JP7683344B2 - Fused false twist yarn and woven/knitted fabrics - Google Patents

Description

The present invention relates to stretch fusion-bonded false-twisted yarn and woven/knitted fabrics that have excellent coolness and surface quality even after repeated washing over a long period of time.

Conventionally, fusion-twisted yarns using thermoplastic filaments such as polyethylene terephthalate fibers have been known as synthetic fibers that have a refreshing feel.

For example, Patent Document 1 discloses a method for producing a fused false-twisted yarn in which highly oriented undrawn polyester yarn is false-twisted under specific false-twist conditions to fuse the single yarns partially or continuously in the length direction. However, in such conventional fused false-twisted yarns, crimp does not appear in the fused parts, and it is not possible to impart high stretchability to woven or knitted fabrics.

Patent Document 2 also proposes a fusion-twisted yarn in which polytrimethylene terephthalate and a second component polymer are compositely spun in a side-by-side or eccentric sheath-core manner. With this method, stretchability can be imparted to woven and knitted fabrics, but if the second component is not polytrimethylene terephthalate, the melting point will be different from that of polytrimethylene terephthalate, and in order to fuse the two types of polymers, it is necessary to set the false twist temperature to the polymer with the higher melting point. This means that the fusion strength must be strong, and coil crimp does not occur in the fused part, which causes a problem of deterioration in the quality of the woven and knitted fabric. On the other hand, even when the second component is also polytrimethylene terephthalate, there is a problem that the fused part is easily unraveled when an external force is applied by repeated washing due to the low Young's modulus characteristic of polytrimethylene terephthalate, and a refreshing feeling is lost.

Japanese Unexamined Patent Publication No. 52-49322 JP 2005-298980 A

The present invention overcomes the problems of the conventional technology and relates to stretch fusion-bonded false-twisted yarn and woven/knitted fabrics that have excellent coolness and surface quality even after repeated washing over a long period of time.

In order to solve the above problems, the fusion-bonded false-twisted yarn of the present invention has the following configuration.
The fusion-twisted yarn is characterized in that it is made of eccentric core-sheath composite fibers composed of two polyethylene terephthalate components, polymer _A and polymer B, the difference between the weight average molecular weight MwA of polymer _A and the weight average molecular weight MwB of polymer _B ( _MwA - MwB) being 2,000 to 15,000, the average length of the fusion parts being 3 to 30 mm, and the average number of the fusion parts being 5 to 100 /m .

The woven or knitted fabric of the present invention has the following structure. That is,

A woven or knitted fabric containing 20% or more by weight of the above-mentioned fused false twist yarn.

In the fusion-twisted yarn of the present invention, in the cross section of the eccentric core-sheath composite fiber, the polymer A component is completely covered with the polymer B component, the ratio S/D of the minimum thickness S of the polymer B component covering the polymer A component to the fiber diameter D is 0.01 to 0.2, and the length of the portion within 1.10 times the minimum thickness S is preferably 1/3 or more of the perimeter of the entire eccentric core-sheath composite fiber.

By using the fusion-twisted yarn defined in this invention, it is possible to provide stretch woven and knitted fabrics that have an excellent cool feel and surface quality even after repeated washing over a long period of time.

1 is a photograph showing an example of a fiber cross section of an eccentric sheath-core composite fiber used in the present invention. 1 is an example of an eccentric sheath-core composite fiber used in the present invention, and is a fiber cross section for explaining the position of the center of gravity in the fiber cross section. 1 is a fiber cross section for explaining the fiber diameter (D) and minimum thickness (S) in the fiber cross section of an eccentric sheath-core composite fiber used in the present invention.

The present invention will be described in detail below along with preferred embodiments.

