Azo dyestuffs containing an amino-pyrazole residue which are sparingly soluble in water, and their use

摘要

The invention comprises sparingly water-soluble azo dyestuffs containing no water-solubilizing groups which dissociate acid in water of the formula wherein A represents a phenyl radical which contains at least one nitro group in o- or p-position to the azo bond, B represents an optionally substituted phenyl or naphthyl radical and R represents a C1-C4 alkyl group. They may be obtained by coupling the diazonium compound of an aromatic amine of the formula with a coupling component of the formula Further substituents which may be present in the phenyl radical A are nitro, trifluoromethyl, cyano, halogen C2-C4 alkanoyl, aroyl, carboxylic acid ester, N-unsubstituted or substituted sulphonic acid amide or carbamyl or sulphamyl, or alkylsulphonyl or arylsulphonyl groups. Substituents in the phenyl or naphthyl radical B are for example halogen, C1-C4 alkyl, C1-C4 alkoxy, acylamino, sulphonic acid aryl ester or sulphonic acid amide groups substituted on the N atom by alkyl. The diazotization may be performed by using nitrosyl sulphuric acid. The coupling is preferably performed in an acid to weakly acid medium. The dyestuffs are suitable for dyeing of hydrophobic, synthetic organic fibres from an aqueous dispersion, for example for dyeing of textile materials such as cellulose di- or triacetate or polymeric esters of aromatic polycarboxylic acids with polyvalent alcohols, mainly polyglycol terephthalates. They are also suitable for dyeing synthetic polyamide fibres such as nylon. Polyester fibres are dyed with aqueous dispersions of the dyestuffs at temperatures of over 100 DEG C. under pressure, or at 100 DEG C. in the presence of carriers or by the pad dyeing process. Dyeings on polyglycol terephthalate fibres give an orange shade.ALSO:Pyrazoles of the formula:- wherein B represents an optionally substituted phenyl or naphthyl and R represents a C1-C4 alkyl radical; are obtained by reacting an alkanol corresponding to R with a cyanoacetic acid hydrazide of the formula B-HN-NH-CO-CH2-CN in the presence of hydrogen chloride. The compounds are useful as intermediates in the preparation of dyestuffs (see Division C4).