Composite fiber

Abstract

To provide a composite fiber capable of obtaining a textile having a natural spot and a soft touch like natural fibers.SOLUTION: There is provided a composite fiber in which two or more components make up a cross section, in which an average circularity of a segment of at least one component constituting the fiber is 0.20 or more and 0.80 or less, and a difference between the minimum and maximum circularity is 0.30 or more.SELECTED DRAWING: None

Description

Technical Field

[0001] The present invention relates to a composite fiber composed of two or more components.

Background Art

[0002] Synthetic fibers made of polyester, polyamide, etc. have excellent mechanical properties and dimensional stability, so they are widely used from clothing applications to non-clothing applications. However, these days, as people's lives have become more sophisticated, fibers with advanced sensibilities and functions that conventional synthetic fibers do not have are being demanded in various applications including clothing. There are a wide variety of sensibilities and functions that can be achieved by fibers, and as a direction for research and technological development of synthetic fibers, there are those that pursue fiber materials with a warm texture that have a certain regularity while having the same diversity of forms as natural fibers. In the process of this research, various fiber materials and elemental technologies related to fibers have been created.

[0003] Conventionally, fiber products such as knitted and woven fabrics made of synthetic fiber filaments mainly seek homogeneity from the perspective of quality control and the like. Naturally, compared with natural fibers such as cotton, hemp, and wool, the color tone, gloss, unevenness, etc. tend to be monotonous. In order to pursue a natural-style textile, it is necessary to complicate and devise the yarn processing and the knitted or woven fabric structure, and various technologies have been proposed in the polymer modification as a raw material, the yarn manufacturing, and the higher-order processing steps.

[0004] As a yarn manufacturing technology aiming at natural-style fibers, there is an example of making the cross-sectional structure of the single yarns that make up the multifilament uneven. For example, there is a proposal of a technology aimed at expressing natural spots and a soft touch like natural fibers by previously forming a single yarn from a plurality of components and eluting one component in a higher-order processing step.

[0005] In Patent Document 1, a multifilament composed of composite fibers with a cross-section laminated by a plurality of components has been proposed. Between the single filaments constituting this multifilament, the composite ratio and composite shape in the cross-section are different. By eluting one component, a multifilament composed of single filaments with an uneven cross-section can be obtained, and thereby, it is described that a fiber product with excellent texture, rich in changes such as color tone, gloss, unevenness, etc., can be obtained. This technology divides the composite polymer flow into layers with a static mixing element and accidentally distributes it to each discharge hole in different states. Therefore, although each component is laminated in a distorted shape in the cross-section of the single filament, a multifilament can be obtained in which the composite ratio and composite shape are different between the single filaments.

[0006] Also in Patent Document 2, a multifilament composed of composite fibers with a cross-section laminated by a plurality of components, and the composite ratio and composite structure are different between the single filaments, has been proposed. Similar to Patent Document 1, it is a technology using a static mixing element. By increasing the number of the mixing elements, a composite polymer flow with a larger number of laminated layers is formed, and by distributing this to each discharge hole, each component is laminated in a distorted shape in the cross-section of the single filament, and a multifilament can be obtained in which the composite ratio and composite shape are different between the single filaments.

[0007] In Patent Document 3, by devising the distribution path when distributing the composite polymer flow divided into layers by a static mixing element to each discharge hole, a multifilament including composite fibers having a multi-branched composite shape in which the single-filament cross-section consists of a trunk portion and branched portions radially extending therefrom has been proposed. This technology is such that some of the single filaments constituting the multifilament become multi-branched composite fibers, and the other single filaments become laminated composite fibers as exemplified in Patent Document 1 and Patent Document 2. By eluting one component, a multifilament composed of single filaments with a more uneven cross-section can be obtained, and it is said that a fiber product with excellent texture like natural fibers can be obtained.

Prior Art Documents

Patent Documents

[0008] [Patent Document 1] Japanese Patent Application Laid-Open No. 59-100717 (pages 5-7) [Patent Document 2] Japanese Patent Application Laid-Open No. 2002-309449 (claims) [Patent Document 3] Japanese Patent Application Laid-Open No. 10-237715 (pages 2-5) [Summary of the Invention] [Problems to be Solved by the Invention]

[0009] In Patent Documents 1 and 2, based on the principle that a static mixing element mixes a composite polymer flow by repeating division and conversion actions, the composite polymer flow will naturally be laminated in layers. Therefore, as the cross-sectional structure of the resulting single fiber, it will also be laminated in a state where the shapes and directions of the respective components are aligned.

[0010] On the other hand, in Patent Document 3, which aims to increase the complexity of the cross-section by applying this static mixing element and devising a distribution path, although the resulting composite fiber has a multi-branched composite shape in the cross-section, which is not seen in Patent Document 1 or Patent Document 2, ultimately, each component is laminated while slightly changing its direction, and it does not greatly exceed the range of composite fibers laminated in a state where the shapes are aligned.

[0011] Thus, in composite fibers that utilize the phenomenon of incomplete mixing by conventional static mixing elements, based on the principle of the static mixing element, even if the spinning pack is devised, the shapes and lamination forms of the components constituting the composite cross-section will be in a relatively aligned state. It is difficult to realize the complex appearance and texture formed by natural fibers, and in processed yarns utilizing these fibers, complex processing may be required in high-order processing, or post-mixing with other materials may be necessary, etc., and there may be restrictions in high-order processing.

[0012] Therefore, there is a high demand for fibers suitable for realizing the complex appearance and texture formed by natural fibers. For example, in the cross-section of a single fiber, a composite fiber having a certain regularity while the forms of the respective components have diversity has been desired.

Means for Solving the Problems

[0013] The above problems are achieved by the following means. That is, (1) In a composite fiber in which two or more components constitute a cross-section, The forms of the respective components have a marble-like composite form with diversity, and the composite form is continuous in the fiber axis direction, the cross-section of at least one component constituting the fiber has an average circularity of 0.20 or more and 0.80 or less, and the difference between the minimum value and the maximum value of the circularity is 0.30 or more. and U% is 1.0% or less Composite fiber characterized by the above. (2) The composite fiber according to (1), characterized in that segments with a circularity of 0.10 or less of the cross-section are present in 1 to 20% with respect to the total number of segments. (3) structure The composite fiber according to (1), characterized in that all the components constituting it are polyester. or (2) as described in. ( 4 )(1) to ( 3 ) A fiber product containing at least a part of the composite fiber described in any one of.

