Nonwoven cloth for absorbent article

Abstract

To provide a nonwoven cloth for absorbent articles capable of enhancing both pressure resistance and softness including cushioning properties and making absorbent articles excel in liquid absorption properties.SOLUTION: In a nonwoven cloth for absorbent articles which includes a first fiber layer, a second fiber layer and a third fiber layer laminated in a thickness direction and further includes a fiber-fusion site where fibers intersect with each other: the first and second fiber layers, and the second and third fiber layers, are integrated by the fiber-fusion site of their respective fibers; the second fiber layer has an uneven structure including a plurality of protrusions and bottoms between adjoining protrusions; each of the plurality of protrusions has a crown and wall parts that support the crown; and the wall parts extend perpendicularly to the plane direction of the nonwoven cloth, with the first fiber layer located on the side of the crown of the second fiber layer, and with the third fiber layer located on the side of the bottom of the second fiber layer.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a nonwoven fabric for absorbent articles. [Background technology]

[0002] Nonwoven fabrics are used in a variety of applications, such as components for absorbent articles such as diapers and sanitary napkins, and come in a variety of structures. For example, Patent Document 1 describes a nonwoven fabric in which a first nonwoven fabric layer and a second nonwoven fabric layer are laminated. The first nonwoven fabric layer has an uneven structure. The second nonwoven fabric layer is formed into a substantially flat shape and is in contact with and bonded to the bottom of the recess of the first nonwoven fabric. Patent Document 2 describes a nonwoven fabric with an uneven structure as a top sheet of an absorbent article, which has a plurality of ridges and a bottom, and has open holes arranged in the bottom. [Prior art documents] [Patent documents]

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

[0004] The nonwoven fabrics described in Patent Documents 1 and 2 have plump thickness and excellent cushioning properties because the tops of the protrusions are supported by vertical walls. In addition, the nonwoven fabric described in Patent Document 1 has excellent liquid absorbency (liquid permeability in the thickness direction) because of the walls and the open holes in the bottom. On the other hand, the nonwoven fabric is required to further improve its pressure resistance under load while maintaining its cushioning properties under the bulkiness due to the uneven shape, and there is room for further improvement in this respect. Further improving this pressure resistance at the same time as cushioning properties has become strongly required from the viewpoints of improving the thick and fluffy softness of the fiber layer of the nonwoven fabric and improving the liquid absorbency under load. However, improving the pressure resistance means improving the thickness retention, which may result in a trade-off with the cushioning properties that are accompanied by deformation, and it has been difficult to achieve both in the past.

[0005] In view of the above, the present invention relates to a nonwoven fabric for absorbent articles which has improved pressure resistance and softness accompanied by cushioning properties, and which has excellent liquid absorbency. [Means for solving the problem]

[0006] The present invention provides a nonwoven fabric for absorbent articles, which has a first fiber layer, a second fiber layer, and a third fiber layer stacked in the thickness direction and includes fiber fusion portions at intersections between fibers, wherein the first fiber layer and the second fiber layer, and the second fiber layer and the third fiber layer are integrated together by the fiber fusion portions between the fibers of each other, respectively, the second fiber layer has an uneven structure including a plurality of protrusions and a bottom portion provided between adjacent protrusions, each of the plurality of protrusions includes an apex and a wall portion supporting the apex, the wall portion extends perpendicular to the planar direction of the nonwoven fabric, and the first fiber layer is located on the side of the second fiber layer where the apex is located, and the third fiber layer is located on the side of the second fiber layer where the bottom is located.

[0007] The present invention also provides a method for producing a nonwoven fabric for absorbent articles using a first fibrous web, a second fibrous web and a third fibrous web, comprising: a pushing step of placing the second fibrous web on a support having an uneven shape with a plurality of protrusions and recesses between the protrusions, and pushing and shaping the second fibrous web along the recesses with a pushing part of a pushing member to form an uneven fibrous web; a step of removing the pushing member from the support, and then blowing a first hot air onto the uneven fibrous web to fuse the fibers together to obtain an uneven nonwoven fabric; a lamination step of bringing the first fibrous web and a third fibrous web into contact with both sides of the uneven nonwoven fabric; and a heat fusion step of blowing a second hot air to fuse the fibers of the uneven nonwoven fabric and the first and third fibrous webs together and to fuse the fibers in the first and third fibrous webs together. Effect of the Invention

[0008] The nonwoven fabric for absorbent articles of the present invention can be improved in both pressure resistance and softness accompanied by cushioning properties, and can be excellent in liquid absorbency. According to the manufacturing method of the nonwoven fabric for absorbent articles of the present invention, the above-mentioned nonwoven fabric for absorbent articles of the present invention can be suitably manufactured. [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 for absorbent articles according to the present invention. [Diagram 2] FIG. 2 is a cross-sectional view illustrating a schematic diagram of another preferred embodiment of the nonwoven fabric for absorbent articles according to the present embodiment. [Diagram 3] FIG. 2 is a cross-sectional view illustrating a schematic diagram of yet another preferred embodiment of the nonwoven fabric for absorbent articles according to the present embodiment. [Figure 4] FIG. 2 is a cross-sectional view illustrating a schematic diagram of yet another preferred embodiment of the nonwoven fabric for absorbent articles according to the present embodiment. [Diagram 5] FIG. 2 is a cross-sectional view illustrating a schematic diagram of yet another preferred embodiment of the nonwoven fabric for absorbent articles according to the present embodiment. [Figure 6]FIG. 2 is a plan view showing a schematic view from one surface side of a specific example of a second fiber layer constituting the nonwoven fabric for absorbent articles of the present embodiment. [Figure 7] 7 is a cross-sectional view taken along the line R1-R1 of the nonwoven fabric for absorbent articles shown in FIG. 6. [Figure 8] 7 is a cross-sectional view taken along the line R2-R2 of the nonwoven fabric for absorbent articles shown in FIG. 6. [Figure 9] 7 is a cross-sectional view taken along the line R3-R3 of the nonwoven fabric for absorbent articles shown in FIG. 6. [Figure 10] FIG. 1 is an explanatory diagram showing a schematic diagram of a preferred embodiment of the method for manufacturing a nonwoven fabric for absorbent articles according to the present invention, in which (A) shows a pushing process, (B) shows a process for obtaining a rugged nonwoven fabric by a first hot air, (C) shows a process for laminating and contacting the first and third fibrous webs with the rugged nonwoven fabric, (D) shows a process for integrating the rugged nonwoven fabric with the first and third fibrous webs by a second hot air to form a nonwoven fabric from the first and third fibrous webs, and further (C1) shows a process for disposing an absorbent polymer in the portion pushed in by the pushing portion of the rugged nonwoven fabric. [Figure 11] FIG. [Figure 12] FIG. [Figure 13] FIG. 13 is a plan view showing a state in which the support body and the push-in member are combined. [Figure 14] FIG. 4 is a cross-sectional view showing another embodiment of the support. [Figure 15] 1A and 1B are photographs and an explanatory diagram showing the thickness and deformation of convex portions in a compression property test for nonwoven fabric samples, where (A) shows Example 1 and (B) shows Comparative Example 2. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] A preferred embodiment of the nonwoven fabric for absorbent articles according to the present invention will be described below with reference to the drawings. In this specification, the nonwoven fabric for absorbent articles may be simply referred to as a nonwoven fabric. The nonwoven fabric 10 of this embodiment is a 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] 1, the nonwoven fabric 10 of this embodiment has a first fiber layer M1, a second fiber layer M2, and a third fiber layer M3 laminated in the thickness direction Z. The first fiber layer M1, the second fiber layer M2, and the third fiber layer M3 each contain thermoplastic fibers as constituent fibers and have the fused fiber portions. Furthermore, the first fiber layer M1 and the second fiber layer M2, and the second fiber layer M2 and the third fiber layer M3 are integrated together by the fused fiber portions at the intersections of the fibers of each layer.

[0012] The nonwoven fabric 10 has a front and back surface, that is, one side 10T and the other side 10B. The first fiber layer M1 is disposed on the one side 10T of the second fiber layer M2, and the third fiber layer M3 is disposed on the other side 10B. In the nonwoven fabric 10, either the one side 10T or the other side 10B may be used as the surface to be used. The used surface means the surface facing the liquid-receiving side of the absorbent article to which the nonwoven fabric 10 is applied, and means the surface relatively close to the wearer's skin (skin-facing side) of each member laminated in the thickness direction of the absorbent article. For example, the one side 10T may be the skin-facing side, which is the used surface. In this case, the first fiber layer M1 is also called the upper layer, and the third fiber layer M3 is also called the lower layer. The one surface side 10T and the other surface side 10B refer to the front and back surfaces of the entire nonwoven fabric 10 as well as the front and back surfaces of each of the first fiber layer M1, the second fiber layer M2, and the third fiber layer M3. The thickness direction Z of the nonwoven fabric 10 also refers to the thickness direction Z of each of the first fiber layer M1, the second fiber layer M2, and the third fiber layer M3.

[0013] The second fiber layer M2 has a plurality of protruding portions 1 protruding on one surface side 10T and a bottom portion 2 provided between adjacent protruding portions 1. This allows the second fiber layer M2 to have an uneven structure with height differences in the thickness direction Z from the one surface side 10T. The protruding portions 1 are three-dimensional fiber layers standing in the thickness direction Z of the second fiber layer M2, 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 supporting the apex portion 1A. The wall portion 1B extends perpendicular to the planar direction of the nonwoven fabric 10. The vertically extending structure of the wall portion 1B will be described later.

[0014] With respect to the uneven structure of the second fiber layer M2, the first fiber layer M1 is disposed on the side where the top portion 1A of the second fiber layer M2 is located, and the third fiber layer M3 is disposed on the side where the bottom portion 2 of the second fiber layer is located. The first fiber layer M1 is integrated with the second fiber layer M2 mainly at the top portion 1A, and extends in the planar direction so as to connect the multiple top portions 1A arranged in the planar direction. The third fiber layer M3 is integrated with the second fiber layer M2 mainly at the bottom portion 2, and extends in the planar direction so as to connect the multiple bottom portions 2 arranged in the planar direction. That is, the integration between the layers by the fiber fusion portion at the intersection between the fibers is mainly performed between the top portion 1A and the first fiber layer M1, and between the bottom portion 2 and the third fiber layer M3. From the viewpoint of improving the durability and the specific cushioning property of the nonwoven fabric 10, it is preferable that one surface side 10T of the first fiber layer M1 and the other surface side 10B of the third fiber layer M3 are flat surfaces.

