Dyes, azoic direct

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. 

For the present purpose anionic dyes are classified as those containing sulfonic acid groups or those capable of solubilization in alkali, such as vat dyes. Such dyes are usually applied to fibres with hydrophilic character such as cotton, which is still the most important single fibre from a point of view of world usage, nylon and wool. Azoic dyes and direct dyes, although economically important, will not be discussed. Pigments, which are sometimes used in cotton printing, are treated separately. 

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

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... 

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... 

Ammonium persulfate Arsenic trioxide dye, animal Sodium arsenate dye, anodized aluminum Acid violet 49 dye, aq. inks Direct green 1 dye, aq. writing inks Direct blue 1 dye, azoic acetate 2-Methoxy-5-nitroaniline dye, azoic cotton 2-Methoxy-5-nitroaniline dye, azoic nylon 2-Methoxy-5-nitroaniline dye, azoic silk 2-Methoxy-5-nitroaniline dye, basic acrylic fiber Basic blue 9 Basic green 4 dye, basic bast Basic orange 14 dye, basic cotton Basic brown 1 dye, basic leather Basic blue 9 Basic violet 10 dye, basic paper Basic violet 10 dye, basic silk Basic orange 14 dye, basic textiles Basic brown 1 dye, bast... 

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 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. 

Depolymerised Carpet printing/dyeing acid, metal-complex dyes Cotton, viscose vat, direct, azoic dyes Polyester disperse dyes Nylon acid, metal-complex dyes Acrylic fibres basic dyes... 

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. 

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... 

Properties Tenacity, 3-6 g/denier (dry), 4—8 g/de-nier (wet) elongation 3-7% d 1.54 moisture regain 7% (21C, 65% relative humidity) yellows slowly at 121C decomposes at approximately 148C low permanent set decomposed by acids swells in caustic but is undamaged. Soluble in cuprammonium hydroxide. Subject to mildew. May be dyed by direct, vat, azoic, sulfur, and basic dyes. Combustible. 

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-... 

Diffusion has been studied most extensively with relatively simple dyes such as anionic sulphonated azo dyes from the levelling acid and direct classes. Also a considerable amount of work has been carried out with reactive dyes, despite the fact that they eventually become immobilised by chemical reactions with the fibre. Other types of reactions, particularly those involving large increases in the relative molecitlar mass of dyes, make studies of diffusion behaviorrr even more complicated. As a consequence, little work has been carried out with chrome, vat, sulphur and azoic dyes. ... 

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