Composite fiber and multifilament

Abstract

The present invention provides a composite fiber in which the total length of interfaces formed by two or more polymers constituting the fiber cross-section is extremely large. The composite fiber of the present invention is made of two or more polymers, has a fiber cross-section in which a plurality of interfaces are formed, and the value obtained by dividing the total length of the interfaces formed by two polymers by the area of the fiber cross-section is 0.0010 nm-1 or more, and the interfaces are continuous in the fiber axis direction.

Description

Technical Field

[0001] The present invention relates to composite fibers and multifilaments composed of two or more components. Background Art

[0002] Synthetic fibers composed of polyester, polyamide, etc. are used in a wide range of applications from clothing to industrial use because of their excellent mechanical properties and dimensional stability. In recent years, the diversification of applications has further progressed, and the required properties have become higher and more functional, and sometimes fibers composed of existing polymers cannot meet the requirements. Although it is also considered to redesign the polymer to achieve the required properties, from the viewpoint of reducing the cost and period required for its development, it is often the case that the composite spinning method of combining existing polymers is selected.

[0003] For fibers obtained by the composite spinning method, so-called composite fibers, in the fiber cross-section (cross-section with respect to the axial direction of the fiber), another polymer coats the main polymer, etc., and can impart sensory effects such as appearance and feel that cannot be achieved by fibers composed of a single polymer. In addition, regarding composite fibers, even functional polymers that have problems in terms of chemical resistance, heat resistance, etc. and are not practical when used alone can be made to have a dramatic improvement in chemical resistance, heat resistance, etc. and be used in practice if coated with other polymers.

[0004] There are various composite forms and target effects in the composite form and target effect of composite fibers, but as a common problem, there is a problem that when the affinity of the combined polymers is poor, when an external force such as an impact is applied to the fiber, the interface between the two polymers peels off. Due to this interface peeling, not only the originally targeted effect is impaired, but also the cracks generated by the peeling spread to the fiber surface, frequently causing thread breakage in the silk-making and high-grade processing processes, making stable manufacturing itself difficult.

[0005] Such a problem has the possibility of being solved by devising the composite form of the composite fiber. For example, the composite form of the fiber is proposed in Patent Document 1, Patent Document 2, and Patent Document 3.

[0006] In Patent Document 1, a fiber having a plurality of joined composite cross-sections in a direction perpendicular to the lamination direction of a series of laminated structures in which two polymers are alternately laminated is proposed. For this technique, a plurality of film-like elements constituting the fiber cross-section are formed to increase the interface occupied in each film-like element, and the ridge-like skeleton portion that binds the laminated structures acts as a core that supports each film-like element, thereby suppressing interface peeling and aiming at improving the process throughput.

[0007] In Patent Document 2, a composite fiber in which the outer periphery of a laminated structure in which two polymers are alternately laminated is covered with a protective layer is proposed. Similar to Patent Document 1, it is a technique aimed at suppressing interfacial peeling of the laminated structure, and by covering the outer periphery of the laminated structure with a high-strength polymer having a specific thickness, it aims to improve wear resistance.

[0008] In Patent Document 3, a composite fiber in which a film is formed on the entire outer periphery of a laminated structure in which two polymers are alternately laminated is also proposed. By providing a film on the outermost periphery of the laminated structure, peeling and fiber cutting during the process are reduced, and it has the same technical idea as Patent Document 2 in terms of aiming to improve process throughput. However, for this technique, by treatment under specific conditions, the outermost film is deteriorated to promote peeling and fiber cutting, thereby aiming to manufacture ultra-fine fibers.

[0009] Prior Art Documents

[0010] Patent Documents

[0011] Patent Document 1: Japanese Patent Laid-Open No. 1-132812 (pages 1-2)

[0012] Patent Document 2: Japanese Patent Laid-Open No. 11-181630 (claims)

[0013] Patent Document 3: Japanese Patent Laid-Open No. 2000-282333 (pages 1-3) Summary of the Invention

[0014] Problems to be Solved by the Invention

[0015] In Patent Document 1, although it is described that the fiber cross-section is composed of a plurality of film-like elements, the actually manufactured substance in the examples is a substance in which a structure laminated up to 50 to 65 layers is joined adjacent to each other by two, and the interface length is limited, and sometimes it is insufficient for suppressing the peeling of each film-like element. In addition, even if the manufacturing method is improved to increase the number of laminated layers, it is impossible in principle to stably increase the number of laminated layers.

[0016] In Patent Documents 2 and 3, due to the presence of a wear-resistant protective layer, there is a possibility of obtaining an effect of suppressing interfacial peeling against weak friction acting on the fiber surface. However, the laminated structure inside the fiber has only the same number of laminated layers as in Patent Document 1, and in the case where a large external force is applied or interfacial peeling occurs due to repeated rubbing. In addition, in the case of interfacial peeling, the cracks generated by the peeling sometimes propagate to the protective layer on the fiber surface, and especially in the case of repeated rubbing, etc., it becomes a weak structure. When the multi-layer laminated structure is exposed to the surface, by being exposed to chemicals and heat, the properties of the fiber are sometimes significantly damaged and the quality is significantly reduced.

[0017] As described above, it is difficult to suppress interfacial peeling in the interior of the obtained fiber for the conventional composite spinning method. In addition, even if apparent fiber splitting, etc. is suppressed by covering the outer periphery of the laminated structure, the possibility of interfacial peeling occurring in its internal laminated structure is high, and sometimes it is restricted in use from the viewpoint of durability.

[0018] Therefore, there is a strong expectation for composite fibers with improved durability such as wear resistance, chemical resistance, and heat resistance.

[0019] Means for Solving the Problem

[0020] The above problems are achieved by the following means.

[0021] (1) A composite fiber made of two or more polymers, having a fiber cross-section with multiple interfaces formed therein, and the value obtained by dividing the total length of the interfaces formed by two polymers by the area of the above fiber cross-section is 0.0010 nm -1 or more, and the above interfaces are continuous in the fiber axis direction.

[0022] (2) The composite fiber according to the above (1), and the value obtained by dividing the total length of the interfaces formed by the above two polymers by the area of the above fiber cross-section is 0.0050 nm -1 or more.

[0023] (3) The composite fiber according to the above (1) or (2), and the above fiber cross-section is a multi-layer laminated structure in which two polymers are alternately laminated.

[0024] (4) The composite fiber according to any one of the above (1) to (3), and the deviation (CV value) of the layer thickness of at least one polymer is 10% or more.

[0025] (5) The composite fiber according to any one of the above (1) to (4), and the average layer thickness of at least one polymer is 1000 nm or less.

[0026] (6) A multifilament composed of flat ultrafine fibers, wherein the flat ultrafine fibers are composed of one polymer remaining after removing one of the two polymers constituting the multilayer laminated structure from the composite fiber described in the above (3).

[0027] (7) The multifilament according to the above (6), wherein the fiber cross-section of the flat ultrafine fiber is flat, the flatness, which is the value obtained by dividing the length of the major axis of the fiber cross-section by the length of the minor axis, is 15 or more, and the average thickness of the flat ultrafine fiber is 1000 nm or less.

[0028] (8) The multifilament according to the above (6) or (7), wherein the deviation (CV value) of the thickness of the flat ultrafine fiber is 10% or more.

[0029] (9) The multifilament according to any one of the above (6) to (8), wherein the polymer constituting the flat ultrafine fiber contains at least one polymer selected from polyester, polyamide, and polyolefin.

[0030] (10) The multifilament according to any one of the above (6) to (9), wherein a functional substance is included in the fiber bundle composed of the flat ultrafine fibers.

[0031] (11) A fiber product containing, in at least a part thereof, the composite fiber according to any one of the above (1) to (5) or the multifilament according to any one of the above (6) to (10).

[0032] Effects of the Invention

[0033] Due to the increase in the interfacial length between polymers, the composite fiber of the present invention is evenly dispersed at a plurality of interfaces present in the fiber cross-section even when an external force is applied to the fiber, suppressing the concentration of load on a part of the fiber cross-section. Therefore, even in the case of a fiber composed of two or more polymers being compounded, the peeling between components is significantly suppressed. Thus, it is possible to provide a composite fiber and a multifilament having excellent durability such as abrasion resistance, chemical resistance, and heat resistance. Description of the Drawings

[0034] Figure 1 It is a schematic view of the cross-section of a unidirectional laminated fiber as one aspect of the present invention.

[0035] Figure 2 It is Figure 1 A partial enlarged view of.

[0036] Figure 3 It is a schematic view of the cross-section of a radial laminated fiber as another aspect of the present invention.

[0037] Figure 4It is a schematic diagram of the cross-section of concentrically laminated fibers as another embodiment of the present invention.

[0038] Figure 5 It is a schematic diagram of the cross-section of flat ultra-fine fibers that make up the multifilament of the present invention.

[0039] Figure 6 It is a schematic diagram of the cross-section of the multifilament of the present invention.

[0040] Figure 7 It is a schematic diagram of the cross-section of the multifilament when a functional substance is imparted to the multifilament of the present invention.

[0041] Figure 8 It is a cross-sectional view of a composite die as an example for explaining the manufacturing method of the composite fiber of the present invention.

[0042] Figure 9 It is a schematic diagram of the cross-section of a conventional film-type unidirectionally laminated fiber.

[0043] Figure 10 It is a schematic diagram of the cross-section of a conventional flat fiber.

[0044] Figure 11 It is a schematic diagram of the cross-section of a fiber bundle composed of conventional flat fibers. Detailed Description of the Invention

[0045] Hereinafter, the present invention will be described in detail together with preferred embodiments.

[0046] The composite fiber in the present invention is composed of two or more polymers. The composite fiber of the present invention is characterized in that, in the cross-section with respect to the axial direction of the fiber (fiber cross-section), compared with conventional composite fibers, it has a composite morphology in which the total length of the interfaces formed by two polymers (interface length) is extremely large.

[0047] The composite morphology in which the total length of the interfaces formed by two polymers is extremely large as described here is defined by the total length of the interfaces and the area of the fiber cross-section (hereinafter, also referred to as the fiber cross-sectional area). It means that the length of the interface formed by two polymers that is continuous in the fiber axial direction in the fiber cross-section is set as the interface length, and the value obtained by dividing the total length of the interfaces by the fiber cross-sectional area is 0.0010 nm -1 The above composite morphology.

[0048] The value obtained by dividing the total length of the interfaces by the fiber cross-sectional area in the present invention is obtained by operating as follows.

[0049] That is, the multifilament composed of the composite fiber is embedded with an embedding agent such as epoxy resin, and an image of its cross-section is taken with a transmission electron microscope (TEM) at a magnification that can identify the interfaces of the respective polymers. When the entire interface of one interface does not completely enter within one image, as long as the position where the image was initially taken is set as the starting position for shooting, a series of images are taken that trace the same interface within the fiber cross-section until it returns to the starting position for shooting again. It should be noted that when the interface reaches the outer peripheral part of the fiber cross-section, a series of images are taken that trace the outer peripheral part until it returns to the starting position for shooting again. At this time, if electron staining is only performed on a specific polymer, the contrast of the interface becomes clear, and the subsequent measurement can be carried out efficiently, so it is suitable.

[0050] Using image analysis software, an arbitrary measurement start point of one interface of the image at the shooting start position is determined, and the length is measured from the measurement start point until the same interface is traced with a series of cross-sectional images and returns to the measurement start point again. At this time, when reaching the outer peripheral part of the fiber cross-section until returning to the measurement start point, the length is measured without including the part passing through the outer peripheral part. The value is set as the interface length of one interface, and is expressed as an integer in nm units (rounding off the decimal part). The same measurement is performed on all the interfaces of the fiber cross-section, and the sum of the interface lengths obtained by adding them up is divided by the fiber cross-sectional area, and the calculated value is rounded off at the fifth decimal place in nm -1 units. In addition, the fiber cross-sectional area is photographed two-dimensionally with a stereomicroscope at a magnification that can observe the entire cross-section of one fiber, and the cross-sectional part is extracted by binary processing using image analysis software, and the area is rounded off at the decimal part as an integer in nm 2 units. It should be noted that when the fiber cross-section of the composite fiber of the present invention is composed of three or more polymers, it is not only the interface between specific two polymers, but also the total interface length formed by the combination of all polymers.

