidised dye derivative which may be assigned to−SO3− , −S − SO2

−

or −S − SO3− species [3].

It was observed that dyed fabric aftertreated with Bayprotect Cl (sample 4) also give rise

to the formation of two peaks at 164 eV and 168 eV that are unoxidised (S2+

) and over-

oxidised (S6+

) species respectively with a slight increase in the oxidised species as

shown in Table 9.4. This explains that the treatment of the dyed fabric with Bayprotect

Cl causes minor oxidation. However, examination of the S (2p) spectra of laundered

samples 2 and 3 against the untreated and unlaundered dyed fabric (sample 1) shows a

rise in the over-oxidised species at 168 eV. On the other hand, the Bayprotect Cl treated

samples mirrored low level of oxidation and minimal loss of sulphur observed for the

comparable laundered untreated cotton fabric. The S (2p) spectra of laundered samples

5 and 6 illustrate a concomitant reduction in over oxidised (S6+

) species at 168 eV. The


237

observed reduction is from 70% to 65% for ISO 1O5 CO6 and from 89% to 85% for

ISO 1O5 CO9 washing systems (Table 9.4).

The S (2p) XP spectra for untreated and Bayprotect Cl treated samples were analysed to

differentiate the possible presence of three main sulphur species namely unoxidised S2+


(−SO3− , −S − SO2

− or −S − SO3−) and partially or

intermediate oxidised S4+

. However, the presence of partially oxidised species could not

be identified. The presence of over-oxidised sulphur species was also confirmed by

FTIR analysis of CI leuco Sulphur Black 1 dyed cotton fabric as discussed in section 8.3

Table 9.4 Relative intensity data of the deconvoluted S (2p) spectra for CI

Leuco Sulphur Black 1 dyed fabric aftertreated with Bayprotect Cl following

ISO 1O5 CO6 and ISO 1O5 CO9 washing

Sulphur dyed

samples

Washing treatment

Peak areas (%)

164 eV 168 eV

Untreated

Sample 1 None 52 48

Sample 2 WF 1 30 70

Sample 3 WF 5 11 89

Treated

Sample 4 None 51 49

Sample 5 WF 1 35 65

Sample 6 WF 5 15 85

Where:




238


(unlaundered)


(ISO 1O5 CO6 laundered)

CasaXP S (Thi s st ring can be edit ed in CasaXPS.DEF/P rintFootNote.txt)

60

70

80

90

100

110

120C

PS

176 172 168 164 160 156

Bindi ng E nergy (eV)


45

50

55

60

65

70

75

80

85

CP

S

176 172 168 164 160 156



239



Figure 9.4 S (2p) spectrum of CI Leuco Sulphur Black 1 dyed fabric

aftertreated with 4% omf Bayprotect Cl (unlaundered)


70

80

90

100

110

120C

PS

176 172 168 164 160 156



40

45

50

55

60

65

70

75

80

85

90

CP

S

176 172 168 164 160 156



240


aftertreated with 4% omf Bayprotect Cl (ISO 1O5 CO6 laundered)




60

70

80

90

100

110

120

CP

S

176 172 168 164 160 156



60

70

80

90

100

110

CP

S

176 172 168 164 160 156



241

9.2.3. Investigation into the effects of aftertreatments with Bayprotect Cl on C (1s)


Relative amounts of carbon with different numbers of oxygen bonds were estimated

from the high resolution C (1s) carbon spectra, Figure 9.7 - Figure 9.12 . The carbon

compound classification was based on the number of oxygen bonds attached to the

carbon atoms: the peaks at 285.0 eV, 286.6 eV, 288.2 eV and 289.4 eV are due to

carbons with 0, 1, 2 or 3 bonds to oxygen respectively [12]. For samples treated with

Bayprotect Cl, deconvolution analysis showed an increase of oxygen-based functional

groups such as C–O (286.6 eV), C=O (288 eV) and O=C–O (289 eV) as shown in Table

9.5. The relative amount of each type of carbon was modified that can be observed in

peak intensity changes in Figure 9.10, where the carbon C2, C3 and C4 peak areas were

significantly increased compared to untreated dyed fabric (sample 1). These results

imply that the surface of the sulphur dyed cotton fabric became partially oxidised by

fixative exposure, resulting in a decrease of C–C/C–H bonds, and significant increase of

oxidised species, although it must be noted that Bayprotect Cl itself is known to contain

carbonyl and carboxylic acid species.

Examination of high resolution C (1s) spectrum of untreated sulphur dyed fabric

laundered with ISO 1O5 CO6, indicated a fall in hydrocarbon signal intensity at 285 eV

(11%) while a rise in the oxidised species at 286.6 eV (2%), 288.0 eV (29%) and 289.0

eV (34%) was observed. The high resolution carbon spectrum of untreated fabric

laundered with ISO 1O5 CO9 portrays a significant rise in oxidised species intensities at

286.6 eV (24%), 288.0 eV (>100%) and 289.0 eV (>100%). Presumably, this change

was due to a concomitant loss in surface hydrocarbon residue and some oxidation of the

cellulosic backbone.

However, on treating the fabric with Bayprotect Cl and exposing it to ISO 1O5 CO6

washing, an associated decrease in C1 (14%) was observed while an increase in C2

(1%), C3 (25%) and C4 (31%) components with respect to sample 4 was being detected.

This percentage increase in oxygen containing functional groups is lesser than untreated

laundered fabric (sample 2). However, on exposing the treated fabric to ISO 1O5 CO9

washing system an increase in C1 and a decrease in C2, C3 and C4 components was

observed. Compared to sample 4, the non-oxidised carbon fraction (C1) in Bayprotect


242

Cl treated fabric (sample 4) has increased significantly (26%), whereas the carbon with

oxygen-based functional groups (C2, C3 and C4) was dramatically reduced, that is 10%,

18% and 60%, respectively. Chemical composition of the aftertreated and ISO 1O5 CO9

laundered fabric suggests that aftertreatments with Bayprotect Cl reduces the formation

of oxidised functionalities and contributes to the formation of carbon compound without

neighbouring oxygen (C-C, C-H). It is therefore proposed that Bayprotect Cl may have

a protecting effect and partially prevent the oxidation of sulphur dyed cotton fabric.

Concentrations of carbon functionalities obtained from deconvoluted C (1s) spectra for

untreated and treated samples are summarised in Figure 9.13.

