JP7574072B2 - Absorbent articles - Google Patents

Description

The present invention relates to an absorbent article.

Absorbent articles generally comprise a liquid-permeable top sheet, a liquid-impermeable back sheet, and an absorbent body disposed between them, and are configured so that the absorbent body absorbs and retains bodily fluids such as urine that permeate the top sheet. There are various types of absorbent articles for adults and infants, depending on the intended use, such as light incontinence pads, light incontinence liners, urine absorption pads, sanitary napkins, pants-type paper diapers, and tape-fastened paper diapers.

Conventionally, the most widely used absorbent material is a fluff absorbent material that combines fluff pulp, a type of absorbent fiber, with a super absorbent polymer (hereinafter referred to as "SAP"). Fluff absorbents are very good, with good absorption performance, texture, and wearing comfort. However, recently, there has been a demand for thin absorbent articles that are not noticeable when worn, do not feel strange when worn, and do not feel like they are being worn. In order to meet this demand, various absorbent sheets (hereinafter referred to as "SAP sheets") have been proposed in which a super absorbent polymer is fixed and supported between two hydrophilic nonwoven fabrics.

Patent Document 1 discloses an absorbent body that includes a first sheet, a second sheet disposed opposite the first sheet, and SAP disposed between the first and second sheets, the surface of the first sheet facing the second sheet being an adhesive-coated surface, the surface of the second sheet facing the first sheet being an adhesive-coated surface, the SAP being bonded intermittently in stripes in the width direction to the adhesive-coated surface of the first sheet and/or the second sheet, and both sides in the width direction being sealed by bonding the adhesive-coated surfaces of the first sheet and the second sheet together.

Patent Document 2 discloses an absorbent body that includes a skin-side absorbent body and a non-skin-side absorbent body laminated on the non-skin-side surface of the skin-side absorbent body, the skin-side absorbent body being a liquid-permeable nonwoven fabric carrying SAP on the skin-side surface, the non-skin-side absorbent body being a silicone-based sponge layer carrying SAP except for a band region extending longitudinally in the widthwise center of the skin-side surface, and further including tissue paper adhered to the skin-side surface (SAP-carrying surface) of the skin-side absorbent body, and tissue paper adhered to the non-skin-side surface (non-SAP-carrying surface) of the non-skin-side absorbent body (or silicone-based sponge layer) (paragraph 0055). The absorbent body does not contain absorbent fibers such as fluff pulp, and is therefore a type of SAP sheet.

JP 2006-158676 A JP 2009-131349 A

Although the absorbent article equipped with the conventional SAP sheet as described in Patent Document 1 has the advantage that the wearer does not notice the wearer's wearing, it has some problems to be improved. First, since the SAP between the hydrophilic nonwoven fabrics is fixed by an adhesive, the SAP swells as a unit when it absorbs bodily fluids, which easily causes gel blocking, which reduces the diffusibility of bodily fluids. Second, in order to prevent the occurrence of gel blocking, it is possible to provide slits in the SAP sheet, but when the weight of the wearer is applied, the swollen SAP fills up the slits, and when bodily fluids are repeatedly absorbed, the absorption speed and absorption capacity decrease. Third, since the SAP sheet is thin and the SAP is arranged relatively densely in the SAP sheet, before the SAP absorbs bodily fluids, a rough feeling due to the SAP occurs, and when the SAP absorbs bodily fluids and swells, a rough feeling (hardness) occurs, which reduces the wearing comfort and fit. Fourth, SAP sheets consisting of SAP and nonwoven fabric derived from resin materials do not have the function of temporarily storing excreted body fluids before the SAP starts absorbing them, so they cannot fully absorb the initial body fluids, and leakage and wetback are likely to occur. Fifth, in the production process of absorbent articles using SAP sheets as absorbents, if the SAP sheet is not given a certain degree of stiffness (rigidity), there is a concern that the SAP sheet will turn up in the direction of travel, reducing the productivity and yield of the absorbent article. On the other hand, if stiffness is given to the SAP sheet, the wearing comfort of the resulting absorbent article is likely to be reduced.

In the absorbent of Patent Document 2, the sponge layer is disposed only on the non-skin side of the absorbent, so the sponge layer does not improve the bodily fluid diffusion of the entire absorbent, and the occurrence of gel blocking and the decrease in absorption performance such as absorption speed and absorption amount cannot be sufficiently prevented. In addition, the rough feeling of the SAP before it absorbs bodily fluids and the rough feeling that appears after the SAP absorbs bodily fluids cannot be alleviated, resulting in a decrease in wearing comfort, fit, etc.

The object of the present invention is to provide an absorbent article including an absorbent sheet that prevents leakage and wetback, has a good wearing comfort and fit, maintains its absorption performance even when repeatedly absorbing body fluids, and does not reduce productivity.

