Polyester multifilament, woven or knitted fabric containing polyester multifilament, and method for producing the same

Abstract

To provide a polyester multifilament which is a filament having both high crimping performance and thick and thin variations and which can give a woven or knitted fabric having high shape stability. [Solution] A multifilament consisting of single fibers, each of which exhibits a cross-sectional shape formed by bonding two types of polyester resins with different intrinsic viscosities, wherein both of the two types of polyester resins constituting the single fibers are polyester resins whose main component is polyethylene terephthalate and in which the copolymerization amount of components other than terephthalic acid and ethylene glycol is 7 mol % or less, and wherein the polyester multifilament simultaneously satisfies the following: (1) a crystallinity of 20 to 40%, (2) a crimp rate after boiling water treatment of 35 to 60%, and (3) a fiber diameter ratio of the thickest single fiber to the thinnest single fiber in a cross section perpendicular to the longitudinal direction at any position of the multifilament of 1.6 to 2.4.

Description

[Technical Field]

[0001] The present invention relates to a polyester multifilament in which two types of polyester resins are bonded in the cross section of a single fiber and which has thick and thin patterns in the longitudinal direction of the fiber, and to a woven or knitted fabric containing the polyester multifilament.Furthermore, the present invention relates to a method for producing the polyester multifilament. [Background technology]

[0002] Conventionally, fibers in which thick and thin variations are imparted in the longitudinal direction of a single fiber have been known, among fibers in which two types of resins with different melt viscosities are conjugated side-by-side. For example, Patent Document 1 discloses that in a conjugated fiber using a polyester resin in which a specific amount or more of a third component is copolymerized with the higher viscosity component of the two types of resins, the coefficient of variation (CV) of the thickness variations is set within a specific range, and thick and thin variations are formed in the longitudinal direction of the single fiber so that thick and thin portions are not localized, thereby obtaining a polyester conjugated multifilament and its woven or knitted fabrics that have stretchability and swelling due to crimp and also exhibit a natural appearance.

[0003] On the other hand, in recent years, woven and knitted fabrics used in the field of clothing have been required to have greater stretchability from the viewpoint of ease of movement. However, the stretchability of the polyester conjugate multifilament obtained in Patent Document 1 is insufficient, and even if the crimp rate of the filament is further increased in order to improve the stretchability of the polyester conjugate multifilament of Patent Document 1, there are problems such as insufficient kickback property (elasticity) being exhibited, the woven and knitted fabric having poor shape stability, and being prone to wrinkling when made into clothing. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent Publication No. 2004-124271 Summary of the Invention [Problem to be solved by the invention]

[0005] Therefore, an object of the present invention is to solve the above-mentioned problems and to provide a polyester multifilament that has both high crimp performance and thick / thin variations, is a multifilament with a high elastic modulus, has stretchability and volume due to crimp, and can give woven or knitted fabrics that have a natural appearance and excellent shape stability. Another object of the present invention is to provide a woven or knitted fabric containing the polyester multifilament and a method for producing the polyester multifilament. [Means for solving the problem]

[0006] As a result of intensive research to solve the above problems, the present inventors have found that a polyester multifilament satisfying specific composition and characteristic values ​​can achieve the above object, and have arrived at the present invention.

[0007] That is, the present invention is summarized as follows:

[0008] 1. A multifilament consisting of single fibers, each of which has a cross-sectional shape formed by bonding two types of polyester resins having different intrinsic viscosities, wherein both of the two types of polyester resins constituting the single fibers are polyester resins containing polyethylene terephthalate as the main component and in which the copolymerization amount of components other than terephthalic acid and ethylene glycol is 7 mol % or less, and wherein the multifilament simultaneously satisfies the following characteristic values ​​(1) to (3): (1) Crystallinity is 20-40% (2) Crimp rate after boiling water treatment: 35-60% (3) The ratio of the fiber diameter of the thickest single fiber to the thinnest single fiber in a cross section perpendicular to the longitudinal direction at any position of the multifilament is 1.6 to 2.4. 2. The polyester multifilament according to 1., having an elastic modulus of 70% or more. 3. A woven or knitted fabric comprising the polyester multifilament according to 1. or 2. 4. A method for producing a polyester multifilament according to any one of 1. to 3., comprising the following steps (a) to (c) in this order: (a) A step of melt-conjugating polyester resin A and polyester resin B that satisfy the following condition (i) to obtain a spun yarn. (i) 0.18≦[η]A−[η]B≦0.30 (b) A step of taking up the spun yarn with a roller at a speed of 2800 to 5000 m / min to obtain an undrawn yarn. (c) A step of aging the undrawn yarn in an environment of 23 to 50°C for 30 hours or more. (iv) A step of drawing the aged undrawn yarn between the first roller and the second roller and between the second roller and the third roller so that the draw ratios DR1 and DR2 satisfy the following formula (ii), and the draw temperature is 90 to 130°C, the heat setting temperature is 130 to 170°C, and the total draw ratio is 1.1 to 2.5 times: (ii) DR1>DR2 Here, DR1 is the draw ratio between the first roller and the second roller, and DR2 is the draw ratio between the second roller and the third roller. [Effects of the Invention]

