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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
JSDC Volume 99 JulyIAugust 1983 183
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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 -
184 JSDC Volu me 99 J uly/A ugu st 1983
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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
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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
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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
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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