WO2024176758A1

WO2024176758A1 - Water-absorbing resin composition

Info

Publication number: WO2024176758A1
Application number: PCT/JP2024/003048
Authority: WO
Inventors: 渉太森島
Original assignee: 住友精化株式会社
Priority date: 2023-02-22
Filing date: 2024-01-31
Publication date: 2024-08-29

Abstract

Provided is a water-absorbing resin composition having an excellent deodorizing effect.　The water-absorbing resin composition contains an antibacterial metal-containing deodorant, a porous deodorant, and water-absorbing polymer particles. The ratio (X/Y) of the content X (parts by mass) of the porous deodorant to the content Y (parts by mass) of the antibacterial metal-containing deodorant is 0.8 or more, and in the entire water-absorbing resin composition, the sum (x + y) of the content x (mass %) of the porous deodorant and the content y (mass %) of the antibacterial metal-containing deodorant is 0.10 mass % or more.

Description

Water-absorbent resin composition

The present invention relates to a water-absorbent resin composition, and more specifically to a water-absorbent resin composition that constitutes an absorbent material suitable for use in sanitary materials such as disposable diapers, sanitary napkins, and incontinence pads.

In recent years, water-absorbent resins have been widely used in the field of sanitary materials such as disposable diapers, sanitary napkins, and incontinence pads.

As such water-absorbent resins, cross-linked polymers of partially neutralized acrylic acid salts have excellent water-absorbing properties, and because the raw material, acrylic acid, is easily available industrially, they can be produced at low cost with consistent quality, and are less susceptible to spoilage or deterioration, making them a preferred water-absorbent resin.

Absorbent articles such as disposable diapers, sanitary napkins, and incontinence pads are mainly composed of an absorbent body located in the center that absorbs and retains bodily fluids such as urine and menstrual blood excreted from the body, a liquid-permeable surface sheet (top sheet) located on the side that comes into contact with the body, and a liquid-impermeable back sheet (back sheet) located on the opposite side that comes into contact with the body. The absorbent body is usually composed of hydrophilic fibers such as pulp and water-absorbent resin.

When such absorbents are used, for example, as sanitary materials, they may emit unpleasant odors such as ammonia after absorbing bodily fluids, particularly urine, blood, sweat, etc.

JP 2001-323155 A

When urine is absorbed into the absorbent, the urea in the urine is broken down by the action of urease contained in the urease-producing bacteria, generating ammonia.

The inventor attempted to inhibit the decomposition reaction of urea by urease and suppress the generation of ammonia by inactivating urease using a deodorant containing an antibacterial metal such as silver. However, the inventor discovered a problem in that when a large amount of L-cystine (a sulfur-containing amino acid) is present in urine, such as in the urine of a patient with cystinuria, the antibacterial metal binds to L-cystine, weakening the antibacterial metal's ability to inactivate urease, and the deodorant effect is not fully exerted.

The main objective of the present invention is to provide a water-absorbent resin composition that has an excellent deodorizing effect on urine that contains a large amount of L-cystine.

The present inventors have conducted extensive research to solve the above problems. As a result, they have found that, in a water-absorbent resin composition containing water-absorbent polymer particles, by combining an antibacterial metal-containing deodorant and a porous deodorant, and further setting the ratio (X/Y) of the content X (parts by mass) of the porous deodorant to the content Y (parts by mass) of the antibacterial metal-containing deodorant to a predetermined ratio or more, and further setting the sum (x+y) of the content x (% by mass) of the porous deodorant and the content y (% by mass) of the antibacterial metal-containing deodorant in the entire water-absorbent resin composition to a predetermined ratio or more, the water-absorbent resin composition exhibits a high deodorizing function against ammonia and the like even when urine containing a large amount of L-cystine is absorbed.

That is, the present invention provides the following configuration.
Item 1. A water-absorbing resin composition comprising an antibacterial metal-containing deodorant, a porous deodorant, and water-absorbing polymer particles,
the ratio (X/Y) of the content X (parts by mass) of the porous deodorant to the content Y (parts by mass) of the antibacterial metal-containing deodorant is 0.8 or more;
A water absorbent resin composition, wherein the sum (x+y) of a content rate x (mass%) of the porous deodorant and a content rate y (mass%) of the antibacterial metal-containing deodorant in the entire water absorbent resin composition is 0.10 mass% or more.
Item 2. The water-absorbing resin composition according to Item 1, wherein the sum (x+y) of the content x (% by mass) and the content y (% by mass) is 0.50% by mass or less.
Item 3. The water absorbent resin composition according to Item 1 or 2, wherein the antibacterial metal contained in the antibacterial metal-containing deodorant contains at least one selected from the group consisting of silver, copper, zinc, bismuth, cobalt, aluminum, and nickel.
Item 4. The water absorbent resin composition according to any one of Items 1 to 3, wherein the antibacterial metal-containing deodorant comprises at least one selected from the group consisting of silver powder, silver chloride (I), silver oxide (I), and a substance carrying at least one metal ion selected from the group consisting of silver ions and zinc ions.
Item 5. The water-absorbing resin composition according to any one of Items 1 to 4, wherein the porous deodorant comprises at least one selected from the group consisting of activated carbon, silicon dioxide, and silicates.
Item 6. The water absorbent resin composition according to any one of Items 1 to 5, wherein the antibacterial metal-containing deodorant has a median particle diameter of 0.1 μm to 100 μm, and the porous deodorant has a median particle diameter of 1 μm to 100 μm.
Item 7. An absorbent article comprising an antibacterial metal-containing deodorant, a porous deodorant, and water-absorbing polymer particles,
the ratio (X/Y) of the content X (parts by mass) of the porous deodorant to the content Y (parts by mass) of the antibacterial metal-containing deodorant is 0.8 or more;
The sum (x+y) of the content x (mass%) of the porous deodorant and the content y (mass%) of the antibacterial metal-containing deodorant based on the total amount of the antibacterial metal-containing deodorant, the porous deodorant, and the water-absorbent polymer particles is 0.10 mass% or more.

The present invention provides a water-absorbent resin composition that has an excellent deodorizing effect on urine that contains a large amount of L-cystine.

FIG. 4 is a schematic diagram of a device for measuring the amount of physiological saline solution absorbed under a load of 4.14 kPa.

In this specification, the term "comprising" includes "consisting essentially of" and "consisting of". In addition, in this specification, "(meth)acrylic" means "acrylic or methacrylic" and "(meth)acrylate" means "acrylate or methacrylate". Furthermore, "water-soluble" refers to a solubility of 5% by mass or more in water at 25°C.

In addition, in this specification, a numerical value connected with "~" means a numerical range that includes the numerical values before and after "~" as the lower and upper limits. When multiple lower limits and multiple upper limits are listed separately, any lower limit and upper limit can be selected and connected with "~".

1. Water-absorbent resin composition The water-absorbent resin composition of the present invention is a water-absorbent resin composition containing an antibacterial metal-containing deodorant, a porous deodorant, and water-absorbent polymer particles, characterized in that the ratio (X/Y) of the content X (parts by mass) of the porous deodorant to the content Y (parts by mass) of the antibacterial metal-containing deodorant is 0.8 or more, and the sum (x+y) of the content x (% by mass) of the porous deodorant and the content y (% by mass) of the antibacterial metal-containing deodorant in the entire water-absorbent resin composition is 0.10% by mass or more. The water-absorbent resin composition of the present invention having such characteristics exerts an excellent deodorizing effect on urine containing a large amount of L-cystine. The water-absorbent resin composition of the present invention will be described in detail below.

As mentioned above, the inventor attempted to inhibit the decomposition reaction of urea by urease and suppress the generation of ammonia by inactivating urease using a deodorant containing an antibacterial metal such as silver. However, the inventor's investigation revealed the problem that when a large amount of L-cystine (a sulfur-containing amino acid) is present in urine, such as in the urine of patients with cystinuria, the antibacterial metal tends to bind to L-cystine, weakening the urease inactivation effect of the antibacterial metal and preventing the deodorant effect from being fully exerted. Furthermore, as a result of further investigations, the present inventors have found that, in a water absorbent resin composition containing water absorbent polymer particles, an antibacterial metal-containing deodorant and a porous deodorant are used in combination, the ratio (X/Y) of the content X (parts by mass) of the porous deodorant to the content Y (parts by mass) of the antibacterial metal-containing deodorant is set to 0.8 or more, and further, the sum (x+y) of the content x (% by mass) of the porous deodorant and the content y (% by mass) of the antibacterial metal-containing deodorant in the entire water absorbent resin composition is set to 0.10% by mass or more, whereby the antibacterial metal-containing deodorant and the porous deodorant function synergistically, and the water absorbent resin composition exhibits a high deodorizing function against ammonia even when absorbing urine containing a large amount of L-cystine. This is thought to be because the porous deodorant adsorbs L-cystine in urine, preventing L-cystine from inhibiting the urease inactivation action of the antibacterial metal-containing deodorant, allowing the urease inactivation action of the antibacterial metal-containing deodorant to be optimally exerted, allowing the water absorbent resin composition to exert a high deodorizing function against ammonia, etc.

In the water absorbent resin composition of the present invention, at least a portion of the antibacterial metal-containing deodorant (e.g., 20% by mass to 100% by mass, 50% by mass to 100% by mass, 80% by mass to 100% by mass, 90% by mass to 100% by mass, 95% by mass to 100% by mass, or 100% by mass) of the entire antibacterial metal-containing deodorant may be disposed on the surface of the water absorbent polymer particle, and at least a portion of the antibacterial metal-containing deodorant may permeate the inside of the water absorbent polymer particle. In addition, in the water absorbent resin composition of the present invention, at least a portion of the porous deodorant (e.g., 20% by mass to 100% by mass, 50% by mass to 100% by mass, 80% by mass to 100% by mass, 90% by mass to 100% by mass, 95% by mass to 100% by mass, or 100% by mass) of the entire antibacterial metal-containing deodorant may be disposed on the surface of the water absorbent polymer particle. In the water-absorbent resin composition of the present invention, at least a portion of the antibacterial metal-containing deodorant and at least a portion of the porous deodorant may be disposed on the surface of the water-absorbent polymer particles.

