Patent ID: 6090325
Filing Date: 2000-07-18
Classification: C08F,C08J,Y10S

Abstract:
In a method for the production of biaxially-oriented film, the steps comprising(a) providing a polypropylene polymer comprising isotactic polypropylene containing at least 0.5% 2,1 insertions and having a isotacticity of at least 96% meso pentads and at least 99% meso dyads and produced by the polymerization of propylene in the presence of a metallocene catalyst, characterized by the formularac-R'R""Si(2-RiInd).sub.2 MeQ.sub.2wherein,R', R"" are each independently a C.sub.1 -C.sub.4 alkyl group or an phenyl group,Ind is an indenyl group or hydrogenated indenyl substituted at the proximal position by the substituent Ri and otherwise unsubstituted,Ri is an ethyl, methyl, isopropyl, or tertiary butyl group,Me is a transition metal selected from the group consisting of titanium, zirconium, hafnium, and vanadium, andeach Q is independently a hydrocarbyl group or containing 1 to 4 carbon atoms or a halogen;b) forming a biaxially-oriented film of said polypropylene by stressing a film formed from said polypropylene polymer in longitudinal and transverse directions to provide the biaxially-oriented film having a non-uniform melt temperature having an average value of less than 160.degree. C. and having a permeability to water of no more than 2.6 grams/m.sup.2 /day and a permeability to oxygen of no more than 2,400 cm.sup.3 /m.sup.2 /day when configured in a film having a thickness of 18 microns.