Table 9.5 Relative intensity data of the deconvoluted C (1s) spectra for CI

Leuco Sulphur Black 1 dyed fabric aftertreated with Bayprotect Cl following

ISO 1O5 CO6 and ISO 1O5 CO9 washing

Sulphur dyed

samples

Washing

treatment

Peak areas (%)

C1(285.0 eV)

C-C, C-H

aliphatic

C2(286.6 eV)

C-O, C-OH

Alcohol, ether

C3(288.1 eV)

C=O, O-C-O

Double ether,

carbonyl

C4(289.5eV)

O=C-O,

COOH

carboxyl

Untreated

Sample 1 None 45.5 39.6 11.9 2.9

Sample 2 WF 1 40.6 40.2 15.3 3.9

Sample 3 WF 5 9.5 49.2 33.2 8.1

Treated

Sample 4 None 37.4 44.0 14.3 4.2

Sample 5 WF 1 32.1 44.5 17.9 5.5

Sample 6 WF 5 47.0 39.6 11.7 1.7

Where:




243


(unlaundered)




x 102

5

10

15

20

25C

PS

300 296 292 288 284 280



x 102

2

4

6

8

10

12

14

16

18

CP

S

300 296 292 288 284 280



244



Figure 9.10 C (1s) spectrum of CI Leuco Sulphur Black 1 dyed fabric



x 102

5

10

15

20

25

30

CP

S

304 300 296 292 288 284 280



x 102

2

4

6

8

10

12

14

16

18

20

22

CP

S

300 296 292 288 284 280



245






x 102

2

4

6

8

10

12

14

16

18

CP

S

300 296 292 288 284 280



x 102

5

10

15

20

25

30

CP

S

300 296 292 288 284 280



246

(a)

(b)

45.5

39.6

11.9

2.9

37.4

44

14.3

4.2

0

5

10

15

20

25

30

35

40

45

50

C-C, C-H (%) C-O, C-OH (%) C=O, O-C-O (%) O=C-O, COOH (%)

Co

nce

ntr

atio

n o

f fu

nct

ion

alit

y b

y C

%

C (1s) peaks for CI leuco Sulphur Black 1 dyed fabric aftertreated with Bayprotect Cl (unlaundered)

Untreated 4% omf Bayprotect Cl

40.6 40.2

15.3

3.9

32.1

44.5

17.9

5.5

0

5

10

15

20

25

30

35

40

45

50


Co

nce

ntr

atio

n o

f fu

nct

ion

alit

y b

y C

%

C (1s) peaks for CI leuco Sulphur Black 1 dyed fabric aftertreated with Bayprotect Cl

(laundered with ISO 1O5 CO6 washing test) Untreated 4% omf Bayprotect Cl


247

(c)

Figure 9.13 Concentration of carbon functionalities determined by curve fitting

of the C (1s) peaks from XPS spectra (fabric dyed with CI Leuco Sulphur Black

1 and aftertreated with Bayprotect Cl): (a) before laundering (b) after

laundering with ISO 1O5 CO6 (c) after laundering with ISO 1O5 CO9

9.2.4. Investigation into the effects of aftertreatments with Bayprotect Cl on N (1s)


The presence of nitrogen content in sulphur dyed cotton is highlighted in Table 9.3,

which shows the presence of nitrogen based proteins, pectins and waxes that are usually

associated with cotton. Also, a slight increase in nitrogen content is observed on dyeing

the cotton fabric with CI Leuco Sulphur Black 1 dye, indicating that some nitrogen

content may also be introduced as a result of sulphur dyeing (Table 9.8, sample 7 and

sample 8). Fabric treated with Bayprotect Cl exhibits the same nitrogen content as

untreated fabric, as illustrated in section 9.2.1, the chemistry of Bayprotect Cl does not

correspond to the presence of nitrogen species which can also be observed in the bulk

analysis of the samples (Table 9.11). The N (1s) spectra of untreated and treated

samples are shown (Figure 9.14 - Figure 9.19).

9.5

49.2

33.2

8.1

47

39.6

11.7

1.7

0

10

20

30

40

50

60


Co

nce

ntr

atio

n o

f fu

nct

ion

alit

y b

y C

%

C (1s) peaks for CI leuco Sulphur Black 1 dyed fabric aftertreated with Bayprotect Cl

(laundered with ISO 1O5 CO9 washing test) Untreated 4% omf Bayprotect Cl


248


(unlaundered)




x 101

42

44

46

48

50

52

54

56

58

60

CP

S

412 408 404 400 396 392 388 384



x 101

28

30

32

34

36

38

CP

S

412 408 404 400 396 392 388 384



249



Figure 9.17 N (1s) spectrum of CI Leuco Sulphur Black 1 dyed fabric



x 101

40

42

44

46

48

50

52C

PS

408 404 400 396 392 388 384



x 101

28

30

32

34

36

CP

S

412 408 404 400 396 392 388 384



250






x 101

40

42

44

46

48

50

52

54

CP

S

408 404 400 396 392 388 384



x 101

36

38

40

42

44

46

48

CP

S

412 408 404 400 396 392 388 384



251

9.2.5. Conclusions

The effects of aftertreatments with Bayprotect Cl on wash fastness of CI Leuco Sulphur

Black 1 have been evaluated with the help of surface sensitive XPS technique. High

resolution spectra of sulphur, carbon and nitrogen were analysed to demonstrate the

improvements in the wash fastness of the sample treated with the tannin. Significant

increase in surface sulphur concentration and the reduced percentage area of oxidised

species S6+

at 168 eV for the treated sample laundered with ISO 105 CO6 and CO9

washing systems were observed. Examination of C (1s) spectra of aftertreated and

laundered samples revealed reduced concentrations of oxidised carbon species (C2, C3

and C4). The detailed examinations of high resolution C (1s) and S (2p) spectra of

untreated, aftertreated, unlaundered and laundered samples indicate that Bayprotect Cl

has the tendency to protect CI Leuco Sulphur Black 1 dyed fabric against the oxidative

bleaching action of ISO 1O5 CO6 and ISO 1O5 CO9 washing regimes.

9.3. Investigation into the effects of aftertreatments with Tinofix ECO and

Bayprotect Cl (one bath–two stage process) on surface chemistry of CI Leuco Sulphur

Black 1 dyed fabric subjected to ISO 105 C09 washing regime

X-Ray photoelectron spectroscopic measurements of untreated sulphur dyed cotton

fabric in comparison to Tinofix ECO and Bayprotect Cl aftertreated samples were

expected to provide indications about the nature of the cation-tannin interface. Therefore

the CI Leuco Sulphur Black 1 dyed cotton fabric reduced with Diresul RAD was treated

with the above mentioned finishing agents and measured after rinsing and drying. The

compositions and colorimetric data of the Tinofix ECO and Bayprotect Cl aftertreated

cotton fabric are presented in Table 9.6 and Table 9.7, respectively.