Advantages of the Invention

[0014] The present invention relates to a composite fiber in which two or more components have a cross-section in which they are kneaded in a so-called marble pattern, and provides a composite fiber suitable for obtaining a natural-finished processed yarn. By utilizing the composite fiber of the present invention, a textile having a natural mottle and a soft touch like a natural fiber can be obtained. Furthermore, due to its characteristic cross-sectional morphology, in high-order processing where repeated rubbing with a yarn guide or the like and compression deformation under heating are performed, the fuzzing of the composite fiber is suppressed, and the high-order processing passability is extremely excellent. Therefore, it is possible to process a high-quality natural-finished textile.

Brief Description of the Drawings

[0015]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Embodiments for Carrying Out the Invention

[0016] Hereinafter, the present invention will be described in detail together with preferred embodiments.

[0017] The composite fiber of the present invention is one in which the cross-section of the fiber is composed of two or more components, and in this cross-section, while the forms of the respective components have diversity, they have a regular marble-patterned composite form.

[0018] The marble-patterned composite form in the cross-section means a form in which each component is kneaded as exemplified in FIG. 1, and components with irregular shapes and directions are scattered.

[0019] For example, it has a composite shape in which circular components (C in FIG. 1), streak-shaped components (D in FIG. 1), triangular components (E in FIG. 1), and furthermore, components with complex shapes such as a plurality of these joined together (F in FIG. 1) are scattered.

[0020] The complex composite form of the cross-section can be defined by the circularity of the scattered components. In the present invention, at least one type of component constituting the fiber has an average circularity of 0.20 or more and 0.80 or less, and the difference between the minimum value and the maximum value of the circularity is 0.30 or more.

[0021] The circularity mentioned here is an index representing the complexity of the shape of the scattered components in the cross-section. In an image obtained by two-dimensionally photographing the cross-section of the fiber, (Circularity of the component) = {4π × area of the component / (perimeter of the component) 2} It can be obtained as follows, and in the present invention, it is obtained as follows.

[0022] That is, the cross-section of the fiber is two-dimensionally photographed with a stereomicroscope or the like at a magnification at which the interfaces of the components constituting the cross-section of the fiber can be observed. At this time, among the components constituting the fiber, if only a specific component is stained, the contrast of the component interface becomes clear and the image processing described later can be efficiently performed, which is preferable.

[0023] The image of the photographed fiber cross-section is converted into a grayscale image with image analysis software or the like, and the threshold value is adjusted to perform binarization processing. The cross-sectional parameters of the segments of a specific component are read from the binarized image, and the circularity of all the segments is obtained. Here, the segment means a component surrounded and separated by different components in the binarized image. The arithmetic mean of the circularities of the obtained segments is the average circularity referred to in the present invention.

[0024] The composite fiber of the present invention aims to create a natural mottle and a soft touch like natural fibers. The above-described marble-like cross-sectional structure gives variations in yarn properties, color tone, gloss, etc. for each single yarn, resulting in a natural texture and appearance. For example, when polyester and cation-dyeable polyester are used as the components constituting the composite fiber of the present invention and cation-dyed after being made into a textile, each component with different shades will be exposed on the surface in various states, creating a fine shade difference on the surface and making it rich in color tone and gloss changes. Also, if one type of the components constituting the composite fiber of the present invention is made into an easily elutable component in advance and then eluted after making the composite fiber of the present invention, extremely fine fibers with an uneven cross-section will be generated. These extremely fine fibers with an uneven cross-section not only give changes in color tone, gloss, unevenness feeling, etc., but also form unique fine and uneven voids at various positions between the extremely fine fibers, resulting in the appearance of a natural mottle and a soft touch. When assuming the utilization of the composite fiber for textiles such as woven and knitted fabrics by these extremely fine fibers, it is preferable that the cross-section of the composite fiber forms various morphologies without one type of component being aligned in a specific shape. In other words, the key point is that the roundness representing the complexity of the shape is widely distributed unevenly without bias.

[0025] As a result of the roundness being widely distributed from a minimum value of 0 to a maximum value of 1, the average roundness approaches 0.50, which is the middle of the minimum and maximum values, and the difference between the minimum and maximum values of the roundness tends to increase.

[0026] As the first and second requirements for obtaining the effects of the present invention, in the cross-section of at least one type of component constituting the fiber, the average roundness needs to be 0.20 or more and 0.80 or less, and moreover, the difference between the minimum value and the maximum value of the roundness needs to be 0.30 or more.

[0027] Within such a range, in the cross-section of the composite fiber, without the one type of component being aligned in a specific shape, there will exist complex shapes close to a circularity of 0, such as branched shapes, to simple circular shapes close to a circularity of 1. By eluting the other component, fibers with an uneven cross-section can be generated. Furthermore, due to the composite shape in which each component defined by this circularity is irregularly kneaded, the composite fiber also exhibits excellent high-order processing passability. This is because, as a result of the circularity being widely distributed, in the cross-section of the composite fiber, there will be components with complex shapes (F in FIG. 1), the contact area between the components will increase, and an anchor effect will act at the intrusion parts of the components with complex shapes into other components, making it difficult for interfacial peeling to occur between the components of the composite fiber. Here, the anchor effect refers to a phenomenon in which, when a certain component takes on a structure that intrudes into an object, it becomes difficult to mechanically peel off, and the peel strength increases.

[0028] In order to enhance the natural mottling and high-order processing passability obtained from the composite fiber, it is preferable to emphasize the unevenness of the components with complex shapes. For this purpose, it is preferable to have slightly more components with complex shapes than components with simple circular shapes, and the average circularity is preferably 0.20 or more and 0.50 or less. Furthermore, when it is desired to emphasize the natural mottling, it is more suitable for the circularity to be distributed more widely, and the difference between the minimum value and the maximum value of the circularity is preferably 0.50 or more.

