| 摘要 |
PURPOSE:To obtain a microporous membrane having a narrow pore size distribution, by supplying a molten mixture of a polyethylene resin and a liquid material to an extruder, cooling an extruded sheet at a specified cooling rate, and extracting said liquid material. CONSTITUTION:100pts.wt. polyethylene resin and 100-500pts.wt. liquid material having a solubility parameter of 8.0-9.5 are melt-mixed together at a temp. which is 30 deg.C higher than the m,p. of said polyethylene resin. Without cooling the molten mixture, the mixture is supplied to an extruder, the temp. of the raw material supply part of the extruder being kept at a temp. which is 30 deg.C higher than the m.p. of the polyethylene resin. The mixture is extruded into a sheet. The both sides of the extruded sheet are uniformly cooled at a cooling rate of at least 50 deg.C/sec. The resulting sheet is immersed in a solvent for said liquid material. The liquid material is dissolved and removed to obtain a porous membrane. |