[0051] The composite fiber of the present invention is characterized in that, in the fiber cross-section, it has a composite form in which the total length (interface length) of the interfaces formed by two adjacent polymers is extremely large. As an index of this composite form, the value obtained by dividing the total interface length by the fiber cross-sectional area needs to be 0.0010 nm -1 or more, and it is required that the interface is continuous in the fiber axis direction. If it is within such a range, it means that the interface length per unit area of the fiber cross-section is extremely large, and it means that two or more polymers forming the composite cross-section are finely divided into multiple elements. It should be noted that the so-called element here refers to a polymer that is separated by being surrounded by different types of polymers in the fiber cross-section.

[0052] The composite fiber of the present invention is as described above, and is characterized in that, in the cross-section of the fiber, different types of polymers are finely divided into a very large number of elements, and the total length of the interfaces formed by two polymers is extremely large compared with the prior art. Through this composite form, various excellent effects as follows can be exerted.

[0053] That is, in the composite fiber of the present invention, since the total length of the interfaces is extremely large, even when an external force is applied to the fiber, the force is dispersed at a plurality of interfaces present in the cross-section of the fiber, suppressing the concentration of the load on a part of the fiber cross-section. Therefore, even for a fiber composed of two or more polymers compounded, the peeling between components can be greatly suppressed.

[0054] If the value obtained by dividing the total length of the interfaces of the composite fiber of the present invention by the fiber cross-sectional area is 0.0010 nm -1 or more, even when the composite fiber is composed of two polymers with poor affinity, the interfacial peeling between components is not likely to occur, and the breakage during wire drawing and high-grade processing processes is not likely to be induced. Not only can good operability be maintained, but also it can be processed into textiles with high quality.

[0055] The larger the value obtained by dividing the total length of the interfaces by the fiber cross-sectional area, the more suitable it is from the viewpoint of evenly dispersing the force at a plurality of interfaces present in the cross-section of the fiber. If the value obtained by dividing the total length of the interfaces by the cross-sectional area is 0.0050 nm -1 or more, even when the composite fiber is composed of two polymers with poor affinity and is used for general clothing and other applications that are subject to weak rubbing, the effect of suppressing the peeling between components can be obtained, and it can be cited as a preferred form. If the above view is advanced, if the value obtained by dividing the total length of the interfaces by the cross-sectional area is 0.0200 nm -1 or more, even when the composite fiber composed of two polymers with poor affinity is used for applications that are subject to medium-strength rubbing, such as outdoor products, the peeling between components can be effectively suppressed, and it can be cited as a more preferred form. In addition, if the value obtained by dividing the total length of the interfaces by the cross-sectional area is 0.0500 nm -1 or more, even when it is used for applications such as work clothes that are repeatedly subject to strong rubbing, the peeling between components is suppressed, and it can be cited as a particularly preferred form.

[0056] In addition, for the composite fiber of the present invention, when the value obtained by dividing the total length of the interfaces by the cross-sectional area is 0.0050 nm -1As described above, in addition to the improvement in the above-mentioned mechanical properties, even when one of the components constituting the composite fiber is a polymer with poor chemical resistance and heat resistance, by using a polymer with excellent properties for the other component, excellent chemical resistance and heat resistance can be imparted. Regarding the improvement in the chemical and thermal properties, the layer having the properties of both polymers formed near the interface exhibits its effect by a remarkable increase in the interface length. That is, for the layer near the interface formed by different polymers, the molecular chains of different polymers sometimes penetrate into each other to form an interface layer having the properties of both polymers. As in the case of the composite fiber of the present invention, when the interface length in the fiber cross-section increases remarkably, the interface layer occupies a large ratio and the properties of the interface layer are exhibited, so excellent effects are exerted from the viewpoint of the compounding of polymer properties.

[0057] In the composite fiber of the present invention, if the value obtained by dividing the total interface length by the fiber cross-sectional area is 0.0050 nm -1 or more, the ratio of the interface layer in the fiber cross-section is high. For example, even when the composite fiber composed of a readily soluble polymer and a hardly soluble polymer is subjected to a dissolution treatment, the reduction in the weight of the treated fiber is slight, and excellent chemical resistance is obtained. Therefore, this can be cited as a preferred form. The larger the value obtained by dividing the total interface length by the fiber cross-sectional area, the more suitable it is from the viewpoint of increasing the ratio of the interface layer in the fiber cross-section. If the value obtained by dividing the total interface length by the cross-sectional area is 0.0200 nm -1 or more, even when subjected to a long-term chemical treatment, the reduction in the fiber weight can be made extremely slight, and this can be cited as a more preferred form. If the above view is advanced, if the value obtained by dividing the total interface length by the cross-sectional area is 0.050 nm -1 or more, the reduction in fiber properties such as mechanical properties is greatly suppressed even after a long-term chemical treatment. Therefore, this can be cited as a particularly preferred form.

[0058] Thus, for the composite fiber of the present invention, the larger the value obtained by dividing the total interface length by the fiber cross-sectional area, the more remarkable the effect exerted by its characteristic cross-sectional morphology. As a preferred upper limit of this value, less than 1.000 nm can be cited -1 . Generally, the interface where different types of polymers come into contact is liable to become unstable hydrodynamically. In the case where the interface length is extremely large as in the present invention, it is sometimes difficult to stably form a continuous interface. If the value obtained by dividing the total interface length by the fiber cross-sectional area is less than 1.000 nm -1, even when polymerizing polymers with different rheological properties, it is possible to relatively easily form an interface continuous in the fiber axis direction. Therefore, as the composite fiber of the present invention, various combinations of polymers can be applied, which can be cited as a preferable upper limit.

[0059] As described above, the composite fiber of the present invention is characterized in that it has a composite form in which the interface length formed by two polymers is extremely large. Through this composite form, not only excellent effects are brought in mechanical properties, but also excellent effects can be exerted in chemical properties and thermal properties by further increasing the interface length. There are various composite forms in the composite form with an extremely large interface length. However, from the viewpoint of promoting the effects exerted by the composite fiber of the present invention, the cross-section of the composite fiber of the present invention is preferably a multi-layer laminated structure in which two polymers are alternately laminated.

[0060] If the composite fiber of the present invention has such a structure, different types of polymers in the fiber cross-section are finely divided into extremely many film-like elements (layers). Even when cracking occurs in one of the multiple layers constituting the cross-section due to interfacial peeling, since the layers are finely structured, crack propagation can be prevented. Therefore, it is possible to suppress the progress of damage in the radial direction of the fiber cross-section, and even when repeated rubbing is applied, fibrillation and fiber splitting can be effectively suppressed.

[0061] From the viewpoint of preventing the propagation of such cracks, the larger the number of laminated layers in the multi-layer laminated structure of the fiber cross-section, the smaller the range in which the cracks can be stopped. In the case of applications where industrial products and the like are repeatedly subjected to strong rubbing, if the number of laminated layers of the two polymers is 250 or more, fibrillation on the fiber surface can be effectively suppressed, which can be cited as a preferable range. In addition, in the case of applications where repeated bending and the like are particularly likely to cause cracking, if the number of laminated layers is 500 or more, the propagation of cracks can be stopped in an extremely small range of the fiber cross-section, so it can be cited as a more preferable range. It should be noted that the number of laminated layers here refers to the total number of film-like elements of the two polymers present in the fiber cross-section.

[0062] It should be noted that in this multi-layer laminated structure, a form in which two polymers are alternately laminated in one direction (uniaxial lamination: Figure 1 and Figure 2 shown uniaxial laminated fiber 1), a form in which they are radially laminated (radial lamination: Figure 3 shown radial laminated fiber 2), a form in which they are concentrically laminated (concentric lamination: Figure 4A variety of laminated forms such as the concentric circle laminated fiber 3) shown in the figure. From the viewpoint of minimizing the propagation of cracks, this multi-layer laminated structure is preferably a unidirectional laminate or a concentric circle laminate. If this multi-layer laminated structure is a unidirectional laminate or a concentric circle laminate, the size of the film-like element (layer) in the outer peripheral portion of the fiber cross-section does not become thick. Even in the outer peripheral portion that is liable to receive a large load due to bending deformation, the propagation of cracks can be limited to a small range, and it can be cited as a preferable laminated structure.

[0063] As described above, the composite fiber of the present invention can enhance the effect of improving mechanical properties by having a multi-layer laminated structure in its cross-section. Further, by making the deviation (CV value) of the layer thickness of at least one polymer constituting the multi-layer laminated structure 10% or more, which is relatively large, the interfacial peeling between components can be more effectively suppressed.

[0064] The deviation of the layer thickness mentioned here is calculated as follows: for 100 layers of one polymer constituting the fiber cross-section, the thickness of the layers existing on the line bisecting the long side of each layer vertically is measured in integer nanometers, and the coefficient of variation obtained by dividing their standard deviation by the arithmetic mean is rounded to an integer in % units after rounding off the decimal part. It should be noted that in the case of a radial laminate, a concentric circle laminate, etc. where the layer thickness cannot be measured by the above method, the average value can be set as the layer thickness by visually selecting the position with the maximum layer thickness and the position with the minimum layer thickness, and the deviation of the layer thickness is calculated from the arithmetic mean and the standard deviation for 100 layers. It should be noted that in the cross-section of one composite fiber, if the number of layers is less than 100, the cross-sections of a plurality of composite fibers are combined to make 100 layers.

[0065] By making the deviation of the layer thickness of one polymer constituting the multi-layer laminated structure relatively large, there are thin and thick positions of the layer in the fiber cross-section. In the thin position of the layer, the influence of the above interfacial layer acts relatively strongly and stress concentration is not likely to occur. In the thick position of the layer, deformation occurs near the interface and the stress is dispersed. Through their synergistic effect, the generation of stress in the cross-section changes complexly, and the stress is alleviated everywhere in the fiber. Therefore, the interfacial peeling between components can be effectively suppressed. If the deviation of the layer thickness of at least one polymer constituting the multi-layer laminated structure is 10% or more, even when compressive deformation is applied in the twisting process or the like, the stress in the cross-section is dispersed complexly and fuzzing of the composite fiber is not likely to occur, and it can be cited as a preferable range. Further, if the deviation of the layer thickness of at least one polymer constituting the multi-layer laminated structure is 30% or more, even when strong compressive deformation is applied under heating in the false-twisting process or the like, fuzzing caused by interfacial peeling is not likely to occur, and it can be processed into a textile with high quality, and it can be cited as a more preferable range.

[0066] Furthermore, from the viewpoint of further improving the effect of enhancing the mechanical properties of the composite fiber of the present invention, the average layer thickness of at least one polymer constituting the multilayer structure is preferably 1000 nm or less. The average layer thickness of the polymer is more preferably 300 nm or less, still more preferably 100 nm or less, particularly preferably 50 nm or less, and most preferably 30 nm or less. It should be noted that the so-called average layer thickness here is calculated by rounding off the decimal part to an integer in nm units for the arithmetic average of the layer thicknesses of 100 layers of one polymer constituting the fiber cross-section calculated above. It should be noted that in the cross-section of one composite fiber, when the number of layers is less than 100, the cross-sections of multiple composite fibers are combined to make 100 layers.

[0067] By making the layer thickness relatively thin, the proportion of the interface layer occupied by each layer relatively increases, and stress is easily transmitted between adjacent interface layers. Even when subjected to deformation such as bending deformation where stress is concentrated locally in the fiber cross-section, the stress is dispersed throughout the cross-section and the interface is not easily peeled off.

[0068] Furthermore, by making the average layer thickness of at least one polymer constituting the multilayer structure 50 nm or less, the effect can be made more remarkable also in terms of chemical properties and thermal properties.

