| 摘要 |
PROBLEM TO BE SOLVED: To provide a method for purifying 3,3',4,4'-biphenyltetracarboxylic dianhydride, by which the 3,3',4,4'-biphenyltetracarboxylic dianhydride having a low metal ion concentration and a high purity and used for polyimide varnishes and molded articles is obtained. SOLUTION: This method for purifying the biphenyltetracarboxylic dianhydride comprises hydrolyzing crude tetramethyl biphenyltetracarboxylate, dehydrating the hydrolysis product, filtering the product through an adsorbent in a solvent, and then recrystallizing the filtered product. Especially, 3,3',4,4'-biphenyltetracarboxylic dianhydride is preferable. The solvent used for the recrystallization is especially acetic anhydride for the method for purifying the biphenyltetracarboxylic dianhydride. COPYRIGHT: (C)2004,JPO&NCIPI
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