Plastic and nonmetallic article shaping or treating: processes – Direct application of fluid pressure differential to... – Production of continuous or running length
Patent
1997-01-30
1998-05-26
Tentoni, Leo B.
Plastic and nonmetallic article shaping or treating: processes
Direct application of fluid pressure differential to...
Production of continuous or running length
264103, 264184, 2642108, 26421115, 26421116, 264233, D01D 506, D01F 626, D01F 674, D02G 302
Patent
active
057560404
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
This invention relates to articles of polybenzazole polymer and, more specifically, to fabrics of polybenzazole fiber.
Nonwoven fabrics are known materials which comprise assemblies of textile fibers held together by mechanical interlocking in a random web or mat, by fusing of thermoplastic fibers, or by bonding the fibers with a cementing medium such as starch, glue, casein, rubber, latex, cellulose derivative, or synthetic resins. Polybenzazole fibers are known fibers which are prepared by extruding filaments of a polybenzazole dope, drawing the filaments across an air gap, combining the filament to form a multifilament structure, and then washing and drying the structure under conditions sufficient to remove the acid solvent and the water from the filament. An efficient process for the preparation of nonwoven fabrics of polybenzazole would be desirable.
BRIEF DESCRIPTION OF THE DRAWINGS
FIGS. 1 and 2 are schematic representations of two embodiments of the process of the invention.
SUMMARY OF THE INVENTION
In one aspect, this invention is a continuous process for preparing nonwoven fabrics of polybenzazole filaments, which comprises spinning at least two polybenzazole dope filaments simultaneously, and intermingling and depositing the filaments on a substantially planar collecting surface.
It has been discovered that the process of the invention provides a means of preparing nonwoven polybenzazole fabrics in a continuous, on-line process which permits the polybenzazole dope to be extruded at a very high speed, since the speed of the on-line process is not limited by the line speed which would be necessary to wash and dry single filaments in an on-line process. Further, since the fabric moves through the washing and drying equipment at a much slower rate of speed than a single fiber, fewer washing and drying cabinets may be required to effectively wash and dry the fabric. These and other advantages of the invention will be apparent from the description which follows.
In the process of the invention, two or more polybenzazole dope filaments are extruded onto a substantially planar collecting surface. The polybenzazole filaments used in the process of the invention may be obtained by spinning a dope containing a polybenzazole polymer. As used herein, "polybenzazole" refers to polybenzoxazole (PBO) homopolymers, polybenzothiazole (PBT) homopolymers, and random, sequential, or block copolymerized polymer of PBO and PBT. Polybenzoxazole, polybenzothiazole, and random, sequential, or block copolymerized polymers thereof are described, for example, in "Liquid Crystalline Polymer Compositions, Process and Products" by Wolfe et. al, U.S. Pat. No. 4,703,103 (Oct. 27, 1987); "Liquid Crystalline Polymer Compositions, Process and Products" U.S. Pat. No. 4,533,692 (Aug. 6, 1985); "Liquid Crystalline Poly(2,6-benzothiazole) Composition, Process and Products," U.S. Pat. No. 4,533,724 (Aug. 6, 1985); "Liquid Crystalline Polymer Compositions, Process and Products," U.S. Pat. No. 4,533,693 (Aug. 6, 1985); "Thermooxidatively Stable Articulated p-Benzobisoxazole and p-Benzobisthiazole Polymers" by Evers, U.S. Pat. No. 4,539,567 (Nov. 16, 1982); and "Method for Making Heterocyclic Block Copolymer" by Tsai, U.S. Pat. No. 4,578,432 (Mar. 25, 1986).
The structural units present in PBZ polymer are preferably selected so that the polymer is lyotropic liquid crystalline. Preferred monomer units are illustrated below in Formulae I-VIII. The polymer more preferably consists essentially of monomer units selected from those illustrated below, and most preferably consists essentially of cis-polybenzoxazole, trans-polybenzoxazole, or trans-polybenzothiazole. ##STR1##
Suitable polybenzazole polymers or copolymers and dopes can be synthesized by known procedures, such as those described in Wolfe et al., U.S. Pat. No. 4,533,693 (Aug. 6, 1985); Sybert et al., U.S. Pat. No. 4,772,678 (Sep. 20, 1988); Harris, U.S. Pat. No. 4,847,350 (Jul. 11, 1989); and Gregory et al., U.S. Pat. No. 5,089,591 (Feb. 18, 1992).
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Tentoni Leo B.
Toyobo Co. Ltd.
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