Multifilament

Abstract

This product provides a multifilament that exhibits fine crimping through a relaxing heat treatment, resulting in high bulkiness and a soft texture when used in fabrics or chenille yarns. [Solution] A multifilament having 5 to 20 crimps / cm in the longitudinal direction of the fiber with a radius of curvature of 0.15 to 1.00 mm after relaxation heat treatment, wherein the single fibers constituting the multifilament are hollow cross-section fibers satisfying the following A to D: A. One or more hollow sections B. Hollow ratio of 10 to 40% C. Outer periphery shape of the fiber cross-section has multiple protrusions D. Degree of irregularity of the fiber cross-section is 1.3 to 2.0

Description

[Technical Field]

[0001] This invention relates to a multifilament that can provide fabrics and chenille yarns that exhibit fine crimp when subjected to relaxation heat treatment, resulting in high bulkiness and a soft texture. [Background technology]

[0002] Synthetic fibers possess numerous excellent properties, including mechanical properties, and are widely used in various fields such as clothing, bedding, and industrial applications. In clothing applications, their durability and ease of handling make them suitable for sports and outdoor wear. In these applications, where the garments are worn for long periods in harsh environments, high-performance synthetic fibers that exhibit lightness and a soft texture when woven into fabric are attracting attention to minimize stress during wear.

[0003] Furthermore, due to the functionality and stable supply inherent in synthetic fibers, synthetic fiber padding is also used in various material forms such as felted cotton, granular cotton, and long-staple cotton. An example of long-staple cotton is chenille yarn, which is made by twisting a core thread and a binding thread together, and then cutting the floss between the core thread and the binding thread. Chenille yarn is a three-dimensional yarn in which the floss extends perpendicularly to the core thread, and is suitable for use as a substitute for wool yarn in bedding stuffing, sweaters, mops, etc. When making chenille yarn, a floss that is bulkier is required.

[0004] A common technique for achieving bulkiness is to impart crimp through false twisting. Furthermore, various methods for altering the fiber cross-section are being explored to obtain even greater bulkiness. Among these, hollow cross-section fibers can provide high bulkiness due to their hollow structure.

[0005] However, when hollow cross-section fibers are false-twisted, the compressive force applied during the false-twisting process causes the cross-sectional shape to deform significantly, crushing the hollow portion and resulting in a problem of impaired bulkiness (Patent Document 1).

[0006] To address this problem, Patent Document 2 proposes a fiber with an irregular cross-section, having at least one hollow portion in its cross-section and a plurality of protrusions that radiate from the outer periphery relative to the center point of the hollow portion. When melt spinning, if cooling air is blown perpendicularly to the yarn immediately after it is extruded from the die surface (hereinafter referred to as anisotropic cooling), the surface area increase effect of the protrusions and the heat insulation effect of the hollow portion can impart a difference in molecular orientation between the windward and leeward sides of the fiber cross-section (hereinafter referred to as cross-sectional anisotropy). By stretching and heat-treating the fiber having cross-sectional anisotropy, the fiber shrinks three-dimensionally due to the difference in molecular orientation, making it possible to obtain a hollow cross-section fiber with crimp. [Prior art documents] [Patent Documents]

[0007] [Patent Document 1] Japanese Patent Publication No. 2002-249936 [Patent Document 2] Japanese Patent Publication No. 2013-23794 [Overview of the Initiative] [Problems that the invention aims to solve]

[0008] However, as shown in Patent Document 2, the anisotropy of the cross-section due to anisotropic cooling during spinning is small, and the resulting crimp has a smaller amplitude and longer wavelength compared to typical false-twisted yarn, resulting in insufficient bulkiness. Furthermore, in the case of a multifilament composed of multiple single fibers, in all single fibers constituting the multifilament, the upwind side of the cooling air is highly oriented and the downwind side is less oriented. As a result, there is no difference in the crimp morphology between the single fibers, so the phase of crimp overlaps among the single fibers, resulting in a crimp that is not random like that of false-twisted yarn, and insufficient bulkiness is obtained.

[0009] Furthermore, in spinning using anisotropic cooling, the passage of cooling air between single fibers is poor, resulting in insufficient cooling of fibers farther from the outlet, causing unevenness in thickness along the fiber's longitudinal direction and leading to variations in cross-sectional shape. When these fibers are used in fabric, for example, as warp threads in woven fabrics, they can cause warp streaks. Also, the more single fibers that make up a multifilament, the worse the passage of cooling air becomes, making it easier for single fibers on the leeward side to be undercooked. In addition, with fibers that have a high degree of irregularity in cross-sectional shape or with a fine single fiber thickness, the time from extrusion from the die to solidification is short, so if the passage of cooling air is poor, insufficient cooling is likely, resulting in poor productivity with anisotropic cooling. Moreover, if the single fiber thickness is thick, the bending rigidity increases, resulting in a stiffer texture when used in fabric.

[0010] In view of the above circumstances, the object of the present invention is to provide a multifilament that can achieve a fabric or chenille yarn that exhibits excellent bulkiness and a soft texture. [Means for solving the problem]

[0011] The multifilament of the present invention has the following configuration in order to solve the above problems. (1) A multifilament having 5 to 20 crimps / cm in the longitudinal direction of the fiber with a radius of curvature of 0.15 to 1.00 mm after relaxation heat treatment, wherein the single fibers constituting the multifilament are hollow cross-section fibers that satisfy the following A to D. A. One or more hollow sections B. Hollow ratio of 10-40% C. The outer periphery of the fiber cross-section has multiple protrusions. D. Degree of irregularity of the fiber cross-section is 1.3-2.0 Here, the degree of irregularity is the circumscribed circle diameter of the fiber cross-section divided by the inscribed circle diameter of the fiber cross-section assuming the fiber is solid. (2) A multifilament having 5 to 20 curls per cm in the fiber longitudinal direction with a radius of curvature of 0.15 to 1.00 mm after relaxation heat treatment, wherein in the cross section of the single fiber constituting the multifilament, the cross-sectional anisotropy of the orientation degree represented by the following formula is 3.0% or more, and the standard deviation of the cross-sectional anisotropy is 1.0% or more. Cross-sectional anisotropy = 100×(A - B) / A (A: The maximum orientation degree, B: The minimum orientation degree) (3) The multifilament according to (1) or (2) above, having a crimp rate of 3 to 10% after relaxation heat treatment. (4) The multifilament according to (1) or (2) above, wherein the fineness of the single fiber is 0.5 to 3.0 dtex. (5) The multifilament according to (1) or (2) above, having a boiling water shrinkage rate of 1 to 15%. (6) The multifilament according to (1) or (2) above, having a crimp rate of less than 1% before relaxation heat treatment.

Advantages of the Invention

[0012] With the multifilament of the present invention, when subjected to relaxation heat treatment, fine curls are developed, providing a fabric or a moire yarn with excellent bulkiness and a soft texture.

