Patent ID: 6031100
Filing Date: 2000-02-29
Classification: C09B

Abstract:
A process for the preparation of quinacridone pigments comprising(a) exposing a reaction mixture comprising(i) 2,5-dianilinoterephthalic acid, 2,5-dianilino-3,6-dihydroterephthalic acid, 2,5-dianilino-3,6-dioxo-1,4-cyclohexadiene-1,4-dicarboxylic acid, or a derivative thereof having one or more substituents in at least one aniline ring; a salt or ester of said acid or derivative thereof; or a mixture thereof,(ii) about 3 to about 20 parts by weight, per part of component (a)(i), of a dehydrating agent, and(iii) 0 to about 20 parts by weight, per part of component (a)(i), of a pigment additive,to microwave radiation at power levels and exposure times that raise the bulk temperature of the reaction mixture to no more than about 250.degree. C., with the proviso that if component (a)(i) is a 2,5-dianilino-3,6dihydroterephthalic acid or derivative thereof, reaction step (a) additionally comprises an oxidation step;(b) drowning the reaction mixture from step (a) by adding said reaction mixture to about 3 to about 15 parts by weight, per part of component (a)(i), of a liquid in which the quinacridone pigment is substantially insoluble;(c) isolating the quinacridone pigment; and(d) optionally, conditioning the quinacridone pigment.