Abstract: This invention relates to improved sheet products and specifically to improved nonwoven sheet products made from highly oriented plexifilamentary film-fibril webs. The improved sheet products have high opacity and strength with a much wider range of porosity or Gurley Hill Porosity Values. In particular, sheet products made in accordance with the present invention have considerably higher Gurley Hill Porosity Values than similar weight sheet products subject to the same finishing treatments in accordance with prior known sheet materials. Similarly, sheet products made in accordance with the present invention can be made which have much lower Gurley Hill Porosity Values than prior sheet materials. The invention includes numerous methods and data characterizing the webs and sheets that form the improved sheet materials.

Abstract: This invention relates to improved sheet products and specifically to improved nonwoven sheet products made from highly oriented plexifilamentary film-fibril webs. The improved sheet products have high opacity and strength with a much wider range of porosity or Gurley Hill Porosity Values. In particular, sheet products made in accordance with the present invention have considerably higher Gurley Hill Porosity Values than similar weight sheet products subject to the same finishing treatments in accordance with prior known sheet materials. Similarly, sheet products made in accordance with the present invention can be made which have much lower Gurley Hill Porosity Values than prior sheet materials. The invention includes numerous methods and data characterizing the webs and sheets that form the improved sheet materials.

Abstract: This invention relates to a system and process for modifying the resulting properties of a flash spun plexifilamentary film-fibril web and spunbonded nonwoven sheets made from such webs. In particular, the system includes specifically designed letdown chamber arrangements wherein the solution of polymer and spin agent transitions from a single phase solution to a two phase solution in the letdown chamber prior to spinning at the spin orifice. The method comprises altering the configuration of the letdown chamber to alter the properties of the web and the sheet products made therefrom.

Abstract: Controlled porosity composite sheets comprising a melt-blown polypropylene fiber web having a spunbonded polypropylene fiber sheet laminated to at least one side thereof are made by calendering an assembly of the component webs in such a manner that, when a two-layer composite sheet is made, the web of melt-blown fibers is in contact with a metal roll heated to 140.degree.-170.degree. C. operating against an unheated resilient roll; and, when a three-layer composite sheet is made, the spunbonded web in contact with the heated metal roll has a dtex per fiber value of less than 6.These composite sheets have a Gurley-Hill porosity of about 5-75 seconds, excellent mechanical and tear strengths, high water vapor penetration rate, and low liquid water permeability. They are particularly suitable for making housewrap sheets and sheets for sterile packaging. In the sterile packaging field, they are significantly better than medical paper used for the same purpose.

Abstract: A process for hydraulically needling a web of staple fibers into an unbonded flash spun web made of continuous plexifilaments to form a spunlaced nonwoven fabric. The web of staple fibers is positioned against the unbonded flash spun web and then hydraulically needled such that the staple fibers are embedded into and entangled with the unbonded flash spun web to form a spunlaced nonwoven fabric. Optionally, the spunlaced nonwoven fabric can be thermally bonded to maintain or increase the permeability of the fabric. Thermal bonding can be used to control the level of permeability depending on the end-use desired. Spunlaced nonwoven fabrics made by the inventive process are particularly useful in filtration applications (e.g., vacuum cleaner bags) when thermal bonding is employed and as bulky, downproof and featherproof barrier liners for garments, sleeping bags, pillows, comforters and the like when thermal bonding is not employed.

Abstract: A bonded composite sheet comprising a layer of flash-spun polyethylene plexifilamentary film-fibril strand sheet in face-to-face contact with a layer of polyethylene synthetic pulp is highly suited for detailed printing thereon.

Abstract: A bonded composite sheet comprising a layer of flash-spun polyethylene plexifilamentary film-fibril strand sheet in face-to-face contact with a layer of polyethylene synthetic pulp is highly suited for detailed printing thereon.

Abstract: Fibrous polyolefin nonwoven sheets are bonded and stretched in a continuous, multiple stage process. First, the sheet is heated without significant stretching to a temperature that is close to, but below, the melting temperature of the polyolefin. Then, as the sheet is forwarded to a first stretching stage, the sheet temperature is decreased by 5.degree. to 40.degree. C. and thereafter the sheet is alternately heated and cooled as it passes through successive stretching stages, before final cooling to below 60.degree. C. In comparison to similar sheets bonded and stretched at constant temperature, the sheets produced by the process of the present invention are significantly more uniform in thickness.

Abstract: A driven stirrer mounted above the melting grid in a melt grid spinning apparatus provides a means to distribute flake, descending from source of supply to the melt grid away from the center of the grid toward its sidewalls.