Brief Description of the Drawings

[0013] [Figure 1] It is a schematic diagram of the fiber cross section of the single fiber constituting the multifilament of the present invention. [Figure 2] It is a schematic diagram showing the measurement position of the shape anisotropy of the single fiber constituting the multifilament of the present invention. [Figure 3] It is a schematic diagram for measuring the radius of curvature of the crimp provided by the multifilament of the present invention. [Figure 4] It is a schematic diagram of a spinneret for manufacturing a hollow cross-section fiber constituting the multifilament of the present invention. [Figure 5] It is a schematic diagram of a drawing device used when manufacturing the multifilament of the present invention. [Figure 6] This is an example of the load-elongation curve of a partially oriented non-drawn yarn for explaining the elongation in the constant stress elongation region.

Embodiments for Carrying out the Invention

[0014] Hereinafter, embodiments of the present invention will be described in detail. The present invention is a multifilament composed of hollow cross-section fibers having at least one hollow part and a plurality of protrusions in a fiber cross-section orthogonal to the fiber axis direction.

[0015] As another embodiment, it is a multifilament composed of single fibers having cross-sectional anisotropy of orientation degree in a fiber cross-section orthogonal to the fiber axis direction.

[0016] The multifilament of the present invention is obtained by subjecting a partially oriented non-drawn yarn (hereinafter referred to as POY) to non-uniform stretching that randomly generates a molecular orientation difference in both the fiber axis direction and the direction perpendicular to the fiber axis direction (fiber cross-section axis direction) after manufacturing, and then performing relaxation heat treatment, resulting in a multifilament in which fine crimps are developed.

[0017] The hollow ratio of the hollow cross-section fibers constituting the multifilament of the present invention is 10 to 40%, preferably 20 to 35%. By setting the hollow ratio within such a range, a large number of fine crimps are developed upon relaxation heat treatment. Due to the development of fine crimps, in addition to the bulkiness due to the hollow, gaps between single fibers are generated due to the crimp, so sufficient bulkiness can be obtained for the fabric or the moire yarn. When the hollow ratio is less than 10%, the hollow part is small, and sufficient bulkiness cannot be obtained when made into a fabric or a moire yarn. When the hollow ratio exceeds 40%, the hollow is easily crushed during yarn processing or fabric processing, and as a result, the bulkiness when made into a fabric or a moire yarn is impaired. Also, during the yarn manufacturing process, hollow cracking is likely to occur due to friction or the like, and from the perspective of productivity, the hollow ratio is preferably 40% or less.

[0018] The heat insulation effect, a benefit of hollow cross-section fibers, significantly contributes to the manifestation of molecular orientation differences. In the present invention, the multifilament is heat-set with a high-temperature hot roller after stretching, creating a difference in molecular orientation between the hot roller contact side and the non-contact side of the fiber, forming a high degree of cross-sectional anisotropy. Due to this cross-sectional anisotropy, the multifilament of the present invention exhibits a great deal of fine crimp when subjected to relaxation heat treatment. However, if the hollowness ratio is less than 10%, the heat insulation effect from the hollow portion is not obtained, the molecular orientation difference between the hot roller contact surface and the non-contact surface is small, and sufficient crimp does not occur.

[0019] The hollow ratio as used in this invention is the value calculated from the following formula (1). Hollow ratio (%) = (Area of ​​hollow portion / Area of ​​the inscribed circle of the fiber cross-section assuming solidity) × 100 ... (1) The hollowness ratio was determined by selecting a number of single fibers in the multifilament calculated by formula (2) below, measuring the hollowness ratio five times at a frequency of once per 1000m, and using the average value shown in the table. If the number calculated by formula (2) was not an integer, it was rounded up to the nearest integer. Number of measured fibers = Number of single fibers constituting the multifilament / 6 ... (2).

[0020] Furthermore, the number and shape of the hollow sections can be any number and shape as long as they do not hinder the objective of the present invention. Figure 1 illustrates the fiber cross-section of the hollow cross-section fibers constituting the multifilament of the present invention. The shape of the hollow sections can be a triangle, a pentagon, a shape in which the hollow section is divided into two vertically, or a grid shape in which the hollow section is divided into four. The hollow shape is not limited to the exemplified shape, and known shapes can be used.

[0021] The hollow cross-section fibers constituting the multifilament of the present invention have multiple protrusions on the outer periphery of the fiber cross-section. By having multiple protrusions, that is, by making the outer periphery of the fiber cross-section an uneven shape, the single fibers are less likely to interlock, resulting in a state where there are gaps in the arrangement of single fibers in the multifilament (a state in which a close-packed structure does not occur), and high bulkiness can be obtained when it is made into fabric or chenille yarn.

[0022] The number of protrusions is preferably three or more, more preferably five, seven, or eight, and particularly preferably five. When the number of protrusions is six, the single fibers tend to interlock, resulting in a close-packed structure, which leads to poor bulk. In order to prevent the single fibers from interlocking and to avoid the formation of a close-packed structure, the number of protrusions on each single fiber in the multifilament does not need to be the same, and a multifilament can be made in which single fibers with different numbers of protrusions are mixed.

[0023] Furthermore, it is preferable that the fiber cross-section of the hollow cross-section fiber constituting the multifilament of the present invention has protrusions that radiate from the center of the cross-section, as this allows for higher bulkiness. In this invention, the term "protrusion" refers to the region that protrudes from the inscribed circle of the fiber cross-section when a single fiber is assumed to be solid.

[0024] The hollow cross-section fibers constituting the multifilament of the present invention have a degree of irregularity (R / r1) of 1.3 to 2.0, preferably 1.6 to 2.0, calculated from the ratio of the circumscribed circle diameter (R) to the inscribed circle diameter (r1) of the fiber cross-section when assumed to be solid. A higher degree of irregularity indicates longer protrusions. If the degree of irregularity is less than 1.3, the gaps in the single-fiber arrangement of the multifilament become small, and sufficient bulkiness cannot be obtained when made into fabric or chenille yarn. If the degree of irregularity exceeds 2.0, the gaps in the single-fiber arrangement of the multifilament become large, and high bulkiness can be obtained. However, because the protrusions become long, abrasion resistance decreases during the manufacturing process of fabric and chenille yarn, leading to fuzzing and yarn breakage. Therefore, from the viewpoint of higher-order passage, a degree of irregularity of 2.0 or less is preferable. The increase in fiber surface area due to the unevenness and the gaps in the single-fiber arrangement greatly contribute to the expression of molecular orientation differences.

[0025] The multifilament of the present invention, when heat-set with a high-temperature hot roller after stretching, creates a difference in molecular orientation between the hot roller contact side and the non-contact side of the fiber, forming a high degree of cross-sectional anisotropy. Due to this cross-sectional anisotropy, the multifilament of the present invention exhibits fine crimp when subjected to relaxation heat treatment. However, when the degree of irregularity is less than 1.3, the gaps between the single filaments are small, the distance between the hot roller contact surface and the non-contact surface is small, the difference in molecular orientation is small, and the crimp is reduced.

[0026] The degree of irregularity was determined by selecting a single fiber from the multifilament based on the number of fibers calculated using formula (2) below, measuring the degree of irregularity five times at a frequency of once per 1000m, and using the average value as the degree of irregularity shown in the table. If the number of fibers calculated using formula (2) was not an integer, it was rounded up to the nearest integer. Number of measured fibers = Number of single fibers constituting the multifilament / 6 ... (2).

