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Also welcomed were Honorary Secretaries f rom most of

the Regions and Student Sections, some members of the

staff of Perkin House, ably led by th e Chief Executive and

General Secretary, Dr M Tordoff, and representatives from

sister societies, including: MrJ Turner and Mr C B Abnett

(a Past Prime Warden and Assistant Clerk respectively of

the Worshipful Company of Dyers), M r D J Holborow (Mas-

ter of the Worshipful Company of Feltmakers), M r D H Tuck

(President of the Society of Leather Technologists and

Chemists), Mr W Sondhe lm (Vice-president of t he Textile

Institute), Mr G Gordon (President of the Guild o f Technical

Dyers) and Mr

K

McLaren (Chairman of the Colour Group).

The Society was also pleased to welcome several leading

figures from the wor lds of education, research, dye man-

ufacturing and textile manufacturing amongst its guests.

Mr Parkinson said that in such a gathering of almost

400

people time did not permit the ment ion of all the guests b y

name. (’Oh, please do‘, shouted someone entering a little

overzealously into the sp irit

of

the occasion.) But to all the

Society’s guests, those who had travelled fro m overseas or

from distant parts of the UK and those who had travelled

from the Manchester area, was bidden a hearty welcome.

Members of the Society were asked to drink a toast to ‘The

Guests‘.

In response Sir W illiam Downward, Lord Lieutenant of

Greater Manchester, said that he was relieved to see that so

many people had turned up. He concluded that Society

members were either enthusiastic, generous o r rich peo-

ple. Whichever

it

was, he was grateful for the splendid

dinner he had enjoyed.

A few people, he said, were disappointed that he had not

come

in

his official uniform, which was based, he thought,

on that worn by men on

duty

outside the major picture

palaces. Uni forms such as this took some gett ing used to,

and Sir William described in detail ho wt o get in and out of a

car whilst encumbered wit h a ceremonial sword and spurs,

without any lasting self-inflicted injury.

Greater Manchester, he said, was a relatively new

county; some parts of it had even formerly belonged to

Yorkshire. However, a change fro m white rose to red had

not been universally unpopular. One old lady who had

become a Greater Mancunian without moving had ex-

pressed a preference for her ne w county ’because the win-

ters were warmer’.

Nevertheless, r ival ry between the

two

sides of the Pen-

nines was strong, and curiously exclusive of outsiders. He

told the (possibly) apocryphal tale of the visiting South-

erner at an Old Trafford Roses match who was clapping the

batting enthusiastically and nterject ing an occasional Well

played sir ’ in cultu red Home Counties tones. Eventually a

disgruntled local turned and silenced the unfortunate

intruder

with

a curt ‘Shurrup It’s now‘t t’do

wi’

thee.’

In thanking members of the Society for their hospitality,

Sir William wished the Society well for its Centenary and

expressed the wis h for conti nuing good relations between

it and the industry it served.

The Structure and Properties

of

Disperse

Dyes

in

Polyester Coloration

J F Dawson

Yorkshire Chemicals plc

Kirkstall Road

LeedsLS3 1LL

Presented to the Society’s 1eicester Student Section on

the 29 October 1980,

to

a joint meeting of the Society’s

West Riding Region and Leeds Student Section on 25

February 1982 and to the Society‘s Scottish Region on 2

March 1982.

JohnDawsonwas educatedat Prince Henry‘s GrammarSchool, Otley, and

the University of Leeds. He graduated from the Department of Colour

Chemistry and Dyeing in 7961 before tak ing up an appointment as a

research chemist with the then Yorkshire Dyeware Chemical Co. Ltd,

working primarily on the synthesis of new disperse and cationic dyes. He

was appointed dye research manager in 1969 and elected to he board in

1976

He

is now technical director

of

Yorkshire Chemicals plc, and also a

member

of

the Society‘s Publications Committee.

INTRODUCTION

Going back to irst principles, the Society defines a disperse

dye as ‘a substant ially water-insoluble dye having substan-

tivity for one or more hydrophobic fibres, e.g. cellulose

acetate, and usually applied fr om a fine aqueous disper-

sion

[ I

1’

The men tion of cellulose acetate should remind us that

this was the fibre that established disperse dyes as a class

and this part of the story is well described in the 13th John

Mercer Lecture entitled ‘The Disperse Dyes Their

Development and Application’ given by R K Fourness in

1956121. It is interesting to note that at the time of this

lecture polyester fibres were still in their i nfancy - the first

sale of terylene filament yarn is said to have taken place on

4 October 1948 [3]. There were some problems nitially with

the coloration of this ne w ibre [41

but

the use of carriers at

the boil and the subsequent exploitation of high-

temperature dyeing eventually overcame them. To quote

Fourness, ’without disperse dyes and the dispersion pro-

cess certain man-made prodigies would have been still-

born or at best remained Peter Pans’

121.