[0069] As described above, for the layers near the interface formed by different types of polymers, sometimes the molecular chains of different polymers penetrate each other to form an interface layer with the characteristics of both polymers. The general thickness of this interface layer is generally considered to be about several nanometers to ten nanometers. That is, by making the layer thickness of the polymers constituting the multilayered structure close to the thickness of this interface layer, most of one layer is composed of this interface layer, and the effect of the interface layer in each layer becomes extremely significant. Therefore, the effect of polymer property compounding is made significant. In the cross-section of the composite fiber of the present invention, if the average layer thickness of at least one polymer constituting the multilayered structure is 50 nm or less, most of the layer of this polymer is occupied by the interface layer. Thus, even when a readily soluble polymer is used as this polymer, if another polymer is selected to be a poorly soluble polymer, the readily soluble polymer hardly dissolves even when a dissolution treatment is carried out, and excellent chemical resistance is exhibited, which can be cited as a preferred range. In addition, when a low melting point polymer and a high melting point polymer are selected and the polymers are alternately laminated so that the average layer thickness of the low melting point polymer becomes 50 nm or less to form a multilayered structure, even when exposed to a high temperature above the melting point of the low melting point polymer, the effect of suppressing fusion between fibers is exhibited. When the average layer thickness is small, the interface layer appears in each layer constituting the fiber cross-section, which is therefore preferred. If the average layer thickness of one polymer is 30 nm or less, even when the composite fiber formed by the combination of the above polymers is subjected to a long-term dissolution treatment or heat treatment, since the weight reduction of the fiber and the fusion between fibers are suppressed, it can be cited as the most preferred range.

[0070] In addition, when the average layer thickness of at least one polymer constituting the multilayered structure is 50 nm or less, from the viewpoint of improving the dispersibility of additives, sometimes the mechanical properties of the composite fiber of the present invention are further improved. That is, the polymers constituting the composite fiber generally contain additives such as titanium oxide, but these additives exist in an aggregated state and are liable to peel at the interface between the coarse aggregates and the polymers. By confining the additives contained in the polymers within the thin film of the multilayered structure below their aggregation size, the aggregated state is eliminated by shear force and the dispersibility is improved, and even when rubbed repeatedly, the effect of suppressing the occurrence of cracks itself is obtained. If the average layer thickness of at least one polymer is 50 nm or less, the additives are confined in a layer sufficiently thinner than the aggregation diameter of the general additives. Therefore, the dispersibility of the additives is improved, and excellent effects are exhibited in terms of abrasion resistance, which can be cited as a preferred range.

[0071] In addition, the composite fiber of the present invention is suitable because the difference in solubility parameter (SP value) between the two polymers compounded in the fiber cross-section is 3.0 or less, so that the refinement below the die is stabilized and the thickness uniformity in the fiber axis direction is excellent. It should be noted that the so-called solubility parameter difference here refers to the parameter reflecting the cohesive force of a substance defined by (vaporization energy / molar volume) 1 / 2 For example, it can be calculated from the values described on page 189, etc., jointly edited by "Plastic Data Book" (Plastic - Data Book), Asahi Kasei Amidas Co., Ltd. / Plastic Editorial Department. The absolute value of the value obtained by subtracting the solubility parameter of one component from the solubility parameter of the other component is the so-called solubility parameter difference in the present invention.

[0072] Generally speaking, for composite fibers composed of two or more polymers, the elongation and deformation behaviors of each polymer are different, so the elongation and deformation in the spinning process and the drawing process are likely to become unstable. In particular, when the difference in solubility parameter between the two polymers constituting the composite fiber is large, this instability is exacerbated, and there is a tendency for the non-uniformity rate of the thickness in the fiber axis direction to increase. By making the difference in solubility parameter between the two polymers constituting the composite fiber 3.0 or less, the elongation and deformation in the spinning process and the drawing process are stabilized, and the occurrence of excessive non-uniformity rate of the thickness in the fiber axis direction is suppressed. As a result, even when an external force such as drawing is applied, the stress can be evenly borne in the fiber axis direction, and the load concentration on a part of the fiber axis direction can be suppressed, so that the occurrence of cracks at the interface between components can be more effectively suppressed. Based on the above, in order to further improve the improvement effect of the mechanical properties of the composite fiber of the present invention, it is preferable that the difference in solubility parameter between the two polymers constituting the composite fiber is 3.0 or less.

[0073] It should be noted that the so-called non-uniformity rate of the thickness in the fiber axis direction here can be represented by the value of U% of Uster (fineness non-uniformity rate) which is an index of the fineness non-uniformity rate. Preferably, U% is 1.5% or less. If U% is 1.5% or less, even when an external force such as repeated drawing is applied, the load concentration on a part of the fiber axis direction can be suppressed, so that the peeling between the components constituting the fiber cross-section and the occurrence of cracks can be suppressed. In addition, from the viewpoints of chemical properties and thermal properties, when the fineness non-uniformity rate is small, the chemical resistance and heat resistance in the fiber axis direction are also homogeneous, and the defects caused by extremely variable thickness parts are also fewer. Therefore, it is suitable to control U% to 1.5% or less.

[0074] The composite fiber of the present invention forms a composite morphology with an extremely large interfacial length that has never existed before, thereby not only exerting excellent effects in improving mechanical properties, but also being able to exert excellent effects in chemical properties and thermal properties by appropriately selecting the combined polymers. Therefore, the composite fiber of the present invention can be widely used in various applications such as general clothing uses like underwear and outerwear, interior uses like curtains and fabrics, vehicle interior uses like car seats, daily life uses like dishcloths and health products, harmful substance removal uses like filters, and industrial material uses like battery separators.

[0075] Furthermore, for the composite fiber of the present invention, by removing one of the two polymers constituting the multilayer laminated cross-section, a multifilament composed of flat ultra-fine fibers formed by the other polymer can be obtained. That is, regarding a composite fiber having a multilayer laminated cross-section in which two polymers are alternately joined as film-like elements (layers), when one polymer is removed, the multiple layers composed of the other polymer are separated. These layers respectively form flat ultra-fine fibers, and a multifilament 5 composed of flat ultra-fine fibers 4 having a shape like a thin layer in cross-section as shown in Figure 5 and Figure 6 is obtained.

[0076] For this multifilament, due to the characteristics of the composite fiber such as the difficulty of interfacial peeling, the generation of flyers and the like is less. Therefore, in addition to being able to be processed into fiber products with high quality, an extremely large specific surface area is generated due to the characteristics of the composite fiber such as an extremely large interfacial length. Through the effect of this specific surface area, when functional processing is performed on this multifilament, a large amount of functional substances can be adsorbed, and excellent functionality can be exerted.

[0077] In terms of the above-mentioned functionality and the quality of the fiber raw material, from the viewpoint of ensuring long-term durability, the cross-sectional shape of the flat ultra-fine fiber constituting the multifilament of the present invention is important. It is important that the fiber cross-section is flat, its flatness is extremely high, and its thickness is thin.

[0078] The so-called flat shape here refers to a shape in which the length of the major axis is different from the length of the minor axis, such as a rectangle or an ellipse, and the flatness of the shape is defined by the flatness which is the value obtained by dividing the length of the major axis by the length of the minor axis. For the multifilament of the present invention, the flatness in the fiber cross-section needs to be 15 or more.

[0079] The flatness in the present invention is obtained by operating as follows (also refer to Figure 5 ).

[0080] The multifilaments of the present invention are embedded using an embedding agent such as epoxy resin, and the cross-section of the fiber is cut with a microtome equipped with a diamond knife. The cross-section is photographed at a magnification that allows the cross-section to be recognized using a scanning electron microscope (SEM) or the like. Regarding the cross-section of the single fiber (flat and extremely fine fiber) present in the captured image, the maximum length of the cross-section is measured using image analysis software, and this value is set as the length of the major axis of the single fiber, which is expressed as an integer in nm units after rounding off the decimal part. Next, the length of the line segment that intersects the fiber cross-section and is orthogonal to the line segment at the midpoint of the maximum length is measured, and this value is used as the length of the minor axis of the single fiber, which is expressed as an integer in nm units after rounding off the decimal part. Using the length of the major axis and the length of the minor axis, the flatness of the single fiber is calculated by the following formula.

[0081] Flatness = Length in the major axis direction (nm) / Length in the minor axis direction (nm)

[0082] The above measurement is performed on 100 fibers, and the flatness of each fiber is calculated. The arithmetic mean of them is set as the flatness of the present invention.

[0083] The first requirement for the multifilaments of the present invention is that the flatness in the fiber cross-section of the flat and extremely fine fibers constituting the multifilaments is high. As an index of the cross-sectional shape, the flatness needs to be 15 or more. If it is within such a range, the specific surface area of the fiber increases by more than 2 times compared to a circular cross-section fiber of the same fineness, and the present invention can improve the adsorption efficiency of the target functional substance.

[0084] In addition, if the flatness of the flat and extremely fine fibers is 15 or more, then as Figure 6 shown, the multifilament 5 becomes a specific fiber bundle structure originating from the shape of the flat and extremely fine fiber 4. That is, due to the high shape anisotropy of the flat and extremely fine fibers, there is a restriction along the arrangement direction of the fibers, and the directions of the respective flat and extremely fine fibers are aligned and coincide. Originating from such a fiber bundle structure, the number of fibers arranged per unit volume increases significantly, and it interacts with the effect of increasing the specific surface area of one fiber as described above, and more excellent adsorption efficiency can be achieved.

[0085] It should be noted that the so-called fiber bundle here, as long as multiple flat and extremely fine fibers are aggregated, is not limited to its aggregation form, and includes a form in which single fibers are clearly separated and a form in which single fibers are aggregated to exactly form one thick fiber.

[0086] If based on the above technical idea, the higher the flatness, not only does the specific surface area of the fiber increase, but also it becomes the densest packing arrangement form with a more highly consistent fiber direction, which is a favorable shape for generating a larger fiber area. That is, if the flatness is 30 or more, not only is the specific surface area of the fiber increased by more than 3 times compared to circular cross-section fibers of the same fineness, but also it becomes a denser arrangement form, resulting in a more significant surface area increase effect. In such a case, the adsorption efficiency of the functional substance is further improved, and its function can be effectively discovered. Therefore, the flatness is preferably 30 or more.

[0087] In addition, if the flatness is 40 or more, due to significant shape anisotropy, the overlapping of fiber directions is inhibited from being disordered in a part of the fiber bundle, and a dense arrangement form with a uniformly consistent fiber direction throughout is obtained. Through such an arrangement form, a homogeneous function without unevenness is obtained as a whole. Therefore, the flatness is more preferably 40 or more.

[0088] Furthermore, if the flatness is 50 or more, even when the fiber bundle of flat ultra-fine fibers is twisted, the fibers are radially arranged relative to the center of the fiber bundle without being disordered. While maintaining the arrangement form with a consistent fiber direction, the arrangement direction can be arbitrarily changed. Such a feature exhibits an excellent effect for controlling the strength of the function derived from the functional substance. When it is desired to give a change to the fiber arrangement direction, the flatness is particularly preferably 50 or more.

[0089] In addition, as the flatness of the cross-section increases, there is a tendency to bend and crack more easily in the long-axis direction of the cross-section when an external force is applied in the processing process. However, if the flatness is less than 500, there is no problem in actual use, and the object of the present invention can be achieved.

[0090] As described above, the multifilament of the present invention has a very high flatness of the fiber cross-section of the flat ultra-fine fiber constituting the multifilament. Thus, compared with ordinary fibers, the specific surface area as the surface area per unit weight increases. Further, due to the dense arrangement of the fibers, a very large fiber surface is generated when a fiber aggregate is formed.

[0091] The specific surface area of the single fiber is greatly affected not only by the flatness of the cross-section but also by the fiber diameter. In order to fully exhibit the surface area increase effect derived from the cross-sectional shape, the fiber diameter also becomes an important factor. As an index of the fiber diameter, for the multifilament of the present invention, it is required that the thickness of the flat ultra-fine fiber, that is, the length of the short axis of the fiber cross-section, is thin as the second factor, and the average thickness is 1000 nm or less.

[0092] It should be noted that the so-called average thickness is obtained by rounding off the arithmetic mean of the lengths of the short axes of the 100 fibers measured above to an integer in nm units, rounding off the digits after the decimal point.

[0093] If the average thickness of the flat ultrafine fiber is 1000 nm or less, at least a specific surface area greater than that of ordinary ultrafine fibers is obtained, achieving a high adsorption efficiency. For this reason, for the multifilament of the present invention, the average thickness of the flat ultrafine fiber needs to be 1000 nm or less.

