Stock material or miscellaneous articles – Coated or structually defined flake – particle – cell – strand,... – Rod – strand – filament or fiber
Reexamination Certificate
2001-04-06
2003-01-21
Acquah, Samuel A. (Department: 1711)
Stock material or miscellaneous articles
Coated or structually defined flake, particle, cell, strand,...
Rod, strand, filament or fiber
C528S272000, C528S296000, C528S300000, C528S302000, C528S308000, C528S308600, C525S437000, C525S444000, C428S357000
Reexamination Certificate
active
06509091
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to polyethylene glycol modified copolyester fibers that have exceptional moisture management characteristics and that can be formed into exceptionally comfortable fabrics.
BACKGROUND OF THE INVENTION
Polyester filament is strong, yet lightweight, and has excellent elastic memory characteristics. Polyester fabric resists wrinkles and creases, retains its shape in garments, resists abrasions, dries quickly, and requires minimal care. Because it is synthetic, however, polyester is often considered to have an unacceptable appearance for garment purposes when initially formed as a filament. Accordingly, polyester filaments require texturing to produce acceptable characteristics of appearance, hand, and comfort in yarns and fabrics. Even then, polyester is often viewed unfavorably in garments.
In pursuit of improved polyesters, various chemical modifications have been attempted to obtain desirable textile features. Unfortunately, some such treatments can produce unexpected or unwanted characteristics in the modified polyester. For example, polyethylene glycol enhances certain polyester properties, such as dye uptake, but diminishes other properties-especially those melt phase characteristics that are critical to filament spinning. Consequently, manufacturers have found that significant fractions of polyethylene glycol in copolyester can complicate—and even preclude—the commercial production of acceptable copolyester filaments. To gain commercial acceptance, modified polyesters must be compatible with commercial equipment with respect to melt-spinning, texturing, yarn spinning, fabric forming (e.g., weaving and knitting), and fabric finishing. This need for processing compatibility through conventional equipment has constrained the development of innovative polyester compositions.
To overcome the limitations of polyester compositions, polyester fibers are often blended with other kinds of fibers, both synthetic and natural. Perhaps most widely used in clothing are blended yarns and fabrics made of polyester and cotton. In general, blended fabrics of polyester and cotton are formed by spinning blended yarn from cotton fibers and polyester staple fibers. The blended yarns can then be woven or knitted into fabrics.
Cotton, like polyester, has certain advantages and disadvantages. Cotton is formed almost entirely of pure cellulose. Cotton fibers are typically about one inch long, but can vary from about one half inch to more than two inches. Mature cotton fibers are characterized by their convolutions. Under a microscope, cotton appears as a twisted ribbon with thickened edges. Cotton is lightweight, absorbs moisture quickly and easily, and has a generally favorable texture (i.e., hand) when woven into fabrics. Cotton, however, lacks strength characteristics and elastic memory. Consequently, garments formed entirely of cotton require frequent laundering and pressing.
Blends of cotton and polyester fibers have found wide-ranging acceptance as they combine the desirable characteristics of each. Even so, there are continuing efforts to develop polyester filament, yarns, and fabrics that more closely resemble those of cotton, silk, rayon, or other natural fibers. One example is polyester microfibers, which are characterized by extremely fine filaments that offer exceptionally good aesthetics and hand, while retaining the benefits of polyester. Polyester microfibers, however, have proved to be difficult to dye because of their high degree of molecular orientation and crystallinity.
A need continues to exist, however, for enhanced polyester compositions that have properties similar to those of cotton and other natural fibers, while retaining the advantages of polyester. Research and development by Wellman, Inc. demonstrates that improved wicking may be achieved in copolyester fibers, yarns, and fabrics by selectively incorporating polyethylene glycol.
For example, one such PEG-modified composition and method for producing the same is disclosed by Nichols et al. in commonly-assigned, pending U.S. patent application Ser. No. 09/141,665, filed Aug. 28, 1998, for Polyester Modified with Polyethylene Glycol and Pentaerythritol. U.S. patent application Ser. No. 09/141,665, which is incorporated entirely herein by reference, discloses a polyester composition that includes polyethylene terephthalate, polyethylene glycol in an amount sufficient to increase the wetting and wicking properties of a fiber made from the composition to a level substantially similar to the properties of cotton, but less than the amount that would reduce the favorable elastic memory properties of the polyester composition, and chain branching agent in an amount that raises the melt viscosity of the polyester composition to a level that permits filament manufacture under substantially normal spinning conditions. Including significant concentrations of branching agents to increase melt viscosity is sometimes undesirable, however, because branching agents promote cross-linking. This reduces filament strength, which can lead to processing failures.
Another method for achieving enhanced polyester fibers is described by Branum in commonly-assigned, pending U.S. patent application Ser. No. 09/444,192, filed Nov. 19, 1999, for a Method of Preparing Polyethylene Glycol Modified Polyester Filaments. U.S. patent application Ser. No. 09/444,192, which, as noted, is incorporated entirely herein by reference, describes copolymerizing polyethylene glycol, which typically makes up between about 4 percent and 20 percent by weight of the resulting copolyester, into polyethylene terephthalate in the melt-phase to a-relatively low intrinsic viscosity (i.e., a viscosity that will not support filament spinning). The resulting PEG-modified polyester is then further polymerized in the solid phase until the copolyester is capable of achieving a melt viscosity sufficient to spin filaments. By introducing a solid state polymerization (SSP) step, this method reduces the need to add branching agents, such as pentaerythritol, to increase the melt-phase polymerization rate and thereby achieve an intrinsic viscosity that facilitates the spinning of filaments. U.S. patent application Ser. No. 09/444,192 explains that branching agents promote cross-linking, which can lead to relatively weaker textiles.
Furthermore, a related method for achieving enhanced polyester fibers is described by Branum in commonly-assigned, pending application Ser. No. 09/484,822, filed Jan. 18, 2000, for Polyethylene Glycol Modified Polyester Fibers and Method for Making the Same. U.S. patent application Ser. No. 09/484,822, which is a continuation-in-part of the aforementioned application Ser. No. 09/444,192 and which is also incorporated entirely herein by reference, describes copolymerizing polyethylene glycol and branching agent into polyethylene terephthalate in the melt-phase to form a copolyester composition having an intrinsic viscosity of at least about 0.67 dl/g. Thereafter, copolyester filaments can be spun from the copolyester composition.
The foregoing PEG-modified copolyester fibers may be advantageously incorporated into products as discussed by Branum et al. in pending application Ser. No. 09/761,446, filed Jan. 17, 2001, for Nonwoven Fabrics Formed from Polyethylene Glycol Modified Polyester Fibers and Method for Making the Same. U.S. patent application Ser. No. 09/761,446, which is a continuation-in-part of the aforementioned application Ser. No. 09/484,822 and which is also incorporated entirely herein by reference, describes a nonwoven fabric that is formed of polyethylene glycol modified copolyester fibers that include polyethylene terephthalate in an amount sufficient for the copolyester staple fibers to possess dimensional stability properties (e.g., shrinkage during home laundering) substantially similar to those of conventional, unmodified polyethylene terephthalate fibers, polyethylene glycol in an amount sufficient for the copolyester fibers to possess wicking characteristics that are superior to those of
Branum James Burch
Carnes Keith James
Nichols Carl Steven
Acquah Samuel A.
Summa & Allan P.A.
Wellman, Inc.
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