Method for manufacturing nonwoven fabric for absorbent articles and absorbent articles

Abstract

To provide a method for manufacturing a nonwoven fabric for absorbent article, which can obtain a nonwoven fabric capable of ensuring desired feeling and absorption rate.SOLUTION: A method for manufacturing a nonwoven fabric for absorbent article (S100) has a web formation step (S101) to form a web by laminating a first fiber layer (11) including thermoplastic resin fibers (51) at a ratio of 90 wt.% to 100 wt.%, a second fiber layer (12) including the thermoplastic resin fibers (51) and cellulosic fibers (52), and a third fiber layer (13) including the thermoplastic resin fibers at a ratio of 90 wt.% to 100 wt.% in a thickness direction, and a hot air penetration step (S105) to make hot air penetrate in the web in a state in which the third fiber layer of the web is disposed so as to face a conveyance surface having air permeability after the web formation step.SELECTED DRAWING: Figure 4

Description

[Technical Field]

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

[0002] Patent Document 1 discloses a nonwoven fabric for use in absorbent articles. The nonwoven fabric includes a first fiber layer and a second fiber layer located on one main surface of the first fiber layer. The first fiber layer includes core-sheath composite fibers (thermoplastic resin fibers), and the second fiber layer includes core-sheath composite fibers (thermoplastic resin fibers) and cellulosic fibers. Nonwoven fabrics used in absorbent articles must have both a good texture (a good feel against the skin) and a high absorption rate for body fluids. Patent Document 1 describes that the air-through method (hot air penetration heat treatment method) can be suitably used as a method for producing nonwoven fabrics to improve the texture (paragraph 0044 of Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2020-171688 Summary of the Invention [Problem to be solved by the invention]

[0004] The air-through method involves forming a web of laminated fibers and passing hot air (e.g., gas at 100°C or higher) through the web. The web is transported by a transport device having a transport surface made of a breathable material, such as a metal or resin wire mesh belt, and hot air is applied to the surface of the web while it is placed on the transport surface. The hot air passes through the web and is released from the transport surface. The thermoplastic resin fibers fuse as the hot air passes through the web. If the hot air is applied with the first fiber layer positioned on the transport surface and the second fiber layer positioned on the surface, cellulosic fibers, which are less susceptible to thermal fusion than thermoplastic resin fibers, may fly off, causing a change in the basis weight of the fibers in the web. On the other hand, when hot air is applied to a fabric in which the second fiber layer is disposed on the conveying surface side and the first fiber layer is disposed on the surface side, cellulosic fibers are less susceptible to thermal fusion than thermoplastic resin fibers, and so they tend to remain on the conveying surface or get into gaps on the conveying surface, making it impossible to continuously produce nonwoven fabrics or to obtain the desired fiber basis weight, which may result in the inability to consistently produce nonwoven fabrics with the desired texture and absorption rate.

[0005] Furthermore, a nonwoven fabric with a good texture can also be obtained by using a spunlace method, in which fibers in a web are entangled using a high-pressure water stream, instead of the air-through method. However, because the spunlace method entangles the fibers using a high-pressure water stream, it is difficult to ensure the thickness of the produced nonwoven fabric. Furthermore, compared to the air-through method, the spunlace method results in smaller spaces between the fibers, making it difficult to ensure the thickness of the nonwoven fabric. Therefore, it is necessary to improve the absorption performance, such as suppressing rewetting of body fluids and improving the ability to draw in body fluids. Furthermore, if the basis weight of the fibers is increased to ensure the thickness of the nonwoven fabric, the fibers will be further pushed together, thereby reducing the spaces between the fibers and potentially reducing the rate at which body fluids move.

[0006] The present invention has been made in view of the above-mentioned problems, and provides a method for producing a nonwoven fabric for an absorbent article, which can provide a nonwoven fabric that can ensure the desired texture and absorption rate. [Means for solving the problem]

[0007] A method for manufacturing a nonwoven fabric for absorbent articles according to one embodiment includes a web formation process in which a web is formed by laminating in the thickness direction a first fiber layer containing 90% to 100% by weight of thermoplastic resin fibers, a second fiber layer containing thermoplastic resin fibers and cellulosic fibers, and a third fiber layer containing 90% to 100% by weight of thermoplastic resin fibers, and a hot air passing process in which, after the web formation process, hot air is passed through the web with the third fiber layer of the web facing a breathable conveying surface.

[0008] An absorbent article according to one embodiment includes a top sheet that contacts the wearer's skin and a non-skin-side member that contacts the non-skin side of the top sheet. The top sheet is a nonwoven fabric manufactured by the air-through method, in which a first fiber layer, a second fiber layer, and a third fiber layer are laminated in the thickness direction. The first fiber layer contains thermoplastic resin fibers in a ratio of 90% to 100% by weight. The second fiber layer contains thermoplastic resin fibers and cellulosic fibers. The third fiber layer contains thermoplastic resin fibers in a ratio of 90% to 100% by weight. [Brief explanation of the drawings]

[0009] [Figure 1] FIG. 1 is a plan view of an absorbent article according to an embodiment. [Figure 2] FIG. 2 is a cross-sectional view taken along the line AA shown in FIG. [Figure 3] FIG. 3 is a schematic cross-sectional view of the top sheet. [Figure 4] FIG. 4 is a diagram illustrating a method for manufacturing a nonwoven fabric for an absorbent article according to an embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0010] (1) Overview of the embodiment At least the following matters will become clear from the description of this specification and the accompanying drawings. A first aspect of the invention is a method for manufacturing a nonwoven fabric for absorbent articles. The manufacturing method includes a web-forming step of forming a web by laminating a first fiber layer containing 90 to 100% by weight of thermoplastic resin fibers, a second fiber layer containing thermoplastic resin fibers and cellulosic fibers, and a third fiber layer containing 90 to 100% by weight of thermoplastic resin fibers in the thickness direction, and a hot air passing step after the web-forming step of passing hot air through the web while the third fiber layer of the web is placed facing a breathable conveying surface. According to this aspect, the third fiber layer of the web is placed facing the conveying surface, and hot air is applied in this state. Therefore, compared to a configuration in which the second fiber layer containing cellulosic fibers faces the conveying surface, the cellulosic fibers are less likely to come into direct contact with the conveying surface, and in addition, a distance corresponding to the thickness of the third fiber layer can be secured between the cellulosic fibers and the conveying surface. This prevents problems such as cellulosic fibers adhering to the conveying surface or getting into the voids in the conveying surface that ensure breathability. Furthermore, because hot air is applied with the first fiber layer positioned on the surface side, scattering of cellulosic fibers is prevented. Therefore, a nonwoven fabric with the desired texture and absorption rate can be obtained by the air-through method while preventing problems such as cellulosic fibers scattering or adhering to the conveying surface.

[0011] The invention according to Aspect 2 may be the invention according to Aspect 1, but may have the following features. In the web forming step, the basis weight of the thermoplastic resin fiber in the first fiber layer is made higher than the basis weight of the cellulosic fiber in the second fiber layer. According to this aspect, a sufficient distance can be maintained between the surface to which hot air is applied and the second fiber layer, thereby further suppressing scattering of cellulosic fibers. Furthermore, in an absorbent article in which the first fiber layer is arranged on the surface that contacts the skin, a sufficient distance can be maintained between the second fiber layer, which is mainly composed of cellulosic fibers, and the skin. Cellulosic fibers are less likely to be arranged on the surface that contacts the skin, which suppresses pilling of the cellulosic fibers when the nonwoven fabric rubs against the skin, thereby maintaining a pleasant feel against the skin. Furthermore, in an absorbent article in which the first fiber layer is arranged on the surface that contacts the skin, the relatively high basis weight of the thermoplastic resin fiber in the first fiber layer ensures sweat absorption and body fluid absorption, and suppresses residual liquid.

[0012] The invention according to Aspect 3 may be the invention according to Aspect 1 or Aspect 2, and have the following features: In the web forming step, the basis weight of the thermoplastic resin fibers in the third fiber layer is made higher than the basis weight of the cellulosic fibers in the second fiber layer. According to this aspect, the distance between the conveying surface and the second fiber layer can be secured, and problems such as the cellulosic fibers remaining on the conveying surface or entering voids in the conveying surface that ensure breathability can be further suppressed.

[0013] The invention according to aspect 4 may be the invention according to any one of aspects 1 to 3, and have the following features. In the web forming process, the basis weight of the fibers of the first fiber layer is made higher than the basis weight of the fibers of the third fiber layer. According to this aspect, in an absorbent article in which the first fiber layer is arranged on the skin-contacting surface, a sufficient distance can be secured between the second fiber layer, which is mainly composed of cellulosic fibers, and the skin. Cellulosic fibers are less likely to be arranged on the skin-contacting surface, which reduces the fluffing of the cellulosic fibers when the nonwoven fabric rubs against the skin, maintaining a comfortable feel against the skin. In addition, the basis weight of the third fiber layer is relatively low, which promotes the migration of body fluids from the second fiber layer side to the non-skin side, thereby preventing rewetting of body fluids.

