JP6928651B2 - Water-absorbent sheet - Google Patents

Description

The present invention relates to a water-absorbent sheet.

There is a need to easily absorb body fluids such as sweat, blood, and urine, pet urine, and water around water such as kitchens and toilets to maintain cleanliness. A water-absorbent sheet that meets such needs is required to have flexibility.

For example, Patent Document 1 describes a soft aqueous liquid absorbing structure in which an aqueous liquid absorbing material containing a heat-melt adhesive and an aqueous liquid absorbing polymer is arranged on a part of the surface of a soft substrate. Further, Patent Document 2 describes a sheet in which a layer of a modified polyalkylene oxide is directly formed on the surface of a base material and maintains lubricity.

WO200412449 (A2) WO2011086980 (A1)

The present invention is a water-absorbent sheet having a base material sheet and a water-absorbent polymer. The water-absorbent polymer is a thermoplastic water-absorbent polymer or a water-absorbent polymer that dissolves in a solvent. Looking at the water-absorbent sheet in a plan view, the polymer-arranged portion on which the water-absorbent polymer is arranged and the polymer non-arranged portion on which the water-absorbent polymer is not arranged are dispersed and arranged in the plane direction. With a cross-sectional view of the water-absorbent sheet, the polymer arranging portion is arranged in an intermediate region spaced from both sides of the base material sheet.

FIG. 1 is a plan view of a water-absorbent sheet, which is a preferred embodiment of the present invention, viewed from one surface side. FIG. 2 is a cross-sectional view taken along the line II-II shown in FIG. FIG. 3 is a plan view of a sheet obtained by using an electron microscope to take a state in which a polymer arrangement portion covers a part of a large number of holes between the fibers constituting the non-woven fabric in a film shape. Is. FIG. 4 is a cross-sectional view of the sheet of FIG. 3 taken by using an electron microscope in a state where the polymer arranging portion is arranged in a region extending from one surface of the sheet to the inside. FIG. 5 is an example of using the water-absorbent sheet shown in FIG. 1 for, for example, men's underwear.

Detailed description of the invention

In the aqueous liquid absorbing structure described in Patent Document 1, since the aqueous liquid absorbing material is arranged on the surface of the substrate, it becomes bulky and thick, and it is difficult to improve the flexibility.

Further, the sheet described in Patent Document 2 uses a base material made of metal or a resin such as polypropylene, which constitutes a wet shaving device typified by a razor, and a polyalkylene oxide modified product is formed on the surface of the base material. It is a layer formed by direct application. As described above, Patent Document 2 does not describe anything about a composite sheet formed by directly applying a polyalkylene oxide modified product onto a sheet such as a non-woven fabric.

The present invention relates to a water-absorbent sheet that eliminates the above-mentioned drawbacks of the prior art, has high flexibility, easily absorbs a liquid inside, and has a small amount of liquid return.

Hereinafter, the present invention will be described based on the preferred embodiment with reference to the drawings.
As shown in FIGS. 1 and 2, the water-absorbent sheet 1, which is a preferred embodiment of the water-absorbent sheet of the present invention, is a sheet having a base sheet 2 and a water-absorbent polymer.

The shape of the water-absorbent sheet of the present invention in a plan view is not particularly limited, but the water-absorbent sheet 1 has a rectangular shape that is long in the vertical direction as shown in FIG. Hereinafter, the rectangular water-absorbent sheet 1 will be described with the vertical direction as the X direction, the direction perpendicular to the vertical direction X as the horizontal direction (Y direction), and the thickness direction as the Z direction. The plan-view shape of the water-absorbent sheet may be, for example, a square shape, a circular shape, an elliptical shape, a polygonal shape, or the like, in addition to the rectangular shape.

The size of the water-absorbent sheet 1 is not particularly limited and may be appropriately set according to the usage situation, usage situation, intended use, etc. of the water-absorbent sheet 1. However, the water-absorbent sheet 1 is used as, for example, a sheet for mild incontinence. When used, the length in the vertical direction (X direction) is preferably 30 mm or more, more preferably 60 mm or more, preferably 500 mm or less, still more preferably 200 mm or less. The length of the water-absorbent sheet 1 in the lateral direction (Y direction) is preferably 20 mm or more, more preferably 40 mm or more, preferably 200 mm or less, still more preferably 150 mm or less. The length of the water-absorbent sheet 1 in the thickness direction (Z direction) is preferably 0.05 mm or more, more preferably 0.1 mm or more, preferably 20 mm or less, still more preferably 15 mm or less.

The base sheet 2 matches the outer shape of the water-absorbent sheet 1. That is, the size of the base sheet 2 (the length of each of the vertical direction X, the horizontal direction Y, and the thickness direction Z) is the size of the water-absorbent sheet 1 (the length of each of the vertical direction X, the horizontal direction Y, and the thickness direction Z). Match.

