| 摘要 |
Copolyimides derived from the reaction product of 3,3'-6 F diamine or 4,4'-6 F diamine, at least one other diamine, and pyromellitic dianhydride can be rendered solvent soluble while at the same time exhibiting an improvement in both mechanical and electrical properties by the inclusion of at least one other dianhydride having a diaryl nucleus in the reaction media. Suitable such dianhydrides include bis (3,4 dicarboxy phenyl) ether dianhydride, 3,3'4,4' benzophenone tetracarboxylic dianhydride, 3,3',4,4' diphenyl tetracarboxylic acid dianhydride and 2,2 bis(3,4 dicarboxyphenyl) hexafluoropropane dianhydride (6F-DA). Such polyimides are soluble in common organic solvents such as methyl ethyl ketone or N-methyl pyrrolidone, and exhibit excellent film forming properties with improved mechanical and electrical properties as compared to the corresponding homopolyimides. They possess excellent heat stability (Tg's in excess of about 350 DEG C.) and have superior electrical properties, for example, dielectric constant of less than about 2.5 at 10 megahertz.
|
