4-Hydroxybenzoic Acid → Benzoic acid, 4-(acetyloxy)-

Participants

Reaction Conditions

Reaction Steps

In a glass flask, were placed under a nitrogen stream 1,380 g of p-hydroxybenzoic acid and 1,120 g of acetic anhydride. The mixture was refluxed at 150° C. for 2 hours and then the temperature was raised while removing acetic acid by distillation. When the temperature reached 230° C., the p-acetoxybenzoic acid formed by acetylation was transferred into a double-arm kneader which had been heated to 230° C. At this stage, the p-acetoxybenzoic acid was liquid. While agitating at low speed, the temperature of this liquid was raised to 330° C. taking a period of one hour. When the temperature had reached 310° C., an increase in torque was observed. Polymerization was continued with increased speed of agitation until the mixture in the kneader was transformed into powder. 100 Grams of the powder were tested for particle diameter. It was found that 73% of the sample had a particle diameter of 0.1 mm or less. The polymerization was continued at 330° C. The degree of conversion when the polymerization system was transformed into a powder was 95%. After a further 2 hours of reaction, there were obtained 1,130 g of fine powder, corresponding to a yield of 94%. Ninety-one percent of the fine powder was found to have a particle diameter of 0.1 mm or less. On differential thermal analysis, the powder showed a heat absorption at 342° C. The loss on heating in the air at 370° C. for one hour was 0.65% by weight. The number average molecular weight was 11,000.

Provenance & Evidence