| 摘要 |
A 3',3'4',4'- or 2,3,3',4'-biphenyltetracarboxylic acid dianhydride is reacted at not above 80 DEG C in an amide-type organic polar solvent with at least one aromatic diamine having 1,2,3 or 4 phenyl groups in its chain and an -NH2 group on each terminal phenyl at the m-position. The resultant viscous solution of polyamide acid is formed to desired shape, e.g. by casting on a flat plate to form a film, and is heated to up to 150 DEG C to remove some solvent and is imidized by further heating to 350 DEG C or by immersion in a benzene solution of pyridine and acetic anhydride. Preferred solvents boil at 170 DEG C or less, e.g. dimethylacetamide and/or dimethylformamide. The resultant shaped polyimide article has bisphenylimide-aromatic recurring units, and has good colorless transparency without yellow or brown color. It is useful as an oriented film in a liquid crystal display or as a plastics lens. |