252

Table 9.6 Application conditions for CI Leuco Sulphur Black 1 dyed fabric

aftertreated with Tinofix ECO and Bayprotect Cl

Aftertreatments to

sulphur dyed cotton

fabric

Concentration

of

Tinofix ECO

Concentration of

Bayprotect Cl

Application

temperature and

time for

Tinofix ECO

Application

temperature

and time for

Bayprotect Cl

Untreated - - - -

TE1 5% omf - 40

oC, 15 minutes -

TE2 5% omf - 40

oC, 20 minutes -

TE1, BP

3 5% omf 5% omf 40

oC, 15 minutes 40

oC, 10 minutes

TE1, BP

1 5% omf 5% omf 40

oC, 15 minutes 40

oC, 15 minutes

Where:

1 5% omf applied for 15 minutes




aftertreated with Tinofix ECO and Bayprotect Cl following ISO 1O5 CO9

washing

Washing


%Colour

loss

GS

Rating DE

Untreated 29.0 -0.8 -4.5 4.6 259.9 8.4

Laundered 41.9 -1.6 -4.1 4.4 248.2 3.4 59% 1 13.0

TE1 29.2 -1.0 -4.5 4.7 257.8 8.4

Laundered 37.9 -1.8 -2.8 3.3 237.2 4.5 47% 1/2 9.0

TE2 29.7 -1.0 -4.5 4.6 258.2 8.0

Laundered 38.5 -1.8 -2.8 3.3 237.7 4.3 47% 1/2 9.0

TE1, BP

3 30.3 -0.5 -4.6 4.7 263.4 7.5

Laundered 37.2 -1.8 -2.9 3.4 237.6 4.7 37% 2 7.2

TE1, BP

1 30.5 -0.6 -4.6 4.6 263.2 7.5

Laundered 35.8 -1.8 -3.0 3.5 239.6 5.2 31% 2/3 5.7

Where:





253

Table 9.8 XPS surface elemental composition for CI Leuco Sulphur Black 1

dyed fabric aftertreated with Tinofix ECO and Bayprotect Cl following ISO

1O5 CO9 washing

Aftertreatments to dyed Cotton fabric

%Atomic Composition

O/C

Carbon

Nitrogen

Oxygen

Sulphur

Unlaundered

Undyed (sample 7) 74.9 0.9 24.2 - 0.3

Untreated (sample 8) 72.0 1.0 26.4 0.6 0.4

TE1 (sample 9) 71.3 6.2 21.9 0.6 0.3

TE2 (sample 10) 69.0 6.3 24.1 0.6 0.3

TE1, BP

3 (sample 11) 71.0 5.6 23.3 0.1 0.3

TE1, BP

1 (sample 12) 69.9 5.1 24.9 0.1 0.4

Laundered (ISO 1O5 CO9)

Untreated (sample 13) 72.2 0.7 26.7 0.4 0.4

TE1 (sample 14) 72.2 5.4 20.9 1.4 0.3

TE2 (sample 15) 71.0 5.5 22.0 1.5 0.3

TE1, BP

3 (sample 16) 71.0 5.8 21.6 1.6 0.3

TE1, BP

1 (sample 17) 72.5 6.5 19.3 1.7 0.3

Where:





254


Bayprotect Cl (one bath–two stage process) on surface elemental compositions of CI

Leuco Sulphur Black 1 dyed fabric

(a) (b)

Figure 9.20 Wide scan XP spectra of CI Leuco Sulphur Black 1 dyed fabric

aftertreated with Tinofix ECO and Bayprotect Cl:

(a) unlaundered (b) laundered with ISO 1O5 CO9

Figure 9.20 shows survey spectra of CI Leuco Sulphur Black 1 dyed cotton fabric

aftertreated with Tinofix ECO and Bayprotect Cl (sample 12). The nitrogen N (1s),

carbon C (1s) and oxygen O (1s) signals from the substrate can be clearly recognised. In

contrast the sulphur S (2p) signal appears as very weak peak feature on the background

of unlaundered sample (Figure a) while it is quite noticeable in the laundered sample

(Figure b). The percentage atomic concentrations of the different elements (C, N, O and

S) present on the surface are tabulated in Table 9.8.

In the case of the unlaundered samples, treatments with Tinofix ECO showed a decrease

in carbon and an increase in nitrogen content. The possible reason for an increase in

nitrogen concentration was due to the nitrogen species being introduced by the cationic

fixative.


wide/9

C 1

s

N 1

s

O 1

s

S 2

p

x 103

10

20

30

40

50

60

CP

S

1200 900 600 300

Bindi ng E nergy (eV)CasaXP S (Thi s st ring can be edit ed in CasaXPS.DEF/P rintFootNote.txt)

wide/2

C 1

s

N 1

s

O 1

s

S 2

p

x 103

5

10

15

20

25

30

35

40

45

CP

S

1200 900 600 300



255

On further application of Bayprotect Cl onto the cationised fabric, a relative decrease in

the sulphur and nitrogen content on the fabric surface with respect to the reference

untreated sample was observed. The Tinofix ECO treatment followed by Bayprotect Cl

application reduced the nitrogen content from 6.2% (sample 9) to 5.6% (sample 11) and

5.1% (sample 12) and this effect can be explained by the reason that possibly Tinofix

ECO treatment before Bayprotect Cl application already functionalises the surface, and

after the tannin treatment some of the nitrogen containing groups generated by Tinofix

ECO may still remain on the surface, “hidden” to the XPS by the chains of the tannin

product. Likewise, the reduction in percentage atomic sulphur of unlaundered samples

can also be explained in the same manner. On examining the nitrogen contents, it is

evident that the percentage atomic nitrogen content concomitantly increases with the

increasing application time for Tinofix ECO, that is an increase from 1% (sample 8) to

6.2% (sample 9) and 6.3% (sample 10). It is evident that the percentage atomic nitrogen

content concomitantly increases with concentration of the fixative applied and the

increase is a reflection of the greater availability of fixative molecule available for

reaction with the cellulose hydroxyl anions or anionic dye molecules.

In contrast on examining the laundered samples, the surface sulphur concentration for

untreated fabric reduced from 0.6% to 0.4% which was due to the oxidative bleaching

environment in the laundering system. Aftertreatments with Tinofix ECO as well as the

sequential application of the two finishing agents show increased sulphur concentrations

of 1.4% (sample 14) to 1.7% (sample 17) on the surface, which is much higher than the

value of 0.4% (sample 13) found on the untreated sample. This indicates that as a result

of aftertreatments, the sulphur containing compounds in the sub-surface may be being

exposed and are retained even after laundering. It can be postulated that the sub-surface

of aftertreated sample has lower level of oxidation showing an increased concentration

of sulphur than the untreated sample. However, on inspecting the nitrogen contents, it

can be observed that Tinofix ECO aftertreated and laundered samples showed an

increased concentrations from 0.7% (untreated, sample 13) to 5.4% (sample 14) which

further increases to 5.8% (sample 16) and 6.5% (sample 17) as a result of Bayprotect Cl

treatments. Bayprotect Cl does not contain nitrogen (discussed in section 9.2.1) and

hence it appears that the tannin based product protects some of the nitrogen species

introduced by Tinofix ECO.


256

However, on examining the O/C ratio of unlaundered aftertreated samples (sample 9

and 12), the related increase in the ratio was observed, which indicates there was slight

surface oxidation of finished samples and the formation of surface oxygen-containing

groups. On the other hand, the ratio of oxygen to carbon atomic contents for aftertreated

and laundered samples remained the same. Nonetheless, all of them are lower than

untreated laundered fabric, indicating comparatively less oxidation of the treated

samples.