As a result of extensive research by the inventors to solve the above problems, it was discovered that by using an air-through nonwoven fabric on the skin side and a valve-containing nonwoven fabric on the non-skin side as the hydrophilic nonwoven fabrics on both sides of the thickness direction of the absorbent sheet, providing a sponge layer containing a foamed resin material in a highly absorbent polymer layer to which SAP is fixedly supported, dividing the highly absorbent polymer layer into two in the thickness direction, and using a cotton nonwoven fabric on the non-skin side of the absorbent sheet, it is possible to obtain an absorbent sheet and absorbent article having the desired characteristics while maintaining a thin shape, and thus completing the present invention. That is, the present invention provides the following absorbent article.

(1) An absorbent article comprising a liquid-permeable top sheet, a liquid-impermeable back sheet, and an absorbent body disposed therebetween,
The absorbent body includes, in order from the skin side,
an air-through nonwoven fabric that diffuses body fluids into the laminated absorbent sheet;
a first superabsorbent polymer layer having a superabsorbent polymer fixed thereto;
a sponge layer including a foam of a resin material;
a second superabsorbent polymer layer having the superabsorbent polymer fixed thereto;
A cotton nonwoven fabric that temporarily stores bodily fluids,
An absorbent article comprising:
(2) The absorbent article of (1) above, wherein the first superabsorbent polymer layer and/or the second superabsorbent polymer layer has, together with a superabsorbent polymer-containing region, a non-superabsorbent polymer-containing region extending in the longitudinal direction with a predetermined width dimension.
(3) The absorbent article according to (1) or (2) above, wherein the resin material of the sponge layer is at least one selected from the group consisting of cellulose, polyethylene, polypropylene, and polyurethane.
(4) The absorbent article according to any one of (1) to (3) above, wherein the thickness of the sponge layer in an unloaded state is 1.0 mm or more and 3.0 mm or less.
(5) The absorbent article according to any one of (1) to (4) above, wherein the cotton nonwoven fabric has a basis weight of 25 gsm or more and 60 gsm or less.
(6) The absorbent article according to any one of (1) to (5) above, wherein the average bending stiffness of the cotton nonwoven fabric is 0.03 gf·cm ² /cm or more and 0.10 gf·cm ² /cm or less.

The present invention provides an absorbent article that includes an absorbent sheet that prevents leakage and wetback, has a good wearing feel and fit, maintains its absorption performance even when repeatedly absorbing body fluids, and does not reduce productivity.

1 is a plan view showing a schematic configuration of an absorbent article according to one embodiment of the present invention. 2 is a schematic cross-sectional view in the width direction taken along the XX cutting line shown in FIG. 1. FIG. 2 is an enlarged cross-sectional view showing a schematic configuration of an absorbent body. 1A and 1B are schematic plan views showing the configuration of a first superabsorbent polymer layer or a second superabsorbent polymer layer, in which (a) shows one embodiment and (b) shows another embodiment.

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 length direction is the direction indicated by Y in the figure that extends from the front to the back of the body via the wearer's crotch when the absorbent article is worn on the body, the width direction is the direction indicated by X in the figure that is perpendicular to the length direction, and the thickness direction is the direction indicated by Z in the figure in which the components are stacked. The skin side is the surface that contacts the wearer's skin or 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>
Hereinafter, an absorbent article 50 according to this embodiment will be described with reference to the drawings. Figures 1 and 2 show the absorbent article 50. Figure 3 shows the absorbent body 20. Figure 4 shows the first superabsorbent polymer layer 22 or the second superabsorbent polymer layer 24. 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 babies and adults, such as pad products such as light incontinence pads, light incontinence liners, urine absorption pads, and sanitary napkins, and paper diaper products such as pants-type paper diapers and tape-fastened paper diapers. Various paper diapers as outerwear may be combined with the absorbent article 50, which is a pad product as innerwear. The longitudinal dimension L (FIG. 1) and width dimension W (FIG. 1) 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. By adjusting the dimensions of the absorbent article 50 to fall within the above ranges, various types of absorbent articles can be easily obtained.

The absorbent article 50 shown in Figs. 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 arranged between the top sheet 10 and the back sheet 30, a second sheet 60 arranged between the top sheet 10 and the absorbent body 20, and a pair of three-dimensional gathers 40 provided on the skin side of the top sheet 10. Furthermore, the absorbent body 20 is an absorbent sheet that does not contain absorbent fibers such as fluff pulp, and as shown in Fig. 3, it is sometimes called a laminated absorbent sheet in which, from the skin side to the non-skin side, an air-through nonwoven fabric 21, a first superabsorbent polymer layer 22 to which a superabsorbent polymer is fixed, a sponge layer 23 containing a foam of a resin material, a second superabsorbent polymer layer 24 to which a superabsorbent polymer is fixed, and a cotton nonwoven fabric 25 are laminated.