[0094] As described above, the thinner the average thickness of the flat ultrafine fiber, the more the specific surface area increasing effect of the single fiber is promoted. Further, the thickness also affects the bending rigidity of the fiber, so an excellent effect is also brought in terms of densification of the fiber bundle. That is, the bending rigidity in the short axis direction decreases in proportion to the cube of the fiber thickness. By thinning the thickness, the fiber can deform softly with respect to unevenness and follow the shape, and the fiber bundle structure is easily densified. If the average thickness is 800 nm or less, not only the specific surface area increasing effect is further enhanced, but also the fiber deforms following the shape, so that the formation of large voids between the fibers can be effectively suppressed, and it is easily changed into a dense structure. For this reason, the average thickness is preferably 800 nm or less.

[0095] In addition, if the average thickness is 500 nm or less, the flexibility of the fiber reaches the limit, and due to the action of intermolecular forces such as van der Waals forces, a fiber bundle is formed in which the single fibers are just bonded to each other. In such a case, the voids between the fibers are extremely small voids of several nm to several hundred nm, and an excellent effect is exhibited in terms of the high-durability functional performance described later. Therefore, the average thickness is more preferably 500 nm or less.

[0096] Furthermore, if the average thickness is 300 nm or less, the structure in which the single fibers are aggregated as described above is uniformly obtained in the whole fiber bundle, and when functional processing is performed, the functions are uniformly exhibited without unevenness in the whole. For this reason, the average length of the short axis is particularly preferably 300 nm or less.

[0097] It should be noted that for the multifilament of the present invention, as the average thickness of the fiber cross-section becomes thinner, there is a tendency to be easily broken when an external force is applied in the processing step, but if the average thickness is 50 nm or more, there is no problem in actual use, and the object of the present invention can be achieved.

[0098] As described above, the multifilament of the present invention has a cross-sectional shape with an extremely high flatness of the flat ultrafine fibers constituting the multifilament, so that the specific surface area of the fibers is greatly increased. Further, by forming a dense fiber bundle with the same orientation, a very large fiber surface is generated per unit volume. If this large fiber surface is effectively utilized, not only can the adsorption efficiency of the functional substance be dramatically improved, but also the durability can be dramatically improved due to this specific fiber bundle structure. That is, when the multifilament of the present invention is subjected to functional processing, not only a large amount of the functional substance is adsorbed on the fiber surface, but also as Figure 7 shown, the functional substance D enters between the flat ultrafine fibers 4 that are overlapped with the same orientation. Therefore, a distribution state is formed in which a large amount of the functional substance is included in the fiber bundle, and on the other hand, almost no functional substance is exposed on the surface of the fiber bundle. The durability in terms of function is improved because the functional substance is not easily detached by rubbing or the like.

[0099] From the viewpoint of effectively expressing the function through functional processing to exhibit the characteristics of the multifilament of the present invention, the impregnation ease of the functional substance is also important, and the deviation in the thickness of the flat ultrafine fiber becomes an index to be concerned about.

[0100] It should be noted that the so-called deviation in thickness here is calculated by obtaining the arithmetic mean and the standard deviation by using the lengths of the short axes of the 100 fibers measured above, and the coefficient of variation obtained by dividing the standard deviation by the arithmetic mean is rounded to an integer in % units after the decimal point.

[0101] As described above, the flexural rigidity of the fiber changes significantly with the thickness. Therefore, when there is a moderate deviation in the thickness, the behavior of each single fiber becomes inhomogeneous. For example, in a liquid containing a functional substance, each single fiber moves with different behaviors and is well dispersed. In such a case, the fiber surface is not blocked by other fibers and is exposed to the liquid, and the functional substance can be efficiently adsorbed.

[0102] If the deviation in thickness is 10% or more, the single fibers are easily well dispersed in the liquid and the functional substance is easily impregnated. Therefore, the deviation in thickness is preferably 10% or more.

[0103] If this consideration is further advanced, the greater the deviation in the thickness of the fiber, the more inhomogeneous the behavior of each single fiber becomes and the easier it is for the single fibers to be dispersed. When it is desired to effectively expose the surface of the single fiber and complete the functional processing in a short time, the deviation in thickness is more preferably 20% or more.

[0104] In addition, if the deviation of the thickness is 40% or more, even in the case of a high-density fabric in which the silk quilt is firmly bound, the liquid easily penetrates between the single fibers. When it is desired to efficiently perform functional processing on a high-density fabric or the like, a deviation of the thickness of 40% or more is particularly preferred.

[0105] In addition, as the deviation of this thickness increases, when an external force is applied in the processing step, breakage is likely to occur in the fibers with a short thickness. However, if the deviation of the thickness is less than 70%, there is no problem in actual use, and the object of the present invention can be achieved.

[0106] In addition, depending on the degree of unevenness of the fiber surface, the dispersion state of the single fibers during functional processing can sometimes be improved, and the degree of unevenness of the cross section also becomes an index to be concerned about. That is, by having an appropriate degree of unevenness on the fiber surface, minute voids of several nm to several hundred nm are formed between the fibers, and starting from these minute voids, the single fibers are easily and effectively dispersed in a liquid containing a functional substance.

[0107] The so-called degree of unevenness here is measured by using an image of the fiber cross section taken. The lengths of the line segments intersecting the fiber cross section that are orthogonal to the line segment of the maximum length of the cross section at the points where the maximum length of the cross section is divided into 10 equal parts are measured respectively, and the arithmetic mean and standard deviation of these 10 lengths are calculated. The value obtained by dividing the standard deviation by the average value and rounding off the decimal places in % units is set as the degree of unevenness of the single fiber. The same measurement is performed on 10 fiber cross sections, and the arithmetic mean of the degrees of unevenness of the 10 fibers calculated is set as the so-called degree of unevenness here.

[0108] If the degree of unevenness is 20% or more, the single fibers are easily dispersed starting from the minute voids between the fibers, and functional processing can be completed in a short time. Therefore, the degree of unevenness is preferably 20% or more.

[0109] On the other hand, as the degree of unevenness increases, there is a tendency for load concentration to occur in a part of the cross section and for cracking to easily occur. However, if the degree of unevenness is less than 60%, there is no problem in actual use, and the object of the present invention can be achieved.

[0110] Due to the specific cross-sectional shape of the multifilament of the present invention passing through the fiber cross-section, the specific surface area can be greatly increased while maintaining the cross-sectional area of the fiber. Therefore, the single fiber has the same strength as a normal fiber, and there are no problems such as an unnecessary reduction in the quality of the fiber product, and the operability is excellent. In addition, the flat ultra-fine fiber of the present invention has a continuous shape along the fiber axis direction, and since there are fewer fiber ends in the fiber bundle, it is not easy to damage the quality of the fiber product, and the operability is excellent. Among the polymers constituting the flat ultra-fine fiber, considering the passability and actual use in normal advanced processing steps, a crystalline polymer is suitable, and it is preferable that the polymer constituting the flat ultra-fine fiber contains at least one polymer selected from polyesters, polyamides, and polyolefins. In addition to the above advantages, among these polymers, since they are thermoplastic, not only can the multifilament of the present invention be manufactured by a highly productive melt spinning method, but also they can be highly oriented and crystallized in the stretching process, which is suitable from the viewpoint of adjusting mechanical properties and the like.

[0111] In the multifilament of the present invention, considering actual use, it is preferable that the strength of the fiber is 1 cN / dtex or more, and when used as a woven fabric or sheet used in a relatively harsh atmosphere, it is suitable that the strength is 2 cN / dtex or more, which can be cited as a more preferable range.

[0112] If the characteristics of the multifilament of the present invention are effectively utilized, not only can a large amount of functional substances be adsorbed through functional processing to effectively exhibit functions, but also the functional substances are encapsulated in the fiber bundle due to the specific fiber bundle structure, so that the functional substances are not easily detached and excellent durability can be exhibited. In addition, if it is effectively utilized, the functional substances diffuse inside the fiber bundle, or the fiber bundle deforms by an external force, so that a sustained release effect in which the functional substances are gradually released can also be obtained. Therefore, when the multifilament of the present invention is combined with a functional substance and used as a functional raw material, it is preferably processed into a state in which the functional substance is encapsulated in the fiber bundle composed of flat ultra-fine fibers.

[0113] It should be noted that the so-called functional substance here refers to a substance that actively imparts functionality to the fiber, and there is no particular limitation as long as it is a compound having a function. In addition, the functional substance can be an organic compound or an inorganic compound. Examples of such functionality include ultraviolet ray cut-off, fragrance, deodorization, antibacterial, insect prevention, moisture absorption, antistatic, flame retardancy, stain resistance, beauty care, health care, etc., but are not limited to these functions.

[0114] In addition, as the state of existence of the functional substance in the fiber, various forms are considered, and as its form, loading by chemical bond, exhaustion, physical adsorption, etc. can be cited. In order to achieve a substantial improvement in functionality, durability, and feel, it is preferable to utilize the characteristics of the flat ultrafine fibers of the present invention to process the functional substance. For example, after a specific functional substance is encapsulated in the fiber bundle by functional processing in a general solution, another functional substance is formed into a film on the surface of the fiber bundle by a paddry method or the like, so that two or more functions can be compounded, or the limit of the function brought about by the mutual effect of different functional substances can be pursued.

[0115] If the characteristics of the multifilament of the present invention are effectively utilized as described above, a functional raw material that efficiently contains a functional substance and has excellent durability can be obtained. Therefore, the multifilament of the present invention can be widely used in various applications such as general clothing uses such as underwear and outerwear, interior uses such as curtains and fabrics, vehicle interior uses such as car seats, daily life uses such as dishcloths and health products, harmful substance removal uses such as filters, and industrial material uses such as battery separators.

[0116] An example of the manufacturing method of the composite fiber and multifilament of the present invention will be described in detail below.

[0117] The composite fiber and multifilament of the present invention can be manufactured by a fiber spinning process using a composite die as described below. From the viewpoint of high productivity, melt spinning is suitable.

[0118] The composite die used in the present invention is preferably, for example, Figure 8 the composite die 10 in which three members, namely, a metering plate E, a composite plate F, and a discharge plate G, are laminated as shown. Incidentally, Figure 8 taking the example of using two polymers, component A and component B, if necessary, three or more polymers can also be used for fiber spinning. For this composite die 10, the polymer amount of each hole of the composite plate F is metered by the metering plate E, and different types of polymer streams that have been metered are made to flow together by the composite plate F to form a composite stream having an interface. The composite stream is divided / recombined to increase the interface in the cross-section of the composite stream, and the discharge plate G is responsible for compressing the composite stream formed by the composite plate F and discharging it. Here, the composite stream refers to a fluid whose cross-section perpendicular to the flow direction is composed of two or more polymers.

[0119] In the composite plate F, the number of micro-flow paths H with converging and branching sections is greater than the number of discharge holes in the discharge plate G. The arrangement of the converging and branching sections can be adjusted appropriately to form the desired cross-section. It should be noted that the converging section herein refers to the portion where two or more flows merge, and the branching section refers to the portion where a flow is divided into two or more sections. With this configuration, when different types of polymers pass through the composite plate F, the polymers flowing out of the various flow path holes merge at the converging section to form a composite flow. This composite flow is then divided at the branching section. This repeated process forms a composite cross-section, which is essential for the composite fiber of the present invention and is characterized by the sum of the interface lengths of the two polymers being significantly greater than the fiber cross-section. It should be noted that the converging and dividing processes mentioned here do not need to be repeated; they can be combined again after converging, or divided again after dividing. Alternatively, the two polymers can be pre-blended in the fluid supplied to the micro-flow paths of the composite plate F, or a composite flow formed by other methods can be used.

[0120] The micro-channels used in the manufacture of the present invention are configured to minimize the turbulence of the flow within the channel, thereby enabling the manufacture of the composite fiber of the present invention. Incidentally, it can be said that the micro-channels have the same characteristics as conventional static mixers in terms of merging or dividing the fluid within the channel. However, since the general static mixer is designed for the purpose of mixing two polymers, turbulence is generated in the inserted polymer flow, making it difficult even for those skilled in the art to manufacture the composite fiber of the present invention. Incidentally, by densely designing the channel configuration of the micro-channels of the present invention, the thickness of each layer constituting the laminated composite flow formed within the channel can be controlled, and a fiber cross-section of any composite form can be formed.

