Wun Presentation

New green chemical techniques in textile coloration processes

Dr. Richard S. BlackburnSenior Lecturer and Head of Green Chemistry Group

Centre for Technical TextilesUNIVERSITY OF LEEDS, LS2 9JT, UK

[email protected]

© University of Leeds 2006

Where can Green Chemistry have an impact in Coloration?

• Dye chemistry– Alternative synthesis, sustainable source, natural platform

chemicals

• Dyes in effluent– Reduction (efficiencies of sorption) and cleaner treatment

technologies

• Auxiliary chemicals– Reduction in use and emission of harmful auxiliaries (e.g. salt,

reducing agents, carriers)

• Application processes– Reduction in energy, water usage, time

• Coloration of ‘greener’ fibres– PLA, PHAs, lyocell, etc.


Sustainable platform chemicals

• Natural dyes derived from plant material represent a more sustainable source of colorants

• Natural dyes colour natural fibres (cotton, wool, silk) to a greater or lesser extent– need application with a mordant (salts of Cr, Sn, Zn, Cu, Al, Fe) to

secure sufficient wash and light fastness and to give good build-up• Natural dyes have found limited success in coloration of synthetic

fibres– PET has a 45% share of the global textile market

• Madder plant (Rubia tinctorum L.) is an important dye plant– produces the dye alizarin (1,2-dihydroxyanthraquinone)– also contains rubiadin (1,3-dihydroxy-2-methylanthraquinone) and

purpurin (1,2,4-trihydroxyanthraquinone)



• Derivatisation of alizarin to produce more hydrophobic molecule– higher affinity for hydrophobic polyesters

• Successful synthesis of 1-hydroxy-2-ethylanthraquinone (1H2EA)– 93% yield– confirmed by FT-IR and NMR– OH at 1-position not derivatised due to intramolecular hydrogen bond

formation and lower intrinsic reactivity

O

O

OH

OHCH3CH2I

KOH, DMSO

alizarin1,2-dihydroxyanthraquinone

O

O

OH

O

1-hydroxy-2-ethylanthraquinone

+ KI, H2O



• Problem with application of alizarin is pH sensitivity

• 1H2EA displays no such sensitivity due to derivatisation of 2-OH

pH Alizarin 1H2EA

4 v. sparingly solubleno colour

insolubleno colour

7 sparingly solubleorange/yellow colour

insolubleno colour

10 solublepurple colour

insolubleno colour

Table: The effect of pH on solubility and colour of alizarin and 1H2EA

O

O

O

O

H

O

O

O

O

H



• Dyes applied with dispersing agent to PET and PLA• Colour strength (K/S) achieved with 1H2EA higher than alizarin• Dyeings unlevel, poor quality with alizarin• Dyeings level, bright, good quality with 1H2EA• Alizarin gives higher K/S on PET w.r.t. PLA, but opposite observed for 1H2EA

– increased interactions with PLA via alkyl chain addition

*O

O

O

O

*

PET

Table: Colour strength (K/S) values of dyed samples

Conditions of application

Alizarin 1H2EA

PET PLA PET PLA

1% omf at 90 °C 1.5 4.3

1% omf at 100 °C 3.1 2.1 4.3 5.1

1% omf at 130 °C 6.5 8.7

4% omf at 115 °C 2.2 10.6

4% omf at 130 °C 19.2 20.9

PLA

O*

O

CH3H

*



• Wash fastness comparable and excellent on all dyeings• Light fastness considerably higher for 1H2EA compared to alizarin

– 2-OH susceptible to photo-oxidation, as it cannot form an intra-molecular H-bond

– In 1H2EA 2-OH derivatised, so not as susceptible to photo-oxidation

Table: Light fastness of dyed samples(1-8 scale)

Conditions of application

Alizarin 1H2EA

PET PLA PET PLA

1% omf at 90 °C 3 5

1% omf at 100 °C 3 3 6 5/6

1% omf at 130 °C 4 6

4% omf at 115 °C 3/4 6

4% omf at 130 °C 5 6

O

O

O

OH*

H


Green ChemistrySulphur Dyeing

• Economical, good colour strength, good fastness dyeings on cellulosics

• Significant share of the colorants market– annual consumption of ca. 70,000 tons