According to this embodiment, an air-through nonwoven fabric 21 and a cotton nonwoven fabric 25 are used as the hydrophilic nonwoven fabrics located closest to the skin and closest to the skin of the laminated absorbent sheet (absorbent body 20), respectively, and the highly absorbent polymer layer (hereinafter also referred to as "SAP layer") existing between these hydrophilic nonwoven fabrics is divided into two in the thickness direction by a sponge layer 23 that contains a foam of a resin material and has liquid permeability and elasticity, and is composed of a first SAP layer 22 located relatively closer to the skin and a second SAP layer 24 located relatively closer to the skin.

This configuration provides the following advantages without compromising the advantages of the absorbent sheet, namely, that it is thin and inconspicuous from the outside. First, even if a large amount of body fluid is discharged at once, the air-through nonwoven fabric 21 allows the body fluid to be distributed almost uniformly throughout the absorbent body 20. Second, the sponge layer 23 functions as a slit, significantly improving the body fluid diffusion in the first SAP layer 22 and the second SAP layer 24, making it difficult for gel blocking to occur, and even if body fluid is repeatedly absorbed, the absorption performance such as the absorption speed and absorption amount is maintained at a high level. In addition, since the sponge layer 23 has elasticity, the laminated absorbent sheet has a soft feel, and absorbs the rough feel before the SAP absorbs body fluid and the rough feel when the SAP absorbs body fluid and swells, making it difficult for them to be transmitted to the wearer's skin, thereby maintaining a good wearing comfort and fit. Third, by placing the cotton nonwoven fabric 25 closest to the skin, the cotton nonwoven fabric 25 is able to temporarily store bodily fluids, preventing leakage of bodily fluids, wetback, and the like before the SAP starts to absorb bodily fluids. Fifth, the use of the cotton nonwoven fabric 25 gives the absorbent sheet an appropriate rigidity without imparting hardness to the absorbent sheet, which makes it less likely for the absorbent sheet to turn over during the production process, and allows for mass production of absorbent articles with a comfortable fit with good productivity and high yield.

The absorbent article 50 of this embodiment has the top sheet 10, absorbent body 20, and back sheet 30 as its basic constituent 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 60 between the top sheet 10 and absorbent body 20. The components of the absorbent article 50 will be described in more detail below in the order of the top sheet 10, absorbent body 20, back sheet 30, and 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 the 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, each nonwoven fabric is preferable.

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 (grammage) of the top sheet 10 is, for example, in the range of 15 gsm (g/m ² ) to 40 gsm (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.

<Second seat>
The second sheet 60 is disposed on the non-skin side of the top sheet 10, more specifically, between the top sheet 10 and the absorbent body 20. By disposing the second sheet 60, cushioning properties are increased, fitting and wearing comfort are improved, and the bodily fluid diffusion properties of the absorbent article 50 are improved.

The base material of the second sheet 60 is a bulky nonwoven fabric that has a faster permeation rate of bodily fluids than the top sheet 10 and quickly diffuses bodily fluids into the absorbent body 20. Air-through nonwoven fabrics, spunbond nonwoven fabrics, etc. are preferred as the nonwoven fabric. The thickness of the second sheet 60 is, for example, in the range of 0.1 mm to 4 mm, and the basis weight is, for example, in the range of 15 g/m ² to 40 g/m ² or in the range of 22 g/m ² to 37 g/m ^2. If the thickness is less than 0.1 mm, or the basis weight is less than 20 g/m ² or more than 60 g/m ² , bodily fluids do not sufficiently diffuse over the entire skin side of the absorbent body 20, and the wearing comfort tends to be reduced. In addition, the shape of the second sheet 60 is not particularly limited, but in a preferred embodiment, it is a shape that can completely cover the surface of the absorbent body 20.

<Absorbent>
The absorbent 20 has a lengthwise dimension (maximum length) L ₂₀ (FIG. 1) 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) W ₂₀ (FIG. 1) of the absorbent 20 is, for example, 50 mm to 500 mm, 60 mm to 400 mm, or 65 mm to 105 mm. When the planar shape of the absorbent 20 is an hourglass shape, the lengthwise dimension is in the range of 180 mm to 800 mm, the widthwise dimensions of the ventral side and posterior side parts 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 part that contacts the wearer's crotch is in the range of 90 mm to 250 mm. The absorbent 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 includes a laminated absorbent sheet that is different from conventional absorbent sheets. As shown in FIG. 3, the laminated absorbent sheet is a type of absorbent sheet that does not contain absorbent fibers such as fluff pulp, and is made by laminating the following members from the skin side to the non-skin side: an air-through nonwoven fabric (hereinafter also referred to as the "first layer") 21, which is a hydrophilic nonwoven fabric; a first SAP layer (hereinafter also referred to as the "second layer") 22 to which SAP is fixed; a sponge layer (hereinafter also referred to as the "third layer") 23 containing a foamed resin material; a second SAP layer (hereinafter also referred to as the "fourth layer") 24 to which SAP is fixed; and a cotton nonwoven fabric (hereinafter also referred to as the "fifth layer") 25. Therefore, the laminated absorbent sheet of this embodiment retains the advantage of an absorbent sheet that is thin and difficult to recognize from the outside. Each laminated member will be described below.

