Composite fiber bundle and fiber product

Abstract

The present invention pertains to a composite fiber bundle characterized by being constituted by composite fibers comprising at least two types of polymers having different melting points, and by being such that the variation coefficient CV for the value of the ((distance between polymer centers of gravity) / (fiber diameter)) among the composite fibers is 5-30%.

Description

Composite fiber bundles and fiber products

[0001] The present invention relates to a conjugated fiber bundle suitable for clothing textiles and a textile product containing the conjugated fiber bundle.

[0002] Synthetic fibers made from polyester, polyamide, etc. have excellent mechanical properties and dimensional stability, and are therefore widely used in a variety of applications, from clothing to non-clothing. However, as people's lives have become more diverse and they are seeking a better quality of life, there is a demand for fibers with more advanced textures and functions.

[0003] As a fiber having such a higher level of texture and functionality, a method of using a composite fiber having a side-by-side cross section in which different polymers are bonded together has been proposed.

[0004] This side-by-side type conjugated fiber is intended to impart a texture such as a moderate sense of resilience and volume by expressing crimp due to the difference in thermal shrinkage between the polymers. However, when a conjugated fiber bundle obtained by bundling a plurality of such conjugated fibers is used to make a textile, all of the conjugated fibers express the same crimp form, which results in the crimp phase being aligned, and this can result in a flat texture lacking volume.

[0005] On the other hand, clothing textiles that come into contact with human skin often require excellent wearing comfort, and there is a strong demand for fibers with a texture that is directly related to human comfort, such as that of natural fibers. This is because natural materials such as wool, cotton, and silk have an excellent balance of texture and functionality, and humans find the complex appearance and tactile sensation they produce attractive and luxurious.

[0006] In synthetic fibers, the crimp phases between the composite fibers are aligned, resulting in a flat texture lacking in volume. To address this issue, various technologies have been proposed that make the texture and feel more complex by improving the individual composite fibers that make up the composite fiber bundle, thereby bringing the texture and feel closer to the unique texture and feel found in natural materials.

[0007] Patent Document 1 discloses that in a conjugated fiber bundle made up of conjugated fibers in which polyethylene terephthalate (PET) fibers of different viscosities are conjugated side-by-side, the conjugation ratio between the conjugated fibers is changed to cause variations in the curvature of the polymer interface, and as a result, the crimp morphology between the conjugated fibers differs depending on the conjugation ratio, and the crimps form independently without interlocking with each other.

[0008] A composite fiber bundle made of such composite fibers exhibits voids between the composite fibers according to the difference in crimp form, and when the composite fiber bundle is made into a textile, it has a fluffy texture.

[0009] Furthermore, Patent Document 2 discloses that by forming a composite fiber bundle in which polyethylene terephthalate (PET) fibers with different viscosities are combined side-by-side to form a modified cross section and further comprising three or more types of composite fiber groups with different states of the composite joining surfaces, which are the joining surfaces between the composite components, each group of composite fibers exhibits a different bending rigidity, thereby obtaining composite fiber groups with different crimp development properties.

[0010] By utilizing such composite fiber bundles, it is possible to obtain textiles that combine the fluffiness and bulkiness of natural fibers with stretchability and resilience.

[0011] Japanese Patent Publication No. 2000-212838 Japanese Patent Publication No. 2001-355132

[0012] As in Patent Document 1, by changing the conjugation ratio between the conjugated fibers constituting the conjugated fiber bundle to cause variations in the curvature of the polymer interface, differences in crimp morphology between the conjugated fibers may occur.

[0013] However, in Patent Document 1, the change in the conjugation ratio that can be used as a means for changing the crimp morphology for each conjugated fiber is substantially within the range of 40:60 to 60:40 in order to maintain spinning stability, and the difference in the crimp morphology obtained here is small, so that the texture obtained may naturally be monotonous.

[0014] Furthermore, as in Patent Document 2, by forming a composite fiber bundle from three or more types of composite fiber groups with different composite joint surface states, different bending stiffnesses may act on each of the composite fiber groups, resulting in composite fiber groups with different crimp development properties.

[0015] However, the conjugated fiber described in Patent Document 2 has a substantially multilobal cross section, and the distance between the polymer centers of gravity required for crimping is naturally short, so the crimping power is low, and the fullness and resilience required for comfortable clothing may be insufficient.

[0016] Therefore, an object of the present invention is to solve the above-mentioned problems of the conventional technology and to provide a conjugated fiber bundle suitable for obtaining a clothing textile having excellent wearing comfort, a smooth feel, a moderate sense of resilience and a fluffy texture, by controlling the crimp form of each conjugated fiber constituting the conjugated fiber bundle.

[0017] The objects of the present invention are achieved by the following means: (1) a conjugated fiber bundle composed of conjugated fibers made of at least two kinds of polymers having different melting points, characterized in that the coefficient of variation CV of the value of (distance between the centers of gravity of polymers / fiber diameter) between the conjugated fibers is 5 to 30%, (2) the conjugated fiber bundle according to (1) above, characterized in that the difference between the maximum and minimum values ​​of flatness between the conjugated fibers is less than 0.5, (3) the conjugated fiber bundle according to (1) or (2) above, characterized in that the average value of flatness between the conjugated fibers is 1.2 to 3.0, (4) the conjugated fiber bundle according to any one of (1) to (3) above, characterized in that the surface layer of the conjugated fiber is covered with one kind of polymer, and (5) a textile product partially containing the conjugated fiber bundle according to any one of (1) to (4).

[0018] The conjugated fiber bundle of the present invention has the above-mentioned characteristics, and therefore the crimp form of each conjugated fiber constituting the conjugated fiber bundle is precisely controlled. Therefore, by using the conjugated fiber bundle of the present invention, it is possible to obtain a clothing textile that has a smooth touch, a moderate resilience, a fluffy texture, and excellent wearing comfort.

[0019] (a), (b), and (c) of Fig. 1 are schematic diagrams showing an example of the cross-sectional structure of the conjugate fiber constituting the conjugate fiber bundle of this embodiment. (a) and (b) of Fig. 2 are schematic diagrams showing an example of the transverse cross-sectional structure of the conjugate fiber constituting the conjugate fiber bundle of this embodiment. Fig. 3 is a schematic diagram showing an example of the transverse cross-sectional structure of the conjugate fiber constituting a conventional conjugate fiber bundle. Fig. 4 is a schematic diagram showing an example of the transverse cross-sectional structure of each conjugate fiber constituting the conjugate fiber bundle of this embodiment. Fig. 5 is a diagram for understanding the coefficient of variation CV of the value of (distance between polymer centers of gravity / fiber diameter) between the conjugate fibers constituting the conjugate fiber bundle of this embodiment, and the dashed lines of the outer frame represent the top, bottom, left, and right sides of the photographed image. Fig. 6 is a schematic diagram showing an example of the crimp morphology of the conjugate fiber constituting the conjugate fiber bundle of this embodiment. Fig. 7 is a transverse cross-sectional view for explaining a method for producing the conjugate fiber constituting the conjugate fiber bundle of this embodiment.

[0020] The present invention will be described in detail below with reference to preferred embodiments. An analysis of cotton, a natural material that is widely used and has a smooth feel and a fluffy, soft texture, reveals that each fiber has a different crimping pattern. By bundling multiple fibers with different crimping patterns together, complex voids and irregularities are formed when the textile is made, and this is thought to be what achieves the unique feel and texture.

[0021] The inventors have conducted extensive research to realize complex voids and irregularities in synthetic fibers similar to those in natural materials, and have discovered that in a composite fiber bundle made of composite fibers made of at least two types of polymers with different melting points, by controlling the distance between the polymer centers of gravity of each composite fiber and appropriately aligning the crimp phase, complex voids and irregularities that were difficult to obtain with conventional synthetic fibers can be formed.

[0022] That is, when all of the conjugate fibers constituting the conjugate fiber bundle exhibit the same crimp form, the conjugate fiber bundle will be a convergent conjugate fiber bundle with the same crimp phase, and the gaps between the conjugate fibers will be small, so that when made into a textile, the texture may be flat and lacking in fluffiness.

[0023] On the other hand, when the conjugate fibers constituting a conjugate fiber bundle each exhibit a different crimp morphology, there is a tendency for voids to form between the conjugate fibers due to the shift in the crimp phase of the conjugate fibers. However, since the morphology of the conjugate fiber bundle does not change and the size of the voids formed between the conjugate fibers is uniform, the appearance and texture of the conjugate fiber bundle when made into a textile may be monotonous.

[0024] In contrast, if the composite fiber bundle is controlled so that the crimp phases of the composite fibers constituting the composite fiber bundle are partially aligned while there are variations in the occurrence of crimp, when the composite fiber bundle is made into a textile, in addition to the fine gaps present in the composite fiber bundle, there will be areas where the crimp phases are aligned and areas where they are not aligned between adjacent composite fibers. This creates complex gaps between the composite fibers and creates complex irregularities in the composite fiber bundle that have not been seen before, and when the composite fiber bundle is made into a textile, it will be possible to achieve a unique feel and texture like that of natural materials.