[0029] Also, in the composite fiber characterized in that at least one type of component constituting the cross-section is not aligned in a specific shape, the larger the number of segments of the components constituting the cross-section, the more components with uneven shapes can be obtained. By eluting the other component, fibers with a more uneven cross-section can be generated. That is, it is more suitable for the number of segments of at least one type of component constituting the cross-section of the fiber to be large. Here, the number of segments refers to the number of segments constituting the cross-section of a single filament in the above-mentioned binarized image. In this case, it is preferable for the number of segments in the binarized cross-section to be 10 or more.

[0030] As described above, the composite fiber of the present invention has a marbled composite form with regularity while the forms of the respective components constituting its cross-section have diversity. Its characteristic cross-sectional form is suitable for obtaining a natural-textured textile that produces a natural mottle and a soft touch like natural fibers, and furthermore, it also exhibits a favorable effect from the viewpoint of higher-order processing passability.

[0031] That is, as described above, the point is that one type of component constituting the cross-section of the composite fiber does not align in a specific shape but forms various forms, and the existence ratio of the segments having a shape that intricately penetrates like the roots of a tree (G in FIG. 1) to the total number of segments is a requirement worthy of attention from the viewpoint of exerting an anchor effect and enhancing the interface peeling suppression effect. Incidentally, the segments having a shape that intricately penetrates like the roots of a tree have a circularity of 0.10 or less as defined in the present invention, and in the composite fiber obtained in the present invention, the segments with a circularity of 0.10 or less effectively act to suppress interface peeling.

[0032] Therefore, in the present invention, in order to improve the higher-order processing passability and obtain good quality when made into a textile, it is preferable that the segments with a circularity of 0.10 or less exist in an amount of 1 to 20% with respect to the total number of segments.

[0033] If the segments with a circularity of 0.10 or less are 1% or more with respect to the total number of segments, even when compression deformation is applied under heating, such as in the twisting process of false twisting, interface peeling is suppressed, not only the fuzzing of the composite fiber and the quality when made into a textile are kept good, but also it is difficult to induce yarn breakage in the higher-order processing step, and good operability is maintained. Further, in the cross-section, if the segments with a circularity of 0.10 or less are 20% or less with respect to the total number of segments, the portion where a specific component excessively surrounds the other component becomes less. For example, even when one type of component is eluted after making it into a textile, the ultrafine fibers with an uneven cross-section, which is a characteristic of the present invention, are efficiently generated, and the effect that the treatment is completed in a short time is achieved.

[0034] In addition, in the composite fiber of the present invention, although the shapes of the components forming the composite cross-section are uneven in the cross-section, they are continuous in the fiber axial direction, and there is no unstable phenomenon of thinning immediately below the die as seen in general blend spinning or the like. Therefore, for stable discharge, the obtained composite fiber is excellent in the thickness uniformity in the fiber axial direction and is suitable for processing a high-quality natural-textured textile.

[0035] Generally, in a composite fiber in which two or more components are mixed, since the elongation deformation behaviors of the respective components are different, the elongation deformation in the spinning process and the drawing process tends to become unstable. In particular, when the components constituting the composite fiber are discontinuous in the fiber axial direction, this instability is promoted, and the thickness unevenness in the fiber axial direction tends to increase. When at least one kind of component constituting the composite fiber is continuous in the fiber axial direction, the elongation deformation in the spinning process and the drawing process becomes stable, the generation of excessive thickness unevenness in the fiber axial direction is suppressed, and as a result, it is possible to avoid coarse color tone unevenness and unevenness of unevenness when processed into a textile, and it is possible to obtain a high-quality natural-textured textile. From this, in order to process a high-quality natural-textured textile in the present invention, it is preferable that at least one kind of component constituting the composite fiber is continuous in the fiber axial direction.

[0036] Note that the thickness unevenness in the fiber axial direction mentioned here can be represented by the value of Uster (fineness unevenness) U% which is an index of fineness unevenness. In order to process a high-quality natural-textured textile, it is preferable that U% is 1.0% or less. If U% is 1.0% or less, the degree of color tone unevenness and unevenness of unevenness expressed when made into a textile becomes more natural, and a high-quality natural-textured textile can be obtained. In particular, when aiming at a natural-textured textile, when made into a textile due to fineness unevenness, dyeing unevenness and the like tend to become prominent and may induce defects in high-order processing such as streaks, and it is preferable that this fineness unevenness can be controlled. Further, when at least one kind of component constituting the composite fiber which is a feature of the present invention is continuous in the fiber axial direction, by stabilizing the elongation deformation in the spinning process and the drawing process, the occurrence of yarn breakage is suppressed, and the effect of stabilizing the operability is also obtained.

[0037] When the composite fiber of the present invention is produced by melt spinning, if the constituent components are thermoplastic polymers, the processability is excellent. Therefore, for example, it is advisable to select from a polymer group such as polyester-based, polyethylene-based, polypropylene-based, polystyrene-based, polyamide-based, polycarbonate-based, polymethyl methacrylate-based, polyphenylene sulfide-based, etc. Also, from the viewpoint of suppressing interfacial peeling and improving the composite cross-section, it is better that the difference in solubility parameters between the components constituting the fiber is small, and it is advisable to select polymers so that the difference in solubility parameters between the two components forming the interface is 3.0 or less. Here, the difference in solubility parameter (SP value) means a parameter reflecting the cohesive force of a substance defined by (vaporization energy / molar volume) 1 / 2 and means a parameter reflecting the cohesive force of a substance, and for example, the values described on page 189 of "Plastic Data Book", jointly edited by Asahi Kasei Amidas Co., Ltd. / Plastic Editorial Department, etc. can be used. In particular, when one type of component is eluted after the composite fiber of the present invention is made into a textile to generate ultrafine fibers with an uneven cross-section, the components constituting the fiber are preferably an alkali-easily soluble polymer and an alkali-difficultly soluble polymer, and an alkali weight reduction treatment may be performed. For example, if the components constituting the fiber are an alkali-easily soluble polyester and an alkali-difficultly soluble polyester, or an alkali-easily soluble polyester and polyamide (alkali-difficultly soluble), uneven cross-section ultrafine fibers made of the alkali-difficultly soluble polymer will be generated by the alkali weight reduction treatment, and natural mottling derived from the cross-sectional shape can be obtained, which is suitable. By utilizing the composite fiber of the present invention, a textile having natural mottling and a soft touch like natural fibers can be obtained. Therefore, the present invention can be widely used as clothing and apparel applications such as general clothing applications such as inner and outer wear, and interior applications such as curtain cloth.

