Process for producing biphenyltetracarboxylic dianhydrides
AssigneeUbe Industries, Ltd.
InventorsHiroshi Itatani, Mikito Kashima, Masaoki Matsuda, Hataaki Yoshimoto, Hiroyuki Yamamoto
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Abstract
A process for separating and purifying biphenyltetracarboxylic dianhdride isomers from a mixture of these isomers by fractional crystallization in aliphatic acid anhydrides or acetone. The isomeric mixture is obtained by heating biphenyltetracarboxylic acids, optionally in the presence of an aliphatic acid anhydride. The biphenyltetracarboxylic acids are obtained by oxidizing coupling dimers of o-xylene or by hydrolyzing coupling dimers of dimethyl phthalate.
Claims3
A process for separating biphenyltetracarboxylic dianhydride isomers from a mixture of these isomers, which comprises fractionally crystallizing said mixture in a solvent selected from the group consisting of saturated aliphatic acid anhydrides and ketones while heating to a temperature of from about 50.degree.C to about 250.degree.C to thereby separate the mixture into its constituent isomers.
Dependencies are inferred from the claim text.