[0015] In this way, the uneven structure of the second fiber layer M2 is integrated with the first fiber layer M1 and the third fiber layer M3 by bonding at the intersections of the fibers (hereinafter also referred to as point bonding), not by bonding the opposing surfaces of the first fiber layer M1 and the third fiber layer M3 with a conventional hot melt adhesive. As a result, the nonwoven fabric 10 has reduced rigidity due to bonding between the layers. In addition, the uneven structure of the second fiber layer M2 is more easily maintained than in a conventional bonding method involving pressing using a hot melt adhesive. In particular, the vertically extending structure of the wall portion 1B of the second fiber layer M2 is less likely to collapse during bonding, and the height (thickness) of the uneven structure of the second fiber layer M1 is more likely to be maintained. Furthermore, when the nonwoven fabric 10 is incorporated as a component of an absorbent article, it is possible to maintain the uneven structure including the wall portion 1B of the second fiber layer M2 while ensuring a bonding area with other laminated members in the first fiber layer M1 and / or the third fiber layer M3 and bonding with sufficient bonding strength. In addition, the first fiber layer M1 and the third fiber layer M3 serve as the base for the top portion 1A and the bottom portion 2, stabilizing and protecting the shape and function of the top portion 1A and the bottom portion 2, as well as the wall portion 1B. This facilitates the second fiber layer M2, which is located in the middle layer, to stably exert the elastic supporting force of the wall portion 1B. Furthermore, since the rigidity is suppressed by the integration of the fused fiber portions through point bonding, the thick and fluffy softness of the fiber layer having the uneven structure of the second fiber layer M2 is easily transmitted to both surfaces of the nonwoven fabric 10 (both surfaces of the one surface side 10T and the other surface side 10B). Furthermore, the uneven structure of the second fiber layer M2 is located in the middle of the sandwich structure from the first fiber layer M1 to the third fiber layer M3 of the nonwoven fabric 10, and is likely to move uniformly in accordance with the fiber layer on the surface to which an external force is applied or the fiber layers on both surfaces. As a result, nonwoven fabric 10 has more stable pressure resistance, thickness deformability and thickness recovery, and provides more uniform, unique cushioning properties in the planar direction, with improved softness accompanying the cushioning properties.

[0016] In particular, in the laminated structure of the nonwoven fabric 10, the wall portion 1B, the first fiber layer M1, and the third fiber layer M3 cooperate with each other to perform the following functions. That is, the vertically extending wall 1B vertically connects the top 1A and bottom 2, and further the first fiber layer M1 and the third fiber layer M3, which are integrated with them by point-bonding of the fused fibers. In other words, the first fiber layer M1 and the third fiber layer M3 are vertically supported equally at multiple points of the top 1A and bottom 2 that are connected in the planar direction by the wall 1B at each point. In this state, when a pressing force is applied from one surface side 10T or the other surface side 10B of the nonwoven fabric 10, the pressing force is likely to be dispersed in the fiber layer on the surface side to which it is applied (the first fiber layer M1 or the third fiber layer M3) before being transmitted to the second fiber layer M2. Due to this dispersion, in the uneven structure of the second fiber layer M2, which is the intermediate layer, the pressing force is distributed and transmitted to the multiple tops 1A and bottoms 2 arranged in the planar direction, and the load of the pressing force on the wall 1B is reduced and equalized. Moreover, the fiber layer on the opposite side (the third fiber layer M3 or the first fiber layer M1) serves as a base for the second fiber layer M2, which is an intermediate layer, and can disperse and absorb the pressing force transmitted to the uneven structure of the second fiber layer M2. In this case, the integration of the first fiber layer M1 and the top portion 1A, and the third fiber layer M3 and the bottom portion 2 at the fused fiber portions by point bonding eliminates the need for adhesive between the layers, reducing the interference with the force transmission caused by the adhesive, and making it easier to disperse the pressing force. In addition, due to the above-mentioned dispersion, the uneven structure of the second fiber layer M2 is easily deformed uniformly as a whole by pressing force, and deformation such as partial sagging or toppling over of the uneven structure is suppressed. As a result, the nonwoven fabric 10 is deformed such that the convex portion 1 consisting of the top portion 1A and the wall portion 1B does not fall sideways, but is compressed in the thickness direction Z, because the uneven structure is sandwiched. This deformation makes it easy for the nonwoven fabric 10 to retain its thickness under pressure while allowing the entire pressed portion to sink. As a result, the skin in contact with the surface of the nonwoven fabric 10 can feel the gentle sinking and good cushioning of the entire continuous layer of the first fiber layer M1 or the third fiber layer M3 while feeling the solid thickness of the nonwoven fabric 10 due to the vertical wall portion 1B. In addition, the nonwoven fabric 10 has excellent thickness recovery due to the action of the vertical wall portion 1B. In addition, the nonwoven fabric 10 is difficult to crush under a small load due to the support action of the wall portion 1B, and the skin can feel a comfortable elasticity and a reassuring thickness when stroking or lightly touching the continuous layer on the surface of the nonwoven fabric 10. In this way, the pressure resistance and unique cushioning properties of the nonwoven fabric 10 are simultaneously improved. In addition, the protrusions 1 exhibit a liquid guide function along the vertical extension of the wall 1B, and the nonwoven fabric 10 has excellent liquid absorbency. This liquid guide function is effective in improving the liquid absorbency of the absorbent article, particularly when the nonwoven fabric 10 is incorporated as a component of the absorbent article. For example, the wall 1B of the second fiber layer M2 forms a wall like a dike in the planar direction of the absorbent article, which further enhances the effect of promoting the descent of liquid in the thickness direction in the absorbent article, thereby improving the liquid absorbency of the absorbent article. The above-mentioned function of the wall 1B can be more effectively exhibited by maintaining the uneven structure of the second fiber layer M2 as described above. In addition, the pressure resistance of the nonwoven fabric 10 tends to enhance the effect of suppressing the return of absorbed excreted liquid. In addition, when the inside of the protrusions 1 is a hollow portion 1C as described later, the hollow portion 1C remains even when pressurized, and the pressure resistance is also high, so that the liquid absorbency is further improved.

[0017] The "vertical" of the wall 1B means that the angle θ with respect to the plane of the other side 10B of the nonwoven fabric 10 (third fiber layer M3) shown in FIG. 1 is not limited to a case where the angle is strictly 90°, but is between 60° and 120°. When the angle is within this range, the wall 1B has a shape that extends at an angle that is substantially recognized as 90° in the thickness direction Z of the nonwoven fabric 10. The angle θ means the intersection angle between the plane tangent to the surface 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 Z including the convex portion 1, the angle θ means the interior angle of the angle formed by the center line K 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 (third fiber layer M3). This angle θ can be obtained by observing a micrograph of the cross section obtained by the above-mentioned microscope.

[0018] In the above-mentioned cross section in the thickness direction Z of the nonwoven fabric 10, including the protrusions 1 and the bottoms 2 of the second fiber layer M2, the fiber layer of the wall portion 1B can be divided by the following method. That is, a nonwoven fabric 10 having a cross section in the thickness direction Z including the first fiber layer M1, the convex portion 1 and the bottom portion 2 of the second fiber layer M2, and the third fiber layer M3 is placed on the base of a microscope VHX6000 (product name, manufactured by Keyence Corporation) with the third fiber layer M3 (the other surface side 10B) facing down. Next, a flat plate (e.g., a flat acrylic plate) is placed on one surface side 10T (the top portion 1A side) of the nonwoven fabric 10, and a pressure of 4.9 mN / cm is applied. 2 A load of 1000 MPa is applied to the cross section in the thickness direction Z in this state. The cross section in the thickness direction Z is observed at 20 times magnification using the microscope, and the fiber layer in the second fiber layer M2 that is in contact with the first fiber layer M1 is designated as the apex portion 1A. The portion connecting the end of the apex portion 1A and the surface of one surface side 10T of the third fiber layer M3 is designated as the wall portion 1B. In specifying the boundary between the top 1A and the wall 1B, the thickness of the top 1A in the portion where the wall 1B does not exist is defined as the thickness of the end of the top 1A, and the portion excluding this thickness is defined as the wall 1B. The wall 1B has an end (also called a root 1D) on the other surface side 10B, and the bottom 2 refers to the area provided between the adjacent protrusions 1, 1, including the root 1D. More specifically, the bottom 2 refers to the area including the bottom of the recess (inter-protrusion recess 2U) recessed into the other surface side 10B between the protrusions 1, 1, and the end (root 1D) of the other surface side 10B of the wall 1B.

[0019] 1, the wall 1B extends linearly between the top 1A and the bottom 2, and the entire wall 1B is provided perpendicular to the third fiber layer M3. However, this is not limited thereto, and the wall 1B may include a portion that extends in a curved or wavy manner between the top 1A and the bottom 2. In this case, the angle θ is specified by taking the line connecting the boundary point between the top 1A and the wall 1B and the boundary point between the wall 1B and the bottom 2 as the center line K. Although all of the walls 1B preferably extend perpendicular to the third fiber layer M3, some of the walls 1B may not extend perpendicular to the plane of the other surface 10B of the third fiber layer M3. In the latter case, the number of perpendicular walls 1B is preferably 60% or more of the walls 1B in all of the protrusions 1, from the viewpoint of further enhancing the cushioning properties and liquid descending promotion effect of the nonwoven fabric 10.

[0020] In the nonwoven fabric 10, the fibers of the wall 1B are preferably oriented longitudinally with respect to the planar direction of the nonwoven fabric 10. The planar direction of the nonwoven fabric 10 referred to here means the direction along a plane (e.g., a flat base) that contacts the surface of the other side 10B of the nonwoven fabric 10 (third fiber layer M3). This longitudinal orientation of the fibers increases the supporting force of the wall portion 1B in the thickness direction Z with respect to the first fiber layer M1 and the top portion 1A, as well as the bottom portion 2 and the third fiber layer M3, making it possible for the wall portion 1B to absorb a load softly and making it easier for the thickness of the protrusions 1 to be maintained even under load. It also increases the thickness recovery of the protrusions 1 when the load is removed. As a result, the nonwoven fabric 10 including the first fiber layer M1 and the second fiber layer M2, combined with the elasticity due to the fiber structure of the fiber layers, is more likely to retain its thickness while undergoing gentle compression deformation, providing excellent pressure resistance and cushioning properties. In addition, when the nonwoven fabric 10 is incorporated as a component of an absorbent article, the permeability of excreted liquid is more likely to be sustained even under load, and liquid return is more likely to be suppressed. The three-dimensional shape of the wall portion 1B that functions in this way can be well maintained by being integrated with the first fiber layer M1 and the third fiber layer M3 with high strength by the fused fiber portions described above.