[0038] An example of the manufacturing method of the composite fiber of the present invention will be described in detail below.

[0039] The composite fiber of the present invention, that is, a composite fiber in which each component is amorphous in a cross section composed of two or more components and has a marble-like form, can be produced by spinning using a composite die. Here, as a method for spinning the composite fiber, melt spinning is preferable from the viewpoint of enhancing productivity.

[0040] As the composite die used for the composite fiber of the present invention, it is preferable to use the die described in JP-A-2018-154934 with a composite die specification. The composite die shown in FIG. 5 is incorporated into a spinning pack in a state where three types of members, namely, a metering plate H, a merging plate I, and a discharge plate J, are laminated from above and are subjected to spinning. Incidentally, FIG. 5 is an example using two types of components such as component A and component B, and if necessary, spinning may be performed using three or more types of components.

[0041] In the composite die illustrated in FIG. 5, the metering plate H measures the amount of each component (polymer) per hole of the merging plate I, and the merging plate I merges and mixes the measured different polymers an arbitrary number of times, so that in the cross section of the polymer stream, each polymer is composited in a marble-like pattern, and the discharge plate J compresses and discharges the polymer stream mixed by the merging plate I.

[0042] Regarding the confluence plate, since it is described in Japanese Patent Application Laid-Open No. 2018-154934, details are omitted here. It is a device that combines multiple channels through which different polymers flow. The polymers flowing from each channel hole are repeatedly combined, resulting in the mixing of different polymers. That is, the confluence plate has multi-stage confluence microchannels K as exemplified in Fig. 5 corresponding to each discharge hole of the discharge plate J. In each stage of this multi-stage confluence microchannel K, the confluence patterns such as the confluence position and angle of different polymer flows are different. Therefore, when the confluence is repeated, a marble-like pattern is formed on the cross-section of the polymer flow, with each component having various forms. Also, by changing the number of confluence stages of the multi-stage confluence microchannel K of the confluence plate I, the composite cross-section can be easily changed. For example, when the number of confluence stages is small, it has a coarse marble-like structure as exemplified in Fig. 2. By increasing the number of confluence stages, it can be made into a delicate marble-like structure as shown in Fig. 1, and further increasing it can make it into the structure shown in Fig. 3. Note that this composite cross-section can be continuously formed in the fiber axis direction. Compared with the method of accidentally distributing the polymer flow unevenly mixed by a static mixing element as in Japanese Patent Application Laid-Open No. 59-100717 (the cross-sectional structure by this method is as shown in Fig. 4), since the composite ratio and composite cross-section of each monofilament do not change over time, the yarn can be stably produced without yarn breakage.

[0043] To avoid complication in the description of the composite die, although not shown, for the members laminated above the metering plate H, members for forming a flow path may be used according to the spinning machine and the spin pack. By designing the metering plate H according to the existing flow path members, the existing spin pack and its members can be utilized as they are. For this reason, it is not particularly necessary to specialize the spinning machine for the die. Also, in practice, a plurality of flow path plates may be laminated between the flow path and the metering plate H or between the metering plate H and the confluence plate I. The purpose is to efficiently provide a flow path through which the polymer is transferred in the die cross-section direction and the single fiber cross-section direction, and to configure it to be introduced into the confluence plate I. The composite polymer stream discharged from the discharge plate J is, after cooling and solidification, applied with an oil agent and taken up by a roller having a specified peripheral speed to become a composite fiber.

[0044] Using the composite die as described above, the composite fiber of the present invention can be produced. Incidentally, it goes without saying that the composite fiber of the present invention can also be produced by a spinning method using a solvent such as solution spinning when using the composite die.

[0045] When melt spinning is selected, the components constituting the composite fiber of the present invention are as described above. For example, melt-moldable polymers such as polyethylene terephthalate or its copolymers, polyethylene naphthalate, polybutylene terephthalate, polytrimethylene terephthalate, polypropylene, polyolefin, polycarbonate, polyacrylate, polyamide, polylactic acid, and thermoplastic polyurethane can be mentioned. In particular, polycondensation polymers represented by polyester and polyamide have a high melting point and are more preferable. In addition, 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, or ultraviolet absorbers may be contained in the polymer. Further, from the viewpoint of suppressing interfacial peeling and improving the composite cross-section, it is preferable that the solubility parameter difference between the components constituting the fiber is 3.0 or less. In particular, when the composite fiber of the present invention is made into a textile and then one type of component is eluted to generate the ultrafine fibers with an uneven cross-section which is a feature of the present invention, it is preferable to contain an alkali-easily soluble polymer and an alkali-difficultly soluble polymer. For example, an alkali-easily soluble polyester and an alkali-difficultly soluble polyester, or an alkali-easily soluble polyester and polyamide (alkali-difficultly soluble) can be used. In particular, as the easily soluble polyester, it is preferable to use a polyester copolymerized with polyethylene glycol, sodium sulfoisophthalic acid alone or in combination from the viewpoints of spinnability and easy dissolution in a low-concentration aqueous solvent. Examples of suitable polymer combinations for generating ultrafine fibers with an uneven cross-section from the composite fiber of the present invention include polyethylene terephthalate copolymerized with 5 mol% to 15 mol% of 5-sodium sulfoisophthalic acid in the easily soluble component and polyethylene terephthalate copolymerized with 5 wt% to 15 wt% of polyethylene glycol having a weight average molecular weight of 500 to 3000 in addition to the aforementioned 5-sodium sulfoisophthalic acid, and polyethylene terephthalate or polyamide-6 in the difficultly soluble component.