• C. I. Sulphur Black 1 alone represents a substantial portion (20-25%) of dyestuff market for cotton– highest consumption of any single textile dye in the world

• Complex mixtures of reproducible, but uncertain, compositions

• Contain within their ring structure thiazole, thiazone, or thianthrene as chromophores

• All sulphur dye molecules contain disulfide linkages


Mechanism ofsulphur dyeing

• Initially dye is in insoluble oxidised (pigment) form• Addition of reducing agent cleaves a proportion of the disulfide linkages to

form the partially soluble ‘leuco’ sulphur form• Further addition of reducing agent and increase in redox potential causes

reduction of the remaining disulfide linkages and quinoneimine groups• After exhaustion of the dye onto fibre, the reduced, adsorbed dye is

reformed in situ within the fibre by air or chemical oxidation

[O]dyestuff particleC.I. Sulphur Black 1

[H]

C.I. Leuco Sulphur Black 1

S

N S

S N

S

S

O

O

S

R

R

2

n

S

N S

S N

S

S

O

O

S

H

H

R

R

[H]

step A step B

e e

[O]


Reducing agents insulphur dyeing

• Sulphur dyes themselves have a relatively low detrimental environmental impact– free from heavy metals and AOX

• Significant environmental problem with the dyeing process– employ sulfides as reducing agents– 90% of all sulphur dyes are reduced using sodium sulfide

• Discharge of sulfides only permissible in very small amounts (usually the legal allowance is 2 ppm)– danger to life from liberated hydrogen sulfide– corrosion of sewerage systems– damage to treatment works– high pH– aquatic life down stream significantly affected

• damage to the DNA of tadpoles– classed as micropollutants– over time the substance can reach high concentrations


Alternative reducing agents

• Thiourea dioxide from both a practical and ecological point of view– dyeings comparable, but environmental effect unclear– significantly more expensive than sodium sulfides

• Indirect cathodic reduction processes– successfully reduce sulphur dyes– some reducing agent was required to prevent premature re-oxidation

of the dye– dyeing was comparable– electrolysis is an appreciably more expensive technology

• Glucose/NaOH– above 90°C has sufficient reducing potential– no current systems in commercial use– dyeings secured had lower colour strength and fastness– no fundamental work on the reducing sugar/NaOH system conducted

to understand optimum


Application of various reducing D-sugars

• D-arabinose• D(-)-fructose• D(+)-galactose

• α-D-glucose

• β-D-lactose• D-maltose

• sodium polysulfide• sodium hydrosulfide

Blackburn, R. S.; Harvey, A. Env. Sci. Technol. 2004, 38 (14), 4034.

R2 = 0.9963

0.0

5.0

10.0

15.0

20.0

25.0

400 450 500 550 600 650 700

-mV

SU

M (

K/S

)

D-arabinose

R2 = 0.9845

0.0

5.0

10.0

15.0

20.0

25.0

400 450 500 550 600 650 700

-mV

SU

M (

K/S

)

D(-)-fructose

R2 = 0.9875

0.0

5.0

10.0

15.0

20.0

25.0

400 450 500 550 600 650 700

-mV

SU

M (

K/S

)

D(+)-galactose

R2 = 0.9975

0.0

5.0

10.0

15.0

20.0

25.0

400 450 500 550 600 650 700

-mV

SU

M (

K/S

)

α-D-glucose

D-maltoseβ-D-lactose

R2 = 0.9912

0.0

5.0

10.0

15.0

20.0

25.0

400 450 500 550 600 650 700

-mV

SU

M (

K/S

)

R2 = 0.9993

0.0

5.0

10.0

15.0

20.0

25.0

400 450 500 550 600 650 700

-mV

SU

M (

K/S

)

0.0

5.0

10.0

15.0

20.0

25.0

400 450 500 550 600 650 700

-mV

SU

M (

K/S

)

