JP6932189B2 - 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 these needs is required to be thin and flexible.

For example, Patent Document 1 describes a thin and 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. A cross-sectional view of the water-absorbent sheet, a polymer arranging portion on which the water-absorbent polymer is arranged is arranged in a region extending from one surface of the base material sheet to the inside. On one surface of the water-absorbent sheet, the polymer-arranged portion and the polymer non-arranged portion on which the water-absorbent polymer is not arranged are dispersed and arranged in the plane direction in a plan view of the water-absorbent sheet. There is.

FIG. 1 is a plan view of a water-absorbent sheet, which is a preferred embodiment of the present invention, as viewed from the surface side of one side on which a polymer arrangement portion is arranged. FIG. 2 is a cross-sectional view taken along the line II-II shown in FIG. FIG. 3 was taken with an electron microscope of a state in which a polymer arrangement portion was formed by covering a part of a large number of pores between the fibers constituting the base sheet of the non-woven fabric in a film shape. It is a top view of the water absorption sheet. FIG. 4 is a cross-sectional view of the water-absorbent sheet of FIG. 3 in which the polymer-arranged portion is arranged in a region extending from one surface of the water-absorbent sheet to the inside using an electron microscope. .. 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, is thin, has high flexibility, and easily absorbs a liquid inside.

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 300 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 inside 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 inside 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. As the non-woven fabric, a single-layer air-through non-woven fabric is preferably used from the viewpoint of easily forming the polymer arranging portion 3 inside the water-absorbent sheet 1 and improving the flexibility. The 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, still more preferably 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, and from the viewpoint of easily forming the polymer arrangement portion 3 inside the water-absorbent sheet 1. 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 100,000. More than 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 bismethylenediphenyldiisocyanate 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. or lower, from the viewpoint of easily forming the polymer arrangement portion 3 inside the water-absorbent sheet 1. It is more preferably 150 ° C. or lower, specifically 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 containing 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. From the viewpoint of easily forming the polymer arrangement portion 3 inside the water-absorbent sheet 1, the amount of the polymer that dissolves in 100 g of ethanol at 25 ° C. 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.
The amount of the water-absorbent polymer that dissolves in the solvent is preferably 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 of easily forming the polymer arrangement portion 3 inside the water-absorbent sheet 1. Is 1 g or more, 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 FIGS. 2 and 4, in the water-absorbent sheet 1, the polymer arranging portion 3 on which the water-absorbent polymer is arranged is arranged in a region extending from one surface 1h of the water-absorbent sheet 1 to the inside. ing. In the water-absorbent sheet 1, the polymer arranging portion 3 is not substantially formed above the surface of the base sheet 2 when the water-absorbent sheet 1 is viewed in cross section, and is inside from one surface of the base sheet 2. It is formed in a state of permeation into. Specifically, the polymer arranging portion 3 is formed in a region extending from one surface 1h of the water-absorbent sheet 1 to the inside at a distance from the other surface 1t of the base sheet 2. The term "substantially" as used herein means that the height of the protrusion is 0.05% or less of the thickness of the water-absorbent sheet 1, even if it protrudes upward from the surface, and 0.01% or less is preferable. , 0.005% or less is more preferable.

The surfaces 1h and 1t of the water-absorbent sheet 1 are obtained 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 Sword 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 secure the air permeability, the water-absorbent sheet 1 is viewed in cross section as shown in FIG. 2 from one surface 1h of the water-absorbent sheet 1 with respect to the thickness T2 of the base sheet 2. The ratio of the thickness T3 of the polymer arrangement portion 3 ((T3 / T2) × 100) is preferably arranged over a region of 1% or more, more preferably 2% or more, still more preferably 5% or more. It is distributed over a region of 90% or less, more preferably 50% or less, still more preferably 30% or less, and specifically. Is preferably arranged over a region of 1% or more and 90% or less, more preferably 2% or more and 50% or less, and further 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-arranged portion 3 region in the water-absorbent sheet 1 is the one surface 1h of the water-absorbent sheet 1 and the most other surface 1t in the polymer-arranged portion 3 in a cross-sectional view as shown in FIG. It is the distance from the part located near.

