Nonwoven fabric, its manufacturing method, and absorbent article

Abstract

To provide a nonwoven fabric that has pleasant touch and has an excellent property of concealing a color of a body fluid.SOLUTION: A nonwoven fabric is made of split fibers in which two or more different types of resins are continuously disposed in a longer direction of the fiber and the resins are disposed in a circumferential direction of the fiber so that the resins can be separated from each other. The nonwoven fabric has a fusion point between fibers. A split portion formed by completely separating the resins and a non-split portion in which the resins are not completely separated are alternately formed in the longer direction of the fiber in the split fiber. A cross-sectional shape at the non-split portion of the split fiber is flat and a long axis of a cross section is oriented in a direction along a surface of the nonwoven fabric. Also provided is a method for manufacturing the nonwoven fabric by sequentially applying air-through treatment, first pressing treatment, and second pressing treatment that applies lower pressure than that used in the first pressing treatment on a fiber web including the split fibers.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a nonwoven fabric, a method for producing the same, and an absorbent article. [Background technology]

[0002] 2. Description of the Related Art As components of absorbent articles that absorb and retain body fluids, nonwoven fabrics have been proposed for the purposes of improving the feel on the skin and improving the ability to conceal the color of urine or menstrual blood.

[0003] The present applicant previously proposed a nonwoven fabric in which split fibers are partly split and separated by heat treatment or pressure applied with rolls, with the aim of providing a nonwoven fabric that is soft and has an excellent feel (see Patent Document 1).

[0004] In addition, the present applicant has previously proposed a three-dimensional nonwoven fabric having a first layer and a second layer, with the first layer containing 20% ​​by mass or more of splittable composite fibers, with the aim of improving the feel and hiding power (see Patent Document 2).

[0005] The applicant has also previously proposed an air-through nonwoven fabric for use as a constituent material for the outermost surface of a disposable diaper, the air-through nonwoven fabric having specified average deviations in surface roughness and average deviations in friction coefficient (see Patent Document 3).

[0006] Patent Document 4 discloses a nonwoven fabric using staples obtained by crimping conjugated fibers in which two or more incompatible thermoplastic polymers are laminated in parallel in an average of three or more layers, with 80% or more of the lamination surface crossing the major axis of the fiber cross section. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] Japanese Patent Application Publication No. 9-273061 [Patent Document 2] JP 2006-2303 A [Patent Document 3] JP 2006-233364 A [Patent Document 4] Japanese Patent Application Publication No. 5-25762 Summary of the Invention [Problem to be solved by the invention]

[0008] The nonwoven fabrics described in Patent Documents 1 to 3 have good feel and hiding power, but there is room for improvement in terms of further improving the feel and hiding power. The nonwoven fabric described in Patent Document 4 is formed by entangling the constituent fibers by spraying a high-pressure water stream, and is therefore inferior in terms of feel such as softness.

[0009] Therefore, the present invention relates to a nonwoven fabric that is pleasant to the touch and has excellent concealing properties for the color of body fluids, a method for producing the same, and an absorbent article including the nonwoven fabric. [Means for solving the problem]

[0010] The present invention relates to a nonwoven fabric. The nonwoven fabric is preferably made from split fibers in which two or more different resins are continuously arranged in the longitudinal direction of the fiber and in the circumferential direction of the fiber, and each resin is configured to be spaced apart. The nonwoven fabric preferably has fusion points where the constituent fibers are fused to each other. It is preferable that the split fiber has split sections in which at least one pair of adjacent resins are completely spaced apart, and non-split sections in which adjacent resins are not completely spaced apart, alternately formed in the longitudinal direction of the fiber. It is preferable that the split fibers have a flat cross-sectional shape in the unsplit portions, and that the major axis of the cross-section is oriented in a direction along the surface of the nonwoven fabric.

[0011] The present invention also relates to an absorbent article comprising the nonwoven fabric.

[0012] The present invention further relates to a method for producing the nonwoven fabric. It is preferable that the manufacturing method uses as a raw material split fibers in which two or more different resins are continuously arranged in the longitudinal direction of the fiber and each resin is arranged in the circumferential direction of the fiber, and each resin is configured to be spaced apart. It is preferable to subject a fiber web containing the split fibers to an air-through treatment to obtain a fiber aggregate having the fusion points formed therein. It is preferable that the fiber assembly is subjected to a first pressing treatment to form split portions in the split fibers. It is preferable to include a step of subjecting the fiber aggregate having the divided portions to a second pressing treatment to orient the major axis of the cross section in the non-divided portions in a planar direction. The second pressing process is preferably carried out under a condition where the degree of pressing is lower than that of the first pressing process. Effect of the Invention

[0013] According to the present invention, there are provided a nonwoven fabric that is pleasant to the touch and has excellent concealing properties for the color of body fluids, a method for producing the same, and an absorbent article including the nonwoven fabric. [Brief description of the drawings]

[0014] [Figure 1] FIG. 1 is a perspective view showing a schematic diagram of one embodiment of split fibers in an unsplit state as a raw material. [Diagram 2] FIG. 2 is a plan view showing a schematic diagram of the state in which split fibers are present in the nonwoven fabric of the present invention. [Diagram 3] 3(a) to 3(d) are cross-sectional views each showing a schematic representation of one embodiment of the state of resin in the divided portions of the nonwoven fabric of the present invention. [Figure 4] 4(a) to 4(c) are cross-sectional views each showing a schematic representation of one embodiment of the state in which resin exists in the non-split portion of the nonwoven fabric of the present invention. [Diagram 5] FIG. 5 is a scanning electron microscope image showing the cross section and orientation state of an undivided portion in a cross-sectional view of the nonwoven fabric of the present invention. [Figure 6] FIG. 6 is a scanning electron microscope image showing the state of bent portions in a plan view of the nonwoven fabric of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0015] The present invention will be described below based on its preferred embodiments. The nonwoven fabric of the present invention is a fiber sheet containing split fibers as a raw material. The constituent fibers of the nonwoven fabric preferably maintain the form of a fiber sheet having fusion points by fusing the fibers together. The nonwoven fabric of the present invention is suitably used as a component of an absorbent article that absorbs body fluids such as urine and menstrual blood. In the following description, depending on the context, the term "split fiber" can refer to either an unsplit fiber that is the raw material itself, or a fiber that has split portions that are present within a nonwoven fabric.

[0016] FIG. 1 shows an embodiment of an unsplit split fiber used as a raw material. As shown in the figure, the split fiber 10 used as a raw material for nonwoven fabric is a composite fiber composed of two or more different resins. It is preferable that each resin is continuously arranged in the longitudinal direction of the fiber and arranged in the circumferential direction of the fiber. The split fiber 10 is configured so that each resin is present in two or more separate locations in the cross section of the fiber, and can be separated by applying at least one of heat and external force to the fiber. The split fiber 10 shown in the figure has each resin present radially in its cross section. The cross section of the fiber means a cross section along a direction perpendicular to the fiber length direction.

