Dyes, azoic reactive

Acid dyes Azoic colouring matters Basic dyes Developers Direct dyes Disperse dyes Fluorescent dyes Food dyes Ingrain dyes Leather dyes Mordant dyes Natural dyes Oxidation dyes Pigments Reactive dyes Reducing agents Solvent dyes Sulphur dyes Condense sulphur dyes Vat dyes... 

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. 

Sulfonic Acid-Based Dyestuffs. Sulfonic acid-derived dyes are utilized industrially in the areas of textiles (qv), paper, cosmetics (qv), foods, detergents, soaps, leather, and inks, both as reactive and disperse dyes. Of the principal classes of dyes, sulfonic acid derivatives find utiUty in the areas of acid, azoic, direct, disperse, and fiber-reactive dyes. In 1994, 120,930 t of synthetic dyes were manufactured in the United States, of which 5,600 t were acidic (74). The three largest manufacturers of sulfonic acid-based dyes for use in the United States are BASF, Bayer, and Ciba-Geigy. 

The alternative approach is to pad the fabric with the alkaline naphthol and dry, foUowed by printing directly onto this prepared fabric diazonium salts or stabilized diazonium salts. Coupling is instant and the only further treatment needed is to remove aU the uncoupled naphthol and surface azo pigment in a subsequent washing treatment. Because the choice of colors is limited from one naphthol component, other shades are obtained by using other classes of dye alongside the azoic colors, eg, reactives. This approach is widely used in the production of African prints. 

Heavy metals are widely used as catalysts in the manufacture of anthraquinonoid dyes. Mercury is used when sulphonating anthraquinones and copper when reacting arylamines with bromoanthraquinones. Much effort has been devoted to minimising the trace metal content of such colorants and in effluents from dyemaking plants. Metal salts are used as reactants in dye synthesis, particularly in the ranges of premetallised acid, direct or reactive dyes, which usually contain copper, chromium, nickel or cobalt. These structures are described in detail in Chapter 5, where the implications in terms of environmental problems are also discussed. Certain basic dyes and stabilised azoic diazo components (Fast Salts) are marketed in the form of tetrachlorozincate complex salts. The environmental impact of the heavy metal salts used in dye application processes is dealt with in Volume 2. 

Dyes used Direct, vat, azoic, basic, mordant, pigment, sulfur, and hber-reactive. WOOL... 

Includes azoic dyes and components, fiber reactive dyes, fluorescent brighteners, F.D. C. Colors, mordant dyes, sulfur dyes, and miscellaneous dyes. 

As shown in Table XII, a broad spectrum of fibers have been successfully dyed in the laboratory with a wide variety of dye classes. A significant process advantage as well as energy savings aspect is the observation that in most cases, the fabrics do not need a back-wash to remove unfixed dyestuffs. The unwashed dyed goods meet all commercial standards for crock and wash fastness. The only exceptions to the no back-wash requirement are in the cases of reactive, sulfur, azoic and pre-metalllzed dyes. 

Azo dyes are by far the largest family of organic dyes. They play a prominent role in acid, direct, reactive, azoic, and disperse dye structures, as shown previously, and include structures that cover the full color spectrum. Generally, the synthesis of azo dyes involves a process known as diazo coupling. In this... 

Another approach for removing reactive dye hydrolysates from the fibre and from the wash water (decolourised waste water) is the use of peroxidases (oxidative active enzymes such as Baylase RP). This multipurpose enzymatic rinse process saves time, energy and water but it is restricted mainly to jet applications. The question of the potential toxicity of the resulting aromatic nitro-compounds (cleavage products of the reactive azoic dyes) has to be resolved. 

DANCO FX is a very efficient general-purpose detergent for all fibers which is unaffected by hard water and is stable at temperatures up to the boil in both acid and alkaline solutions. It is a blend of nonionic and anionic surfactants which has been specially compounded for textile use. It is especially useful for soaping fiber reactive, azoic and vat dyes after dyeing or printing and for scouring prior to dyeing. 

The nature of substrate selects the type of dye needed, and methods of dye application. The development of new substrates led to new dyes and dyeing methods and influenced the dyeing technology in a fundamental manner. The dyeing of any substance (e.g., textile fiber) is based on a physico-chemical equilibrium process, namely diffusion and sorption of dye molecules or ions. These processes may be followed by chemical reactions in the substrate, for example, in the application of vat, reactive, azoic, and chrome dyes [9]. 

With regard to cellulosic fibres, the simplest test for the dyes which will probably be present, ignoring unlikely ones such as acid or basic dyes, is to boil for 1 to 2 minutes with a 5 per cent caustic soda solution. If a considerable quantity of colour is stripped a substantive dye is indicated, and it will probably be an azo dye if the colour of the fresh sample is destroyed by boiling for 2 minutes with Formosul G. If, on the other hand, very little or no dye is stripped, the inference is that the material has been dyed with a sulphur, vat, or reactive dye. When boiled for 1 to 2 minutes with Formosul G and a few drops of sodium hydroxide solution, azoic or reactive dyes are virtually stripped. They can, however, be distinguished because only reactive dyes and certain phthalocyanine derivatives, usually recognizable by their distinctive colour, will withstand the following treatment (Giles et. al., J.S.D.C., 1962, 78, 126) ... 

Serviprint [Chonloid) Printing assistants for pigments, vat, disperse, fiber reactive, azoic, and add dyes. 

Most dyes do not chemically react with the cellulose molecule to affix the color. The roles of interchain hydrogen bonding and van der Waals forces in the application of azoic, direct, sulfur, and vat dyes are the physical and chemical effects and are not classical chemical reactions. Tme chemical reaction between cellulose and the dye molecule occurs with reactive dyes, which comprise different chemical types (see Section 9.6.2.3). Such chemical reaction results in covalent bond formation between the dye molecules and the C6 hydroxyl groups of... 

Dye allergens are found in the disperse, acid, azoic, basic, direct, pigment, reactive, solvent, and vat application classes. No dye allergens belong to the mordant and sulfur application classes. Almost 50% of the 70 reported dye allergens are disperse, about 20% are reactive, and 10% are acid. 

In certain cases, identifying the specific garment or textile product and the allergen it contains will be an important undertaking. The fiber content of the fabric will narrow the possible dyes, as certain dyes are used to color certain fibers. Cotton, rayon, and linen fabrics are dyed with direct, fiber-reactive, mordant, azoic, sulfur, and vat dyes. Wool fabrics are dyed with acid, mordant, and fiber-reactive dyes. Polyester fabrics are dyed with disperse dyes unless the polyester is modified to accept basic dyes. Nylon fabrics are colored with acid and disperse dyes unless modified to accept basic dyes. Acrylic fabrics are dyed with basic and disperse dyes. Acetate fabrics are dyed with disperse dyes. Other synthetic fibers are dyed with disperse dyes. 

Such has been the success of reactive dyes over the last thirty years that they seriously rival vat, sulphur, direct and azoic classes with consequent curtail-... 

Note on polyamide (PA) and wool dyes. PA fibres can be dyed with a wide range of dyes, but disperse azoic, acid 1 2 metal complex acid and reactive dyes are mainly used. 

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