Nonwoven fabric

Abstract

To provide a nonwoven fabric having liquid permeability at apertures thereof and high pressure resistance.SOLUTION: A nonwoven fabric includes fiber fused parts at intersections between fibers and has an uneven surface structure having a plurality of protrusions and bottoms provided between the protrusions adjacent to each other. Each of the plurality of protrusions has an apex and a wall part supporting the apex. An aperture penetrating in a thickness direction is provided on the bottom. The wall part is provided so as to surround an outer periphery of the aperture. Constituent fibers of the wall part are oriented in a horizontal direction at least at a portion along one direction and a direction orthogonal to the one direction in a plane direction of the nonwoven fabric.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to nonwoven fabrics. [Background technology]

[0002] Nonwoven fabrics are used in a variety of applications, such as components of absorbent articles such as diapers, sanitary napkins, etc. For example, nonwoven fabrics used as topsheets of absorbent articles include those with various structures. For example, Patent Document 1 describes a nonwoven fabric having a concave-convex structure with a plurality of ridges and a bottom with holes at the bottom as a top sheet of an absorbent article. Patent Document 2 describes a nonwoven fabric having a first nonwoven fabric layer and a second nonwoven fabric layer laminated together. The first nonwoven fabric layer has a concave-convex structure, and the second nonwoven fabric layer has a substantially flat shape. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2020-467 A [Patent Document 2] JP 2019-44293 A Summary of the Invention [Problem to be solved by the invention]

[0004] When a nonwoven fabric having openings at the bottom of the uneven structure is used as a topsheet of an absorbent article, the presence of the openings can enhance the liquid absorbency of the absorbent article. On the other hand, from the viewpoint of preventing liquid return through the openings, it is desired to improve the pressure resistance of the nonwoven fabric so that the thickness of the nonwoven fabric can be maintained even under pressure.

[0005] In view of the above, the present invention relates to a nonwoven fabric having high pressure resistance as well as liquid permeability due to the open pores. [Means for solving the problem]

[0006] The present invention provides a nonwoven fabric including fiber fusion portions at the intersections of fibers, the nonwoven fabric having an uneven structure including a plurality of convex portions and a bottom portion provided between adjacent convex portions, each of the plurality of convex portions including a top portion and a wall portion supporting the top portion, the bottom portion having an opening portion penetrating in the thickness direction, the wall portion being arranged surrounding the outer periphery of the opening portion, and the constituent fibers being oriented laterally in a portion of the wall portion along at least one direction in the planar direction of the nonwoven fabric and a direction perpendicular to the one direction.

[0007] The present invention also provides a pressing step, which includes placing a fiber web on a support having an uneven shape with a plurality of protrusions and recesses between the protrusions, pressing the fiber web along the recesses with a pressing part of a pressing member to form a shape, and opening holes in the fiber web at locations corresponding to the protrusions, thereby forming an unevenly perforated fiber web having an open surface on the pressing member side; The method for producing a nonwoven fabric includes the steps of: removing the pushing member from the support, blowing air onto the porous fibrous web to push the fibers on the surfaces of the protrusions along the wall surfaces of the protrusions and orienting them laterally; and blowing hot air onto the porous fibrous web to fuse the fibers together and obtain an porous nonwoven fabric. Effect of the Invention

[0008] The nonwoven fabric of the present invention can have improved pressure resistance as well as liquid permeability due to the open pores. According to the method for producing a nonwoven fabric of the present invention, the above-mentioned nonwoven fabric of the present invention can be suitably produced. [Brief description of the drawings]

[0009] [Figure 1] 1 is a cross-sectional view showing a schematic diagram of a preferred embodiment of a nonwoven fabric according to the present invention. [Diagram 2] 2 is a partially enlarged plan view illustrating an example of one surface side of the nonwoven fabric illustrated in FIG. 1. FIG. [Diagram 3] 3 is a cross-sectional view showing a cross section along a plane direction of a wall portion surrounding the outer periphery of an aperture portion in the nonwoven fabric shown in FIG. 2. [Figure 4] 4(A) is a plan view showing a portion along one direction of the wall portion shown in FIG. 3, and (B) is a plan view showing a portion along a direction perpendicular to the one direction of the wall portion shown in FIG. [Diagram 5] FIG. 2 is a plan view showing a schematic view of one surface of a specific example of the nonwoven fabric according to the present embodiment. [Figure 6] 6 is a cross-sectional view of the nonwoven fabric shown in FIG. 5 along the line R1-R1. [Figure 7] 6 is a cross-sectional view of the nonwoven fabric shown in FIG. 5 along the line R2-R2. [Figure 8] FIG. 1 is an explanatory diagram showing a schematic diagram of a preferred embodiment of a method for producing a nonwoven fabric according to the present invention, in which (A) shows a pushing step, (B) shows a step of laterally orienting fibers by blowing air, (C) shows a step of fusing the fibers together by blowing hot air to form a nonwoven fabric, and (D) shows a schematic diagram of an example of a nonwoven fabric obtained thereby. [Figure 9] FIG. [Figure 10] FIG. [Figure 11] FIG. 13 is a plan view showing a state in which the support body and the push-in member are combined. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] A preferred embodiment of the nonwoven fabric according to the present invention will be described below with reference to the drawings. The nonwoven fabric 10 of this embodiment is a so-called thermal bonded nonwoven fabric having fiber fusion parts at the intersections of the fibers. For example, an air-through nonwoven fabric in which the fiber fusion parts are formed by an air-through method can be mentioned. Therefore, the nonwoven fabric 10 contains thermoplastic fibers as its constituent fibers.

[0011] The nonwoven fabric 10 of this embodiment has a front and back surface, that is, one surface side 10T and the other surface side 10B, as shown in Fig. 1. In the nonwoven fabric 10, for example, the one surface side 10T can be used as the surface to be used. For example, when the nonwoven fabric 10 is used as a topsheet of an absorbent article, the one surface side 10T can be used as the skin-facing side.

[0012] The nonwoven fabric 10 has a plurality of protruding portions 1 protruding on one surface side 10T, and a bottom portion 2 provided between adjacent protruding portions 1, 1. This gives the nonwoven fabric 10 an uneven structure in the thickness direction Z. The protruding portions 1 are three-dimensional fiber layers standing in the thickness direction Z of the nonwoven fabric 10, and are located higher on the one surface side 10T than the bottom portion 2. Each of the plurality of protruding portions 1 has an apex 1A and a wall portion 1B that supports the apex 1A.

[0013] The outer shape of one surface side 10T of the top portion 1A may be a flat surface or a curved surface. From the viewpoint of increasing the pressure resistance of the thickness against the pressure of the top portion 1A and the wall portion 1B while providing a soft feel to the skin by the fiber layer, it is preferable that one surface side 10T of the top portion 1A is a flat surface.

[0014] The bottom 2 is at the bottom of a recess recessed into the other surface side 10B between the protrusions 1, 1. The bottom 2 has openings 3 penetrating in the thickness direction Z. The "penetrating" of the openings 3 here means that the portions where no constituent fibers of the fiber layer are arranged penetrate both sides of the nonwoven fabric 10 in the thickness direction Z. This improves the liquid permeability of the nonwoven fabric 10 in the thickness direction Z.

[0015] The openings 3 are holes formed by processing the fiber layer of the nonwoven fabric 10, and have a much larger area than the fine holes formed between the fibers. In FIG. 1, the entire bottom 2 is shown as openings 3, but the size of the openings 3 can be appropriately selected depending on the width of the bottom 2, etc. For example, the fiber layer of the bottom 2 may be present around the openings 3, and the openings 3 may be in part of the bottom 2. At least 1.0 mm 2 It is preferable that the opening area is equal to or larger than this. The size of the opening 3 can be measured using the above-mentioned microscope. Specifically, the area of ​​the opening 3 is measured at five points using the microscope, and the average value of the areas is regarded as the opening area of ​​each opening.

