staple fiber and staple yarn

Abstract

A staple fiber, characterized in that it is composed of at least two polymers with different melting points, has a crimp number / crib diameter ratio of 75 to 500, and a coefficient of variation (CV%) of 15% to 50% for the crimp number between staple fibers. A staple yarn, characterized in that it contains flat staple fibers composed of at least two polymers with different melting points, and a coefficient of variation (CV%) of 60% to 90% for the interfiber spacing. By controlling the crimp morphology of each staple fiber in the staple yarn, staple fibers and staple yarns can be provided that are suitable for clothing fabrics that, in addition to having a warm and delicate touch and a fluffy and soft texture like cotton, also possess functional properties such as water absorption and excellent wearing comfort.

Description

Technical Field

[0001] This invention relates to short fibers and short yarns suitable for fabrics used in comfortable clothing. Background Technology

[0002] Staple fiber yarn is made by twisting and plying short fibers with a length of tens of millimeters. By using natural fibers such as cotton and wool, and regenerated fibers such as rayon, fabrics with excellent moisture absorption and heat retention can be obtained. However, these fibers are inherently weak, and if they absorb a large amount of sweat and moisture, it will penetrate into the fiber interior, resulting in drawbacks such as difficulty in drying and a sticky, uncomfortable feeling.

[0003] Synthetic fibers, such as polyester or polyamide, possess excellent mechanical properties and dimensional stability. By spinning short fibers cut to a certain length, they can be used as staple yarn. To address the challenges posed by natural fibers, staple yarn is made from synthetic fibers with superior mechanical, chemical, and water-absorbing properties, or from blends of synthetic, natural, and regenerated fibers. Based on the unique texture and natural appearance of staple yarn, it is widely used in numerous fields, including jackets, outerwear, shirts, underwear, and sportswear.

[0004] However, as people's lives become increasingly diversified and they seek a better life, there is a demand for staple fiber yarns to have a tactile feel that is closer to that of natural materials, while also endowing synthetic fibers with unique functionality and higher performance. As such staple fiber yarns with higher tactile feel and performance, a staple fiber yarn composed of short fibers with parallel cross-sections bonded together with different polymers has been proposed.

[0005] Short fibers with this parallel cross-section are designed to exhibit crimp by utilizing the difference in thermal shrinkage between polymers, thereby imparting textures such as bulkiness and functionality such as stretch. However, when using short fiber yarns composed of these short fibers as fabrics, because all the short fibers exhibit the same crimp shape, the crimp phase between the short fibers tends to be uniform. Sometimes, this can result in a dense clustering that leads to bulkiness or lack of stretch, or wrinkles or spots appearing on the fabric surface, thus impairing the appearance.

[0006] In contrast, various techniques have been proposed to improve the bulkiness, elasticity, and appearance quality of the aforementioned issues by controlling the cross-sectional shape of short fibers, and to further enhance functionality.

[0007] Patent document 1 discloses acrylic short fibers containing two acrylonitrile polymers in different proportions in a parallel structure and having a flatness of 1.5 to 8, as well as short fiber yarn containing the acrylic short fibers.

[0008] In the acrylic staple fibers described above, due to their flat shape, compared to acrylic staple fibers with a near-circular cross-sectional shape, the cross-sectional second moment in the short axis direction is reduced, resulting in increased fiber softness or a tendency to exhibit crimp caused by parallel compounding. Therefore, staple yarns containing these acrylic staple fibers exhibit excellent bulkiness, providing a fluffy texture when used in fabrics, and are less prone to deformation even after repeated washing, resulting in fabrics with excellent durability.

[0009] In addition, Patent Document 2 discloses a polyester staple fiber and a staple yarn containing the polyester staple fiber, which are made of poly(1,3-propanediol terephthalate, PTT) and at least one of polyethylene terephthalate (PET), PTT and polybutylene terephthalate (PBT), having a flat cross-section with a long axis length: short axis length ratio of 2:1 to 5:1, and having multiple longitudinal grooves through parallel compounding or eccentric core-sheath compounding in a direction perpendicular to the long axis side of the flat cross-section.

[0010] Short-fiber yarn containing the polyester short fibers described above exhibits high elasticity by combining at least one component of the short fibers with PTT in a parallel or eccentric core-sheath composite direction perpendicular to the long axis of the flat cross-section. Furthermore, the flat cross-section with a long axis to short axis length ratio of 2:1 to 5:1 results in high homogeneity. Moreover, the presence of multiple longitudinal grooves in the short fibers imparts excellent water absorption. Therefore, short-fiber yarn containing this polyester short fiber can produce fabrics that, in addition to high elasticity, also possess a uniform fabric appearance and excellent water absorption.

[0011] Existing technical documents

[0012] Patent documents

[0013] Patent Document 1: Japanese Patent Application Publication No. 2020-007667

[0014] Patent Document 2: Japanese Patent Publication No. 2009-510275 Summary of the Invention

[0015] The problem that the invention aims to solve

[0016] As shown in Patent Document 1 or Patent Document 2, by making the cross-sectional shape of short fibers with parallel cross sections flat, it is difficult to be most densely packed by twisting during spinning. Therefore, the crimp phase of adjacent short fibers is also difficult to be consistent, and sometimes the bulkiness, elasticity, and appearance quality are improved.

[0017] However, in Patent Document 1 and Patent Document 2, the short fibers exhibit the same crimped shape, sometimes resulting in insufficient improvement in fluffiness and appearance quality, and the texture becomes monotonous.

[0018] Furthermore, in Patent Document 2, in order to obtain high elasticity, short fibers need to have high crimp. However, when short fibers exhibit high crimp in a twisted and constrained state during spinning, adjacent short fibers will pile up tightly together, resulting in the loss of gaps between fibers. As a result, sometimes the fluffy and soft texture required for comfortable clothing is insufficient, or the water absorption caused by capillary action due to gaps is reduced.

[0019] Therefore, the purpose of this invention is to solve the problems of the prior art mentioned above, and to provide a short fiber and short yarn that, in addition to having a comfortable touch and fluffy and soft texture caused by the warm and delicate texture of cotton, also has functional properties such as water absorption, and is suitable for use in clothing fabrics with excellent wearing comfort.

[0020] Problem-solving methods

[0021] The objective of this invention is achieved through the following means.

[0022] [1] A short fiber, characterized in that it is composed of at least two polymers with different melting points, the number of curls / curl diameter is 75 to 500, and the coefficient of variation (CV%) of the number of curls between short fibers is 15 to 50%.

[0023] [2]. The short fiber as described in [1] above is characterized in that the coefficient of variation (CV% of the distance between polymer centroids / fiber diameter) between the short fibers is 5~30%.

[0024] [3]. The short fiber as described in [1] or [2] above is characterized in that the flatness of the fiber cross section is 1.2 to 5.0.

[0025] [4]. The short fiber as described in any of [1] to [3] above is characterized in that the fiber cross-section has three or more protrusions.

[0026] [5]. A fiber product, characterized in that it contains short fibers as a part of any one of [1] to [4].

[0027] [6]. A short fiber yarn, characterized in that it contains any of the short fibers described in any one of [1] to [4] above.

[0028] [7]. A short fiber yarn, characterized in that it contains flat short fibers composed of at least two polymers with different melting points, and the coefficient of variation (CV%) of the interfiber gap distance is 60-90%.

[0029] [8]. The short fiber yarn as described in [7] above is characterized in that the gap distance between fibers is 4 to 10 μm.

[0030] [9]. The short fiber yarn as described in [7] or [8] above is characterized by having a void structure with a void ratio of 30 to 60%.

[0031]

[10] . The short fiber yarn as described in any of [7] to [9] above, characterized in that the mixing rate of the flat short fibers is 30 to 100 by mass.

[0032]

[11] . A fabric characterized in that it comprises short fiber yarn as a part of any one of [7] to

[10] above.

[0033] Invention Effects

[0034] The short fibers and short yarns of the present invention, by having the above-mentioned characteristics, achieve dense control over the crimping morphology of each short fiber in the short fibers constituting the short yarn, forming a complex surface irregularity and inter-fiber gaps in the short yarn. Therefore, by using the short fibers and short yarns of the present invention, it is possible to obtain clothing fabrics that, in addition to the comfort caused by the warm and delicate irregularity of cotton and the fluffy and soft texture, also possess functional properties such as water absorption and excellent wearing comfort. Attached Figure Description

[0035] Figure 1 (a), (b), (c), and (d) are schematic diagrams illustrating an example of the cross-sectional structure of the short fiber in this embodiment.

[0036] Figure 2 (a) and (b) are schematic diagrams showing an example of the cross-sectional structure of the short fiber in this embodiment.

[0037] Figure 3 This is a schematic diagram illustrating an example of the cross-sectional structure of a conventional short fiber.

[0038] Figure 4 This is a schematic diagram showing an example of the cross-sectional structure of each short fiber in the short fiber of this embodiment.

[0039] Figure 5 This is a diagram used to understand the method for measuring the interfiber gap distance of the short fiber yarn in this embodiment.

[0040] Figure 6 This is a diagram used to understand the method for measuring the crimp diameter in short fibers according to this embodiment.

[0041] Figure 7 This is a cross-sectional view used to illustrate the method for manufacturing short fibers according to this embodiment. Detailed Implementation

[0042] The present invention will now be described in detail with reference to preferred embodiments.

[0043] (1) Short fibers

[0044] Analysis of cotton, a widely used natural material known for its comfortable feel and absorbency due to its smooth, delicate texture, reveals that each short fiber possesses a different twist. By twisting multiple short fibers with varying twists together, complex surface textures and inter-fiber gaps are created on the short fiber yarn, resulting in a unique feel and texture when used as fabric.

[0045] In order to achieve a complex surface texture and inter-fiber gaps like cotton using synthetic fibers, the inventors conducted in-depth research and found that by setting the relationship between the number of crimps and the crimp diameter in short fibers composed of at least two polymers with different melting points to a specific range, and then by controlling the distance between the centers of gravity of the polymers in each short fiber to change the number of crimps, it is possible to achieve short fiber yarns with complex surface textures and inter-fiber gaps that are difficult to obtain with conventional synthetic fibers.

[0046] That is, short fiber yarn obtained by twisting and plying short fibers. Because the short fibers are constrained by twisting, if heat treatment is performed to show excessive crimp number or fine crimp diameter of the short fibers, there is a tendency for adjacent short fibers to be tightly packed together and lose the gaps between fibers.

[0047] In contrast, if the number of crimps or the crimp diameter are controlled within a specific range during the crimping process of short fibers, adjacent short fibers will not pile up tightly. In addition to the gaps that originally existed between the short fibers, gaps based on the crimping process will also be formed. Furthermore, by controlling the distance between the polymer centers of gravity of each short fiber to vary the number of crimps, differences in linear length will appear between the short fibers during crimping, creating complex inter-fiber gaps with various gap sizes. At the same time, complex unevenness will appear on the surface of the short fiber yarn that was not present before. Therefore, when short fiber yarn is made into fabric, it can exhibit the unique touch and texture of natural materials.

[0048] Based on this concept, the short fibers of the present invention are constructed. Specifically, they are composed of at least two polymers with different melting points, and it is important that the crimp number / crim diameter ratio is 75 to 500, and the coefficient of variation (CV%) of the crimp number between the short fibers is 15 to 50%. Preferred embodiments will be described below.

[0049] Polymers with different melting points

[0050] In order to control the curling shape, the short fibers in this embodiment need to be composed of at least two polymers with different melting points.

[0051] If polymers with different melting points (low-melting-point polymers and high-melting-point polymers) are arranged on the cross-section of short fibers with their centers of gravity differing, the short fibers will bend significantly towards the side of the low-melting-point polymer, which becomes highly shrinkable, after heat treatment. Through this continuity, a coil-like curled shape can be exhibited. Furthermore, by controlling the distance between the centers of gravity of the polymers, any curled shape can be exhibited, thereby achieving the objective of this invention: control of the curled shape.

[0052] That is, in this embodiment, the cross-section of the short fiber is preferably a composite cross-section in which polymers with different melting points are arranged in a manner that their respective centers of gravity are different. Examples of such a composite cross-section include... Figure 1 The parallel type shown in A Figure 1 In addition to the eccentric core-sheath type shown in B, other types such as island type and mixed type can also be listed.

[0053] Furthermore, in the cross-section of the short fiber in this embodiment, if it is as follows... Figure 1 (d) shows a cross-section with a hollow section in the center of the fiber, which can further improve the bulkiness and obtain a lightweight material, and is therefore more preferable.

[0054] [Thin-skin coating]

[0055] Furthermore, in this embodiment, it is preferable that the surface layer of the short fibers is coated with a polymer. By coating the surface layer of the short fibers with a polymer, even if a polymer with low heat resistance or abrasion resistance is used as a component of the composite fiber, peeling will not occur at the interface due to friction or impact, thus maintaining the fiber properties well and improving the processing stability and quality of the short fiber yarn during spinning.

