Microporous biaxially stretched film comprising a composition of high molecular weight polyethylene and high molecular weight polypropylene, its production method and its use

摘要

PURPOSE:To obtain a microporous biaxially oriented film, excellent in tensile strength and air permeability and comprising microfibrils. CONSTITUTION:The characteristic of this microporous biaxially oriented film comprises using a composition containing a specific amount of a high-molecular weight polyethylene having a specified intrinsic viscosity [eta] and a specific amount of a high-molecular weight polypropylene having a specified intrinsie viscosity [eta] and further having physical properties of (a)=900kg/cm2 tensile strength in all the directions, (b) 0.5-50sec/10cc air permeability, (c) microfibrils of the polyethylene and polypropylene constituting the film, (d) a continuous layer formed from at least a part of the respective microfibrils and (e) observation of two peaks of the melting points assigned to the polyethylene and one peak of the melting point assigned to the polypropylene when the film is observed with a differential scanning calorimeter.