| 摘要 |
PURPOSE:To obtain the titled substance having enlarged crystal size and reduced colored component in crystal, by dehydrating 3,4,3',4'-biphenyltetracarboxylic acid while keeping the concentration of the acid at <=a specific value. CONSTITUTION:In producing 3,4,3',4'-biphenyltetracarboxylic acid dianhydride by dehydrating 3,4,3',4'-biphenyltetracarboxylic acid(S-BTC) in acetic anhydride solvent, the concentration of S-BTC in the reaction system is kept at <=15wt% (preferably <=13wt%) and the reaction is carried out at 120 deg.C- the boiling point (about 139 deg.C) of the mixture for 1-100hr. Before the dehydration, the mixture is in contact with an organic solvent (in an amount of 0.5 as much as the amount of S-BTC) consisting of a ketone, aliphatic alcohol or ether at 0-40 deg.C for 3min to extremely improve effects. USE:A heat-resistant polyimide raw material.
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