Bleaching and dyeing; fluid treatment and chemical modification – Nontextile – dyeing process or product – including inorganic... – Polymer from polyol and a polycarboxylic acid or derivative...
Reexamination Certificate
2000-11-08
2003-11-18
Gupta, Yogendra N. (Department: 1751)
Bleaching and dyeing; fluid treatment and chemical modification
Nontextile, dyeing process or product, including inorganic...
Polymer from polyol and a polycarboxylic acid or derivative...
C008S922000, C008S924000, C008S932000, C008S933000, C442S182000, C442S199000
Reexamination Certificate
active
06648926
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a method of heat-setting fabrics containing bicomponent fibers comprising poly(ethylene terephthalate) and poly(trimethylene terephthalate).
2. Description of Background Art
Fabrics containing poly(ethylene terephthalate) fibers can be heat-set in order to stabilize their dimensions, for example at about 350-360° F. (177-182° C.), but such fabrics exhibit little or none of the stretch-and-recovery which has become increasingly desirable.
Polyester bicomponent fibers having latent crimp can also be used in making stretch fabrics, for example as described in Japanese Patent JP61-32404 and U.S. Pat. No. 5,874,372. However, not all such bicomponent fibers have adequate stretch-and-recovery properties, and fabrics made from such fibers can also have undesirable characteristics such as poor dye washfastness and uneven surface appearance.
Japanese Published Patent Applications JP58-115144, JP11-189923, and JP05-295634 and Japanese Patent JP63-42021 disclose various processes for treating fabrics comprising bicomponent fibers made from poly(ethylene terephthalate) and other polyesters, copolyesters, or poly(ethylene terephthalate) having a different molecular weight. However, these fibers generally have inadequate crimp, and the methods require excessively high temperatures, additional twisting of the bicomponent fibers, and/or two heat-setting steps, in order to obtain the desired flat but stretchy fabric. Such additional processing of fiber and/or fabric is inefficient and costly, and an improved method of making stretch fabrics comprising polyester bicomponent fibers is needed.
SUMMARY OF THE INVENTION
A process for treating a knit fabric comprising a plurality of self-crimping bicomponent fibers comprised of poly(ethylene terephthalate) and poly(trimethylene terephthalate) and having a crimp contraction value (CC
a
) of at least about 10%, comprising the steps of:
a) stretching the fabric cross-directionally by about 1-15% based on the dry width of the fabric;
b) heat-setting the stretched fabric by dry heat-setting at a temperature of about 160-177° C. for a period of about 20-60 seconds or steam heat-setting at a temperature of about 120-145° C. for a period of about 3-40 seconds;
c) dyeing the fabric; and
d) drying the fabric without heat-setting it further.
DETAILED DESCRIPTION OF THE INVENTION
As used herein, “self-crimping” refers to the ability of certain polyester bicomponent fibers spontaneously to form a spiral crimp when drawn, heat-treated and allowed to relax. Additional crimp, beyond that generated by drawing and heat-treating the fiber, can be created during hot-wet finishing of the fabric, for example during dyeing. Such fibers can be knit and woven to create stretch fabrics, for example into tricot, double knit, plain woven, and twill constructions.
As used herein, “bicomponent fiber” means a fiber comprising a pair of polymers adhered to each other along the length of the fiber, so that the fiber cross-section is a side-by-side or eccentric sheath-core cross section.
It has now been unexpectedly found that use of a single heat-setting step in a specific temperature range, carried out on woven or knit fabrics comprising certain self-crimping bicomponent fibers, under low cross-direction tension, and before dyeing, results in fabrics having a highly desirable combination of high recovery from stretching (“unload power”), excellent dye washfastness, and a smooth surface appearance and hand.
