JP7498014B2 - Top sheet for absorbent article and absorbent article including same - Google Patents

Description

The present invention relates to a top sheet for absorbent articles and an absorbent article equipped with the same.

Absorbent articles used to absorb fluids discharged from the body, such as sanitary napkins, incontinence pads, and panty liners, generally use a liquid-permeable sheet such as a nonwoven fabric as the top sheet that forms the skin-facing surface.

Patent Document 1 discloses an absorbent article in which an absorbent body is interposed between a top sheet and a back sheet. The top sheet used in this absorbent article includes a non-thermal adhesive layer made of cellulosic fibers arranged on the skin side and a thermal adhesive layer made of thermal adhesive fibers arranged on the non-skin side, with the aim of allowing bodily fluids absorbed in the top sheet to migrate to the non-skin side without reducing the soft feel of cotton. The document discloses that a second sheet made of thermal adhesive fibers is arranged on the non-skin side of the top sheet, and that the non-skin side of the second sheet has multiple compressed sections formed by recessing the second sheet and the top sheet together toward the skin side.

JP 2019-162218 A

However, the top sheet arranged in the absorbent article described in Patent Document 1 may be configured as a sheet containing hydrophilic fibers and synthetic fibers, and such a sheet may cause excreted liquid to remain on the sheet surface due to the hydrophilic fibers, or liquid to flow on the sheet surface due to the synthetic fibers. There is room for improvement in terms of achieving both of these issues and reducing them.

Therefore, the object of the present invention is to provide a top sheet for absorbent articles that achieves both a reduction in residual liquid on the sheet and a reduction in liquid flow on the sheet surface, and an absorbent article equipped with the same.

The present invention provides a top sheet for absorbent articles, comprising cotton and a second fiber other than cotton, and having a first surface and a second surface opposite to the first surface,
The present invention provides a top sheet for absorbent articles, in which, when the top sheet is virtually divided into thirds in the thickness direction, the mass ratio of the cotton to the mass of all fibers in the portion located on the second surface side is less than 50 mass%.

The present invention also provides an absorbent article that includes a top sheet for an absorbent article, the top sheet being arranged so that a first surface side of the top sheet faces the body of a wearer.

The present invention provides a top sheet for absorbent articles that reduces residual liquid on the sheet and reduces liquid flow on the sheet surface, and an absorbent article that includes the top sheet.

FIG. 1 is a cross-sectional view that illustrates one embodiment of the top sheet for absorbent articles of the present invention. 2(a) and (b) are cross-sectional views that typically show another embodiment of the topsheet for absorbent articles of the present invention. 3(a) and (b) are perspective views each showing a schematic state of the embossed portion of the topsheet for absorbent articles of the present invention. FIG. 4 is a side view showing a schematic diagram of an embodiment of a manufacturing apparatus for manufacturing the topsheet for absorbent articles of the present invention. FIG. 5 is a side view that shows a schematic diagram of another embodiment of a manufacturing apparatus for manufacturing the topsheet for absorbent articles of the present invention.

The present invention will be described below based on preferred embodiments with reference to the drawings. The top sheet 1 for absorbent articles shown in FIG. 1 (hereinafter, simply referred to as "top sheet 1") is a liquid-permeable sheet having a first surface F and a second surface R located on the opposite side of the first surface F.

The top sheet 1 contains cotton 1a and a second fiber 2 other than cotton (hereinafter, simply referred to as "second fiber 2") as its constituent fibers, and is formed by intertwining the constituent fibers. Typically, the top sheet 1 of the present invention is a spunlace nonwoven fabric.

The top sheet 1 shown in FIG. 1 has one fiber group G1, one side of the fiber group G1 forms a first surface F, and the surface of the fiber group G1 opposite the first surface F forms a second surface R. The top sheet 1 shown in the figure has a first fiber layer 11 including the first surface F as the fiber group G1 and containing cotton 1a as a constituent fiber, and a second fiber layer 12 including the second surface R and containing the second fiber 2 as a constituent fiber. In other words, the top sheet 1 shown in the figure is a sheet having a fiber group G1 in which the first fiber layer 11 and the second fiber layer 12 are arranged adjacent to each other to form a two-layer structure, and the boundary surface between each fiber layer 11, 12 is unclear.

In addition, the fiber diameters of the cotton 1a and the second fiber 2 shown in FIG. 1 are different, but this is shown only for the convenience of explaining the fibers and their arrangement, and the fiber diameters of both fibers may be the same or different.

The top sheet 1 is suitable for use as a component of an absorbent article that absorbs bodily fluids such as urine and menstrual blood. When the top sheet 1 is incorporated into an absorbent article, the first side F is arranged as the skin-contacting side that contacts the wearer's skin, and the second side R is arranged as the non-skin-contacting side that is the side opposite to the skin-contacting side. Typically, the first side F is used as the liquid-receiving side that is the first surface that comes into contact with the top sheet 1 and excreted liquid, and the second side R is arranged in contact with a liquid-retentive absorbent.

Examples of the second fiber 2 include natural fibers, regenerated fibers, and synthetic fibers. Examples of the natural fibers include cellulose fibers other than cotton fibers such as pulp. Examples of the regenerated fibers include rayon and acetate fibers. Examples of the synthetic fibers include thermoplastic fibers containing thermoplastic resins, and specific examples of the thermoplastic resins include polyolefin resins such as polyethylene (PE) and polypropylene (PP), polyester resins such as polyethylene terephthalate (PET), polyamide resins, vinyl resins such as polyvinyl chloride and polystyrene, acrylic resins such as polyacrylic acid and polymethyl methacrylate, and fluororesins such as polyperfluoroethylene. These fibers can be used alone or in combination of two or more types. Of these fibers, it is more preferable to use thermoplastic fibers as the second fiber 2.

When a thermoplastic fiber is used, the fiber may or may not have heat shrinkability. An example of a thermoplastic fiber having heat shrinkability (hereinafter also referred to as a heat shrinkable fiber) is, for example, a latent shrink fiber. A latent shrink fiber can be handled in the same way as a conventional fiber for nonwoven fabric before being heated, and has the property of shrinking by developing a spiral crimp when heated at a predetermined temperature. A latent shrink fiber is, for example, an eccentric core-sheath type or a side-by-side type composite fiber made of two types of thermoplastic resins with different shrinkage rates. Examples of such fibers include those described in JP-A-9-296325 and JP-A-2-191720.

