Polyester multifilament and sea-island composite polyester fiber

Abstract

The present invention addresses the problem of providing a polyester multifilament and a sea-island composite polyester fiber from which a fabric having mild gloss, a voluminous look, and excellent soft and smooth texture can be obtained. The present invention pertains to a polyester multifilament containing two or more types of polyester fibers, in which the cross-sectional shape of the two or more types of polyester fibers has a multi-lobal shape with three or more protrusions, and the glossiness is 60-90.

Description

Polyester multifilament and sea-island composite polyester fiber

[0001] The present disclosure relates to polyester multifilaments and sea-island composite polyester fibers.

[0002] Fibers made from thermoplastic polymers such as polyester and polyamide have excellent mechanical properties and dimensional stability, and are therefore widely used not only in clothing but also in interiors, vehicle interiors, industrial applications, etc. As the applications of fibers become more diverse, the required properties also become more diverse, and technologies have been proposed to impart sensory effects such as texture and bulkiness by varying the cross-sectional morphology of the fiber. Among these, ultra-fine fiber production has a significant effect on the properties of the fiber itself and the properties of the fabric made from it, and is a mainstream technology in terms of controlling the cross-sectional morphology of the fiber.

[0003] When spinning a single polymer to produce ultrafine fibers, even if the spinning conditions are highly controlled, the diameter of the obtained fibers is limited to about several μm. Therefore, an islands-in-sea type conjugate spinning method is often used to obtain conjugate fibers using a conjugate spinneret.

[0004] In this conjugate spinning method, a plurality of island component polymers made of slightly soluble components are arranged in a sea component polymer made of a soluble component in a fiber cross section, and after forming a fiber or a textile product, the sea component polymer is removed to generate ultrafine fibers made of the island component polymers. This conjugate spinning method is widely adopted in the production of industrially produced ultrafine fibers because it can form a highly accurate yarn cross-sectional form uniformly and homogeneously in the running direction of the yarn.

[0005] Widely known methods for easily producing ultrafine fibers include using islands-in-sea type composite fibers, which contain sparingly soluble island regions in a sea region made of a soluble polymer, and split type composite fibers, in which sparingly soluble ultrafine fibers are separated by a soluble polymer. In these techniques, after being wound up as a composite fiber, the composite fiber or a fabric product is immersed in a solvent to remove the soluble polymer, thereby making it possible to obtain sparingly soluble ultrafine fibers.

[0006] Fibers with extremely fine fibers can exhibit a soft touch and fineness that cannot be achieved with ordinary fibers, and are therefore widely used in clothing as suede-like fabrics and in industrial materials as wiping cloths.

[0007] For example, Patent Document 1 proposes ultrafine fibers suitable for use as a suede-like material with excellent openability and bulkiness, in which island parts exhibit differential shrinkage, by fabricating a sea-island composite fiber composed of two or more polymers having island parts with differential shrinkage, and then dissolving and removing the sea part polymer. Patent Document 2 proposes ultrafine fibers suitable for use as a wiper cloth or a precision polishing cloth material for IT, in which a sea-island composite fiber having island parts with a modified cross section is fabricated into a fabric, and then dissolving and removing the sea part polymer.

[0008] International Publication No. 2022 / 107671 Japanese Patent Application Laid-Open No. 2012-127022

[0009] In clothing applications, ultra-fine fibers have become widespread in a wide range of applications, including formal wear, sports and casual wear, and innerwear, and further advancements are being sought. In particular, for women's clothing, such as blouses and skirts, which require aesthetic effects, there are strong demands for aesthetic qualities such as a glossy surface and a smooth drape when worn.

[0010] However, by converting the fibers into ultrafine fibers, the glossiness and supple drape are lost, and the texture of the fabric surface is also changed. The sea-island composite fiber described in Patent Document 1 exhibits a difference in yarn length after sea-removal, resulting in a fabric with excellent volume and a supple drape, but does not achieve a mild luster like silk or pearl luster, and lacks "glossiness." It also has a unique suede-like, slippery texture. The composite fiber described in Patent Document 2, on the other hand, becomes a nano-level ultrafine yarn after sea-removal, but is too soft and stiff, resulting in a fabric that does not achieve a supple drape and lacks volume. It also has a unique slippery texture. Furthermore, because the cross-sectional shape of the island portions is a polygon composed of straight lines, there is a glossiness, but the luster is sparkling and artificial, and lacks "glossiness."

[0011] The present disclosure has been made to solve the above problems, and an object of the present disclosure is to provide a polyester multifilament and a sea-island composite polyester fiber that can provide fabrics excellent in mild luster, fluffy feeling, and soft and smooth texture.

[0012] In order to solve the above problems, the present disclosure employs the following configurations. (1) A polyester multifilament comprising two or more types of polyester fibers, wherein the cross-sectional shape of the two or more types of polyester fibers is multilobal with three or more protrusions, and wherein the polyester multifilament has a gloss of 60 to 90. (2) The polyester multifilament according to (1) above, wherein the yarn length difference is 15 to 40%. (3) A multifilament comprising two or more types of polyester fibers having different shrinkage rates, wherein the cross-sectional shape of the two or more types of polyester fibers is multilobal with three or more protrusions, and wherein the polyester multifilament has a gloss of 60 to 90. (4) The polyester multifilament according to (2) or (3) above, wherein the average value of the circumscribed circle diameter R of the cross-section of the polyester fiber is 4.0 to 10.0 μm, and the average value of the non-circularity (d / L), which is the ratio of the height d of the irregular portions constituting the multilobal shape to the distance L between adjacent vertices of the polyester fiber in the cross-section, is 0.05 to 0.3. (5) The polyester multifilament according to (2) or (3), wherein the number of filaments of the two or more types of polyester fibers is 200 to 800. (6) The polyester multifilament according to (2) or (3), wherein the irregularity variation CV is 20% or more. (7) The polyester multifilament according to (2) or (3), wherein the content of inorganic fine particles is 0 to 0.1% by mass. (8) A sea-island composite polyester fiber comprising a sea portion and two or more types of island portions, wherein the cross-sectional shape of the two or more types of island portions is multilobal having three or more protrusions, the average irregularity (d / L) of the multilobal shape being the ratio of the height d of the irregular portions to the distance L between adjacent vertices is 0.05 to 0.3, and the mass proportion of the sea portion is 10 to 30% by mass.

[0013] The present disclosure relates to a polyester multifilament containing two or more types of polyester fibers, wherein the two or more types of polyester fibers have a multilobal cross-sectional shape with three or more protrusions, and wherein the polyester fibers derived from the island portions of the sea-island composite polyester fiber are multilobal cross-sectional shapes with three or more protrusions, and the polyester multifilament has a gloss of 60 to 90. This polyester multifilament is, for example, a polyester multifilament obtained by subjecting a sea component polymer of a sea-island composite polyester fiber to a dissolution removal treatment, and wherein the polyester fibers derived from the island portions of the sea-island composite polyester fiber have a multilobal cross-sectional shape with three or more protrusions. Therefore, fabrics obtained from the polyester multifilament and sea-island composite polyester fiber of the present disclosure are excellent in mild gloss, fluffy feel, and soft, smooth texture.