The base material sheet 2 is preferably a porous sheet, and more preferably a porous sheet and a breathable sheet, from the viewpoint of forming the polymer arranging portion 3 in the intermediate region of the water-absorbent sheet 1 described later. Here, as the porous sheet, a non-woven fabric (see FIGS. 3 and 4) in which the outer periphery is surrounded by the fibers and is a hole between the fibers, and a hole is formed between the fibers. Non-woven fabric, knitting, lace, cloth such as felt, foam-molded synthetic resin such as polyurethane, sponge with innumerable fine holes on the inside and surface, paper with breathable holes, with breathable holes From the viewpoint that the polymer arrangement portion 3 can be easily formed in the intermediate region of the water-absorbent sheet 1, the base material sheet 2 is formed of a non-woven fabric in the water-absorbent sheet 1.

When a non-woven fabric is used as the base sheet 2, examples of the non-woven fabric include an air-through non-woven fabric, a spunbonded non-woven fabric, a spunlaced non-woven fabric, a melt blown non-woven fabric, a resin-bonded non-woven fabric, and a needle punched non-woven fabric. Further, a laminated body in which two or more kinds of these non-woven fabrics are laminated may be used, or a laminated body of a breathable and liquid-impermeable resin film and these non-woven fabrics may be used. From the viewpoint of easily forming the polymer arrangement portion 3 in the intermediate region of the water-absorbent sheet 1 and improving the flexibility, a non-woven fabric laminate in which a single-layer air-through non-woven fabric and a single-layer air-through non-woven fabric are laminated is preferably used as the non-woven fabric. Be done. The basis weight of the non-woven fabric (in the case of a laminated non-woven fabric, the total basis weight of the non-woven fabric) is preferably 5 g / m ² or more, more preferably 10 g / m ² or more, and preferably 200 g / m ² or less, further preferably 200 g / m 2 or less. Is 150 g / m ² or less.

The water-absorbent polymer constituting the water-absorbent sheet 1 is a thermoplastic water-absorbent polymer or a water-absorbent polymer that dissolves in a solvent. The weight average molecular weight of the water-absorbent polymer is preferably 30,000 or more, more preferably 50,000 or more, still more preferably 100,000 or more, from the viewpoint of easily forming the polymer arrangement portion 3 in the intermediate region of the water-absorbent sheet 1. Then, it is preferably 1 million or less, more preferably 700,000 or less, further preferably 500,000 or less, specifically, preferably 30,000 or more and 1 million or less, still more preferably 50,000 or more and 700,000 or less, still more preferably 10. It is 10,000 or more and 500,000 or less. The weight average molecular weight is a standard polystyrene-equivalent value measured by gel permeation chromatography (GPC).

The thermoplastic water-absorbent polymer is a water-absorbent polymer having a melting point, which has a property of being melted by heat and absorbing water, and examples thereof include polyalkylene oxide-based resins. Examples of the polyalkylene oxide-based resin include homopolymers of alkylene oxides such as ethylene oxide, copolymers of alkylene oxides such as ethylene oxide and monomers copolymerizable therewith. When ethylene oxide is used as the alkylene oxide, for example, propylene oxide, butylene oxide or the like can be used as the monomer copolymerizable with the ethylene oxide.

As the polyalkylene oxide-based resin, it is particularly preferable to use a polyethylene oxide-based resin. Specific examples of the polyethylene oxide-based resin include polyethylene glycol, ethylene oxide / propylene oxide copolymer, ethylene oxide / saturated bismethylene diphenyldiisocyanate copolymer, ethylene oxide / isocyanate copolymer, and the like. Specific examples of the ethylene oxide / isocyanate copolymer include an ethylene oxide / saturated bismethylene diphenyl diisocyanate copolymer and an ethylene oxide / hexamethyl diisocyanate copolymer. Among these, a commercially available product can be used as the ethylene oxide / saturated bismethylene diphenyl diisocyanate (SMDI) copolymer, and as such a commercially available product, for example, "Aquacork TWB" (trade name: Sumitomo Seika Chemical Co., Ltd.) Made) and the like. The melting point of the thermoplastic water-absorbent polymer is preferably 40 ° C. or higher, more preferably 50 ° C. or higher, and preferably 200 ° C. from the viewpoint of easily forming the polymer arrangement portion 3 in the intermediate region of the water-absorbent sheet 1. Hereinafter, it is more preferably 150 ° C. or lower, specifically, preferably 40 ° C. or higher and 200 ° C. or lower, and further preferably 50 ° C. or higher and 150 ° C. or lower. From the viewpoint of ease of manufacturing the water-absorbent sheet 1, the melting point of the thermoplastic water-absorbent polymer is preferably lower than the melting point of the constituent fibers of the non-woven fabric when the non-woven fabric is used as the base sheet 2.

