2,5-Dianilinoterephthalic acid → Quinacridone

Participants

Reaction Conditions

Reaction Steps

A stirred vessel is charged with 450 parts of polyphosphoric acid containing 83.0% P2O5. Then 37.5 parts of 2,5-dianilinoterephthalic acid and 112.5 parts of 2,5-di-(4-toluidino)terephthalic acid are introduced at 125° C. with stirring and the mixture is heated at 125° C. for 1 hour during which ring closure taking place to form the quinacridone. The reaction is then metered over the course of 5 minutes into a second stirred vessel containing 1431 parts of 70% strength phosphoric acid and is hydrolyzed at 25° C. with stirring. During hydrolysis the temperature rises to 60° C. Following the hydrolysis, the phosphoric acid strength is 80%. The mixture is heated to 125° C. and stirred at 125° C. for 5 hours. It is then cooled to 90° C., 1900 parts of water at 25° C. are metered in and the mixture is stirred at 90° C. for 1 hour. Thereafter, the mixed-crystal pigment is filtered off with suction, washed to neutrality with water and dried at 80° C.

Provenance & Evidence