In addition, in the above two types of polyethylene terephthalate components, the difference between the weight average molecular weight Mw _A of polymer A and the weight average molecular weight Mw _B of polymer B (Mw _A -Mw _B ), i.e., the weight average molecular weight difference, is 2,000 to 15,000, so that the fiber is greatly curved toward the high weight average molecular weight side after heat treatment, and this continues to form a three-dimensional coil structure. Therefore, the structure expands and contracts like a spring, and excellent stretchability can be obtained after false twisting. In addition, in order to obtain stretchability in woven and knitted fabrics using conventional fusion false twist yarns, there was a problem that the difference in shape between the crimped shape of the non-fused part and the non-crimped shape of the fused part became large, resulting in a moth-eaten quality in the woven and knitted fabrics. However, in the fusion false twist yarn of the present invention, by using the above polymer configuration, coil crimp is expressed even in a part of the fusion part, making it possible to obtain woven and knitted fabrics with excellent surface quality. If the weight average molecular weight difference is less than 2,000, it is not possible to produce coil crimp in the fused portion of the fusion-twisted yarn, and the quality of the woven or knitted product deteriorates. If the weight average molecular weight difference exceeds 15,000, spun yarn breakage occurs frequently, and stable production is not possible. The preferred weight average molecular weight difference is 4,000 to 13,000.

The range of Mw _A is preferably 20,000 to 28,000, and the range of Mw _B is preferably 12,000 to 20,000. These ranges are preferable because they provide good spinnability of the eccentric core-sheath composite fiber and good stretchability of the woven or knitted fabric.

The weight average molecular weight in the present invention is measured by preparing a measurement solution in which 2.0 mg of composite fiber is completely dissolved in 2.5 ^cm3 of tetrahydrofuran, and performing a gel permeation chromatography test using polystyrene as a standard substance. For example, a gel permeation chromatography (GPC) tester such as "TOSO GMHHR-H(S)HT" manufactured by Tosoh Corporation is used.

The polyethylene terephthalate component used in the present invention may be a polyester consisting of 90 mol % or more of repeating units of ethylene terephthalate, with terephthalic acid as the main acid component and ethylene glycol as the main glycol component. In addition, other copolymerizable components capable of forming ester bonds may be included within a range that does not impair the effects of the present invention. Examples of copolymerizable compounds include dicarboxylic acids such as isophthalic acid, cyclohexanedicarboxylic acid, adipic acid, dimer acid, sebacic acid, and sulfoisophthalic acid, diol components, and oxycarboxylic acid components.

The polyethylene terephthalate of the present invention may contain one or more of the following, as necessary, within the scope of the object of the present invention: titanium oxide, micropore-forming agents, cationic dyeable agents, coloring inhibitors, heat stabilizers, flame retardants, fluorescent brighteners, matting agents, colorants, antistatic agents, moisture absorbents, antibacterial agents, inorganic fine particles, etc.

The fiber cross section of the eccentric sheath-core composite fiber used in the present invention has a composite cross section formed by bonding two different polymers, and it is preferable that the two polymers with different polymer properties are present in a bonded state without being substantially separated, and that the B component completely covers the A component, making it an eccentric sheath-core type.

Here, eccentricity in the present invention refers to the position of the center of gravity of the polymer A component in the cross section of the composite fiber being different from the center of the cross section of the composite fiber. Hereinafter, a specific explanation will be given using FIG. 2. In FIG. 2, the horizontal hatching is the polymer B component, the 30 degree hatching (diagonal lines going up to the right) is the polymer A component, the center of gravity of the polymer A component in the cross section of the composite fiber is center of gravity a, and the center of gravity of the cross section of the composite fiber is center of gravity C.

In the eccentric sheath-core composite fiber used in the present invention, the center of gravity a is far from the center of gravity C of the composite fiber cross section (eccentricity), so that the fiber is curved significantly toward the high weight average molecular weight side after heat treatment. In this way, the high weight average molecular weight component shrinks relatively more strongly than the low weight average molecular weight component, so that the eccentric sheath-core composite fiber continues to curve in the fiber axis direction. As a result, the eccentric sheath-core composite fiber has a three-dimensional coil structure and exhibits good crimp. Here, the farther the center of gravity is, the better the crimp is exhibited and the better the stretch performance is obtained. In the fusion-bonded false twist textured yarn of the present invention, the polymer B component completely covers the polymer A component, so that the fusion state can be made stronger and an excellent cool feeling can be maintained even after long-term repeated washing and use, which is preferable.

Furthermore, in the fusion-bonded false twisted yarn of the present invention, if the ratio S/D of the minimum thickness S of the B component covering the polymer A component to the fiber diameter (diameter of the composite fiber) D is 0.01 to 0.2, it is preferable because better stretch performance and a stronger fusion form can be obtained, and more preferably 0.02 to 0.08.

