| 摘要 |
PURPOSE:To obtain the subject sheet having good surface state and excellent heat-resistance without causing foaming, etc., by heating and melting a polyimide having a specific recurring structural unit at a specific temperature and forming the molten polymer under cooling. CONSTITUTION:The objective sheet is produced by melting a polyimide having a recurring structural unit of formula I (R is a tetravalent group selected from >=2C aliphatic, cycloaliphatic, monocyclic aromatic and condensed polycyclic aromatic groups and non-condensed polycyclic aromatic group having aromatic groups linked with each other directly or through crosslinking members; X is bivalent group selected from single bond, S, sulfone, carbonyl, isopropylidene and hexafluoroisopropylidene) at 300-450 deg.C with an extruder and forming the molten polymer under cooling. The water-content of the above polyimide is preferably <=200ppm at the stage immediately before supplied to the extruder. The group R in the formula I is preferably group of formula II-VI. |
