Patent Application
20080318485
This invention relates generally to core spun yarns with bi-component polyester filaments and an elastomeric fiber and fabrics made there from, and more particularly, the present invention relates to core spun yarns comprising poly (trimethylene terephthalate) and poly (ethylene terephthalate) and an elastomeric fiber comprising spandex, or poly (trimethylene terephthalate) and poly (tetramethylene terephthalate) and an elastomeric fiber comprising spandex.
Conventional stretch fabrics made by using core spun spandex yarn has, in general, too much stretch power. As used herein, core spun yarn refers to a yarn consisting of a number of component yarns, of which one or more are constrained to lie permanently at the central axis of the composite thread, while the remaining yarns act as covering yarns. Therefore, heat set is necessary to prevent retraction of the elastic fibers and the resultant compression of the fabric. Without heat setting, there will be high shrinkage and poor appearance after a finishing operation or in-house washing. However, the required heat setting process is time and cost consuming with many side affects such as affected elongation, growth and the stability of the fabric width.
Bi-component polyester filaments are disclosed in U.S. Pat. No. 3,671,379 and woven stretch fabrics comprising bi-component polyester filaments are disclosed in U.S. Pat. No. 5,922,433, U.S. Pat. No. 7,143,790, and U.S. Pat. No. 6,782,923. The disclosure of each of these patents is incorporated herein by reference in its entirety. However, the fabrics disclosed in these patents use bare bi-component polyester and have a strong synthetic feel and appearance. This undesirable synthetic characteristic can only be overcome by dyeing the fabric in two separate dyeing steps. This is a tedious process and can reduce the elastic properties of the fabric. Also, it is limited to denim fabric.
Core spun yarns with bi-component polyester filaments in the center and fabrics made from them are disclosed in U.S. Patent Application publication US 2006/0179810. The disclosure of this patent application publication is incorporated herein by reference in its entirety. The fabrics produced using the yarn as disclosed in the patent application publication have improved appearance, hand feel and the bi-component polyester filament is covered by the staple fibers, but it still has a “grinning effect”. As used in the art, grinning refers to a flaw in the fabric wherein the inner fibers show through the outer fibers. For example, the case where the bi-component polyester filament which is covered by staple fibers shows through the covering of the staple fibers. Additionally, the elongation of the fabric is limited and can only be adjusted by the fabric construction which, in order to get a higher stretchability, resulted in a fabric that was “too soft”.
According to one aspect there is provided a core spun yarn comprising a bi-component polyester filament and an elastomeric fiber. The polyester filament has a denier from about 20 to about 150 and the elastomeric fiber has a denier from 20 to 140.
According to another aspect there is provided a core spun yarn comprising a bi-component polyester filament and an elastomeric fiber. The polyester filament has a denier from about 20 to about 150 and the elastomeric fiber has a denier from 20 to 140. The polyester filament is about 2 weight percent to about 60 weight percent, based on total weight of the yarn and the elastomeric fiber is from about 1 percent to about 40 percent, based on total weight of the yarn.
According to yet another aspect there is provided a core spun yarn comprising a bi-component polyester filament and an elastomeric fiber. The elastomeric fiber has a higher draft than the bi-component polyester fiber.
According to still another aspect there is provided a core spun yarn comprising a bi-component polyester filament and an elastomeric fiber. The polyester filament comprises poly (ethylene terephthalate) and poly (trimethylene terephthalate) and said elastomeric fiber is spandex.
According to still further aspect there is provided a core spun yarn comprising a bi-component polyester filament and an elastomeric fiber. The polyester filament comprises poly (ethylene terephthalate) and poly (trimethylene terephthalate) and said elastomeric fiber is spandex. The yarn includes a sheath of at least one staple fiber.
According to still further aspect there is provided a core spun yarn comprising a bi-component polyester filament and an elastomeric fiber. The polyester filament comprises poly (trimethylene terephthalate) and poly (tetramethylene terephthalate) and an elastomeric fiber comprising spandex. The yarn includes a sheath of at least one staple fiber.
