GB403105A - The manufacture of azo dyestuffs - Google Patents

Abstract

Direct cotton dyeing azo dyes are made (1) by linking two molecules of the azo dyes derived from diazotised 4 : 4<1>-nitroaminostilbene-2 : 2<1>-disulphonic acid or the corresponding dibenzyl compounds, by a suitable conversion of their nitro groups, e.g. by reduction to azo or azoxy groups or by conversion into the group -NH-X-NH- where X = a bivalent radicle, such as -CO- or cyanuryl or (2) by linking two molecules of the 4: 4<1>-nitroaminostilbene- or dibenzyl-: 2<1>-2 disulphonic acid itself, tetrazotising the intermediate product thus obtained e.g. the dinitrodistilbeneureatetrasulphonic acid or the diaminoazoxydistilbenetetrasulphonic (if necessary after reduction) and coupling with suitable components. The dyestuffs may be after-treated e.g. by oxidation, reduction, alkylation or formation of metallic complexes. The following examples are given: (1) the dyestuff 4 : 4<1>-nitroaminostilbene - 2 : 2<1> - disulpho acid--> salicylic acid is reduced with caustic soda and dextrose to the azoxy compound; the same product is obtained by reducing the nitroaminostilbenedisulphonic acid to the azoxy stage, tetrazotising and coupling with salicylic acid, (2) the monoazo dyestuff in (1) is reduced with sodium sulphide and phosgenated, (3) the dyestuff 4 : 4<1>-nitroaminostilbene-2 : 2<1>-disulphonic acid-->N-phenyl J acid or N-(4<1>-hydroxy-3<1>-carboxy)-phenyl J acid is reduced as above, (4) the monoazo dyestuff in (3) is reduced with sodium sulphide and phosgenated, (5) the methylated or ethylated dyestuff 4 : 4<1>-nitroaminostilbene-2 : 2<1>-disulpho acid-->phenol is reduced with caustic soda and dextrose or with caustic soda alone, (6) the monoazo dyestuff of (5) is reduced with sodium sulphide and phosgenated, (7) and (8) the dyestuff 4 : 4<1>-nitroaminostilbene-2 : 2<1>-disulpho acid-->acetoacetic anilide is reduced with caustic soda and destrose to the azoxy compound or with sodium sulphide and treated with phosgene, (9) cyanuric chloride is condensed with 4 : 4<1>-nitroaminostilbene-2 : 2<1>-disulpho acid and the product is reduced, tetrazotised, coupled with phenol, and finally methylated; the same dyestuff is obtained by reducing the methylated dyestuff 4 : 4<1>-nitroaminostilbene-2 : 2<1>-disulpho acid and condensing with cyanuric chloride, (10) diaminoazo-distilbene-tetrasulphonic acid (by reduction of 4 : 4<1>-nitroaminostilbene-2 : 2<1>-disulpho acid with zinc dust and oxidation of the hydrazo-compound formed) is tetrazotised and coupled with phenol and the product methylated, (11) the reduced and methylated dyestuff 4 : 4<1>-nitroaminostilbene-2 : 2<1>-disulpho acid-->phenol is refluxed with the unreduced dyestuff in caustic soda; the product is practically identical with that of (10), (12) the methylated azo dyestuff 4 : 4<1>-nitroaminostilbene-2 : 2<1>-disulpho acid -->1-naphthylamine-7-sulpho acid-->phenol is reduced with caustic soda and glucose. Dyeings with the above dyestuffs may be after-treated with metal compounds e.g. copper sulphate.