Flaechengebilde und Verfahren zur Herstellung desselben

摘要

A coherent non-woven sheet which may be coated with polymeric or non-polymeric material (see below) comprises one or more continuous plexifilaments (a plexifilament being, as disclosed in Specification 891,943, a yarn-like strand which is defined as a continuous extruded or spun shaped filamentary structure of a crystalline synthetic polymer comprising a three dimensional integral plexus and characterized in that the plexus is composed of a multitude of molecularly oriented film-like and/or ribbon-like structural units, referred to as "film fibrils", which unite and separate at random intervals along and across the plexus) in which the film fibrils have an average thickness less than 4 microns, the plexifilament or plexifilaments being arranged in an overlapping and intersecting relationship and the sheet being consolidated to such a degree that it has an overall tensile strength greater than 0,3 lb./in./oz./yd.2. The plexifilaments may be in two or more layers, each layer consisting essentially of a plurality of substantially parallel strands of plexifilamentary material. The plexifilaments may be fused together either by heat or mechanical means and the sheet may be embossed so as to give raised and depressed portions, the plexifilaments being self-bonded in the depressed portions to a greater density than in the raised portions. The synthetic polymer of some or all the plexifilaments is preferably polyethylene or a blend of linear polyethylene and minor amounts of branched polyethylene or a blend of polyethylene and polyisobutylene. In forming such non-woven sheets a batt is formed by arranging in an overlapping and intersecting relationship one or more continuous plexifilaments and the batt is then consolidated into a sheet. The spinning of the plexifilament or plexifilaments and the formation of the batt may be carried out in a continuous operation and the consolidating may be done by calendering with or without heat fusing of some of the plexifilaments. The batt may be formed in layers by laying first in one direction and then at approximately 90 degrees thereto and such a batt may be subjected to calendering to produce a single sheet. The sheet material may be coated with polymeric or non-polymeric materials. The latter include waxes, dyes, pigments, &c. Polymeric compositions include polyethylene, polypropylene, polyisobutylene, natural rubber, neoprene, chlorosulphonated polyethylene, polyvinyl chloride and various vinyl halide and vinyl ester polymers and interpolymers. These polymeric compositions may be applied by either melt, solvent or dispersion techniques, calendering, dipping, direct extrusion and "kiss-roll" methods. Specifications 887,008 and 891,944 also are referred to.