Textiles: manufacturing – Thread finishing – Surface modification of running length
Reexamination Certificate
2000-02-14
2001-10-16
Vanatta, Amy B (Department: 3765)
Textiles: manufacturing
Thread finishing
Surface modification of running length
C280S245000, C280S246000
Reexamination Certificate
active
06301760
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates generally to the production and processing of elastane filaments and, more particularly, to a method for selectively altering physical properties, especially denier, elongation and tenacity, of such filaments.
Elastane filaments, sometimes more commonly referred to in the textile industry as spandex filaments, are highly elastic synthetic fibers well known and commonly used throughout the textile industry, particularly for imparting a desired degree of elasticity to textile fabrics. As is well known, elastane filaments are essentially comprised of linear macromolecules primarily of segmented polyurethane, either polyetherurethane or polyesterurethane. Such elastane filaments are known to be produced by several differing spinning processes commonly referred to as dry spinning, wet spinning, reactive spinning and melt spinning.
Regardless of the precise chemical composition and the method of manufacture of an elastane filament, such filaments characteristically exhibit a very high degree of longitudinal elongation to breakage of several hundred percent, typically between four hundred and eight hundred percent of the relaxed longitudinal dimension of the filaments, with the ability to substantially completely recover from such elongation repeatedly (e.g. 95% to 98% recovery). Thus, as indicated, elastane filaments are uniquely and advantageously suited to use in textile fabrics, e.g., apparel fabrics, wherein a degree of stretchability is desirable to enhance the functionality and usability of such fabrics.
As used herein, the term “elastane” is accordingly intended to have the broadest interpretation and scope in accordance with conventional textile industry usage so as to encompass any and all filaments and fibers of the type afore-described, whether now known or subsequently developed. Reference may be had to the
Manmade Fiber Year Book
(
CFI
), Second Issue, 1995, at pages 30-40, for a more detailed technical description and understanding of elastane filaments and fibers, which work is incorporated herein for reference purposes.
Whether elastane filaments are produced by any of the known manufacturing processes of dry, wet, reactive or melt spinning, the physical properties of the filaments thusly produced are conventionally considered to be suitable for immediate use in textile fabric forming operations without the need for, or any perceived benefit from, subsequent processing. In contrast, with certain other types of extruded synthetic filaments used in the textile industry, most notably polyester and nylon, conventional wisdom and experience holds that, before such filaments are suitable for use in the manufacture of textile fabrics, manipulation of the physical characteristics of the filaments is necessary through a drawing operation, including heat setting in the case of polyester filaments, in order to improve and stabilize molecular orientation within the filaments. Such drawing and heat setting of polyester, nylon and like filaments is known to be performed either on a single filament, e.g., through a draw twisting or like process, or on multiple filaments simultaneously, e.g., in a so-called draw warping process predominantly utilized to prepare the filaments for use in weaving or warp knitting of a textile fabric.
Heretofore, drawing and heat setting of elastane filaments, whether performed on a single filament or multiple filaments, is not known to have been utilized or even attempted in the textile industry and it is believed that conventional wisdom holds that no particular benefits would result since, in contrast to polyester and nylon filaments, the molecular structure within such filaments is stable in the state of the filaments exiting the spinning process and the attendant physical characteristics of the filaments as so produced are already well suited to textile fabric applications without further processing.
SUMMARY OF THE INVENTION
In substantial contrast to the foregoing, it has surprisingly been discovered that elastane filaments will respond to a drawing and heat setting operation in manners which favorably enable the physical properties of such filaments to be altered and thereby selectively engineered, e.g., as may be desirable or even necessary to tailor such filaments to particular textile fabric applications. It is accordingly a basic object of the present invention to provide a novel method by which the physical properties of elastane filaments may be selectively altered and engineered. A more particular object of the present invention is to provide such a methodology by which elastane filaments may be engineered to modify the physical properties imparted by the conventional spinning processes and, in particular cases, to achieve properties in such filaments which may not normally be achieved through conventional spinning.
Briefly summarized, the method of the present invention contemplates the selective alteration of physical properties of an elastane filament basically by stretching the filament to a selected degree while heating the filament to a selected temperature above its glass transition temperature so as to cause the filament to become set at a reduced denier and a reduced degree of elongation. Typically and preferably, the elastane filament will be caused to travel longitudinally during performance of the present method, e.g., in a single filament drawing operation or in a multiple filament draw warping operation, wherein the uniformity of the stretching and heating imposed on the filament or filaments may be controlled via establishment of a uniform traveling speed.
Thus, by selective control of the degree of stretching imparted to the filament or filaments in coordination with selective control of the temperature to which the filament or filaments are heated and selective control of the traveling speed of the filament or filaments to determine a selected time interval over which the filament or filaments are exposed to the stretching and heating, it is possible to achieve a selective reduction in the denier of the elastane filament in conjunction with a selected reduction of its degree of elongation and, also, either a selected increase or decrease in the tenacity of the filament or filaments, depending upon the combination of processing parameters being utilized.
As persons skilled in the art will recognize, even a reduction of up to 50 percent of the degree of available elongation of an elastane filament to the point of breakage generally will not deleteriously affect the performance or usability of such filaments in textile fabric constructions because such filaments would still generally have a maximum degree of elongation in excess of one hundred to several hundred percent of the relaxed length. On the other hand, reduction of the denier of an elastane filament quite often will be highly desirable. As is known, the cost of spinning an elastane or any other synthetic filament generally increases substantially as the spun denier decreases because correspondingly fewer pounds of filament may be produced per hour. Thus, generally speaking, elastane filaments of higher denier are less costly to produce; however, since elastane filaments are typically used in combination with other non-stretchable or less-stretchable filaments or yarns for the purpose of imparting stretchability to the resultant fabric but not normally to add bulk or weight to the fabric, it is generally desirable to use elastane filaments of smaller deniers. Thus, the present invention enables these competing factors to be reconciled by enabling elastane filaments to be produced more economically and less costly at higher deniers and then to be selectively engineered to a reduced denier best suited to a given fabric application.
Broadly, it is believed that the range and combination of physical characteristics in an elastane filament achievable through the present invention is limited only by the practical minimum values of denier, tenacity and elongation the resultant filament or filaments must have to be
Beard McDaniel L.
Isbell James R.
Lawson James Lowell
Guilford Mills Inc.
Kennedy Covington Lobdell & Hickman LLP
Vanatta Amy B
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