[0027] The multifilament of the present invention achieves sufficient bulkiness and a soft texture due to the presence of many crimps with a small radius of curvature (hereinafter referred to as fine crimps) after relaxation heat treatment (treatment with boiling water without load). In this invention, fine crimps refer to crimps with a radius of curvature of 0.15 to 1.00 mm, and are present in the single fibers that make up the multifilament.

[0028] The number of crimps required for the multifilament was calculated using the following method. The multifilament was wound 10 times using a measuring machine with a circumference of 1.0 m to form a skein. This skein was then immersed in a 100°C boiling water bath for 15 minutes without applying any load (relaxation heat treatment). After removing it from the boiling water bath, it was left to air dry at room temperature below 40°C for at least 24 hours. After air drying, the multifilament was observed using a digital microscope, and the number of fine crimps with a radius of curvature of 0.15 to 1.00 mm per 1 cm of length of the single fiber was counted. Twenty single fibers were observed, and the average number of crimps was used as the crimp count.

[0029] Here, the radius of curvature is evaluated using images of the multifilament observed with a digital microscope, and as shown in Figure 3, it is the radius (r3) of the curved portion formed by the single fiber constituting the multifilament.

[0030] A crimping rate of 5 to 20 fibers / cm provides sufficient bulkiness and a soft texture. If the crimping rate is less than 5 fibers / cm, there is insufficient fine crimping, resulting in small gaps in the arrangement of single fibers of the multifilament when woven into fabric or chenille yarn. This results in a multifilament that lacks volume, and therefore, sufficient bulkiness and a soft texture cannot be obtained. If the crimping rate exceeds 20 fibers / cm, the effect obtained by increasing the gaps in the arrangement of single fibers of the multifilament due to crimping remains constant, but the fibers shrink too much, shortening the apparent length of the fibers, increasing the density, and compromising bulkiness.

[0031] Regarding the cross-sectional anisotropy of the multifilament of the present invention, the cross-sectional anisotropy of the degree of orientation in the cross-section of the single fiber constituting the multifilament is 3.0% or more, and the standard deviation of the said cross-sectional anisotropy is 1.0% or more. The cross-sectional anisotropy is the value calculated from equation (8) below. Cross-sectional anisotropy = 100 × (AB) / A···(8) (A: maximum degree of orientation, B: minimum degree of orientation) The degree of orientation is 1615 cm² in a deflected arrangement in a fiber cross-section perpendicular to the fiber axis. -1 The Raman band is defined as the intensity at each measurement point when mapping measurements are performed on the cross-section of a single fiber.

[0032] Furthermore, in measuring the cross-sectional anisotropy, a number of single fibers calculated by equation (2) below was selected from the multifilament, and the degree of orientation was measured five times at a frequency of once per 1000m. The average value was taken as the cross-sectional anisotropy. The standard deviation of all measurement results was also calculated and taken as the standard deviation of the cross-sectional anisotropy. If the number calculated by equation (2) was not an integer, it was rounded up to the nearest integer. Number of measured fibers = Number of single fibers constituting the multifilament / 6 ... (2) The cross-sectional anisotropy is 3.0% or higher, preferably 5.0 to 20.0%. By keeping the orientation anisotropy within this range, sufficient crimp occurs after the relaxation heat treatment, improving bulkiness and texture.

[0033] The standard deviation of the cross-sectional anisotropy is 1.0% or more, preferably 1.5 to 15.0%. By setting the standard deviation of the surface anisotropy to 1.0% or more, a certain degree of non-uniformity is maintained between individual fibers, resulting in different crimping phases and complex crimping. Therefore, when used in fabrics or chenille yarns, it has sufficient bulkiness, and especially in fabrics, it exhibits a soft texture.

[0034] The multifilament of the present invention preferably has a crimp rate of 3 to 10% after relaxation heat treatment, and more preferably 5 to 10%. A crimp rate of 3% or more results in large gaps in the arrangement of the single fibers of the multifilament, creating a bulging multifilament, which provides sufficient bulkiness when used in fabrics or chenille yarns. A crimp rate of 10% or less prevents excessive shrinkage of the fibers, while still providing sufficient bulkiness when used in fabrics or chenille yarns.

[0035] The crimp ratio as used in this invention is the value calculated from the following formula (3). Marfilament was wound 10 times using a measuring machine with a circumference of 1.0 m to form a skein. This skein was then immersed in a 100°C boiling water bath for 15 minutes without applying any load (relaxation heat treatment). After removing it from the boiling water bath, it was left to air dry at room temperature below 40°C for at least 24 hours. After air drying, a measuring load of 5 g / detx was applied to the skein and left for 1 minute. The length of the skein after this period was measured and designated as L1. Next, the measuring load was removed and the skein was left unloaded for 3 minutes, and the length of the skein was measured and designated as L0. The crimp rate was calculated using the following formula (3). Three measurements were taken, and the average value was taken as the crimp rate. Crimp rate (%)={(L1-L0) / L1}×100···(3).

[0036] The fineness of the single fibers constituting the marfilament of the present invention is preferably 0.5 to 3.0 dtex, and more preferably 1.3 to 2.0 dtex. When the fineness is 0.5 dtex or more, the fiber cross-sectional area is large, and the distance between the hot roller contact side and the non-contact side is large during hot roller heat setting, making it easier for a difference in the amount of heat transferred to occur, thus allowing for a large difference in molecular orientation. By performing a relaxation heat treatment on these fibers, many fine crimps are produced, resulting in bulkiness when made into fabric or chenille yarn. On the other hand, when the fineness is 3.0 dtex or less, the fiber diameter becomes smaller, resulting in lower bending rigidity of the fiber, and a soft texture is obtained when made into fabric.

[0037] The multifilament of the present invention preferably has a boiling water shrinkage rate of 1 to 15%, more preferably 1 to 8%. By setting the boiling water shrinkage rate to 15% or less, shrinkage during the dyeing process of the fabric can be suppressed, preventing the texture from becoming stiff. When made into chenille yarn, shrinkage of the fibers during the heat setting process can be suppressed, reducing the density of the chenille yarn and enabling bulkiness.

[0038] The boiling water contraction rate referred to in this invention is the value calculated by the following formula (4). After winding the multifilament 10 times using a measuring machine with a circumference of 1.0 m and taking a skein, an initial load of 0.6 g / dtex was applied to the skein, and the length of the skein was measured and defined as La. The skein was removed, immersed in a 100°C boiling water bath for 15 minutes, and then removed from the boiling water bath and left to air dry at room temperature below 40°C for at least 24 hours. After air drying, a measuring load of 0.6 g / dtex was applied to the skein, and the length of the skein was measured and defined as Lb. The boiling water shrinkage rate was calculated using the following formula (4). Three measurements were taken, and the average value was taken as the boiling water shrinkage rate. Boiling water contraction rate (%) = {(La-Lb) / La} × 100 ... (4).