When considering an imaginary plane parallel to the first surface F, it is preferable that the mass ratio of cotton 1a in the surface sheet 1 decreases continuously, stepwise, or a combination thereof from the first surface F to the second surface R when viewed from the first surface F along the thickness direction Z. In other words, the boundary between the area where cotton 1a is present and the area containing the second fibers 2 may be clear or unclear.

In detail, consider virtual dividing planes L1 and L2 that virtually divide the surface sheet 1 into three in the thickness direction Z, and consider the first portion 10A including the first surface F, the second portion 10B including the second surface R, and the central portion 10C that is the area sandwiched between the virtual dividing planes L1 and L2 (see FIG. 1). At this time, the ratio B1 of the mass Wb of cotton 1a to the mass Wtb of all fibers in the second portion 10B is preferably less than 50% by mass. With this configuration, the touch and flexibility of the sheet due to the texture of cotton are maintained, while the residual liquid on the sheet and the unintended liquid flow on the sheet surface are reduced. The virtual dividing planes L1 and L2 can be determined by dyeing the surface sheet 1 with a fiber identification reagent (BOKENSTAIN II, manufactured by the Boken Quality Evaluation Organization, a general incorporated foundation) whose color changes depending on the type of fiber, and visually judging and defining the surfaces with different fiber composition ratios in the thickness direction Z from the color of the dyed fibers. If it is determined that there are two faces with different fiber composition ratios, these faces are designated as virtual dividing faces L1 and L2. If it is determined that there is one face with different fiber composition ratios, or three or more faces, the faces are designated as virtual dividing faces L1 and L2 by dividing the sheet into three equal parts in the thickness direction.

The mass and ratio of cotton 1a constituting the top sheet 1 can be measured by the following method. First, the top sheet 1 to be measured is divided into three in the thickness direction to obtain a sample corresponding to the second portion 10B. This sample is immersed in an aqueous solution of 1000 ppm ascorbic acid/10 ppm riboflavin, and then exposed to sunlight to extract only the fiber components. The mass of these fiber components is measured and taken as the mass Wtb of all fibers in the second portion 10B. Next, the fibers constituting the second portion 10B are dyed with a fiber identification reagent (BOKENSTAIN II, manufactured by the Boken Quality Evaluation Organization, a general incorporated foundation), and only the fibers that have discolored to a grayish blue-green color are taken out. The discolored fibers are separated and dried one by one, and the total mass of the discolored fibers is measured and taken as the mass Wb of cotton 1a in the second portion 10B. The percentage of the mass Wb of cotton 1a to the mass Wtb of the total fibers in the second portion 10B is calculated, and the mass ratio B1 in the second portion 10B is calculated. The mass of the second fiber 2 in the second region 10B is calculated by subtracting the mass Wb of the cotton 1a from the mass Wtb of all the fibers in the second region 10B.

The mass ratio B1 of cotton 1a to the mass of all fibers in the second portion 10B of the top sheet 1 is preferably less than 50% by mass, more preferably 30% by mass or less, and preferably 10% by mass or more, and more preferably 20% by mass or more. This mass ratio can further reduce both the residual liquid on the sheet and the unintended flow of liquid on the sheet surface.

The mass ratio B2 of the second fibers 2 to the mass of all fibers in the second portion 10B of the top sheet 1 is preferably 50 mass% or more, more preferably 70 mass% or more, and preferably 90 mass% or less, more preferably 80 mass% or less. Such a mass ratio can further reduce both the liquid residue on the sheet and the unintended flow of liquid on the sheet surface. This effect is particularly pronounced when thermoplastic fibers are used as the second fibers 2.

The top sheet 1 having the above-mentioned configuration contains cotton, so that it is easy to give the wearer of an absorbent article including the top sheet 1 the softness of cotton fibers and the positive image of "gentleness" and "sense of security" that the wearer associates with cotton. In addition, since it contains a second fiber other than cotton and is configured so that the mass ratio of cotton present in the second portion 10B is less than a predetermined value, the amount of residual liquid in the sheet 1 is reduced and the liquid flow on the surface of the sheet is reduced. As a result, when the top sheet 1 is incorporated into an absorbent article, the feel and usability of the absorbent article are improved. In particular, according to a preferred embodiment in which thermoplastic fibers are used as the second fiber 2 and the mass ratio of the thermoplastic fibers present in the second portion 10B is set to a predetermined value or more, the residual liquid in the sheet 1 and the liquid flow on the surface of the sheet are further reduced, and the usability is further improved.

Focusing on the first region 10A in the top sheet 1, the mass ratio A1 of cotton 1a to the mass of all fibers in the first region 10A is preferably 50 mass% or more, more preferably 80 mass% or more, particularly preferably 90 mass% or more , and preferably 100 mass% or less.
In addition, the mass ratio A2 of the second fibers 2 to the mass of all fibers in the first region 10A is preferably 50 mass% or less, more preferably 30 mass% or less, particularly preferably 10 mass% or less, and preferably 0 mass% or more.
By setting the mass ratios A1 and A2 as described above, it is possible to more easily give to the wearer of an absorbent article including the top sheet 1 the positive images such as "gentleness" and "sense of security" that the wearer associates with cotton, and it is also possible to express the high water absorbency that is characteristic of cotton 1a.

In the central region 10C, the mass ratio C1 of cotton 1a to the mass Wtc of all fibers in the central region 10C is preferably 10% by mass or more, more preferably 20% by mass or more, and preferably 70% by mass or less, more preferably 40% by mass or less. With such a mass ratio, when the first surface F of the topsheet 1 is used as the liquid-receiving surface, the liquid can be quickly transferred to the second surface R, thereby further reducing the amount of liquid remaining in the sheet and the liquid flow on the surface of the sheet.

The mass ratio C2 of the second fibers 2 to the mass Wtc of all fibers in the central region 10C is preferably 30% by mass or more, more preferably 60% by mass or more, and preferably 90% by mass or less, more preferably 80% by mass or less. Such a mass ratio can further reduce liquid residue in the sheet and liquid flow on the sheet surface.

