| 摘要 |
PROBLEM TO BE SOLVED: To provide a method for purifying a trans-dicyclohexyl-3,3'4,4'- tetracarboxylic acid isomer being a new starting raw material for a polyimide resin. SOLUTION: This method for purifying a trans-dicyclohexyl-3,3',4,4'- tetracarboxylic acid comprises heating (1R,1'S,3R,3'S,4R,4'S)-dicyclohexyl-3,3'4,4'- tetracarboxylic acid, (1S,1'S,3S,3'S,4S,4'S)-dicyclohexyl-3,3'4,4'-tetracarboxylic acid and (1R,1'R,3R,3'R,4R,4'R)-dicyclohexyl-3,3'4,4'-tetracarboxylic acid in a solvent, cooling and filtering to improve the purities of these compounds.
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