[0014] Fig. 1 is a schematic diagram showing an example of the cross-sectional shape of an island portion of a sea-island composite polyester fiber according to the present disclosure and an example of the cross-sectional shape of a polyester fiber of a polyester multifilament according to the present disclosure. Fig. 2 is a schematic diagram showing the cross-sectional shape of a sea-island composite polyester fiber according to the present disclosure.

[0015] The present disclosure will be described in further detail below. In this specification, numerical ranges expressed as "to" are used to mean that the numerical values ​​before and after the range are included as the lower and upper limits. In this specification, proportions (percentages, parts, etc.) based on weight are the same as proportions (percentages, parts, etc.) based on mass.

[0016] [1. Polyester multifilament] The polyester multifilament of the present disclosure includes two or more types of polyester fibers. Here, the different types of polyester fibers may have different shrinkage rates, or may differ in polyester fiber components, intrinsic viscosity, molecular weight, or content of additives such as fine particles. In this specification, polyester fibers that differ only in cross-sectional shape are considered to be the same type of polyester fiber.

[0017] The polyester multifilament of the present disclosure may be composed of two or more types of polyester fibers with different shrinkage rates. In this case, the difference in shrinkage results in a difference in yarn length, and the shrinkage of the entire fabric results in a fluffy feel. As a result, the stiffness reduced by the ultrafine fiberization is compensated for, resulting in a supple drape. The polyester referred to here is a polyester-based polymer such as polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polytrimethylene terephthalate (PTT), or polylactic acid (PLA).

[0018] The polyester multifilament of the present disclosure has a glossiness of 60 to 90 as measured with a variable-angle glossmeter. The glossiness referred to here can be measured in accordance with JIS Z8741 (1997). The glossiness measurement method used in this specification is as follows. First, a polyester multifilament is wound 5 to 10 times around an appropriate aluminum plate approximately 6 cm wide, i.e., the polyester multifilament is wound to a thickness such that the aluminum plate is not visible, to create a plate for glossiness measurement. Next, the glossiness is measured twice using a digital variable-angle glossmeter (Gloss Meter UGV-5DP, Suga Test Instruments Co., Ltd.) under conditions of a light receiving angle of 45° and an incident angle of 45°, and the average value is calculated and used as the glossiness. When the polyester multifilament is used in a fabric, the fabric is decomposed into threads before being used in the above measurement.

[0019] By setting the gloss level within this range, moderate diffuse reflection of incident light occurs, resulting in a fine, soft, and natural gloss (mild gloss). If the gloss level is less than 60, the incident light is diffused and the reflectance is low, resulting in no gloss being exhibited or a gloss that is differentiated from that of a typical round cross section being not obtained, and the glossiness is not perceived. If the gloss level exceeds 90, the reflectance of the incident light is high, resulting in a glossiness that is shiny, glittering, and artificial. A gloss level of 70 to 85 is preferable for exhibiting a mild gloss such as pearlescent gloss. Furthermore, a gloss level of 70 to 75 is preferable for exhibiting a mild gloss such as silk-like gloss.

[0020] As will be described later, a polyester multifilament having a gloss within the above range can be obtained by forming the polyester fiber into a multi-lobed cross section having three or more projections, or by using two or more types of polyester fiber.

[0021] The cross-sectional shape of the polyester fiber of the polyester multifilament of the present disclosure is a multi-lobal shape having three or more projections.

[0022] The protrusions referred to here refer to regions protruding from the inscribed circle in the cross section of the polyester fiber. The shape of the protrusions may be rounded, sharp, or a mixture of rounded and sharp.

[0023] In the multi-lobed shape referred to in the present disclosure, the sides of the multi-lobed shape are not limited to concave, convex, straight, etc., but at least one side is a concave or convex side. In a polygonal shape, i.e., a shape in which all sides are straight, the direction of light reflection is aligned, resulting in a strong bright line and a large, sparkling luster, which is different from the mild luster that is the objective of the present disclosure.

[0024] Furthermore, by making the cross-sectional shape of the polyester fiber multi-lobed, having three or more protrusions, gloss is developed due to diffused reflection of light. Furthermore, since the cross-sectional shape has no bending directionality, the fiber becomes firm and has a fluffy feel. Furthermore, the unevenness of the fabric surface provides a smooth texture. On the other hand, when the cross-sectional shape of the polyester fiber is a bi-lobed shape with two protrusions, such as a flat or bale-shaped cross-section, the directionality of light reflection tends to be uniform, resulting in a dazzling gloss with strong bright lines, which is different from the mild gloss desired by the present disclosure. Furthermore, the fiber tends to bend in the long axis direction in the cross-section, resulting in a fiber with no firmness and lacking a fluffy feel. Furthermore, since the unevenness of the fabric surface is less than when the cross-sectional shape of the polyester fiber is round, a slick texture is achieved.

[0025] Although it depends on the degree of adjustment of the gloss by a matting agent or the like, the number of protrusions that can express a fine, soft, and natural gloss, that is, a mild gloss, in the multi-lobed cross section of the polyester fiber is preferably 3 to 5. The number of protrusions that can express a mild gloss such as a silk-like gloss or a pearl gloss is preferably 3.

[0026] Furthermore, the cross-sectional shape of the polyester fiber of the polyester multifilament of the present disclosure may be a multilobal shape having three or more protrusions, but the homogeneity (identity) of the cross-sectional shape is not limited. In order to obtain a fine, soft, and natural luster (mild luster), the cross-sectional shape of the polyester fiber preferably has a mixture of similar cross-sectional shapes. The mixture of similar cross-sectional shapes means, for example, a trilobal shape, but also a mixture of Y-shaped, fan-shaped, and γ-shaped shapes, as shown in Figure 2.

[0027] FIG. 1 is a schematic diagram of an example of the cross-sectional shape of a polyester fiber of a polyester multifilament according to the present disclosure. The non-circularity and circumscribed circle diameter when the cross section of the fiber is trilobal will be specifically described with reference to FIG. 1 . (1) Determine the vertices C of the trilobal projections (points C1, C2, and C3). (2) Draw a circumscribed circle that passes through three of the vertices C of the projections, and define its diameter as the circumscribed circle diameter R. The circumscribed circle of a multilobal shape with four or more projections passes through at least three of the vertices C of the projections, and the vertices of the projections that are not passed through by the circumscribed circle are located inside the circumscribed circle. (3) Draw line segments CC connecting adjacent vertices C of the projections (line segments C1C2, C2C3, and C1C3). (4) Determine the convex or concave vertex T of each side that constitutes the trilobal shape (vertex T1, T2, and T3). In the case of a straight line, the midpoint T of the line segment is defined as T. (5) Determine the intersection X that perpendicularly intersects each line segment CC connecting the concave vertex T or convex vertex T to the adjacent protrusion vertices C (intersection X1, intersection X2, intersection X3). (6) Connect the concave vertex T or convex vertex T to the intersection X and measure the length of the line segment TX. (7) The longest length of the multiple line segments TX (e.g., line segment T3X3) is set as the uneven portion height d. (8) The length of the line segment CC (e.g., line segment C1C3) connecting the protrusion vertices C from which the uneven portion height d was derived is set as the distance L between adjacent vertices. The distance L between adjacent vertices can also be determined by the following procedure. Identify the intersection X, which is the endpoint of the line segment TX (e.g., line segment T3X3) whose length is set as the uneven portion height d. Identify the two protrusion vertices C, which are the endpoints on both sides of the line segment CC containing this intersection X. Identify the length L of the line segment CC (e.g., line segment C1C3) connecting these two protrusion vertices C. This is the distance between adjacent vertices L. (9) The ratio (d / L) of the height d of the uneven portion to the distance L between adjacent vertices is defined as the irregularity.

