2,5-Dianilinoterephthalic acid → Quinacridone

Participants

Reaction Conditions

Reaction Steps

450 parts of polyphosphoric acid containing 85.0% P2O5 are metered into a stirred vessel. Then 127.5 parts of 2,5-dianilinoterephthalic acid and 22.5 parts of 2,5-di(3-chloroanilino) terephthalic acid are introduced at 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 subsequently metered with stirring over 3 minutes (CG: 33.3%/min) into 860.8 parts of 85% strength phosphoric acid at 140° C., during which it is hydrolyzed. During this hydrolysis the temperature rises to 160° C. The phosphoric acid concentration after the hydrolysis is 95%. Then 294.5 parts of 40% strength phosphoric acid are added dropwise and the suspension is cooled to 150° C. The phosphoric acid connotation thereafter is 85%. The mixture is stirred at 150° C. for 5 hours. The mixture is then cooled to 120° C. and 1822.3 parts of water are added dropwise. Thereafter the concentration of phosphoric acid is 40%. Subsequently the mixed crystal pigment is filtered off with suction, washed with 40% strength phosphoric acid until the runoff is colorless, washed to neutrality with water, and dried at 80° C. This gives 130.5 parts of mixed crystal pigment (Pigment Violet 19, γIV phase). At twice the Bragg angle, 2θ, X-ray spectrum shows three strong lines at 6.4°, 13.5° and 26.4° and five moderate lines at 17.0°, 20.5°, 21.4°, 23.9° and 28.2°.

Provenance & Evidence