[0021] The longitudinal orientation of the fibers in the wall portion 1B means that many fibers are aligned along the thickness direction Z of the first fiber layer M1, and that the longitudinal orientation rate obtained by the measurement method described below is 60% or more. From the viewpoint of further enhancing the above-mentioned effect, 61% or more is preferable, and 62% or more is more preferable. There is no particular upper limit to the longitudinal orientation rate, but from the viewpoint of forming intersections between oriented fibers to form fused parts and forming columns between the fibers to form a structure that can withstand force, it is preferable that the longitudinal orientation rate is 90% or less, more preferably 85% or less, and even more preferably 80% or less.

[0022] (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, the fiber layer cross section of the wall portion 1B defined in the cross section in the thickness direction of the nonwoven fabric 10, including the first fiber layer M1, the convex portion 1 and the bottom portion 2 of the second fiber layer M2, and the third fiber layer M3, is observed at 35 times magnification with a scanning electron microscope (SEM). A square line with a side of 500 μm is added to the observed image as a reference line. Each side (reference line) of the square is defined as a side perpendicular to the thickness direction and the planar direction in the cross section of the nonwoven fabric 10. The total number of fibers passing through the reference lines consisting of each side of the square is counted. The fibers passing through the square reference line perpendicular to the planar direction of the nonwoven fabric 10 are defined as the "number of horizontal fibers", and the fibers passing through the square reference line perpendicular to the thickness direction of the nonwoven fabric 10 are defined as the "number of vertical fibers". The longitudinal orientation rate is calculated as (number of vertical fibers) / (number of horizontal fibers+number of vertical fibers)×100=longitudinal orientation rate (%). Ten points are measured for each film, and the average is taken as the longitudinal orientation ratio. The planar direction in the cross section of the nonwoven fabric 10 corresponds to a straight line L tangent to the surface of the other side 10B of the third fiber layer M3 shown in Figure 1. The thickness direction corresponds to a direction Z perpendicular to the straight line L. When the nonwoven fabric to be measured is incorporated in a sanitary product such as an absorbent article, the sanitary product is sprayed with cold spray to solidify the hot melt adhesive, and then the nonwoven fabric to be measured is carefully peeled off. This method is common to other measurements in this specification.

[0023] In the nonwoven fabric 10, as shown in FIG. 2, at least one of the first fiber layer M1 and the third fiber layer M3 preferably has a raised portion 5 that enters an area partitioned by the wall portion of the second fiber layer M2. The raised portions 5 formed in the first fiber layer M1 may be referred to as raised portions 5A, and the raised portions 5 formed in the third fiber layer M3 may be referred to as raised portions 5B. When the first fiber layer M1 has a raised portion 5A, the raised portion 5A enters the inter-protruding recessed portion 2U of the second fiber layer M2. When the third fiber layer M3 has a raised portion 5B, the inside of the protruding portion 1 of the second fiber layer M2 becomes a hollow portion 1C, and the raised portion 5B enters the hollow portion 1C within the protruding portion 1.

[0024] The presence of at least one of the raised portions 5A made of the constituent fibers of the first fiber layer M1 and the raised portions 5B made of the constituent fibers of the third fiber layer M3 enhances the ability to draw liquid into the second fiber layer M2. This, combined with the liquid guide effect along the wall portion 1B described above, can further enhance the liquid absorbency of the nonwoven fabric 10, and further of an absorbent article incorporating the nonwoven fabric 10 as a constituent member. To make the above effect more effective, it is preferable that the surfaces of the raised portions 5 (5A and 5B) have fuzz that penetrates further. Furthermore, the presence of the raised portions 5 (5A, 5B) prevents the wall portion 1B from collapsing sideways due to external pressure, and the various functions of the wall portion 1B described above can be maintained, thereby improving the pressure resistance and cushioning softness of the nonwoven fabric 10. Of the above-mentioned raised portions 5A and 5B, it is preferable that at least the raised portion 5B is present. When used as a component of an absorbent article, the first fiber layer M1 is usually the skin-facing side, and if the raised portion 5B is present, liquid can be more actively drawn from the upper layer toward the absorbent body. In addition, when an absorbent polymer is placed in the hollow portion 1C as described below, the raised portion 5B is preferable because it can firmly seal the absorbent polymer within the uneven structure of the second fiber layer M2.

[0025] The ratio (H2 / H1) of the thickness H2 of the protrusions 5 (5A, 5B) to the thickness H1 of the second fiber layer M2 is preferably 0.05 or more, more preferably 0.10 or more, and even more preferably 0.15 or more, from the viewpoint of providing appropriate cushioning properties through the hollow structure. The ratio (H2 / H1) of the thickness H2 of the protrusions 5 (5A, 5B) to the thickness H1 of the second fiber layer M2 is preferably 0.9 or less, more preferably 0.85 or less, and even more preferably 0.8 or less, from the viewpoint of improving the liquid drawing ability. The thickness H1 of the second fiber layer M2 refers to the height from the surface of one side 10T of the top portion 1A in contact with the first fiber layer M1 to the surface of the other side 10B of the bottom portion 2 in contact with the third fiber layer M3. 2This can be done in the same manner as the method for dividing the fiber layer of the wall portion 1B described above, with the load being applied. In addition, if there is fuzz on the surface of the raised portion 5 (5A, 5B), this portion is included in the thickness H2 of the raised portion 5 (5A, 5B).

[0026] In the nonwoven fabric 10, the number of fibers per unit area of ​​the third fiber layer M3 is preferably smaller than the number of fibers per unit area of ​​the first fiber layer M1. As a result, when a pressing force is applied to the nonwoven fabric 10, the thickness of the first fiber layer M1, which has a relatively dense number of fibers, tends to remain, and the third fiber layer M3, which has a relatively sparse number of fibers, tends to sink. At that time, since the second fiber layer M2 is protected by the first fiber layer M1, the collapse of the above-mentioned protrusions 1 in the thickness direction Z tends to occur after the sinking of the third fiber layer M3. As a result, the nonwoven fabric 10 is improved in both the above-mentioned pressure resistance and softness with cushioning properties. Furthermore, in the first fiber layer M1, the dense number of fibers makes it easier to absorb and acquire liquid from the skin surface, and the second fiber layer M2, which is an intermediate layer, is more likely to retain liquid. In the third fiber layer M3, the relatively sparse number of fibers makes it possible to create a sparse structure so as not to absorb the retained liquid (the liquid is trapped inside the unevenness). This configuration can further improve the absorption performance of the absorbent article when the nonwoven fabric 10 is used as an absorbent body or sublayer. When the nonwoven fabric 10 is used as an absorbent body, if an absorbent polymer is disposed inside the convex parts 1 of the second fiber layer M2 as described below, the liquid retention of the second fiber layer M2 is further improved, and the above difference in the number of fibers can make the absorption performance of the absorbent body more excellent. In addition, when the second fiber layer M2 is arranged in a lattice pattern as the convex portions 1, in a plan view from one surface side 10T as shown in FIG. 6, with the ridge portions 11 extending in one direction Y and the saddle portions 15 connecting the adjacent ridge portions 11 and 11, and the bottom portions 12 scattered in the lattice, there are the following advantages. That is, when the nonwoven fabric 10 is configured as described above, the contact area between the first fiber layer M1 and the ridge portions 11 is larger than the contact area between the third fiber layer M3 and the bottom portion 12 as shown in FIG. 8. In this form, the first fiber layer M1 is made dense in number of fibers to form more fused fiber portions, thereby ensuring the integrated strength corresponding to the contact area. At the same time, the third fiber layer M3 is made relatively sparse in number of fibers to form sufficient fused fiber portions in a small contact area, thereby ensuring the integrated strength. This can further increase the overall integrated property of the nonwoven fabric 10, and at the same time, achieve softness with cushioning properties.

[0027] The difference (F1-F3) between the number of fibers per unit area in the first fiber layer M1 (F1) and the number of fibers per unit area in the third fiber layer M3 (F3) is preferably at least 1, more preferably at least 2, even more preferably at least 3, and even more preferably at least 4. From the viewpoint of increasing the liquid-drawing force while further improving the pressure resistance and softness accompanied by cushioning properties, the difference (F1-F3) is preferably at most 50, more preferably at most 45, even more preferably at most 40, and even more preferably at most 30. Furthermore, from the viewpoints of increasing the liquid-drawing force while further improving pressure resistance and shape stability, the number of fibers (F1) per unit area of ​​the first fiber layer M1 is preferably 3 or more, more preferably 4 or more, and even more preferably 5 or more. From the viewpoints of improving cushioning properties, the number of fibers (F1) per unit area of ​​the first fiber layer M1 is preferably 150 or less, more preferably 145 or less, and even more preferably 140 or less. From the viewpoint of making it easier for the third fiber layer M3 to sink, the number of fibers (F3) per unit area of ​​the third fiber layer M3 is preferably 130 or less, more preferably 125 or less, and even more preferably 120 or less. From the viewpoint of maintaining the shape retention of the second fiber layer, the number of fibers (F3) per unit area of ​​the third fiber layer M3 is preferably 2 or more, more preferably 3 or more, even more preferably 4 or more, and even more preferably 5 or more. The number of fibers per unit area means the average number of constituent fibers in each of the first fiber layer M1 and the third fiber layer M3.

