| 摘要 |
PURPOSE:To provide a finely porous polyolefin film excellent in drawability, mechanical strength, reduction in the amount of solvent to be used, etc., useful for battery separators, electrolytic capacitors, etc., consisting of a polyolefin having each specific pore characteristics, film thickness, breaking strength and molecular weight characteristics. CONSTITUTION:The porous film consisting of a multistage-polymerized polyolefin having the following characteristics: (1) film thickness: 0.1-50mum, (2) porosity: 35-95%; (3) mean penetrated pore diameter: 0.001-0.02mum; (4) breaking strength (15mm width): >=0.2kg; (5) content of the components >=7X10<5> in molecular weight: >=1wt.%; and (6) weight-average molecular weight/number-average molecular weight: 10-300. This porous film can preferably be obtained by the following process: a solution composed of 10-50wt.% of a multistage-polymerized polyolefin having the above-mentioned molecular weight characteristics and 50-90wt.% of a solvent is first prepared and then extruded through a die and cooled into a gel-like composition, which is then heat set at a temperature between the crystal dispersion temperature and the melting point of the polyolefin followed by drawing at a temperature not higher than the melting point plus 10 deg.C and then disolvation. |
