GB428965A - Manufacture of chromiferous azo-dyestuffs - Google Patents

Abstract

Chromiferous azo dyestuffs are made by heating in an aqueous medium with an alkali salt which is not hydrolyzed or is only slightly hydrolyzed in aqueous solution a mixture of an azo dyestuff of the general formula <FORM:0428965/IV/1> (wherein the hydroxy and the azo groups are in o-position, n = 1--3 and the naphthalene residue contains no further substituents and R = a naphthol residue) and a complex chromium compound of such a dyestuff. They dye wool in fast navy blue tints which are uniform when dyed in deep shades; the dyeing processes of Specifications 364,148 and 408,497 may be used. In examples the chromed dyestuff 1-amino-2-naphthol-4-sulphonic acid --> a - or b -naphthol is heated with the unchromed dyestuff in an aqueous solution containing sodium sulphate or sodium acetate. Examples of the dyeing of wool are also given. Specifications 297,331, [Class 2 (iii)], and 384,767 also are referred to. The Specification as open to inspection under Sect. 91 comprises also chromiferous azo dyestuffs made from mixtures of chromed and chromable azo dyestuffs which mixtures contain at least one dyestuff of the above formula whether chromed or unchromed. An example of the dyeing of silk is also given. This subject-matter does not appear in the Specification as accepted.