[0017] In the following description, for convenience of explanation, a split fiber made of two different types of resin will be used as an example, but the present invention is not particularly limited and can be applied to split fibers containing three or more different types of resin. The split fiber 10 shown in FIG. 1 is composed of two different resins, a first resin 11 and a second resin 12 different from the first resin 11. These resins 11, 12 are continuously arranged in the longitudinal direction of the fiber (fiber length direction) and alternately arranged in the circumferential direction of the fiber. Each of the resins 11, 12 constitutes the outer surface of the split fiber. When viewed in cross section, each of the resins 11, 12 shown in the figure is radially arranged in the circumferential direction of the fiber, and the maximum diameter is smaller than the fiber diameter of the split fiber in an unsplit state. Details of the constituent resins and fiber diameter of the split fiber 10 will be described later.

[0018] 2 to 4 are schematic diagrams showing the state of split fibers 10 in a nonwoven fabric. The split fibers 10 present in the nonwoven fabric have split portions 20 and non-split portions 30. The split portions 20 and non-split portions 30 are alternately formed along the longitudinal direction of the fiber.

[0019] The split portion 20 is formed such that at least a pair of adjacent resins in each of the resins constituting the split fiber 10 are completely separated from each other. Specifically, as shown in Figs. 3(a) to (d), the split portion 20 is configured in any one of the following modes (i) to (v). These modes may be the same or different in each split portion 20. (i) A state in which the first resin 11 and the second resin 12 adjacent to the first resin 11 are completely separated from each other, and the resins 11, 12 are not in contact with each other (see FIG. 3(a)). (ii) A state in which a part of the first resin 11 constituting the split fiber 10 is completely separated from the adjacent second resin 12 due to peeling or the like (see FIG. 3(b)). (iii) A state in which a part of the second resin 12 constituting the segmented fiber 10 is completely separated from the adjacent first resin 11 due to peeling or the like (see FIG. 3(b)). (iv) When focusing on one first resin 11, the first resin 11 is completely separated from one of the second resins 12 adjacent to the first resin 11, but is not completely separated from the other second resin 12 adjacent to the first resin 11, and is completely separated from the adjacent resin due to, for example, part of the constituent resin peeling off (see Figures 3(c) and (d)). (v) When focusing on one second resin 12, the second resin 12 is completely separated from one of the first resins 11 adjacent to it, but is not completely separated from the other first resin 11 adjacent to it, and a part of the constituent resins has peeled off, etc., resulting in the second resin 12 being completely separated from the adjacent resin (see Figures 3(c) and (d)). (vi) A state in which two or more of the above forms (i) to (v) are mixed.

[0020] As a result, in the split portion 20, there is one or more second fibers 15 having a fiber diameter smaller than that in the non-split portion 30. The second fibers 15 are derived from the resins 11 and 12 constituting the split fiber 10. In the above-mentioned forms (i) to (iii), the second fibers 15 are formed from only the first resin 11 or the second resin 12. In the above-mentioned forms (iv) and (v), the second fibers 15 are formed containing the first resin 11 and the second resin 12 and having a fiber diameter smaller than that of the split fiber in an unsplit state, and also include a form in which the adjacent resins in the second fibers 15 are not completely separated from each other as shown in FIG. 3(d). In any case, by having such second fibers 15, it is possible to realize a smooth touch on the surface of the nonwoven fabric and a fluffy and high flexibility of the nonwoven fabric.

[0021] On the other hand, the non-dividable portions 30 are formed such that the adjacent resins constituting the split fiber 10 are not completely spaced apart from each other. Specifically, as shown in Figs. 4(a) to (c), when focusing on one non-dividable portion 30, the non-dividable portion 30 is configured in any one of the following modes (a) to (e), and these modes may be the same or different in each non-dividable portion 30. Note that the resins that are partially spaced apart in the non-dividable portions 30 are not included in the second fiber of the present invention. (A) A state in which a first resin 11 and a second resin 12 adjacent to the first resin 11 are in contact with each other, and no gap is formed (see FIG. 4(a)). (a) A state in which a first resin 11 and a second resin 12 adjacent to the first resin 11 are in contact with each other, but a portion of the first resin 11 is partially separated from the adjacent second resin 12 to form a gap S (see Figure 4(b)). (c) A state in which a first resin 11 and a second resin 12 adjacent to the first resin 11 are in contact with each other, but a portion of the second resin 12 is partially separated from the adjacent first resin 11 to form a gap S (see Figure 4(b)). (e) A state in which the cross-sectional outline of the non-split portion 30 is a non-circular shape, such as an ellipse, so that adjacent resins 11, 12 are in contact with each other, but adjacent resins 11, 12 are partially separated from each other to form a gap S (see Figure 4(c)). (E) A state in which two or more of the above forms (A) to (D) are mixed.

[0022] The non-split portions 30 include those having an isotropic cross-section as shown in Figure 4(a) and those having an anisotropic cross-section, such as in which the fibers are flattened, as shown in Figure 4(c). Preferably, the non-split portions 30 having flat, anisotropic cross-sections are formed in greater numbers than those having isotropic cross-sections. In either case, the fiber diameter of the unsplit portion 30 is equal to or larger than the fiber diameter of the split fiber in an unsplit state.

[0023] From the viewpoint of further increasing the flexibility of the nonwoven fabric, it is preferable that the non-dividable portion 30 has voids S formed by partially separating the resins 11, 12 as shown in Fig. 4(b) and (c). The voids S are preferably formed along the fiber length direction. Such voids S can be formed, for example, by appropriately adjusting the degree of pressing in the first pressing process in the manufacturing method described later.

[0024] 5 shows a scanning electron microscope (SEM) image of the cross section of an unsplit portion 30 of a split fiber 10 in a nonwoven fabric. As shown in the figure, it is preferable that the cross section of the split fiber 10 in the nonwoven fabric is flattened at the unsplit portion 30. In other words, it is preferable that the cross section of the unsplit portion 30 in the direction perpendicular to the fiber length direction has a shape having a major axis and a minor axis.

[0025] In addition, in the non-divided portion 30 having a flat cross-sectional shape, it is also preferable that the long axis of the cross-section (the line segment indicated by symbol A1 in Fig. 5) is oriented in the direction along the surface direction of the nonwoven fabric (indicated by symbol X in Fig. 5). With this configuration, when the nonwoven fabric is viewed in plan, the part of the non-divided portion 30 having a large planar area faces along the surface direction of the nonwoven fabric, making it difficult to see the color of bodily fluids present on the other surface side, improving concealment.

[0026] In this specification, "having a flat cross-sectional shape" means that when a cross section of the non-divided portion 30 is observed, the ratio of the length of the long axis to the length of the short axis in the non-divided portion 30 (long axis length / short axis length) (hereinafter, this is also referred to as the flattening ratio) is 1.3 or more. From the viewpoint of further improving the hiding power, the flattening ratio is preferably 1.4 or more, more preferably 1.5 or more, and is preferably 3.0 or less, more preferably 2.5 or less. It is preferable that this flattening ratio is satisfied over the entire length of the non-divided portion 30. The above-mentioned flattening ratio can be achieved, for example, by appropriately adjusting the degree of pressing in the first pressing process in the manufacturing method described below.

