JP4514668B2 - Absorbent articles - Google Patents

Description

  The present invention relates to absorbent articles such as sanitary napkins, disposable diapers, incontinence pads, panty liners, and the like, and more specifically, relates to absorbent articles having excellent absorption performance, little stuffiness, and extremely excellent wearing feeling.

Hitherto, absorbent articles have been proposed in which the increase in humidity during wear is suppressed to reduce stuffiness, such as those described in JP-A-6-218007 and JP-A-7-132126. The technologies described in these publications include an absolutely dry pulp, a large amount of highly water-absorbing polymer, a material having hygroscopic properties such as silica gel and lithium chloride in the absorber, and a combination of a moisture-permeable back sheet. is there.
In addition, JP-A-10-508521 discloses an absorbent article using a moisture-permeable back sheet. By combining two sheets having moisture permeability, it is a technique that prevents the liquid from oozing out through the moisture-permeable back sheet even under pressure.
However, even in these techniques, the excreted body fluid remains as a liquid that is not fixed between the fibers of paper and pulp, so that when the amount of fluid excreted is large, water vapor is generated from the liquid that is not fixed. This tends to cause stuffiness.

In addition, in JP-A-7-184956, by using an absorber whose centrifugal retention capacity and simulated blood permeation rate after equilibrium absorption and swelling of simulated blood are each equal to or higher than a predetermined value, liquid return from the absorber is prevented. A sanitary napkin designed to prevent the above has been proposed, and Japanese Patent Application Laid-Open No. 6-28788 discloses a paper layer made by mixing bulky cellulose fibers. A multilayer absorbent paper having a base layer is proposed. JP-A-9-156013 discloses an absorbent sheet containing a superabsorbent polymer and bulky cellulose fibers, hydrophilic fine fibers or An absorbent sheet containing a hydrophilic fine powder has been proposed.
However, in these publications, even when the excretion amount (liquid absorption amount) is large, the generation of water vapor can be remarkably suppressed and the structure of the absorbent article that can remarkably suppress the generation of stuffiness is not described at all. .

JP-A-6-218007 JP-A-7-132126 Japanese National Patent Publication No. 10-508521 Japanese Patent Laid-Open No. 7-184958 JP-A-6-28788 Japanese Patent Laid-Open No. 9-156013

Accordingly, a first object of the present invention is to provide an absorbent article that is less likely to cause stuffiness even when the amount of excretion is large, has a good wearing feeling, is highly absorbent, and has excellent leakage prevention properties.
A second object of the present invention is to provide an absorbent article that is less likely to cause stuffiness even when used for a long time, has excellent wearing feeling, is highly absorbent, and has excellent leakage prevention properties.

  The present invention relates to an absorbent article having a liquid-permeable surface layer, a liquid-impermeable leak-proof layer, and a liquid-retaining absorbent layer, wherein the absorbent layer is a hydrophilic fiber or hydrophilic foam that does not swell with water. Or a hydrophilic fiber or hydrophilic foam having a water retention amount of 0.7 g / g or less when swelled with water and then centrifuged and dehydrated, and a superabsorbent polymer. The first object was achieved by providing an absorbent article characterized in that 10 g of water was absorbed and the physiological saline was immobilized at a rate of 90% or more when centrifugally dehydrated after 5 minutes. (Hereinafter, the first invention refers to this invention.)

  In the absorbent article having a liquid-permeable surface layer, a liquid-impermeable leak-proof layer, and a liquid-retaining absorbent layer, the leak-proof layer is water vapor-permeable, and the absorption The absorbent article is characterized in that 10 g of physiological saline is absorbed in the absorbent article, and the fixing rate of the physiological saline is 90% or more when centrifugally dehydrated after 5 minutes. (Hereinafter, the second invention is referred to as this invention).

According to the first aspect of the present invention, it is possible to provide an absorbent article that is less likely to cause leakage and stuffiness even when there is a large amount of excretion, has excellent wearing feeling, is highly absorbent, and has excellent leakage prevention properties.
For example, in the absorbent article of the present invention, even if the amount of excretion is large, most of the absorbed liquid can be completely fixed. The stickiness can be reduced and a comfortable wearing feeling can be obtained. When a moisture-permeable sheet is used for the leak-proof layer, an increase in humidity and temperature due to perspiration can be effectively suppressed, and the comfort can be further improved. In addition, the hydrophilic material used for the absorbent body does not hold the body fluid or the amount of liquid held is small, so that the body fluid in the voids (or the voids of the foam) in the fiber assembly stays. The easy-to-part void structure is stable even when liquid is absorbed, and since the void structure promotes the diffusion of body fluid to the superabsorbent polymer, most of the absorbed body fluid has high water absorption. It is guided to the polymer and can be completely retained by the polymer.

According to the second aspect of the present invention, it is possible to provide an absorbent article that is less likely to cause stuffiness even when used for a long time, has excellent wearing feeling, is highly absorbent, and has excellent leakage prevention properties.
That is, the absorbent article of the second invention has a predetermined liquid retention and immobilization rate, so that there is no leakage due to stuffiness in the wearing due to water vapor generated from the absorption layer or liquid return from the absorption layer, and there is no leakage prevention layer. Since it is water vapor permeable, stuffiness in the dressing is less likely to occur.
In particular, when the wetting tension of the leak-proof layer is 37 mN / m or less, even if the surface tension of the excretory liquid is low, the liquid is difficult to bleed through the leak-proof layer and has excellent leak prevention properties. In an absorbent article in which liquid return from the absorbent layer is unlikely to occur, the wearer is further provided with a feeling of wearing and a sense of security.

Hereinafter, the present invention will be described based on preferred embodiments with reference to the drawings. FIG. 1 shows a sanitary napkin as an embodiment of the absorbent article of the first and second inventions, and FIG. 2 schematically shows a cross-section in the width direction of the sanitary napkin of FIG. ing.
The sanitary napkin 1 of the present embodiment has a substantially vertically long shape, a top sheet 2 as a liquid-permeable surface layer, a back sheet 3 as a liquid-impermeable leak-proof layer, and both layers The absorbent body 4 is provided as a liquid-retaining absorbent layer interposed between the two.
The top sheet 2, the back sheet 3, and the absorbent body 4 each have a vertically long shape, and are integrated with their longitudinal directions matched.
The absorber 4 is bonded and fixed to the back sheet 3 via a hot melt pressure-sensitive adhesive 5. A liquid-impermeable leak-proof sheet 6 is disposed on both sides of the napkin 1 so as to cover both side edges of the absorbent body 4 to form a leak-proof portion. On the lower surface side of the back sheet 3, an adhesive 7 is applied in two strips to form an adhesive part for fixing the napkin 1 to a wearing tool such as shorts. The adhesive part is a release sheet 8. Protected.
Further, the top sheet 2, the back sheet 3, and the leak-proof sheet 6 are bonded and fixed to each other by a heat seal 13 at a portion extending outward from the peripheral edge of the absorber 4. Further, the top sheet 2 and the leak-proof sheet 6 are joined to each other on the upper surface side of the both sides of the absorber 4 by a heat seal 11, and the upper surface portion of the absorber 4 is joined by the top sheet 2 and the heat seal 12. It is integrated.

The absorbent layer (absorbent body) 4 in the absorbent article of the first invention has a hydrophilic fiber or hydrophilic foam that does not swell with water, or a water retention amount of 0.7 g / centre when swelled with water and then centrifugally dehydrated. g or less, preferably 0.5 g / g or less of hydrophilic fiber or hydrophilic foam and a superabsorbent polymer.
Examples of the material for forming hydrophilic fibers or hydrophilic foams that do not swell with water include resins that do not swell themselves, such as synthetic resins such as polyethylene, polypropylene, polyester, polyurethane, and composites of two or more of these. Since these synthetic resins have a hydrophobic surface, it is necessary to perform a hydrophilic treatment. As a method of hydrophilization treatment, a solution of a surfactant is sprayed and applied to the fiber made of the synthetic resin or a foam after molding, and the surface is adhered to the surface, or a hydrophilic surfactant is previously added. There is a method of kneading into the synthetic resin, then molding into a fiber or foam, and bleeding a surfactant on the surface.

  The surfactant used for the hydrophilization treatment is not particularly limited as long as it is a hydrophilic surfactant having a hydrophilic group and a lipophilic group, but an anionic surfactant and an ethylene oxide-based addition mole number is high. Nonionic surfactants are preferred. Specifically, sulfosuccinic acid ester, alkyl ether sulfate, polyoxyethylene alkyl ether, polyoxyethylene alkyl phenyl ether, glycerin fatty acid ester and the like are preferable. Among these surfactants, those capable of imparting sufficient hydrophilicity at a use ratio of about 0.05 to 3% by weight with respect to the synthetic resin are preferable. Surfactant can be used individually by 1 type or in mixture of 2 or more types.

  A hydrophilic fiber or hydrophilicity having a water retention amount (hereinafter referred to as “centrifugal retention amount of water”) of 0.7 g / g or less, more preferably 0.5 g / g or less when centrifugal dehydration is performed after swelling with water. Examples of the foam-forming material include materials that do not require hydrophilic treatment, that is, materials that themselves have a hydrophilic surface, and crosslinked cellulose fibers in which cellulose molecules or molecules are crosslinked with an appropriate crosslinking agent. (Pulp fiber), cellulose sponge, polynosic rayon fiber with improved crystallinity of cellulose, polyvinyl alcohol fiber, polyvinyl alcohol sponge, acrylic fiber, acrylic sponge and the like. Among these, from the viewpoint of production cost, a crosslinked pulp fiber obtained by crosslinking a wood pulp made of cellulose is preferable.