It is evident from the atomic composition data that the laundering removed significant

amount of the surface sulphur dye from the untreated fabric surface and accordingly the

sulphur concentration decreased. In fact the laundering appears to expose the sulphur

dye in the fibre sub-surface and that on exposure it was oxidised and lost into solution or

decolourised. It was also apparent that the Tinofix ECO and Bayprotect Cl were

effective in not only reducing the visual colour fade but that this protective visual effect

was similarly reflected in protecting the sulphur dye at the fibre surface where less

sulphur was lost on laundering.


Bayprotect Cl (one bath–two stage process) on S (2p) spectra of CI Leuco Sulphur

Black 1 dyed fabric

Examination of the S (2p) spectra of the sulphur dyed cotton fabric indicate the presence

of sulphur at the surface of the cotton fibres and the presence of a number of different

oxidation states of sulphur. As depicted in the inset of Figure 9.21 - Figure 9.30, all

samples show broad sulphur signals in the range from 164 to 168 eV, which exhibit

well-separated peak structures at low (164 eV) and high (168 eV) binding energies.

In the case of the untreated and unlaundered sulphur dyed fabric, a distinctive peak can

be seen at 168 eV contributing around 52% of the total surface sulphur content. This

peak intensity results occurs during the re-oxidation of the alkali reduced sulphur dye

thiols to reform the insoluble disulphide bond-based sulphur dye and resulting in over-

oxidation to S6+

species [3]. The reason for the presence of oxidised species could be the

over oxidation caused by the use of hydrogen peroxide in the final dyeing stage for


257

converting the thiol derivative into the parent insoluble form of the dye (Figure 9.21),

that is the over-oxidation of the disulphide groups forming ionisable sulpho groups

caused by active peroxide [10]. The effect of ISO 1O5 CO9 washing with perborate and

TAED was to increase the amount of higher binding energy spectral component at 168.0

eV (Figure 9.22). Most likely the precursor to the loss of the dye from the fibre surface

is S6+

oxidised dye derivative which may be assigned to −SO3− , −S − SO2

− or −S −

SO3− species [3].

As discussed in chapter 7, various aftertreatments were undertaken to improve the

resistance of sulphur dyed fabric against the oxidative bleaching effects of sodium

perborate and TAED. On comparing the S (2p) spectra of unlaundered samples 9, 10, 11

and 12 against the untreated dyed fabric (sample 8), it is observed that treated samples

also give rise to the formation of two peaks at 164 eV and 168 eV that are unoxidised

(S2+

) and over-oxidised (S6+

) species respectively with a slight increase in the oxidised

species as shown in Table 9.9. This suggests that the treatment of the dyed fabric with

Tinofix ECO and Bayprotect Cl causes minor oxidation. However, examination of the S

(2p) spectra of laundered samples 14 and 15 against the untreated (sample 13) interprets

concomitant reduction of the over-oxidised species at 168 eV. The two treated samples

mirrored low level of oxidation and minimal loss of sulphur observed for the

comparable ISO 1O5 CO9 untreated cotton fabric. The observed reduction is from

100% to 91%, as shown Table 9.9. Increasing the application time of Tinofix ECO for 5

minutes, however, did not significantly reduce the surface oxidation.

In order to further improve the wash fastness of the dye against the aggressive TAED

catalysed perborate treatment, the introduction of a tannin based product, Bayprotect Cl

is a novel approach. Examining the S (2p) spectra of unlaundered cation-tannin treated

samples 11 and 12 specifies the presence of two peaks at 164 eV and 168 eV, similar to

Tinofix ECO treated samples. Likewise, the S (2p) spectra of laundered samples 16 and

17 illustrate a concomitant reduction in over oxidised (S6+

) species at 168 eV from 91%

for sample 14 to 88% and 87%, respectively.

The S (2p) XP spectra for untreated, cationised and cation-tannin treated samples were

analysed to differentiate the possible presence of three main sulphur species namely

unoxidised S2+


(-SO3-,-S-SO2

- or –S-SO3

-) and partially or


258

intermediate oxidised S4+

. However, the presence of partially oxidised species could not

be identified.

Table 9.9 Relative intensity data of the deconvoluted S (2p) spectra for CI

Leuco Sulphur Black 1 dyed fabric aftertreated with Tinofix ECO and

Bayprotect Cl following ISO 1O5 CO9 washing

Aftertreatments to dyed cotton fabric Peak areas (%)

164 eV 168 eV

Unlaundered

Untreated (sample 8) 47 52

TE1 (sample 9) 45 54

TE2 (sample 10) 45 54

TE1, BP

3 (sample 11) 36 64

TE1, BP

1 (sample 12) 34 66


Untreated (sample 13) - 100



TE1, BP

3 (sample 16) 12 88

TE1, BP

1 (sample 17) 13 87

Where:





259


(unlaundered)




45

50

55

60

65

CP

S

176 172 168 164 160 156



70

80

90

100

110

120

130

CP

S

176 172 168 164 160 156



260


aftertreated with TE1 (unlaundered)


aftertreated with TE1 (ISO 1O5 CO9 laundered)


50

55

60

65

70

75

80

85C

PS

176 172 168 164 160 156



x 101

6

8

10

12

14

16

18

20

CP

S

176 172 168 164 160 156



261






70

80

90

100

110

120

130

140

150

CP

S

176 172 168 164 160 156



x 101

8

10

12

14

16

18

20

22

CP

S

176 172 168 164 160 156



262


aftertreated with TE1, BP

3 (unlaundered)



3 (ISO 1O5 CO9 laundered)


60

65

70

75

80

85

CP

S

176 172 168 164 160 156



x 101

8

10

12

14

16

18

20

22

24

26

CP

S

176 172 168 164 160 156



263



1 (unlaundered)





60

65

70

75

80

85

CP

S

176 172 168 164 160 156



x 101

6

8

10

12

14

16

18

20

CP

S

176 172 168 164 160 156



264


Bayprotect Cl (one bath–two stage process) on C (1s) spectra of CI Leuco Sulphur

Black 1 dyed fabric

Examination of the undyed cotton fabric, based on the structure of cellulose, it would be

expected that only two carbon spectral features would be observed, that is the C-OH

(286.6 eV) and O-C-O (288.0 eV) species with relative intensities of 5:1. However it is

evident that significant hydrocarbon-based material, at a binding energy of 285.0 eV

was present at the fibre surface and the expected C-OH and O-C-O species ratio of 5:1

was not observable. In addition the peak intensity at 288.0 eV indicates the presence of

oxidised C=O species. The scouring and bleaching of cotton fabric is known to oxidise the

fibre surface giving rise to oxycellulose. Chemical composition of the undyed and

untreated cotton fabric, with an O/C ratio of 0.32 does not correspond to the typical

structure of cellulose with O/C of 0.83 and confirms that the fabric has undergone

scouring treatment [4,11].