[0028] In the cross section of the polyester fiber of the polyester multifilament of the present disclosure, the average irregularity (d / L) is preferably 0.05 to 0.3. By making the average irregularity value 0.05 or more, gloss is easily developed. Furthermore, by making the surface of the fabric uneven, the slimy (sucking) texture (suede-like) (feeling like it clings to the hand) unique to ultrafine fibers is eliminated, resulting in a soft and smooth texture. By making the average irregularity value 0.3 or less, diffuse reflection of light is increased. This phenomenon, combined with the loss of gloss due to ultrafine fiber thickness and the increase in gloss due to differences in yarn length, makes it easy to develop a mild gloss.

[0029] In the cross section of the polyester fiber of the polyester multifilament of the present disclosure, the average value of the circumscribed circle diameter R is preferably 4.0 to 10.0 μm. When the average value of the circumscribed circle diameter R is 4.0 μm or more, the fiber specific surface area does not increase too much, the unevenness of the fabric surface is not noticeable, and diffuse reflection of light on the fabric surface is not promoted, so that a moderate gloss tends to be obtained. In addition, the fiber tends to be not too soft and tends to maintain a moderate stiffness, so that a fluffy feel tends to be obtained. In addition, the slippery texture characteristic of ultrafine fibers tends to be less likely to be obtained. Therefore, by setting the average value of the circumscribed circle diameter R within this range, a mild gloss, a fluffy feel, and a soft and smooth texture can be obtained in a balanced manner.

[0030] The average value of the irregularity (d / L) and the average value of the circumscribed circle diameter R can be calculated by the following procedure. First, the cross section of the polyester multifilament is embedded in epoxy resin and cut using a Reichert-Nissei Ultracut N (ultramicrotome) equipped with a diamond knife. Then, the cut surface is photographed using a microscope VHX-2000 manufactured by Keyence Corporation. From the photograph obtained, the irregularity (d / L) and the circumscribed circle diameter R are calculated for all single yarns. The average values ​​of the irregularity (d / L) and the circumscribed circle diameter R obtained for all the single yarns are calculated.

[0031] In the polyester multifilament of the present disclosure, the number of filaments of the two or more types of polyester fibers is preferably 200 to 800, more preferably 260 to 600. As the number of filaments increases, the fiber surface area increases, causing diffuse reflection of light on the fabric surface and making it difficult to obtain gloss. Although it depends on the average circumscribed circle diameter of the fiber, by setting the number of filaments to 200 to 800, a balanced mild gloss and a soft, smooth texture with a fluffy feel can be obtained.

[0032] In the multifilament of the present disclosure, the irregularity variation CV (%) of the cross section of the polyester fiber is preferably 20% or more. This range indicates that fibers with different multilobal shapes are mixed in the multifilament, and when made into a fabric, fine gaps are generated between the fibers, promoting a fluffy feel, and the directionality of light reflection on the fabric surface becomes random, thereby exhibiting a mild gloss suitable for the purpose of the present disclosure. On the other hand, in order to suppress diffuse reflection of light and not impair gloss, the upper limit of the irregularity variation in the present disclosure is preferably 50%. In this specification, the irregularity variation CV is a value calculated by the following formula (5) based on the irregularity (d / L) calculated by the above-mentioned method. Irregularity variation = (standard deviation of irregularity / average irregularity) × 100 ... (5)

[0033] In the polyester multifilament of the present disclosure, the yarn length difference is preferably 15 to 40%, more preferably 20 to 35%. By setting the yarn length difference to 15% or more, a fluffy feel can be obtained due to shrinkage of the entire fabric. By setting the yarn length difference to 40% or less, deterioration in texture (roughness) due to shrinkage of the entire fabric can be suppressed, resulting in a high-quality, soft fabric.

[0034] In this specification, the yarn length difference is a value calculated by the following formula (1) where L2 is the length of the longest filament and L1 is the length of the shortest filament among the polyester fibers (filaments) contained in the polyester multifilament. Note that when measuring the length of the filament, a load of 0.1 g / dtex is applied. Yarn length difference (%) = {(L2 - L1) / L1} × 100 (1) The yarn length difference is a value that varies depending on, for example, differences in the shrinkage rate of the polyester fibers.

[0035] When calculating the yarn length difference of polyester multifilaments contained in a fabric, the fabric is marked at a length of approximately 15 cm, and the filament sample is cut to obtain decomposed yarns, which are then further decomposed into individual filaments using tweezers, and the above measurement can be performed. As described below, when calculating the yarn length difference of polyester multifilaments obtained from sea-island composite polyester fiber, the yarn length difference can be calculated by the following procedures (a) to (c). (a) A single filament from a sea-island composite polyester fiber sample having a length of 15 to 20 cm is collected, knotted and marked at two locations approximately 5 cm apart, and both ends of the filament are tied and fixed to an appropriate metal frame approximately 10 cm long. (b) The metal frame prepared in (a) is immersed in an alkaline solution to remove the sea component. After the sea component removal process, the metal frame is removed, and the filament sample is washed with raw water. (c) After heat treatment in a dryer at 190°C for 1 minute and cooling, the filament sample is cut along the two knots, and the filament is disassembled into single islands using tweezers, and each island is measured. The length of the longest island is L2, and the length of the shortest island is L1, and the yarn length difference is calculated using the above formula (1). When measuring the yarn length, a load of 0.1 g / dtex is applied.

[0036] The polyester multifilament of the present disclosure may contain inorganic fine particles, such as titanium dioxide as a matting agent or silica fine particles as a lubricant, as needed. These inorganic fine particles are not only used to adjust the gloss of the fiber, but are also commonly used for the purposes of stable spinnability and high-order passability due to reduced friction. Therefore, they may be contained to an extent that does not impair the gloss that is the objective of the present disclosure. In the polyester multifilament of the present disclosure, the content of inorganic fine particles is preferably 0 to 0.1% by mass from the viewpoint of gloss development.

[0037] In order for the multifilament to exhibit a mild luster, the proportion of the number of the two or more types of polyester fibers having the above-mentioned multilobal cross section having three or more protrusions relative to the total number of fibers contained in the polyester multifilament of the present disclosure is preferably 80% or more, more preferably 90% or more, even more preferably 95% or more, and particularly preferably 100%. The polyester multifilament of the present disclosure may contain polyester fibers other than the above-mentioned polyester fibers having the multilobal cross section having three or more protrusions, fibers of components other than polyester, etc.