When an absorbent body is formed with hydrophilic fibers or hydrophilic foams having a centrifugal retention amount of water exceeding 0.7 g / g, body fluid is absorbed in these hydrophilic fibers or foams, and the elasticity of the fibers or foams The rate decreases and body fluid tends to remain between the fibers and in the pores of the foam, so that moisture in the wearing environment increases due to water vapor released from the remaining body fluid.
A method for measuring the amount of centrifugal retention of water will be described later in Examples.
In addition, chemical pulp, such as normal conifer pulp and hardwood pulp, has a centrifugal retention amount of about 1 to 2 g / g. Hereinafter, hydrophilic fibers having a centrifugal retention of water of 0.7 g / g or less are referred to as “low swelling hydrophilic fibers”, and hydrophilic foams having a centrifugal retention of water of 0.7 g / g or less are referred to as “low swelling”. May be referred to as a “hydrophilic foam”.
Cellulose crosslinking agents include N-methylol compounds such as dimethylolethyleneurea and dimethylolhydroxyethyleneurea, polycarboxylic acids such as tricarballylic acid citrate and butanetetracarboxylic acid, polyglycidyl ether compounds, Aldehyde compounds are preferably used.

  The absorbent layer (absorber) 4 in the absorbent article of the first invention contains a highly water-absorbing polymer in addition to the non-swellable or low-swellable hydrophilic fibers or hydrophilic foams described above. Generation of water vapor from the excreted body fluid by allowing most of the body fluid that has permeated the top sheet to be absorbed and retained by the superabsorbent polymer without retaining between the fibers or in the pores of the foam. Is reduced, and an increase in humidity in the wearing environment can be effectively prevented.

  As the superabsorbent polymer, a polymer that can absorb and retain a body fluid 20 times or more of its own weight and can gelate is preferable. Examples thereof include starch, crosslinked carboxylmethylated cellulose, a polymer of acrylic acid or an alkali metal acrylate or a copolymer thereof, polyacrylic acid and a salt thereof, and a polyacrylate graft polymer. As the polyacrylate, sodium salt is preferable.

  As a superabsorbent polymer, it has the function of quickly absorbing and retaining body fluids between fibers and from pores in the foam, and the polymer surface is kept dry even after absorbing and swelling body fluids, Those which do not easily diverge and do not hinder the movement of body fluid between the polymers even after absorption and swelling are preferable. Such a function is difficult to express when the polymer has a uniform cross-linked structure, and therefore, the superabsorbent polymer preferably has a cross-linking density gradient.

  As a method of giving a crosslink density gradient to the superabsorbent polymer, for example, when a polyacrylate is used as the superabsorbent polymer, a crosslinker that can react with the functional group of the polyacrylate (hereinafter referred to as polymer crosslinking). And a method of causing the polymer surfaces to crosslink with each other by further reacting with a polyacrylate. As said polymer crosslinking agent, the compound which has a 2 or more functional group which can react with a carboxyl group is preferable, for example, polyglycidyl ethers, such as ethylene glycol diglycidyl ether, polyethyleneglycol diglycidyl ether, glycerol triglycidyl ether, etc. And polyols such as glutaraldehyde and glyoxal and polyamines such as ethylenediamine.

  The particle form of the superabsorbent polymer is preferably a non-spherical shape. When the particle form is non-spherical, it is possible to prevent the voids between the polymer particles from being reduced due to the rearrangement and adhesion of the particles when the superabsorbent polymer absorbs the body fluid and swells. As a result, gel blocking that is likely to occur in the case of spherical particles can be prevented, and rapid and sufficient absorption by the polymer is performed.

  As a method of obtaining a non-spherical superabsorbent polymer, a method of pulverizing a superabsorbent polymer obtained by bulk polymerization into a non-spherical shape, or polymer particles obtained during the production of a superabsorbent polymer, A method of obtaining an amorphous superabsorbent polymer composed of aggregates in which polymer particles are primary particles by further bonding with a polymer cross-linking agent by a catalytic reaction, and an amorphous polymer by selecting a polymer dispersant during polymer production. There is a method to get etc.

The superabsorbent polymer is used in combination with the above-described hydrophilic fiber or hydrophilic foam. As an aspect of the combined use, the superabsorbent polymer is layered by spreading or the like in an aggregate of hydrophilic fibers or a hydrophilic foam. The superabsorbent polymer is preferably three-dimensionally dispersed in the aggregate or foam of hydrophilic fibers. When dispersed three-dimensionally, the contact area between the fiber or foam and the superabsorbent polymer increases, so that the body fluid that has permeated the top sheet can be quickly retained without retaining between the fibers or in the pores of the foam. Can be absorbed by the highly water-absorbing polymer, and the effect of preventing an increase in humidity is further improved.
Here, “three-dimensionally dispersed” is not a form in which a water-absorbing polymer exists linearly or in layers between fiber aggregates or foams, but only in the plane direction between the fiber aggregates or foams. It means that the superabsorbent polymer is also dispersed in the thickness direction.

  The superabsorbent polymer preferably has a centrifugal retention amount of 25 g or more with respect to physiological saline, and more preferably 30 g or more. In addition, about the measuring method, it mentions later in an Example.

In the absorbent layer (absorber) 4, the content of hydrophilic fibers or hydrophilic foams that do not swell with water, or hydrophilic fibers or hydrophilic foams with a centrifugal retention amount of 0.7 g / g or less is as follows. The content of the absorbent layer (absorber) 4 is preferably 30 to 70%, particularly 40 to 70%.
When the content of the non-swellable or low-swellable hydrophilic fiber or hydrophilic foam is within the above range, the liquid immobilization rate of the absorbent article can be further increased, and the form of the absorbent body Stability and polymer fixability can be improved.
Both the non-swellable hydrophilic fiber or hydrophilic foam and the low-swellable hydrophilic fiber or hydrophilic foam may be contained in the absorbent layer (absorbent), in which case the total of both The content is preferably within the above range.

The content of the superabsorbent polymer in the absorbent layer (absorber) 4 is preferably 30 to 70%, particularly 35 to 60%, based on the total weight of the absorbent layer (absorber) 4. It is preferable that When the content of the superabsorbent polymer is within the above range, the liquid immobilization rate of the absorbent article is high, and the form stability of the absorbent body due to the movement of the wearer and the stability of the polymer are better. Easy to design.
The mixing ratio of the non-swellable or low-swelling hydrophilic fiber or hydrophilic foam and the superabsorbent polymer in the absorbent layer (absorbent body) 4 is 3 / in weight ratio (the former / the latter). 7-7 / 3 is preferable.

As the absorbent layer (absorbent body) 4 in the absorbent article of the second invention, the above-mentioned non-swellable or low-swellable hydrophilic fibers or those comprising the hydrophilic foam and a superabsorbent polymer are used. However, the present invention is not limited to this, and for example, a fiber or foamed material having a centrifugal retention amount of 0.7 g / g or more can be used.
In the absorbent article of the second invention, since the liquid-impermeable leak-proof layer has water vapor permeability, non-fixed water that is not fixed in the absorber has evaporated to become water vapor. Emanates through the leak-proof layer, resulting in a decrease in the amount of non-fixed liquid. That is, the use range of the hydrophilic fiber or foam that can be used in the absorbent body is expanded, and the centrifugal retention amount of water is not limited to the fiber or foam that is 0.7 g / g or less.

The absorbent article (sanitary napkin) 1 of the present invention absorbs 10 g of physiological saline, and has a 90% fixed rate of physiological saline (hereinafter referred to as a liquid holding and fixed rate) when centrifugally dehydrated after 5 minutes. % Or more, preferably 93% or more. The higher the liquid retention and immobilization rate, the better and the upper limit is 100%. The method for measuring the liquid retention and immobilization rate will be described later in Examples.
If the liquid retention and immobilization rate is less than 90%, the amount of vapor emitted from the absorber increases, the humidity increases, and the feeling of stuffiness during mounting increases. On the other hand, if it is 90% or more, leakage due to the retained liquid being discharged again does not occur.

  The configuration for setting the liquid holding and fixing ratio to 90% or more is not particularly limited, but the absorbent body 4 is composed of the above-described hydrophilic fiber or hydrophilic foam and the above-described superabsorbent polymer. The body fluid that has permeated through the top sheet is preferably absorbed by the superabsorbent polymer quickly without staying between the fibers or in the pores of the foam. It is preferable to absorb and diffuse quickly from the surface of the absorber to the entire superabsorbent polymer blended inside the absorber.

  Specifically, an aggregate composed of hydrophilic fibers in the vicinity of a superabsorbent polymer or a hydrophilic foam is measured in accordance with JIS P8141, and the water absorption of Klem after 1 minute with respect to physiological saline (hereinafter, simply referred to as “water absorption polymer”). The Klem water absorption) is preferably 40 mm or more, particularly preferably 50 mm or more. Such diffusibility can be adjusted by increasing the specific surface area by appropriately selecting the fiber diameter of the hydrophilic fiber or adjusting the pore diameter of the voids in the foam.

  Furthermore, the diffusibility of the aggregate of hydrophilic fibers or hydrophilic foam is given a gradient from the absorber surface to the vicinity of the superabsorbent polymer, and the aggregate or foam of hydrophilic fibers near the superabsorbent polymer is provided. It is preferable to improve the diffusivity of the material more than the diffusivity on the surface of the absorber.