The polyester bicomponent fibers used to make the fabrics treated by the present process comprise poly(ethylene terephthalate) and poly(trimethylene terephthalate), which can be in a side-by-side or eccentric sheath/core relationship; side-by-side is preferred for maximum crimp development. The weight ratio of the two components is about 70:30 to 30:70. The bicomponent fibers have a crimp contraction value, as hereinafter defined, of at least about 10%. In the fibers, it is preferred that poly(ethylene terephthalate) have a lower intrinsic viscosity (IV) than poly(trimethylene terephthalate). It is not required to twist the bicomponent fibers in order to make the fabrics to be treated, and in fact it is preferred that such a twist not be introduced, since it requires an additional step and therefore generates additional cost.
Optionally, either or both components of the fibers of the fabrics treated by the present process can incorporate comonomers, as long as the beneficial effects of the invention are not adversely affected. For example, the poly(ethylene terephthalate) can incorporate comonomers selected from the group consisting of linear, cyclic, and branched aliphatic dicarboxylic acids having 4-12 carbon atoms (for example, butanedioic acid, pentanedioic acid, hexanedioic acid, dodecanedioic acid, and 1,4-cyclo-hexanedicarboxylic acid); aromatic dicarboxylic acids other than terephthalic acid and having 8-12 carbon atoms (for example isophthalic acid and 2,6-naphthalenedicarboxylic acid); linear, cyclic, and branched aliphatic diols having 3-8 carbon atoms (for example 1,3-propane diol, 1,2-propanediol, 1,4-butanediol, 3-methyl-1,5-pentanediol, 2,2-dimethyl-1,3-propanediol, 2-methyl-1,3-propanediol, and 1,4-cyclohexanediol); and aliphatic and araliphatic ether glycols having 4-10 carbon atoms (for example, hydroquinone bis(2-hydroxyethyl) ether, or a poly(ethyleneether) glycol having a molecular weight below about 460, including diethyleneether glycol). Isophthalic acid, pentanedioic acid, hexanedioic acid, 1,3-propane diol, and 1,4-butanediol are preferred because they are readily commercially available and inexpensive. Isophthalic acid is more preferred because copolyesters derived from it discolor less than copolyesters made with some other comonomers. The comonomer can be present in poly(ethylene terephthalate) at a level of about 0.5-15 mole percent.
Further, the fiber of the invention can contain minor amounts of other comonomers in one or both components, provided such comonomers do not adversely affect the level of fiber crimp or other properties. Such other comonomers include 5-sodium-sulfoisophthalate, at levels of about 0.2-5 mole percent. Very small amounts of trifunctional comonomers, for example trimellitic acid, can be incorporated for viscosity control.
The fabrics to be treated can also include wool, cotton, acetate, rayon, and other suitable fibers along with the polyester bicomponent fibers. Weft (circular and flat bed) and warp knit fabrics can be used in the process of the invention.
In the process of the invention, the heat-setting can be carried out dry or with steam. Dry heat-setting temperatures of about 320-355° F. (160-179° C.), preferably 165-175° C., are used, and the heat-setting time is about 20-60 seconds. Steam setting is carried out at about 248-293° F. (120-145° C.), preferably 120-130° C., for about 3 to 40 seconds. In either case, the longer times can be used at the lower temperatures, and the shorter times can be used at the higher temperatures. During heat-setting, the fabric is kept stretched in the cross-direction by about 1-15%, based on the dry width of the fabric. This is done in order to avoid crepe in the final fabric. By “1%” stretch is meant restraint to prevent relaxation during heat-setting; in practice, this means just sufficient tension (stretch) to hold the fabric or apparel on the heat-setting equipment. When the bicomponent fiber has a low crimp contraction value (as defined below), the cross-direction stretch can be low (but within the stated range), and when the fiber has a high crimp contraction value, the stretch can be higher (again within the stated range). The tension (stretch) applied can be used to adjust the finished fabric weight and stretch. Heat setting can be carried out in fabric or apparel form and with any suitable equipment, for example a tenter frame or boarding form.
Dyeing of the heat-set fabric can be conducted with any suitable dye, for example, disperse or acid dyes, by any suitable means, for example beck, p
E. I. du Pont de Nemours and Company
Elhilo Eisá
Gupta Yogendra N.
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