[0016] The area of ​​the opening 3 is set to 1.0 mm2 in order to enhance the liquid permeability.2 More than 1.5mm is preferable. 2 More preferably, 2.0 mm or more 2 More preferably, the area of ​​the opening 3 is 50.0 mm2 or less from the viewpoint of suppressing liquid return. 2 Less than 40.0mm is preferable 2 Less than 35.0mm is more preferable. 2 The following is even more preferred:

[0017] The planar shape of the openings 3 may be various endless shapes from the viewpoint of enhancing liquid permeability, such as a circle, an ellipse, a rectangle, etc. In the example shown below, the openings 3 are shown to have a rectangular planar shape, but are not limited thereto.

[0018] In the uneven structure of nonwoven fabric 10, bottom portion 2 having openings 3 arranged therein is surrounded by a plurality of protruding portions 1, 1, as shown in Fig. 2. This causes wall portions 1B constituting protruding portions 1 to be arranged surrounding the outer periphery of openings 3, as shown in Fig. 3. Wall portions 1B may be in direct contact with and surround openings 3, as shown in Fig. 3, or may indirectly surround openings 3 via a fiber layer of bottom portion 2. The planar shape and arrangement of one surface side 10T of the protrusions 1 are not limited to the embodiment shown in Fig. 2, and may be in various forms that allow the wall portions 1B to surround the outer peripheries of the openings 3. The wall portions 1B are not limited to having the cross-sectional shape shown in Fig. 3, and may have various shapes that allow the wall portions 1B to surround the outer peripheries of the openings 3, and may be appropriately set according to the planar shape of the openings 3. In this regard, preferred embodiments of the uneven structure of the nonwoven fabric 10 will be described later.

[0019] The wall portion 1B surrounds the outer periphery of the endless aperture 3, supports the top portion 1A of the projection 1 as described above, and forms part of the thickness H1 of the nonwoven fabric 10 in the thickness direction Z. The constituent fibers of this wall portion 1B are oriented laterally in at least one direction in the planar direction of nonwoven fabric 10 and in a portion along a direction perpendicular to the one direction. That is, in all of the mutually perpendicular portions of wall portion 1B, the constituent fibers are oriented laterally along the planar direction of nonwoven fabric 10, not along the thickness direction Z in which wall portion 1B is erected. The planar direction of nonwoven fabric 10 here means the direction along a plane (e.g., a flat base) that contacts the surface of the other side 10B of nonwoven fabric 10 (the same applies hereinafter).

[0020] 2 and 3, the wall portion 1B is shown as having two wall portions 1BY extending along one direction Y1 and two wall portions 1BX extending along a direction X1 perpendicular to the one direction Y1. In both the wall portions 1BY and 1BX, the nonwoven fabric 10 is oriented laterally not in the thickness direction Z but in the planar direction as shown in FIGS. 4(A) and 4(B). The direction Y1 and the direction X1 perpendicular to the direction Y1 can be appropriately set in a plane along the planar direction of the nonwoven fabric 10 according to the purpose of the nonwoven fabric 10. For example, when the nonwoven fabric 10 is used as a component such as a topsheet in an absorbent article, it is preferable that the direction Y1 is the longitudinal direction of the absorbent article, and the direction X1 perpendicular to the direction Y1 is the width direction of the absorbent article. It is also preferable that the directions of the nonwoven fabric 10 along the machine direction (MD) and the cross direction (CD) perpendicular to the machine direction in the manufacturing process of the nonwoven fabric 10 are the above-mentioned direction Y1 and the direction X1 perpendicular to the direction.

[0021] The fact that the constituent fibers are oriented laterally in any of the portions of the erected wall portion 1B along at least two mutually perpendicular directions in the planar direction is achieved for the first time by the manufacturing method described below. Even if the conventional nonwoven fabric after the fibers are fused to each other is unevenly shaped in the thickness direction, the orientation direction of the fibers hardly changes. In the manufacture of the nonwoven fabric 10, the fibers generally tend to be aligned in the MD direction. Even if the fibers are fused and fixed and unevenly shaped in the thickness direction, they remain aligned in the MD direction, and it is difficult for the orientation of the constituent fibers to be the same in the walls along mutually perpendicular directions in the nonwoven fabric plane. In addition, if the fiber web before being made into a nonwoven fabric is simply unevenly shaped, the fibers are aligned in the pushing direction and vertically oriented. In contrast, in the nonwoven fabric 10 of this embodiment, the constituent fibers of the erected wall portion 1B are oriented laterally in any of the portions along at least two mutually perpendicular directions in the planar direction, resulting in a fiber structure that is not found in conventional nonwoven fabrics.

[0022] The horizontal orientation of the constituent fibers in the wall portion 1B allows the load (pressure) in the thickness direction Z of the nonwoven fabric 10 to be dispersed in the planar direction (horizontal direction), thereby improving the pressure resistance of the nonwoven fabric 10. Moreover, the horizontal orientation of the constituent fibers in the wall portion 1B exists in at least two mutually orthogonal directions in the planar direction, so that the pressure resistance of the nonwoven fabric 10 is improved in the entire planar direction even if the load is applied in various directions. As a result, the nonwoven fabric 10 can reduce the change in thickness H1 of the nonwoven fabric 10 due to the load while maintaining the soft cushioning due to the fiber network structure including the fused fiber portion. Since the change in thickness H1 is small, when the nonwoven fabric 10 is used as a member on the skin side of the absorbent body in an absorbent article, such as a top sheet, it can improve the prevention of liquid returning from the absorbent body side. Moreover, each wall portion 1B that stands in the thickness direction Z surrounding the opening portion 3 can diffuse the liquid that is about to seep up from the opening portion 3 in the planar direction due to the horizontal orientation of the constituent fibers. This further enhances the aforementioned ability of nonwoven fabric 10 to prevent liquid backflow. Meanwhile, from the skin-facing side (one surface side 10T), bodily fluids flow downward from top 1A along wall 1B with the same momentum as when they were excreted, quickly reaching openings 3. In the process, the horizontal orientation of the constituent fibers of wall 1B equalizes the amount of liquid. This prevents unevenness in the amount of liquid descending on the outer periphery of openings 3 surrounded by wall 1B, and nonwoven fabric 10 is more likely to exhibit high liquid permeability even when it receives a large amount of liquid.

[0023] From the viewpoint of further increasing the pressure resistance of the nonwoven fabric 10, it is preferable that the constituent fibers of the wall portion 1B be oriented laterally over the entire circumference surrounding the openings 3.

[0024] The wall shape of each part of the wall 1B surrounding the hole 3 is not limited to the rectangular shape shown in Figures 4(A) and (B) and can be set in various ways, and is preferably set according to the outer periphery of the hole 3. For example, the number of walls is not limited to four, and may be three, five or more. The connecting parts of the walls may be rounded, and each wall may be curved instead of flat. When each wall is curved, the aforementioned one direction Y1 is defined as the longitudinal direction of the nonwoven fabric 10, and the direction X1 perpendicular to the one direction Y1 is defined as the width direction of the nonwoven fabric 10, and the lateral orientation of the constituent fibers is confirmed at least in the parts of the wall 1B that are tangent to straight lines along the longitudinal and width directions.

[0025] The "transverse orientation" of the constituent fibers of the wall portion 1B means that the longitudinal orientation rate of the fibers is less than 45% as determined by the measurement method described below. By setting the longitudinal orientation rate of the fibers to less than 45%, the fibers are sufficiently aligned in the planar direction, and the above-mentioned pressure resistance can be increased. From the viewpoint of further increasing the above-mentioned pressure resistance, the longitudinal orientation rate of the wall portion 1B is preferably 44% or less, more preferably 42% or less, and even more preferably 40% or less. Moreover, from the viewpoint of pressure resistance, the longitudinal orientation rate of the wall portion 1B is preferably 10% or more, more preferably 15% or more, and even more preferably 20% or more.