According to another aspect there is provided a woven stretch fabric comprising a core spun yarn comprising a bi-component polyester filament and an elastomeric fiber. The polyester filament has a denier from about 20 to about 150 and the elastomeric fiber has a denier from 20 to 140.
a is an image of the back side of fabric number 4 referred to in Table 2;
b is a back side view of fabric number 5 referred to in Table 2;
a is an image of a front face view of a fabric produced as disclosed herein; and
b is a back side view of the fabric shown in
This disclosure relates to a bi-component filament core spun yarn which may comprise a bi-component polyester filament and an elastomeric fiber. The bi-component polyester filament may comprise poly (trimethylene terephthalate) and at least one polymer selected from the group consisting of poly (ethylene terephthalate) and poly (tetramethylene terephthalate). The denier of the bi-component polyester filament should be in the range of from 20 to 150.
The elastomeric fabric is preferably a bare spandex from 20 to 140 denier.
According to another aspect of the disclosure, the bi-component polyester filament and the elastomeric fiber are provided with a different draft. By draft is meant the reduction in the linear density of the fiber by drawing. When drafting, the degree of attenuation is calculated as the ratio of the surface speeds of the output and input machine components which bring out drafting. The bi-component polyester filament is drafted from about 1.01 to about 1.30 times is original length and the bare spandex is drafted from about 2.50 to about 4.50 times its original length.
According to another aspect, the yarn includes a sheath which forms a composite yarn with the bi-component filaments and elastomeric yarns. The sheath may be staple fibers of a hard yarn. “Hard yarn” refers to relatively unelastic yarns such as polyester, cotton, nylon, rayon, or wool. The sheath may range from Ne 4 to Ne 60. As used herein, Ne is an indirect system of expressing the mass per unit length as one lb. per 840 yards. The fibers of cotton, viscose rayon, wool, polyester and blends thereof may be used. In general, there is no particular restriction on the staple fibers that can be used provided that the benefits are not affected.
An apparatus for making yarn is shown in
Both the bi-component polyester filament and spandex are unwound in a counter-clockwise direction as shown in the figures. The draft of the bi-component polyester 4 is controlled by the surface feed ratio of the feed rollers 6 and front roller 16. The draft of the spandex 10 is controlled by the surface speed of its feed rollers 12 and the front roller 16. The speed of the feed rollers 6 of the bi-component filament and 12 of the spandex can be adjusted separately to give the desired draft or stretch ratio.
The draft ratio of the bi-component polyester ranges from about 1.01 to 1.3. This ratio is designed based upon the stability of the coverage of the bare bi-component polyester and is not related to the stretchability of the woven fabric. A draft ratio of the spandex ranges from about 2.5 to about 4.5. The ratio is designed according to the stretchability requested on the resulting woven fabric.
The bi-component polyester and spandex are combined and controlled by the guide roller 14 properly positioned to achieve the proper coverage. To achieve similar or even higher fabric stretch level as compared to previously known stretch fabrics made from core bi-component polyester spun yarn or bare bi-component polyester filament, it is possible to use just 75 denier of the bi-component polyester filament and 40 denier of spandex to replace, for example, a core 150 denier of the bi-component polyester filament. As the percent of the bi-component polyester is generally less than the prior art core bi-component polyester filament spun yarn, there is no special technique that has to be done in order to improve the coverage of the bare polyester filament.
A possible common yarn defect that could happen during the core yarn spinning process is for the bi-component polyester filament or the spandex to somehow break off and not be fed into the guide roller. Such defect would only be noticed upon the manual checking after the full cop or yarn breakage. One way of providing a recognition of this problem at an early stage is to provide turning rollers 34 and 36 for the bi-component filament 4 and spandex fiber 10 as shown in
Another embodiment of the core spinning apparatus is shown in
The core spun bi-component polyester filament and spandex yarn can be used to provide a woven stretch fabric designed as a weft stretched, warp stretched, or bi-stretched by using the core spun yarn in a warp, weft and warp and weft directions respectively. The woven stretch fabric may have a fabric weft ranging from 4 oz./sq. yd. to 16 oz./sq. yd. The yarn as described herein is suitable for any woven fabric with construction as a plain, Z-twill, S-twill, satin, sateen and any other common construction which is used in such items as denim, pants, and shirts. The fabric construction is designed similar to previously-known stretch fabric made from core spandex yarn or bi-component polyester filament. However, there is no need to have an open construction in order to get stretchability. In the case of the denim stretch woven fabric using the yarn as described herein, the fabric does not require heat set up to maintain good dimensional stability with shrinking less than 7%, elongation not less than 20% and growth less than 4%.
