| 摘要 |
PURPOSE:To separate and to obtain the titled compound useful as a raw material for producing aromatic polyimide directly from the dimerization reaction product of an o-phthalic acid diester by a simple operation, in high yield, in high purity and efficiently without hydrolysis. CONSTITUTION:A molecular oxygen-containing gas is fed to an o-phthalic acid diester under heating in the presence of a catalyst containing a bivalent palladium salt in a solventless state. Then a catalytic compound and an unreacted o-phthalic acid diester are removed from the reaction mixture containing the prepared aimed compound, 2,3,3',4'-biphenyltetracarboxylic acid tetraester, biphenyltricarboxylic acid triester and a high-boiling product. Then the rest are heated under reduced pressure, the reaction products except the high-boiling product are evaporated and recovered, then rectified at <=5Torr pressure of column head and <=320 deg.C temperature of column bottom to give 3,3',4,4'- biphenyltetracarboxylic acid tetraester as distillate. |