[0028] (Method of measuring the number of fibers per unit area of ​​the first fiber layer M1 and the third fiber layer M1) The number of fibers per unit area of ​​the first fiber layer M1 is measured at the center in the thickness direction of the portion where the first fiber layer M1 contacts the top portion 1A. The number of fibers per unit area of ​​the third fiber layer M3 is measured at the center in the thickness direction of the portion where the third fiber layer M3 contacts the bottom portion 2. Specifically, the cross section of the nonwoven fabric 10 is observed and the number of fiber cross sections is counted according to the following procedure. First, cross sections are prepared for the site to be measured along two directions, the longitudinal direction of the nonwoven fabric 10 and the width direction perpendicular to the longitudinal direction (for example, cross sections of the nonwoven fabric 10 including the cross sections shown in Figs. 7 and 8 in the concave-convex structure of the second fiber layer M21 described below). If it is not possible to prepare a cross section including both the overlapping portion between the first fiber layer M1 and the top portion 1A of the second fiber layer M2 and the overlapping portion between the third fiber layer M3 and the bottom portion 2 of the second fiber layer M2, cross sections in the above two directions may be prepared for each site. Next, a scanning electron microscope (JCM-6000Plus (product name) manufactured by JEOL Ltd.) is used to enlarge and observe the cross section at a magnification (100 to 500 times) that allows measurement of about 2 to 40 fiber cross sections. At this time, metal vapor deposition is performed on the cross section. For the first fiber layer M1, five points on each of the cross sections in the two directions were measured to determine a certain area (0.12 mm 2 The number of cut fiber cross sections in the cut surface of the fiber was counted and divided by the fixed area to obtain the unit area (1 mm 2The average of the 10 points (5 locations + 5 locations) is calculated as the number of fibers per unit area (fibers / mm2) of the first fiber layer M1. 2 ) Similarly, the third fiber layer M3 is measured at five points in each of the two cross sections in the same manner as above, and the average of the ten points is calculated as the number of fibers per unit area (fibers / mm 2 ) The above-mentioned large number of fibers per unit area means that the fiber density is high, and that the capillary force acts more strongly.

[0029] In the nonwoven fabric 10, as shown in FIG. 3, it is preferable that the bottom 2 of the second fiber layer M2 has an opening 3 penetrating in the thickness direction Z. In the example shown in FIG. 3, the bottom 2 has an opening 3 in its entirety except for the base 1D. In this case, the base 1D of the wall 1B becomes the bottom 2. The opening 3 penetrating here means that, when focusing on the second fiber layer M2, the portion of the second fiber layer M2 in which no constituent fibers are arranged penetrates both sides of the second fiber layer M2 in the thickness direction Z. The opening 3 in the bottom 2 can reduce pressure loss and improve the transfer of liquid between the second fiber layer M2 and the third fiber layer M3. This can further improve the liquid absorbency of the nonwoven fabric 10, and further the liquid absorbency of absorbent articles incorporating the nonwoven fabric 10 as a constituent member.

[0030] The openings 3 are holes formed by processing the second fiber layer M2, and have a hole area that is much larger than the fine holes formed between the fibers. In FIG. 3, the entire bottom 2 except for the base 1D is shown as the openings 3, but the size of the openings 3 can be appropriately selected depending on the width of the bottom 2, etc. For example, in the second fiber layer M2, the entire bottom 2 except for the base 1D may not be the openings 3, and a fiber layer (fiber layer of the bottom 2) may be present around the openings 3, extending from the base 1D. At least 1.0 mm 2It is preferable that the opening area is equal to or more 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 10 points using the microscope, and the average value of these is regarded as the opening area of ​​each opening.

[0031] The hole area of ​​the opening 3 is set to 1.0 mm 2 More than 1.5mm is preferable. 2 More preferably, 2.0 mm or more 2 More preferably, the opening area of ​​the opening 3 is 50 mm 2 Less than 40mm is preferable 2 Less than or equal to 35mm is preferred 2 The following is even more preferred:

[0032] The planar shape of the openings 3 may be various from the viewpoint of enhancing liquid permeability, and examples thereof include a circle, an ellipse, a rectangle, and a diamond.

[0033] When a fiber layer (fiber layer of bottom portion 2) extending from root portion 1D is present around hole 3, the distance in the planar direction between root portion 1D of wall portion 1B and the outer periphery of hole 3 is preferably 0.5 mm or less from the viewpoint of liquid permeability. When fibers constituting second fiber layer M2 are present in bottom portion 2 in this manner, the fibers constituting second fiber layer M2 are not considered to be part of wall portion 1B.

[0034] Furthermore, when the bottom portion 2 of the second fiber layer M2 has an opening 3, the above-mentioned raised portion 5B of the third fiber layer M3 may enter the opening 3 (not shown). In this case, the raised portion 5B of the third fiber layer M3 will enter not only the hollow portion 1C in the protrusion 1, but also the inter-protrusion recess 2U of the second fiber layer M2 through the opening 3. In the inter-protrusion recess 2U, the raised portion 5B of the third fiber layer M3 and the raised portion 5A of the first fiber layer M1 enter from both sides and are arranged opposite to each other. This further enhances the above-mentioned liquid drawing ability.

[0035] In the nonwoven fabric 10, it is preferable that the second fiber layer M2 has an absorbent polymer 8 in the multiple protrusions 1 (hollow portions 1C) as shown in Fig. 4. The absorbent polymer 8 is a surface-crosslinked polymer material called SAP (superbsorbent polymer), and is used as a liquid absorbing material in absorbent bodies in absorbent articles. The nonwoven fabric 10 has better liquid absorption properties because it does not use adhesives such as hot melt. Such a nonwoven fabric 10 can be used as an absorbent or sublayer of an absorbent article. In addition, the nonwoven fabric 10 can be used as a unit member having a unique cushioning property, in which the first fiber layer M1 is positioned as a top sheet and the top sheet and the absorbent (or sublayer) of the absorbent article are integrated. This is expected to simplify the manufacturing process of the absorbent article, shorten the time, and reduce the cost. In addition, in the unit member, when a force is applied to stroke the surface of the first fiber layer M1, which is the top sheet, in a planar direction, a continuous soft cushioning property is also exhibited, and the movement following property is also improved. In addition, when the skin of the buttocks or the like moves on the first fiber layer M1, which is the top sheet, the first fiber layer M1 holds the buttocks with a surface, while the second fiber layer M2 moves with the third fiber layer M3 as a base. Accordingly, the first fiber layer M1 can easily follow the movement of the skin. As a result, the skin held by the first fiber layer M1 is less likely to be rubbed even when moving.

[0036] In the above structure, the absorbent polymer 8 is contained within the protrusions 1, and is further sealed by the third fiber layer M3. This results in the nonwoven fabric 10 having a structure in which the absorbent polymer 8 is confined within the uneven structure of the second fiber layer M2, which is an intermediate layer, and is suppressed from moving or flowing out to other areas. Furthermore, the absorbent polymer 8 is divided into a plurality of protrusions 1 in the second fiber layer M2. The divided state of the absorbent polymer 8 is easily maintained by the above-mentioned sealing, making it difficult for unevenness or loss of liquid absorption performance in the nonwoven fabric 10 to occur. In addition, the hollows 1C in each of the convex portions 1 containing the absorbent polymer 8 are easily maintained under load due to the pressure resistance of the nonwoven fabric 10 described above, and are easily restored even if deformed. As a result, the nonwoven fabric 10 containing the absorbent polymer 8 can prevent gel blocking of the absorbent polymer 8 due to liquid absorption, while allowing the absorbent polymer 8 to swell due to liquid absorption, thereby improving the liquid absorption performance. At this time, in the uneven structure of the second fiber layer M2, not only the hollows 1C in the convex portions 1 but also the inter-convex concave portions 2U adjacent to the convex portions 1 can provide an allowable space for the absorbent polymer 8 to swell. At the same time, the inter-convex concave portions 2U become a primary storage space for liquid, and the time until the absorbent polymer 8 absorbs water can be gained. In addition, since the uneven structure is not easily crushed, the pressure on the absorbent polymer 8 is reduced even when a load is applied, and the liquid is less likely to return to the first fiber layer M1 side (the amount of wetback is small). Furthermore, in each of the protrusions 1, the vertically extending structure of the wall 1B, which tends to maintain its thickness, quickly guides the excreted liquid from the top 1A side to the bottom 2 side, making it possible for the excreted liquid to be distributed and absorbed by the multiple contained absorbent polymers 8. This allows the nonwoven fabric 10 having the absorbent polymers 8 divided (distributed) in the multiple protrusions 1 to uniformly and fully exhibit the absorption performance of the absorbent polymers 8 enclosed in the intermediate layer.

[0037] In a configuration in which the nonwoven fabric 10 has the absorbent polymer 8 in the multiple protrusions 1, the presence of the above-mentioned raised portions 5B of the third fiber layer M3 is preferable because it allows the absorbent polymer 8 to be better held and less biased. In this embodiment, when the first fiber layer M1 is used facing the skin side, it is preferable to make the number of fibers per unit area of ​​the first fiber layer M1 greater (denser) than the number of fibers per unit area of ​​the third fiber layer M3, since this makes it easier to prevent the absorbent polymer 8 from flowing to the skin side. In addition, the high liquid acquisition ability of the first fiber layer M1 can further improve the dryness of the skin side, and at the same time, the absorption performance as an absorbent body or sublayer can be further improved. Furthermore, in this embodiment, if there is an aperture 3 penetrating in the thickness direction Z at the bottom 2 of the second fiber layer M2, the liquid can flow quickly to the third fiber layer M3, the liquid circulates within the third fiber layer M3, and the liquid is quickly transmitted by the absorbent polymer 8, resulting in faster absorption, which is preferable. In addition, in a form where the nonwoven fabric 10 has ridge portions 11 extending in one direction Y and saddle portions 15 connecting adjacent ridge portions 11, 11 in a plan view from one surface side 10T as shown in FIG. 6, it is preferable that the liquid is absorbed while diffusing in one direction Y, so that a polymer with a large area can be effectively utilized and excellent absorbency can be exhibited.

[0038] Furthermore, the nonwoven fabric 10 having the absorbent polymer 8 preferably has a liquid-impermeable sheet 9 on the surface of the third fiber layer M3 on the side opposite to the second fiber layer M2 (the other surface side 10B) as shown in FIG. 5. Thereby, the nonwoven fabric 10 having the absorbent polymer 8 can be used as a unit member integrating the absorber and the back sheet of the absorbent article, or a unit member integrating the surface sheet, the absorber, and the back sheet, and the above-described effects can be further enhanced.

[0039] The "liquid impermeability" means the property of suppressing the exudation of the excreted liquid reaching the third fiber layer M3 to the other surface side 10B. This liquid impermeability can be evaluated by the water pressure resistance measured by the following method. When the sheet to be evaluated is preferably 1000 mmAq or more, more preferably 1500 mmAq or more, the sheet can be evaluated as having liquid impermeability.

[0040] (Method for measuring water pressure resistance) The water resistance of the sheet to be measured is measured in accordance with JIS L1092-1998 Water Resistance Test (Hydrostatic Pressure Method) Method A (Low Water Pressure Method). When performing the water resistance test, a nylon mesh sheet (pore size: 133 μm, thickness: 121 μm, Kurabo Industries, DO-ML-20) is placed on top of the test piece. If the size of the test piece does not meet the regulations, a device with a reduced measurement area can be set up so that water hits the test piece of the area that can be collected, and the water resistance can be measured in the same way. Three test pieces are prepared for the sheet to be measured, and measurements are taken for each, and the arithmetic average of the measured values ​​is taken as the water resistance of the sheet to be measured.