(Air-through nonwoven fabric)
The air-through nonwoven fabric 21, which is the first layer of the laminated absorbent sheet of this embodiment, is a nonwoven fabric having liquid permeability and liquid diffusibility, and specific examples thereof include air-through nonwoven fabrics containing one or more types of synthetic resin fibers made of resin materials such as olefin resins, polyester resins, etc. The air-through nonwoven fabric, for example, diffuses body fluids almost uniformly throughout the entire surface direction of the absorbent body 20, particularly through the first SAP layer 22 and the sponge layer 23 to the second SAP layer 24. As a result, almost all of the superabsorbent polymers 12 (FIG. 4) in the first SAP layer 22 and the second SAP layer 24 contribute to body fluid absorption, so that the body fluid absorption amount and body fluid absorption speed are maintained at a high level even after multiple body fluid absorptions.

The basis weight of the air-through nonwoven fabric 21 used here is not particularly limited, but from the viewpoint of bodily fluid permeability and mechanical strength, it is, for example, in the range of 20 gsm to 120 gsm, or 30 gsm to 100 gsm. In addition, from the viewpoint of mechanical strength, the thickness of the fibers constituting the air-through nonwoven fabric 21 is, for example, in the range of 1.6 dtex to 14 dtex, 1.8 dtex to 9.0 dtex, or 2.0 dtex to 6.0 dtex.

(SAP layer)
The first SAP layer 22, which is the second layer of the laminated absorbent sheet of this embodiment, and the second SAP layer 24, which is the fourth layer of the laminated absorbent sheet of this embodiment, are both fixed-support layers for the superabsorbent polymer 12. The basis weight of the superabsorbent polymer 12 in the first SAP layer 22 and the second SAP layer 24 is, for example, in the range of 20 gsm to 150 gsm, or 30 gsm to 120 gsm, from the viewpoints of absorption performance such as the amount of body fluid absorption and the rate of body fluid absorption, wearing comfort and fit of the absorbent article 50, suppression of the occurrence of gel blocking, etc. The superabsorbent polymer 12 is fixed by, for example, a hot melt adhesive.

(Superabsorbent polymer)
The superabsorbent polymer 12 is not particularly limited as long as it is capable of absorbing body fluids and preventing backflow, and examples thereof include polyacrylates, polyaspartates, (starch-acrylic acid) graft copolymers, (acrylic acid-vinyl alcohol) copolymers, (isobutylene-maleic anhydride) copolymers, and saponification products thereof. Among these, from the viewpoint of the absorption amount per weight, polyacrylates are preferred, alkali metal polyacrylates are more preferred, and sodium polyacrylate is even more preferred. The superabsorbent polymer 12 may be used alone or in combination of two or more types.

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.

For example, a hot melt adhesive is used to fix and support the superabsorbent polymer 12 to each of the non-skin sides of the air-through nonwoven fabric 21 and the sponge layer 23. As the hot melt adhesive, any hot melt adhesive 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 hot melt adhesives such as styrene-butadiene-styrene copolymers and styrene-isoprene-styrene copolymers, and olefin hot melt adhesives such as ethylene-vinyl acetate copolymers. As a method for applying the hot melt adhesive, known methods such as the curtain coat method and spiral method in which the molten hot melt adhesive is applied from a nozzle in a non-contact manner, and the slot method in which the adhesive is applied in a contact manner can be used. The basis weight of the hot melt adhesive is, for example, in the range of 10 gsm or less from the viewpoint of not impairing the absorbency of the superabsorbent polymer 12 and the feel on the skin when worn.

In a preferred embodiment, the first SAP layer 22 and/or the second SAP layer 24, as shown in Fig. 4(a) and (b), have a superabsorbent polymer-carrying region (hereinafter also referred to as "SAP-carrying region") 31 and a band-shaped superabsorbent polymer-free region (hereinafter also referred to as "slit") 32 that is provided to extend in the longitudinal direction with a predetermined width dimension. The basis weight of the superabsorbent polymer 12 in the SAP-carrying region 31 is in the same range as the basis weight of the superabsorbent polymer 12 in the first SAP layer 22 and the second SAP layer 24. The slit 32 is a region where the superabsorbent polymer 12 is not fixedly carried, and when there are multiple slits 32, the SAP-carrying region 31 that extends in the longitudinal direction in a band shape with a predetermined width dimension and the above-mentioned slits 32 are arranged alternately in the width direction.

