Methanol → Quinacridone

Participants

Reaction Conditions

Reaction Steps

To 300 g of polyphosphoric acid (117% phosphoric acid) heated to 80° C. was added 68.2 g of 2,5-dianilinoterephthalic acid. The reaction mixture was heated at 120°-125° C. for two hours. After the melt was cooled to 90°-95° C., the acid strength was adjusted to 112% by the dropwise addition of phosphoric acid. The resultant melt was stirred for 20 minutes and then slowly poured into 453 g of methanol at 24° C. During the drown, the temperature was allowed to increase to 55° C., with the temperature being controlled by external cooling and adjustment of melt addition rate. The slurry was heated at reflux (68°-72° C.) for one hour, diluted with water, and stirred at 60° C. for 30 minutes. The solid component was collected by filtration and washed with water until acid free. The resultant presscake was reslurried in water. After adjustment of the pH to about 7, 7.5 g of 50% sodium hydroxide was added and the resultant slurry was heated at 90°-95° C. for one hour. The slurry was cooled, filtered, and washed with water until alkali free, then reslurried in water (595 g total, including water from the presscake). After adjustment of the pH to 9.0-9.5, 3.2 g of a cycloaliphatic carboxylic acid was added. The resultant slurry was heated at about 140°-145° C. for two hours in a closed system, cooled, acidified with phosphoric acid, and stirred. The solid component was collected by filtration and washed with water. The wet cake can be dried or used as is for specific applications. Here, the wet cake was dried in an oven at 60° C. to give approximately 53 g of quinacridone as a violet pigment.

Provenance & Evidence