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Disperse Dyes
Introduction:
Disperse dyes are colorants with low water solubility that, in their disperse
colloidal form, are suitable for dyeing and printing hydrophobic fibers and
fabrics. Forerunners of the disperse dyes were the ionamine dyes of British
Dyestuffs Corp.; these were N-methanesulfonic acids of aminoazo or
aminoanthraquinone dyes that released the N-methanesulfonic acid group in
the yeing process and, thereby, precipitated as disperse dyes on the acetate
fibers. The understanding of this mechanism in 1923 initiated the
development of genuine disperse dyes. British Celanese and British
Dyestuffs Corp. were the first companies to introduce these dyes into the
market for coloring acetate fibers. The dyes were dispersed with
sulforicinoleic acid, soap, or Turkey red oil [1].
From 1924 to 1930, products of other companies appeared on the
market, initially as pastes; later, when the materials could be dried
successfully without interfering with their dispersibility, they were also
marketed as powders. Since1950, the production of disperse dyes has
increased sharply, closely following the growth in worldwide production of
synthetic fibers, especially polyester [poly(ethylene terephthalate)] fibers,
production ofwhich has grown steadily fromca. 2× 106 t/a in 1970 to about
16 ×106 t/a in 1999 [2]. Furthermore, newdyeing processes necessitated the
development of special disperse dyes. For instance, dyes characterized by
special ease of sublimation are preferred for transfer printing [3]. The
demand for new fastness properties such as thermomigration fastness and
automotive light fastness [4.7] also led to new dyes, as has the ongoing
pressure on market prices.
Models for the dyeing of polyester fibers with disperse dyes have been
developed [8]. When the dye is applied from aqueous medium, it is adsorbed
from the molecularly dispersed aqueous solution onto the fiber surface and
then diffuses into the interior of the fiber. The following parameters determine
the rate of dyeing and, to some extent, the leveling properties: (1) the
dissolution rate during the transition from the dispersed crystalline state of
the dye into the molecularly dispersed phase, and (2) the diffusion rate at the
fiber surface and, especially, in the interior of the fiber. The rates of both
processes vary with temperature.
Differences in geometry and polarity of the dye molecules can lead to
wide variations in these finishing or dye-specific properties and can have a
marked effect on the absorption characteristics of all dyes, irrespective of
whether singlecomponent or combination dyeing processes are used. For
instance, uneven dyeing may occur when an unequal distribution of particle
size results in insufficient dispersion stability and hence crystal growth and
precipitation at the substrate surface.
1
Chemical Constitution:
Industrially applied disperse dyes are based on numerous chromophore
systems. Approximately 60 % of all products are azo dyes, and ca. 25 % are
anthraquinone dyes, with the remainder distributed among quinophthalone,
methine, naphthalimide, naphthoquinone, and nitro dyes [9].
Azo Dyes:
The diazo component is further subdivided where appropriate into aromatic
and heteroaromatic amines.
DisperseDyes:
2-Amino-6-nitrobenzthiazole [6285-57-0] and 2-amino-5,6- or 6,7dichlorobenzthiazole[ 24072-75-1], [25150-27-0] are widely employed to give
scarlet to ruby shades because of their facile accessibility by ring closure of
4-nitrophenylthiourea (e.g., 4) [20] or 3,4-dichlorophenylthiourea,
respectively. In the latter case the resulting mixture of isomers is directly
utilized for diazotization and transformed into the mixture of dye isomers 5.
2
Dyes with aromatic hydroxy compounds as coupling components, of which
C.I. DisperseYellow 3, 11855 [2832-40-8] is a representative
Substitution of the first benzene nucleus by electron acceptors also causes
bathochromic shifts. Disazo dyes of this type such as 6 are frequently
incorporated as components of black mixtures.
Anthraquinone Dyes:
The brilliant red, blue, and turquoise anthraquinone dyes have major
industrial significance. The most important red shades are produced by alkyl
or aryl ethers of 4-amino-1,3-dihydroxyanthraquinone [81-51-6] (7).