Sugars

Sulfide-based reducing agents0.0

10.0

20.0

30.0

40.0

50.0

60.0

70.0

400 450 500 550 600 650 700

-mV

Lc

(%)

Sugars

Sulfide-based reducing agents


Environmental and economical considerations

Relative theoretical COD and price of reducing agents per kg dyed cotton

Reducing agent g O2 kg-1 dyed cottona £ kg-1 dyed cottona

sodium sulfide 51.3 1.60

sodium hydrosulfide 71.3 1.18

D-arabinose 66.6 28.06

D(-)-fructose 66.6 1.65

D(+)-galactose 66.6 4.14

α-D-glucose 66.6 0.58

β-D-lactose 70.1 2.08

D-maltose 70.1 4.30a Based on 2.5 g dm-3 reducing agent (typical optimum concentration) at a liquor ratio of 25:1


Greener reactive dyeingof cellulose

• Treatment of cellulose with cationic, nucleophilic polymers to enable reactive dyeing at neutral pH without electrolyte addition

• Reactive dyeing problems– High electrolyte concentrations used– High colour concentrations in effluent– High volume of water consumed


Problems with high electrolyte concentration

• High levels of salt (sodium sulfate/chloride) used when dyeing cotton– Particularly reactive dyes– Fibre has negative charge in water– Repels anionic dyes – low adsorption– Electrolyte screens negative charge– Overcomes repulsion between dye anions and negative fibre

surface to allow adsorption

• Soil too alkaline to support crops• Kills aquatic life• Examples of fresh water courses turned saline

downstream from reactive dyeing operations• Difficult to remove from effluent

Mechanism of reactive dye fixation to cellulose

(Nucleophilic substitution)

6

R

NC

X

reaction withcellulose

reaction withwater

W D

OH

O Cell

W = water solubilising groupD = dye chromophoreX = leaving group (e.g. Cl)

W D

NC

X

R

6

6

R

NC

X

W D

6

R

NC

OCell

W D

W D

NC

OH

R

6

Mechanism of reactive dye fixation to cellulose(Michael Addition)

reaction withcellulose

reaction withwater

W D SO2 CH CH2H

O Cell

W D SO2 CH CH2

W D SO2 CH CH2H

OH

W D SO2 CH2 CH2 O Cell

W D SO2 CH2 CH2 OH


Colour (unfixed dye)in effluent

• Reactive dyes poor fixation– 10-40% dyestuff hydrolysed– Goes down drain– Aesthetically unpleasant– Blocks sunlight

• Algae overpopulate• Reduction in O2 levels in water• Suffocation of flora and fauna in watercourses

• Clean effluent– High cost


High water consumption

• High level of water used in reactive dyeing

• Incredible volume used in wash-off of hydrolysed dye– Up to 10 separate rinsings– High energy consumption– 50% total cost dyeing procedure


Pre-treatment agents

N

H3C CH3

NH2

Cl

mn

Copolymer of diallyldimethylammonium chloride and3-aminoprop-1-ene (PT1)

N N

NH2

Cl

m n

Copolymer of4-vinylpyridine quaternised with 1-amino-2-chloroethane(PT2)


High substantivity ofpre-treatments for cotton

• Both pre-treatment polymers are highly substantive to cellulosic fibre

• ion-ion interactions between cationic groups in the agent and the anionic carboxylic acid groups in the substrate– low pKa values will be ionised at the pH values of

application (pH 6-7)

• Other forces of attraction– H-bonding, van der Waals


PT1

Conformational interaction betweenPT1 and cellulose

O

HOOH

O

OH

CH3

NCH3

cellulose

PT1


PT2

(a) Ion-dipole interactions between cellulose hydroxyl groups and pyridinium residues of PT2

(b) Yoshida H-bonding between cellulose hydroxyl groups and pyridine residues in PT2

poly(4-vinylpyridine)quaternary ammoniumcompound - pyridineresidue

poly(4-vinylpyridine)quaternary ammoniumcompound - pyridiniumresidue

(a) (b)