Examples of the water-absorbent polymer that dissolves in the solvent include a copolymer containing saturated bismethylenediphenyldiisocyanate (SMDI), a copolymer containing hexamethyldiisocyanate (HDI), and a copolymer containing dimethylacrylamide (DMAA). Examples thereof include a triblock copolymer or a multiblock copolymer having a segment having a hydrophilic portion, a copolymer containing ureidopyrimidinone (UPy), and the like. Examples of the copolymer containing saturated bismethylene diphenyl diisocyanate (SMDI) include the above-mentioned "Aquacork TWB" (trade name: manufactured by Sumitomo Seika Chemical Co., Ltd.) as a commercially available product, and "Accurin 46N". (Product name: manufactured by Dow Chemical Co., Ltd.), "Accurin 44" (trade name: manufactured by Dow Chemical Co., Ltd.) and the like can be mentioned. Examples of commercially available copolymers containing hexamethyldiisocyanate (HDI) include "Adecanol GT-700" (trade name: manufactured by ADEKA Corporation). Examples of the copolymer containing dimethylacrylamide (DMAA) include block copolymers of dimethylacrylamide (DMAA) and Nt-butylacrylamide (TBAA). Examples of the copolymer containing ureidopyrimidinone (UPy) include a random copolymer of dimethylacrylamide (DMAA) and a methacrylic acid derivative monomer (UPyMA) containing ureidopyrimidinone (UPy).

"Soluble in solvent" means that 100 g of ethanol / water = 90/10 (weight ratio) mixed solvent and water absorption of (A) at the operating temperature of the surface treatment composition of the present invention. It means that the mass of the undissolved polymer remaining in the solvent is 0.1 g or less when 5 g of the polymer is mixed and stirred for 20 minutes.

The amount of the water-absorbent polymer that dissolves in the solvent is preferably 1 g or more, more preferably 1 g or more, from the viewpoint of easily forming the polymer arrangement portion 3 in the intermediate region of the water-absorbent sheet 1. It is 5 g or more. The upper limit of the amount to be dissolved is not particularly limited, and the higher the value, the more preferable, but if it is about 3 g, a sufficiently satisfactory effect can be obtained.
Further, the water-absorbent polymer that dissolves in the solvent has an amount that dissolves in 100 g of a mixed solvent of 70 g of ethanol and 30 g of water at 25 ° C. from the viewpoint that the polymer arrangement portion 3 is easily formed in the intermediate region of the water-absorbent sheet 1. It is preferably 1 g or more, and more preferably 5 g or more. The upper limit of the amount to be dissolved is not particularly limited, and the higher the value, the more preferable, but if it is about 3 g, a sufficiently satisfactory effect can be obtained.

As shown in FIG. 1, the water-absorbent sheet 1 has a polymer-arranged portion 3 in which a water-absorbent polymer is arranged and a polymer non-arranged portion 4 in which a water-absorbent polymer is not arranged in a plane direction (X direction and). It is distributed in the Y direction). In the water-absorbent sheet 1, the polymer arranging portion 3 is not arranged on one surface 1h or on the other surface 1t, but is arranged only in the intermediate region inside the water-absorbent sheet 1. That is, as shown in FIG. 2, the polymer non-arranged portion 4 is formed over both sides of the base sheet 2 in a cross-sectional view of the water-absorbent sheet 1, in other words, one of the water-absorbent sheets 1. It is a portion formed from the surface 1h to the other surface 1t and does not overlap with the polymer arranging portion 3 in the thickness direction (Z direction).

When the water-absorbent sheet 1 is viewed in cross section as shown in FIG. 2, the polymer arranging portion 3 is viewed from both sides of the base sheet 2, in other words, one surface 1h and the other surface 1t of the water-absorbent sheet 1, respectively. It is formed in the intermediate region at intervals. In the water-absorbent sheet 1, the polymer arranging portion 3 is formed only in the intermediate region inside the water-absorbent sheet 1 in a cross-sectional view of the water-absorbent sheet 1, and is formed in a plan view as shown in FIG. They are unevenly dispersed in the directions (X direction and Y direction).

The surfaces 1h and 1t of the water-absorbent sheet 1 are defined by cutting the water-absorbent sheet 1 along the thickness direction (Z direction) using a feather shaving sword (product number FAS-10, manufactured by Feather Safety Razor Co., Ltd.) to absorb water. When a cross section of the sheet 1 along the thickness direction (Z direction) is observed using a scanning electron microscope (VE-8800, manufactured by Keyence Co., Ltd., hereinafter also referred to as "SEM"), the thickness direction Z in the image. It is a plane formed by the outermost portion of the water-absorbent sheet 1 and orthogonal to the thickness direction Z of the water-absorbent sheet 1. For example, when the base sheet 2 constituting the water-absorbent sheet 1 is a non-woven fabric, a surface orthogonal to the non-woven fabric thickness direction Z formed by a plurality of fibers located on the outermost side in the non-woven fabric thickness direction Z ( It is a surface that can be observed when the non-woven fabric is observed from the outside). When determining the surface of the non-woven fabric based on the enlarged image, irregular fibers that independently greatly protrude outward in the thickness direction Z of the non-woven fabric are excluded.