[0038] [2. Sea-island composite polyester fiber] The island components of the sea-island composite polyester fiber of the present disclosure are polyester-based polymers, such as polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polytrimethylene terephthalate (PTT), and polylactic acid (PLA).

[0039] These polyesters may contain copolymerizable components capable of forming other ester bonds in a proportion of 20 mol % or less, more preferably 10 mol % or less, of the diol component and the acid component, respectively. Examples of copolymerizable compounds include dicarboxylic acids such as isophthalic acid, succinic acid, cyclohexanedicarboxylic acid, adipic acid, dimer acid, sebacic acid, and 5-sodium sulfoisophthalic acid, and diols such as ethylene glycol, diethylene glycol, butanediol, neopentyl glycol, cyclohexanedimethanol, polyethylene glycol, and polypropylene glycol.

[0040] The sea-island composite polyester fiber of the present disclosure has a sea-island structure in which a sea portion and two or more different types of island portions are arranged in the same fiber cross section. Here, the different types of island portions may have different island portion components, may have different intrinsic viscosities or molecular weights, or may have different contents of additives such as fine particles. In this specification, polyester fibers that differ only in the cross-sectional shape of the island portions are considered to be the same type of island portions. In this specification, the component that constitutes the sea portion is also referred to as the sea component, and the component that constitutes the island portions is also referred to as the island component.

[0041] For example, in the sea-island composite polyester fiber of the present disclosure, the sea component is removed by alkali treatment or the like (hereinafter referred to as sea-removal), and in some cases, a difference in yarn length is caused by heat treatment, thereby obtaining the polyester multifilament of the present disclosure.

[0042] One of the island components is preferably a homopolyester polymer, and the other is preferably a copolymer polyester such as isophthalic acid. Furthermore, using a plant-derived biopolymer or a recycled polymer as the island component is also preferable from the viewpoint of reducing environmental impact, and the polyester used in the present disclosure can be a recycled polymer recycled by any of chemical recycling, material recycling, and thermal recycling.

[0043] The sea component constituting the sea-island composite polyester fiber of the present disclosure is preferably composed mainly of polyester, since alkaline dissolution using caustic soda as a dissolving agent is widely used industrially. More preferably, a copolymer polyester is used in combination with isophthalic acid or a derivative thereof having a metal sulfonate group and polyalkylene glycol, and a combination of 5-sodium sulfoisophthalic acid and polyethylene glycol is particularly preferred.

[0044] In the sea component, the content of isophthalic acid having a metal sulfonate group (SI component) is preferably 5.0 to 15.0 mol %. When the content of the SI component is 5.0 mol % or more, the elution of the sea part during sea-removal treatment is improved, and fusion between single yarns due to uneluted sea component is suppressed. Furthermore, when the content of the SI component is 15 mol % or less, softening of the polymer is suppressed, and process passability during weaving and knitting is improved.

[0045] The number-average molecular weight of the polyalkylene glycol is preferably 500 to 2000. A number-average molecular weight of 500 or more improves the elution of the sea part during sea-removal treatment, and suppresses fusion between single yarns due to uneluted sea component. Furthermore, this is preferable because it increases the molecular mobility of the sea part during melt spinning, making it easier to orient the island parts, resulting in the development of a difference in yarn length and excellent openability and bulkiness. A number-average molecular weight of the polyalkylene glycol of 2000 or less improves compatibility with polyester, resulting in excellent spinnability.

[0046] The content of polyalkylene glycol in the sea component polyester polymer is preferably 5.0 to 15.0% by mass. When the content of polyalkylene glycol is 5.0% by mass or more, the elution property of the sea part during sea removal is improved, and fusion between single yarns due to uneluted sea component is suppressed. Furthermore, since the molecular mobility of the sea component is increased during melt spinning, the orientation of the island parts is facilitated, and a difference in yarn length is generated, resulting in excellent openability and bulkiness, which is preferable. Even if the content of polyalkylene glycol is greater than 15.0% by mass, the effect of improving the elution property of the sea part reaches a plateau.

[0047] Within the scope of the present disclosure, copolymerization components other than those mentioned above may be copolymerized in an amount of 10 mol % or less with each of the sea component polymer and the island component polymer. If necessary, a matting agent such as titanium dioxide and inorganic fine particles such as silica fine particles as a lubricant may be added to the island component polymers.

[0048] Inorganic fine particles, such as titanium dioxide as a matting agent and silica fine particles as a lubricant, are generally used not only to adjust the gloss of fibers but also to stabilize spinnability and achieve high-order passability by reducing friction. Therefore, inorganic fine particles may be contained to an extent that does not impair the gloss that is the objective of the present disclosure. The polyester multifilament of the present disclosure may exhibit differences in yarn length due to differences in shrinkage. In this case, many filaments consisting of low-shrinkage island component fibers are present on the fabric surface, and the content of the fine particles affects the gloss of the fabric. Therefore, the content of the fine particles in the low-shrinkage island component fibers is preferably 0 to 0.15%, and more preferably 0% (none).

[0049] In the sea-island composite polyester fiber of the present disclosure, the mass proportion of the sea parts is preferably 10 to 30 mass%. By containing 10 mass% or more of the sea parts, fusion between the island parts can be prevented, the efficiency of the sea-part removal process is excellent, and a high-strength, high-quality fabric can be obtained. Furthermore, if the sea part content is 30 mass% or less, the time required for dissolving and removing the sea parts can be shortened and the amount of polymer eluted is reduced, thereby increasing the productivity of the polyester multifilament. The mass proportion of the sea parts in the sea-island composite polyester fiber is more preferably in the range of 15 to 25 mass%.

[0050] In the sea-island composite polyester fiber of the present disclosure, the cross-sectional shape of the island portions is preferably multilobal having three or more protrusions, and the average irregularity (d / L), which is the ratio of the height d of the irregular portions to the distance L between adjacent vertices constituting the multilobal shape, is preferably 0.05 to 0.3. Furthermore, in the cross-sectional shape of the island portions, the average circumscribed circle diameter R is preferably 4.0 to 10.0 μm. By adopting such a cross-sectional shape, the cross-sectional shape of the polyester fiber in the polyester multifilament of the present disclosure described above can be obtained.

[0051] Fig. 1 also shows an example of the cross-sectional shape of the island portions of the sea-island composite polyester fiber of the present disclosure. Therefore, as a method for calculating the irregularity (d / L) and circumscribed circle diameter R of the cross-sectional shape of the polyester fiber of the polyester multifilament, the irregularity (d / L) and circumscribed circle diameter R of the island portions of the sea-island composite polyester fiber can be calculated using the same procedure as described above with reference to Fig. 1.

[0052] The average irregularity (d / L) and the average circumscribed circle diameter R of the island portions of the sea-island composite polyester fiber of the present disclosure can be calculated by the following procedure. First, the cross section of the sea-island composite polyester fiber is embedded in epoxy resin and cut with a Reichert-Nissei Ultracut N (ultramicrotome) equipped with a diamond knife. Then, the cut surface is photographed with a microscope VHX-2000 manufactured by Keyence Corporation. From the obtained photograph, five single yarns are randomly selected, and the irregularity (d / L) and circumscribed circle diameter R of the island portions are measured for half the number of island portions per single yarn. If the measured number is not an integer, the number is rounded up to the nearest integer. The average irregularity (d / L) and circumscribed circle diameter R measured in this way are calculated.