[0027] The lengths of the major and minor axes and the flattening ratio of the cross-sectional shape of the undivided portion 30 can be measured and calculated by the following method. First, the nonwoven fabric to be measured is frozen with liquid nitrogen to fix the state of fiber existence. Next, the frozen nonwoven fabric is cut using a razor blade or the like so that the cross section of the constituent fibers is formed to prepare a measurement sample. Next, the cross section of the measurement sample is observed using a microscope or SEM at any magnification that allows the cross section of the constituent fibers to be recognized and the dimensions of the fiber cross section to be measured. The portion where the resins are not completely separated is identified as the non-split portion 30. The magnification in this case can be, for example, 100 times. This observation method is similarly applied to the observation methods in other measurement methods in this specification. Next, the line segment that connects two points on the periphery of the non-split portion 30 in the cross section and has the maximum diameter length in the cross section is defined as the long axis, and the line segment that is perpendicular to the long axis and has the maximum length is defined as the short axis. The lengths of the long axis and the short axis are then analyzed and calculated using image analysis software or the like, and the value obtained by dividing the length of the long axis by the length of the short axis is calculated. This procedure is performed on the non-split portion 30 of 100 or more fibers present in the observed cross section, and the arithmetic average value of the values ​​obtained by dividing the length of the long axis by the length of the short axis is defined as the flattening in the present invention.

[0028] In addition, in this specification, "the long axis of the cross section is oriented in the direction along the surface direction of the nonwoven fabric" means that when the cross sections of 100 or more non-divided portions 30 are observed by the above-mentioned method, 70% or more, preferably 80% or more of the non-divided portions 30, based on the number of non-divided portions 30 in the observed fibers, have an acute angle between the long axis of the non-divided portions 30 and the surface of the nonwoven fabric of less than 45 degrees. When the long axis of the non-divided portions 30 extends in a direction parallel to the surface of the nonwoven fabric, the angle between the long axis of the non-divided portions 30 and the surface of the nonwoven fabric is considered to be 0 degree. Such a state can be achieved, for example, by appropriately adjusting the degree of pressing in the second pressing process in the manufacturing method described below.

[0029] Whether or not the long axis of the cross section is oriented in a direction along the surface direction of the nonwoven fabric can be calculated by identifying the long axis in the non-split portion 30 in a manner similar to that described above and analyzing the angle between that long axis and the surface of the nonwoven fabric using image analysis software or the like.

[0030] The nonwoven fabric of the present invention has fusion points where the constituent fibers are fused together. In this case, the fusion points are present in a three-dimensionally distributed manner in the nonwoven fabric. The fusion points between the fibers are formed in at least one of the divided parts 20, the non-divided parts 30, and the second fibers 15, as described above, such that the boundaries of the fibers at the intersections between the fibers are unclear, due to the resin constituting the fibers being melted by at least one of heat and pressure. The fusion points between the fibers are formed in at least one of the divided parts 20, the non-divided parts 30, and the second fibers 15. By forming such fusion points, even if the second fibers 15 are formed in the divided parts 20, it is possible to prevent the fibers from becoming fuzzed or falling out, resulting in a nonwoven fabric that is pleasant to the touch. The presence or absence of fusion points in the nonwoven fabric can be determined by obtaining a cut surface in the same manner as described above and observing the fibers present on the cut surface.

[0031] The nonwoven fabric having the above configuration contains split fibers in which the split portions 20 and the non-split portions 30 are alternately present in the circumferential direction of the fibers, and therefore can simultaneously exhibit a good feel due to the second fibers 15 present in the split portions 20 and softness due to the moderate resistance to external forces due to the non-split portions 30. As a result, compared to nonwoven fabrics composed only of small-diameter fibers, the nonwoven fabric can exhibit fluffy softness while improving the smoothness of the surface, resulting in a nonwoven fabric with good feel and usability. The physical properties of the nonwoven fabric, such as the smoothness and fluffy softness, can be quantitatively evaluated as the standard deviation MMD value of the friction coefficient and the value of the compression work, as described in detail in the examples below.

[0032] Furthermore, the nonwoven fabric has a flat cross section of the non-divided parts 30, and the major axis of the flat cross section is oriented in a direction along the surface of the nonwoven fabric, so that when the surface of the nonwoven fabric is touched, the unevenness caused by the cross-sectional structure of the fibers is hardly felt, and the fabric has a good texture. In addition, when the nonwoven fabric is viewed from one side, the area of ​​the non-divided parts 30 with a large planar area is mainly visible, and the colors of body fluids such as urine and menstrual blood that are present through the other side are less visible. As a result, the ability to conceal the colors of body fluids is improved. Furthermore, the presence of fusion points between fibers in the nonwoven fabric allows the nonwoven fabric to exhibit strength sufficient for practical use while preventing the fibers from fuzzing or falling out, which also results in a nonwoven fabric that feels good against the skin.

[0033] From the viewpoint of improving the smoothness of the nonwoven fabric surface and improving the feel against the skin, the split fibers 10 present in the nonwoven fabric preferably have bent portions 40 in which the fibers are bent at locations other than the fusion points, as shown in FIG. 6. It is also preferable that the bent portions 40 are formed along the surface direction of the nonwoven fabric. The bent portions 40 are formed in at least one of the divided portions 20 and the non-divided portions 30. By forming the bent portions, when an external force is applied to the nonwoven fabric, the constituent fibers are more likely to deform starting from the bent portions, thereby reducing the resistance caused by the constituent fibers and improving the feel against the skin.

[0034] Whether or not the split fiber has a bent portion can be determined by the following method. First, one side of the nonwoven fabric to be treated is observed in the same manner as the observation method described above, and a 100-fold enlarged image is obtained. From the obtained enlarged image, fibers having a bent portion are visually identified, and the virtual center line of the fiber is drawn by image software or manually. Next, three virtual points are taken on the virtual center line at intervals of 100 μm. Then, the portion in which the smaller angle of the two virtual lines passing through adjacent virtual points is 60 degrees or more and less than 180 degrees is defined as the bent portion of the present invention. In other words, the angle of the bent portion is 60 degrees or more, preferably 65 degrees or more. In addition, from the viewpoint of preventing a significant decrease in the strength of the fiber, the angle of the bent portion is preferably 150 degrees or less.

[0035] The details of the configuration of the split fiber are described below. As described above, the split fiber is composed of two or more different resins, and the resins are continuously arranged in the longitudinal direction of the fiber and in the circumferential direction of the fiber. The cross-sectional shape of the split fiber in an unsplit state can be, for example, a circular shape such as a perfect circle or an ellipse, or a convex polygon or a regular polygon such as a triangle, a square, a pentagon, or a hexagon, or a geometric shape. The split fiber shown in FIG. 1 has a circular cross-sectional shape and is an isotropic shape.