The mass and ratio of each constituent fiber in the first region 10A and the central region 10C of the topsheet 1 are measured in the same manner as described above by dividing the topsheet 1 to be measured into three in the thickness direction to obtain samples corresponding to the first region 10A and the central region 10C. Then, the mass Wta of all fibers in the first region 10A, the mass Wtc of all fibers in the central region 10C, the mass Wa of cotton 1a in the first region 10A, the mass ratio A1 in the first region 10A, the mass ratio A2 of the second fiber 2 in the first region 10A, the mass Wc of cotton 1a in the central region 10C, the mass ratio C1 of cotton 1a in the central region 10C, and the mass ratio C2 of the second fiber 2 relative to the mass Wtc of all fibers in the central region 10C are measured and calculated.

From the viewpoint of achieving a high level of both reduction in residual liquid on the sheet and reduction in liquid flow on the sheet surface, it is preferable that the top sheet 1 has a fiber group G1 (hereinafter also referred to as the first fiber group G1) containing cotton 1a, and a second fiber group G2 containing thermoplastic fibers as the second fiber 2 in addition to the first fiber group G1, and that an embossed portion 15 is formed on the top sheet 1. The embossed portion 15 is a portion in which some or all of the constituent fibers are fused, or are compacted without being fused. By forming such an embossed portion 15, the embossed portion 15 becomes an absorption starting point, making it easier to draw liquid into the top sheet 1, and further reducing liquid flow on the sheet surface.

2(a) and 2(b) is a sheet in which a first fiber group G1 and a second fiber group G2 are arranged adjacent to each other, with the outer surface of the first fiber group G1 constituting a first surface F and the outer surface of the second fiber group G2 constituting a second surface F. In other words, the first fiber group G1 is configured to include the first surface F, and the second fiber group G2 is configured to include the second surface R. The topsheet 1 is provided with a plurality of embossed portions 15.
In the region where the embossed portion 15 is not formed, the boundary between the first fiber group G1 and the second fiber group G2 may be clear or unclear. In the region where the embossed portion 15 is not formed, the first fiber group G1 and the second fiber group G2 may be configured to be inseparable or separable.

As long as the effects of the present invention are achieved, the first fiber group G1 may be formed from a single fiber layer, or may be formed from multiple fiber layers including, for example, the first fiber layer 11 and the second fiber layer 12 as described above. When the first fiber group G1 is formed from a single fiber layer, it may be composed of only cotton 1a, or may be composed of fibers other than cotton in addition to cotton 1a. When the first fiber group G1 is formed from multiple fiber layers, the interface between each fiber layer may be clear or unclear, independently of each other. Furthermore, each fiber layer may be independently configured to be non-peelable or peelable.

In addition, as long as the effects of the present invention are achieved, the second fiber group G2 may be formed from a single fiber layer, or may be formed from multiple fiber layers. When the second fiber group G2 is formed from a single fiber layer, it may be composed only of thermoplastic fibers as the second fibers 2, or may be composed of other fibers other than thermoplastic fibers in addition to the thermoplastic fibers. When the second fiber group G2 is formed from multiple fiber layers, the interface between each fiber layer may be clear or unclear. Furthermore, each fiber layer may be independently configured to be non-peelable or peelable.

When the top sheet 1 has an embossed portion 15, it is preferable that at least the first surface F of the top sheet 1 is formed with an uneven shape, as shown in Figures 2(a) and (b). This increases the surface area of the sheet, which further reduces the flow of liquid on the sheet surface.

As shown in Figs. 2(a) and (b), the top sheet 1 preferably has a plurality of recesses 17 formed in the area where the embossed portion 15 is formed, and protrusions 18 formed between the recesses 17. It is also preferable that the first surface F has an uneven shape due to the formation of the recesses 17 and protrusions 18. In other words, in this embodiment, it is preferable that the recesses 17 are areas where the embossed portion 15 is formed, and the protrusions 18 are areas where the embossed portion 15 is not formed. The boundary surface between the fiber groups G1 and G2 in the protrusions 18 is preferably clear. In the embossed portion 15, there is no boundary surface between the fiber groups G1 and G2, or the boundary surface is unclear.

Similarly, the second surface R has an uneven shape with multiple recesses 17 and protrusions 18 formed so that the positions of the recesses 17 and protrusions 18 match those of the first surface F. The recesses 17 are the areas where the sheet thickness is the smallest. Alternatively, the second surface F may be flat.

The protrusion 18 may have a solid structure in which the first fiber group G1 and the second fiber group G2 are in contact with each other, as shown in FIG. 2(a), or may have a hollow structure in which the first fiber group G1 and the second fiber group G2 are spaced apart, with a space S defined by the lower surface of the first fiber group G1 and the upper surface of the second fiber group G2, as shown in FIG. 2(b).

As shown in FIG. 2, it is preferable that the density of the fibers constituting the first fiber group G1 is higher than the density of the fibers constituting the second fiber group G2 in the areas where the embossed portion is not formed, i.e., the convex portion 18. This configuration makes it easier for the liquid absorbed from the first fiber group G1 to transfer to the second fiber group G2, which has a lower fiber density, when the first surface F is used as a liquid-receiving surface, and prevents the liquid from diffusing in the sheet surface direction. As a result, the amount of liquid remaining in the sheet can be further reduced.

The density of fibers of each fiber group G1, G2 in the area where the embossed portion is not formed can be calculated by the following method. In detail, first, the fibers are dyed in the same manner as in the above-mentioned method, and then the topsheet 1 is dried. The topsheet 1 is cut in an unloaded state along the thickness direction Z so as to pass through the topmost part of the convex portion 18 (i.e., the part where the thickness of the topsheet 1 is the largest) in the area where the embossed portion is not formed, to obtain a cross section of the topsheet 1. Next, with a load of 49 Pa applied to the topsheet 1, an enlarged photograph of the cross section is obtained using a microscope (Keyence Corporation, VHX-1000). An object of known dimensions is also photographed on the enlarged photograph. Next, a scale is set on the enlarged photograph of the cross section, and the thickness T1 of the first fiber group G1 and the thickness T2 of the second fiber group G2 in the cross section are measured. The thickness of each fiber group G1, G2 is measured by visually determining areas in the thickness direction Z where the fiber composition ratio is different from the color of the dyed fibers, and the boundaries of these areas are taken as the boundaries of each fiber group G1, G2, and the thickness of each fiber group G1, G2 is measured using these boundaries as a reference.
The above operation is performed on three different convex portions 18 on the same sheet, and the arithmetic mean value A (mm) of the thickness of the first fiber group G1 and the arithmetic mean value B (mm) of the thickness of the second fiber group G2 are calculated from the three measurements. The measurement environment is a temperature of 20±2° C. and a relative humidity of 65±5%.
Separately from this, an area including the convex portion 18, which is a portion where no embossing is formed, is cut under no load, and the mass (g) and the planar area ( ^cm2 ) of the area under no load are measured and calculated, and the basis weight (g/ ^cm2 ) is calculated. The calculated basis weight (g/ ^cm2 ) is then divided by the above-mentioned arithmetic mean value A to calculate the density D1 (g/ ^cm3 ) of the fibers of the first fiber group G1. Similarly, the calculated basis weight (g/ ^cm2 ) is divided by the arithmetic mean value B to calculate the density D2 (g/ ^cm3 ) of the fibers of the second fiber group G2.