The water-absorbent sheet 1 is viewed in a plan view as shown in FIGS. 1 and 3, and the polymer-arranged portion 3 and the polymer non-arranged portion 4 in which the water-absorbing polymer is not arranged are arranged in the plane direction (X) on one surface 1h. It is distributed in the direction (direction and Y direction). In the water-absorbent sheet 1, the polymer-arranged portion 3 and the polymer-non-arranged portion 4 are randomly dispersed and arranged in the surface direction only on one surface 1h. The polymer arranging portion 3 is a portion where the water-absorbent sheet 1 is viewed in a plan view from one surface 1h side, and the water-absorbent sheet 1 is visually or SEM-observed to determine that the water-absorbent polymer is arranged. That is, the polymer non-arranged portion 4 means that the water-absorbent sheet 1 is viewed in a plan view from one surface 1h side, and the water-absorbent sheet 1 is visually or SEM-observed to determine that the water-absorbent polymer is not arranged. It is the part that can be done.

The shape of the water-absorbent polymer is not particularly limited as long as the water-absorbent polymer is arranged inside the base sheet 2, and the shape of the water-absorbent polymer is spherical, lumpy, or bale-shaped. It may be in the form of particles such as, fibrous, etc., in the form of a thin film, or in the form of a combination of these, but in the water-absorbent sheet 1, it is shown in FIG. As shown, 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.

For example, when the water-absorbent polymer is a thermoplastic water-absorbent polymer, the water-absorbent sheet 1 is melted by applying heat to the water-absorbent polymer after arranging the water-absorbent polymer on the surface of the base sheet 2. , The melted water-absorbent polymer can be produced by infiltrating the inside from one surface of the base sheet 2 and then cooling. Further, for example, in the case of a water-absorbent polymer in which the water-absorbent polymer is dissolved in a solvent, the base sheet 2 is prepared by dissolving the water-absorbent polymer in the solvent and then using a brush, for example, to prepare a solution in which the water-absorbent polymer is dissolved. It can be manufactured by applying it to one surface and then drying it.

As shown in FIG. 2, the water-absorbent sheet 1 described above has a polymer arranging portion 3 arranged in a region extending from one surface 1h of the water-absorbent sheet 1 to the inside in a cross-sectional view. Therefore, the thickness is thin and the flexibility is high. Further, in the water-absorbent sheet 1, the polymer-arranged portion 3 and the polymer-non-arranged portion 4 are dispersed in the surface direction (X direction and Y direction) on one surface 1h in a plan view as shown in FIG. It is arranged. Since the polymer non-arranged portions 4 are dispersed and arranged in this way, the flexibility is improved and the liquid is easily absorbed inside the water-absorbent sheet 1.

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 thickness is further reduced and 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-absorbent 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.

The total area of the polymer arrangement portion 3 is preferably 1% or more, more preferably 5% or more of the surface area of the base material sheet 2 when viewed in a plan view from one surface 1h side of the water-absorbent sheet 1. , More preferably 10% or more, and preferably 99% or less, still more preferably 95% or less, still more preferably 90% or less, specifically, preferably 1% or more and 99%. It is less than or equal to, 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 on one surface 1h. The area of the polymer arrangement portion 3 is measured by the method described in the examples.

When viewed in a plan view from one surface 1h side of the water-absorbent sheet 1, the total area of the polymer non-arranged portion 4 is preferably 1% or more, more preferably 5% of the total area of the polymer-arranged portion 3. The above, more preferably 10% or more, preferably 99% or less, further preferably 95% or less, still more preferably 90% or less, specifically, preferably 1%. It is 99% or more, 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 on one surface 1h.

