Dyeing classes

Dyeing accelerants Dyeing classes Dyeing of leather Dyeing paper Dyeing processes Dye initiators Dye-in-polymer systems Dye intermediates... 

The hterature on polymethine dyes has been reviewed (3,4,7,9—11,21). Reference 3 is the best among recent (1995) sources on the chemistry and spectral properties of this dye class it also contains a large bibhography. 

The range of colors covers all hue classification groups except a tme red. As a rule, the hues are dull compared with other dye classes. Black is the most important, followed by blues, oHves, and browns (see Dyes and dye intermediates). 

The carbocychc azo dye class provides dyes having high cost-effectiveness combined with good all-around fastness properties. However, they lack brightness, and consequendy, they cannot compete with anthraquinone dyes for brightness. This shortcoming of carbocychc azo dyes is overcome by heterocychc azo dyes. 

In 1923, the first disperse dye was developed for dyeing cellulose acetate fibers. However, in recent years the most important appHcation of disperse dyes has been to dye polyester fibers. Accompanied by the rapid growth of polyester fibers after World War II, disperse dyes have currendy achieved the largest production among all dye classes in terms of quantity (106). 

Anthraquiaone vat dyes have been used to dye cotton and other cellulose fibers for many decades. Despite their high cost, relatively muted colors, and difficulty ia appHcation, anthraquiaone vat dyes stUl form one of the most important dye classes of synthetic dyes because of their all-around superior fastness. 

Benzanthrone Pyrazolanthrones andBenzanthrone Acridones. Ben2anthrone pyra2olanthrones give from navy blue to gray shades and have good fastness. However, the only example of industrial use is Cl Vat Black 8 [2278-50-4] (141) (Cl 71000). Cl Vat Blue 25 [6247-39-8] (Cl 70500) has the basic stmcture of this dye class, but it is not produced today. 

Acylaminoanthraquinones. This dye class consists mainly of ben2oyl derivatives of aminoanthraquinones. Due to the relatively low molecular weight, this dye class is appHed in dyeing at low temperature. Yellow, orange, red, and even violet colors are covered by acylamino anthraquinones. 

Anthraquinone dyes have been produced for many decades and have covered a wide range of dye classes. In spite of the complexity of production and relatively high costs, they have played an important role in the areas where excellent properties ate requited, because they have excellent lightfastness and leveling properties with brUhant shades that ate not attainable with other chtomophotes. However, recent increases in environmental costs have become a serious problem, and future prospects for the anthraquinone dye industry ate not optimistic. Some traditional manufacturers have stopped the production of a certain dye class or dye intermediates that were especially burdened by environmental costs, eg, vat dyes and their intermediates derived from anthraquinone-l-sulfonic acid and 1,5-disulfonic acid. However, several manufacturers have succeeded in process improvement and continue production, even expanding their capacity. In the forthcoming century the woddwide framework of production will change drastically. 

Consumption. Anthraquinone dyes are the most important dye class after azo dyes. Wodd textile production is estimated in Table 14. Estimates of the consumption of dyes for textiles ate given in Figure 14, together with the figures for fiber consumption. This shows that the consumption of each dye class or classes is approximately parallel to the consumption of fibers to which they ate apphed. 

Among these dye classes, anthraquiaone dyes are ia an important position ia reactive dyes and vat dyes for cellulose fibers, disperse dyes for polyester, and acid dyes for polyamide. Application for high performance organic pigments for plastics and paints are also important areas. 

Azoic Dyes. These are used to produce cost-effective heavy yellow, orange, red, maroon, navy blue, brown, and black shades and are ptinted alongside other dye classes to extend the coloristic possibiUties for the designer. Two approaches are adopted. The common method ia the United States is to use both a naphthol derivative and a stabilized color base, usually in the form of a diazo imino compound in the same print paste. This mixture is soluble in dilute caustic soda and no coupling takes place at this stage. The dried prints are passed through steam at 100—105°C that contains acetic and/or formic acid vapor. As neutralization takes place on the print, the coupling occurs rapidly and the insoluble azoic dye is formed. 

Dye Combinations. In certain cases it is desirable to print fiber blends with combiaations of the appropriate dye classes, rather than with pigments. Only polyester—ceUulose blends are of commercial importance and the foUowing dye systems have been developed for them. The dyes of the different classes are contained in the same print paste and, therefore, are appUed simultaneously in one print operation. 

Theoretically, the dye or chromogen can be any colored species. Of course, requirements for fastness, solubiUty, tinctorial value, ecology, and economy must be met. Most commonly used chromophores parallel those of other dye classes. Azo dyes (qv) represent the largest number with anthraquiaone and phthalocyanine making up most of the difference. Metallized azo and formazan dyes are important and have gained ia importance as a chromophore for blue dyes duriag receat years (6) (see Dyes and dye intermediates). 

A useful classification of sensitizing dyes is the one adopted to describe patents in image technology. In Table 1, the Image Technology Patent Information System (ITPAIS), dye classes and representative patent citations from the ITPAIS file are Hsted as a function of significant dye class. From these citations it is clear that preferred sensitizers for silver haUdes are polymethine dyes (cyanine, merocyanine, etc), whereas other semiconductors have more evenly distributed citations. Zinc oxide, for example, is frequendy sensitized by xanthene dyes (qv) or triarylmethane dyes (see Triphenylmethane and related dyes) as well as cyanines and merocyanines (see Cyanine dyes). 

Neady every significant class of dyes and pigments has some members that function as sensitizers. Toxicological data are often included in surveys of dyes (84), reviews of toxic substance identification programs (85), and in material safety data sheets provided by manufacturers of dyes. More specific data about toxicological properties of sensitizing dyes are contained in the Engchpedia under the specific dye classes (see Cyanine dyes Polymethine dyes Xanthene dyes). 

CHAPTER 12 Auxiliaries associated with main dye classes... 

More detailed information on attempts to reduce the impact of electrolytes on the environment is given under the individual dye classes discussed in Chapter 12. 

The aim in this chapter is to summarise the properties of auxiliaries normally used with each of the main dye classes. Where these agents have been dealt with earlier, the emphasis here is on application behaviour. Chemical details are included, however, for those auxiliaries that have not yet been mentioned emphasis is given to the auxiliaries used rather than to processing details. 

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