[0046] When spinning the composite fiber of the present invention, the spinning temperature shall be the temperature at which mainly high melting point or high viscosity polymers exhibit fluidity among two or more components. As this temperature at which fluidity is exhibited, although it varies depending on the molecular weight, it may be set from the melting point of the polymer to the melting point + 60°C or lower. If it is below this, it is preferable because the polymer is not thermally decomposed or the like in the spinning head or spinning pack, and the decrease in molecular weight is suppressed.

[0047] The discharge amount when spinning the composite fiber of the present invention can be stably produced by setting it to 0.1 g / min·hole to 20.0 g / min·hole. In particular, when the single-hole discharge amount is such that the fineness of the single fiber after stretching is less than 4 dtex, a soft texture can be obtained when made into a fabric due to its fineness, which is preferable. The ratio of component A to component B when spinning the composite fiber of the present invention can be selected in the range of 5 / 95 to 95 / 5 in terms of the A component / B component ratio based on the discharge amount. When generating ultrafine fibers with an uneven cross-section from the composite fiber of the present invention using a hardly soluble component as component A and an easily soluble component as component B, the higher the ratio of the hardly soluble component, the more preferable it is in terms of the productivity of ultrafine fibers. If the A component / B component ratio is 30 / 70 to 20 / 80, the hardly soluble component does not excessively surround the easily soluble component in the cross-section of the fiber, and the dissolution treatment can be completed in a short time.

[0048] The polymer stream discharged in this way is cooled and solidified, an oil agent is applied, and it is taken up by a roller with a specified peripheral speed to become a composite fiber. Here, this take-up speed may be determined from the discharge amount and the target fiber diameter, but in order to stably produce the composite fiber used in the present invention, it is preferably in the range of 100 to 7000 m / min. From the viewpoint of improving the mechanical properties by making it highly oriented, this composite fiber may be stretched. This stretching may be performed after being once wound up in the spinning process, or stretching may be continuously performed without winding up once.

[0049] As the stretching conditions, for example, in a stretching machine composed of one or more pairs of rollers, for a fiber made of a polymer that generally exhibits thermoplasticity capable of melt spinning, by the peripheral speed ratio of the first roller set at a temperature equal to or higher than the glass transition temperature and lower than the melting point and the second roller corresponding to the crystallization temperature, the fiber can be stretched smoothly in the fiber axis direction and heat-set and wound up to obtain a composite fiber having a composite cross-section as shown in Fig. 1. As the upper limit of the temperature of the first roller, it is preferably set to a temperature at which yarn path disturbance of the fiber does not occur during the preheating process. For example, in the case of polyethylene terephthalate whose glass transition temperature is around 70°C, this preheating temperature is usually set to about 80 to 95°C.

[0050] The composite polymer stream discharged from the discharge plate 3 is, according to the above-described manufacturing method, cooled and solidified, then an oil agent is applied, taken up by a roller having a specified peripheral speed, and then stretched by a heating roller to become a desired composite fiber.

[0051] The composite fiber of the present invention obtained in this way has a marble-like cross-sectional structure that gives variations in yarn properties, color tone, gloss, etc. for each single fiber, thus creating a natural texture and appearance. Further, in order to obtain ultrafine fibers with an uneven cross-section from the composite fiber of the present invention, the composite fiber can be immersed in a solvent in which the easily soluble component can be dissolved to remove the easily soluble component, thereby obtaining ultrafine fibers with an uneven cross-section made of the hardly soluble component. When the easily soluble component is a copolymerized polyethylene terephthalate copolymerized with 5-sodium sulfoisophthalic acid or the like, an alkaline aqueous solution such as an aqueous sodium hydroxide solution can be used. As a method of treating the composite fiber of the present invention with an alkaline aqueous solution, for example, after forming the composite fiber or a textile made thereof, it may be immersed in the alkaline aqueous solution. At this time, heating the alkaline aqueous solution to 50°C or higher is preferable because it can accelerate the progress of hydrolysis. Note that the method of generating ultrafine fibers with an uneven cross-section from the composite fiber of the present invention is not limited to the above-described dissolution treatment, and can also be implemented by physical methods such as stretching, carding, and raising, chemical methods such as heat treatment, boiling water treatment, and swelling treatment, or a combination thereof.

[0052] As described above, the method for producing the composite fiber of the present invention has been described based on the general melt spinning method. Needless to say, it can also be produced by the melt blowing method and the spunbond method. Furthermore, it can also be produced by solution spinning methods such as wet and dry-wet methods.

Examples

[0053] The composite fiber of the present invention will be specifically described below with reference to examples. The following evaluations were performed on the examples and comparative examples.

[0054] A. Melt viscosity of polymer The measurement temperature was the same as the spinning temperature, and the melt viscosity of 1216 s -1 was described in the examples or comparative examples. The time from when the sample was put into the heating furnace until the start of measurement was set to 5 minutes, and the measurement was performed under a nitrogen atmosphere.

[0055] B. Melting point of polymer The chip-shaped polymer was dried in a vacuum dryer to a moisture content of 200 ppm or less, about 5 mg was weighed, and using a differential scanning calorimeter (DSC) Q2000 type manufactured by TA Instruments, after heating from 0 °C to 300 °C at a heating rate of 16 °C / min, it was held at 300 °C for 5 minutes and DSC measurement was performed. The melting point was calculated from the melting peak observed during the heating process. The measurement was performed 3 times for each sample, and the average value was taken as the melting point. When multiple melting peaks were observed, the melting peak top on the highest temperature side was taken as the melting point.

[0056] C. Solubility parameter difference The solubility parameter (SP value) is a parameter that reflects the cohesive force of a substance defined as the square root of (vaporization energy / molar volume). It can be determined by immersing a polymer in various solvents and taking the value of (vaporization energy / molar volume) of the solvent at which the swelling pressure becomes maximum as the (vaporization energy / molar volume) of the polymer. The SP value obtained in this way is described, for example, on page 189 of "Plastic Data Book" co-edited by Asahi Kasei Amidas Co., Ltd. / Plastic Editorial Department, and this value can be used. Also, the difference in solubility parameters of the polymers to be combined is calculated as the absolute value of (SP value of component A - SP value of component B).