[0014] A fifth aspect of the invention may be the invention of any one of the first to fourth aspects, and may have the following features. The invention further includes an entangling step, which involves spraying a high-temperature fluid onto the web to entangle the thermoplastic resin fibers before the hot air passing step. The entangling step forms fused portions by fusing the thermoplastic resin fibers together, and the number of fused portions per unit area in the third fiber layer is greater than the number of fused portions per unit area in the first fiber layer. According to this aspect, the third fiber layer facing the conveying surface has many fused portions, which can prevent unfused fibers from remaining on the conveying surface or from entering voids in the conveying surface. Furthermore, by forming many fused portions in the third fiber layer, which is one of the first and third fiber layers constituting the outer surface of the nonwoven fabric, and forming fewer fused portions in the first fiber layer, which is the other, the nonwoven fabric can have both a relatively hard surface and a relatively soft surface. An absorbent article in which the first fiber layer is disposed so as to contact the skin can improve the feel of the absorbent article against the skin.

[0015] The invention according to aspect 6 may be the invention according to any one of aspects 1 to 5, and may have the following features. After the hot air passing step, the method includes a concave-convex forming step of pressing the web to form, on one surface of the first fiber layer and the third fiber layer, a plurality of convex portions protruding outward in the thickness direction and a plurality of concave portions recessed inward in the thickness direction between the convex portions. The thickness of the fiber layer disposed on one surface of the first fiber layer and the third fiber layer is thicker than the thickness of the fiber layer disposed on the other surface. Because the thickness of the fiber layer (first fiber layer or third fiber layer) on one side on which the convex portions and concave portions are formed is relatively thick, a predetermined thickness can be maintained even in the concave portions, and exposure of cellulosic fibers to the outer surface of the nonwoven fabric can be suppressed. Furthermore, compared to the fiber layer on one side, the fiber layer on the other side (third fiber layer or first fiber layer) is less likely to be unevenly formed due to the formation of the convex portions and concave portions, making it easier to ensure a uniform thickness throughout the fiber layer. Therefore, by reducing the thickness of the fiber layer on the other side, the weight of the fiber can be reduced, thereby reducing manufacturing costs.

[0016] The invention according to aspect 7 may be the invention according to any one of aspects 1 to 6, and may have the following features. After the hot air passing step, the method includes a concave-convex forming step of pressing the web to form, on one surface of the first fiber layer and the third fiber layer, a plurality of convex portions protruding outward in the thickness direction and a plurality of concave portions recessed inward in the thickness direction between the convex portions. In the concave-convex forming step, the convex portions and the concave portions are provided so as to extend in the front-rear direction and be spaced apart in the width direction, and the convex portions and the concave portions are provided in the center of the web in the width direction, rather than on the sides of the web in the width direction. Providing the convex portions and the concave portions extending in the front-rear direction and spaced apart in the width direction W shortens the width of the web, which may increase manufacturing costs. Therefore, by providing convex and concave portions in areas that are likely to come into contact with the excretory opening (vaginal opening, urinary opening) (the center in the width direction of the web) and not providing convex and concave portions in areas that are unlikely to come into contact with the excretory opening (outer parts of the web), manufacturing costs can be reduced. Furthermore, by using a nonwoven fabric as the top sheet, the presence of the convex and concave portions can reduce the contact area of ​​the top sheet with the skin.

[0017] The invention according to aspect 8 may be the invention according to any one of aspects 1 to 7, and may have the following features. In the web forming step, the length of the first fiber layer in an orthogonal direction perpendicular to the web conveying direction is made longer than the length of the second fiber layer in the orthogonal direction. By making the length of the first fiber layer in the orthogonal direction longer than the length of the second fiber layer in the orthogonal direction, the entire second fiber layer can be covered by the first fiber layer. The second fiber layer contains a relatively large amount of cellulosic fibers, and therefore the fusion properties of the fibers are weak. If the hot air is directly applied to the second fiber layer in the hot air passing step, the cellulosic fibers may curl up. However, by covering the second fiber layer with the first fiber layer, the curling up of the cellulosic fibers in the second fiber layer can be suppressed.

[0018] A ninth aspect of the invention may be the invention of any one of the first to seventh aspects, and may have the following features. In the web forming step, the length of the third fiber layer in an orthogonal direction perpendicular to the web conveying direction is made longer than the length of the second fiber layer in the orthogonal direction. By making the length of the third fiber layer in the orthogonal direction longer than the length of the second fiber layer in the orthogonal direction, the entire second fiber layer can be covered by the third fiber layer. The second fiber layer contains a relatively large amount of cellulosic fibers, which results in poor fiber fusion. If the cellulosic fibers come into contact with a conveying surface such as a mesh belt during the hot air passing step, the cellulosic fibers may become caught in the voids on the conveying surface. However, by covering the second fiber layer with the third fiber layer, the cellulosic fibers of the second fiber layer can be prevented from becoming caught on the conveying surface.

[0019] A tenth aspect of the invention relates to an absorbent article comprising a top sheet that contacts the wearer's skin and a non-skin-side member that contacts the non-skin side of the top sheet. The top sheet is a nonwoven fabric manufactured by the air-through method, in which a first fiber layer, a second fiber layer, and a third fiber layer are laminated in the thickness direction. The first fiber layer contains 90% to 100% by weight of thermoplastic resin fibers. The second fiber layer contains thermoplastic resin fibers and cellulosic fibers. The third fiber layer contains 90% to 100% by weight of thermoplastic resin fibers. According to this aspect, the surface that contacts the skin is either the first fiber layer or the third fiber layer, ensuring a constant distance between the skin and the second fiber layer. When the nonwoven fabric rubs against the skin, fluffing of the cellulosic fibers is suppressed, maintaining a pleasant feel against the skin. Furthermore, body fluids discharged onto the top sheet can be quickly absorbed by the first fiber layer or the third fiber layer, ensuring body fluid absorption and reducing residual fluid. The surface that comes into contact with the non-skin-side member is the other of the first fiber layer or the third fiber layer. Both the first fiber layer and the third fiber layer contain a large amount of thermoplastic resin fibers, and have higher liquid transfer properties than the second fiber layer. This ensures liquid transfer from the top sheet to the non-skin-side member. The cellulosic fibers in the second fiber layer retain body fluids, improving the body fluid absorption performance. Furthermore, the second fiber layer is sandwiched between the first fiber layer and the third fiber layer, making it less likely to come into direct contact with the skin. This reduces stickiness caused by the cellulosic fibers retaining body fluids coming into contact with the skin.

[0020] (2) Method for manufacturing absorbent articles and nonwoven fabrics for absorbent articles according to embodiments An absorbent article 1 and a method for manufacturing a nonwoven fabric for an absorbent article according to an embodiment will be described below with reference to the drawings. In the following description of the drawings, identical or similar parts are designated by identical or similar reference numerals. It should be noted, however, that the drawings are schematic, and the dimensional ratios and the like may differ from those of the actual product. Therefore, specific dimensions and the like should be determined with reference to the following description. Furthermore, the drawings may include parts with different dimensional relationships and ratios. The absorbent article 1 may be a sanitary napkin, panty liner, incontinence pad, fecal pad, disposable diaper, shorts-type napkin, or other absorbent article. The absorbent article 1 may be an article that is used by being attached to a worn article such as underwear, or may be an absorbent article that is used without being attached to a worn article. The absorbent article 1 of the embodiment is a sanitary napkin. In the following description of the drawings, identical or similar parts are designated by identical or similar reference numerals. It should be noted, however, that the drawings are schematic, and the dimensional ratios and the like may differ from those of the actual product. Therefore, specific dimensions should be determined with reference to the following explanation. Also, the drawings may contain parts with different dimensional relationships and ratios. Also, in the cross-sectional views, the components are shown separated for ease of explanation, but in the actual product, the components are in contact with each other.

[0021] FIG. 1 is a plan view of the absorbent article 1 as seen from the skin side T1. FIG. 2 is a cross-sectional view taken along line AA in FIG. 1. FIG. 3 is a schematic cross-sectional view of the top sheet 10. FIG. 3(A) is a diagram schematically showing a cross-section of a top sheet in which no protrusions 18 or recesses 19 are formed. FIG. 3(B) is a diagram schematically showing a cross-section of a first form of top sheet in which protrusions 18 and recesses 19 are formed. FIG. 3(C) is a diagram schematically showing a cross-section of a second form of top sheet in which protrusions 18 and recesses 19 are formed. Here, the "skin side" corresponds to the side that faces the wearer's skin during use. The "non-skin side" corresponds to the side that faces away from the wearer's skin during use. The absorbent article 1 has a front-to-rear direction L, a width direction W, and a thickness direction T that are perpendicular to each other. In the front-to-rear direction L of the absorbent article 1, the side that contacts the user's lower abdominal region is referred to as the "front side," and the side that contacts the user's buttocks is referred to as the "rear side."

