Patent ID: 7629042

Claim:
A breathable, multilayer microporous film, comprising a first outer film layer, a second inner film layer and a third outer film layer, wherein the first, second and third film layers are coextruded, wherein each film layer comprises from about 40% to about 60%, by weight of the respective layer, of at least one pore-forming filler and from about 37% to about 60%, by weight of the respective layer, of thermoplastic polymer, with each film layer rendered microporous and breathable by stretching the film layer having the pore-forming filler therein, wherein the first and third outer film layers have first and third maximum pore sizes, respectively, and the second inner film layer has a second maximum pore size which is the smallest of the first, second and third maximum pore sizes, and wherein the multilayer microporous film is liquid impervious at atmospheric pressure.