HK1074860B - Stretch polyester/cotton spun yarn - Google Patents

Description

Elastic polyester/cotton yarn

Cross reference to related applications

The present application is a pending partial continuation application having a pending application number of 10/286,683 filed on day 11, month 2, 2002, which is a pending partial continuation application having a pending application number of 10/029,575 filed on day 12, month 21, 2001.

Background

Technical Field

This application relates to spun yarns comprising polyester staple fibers and cotton fibers, and more particularly to such spun yarns wherein the polyester staple fibers are bicomponent fibers that impart the desired properties to the spun yarn and have selected properties for the polyester bicomponent fibers, and more particularly to such fibers comprising poly (ethylene terephthalate) and poly (trimethylene terephthalate).

Background

Polyester bicomponent fibers are known from us patents 3,454,460 and 3,671,379, which disclose spun yarns made of bicomponent fibers having some crimp properties on the outside thereof, said yarns being considered to be harsh, rough and unaesthetic to the touch.

Spun yarns comprising bicomponent staple fibers are also disclosed in japanese published patent applications JP 62-085026 and JP 2000-328382, and us patents 5,723,215 and 5,874,372, but these fibers have little retractive power and may require mechanical crimping, which increases their cost.

Polyester fibers having radial grooves on their surface are described in U.S. patents 3,914,488, 4,634,625, 5,626,961 and 5,736,243 and published international patent application WO01/66837, but such fibers typically lack good drawdown performance and retractive ability.

Published international patent application WO 00-77283 discloses polyester bicomponent fiber bundles, but these fiber bundles are said to require de-registration to become usable, which increases costs.

There remains a need for polyester bicomponent staple fibers and spun yarns of cotton having high stretchability and uniformity, just as there is a need for polyester bicomponent staple fibers having improved processability, stretch properties and recovery properties.

Summary of The Invention

The present invention provides a spun yarn having a total scouring shrinkage of at least about 22% and comprising cotton fibers and bicomponent staple fibers comprising poly (ethylene terephthalate) and poly (trimethylene terephthalate), wherein the bicomponent fibers have a tow pick up discovery value of about 35% to 70%, a tow crimp index value of about 14% to 45%, a length of about 1.3 to 5.5cm, a linear density of about 0.7 to 3.0 dtex per fiber, and the weight of bicomponent fibers is about 20 wt% to 65 wt% and the weight of cotton fibers is about 35 wt% to 80 wt% based on the total weight of the spun yarn.

The present invention also provides a bicomponent staple fiber comprising poly (ethylene terephthalate) and poly (trimethylene terephthalate) and having a tow crimp development value of from about 40% to about 60% and a tow crimp index value of from about 14% to about 27%, wherein the absolute value of the difference between the take-up index value and the crimp development value is from about 24% to about 35%.

The invention also provides a method of producing the spun yarn of the invention, comprising the steps of:

a) providing a bicomponent staple fiber having a tow crimp development value of from about 35% to about 70%, a tow crimp index value of from about 14% to about 45%, a length of from about 1.3 to about 5.5cm, and a linear density of from about 0.7 dtex per fiber to about 3.0 dtex per fiber;

b) supplying cotton fibers;

c) mixing at least said cotton fibers and bicomponent staple fibers such that said bicomponent staple fibers are present in an amount of from about 20 wt% to about 65 wt% based on the total weight of the mixed fibers and said cotton fibers are present in an amount of from about 35 wt% to about 80 wt% based on the total weight of the mixed fibers;

d) carding the mixed fibers to form a sliver;

e) drafting the raw sliver;

f) plying and redrawing the raw sliver up to about 3 times;

g) converting the drawn sliver into roving; and

h) ring spinning the roving to form a spun yarn.

In a second embodiment, the present invention provides a method for making a spun yarn of the present invention, comprising the steps of:

a) providing bicomponent staple fibers having a tow crimp development value of from about 35% to about 70%, a tow crimp index value of from about 14% to about 45%, a length of from about 1.3 to about 5.5cm, and a linear density of from about 0.7 dtex per fiber to about 3.0 dtex per fiber;

b) providing cotton fibers;

d) respectively carding the bicomponent staple fibers and the cotton fibers to produce bicomponent staple fiber raw slivers and raw cotton slivers;

e) a drawing frame for mixing said bicomponent staple fiber sliver and said tampon so that (i) the bicomponent fibers comprise from about 20 wt% to about 65 wt%; and (ii) about 35 wt% to about 80 wt% cotton fibers, based on the total weight of the combined fibers,

f) plying and redrawing the mixed sliver of step (e) up to about 3 times;

g) converting the drawn sliver into roving; and

h) ring spinning the roving to form a spun yarn.

The invention further provides a fabric selected from the group consisting of knitted fabrics and woven fabrics and comprising the spun yarns produced by the method of the invention.

Drawings

FIG. 1 shows a schematic cross-section of a spinneret useful in the production of bicomponent polyester fiber bundles.

Figure 2 schematically shows a roll arrangement that can be used to make the tow precursor of the present invention to bicomponent staple fibers.

Detailed Description

It has now been found that spun yarns comprising cotton fibers and bicomponent staple fibers, which in turn comprise poly (ethylene terephthalate) and poly (trimethylene terephthalate) and have selected mechanical properties, have unexpectedly high drawdown, carding and uniformity properties.

