Verfahren zur Herstellung von in Wasser dispergierbaren, schwer löslichen Azofarbstoffen

The invention comprises dyes of formula where A is a radicle of the benzene series which contains no hydroxy group ortho to the azo group but contains electrophilic substituents in the ortho and/or para position to that group, R1 is an alkyl group of 1-3 C atoms, or a phenyl group which may be substituted, and R2 is H or an aliphatic, cycloaliphatic, araliphatic, heterocyclic or aromatic radicle, which latter has no alkenylsulphonyl groups and the dye is free from water solubilizing groups which dissociate acid in water. The dyes are made in conventional fashion from appropriate benzene diazo, and aminopyrazole coupling, components. Coupling is preferably effected in buffered acid solution. Representative of indicated electrophilic substituents are nitro, trifluoromethyl, cyano, chloro, keto, butyl- and xylyl-sulphonyl, sulpho-dimethyl- and cyclohexyl-amide and morpholide groups. In addition to the electrophilic substituents other groups such as hydrocarbon, ether, acylamino or amino groups may be present in the diazo residue of the dye molecule. Preferably R1 is Me and R2 is an aliphatic, cycloaliphatic or aromatic group. Indicated values for R2 are phenyl, which may be non-ionogenically substituted, alkyl of 1-5 C atoms, which may be substituted, aralkyl, e.g. benzyl, cycloalkyl, e.g. cyclohexyl and furfuryl-(2) radicles. Nucleophilic substituents are preferred for R2 when phenyl, e.g. alkyl of 1-4 C atoms, alkyl-ether of 2-6 C atoms, phenylether and acetyl- and methyl-sulphonyl-amino groups. The dyes are disperse dyes and colour hydrophobic synthetic textile fibres, e.g. cellulose acetate and triacetate, high molecular glycol terephthalates, polyamide and polyacrylonitrile. Colour carriers, e.g. phenylphenol, should be present in the dye-bath. Yellow, orange, red and brown shades are obtained. Examples are provided of the preparation of the dyes and their use in colouring polyester fibres representative of the values for R2 in the products obtained being isopropyl, 1,2-dimethyl-n-propyl, b -hydroxy- and cyano-ethyl, ethyl, a -phenylethyl, cyclohexyl, 21-furfuryl, phenyl, 41-acetylaminophenyl, 31-methoxyphenyl and 11-naphthyl, and some diazo components have a carboethoxy group as an electrophilic substituent which ester value is additional to those indicated above.