Core spun yarn and woven stretch fabric

Abstract

 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. The elastomeric fiber may have higher draft than the bi-component polyester fiber. The polyester filament comprises poly (trimethylene terephthalate) and at least one polymer selected from the group consisting of poly (ethylene terephthalate) and poly (tetramethylene terephthalate) and said elastomeric fiber is spandex. The yarn may include a sheath of at least one staple fiber. The disclosure also includes a fabric of the bi-component polyester filament and an elastomeric fiber.

Description

TECHNICAL FIELD

[0001] 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.

BACKGROUND

[0002] 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.

[0003] Bi-component polyester filaments are disclosed in US Patent No. 3,671,379 and woven stretch fabrics comprising bi-component polyester filaments are disclosed in US Patent No. 5,922,433, US Patent No. 7,143,790, and US Patent 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.

[0004] 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".

SUMMARY OF THE INVENTION

[0005] 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.

[0006] According to another aspect, there is provided the core spun yarn, in which 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.

[0007] According to yet another aspect, there is provided the core spun yarn, wherein the elastomeric fiber has a higher draft than the bi-component polyester fiber.

[0008] According to still another aspect, there is provided the core spun yarn, wherein the bi-component polyester filament is drafted from 1.01 to about 1.3 times its original length and the elastomeric fiber is drafted from 2.5 to about 4.5 times its original length.

[0009] According to still further aspect, there is provided the core spun yarn, wherein said polyester filament comprises poly (trimethylene terephthalate) and at least one polymer selected from the group consisting of poly (ethylene terephthalate) and poly (tetramethylene terephthalate) and said elastomeric fiber is spandex.

[0010] The polyester filament may comprise poly (ethylene terephthalate) and poly (trimethylene terephthalate) and said elastomeric fiber is spandex or the polyester filament may comprise poly (tetramethylene terephthalate) and poly (trimethylene terephthalate) and said elastomeric fiber is spandex.

[0011] According to still further aspect, there is provided a core spun yarn including a sheath of at least one staple fiber.

[0012] Said staple fiber is selected from a group consisting of cotton, viscose rayon, wool, polyester and blends thereof.

[0013] The yarn may comprise a sheath of at least one hard fiber having an English cotton count (Ne) from about 4 to about 60.

[0014] According to another aspect, there is provided the core spun yarn comprising a bi-component polyester filament and an elastomeric fiber, said bi-component polyester filament being drafted from about 1.01 to about 1.3 times its original length and the elastomeric fiber is drafted from about 2.5 to about 4.5 its original length.

[0015] According to yet another aspect, there is provided the core spun yarn further including a sheath of at least one staple fiber.

[0016] According to still another aspect, there is provided the core spun yarn, wherein said staple fiber is selected from a group consisting of cotton, viscose rayon, wool, polyester and blends thereof.

[0017] According to another aspect, there is provided a woven stretch fabric comprising one of the core spun yarn as previously defined or described in the weft and/or warp.

[0018] The woven stretch fabric can be a plain woven, twill or satin fabric.

[0019] Said woven stretch fabric can also be denim and has been subjected to a one-step dyeing process of piece dyed fabric.

[0020] According to yet another aspect, this fabric has a weft and/or warp elongation from about 10% to about 35%.

[0021] According to still another aspect, the woven stretch fabric is substantially free of any bi-component polyester filament grinning effect.

BRIEF DESCRIPTION OF THE DRAWINGS

[0022] 

Fig. 1 is a schematic side view of one embodiment of a core spinning apparatus;

Fig. 2 is a schematic front view of the core spinning apparatus of Fig. 1;

Fig. 3 is a schematic side view of the second embodiment of a core spinning apparatus;

Fig. 4 is a schematic front view of the core spinning apparatus of Fig. 3;

Fig. 5 is a schematic side view of the third embodiment of a core spinning apparatus;

Fig. 6 is a schematic front view of the core spinning apparatus of Fig. 5;

Fig. 7a is an image of the back side of fabric number 4 referred to in Table 2;

Fig. 7b is a back side view of fabric number 5 referred to in Table 2;

Fig. 8a is an image of a front face view of a fabric produced as disclosed herein; and

Fig. 8b is a back side view of the fabric shown in Fig. 8a.

