2,5-Dianilinoterephthalic acid → Quinacridone

Participants

Reaction Conditions

Reaction Steps

382 parts of polyphosphoric acid containg 85.0% P2O5 are metered into a pressure vessel. Then 64.9 parts of 2,5-dianilinoterephthalic acid and 11.5 parts of 2,5-di-(4-toluidino)terephthalic acid are introduced with stirring at from 80 to 90° C. and the mixture is heated at 125° C. for 1 hour, during which ring closure takes place to form the quinacridone. The reaction mixture is subsequently metered into a second pressure vessel and is hydrolyzed under pressure and with stirring with a mixture of 1721 parts of 30% strength phosphoric acid at 140° C. In the course of hydrolysis the temperature rises to 155° C. The mixture is stirred at 155° C. for 0.5 hours. It is subsequently cooled to 60° C., and the mixed-crystal pigment is filtered off with suction, washed to neutrality with water and dried at 80° C. 68.6 parts of mixed-crystal pigment are obtained. The spectrum is that of the mixed-crystal pigment. The typical reflections of 2,9-dimethylquinacridone are not detectable.

Provenance & Evidence