  As a method for improving the diffusibility, for example, when using a fiber obtained by hydrophilizing a synthetic fiber that does not swell in water as the hydrophilic fiber, the fiber diameter may be reduced to increase the specific surface area of the fiber. In this case, the average fiber diameter is preferably 20 μm or less, particularly preferably 0.1 to 10 μm. As a fiber assembly including fibers having such an average fiber diameter, it is preferable to use a melt blown nonwoven fabric capable of making the fibers extremely fine. Furthermore, in order to make three-dimensional entanglement with the superabsorbent polymer, the sheet material is obtained by spraying the polymer from the blowout opening of the meltblown until the fiber is deposited, and entwining the polymer and the fiber three-dimensionally. Can be obtained.

  Moreover, as an absorption layer (absorber) in which the diffusibility of the hydrophilic fiber or hydrophilic foam in the vicinity of the superabsorbent polymer is improved as compared with the surface of the absorption layer (absorber), the absorption layer (absorber) is Whether it has a surface fiber layer that forms the surface on the surface layer (surface sheet) side, and an internal fiber layer laminated on the back side of the surface fiber layer, does the internal fiber layer contain a superabsorbent polymer? Alternatively, it is preferable that the surface fiber layer is in contact with the highly water-absorbing polymer and the surface fiber layer has a smaller water absorption than the inner fiber layer.

As described above, the inner fiber layer preferably has a Krem water absorption of 40 mm or more, particularly 50 mm or more, and the surface fiber layer preferably has a Klem water absorption of less than 40 mm, particularly 5 to 35 mm.
When the surface fiber layer and the inner fiber layer have different clem water absorptions and have a diffusive gradient, the surface fiber layer particularly has a clem water absorption of less than 40 mm and the inner fiber layer has a clem water absorption of 40 mm or more. In this case, a liquid such as a body fluid absorbed by the surface fiber layer can be quickly guided to and absorbed by the superabsorbent polymer in the inner fiber layer by capillary osmotic pressure.
The internal fiber layer may have a structure in which a superabsorbent polymer is dispersed in one non-woven fabric or a structure in which a superabsorbent polymer is sandwiched between two non-woven fabrics.
In addition, while making the hydrophilic fiber near the superabsorbent polymer very fine 0.1 to 10 μm, thickening the fiber on the absorber surface to 10 to 100 μm, and using two kinds of fibers having different diameters, the blending ratio Is preferably 3/7 to 9/1 by weight ratio (the former / the latter).

  Further, as a method for improving the diffusibility of the hydrophilic fiber or hydrophilic foam in the vicinity of the superabsorbent polymer as compared with the surface of the absorber, for example, the superabsorbent polymer is inserted in the fiber gap of the above-described melt-blown nonwoven fabric having a small fiber diameter. A nonwoven fabric (surface fiber layer) made of a synthetic fiber with a large fiber diameter that does not swell in water is hydrophilized on the composite sheet (inner fiber layer) that holds the fiber. The absorber is manufactured so as to be positioned on the surface side of the substrate. The nonwoven fabric disposed on the surface side of the absorbent body is a synthetic fiber having a fiber diameter of 10 μm to 100 μm, which is larger than the fiber in the vicinity of the polymer, and is made of polyethylene, polypropylene, polyester, polyurethane, and two or more kinds thereof. Spunbond nonwoven fabrics, heat roll nonwoven fabrics, suction heat bond nonwoven fabrics and the like made of synthetic fibers such as these composites are preferred.

In addition, when hydrophilic fibers having a centrifugal retention of water of 0.7 g / g or less are used as hydrophilic fibers, the fiber density of the fiber assembly made of hydrophilic fibers is appropriately set. It is preferable to mix a small amount of ultrafine pulp having a high specific surface area, for example, hardwood pulp.
As a method of giving a gradient to diffusivity, increase the fiber density near the polymer than the absorber surface, or blend a small amount of the above-mentioned ultrafine pulp with a high specific surface area, for example, hardwood pulp, in the vicinity of the polymer, A diffusion gradient is formed.

In order to obtain an absorbent body in which a hydrophilic fiber having a centrifugal retention amount of 0.7 g / g or less and a superabsorbent polymer are combined, the method such as a dry method and a wet method is not limited.
For example, in the dry method, the hydrophilic fibers are stacked in the air, and then the superabsorbent polymer is sprayed on the fiber assembly, or the hydrophilic fibers and the superabsorbent polymer are mixed and stacked in a sheet form. Produce fine. In addition, in order to obtain dry and wet strength in a sheet state, heat-fusible fibers made of polyethylene, polypropylene, polyester fibers, and composite fibers thereof are mixed with the hydrophilic fibers and then heated by heat treatment or the like. It can be produced by bonding fused fibers to each other, or spraying and drying binders such as acrylate copolymers, acrylate esters / vinyl acetate copolymers, ethylene / vinyl acetate copolymers, etc. And a sheet material with wet strength can be obtained.

As a method obtained by a wet method, a hydrophilic fiber is dispersed in water, and then the hydrophilic fiber is piled up in a sheet state with a papermaking wire, and then superabsorbent polymer on a wet sheet before drying with a dryer. By spraying, the superabsorbent polymer absorbs water from the sheet, expresses tackiness, and another sheet material is stacked and dried with a dryer, so that the superabsorbent polymer adheres to the hydrophilic fibers and dries. And a method for obtaining a sheet material. In particular, in the case of a method obtained by a wet method, the fibers in the vicinity of the water-absorbing polymer are collected around the polymer by expressing the adhesiveness due to the water content of the polymer and then dried, resulting in a higher fiber density, This is a more preferable production method because a fiber diffusion gradient can be automatically formed.
Alternatively, a hydrophilic gradient having a centrifugal retention amount of 0.7 g / g or less and a synthetic fiber that does not swell in water may be combined to give a diffusion gradient.

In the present invention, the occupied volume V ₀ of the absorbent layer (absorber) 4 and the physiological saline retention amount V ₁ (g) when the absorbent layer (absorber) 4 is swollen with physiological saline and then subjected to centrifugal dehydration. The ratio (V ₁ / V ₀ ) is preferably 1 g / cm ³ or more. The ratio between the occupied volume V ₀ and the physiological saline holding amount V ₁ (hereinafter referred to as the volume holding amount ratio P) is more preferably 1.5 g / cm ³ or more, and the higher the better.
When the volume retention ratio P is 1 g / cm ³ or more, the retention absolute amount of the absorbent layer (absorber) is sufficient, and the body fluid remains between the fibers of the fiber assembly or in the absorption space in the foam. Therefore, it is possible to further prevent the occurrence of leakage or the emission of vapor.

Absorbing layer occupying volume V ₀ which (cm ³⁾ refers to the volume occupied in the load of a 2.5 g / cm ² of the absorbent layer, the thickness and the absorbent layer in the 2.5 g / cm ² under a load of absorbent layer Obtained by multiplying by the occupied area (planar area). In addition, the physiological saline holding amount V ₁ when the absorbent layer is swollen with physiological saline and then centrifuged and dehydrated will be described in detail later. A physiological saline solution that can be completely fixed in the absorbent layer will be described later. The retention amount (g) is obtained. When the volume retention ratio P is 1 g / cm ³ or more, if the flow of the body fluid in the absorption layer is idealized, the body fluid absorbed in the occupied volume V ₀ of the absorption layer is converted into a superabsorbent polymer. Can be absorbed and retained.

Although the physiological saline holding amount V ₁ varies depending on the use of the absorbent article and the product size, for example, in a sanitary product, the physiological saline holding amount V ₁ is expressed by the area of the absorbent body (planar area). The absorbed retention amount per 1 m ² of the absorbent (absorbing layer) is preferably 1000 g / m ² or more, more preferably 2000 g / m ² or more.

In this invention, it is preferable that the thickness of the absorption layer (absorber) 4 is 2.5 mm or less.
When the thickness of the absorbent layer is 2.5 mm or less, the uncomfortable feeling at the time of wearing can be further reduced, and since the unit volume of the absorbent article is reduced, the amount of vapor emitted from the absorber is reduced, and the inside of the wearing It is possible to further reduce or prevent the humidity rise and stuffiness. In consideration of the balance with the absorption performance, the lower limit of the thickness of the absorption layer is about 0.5 mm. The thickness of the absorption layer is measured under a load of 2.5 g / cm ² .

The absorbent body 4 in the sanitary napkin 1 of this embodiment has the thick part 4a in the part distribute | arranged to a wearer's excretion part at the time of wear, as shown to FIG. More specifically, it has a thick portion 4a in the central portion arranged in the excretion portion, and a raised portion is formed on the upper surface (skin contact surface P) of the napkin 1 by the thick portion 4a. .
The thickness W1 of the absorber 4 in the thick portion 4a is preferably as thin as 1.5 to 2.5 mm, and the thickness W2 of the absorber 4 in the peripheral portion of the thick portion 4b is 0.5 to 2.0 mm. It is more preferable that Moreover, it is preferable that ratio (W1 / W2) of thickness W1 with respect to thickness W2 is 1.5-4.
By making the absorbent material unevenly distributed in the excretory part, the excreted body fluid can be concentrated and absorbed in the central part without spreading. As a result, the area absorbed by the absorber is smaller, the increase in humidity is small, and by making the periphery thinner, the divergence of humidity / temperature can be more effective.