(Antibacterial metal-containing deodorant)
The antibacterial metal-containing deodorant is a deodorant containing an antibacterial metal. The antibacterial metal is preferably a metal that exerts an inactivating effect on urease. Here, the "antibacterial metal" is at least one selected from the group consisting of gold, silver, copper, platinum, zinc, bismuth, titanium, tungsten, nickel, iron, tin, mercury, lead, palladium, aluminum, cobalt, molybdenum, chromium, vanadium, and zirconium. The "antibacterial metal-containing deodorant" is a deodorant containing an antibacterial metal to a degree that exerts a substantial antibacterial effect, for example, a deodorant containing 1 mass % or more of antibacterial metal (when two or more kinds of antibacterial metals are contained, the total amount is used as the basis). The antibacterial metal-containing deodorant is, for example, contained in the water absorbent resin composition in the form of particles.

Because the water-absorbent resin composition of the present invention is typically used in sanitary materials such as diapers, and is expected to have excellent urease inactivation properties, the antibacterial metal may include at least one selected from the group consisting of silver, copper, zinc, bismuth, cobalt, aluminum, and nickel, may include at least one selected from the group consisting of silver, copper, and zinc, or may include at least one of silver and zinc.

Antibacterial metal-containing deodorants include, for example, at least one selected from the group consisting of silver powder, silver chloride (I), silver oxide (I), and materials carrying at least one of the metal ions silver ions and zinc ions. The material on which the metal ions are carried (the carrier) may be, for example, a porous material. The porous material may include, for example, at least one selected from the group consisting of zeolite, activated carbon, silicon dioxide, silicate, titania, alumina, aluminum hydroxide, and magnesium hydroxide, may include at least one selected from the group consisting of zeolite, activated carbon, and silicon dioxide, or may include zeolite. Specifically, silver zinc zeolite is suitable as a porous material carrying silver ions and zinc ions.

In addition, when the substance that carries the metal ions is a porous substance, the porous substance may be a substance that can function as a deodorant by itself. In this case, the porous substance and the porous deodorant described below may be substances with the same chemical composition or different substances.

From the viewpoint of more suitably exerting the effects of the present invention, when the antibacterial metal-containing deodorant is contained in the water absorbent resin composition in a particulate form, the median particle diameter (D50 (median diameter), volume basis) of the antibacterial metal-containing deodorant is 0.1 μm to 100 μm, 0.1 μm to 50 μm, 0.1 μm to 10 μm, 0.1 μm to 5 μm, 0.1 μm to 3 μm, 0.5 μm to 1 00 μm, 0.5 μm to 50 μm, 0.5 μm to 10 μm, 0.5 μm to 5 μm, 0.5 μm to 3 μm, 0.8 μm to 100 μm, 0.8 μm to 50 μm, 0.8 μm to 10 μm, 0.8 μm to 5 μm, 0.8 μm to 3 μm, 1 μm to 100 μm, 1 μm to 50 μm, 1 μm to 10 μm, 1 μm to 5 μm, or 1 μm to 3 μm. The median particle size (D50 (median size), volume basis) of the antibacterial metal-containing deodorant can be measured using a laser diffraction particle size distribution measuring device, and specifically, it is a value measured by the method described in the examples.

In addition, if the BET specific surface area of the antibacterial metal-containing deodorant is large, the frequency of contact between the antibacterial metal and urease increases, while the frequency of contact between the antibacterial metal and L-cystine also increases. Also, if the BET specific surface area of the antibacterial metal-containing deodorant is too large, there is a possibility that the degree of dust generation increases. Considering this, the BET specific surface area of the porous deodorant is preferably 100 m ² /g to 2000 m ² /g, 100 m ² /g to 1500 m ² /g, 100 m ² /g to 1000 m ² /g, 100 m ² /g to 800 m ² /g, 300 m ² /g to 2000 m ² /g, 300 m ² /g to 1500 m ² /g, 300 m ² /g to 1000 m ² /g, 300 m ² /g to 800 m ² /g, 500 m ² /g to 2000 m ² /g, 500 m ² /g to 1500 m ² /g, 500 m ² /g to 1000 m ² /g or 500 m ² /g to 800 m ² /g.

The BET specific surface area of the antibacterial metal-containing deodorant can be measured using a specific surface area measuring device, and specifically, is a value measured by the method described in the Examples.

In the entire water absorbent resin composition of the present invention, the sum (x+y) of the content x (mass%) of the porous deodorant and the content y (mass%) of the antibacterial metal-containing deodorant is 0.10 mass% or more. From the viewpoint of more suitably exerting the effects of the present invention, the sum (x+y) is 0.10 mass% to 0.80 mass%, 0.10 mass% to 0.60 mass%, 0.10 mass% to 0.50 mass%, 0.10 mass% to 0.40 mass%, 0.10 mass% to 0.35 mass%, 0.10 mass% to 0.30 mass%, 0.13 mass% to 0.80 mass%, 0.13 mass% to 0.60 mass%, 0. 13 mass% to 0.50 mass%, 0.13 mass% to 0.40 mass%, 0.13 mass% to 0.35 mass%, 0.13 mass% to 0.30 mass%, 0.18 mass% to 0.80 mass%, 0.18 mass% to 0.60 mass%, 0.18 mass% to 0.50 mass%, 0.18 mass% to 0.40 mass%, 0.18 mass% to 0.35 mass% Mass%, 0.18 mass% to 0.30 mass%, 0.20 Mass% to 0.80 mass%, 0.20 mass% to 0.60 mass%, 0.20 mass% to 0.50 mass%, 0.20 mass% to 0.40 mass%, 0.20 mass% to 0.35 mass%, 0.20 mass% to 0.30 mass%, 0.25 mass% to 0.80 mass%, 0.25 mass% to 0.60 mass%, 0.25 mass% to 0.50 mass% , 0.25% by mass to 0.40% by mass, 0.25 quality The content may be 0.35% by mass, 0.25% by mass to 0.30% by mass, 0.30% by mass to 0.80% by mass, 0.30% by mass to 0.60% by mass, 0.30% by mass to 0.50% by mass, 0.30% by mass to 0.40% by mass, 0.35% by mass to 0.80% by mass, 0.35% by mass to 0.60% by mass, 0.35% by mass to 0.50% by mass, or 0.35% by mass to 0.40% by mass. If the sum (x+y) of the content x (mass%) of the porous deodorant and the content y (mass%) of the antibacterial metal-containing deodorant is large, the dust generation rate increases, which may reduce the handleability of the water absorbent resin composition. Considering this dust generation rate, the sum (x+y) is preferably 0.50% by mass or less.

In addition, from the viewpoint of more suitably exerting the effects of the present invention, the content y (mass%) of the antibacterial metal-containing deodorant in the entire water absorbent resin composition of the present invention is 0.020 mass% to 0.12 mass%, 0.020 mass% to 0.08 mass%, 0.020 mass% to 0.06 mass%, 0.020 mass% to 0.04 mass%, 0.024 mass% to 0.12 mass%, 0.024 mass% to 0. 08 mass%, 0.024 mass% to 0.06 mass%, 0.024 mass% to 0.04 mass%, 0.028 mass% to 0.12 mass%, 0.028 mass% to 0.08 mass%, 0.028 mass% to 0.06 mass%, 0.028 mass% to 0.04 mass%, 0.05 mass% to 0.12 mass%, 0.05 mass% to 0.08 mass% % or 0.05% to 0.06% by weight.

Furthermore, in the water absorbent resin composition of the present invention, the ratio (X/Y) of the content X (parts by mass) of the porous deodorant to the content Y (parts by mass) of the antibacterial metal-containing deodorant is 0.8 or more. From the viewpoint of more suitably exerting the effects of the present invention, the ratio (X/Y) may be 0.8 to 15.0, 0.8 to 12.0, 0.8 to 10.0, 0.8 to 8.0, 0.8 to 5.0, 1.0 to 15.0, 1.0 to 12.0, 1.0 to 10.0, 1.0 to 8.0, 1.0 to 5.0, 2.0 to 15.0, 2.0 to 12.0, 2.0 to 10.0, 2.0 to 8.0, 2.0 to 5.0, 3.0 to 15.0, 3.0 to 12.0, 3.0 to 10.0, 3.0 to 8.0, or 3.0 to 5.0.

As described above, in the water-absorbent resin composition of the present invention, the antibacterial metal-containing deodorant may be disposed on the surface of the water-absorbent polymer particles (i.e., the antibacterial metal-containing deodorant is present on the surface of the water-absorbent polymer particles). For example, by mixing the water-absorbent polymer particles and the particulate antibacterial metal-containing deodorant in a solid phase state, the antibacterial metal-containing deodorant adheres to the surface of the water-absorbent polymer particles, and the antibacterial metal-containing deodorant can be disposed on the surface of the water-absorbent polymer particles.

(Porous deodorant)
The porous deodorant is a deodorant that is porous and does not substantially contain the above-mentioned antibacterial metal. Here, the term "deodorant that does not substantially contain antibacterial metal" includes deodorants that contain antibacterial metal to an extent that they do not exhibit substantial antibacterial properties and deodorants that do not contain antibacterial metal at all, for example, a deodorant that contains less than 1 mass % of antibacterial metal.

In order to more suitably exert the effects of the present invention, the porous deodorant may contain at least one selected from the group consisting of activated carbon, silicon dioxide, and silicates, or may contain at least one of activated carbon and silicon dioxide. In particular, since an excellent adsorption effect on L-cystine can be expected, it is preferable that the porous deodorant contains at least activated carbon, and the proportion (mass %) is, for example, 80% to 100% by mass, 90% to 100% by mass, or 95% to 100% by mass.

In order to more effectively exert the effects of the present invention, the median particle size of the porous deodorant may be 1 μm to 100 μm, 1 μm to 80 μm, 1 μm to 60 μm, 10 μm to 100 μm, 10 μm to 80 μm, 10 μm to 60 μm, 15 μm to 100 μm, 15 μm to 80 μm, 15 μm to 60 μm, 20 μm to 100 μm, 20 μm to 80 μm, or 20 μm to 60 μm.

The median particle size (D50 (median size), volume basis) of the porous deodorant can be measured using a laser diffraction particle size distribution measuring device, and specifically, is a value measured by the method described in the Examples.

In order to more effectively exert the effects of the present invention, the shape of the porous deodorant is preferably crushed or cylindrical, and more preferably crushed.