[0025] The present invention is based on this idea, and specifically relates to a conjugate fiber bundle made of conjugate fibers made of at least two types of polymers having different melting points, and it is important that the coefficient of variation CV of the value of (distance between the centers of gravity of polymers / fiber diameter) between the conjugate fibers is 5 to 30%.

[0026] The composite fiber bundle in this embodiment refers to a composite fiber bundle formed by bundling, for example, 20 or more composite fibers made of at least two types of polymers, and includes multifilaments made of long fibers and spun yarns made of short fibers.

[0027] The polymer used for the conjugate fibers constituting the conjugate fiber bundle of this embodiment is preferably a thermoplastic polymer because of its excellent processability. Examples of thermoplastic polymers include polyester-based, polyethylene-based, polypropylene-based, polystyrene-based, polyamide-based, polycarbonate-based, polymethyl methacrylate-based, and polyphenylene sulfide-based polymers and copolymers thereof. From the viewpoint of being able to impart particularly high interfacial affinity and obtaining fibers without abnormalities in the composite cross section, it is preferable that all of the thermoplastic polymers used for the conjugate fibers be from the same polymer group or copolymers thereof.

[0028] The polymer may also contain various additives such as inorganic substances such as titanium oxide, silica, and barium oxide, colorants such as carbon black, dyes, and pigments, flame retardants, fluorescent brighteners, antioxidants, and ultraviolet absorbers.

[0029] Among these, it is preferable to incorporate titanium oxide into the polymer. By incorporating titanium oxide into the polymer, the titanium oxide on the surface of the composite fiber diffuses light, thereby improving the appearance quality by suppressing uneven appearance (glare) caused by increases and decreases in reflection depending on the angle of incidence of light. Not only that, but also the titanium oxide inside the composite fiber provides functionality such as anti-transparency and UV protection. In order to fully obtain the above effects, the content of titanium oxide in the polymer is preferably 1.0 wt% or more. Furthermore, because increased diffuse reflection of light by titanium oxide may cause a decrease in color development, the content of titanium oxide is preferably 10.0 wt% or less.

[0030] In order to control the crimp form, the conjugate fibers constituting the conjugate fiber bundle of this embodiment must be made of at least two types of polymers with different melting points.

[0031] If polymers with different melting points are arranged so that their centers of gravity are different in the cross section of the composite fiber, the composite fiber will bend significantly toward the low-melting-point polymer, which exhibits high shrinkage, after heat treatment, and this continuation will result in the development of a coil-like crimp morphology. Furthermore, by controlling the distance between the centers of gravity of the polymers, it is possible to develop any desired crimp morphology, thereby achieving the objective of the present invention of controlling the crimp phase.

[0032] In this embodiment, polymers with different melting points refer to a combination of polymers with melting points that differ by 10°C or more, selected from a group of melt-moldable thermoplastic polymers such as polyesters, polyethylenes, polypropylenes, polystyrenes, polyamides, polycarbonates, polymethyl methacrylates, and polyphenylene sulfide, and copolymers thereof.

[0033] In the composite fibers constituting the composite fiber bundle of this embodiment, the purpose is to express a crimped form by the difference in shrinkage of polymers with different melting points, so it is preferable that the combination of polymers with different melting points is such that one type is a high-shrinkage low-melting point polymer and the other type is a low-shrinkage high-melting point polymer.

[0034] In particular, from the viewpoint of suppressing peeling and imparting stability to advanced processing and durability to textiles, it is more preferable to select polymer combinations from the same group of polymers in which the bonds present in the main chain are the same, such as polyesters with ester bonds and polyamides with amide bonds.

[0035] Examples of such combinations of low-melting point polymers and high-melting point polymers in the same polymer group include various combinations such as copolymerized polyethylene terephthalate / polyethylene terephthalate, polypropylene terephthalate / polyethylene terephthalate, polybutylene terephthalate / polyethylene terephthalate, thermoplastic polyurethane / polyethylene terephthalate, polyester elastomer / polyethylene terephthalate, polyester elastomer / polybutylene terephthalate as polyesters; nylon 66 / nylon 610, nylon 6-nylon 66 copolymer / nylon 6 or 610, PEG copolymerized nylon 6 / nylon 6 or 610, thermoplastic polyurethane / nylon 6 or 610 as polyamides; and ethylene-propylene rubber finely dispersed polypropylene / polypropylene, propylene-α-olefin copolymer / polypropylene as polyolefins.

[0036] Among these, it is particularly preferable to use a combination of copolymerized polyethylene terephthalate / polyethylene terephthalate as the polymers having different melting points, from the viewpoint that when the composite fiber bundle is made into a textile, a moderate sense of resilience is obtained due to high bending recovery, and good color development is obtained when dyed.

[0037] Examples of copolymerization components in copolymerized polyethylene terephthalate include succinic acid, adipic acid, azelaic acid, sebacic acid, 1,4-cyclohexanedicarboxylic acid, maleic acid, phthalic acid, isophthalic acid, 5-sodium sulfoisophthalic acid, etc. Among these, from the viewpoint of maximizing the difference in shrinkage from polyethylene terephthalate, it is preferable to use polyethylene terephthalate copolymerized with 5 to 15 mol % isophthalic acid.

[0038] Furthermore, with environmental issues gaining attention, the use of plant-derived biopolymers and recycled polymers in this embodiment is also suitable from the viewpoint of reducing environmental impact. Therefore, the polymer used in this embodiment can be a recycled polymer recycled by any of chemical recycling, material recycling, and thermal recycling.

[0039] Even when a biopolymer or recycled polymer is used, the polyethylene terephthalate resin can accentuate the features of the present invention as a polymer characteristic thereof. Therefore, as described above, recycled polyethylene terephthalate can be suitably used as the polymer used in this embodiment from the viewpoints of obtaining a moderate resilience due to high bending recovery and obtaining good color development when dyed.

[0040] The cross section of the conjugated fiber of this embodiment is preferably a conjugated cross section in which polymers with different melting points are arranged so that their centers of gravity are different. Examples of such conjugated cross sections include a side-by-side type as shown in Fig. 1(a) and an eccentric core-sheath type as shown in Fig. 1(b), as well as an islands-in-the-sea type and a blend type.

[0041] In this embodiment, the surface layer of the composite fiber is preferably covered with one type of polymer. By covering the surface layer of the composite fiber with one type of polymer, even if a polymer with low heat resistance or low abrasion resistance is used as one component of the composite fiber, peeling does not occur at the interface due to friction or impact, and the fiber properties can be well maintained.

[0042] In addition, when producing the composite fiber bundle of this embodiment, if a melt of polymers with a large difference in melting point is spun from a spinneret as a composite flow, the difference in cooling after discharge will cause the high-melting-point polymer to bend toward the low-melting-point polymer, resulting in yarn bending, which will come into contact with the spinneret or interfere with the composite flow spun from another location, causing yarn breakage. However, since the surface layer of the composite fiber is covered with one type of polymer, the difference in cooling will be mitigated and yarn bending will be suppressed, making it possible to stably spin a fiber even when a combination of polymers with a large difference in melting point is used.

[0043] Examples of one type of polymer that can be used to cover the surface layer of the composite fiber include polyesters such as polyethylene terephthalate, copolymerized polyethylene terephthalate, polypropylene terephthalate, and polybutylene terephthalate, polyamides such as nylon 6, nylon 66, and nylon 610, and polyolefins such as polypropylene. Among these, it is preferable to use polyethylene terephthalate or copolymerized polyethylene terephthalate to cover the surface layer of the composite fiber, from the viewpoint of excellent heat resistance and color development.

[0044] Furthermore, the thickness of one type of polymer covering the surface layer of the composite fiber can be adjusted as appropriate, but for example, it is preferable that the ratio S / D, where S is the minimum thickness of the polymer covering the surface layer of each composite fiber constituting the composite fiber bundle and D is the fiber diameter, be 0.01 to 0.1. By setting the ratio within this range, whitening or fuzzing does not occur even when the composite fiber or textile is subjected to friction or impact, and yarn processing stability and textile quality can be maintained. Furthermore, 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, allowing maximum expression of crimp due to shrinkage difference, and this is considered a more preferable range.

[0045] In this embodiment, the ratio S / D of the minimum thickness S of the polymer covering the surface layer of the composite fiber to the fiber diameter D can be determined by embedding the composite fiber bundle in an embedding agent such as epoxy resin, then photographing the cross section of the bundle with a transmission electron microscope (TEM) at a magnification that allows observation of 10 or more composite fibers, and observing the composite cross section. In this case, applying metal staining creates a dye difference between the polymers, which makes it possible to clarify the contrast of the joints in the composite cross section.

[0046] Furthermore, when the composite cross section of the photographed image is an eccentric sheath-core cross section as shown in Figure 1(b), the minimum thickness of the polymer covering the surface layer of each composite fiber is determined in μm for 10 composite fibers randomly sampled within the same image. The obtained minimum thickness S is divided by the fiber diameter D, which is determined by measuring the area of ​​each composite fiber and measuring the diameter calculated as a perfect circle in μm units to one decimal place, and the average value is rounded to two decimal places to obtain the ratio S / D of the minimum thickness S of the polymer covering the surface layer of the composite fiber to the fiber diameter D.