[0041] The basis weight of the nonwoven fabric 10 is set to 20 g / m from the viewpoint of creating a concave-convex structure and increasing pressure resistance (preventing the collapse of the concave-convex structure and the decrease in pressure resistance due to a low basis weight). 2 More than 30 g / m is preferable. 2 More preferably, 40 g / m 2 The basis weight of the nonwoven fabric 10 is preferably 120 g / m2 or more from the viewpoint of providing appropriate cushioning (preventing hardening of the nonwoven fabric 10 due to a high basis weight). 2 Less than 110 g / m 2 Less than 100 g / m is more preferable. 2 The following is even more preferred:

[0042] Nonwoven fabric 10: 4.9mN / cm 2 (0.05gf / cm 2 ) The thickness 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, from the viewpoint of creating an uneven structure and increasing pressure resistance. This thickness is 4.9 mN / cm 2 The above 4.9mN / cm can be measured using a laser displacement meter or similar device under a load. 2 The load is a load that assumes fluffing on the surface of the nonwoven fabric. 2 By having the thickness under load within the above range, the liquid backflow prevention performance is improved, making it difficult for the wearer's skin to become wet. In addition, the nonwoven fabric 10 has a strength of 4.9 mN / cm 2From the viewpoint of improving cushioning properties, the thickness under load is preferably 12 mm or less, more preferably 11 mm or less, and even more preferably 10 mm or less.

[0043] Next, a specific example of the second fiber layer M2 (second fiber layer M21) in the nonwoven fabric 10 shown in Fig. 1 will be described with reference to Fig. 6 to Fig. 9. In Fig. 7 to Fig. 9, the first fiber layer M1 and the third fiber layer M3 are indicated by dashed lines, and the lamination state of these and the second fiber layer M21 is virtually shown. 6 to 9, in plan view from one surface side 10T, the second fiber layer M21 has, as the above-mentioned protrusions 1, a plurality of ribs 11 extending in one direction Y and arranged at a distance from each other in a direction X intersecting the one direction Y. A hollow portion 11C is arranged on the other surface side 10B of the ribs 11. The one direction Y and the direction X intersecting the one direction Y can be appropriately set depending on the purpose on the second fiber layer M21 and one surface side 10T of the nonwoven fabric 10 including the second fiber layer M21. For example, the one direction Y and the direction X intersecting the one direction Y are preferably perpendicular to each other. When the nonwoven fabric 10 including the second fiber layer M21 is used as a component of 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.

[0044] The ridges 11 have the same height in the extension direction. The "same height" means that the height measured using the microscope is within a range of 0.8 to 1.2 times the average measurement value.

[0045] Each of the ridges 11 protrudes from the other surface side 10B to the one surface side 10T, and is a three-dimensional fiber layer erected in the thickness direction. More specifically, the ridges 11 include a crest 11A on the one surface side 10T and a wall portion 11B supporting the crest 11A. The wall portion 11B extends perpendicular to the planar direction as described above. The fibers of the wall portion 11B are preferably oriented vertically as described above. The angle θ indicating the "perpendicular" of the wall portion 11B means the interior angle between the center line K of the width of the fiber layer of the wall portion 11B and the straight line L tangent to the surface of the other surface side 10B as described above in a cross section perpendicular to the extending direction of the ridges 11 (a cross section in the thickness direction at the position of the R1-R1 line along the direction X intersecting with the one direction Y in FIG. 6), as shown in FIG. 7. This angle θ can be obtained by observing a micrograph of the cross section along the line R1-R1 obtained by the above-mentioned microscope. The longitudinal orientation ratio, which indicates the longitudinal orientation of the fibers in the wall portion 11B, can be measured based on the above-mentioned method (method for measuring the longitudinal orientation ratio of the fibers in the wall portion 1B) in a cross section perpendicular to the extending direction of the ridge portion 11 (a thickness direction cross section at the position of the line R1-R1 along the direction X intersecting with the one direction Y in FIG. 6), as shown in FIG.

[0046] The second fiber layer M21 has, as the above-mentioned convex portion 1, a plurality of saddle portions 15 connecting adjacent ribs 11, 11 together with the ridge portion 11. A hollow portion 15C is arranged on the other surface side 10B of the saddle portion 15. Each of the plurality of saddle portions 15 protrudes from the other surface side 10B to the one surface side 10T, similar to the ridge portion 11, and is a three-dimensional fiber layer erected in the thickness direction. More specifically, the saddle portion 15 has a top portion 15A on the one surface side 10T and a wall portion 15B supporting the top portion 15A. The wall portion 15B extends perpendicular to the planar direction. The above-mentioned "perpendicular" is synonymous with the "perpendicular" defined in the above-mentioned ridge portion 11. In addition, it is preferable that the fibers of the wall portion 15B are vertically oriented as described above. The longitudinal orientation rate, which indicates the “vertical” and longitudinal orientation of wall portion 15B in saddle portion 15, 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. 6) as shown in FIG. 8, in the same manner as the measurement method described above for wall portion 11B.

[0047] 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 10 including the second fiber layer M21 is incorporated as a component of an absorbent article, the distance between the top 11A and the other surface side 10B is more easily maintained even under the body pressure of the wearer when wearing the absorbent article, making it even harder for the excreted liquid once absorbed to return. Furthermore, the presence of the saddle portion 15 acts to block the excreted liquid between the ridges 11, 11, and improves the liquid flow prevention on one surface side (skin contact side) 10T of the nonwoven fabric 10 including the second fiber layer M21. On the other hand, excreted liquid can be diffused in one direction Y along the ridges 11, and effective liquid absorbency can be achieved.

[0048] The saddle portion 15 extends in a direction X intersecting the direction Y in which the rib portion 11 extends, in a plan view from one surface side 10T of the second fiber layer M21. The direction X in which the saddle portion 15 extends can be various directions as long as it connects adjacent ribs 11, and is preferably a direction perpendicular to the direction Y in which the rib portion 11 extends. For example, it is preferable that the 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 direction Y is the width direction of the absorbent article. Hereinafter, the direction Y and the direction X perpendicular to the 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 10T is not limited to a rectangle as shown in Fig. 6, and may be various shapes. For example, the planar shape of the saddle portion 15 as viewed from one surface side 10T may be such that the width increases toward the ridge portion 11.

[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 10T of the second fiber layer M21. 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 inter-convex recess 2U and its bottom 12 are located at the intervals between the saddle portions 15. That is, in each band region 16, the saddle portions 15 and the bottom 12 are alternately arranged. As a result, the bottom 12 is surrounded by the wall 11B of the rib portion 11 and the wall 15B of the saddle portion 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 inter-convex recess 2U. It is preferable that the above-mentioned opening portion 3 is located at the bottom 12.

[0050] In the example shown in Figs. 6 to 9, in a plan view from one surface side 10T of the second fiber layer M21, the ridges 11 and the saddles 15 are arranged in a lattice pattern, and the bottoms 12 are arranged in a square pattern by being scattered in the lattice pattern. In this arrangement, the aforementioned inter-protrusion recesses 2U are formed in a lattice pattern partitioned by the walls 11B and 15B. It is preferable that the raised portions 5A of the first fiber layer M1 enter the lattice-shaped inter-protrusion recesses 2U. With respect to the second fiber layer M21, the raised portions 5A of the first fiber layer M1 are surrounded in a lattice pattern by the walls 11B and 15B, thereby further enhancing the cushioning properties, the aforementioned liquid blocking action, and the liquid descending promotion action of the walls 11B and 15B, and further improving the liquid permeation speed to the second fiber layer M2 side, thereby further reducing the amount of liquid remaining. In other words, both the cushioning properties and the liquid permeability can be further improved. From the same viewpoint, it is preferable that the above-mentioned raised portions 5B of the third fiber layer M3 extend into the ridge portions 11 and / or the saddle portions 15 (hollow portions).

[0051] Although the saddle portion 15 has a three-dimensional fiber structure similar to that of the rib portion 11, it is preferable that the saddle portion 15 has a portion that is lower in height from the bottom portion 12 than the rib portion 11, as shown in Figures 8 and 9. This reduces the contact area between the second fiber layer M21 and the first fiber layer M1, thereby improving the cushioning property as well as the breathability, and thus improving the prevention of stuffiness. The difference (H3-H4) between the thickness direction height H3 of the rib portion 11 and the thickness direction height H4 of the saddle portion 15 is preferably 0.5 mm or more and 7.0 mm or less in order to improve the above-mentioned action. The thickness direction height H3 of the rib portion 11 is the thickness direction distance from a plane contacting the surface of the other side 10B of the second fiber layer M21 to one side 10T of the crest 11A of the rib portion 11. The thickness direction height H4 of the saddle portion 15 is the thickness direction distance from a plane contacting the surface of the other side 10B of the second fiber layer M21 to one side 10T of the lowest position of the crest 15A of the saddle portion 15.

[0052] (Method of measuring the difference between the height H3 of the ridge portion 11 in the thickness direction and the height H4 of the saddle portion 15 in the thickness direction) As shown in FIG. 8, a thickness direction cross section (a thickness direction cross section at the position of the line R2-R2 along one direction Y in FIG. 6) of the second fiber layer M21 is prepared along the extension direction of the band region 16 in which the saddle portions 15 are arranged at the lowest position of the saddle portions 15, and the second fiber layer M21 is placed on a horizontal table so that the surface of the other side 10B abuts against the horizontal table. The height H3 from the horizontal table to the one side 10T of the crest 11A of the ridge portion 11 and the height H4 from the horizontal table to the one side 10T of the crest 15A of the saddle portion 15 are measured. The height difference (H3-H4) is calculated from these measured values. The above-mentioned microscope can be used to measure the height from the horizontal table. The above measurement may be performed on the second fiber layer M21 alone, or on the nonwoven fabric 10 including the second fiber layer M21. In the latter case, the distance in the thickness direction from a plane in contact with the surface of the other side 10B of the third fiber layer M3 to one side 10T of the crests 11A of the ridges 11 and the crests 15A of the saddles 15 is measured, and then the thickness of the third fiber layer M3 is subtracted from the measured distance to determine the heights H3 and H4.

