JP7594451B2 - Absorbent bodies and absorbent articles - Google Patents

Description

The present invention relates to an absorbent body and an absorbent article equipped with the absorbent body.

Generally, absorbent articles are composed of a liquid-permeable top sheet, a liquid-impermeable back sheet, and an absorbent body disposed between them, and body fluids such as urine pass through the top sheet and are absorbed and held by the absorbent body. In recent years, there has been a demand for thin absorbent articles that are not noticeable when worn, and that do not feel strange or uncomfortable when worn. When designing thin absorbent articles, consideration is usually given to making the absorbent body, which makes up the majority of the absorbent article, thinner, and many absorbent articles using thin absorbent bodies have been proposed (Patent Documents 1 to 4).

Patent Document 1 discloses an absorbent article in which a second sheet is disposed between a top sheet and an absorbent body, the absorbent body having a density higher than 0.12 g/ ^cm3 , and the second sheet having a capillary force of 1.5 x ¹⁰³ N or more. Patent Document 1 describes that by optimizing the density of the absorbent body and the capillary force of the second sheet, it is possible to achieve a high level of both thinness of the absorbent body and excellent absorbency, thereby providing a sense of security and comfort when worn.

Patent Document 2 discloses an absorbent article having a skin-side absorbent layer containing a nonwoven fabric and a superabsorbent polymer, and a non-skin-side absorbent layer containing a hydrophilic porous material and a superabsorbent polymer, the non-skin-side absorbent layer being substantially elongated, with the amount of superabsorbent polymer distributed in the widthwise center portion being smaller than in other portions. Patent Document 2 describes that by using a hydrophilic porous material for the non-skin-side absorbent layer and optimizing the distribution of the superabsorbent polymer, it is possible to achieve a thin layer and a fast absorption rate while maintaining high liquid diffusion and liquid retention.

Patent Document 3 discloses an absorbent body including a laminate in which a base layer including a polyurethane foam layer as an absorbent gel material, a superabsorbent polymer layer, an adhesive layer, and a cover layer are laminated in this order, the adhesive layer including a hot melt adhesive, and the cover layer including a nonwoven fabric (claims 1, 2, 4, paragraphs 0010 and 0016). As materials constituting the base layer and the cover layer, only nonwoven fabric materials such as spunbond nonwoven fabric, carded nonwoven fabric, and airlaid nonwoven fabric are described (paragraph 0045). Patent Document 3 describes that by incorporating a polyurethane foam layer that is stably attached to the base layer, the absorbent body has a good fit and is comfortable, and the utilization rate of the absorbent body's absorption capacity can be maintained (paragraphs 0009 and 0043).

Patent document 4 discloses a layered absorbent body including a plastic foam layer and/or a latex foam layer and a body fluid absorbent layer including a particulate superabsorbent polymer, in which the superabsorbent polymer is disposed in a predetermined amount and/or at a predetermined position directly on, between, or below the plastic foam layer and/or the latex foam layer, and the quantitative ratio of the foamed plastic layer and/or the foamed latex layer to the superabsorbent polymer is 1:500 to 50:1, preferably 1:50 to 25:1, and most preferably 1:5 to 10:1. Patent document 4 describes that the use of the above-mentioned layered absorbent body improves the absorption performance for water and aqueous liquids, particularly the absorption performance under load.

JP 2016-67897 A JP 2009-131349 A JP2014-140770A Special Publication No. 09-509909

All of the absorbents described in Patent Documents 1 to 4 are thin absorbent sheets that do not contain absorbent fibers such as fluff pulp, and although they are effective in making absorbent articles thinner and lighter, they must sacrifice some absorption performance. In particular, they are unable to maintain sufficient absorption performance in light incontinence products and urine pads, which have a small absorbent surface area.

In addition, in absorbent articles, both the speed of absorption (hereinafter also referred to as "absorption rate") and the small amount of return are important indicators of absorption performance, but it is difficult to satisfy both of them at a high level in thin absorbent articles that use conventional absorbent sheets as the absorbent body.

The object of the present invention is to provide an absorbent article with a thin absorbent body that has excellent bodily fluid diffusion properties, high levels of absorption performance, absorption speed, and backflow prevention properties, and that has excellent wearing comfort and fit.

As a result of intensive research conducted by the inventors to solve the above problems, they discovered that by forming a thin absorbent body (highly absorbent sheet) using a polyurethane continuous porous sheet, a perforated film, and highly absorbent polymer particles, it is possible to obtain a thin absorbent body having high absorption performance, in particular an absorption performance in which the absorption rate is maintained at a high level even when body fluids are absorbed multiple times, and a thin absorbent article equipped with the thin absorbent body, and thus completed the present invention. That is, the present invention relates to the following absorbent article.

