Patent ID: 11872740
Assignee: BERRY PLASTICS CORPORATION
Field: Other special machines (Mechanical engineering)
Classification: CPC B  Y | IPC B

Claim 16:
17. A process for making a multi-layer breathable barrier film comprising the steps of
co-extruding a first composition that comprises polyethylene, polypropylene, or a combination thereof and an alkaline earth metal carbonate and a second composition that comprises a hygroscopic polymer to form a multi-layer molten web, the alkaline earth metal carbonate comprising at least about 50% by weight of the microporous breathable film, the multi-layer molten web comprising a microporous breathable film layer and a moisture-permeable barrier layer,
casting the molten web against a surface of a chill roll under negative pressure by a vacuum box, and without use of a nip, to form a quenched film, wherein the molten web is configured to hit the surface of the chill roll within a distance of less than about 3 inches,
stretching the quenched film by cross-directional intermeshing gear (CD IMG) stretching and machine direction (MD) stretching to form the multi-layer breathable barrier film, wherein at least a portion of the stretching is performed at a temperature of between about 60 degrees Fahrenheit and about 200 degrees Fahrenheit, and
annealing the multi-layer breathable barrier film at a temperature of between about 75 and about 225 degrees Fahrenheit;
wherein the process for making the multi-layer breathable barrier film does not include MD-IMG stretching, and wherein the MD stretching occurs after the CD-IMG stretching; and
wherein the microporous breathable film layer made by the process has a basis weight of less than about 10 gsm, a Dart Impact Strength of greater than about 90 grams, and a strain at peak machine direction of at least about 125%.