| 摘要 |
PROBLEM TO BE SOLVED: To prepare a porous polyolefin film having a high pore-blocking property, heat resistance and polar organic solvent-impregnating ability, to provide a preparation process thereof and to prepare separator film for high- capacity batteries. SOLUTION: A porous film comprises a polyolefin, has a carbonyl ratio of 0.04 or larger measured by a differential scanning calorimeter and has characteristics wherein (1) the film thickness is from 5 to 100μm, (2) the maximum pore size of from 0.05 to 10.0μm, (3) a porosity is from 30 to 80%, (4) the gas transmission rate is from 10 to 1,000 sec/100 ml, (5) the gel percentage is from 1 to 20%, (6) the heat resistant temperature is 170 deg.C or higher and (7) the pore-blocking temperature is 130 deg.C or lower. Furthermore, this porous film is prepared by subjecting a porous polyolefin film to an electron ray irradiation with a radiation does of from 1 to 50 Mrad in the presence of oxygen and then extinguishing the residual radicals in the presence or absence of oxygen. |
