Stock material or miscellaneous articles – Coated or structually defined flake – particle – cell – strand,... – Rod – strand – filament or fiber
Reexamination Certificate
1999-02-26
2001-01-16
Edwards, N. (Department: 1774)
Stock material or miscellaneous articles
Coated or structually defined flake, particle, cell, strand,...
Rod, strand, filament or fiber
C428S370000, C264S172150
Reexamination Certificate
active
06174601
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to composite bicomponent fibers having a sheath-core structure. The advantages of the composite bicomponent fiber are achieved principally by the cooperation of the characteristics of the core component, such as high tensile strength and low cost, with the enhanced surface properties of the sheath component, particularly resistance to staining, water, chemicals, and high temperatures, along with low electrical conductivity.
2. Prior Art
Composite bicomponent sheath-core fibers and production processes therefor are known. Typically, nylon fibers, nylon 6, nylon 6,6, or copolymers thereof, are used as a core component (see for example U.S. Pat. No. 5,447,794-Lin). The sheath component is typically a variation of the same material as the core material, as shown by Lin, or a polymer such as a polyester or polyolefin (see Hoyt and Wilson European Patent Application No. 574,772). Composite, bicomponent, sheath-core fibers are generally made by delivery of the two component materials through a common spinnerette or die-plate adapted for forming such composite, bicomponent, sheath-core fibers.
Generally, composite bicomponent sheath-core fibers have been used in the manufacture of non-woven webs, wherein a subsequent heat and pressure treatment to the non-woven web causes point-to-point bonding of the sheath components within the web matrix to enhance strength or other such desirable properties in the finished web or fabric product. Other uses of composite bicomponent sheath-core fibers include the production of smaller denier filaments, using a technology generally referred to as “islands-in-the-sea”, to produce velour-like woven fabrics typically used for apparel.
Such technology is typically employed in the production of relatively large diameter, monofilament, composite, bicomponent sheath-core fibers for specialized end uses. Typically, many individual monofilaments are grouped into a multifilament yarn. However, the spinning of a small denier multifilament yarn bundle, e.g. less than 100 denier comprised of many (e.g. ten or more) individual sheath-core continuous filaments, is generally commercially unavailable because of the complexities associated with the process and materials used for the sheath and core components.
In order to successfully spin a small denier multifilament yarn bundle comprised of a plurality of individual, composite, bicomponent, sheath-core fibers, the limitations imposed by the known production processes and the materials used as the core and sheath components must be overcome. The demanding requirements of the final composite yarn would be met by simultaneously extruding two different materials in a common process, which requires a degree of Theological, thermal and viscoelastic similarity between the two materials. Additionally, the complexity of quality extrusion increases as the diameter of the individually extruded composite bicomponent sheath-core fibers decreases. Further, once the extruded filaments exit the spin-plate of the spinnerette or die-plate, the filaments must be drawn, typically employing an annealing process done at high speed and under tension, to align the crystal structure and develop strength in the overall composite.
A similarity in stress/strain behavior of the materials used for the core component and the sheath component is required to avoid premature overstretching and breaking (% elongation) during the drawing process. Additionally, sufficient elongation, and tensile strength (tenacity) must be achieved in the final composite yarn to withstand the physical rigors of weaving. Further, the generally thin sheath component should withstand high abrasion while maintaining its integrity and encapsulation of the core component.
The choice of materials used for the sheath-core components is limited by both the rigors of the manufacturing process and the requirements of the final composite yarn. The prior art includes at least the following combinations of materials for sheath-core fibers:
sheath
core
polyethylene terephtalate
polyethylene (PE)
(polyester, PET)
PET
polypropylene (PP)
PP
PET
nylon 6
nylon 6,6
PET, PP, nylon 6
water soluble components
The rheological and viscoelastic properties of thermoplastic fluoropolymers such as polytrifluoroethylene (PTFE), are very dissimilar to the above listed materials. Consequently few such fluoropolymers have been made as one component fibers, particularly in a multifilament format. For example, PTFE has not been known to be melt processible and has only been described as extruded in a proprietary wet spinning process wherein the PTFE latex is mixed and coextruded with a cellulosic dope.
SUMMARY OF THE INVENTION
HALAR® (ethylenemonochlorotrifluoroethylene, E-CTFE), which is supplied by Ausimont USA, Inc., possesses certain enhanced surface properties which are desirable in a sheath component. However, ordinary E-CTFE also has several properties which are adverse to its use as a sheath component. E-CTFE exhibits high viscosity in the melted state and also requires stabilization against thermal degradation by inclusion of volatile additives which may off-gas and interfere with extrusion. Standard E-CTFE also rapidly crystallizes, cools and sets before the drawing process and other necessary fiber making parameters can be applied. Experimental composite bicomponent sheath-core fibers made with standard E-CTFE as a sheath component typically have exhibited low elongation capability, exhibit fracture even when not under tension, and exhibit discontinuities in the sheath component and strength too low to successfully weave into a fabric comprised of small denier yarn bundles.
While different ones of the prior composite bicomponent sheath-core fibers have certain desirable properties, there has been a continuing need and a desire in the art to develop a bicomponent sheath-core fiber having a material such as E-CTFE as the sheath component, while possessing the advantages of the cooperation of the desirable characteristics of a strong core component and the enhanced surface properties of a sheath component.
Accordingly, it is an object of the present invention to provide an E-CTFE coating (sheath) material which overcomes the physical and manufacturing disadvantages of prior E-CTFE components when used as the sheath component in a composite, bicomponent sheath-core fiber.
It is another object of the present invention to provide a composite bicomponent fiber having a sheath-core structure where the core component is any spinnable polymer with fiber properties similar to nylon 6, nylon 6,6, polyethylene terephtalate and copolymers thereof and a sheath component of the fluoroploymer ethylenemonochlorotrifluoroethylene having a range of volume crystallinity between about 10% and 49%, and extending at the lower end of the range to about 1%.
It is another object of the present invention to provide composite bicomponent fiber having a sheath-core structure where the sheath component is ethylenemonochlorotrifluoroethylene having a non 1:1 molar ratio of ethylene to monochlorotrifluoroethylene.
It is another object of the present invention to provide composite bicomponent fiber having a sheath-core structure where the sheath component is ethylenemonochlorotrifluoroethylene having a volume crystallinity between about 20% and 30%.
It is another object of the present invention to provide a composite, bicomponent, sheath-core fiber using E-CTFE as the sheath component which ensures better utilization of the properties of the sheath-core bicomponent fiber without deterioration in the properties of the sheath component.
It is another object of the present invention to provide new and better performing, small denier continuous yarns comprised of a plurality of sheath-core fibers having E-CTFE as the sheath component without a deterioration of the properties of the yarns.
It is another object of the present invention to provide a process for producing such an E-CTFE component and a composite, bicomponent sheath-core fiber and a pr
Fagan Joseph P.
Stanitis Gary E.
Ausimont USA, Inc.
Edwards N.
Norris & McLaughlin & Marcus
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