Potassium Hydroxide → Quinacridone

Participants

Reaction Steps

100 parts of 2,5-dianilinoterephthalic acid are added with stirring at 100°-120° C. to 450 parts of polyphosphoric acid (P2O5 content 85.5%), the mixture is stirred at said temperature until the reaction has ended (which takes about 2 hours) and is then poured onto 1,350 parts of ice-water, and the hydrolysis suspension attains a temperature of 15°-20° C. After the hydrolysis has ended the precipitated crude quinacridone is filtered off and is washed with water until free of acid. The water-moist approximately 20-22% strength crude quinacridone thus obtained is suspended in 600 parts of water. A solution of 1.2 parts of dehydroabietylamine, 10.6 parts of water and 0.24 part of acetic acid is then added dropwise, and the mixture is stirred for 30 minutes. 150 parts of 10% strength aqueous potassium hydroxide solution are then added, and the mixture is bulked with water to a total of 1,500 parts. The suspension is then refluxed with stirring for 10 hours and is then filtered at 70°-80° C., and the filter cake is washed with water until neutral. The water-moist approximately 18-22% strength quinacridone thus isolated is suspended in 600 parts of 80% strength isobutanol, and the suspension is then stirred at 145°-150° C. in a sealed vessel for 5 hours. The isobutanol is then distilled off with steam, and the pigment is then filtered off, is washed with water and is dried at 80° C. The pigment yield is at least 96%.

Provenance & Evidence