[0053] In the sea-island composite polyester fiber of the present disclosure, the irregularity coefficient of variation CV (%) of the island portions is preferably 20% or more. Within this range, a polyester multifilament can be obtained in which fibers with different multilobal morphologies are mixed in the multifilament. Note that, as a range that satisfies the cross-sectional shape of the polyester fiber in the polyester multifilament of the present disclosure, the upper limit of the irregularity coefficient of variation of the island portions in the sea-island composite polyester fiber of the present disclosure is preferably 50%.

[0054] From the viewpoint of uniform spreadability and bulkiness, it is preferable that the island parts of the sea-island composite polyester fiber of the present disclosure be arranged scattered throughout the sea part as shown in Fig. 2. Fig. 2 shows an example in which two types of island parts (first island parts A and second island parts B) are arranged.

[0055] In the sea-island composite polyester fiber of the present disclosure, the number of island portions per single yarn is preferably 12 to 432, and more preferably 24 to 144. Increasing the number of island portions per single yarn to 12 or more allows the island portions to be arranged in the sea portion without any gaps, which is preferable because it improves the dimensional stability of the composite fiber. Furthermore, setting the number of island portions per single yarn to 432 or less makes it possible to avoid fusion defects in the island portions. Furthermore, by reducing the difference in contact time between the island portions in the surface layer and the inner layer of the composite fiber with the dissolving agent during dissolution and removal of the sea portion, it becomes possible to reduce the fiber diameter variation of the fibers obtained from the island portions, and to obtain a high-strength polyester multifilament.

[0056] In order for the multifilament obtained from the sea-island composite polyester fiber of the present disclosure to exhibit a mild luster, the ratio of the number of two or more types of island parts whose cross section is multilobal having three or more protrusions to the total number of island parts in the sea-island composite polyester fiber of the present disclosure is preferably 80% or more, more preferably 90% or more, even more preferably 95% or more, and particularly preferably 100%. The island parts contained in the sea-island composite polyester fiber of the present disclosure may include island parts other than the above-mentioned island parts whose cross section is multilobal having three or more protrusions, such as island parts made of a polyester-based polymer and having a different cross section, or island parts made of a component other than a polyester-based polymer.

[0057] [3. Method for Producing Sea-Island Composite Polyester Fiber] Next, an example of a method for producing the sea-island composite polyester fiber of the present disclosure will be specifically described.

[0058] In the two or more different island components, the polyester polymer of the island portion preferably has a different intrinsic viscosity (hereinafter also referred to as IV) for each of the various island components, and the value obtained by dividing the highest IV by the lowest IV (hereinafter also referred to as intrinsic viscosity ratio or IV ratio) is preferably 1.6 or less. When the IV ratio is 1.6 or less, stress concentration on the high viscosity component during spinning is suppressed, and the increase in yarn shrinkage is suppressed, resulting in a fabric of high quality.

[0059] Furthermore, when polyester is used as the sea portion, the IV of the sea component polymer is preferably 0.50 to 0.75. If the IV of the sea component polymer is 0.50 or more, stress to the sea portion increases during spinning, and stress concentration to the island portions is suppressed, thereby suppressing an increase in yarn shrinkage and making it possible to obtain a fabric of good quality. On the other hand, if the IV of the sea component polymer is 0.75 or less, stress concentration to the sea portion during spinning is suppressed, and stress to the island portions is increased, thereby causing a yarn length difference to appear and resulting in a raw yarn excellent in openability and bulkiness, which is preferable. The IV of the sea component polymer is more preferably 0.55 to 0.70.

[0060] The IV of these polymers can be adjusted to a desired value by adjusting the polymerization conditions, i.e., polymerization time and polymerization temperature. The IV of the polymer can also be adjusted by the amount of catalyst added, the addition ratio, the order of addition, the addition interval, etc. It is preferable to set conditions according to the polymer production method and produce a polymer with a desired IV.

[0061] The sea-island composite polyester fiber of the present disclosure can be produced by either a two-step method in which the extruded polymer is once wound as an undrawn yarn and then drawn to a predetermined breaking elongation in a conventional drawing machine, or a one-step method in which the extruded polymer is once drawn without winding. However, in consideration of the quality stability in the fiber longitudinal direction and production stability, the direct spinning and drawing method is the most suitable.

[0062] The spinneret used to produce the fiber can be an existing conjugate spinning spinneret, but it is preferable to use the composite spinneret described in JP 2011-174215 A, which is composed of three major types of laminated members, namely, a metering plate, a distributor plate, and a discharge plate, because it enables the stable production of sea-island composite fibers.

[0063] From the viewpoint of precisely controlling the island component shapes of the sea-island composite polyester fiber of the present disclosure, it is preferable to produce the sea-island composite polyester fiber using a spinneret in which polymer discharge holes are arranged in consideration of the IV ratios of all the island component and sea component polymers. This is because, when the island component and sea component polymers join to form a composite polymer stream, unevenness in the polymer interface is formed due to the IV ratio and the distance between the discharge holes, and is advantageous in that it is possible to obtain a polyester multifilament having a mixture of Y-shaped, fan-shaped, and γ-shaped polymers. From this viewpoint, the IV ratios of all the island component polymers to the sea component polymer are preferably within the range of 0.8 to 1.3, which is preferable in terms of controlling the unevenness in the polymer interface. Here, the IV ratios of all the island component polymers to the sea component polymer being within the range of 0.8 to 1.3 means that when there are multiple types of island component polymers, the IV ratios of the island component polymers to the sea component polymer are within the above range for all the types of island component polymers.

[0064] [4. Manufacturing method of polyester multifilament] The polyester multifilament of the present disclosure can be obtained, for example, by forming the sea-island composite polyester fiber of the present disclosure into a woven or knitted fabric, removing the sea component (sea-removal) by alkali treatment, and, in some cases, by heat treatment to develop a yarn length difference.

[0065] There are no particular limitations on the weave or material blend ratio of woven or knitted fabrics. For example, in the case of woven fabrics, there are several weaves, such as plain weave, twill weave, and satin weave, depending on the weft weft placement method, and any of these can be selected depending on the purpose. A weave in which the sea-island composite polyester fiber of the present disclosure is distributed in large amounts on the surface of the fabric is preferred, as it is likely to exhibit the characteristics of a mild luster and a smooth texture. Furthermore, it is sufficient that at least a portion of the warp and weft yarns are made of the sea-island composite polyester fiber of the present disclosure, and the other fibers may be natural fibers, chemical fibers, or the like, and are not particularly limited. The same applies to knitted fabrics.

