31 августа, 2015 
Pokraskin Sulfur dyes are a special class of dyes with regard to both preparation and application, and knowledge of their chemical constitution [1]. They are made by heating aromatic or heterocyclic compounds with sulfur or species that release sulfur. Sulfur dyes are classified by method of preparation as sulfur bake, polysulfide bake, and polysulfide melt dyes. Sulfur dyes are not well-defined chemical compounds but mixtures of structurally similar compounds, most of which contain various amounts of both heterocyclic and thiophenolic sulfur.
On oxidation, the monomeric dye molecules cross-link into large molecules by forming disulfide bridges. When a sulfur dye is dissolved by heating with aqueous sodium sulfide solution, the disulfide groups are cleaved to mercapto groups. In this leuco form, the sulfur dye is applied substantively to cotton and other cel — lulosic fibers. The dyeing is oxidized after rinsing, and the dye molecules re-crosslink on the fiber through disulfide groups.
Pseudo sulfur dyes are dyes that can be applied in the same way as sulfur dyes but are not prepared by classical sulfurization.
History. Croissant and Bretonniere found in 1873 that heating sawdust with sulfur-containing substances yielded a dye that could be applied to cotton from an alkaline bath. Such products appeared on the market under the name “Cachou de Laval”, but the true birth of sulfur dyes was in 1893, when Vidal first prepared them by heating well-defined aromatic compounds with sulfur or alkali metal polysulfides. Development then proceeded rapidly. Leopold Cassella & Co. brought Immedial Black V Extra, prepared by the sulfurization of 2,4-dinitro-4′- hydroxydiphenylamine, onto the market in 1897. Priebs and Kaltwasser, working for Agfa in 1899, obtained Sulfur Black T by sulfurizing 2,4-dinitrophenol; this appears to be the highest-tonnage textile dye even today. In 1900, Weinberg and Herz found that valuable blue to violet dyes result when indophenols are melted in aqueous or alcoholic media. The preparation of Hydron Blue from N-(4-carba- zolyl)-p-aminophenol was discovered by Haas and Herz in 1909, and that of Indocarbon from 4-(2-naphthylamino)phenol by Hellmann in 1927. In the years 1934-1937, Hagge and Hagen found lightfast brown dyes based on decacyclene and its nitro derivatives; these were marketed by IG Farben. Working at ICI in 1941, Haddock prepared pseudo sulfur dyes by inserting mercapto or thiocyanate groups into phthalocyanine and perylene tetracarboxylic diimide pigments.
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