DETAILED DESCRIPTION

[0023] 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.

[0024] The elastomeric fiber is preferably a bare spandex from 20 to 140 denier.

[0025] 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 its original length and the bare spandex is drafted from about 2.50 to about 4.50 times its original length.

[0026] 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, viscose 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, nylon, 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.

[0027] An apparatus for making yarn is shown in Figs. 1 and 2. As shown in those figures, there is provided a tube 2 or other source of the bi-component filament 4 mounted on a pair of feed rollers 6. A tube or other source 8 of elastomeric fiber 10 is mounted on a pair of feed rollers 12. The bi-component polyester filament 4 and elastomeric fiber 10 (spandex) are combined and controlled by a guide roller 14 from which the combined bi-component polyester and spandex is fed to the front rollers 16. A tube 18 of roving or hard fibers 20 is provided with the hard fiber being fed through a set of back rollers 22 and then to the front rollers 16. The combined spandex 10 and bi-component polyester filament 4 along with the hard fiber 20 is fed from the front rollers 16 thorough a snail wire 24 into a conventional spinning device 26. As is well known in the art, the spinning device 26 may include a spindle 28, a spinning ring 30 and a balloon controlled ring 32. The combined bi-component polyester filament and spandex and hard fiber are core spun together in the spinning device during the spinning process, the bi-component polyester filament and spandex is covered by the hard fibers to form a component yarn.

[0028] 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.

[0029] 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.

[0030] 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.

[0031] 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 Figs. 3 and 4. As shown in those figures, a turning roller 34 for the bi-component filament 4 is mounted between its feed rollers 6 and the front rollers 16 and the turning roller 36 for the spandex 10 is similarly mounted between its feed rollers 12 and front roller 16. If either the bi-component polyester filament 4 or the spandex 10 is broken, a respective turning roller 34 or 36 will stop rotating providing an indication to a worker that a breakage has occurred and that the operation should be shut down until such problem is corrected. Other than the turning rollers, the remainder of the apparatus of Figs. 3 and 4 is the same as that of Figs. 1 and 2 except that the guide 14 roller may be omitted.

[0032] Another embodiment of the core spinning apparatus is shown in Figs. 5 and 6. In those figures, the bi-component polyester filament and spandex have been combined together in a separate device and are provided for feeding into the spinning device 40 on a tube mounted on feed rollers 42. In this case, the combined bi-component filament and spandex is fed over a single turning roller 44 to the front rollers 16. The roving or hard fiber is fed through the back rollers 22 to the front rollers 16 at which point the two sets of fibers pass into the spinning apparatus 26. In the case where the bi-component polyester filament and spandex are wound together before being put on the feed rollers, such bi-component polyester filament and spandex will have been wound together at their desirable respective draft. However, in this case, there may be a draft of from 1.0 to 1.1 controlled by the surface speed ratio of the feed roller 42 and front roller 16.

[0033] 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 weft, warp and warp and weft directions respectively. The woven stretch fabric may have a fabric weft ranging from 136 g/m² to 542 g/m² (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%.

[0034] 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.

[0035] The following examples demonstrate the yarn of the present disclosure and its capability for use in manufacturing a variety of woven stretch fabrics.

Example 1 - Denim Weft Stretch Fabric

[0036] 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.