The thickness T1 of the first fiber group G1 measured by the above-mentioned method is preferably 0.2 mm or more, more preferably 0.3 mm or more, and is preferably 1 mm or less, more preferably 0.7 mm or less.
The thickness T2 of the second fiber group G2 measured by the above-mentioned method is preferably 0.5 mm or more, more preferably 0.7 mm or more, and is preferably 2.2 mm or less, more preferably 2 mm or less.

The density D1 of the fibers in the first fiber group G1 calculated by the above-mentioned method is preferably 0.03 g/ ^cm3 or more, more preferably 0.05 g/ ^cm3 or more, and is preferably 0.5 g/ ^cm3 or less, more preferably 0.2 g/ ^cm3 or less.
Under the same conditions, the density D2 of the fibers in the second fiber group G2 is preferably 0.01 g/cm ³ or more, more preferably 0.02 g/cm ³ or more, and is preferably 0.1 g/cm ³ or less, more preferably 0.06 g/cm ³ or less.
Further, under the same conditions, the ratio (D1/D2) of the density D1 of the fibers of the first fiber group G1 to the density D2 of the fibers of the second fiber group G2 is preferably 0.3 or more, more preferably 0.8 or more, and is preferably 50 or less, more preferably 10 or less.

The embossed portion 15 formed on the top sheet 1 may be configured, for example, as shown in FIG. 3(a) in a plan view of the top sheet 1, as a series of straight lines inclined in opposite directions relative to the X direction.

In the formation mode of the embossed portion 15 shown in FIG. 3(a), when the top sheet 1 is viewed in a plane, the first embossed portion line 15A formed as a continuous straight line and the second embossed portion line 15B formed as a continuous straight line are formed to be inclined in opposite directions to each other with respect to the X direction. The first embossed portion line 15A and the second embossed portion line 15B shown in the same figure are formed in large numbers parallel to each other. In addition, the intervals between adjacent first embossed portion lines 15A and the intervals between adjacent second embossed portion lines 15B are approximately the same. The positions where the first embossed portion line 15A and the second embossed portion line 15B are formed are the positions of the recessed portion 17 in the cross-sectional view of the top sheet 1. In addition, the area defined by the two first embossed portion lines 15A and the two second embossed portion lines 15B is the position of the protruding portion 18 in the cross-sectional view of the top sheet 1.

As another embodiment of the embossed portion 15 formed on the top sheet 1, for example as shown in FIG. 3(b), when the top sheet 1 is viewed in plan, the embossed portion 15 may be formed in a scattered dot pattern in the sheet surface direction.

In the formation mode of the embossed portion 15 shown in FIG. 3(b), when the top sheet 1 is viewed in plan, multiple circular embossed portions 15 are formed at a predetermined interval. The embossed portion 15 shown in the figure constitutes multiple embossed portion rows 15C extending in a direction perpendicular to the X direction, and adjacent embossed portion rows 15C are formed with the same pitch and a phase shift of half a pitch. Alternatively, adjacent embossed portion rows 15C may have different pitches. In addition, the phase shift of each adjacent embossed portion row 15C may be periodic or non-periodic.

The shape of the embossed portions 15 formed in a scattered pattern may be a circle as shown in the figure, a polygon such as a rectangle or a hexagon, an alphabet shape such as an X-shape or a Y-shape, a lattice shape, or a combination of these. The position where the embossed portion 15 is formed is the position of a recess 17 in a cross-sectional view of the top sheet 1. The area surrounded by four embossed portions 15 is the position of a protrusion 18 in a cross-sectional view of the top sheet 1. Of the above-mentioned formation modes of the embossed portions 15, it is preferable that the embossed portions 15 are formed in a scattered pattern in the sheet surface direction.

When the embossed portion 15 is formed on the top sheet 1, the height H1 of the convex portion 18 (see Figs. 2(a) and (b)) is preferably 1 mm or more, more preferably 1.3 mm or more, and preferably 3 mm or less, more preferably 2.5 mm or less, under a load of 49 Pa on the top sheet 1. The height H1 of the convex portion 18 is obtained by cutting the top sheet 1 in an unloaded state along the thickness direction Z so as to pass through the topmost portion of the convex portion 18 (i.e., the portion where the thickness of the top sheet 1 is the largest) to obtain a cross section of the top sheet 1. Next, with a load of 49 Pa applied to the top sheet 1, an enlarged photograph of the cross section is obtained using the above-mentioned microscope. An object of known dimensions is also photographed on this enlarged photograph at the same time. Next, a scale is set on the enlarged photograph of the cross section to measure the maximum length along the thickness direction Z of the sheet cross section.
The above operation is performed on three different convex portions 18 on the same sheet, and the arithmetic mean value of the three measurements is defined as the height H1 (mm). The measurement environment is a temperature of 20±2° C. and a relative humidity of 65±5%.