[0022] In the present invention, the outer portion refers to a portion occupying a certain range in the width direction W, including the outer edge in the width direction W, and the outer edge refers to the outer edge in the width direction W. The outer edge of a component occupying a certain range in the front-to-rear direction is an edge connecting points located on the outer side in the width direction of the component, over the entire component. In the present invention, the inner portion refers to a portion occupying a certain range in the width direction W, including the inner edge in the width direction W, and the inner edge refers to the inner edge in the width direction W. The inner edge of a component occupying a certain range in the front-to-rear direction is an edge connecting points located on the inner side in the width direction of the component, over the entire component. In the present invention, the front end and rear end refer to portions occupying a certain range in the front-to-rear direction L, including edges in the front-to-rear direction L, and the front edge and rear edge are edges in the front-to-rear direction L. The outer end refers to the front end and rear end, and the outer edge refers to the front edge and rear edge. The inner side refers to a side that includes the inner side edge and extends along the front-to-rear direction L. The outer side is a side that includes the outer edge and extends along the front-to-rear direction L. In this specification, the term "along the front-to-rear direction L" means a direction that has an angle of less than 45° with respect to the front-to-rear direction L, and the term "along the width direction W" means a direction that has an angle of less than 45° with respect to the width direction W.

[0023] The absorbent article 1 has front side regions S1, rear side regions S2, and a crotch region S3. The crotch region S3 is located in the crotch of the absorbent article when the absorbent article 1 is worn on the worn article, and is positioned between the wearer's legs. The front side regions S1 are located forward of the crotch region S3. The front edge of the front side region S1 defines the front edge of the absorbent article 1. The rear side region S2 is located rearward of the crotch region S3. The rear edge of the rear side region S2 defines the rear edge of the absorbent article 1. The crotch region S3 may be the region where the wings are provided in an absorbent article having wings, or may be the region where the constricted portion is provided in an absorbent core having a constricted portion that is constricted inward in the width direction. Alternatively, the crotch region S3 may be the central region among three equal regions obtained by dividing the absorbent article in the front-to-rear direction L.

[0024] The absorbent article 1 has at least an absorbent core 31, a top sheet 10, and a back sheet 20. The absorbent article 1 has a vertically elongated shape. The top sheet 10 is a sheet that comes into contact with the wearer's skin. The top sheet 10 is a liquid-permeable sheet. The top sheet 10 may be configured to cover the entire skin surface of the absorbent article 1 with a single sheet, as in this embodiment, or may have a center sheet that covers the center of the absorbent core 31 in the width direction W, and side sheets that are positioned outside the center sheet in the width direction W. The top sheet 10 is made of any sheet-like material that has a liquid-permeable structure, such as a nonwoven fabric, a woven fabric, a perforated plastic sheet, or a mesh sheet. The top sheet 10 of this embodiment is made of a nonwoven fabric manufactured by a manufacturing method described below. The top sheet 10 will be described in detail below.

[0025] The back sheet 20 is a liquid-impermeable sheet that is disposed closer to the skin side T2 than the absorbent core 31. The back sheet 20 is a liquid-impermeable sheet. The back sheet 20 can be made of a laminated nonwoven fabric mainly made of polyethylene sheet or polypropylene, a breathable resin film, or a sheet in which a breathable resin film is bonded to a nonwoven fabric such as spunbond or spunlace.

[0026] The absorbent core 31 constitutes the absorbent body. The absorbent core 31 may be made of an absorbent material that absorbs liquid. The absorbent material that constitutes the absorbent core 31 may be formed from, for example, hydrophilic fibers, pulp, and superabsorbent polymers (SAPs). As shown in FIG. 2, the absorbent body may have a core wrap sheet 32 ​​that covers the absorbent core 31, or in a modified example, may not have a core wrap sheet.

[0027] The absorbent article 1 has a non-skin side member 40 that contacts the non-skin side of the top sheet 10. The non-skin side member 40 is a member that contacts the non-skin side of the top sheet 10, and in this embodiment is constituted by a core wrap sheet 32. Examples of the non-skin side member 40 include a second sheet and an absorbent body (core wrap sheet). In an embodiment in which multiple members contact the non-skin side of the top sheet 10, each of the multiple members may constitute a non-skin side member 40. The top sheet 10 and the non-skin side member 40 may be joined by an adhesive or the like, or may overlap without being joined.

[0028] The absorbent article 1 of this embodiment is configured to ensure that the top sheet 10 has a good feel against the skin and that liquid can be transferred from the top sheet 10 to the non-skin-side member 40. Next, the configuration for ensuring liquid transfer will be described in detail. The top sheet 10 is a nonwoven fabric manufactured by the air-through method, and includes a first fiber layer 11, a second fiber layer 12, and a third fiber layer 13. As shown in FIG. 3(A), the first fiber layer 11, the second fiber layer 12, and the third fiber layer 13 are laminated in the thickness direction T. The air-through method is an example of a method for manufacturing a nonwoven fabric, and includes a hot air passing step in which a web of laminated fibers is formed and hot air (for example, gas at 100°C or higher) is passed through the web. The method for manufacturing the top sheet 10 will be described in detail below.

[0029] The first fiber layer 11 contains thermoplastic resin fibers 51 in a proportion of 90 to 100% by weight, based on the total weight of the first fiber layer 11. Examples of the thermoplastic resin fibers 51 include fiber-forming ester polymers, olefin polymers, amide polymers, acrylic polymers, vinyl alcohol polymers, copolymers containing these as main components, and blends of these polymers. When the weight percentage of the thermoplastic resin fibers 51 is 90% or more but less than 100%, the first fiber layer 11 may contain cellulosic fibers such as rayon as fibers other than the thermoplastic resin fibers 51. The proportion of fibers constituting the fiber layer can be calculated by pulling out a predetermined number of fibers (e.g., 100 fibers) from the surface of the nonwoven fabric and calculating the weight ratio of the pulled fibers. When 90% or more by weight of the first fiber layer 11 is thermoplastic resin fibers 51, stickiness to the skin is reduced and the skin surface of the topsheet 10 can be kept dry compared to a first fiber layer 11 containing a large amount of cellulosic fibers 52. Furthermore, because the first fiber layer 11 mainly contains thermoplastic resin fibers 51, body fluids drawn into the first fiber layer 11 can be quickly transferred to the non-skin side, improving fluid drainage. Furthermore, compared to a configuration in which 90% by weight or more of the first fiber layer is thermoplastic resin fibers 51 and the first fiber layer 11 contains a large amount of cellulosic fibers 52, the cellulosic fibers 52 are not arranged on the skin side of the top sheet 10, reducing the probability that the cellulosic fibers will come into direct contact with the skin, thereby suppressing pilling of the cellulosic fibers 52.

[0030] The second fiber layer 12 includes thermoplastic resin fibers 51 and cellulosic fibers 52. The thermoplastic resin fibers 51 may be the same as the thermoplastic resin fibers 51 of the first fiber layer 11. The cellulosic fibers 52 may be natural fibers such as hemp; or regenerated fibers such as viscose rayon, cupra, and solvent-spun cellulosic fibers (e.g., lentilized lyocell (registered trademark) and Tencel (registered trademark)). The proportions of the thermoplastic resin fibers 51 and the cellulosic fibers 52 in the second fiber layer 12 are not particularly limited, but preferably, based on the total weight of the second fiber layer 12, the thermoplastic resin fibers 51 may be 30 to 90 wt % and the cellulosic fibers 52 may be 10 to 70 wt %. When the second fiber layer 12 contains 10 wt % or more of the cellulosic fibers 52, the sweat absorption performance of the nonwoven fabric can be improved. Furthermore, since the second fiber layer 12 contains 30% or more of the thermoplastic resin fibers 51, the thermoplastic resin fibers 51 are mixed in the cellulosic fibers 52, and the sheet strength of the second fiber layer 12 can be maintained.

[0031] The third fiber layer 13 contains thermoplastic resin fibers 51 in a proportion of 90% to 100% by weight based on the total weight of the third fiber layer 13. The thermoplastic resin fibers 51 may be the same as the thermoplastic resin fibers 51 of the first fiber layer 11. When the weight percentage of the thermoplastic resin fibers 51 is 90% or more but less than 100%, the third fiber layer 13 may contain cellulosic fibers such as rayon as fibers other than the thermoplastic resin fibers 51.

[0032] The basis weight of the fibers in the first fiber layer 11 is 9 g / m 2 More than 18g / m 2 The basis weight of the fibers of the second fiber layer 12 may be 9 g / m or less. 2 More than 18g / m 2 The basis weight of the fibers of the third fiber layer 13 may be 6 g / m or less. 2 More than 12g / m 2 The topsheet 10 of this embodiment is configured as follows: The first fiber layer 11 contains 100% by weight of thermoplastic resin fibers 51, and the basis weight of the entire first fiber layer 11 is 12 g / m 2The second fiber layer 12 contains 50% by weight of thermoplastic resin fibers 51 and 50% by weight of cellulosic fibers 52, and the basis weight of the entire second fiber layer 12 is 12 g / m 2 The third fiber layer 13 contains 100% by weight of thermoplastic resin fibers 51, and the basis weight of the entire third fiber layer 13 is 9 g / m 2 is.