[0066] The sea component removal treatment is carried out using a batch-type treatment tank, which is a common dyeing machine (such as a winch dyeing machine, jigger dyeing machine, beam dyeing machine, or jet dyeing machine). Jet dyeing machines are preferred, as they are expected to produce a "crump" effect by stirring and flowing the fabric. Examples of the alkali include strong alkalis such as sodium hydroxide, potassium hydroxide, and lithium hydroxide, but sodium hydroxide is preferred. The alkali concentration and temperature can be set as desired so that 95% or more of the sea component is eluted. Since heat can cause differences in yarn length, the temperature is preferably 85°C or higher, and more preferably 90°C or higher.

[0067] As described above, the present specification discloses the following. <1> A polyester multifilament comprising two or more types of polyester fibers, wherein the cross-sectional shape of the two or more types of polyester fibers is multilobal having three or more protrusions, and wherein the glossiness is 60 to 90. <2> The polyester multifilament according to the above <1>, wherein the yarn length difference is 15 to 40%. <3> A multifilament comprising two or more types of polyester fibers having different shrinkage rates, wherein the cross-sectional shape of the two or more types of polyester fibers is multilobal having three or more protrusions, and wherein the glossiness is 60 to 90. <4> The polyester multifilament according to any one of the above <1> to <3>, wherein the average value of the circumscribed circle diameter R of the cross-section of the polyester fiber is 4.0 to 10.0 μm, and the average value of the irregularity (d / L), which is the ratio of the height d of the irregular portions to the distance L between adjacent vertices constituting the multilobal shape in the cross-section of the polyester fiber, is 0.05 to 0.3. <5> The polyester multifilament according to any one of <1> to <4> above, wherein the number of filaments of the two or more types of polyester fibers is 200 to 800. <6> The polyester multifilament according to any one of <1> to <5> above, wherein the irregularity variation CV is 20% or more. <7> The polyester multifilament according to any one of <1> to <6> above, wherein the content of inorganic fine particles is 0 to 0.1% by mass. <8> A sea-island composite polyester fiber comprising a sea portion and two or more types of island portions, wherein the cross-sectional shape of the two or more types of island portions is multilobal having three or more protrusions, the average irregularity (d / L) of the multilobal shape, which is the ratio of the height d of the irregular portions to the distance L between adjacent vertices, is 0.05 to 0.3, and the mass proportion of the sea portion is 10 to 30%.

[0068] The present disclosure will now be described in further detail with reference to examples.

[0069] <A. Intrinsic Viscosity IV> The intrinsic viscosity IV of a polymer was calculated from the following formula (2). The relative viscosity ηr in formula (2) was determined by dissolving 0.8 g of a sample polymer in 10 mL of o-chlorophenol (OCP) with a purity of 98% or higher and using an Ostwald viscometer at a temperature of 25°C according to the following formula (3): Intrinsic viscosity IV = 0.0242ηr + 0.2634 ... (2) ηr = η / η0 = (t × d) / (t0 × d0) ... (3) [In formula (3), η is the viscosity of the polymer solution, η0 is the viscosity of OCP, t is the falling time of the polymer solution (seconds), and d is the density of the polymer solution (g / cm ３ ), t0 is the falling time of the OCP (seconds), d0 is the density of the OCP (g / cm ３ )

[0070] <B. Photographing Fiber Cross Sections and Shape Measurement> The cross section of a fiber sample was embedded in epoxy resin and cut using a Reichert-Nissei Ultracut N (ultramicrotome) equipped with a diamond knife. Thereafter, the cut surface was photographed using a microscope VHX-2000 manufactured by Keyence Corporation.

[0071] When the fiber sample was a sea-island composite polyester fiber, five single yarns were randomly extracted from the obtained photograph, and the number of islands was measured, which was half of the total number of islands per single yarn. If the measured number was not an integer, it was rounded up to the nearest whole number. In the case of Example 1, 5 yarns x 24 islands / 2 = 60 islands were measured. When the fiber sample was a polyester multifilament, all single yarns were measured from the obtained photograph. The average values ​​of the measured values ​​were calculated for both the case where the fiber sample was a sea-island composite polyester fiber and the case where the fiber sample was a polyester multifilament.

[0072] <(a) Circumscribed Circle Diameter R> The vertex C of the protrusion was determined, and a circumscribed circle was drawn that passed through the vertex C of the protrusion at least three times, and the diameter of the circumscribed circle was defined as the circumscribed circle diameter R. If there was a protrusion vertex that the circumscribed circle did not pass through, the protrusion vertex was positioned inside the circumscribed circle.

[0073] <(b) Height d of uneven portion> A line segment CC was drawn connecting adjacent protrusion vertices C. The concave vertex T or convex vertex T of each side constituting the multi-lobed shape was determined. In the case of a straight line, the midpoint T of the line segment was taken as the line segment. An intersection point X perpendicular to each line segment was determined from the concave vertex T or convex vertex T. The concave vertex T or convex vertex T was connected to the intersection point X, and the length of the line segment TX was measured. The longest length of each line segment TX was taken as the height d of the uneven portion.

[0074] (c) Distance L Between Adjacent Vertices The length of the line segment CC connecting the vertices C of the protrusions from which the height d of the concave-convex portion was derived was taken as the distance L between the adjacent vertices.

[0075] <(d) Degree of irregularity (d / L)> The degree of irregularity (d / L) was calculated from the following formula (4): Degree of irregularity = height of irregularity portion d / distance between adjacent vertices L (4)

[0076] <(e) Irregularity Variation CV (%)> The irregularity variation was calculated using the following formula (5): Irregularity Variation = (Standard deviation of irregularity / Average irregularity) × 100 (5)

[0077] <C. Strength and Elongation> Using threads (fiber samples) disassembled from fabrics obtained by the procedure described below, the fiber samples were measured in accordance with JIS L1013-2010 tensile strength and elongation, and a tensile strength-elongation curve was plotted. The test conditions were a constant-speed extension type tester, a grip distance of 50 cm, and a pulling speed of 50 cm / min. When the tensile strength at break was smaller than the maximum strength, the maximum tensile strength and the elongation at that time were measured. The fineness was calculated by the method in item D below. The elongation and strength were calculated using the following formulas (6) and (7), respectively. Elongation = elongation at break (%) ... (6) Strength = tensile strength at break (cN) / fineness (dtex) ... (7)

[0078] <D. Fineness> When the fiber sample was a sea-island composite fiber, the weight of 100 m of the sea-island composite fiber was measured in an atmosphere at a temperature of 25°C and a humidity of 55% RH, and this value was multiplied by 100 to calculate the weight. This operation was repeated 10 times, and the simple average value was rounded off to the nearest whole number to obtain the fineness of the sea-island composite fiber. When the fiber sample was a yarn disassembled from a fabric obtained by the procedure described below, the weight per unit length of the fiber sample was measured in an atmosphere at a temperature of 25°C and a humidity of 55% RH, and the weight equivalent to 10,000 m was calculated from this value. This measurement was repeated 10 times, and the simple average value was rounded off to the nearest whole number to obtain the fineness.

