Nonwoven sheets of filaments of anisotropic melt-forming polymers and method thereof
AssigneeE. I. Du Pont de Nemours and Company
InventorPhilip E. Miller
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Abstract
Strong dimensionally stable high-melting nonwoven fibrous sheets comprised of filaments from an optically anisotropic melt-forming polymer and self-bonded at a plurality of filament cross-over points, and a process for making such sheets.
Claims10
A strong dimensionally stable high-melting nonwoven sheet comprised of filaments from an optically anisotropic melt-forming polymer, the filaments being disposed in multiple directions within the plane of the sheet and being self-bonded at a plurality of cross-over points, the filaments between bond points being substantially undeformed, the fibrous sheet having a tensile strength in at least one direction of at least 1.0 N/cm//g/m.sup.2 and having a tensile strength in a direction perpendicular to that direction which is at least 25% of the strength in that direction.
A process for preparing strong dimensionally stable high-melting nonwoven fibrous sheets comprising:
- (1) melt spinning a plurality of filaments from an optically anisotropic melt-forming polymer,
- (2) depositing the filaments on a collecting surface in the form of a loose web within which the filaments are substantially separated except for contact at cross-over points and are disposed in multiple directions within the plane of the web,
- (3) hot-pressing the web at a pressure, temperature and for a time sufficient to fuse the filaments at the cross-over points while avoiding substantial deformation of the filaments between cross-over points, and
- (4) removing the pressure from the hot-pressed web and heating it in a purged inert atmosphere at a temperature below the filament flow temperature and for a time sufficient to increase tensile strength of the sheet by at least 25%.
Dependencies are inferred from the claim text.