| 摘要 |
PURPOSE:To obtain a polyolefin fine porous film for ultrafilter membrane, etc., having sharp pore diameter distribution by dissolving a polyolefin having a high molecular weight and broad molecular weight distribution in a solvent mixture consisting of a good solvent and a poor solvent, extruding the solution from die, drawing the extruded material and then removing the solvent mixture from the drawn material. CONSTITUTION:When a polyolefin fine porous film is produced by preparing a solution consisting of 10-50wt.% polyolefin containing >=1wt.% component having >=7X10<5> molecular weight, 10-300 weight-average molecular weight/ number-average molecular weight and 50-90wt.% solvent and extruding the solution from a die, cooling the extruded material to form a still not drawn gel-like composition and drawing the gel-like composition at a temperature 10 deg.C lower than the melting point of the polyolefin and then removing the residual solvent, the solvent consists of a good solvent to the polyolefin (e.g. paraffin oil) and a poor solvent (e.g. caster oil) and the weight ratio of the good solvent to the poor solvent is within the range of (50:50) to (99:1) is used to provide the objective polyolefin fine porous film having proper pore diameter and sharp poor diameter distribution. |