From the viewpoint that the water-absorbent sheet 1 can easily reduce the amount of liquid return, the water-absorbent sheet 1 is a polymer-arranged portion 3 arranged in an intermediate region with respect to the thickness T2 of the base material sheet 2 in a cross-sectional view as shown in FIG. The ratio of the thickness T3 ((T3 / T2) × 100) is preferably 1% or more, more preferably 2% or more, further preferably 5% or more, and preferably 90% or less, further preferably 50. % Or less, more preferably 30% or less, specifically, preferably 1% or more and 90% or less, still more preferably 2% or more and 50% or less, still more preferably 5% or more and 30% or less. The thickness T2 of the base sheet 2 is the distance between one surface 1h of the water-absorbent sheet 1 and the other surface 1t described above. Further, the thickness T3 of the polymer arranging portion 3 in the water-absorbent sheet 1 is a portion of the polymer arranging portion 3 located near the most one surface 1h in a cross-sectional view as shown in FIG. 2, and the polymer arranging portion 3 It is the distance from the portion located near the outermost surface 1t in the above.

The shape of the water-absorbent polymer is not particularly limited as long as the water-absorbent polymer is arranged in the intermediate region of the base sheet 2, and the shape of the water-absorbent polymer is spherical, lumpy, or bale. It may be in the form of particles such as a shape, it may be in the form of fibers, it may be in the form of a thin film, or it may be in the form of a combination of these, but in the water-absorbent sheet 1, FIG. As shown in, it is formed in the form of a film. In the water-absorbent sheet 1, the base sheet 2 is a non-woven fabric, and the polymer arranging portion 3 covers a part of the holes of the base sheet 2 in a film shape. Specifically, in the water-absorbent sheet 1, the polymer arranging portion 3 is formed by covering at least a part of a large number of holes between the fibers constituting the base sheet 2 made of a non-woven fabric in a film shape. Has been done. The shape of the water-absorbent polymer that covers the film shape may be a shape that covers the entire area of the pores between the fibers constituting the base sheet 2, or a shape that covers a part of the entire area of the holes. Often, the shape may be a combination of these.

The water-absorbent sheet 1 is manufactured by using, for example, two base sheets 2b and 2b having the same shape and the same size. Specifically, when the water-absorbent polymer is a thermoplastic water-absorbent polymer, for example, (a) after arranging the water-absorbent polymer on the surface of the first base sheet 2b, heat is applied to the water-absorbent polymer. The polymer arrangement portion 3 is moved from one surface of the base sheet 2b to the inside by infiltrating the melted water-absorbent polymer from one surface of the base sheet 2b into the inside and then cooling the polymer. The sheet 1b shown in FIGS. 3 and 4 is manufactured over the entire region. Then, the remaining one base material sheet 2b is superposed on one surface 1bh of the manufactured sheet 1b, and then heat is applied to melt the water-absorbent polymer, and then the two base sheets are cooled. By fixing the material sheets 2b and 2b to each other, it is possible to manufacture the water-absorbent sheet 1 in which the polymer arranging portion 3 is arranged in the intermediate region of the base sheet 2. Further, for example, (b) after arranging the water-absorbent polymer on the surface of the first base sheet 2b, the remaining one base sheet 2b is superposed on the two base sheets 2b, 2b. The water-absorbent polymer is sandwiched between the two sheets, and then the water-absorbent polymer is melted by applying heat, and the melted water-absorbent polymer is permeated into the two base sheets 2b and 2b, and then cooled to obtain two sheets. By fixing the base sheets 2b and 2b to each other, it is possible to manufacture the water-absorbent sheet 1 in which the polymer arranging portion 3 is arranged in the intermediate region of the base sheet 2.

Further, in the case of the water-absorbent polymer in which the water-absorbent polymer is dissolved in the solvent, for example, (c) the water-absorbent polymer is dissolved in the solvent, and then the solution in which the water-absorbent polymer is dissolved is prepared, for example. After applying with a brush to the surface of the first base sheet 2b as shown in FIGS. 3 and 4, the remaining one base sheet 2b is overlapped and the two base sheet 2b are overlapped. , 2b sandwiches the water-absorbent polymer and then dries to fix the two base sheet 2b, 2b to each other, and the water-absorbent sheet 1 in which the polymer arrangement portion 3 is arranged in the intermediate region of the base sheet 2. Can be manufactured.

In the water-absorbent sheet 1 described above, the polymer-arranged portion 3 and the polymer-non-arranged portion 4 are dispersed and arranged in the plane direction (X direction and Y direction) in a plan view as shown in FIG. Since the polymer non-arranged portions 4 are dispersed and arranged in this way, the flexibility is improved and the liquid is easily absorbed in the intermediate region of the water-absorbent sheet 1. Further, in the water-absorbent sheet 1, when viewed in cross section as shown in FIG. 2, the polymer arranging portion 3 is intermediate between both sides of the base sheet 2, that is, both sides 1h and 1t of the water-absorbent sheet 1 at intervals. It is arranged in the area. Therefore, the amount of liquid returned is reduced.

Further, in the water-absorbent sheet 1 described above, the base sheet 2 is a porous sheet, and as shown in FIG. 3, the polymer arranging portion 3 is formed by covering the pores of the base sheet 2 in a film shape. Therefore, the flexibility is further improved. In particular, in the water-absorbent sheet 1 described above, since the base sheet 2 is made of a non-woven fabric which is a porous sheet and a breathable sheet, the polymer non-arranged portion 4 can sufficiently secure the breathability.