[0033] A first fiber layer 11 and a third fiber layer 13 are disposed on the outer surfaces (skin-facing surface and non-skin-facing surface) of the top sheet 10 of this embodiment. The cellulosic fibers 52 are less likely to heat-seal than the thermoplastic resin fibers 51, and may be more likely to come off or fluff in the nonwoven fabric. On the other hand, the thermoplastic resin fibers 51 are more likely to heat-seal when heated during the production of the nonwoven fabric, and are less likely to come off or fluff in the nonwoven fabric. Because one of the first fiber layer 11 and the third fiber layer 13 comes into contact with the wearer's skin, fluffing of the cellulosic fibers 52 is suppressed when the nonwoven fabric rubs against the skin, maintaining a pleasant feel against the skin.

[0034] The first fiber layer 11 and the third fiber layer 13, which have a high proportion of thermoplastic resin fibers 51, have a higher liquid absorption ability than the second fiber layer 12, which has a high proportion of cellulosic fibers 52. Because one of the first fiber layer 11 and the third fiber layer 13 is positioned on the wearer's skin side (the side from which body fluids are excreted), body fluids can be quickly absorbed into the top sheet 10, reducing residual liquid and keeping the surface of the top sheet 10 dry. The other of the first fiber layer 11 or the third fiber layer 13 comes into contact with the non-skin-side member 40. Both the first fiber layer 11 and the third fiber layer 13 contain a large amount of thermoplastic resin fibers 51, and have a higher liquid transfer ability than the second fiber layer 12. This ensures liquid transfer from the top sheet 10 to the non-skin-side member 40. Although the top sheet 10 of this embodiment has the first fiber layer 11 positioned on the skin-side surface, in a modified example, the third fiber layer 13 may be positioned on the skin-side surface.

[0035] The second fiber layer 12 contains cellulosic fibers 52. The cellulosic fibers 52 retain body fluids, thereby improving the body fluid absorption performance. Furthermore, the second fiber layer 12 is sandwiched between the first fiber layer 11 and the third fiber layer 13 and is therefore less likely to come into direct contact with the skin. Therefore, the cellulosic fibers 52 of the second fiber layer 12 retain body fluids, thereby maintaining the body fluid absorption performance, and reducing stickiness on the skin caused by the cellulosic fibers 52 retaining the body fluids coming into contact with the skin. To reduce stickiness on the skin, it is preferable that the first fiber layer 11 does not contain cellulosic fibers 52. Furthermore, to quickly transfer body fluids to the absorbent body without retaining them in the second fiber layer 12, it is preferable that the third fiber layer 13 also does not contain cellulosic fibers 52.

[0036] The cellulosic fibers 52 of the second fiber layer 12 may be rayon fibers. The cellulosic fibers 52 may not be present in the nonwoven fabric as fiber clumps, but may be dispersed throughout the entire second fiber layer 12. That is, the cellulosic fibers may be distributed continuously and in layers in the planar directions (front-to-back direction L and width direction). Rayon fibers are particularly good at absorbing sweat in addition to excrement such as menstrual blood, and can improve sweat absorption performance. Because the rayon fibers are dispersed throughout the planar direction, sweat can be absorbed throughout the entire surface of the top sheet 10. Furthermore, because the cellulosic fibers 52 are not present in the nonwoven fabric as fiber clumps, but are dispersed throughout the entire nonwoven fabric, it is possible to obtain a nonwoven fabric with little variation in fiber basis weight and good texture. In addition, compared to natural fibers such as cotton, the fiber length of rayon fibers can be controlled, which means that small pieces of natural fibers are less likely to remain on the production line, making it possible to stably produce nonwoven fabrics with better texture than other natural fibers. The fiber length of rayon may be 20 mm or more and 60 mm or less, and preferably 35 mm or more and 50 mm or less.

[0037] The topsheet 10 may contain 50% by weight or more and less than 90% by weight of thermoplastic resin fibers 51, based on the total weight of the topsheet 10. Furthermore, the topsheet 10 may contain 10% by weight or more and 40% by weight or less of cellulosic fibers 52, based on the total weight of the topsheet 10.

[0038] The bond strength between the first fiber layer 11 and the second fiber layer 12 is lower than the bond strength between the top sheet 10 and the non-skin side member 40. The bond strength between the top sheet 10 and the non-skin side member 40 is the bond strength between the fiber layer constituting the non-skin side of the top sheet 10 and the non-skin side member 40. For example, in a configuration in which the third fiber layer 13 constitutes the non-skin side of the top sheet 10, as in the present embodiment, it is the bond strength between the third fiber layer 13 and the non-skin side member 40. In a modified configuration in which the first fiber layer 11 constitutes the non-skin side of the top sheet 10, it is the bond strength between the first fiber layer 11 and the non-skin side member 40. The first fiber layer 11 and the second fiber layer 12 may be bonded by fiber intersection or fiber fusion without being bonded by adhesive. On the other hand, the top sheet 10 and the non-skin side member 40 may be bonded by adhesive or by heat fusion using a compressed section or the like. Furthermore, when comparing bond strength, the strength when peeled in the same direction can be compared. For example, this can be evaluated using the following method. (1) Color cellulosic fibers such as rayon fibers and check the interlayer thickness between the first and second fiber layers. (2) Prepare another nonwoven fabric from the same lot (80 mm in the peel direction x 25 mm in the width direction). Peel the interlayer thickness confirmed in (1) by hand to create a 30 mm grip. (3) Set the conditions for a constant-speed extension tensile tester (Shimadzu Autograph). Conditions: Peel test mode, grip spacing 30 mm, chuck spacing 50 mm, tensile speed 100 mm / min. (4) Clamp the upper and lower layers in the upper and lower chucks of the tensile tester, respectively, and measure. (1) Since the interlayer can be easily distinguished, the peel strength between the top sheet and non-skin-side component can be measured using the same procedures as in (2) to (4) above, omitting (1) above. Five samples are measured, and the average values ​​are compared. Furthermore, if it is not possible to obtain a sample with the specified dimensions (width direction and peeling direction), a sample with a measurable dimension shall be obtained and evaluated, and the evaluation results shall be converted to a width length of 25 mm for comparison.

[0039] Because the bond strength between the first fiber layer 11 and the second fiber layer 12 is relatively low, the first fiber layer 11 easily conforms to the skin when the top sheet 10 rubs against it, preventing a decrease in the feel of the top sheet 10 against the skin. Furthermore, in nonwoven fabrics manufactured by integrating the fiber layers, such as air-through nonwoven fabrics, fibers that bridge the first fiber layer 11 and the second fiber layer 12 are arranged at least by fiber intersections. This prevents separation of the first fiber layer 11 and the second fiber layer 12 even when the bond strength between the first fiber layer 11 and the second fiber layer 12 is relatively low, thereby maintaining the performance of the nonwoven fabric. Because the bond strength between the top sheet 10 and the non-skin-side member 40 is relatively high, delamination between the top sheet 10 and the non-skin-side member 40 is prevented, misalignment between the top sheet 10 and the non-skin-side member 40 is suppressed, and bodily fluid transfer is ensured. This allows the absorption performance of the absorbent article 1 to be maintained.

[0040] The weight ratio of the thermoplastic resin fibers 51 in the third fiber layer 13 may be higher than the weight ratio of the thermoplastic resin fibers 51 in the second fiber layer 12. The third fiber layer 13 is disposed on the non-skin side T2 of the second fiber layer 12, and because the third fiber layer 13 has a high weight ratio of the thermoplastic resin fibers 51, body fluids drawn into the second fiber layer 12 are easily drawn into the third fiber layer 13. In particular, when the third fiber layer 13 has a high weight ratio of the thermoplastic resin fibers 51 and is relatively thin, the fiber density of the third fiber layer is increased, further improving the body fluid drawing ability. This further reduces fluid residue on the skin side of the top sheet 10, keeping the skin side of the top sheet 10 dry. The first fiber layer 11 and the third fiber layer 13, which have a high weight ratio of thermoplastic resin fibers 51, are arranged on the skin side and the non-skin side of the top sheet 10, respectively, and the strength of both sides of the top sheet 10 is improved by fusion of the thermoplastic resin fibers 51, thereby maintaining the functionality (such as the ability to absorb body fluids) of the top sheet 10. Furthermore, the formation of fused fiber portions on both sides of the top sheet 10 prevents fibers from coming off the top sheet 10.

[0041] The bond strength between the first fiber layer 11 and the second fiber layer 12 along the width direction W may be higher than the bond strength between the first fiber layer 11 and the second fiber layer 12 along the front-to-back direction L. When worn, the absorbent article 1 is subjected to forces from various directions, such as being pinched between the legs when sitting and being pulled by leg movement when walking. At this time, the absorbent article 1 is more susceptible to forces along the width direction W than to forces along the front-to-back direction L. Because the bond strength between the first fiber layer 11 and the second fiber layer 12 along the width direction W is high, unintentional peeling between the first fiber layer 11 and the second fiber layer 12 due to external forces can be suppressed. Furthermore, because the bond strength between the first fiber layer 11 and the second fiber layer 12 along the front-to-back direction L is low, when the first fiber layer 11 rubs against the skin, the first fiber layer 11 and the second fiber layer 12 partially weaken or peel in the front-to-back direction L, which allows the first fiber layer 11 to easily conform to the skin and improves the feel against the skin.