[0053] Furthermore, as shown in the cross section in the extending direction of the saddle portion 15 in Fig. 9 (thickness direction cross section at the position of the line R3-R3 along the direction X intersecting with the direction Y in Fig. 6), it is preferable that the hollow portion 15C of the saddle portion 15 is connected to the hollow portion 11C of the rib portion 11 at the intersection of the saddle portion 15 and the rib portion 11. This allows liquid to flow vertically and horizontally between the hollow portion 15C and the hollow portion 11C on the other surface side 10B of the second fiber layer M21, thereby improving the liquid drawing ability of the second fiber layer M2. In addition, the breathability between the hollow portion 15C and the hollow portion 11C is improved, and stuffiness can be suppressed.

[0054] Next, a preferred embodiment of a method for producing a nonwoven fabric 10 including the second fiber layer M21 will be described with reference to Fig. 10 to Fig. 14. The production method described below can also be applied to the formation of uneven structures of various shapes including the peaks 1 and the bottoms 2 in the second fiber layer M2 described above, and to the production method of a nonwoven fabric 10 including the uneven structure. The manufacturing method of this embodiment includes the following four steps using a first fiber web 101, a second fiber web 102 and a third fiber web 103, as shown in Figure 10 (hereinafter, each step may be referred to as step (I), step (II), step (III) and step (IV)). (I) A pressing process in which the second fiber web 102 is placed on a support 120 having an uneven shape having a plurality of protrusions 121 and recesses 125 between the protrusions 121, 121, and the second fiber web 102 is pressed and shaped along the recesses 125 by the pressing portion 131 of the pressing member 130 to form an uneven fiber web 104. (II) A step of removing the pushing member 130 from the support 120, and then blowing a first hot air W1 onto the uneven fiber web 104 to fuse the fibers together to obtain an uneven nonwoven fabric 105. (III) A lamination step of contacting the first fibrous web 101 and the third fibrous web 103 on both sides of the uneven nonwoven fabric 105 . (IV) A heat-sealing process in which a second hot air W2 is blown to fuse the fibers of the uneven nonwoven fabric 105 to the fibers of the first fibrous web 101 and the third fibrous web 103, and also to fuse the fibers in the first fibrous web 101 and the third fibrous web 103 to each other.

[0055] The first fibrous web 101 and the third fibrous web 103 are precursors of the first fibrous layer M1 and the third fibrous layer M3 in the nonwoven fabric 10, and contain thermoplastic fibers. The second fibrous web 102 is a precursor of the second fibrous layer M21, and contains thermoplastic fibers. The "fiber web" in the first fiber web 101, the second fiber web 102, and the third fiber web 103 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 first fiber web 101, the second fiber web 102, and the third fiber web 103 are each supplied from a carding machine (not shown) to a predetermined thickness.

[0056] In step (I), as shown in FIG. 10(A), the second fiber web 102 on the support 120 is directly pressed with mechanical pressure using a pressing member 130. This forms an uneven fiber web 104 that becomes the second fiber layer M21 in the nonwoven fabric 10. This type of shaping results in stronger fiber orientation and can obtain an orientation perpendicular to the nonwoven fabric plane, compared to when the fibers are pressed with non-mechanical pressure such as wind. Furthermore, it is not necessary to apply a large pressing force to increase the unevenness height difference formed on the second fiber web 102, and the second fiber web 102 can be shaped softly. Furthermore, fiber disorder can be suppressed to improve shaping properties.

[0057] The support 120 is drum-shaped as shown in Fig. 10, for example, and has protrusions 121 as shown in Fig. 10(A) on the drum peripheral surface. 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. 11, for example. 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 planar shape of the projection 121 as viewed from the tip end side is not limited to a rectangle as shown in Fig. 11, 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 located between the protrusions 121, 121 in the protrusion row 121A. The second recess 125C is connected to the adjacent first recess 125A and extends intermittently in the second direction D2 via the first recess 125A.

[0058] In the support 120, a plurality of protrusions 121 are arranged corresponding to positions where the bottom portions 12 of the second fiber layer M21 of the nonwoven fabric 10 will 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 second fiber layer M21 of the nonwoven fabric 10 will 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 second fiber layer M21 of the nonwoven fabric 10. The first recesses 125A are located at a position that will become the ribs 11 of the second fiber layer M21 of the nonwoven fabric 10. The bottom of each recess 125 has a structure that allows hot air to pass through, and for example, has a plurality of holes (not shown).

[0059] The pushing member 130 is in the form of a roll as shown in Fig. 10, for example, and has a pushing portion 131 as shown in Fig. 10(A) on the roll peripheral surface. On the roll peripheral surface of the pushing member 130, a plurality of pushing portions 131 continuing in the first direction D1 are arranged at intervals in the second direction D2 as shown in Fig. 12, for example. 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, a plurality of holes (not shown) are provided therein.

[0060] 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 .

[0061] The first direction D1 and the second direction D2 in the support 120 and the pushing member 130 are preferably a machine direction (MD) and a 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 crossing the one direction Y in the nonwoven fabric 10, and preferably correspond to the longitudinal direction and the cross direction in an absorbent article including the nonwoven fabric 10. However, the first direction D1 and the second direction D2 are not limited to these.

[0062] In step (I), the protrusions 121 of the support 120 are inserted into the recesses 132 of the pushing member 130. The pushing parts 131 of the pushing member 130 are inserted into the first recesses 125A of the support 120 (FIGS. 10(A) and 13). This pushing between the support 120 (FIG. 11) and the pushing member 130 (FIG. 12) can favorably form the uneven shape of the second fiber layer M21. The second fiber web 102 is pressed and shaped by the pressing portion 131 of the pressing member 130 at the position of the first recess 125A of the support 120. This portion becomes the rib portion 11 in the second fiber layer M21. At this time, between the protrusion 121 of the support 120 and the pressing portion 131 of the pressing member 130, the fibers of the second fiber web 102 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 second fiber layer M21. On the other hand, the fibers of the second fiber web 102 at the positions of the protrusions 121 of the support 120 are pushed up to the bottoms of the recesses 132 of the pushing member 130, forming the bottoms 12 of the second fiber layer M21. The second recess 125C between the protrusions 121, 121 in the protrusion row 121A of the support 120 corresponds to the recess 132 of the pushing member 130, so 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 second fiber web 102 in the second recess 125C of the protrusion row 121A. Due to this action, the fibers of the second fiber web 102 in the second recess 125C are stretched in the second direction D2 by the pushing portions 131, 131 on both sides and pushed in the thickness direction, so that the fibers are shaped in the thickness direction and the fiber orientation changes. This portion becomes the saddle portion 15 in the second fiber layer M21. The saddle portion 15 has a top portion 15A and a wall portion 15B, and the wall portion 15B is similar to the wall portion 11B of the ridge portion 11.

[0063] 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, etc. For example, it is preferably 2 mm or more, more preferably 3 mm or more, even more preferably 5 mm or more, and preferably 50 mm or less, more preferably 40 mm or less, and even more preferably 30 mm or less. Specifically, it is preferably 2 mm or more and 50 mm or less, more preferably 3 mm or more and 40 mm or less, and even more preferably 5 mm or more and 30 mm or less.

[0064] Next, in step (II), after removing the pushing member 130 from the support 120, a first hot air W1 is blown onto the uneven fiber web 104 to fuse the fibers together to obtain an uneven nonwoven fabric 105 (FIG. 10(B)). This uneven nonwoven fabric 105 becomes the second fiber layer M21 of the nonwoven fabric 10. For example, as shown in FIG. 10, after removing the pushing member 130 inserted into the support 120, the support 120 rotates while holding the uneven fiber web 104, and after passing through the meshing portion between the support 120 and the pushing member 130, the first hot air W1 is blown onto the uneven fiber web 104 at the position of the hot air blowing section 140 in FIG. 10(B). The support 120 preferably has a hot air suction section 141 at a position facing the hot air blowing section 140 inside the drum.

[0065] The temperature of the first hot air W1 is set to a temperature capable of melting the thermoplastic fibers constituting the uneven fiber web 104 and forming fused fiber portions at the intersections of the fibers. Considering typical fiber materials used in this type of product, the temperature is preferably 0°C to 70°C higher than the melting point of the thermoplastic fibers constituting the uneven fiber web 104, and more preferably 5°C to 50°C higher. From the viewpoint of effective fusion, the wind speed of the first hot air W1 is preferably 1 m / s or more, and more preferably 2 m / s or more. Also, from the viewpoint of making the device scale compact, the wind speed of the first hot air W1 is preferably 100 m / s or less, and more preferably 80 m / s or less.

[0066] Next, in step (III), the first fiber web 101 and the third fiber web 103 are supplied and laminated on both sides of the uneven nonwoven fabric 105 and brought into contact with each other (FIG. 10(C)). For example, the uneven nonwoven fabric 105 formed by blowing the first hot air W1 is separated from the drum peripheral surface of the support 120. At this time, the fabric is transported downstream by a belt conveyer with the side on which the bottom 12 is formed by being pushed up by the protrusions 121 facing up and the side on which the crests 11A of the ridges 11 and the crests 15A of the saddles 15 are formed by being pushed by the pushing parts 131 of the pushing members 130 facing down. During transport, the first fiber web 101 is joined to the surface side of the crests 11A of the ridges 11 and the crests 15A of the saddles 15, and the third fiber web 103 is joined to the surface side of the bottom 12 and laminated.

[0067] Next, in step (IV), a second hot air W2 is blown in a fusion furnace 170 to fuse the fibers of the uneven nonwoven fabric 105 and the first and third fibrous webs 101 and 103, and also fuse the fibers in the first and third fibrous webs 101 and 103 (FIG. 10(D)). This integrates the uneven nonwoven fabric 105 and the first and third fibrous webs 101 and 103, and simultaneously turns the first and third fibrous webs 101 and 103 into a nonwoven fabric. The nonwoven fabrics of the first and third fibrous webs 101 and 103 become the first and third fiber layers M1 and M3 of the nonwoven fabric 10.

[0068] The bottom portion 12 including the wall portion 11B and the base portion 1D of the wall portion 15B in the uneven nonwoven fabric 105 is integrated with the third fiber web 103 by forming a fiber fusion portion at the intersection of the fibers. The top portion 11A and the top portion 15A in the uneven nonwoven fabric 105 are integrated with the first fiber web 101 by forming a fiber fusion portion at the intersection of the fibers. In this manner, the first fiber layer M1 (the first fiber web 101 made into a nonwoven fabric) is integrated with one surface 10T of the uneven nonwoven fabric 105 (the second fiber layer M21), and the third fiber layer M3 (the third fiber web 103 made into a nonwoven fabric) is integrated with the other surface 10B of the uneven nonwoven fabric 105 (the second fiber layer M21), thereby obtaining the nonwoven fabric 10 described above.