[0057] D. Denier The weight of 100 m of the composite fiber was measured, and a value obtained by multiplying that value by 100 was calculated. This measurement was repeated 10 times, and the average value was taken as the denier (dtex). Also, the value obtained by dividing the above denier by the number of filaments was taken as the fineness of a single filament (dtex).

[0058] E. Uster U% Using a fineness variation measuring device Zellweger (UT-4), the Uster U% (H) of the composite fiber was measured under the conditions of a supply speed of 100 m / min, a twister rotation speed of 6000 rpm, and a measurement length of 100 m.

[0059] F. Average circularity and difference between the maximum and minimum values of circularity The composite fiber immediately after extrusion was cut almost perpendicular to the fiber axis direction at an arbitrary position in the fiber axis direction, and the cut surface was photographed at a magnification at which the interface of the components constituting the cross-section of a single filament could be observed with an OLYMPUS optical microscope. After extracting the cross-section of a single filament using image processing software (WINROOF), it was converted into a grayscale image, and threshold adjustment was performed for binarization processing. Cross-section parameters of segments representing a specific component were read from the binarized image, and the circularity of all the extracted segments was measured. The same processing was repeated for the cross-sections of 5 single filaments, and the circularity of each obtained segment was arithmetically averaged, and the average circularity was obtained by rounding off the digits below the third decimal place. The circularity of each segment was calculated by the following formula using the image processing software. (Circularity of segment) = {4π × Area of segment / (Perimeter of segment) 2} Among all the extracted segments, the difference between the circularity of the segment with the maximum circularity and the circularity of the segment with the minimum circularity was determined.

[0060] G. Ratio of the total number of segments with a circularity of 0.10 or less to the total number of segments Among all the segments extracted from the above-mentioned binarized image, the ratio of the number of segments with a circularity of 0.10 or less to the total number of segments was calculated.

[0061] H. Appearance (dyed fabric) The number of fibers of the composite fiber was adjusted so that the weaving density became 180 fibers / 2.54 cm, and a plain weave fabric was produced. The obtained plain weave fabric was scoured at 80°C for 20 minutes and then dyed under the following dyeing conditions. Dye: NICHILON BLUE (manufactured by Nichisei Kasei) 3.0% owf Auxiliary agent: ULTRA N-2 (manufactured by Mitajima Chemical) 0.5 g / L[[ID=2"2]] Dispersant: RAP-250 (manufactured by Meisei Chemical) 0.5 g / L Dyeing conditions: 50°C × 20 minutes → 100°C × 30 minutes.

[0062] The appearance of the plain weave fabric dyed above was judged by 5 inspectors based on the following criteria in three grades. A: There is a distinct shade. B: It is slightly unclear but has a shade. C: Monotonous.

[0063] I. Appearance (alkali-treated fabric) The number of fibers of the composite fiber was adjusted so that the weaving density became 180 fibers / 2.54 cm, and a plain weave fabric was produced. The obtained plain weave fabric was immersed in a 1% sodium hydroxide aqueous solution heated to 90°C for 30 minutes, then washed with water, and dried in a hot air dryer set at 60°C for 30 minutes. The appearance of the alkali-treated plain weave fabric was judged by 5 inspectors based on the following criteria in four grades. S: It has a natural and shiny luster. A: It has a natural luster. B: There is fine flickering. C: There is flickering.

[0064] J. Touch (alkali-treated fabric) Regarding the alkali-treated plain weave fabric used for appearance evaluation, the touch was judged in four grades based on the following criteria by the tactile sensations of five inspectors. S: It is soft and has excellent touch. A: The touch is good. B: At a level where it can be used for clothing purposes. C: The touch is bad.

[0065] K. Peel resistance The number of fibers of the composite fiber was adjusted so that the weaving density became 180 fibers / 2.54 cm to produce a plain weave fabric. Regarding the obtained plain weave fabric, after performing frosting treatment under strong conditions (wet state, load: 7.36 N) or weak conditions (dry state, load: 4.12 N), the plain weave fabric was cut perpendicular to the fiber axis direction, and the cross-section of the fiber was photographed with a scanning electron microscope (SEM) manufactured by HITACHI to observe whether interfacial peeling exists on the cut surface of the obtained fiber cross-section photograph. At this time, the peel resistance was judged in three grades based on the following criteria. A: There is no interfacial peeling even after frosting under strong conditions. B: Interfacial peeling exists after frosting under strong conditions, but there is no interfacial peeling under weak conditions. C: Interfacial peeling exists even after frosting under weak conditions.

[0066] L. High-order processing passability (number of thread breaks in false twisting processing) The high-order processing passability of the composite fiber was evaluated in three levels according to the number of thread breaks when a 3 kg wound package was false-twisted. The false-twisting conditions were a processing speed of 500 m / min, a draw ratio of 1.05 times, a false-twisting temperature of 130 °C (hot plate length 2.0 m), and a false-twist number of 3000 T / M. The high-order processability was evaluated from the number of thread breaks including single-fiber breaks during false-twisting. As a range that minimizes the hindrance to the operation of false-twisting, a range where the number of thread breaks during processing is 4 or less was defined as a suitable range. Furthermore, if the number of thread breaks is 1 or less, it can be said that there is no hindrance to the operation of false-twisting, so it was determined to have excellent high-order processing passability. A: Number of thread breaks 0 - 1 time B: Number of thread breaks 2 - 4 times C: Number of thread breaks 5 times or more.

[0067] [Example 1] As component A, polyethylene terephthalate (PET, melt viscosity: 120 Pa·s, melting point: 254 °C, SP value: 21.4 MPa 1 / 2 ) and, as component B, polyethylene terephthalate copolymerized with 8.0 mol% of 5-sodium sulfoisophthalic acid and 9 wt% of polyethylene glycol (SSIA-PEG copolymerized PET, melt viscosity: 95 Pa·s, melting point: 233 °C, SP value: 22.9 MPa 1 / 2 ) were prepared. The solubility parameter difference of the combined polymers was 1.5 MPa.