[0121] It should be noted that, in order to avoid the complexity of the description of the composite die, although not shown in the figure, as for the components stacked above the metering plate E, it is sufficient to use components that form a flow path according to the spinning machine and the spinning assembly. By designing the metering plate E according to the existing flow path components, the existing spinning assembly and its components can be directly and effectively utilized. Therefore, it is not necessary to specialize the spinning machine for this die. In addition, in fact, it is better to stack multiple flow path plates between the flow path and the metering plate E or between the metering plate E and the composite plate F. Its purpose is to form a flow path that efficiently transfers the polymer along the cross-sectional direction of the die and the cross-sectional direction of the single fiber, and to be introduced into the structure of the composite plate F. After the composite polymer flow discharged from the discharge plate G is cooled and solidified, an oil agent is applied, and it is pulled by a roller with a specified circumferential speed to form a composite fiber.

[0122] The composite fiber of the present invention can be manufactured using the composite die as described above. Incidentally, if this composite die is used, it goes without saying that the composite fiber of the present invention can be manufactured even by a spinning method using a solvent such as solution spinning.

[0123] In the case of selecting melt spinning, the polymers constituting the composite fiber of the present invention are as described above. For example, polymers capable of melt molding such as polyethylene terephthalate or its copolymer, polyethylene naphthalate, polybutylene terephthalate, polypropylene terephthalate, polypropylene, polyolefin, polycarbonate, polyacrylate, polyamide, polylactic acid, thermoplastic polyurethane, etc. can be cited. In particular, condensation 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 can be contained in the polymer. Further, in the case of selecting a polymer containing these additives, unevenness is generated in each layer of the multilayer laminated fiber corresponding to the particle diameter of the additive particles as the additive, and arbitrary unevenness can be imparted to the generated flat ultrafine fiber based on this.

[0124] Two or more of these polymers are combined to form a multilayer laminated fiber, and the combination of the polymers is also important from the viewpoint of making the laminated structure good.

[0125] That is, the smaller the difference in solubility parameter (SP value) between the combined polymers, the better the laminated structure without interlayer confluence or the like is formed, and it is preferable to select polymers such that the difference in solubility parameter between the two polymers forming the interface is 3.0 or less. The solubility parameter as mentioned above is meant here.

[0126] Furthermore, from the viewpoint of making the interfacial layer having the characteristics of two kinds of polymers formed near the interface, which is a characteristic of the composite fiber of the present invention, it is preferable that if the polymers are polyesters with each other, the interfacial layer is formed more extensively at one interface. In particular, in the case where one polymer is an easily soluble polyester copolymerized with a metal base of sulfonic acid, if the other polymer is a hardly soluble polyester, excellent chemical resistance can be imparted even to the fiber containing the easily soluble polyester, and thus it is suitable. In particular, as the polyester copolymerized with a metal base of sulfonic acid, in the case of using a polyester copolymerized with sodium 5-sulfoisophthalate, polyethylene glycol alone or in combination, in addition to excellent chemical resistance, the color developability after dyeing also becomes good, and it is preferable. As an example of the combination of these polymers, it can be cited that according to the relationship of the melting point, one polymer uses polyethylene terephthalate copolymerized with 5 mol% to 15 mol% of sodium 5-sulfoisophthalate 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 above-mentioned sodium 5-sulfoisophthalate, and the other polymer uses polyethylene terephthalate.

[0127] When spinning the composite fiber of the present invention, the spinning temperature is the temperature at which the mainly high melting point and high viscosity polymer among two or more polymers shows fluidity. As this temperature at which fluidity is shown, it varies depending on the molecular weight, but it is preferably set to be from the melting point of the polymer to 60 °C or less above the melting point. If it is at or below this temperature, the polymer will not thermally decompose, etc. in the spinneret or spinning pack, and the decrease in molecular weight is suppressed, and thus it is preferable. As the discharge amount when spinning the composite fiber of the present invention, it can be stably manufactured by being 0.1 g / min·hole to 20.0 g / min·hole. In particular, if the single-hole discharge amount is such that the fineness of the single fiber after stretching becomes less than 4 dtex, since it is thin, a soft hand feeling is obtained when making a woven fabric, and thus it is preferable.

[0128] 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. Even in the case where a polymer with poor chemical resistance and heat resistance is used, by increasing the interface between the components, when excellent chemical resistance and heat resistance are desired to be imparted, it is preferable to compound another polymer with excellent chemical resistance and heat resistance and increase their ratio. For example, in the case where component A is a polymer with high chemical resistance and component B is a polymer with low chemical resistance, if the A component / B component ratio is 99 / 1 to 70 / 30, even if a long-time dissolution treatment is carried out, the weight reduction of the fiber is extremely small, and thus it is preferable.

[0129] The polymer stream thus discharged is cooled and solidified, an oil agent is applied, and it is drawn by a roll with a specified circumferential speed to form a composite fiber. Here, the drawing speed only needs to be determined by 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 mechanical properties for high orientation, it is preferable to stretch this composite fiber. This stretching can be carried out after being temporarily wound in the spinning process, or can be carried out without temporary winding.

[0130] As the stretching conditions, for example, in a stretching machine composed of one or more pairs of rolls, if the fiber is composed of a polymer showing thermoplasticity that can generally be melt-spun, it is naturally stretched in the fiber axis direction and heat-set and wound by the circumferential speed ratio of the first roll set at a temperature above the glass transition temperature and below the melting point and the second roll equal to the crystallization temperature, and a composite fiber having Figure 1 such a composite cross-section can be obtained. As the upper limit of the temperature of the first roll, it is preferably a temperature at which the filament path of the fiber does not become disordered during the preheating process. For example, in the case of polyethylene terephthalate where the glass transition temperature is around 70°C, this preheating temperature is usually set at around 80 to 95°C.

[0131] As described above, although the manufacturing method of the composite fiber of the present invention has been described based on the general melt-spinning method, it is self-evident that it can also be manufactured by the meltblowing method and the spunbond method. Further, it can also be manufactured by solution spinning methods such as wet and dry-wet methods.

[0132] In order to obtain the multifilament of the present invention from the composite fiber of the multilayer laminated structure obtained by the above operations, the easily soluble polymer is removed by impregnating the multilayer laminated fiber in a solvent in which the easily soluble polymer can dissolve, so that flat ultrafine fibers and fiber bundles composed of the hardly soluble polymer can be obtained. When the easily soluble polymer is a copolyethylene terephthalate copolymerized with sodium 5-sulfoisophthalate, etc., an alkaline aqueous solution such as an aqueous sodium hydroxide solution can be used. As the method, for example, after forming the multilayer laminated fiber or a textile formed therefrom, it can be impregnated in the alkaline aqueous solution. At this time, if the alkaline aqueous solution is heated to 50°C or higher, the progress of hydrolysis can be accelerated, so it is preferable. It should be noted that as the method for producing multifilament from the multilayer laminated fiber, it is not limited to the above dissolution treatment, but by dissolving and removing the easily soluble polymer, the single fibers of the flat ultrafine fibers composed of the hardly soluble polymer can be surely separated, and at the same time, the damage of the fibers can be suppressed to the minimum, and the multifilament of the present invention can be produced well.

[0133] Examples

[0134] Hereinafter, examples will be given to specifically illustrate the composite fiber of the present invention.

[0135] The following evaluations were performed on the examples and comparative examples.

[0136] A. Melt viscosity

[0137] The sheet-like polymer was dried by a vacuum dryer to a moisture content of 200 ppm or less, and the melt viscosity was measured using a Capillograph manufactured by Toyo Seiki Seisaku-sho, Ltd., while changing the strain rate step by step. It should be noted that the measurement temperature was the same as the spinning temperature, and in the examples or comparative examples, the melt viscosity at a shear rate of 1216 s -1 was recorded. It should be noted that 5 minutes was set from when the sample was put into the heating furnace until the start of measurement, and the measurement was performed under a nitrogen atmosphere.

[0138] B. Melting point

[0139] Approximately 5 mg of the sheet-like polymer dried by a vacuum dryer to a moisture content of 200 ppm or less was weighed, and a differential scanning calorimeter (DSC) Q2000 type manufactured by TA Instruments Japan Co., Ltd. was used. After heating from 25°C to 300°C at a heating rate of 16°C / minute, DSC measurement was performed while maintaining at 300°C for 5 minutes. The melting point was calculated from the melting peak observed during the heating process. The measurement was performed 3 times for 1 sample, and the average value was set as the melting point. It should be noted that in the case where multiple melting peaks were observed, the melting peak on the highest temperature side was set as the melting point.

[0140] C. Solubility parameter difference

[0141] The solubility parameter (SP value) is a parameter reflecting the cohesive force of a substance defined as the square root of (evaporation energy / molar volume). By immersing the polymer in various solvents, the value of (evaporation energy / molar volume) of the solvent that maximizes the swelling pressure is set as the (evaporation energy / molar volume) of the polymer and calculated. The SP value obtained in this way is recorded, for example, in "Plastic Data Book", jointly edited by Asahi Kasei Amidas Co., Ltd. / Plastic Editorial Department, page 189, etc., and this value can be used. In addition, the solubility parameter difference of the combined polymers is calculated as the absolute value of (SP value of component A - SP value of component B).

[0142] D. Fiber fineness

[0143] The weight of 100 m of the composite fiber was measured, and the value obtained by multiplying this value by 100 was calculated. This measurement was repeated 10 times, and the average value was set as the fiber fineness (dtex). In addition, the value obtained by dividing the above fiber fineness by the number of filaments was set as the single fiber fineness (dtex).

[0144] E. Uster U%

[0145] Using a fineness unevenness measuring device Zellweger (UT-4), under the conditions of a supply speed of 100 m / min, a twisting machine speed of 6000 rpm, and a measurement length of 100 m, the Uster U%(H) of the composite fiber was measured.

[0146] F. Total interface length / fiber cross-sectional area (nm -1 )

[0147] The composite fiber was embedded with an embedding agent such as epoxy resin, frozen with a Reichert FC·4E type cryosectioning system, and cut with a Reichert-Nissei ultracut N (ultramicrotome) equipped with a diamond knife. Then, the cut surface was photographed with a Hitachi High-Technologies Corporation H-7100FA type transmission electron microscope (TEM) at a magnification that could identify the interface formed by two kinds of polymers. Using image analysis software (WINROOF), the length from an arbitrarily determined measurement start point to the point where it returned to the measurement start point again for one interface was measured, and the length of one interface (interface length) was obtained by rounding off the decimal part to an integer in nm units. It should be noted that in the case where the outer peripheral part of the fiber cross-section is reached until returning to the measurement start position, the length of the part passing through the outer peripheral part among the lengths from the measurement start point following the interface / outer peripheral part until returning to the measurement start position again is not included in the measurement. The same measurement was performed on all the interfaces present in the fiber cross-section, and the sum of the interface lengths was calculated by adding up all the interface lengths. By dividing the obtained sum of the interface lengths by the fiber cross-sectional area, the value of the total interface length / fiber cross-sectional area was calculated by rounding off the fifth decimal place in nm -1 units. It should be noted that when calculating the fiber cross-sectional area, the composite fiber was cut perpendicularly to the fiber axis at an arbitrary position in the fiber axis direction, and the cut surface was two-dimensionally photographed with an OLYMPUS optical microscope at a magnification that could observe the entire cross-section of a single filament. After using image analysis software (WINROOF) to extract the cross-section of a single filament and performing binarization processing, the fiber cross-section was calculated by rounding off the decimal part to an integer in nm units from the obtained cross-sectional parameters.

[0148] G. Deviation of layer thickness (composite fiber)

[0149] The length of the layer present on the straight line that bisects perpendicularly the long side of one layer constituting the fiber cross-section is defined as the layer thickness. From the cross-sectional image of the composite fiber taken by the same method as that for measuring the sum of the above interface lengths, 100 elements of the B component are optionally extracted, and their layer thicknesses are measured by rounding off the digits after the decimal point to an integer in nm units. It should be noted that in the cross-section of one composite fiber, when the number of layers is less than 100, the cross-sections of multiple composite fibers are combined to make 100 layers. The arithmetic mean and standard deviation of the obtained values are calculated, and the coefficient of variation obtained by dividing the standard deviation by the arithmetic mean is calculated by rounding off the digits after the decimal point to an integer in % units as the deviation of the layer thickness. It should be noted that in the case of a radial laminate or concentric circle laminate where the layer thickness cannot be measured by the above method, the position with the maximum thickness and the position with the minimum thickness of each layer are visually selected, and their average value is set as the thickness of each layer, and the coefficient of variation obtained by dividing the standard deviation by the arithmetic mean in the same way as above is calculated as the deviation of the layer thickness.