Whilst this was

certainly true

in

the case of both cellulose acetate and

polyester fibres, there i s no doubt that the commercialisa-

tion of polyester fibres also proved to be a landmark for

disperse dyes and their manufacturers.

Information s available to compare the world production

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of polyester and cel lu lose acetate f ibres since the form er

was launched [5], as show n in Figure 1.

Figure - World fibre production 7950-1980)

Cellulose acetate production has remained compara-

t ively stat ic whi lst polyester f ibre production, which was

sti l l re lat ively smal l at the t ime of the 13th John Mercer

Lecture in 1956, has since u ndergone a per io d of p heno-

mena l g rowth . It is fa ir to assume that th is increase

in

f ib re

production has been fo l lowed by a s imi la r t ren d in dye

manufacture and use; hence he dye m akers’ research work

has been pr imar i ly d irected towards dyes for polyester

fibre. In any case, the dyes u sed for the colorat ion o f cellu-

lose acetate are in ma ny cases wel l establ ished and have

adequate prope rties for the fibre’s intend ed use,

with

the

possible exception of wet fastness.

APPLICATION TECHNIQUES AND FASTNESS PROPER

TIES ON POLYESTER FIBRES

Application Techniques

Six d i f ferent methods o f applying disperse dyes have been

developed since the introduction o f polyester f ibres.

1. Batchwise dyeing at the bo i l in the presence of a carrier

is sometimes used for del icate fabrics, poly este r/wo ol

blends, etc.

2. Ba tchw ise dye ing at 120-135°C in pressuris ed vessels

was in i t ial l y used fo r dubb ing and yarn. Compared wi th

carr ier dyeing th is technique gave better exhaustion and

often improved fastness to light (as there were

no

residual carr ier problems), rubbing and perspirat ion.

Fabrics were or ig inal ly beam dyed, bu t jets are n o w

mo re comm only used.

3.

Thermofixation techniques at 190-220°C are used for

the continuous processing of certa in types

o f

fabric.

4. Transfer printing, usually at 210°C for 30

s,

i s an impo r -

tant recent development.

5. Solvent dyeing techniques are available

but

are no t

popular despi te th e development of specia l dy e ranges

and appropr iate appl icat ion methods.

6.

Print ing and co ntinuous dyeing processes are avai lable

for polyester/cotton blends using specia l ist dyes and

application tec hniques such as th e D ybln (DUP), Celles-

tre n (BASF) and Dispers ol PC (ICI) ranges.

Dyeing and Fastness Properties

Before consider ing specif ic examples of th e re lat ionships

between disperse dye structure, and dyeing behaviour an d

fastness propert ies, som e general points are worth y o f

note.

1. The use of h igher dyeing temperatures for polyester

f ibres c ompared w ith those used for cel lu lose acetate

has made possib le the use of dyes o f h igher mo lecular

weight, the so-cal led h igh-energy dyes. This has had he

ef fect o f open ing up man y m ore s t ructu ra l poss ib i li t ies

for dy e synthesis.

2. The uptake of d isperse dyes by synthetic-polymer f ibres

takes place by progres sive adsorpt ion of the smal l con-

centrat ion of dye in solu t ion always present in an aque-

ous dispersion. The substantiv i ty of the dye, which

determines i ts tendency to par t it ion in favou r o f the f ib re

depends on factors such as molecular size, geometry

and, in part icular , the po lar i ty of the molecule. I t is qui te

possib le for a sm al l var iat ion

in

molecu la r s t ructu re to

produce a dye of greater substantiv i ty for cel lu lose ace-

tate than fo r polyester, and vice versa.

3. Many disperse dyes give sl ight ly, or sometimes mar-

kedly, d i f ferent hues on nylo n and on cel lu lose acetate

f ibres. This is no problem on polyester, a g iven dye

general ly yie ld ing sim i lar hues on polyester and cel lu-

lose acetate.

4. The l igh t fad ing o f dyes invo lves a com plex series o f

processes, w hic h are

only

understoo d n genera l te rms.

The way

in

whic h l igh t fastness var ies with the na ture of

the substrate is even less easi ly expla ined. Conse-

quently it i s d i f fi cu lt t o d o o ther than dra w u p a ser ies o f

empir ical ru les appl icable to a range of structural ly

re lated dyes o n a part icular f ibre. In general it can be said

tha t h igh l igh t fastness is favoured by the fo l lowing 161.

( a) S tab le a roma ti c compounds w i th a m in im um

number o f doub le bonds or react ive subst i tuents

ava ilable fo r chem ica l at tack sho w improved l igh t

fastness. It is wort h notin g that t he 13-hydroxyethyl

g roup, w h ich has been wide ly used in d isperse dyes

for cel lu lose acetate, general ly g ives rather poor

l ight fastness on polyester f ibres.