This will be explained in more detail using the fiber cross section shown in Figure 3. Here, the thinnest part of component B in the core-sheath composite fiber is the minimum thickness S.

Furthermore, it is preferable that the length of the part with a thickness within 1.10 times the minimum thickness S (hereinafter sometimes referred to as the "minimum thickness part") occupies 1/3 or more of the entire circumference of the composite fiber. This means that the polymer A component is present along the contour of the fiber, and compared to conventional eccentric core-sheath composite fibers with the same area ratio, the present invention has the centers of gravity of each component farther apart in the fiber cross section, forming fine coils and exhibiting good crimping. More preferably, good stretch performance is obtained by making the length of the part with a thickness within 1.10 times the minimum thickness S 2/5 or more of the entire circumference of the fiber.

The method for measuring the minimum thickness S and fiber diameter D is shown below.

A multifilament made of eccentric sheath-core composite fibers is embedded in an embedding agent such as epoxy resin, and an image is taken of the cross section perpendicular to the fiber direction with a transmission electron microscope (TEM) at a magnification that allows observation of 10 or more fibers (locations). In this case, if metal dyeing is applied, the dye difference between the polymers can be used to clarify the contrast of the joint between the polymer A component and the polymer B component. The presence of the joints makes it possible to confirm that the eccentric sheath-core composite fiber is two-component. A circle circumscribing the cross section of 10 single yarns of eccentric sheath-core composite fibers randomly selected within the same image is set, and the value of the circumscribing circle diameter is equivalent to the fiber diameter D referred to in this invention. The circle circumscribing the cross section referred to here is the true circle that circumscribs the cross section at two or more points most frequently at two or more points on the cross section taken from a two-dimensionally photographed image. The circumscribing circle diameter refers to the diameter of the true circle. In addition, the minimum thickness S of the polymer B component covering the polymer A component is measured for 10 or more fibers (locations) using the image in which the fiber diameter D is measured. Furthermore, the fiber diameter D and the minimum thickness S are measured in units of μm and rounded off to the nearest third decimal place. The simple number average of the measured values and their ratios (S/D) are calculated for the 10 images taken during the above operation. The center of specific gravity and the area ratio can be calculated after the area of the entire fiber and the areas of the A and B components are calculated using the images taken above and the image analysis software "WinROOF2015" (Mitani Shoji Co., Ltd.).

In addition, it is preferable that the length of the portion within 1.10 times the minimum thickness S is at least 1/3 of the circumference of the entire fiber, and more preferably, the length of the portion within 1.05 times the minimum thickness S is at least 2/5 of the circumference of the entire fiber to obtain good stretch performance, and this length can also be measured using the same method as above.

In order to improve the stretch characteristics of the fusion-twisted yarn of the present invention, the ratio of the two components is preferably polymer A component:polymer B component = 70:30 to 30:70 (area ratio), more preferably 65:35 to 45:55.

The fusion-twisted yarn of the present invention is a false-twisted yarn that has a partially fused portion. By performing false-twist processing at high temperatures on an eccentric core-sheath composite fiber, a fusion portion can be formed in a portion of the processed yarn, imparting a cool feel to the woven or knitted fabric.

The fiber cross section of the fusion-twisted yarn of the present invention can be selected from any shape, including round, triangular, flat, hexagonal, L-shaped, T-shaped, W-shaped, octagonal, dog-bone, and other polygonal, multi-sided, and hollow shapes, but a round shape is preferred to enhance stretch properties.

The fineness of the fused false-twist yarn of the present invention is preferably 30 to 330 dtex, and the single yarn fineness is preferably 0.5 to 10 dtex, in order to impart stretchability and a cool feel to the woven or knitted fabric.

It is also possible to use the fusion-twisted yarn of the present invention and two or more other polyethylene terephthalate fibers (which may be the same eccentric sheath-core composite fibers) in a doubling or blend. In a blended yarn of the eccentric sheath-core composite fiber used in the present invention and other fibers, the ratio of the eccentric sheath-core composite fiber is preferably in the range of 20 to 80% by mass.