[0056] Furthermore, when manufacturing the short fibers of this embodiment, if a melt of polymers with large melting point differences is spun from the spinneret as a composite flow, the yarn will bend from the high-melting-point polymer to the low-melting-point polymer side due to the cooling difference after ejection. This yarn may come into contact with the spinneret or interfere with the composite flow spun from another part, resulting in yarn breakage. However, by coating the surface of the short fibers with a single polymer, the cooling difference can be mitigated, yarn bending can be suppressed, and stable yarn production can be achieved even when using a combination of polymers with large melting point differences.

[0057] Examples of polymers that can be used to coat the surface of short fibers include, for example, polyethylene terephthalate (PET), polyethylene terephthalate copolymers (PET), propylene terephthalate (PPT), and polybutylene terephthalate (PET), which are polyesters; nylon 6, nylon 66, and nylon 610, which are polyamides; and polypropylene, which is a polyolefin. From the viewpoint of excellent heat resistance and color development, polyethylene terephthalate or polyethylene terephthalate copolymers are preferred for coating the surface of the short fibers. Furthermore, the polymer used for coating the surface is preferably the same polymer as one of the polymers with a different melting point than the polymers constituting the short fibers.

[0058] Furthermore, the thickness of the polymer coating the surface of the short fibers can be appropriately adjusted. For example, the ratio S / D of the minimum thickness S of the polymer coating the surface of the short fibers to the fiber diameter D is preferably 0.01 to 0.1. Within this range, even if friction or impact is applied to the short fibers, whitening or fuzzing will not occur, resulting in good operability during spinning and improving the quality of the obtained short fiber yarn. Moreover, if S / D is set to 0.02 to 0.08, the centers of gravity of the high-melting-point polymer and the low-melting-point polymer are separated, maximizing the manifestation of crimp caused by the shrinkage difference, and therefore this range is listed as more preferred.

[0059] Furthermore, the ratio S / D of the minimum polymer thickness S covering the surface of the short fibers in this embodiment to the fiber diameter D is determined by embedding the short fibers with an embedding agent such as epoxy resin and then photographing the cross-section using a transmission electron microscope (TEM) to observe the composite cross-section. In this case, by performing metallic staining, a staining difference between the polymers can be formed, thus making the contrast at the joints of the composite cross-section clearer.

[0060] Specifically, the composite cross-section of the captured image is as follows: Figure 1 In the case of the eccentric core-sheath cross-section shown in B, the minimum thickness of the polymer coating the surface of the short fiber is determined in μm by analyzing a single short fiber from the captured image. The obtained minimum thickness S is divided by the fiber diameter D, which is calculated by measuring the area of ​​each composite fiber, converting it to a circle, and measuring it to one decimal place in μm. This operation is performed on 20 short fibers, and the average value is rounded to three decimal places. This yields the ratio S / D of the minimum polymer coating surface to the fiber diameter D.

[0061] [Area Ratio]

[0062] As the area ratio of the low-melting-point polymer to the high-melting-point polymer within the composite cross-section of the short fiber in this embodiment, the ratio of the area of ​​the low-melting-point polymer to the area of ​​the high-melting-point polymer is preferably 70 / 30 to 30 / 70, more preferably 60 / 40 to 40 / 60. If it is within this range, it is not affected by the texture hardening caused by the high shrinkage of the low-melting-point polymer during heat treatment, and the curling shape caused by the difference in polymer shrinkage can be fully exhibited.

[0063] [Number of curls / Curl diameter]

[0064] In the short fibers of this embodiment, by controlling the crimp morphology exhibited during heat treatment, a specific number of crimps corresponding to the crimp diameter is formed. Even in short fiber yarns where the short fibers are constrained by twisting, adjacent short fibers do not pile up tightly, and gaps can be formed between the short fibers. Specifically, when the crimp diameter is large, it is difficult to exhibit crimp due to being constrained by twisting, so it is necessary to increase the number of crimps. When the crimp diameter is small, crimp is easily exhibited, but on the other hand, short fibers tend to pile up tightly, so it is necessary to reduce the number of crimps.

[0065] That is, in the short fibers of this embodiment, a crimp number / crimping diameter of 75 to 500 is important.

[0066] Here, the number of curls and the curl diameter are determined by the following method.

[0067] First, the short fibers were subjected to dry heat treatment at 180°C for 5 minutes without load. Then, the crimp morphology of one short fiber was observed according to JIS L1015 (2010) 8.12.1, and the crimp number was determined. This treatment was performed on 20 different short fibers, and their average value was calculated. The value was rounded to the nearest whole number, and the result was taken as the crimp number (peak / 25mm).

[0068] Next, in the same curling morphology observed according to the method of JIS L 1015 (2010) 8.12.1 as described above, the following will be applied... Figure 6 The apex of the first peak (M1) and the last valley (V2) in the peak (M1) → valley (V1) → peak (M2) → valley (V2) section is connected by a straight line (S1). The distance Le (mm) between the two points where "two straight lines (S2, S3) parallel to this straight line (S1) and passing through the apex of the valley (V1) and peak (M2)" intersect with "a straight line perpendicular to them" is calculated. This operation is performed at any three or more locations on each short fiber, and the arithmetic mean is calculated. Furthermore, the above measurements are performed on 20 different short fibers, and the arithmetic mean of the results is calculated. The result is rounded to the third decimal place and used as the curl diameter (mm).

[0069] In addition, the value obtained by dividing the number of curls by the curl diameter is rounded to the nearest whole number and is used as the number of curls / curl diameter.

[0070] If the crimp number / crib diameter is 75–500, then in the short fiber yarn obtained by twisting and plying short fibers, in addition to the gaps that originally existed between the fibers, gaps caused by the crimp are also formed. Therefore, when made into fabric, the increase in large gaps not only results in a fluffy and soft texture, but also in water absorption due to the capillary effect caused by the fine gaps.

[0071] Furthermore, if the crimp number / crib diameter is set to 100 to 300, the increased porosity due to the crimping enhances the fluffy, soft texture and absorbency, making it even more preferable. Moreover, if the crimp number / crib diameter is set to 125 to 200, even short-fiber yarns obtained through strong twisting with strong constraint on short fibers can have porosity formed by the crimping, thus this range is listed as particularly preferred.

[0072] [Crimp diameter]

[0073] In the short fibers of this embodiment, it is preferable that they have a curled shape with a curl diameter of 0.10 to 0.40 mm.

[0074] If the curl shape has a curl diameter of 0.10 mm or more, gaps can be formed between the short fibers based on the curl. In the short fiber yarn formed by twisting and plying the short fibers of the present invention, complex gaps or surface irregularities can be formed. Therefore, in the case of fabric, the increase in large gaps not only results in a fluffy and soft texture, but also in water absorption through capillary action caused by the fine gaps. In addition, if the curl diameter is 0.15 mm or more, the effect of increased fluffiness due to the increased gaps between the short fibers can also be obtained.

[0075] From a fluffy perspective, a larger crimp diameter is preferred, but if the crimp diameter exhibited by the short fibers becomes too large, the crimp may sometimes be hindered by the constraint of twisting. Therefore, in this embodiment, the crimp diameter is preferably 0.40 mm or less, and more preferably 0.30 mm or less.

[0076] [Number of curls]

[0077] In the short fibers of this embodiment, it is preferable that they have a crimped shape with 20 to 200 crimps per 25 mm.

[0078] If the fibers have a crimp count of 20 crimps / 25mm or more, gaps can be formed between the short fibers based on the crimp. In short-fiber yarns formed by twisting and plying the short fibers of this invention, complex gaps or surface irregularities can be formed. Therefore, when making fabrics, the increased large gaps not only result in a fluffy and soft texture but also provide water absorption through capillary action caused by the fine gaps. Furthermore, if the crimp count is 40 crimps / 25mm or more, stretchability can also be imparted through the helical structure.

[0079] From the viewpoint of elasticity, a higher crimp number is preferred. However, since short fibers are constrained by twisting, when short fibers exhibit an excessive crimp number, the gaps between fibers may be lost due to the close packing of adjacent short fibers. Therefore, in this embodiment, the crimp number is preferably 200 peaks / 25mm or less, and more preferably 100 peaks / 25mm or less.

[0080] [Coefficient of variation of curl number]

[0081] In this embodiment, the number of crimps is varied by controlling the distance between the polymer centers of gravity of each short fiber. Furthermore, in the short fiber yarn obtained by twisting and plying this short fiber, the difference in linear length between the short fibers is exhibited when the crimp is displayed, resulting in a complex inter-fiber gap with various gap sizes. Therefore, when the fabric is made, it can exhibit a unique tactile feel similar to that of natural materials.

[0082] As a necessary condition for forming the aforementioned complex interfiber gaps in staple fiber yarn, it is important to ensure that the coefficient of variation (CV%) of the crimp number between staple fibers is 15% to 50%.

[0083] The coefficient of variation (CV%) of the number of curls between short fibers mentioned in this embodiment can be calculated using the following method.

[0084] First, the short fibers were subjected to dry heat treatment at 180°C for 5 minutes without load. The number of crimps (peaks / 25mm) was determined based on the crimp morphology of a single short fiber observed according to JIS L1015 (2010) 8.12.1. This operation was performed on 20 different short fibers, and their standard deviation and mean were calculated. The standard deviation was divided by the mean and then multiplied by 100. The result was rounded to the nearest decimal and used as the coefficient of variation (CV%) of the number of crimps among the short fibers.

[0085] If the coefficient of variation (CV%) of the crimp number between short fibers is greater than 15%, then in the short fiber yarn obtained by twisting and plying short fibers, the presence of short fibers with different crimp numbers creates various inter-fiber gaps due to differences in linear length, forming complex unevenness on the surface. Therefore, when this short fiber yarn is made into fabric, the unevenness easily allows fingers to grip it, increasing the fit to the fingers and resulting in a warm and delicate touch. Furthermore, it provides a natural, comfortable, uneven feel with moderate friction when the fingers slide across the surface.

[0086] Furthermore, from the viewpoint of making the effects of the present invention (the comfortable tactile sensation caused by the warm and delicate texture) more pronounced, it is preferable to increase the coefficient of variation (CV%) of the crimp number between short fibers, making the texture of the short fiber yarn surface more complex. Therefore, the coefficient of variation (CV%) of the crimp number is more preferably 20% or more, and particularly preferably 25% or more.

[0087] However, if the coefficient of variation of the crimp number becomes too large, the surface of the short fiber yarn becomes monotonous due to the polarization between fibers with a high crimp number and those with a low crimp number. Sometimes it feels like there is a foreign object, and sometimes it feels like there is a rough surface. Therefore, the upper limit of the coefficient of variation of the crimp number CV% in this invention is 50%.

[0088] [Coefficient of variation of (distance between polymer centroids / fiber diameter)]

[0089] The short fibers of this embodiment can have their crimping pattern controlled by the distance between the polymer centers of gravity and the fiber diameter, exhibiting a crimping pattern where a larger distance between the polymer centers of gravity and a smaller fiber diameter results in a higher number of crimps. That is, the number of crimps is represented by (distance between polymer centers of gravity / fiber diameter). By making this (distance between polymer centers of gravity / fiber diameter) different for each short fiber, the number of crimps can be varied, thus controlling the gap size and surface unevenness of the short fiber yarn. Therefore, in this embodiment, the coefficient of variation (CV%) of the (distance between polymer centers of gravity / fiber diameter) value between short fibers is preferably 5% or higher.

[0090] The coefficient of variation (CV%) of the (distance between polymer centroids / fiber diameter) value between short fibers mentioned in this embodiment can be calculated by the following method.

[0091] First, short fibers or short yarns are embedded with an embedding agent such as epoxy resin. A scanning electron microscope (SEM) is used to capture an image of the fiber cross-section perpendicular to the fiber axis. Next, image analysis software is used to analyze a randomly selected short fiber from the captured image, thereby determining the area of ​​the composite fiber. The diameter is then calculated by converting the area to a perfect circle and measured in μm to one decimal place. This value is taken as the fiber diameter (μm).

[0092] Next, for the same short fibers as described above, such as... Figure 2 As shown in (a), the length of the straight line connecting the centroids (Gx, Gy) of the low-melting-point polymer x and the high-melting-point polymer y in the cross-section of the composite fiber is measured in μm, to one decimal place. The obtained value is taken as the distance between the centroids of the polymers (μm).