Other fibers that may be included in the fiber group G1 include cellulosic fibers other than cotton 1a and thermoplastic fibers.
Examples of cellulosic fibers other than cotton include natural cellulose fibers other than cotton, regenerated cellulose fibers, refined cellulose fibers, and semi-synthetic cellulose fibers. These may be used alone or in combination of two or more.
Examples of natural cellulose fibers include bast fibers of hemp and the like, leaf vein fibers of Manila hemp and the like, and fruit fibers of palm and the like.
Examples of regenerated cellulose fibers include viscose rayon, polynosic, and modal, as well as rayon fibers such as cuprammonium rayon obtained from a cuprammonium salt solution of cellulose.
Refined cellulose fibers include Lyocell, commercially available as Tencel™ and Veocel™.
Semi-synthetic cellulosic fibers include, for example, acetate fibers such as triacetate and diacetate.
The thermoplastic fibers include, for example, fibers containing the above-mentioned thermoplastic resin. When the fiber group G1 includes the second fibers 2, the thermoplastic fibers may be of a different fiber type from the second fibers 2. The term "different fiber types" includes not only cases where the types of resin constituting the fibers are different, but also cases where the type of resin is the same but the fiber thicknesses are different.
Of these, it is preferable to use natural cellulose fibers other than cotton as the other fibers, from the viewpoint of imparting a positive image such as "gentleness" and "sense of security" to the wearer and improving the feel of the sheet against the skin.

Other fibers that may be included in the second fiber group G2 include, for example, the above-mentioned cellulosic fibers and thermoplastic fibers. The cellulosic fibers used as other fibers that may be included in the second fiber group G2 may be natural cellulose fibers such as cotton. When the second fiber group G2 includes the second fiber 2, examples of the other fibers that may be included in the second fiber group G2 include thermoplastic fibers of a different fiber type from the second fiber 2.

The top sheet 1 of the present invention can be suitably used as a component of an absorbent article. An absorbent article typically comprises a top sheet 1 and a back sheet, and can be used with an absorbent disposed between the top sheet 1 and the back sheet. Absorbent articles include, but are not limited to, incontinence pads, sanitary napkins, disposable diapers, etc., and broadly include articles used to absorb liquids discharged from the human body.

When the top sheet 1 is used as a component of an absorbent article, it is preferable that the top sheet 1 is arranged so that its first surface F forms the surface facing the skin of a wearer wearing the absorbent article when the absorbent article is worn in the correct position (hereinafter, this surface is also referred to as the "skin-facing surface"). It is also preferable that the top sheet 1 is arranged in a region where the absorbent article comes into direct contact with the wearer's skin, with the first surface F serving as the skin-facing surface.

The back sheet is a sheet that constitutes the surface side facing away from the skin of the wearer of the absorbent article. The back sheet used in the absorbent article can be any sheet that has been conventionally used in absorbent articles, without any particular restrictions. The back sheet can be the same as the top sheet, or it can be a resin film that is poorly permeable to liquids or water repellent, or a laminate of a resin film and a nonwoven fabric, etc.

The absorbent body used in absorbent articles has an absorbent core. The absorbent core is composed of, for example, a pile of hydrophilic fibers such as cellulose including pulp, a mixed pile of the hydrophilic fibers and a water-absorbent polymer, or a pile of water-absorbent polymer. At least the skin-facing surface of the absorbent core may be covered with a liquid-permeable core wrap sheet, or the entire surface including the skin-facing surface and the non-skin-facing surface may be covered with the core wrap sheet. For example, a tissue paper made of hydrophilic fibers or a liquid-permeable nonwoven fabric may be used as the core wrap sheet.

The fiber diameter of the cotton 1a fibers used in the topsheet 1 is not particularly limited as long as it is one commonly used in this technical field, but is preferably 10 μm or more, more preferably 20 μm or more, and is preferably 50 μm or less, more preferably 45 μm or less.
The fiber length of the cotton 1a used in the top sheet 1 is preferably 10 mm or more, more preferably 20 mm or more, from the viewpoint of increasing the degree of entanglement in the fiber layer and fully exerting the sheet strength, and is preferably 50 mm or less, more preferably 45 mm or less.

The fiber diameter of the second fiber 2 is not particularly limited as long as it is one that is commonly used in this technical field, but is preferably 0.5 dtex or more and preferably 5 dtex or less in terms of fineness.

The fiber diameter of the fibers of Cotton 1a can be calculated as the arithmetic average value by measuring the maximum diameter of the cross section of 10 fibers cut perpendicular to the fiber length direction using a scanning electron microscope (DSC6200 manufactured by Seiko Instruments Inc.).
The fiber diameter of the second fibers 2 can be calculated as a fineness expressed as a mass per a predetermined fiber length.

The basis weight of the top sheet 1 can be appropriately changed depending on the type and application of the absorbent article to be used, but is preferably 25 g/ ^m2 or more, more preferably 40 g/ ^m2 or more, and is preferably 100 g/ ^m2 or less, more preferably 80 g/ ^m2 or less.

The above describes the absorbent article topsheet of the present invention and the absorbent article comprising said sheet. Below, a preferred method for manufacturing the absorbent article topsheet of the present invention will be described. This manufacturing method can use, for example, a manufacturing apparatus 10 shown in FIG. 4. The manufacturing apparatus 10 comprises, in this order, a web forming section 20 and a hydroentanglement section 30 along the conveying direction MD. In the following description, an example will be given in which a web mainly comprising cotton 1a and a web mainly comprising second fibers 2 are formed separately.

The web forming section 20 includes carding machines 21A and 21B that produce fiber webs 21a and 21b to form the fiber aggregate that constitutes the top sheet 1, and guide rolls 23 for the fiber webs 21a and 21b.

The water flow entanglement section 30 entangles the fiber webs 21a and 21b with a water flow to form an entangled body 5 in which the constituent fibers are integrally entangled. The water flow entanglement section 30 includes a water flow nozzle 35 that sprays a water flow onto the fiber web 21a, and a support belt 36 made of an endless belt. The water flow nozzle 35 is located above the support belt 36, and is capable of spraying a high-pressure water flow across the entire width of the fiber webs 21a and 21b (direction perpendicular to the conveying direction MD). The support belt 36 is disposed opposite the water flow nozzle 35, and has a structure with holes in various patterns, such as a lattice pattern, to allow the sprayed water to pass through (not shown).

The method for manufacturing the topsheet 1 using the manufacturing device 10 shown in FIG. 4 is, for example, as follows. First, the fiber webs 21a, 21b are unwound from the carding machines 21A, 21B in the web forming section 20 via the guide rolls 23, 23, respectively. Through these unwound operations, the laminate 4 in which the fiber webs 21a, 21b are stacked is formed (lamination process).