[0036] The resins constituting the split fibers are arranged in a non-circular shape, for example, radially or in layers, in the cross section of the split fibers, and are preferably arranged radially in the circumferential direction of the fibers. Therefore, when the split fibers are split and separated, the second fibers formed by the separation between the resins have a smaller fiber diameter than the split fibers in an unsplit state, and have a non-circular cross section.

[0037] From the viewpoint of appropriately reducing the fiber diameter of the second fibers generated after splitting and improving the feel of the nonwoven fabric, the number of resin segments in the cross section of the split fiber is preferably 4 or more, more preferably 8 or more. Moreover, from the viewpoint of improving the splittability of the split fiber, the number of resin segments in the cross section of the split fiber is preferably 48 or less, more preferably 32 or less, and even more preferably 16 or less.

[0038] The number of resin segments in the cross section of the split fiber can be measured by the following method. First, the nonwoven fabric to be measured is frozen with liquid nitrogen to fix the state of fiber existence. Next, the frozen nonwoven fabric is cut using a razor blade or the like so that the cross section of the constituent fibers is formed to prepare a measurement sample. Next, the cross section of the measurement sample is observed using a microscope or SEM at any magnification that allows the cross section of the constituent fibers to be recognized and the dimensions of the fiber cross section to be measured. The portion where each resin is not completely separated is identified as the non-divided portion 30. The number of resin divisions in the cross section of the non-divided portion 30 is visually measured. In this case, the magnification can be, for example, 100 times.

[0039] The constituent resin of the split fiber may be, for example, a combination of thermoplastic resins. Specifically, the constituent resin of the split fiber may be a combination of two or more different resins, such as polyolefin resins such as polyethylene (PE) and polypropylene, polyester resins such as polyethylene terephthalate (PET), polyamide resins such as nylon 6 and nylon 66, vinyl resins such as polyvinyl chloride and polystyrene, acrylic resins such as polyacrylic acid and polymethyl methacrylate, and copolymers thereof.

[0040] From the viewpoint of increasing the separation of the split fibers while facilitating the formation of fusion points in the nonwoven fabric and facilitating the production of a nonwoven fabric with an even better texture, it is preferable that the split fibers 10 are made of two different resins. That is, as shown in Fig. 1, the split fibers 10 are preferably made of a first resin 11 and a second resin 12, and it is also preferable that the second resin 12 is a resin having a higher melting point than the first resin 11.

[0041] When split fibers composed of a first resin 11 and a second resin 12 are used as raw materials, the fusion points of the nonwoven fabric are typically formed by the first resin 11, which has a lower melting point, melting and fusing with the other constituent fibers. In the split section 20, the resins 11, 12 are completely separated to form at least one type of second fiber 15 composed of the first resin 11 and the second fiber 15 composed of the second resin 12, and the second fiber 15 containing the first resin 11 and the second resin 12 and having a smaller number of resin segments than the split fiber in an unsplit state.

[0042] From the viewpoint of easily obtaining a nonwoven fabric with sufficient strength, the first resin is preferably a thermoplastic resin, more preferably a thermoplastic resin having a melting point of 160°C or less, and even more preferably a thermoplastic resin having a melting point of 140°C or less. In addition, from the viewpoint of improving the separation property of the split fibers, the second resin is preferably a thermoplastic resin, more preferably a thermoplastic resin having a melting point exceeding 140°C, even more preferably a thermoplastic resin having a melting point 10°C or more higher than the melting point of the first resin, and even more preferably a thermoplastic resin having a melting point 20°C or more higher than the melting point of the first resin.

[0043] Combinations of the first resin 11 and the second resin 12 having different melting points from each other include, for example, polyethylene / polypropylene, polyethylene / polyethylene terephthalate, polypropylene / polyethylene terephthalate, polyethylene / nylon 6, polypropylene / nylon 6, and nylon 6 / polyethylene terephthalate, expressed as "first resin / second resin". However, as long as the effects of the present invention are achieved, the combination of the constituent resins is not particularly limited.

[0044] Of these, from the viewpoint of melting at a relatively low temperature and bonding the fibers well, the first resin is preferably polyethylene, and more preferably high-density polyethylene. From the viewpoint of obtaining a nonwoven fabric that is resistant to collapse even after thermal bonding treatment and has high flexibility, it is preferable to use polyethylene terephthalate or polypropylene as the second resin, and it is more preferable to use polyethylene terephthalate because the resin itself has a high elastic modulus and can further increase the flexibility of the nonwoven fabric.

[0045] The melting point of the resin can be calculated from a DSC curve measured in accordance with JIS K7121 (1987). In detail, the melting point of the resin can be measured using a differential scanning calorimeter (DSC7000x, manufactured by Hitachi High-Tech Science Corporation). First, a finely cut fiber sample (1 mg) is subjected to thermal analysis at a heating rate of 10°C / min to measure the melting peak temperature of each resin. The melting point is defined as the melting peak temperature at the first heating. If the melting point cannot be clearly measured by this method, the resin is defined as a "resin having no melting point". For a resin having no melting point, the softening point is taken as the melting point.

[0046] The fiber diameter of the split fibers 10 in an unsplit state is preferably 0.8 dtex or more, more preferably 1.0 dtex or more, and from the viewpoint of obtaining a smooth nonwoven fabric, the fiber diameter is preferably 4.4 dtex or less, more preferably 3.9 dtex or less. This configuration can prevent the fibers from wrapping around the manufacturing equipment during production, thereby improving the manufacturing efficiency of the nonwoven fabric, and also makes the fibers less likely to become slack, improving the smoothness and fluffy softness of the obtained nonwoven fabric.

[0047] From the viewpoint of obtaining a nonwoven fabric that is smoother to the touch, the fiber diameter of the second fibers 15 present in the divided portions 20 is preferably 1.0 dtex or less, more preferably 0.8 dtex or less, and even more preferably 0.5 dtex or less, in terms of fineness. From the viewpoint of reducing fiber fluffing and shedding and obtaining a fluffy and soft nonwoven fabric, the fiber diameter is preferably 0.01 dtex or more, more preferably 0.1 dtex or more. The fineness of the second fibers 15 can be adjusted by appropriately changing the fineness or number of segments of the split fibers used, or the resin components. From the same viewpoint, it is preferable that the above-mentioned fineness is satisfied in the second fibers 15 made of the first resin 11 and the second fibers 15 made of the second resin 12. In order to improve the smoothness and fluffy flexibility of the nonwoven fabric, the fineness of the unsplit portions 30 is preferably in the same range as the fineness of the split fibers 10 in an unsplit state described above.