The woven or knitted fabric of the present invention can be endowed with a cool and refreshing feel by containing at least 20% by weight of fusion false-twisted yarn. If the content is less than 20%, the woven or knitted fabric will lack a cool and refreshing feel. In order to maintain a cool and refreshing feel, the average length of the fusion false-twisted yarn of the present invention is 3 to 30 mm, and the average number of fusion parts is 5 to 100 parts /m . Preferably , the average length is 5 to 20 mm, and the average number of fusion parts is 10 to 50 parts /m .

To maintain a refreshing feel even after repeated washing, it is preferable that the average length of the fused parts after 20 washes is 3 mm or more.

The woven or knitted fabric of the present invention preferably has an elongation rate of 10% or more when subjected to a load of 1.5 kgf (14.7 N) in at least one of the warp and weft directions. More preferably, it is 15% or more. This makes it suitable for a wide range of clothing applications, such as jackets, suits, bottoms, uniforms, shirts, student clothing, sportswear, skirts, and innerwear, as it maintains a refreshing feel even after repeated washing.

Next, we will describe a preferred method for producing the fusion-twisted yarn of the present invention.

It is preferable to precisely control the sheath thickness and the perimeter of the thin skin portion of the eccentric core-sheath composite fiber used in the present invention, and a method using a distribution plate as exemplified in JP-A-2011-174215, JP-A-2011-208313, and JP-A-2012-136804 is preferably used for the spinning nozzle. When a composite yarn having an eccentric core-sheath type cross section is produced using a conventionally known composite nozzle, it is often very difficult to precisely control the position of the center of gravity of the core and the sheath thickness. For example, if the sheath thickness becomes thin and the core component is exposed, this can cause a decrease in fusibility over long-term repeated washing, and conversely, if the sheath thickness becomes thick, the expression of crimping decreases, which can cause problems such as a decrease in stretch performance.

The eccentric core-sheath composite fiber used in the present invention is wound as an undrawn yarn or highly oriented undrawn yarn, preferably at a spinning speed of 1,500 to 3,800 m/min.

In the eccentric core-sheath composite fiber used in the present invention, it is preferable that the polymer A component is completely covered by the polymer B component as shown in Figure 2. By making the cross section as specified in the present invention, it is possible to suppress the bending of the discharge line (kneeing phenomenon) that occurs due to the difference in flow speed of the two polymers when they are discharged from the spinneret. In addition, in the case of a conventional simple laminated structure (bimetal structure), there is a difference in the balance of stress applied to each polymer when thinning on the spinning line after discharge from the spinneret, which causes unevenness in the elongation deformation, which manifests as uneven fineness and increases U%. This tendency is very noticeable when combining polymers with large differences in viscosity or molecular weight, but in the present invention, the stress balance is balanced within the fiber cross section by covering it with one of the polymers, and uneven fineness can be suppressed.

Next, the fusion-twisted yarn used in the present invention can be obtained by processing the above-mentioned eccentric core-sheath composite fiber under high-temperature false-twisting conditions. Any false-twisting conditions can be selected as the false-twisting conditions, but the false-twisting temperature is preferably 180 to 235°C in the case of a contact heater. It is more preferably 210 to 230°C. The twister may be any of a spindle type, a friction disk type, and a belt nip type. The false-twist number is preferably set in the range where the false-twist coefficient (false-twist number (T/M) x fineness (dtex) ^0.5 ) is 15,000 to 33,000, in order to impart strong crimp and fusion.

To further improve the cool feeling, low-magnification hot drawing can be performed before false twisting to give the fibers thick and fine details. To reduce residual torque, heat setting with a heater can also be performed after false twisting. As for the yarn processing speed, the faster the better, as this increases productivity, but in terms of stable processing, a speed of 100 to 800 m/min is preferable.

In the woven and knitted fabrics using the fused false twist yarn of the present invention, any weave can be selected for the woven fabric, such as plain, twill, satin, amunzen, or double weave. Any weave can be selected for the knitted fabric, such as plain, smooth, half, or double raschel. The woven and knitted fabrics of the present invention thus obtained have sufficient stretch performance, and can provide excellent coolness and surface quality even after repeated washing over a long period of time. These woven and knitted fabrics are suitable for use in a wide range of clothing applications, such as jackets, suits, bottoms, uniforms, shirts, student clothing, sports clothing, skirts, and innerwear.

