| 摘要 |
<p>PROBLEM TO BE SOLVED: To prepare a high strength porous film of polypropylene, produced form polypropylene film obtained substantially without using a plasticizer or a solvent and hardly having gas permeability, excellent in mechanical properties and suitable for a food use and as a packing material, etc., and to provide a method for producing the film. SOLUTION: This high strength porous film is prepared by forming a polypropylene film obtained substantially without using a plasticizer or a solvent and hardly having gas permeability into a porous one by drawing and/or heat- treating the film. Moreover, the porous film has (1) >=35MPa tensile strengths both in the machine direction(MD) and in the transverse direction(TD), (2) <=80% porosity and (3) >=20g/m<2> /day moisture permeability. The porous film is obtained, for example, by performing a heat treatment of a biaxially oriented film or an inflation film of polypropylene having >=40% crystallinity for increasing the crystallinity in a limited state and/or a drawing treatment thereof to make the film porous.</p> |
