US Patent 7678316 Coextruded profiled webs

A method that includes coextruding two or more thermoplastic resin streams through a profiled die plate, which die plate is shaped to form a nonplanar film (three dimensional) preferably with a regularly oscillating peak and valley structure that oscillates from a top surface to a bottom surface forming longitudinally extending ridges on both faces of the film. The film is formed by coextruding the film through the oscillating die plate opening causing partitioning of the resins in different zones in the width direction of the film. Flattening of the film results in a film with side-by-side zones formed of different polymers or relative proportions of polymers.