[0068] After melting these components separately at 290 °C, with the composite ratio of A / B components being 50 / 50, they were made to flow into a spinning pack incorporated with the composite die illustrated in Fig. 5, and a composite polymer stream was discharged from the discharge holes. For the confluence plate, a multi-stage confluence micro-channel A with two confluence stages was used, and it was discharged so as to have a marble-patterned composite cross-sectional shape as shown in Fig. 1. After cooling and solidifying the discharged composite polymer stream, an oil agent was applied, and it was wound at a spinning speed of 1000 m / min to collect an undrawn yarn of 200 dtex - 8 filaments (total discharge amount 20 g / min). The wound undrawn fibers were drawn 3.5 times between rollers heated to 90 °C and 130 °C to obtain drawn fibers of 56 dtex - 8 filaments. U%, which is an index of fineness variation, was 0.6%, and it had excellent thickness uniformity in the fiber axis direction. In addition, when producing 100 kg of this composite fiber, there was no yarn breakage, and the yarn production property was good.

[0069] When observing the cross-section of the obtained composite fiber, each component had a structure kneaded in a marble-patterned shape. Focusing on the A component, it was widely distributed from a complex shape with branches to a simple shape like a circle without being biased towards a specific shape. The average circularity was 0.37, and the difference between the maximum and minimum values of circularity was 0.71. Also, segments with a shape that penetrated like the roots of a tree were observed, and the ratio of segments with a circularity of 0.1 or less was 6%. In addition, the number of segments in the cross-section of one single yarn was 18. The marble-patterned composite form in the cross-section was continuous in the fiber axis direction.

[0070] When the 3 kg wound package of the obtained composite fiber was subjected to false twisting, since each component had a cross-sectional form with a marble-patterned penetration, there was no yarn breakage, and the high-order processing passability was good. Also, as a result of evaluating the peel resistance of the fabric woven from the obtained composite fiber, no interfacial peeling was observed even after frosting under strong conditions.

[0071] The woven fabric made from the obtained composite fiber was scoured at 80°C for 20 minutes and cationically dyed to obtain a dyed fabric. Since the components with different dyeabilities that make up the single fiber were exposed on the surface in a diverse state, the dyed fabric had natural shading and was rich in color tone changes.

[0072] The woven fabric made from the obtained composite fiber was immersed in a 1% sodium hydroxide aqueous solution (bath ratio 1:50) heated to 90°C for 30 minutes, removing more than 99% of the SSIA-PEG copolymerized PET of component B, generating ultrafine fibers with uneven cross-sections, and obtaining a woven fabric composed of this. When evaluating the woven fabric composed of these ultrafine fibers, due to having uneven cross-sections, the surface of the woven fabric had a natural and glossy luster. Furthermore, due to forming unique voids between the single fibers with uneven cross-sections, the touch was also excellent, and it had a warm texture like natural fibers. The results are shown in Table 1.

[0073] [Examples 2, 3, 4, 5] In the method described in Example 1, it was carried out in the same manner as Example 1 except that the number of confluence stages of the confluence plate was changed to 1 stage (Example 2), 3 stages (Example 3), 6 stages (Example 4), and 7 stages (Example 5). The evaluation results of these composite fibers are as shown in Table 1. However, regardless of the number of confluence stages, each component formed a structure kneaded in a marble pattern shape in the cross-section of the composite fiber. The marble pattern-like composite form in the cross-section was continuous in the fiber axis direction. In Example 2 and Examples 4 to 5, since there were no segments with a circularity of 0.1 or less, interfacial peeling was observed in the severe frosting condition, and the peel resistance decreased slightly, but the high-order processing passability was good. Also, in Examples 4 to 6, as the number of confluence stages increased, a finer marble pattern-like structure was formed. Therefore, the ultrafine fibers with uneven cross-sections obtained after the dissolution treatment had a diameter on the nanofiber order and had a particularly soft and supple texture. In all of Examples 2 to 5, when 100 kg of the composite fiber was spun, the number of thread breaks did not occur, and the spinnability was good.

[0074] [Examples 6, 7] In the method described in Example 1, the method was carried out in the same manner as in Example 1 except that the composite ratio of the A / B components was changed to 30 / 70 (Example 5) and 70 / 30 (Example 6). The evaluation results of these composite fibers are as shown in Table 1. They had a marble-like composite cross-section similar to that of Example 1, and had good peel resistance and high-order processing passability. In Example 6, in the cross-section, a structure in which PET, the hardly soluble component, surrounded the SSIA-PEG copolymerized PET, the easily soluble component, was partially observed. Under the dissolution treatment conditions used in Examples 1 to 5, 30% of the SSIA-PEG copolymerized PET remained. Therefore, although it was at an acceptable level, it was slightly inferior in appearance and feel. Also, in Examples 5 and 6, when 100 kg of the composite fiber was spun, no yarn breakage occurred and the spinnability was good.

[0075] [Example 8] In the method described in Example 1, component A was polyamide-6 (N6, melt viscosity: 100 Pa·s, melting point: 225 °C, SP value: 23.7 MPa 1 / 2 ), and component B was polyethylene terephthalate copolymerized with 8.0 mol% of 5-sodium sulfoisophthalic acid and 9 wt% of polyethylene glycol (SSIA-PEG copolymerized PET, melt viscosity: 95 Pa·s, melting point: 233 °C, SP value: 22.9 MPa 1 / 2 ). The method was carried out in the same manner as in Example 1 except that spinning was performed at 280 °C. The solubility parameter difference of the combined polymers was 0.8 MPa. The evaluation results of these composite fibers are as shown in Table 1. Even when the polymers to be compounded were changed, each component formed a structure kneaded in a marble-like pattern as shown in Fig. 1 in the fiber cross-section. Since there were segments with a circularity of 0.1 or less, no interfacial peeling was observed even under severe frosting conditions, and the peel resistance was good. When a fabric in which ultrafine fibers with an uneven cross-section were generated by dissolution treatment was evaluated, due to the uneven cross-sectional shape, the fabric surface exhibited a natural and glossy luster, and furthermore, unique voids were formed between the single filaments with an uneven cross-section, so it was also excellent in terms of feel. When 100 kg of the composite fiber was spun, the number of yarn breakages did not occur and the spinnability was good.

