METHOD FOR PREPARING THERMOPLASTIC POLYIMIDE Russian patent published in 1997 - IPC

FIELD: chemistry of high molecular weight compounds, more particularly highly heat resistant incombustible composite materials. The claimed method for preparing thermoplastic aromatic polyimide comprises synthesizing polyimide in two steps. SUBSTANCE: first step involves polycondensation of 3,3′-diaminobenzophenone and 3,3′,4,4′- benzophenone tetracarboxylic acid dianhydride in the presence of phthalic anhydride in organic solvent. Second step involves chemical imidization of the resulting prepolymer such as polyamidoacid with acetic anhydride-triethyl amino (3:2) mixture in the same solvent. To carry out polycondensation, 12-25 wt % solution of 3,3-diaminobenzophenone is prepared in diglyme organic solvent at 3,3′, 4,4′-benzophenone tetracarboxylic acid to phthalic anhydride molar ratio of 1.00: 1.00-0.75: 0.60-0.25. Prior to chemical imidization, and two synthesis steps are carried out at 30-50 C. The resulting polyimides have vitrification temperature of 215-227 C; lgη 330 C (melt) is 1.4-1.7 Pa.s; molecular weight is (15-25)*10³. EFFECT: improved properties of the title compound. 1 dwg