| 摘要 |
PROBLEM TO BE SOLVED: To provide a manufacturing method of a polyolefin-based microporous film which is excellent in balance of porosity, permeability and mechanical strengths, and has good dimensional stability. SOLUTION: The manufacturing method of the thermoplasitic resin-based microporous film includes some processes in which a solution obtained by melt- kneading a thermoplastic resin and a solvent is extruded, the residual solvent is removed from the gel molded article obtained by cooling with a washing solvent, three steps or more heat treatments are performed after drying. In this method, a washing solvent (A) of which the surface tension is 24 mN/m or less at 25 deg.C is used as the washing solvent, the heat treatment process includes a heating process (1) with contracting in machine direction(MD) and/or transverse direction(TD) while both MD and TD are fixed, a heating process (2) with contracting in MD and/or TD and a final heating process (3) with contracting in neither MD nor TD, and the resin is contracted 10-50% in MD and/or TD at whole heat treatment process. |
