Method of making oxydiphthalic anhydride

摘要

Disclosed is a method of making oxydiphthalic anhydride from oxydiphthalic acid. The oxydiphthalic acid is mixed with an organic liquid that codistills with water and the resulting slurry is heated to the boiling point of the slurry to remove any water. About 1 to about 4 moles of acetic anhydride per mole of oxydiphthalic acid are added to the slurry and the slurry is heated to a temperature between 50 DEG and 160 DEG C. until the oxydiphthalic acid content thereof is less than 0.1 weight percent. The slurry is filtered and the filter cake is heated to a temperature between about 180 DEG C. and below its melting point for about 12 to about 24 hours.