Figure 9.31 C (1s) spectrum of undyed and unlaundered cotton fabric


x 102

5

10

15

20

25

30

35

CP

S

300 296 292 288 284 280



265

The relative amounts of carbon with different numbers of oxygen bonds were estimated

from high resolution C (1s) carbon spectra, shown in Figure 9.31 to Figure 9.41. The

carbon compound classification is based on the number of oxygen bonds: the peaks at

285.0 eV, 286.6 eV, 288.2 eV and 289.4 eV are due to carbons with 0, 1, 2 or 3 bonds to

oxygen, respectively [12]. For samples treated with Tinofix ECO, deconvolution

analysis showed an increase of oxygen-based functional groups such as C–O (286.6

eV), C=O (288 eV) and O=C–O (289 eV) as shown in Table 9.10. These results suggest

that sulphur dyed cotton fabric became oxidised by cationic fixative exposure, resulting

in a decrease of C–C/C–H bonds, and remarkable increase of oxidised species.

After application of Bayprotect Cl over Tinofix ECO, significant changes in chemical

constitution of dyed fabric appear, such as increase of oxygen content and reduction of

carbon content in the surface layer (O/C ratio of sample 12 is higher compared to

sample 9 as shown in Table 9.8). The relative amount of each type of carbon is also

modified after Bayprotect Cl treatment; this can be observed in peak intensity changes

in Table 9.10, where carbon C2, C3 and C4 area is significantly increased compare to

Tinofix ECO treated dyed fabric (sample 9). Compared to sample 8; non-oxidised

carbon fraction (C1) in Bayprotect Cl treated samples is reduced by 86% and 81% for

samples 11 and 12, respectively, whereas carbon with oxygen-based functional groups

(C2, C3 and C4) was dramatically increased. Chemical composition of the treated

sample suggests that the main chemical change occurs on C1 carbon by removing non-

cellulosic cotton components and increasing oxygen polar group content due to

oxidative chemical changes on the surface.

The fitting of the high resolution C (1s) spectra of unlaundered aftertreated samples

confirms the functionalisation of the cotton surface by showing a decrease of aliphatic

bonds and increase of alcohol, carbonyl and carboxyl groups.

Examination of the high resolution C (1s) spectrum of untreated sulphur dyed laundered

samples showed a fall in hydrocarbon signal intensity at 285 eV (68%) and a rise in the

oxidised species intensities at 286.6 eV (30%), 288.0 eV (54%) and 289.0 eV (92%) [3].

However, on treating the fabric with Tinofix ECO (sample 14) there was a further

decrease in the C1 (71%) component and slight increase in C2 component (32%).

However, the increase in C3 (23%) and C4 (32%) species was significantly less than the

untreated fabric. On applying Bayprotect Cl for 10 minutes, a concomitant increase in


266

C1 (18%) and C2 (7%), while a decrease in C3 (10%) and C4 (8%) components was

observed with respect to sample 11. This trend was further amplified on increasing the

application time for 15 minutes, non-oxidised carbon fraction (C1) in Bayprotect Cl

treated fabric (sample 12) is increased intensely (>100%) after laundering. Carbon with

oxygen-based functional groups (C3 and C4) was dramatically reduced, that is to 48%

and 36%, respectively, while the increase in C2 is 32%. The chemical composition of

the treated sample 12 suggests that sequential aftertreatments with Tinofix ECO and

Bayprotect Cl reduced the formation of oxidised functionalities and contributes to the

formation of carbon compound without neighbouring oxygen (C-C, C-H).

Concentrations of carbon functionalities obtained from deconvoluted C (1s) spectra for

untreated and treated samples are summarised in Figure 9.42.


267

Table 9.10 Relative intensity data of the deconvoluted C (1s) spectra for CI

Leuco Sulphur Black 1 dyed fabric aftertreated with Tinofix ECO and

Bayprotect Cl following ISO 1O5 CO9 washing

Aftertreatments to dyed

cotton fabric

Peak areas (%)

C1 C2 C3 C4

285.0 eV 286.6 eV 288.1 eV 289.5 eV

C-C, C-H

C-O, C-OH

C=O, O-C-O

O=C-O, COOH

Aliphatic

(%)

Alcohol,

ether (%)

Double ether,

carbonyl (%)

Carboxyl

(%)

Unlaundered

Untreated (sample 8) 38.3 38.9 18.4 4.4

TE1 (sample 9)

28.7 38.6 25.6 7.1

TE2 (sample 10)

5.3 43.2 40.5 11.1

TE1, BP

3 (sample 11)

5.4 48.4 36.3 9.8

TE1, BP

1 (sample 12)

7.5 42.8 40.1 9.6

Laundered

Untreated (sample 13) 12.4 50.6 28.4 8.5

TE1 (sample 14)

8.4 50.9 31.5 9.3

TE2 (sample 15)

4.9 52.8 32.7 9.7

TE1, BP

3 (sample 16)

6.4 51.7 32.8 9.1

TE1, BP

1 (sample 17)

16.5 56.4 21.0 6.1





268


(unlaundered)




x 102

2

4

6

8

10

12

14

16

18

20

CP

S

304 300 296 292 288 284



x 102

5

10

15

20

25

30

CP

S

304 300 296 292 288 284



269


aftertreated with TE1 (Unlaundered)




x 102

5

10

15

20

25C

PS

304 300 296 292 288 284 280



x 102

5

10

15

20

25

30

35

CP

S

304 300 296 292 288 284 280



270


aftertreated with TE2 (Unlaundered)




x 102

5

10

15

20

25

30C

PS

304 300 296 292 288 284



x 102

5

10

15

20

25

30

35

CP

S

304 300 296 292 288 284



271



3 (Unlaundered)





x 102

5

10

15

20

25

30

35

CP

S

304 300 296 292 288 284



x 102

5

10

15

20

25

30

35

40

45

CP

S

304 300 296 292 288 284 280



272



1 (Unlaundered)





x 102

5

10

15

20

25

30C

PS

304 300 296 292 288 284 280



x 102

5

10

15

20

25

30

CP

S

304 300 296 292 288 284



273

(a)

(b)

Figure 9.42 Concentration of carbon functionalities determined by curve fitting

the C (1s) peaks from XPS spectra (fabric dyed with CI Leuco Sulphur Black 1

and aftertreated with Tinofix ECO and Bayprotect Cl):

(a) before laundering (b) after laundering with ISO 1O5 CO9

38.3 38.9

18.4

4.4

28.7

38.6

25.6

7.1 5.3

43.2 40.5

11.1

5.4

48.4

36.3

9.8 7.5

42.8 40.1

9.6

0

10

20

30

40

50

60


Co

nce

ntr

atio

n o

f fu

nct

ion

alit

y b

y C

%

C (1s) peaks for CI leuco Sulphur Black 1 dyed fabric aftertreated with Tinofix ECO and Bayprotect Cl

(unlaundered)

untreated

5% TE (15 min)

5% TE (20 min)

5% TE (15 min) +5% BP (10 min)

5% TE (15 min) +5% BP (15 min)

