Patent ID: 6610163
Filing Date: 2003-08-26
Classification: B29C,B29K,B32B,Y10T

Abstract:
A method for producing a stretched moisture vapor permeable multi-ply film comprising the steps of:extruding a polymer comprising a filler having a particle size suitable for pore formation, said polymer suitable for use as a polymeric film; hot blowing the extruded film, forming a hot blown film bubble; collapsing said hot blown film bubble, forming a multi-ply film comprising a plurality of film plies; and stretching said plurality of film plies, forming a stretched multi-ply film having a plurality of micropores in each of said film plies, said micropores having an average pore size not greater than about 0.06 microns; wherein the stretched multi-ply film has a moisture vapor transmission rate of at least about 1200 grams/m2-24 hours and meets the barrier standards defined in ASTM F1670 and ASTM F1671.