From the viewpoint of further exerting the above-mentioned effects, the water-absorbent sheet 1 preferably has one or more of the following configurations.

The ratio of the mass of the water-absorbent polymer to the mass of the base sheet 2 is preferably 1% by mass or more, more preferably 5% by mass or more, and preferably 200% by mass or less, further preferably 150. It is mass% or less, specifically, preferably 1 mass% or more and 200 mass% or less, and more preferably 5 mass% or more and 150 mass% or less.
The mass of the base sheet 2 is the mass of the base sheet 2 from which the water-absorbent polymer is removed from the base sheet 2 when measured from the water-absorbent sheet 1 in which the water-absorbent polymer is arranged inside the base sheet 2. Is measured and calculated. Specifically, first, the mass of the water-absorbent sheet 1 is measured. Next, the water-absorbent polymer arranged inside the base sheet 2 is melted when the water-absorbent polymer is a thermoplastic water-absorbent polymer, or the water-absorbent polymer is dissolved in a solvent. In the case, the sheet obtained by dissolving it in a solvent, removing it from the inside of the base sheet 2, and removing the water-absorbing polymer from the base sheet 2 is used as the base sheet 2 and its mass is measured. Then, the mass of the water-absorbent polymer is obtained by subtracting the mass of the base material sheet 2 from the mass of the water-absorbent sheet 1 to obtain a difference, and this is taken as the mass of the water-absorbent polymer.
When the mass of the base sheet 2 is known in advance, the mass of the water-absorbing polymer is first measured by measuring the mass of the base sheet 2. Next, when the water-absorbent polymer is a thermoplastic water-absorbent polymer, it is melted and composited with the base sheet 2 to prepare the water-absorbent sheet 1. Alternatively, in the case where the water-absorbent polymer is a water-absorbent polymer that dissolves in a solvent, the water-absorbent polymer is dissolved in the solvent and composited with the base sheet 2, and the solvent is sufficiently volatilized to prepare the water-absorbent sheet 1. The mass of the base sheet 2 is subtracted from the mass of the water-absorbent sheet 1 to obtain a difference, which is used as the mass of the water-absorbent polymer.

When viewed in a plan view from one surface 1h side or the other surface 1t side of the water-absorbent sheet 1, the total area of the polymer arranging portions 3 is preferably 1% or more of the surface area of the base sheet 2, more preferably. Is 5% or more, more preferably 10% or more, and preferably 99% or less, still more preferably 95% or less, still more preferably 90% or less, and specifically preferably. Is 1% or more and 99% or less, more preferably 5% or more and 95% or less, and further preferably 10% or more and 90% or less. The total area of the polymer arranging portions 3 is the total area surrounded by the contours of the polymer arranging portions 3 dispersed and arranged in the plane direction (X direction and Y direction). The total area of the polymer arrangement portion 3 can be measured by the method described in Examples.

When viewed in a plan view from one surface 1h side or the other surface 1t side of the water-absorbent sheet 1, the total area of the polymer non-arranged portion 4 is preferably 1% or more of the total area of the polymer-arranged portion 3. More preferably 5% or more, further preferably 10% or more, and preferably 99% or less, further preferably 95% or less, still more preferably 90% or less, specifically. Is preferably 1% or more and 99% or less, more preferably 5% or more and 95% or less, and further preferably 10% or more and 90% or less. The total area of the polymer non-arranged portions 4 is the total area surrounded by the contours of the respective polymer non-arranged portions 4 dispersed and arranged in the plane direction (X direction and Y direction).

The above-mentioned water-absorbent sheet 1 has high flexibility, easily absorbs liquid, and has a small amount of liquid return. It can easily absorb water, etc., and can meet the need to maintain cleanliness. In particular, the above-mentioned water-absorbent sheet 1 can be used as a method for absorbing incontinence urine. As a method of absorbing incontinence urine, for example, as shown in FIG. 5, the above-mentioned water-absorbent sheet 1 is used by arranging the above-mentioned water-absorbent sheet 1 on the inner or outer crotch of underwear 10 such as briefs for men. Specifically, the above-mentioned water-absorbent sheet 1 is arranged and used in the inseam of the underwear 10 so as to face the excretion portion facing the portion where the wearer's penis is located when worn. If the water-absorbent sheet 1 described above is used by arranging it on the inner or outer crotch of the underwear 10, the flexibility is high, so that it is comfortable to wear and incontinence urine can be absorbed. In addition, since the amount of liquid returned is small, the usability is improved.

The water-absorbent sheet 1 described above preferably has inorganic particles having an average particle size of 0.1 μm or more, more preferably 1 μm or more, and further preferably 5 μm or more. It is preferable to have inorganic particles of 500 μm or less, more preferably 300 μm or less, further preferably 100 μm or less, and specifically 0.1 μm or more and 500 μm or less. It is more preferable to have inorganic particles having an average particle size of 1 μm or more and 300 μm or less, and even more preferably to have inorganic particles having an average particle size of 5 μm or more and 100 μm or less. Examples of the inorganic particles include silica, alumina, titania, calcium carbonate, bentonite, talc, kaolin, zeolite and the like. The average particle size of the inorganic particles can be measured according to a conventional method using a laser diffraction / scattering type particle size distribution measuring device (for example, LA-960 manufactured by HORIBA, Ltd.).