  The area of the thick part 4a is preferably 10 to 50% with respect to the total area of the surface (upper surface) of the absorbent body 4 on the skin contact surface P side. The shape and size of the thick portion 4a can be appropriately determined according to the application of the absorbent article, but a vertically long shape whose length direction coincides with the longitudinal direction of the napkin is preferable. It is preferable that the width is 20 to 50 mm and the length is 60 to 150 mm in the size of product length 180 to 260 mm, which is a regular size napkin for night use, and the width 20 in the size of product length 260 to 350 mm for night size. It is preferable that the length is 50 mm and the length is 100 to 250 mm.

  The backsheet (leakproof layer) 3 is preferably water vapor permeable. By making the leak-proof layer water vapor permeable, water vapor caused by sweating of the wearer due to exercise etc. can be efficiently diffused to the outside through the leak-proof layer, and the absorber absorbs and holds most of the body fluids The synergistic effect of being possible can effectively prevent an increase in humidity in the dress and the occurrence of stuffiness. In addition, when the absorbent body is thin, it is easy to release the temperature trapped in the dressing, and the absorbent article has a structure that keeps the temperature / humidity comfortable.

The degree of water vapor permeability of the backsheet (leak-proof layer) 3 is 0.3 g / (moisture permeability measured in accordance with JIS Z0208 (hereinafter referred to as moisture permeability measured by this method). 100 cm ² · hr) or more, particularly 0.7g / (100cm ² · hr) or more, and further it is 1.0~5.0g / (100cm ² · hr) is, in terms of increase in humidity prevention in wearing preferable.
The material for forming the leak-proof layer in the case of water vapor permeability is not particularly limited as long as it is waterproof and has water vapor permeability, but to a hydrophobic thermoplastic resin made of polyethylene or polypropylene or a mixture thereof, Porous film obtained by melting and mixing fine inorganic fillers such as calcium carbonate and barium sulfate to form a film, and stretching the film uniaxially or biaxially, and sized waterproof paper And a nonwoven fabric made of a hydrophobic fine thermoplastic fiber obtained by a production method such as a melt blown, a porous film, waterproof paper, a composite sheet of a nonwoven fabric made of a hydrophobic fine thermoplastic fiber, and the like.

Usually, the surface tension of excreted fluid such as urine is 50 to 60 mN / m and the surface tension of blood is about 50 mN / m. However, in sanitary napkins and the like, the surface tension is extremely low. Blood may be excreted. In addition, even in the case of disposable diapers, when the surface material or the constituent material of the absorbent body is subjected to a treatment such as attaching a surfactant to the material to increase the hydrophilicity, the urine etc. excreted in large quantities The surfactant may dissolve and reduce the surface tension of the urine.
When such a liquid such as urine or menstrual blood having a very low surface tension is absorbed by the absorbent body, if a moisture-permeable back sheet is used for the leak-proof layer, the liquid is introduced into the micropores of the moisture-permeable sheet. May permeate and ooze out to the outside.
The technique described in the above-mentioned Japanese translations of PCT publication No. 10-508521 is a technique that prevents the liquid from leaking through the moisture-permeable back sheet, but prevents the seepage due to the physical thickness and structure of the moisture-permeable back sheet. However, two backsheets are required, the processing raw material increases, the processing machine becomes complicated and the cost increases, and when menstrual blood with low surface tension is excreted, There is a risk of seeping outside. Furthermore, as described above, when the amount of excreted body fluid is large, water vapor is generated and stuffiness is likely to occur.

The water vapor-permeable leak-proof layer is a viewpoint that prevents the liquid from penetrating into the micropores of the leak-proof layer and exuding to the outside even when the surface tension of the excretory liquid to be absorbed and retained by the absorbent article is extremely low. Therefore, the wetting tension is preferably 37 mN / m or less, and more preferably 35 mN / m or less. Here, the wetting tension of the leak-proof layer means that when the sheet material constituting the leak-proof layer is placed on a horizontal surface and a test liquid having a predetermined surface tension is dropped from above, the test liquid is on the back side. This means the value of the surface tension of the test liquid having the lowest surface tension among the test liquids that do not ooze out, and a specific measuring method will be described later in Examples.
Such a leak-proof layer having a low wetting tension is obtained by, for example, using a porous film obtained by mixing an inorganic filler such as calcium carbonate or barium sulfate with a thermoplastic resin, and forming and stretching the film. As a dispersant for uniformly dispersing in a plastic resin, it can be obtained by using a lipophilic dispersant having a lower surface energy. The water vapor permeable leak-proof layer may be composed of a plurality of sheet materials, but is preferably composed of a single sheet material.

  As a material for forming the top sheet (surface layer) 2, various materials conventionally used for absorbent articles, such as non-woven fabric types and perforated films obtained by perforating a film, should be used without particular limitation. However, polyethylene, polypropylene, polyester, polyethylene-polypropylene conjugate fiber, polyethylene-polypropylene conjugate fiber, and a mixture thereof are preferably used to produce a nonwoven fabric and subjected to three-dimensional pore opening treatment. The perforated film has a large contact area with the wearer's skin, and the non-perforated part does not have air permeability. Since the part has air permeability, and the holes are three-dimensionally opened, there is also air permeability in the plane direction of the opening side part of the surface material. It can suppress more effectively.

Conventionally, the surface material made of non-woven fabric has a drawback that the liquid is liable to leak and easily leak due to liquid return from the absorbent in the non-woven fabric, compared with the apertured film. Since most of the body fluid absorbed in the absorption layer is absorbed and held by the polymer and the liquid return to the surface layer is extremely small, the disadvantages of the conventional nonwoven fabric type are solved.
The present invention can be applied to disposable diapers, incontinence pads, panty liners and the like in addition to sanitary napkins.

Hereinafter, the present invention will be further described based on examples and comparative examples.
<Superabsorbent polymer A>
In a 500 ml four-necked round bottom flask equipped with a stirrer, reflux condenser, dropping funnel and nitrogen gas inlet tube, 230 ml of cyclohexane and sorbitan monostearate [trade name: Leodol SPS-12, Kao Corporation] Made] 1.4 g was charged and stirred to obtain a homogeneous solution. Separately, in an Erlenmeyer flask, 30 g of acrylic acid monomer was neutralized with 13.4 g of caustic soda dissolved in 39 g of water to obtain a monomer aqueous solution having a monomer concentration of 45% (water content 55%).
Subsequently, 0.1 g of potassium persulfate was added and dissolved in this monomer aqueous solution. The obtained aqueous monomer solution was dropped into the above four-necked round bottom flask charged with cyclohexane or the like under a nitrogen atmosphere, and then the temperature was raised to 70 to 75 ° C. to initiate polymerization. Subsequently, the water content in the polymer suspended in cyclohexane was controlled to 35% by azeotropic dehydration (cyclohexane was refluxed). Thereafter, an aqueous solution in which 0.03 g of ethylene glycol diglycidyl ether was dissolved in 1 ml of water was added at 73 ° C., and kept at this temperature for 2 hours. Then, cyclohexane was removed, and the resulting polymer was added at 80 to 100 ° C. And dried under reduced pressure to obtain a superabsorbent polymer A. This superabsorbent polymer A has a crosslink density gradient on the surface, the particle surface is indefinite, and the centrifugal retention amount with respect to physiological saline is 33 g / g.

<Superabsorbent polymer B>
In the same four-necked round bottom flask used for the production of the superabsorbent polymer A, 230 ml of cyclohexane and 1.94 g of ethyl cellulose [trade name; N-200, manufactured by Hercules Far East Co., Ltd.] were charged and stirred. A homogeneous solution. Further, an aqueous monomer solution having the same amount as the aqueous monomer solution of acrylic acid used for the production of the superabsorbent polymer A was prepared.
Next, the temperature of the solution in the above four-necked round bottom flask was raised to 70 to 75 ° C., and an aqueous monomer solution was dropped into the reactor over 1.5 hours in a nitrogen atmosphere. For 0.5 hour to complete the polymerization. Thereafter, cyclohexane was removed, and the resulting polymer was dried at 80 to 100 ° C. under reduced pressure to obtain a superabsorbent polymer B. This superabsorbent polymer B has no crosslink density gradient, the particles are spherical, and the centrifugal retention amount with respect to physiological saline is 28 g / g.