The composition ratio of fibers in each fiber web 21a, 21b may be adjusted according to the composition of the desired top sheet 1. Specifically, for example, a fiber web containing only cotton 1a or a fiber web containing cotton 1a and thermoplastic fibers may be used as the first fiber web 21a, and a fiber web containing only the second fiber 2 or a fiber web in which cotton 1a and the second fiber 2 are mixed in a predetermined ratio may be used as the second fiber web 21b.

Next, in the water flow entanglement section 30, the laminate 4 is entangled by high-pressure water jets from the water flow nozzles 35 while being transported by the support belt 36 (entanglement process). Through the entanglement process, the constituent fibers of the fiber webs 21a and 21b that make up the laminate 4 are three-dimensionally entangled to form the entangled body 5.

In this step, for example, the water pressure sprayed from the water flow nozzle 35 is preferably 2 MPa or more, more preferably 3 MPa or more, and is preferably 10 MPa or less, more preferably 5 MPa or less.
The transport speed in the MD direction of the laminate 4 is preferably 3 m/min or more, more preferably 5 m/min or more, and is preferably 180 m/min or less, more preferably 30 m/min or less.

After the entanglement process, the laminate 4 becomes an entangled body 5 in which the constituent fibers are three-dimensionally entangled and integrated. One side of this entangled body 5 is made up of a first fiber group G1 containing cotton 1a, and the other side is a continuous sheet made up of a second fiber group G2 containing second fiber 2.

When manufacturing a top sheet 1 having an embossed portion 15 formed thereon, a step of forming the embossed portion 15 from one side of the continuous sheet obtained through the intertwining step can be further carried out (not shown). The embossed portion 15 can be formed by bringing a roll or the like having a shape complementary to the shape of the desired embossed portion 15 into contact with the continuous sheet, and carrying out embossing with or without heat, ultrasonic embossing, or the like. When forming the embossed portion 15, it is even more preferable to use a thermoplastic fiber as the second fiber 2 from the viewpoint of increasing the efficiency of forming the embossed portion 15.

Finally, the interlaced body 5 is shaped (not shown) to the desired dimensions by cutting or other methods to obtain the top sheet 1.

Instead of the above-mentioned manufacturing method, when manufacturing a topsheet 1 having a first fiber group G1 and a second fiber group G2, the topsheet 1 may be manufactured using, for example, a manufacturing device 50 shown in FIG. 5. This manufacturing device 50 has the same configuration as the devices described in JP-A-2007-182662 and JP-A-2002-187228.

In detail, first, a fiber web or nonwoven fabric mainly containing cotton is formed, for example, by a method using a carding machine, to form the first fiber group G1. At the same time, a fiber web or nonwoven fabric mainly containing thermoplastic fibers is formed, for example, by a method using a carding machine, to form the second fiber group G2. When forming multiple fiber layers in at least one of the first fiber group G1 and the second fiber group G2, multiple types of fiber webs or nonwoven fabrics containing at least one of cotton 1a and second fiber 2 are formed, for example, by a method using a carding machine, and then the obtained fiber webs or nonwoven fabrics are laminated and used.

When nonwoven fabric is used for at least one of the first fiber group G1 and the second fiber group G2, various types of nonwoven fabric can be used, such as air-through nonwoven fabric, spunlace nonwoven fabric, spunbond nonwoven fabric, meltblown nonwoven fabric, etc.

Next, the first fiber group G1 and the second fiber group G2 are laminated so that the first fiber group G1 forms one outer surface and the second fiber group G2 forms the other outer surface to form a laminate 41, which is then conveyed along the conveying direction MD to emboss the laminate 41 and form the embossed portions 15 in a continuous linear or scattered pattern. The embossing can be performed, for example, by introducing the laminate 41 conveyed along the conveying direction MD into a heat embossing device 51. The heat embossing device 51 is performed by introducing the laminate 41 between a smooth roll 52 having a smooth peripheral surface and an engraved roll 53 having a number of convex portions formed on its peripheral surface that are complementary to the shape of the desired embossed portion 15. Both the smooth roll 52 and the engraved roll 53 are heated to a predetermined temperature, and the first fiber group G1 and the second fiber group G2 are pressed or fused together by applying heat and pressure to form the embossed portion 15.

At this time, from the viewpoint of achieving both the efficiency of forming the embossed portion 15 and the texture of the top sheet 1, it is preferable that the heating temperature of the smooth roll 52 and the engraved roll 53 is equal to or higher than the melting point of the thermoplastic fiber. When the thermoplastic fiber contains two or more components, the heating temperature of each roll may be 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. It is also preferable that the laminate 41 is introduced between the engraved roll 53 and the first fiber group G1 in the laminate so that they face each other.

When forming a concave-convex shape on the target surface sheet 1, it is preferable to introduce the second laminate 42 on which the embossed portion 15 is formed into a hot air blowing device 55 and blow hot air onto the second laminate 42 to perform a bulking process. From the viewpoint of efficiently and clearly forming a concave-convex shape on the target surface sheet 1, it is more preferable to use a heat-shrinkable fiber, particularly a latent shrinkable fiber, as the thermoplastic fiber. As a result, the heat-shrinkable fiber present at the position where the convex portion 18 surrounded by the embossed portion 15 is to be formed shrinks in the sheet surface direction, and the first fiber group G1 present at that position moves so as to protrude to one side, forming the convex portion 18.

When forming a concave-convex shape on the intended surface sheet 1, in order to form solid convex portions 18 as shown in FIG. 2(a), for example, when using a concentric core-sheath type composite heat-fusible thermoplastic fiber with a core of PET and a sheath of PE, a core-to-sheath mass ratio of 1:1, a fiber length of 51 mm, and a fineness of 2.4 dtex, the temperature of the blown hot air can be preferably 125°C to 145°C, and the blowing time of the hot air can be preferably 5 seconds to 10 seconds.

In addition, when forming a concave-convex shape on the intended surface sheet 1, in order to form hollow convex portions 18 as shown in FIG. 2(b), for example, when a thermoplastic fiber is a side-by-side type latent shrinkable fiber having two components, polyethylene and polypropylene, with a fiber length of 51 mm and a thermal shrinkage rate of 9.5% at the melting point of polypropylene + 10°C, the temperature of the blown hot air can be preferably 100°C or more and 120°C or less, and the blowing time of the hot air can be preferably 5 seconds or more and 10 seconds or less.