[0009] The polyester multifilament of the present invention has a high crimp percentage after boiling water treatment and a large fiber diameter ratio (thick-thin unevenness) between the thickest and thinnest single fibers in a cross section perpendicular to the longitudinal direction at any position of the multifilament, allowing for the production of woven and knitted fabrics having stretchability and a natural feel. Furthermore, the polyester multifilament of the present invention has a high crystallinity, allowing for the production of woven and knitted fabrics having a high elastic modulus and excellent shape stability. The woven or knitted fabric of the present invention contains the polyester multifilament of the present invention, and therefore can be suitably used for various clothing applications such as sportswear, outerwear, innerwear, men's clothing, women's clothing, and workwear. Moreover, according to the production method of the present invention, the polyester multifilament of the present invention can be obtained with good productivity. DETAILED DESCRIPTION OF THE INVENTION

[0010] The present invention will be described in detail below. The polyester multifilament of the present invention is a multifilament composed of single fibers in which two types of polyester resins (polyester resin A and polyester resin B) with different intrinsic viscosities are bonded in the cross section of the single fiber. In the polyester multifilament of the present invention, polyester resin A on the high-viscosity side of the single fiber acts as a high-shrinkage component, and polyester resin B on the low-viscosity side acts as a low-shrinkage component, so that when subjected to a boiling water shrinkage treatment, the polyester multifilament develops a three-dimensional coil spring-like crimp (spiral crimp), and this crimp can impart stretchability when made into a woven or knitted fabric.

[0011] The two polyester resins of the present invention, each with a different intrinsic viscosity, are primarily composed of polyethylene terephthalate (PET), a polymer made from terephthalic acid and ethylene glycol. Here, "based on PET" means that the ethylene terephthalate repeating unit accounts for 70 mol% or more of the total repeating units constituting the polyester resin. The content of ethylene terephthalate repeating units is preferably 80 mol% or more, more preferably 85 mol% or more, and even more preferably 95 mol% or more. In the case of homo-PET in which no other components are copolymerized, the content is 100 mol%.

[0012] The combination of two polyester resins having different intrinsic viscosities is not particularly limited, and may be any of a combination of homo-PETs having different intrinsic viscosities, a combination of PET copolymerized with a component other than terephthalic acid and ethylene glycol and homo-PET, and a combination of PET copolymerized with a component other than terephthalic acid and ethylene glycol.

[0013] In the cross-sectional shape of a single fiber, the form in which two types of polyester resins with different intrinsic viscosities are bonded is not limited, and examples include composite forms such as a side-by-side type or an eccentric core-sheath type, with the side-by-side type being more preferred from the viewpoint of stretchability.

[0014] In the single fibers constituting the polyester multifilament of the present invention, the conjugation ratio (volume ratio) of polyester resin A to polyester resin B is preferably polyester resin A / polyester resin B=70 / 30 to 30 / 70, more preferably 60 / 40 to 40 / 60. When the ratio of polyester resin A / polyester resin B is within the above range, the crimping performance is excellent, and the fiber strength and spinnability are also improved.

[0015] In the present invention, it is necessary that both of the two polyester resins constituting the single fiber have polyethylene terephthalate (PET) as the main component and have a copolymerization amount of components other than terephthalic acid and ethylene glycol of 7 mol % or less. Among these, PET having a copolymerization amount of components other than terephthalic acid and ethylene glycol of 6 mol % or less is preferred, more preferably 4 mol % or less, and even more preferably 3 mol % or less. In the present invention, if at least one of the two polyester resins is PET having a copolymerization amount of components other than terephthalic acid and ethylene glycol of more than 7 mol %, the crystallinity and elastic modulus of the resulting polyester multifilament will be reduced, and woven or knitted fabrics obtained using the polyester multifilament will have poor kickback properties and reduced dimensional stability.

[0016] Examples of components other than terephthalic acid and ethylene glycol include acid components such as aromatic dicarboxylic acids other than terephthalic acid and aliphatic dicarboxylic acids, and diol components such as aliphatic diols other than ethylene glycol, alicyclic diols, and aromatic diols. Specific examples include dibasic acids such as isophthalic acid, 5-sodium sulfoisophthalic acid, succinic acid, and adipic acid, and glycols such as diethylene glycol, propanediol, butanediol, and hexanediol. Two or more components may be copolymerized in each of the two polyester resins used for the single fiber, as long as the copolymerization amount does not exceed 7 mol%.