The water-absorbent sheet of the present invention is not limited to the water-absorbent sheet 1 of the above-described embodiment, and can be appropriately changed.
For example, in the water-absorbent sheet 1 of the above-described embodiment, a non-woven fabric is used as the base sheet 2, but a laminate obtained by laminating a liquid-impermeable resin film on the non-woven fabric may be used.

Further, in the water-absorbent sheet 1 of the above-described embodiment, the two base sheets 2b and 2b having the same shape and the same size are used for manufacturing. For example, one single-layer base sheet 2 is used. The water-absorbent sheet 1 in which the polymer arrangement portion 3 is arranged in the intermediate region of the base sheet 2 is obtained by injecting a solution prepared by dissolving the water-absorbent polymer in a solvent into the base sheet 2 and then drying the base sheet 2. It may be manufactured.

Regarding the above-described embodiment, the present invention further discloses the following water-absorbent sheet.
<1>
A water-absorbent sheet having a base sheet and a water-absorbent polymer.
The water-absorbent polymer is a thermoplastic water-absorbent polymer or a water-absorbent polymer that dissolves in a solvent.
Looking at the water-absorbent sheet in a plan view, the polymer-arranged portion on which the water-absorbent polymer is arranged and the polymer non-arranged portion on which the water-absorbent polymer is not arranged are dispersed and arranged in the plane direction.
A water-absorbent sheet in which the polymer-arranged portions are arranged in intermediate regions spaced apart from both sides of the base material sheet in a cross-sectional view of the water-absorbent sheet.

<2>
The water-absorbent sheet according to <1>, wherein the base material sheet is a porous sheet, and the polymer arranging portion covers a part of the pores of the base material sheet in a film shape.
<3>
The water-absorbent sheet according to <1> or <2>, wherein the ratio of the mass of the water-absorbent polymer to the mass of the base material sheet is 1% by mass or more and 200% by mass or less.
<4>
The water-absorbent sheet according to any one of <1> to <3>, wherein the polymer non-arranged portion extends between both sides of the base material sheet when the water-absorbent sheet is viewed in cross section.
<5>
The water-absorbent sheet according to any one of <1> to <4>, further comprising inorganic particles having an average particle size of 0.1 μm or more and 500 μm or less.
<6>
The water-absorbent sheet according to any one of <1> to <5>, wherein the water-absorbent polymer has a weight average molecular weight of 30,000 or more and 1 million or less.
<7>
The water-absorbent sheet according to any one of <1> to <6>, wherein the thermoplastic water-absorbent polymer has a melting point of 40 ° C. or higher.
<8>
The amount of the water-absorbent polymer that dissolves in the solvent is 1 g or more in 100 g of ethanol at 25 ° C. or 100 g of a mixed solvent of 70 g of ethanol and 30 g of water at 25 ° C. The water-absorbent sheet according to any one of.
<9>
The water-absorbent sheet according to any one of <1> to <8>, wherein the base material sheet is a non-woven fabric.
<10>
The water-absorbent sheet according to any one of <1> to <9>, wherein the base material sheet is formed of two sheets having the same shape and the same size, and each sheet is a single-layer air-through non-woven fabric.
<11>
The water-absorbent sheet according to any one of <1> to <10>, wherein the base material sheet is a non-woven fabric having a basis weight of 5 g / m ² or more and 200 g / m ^{2 or less.}
<12>
When viewed in a plan view from one surface side of the water-absorbent sheet, the total area of the non-polymer-arranged portion is 1% or more and 99% or less of the total area of the polymer-arranged portion. The water-absorbent sheet according to any one of <11>.
<13>
A method for absorbing incontinence urine, which is used by arranging the water-absorbent sheet according to any one of <1> to <12> on the inner or outer crotch of underwear such as briefs for men.

Hereinafter, the present invention will be described in more detail with reference to Examples. However, the scope of the present invention is not limited to such examples.

[Example 1]
As the original two base sheets 2b and 2b having the same shape and the same size as the base sheet ² , an air-through non-woven fabric made of 30 g / m 2 of PE was prepared. The air-through nonwoven fabric had a length of 100 mm in the vertical direction (X direction), a length of 100 mm in the horizontal direction (Y direction), and a length of 4 mm in the thickness direction (Z direction). Then, a commercially available product "Aquacork TWB" (trade name: manufactured by Sumitomo Seika Chemical Co., Ltd.) was dissolved in methanol (dissolved at 60 ° C. and then cooled to room temperature. Concentration: 10 wt%), and then the water-absorbent polymer was dissolved. The solution was applied to a part of the surface of the first base sheet 2b using a brush, and then dried. After that, the remaining one base sheet 2b is overlapped, the water-absorbent polymer is sandwiched between the two base sheets 2b and 2b, and a hot press (using a spacer PET 0.3 mm, at 70 ° C. and 2 MPa). 2 minutes) to fix the two base sheet sheets 2b and 2b to each other, and the water-absorbent sheet of Example 1 having a thickness of 1 mm or less in which the polymer arranging portion 3 is arranged in the intermediate region of the base material sheet 2 is obtained. Manufactured. Regarding the water-absorbent sheet of Example 1, the ratio of the mass of the water-absorbent polymer to the mass of the base material sheet 2 obtained by the above-mentioned method is 33% by mass, and is based on the surface area of the base material sheet obtained by the method described later. The ratio of the total area of the polymer arrangement portion 3 was 15%.