<Absorber A>
A surfactant in which a sheath / core having a fiber diameter of 15 μm (2.2 dtex) / core / polyethylene / polyester (polyethylene terephthalate) is mixed with an alkyl phosphate and a sorbitan fatty acid ester in a one-to-one relationship with the fiber. To obtain a hydrophilic fiber which does not swell with water by being attached to 0.4% by weight, and a suction heat bond nonwoven fabric (surface fiber layer) comprising 100% of the hydrophilic fiber and having a water absorption of Krem of 10 mm and a basis weight of 20 g / m ^2. Manufactured.
Subsequently, polyoxyethylene sorbitan monolaurate [6 ethylene oxide addition moles, Kao (as a hydrophilizing surfactant) in linear low density polyethylene [ethylene / 1 octene copolymer, Mitsui Petrochemical Co., Ltd.] Co., Ltd.] 1% by weight was mixed, and this was laminated on the suction heat bond nonwoven fabric at a basis weight of 30 g / m ² as a fiber that does not swell with water having an average fiber diameter of 8 μm by the melt jetting method (melt blown method). A laminated sheet made of two types of nonwoven fabric was obtained. The melt blown nonwoven fabric (inner fiber layer) formed on the suction heat bond nonwoven fabric had a Klem water absorption of 55 mm. Then, the superabsorbent polymer A is sprayed on the meltblown nonwoven fabric side of the laminated sheet at a basis weight of 40 g / m ² , and the meltblown nonwoven fabric is formed on the superabsorbent polymer A in a hydrophilic manner. The linear low density polyethylene fiber (average fiber diameter: 8 μm) internally added with an agent was sprayed at a basis weight of 30 g / m ² to obtain a polymer sheet A having a total basis weight of 120 g / m ² .
Separately, the same amount of the superabsorbent polymer A as that of the fiber is deposited during the period from when the linear low density polyethylene fiber (with an average fiber diameter of 8 μm) internally added with a hydrophilizing agent is deposited on the net from the melt outlet. A polymer sheet B having a total basis weight of 80 g / m ² (a basis weight of the inner superabsorbent polymer A 40 g / m ² ) was produced by mixing and depositing.
Then, the polymer sheet A is cut out to a size of 175 mm in length and 140 mm in width, and two polymer sheets B are cut out to a size of 80 mm in length and 35 mm in width, and the polymer sheet as shown in FIGS. 2 is folded in the width direction as the sheet 41 in FIG. 2 with the suction heat bond nonwoven fabric side as the surface side, and the polymer sheet B is 2 in the center of the polymer sheet A as in the sheet 42 in FIG. Sheets were stacked and arranged to obtain an absorber. This was designated as Absorber A.

<Absorber B>
The polymer sheet A used for the absorber A was cut out to a size of 175 mm in length and 140 mm in width, and the polymer sheet B used in the absorber A was cut out to a size of 175 mm in length and 70 mm in width. The polymer sheet A was folded in the width direction so that the suction heat bond nonwoven fabric side was the surface side to form two layers, and the polymer sheet B was interposed between the two layers to obtain an absorber. This was designated as Absorber B.

<Absorber C>
Dimethylol dihydroxyethylene urea (trade name: Sumitex Resin NS-19, Sumitomo) using 100 g of wood chemical pulp (trade name: NB-416L, Wafer User Co., Ltd.) having a water retention of 1.1 g / g as a crosslinking agent Chemical Industry Co., Ltd.] is dispersed in 1000 g of a crosslinking agent aqueous solution containing 5% by weight of a metal catalyst [trade name; Sumitex Accelerator X-110, Sumitomo Chemical Co., Ltd.] 3% by weight. Is drained until the amount of water becomes 200% by weight with respect to the weight of the wood pulp, and heated in an electric dryer at 135 ° C. for 10 minutes to crosslink between and within the molecules of cellulose in the pulp to crosslink the pulp A. The centrifugal retention amount of water of the obtained crosslinked pulp A was 0.35 g / g.
Further, 100 g of hardwood wood pulp LBKP (trade name; PRIME ALBEAT ASPEN HANDWOOD, Wafer User Co., Ltd.) having a centrifugal retention amount of 1.3 g / g of water was subjected to crosslinking treatment in the same procedure to obtain crosslinked pulp B. Got. The centrifugal retention amount of water of the obtained crosslinked pulp B was 0.45 g / g.
Cross-linked pulp A and superabsorbent polymer A are mixed and mixed in the air 1: 1 to obtain a sheet having a basis weight of 90 g / m ² , and further an acrylic ester copolymer [trade name; Mobile 710, Hoechst Synthetic Co., Ltd.] was sprayed, compressed, and dried in an actual amount of 10 g / m ^{2 over the} entire sheet to obtain a polymer sheet C (inner fiber layer) having a total basis weight of 100 g / m ² . This sheet has a Clem water absorption of 43 mm.
Cross-linked pulp A, cross-linked pulp B, and superabsorbent polymer A were mixed and stacked in air at a ratio of 4 to 1: 5 to obtain a sheet having a basis weight of 90 g / m ² , and an acrylic ester copolymer [ Product name: Movinyl 710, manufactured by Hoechst Synthesis Co., Ltd.] was sprayed, compressed and dried in an actual amount of 10 g / m ² on the entire sheet to obtain a polymer sheet D having a total basis weight of 100 g / m ² . This sheet has a Klem water absorption of 50 mm.
The obtained polymer sheet C and a suction heat bond nonwoven fabric (surface fiber layer) having the same Krem water absorption 10 mm and a basis weight 20 g / m ² as used in the manufacture of the absorbent body A are laminated, and the obtained laminated sheet Is cut into a dimension of 175 mm in length and 140 mm in width, and the polymer sheet D is cut into a dimension of 80 mm in length and 35 mm in width, and the laminated sheet cut out like the absorbent body 4 shown in FIGS. The sheet is folded in the width direction like the sheet 41 in FIG. 2 so that the side is the front side, and one polymer sheet D is disposed at the center so as to be interposed between the laminated sheets, thereby obtaining an absorbent body. . This was designated as Absorber C.

<Absorber D>
Cross-linked pulp A and polyvinyl alcohol fiber [trade name; Fibrybond Sansho Co., Ltd.] are dispersed in water at a ratio of 97: 3, mixed, paper-dried with a paper-making net, Klem water absorption 50 mm, basis weight 35 g A wet nonwoven fabric A (inner fiber layer) of / m ² was obtained. From the slurry having the same composition as that of the wet nonwoven fabric A, a web is made with a papermaking net so that the basis weight when dried is 25 g / m ^2, and the superabsorbent polymer A is formed on the wet web before drying. After uniformly spreading so that the basis weight is 40 g / m ^2, and further laminating the wet nonwoven fabric A on the polymer A, it is integrated by compressing and drying with a drying dryer, and the total basis weight is 100 g / m ² . A polymer sheet F was obtained.
Cross-linked pulp A, cross-linked pulp B, and the above-mentioned polyvinyl alcohol fiber were dispersed in water at a ratio of 87: 10: 3, mixed, and paper-dried with a paper-making net to have a Klem water absorption of 55 mm and a basis weight of 30 g / A wet nonwoven fabric B of m ² was obtained. From the slurry having the same composition as that of the wet nonwoven fabric B, a web is made with a paper net so that the basis weight when dried is 20 g / m ^2, and the superabsorbent polymer A is formed on the wet web before drying. After uniformly spreading so that the basis weight is 50 g / m ^2, and further laminating the wet non-woven fabric B on the polymer A, it is integrated by compressing and drying with a drying dryer, and the total basis weight is 100 g / m ² . A polymer sheet G was obtained.
The obtained polymer sheet F was cut into a size of 175 mm in length and 140 mm in width, and two polymer sheets G were cut out into a size of 80 mm in length and 35 mm in width, and cut out like the absorbent body 4 shown in FIGS. The polymer sheet F was folded in the width direction like a sheet 41 in FIG. 2, and two polymer sheets G were laminated at the center of the polymer sheet F like a sheet 42 in FIG. 2. Furthermore, a suction heat bond nonwoven fabric (surface fiber layer) having a water absorption of 10 mm used for the absorbent body A is cut into a length of 175 mm and a width of 70 mm on the skin contact surface side of the polymer sheet F containing the polymer sheet G in the center. It laminated | stacked and the absorber was obtained. This was designated as Absorber D.

<Absorber E>
Wood chemical pulp (trade name; NB-416L, Wafer User Co., Ltd.) having a centrifugal retention amount of water of 1.1 g / g and a superabsorbent polymer A are mixed in air in a one-to-one relationship with air. A sheet having a basis weight of 90 g / m ² is obtained, and an acrylic acid ester copolymer [trade name: Movinyl 710, manufactured by Hoechst Synthesis Co., Ltd.] is sprayed and dried in an actual amount of 10 g / m ^{2 over the} entire sheet. to obtain a polymer sheet H total basis weight of 100 g / m ^2. This sheet has a Klem water absorption of 40 mm.
The obtained polymer sheet H was cut into one piece having a length of 175 mm and a width of 140 mm and two pieces having a length of 80 mm and a width of 35 mm, and a single large polymer sheet H like the absorbent body shown in FIGS. Two small polymer sheets H were laminated on the central part of each to obtain an absorber. This was designated as Absorber E.

<Absorber F>
Wood chemical pulp (trade name; SKEENA PRIME, Skeena Cellulose Co.) having a centrifugal retention amount of water of 1.3 g / g is dispersed and mixed in water, and paper-dried with a paper-making net. A wet absorbent paper having a Klem water absorption of 30 mm and a basis weight of 18 g / m ² was obtained. The obtained absorbent paper was cut into a length of 175 mm and a width of 70 mm, and the superabsorbent polymer B was spread almost uniformly on the absorbent paper with a basis weight of 40 g / m ² on a length of 175 mm and a width of 70 mm. Furthermore, the wood chemical pulp having a centrifugal retention amount of 1.1 g / g of water used in the absorbent body E was piled in air at a length of 175 mm, a width of 70 mm, and a basis weight of 200 g / m ^2. The above-mentioned wet absorbent paper cut with a width of 175 mm and a width of 140 mm, and the above-mentioned pulp, superabsorbent polymer B, and absorbent paper wrapped together and compressed and integrated, were used as the absorber F.

