Multilayer microporous films and methods of making

• Main Authors: PAIUAN WU, GREGORY K JONES, KENNETH L LILLY, LARRY HUGHEY MCAMISH, MARK ANDREW WENDORF, CHRISTOPHER AARON SHELLEY
• Format: Patent
• Language: English
• Published: 13.09.2007
• Subjects: AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING; INDEXING SCHEME ASSOCIATED WITH SUBCLASS B29C, RELATING TO PARTICULARARTICLES; INDEXING SCHEME ASSOCIATED WITH SUBCLASSES B29B, B29C OR B29D, RELATING TO MOULDING MATERIALS; LAYERED PRODUCTS; LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT ORNON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM; PERFORMING OPERATIONS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDEDFOR; SHAPING OR JOINING OF PLASTICS; TRANSPORTING; WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE, IN GENERAL

Multilayer microporous films comprise first and second microporous film layers. The first film layer has a first maximum pore size and the second film layer has a second maximum pore size different from the first maximum pore size. In a more specific embodiment, the multilayer microporous films comprise coextruded first, second and third microporous film layers. One of the first, second and third film layers has a maximum pore size smaller than the respective maximum pore sizes of the remaining layers of the multilayer film or larger than the respective maximum pore sizes of the remaining layers of the multilayer film, and the one layer does not have an unconstrained surface in the multilayer film. Methods for producing multilayer microporous films provide a first film layer having a maximum pore size upon stretching which is different from that of a second film layer upon stretching.