Table 1

Denim Woven Stretch Fabric-Weft Stretch
Yarn	Fabric Sample No.				Fabric No. 1	Fabric No. 2	Fabric No. 3
	Warp Yarn				Ne7 Slub	Ne7 Slub	Ne7 Slub
	Weft Yarn				Ne10 CSY 75D bi-component polyester filament & 40D spandex	Ne10 CSY 150D bi-component polyester filament	Bare 600D bi-component polyester filament
	Composition	Warp			100% cotton	100% cotton	100% cotton
		Weft			83% cotton	72% cotton	100% polyester
					14% polyester	28% polyester	-
					3% spandex	-	-
	Draft	Polyester			1.02	1.02	-
		Spandex			2.5	-	-
Fabric	Fabric Construction				3/1 "Z"	3/1 "Z"	3/1"Z"
	Fabric Weight (g/m2 (oz/sq.yd))	Before Wash			417 (12.3)	397 (11.7)	447 (13.2)
		After Wash			454 (13.4)	407 (12.0)	464 (13.7)
	Greige Fabric Density (per cm (per inch))		Warp		24.4 (62)	23.6 (60)	22.8 (58)
			Weft		18.1 (46)	17.7 (45)	16.5 (42)
	Finished Fabric Density (per cm (per inch))		Warp		28.3 (72)	27.6 (70)	28.3 (72)
			Weft		19.3 (49)	18.9 (48)	18.1 (46)
Test#	Dimensional Stability (%)	3 Washes	Warp		-3.3	-2.5	-1.8
			Weft		-6.2	-2	-4
	Tearing Strength	Warp	g		>6400	>6400	>6400
			lb		> 14.08	> 14.08	> 14.08
		Weft	g		5300	5600	>6400
			lb		11.7	12.3	> 14.08
	Tensile Strength	Warp	kg		135	139	106
			lb		297.4	304.9	232.8
		Weft	kg		43.7	47.7	157.6
			lb		96.1	104.9	346.7
	Seam Slippage ¼" (kg)	Parallel to Warp			>18.2	>18.2	>18.2
		Parallel to Weft			>18.2	>18.2	>18.2
	Crocking Fastness		Dry		3.5	3.5	3.0
			Wet		1	1	1
	Elongation &	Warp	E/G		-	-
	Growth (%)	Weft	E/G		20/2.5	14/1.3	20/2.0

Example 2 - One Step Dyed Weft Stretch Fabric

[0037] 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 Fig. 7a, no bare polyester can be seen on fabric no. 4. On the other hand, Fig. 7b shows exposure of the bare polyester filament of the fabric no. 5. Using yarns according to the present disclosure eliminates necessity of a two-step dyeing process which is cost consuming.

Table 2

Piece Dyed Woven Stretch Fabric - Weft Stretch < one part dyed >
Yarn	Fabric Sample No.				Fabric No. 4	Fabric No. 5
	Warp Yarn				Ne7 Slub	Ne7 Slub
	Weft Yarn				Ne10 CSY 75D bi-component polyester filament & 40D spandex	Ne10 CSY 150D bi-component polyester filament
	Composition	Warp			100% cotton	100% cotton
		Weft			84% cotton	73% cotton
					13% polyester	27% polyester
					3% spandex	-
Fabric	Fabric Construction				3/1"Z"	3/1"Z"
	Fabric Weight (g/m2 (oz/sq.yd))	Before Wash			373 (11.0)	373 (11.0)
		After Wash			386 (11.4)	383 (11.3)
	Greige Fabric Density (per cm (per inch))		Warp		22.8 (58)	22.8 (58)
			Weft		16.5 (42)	16.5 (42)
	Finished Fabric Density (per cm (per inch)		Warp		27.2 (69)	26 (66)
			Weft		17.3 (44)	17.3 (44)
Test	Dimensional Stability (%)	3 Washes	Warp		-1.5	-1.5
			Weft		-3.5	-2.7
	Elongation & Growth (%)	Warp	E/G		-
		Weft	E/G		21.6/1.9	16/1.5

Example 3 - Bi-stretch Denim Fabric

[0038] 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.