(b)

Many d isperse dyes conta in amino groups.

Imp roved light fastness is usual ly obtained i f these

are substi tuted in such a wa y as to reduce the bas i -

city

of

the am ino g roup .

(c) Other factors, such as intramolecular d ipo le forces

or hydrogen bond ing be tween ad jacent or per;

atoms or g roups, can a lso g ive r ise to improve d igh t

fastness.

5. Fastness to wash ing is usua l ly less o f a p rob lem on

po lyester than on acetate fib res, wh ich is no t s urpr is ing

i f we bear in mind the easy on/easy off pr incip le. A

prob lem pecu l ia r to po lyester fib res is tha t migra t ion o f

the dy e t o he f ib re sur face can take p lace dur ing s ten ter -

ing , wh ich g ives p oor wash fastness

but

on ly usua l ly fo r

the f i rs t wash. The reasons fo r th is a re no t ye t fu l ly

understood, especially in re lat ion to dy e structure.

6. The sub l ima tion fastness of a dye is not part icular ly f ibre

dependent. However, the use of h igher appl icat ion

tempera tures and heat t rea tments fo r the p lea t ing or

stabi l isat ion of po lyester fabr ics hav e necessi tated the

developme nt of dyes of h igher sub l imat ion fastness.

7. Fastness to burn t gas fume s is usua l ly less o f a p ro b lem

o n polyester f ibres. Presumably the oxides of n i troge n

penetrate cellulose acetate fibres m or e easily because of

their re lat ively h ydro phi l ic character.

CLASSIFICATION

OF

DISPERSE DYES ACCORDING TO

CHROMOPHORICGROUPS

The fo l l ow ing ch rom opho res commo n ly occu r i n d i spe rse

dyes:

1 . N i t rod iphenylamine

2. zo

3.

Anthraquinone

4.

Styryl

or m eth ine .

These will no w b e cons idered ind iv idua l ly as regards

their use in conventional d isperse dyes notingappropr iate

po in ts of in terest re lat ing to a ppl icat ion an d fastness prop -

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erties. Dyes for speciality applications will be considered

later.

Nitrodiphenylamine

Dyes

Numerically these are a small class of ye llow disperse dyes.

They have survived because they are cheap and have good

light fastness despite being rather weak tinctorially. They

are manufactured by condensing an o-nitrochlorobenzene

derivative with an arylamine as shown in Figure 2. The

ortho

nitro group is particularly important as

it

confers

stability by intramolecular bonding; this is one of the

reasons for the high light fastness of these dyes.

A

0,”

O=N

igure 2 Manufacture of nitrodiphenylarnine dyes

R=NO,or S o p H which may besubstituted y Alk orAr;

A

may be further substituted usually in the 4-position

In some cases the older disperse dyes for cellulose ace-

tate had a lower substantitivity for polyester, but slight

structural modifications improved this (Figure

3).

The

upper dye shown in Figure

3

has better substantivity for

secondary cellulose acetate whilst the lower one is more

appropriate for polyester, which is more hydrophobic.

Serisol

Fast Yellow

GGL

(C.I. Disperse Yellow 33 *

e N H p o 2 N H 2

O2N

Dispersol

Yellow C-T (ICI, C.I. Disperse Yellow 42)

f igure

3

Structural modification to improve substantivity

of a nitrodiphen ylamine disperse dye

The sublimation fastness of many of the original disperse

dyes was also inadequate for the more severe end uses on

polyester, but this has been improved by increasing the

molecular size. For example, an existing dye has been

diazotised and coupled to a substituted phenol; this also

has the advantage of introducing an additional

chromophoric group (Table

1).

Azo Dyes

Numerically these fo rm by far the largest chemical class,

accounting for more than half the total of disperse dyes.

They n ow cover virtua lly the whole of the spectrum from

greenish yellows through oranges, browns, reds, bright

pinks, rubines, violets, roya l blues, navy blues, greens and

blacks if diazotised and developed products are consi-

dered. When the dyes then available were first applied t o

polyester fibres they had several defects:

1.

The colour gamut was rather limited, particularly with

2. Some dyes had relatively low l ight fastness

3.

Sublimation fastness was inadequate

in

many cases.

The extension of the colour gamut has also resulted in

brighter colours and this, coupled with improved fastness

regard to hue and brightness

All

the dyes mentioned in his paper are manufactured

by

Yorkshire Chem-

icals plc unless stated otherwise.

TABLE

1

Improving Sublimation fastness

of

a Nitrophenylamine

Dye by Increasing Molecular Size

Sublimation fastness

(30

s a t

180°C)

Colour Polyester

change s ta in

Serisol Fast

Yellow PL

(C.I.