[0048] The fiber fineness is measured by measuring the cross-sectional area of ​​each fiber from a 100x magnified image obtained by observing the nonwoven fabric in the same manner as described above. The fineness of each fiber is calculated from this value and the density of the resin. The density of the resin in the fibers in the nonwoven fabric is measured by confirming the melting point of the resin that constitutes the fiber by differential scanning calorimetry using a fiber sample (1 mg) obtained by finely cutting the nonwoven fabric, and identifying the resin type in the fiber and the weight average ratio of each resin type by infrared spectroscopy (IR), scanning electron microscope (SEM), and nuclear magnetic resonance analysis (NMR analysis). The weight average value of the density of each resin is taken from the literature value of the density of non-foamed resin measured in accordance with JIS K7112:1999, and is used as the density of the resin used to calculate the fineness.

[0049] As long as the effects of the present invention are achieved, the nonwoven fabric of the present invention may further contain, in addition to the split fibers, other fibers other than the split fibers (hereinafter, simply referred to as "other fibers"). Examples of other fibers that may be contained in the nonwoven fabric include fibers containing the various thermoplastic resins described above, and composite fibers other than the split fibers, such as core-sheath composite fibers or side-by-side composite fibers containing two types of thermoplastic resins with different shrinkage rates. The cross-sectional shape of the other fibers may be any of the various geometric shapes described above.

[0050] The fiber diameter of the other fibers, expressed in terms of fineness, is preferably 0.8 dtex or more, more preferably 1.0 dtex or more, and is preferably 4.4 dtex or less, more preferably 3.9 dtex or less.

[0051] From the viewpoint of achieving both good touch and hiding power at a high level, the content of split fibers in the nonwoven fabric is preferably 20% by mass or more, more preferably 40% by mass or more, and even more preferably 60% by mass or more. Also, from the viewpoint of increasing the strength of the nonwoven fabric, the content of split fibers in the nonwoven fabric is preferably 100% by mass or less, more preferably 95% by mass or less, and even more preferably 90% by mass or less.

[0052] The nonwoven fabric may be composed only of split fibers (i.e., 100% by mass of split fibers) and contain no other fibers (i.e., 0% by mass of other fibers). When the nonwoven fabric further contains other fibers, from the viewpoint of increasing the strength and flexibility of the nonwoven fabric, the content of the other fibers is preferably 20% by mass or more, more preferably 40% by mass or more, and is preferably 80% by mass or less, more preferably 70% by mass or less, and even more preferably 60% by mass or less.

[0053] The nonwoven fabric of the present invention may be a single layer or a multilayer depending on the purpose. Specifically, the nonwoven fabric may be composed of only one fiber assembly (whether single layer or multilayer), or may have a multi-ply laminated structure in which a first fiber assembly is laminated with another fiber assembly or a sheet material other than the fiber assembly.

[0054] The nonwoven fabric preferably has a total basis weight of 8 g / m 2 More preferably, 10 g / m 2 More preferably, 15 g / m 2 More preferably, it is 80 g / m 2 Less than 50 g / m 2 More preferably, 40 g / m 2 The following is the result. With the above-described structure, even when a nonwoven fabric has a relatively low basis weight, the flat orientation in the non-divided portions 30 can be maintained while the apparent fiber amount can be increased by the second fibers 15 in the divided portions 20, so that the feel of the nonwoven fabric and the ability to conceal the color of bodily fluids are fully exhibited.

[0055] From the viewpoint of improving the texture of the nonwoven fabric, the nonwoven fabric of the present invention has a thickness of preferably 0.05 mm or more, more preferably 0.3 mm or more, and preferably 10 mm or less, more preferably 5 mm or less. 2 The measurement is carried out under load using a laser displacement meter or the like.

[0056] The nonwoven fabric described above may be used as it is, or may be used as a component of an absorbent article, thereby forming the absorbent article comprising the nonwoven fabric. In other words, the nonwoven fabric of the present invention is suitably used for absorbent articles.

[0057] An absorbent article typically comprises a top sheet, a back sheet, and an absorbent disposed between the top sheet and the back sheet. The absorbent article can be used in a state in which the nonwoven fabric of the present invention is disposed as a constituent member of the top sheet or the back sheet. Absorbent articles include disposable articles such as disposable diapers, incontinence pads, sanitary napkins, panty liners, etc., but are not limited thereto, and broadly include articles used to absorb liquids discharged from the human body.

[0058] The absorbent body used in the absorbent article includes an absorbent core, which is composed of, for example, a laminate of hydrophilic fibers such as cellulose including pulp, a mixed laminate of the hydrophilic fibers and a water-absorbent polymer, a laminate of a water-absorbent polymer, or the like, and typically contains hydrophilic fibers and a water-absorbent polymer. The absorbent core may be covered with a core wrap sheet. As a covering mode of the core wrap sheet, for example, at least the skin-facing surface may be covered with a liquid-permeable core wrap sheet, or the entire surface including the skin-facing surface and the non-skin-facing surface may be covered with the core wrap sheet. As the core wrap sheet, for example, a thin paper made of hydrophilic fibers or a liquid-permeable nonwoven fabric can be used.

[0059] The above has been a description of the nonwoven fabric of the present invention and an absorbent article comprising said nonwoven fabric. Below, a preferred method for producing the nonwoven fabric of the present invention will be described. This method comprises a step of performing an air-through process on a fiber web containing split fibers as raw material to obtain a fiber aggregate. In addition, it also comprises a step of performing a pressing process on the obtained fiber aggregate. The split fibers as raw material are preferably configured such that two or more different resins are continuously arranged in the longitudinal direction of the fibers and each resin is arranged in the circumferential direction of the fibers, and each resin can be separated from the other resins.

[0060] First, a fiber web containing split fibers is formed. This fiber web can be formed, for example, by a carding method using a known carding machine. When other fibers are contained in addition to the split fibers, one fiber web may be formed in a state in which the split fibers and other fibers are mixed, or a fiber web containing split fibers may be formed by overlapping a web of other fibers formed separately. The split fibers that have undergone this process are in an unsplit state, and split portions 20 are not formed.

[0061] Next, an air-through process is performed in which hot air is blown onto the fiber web to obtain a fiber aggregate containing split fibers (air-through process). This process is a process for making the fiber web into a nonwoven fabric, and the fiber aggregate thus produced is generally called an air-through nonwoven fabric, in which fusion points between the constituent fibers are formed. The split fibers that have undergone this process are in an unsplit state, and split portions 20 are not formed.

[0062] In the air-through process, it is preferable that the temperature and wind speed of the hot air blown onto the fiber web be within a specific range, from the viewpoint of efficiently forming fusion points and improving the texture and feel of the nonwoven fabric. In detail, the temperature of the hot air blown onto the fiber web is preferably at least melting point M-10°C, more preferably at least melting point M-5°C, even more preferably at least the temperature of melting point M, in relation to the lowest melting point M (°C) of the resins contained in the constituent fibers, and is preferably at most melting point M+40°C, more preferably at most melting point M+20°C, even more preferably at most melting point M+10°C. The above-mentioned temperature of the hot air is the temperature at the hot air outlet.

