GB749142A - Improvements in or relating to chromium-containing disazo dyestuffs - Google Patents

Abstract

The invention comprises chromium-containing dyestuffs which in the metal-free state are of formula <FORM:0749142/IV(c)/1> where R is a residue of the benzene or <FORM:0749142/IV(c)/2> naphthalene series, is a residue of the hydroxynaphthalene or pyrazolone series and the OH-group of R2 is ortho to -azo-. The dyestuffs are made by treating the unmetallized dyestuffs with chromiumyielding agents preferably so that for 2 molecules of disazo compound less than one atom, e.g. 0.5-0.7 atoms, of metal are used. Chroming may be effected at elevated temperature in aqueous solution or magnesium in an organic medium, e.g. in a melt of an alkali metal salt of a low molecular weight aliphatic monocarboxylic acid. Specified chromium-yielding agents are chromic fluoride, sulphate, formate and acetate, potassium chromium sulphate and sodium and potassium chromates and bichromates. Preferably dyestuffs are obtained which have one atom of chromium per 2 molecules of disazo dyestuffs. Wool, silk, synthetic polyamide fibres and leather are dyed from neutral to weak acid baths in yellow, orange, brown, olive or grey shades. In Examples chromium complexes are made from dyestuffs prepared from the following diazo components 3-amino-4-hydroxy-1, 11-azobenzene, 3-amino-4-hydroxy-2, 31-, - 2, 41- and 2, 51-dimethyl-, -41methyl-, methoxy-, -ethoxy-, nitro- and -tert-amyl-, -31-chloro-, 21, 41, 6-trimethyl, -21-bromo-41-nitro-and 21-methyl-41-chloro-1-, 11-azobenzene and 1 (31 - amino - 41 - hydroxy) - benzene - azonaphthalene and the following coupling components 2-hydroxy-naphthalene-4-, -6- and -7-sulphonic acid, 1-hydroxy-naphthallene - 4 - sulphonic acid and 1 - phenyl - 3-methyl-5-pyrazolone-31- and -41-sulphonic acid. In the examples chroming is also effected with ammonium chromium sulphate and further may be effected in the presence of salicylic acid under alkaline conditions.