Disperse Yellow

9)

NO2

0 - N H 2

Serilene Golden Yellow T-FS

(C Disperse Yellow

70)

4-5

3

5

4-5

properties, has enabled these dyes to challenge in the areas

traditionally held by anthraquinone dyes. Their main

advantage is an economic one, although initially his had o

be balanced against prob lems of dy e stability and difficul-

ties in covering barre effects. As the quality of fibre produc-

tion has n ow improved, this is less of a problem. There are

three main groups of azo disperse dyes.

Aminoazobenzene Dyes

These are traditionally the most important dyes and the

major ity are represented

by

the general formula shown in

Table

2.

Commercially these cover the ranges from orange

to blue as shown.

The colour range described is probably not appreciably

different fr om that theoretically available for cellulose ace-

tate. The most significant advance in recent years has been

the replacement of halogen atoms ortho to the azo linkage

with cyano groups using cuprous cyanide in dimethylf or-

mamide, which gives

bright

blue dyes

[71,

see Figure

4.

These dyes cannot be. prepared economical ly by direct

coupling because of the instability of this heavily substi-

tuted diazo component.

The structures described

in

Table 2 rely by and large on

traditional diazo components, but the coupling compo-

nents are specially designed to make the dyes more suit-

able for polyester fibres. The origi nal coup ling components

for disperse dyes on cellulose acetate were manufactured

by reacting aniline or its derivatives with ethylene oxide

(see Figure 5). These coupling components are rather too

hydrophilic to be ideal for polyester fibres and the

P-hyd roxye thyl groups are responsible for the relatively

poor light fastness of the derived dyes on this fibre. The

mor e modern coupling components are typically manufac-

tured by acylating the hydro xyl groups in the previously

described couplers, or by replacing the ethylene oxide

with

acrylonitrile or methyl acrylate as shown in Figure 6.

The effect of this type of development on the light fast-

ness of disperse dyes,on polyester fibres has been

described I81 and is illustrated in Table

3.

As

previously ment ioned he presence of P-hydroxyethyl

groups in these dyes gives rise to relatively poor l ight fast-

ness. Their replacement by groups such as cyano and

acetoxy gives dyes of very good light fastness, and

it

should be noted that these groups are electron deficient

and

so

should reduce the basicity of the tertiary amino

group. The sublima tion fastness of some o f the a20 dyes

already described does not meet the more critical require-

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TABLE 2

Some Comm ercial Arnin oazobenzene Dyes

X

~ ~

ye

Seri lene Orange

2RL NO2

Ser i lene Yel low Brow n R-LS

NO2

Resolin Red

RL

NO2

Foron B lue

SE-2R NO2

Seri lene

N avy

Blue

ZGN-LS NO2

(C.I. Disperse Orange

25)

(C.I. Disperse

Orange 30)

(BAY, C.I. Disperse Red 90)

(S,

C.I.

Disperse Blue

183

(C.I. Disperse Blue 7 9 )

~~

___ ~ _ _ _ _

_ _ _ _ ~ _ _ _

_ _

R“

~-

Y

Z R ‘ R2

R 3

H H

H H Et C2H,CN

CI CI

H H C,H,CN C2 H,0C OM e

CN H

H H C,H,CN C,H,COOMe

C N Br

H NHCOEt

Et

Et

NO, Br

OE t N H CO M e C,H,OCOMe C,H,OCOMe

~

-

,CN

\

‘CN F(IHC0Me

Resolin

Blue

BBLS

(BAY,

C.I.

Disperse Blue 165)

~

Figure 4 -Manufacture of C.I. Disperse Blue 765

Figure 5 Method of manufacture of original coupling

components for disperse dyes on cellulose acetate

C~HICN

@HC2H4CN + H,C:CHCOOMe - \

N’C2H4COOMe

Figure 6 -Method of manufacturing coupling components

for disperse dyes on polyester

TABLE 3

Light

Fastness of Som e Am inoazobenzene Disperse Dyes

on Polyester

O z N q N . 0 N ” H 4 R ’CzH4RZ

~

L igh t fastness

X

Y

R’

R Z on polyester

CI H

CI

H

CI H

CI H

CI

H

CI H

CI H

CI H

H

H

C N

C N

C N

C N

OCOMe

OCOMe

O H

H

OH

H

OCOMe

C N

H

OCOMe

3

3 4

4

6

7

7

6

6-7

ments of pad-Thermos01 dyeing and durable-press finish-

ing. This has been solved by int roducing additional polar

groups or increasing the molecular size of the dye; Table

4

exemplifies the latter approach [91.