[Example 2]
The water-absorbent sheet of Example 2 was produced in the same manner as the water-absorbent sheet of Example 1 except that the original two base sheet sheets 2b and 2b ^{were changed to 45 g / m 2 air-through non-woven fabric.} Regarding the water-absorbent sheet of Example 2, the ratio of the mass of the water-absorbent polymer to the mass of the base sheet 2 obtained by the above-mentioned method is 33% by mass, and is based on the surface area of the base sheet obtained by the method described later. The ratio of the total area of the polymer arrangement portion 3 was 20%.

[Example 3]
The water-absorbent sheet of Example 3 was produced in the same manner as the water-absorbent sheet of Example 1 except that the original two base sheet sheets 2b and 2b ^{were changed to 45 g / m 2 air-through non-woven fabric.} Regarding the water-absorbent sheet of Example 3, the ratio of the mass of the water-absorbent polymer to the mass of the base material sheet 2 obtained by the above-mentioned method is 67% by mass, and is based on the surface area of the base material sheet obtained by the method described later. The ratio of the total area of the polymer arrangement portion 3 was 40%.

[Comparative Example 1]
^{The sheet of Comparative Example 1 was obtained by heat-pressing the 45 g / m 2} air-through non-woven fabric used for producing the water-absorbent sheet of Example 2 (using a spacer PET 0.3 mm, 70 ° C., 2 MPa for 2 minutes). Used as.

[Comparative Example 2]
The original two base sheets 2b and 2b ^{were changed to 45 g / m 2} air-through non-woven fabric, and the solution in which the water-absorbing polymer was dissolved was applied to the entire surface of one surface of the first base sheet 2b. A sheet of Comparative Example 2 was produced in the same manner as in Example 1 except for the above.
Regarding the sheet of Comparative Example 2, the ratio of the mass of the water-absorbent polymer to the mass of the base sheet 2 obtained by the above method was 222% by mass, and the polymer arrangement with respect to the surface area of the base sheet obtained by the method described later. The ratio of the total area of the parts was 100%.

[Reference Example 1]
A single-layer air-through non-woven fabric made of 30 g / m ^{2 PE was prepared.} The air-through nonwoven fabric had a length of 100 mm in the vertical direction (X direction), a length of 100 mm in the horizontal direction (Y direction), and a length of 4 mm in the thickness direction (Z direction). Then, a solution in which the same water-absorbent polymer as in Example 1 is dissolved is applied to one surface of the spunbonded non-woven fabric using a brush, dried, and then heat-pressed (using a spacer PET 0.3 mm, 70 ° C.). , 2 MPa for 2 minutes) to produce the sheet of Reference Example 1. Regarding the sheet of Reference Example 1, the ratio of the mass of the water-absorbent polymer to the mass of the air-through nonwoven fabric obtained by the above method is 67% by mass, and the polymer arrangement portion 3 with respect to the surface area of the air-through nonwoven fabric obtained by the method described later The ratio of the total area was 15%.

[Reference example 2]
A sheet of Reference Example 2 was produced in the same manner as in Reference Example 1 except that the non-woven fabric was changed to a single-layer spunbonded non-woven fabric made of 45 g / m ^{2 PE.} Regarding the sheet of Reference Example 2, the ratio of the mass of the water-absorbent polymer to the mass of the spunbonded nonwoven fabric obtained by the above method is 67% by mass, and the polymer-arranged portion with respect to the surface area of the spunbonded nonwoven fabric obtained by the method described later. The ratio of the total area of 3 was 20%.

[Performance evaluation]
The absorbed capacity and the amount of liquid return were evaluated for each of the produced water-absorbing sheets of Examples 1 to 3, the sheets of Comparative Examples 1 and 2 and the sheets of Reference Examples 1 and 2 by the following methods, respectively. The results are shown in Table 1 below. The ratio of the total area of the polymer-arranged portion 3 to the surface area of the base sheet was determined by the method described later.