From the viewpoint of more suitably exerting the effects of the present invention, the BET specific surface area of the porous deodorant is preferably 100 m ² /g to 3000 m ² /g, 100 m ² /g to 2500 m ² /g, 100 m 2 /g to 2000 m ² /g, 100 m ² /g to 1500 m ² /g, 500 m ² /g to 3000 m ² /g, 500 m ² /g to 2500 m ² /g, 500 m ² /g to 2000 m ² /g, 500 m ² /g ^{to 1500 m 2 /g, 1000 m 2 /g to 3000 m 2 /g, 1000 m 2} ^/ ^g ^to ²⁵⁰⁰ m ² /g, 1000 m ² The BET specific surface area may be from 1000 m ² /g to 2000 m 2 /g or from 1000 m ² /g to 1500 m ² /g. If the BET specific surface area of the porous deodorant is large, it can efficiently adsorb L-cystine contained in urine. On the other hand, if the BET specific surface area of the porous deodorant is too large, the strength of the porous deodorant decreases due to the individual pores becoming finer, and there is a possibility that the above-mentioned dust generation rate increases, so that the upper limit of the BET specific surface area is preferably 2000 m ² /g.

The BET specific surface area of the porous deodorant can be measured using a specific surface area measuring device, and specifically, is a value measured by the method described in the Examples.

In order to more effectively exert the effects of the present invention, it is preferable that the activated carbon used as the porous deodorant is activated carbon having a polar functional group (hydrophilic functional group) on the surface (i.e., hydrophilic activated carbon). Examples of polar functional groups include hydroxyl groups, carboxyl groups, and phenol groups. Activated carbon having polar functional groups on the surface is commercially available, for example, as activated carbon for liquid phase and activated carbon for water treatment.

Sources of activated carbon include, for example, coconut shells, infusible or carbonized organic materials, and infusible resins such as phenolic resins. Examples of organic materials include polyacrylonitrile, pitch, polyvinyl alcohol, and cellulose. Of these, it is preferable that activated carbon is derived from wood (sawdust), coconut shells, and pitch (for example, coal pitch).

From the viewpoint of more suitably exerting the effects of the present invention, the content x (mass%) of the porous deodorant in the water absorbent resin composition of the present invention is, for example, 0.05 mass% to 0.40 mass%, 0.05 mass% to 0.35 mass%, 0.05 mass% to 0.30 mass%, 0.08 mass% to 0.40 mass%, 0.08 mass% to 0.35 mass%, 0.08 mass% to 0.30 mass%, 0.10 mass% to 0.4 ... % to 0.35 mass%, 0.10 mass% to 0.30 mass%, 0.15 mass% to 0.40 mass%, 0.15 mass% to 0.35 mass%, 0.15 mass% to 0.30 mass%, 0.20 mass% to 0.40 mass%, 0.20 mass% to 0.35 mass%, 0.20 mass% to 0.30 mass%, 0.25 mass% to 0.40 mass% , 0.25% to 0.35% by weight, or 0.25% to 0.30% by weight.

The iodine adsorption amount of the porous deodorant may be, for example, 100 mg/g to 3000 mg/g, 100 mg/g to 2000 mg/g, 500 mg/g to 3000 mg/g, or 500 mg/g to 2000 mg/g.

The iodine adsorption capacity of activated carbon here is a value measured in accordance with JIS K1474:2014.

When the drying loss of a porous deodorant is low (in other words, the purity of the porous deodorant is high), it is easier to exert a deodorizing effect, but it also tends to generate dust. Taking this into consideration, the drying loss of the porous deodorant may be, for example, 0.1% to 15.0%, 0.1% to 10.0%, 0.1% to 5.0%, 0.5% to 15.0%, 0.5% to 10.0%, 0.5% to 5.0%, 1.0% to 15.0%, 1.0% to 10.0%, or 1.0% to 5.0%.

The loss on drying of the porous deodorant here is the value measured in accordance with JIS K1474:2014.

The pH of the porous deodorant may be, for example, 3.0 to 12.0, 3.0 to 11.0, 3.0 to 8.0, 3.0 to 5.0, 4.0 to 12.0, 4.0 to 11.0, 4.0 to 8.0, or 4.0 to 5.0.

The pH of the porous deodorant here is the value measured in accordance with JIS K1474:2014.

As described above, in the water-absorbent resin composition of the present invention, the porous deodorant may be disposed on the surface of the water-absorbent polymer particles (i.e., the porous deodorant may be present on the surface of the water-absorbent polymer particles). For example, by mixing the water-absorbent polymer particles and the porous deodorant in a solid phase state, the porous deodorant can be attached to the surface of the water-absorbent polymer particles, and the porous deodorant can be disposed on the surface of the water-absorbent polymer particles.

Next, the water-absorbent polymer particles (water-absorbent resin particles) contained in the water-absorbent resin composition of the present invention will be described in detail.

(Water-absorbing polymer particles)
The water-absorbent polymer particles contained in the water-absorbent resin composition of the present invention are crosslinked polymers of water-soluble ethylenically unsaturated monomers, i.e., structural units derived from water-soluble ethylenically unsaturated monomers. The polymer is composed of a crosslinked polymer having the following structure:

From the viewpoint of preventing the water-absorbent polymer particles from absorbing urine before the porous deodorant has sufficiently adsorbed L-cystine while ensuring sufficient water absorption capacity for practical use, the water-absorbent polymer particles' water-absorption speed by the Vortex method may be, for example, 10 to 80 seconds, 10 to 60 seconds, 10 to 40 seconds, 20 to 80 seconds, 20 to 60 seconds, 20 to 40 seconds, 30 to 80 seconds, 30 to 60 seconds, or 30 to 40 seconds.

The water absorption rate of water-absorbent polymer particles using the Vortex method is a value measured using the method described in the Examples.

The saline water retention capacity of the water-absorbent polymer particles may be, for example, 20 g/g to 60 g/g, 20 g/g to 55 g/g, 20 g/g to 50 g/g, 25 g/g to 60 g/g, 25 g/g to 55 g/g, 25 g/g to 50 g/g, 30 g/g to 60 g/g, 30 g/g to 55 g/g, or 30 g/g to 50 g/g.

The physiological saline water absorption capacity of the water-absorbent polymer particles under a load of 4.14 kPa may be, for example, 10 mL/g to 40 mL/g, 10 mL/g to 35 mL/g, 10 mL/g to 30 mL/g, 13 mL/g to 40 mL/g, 13 mL/g to 35 mL/g, 13 mL/g to 30 mL/g, 15 mL/g to 40 mL/g, 15 mL/g to 35 mL/g, or 15 mL/g to 30 mL/g.

The saline water retention capacity of the water-absorbent polymer particles and the saline water absorption capacity under a load of 4.14 kPa were each measured using the method described in the Examples.

The median particle size of the water-absorbing polymer particles is, for example, 150μm to 850μm, 150μm to 600μm, 150μm to 550μm, 150μm to 500μm, 150μm to 450μm, 150μm to 400μm, 200μm to 850μm, 200μm to 600μm, 200μm to 550μm, 200μm to 500μm, 200μm to 450μm, 200μm to 400μm, 240μm to 850μm, 240μm to 600μm, 240μm to 550μm, 240μm to 500μm, 240μm to 450μm, 240μm It may be up to 400 μm, 260 μm to 850 μm, 260 μm to 600 μm, 260 μm to 550 μm, 260 μm to 500 μm, 260 μm to 450 μm, 260 μm to 400 μm, 280 μm to 850 μm, 280 μm to 600 μm, 280 μm to 550 μm, 280 μm to 500 μm, 280 μm to 450 μm, 280 μm to 400 μm, 300 μm to 850 μm, 300 μm to 600 μm, 300 μm to 550 μm, 300 μm to 500 μm, 300 μm to 450 μm, or 300 μm to 400 μm.

In addition, the water-absorbing polymer particles may be in a form consisting of a single particle, or in a form consisting of an aggregate of fine particles (primary particles) (secondary particles). Examples of the shape of the primary particles include an approximately spherical shape, an irregularly crushed shape, a plate shape, etc. In the case of primary particles produced by reversed-phase suspension polymerization, examples of the shape include an approximately spherical single particle shape having a smooth surface shape such as a perfect sphere or an oval sphere.

The median particle size of the water-absorbent polymer particles can be measured using a JIS standard sieve, and specifically, is the value measured by the method described in the examples.

The typical polymerization methods used for polymerizing water-soluble ethylenically unsaturated monomers include aqueous solution polymerization, emulsion polymerization, and reversed-phase suspension polymerization. In the aqueous solution polymerization method, polymerization is carried out by heating an aqueous solution of the water-soluble ethylenically unsaturated monomer, with stirring as necessary. In the reversed-phase suspension polymerization method, polymerization is carried out by heating the water-soluble ethylenically unsaturated monomer in a hydrocarbon dispersion medium, with stirring.

One example of a method for producing water-absorbent polymer particles is described below.

A specific example of a method for producing water-absorbent polymer particles is a method for producing water-absorbent polymer particles by reverse phase suspension polymerization of a water-soluble ethylenically unsaturated monomer in a hydrocarbon dispersion medium, which includes a step of carrying out polymerization in the presence of a radical polymerization initiator and a step of surface cross-linking the hydrogel-like material obtained by polymerization in the presence of a surface cross-linking agent. In the method for producing water-absorbent polymer particles of the present invention, an internal cross-linking agent may be added to the water-soluble ethylenically unsaturated monomer as necessary to form a hydrogel-like material having an internal cross-linking structure.

<Polymerization step>
[Water-soluble ethylenically unsaturated monomer]
Examples of water-soluble ethylenically unsaturated monomers include (meth)acrylic acid (in the present specification, "acrylic" and "methacrylic" are collectively referred to as "(meth)acrylic", the same applies below) and salts thereof; 2-(meth)acrylamido-2-methylpropanesulfonic acid and salts thereof; nonionic monomers such as (meth)acrylamide, N,N-dimethyl(meth)acrylamide, 2-hydroxyethyl(meth)acrylate, N-methylol(meth)acrylamide, and polyethylene glycol mono(meth)acrylate; and amino group-containing unsaturated monomers and quaternized products thereof such as N,N-diethylaminoethyl(meth)acrylate, N,N-diethylaminopropyl(meth)acrylate, and diethylaminopropyl(meth)acrylamide. Among these water-soluble ethylenically unsaturated monomers, from the viewpoint of industrial ease of availability, etc., (meth)acrylic acid or a salt thereof, (meth)acrylamide, and N,N-dimethylacrylamide are preferred, and (meth)acrylic acid and a salt thereof are more preferred. These water-soluble ethylenically unsaturated monomers may be used alone or in combination of two or more kinds.