The false twist fusion yarn and woven/knitted fabric of the present invention will be specifically described below with reference to examples. The following evaluations were carried out for the examples and comparative examples.

(1) Measurement of Weight Average Molecular Weight of Thermoplastic Resin As a gel permeation chromatography (GPC) tester, a "TOSO GMHHR-H(S)HT" manufactured by Tosoh Corporation was used.

(2) Fineness: 100 skeins were prepared using a measuring machine with a frame circumference of 1.0 m, and the fineness was measured according to the following formula.

Fineness (dtex) = weight of skein for 100 times (g) x 100
(3) Shrinkage The yarn was wound 10 times around a measuring machine with a circumference of 0.8 m under a tension of 90 mg/dtex to take a skein, and then hung on a rod of 2 cm or less and left for about 24 hours. The skein was wrapped in gauze, treated with hot water at 90°C for 20 minutes under no tension, and then hung on a rod of 2 cm or less and left for about 12 hours. One end of the skein after leaving was hung on a hook, and the other end was subjected to an initial load and a measurement load, and the skein was left for 2 minutes. The initial load (g) at this time was 2 mg/dtex, the measurement load (g) was 90 mg/dtex, and the water temperature was 20 ± 2°C. The inner length of the left skein was measured and designated as L. Furthermore, the measurement load was removed and the skein was left for 2 minutes with only the initial load, and the inner length of the left skein was measured and designated as L1. The shrinkage was calculated using the following formula, and this operation was repeated 5 times to determine the average value.

Crimp rate (%) = {(L-L1)/L} x 100
(4) Elongation The elongation was measured at a load of 1.5 kgf (14.7 N) according to the method B described in JIS L 1096 (2010). This elongation was used as a measure of stretchability.

(5) Average length and number of fused parts Observation was performed using an optical microscope (VHX-2000, manufactured by Keyence Corporation) to measure the average length and number of fused parts per meter of yarn. This operation was repeated five times and the average value was calculated.

The average length of the fused part and the number of fused pieces after repeated washing were determined by carefully extracting the fused false twist yarn from the woven/knitted fabric so as not to break the fused part, and the repeated washing process was performed by washing the woven/knitted fabric once in a two-tub washing machine with a liquid temperature of 40°C, a washing time of 5 minutes, rinsing at 30°C for 2 minutes twice, and spinning for 30 seconds. The detergent used was 1 g/L of "Attack" (registered trademark) manufactured by Kao Corporation, with a liquid volume of 40 L and a combined weight of 830 g for the test cloth and the cotton cloth used as the guide cloth. This washing process was repeated 20 times, and the above evaluation was performed.
(6) Cool Feeling: Woven and knitted fabrics were subjected to the same repeated washing treatment as in (5) above. The cool feeling was evaluated by sensory evaluation using a four-level scale: very excellent cool feeling, excellent cool feeling, slightly insufficient cool feeling, and insufficient cool feeling. The result was determined to be closest to the average of the ratings of 10 randomly selected persons.
(7) Surface quality Woven and knitted fabrics that had been repeatedly washed in the same manner as in (5) were subjected to a sensory evaluation using a four-level scale: very good surface quality, good surface quality, surface wrinkles, and wormholes. The result was determined to be closest to the average of the ratings of 10 randomly selected panelists.

[Example 1]
The polymer A component was polyethylene terephthalate having a weight average molecular weight of 25,000, and the polymer B component was polyethylene terephthalate having a weight average molecular weight of 15,000. The polymers were fed into a spinneret for eccentric sheath-core composite fiber having a weight composite ratio of 50/50 and 24 nozzles. The polymers were joined inside the spinneret to form an eccentric sheath-core composite form in which the polymer A component was contained in the polymer B component. The spinneret was spun at a spinning speed of 2,800 (m/min) to obtain a highly oriented undrawn yarn with a fineness of 125 dtex, 36 filaments, and an elongation of 145%. In the spinning of Example 1, a distributor type spinneret was used to obtain the eccentric sheath-core composite fiber shown in FIG. 1. The S/D ratio in the fiber cross section was 0.02, and the length of the minimum thickness portion accounted for 40% of the circumference of the entire eccentric sheath-core composite fiber.