It has now also been found that polyester bicomponent staple fibers can be made with an unexpectedly and advantageously large difference between the tow crimp index and the tow crimp development value, this difference being manifested in the surprising combination of good processability as indicated by ease of carding and good recovery as indicated by high refining shrinkage. Such fibers are one preferred bicomponent staple fiber for the cotton fiber/bicomponent fiber spun yarn of the present invention.

As used herein, "bicomponent fibers" refers to fibers in which the two polymers are in a side-by-side or bias sheath-core relationship, and includes self-crimped fibers and latent self-crimped fibers that have not yet been achieved.

"intimate mixing" refers to the process of mixing different fibers thoroughly by weight in a picking booth (e.g., by a weigh hopper feeder) before feeding the mixture to the card, or to the process of mixing fibers in two end feed lines on the card and distinguishing them from the mixing at the draw frame.

"Natural draft" ("NDR") means the upper limit of the yield region on the stress-strain curve of an undrawn virgin fiber, as determined by the intersection of tangent lines drawn respectively to the yield and stress-hardened regions of the curve.

The spun yarn of the present invention comprises cotton fiber and polyester bicomponent staple fiber comprising poly (ethylene terephthalate) ("2G-T") and poly (trimethylene terephthalate) ("3G-T"), and has a total scouring shrinkage of at least about 22%. Such a shrinkage corresponds to an elongation of about 20% when a load of 0.045g/den (0.04dN/teX) is applied to the spun yarn after the spun yarn is refined. When the total scouring shrinkage is less than about 22%, the elongation-and-shrinkage properties of the yarn may be insufficient. The bicomponent staple fibers have a tow crimp development value ("CD") of from about 35% to about 70%, preferably from about 40% to about 60%, and have a tow index value of from about 14% to about 45%, preferably from about 14% to about 27%.

When the CD is below about 35%, the spun yarns typically have an overall scouring shrinkage that is too low to produce good shrinkage in the fabrics made from them. When the CI value is low, mechanical crimp is necessary for satisfactory carding and spinning. When the CI value is high, the bicomponent staple fiber may have too much crimp to be easily carded and the uniformity of the spun yarn may be insufficient.

The bicomponent staple fibers have a length of about 1.3 to 5.5 cm. When the bicomponent staple fiber is shorter than about 1.3cm, it is difficult to card, and when it is longer than about 5.5cm, it is difficult to spin on a cotton spinning system equipment. The cotton fibers have a length of from about 2-4 cm. The bicomponent staple fibers have a linear density of about 0.7 to 3.0 dtex (dtex) per fiber, preferably about 0.9 to 2.5 dtex per fiber. When the bicomponent staple fiber has a linear density of about 3.9 dtex or more per fiber, the spun yarn has a harsh hand and is difficult to blend with cotton fibers, resulting in a poorly consolidated, low tenacity yarn. It is difficult to comb when it has a linear density of less than about 0.7 dtex per fiber.

The bicomponent staple fiber comprises about 20 wt% to about 65 wt%, preferably about 35 wt% to about 50 wt% of the yarn, based on the total weight of the yarn. When the spun yarn of the present invention contains less than about 20 wt% polyester bicomponent fiber, the spun yarn exhibits insufficient drawdown and shrinkability as indicated by low total scouring shrinkage; when the spun yarn contains more than about 65 wt% bicomponent staple fiber, the uniformity of the spun yarn will be adversely affected.

In the spun yarn of the present invention, the cotton fiber is present in an amount of about 35 to 80 wt% based on the total weight of the spun yarn. Alternatively, from about 1 wt% to about 30 wt%, based on the total weight of the spun yarn, can be another staple fiber, such as a monocomponent fiber poly (ethylene terephthalate) staple fiber.

When CI is low, in the range of acceptable values, higher ratios of polyester bicomponent staple fibers can be applied without compromising combability and spun yarn uniformity. When CI is higher, in the range of acceptable values, a lower ratio of polyester bicomponent staple fiber can be applied without compromising refining shrinkage. In particular, since the blend value CI and the combability of the fibers are interrelated, if the amount of bicomponent fibers in the blend is low (e.g., as low as about 20 wt% based on the total weight of the spun yarn), satisfactory combability can be maintained even by high C1 (e.g., as high as about 45%) values. Similarly, since the fiber mix value CD and the total refining shrinkage are interrelated, if the CD is high, for example, about 60% or more, a satisfactory total refining shrinkage may be maintained even at about 20 wt% of the bicomponent fiber based on the total weight of the spun yarn.

Preferably, the spun yarn of the present invention has a coefficient of variation of mass ("CV") of no greater than about 22%, for example when measured on a spun yarn containing 40 cotton counts or less, more preferably no greater than about 18%, for example, when measured on a spun yarn containing 20 cotton counts or less. Beyond those values, the use of said yarns in some types of fabric may become even more unsatisfactory.