Among these, acrylic acid and its salts are widely used as raw materials for water-absorbent polymer particles, and these acrylic acid and/or its salts may be copolymerized with the other water-soluble ethylenically unsaturated monomers mentioned above. In this case, it is preferable that acrylic acid and/or its salts are used as the main water-soluble ethylenically unsaturated monomer in an amount of 70 to 100 mol % based on the total water-soluble ethylenically unsaturated monomers.

The water-soluble ethylenically unsaturated monomer may be dispersed in a hydrocarbon dispersion medium in the form of an aqueous solution and subjected to reversed-phase suspension polymerization. By forming the water-soluble ethylenically unsaturated monomer into an aqueous solution, the dispersion efficiency in the hydrocarbon dispersion medium can be increased. The concentration of the water-soluble ethylenically unsaturated monomer in this aqueous solution is preferably in the range of 20% by mass to the saturated concentration or less. The concentration of the water-soluble ethylenically unsaturated monomer is more preferably 55% by mass or less, even more preferably 50% by mass or less, and even more preferably 45% by mass or less. On the other hand, the concentration of the water-soluble ethylenically unsaturated monomer is more preferably 25% by mass or more, even more preferably 28% by mass or more, and even more preferably 30% by mass or more.

When the water-soluble ethylenically unsaturated monomer has an acid group, such as (meth)acrylic acid, 2-(meth)acrylamide-2-methylpropanesulfonic acid, etc., the acid group may be neutralized in advance with an alkaline neutralizing agent, if necessary. Examples of such alkaline neutralizing agents include alkali metal salts such as sodium hydroxide, sodium carbonate, sodium hydrogencarbonate, potassium hydroxide, potassium carbonate, etc.; ammonia, etc. Furthermore, these alkaline neutralizing agents may be used in the form of an aqueous solution to simplify the neutralization operation. The alkaline neutralizing agents described above may be used alone or in combination of two or more types.

The degree of neutralization of the water-soluble ethylenically unsaturated monomer by the alkaline neutralizing agent is preferably 10 to 100 mol%, more preferably 30 to 90 mol%, even more preferably 40 to 85 mol%, and even more preferably 50 to 80 mol%, in terms of the degree of neutralization of all acid groups possessed by the water-soluble ethylenically unsaturated monomer.

[Radical Polymerization Initiator]
Examples of the radical polymerization initiator added to the polymerization step include persulfates such as potassium persulfate, ammonium persulfate, and sodium persulfate, peroxides such as methyl ethyl ketone peroxide, methyl isobutyl ketone peroxide, di-t-butyl peroxide, t-butyl cumyl peroxide, t-butyl peroxyacetate, t-butyl peroxyisobutyrate, t-butyl peroxypivalate, and hydrogen peroxide, as well as 2,2'-azobis(2-amidinopropane) dihydrochloride and 2,2'-azobis[2-(N-phenylenediamine)-2-methylpropane]. Examples of the azo compounds include 2,2'-azobis[2-(N-allylamidino)propane] dihydrochloride, 2,2'-azobis{2-[1-(2-hydroxyethyl)-2-imidazolin-2-yl]propane} dihydrochloride, 2,2'-azobis{2-methyl-N-[1,1-bis(hydroxymethyl)-2-hydroxyethyl]propionamide}, 2,2'-azobis[2-methyl-N-(2-hydroxyethyl)-propionamide], and 4,4'-azobis(4-cyanovaleric acid). Among these radical polymerization initiators, potassium persulfate, ammonium persulfate, sodium persulfate, and 2,2'-azobis(2-amidinopropane) dihydrochloride are preferred from the viewpoint of easy availability and ease of handling. These radical polymerization initiators may be used alone or in combination of two or more. The radical polymerization initiator can also be used as a redox polymerization initiator in combination with a reducing agent such as sodium sulfite, sodium hydrogen sulfite, ferrous sulfate, or L-ascorbic acid.

The amount of radical polymerization initiator used is, for example, 0.00005 to 0.01 mole per mole of water-soluble ethylenically unsaturated monomer. By using such an amount, it is possible to avoid a sudden polymerization reaction and to complete the polymerization reaction within an appropriate time.

[Internal crosslinking agent]
The internal crosslinking agent may be one capable of crosslinking the polymer of the water-soluble ethylenically unsaturated monomer used, such as (poly)ethylene glycol (the term "(poly)" refers to the case where the "poly" prefix is used or not). the same applies below)], unsaturated polyesters obtained by reacting polyols such as diols and triols, such as (poly)propylene glycol, 1,4-butanediol, 1,6-hexanediol, trimethylolpropane, and (poly)glycerin, with unsaturated acids, such as (meth)acrylic acid, maleic acid, and fumaric acid; bisacrylamides such as N,N-methylenebisacrylamide; di(meth)acrylic acid esters or tri(meth)acrylic acid esters obtained by reacting polyepoxides with (meth)acrylic acid; di(meth)acrylic acid carbamyl esters obtained by reacting polyisocyanates, such as tolylene diisocyanate and hexamethylene diisocyanate, with hydroxyethyl (meth)acrylate; allylated starch, allylated cellulose, diallyl phthalate, N,N',N''-triallyl isocyanurate, divinyl Examples of the compound include a compound having two or more polymerizable unsaturated groups such as benzene; a diglycidyl compound such as (poly)ethylene glycol diglycidyl ether, (poly)propylene glycol diglycidyl ether, (poly)glycerin diglycidyl ether, and the like, and a polyglycidyl compound such as a triglycidyl compound; an epihalohydrin compound such as epichlorohydrin, epibromohydrin, and α-methylepichlorohydrin; a compound having two or more reactive functional groups such as an isocyanate compound such as 2,4-tolylene diisocyanate and hexamethylene diisocyanate; and an oxetane compound such as 3-methyl-3-oxetane methanol, 3-ethyl-3-oxetane methanol, 3-butyl-3-oxetane methanol, 3-methyl-3-oxetane ethanol, 3-ethyl-3-oxetane ethanol, and 3-butyl-3-oxetane ethanol. Among these internal cross-linking agents, it is preferable to use a polyglycidyl compound, more preferably a diglycidyl ether compound, and it is preferable to use (poly)ethylene glycol diglycidyl ether, (poly)propylene glycol diglycidyl ether, or (poly)glycerin diglycidyl ether. These internal cross-linking agents may be used alone or in combination of two or more kinds.

The amount of the internal crosslinking agent used is preferably 0.000001 to 0.02 mol, more preferably 0.00001 to 0.01 mol, even more preferably 0.00001 to 0.005 mol, and even more preferably 0.00005 to 0.002 mol per mol of the water-soluble ethylenically unsaturated monomer.

[Hydrocarbon Dispersion Medium]
Examples of the hydrocarbon dispersion medium include aliphatic hydrocarbons having 6 to 8 carbon atoms, such as n-hexane, n-heptane, 2-methylhexane, 3-methylhexane, 2,3-dimethylpentane, 3-ethylpentane, and n-octane; alicyclic hydrocarbons, such as cyclohexane, methylcyclohexane, cyclopentane, methylcyclopentane, trans-1,2-dimethylcyclopentane, cis-1,3-dimethylcyclopentane, and trans-1,3-dimethylcyclopentane; and aromatic hydrocarbons, such as benzene, toluene, and xylene. Among these hydrocarbon dispersion media, n-hexane, n-heptane, and cyclohexane are particularly preferred because they are easily available industrially, have stable quality, and are inexpensive. These hydrocarbon dispersion media may be used alone or in combination of two or more types. As an example of a mixture of hydrocarbon dispersion media, a commercially available product such as Exxol Heptane (manufactured by Exxon Mobil Corp.: contains 75 to 85% by mass of heptane and its isomers) can also be used to obtain favorable results.

The amount of the hydrocarbon dispersion medium used is preferably 100 to 1500 parts by mass, and more preferably 200 to 1400 parts by mass, per 100 parts by mass of the water-soluble ethylenically unsaturated monomer in the first stage, from the viewpoint of uniformly dispersing the water-soluble ethylenically unsaturated monomer and facilitating control of the polymerization temperature. As will be described later, reversed-phase suspension polymerization is carried out in one stage (single stage) or in multiple stages of two or more stages, and the above-mentioned first stage polymerization refers to the polymerization reaction in a single stage or in a multiple stage polymerization (the same applies below).

[Dispersion stabilizer]
(Surfactant)
In the reversed-phase suspension polymerization, a dispersion stabilizer can be used to improve the dispersion stability of the water-soluble ethylenically unsaturated monomer in the hydrocarbon dispersion medium. As the dispersion stabilizer, a surfactant can be used.

Surfactants that can be used include, for example, sucrose fatty acid esters, polyglycerin fatty acid esters, sorbitan fatty acid esters, polyoxyethylene sorbitan fatty acid esters, polyoxyethylene glycerin fatty acid esters, sorbitol fatty acid esters, polyoxyethylene sorbitol fatty acid esters, polyoxyethylene alkyl ethers, polyoxyethylene alkylphenyl ethers, polyoxyethylene castor oil, polyoxyethylene hydrogenated castor oil, alkylarylformaldehyde condensed polyoxyethylene ethers, polyoxyethylene polyoxypropylene block copolymers, polyoxyethylene polyoxypropyl alkyl ethers, polyethylene glycol fatty acid esters, alkyl glucosides, N-alkyl gluconamides, polyoxyethylene fatty acid amides, polyoxyethylene alkylamines, phosphate esters of polyoxyethylene alkyl ethers, and phosphate esters of polyoxyethylene alkyl allyl ethers. Among these surfactants, it is particularly preferable to use sorbitan fatty acid esters, polyglycerin fatty acid esters, and sucrose fatty acid esters from the standpoint of dispersion stability of the monomer. These surfactants may be used alone or in combination of two or more.

The amount of surfactant used is preferably 0.1 to 30 parts by mass, and more preferably 0.3 to 20 parts by mass, per 100 parts by mass of the first stage water-soluble ethylenically unsaturated monomer.

(Polymer-based dispersant)
As the dispersion stabilizer used in the reversed phase suspension polymerization, a polymeric dispersant may be used in combination with the above-mentioned surfactant.