In the embodiment shown in FIG. 4(a), SAP-holding regions 31 and slits 32 having approximately the same width dimension are alternately arranged from the width center toward the width outside, and slits 32 relatively narrower than these are arranged at both width ends. In the embodiment shown in FIG. 4(b), a relatively narrow SAP-holding region 31 is provided at the width center, and slits 32 of approximately the same width as the narrow SAP-holding region 31 at the width center are provided on both width sides of the narrow SAP-holding region 31, and relatively wide SAP-holding regions 31 are provided on each width outside, and slits 32 of approximately the same width as the SAP-holding region 31 at the width center are provided on each width outside. According to these embodiments, the body fluid diffusion in the longitudinal direction of the laminated absorbent sheet (absorbent body 20) is improved, gel blocking is prevented, and even if body fluid is repeatedly absorbed, the absorption performance such as the absorption speed and absorption amount is maintained at a high level at the beginning of use.

The width dimension of the slits 32 can be appropriately selected depending on the number of slits 32, and is, for example, in the range of 3 mm to 20 mm, or 5 mm to 15 mm. The number of slits 32 can be appropriately selected depending on the width dimension of the slits 32 themselves, and is, for example, in the range of 1 to 5, or 1 to 3. By providing slits 32 in the first SAP layer 22, the longitudinal diffusion of bodily fluids is improved, the occurrence of gel blocking is further prevented, and the absorption performance is maintained at a higher level. In a more preferred embodiment, the total area of the SAP-carrying regions 31 on the skin side of the first SAP layer 22 is configured to be larger than the total area of the slits 32.

(Sponge layer)
The sponge layer 23, which is the fourth layer of the laminated absorbent sheet of this embodiment, contains a foam having open cells and liquid permeability, and for example, imparts softness to the laminated absorbent sheet, improves bodily fluid diffusion in the first SAP layer 22 and the second SAP layer 23 by its own liquid permeability, the first SAP layer 22 and the second SAP layer 23 have slits 32, and even when the wearer's weight is applied to the slits 32, the shape of the slits 32 is maintained, maintaining the improvement in bodily fluid diffusion by the slits 32 and thus the absorption performance when repeatedly absorbing bodily fluids, and suppressing the deterioration of wearing comfort and fit by mitigating the rough feeling that occurs when the superabsorbent polymer 12 absorbs bodily fluids. The reasons for obtaining such excellent effects include the liquid permeability and flexibility (elasticity) of the sponge layer 23 itself, but it is believed that the sponge layer 23 is mainly located between the first SAP layer 22 and the second SAP layer 24. If the sponge layer 23 is the first layer of the laminated absorbent sheet, the sponge layer 23 itself will absorb body fluids and tend to cause wet-back (return of fluid) onto the surface of the absorbent article 50 .

The sponge layer 23 includes a foam of a resin material, and is preferably made of a foam of a resin material. Here, the resin material is not particularly limited as long as it is a resin material that can easily form a sponge that is a hydrophilic open-cell foam. However, from the viewpoint of reducing the overall thickness of the laminated absorbent sheet and increasing the elasticity and flexibility of the foam to form a sponge layer 23 that fits the wearer's body, it is preferable that the resin material is one or more selected from cellulose, polyethylene, polypropylene, polyurethane, etc. If the foam of these resin materials is used, the thickness of the sponge layer 23 can be easily adjusted to 1.0 mm or more and 3.0 mm or less in the unloaded state. If the thickness of the sponge layer 23 is within the above-mentioned range, the absorbent article 50 becomes thin, the wearing of the absorbent article becomes less noticeable, and the above-mentioned effects of the sponge layer 23 become particularly good. The hydrophilic foam may have hydrophilic properties in the skeleton of the foam itself, or may be made hydrophilic by bonding hydrophilic groups such as alkyleneoxy groups and surfactant-derived substituents that can impart hydrophilicity to the foam.

From the viewpoint of liquid permeability, the expansion ratio of the hydrophilic foam is, for example, in the range of 10 to 60 times. By setting the expansion ratio in the above-mentioned range, the mechanical strength of the hydrophilic foam (or sponge layer 23) is maintained while improving the flexibility of the hydrophilic foam, improving the fit of the laminated absorbent sheet to the wearer's body, and the effect of reducing the roughness of the superabsorbent polymer 12 after absorbing body fluids is increased, thereby maintaining a high level of wearing comfort.