Heterocyclic Dyes

The use of heterocyclic diazo and coupling components has

enabled the colour ranges o be extended and has made the

production of brighter colours possible; therefore, as pre-

viously mentioned, some of the very brigh t dyes are no w

challenging the traditional strongholds of the anthra-

quinone and styr yl dyes. The high neat colour strengths of

many of these dyes coupled with their relative ease of

manufacture helps to offset the high cost of some of the

heterocyclic intermediates.

A

selection of disperse dyes for

polyester fibres using typical heterocyclic diazo and coupl-

ing components covering a wide colour gamut is shown in

Table

5.

It can be seen that pyridone, thiazole, thiadiazole

and thiophene rings are present in the above dyes, which

all have acceptable fastness properties on polyester fibres

for mos t end uses.

Disazo Dyes

Several disperse dyes of this type have proved useful for

the coloration of cellulose acetate. Most of these are

derived from simple, cheap intermediate:;, which helps to

offset the cost of the tw o diazotisations and couplings usu-

ally required. The dyes are mainly yell ows and oranges and

occasionally reds. Many of the original dyes were useful for

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TABLE

4

Improving Sublimatio n Fastness

of an

Aminoazobenzene Dye by Increasing Molecular Size

0 2 N @ 4 :

e N / c 2 H 4 R ’

C2H,R2

Subl imat ion fastness

(30 s at 210°C)

X Y

R ’

R Z

Colour Polyester

change stain

Dye

Ser ilene Ye l low B rown R-LS

CI

CI CN OCO Me

5 3 4

_

(C.I.

Disperse Orange 30)

Ser i lene Yel low Brown G-LS CI CI CN OCO Ph

5

4-5

(C.I. Disperse Orange

62)

TABLE 5

Some Heterocyclic Disperse Dyes for Polyester

Subl imat ion fastness

(30 s at 180°C)

Light Colour Polyester

Dye fastness change stain

B r igh t g reen ish ye l low [ lo ] 6-7

5

4

::N

HO

Et

Scarlet

[ I

11

Brig ht blu ish red 1121

,CH,Ph

EtS ‘Et

AcHN

Violet

1131

Greenish blue [14]

Bluish green [ IS ]

5 6

6

6

5 6

4-5

5

5

5

5

5

4-5

4

4-5

5

4-5

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TABLE 6

I

Res olin Gree n C-FGS (BAY, C.I. Dispers e Gree n

5)

Som e Disazo Disperse Dyes for Polyes ter

MH2

R

v

Serisol B ri l l ian t Blue BG (C.I. Disperse Blue

3)

Subl im at ion fastness

30

s

at

180°C

~

Light Colour Polyester

Dye

X

Y

R

R Z R'

R

fastness change stain

Foron Yellow E-RGFL

H

H H H H OH 7 4 3

S , C.I. Disperse Yellow 23)

Golden yel low

1161

NHAc H

Me H H OH 7 5 4-5

Orange 1171

NO2

H

M e M e

M e OH

6 7 t l

3-4

Br igh t ye l low ish red

I181

H NHAc

H

H H

N 6

I 5

,C,H,CN

C,H,OCOMe

the coloration of polyester fibres, but

did

not always have

the requisite sublimation fastness. This was overcome

primarily by the introduction of more polar groups as

shown in Table

6.

It should also

be

noted that all t he dyes

in

Table

6

have

good light fastness as they are relatively simple stable

molecules.

Anthraquinone Dyes

Theoretically

it

is quite possible to cover the who le spec-

trum with anthraquinone disperse dyes, but traditionally

they complemented the nitrodiphenylamine and azo dyes,

being particularly useful for the production o f bright red,

I

isperso l Red A-28 (ICI, C.I. Disperse Red

15)

O

Serisol Bri l l ia nt Violet 2R (C.I. Disperse Viole t

1

0

NH2

Serisol B ri l l ian t Blue BG (C.I. Disperse Blue 3)

Serisol

Fast

Blue Green

BW

(C.I. Disperse B lue

7)

W W H

HO

NHC,H,OH

1

Figure 7 Original anthraquinone disperse dyes

for

cellul-

ose acetate

violet, blue and blue green colours. However, a major dis-

advantage with many

of

the anthraquinone dyes is the

number of intermediate stages or isomer separations

involved in their produc tion, which often has necessitated

Seri lene Red 2BL (C.I. Disperse Red 60

O H

Latyl Viole t BN (DUP, C.I. Disperse Violet 2 7)

OH

Fo ro n Blue S-BGL (S, C.I. Dispe rse Blu e 73)

Seri lene Bri l l ian t Blue 2G (C.I. Disperse Blue 60)

I I

Figure 8 Some anthraquinone disperse dyes

188 JSDC Volume 99 July/August

1983

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the use of dedicated plant of relatively high capital and

maintenance costs, mak ing them somewhat expensive.

They have the advantage of brightness and molecu lar sta-

bility, which is not always achievable wit h azo dyes, bu t the

gap between the two classes is now closing rapidly.