Next, the highly oriented undrawn yarn was fed from a feed roller using a friction false twisting machine (ATF12, manufactured by TMT Machinery Co., Ltd.) and false twisted at a processing speed of 400 m/min, a draw ratio of 1.5 times, a heater temperature of 220°C, and a false twist coefficient of 28,000 to obtain a fused false twisted yarn with a fineness of 84 dtex, a crimp rate of 38%, an average length of the fused portion of 15.3 mm, and a number of fused portions of 24.1/m.

The yarns were then used as warp and weft yarns to weave a plain weave fabric on an air jet loom. The resulting woven fabric was then subjected to continuous scouring at 98°C, liquid flow relaxation at 120°C, intermediate setting at 180°C, dyeing at 130°C, and finishing setting at 160°C to produce a product with a processing density (warp: 95 threads/2.54 cm, weft: 90 threads/2.54 cm). The elongation of the resulting fabric was 15.5% in the warp and 20.4% in the weft, showing excellent stretchability. In addition, the average length of the fused portion after 20 washes was 15.1 mm, and the number of fused pieces was 22.9 pieces/m, showing that the stretch fabric had excellent coolness and woven quality even after repeated washing over a long period of time. The evaluation results of the properties of the eccentric core-sheath composite fiber, the properties of the fused false twist yarn, and the properties of the woven fabric are shown in Table 1.

[Example 2]
Spinning was performed in the same manner as in Example 1, except that polyethylene terephthalate with a weight average molecular weight of 19,000 was used as the polymer A component, to obtain a highly oriented undrawn yarn with a fineness of 125 dtex, 36 filaments, and elongation of 142%. The S/D ratio in the fiber cross section was 0.1, and the length of the minimum thickness part accounted for 35% of the circumference of the entire eccentric core-sheath composite fiber.

Next, the highly oriented undrawn yarn was fed from a feed roller using a friction false twisting machine (ATF12, manufactured by TMT Machinery Co., Ltd.) and false twisted at a processing speed of 400 m/min, a draw ratio of 1.45 times, a heater temperature of 225°C, and a false twist coefficient of 27,000 to obtain a fused false twisted yarn with a fineness of 88 dtex, a crimp rate of 30%, an average length of the fused portion of 17.2 mm, and a number of fused portions of 32.5/m.

The fabric was then woven and dyed in the same manner as in Example 1 to obtain a product. The elongation of the fabric was excellent, with a warp stretch rate of 12.1% and a weft stretch rate of 17.8%. After 20 washes, the average length of the fused parts was 16.9 mm, and the number of fused parts was 28.0/m, showing that the fabric had an excellent cool feel and woven quality even after repeated washing over a long period of time. The evaluation results of the properties of the eccentric core-sheath composite fiber, the properties of the fused false twist yarn, and the properties of the fabric are shown in Table 1.

[Example 3]
Spinning was performed in the same manner as in Example 1, except that polyethylene terephthalate having a weight average molecular weight of 28,000 was used as the polymer A component, to obtain a highly oriented undrawn yarn having a fineness of 125 dtex, 36 filaments, and an elongation of 141%. The S/D ratio in the fiber cross section was 0.02, and the length of the minimum thickness part accounted for 40% of the circumference of the entire eccentric core-sheath composite fiber.

Next, the highly oriented undrawn yarn was fed from a feed roller using a friction false twisting machine (ATF12, manufactured by TMT Machinery Co., Ltd.) and false twisted at a processing speed of 400 m/min, a draw ratio of 1.5 times, a heater temperature of 215°C, and a false twist coefficient of 29,000 to obtain a fused false twisted yarn with a fineness of 84 dtex, a crimp rate of 44%, an average length of the fused portion of 8.6 mm, and a number of fused portions of 11.2/m.