The bicomponent staple fiber may have a weight ratio of poly (ethylene terephthalate) to poly (trimethylene terephthalate) of about 30:70 to 70:30, preferably 40:60 to 60: 40. One or both of the polyesters comprising the bicomponent fiber may be a copolyester, and "poly (ethylene terephthalate)" and "poly (trimethylene terephthalate)" include such copolyesters in their sense. For example, a co (ethylene terephthalate) may be used in situations where the comonomer used to make the copolyester is selected from: linear, cyclic and branched aliphatic dicarboxylic acids having 4 to 12 carbon atoms (e.g., succinic acid, glutaric acid, adipic acid, dodecanedioic acid, and 1, 4-cyclohexanedicarboxylic acid); aromatic dicarboxylic acids which are not terephthalic acid and have from 8 to 12 carbon atoms (e.g., isophthalic acid, and 2, 6 naphthalene dicarboxylic acid); linear, cyclic and branched aliphatic diols having 3 to 8 carbon atoms (e.g., 1,3 propanediol, 1, 2-propanediol, 1, 4-butanediol, 3-methyl-1, 5-pentanediol, 2-dimethyl-1, 3-propanediol, 2-methyl-1, 3-propanediol and 1, 4-cyclohexanediol); and aliphatic and araliphatic ether glycols having 4 to 10 carbon atoms (e.g., hydroquinone bis (2-hydroxyethyl) ether, or poly (vinyl ether) glycols having a molecular weight of less than about 460, including diethylene ether glycol). The comonomer may be present to the extent that it does not detract from the benefits of the invention, for example, from about 0.5 to 15 mole percent based on the total polymer formulation. Isophthalic acid, glutaric acid, adipic acid, 1, 3-propanediol and 1, 4-butanediol are preferred comonomers.

Copolyesters can also be made with small amounts of other comonomers, provided that such comonomers do not adversely affect the advantages of the invention. Such other comonomers include 5-sodium-sulfoisophthalate (5-sodium-sulfoisophthalate), the sodium salt of 3- (2-sulfoethyl) adipic acid, and its dialkyl ester, which may be combined in about 0.2 to 4 mole percent based on the total polyester. For improved acid dyeability, the (co) polyester may also be mixed with a polymeric secondary amine additive, such as poly (6, 6' -imino-bis-hexamethylene terephthalamide) and its copolyamide containing hexamethylene diamine, preferably phosphoric acid and its phosphate. To control the viscosity, small amounts, for example about 1 to 6 milliequivalents, of 3-or 4-functional comonomers per kg of polymer, for example 1,2, 4-trimellitic acid (including its precursors) or pentaerythritol, may be incorporated.

The cross-section of the outer edge of the bicomponent fiber is not particularly limited and may be round, oval, triangular, "snowflake," and the like. A "snowflake-like" cross-section may be described as a side-by-side cross-section having a major axis, a minor axis, and at least two maxima along the length of the minor axis when plotted along the major axis. In one embodiment, the spun yarn of the present invention comprises cotton fibers and bicomponent staple fibers comprising poly (ethylene terephthalate) and poly (trimethylene terephthalate) and having a plurality of radial grooves in the surface thereof. Such bicomponent staple fibers can be considered to have a "scalloped oval" cross-section that can enhance the wicking properties of the polyester bicomponent fibers.

The polyester bicomponent staple fibers in the spun yarns of the present invention may also include conventional additives such as antistatic agents, antioxidants, antimicrobials, flame retardants, dyes, light stabilizers, and delustrants such as titanium dioxide, provided they do not detract from the advantages of the present invention.

The polyester bicomponent staple fibers of the present invention have a tow crimp development value of from about 40% to about 60% and a crimp index value of from about 14% to about 27%, wherein the absolute value of the difference between said crimp index value and said crimp development value is from about 24% to about 35%, preferably from about 30% to about 35%.

Preferably, the spun yarn of the present invention comprises the fiber of the present invention and has a break strength of at least about 3.5dN/tex and not greater than 5.5 dN/tex. When the strength is too low, carding and spinning can become difficult, and when the strength is too high, fabrics woven from the spun yarns of the present invention can exhibit undesirable pilling. It is also preferred that the linear density of the spun yarn be in the range of about 100 to 700 denier (111 to 778 dtex).

Knitted (e.g., circular knit and jersey) and woven (e.g., plain and twill) elastic fabrics can be woven from the spun yarns of the present invention.

The process for making the spun yarn of the present invention comprises a mixing step, preferably by intimate mixing, of cotton fibers (which may optionally be carded) and bicomponent staple fibers having the composition and characteristics described hereinbefore, wherein the bicomponent staple fibers comprise from about 20 wt% to about 65 wt%, preferably from about 35 wt% to about 50 wt%, based on the total weight of the mixed fibers. The cotton fibers comprise from about 35 wt% to about 80 wt% based on the total weight of the blend. Alternatively, from about 1 wt% to about 30 wt%, based on the total weight of the spun yarn, can be other staple fibers, such as monocomponent poly (ethylene terephthalate) fibers.

It is not necessary that the crimp of the bicomponent fibers in the tow precursor to staple fibers be 'realigned' in such a way that the crimp of the fibers do not coincide, preferably no attempt is made to 'realign' them in order to save the cost of such an unnecessary step. Similarly, bicomponent staple fiber tows do not require mechanical crimping to give good processability and useful properties to the staple fibers made from them. And preferably the tow is not subjected to a mechanical crimping step.

The commingled fibers are further processed by carding the commingled fibers to form a sliver, drafting the sliver, plying and redrawing the sliver up to 3 times, converting the drafted sliver to a roving, ring spinning the spun roving, preferably with a twist multiplier of about 3 to 5.5, to form a spun yarn having an overall refined shrinkage of at least about 22%.