Since the water-absorbent sheet 1 described above is thin and highly flexible, it can easily absorb body fluids such as sweat, blood, and urine, pet urine, and water around water such as kitchens and toilets. It is possible to meet the needs of maintaining 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, one surface 1h of the above-mentioned water-absorbent sheet 1 faces the wearer side at the excretion portion facing portion of the crotch portion of the underwear 10 which is arranged to face the portion where the wearer's penis is located at the time of wearing. As described above, or one surface 1h of the water-absorbent sheet 1 described above is arranged and used so as to face the underwear 10 side. If the above-mentioned water-absorbent sheet 1 is used by arranging it on the inner or outer crotch of the underwear 10, it is thin and highly flexible, so that it is comfortable to wear and can absorb incontinent urine. If one surface 1h of the water-absorbent sheet 1 is used so as to face the wearer side on the inner surface of the underwear 10 facing the excretion portion, the polymer arrangement portion 3 on the surface 1h side can efficiently absorb the water-absorbent sheet 1. If one surface 1h of 1 is used so as to face the underwear 10 side, the other surface 1t on which the polymer arranging portion 3 is not arranged can be used in a state of being comfortable to the touch.

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 single-layer non-woven fabric is used as the base sheet 2, but a laminate in which a liquid-impermeable resin film is laminated on the single-layer non-woven fabric is used. May be good. When such a laminate is used for the base sheet 2, the polymer arranging portion 3 is formed on the surface on the non-woven fabric side.

Further, in the water-absorbent sheet 1 of the above-described embodiment, as shown in FIGS. 2 and 4, the polymer arranging portion 3 is spaced from the other surface 1t of the base material sheet 2 and is the water-absorbent sheet 1. Although it is formed in a region extending from one surface 1h to the inside, it may be formed in a region extending from one surface 1h of the water-absorbent sheet 1 to the inside. That is, a part of the polymer arranging portion 3 may be formed from one surface 1h of the water-absorbent sheet 1 to the other surface 1t.

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.
When the water-absorbent sheet is viewed in cross section, the polymer arranging portion on which the water-absorbent polymer is arranged is arranged in a region extending from one surface of the base material sheet to the inside.
On one surface of the water-absorbent sheet, the polymer-arranged portion and the polymer-non-arranged portion on which the water-absorbent polymer is not arranged are dispersed and arranged in the plane direction in a plan view of the water-absorbent sheet. There is a 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>
Any one of <1> to <3>, wherein the total area of the polymer-arranged portions is 1% or more 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 described in.
<5>
When the water-absorbent sheet is viewed in cross section, the polymer-arranged portion is arranged from one surface of the base material sheet over a region of 1% or more of the thickness of the base material sheet. The water-absorbent sheet according to any one of <4>.
<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 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 base sheet 2, a single-layer air-through non-woven fabric ^{made of 45 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 one surface of the substrate sheet 2 using a brush, then dried and pressed at 70 ° C. and 2 MPa for 2 minutes using a 0.3 mm spacer made of PET to 0.6 mm. The water-absorbent sheet of Example 1 having the same thickness as that of Example 1 was produced. 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 22% 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 20%. When the obtained sheet was cross-sectionally viewed, it was confirmed that a part of the water-absorbent polymer was arranged in a region covering 10% of the base sheet from the surface of the base sheet.

[Example 2]
The water-absorbent sheet of Example 2 was produced in the same manner as the water-absorbent sheet of Example 1. Regarding the water-absorbent sheet of Example 2, 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%. When the obtained sheet was cross-sectionally viewed, it was confirmed that a part of the water-absorbent polymer was arranged in a region covering 12% of the base sheet from the surface of the base sheet.

[Example 3]
The water-absorbent sheet of Example 3 was produced in the same manner as the water-absorbent sheet of Example 1. 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 133% 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 80%. When the obtained sheet was cross-sectionally viewed, it was confirmed that a part of the water-absorbent polymer was arranged in a region extending from the surface of the base sheet to 16% of the base sheet.