[0042] The non-skin side member 40 is a core wrap sheet 32, and the bond strength between the core wrap sheet 32 ​​and the absorbent core 31 along the width direction W may be lower than the bond strength between the first fiber layer 11 and the second fiber layer 12 along the width direction. The absorbent article 1 is more susceptible to force along the width direction W than to force along the front-to-back direction L. In this case, the skin side T1 of the absorbent article 1 is more susceptible to force from the legs than the non-skin side T2. The shape of the absorbent article 1 in a cross-section taken along the width direction W is a trapezoid or triangle in which the length in the width direction W of the skin side T1 is shorter than the length in the width direction W of the non-skin side T2. Because the bond strength between the first fiber layer 11 and the second fiber layer 12 located on the skin side T1 in the top sheet 10 along the width direction W is high, unintentional peeling of the first fiber layer 11 and the second fiber layer 12 due to external force can be suppressed. Furthermore, even if the bond strength in the width direction W between the core wrap sheet 32 ​​located on the non-skin side T2 and the absorbent core 31 is relatively low, the external force received is small and the bonded state can be maintained.

[0043] The top sheet 10 and the non-skin side member 40 may be joined by adhesives 35 (see FIG. 3 ) spaced apart in the planar direction. The spacing between the adhesives 35 joining the top sheet 10 and the non-skin side member 40 may be shorter than the average fiber length of the fibers arranged on the non-skin side of the top sheet 10. According to this embodiment, the fibers arranged on the non-skin side of the top sheet 10 are likely to be arranged overlapping the adhesives 35 and be easily bonded by the adhesives 35. As a result, the fibers arranged on the non-skin side of the top sheet 10 are less likely to come out of the nonwoven fabric and are more likely to remain within the top sheet 10, thereby maintaining the performance of the absorbent article. Furthermore, the fibers are not bonded between the adhesives 35, which increases the degree of freedom of fiber deformation. This prevents delamination between the first fiber layer 11 and the second fiber layer 12 and further improves the conformability of the top sheet 10. In addition, the high degree of freedom of fiber deformation prevents fiber breakage and reduces deterioration of the feel against the skin due to fluffing of the cut fibers. In this embodiment, the third fiber layer 13 is disposed on the non-skin side of the top sheet 10, and the third fiber layer 13 contains 100% by weight of thermoplastic resin fibers. Therefore, the spacing between the adhesives 35 is configured to be shorter than the average fiber length of the thermoplastic resin fibers 51. In an embodiment in which the spacing between the adhesives 35 varies, it is sufficient that the average fiber length is configured to be shorter than the spacing between at least some of the adhesives 35. The average fiber length is measured by pulling out a predetermined number of fibers (e.g., 100 fibers) from the non-skin side of the top sheet 10 with tweezers or the like, and calculating the average length of the pulled fibers.

[0044] The distance between the adhesives joining the top sheet 10 and the non-skin side member 40 may be shorter than the average fiber length of the cellulosic fibers 52. Cellulosic fibers 52 are less susceptible to thermal fusion than thermoplastic resin fibers, and when formed into a nonwoven fabric, they are more likely to come off than thermoplastic resin fibers 51. Because the distance between the adhesives is shorter than the average fiber length of the cellulosic fibers 52, the cellulosic fibers 52 are bonded by the adhesive, and it is possible to prevent the cellulosic fibers 52 from coming off.

[0045] In a modified example, the top sheet 10 and the non-skin side member 40 may be joined by compressed sections (not shown) spaced apart in the planar direction. The distance between the compressed sections may be shorter than the average fiber length of the fibers arranged on the non-skin side of the top sheet 10. According to this embodiment, the fibers arranged on the non-skin side of the top sheet are likely to overlap the compressed sections and be easily bonded by the compressed sections. As a result, the fibers arranged on the non-skin side of the top sheet 10 are less likely to come out of the nonwoven fabric and are more likely to remain within the top sheet 10, maintaining the performance of the absorbent article. Furthermore, the fibers are not bonded between the compressed sections, which increases the degree of freedom for fiber deformation. This prevents delamination between the first fiber layer 11 and the second fiber layer 12 and further improves the conformability of the top sheet 10. In addition, the high degree of freedom for fiber deformation prevents fiber breakage and reduces deterioration of the feel against the skin due to fluffing of the cut fibers.

[0046] In the top sheet 10, the thickness of the first fiber layer 11 may be equal to or greater than the thickness of the second fiber layer 12. According to this embodiment, the first fiber layer 11 is thick, ensuring a sufficient distance between the second fiber layer 12, which is primarily composed of cellulosic fibers 52, and the skin. This reduces liquid retention on the skin side of the top sheet 10, keeping the skin side of the top sheet 10 dry. Furthermore, because the first fiber layer 11 primarily contains thermoplastic resin fibers 51, bodily fluid absorbed into the first fiber layer 11 can be quickly transferred to the non-skin side T2, improving liquid drainage.

[0047] In the top sheet 10, the thickness of the third fiber layer 13 may be equal to or greater than the thickness of the second fiber layer 12. According to this embodiment, the third fiber layer 13, which is primarily composed of thermoplastic resin fibers 51, is thick, which can improve the transfer of body fluids from the top sheet 10 to the non-skin side member 40. Furthermore, the thickness of the first fiber layer 11 may be equal to or greater than the thickness of the third fiber layer 13. When the nonwoven fabric rubs against the skin, fluffing of the cellulosic fibers 52 is suppressed, thereby maintaining a good feel against the skin. Furthermore, because the thickness of the third fiber layer 13 is relatively small, the transfer of body fluids from the second fiber layer 12 side to the non-skin side member 40 is promoted, and rewetting of body fluids can be suppressed.

[0048] The thicknesses of the first fiber layer 11, the second fiber layer 12, and the third fiber layer 13 are measured using the following method: (1) The absorbent article is frozen with liquid nitrogen, cut in the cross-sectional direction with a cutter, and allowed to dry. (2) The article is immersed in PAC fabric dye dissolved in water at 40 to 50°C for one hour, then removed and allowed to dry naturally. (3) Because the dyed portion becomes a cellulosic fiber, the layer containing the dyed portion is identified as the second fiber layer, and the layers on either side of the second fiber layer in the thickness direction are identified as the first fiber layer and the third fiber layer. (4) An enlarged photograph of the cross section is taken using a Keyence VHX-7000 digital microscope, and the distance between two points for planar measurement is selected to measure the thickness of each fiber layer of the nonwoven fabric. (5) For each nonwoven fabric, distances are measured at 10 random points, and the average value is used as the thickness. When comparing the thicknesses of each fiber layer, comparisons are made at positions where the protrusions 18 and recesses 19 are not formed.

[0049] As shown in Figure 3(B), the skin surface of the top sheet 10 may be formed with a plurality of protruding portions 18 that protrude toward the skin side, and a plurality of recessed portions 19 that are recessed between the protruding portions 18 toward the non-skin side T2. The protruding portions 18 may protrude toward the skin side T1 and be solid. As used herein, "solid" means that there are no spaces within the protruding portions 18 where the fiber density is significantly lower than the surrounding area, which would prevent the movement of liquid. If the difference in height between the highest portion 16, which has the highest height on the skin surface of the top sheet, and the deepest portion 17, which has the lowest height on the skin surface of the top sheet, is d, then the portions that protrude upward from a height of d / 2 from the deepest portion 17 can be called protruding portions 18, and the portions that recess downward can be called recessed portions 19.

[0050] In the top sheet 10, the thickness Td1 of the first fiber layer 11 in the recesses 19 is thinner than the thickness Tc1 of the first fiber layer 11 in the protrusions 18. Here, the thickness Td1 of the first fiber layer 11 in the recesses 19 is the thickness of the first fiber layer 11 in the deepest parts 17, and the thickness Tc1 of the first fiber layer 11 in the protrusions 18 is the thickness of the first fiber layer 11 at the highest parts 16. The dimensions of the protrusions 18 can be, for example, a width of 0.25 to 5 mm, a height of 0.25 to 5 mm, and a pitch of 0.5 to 10 mm. These dimensions of the protrusions 18 can be measured from a planar photograph or planar image of the top sheet 10 in an unpressurized state, which is observed at a magnification using a magnification observation means such as a scanning electron microscope.

[0051] The multiple convex portions 18 are formed as multiple ridges extending continuously in the front-to-rear direction L, and the multiple recessed portions 19 are adjacent to the ribs in the width direction W (i.e., located between adjacent ribs in the width direction W) and may be formed as multiple grooves extending continuously in the front-to-rear direction L. Because the topsheet 10 has such a ridge-groove structure, it has excellent cushioning properties in the thickness direction T, feels good against the skin, and can diffuse body waste along the front-to-rear direction L along which the ribs and grooves extend. The convex portions 18 may be formed in at least the first fiber layer 11 and the second fiber layer 12, or may be formed in the first fiber layer 11, the second fiber layer 12, and the third fiber layer 13.