[0017] The single fibers constituting the polyester multifilament of the present invention may contain various additives such as a matting agent, an antioxidant, an antibacterial agent, etc., as long as the effects are not impaired. Specific examples of matting agents include inorganic oxides such as titanium oxide, zinc oxide, and calcium oxide. Titanium oxide is preferred from the viewpoint of the matting effect of inorganic compounds and the thermal stability it exerts on the resin. Various additives may be contained only in the high-viscosity polyester resin A, or only in the low-viscosity polyester resin B, or in both polyester resin A and polyester resin B.

[0018] The crystallinity of the polyester multifilament of the present invention must be 20 to 40%, and preferably 22 to 38%. If the crystallinity is less than 20%, the elastic modulus of the multifilament tends to be low, and when made into a woven or knitted fabric, it will not have sufficient kickback properties and will have poor shape stability. On the other hand, if the crystallinity is greater than 40%, yarn breakage will be more likely to occur when the polyester multifilament is subjected to a false twisting process or a weaving and knitting process, and processability will be reduced.

[0019] In the present invention, it is important that the polyester multifilament satisfies the crystallinity range described above. Typically, in a multifilament composed of single fibers in which two types of polyester resins with different intrinsic viscosities are bonded together in the cross-sectional shape of the single fiber, increasing the difference in intrinsic viscosities, as described in the production method described below, tends to improve crimpability while decreasing the modulus of elasticity. However, in the present invention, by setting the crystallinity within a specific range, it is possible to increase the crimpability without decreasing the modulus of elasticity of the resulting polyester multifilament. Therefore, when the polyester multifilament of the present invention is used to produce a woven or knitted fabric, it is possible to obtain a woven or knitted fabric that is excellent in crimpability and kickback properties (shape stability). In the present invention, the crystallinity of the polyester multifilament can be adjusted to the above range by using a polyester resin having the above composition and employing the production method for a polyester multifilament described below. The degree of crystallinity in the present invention refers to the degree of crystallinity of a polyester multifilament obtained by measuring the degree of crystallinity of the polyester multifilament by the measuring method described below.

[0020] As described above, the polyester multifilament of the present invention has excellent crimp performance. Specifically, it is necessary that the crimp percentage after boiling water treatment (after shrinking treatment in boiling water for 30 minutes, as described below) is 35 to 60%. The crimp percentage is preferably 37 to 59%, more preferably 40 to 58%. In the present invention, the crimp percentage can be adjusted to the above range by using two polyester resins whose intrinsic viscosity difference in the above composition satisfies a specific range and producing the polyester multifilament by the production method of the present invention described below. If the crimp percentage is less than 35%, the stretchability of the woven or knitted fabric obtained using the composite multifilament will be insufficient. On the other hand, if the crimp percentage is more than 60%, the shape stability of the woven or knitted fabric obtained using the composite multifilament will be reduced.

[0021] The polyester multifilament of the present invention has thick and thin variations in the longitudinal direction of the fiber. As an indicator of this thick and thin variation, the ratio of the fiber diameters of the thickest and thinnest single fibers in a cross section perpendicular to the longitudinal direction at any position of the multifilament must be 1.6 to 2.4. The fiber diameter ratio is preferably 1.8 to 2.4, more preferably 1.9 to 2.4. If the fiber diameter ratio is less than 1.6, the thickness and thin variations in the longitudinal direction of the polyester multifilament are small, resulting in a weaker fluffiness and a poorer natural feel when made into a woven or knitted fabric. On the other hand, if the fiber diameter ratio is greater than 2.4, the difference in the degree of orientation of the polyester resin between the thick and thin portions is large, resulting in a large difference in elongation between the thick and thin portions, which may cause problems with process stability, such as yarn breakage during spinning.

[0022] The polyester multifilament of the present invention preferably has a modulus of elasticity of 70% or more. The modulus of elasticity is preferably 73% or more, more preferably 74% or more. If the modulus of elasticity is 70% or more, a woven or knitted fabric obtained using the polyester multifilament will have high resilience and excellent kickback properties, and will have better shape stability. In the present invention, by using a polyester resin having the above composition and adopting the method for producing a polyester multifilament described below, the crystallinity of the polyester multifilament can be set within a specific range, and the modulus of elasticity can be adjusted to the above range.

[0023] The polyester multifilament of the present invention preferably has an elongation of 15 to 45%, more preferably 20 to 35%, and even more preferably 20 to 33%. If the elongation is less than 15%, the thick and thin spots formed in the longitudinal direction of the single filaments will be small, and the resulting woven or knitted fabric will have less volume and a less natural feel. On the other hand, if the elongation exceeds 45%, the elasticity of the polyester multifilament will not be fully expressed, and the resulting woven or knitted fabric will tend to have poor kickback properties and poor shape stability. As described above, the polyester multifilament of the present invention has a crystallinity within the specific range and high crimp performance, so that the thick and thin spots are fully expressed without increasing the elongation of the polyester multifilament, and the resulting woven or knitted fabric will have a sufficient volume and excellent stretchability.