Whether the sponge layer 23 is an open-cell foam can be confirmed by cutting the layer and observing the cut surface under a microscope. In addition, whether the skeletal surface of the foam is hydrophilic can be confirmed by the following method. First, a foam sample (width 10 mm or more, length 10 mm or more) is left to stand without bending, and 10 drops of ion-exchanged water (0.05 mL) are dropped onto the surface of the sample and the time until the sample is absorbed is measured. If this time is within 5 seconds or if 8 or more drops are absorbed, it is judged to be hydrophilic.

In a preferred embodiment, the thickness of the sponge layer 23 is in the range of 1.0 mm to 3.0 mm in the unloaded state. If the thickness of the sponge layer 23 is less than 1.0 mm or exceeds 3.0 mm, the effect of imparting flexibility to the laminated absorbent sheet and the effect of reducing the roughness of the superabsorbent polymer 12 after absorbing bodily fluids tend to be insufficient.

In another preferred embodiment, the apparent density of the sponge layer 23 is, for example, in the range of 0.05 g/ ^cm3 to 0.4 g/ ^cm3 , or 0.1 g/ ^cm3 to 0.3 g/ ^cm3 . If the apparent density is less than 0.05 g/ ^cm3 , the mechanical strength of the sponge layer 23 decreases, the boundary between the first SAP layer 22 and the second SAP layer 24 becomes unclear, and the body fluid diffusibility tends to decrease. If the apparent density exceeds 0.4 g/ ^cm3 , the liquid permeability of the sponge layer 23 becomes insufficient, and gel blocking tends to occur and the absorption performance during repeated absorption tends to decrease.

(cotton nonwoven fabric)
The cotton nonwoven fabric 25, which is the fifth layer of the laminated absorbent sheet of this embodiment, temporarily stores bodily fluids before the superabsorbent polymer 12 starts absorbing the bodily fluids at the beginning of excretion of the bodily fluids, preventing the occurrence of wetback and leakage, and imparts rigidity to the laminated absorbent sheet or absorbent body 20 while maintaining the softness of the absorbent body 20, thereby improving the productivity of the absorbent article 50. As the cotton nonwoven fabric 25, a nonwoven fabric containing cotton fibers is preferable, and a nonwoven fabric made of cotton fibers (a nonwoven fabric made of 100% cotton fibers) is more preferable. As the form of the cotton nonwoven fabric 25, a spunlace nonwoven fabric is preferable, and a spunlace nonwoven fabric in which cotton fibers are entangled with each other by a water flow to form a nonwoven fabric is more preferable.

In the spunlace process, cotton fibers are generally placed on a support such as a net and sprayed with a high-pressure water stream, which results in the formation of fine irregularities on the surface of the resulting cotton nonwoven fabric 25. These irregularities increase the adhesive strength at the interface between the second SAP layer 24 and the cotton nonwoven fabric 25, allowing the cotton nonwoven fabric 25 to function satisfactorily until the absorbent article 50 is no longer in use.

The basis weight of the cotton nonwoven fabric 25 is, for example, in the range of 25 gsm to 60 gsm in terms of the temporary storage of bodily fluids. If the basis weight is less than 25 gsm, the function of temporarily storing bodily fluids tends to be insufficient, and the laminated absorbent sheet (or absorbent body 20) tends to become too soft in the production process of the absorbent article 50, causing the side in the direction of travel to turn up, resulting in reduced productivity. On the other hand, if the basis weight is more than 60 gsm, the sheet itself becomes too thick, which is undesirable as a sheet that constitutes part of the laminated absorbent sheet (or absorbent body 20), and also tends to cause the laminated absorbent sheet (or absorbent body 20) to become hard, resulting in a reduced wearing comfort.

Furthermore, by setting the average bending stiffness of the cotton nonwoven fabric 25 in the range of 0.03 gf·cm ² /cm or more and 0.10 gf·cm ² /cm or less, the hardness of the laminated absorbent sheet (or absorber 20) is reduced, and the wearing comfort and fit of the absorbent article 50 are improved. Note that the higher the average bending stiffness, the harder the feel. The average bending stiffness of the cotton nonwoven fabric 25 can be adjusted, for example, by appropriately changing the pulp fiber content, the fiber diameter of the pulp fibers, the basis weight of the cotton nonwoven fabric 25, etc. The average bending stiffness of the cotton nonwoven fabric 25 can be measured, for example, using a pure bending tester (product name: KES-FB2-S, manufactured by Kato Tech Co., Ltd.).

In the absorbent body 20, a carrier sheet may be provided under the absorbent body 20 to prevent leakage of SAP particles and stabilize the shape of the absorbent body 20. The base material of the carrier sheet may be any material that has hydrophilicity, and examples of such base materials include tissue, absorbent paper, and hydrophilic nonwoven fabrics such as airlaid nonwoven fabrics. When multiple carrier sheets are provided, the base materials of the multiple carrier sheets may be the same or different.