The original disperse dyes for cellulose acetate were rela-

tively small simple molecules often containing

P-hydroxyethyl groups (see Figure 7) . If we compare these

structures with the previously described azo and nit-

rodiphenylamine dyes, we would expect that the molecules

of anthraquinone derivatives for polyester dyeing would be

slightly larger and more hydrophobic, and that

P-hydroxyethyl groups would be absent. This proves to be

so, as shown in Figure 8.

It

is difficult to produce rules covering l ight fastness, but

some general trends can be seen from Table 7.

The presence of o ne or more pri mary amino groups o n

an anthraquinone ri ng results in only moderate li ght fast-

ness, lower than the hydroxyanthraquinone analogues. A

methylamino group is electron releasing, giving greater

basicity and therefore even lower light fastness. Anilino

and especially benzoylamino groups, however, are elec-

tron attracting and less basic, which favours higher light

fastness. Further improvements in light fastness can be

obtained by incorporating electron-attracting groups into

the P-positions of l,Cdiaminoanthraquinone, which also

reduces the basicity of the amino groups. A g ood example

of this is Serilene Brilliant Blue 2G (C.I. Disperse Blue

60 ,

which has a light fastness of 7 on polyester fibres.

TABLE

7

Light Fastness of Some Anthraquinone Disperse Dyes

R Light fastness of polyester

NHMe

NH,

NHPh

OH

/-Y

NHCOPh

TABLE 8

4

4-5

5-6

6

Improving Sublimation Fastness of Anthraquinone Dyes

o on

Sublimation

fastness

(30 s a t 180°C)

Colour Polyester

R change sta in

~~

H

5

2-3

SMe 1191

5 5

SO,NHC,H,OEt 120J

5 5

Sublima tion fastness is also improved by the incorpora-

tion of polar groups

or

by increasing molecular size, as.

shown in the bri ght bluish-red dyes shown i n Table 8.

Styryl or Methine Dyes

This small class of dyes was particularly suitable for the

production of greenish-yellow colours on acetate fibres.

One of the original dyes is Celliton Fast Yellow7G (GAF, C.I.

Disperse Yellow 31 , hich is shown in Figure 9. Unfortu-

nately this dye d id not have muc h substantivity fo r polyes-

ter, was pH sensitive and was rather unstable in the

dyebath under typical application conditions, presumably

because of hydrolysis. Structures with a rather more hyd-

rophobic character were produced by simila r methods and

these had acceptable affinity for polyester, although the

early versions had poor sub limation fastness. An’ increase

in molecular size or the incorporation of polar groups over-

came the prob lem. Table 9 illustrates ho w the use of the

bifunctional adipoyl chloride effectively doubles the

molecular size, C.I. Disperse Yellow 99 having the greater

sublimation fastness.

TABLE 9

Increasing Molecular Size in a Styryl Dye t o Improve Sub

limation Fastness

Sublimation fas tness

(30 s a t

180°C)

Colour

Polyester

Dye change stain

Serisol Brilliant Yellow

6GL

4-5

3 4

(C.I. Disperse Yellow 90)

k e

Terasil Brilliant Yellow

6G

(BAY, C.I.

Disperse Yellow

99)

5 5

CIC H \N+Cn:cfN

\COOEt

/

C4H9

I

Figure 9 Celliton Fast Yellow 7G C.I. Disperse Yellow 3

DYES FOR SPECIAL APPLICATION TECHNIQUES

Transfer Printing

The commercialisation of th is process led to a reversal of

some of th e recent trends in disperse dye chemistry. The

abilit y to sublime rather than sublimation fastness became

the order of t he day, and this and goo d ligh t fastness are

no w the main requirements. The typical three-dye combi-

nation of ’low energy’ disperse dyes originally used

i s

shown i n Table

10.

Occasionally the light fastness obtained by a transfer

printing process with this m ixture was slightly inferior to

more conventional dyeing techniques, presumably as a

result of lack of diffusion into the fibre leaving a proportion

of dye o n the surface.

In

addition,

it

soon became clear that

JSDC Volume 99 Ju ly/August 1983 189

7/21/2019 JSDC Volume 99 (1983) 183-191


TABLE

10

Three-dye Combination of Low-energy Disperse Dyes

Dve

Light fastness

(1 1 standard deDth)

Ser i lene Ye l low

3GL

(C.I.

Disperse Yel low 54)

Ser i lene Red 2BL

(C.I.

Disperse Red

60)

O H

Dispersol

Blue

G

(ICI,

C.I. Disperse Blue 14)

6 7

6

NHMe

NHMe

the blue component did not have satisfactory light fastness

for many end uses.