The intrinsic viscosity ("IV") of the polyester was measured by a model Y-900 Viscotek formed fluid viscometer at 19 deg.C, 0.4% concentration, and according to ASTM D-4603-96 with 50/50 wt% trifluoroacetic acid/dichloromethane instead of the prescribed 60/40 wt% phenol/1, 1,2, 2-tetrachloroethane. The measured viscosity values were then correlated with the standard viscosity in 60/40 wt% phenol/1, 1,2, 2-tetrachloroethane to give the reported intrinsic viscosity values.

The following methods of measuring the tow crimp development value and the tow crimp index value of the bicomponent fibers were applied in the examples, unless otherwise noted. To measure the crimp index value ("c.i"), a 1.1 meter sample of polyester bicomponent fiber tow was weighed and its denier calculated. The thickness of the tow is typically about 38,000 to 60,000 denier (42,000 to 66700 decitex). Two knots spaced 25mm apart were tied up at each end of the tow. Tension was applied to the vertical samples by applying a first clamp at the inner knot of the first end and hanging a 40mg/den (0.035dN/tex) weight between the knots of the second end. This weight sample was measured three times by lifting and slowly lowering. A second clamp was then clamped 100cm below the inner knots at the first end with the weight in place between the knots at the second end, the 0.035dN/tex weight was removed from the second end and the sample was inverted while maintaining tension so that the first end was at the bottom. A1.5 mg/den (0.0013dN/tex) weight was suspended between the knots at the first end, the first clamp was removed from the first end, the sample was allowed to retract against the 0.0013dN/tex weight, and the (retracted) length from the clamp to the knot inside the first end was measured in cm at the first end and was called L_r. C.i. is calculated by formula (I). To measure the tow crimp development value ("c.d"), the same procedure was followed except that the 1.1m sample was placed in tension-free-boiling water for 1 minute and completely dried before applying a 40mg/den (0.035dN/tex) weight.

C.i. and c.d. (%) 100 × (100 cm-L)_r)/100cm(I)

Since merely cutting the tow into staple fibers does not affect crimp, it is purposeful and it is understood that the measurements made on the tow precursors of these fibers are shown herein with reference to the crimp values of the staple fibers.

To determine the total refined shrinkage of the spun yarn in the examples, the spun yarn was made into a 25-end hank on a standard hank winder. One 10 inch (25.4cm) length ("L") when the sample was wound on the winder₀") was marked on the sample with a dye marker. The skein was removed from the winder, boiled in boiling water for 1 minute without restriction, removed from the water, and dried at room temperature. The dry skein was laid flat and the distance between the dye markers was measured again ("L_bo"), the total refining shrinkage was calculated by equation II:

total b.o.s. (%) 100 × (L)_o—L_bo)/L_o (II)

The total refining shrinkage test was performed using the same samples, and the "true" shrinkage of the spun yarn was measured by applying a load of 200mg/den (0.18dN/tex), measuring the extended length, and calculating the percent difference between the pre-refining and post-extended refining lengths. The true shrinkage of the samples is typically less than about 5%. Since the true shrinkage is only a very small fraction of the total refining shrinkage, the latter is used here as a reliable measure of the draw characteristics of the spun yarn. A higher total refining shrinkage corresponds to a higher stretch that is desired.

The uniformity of the mass of the spun yarns along their length is measured by a uniformity tester 1-B (manufactured by zellweger uster) and reported as a coefficient of variation percentage ("CV"). In this test, the spun yarn was fed to the tester at 400yds/min (366m/min) for 2.5 minutes, during which time the mass of the spun yarn was tested every 8 mm. The standard deviation of the resulting data is calculated, multiplied by 100, and divided by the test spun yarnAverage mass to get CV percent. The data of conventional and commercial spun yarn can be in "Statistics 2001 "(Zellweger Luwa AG).

The tensile properties of the spun yarn were determined by a Tensojet (also manufactured by Zellweger Uster).

The combability of the mixed fibers used to make the spun yarns in the examples was evaluated by a short fiber carding machine of Trutzschler, and its speed of 45 pounds/hr (20kg/hr) was considered to be "100% speed" unless otherwise noted. Carding is known as "good" if the card is capable of operating at 100% speed and is not parked more than once in a 40 pound (18kg) running test, which is not parked more than three times in at least 80% speed operation; "poor" is when the speed of operation is very low or the number of stops is much higher than when "satisfactory". Parking is typically caused by web breaks or roll jamming.

To determine the available stretch in the fabrics of examples 6A and 6B, three 60X 6.5cm samples were cut from the fabrics of examples 4A and 4B. The length dimension corresponds to the direction of stretching. Each sample was equally disassembled on either side until it became 5cm wide. One end of the fabric is folded to form a loop, and a sewing thread is sewn in the width direction for fixing the loop. A first line was drawn 6.5cm from the unlooped end of the fabric and a second line was drawn 50cm ("GL") from the first line. This sample was treated at 20 +/-2 ℃ and 65 +/-2% relative humidity for at least 16 hours. The sample is clamped in the first line and suspended vertically. A 30 newton weight was suspended from the loop of fabric and this sample was tested 3 times by alternately stretching it with the weight for 3 seconds and then holding the weight so that the fabric was unloaded. This weight is applied repeatedly and the distance between two lines ("ML") is recorded in the nearest millimeter. The results obtained from the three samples were then averaged using the tensile calculation via equation (III).