[0047] The area ratio of the low-melting point polymer to the high-melting point polymer in the composite cross section of the composite fiber constituting the composite fiber bundle of this embodiment, i.e., the area of ​​the low-melting point polymer / the area of ​​the high-melting point polymer, is preferably in the range of 70 / 30 to 30 / 70, and more preferably 60 / 40 to 40 / 60. Within this range, the crimp morphology due to the difference in shrinkage of the polymers can be fully expressed without being affected by the hardening of texture that occurs when the low-melting point polymer undergoes high shrinkage during heat treatment.

[0048] In this embodiment, by partially aligning the crimp phases between the composite fibers that make up the composite fiber bundle, a difference in the gaps is created between areas where the crimp phases are aligned and areas where they are not aligned between adjacent composite fibers, and therefore, when the composite fiber bundle is made into a textile, it is possible to form unevenness on the surface.

[0049] In order to form the complex voids between the conjugate fibers and the irregularities on the textile surface, which are the characteristics of the present invention, it is important that the coefficient of variation CV of the value of (distance between the centers of gravity of the polymer / fiber diameter) between the conjugate fibers is 5 to 30%.

[0050] The coefficient of variation CV of the value of (distance between polymer centers of gravity / fiber diameter) in this embodiment can be calculated by the following method.

[0051] First, for a textile made of composite fiber bundles, an image of the cross section of the textile perpendicular to the thickness direction of the textile and the fiber axis direction of the composite fibers is taken using a scanning electron microscope (SEM) at a magnification that allows observation of 20 or more composite fibers. One composite fiber randomly extracted from within the same captured image is analyzed to measure the area of ​​the composite fiber, and the diameter calculated as a perfect circle is measured in μm units to one decimal place. The obtained value is the fiber diameter (μm) of the composite fiber.

[0052] Next, for the same conjugate fiber as above, the length of the line connecting the centers of gravity (Gx, Gy) of the low-melting point polymer x and the high-melting point polymer y in the cross section of the conjugate fiber is measured in μm units to one decimal place as shown in Figure 2(a). The obtained value is the distance between the polymer centers of gravity (μm).

[0053] For the fiber diameter and the distance between the polymer centers of gravity obtained above, a simple number average of the ratio (distance between the polymer centers of gravity / fiber diameter) is calculated, and the value rounded off to one decimal place is defined as (distance between the polymer centers of gravity / fiber diameter).

[0054] This evaluation was performed on 20 composite fibers ((1) to (20) in Figure 5) randomly sampled from the same image as above, and their standard deviation and average value were calculated. The standard deviation was divided by the average value, multiplied by 100, and the result was rounded off to the nearest whole number. The obtained value was defined as the coefficient of variation CV (%) of the value of (distance between polymer centers of gravity / fiber diameter).

[0055] In the conjugate fibers constituting the conjugate fiber bundle of this embodiment, the crimp morphology can be controlled by the distance between the polymer centers of gravity and the fiber diameter, and the larger the distance between the polymer centers of gravity and the smaller the fiber diameter, the finer the crimp morphology that can be produced. That is, the crimp development force is expressed by (distance between the polymer centers of gravity / fiber diameter), and by controlling this crimp development force for each conjugate fiber, it is possible to control the formation of complex voids and unevenness on the textile surface that are produced when the crimp phases between the conjugate fibers are aligned.

[0056] That is, in this embodiment, the coefficient of variation CV of the value of (distance between polymer centers of gravity / fiber diameter) between the conjugate fibers constituting the conjugate fiber bundle is 5% or more. By setting the coefficient of variation CV within the above range, the crimp phases are partially aligned, resulting in unevenness on the textile surface, and a smooth feel due to large friction fluctuations when the surface is touched. In addition, complex voids are generated between the conjugate fibers, which can produce a texture with a moderate sense of resilience and an effect of suppressing uneven appearance (glare) due to diffuse reflection of light.

[0057] 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 to 20%, and even more preferably in the range of 15 to 20%. If the coefficient of variation CV is in the above range, when the composite fiber bundle is made into a textile, the pitch of the unevenness on the textile surface becomes finer, and the smooth feel is outstanding. Furthermore, by increasing the voids between the composite fibers, when the composite fiber bundle is made into a textile, the apparent density decreases, and the effect of improving fluffiness is also added.

[0058] On the other hand, if the coefficient of variation CV becomes too large, the unevenness appearing on the textile surface becomes finer, and the frictional fluctuation also becomes smaller, resulting in a monotonous texture. Therefore, the coefficient of variation CV is 30% or less.

[0059] In the conjugate fibers constituting the conjugate fiber bundle of this embodiment, one possible method for controlling (distance between polymer centers of gravity / fiber diameter) is to change the cross-sectional shape or conjugation ratio of the conjugate fibers for each conjugate fiber, but from the viewpoint of controlling the crimp phase alignment and spinning stability, a method is preferred in which the cross-sectional shapes of the conjugate fibers constituting the conjugate fiber bundle are flattened and the difference between the maximum and minimum flatness values ​​among the conjugate fibers is less than 0.5. Here, "flat" refers to an elongated shape in a planar view, and specifically refers to a conjugate fiber whose cross section, described below, has a "flatness" of 1.1 or more.

[0060] If the cross-sectional shape of the composite fiber is flat (flat cross section), the distance between the polymer centers of gravity will be maximum when polymers with different melting points are bonded in the major axis direction of the flat cross section as shown in (a) of Figure 2, and the distance between the polymer centers of gravity will be minimum when they are bonded in the minor axis direction of the flat cross section as shown in (b) of Figure 2. In this way, by flattening the cross-sectional shape of the composite fiber and changing the direction of the bonded surfaces of the composite fiber, it becomes possible to control the value of (distance between polymer centers of gravity / fiber diameter).

[0061] Therefore, it is preferable that the difference between the maximum and minimum flatness values ​​between the composite fibers be less than 0.5, and more preferably, the composite cross section is formed by changing the bonding surface direction for each composite fiber, as shown in Figure 4. When the composite fiber has the above configuration, the crimp phases between the composite fibers tend to be partially aligned, and the coefficient of variation CV of the value of (distance between polymer centers of gravity / fiber diameter) can be easily set within the desired range. Furthermore, from the viewpoints of suppressing yarn breakage due to yarn interference caused by cooling unevenness and improving spinning stability compared to when the cross-sectional shape or conjugation ratio is changed for each composite fiber, it is more preferable that the difference between the maximum and minimum flatness values ​​between the composite fibers be less than 0.2.

[0062] To further exhibit the above-mentioned effects, in this embodiment, the average value of the flatness between the conjugated fibers is preferably 1.2 or more, more preferably 1.4 or more, and even more preferably 1.6 or more. By making the average value of the flatness between the conjugated fibers 1.2 or more, the coefficient of variation CV of the value of (distance between the centers of gravity of the polymers / fiber diameter) can be brought closer to an optimum range. Furthermore, when conjugated fibers having a flat cross section exhibit crimp, steric hindrance forms voids between the conjugated fibers, and when the conjugated fiber bundle is made into a textile, the textile becomes swollen.

[0063] As described above, from the viewpoints of controlling the coefficient of variation CV of the value of (distance between polymer centers of gravity / fiber diameter) and stably forming voids between composite fibers, the higher the average flatness, the better. On the other hand, if the average flatness is too high, the light reflected by the composite fiber surface will be intensified, which may cause uneven appearance (glare). In addition, a cross-sectional shape with edges may cause bending rigidity to be higher than necessary, which may impair flexibility. Therefore, the average flatness in this embodiment is preferably 3.0 or less, more preferably 2.5 or less, and even more preferably 2.0 or less.

[0064] In this embodiment, the average flatness and the difference between the maximum and minimum values ​​among the composite fibers are determined by the following method. First, a composite fiber bundle is embedded in 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) at a magnification that allows observation of 10 or more composite fibers. Next, one composite fiber randomly selected from the captured image is analyzed using image analysis software. As shown in FIG. 1(a), the major axis is defined as a line connecting the two most distant points (a1, a2) on the periphery of the composite fiber, and the minor axis is defined as a line connecting the intersection (b1, b2) of the periphery of the fiber with a line passing through the midpoint of the major axis and perpendicular to the major axis. The length of the major axis is divided by the length of the minor axis to calculate the flatness. This value is then used as the simple number average of the results, rounded to one decimal place, to determine the average flatness. In addition, among the composite fibers whose flatness has been determined, the largest value is subtracted from the smallest value, and the difference is rounded to two decimal places to determine the difference between the maximum and minimum flatness values.

[0065] The cross-sectional shape of the composite fibers constituting the composite fiber bundle of this embodiment may be a flat shape as shown in FIG. 1(a), as well as a multi-lobed shape as shown in FIG. 1(c), and other shapes such as polygonal, gear-shaped, petal-shaped, and star-shaped.