[0093] For the fiber diameter and polymer centroid distance obtained above, calculate the arithmetic mean of their ratio (polymer centroid distance / fiber diameter), round to one decimal place, and use the result as (polymer centroid distance / fiber diameter). Perform the same evaluation on 20 randomly selected short fibers, calculate the standard deviation and mean of the results, and calculate the value of dividing the standard deviation by the mean and then multiplying by 100, rounding to the nearest decimal. Use the resulting value as the coefficient of variation (CV%) (%) for the (polymer centroid distance / fiber diameter) value.

[0094] If the coefficient of variation (CV% of the distance between polymer centroids / fiber diameter) between short fibers is greater than 5%, then the coefficient of variation (CV% of the number of crimps between short fibers) increases. Short fibers with different numbers of crimps are mixed together, and various interfiber gaps are generated by the difference in linear length between short fibers, which can form complex unevenness on the surface.

[0095] Furthermore, the coefficient of variation (CV%) of the value of (distance between polymer centers of gravity / fiber diameter) is more preferably in the range of 10% or more, and even more preferably in the range of 15% or more. If the coefficient of variation (CV%) is set to the above range, the coefficient of variation (CV%) of the crimp number between short fibers can be increased, making the surface texture of the short fiber yarn more complex, thus making the comfortable touch of the cotton-like warm and delicate texture more obvious.

[0096] In addition, if the coefficient of variation (CV%) becomes too large, the crimped shape will become polarized into coarse fibers and fine fibers, and the surface texture of the resulting short fiber yarn will become monotonous. Sometimes it is impossible to obtain the comfortable touch of cotton-like warm and delicate texture. Therefore, the coefficient of variation (CV%) is preferably below 30%.

[0097] [Flatness]

[0098] As a method for controlling the (polymer centroid distance / fiber diameter) in the short fibers of this embodiment, it is possible to consider making the cross-sectional shape and composite ratio of the short fibers different (variable) for each short fiber. However, from the viewpoint of controlling the consistency of crimp phase and yarn stability, it is preferable to make the cross-sectional shape of the short fibers flat with a flatness of 1.2 or more. In this invention, "flat" refers to an elongated shape when viewed from above, and more specifically, to a shape with a "flatness" of 1.1 or more in the cross-section of the short fibers described later.

[0099] In this embodiment, the flatness is determined using the following method. First, short fibers are embedded with an embedding agent such as epoxy resin, and an image of the fiber cross-section perpendicular to the fiber axis is captured using a scanning electron microscope (SEM). Next, image analysis software is used to analyze a randomly selected short fiber from the captured image, such as... Figure 1 As shown in (a), the line connecting the two furthest points (a1, a2) on the outer periphery of the composite fiber is taken as the major axis. The line connecting the intersection points (b1, b2) of the line passing through the midpoint of the major axis and orthogonal to the major axis with the outer periphery of the fiber is taken as the minor axis. The value obtained by dividing the length of the major axis by the length of the minor axis is calculated. The same operation is performed on 20 short fibers, and the arithmetic mean of the results is calculated. The value rounded to two decimal places is taken as the flatness.

[0100] If the cross-sectional shape of the short fiber is set to flat (flat cross-section), then as follows: Figure 2 As shown in (a), the distance between the centroids of polymers is greatest when they are bonded along the long axis of a flat cross-section when they have different melting points. Figure 2 As shown in (b), the distance between the polymer centroids is minimized when the fibers are joined along the short axis of the flat cross-section. Thus, by making the cross-sectional shape of the short fibers flat, the orientation of the joining surfaces of each short fiber is different (variable), and the value of (distance between polymer centroids / fiber diameter) can be controlled.

[0101] Therefore, it is preferable that the flatness of the short fibers is 1.2 or higher, and more preferably formed as follows: Figure 4 The composite cross-section is designed such that the bonding surfaces of each short fiber have different orientations. By having the short fibers with the above-described configuration, the coefficient of variation (CV%) of the value of (distance between polymer centroids / fiber diameter) can be easily made to the target range. Moreover, compared to the case where the cross-sectional shape and composite ratio are different (variable) for each short fiber, yarn breakage caused by uneven cooling and other issues can be suppressed, and yarn production stability can be improved.

[0102] Furthermore, to further demonstrate the above-mentioned effects, the flatness is more preferably 1.4 or higher, and even more preferably 1.6 or higher. By making the flatness of the short fibers 1.4 or higher, not only can the coefficient of variation (CV%) of the value of (distance between polymer centers of gravity / fiber diameter) be closer to the optimal range, but also, since the short fibers with flat cross-sections exhibit three-dimensional barriers when crimped, the gaps between short fibers in the short fiber yarn formed from the short fibers increase, resulting in a fluffy and soft texture when the fabric is made from the short fiber yarn.

[0103] As described above, from the viewpoint of controlling the coefficient of variation (CV%) of the (polymer centroid distance / fiber diameter) value and increasing the porosity of short fiber yarns formed from short fibers, higher flatness is better. On the other hand, if the flatness is too high, the light reflected on the surface of the composite fiber becomes stronger, which may produce uneven appearance (glare). In addition, the bending stiffness becomes higher than necessary due to the cross-sectional shape with edges, which may impair softness, and there is also a risk of reduced water absorption due to capillary action caused by the increased gap distance between fibers. Therefore, the flatness in this embodiment is preferably 5.0 or less, more preferably 4.0 or less, and even more preferably 3.0 or less.

[0104] [Cross-sectional shape]

[0105] As for the cross-sectional shape of the short fiber in this embodiment, besides Figure 1 Besides the flat shape like (a), we can also list Figure 1 (c) and other multi-lobed, as well as polygonal, gear-shaped, petal-shaped, star-shaped, etc.

[0106] In this embodiment, it is preferable to combine short fibers having a cross-sectional shape with three or more protrusions on the surface. By combining short fibers with a cross-sectional shape having three or more protrusions on the surface, it is possible to suppress uneven appearance (glare) caused by diffuse reflection of light, and to improve water absorption through the micro-pores between the short fibers. The number of protrusions is more preferably five or more, and even more preferably eight or more.

[0107] However, if the number of protrusions is too large, their effect gradually diminishes. Therefore, the actual upper limit for the number of protrusions is 20, and more preferably 12 or less.

[0108] [Fiber diameter]

[0109] In this embodiment, the short fibers preferably have a diameter of 20 μm or less. Within this range, not only can light reflection on the surface of the short fibers be suppressed, thus reducing unevenness (glare) in the appearance of the fabric, but also sufficient elasticity can be achieved. Therefore, it is suitable for use in clothing applications such as trousers and shirts where a crisp texture is required.

[0110] Furthermore, it is even more preferable to have a fiber diameter of 12 μm or less. By having a fiber diameter of 12 μm or less, the softness of the composite fiber bundle is increased, making it suitable for clothing applications such as underwear or blouses that come into contact with the skin.

[0111] Furthermore, from the viewpoint of bending recovery and suppressing the reduction of color development, the fiber diameter is preferably 5 μm or more, and even more preferably 10 μm or more in order to ensure good carding passage during spinning.

[0112] (2) As a staple fiber yarn, in order to maximize the cotton-like warm and delicate texture caused by the complex gaps and unevenness of the natural material, as well as the comfortable touch and fluffy and soft texture caused by it, the inventors conducted in-depth research and found that by containing flat short fibers with controlled crimp, the distance between the fibers is deviated, and the complex surface unevenness and interfiber gaps that are difficult to obtain in the previous staple fiber yarns can be formed, which is similar to those of natural fibers.

[0113] That is, in short-staple yarn containing flat short fibers that do not have a crimped shape, the fibers are tightly packed together by twisting and plying them during the spinning process, resulting in smaller gaps between fibers and a flatter surface. On the other hand, in the case of short-staple yarn containing flat short fibers that have the same crimped shape, the uniform crimped shape of each short fiber sometimes results in a monotonous shape with gaps or unevenness between fibers.

[0114] In contrast, in short-fiber yarns containing flat short fibers with different crimping shapes, the spacing between fibers varies under different crimping shapes, resulting in complex surface irregularities and inter-fiber gaps. Therefore, in addition to exhibiting the comfortable touch and fluffy, soft texture of cotton-like textures, it also achieves water absorption due to capillary action.

[0115] Based on this idea, the short fiber yarn of the present invention was constructed. Specifically, it contains flat short fibers composed of two polymers with different melting points, and the coefficient of variation (CV%) of the inter-fiber gap distance is 60% to 90%, which is a requirement of the present invention. Preferred embodiments will be described below.

[0116] [Flat short fiber]

[0117] The short fiber yarn of this embodiment is important because it contains flat short fibers composed of two polymers with different melting points.

[0118] If polymers with different melting points are arranged on the cross-section of short fibers with their respective centers of gravity at different locations, the short fibers will bend significantly towards the side of the low-melting-point polymer, which has high shrinkage, after heat treatment. Through this continuous arrangement, a coil-like curled shape can be exhibited. Furthermore, by controlling the distance between the centers of gravity of the polymers, any curled shape can be exhibited, thereby achieving control over the curled shape of each short fiber, which is the object of this invention.

[0119] That is, the cross-section of the flat short fibers used in the short fiber yarn of this embodiment is preferably a composite cross-section in which polymers with different melting points are arranged in a manner that their respective centers of gravity are different. Examples of such a composite cross-section include... Figure 1 Parallel structure like (a), Figure 1In addition to the eccentric core-sheath type like (b), other types such as island type or blended type can also be listed.

[0120] Furthermore, if the cross-section of the flat short fibers used in the short fiber yarn of this embodiment has a hollow portion at the center of the fiber, the bulkiness can be improved, and a further lightweight feel can be obtained, which is therefore more preferable.

[0121] As a method to control the distance between the centers of mass of the polymer, it is possible to consider making the cross-sectional shape and composite ratio of the short fibers different for each short fiber. However, from the viewpoint of controlling the consistency of the crimp phase and the stability of the yarn, it is important to make the short fiber cross-sectional shape of the short fiber into a flat short fiber in the short fiber yarn of this embodiment.

[0122] As a flat short fiber, the distance between the centers of gravity of the polymer can be controlled by changing the direction of the bonding surface of the short fiber.

[0123] The flatness of the flat short fiber is preferably 1.2 or higher, and further, such as Figure 4 As shown, a more preferable composite cross-section is one in which the bonding surfaces of each composite fiber have different orientations. By having the above-described structure in the short fibers, the difference in crimping morphology when the distance between the polymer centers of gravity is different increases, thereby increasing the coefficient of variation (CV%) of the inter-fiber gap distance (described later). Furthermore, compared to cases where the cross-sectional shape and composite ratio are different for each short fiber, yarn breakage due to uneven cooling or interference can be suppressed, and yarn production stability can be improved. In addition, to further demonstrate the above effects, a flatness of 1.4 or higher is more preferable, and even more preferably 1.6 or higher. By making the flatness between the composite fibers 1.4 or higher, not only can the coefficient of variation (CV%) of the inter-fiber gap distance be further increased, but the flat short fibers also exhibit greater three-dimensional resistance during crimping. Therefore, the porosity of the short fiber yarn containing this flat short fiber increases, resulting in a fluffy and soft texture when the short fiber yarn is made into a fabric.

[0124] From the viewpoint of the coefficient of variation (CV%) of the interfiber spacing and the increase in porosity of short fiber yarns, higher flatness is better. On the other hand, if the flatness is too high, the light reflected on the surface of the composite fiber becomes stronger, which may result in uneven appearance (glare). In addition, the cross-sectional shape with edges may make the bending stiffness higher than necessary, thereby impairing softness. There is also a risk of reduced water absorption due to capillary action caused by the increased interfiber spacing. Therefore, the flatness in this embodiment is preferably 5.0 or less, more preferably 4.0 or less, and even more preferably 3.0 or less.

[0125] [Interfiber gap distance]

[0126] In the short fiber yarn of this embodiment, the interfiber gap distance is preferably 4 to 10 μm.

[0127] The longer the interfiber spacing, the more space is created for the fibers fixed at the interlacing points of the fabric to move. This results in improved softness and capillary action caused by the fine gaps, leading to increased water absorption. Therefore, an interfiber spacing of 4 μm or more is preferred. Furthermore, if the interfiber spacing is 6 μm or more, the apparent density of the fabric decreases due to its bulkiness, further enhancing its bulkiness. This can be considered an even more desirable range.

[0128] From the viewpoint of fluffiness or softness, the greater the gap between fibers, the better. However, if the gap between fibers becomes too large, the texture becomes too soft, and sometimes the required crispness for clothing applications cannot be obtained. Moreover, the water absorption caused by capillary action due to the fine gaps will also decrease. Therefore, in this embodiment, the gap between fibers is preferably 10 μm or less, and more preferably 8 μm or less.

[0129] [Coefficient of variation (CV%) of interfiber gap distance

[0130] The short-fiber yarn of this embodiment can cause deviations in the inter-fiber gap distance due to the crimped shape of the flat short fibers, making the surface unevenness and inter-fiber gaps more complex. In order to approximate the comfortable touch brought by the warm and delicate unevenness of cotton, which is the object of this invention, it is important that the coefficient of variation (CV%) of the inter-fiber gap distance be 60% to 90%.