[0079] <E. Glossiness> A polyester multifilament fiber sample was prepared as a thread disassembled from a fabric obtained by the procedure described below, and was measured by the following procedures (a) and (b). (a) A fiber sample was wrapped 5 to 10 times around an appropriate aluminum plate approximately 6 cm wide (thick enough to prevent the aluminum plate from showing through) to prepare a plate for measuring glossiness. (b) The glossiness of the sample prepared in (b) was measured twice using a digital variable-angle glossmeter (Glossmeter UGV-5DP, Suga Test Instruments Co., Ltd.) under conditions of a light receiving angle of 45° and an incident angle of 45°, and the average value was calculated and used as the glossiness.

[0080] <F. Yarn Length Difference> For polyester multifilament fiber samples, a mark was made on the fabric at a length of approximately 15 cm, and the filament sample was cut to obtain decomposed yarns. The filaments were further decomposed using tweezers, and each filament was measured. The length of the longest filament was designated L2, and the length of the shortest filament was designated L1, and the yarn length difference was calculated using the following formula (1): Yarn length difference (%) = {(L2 - L1) / L1} × 100 (1).

[0081] <G. Titanium Oxide Content> The titanium oxide content in the polyester multifilament was calculated by the following procedure. Five grams of the fiber sample was weighed using decomposed yarn (fiber sample) from a fabric obtained by the procedure described below, and the fiber sample was heated and incinerated in an electric furnace at 550°C for 90 minutes. The residue of the sample was then weighed, and the ash content calculated by the following formula (8) was taken as the titanium oxide content. Titanium oxide content = (mass of sample after heating and incineration / mass of sample before heating and incineration) × 100 (8)

[0082] <H. Fabric Evaluation> (a) Gloss The gloss of the satin fabric was visually evaluated by skilled inspectors (5 people) under fluorescent light according to the following criteria. The results were calculated by taking the average of the inspectors' evaluation scores and rounding off the decimal point, with an average of 3 points being ○, 2 points being △, and 1 point being ×. 3 points and 2 points were considered acceptable. ○ (3 points): A mild gloss similar to pearl gloss or silk gloss is perceived. △ (2 points): A fine, soft, and natural gloss (mild gloss) is perceived. × (1 point): There is a glossy feeling, but it is sparkling and glittering, and has an artificial appearance. × (1 point): No gloss is perceived.

[0083] (b) Texture The texture of the satin fabric was evaluated by five skilled technicians using the following criteria. The results were calculated by averaging the scores of each technician and rounding off the decimal point. A score of 3 was marked as O, a score of 2 as △, and a score of 1 as ×. A score of 3 or 2 was considered a pass.

[0084] (b-1) Smoothness The feel of the satin fabric surface when the hand is slid across it in the vertical and horizontal directions was evaluated according to the following criteria: ○: Smooth △: Smooth ×: Slimy (suede-like)

[0085] (b-2) Softness The feel of the satin fabric when held in the hand was evaluated according to the following criteria: ○: Very soft △: Somewhat soft ×: Not soft

[0086] (b-3) Fluffiness The feel of the satin fabric when gripped and lifted by hand was evaluated according to the following criteria: ○: Fluffy (firm and slightly bouncy) △: Slightly fluffy (firm) ×: No fluffy (no firmness)

[0087] (b-4) Overall Evaluation of Feeling The feeling was evaluated overall based on the following criteria: ○: All evaluations were 2 to 3 points, with a total score of 8 to 9 points. △: All evaluations were 2 to 3 points, with a total score of 6 to 7 points. ×: At least one evaluation item received a score of 1.

[0088] Example 1 (Production of sea-island composite polyester fiber) Copolymerized polyethylene terephthalate (PET1) having an IV of 0.67 and a titanium oxide content of 0.05% was prepared as the island component A polymer for forming island parts A. The copolymerized polyethylene terephthalate (PET1) was prepared by copolymerizing isophthalic acid and bisphenol A-ethylene oxide adduct in amounts of 7.1 mol % and 4.4 mol % relative to the total acid components, respectively. The copolymer had an IV of 0.67 and a titanium oxide content of 0.05%. The island component B polymer for forming island parts B was prepared as polyethylene terephthalate (PET2) having an IV of 0.65 and a titanium oxide content of 0%. The intrinsic viscosity ratio (IV ratio) of the copolymerized polyethylene terephthalate was adjusted to 1.03.

[0089] As a readily soluble sea component polymer, an alkali-soluble polyethylene terephthalate (easily soluble PET) having an IV of 0.69 was prepared, which was copolymerized with 8.0 mol % of 5-sodium sulfoisophthalic acid and 9.0 wt % of polyethylene glycol having a number average molecular weight of 1,000.

[0090] The island component A polymer, island component B polymer, and sea component polymer were melted in an extruder at 265°C, 280°C, and 280°C, respectively, and then metered with a pump to a spinning temperature of 275°C. The resulting mixture was then fed into a spinneret while maintaining the temperature. The weight ratio of island A, island B, and sea portion was 42 / 42 / 16, and the mixture was fed into a sea-island composite spinneret with 24 islands (12 islands A, 12 islands B), 12 filaments, and a trilobal cross-sectional shape of the islands, each with three protrusions and a mixture of Y-, sector, and γ-shapes, as shown in Figure 2. The individual polymers merged inside the spinneret, and the island component polymers (island component A polymer, island component B polymer) were encased in the sea component polymer, forming a composite morphology in which island A and island B were mutually arranged, and the resulting mixture was extruded from the spinneret. The yarn extruded from the spinneret was cooled and solidified by an air cooler with a cooling start distance of 330 mm, then an oil was applied, and the yarn was taken up at a speed of 1200 m / min with a roll heated to 90°C, drawn at a draw ratio of 3.3, heat set with a roll heated to 150°C, and then taken up with a winder at a speed of 3950 m / min to obtain a sea-island composite polyester fiber of 70 dtex-12 filaments. Here, the number of filaments in the sea-island composite polyester fiber refers to the number of filaments in the sea-island composite polyester fiber itself. The evaluation results of the obtained sea-island composite polyester fiber are shown in Table 1.

[0091] (Production of satin fabric) Next, the sea-island composite polyester fiber was twisted in the S direction at 800 T / m using a double twister twisting machine, and then steam twist-setting was performed at 75°C for 30 minutes, and the fabric was used for warping. Similarly, sea-island composite polyester fiber was used for the weft.

[0092] These warp and weft yarns were used to weave a five-ply satin weave on an air jet loom at a greige density (warp: 222 threads / 2.45 cm (inch), weft: 97 threads / 2.54 cm (inch)). The resulting woven fabric was then continuously scoured at 98°C, subjected to a liquid flow relaxation treatment at 130°C, and intermediate set at 180°C. The fabric was then immersed in an aqueous sodium hydroxide solution (1 g / L) at 92°C for 30 minutes to remove at least 95% of the sea portion weight. The resulting fabric was then finish-set at 160°C to obtain a satin fabric. This satin fabric is also referred to herein as "fabric." The resulting polyester multifilament had sufficient mechanical properties for clothing applications, with a strength of 4.1 cN / dtex and an elongation of 43%, and the resulting satin fabric had a mild luster similar to that of silk. The evaluation results are shown in Table 1. The number of filaments in the polyester fibers of the polyester multifilament was 288. In the examples of this specification, the number of filaments in the polyester fibers of the polyester multifilament is the product of the number of islands contained in the sea-island composite fiber and the number of filaments in the sea-island composite fiber (the number of filaments in the sea-island composite polyester fiber itself). The evaluation results of the obtained satin fabrics and the polyester multifilaments contained therein are shown in Table 1.

