PURPOSE: To improve melt fluidity of polyimide and to obtain a laminated molded article excellent in heat resistance by using a new prepreg sheet having excellent strength at high temperature prepared from a specific polyamic acid and a fibrous reinforcing material by a new method.
CONSTITUTION: First, a solution of a polyamic acid having a unit of formula I (R1 is bifunctional group selected from ≥2C aliphatic group, monocyclic aromatic group, etc.; R2 is tetrafunctinonal group selected from ≥2C aliphatic group, heterocylic group, etc.; Y is H, alkyl, etc.) in an organic solvent is impregnated into a fibrous reinforcing material and the fibrous reinforcing material is brought into contact with a dehydrated imidating agent (e.g. acetic anhydride) so that the polyamic acid is chemically imidated and made into a polyimide having a unit of formula II. Successively, the prepreg sheet impregnated with the polyamide is laminated and heated to ≥ the glass transition temperature of the polymide under pressure to give the objective product. The polyamic acid is preferably obtained by reacting 3, 3'-diaminobenzophenone with 3, 3', 4, 4'-benzophenonetetracarboxylic acid dianhydride.
TAKAHASHI SHIGERU
SATO TAKUSHI
SHISHIDO SHIGEYUKI
NAKAJIMA HISAE
