Patent ID: 6368742
Filing Date: 2002-04-09
Classification: B32B,C08J,H01M,Y02E,Y10S

Abstract:
A process for making a battery separator having an electrical resistance of less than 30 ohms-inch per mil and a puncture strength of greater than 400 grams force per mil comprising the steps of:providing a precursor having a beta crystal content of 46-60%; and biaxially stretching the precursor, a machine direction (MD) stretch being conducted at a temperature ranging between 70Â° and 110Â° C. and a MD stretch ratio ranging between 1.5 and 6.0, and a transverse direction (TD) stretch being conducted at a temperature ranging between 110Â° and 140Â° C. and a TD stretch ratio ranging between 1.5 and 6.0.