Disperse Anthraquinone Dyes

Disperse anthraquinone dyes, 9 321-327 Disperse Blue 1, semipermanent hair dye, 7 857t... 

Anthraquinone Dyes. These dyes have much supeiioi weatheiabihty and heat stabihty compared with the azos, but at higher cost. Typical examples ate Solvent Red 111, Disperse Violet 1, Solvent Blue 56, and Solvent Green 3. 

Dyes may be classified according to chemical stmcture or by thek usage or appHcation method. The former approach is adopted by practicing dye chemists who use terms such as a2o dyes, anthraquinone dyes, and phthalocyanine dyes. The latter approach is used predominantiy by the dye user, the dye technologist, who speaks of reactive dyes for cotton and disperse dyes for polyester. Very often, both terminologies are used, for example, an a2o disperse dye for polyester and a phthalocyanine reactive dye for cotton. 

The appearance of synthetic fibers in the 1920s accelerated the further development of anthraquinone dyes. Soon after British Celanese succeeded in commerciali2ing cellulose acetate fiber in 1921, anthraquinone disperse dyes for this fiber were invented by Stepherdson (British Dyestuffs Corp.) and Celatenes (Scottish Dyes) independendy. Anthraquinone disperse dyes for polyester fiber were developed after the introduction of this fiber by ICI and Du Pont in 1952. These dyes were improved products of the disperse dyes that had been developed for cellulose acetate fiber 30 years before. 

The synthesis of an anthraquinone dye generally involves a large number of steps. For example. Cl Disperse Red 60 [17418-58-5] (10) (Cl 60756) (a typical disperse red dye) requites five steps starting from anthraquinone, and Cl Disperse Blue 56 [31810-89-6] (11) (Cl 63285) requites six steps. 

Efforts have also been made to overcome compHcated processes. Methods to reduce the number of steps or to use new starting materials have been studied extensively. l-Amino-2-chloro-4-hydroxyanthraquinone (the intermediate for disperse red dyes) conventionally requires four steps from anthraquinone and four separation (filtration and drying) operations. In recent years an improved process has been proposed that involves three reactions and only two separation operations starting from chloroben2ene (Fig. 2). 

Anthraquinone-a,a -disulfonic acids and Related Compounds. Anthraquinone-a,a -disulfonic acids and their derivatives are important intermediates for manufacturing disperse blue dyes (via 1,5-, or 1,8-dihydroxyanthraquinone, or 1,5-dichloroanthraquinone) and vat dyes (via... 

In order to develop the dyes for these fields, characteristics of known dyes have been re-examined, and some anthraquinone dyes have been found usable. One example of use is in thermal-transfer recording where the sublimation properties of disperse dyes are appHed. Anthraquinone compounds have also been found to be usehil dichroic dyes for guest-host Hquid crystal displays when the substituents are properly selected to have high order parameters. These dichroic dyes can be used for polarizer films of LCD systems as well. Anthraquinone derivatives that absorb in the near-infrared region have also been discovered, which may be appHcable in semiconductor laser recording. 

There is a wide diversity of chemical structures of anthraquinone colorants. Many anthraquinone dyes are found in nature, perhaps the best known being alizarin, 1,2-dihydroxyanthraquinone, the principal constituent of madder (see Chapter 1). These natural anthraquinone dyes are no longer of significant commercial importance. Many of the current commercial range of synthetic anthraquinone dyes are simply substituted derivatives of the anthraquinone system. For example, a number of the most important red and blue disperse dyes for application to polyester fibres are simple non-ionic anthraquinone molecules, containing substituents such as amino, hydroxy and methoxy, and a number of sul-fonated derivatives are commonly used as acid dyes for wool. 

In a recent study of twenty disperse and solvent dyes, data for water solubility, octanol/ water partition coefficient, entropy of fusion and melting point were subjected to regression analysis. Complicating factors such as impurities, polymorphism, tautomerism, polarisation and hydrogen bonding precluded the development of reliable predictions of solubility and partition coefficient. Anthraquinone dyes exhibited much lower entropy of fusion than many of the azo dyes [64,65]. 

Derivatives of diaminoanthrarufin (3.77 X = Y = H) and its 1,8-dihydroxy-4,5-diamino isomer (diaminochrysazin) have been among the most widely used anthraquinone dyes for ester fibres. For example, methylation of diaminoanthrarufin gives Cl Disperse Blue 26, a mixture of several components. Study of the pure N-alkylated derivatives from the base confirmed that monosubstitution (3.77 X = H, Y = alkyl) gives mid-blue dyes with excellent dyeing properties and acceptable fastness on polyester, but the bis-alkyl dyes (3.77 X = Y = alkyl) are greener and inferior in application properties. Mixtures of the unsubstituted base with alkylated components, as obtained industrially, were especially advantageous for build-up to heavy depths, however [93]. 

Anthraquinone dyes are second only to azo dyes in importance as disperse dyes and are predominant in the red, violet, blue and blue-green sectors [14]. Because anthraquinone disperse dyes are relatively expensive to manufacture, successful attempts were made to replace some of them with technically equivalent and more economical products [15]. The replacement process has been most successful in the red region using, for example, heterocyclic azo dyes and novel chromogens. The brilliance of the anthraquinones with their narrow spectral absorption bands is difficult to attain with other structures, however, as is their high light fastness and chemical stability. The development of anthraquinone disperse dyes is included in a review by Dawson [16]. 

