GB461884A - Improvements in the manufacture and production of azo dyestuffs - Google Patents

Abstract

Azo dyes are made by coupling 5 : 6-dihydro1 : 3-dihydroxybenzenes or cyclohexane-1 : 3-diones with diazotized aromatic amines which contain in o-position to an amino group a carboxylic, carboxylic ester, hydroxy or alkoxy group and, if desired, treating the resulting dyestuffs with agents supplying metals in substance or on the fibre. In examples, dyes from the following components are described: diazo components; 4 : 6-dinitro-2-aminophenol, 4-nitro-2-aminophenol, 6-nitro-2-aminophenol-4-sulphonic acid, 4 - nitro - 2 - aminophenol - 6 - sulphonic acid, 2 - aminophenol - 4 - sulphonic acid, 4-chlor-2-aminophenol-6-sulphonic acid, 1-amino-2-naphthol-4-sulphonic acid, 2-amino-5-sulphobenzoic acid, anthranilic acid, 4-nitro-1-amino-2-benzene carboxylic acid and 5-nitro-2-aminoanisole-4-sulphonic acid: coupling components; 5 : 6-dihydro-1 : 3-dioxybenzene and 4 - methyl - 5 : 6 - dihydro - 1 : 3 - dioxybenzene. The dyeings may be after-chromed or the dyes may be applied to wool with ammonium chromate by the single-bath process. Brown shades are generally obtained. The complex chromium and copper compounds also dye wool and leather in brown and violet shades whilst the dyes from diazotized o-amino carboxylic acids yield yellow shades. Samples have been furnished under Sect. 2 (5) of the dyestuffs: (1) 4 - nitro - 2 - aminophenol - 6 - sulphonic acid --> 4-o -phenylethyl-5 : 6-dihydro-1 : 3-dioxybenzene (brown-red on wool becoming yellow-brown on after-chroming); (2) anthranilic acid n-butyl ester --> 5 : 5-dimethylcyclohexane-1 : 3-dione (colours nitrocellulose ester lacquers yellow). 5 : 6-Dihydro-1 : 3-dioxybenzene and its alkyl or aralkyl derivatives are obtainable by catalytic hydrogenation of the corresponding 1 : 3-dihydroxybenzenes in the presence of at least one molecular equivalent of strongly basic substances, e.g. alkali metal hydroxides.