[0131] In this embodiment, the interfiber gap distance and its coefficient of variation (CV%) can be calculated using the following method.

[0132] First, for fabrics made of staple yarn, a scanning electron microscope (SEM) can be used to observe more than 20 short fibers that make up the staple yarn. Images are then taken of the fabric cross-section perpendicular to the fiber axis of the staple yarn. For each image taken, such as... Figure 5 Depict a circle containing 20 short fibers as shown. Select any one of the 20 short fibers located inside this circle. Find the intersection points of the straight line connecting the centroid G of the selected short fiber and its adjacent short fibers with the surfaces of each fiber. Measure the distance between the intersection points in μm to one decimal place. "Adjacent" here means that there are no other short fibers on the straight line connecting the centroids of any two fibers. Among the 20 short fibers located inside the circle, such as... Figure 5As shown, this operation is performed on all adjacent short fibers to calculate their mean and standard deviation. For the mean, the value is rounded to the nearest whole number and taken as the interfiber gap distance (μm). For the value obtained by dividing the standard deviation by the mean and then multiplying by 100, the value is rounded to the nearest whole number and taken as the coefficient of variation (CV%) of the interfiber gap distance.

[0133] If the coefficient of variation (CV%) of the interfiber spacing in staple fiber yarn is above 60%, complex irregularities can be formed on the surface through various interfiber gaps. Therefore, when this staple fiber yarn is made into fabric, the irregularities easily grip the fingers, increasing the fit and resulting in a warm, delicate touch. Furthermore, it provides a comfortable, natural feel with moderate friction when the fingers slide across the surface.

[0134] Furthermore, from the viewpoint of highlighting the cotton-like comfortable touch that is a feature of the present invention, it is preferable to increase the coefficient of variation (CV%) of the interfiber gap distance and make the surface of the short fiber yarn more complex. Therefore, it is preferable to make the coefficient of variation (CV%) of the interfiber gap distance 65% or more, and more preferably 70% or more.

[0135] However, if the coefficient of variation (CV%) of the interfiber gap distance becomes too large, the polarization becomes positions with small and large interfiber gap distances, and the resulting surface unevenness becomes monotonous, sometimes with a rough feel. Therefore, it is important that the coefficient of variation (CV) is below 90%, further preferably below 85%, and more preferably below 80%.

[0136] [Porosity]

[0137] The short fiber yarn in this embodiment preferably has a void structure with a void ratio of 30% to 60%.

[0138] In this embodiment, the porosity can be calculated using the following method.

[0139] First, for fabrics made of staple yarns, a scanning electron microscope (SEM) is used to observe at a magnification of more than 20 short fibers constituting the staple yarn. Images are then taken of the fabric cross-section perpendicular to the fiber axis of the staple yarn. For each image captured, such as... Figure 5 A circle containing 20 short fibers is depicted as shown. The cross-sectional area of ​​this circle is calculated by subtracting the total cross-sectional area of ​​the 20 fibers present inside the circle from the cross-sectional area of ​​the circle itself. In this case, if the area inside the circle contains more than half of the fibers, it is counted as one fiber, and the value is expressed in μm. 2 The cross-sectional area is measured to one decimal place. The calculated value is then divided by the cross-sectional area of ​​the circle, multiplied by 100, and rounded to the first decimal place. The resulting value is taken as the porosity (%).

[0140] If the short fiber yarn has a porosity of 30% or more, the fibers fixed at the interlacing points of the fabric will have sufficient space to move, resulting in improved softness, which is therefore preferred. Furthermore, if the porosity is 40% or more, the apparent density of the fabric will be reduced after it is made due to the high porosity, and it will also have a fluffing effect, which can be listed as an even more preferred range.

[0141] From the viewpoint of fluffiness or softness, a higher porosity is preferred. However, if the porosity is too high, the texture becomes too soft, and the required crispness for clothing applications may not be achieved. In addition, when the fabric is rubbed, short fibers are pulled out and tangled, which may sometimes result in pilling that looks undesirable. Therefore, the porosity in this embodiment is preferably 60% or less, and more preferably 50% or less.

[0142] [Blending rate of flat short fibers]

[0143] In the short fiber yarn of this embodiment, the mixing ratio of flat short fibers is preferably 30 to 100 by mass.

[0144] From the viewpoint of fully utilizing the characteristics of the flat short fibers used in this embodiment, the blending rate when blending with other fibers is preferably 30% by mass or more for the flat short fibers and 70% by mass or less for the other fibers; more preferably, it is 45% by mass or more for the flat short fibers and 55% by mass or less for the other fibers. Furthermore, from the viewpoint of fully utilizing the characteristics of the other fibers, it is preferable that the flat short fibers are 65% by mass or less and the other fibers are 35% by mass or more.

[0145] Within the aforementioned range, short-fiber yarns can be obtained that possess the characteristics of this invention, such as a comfortable touch caused by the warm and delicate texture of cotton, a fluffy and soft texture, and water absorption, while also exhibiting the characteristics of other fibers. This has excellent advantages in practical application.

[0146] There are no particular limitations on the types of other short fibers that constitute the short fiber yarn, but the use of at least one of polyester short fibers, acrylic short fibers, polyamide short fibers, rayon, cotton, linen, wool, and silk can achieve the effects of the present invention, and is therefore preferred.

[0147] The following are particularly preferred: 100% by mass of flat short fibers used in this invention; flat short fiber / cotton blend used in this invention; flat short fiber / rayon blend used in this invention; etc.

[0148] In addition, the process of blending flat short fibers with other fibers can be carried out in any process, such as opening or drawing, carding or twisting.

[0149] (3) Polymer

[0150] The polymer used in this embodiment is preferably a thermoplastic polymer due to its excellent processability. Preferred thermoplastic polymers include, for example, polyester-based, polyethylene-based, polypropylene-based, polystyrene-based, polyamide-based, polycarbonate-based, polymethyl methacrylate-based, and polyphenylene sulfide-based polymers and their copolymers. In particular, from the viewpoint that it can impart high interfacial affinity and produce short fibers with no abnormal composite cross-sections, the thermoplastic polymers used in this embodiment are preferably all from this polymer group and their copolymers. Furthermore, from the viewpoint that good color development can be obtained during dyeing when the short fibers and short fiber yarns of this embodiment are made into fabric, the thermoplastic polymers used are more preferably polyester-based or polyamide-based polymer groups and their copolymers. Polyethylene terephthalate and its copolymers are even more preferred because they provide appropriate resilience due to their high flexural recovery.

[0151] Furthermore, given the significant environmental concerns, and from the perspective of reducing environmental impact, this embodiment preferably uses biomass polymers or recycled polymers derived from plants. Therefore, the polymer used in this embodiment can be a recycled polymer that has been recovered through any one of chemical recycling, material recycling, or thermal recycling.

[0152] Even when using biopolymers or recycled polymers, as mentioned above, from the viewpoint of obtaining good color development during dyeing, polyester or polyamide polymer groups and their copolymers are preferred, among which recycled polyethylene terephthalate and its copolymers are further preferred because they provide a moderate sense of elasticity due to their high flexural recovery.

[0153] In addition, the polymer may contain various additives such as inorganic compounds such as titanium dioxide, silicon dioxide, and barium oxide, carbon black, colorants such as dyes or pigments, flame retardants, fluorescent whitening agents, antioxidants, or ultraviolet absorbers.

[0154] Preferably, the polymer contains titanium dioxide. By including titanium dioxide in the polymer, the titanium dioxide within the fiber diffusely reflects light, which not only suppresses uneven appearance (glare) caused by the increase or decrease in reflection due to the angle of light incidence, thus improving the appearance quality, but also provides functional properties such as anti-seepage and UV protection through the titanium dioxide within the fiber. To fully obtain the above effects, the titanium dioxide content in the composite fiber is preferably 0.5% by mass or more, more preferably 1.0% by mass or more, and even more preferably 3.0% by mass or more. In addition, when the diffuse reflection of light by titanium dioxide increases, it may sometimes cause a decrease in color rendering; therefore, the titanium dioxide content in the fiber is preferably 10.0% by mass or less.

[0155] In this embodiment, the combination of polymers with different melting points is a combination of polymers with melting points differing by more than 10°C if it is selected from melt-formable thermoplastic polymer groups and their copolymers such as polyester, polyethylene, polypropylene, polystyrene, polyamide, polycarbonate, polymethyl methacrylate, and polyphenylene sulfide. If it is the same group of polymers with the same main chain, such as polyester with ester bonds or polyamide with amide bonds, it is a combination of polymers with melting points differing by more than 5°C.

[0156] The purpose of the short fibers and short yarns in this embodiment is to exhibit a crimped shape by utilizing the shrinkage difference of polymers with different melting points. Therefore, as a combination of polymers with different melting points, it is preferable to use one high-shrinkage low-melting-point polymer and the other low-shrinkage high-melting-point polymer.

[0157] In particular, from the viewpoint of suppressing peeling to impart stability for higher processing or to impart durability to the fabric, it is more preferable to select from the same group of polymers with the same bonds in the main chain, such as polyesters with ester bonds or polyamides with amide bonds, as the combination of polymers.

[0158] Combinations of low-melting-point and high-melting-point polymers within the same polymer group, for example, as polyesters, can include copolymers of polyethylene terephthalate / polyethylene terephthalate, polyethylene terephthalate / propylene terephthalate, polyethylene terephthalate / butylene terephthalate, thermoplastic polyurethane / polyethylene terephthalate, polyester elastomer / polyethylene terephthalate, polyester elastomer / polybutylene terephthalate, as polyamides, nylon 6 / nylon 66, nylon 6 / nylon 610, nylon 6-nylon 66 copolymer / nylon 6 or 610, PEG copolymer of nylon 6 / nylon 6 or 610, thermoplastic polyurethane / nylon 6 or 610, as polyolefins, ethylene-propylene rubber microdispersed polypropylene / polypropylene, propylene-α-olefin copolymer / polypropylene, and various other combinations.

[0159] In this embodiment, when the short fibers and short yarns are made into fabric, from the viewpoint that good color development can be obtained by dyeing, polymers with different melting points are more preferably a combination of polyester or polyamide. Among them, if it is a combination of polyethylene terephthalate / polyethylene terephthalate copolymers as polyester, it has a suitable elasticity due to high bending recovery, and is therefore listed as a particularly preferred combination.

[0160] In addition, examples of copolymer components in the aforementioned copolymerized polyethylene terephthalate include succinic acid, adipic acid, azelaic acid, sebacic acid, 1,4-cyclohexanedicarboxylic acid, maleic acid, phthalic acid, isophthalic acid, and 5-sodium sulfonyl isophthalic acid. From the viewpoint of maximizing the shrinkage difference with polyethylene terephthalate, polyethylene terephthalate copolymerized with 5 to 15 mol% isophthalic acid is preferred.

[0161] (4) Uses

[0162] The short fibers and short yarns of this embodiment, by controlling the crimping method of each short fiber, not only exhibit a comfortable touch and fluffy and soft texture caused by the warm and delicate texture of cotton, but also exhibit functional properties such as water absorption.

[0163] Therefore, by containing short fibers of this embodiment in a portion, a unique fluffy and soft texture and water absorption caused by the gaps can be obtained. Thus, it can be well used in general clothing such as jackets, skirts, pants, and underwear, as well as sportswear and clothing materials. In addition, it can take full advantage of its comfort and be well used in a variety of fiber products for various daily uses such as carpets, sofas and other interior decoration products, car interior parts such as car seats, cosmetics, face masks, and health products. However, from the viewpoint that it can exhibit the unique touch and texture of natural materials, it is particularly preferred for clothing use as a short fiber yarn.

[0164] Furthermore, the short fibers of this embodiment can be used in various fabrics such as nonwoven fabrics and woven fabrics, but from the viewpoint of being suitable for the above-mentioned clothing applications, as a fabric that includes the short fiber yarn of this embodiment in part, it is particularly preferred to be a clothing fabric with excellent wearing comfort.

[0165] The following details an example of the method for manufacturing short fibers and short fiber yarns according to this embodiment.