Consequently, the search for a blue dye with good light

fastness has received the most attention. It should be noted

that none of the previously mentioned dyes are of the azo

type and to date

it

has not been possible to produce

a n

azo

blue of sufficient brightness coupled with an acceptable

transfer rate. Modifications have therefore been concen-

trated on anthraquinone dyes, building on the principles

already mentioned. The replacement of one of the

methylamino groups in Dispersol Blue G by an amino

group and the incorporation of an electron-attracting group

in the P-position improves the l ight fastness whilst main-

taining acceptable colour and transfer properties. Thus

1-amino-2-cyano-4-ethylaminoanthraquinone

[211 and

1-amino-2-cyano-4-anilinoanthraquinone 221 have light

fastness ratings of

4-5

and

5

respectively.

Solvent Dyeing

Interest in this method of application does not appear to b e

increasing and, unless there

is

greater commercial exploi-

tation than a t present, little further work from the dye mak-

ers appears likely. There are two main application pos-

sibilities:

(a) Exhaustion processes from

a

solution or dispersion in

perchloroethylene using specially selected disperse

dyes at temperatures up to 130°C; the dyeing rate is

said to be enhanced by the presence of small amounts

of water 1231 but the major problem appears to be the

selection of dyes having a high partition coefficient in

favour of the fibre.

(b) Padding processes for continuous dyeing systems

using disperse dye solutions i n perchloroethylene fol-

lowed by drying (typically 1 min at 80°C) and then

fixation at 190-220°C for

45 s;

solubility in the solvent

is usually achieved by the use of long alkyl chains,

a

typical example being the substitution of the phenolic

ring in

l-amino-2-phenoxy-4-hydroxyanthraquinone

with a chain such as iso-octyl by the use of 4-

iso-octylphenol instead of phenol in the condensation

reaction.

Dyes for PolyesterKotton Blends

Polyester/cotton blends have become very important

commercially and two main approaches irivolving the use

of special dyes have been introduced.

Dyb ln Process DUP)

This process was pioneered by du Pont

1241.

The fabric is

printed or padded with specially developed dyes from an

aqueous dispersion containing a selected polyethylene

glycol capable of maintaining he cellulosic fibres in a swol-

len condition during subsequent fixation a t 180-220°C.

The selection of the disperse dye was of crucial impor-

tance as dif ficulties were encountered both in dyeing the

cellulosic fibres on tone and in obtain ing adequate fastness

to skin fat. A typical commercial dye is shown

in

Figure

10

and its similarity to an azoic combination should be noted.

The Cellestren process (BASF) has been described

[25]

nd

appears similar in concept. The success of this type

of

process is likely to depend on the skill of the dye chemists in

synthesising appropriate dyes.

Figure

70

Dyb ln Scar let

G

DUP, C I Disperse Red 220)

Special Dyes fo r Ap p l ica t ion in Con junct io t i w i th React ive

Dyes

The most important advance appears to be the Dispersol

PC range (ICI), which may be applied in conjunction with a ll

types of reactive dye.

Conventional disperse dyes usually stain the cellulosic

portion of the blend to some degree and removal of this

stain can be problematical. The Dispersol

PC

dyes generally

contain two alkoxycarbonyl groups,

a

typical example

being shown i n Figure 11 [26] hich dyes polyester fibres

red. In the presence of hydroxyl ions the ialkoxycarbonyl

groups can be converted to the corresponding carboxylic

acids, which are water-soluble products and have little or

no substantiv ity for cellulose or polyester. These dyes are

particularly useful in printing, and if a little sodium hydrox-

ide is added to the wash liquor staining of the white

unprin ted areas is virtually eliminated.

Figure

I

REFERENCES

1. J.S.D.C., 89 (1973)

414.

2.

Fourness,

J S D C

72

(1956) 513.

3. ICI,

The Launching

of

a New Synthet ic Fibre

-

A Histor ical Survey ,

(June 1954).

4. Waters, J.S.D.C..

66

(1950)

609

5.

Texti le Organon

(1951-1977).

6. Schroeder and Boyd, Text. Research J.,

27

(1957) 275.

7.

BAY,

BP 1125683 (1966).

8. Mul ler , Am er. Dyestuff Rep., 59 (Mar 1970) 37.

9. YCL, BP 1055399 (1964).

10. ICI, BP 1256093

1968) .

190 JSDC Volume 99 JulyIAugust 1983

7/21/2019 JSDC Volume 99 (1983) 183-191


11. Marti n Marietta, BP 1256434 (1968).

12. Eastman Kodak

Co.,

BP 1275603 (1968).

13. CFM.

BP

1123103 (1965).

14. BASF, BP 1112146 (1965).

15. ICI,

BP

1394368 (1972).

16. YCL, BP 128804 (1969).

17. ICI, BP 1533121 (1975).

18. S, BP 1395791 (1971).

19. BAY,

BP

952045 (1962).