Blue and turquoise dyes also play an important role. The most important blue
dyes come from ring- or N-substituted derivatives of the two isomers of
aminodihydroxy- anthraquinone 8 and 9.
3
. The value usually has a range of 12 000.34 000 L mol.1 cm.1 for
anthraquinone dyes, depending on the shade, whereas azo dyes of similar
shade attain values of 30 000.84 000 L mol.1 cm.1. This is the reason why
disperse anthraquinone dyes have been increasingly
displaced by azo dyes. Reviews of this ongoing process are given in [26,
27].Research on new dyes has therefore been concentrated on nonanthraquinoid dyestuffs. The only exception to this is the brilliant blue dye
(49) [28].
Other Chromophores:
employed extensively in a number of product lines used to dye synthetic
fibers in greenish yellow hues with good lightfastness and generally sufficient
sublimationfastness. Suitable substitution in the phthalic acid residue or the
quinoline nucleus may improve thermosetting fastness [29].
Yellow54, 47020 [7576-65-0] (10):
Methine Dyes. The condensation products of 4-dialkylaminobenzaldehydes
with cyanoacetic esters have long been used to dye acetate fibers. Brilliant
greenish yellow dyes with excellent lightfastness are obtained on polyester
fibers with the corresponding condensation products of malonodinitrile. The
sublimation fastness of this dye type can be improved by introducing suitable
substituents into the alkyl residue of the amino group or by doubling the
molecular size, e.g., C.I
4
Brilliant blue dyes such as C.I. Disperse Blue 354, 48480 [74239-96-6] (12)
[32]are produced from aminobenzaldehydes and benzothiophene
derivatives.
By condensation of 2-hydroxy-4,4´-diethylaminobenzaldehydes with
hetarylacetonitriles, 3-heteroaryl-7-diethylaminocoumarins such as 13 and
14 are obtained, which dye polyester fibers fluorescent yellow with a strong
green tint.
C.I. Disperse Yellow 82, [27425-55-4] [33]
C.I.
DisperseYellow332,
55165 [35773-43-4]
5
[34]
Further
condensation with malonodinitrile results in fluorescent red dyes such as
(15).
Red [53272-39-1] [35]
Oxidative cyanation of yellow 3-heteroaryl-4H-7 diethylaminocoumarin dyes
such as 13 and 14 introduces a 4-cyano group and yields fluorescent red
dyes [36]. For example, treatment with NaCN followed by Br2 gives 16.
By elongation of the methine chromophore even brilliant blues such as 17
can be produced. Because of limited fastness properties, this interesting new
dye could not yet pose a threat to anthraquinone dyes.
C.I. Disperse Blue 365 [108948-36-3] [37]
Condensation of mandelic acids and hydroquinone, followed by
oxidation,results in yellow to red polyester dyes [38]. This new chromophore
shows excellent thermo-migration fastness and has been frequently varied to
cover all red shades (e.g., 18) and to improve build up.
Red [79694-17-0] [38]
Naphthalimide Dyes. Derivatives of 4-aminonaphthalimide were used initially
to dye acetate fibers. For polyesters, condensation products of 1,8-
6
naphthalenedicarboxylic acid (e.g., 19) or 1,4,5,8-naphthalenetetracarboxylic
acid [128-97-2] with 1,2-diaminobenzenes are used.
Yellow [15220-29-8]
Indigo Dyes. Whereas indigo itself is not suitable for exhaustion dyeing of
polyester, thioindigo gives fast brilliant red shades in pale to medium depth
[39].Nitro Dyes. 2-Nitrodiphenylamines are readily obtained by condensation
of derivatives of 2-nitrochlorobenzene [88-73-3] with suitable aromatic
amines. product of 1 mol of 3-nitro-4-chlorobenzenesulfonyl chloride [97-085] and 2 mol of aniline. An exhaustive review of the constitution and color of
nitro dyes is given by Merian [40]. The yellow nitroacridones may also be
classified in this group.