[0166] (5) Methods for manufacturing short fibers

[0167] The objective of this invention is to obtain a short fiber yarn with a complex surface texture and inter-fiber gaps, similar to those of natural fibers, by incorporating short fibers with controlled crimp morphology and varying inter-fiber spacing. To obtain such a short fiber yarn, it is crucial to set the relationship between the crimp number and crimp diameter of the short fibers, composed of at least two polymers with different melting points, within a specific range, thereby varying the crimp number of each short fiber. To ensure that the crimp numbers of each short fiber are different, various methods can be employed, such as methods that differentiate the bonding surface directions of the short fibers in flat short fibers with the same cross-section and composite ratio, thereby differentiating the distance between the polymer centers of gravity; methods that differentiate the cross-sectional shape and composite ratio of the short fibers; and methods that blend flat short fibers with different crimp numbers that have been separately spun into yarns during the spinning process. In particular, from the viewpoints of yarn-making stability during spinning, processing stability during spinning, and yarn quality, the method that differentiates the bonding surface directions of the short fibers in flat short fibers with the same cross-section and composite ratio, thereby differentiating the distance between the polymer centers of gravity, is preferred.

[0168] As a method for producing short fiber yarn according to this embodiment, it can be manufactured by melt spinning, wet spinning, and dry-wet spinning, etc., which aim to produce short fibers from long fibers by cutting them short. However, from the viewpoint of improving productivity, melt spinning is preferred.

[0169] Alternatively, in melt spinning, it can be manufactured using a composite spinneret described later. Regarding the spinning temperature, it is preferable to set it to a temperature at which the polymer used primarily exhibits high melting point or high viscosity, thus demonstrating good flowability. This flowability temperature varies depending on the molecular weight, but stable manufacturing can be achieved if it is set between the polymer's melting point and melting point +60°C.

[0170] Spinning speeds can be implemented at around 500–6000 m / min, but can be appropriately varied depending on the properties of the polymer and the intended use of the short fibers. In particular, from the viewpoint of achieving high orientation and improving mechanical properties, setting the spinning speed to 500–2000 m / min and then stretching it promotes uniaxial orientation of the fibers, and is therefore preferred.

[0171] During stretching, the preheating temperature is preferably set appropriately based on the softening temperature, such as the glass transition temperature of the polymer. The upper limit of the preheating temperature is preferably a temperature that prevents yarn path disruption due to the spontaneous elongation of the composite fiber bundles during preheating. For example, in the case of PET with a glass transition temperature around 70°C, this preheating temperature is typically set to around 80–95°C.

[0172] Furthermore, the output per orifice in the spinneret used to manufacture the short fibers in this embodiment is preferably 0.1 to 10 g / min·orifice. By keeping the output within the above range, stable manufacturing is possible. After the extruded polymer stream is cooled and solidified, an oiling agent is applied, and the yarn is drawn by rollers reaching a predetermined circumferential speed. Then, it is stretched under heat and subjected to further post-processing, thereby obtaining a short fiber yarn made by twisting and plying the desired short fibers.

[0173] Furthermore, in this embodiment, the short fibers formed from at least two polymers with different melting points preferably have a melt viscosity ratio of less than 5.0 for the composite polymers. Setting the melt viscosity ratio within this range helps suppress excessive curling, making it easier to control the curling of the short fibers, which is the objective of this invention, and enabling the formation of complex inter-fiber voids and surface irregularities.

[0174] Furthermore, when manufacturing the short fibers of this embodiment, if a melt of a polymer with a large difference in melt viscosity is spun from the spinneret as a composite flow, a flow velocity difference arises due to the different resistance experienced by the walls within the spinneret orifice. This can sometimes cause the yarn to bend, resulting in the polymer on the lower viscosity side squeezing the polymer on the higher viscosity side. This yarn may then come into contact with the spinneret or interfere with the composite flow spun from other parts, leading to yarn breakage. From the above perspective, the melt viscosity ratio of the composite polymer is preferably less than 5.0.

[0175] In addition, a difference of less than 2.0 in the solubility parameter value is preferred, because it allows for the stable formation of a composite polymer flow, resulting in composite fibers with a good composite cross-section.

[0176] As the spinneret used in manufacturing the composite fiber bundle of this embodiment, the composite spinneret described in Japanese Patent Application Publication No. 2011-208313 is preferably used, for example.

[0177] Figure 7 The composite spinneret shown is assembled within the spinning assembly in a stacked configuration, consisting of three main components: metering plate 1, distribution plate 2, and discharge plate 3, for use in spinning. Incidentally, Figure 7 This example uses three polymers: polymer A, polymer B, and polymer C. Conventional composite spinnerets struggle to combine more than three polymers; therefore, in the manufacture of short fibers in this embodiment, it is preferable to use... Figure 7 The composite spinneret shown utilizes a micro-flow path.

[0178] exist Figure 7 In the spinneret component shown, the metering plate 1 measures the amount of polymer in each discharge hole and each distribution hole and allows the polymer to flow in. The distribution plate 2 controls the cross-section and cross-sectional shape of each composite fiber. The discharge plate 3 compresses the composite polymer flow formed by the distribution plate 2 and discharges it.

[0179] At this point, in order to achieve a composite cross-section where the short fibers have a flat cross-section, as listed in the preferred scope of this embodiment, and the bonding surface direction is different for each short fiber, it is only necessary to set the shape of the discharge orifice of the discharge plate 3 to a flat orifice, and to control the flow of the composite polymer in the distribution plate 2 in a manner that the bonding surface direction of the polymer is different for each discharge orifice. From the viewpoint that it is possible to control any composite cross-section for each discharge orifice, in this embodiment, it is preferable to use a composite cross-section such as... Figure 7 The composite spinneret shown utilizes a micro-flow path.

[0180] Furthermore, to avoid complicating the explanation of the composite spinneret, it is not illustrated. However, regarding the components stacked on the metering plate 1, any components that form a flow path in conjunction with the spinning machine and spinning assembly will suffice. By designing the metering plate 1 incorporating existing flow path components, existing spinning assemblies and their components can be directly utilized. Therefore, it is not necessary to develop a dedicated spinning machine specifically for this spinneret.

[0181] Alternatively, multiple flow path plates can actually be stacked between the flow path and metering plate 1 or between metering plate 1 and distribution plate 2. The purpose is to establish an efficient flow path for transporting polymer in both the spinneret cross-sectional direction and the composite fiber cross-sectional direction, leading to the distribution plate 2. The composite polymer stream ejected from the ejector plate 3, after cooling and solidification according to the above manufacturing method, is coated with an oil and drawn by rollers at a predetermined circumferential speed. Then, it is stretched under heat and further post-processed to become a short-fiber yarn made by twisting and plying the desired short fibers.

[0182] In the process of stretching the unstretched yarn after spinning, the unstretched yarn is bundled into 30-300 ktex bundles and stretched by 2-5 times under steam or hot water to form a stretched yarn bundle. Then, it undergoes tension heat treatment and is mechanically crimped using a stuffing crimping machine or similar device to obtain a crimped yarn bundle.

[0183] Next, the crimped filaments are dried, and an aqueous solution of finishing oil is applied to the filaments by spraying, thereby cutting them to produce the short fibers of this embodiment.

[0184] [Fiber length]

[0185] In this embodiment, the preferred fiber length of the short fibers is 20 to 120 mm. Within this range, the process flow in the spinning process is good, and stable production of short fiber yarn becomes possible. Furthermore, if the length is 30 to 90 mm, pilling during twisting and plying can be suppressed, resulting in fabric with excellent appearance quality; therefore, this range can be listed as a more preferred option.

[0186] [Number of curls before heat treatment]

[0187] In this embodiment, the short fibers have a crimp number of 5 to 30 peaks / 25 mm before heat treatment.

[0188] The crimp number mentioned here before heat treatment is the value of the crimp number obtained by cutting the crimped fiber bundle without heat treatment, according to the method of JIS L1015 (2010) 8.12.1.

[0189] By achieving a crimp count of 5 crimps / 25mm or higher, the short fibers exhibit good entanglement, resulting in excellent carding throughput. From this perspective, a higher crimp count is better, with 8 crimps / 25mm or higher being more preferred, and 10 crimps / 25mm or higher being particularly preferred.

[0190] Furthermore, since the crimp count is below 30 crimps / 25mm, the number of neps will not increase significantly after passing through the carding machine, and the unevenness of the staple yarn will not increase drastically, resulting in good high-level processing performance and staple yarn quality. From this perspective, the lower the crimp count, the better, preferably below 25 crimps / 25mm, and especially preferably below 20 crimps / 25mm.

[0191] [Heat Treatment Conditions]

[0192] In order to control the crimping morphology of the short fibers, which is important for embodiments of the present invention, it is important to set the tension heat treatment temperature, the temperature of the stretched filaments entering the crimping machine, the crimping pressure of the crimping machine, and the drying temperature of the crimped filaments after crimping.

[0193] Tension heat treatment involves heat setting while maintaining tension, followed by cooling with cooling water to below the glass transition temperature to fix the molecular chain structure. This suppresses the crimping of the yarn bundle during the drying process, improves the carding permeability of short fibers, and allows the desired crimp shape to be achieved through heat treatment after spinning.

[0194] The preferred heat treatment temperature is 100–190°C, and the preferred heat treatment time is 3 seconds or more but less than 20 seconds. When the treatment temperature is below 100°C, excessive crimping may occur during the subsequent drying process of the crimped filaments, leading to deterioration in the carding permeability of the short fibers. Furthermore, when the treatment temperature is above 190°C, the desired crimp shape may not always be achieved through heat treatment after spinning.

[0195] The temperature of the drawn yarn bundle entering the crimping machine is preferably 20–60°C. Below 20°C, the carding passability may sometimes deteriorate due to the low crimp count of the short fibers. In addition, above 60°C, the carding process may sometimes result in more neps after carding due to the high crimp count of the short fibers, and the unevenness of the short fiber yarn may sometimes increase drastically.

[0196] The preferred packing pressure for a packing crimping machine is 98–294 kPa. When the pressure is less than 98 kPa, the number of crimps in the short fibers decreases, while when the pressure is higher than 294 kPa, the number of crimps in the short fibers tends to increase.

[0197] The preferred drying temperature for the crimped filament bundles is 80–120°C. If the temperature is below 80°C, the crimped filament bundles may not dry sufficiently. If the temperature is above 120°C, crimping may occur during the drying process. Since the short fibers have a high number of crimps, more neps may form after carding, or the unevenness of the short fiber yarn may increase drastically.

[0198] (7) Method for manufacturing staple fiber yarn

[0199] When the short fibers of this embodiment are made into short fiber yarn, the short fiber yarn can be manufactured by known spinning methods, such as using a ring spinning machine (including a compaction / vortex spinning machine) or an air-jet spinning machine, to twist and ply the short fibers to form short fiber yarn. In addition, when making short fiber yarn, it can also be compounded and blended with filaments as needed.

[0200] In this embodiment, the short fibers are twisted and plied into short-fiber yarn, and then temporarily subjected to advanced processing such as weaving and knitting. During subsequent heat treatment, the short fibers curl, thereby creating a complex surface texture or inter-fiber gaps in the short-fiber yarn. Due to its unique fiber morphology, this short-fiber yarn can produce clothing fabrics with excellent wearing comfort, in addition to a comfortable touch and soft, fluffy texture caused by the warm and delicate texture of cotton, which is not found in conventional materials, and functional properties such as water absorption. To maximize the above effects, the twist coefficient of the short-fiber yarn in this embodiment is preferably 2 to 6.

[0201] The twist coefficient mentioned here can be calculated using the following method.

[0202] First, the yarn count was determined according to the cotton yarn count determination method of JIS L1095 (2010) 9.4.1, which specifies the standard tex count for general staple yarns. Next, the twist was determined according to JIS L1095 (2010) 9.15.1A, and the result was calculated as follows: "Twist coefficient = Twist / (Yarn count)". 1 / 2 The value obtained by the formula is rounded to the nearest whole number and used as the twist coefficient.

[0203] If the twist coefficient is 2 or higher, the torque caused by the curling of the short fibers in this embodiment is close to the torque caused by twisting during spinning. Therefore, even under the constraints of fabric structures such as woven and knitted fabrics, the short fibers can easily exhibit curling through heat treatment, which is preferable. Furthermore, from the viewpoint that a stronger twisting constraint can suppress pilling that results in poor appearance due to the short fibers being pulled out and entangled during fabric friction, a twist coefficient of 3 or higher is more preferable.

[0204] However, if the twist coefficient is too large, the torque during spinning is greater than the torque caused by the crimping of short fibers, which may sometimes inhibit the crimping of short fibers during heat treatment. Therefore, the twist coefficient is preferably 6 or less, and more preferably 5 or less.

[0205] The staple fiber yarn of this embodiment preferably has a count of 20 to 100. This count is frequently used not only in thin fabrics such as shirts, underwear, and sportswear, but also in denim and workwear uniforms. The count can be appropriately selected according to the intended use. Furthermore, the staple fiber of this embodiment exhibits crimp after heat treatment when it is made into staple fiber yarn. Therefore, it can be controlled to a crimp shape suitable for processing during spinning. Unlike conventional staple fibers with parallel cross-sections that exhibit the same crimp shape, each staple fiber has a different crimp, resulting in inconsistent crimp phases. This improves fiber opening during carding, and even fine counts of 60 to 100 can produce staple fiber yarn with excellent handling and quality.