Examples of polymeric dispersants include maleic anhydride modified polyethylene, maleic anhydride modified polypropylene, maleic anhydride modified ethylene-propylene copolymer, maleic anhydride modified EPDM (ethylene-propylene-diene terpolymer), maleic anhydride modified polybutadiene, maleic anhydride-ethylene copolymer, maleic anhydride-propylene copolymer, maleic anhydride-ethylene-propylene copolymer, maleic anhydride-butadiene copolymer, polyethylene, polypropylene, ethylene-propylene copolymer, oxidized polyethylene, oxidized polypropylene, oxidized ethylene-propylene copolymer, ethylene-acrylic acid copolymer, ethyl cellulose, ethylhydroxyethyl cellulose, etc. Among these polymeric dispersants, it is particularly preferable to use maleic anhydride-modified polyethylene, maleic anhydride-modified polypropylene, maleic anhydride-modified ethylene-propylene copolymer, maleic anhydride-ethylene copolymer, maleic anhydride-propylene copolymer, maleic anhydride-ethylene-propylene copolymer, polyethylene, polypropylene, ethylene-propylene copolymer, oxidized polyethylene, oxidized polypropylene, and oxidized ethylene-propylene copolymer, from the viewpoint of dispersion stability of the monomer. These polymeric dispersants may be used alone or in combination of two or more kinds.

The amount of polymeric dispersant used is preferably 0.1 to 30 parts by mass, and more preferably 0.3 to 20 parts by mass, per 100 parts by mass of the first stage water-soluble ethylenically unsaturated monomer.

[Other ingredients]
In the method for producing water-absorbing polymer particles, if desired, other components may be added to the aqueous solution containing the water-soluble ethylenically unsaturated monomer to carry out reverse phase suspension polymerization. As other components, various additives such as a thickener and a chain transfer agent can be added.

As an example, a thickener can be added to an aqueous solution containing a water-soluble ethylenically unsaturated monomer to carry out reverse suspension polymerization. By adding a thickener in this way to adjust the viscosity of the aqueous solution, it is possible to control the median particle size obtained in reverse suspension polymerization.

As thickeners, for example, hydroxyethyl cellulose, hydroxypropyl cellulose, methyl cellulose, carboxymethyl cellulose, polyacrylic acid, partially neutralized polyacrylic acid, polyethylene glycol, polyacrylamide, polyethyleneimine, dextrin, sodium alginate, polyvinyl alcohol, polyvinylpyrrolidone, polyethylene oxide, etc. can be used. Note that, if the stirring speed during polymerization is the same, the higher the viscosity of the water-soluble ethylenically unsaturated monomer aqueous solution, the larger the primary particles and/or secondary particles obtained tend to be.

[Reverse Phase Suspension Polymerization]
In carrying out the reversed-phase suspension polymerization, for example, an aqueous monomer solution containing a water-soluble ethylenically unsaturated monomer is dispersed in a hydrocarbon dispersion medium in the presence of a dispersion stabilizer. In this case, the dispersion stabilizer (surfactant or polymeric dispersant) may be added either before or after the addition of the aqueous monomer solution, so long as it is before the start of the polymerization reaction.

Among these, from the viewpoint of facilitating the reduction of the amount of hydrocarbon dispersion medium remaining in the obtained water-absorbent polymer particles, it is preferable to disperse an aqueous monomer solution in a hydrocarbon dispersion medium in which a polymeric dispersant has been dispersed, and then further disperse a surfactant before carrying out polymerization.

Such reverse phase suspension polymerization can be carried out in one stage or in multiple stages (two or more stages). From the viewpoint of increasing productivity, it is preferable to carry out the polymerization in two to three stages.

When performing reversed-phase suspension polymerization in two or more stages, after the first stage of reversed-phase suspension polymerization, the water-soluble ethylenically unsaturated monomer is added to the reaction mixture obtained in the first stage of polymerization reaction and mixed, and the second and subsequent stages of reversed-phase suspension polymerization can be performed in the same manner as the first stage. In the reversed-phase suspension polymerization in each stage from the second stage onwards, in addition to the water-soluble ethylenically unsaturated monomer, it is preferable to add a radical polymerization initiator within the molar ratio range of each component to the water-soluble ethylenically unsaturated monomer described above, based on the amount of water-soluble ethylenically unsaturated monomer added during the reversed-phase suspension polymerization in each stage from the second stage onwards, to perform reversed-phase suspension polymerization. Note that in the second and subsequent stages of polymerization, an internal crosslinking agent may also be added to the water-soluble ethylenically unsaturated monomer as necessary.

The reaction temperature for the polymerization reaction is preferably 20 to 110°C, and more preferably 40 to 90°C, from the viewpoints of promoting rapid polymerization and shortening the polymerization time, thereby improving economy, and of easily removing the heat of polymerization to allow the reaction to proceed smoothly.

<Surface cross-linking process>
Next, the water-absorbent polymer particles of the present invention are obtained by adding a surface crosslinking agent to the hydrogel having an internal crosslinked structure obtained by polymerizing a water-soluble ethylenically unsaturated monomer to crosslink (surface crosslinking reaction). This surface crosslinking reaction is preferably carried out in the presence of a surface crosslinking agent after the polymerization of the water-soluble ethylenically unsaturated monomer. In this way, by carrying out a surface crosslinking reaction on the hydrogel having an internal crosslinked structure after the polymerization, the crosslinking density near the surface of the water-absorbent polymer particles can be increased, and water-absorbent polymer particles with improved performance such as water absorption capacity under load can be obtained.

Examples of surface cross-linking agents include compounds having two or more reactive functional groups. For example, polyols such as ethylene glycol, propylene glycol, 1,4-butanediol, diethylene glycol, triethylene glycol, trimethylolpropane, glycerin, polyoxyethylene glycol, polyoxypropylene glycol, and polyglycerin; polyglycidyl compounds such as (poly)ethylene glycol diglycidyl ether, (poly)glycerin diglycidyl ether, (poly)glycerin triglycidyl ether, trimethylolpropane triglycidyl ether, (poly)propylene glycol polyglycidyl ether, and (poly)glycerol polyglycidyl ether; haloepoxy compounds such as epichlorohydrin, epibromohydrin, and α-methylepichlorohydrin; isocyanate compounds such as 2,4-tolylene diisocyanate and hexamethylene diisocyanate; 3-methyl-3-oxetane methanol, 3-ethyl-3-oxetane Oxetane compounds such as methanol, 3-butyl-3-oxetanemethanol, 3-methyl-3-oxetaneethanol, 3-ethyl-3-oxetaneethanol, and 3-butyl-3-oxetaneethanol; oxazoline compounds such as 1,2-ethylenebisoxazoline; ethylene carbonate, propylene carbonate, 4,5-dimethyl-1,3-dioxolan-2-one, 4,4-dimethyl-1,3-dioxolan-2-one, 4-ethyl 1,3-dioxolane-2-one, 4-hydroxymethyl-1,3-dioxolane-2-one, 1,3-dioxan-2-one, 4-methyl-1,3-dioxan-2-one, 4,6-dimethyl-1,3-dioxan-2-one, 1,3-dioxopan-2-one, and other carbonate compounds (e.g., alkylene carbonates); and hydroxyalkylamide compounds such as bis[N,N-di(β-hydroxyethyl)]adipamide. Among these surface crosslinking agents, polyglycidyl compounds such as (poly)ethylene glycol diglycidyl ether, (poly)glycerin diglycidyl ether, (poly)glycerin triglycidyl ether, trimethylolpropane triglycidyl ether, (poly)propylene glycol polyglycidyl ether, and (poly)glycerol polyglycidyl ether are preferred. These surface crosslinking agents may be used alone or in combination of two or more.

The amount of the surface cross-linking agent used is preferably 0.00001 to 0.01 mol, more preferably 0.00005 to 0.005 mol, and even more preferably 0.0001 to 0.002 mol, per mol of the total amount of water-soluble ethylenically unsaturated monomers used in the polymerization.

As a method for adding the surface cross-linking agent, the surface cross-linking agent may be added as it is or as an aqueous solution, but if necessary, it may be added as a solution using a hydrophilic organic solvent as a solvent. Examples of hydrophilic organic solvents include lower alcohols such as methyl alcohol, ethyl alcohol, n-propyl alcohol, isopropyl alcohol, etc.; ketones such as acetone and methyl ethyl ketone; ethers such as diethyl ether, dioxane, tetrahydrofuran, etc.; amides such as N,N-dimethylformamide; sulfoxides such as dimethyl sulfoxide, etc. These hydrophilic organic solvents may be used alone, in combination of two or more types, or as a mixed solvent with water.

The timing of adding the surface cross-linking agent may be after the polymerization reaction of the water-soluble ethylenically unsaturated monomer has been almost completely completed. It is preferable to add the agent in the presence of moisture in the range of 1 to 400 parts by mass, more preferably in the range of 5 to 200 parts by mass, even more preferably in the range of 10 to 100 parts by mass, and even more preferably in the range of 20 to 60 parts by mass, relative to 100 parts by mass of the water-soluble ethylenically unsaturated monomer. The amount of moisture means the total amount of moisture contained in the reaction system and the moisture used as necessary when adding the surface cross-linking agent.

The reaction temperature in the surface cross-linking reaction is preferably 50 to 250°C, more preferably 60 to 180°C, even more preferably 60 to 140°C, and even more preferably 70 to 120°C. The reaction time in the surface cross-linking reaction is preferably 1 to 300 minutes, and more preferably 5 to 200 minutes.

<Drying process>
After the above-mentioned reversed-phase suspension polymerization, a drying step may be included in which water, the hydrocarbon dispersion medium, and the like are removed by distillation by adding energy such as heat from the outside. When dehydrating the hydrogel after the reversed-phase suspension polymerization, the system in which the hydrogel is dispersed in the hydrocarbon dispersion medium is heated, and the water and the hydrocarbon dispersion medium are once distilled out of the system by azeotropic distillation. At this time, if only the distilled hydrocarbon dispersion medium is returned to the system, continuous azeotropic distillation is possible. In that case, the temperature in the system during drying is maintained below the azeotropic temperature with the hydrocarbon dispersion medium, which is preferable from the viewpoint of the resin being less likely to deteriorate. Subsequently, the water and the hydrocarbon dispersion medium are distilled off to obtain water-absorbing polymer particles. By controlling the processing conditions of the drying step after this polymerization to adjust the amount of dehydration, it is possible to control the various properties of the obtained water-absorbing polymer particles.

