GB636771A - Disazo dyestuffs - Google Patents

Abstract

A cupriferous disazo dyestuff is manufactured by heating in alkaline solution with an agent yielding divalent copper ions (especially cupric tetrammine ions), until the alkyl groups are split off, the disazo dyestuff obtained by coupling tetrazotized dianisidine in alkaline medium with equimolecular proportions of 1 : 8 : 4 : 6- and 1 : 8 : 2 : 4-aminonaphtholdisulphonic acids. The couplings may be effected simultaneously or successively in either order, but preferably in the order indicated, the first coupling being carried out in mildly alkaline medium and the alkalinity then increased slightly. The coppering may be performed by heating the dyestuff, with or without isolation from the coupling medium, with an aqueous solution of an agent yielding divalent copper ions, e.g. copper sulphate, rendered alkaline, preferably by means of ammonia or ammonium carbonate. The product dyes cellulosic fibres, e.g. cotton or rayon, in greenish-blue tints, the light-fastness of which is substantially unaffected by after-treatment with crease-proofing thermosetting resins.