[0069] 10(D), the first fibrous web 101 is placed on the net 180 with the side of the first fibrous web 101 facing down, and the second hot air W2 is blown onto the third fibrous web 103, thereby pressing the third fibrous web 103 in. By appropriately controlling the blowing conditions of the second hot air W2, the pressed third fibrous web 103 enters the region defined by the wall 11B and the wall 15B in the ridge portion 11 and / or the saddle portion 15 (hollow portion) of the uneven nonwoven fabric 105, and the raised portion 5B is formed. The formation of the raised portion 5B can increase the liquid absorbency and the sealing power of the absorbent polymer 8, as described above. At the same time, the uneven nonwoven fabric 105 is pressed into the first fibrous web 101. At this time, by appropriately controlling the blowing conditions of the second hot air W2, the ridges 11 and saddles 15 of the pressed uneven nonwoven fabric 105 are pressed against the first fibrous web 101. As a result, the first fibrous web 101 relatively enters the lattice-shaped inter-protruding recesses 2U of the uneven nonwoven fabric 105, and the raised portions 5A are formed. In addition, by blowing the second hot air W2 from the side of the third fibrous web 103, pilling of the surface of the first fibrous layer M1 on the side of the rib portion 11 used on the skin side can be suppressed, making it possible to produce a nonwoven fabric that is soft to the touch.

[0070] Taking into consideration the typical fiber materials used in this type of product, the temperature of the second hot air W2 is preferably 0°C to 70°C higher than the melting point of the thermoplastic fibers that make up the uneven nonwoven fabric 105, the first fiber web 101, and the third fiber web 103, and more preferably 5°C to 50°C higher. The wind speed of the second hot air W2 is preferably 0.3 m / s or more, and more preferably 0.4 m / s or more, from the viewpoint of fusing the fibers in the first fibrous web 101 and the third fibrous web 103 and from the viewpoint of sufficiently fixing the uneven nonwoven fabric 105 to the first fibrous web 101 and the third fibrous web 103. Moreover, from the viewpoint of further increasing the softness of the nonwoven fabric 10, the wind speed of the second hot air W2 is preferably 50 m / s or less, and more preferably 30 m / s or less.

[0071] In the above manufacturing method, the projections 121 of the support 120 are not limited to the shapes shown in Figs. 10(A) and 11, but may have various shapes. For example, a support male member 120A having a spire portion 122 at the tip of a projection 121 as shown in FIG. 14 may be used.

[0072] When the support male member 120A as shown in FIG. 14 is used, the portions of the second fiber web 102 corresponding to the projections 121 (spires 122) can be perforated in the pushing step of the above-mentioned step (I) to form openings on the side of the pushing member 130 of the uneven fiber web 104. As a result, the uneven nonwoven fabric 105 obtained in the above-mentioned step (II) has openings 3 formed in the bottom portion 12 of the second fiber layer M21. Next, in the lamination step of the above-mentioned step (III), the third fiber web is brought into contact with the openings side of the uneven nonwoven fabric 105. As a result, in the nonwoven fabric 10 obtained by the heat fusion step of the above-mentioned step (IV), the bottom portion 12 including the openings 3 of the second fiber layer M21 is integrated with the third fiber layer M3.

[0073] 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. 12. 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 height of the saddle portion 15 to be formed becomes higher, and the unevenness becomes more distinct.

[0074] Furthermore, in the method for producing the nonwoven fabric of this embodiment, it is preferable to include the following treatment. That is, in the lamination step of the above-mentioned step (III), it is preferable to carry out a process of disposing the absorbent polymer 8 in the portion of the uneven nonwoven fabric 105, which is the second fiber layer M21, pushed in by the pushing portion 131, i.e., in the ridge portion 11 and / or the saddle portion 15 (hollow portion) (FIG. 10(C1)). After that, it is preferable to laminate the third fiber web 103 so as to close the open side of the pushed in portion. In this case, the order of the lamination process in the aforementioned step (III) is preferably as follows: as shown in FIG. 10, the uneven nonwoven fabric 105 and the first fibrous web 101 are laminated together, a process of distributing the absorbent polymer 8 is performed, and finally the third fibrous web 103 is laminated. In the process of distributing the absorbent polymer 8, it is preferable to use, for example, a spraying device 190 as shown in FIG.

[0075] In addition, in the manufacturing method of the nonwoven fabric of this embodiment, it is preferable to have a cooling process after blowing the first hot air W1. For example, as shown in FIG. 10, it is preferable to arrange a cooling section 160 having a cooling nozzle and a cooling suction section 161 inside the drum of the support 120 opposite each other at a position where the uneven nonwoven fabric 105 obtained by blowing the first hot air W1 is aligned along the outer periphery of the drum of the support 120. This makes it possible to keep the support 120 at a certain temperature or lower, and to peel off the obtained nonwoven fabric while maintaining its shape. As a result, in the manufactured nonwoven fabric 10, the shapes of the wall portion 11B and the wall portion 15B of the second fiber layer M21 can be well maintained, and good pressure resistance, cushioning properties, and liquid absorbency can be further improved.

[0076] As the thermoplastic fibers constituting the nonwoven fabric of the present invention, those commonly used as the material of the nonwoven fabric can be adopted without particular limitation. For example, fibers composed of a single resin component, composite fibers composed of a plurality of resin components, etc. may be used. Examples of the composite fibers include a core-sheath structure, a side-by-side structure, and the like. When using a composite fiber containing a low melting point component and a high melting point component as the thermoplastic fiber (for example, 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), the temperature of the hot air sprayed 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, it is a temperature that 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. Even more preferably, it is a temperature that is 5°C or more higher than the melting point of the low melting point component and 20°C or more lower than the melting point of the high melting point component. Also, from the viewpoint of elasticity, among the composite fibers having a core-sheath structure, the more the core, which is the high melting point component, the higher the elasticity. Therefore, it is preferable that the core component has a larger cross-sectional area ratio. Specific examples of the 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 include 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). In addition, in the composite fiber having 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), by reducing the mass ratio of the low glass transition point resin component, the thickness recoverability of the nonwoven fabric can be further enhanced.

[0077] The absorbent polymer 8 is what is called SAP in the absorbent article as described above, and has the property of taking in the liquid inside the crosslinked surface, swelling, and becoming gel-like to hold the liquid inside. For example, those that can absorb and hold a liquid 20 times or more its own weight and can gel are preferable. The absorbent polymer 8 may include various types of absorbent polymers used in absorbents of absorbent articles without any particular limitations. For example, it may include a hydrogel material obtained by polymerizing a water-soluble ethylenically unsaturated monomer composed mainly of acrylic acid or an acrylic acid salt, and optionally containing a crosslinking agent. It may also include one or more selected from the group consisting of polyethylene oxide, polyvinylpyrrolidone, crosslinked products of sulfonated polystyrene and polyvinylpyridine, saponified products of starch-poly(meth)acrylonitrile graft copolymers, starch-poly(meth)acrylic acid graft copolymers, and hydrolyzates of starch-poly(meth)acrylic ester graft copolymers. There are no particular limitations on the shape of the absorbent polymer 8, and various shapes used in absorbents can be used, such as spheres, granules, fibers, bales, and blocks.

[0078] The nonwoven fabric for absorbent articles of the present invention can be used as a component of various absorbent articles, which broadly include articles used to absorb liquids discharged from the body, such as diapers for adults and infants, sanitary napkins, panty liners, and urine pads.

[0079] An absorbent article having the nonwoven fabric for absorbent articles 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 for absorbent articles of the present invention can be suitably used as the top sheet that contacts the wearer's skin, the absorbent body, a sublayer sandwiched between the top sheet and the absorbent body, or as a unit member combining a plurality of components. EXAMPLES

[0080] 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. "-" means that there is no value corresponding to that item. "←" means that the value is the same as the value in the left column.

[0081] Example 1 A nonwoven fabric sample of Example 1 was produced by carrying out steps (I), (II), (III) and (IV) based on the production method shown in Fig. 10. That is, the second fiber layer M21 shown in Figs. 6 to 9 was produced, and the second fiber layer M21 was laminated with the first fiber layer M1 and the third fiber layer M3 and integrated at the fused fiber parts to produce a nonwoven fabric having the laminated structure shown in Fig. 1. This nonwoven fabric was used as the nonwoven fabric sample of Example 1. The nonwoven fabric sample was produced under the following conditions. The first fiber web 101 and the third fiber web 103 are made of thermoplastic fibers having a fiber diameter of 14 μm and a core-sheath type (polyethylene terephthalate (PET) (core): polyethylene (PE) (sheath) = 5:5 (mass ratio)) and a basis weight of 20 g / m shown in Table 1. 2 It was decided that it was. The second fiber web 102 is made of thermoplastic fibers having a fiber diameter of 14 μm and a core-sheath type (polyethylene terephthalate (PET) (core): polyethylene (PE) (sheath) = 5:5 (mass ratio)) and has a basis weight of 30 g / m shown in Table 1. 2 It was decided that it was. The first hot air W1 had a temperature of 160° C. and a wind speed of 3.5 m / sec. The second hot air W1 had a temperature of 160° C. and a wind speed of 1.8 m / sec.

[0082] In the nonwoven fabric sample of Example 1, the tops 11A and 15A of the first fiber layer M1 and the second fiber layer M21 were integrated by the fiber fusion at the intersection of the fibers. The third fiber layer M3 and the bottom 12 of the second fiber layer M21 were integrated by the fiber fusion at the intersection of the fibers. The walls 11B and 15B of the second fiber layer M21 extended vertically, and the fibers were oriented vertically. The number of fibers per unit area of ​​the first fiber layer M1 and the third fiber layer M3 were as shown in Table 1. The raised portion 5A of the first fiber layer M1 and the raised portion 5B of the third fiber layer M3 entered the area partitioned by the walls 11B and 15B of the second fiber layer M2.

[0083] Example 2 A nonwoven fabric sample of Example 2 was prepared in the same manner as in Example 1, except that an opening 3 was formed in the bottom 12 of the uneven nonwoven fabric 105, which was the second fiber layer M21, using a support male element 120A having a peak 122 at the tip of a protrusion 121 as shown in FIG. 14 .