[0039] The multifilament of the present invention preferably has a crimp rate of less than 1% before the relaxation heat treatment. If crimp occurs before heat treatment, especially when used as embroidery floss in chenille yarn, tension is applied to the embroidery floss to straighten the crimp, and then it is sandwiched between the core threads and cut. If there is crimp, the thread will shrink after cutting, shortening the length of the embroidery floss and impairing the bulkiness of the chenille yarn.

[0040] The multifilament of the present invention is a fiber made of a thermoplastic polymer. Examples of thermoplastic polymers include polyesters such as polyethylene terephthalate, polybutylene terephthalate, polytrimethylene terephthalate, and polylactic acid; polyamides such as polycaproamide (polyamide 6), polydodecanoamide (polyamide 12), polyhexamethylene adipamide (polyamide 66), polyhexamethylene sevacamide (polyamide 610), and polyhexamethylene dodecanoamide (polyamide 612); polyolefins such as polypropylene, polyethylene, and polyurethane; and combinations thereof.

[0041] Polyester, which is generally widely used as a fiber for clothing and as padding, is preferred. The polymer intrinsic viscosity of polyester is appropriately 0.5 to 0.7. Furthermore, within the limits that do not hinder the objectives of the present invention, polymers derived from PET bottles or recycled clothing, so-called recycled polymers, or polymers derived from biomass can also be used.

[0042] The polymer may be blended with additives, such as matting agents, pigments, dyes, antifouling agents, fluorescent whitening agents, flame retardants, fire retardants, weather-resistant agents, ultraviolet absorbers, infrared absorbers, lubricants, antibacterial agents, antiviral agents, deodorizers, or moisture absorbers, as long as they do not hinder the objectives of the present invention. If such functional agents are incompatible with the polymer, they may be added after preparing a masterbatch using a method such as melt-blending spinning.

[0043] The multifilament of the present invention preferably has a total fineness of 33 to 330 dtex. A total fineness of 33 to 330 dtex is advantageous in garment applications because it facilitates processing at an appropriate weave density during the manufacturing of woven or knitted fabrics, thus improving productivity. Furthermore, this range is also advantageous in chenille yarn applications because it facilitates processing at an appropriate filament density, thus improving productivity. A more preferable total fineness is 33 to 300 dtex.

[0044] The multifilament of the present invention can be made with multiple filaments to the extent that it does not hinder the objective of the present invention, but the number of single fibers is preferably 12 to 144. By increasing the number of single fibers to 12 or more, a difference in the amount of heat transferred between single fibers is created when the hot roller heat set, resulting in a complex crimp with different phases of crimping between single fibers. As a result, it has sufficient bulkiness when used as a fabric or chenille yarn, and especially in the case of fabrics, it exhibits a soft texture.

[0045] The elongation of the multifilament of the present invention is preferably 50 to 150%, and more preferably 50 to 100%. By keeping it within this range, the cross-sectional anisotropy of molecular orientation after stretching and heat setting with a hot roller is increased, and crimp can be achieved.

[0046] Increasing the draw ratio homogenizes the molecular orientation of the entire fiber, making it difficult for crimp to occur. However, by increasing the elongation to 50% or more, the orientation difference in the fiber's cross-sectional direction can be maintained, allowing crimp to occur and providing sufficient bulkiness when used in fabrics or chenille yarns.

[0047] Furthermore, in the elongation range of 50-150%, stretching irregularities occur in the longitudinal direction of the fiber, resulting in the presence of oriented and unoriented regions. Due to these orientation irregularities, the crimp that develops when a relaxation heat treatment is applied also exhibits irregularities in the longitudinal direction of the fiber, resulting in a complex crimp with different phases, which can produce a soft texture when used in fabrics or chenille yarns. However, the design of the elongation is not limited to these factors and should be set considering the crimp form and quality of fluff, etc., after the relaxation heat treatment.

[0048] The U% of the multifilament of the present invention is preferably 1.0 to 12.0%. By adjusting the draw ratio so that the U% is 1.0% or higher, unevenness in the length of the fiber can be generated, resulting in the presence of oriented and unoriented regions. Due to this unevenness in orientation, the crimp that appears when a relaxation heat treatment is applied also becomes a complex crimp with different phases due to unevenness in the length of the fiber, which can result in a soft texture when used in fabrics or chenille yarns.

[0049] The degree of entanglement of the multifilament of the present invention is preferably 0 to 5 fibers / m. When subjected to relaxation heat treatment, the fibers shrink due to differences in molecular orientation in the direction of the fiber cross-section, and crimp is produced. However, if the multifilament is strongly constrained, the fibers cannot shrink, inhibiting the production of crimp. Therefore, it is preferable to keep the degree of entanglement at 5 fibers / m or less. Since the fibers are not constrained and can shrink and produce crimp through relaxation heat treatment, sufficient bulkiness can be obtained when used in fabrics or chenille yarns.

[0050] Next, the method for manufacturing the multifilament of the present invention will be described. The multifilament of the present invention can be obtained by a known melt spinning method using a thermoplastic polymer. An example of a melt spinning method for a thermoplastic polymer is as follows: the thermoplastic polymer is melted, metered and transported by a gear pump, and extruded from a spinneret to form a yarn. The yarn is cooled by blowing cooling air from a yarn cooling device such as a chimney, lubricated by a lubrication device, bundled, entangled in a fluid processing device, taken up by rollers, and wound up by a winding device. The fiber is classified as a so-called Partially Oriented Yarn (POY), and its manufacturing method conforms to the POY method (high-speed spinning method). In this case, the polymer is extruded from a spinneret with an extrusion hole shape as illustrated in Figure 4, and by raising the solidification point of the polymer immediately after extrusion (rapid cooling conditions), a stable cross-sectional shape can be easily obtained. A distance of 20-100 mm from the spinneret surface to the cooling air outlet surface is preferable because it allows for the acquisition of POY with appropriate deformation and stable spinnability.

[0051] Furthermore, when there are many single fibers constituting a multifilament, the airflow for cooling becomes poor, and the fibers on the leeward side tend to be undercooked. Therefore, it is preferable to use an annular cooling device to cool each single fiber evenly. In particular, when the single fiber thickness is fine, there is a concern that the spinning properties will deteriorate due to insufficient cooling, so it is preferable to cool evenly using an annular cooling device.

[0052] In the production of POY, the melting temperature is preferably in the range of 250 to 295°C. Lowering the melting temperature reduces the amount of heat carried by the polymer extruded from the die, allowing for faster solidification and thus enabling a high degree of deformation. However, if the melting temperature is too low, the strength of the fibers will decrease, which can cause the yarn to break, so it should be adjusted appropriately depending on the target fineness, number of single fibers, and fiber cross-section. The spinning speed is preferably in the range of 2000 to 4000 m / min. More preferably, the spinning speed is 2000 to 3000 m / min. A spinning speed of 2000 m / min or higher results in fiber strength at a practical level after drawing, which is also advantageous from the viewpoint of productivity. Furthermore, when the spinning speed is 3000 m / min or lower, the constant stress elongation of the POY is more likely to occur, resulting in good orientation unevenness in the longitudinal direction of the fibers during the drawing process.

