| 摘要 |
PURPOSE:To obtain the title molding having excellent heat resistance and mechanical properties, by blending a polyamic acid soln. comprising an arom. diamine and an arom. tetracarboxylic acid with a specific quantity of a chemical ring-closing agent, and carrying out a dry molding thereafter. CONSTITUTION:An arom. diamine (e.g. p-phenylenediamine) and an arom. tetracarboxylic anhydride (e.g. pyromellitic anhydride) are solution-polymerized in a solvent (e.g. N-methylpyrrolidone) to obtain a polyamic acid soln. (A). A stock soln. (B) is prepd. by blending component A with a chemical ring-closing agent comprising an anhydride (e.g. acetic anhydride) and a tertiary amine (e.g. pyridine), in which the quantity of the chemical ring-closing agent is such that the fluidity of the obtd. stock soln. is defined on such a level that the gelation of the stock soln. may terminate within 24hr at 20 deg.C and that the ratio of ring closure of the polyamic acid may be 50% or more. This stock soln. is reserved at -50-50 deg.C and molded by dry molding before the soln. loses the fluidity and the molding obtd. is heat-treated at 200-600 deg.C, if necessary. |
