2,5-Dianilinoterephthalic acid → Quinacridone

Participants

Reaction Conditions

Reaction Steps

A pressure vessel is charged with 405.7 parts of polyphosphoric acid containing 85.0% P2O5. Then 20.3 parts of 2,5-dianilinoterephthalic acid and 60.9 parts of 2,5-di-(4-toluidino)terephthalic acid are introduced at 80 to 90° C. with stirring, and the mixture is heated at 125° C. and stirred at 125° C. for 1 hour during which ring closure takes place to form the quinacridone. The reaction mixture is then metered over the course of 10 seconds into a second pressure vessel containing 184 parts of water and is hydrolyzed at 150° C. under pressure. Following the hydrolysis, the phosphoric acid strength is 89.7%. During this procedure the temperature rises to 180° C. The mixture is cooled to 150° C. and stirred at 150° C. for 3 hours. It is cooled to 90° C. and the hydrolysis mixture is poured into 6000 parts of water at 25° C. with stirring. Thereafter, the mixed-crystal pigment is filtered off with suction, washed to neutrality with water and dried at 80° C.

Provenance & Evidence