<Absorber G>
The wood chemical pulp having a centrifugal retention amount of 1.3 g / g of water used in the absorber F and the crosslinked pulp A used in the absorber B are uniformly dispersed and mixed in water at a ratio of 80:20, and papermaking dried paper making net to give Klemm water absorbency 35 mm, a wet absorbent paper having a basis weight of 45 g / m ^2. From the slurry having the same composition as that of the wet absorbent paper, a web is made with a paper net so that the basis weight when dried is 45 g / m ^2, and the superabsorbent polymer B is formed on the wet web before drying. Is uniformly sprayed to a basis weight of 10 g / m ^2, and wet absorbent paper made in advance is pasted on the polymer B, and compression-dried and integrated to form a polymer sheet having a total basis weight of 100 g / m ^2. Obtained. Two polymer sheets were cut into a size of 80 mm in length and 35 mm in width, and one in a size of 175 mm in length and 140 mm in width, and the larger polymer sheet and the smaller two in the size of the absorber shown in FIGS. An absorbent body was obtained by wrapping one polymer sheet, and this was used as the absorbent body G.

<Absorber H>
Wood chemical pulp with a centrifugal retention amount of 1.3 g / g of water used in Absorbent F is uniformly dispersed in water, mixed, paper-dried with a paper-making net, Klem water absorption 30 mm, basis weight 18 g / m ² wet absorbent papers were obtained. The obtained absorbent paper was cut into a length of 175 mm and a width of 70 mm, and the superabsorbent polymer B was almost uniformly formed on the absorbent paper so that the basis weight was 10 g / m ² at a length of 175 mm and a width of 70 mm. Furthermore, the wood chemical pulp having a centrifugal retention amount of 1.1 g / g of water used for the absorbent body E is 175 mm in length, 70 mm in width and 300 g / m ² in basis weight, and is further piled in air. Cut into a dimension of 175 mm in length and 140 mm in width, and a suction heat bond nonwoven fabric with a basis weight of 20 g / m ² and a Krem water absorption of 10 mm used in the absorbent body A, and wrapping the pulp, water-absorbing polymer B, and absorbent paper described above. The compression-integrated product was used as the absorber H.

Regarding each of the absorbent bodies A to H obtained as described above, the type of the hydrophilic fiber used, the type of the superabsorbent polymer used, the hydrophilic fiber that does not swell in water in each absorber or the centrifugal retention of water. The content of hydrophilic fibers with an amount of 0.7 g / g or less (in Table 1, indicated as “content of hydrophilic fibers in the absorber”), the content of superabsorbent polymer in each absorber, and the absorber Presence or absence of diffusion gradient of fiber aggregate from surface to superabsorbent polymer (presence or absence of gradient of Krem absorbency), thickness of the central part (thick part) of the absorbent, other than the central part (peripheral part) of the absorbent Table 1 shows the thickness, the occupied volume V _{0 of} the absorber, the physiological saline holding amount V _{1 of} the absorber, and the volume holding ratio P (= V ₁ / V ₀ ).

1. 1. “Retention amount of water when centrifugal dehydration is performed after swelling with water (centrifugal retention amount of water)” of hydrophilic fiber or hydrophilic foam; 2. thickness of the absorber; 3. Occupied volume V _{0 of} the absorber, and The physiological saline holding amount V ₁ and the volume holding amount ratio P of the absorber were measured by the methods described below.

<Measurement of centrifugal retention of water>
The measurement is performed in a constant temperature and humidity room at 20 ° C. and 65%. 1 g of a hydrophilic material sample of fiber or foam was weighed, placed in a bag made of nylon mesh (250 mesh), placed in a beaker containing 500 ml of ion-exchanged water, and left for 30 minutes. Then, in a centrifuge [H-130C (trade name) manufactured by Kokusan Centrifuge Co., Ltd.], the bag containing the sample taken out of the beaker was rotated for 10 minutes at 2000 rpm (895G centrifugal acceleration). And then spin-dehydrated. Then, the weight of the sample after centrifugal dehydration was measured, and the “water retention amount (centrifugal retention amount of water) when swollen with water and then centrifugal dewatered” was determined from the following formula.
Centrifugal retention amount of water (g / g) = [sample weight after centrifugation−initial sample weight] / initial sample weight

  Centrifugal retention amount of the superabsorbent polymers A and B with respect to physiological saline, except that the hydrophilic material sample of fiber and foam and ion-exchanged water are replaced with polymer and physiological saline [Otsuka Pharmaceutical Co., Ltd.], respectively. The measurement was performed in the same manner as the method for measuring the amount of water retained by centrifugation. Note that, under the above-mentioned greenhouse temperature, the superabsorbent polymer absorbs moisture and increases its weight. Therefore, the initial sample weight was quickly taken from a sealed polymer container and weighed.

<Measurement of absorber thickness>
The thickness L was measured with a thickness meter [PEACOCK DIAL GAUGE, Ozaki Mfg. Co., Ltd.] at a load area of 3 cm ² (disc with a radius of 9.8 mm) and a measurement load of 2.5 g / cm ^{2 on} the upper surface of the absorber. .

<Measurement of occupied volume V ₀ of absorber>
The occupied volume V ₀ (cm ³ ) of the absorber was determined by the product of the thickness L (cm) under a load of 2.5 g / cm ² of the absorber and the occupied area (plane area, cm ² ) of the absorber. .

<Measurement of Saline Retention Volume V ₁ and Absorber Volume Retention Ratio P>
The measurement is performed in a constant temperature and humidity room at 20 ° C. and 65%. The absorbent body was put in a bag made of nylon mesh (250 mesh), and the whole bag was put in a beaker containing 3000 mL of physiological saline [Otsuka Pharmaceutical Co., Ltd.] and left as it was for 30 minutes. Then, the bag containing the sample is taken out of the beaker, and the bag containing the sample is 2,000 rpm / 895 (centrifugal acceleration of 895 G) using a centrifuge (H-130C (trade name) manufactured by Kokusan Centrifuge Co., Ltd.). ) For 10 minutes to perform spin-drying.
The weight of the sample after centrifugal dehydration was measured, and the “retention amount of physiological saline (saline retention amount) when swollen with physiological saline and then subjected to centrifugal dehydration” was determined from the following formula. Saline retention amount V1 (g) = sample weight after centrifugation (g) −initial sample weight (g)
Then, the obtained saline holding amount V1 (g) is divided by the occupied volume V ₀ (cm ³ ) of the absorbent body measured as described above, and the volume holding ratio P (g / cm ^3). )

[Examples and Comparative Examples of the First Invention]
Using the absorbent bodies A to H obtained as described above, the absorbent articles 1 to 4 (invention products 1 to 4) as examples of the first invention and the comparative examples as follows. Absorbent articles 1 to 4 (comparative products 1 to 4) were produced.

<Manufacture of Absorbent Article 1 as Example>
As shown in FIGS. 1 and 2, the absorbent body A is used as the absorbent body 4, and the top sheet 2 is made of a suction heat-bonded nonwoven fabric having a basis weight of 25 g / m ^{2 made} of a PET / PE core-sheath composite fiber with a porosity of 10%. An apertured non-woven fabric having an aperture diameter of 0.8 mm per aperture was superposed on the absorbent body 4, and the surface sheet and the absorbent body had a pattern 12 as shown in FIG. The surface sheet and the absorbent body were integrated by a heat seal 12 through a heated roll. On both sides, a leak-proof sheet 6 made of a spunbonded nonwoven fabric having a basis weight of 20 g / m ^{2 made} of water-repellent PET / PE core-sheath composite fiber was laminated in a double layer, and then passed through a heat roll in the same manner. The leak-proof sheet 6, the top sheet 2, and the absorber 4 were integrated by a heat seal 11. Thereafter, the hot melt 5 coated in a spiral shape with a width of 50 mm and a length of 150 mm and a basis weight of 5 g / m ² at the central portion of the absorbent body 4 on the non-skin contact surface side, and a width of 1 mm and a length of 150 mm and a basis weight of 150 g on both sides thereof. in / m ^2, a hot melt 5 coated on bead coating, further, superposed polyethylene backsheet 3 having a basis weight of 25 g / m ^2. Thereafter, the periphery of the absorbent body 4 was adhered by a heat seal 13, and the leak-proof sheet 6, the top sheet 2, and the back sheet 3 were integrated, and cut into a shape shown in FIG. 1 with a length of 200 mm and a width of 95 mm. Furthermore, the non-skin facing side of the backsheet 3, as an adhesive 7 for displacement preventing, length 150 mm, width of 20 mm, a hot-melt adhesive at a basis weight 30 g / m ² was applied to the two strip This was covered with a release sheet 8 having a width of 60 mm and a length of 170 mm to obtain an absorbent article (sanitary napkin) 1 as an example.

<Production of Absorbent Articles 2 to 4 as Examples and Absorbent Articles 1 to 4 as Comparative Examples>
Absorbent articles 2 to 4 as examples were obtained in the same manner as in the manufacture of the absorbent article 1 except that the absorbent bodies B to D were used instead of the absorbent body A. Also, absorbent articles 1 to 4 as comparative examples were obtained in the same manner as in the manufacture of the absorbent article 1 except that the absorbent bodies E to H were used instead of the absorbent body A.

  About each of the obtained absorbent articles, “10 g of physiological saline was absorbed and centrifugal dehydration was performed after 5 minutes, and the rate of immobilization of the physiological saline (liquid retention immobilization ratio)”, anti-moisture performance of the absorbent article (Mole generation number) and liquid return amount were measured and evaluated by the following methods, respectively, and the results are shown in Table 2.