[0093] Example 2 A 70 dtex, 12 filament sea-island composite polyester fiber was obtained in the same manner as in Example 1, except that the spinneret was changed to one that formed a trilobal cross-sectional shape (not shown) with each side formed only with a convex portion, and a satin fabric was obtained. The obtained satin fabric had a mild luster similar to that of silk, but the fluffiness was slightly inferior to that of Example 1. The evaluation results are shown in Table 1.

[0094] Example 3 A 70 dtex, 12 filament sea-island composite polyester fiber was obtained in the same manner as in Example 1, and a satin fabric was obtained, except that the spinneret was changed to form a four-lobe cross-sectional shape (X-shaped, not shown) with each side formed only with recesses, and the number of islands was changed to 20 (island A = 10 islands, island B = 10 islands). The resulting satin fabric had a mild luster similar to pearl luster. The evaluation results are shown in Table 1.

[0095] Example 4 A 70 dtex, 12 filament sea-island composite polyester fiber was obtained, and a satin fabric was also obtained, in the same manner as in Example 1, except that the spinneret was changed to one that formed a five-lobe cross section of the island parts, each side of which was formed only with recesses (round star shape, not shown). The evaluation results are shown in Table 1.

[0096] Comparative Example 1 A 70 dtex, 12 filament sea-island composite polyester fiber was obtained in the same manner as in Example 1, except that the spinneret was changed to form a round cross section of the island portions, and a satin fabric was obtained. The resulting satin fabric had no sense of gloss. In addition, the fabric had a slimy texture specific to ultrafine fibers. The evaluation results are shown in Table 1.

[0097]

[0098] [Example 5] [Comparative Example 2] A 70 dtex sea-island composite polyester fiber was obtained and a satin fabric was produced in the same manner as in Example 1, except that the number of filaments in the sea-island composite polyester fiber was changed to 24 (Example 5) and 36 (Comparative Example 2), and other conditions were met as shown in Table 2. The evaluation results are shown in Table 2. The satin fabric obtained in Comparative Example 2 had a large number of filaments and an increased fiber surface area, which resulted in a decrease in glossiness due to the large diffusion of incident light, and no perceived glossiness.

[0099] [Example 6] [Comparative Example 3] A 70 dtex, 12 filament sea-island composite polyester fiber was obtained, and a satin fabric was also obtained, in the same manner as in Example 1, except that the number of islands in the sea-island composite polyester fiber was changed to 18 islands (island part A = 9 islands, island part B = 9 islands) (Example 6) or 12 islands (island part A = 6 islands, island part B = 6 islands) (Comparative Example 3), and other conditions were met as shown in Table 2. The evaluation results are shown in Table 2. The satin fabric obtained in Comparative Example 3 had a glossy feel, but a sparkling, artificial gloss, due to the reduced number of filaments and reduced fiber surface area, which increased the reflection of incident light.

[0100]

[0101] Examples 7 to 9 and Comparative Examples 4 and 5: A 70 dtex, 12-filament sea-island composite polyester fiber was obtained in the same manner as in Example 1, and a satin fabric was also obtained, except that the island component A polymer (PET3, PET4, PET5) for forming island portions A, the island component B polymer (PET6) for forming island portions B, and the weight composite ratios of island portions A, island portions B, and the sea portion were changed as shown in Table 3. The evaluation results are shown in Table 3. (PET3) In PET3, the island component A polymer for forming island portions A was polyethylene terephthalate with an IV of 0.65 containing 0.3% by mass of titanium oxide as inorganic particles. (PET4) In PET4, the island component A polymer for forming island portions A was polyethylene terephthalate with an IV of 0.76 containing 0.5% by mass of titanium oxide as inorganic particles. (PET5) PET5 was a polyethylene terephthalate having an IV of 0.72 containing 0.1% by mass of titanium oxide as inorganic particles as the island component A polymer for forming island portions A. (PET6) PET6 was a polyethylene terephthalate having an IV of 0.51 containing 0.4% by mass of titanium oxide as inorganic particles as the island component B polymer for forming island portions B.

[0102]

[0103] Examples 10 and 11 A 70 dtex, 12 filament sea-island composite polyester fiber and a satin fabric were obtained in the same manner as in Example 1, except that the shape of the sea-island composite spinneret holes was changed to form a trilobal cross-sectional shape in which the island portions had a mixed Y-shape, sector shape, and γ-shape as shown in Fig. 2, and the non-circularity was changed to 0.06 (Example 10) or 0.28 (Example 11). The evaluation results are shown in Table 4.

[0104]

[0105] Although the present invention has been described in detail and with reference to specific embodiments, it will be apparent to those skilled in the art that various changes and modifications can be made without departing from the spirit and scope of the present invention. This application is based on a Japanese patent application (Patent Application No. 2023-104072) filed on June 26, 2023, the contents of which are incorporated herein by reference.

[0106] C: Trilobal protrusion T: Concave or convex vertex of each side constituting the trilobal shape X: Intersection point perpendicular to the line segment connecting the concave or convex vertex to the adjacent protrusion vertex R: Diameter of circumscribed circle A: First island B: Second island U: Sea

Claims

1. A polyester multifilament comprising two or more types of polyester fibers, the cross-sectional shape of the two or more types of polyester fibers being a multi-lobed shape having three or more protrusions, and having a gloss of 60 to 90.

2. The polyester multifilament according to claim 1, wherein the yarn length difference is 15 to 40%.

3. A polyester multifilament comprising two or more types of polyester fibers having different shrinkage rates, the cross-sectional shape of the two or more types of polyester fibers being a multi-lobed shape having three or more protrusions, and having a gloss of 60 to 90.

4. The polyester multifilament according to claim 2 or 3, wherein the average value of the circumscribed circle diameter R of the cross section of the polyester fiber is 4.0 to 10.0 μm, and the average value of the irregularity (d / L) which is the ratio of the height d of the uneven portion to the distance L between adjacent vertices constituting the multi-lobed shape in the cross section of the polyester fiber is 0.05 to 0.

3.

5. The polyester multifilament according to claim 2 or 3, wherein the number of filaments of the two or more types of polyester fibers is 200 to 800.

6. The polyester multifilament according to claim 2 or 3, having a non-circularity variation (CV) of 20% or more.

7. The polyester multifilament according to claim 2 or 3, wherein the content of inorganic fine particles is 0 to 0.1 mass %.

8. A sea-island composite polyester fiber comprising a sea portion and two or more kinds of island portions, wherein the two or more kinds of island portions have a multi-lobal cross-sectional shape having three or more protrusions, the average irregularity (d / L) which is the ratio of the height d of the uneven portions to the distance L between adjacent vertices constituting the multi-lobal shape is 0.05 to 0.3, and the mass proportion of the sea portion is 10 to 30 mass%.

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