Table 3

Denim Woven Stretch Fabric - bi-stretch
Fabric Sample No.			Fabric No. 6	Fabric No. 7
Warp Yarn			Ne 7 CSY 75 denier bi-component filament + 40D spandex slub	Ne 7 CSY 150 denier bi-component filament slub
Weft Yarn			Ne 10CSY 75 denier bi.component filament + 70D spandex	Ne 10CSY 150 denier bi-component filament
Composition	Warp		88% cotton, 10% polyester, 2% spandex	81 % cotton, 19% polyester
	Weft		82% cotton, 14% polyester, 4% spandex	73% cotton, 27% polyester
Draft	Polyester		1.02	1.06
	Spandex 40D		2.5	-
	Spandex 70D		3.5	-
Fabric Construction			3/1 "Z"	3/1"Z"
Greige Fabric Width (cm (Inch))			170 (67.0)	170 (67.0)
Finished Fabric Width (cm (Inch))			132 (52.0)	146 (57.5)
Fabric Weight (g/m2 (oz/sq.yd))	Before Wash		464 (13.7)	424 (12.5)
	After Wash		522 (15.4)	427 (12.6)
Greige Fabric Density (per cm (per inch))		Warp	21.3 (54)	21.3 (54)
		Weft	19.7 (50)	16.5 (42)
Finished Fabric Density (per cm (per inch))		Warp	27.2 (69)	24.8 (63)
		Weft	23.2 (59)	20.1 (51)
Dimensional Stability (%)	3 Washes	Weft	-6	-3.0
		Warp	-6.5	-2.3
Elongation (%)	Warp	E/G	20 / 3.2	20.6 / 2.6
Growth (%)	Weft	E/G	29 / 2.2	16.0 / 1.2

Example 4 - Bi-stretch Denim Fabric with Different Combination of the Denier

[0039] This example shows the availabilitv 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:

• Fabric no. 8: 75 denier filament and 70 denier spandex, in accordance with the present disclosure.
• Fabric no. 9: 75 denier filament and 40 denier spandex, in accordance with the present disclosure.
• Fabric no. 10: 150 denier filament and 40 denier spandex, in accordance with the present disclosure.
• Fabric no. 11: 150 denier filament (previously known stretch fabric).

[0040] 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.

Table 4

Denim Woven Stretch Fabric - combination of denier and draft
	Sample No.			Fabric No. 8*	Fabric No. 9*	Fabric No. 10*	Fabric No. 11*
Yarn	Warp			Ne7 CSY 150D bi-component filament Slub	Ne7 CSY 150D bi-component filament Slub	Ne7CSY 150D bi-component filament Slub	Ne7CSY 150D bi-component filament Slub
	Weft			Ne 8 CSY 75 denier bi-component filament + 70D spandex	Ne 8 CSY 75 denier bi-component filament + 40D spandex	Ne 8 CSY 150 denier bi-component filament + 40D spandex	Ne 8 CSY 150 denier bi-component filament
	Composition	Warp		81.4% cotton, 18.6% polyester	81.4% cotton, 18.6% polyester	81.4% cotton, 18.6% polyester	81.4% cotton, 18.6% polyester
		Weft		86% cotton, 11% polyester, 3% spandex	87% cotton, 11 % polyester, 2% spandex	77% cotton, 21% polyester, 2% spandex	78% cotton, 22% polyester
	Draft	Polyester 150D		1.06	1.06	1.06	1.06
		Polyester 75D		1.02	1.02	-	-
		Spandex 70D		3.5	-	-	-
		Spandex 40D		-	3.5	3.5	-
Fabric	Fabric Construction			3/1"Z"	3/1 "Z"	3/1"Z"	3/1 "Z"
	Greige Fabric Width (cm (inch)			170 (67.0)	171 (67.5)	170 (67.0)	169 (66.6)
	Finished Fabric Width (cm (inch)			138 (54.5)	143 (56.5)	141 (55.5)	149 (58.5)
	Fabric Weight (g/m2((oz/sq.yd))	Before Wash		458 (13.5)	434 (12.8)	451 (13.3)	414 (12.2)
		After Wash		515 (15.2)	468 (13.8)	478 (14.1)	441 (13.0)
	Greige Fabric Density (per cm (per inch))		Warp	21.3 (54)	21.3 (54)	21.3 (54)	21.3 (54)
			Weft	17.3 (44)	17.3 (44)	17.3 (44)	17.3 (44)
	Finished Fabric Density (per cm (per inch))		Warp	26.8 (68)	24.8 (63)	25.2 (64)	23.6 (60)
			Weft	19.3 (49)	19.3 (49)	19.3 (49)	19.3 (49)
Test	Dimensional Stability (%)	3 Washes	Warp	-4.5	-5.5	-5	-5.0
			Weft	-7	-6	-5.7	-2.5
	Elongation (%)	Warp	E/G	18 / 1.6	18/1.4	18/1.6	18.0/2.0
	Growth (%)	Waft	E/G	27 / 2.4	21/2.2	22/1.8	15.0/1.8