[0063] In the air-through step, the speed of the hot air blown onto the fiber web is preferably 0.30 m / sec or more, more preferably 0.35 m / sec or more, and is preferably 2 m / sec or less, more preferably 1.5 m / sec or less, from the viewpoint of allowing the hot air to pass sufficiently in the thickness direction of the fiber web and facilitating fusion bonding between the fibers. The above-mentioned hot air speed is the speed at the hot air outlet. By carrying out the air-through process under the above-mentioned temperature and wind speed conditions, the resin with a low melting point (e.g., the first resin 11) in the split fibers that make up the fiber web can be melted or softened to randomly form sites where the fibers are fused together, so that the produced nonwoven fabric exhibits the flexibility and good texture inherent to an air-through nonwoven fabric while also exhibiting strength sufficient for use.

[0064] The conveying speed of the fiber web in the air-through process is preferably 2 m / min or more, more preferably 5 m / min or more, even more preferably 50 m / min or more, and preferably 150 m / min or less, more preferably 120 m / min or less, even more preferably 60 m / min or less, in the above-mentioned temperature and wind speed ranges.

[0065] Next, the obtained fiber aggregate is subjected to a pressing process. This pressing process is roughly divided into a first pressing process and a second pressing process which is different from the first pressing process in the degree of pressing. That is, the pressing process in this manufacturing method is performed multiple times. In either pressing process, a method capable of compressing the fiber aggregate by pressing it in its thickness direction can be adopted. In the following description, as an embodiment of the pressing process, a method of introducing the fiber aggregate between a pair of rolls and pressing it will be described as an example.

[0066] The first pressing process is a process in which an external force is applied to the unsplit split fiber to completely separate the resins that make up the split fiber, forming split sections 20. In addition, this process crushes the split fiber to form non-split sections 30 in which the cross-sectional shape of the split fiber is flattened. In addition, this process can also form bent sections of the fiber. The first pressing process may be performed only once, or may be performed multiple times as necessary. The temperature in the first pressing process may be in a non-heated state such as room temperature, in a heated state, or in a combination of these.

[0067] From the viewpoint of facilitating partial formation of the split portions 20 and facilitating formation of the non-split portions 30 having a high flattening ratio, the pressure conditions in the first pressing process are preferably 50 N / cm or more, more preferably 100 N / cm or more, and even more preferably 150 N / cm or more, expressed in terms of the linear pressure generated between a pair of rolls. Furthermore, from the viewpoint of not forming the fiber aggregate into a film, maintaining a fiber shape in which the boundaries between the constituent fibers are clearly defined, and obtaining a nonwoven fabric with a good texture, the linear pressure is preferably 700 N / cm or less, more preferably 450 N / cm or less, and even more preferably 300 N / cm or less.

[0068] The pressurizing time in the first pressing process can be appropriately set as long as the fiber shape of the fibers constituting the fiber aggregate is maintained and each resin of the split fiber can be completely separated. For example, the pressurizing time under the above pressure conditions can be preferably 0.01 seconds or more, more preferably 0.04 seconds or more, and preferably 0.1 seconds or less, more preferably 0.08 seconds or less per pressurizing. The pressurizing time can be set, for example, by appropriately adjusting the conveying speed of the fiber web.

[0069] Next, a second pressing process is performed on the fiber assembly in which split fibers have been formed with split sections 20 through the first pressing process. The second pressing process is a process for orienting the major axis of the cross section of the non-split sections 30, whose cross section shape has become flat, in the plane direction of the fiber assembly. In addition, the second fibers 15 and bent sections 40 generated by the formation of the split sections 20 can be leveled and oriented in the plane direction.

[0070] It is preferable that the second pressing process is performed with a lower degree of pressing than the first pressing process. As a method for lowering the degree of pressing, for example, the distance between the pair of rolls in the second pressing process is made wider than the distance between the pair of rolls in the first pressing process, so that the external force applied to the fiber aggregate can be reduced. Alternatively, as another example of a method for lowering the degree of pressing, the distance between the pair of rolls in each pressing process is made the same, and the peripheral surface of the roll used in the first pressing process is made of a member with a relatively high hardness, such as a hard member such as a non-elastic body, and the peripheral surface of the roll used in the second pressing process is made of a member with a relatively low hardness, such as a soft member such as an elastic body, so that the external force applied to the fiber aggregate can be reduced. By configuring in this way, the long axis of the cross section of the flat non-divided portion 30 can be efficiently oriented in the planar direction.

[0071] From the viewpoint of further enhancing the orientation of the major axis in the planar direction in the non-split portion 30, the pressure conditions in the second pressing process are preferably 20 N / cm or more, more preferably 30 N / cm or more, expressed in terms of the linear pressure generated between the pair of rolls, provided that the pressure conditions are lower than those in the first pressing process. Also, from the viewpoint of easily maintaining the flattening within a predetermined range, the linear pressure is preferably 150 N / cm or less, more preferably 100 N / cm or less.

[0072] Each pair of rolls used in each pressing process can be made of a non-elastic material such as metal or an elastic material such as rubber. Examples of elastic materials include elastically deformable elastic resins such as hard rubber, silicon rubber, urethane rubber, acrylonitrile-butadiene rubber (NBR), and ethylene-propylene-diene rubber (EPDM). These resins have a type D hardness of preferably 20 or more, more preferably 70 or more, and preferably 100 or less, more preferably 95 or less, as measured in accordance with JIS K6253. Type D hardness is an index of hardness, and a higher value indicates a higher hardness.

[0073] From the viewpoint of forming a balanced and efficient split section 20 by splitting and separating the constituent resin of the split fiber and a non-split section 30 in which the constituent resin is not completely separated and has a flat cross-sectional shape, it is preferable to use a pair of rolls in the first pressing process, at least one of which has a non-elastic peripheral surface, and introduce the fiber aggregate between the two rolls. In this case, the pair of rolls used in the first pressing process may, for example, have one roll having a metallic peripheral surface and the other roll having a metallic surface or the elastic resin. The peripheral surfaces of these rolls are preferably all smooth.

[0074] From the viewpoint of efficiently orienting the major axis of the cross section of the flat non-divided portions 30 in the planar direction while maintaining the texture of the nonwoven fabric and without applying excessive external force, it is preferable to use a pair of rolls both having elastic peripheral surfaces and introduce the fiber aggregate having the divided portions 20 between the two rolls in the second pressing process. In this case, the pair of rolls used in the second pressing process may have peripheral surfaces made of the above-mentioned elastic resin, for example.

[0075] Each pair of rolls used in each pressing process may independently have a smooth peripheral surface or may have a non-smooth peripheral surface having an uneven structure formed thereon. In addition, both peripheral surfaces of the pair of rolls may be smooth or non-smooth, or one of the rolls may have a smooth peripheral surface and the other non-smooth peripheral surface.

