DISAZOVERBINDUNGEN UND DIESE DISAZOVERBINDUNGEN ENTHALTENDEN ZUBEREITUNGEN

Disazo compounds based on 4,4'-diaminodiphenyl compounds contain not less than 50% by weight of a disazo compound of the general formula A-N=N-Z-N=N-B (I) where Z is a radical of an unsubstituted of symmetrically substituted diphenylene, A is a radical of a coupling component of a 1-phenylpyrazolone or of an acetoacetarylide, where the phenyl and the aryl radical is substituted by sulfo or carboxyl groups, and B is a radical of a coupling component based on 1-phenylpyrazolone or acetoacetarylide, which are free of sulfo and/or carboxyl groups. The disazo compounds can be obtained by coupling the tetrazotized diamine H2N-Z-NH2 to the coupling component AH containing an acidic group in a medium containing a mineral acid, and then coupling the product to BH in a buffered medium (pH about 4). The novel disazo compounds are suitable as additives to pigments, in particular azo and disazo pigments, for improving the transparency and heat stability of the pigment particles, and the flow behavior.