[0206] (8) Fabric manufacturing methods

[0207] The short fiber yarn used in this embodiment can be used as at least a part to manufacture woven fabrics and knitted fabrics of the above-described fabric structure using known methods.

[0208] Example

[0209] The following examples illustrate the short fibers and short fiber yarns of the present invention.

[0210] The following evaluations were conducted on the embodiments and comparative examples.

[0211] A. Melt viscosity of the polymer

[0212] The sheet polymer was dried using a vacuum dryer to reduce its moisture content to below 200 ppm. The melt viscosity was measured using a Capilograph capillary rheometer from Toyo Seiki, with the strain rate gradually varied. The measurement temperature was the same as the spinning temperature, and the time from sample introduction into the heating furnace under a nitrogen atmosphere to the start of the measurement was 5 minutes. The shear rate was 1216 s⁻¹. 1 The value is used to evaluate the melt viscosity of the polymer.

[0213] B. Melting point of the polymer

[0214] The sheet polymer was dried in a vacuum dryer to a moisture content of less than 200 ppm. Approximately 5 mg was weighed and subjected to DSC analysis using a TA Instruments Q2000 differential scanning calorimeter. The temperature was increased from 0°C to 300°C at a rate of 16°C / min, and then held at 300°C for 5 minutes. The melting point was calculated based on the observed melting peaks during the heating process. Each sample was measured three times, and the average value was taken as the melting point. Additionally, in cases where multiple melting peaks were observed, the temperature of the highest melting peak was taken as the melting point.

[0215] C. Fineness, fiber length

[0216] The fineness and fiber length of short fibers were determined according to the methods shown in JIS L 1015 (2010) 8.4A and 8.5A.

[0217] D. Flatness

[0218] Short fibers or short yarns were embedded with embedding agents such as epoxy resin, and images of the fiber cross-section perpendicular to the fiber axis were captured using a HITACHI scanning electron microscope (SEM). Then, a randomly selected short fiber from the captured images was analyzed using Mitani Shoji's image analysis software (WinROOF). Figure 1 As shown in (a), the line connecting the two furthest points (a1, a2) on the outer periphery of the composite fiber is taken as the major axis, and the line connecting the intersection point (b1, b2) of the line passing through the midpoint of the major axis and orthogonal to the major axis and the outer periphery of the fiber is taken as the minor axis. The length of the major axis is divided by the length of the minor axis to calculate the flatness. The same operation is performed on 20 short fibers, and the arithmetic mean of these results is calculated. The result is rounded to two decimal places and taken as the flatness.

[0219] E. Fiber diameter

[0220] Short fibers or short yarns were embedded with embedding agents such as epoxy resin, and images of the fiber cross-section perpendicular to the fiber axis were captured using a HITACHI scanning electron microscope (SEM). Next, a randomly selected short fiber from the captured images was analyzed using WinROOF image analysis software manufactured by Mitani Shoji. The area of ​​the short fiber was measured, and the diameter of the circle was calculated in μm, rounded to one decimal place. The same operation was performed on 20 short fibers, and the arithmetic mean of the results was calculated, rounded to one decimal place, and the resulting value was taken as the fiber diameter (μm).

[0221] F. Coefficient of variation (CV%) of the value of (distance between polymer centroids / fiber diameter)

[0222] Short fibers or short yarns were embedded with embedding agents such as epoxy resin, and images of the fiber cross-section perpendicular to the fiber axis were captured using a HITACHI scanning electron microscope (SEM). Next, a single short fiber randomly selected from the captured images was analyzed using WinROOF, a computer software manufactured by Mitani Shoji, to determine the area of ​​the composite fiber. The diameter of the composite fiber was calculated in μm and converted to one decimal place. This value was taken as the fiber diameter (μm).

[0223] In addition, for the same short fibers as described above, such as Figure 2 As shown in Figure A, the centroids (Gx, Gy) of the low-melting-point polymer x and the high-melting-point polymer y in the cross-section of the composite fiber are connected by a straight line, and the length of this line is measured to one decimal place in μm. The obtained value is taken as the distance between the centroids of the polymers (μm).

[0224] For the fiber diameter and polymer centroid distance obtained above, calculate the arithmetic mean of their ratio (polymer centroid distance / fiber diameter), round to one decimal place, and use the result as (polymer centroid distance / fiber diameter). Perform the same evaluation on 20 randomly selected short fibers, calculate the standard deviation and mean of the evaluation results, and calculate the value obtained by dividing the standard deviation by the mean and then multiplying by 100, rounding to the nearest decimal. Use the resulting value as the coefficient of variation (CV%) (%) of the (polymer centroid distance / fiber diameter) value.

[0225] G. Number of curls and coefficient of variation (CV%) of number of curls

[0226] Short fibers were subjected to dry heat treatment at 180°C for 5 minutes without load. The crimp morphology of a single short fiber was observed according to JIS L1015 (2010) 8.12.1, and the crimp number was determined accordingly. This treatment was performed on 20 different short fibers, and their mean and standard deviation were calculated. For the mean, the value was rounded to the nearest whole number as the crimp number (peak / 25mm). The standard deviation was divided by the mean and then multiplied by 100, and the value was rounded to the nearest whole number. The resulting value was used as the coefficient of variation (CV%) of the crimp number among short fibers.

[0227] In addition, the short fibers obtained by cutting the crimped filament bundles are not subjected to heat treatment. Instead, the crimp number is calculated according to the method of JIS L1015 (2010) 8.12.1, and this value is the crimp number (peak / 25mm) before heat treatment.

[0228] H. Curl diameter, number of curls / curl diameter

[0229] After subjecting short fibers to dry heat treatment at 180°C without load for 5 minutes, the crimp morphology of one short fiber was observed according to JIS L1015 (2010) 8.12.1. In this morphology, the fiber crimped as follows... Figure 6 The apex of the first peak (M1) and the last valley (V2) in the peak (M1) → valley (V1) → peak (M2) → valley (V2) section shown is connected by a straight line (S1). The distance Le (mm) between the intersection points of two straight lines (S2, S3) parallel to this line and passing through the apex of the valley (V1) and peak (M2), and a straight line perpendicular to S1, is calculated. This operation is performed at any three or more locations on each short fiber, and the arithmetic mean is calculated. Furthermore, the arithmetic mean of the above measurements is calculated for 20 different short fibers, rounded to the third decimal place, and the resulting value is taken as the curl diameter (mm).

[0230] In addition, divide the number of curls obtained in item G by the curl diameter obtained above, round the result to the nearest whole number, and use the result as the number of curls / curl diameter.

[0231] I. Yarn stability

[0232] In the yarn manufacturing process of each embodiment and comparative example, the yarn manufacturing stability was determined according to the following criteria in four levels based on the number of yarn breaks per million meters (times / million meters).

[0233] S: Excellent yarn stability (number of yarn breaks < 1.0)

[0234] A: Good yarn stability (1.0 ≤ number of yarn breaks < 5.0)

[0235] B: Possesses yarn-making stability (5.0 ≤ number of yarn breaks < 10.0)

[0236] C: Poor yarn stability (10.0≤ number of yarn breaks).

[0237] J. Count, twist coefficient

[0238] The count is determined by the cotton count determination method according to JIS L1095 (2010) 9.4.1, which specifies the standard tex count for general staple yarns.

[0239] Next, the twist was determined according to JIS L1095 (2010) 9.15.1A. The twist coefficient was calculated as follows: Twist Coefficient = Twist / (Number of Count) 1 / 2 The value obtained by the formula is rounded to the nearest whole number and used as the twist coefficient.

[0240] K. Interfiber gap distance, coefficient of variation (CV%) of interfiber gap distance

[0241] For fabrics made of staple fiber yarns, images of the fabric cross-section perpendicular to the fiber axis of the staple fiber yarn are captured using a HITACHI scanning electron microscope (SEM) at a magnification that allows observation of more than 20 short fibers constituting the staple fiber yarn. For each image captured, such as... Figure 5 Draw a circle to accommodate 20 short fibers as shown. For the 20 short fibers inside this circle, select any one short fiber and find the intersection points of the straight line connecting the centroid G of this short fiber and its adjacent short fibers with the surfaces of each fiber. Measure the distance between the intersection points in μm to one decimal place. Here, "adjacent" means that there are no other short fibers on the straight line connecting the centroids of any two fibers. Among the 20 short fibers inside the circle, such as... Figure 5 As shown, this operation is performed on all adjacent short fibers to calculate their mean and standard deviation. The mean is rounded to the nearest whole number and used as the interfiber gap distance (μm). The standard deviation is divided by the mean and then multiplied by 100 and rounded to the nearest whole number. The resulting value is used as the coefficient of variation (CV%) of the interfiber gap distance.

[0242] L. Porosity

[0243] For fabrics made of staple fiber yarns, images of the fabric cross-section perpendicular to the fiber axis of the staple fiber yarn were captured using a scanning electron microscope (SEM) at a magnification that allows observation of more than 20 short fibers constituting the staple fiber yarn. For each image captured, such as... Figure 5 A circle containing 20 short fibers is depicted as shown. The cross-sectional area of ​​this circle is calculated by subtracting the total cross-sectional area of ​​the 20 fibers present inside the circle from the cross-sectional area of ​​the circle itself. In this case, if more than half of the fibers are present inside the circle, they are counted as one fiber. The cross-sectional area is expressed in μm. 2 The measurement is taken to one decimal place. The value is then calculated by dividing the calculated value by the cross-sectional area of ​​the circle, multiplying by 100, and rounding to the first decimal place. The resulting value is taken as the porosity (%).

[0244] M. Processing stability

[0245] In the spinning process of each embodiment and comparative example, the processing stability was judged according to the following criteria in four grades based on the number of yarn breaks per million meters (times / million meters).

[0246] S: Excellent processing stability (number of wire breaks < 5.0)

[0247] A: Good processing stability (5.0 ≤ number of wire breaks < 10.0)

[0248] B: It has processing stability (10.0 ≤ number of wire breaks < 20.0)

[0249] C: Poor processing stability (20.0≤ number of wire breaks).

[0250] N. Short fiber yarn quality

[0251] For the staple fiber yarns of each embodiment and comparative example, a yarn defect detection machine (USTER Evenese Tester (Tester5)) was used to determine the coarseness unevenness, fineness unevenness, and number of neps relative to the average thickness per kilometer, according to JIS L1095 (2010) 9.20.2B. Based on the total number of yarn unevenness and neps, the yarn quality was judged into 4 grades according to the following criteria.

[0252] S: Excellent yarn quality (yarn unevenness, nipple count <100)

[0253] A: Good yarn quality (100≤ yarn unevenness, neps count<200)

[0254] B: Meets yarn quality requirements (200≤ yarn unevenness, neps count<500)

[0255] C: Poor yarn quality (500≤ yarn unevenness, number of knots).

[0256] O. Fabric texture evaluation (fluff, softness, warm and delicate feel, texture)

[0257] The number of staple yarns is adjusted to achieve a warp cover factor (CFA) of 20 and a weft cover factor (CFB) of 15 to weave a plain weave fabric. The CFA and CFB mentioned here refer to the warp and weft densities of the fabric measured in a 2.54 cm interval according to JIS L1096 (2010) 8.6.1, based on the formula: "CFA = warp density / (warp count)". 1 / 2 "CFB = weft density / (weft yarn count)" 1 / 2 The value is obtained by using the formula "".

[0258] After dyeing the obtained fabric under the following conditions, the following methods were used to evaluate the four textures: fluffiness, softness, warm and delicate feel, and texture.

[0259] (Dyeing process)

[0260] After refining in 80°C hot water containing surfactant for 10 minutes, it undergoes a relaxation treatment in 130°C hot water for 30 minutes. Next, it is heat-set at 180°C dry heat for 5 minutes. Afterwards, finishing processes such as singeing, weight reduction, and sanding are performed as needed.

[0261] O-1. Fluffiness

[0262] A Telotec PG-14J compression tester was used to measure the thickness (cm) of a 20cm × 20cm fabric under a constant pressure (0.7kPa), and the fabric volume was calculated. Next, the weight (g) of the fabric was calculated and divided by the resulting volume, rounded to two decimal places. This value was then used as the apparent density of the fabric (g / cm³). 3 Based on the obtained apparent density, the fluffiness is judged according to four levels based on the following criteria.

[0263] S: Excellent fluffiness (apparent density ≤ 0.5)

[0264] A: Good fluffiness (0.5 < apparent density ≤ 0.7)

[0265] B: Fluffiness (0.7 < apparent density ≤ 0.9)

[0266] C: Poor fluffiness (0.9 < apparent density).