[Example 4]
The water-absorbent sheet of Example 4 was produced in the same manner as in Example 1 except that the polymer A produced as described below was used as the water-absorbent polymer.
The method for producing the water-absorbent polymer A used for producing the water-absorbent sheet of Example 4 is shown below.
Flask of 170 g of N-tert-butylacrylamide (TBAA), 1 g of trithiobis carbonate {4- [ethyl- (2-hydroxyethyl) carbamoyl] benzyl}, 0.032 g of 2,2'-azoisobutyronitrile, and 680 g of methanol. In addition, nitrogen bubbling was performed for 30 minutes. The solution was heated to 65 ° C. in an oil bath with stirring. After reacting the reaction solution at 65 ° C. for 4.5 hours, dilute with acetone so that the solid content becomes 10%, and reprecipitate with a poor solvent of 20 times the volume of water / ethanol (volume ratio). bottom. The obtained solid was vacuum dried at 80 ° C. to obtain a solid 1. As a result of analysis of GPC of this solid, the number average molecular weight was 50,000 and the weight average molecular weight was 67,000.
DMAA was purified by passing 1 g of N, N-dimethylacrylamide (DMAA) through 1 g of activated alumina. After adding 81 g of purified DMAA, 10 g of solid 1, 0.0032 g of 2,2'-azoisobutyronitrile and 320 g of ethyl acetate to the flask, nitrogen bubbling was performed for 30 minutes. It was heated to 65 ° C. with stirring. The reaction solution was reacted at 65 ° C. for 2 hours, diluted with acetone so that the solid content became 10%, and reprecipitated with 20 times the volume of hexane. The obtained solid was vacuum dried at 80 ° C. to obtain a water-absorbent polymer A (TBAA-b-DMAA-b-TBAA). As a result of GPC analysis, the number average molecular weight was 180,000 and the weight average molecular weight was 320,000. It was dissolved in ethanol so that the solid content became 10% to obtain an ethanol solution of the water-absorbent polymer A.
Regarding the water-absorbent sheet of Example 4, the ratio of the mass of the water-absorbent polymer A to the mass of the base sheet 2 obtained by the above-mentioned method is 67% by mass, and 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 to the total area was 40%. When the obtained sheet was cross-sectionally viewed, it was confirmed that a part of the water-absorbent polymer was arranged in a region covering 13% of the base sheet from the surface of the base sheet.

[Example 5]
The water-absorbent sheet of Example 5 was produced in the same manner as in Example 1 except that the water-absorbent polymer B produced as described below was used.
The method for producing the water-absorbent polymer B used for producing the water-absorbent sheet of Example 5 is shown below.
35.8 g of methyl cytositocin and 253 g of dimethyl sulfoxide (DMSO) were added to the flask and heated to 150 ° C. in an oil bath. While maintaining the internal temperature of the flask, 48.8 g of isocyanate ethyl methacrylate was added and reacted for 30 minutes. The reaction solution was then cooled to room temperature and the precipitate was washed with methanol. The obtained solid was vacuum dried at 80 ° C. to obtain 2- [3- (6-methyl-4--oxo-1,4-dihydropyrimidine-2-yl) ureido] ethyl methacrylate of solid 2. ..
2.80 g of Solid 2, 18.8 g of DMAA and 115 g of DMSO were added to the flask and heated to 65 ° C. in an oil bath. After the internal temperature reached 65 ° C., a solution prepared by dissolving 0.0497 g of 2,2'-azobis (2,4-dimethylvaleronitrile) in 5 g of DMSO was added in a batch and reacted for 6 hours. Then, the reaction solution was cooled to room temperature and reprecipitated with 20 times the volume of diethyl ether. Then, it was dissolved in ethanol so that the solid content became 10% to obtain an ethanol solution of the water-absorbent polymer B.
Regarding the water-absorbent sheet of Example 5, the ratio of the mass of the water-absorbent polymer B to the mass of the base sheet 2 obtained by the above method is 67% by mass, and the surface area of the base sheet obtained by the method described later is The ratio of the total area of the polymer arrangement portion 3 to the total area was 40%. When the obtained sheet was cross-sectionally viewed, it was confirmed that a part of the water-absorbent polymer was arranged in a region extending from the surface of the base sheet to 12% of the base sheet.

[Comparative Example 1]
The base sheet 2 used for producing the water-absorbent sheet of Example 1 was pressed for 2 minutes at 70 ° C. and 5 MPa without using a spacer during hot pressing, and was used as it was as the sheet of Comparative Example 1.