[0066] In this embodiment, it is preferable to combine composite fibers having a cross-sectional shape with three or more convex portions on the surface of the composite fiber. By combining composite fibers having a cross-sectional shape with three or more convex portions on the surface of the composite fiber, it is possible to suppress uneven appearance (glare) due to diffuse reflection of light and to increase water absorbency due to fine voids between the composite fibers. The number of convex portions is more preferably five or more, and even more preferably eight or more. However, as the effect gradually decreases as the number of convex portions becomes too large, the substantial upper limit of the number of convex portions is 20, and more preferably 12 or less.

[0067] The conjugate fibers constituting the conjugate fiber bundle of this embodiment preferably have a crimped form with the number of crimps being 5 crimps / cm or more.

[0068] The crimp peak count is determined by the following method. First, a composite fiber is extracted from a textile without plastic deformation, one end of the composite fiber is fixed, and a load of 1 mg / dtex is applied to the other end. After 30 seconds or more, markings are made at any positions where the distance between two points is 1 cm in the fiber axis direction of the composite fiber. The composite fiber is then fixed on a glass slide, adjusted so that the distance between the pre-marked marks is the original 1 cm, without plastic deformation. Images of this sample are taken with a digital microscope at a magnification that allows the 1 cm markings to be observed. If the composite fiber CF has a crimped morphology as shown in Figure 6 in the image, the number of crimp peaks Cr present between the markings is determined. This procedure is performed on 10 composite fibers, and the simple number average is calculated. The value rounded to one decimal place is used as the crimp peak count (peaks / cm).

[0069] If the crimp morphology has a crimp peak count of 5 peaks / cm or more, the crimp phases between the composite fibers will be aligned, resulting in complex voids between the composite fibers and unevenness on the textile surface. A crimp peak count of 10 peaks / cm or more is more preferable. Having a crimp peak count of 10 peaks / cm or more not only improves the volumetric expansion by increasing the voids between the composite fibers due to the excluded volume effect between the composite fibers, but also imparts stretchability by forming a fine spiral crimp morphology.

[0070] From the viewpoint of volume and stretchability, it is preferable to increase the number of crimp peaks, but if the number of crimp peaks is excessive, the crimp phase is likely to be shifted, and the gaps between the composite fibers become uniform, which may result in a monotonous feel when the composite fiber bundle is made into a textile. Therefore, the number of crimp peaks in this embodiment is preferably 50 peaks / cm or less, more preferably 40 peaks / cm or less, and even more preferably 30 peaks / cm or less.

[0071] The composite fibers constituting the composite fiber bundle of this embodiment preferably have a fiber diameter of 20 μm or less. If the fiber diameter is within this range, the diffuse reflection of light from the composite fiber increases, and not only can uneven appearance (glare) be suppressed when the composite fiber is made into a textile, but also a sufficient sense of resilience can be obtained. This makes the composite fiber suitable for clothing applications such as pants and shirts that require a firm and resilient texture.

[0072] Furthermore, it is more preferable that the fiber diameter is 15 μm or less. By making the fiber diameter 15 μm or less, the flexibility of the composite fiber bundle increases, and it can be suitably used for clothing applications such as innerwear and blouses that come into contact with the skin. The fiber diameter is more preferably 12 μm or less.

[0073] From the viewpoint of suppressing deterioration in bending recovery and color development, the fiber diameter is preferably 5 μm or more, and more preferably 8 μm or more.

[0074] As described above, in the composite fiber bundle of this embodiment, differences in voids occur between areas where the crimp phases of adjacent composite fibers are aligned and areas where they are not aligned, resulting in the formation of complex voids and unevenness between the composite fibers.

[0075] Therefore, when a textile product contains at least a portion of the conjugated fiber bundle of this embodiment, it is possible to obtain a textile that not only exhibits a unique smooth feel but also achieves a moderate sense of resilience and a fluffy texture due to the complex voids between the conjugated fibers, and is therefore excellent in wear comfort. The conjugated fiber bundle of this embodiment can be suitably used in a wide range of textile products, from general clothing such as jackets, skirts, pants, and underwear to sportswear and clothing materials, and, taking advantage of its comfort, in interior products such as carpets and sofas, vehicle interior parts such as car seats, cosmetics, cosmetic masks, health products, and other daily uses.

[0076] An example of a method for producing the conjugate fiber bundle of this embodiment will be described in detail below. The conjugate fiber bundle of this embodiment can be produced by a melt spinning method intended for producing a multifilament or a spun yarn, a wet or dry solution spinning method, a melt blowing method, a spunbonding method, or the like, which are suitable for obtaining a sheet-like fiber structure. Among these, from the viewpoint of obtaining a conjugate fiber bundle that can be used in textiles with high productivity, it is preferable to produce a multifilament or a spun yarn by a melt spinning method.

[0077] In the melt spinning method, the production can be achieved by using a composite spinneret described below, and the spinning temperature is preferably set to a temperature at which the polymers used, mainly the high-melting-point polymer and the high-viscosity polymer, exhibit fluidity. The temperature at which the fluidity is exhibited varies depending on the molecular weight, but stable production can be achieved by setting the temperature between the melting point of the polymer and the melting point + 60°C.

[0078] The spinning speed is preferably about 500 to 6000 m / min, but can be changed appropriately depending on the physical properties of the polymer and the intended use of the composite fiber bundle. In particular, from the viewpoint of achieving high orientation and improving mechanical properties, it is more preferable to set the spinning speed to 500 to 4000 m / min and then perform drawing. By setting the spinning speed to 500 to 4000 m / min, uniaxial orientation of the composite fiber can be promoted.

[0079] During drawing, it is preferable to set an appropriate preheating temperature using the softening temperature, such as the glass transition temperature of the polymer, as a guide. The upper limit of the preheating temperature is preferably set to a temperature at which yarn path disturbance due to spontaneous elongation of the composite fiber bundle does not occur during the preheating process. For example, in the case of PET, which has a glass transition temperature of around 70°C, the preheating temperature is usually set to about 80 to 95°C.

[0080] The output per hole of the spinneret used to produce the composite fiber bundle of this embodiment is preferably 0.1 to 10 g / min / hole. Setting the output within this range enables stable production. The discharged polymer flow is cooled and solidified, and then an oil is applied thereto, and the polymer flow is taken up by rollers set to a specified peripheral speed. The polymer flow is then stretched by heated rollers, and further post-processed as necessary to produce a composite fiber bundle in which the desired composite fibers are bundled together.

[0081] In the conjugated fibers constituting the conjugated fiber bundle of this embodiment, the melt viscosity ratio of the conjugated polymers is preferably less than 5.0. If the melt viscosity ratio is within this range, excessive crimping is suppressed, and it becomes easy to control the formation of complex voids and unevenness on the textile surface that occur when the crimp phases between the conjugated fibers are aligned, which is an object of the present invention.

[0082] In addition, when producing the composite fiber bundle of this embodiment, if melts of polymers with a large difference in melt viscosity are spun from a spinneret as a composite flow, the difference in flow rate caused by the difference in resistance from the wall surface inside the spinneret hole will cause the polymer on the lower viscosity side to push out the polymer on the higher viscosity side, resulting in yarn bending, which may come into contact with the spinneret or interfere with the composite flow spun from another location, causing yarn breakage.From the above perspective, it is preferable that the melt viscosity ratio of the polymers to be composited be less than 5.0.

[0083] It is also preferable that the difference in solubility parameter values ​​is less than 2.0, since this allows a stable formation of a composite polymer flow and enables the production of composite fibers having a good composite cross section.

[0084] As the spinneret used when producing the composite fiber bundle of this embodiment, for example, the composite spinneret described in Japanese Patent Application Laid-Open No. 2011-208313 is suitably used.

[0085] The composite spinneret shown in Fig. 7 is assembled into a spin pack and used for spinning, with three main components stacked from top to bottom: a metering plate 1, a distributor plate 2, and a discharge plate 3. Fig. 7 shows an example in which three types of polymers, i.e., polymer A, polymer B, and polymer C, are used. Since it is difficult to combine three or more types of polymers with conventional composite spinnerets, it is preferable to use a composite spinneret utilizing fine flow channels as shown in Fig. 7 in the production of the composite fiber bundle of this embodiment.

[0086] In the spinneret member exemplified in FIG. 7 , the metering plate 1 measures and introduces the amount of polymer per discharge hole and per distribution hole, the distribution plate 2 controls the cross section and cross-sectional shape of each composite fiber, and the discharge plate 3 compresses the composite polymer stream formed by the distribution plate 2 and discharges it.

[0087] In this case, to achieve a composite cross section in which all of the composite fibers constituting the composite fiber bundle have flat cross sections while varying the bonding surface direction for each composite fiber, which is cited as a preferred range in this embodiment, the nozzle holes of the nozzle plate 3 may be flat, and the composite polymer flow may be controlled so that the polymer bonding surface direction varies for each nozzle hole in the distributor plate 2. Also from the viewpoint of being able to control an arbitrary composite cross section for each nozzle hole in this way, it is preferable in this embodiment to use a composite spinneret utilizing fine channels as exemplified in Figure 7.