Thereafter, the fabric was woven and dyed in the same manner as in Example 1 to obtain a product. The elongation of the fabric was 21.2% in the warp direction and 25.6% in the weft direction, showing excellent stretchability. After 20 washes, the average length of the fused portion was 8.0 mm, and the number of fused portions was 11.0/m, showing that the fabric had excellent coolness and woven quality even after repeated washing over a long period of time. The evaluation results of the properties of the eccentric core-sheath composite fiber, the properties of the fused false twist yarn, the properties of the fabric, etc. are shown in Table 1.
[Comparative Example 1]
The polymer A component was polyethylene terephthalate with a weight average molecular weight of 32,000, and the polymer B component was polyethylene terephthalate with a weight average molecular weight of 15,000. The weight composite ratio of the polymer A component to the polymer B component was 50/50, and the fibers were spun at a spinning speed of 2,800 m/min from a side-by-side spinneret with 24 discharge holes to obtain a highly oriented undrawn yarn with a fineness of 125 dtex, 36 filaments, and elongation of 144%, but the spinneret discharge bending was large and yarn breakage occurred frequently. The S/D in the fiber cross section was 0, and the proportion of the length of the minimum thickness part to the circumference of the entire eccentric core-sheath composite fiber was 0%.

Next, the highly oriented undrawn yarn was fed from a feed roller using a friction false twisting machine (ATF12, manufactured by TMT Machinery Co., Ltd.) and false twisted at a processing speed of 400 m/min, a draw ratio of 1.5 times, a heater temperature of 220°C, and a false twist coefficient of 28,000 to obtain a fused false twisted yarn with a fineness of 84 dtex, a crimp rate of 48%, an average length of the fused portion of 6.5 mm, and a number of fused portions of 10.6/m.

The fabric was then woven and dyed in the same manner as in Example 1 to obtain a product. The elongation of the fabric was 22.2% in the warp direction and 26.1% in the weft direction, showing excellent stretchability. After 20 washes, the average length of the fused parts was 2.5 mm, and the number of fused parts was 9.0/m. After repeated washing over a long period of time, the fused parts came off, the cool feeling was insufficient, and the fabric had a grained texture. The evaluation results of the properties of the eccentric core-sheath composite fiber, the properties of the fused false twist yarn, and the properties of the fabric are shown in Table 1.

[Comparative Example 2]
Spinning was carried out in the same manner as in Example 1, except that polyethylene terephthalate with a weight average molecular weight of 16,000 was used as the polymer A component, and a highly oriented undrawn yarn with a fineness of 125 dtex, 36 filaments, and elongation of 143% was obtained. The S/D ratio in the fiber cross section was 0.02, and the length of the minimum thickness part accounted for 40% of the circumference of the entire eccentric core-sheath composite fiber. Next, using a friction false twisting machine (ATF12: manufactured by TMT Machinery Co., Ltd.), the highly oriented undrawn yarn was fed from a feed roller and false twisted at a processing speed of 400 m/min, a draw ratio of 1.5 times, a heater temperature of 220°C, and a false twist coefficient of 28,000, to obtain a fused false twisted yarn with a fineness of 84 dtex, a crimp rate of 20%, an average length of the fused part of 17.4 mm, and a number of fused pieces of 18.1 pieces/m.

The fabric was then woven and dyed in the same manner as in Example 1 to obtain a product. The elongation of the resulting fabric was 12.1% in the warp direction and 13.8% in the weft direction. After 20 washes, the average length of the fused parts was 17.0 mm, and the number of fused parts was 17.5/m. Even after repeated washing over a long period of time, the fabric had an excellent cool feeling, but the fused parts did not have coil crimp, and the fabric had a moth-eaten appearance. The evaluation results of the properties of the eccentric core-sheath composite fiber, the properties of the fused false twist yarn, and the properties of the woven fabric are shown in Table 1.

[Comparative Example 3]
Spinning was performed in the same manner as in Example 1, except that polytrimethylene terephthalate having a weight average molecular weight of 25,000 was used as the polymer A component, and polytrimethylene terephthalate having a weight average molecular weight of 15,000 was used as the polymer B component, to obtain a highly oriented undrawn yarn having a fineness of 125 dtex, 36 filaments, and an elongation of 140%. The S/D ratio in the fiber cross section was 0.02, and the length of the minimum thickness part accounted for 40% of the circumference of the entire eccentric core-sheath composite fiber. Next, using a friction false twisting machine (ATF12, manufactured by TMT Machinery Co., Ltd.), the highly oriented undrawn yarn was fed from a feed roller and false twisted at a processing speed of 400 m/min, a draw ratio of 1.5 times, a heater temperature of 210° C., and a false twist coefficient of 28,000, to obtain a fused false twisted yarn having a fineness of 84 dtex, a crimp rate of 41%, an average length of the fused portion of 9.8 mm, and a number of fused portions of 15.0 pieces/m.