% of the total amount of the resulting product obtained by stretching 100X (ML-GL)/GL (III)

To measure the percent increase (measure of retraction after stretching) for examples 6A and 6B, three new samples were prepared as described for the available stretch test, extended to 80% of the previously determined available stretch, held under tension for 30 minutes. They then relax again without restriction for 60 minutes, the length between the two lines ("L₂") is measured again. The fabric growth rate was calculated by formula IV and the results of the three samples were averaged.

% fabric growth rate of 100 × (L)₂—GL)/GL (IV)

In these examples, the cotton fibers were strictly standard low-priced middle east type fibers with an average value of 4.3 micronaire (about 1.5 denier per fiber (1.7 dtex per fiber)). The cotton fibers and polyester bicomponent staple fibers were mixed by feeding them into a two-channel feeder, which was fed into a Trutzschler carding machine. The resulting green sliver was 70grain/yard (approximately 49,500 dtex). Either of the six strands was drawn together 6.5 times to obtain a 60grain/yam (approximately 42, 500 dtex) strand, which was then converted into a roving unless otherwise noted. The total draw in the roving process was 9.9 times. Unless otherwise noted, the roving was then plied and wound up on a Saco-Lowell machine using a post-draw of 1.35 and a ring spun of total draw of 29 to obtain a spun yarn of 22/1 cotton count (270 dtex) with twist multiplier of 3.8 and 17.8 revolutions per inch. When 100% of the cotton fiber was thus treated, the resulting spun yarn had a CV of 22% and a total scouring shrinkage of 5%.

In each sample of bicomponent staple fibers, the fibers had substantially equal linear densities and polymerization rates of poly (ethylene terephthalate) and poly (trimethylene terephthalate). No mechanical crimp was applied to the bicomponent staple fibers in the examples.

In the table, "comp." refers to a comparative sample, "NDR" refers to natural elongation, "b.o.s" refers to refining shrinkage, "Ne_c"means the cotton count (uk),and "nm" means "not measured".

Detailed Description

Example 1A

Polyester bicomponent staple fibers are continuous bicomponent filaments of poly (ethylene terephthalate) ((5-763, registered trademark of e.i. dupont), an inherent viscosity ("IV") of 0.52dl/g, andpoly (trimethylene terephthalate) (Sorona, e.i. dupont, registered trademark) brand IV of 1.00, melt spun through a 68-hole post-coagulation spinneret at a spinneret temperature of 255-265 ℃. The weight ratio of the polymer was 60/402G-T/3G-T. The filaments are drawn from the spinneret at a speed of 450-550 m/min and are blown transversely with a cooling air. The filaments with a "snowflake" cross-section were drawn 4.4 times, heat-set at 170 ℃, interlaced, and wound at a speed of 2100-2400 m/min. The filaments had a CI of 12% (a value believed to be reduced due to interlacing of continuous filaments), a CD of 51%, and a linear density of 2.4 dtex per filament. To convert to staple, the filaments from the package were gathered into a bundle and fed into a conventional staple bundle cutter with the spacing of the blades adjusted to achieve a staple length of 1.5 inches (3.8 cm).

Example 1B

The polyester bicomponent staple fibers and cotton fibers of example 1A were intimately blended to obtain two fibers at different weight percentages, and the blended fibers were carded, drawn, roving, and ring spun into an 22/1 yarn. The resulting spun yarn had CV and total refined shrinkage values as shown in table 1.

TABLE 1

Spun yarn	Bicomponent staple fiber wt%	Combing performance	Spun yarn CV%	Total B.O.S. of spun yarn%
					Comparative sample 1A	30	Good taste	17	18
Sample 1B	40	Good taste	18	24
					Sample 1C	50	Satisfaction	19	34
Sample 1D	60	Satisfaction	22	36
					Comparative sample 1E	70	Difference (D)	25	nm

Interpolation of the data in table 1 shows that when the bicomponent staple fiber is less than about 35% wt of the weight of the spun yarn, the overall refining shrinkage is low. These data also show that when the amount of polyester bicomponent staple fiber exceeds about 65 wt% based on the weight of the spun yarn, the carding performance of the fiber is compromised. If the ratio of the polyester bicomponent staple fiber is lower by 50 wt%, the uniformity thereof is improved.

Comparative example 1

Polyester bicomponent staple fibers were prepared as described in example 1A with the following differences. The weight ratio of 2G-T/3G-T was 40/60, the spinneret had 34 holes, and the resulting filaments had a linear density of 4.9 dtex/fil. The CI value was 16% and the CD value was 50%, but the combing property with cotton was poor at polyester bicomponent staple fiber contents of 65 wt%, 40 wt% or even 20%, and unsatisfactory results were shown when the polyester bicomponent staple fiber had a high linear density.

Comparative example 2

Polyester bicomponent staple fibers were made essentially as described in example 1A, except that the continuous filaments used were drawn 2.6 times and had a CI of only 3% and a CD of 29%. 60/40 polyester/cotton blended yarns have good combing properties, but the total refined shrinkage of the spun yarn spun from such blended yarns is only 15%, indicating inadequate yarn performance when the CD value of the spun yarn is too low.