12.4

50.6

28.4

8.5 8.4

50.9

31.5

9.3

4.9

52.8

32.7

9.7 6.4

51.7

32.8

9.1

16.5

56.4

21.0

6.1

0

10

20

30

40

50

60


Co

nce

ntr

atio

n o

f fu

nct

ion

alit

y b

y C

%

C (1s) peaks for CI leuco Sulphur Black 1 dyed fabric aftertreated with Tinofix ECO and Bayprotect Cl

(laundered with ISO 1O5 CO9) untreated

5% TE (15 min)

5% TE (20 min)

5% TE (15 min) +5% BP (10 min)

5% TE (15 min) +5% BP (15 min)


274


Bayprotect Cl (one bath–two stage process) on N (1s) spectra of CI Leuco Sulphur

Black 1 dyed fabric

In a typical N(1s) XPS spectrum nitrogen bound to carbon in primary, secondary or

tertiary amines or amides occurs at B.E values of 399-400 eV, whereas for cationic

quaternary ammonium nitrogen species the peak is shifted to a higher B.E value of

401.5-402.5 eV [13-15]. The N (1s) XPS spectra of Tinofix ECO treated samples

indicate the presence of “uncharged” quaternary nitrogen species at around 399 eV. This

indicates that the commercial product has surprisingly high content of uncharged

nitrogen species either due to the contamination or possibly due to undesired free-

radical side reactions occurring during the cyclo-polymerisation. These uncharged

nitrogen species may be part of the polymer backbone itself or distinct uncharged

moieties [15].

The elemental nitrogen concentrations for Tinofix ECO treated unlaundered samples 9

and 10 were 6.2% and 6.3%, respectively. However, on treating the cationised fabric

with Bayprotect Cl causes a reduction in nitrogen content. It can be seen from Figure

9.43 to Figure 9.52, that all the samples represent the presence of nitrogen species at

around 399 eV. This designates that the commercial product Tinofix ECO has a high

content of uncharged nitrogen species and surprisingly little cationic nitrogen.

Bayprotect Cl does not contain nitrogen species which can also be observed in the bulk

analysis of the samples (Table 9.11). Hence, it can be postulated that the amount of

nitrogen introduced by Tinofix ECO on the dyed fabric is retained by the protective

action of Bayprotect Cl. This can be seen in Table 9.8, that the nitrogen content of

sample 9 was reduced from 6.2% to 5.4% after laundering. However, the same sample

when aftertreated with Bayprotect Cl preserves more nitrogen even after washing (5.8%

and 6.5% for sample 16 and 17, respectively). The effect of washing in

detergent/perborate liquor was to remove the uncharged nitrogen containing species due

to the alkaline cleaning conditions and the oxidative nature of the detergent formulation,

but it can be seen that the amount of nitrogen reduction is less than expected. The

purpose of aftertreatments with cationic fixing agent and tannin was to reduce the colour

loss during washing and hence extend the lifetime of the garment. Examination of the

N (1s) XPS spectrum of the treated samples indicate the presence of amines or amides


275

due to the presence of uncharged nitrogen species at BE value of 399 eV. The effect of

repeated laundering was to reduce the surface nitrogen intensity, but even after

aggressive ISO 1O5 CO9 washing; a significant quantity of nitrogen can still be clearly

demonstrated. Hence, it can be presumed that there might be either electrostatic forces

of attraction, Van der Waals’ forces or hydrophobic bonding between the dye molecule

and uncharged nitrogen species that may increase dye insolubilisation leading to the

observed improvements in dye wash fastness [15].


276


(unlaundered)




x 101

32

34

36

38

40

CP

S

412 408 404 400 396 392 388 384



x 101

46

48

50

52

54

56

CP

S

412 408 404 400 396 392 388 384



277






x 101

40

50

60

70

80

90

CP

S

412 408 404 400 396 392 388



x 101

50

60

70

80

90

100

CP

S

412 408 404 400 396 392 388 384



278






x 101

50

60

70

80

90

100

110

120

130

CP

S

412 408 404 400 396 392 388 384



x 101

50

60

70

80

90

100

110

CP

S

412 408 404 400 396 392 388 384



279

Figure 9.49 N(1s) spectrum of CI Leuco Sulphur Black 1 dyed fabric


3 (unlaundered)





x 101

50

60

70

80

90

100

110

120

CP

S

412 408 404 400 396 392 388 384



x 101

60

70

80

90

100

110

120

130

CP

S

412 408 404 400 396 392 388 384



280



1 (unlaundered)





x 101

50

60

70

80

90

100

110

CP

S

408 404 400 396 392 388 384



x 101

50

60

70

80

90

100

CP

S

412 408 404 400 396 392 388 384



281

9.4. Elemental bulk analysis of CI Leuco Sulphur Black 1 dyed fabric aftertreated

with Tinofix ECO and Bayprotect Cl (one bath–two stage process) following ISO 105

C09 washing regime

The wash durability of Tinofix ECO and Bayprotect Cl on sulphur black dyed cotton

fabric under ISO 105 CO9 test condition was also investigated by elemental bulk

analysis. The CI Leuco Sulphur Black 1 dyed fabric was aftertreated with Tinofix ECO

and Bayprotect Cl individually as well as with the one bath–two stage process discussed

previously (section 9.3). The application methods and bulk elemental compositions of

the untreated and treated samples are shown in Table 9.11.

Unfortunately with all the unlaundered samples, the sulphur content in all fabrics was

below the accurate detection limit, so limited useful information could be achieved with

the analysis. However, as expected the amount of nitrogen content has been increased in

Tinofix ECO treated fabric, while no increase was observed with the following

Bayprotect Cl treatment. The individual application of the Bayprotect Cl also did not

introduce any nitrogen species to the dyed fabric which is in good agreement with the

XPS data.

Elemental analysis was useful in terms of getting information about hydrogen, as it is

not possible to detect this element with XPS technique. The surface hydrogen is useful

in determining the chemical behaviour of a surface [16].

The increase in hydrogen content with individual application of Tinofix ECO and

Bayprotect Cl possibly indicates the presence of hydrogen rich materials introduced to

the treated fabrics as a result of aftertreatments.

With laundering, the untreated and aftertreated samples exhibit a fixed loss in nitrogen

content while a significant amount of hydrogen can still be seen signifying the existence

of hydrogen species and possible reason for the improved wash fastness.