[0053] In the multifilament of the present invention, when subjected to relaxation heat treatment, the fibers shrink and crimp occurs due to differences in molecular orientation in the fiber cross-sectional direction. However, when the single fibers constituting the multifilament are entangled and converged, the fibers are constrained and cannot shrink, resulting in insufficient crimp. Therefore, a preferred degree of POY entanglement is 0 to 5 fibers / m.

[0054] The multifilament of the present invention is obtained by non-uniformly stretching the POY at a predetermined magnification using a friction resistor. When the yarn is gripped by the friction resistor, the fiber is stretched, and when the stretch tension exceeds the maximum static friction force on the friction resistor, the fiber slips and is not stretched. By repeating this slipping, an oriented portion and an unoriented portion are formed in the longitudinal direction of the fiber. For the fiber to be gripped by the friction resistor, the coefficient of friction between the fiber and the friction resistor is important, and the higher the coefficient of friction, the greater the difference between the oriented portion and the unoriented portion. Therefore, the coefficient of friction between the fiber and the friction resistor is preferably 0.25 to 0.45, and more preferably 0.35 to 0.45. In order to increase the coefficient of friction, it is preferable to add 0.6 to 2.2% by mass of a high-viscosity spinning oil to the polymer during spinning.

[0055] While the non-uniform stretching process can be performed immediately after the spinning process, the constant stress elongation region of POY immediately after spinning is not clearly defined, making it difficult to form orientation irregularities in the longitudinal direction of the fibers even with non-uniform stretching. Therefore, it is preferable to wind the POY and leave it at room temperature of 25-40°C for 12 hours or more before performing non-uniform stretching.

[0056] In the present invention, it is preferable to perform non-uniform stretching after the production of the POY. Figure 5 shows one embodiment of a preferred non-uniform stretched yarn manufacturing apparatus that can be used in the present invention. In Figure 5, the POY 5 is stretched at a low magnification between a feed roller 6 and a hot roller 8 via a friction resistance member 7, heated and set by the hot roller 8, taken up by a non-heated roller 9, and wound onto a bobbin by a winder 10.

[0057] A cylindrical heat pin is preferred as the friction resistor. The material of the heat pin is not particularly limited, but stainless steel or ceramic is preferred from the viewpoint of durability and temperature stability. Furthermore, the surface roughness of the friction resistor is preferably Rz 2.0 to 8.0 μm. By keeping it within this range, the yarn slips appropriately on the heat pin, making it easy to create molecular orientation differences in the longitudinal direction of the fiber. In the case of a cylindrical heat pin, its diameter is preferably 1.5 to 3.0 cm. By making the diameter of the heat pin 3.0 cm or less, the slip frequency increases, and the highly oriented and low oriented regions in the longitudinal direction of the fiber switch frequently (forming molecular orientation variations in the longitudinal direction of the fiber), so that the resulting multifilament can exhibit complex and fine crimping by relaxation heat treatment.

[0058] Furthermore, the temperature of the heat pin is preferably between the glass transition temperature Tg°C and 100°C of the polymer. When the heat pin temperature is above Tg°C, the dispersion of orientation in the longitudinal direction of the fiber is good. On the other hand, if the heat pin temperature is below 100°C, the decrease in molecular orientation difference in the longitudinal direction of the fiber can be suppressed. For example, when polyester is used, the heat pin temperature is preferably between 75 and 100°C.

[0059] Furthermore, the contact time between the thermal pin and the POY is 3.0 × 10⁻⁶ -3 ~6.0×10- 3 It is preferable that the contact time is 3.0 × 10⁻⁶. 3 If the contact time is 6.0 × 10⁻⁶ seconds or longer, the oscillation of the running yarn on the heated pin is small, there is no yarn breakage during processing, and the stabilization of the slip phenomenon reduces the variation in the frequency of molecular orientation unevenness. -3 If the time is less than a second, the proportion of unoriented areas will be good, resulting in a good crimp shape due to the relaxation heat treatment.

[0060] Furthermore, the stretch ratio is determined by the speed ratio of the feed roller 6 and the hot roller 8. However, in order to produce stable molecular orientation patterns, it is preferable to stretch the material at a stretch ratio less than or equal to the constant stress elongation of the POY, and when determined according to the following equation (5), 0.4 ≤ α ≤ 1.0 is preferred. Note that the constant stress elongation refers to I in Figure 6. When α is 1.0 or less, the frequency of molecular orientation irregularities in the longitudinal direction of the fiber becomes favorable, and the desired crimp can be obtained by relaxation heat treatment. Furthermore, when α is 0.4 or more, the strength and toughness of the hollow cross-section fibers become practical, and the occurrence of yarn breakage during higher-order processing is reduced. (1 + constant stress elongation / 100) × α times ... (5) (α: coefficient in the stretching ratio) In the drawing process, a high-temperature contact heater is used to firmly heat the running yarn. High-temperature contact heaters include hot rollers, hot plates, and slit heaters, but in this invention, a hot roller is preferred. Heating with a hot roller causes the running yarn to be strongly contacted with the heating element, and a difference in the amount of heat generated is easily created between the single fibers on the side in contact with the hot roller and the single fibers on the side that is not in contact with the hot roller.

[0061] The heat setting temperature (hot roller setting temperature) is preferably 100 to 130°C, and more preferably 100 to 120°C. If the heat setting temperature is 130°C or lower, a difference in the amount of heat generated will occur between the single fibers on the hot roller contact side and the single fibers on the non-contact side. In other words, a difference in molecular orientation will occur in the direction of the fiber cross-section, resulting in fine crimping.

[0062] When the heat set temperature is 100°C or higher, the boiling water shrinkage rate can be controlled to a desired range (1-15%).

[0063] Contact time with the hot roller: 9.0 × 10 -2 ~24.0×10 -2 It is preferable that the interval be in seconds. This range makes it easier to introduce differences in molecular orientation in the fiber cross-sectional direction.

[0064] The multifilament fiber structure of the present invention can be suitably used in innerwear, outerwear, shirts, blouses, sweaters, pants, etc., by being made into woven or knitted fabrics, and can be used as bedding stuffing, etc., by being made into long-fiber batting. The multifilament of the present invention may also be blended with other yarns to produce woven fabrics, knitted fabrics, batting, etc., to the extent that it does not hinder the purpose of the present invention. One method for exhibiting the characteristics of the multifilament of the present invention is to process it into chenille yarn using the multifilament of the present invention as the main filament.

[0065] The chenille yarn can be manufactured using a conventionally known chenille yarn twisting machine, for example, a chenille yarn twisting machine as shown in Japanese Patent Publication No. 53-6642 can be used. The heat treatment temperature of the chenille yarn is preferably in the range of 90 to 120°C. By setting the temperature within this range, the multifilament of the present invention develops a moderate crimp, resulting in a bulky chenille yarn. [Examples]

[0066] The present invention will be described in more detail below with reference to examples. The characteristic values ​​in the examples were determined by the following method.