Below, the measurement method and evaluation method of the physiological saline fixation rate (liquid retention fixation rate), the anti-moisture performance of the absorbent article (the number of occurrences of liquid leakage), and the liquid return amount will be described.
<Liquid retention immobilization rate>
The measurement is performed in a constant temperature and humidity room at 20 ° C. and 65%. As shown in FIG. 4, the absorbent article is placed horizontally, the acrylic plate 15 shown in FIG. 3 having a 10 mm diameter injection port is placed, and the sanitary napkin for the test is 5 g / The weights 16 and 16 are placed so that a load of cm ² is applied. Next, 10 g of physiological saline [Otsuka Pharmaceutical Co., Ltd.] is injected from the injection port with a 10 ml beaker in about 2 seconds, and after the liquid is completely absorbed, it is left for 5 minutes with the acrylic plate on it. Then, a sample is put in the bag which consists of a nylon mesh (250 mesh) of the dimension into which an absorbent article enters without bending. In the physiological saline absorbed by the absorbent article, the top sheet side of the absorbent article is directed outward (from the absorbent to the top so that the physiological saline that is not completely fixed to the absorbent can be centrifuged. Install in a centrifuge so that centrifugal acceleration is applied to the seat side. Using a centrifuge [H-130C (trade name) manufactured by Kokusan Centrifuge Co., Ltd.], the bag containing the sample was spun at 2000 rpm for 10 minutes (895G centrifugal acceleration) for 10 minutes. Thereafter, the weight of the sample was measured, and 10 g of physiological saline was absorbed from the formula shown below, and the immobilization rate (liquid retention immobilization rate) of the physiological saline when centrifugally dehydrated after 5 minutes was determined.
Liquid retention immobilization rate (%) = [(C−A) / (B−A)] × 100
A = initial weight of absorbent article (g)
B = weight of absorbent article after injection of physiological saline (10 g) (g)
C = weight of absorbent article after centrifugation (g)

<Measurement of leakage prevention performance (number of leakage occurrence)>
Each of the obtained absorbent articles was used as a test sample 80, as shown in FIG. 5, after being mounted on a movable female waist model 90 and wearing shorts, the waist model 90 was walked at a walking speed of 100 steps / minute. And walked for 10 minutes. Thereafter, 5 g of defibrinated horse blood (manufactured by Nippon Biotest Laboratories) was injected through the tube 91 at a rate of 4 g / min while walking. Thereafter, walking was continued for 20 minutes, and 3 g (8 g in total) was injected at a rate of 4 g / min while walking with defibrinated horse blood, and allowed to walk for 20 minutes. Further, 3 g (total 11 g) of defibrinated horse blood was injected at a rate of 4 g / min and allowed to walk for 20 minutes. Each of the 10 samples was counted at the respective time points after 20 g walking for 5 g injection, 20 minutes after 8 g injection, and 20 minutes after 11 g injection.

<Measurement of liquid return amount>
As shown in FIG. 4, each of the obtained absorbent articles was placed horizontally with the top sheet facing upward as shown in FIG. 4, and the acrylic plate 15 shown in FIG. Further, weights 16 and 16 are placed on the test sanitary napkin so that a load of 5 g / cm ² is applied to the area of the absorbent body. Next, 6 g of the above-mentioned defibrinated horse blood is injected from the injection port with a 10 ml beaker in about 2 seconds, and after the liquid is completely absorbed, it is left for 5 minutes with the acrylic plate 15 mounted.
Thereafter, 10 sheets of absorbent paper (100% coniferous chemical pulp) with a basis weight of 30 g / m ² cut to a width of 75 mm and a length of 195 mm were stacked on the skin contact surface side of the test sanitary napkin 80, and the physiology was continued. The napkin 80 for use was attached to the movable female waist model 90 shown in FIG. 5 and shorts were put on, and then the walking movement was performed for 10 minutes at a walking speed of 100 steps / minute. After walking for 10 minutes, the test sanitary napkin 80 and 10 sheets of absorbent paper were taken out, and the amount of blood absorbed from the absorbent paper was determined to determine the amount of blood returned from the surface of the sanitary napkin. . Five samples were measured, and the average value was obtained as the liquid return amount.

As shown in the results of Table 2, the absorbent articles (product of the present invention) 1 to 4 as examples of the present invention have hydrophilic fibers that do not swell in water or a centrifugal retention amount of water of 0.7 g / g or less. 90% or more of the physiological saline is completely absorbed and retained by the absorbent article when the physiological saline is absorbed and retained, and the amount of free liquid is small.
As a result, although it is thin, it can be seen that it is a comfortable state in which the number of moles generated and the amount of liquid returning to the surface are small, and there is little stickiness and stuffiness. This is a result of configuring a specific hydrophilic fiber and a superabsorbent polymer in a predetermined combination and blending formulation, and idealizing the flow of liquid from the surface material to the superabsorbent polymer after being absorbed by the surface material. .
On the other hand, absorbent articles (comparative products) 1 to 4 as comparative examples have a physiological saline fixation rate as low as 80% or less, and a large number of moles and liquid return.

<Manufacture of Absorbent Article 5 (Invention Product 5) as Examples of the First and Second Inventions>
In the absorbent article 1, in place of the non-moisture permeable back sheet used, a porous moisture permeable back sheet (biaxially stretched by melt-mixing 50% by weight of calcium carbonate and 50% by weight of polyethylene, forming a film) An absorbent article was produced in the same manner as the absorbent article 1 except that 1.7 g / (100 cm ² · hr) was used, and an absorbent article 5 as an example of the present invention was obtained.

<Manufacture of Absorbent Article 6 (Invention Product 6) as Examples of the First and Second Inventions>
Absorption as an example in the absorbent article 4 except that the porous moisture-permeable back sheet described above (moisture permeability of 1.7 g / (100 cm ² · hr)) was used instead of the non-moisture-permeable back sheet used. An absorbent article was produced in the same manner using the same material as that of the absorbent article 4 to obtain an absorbent article 6 as an example of the present invention.

<Manufacture of Absorbent Article 5 as Comparative Example (Comparative Product 5)>
In the absorbent article 4 (comparative product 4) as a comparative example, the above-described porous moisture-permeable back sheet (moisture permeability of 1.7 g / (100 cm ² · hr)) was used instead of the non-moisture-permeable back sheet used. Except having done, the absorbent article was manufactured similarly using the material similar to the absorbent article 4 as the comparative example 4, and the absorbent article 5 as a comparative example was obtained.

  Absorbent articles obtained as described above [absorbent articles 5 and 6 (inventive products 5 and 6) as examples and absorbent articles 4 and 5 (comparative products 4 and 5) as comparative examples]] In order to examine the temperature and humidity increase suppressing effect during wearing, the temperature and humidity change when the liquid was absorbed was examined by the method shown below, and the results are shown in Table 3.

<Measurement of temperature and humidity>
It is measured in a constant temperature and humidity environment of 30 ° C. and 65% relative humidity. In the environmental humidity shown on the left, the subject becomes an upper body nude and rests for 30 minutes in a prone state. Then, 3 g of physiological saline is injected into the absorption center of the test sample (absorbent article), and the sample left for 10 minutes is placed so that the absorption surface (skin contact surface) side of the sample is the back side of the subject. To do. Between the absorbent article and the skin, sandwich the probe sensor of the temperature / humidity sensor [trade name; body data-stocker TRH-DM2 sensor part; dedicated probe THP-28 manufactured by Shinei Co., Ltd.] Sealed with adhesive tape so that the humidity does not diverge. Thereafter, the sample was rested for 2 hours, and the temperature and humidity between the absorbent article and the skin after 2 hours were measured. The results are shown in Table 3.

  As shown in Table 3, non-moisture permeable BS (back sheet) is used, and in the case of the comparative product 4 having a low physiological saline immobilization rate, the humidity is 96%, and the same absorber as the comparative product 4 In the comparative product 5 that is changed to the moisture permeable BS, the humidity is reduced by about 10%. On the other hand, when a moisture-permeable back sheet is used as in the products 5 and 6 of the present invention and the fixation rate of physiological saline is high, the humidity can be lowered to about 70% and the temperature can be kept low. You can see that From the results shown in Table 3, it can be seen that according to the present invention, it is possible to provide a comfortable and comfortable absorbent article that does not have a temperature / humidity in the dressing and is cool without being swollen.

[Examples and Comparative Examples of the First and Second Inventions]
<Manufacture of Absorbent Articles 7 and 8 (Inventive Products 7 and 8) as Examples of the First and Second Inventions and Absorbent Articles 6 and 7 (Comparative Products 6 and 7) as Comparative Examples>
Instead of the absorbent body A and the non-moisture permeable back sheet used in the manufacture of the absorbent article 1 (invention product 1) as an example, the following absorbent body and the moisture permeable back sheet shown below were used, respectively. Produced an absorbent article in the same manner as in the production of the absorbent article 1 (product 1 of the present invention).

Absorbent article 7 (Example 7 of the present invention); Absorbent body D, moisture-permeable back sheet A
Absorbent article 8 of the example (invention product 8); Absorbent body D, moisture-permeable back sheet B
Absorbent article 6 of comparative example (Comparative product 6); Absorbent body F, moisture-permeable back sheet A
Absorbent article 7 of comparative example (Comparative product 7); Absorbent body F, moisture-permeable back sheet C

The moisture permeable back sheets A to C are obtained by melting and mixing polyethylene and calcium carbonate and biaxially stretching the film formed, and using different dispersants for uniformly dispersing calcium carbonate in polyethylene. The moisture permeability and / or the wetting tension are made different.
Table 4 shows the basis weight, moisture permeability, and wetting tension of moisture permeable back sheets A to C.
The moisture permeability is a value measured according to JIS Z0208, and the wetting tension is a value measured according to the measuring method of the wetting tension shown below.