[0150] H. Average layer thickness (composite fiber)

[0151] The length of the layer present on the straight line that bisects perpendicularly the long side of one layer constituting the fiber cross-section is defined as the layer thickness. From the cross-sectional image of the composite fiber taken by the same method as that for measuring the sum of the above interface lengths, 100 elements of the B component are optionally extracted, and their layer thicknesses are measured by rounding off the digits after the decimal point to an integer in nm units. It should be noted that in the cross-section of one composite fiber, when the number of layers is less than 100, the cross-sections of multiple composite fibers are combined to make 100 layers. The arithmetic mean of the obtained values is calculated by rounding off the digits after the decimal point to an integer in nm units as the average layer thickness. It should be noted that in the case of a radial laminate or concentric circle laminate where the layer thickness cannot be measured by the above method, the position with the maximum thickness and the position with the minimum thickness of each layer are visually selected, and their average value is set as the thickness of each layer, and the arithmetic mean in the same way as above is calculated as the average layer thickness.

[0152] I. Abrasion resistance

[0153] The number of fibers of the composite fiber was adjusted so that the weft density became 180 fibers / 2.54 cm to produce a plain weave fabric. The plain weave fabric cut to a diameter of 10 cm was placed on the specimen holder of the Appearance Retention Tester (ART type tester) manufactured by Daisei Kagaku Seiki Co., Ltd., the pushing load was set to 3.9 N, and it was rubbed with a silicon carbide friction plate (3K). The friction plate was stopped every time it rotated once, and the number of friction times when fibrils were confirmed on the fiber surface was measured, and the average value of 5 measurements was obtained. The so-called number of friction times here is obtained by rounding off the digits after the decimal point, and the abrasion resistance of the fiber was evaluated using the following 4-grade evaluation.

[0154] 〔Evaluation Criteria〕

[0155] A (Excellent): The number of friction times is 100 times or more

[0156] B (Good): The number of friction times is 50 times or more and less than 100 times

[0157] C (Qualified): The number of friction times is 20 times or more and less than 50 times

[0158] D (Unqualified): The number of friction times is less than 20 times

[0159] J. Chemical Resistance

[0160] A tubular knitted fabric of the composite fiber was produced, treated with a 1% aqueous sodium hydroxide solution at 90 °C for 30 minutes, washed with water, and dried thoroughly at 60 °C. The weight loss rate was calculated from the weights before and after the treatment. The value of the so-called weight loss rate here is the value obtained by rounding off the second digit after the decimal point, and the chemical resistance was evaluated using the following 4-grade evaluation.

[0161] 〔Evaluation Criteria〕

[0162] A (Excellent): The weight loss rate is 0.0% or more and less than 2.0%

[0163] B (Good): The weight loss rate is 2.0% or more and less than 5.0%

[0164] C (Qualified): The weight loss rate is 5.0% or more and less than 10.0%

[0165] D (Unqualified): The weight loss rate is 10.0% or more

[0166] K. Heat Resistance

[0167] The compound fiber was measured for the length of the hank before treatment using a length measuring machine with a frame circumference of 1.0 m. Ten turns of the hank were taken, and a load of 0.0294 cN / dtex was applied to measure the length of the hank. The hank was placed in a hot air dryer at 160 °C for 15 minutes under no load, and the length of the hank after treatment was measured again by applying a load of 0.0294 cN / dtex. The dry heat shrinkage rate was calculated from the length of the hank before treatment and the length of the hank after treatment using the formula [dry heat shrinkage rate (%) = (length of the hank before treatment - length of the hank after treatment) / length of the hank before treatment × 100]. The dry heat shrinkage rate was obtained from 5 measurements, and the arithmetic mean was calculated by rounding off the second digit after the decimal point. In addition, the fiber surface of the hank after treatment was observed using an optical microscope manufactured by Olympus Corporation to confirm whether fusion occurred between the fibers, and the heat resistance was evaluated by the following three-level evaluation.

[0168] 〔Evaluation Criteria〕

[0169] A (Good): The dry heat shrinkage rate is less than 15.0%, and there is no fusion between the fibers

[0170] B (Qualified): The dry heat shrinkage rate is 15.0% or more, and there is no fusion between the fibers

[0171] C (Unqualified): There is fusion between the fibers

[0172] L. Flatness

[0173] The multifilament composed of flat ultrafine fibers was embedded with an embedding agent such as epoxy resin, frozen using a Reichert FC·4E type cryostat, cut using a Reichert-Nissei ultracut N (ultramicrotome) equipped with a diamond knife, and an image of the cut surface was taken using a Hitachi High-Technologies Corporation H-7100FA type transmission electron microscope (TEM) at a magnification that could identify the cross-section. Using image analysis software (WINROOF), the maximum length of the cross-section of a single fiber was measured, and this value was set as the length of the major axis of the single fiber, and the decimal part was rounded off to an integer in nm units. Next, the length of the line segment intersecting the fiber cross-section that is orthogonal to the line segment at the midpoint of the maximum length was measured, and this value was used as the length of the minor axis of the single fiber, and the decimal part was rounded off to an integer in nm units. Using the length of the major axis and the length of the minor axis, the flatness of the single fiber was calculated by the following formula.

[0174] Flatness = length in the major axis direction (nm) / length in the minor axis direction (nm)

[0175] The above measurement is performed on 100 fibers to calculate the flatness of each fiber, and the flatness of the flat ultra-fine fiber is calculated by rounding off the arithmetic mean to four decimal places.

[0176] M. Average thickness of fibers (flat ultra-fine fibers)

[0177] The arithmetic mean of the lengths of the minor axes of the 100 fibers measured above is rounded off to an integer in nm units to calculate the average thickness of the flat ultra-fine fibers.

[0178] N. Deviation of fiber thickness (flat ultra-fine fibers)

[0179] Using the lengths of the minor axes of the 100 fibers measured above, the arithmetic mean and standard deviation are calculated, and the coefficient of variation obtained by dividing the standard deviation by the arithmetic mean is rounded off to an integer in % units to calculate the deviation of the thickness of the flat ultra-fine fibers.

[0180] O. Degree of unevenness

[0181] Using the image of the fiber cross-section taken above, the lengths of the line segments intersecting the fiber cross-section that are orthogonal to the line segment of the maximum length of the cross-section at the points where the maximum length of the cross-section is divided into 10 equal parts are measured respectively, the arithmetic mean and standard deviation of these 10 lengths are calculated, and the value obtained by dividing the standard deviation by the average value and rounding off to the decimal place in % units is calculated as the degree of unevenness of the single fiber. The same measurement is performed on 10 fiber cross-sections, and the arithmetic mean of the degrees of unevenness of the 10 single fibers calculated is calculated as the degree of unevenness of the flat ultra-fine fibers.

[0182] P. Distribution state of functional substances

[0183] In order to model-evaluate the distribution state of functional substances when the fiber bundle is treated with functional substances, using a dyeing solution prepared by adjusting the Dystar-made acid dye telon Black LD02, which is non-staining to polyester, to 10% owf, treating the woven fabric at a bath ratio of 1:50, a treatment temperature of 30 °C, and a treatment time of 30 minutes, and then observing the surface and cross-section of the woven fabric using a VHX-6000 digital microscope manufactured by Keyence Corporation. The distribution state at this time was judged based on the following criteria.

[0184] 〔Evaluation criteria〕

[0185] In the fiber bundle: Dye (colored matter) exists between the fibers in the cross-section of the fiber bundle.

[0186] None: No dye (colored matter) exists between the fibers in the cross-section of the fiber bundle.

[0187] Q. Functional processing (deodorant processing)

[0188] A 10% aqueous solution of dodecanedioic dihydrazide, which has an adsorption capacity for acetaldehyde, was used to treat a woven fabric at a solid content of 20% owf, a liquor ratio of 1:20, a treatment temperature of 130°C, and a treatment time of 1 hour.

[0189] R. Deodorizing property (acetaldehyde concentration)

[0190] In a conditioned environment at a temperature of 20°C and a humidity of 65% RH, 1 g of the functionally processed woven fabric processed in the above Q was previously placed in a 5 L Tetra Pak. 3 L of acetaldehyde with a concentration of 30 ppm was injected into the Tetra Pak, and the gas concentration (ppm) inside the Tetra Pak after 10 minutes was measured using a gas detector tube (manufactured by Gastech).

[0191] S. Content rate of functional substance

[0192] The woven fabric before processing was dried at 110°C for 2 hours, and its weight (W1) was measured. The functionally processed woven fabric processed in the above Q was dried at 110°C for 2 hours, and its weight (W2) was measured. From the weights before and after processing, the content rate (%) of the functional substance was calculated by the following formula.

[0193] Content rate of functional substance (%) = (W2 - W1) / W1 × 100

[0194] T. Content rate of functional substance after washing and processing

[0195] The functionally processed woven fabric processed in the above Q was subjected to 50 cycles in the order of washing (15 minutes) → dehydration (1 minute) → rinsing (6 minutes) → dehydration (1 minute) → drying. The washing conditions were a water temperature of 40°C and a liquor ratio of 1:30, and 0.5 g / l of "Top" (manufactured by Lion Corporation) was used as the detergent. The rinsing conditions were set to a water temperature of 20°C and an overflow liquor ratio.

[0196] The washed woven fabric was dried at 110°C for 2 hours, and its weight (W3) was measured. From the weights before and after washing, the content rate (%) of the functional substance was calculated by the following formula.

[0197] Content rate of functional substance after washing (%) = (W3 - W1) / W1 × 100

[0198] [Example 1]

[0199] As component A, polyethylene terephthalate (PET, melt viscosity: 120 Pa·s, melting point: 254°C, SP value: 21.4 MPa) was prepared 1 / 2), and as Component B, polyethylene terephthalate copolymerized with 8.0 mol% of sodium 5-sulfoisophthalate 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 )

[0200] After melting Component A and Component B separately at 290 °C, the composite ratio of A / B components was made 90 / 10, and it was made to flow into the spinning assembly incorporating the Figure 8 composite die 10 exemplified, and the composite polymer stream was discharged from the discharge holes. It should be noted that in the composite plate F, there is a fine flow path H capable of alternately laminating the two components into 1024 layers, Figure 1 and the two types of polymers as shown are discharged in such a manner as to form a composite form in which they are alternately multi-layer laminated in one direction. 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 / minute to obtain an unstretched yarn of 200 dtex - 24 filaments (total discharge amount 20 g / minute). The wound unstretched fiber was stretched 3.6 times between rollers heated to 90 °C and 130 °C to obtain a stretched fiber of 56 dtex - 24 filaments. U%(H) as an index of fineness unevenness was 0.6%, and the thickness uniformity in the fiber axis direction was excellent.

[0201] The cross-section of the obtained composite fiber was observed, and as a result, the total length of the interfaces / fiber cross-sectional area was 0.0557 nm -1 , and the total length of the interfaces with respect to the fiber cross-sectional area was extremely large, and the same interface was continuous in the fiber axis direction. In addition, the average layer thickness of Component B was 4 nm, and the layer thickness deviation was 32%, which was large, and it was divided into extremely thin film-like elements.

[0202] The peel resistance was evaluated using a woven fabric made from the obtained composite fiber. As a result, fibrillation was not observed even when the number of friction times was 100 or more. Incidentally, the cross-section of the composite fiber after evaluating the abrasion resistance was observed with a scanning electron microscope (SEM) manufactured by Hitachi, Ltd., and peeling between the components was not confirmed.

[0203] The obtained tubular knitted fabric of the composite fiber was immersed in a 1% sodium hydroxide aqueous solution (bath ratio 1:50) heated to 90 °C for 30 minutes, and as a result, the weight loss rate was 0.6%.

[0204] The results are shown in Table 1.