[0052] The fiber density of the recesses 19 may be higher than the fiber density of the protrusions 18. The spacing between the protrusions 18 may be shorter than the average fiber length of the fibers arranged on the non-skin side of the top sheet 10. The spacing between the protrusions 18 is shorter than the average fiber length of the fibers arranged on the non-skin side of the top sheet 10. Fibers are likely to be arranged in the recesses, which are the spacing between the protrusions. The recesses have a relatively high fiber density, making fiber shedding less likely to occur. Furthermore, while the protrusions 18 are likely to come into contact with the skin, the recesses 19 are less likely to come into contact with the skin, which prevents fiber shedding and keeps the fibers within the top sheet 10, thereby maintaining the performance of the absorbent article. On the other hand, the protrusions 18 have a relatively low fiber density. As a result, there are gaps between the fibers, providing high cushioning and preventing the ends of the fibers from being exposed to the skin side of the top sheet 10, thereby preventing deterioration of the feel against the skin due to pilling. Furthermore, the low fiber density of the protrusions 18 allows for greater freedom of fiber deformation, further improving the conformability of the top sheet. In addition, since the fibers have a high degree of freedom in deformation, breakage of the fibers can be suppressed, and deterioration of the feel on the skin due to fluffing of the cut fibers can be suppressed.

[0053] As shown in Figure 3(B), the non-skin surface of the top sheet 10 may have a substantially flat surface structure. Therefore, the non-skin surface of the top sheet 10 in the areas where the protrusions 18 are arranged may be located at the same position in the thickness direction as the non-skin surface of the surrounding top sheet, or may be located closer to the skin than the non-skin surface of the surrounding top sheet 10. Because the non-skin surface of the top sheet 10 in the areas where the protrusions 18 are arranged does not rise toward the skin relative to the surrounding area, this further promotes the transfer of bodily fluids from the top sheet 10 to the non-skin-side member 40, improving the transfer of bodily fluids to the non-skin side. In addition, because the non-skin surface of the top sheet in the areas where the protrusions 18 are arranged does not rise toward the skin relative to the surrounding area, the protrusions 18 are less likely to be crushed during use of the absorbent article, and the shape of the protrusions 18 is more likely to be maintained.

[0054] As another example, as shown in FIG. 3(C), the protrusions 18 may protrude toward the skin side T1 and have hollows instead of being solid. The non-skin side of the top sheet 10 in the region where the protrusions 18 are arranged may be located closer to the skin side T1 than the non-skin side of the surrounding top sheet 10. The non-skin side of the top sheet 10 in the region where the protrusions 18 are arranged is located closer to the skin side T1 than the non-skin side of the surrounding top sheet 10, and is raised above the surrounding non-skin side member 40. The protrusions 18 may be formed on at least the first fiber layer 11 and the second fiber layer 12, and may also be formed on the third fiber layer 13. When the protrusions 18 rub against the body, the fibers of the first fiber layer 11 and the second fiber layer 12 may come off due to the rubbing. In this case, the unfused cellulosic fibers 52 are more likely to come off than the fused thermoplastic resin fibers 51. However, because spaces are formed between the top sheet 10 and the non-skin side member 40 in the areas where the protrusions 18 are arranged, the cellulosic fibers 52 are likely to be guided into these spaces when they come loose due to friction between the skin and the protrusions 18. This makes it possible to reduce the discomfort felt by the cellulosic fibers 52 exposed from the fiber layer touching the skin.

[0055] The protrusions 18 and recesses 19 extend in the front-to-rear direction L and are spaced apart in the width direction; they may be located in the center of the top sheet 10 in the width direction W, but not on the sides of the top sheet 10 in the width direction W. For example, the protrusions 18 and recesses 19 may be located at least within a range of 20 mm to the left and right from the center of the top sheet 10 in the width direction W, but may not be located at least within a range of 20 mm from the outer edges of the top sheet 10 in the width direction W. Providing the protrusions 18 and recesses 19 reduces the contact area of ​​the top sheet 10 with the skin. On the other hand, providing the protrusions 18 and recesses 19 extending in the front-to-rear direction and spaced apart in the width direction W shortens the length of the top sheet in the width direction W, which may increase manufacturing costs. Therefore, by providing the convex portions 18 and concave portions 19 in areas that are likely to come into contact with the excretory opening (vaginal opening, urinary opening) (the center in the width direction W of the top sheet) and not providing the convex portions 18 and concave portions 19 in areas that are unlikely to come into contact with the excretory opening (the outer portions of the top sheet), manufacturing costs can be reduced. Furthermore, in a configuration in which the outer portions of the top sheet overlap with the side sheets, areas of the top sheet where the convex portions 18 and concave portions 19 are not formed can be joined to the side sheets, allowing for a stable joining of the top sheet 10 and the side sheets.

[0056] As shown in FIG. 3(B), the top sheet 10 may include compressed sections 14. The compressed sections 14 may compress at least the first fiber layer 11 and the second fiber layer 12 in the thickness direction. In this embodiment, the compressed sections 14 are arranged intermittently in the front-to-back direction L in the recesses 19. The compressed sections 14 may be arranged at equal or unequal intervals in the front-to-back direction L in the recesses 19. The compressed sections 14 may be arranged at the same or different positions in the front-to-back direction L in recesses 19 adjacent to each other in the width direction W. The compressed sections 14 may be formed across the first fiber layer 11 and the second fiber layer 12, or across the first fiber layer 11, the second fiber layer 12, and the third fiber layer 13. According to this embodiment, the compressed sections 14 prevent the fibers of the first fiber layer 11 and the second fiber layer 12 from coming loose, thereby suppressing pilling due to fiber loss. Furthermore, the compression parts 14 are provided in the recessed parts 19 that are more recessed than the protruding parts 18, and are less likely to come into direct contact with the body. This can prevent discomfort caused by the compression parts 14 coming into contact with the body.

[0057] Here, the basis weight, thickness, fiber density and fineness of the nonwoven fabric constituting the top sheet are measured by the following methods. (1) Basis weight of nonwoven fabric: A sample of 5 cm x 5 cm is cut from the nonwoven fabric and dried in an atmosphere of 100°C or higher, after which its mass is measured. The measured mass is divided by the area of ​​the sample to calculate the basis weight of the sample. The average value of the basis weights of the 10 samples is taken as the basis weight of the nonwoven fabric. (2) Thickness of nonwoven fabric: This can be measured using a method similar to that for measuring the thickness of the fiber layer described above. Specifically, the absorbent article is frozen with liquid nitrogen, cut in the cross-sectional direction with a cutter, and an enlarged photograph of the cross-section is taken with a digital microscope VHX-7000 manufactured by Keyence Corporation. The distance between two points for planar measurement is selected, and the thickness of the nonwoven fabric is measured. (3) Fiber density of nonwoven fabric: The fiber density of the nonwoven fabric is calculated by dividing the weight of the nonwoven fabric determined by the above method by the thickness of the nonwoven fabric determined by the above method. (4) Fiber fineness: The fiber fineness is determined by measuring the cross-sectional area of ​​the fiber under magnification using a scanning electron microscope, and calculating the fiber fineness from the cross-sectional area and the specific gravity of the fiber (i.e., the specific gravity of the components that make up the fiber).

[0058] Next, a manufacturing method S100 for a nonwoven fabric for absorbent articles will be described with reference to Figure 4. The manufacturing method S100 is configured to obtain a nonwoven fabric that can ensure the desired texture and absorption rate. Figure 4 is a diagram schematically illustrating the manufacturing method S100, where MD indicates the machine direction, and the nonwoven fabric is manufactured sequentially along the MD direction. In this embodiment, the nonwoven fabric obtained by this manufacturing method is used for a top sheet 10, but it may also be used in other forms other than a top sheet, such as a side sheet. The manufacturing method S100 is an air-through method and includes at least a web-forming step S101 and a hot air-passing step S105.

[0059] In the web formation step S101, a web is formed by laminating a first fiber layer 11 containing 90% to 100% by weight of thermoplastic resin fibers 51, a second fiber layer 12 containing thermoplastic resin fibers 51 and cellulosic fibers 52, and a third fiber layer 13 containing 90% to 100% by weight of thermoplastic resin fibers 51 in the thickness direction T. In this embodiment, fibers forming the third fiber layer 13 are supplied from a third supply unit (not shown), and the fibers constituting the third fiber layer 13 are laminated. Therefore, the third fiber layer 13 abuts on the conveying surface 121 of the conveying device 120. Next, fibers forming the second fiber layer 12 are supplied from a second supply unit (not shown), and the fibers constituting the second fiber layer 12 are laminated. The second fiber layer 12 is laminated on the third fiber layer 13. Therefore, the third fiber layer 13 is disposed between the conveying surface 121 and the second fiber layer 12, and the second fiber layer 12 is not in direct contact with the conveying surface 121. Next, fibers forming the first fiber layer 11 are supplied from a first supply unit (not shown), and the fibers constituting the first fiber layer 11 are layered. The first fiber layer 11 is layered on the second fiber layer 12. Therefore, from the conveying surface 121 upward, the third fiber layer 13, the second fiber layer 12, and the first fiber layer 11 are layered in this order. In this state, the fibers are simply layered, not bonded to each other, and can be easily separated.