[0088] Although not shown in the drawings to avoid complicating the explanation of the composite spinneret, the components stacked above the metering plate 1 may be components with flow paths formed to match the spinning machine and spin pack. By designing the metering plate 1 to match existing flow path components, the existing spin pack and its components can be used as they are. Therefore, there is no need to dedicate a spinning machine specifically to this spinneret.

[0089] In practice, it is advisable to stack multiple flow path plates between the flow path and the metering plate 1 or between the metering plate 1 and the distributor plate 2. This is intended to provide a flow path through which the polymer is efficiently transported in the cross-sectional direction of the spinneret and the cross-sectional direction of the composite fiber, and to configure the polymer to be introduced into the distributor plate 2. The composite polymer stream discharged from the discharge plate 3 is cooled and solidified according to the above-mentioned production method, and then an oil is added thereto, and the composite polymer stream is taken up by rollers set to a specified peripheral speed. Thereafter, the composite polymer stream is stretched by heated rollers, and post-processed as necessary to form a composite fiber bundle in which the desired composite fibers are bundled together.

[0090] The post-processing referred to here is carried out when producing spun yarn made of staple fibers, and after drawing, the yarn is crimped using a press-type crimper or the like, and then cut into staple fibers with a fiber length of 20 to 120 mm, and then is preferably subjected to a known spinning processing technique.

[0091] When producing a multifilament made of long fibers, known yarn processing techniques such as false twisting and non-uniform drawing may be applied simultaneously with drawing.

[0092] In particular, from the viewpoint of changing the crimp form to a non-uniform form and making the resulting feel and texture complex, it is preferable to perform non-uniform stretching at a stretch ratio not exceeding the natural stretch ratio of the conjugate fiber to obtain a thick and thin structure in which stretched and unstretched parts appear randomly in the fiber axis direction (thick and thin). By performing non-uniform stretching, differences in dyeability occur between the stretched and unstretched parts, which further emphasizes the color shading and allows the fabric to express a mottled texture like that of natural materials when made into a textile.

[0093] As a method of performing non-uniform stretching, it is preferable to set the stretching ratio in the range of the lower limit of the natural stretching ratio × 1.2 to the upper limit, since this allows a natural and clear figured tone to be obtained, and the ratio can be determined depending on the desired figured tone.

[0094] Furthermore, when false twisting is performed, there are no particular limitations on the method as long as it is a method commonly used for polyester, but in consideration of productivity, it is preferable to perform the processing using a friction false twisting machine that uses a disk or belt.

[0095] In order to stably produce the crimped yarn of the present invention by false twisting, it is preferable to control the crimp diameter of the crimped yarn by the actual twist number of the yarn bundle in the twisting region. That is, it is preferable to set the false twist conditions, such as the rotation speed of the twisting mechanism and the processing speed, so that the false twist number T (unit: turns / m), which is the twist number of the yarn bundle in the twisting region, is determined according to the total fineness Df (unit: dtex) of the yarn bundle after false twisting, and satisfy the following condition: 20000 / Df ０．５ ≦T≦40000 / Df ０．５

[0096] Here, the false twist number T is measured by the following method. That is, a yarn bundle running in the twisting region of the false twisting process is sampled to a length of 50 cm or more so as not to untwist immediately before the twister. The sampled yarn sample is then attached to a twist detector, and the number of twists is measured by the method described in JIS L1013 (2010) 8.13, which is the false twist number T. When the false twist number satisfies the above-mentioned condition, the obtained yarn bundle can control a coarse crimp diameter of 300 μm or more, and deterioration of the textile surface quality, such as wrinkles and streaks, can be suppressed.

[0097] Furthermore, under the above false twist conditions, in order to impart uniform crimp to the entire composite fibers constituting the composite fiber bundle and obtain a high-quality textured yarn of the present invention, it is advisable to adjust the draw ratio in the twisting region. The draw ratio here is calculated as Vd / V0, where V0 is the peripheral speed of the roller supplying the yarn to the twisting region and Vd is the peripheral speed of the roller installed immediately after the twisting mechanism, and is preferably determined depending on the properties of the yarn being supplied.

[0098] When a drawn yarn is used as the supply yarn, Vd / V0 may be set to 0.9 to 1.4 times, and when an undrawn yarn is used as the supply yarn, Vd / V0 may be set to 1.2 to 2.0 times, and drawing may be performed simultaneously with false twisting. By setting the draw ratio within this range, excessive tension in the twisting region and slack in the yarn bundle do not occur, and uniform crimp can be imparted to all of the conjugate fibers constituting the conjugate fiber bundle.

[0099] Furthermore, from the viewpoint of firmly fixing the crimp obtained in the twisting step, it is preferable to determine the false twisting temperature within the range of Tg+50 to Tg+150°C, using the Tg of the higher Tg polymer in the composite polymers as the reference.

[0100] The false twist temperature referred to here means the temperature of the heater installed in the twisting region. By setting the false twist temperature within this range, the polymer that has been significantly twisted and deformed within the cross section of the composite fiber can be sufficiently fixed in structure, resulting in good dimensional stability of the crimp obtained in the twisting process and a high-quality textile free of wrinkles and streaks. In order to fix the crimp obtained in the twisting process and not impair the ability to develop crimp obtained by polymer compounding, it is preferable to use a one-heater method in which a heater is installed only in the twisting region.

[0101] The composite fiber bundle of the present invention will be specifically described below with reference to examples. The examples and comparative examples were evaluated as follows.

[0102] A. Melt Viscosity of Polymer Chip-shaped polymer was dried to a moisture content of 200 ppm or less using a vacuum dryer, and the melt viscosity was measured using a Toyo Seiki Capillograph while changing the strain rate stepwise. The measurement temperature was the same as the spinning temperature, and the time from when the sample was placed in a heating furnace under a nitrogen atmosphere to when the measurement started was 5 minutes. The shear rate was 1216 s －１ The value was evaluated as the melt viscosity of the polymer.

[0103] B. Melting Point of Polymer Chip-shaped polymer was adjusted to a moisture content of 200 ppm or less using a vacuum dryer, and approximately 5 mg was weighed out. Using a TA Instruments differential scanning calorimeter (DSC) Model Q2000, the temperature was raised from 0°C to 300°C at a heating rate of 16°C / min, and then held at 300°C for 5 minutes for DSC measurement. The melting point was calculated from the melting peak observed during the heating process. Measurements were performed three times per sample, and the average value was taken as the melting point. When multiple melting peaks were observed, the melting point was determined to be the top of the melting peak with the highest temperature.

[0104] C. Fineness The weight of a 100 m composite fiber bundle was measured, and the weight was multiplied by 100. This operation was repeated 10 times, and the average value was rounded to one decimal place to obtain the fineness (dtex).

[0105] D. Flatness A composite fiber bundle was embedded in an embedding agent such as epoxy resin, and an image of the fiber cross section perpendicular to the fiber axis was taken using a Hitachi scanning electron microscope (SEM) at a magnification sufficient to observe 10 or more composite fibers. One composite fiber randomly selected from the image was analyzed using image analysis software. As shown in Figure 1(a), the line connecting the two most distant points (a1, a2) on the periphery of the composite fiber was defined as the major axis, and the line connecting the intersection (b1, b2) of the periphery of the fiber with a line passing through the midpoint of the major axis and perpendicular to the major axis was defined as the minor axis. The length of the major axis was divided by the length of the minor axis to calculate the flatness. This was repeated for 10 composite fibers randomly selected from the same image. The simple number average of the results was calculated, and the value rounded to one decimal place was used as the average flatness. In addition, among the composite fibers whose flatness was determined, the largest value was subtracted from the smallest value, and the difference was rounded to two decimal places to obtain the difference between the maximum and minimum flatness values.

[0106] E. Fiber Diameter A composite fiber bundle was embedded in an embedding agent such as epoxy resin, and an image of the fiber cross section perpendicular to the fiber axis was taken with a scanning electron microscope (SEM) at a magnification such that 10 or more composite fibers could be observed. The area of ​​one composite fiber randomly selected from the image was measured, and the diameter calculated as a perfect circle was measured in μm units to one decimal place. The same procedure was carried out for 10 composite fibers randomly selected from the same image as above, and the simple number average of the results was calculated, and the value rounded to one decimal place was used as the fiber diameter (μm).

[0107] F. Coefficient of variation CV of (distance between polymer centers of gravity / fiber diameter) For a textile consisting of a composite fiber bundle, an image of the cross section of the textile perpendicular to the length direction of the textile and perpendicular to the fiber axis direction of the composite fibers was taken using a scanning electron microscope (SEM) manufactured by Hitachi at a magnification such that 20 or more composite fibers could be observed. One composite fiber randomly extracted from the captured image was analyzed using computer software WinROOF manufactured by Mitani Shoji to measure the area of ​​the composite fiber, and the diameter calculated as a perfect circle was measured in μm units to one decimal place. The obtained value was taken as the fiber diameter (μm).