The fabric was then woven and dyed in the same manner as in Example 1 to obtain a product. The elongation of the resulting fabric was 19.5% in the warp direction and 23.4% in the weft direction, giving it excellent stretchability. However, after 20 washes, the average length of the fused parts was 2.6 mm, and the number of fused parts was 4.6/m. Although the fabric had excellent quality after repeated washing over a long period of time, the fusion had come off and the fabric lacked a refreshing feel. The evaluation results of the properties of the eccentric core-sheath composite fiber, the properties of the fused false twist yarn, and the properties of the fabric are shown in Table 1.

[Comparative Example 4]
A highly oriented, undrawn yarn obtained by the same method as in Example 1 was fed from a feed roller using a friction false twisting machine (ATF12, manufactured by TMT Machinery Co., Ltd.) and false twisted at a processing speed of 400 m/min, a draw ratio of 1.5 times, a heater temperature of 160° C., and a false twist coefficient of 28,000 to obtain a false twisted yarn with a fineness of 84 dtex, a crimp rate of 41%, an average length of fused parts of 0 mm, and a number of fused parts of 0/m. The S/D ratio in the fiber cross section of the highly oriented, undrawn yarn was 0.02, and the length of the minimum thickness part accounted for 40% of the circumference of the entire eccentric core-sheath composite fiber.

Thereafter, the false-twisted yarn was used as the warp yarn, and the false-twisted yarn and the fused false-twisted yarn obtained by the same method as in Example 1 were used as the weft yarn in a 2:1 arrangement, and a plain weave fabric was woven on an air jet loom (the ratio of the fused false-twisted yarn was 16%).
Next, the obtained woven fabric was subjected to continuous scouring at 98°C, liquid flow relaxation at 120°C, intermediate setting at 180°C, dyeing at 130°C, and finishing setting at 160°C to obtain a product with a processing density (warp: 95/2.54 cm, weft: 90/2.54 cm). The elongation of the obtained woven fabric was 20.5% in the warp and 23.4% in the weft, and it had excellent stretchability. In addition, after 20 washes, the average length of the fused part of the fusion false-twisted yarn was 15.3 mm, and the number of fusions was 23.0/m, but the effect of the fusion false-twisted yarn was small, and the woven fabric lacked a refreshing feel. The evaluation results of the properties of the eccentric core-sheath composite fiber, the properties of the fusion false-twisted yarn, and the properties of the woven fabric are shown in Table 1.

According to the present invention, by using the specified fusion-twisted yarn, it is possible to provide a stretch woven or knitted fabric that has an excellent cool feeling and surface quality even after repeated washing over a long period of time.

1 Polymer A component 2 Polymer B component a: Center of gravity of polymer A component in cross section of composite fiber C: Center of gravity of cross section of composite fiber S: Minimum thickness of polymer B component D: Fiber diameter

Claims (3)

A fusion-twisted yarn comprising an eccentric core-sheath composite fiber composed of two polyethylene terephthalate components, a polymer _A and a polymer B, characterized in that the difference (MwA - _{MwB )} between the weight average molecular weight MwA of said polymer A and the weight average molecular weight MwB of said polymer _B is 2,000 to 15,000, the average length of the fusion parts is 3 to 30 mm, and the average number of the fusion parts is 5 to 100 /m . The fusion-twisted yarn according to claim 1, characterized in that in the cross section of the eccentric core-sheath composite fiber, the polymer A component is completely covered with the polymer B component, the ratio S/D of the minimum thickness S of the polymer B component covering the polymer A component to the fiber diameter D is 0.01 to 0.2, and the length of the portion within 1.10 times the minimum thickness S is 1/3 or more of the perimeter of the entire eccentric core-sheath composite fiber. A woven or knitted fabric containing 20% or more by weight of the fused false twist yarn according to claim 1 or 2.

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