Patent ID: 6358457
Filing Date: 2002-03-19
Classification: B29C,B29K,C08J,C09J,Y10T

Abstract:
A method of biaxially stretching a polymeric film according to an overbias or overstretch stretch profile to a final first direction stretch parameter and a final second direction stretch parameter, the method comprising the steps of:a) imparting a sufficiently high temperature to the film to allow biaxial stretch; b) biaxial tenter stretching the film to a peak first direction stretch parameter which is greater than the final first direction stretch parameter, wherein the final first direction stretch parameter is less than the uniaxial natural stretch parameter, wherein at least 75% of the final first direction stretch parameter is attained before no more than 50% of the final second direction stretch parameter is attained, and wherein the final first direction stretch parameter is no greater than the final second direction stretch parameter; and c) subsequent to step b), retracting the film in the first direction from the peak first direction stretch parameter to the final first direction stretch parameter; wherein uniformity of properties is attained in the film in the first direction by steps a) through c) despite the final first direction stretch parameter being less than the uniaxial natural stretch parameter.