| 摘要 |
PURPOSE: To obtain a microporous film excellent in tensile strength, piercing strength, void content, and air permeability while using a solvent excellent in safety, environmental compatibility, and hygienic properties by subjecting a sheet made from a mixture of a high-mol.-wt. polyethylene with a paraffin wax to biaxial stretching, thermal treatment, and solvent removal. CONSTITUTION: A mixture of a high-mol.-wt. polyethylene with a paraffin wax is melt kneaded and solidified by cooling to give a sheet, which is then biaxially stretched at a temp. higher than the m.p. of the paraffin wax and lower then the m.p. of the polyethylene. The resulting stretched film is thermally treated at a temp. higher than the m.p. of the wax and lower than the m.p. of the polyethylene, is freed from the remaining wax with a lower alcohol solvent at a temp. lower that the m.p. of the wax, and is dried, thus giving a microporous high-mol.-wt. polyethylene film having an intrinsic viscosity [η]of 3.5dl/g or higher. |
