| abstract |
A porous film made from a polymer composition comprising (a) a polymer having in the main chain carbon-carbon double bonds and C5-C10 aliphatic rings and (b) another resin, a porous film as described above wherein the whole or part of the carbon-carbon double bonds are vanished, and a porous film as described above wherein the polymer (a) and the resin (b) are crosslinked, which have proper porosity, gas permeability and piercing strength and are particularly excellent in latent heat resistance or heat resistance; processes for the production of the porous films; battery separators made of the films; and batteries wherein the separators are arranged. |