[0026] (Method of measuring longitudinal orientation rate of fibers in wall portion 1B) As shown in FIG. 1, the wall portion 1B is measured in the following procedure. That is, of the fiber layer of the wall portion 1B formed in the thickness direction of the nonwoven fabric 10 including the protrusions 1 and the bottom portion 2, fibers are cut out from a portion between the middle of the length of the thickness direction Z of the wall portion 1B and the bottom portion 2, and observed at 85 times magnification with an SEM. This observation image is created for a portion of the wall portion 1B along the aforementioned one direction Y1 and the direction X1 perpendicular to the one direction Y1. For example, observation images corresponding to the wall portion 1BY and the wall portion 1BX in FIG. 3 are created. Also, when all the wall surfaces are curved, as described above, the longitudinal direction and width direction of the nonwoven fabric 10 are set to one direction Y1 and the direction X1 perpendicular to the one direction Y1, and the above observation images are created for a portion of the wall portion 1B tangent to a straight line along these directions. Lines with sides of 1000 μm are placed in the vertical and horizontal directions on the observed image as reference lines. Each reference line is in the thickness direction and planar direction of the nonwoven fabric 10. The total number of fibers passing through each reference line is counted. The fibers passing through the reference line in the planar direction of the nonwoven fabric 10 are defined as the "number of vertical fibers," and the fibers passing through the reference line in the thickness direction of the nonwoven fabric 10 are defined as the "number of horizontal fibers." The vertical orientation rate is calculated as (number of vertical fibers) / (number of horizontal fibers+number of vertical fibers)×100=vertical orientation rate (%). Nine points are measured for each, and the average is taken as the value of the vertical orientation rate.

[0027] The fiber layer of the wall portion 1B can be divided in the thickness direction Z of the nonwoven fabric 10 by the following method. That is, a nonwoven fabric 10 having a cross section in the thickness direction including a top portion 1A, a wall portion 1B, and a bottom portion 2 is placed on a base of a microscope VHX6000 (product name, manufactured by Keyence Corporation) with the other surface side 10B facing down. Next, a flat plate (e.g., a flat acrylic plate) is placed on the top portion 1A side (one surface side 10T) of the nonwoven fabric, and a load of 0.05 kPa is applied. In this state, the cross section in the thickness direction Z described above is observed at 20 times with the microscope, and the fiber layer of the portion of the nonwoven fabric that is in contact with the flat plate is defined as the top portion 1A. The portion extending from the end of the top portion 1A to the other surface side 10B is defined as the wall portion 1B. In specifying the boundary between top 1A and wall 1B, the thickness of top 1A in the portion where wall 1B does not exist is defined as the thickness of the end portion of top 1A, and the portion excluding this thickness is defined as wall 1B.

[0028] In the nonwoven fabric 10, it is preferable that the fiber density of the wall portion 1B is higher than that of the top portion 1A. This allows the top portion 1A to have a soft feel while still having high pressure resistance, and allows the fabric to feel elastic and thick. In addition, by increasing the pressure resistance, the thickness change due to the load can be further reduced, and the ability to prevent liquid backflow can be further improved.

[0029] From the viewpoint of further increasing pressure resistance, the ratio (K1 / K2) of the fiber density (K1) of the wall portion 1B to the fiber density (K2) of the top portion 1A is preferably 1.05 or more, more preferably 1.08 or more, and even more preferably 1.10 or more. Moreover, from the viewpoint of maintaining a resilient feel, the ratio (K1 / K2) is preferably 2.00 or less, more preferably 1.90 or less, and even more preferably 1.80 or less.

[0030] (Method of measuring fiber density) The fiber density can be measured by observing the cross section of the nonwoven fabric 10 using the following method. The nonwoven fabric 10 is cut in the thickness direction so that the cross sections of the fiber layer of the top portion 1A and wall portion 1B to be measured can be observed. The wall portion 1B is observed at a cross section located from the middle portion in the thickness direction Z to the middle portion of the bottom portion 2. A scanning electron microscope (JCM-6000Plus (product name) manufactured by JEOL Ltd.) is used to observe the cut surface of the fiber layer at a magnification of 130 times, and square reference lines with sides of 600 μm are drawn vertically and horizontally on the observed image. The number of cut fiber cross sections within a certain area of ​​the cut surface defined by these reference lines is then counted. Next, a measurement is performed at a magnification of 1 mm. 2 This is converted into the number of fiber cross sections per unit area, and the fiber density (fibers / mm 2 The results of the nine measurements shall be averaged to determine the fiber density of the sample.

[0031] The basis weight of the nonwoven fabric 10 is set to 15 g / m from the viewpoint of improving the texture of the nonwoven fabric and further increasing the pressure resistance. 2 More than 25 g / m is preferable. 2 More preferably, 30 g / m 2 The weight of the nonwoven fabric 10 is preferably 100 g / m2 or more so as not to impede the comfortable feel of the wearer. 2 Less than 90 g / m is preferable. 2 Less than 85 g / m is more preferable. 2 The following is even more preferred:

[0032] The thickness H1 of the nonwoven fabric 10 is 4.9 mN / cm 2 (0.05gf / cm 2 ) means the thickness under the load of 4.9mN / cm 2 The load is a load that assumes fluffing on the surface of the nonwoven fabric, and is essentially a no-load state. This thickness is 4.9 mN / cm 2The measurement can be performed under load using a laser displacement meter or the like. Nonwoven fabric 10: 4.9mN / cm 2 The thickness H1 under load is preferably 0.8 mm or more, more preferably 1.0 mm or more, and even more preferably 1.2 mm or more. When the thickness H1 of the nonwoven fabric 10 is within the above range, the liquid return prevention performance is improved, and the wearer's skin is less likely to become wet. From the viewpoint of not interfering with the wearer's comfortable use, the thickness H1 is preferably 6 mm or less, more preferably 5.0 mm or less, and even more preferably 4.0 mm or less.

[0033] From the above thickness H1 of the nonwoven fabric 10, 108.9 mN / cm 2 (1.11gf / cm 2 The thickness change percentage (=[(H1-H1A) / H1]×100) to thickness H1A when pressed with a load of 4.9 mN / cm is preferably 40% or less, more preferably 38% or less, and even more preferably 36% or less, from the viewpoint of further improving the resistance to liquid return due to the above-mentioned pressure resistance. From the viewpoint of maintaining a soft texture, the above-mentioned thickness change percentage is preferably 10% or more, more preferably 12% or more, and even more preferably 14% or more. The thickness in the pressed state is the above-mentioned 4.9 mN / cm 2 The measurement can be performed in the same manner as under load. The load applied to the surface material when pressed is equivalent to the load applied when the surface material is touched with a finger to feel its texture.

[0034] The nonwoven fabric 10 preferably has a sublayer including fused fiber portions on the side of the bottom portion 2. This suppresses thickness deformation of the wall portion 1B due to compression, improving pressure resistance. The sublayer preferably has an end portion (also called a root portion 1D) of the other surface side 10B of the wall portion 1B in contact with the sublayer. In the contact area between the wall portion 1B and the sublayer, the root portion 1D of the wall portion 1B is preferably integrated (fixed) into the sublayer by being embedded therein. From the viewpoints of increasing the bonding strength and maintaining the uneven shape of the nonwoven fabric 10, the root portion 1D of the wall portion 1B and the sublayer are preferably integrated by a fiber fusion portion at an intersection between the constituent fibers of the root portion 1D of the wall portion 1B and the constituent fibers of the sublayer.

[0035] Next, a more preferred embodiment of the uneven structure described above in the nonwoven fabric 10 of this embodiment will be described.