In the drying step, the drying process by distillation may be performed under normal pressure or under reduced pressure. From the viewpoint of increasing the drying efficiency, it may also be performed under a stream of nitrogen or the like. When the drying process is performed under normal pressure, the drying temperature is preferably 70 to 250°C, more preferably 80 to 180°C, even more preferably 80 to 140°C, and even more preferably 90 to 130°C. When the drying process is performed under reduced pressure, the drying temperature is preferably 40 to 160°C, and more preferably 50 to 110°C.

In addition, when a surface cross-linking step using a surface cross-linking agent is carried out after polymerization of monomers by reversed-phase suspension polymerization, the above-mentioned drying step by distillation is carried out after the surface cross-linking step is completed. Alternatively, the surface cross-linking step and the drying step may be carried out simultaneously.

The water-absorbent resin composition of the present invention may contain additives according to the purpose. Examples of such additives include inorganic powders, surfactants, oxidizing agents, reducing agents, metal chelating agents, radical chain inhibitors, antioxidants, antibacterial agents, and the like. For example, the fluidity of the water-absorbent resin composition can be further improved by adding 0.05 to 5 parts by mass of amorphous silica as inorganic powder per 100 parts by mass of water-absorbent polymer particles. The additives are preferably hydrophilic or water-soluble.

In the water-absorbent resin composition of the present invention, the content of water-absorbent polymer particles (excluding additives) is preferably 70% by mass or more, more preferably 80% by mass or more, and even more preferably 90% by mass or more.

The water-absorbent resin composition of the present invention can be produced, for example, by mixing water-absorbent polymer particles, a particulate antibacterial metal-containing deodorant, and a porous deodorant in a solid phase.

2. Absorbent, absorbent article The water-absorbing resin composition of the present invention is preferably used for absorbent articles such as sanitary napkins and paper diapers. The absorbent article of the present invention is an absorbent article containing an antibacterial metal-containing deodorant, a porous deodorant, and water-absorbing polymer particles, and the ratio (X/Y) of the content X (parts by mass) of the porous deodorant to the content Y (parts by mass) of the antibacterial metal-containing deodorant is 0.8 or more, and the sum (x+y) of the content x (% by mass) of the porous deodorant and the content y (% by mass) of the antibacterial metal-containing deodorant based on the total amount of the antibacterial metal-containing deodorant, the porous deodorant, and the water-absorbing polymer particles is 0.10% by mass or more. The more detailed configuration of the absorbent article of the present invention can be set in the same manner as the above-mentioned water-absorbing resin composition.

Here, the absorbent using the water-absorbing resin composition of the present invention includes the particulate water-absorbing resin composition of the present invention. The absorbent may further include hydrophilic fibers. Examples of the absorbent configuration include a sheet-like structure in which water-absorbing polymer particles are fixed on a nonwoven fabric or between multiple nonwoven fabrics, a mixed dispersion obtained by mixing the particulate water-absorbing resin composition and hydrophilic fibers to a uniform composition, a sandwich structure in which the particulate water-absorbing resin composition is sandwiched between layered hydrophilic fibers, and a structure in which the particulate water-absorbing resin composition and hydrophilic fibers are wrapped in tissue. The absorbent may also contain other components, such as adhesive binders such as heat-fusible synthetic fibers, hot melt adhesives, and adhesive emulsions, in order to improve the shape retention of the absorbent.

The content of the water-absorbent resin composition in the absorbent is preferably 5 to 100% by mass, more preferably 10 to 95% by mass, even more preferably 20 to 90% by mass, and even more preferably 30 to 80% by mass.

Hydrophilic fibers include cellulose fibers such as cotton-like pulp obtained from wood, mechanical pulp, chemical pulp, and semi-chemical pulp, artificial cellulose fibers such as rayon and acetate, and fibers made of synthetic resins such as polyamide, polyester, and polyolefin that have been hydrophilically treated. The average fiber length of hydrophilic fibers is usually 0.1 to 10 mm, or may be 0.5 to 5 mm.

The absorbent article of the present invention can be produced by holding an absorbent using the particulate water-absorbent resin composition of the present invention between a liquid-permeable sheet (top sheet) through which liquid can pass and a liquid-impermeable sheet (back sheet) through which liquid cannot pass. The liquid-permeable sheet is placed on the side that comes into contact with the body, and the liquid-impermeable sheet is placed on the opposite side that comes into contact with the body.

Liquid-permeable sheets include nonwoven fabrics such as air-through, spunbond, chemical bond, and needle-punch types made of fibers such as polyethylene, polypropylene, and polyester, as well as porous synthetic resin sheets. Liquid-impermeable sheets include synthetic resin films made of resins such as polyethylene, polypropylene, and polyvinyl chloride.

3. Supplementary Notes This specification includes at least the inventions set forth in (1) to (14) below.
(1)
A water-absorbent resin composition comprising an antibacterial metal-containing deodorant, a porous deodorant, and water-absorbent polymer particles, wherein a ratio (X/Y) of a content X (parts by mass) of the porous deodorant to a content Y (parts by mass) of the antibacterial metal-containing deodorant is 0.8 or more, and a sum (x+y) of a content x (% by mass) of the porous deodorant and a content y (% by mass) of the antibacterial metal-containing deodorant in the entire water-absorbent resin composition is 0.10% by mass or more.
(2)
The sum (x+y) of the content x (mass%) and the content y (mass%) is 0.10 mass% to 0.80 mass%, 0.10 mass% to 0.60 mass%, 0.10 mass% to 0.50 mass%, 0.10 mass% to 0.40 mass%, 0.10 mass% to 0.35 mass%, 0.10 mass% to 0.30 mass%, 0.13 mass% to 0.80 mass% %, 0.13% by mass to 0.60% by mass, 0.13% by mass % to 0.50 mass%, 0.13 mass% to 0.40 mass%, 0.13 mass% to 0.35 mass%, 0.13 mass% to 0.30 mass%, 0.18 mass% to 0.80 mass%, 0.18 mass% to 0.60 mass%, 0.18 mass% to 0.50 mass%, 0.18 mass% to 0.40 mass%, 0.18 mass% to 0.35 mass%, 0.18% by mass to 0.30% by mass, 0.20% by mass to 0.8 0 mass%, 0.20 mass% to 0.60 mass%, 0.20 mass% to 0.50 mass%, 0.20 mass% to 0.40 mass%, 0.20 mass% to 0.35 mass%, 0.20 mass% to 0.30 mass%, 0.25 mass% to 0.80 mass%, 0.25 mass% to 0.60 mass%, 0.25 mass% to 0.50 mass%, 0.25 Mass% to 0.40 mass%, 0.25 mass% to 0.35 mass%, 0.25 mass% to 0.30 mass%, 0.30 mass% to 0.80 mass%, 0.30 mass% to 0.60 mass%, 0.30 mass% to 0.50 mass%, 0.30 mass% to 0.40 mass%, 0.35 mass% to 0.80 mass%, 0.35 mass% to 0.60 mass%, 0.35 mass% to 0.50 mass% or 0.35 mass% to 0. The water absorbent resin composition according to (1) above, which has a content of 40% by mass.
(3)
The water absorbent resin composition according to the above (1) or (2), wherein the antibacterial metal contained in the antibacterial metal-containing deodorant comprises at least one selected from the group consisting of silver, copper, zinc, bismuth, cobalt, aluminum and nickel.
(4)
The water absorbent resin composition according to any one of the above (1) to (3), wherein the antibacterial metal-containing deodorant comprises at least one selected from the group consisting of silver powder, silver chloride (I), silver oxide (I), and a substance carrying at least one metal ion selected from the group consisting of silver ion and zinc ion.
(5)
The water-absorbing resin composition according to any one of the above (1) to (4), wherein the porous deodorant comprises at least one selected from the group consisting of activated carbon, silicon dioxide, and silicates.
(6)
The water absorbent resin composition according to any one of (1) to (5), wherein the antibacterial metal-containing deodorant has a median particle diameter of 0.1 μm to 100 μm, and the porous deodorant has a median particle diameter of 1 μm to 100 μm.
(7)
The water absorbent resin composition according to any one of (1) to (6) above, wherein the ratio (X/Y) of the content X (parts by mass) of the porous deodorant to the content Y (parts by mass) of the antibacterial metal-containing deodorant is 0.8 to 15.0, 0.8 to 12.0, 0.8 to 10.0, 0.8 to 8.0, 0.8 to 5.0, 1.0 to 15.0, 1.0 to 12.0, 1.0 to 10.0, 1.0 to 8.0, 1.0 to 5.0, 2.0 to 15.0, 2.0 to 12.0, 2.0 to 10.0, 2.0 to 8.0, 2.0 to 5.0, 3.0 to 15.0, 3.0 to 12.0, 3.0 to 10.0, 3.0 to 8.0, or 3.0 to 5.0.
(8)
The water-absorbing polymer particles have a water-absorbing speed measured by a Vortex method of 10 seconds to 80 seconds, 10 seconds to 60 seconds, 10 seconds to 40 seconds, 20 seconds to 80 seconds, 20 seconds to 60 seconds, 20 seconds to 40 seconds, 30 seconds to 80 seconds, 30 seconds to 60 seconds, or 30 seconds to 40 seconds. The water-absorbing resin composition according to any one of (1) to (7) above.
(9)
An absorbent article comprising an antibacterial metal-containing deodorant, a porous deodorant, and water-absorbent polymer particles, wherein a ratio (X/Y) of a content X (parts by mass) of the porous deodorant to a content Y (parts by mass) of the antibacterial metal-containing deodorant is 0.8 or more, and a sum (x+y) of a content x (% by mass) of the porous deodorant and a content y (% by mass) of the antibacterial metal-containing deodorant based on a total amount of the antibacterial metal-containing deodorant, the porous deodorant, and the water-absorbent polymer particles is 0.10% by mass or more.
(10)
The sum (x+y) of the content x (mass%) and the content y (mass%) is 0.10 mass% to 0.50 mass%, 0.10 mass% to 0.40 mass%, 0.10 mass% to 0.35 mass%, 0.10 mass% to 0.30 mass%, 0.18 mass% to 0.50 mass%, 0.18 mass% to 0.40 mass%, 0.18 mass% to 0.35 mass% %, 0.18% by mass to 0.30% by mass, 0.30% by mass to 0.50% by mass, or 0.30% by mass to 0.40% by mass.
(11)
The absorbent article according to (9) or (10) above, wherein the ratio (X/Y) of the content X (parts by mass) of the porous deodorant to the content Y (parts by mass) of the antibacterial metal-containing deodorant is 0.8 to 15.0, 0.8 to 12.0, 0.8 to 10.0, 0.8 to 8.0, 0.8 to 5.0, 1.0 to 15.0, 1.0 to 12.0, 1.0 to 10.0, 1.0 to 8.0, 1.0 to 5.0, 2.0 to 15.0, 2.0 to 12.0, 2.0 to 10.0, 2.0 to 8.0, 2.0 to 5.0, 3.0 to 15.0, 3.0 to 12.0, 3.0 to 10.0, 3.0 to 8.0, or 3.0 to 5.0.
(12)
The absorbent article according to any one of (9) to (11) above, wherein the antibacterial metal-containing deodorant comprises at least one selected from the group consisting of silver powder, silver chloride (I), silver oxide (I), and a substance carrying at least one metal ion selected from the group consisting of silver ions and zinc ions.
(13)
The absorbent article according to any one of the above (9) to (12), wherein the porous deodorant comprises at least one selected from the group consisting of activated carbon, silicon dioxide, and silicates.
(14)
The water absorption speed of the water-absorbent polymer particles by the Vortex method is 10 seconds to 80 seconds, 10 seconds to 60 seconds, 10 seconds to 40 seconds, 20 seconds to 80 seconds, 20 seconds to 60 seconds, 20 seconds to 40 seconds, 30 seconds to 80 seconds, 30 seconds to 60 seconds, or 30 seconds to 40 seconds. The absorbent article according to any one of (9) to (13).