[0067] (1) Hollowness ratio Multifilaments were embedded in methacrylic resin, cut perpendicular to the fiber axis, and observed using a digital microscope (Keyence VHX-5000) to capture cross-sectional images of the single fibers constituting the multifilament. From the captured images, the area of ​​the hollow portion was determined, and the inscribed circle diameter of the single fiber cross-section (Figure 2: r1) was measured and calculated using the following formula. If there were multiple hollow portions, the sum of the areas of each hollow portion was used as the total hollow portion area. Hollowness = Area of ​​the hollow part / Area of ​​the inscribed circle of a single fiber assuming it is solid × 100 Here, the inscribed circle of a single fiber refers to the circle with the maximum radius that can be formed inside the cross-section of the single fiber, assuming the single fiber is solid. A number of single fibers were selected based on the number of single fibers constituting the multifilament, calculated using the following formula. The hollowness of all these single fibers was measured five times at a frequency of once per 1000m, and the average value was taken as the hollowness shown in the table. If the number calculated using the following formula was not an integer, it was rounded up to the nearest integer. In addition, if the length of a single fiber was 1000m or less, the total length was divided into six equal parts, and measurements were taken at five points excluding the ends. Number of hollow fibers measured = Number of single fibers constituting the multifilament / 6.

[0068] (2) Degree of irregularity For the observation images in (1) above, the value obtained by dividing the circumscribed circle diameter (R) of the single fiber cross-section by the inscribed circle diameter (r1) of the single fiber cross-section was calculated. The circumscribed circle is the smallest radius circle that encloses the entire area of ​​the single fiber cross-section, and the inscribed circle is the largest radius circle that can be formed inside the single fiber cross-section when the single fiber is assumed to be solid. A number of single fibers calculated from the number of single fibers constituting the multifilament using the following formula was selected, and the degree of deformation of all of these single fibers was measured five times at a frequency of once per 1000m, and the average value was taken as the degree of deformation listed in the table. If the number calculated using the following formula was not an integer, it was rounded up to the nearest integer. In addition, if the length of the single fiber was 1000m or less, the total length was divided into six equal parts, and measurements were taken at five locations excluding the ends. The number of fibers measured for deformation = number of single fibers constituting the multifilament / 6.

[0069] (3) Number of folds The multifilament was wound 10 times using a measuring machine with a circumference of 1.0 m to create a hank. This hank was then immersed in a 100°C boiling water bath without any load for 15 minutes. After removing it from the boiling water bath, it was left to air dry at room temperature below 40°C for at least 24 hours. The air-dried fibers were observed under a microscope, and the number of crimps with a radius of curvature of 0.15 to 1.00 mm per 1 cm of single filament was counted. A number of single fibers were selected based on the number of single fibers constituting the multifilament using formula (6) below. The crimp count of all selected single fibers was measured 5 times at a frequency of 1 time / 1000 m, and the average value obtained using formula (7) below was taken as the crimp count. If the number calculated using formula (6) below was not an integer, it was rounded up to the nearest integer. In addition, if the length of a single fiber was 1000 m or less, the total length was divided into 6 equal parts, and measurements were taken at 5 points excluding the ends. Number of crimped fibers = Number of single fibers constituting the multifilament / 2 ... (6) Number of crimps = (Total number of crimps counted) / (Number of selected single fibers × 5) ... (7).

[0070] (4) Cross-sectional anisotropy Multifilaments were embedded in methacrylic resin, cut perpendicular to the fiber axis, and the degree of orientation was measured using a Raman spectrometer (RENISHAW inVia). Using a 100x objective lens, a semiconductor laser with a beam diameter of 1 μm and a wavelength of 532 nm was used as the light source. Under conditions of a laser power of 15 mW, a single diffraction grating of -3000 gr / mm, a 65 μm slit, and a CCD / RENISHAW 1024 × 256 detector, the degree of orientation was measured in a deflected configuration at 1615 cm² in the fiber cross-section perpendicular to the fiber axis. -1 The Raman bands were mapped at 1 μm steps. The intensity obtained at each measurement point was defined as the degree of orientation, and the cross-sectional anisotropy was calculated using the following formula. The cross-sectional anisotropy = 100 × (AB) / AA is the maximum degree of orientation, and B is the minimum degree of orientation. A number of single fibers were selected based on the number of single fibers constituting the multifilament, calculated using the formula below. The degree of orientation of all these single fibers was measured five times at a frequency of once per 1000m. The average of these measurements was taken as the cross-sectional anisotropy listed in the table, and its standard deviation was taken as the standard deviation of cross-sectional anisotropy listed in the table. If the number calculated using the formula below was not an integer, it was rounded up to the nearest integer. Furthermore, if the length of a single fiber was 1000m or less, the total length was divided into six equal parts, and measurements were taken at five points excluding both ends. The number of measurements required for cross-sectional anisotropy is equal to the number of single fibers constituting the multifilament / 6.

[0071] (5) Crimp rate After winding the multifilament 10 times using a measuring machine with a circumference of 1.0m to create a skein, the skein was immersed in a 100°C boiling water bath without any load for 15 minutes. After removing it from the boiling water bath, it was left to air dry at room temperature below 40°C for at least 24 hours. After air drying, a measuring load of 5g / detx was applied to the skein and left for 1 minute. The length of the skein after this period was measured and designated as L1. Furthermore, the measuring load was removed and the skein was left unloaded for 3 minutes, and the length of the skein was measured and designated as L0. The crimp rate was calculated using the following formula. Three tests were performed, and the average value was taken as the crimp rate. Crimp rate (%)={(L1-L0) / L1}×100.

[0072] (6) Boiling water contraction rate After winding the multifilament 10 times using a measuring machine with a circumference of 1.0 m and taking a skein, an initial load of 0.6 g / dtex was applied to the skein, and the length of the skein was measured and defined as La. The skein was removed, immersed in a 100°C boiling water bath for 15 minutes, removed from the boiling water bath, and left to air dry at room temperature below 40°C for at least 24 hours. After air drying, a measuring load of 0.6 g / dtex was applied to the skein, and the length of the skein was measured and defined as Lb. The boiling water shrinkage rate was calculated using the following formula. Three tests were performed, and the average value was taken as the boiling water shrinkage rate. Boiling water contraction rate (%) = {(La-Lb) / La} × 100.

[0073] (7) Total fineness The multifilament was wound 100 times on a measuring machine with a frame circumference of 1.0 m at an unwinding tension of 1 / 11.1 (g / dtex), and the weight was measured using a balance scale. The total fineness was calculated by multiplying the weight by 100.

[0074] (8) Single fiber The value obtained by dividing the total fineness in (7) above by the number of single fibers constituting the multifilament was defined as the single fineness.

[0075] (9) Elongation The elongation (%) of the multifilament was measured in a temperature-controlled chamber at 20°C and 65% humidity under the constant-speed elongation conditions specified in JIS L1013 (2010) 8.5.1 standard time test. Measurements were taken under conditions of a test length of 200 mm and a tensile speed of 200 mm / min to obtain stress-strain curves. The test was performed five times. Elongation was the average value of the strain at the point where the maximum stress was observed (II in Figure 6), and constant-stress elongation was the average value of the strain at the point where the stress began to increase proportionally with respect to the strain after exceeding the yield point (I in Figure 6).