[0076] [Example 9] In the method described in Example 1, component A is polypropylene (PP, melt viscosity: 70 Pa·s, melting point: 165°C, SP value: 16.8 MPa 1 / 2 ), component B is polyethylene terephthalate copolymerized with 8.0 mol% of 5-sodium sulfoisophthalic acid and 9 wt% of polyethylene glycol (SSIA-PEG copolymer PET, melt viscosity: 95 Pa·s, melting point: 233°C, SP value: 22.9 MPa 1 / 2 ), and the procedure was the same as in Example 1 except that spinning was carried out at 280°C. The solubility parameter difference of the combined polymers was 6.1 MPa 1 / 2 . The evaluation results of these composite fibers are as shown in Table 1. Although each component formed a structure kneaded in a marble pattern in the fiber cross-section, due to the large solubility parameter difference of the polymers to be combined, simple circular segments with a large circularity were formed, and the average circularity was 0.69. Since there were no segments with a circularity of 0.1 or less, interfacial peeling was observed under strong-condition frosting, and the peel resistance decreased. When 100 kg of composite fibers were spun, there was no occurrence of yarn breakage, and the spinning property was good.

[0077] [Examples 10, 11, 12, and 13] In the method described in Example 1, a joining plate composed of a multi-stage joining microchannel B with different joining positions and joining angles of the polymer flow was used instead of the multi-stage joining microchannel A, and the number of joining stages was changed to 2 stages (Example 10), 1 stage (Example 11), 3 stages (Example 12), and 6 stages (Example 13). Otherwise, the procedure was the same as in Example 1. The evaluation results of these composite fibers are as shown in Table 2. Regardless of the number of joining stages, each component formed a structure kneaded in a marble pattern on the cross-section of the composite fiber, and the structure was continuous in the fiber axis direction. In Examples 10 to 13, compared with Examples 1 to 5, the difference between the minimum and maximum values of the circularity was small, and although it was composed of segments with relatively similar shapes, the surface of the alkali-treated fabric had a natural luster. In Examples 10 and 12, since segments with a circularity of 0.1 or less existed, interfacial peeling was not observed even under severe frosting conditions, and the peel resistance was good. In addition, in all of Examples 10 to 13, when 100 kg of the composite fiber was spun, the number of thread breaks did not occur, and the spinnability was good.

[0078] [Comparative Example 1] In the method described in Example 1, the same procedure as in Example 1 was carried out except that a composite die equipped with a static mixing element (number of mixing elements: 2) described in JP-A-10-237715 and JP-A-59-100717 was used. The results of the composite fiber obtained in Comparative Example 1 are as shown in Table 1. It had a cross-sectional structure in which each component was laminated in an uneven shape in 4 to 5 layers, and the cross-sectional structure changed along the fiber axis direction. The U% was 1.2%, and there was a large thickness variation in the fiber axis direction. The difference between the minimum and maximum values of the circularity was as small as 0.14. In addition to the poor shape distribution, since the number of segments was as small as 2, the appearance of the fabric after the dissolution treatment was monotonous, cold, and felt rough. Also, because the cross-section was uneven but had a monotonous laminated structure, interfacial peeling occurred even under weak frosting conditions, and yarn breakage frequently occurred during the false-twist processing, resulting in problems with the passability of higher-order processing. Moreover, since it was a method of accidentally distributing the non-uniformly mixed composite polymer flow to each discharge hole, there was a difference in the composite ratio between single yarns, and the composite ratio also changed over time. When producing 100 kg of this composite fiber, yarn breakage occurred 8 times.

[0079] [Comparative Example 2] In Comparative Example 1, the same procedure was carried out except that the number of mixing elements of the static mixing element was increased to 4. Compared with Comparative Example 1, a composite fiber having a cross-sectional structure in which each component was laminated in more layers and unevenly was obtained. The cross-sectional structure changed along the fiber axis direction. The difference between the minimum and maximum values of the circularity was very small, at 0.09, resulting in a cross-section with a poor shape distribution with only segments of complex shapes. Although the appearance of the fabric after the dissolution treatment changed slightly, it was still monotonous and cold. Also, although interfacial peeling was not observed under weak frosting conditions, there was a difference in the composite ratio between single yarns, and the composite ratio also changed over time. When producing 100 kg of the composite fiber, yarn breakage occurred 6 times, and yarn breakage frequently occurred during the false-twist process.

[0080] [Table 1]

[0081]

Table 2

Explanation of Symbols

[0082] A: Component A B: Component B C: Example of a circular-shaped component (Component A) D: Example of a streak-shaped component (Component A) E: Example of a triangular-shaped component (Component A) F: Example of a complex-shaped component with combined various shapes (Component A) G: Example of a component with an intrusive shape like a tree root (Component A) H: Measuring plate I: Confluence plate J: Discharge plate K: Multi-stage confluence microchannel

Claims

1. In a composite fiber in which two or more types of components constitute a cross-section, the form of each component has a marble-like composite form with diversity, the composite form is continuous in the fiber axis direction, the average circularity of segments of at least one type of component constituting the fiber is 0.20 or more and 0.80 or less, the difference between the minimum value and the maximum value of the circularity is 0.30 or more, and U% is 1.0% or less. A composite fiber characterized by the above.

2. The composite fiber according to claim 1, characterized in that segments having a circularity of 0.10 or less are present in an amount of 1 to 20% based on the total number of segments.

3. The composite fiber according to claim 1 or 2, characterized in that all of the components constituting the fiber are polyester.

4. A fiber product containing at least a part of the composite fiber according to any one of claims 1 to 3.

Images