[0267] O-2. Softness

[0268] Using a KATO TECH pure bending tester (KES-FB2), a 20cm x 20cm fabric was held with an effective sample length of 20cm x 1cm, and the maximum curvature in the warp direction was measured to be ±2.5cm. -1 Under the condition of bending the fabric, the curvature was calculated to be 0.5 cm. -1 and 1.5cm -1 The difference in bending moment per unit width (gf·cm / cm) divided by the curvature difference per cm -1 The value of "" and "curvature -0.5cm" -1 and -1.5cm -1 The difference in bending moment per unit width (gf·cm / cm) divided by the curvature difference per cm -1 The values ​​of "" are calculated, and their average is calculated. This operation is performed 3 times at each location, for a total of 10 locations. The arithmetic mean of these results is calculated, rounded to the fourth decimal place, and then divided by 100. The resulting value is taken as the bending stiffness B × 10. -2 (gf·cm) 2 / cm). Based on the obtained bending stiffness B×10 -2 The softness is judged according to the following standards in four grades.

[0269] S: Excellent flexibility (bending stiffness B×10) -2 ≤2.0)

[0270] A: Good flexibility (2.0 < bending stiffness B × 10) -2 ≤3.0)

[0271] B: Flexibility (3.0 < Flexural stiffness B × 10) -2 ≤4.0)

[0272] C: Poor flexibility (4.0 < flexural stiffness B × 10) -2 ).

[0273] O-3. Warm and delicate feel, textured feel

[0274] Using the TL201Tt static tribometer manufactured by Trinity Lab, at 1 cm 2 A component with a geometric fingerprint pattern applied to polyurethane and having a hardness equivalent to a fingertip is installed on the contact terminal of the area. While applying a load of 20g, it slides 30mm across the surface of the test object at a speed of 10mm / sec, obtaining a friction curve representing the frictional force (gf) relative to the travel distance. Based on the obtained friction curve, the static friction coefficient and kinetic friction coefficient are calculated according to JIS K7125 (1999). The kinetic friction coefficient is subtracted from the obtained static friction coefficient, and the result is rounded to the third decimal place. This value is taken as the difference between the static friction coefficient and the kinetic friction coefficient. Based on the difference between the obtained static friction coefficient and the kinetic friction coefficient, the smooth and delicate feel is judged into four levels according to the following criteria.

[0275] S: Excellent smooth and delicate feel (0.40≤difference between static friction coefficient and dynamic friction coefficient)

[0276] A: A pleasantly smooth and delicate feel (0.35 ≤ the difference between static and dynamic friction coefficients < 0.40)

[0277] B: It has a warm and delicate feel (0.30 ≤ the difference between the static friction coefficient and the dynamic friction coefficient < 0.35)

[0278] C: Poor smooth and delicate feel (difference between static friction coefficient and dynamic friction coefficient < 0.30).

[0279] In addition, calculate the standard deviation of the coefficient of kinetic friction within the range of 5–25 mm, and round the value to the third decimal place as the variation in kinetic friction. Based on the obtained variation in kinetic friction, determine the unevenness of the surface according to the following four levels.

[0280] S: Excellent texture (0.70≤ dynamic friction variation)

[0281] A: Good texture (0.65 ≤ dynamic friction variation < 0.70)

[0282] B: Has a textured feel (0.60 ≤ dynamic friction variation < 0.65)

[0283] C: Poor texture (dynamic friction variation < 0.60).

[0284] P. Fabric Function Evaluation (Water Absorption and Quick-Drying Properties, Stretchability)

[0285] After fabrication and dyeing under the same conditions as the fabric texture evaluation, the following methods were used to evaluate the water absorption and quick-drying properties and the stretchability.

[0286] P-1. Absorbent and quick-drying properties

[0287] Regarding water absorption and quick-drying properties, 0.1 cc of water was added to a 10cm x 10cm fabric. The weight of the fabric was measured every 5 minutes at a temperature of 20°C and a relative humidity of 65% RH. The time (in minutes) for the residual moisture content to drop below 1.0% was calculated. This operation was performed at a total of 3 locations. The arithmetic mean of these results was rounded to the nearest decimal and used as the moisture diffusion time (in minutes). Based on the obtained moisture diffusion time, water absorption and quick-drying properties were judged into 4 levels according to the following criteria.

[0288] S: Excellent absorbency and quick-drying properties (moisture diffusion time ≤ 15).

[0289] A: Excellent water absorption and quick-drying properties (15 < moisture diffusion time ≤ 30)

[0290] B: It has water-absorbing and quick-drying properties (30 < moisture diffusion time ≤ 60).

[0291] C: Absorbs water quickly but dries poorly (60 < moisture diffusion time).

[0292] P-2. Elasticity

[0293] The stretchability was tested according to the elongation rate method A (constant rate elongation method) as described in JIS L1096 (2010), section 8.16.1. Additionally, using the strip method with a load of 17.6 N (1.8 kg), the test conditions were: sample width 5 cm × length 20 cm, clamping interval 10 cm, and stretching speed 20 cm / min. Furthermore, following JIS L1096 (2010), an initial load equivalent to 1 m of sample width was used. The arithmetic mean of three tests conducted in the weft direction of the fabric was calculated, and the value rounded to the nearest whole number was taken as the elongation rate (%). Based on the obtained elongation rate, the stretchability was judged into four grades according to the following standards.

[0294] S: Excellent elasticity (10≤ elongation)

[0295] A: Good elasticity (7 ≤ elongation < 10)

[0296] B: It has elasticity (4 ≤ elongation < 7).

[0297] C: Poor elasticity (elongation < 4%).

[0298] Q. Fabric quality evaluation (appearance quality)

[0299] After fabric production and dyeing under the same conditions as for fabric texture evaluation, an automatic angle-dependent photometer (GONIOPHOTOMETER GP-200 model) manufactured by the Murakami Color Technology Research Institute was used to incident light on each sample at an incident angle of 60°. The light intensity was determined every 0.1° within the range of 0° to 90° by measuring the two-dimensional reflected light distribution. The maximum light intensity (spectral reflection) near the 60° incident angle was calculated, divided by the minimum light intensity (diffuse reflection) near the 0° incident angle. This operation was performed three times at each location, for a total of 10 locations. The arithmetic mean of these results was calculated, and the value rounded to two decimal places was taken as the glare level. Based on the obtained glare level, the appearance quality of the fabric was judged into four grades according to the following standards.

[0300] S: Excellent appearance quality (glare ≤ 1.2)

[0301] A: Good appearance quality (1.2 < glare ≤ 1.6)

[0302] B: Possesses aesthetic appeal (1.6 < glare ≤ 2.0)

[0303] C: Poor appearance quality (2.0 < glare).

[0304] R. Anti-pilling properties

[0305] After fabric production and dyeing under the same conditions as for fabric texture evaluation, the pilling was measured according to the method shown in JIS L1076 (2012) Method A, with each 0.5 grade representing a level from 1 to 5. Based on the obtained level assessment results, the anti-pilling properties were judged into 4 grades according to the following criteria.

[0306] S: Excellent anti-pilling properties (Grade rating: 4.5 or above)

[0307] A: Good anti-pilling properties (Grade rating: 3.5, 4)

[0308] B: Good anti-pilling properties (Grade rating: 2.5, 3)

[0309] C: Poor anti-pilling properties (Level 2 or below).

[0310] [Example 1]

[0311] Polyethylene terephthalate (IPA copolymer PET, melt viscosity: 140 Pa·s, melting point: 232 °C) was prepared as polymer 1, and polyethylene terephthalate (PET, melt viscosity: 130 Pa·s, melting point: 254 °C) was prepared as polymer 2.

[0312] After these polymers were melted separately at 290°C, polymer 1 and polymer 2 were weighed to achieve a 50 / 50 area ratio for the composite cross-section. Then, the polymers were fed into the assembly... Figure 7 In the spinning assembly of the composite spinneret shown, the polymer flowing in is ejected from the ejection orifice, forming a structure like... Figure 1 The flattened composite cross section shown in (a) is formed by polymer 1 and polymer 2 joined together in a parallel manner, and the bonding surfaces of the composite fibers are oriented differently. Figure 4 (The six types are examples of this composite cross-section). In this case, the discharge hole has 500 holes.

[0313] After the extruded composite polymer stream is cooled and solidified, an oiling agent is applied, and the yarn is drawn at a spinning speed of 1300 m / min to obtain undrawn yarn. Then, while 20 undrawn yarns are aligned, they are guided to hot water at 90°C for stretching to obtain a drawn yarn bundle. The stretched yarn bundle is then subjected to tension heat treatment using heated rollers at 140°C and fed into a crimping machine at a temperature of 30°C and a packing pressure of 1.5 kg / cm². 2 Mechanical crimping is applied under condition G to obtain crimped filament bundles. After drying the obtained crimped filament bundles at 80°C, a finishing oil is applied, and the bundles are cut into 38mm long fibers using a rotary cutter to obtain short fibers with a fineness of 1.5 dtex (fiber diameter 12μm). At this point, the number of yarn breaks is 2.5 times / million meters, exhibiting good yarn-making stability.

[0314] All the obtained short fibers have a flat cross-sectional shape with a flatness of 1.8, and the coefficient of variation (CV%) of the (distance between polymer centroids / fiber diameter) between the short fibers is 18%. In addition, the number of crimps is 42 peaks / 25mm (the number of crimps before heat treatment is 15 peaks / 25mm), the coefficient of variation (CV%) of the number of crimps is 25%, the crimp diameter is 0.21mm, and the number of crimps / crab diameter is 200, which confirms that it is the short fiber of this embodiment.

[0315] Using 100% of the obtained short fibers, a short fiber yarn with a count of 40 and a twist coefficient of 4 is obtained. In addition, the number of yarn breaks during spinning is 6.7 times / million meters, which shows good processing stability. The yarn unevenness and the total number of neps are 155 / million meters, which shows good short fiber yarn quality.

[0316] Using the obtained staple fiber yarn, the yarn count is adjusted to achieve a warp cover factor (CFA) of 20 and a weft cover factor (CFB) of 15 to weave a plain weave fabric. Then, after scouring in hot water containing surfactant at 80°C for 10 minutes, it undergoes a relaxation treatment in hot water at 130°C for 30 minutes. Next, it is heat-set at 180°C for 5 minutes. Finally, as needed, it undergoes finishing processes such as singeing, weight reduction, and napping to obtain a fabric composed of staple fiber yarn.

[0317] This fabric, composed of short-fiber yarns, exhibits crimp by being made of short fibers with a specific number of crimps corresponding to the crimp diameter. Even in short-fiber yarns where the short fibers are twisted and constrained, adjacent short fibers can not be densely packed together, thus exhibiting crimp. By forming voids caused by crimping, it has high porosity (porosity: 55%) and large inter-fiber voids (inter-fiber void distance: 8μm), thus achieving a fluffy texture (apparent density: 0.6g / cm³). 3 ), soft (bending stiffness B: 2.7×10), soft (flexural stiffness B: 2.7×10). -2 gf·cm / cm) and good elasticity (elongation: 9%).

[0318] Furthermore, due to the mixture of short fibers with different crimp numbers, the complex inter-fiber gaps, with a coefficient of variation (CV%) of 80% for the inter-fiber spacing, create a complex uneven surface. This results in a fabric that combines a smooth, delicate feel (difference between static and dynamic friction coefficients: 0.37) with a pleasantly textured feel (dynamic friction variation: 0.67), providing a comfortable touch reminiscent of cotton. Simultaneously, the presence of fine gaps allows for excellent water absorption and quick-drying properties (moisture content: 25 minutes). Therefore, fabrics formed from this short-fiber yarn are excellent clothing fabrics that combine superior texture and functionality directly related to human comfort.

[0319] Furthermore, the complex inter-fiber gaps that create diffuse light reflection suppress uneven appearance (glare), resulting in a fabric with excellent appearance quality (glare: 1.3). Additionally, even with well-constrained twist of short fibers, crimping is still achieved, thus providing properties suitable for apparel fabrics such as "few appearance defects caused by short fibers being pulled out and entangled during fabric friction" and "good anti-pilling properties (level 4)." These results are shown in Table 1-1.

[0320] [Comparative Example 1]

[0321] Except for the fact that the orientation of the bonding surfaces of the short fibers remains unchanged (only... Figure 1 Except for (a), all other cases were carried out in accordance with Example 1.

[0322] In Comparative Example 1, since the coefficient of variation (CV%) of the number of crimps between short fibers was 14%, there were few short fibers with different numbers of crimps. Therefore, the coefficient of variation (CV%) of the interfiber gap distance in the resulting short fiber yarn was also 57%, indicating a small deviation in gap size. Consequently, the fabric made from this short fiber yarn had a small surface roughness and lacked the comfortable feel caused by a warm and delicate texture. The results are shown in Table 1-1.