Example 2

To make the polyester bicomponent staple fibers used in examples 3 and 4, 0.58IV poly (ethylene terephthalate) was made from terephthalic acid and ethylene glycol in a continuous polymerizer using a two-step process using an antimony transesterification catalyst in the second step. Adding TiO₂(0.3 wt% based on polymer weight) and the polymer was transferred at 285 ℃ and maintained at 280 ℃ and fed by a metering pump to a 790-hole bicomponent fiber spinneret. Poly (trimethylene terephthalate) (1.00IV Sorona)Poly (trimethylene terephthalate)) was dried, melt extruded at 258 ℃ and separately metered into a spinneret.

The drawing shows the cross section of the spinneret used. Molten poly (ethylene terephthalate) and poly (trimethylene terephthalate) enter distributor plate 2 at orifices 1a and 1b, are distributed radially through respective annular channels 3a and 3b, and contact each other first in slots 4 in distributor plate 5. The two polyesters are passed through holes 6 in metering plate 7 and through counter-holes 8 in spinneret plate 9, exiting the spinneret plate through capillary 10. The bore 6 and capillary 10 have substantially the same internal diameter.

The fibers are sprayed at 0.5-1.0 g/min into a radial fluid having an air supply of 142-200 standard cubic feet per minute (4.0-5.6 cubic meters/min) in each capillary so that the mass ratio of air to polymer is in the range of 9: 1-13: 1, in the range of 1. The cooling chamber is substantially the same as that disclosed in US5,219,506, but with a foraminous cooling gas distribution cylinder having similarly sized apertures to be able to provide a "continuous" flow of air. The spin finish is applied to the fiber at 0.07 to 0.09 wt% based on the weight of the fiber using a tapered applicator and then wound into a package.

Approximately 48 prepared side-by-side packages of circular cross-section fibers were combined to obtain a tow of approximately 130,000 denier (1444,400 dtex), passed around a feed roll to a first draw roll operating at below 35 ℃, passed to a second draw roll operating at 85-90 ℃ and supplied with a hot water spray, heat treated by contact with six rolls operating at 170 ℃, optionally overfed to 14% to a draw roll (pulleroll), and, after 0.14 wt% finish based on the weight of the fiber, passed through a continuous, forced convection dryer below 35 ℃. The tow is collected in a box with substantially no tension. The first draw is 77-90% of the total draw applied to the fiber. The drawn tow is about 37,000 denier (41,200 dtex) to 65,000 denier (72,200 dtex) depending on draw ratio. Additional spinning and drawing conditions and fiber properties are given in table II.

TABLE II

^*Sample 2A had a weight ratio of 70/302G-T/3G-T; others are 60/402G-T/3G-T

^**(speed of stretching roller 2-speed of pulling roller)/(pulling)Speed of roller)

Example 3

The tow sample selected in example 2 was cut into 1.5 inches (3.8cm), the resulting bicomponent staple fibers and cotton fibers were intimately mixed, carded, and ring spun at a polyester/cotton weight ratio of 60/40 to spin a 22/1 cotton count spun yarn. The fiber properties, the carding properties when blended with cotton fibers, and the properties of the resulting spun yarn are given in table III.

TABLE III

Bicomponent staple fibers	Filament bundle C.I. -%)	Combing performance	Filament bundle C.D.%	Spun yarn sample	Weight percent of yarn B.O.S.)	CV of the yarn%
							Comparative sample 2J	9	Good taste	26	Comparative sample 3A	20	15
Sample 2B	16	Good taste	35	Sample 3B	24	19
							Sample 2A	28	Satisfaction	49	Sample 3C	34	20
Sample 2H	34	Satisfaction	53	Sample 3D	39	19
							Sample 2E	36	Satisfaction	53	Sample 3E	38	22

Interpolation and extrapolation calculations of the data in table III show that refining shrinkage is insufficient when CI is below about 14%, and carding performance can remain satisfactory when CI is as high as about 42%.

Comparative example 3

Tow sample 2B was cut into 3.8cm bicomponent staple fibers, blended with cotton fibers at a polyester bicomponent staple fiber/cotton fiber weight ratio of 60/40, and the blend was carded and drawn as above, but not spun into roving. The drawn sliver was air jet spun on a Murata 802H spinning machine at an air nozzle pressure ratio (N1/N2) of 2.5/5.0 to 22/1 spun yarn with a total draw of 160 and a take-up speed of 200 m/min. The total refined shrinkage of the yarn was only 14%, indicating that the air-jet spun yarn had unsatisfactory draw and recovery.

Example 4

The tow sample prepared in example 2 was cut to 1.5 inches (3.8cm) and the resulting bicomponent staple fiber sample was intimately mixed with cotton fibers, carded, and ring spun into a 22/1 cotton count yarn at polyester/cotton weight ratios of 60/40 and 40/60. The fiber properties, the carding properties of the blend, and the properties of the resulting spun yarn are given in table IV.