282

Table 9.11 Elemental analysis for CI Leuco Sulphur Black 1 dyed fabric

aftertreated with Tinofix ECO and Bayprotect Cl following ISO 1O5 CO9

washing

Aftertreatments

Carbon

(%)

Nitrogen

(%)

Hydrogen

(%)

Sulphur

(%)

Unlaundered

Untreated 42.3 None found 6.4 Less than 0.3%

TE1 42.2 0.5 6.7 Less than 0.3%

TE1, BP

2 42.6 0.5 6.6 Less than 0.3%

TE1, BP

3 42.8 0.5 6.7 Less than 0.3%

BP3 41.8 None found 6.9 Less than 0.3%


Untreated 41.9 None found 6.3 Less than 0.3%

TE1 41.6 0.4 6.5 Less than 0.3%

TE1, BP

2 42.1 0.4 6.5 Less than 0.3%

TE1, BP

3 41.9 0.4 6.5 Less than 0.3%

BP3 41.4 None found 6.4 Less than 0.3%

Where:

1 5% omf applied for 30 minutes at 40

oC

2 5% omf applied for 20 minutes at 40

oC

310% omf applied for 20 minutes at 40

oC

9.5. Conclusions

The surface sensitive XPS technique has been used to successfully probe the outer

surface of the CI Leuco Sulphur Black 1 dyed cotton fabric treated with cationic fixative

(Tinofix ECO) and tannin (Bayprotect Cl). Examination of the sulphur dyed cotton

showed the presence of sulphur at the fibre surface and it was evident that in addition to

unoxidised disulphide bond species, S2+

, there was also oxidation of the surface sulphur

to the S6+

form. The effects of the two finishes on wash fastness of the untreated and

aftertreated fabrics have been evaluated with the help of the high resolutions spectra of

sulphur, carbon and nitrogen. The improvements in the wash fastness of the sample

treated with the cation-tannin system were demonstrated through significant


283

concomitant increase in surface sulphur concentration as well as the reduced percentage

area of oxidised species S6+

at 168 eV. The effect of the ISO 105 CO9 laundering on C

(1s) spectral intensities of untreated fabric was to reduce the hydrocarbon signal

intensity at 285.0 eV and to increase the oxidised species intensities at 286.6, 288.0 and

289.0 eV. However, the examination of treated fabric revealed reduced concentrations

of oxidised species (C2, C3 and C4) and increase in aliphatic carbon species at 285 eV.

The effect of laundering was also to expose the fibre sub-surface and the Bayprotect Cl

and Tinofix ECO were able to reduce oxidation of the sulphur dye.

The elemental bulk analysis did not provide useful information on sulphur content of the

samples, however, significant amount of hydrogen was detected which possibly

indicates the presence of hydrogen bonding.

9.6. References

[1] Soignet D, Berni R and Benerito R. Electron spectroscopy for chemical analyses

(ESCA)-a tool for studying treated textiles. Journal of Applied Polymer Science.

1976;20(9):2483-95.

[2] Soignet DM, Berni RJ and Benerito RR. Electron spectroscopy for chemical

analyses (ESCA) of THPOH-NH3-treated fabrics. Textile Research Journal.

1975;45(1):28-9.


effect of extended laundering on C. I. Sulphur Black 1 dyed cotton fabric. Dyes and

Pigments. 2013;96(1):25-30.

[4] Topalovic T, Nierstrasz VA, Bautista L, Jocic D, Navarro A and Warmoeskerken

MM. XPS and contact angle study of cotton surface oxidation by catalytic bleaching.

Colloids and Surfaces A: Physicochemical and Engineering Aspects. 2007;296(1):76-

85.

[5] Varma A. Photoelectron spectroscopic studies of cellulose, starch and their oxidation

products, in powdered form. Carbohydrate Polymers. 1984;4(6):473-9.


284

[6] Topalovic T, Nierstrasz VA, Bautista L, Jocic D, Navarro A and Warmoeskerken

MM. Analysis of the effects of catalytic bleaching on cotton. Cellulose. 2007;14(4):385-

400.

[7] Mitchell R, Carr CM, Parfitt M, Vickerman J and Jones C. Surface chemical analysis

of raw cotton fibres and associated materials. Cellulose. 2005;12(6):629-39.

[8] Soignet D, Connick W and Benerito R. Use of electron spectroscopy for chemical

analyses (ESCA) in a study of oil-repellent finishes. Textile Research Journal.

1976;46(8):611-6.

[9] Haule L, Rigout M, Carr CM and Jones C. Surface and bulk chemical analysis of the

durability of an easy care finish on cotton. Cellulose. 2012;19(3):1023-30.


[11] Patiño A, Canal C, Rodríguez C, Caballero G, Navarro A and Canal JM. Surface

and bulk cotton fibre modifications: plasma and cationization. Influence on dyeing with

reactive dye. Cellulose. 2011;18(4):1073-83.

[12] Buchert J, Pere J, Johansson LS and Campbell J. Analysis of the surface chemistry

of linen and cotton fabrics. Textile Research Journal. 2001;71(7):626-9.

[13] Vickerman JC and Gilmore IS. Surface analysis: the principal techniques: Wiley

Online Library, 2009.

[14] Kistamah N, Carr CM and Rosunee S. Surface chemical analysis of tencel and

cotton treated with a monochlorotriazinyl (MCT) β-cyclodextrin derivative. Journal of

Materials Science. 2006;41(8):2195-200.

[15] Rosunee S, Carr CM, Hibbert S and Jones C. Surface chemical analysis of Tencel

treated with a cationic fixing agent. Journal of Materials Science. 2003;38(10):2179-85.

[16] Riviere JC and Myhra S. Handbook of surface and interface analysis: methods for

problem - solving. 2 ed: CRC Press, 2009.

Conclusions and recommendations for future work

285

10. Conclusions and recommendations for future work

10.1. Conclusions

In this study, a one bath-two stage aftertreatments process was developed to improve the

resistance of the sulphur dyed cotton fabric against the oxidative bleaching action of

modern detergent formulations based washing treatment ISO 1O5 CO9. The process

offers potential commercial utility, due to the reduction of the percentage colour loss of

the dyed and aftertreated fabric to half as compared to the untreated cotton fabric.

The results indicated that the developed process is most suitable for sulphur black dyed

with two reducing systems that are the conventional reducing agent (sodium sulphide)

and biodegradable reducing agent (Diresul reducing agent D). The resultant fabrics

possess good colourfastness to laundering and have no deleterious effects on crocking,

light fastness and tensile strength.

The studies aimed at modifying the surface of sulphur dyed cotton with a view to

improving fastness, in particular improving the wash fastness, involved four different

approaches based on application of Bayprotect Cl on its own (Chapter 4), two stage

application of Bayprotect Cl, Fixapret CP and choline chloride (chapter 5), two stage

application of different cationic fixatives (Tinofix ECO, Solfix E and Indosol E-50) and

Bayprotect Cl (Chapter 6), optimisation of the process parameters for the one-bath two-

stage application of Tinofix ECO and Bayprotect Cl (Chapter 7).

Aftertreating the sulphur dyed cotton fabric individually with the tannin based product

(Bayprotect Cl) improved the wash fastness performance for ISO 1O5 CO6 system,

however only a small improvement was observed for ISO 1O5 CO9 laundering. In

addition, the light fastness of the samples was significantly enhanced while slight

improvements were noticed for wet crocking. However, dry rub fastness was not

significantly enhanced. The level of improvement in fading for the treated fabric could

not be distinguished visually to any great extent; therefore, the application of Bayprotect

Cl with the crease resistant finish (Fixapret CP) and cationic reactant (choline chloride)

were investigated to develop visual enhancements.


