Mordant dyes applications

Stannic chloride is also used widely as a catalyst in Eriedel-Crafts acylation, alkylation and cycHzation reactions, esterifications, halogenations, and curing and other polymerization reactions. Minor uses are as a stabilizer for colors in soap (19), as a mordant in the dyeing of silks, in the manufacture of blueprint and other sensitized paper, and as an antistatic agent for synthetic fibers (see Dyes, application and evaluation Antistatic agents). 

The ability of transition metal ions, and especially chromium (as Cr3+), to form very stable metal complexes may be used to produce dyeings on protein fibres with superior fastness properties, especially towards washing and light. The chemistry of transition metal complex formation with azo dyes is discussed in some detail in Chapter 3. There are two application classes of dyes in which this feature is utilised, mordant dyes and premetallised dyes, which differ significantly in application technology but involve similar chemistry. 

The application range designated by this generic name in the Colour Index incorporates those acid, direct and mordant dyes with substantivity for leather and satisfactory fastness on that substrate [55]. It is a commercially important sector, the number of products listed being exceeded only by the complete acid or direct dye ranges. As expected from the sources of this selection, about 85% of leather dyes are azo compounds (35% disazo, 30% monoazo, 20% metal-complex monoazo) and the remainder are mainly yellow to orange stilbene dyes and anthraquinone or triarylmethane types in the violet to green sectors. 

Mordant dyes - [AMINOPHENOLS](Vol2) - [DYES, APPLICATION AND EVALUATION] (Vol 8) -from alizarin [DYES, ANTHRAQUINONE] (Vol 8) -for wool [DYES, APPLICATION AND EVALUATION] (Vol 8)... 

Triarylmethane dyes are derivatives of triphenylmethane and diphenylnaphthylmethane. The presence of one or more primary, secondary, or tertiary amino or -OH groups in the para position to the methane carbon determines the dye color. Halogen, carboxyl, or sulfonic acid substituents also may be present on the aromatic rings. Triarylmethane colorant applications include basic, acid, solvent, and mordant dyes. Major uses are in printing inks. 

Acid dyes include metal-complexed azo structures, where the metals used are cobalt, chromium, and iron.10 Examples are 1 1 and 2 3 chromium complexes and 1 2 cobalt complexes, where the numbers employed represent the ratio of metal atoms to dye molecules. Metal-complexed dyes can be formed inside textile fibers by treating suitably dyed fibers with a solution containing metal ions.11 In this case, the metal-free forms of these azo dyes are known as mordant dyes and contain mainly ortho, ortho -bis-hydroxy or ortho-carboxy, ortho -hydroxy groups (e.g., C.I. Mordant Black 11, Mordant Yellow 8, and Mordant Orange 6). When the metal complexes are formed prior to the dye application process, the resultant dyes are known as... 

The dyeing of cotton fiber is accomplished by three principal processes. Cotton may be chemically reacted with fiber-reactive dyes in solution. The dyeing takes place by reaction with hydroxyl groups in cotton. A second method is the use of substantive dyes that diffuse directly into fiber from a dye solution. The dyeing rate is increased by the addition of electrolytes. The third method is referred to as mordant dyeing in which the dye in solution reacts with metals previously applied to the fiber to form insoluble colored compounds on the cotton. Vat dyes are another important class of dyes for cotton. These are applied in a soluble reduced form and after application they are oxidized, forming an insoluble molecule [8]. 

Dyes are also classified on the basis of their application. The water-soluble dyes which are the salts of sulfonic acid or phenolic compounds are named acid dyes] those which are the salts of amino compounds are called basic. If the dyeing is accomplished without use of mordants the dyes are called direct. Dyes which require the use of metallic oxides, tannin, and other substances to give fast shades are called mordant dyes. The water-insoluble dyes are known as vat dyes. The insoluble colored substance is reduced in a fermentation vat or by hydrosulfite to a soluble form which is applied to the fiber then oxidized by air to the insoluble color. Finally ingrain dyes are produced by performing one or more of the chemical reactions used for the preparation of the dye directly on the fiber. 

There are three general classifications of acid dyes depending on their method of application acid dyes that dye directly from the dyebath, mordant dyes that are capable of forming metallic lakes on the fiber when aftertreated with metallic salts, and premetallized dyes. 

For other major apparel fibers such as wool, silk, and nylon a dye class referred to as acid dyes is routinely used for coloration. Reactive dyes have also been developed for wool and are widely used for fashion apparel items because of their bright, broad color range. A range of mordant dyes is also available for wool and other animal fibers. The mordant dyes provide very high levels of fastness, but the shade range is limited, the shades are typically dull, and the application process is complicated. For acrylic fibers the dominant dye class is the basic dye. For polyester apparel, the insoluble disperse dye range is almost exclusively used. 

Reactive Dyes Reactive dyes are dyes which usually have the basic structure of acid, direct, or mordant dyes but which in addition have a reactive group capable of covalent bond formation with the fiber. Since the fiber must have reasonable reactivity toward the dye reactive group, application of these dyes has been limited to cellulosic, protein, and nylon fibers for the most part. 

There are, of course, many varieties in each of these chemical classifications, so that the result is hundreds of individual dyes each with its own specific characteristics for hue and use on substrates. Dyers have arranged this very complex and large group of chemical products into ten categories arranged by the method of application to the fiber or substrate acid dyes, azoic dyes, basic dyes, direct dyes, disperse dyes, reactive dyes, solvent dyes, sulfur dyes, vat dyes, and mordant dyes. It is in these categories that dyestuffs are discussed in the trade. 

The formulation of dyes with regard to the substrate is critical to successful dye adhesion. Dye formulations have evolved from natural forms to synthetics because the latter offer lower cost, a greater color gamut, and improved performance properties delivered to substrates. Synthetic dyes generally have a strong affinity to substrates to be dyed, but that does not guarantee that adhesion promotion is not required. On the contrary, there are a multitude of dye applications where colorfastness is only possible with the addition of a promoter or mordant (etchant). Each dye must therefore be examined relative to how they are utilized in order to prescribe the most successful protocol for adhesion. 

The mordants may be applied to the substrate either before, during, or after application of the dye. Premordants, as the mordants applied before the dye are known, seem to have been the most commonly used in antiquity. Some mordants not only are instrumental in attaching the dye to the fibers but also alter the shade and even the hue of some dyes a single dye often provides a range of hues when used with different mordants. The color or hue of textiles dyed with madder, weld, and logwood, for example, are determined by the chemical nature of the mordant used Table 95 lists hues obtained when dyeing with the same dye but with different mordants. 

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