A piece dyed stretch fabric, for example, using the weft stretch, using the yarn of the present disclosure, can achieve the lower shrinkage, less than 7%, good elongation not less than 20%, and growth less than 4%, with only an acceptable number of “white spots” occurring on the fabric surface. Also, it is not necessary to use a two-step dyeing process on a woven bi-stretch fabric using the yarn of the present invention as one can achieve a comfort stretch greater than 15% of in the warp and weft direction without any problem of grinning.
The following examples demonstrate the yarn of the present disclosure and its capability for use in manufacturing a variety of woven stretch fabrics.
This example shows the weft stretch denim fabric as shown in Table 1 below. Fabric no. 1 is in accordance with the present disclosure and uses a core bi-component polyester and spandex spun yarn in the weft, whereas fabric no. 2 and fabric no. 3 are previously known stretch fabrics made by using core bi-component polyester filament and a bare bi-component polyester filament respectively. As will be noted, fabric no. 1, in accordance with the present invention, obtains a better elongation as compared to fabrics no. 2 and fabric no. 3, and has a 100% cotton feel. Without any heat set process, fabric no. 1 achieves a good dimensional stability (−6.2%), good elongation (20%) and growth (2.5%). Other characteristics are summarized in Table 1.
This example demonstrates a weft stretch fabric which has been dyed with a single step process. As shown in Table 2, fabric no. 4 is a fabric which uses a weft yarn in accordance with the present disclosure, which is a core bi-component polyester filament and spandex. Fabric no. 5 is a common stretch fabric with the weft yarn being a core bi-component polyester filament only. Both weft yarns had a cotton sheath, and were subjected to a one step dyeing process. As will be noted, fabric no. 4, in accordance with the present disclosure, achieved weft elongation of 21.6% and had growth of 1.9% and good stability of 3.5%. One significant advantage as compared to the use of the bare bi-component polyester filament or core bi-component polyester filament spun yarn is that the exposure of the bare polyester filament is improved. As shown in
This example shows the advantage of the use of yarns in accordance with the present disclosure in bi-stretch denim fabric as shown in Table 3. Fabric no. 6 uses yarns in accordance with the present disclosure and comprises a core bi-component polyester filament and spandex spun yarn both in the warp and weft direction. Fabric no. 7 comprises only a core bi-component polyester filament in the warp and weft as in previously known stretch fabrics. As shown in the table, fabric no. 6, has a higher stretch power (29%) in the weft direction. Further, the concern of exposure of the bare polyester in the warp of the previously known core bi-component polyester filament spun yarn is not a problem with the fabric no. 6 as the percentage of the polyester is much less. In this example, the exposure of the bare polyester was not seen on the finished fabric using the yarns in the present disclosure. The fabric's characteristic is summarized in Table 3.
This example shows the availability of fabrics using yarns in accordance with the present disclosure to reach the desired stretchability by adjusting the denier of the spandex/bi-component filament and the draft (if needed). The warp yarn in each of the Fabrics no. 8-11 is in accordance with the present disclosure and uses a core bi-component polyester filament spun yarn at Ne7. The weft yarn in each of the fabrics comprises a different denier of the filament/spandex spun yarn at Ne8. They are:
The fabric characteristics are summarized in Table 4. After finishing, fabrics nos. 8, 9 and 10, those in accordance with the present disclosure, have reasonable stretch ranging from 21% to 27% with good recovery, (growth less than 2.4%). With the conventional fabric no. 11, with a core bi-component polyester filament only, the stretch power was much lower at 15%. It should be noted that since the warp yarn is all the same, the elongation and growth are substantially the same at 18% and between 1.4% and 2.0% respectively. This shows that without using the open end construction, it is possible to get desirable stretch power in any application with yarns according to the present disclosure.
/1.8
indicates data missing or illegible when filed
This example shows the use of the yarns of the present disclosure on a bi-stretch fabric undergoing a one-step dyeing process as set forth in Table 5. The example demonstrates a fabric with a core bi-component polyester filament and spandex in Ne10 both in the warp and the weft. Using only a one-step dyeing process the finished fabric still has a good appearance with an acceptable grinning effect.
While various embodiments have been shown and described, various modifications and substitutions should be made thereto. Accordingly, it is understood that the present embodiments have been described by way of illustration and not limitations.