(1) An absorbent article comprising a liquid-permeable top sheet, a liquid-impermeable back sheet, and an absorbent body provided therebetween,
The absorbent body does not contain absorbent fibers and has a highly absorbent sheet,
the highly absorbent sheet is formed by laminating the first continuous polyurethane porous body sheet, a perforated film and a second continuous polyurethane porous body sheet in this order from the side facing the skin of a wearer, and has a highly absorbent polymer enclosed between the first and second continuous polyurethane porous body sheets;
the apertured film has a plurality of apertures penetrating from the skin side to the non-skin side, the aperture diameter of the apertures on the skin side being larger than the aperture diameter of the non-skin side, and the number of the apertures being 50 pcs/ ^cm2 or more;
An absorbent article, characterized in that the first continuous polyurethane porous body sheet and the perforated film, and the perforated film and the second continuous polyurethane porous body sheet are bonded together so as to form a block-shaped space in which the superabsorbent polymer is enclosed.
(2) The absorbent article according to (1) above, wherein the first or second continuous porous polyurethane sheet has a basis weight of 30 g/ ^m2 or more and 300 g/m2 ^or less and an apparent density of 100 kg/m3 or ^more and 200 kg/m3 ^or less.
(3) The absorbent article according to (1) or (2) above, wherein the first or second open porous polyurethane sheet has a hydrophilic skeleton surface.
(4) The absorbent article according to any one of (1) to (3) above, wherein the apertures in the perforated film have an aperture diameter of 0.3 mm or more and 1.5 mm or less.
(5) An absorbent article according to any one of (1) to (4) above, wherein the aperture diameter of the aperture on the skin side of the perforated film is greater than the aperture diameter of the through-hole on the non-skin side by 0.03 mm or more and 0.15 mm or less.
(6) The absorbent article according to any one of (1) to (5) above, wherein the basis weight of the superabsorbent polymer in the block-shaped spaces is 30 g/ ^m2 or more and 300 g/ ^m2 or less.

The present invention provides an absorbent article that has a thin absorbent body that has excellent bodily fluid diffusion properties, high levels of absorption performance, absorption speed, and backflow prevention, and that has excellent wearing comfort and fit.

FIG. 1 is a plan view illustrating a schematic configuration of an absorbent article according to an embodiment of the present invention. 2 is a schematic cross-sectional view in the width direction taken along the X ₁ -X ₁ cutting line shown in FIG. 1 . 2 is a schematic longitudinal cross-sectional view taken along line Y ₁ -Y ₁ shown in FIG. 1. FIG. 2 is a schematic cross-sectional view showing the configuration of a highly absorbent sheet. 2 is a schematic cross-sectional view showing the flow of bodily fluids in the absorbent article shown in FIG. 1. FIG. 2 is a schematic cross-sectional view showing the configuration of an absorbent article according to Comparative Example 1. 5 is a schematic cross-sectional view showing the configuration of absorbent articles according to comparative examples 3 and 4. FIG. FIG. 11 is a schematic cross-sectional view showing the configuration of an absorbent article according to Comparative Example 5.

In this specification, wearing an absorbent article refers to the state in which the absorbent article is worn on the body, regardless of whether bodily fluids have been absorbed or not. In an absorbent article, the longitudinal direction is the direction that spans the front and back of the body via the wearer's crotch when the absorbent article is worn on the body, the width direction is the direction perpendicular to the longitudinal direction, and the thickness direction is the direction in which each component is layered. The skin side is the surface that contacts the wearer's skin and faces the skin when the absorbent article is worn, and the non-skin side is the surface that contacts the wearer's clothing or faces the clothing. Body fluids refer to liquids discharged from the body to the outside, such as urine, blood, and water in loose stools.

<Absorbent Articles>
The absorbent article 50 according to this embodiment will be described below with reference to the drawings. Figures 1 to 3 show the absorbent article 50. Figure 4 shows the super absorbent sheet 25. Figure 5 shows a typical flow of bodily fluids in the absorbent body 20. Figures 6 to 8 show absorbent articles 70, 80, and 90 according to comparative examples 1, 3 (or 4), and 5, respectively. These drawings do not stipulate the shape, dimensions, size relationship, etc. of each component member in the absorbent article 50.

The absorbent article 50 of this embodiment can be used as various absorbent articles for infants and adults, such as light incontinence products, light incontinence liners, urine absorption pads, pad products such as sanitary napkins, pants-type paper diapers, tape-type paper diapers, and other paper diaper products. Among these, the absorbent article 50 can be particularly used as a pad product such as a light incontinence product or a urine absorption pad, taking advantage of its thinness and the fact that the absorption amount and absorption speed do not decrease even after multiple absorptions. In addition, various paper diapers as outerwear and the absorbent article 50 as innerwear may be combined. The longitudinal dimension (maximum dimension) and width dimension (maximum dimension) of the absorbent article 50 are not particularly limited, but are, for example, in the range of 100 mm to 800 mm and 50 mm to 500 mm, respectively. By adjusting the dimensions of the absorbent article 50 to the above ranges, various types of absorbent articles can be easily obtained.

The absorbent article 50 shown in Figures 1 and 2 comprises a liquid-permeable top sheet 10 located on the skin side, a liquid-impermeable back sheet 30 located opposite the top sheet 10 and on the non-skin side, an absorbent body 20 disposed between the top sheet 10 and the back sheet 30, and a pair of three-dimensional gathers 40 provided on the skin side of the top sheet 10.

The absorbent body 20 includes a highly absorbent sheet 25 that does not contain absorbent fibers such as fluff pulp, and as shown in Figures 2 and 3, a first polyurethane continuous porous body sheet 21, a perforated film 22 as an intermediate sheet, and a second polyurethane continuous porous body sheet 21 are laminated in this order from the skin side to the non-skin side, and has a first SAP layer in which a highly absorbent polymer is encapsulated between the first polyurethane continuous porous body sheet 21 and the perforated film 22, and a second SAP layer in which a highly absorbent polymer is encapsulated between the perforated film 22 and the second polyurethane continuous porous body sheet 21. The first SAP layer is provided with a first joint portion 60 that is band-shaped in plan view, dividing the layer into block-shaped spaces 61 in the surface direction and partially joining the first continuous polyurethane porous body sheet 21 and the perforated film 22, and the second SAP layer is provided with a second joint portion 60 that is band-shaped in plan view, dividing the layer into block-shaped spaces 61 in the surface direction and partially joining the perforated film 22 and the second continuous polyurethane porous body sheet 21. The first continuous polyurethane porous body sheet 21 and the second continuous polyurethane porous body sheet 21 each contain an open-cell polyurethane foam.

