PURPOSE: To prepare the titled polymer having excellent heat resistance, mechanical characteristics and electrical characteristics, and suitable for heat-resistant sheet, etc., by reacting a polyisocyanate with a polycarboxylic acid containing acid anhydride group, etc. in the presence of a non-aqueous organic liquid.
CONSTITUTION: A granular polymer having an average particle size of 0.05W 2000μ and containing imide group is prepared by mixing (A) a polyisocyanate (preferably 4,4'-diphenylmethane diisocyanate, etc.) with (B) a polycarboxylic acid containing acid anhydride group (preferably trimellitic anhydride, etc.) and if necesary (C) a polycarboxylic acid other than the component (B) (e.g. trimellitic acid) in the presence of an essentially insoluble non-aqueous organic liquid (e.g. acetone), and heating and stirring the mixture. The equivalent ratio of the total carboxyl group of the polycarboxylic acid to the total isocyanate group of the polyisocyanate is preferably 0.5W2.0.
HIRAI OSAMU
MUKOUYAMA YOSHIYUKI
