| 摘要 |
PROBLEM TO BE SOLVED: To provide a porous film having a high pore-blocking property, a good piercing strength at an elevated temperature around the blocking temperature and a high film-fracture resistance and a separator film for high-capacity batteries using this. SOLUTION: A porous polyolefin film has characteristics wherein (1) the intrinsic viscosity [η] is 2.5 dl/g or larger, (2) Mw/Mn is 10 or smaller, (3) the film thickness is from 10 to 100μm, (4) the gas transmission rate is from 50 to 1,500 sec/100 ml, (5) the porosity is from 30 to 80% (6) the piercing strength (25 deg.C) is 12 g/μm or larger and (7) the piercing strength (135 deg.C) is 9 g/μm or larger. Furthermore, this film satisfies at least one of the required conditions wherein the blocking temperature is 140 deg.C or lower, the film-fracture resistance time is 2 min or longer and the heat shrinkage ratio at 105 deg.C is less than 6%, so it is useful as a separator film for batteries, especially a separator film for high-capacity batteries. |
