GB885457A - Cobaltiferous mono-azo dyestuffs of the benzene-azo-pyrazolone series - Google Patents

Abstract

The invention comprises cobaltiferous dyes of formula <FORM:0885457/IV (c)/1> wherein R1 and R2 are the same or different and each is a hydrogen or chlorine atom or a nitro, alkyl of acetylamino group, R3 is a hydrogen or chlorine atom or an alkyl group and R4 and R5 are the same or different and each is a hydrogen atom or an alkyl group containing not more than four carbon atoms at least one of the <FORM:0885457/IV (c)/2> groups containing at least one such alkyl group. They are prepared by treating a mixture of the corresponding ortho-dihydroxy-azo dyes with a cobalt-yielding agent in a proportion giving a complex with less than 1 atom of cobalt per dyestuff molecule. The process yields a preponderant proportion of the unsymmetrical complex but small amounts of the symmetrical complexes may be formed. The dyes give brown shades on nitrogenous fibres such as wool, superpolyamides and superpolyurethanes. In an example the monoazo dyes 2 - amino - 6 - chlorophenol - 4 - sulphonamide --> 1 - (31 : 41 - dichlorophenyl) - 3 - methyl-5-pyrazolone and 2-amino-4 : 6-dinitrophenol --> 1 - (41 - sulphon - N - methylamido - phenyl) - 3 - methyl - 5 - pyrazolone are prepared by known processes and the mixed dyes treated in aqueous sodium hydroxide solution with cobalt chloride to give the cobalt complexes. Further examples of cobalt complexes and intermediate monoazo dyes are specified.