STRETCHED-FILLED MICROPOROUS FILMS AND METHODS OF MAKING THESAME

摘要

A breathable microporous film is prepared by extruding a film comprising abo ut 30 to 70 % by weight of a thermoplastic polymer, about 30 to 70 % by weight of filler particles having an average particle si ze less than about 10 microns and about 100 to 1000 PPM of a mono-functional hindered phenol, such as .alpha.-tocopherol, and then sufficiently stretching the filled film in at least one direction thereby creating a fine pore network therein and a water vapor transmission rate in excess of 300 g/m2/24 hours.