According to this embodiment, a first continuous polyurethane porous body sheet 21 containing a polyurethane open-cell foam, a perforated film 22, and a second continuous polyurethane porous body sheet 21 containing a polyurethane open-cell foam are arranged in this order from the skin side of the wearer, and the highly absorbent sheet 25 is partially joined at first and second joining parts 60 so that a block-shaped space 61 containing a highly absorbent polymer 12 is formed between each of the layers. This makes it possible to obtain a thin absorbent body 20 and an absorbent article 50 comprising the thin absorbent body 20, which has good absorbency and wearing comfort, with no decrease in absorption speed, little backflow, and excellent diffusion of body fluids, particularly during repeated absorption. The first and second open-porous polyurethane sheets 21, which contain open-cell polyurethane foam, have elasticity and other properties that make it difficult to feel the hardness and roughness of the superabsorbent polymer 12 before urination, and the lumpy feel of the superabsorbent polymer 12 that has absorbed and swelled with body fluids after urination. The block-shaped spaces 61 also prevent the superabsorbent polymer 12 from shifting or moving, and the thickness and feel can be kept more uniform in the length and width directions even after absorbing body fluids, improving the wearing comfort.

The absorbent article 50 of this embodiment has a top sheet 10, an absorbent body 20, and a back sheet 30 as basic structural units, and can be modified as necessary with various known modifications, such as the provision of the three-dimensional gathers 40 as described above, and the provision of a liquid-permeable transfer sheet (not shown) or a liquid-permeable second sheet between the top sheet 10 and the absorbent body 20. The components of the absorbent article 50 are described in more detail below in the order of the top sheet 10, the absorbent body 20, the back sheet 30, and the three-dimensional gathers 40.

<Top sheet>
The top sheet 10 is a liquid-permeable sheet-like substrate that allows bodily fluids to pass quickly toward the absorbent 20. The top sheet 10 is preferably a substrate that has a soft feel and does not irritate the skin so that it may come into contact with the wearer's skin. Examples of the substrate include hydrophilic sheets, composite nonwoven fabrics that are laminates of the same or different hydrophilic sheets, open-ended films such as open-ended polyethylene films, and foamed films such as polyethylene foam and urethane foam. Examples of hydrophilic sheets include air-through nonwoven fabrics, thermal bond nonwoven fabrics, spunlace nonwoven fabrics, spunbond nonwoven fabrics, and the like, which are made using synthetic fibers made of synthetic resins such as polypropylene and polyethylene, regenerated fibers such as rayon, and natural fibers such as cotton. Among these, nonwoven fabrics are preferred, and air-through nonwoven fabrics, thermal bond nonwoven fabrics, spunbond nonwoven fabrics, and the like are more preferred.

The top sheet 10 may be embossed or perforated on the surface in order to improve liquid permeability. The top sheet 10 may contain one or more of lotion, antioxidant, anti-inflammatory component, pH adjuster, antibacterial agent, moisturizer, etc. in order to reduce irritation to the skin. The basis weight of the top sheet 10 is, for example, in the range of 18 g/m ² to 400 g/m ² in terms of strength, processability, and liquid return amount. The shape of the top sheet 10 is not particularly limited, and may be any shape that covers a part or all of the absorbent body 20, which is necessary to guide bodily fluids to the absorbent body 20 without leakage.

<Absorbent>
The absorbent body 20 has a longitudinal dimension (maximum length) in the range of, for example, 100 mm to 800 mm, 150 mm to 500 mm, or 270 mm to 500 mm. The widthwise dimension (maximum width) of the absorbent body 20 is, for example, 50 mm to 500 mm, 60 mm to 400 mm, or 70 mm to 105 mm. When the planar shape of the absorbent body 20 is an hourglass shape, the longitudinal dimension is in the range of 180 mm to 800 mm, the widthwise dimensions of the ventral side portion and the back side portion that contact the wearer's abdomen and back, respectively, are both in the range of 60 mm to 400 mm, and the widthwise dimension of the crotch portion that contacts the wearer's crotch is in the range of 90 mm to 250 mm. The absorbent body 20 may be embossed on the entire surface or a part thereof. Examples of the shape of the absorber 20 in a plan view include an hourglass shape, an I-shape, a rectangle, a rounded rectangle with rounded corners, an oval, and the like.

The absorbent body 20 of this embodiment includes a highly absorbent sheet 25 that does not contain absorbent fibers such as fluff pulp, and a hydrophilic sheet 24 that wraps the highly absorbent sheet 25. The highly absorbent sheet 25 will be described in detail later. For example, the non-skin side of the highly absorbent sheet is placed near the center of the width direction of the hydrophilic sheet 24, and after bonding them as necessary, both sides of the hydrophilic sheet 24 are folded in a C-shape to overlap the skin side of the highly absorbent sheet 25, and the overlapped parts are bonded as necessary, thereby wrapping the highly absorbent sheet 25 in its entirety. The hydrophilic sheet 24 may not only wrap the highly absorbent sheet 25 in its entirety as described above, but also cover the non-skin side, both width direction sides, and the vicinity of both width direction ends of the skin side of the highly absorbent sheet 25, and wrap the highly absorbent sheet 25 so that both width direction ends of the hydrophilic sheet 24 face each other and are separated from each other to form a slit-like space extending in the longitudinal direction between the top sheet 10 and the highly absorbent sheet 25.

