GB512618A - Process for the preparation of disazo dyestuffs - Google Patents

Abstract

512,618. Dyes. CHEMICAL WORKS, FORMERLY. SANDOZ. March 7, 1938, No. 7107. Convention date, March 8, 1937. [Class 2 (iii)] Dyes for wool or hair are made by coupling one mol. of the tetrazo compound of 4.4<1>- diamino-diphenyl-3.3<1>-disulphonic acid or of 2.7-diamino-diphenylene-sulphonedisulphonic acid in an acid medium with two mols. of the same or different 2-amino-8-naphthol-6-sulphonic acids of the formula in which R is H, alkyl or an'aryl radicle substituted by alkyl radicles in at least the two vicinal positions, whereby the azo groups enter in o-position to the amino groups. The coupling components may be used in the form of their O-arylsulphonyl derivatives, the arylsulphonic radicles being subsequently split off. R may be vic-xylyl or mesidyl, and the coupling may be carried out in acid solution in presence of sodium formate, sodium acetate, chalk, magnesium carbonate, sulpho-cyanides, xanthogenates or thiosulphates. In examples, (1) benzidine-3.3<1>-disulphonic acid sodium salt is tetrazotised and coupled with 2-amino-8- hydroxynaphtholene-6-sulphonic acid, or its 0-toluene-sulphonyl derivative' followed by saponification (violet shades on wool or hair), or with 2-mesidylamino-8-hydroxynaphthalene- 6-sulphonic acid (blue shades) ; (2) 2.7 diaminodiphenylenesulphone-disulphonic acid is tetrazotised and coupled with 2-amino-8-hydroxygraph-thalene-6-sulphonic acid (blue shades). The O-toluene-sulphonyl derivative of 2 amino-8-hydroxy-naphthalene-6-sulphonic acid is obtained by treating an alkaline solution of 2 - acetylamino - 8 - hydroxy - naphthalene - 6- sulphonic acid with p-toluene-sulphonyl chloride, followed by boiling the product with dilute mineral acid. Specification 13743/96, [Class 2], is referred to.