<Measurement method of wetting tension>
The wetting tension of the leak-proof layer (moisture permeable sheet) was measured according to the following method with reference to “wetting tension test method for plastic film and sheet” of JIS K6768. About the point which is not described in this specification, it measures according to JISK6768.
Evaluation was carried out in a measurement chamber at a temperature of 23 ° C. and a relative humidity of 50%.
A sheet material (moisture permeable sheet) used as a leak-proof layer was cut into a size of 200 mm long × 100 mm wide to prepare a test sample. The test sample need not be of this size as long as it can be dropped at three locations.
As a test solution for the wetting test, a commercially available test solution (made by Wako Pure Chemical Industries, Ltd.) prepared with two types of reagents of formaldehyde and ethylene glycol monoethyl ether and adjusted to a surface tension of 30 to 50 mN / m. Prepared.

First, as shown in FIG. 6, a test sample was placed on a stainless steel plate (250 mm long × 150 mm wide) placed horizontally.
Then, a test liquid having a surface tension of 50 mN / m was dropped on three portions of this measurement sample at about 1 ml, as shown in the figure, and allowed to stand for 3 minutes.
Three minutes after dropping, the test sample was separated from the stainless steel plate, and it was evaluated whether the test solution leaked out to the stainless steel plate through the test sample.
When no leakage occurred in all three places, the surface tension of the test solution was lowered to 49 mN / m and the same evaluation was performed. If there was still no leakage, the surface tension was successively lowered by 1 mN / m in the same manner, and the evaluation was repeated until the test solution leaked out even at one location.
And the value of the surface tension of the evaluation liquid used immediately before the evaluation liquid in which leakage of the test liquid was observed for the first time was taken as the wetting tension of the leak-proof layer (moisture permeable sheet). For example, when the leak due to the measurement sample does not leak up to a test solution of 40 mN / m and is first observed in a test solution of 39 mN / m, the wet tension of the moisture-permeable sheet is 40 mN / m.

  For each of the absorbent articles 7 and 8 of the Examples (Products 7 and 8 of the present invention) and the absorbent articles 6 and 7 of the Comparative Examples (Comparative Products 6 and 7), the rate of fixation of physiological saline by the method described above. (Liquid retention immobilization ratio) was measured, and the results are shown in Table 5.

<Evaluation of difficulty in exuding>
Further, each of the absorbent articles 7 and 8 of the examples (inventive products 7 and 8) and the absorbent articles 6 and 7 of the comparative examples (comparative products 6 and 7) are passed through the leak-proof layer by the following method. The difficulty of seeping out was evaluated.
That is, a bleeding test was performed using simulated blood having a surface tension of 35 mN / m. The test was conducted under a temperature environment of 20 ° C. and 65% humidity.
As shown in FIG. 7 (a), an absorbent article (sanitary napkin) was overlaid as a test sample on a filter paper (type 2, manufactured by Toyo Filter Paper Co., Ltd.) cut to 230 mm in length and 100 mm in width.
Then, 10 g of simulated blood having a surface tension of 35 mN / m was absorbed at the center of the overlapped napkin using a microtube pump at an injection rate of 10 g / min, and left for 1 minute.
After leaving, as shown in FIG. 7B, a circular acrylic plate having a diameter of 60 mm and a thickness of 5 mm was placed on the absorption central portion where the simulated blood was absorbed, and further a 2 kg weight was placed thereon and pressurized for 3 hours. At 30 minutes, 1 hour and 3 hours after the start of pressurization during pressurization for 3 hours, it was observed with the naked eye whether or not the pseudo blood exudes to the filter paper. The results are shown in Table 5.

The simulated blood with a surface tension of 35 mN / m was prepared as follows.
First, 5.3 g of sodium carboxymethylcellulose (CMC • Na, manufactured by Kanto Chemical Co., Inc.) was added to 1500 g of ion-exchanged water and completely dissolved.
Separately, 27 g of sodium chloride and 12 g of sodium hydrogen carbonate were added to 556 g of ion-exchanged water and completely dissolved. The obtained CMC · Na aqueous solution, NaCl · NaHCO ₃ aqueous solution and 900 g of glycerin are stirred and mixed, and 0.3 g of Red No. 2 (Hodogaya Chemical Co., Ltd.) is added and completely dissolved. To this, surfactant alkyl glucoside (trade name; AG-10L, manufactured by Kao Corporation) is added (0.432 g) so that the total concentration of the active agent is 0.015 wt%.
The temperature of the obtained mixed solution was set to 20 ° C., surface tension was measured, and it was confirmed that it was 35 ± 1 mN / m, and used as a test solution. When the surface tension was not in the range of 35 ± 1 mN / m, the alkyl glucoside concentration was slightly adjusted to 35 ± 1 mN / m.

  As shown in Table 5, in Comparative products 6 and 7, leakage occurred through the leak-proof layer (moisture permeable back sheet). From this result, when the liquid retention immobilization rate (physiological saline immobilization rate) is low or the wetting tension of the leak-proof layer is not less than the predetermined value, if the surface tension of the excretory liquid is low, It can be seen that liquid oozes out. On the other hand, in the products 7 and 8 of the present invention, no oozing out of the liquid was observed even after pressing for 1 hour. In particular, when the wetting tension of the leak-proof layer of the product 7 of the present invention is 37 mN / m or less, no seepage is observed even after 3 hours of pressurization, and even though the excretory liquid has a low surface tension, it passes through the leak-proof layer. It can be seen that the exudation of water is prevented particularly well.

FIG. 1 is a plan view showing a sanitary napkin as an embodiment of the absorbent article of the present invention. 2 is a cross-sectional view schematically showing a cross section taken along line XX of FIG. 3A is a side view and FIG. 3B is a plan view showing an acrylic plate used for measuring the liquid holding and fixing rate and the liquid return amount. FIG. 4 is an explanatory diagram for explaining a method for measuring the liquid holding immobilization rate and the liquid return amount. FIG. 5 is an explanatory diagram for explaining a method for measuring the leakage prevention performance (number of leakage occurrences). FIG. 6 is an explanatory diagram for explaining a method of measuring the wetting tension. FIG. 7 is an explanatory diagram for explaining a method of evaluating the difficulty of bleeding.

Explanation of symbols

1 Sanitary napkin (absorbent article)
2 Top sheet (surface layer)
3 Back sheet (leak-proof layer)
4 Absorber (absorbing layer)
4a Thick part 4b Peripheral part 5 Hot melt adhesive 6 Leak-proof sheet 7 Adhesive 8 Release sheet

Claims (3)

In an absorbent article having a liquid-permeable surface layer, a liquid-impermeable leak-proof layer and a liquid-retaining absorbent layer,
The absorbent article is a sanitary napkin,
The absorbent layer includes hydrophilic fibers that do not swell with water, crosslinked cellulose fibers that have a water retention of 0.7 g / g or less when swelled with water and then centrifugally dehydrated, and a superabsorbent polymer. Consists of
The absorption layer has a thick portion in a portion disposed in the excretion portion, the thickness in the thick portion is 1.5 to 2.5 mm, and the thickness in the peripheral portion around the thick portion is 0.5-2.0 mm,
The absorption layer is integrated with the surface layer by heat sealing in the peripheral portion,
The area of the thick part is 10 to 50% with respect to the total area on the skin contact surface side of the absorbent layer,
The absorbent layer includes a surface fiber layer that forms a surface on the surface layer side of the absorbent layer , and is laminated on the back side of the surface fiber layer and contains or is in contact with the superabsorbent polymer. An inner fiber layer, the surface fiber layer has a Klem water absorption of less than 40 mm, the inner fiber layer has a Klem water absorption of 40 mm or more,
The internal fiber layer is one in which the superabsorbent polymer is dispersed in one nonwoven fabric or web, or the superabsorbent polymer is sandwiched between two nonwoven fabrics,
The fiber diameter of the fiber near the superabsorbent polymer in the internal fiber layer is 0.1 to 10 μm, and the fiber diameter of the constituent fibers of the surface fiber layer is 10 to 100 μm,
10 g of physiological saline is absorbed into the absorbent article, and the rate of fixation of the physiological saline when centrifugally dehydrated after 5 minutes is 90% or more,
The said leak-proof layer is arrange | positioned at the lower surface of the said absorption layer, is water-vapor-permeable, and wet tension is 37 mN / m or less, The absorbent article characterized by the above-mentioned. The absorption layer has a thickness of 2.5 mm or less, the occupied volume V ₀ (cm ³ ) of the absorption layer, and the amount of physiological saline retained when the absorption layer is swelled with physiological saline and then subjected to centrifugal dehydration. The absorbent article according to claim ₁ , wherein a ratio (V ₁ / V ₀ ) to V ₁ (g) is 1 g / cm ³ or more.   The total content of the hydrophilic fibers not swollen in water and the cellulose fibers having a water retention amount of 0.7 g / g or less when swollen with water and then centrifuged and dehydrated is 30 to 70%. The content of the superabsorbent polymer in the absorbent layer is 30 to 70%, and the superabsorbent polymer is three-dimensionally dispersed in the inner fiber layer. 2. The absorbent article according to 2.

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