Method for making aromatic bis(ether dicarboxylic acid)s

In a method for making aromatic bis(ether dicarboxylic acid)s involving

• 1 hydrolyzing the coresponding aromatic bis (etherimide) with an alkali hydroxide to produce a tetraacid salt base hydrolysis mixture,
• 2 acidifying the tetraacid salt by pouring the base hydrolysis mixture into an aqueous solution of a mineral acid to produce a tetraacid acidification mixture, and
• 3effecting the gravity separation of tetraacid from the resulting acidification mixture,
• resulting in the build up of unrecovered aqueous mineral acid which method for making aromatic bis(ether dicarboxylic acid) involves the improvement comprising,
• 4 acidifying the aromatic bis(ether diacid) salt by directly adding a concentrated mineral acid to the base hydrolysis mixture at a temperature in the range of from about 15.degree. C to 75.degree. C until the pH of the resulting mixture is reduced to less than about 1,
• 5 heating the resultant mixture to a temperature in the range of between 80.degree. C to reflux, and
• 6 effecting the separation of the tetraacid from the resulting mixture,
• whereby the amount of unrecovered aqueous mineral acid in the acidification mixture is substantially reduced.