[0076] When heating is performed in each pressing treatment, the heating temperature can be independently set to preferably 50° C. or higher, more preferably 60° C. or higher, and preferably 120° C. or lower, more preferably 100° C. or lower. When the pressing treatment is performed in a heated state, the peripheral surface of the roll may be heated to the above-mentioned temperature range.

[0077] By carrying out each pressing treatment under the above conditions, a nonwoven fabric having divided portions 20 each having a plurality of second fibers 15 and non-divided portions 30 whose major axes are oriented in the planar direction can be easily obtained. The nonwoven fabric obtained by the above-mentioned method is an air-through nonwoven fabric even after undergoing each of the above-mentioned pressing treatments.

[0078] Through the above steps, the nonwoven fabric of the present invention can be obtained. This nonwoven fabric is preferably incorporated as a constituent member of an absorbent article in a subsequent step. When a nonwoven fabric is used as a constituent material of an absorbent article, the desired absorbent article can be manufactured by using the nonwoven fabric manufactured by the above-mentioned method as one of the constituent materials in any of the processes for manufacturing the absorbent article, and by including one or more of the processes of cutting the nonwoven fabric and performing various operations such as laminating or joining the nonwoven fabric with other constituent materials that make up the absorbent article (e.g., an absorbent body, a sheet, etc.).

[0079] Although the present invention has been described based on the preferred embodiment, the present invention is not limited to the above embodiment. EXAMPLES

[0080] The present invention will be described in more detail below with reference to examples, but the scope of the present invention is not limited to these examples.

[0081] Example 1 As a raw material, a split fiber with a circular cross section and a fineness of 1.8 dtex was used. In this split fiber, the first resin PE (melting point: 132°C) and the second resin PET (melting point: 255°C) were continuously arranged in the longitudinal direction of the fiber and the resins were arranged in the circumferential direction of the fiber, and the resins were configured to be spaced apart. In the cross section of this split fiber, PE and PET were divided into four each, for a total of eight pieces (number of sections: 8), and these resins were arranged radially.

[0082] First, the basis weight is 30 g / m 2The fiber web consisting of only the split fibers adjusted to have the above structure was subjected to an air-through treatment to obtain a nonwoven fiber assembly. The conditions for the air-through treatment were that the fiber assembly was conveyed at a speed of 10 m / min, and hot air at 138°C was blown onto the fiber assembly at a speed of 1.0 m / sec. Next, the fiber assembly was introduced between a pair of metal rolls, both of which had inelastic and smooth peripheral surfaces, and subjected to a first pressing treatment. The conditions for the first pressing treatment were that the temperature was room temperature and the linear pressure applied to the fiber assembly was 200 N / cm. Next, a pair of resin rolls, both of which have elastic and smooth peripheral surfaces made of hard rubber (type D hardness: 88 degrees), were used to introduce the fiber aggregate that had been subjected to the first pressing treatment between the rolls to perform a second pressing treatment. The conditions for the second pressing treatment were that the temperature was room temperature and the linear pressure applied to the fiber aggregate was 50 N / cm.

[0083] Through these steps, the desired nonwoven fabric was obtained. This nonwoven fabric had fusion points between the fibers, and divided portions 20 and non-divided portions 30 were alternately formed in the divided fibers in the longitudinal direction of the fibers. In the divided portions 20, a plurality of second fibers 15 having a fineness of 1 dtex or less and made of PE or PET were formed. In the non-divided portions 30, the fiber cross section in that portion was flattened, and the major axis of the cross section was oriented in a direction along the surface of the nonwoven fabric. The flatness and tensile strength of the non-divided portions 30 were 0.5 g / cm 2 The thickness of the nonwoven fabric under the load was as shown in Table 1 below.

[0084] [Examples 2 to 4] The air-through treatment, the first pressing treatment, and the second pressing treatment were sequentially performed in the same manner as in Example 1, except that a fiber web was used in which the split fibers used in Example 1 and core-sheath composite fibers (fineness: 2.4 dtex, resin content ratio: core 48.8% by mass, sheath 51.2% by mass) in which the core was made of PET resin and the sheath was made of PE resin were mixed. The target single-layer nonwoven fabric (basis weight 30 g / m 2 The mixing ratio of the split fibers and the core-sheath composite fibers was as shown in Table 1 below. All of these nonwoven fabrics had fusion points between the fibers, and the split fibers had split sections 20 and non-split sections 30 alternately formed in the longitudinal direction of the fibers. In the split sections 20, a plurality of second fibers 15 having a fineness of 1 dtex or less and made of PE or PET were formed. In the non-split sections 30, the fiber cross section in that portion was flattened, and the major axis of the cross section was oriented in a direction along the surface of the nonwoven fabric. The flatness and tensile strength of the non-split sections 30 were 0.5 g / cm 2 The thickness of the nonwoven fabric under the load was as shown in Table 1 below.

[0085] Comparative Example 1 A nonwoven fabric (basis weight 30 g / m) was produced in the same manner as in Example 2, except that no split fibers were used, only the core-sheath composite fibers used in Example 2 were used, and neither the first pressing treatment nor the second pressing treatment was performed. 2 Although each of these nonwoven fabrics had fusion points between the fibers, the constituent fibers did not have divided portions 20 and non-divided portions 30, and the fiber cross sections were not flat.

[0086] [Comparative Examples 2 to 5] Except for changing the mixing ratio of split fibers and core-sheath composite fibers as shown in Table 1 below and not carrying out either the first pressing process or the second pressing process, nonwoven fabrics were obtained in the same manner as in Example 1. All of these nonwoven fabrics had fusion points between the fibers, but the split fibers did not have split parts 20 and non-split parts 30, and the fiber cross sections were not flat.

[0087] [Comparative Examples 6 to 9] A nonwoven fabric (basis weight 30 g / m) was produced in the same manner as in Example 1, except that the mixing ratio of the split fibers and the core-sheath composite fibers was changed as shown in Table 1 below and the second pressing treatment was not performed. 2 ) was obtained. All of these nonwoven fabrics had fusion points between the fibers, and the split fibers had split sections 20 and non-split sections 30 alternately formed in the longitudinal direction of the fibers. In the split sections 20, a plurality of second fibers 15 having a fineness of 1 dtex or less and made of PE or PET were formed. In all of these nonwoven fabrics, the fiber cross section in the non-split sections 30 was flattened, but the long axis of the cross section was not oriented in a direction along the surface of the nonwoven fabric.

[0088] Comparative Example 10 A nonwoven fabric was obtained in the same manner as in Example 1, except that the same core-sheath composite fibers as in Comparative Example 1 were used. All of the nonwoven fabrics had fusion points between the fibers, but the constituent fibers did not have divided portions 20 and non-divided portions 30, and the fiber cross sections were not flat.

[0089] [Evaluation of the smoothness of nonwoven fabric surfaces] The smoothness of the nonwoven fabric surface was evaluated using as an index the mean deviation MMD value of the coefficient of friction measured by the method described in the following publication. "Standardization and Analysis of Hand Evaluation" by Toshio Kawabata, 2nd Edition, Hand Measurement and Standardization Research Committee of the Japan Textile Machinery Society, published July 10, 1980.