[0024] The polyester multifilament fiber of the present invention preferably has a tenacity of 1.5 cN / dtex or more, more preferably 2.0 cN / dtex or more. The upper limit of the tenacity is not particularly limited, but is about 5.0 cN / dtex. If the tenacity is less than 1.5 cN / dtex, clothing made using the polyester multifilament is prone to yarn breakage during repeated use or washing, and problems such as yarn breakage occur during weaving and knitting, resulting in poor processability.

[0025] The single fiber fineness constituting the polyester multifilament of the present invention is not particularly limited, but is preferably 0.5 to 7 dtex, and more preferably 0.8 to 6 dtex. When the single fiber fineness is 0.5 dtex or more, the expression of crimp performance is improved and spinning stability is further improved. On the other hand, when the single fiber fineness is 7 dtex or less, the thick-thin unevenness is improved and the dyeing quality is further improved. In addition, the total fineness of the polyester multifilament is not particularly limited, but is preferably 10 to 200 dtex, more preferably 25 to 180 dtex, and even more preferably 40 to 150 dtex.

[0026] Next, a method for producing the polyester multifilament of the present invention will be described.

[0027] The method for producing the polyester multifilament of the present invention can be carried out using a conventional spinning machine and includes the following steps (a) to (d) in this order. (a) A step of melt-conjugating polyester resin A and polyester resin B that satisfy the following condition (i) to obtain a spun yarn. (i) 0.18≦[η]A−[η]B≦0.30 (b) A step of taking up the spun yarn with a roller at a speed of 2800 to 5000 m / min to obtain an undrawn yarn. (c) A step of aging the undrawn yarn under conditions of 23°C to 50°C for 30 hours or more. (iv) A step of drawing the aged undrawn yarn between the first roller and the second roller and between the second roller and the third roller so that the draw ratios DR1 and DR2 satisfy the following formula (ii), and the draw temperature is 90 to 130°C, the heat setting temperature is 130 to 170°C, and the total draw ratio is 1.1 to 2.5 times: (ii) DR1>DR2 Here, DR1 is the draw ratio between the first roller and the second roller, and DR2 is the draw ratio between the second roller and the third roller.

[0028] In step (a), two types of polyester resins A and B with different intrinsic viscosities are melt-spun into conjugate fibers so that they are bonded together. The difference ([η]A-[η]B) between the intrinsic viscosity [η]A of the high-viscosity polyester resin A and the intrinsic viscosity [η]B of the low-viscosity polyester resin B is 0.18 to 0.30. It is preferably 0.20 to 0.28, and more preferably 0.21 to 0.28. If the difference in intrinsic viscosity is 0.18 or more, the polyester multifilament will have high crimping performance, and woven or knitted fabrics obtained using the polyester multifilament will have excellent stretchability. On the other hand, if the difference is 0.30 or less, the resin extruded from the nozzle during the spinning process will be less likely to bend, improving the operability of the spinning process. After spinning, the spun yarn can be obtained by cooling and solidifying the resin or adding an oil agent using a known method.

[0029] The intrinsic viscosity of the high-viscosity polyester resin A is preferably 0.50 to 0.80, more preferably 0.60 to 0.78, provided that it is higher than the intrinsic viscosity of the polyester resin B. On the other hand, the intrinsic viscosity of the low-viscosity polyester resin B is preferably 0.20 to 0.62, more preferably 0.30 to 0.60.

[0030] When joining in a side-by-side manner, the joining surfaces of the two types of polyester resins may be linear and joined in approximately equal portions, or the joining surfaces may be curved and joined.

[0031] In step (b), the resulting spun yarn is taken up with a roller to obtain an undrawn yarn. In the present invention, increasing the spinning speed (take-up speed) can increase the crystallinity of the fiber, resulting in a crystallinity of 20 to 40% for the resulting polyester multifilament. The spinning speed is preferably 2800 to 5000 m / min, more preferably 3000 to 4000 m / min, and even more preferably 3000 to 3500 m / min. If the spinning speed is less than 2800 m / min, the orientation of the polyester multifilament is insufficient, resulting in a low crystallinity, and the shape stability of the resulting woven or knitted fabric tends to decrease. On the other hand, if the spinning speed exceeds 5000 m / min, it becomes difficult to increase the draw ratio in subsequent steps, the thick and thin spots formed in the longitudinal direction of the single filaments become smaller, and the resulting woven or knitted fabric may have a reduced volume and a loss of natural feel. Furthermore, if the crystallinity of the polyester multifilament becomes too high, yarn breakage may occur easily when the polyester multifilament is subjected to a false twisting process or a weaving / knitting process, and processability may decrease.