[0036] The wall 1B preferably has a shape extending perpendicular to the plane of the other surface 10B of the nonwoven fabric 10. This makes it easier for the soft fiber layer of the top 1A to remain vertically supported by the elastic fiber layer of the wall 1B, further enhancing the pressure resistance of the nonwoven fabric 10. When the wall 1B supports the top 1A vertically, the thickness of the fiber layer of the protrusion 1 is felt through the top 1A, and a plump touch is easily obtained. More specifically, a gentle and reassuring thickness is felt at the top 1A under light pressure to the touch, and the protrusion 1 is difficult to wear down even when deformed under further pressure, and is felt as a soft and elastic thickness. Such excellent cushioning properties further improve the feel of the skin due to the uneven structure described above.

[0037] The "perpendicular" of the wall 1B means that the angle θ with respect to the plane of the other side 10B of the nonwoven fabric 10 shown in FIG. 1 is not limited to a case where the angle is strictly 90°, but is between 60° and 120°. In this range, the wall 1B has a shape that extends at an angle that is substantially recognized as 90° in the thickness direction of the nonwoven fabric 10. The angle θ means the intersection angle between the plane of the other side 10B of the nonwoven fabric 10 and the extension line of the wall 1B. Specifically, as shown in FIG. 1, in a cross section in the thickness direction including the convex portion 1, it means the angle of the interior angle among the angles formed by the center line M of the width of the fiber layer of the wall 1B and the straight line L tangent to the surface of the other side 10B of the nonwoven fabric 10. This angle θ can be obtained by observing a micrograph of the cross section obtained by the above-mentioned microscope.

[0038] 1, the wall 1B extends linearly in a cross section in the thickness direction Z of the nonwoven fabric 10, and the entire wall 1B is provided perpendicular to the other surface 10B of the nonwoven fabric 10. However, this is not limited thereto, and the wall 1B may include a portion that extends in a curved or wavy manner in the thickness direction Z of the nonwoven fabric 10. In this case, the extension direction of the wall 1B is determined by a center line M that connects a boundary point between the top 1A and the wall 1B and an end portion (base portion) 1D of the other surface side 10B of the wall 1B and passes through the boundary point and the center of the width of the fiber layer of the base portion 1D, and the angle θ is specified. In addition, it is preferable that all of the multiple walls 1B extend perpendicular to the plane of the other surface side 10B, but some of the walls 1B may not extend perpendicular to the plane of the other surface side 10B. In the latter case, the number of perpendicular walls 1B is preferably 60% or more of the walls 1B in all of the multiple protrusions 1, from the viewpoint of further effectively improving the pressure resistance of the nonwoven fabric 10.

[0039] In addition, it is preferable that the other surface side 10B of the protrusion 1 has a hollow region 1C. The hollow region 1C is a space that is not substantially filled with the fibers of the nonwoven fabric 10. Specifically, when the fiber density determined by the above-mentioned method is 10 fibers / mm 2 The lower the fiber density in the hollow region 1C, the better.

[0040] The hollow region 1C on the other surface side 10B of the projection 1 further improves the soft feel of the projection 1, further enhances the cushioning, and further improves the feel of the nonwoven fabric 10. In addition, the wall portion 1B, in which the fibers are oriented laterally, reduces the change in thickness H1 of the nonwoven fabric 10, so that the cushioning is more reliably maintained even when subjected to repeated loads. Furthermore, when the nonwoven fabric 10 is used as a member on the skin side of the absorbent body in an absorbent article, such as a top sheet, the presence of the hollow region 1C cuts off the liquid return path from the absorbent body, further improving the prevention of liquid return. In addition, the hollow region 1C also serves as a primary storage space in the event of excessive excretion, and can reduce the amount of liquid remaining on the skin-contacting side of the top sheet.

[0041] Next, a specific example (nonwoven fabric 20) of the nonwoven fabric 10 shown in Figures 1 to 4 will be described with reference to Figures 5 to 7. The nonwoven fabric 20 has the configuration described above with respect to the nonwoven fabric 10. 5 to 7, in plan view from one surface side 20T, the nonwoven fabric 20 has a plurality of ridge portions 11 extending in one direction Y as the above-mentioned protrusions 1 and arranged at a distance from each other in a direction X intersecting the one direction Y. The other surface side 20B of the rib portions 11 is formed as a hollow region 11C. The one direction Y and the direction X intersecting the one direction Y can be appropriately set according to the purpose on one surface side 20T of the nonwoven fabric 20. For example, the one direction Y and the direction X intersecting the one direction Y are preferably perpendicular to each other (the one direction Y1 and the direction X1 perpendicular to the one direction Y1 in the nonwoven fabric 10 described above). When the nonwoven fabric 20 is used as a component such as a topsheet in an absorbent article, it is preferable that the one direction Y is the longitudinal direction of the absorbent article, and the direction X intersecting the one direction Y is the width direction of the absorbent article.

[0042] The ridges 11 have the same height in the extension direction. The "same height" means that the height measured using a microscope VHX900 (product name, manufactured by Keyence Corporation) is within a range of 0.8 to 1.2 times the average measurement value.

[0043] Each of the multiple ridges 11 includes a crest 11A and a wall 11B supporting the crest 11A. The crest 11A is a fiber layer that contacts the wearer's skin in an absorbent article, and the wall 11B is a fiber layer that supports the crest 11A in the thickness direction. That is, when the nonwoven fabric 20 is applied to an absorbent article, the one surface side 20T becomes the skin contact side, and the other surface side 20B becomes the non-skin contact side. The fibers of the wall 11B are oriented horizontally as described above. As described above, the wall 11B preferably extends perpendicular to the other surface side 20B.

[0044] The longitudinal orientation rate, which is an indicator of the horizontal orientation of the constituent fibers of this wall portion 11B, can be measured based on the above-mentioned method (method for measuring the longitudinal orientation rate of fibers in wall portion 1B) in a cross section perpendicular to the extension direction of the rib portion 11 (a thickness direction cross section at the position of line R1-R1 along direction X in FIG. 5), as shown in FIG. 6. 6, the "vertical" of wall 11B means an interior angle θ between center line M of the width of the fiber layer of wall 11B and straight line L tangent to the surface of other side 20B of nonwoven fabric 20 in a cross section perpendicular to the extending direction of rib 11 (a thickness direction cross section at line R1-R1 along direction X intersecting with direction Y in FIG. 5). This angle θ can be determined by observing a micrograph of the cross section along line R1-R1 obtained with the above-mentioned microscope.

[0045] The nonwoven fabric 20 has, as the above-mentioned convex portion 1, a saddle portion 15 that extends in a direction intersecting the rib portion 11 and connects adjacent ribs 11, 11 together with the above-mentioned ridge portion 11. The saddle portion 15, like the ridge portion 11, protrudes from the other surface side 20B of the nonwoven fabric 20 to one surface side 20T, and is a three-dimensional fiber layer erected in the thickness direction of the nonwoven fabric 20. More specifically, the saddle portion 15 has a crest 15A on one surface side 20T and a wall portion 15B supporting the crest 15A. The fibers of the wall portion 15B are oriented horizontally as described above. In addition, it is preferable that the wall portion 15B extends perpendicular to the other surface side 10B. The above-mentioned "perpendicular" has the same meaning as the "perpendicular" defined in the above-mentioned ridge portion 11. The longitudinal orientation rate, which is an indicator of the horizontal orientation of the constituent fibers of wall portion 15B in saddle portion 15, and the “vertical” of wall portion 15B can be measured in a cross section perpendicular to the extension direction of saddle portion 15 (thickness cross section at the position of line R2-R2 along one direction Y in FIG. 5) as shown in FIG. 7, in the same manner as the measurement method described above for wall portion 11B.

