ISOTROPIC POLYIMIDE FILM AND PROCESS FOR ITS PREPARATION

摘要

Preparing a stretched biaxially isotropic polyimide by applying a solution of a precursor polyamic acid in an organic solvent containing a cyclization catalyst and a dehydrating agent on the surface of a support, by imidizing the polyamic acid to produce a continuous self-supporting gel film containing from 5 to 50% by weight solids, by stretching the gel film in the machine direction (MD) at a ratio between 1.1 and 1.9, and the stretching transversely (TD) relative to the machine direction, so as to maintain a TD / MD stretch ratio of between 0.9 and 1.3.