| 摘要 |
PROBLEM TO BE SOLVED: To impart excellent air permeability, liquid permeability, osmosis and good strength by using a polyolefin resin and specifying the pore structure parameterκof the film and the tensile strength. SOLUTION: This porous film has a pore structure parameterκof the film of 0.15-0.80 and a tensile strength of 500 kg/cm2 or more. This porous film normally has a pore rate of 0.30-0.95, a peak pore diameter of 0.05-0.5μm, a thickness of 10-50μm and an air permeability of 10-1000 sec/100 cc. Although no specific limitation is imposed on the method to obtain the porous film, it is preferred that a resin composition containing a high molecular weight polyolefin resin and a plasticizer is melt-extruded into a film, which is cooled, stretched to remove the plasticizer in the stretched film and then stretched again or subjected to a heat treatment. 10-50 wt.% of the polyolefin and 90-50 wt.% of the plasticizer are preferably mixed. |