(hydrophilic sheet)
As the hydrophilic sheet 24, any of those commonly used in this field can be used, and examples thereof include hydrophilic nonwoven fabrics such as thermal bonded nonwoven fabrics, spunbonded nonwoven fabrics, airlaid nonwoven fabrics, air-through nonwoven fabrics, and pulp-containing nonwoven fabrics, tissue paper, absorbent paper, etc. Among hydrophilic nonwoven fabrics, hydrophilic nonwoven fabrics such as thermal bonded nonwoven fabrics, spunbonded nonwoven fabrics, air-through nonwoven fabrics, and pulp-containing nonwoven fabrics are more preferred, and air-through nonwoven fabrics, pulp-containing nonwoven fabrics, spunbonded nonwoven fabrics, etc. are even more preferred. The thickness of the hydrophilic sheet 24 is, for example, in the range of 0.10 mm to 0.25 mm, and the basis weight is, for example, in the range of 5 g/m ² to 40 g/m ^2. Hereinafter, each member constituting the highly absorbent sheet will be described.

(Polyurethane open-cell sheet)
The first and second continuous porous polyurethane sheets 21 each contain an open-cell polyurethane foam (hereinafter also referred to as "flexible polyurethane foam") as a main component, and are excellent in bodily fluid diffusibility and flexibility. Here, "containing as a main component" means that the flexible polyurethane foam accounts for 50% by mass or more of the total. For the first and second continuous porous polyurethane sheets 21, for example, a single-layer sheet containing flexible polyurethane foam as a main component, a single-layer sheet made of flexible polyurethane foam, etc. can be used.

The first continuous polyurethane porous sheet 21, for example, diffuses bodily fluids that have permeated the top sheet 10 evenly throughout the absorbent 20 (highly absorbent sheet 25). The second continuous polyurethane porous sheet 21 contains soft polyurethane foam and is located on the non-skin side of the highly absorbent sheet 25, and therefore exhibits the function of temporarily storing bodily fluids until they are absorbed into the first and second SAP layers, preventing the return of the fluid. The first and second continuous polyurethane porous sheets 21 also have flexibility, which reduces the roughness of the particles of the highly absorbent polymer 12 before absorbing bodily fluids and reduces the roughness caused by the swelling of the highly absorbent polymer 12 after absorbing bodily fluids, greatly improving the wearing comfort of the absorbent article 50.

Flexible polyurethane foam can be obtained by mixing raw material compounds such as polyol and polyisocyanate, additives such as foaming agent, foam stabilizer, and catalyst, and heating the resulting mixture to foam. Alternatively, a gaseous foaming agent may be injected while reacting the raw material compounds under heating. By appropriately selecting reaction conditions such as the type of raw material compound, the type and amount of additive, the heating temperature during foaming, the foaming time, and the pressure during foaming, the properties of the flexible polyurethane foam, such as the foaming ratio, apparent density, tensile strength, tensile elongation at break, elongation stress, average coefficient of friction (MIU), and coefficient of friction variation (MMD), can be adjusted. For example, the foaming ratio of the flexible polyurethane foam is in the range of 10 to 60 times from the viewpoint of body fluid diffusibility, flexibility, etc. Flexible polyurethane foam can also be produced according to an extraction method, a W/O emulsion method, etc.

The basis weight and apparent density of the first and second continuous polyurethane porous body sheets 21 are selected, for example, from the range of 30 g/ ^m2 to 300 g/ ^m2 , or from the range of 50 g/ ^m2 to 250 g/m2, respectively, from the viewpoints of bodily fluid diffusion, flexibility, prevention of return of liquid and leakage of bodily fluids, breathability, stuffiness, etc., and the apparent density is selected, for example, from the range of 100 kg/ ^m3 to 200 kg/ ^m3 , or from the range of 120 g/ ^m2 to 180 g/ ^m2 , from the viewpoints of ^the mechanical strength of the absorbent body 20 as a whole, prevention of slipping of the absorbent body 20 after absorbing bodily fluids, flexibility, etc. The basis weight and/or apparent density of the first and second continuous polyurethane porous body sheets 21 may be the same or different within the aforementioned ranges.

In one embodiment, the basis weight of the first continuous polyurethane porous body sheet 21 is greater than that of the second continuous polyurethane porous body sheet 21, and the apparent density of the first continuous polyurethane porous body sheet 21 is smaller than that of the second continuous polyurethane porous body sheet 21. According to this embodiment, the first continuous polyurethane porous body sheet 21 arranged relatively closer to the skin has a bulky structure, and the absorption speed during repeated absorption is improved. In addition, by arranging the second continuous polyurethane porous body sheet 21, which has a relatively low basis weight and high apparent density, from the skin side to the non-skin side, the flow of bodily fluids becomes more in the lengthwise and widthwise directions (longitudinal direction) than in the thickness direction, and the diffusion of the high absorbent sheet 25 or the entire absorbent body 20 is improved. Even if the basis weight and bulk density of the first continuous polyurethane porous body sheet 21 are the same as those of the second continuous polyurethane porous body sheet 21, the same effect can be obtained, although the degree of the above is slightly lower.