[0032] In step (c), after the undrawn yarn is obtained, it is aged for 30 hours or more in an environment of 23 to 50°C. Aging is more preferably carried out under conditions of 23 to 40°C. Conditions below 23°C result in insufficient aging of the undrawn yarn, which reduces the size of the thick and thin spots formed in the longitudinal direction of the single fiber in the subsequent drawing step, resulting in reduced swelling and a loss of natural feel when the yarn is made into a woven or knitted fabric. On the other hand, temperatures above 50°C are undesirable because they cause denaturation of the spinning oil adhering to the surface of the undrawn yarn, which deteriorates the processability in subsequent steps. Furthermore, aging for less than 30 hours results in insufficient aging of the undrawn yarn, which reduces the size of the thick and thin spots, resulting in reduced swelling and a loss of natural feel when the yarn is made into a woven or knitted fabric. Aging is preferably carried out for 40 hours, and even more preferably for 40 to 50 hours. Aging may be carried out for a longer time, but this will have almost no effect on the final polyester multifilament and woven or knitted fabrics using the polyester multifilament. Note that aging can be carried out by leaving the wound undrawn yarn in a room or the like within the above temperature range for a predetermined time.

[0033] In the production method of the present invention, by aging the undrawn yarn, the residual strain in the undrawn yarn is alleviated, and the drawing points in the subsequent drawing step are delocalized, allowing for roughly uniform thick and thin patterns to be imparted to the single fiber in the longitudinal direction. If the aging is insufficient, the drawing points are localized, and thick and thin portions are localized by drawing, which can result in a slubby appearance when dyed, impairing the natural appearance.

[0034] In step (iv), the aged undrawn yarn is drawn to form thick and thin irregularities in the longitudinal direction of the single filaments. Drawing conditions require that DR1 > DR2, where DR1 is the draw ratio between the first roller and the second roller and DR2 is the draw ratio between the second roller and the third roller. Furthermore, drawing is performed at a drawing temperature of 90 to 130°C, a heat setting temperature of 130 to 170°C, and a total draw ratio of 1.1 to 2.5 to obtain the polyester multifilament of the present invention. If DR1 ≦ DR2, the thick and thin irregularities formed in the longitudinal direction of the single filaments become smaller, resulting in reduced fluffiness when made into a woven or knitted fabric, and a loss of natural feel.

[0035] DR1 is preferably 1.2 to 1.6, more preferably 1.2 to 1.5. DR2 is preferably 1.0 to 1.2, more preferably 1.0 to 1.1. By setting DR1 and DR2 within the above ranges and satisfying DR1>DR2, the undrawn yarn is pulled rapidly between the first roller and the second roller and partially elongated, thereby forming thick and thin spots in the longitudinal direction of the single fiber.

[0036] The stretching temperature is preferably 100 to 125° C., more preferably 110 to 125° C. If the stretching temperature is less than 90° C., the thick and thin spots become small, the volume of the woven or knitted fabric decreases, and the natural feel tends to be impaired.

[0037] The heat setting temperature is preferably 135 to 165°C, more preferably 140 to 160°C. If the heat setting temperature is less than 130°C, the crystallinity of the resulting polyester multifilament will be low, the elastic modulus will be reduced, and the shape stability of woven or knitted fabrics made from the polyester multifilament will be reduced. On the other hand, if the heat setting temperature exceeds 170°C, productivity problems such as single fiber breakage will be more likely to occur, resulting in a decrease in productivity.

[0038] The total draw ratio (=DR1×DR2) is preferably 1.2 to 2.0 times, more preferably 1.3 to 1.7 times. If the total draw ratio is less than 1.1 times, the resulting polyester multifilament will have poor crimping performance and may lose stretchability. On the other hand, if the total draw ratio exceeds 2.5 times, the thick and thin spots formed in the longitudinal direction of the single filaments will become smaller, reducing the fluffiness of the woven or knitted fabric and possibly impairing the natural feel.

[0039] By employing the manufacturing method of the present invention, the polyester multifilament of the present invention as described above can be obtained. The polyester multifilament of the present invention may be false-twisted or may be false-twisted and mixed, as long as the effects of the present invention are not impaired. Furthermore, real twist may be imparted or real twist and mixed, or these processes may be combined.

[0040] Furthermore, woven and knitted fabrics obtained using the polyester multifilament of the present invention have excellent stretchability and shape stability, and also have a fluffy feel and a natural texture. The woven and knitted fabric of the present invention contains the polyester multifilament of the present invention. The polyester multifilament may be used alone as a warp or weft to form a woven or knitted fabric, or may be mixed with other filaments. The blend ratio of the polyester multifilament in the woven and knitted fabric of the present invention is not particularly limited and can be selected appropriately depending on the application, desired physical properties, etc. Furthermore, the knitting density or weaving density, knitting structure or weaving structure, etc. are also not particularly limited and can be selected appropriately depending on the application, desired physical properties, etc. In addition, dyeing and post-processing can be performed by known methods.