[0060] The hot air passing step S105 is a step subsequent to the web formation step S101. The third fiber layer 13 of the web is placed facing the breathable conveying surface 121, and hot air is passed through the web. In the hot air passing step S105, hot air is blown from the first fiber layer 11 side toward the conveying surface 121, with the first fiber layer 11, second fiber layer 12, and third fiber layer 13 stacked. The conveying surface 121 has a mesh-like or other voids to ensure breathability. The hot air passes through the web and passes through the voids in the conveying surface 121. The hot air has a predetermined temperature (e.g., 100°C or higher). As the hot air passes through, the fibers in the web cross each other, causing the fiber layers to blend together. Therefore, after the hot air passing step S105, the fibers and fiber layers partially cross each other, making them less likely to separate.

[0061] The manufacturing method S100 may include an entangling step S103 after the web forming step S101 and before the hot air passing step S105. In the entangling step S103, a high-temperature fluid is sprayed onto the web to entangle the fibers of the web. Furthermore, fused portions 15 may be formed at the intersections of the thermoplastic resin fibers 51 by the heat generated during the entangling.

[0062] The manufacturing method S100 may include a concave-convex forming step (not shown) after the hot air passing step S105. In the concave-convex forming step, the web is passed between a pair of gear rolls (not shown) and pressed to form, on at least one surface of the first fiber layer 11 and the third fiber layer 13, a plurality of convex portions 18 (see FIG. 3) that protrude outward in the thickness direction T and a plurality of concave portions 19 (see FIG. 3) that are recessed inward in the thickness direction between the convex portions 18. The concave-convex forming step may be performed immediately after the hot air passing step S105, or may be performed as a separate step after the web is wound up as a nonwoven fabric. The above-mentioned nonwoven fabric can be obtained by this manufacturing method S100.

[0063] According to the manufacturing method S100 of this embodiment, the third fiber layer 13 of the web is placed facing the conveying surface 121, and hot air is applied in this state. Therefore, compared to a configuration in which the second fiber layer 12 containing the cellulosic fibers 52 faces the conveying surface 121, the cellulosic fibers 52 are less likely to come into direct contact with the conveying surface 121. Furthermore, a distance corresponding to the thickness of the third fiber layer 13 can be secured between the cellulosic fibers 52 and the conveying surface 121. This prevents the cellulosic fibers 52 from adhering to the conveying surface 121 or from entering the voids in the conveying surface 121 that ensure breathability. Furthermore, because the hot air is applied with the first fiber layer 11 placed on the surface side, scattering of the cellulosic fibers 52 can be prevented. Therefore, a nonwoven fabric with the desired texture and absorption rate can be obtained by the air-through method while preventing the cellulosic fibers 52 from scattering or adhering to the conveying surface.

[0064] In the web forming step S101, the basis weight of the thermoplastic resin fibers 51 in the first fiber layer 11 may be higher than the basis weight of the cellulosic fibers 52 in the second fiber layer 12. This configuration ensures a sufficient distance between the surface to which hot air is applied and the second fiber layer 12, thereby further suppressing scattering of the cellulosic fibers 52. Furthermore, in an absorbent article in which the first fiber layer 11 is disposed on the skin-contacting surface, a sufficient distance can be maintained between the skin and the second fiber layer, which is primarily composed of cellulosic fibers. This reduces the likelihood of cellulosic fibers being disposed on the skin-contacting surface, thereby suppressing pilling of the cellulosic fibers 52 when the nonwoven fabric rubs against the skin, thereby maintaining a comfortable feel against the skin. Furthermore, in an absorbent article in which the first fiber layer 11 is disposed on the skin-contacting surface, the relatively high basis weight of the thermoplastic resin fibers in the first fiber layer 11 ensures sweat absorption and body fluid absorption, thereby suppressing residual fluid. The basis weight of the thermoplastic resin fibers 51 of the first fiber layer 11 may preferably be 1.5 times or more the basis weight of the cellulosic fibers 52 of the second fiber layer 12, and more preferably be 2.0 times or more the basis weight of the cellulosic fibers of the second fiber layer 12.

[0065] In the web forming step S101, the basis weight of the thermoplastic resin fibers in the third fiber layer 13 may be higher than the basis weight of the cellulosic fibers in the second fiber layer 12. This embodiment ensures a sufficient distance between the conveying surface 121 and the second fiber layer 12, thereby further preventing problems such as the cellulosic fibers 52 remaining on the conveying surface 121 or getting into voids in the conveying surface 121 that ensure breathability. The basis weight of the thermoplastic resin fibers in the third fiber layer 13 may be preferably 1.5 times or more the basis weight of the cellulosic fibers 52 in the second fiber layer 12, and more preferably 2.0 times or more the basis weight of the cellulosic fibers in the second fiber layer 12.

[0066] In the web forming step S101, the basis weight of the fibers of the first fiber layer 11 may be higher than the basis weight of the fibers of the third fiber layer 13. According to this embodiment, in an absorbent article 1 in which the first fiber layer 11 is disposed on the skin-contacting surface, a sufficient distance can be secured between the second fiber layer, which is mainly composed of cellulosic fibers, and the skin. Cellulosic fibers are less likely to be disposed on the skin-contacting surface, which reduces pilling of the cellulosic fibers 52 when the nonwoven fabric rubs against the skin, maintaining a comfortable feel against the skin. Furthermore, the relatively low basis weight of the third fiber layer 13 promotes the migration of body fluids from the second fiber layer 12 side to the non-skin-side member 40, thereby preventing rewetting of body fluids.

[0067] In the entangling step S103, a high-temperature fluid is sprayed onto the web to entangle the thermoplastic resin fibers 51. In the entangling step S103, fused portions 15 may be formed by fusing the thermoplastic resin fibers 51 together. In the entangling step S103, the number of fused portions 15 per unit area in the third fiber layer 13 may be greater than the number of fused portions 15 per unit area in the first fiber layer 11. According to this embodiment, since many fused portions 15 are formed in the third fiber layer 13 facing the conveying surface 121, problems such as unfused fibers remaining on the conveying surface 121 or unfused fibers entering gaps in the conveying surface 121 can be prevented. Furthermore, by forming many fused portions 15 in the third fiber layer 13 (one of the first and third fiber layers 11 and 13 that constitute the outer surface of the nonwoven fabric) and few fused portions 15 in the first fiber layer 11 (the other), it is possible to form both a relatively hard surface and a relatively soft surface in the nonwoven fabric. Therefore, by manufacturing an absorbent article in which the first fiber layer 11 is positioned so that it contacts the skin, the feel of the absorbent article can be improved. Furthermore, by forming many fused points in the third fiber layer 13, which is less likely to contact the skin, the shape of the nonwoven fabric can be more easily maintained in areas that are less likely to rub against the skin. Therefore, it is possible to suppress twisting of the nonwoven fabric while maintaining the texture of the nonwoven fabric itself.

[0068] In the irregularity forming step, convex portions 18 and concave portions 19 are formed on at least one surface of the web. Either the first fiber layer 11 or the third fiber layer 13 is disposed on the one surface. The thickness of the fiber layer (first fiber layer or third fiber layer) disposed on the one surface may be configured to be thicker than the fiber layer (third fiber layer or first fiber layer) disposed on the other surface. According to this embodiment, the thickness of the fiber layer (first fiber layer or third fiber layer) on the one side on which the convex portions 18 and concave portions 19 are formed is relatively thick, so that a predetermined thickness can be maintained even in the concave portions, and exposure of the cellulosic fibers 52 to the outer surface of the nonwoven fabric can be suppressed. Furthermore, compared to the fiber layer on the one side, the fiber layer on the other side (third fiber layer or first fiber layer) is less likely to be biased due to the formation of the convex portions and concave portions, making it easier to ensure a uniform thickness throughout the fiber layer. Therefore, by reducing the thickness of the fiber layer on the other side, the weight of the fiber can be reduced, thereby reducing manufacturing costs.

[0069] In the unevenness forming step, a plurality of protrusions 18 and recesses 19 are provided extending in the front-to-rear direction L and spaced apart in the width direction W, and the protrusions 18 and recesses 19 may be provided in the center of the width direction W of the web rather than on the sides of the web in the width direction W. In other words, the protrusions 18 and recesses 19 extend in the front-to-rear direction L and are spaced apart in the width direction, and may be provided in the center of the top sheet 10 in the width direction W, but not on the sides of the top sheet 10 in the width direction W. For example, the protrusions 18 and recesses 19 may be provided at least within a range of 20 mm to the left and right of the center of the top sheet 10 in the width direction W, but may not be provided at least within a range of 20 mm from the outer edges of the top sheet 10 in the width direction W. Providing the protrusions 18 and recesses 19 reduces the contact area of ​​the top sheet 10 with the skin. On the other hand, providing the protrusions 18 and recesses 19 that extend in the front-to-rear direction and are spaced apart in the width direction W may shorten the width of the top sheet 10, increasing manufacturing costs. Therefore, manufacturing costs can be reduced by providing the protrusions 18 and recesses 19 in areas that are likely to come into contact with the excretory opening (vaginal opening, urinary opening) (the center of the top sheet 10 in the width direction W) and not providing the protrusions 18 and recesses 19 in areas that are unlikely to come into contact with the excretory opening (outer parts of the top sheet 10). Furthermore, when the outer parts of the top sheet 10 overlap the side sheets, areas of the top sheet where the protrusions 18 and recesses 19 are not formed can be joined to the side sheets, allowing for a stable joining of the top sheet 10 and the side sheets.