C.I. DisperseYellow42, 10338 [5124-25-4]
Yellow [19309-55-8] [41]
Synthesis:
Monoazo Dyes:
7
The synthesis of monoazo disperse dyes by diazotization and coupling is
described under Azo Dyes (see Section 2.2). Additional chemical treatment
subsequent to synthesis of the azo compounds is performed only rarely.
Frequently, weakly basic amines, such as negatively substituted 4nitroanilines or aminoheterocycles, must be diazotized.
By modification of the substituent in the 4-position of the diazo
component,this process yields further 2,6-dicyanoazo dyes, for example, 4methyl- or 4-bromo-2,6-dicyano derivatives, for which the basic diazo
component is otherwise not readily accessible. In this way clear red shades
on polyester can be obtained.
Disazo Dyes:
The simplest route to disazo dyes is by using p-aminoazobenzene [60-9-3].
As paminoazobenzene has been classified in the EU as carcinogenic, the
use of derived disazo dyes like Disperse Red 151, DisperseYellow
7,Disperse Yellow 23, and DisperseYellow56 has diminished.
Anthraquinone Dyes:
For synthesis of anthraquinone dyes, see Sections 2.3 and 3.4.
Other Chromophores:
For synthesis of methin dyes see Section 3.8, and for quinaphtholone dyes
see Section 2.12.1.
Aftertreatment:
Chemical synthesis produces dyes of varying particle size. When the dyes
are applied in this form, uneven and spotty dyeing results, and the dyeing
process may be slow and frequently accompanied by incomplete absorption
[46]. To assure high yield, good reproducibility, and faultless dyeing and
8
printing in commercial
use, especially when densely woven fabric or wound material is involved, the
dye must be applied as a fine dispersion that is stable under the process
conditions.
Examples of Commercially Available Dyes:
Disperse dyes are currently used to dye cellulose 2.5-acetate, cellulose
triacetate,synthetic polyamides, and
polyacrylonitrile and polypropylene.
to
a
lesser
degree,
Monoazo Dyes:
Monoazo dyes derived from aromatic amines as coupling components and
carbocyclic aromatic amines as diazo components are the class of disperse
azo dyes with the greatest economic importance.
C.I. Disperse Orange 44, [4058-30-4] [50]
C.I. Disperse Red 72, 11114, [12223-39-1] [51]
C.I. DisperseBlue 79, 11345, [3956-55-6] [52]
9
C.I. DisperseBlue 165 [41642-51-7] [53]
Representatives of this class are also suitable for dyeing cellulose
triacetate.However, sufficient lightfastness is not obtained on synthetic
polyamides [10].Other industrially important 2,6-dicyanoazo dyes are
obtained
by
using
diethylm-toluidine
and
3diethylaminophenylmethansulfonamide
[52603-47-1]
as
coupling
components (see 23 and 24, respectively).
C.I. Disperse Blue 366 [84870-65-5] [54]
Red [68385-96-6] [55]
By mixing the reddish blue C.I. DisperseBlue 366 with C.I. DisperseBlue 165
[56] or heteroarylazo dyes [57], technically equivalent replacement products
[13] for the anthraquinoid Disperse Blue 56 were obtained. The red dye 24
has been similarly used as a substitute [26] for the anthraquinoid C.I.
Disperse Red 60, 60765 [1741858-5]. With heteroaromatic amines as diazo
component, e.g., the red dye 25, which isan example for the use of the
methanesulfonyl group as an acceptor in azo dyes.
Red [63467-01-6] [58]
2-Amino-5-ethylsulfanyl-1,3,4-thiadiazole [25660-70-2], accessible by
alkylation of bithiourea with diethyl sulfate and ring closure [59], is
10
suitable for the manufacture of bright reds, e.g., 26.
C.I. DisperseRed 338, 111430 [63134-15-6] [60]
2-Amino-4,5-dicyanoimidazole [40953-34-2] can be made by reaction of
diaminomaleonitrile with cyanogen chloride. By coupling with aniline couplers
and alkylating the resultant azo dye precursor bright reds such as 27 are
obtained.