[0108] Furthermore, for the same conjugate fiber as above, the length of the line connecting the centers of gravity (Gx, Gy) of the low-melting point polymer x and the high-melting point polymer y in the cross section of the conjugate fiber was measured in μm units to one decimal place as shown in (a) of Figure 2. The obtained value was defined as the distance between the polymer centers of gravity (μm).

[0109] For the fiber diameter and the distance between the polymer centers of gravity obtained above, a simple number average of the ratio (distance between the polymer centers of gravity / fiber diameter) was calculated, and the value rounded to one decimal place was used as (distance between the polymer centers of gravity / fiber diameter). This evaluation was performed in the same manner for 20 composite fibers ((1) to (20) in Figure 5) randomly sampled from the same image, and the standard deviation and average of the results were calculated. The standard deviation was divided by the average value, multiplied by 100, and the value was rounded to the nearest whole number. The obtained value was used as the coefficient of variation CV (%) of the value of (distance between the polymer centers of gravity / fiber diameter).

[0110] G. Number of crimp peaks (peaks / cm) In a textile consisting of a composite fiber bundle, a composite fiber was extracted from the textile without plastic deformation, one end of the composite fiber was fixed, and a load of 1 mg / dtex was applied to the other end. After 30 seconds or more, markings were made at random locations where the distance between the two points was 1 cm in the fiber axis direction of the composite fiber. The composite fiber was then fixed on a glass slide, adjusting the distance between the pre-marked marks to the original 1 cm so as not to plastically deform the composite fiber. Images of this sample were taken with a digital microscope at a magnification that allowed observation of the 1 cm markings. When the composite fiber in the photographed image had a crimp morphology as shown in Figure 6, the number of crimp peaks present between the markings was determined. This procedure was performed on 10 composite fibers, and the simple number average was calculated. The value, rounded to one decimal place, was used as the number of crimp peaks (peaks / cm).

[0111] H. Spinning stability Spinning was carried out for each example and comparative example, and the spinning stability was evaluated based on the number of yarn breakages per 10 million meters (times / 10 million meters) and rated into four levels based on the following criteria: S: Excellent spinning stability (number of yarn breakages < 1.0) A: Good spinning stability (1.0 ≦ number of yarn breakages < 2.0) B: Spinning stability (2.0 ≦ number of yarn breakages < 3.0) C: Poor spinning stability (3.0 ≦ number of yarn breakages).

[0112] I. Textile Texture Evaluation (Fluffiness, Resilience, and Smoothness) A 3 / 1 twill fabric was prepared by adjusting the number of conjugated fibers so that the warp cover factor (CFA) was 800 and the weft cover factor (CFB) was 1200. The CFA and CFB values ​​were calculated by measuring the warp density and weft density of the fabric in a 2.54 cm interval in accordance with JIS-L-1096:2010 8.6.1, where CFA = warp density × (warp fineness). １／２ , CFB = weft density × (weft fineness) １／２ The obtained woven fabric was subjected to the following conditions of scouring, relaxation and heat setting in this order, and then evaluated for three properties of texture: bulkiness, resilience and smoothness using the following methods.

[0113] (Scouring, wet heat treatment, and heat setting) After scouring for 10 minutes in warm water at 80° C. containing a surfactant, the fabric was subjected to a relaxation treatment for 30 minutes in warm water at 130° C. Then, heat setting was performed at 180° C. for 5 minutes.

[0114] I-1. Fluffiness Using a Terotec constant pressure thickness gauge (PG-14J), the thickness (cm) of a 20 cm x 20 cm woven fabric was measured under a constant pressure (0.7 kPa), and the volume of the woven fabric was calculated. The weight (g) of the woven fabric was then divided by the volume obtained, and the value was rounded to one decimal place to obtain the apparent density (g / cm) of the woven fabric. ３ From the apparent density obtained, the fluffiness was evaluated on a four-point scale based on the following criteria: S: Excellent fluffiness (apparent density ≦ 0.5) A: Good fluffiness (0.5 < apparent density ≦ 0.8) B: Some fluffiness (0.8 < apparent density ≦ 1.1) C: Poor fluffiness (1.1 < apparent density).

[0115] I-2. Resilience Using a pure bending tester (KES-FB2) manufactured by Kato Tech, a 20 cm x 20 cm woven fabric was held with an effective sample length of 20 cm x 1 cm and bent in the weft direction to a curvature of ±1.0 cm. －１ This operation was performed three times per location, and a simple number average of the results was calculated for a total of 10 locations. The average was rounded to the fourth decimal place and then divided by 100 to obtain the bending recovery 2HB x 10 －２ (gf cm / cm). The bending recovery obtained was 2HB x 10 －２ The resilience was evaluated based on the following criteria: S: Excellent resilience (bending recovery 2HB x 10 －２ ≦0.8) A: Good resilience (0.8<bend recovery 2HB×10 －２ ≦1.5) B: Feels resilient (1.5<bend recovery 2HB×10 －２ ≦2.5) C: Poor resilience (2.5<bend recovery 2HB×10 －２ ).

[0116] I-3. Smoothness Using a Kato Tech automated surface tester (KES-FB4), a 50 g load was applied to a 1 cm x 1 cm terminal wound with piano wire over a 10 cm x 10 cm area of ​​a 20 cm x 20 cm woven fabric, and the terminal was slid at a speed of 1.0 mm / sec to determine the variation in the average coefficient of friction (MMD). This operation was performed three times per location, and a simple number average was calculated for the results of a total of 10 locations. The value was rounded to four decimal places to determine the friction variation (x 10 －２ ) The smoothness was evaluated based on the obtained friction fluctuation and rated on a four-point scale according to the following criteria: S: Excellent smoothness (1.5≦friction fluctuation) A: Good smoothness (1.2≦friction fluctuation<1.5) B: Smoothness (0.9≦friction fluctuation<1.2) C: Poor smoothness (friction fluctuation<0.9).

[0117] J. Textile Functionality Evaluation (Water Absorption, Quick Drying, Stretchability) A 3 / 1 twill fabric was prepared by adjusting the number of conjugated fibers so that the warp cover factor (CFA) was 800 and the weft cover factor (CFB) was 1200. Here, CFA and CFB refer to the warp density and weft density of the fabric measured in a 2.54 cm section in accordance with JIS-L-1096:2010 8.6.1, where CFA = warp density × (warp fineness). １／２ , CFB = weft density × (weft fineness) １／２ The value was calculated from the formula. The obtained woven fabric was subjected to scouring, wet heat treatment, alkali treatment and heat setting in this order, and then the two functions of water absorption, quick drying and stretchability were evaluated using the following methods. Note that scouring, relaxation treatment and heat setting were carried out under the same conditions as those used in the textile texture evaluation, and alkali treatment was carried out under the following conditions.

[0118] (Alkali Treatment) The sample was immersed in an aqueous solution of sodium hydroxide having a concentration of 0.5 to 2% by mass at a temperature of 90° C. for 30 minutes.

[0119] J-1. Moisture absorption and quick-drying property Moisture absorption and quick-drying property was measured by dropping 0.1 cc of water onto a 10 cm x 10 cm woven fabric, and then measuring the weight of the fabric every 5 minutes in an environment with a temperature of 20°C and a relative humidity of 65% RH, and determining the time (minutes) until the residual moisture content reached 1.0% or less. This operation was performed at a total of three locations, and the simple number average of the results was calculated, and the value rounded to the nearest whole number was used as the moisture diffusion time (minutes). The moisture absorption and quick-drying property was evaluated based on the obtained moisture diffusion time in three stages according to the following criteria: S: Excellent moisture absorption and quick-drying property (moisture diffusion time ≦ 15) A: Good moisture absorption and quick-drying property (15 < moisture diffusion time ≦ 30) C: Poor moisture absorption and quick-drying property (30 < moisture diffusion time).

[0120] J-2. Stretchability Stretchability was measured in accordance with the Elongation A Method (constant rate elongation method) described in Section 8.16.1 of JIS-L-1096:2010. The strip method was used with a load of 17.6 N (1.8 kg), and the test conditions were a sample width of 5 cm x length of 20 cm, a clamp spacing of 10 cm, and a tensile speed of 20 cm / min. The initial load was a weight equivalent to a sample width of 1 m, in accordance with the method of JIS-L-1096:2010. The test was performed three times in the weft direction of the fabric, and the simple average of the results was calculated. The value was rounded to the nearest whole number to obtain the elongation percentage (%). From the obtained elongation percentage, the stretchability was evaluated on a three-level scale based on the following criteria: S: Excellent stretchability (20≦elongation percentage); A: Good stretchability (5≦elongation percentage<20); C: Poor stretchability (elongation percentage<5).

[0121] K. Textile Quality Evaluation (Appearance Quality) A 3 / 1 twill fabric was prepared by adjusting the number of conjugated fibers so that the warp cover factor (CFA) was 800 and the weft cover factor (CFB) was 1200. The CFA and CFB herein are values ​​calculated by measuring the warp density and weft density of the fabric in a 2.54 cm interval in accordance with JIS-L-1096:2010 8.6.1, and then using the formulas: CFA = warp density × (warp fineness) 1 / 2, CFB = weft density × (weft fineness) 1 / 2.