Red Anthraquinone Dyes. All the most important red disperse dyes are based upon a l-amino-4-hydroxy substitution pattern. The bluish red shade of the parent dye. Cl Disperse Red 15, can be shifted hypsochromically by putting an elecuon-donating group in position 2, e.g. the 2-OCH3 (Cl Disperse Red 4), the important 2-OPh derivative. Cl Disperse Red 60 and Cl Disperse Red 91 and Red 92. The synthetic pathway to these red anthraquinone disperse dyes is shown in Figure 2.11. 

Blue Anthraquinone Dyes. All the important blue anthraquinone disperse dyes contain at least two amino groups in either the 1,4- or 1,5-positions, often with two additional hydroxy groups in the 5,8- or 4,8-respectively. The 1,4-substituted compounds are obtained by condensing the reduction product of quinizarin, 1,4-dihydroxyan-thraquinone, often called the leuco form, with the desired amines as shown in Figure 2.12. It should be noted that most anthraquinone disperse dyes are mixtures of products and not single compounds as drawn, a fact beneficial to their dyeing performance on polyester. 

Dichloroanlhraquinonc is an important intermediate for vat dyes and disperse blue dyes. 1.5-Dichloroanlhraquinone is prepared by the reaction of anthraquinone- 1,5-disuifonic acid with NaCIO in hot hydrochloric acid solution. 

Anthraquinone dyes are characterized by the presence of one or more carbonyl groups in association with a conjugated system. These dyes also may contain hydroxy, amino, or sulfonic acid groups as well as complex heterocyclic systems. Anthraquinones uses include disperse, vat, acid, mordant, and fiber reactive applications. 

Baughman (1992) measured the disappearance rate constants for a number of solvent and disperse azo, anthraquinone, and quinoline dyes in anaerobic sediments. The half-lives ranged from 0.1 to 140 days. Product studies of the azo dyes showed that reduction of the azo linkages and nitro groups resulted in the formation of substituted anilines. The 1,4-diaminoanthraquinone dyes underwent complex reactions thought to involve reduction and replacement of amino with hydroxy groups. Demethylation of methoxyanthraquinone dyes and reduction of anthraquinone dyes to anthrones also was observed. 

Solvent dyes [1] cannot be classified according to a specific chemical type of dyes. Solvent dyes can be found among the azo, disperse, anthraquinone, metal-complex, cationic, and phthalocyanine dyes. The only common characteristic is a chemical structure devoid of sulfonic and carboxylic groups, except for cationic dyes as salts with an organic base as anion. Solvent dyes are basically insoluble in water, but soluble in the different types of solvents. Organic dye salts represent an important type of solvent dyes. Solvent dyes also function as dyes for certain polymers, such as polyacrylonitrile, polystyrene, polymethacrylates, and polyester, in which they are soluble. Polyester dyes are principally disperse dyes (see Section 3.2). 

The more intensely colored 1,4-naphthoquinones with amino and/or hydroxyl groups in the 5- and 8-positions are analogous to the commercial anthraquinone dyes, but are generally more bathochromic [10], For example, 5-methylamino-1,4-naphthoquinone has Xmax 529 nm in cyclohexane, whereas 1-methylaminoanthraquinone has Xmax 495 nm. This is also true for the 5,8-disubstituted naphthoquinones, but this potential advantage has not proved of commercial significance, and few such compounds have been considered as textile dyes. An exception is 5-amino-2,3-dichloro-8-hydroxy-l,4-naphthoquinone (4) [68217-33-4], which has been claimed as a violet disperse dye for acetate fibers [14], Naphthazarin (1) is an example of a 5,8-disubstituted naphthoquinone of greater value as an intermediate than as a dyes. 

Disperse dyes vary in the type of chromophore present and include azo, anthraquinone, nitro, methine, benzodifuranone, and quinoline based structures. Examples of the first three types are given in Table 13.4, and representative of the latter three types are C.I. Disperse Blue 354, C.I. Disperse Yellow 64, and C.I. Disperse Red 356. Most disperse dyes have azo ( 59%) or anthraquinone ( 32%) structures. Azo disperse dyes cover the entire color spectrum, whereas the important anthraquinone disperse dyes are mainly red, violet, and blue. The azo types offer the advantages of higher extinction coefficients (emax = 30,000-60,000) and ease of synthesis, and the anthraquinones are generally brighter and have better photostability (lightfastness). The key weaknesses associated with the anthraquinone dyes are their low extinction... 

Disperse dyes are relatively small molecules, with very low water solubility, which possess a high affinity for hydrophobic fibres such as cellulose acetate, polyester or blends thereof. The dyes are applied by transfer printing or high temperature steam fixation. Azo and anthraquinone dyes constitute the major portion of disperse dyes. 

Disperse Orange 76 (Figure 13) is often positive and was thought to be one of the main causes of dye allergy in men, together with Disperse Blue 3 (an anthraquinone dye). 

L.S. Sorokina, G.E. Krichevskiy Effect of physicalstmcture of polyamide and polyester fibres on photodestmction of dispersed azo and anthraquinone dyes. Proceedings of higher schools. Technology of textile industry (1978), No 4, 82-86 (in Russian). 

Examples of anthraquinone dyes are Disperse Blue 3 and Disperse Red 60. These dyes, which are used in the colouration of polyester fabrics, are prepared for the dyeing process as a fine dispersion in water. 

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