Plastic and nonmetallic article shaping or treating: processes – Direct application of electrical or wave energy to work – Extrusion molding
Reexamination Certificate
2001-10-09
2004-07-27
Tentoni, Leo B. (Department: 1732)
Plastic and nonmetallic article shaping or treating: processes
Direct application of electrical or wave energy to work
Extrusion molding
C028S271000, C057S287000, C264S103000, C264S147000, C264S171100, C264S210200, C264S210500, C264S210800
Reexamination Certificate
active
06767498
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention is related to fine denier fibers. In particular, the invention is related to fine denier fibers obtained by splitting multicomponent fibers having an elastomeric component and to fabrics made from such fibers.
2. Description of the Related Art
Fibers formed of synthetic polymers have long been recognized as useful in the production of textile articles. Such fibers can be used in diverse applications such as apparel, disposable personal care products, medical garments, filtration media, and carpet.
It can be desirable to incorporate fine or ultrafine denier fibers into a textile structure, such as filtration media. Fine denier fibers may be used to produce fabrics having smaller pore sizes, thus allowing smaller particulates to be filtered from a fluid stream. In addition, fine denier fibers can provide a greater surface area per unit weight of fiber, which can be beneficial in filtration applications. Fine denier fibers can also impart u soft feel and touch to fabrics.
Fine denier fibers are also advantageous in producing synthetic yarns and fabrics. Yarns and fabrics made from synthetic fibers aim to be competitive with yarns and fabrics made from natural fibers by simulating spun yarns, and a variety of techniques have been attempted to produce synthetic materials having improved characteristics such as greater bulkiness and softness, superior flexibility and drape, and better barrier and filtration properties.
One method of simulating spun yarns involves cutting continuous synthetic filaments into staple fibers and spinning the staple fibers into yarns by conventional spinning methods used for natural fibers. However, this approach is a time consuming and costly. Alternatively, continuous filaments can be converted into yarns by various texturing methods at lower cost, but these yarns often inadequately simulate spun yarns.
Another technique for converting filament yarns into simulated spun yarns is the air-jet texturing process. In this process, a cold air stream is used to produce loopy bulked yarns of low extensibility. The yarn surface is covered with fixed resilient loops, which serve the same purpose as the protruding hairs in spun yarns by forming an insulating layer of entrapped still air between neighboring layers or garments (see FIG.
5
A). Synthetic yarns produced by the air-jet texturing more closely simulate spun yarn structures and resemble spun fiber yarns in their appearance and physical characteristics, although these air-jet textured yarns are not stretchable. Currently, air-jet textured yarns are widely used in outerwear and lighter-wear fabrics, upholstery fabrics and other textile applications. The use of fine denier fibers results in synthetic yarns and fabrics having desirable properties such as good softness and bulkiness as well as good flexibility and fabric drape, with superior filtration and barrier properties and coverage at low weight.
It is, however, difficult to produce fine denier fibers, in particular fibers of 2 denier or less, using conventional melt extrusion processes. Meltblowing technology is one avenue by which to produce fabric from fine denier filaments. However, meltblown webs typically do not have good physical strength, primarily because less orientation is imparted to the polymer during processing and lower molecular weight resins are employed.
Multicomponent or composite fibers having two or more polymeric components may be split into fine fibers comprised of the respective components. The single composite filament thus becomes a bundle of individual component microfilaments. Typically, multicomponent fibers are divided or split by mechanically working the fibers. Methods commonly employed to work fibers include drawing on godet rolls, beating or carding. Fabric formation processes such as needle punching or hydroentangling may supply sufficient energy to a multi component fiber to effect separation.
In addition, fine denier fibers can be prepared using a multicomponent fiber comprised of a desired polymer and a soluble polymer. The soluble polymer is then dissolved out of the composite fiber, leaving microfilaments of the other remaining insoluble polymer. The use of dissolvable matrixes, however, to produce fine denier filaments is problematic. Manufacturing yields are inherently low because a significant portion of the multiconstituent fiber must be destroyed to produce the microfilaments. The wastewater or spent hydrocarbon solvent generated by such processes poses an environmental issue. In addition, the time required to dissolve the matrix component out of the composite fiber further exacerbates manufacturing inefficiencies.
In addition to fine denier fibers, it can also be desirable to incorporate elastomeric fibers into textile structures to impart stretch and recovery properties. Elastomeric fibers or filaments are typically incorporated into fabrics to allow the fabrics to conform to irregular shapes and to allow more freedom of body movement than fabrics with more limited extensibility.
Elastomers used to fabricate elastic fabrics, however, often have an undesirable rubbery feel. Thus, when these materials are used in fabrics, the hand and texture of the fabric can be perceived by the user as sticky or rubbery and therefore undesirable. Non-elastomeric fibers can be commingled with elastomeric fibers and/or coated with an elastomeric solution to improve the feel of articles formed using elastic fibers. However, this requires additional processing steps, which can add manufacturing and materials costs. For example, a stretchable fabric is commonly produced with filament yarns or spun (staple) yarns in combination with an elastic yarn. One commonly used elastic yarn is a wrapped yarn, which has elastic filament yarn, such as Spandex yarn, in the core and wrapped by a synthetic filament yarn (see FIG.
5
B). The synthetic filament wrap yarn provides abrasive protection to the elastic core yarn. The process of making such a wrapped yarn is slow and costly. To acquire both soft and stretchable properties, the conventional yarns need to be processed through many steps of blending and twisting, which are impractical and expensive.
Further, it can be difficult to process elastomeric materials to make elastic fibers or filaments. For example, many elastomeric yarns arc formed of solvent spun elastomeric materials (Spandex). Elastomeric yarns can be produced by thermally extruding elastomeric filaments. However, one problem with this approach is breakage or elastic failure during extrusion and drawing. Due to the stretch characteristics of elastomeric polymers, the filaments tend to snap and break while being attenuated. If a filament breaks during production, the ends of the broken filament can either clog the flow of filaments or enmesh the other filaments, resulting in a mat of tangled filaments.
Elastic webs having fine denier elastomeric fibers can be produced using meltblowing technology. However, as noted above, meltblown webs typically do not have good physical strength. In addition, meltblown elastomeric webs generally have less aesthetic appeal.
SUMMARY OF THE INVENTION
The present invention provides splittable multicomponent fibers and fiber bundles which include a plurality of fine denier filaments having many varied applications in the textile and industrial sector. The fibers can exhibit many advantageous properties, such as a soft, pleasant hand, high covering power, stretch and recovery and the like. The present invention further provides fabrics formed of the multicomponent fibers and fiber bundles, as well as processes by which to produce fine denier filaments.
In particular, the invention provides thermally divisible or splittable fibers formed of elastomeric components and non-elastomeric components. The elastomeric and non-elastomeric components are selected to have sufficient mutual adhesion to allow the formation of a unitary multicomponent fiber. Indeed, the fibers can be mechanically worked, for example, by drawing, carding,
Dugan Jeffrey S.
Harris Frank O.
Talley, Jr. Arthur
Wilkie Arnold E.
Yu Jing-Peir
Edell Shapiro & Finnan LLC
Hills, Inc.
Tentoni Leo B.
Yu Shiang-Jung Ma
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