Then, the third laminate 43 with the embossed portions 15 and protruding portions 18 formed therein is shaped by cutting or other methods (not shown) to the desired dimensions to obtain the top sheet 1.

Although the present invention has been described above based on its preferred embodiments, the present invention is not limited to the above embodiments. For example, the top sheet of the present invention may have both the first surface F and the second surface R flat, or may be unevenly shaped by a method other than forming the embossed portion 15. An example of a method for imparting unevenness is to introduce the top sheet 1 between a pair of uneven rolls arranged in an interlocking state.

When continuous linear embossed lines 15A, 15B are formed as the embossed portion 15, the distance W1 (see FIG. 3(a)) between adjacent first embossed lines 15A formed on the top sheet 1 is preferably 4 mm or more, more preferably 6 mm, and preferably 16 mm or less, more preferably 14 mm or less. The distance W2 (see FIG. 3(a)) between adjacent second embossed lines 15B can be in the same range as the distance W1 described above.

When forming scattered embossed portions 15, the spacing W5 (see FIG. 3(b)) between the embossed portions 15 along the extension direction of the embossed portion row 15C composed of the embossed portions 15 formed on the top sheet 1 is preferably 1 mm or more, more preferably 5 mm, and preferably 10 mm or less, more preferably 7 mm or less. The spacing W6 (see FIG. 3(b)) between adjacent embossed portion rows 15C can be in the same range as the spacing W5 described above.

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

Example 1
A first fiber web (basis weight 15 g/m ² ) made of 100% cotton (manufactured by Marusan Sangyo Co., Ltd., model number: UDX-MS) and a second fiber web (basis weight 25 g/m 2 ) made of a mixture of 25% cotton and 75% non-thermally shrinkable thermoplastic fiber (manufactured by Daiwabo Polytech Co., Ltd., model number: SHW-15, raw material: concentric core-sheath composite heat-fusible fiber with a PET core and a PE sheath, fineness: ^2.4 dtex) were formed, and each fiber web was laminated to form a laminate. This laminate was hydroentangled to obtain a surface sheet 1 with a basis weight of 40 g/m ^2. The hydroentanglement conditions were a water pressure of 3 MPa and a conveying speed of the laminate of 5 m/min. The obtained topsheet 1 was formed only from fiber group G1, with the first fiber web disposed on the first side F and the second fiber web disposed on the second side R. The topsheet 1 of this example did not have an embossed portion 15, and both the first side F and the second side R had flat sheet surfaces. The mass proportions of cotton and thermoplastic fiber in the first region 10A and the second region 10B are shown in Table 1 below.

Example 2
The first fiber web (basis weight 12.5 g/ ^m2 ) was 100% cotton by mass, the second fiber web (basis weight 12.5 g/ ^m2 ) was a mixture of 25% cotton by mass and 75% thermoplastic fiber by mass described above, and the third fiber web (basis weight 25 g/ ^m2 ) was 100% thermoplastic fiber by mass (manufactured by JNC Corporation, model number: ETC255SDLV, raw material: PET/PE, fineness: 2.2 dtex).

First, a laminate of the first and second fibrous webs was hydroentangled to obtain a spunlace nonwoven fabric in which each fibrous web was inseparable. Next, the spunlace nonwoven fabric and the third fibrous web were laminated so that the surface of the spunlace nonwoven fabric facing the first fibrous web was the outer surface. Then, embossing was performed from the spunlace nonwoven fabric side to obtain a topsheet 1 (basis weight 50 g/ ^m2 ) having a continuous linear embossed portion 15 as shown in Figure 3(a). The interval W1 between adjacent first embossed lines 15A was 7.6 mm, and the interval W2 between adjacent second embossed lines 15B was 7.6 mm.
This topsheet had a spunlace nonwoven fabric as the first fiber group G1 arranged on the first surface F side, and a third fiber web as the second fiber group G2 arranged on the second surface R side. The topsheet had an uneven shape with solid protrusions 18 formed therein, and the height H1 of the protrusions 18 was 2.2 μm. The mass proportions of the cotton and the thermoplastic fiber in the first region 10A and the second region 10B are shown in Table 1 below.

Example 3
The first fiber web (basis weight 11 g/m ² ) was 100% cotton by mass, the second fiber web (basis weight 11 g/m 2 ) was a mixture of 25% cotton by mass and 75% non-heat-shrinkable thermoplastic fiber (manufactured by Daiwabo Polytech Co., Ltd., model number: SHW-15; raw material: PET/PE, fineness: 2.4 dtex) by mass, and the third fiber web (basis weight 17 g/m ² ) was 100% side-by-side type latent crimp fiber (manufactured by Daiwabo Polytech Co., Ltd., model number: LV-3, raw material: PP/ ^PE , fineness: 2.3 dtex) by mass.

In this example, the first and second fibrous webs were hydroentangled to obtain a spunlace nonwoven fabric (basis weight 22 g/ ^m2 ) in which each fibrous web was inseparable, as in Example 2. The spunlace nonwoven fabric and the third fibrous web were then laminated so that the surface of the spunlace nonwoven fabric on the side of the first fibrous web was the outer surface. Then, embossing was performed from the spunlace nonwoven fabric side to obtain a laminate (basis weight 39 g/ ^m2 ) having the scattered embossed portions 15 shown in Figure 3(b). After that, hot air at 120°C was blown onto the laminate for 5 to 10 seconds to cause thermal shrinkage, and a surface sheet 1 (basis weight 51 g/ ^m2 ) having an uneven shape was obtained.
This surface sheet had embossed portions 15 formed in a scattered manner and hollow convex portions 18 formed therein, the height H1 of the convex portions 18 being 2 μm. The arrangement pattern of the embossed portions 15 was such that the spacing W5 between the embossed portions 15 along the extension direction of the embossed portion row 15C was 5 mm, and the spacing W6 between adjacent embossed portion rows 15C was 5 mm. In addition, the adjacent embossed portion rows 15C had the same pitch and were in a houndstooth pattern with a phase shift of half a pitch. The embossed portion 15 was a circle having a diameter of 5 mm.
The mass proportions of cotton and thermoplastic fiber in the first region 10A and the second region 10B are shown in Table 1 below.