[0041] The woven or knitted fabric of the present invention has high stretchability because it contains the polyester multifilament of the present invention, and also has excellent elastic modulus and kickback properties due to satisfying a specific range of crystallinity, and therefore has excellent shape stability, such as wrinkles being less likely to remain even after repeated washing when used in clothing, etc. Furthermore, the polyester multifilament of the present invention has both high crimp performance and moderately sized thick and thin spots, and therefore the woven or knitted fabric of the present invention has a fluffy feel, a natural texture, and a natural appearance. [Example]

[0042] The present invention will be described in more detail below with reference to examples, which were evaluated by the following methods.

[0043] <Intrinsic viscosity of polyester resin> Using the high-viscosity polyester resin A and the low-viscosity polyester resin B as samples, measurements were carried out using an Ubbelohde viscometer at 20°C using an equal mass mixture of phenol and tetrachloroethane as a solvent. <Single fiber diameter ratio (thick / thin ratio)> The cross section perpendicular to the longitudinal direction of the obtained polyester multifilament was observed with an optical microscope at any position, and the single fiber diameter was measured to determine the ratio of the single fiber diameter of the thickest single fiber to the single fiber diameter of the thinnest single fiber. The above measurement was performed on the cross section at any five positions, and the average value was used.

[0044] <Strength and elongation of polyester multifilament> The obtained polyester multifilament was used as a sample, and the strength and elongation were measured at the time of elongation break using a Tensilon RTC-1210 (manufactured by Orientec Co., Ltd.) in accordance with JIS-L-1013, under the conditions of a sample thread length of 50 cm and a pulling speed of 50 cm / min. <Crimp rate and elastic modulus of polyester multifilament> The obtained polyester multifilament was cut into five hanks using a measuring machine (frame circumference 1.125 m) and used as a sample. The sample was treated in boiling water for 30 minutes under a load of 1 / 6000 g / D. After treatment, the sample was drained with filter paper and air-dried for 30 minutes. After air-drying, the sample was measured for length a under a load of 1 / 500 g / D. The load was then changed to 1 / 20 g / D and the sample's length b was measured. After applying a load of 1 / 20 g / D for 2 minutes, the load was changed to 1 / 500 g / D and the sample's length c was measured. The crimp percentage and modulus of elasticity were calculated based on the values ​​a, b, and c obtained in this way using the following formula. Crimp rate (%)={(ba) / b}×100 Elastic modulus (%) = {(bc) / (ba)} × 100

[0045] <Polyester multifilament thickness variation: C%> The obtained polyester multifilament was used as a sample and measured using an EVENESS TESTER 80 (Type C) manufactured by Keisokuki Kogyo Co., Ltd. under the conditions of a yarn speed of 25 m / m, a twist rotation speed of 3000 rpm, and a measurement mode of half inert. <Crystallinity of Polyester Multifilament> The obtained polyester multifilament was used as a sample, and DSC was measured using a DSC7020 manufactured by Hitachi High-Tech Science Corporation while the temperature was raised from 25°C to 280°C at a heating rate of 20°C / min, and the crystallinity of the polyester multifilament was calculated based on the following formula. Crystallinity (%)=(ΔHm-ΔHc) / 140.2×100 Here, ΔHm is the heat of fusion (mJ / mg), and ΔHc is the heat associated with crystallization (mJ / mg). <Polyester multifilament composition> The obtained polyester multifilament was used as a sample and dissolved in a mixed solvent of deuterated hexafluoroisopropanol and deuterated chloroform in a volume ratio of 1 / 20. 1H-NMR was measured using a JEOL LA-400 NMR apparatus, and the type and content of copolymerized components were determined from the integrated intensity of the proton peaks of each component in the obtained chart.

[0046] <Spinning operability> Spinning was carried out using 16 spindles, and the number of times that the yarn broke per day was evaluated according to the following criteria. 〇: The number of thread breakages per day is less than 3 ×: The number of thread breakages per day is more than 3 <Stretching operability> Drawing was carried out using 144 spindles, and the number of times the yarn broke during drawing until the full winding was collected was used to evaluate the yarn quality according to the following criteria. 〇: The number of broken threads is 10 or less ×: The number of broken yarns is more than 10

[0047] <Texture and appearance of fabric> The texture and appearance of the resulting woven fabric were checked by touch and visual inspection and evaluated according to the following criteria. ○: It has a plump feel and a natural appearance with no dye streaks or uneven coloring. ×: Poor fullness or dye streaks or uneven coloring, not a natural appearance <Stretchability of fabric> The tensile elasticity of the resulting fabric was evaluated by a sensory test according to the following criteria. 〇: Good elongation and rebound resilience ×: Both elongation and resilience are insufficient <Fabric shape stability> A sensory evaluation was carried out according to JIS L1924:2017 8.2 a) Appearance smoothness of knitted or woven fabrics after washing using the following method: A 1m x 1m sample of the obtained woven fabric was washed 20 times according to the JIS-L1096-C4M method, and then tumble dried.The appearance of the sample was then sensory evaluated according to the following criteria. 〇: No wrinkles ×: Wrinkles were found

