| 摘要 |
PROBLEM TO BE SOLVED: To provide a method for manufacturing a polyolefin microporous membrane capable of inhibiting, when used as a separator for a lithium ion secondary battery, a spontaneous discharge and excellent in terms also of liquid dispensability.SOLUTION: The provided method for manufacturing a polyolefin microporous membrane includes (a) an extrusion step of melt-kneading and extruding a resin composition including a polyolefin resin and a pore formation material, (b) a sheet molding step of molding, as a sheet, the extruded product obtained at the step (a), (c) a primary stretching step of stretching the sheet-shaped molding obtained at the step (b) at least once at least along a monoaxial direction, (d) an extracting step of extracting the pore formation material from the stretched sheet obtained at the step (c), and (e) a secondary stretching step of stretching the sheet obtained at the step (d) at a stretching rate of at least 60%/sec at least once at least along a monoaxial direction. |