<Method of manufacturing absorbent body>
The absorbent body 20 can be manufactured by a manufacturing method including the steps of preparing an air-through nonwoven fabric 21, a sponge layer 23, and a cotton nonwoven fabric 25, which are separately manufactured; forming a first SAP layer 22 (with slits 32, if necessary) on the non-skin side of the air-through nonwoven fabric 21 using a superabsorbent polymer 12 and a hot melt adhesive; forming a second SAP layer 24 (with slits 32, if necessary) on the non-skin side of the sponge layer 23 using a superabsorbent polymer 12 and a hot melt adhesive; and laminating the air-through nonwoven fabric 21 supporting the first SAP layer 22, the sponge layer supporting the second SAP layer 23, and the cotton nonwoven fabric 25 in this order so that the non-skin side of the first SAP layer 22 contacts the skin side of the sponge layer 23 and so that the non-skin side of the second SAP layer 24 contacts the skin side of the cotton nonwoven fabric 25.

<Back seat>
The back sheet 30 may be formed using a liquid-impermeable substrate that prevents body fluids held by the absorbent 20 from wetting 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 gsm to 60 gsm in terms of strength and processability. In addition, in order to prevent stuffiness when worn, it is preferable that the back sheet 30 is breathable. In order to provide breathability to the back sheet 30, 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 can be any known method without any restrictions.

<3D gathers>
The three-dimensional gathers 40 are fixed to the skin side of the top sheet 10 along the length of the absorbent article 50 near both ends in the width 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 along the length of the sheet member 40b near the free end (other end), imparting uprightness to the free end, and allowing the free end and the area nearby 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, the skin side or non-skin side near both widthwise ends of the joint between the top sheet 10 and the back sheet 30, which contains the absorbent body 20 inside, and the skin side near both widthwise ends 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 4 and Comparative Examples 1 to 7)
(Preparation of absorbent articles)
An absorbent article having the structure shown in FIG. 2 was produced.
As the absorbent, a laminated SAP sheet (with slits) having the configuration shown in Table 1 was used. As the liquid-permeable top sheet, an air-through nonwoven fabric (25 gsm basis weight) was used. As the liquid-impermeable back sheet, a breathable polyethylene sheet (32 gsm basis weight) was used. As the second sheet, an air-through nonwoven fabric (30 gsm basis weight) was used. As the three-dimensional gather, a composite nonwoven fabric (15 gsm basis weight) in which a spunbond nonwoven fabric/meltblown nonwoven fabric/spunbond nonwoven fabric were laminated in this order was used. When the top sheet, back sheet, and absorbent were integrated, the top sheet and the upper surface of the absorbent were joined using a hot melt adhesive to produce absorbent articles having a longitudinal dimension of 270 mm and a width dimension of 105 mm for Examples 1 to 4 and Comparative Examples 1 to 7.