[0046] The above structure makes it difficult for the ridges 11 connected by the saddle portion 15 to approach each other, and prevents the ridges 11 from falling in one direction due to an external force such as pressure. That is, the saddle portion 15 supports the ridges 11 from the side, improving the shape retention of the ridges 11. This makes it easier for the ridges 11 to maintain their thickness under load. For example, when the nonwoven fabric 20 is used as a member on the skin side of the absorbent body in an absorbent article, such as a top sheet, the distance between the top portion 11A and the absorbent body side of the other surface side (non-skin contact surface side) 20B is more easily maintained even under the body pressure of the wearer when wearing the absorbent article, and liquid return to the one surface side (skin contact surface side) 20T is more unlikely to occur. Furthermore, the presence of the saddle portion 15 acts to block excreted liquid between the ridges 11, 11, enhancing the ability to prevent liquid from flowing on one surface side (skin contact surface) 20T of the nonwoven fabric 20.

[0047] The saddle portion 15 extends in a direction X intersecting the one direction Y in which the rib portion 11 extends, in a plan view from one surface side 20T of the nonwoven fabric 20. The direction X in which the saddle portion 15 extends can be various directions as long as it is a direction connecting adjacent ribs 11, and is preferably a direction perpendicular to the one direction Y in which the rib portion 11 extends (corresponding to the one direction Y1 and the direction X1 perpendicular to the one direction Y1 in the nonwoven fabric 10 described above). For example, it is preferable that the one direction Y in which the rib portion 11 extends is the longitudinal direction of the absorbent article, and the direction X in which the saddle portion 15 extends and intersects with the one direction is the width direction of the absorbent article. Hereinafter, the one direction Y and the direction X perpendicular to the one direction Y are also referred to as the extension direction Y of the rib portion 11 and the extension direction X of the saddle portion 15. In addition, the planar shape of each saddle portion 15 as viewed from one surface side 20T is not limited to a rectangle as shown in Fig. 5, and may be various shapes. For example, the planar shape of the saddle portion 15 as viewed from one surface side 20T may be such that the width increases toward the ridge portion 11.

[0048] As shown in Figs. 6 and 7, the saddle portion 15 is preferably made to have the same height in the thickness direction as the ridge portion 11. The term "same" is as defined above. As a result, one surface side 20T of the nonwoven fabric 20 is made almost flush with the thickness H1 of the nonwoven fabric 20, except for the bottom portion 12. As a result, even if the load is applied in various directions, both the ridge portion 11 and the saddle portion 15 can support the load uniformly, and the pressure resistance can be further improved. In particular, in combination with the fact that the constituent fibers in the wall portions of the ridge portion 11 and the saddle portion 15 are laterally oriented, the load can be distributed more uniformly, and the pressure resistance can be further improved in the entire planar direction.

[0049] The saddle portions 15 are arranged in a plurality of band regions 16 extending parallel to the ribs 11 between the ribs 11, 11 in a plan view of one surface side 20T of the nonwoven fabric 20. In each band region 16, a plurality of saddle portions 15 are arranged at intervals along the extension direction Y of the ribs 11 running in parallel. The above-mentioned openings 3 of the bottom portion 12 are located in the portions where the saddle portions 15 are spaced apart. That is, in each band region 16, the saddle portions 15 and the openings 3 are alternately arranged. As a result, the openings 3 are surrounded and partitioned by the wall portions 11B of the ribs 11 and the wall portions 15B of the saddle portions 15. More specifically, the region surrounded by the plurality of ribs 11 and the plurality of saddle portions 15, which are three-dimensional fiber layers erected in the thickness direction, is a box-shaped or cylindrical recess, and the openings 3 are arranged in the bottom portion 12.

[0050] In the examples shown in Figs. 5 to 7, in a plan view from one surface side 20T of the nonwoven fabric 20, the band regions 16, 16 adjacent to each other through the ribs 11 are arranged in a staggered manner such that the saddle portions 15 of one band region 16 correspond to the saddle portions 15 between the saddle portions 15 of the other band region 16. As a result, the positions of the ends of the openings 3 in the band regions 16 adjacent to each other through the ribs 11 in one direction Y are not aligned, but are arranged shifted in the one direction Y, and the openings 3 are always present along the longitudinal direction as viewed from the direction X (in the example shown in Fig. 5, the openings 3 adjacent to each other in the direction X are partially overlapped along the direction Y as viewed from the direction X). This staggered arrangement extends over the entire planar direction of the nonwoven fabric 20. As a result, when viewed from direction X, there are no areas where the openings 3 are not arranged, and therefore there are no areas where the wall portions in which the constituent fibers of the ridge portions 11 and saddle portions 15 are oriented laterally are not arranged, so that the load can be supported uniformly in the planar direction during compression, improving pressure resistance.

[0051] In the nonwoven fabric 20, the arrangement of the ribs 11 and saddle portions 15 is not limited to the staggered arrangement described above, and various arrangements are possible. For example, the openings 3 in adjacent band-like regions 16 that are separated by a rib 11 may be arranged so that the positions of the ends in one direction Y are aligned. In this case, the ribs 11 and the saddle portions 15 are arranged in a lattice pattern, and the openings 3 in the bottom portion 12 are dotted in the lattice and arranged in a square pattern.

[0052] In addition, it is more preferable that the saddle portion 15 has a hollow region 15C as shown in FIG. 7 from the viewpoint of further promoting drainage of liquid to the other surface side 20B of the nonwoven fabric 20 when the nonwoven fabric 20 is used as a top sheet of an absorbent article. The definition and measurement method of this hollow region 15C are the same as those of the hollow region 11C in the ridge portion 11. It is preferable that the hollow region 15C of the saddle portion 15 communicates with the hollow region 11C of the adjacent ridge portion 11 as shown in FIG. 6. This promotes the diffusion of excreted liquid on the other surface side 20B of the nonwoven fabric 20, and further suppresses liquid retention on the one surface side 20T. As a result, the amount of liquid remaining in the nonwoven fabric 20 is further reduced, making it possible to further reduce the amount of liquid adhering to the skin.

[0053] Next, a preferred embodiment of a method for producing the nonwoven fabric 20 will be described with reference to Figures 8 to 11. The production method described below can also be applied to the production method for the nonwoven fabric 10. As shown in FIGS. 8(A) to 8(D), the manufacturing method of this embodiment includes the following three steps (hereinafter, each step may be referred to as step (I), step (II), and step (III)). (I) A pressing process in which a fiber web 100 is placed on a support 120 having an uneven shape with a plurality of protrusions 121 and recesses 125 between the protrusions 121, 121, and the fiber web 100 is pressed along the recesses 125 by a pressing portion 131 of a pressing member 130 to form a shape, and holes are opened at locations of the fiber web 100 corresponding to the protrusions 121, thereby forming an unevenly perforated fiber web 101 having an open surface on the pressing member 130 side. (II) A step of removing the pushing member 130 from the support 120, and then blowing air W1 onto the porous fibrous web 101 to push the fibers on the surfaces of the protrusions along the walls of the protrusions and orient them laterally. (III) A step of blowing hot air W2 onto the porous web 101 to fuse the fibers together to obtain a porous nonwoven fabric.

[0054] The above-mentioned fiber web 100 contains thermoplastic fibers. The "fiber web" refers to a fiber assembly in which constituent fibers including thermoplastic fibers are not fused and fixed but are gently intertwined, and which does not have the shape retention of a sheet by itself. In other words, it is a fiber assembly before being made into a nonwoven fabric. Therefore, the mobility between fibers in the fiber web is high, and the fiber web is highly deformable in the pushing process. Such a fiber web 100 is supplied from a carding machine (not shown) to a predetermined thickness.

[0055] In step (I), as shown in FIG. 8(A), a pressing member 130 is used to directly press the fiber web 100 on the support 120 with mechanical pressure. This forms the uneven perforated fiber web 101 that will become the nonwoven fabric 20. This type of shaping can form walls that are perpendicular to the nonwoven fabric plane, compared to pressing with non-mechanical pressure such as wind. Furthermore, it is not necessary to apply a strong pressing force to increase the unevenness height difference formed in the fiber web 100, and the fiber web 100 can be shaped softly. Furthermore, fiber disorder can be suppressed to improve shaping properties.

