Patent ID: 6284890
Filing Date: 2001-09-04
Classification: C09B

Abstract:
A process for the preparation of a quinacridone of the formula: ##STR3##wherein A and B each independently represent a substituent selected from H, F, Cl, C.sub.1 -C.sub.3 alkyl and C.sub.1 -C.sub.3 alkoxy, said process comprising:(A) heating a reaction mixture containing (a) at least one unsubstituted and/or substituted 2,5-diarylaminoterephthalic 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.degree. 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.