| 摘要 |
A process for making a polyamide-acid powder comprises reacting at least one diamine of the formula H2N-R1-NH2, where R is a divalent polycyclic aromatic radical in which no more than one NH2 group is substituted in any one aromatic ring, with at least one tetracarboxylic acid dianhydride of the formula <FORM:0980855/C3/1> where R is a tetravalent radical containing at least one 6-carbon atom ring having benzenoid unsaturation and wherein the four carbonyl groups are attached to different carbon atoms in a ring of the R radical and wherein each pair of carbonyl groups is attached to adjacent carbon atoms in a 6-membered benzenoid ring of the R radical, in an organic solvent for at least one of the reactants, the solvent being inert to the reactants, at a temperature below 75 DEG C., to form a solution of a polymer containing polyamide-acid having an inherent viscosity of at least 0.1, and then mixing the solution with a precipitant for the polyamide-acid to precipitate a particulate, polymeric solid. The precipitate may be converted to the corresponding polyimide by (1) reacting with a lower fatty monobasic acid preferably in the presence of a tertiary amine and/or (2) heating at a temperature above 50 DEG C. The inherent viscosity is measured at 35 DEG C. at a concentration of 0.5% by weight of the polymer in N:N-dimethyl acetamide. Many diamines, tetracarboxylic acid dianhydrides, solvents and precipitants are specified. The examples describe the preparation of polyamide-acid powders from:-(1) 4:41-diamino diphenyl ether and pyromellitic dianhydride and (2) bis-(3:4-dicarboxyphenyl) ether dianhydride and 1:3-bis-(p-amino-phenoxy) benzene. |