* represents this present invention in the weft

Example 5

[0041] 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. Fig. 8a shows the front face side of the fabric no. 12 of this example while Fig. 8b shows the backside view of fabric no. 12. As will be noted, neither the front nor the back view show any significant sign or grinning. This is achieved with the elongation in the warp and weft being 15% and 16.6% respectively. Other characteristics of the finished fabric are shown in Table 5.

Table 5

Piece Dyed Woven Stretch Fabric - bi-stretch
	Fabric Sample No.				Fabric No. 12
Yarn	Warp Yarn				Ne10 CSY 75D bi-component polyester filament & 40D spandex
	Weft Yarn				Ne10 CSY 75D bi-component polyester filament & 40D spandex
		Warp			83% cotton, 14% polyester, 3% spandex
	Composition	Weft			83% cotton, 14% polyester, 3% spandex
	Draft	Polyester			1.02
		Spandex			2.5
Fabric	Fabric Construction				3/1"Z"
	Fabric Weight (g/m2 (oz/sq.yd))	Before Wash			376 (11.1)
		After Wash			397 (11.7)
	Greige Fabric Density (per cm (per inch))		Warp		26.8 (68)
			Weft		15.7 (40)
	Finished Fabric Density (per cm (per inch))		Warp		32.7 (83)
			Weft		18.5 (47)
Test	Dimensional Stability (%)	3 Washes	Warp		-5
			Weft		-1.6
	Elongation (%) & Growth (%)	Warp	E/G		15.1/2
		Weft	E/G		16.6/2

[0042] 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.

Claims

1. A core spun yarn comprising:

a bi-component polyester filament; and

an elastomeric fiber,

said polyester filament having a denier from about 20 to about 150 and said elastomeric fiber having a denier from 20 to 140.

2. The yarn of claim 1, wherein the elastomeric fiber has a higher draft than the bi-component polyester filament.

3. The yarn of claim 1 or 2, wherein the bi-component polyester filament is drafted from 1.01 to about 1.3 times its original length and the elastomeric fiber is drafted from 2.5 to about 4.5 times its original length.

4. The yarn according to any one of claims 1 to 3, in which 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.

5. The yarn according to any one of claims 1 to 4, wherein said polyester filament comprises poly (trimethylene terephthalate) and at least one polymer selected from the group consisting of poly (ethylene terephthalate) and poly (tetramethylene terephthalate) and said elastomeric fiber is spandex.

6. The yarn according to any one of claims 1 to 5 further including a sheath of at least one staple fiber.

7. The yarn of claim 6, wherein said staple fiber is selected from a group consisting of cotton, viscose rayon, wool, polyester and blends thereof.

8. The yarn of claim 6 or 7, comprising a sheath of at least one hard fiber having an English cotton count (Ne) from about 4 to about 60.

9. A woven stretch fabric comprising the core spun yarn according to any one of claims 1 to 8 in the weft and/or warp.

10. The woven stretch fabric of claim 9, wherein the fabric is a plain woven, twill or satin fabric.

11. The woven stretch fabric of claim 10, wherein the fabric is denim and has been subjected to a one-step dyeing process of piece dyed fabric.

12. The woven stretch fabric according to any one of claims 9 to 11 which has a weft and/or warp elongation from about 10% to about 35%.

13. The woven stretch fabric according to any one of claims 9 to 12 which is substantially free of any bi-component polyester filament grinning effect.

Drawing