[0323] [Comparative Example 2]

[0324] In addition to changing the cross-sectional shape of short fibers to Figure 3 Except for the circular cross-section shown (where the orientation of the joint surfaces of the composite fibers remains unchanged), all other procedures were carried out in accordance with Example 1.

[0325] In Comparative Example 2, besides the coefficient of variation (CV%) of the number of crimps between short fibers being 11%, indicating a small number of short fibers with different crimp numbers, the circular cross-section facilitated the consistency of crimp phases between short fibers with the same crimp morphology. Consequently, the resulting short fiber yarn had a small inter-fiber gap distance of 3 μm, and a low CV% of 49%, indicating minimal deviation in gap size. Therefore, the fabric formed from this short fiber yarn, besides lacking sufficient bulk, had a small surface texture, lacking the comfortable feel derived from a warm and delicate texture. The results are shown in Table 1-1.

[0326] [Comparative Example 3]

[0327] Except for replacing polymer 1 with PET, which is the same as polymer 2, all procedures were carried out in accordance with Comparative Example 1.

[0328] In Comparative Example 3, since the short fibers were composed of the same polymer, the gaps caused by crimping could not be obtained in the short fiber yarn. Therefore, the fabric formed from this short fiber yarn not only lacked a fluffy and soft texture, but also failed to exhibit surface texture. It not only lacked the comfortable touch brought by a warm and delicate texture, but also had insufficient water absorption, quick-drying properties, elasticity, and appearance quality. The results are shown in Table 1-1.

[0329] [Example 2]

[0330] In addition to using the same PET as polymer 2 to coat the short fiber surface and becoming as... Figure 1 Except for the composite cross section shown in (b), all other procedures were carried out according to Example 1. Furthermore, the ratio of the minimum PET thickness S to the fiber diameter D, obtained by the above method, is S / D, which is 0.03.

[0331] In Example 2, since the surface layer of the short fibers is only PET, peeling at the interface does not occur due to friction or impact, thus maintaining the fiber properties well. This results in excellent processing stability and short fiber yarn quality during spinning. Furthermore, by mitigating the cooling difference between PET and copolymer PET, yarn bending after exiting the spinneret can be suppressed, leading to excellent yarn production stability. The results are shown in Table 1-1.

[0332] [Example 3]

[0333] In addition to changing the cross-sectional shape of short fibers to, for example Figure 1 Except for the flat, multi-leaf shape with four protrusions on the surface shown in (c), all other embodiments are carried out in accordance with Example 1.

[0334] In Example 3, by creating an uneven surface on the short fibers, diffuse reflection of light is increased, and the uneven appearance (glare) of the fabric made from the short fiber yarn is suppressed, resulting in excellent appearance quality. Furthermore, by combining short fibers with an uneven surface, and adding fine irregularities to the surface of the short fiber yarn, the comfortable touch and quick-drying properties caused by the smooth and delicate texture are also improved. The results are shown in Tables 1-2.

[0335] [Example 4]

[0336] In addition to changing the cross-sectional shape of short fibers to, for example Figure 1 Except for the flat hollow shape shown in (d) which has a hollow center with a hollow ratio of 20%, all other cases were carried out in accordance with Example 1.

[0337] In Example 4, by creating hollow spaces within the short fibers, diffuse light reflection increased, suppressing uneven appearance in the fabric composed of short fiber yarns and achieving excellent appearance quality. Furthermore, by combining short fibers with hollow interiors, not only were fine interfiber gaps created in the short fiber yarns, but bulkiness and quick-drying properties were also improved. The results are shown in Tables 1-2.

[0338] [Examples 5 and 6]

[0339] Except for changing the flatness of the short fibers to 1.3 (Example 5) and 3.5 (Example 6), all other procedures were carried out in accordance with Example 1.

[0340] In Example 5, as the flatness of the short fibers decreased, the number of crimps exhibited by the heat treatment of the short fibers increased. Consequently, the fabric composed of short fiber yarns not only exhibited increased elasticity, but also, due to the smaller flat portion, reduced specular reflection of light and suppressed unevenness (glare), resulting in excellent appearance quality. The results are shown in Tables 1-2.

[0341] In Example 6, as the flatness of the short fibers increased, the changes in the crimp morphology exhibited by each short fiber after heat treatment were significant, and the coefficient of variation (CV%) of the number of crimps between short fibers increased. Simultaneously, the coefficient of variation (CV%) of the interfiber spacing and interfiber gap distance of the short fiber yarn also increased. Therefore, the fabric composed of short fiber yarn not only improved its fluffiness but also enhanced the comfortable feel produced by its warm and delicate texture. The results are shown in Tables 1-2.

[0342] [Example 7]

[0343] Except for replacing polymer 2 with PET with a melt viscosity of 31 Pa·s, all other procedures were carried out in accordance with Example 1.

[0344] In Example 7, the short fibers strongly exhibited a crimped shape, which not only increased the elasticity of the resulting fabric, but also caused light to be diffusely reflected, thereby suppressing uneven appearance (glare) and achieving excellent appearance quality. The results are shown in Tables 1-2.

[0345] [Examples 8 and 9]

[0346] Except for changing the amount of short fibers to be extruded with a fiber diameter of 9 μm (Example 8) and 15 μm (Example 9), all other procedures were carried out in accordance with Example 1.

[0347] In Example 8, by setting the diameter of the short fibers to 9 μm, the bending stiffness of a single short fiber was reduced, the softness of the fabric made from the short fiber yarn was improved, and the number of fibers constituting the short fiber yarn was increased, thereby increasing diffuse reflection of light, suppressing uneven appearance (glare), and obtaining excellent appearance quality. Furthermore, the increased crimp number exhibited by the heat treatment of the short fibers also improved the elasticity of the fabric made from the short fiber yarn. The results are shown in Table 2-1.

[0348] In Example 9, by setting the fiber diameter to 15 μm, the changes in the crimp morphology exhibited by each short fiber during heat treatment increased, the coefficient of variation (CV%) of the number of crimps between short fibers increased, and the coefficient of variation (CV%) of the interfiber gap distance and interfiber gap distance of the short fiber yarn also increased. As a result, the fabric composed of short fiber yarn can improve its fluffiness while also enhancing the comfortable feel produced by its warm and delicate texture. The results are shown in Table 2-1.

[0349] [Examples 10 and 11]

[0350] Except for changing the twist coefficient of the staple fiber yarn to 2 (Example 10) and 6 (Example 11), all other procedures were carried out in accordance with Example 1.

[0351] In Example 10, by weakening the twisting of the staple fiber yarn, the staple fibers are more prone to crimping, and the interfiber gap distance and the coefficient of variation (CV%) of the interfiber gap distance also increase. As a result, the fabric made of staple fiber yarn achieves a more fluffy and soft texture, while also enhancing the comfortable feel of its smooth and delicate texture. The results are shown in Table 2-1.

[0352] In Example 11, by increasing the twisting of the short fiber yarn, a unique elasticity is achieved not only through the close stacking of short fibers, but also because there is less pulling and tangling of short fibers during fabric friction, resulting in excellent anti-pilling properties without any unsightly appearance. The results are shown in Table 2-1.

[0353] [Example 12]

[0354] Except for changing the count of the short fiber yarn to 60, everything was carried out in accordance with Example 1.

[0355] In Example 12, by setting the count to a finer number, the number of short fibers constituting the staple yarn was reduced, resulting in increased softness of the fabric made from the staple yarn and a fabric more suitable for clothing. The results are shown in Table 2-1.

[0356] [Example 13]

[0357] Except for replacing polymer 2 with polyethylene terephthalate (PET containing TiO2) containing 5.0 wt% titanium dioxide, all other procedures were carried out in accordance with Example 1.

[0358] In Example 13, the diffuse reflection of light by titanium dioxide within the short fibers suppressed uneven appearance (glare), resulting in excellent aesthetic quality. Furthermore, the titanium dioxide also reflects ultraviolet and infrared rays, providing functionalities such as anti-seepage and ultraviolet shielding. The results are shown in Table 2-2.

[0359] [Example 14]

[0360] Except for converting polymer 1 into polypropylene terephthalate (PPT), all other procedures were carried out in accordance with Example 1.

[0361] In Example 14, by taking advantage of the rubber-elastic properties of PPT used as polymer 1, the fabric made of short-fiber yarn not only exhibited excellent softness but also significantly improved stretchability. The results are shown in Table 2-2.

[0362] [Example 15]

[0363] Except for preparing nylon 610 (N610, melt viscosity: 84 Pa·s, melting point: 220 °C) as polymer 1 and nylon 6 (N6, melt viscosity: 96 Pa·s, melting point: 225 °C) as polymer 2, and spinning these polymers separately by melting them at 260 °C, all other procedures were carried out in accordance with Example 1.

[0364] The resulting fabric, composed of short-fiber yarns, is made of low-elasticity nylon. Therefore, in addition to its excellent softness, it also exhibits excellent bulkiness due to its low specific gravity and reduced apparent density. The results are shown in Table 2-2.

[0365] [Examples 16 and 17]

[0366] Except for the short fiber and cotton of the present invention described in Example 1 being blended into 80% / 20% (Example 16) and 20% / 80% (Example 17) to obtain a short fiber yarn with a count of 40 and a twist coefficient of 4, all other procedures were carried out in accordance with Example 1.

[0367] In Examples 16 and 17, by blending the short fibers of the present invention with cotton, the crimp of the short fibers creates a difference in yarn length with that of the cotton. In fabrics composed of short fiber yarns, the higher the cotton blending rate, the more fluffy and soft the texture, and the more comfortable the touch caused by the warm and delicate texture. The results are shown in Table 2-2.

[0368]

[0369]

[0370]

[0371] Industry availability

[0372] By incorporating the short fibers of this embodiment into a portion of the fabric, a unique fluffy and soft texture and absorbency due to the porosity can be obtained. Therefore, it can be well used in general clothing such as jackets, skirts, trousers, and underwear, as well as sportswear and clothing materials. Furthermore, its comfort can be fully utilized in various fiber products for everyday use, including carpets, sofas, interior decoration products, car seats, cosmetics, face masks, and health products. It is particularly preferred as a short-fiber yarn for clothing applications.

[0373] Furthermore, the fabric (woven fabric, knitted fabric) that includes the short fiber yarn of this embodiment in a part is preferably a clothing fabric with excellent wearing comfort.

[0374] Explanation of symbols in attached drawings

[0375] x: Low melting point polymer

[0376] y: High melting point polymer

[0377] a1, a2: The two points furthest apart on the outer periphery of the fiber.

[0378] b1, b2: The intersection of the line passing through the midpoint of the line connecting the two furthest points on the outer periphery of the fiber and perpendicular to it, with the outer periphery of the fiber.

[0379] Gx: Center of gravity of low-melting-point polymers

[0380] Gy: Center of gravity of high-melting-point polymers

[0381] G: Center of gravity of short fibers

[0382] 1. M2: Curled peak

[0383] V1, V2: Curled Valley

[0384] S1: The straight line connecting the vertices of M1 and V2.

[0385] S2, S3: Straight lines parallel to S1 and passing through vertices V1 and M2.

[0386] Le: The distance between the intersection points of a straight line perpendicular to S1 and S2 and S3.

[0387] 1: Measuring plate

[0388] 2: Distribution board

[0389] 3: Dispensing plate

Claims

1. A short fiber, characterized in that, It is composed of at least two polymers with different melting points, with a curl number / curl diameter of 75 to 500 and a coefficient of variation (CV%) of 15 to 50% for the curl number between short fibers.

2. The short fiber as described in claim 1, characterized in that, The coefficient of variation (CV%) of the distance between polymer centroids / fiber diameter between short fibers is 5-30%.

3. The short fiber as described in claim 1 or 2, characterized in that, The flatness of the fiber cross-section is 1.2 to 5.

0.

4. The short fiber as described in claim 1 or 2, characterized in that, The fiber cross-section has more than three protrusions.

5. A fiber product, characterized in that, It contains the short fibers as described in claim 1 or 2 as a component.

6. A staple fiber yarn, characterized in that, It contains the short fibers as described in claim 1 or 2.

7. A staple fiber yarn, characterized in that, It contains flat short fibers composed of at least two polymers with different melting points, and the coefficient of variation (CV%) of the interfiber spacing is 60-90%.

8. The staple fiber yarn as described in claim 7, characterized in that, The interfiber spacing is 4–10 μm.

9. The staple fiber yarn as described in claim 7 or 8, characterized in that, It has a void structure with a porosity of 30-60%.

10. The staple fiber yarn as described in claim 7 or 8, characterized in that, The blending rate of the flat short fibers is 30-100% by mass.

11. A fabric, characterized in that, It includes the short fiber yarn as described in claim 6 or 7 as a part.

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