The thickness of the first and second continuous polyurethane porous sheets 21 is, for example, in the range of 1.0 mm to 4.0 mm, or in the range of 1.5 mm to 3.2 mm. The thickness is measured under no-load conditions, for example, using a "height gauge" (manufactured by Mitutoyo Corporation). The thicknesses of the first and second continuous polyurethane porous sheets 21 may be the same or different.

The skeleton surface of the soft polyurethane foam contained in the first and second continuous polyurethane porous sheets 21 may be hydrophilic or hydrophobic, but in a preferred embodiment, the skeleton surface is hydrophilic from the viewpoint of wettability with body fluids, etc. Examples of skeletons having hydrophilic properties include those containing polyol and polyalkylene oxide polyol. In addition, the hydrophobic skeleton may be hydrophilized by introducing hydrophilic groups derived from surfactants, ethylene oxide, etc. into the hydrophobic skeleton. Whether the skeleton surface is hydrophilic or not is determined by first cutting a sample with dimensions of 10 mm or more in width and 10 mm or more in length from the first or second continuous polyurethane porous sheet 21 and placing it on a flat surface without bending, then dropping 10 drops (0.05 mL) of ion-exchanged water onto the sample and measuring the time until the sample is absorbed. If this time is within 5 seconds or if 8 or more drops of water are absorbed, it is determined to be hydrophilic.

(perforated film)
The perforated film 22 exhibits liquid permeability by having a plurality of openings 23 penetrating from one surface to the other surface, as shown in Fig. 4. The perforated film 22 is provided as an intermediate sheet between a first continuous porous polyurethane sheet 21 which is a skin-side sheet located on the skin side and a second continuous porous polyurethane sheet 21 which is a non-skin-side sheet located on the non-skin side in the superabsorbent sheet 25, and the fixed-support layer of the superabsorbent polymer 12 between the first and second continuous porous polyurethane sheets 21 is divided in the thickness direction into a first SAP layer (skin-side SAP layer) and a second SAP layer (non-skin-side SAP layer), and is arranged between the first SAP layer and the second SAP layer to allow body fluids to pass therethrough.

As shown in FIG. 5, body fluids excreted into the absorbent 20 (or the highly absorbent sheet 25) are subjected to the resistance of the perforated film 22 and spread in the first SAP layer in the planar direction (particularly in the longitudinal direction), and at the same time flow into the second SAP layer through the multiple perforations 23 in the perforated film 22, thereby enhancing the body fluid diffusion properties of the first and second SAP layers, particularly in the longitudinal direction. At the same time, the perforated film 22 prevents, for example, gel blocking, which occurs when the highly absorbent polymer 12 that has absorbed body fluid swells and bonds, from occurring over a wide area, resulting in a decrease in the absorption rate and amount of absorption. As a result, even after multiple body fluid absorptions, there is very little decrease in the absorption rate of body fluids, and body fluids can be absorbed while preventing leakage.

As described above, the perforated film 22 has a plurality of openings 23 penetrating from one surface to the other surface and having openings on both surfaces. The number of openings 23 in the perforated film 22 is, for example, 50/ ^cm2 or more, and the upper limit may be appropriately selected according to the opening diameter of the openings 23 so that a high level of balance can be obtained between the effect of creating a flow of body fluid in the plane direction in the first SAP layer and the effect of diffusing body fluid from the first SAP layer to the second SAP layer by the openings 23. In addition, from the viewpoint of body fluid permeability, the open area ratio is in the range of 25% to 50%, or in the range of 30% to 50%. The openings 23 have, for example, a funnel-shaped three-dimensional shape in which the opening diameter on one surface is larger than the opening diameter on the other surface. As shown in Figures 2 and 3, the perforated film 22 in this embodiment is arranged so that the pore diameter on the skin-side surface is larger than the pore diameter on the non-skin-side surface. This arrangement improves the bodily fluid diffusion from the first SAP layer to the second SAP layer, and improves the bodily fluid diffusion of the highly absorbent sheet 25 as a whole.

In the perforated film 22, the pore size on one and the other surfaces is selected, for example, from a range of 0.3 mm to 1.5 mm. If the pore size is less than 0.3 mm, the permeability of body fluids from the first SAP layer to the second SAP layer tends to decrease. If the pore size is more than 1.5 mm, the body fluids tend to pass through too easily and do not flow in the surface direction of the first SAP layer, particularly in the longitudinal direction. In a preferred embodiment, the perforated film 22 has a pore size on the skin side that is 0.03 mm to 0.15 mm larger than the pore size on the non-skin side. By setting the difference between the pore size on the skin side and the pore size on the non-skin side within the above-mentioned range, the flow of body fluids in the surface direction in the first SAP layer through the perforated film 22 and the diffusion of body fluids to the second SAP layer are both balanced, and the body fluid diffusion of the superabsorbent sheet 25 as a whole is improved.

The basis weight of the perforated film 22 is, for example, in the range of 10 g/ ^m2 to 100 g/ ^m2 from the viewpoint of preventing the absorbent article 50 from feeling hard and reducing the wearing comfort. As the perforated film 22, any plastic film having through holes with a three-dimensional shape of a funnel can be used without any particular limitation, and examples thereof include perforated polyethylene film and perforated polypropylene film.