<Absorption capacity>
The absorption capacity of each sample was measured according to JIS K 7223-1996, which is a water absorption test method for highly water-absorbent resins. Each sample was immersed in physiological saline (0.9 mass% sodium chloride solution) whose temperature was adjusted to 25 ° C. so that the whole was immersed. Ten minutes after the start of immersion, each sample was taken out from physiological saline and dehydrated using a centrifugal dehydrator (Kokusan Co., Ltd., model 130c special type). The dehydration condition was 800 rpm × 5 minutes. After dehydration, the mass of each sample was measured, the centrifugal holding amount (unit: g / g) was calculated according to the following formula, and the calculated value was used as the absorption capacity of each sample. In the following equation, each mass is in g units.
Centrifugal retention = (mass of sample after centrifugal dehydration-mass of sample before water absorption) / mass of sample before water absorption The measurement is performed at 23 ± 2 ° C and humidity of 50 ± 5RH%. The sample was stored for 24 hours or more in the same environment as the measurement.
The legend in the table is as follows.
A:> 3g / g
B: 1-3 g / g
C: <1 g / g

<Liquid return amount>
The test pieces (50 × 50 mm) obtained in Examples, Comparative Examples and Reference Examples were placed on a horizontal table. Under this condition, 0.5 g of a blue-colored physiological saline solution manufactured by Otsuka Pharmaceutical Co., Ltd. was added dropwise. Thirty seconds after the completion of the dropping, a filter paper (No. 2, 90 mm, manufactured by Advantech) was placed on the test piece, an acrylic plate was further placed on the filter paper, and ^{a pressure of 3 g / cm 2} was applied for 30 seconds. The mass of the filter paper before and after the dropping of the physiological saline was measured, and the amount of absorption of the filter paper was determined from the amount of change. Then, the liquid return rate was calculated by the following formula.

Liquid return rate (%) = filter paper absorption amount (g) /0.5 (g) x 100
The measurement was performed at 23 ± 2 ° C. and a humidity of 50 ± 5 RH%, and each sample was stored in the same environment as the measurement for 24 hours or more before the measurement.
The legend in the table is as follows.
A: <5%
B: 5 to 20%
C:> 20%

<Ratio of the total area of the polymer placement part to the surface area of the base sheet>
Images at 5 locations were randomly taken out using SEM (50 times), and the area of the polymer value distribution part was determined by the image analysis software "ImageJ". The area value was the average value of five images.

As is clear from the results shown in Table 1, it was found that the water-absorbent sheets of Examples 1 to 3 had a higher absorption capacity and were more easily absorbed by the liquid than the sheets of Comparative Example 1. Further, it was found that the water-absorbent sheets of Examples 1 to 3 had a smaller amount of liquid return than the sheets of Comparative Examples 1 and 2 and the sheets of Reference Examples 1 and 2.

According to the water-absorbent sheet of the present invention, the flexibility is high, the liquid is easily absorbed inside the sheet, and the amount of liquid returned is small.

Claims (8)

Have a base sheet and a water-absorbing polymer, a water-absorbent sheet used to absorb body fluids,
The base material sheet is a porous sheet and is
The water-absorbent polymer is a thermoplastic water-absorbent polymer or a water-absorbent polymer that dissolves in a solvent.
The amount of the water-absorbent polymer that dissolves in the solvent is 1 g or more in 100 g of ethanol at 25 ° C. or 100 g of a mixed solvent of 70 g of ethanol and 30 g of water at 25 ° C.
Looking at the water-absorbent sheet in a plan view, the polymer-arranged portion on which the water-absorbent polymer is arranged and the polymer non-arranged portion on which the water-absorbent polymer is not arranged are dispersed and arranged in the plane direction.
The polymer arrangement portion is
It is formed by heating the thermoplastic water-absorbent polymer to melt it, allowing the melted thermoplastic water-absorbent polymer to permeate the inside of the base material sheet, and then cooling it.
The water-absorbent polymer dissolved in the solvent is formed by applying a solution dissolved in the solvent to the base sheet and then drying the base sheet, whereby some pores of the base sheet are formed into a film. Covering
When the water-absorbent sheet is viewed in cross section, the polymer arranging portion is arranged in an intermediate region spaced from both sides of the base material sheet .
A water-absorbent sheet in which the total area of the polymer-arranged portions is 15% or more and 40% or less of the surface area of the base material sheet when viewed in a plan view from one surface side of the water-absorbent sheet. The water-absorbent sheet according to claim 1 , wherein the ratio of the mass of the water-absorbent polymer to the mass of the base material sheet is 1% by mass or more and 200% by mass or less. The water-absorbent sheet according to claim 1 or 2 , wherein the polymer non-arranged portion extends between both sides of the base material sheet when the water-absorbent sheet is viewed in cross section. The water-absorbent sheet according to any one of claims 1 to 3 , further comprising inorganic particles having an average particle size of 0.1 μm or more and 500 μm or less. The water-absorbent sheet according to any one of claims 1 to 4 , wherein the water-absorbent polymer has a weight average molecular weight of 30,000 or more and 1 million or less. The water-absorbent sheet according to any one of claims 1 to 5 , wherein the thermoplastic water-absorbent polymer has a melting point of 40 ° C. or higher. The water-absorbent sheet according to any one of claims 1 to 6 , wherein the base material sheet is a non-woven fabric. A method for absorbing incontinence urine, which is used by arranging the water-absorbent sheet according to any one of claims 1 to 7 on the inner or outer crotch of underwear such as briefs for men.

Images