Aqueous process for the preparation of linear quinacridones having a reduced particle size

Abstract

A process for the preparation of a quinacridone of the formula: wherein A and B each independently represent a substituent selected from H, F, Cl, C1-C3alkyl and C1-C3alkoxy, including the steps of: (A) heating a reaction mixture containing (a) at least one unsubstituted and/or substituted 2,5-diarylamino-6,13-dihydroterephthalic acid and (b) about 3 to about 10 parts by weight of polyphosphoric acid per part of component (a) to a temperature of above about 125° C. to form a quinacridone melt; (B) treating the quinacridone melt resulting from (A) with about 1% to about 30% by weight, based on the weight of component (a), of concentrated sulfuric acid, to form a reaction mixture; (C) drowning the reaction mixture of (B) in a liquid in which the quinacridone is substantially insoluble; and (D) recovering the resulting quinacridone pigment.

Dependencies are inferred from the claim text.