(Superabsorbent polymer)
In this embodiment, a first SAP layer is formed by sealing a superabsorbent polymer between the first continuous polyurethane porous body sheet 21 and the porous film 22, and a plurality of first block-shaped spaces (closed spaces) 61 are formed in the first SAP layer by first bonding parts 60. A second SAP layer is formed by sealing a superabsorbent polymer between the porous film 22 and the second continuous polyurethane porous body sheet 21, and a plurality of second block-shaped spaces (closed spaces) 61 are formed in the second SAP layer by second bonding parts 60.

In the first and second SAP layers, the first and second joints 60 are arranged linearly at a predetermined interval in the vertical and horizontal directions, dividing each layer into a plurality of block-shaped spaces 61 in the surface direction and partially joining the first and second continuous polyurethane porous body sheets 21 and the perforated film 22. The first and second SAP layers of this embodiment extend substantially parallel to the outer edge of the absorbent article 50 in the longitudinal and width directions at a predetermined interval to form a rectangular closed space substantially similar to the shape of the outer edge of the absorbent article 50, and further, a plurality of first and second joints 60 extend substantially parallel and at substantially equal intervals in the width direction within the closed space to be connected to the first and second joints 60 that form the closed space, forming a plurality of first and second SAP layers arranged in parallel in the longitudinal direction. The first and second joints 60 may be arranged along the outer edge of the absorbent article 50.

A predetermined amount of superabsorbent polymer 12 is enclosed in a plurality of first and second block-shaped (or rectangular) spaces 61 separated by the first and second joints 60. The amount of superabsorbent polymer 12 enclosed in the block-shaped spaces 61 may be the same or different, but for example, the basis weight of the superabsorbent polymer 12 in the block-shaped spaces 61 is preferably selected from the range of 30 g/ ^m2 to 300 g/ ^m2 . This allows the superabsorbent polymer 12 swollen by absorbing body fluids to be bound over a wide range, preventing the occurrence of gel blocking that impedes the diffusion of body fluids, and therefore significantly reduces the decrease in absorption performance such as absorption speed and absorption amount even when body fluids are repeatedly absorbed.

The planar shape of the block-shaped space 61 provided in the first SAP layer and the second SAP layer is substantially rectangular in this embodiment, but is not limited thereto and may be various shapes such as a triangle (particularly an equilateral triangle), a hexagon (particularly a regular hexagon), a circle, or a concentric circle. In addition, the width dimension of the first joint 60, the number and arrangement in the longitudinal and width directions, etc. are appropriately selected depending on the amount of highly absorbent polymer enclosed in the block-shaped space 61, etc. The first and second joints 60 may be configured to include, for example, a hot melt adhesive, or may be a welded region by heat sealing, ultrasonic sealing, etc.

In this embodiment, the number of block-shaped spaces 61 formed in the second SAP layer is configured to be greater than the number of block-shaped spaces 61 formed in the first SAP layer. This configuration further improves the diffusion of bodily fluids into the highly absorbent sheet 25 or the entire absorbent body 20, and while preventing the occurrence of gel blocking, it is possible to maintain the absorption rate at the initial setting and further increase the absorption amount.

The superabsorbent polymer 12 used in the superabsorbent sheet 25 is not particularly limited as long as it can absorb body fluids and prevent backflow, and examples of such polymers include polyacrylates, polyaspartates, (starch-acrylic acid) graft copolymers, (acrylic acid-vinyl alcohol) copolymers, (isobutylene-maleic anhydride) copolymers, and saponified versions thereof. Among these, from the viewpoint of absorption per weight, polyacrylates are preferred, alkali metal polyacrylates are more preferred, and sodium polyacrylate is even more preferred. The superabsorbent polymers can be used alone or in combination of two or more.

The superabsorbent polymer 12 is used in the form of particles, fibers, etc., but is preferably used in the form of particles from the viewpoint of ease of handling, etc. In this case, by avoiding the use of a fine powder of superabsorbent polymer 12 that has poor fluidity as a powder and using a superabsorbent polymer 12 with a medium particle size, it is possible to improve the basic absorption performance and reduce the rough feel caused by the absorbent body 20 becoming hard. The medium particle size of the superabsorbent polymer 12 is, for example, in the range of 50 μm to 600 μm or in the range of 100 μm to 500 μm.

To seal the superabsorbent polymer 12 in the first and second block-shaped spaces 61, for example, a hot melt adhesive is used. As the hot melt adhesive, one having a melting point of 100°C or more and 180°C or less can be used without any particular limitation, and examples thereof include synthetic rubber-based hot melt adhesives such as styrene-butadiene-styrene copolymers and styrene-isoprene-styrene copolymers, and olefin-based hot melt adhesives such as ethylene-vinyl acetate copolymers. As a method for applying the hot melt adhesive, known methods such as a curtain coat method or a spiral method in which the hot melt adhesive in a molten state is applied from a nozzle in a non-contact manner, and a slot method in which the hot melt adhesive is applied in a contact manner can be used. The content of the hot melt adhesive is, for example, in the range of 10 g/ ^m2 or less from the viewpoint of not impairing the absorbency of the superabsorbent polymer 12 and the feel on the skin when worn.