TABLE IV

Bicomponent staple fibers	Bicomponent staple fiber,% by weight	Tow C.I., -%)	Combing performance	Filament bundle C.D., -%)	Spun yarn	B.o.s.,% of the yarn	CV of the yarn%
								Sample 21	60	24	Satisfaction	48	Sample 4A	28	18
Sample 2C	60	34	Satisfaction	56	Sample 4B	37	19
								Sample 2F	60	28	Satisfaction	49	Sample 4C	31	20
Comparative sample 2D	60	47	Difference (D)	57	Comparative sample 4D	38	25
								Sample 2G	60	44	Difference (D)	54	Comparative sample 4E	28	22
Sample 2F	40	28	Good taste	49	Sample 4F	24	18
								Sample 2G	40	44	Satisfaction	54	Sample 4G	25	22

The data in Table IV show that a bicomponent staple fiber weight ratio of 60 wt% is difficult to card when CI is above about 42%, and satisfactory carding can be achieved at 40 wt%. The processing data by interpolation shows that about 20 wt% bicomponent staple fiber has a CI as high as about 45%, carding well, and the total refining shrinkage and yarn uniformity (CV) remain acceptable.

Example 5

A female 3 x 1 quart sock with 1/2 cushioned sockets was woven using only the spun yarns of example 1. Each woman's sock was bleached with aqueous hydrogen peroxide at 180 ℉ (82 deg.C) and dry heat set (boarded) at 250 ℉ (121 deg.C) for 1.5 minutes.

The force with which the sock is unloaded is determined as follows. To avoid curling, the sock is not cut. It is marked in a 2.5 inch by 2.5 inch (6.4cm by 6.4cm) square in the center of the sock foot, between the toe and the heel. The Instron tensile tester clamp was placed between the top and end of the sock foot, avoiding the toe and heel from leaving the square in the middle between the clamps, so that the samples tested had a 2.5 inch (6.6cm) gauge. Each sample was cycled 3 times to 50% elongation at a rate of 200% elongation per minute. The unload force was measured at 30% residual effective tension over 3 cycles release and is given in kilogram force and is given in table V. In this test, "30% residual" effective stretch "means that the fabric is relaxed 30% from the maximum force over 3 cycles.

TABLE V

Knitted sample	Spun yarn	Weight of sock fabric, g/m	Content of bicomponent staple fibers,% by weight	Unload force (kg)
5A	Sample 1D	180	60	0.10
					5B	Sample 1C	177	50	0.09
5C	Sample 1B	165	40	0.08
					Comparison 5E	Is not provided with	127	0	0.04

The data in table V show that the knitted fabric comprising the spun yarns of the present invention has high fabric unload force and good stretch-rebound properties, which are retained even in knitted fabrics woven with spun yarns comprising low amounts of polyester bicomponent staple fibers.

Example 6A

A twill of 3/1 was woven from warp yarns of 100% 40/1 cotton count ring spun cotton on an air jet loom and reed (reed) to 96 threads/inch (38 threads/cm). The fill yarn consisted of an 22/1 cotton count ring spun yarn having 40 wt% cotton fibers and 60 wt% bicomponent staple fibers cut 3.8cm from tow sample 2H, with 65 picks per inch (251/2 picks per cm) and 500 picks per min. The fabric was scoured in boiling water for 1 hour and conventionally dyed with direct and disperse dyes. The effective draft is 22% and the growth rate is 3.8%, both of which are desirable characteristics.

Example 6B

Example 6A was repeated but ring spun with bicomponent staple fiber spun from tow sample 2E cut to 3.8cm at the same mix rate as the cotton fiber with 45 picks per inch (18 picks per cm). The fabric was scoured in boiling water for 1 hour and conventionally dyed with direct and disperse dyes. The effective draw was 25% higher than desired and the growth rate was 4.6% lower than desired.

Example 7A

To make tow samples of 7A to 7E, poly (ethylene terephthalate) s unless otherwise noted1.00IV) was extruded at a maximum temperature of about 260 c and poly (ethylene terephthalate) ('conventional', semi-dull, fiber grade 211, 0.54dl/gIV from Intercontinental Polymers, inc.) was extruded at a maximum temperature of 285 c, with the exception of the absence of metering sheet 7, which were separately metered to the spinneret as shown in fig. 1. The spinneret was heated to 280 ℃ and had 2622 capillaries. The side-by-side circular cross-section fiber produced had 2G-T of 52 wt%, 3G-T of 48 wt% and an IV of 0.94 dl/G. The fibers are collected from a plurality of spinneret positions by drawing rollers at 1200-1500 m/min and fed into a can.

The tows from about 50 cans are combined, fed at below 35 ℃ from a feed roll to a first draw roll, passed through a steam box operating at 80 ℃ and then to a second draw roll. The first draw was about 80% of the total draw applied to the fiber. The drawn tow is about 800,000 denier (888,900 dtex) to 1,000,000 denier (1,111,100 dtex). Referring to fig. 2, the drafted tow 16 is heat-treated by contact with a roller 11 having an operating temperature of 110 ℃, by a roller 12 having an operating temperature of 140 ℃ to 160 ℃, and by a roller 13 having an operating temperature of 170 ℃. The roll speed ratio between rollers 11 and 12 is about 0.91-0.99 (slack), the roll speed ratio between rollers 12 and 13 is about 0.93-0.99 (slack), and the roll speed ratio between rollers 13 and 14 is about 0.88-1.03. Finish sprayer 15 is applied so that the amount of finish sprayed on the tow is 0.15 to 0.35 wt%. The operating temperature of the drawing/cooling roller 14 is 35-40 ℃. The tow then passes through a continuous, forced convection dryer operating at less than 35 ℃ and is collected into boxes under essentially no tension. Additional processing conditions and fiber properties are given in table VI.