[0122] The resulting woven fabrics were subjected to scouring, relaxation, and heat setting under the same conditions as those for the textile texture evaluation. Then, using an automatic variable angle photometer (GONIOPHOTOMETER GP-200 model) manufactured by Murakami Color Research Laboratory, light was incident on each sample at an incident angle of 60°, and the light intensity at acceptance angles of 0° to 90° was measured by two-dimensional reflected light distribution measurement in 0.1° increments. The maximum light intensity (specular reflection) near an acceptance angle of 60° was divided by the minimum light intensity (diffuse reflection) near an acceptance angle of 0° to calculate the value. This operation was performed three times per location, and a simple number average of the results for a total of 10 locations was calculated. The value rounded to one decimal place was used as the glare index. The appearance quality of the textile was evaluated based on the obtained glare index using four levels according to the following criteria. S: Excellent appearance quality (glare level < 2.0) A: Good appearance quality (2.0 ≦ glare level < 2.5) B: Appearance quality is good (2.5 ≦ glare level < 3.0) C: Poor appearance quality (3.0 ≦ glare level).

[0123] L. Abrasion Resistance A plain woven fabric was prepared by adjusting the number of composite fibers so that the warp cover factor (CFA) was 1100 and the weft cover factor (CFB) was 1100. The resulting plain woven fabric was dyed black using the disperse dye Sumikaron Black S-3B (10% owf). The dyed plain woven fabric was cut into a 10 cm diameter circle, moistened with distilled water, and attached to a disk. Further, a 30 cm square piece of plain woven fabric was cut and fixed on a horizontal plate while still dry. The disk with the fabric moistened with distilled water attached was horizontally brought into contact with the fabric fixed on the horizontal plate, and the disk was moved circularly for 10 minutes at a load of 420 g and a speed of 50 rpm so that the center of the disk drew a 10 cm diameter circle, causing the two pieces of fabric to rub against each other. After rubbing, the fabric was left to stand for 4 hours, and the degree of discoloration of the fabric attached to the disk was graded on a scale of 1 to 5 in increments of 0.5 using a gray scale for discoloration. From the grades obtained, the abrasion resistance was graded on a four-level scale based on the following criteria: S: Excellent abrasion resistance (grade: 4.5 or higher) A: Good abrasion resistance (grade: 3.5, 4) B: Good abrasion resistance (grade: 2.5, 3) C: Poor abrasion resistance (grade: 2 or lower).

[0124] [Example 1] Polymer 1 was prepared as polyethylene terephthalate copolymerized with 7 mol% isophthalic acid (IPA copolymerized PET, melt viscosity: 140 Pa·s, melting point: 232°C), and polymer 2 was prepared as polyethylene terephthalate (PET, melt viscosity: 130 Pa·s, melting point: 254°C).

[0125] These polymers were melted separately at 290°C, and then weighed so that the area ratio of polymer 1 / polymer 2 in the composite cross section was 50 / 50. Next, the above polymers were introduced into a spinning pack incorporating the composite spinneret shown in Figure 7, and the introduced polymers were discharged from the discharge holes so as to produce a flat composite cross section as shown in Figure 1(a) in which polymer 1 and polymer 2 were bonded side-by-side, with the bonding surface direction varying for each composite fiber (the six types in Figure 4 are examples of such composite cross sections).

[0126] The discharged composite polymer stream was cooled and solidified, then an oil was applied, and the stream was taken up at a spinning speed of 1,500 m / min, followed by drawing between rollers heated to 90°C and 130°C to spin a composite fiber bundle of 84 dtex-36 filaments (fiber diameter 15 μm). The number of yarn breakages was 1.5 times per 10 million meters, demonstrating good spinning stability.

[0127] All of the conjugate fibers constituting the obtained conjugate fiber bundle had a flat cross-sectional shape, the average flatness among the conjugate fibers was 1.8, and the difference between the maximum and minimum flatness values ​​was 0.1. In addition, the coefficient of variation CV of the value of (distance between the centers of gravity of the polymer / fiber diameter) among the conjugate fibers was 18%, confirming that the conjugate fiber bundle was the conjugate fiber bundle of this embodiment.

[0128] The obtained composite fiber bundle was woven, and subjected to a scouring treatment at 80°C and a wet heat treatment at 130°C, followed by heat setting at 180°C, to obtain a woven fabric made of composite fiber bundles having a crimped morphology with a crimp peak count of 18 peaks / cm of the composite fibers.

[0129] The fabric made of the composite fiber bundle has a smooth texture due to the unevenness of the textile surface caused by the partial alignment of the crimp phase (friction fluctuation: 1.3 × 10 －２Furthermore, the fabric made of the composite fiber bundles exhibited a moderate resilience (bending recovery 2HB: 1.1 × 10 －２ gf cm / cm) and swelling (apparent density: 0.8 g / cm ３ ) and had excellent stretchability (elongation: 18%) and quick-drying water absorption due to the formation of voids between the composite fibers (moisture diffusion time: 25 minutes). Therefore, the woven fabric made of the composite fiber bundle was a woven fabric excellent in wear comfort, achieving both texture and functionality that are directly related to human comfort.

[0130] Furthermore, the appearance of the fabric was excellent (glare level: 2.4), as uneven appearance (glare) due to diffused reflection of light caused by the voids formed between the composite fibers was suppressed. Furthermore, because the composite fiber was made of polyethylene terephthalate and its copolymer, it was found to have good abrasion resistance (grade 4) without discoloration due to fibrillation caused by the polymer, and thus had properties suitable for clothing textiles. The results are shown in Table 1.

[0131] Comparative Example 1 The same procedure as in Example 1 was repeated except that the bonding surface direction of each of the conjugate fibers constituting the conjugate fiber bundle was not changed.

[0132] In Comparative Example 1, the coefficient of variation CV of the value of (distance between polymer centers of gravity / fiber diameter) was 0%, so all of the conjugate fibers constituting the conjugate fiber bundle exhibited the same crimp morphology, resulting in a conjugate fiber bundle with a uniform crimp phase. As a result, the textile surface had little unevenness and lacked a smooth feel, and the gaps between the conjugate fibers were small, resulting in a lack of fluffy feel. The results are shown in Table 1.

[0133] Comparative Example 2 The procedure of Comparative Example 1 was repeated except that polymer 1 was changed to the same PET as polymer 2, and after stretching, false twisting was carried out using a friction disc at a rotation speed such that the false twist number was 3,000 T / m while heating with a heater set at 180°C between rollers at a processing speed of 250 m / min and a stretch ratio of 1.05.

[0134] In Comparative Example 2, since the conjugate fibers were made of the same polymer, all of the conjugate fibers constituting the conjugate fiber bundle exhibited a uniform crimp morphology. As a result, the unevenness of the textile surface was monotonous, and the textile lacked a smooth feel. The results are shown in Table 1.

[0135] Comparative Example 3 Polyethylene terephthalate copolymerized with 7 mol% isophthalic acid (IPA copolymerized 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.

[0136] These polymers were melted separately at 290°C, and then weighed so that the area ratio in the composite cross section would be 50 / 50, and the incoming polymers were discharged from the discharge holes so as to form a composite cross section with a circular cross section in which polymer 1 and polymer 2 were bonded side-by-side as shown in Figure 3. At this time, the discharge rate from each discharge hole was adjusted so that the composite fiber bundle would be composed of two types of composite fibers with different fiber diameters.

[0137] The discharged composite polymer stream was cooled and solidified, then an oil agent was applied, and the stream was taken up at a spinning speed of 1500 m / min. The stream was stretched between rollers heated to 90°C and 130°C to produce a composite fiber bundle of 84 dtex-36 filaments (fiber diameter 14 μm (minimum value: 11 μm (18 filaments), maximum value: 17 μm (18 filaments))). The fiber diameter of the composite fiber bundle here was calculated by (minimum value + maximum value) / 2. The obtained composite fiber bundle was woven, and subjected to a scouring treatment at 80°C and a wet heat treatment at 130°C, followed by heat setting at 180°C, thereby obtaining a woven fabric composed of the above composite fiber bundle.

[0138] In Comparative Example 3, the coefficient of variation CV of the value of (distance between polymer centers of gravity / fiber diameter) was 0%, so the conjugate fibers constituting the conjugate fiber bundle showed the same crimp development ability, resulting in a conjugate fiber bundle with a uniform crimp phase. As a result, the textile surface had little unevenness and lacked a smooth feel. In addition, the gaps between the conjugate fibers were small, and the textile lacked volume and resilience. Furthermore, since conjugate fibers with different fiber diameters were wound simultaneously during fiber production, yarn interference occurred due to different cooling and solidification behaviors, resulting in poor spinning stability. The results are shown in Table 1.