[0048] Example 1 The high-viscosity polyester resin A had an intrinsic viscosity of 0.695 and contained 0.3% by mass of titanium oxide, while the low-viscosity polyester resin B had an intrinsic viscosity of 0.480 and contained 0.3% by mass of titanium oxide. These resins were fed at equal volumes into a multi-component melt extruder. The spinning temperature was 285°C, and the two resins were joined at the back of a spinneret with 24 spinning holes. A multifilament consisting of side-by-side (S / S) monofilaments was spun. The spun yarn was cooled by airflow and passed through an oiling device (oil supplying device) to apply spinning oil. The yarn was taken up at a spinning speed of 3300 m / min, and an undrawn multifilament yarn was collected. The undrawn yarn was then left to age at 30°C for 48 hours. After aging, the yarn was stretched at a draw ratio of 1.417 between the first roller and the second roller, a draw ratio of 1.018 between the second roller and the third roller, a draw temperature of 121°C, and a heat setting temperature of 148°C to obtain a polyester multifilament of 120 dtex 24 fil.

[0049] The resulting polyester multifilament was then false-twisted at a twist coefficient of K = 100 (T = K × √D: T is the number of twists per meter, and D is the fineness of the polyester multifilament), and set for 40 minutes at a temperature of 70°C and a humidity of 90% RH to obtain a false-twisted yarn. Using the resulting polyester multifilament as the warp and weft, a plain weave gray fabric with a warp density of 125 threads / inch and a weft density of 117 threads / inch was woven.

[0050] The resulting grey fabric was then scoured with a nonionic surfactant (Nicca Chemical's "Sunmol FL" 2g / L) at 80°C for 20 minutes and relaxed at 100°C for 20 minutes. It was then dyed under the dyeing conditions below and finished at 170°C to obtain a plain weave fabric. (Dyeing conditions) Dye: Dianix Blue UN-SE (Dianix) (1% 0.mf) Auxiliary agent: Nikka Sunsalt SN-130 (manufactured by Nicca Chemical Co., Ltd.) (concentration 0.5 g / L), acetic acid 0.2 cc / L

[0051] Example 2 Using the same resin as in Example 1, a polyester multifilament of 56 dtex 24 fil was obtained in the same manner as in Example 1, except that the spinning speed was changed to 3000 m / min, the drawing temperature to 116°C, and the heat setting temperature to 157°C, as shown in Table 1. Next, false twist textured yarn was obtained using the obtained polyester multifilament in the same manner as in Example 1, and then woven and dyed to obtain a woven fabric.

[0052] Examples 3 and 4 A polyester multifilament of 56 dtex 24 fil was obtained in the same manner as in Example 1, except that the same resin as in Example 1 was used and the aging temperature was changed to satisfy the conditions shown in Table 1. Next, a false twist textured yarn was obtained using the obtained polyester multifilament in the same manner as in Example 1, and then the yarn was woven and dyed to obtain a woven fabric.

[0053] Examples 5 and 6 A polyester multifilament of 56 dtex 24 fil was obtained in the same manner as in Example 1, except that the polyester resin A on the high viscosity side and the polyester resin B on the low viscosity side were changed so that the intrinsic viscosity would be within the conditions shown in Table 1. Next, a false twist textured yarn was obtained using the obtained polyester multifilament in the same manner as in Example 1, and then the yarn was woven and dyed to obtain a woven fabric.

[0054] Comparative Example 1 A polyester multifilament of 56 dtex and 24 fil was obtained in the same manner as in Example 1, except that 8 mol % of isophthalic acid was copolymerized in each of the high-viscosity polyester resin A and the low-viscosity polyester resin B. Next, a false twist textured yarn was obtained using the obtained polyester multifilament in the same manner as in Example 1, and then the yarn was woven and dyed to obtain a woven fabric.

[0055] Comparative Examples 2 to 4, Comparative Examples 6 to 14 A polyester multifilament was obtained in the same manner as in Example 1, except that the conditions were changed as shown in Table 1. Next, a false twist textured yarn was obtained using the obtained polyester multifilament in the same manner as in Example 1, and then the yarn was woven and dyed to obtain a woven fabric.

[0056] Comparative Example 5 An undrawn yarn was obtained in the same manner as in Example 1, except that the same resin as in Example 1 was used and the spinning speed was changed to 6000 m / min. The undrawn yarn obtained had no residual elongation, and could not be drawn in a subsequent step. The obtained polyester multifilament was used to obtain a false twist textured yarn, which was then woven and dyed to obtain a woven fabric.

[0057] [Table 1]

[0058] As is clear from the results in Table 1, the polyester multifilaments obtained in Examples 1 to 6 had specific resin compositions, and the crystallinity, crimp rate, and single fiber diameter ratio of the filaments satisfied specific ranges, and were filaments with both high crimp performance and thick-thin variations. Furthermore, because the crystallinity of the polyester multifilaments was within the specific range, it was possible to obtain woven fabrics that were excellent in elasticity, shape stability, and a fluffy texture, even though they had a high crimp rate.