[0056] The support 120 is, for example, drum-shaped, and has protrusions 121 on the drum peripheral surface, for example, as shown in FIG. 8(A). On the drum peripheral surface of the support 120, a plurality of protrusions 121 are arranged at intervals in one direction (first direction D1) and a direction perpendicular thereto (second direction D2), as shown in FIG. 9. A plurality of protrusion rows 121A, each of which is formed by arranging a plurality of protrusions 121 in the first direction D1, are arranged at a distance from each other in the second direction D2. The protrusions 121 have spires 122 at their tips. The spires 122 form the openings 3 in the bottom portion 12 of the nonwoven fabric 20. The planar shape of the projection 121 as viewed from the spire 122 side is not limited to a rectangle as shown in Fig. 9, but may be various shapes, such as a circle, an ellipse, or a diamond. The recess 125 has a first recess 125A extending in the first direction D1 between the protrusion rows 121A, 121A, and a second recess 125C between the protrusions 121, 121 in the protrusion row 121A. The second recess 125C is connected to the adjacent first recess 125A. In addition, the protrusion rows 121A, 12A adjacent to each other via the first recess 125A are arranged in a staggered manner such that the second recess 125C of one protrusion row 121A corresponds to the second recess 125C of the other protrusion row 121A between the second recess 125C and the second recess 125C of the other protrusion row 121A. As a result, the second recesses 125C extend intermittently in the second direction D2 via the first recess 125A and the protrusion 121.

[0057] In the support 120, a plurality of protrusions 121 are arranged corresponding to positions where the apertures 3 of the bottom portion 12 of the nonwoven fabric 20 are to be formed. Second recesses 125C between the protrusions 121, 121 in the protrusion row 121A are located at positions where the saddle portions 15 of the nonwoven fabric 20 are to be formed. In other words, the protrusion row 121A is located at a position that will become the band regions 16 between the ribs 11, 11 of the nonwoven fabric 20. The first recesses 125A are located at a position that will become the ribs 11 of the nonwoven fabric 20. The bottom of each recess 125 is structured to allow hot air to pass through, and has, for example, a plurality of holes (not shown).

[0058] The pushing member 130 is, for example, in the form of a roll, and has, for example, a pushing portion 131 as shown in Fig. 8(A) on the roll peripheral surface. On the roll peripheral surface of the pushing member 130, for example, as shown in Fig. 10, a plurality of pushing portions 131 continuing in a first direction D1 are arranged at intervals in a second direction D2. Between the pushing portions 131, 131, a recess 132 continuing in the first direction D1 is formed. The pushing portion 131 of the pushing member 130 corresponds to the first recess 125A of the support body 120. The recess 132 of the pushing member 130 corresponds to the protrusion row 121A of the support body 120. The bottom of the recess 132 of the pushing member 130 has a structure that allows hot air to pass through, and for example, has a plurality of holes (not shown).

[0059] The height of the pushing portion 131 of the pushing member 130 is preferably 1 mm or more so that it can be sufficiently inserted between the protrusions 121 of the support 120 .

[0060] The first direction D1 and the second direction D2 in the support 120 and the pushing member 130 are preferably the machine direction (MD) and the cross direction (CD) perpendicular to the machine direction in the manufacturing process. The machine direction and the cross direction in the manufacturing process preferably correspond to one direction Y and a direction X intersecting the one direction Y in the nonwoven fabric 20, and preferably correspond to the longitudinal direction and the cross direction in the nonwoven fabric 20 or an absorbent article including the nonwoven fabric 20. However, the first direction D1 and the second direction D2 are not limited to these.

[0061] In step (I), the protrusions 121 of the support 120 are inserted into the recesses 132 of the pushing member 130. The pushing portion 131 of the pushing member 130 is inserted into the first recesses 125A of the support 120 (FIGS. 8(A) and 11). This pushing between the support 120 (FIG. 9) and the pushing member 130 (FIG. 10) allows the uneven shape of the nonwoven fabric 20 to be suitably formed. At the position of the first recess 125A of the support 120, the fiber web 100 is pressed and shaped by the pressing portion 131 of the pressing member 130. This portion becomes the rib portion 11 of the nonwoven fabric 20. At this time, between the protrusions 121 of the support 120 and the pressing portion 131 of the pressing member 130, the fibers of the fiber web 100 are shaped into a vertically standing shape along the thickness direction. The shaped fibers are not fused and have high mobility, so they are oriented in the thickness direction. This portion becomes the wall portion 11B of the rib portion 11 in the nonwoven fabric 20 through the process (II) described below. Meanwhile, the fibers of the fibrous web 100 are pushed up to the bottom of the recess 132 of the pushing member 130 at the positions of the protrusions 121 of the support 120 and are opened. Since the recess 132 of the pushing member 130 corresponds to the second recess 125C between the protrusions 121, 121 in the protrusion row 121A of the support 120, the pushing portion 131 does not enter. However, the pushing force of the pushing portions 131, 131 of the pushing member 130 acts on both sides of the fibers of the fiber web 100 in the second recess 125C of the protrusion row 121A. By this action, the fibers of the fiber web 100 in the second recess 125C are stretched in the second direction D2 by the pushing portions 131, 131 on both sides, pushed in the thickness direction, shaped in the thickness direction, and the orientation of the fibers changes. This portion becomes the saddle portion 15 of the nonwoven fabric 20 through the process (II) described later. The saddle portion 15 has an apex 15A and a wall portion 15B, and the wall portion 15B is similar to the wall portion 11B of the ridge portion 11.

[0062] The height of the protrusions 121 of the support 120 and the height of the pushing portion 131 of the pushing member 130 are appropriately determined depending on the thickness of the nonwoven fabric to be manufactured. For example, it is preferably 2 mm or more, more preferably 3 mm or more, even more preferably 5 mm or more, and preferably 15 mm or less, more preferably 10 mm or less, and even more preferably 9 mm or less. Specifically, it is preferably 2 mm or more and 15 mm or less, more preferably 3 mm or more and 10 mm or less, and even more preferably 5 mm or more and 9 mm or less.

[0063] Next, in step (II), as shown in Fig. 8(B), air W1 is blown onto the unevenly perforated fiber web 101. This blowing presses the fibers on the surfaces of the protrusions, such as (i) the fibers remaining on the tops of the protrusions 121 and (ii) the fibers shaped in the thickness direction along the wall surfaces of the protrusions 121, into the wall surfaces of the protrusions 121. The pressed fibers are pressed down by the air W1, so that they are laid down from the direction along the protrusions 121 and are laterally oriented. This forms wall portions 11B and 15B in which the constituent fibers are laterally oriented.

[0064] The unevenly perforated fibrous web 101 is in a bulky state in which the interfiber distance is expanded by the uneven shaping in step (I). Among them, the interfiber distance of the fibers pushed in in step (II) is reduced by the movement of the fibers, resulting in a higher fiber density. As a result, in the nonwoven fabric 20, the fiber density of the walls 11B and 15B is higher than the fiber density of the tops 11A and 15A.

[0065] Furthermore, the fiber layers pressed into the first recess 125A and the second recess 125C of the support 120 in step (I) are further pressed in by blowing air W1 in step (II) so that the pressed positions are aligned with each other. As a result, the heights of the ridges 11 and the saddles 15 in the nonwoven fabric 20 in the thickness direction become equal.

[0066] The air W1 can be blown by a commonly used means, for example, an air duster gun or a hot air generator.

[0067] From the viewpoint of more clearly forming the lateral orientation of the constituent fibers, the air W1 is preferably blown from directly above the porous fibrous web 101 shaped along the support 120. Specifically, the blowing angle of the air W1 is preferably 45 degrees or more with respect to the planar direction of the porous fibrous web 101.