The following evaluations were carried out on the absorbent articles of Examples 1 to 4 and Comparative Examples 1 to 7. The results are shown in Table 1.
[evaluation]
(Evaluation of the ease of rolling up the fifth layer of the laminated absorbent sheet)
The absorbent bodies (laminated absorbent sheets) of Examples 1 to 4 and Comparative Examples 1 to 7 were placed on a horizontal laboratory bench, and the sheet was held down by hand at a point 30 cm from the edge and moved horizontally at a speed of 100 cm/sec. This operation was carried out 10 times, and those that did not roll up 2 or less times out of the 10 were marked with "◯", and those that rolled up 3 or more times out of the 10 were marked with "X".
(Average bending stiffness of the fifth layer of cotton nonwoven fabric in the laminated absorbent sheet)
The average bending stiffness was measured using a pure bending tester, friction tester KES-FB2-S (manufactured by Kato Tech Co., Ltd.). A 100 m x 100 m sample was attached to the device with a clamp distance of 10 mm, and the curvature increase rate was measured at 5 mm/sec.
(Confirmation of temporary absorption)
With the top sheet facing up, 200 ml of saline was poured toward the center of the absorbent body. If no leakage occurred from the absorbent article during the pouring process, it was rated as "O", and if leakage occurred, it was rated as "X".
(Absorption rate 3 times method)
A measuring tool with a base area of 16.8 ^cm2 , a hole with an inner diameter of 19 mm at the center, and a weight of 755.6 g was placed on the center of the absorbent article in the longitudinal and width directions, and 20 ml of saline was dropped from the hole at the top. The time was measured from the time the saline came into contact with the absorbent article to the time when the liquid was completely absorbed into the circumference of the center circle of the tool (first time). The same time was then measured after 3 minutes had passed (second time), and a third time was measured in the same manner.
(Amount of liquid returned)
With the top sheet facing up, 120 ml of saline was poured towards the centre of the absorbent body and left for 10 minutes. After that, a filter paper (Advantec No. 2 filter paper, diameter 55 mm) whose weight had been measured in advance was placed on the area where the saline had been absorbed, and a 35 kgf/ ^cm2 weight was placed on top of it. After 30 seconds, the weight of the filter paper was measured and the difference in the weight of the filter paper was recorded as the amount of liquid wetback.
(Firmness of absorbent articles)
The prototype absorbent article was worn by 20 monitors, and a sensory evaluation was conducted on the hardness of the absorbent article itself. For the sensory evaluation, each evaluation was conducted by selecting either "good" or "bad," and the evaluation was conducted according to the following criteria.
○: When there are 12 to 20 people who choose "Good" △: When there are 5 to 11 people who choose "Good" ×: When there are no people who choose "Good" or when there are 1 to 4 people who choose "Good"
(Absorbent body resistance to twisting)
The prototype absorbent article was worn by 20 test subjects, and a sensory evaluation was conducted on the resistance of the absorbent body to twisting. For the sensory evaluation, the subjects were asked to select either "good" or "bad," and the evaluation was based on the following criteria.
○: When there are 12 to 20 people who think it is "good" △: When there are 5 to 11 people who think it is "good" ×: When there are no people who think it is "good" or when there are 1 to 4 people who think it is "good" (fit with the body)
The prototype absorbent article was worn by 20 monitors, and a sensory evaluation was conducted on the fit of the article when worn. The sensory evaluation was conducted by selecting either "good" or "bad" for each evaluation, and the evaluation was conducted according to the following criteria.
○: When there are 12 to 20 people who choose "Good" △: When there are 5 to 11 people who choose "Good" ×: When there are no people who choose "Good" or when there are 1 to 4 people who choose "Good"

From the results in Table 1, it can be seen that temporary storage was performed without any problems in Examples 1 to 4, and the absorption rate was fast even after multiple absorptions. In addition, the return of liquid was low. In the sensory evaluation, there were no problems with hardness, resistance to creasing, or fit.
On the other hand, Comparative Examples 1 to 7 had poor results in the sensory evaluation, and also had poor temporary absorption and absorption speed.
Therefore, according to the present invention, an absorbent article can be obtained which is less susceptible to gel blocking, has a fast absorption rate, is excellent in temporary absorption, and has suitable hardness and resistance to wrinkling, resulting in an excellent fit.

10 Liquid-permeable top sheet 12 Superabsorbent polymer (SAP)
20 Absorbent body 21 Air-through nonwoven fabric 22 First highly absorbent polymer layer (first SAP layer)
23 Sponge layer 24 Second superabsorbent polymer layer (second SAP layer)
25 Cotton nonwoven fabric 30 Liquid impermeable back sheet 31 Highly absorbent polymer carrying region (SAP carrying region)
32 Superabsorbent polymer non-supporting region (slit)
40: Three-dimensional gather 40a: Elastically stretchable member 40b: Sheet member 50: Absorbent article 60: Second sheet

Claims (6)

An absorbent article comprising a liquid-permeable top sheet, a liquid-impermeable back sheet, and an absorbent body disposed therebetween,
The absorbent body includes, in order from the skin side,
An air-through nonwoven fabric that diffuses body fluids into the absorbent body;
a first highly absorbent polymer layer having a highly absorbent polymer fixedly supported on the non-skin side of the air-through nonwoven fabric ;
a sponge layer including a foam of a resin material;
a second superabsorbent polymer layer having the superabsorbent polymer fixed and supported on the non-skin side of the sponge layer ;
A cotton nonwoven fabric that temporarily stores bodily fluids,
An absorbent article comprising: The absorbent article according to claim 1, wherein the first superabsorbent polymer layer and/or the second superabsorbent polymer layer has a superabsorbent polymer non-carrying region that is arranged to extend in the longitudinal direction with a predetermined width dimension together with the superabsorbent polymer carrying region. The absorbent article according to claim 1 or 2, wherein the resin material of the sponge layer is at least one selected from the group consisting of cellulose, polyethylene, polypropylene, and polyurethane. The absorbent article according to any one of claims 1 to 3, wherein the thickness of the sponge layer in an unloaded state is 1.0 mm or more and 3.0 mm or less. The absorbent article according to any one of claims 1 to 4, wherein the cotton nonwoven fabric has a basis weight of 25 gsm or more and 60 gsm or less. The absorbent article according to any one of claims 1 to 5, wherein the average bending stiffness of the cotton nonwoven fabric is 0.03 gf·cm ² /cm or more and 0.10 gf·cm ² /cm or less.