Improved multilayer porous membranes and methods of making the same

Abstract

A multilayer membrane comprising at least two co-extruded layers where the two co-extruded layer contain different polymers and one of the two co-extruded layers contains an extrusion additive. Examples of useful extrusion additives may include a nucleating agent or a pore-forming particulate. A method for making the membrane is also disclosed. Using an extrusion additive when co-extruding two different polymers avoids some of the drawbacks associated with processes involving the co-extrusion of different polymers, particularly processes where a co-extruded non-porous precursor is later stretched to form pores. For example, the drawback of lower permeability, difficulty to make lower Gurley, and splittiness may be improved.

Dependencies are inferred from the claim text.