20. BASF, BP 913902 (1961).

21.

LBH, BP

1390864 (1972).

22. CGY, 6P 1334114 (1970).

23. Harris and Guion, Text. ResearchJ., 42 (1972) 626.

24. Sklar,

AATCC

National Technical Conference Papers (1976) 380.

25. Miksovsky,

J.S.D.C.,

96 (1980) 347.

26. ICI, BP 1012238 (1963).

An Introduction to the Burning Behaviour of

Cellulosic Fibres

A R Horrocks

Department of Textile Studies

Bolton Institute of Higher Education

Deane Road

Bolton BL3 5AB

Presented to the Society’s Huddersfield Region on 16

September 1982

The actions of heat and flame on cellulosic fibres are

compared w ith the physical and chemical behaviour of

other fibres. The combustion mechanism is discussed in

terms of concerted p yrolysis and oxidative stages, which

can be represented as an energy feedback system. The

action

of

different flame retardants are seen to interfere

with the system and thereby inh ibit burning. The

condensed-phase synergistic mechanism of

phosphorus-nitrogen-containing retardants used

for

cotton and viscose rayon are discussed in terms of char

enhancement whereas halogen-based retardants operate

in the vapour phase. The latter

s

ynergistically function in

the presence of antimon

y

Ill)oxide and, although acking

extreme durability, offer the advantage of conferring

flame retardance to adjacent fibrous and non-fibrous

materials. The effect of retardants on smoke and

combustion product toxicity is also considered.

INTRODUCTION

The importance of cotton during bo th classical and modern

times as a textile fibre of both versatility and economy has

enabled certain disadvantageous properties to be

accepted. The poor creasing character and dimensional

stability of co tton fabrics has been largely overcome by use

of resin formulations and preshrinkage treatments

developed during the present century. The very highly

flammable behaviour of cellulose-containing textiles has

been realised as a hazard rather than an inconvenience and

so perhaps this aspect received attention earlier than did

poor setting properties.

Both wood and cotton have been treated with flame-

retardant formulations, usually based on salts such as

alum, for very many years. Dur ing the nineteenth century,

as chemical science became established, more systematic

researches showed that a variety of formulations, often

based on soluble inorganic salts, were effective retardants.

For instance, the use of boric acid/ sodium borate mixtures

and sodium phosphates is well known. Unfortunately,

such simple treatments lack durability and

so

develop-

ments since the Second Wor ld War have emphasised the

need to f ind durable flame-retardant systems for cellulosic

fibres, in particular cotton and viscose rayon. Within

Europe and in especially th e Unit ed Kingdom, commercial

retardants, such as Proban 210 (AW) and Pyrovatex CF

(CGY),

have proved to be extremely long-lasting treat-

ments for cotton; these interact with in the fibre’s po lymeri c

matrix and so do not adversely interfere with either the

technological or the aesthetic characteristics of cellulose

textiles.

Insoluble halogen derivatives (usually containing

chlorine or bromine) combined with the antimony

(Ill)

oxide usually present

within

a polymeric binding ma trix are

applied as coatings and

so

are more restrictive in heir use.

Unfortunately the chemical complexity of flame retar-

da nts can cause toxicolog ca and physiological hazards

and in recent years certain formulations have been banned

from use, especially in the USA. Of particular note here is

‘tris’ or t r i s - (2 ,3-d ibromopropy l ) -phosphonate used in

some flame-retardant viscose rayon fibres until the

mid-1970s [ I ] .

Most commercial flame-retardant systems fall into one of

the three main groups:

1.

Inorganic salts, e.g. zinc chloride, borates, d iammonium

phosphate

2. Organophosphorus compounds, e.g. Proban 210,

Pyrovatex CF

3.

Halogen compounds often used in conjunction with

antimony 111) oxide to give a synergistic system.

It is interesting to note that the phenomenon of synerg-

ism, whereby two chemical species together provide an

effect greater than the sum o f their i ndividual actions, is

quite com mon in flame-retardant systems. Not only does

the halogen and antimony

in

above interact

in

this man-

ner, but the elements of phosphorus and nitrogen when

incorporated together

in

certain typ e 1 and 2 systems are

considered to suppress burn ing synergistically.

To

understand ho w the above types of retardants func-

tion, it would be useful t o consider

why

fibres in general

and cellulose (cotton) in particular are flammable. Once a

simple mechanism of flammability has been developed,

then the action of the various retardant systems may be

understood.

ACTION OF HEAT ON FIBROUS MATERIALS

The effect of heat on a f ibre can produce a physical

as

well

as a chemical effect. Physical changes are shown pr imaril y

by hermoplastic fibres, whi ch soften above a second-order

JSDC Volume 99 July/August 1983 191

Documents

JSDC Volume 99 (1983) 183-191