OH

cellulose

O

H

NN

NH2


Mechanism of operation (schematic)

cellulose

Nu Nu Nu NuNu Nu Nu Nu

Nu NuNu Nu Nu NuNu Nu

cellulose

DYE X

DYE XDYE X

DYE X

pre-treatment agent

Nu = pre-treatment nucleophilesX = leaving group in reactive dye


Advantages ofpre-treatment system

• Polymers cationic– No requirement for salt

• Nucleophiles in polymer more reactive than hydroxyl groups in fibre– Neutral pH of application– Hydrolysis minimised– Colour fixation yield maximised– Less colour in effluent– Less wash-off requirement– Significant reduction in operation time– Significant reduction in water consumption

System comparison

Procedure Wash-off stages

Time(mins)

Water(ℓ/kg

fabric)

NaCl(g/kg

fabric)

Na2SO4

(g/kg fabric)

Na2CO3

(g/kg fabric)

Other Chemicals(g/kg fabric)

Remazol RR 6 355 145 0 1250 500acetic acid (60), detergent (20)

Procion H-EXL 4 365 105 1625 0 500 detergent (20)

Cibacron F 5 295 125 0 1500 500acetic acid (60), detergent (20)

Pre-treatment 1 195 50 0 0 0pre-treatment (10),

detergent (20)


Publications

Blackburn, R. S.; Burkinshaw, S. M. Green Chemistry 2002 4 (1), 47.

Blackburn, R. S.; Burkinshaw, S. M. Green Chemistry 2002, 4 (3), 261.

Blackburn, R. S.; Burkinshaw, S. M. Journal of Applied Polymer Science, 2003, 89, 1026-1031.

• “Dye Hard”, New Scientist,1st December 2001

• “Greener Dyes”, The Alchemist,6th February 2002

• “Problem Fixed”, Chemistry in Britain, April 2002


DyeCat Ltd.

• A University of Leeds Spinout Company

• Dr. Patrick McGowan– Organometallic chemistry– Novel polymerisation catalysts– Organometallic anticancer drugs

• Dr. Richard Blackburn– Coloration of natural and synthetic polymers and

fibres– Physical organic chemistry of dyeing processes– Green Chemistry in the textile and coloration

industries• Prof. Chris Rayner

– Organic synthesis (pharmaceuticals and fine chemicals)

– Supercritical carbon dioxide– Green Chemistry

©DyeCat 2006


DyeCat Technology

• Patented technology for the preparation of light absorbing polymeric materials (IR, visible, UV).

• Variety of approaches; allows flexibility in – Polymer composition– Polymer molecular weights and polydispersities– Coloration strength– Range of light absorbing chromophores

• Applicable to natural and synthetic polymers (particularly polyesters such as PLA and PET).

• Superior coloration technology– Homogeneous colorant throughout cross section of polymer– Increased wash and light fastness

• Greatly improved preparative method– Significant cost reductions on comparable conventional technology– Reduced environmental impact

• Applicable to sustainable, biodegradable polymers such as PLA and PHB.

©DyeCat 2006


Contacts

• Laura Bond (general inquiries)– [email protected]

• Dr. Patrick McGowan– [email protected]

• Dr. Richard Blackburn– [email protected]

• Prof. Chris Rayner– [email protected]

www.dyecat.com

©DyeCat 2006


Acknowledgements

• Colleagues– Prof. Chris Rayner– Prof. Tony Clifford– Prof. Stephen Burkinshaw– Prof. Carl Lawrence– Prof. Paul Knox– Dr. Patrick McGowan– Dr. Steve Russell– Dr. Abbas Dehghani

• Research Assistants– Dr. Tony Blake– Dr. Nagitha Wijayathunga– Dr. Xiangfeng Zhao

• PhD Students– Iram Abdullah– Nabeel Amin– Ioannis Drivas– Parikshit Goswami– Anna Harvey– Andrew Hewitt– Nandan Kumar– Wei Zhang

• Industrial Partners– Body Shop International plc

(UK)– DyStar (Germany)– Lenzing Fibers Ltd. (Austria)– NatureWorks LLC (USA)– Reilly Industries inc. (USA)– Uniqema (UK)

Business

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