| 摘要 |
PURPOSE: To provide porous film which is made of a high-molecular weight PE having specific thickness, permeability, porosity and tensile elongation, thus is useful for lithium cells because of its excellency in film breakage resistance, charge and discharge behavior, safety and processability. CONSTITUTION: This porous film comprises a high-molecular weight PE porous film or sheet of 100,000 or higher viscosity-average molecular weight and has 5-100μm thickness, 10-500 seconds/100cc air permeability, 10-90% porosity and more than 150% stretch elongation. This porous film is obtained, for example, by kneading 25 pts.wt. of high-molecular weight PE powder and 75 pts.wt. of paraffin wax of 1mm average particle size and melt-extruding into a film, soaking the film in isopropyl alcohol to remove the paraffin from the film and subjecting the film to heat treatment. |