[Comparative Example 2]
A sheet of Comparative Example 2 was produced in the same manner as in Example 1 except that the solution in which the water-absorbing polymer was dissolved was applied to the entire surface of one surface of the base sheet 2.
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 is 300% 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%. When the obtained sheet was cross-sectionally viewed, it was confirmed that a part of the water-absorbent polymer was arranged in a region extending from the surface of the base sheet to 32% of the base sheet.

[Comparative Example 3]
A non-breathable film was used instead of the base sheet 2 made of the air-through non-woven fabric used in the production of the water-absorbent sheet of Example 1. The film is a commercially available PET film (trade name: Lumirror, 80 μm manufactured by Toray Co., Ltd.), the length in the vertical direction (X direction) is 100 mm, and the length in the horizontal direction (Y direction) is 100 mm. The length in the thickness direction (Z direction) was 0.03 mm. Other than that, the sheet of Comparative Example 3 was produced in the same manner as the water-absorbent sheet of Example 1. Regarding the sheet of Comparative Example 3, the polymer-arranged portion on which the water-absorbent polymer was arranged was not arranged in the region extending from the surface of the sheet to the inside, but was formed above the surface of the film sheet. 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 67% by mass, and the ratio of the total area of the polymer-arranged portion to the surface area of the base sheet obtained by the method described later. Was 100%.

[Performance evaluation]
For each sample of the produced water-absorbent sheets of Examples 1 to 5 and the sheets of Comparative Examples 1 to 3, the one-drop absorption time, absorption capacity, and air permeability were evaluated 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.

<1 drop absorption time>
One drop (0.05 g) of raw food (colored with blue No. 1 0.1%) was dropped onto the treated surface treated with the polymer of each sample using a dropper, and one drop of raw food was dropped onto the sample. However, it is absorbed and diffused inside and in the gaps of the sample, and the time until the reflected light of the raw food on the treated surface of the sample disappears is measured. The measurement was taken as an average value of 3 times, and this value was taken as one drop absorption time (s).
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 Table 1 is as follows.
A: <3 sec
B: 3 to 20 sec
C:> 20 sec

<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. Thirty 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 Table 1 is as follows.
A:> 3g / g
B: 1-3 g / g
C: <1 g / g

<Breathability>
Using an air permeability measuring machine (KES-F8-AP1 manufactured by Kato Tech Co., Ltd.), each sample was fixed so as to block the ventilation holes, and the air permeability resistance R (KPa · s / m) was measured.
The legend in Table 1 is as follows.
A: 0-5KPa ・ s / m
B: 5 to 25 KPa · s / m
C:> 25KPa ・ s / m

<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 price 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, the water-absorbent sheets of Examples 1 to 5 have a higher absorption rate, easier absorption of liquid, and higher air permeability than the sheets of Comparative Examples 2 and 3. I found out. Further, it was found that the water-absorbent sheets of Examples 1 to 5 had a larger absorption capacity than the sheets of Comparative Example 1.

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

Claims (7)

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.
When the water-absorbent sheet is viewed in cross section, the polymer arranging portion on which the water-absorbent polymer is arranged is arranged in a region extending from one surface of the base material sheet to the inside.
On one surface of the water-absorbent sheet, the polymer-arranged portion and the polymer non-arranged portion on which the water-absorbent polymer is not arranged are dispersed and arranged in the plane direction in a plan view of the water-absorbent sheet. Ori,
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 from one surface of the base material sheet, and then cooling it.
The water-absorbent polymer that dissolves in the solvent is formed by applying a solution dissolved in the solvent to the surface of the base sheet and then drying it, so that some pores of the base sheet are formed into a film. It covers like a shape
A water-absorbent sheet in which the total area of the polymer-arranged portions is 20% or more and 80% 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. Claim 1 or 2 in which the polymer-arranged portion is arranged from one surface of the base material sheet over a region of 1% or more of the thickness of the base material sheet in a cross-sectional view of the water-absorbent sheet. The water-absorbent sheet described in. The water-absorbent sheet according to any one of claims 1 to 3 , 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 4 , 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 5 , 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 6 on the inner or outer crotch of underwear such as briefs for men.

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