TABLE VI

Sample (I)	NDR	Total draft ratio	Average decitex per fiber	Filament bundle CI%	Tow CD%	CD—CI，％
							7A	1.90	2.92	nm	14	47	34
7B	1.90	3.08	nm	24	54	30
							7C	1.90	2.93	1.7	14	43	30
7D(1)	1.95	2.99	1.6	27	54	28
							2I	1.87	3.37	1.0	24	48	24
7E (comparison)	1.90	2.93	nm	7	29	22

(1) Using 0.55dlg/IVPoly (ethylene terephthalate) to which 500ppm of trimethyl 1,2, 4-trimellitate was added; the hole 6 (shown in FIG. 1) of about 1/2 in the metering plate 7 is not present; the IV of the poly (trimethylene terephthalate) in the fiber was 0.88 dl/g; roller 13 was operated at 175 ℃.

EXAMPLE 7B

Tow samples 7B, 7C and 7E were sheared into 1.75 inch (4.4cm) staple fibers, combined with cotton fibers by intimate mixing, carded at 60 pounds (27kg) per hour on a j.d. hollingsworth carding machine, and then ring spun into yarns of different cotton counts. The yarns and their properties are described in table VII; combing performance was evaluated on a qualitative basis.

TABLE VII

The data in table VII show the improved overall refining shrinkage of the yarns of the invention, and their unexpected uniform CV despite the increased CI.

The yarns of the invention produced in the examples and the fabrics made therefrom are soft and aesthetically pleasing.

Claims (11)

1. A spun yarn having an overall refined shrink of at least 22% comprising cotton fiber and bicomponent staple fiber comprising poly (ethylene terephthalate) and poly (trimethylene terephthalate), said bicomponent staple fiber having:

a) a tow crimp development value of 35% to 70%;

b) a tow crimp index value of 14% to 45%;

c) a length of 1.3cm to 5.5 cm; and

d) a linear density of 0.7 dtex per fiber to 3.0 dtex per fiber;

wherein said bicomponent staple fiber is present in an amount of from 20 wt% to 65 wt%, based on the total weight of said spun yarn;

wherein said cotton fibers are present in an amount of from 35 wt% to 80 wt% based on the total weight of said spun yarn.

2. The spun yarn of claim 1 having a coefficient of variation of mass of not greater than 22%, and wherein the bicomponent staple fiber is present in an amount of 20 wt% to less than 50 wt% based on the total weight of the spun yarn.

3. The spun yarn of claim 1 further comprising 1 wt% to 30 wt% poly (ethylene terephthalate) monocomponent staple fiber.

4. A bicomponent staple fiber comprising poly (ethylene terephthalate) and poly (trimethylene terephthalate) and having a tow crimp development value of from 40% to 60% and a tow crimp index value of from 14% to 27%, wherein the crimp index value and the crimp development value differ by from 24% to 35% absolute.

5. The spun yarn of claim 1 comprising the bicomponent staple fiber of claim 4.

6. A bicomponent staple fiber according to claim 4, wherein the difference between said index value and the crimp development value is from 30% to 35% absolute.

7. A process for producing the spun yarn of claim 1, comprising the steps of:

a) providing a bicomponent staple fiber having:

(i) a tow crimp development value of 35% to 70%;

(ii) a tow crimp index value of 14% to 45%;

(iii) a length of 1.3-5.5 cm; and

(iv) a linear density of 0.7 dtex per fiber to 3.0 dtex per fiber;

b) supplying cotton fibers;

c) mixing at least said cotton fibers and bicomponent staple fibers such that the weight content of said bicomponent staple fibers is from 20 wt% to 65 wt% based on the total weight of the mixed fibers and the weight content of said cotton fibers is from 35 wt% to 80 wt% based on the total weight of the mixed fibers;

d) carding the mixed fibers to form a sliver;

e) drafting the raw sliver;

f) plying and redrawing the raw sliver up to 3 times;

g) converting the drawn sliver to roving; and

h) ring spinning the roving to form a spun yarn.

8. The process of claim 7 wherein said bicomponent staple fiber has a tow crimp development value of from 40% to 60% and a tow crimp index value of from 14% to 27%, wherein the difference between said tow crimp index value and said tow crimp development value is from 24% to 35% absolute.

9. The method of claim 7 wherein said spun yarn has a coefficient of variation of mass of no more than 22%, step c) is an intimate mixing step, and said bicomponent staple fiber is present in an amount of 20 wt% to less than 50 wt%.

10. A fabric selected from the group consisting of knits and wovens and comprising the spun yarn of claim 1 made by the method of claim 7.

11. A method for making the spun yarn of claim 1, comprising the steps of:

a) providing a bicomponent staple fiber;

b) providing cotton fibers;

d) respectively carding the bicomponent staple fibers and the cotton fibers to produce bicomponent staple fiber raw slivers and raw cotton slivers;

e) a drawing frame for mixing said bicomponent staple fiber sliver and said tampon so that (i) the bicomponent staple fiber is from 20 wt% to 65 wt%; and (ii) cotton fibers in an amount of from 35 wt% to 80 wt%, based on the total weight of the mixed fibers;

f) plying and redrawing the mixed sliver of step (e) up to 3 times;

g) converting the drawn sliver to roving; and

h) ring spinning the roving to form a spun yarn.