<Method of manufacturing the highly absorbent sheet and absorbent body>
The superabsorbent sheet 25 of this embodiment can be produced by a manufacturing method including, for example, a step of spraying the superabsorbent polymer 12 in a predetermined pattern on each non-skin side of the first continuous polyurethane porous body sheet 21 and the perforated film 22 with the first and second bonding portions 60 remaining in the reversed positions, a step of supplying a hot melt adhesive as necessary to fix and support the superabsorbent polymer 12, a step of superimposing the skin side of the perforated film 22 on the non-skin side of the first continuous polyurethane porous body sheet 21 on which the superabsorbent polymer 12 has been sprayed or fixed, and a step of superimposing the second continuous polyurethane porous body sheet 21 on the non-skin side of the perforated film 22 on which the superabsorbent polymer 12 has been sprayed or fixed to obtain a laminate, and a step of forming the first and second bonding portions 60 while pressing and/or heating the laminate as necessary. The first and second bonding portions 60 can be formed, for example, by using a hot melt adhesive or by a welding method such as heat sealing or ultrasonic sealing. The obtained highly absorbent sheet 25 is wrapped in the hydrophilic sheet 24 as described above to obtain the absorbent body 20. The hot melt adhesive used here and the method of applying it are the same as those used for the hot melt adhesive that fixes and supports the highly absorbent polymer 12.

<Back seat>
The back sheet 30 may be formed using a breathable or non-breathable substrate that is impermeable to liquids so that the body fluids held by the absorbent 20 do not wet clothing, and examples of the substrate include a resin film and a composite sheet that is a laminate of a resin film and a nonwoven fabric. The nonwoven fabric used in the composite sheet is not particularly limited in its manufacturing method, and examples thereof include single-layer nonwoven fabrics such as spunbond nonwoven fabrics and meltblown nonwoven fabrics, composite nonwoven fabrics such as spunbond nonwoven fabrics/meltblown nonwoven fabric laminates, and composite materials thereof. Examples of the resin film include polyester, polyvinyl alcohol, polyethylene, polypropylene, and composite films of polyethylene and polypropylene.

The basis weight of the back sheet 30 is, for example, in the range of 15 g/ ^m2 to 60 g/ ^m2 or in the range of 15 g/ ^m2 to 40 g/ ^m2 in terms of strength and processability. In order to prevent stuffiness during wearing, it is preferable that the back sheet 30 has breathability. In order to provide the back sheet 30 with breathability, for example, a filler may be blended into the resin film of the base material, or the back sheet 30 may be embossed. An example of the filler is calcium carbonate, and the blending method may be a known method without any restrictions.

<3D gathers>
The three-dimensional gathers 40 are fixed to the skin side of the top sheet 10 near both ends in the width direction of the absorbent article 50 along the longitudinal direction of the absorbent article 50 in order to prevent, for example, lateral leakage of bodily fluids excreted by the wearer of the absorbent article 50. The three-dimensional gathers 40 include an elastic stretch member 40a and a water-repellent and/or waterproof sheet member 40b.

The elastic stretch member 40a is disposed in the longitudinal direction near the free end (other end) of the sheet member 40b, imparting uprightness to the free end, and allowing the free end of the sheet member 40b and its neighboring area to be deformed to fit the wearer's body shape. In this embodiment, the sheet member 40b has one widthwise end (fixed end) fixed near both widthwise ends of the skin side of the back sheet 30, a middle part in the widthwise direction fixed near both widthwise ends of the skin side of the top sheet 10, and the other widthwise end being a free end having uprightness. The fixing position of the fixed end (one widthwise end) of the sheet member 40b is not limited to this embodiment, and examples include the non-skin side of the back sheet 30, near both widthwise ends of the skin side or non-skin side of the joint of all or part of each edge of the top sheet 10 and the back sheet 30 with the absorbent body 20 stored therein, and near both widthwise ends of the skin side of the top sheet 10.

The sheet member 40b is a water-repellent and/or waterproof sheet, and is made of, for example, nonwoven fabric. As the nonwoven fabric for the first sheet member, any water-repellent and/or waterproof (liquid-impermeable) nonwoven fabric made of hydrophobic fibers can be used without any particular limitation, and examples thereof include spunbond nonwoven fabric, meltblown nonwoven fabric, and composite nonwoven fabric (SMS nonwoven fabric) which is a spunbond nonwoven fabric/meltblown nonwoven fabric/spunbond nonwoven fabric laminate. The basis weight of the sheet member 40b is, for example, in the range of 13 gsm to 20 gsm. As the elastic stretch member 40a, for example, thread-shaped, string-shaped, or band-shaped materials made of natural rubber, synthetic rubber, polyurethane, etc. can be used as appropriate.

<Method of manufacturing absorbent articles>
The absorbent article 50 can be manufactured by a known manufacturing method, for example, a manufacturing method including a step of arranging the absorbent body 20 between the top sheet 10 and the back sheet 30, a step of fixing the top sheet 10 and the back sheet 30 partially or entirely around the periphery using a hot melt adhesive, heat embossing, ultrasonic embossing, high frequency embossing, or the like, and a step of providing three-dimensional gathers 40 at predetermined positions on the back sheet 30 and the top sheet 10. When the absorbent article 50 is a urine absorption pad or a light incontinence pad, it may be individually packaged in a package and then folded in thirds in the longitudinal direction. Leg gathers, waist gathers, side flaps, and the like may be provided as necessary.

Although the present invention has been described above using embodiments, it goes without saying that the technical scope of the present invention is not limited to the scope described in the above embodiments and examples. It will be clear to those skilled in the art that various modifications and improvements can be made to the above embodiments. Furthermore, it is clear from the claims that forms incorporating such modifications or improvements can also be included in the technical scope of the present invention.

The following examples and comparative examples will explain this embodiment in more detail.