[0076] (10) Confounding The degree of entanglement is the number of entangled areas per meter under a tension of 0.11 g / dtex. A pin is inserted into an unentangled area of ​​a multifilament under a tension of 0.022 g / dtex. The pin is then moved up and down along the longitudinal direction of the fiber over a distance of 1 meter under a tension of 0.11 g / dtex. The areas where the pin moves without resistance are considered unentangled, and the distance moved is recorded. The areas where the pin stops are considered entangled. This process is repeated 5 times, and the number of entanglements per meter is calculated from the average distance of the unentangled areas (n=5).

[0077] (11) U% The results were obtained by using a Zellweger USTER TESTER UT-4, selecting the appropriate measuring throttle based on the total fineness of the marfilament, and then measuring for 1 minute under the conditions of a yarn speed of 25 m / min and a twist count of 5000 T / m.

[0078] (12) Bulky To evaluate bulkiness, chenille yarns were created using marfilaments obtained by the following method as embroidery threads, and their bulkiness was compared.

[0079] As the core yarn and the holding yarn, one nylon 66 fiber (product name "Promilan" 44T-34f manufactured by Toray Industries, Inc.) was used, and as the fusing yarn, one polyamide-based fusing fiber (copolymer polyamide fiber: product name "Elder" 22T-10f manufactured by Toray Industries, Inc.) was used. As the decorative yarn, multifilament was used.

[0080] Using a conventionally known mold yarn twisting machine, with the ratio of the supply speed of the core yarn and the holding yarn to the supply speed of the decorative yarn being 1:13, the decorative yarn was supplied to the flyer part, the fusing yarn was attached to the holding yarn, and the core yarn and the holding yarn were supplied from two directions. The decorative yarn was wound around a guide piece with a width of 30 mm at the lower end, the decorative yarn was cut with a cutter and sandwiched between the core yarn and the holding yarn, and the twist was adjusted to 250 turns per meter (T / m) and twisted together, and then wound up with a spindle.

[0081] Subsequently, the mold yarn was wound into skeins at 200 g each using a skein winding machine, the skein was hooked onto the rod of a transport cart equipped with a skein hanging rod, and then put into a pressure steam heat treatment furnace, and pressure steam treatment (steam pressure of about 0.07 MPa) was performed at 98 °C for 20 minutes to melt the fusing yarn and obtain a mold yarn with the decorative yarn fused and fixed.

[0082] 10 g of the obtained mold yarn was weighed in a container placed on an electronic balance, the weighed mold yarn was put into a cylindrical container with an inner diameter of 15 cm, and a circular plate whose mass was adjusted to 0.15 g / cm 2 with respect to the cross-sectional area inside the cylinder was placed on the mold yarn, and after leaving it for 1 minute, the height of the mold yarn was measured, and the height up to the first digit after the decimal point was read and taken as the height L0 of the mold yarn. From this height, the volume of the mold yarn per unit mass (= bulkiness) was calculated using the following formula. Bulkiness (cm 3 / g) = cross-sectional area inside the cylinder × L0 / mass of the mold yarn.

[0083] (13) Texture Using a 28G single circular knitting machine at 100 g / m 2The plain knit fabric was knitted and heat-treated in boiling water for 20 minutes. The texture of the knitted fabric was inspected by 10 skilled inspectors. The texture was evaluated on the following three levels. The passing levels are ◎ and ○. ◎: The texture is soft and extremely good. ○: The texture is good. ×: The texture is stiff.

[0084] (Example 1) Polyethylene terephthalate (PET) with a titanium dioxide concentration of 0.3% by mass was melted at a spinning temperature of 285°C and extruded from a spinneret having 48 extrusion holes as shown in Figure 4A. Cooling air was then blown from a position 27 mm from the spinneret surface using an annular cooling device, and a spinning oil was supplied at a rate of 0.9% by mass relative to the polymer to concentrate the yarn. The yarn was then wound up at a spinning speed of 2000 m / min to obtain partially oriented undrawn yarn (POY) with a total fineness of 137 dtex. The entanglement number of the obtained POY was 1, and the coefficient of dynamic friction against a friction resistor with a surface roughness Rz of 4.5 μm was 0.40.

[0085] The obtained POY was left in a room temperature-controlled to 38°C for 24 hours, after which it was subjected to uneven stretching, heat setting, and winding using the stretching machine shown in Figure 5. A 2.0 cm diameter stainless steel (surface roughness: Rz 4.5 μm) heated pin was heated to 80°C, and the yarn was stretched 1.37 times between the feed roller and the hot roller so that the stretching ratio coefficient was 0.9. The contact time between the heated pin and the yarn was 4.6 × 10⁻⁶. -3 The yarn speed was adjusted to 820 m / min to achieve a specific result in seconds. The yarn was then heated using a hot roller heated to 110°C, taken up with a draw roller, and then wound onto a bobbin with a winder to obtain a multifilament with a total fineness of 98 dtex. As shown in the table, the chenille yarn and tubular knit produced from this multifilament exhibited excellent bulkiness and texture.

[0086] (Example 2) A multifilament was obtained in the same manner as in Example 1, except that the extrusion holes of the spinneret were modified and the hollowness ratio of the fiber cross-section was set to 12%. The chenille yarn and tubular knit fabric produced from this multifilament exhibited excellent bulkiness and texture.

[0087] (Example 3) By changing the hole shape of the extrusion nozzle, the spinning temperature to 280°C, and the cooling start distance to 24 mm, the hollowness ratio of the fiber cross-section was set to 35%. Multifilament was obtained by stretching in the same manner as in Example 1, except that the stretch ratio was adjusted to 1.30 times in order to achieve a stretch ratio coefficient of 0.9. The chenille yarn and tubular knit fabric produced from this multifilament exhibited excellent bulkiness and texture.

[0088] (Comparative Example 1) The extrusion holes of the spinneret were modified to achieve a hollowness ratio of 8% in the fiber cross-section. Except for setting the draw ratio coefficient to 0.9, the yarn was drawn in the same manner as in Example 1 to obtain a multifilament. The chenille yarn produced from this multifilament had poor bulkiness. Furthermore, the texture of the tubular knit was also stiff.

[0089] (Example 4) A multifilament was obtained in the same manner as in Example 1, except that the extrusion holes of the spinneret were changed and the degree of irregularity of the fiber cross-section was set to 1.4. The chenille yarn and tubular knit fabric produced from this multifilament had excellent bulkiness and texture.

[0090] (Example 5) The spinneret's discharge hole was modified to achieve a fiber cross-sectional irregularity of 1.9. Except for adjusting the draw ratio to 1.35 times to achieve a draw ratio coefficient of 0.9, the yarn was drawn in the same manner as in Example 1 to obtain a multifilament. The chenille yarn and tubular knit fabric produced from this multifilament exhibited excellent bulkiness and texture.

