Importance

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Abstract

An apertured film extruded from a crystalline, thermoplastic, extrudable fluoroplastic material. The film includes spaced-apart strand segments defining apertures therebetween and has at least 10 strand segments per inch. The film has a thickness of 2-12 mils and a Frazier air permeability number in the range of 200-2,000. The invention includes a process for preparing an apertured thermoplastic film by a single-sided embossing method. The process includes the steps of extruding in the machine direction, a film of a molten, crystalline, thermoplastic, extrudable, fluoroplastic material. The molten extruded film is passed in the machine direction through the nip of two metal rollers. One of the rollers has a substantially smooth surface, having a convex configuration as viewed from a direction substantially parallel to the axis of the roll, such that the diameter in the center of the roll is in the range of 8-12 mils greater than the diameter at the ends of the roller for a 40 inch roller. The other roller includes a plurality of discrete, raised projections disposed in a pattern. Each of the projections terminates in a distal end. The ends are separated from each other and are completely surrounded by continuous surface regions located proximate of the distal ends. A sufficient pressure is applied at the nip to cause a plurality of small apertures and/or thin areas to be formed in the extruded film in substantially the same pattern as the pattern of discrete, raised projections of the other of the rollers. The film is stretched in both the cross-machine direction and in the machine direction to increase the open area of the apertures and cause the thin areas to open into apertures. The invention also includes a laminated structure.

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First Claim