GB491019A - Improvements in the manufacture and production of azo dyestuffs - Google Patents

Abstract

Azo dyes are made by treating disazo dyes of the formula A-N=N-B-N=N-C (in which A is the residue of salicylic acid or a derivative thereof, B is the residue of an aromatic middle component and C is the residue of an aromatic amine coupled in p-position to the amino group) with phosgene, or by coupling tetrazotized aromatic amines of the general formula D-NH-CO-NH-D (in which D is the residue of a diazotizable aromatic amine containing the amino group in p-position to the urea group) with two molecular proportions of a diazotizable amine, again tetrazotizing and coupling with two molecular proportions of salicylic acid or a derivative thereof, and in each case the initial materials being so selected that the final dyestuff contains at least two sulphonic groups. They dye vegetable fibres or regenerated cellulose red to violet-brown shades and may be used in admixture with acid wool dyes for dyeing mixed materials, the dyeings preferably being after-treated with metal salts. In an example, the dyestuff p-aminosalicylic acid or o-amino-p-cresotinic acid --> 1-naphthylamine - 7 - sulphonic acid --> m-toluidine is treated with phosgene. A sample has been furnished under Sect. 2 (5) of the dyestuff; 4 : 41 - diaminodiphenylurea \sQ 1 - naphthylamine-7-sulphonic acid \sQ salicylic acid. According to the Provisional Specification the urea made by treating the amine capable of coupling with phosgene is coupled with the corresponding diazoazo compound (2 mols.).