[0068] The temperature of the air W1 is set to be equal to or lower than the melting point of the constituent fibers of the porous fibrous web 101. Considering typical fiber materials used in this type of product, the temperature of the air W1 is preferably 5°C or less lower than the melting point of the constituent fibers (thermoplastic fibers) of the porous fibrous web 101, and more preferably 10°C or less lower. From the viewpoint of efficiently forming the laterally oriented wall portions, the wind speed of the air W1 is preferably 1 m / s or more, more preferably 2 m / s or more, and even more preferably 3 m / s or more. Also, from the viewpoint of maintaining a good texture of the porous fiber web 101, the wind speed of the air W1 is preferably 100 m / s or less, more preferably 90 m / s or less, and even more preferably 80 m / s or less.

[0069] Next, in step (III), as shown in Fig. 8(C), hot air W2 is blown onto the nonwoven fabric 101. This causes the fibers in the nonwoven fabric 101 to fuse together, forming a nonwoven fabric 20 having holes. This nonwoven fabric 20 having holes becomes the nonwoven fabric 20 described above (Fig. 8(D)).

[0070] The temperature of the hot air W2 is set to be equal to or higher than the melting point of the constituent fibers of the porous fibrous web 101. Considering typical fiber materials used in this type of product, the temperature of the hot air W2 is preferably 0°C to 70°C higher than the melting point of the constituent fibers (thermoplastic fibers) of the porous fibrous web 101, and more preferably 5°C to 50°C higher. The wind speed of the hot air W2 is preferably 0.2 m / s or more, and more preferably 0.3 m / s or more, from the viewpoint of satisfactorily forming a nonwoven fabric from the porous fibrous web 101. The wind speed of the hot air W2 is preferably 50 m / s or less, and more preferably 30 m / s or less, from the viewpoint of further enhancing the softness of the nonwoven fabric 20 and satisfactorily forming the hollow regions 1C (11C, 15C). The blowing time of the hot air W2 is preferably 0.1 seconds or more, more preferably 0.2 seconds or more, and even more preferably 0.3 seconds or more, from the viewpoint of forming a sufficient thermally bonded joint.

[0071] In this manner, the nonwoven fabric of the present invention can be suitably produced by the method for producing a nonwoven fabric of this embodiment, which includes the above-mentioned steps (I), (II) and (III).

[0072] In the above manufacturing method, the push-in member 130 is not limited to one having push-in portions 131 continuous in the first direction D1 as shown in Fig. 10. For example, the push-in portions 131 may be formed in a lattice shape, with square-shaped recesses 132 between the lattice-shaped push-in portions 131. In this case, the ridge portions 11 and saddle portions 15 to be formed form lattice-shaped protrusions, and the height of the saddle portions 15 becomes higher, making the unevenness more distinct.

[0073] The thermoplastic fibers constituting the nonwoven fabric of the present invention can be any fibers commonly used as materials for nonwoven fabrics without any particular limitations. For example, they may be fibers made of a single resin component or composite fibers made of multiple resin components. Composite fibers may have, for example, a core-sheath structure or a side-by-side structure. When using composite fibers containing a low melting point component and a high melting point component as the thermoplastic fiber (for example, composite fibers having a core-sheath structure in which the sheath is a low melting point component and the core is a high melting point component), the temperature of the hot air blown onto the fiber web in the manufacturing process is preferably equal to or higher than the melting point of the low melting point component and lower than the melting point of the high melting point component. More preferably, the temperature is equal to or higher than the melting point of the low melting point component and 10°C lower than the melting point of the high melting point component, and even more preferably, the temperature is 5°C or higher than the melting point of the low melting point component and 20°C or lower than the melting point of the high melting point component. In terms of elasticity, the more the core of the core-sheath structure composite fibers have, the higher the elasticity. Therefore, it is preferable that the core component is larger in terms of cross-sectional area ratio. A specific example of a composite fiber having a core-sheath structure in which the sheath is a low melting point component and the core is a high melting point component is a composite fiber having a core-sheath structure in which the sheath is a polyethylene resin (hereinafter also referred to as PE) and the core is a polyethylene terephthalate resin (hereinafter also referred to as PET). Furthermore, in composite fibers with a core-sheath structure, when the resin component of the sheath has a lower glass transition point than the resin component of the core (hereinafter referred to as a low-glass transition point resin component; for example, the resin component of the core is PET and the resin component of the sheath is PE), the thickness recovery of the nonwoven fabric can be further improved by reducing the mass ratio of the low-glass transition point resin component.

[0074] The nonwoven fabric of the present invention can be used in various applications. For example, it can be used as a component of various absorbent articles. The various absorbent articles broadly include articles used to absorb liquids discharged from the body, such as diapers for adults and infants, sanitary napkins, panty liners, and urine absorption pads. The nonwoven fabric of the present invention can also be used as baby wipes, cleaning sheets, filters, and covering sheets for heating devices.

[0075] An absorbent article having the nonwoven fabric of the present invention typically comprises a top sheet, a back sheet, and a liquid-retentive absorbent interposed between the two sheets. In the absorbent article, the nonwoven fabric of the present invention can be suitably used as the top sheet that contacts the wearer's skin. The nonwoven fabric of the present invention can also be used as a sublayer interposed between the top sheet and the absorbent, a cover sheet (core wrap sheet) for the absorbent, etc. In addition, the nonwoven fabric of the present invention can also be used as the top sheet, gathers, exterior sheet, and wings of the absorbent article. EXAMPLES

[0076] The present invention will be described in more detail below based on examples, but the present invention is not limited thereto. In the examples, "parts" and "%" are all based on mass unless otherwise specified.

[0077] [Example] Based on the manufacturing method shown in FIG. 8, the following steps were carried out using a support 120 and a pushing member 130, and air W1 and hot air W2 were blown to produce the nonwoven fabric (20 mm x 15 mm) shown in FIGS. 5 to 7, which was used as the nonwoven fabric sample of the embodiment. A core-sheath type (polyethylene terephthalate (PET) / polyethylene (PE)=5:5) thermoplastic fiber having a fineness of 1.3 dtex was used to produce a fiber web 100. The thermoplastic fiber had been subjected to a hydrophilization treatment. First, the fiber web 100 was placed on the support 120, and a pushing member 130 was pushed into the support 120 from above the fiber web 100 to perform a shaping process, thereby forming the unevenly perforated fiber web 101. Next, air W1 was blown onto the unevenly perforated fiber web 101 on the support 120 from directly above using an air duster gun. The air W1 was blown at room temperature, at a wind speed of 30 m / sec, for a blowing time of 10 seconds. Next, hot air W2 was blown onto the nonwoven fabric to fuse the fibers together, producing an unevenly porous nonwoven fabric. This was used as a nonwoven fabric sample of the example. The second hot air W2 had a temperature of 160° C., a wind speed of 3.0 m / sec, and a blowing time of 3 seconds. The pressing by the pressing member 130 was performed as follows. In the support 120, the MD length of the protrusion 121 including the spire 122 in plan view was 9 mm, and the protrusion interval in the MD direction was 6 mm. The CD length was 3 mm, and the protrusion interval in the CD direction was 3 mm. The protrusion height including the spire 122 was 17 mm. The planar shape of the protrusion 121 from the spire 122 side was square. The width of the pressing member 130 was 2 mm, the interval between the pressing members 130 in the CD direction was 6 mm, and the pressing amount by the pressing member 130 was 17 mm.

[0078] [Comparative Example 1] A nonwoven fabric having concave and convex openings was produced in the same manner as in Example 1 above, except that the step of blowing air W1 was omitted. This was used as a nonwoven fabric sample for Comparative Example 1.

[0079] [Comparative Example 2] A nonwoven fabric similar to that described in Example 1 of JP 2019-44319 A was prepared and used as a nonwoven fabric sample for Comparative Example 2.

[0080] The structures of the nonwoven fabric samples of the examples and comparative examples were examined. Specifically, the basis weight, the hole area of ​​the openings 3, the thickness, the angle of the walls 11B and 15B (the angle between the extending direction of the walls 11B and 15B and the plane of the other side 20B of the nonwoven fabric sample), the longitudinal orientation rate of the walls 11B and 15B, and the fiber density were measured by the following methods.

