PURPOSE:To obtain the titled copolymer having improved heat resistance, by reacting a specific diaminosiloxane with a diaminoamide and a diamine, an aromatic tetracarboxylic acid dianhydride, and reacting further an aromatic diisocyanate with the product of the first reaction. CONSTITUTION:(A) A diaminosiloxane of formulaI(R is bifunctional hydrocarbon; R' is monofunctional hydrocarbon; m is an integer =1) is reacted with (B) a diaminoamide of formula II (Y is SO2 or CO, and one amino group and the Y-NH2 group are at the o-position to each other), (C) a diamine, e.g. 4,4'-diaminodiphenyl ether, and (D) pyromellitic acid dianhydride, and the reaction product is then reacted with (E) an aromatic diisocyanate in an amount of almost equivalent to the acid anhydride group in the reaction product at 50-100 deg.C while removing the liberated and generated CO2 from the reaction system to afford the aimed copolymer. The amount of the component (D) is 1.5-2.0mol based on one mole components (A) and (B) and/or component (C).
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