286

The crosslinking treatments of Fixapret CP enhanced the colour fastness performance

due to the improvement of the bonding between the dye and fabric. The reduced colour

fading after washing could visually be observed for samples treated with Bayprotect Cl

and Fixapret CP, particularly for ISO 1O5 CO9 system. However, the crosslinking post-

treatment on its own offers better performance for ISO 1O5 CO6 system than the

sequential application with Bayprotect Cl as it tends to deteriorate the shade and the

chroma.

The addition of choline chloride to the Fixapret CP bath did not produce significant

impact on overall fastness properties. On the other hand, the sequential application of

Bayprotect Cl and choline chloride appeared to produce some improvements in both

washing systems; however, the impact was not great. Since choline chloride is a cationic

monomeric reagent, and the use of cationic polymers for improving the wash fastness of

sulphur dyes have been previously explored by a number of researchers [1-5], hence the

sequential application of the latter and Bayprotect Cl were examined.

The effects of three different cationic polymers (Solfix E, Tinofix ECO and Indosol E-

50) were studied. Tinofix ECO was found to be the most effective in terms of improving

the wash fastness of the dye against the aggressive action of ISO 1O5 CO9 system and

contributing less influence on the L*a*b* values (colour change). The cationisation is

most likely changing the surface interface chemistry and improving adhesion and

covalent bonding to the fibre surface. Hence, the sequential application of Tinofix ECO

and Bayprotect Cl was explored which turned out to be the best option and was selected

to be optimised in terms of the process application parameters (concentrations, time and

temperature) on two reducing systems (sodium sulphide and Diresul RAD). The fabrics

aftertreated with optimised parameters were evaluated for surface morphology and

characterisation of functional groups produced as a result of aftertreatments.

SEM analyses of the untreated and aftertreated dyed fabrics was carried out and did not

indicate the existence of any coating or depositions that could affect the overall fabric

appearance.

The surface characterisation of the untreated and treated fabrics has been achieved with

surface sensitive XPS and FTIR spectroscopic techniques. Low resolution spectra of

XPS were taken to estimate the percentage elemental compositions of the samples.

FTIR and high resolution spectra of XPS were examined to explore the existence of


287

possible functional groups produced on the fabric surface as a result of the

aftertreatments. The XPS data supports the improved results achieved through

colorimetric data obtained for aftertreated samples and demonstrates the beneficial

effects of the aftertreatments in reducing sulphur dye loss and oxidation from the

surface.

Besides having improved dye fixation in the one-step finishing process on sulphur dyed

cotton, a key factor of the devised method is the use of eco-friendly cationic fixative and

the tannin, which is an exciting outcome from an environmental viewpoint.

Furthermore, the study also gives a comparative analysis on the use of the two different

kinds of reducing systems and the impact of aftertreatments on the same.

10.2. Recommendations for future work

The initial investigations involved the sequential applications of Bayprotect Cl and

Fixapret CP. The combinations seem to provide significant improvements in terms

of the increased wash fastness durability of CI Leuco Sulphur Black 1 dyed cotton

fabric against ISO 1O5 CO9 washing. A more thorough investigation for the use of

crease resistant finish and tannin could be undertaken. For this to occur, various

types of the environment friendly durable press finishes could be sequentially

applied after Bayprotect Cl to see the relative impact on the fastness properties.

The main aim of the project was achieved by developing a process involving the

fabric treatment with tannin (Bayprotect Cl) and cationic fixative (Tinofix ECO).

The possible suggested reason for the improved wash fastness could be the

formation of complexes between the two finishing agents. According to the previous

studies, nylon and silk fabric tend to have improved wash fastness for direct and

acid dyes by commercial syntan/cation system [6-10]. The improved results

obtained with Bayprotect Cl (tannin) suggest that sequential application of syntans

together with cationic fixatives can also to be explored to improve the resistance of

the dyes against oxidative action of bleaches. Since syntans are synthetic tanning

agents and their chemistry is similar to tannins so their application for sulphur dyes

might yield further productive results.


288

The use of tannin/syntans on their own and in combinations with cationic fixatives

has been explored several times [6-14]. Aftertreatment of sulphur dyed fabric with

lanthanides has already been explored to achieve the improved wash fastness [15].

However, the application of these metal ions along with tannin/syntan, for

improving the wash fastness of the dyes could be considered.

In order to achieve sulphur dyeings with good rubbing fastness, the dyed fabric is

thoroughly rinsed before oxidation stage to remove unfixed dye on the fabric

surface. However, before the oxidation stage the dyes are in water soluble or leuco

form and the pre-oxidation rinse might remove a significant amount of dye resulting

in reduced colour strength of the dyed fabric. If a mild oxidation treatment is given

before the rinse, the unfixed dye can be partially fixed and result in a dyed fabric

with a better colour yield and improved rubbing fastness. This mild oxidation can be

carried out either with air or lower concentrations of perborate/alkali liquor.

10.3. References







1997;33(1):1-9.



Colourists. 1998;114(5-6):165-8.





289

[6] Blackburn R and Burkinshaw S. Aftertreatment of acid dyes on conventional nylon

6,6 with a commercial syntan/cation system. Part 3: Improvements to the Fixogene AC

system. Coloration Technology. 2000;116(1):3-9.

[7] Blackburn R and Burkinshaw S. Aftertreatment of 1: 2 metal complex acid dyes on

conventional and microtibre nylon 6. 6 with a commercial syntan/cation system. Journal

of the Society of Dyers and Colourists. 1998;114(3):96-100.

[8] Blackburn R and Burkinshaw S. Aftertreatment of 1: 2 metal‐complex acid dyes on

conventional and microfibre nylon 6.6 with a commercial syntan/cation system. Part 2:


[9] Feiz M and Radfar Z. Improvement of wash fastness of direct and acid dyes applied

to silk by aftertreatment with syntan, syntan/cation, and full backtan processes. Iranian

Polymer Journal. 2006;15(4):299.

[10] Feiz M and Salimpour S. Improvement in wash fastness of dyed silk by

aftertreatment with commercial syntan/metal salts. Progress in Color, Colorants and

Coatings. 2008;1(1):27-36.

[11] Burkinshaw S and Paraskevas M. The dyeing of silk part 2: Aftertreatment with

natural and synthetic tanning agents. Dyes and Pigments. 2011;88(2):156-65.

[12] Burkinshaw S and Kumar N. A tannic acid/ferrous sulfate aftertreatment for dyed

nylon 6,6. Dyes and Pigments. 2008;79(1):48-53.

[13] Burkinshaw S and Son YA. The aftertreatment of acid dyes on nylon 6, 6 fibres

Part 1. 1: 2 Pre-metallised acid dyes. Dyes and Pigments. 2001;48(1):57-69.

[14] Burkinshaw S and Maseka K. Improvement of the wash fastness of non-metallised

acid dyes on conventional and microfibre nylon 6,6. Dyes and Pigments. 1996;30(1):21-

42.

[15] Zhou W and Yang Y. Improving the resistance of sulfur dyes to

oxidation Industrial and Engineering Chemistry Research. 2010;49(10):4720-5.

Documents

investigation into the chemical processing and colorimetric