[0139] Comparative Example 4: As polymer 1, polyethylene terephthalate copolymerized with 7 mol% isophthalic acid (IPA copolymerized PET, melt viscosity: 140 Pa s, melting point: 232°C) was prepared, and as polymer 2, polyethylene terephthalate (PET, melt viscosity: 130 Pa s, melting point: 254°C) was prepared.

[0140] These polymers were melted separately at 290°C, and then weighed so that the area ratio in the composite cross section was 50 / 50, and the inflow polymers were discharged from the discharge hole so as to form a flat composite cross section in which polymer 1 and polymer 2 were bonded side-by-side (without changing the bonding surface direction for each composite fiber) as shown in Figure 1(a). At this time, the discharge hole was adjusted so that the average flatness between the composite fibers constituting the composite fiber bundle was 1.8, and the difference between the maximum and minimum flatness values ​​was 0.5.

[0141] The discharged composite polymer stream was cooled and solidified, and then an oil was applied thereto, followed by winding at a spinning speed of 1500 m / min and drawing between rollers heated to 90°C and 130°C to produce a composite fiber bundle of 84 dtex-36 filaments (fiber diameter 15 μm). The obtained composite fiber bundle was woven, subjected to a scouring treatment at 80°C and a wet heat treatment at 130°C, and then heat set at 180°C to obtain a woven fabric composed of the above composite fiber bundle.

[0142] In Comparative Example 4, the coefficient of variation CV of the value of (distance between the centers of gravity of polymers / fiber diameter) was 31%, so when the textile was made, the unevenness of the textile surface became fine, the friction fluctuation was small, and the texture was monotonous. Furthermore, since composite fibers with significantly different flatness were wound simultaneously during fiber production, yarn interference occurred due to different cooling solidification behaviors, and the spinning stability was poor.

[0143] [Example 2] The same procedure as in Example 1 was repeated except that the surface layer of the composite fiber was covered with PET to change the composite cross section to that shown in Fig. 1(b). The ratio S / D of the minimum thickness S of the PET to the fiber diameter D, determined by the above-mentioned method, was 0.03.

[0144] In Example 2, the copolymerized PET was not exposed on the surface layer of the composite fiber, which not only improved abrasion resistance but also reduced the difference in cooling between the PET and the copolymerized PET, thereby suppressing yarn bending after discharge from the spinneret and providing excellent spinning stability. The results are shown in Table 1.

[0145] Example 3 The same procedures as in Example 1 were repeated except that the cross-sectional shape of the composite fiber was changed to a flattened multilobe shape having eight projections on the surface as shown in FIG. 1(c).

[0146] In Example 3, the formation of irregularities on the surface of the composite fiber suppressed uneven appearance (glare) of the textile due to diffused reflection of light, improving the appearance quality. Furthermore, by combining composite fibers with irregularities on the surface, fine interfiber voids were formed in the composite fiber bundle, improving the dry feel and quick-drying properties of the fiber. The results are shown in Table 1.

[0147] Example 4 The same procedures as in Example 1 were carried out except that the average flatness between the composite fibers was changed to 1.3.

[0148] In Example 4, as the average flatness of the composite fiber decreased, the crimp morphology developed upon heat treatment became finer and closer to a coil shape. This not only increased stretchability, but also reduced the flattened edges, reducing friction and improving abrasion resistance. The results are shown in Table 2.

[0149] Comparative Example 5 The same procedures as in Example 1 were carried out except that the cross-sectional shape of the composite fibers was changed to a round cross-section as shown in FIG. 3 (the bonding surface direction for each composite fiber was not changed).

[0150] In Comparative Example 5, the coefficient of variation CV of the value of (distance between polymer centers of gravity / fiber diameter) was 0%, so all of the conjugate fibers constituting the conjugate fiber bundle exhibited the same crimp morphology, resulting in a convergent conjugate fiber bundle with a uniform crimp phase. As a result, the textile surface had no unevenness, resulting in a flat texture. In addition, there were no voids between the conjugate fibers, so the textile lacked fluffiness, resilience, and moisture absorption / quick-drying properties. The results are shown in Table 2.

[0151] Example 5 The same procedures as in Example 1 were repeated except that Polymer 2 was changed to PET having a melt viscosity of 30 Pa·s.

[0152] In Example 5, the crimping morphology was more pronounced, and not only was the resulting woven fabric more fluffy, but the stretchability was also improved. The results are shown in Table 2.

[0153] [Examples 6 and 7] The same procedures as in Example 1 were repeated except that the discharge rate was changed so that the fiber diameter of the composite fiber was 10 μm (Example 6) or 20 μm (Example 7).

[0154] In Example 6, by setting the fiber diameter of the composite fiber to 10 μm, diffused reflection of light was increased, and uneven appearance (glare) was suppressed when the textile was made, improving the appearance quality. In addition, the bending rigidity of each fiber was reduced, improving flexibility. The results are shown in Table 2.

[0155] In Example 7, by setting the fiber diameter to 20 μm, the loops in the crimped form that appeared upon heat treatment became larger, improving the smooth feel and fluffy feel, and also increasing the bending stiffness, resulting in a characteristic elastic feel to the touch. The results are shown in Table 2.

[0156] [Example 8] Polymer 2 was mixed with polyethylene terephthalate (TiO ２ The same procedure as in Example 1 was repeated except that the resin was changed to a resin containing PET.

[0157] In Example 8, the titanium oxide on the surface of the composite fiber diffused light, suppressing glare (reflection) caused by the angle of incidence of light, improving the appearance quality of the textile. In addition, the titanium oxide inside the composite fiber provided functionality such as anti-transparency and UV protection. The results are shown in Table 2.

[0158] Examples 9 and 10 The same procedures as in Example 1 were repeated except that Polymer 1 was changed to polypropylene terephthalate (PPT) (Example 9) or polybutylene terephthalate (PBT) (Example 10).

[0159] In Examples 9 and 10, when the composite fiber bundles were made into textiles, the combined use of the rubber elastic properties of the PPT and PBT used as polymer 1 not only resulted in a texture with excellent flexibility, but also in a significantly improved stretch function. The results are shown in Table 2.

[0160] [Example 11] The procedure of Example 1 was repeated except that the composite fiber bundle was wound at a spinning speed of 2500 m / min, stored for one month under standard conditions (temperature 23°C, relative humidity 65%), and then subjected to non-uniform drawing processing at a hot pin temperature of 70°C and a set temperature of 130°C at a draw ratio equal to the upper limit of the natural draw ratio of the composite fiber bundle. In Example 11, differences in dyeability occurred between the drawn and undrawn portions of the composite fiber, so when the composite fiber bundle was made into a textile, the color shading was more emphasized and a heathered texture like that of natural materials was obtained. The results are shown in Table 2.

[0161]

[0162]

[0163] Although the present invention has been described in detail and with reference to specific embodiments, it will be apparent to those skilled in the art that various changes and modifications can be made without departing from the spirit and scope of the present invention. This application is based on a Japanese patent application (Patent Application No. 2021-122063) filed on July 27, 2021, the contents of which are incorporated herein by reference.

[0164] In the composite fiber bundle of this embodiment, by precisely controlling the crimp form of each of the composite fibers that make up the composite fiber bundle, differences in the voids are created between areas where the crimp phases are aligned and areas where they are not aligned between adjacent composite fibers, and complex voids and unevenness can be formed between the composite fibers, resulting in a unique smooth feel.

[0165] Therefore, by utilizing the conjugated fiber bundle of the present invention, a textile can be obtained which has excellent wearing comfort and which also realizes a moderate resilience and a fluffy texture due to the complex voids between the conjugated fibers. Therefore, the present invention can be suitably used in a wide range of textile products, from general clothing such as jackets, skirts, pants, and underwear to sports clothing and clothing materials, and, taking advantage of its comfort, in interior products such as carpets and sofas, vehicle interior parts such as car seats, cosmetics, cosmetic masks, health products, and other daily uses.

[0166] x: low melting point polymer y: high melting point polymer a1, a2: two points on the outer periphery of the fiber that are the furthest apart b1, b2: intersection of a line that passes through the midpoint of a line connecting the two furthest points on the outer periphery of the fiber and intersects at right angles with the outer periphery of the fiber Gx: center of gravity of low melting point polymer Gy: center of gravity of high melting point polymer CF: composite fiber Cr: crimp peak 1: metering plate 2: distribution plate 3: discharge plate

Claims

1. A composite fiber bundle constituted by composite fibers made of at least two kinds of polymers having different melting points, characterized in that the coefficient of variation CV of the value of (distance between polymer centers of gravity / fiber diameter) between the composite fibers is 5 to 30%.

2. 2. The composite fiber bundle according to claim 1, wherein a difference between a maximum value and a minimum value of flatness between the composite fibers is less than 0.

5.

3. The composite fiber bundle according to claim 1 or 2, characterized in that an average flatness between the composite fibers is 1.2 to 3.

0.

4. 3. The composite fiber bundle according to claim 1, wherein the surface layer of the composite fiber is covered with one kind of polymer.

5. A textile product comprising, as a part thereof, the composite fiber bundle according to claim 1 or 2.