Patent GB-431598-A (GB)
Title: Manufacture of new chromiferous dyestuffs
IPC: C09B45/01
Filed: 1934-04-17
Abstract: Azo dyes, soluble chromium compounds of: dye mixtures: acid wool dyes, dyeing with.--An azo dyestuff of the general formula <FORM:0431598/IV/1> in which R1 is a naphthalene radicle, R2 is a naphthol radicle, N is 1, 2 or 3 and the hydroxyl group is in o-position to the azo group, or a mixture of chromable azo dyestuffs of which at least one is of this general formula, is chromed by treatment with an alkaline solution of chromium oxide in quantity such that there is less than 1 atom of chromium for each chromable group in the dyestuff or mixture of dyestuffs.  The production and chroming of the azo dyestuff may be effected in a single operation. The following examples are specified: (1) 416 parts of the dyestuff 1 : 2-aminonaphthol-4-sulphonic acid --> 1-naphthol, are stirred into a potassium hydroxide solution of 444 parts of a fresh 12 per cent chromium hydroxide paste and the mixture is heated for 6--8 hours at 74--78 DEG  C., diluted with water, neutralized with dilute mineral acid and filtered and the filtrate is either evaporated to dryness in vacuo or concentrated in vacuo and the dyestuff salted out therefrom; (2) a paste containing 204 parts of the dyestuff, 1 : 2-aminonaphthol-4-sulphonic acid --> 2-naphthol, is added to a solution in 30 per cent caustic soda of 203 parts of a chromium hydroxide paste containing 15 per cent of Cr2O3, and the whole is heated for 7--8 hours at 75--78 DEG  C., diluted with water, neutralized with dilute mineral acid, feebly acidified with acetic acid and filtered and the dyestuff is salted out from the filtrate; the product dyes wool fast navy blue tints form an acid bath; (3) 83,2 parts of the dyestuff, 1 : 2 - aminonaphthol - 4 - sulphonic acid --> 1-naphthol and 83,2 parts of the dyestuff 1 : 2-aminonaphthol-4-sulphonic acid --> 2-naphthol, are stirred into a solution in caustic soda lye of a mixture of potassium hydroxide and a chromium hydroxide paste containing 21,3 parts of Cr2O3, the mixture is heated for 6--8 hours at 75--78 DEG  C. and the product is extracted as in (1) or (2); it dyes wool fast navy blue tints; alternatively, the coupling of the diazo compound with both coupling components may be effected in potassium chromite solution; (4) 124,8 parts of the dyestuff, 1 : 2-aminonaphthol-4-sulphonic acid --> 2-naphthol, and 40,2 parts of the dyestuff, 1-oxy-2-amino-4-methylbenzene-5-sulphonic acid --> 2-naphthol, are stirred into a potassium hydroxide solution of 174 parts of a chromium hydroxide paste containing 14 per cent of Cr2O3 and the mixture is heated for 4--6 hours at 75--78 DEG  C., diluted, neutralized with mineral acid and filtered and the dyestuff is salted out from the filtrate; the product dyes wool fast navy blue tints from a bath containing organic acid and sulphuric acid.  Examples are also given of the dyeing of wool from a sulphuric acid bath with the dyestuff of (2), from a formic acid-sulphuric acid bath with the dyestuff of (3) and from a sulphuric acid-benzenesulphonic acid bath with the dyestuff of (2) and of the dyeing of ordinary or loaded silk from an acetic acid bath with the dyestuff of (2).  Specifications 364,148 and 408,497 are referred to.