| 摘要 |
<p>PROBLEM TO BE SOLVED: To provide a process for producing porous films suitable as electric automobile battery separators. SOLUTION: A process for producing porous films comprises kneading at 115-240 deg.C a solution obtained by heating a mixture of 5-30 wt.% ultra-high- molecular-weight polyolefin resin and 95-70 wt.% solvent having a freezing point of not higher than -10 deg.C to mold a first gel sheet at a temperature of not higher than the freezing point of the solvent, separately kneading at 115-240 deg.C a solution obtained by heating a mixture of 5-30 wt.% ultra-high- molecular-weight polyolefin resin and 95-70 wt.% solvent having a freezing point of not higher than -10 deg.C to mold a second sheet, then applying the first gel sheet on to the second sheet at its surface temperature of (M+30) deg.C to (M-10) deg.C (wherein M is a melting of the ultra-high-molecular-weight polyolefin resin of the second sheet), then molding the resulting laminate into an integrally laminated gel sheet at a temperature of not higher than the freezing point of the solvent used in the second sheet, subsequently biaxially stretching the integrally laminated sheet at a temperature of (M+5) deg.C to (M-30) deg.C, and subjecting the stretched sheet to desolvation treatment.</p> |
