2,5-Dianilinoterephthalic acid → Quinacridone

Participants

Reaction Conditions

Reaction Steps

A stirred vessel is charged with 500 parts of polyphosphoric acid containing 85.0% P2O5. Then 25 parts of 2,5-dianilinoterephthalic acid and 75 parts of 2,5-di-(4-toluidino)terephthalic acid are introduced at from 90 to 125° C. with stirring 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 then metered over the course of 5 minutes into a second stirred vessel containing 1200 parts of 85% strength phosphoric acid and the mixture is hydrolyzed with stirring at 140° C. During hydrolysis, the temperature rises to 160° C. Following the hydrolysis, the phosphoric acid strength is 94%. The mixture is heated to 176° C. and stirred at 176° C. for 4 hours. The hydrolysis mixture is cooled to 90° C. and the solid product is filtered off with suction and washed with 500 parts of 85% strength phosphoric acid until the runoff is colorless. The filter residue is introduced into 2000 parts of water with stirring and stirred for 0.5 hour. Subsequently the crude pigment is filtered off with suction, washed to neutrality with water and dried at 80° C.

Provenance & Evidence