(Examples 1 to 2 and Comparative Examples 1 to 5)
(Preparation of absorbent articles)
Absorbent articles having the configurations shown in Fig. 2 (Examples 1 and 2), Fig. 6 (Comparative Example 1), Fig. 2 (Comparative Example 2), Fig. 7 (Comparative Example 3), Fig. 7 (Comparative Example 4) or Fig. 8 (Comparative Example 5) were produced. Note that the absorbent article of Comparative Example 2 has an intermediate sheet (perforated film) with 30 perforations/ ^cm2 .

A polyurethane open-cell foam sheet (hydrophilic skeleton surface, basis weight 80 g/m2, thickness 2.0 mm, apparent density 140 kg/ ^m3 ) was used as the skin side sheet (first continuous porous polyurethane sheet) placed on the skin side and the non-skin side sheet (second continuous porous polyurethane sheet) placed on the non-skin side, and a perforated film (Examples 1 and 2, Comparative Examples 1 and 2), an air- ^through nonwoven fabric (Comparative Example 3), a spunbond nonwoven fabric (Comparative Example 4) or no intermediate sheet (Comparative Example 5) was used as the intermediate sheet to prepare a highly absorbent sheet. The highly absorbent sheet thus obtained was folded in a C shape and wrapped in a spunbond nonwoven fabric (hydrophilic sheet, basis weight 12 g/ ^m2 ) to prepare an absorbent body measuring 420 mm x 150 mm.

An air-through nonwoven fabric (basis weight 20 g/ ^m2 ) was used as the liquid-permeable top sheet, a breathable polyethylene sheet (basis weight 35 g/ ^m2 ) was used as the liquid-impermeable back sheet, and a composite nonwoven fabric (basis weight 15 g/ ^m2 ) in which a spunbond nonwoven fabric/meltblown nonwoven fabric/spunbond nonwoven fabric were laminated in this order was used as the three-dimensional gathers. When the top sheet, back sheet, and absorbent body were integrated, the top sheet and the skin side of the absorbent body were bonded using a hot melt adhesive to produce absorbent articles with a longitudinal dimension of 480 mm and a width dimension of 200 mm in Examples 1 and 2 and Comparative Examples 1 to 5.

The following evaluations were carried out on the absorbent articles of Examples 1 and 2 and Comparative Examples 1 to 5. The results are shown in Table 1.
(Total Absorption)
After immersion in physiological saline for 5 minutes, the sample is drained on a wire mesh for 30 seconds, and the weight difference before and after absorption is measured.
(Repeated absorption rate)
Using a jig with a base of 140×100 mm, outer diameter of 40 mm, inner diameter of 35 mm and weight of 1400 g, 120 ml of physiological saline is poured under load three times at 10 minute intervals and the time taken to absorb the third 120 ml of water is measured.
(liquid return)
After three absorption rate measurements have been completed, the amount of water absorbed back into a 55 mm diameter filter paper in 1 minute is measured 10 minutes later under a load of 35 gf/cm ² .
(Diffusion Length)
After the absorption rate was measured three times, the maximum length of the part that absorbed the physiological saline was measured.

From Table 1, it can be seen that by using an absorbent body in which the highly absorbent sheet of this embodiment is folded into a C shape with a hydrophilic sheet, a thin absorbent article can be obtained that maintains a high level of body fluid absorption amount and repeated absorption speed and also has excellent resistance to liquid return.

REFERENCE SIGNS LIST 10 Top sheet 12 Highly absorbent polymer 20 Absorbent body 21 Continuously porous polyurethane sheet 22 Perforated film 23 Perforations 24 Hydrophilic sheet 25 Highly absorbent sheet 30 Back sheet 40 Three-dimensional gathers 40a Elastically stretchable member 40b Sheet member 50 Absorbent article 60 Joint 61 Block-shaped space

Claims (6)

An absorbent article comprising a liquid-permeable top sheet, a liquid-impermeable back sheet, and an absorbent body provided therebetween,
The absorbent body does not contain absorbent fibers and has a highly absorbent sheet,
the highly absorbent sheet is formed by laminating a first continuous polyurethane porous body sheet, a perforated film and a second continuous polyurethane porous body sheet in this order from the side facing the skin of a wearer, and has a highly absorbent polymer enclosed between the first and second continuous polyurethane porous body sheets;
the apertured film has a plurality of apertures penetrating from the skin side to the non-skin side , the number of apertures being 50 or more per ^cm2 ;
An absorbent article, characterized in that the first continuous polyurethane porous body sheet and the perforated film, and the perforated film and the second continuous polyurethane porous body sheet are bonded together so as to form a block-shaped space in which the superabsorbent polymer is enclosed. 2. The absorbent article according to claim 1, wherein the first or second continuous porous polyurethane sheet has a basis weight of 30 g/m2 or ^more and 300 g/ ^m2 or less and an apparent density of 100 kg/m3 or ^more and 200 kg/ ^m3 or less. The absorbent article according to claim 1 or 2, wherein the skeleton surface of the first or second polyurethane continuous porous sheet is hydrophilic. The absorbent article according to any one of claims 1 to 3, wherein the aperture diameter of the perforated film is 0.3 mm or more and 1.5 mm or less. The absorbent article according to any one of claims 1 to 4, wherein the aperture diameter of the perforated film on the skin side of the perforations is greater than the aperture diameter of the non-skin side of the through-holes by 0.03 mm or more and 0.15 mm or less. The absorbent article according to claim 1 , wherein the basis weight of the superabsorbent polymer in the block-shaped spaces is 30 g/m ² or more and 300 g/m ² or less.

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