GB774925A - New monoazo dyestuffs derived from cyanuric chloride - Google Patents

Abstract

The invention comprises dyestuffs, which in their free acid form, are of formula <FORM:0774925/IV(b)/1> where A may contain substituents other than OH and NH2 groups, R is H or alkyl and one of X1 and X2 is H and the other SO3H. They are made by condensing equivalent quantities of cyanuric chloride and the appropriate naphthalene - azo - benzene dyestuff, preferably in an aqueous medium at below 5 DEG C. When the rate of reaction is slow an excess of cyanuric chloride may be used. To avoid side reactions the dyestuffs are isolated at a pH of 6 to 8 and dried at 20-40 DEG C., preferably in the presence of buffering agents which maintain a pH of about 6.5 e.g. mixtures of disodium hydrogen phosphate with sodium or potassium dihydrogen phosphate. The starting azo dyestuff may be made by diazotising 2 - naphthylamine - 4, 8 - or - 6, 8 - disulphonic acids and coupling them with appropriate primary or secondary amines e.g. in aqueous acid medium, or with N - (o - sulphomethyl) - derivatives of the amines with subsequent removal of the N - o - group by alkaline hydrolysis. Specified amines are aniline, o- and mtoluidine and anisidine, 2, 5 - dimethyl - and - dimethoxy - anilines, 3 - amino - 4 - methoxytoluene and N - methyl - and -ethyl - aniline, - o - and m - toluidines, - cresidine and - m - anisidine. The dyestuffs, as their alkali metal salts, yield orange colours on cellulosic textile material e.g. when they are impregnated with a solution of the dyestuff and after treated with an acid-binding agent such as caustic soda in an aqueous medium containing an electrolyte such as sodium chloride or sulphate or when printed with a paste containing the dyestuff and a substance such as sodium bicarbonate, which on subsequent heating or steaming liberates an acid-binding agent. When R is an alkyl group the dyeings or prints show little shade change when dotted with alkali. Examples are provided of the preparation of the dyestuffs and their use in dyeing cotton, cresidine being an amine used in addition to certain of those specified above. Specification 209,723 [Class 2(iii)] is referred to.