The present invention will be explained in detail below with reference to examples and comparative examples. However, the present invention is not limited to the examples.

The following water-absorbent polymer particles, activated carbon as a porous deodorant, and water-absorbent resin compositions obtained in the examples and comparative examples were evaluated by the following various tests. Unless otherwise specified, measurements were performed in an environment with a temperature of 25±2°C and a humidity of 50±10%.

[Production Example of Water-Absorbent Polymer Particles]
A round-bottomed cylindrical separable flask with an inner diameter of 11 cm and a volume of 2 L was prepared, which was equipped with a reflux condenser, a dropping funnel, a nitrogen gas inlet tube, and a stirring blade having two stages of four inclined paddle blades with a blade diameter of 5 cm. 293 g of n-heptane was added to this flask as a hydrocarbon dispersion medium, and 0.736 g of maleic anhydride-modified ethylene-propylene copolymer (Mitsui Chemicals, Inc., Hiwax 1105A) was added as a polymeric dispersant. The mixture was heated to 80°C with stirring to dissolve the dispersant, and then cooled to 50°C. Meanwhile, 92.0 g (1.03 mol) of an 80.5 mass% aqueous acrylic acid solution was placed in a 300 mL beaker as a water-soluble ethylenically unsaturated monomer, and while cooling with ice water, 147.7 g of a 20.9 mass% aqueous sodium hydroxide solution was added dropwise to carry out 75 mol% neutralization, and then 0.092 g of hydroxylethyl cellulose (Sumitomo Seika Chemicals Co., Ltd., HEC AW-15F) as a thickener, 0.0736 g (0.272 mmol) of potassium persulfate as a water-soluble radical polymerization agent, and 0.010 g (0.057 mmol) of ethylene glycol diglycidyl ether as an internal crosslinking agent were added and dissolved to prepare a first-stage aqueous liquid. The aqueous liquid prepared above was added to a separable flask and stirred for 10 minutes. A surfactant solution prepared by heating and dissolving 0.736 g of sucrose stearate with an HLB of 3 (Ryoto Sugar Ester S-370, Mitsubishi Chemical Foods Corporation) in 6.62 g of n-heptane as a surfactant in a 20 mL vial was then added. The system was thoroughly purged with nitrogen while stirring at a stirrer speed of 550 rpm, and the flask was immersed in a water bath at 70° C. to raise the temperature, and polymerization was carried out for 60 minutes to obtain a first-stage polymerization slurry.

Meanwhile, 128.8 g (1.43 mol) of 80.5% by mass acrylic acid aqueous solution was placed in a separate 500 mL beaker as the water-soluble ethylenically unsaturated monomer, and while cooling with ice water, 159.0 g of 27% by mass sodium hydroxide aqueous solution was added dropwise to neutralize 75 mol%, after which 0.103 g (0.381 mmol) of potassium persulfate as a water-soluble radical polymerization initiator and 0.0117 g (0.067 mmol) of ethylene glycol diglycidyl ether as an internal crosslinking agent were added and dissolved to prepare the second stage aqueous liquid.

　The contents of the separable flask system were cooled to 25°C while stirring at a stirrer speed of 1000 rpm, and then the entire amount of the second-stage aqueous liquid was added to the first-stage polymerization slurry liquid, and the system was replaced with nitrogen for 30 minutes. After that, the flask was again immersed in a 70°C water bath to raise the temperature, and the polymerization reaction was carried out for 60 minutes to obtain a hydrous gel polymer.

Then, the flask was immersed in an oil bath set at 125°C, and 259.9 g of water was extracted from the system by azeotropic distillation of n-heptane and water while refluxing n-heptane. Then, 4.42 g (0.507 mmol) of a 2% by mass aqueous solution of ethylene glycol diglycidyl ether was added to the flask as a surface crosslinking agent, and the flask was kept at 83°C for 2 hours.

Then, the n-heptane was evaporated at 125°C to dry the particles, and the particles were passed through a sieve with 850 μm mesh to obtain 226.1 g of water-absorbent polymer particles. The saline water retention capacity of the water-absorbent polymer particles was 42 g/g, the water absorption speed was 39 seconds, the median particle size was 360 μm, and the saline water absorption capacity under a load of 4.14 kPa was 20 ml/g.

[Evaluation of Water-Absorbent Polymer Particles]
<Saline water retention capacity>
A cotton bag (membrane broad 60, 100 mm wide x 200 mm long) containing 2.0 g of water-absorbent polymer particles was placed in a 500 ml beaker. 500 g of 0.9% by mass sodium chloride aqueous solution (physiological saline) was poured into the cotton bag containing the water-absorbent polymer particles at once so as not to cause the bag to become lumpy, the top of the cotton bag was tied with a rubber band, and the bag was left to stand for 30 minutes to swell the water-absorbent polymer particles. After 30 minutes, the cotton bag was dehydrated for 1 minute using a dehydrator (Kokusan Co., Ltd., product number: H-122) set to a centrifugal force of 167 G, and the mass Wd (g) of the cotton bag containing the swollen gel after dehydration was measured. The same operation was performed without adding the water-absorbent polymer particles, the empty mass We (g) of the cotton bag when wet was measured, and the physiological saline water retention was calculated from the following formula.
Saline water retention capacity (g/g) = [Wd-We]/2.0

<Measurement of Water Absorption Rate by Vortex Method>
50±0.1 g of physiological saline adjusted to a temperature of 25±0.2°C in a thermostatic water bath was weighed into a 100 ml beaker and stirred with a magnetic stir bar (8 mmφ×30 mm without ring) to generate a vortex at a rotation speed of 600 rpm. 2.0±0.002 g of water-absorbent polymer particles were added to the physiological saline at once, and the time (seconds) from the addition of the water-absorbent polymer particles to the time when the vortex on the liquid surface converged was measured, and this time was taken as the water absorption speed of the water-absorbent polymer particles. This water absorption speed is also expressed as the Vortex method or vortex time.

<Median particle size (particle size distribution) of water-absorbing polymer particles>
50 g of water-absorbing polymer particles were used for measuring the median particle size (particle size distribution). JIS standard sieves were combined in the following order from the top: a sieve with an opening of 850 μm, a sieve with an opening of 500 μm, a sieve with an opening of 425 μm, a sieve with an opening of 300 μm, a sieve with an opening of 250 μm, a sieve with an opening of 180 μm, a sieve with an opening of 150 μm, and a tray. Water-absorbing polymer particles were placed on the top sieve of the combination, and classified by shaking for 20 minutes using a rotor shaker. After classification, the mass of the water-absorbing polymer particles remaining on each sieve was calculated as a mass percentage relative to the total amount to obtain the particle size distribution. The particle size distribution was calculated by accumulating the particles remaining on the sieve in order of particle size from the largest to the smallest, and the relationship between the sieve opening and the accumulated value of the mass percentage of the water-absorbent polymer particles remaining on the sieve was plotted on a logarithmic probability paper. The particle size corresponding to an accumulated mass percentage of 50% by mass was determined as the median particle size by connecting the plots on the probability paper with a straight line.

<Saline absorption amount under a load of 4.14 kPa>
The physiological saline water absorption amount under a load of 4.14 kPa (water absorption amount under load) was measured using a measuring device shown in FIG. 1. The measurement was performed twice for one type of water-absorbent polymer particle, and the average value was calculated. The measuring device includes a burette part 1, a clamp 3, a conduit 5, a stand 11, a measurement table 13, and a measurement part 4 placed on the measurement table 13. The burette part 1 has a burette tube 21 with a scale, a rubber plug 23 that seals the opening at the top of the burette tube 21, a cock 22 connected to the tip of the bottom of the burette tube 21, and an air introduction tube 25 and a cock 24 connected to the bottom of the burette tube 21. The burette part 1 is fixed with a clamp 3. The flat measurement table 13 has a through hole 13a with a diameter of 2 mm formed in its center, and is supported by a height-variable stand 11. The through hole 13a of the measuring table 13 and the cock 22 of the burette part 1 are connected by a conduit 5. The inside diameter of the conduit 5 is 6 mm.

The measuring section 4 has a Plexiglas cylinder 31, a polyamide mesh 32 attached to one opening of the cylinder 31, and a weight 33 that can move up and down inside the cylinder 31. The cylinder 31 is placed on the measuring table 13 via the polyamide mesh 32. The inner diameter of the cylinder 31 is 20 mm. The opening of the polyamide mesh 32 is 75 μm (200 mesh). The weight 33 has a diameter of 19 mm and a mass of 119.6 g, and can apply a load of 4.14 kPa (0.6 psi) to the water-absorbent polymer particles 10a that are uniformly arranged on the polyamide mesh 32 as described below.