Red [86772-44-3] [61]
3-Amino-5-nitro-2,1-benzisothiazole is manufactured by thiolysis of 2-amino5-nitrobenzonitrile and oxidative ring closure. With aniline coupling
components,shades from navy to greenish blue are obtainable (e.g., 28 and
29).
C.I. DisperseBlue 148, 11124 [52239-04-0] [62]
Blue [105076-77-5] [63]
11
Since the first appearance of thienylazo dyes like DisperseGreen 9 in the
early1970s, this field has been intensely exploited. The interest originates
from the fact that thienylazo dyes are nearly 100 nm more bathochromic than
their carbocycliccounterparts
C.I. DisperseGreen 9, 110795 [58979-46-7] [64]
k = 545 nm e = 46 000 Lmol .1 cm.1 [65]
Furthermore, the Gewald reaction [66] opened a simple and economic route
from aliphatic reactants to aminothiophenes that were formerly only
accessible from multistep reactions [67] (see, e.g., the dye 31). For example,
2-amino-3-carbethoxy- 5-nitrothiophene, a precursor for the dye 32, can be
prepared by reaction of 1,4-dithiane with ethyl cyanoacetate and subsequent
nitration.
Blue [42783-06-2] [68]
Blue [210758-04-6] [69]
Whereas the blue dyes 31 and 32 are claimed to have good thermomigration
fastness, 33, 34, and 35 have superior pH stability and are proposed as
substitutes for bright anthraquinone blues.
12
Blue [104366-25-8] [70]
Blue [122063-39-2] [71]
Blue [167940-11-6]
By combination of the thiophene diazo moiety with a diaminopyridine
coupler,the hue is shifted to a bright red with good lightfastness (36).
Red [ 107815-88-3] [72]
The chemistry and physics of azo dyes based on heterocyclic amines has
been surveyed in many reviews [73.75]. Monoazo dyes with aromatic
hydroxy compounds as coupling components:
Disperse Yellow 3, C.I. 11855 [2832-40-8]
When 2-hydroxynaphthalene [135-19-3] and its derivatives are used as
13
coupling components, clear orange (e.g., 37) and red shades result. Their
commercial importance is minor.
Orange [17947-32-9] [76]
The chemistry of 4-hydroxynaphthalimides as coupling components has
mainly been investigated in Japan. Brilliant reds with good fastness
properties are obtainable (e.g., 38).
Red [ 42357-98-2] [77]
Monoazo dyes with heterocyclic compounds as coupling components:
C.I. DisperseOrange 56 [67162-11-2] [78]
C.I. DisperseYellow5, 12790 [6439-53-8]
By reaction of ethyl acetoacetate with cyanoacetamides, pyridones are easily
accessible. By selection of suitable substituents in the diazo components,
shade and fastness properties and build up can be controlled (e.g., 39.42
and Disperse Yellow211).
14
Greenish Yellow [59312-61-7] [79]
Greenish Yellow [37781-00-3] [80]
Greenish Yellow [88938-37-8] [81]
C.I. DisperseYellow241, 128450 [83249-52-9] [82]
C.I. DisperseYellow211, 12755 [70528-90-4] [83]
Chlorination of 2,6-dihydroxy-3-cyano-4-methylpyridine with phosphorus
oxychloride and successive reaction with amines yields 2,6
diaminopyridines. With these coupling components brilliant orange and red
dyes with excellent lightfastness are obtained (e.g., 43 [4]).
15
Examples of Commercially Available Dyes 153
C.I. DisperseOrange 29, 26077 [19800-42-1] [25]
3.2.5.3 Anthraquinone DyesTurquoise shades are obtained from derivatives
of 1,4-diaminoanthraquinone-2,3-dicarboximide [128-81-4] (47).
Other
Chromophores:
16
Quinapththolones:
C.I. DisperseYellow 64, 42023 [10319-14-9] [86]
C.I. DisperseYellow160 [75216-43-2] [87]
17