improved processes for the manufacture of extended filled microporous films

摘要

Breathable barriers, comprising a thermoplastic polymer and at least 30% by weight filler, are stretched in one direction in multiple discrete steps wherein the strain rate of each discrete stretching step is less than about 100,000%/minute and wherein the line speed of the last stretching step is in excess of 500 feet per minute. The resulting films may be stretched, as a result of the cumulative discrete stretching operations, from about 2 to 7 times its original length in order to create a breathable barrier having a WVTR in excess of 800 g/m²/day and a hydrohead of at least 60 cm.