Process for the preparation of organic pigments

Abstract

This invention relates to a process for the preparation of quinacridone pigments comprising (a) heating, at a temperature of about 80.degree. C. to about 145.degree. C., a reaction mixture comprising (i) 2,5-dianilinoterephthalic acid or a 2,5-dianilinoterephthalic acid derivative having one or more substituents in at least one aniline ring, (ii) about 2 to about 10 parts by weight, relative to component (i), of a strong acid, and (iii) at least about 0.4 mole percent, relative to component (i), of iron in the form of an iron salt; (b) drowning the reaction mixture from step (a) by adding said reaction mixture to about 3 to about 15 pads by weight, relative to component (i), of a liquid in which the pigment is substantially insoluble; (c) isolating the quinacridone pigment; and (d) optionally, conditioning the quinacridone pigment.

Dependencies are inferred from the claim text.