Example 4
A spunlace nonwoven fabric (basis weight 22 g/ ^m2 ) was arranged on the first surface F side as the first fiber group G1, and a fiber web (basis weight 17 g/m2) composed of 100 mass% side-by-side type latent crimpable fiber (manufactured by Daiwabo Polytech Co., Ltd., model number: LV-3, PET/PE, fineness: 2.3 dtex) was used as the third fiber web on the second surface R side as the second fiber group G2. Except for this, a surface sheet 1 (basis weight 74 g/ ^m2 ) having an uneven shape was obtained by manufacturing and heat shrinking in the same manner as in Example ³ .
In the topsheet of this example, the embossed portions 15 were formed in a scattered manner, and solid protrusions 18 were formed, and the height H1 of the protrusions 18 was 1.6 mm. The mass proportions of the cotton and the thermoplastic fiber in the first region 10A and the second region 10B are shown in Table 1 below.

Comparative Example 1
A fiber web formed using only cotton was hydroentangled to obtain a topsheet 1 having a basis weight of 30 g/ ^m2 and consisting of a single fiber group. The hydroentanglement conditions were the same as those in Example 1.

Comparative Example 2
A fiber web formed by mixing 35% by mass of cotton and 65% by mass of the thermoplastic fiber (model number: SHW-15) used in Example 1 was hydroentangled to obtain a topsheet 1 having a basis weight of 30 g/ ^m2 and consisting of a single fiber group. The hydroentanglement conditions were the same as those in Example 1.

[Measurement of remaining liquid amount]
The topsheets 1 of the examples and comparative examples were arranged so that the first surface F was positioned outward to produce an absorbent article (sanitary napkin). The configuration of the absorbent article other than the topsheet 1 was the same as that of a sanitary napkin manufactured by Kao Corporation (Laurier (registered trademark) F Happy Skin Soft Type 22.5 cm, manufactured in 2018).
This sanitary napkin was placed on a flat table with the topsheet 1 facing upward. An acrylic liquid injection plate, which was an integrally molded cylinder with a diameter of 10 mm and a height of 50 mm, was placed on the topsheet 1 with the liquid injection hole positioned at the center of the topsheet. In this state, 6 g of artificial blood was injected into the cylinder at once. One minute after the injection, the liquid injection plate was removed, and the topsheet 1 was removed from the sanitary napkin and its mass was measured. The value obtained by subtracting the mass of the topsheet, which was measured before injection, from the measured mass was taken as the amount of remaining liquid (g), and this value was divided by the area ( ^m2 ) of the topsheet used to calculate the amount of remaining liquid per unit area. The smaller the amount of remaining liquid, the better the results. The results are shown in Table 1 below.

The artificial blood used in the measurements was prepared from defibrinated horse blood manufactured by Japan Biotest Laboratory Co., Ltd. When defibrinated horse blood is left to stand, the highly viscous parts (red blood cells, etc.) settle, while the less viscous parts (plasma) remain as the supernatant. The mixing ratio of these parts was adjusted so that the viscosity was 8.0 cP (25°C) to prepare the artificial blood. A TVB10 viscometer manufactured by Toki Sangyo Co., Ltd. was used for the adjustment. The condition was 30 rpm.

[Measurement of the length of liquid flow on the sheet surface]
Absorbent articles (sanitary napkins) each having the topsheet 1 of the Examples and Comparative Examples were manufactured in the same manner as in the above-mentioned "Measurement of remaining liquid amount".
This sanitary napkin was placed on a surface inclined at 45 degrees to the horizontal plane with the topsheet 1 facing upward. Then, 0.5 g of the above-mentioned defibered horse blood was dropped onto the topsheet 1 at a rate of 0.1 g/sec. The distance from the drop point on the topsheet 1 to the point where the defibered horse blood stopped flowing was measured. This operation was carried out three times, and the arithmetic average value of the three measurements was taken as the liquid flow length (mm). The smaller the liquid flow length, the better the results. The results are shown in Table 1 below.

As shown in Table 1, the topsheet 1 of each embodiment has less residual liquid and less liquid flow on the sheet surface compared to the comparative example. In particular, as shown in Examples 2 to 4, this effect is more pronounced when the topsheet 1 is composed of a first fiber group G1 mainly made of cotton and a second fiber group G2 mainly made of thermoplastic fibers or heat-shrinkable fibers.

1: Surface sheet for absorbent article 1a: Cotton 2: Second fiber F: First surface R: Second surface Z: Thickness direction

Claims (4)

A top sheet for absorbent articles comprising cotton and a second fiber other than cotton, the top sheet having a first surface and a second surface opposite to the first surface,
The second fiber includes a thermoplastic fiber;
an embossed portion is formed, and thereby a concave-convex shape having a plurality of concave portions formed by the embossed portion and convex portions formed between the concave portions is formed on the first surface side,
When the surface sheet for absorbent articles is virtually divided into three in the thickness direction,
a mass ratio of the cotton to a mass of all fibers in a portion located on the first surface side is 90 mass% or more and 100 mass% or less, and a mass ratio of the thermoplastic fiber to a mass of all fibers in a portion located on the first surface side is 0 mass% or more and 10 mass% or less,
a mass ratio of the cotton to the mass of all fibers in a portion located on the second surface side is less than 50 mass%, and a mass ratio of the thermoplastic fiber to the mass of all fibers in a portion located on the second surface side is 50 mass% or more,
a first fiber group including a first surface and including the cotton;
a second fiber group including the second surface and including the thermoplastic fibers;
the first fiber group and the second fiber group are spaced apart from each other in the protruding portion, thereby forming a hollow structure having a space defined by the second surface side of the first fiber group and the first surface side of the second fiber group,
The top sheet for absorbent articles is used so that the first surface is disposed on the skin contact side, which is the surface that contacts the skin of the wearer . The topsheet for absorbent articles according to claim 1 , wherein the embossed portions are formed in a scattered manner in the sheet surface direction. 3. The topsheet for absorbent articles according to claim 1 , wherein in areas where the embossed portions are not formed, the density of the fibers constituting the first fiber group is higher than the density of the fibers constituting the second fiber group. The top sheet for absorbent articles according to any one of claims 1 to 3 is provided,
The absorbent article has a top sheet for absorbent articles , the first surface side of the top sheet being disposed so as to face the body of a wearer.