[0070] In the web forming step S101, the length of the first fiber layer 11 in the orthogonal direction perpendicular to the web conveying direction may be longer than the length of the second fiber layer 12 in the orthogonal direction. During web conveyance, the first fiber layer 11 and the second fiber layer 12 are continuous in the conveying direction MD. By making the length of the first fiber layer 11 in the orthogonal direction longer than the length of the second fiber layer 12 in the orthogonal direction, the entire second fiber layer 12 can be covered by the first fiber layer 11. The second fiber layer contains a relatively large amount of cellulosic fibers, which means that the fibers have poor fusion properties. Therefore, if the hot air directly hits the second fiber layer 12 during the hot air passing step, the cellulosic fibers may curl up. However, by covering the second fiber layer 12 with the first fiber layer 11, the curling up of the cellulosic fibers in the second fiber layer 12 can be suppressed.

[0071] In the web forming process, the length of the third fiber layer in the orthogonal direction perpendicular to the web conveying direction may be longer than the length of the second fiber layer in the orthogonal direction. During web conveyance, the third fiber layer 13 and the second fiber layer 12 are continuous in the conveying direction MD. By making the length of the third fiber layer 13 in the orthogonal direction longer than the length of the second fiber layer 12 in the orthogonal direction, the entire second fiber layer 12 can be covered by the third fiber layer 13. Because the second fiber layer contains a relatively large amount of cellulosic fibers, the fibers have poor fusion properties. If the cellulosic fibers come into contact with a conveying surface such as a metal or resin mesh belt during the hot air passing process, they may become caught in the voids on the conveying surface. However, by covering the second fiber layer 12 with the third fiber layer 13, the cellulosic fibers of the second fiber layer 12 can be prevented from becoming caught on the conveying surface.

[0072] Although the present invention has been described in detail using the above-described embodiments, it will be apparent to those skilled in the art that the present invention is not limited to the embodiments described herein. The present invention can be implemented in modified and altered forms without departing from the spirit and scope of the present invention as defined by the claims. Therefore, the description in this specification is intended to be illustrative and does not have any limiting meaning on the present invention.

[0073] In a modified example, the absorbent article may have a side sheet that covers the side of the top sheet 10. The side sheet may cover either the skin side T1 of the top sheet 10 or the non-skin side T2 of the top sheet 10. At least a portion of the side sheet may be joined to a liquid-impermeable back sheet that is positioned on the non-skin side of the absorbent core. The joining strength between the top sheet and the side sheet may be greater than the joining strength between the first fiber layer and the second fiber layer. According to this embodiment, even if the first fiber layer 11 and the second fiber layer 12 delaminate and conform to the body, the side sheet can prevent the entire absorbent article from shifting. [Explanation of symbols]

[0074] 1: Absorbent articles 10: Top sheet 11: First fiber layer 12: Second fiber layer 13: Third fiber layer 15: Fusion part 18: Convex part 19: Recess 40: Non-skin side member 51: Thermoplastic resin fiber 52: Cellulose-based fibers 121: Conveying surface S100: Manufacturing method S101: Web forming process S103: Interlacing process S105:Hot air penetration process T: Thickness direction T1: Skin side T2: Non-skin side W: Width direction

Claims

1. A method for manufacturing a nonwoven fabric for absorbent articles, comprising: a web forming step of forming a web by laminating in a thickness direction a first fiber layer containing thermoplastic resin fibers in a ratio of 90% by weight to 100% by weight, a second fiber layer containing thermoplastic resin fibers and rayon fibers, and a third fiber layer containing thermoplastic resin fibers in a ratio of 90% by weight to 100% by weight; a hot air passing step of passing hot air through the web after the web forming step, in a state where the third fiber layer of the web is placed opposite an air-permeable conveying surface, In the web forming step, the rayon fibers are arranged not in the form of fiber clumps but dispersed throughout the second fiber layer.

2. 2. The method for manufacturing a nonwoven fabric for an absorbent article according to claim 1, wherein the web forming step comprises making the basis weight of the thermoplastic resin fibers in the first fiber layer higher than the basis weight of the rayon fibers in the second fiber layer.

3. 2. The method for manufacturing a nonwoven fabric for an absorbent article according to claim 1, wherein the web forming step comprises making the basis weight of the thermoplastic resin fibers of the third fiber layer higher than the basis weight of the rayon fibers of the second fiber layer.

4. The method for manufacturing a nonwoven fabric for an absorbent article according to claim 1 , wherein the web forming step comprises forming the first fibrous layer with a basis weight greater than that of the third fibrous layer.

5. an entanglement step of blowing a high-temperature fluid onto the web to entangle the thermoplastic resin fibers before the hot air penetration step, 5. The method for manufacturing a nonwoven fabric for absorbent articles according to claim 1, wherein the entanglement step forms fused portions by fusing the thermoplastic resin fibers together, and forms a number of fused portions per unit area in the third fiber layer greater than the number of fused portions per unit area in the first fiber layer.

6. and a concave-convex forming step of pressing the web after the hot air passing step to form, on one surface of the first fiber layer and one surface of the third fiber layer, a plurality of convex portions protruding outward in the thickness direction and a plurality of concave portions recessed inward in the thickness direction between the convex portions, 5. The method for manufacturing a nonwoven fabric for an absorbent article according to claim 1, wherein the thickness of the fiber layer arranged on one side of the first fiber layer and the third fiber layer is thicker than the thickness of the fiber layer arranged on the other side.

7. and a concave-convex forming step of pressing the web after the hot air passing step to form, on one surface of the first fiber layer and one surface of the third fiber layer, a plurality of convex portions protruding outward in the thickness direction and a plurality of concave portions recessed inward in the thickness direction between the convex portions, 5. The method for manufacturing a nonwoven fabric for absorbent articles according to claim 1, wherein the unevenness forming step provides a plurality of the convex portions and concave portions extending in the front-rear direction and spaced apart in the width direction, and the convex portions and concave portions are not provided on the sides of the web in the width direction, but are provided in the center of the web in the width direction.

8. 5. The method for manufacturing a nonwoven fabric for absorbent articles according to claim 1, wherein the web forming step makes the length of the first fiber layer in a direction perpendicular to the conveying direction of the web longer than the length of the second fiber layer in the orthogonal direction.

9. 5. The method for manufacturing a nonwoven fabric for absorbent articles according to claim 1, wherein the web forming step makes the length of the third fiber layer in a direction perpendicular to the conveying direction of the web longer than the length of the second fiber layer in the orthogonal direction.

10. A method for manufacturing a nonwoven fabric for absorbent articles described in any one of claims 1 to 4, wherein the web forming process forms the second fiber layer by stacking the rayon fibers having a fiber length of 35 mm or more and 50 mm or less.

11. A method for manufacturing a nonwoven fabric for absorbent articles described in any one of claims 1 to 4, wherein, after the web forming process, the fibers of the second fiber layer are simply stacked, not joined to each other, and can be easily separated.

12. After the hot air penetration process, the web is pressed to form, on the surface of the first fiber layer, a plurality of convex portions that protrude outward in the thickness direction and a plurality of concave portions that are recessed inward in the thickness direction between the convex portions, 5. The method for manufacturing a nonwoven fabric for an absorbent article according to claim 1, wherein the unevenness forming step forms the convex portions on the first fiber layer and the second fiber layer without forming the convex portions on the third fiber layer.

13. a top sheet that contacts the wearer's skin; a non-skin side member that contacts the non-skin side of the top sheet, the top sheet is a nonwoven fabric produced by an air-through method, in which a first fiber layer, a second fiber layer, and a third fiber layer are laminated in the thickness direction; the first fiber layer contains thermoplastic resin fibers in a ratio of 90% by weight to 100% by weight; the second fiber layer contains thermoplastic resin fibers and rayon fibers, the third fiber layer contains thermoplastic resin fibers in a ratio of 90% by weight to 100% by weight; An absorbent article, wherein the rayon fibers are not present in a fiber mass within the second fiber layer, but are dispersed throughout the second fiber layer.

14. An absorbent article as described in claim 13, wherein the fiber length of the rayon fibers is 35 mm or more and 50 mm or less.

15. The skin surface of the top sheet is formed with a plurality of convex portions protruding toward the skin side and a plurality of concave portions recessed toward the non-skin side between the convex portions, The absorbent article according to claim 13 or 14, wherein the protrusions are solid.

16. The skin surface of the top sheet is formed with a plurality of convex portions protruding toward the skin side and a plurality of concave portions recessed toward the non-skin side between the convex portions, 15. The absorbent article according to claim 13 or 14, wherein the non-skin side of the top sheet in the region where the convex portions are arranged is located at the same position in the thickness direction as the surrounding non-skin side of the top sheet, or is located closer to the skin than the surrounding non-skin side of the top sheet.

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