PROCESS FOR PRODUCING POROUS, THIN AND HIGH-STRENGTH FILM USED AS SEPARATOR FOR BATTERY

摘要

PURPOSE: A process for producing porous films is provided to produce a thin, high-strength film which has an excellent ventilation due to a high porosity and are suitable for a separator for a battery. CONSTITUTION: The process for producing porous films comprises the steps of: melting and kneading a composition comprising a polyolefin resin, a thermoplastic elastomer and a solvent; preparing a sheet molding by extruding and cooling the melted and kneaded material; rolling the sheet molding; and drawing and desolvating the rolled sheet molding. The rolling step is carried out under a condition that an elastic recovery of the sheet molding after rolling is 20% or less. The elastic recovery is calculated by the following formula: elastic recovery(r)(%) = 100 x (t - t0)/t0(wherein, t0 is a minimum clearance of a sheet rolling part at rolling and t is a thickness of the sheet after releasing a pressure).