[0084] Example 3 A nonwoven fabric sample of Example 3 was produced in the same manner as in Example 1, except that in the production method shown in FIG. 10, a treatment of disposing an absorbent polymer was performed in the lamination step (II) (FIG. 10(C1)).

[0085] Example 4 10, a nonwoven fabric sample of Example 4 was produced in the same manner as in Example 1, except that the first fiber layer M1 and the third fiber layer M3, which had been previously made into a nonwoven fabric, were laminated onto the uneven nonwoven fabric 105, which is the second fiber layer M21, in the lamination step (III). In the nonwoven fabric sample of Example 4, the first fiber layer M1 and the top portions 11A and 15B of the second fiber layer M21 were also integrated together by fused fiber portions at the intersections of the fibers, and the third fiber layer M3 and the bottom portion 12 of the second fiber layer M21 were also integrated together by fused fiber portions at the intersections of the fibers.

[0086] Comparative Example 1 The second fibrous web 102 used in Example 1 was laminated, without being shaped, with the first fibrous web 101 and the second fibrous web 103, and integrated by blowing hot air onto them. The resulting three-layer flat air-through nonwoven fabric was used as a nonwoven fabric sample of Comparative Example 1. The hot air was blown under the same conditions as the second hot air in Example 1.

[0087] Comparative Example 2 A nonwoven fabric sample of Comparative Example 2 was prepared in the same manner as in Example 1, except that the first fiber layer M1 made of the first fiber web 101 was not laminated.

[0088] The nonwoven fabric samples of each of the Examples and Comparative Examples were subjected to the following tests (1) to (3).

[0089] (1) Compression characteristics Using the KES-FB3 (product name) manufactured by Kato Tech Co., Ltd., the terminal speed was set to 0.1 mm / s and the measuring area was set to 2 cm 2 At a compression load of 0.5gf / cm 2 More than 50gf / cm 2 The sheet was compressed by the gauge in the following range, and the thickness and the load at that time were measured when the sheet was moved in the recovery direction immediately after applying the maximum load. 2 The thickness of the nonwoven fabric under load was defined as Tm (mm). The compression resilience was calculated as Rc (%). The measurement surface was set so that the front surface (one side 10T) side was the measuring probe side. Each measurement value was calculated by measuring three points on the sheet and averaging the results. ·Under high load (50gf / cm 2 Because the total thickness (Tm) under pressure is large, crushing is prevented even under high load, and plastic deformation (sag) is felt to be small. The higher the compression resilience (Rc), the smaller the hysteresis in the elastic stress between compression and recovery, and the better the cushioning tends to feel. 1.5gf / cm 2 ~25gf / cm 2 The amount of deformation up to this point was taken as the "amount of compression deformation." The larger this value, the more difficult it is to be crushed in the compression direction by a small load, and similarly, the more elastic it is.

[0090] (2) Absorption speed A commercially available baby diaper (product name "Meries Sarasara Air Through S size", Kao Corporation, manufactured in 2022) was used to remove the top sheet from an absorbent core, and nonwoven fabric cut to 150 x 400 mm from each of the nonwoven fabric samples of the Examples and Comparative Examples was laminated at the widthwise center of the absorbent core, and the top sheet was then laminated again. Each nonwoven fabric sample was laminated so that the third fiber layer side faced the absorbent body side, and the periphery of the laminated nonwoven fabric was fixed to prepare a diaper for evaluation. Each diaper sample was unfolded and spread out flat, and the test piece was subjected to a load of 13.6 g / cm 2A load equal to the pressure of the cylinder (cross-sectional area 1017 mm2) was applied evenly to the cylinder, which was placed 165 mm from the ventral edge in the longitudinal direction and approximately in the center in the width direction. 2 ) and poured 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 (96.886% by mass). 40 g of artificial urine was poured and the time (seconds) until the entire amount was absorbed was measured. The time when the artificial urine could no longer be seen on the surface of the diaper was considered to be "all amount absorbed." The above operation was carried out three times, and the average 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. In other words, the liquid absorption ability is excellent.

[0091] (3) Liquid return (30gf / cm 2 and 70 gf / cm 2 Pressurization) The same diaper samples as those prepared in (2) above were prepared. Each diaper sample was unfolded and spread out flat, and 30 g of the artificial urine was poured over 10 seconds at a position 165 mm from the abdominal edge in the longitudinal direction and at the center in the width direction. 10 minutes after the start of the pouring, 30 g was poured again. 10 minutes after the start of the second pouring, 30 g was poured again, for a total of 90 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 injection was completed, four resin films (70 mm x 70 mm, mass measurement W1) were stacked and placed on the nonwoven fabric with the injection point at the center. 2 and 70 gf / cm 2 After 30 seconds, the masses of the four resin films were measured (W2), and the amount of liquid return was calculated according to the following formula (S). Liquid return (mg) = mass of four plastic films after pressure application (W2) - initial mass of four plastic films (W1) (S) 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 better the ability to prevent liquid return.

[0092] (4) Liquid diffusion length After carrying out the liquid return evaluation in (3) above, the total length of the artificial urine that has been diffused in the longitudinal direction in the absorbent is measured. The above operation is carried out three times, and the average of the three measurements is taken as the liquid diffusion length (mm). The longer the liquid diffusion length, the more the liquid can be diffused along the Y direction, and the more effective the liquid absorption is, using the entire diaper rather than confining the liquid to one place.

[0093] [Table 1]

[0094] As shown in Table 1, each of the Examples had a higher strength under a high load (50 gf / cm 2 The total thickness (Tm), compression resilience (Rc) and compression deformation amount under pressure (under pressure) were large, the thickness was easily retained, it was not easily crushed by a small load, it had moderate elasticity and excellent cushioning properties. That is, each Example had high pressure resistance and softness accompanied by cushioning properties compared to each Comparative Example. Regarding this compression property, the following difference occurred in the deformation of the convex parts under load between Example 1 and Comparative Example 2. That is, in Comparative Example 2, the convex parts 1 were lying sideways, whereas in Example 1, the convex parts 1 were deformed so as to be compressed in the thickness direction Z (FIGS. 15(A) and (B)). As a result, in Example 1, the thickness of the nonwoven fabric 10 remained under pressure compared to Comparative Example 2, and gentle sinking and good cushioning properties were obtained for the entire continuous layer of the first fiber layer M1. At the same time, each of the examples had a higher load of 30 gf / cm than each of the comparative examples. 2 and 70 gf / cm 2 In all cases, the amount of liquid returning was small, and the liquid returning prevention was excellent. In addition, each Example had a longer liquid diffusion length in the longitudinal direction than each Comparative Example, and the liquid was not confined to one place, but was absorbed effectively using the entire diaper. In other words, each Example had better liquid absorbency than each Comparative Example. [Explanation of symbols]

[0095] M1 First fiber layer M2, M21 Second fiber layer M3 3rd fiber layer 1 Convex part 1A Top 1B Wall section 1D Base 2, 21 bottom 3 Opening part 5, 5A, 5B ridges 8. Absorbent Polymers 10. Nonwoven Fabrics 10T One side 10B The other side

Claims

1. A nonwoven fabric for absorbent articles, comprising a first fiber layer, a second fiber layer, and a third fiber layer laminated in a thickness direction, the nonwoven fabric including fused fiber portions at intersections of the fibers, the first fiber layer and the second fiber layer, and the second fiber layer and the third fiber layer are integrated with each other by the fiber fusion portions between the fibers of each fiber layer, the second fiber layer has a concave-convex structure including a plurality of convex portions and a bottom portion provided between adjacent convex portions, each of the plurality of convex portions includes a top portion and a wall portion supporting the top portion, the wall portion extending perpendicular to a planar direction of the nonwoven fabric, A nonwoven fabric for absorbent articles, comprising the first fiber layer on the side where the top of the second fiber layer is located, and the third fiber layer on the side where the bottom of the second fiber layer is located.

2. The nonwoven fabric for absorbent articles according to claim 1 , wherein at least one of the first fibrous layer and the third fibrous layer has a protruding portion extending into an area defined by the wall portion of the second fibrous layer.

3. 3. The nonwoven fabric for absorbent articles according to claim 1, wherein the number of fibers per unit area of ​​said third fibrous layer is smaller than the number of fibers per unit area of ​​said first fibrous layer.

4. The nonwoven fabric for absorbent articles according to any one of claims 1 to 3, wherein the bottom portion of the second fiber layer has an opening penetrating therethrough in the thickness direction.

5. The nonwoven fabric for absorbent articles according to any one of claims 1 to 4, wherein the second fibrous layer has an absorbent polymer in the plurality of protruding portions.

6. 6. The nonwoven fabric for absorbent articles according to claim 5, further comprising a liquid-impermeable sheet on a surface of said third fibrous layer opposite to said second fibrous layer.

7. An absorbent article comprising the nonwoven fabric for absorbent articles according to any one of claims 1 to 6.

8. A method for producing a nonwoven fabric for absorbent articles using a first fibrous web, a second fibrous web, and a third fibrous web, comprising the steps of: a pressing step of placing the second fiber web on a support having an uneven shape including a plurality of protrusions and recesses between the protrusions, and pressing and shaping the second fiber web along the recesses with a pressing part of a pressing member to form an uneven fiber web; a step of removing the pushing member from the support, and then blowing a first hot air stream onto the uneven fiber web to fuse the fibers together to obtain an uneven nonwoven fabric; a lamination step of contacting a first fibrous web and a third fibrous web on both sides of the uneven nonwoven fabric; A method for manufacturing a nonwoven fabric for absorbent articles, comprising a heat fusing process in which a second hot air is blown to fuse the fibers of the uneven nonwoven fabric to the fibers of the first fiber web and the third fiber web, and to fuse the fibers in the first fiber web and the third fiber web to each other.

9. The method for producing a nonwoven fabric for absorbent articles according to claim 8 , wherein in the heat fusion step, the second hot air is blown onto the third fibrous web side.

10. In the pushing step, holes are opened at locations of the second fiber web corresponding to the protrusions, and openings are formed on the pushing member side of the uneven fiber web, In the lamination step, the third fiber web is brought into contact with the side of the openings of the uneven nonwoven fabric. A method for producing the nonwoven fabric for absorbent articles according to claim 8 or 9.

11. The method for manufacturing a nonwoven fabric for absorbent articles according to any one of claims 8 to 10, wherein in the lamination step, a process is carried out to dispose an absorbent polymer in the portion of the second fiber layer pushed in by the pushing section, and then the third fiber web is laminated so as to close the open side of the pushed-in portion.

Images