Stock material or miscellaneous articles – Web or sheet containing structurally defined element or... – Including interlaminar mechanical fastener
Patent
1993-01-11
1994-03-22
Bell, James J.
Stock material or miscellaneous articles
Web or sheet containing structurally defined element or...
Including interlaminar mechanical fastener
162146, 1621573, 264 12, 264 14, 264141, 264178F, 264180, 264181, 264184, 264200, 264517, 264518, 428364, D03D 300
Patent
active
052962865
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a process for preparing subdenier fibers from isotropic polymer solutions which may be collected in the form of pulp-like short fibers, fibrids, rovings, and mats. The invention also contemplates and includes products having novel subdenier fiber structures which are produced according to the aforementioned process.
2. Description of the Prior Art
Different methods are known in the art for preparing sheet structures and non-woven articles of discontinuous thermoplastic fibers.
For example, Butin et al., U.S. Pat. No. 3,849,241, and European Publication 0166830, disclose directing gas streams at a fiber-forming polymer in the molten state and then collecting the fibers on a screen.
It is also known in the art to flash extrude a continuous fibrillated polymeric structure and to shred it by directing a stream of fluid against the structure at the moment of its formation. (See, Raganato et al., U.S. Pat. No. 4,189,455).
However, none of the foregoing references disclose a jet-attenuating process for preparing subdenier fibers from isotropic solutions.
Morgan, U.S. Pat. No. 2,999,788 describes the preparation of fibrids of various synthetic organic polymers and their use in making synthetic sheet structures, such as papers. Such papers, when prepared from poly(meta-phenylene isophthalamide) fibrids, are useful in electrical applications, especially when combined with poly(meta-phenylene isophthalamide) short fibers (floc). As disclosed by Gross, U.S. Pat. No. 3,756,908, the poly(meta-phenylene isophthalamide) fibrids of the art are filmy particles which act as a binder for the floc and impart good electrical properties. However, these fibrids have a deficiency in that they seal the papers excessively and so act to reduce porosity. Porosity is a valuable property because it facilitates coating and saturation of the papers with varnishes and resins, a method well known in the art to modify and improve properties of electrical papers.
An object of the present invention is to prepare new pulp-like poly(meta-phenylene isophthalamide) fibrids. These pulp-like fibrids may be used to prepare sheet structures, such as papers which demonstrate improved porosity and electrical properties. These sheet structures may be used in preparing laminate and composite structures.
SUMMARY OF THE INVENTION
This invention provides a process for preparing subdenier fiber from isotropic polymer solutions. The process comprises 1) extruding a stream of an isotropic solution of a polymer through a spinneret orifice into a chamber, 2) introducing a pressurized gas into said chamber, 3) directing the gas in the flow direction of and in surrounding contact with said stream within the chamber, 4) passing both the gas and stream through an aperture into a zone of lower pressure at a velocity sufficient to attenuate the stream and fragment it into fibers, and 5) contacting the fragmented stream in said zone with a coagulating fluid. A suitable gas for contacting the extruded stream in the chamber is air and the zone of lower pressure wherein both the gas and stream pass may be air at atmospheric pressure. Preferably, the coagulating fluids are water, dimethylsulfoxide or dimethylacetamide.
Preferred embodiments of the present invention include spinning isotropic polymer solutions of polyacrylonitrile, poly(m-phenylene isophthalamide), a copolymer of 3,4'-diaminodiphenyl ether and isophthaloyl-bis-(caprolactam), and a mixture of poly(m-phenylene isophthalamide) and a copolymer of 3,4'-diaminodiphenyl ether and isophthaloyl-bis-(caprolactam).
The fragmented stream of subdenier fibers may be collected in the form of pulp-like short fibers, fibrids, rovings, or mats, and such products are contemplated as part of the present invention.
In one embodiment of the invention, poly(m-phenylene isophthalamide) pulp-like fibrids are produced by spinning a polymer solution comprising about 12 to 19% by weight poly(m-phenylene isophthalamide) polymer. Hot air having a p
REFERENCES:
patent: 3441473 (1969-04-01), Brundige et al.
patent: 3849241 (1974-11-01), Butin et al.
patent: 4013744 (1977-03-01), Huerten et al.
patent: 4189455 (1980-02-01), Raganato et al.
patent: 4818463 (1989-04-01), Buehning
patent: 4963298 (1990-10-01), Allen et al.
Allen Steven R.
Gale David M.
Mian Aziz A.
Samuels Sam L.
Shih Hsiang
Bell James J.
E. I. Du Pont de Nemours and Company
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