[0205] [Examples 2, 3, 4, 5, 6]

[0206] In the method described in Example 1, the composite plate with microchannels having the total number of layers of Component A and Component B laminated to 512 layers (Example 2), 256 layers (Example 3), 128 (Example 4), 64 (Example 5), 32 (Example 6) was used, and other than this, it was carried out in the same manner as in Example 1. The evaluation results of these composite fibers are as shown in Table 1.

[0207] The composite fibers of Examples 2 to 6 are of a composite structure in which two polymers are alternately laminated in multiple layers in one direction, and the same interface is continuous in the fiber axis direction. In Example 2, even when the number of friction times was 100 times or more, no fibrillation was observed. However, in Examples 3 to 6, compared with Example 2, as the number of laminated layers of the two polymers in the fiber cross-section decreased, the value of the total interface length / fiber cross-sectional area decreased. Therefore, when the number of friction times was 50 times or more, fibrillation was observed in several single filaments. The cross-section of the fibrillated composite fiber was observed by the same method as above, and as a result, the two polymers were fiber-split in the adhered direction, presumably due to peeling between the components. In addition, in Examples 2 and 3, as the value of the total interface length / fiber cross-sectional area decreased, the weight loss rate increased slightly, but was less than 2.0%, and the chemical resistance was excellent. On the other hand, in Examples 5 and 6 where the value of the total interface length / fiber cross-sectional area was further reduced, the weight loss rate increased to 5.0% or more, resulting in a decrease in chemical resistance compared with Examples 1 to 3. Figure 1 shown

[0208] [Comparative Example 1]

[0209] In the method described in Example 1, the composite plate with microchannels having the total number of layers of Component A and Component B laminated to 8 layers (Comparative Example 1) was used, and other than this, it was carried out in the same manner as in Example 1. The evaluation results of these composite fibers are as shown in Table 1.

[0210] The composite fiber of Comparative Example 1 is Figure 1 a composite structure in which two polymers are alternately laminated in multiple layers in one direction as shown, but the number of segments (number of laminated layers) is much less than that of the composite fiber of the present invention, and the value of the total interface length / fiber cross-sectional area is small. Therefore, when the number of friction times was 20 times or more, fibrillation was observed in multiple single fibers, and the abrasion resistance was poor. In addition, the chemical resistance of the obtained tubular knitted fabric of the composite fiber was evaluated, and as a result, the weight loss rate was 10.0% or more, and the chemical resistance was poor. Incidentally, the tubular knitted fabric after the chemical resistance evaluation was dyed under the same conditions as above, and as a result, the tubular knitted fabric was not dyed, presumably because almost all of the easily soluble SSIA-PEG copolymerized PET constituting the composite fiber was dissolved by the chemical resistance evaluation.

[0211] [Example 7]

[0212] In the method described in Example 1, Component B was a copolyester of ethylene terephthalate with 21 mol% of spiro diol and 29 mol% of cyclohexanedicarboxylic acid (SPG-CHDC copolyester, melt viscosity 75 Pa·s, melting point: none [glass transition temperature: 76 °C], SP value: 23.0 MPa 1 / 2 ), which was melted at 285 °C, and the composite ratio of Component A / Component B was 50 / 50. Otherwise, it was carried out in the same manner as in Example 1. The evaluation results of this composite fiber are shown in Table 2.

[0213] The composite fiber of Example 7 had a composite structure in which two polymers were alternately laminated in multiple layers in one direction Figure 1 as shown, and the same interface was continuous in the fiber axis direction. The peel resistance was evaluated using a woven fabric of the obtained composite fiber, and as a result, fibrillation was not observed even when the number of friction cycles was 100 or more. In addition, the skein of the obtained composite fiber was treated with a hot air dryer at 160 °C for 15 minutes, and as a result, the dry heat shrinkage rate was less than 15.0%, and the thermal dimensional stability was excellent. Although SPG-CHDC copolyester, which is amorphous and has a glass transition temperature below the treatment temperature of the hot air dryer, was used, fusion between fibers was not observed.

[0214] [Examples 8 and 9]

[0215] In the method described in Example 7, it was changed to a composite plate having a microchannel in which the total number of layers of Component A and Component B was laminated to 512 layers (Example 8) and 256 layers (Example 9). Otherwise, it was carried out in the same manner as in Example 7. The evaluation results of these composite fibers are shown in Table 2.

[0216] In Example 8, fibrillation was not observed even when the number of friction cycles was 100 or more. However, in Example 9, compared with Example 8, as the number of laminated layers of the two polymers in the fiber cross-section decreased, the value of the total interface length / fiber cross-sectional area decreased. Therefore, fibrillation was observed in several single fibers when the number of friction cycles was 50 or more. In addition, as the composite ratio of SPG-CHDC copolyester with poor heat resistance increased, the dry heat shrinkage rate increased. Although it was at an acceptable level in Example 9, the heat resistance decreased as a result. In addition, in Example 9, since two polymers with different properties were alternately laminated with layer thicknesses that caused thin film interference of visible light, the resulting composite fiber structure was colored blue.

[0217] [Comparative Example 2]

[0218] The method described in Example 7 was carried out in the same manner as in Example 7 except that a composite plate having microchannels in which the total number of layers of components A and B was laminated was eight. The evaluation results of these composite fibers are shown in Table 2.

[0219] The composite fiber of Comparative Example 2 is Figure 1 The composite structure shown above is a composite structure in which two polymers are alternately laminated in multiple layers in one direction. However, the number of divisions (number of layers) is significantly smaller than that of the composite fiber of the present invention, resulting in a smaller value for the sum of the interface lengths / fiber cross-sectional area. Consequently, when the number of friction cycles is 20 or more, fibrils are observed in many individual fibers, resulting in poor abrasion resistance. Furthermore, heat resistance evaluation of the resulting tubular knitted composite fiber revealed a dry heat shrinkage of 20.0% or more, significant interfiber fusion, and a very hard texture.

[0220] [Examples 10, 11, and 12]

[0221] In the method described in Example 7, the component B was polyamide-6 (N6, melt viscosity 100 Pa·s, melting point: 225° C.), SP value: 23.7 MPa. 1 / 2 ), melted at 280°C, and using composite plates having microchannels in which the two components were laminated into 1024 layers (Example 10), 512 layers (Example 11), and 256 layers (Example 12), all other operations were carried out in the same manner as in Example 7. The evaluation results of these composite fibers are shown in Table 3.

[0222] In Examples 10 to 12, polymers having greatly different solubility parameters were composited to form composite fibers. Therefore, when the number of frictions was 50 or more, fibrils were observed in some single fibers, but the abrasion resistance was generally good.

[0223] [Examples 13 and 14]

[0224] The method described in Example 10 was carried out in the same manner as in Example 10, except that the composite plate having fine flow paths was changed to a total of 256 layers of components A and B, and the flow path arrangement was changed to a concentric laminated structure (Example 13) or a radial laminated structure (Example 14). The evaluation results of these composite fibers are shown in Table 3.

[0225] In Example 13, two types of polymers were alternately stacked concentrically to form a multilayer structure. Figure 4 In Example 14, a composite structure is formed in which two polymers are radially and alternately laminated. Figure 3A composite structure as shown, with the same interface being continuous along the fiber axis direction. Composite fibers are formed by compounding polymers with a large difference in solubility parameters. Therefore, fibrils are observed in several single fibers when the number of friction cycles is 50 or more, but the wear resistance is generally good.

[0226] [Comparative Example 3]

[0227] In the method described in Example 10, a composite plate having a microchannel in which the total number of layers of Component A and Component B is laminated to 8 layers was used, and otherwise, it was carried out in the same manner as in Example 10. The evaluation results of the composite fiber are as shown in Table 3.

[0228] The composite fiber of Comparative Example 3 is Figure 1 a composite structure in which two types of polymers as shown are alternately laminated in multiple layers in one direction, but the number of divisions (number of laminated layers) is significantly less than that of the composite fiber of the present invention, and the value of the total interface length / fiber cross-sectional area becomes smaller. Therefore, fibrils are generated in multiple single fibers even when the number of friction cycles is 20 or less, and the wear resistance is poor. In addition, in the weaving process, fibrillation also occurs, and frequent thread breakage causes problems in high-grade processing passability.

[0229] [Comparative Example 4]

[0230] In the method described in Comparative Example 3, a composite plate having a flow path for discharging only Component A was provided around a microchannel in which two components were laminated to 8 layers, and otherwise, it was carried out in the same manner as in Comparative Example 3. The evaluation results of the composite fiber are as shown in Table 3. Although it is Figure 9 a composite structure in which a multilayer laminated structure as shown is coated with Component A (coated type unidirectional laminated fiber 6), the number of laminated layers is significantly less than that of the composite fiber of the present invention, and the value of the total interface length / fiber cross-sectional area becomes smaller. Therefore, even when a coating is provided on the fiber surface, multiple single fiber fibrillations occur when the number of friction cycles is 20 or less, and the wear resistance is poor.

[0231] [Example 15]

[0232] As Component A, polyethylene terephthalate (PET, melt viscosity: 120 Pa·s, melting point: 254 °C, SP value: 21.4 MPa 1 / 2 ) was prepared, and as Component B, polyethylene terephthalate copolymerized with 8.0 mol% of sodium 5-sulfoisophthalate 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 ) was prepared. It should be noted that the difference in solubility parameters of these polymers is 1.5 MPa 1 / 2 .

[0233] After melting Component A and Component B separately at 290°C, the composite ratio of A / B components is made 80 / 20, and it is made to flow into the spinning assembly incorporating the Figure 8 exemplified composite die 10, and a composite polymer stream is discharged from the discharge holes. It should be noted that in the composite plate F, there is a fine flow path H capable of alternately laminating the two components into 128 layers, so as to be Figure 1 discharged in such a way that the two kinds of polymers are alternately multi-layer laminated in one direction in a composite form. After cooling and solidifying the discharged composite polymer stream, an oil agent is applied, and it is wound at a spinning speed of 1000 m / minute to obtain an unstretched yarn of 300 dtex - 24 filaments (total discharge amount 30 g / minute). The wound unstretched fiber is stretched 3.6 times between rollers heated to 90°C and 130°C to obtain a stretched fiber of 84 dtex - 24 filaments. U%(H) as an index of fineness unevenness is 0.6%, and the thickness uniformity in the fiber axis direction is excellent.

[0234] The cross-sectional morphology of the obtained composite fiber was observed, and as a result, it had Figure 1 a plate-like laminated structure with the same lamination direction as shown, and it was confirmed to be a multi-layer laminated fiber.

[0235] The peel resistance was evaluated using a woven fabric woven from the obtained composite fiber. As a result, fibrillation was not observed even when the number of friction times was 50 or more. Incidentally, the cross-section of the composite fiber after abrasion resistance evaluation was observed with a scanning electron microscope (SEM) manufactured by Hitachi, Ltd. As a result, no peeling between components was confirmed, and it had excellent abrasion resistance.

[0236] By immersing the composite fiber in a 1% sodium hydroxide aqueous solution (bath ratio 1:50) heated to 90°C for 30 minutes or more, more than 99% of the SSIA-PEG copolymerized PET of Component B was removed to obtain a multifilament composed of flat ultrafine fibers. The woven fabric woven from the composite fiber was treated in the same way to obtain a woven fabric composed of flat ultrafine fibers.

[0237] The cross-section of the obtained flat ultrafine fiber was observed, and as a result, it became a band-shaped cross-section with a significant difference in the lengths of the major axis and the minor axis. The flatness was 80, and the average thickness was 225 nm. In addition, the deviation of the thickness of the cross-section was 36%, and the concavity and convexity was 30%. The thickness had a moderate deviation, and there were moderately uneven surfaces.

[0238] Regarding the woven fabric of the obtained flat ultra-fine fibers, the cross-section was also observed. As a result, multiple flat ultra-fine fibers overlapped with the same orientation in the short-axis direction, forming a dense fiber bundle structure. In addition, each flat ultra-fine fiber aggregated in a just-bonded manner, and extremely fine voids of several nm to several hundred nm existed between the fibers.

[0239] The woven fabric composed of flat ultra-fine fibers was immersed in a dyeing solution in which a non-staining dye (acid black dye) was adjusted to 10% owf, and treated at a bath ratio of 1:50, a treatment temperature of 30 °C, and a treatment time of 30 minutes. As a result, the space between the flat ultra-fine fibers in the cross-section was colored black, the dye was encapsulated inside the fiber bundle, and the surface of the woven fabric was also colored black.