[0059] In Comparative Example 1, the amount of copolymerization component was too large, so the crystallinity and modulus of the polyester multifilament were reduced, and the dimensional stability of the woven fabric was reduced. In Comparative Example 2, the difference in intrinsic viscosity between the high-viscosity polyester resin A and the low-viscosity polyester resin B was too large, resulting in frequent yarn breakage due to yarn bending directly below the nozzle, and making it impossible to stably obtain polyester multifilaments. In Comparative Example 3, the difference in intrinsic viscosity between the high-viscosity polyester resin A and the low-viscosity polyester resin B was too small, resulting in a low crimp rate for the polyester multifilament and poor stretchability for the woven fabric.

[0060] In Comparative Example 4, since the spinning speed was too slow, the crystallinity and elastic modulus of the polyester multifilament became low, and the morphological stability of the fabric decreased. In Comparative Example 5, since the spinning speed was too fast, the residual elongation of the undrawn yarn became low, and subsequent drawing could not be performed. Therefore, the formed thickness irregularities were small, the ratio of the fiber diameters of the single fibers became small, and the texture of the fabric deteriorated. Further, since the crystallinity was too high, yarn breakage occurred when obtaining the false-twisted yarn, and it was inferior in processability.

[0061] In Comparative Example 6, since the aging temperature was too low, the drawing point was localized in the drawing process, the formed thickness irregularities were small, and the ratio of the fiber diameters of the single fibers became small. Therefore, the texture of the obtained fabric deteriorated. In Comparative Example 7, since the aging temperature was too high, the spinning oil agent was thermally deteriorated, the operability in the drawing process deteriorated, and a polyester multifilament could not be stably obtained. In Comparative Example 8, since the aging time was too short, the drawing point was localized in the drawing process, the formed thickness irregularities were small, and the ratio of the fiber diameters of the single fibers became small. Therefore, the texture of the obtained fabric deteriorated.

[0062] In Comparative Example 9, since DR1 < DR2, thickness irregularities were not formed and a fabric with a natural appearance could not be obtained. In Comparative Example 10, since the total draw ratio was too high, thickness irregularities were not formed and a fabric with a natural appearance could not be obtained.

[0063] In Comparative Example 11, since the drawing temperature was too low, the crystallinity and elastic modulus of the polyester multifilament became low, and the morphological stability of the obtained fabric decreased. In Comparative Example 12, since the drawing temperature was too high, single fiber breakage frequently occurred in the drawing process, and a polyester multifilament could not be stably obtained.

[0064] In Comparative Example 13, the heat setting temperature was too low, resulting in a low crystallinity and modulus of the polyester multifilament, and the shape stability of the resulting woven fabric was reduced. In Comparative Example 14, the heat setting temperature was too high, so that many single fiber breaks occurred in the drawing step, and polyester multifilaments could not be stably obtained.

Claims

1. A multifilament made of single fibers, each of which exhibits a cross-sectional shape in which two types of polyester resins having different intrinsic viscosities are bonded together, wherein both of the two types of polyester resins constituting the single fibers are polyester resins containing polyethylene terephthalate as a main component and having a copolymerization amount of components other than terephthalic acid and ethylene glycol of 7 mol % or less, and wherein the multifilament simultaneously satisfies the following characteristic values ​​(1) to (3): (1) Crystallinity of 20 to 40% (2) Crimp rate after boiling water treatment: 35-60% (3) The ratio of the fiber diameter of the thickest single fiber to the thinnest single fiber in a cross section perpendicular to the longitudinal direction at any position of the multifilament is 1.6 to 2.4

2. The polyester multifilament according to claim 1, having an elastic modulus of 70% or more.

3. A woven or knitted fabric comprising the polyester multifilament according to claim 1 or 2.

4. The method for producing a polyester multifilament according to claim 1, comprising the following steps (a) to (c) in this order: (a) A step of melt-conjugating polyester resin A and polyester resin B that satisfy the following condition (i) to obtain a spun yarn. (i) 0.18≦[η]A-[η]B≦0.30 (b) A step of taking up the spun yarn with a roller at a speed of 2800 to 5000 m / min to obtain an undrawn yarn. (c) Aging the undrawn yarn in an environment of 23 to 50°C for 30 hours or more. (d) A step of drawing the undrawn yarn after the aging between the first roller and the second roller and between the second roller and the third roller so that the draw ratios DR1 and DR2 satisfy the following formula (ii), and the draw temperature is 90 to 130°C, the heat setting temperature is 130 to 170°C, and the total draw ratio is 1.1 to 2.5 times: (ii) DR1>DR2 Here, DR1 is the draw ratio between the first roller and the second roller, and DR2 is the draw ratio between the second roller and the third roller.

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