[0090] In detail, a measuring device (KES-FB4 surface tester manufactured by Kato Tech Co., Ltd.) was used. A nonwoven fabric sample cut to a size of 20 cm x 20 cm was cut on one side thereof, and a frictional element made of a 0.5 mm diameter piano wire bent into a U-shape with a width of 5 mm, which was attached to the measuring device, was used to press the frictional element against the test piece with a weight at a load of 49 cN, and the frictional element was moved horizontally 2 cm along one direction of the nonwoven fabric at a constant speed of 0.1 cm / sec to measure. This measurement was performed at three locations using one sample, and the arithmetic mean value of the average deviation of the friction coefficients was taken as the MMD value, which is an evaluation index. The MMD value is an index of the roughness of the nonwoven fabric surface, and the smaller the MMD value, the smoother the surface of the object to be measured and the better the texture. The results are shown in Table 1 below.

[0091] [Evaluation of softness of nonwoven fabric] The softness of the nonwoven fabric was evaluated using the compression work (WC) measured by the method described in the above publication as an index. In detail, a measurement device (KES-G5 compression tester, manufactured by Kato Tech Co., Ltd.) was used, and a nonwoven fabric sample cut to a size of 100 mm x 100 mm was attached to the test table of the measurement device, and the sample was pressed against the test table with an area of ​​2 cm 2 The specimen was compressed between two steel plates with circular flat surfaces. The compression speed was 0.02cm / sec, and the maximum compression load was 490mN / cm. 2 It was decided. The compression work (WC) is calculated using the following formula (1), and its unit is "mN cm / cm 2 In the following formula (1), Tm, T0 and Pa are 490 mN / cm 2 Sample thickness under load: 4.9mN / cm 2 The sample thickness when loaded and the load during measurement (compression process) (mN / cm 2 ) is shown. This measurement was performed using three samples, and the arithmetic average value was used as the compression work value, which is an evaluation index. The larger the compression work (WC) value, the better the softness of the nonwoven fabric and the more fluffy it can be perceived. The results are shown in Table 1 below.

[0092]

number

[0093] [Evaluation of Concealment] The color hiding power of the nonwoven fabric was evaluated as the L* value per unit basis weight based on the L* value, which indicates brightness (degree of whiteness) in the L*a*b* color system. In detail, a handy spectrophotometer NF333 manufactured by Nippon Denshoku Industries Co., Ltd. was used to place the nonwoven fabric sample to be measured on a red reference plate, and the L* value was measured from the upper surface of the sample in accordance with JIS Z 8781-4:2013. The measurement was set to a viewing angle of 2° and light source C. This measurement was performed at three points on one nonwoven fabric, and the arithmetic average value was used as the L* value to be evaluated. Separately from this, the basis weight (g / cm2) of the sample used for measurement was measured. 2 ) was measured and calculated. The L* value per unit basis weight is calculated by dividing the L* value by the basis weight of the sample. An L* value of +100 indicates white, so the higher the L* value per unit basis weight, the higher the degree of whiteness and the better the hiding power of urine, menstrual blood, etc. The results are shown in Table 1 below.

[0094] [Table 1]

[0095] As shown in Table 1, the nonwoven fabrics of the Examples have a smoother surface, better flexibility, and a better texture than the nonwoven fabrics of the Comparative Examples. It is also clear that the nonwoven fabrics of the Examples have better color hiding properties than the nonwoven fabrics of the Comparative Examples.

Claims

1. A nonwoven fabric made from split fibers in which two or more different resins are continuously arranged in the longitudinal direction of the fibers and in the circumferential direction of the fibers, and each resin is configured to be spaced apart from the other resins, The nonwoven fabric has fusion points where constituent fibers are fused to each other, The split fiber has split portions in which at least a pair of adjacent resins are completely spaced from each other and non-split portions in which adjacent resins are not completely spaced from each other, which are alternately formed in the longitudinal direction of the fiber, The split fibers have a flat cross-sectional shape in the unsplit portions, and the major axis of the cross-section is oriented in a direction along the surface of the nonwoven fabric.

2. 2. The nonwoven fabric according to claim 1, wherein in the cross-sectional shape of the undivided portion, the ratio of the length of the major axis to the length of the minor axis (major axis length / minor axis length) is 1.3 or more.

3. The nonwoven fabric according to claim 1 or 2, wherein the non-divided portions have voids formed by partially separating the resins from each other.

4. The nonwoven fabric according to any one of claims 1 to 3, wherein the split fibers have bent portions at locations other than the fusion points.

5. The nonwoven fabric according to any one of claims 1 to 4, wherein the number of resin segments in the cross section of the split fiber is 4 or more and 48 or less.

6. The split fibers are made of two different types of resins, The nonwoven fabric according to any one of claims 1 to 5, comprising as the resin a first resin and a second resin having a melting point higher than that of the first resin.

7. The split portion has second fibers made of a first resin or a second resin, 7. The nonwoven fabric according to claim 6, wherein the second fibers have a fineness of 1 dtex or less.

8. The nonwoven fabric according to any one of claims 1 to 7, comprising 20% ​​by mass or more of the split fibers.

9. Basis weight 8g / m ２ 80g / m or more ２ The nonwoven fabric according to any one of claims 1 to 8, wherein:

10. 0.5 g / cm ２ The nonwoven fabric according to any one of claims 1 to 9, having a thickness under load of 0.05 mm or more and 10 mm or less.

11. An absorbent article comprising the nonwoven fabric according to any one of claims 1 to 10.

12. A method for producing the nonwoven fabric according to any one of claims 1 to 10, A split fiber is used as a raw material, in which two or more different resins are continuously arranged in the longitudinal direction of the fiber and each resin is arranged in the circumferential direction of the fiber, and each resin is configured to be spaced apart from the other resins, The fiber web containing the split fibers is subjected to an air-through treatment to obtain a fiber aggregate having the fusion points formed therein, A first pressing process is performed on the fiber aggregate to form a split portion in the split fiber; a step of subjecting the fiber aggregate having the divided portions to a second pressing treatment to orient the major axis of the cross section in the non-divided portions in a planar direction; The second pressing process is performed under a condition where the degree of pressing is lower than that of the first pressing process, The pressure conditions in the first pressing process are 150 N / cm or more and 700 N / cm or less, A method for producing a nonwoven fabric, wherein the pressure conditions in the second pressing treatment are 20 N / cm or more and 100 N / cm or less.

13. A pair of rolls is used, at least one of which has a non-elastic peripheral surface, The method according to claim 12, wherein the fiber aggregate is introduced between the rolls to perform a first pressing treatment.

14. A pair of rolls, both of which have elastic peripheral surfaces, is used. The method according to claim 12 or 13, further comprising the step of: introducing the fiber aggregate having the divided portions between the two rolls to perform a second pressing treatment.

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