[0081] <Metsuke> The area and mass of a nonwoven fabric sample stored for 24 hours or more in an environment of 23±2°C and a relative humidity of 50±5% were measured. <Area of ​​hole of opening 3> For nonwoven fabric samples stored for 24 hours or more in an environment of 23±2° C. and a relative humidity of 50±5%, the areas of the openings 3 were measured at five points using a microscope, and the average value was taken as the opening area of ​​each opening. <Thickness> For each nonwoven sample, 4.9mN / cm 2 (0.05gf / cm 2 ) and the thickness (H1) when a load of 108.9 mN / cm2 (1.11gf / cm 2 The thickness (H1A) in the pressed state under a load of 1000 mm was measured using a thickness gauge. A laser displacement meter manufactured by Omron Corporation was used as the thickness gauge. Measurements were taken at 10 points, and the average value was calculated to determine the thickness. Furthermore, the thickness change rate (% = [(H1-H1A) / H1] x 100) was calculated from the thickness.

[0082] <Angle of Wall 11B and Wall 15B> In accordance with the above-mentioned method (method for measuring the longitudinal orientation rate of fibers in wall portion 1B), cross sections of the fiber layer of wall portion 11B and wall portion 15B were prepared and microscopic photographs were taken, and the angle θ between the extension direction of wall portion 11B and wall portion 15B and the plane of the other side 20B of the nonwoven fabric sample was determined. <Longitudinal Orientation Ratio of Wall Portion 11 and Wall Portion 15> Based on the above-mentioned method (method for measuring the longitudinal orientation rate of fibers in wall portion 1B), the longitudinal orientation rate was determined in one direction (longitudinal direction) Y of wall portion 11B and in a direction (width direction) X perpendicular to one direction Y of wall portion 15B.

[0083] <Fiber Density of Wall Portion 11B and Wall Portion 15B, and Fiber Density of Top Portion 11A and Top Portion 15> The fiber density of each of the above-mentioned portions was measured based on the above-mentioned method (method for measuring fiber density).

[0084] Furthermore, the liquid absorption time and the amount of liquid wetback were measured for each of the nonwoven fabric samples of the Examples and Comparative Examples, and the results are shown in Table 1 below. The following tests were carried out on diaper samples prepared using each nonwoven fabric sample. The diaper samples were prepared as follows. A commercially available baby diaper (product name "Meries Sarasa Air Through M size", Kao Corporation, manufactured in 2022) was used with the top sheet removed to form an absorbent core, and nonwoven fabric cut to 100 x 250 mm from each nonwoven fabric sample of the examples and comparative examples was laminated. The nonwoven fabric was laminated so that the other surface side 10B faced the absorbent core, and the periphery of the laminated nonwoven fabric was fixed to prepare a diaper for evaluation.

[0085] <Liquid absorption time> In the diaper sample, the nonwoven fabric had a load of 13.6 g / cm 2 A pressure load of 1017 mm was evenly applied to the nonwoven fabric. 2 Artificial urine (composition: urea 1.940% by mass, sodium chloride 0.795% by mass, magnesium sulfate 0.110% by mass, calcium chloride 0.062% by mass, potassium sulfate 0.197% by mass, Red No. 2 (dye) 0.010% by mass, and water (approximately 96.88% by mass) was injected through the tube. 40 g of artificial urine was injected three times at 10 minute intervals, and the time (seconds) until the entire amount was absorbed was measured. The time when artificial urine could no longer be observed inside the tube was recorded as "the entire amount was absorbed." The above operation was performed three times, and the average value of the three times was recorded as the liquid absorption time (seconds). The shorter the liquid absorption time, the easier the liquid will penetrate into the interior and the better the liquid permeability.

[0086] <Amount of liquid returning> 40 g of colored artificial urine was poured into the diaper at a position 165 mm from the abdominal edge in the longitudinal direction and at the center in the width direction over 10 seconds. 10 minutes after the start of the pouring, 40 g was poured again. 10 minutes after the start of the second pouring, 40 g was poured again, for a total of 120 g of artificial urine. The temperature of the test atmosphere was room temperature (20±5°C), and the temperature of the artificial urine was room temperature (20±5°C). Ten minutes after the completion of the injection, ten sheets of Advantech filter paper No. 4A (100 mm x 100 mm, mass measurement W1) were stacked and placed on the nonwoven fabric with the injection point at the center. A pressure of 3.5 kPa was applied through a 5 mm thick, 100 mm x 100 mm acrylic plate, and the mass of the filter paper was measured after two minutes (W2), and the amount of liquid return was calculated according to the following formula (I). Amount of liquid returned (mg) = Mass of filter paper after pressure (W2) - Initial mass of filter paper (W1) The above procedure was carried out three times, and the average of the three measurements was taken as the amount of liquid return (mg). The smaller the amount of liquid return, the less likely liquid return would occur, and the higher the evaluation (the higher the ability to prevent liquid return).

[0087] [Table 1]

[0088] As shown in Table 1, the nonwoven fabric samples of the Examples had a smaller thickness change rate, a shorter liquid absorption time, and a smaller amount of liquid return than the nonwoven fabric samples of Comparative Examples 1 and 2. That is, the nonwoven fabric samples of the Examples had higher breathability due to the open pores and higher pressure resistance than the nonwoven fabric samples of Comparative Examples 1 and 2. [Explanation of symbols]

[0089] 1 Convex part 1A Top 1B Wall section 1C hollow area 1D Base 2 bottom 3 Opening part 11 Ridge 11A Top 11B Wall section 11C hollow area 12 Bottom 15 Saddle 15A top 15B Wall section 15C hollow area 16 Band Area 10, 20 Nonwoven fabric 10T, 20T One side 10B, 20B other side

Claims

1. A nonwoven fabric including fiber fusion portions at the intersections of fibers, It has a concave and concave structure comprising multiple protrusions and a base provided between adjacent protrusions, each of the multiple protrusions comprising a top and a wall supporting the top, and the base has an opening that penetrates in the thickness direction. The aforementioned wall portion is arranged to surround the outer periphery of the opening portion. A nonwoven fabric in which the constituent fibers are transversely oriented in portions of the wall portion along at least one direction in the planar direction of the nonwoven fabric and a direction perpendicular to that direction.

2. The aforementioned protrusion has a plurality of ridges extending in one direction and saddles extending in a direction intersecting the ridges and connecting adjacent ridges. The nonwoven fabric according to claim 1, wherein the heights in the thickness direction of the ridge portion and the saddle portion are equal.

3. The nonwoven fabric according to claim 1 or 2, wherein the fiber density of the wall portion is higher than the fiber density of the top portion.

4. Weight: 15 g / m ２ More than 100g / m ２ The nonwoven fabric according to claim 1 or 2, which is as follows:

5. 4.9 mN / cm ２ The nonwoven fabric according to claim 1 or 2, wherein the thickness under load is 0.8 mm or more and 10.0 mm or less.

6. The nonwoven fabric according to claim 1 or 2, further comprising a sublayer including the fiber fusion portion on the bottom side.

7. A pressing step is performed in which a fiber web is placed on a support having an uneven shape with multiple protrusions and recesses between the protrusions, the fiber web is pressed along the recesses by the pressing portion of a pressing member to shape it, and holes are made in the fiber web at locations corresponding to the protrusions, thereby forming an uneven, perforated fiber web having an open surface on the side facing the pressing member, After removing the pressing member from the support, the process involves blowing air onto the uneven perforated fiber web to push the fibers on the surface of the protrusions along the walls of the protrusions and orient them laterally, A method for producing a nonwoven fabric, comprising the step of blowing hot air onto the aforementioned uneven perforated fiber web to fuse the fibers together and obtain an uneven perforated nonwoven fabric.

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