[0091] (Comparative Example 2) A multifilament was obtained in the same manner as in Example 1, except that the extrusion holes of the spinneret were changed and the degree of irregularity of the fiber cross-section was set to 1.2. The chenille yarn produced from this multifilament had poor bulkiness. In addition, the texture of the tubular knit was stiff.

[0092] (Comparative Example 3) By changing the discharge hole of the spinneret, setting the spinning temperature to 280°C, and the cooling start distance to 24 mm, the degree of irregularity of the fiber cross-section was set to 2.3. Multifilament was obtained in the same manner as in Example 1, except that the draw ratio was set to 1.30 times in order to achieve a draw ratio coefficient of 0.9. The chenille yarn produced from this multifilament had poor bulkiness. In addition, the texture of the tubular knit was also stiff.

[0093] (Example 6) A multifilament was obtained in the same manner as in Example 1, except that the POY obtained in the same manner as in Example 1 was stretched to a draw ratio coefficient of 1.1 and a draw ratio of 1.60. The obtained multifilament had a uniform molecular orientation and a small difference in orientation in the cross-sectional direction due to stretching, resulting in a crimp count of 5 crimps / cm after relaxation heat treatment. The resulting chenille yarn had slightly less bulkiness than Example 1, but it was still practically bulky, and the texture of the resulting tubular knit was good.

[0094] (Comparative Example 4) A multifilament was obtained in the same manner as in Example 1, except that the draw ratio coefficient was 1.2 and the draw ratio was 1.80. The obtained multifilament showed increased orientation upon stretching, resulting in less anisotropy in the cross-section, and the crimp count after relaxation heat treatment was 1 crimp / cm. The resulting chenille yarn had inferior bulkiness compared to Example 1. In addition, the texture of the tubular knit was also harder.

[0095] [Table 1]

[0096] (Example 7) The number of discharge holes in the spinneret was changed to achieve a single fineness of 1.0 dtex. Except for setting the draw ratio coefficient to 0.9 by setting the draw ratio to 1.28, the yarn was drawn in the same manner as in Example 1 to obtain a multifilament. The resulting chenille yarn had slightly less bulkiness than that of Example 1, but it was still bulky enough for practical use, and the texture of the resulting tubular knit was good.

[0097] (Example 8) The number of discharge holes in the spinneret was changed to achieve a single fineness of 2.7 dtex. Except for setting the draw ratio coefficient to 0.9, the yarn was drawn in the same manner as in Example 1 to obtain a multifilament. The resulting chenille yarn had the same bulkiness as in Example 1. The resulting tubular knit was slightly stiffer than in Example 1, but had a usable texture.

[0098] (Example 9) A multifilament was obtained in the same manner as in Example 1, except that the hot roller temperature was set to 130°C. The chenille yarn and tubular knit fabric produced from this multifilament exhibited excellent bulkiness and texture.

[0099] (Example 10) A multifilament was obtained in the same manner as in Example 1, except that the hot roller temperature was set to 100°C. The chenille yarn produced from this multifilament had slightly shorter filament lengths and less bulk compared to Example 1, but was still within a usable range. The resulting tubular knit was also slightly stiffer than that of Example 1, but had a usable texture.

[0100] (Example 11) The spinneret's discharge hole was changed to D in Figure 4, and the number of protrusions on the outer circumference of the fiber cross-section was set to 8. Except for setting the draw ratio coefficient to 0.9, the fibers were drawn in the same manner as in Example 1 to obtain a multifilament. The chenille yarn and tubular knit fabric produced from this multifilament exhibited excellent bulkiness and texture.

[0101] (Example 12) A multifilament was obtained in the same manner as in Example 1, except that the PET raw material used was PET resin derived from PET bottles. The chenille yarn and tubular knit fabric produced from this multifilament exhibited excellent bulkiness and texture.

[0102] (Example 13) A multifilament was obtained in the same manner as in Example 1, except that the PET raw material used was a full-dull PET resin with a titanium dioxide concentration of 2.2% by mass. The chenille yarn and tubular knit fabric produced from this multifilament exhibited excellent bulkiness and texture.

[0103] (Example 14) POY was prepared in the same manner as in Example 1, except that the PET raw material used was a cationic dyeable copolymer PET resin containing 1.6 mol% isophthalic acid, and the spinning temperature was set to 290°C and the cooling start distance to 36 mm accordingly. Multifilament was obtained by stretching in the same manner as in Example 1, except that the stretching ratio was set to 1.25 times in order to achieve a stretching ratio coefficient of 0.9. The chenille yarn and tubular knit fabric produced from this multifilament exhibited excellent bulkiness and texture.

[0104] [Table 2] [Explanation of Symbols]

[0105] a: Schematic diagram of a fiber cross-section with five protrusions. b: Schematic diagram of a fiber cross-section where the five protrusions are not radially arranged. c: Schematic diagram of a fiber cross-section with a triangular hollow section and six protrusions. d: Schematic diagram of a fiber cross-section with 8 protrusions. 1: Inscribed circle 2: Circumscribed circle R: Circumscribed circle diameter r1: Diameter of the inscribed circle of the fiber cross-section, assuming the fiber is solid. r3: radius of curvature 3: Monofiber 4: Circles formed by curved sections A: An example of a spinneret with five protrusions B: An example of a spinneret with five protrusions that are not arranged radially. C: An example of a spinneret with a triangular hollow section and six protrusions. D: An example of a spinneret with 8 protrusions 5: POY 6: Feed Roller 7: Friction resistor 8: Hot Roller 9: Non-heated rollers 10: Winder I: Constant stress elongation II: Elongation

Claims

1. A multifilament having 5 to 20 crimps / cm in the longitudinal direction of the fiber, with a radius of curvature of 0.15 to 1.00 mm after relaxation heat treatment, A multifilament in which the single fibers constituting the multifilament are hollow cross-section fibers that satisfy the following conditions A to D. A. One or more hollow sections B. Hollow ratio of 10-40% C. The outer periphery of the fiber cross-section has multiple protrusions. D. The degree of irregularity of the fiber cross-section is 1.3 to 2.0 Here, the degree of irregularity is the circumscribed diameter of the fiber cross-section divided by the inscribed diameter of the fiber cross-section assuming the fiber is solid.

2. A multifilament having 5 to 20 crimps / cm in the longitudinal direction of the fiber, with a radius of curvature of 0.15 to 1.00 mm after relaxation heat treatment, In the cross-section of a single fiber constituting a multifilament, The cross-sectional anisotropy of the degree of orientation shown in the following formula is 3.0% or more. A multifilament having a standard deviation of cross-sectional anisotropy of 1.0% or more. Cross-sectional anisotropy = 100 × (A - B) / A (A: maximum degree of orientation, B: minimum degree of orientation)

3. The multifilament according to claim 1 or claim 2, wherein the crimp rate after relaxation heat treatment is 3 to 10%.

4. The multifilament according to claim 1 or claim 2, wherein the fineness of the single fiber is 0.5 to 3.0 dtex.

5. The multifilament according to claim 1 or claim 2, wherein the boiling water shrinkage rate is 1 to 15%.

6. The multifilament according to claim 1 or claim 2, wherein the crimp rate before relaxation heat treatment is less than 1%.

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