[0240] The woven fabric composed of flat ultra-fine fibers was treated with a 10% aqueous solution of dodecanedioic dihydrazide at a solid content of 20% owf, a bath ratio of 1:20, a treatment temperature of 130 °C, and a treatment time of 1 hour for deodorizing functional processing. The acetaldehyde removal ability was evaluated. As a result, the concentration decreased from the initial concentration of 30 ppm to 2 ppm in 10 minutes, showing high deodorization performance. In addition, the content rate of the functional substance was 5.0%, and the content rate after washing was also 4.2%, not greatly reduced. The functional substance was adsorbed in large amounts and was not easily detached, showing high durability.

[0241] The results are shown in Table 4.

[0242] [Examples 16, 17]

[0243] In the method described in Example 15, it was changed to a composite plate having a microchannel in which the total number of layers of Component A and Component B was laminated to 64 layers (Example 16) and 32 layers (Example 17). Except for this, all were carried out in the same manner as in Example 15. These composite fibers were subjected to the same dissolution treatment as above to produce flat ultra-fine fibers. The evaluation results of these composite fibers and flat ultra-fine fibers are shown in Table 4.

[0244] In Examples 16 and 17, although to different extents, they had an extremely thin cross-sectional shape with a high flatness, and had a moderate deviation in the length of the short axis and unevenness. In addition, similar to Example 15, although they had a dense fiber bundle structure in which the directions of the flat ultra-fine fibers overlapped, compared with Example 15, the flatness decreased and the average layer thickness increased. Therefore, the voids between the fibers in the fiber bundle were coarser, and the aggregated parts of the single fibers were fewer. When immersed in the non-staining dye, as a result, the dye was distributed in a manner of being encapsulated in the fiber bundle. In addition, compared with Example 15, the specific surface area decreased. Therefore, although the content rate of the functional substance decreased slightly, a high content rate was maintained, and sufficient deodorization performance was exhibited. In addition, after washing, a high content rate of the functional substance was also maintained, and the functional substance was not easily detached.

[0245] [Examples 18 and 19]

[0246] In the method described in Example 15, change to a composite plate with a microchannel that stacks the total number of layers of Component A and Component B to 256 layers (Example 18) and 512 stacks (Example 19). Except for this, all are carried out in the same manner as in Example 15. These composite fibers are subjected to the same dissolution treatment as described above to produce flat ultrafine fibers. The evaluation results of these composite fibers and flat ultrafine fibers are shown in Table 4 below.

[0247] In Examples 18 and 19, the cross-section is an extremely thin ribbon shape with an extremely high flatness, having a moderate deviation in the length of the short axis and unevenness. In addition, similar to Example 15, it has a dense fiber bundle structure in which the flat ultrafine fibers are overlapped in the same direction. However, compared with Example 15, the flatness increases and the average length of the short axis decreases. Therefore, the inter-fiber voids in the fiber bundle are several nanometers to dozens of nanometers, becoming extremely small, and the single fibers in the entire fiber bundle aggregate in a manner as if they are just adhered. When immersed in a non-staining dye, as a result, the dye is distributed in a manner of being encapsulated in the fiber bundle. During functional processing, the average length of the short axis is extremely short, so the woven fabric is overly soft and has poor operability. Compared with Example 15, the specific surface area increases, so the content rate of the functional substance increases and the deodorizing property is excellent. In addition, since the fiber bundle becomes a firm aggregated structure encapsulating the functional substance, the content rate of the functional substance is not easily reduced after washing, and it has high durability and can maintain the functional substance.

[0248] [Comparative Example 5]

[0249] Using polyethylene terephthalate (PET, melt viscosity: 120 Pa·s, melting point: 254 °C, SP value: 21.4 MPa1 / 2), after melting at 290 °C, it is made to flow into the spinning pack alone and discharged from the discharge hole. Except for this, all are carried out in the same manner as in Example 15. The evaluation results of this single fiber are shown in Table 4 below.

[0250] Comparative Example 5 is a fiber with a circular cross-section of a general fiber diameter, having a small specific surface area. As a fiber bundle, it also has a sparse structure with a large distance between single fibers. Even when immersed in a non-staining dye, no attachment of the dye was observed. In addition, due to the small specific surface area, the content rate of the functional substance is extremely small and the deodorizing property is poor. In addition, through washing, the content rate of the functional substance is reduced to almost 0, and the functional substance attached to the fiber surface is easily detached.

[0251] [Comparative Example 6]

[0252] A spinning component using an 8-island sea-island composite die in which component A is incorporated as the island component and component B is the sea component was used, and the rest was carried out in the same manner as in Example 15. The same dissolution treatment as described above was performed on this sea-island composite fiber to generate ultrafine fibers. The evaluation results of the ultrafine fibers are shown in Table 4 as follows.

[0253] Comparative Example 6 resulted in ultrafine fibers with a significantly reduced fiber diameter and a large specific surface area. In addition, for the fiber bundle, the distance between single fibers was close. When immersed in a non-staining dye, the woven fabric did not color, and no dye attachment was observed between the fibers. Functional processing was carried out. As a result, due to the increase in specific surface area caused by ultrafinement, the functional substance was moderately attached, but it did not reach the level of exhibiting high deodorizing performance. Through washing, the adsorption amount of the functional substance was significantly reduced.

[0254] [Comparative Example 7]

[0255] In the method described in Example 15, it was changed to a composite plate having a microchannel in which the total number of layers of component A and component B was laminated to 8 layers, and the rest was carried out in the same manner as in Example 15. The same dissolution treatment as described above was performed on this composite fiber to generate flat fibers. The evaluation results of the composite fiber and the flat fiber are shown in Table 4 as follows.

[0256] As Figure 10 shown, the flat fiber 7 of Comparative Example 7 had a cross-sectional shape with a low flatness. In addition, due to the low flatness, in the multifilament, Figure 11 As shown, the directions of the flat fibers 7 were inconsistent, resulting in a fiber bundle structure with a large distance between single fibers. Even when immersed in a non-staining dye, no dye attachment was observed. In addition, due to the small specific surface area, the content rate of the functional substance was extremely small, and the deodorizing performance was poor. In addition, through washing, the content rate of the functional substance was reduced to nearly 0, and the functional substance attached to the fiber surface was easily detached.

[0257] [Example 20]

[0258] In the method described in Example 15, a composite plate with a different flow path diameter from the microchannel having a confluence part and a branch part was used, and the rest was carried out in the same manner as in Example 15. The same dissolution treatment as described above was performed on this composite fiber to generate flat ultrafine fibers. The evaluation results of the composite fiber and the flat ultrafine fiber are shown in Table 5 as follows.

[0259] Example 20 Although it has the same extremely thin cross-sectional shape with high flatness as Example 15, through the change in the flow path design of the composite plate, it is a homogeneous substance with small deviations in the length of the short axis and small unevenness. In addition, although it has the same dense fiber bundle structure in which flat ultra-fine fibers are overlapped in the same direction as in Example 15, due to the small unevenness, the proportion of fine voids in the range of several nm to several hundred nm between the fibers in the fiber bundle is larger compared to Example 15. When impregnated with a non-staining dye, although the dye is encapsulated in the fiber bundle, it is not uniformly distributed throughout, and some parts without the encapsulated dye are observed. In addition, compared to Example 15, due to the low dispersibility of the single fibers, the content rate of the functional substance is somewhat poor, but the functional substance is not easily detached by washing.

[0260] [Example 21]

[0261] In the method described in Example 15, component A is polyamide-6 (N6, melt viscosity: 100 Pa·s, melting point: 225 °C, SP value: 23.7 MPa 1 / 2 ), and component B is polyethylene terephthalate copolymerized with 8.0 mol% of sodium 5-sulfoisophthalate 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 ), and spinning is carried out at 280 °C. Except for this, all are carried out in the same manner as in Example 15. It should be noted that the solubility parameter difference of the combined polymers is 0.8 MPa 1 / 2 . The same dissolution treatment as above is carried out on this composite fiber to produce flat ultra-fine fibers. The evaluation results of this composite fiber and flat ultra-fine fibers are shown in Table 5.

[0262] Example 21 Although it has the same extremely thin cross-sectional shape with high flatness as Example 15, due to hydrogen bonding between the fibers, it has a more densely aggregated structure in the fiber bundle compared to Example 15. Functional processing is carried out, and as a result, it shows the same content rate of the functional substance as in Example 15. Since the fibers are connected by hydrogen bonds, they swell during washing and are easily redispersed into single fibers, and the functional substance is more easily detached by washing compared to Example 15.

[0263] [Example 22]

[0264] In the method described in Example 15, 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 sodium 5-sulfoisophthalate 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 ), Spinning is carried out at 280 °C, and in other respects, it is carried out in the same manner as in Example 15. It should be noted that the solubility parameter difference of the combined polymers is 6.1 MPa 1 / 2 . The cross-sectional morphology of this composite fiber was observed. As a result, due to the large solubility parameter difference, the cross-sectional formability became unstable, and it had an irregular laminated structure different from that of Example 15, with a change in the local lamination direction of the cross-section. The same dissolution treatment as above was performed on this composite fiber to produce flat ultrafine fibers. The evaluation results of this composite fiber and flat ultrafine fibers are shown in Table 5 as follows.

[0265] Compared with Example 15, Example 22 has a lower flatness and a reduced specific surface area. Therefore, although the content rate of the functional substance is reduced, it has a high content rate. In addition, the functional substance is not easily detached by washing.

[0266] [Table 1]

[0267]

[0268] [Table 2]

[0269]

[0270] [Table 3]

[0271]

[0272] [Table 4] 0]

[0273]

[0274] [Table 5]

[0275]

[0276] The present invention has been described in detail using specific embodiments, but it will be obvious 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. It should be noted that this application is based on Japanese Patent Application (Japanese Patent Application No. 2020-210112) filed on December 18, 2020, the entire content of which is incorporated herein by reference.

[0277] Explanation of symbols

[0278] 1: Unidirectionally laminated fiber

[0279] 2: Radially laminated fiber

[0280] 3: Concentric circle laminated fiber

[0281] 4: Flat ultra-fine fiber

[0282] 5: Multifilament

[0283] 6: Coated unidirectional laminated fiber

[0284] 7: Flat fiber

[0285] 10: Composite die

[0286] A: Component A

[0287] B: Component B

[0288] D: Functional substance

[0289] E: Metering plate

[0290] F: Composite plate

[0291] G: Discharge plate

[0292] H: Microchannel.

Claims

1. A composite fiber is a composite fiber made of two or more polymers, having a fiber cross-section with multiple interfaces formed therein. The value obtained by dividing the total length of the interfaces formed by two polymers by the area of the fiber cross-section is 0.0010 nm -1 or more. The interfaces are continuous in the fiber axis direction. The fiber cross-section has a multi-layered laminated structure in which two polymers are alternately laminated. The coefficient of variation (CV) of the layer thickness of at least one polymer is 10% or more, and the average layer thickness of at least one polymer is 1000 nm or less.

2. The composite fiber according to claim 1, wherein the value obtained by dividing the sum of the interfacial lengths formed by 2 polymers by the area of the fiber cross-section is 0.0050 nm -1 or more.

3. A multifilament composed of flat ultrafine fibers, the flat ultrafine fibers being composed of one polymer remaining after removing one of the two polymers constituting the multilayer laminate structure from the composite fiber according to claim 1, the fiber cross-section of the flat ultrafine fiber being flat, the flatness, which is the value obtained by dividing the length of the major axis of the fiber cross-section by the length of the minor axis, being 15 or more, and the average thickness of the flat ultrafine fiber being 1000 nm or less.

4. The multifilament according to claim 3, wherein the deviation of the thickness of the flat ultrafine fiber, i.e., the CV value, is 10% or more.

5. The multifilament according to claim 3 or 4, wherein the polymer constituting the flat ultrafine fiber contains at least one polymer selected from polyester, polyamide, and polyolefin.

6. The multifilament according to claim 3 or 4, wherein a functional substance is included in the fiber bundle composed of the flat ultrafine fibers.

7. A fiber product containing the composite fiber according to claim 1 or 2 or the multifilament according to any one of claims 3 to 6 in at least a part thereof.

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