First, the stopcocks 22 and 24 of the burette part 1 were closed, and 0.9% by mass physiological saline adjusted to 25°C was poured into the burette tube 21 through the opening at the top of the burette tube 21. Next, the top opening of the burette tube 21 was sealed with a rubber stopper 23, and then the stopcocks 22 and 24 were opened. The inside of the conduit 5 was filled with 0.9% by mass saline 50 to prevent air bubbles from entering. The height of the measurement table 13 was adjusted so that the height of the water surface of the 0.9% by mass saline solution 50 that reached the through hole 13a was the same as the height of the upper surface of the measurement table 13. After the adjustment, the height of the water surface of the 0.9% by mass saline solution 50 in the burette tube 21 was read on the scale of the burette tube 21, and this position was set as the zero point (the reading at 0 seconds).

In the measurement section 4, 0.10 g of water-absorbent polymer particles 10a were uniformly arranged on the polyamide mesh 32 in the cylinder 31, a weight 33 was placed on the water-absorbent polymer particles 10a, and the cylinder 31 was installed so that its center coincided with the conduit port at the center of the measurement table 13. The amount of reduction in the saline solution in the burette tube 21 (i.e., the amount of saline solution absorbed by the water-absorbent polymer particles 10a) Wc (ml) 60 minutes after the water-absorbent polymer particles 10a started to absorb the saline solution from the conduit 5 was read, and the saline solution absorption capacity of the water-absorbent polymer particles 10a under a load of 4.14 kPa was calculated by the following formula.
4. Absorption capacity of physiological saline solution under a load of 14 kPa (ml/g)=Wc (ml)/mass of water-absorbent polymer particles (g)

[Preparation of activated carbon]
Activated carbon (Carborafine-6, manufactured by Osaka Gas Chemicals Co., Ltd.) having a BET specific surface area of 1345 m ² /g, a median particle size of 46 μm, an ignition residue of 0.4%, a loss on drying of 3.2%, a pH of 4.9 and a crushed shape was prepared.

[Evaluation of activated carbon]
<Median particle size of activated carbon (laser diffraction)>
The median particle size (D50 (median size), volume basis) of the activated carbon used was measured with a laser diffraction particle size distribution measuring device (Shimadzu Corporation, SALD2300).

<BET specific surface area of activated carbon>
0.1 g of the activated carbon to be measured was dried under degassing conditions of heating and vacuum exhaust at 60° C. for 24 hours using a pretreatment device (MicrotracBel, BELPREP VAC II). Thereafter, an adsorption isotherm was measured at a temperature of 77 K using a method using nitrogen gas as the adsorption gas using a specific surface area measurement device (MicrotracBel, BELSORP MINI II), and the specific surface area was calculated from a multipoint BET plot, which was defined as the BET specific surface area of the activated carbon.

[Production of water-absorbent resin composition]
Example 1
To 100 parts by mass of the water-absorbent polymer particles obtained in the manufacturing example, 0.03 parts by mass of silver-zinc zeolite (Zeomic HD10N, manufactured by Sinanen Zeomic Co., Ltd., median particle size 2.1 μm, BET specific surface area 653 ^m2 /g) was added as an antibacterial metal-containing deodorant, and 0.10 parts by mass of the above-mentioned activated carbon was added as a porous deodorant, and these were mixed by rotating them for 30 minutes under conditions of a rotation speed of 50 rpm and a revolution speed of 50 rpm using a cross rotary mixer manufactured by Meiwa Kogyo Co., Ltd., to obtain a water-absorbent resin composition.
The median particle size and BET specific surface area of the antibacterial metal-containing deodorant were measured by the same measuring method as that for the activated carbon described above.

Example 2
A water-absorbent resin composition was obtained in the same manner as in Example 1, except that the amount of activated carbon added was changed to 0.30 parts by mass.

Example 3
A water-absorbent resin composition was obtained in the same manner as in Example 1, except that the amount of silver-zinc zeolite added was changed to 0.10 parts by mass.

Example 4
A water-absorbent resin composition was obtained in the same manner as in Example 1, except that the amount of silver-zinc zeolite added was 0.10 parts by mass and the amount of activated carbon added was 0.30 parts by mass.

Example 5
A water-absorbent resin composition was obtained in the same manner as in Example 1, except that the amount of silver-zinc zeolite added was 0.06 parts by mass and the amount of activated carbon added was 0.20 parts by mass.

<Comparative Example 1>
A water-absorbent resin composition was obtained in the same manner as in Example 1, except that the amount of silver-zinc zeolite added was 0.015 parts by mass and the amount of activated carbon added was 0.05 parts by mass.

<Comparative Example 2>
A water-absorbent resin composition was obtained in the same manner as in Example 1, except that the amount of silver-zinc zeolite added was 0.06 parts by mass and the amount of activated carbon added was 0.03 parts by mass.

<Comparative Example 3>
A water-absorbent resin composition was obtained in the same manner as in Example 1, except that the amount of silver-zinc zeolite added was 0.015 parts by mass and no activated carbon was added.

<Comparative Example 4>
A water-absorbent resin composition was obtained in the same manner as in Example 1, except that the amount of silver-zinc zeolite added was 0.03 parts by mass and no activated carbon was added.

<Comparative Example 5>
A water-absorbent resin composition was obtained in the same manner as in Example 1, except that the amount of silver-zinc zeolite added was 0.06 parts by mass and no activated carbon was added.

<Comparative Example 6>
A water-absorbent resin composition was obtained in the same manner as in Example 1, except that the amount of silver-zinc zeolite added was 0.10 parts by mass and no activated carbon was added.

<Comparative Example 7>
A water-absorbent resin composition was obtained in the same manner as in Example 1, except that the silver-zinc zeolite was not added and the amount of activated carbon added was 0.03 parts by mass.

<Comparative Example 8>
A water-absorbent resin composition was obtained in the same manner as in Example 1, except that the silver-zinc zeolite was not added and the amount of activated carbon added was 0.05 parts by mass.

<Comparative Example 9>
A water-absorbent resin composition was obtained in the same manner as in Example 1, except that the silver-zinc zeolite was not added and the amount of activated carbon added was 0.10 parts by mass.

<Comparative Example 10>
A water-absorbent resin composition was obtained in the same manner as in Example 1, except that the silver-zinc zeolite was not added and the amount of activated carbon added was 0.20 parts by mass.

<Comparative Example 11>
A water-absorbent resin composition was obtained in the same manner as in Example 1, except that the silver-zinc zeolite was not added and the amount of activated carbon added was 0.30 parts by mass.

<Reference Example 1>
The water-absorbing polymer particles obtained in the Production Example were used as Reference Example 1.

[Evaluation of Water-Absorbent Resin Composition]
<Ammonia generation suppression test>
Artificial urine was prepared by dissolving 25.0 g of urea, 9.0 g of sodium chloride, 0.6 g of magnesium sulfate heptahydrate, 0.7 g of calcium lactate, 4.0 g of potassium sulfate, 2.5 g of ammonium sulfate, and 0.1 g of L-cystine in 958.1 g of distilled water. Urease (MERCK, 50% glycerin solution derived from jack bean, 1000 U/mL) was diluted with distilled water to 2 U/mL to prepare a urease solution. 0.500 g of the water-absorbing resin composition or water-absorbing polymer particles was placed in a sterile petri dish (diameter 88 mm, height 17 mm), and a test liquid (prepared by mixing 30.0 mL of the above-mentioned artificial urine and 1.0 mL of the urease solution) was added to swell the sample. After adding the test liquid, the sample was sealed in a 2L polyester sampling bag (GL Science Co., Ltd., PAAAK2), the air in the bag was removed, and 900mL of dry air was added to the bag instead. The sample was then stored at 35°C, and after 24 hours, the ammonia concentration was measured using a gas detector (Gastec Co., Ltd., Ammonia 3L, 3La, 3M). The measured value and the deodorization rate calculated from the following formula 1 are shown in Table 1.
Formula 1: Deodorization rate (%) = [(ammonia concentration in Reference Example 1 - ammonia concentration in Examples or Comparative Examples) / ammonia concentration in Reference Example 1] x 100

<Dust generation test>
A glass suction bottle with a capacity of 500 mL was prepared. A SUS hopper (upper inner diameter 88 mm x foot inner diameter 18 mm) was set so that the height from the bottom of the suction bottle to the outlet of the hopper was 180 mm, and the suction port of the suction bottle and a dust generation meter (manufactured by Shibata Scientific Co., Ltd., digital indicator LD-5R type) were connected with a glass tube (inner diameter 7.7 mm x length 300 mm). 3.0 g ± 0.1 g of a water-absorbent resin composition was put into the hopper as a sample, and the start button of the dust generation meter was pressed at the same time as the damper of the hopper was pulled out, and the counter after 1 minute (counter (A) for the sample) was recorded. A blank test was performed before measuring the sample to determine the counter (B) during the blank test, and the dust generation rate was calculated by the following formula.
Dust generation level (cpm) = AB
In the formula, A represents the counter (cpm) for the sample, and B represents the counter (cpm) for the blank test.
The above-mentioned dust generation rate was measured three times for each type of sample, and the average value was used as the dust generation rate of the sample. The results are shown in Table 2.

As shown in Table 1, the deodorizing rate of Comparative Example 9, in which the content x of the porous deodorant in the water absorbent resin composition is 0.10 mass%, is 20%, and the deodorizing rate of Comparative Example 6, in which the content y of the antibacterial metal-containing deodorant in the water absorbent resin composition is 0.10 mass%, is 60%. In contrast, the deodorizing rate of Example 3, in which the content x of the porous deodorant in the water absorbent resin composition is 0.10 mass% and the content y of the antibacterial metal-containing deodorant is 0.10 mass%, is extremely high at 98%, and it can be seen that a synergistic effect between the antibacterial metal-containing deodorant and the porous deodorant is exerted, which cannot be predicted from the results of Comparative Examples 6 and 9 (the sum of the deodorizing rates of Comparative Examples 6 and 9 is 80%). The synergistic effect of the deodorizing rate of the water-absorbent resin composition shown in Table 2 is the deodorizing rate of the example divided by the sum of the deodorizing rates of the comparative examples in which each deodorant was used alone. For example, the synergistic effect of Example 3 is a value calculated by deodorizing rate of Example 3 (98) / (deodorizing rate of Comparative Example 9 (20) + deodorizing rate of Comparative Example 6 (60)). If the standard value exceeds 1.00, it can be said that a synergistic effect is being exerted.

The results shown in Table 2 also show that, among the water-absorbent resin compositions of Examples 1 to 5, Examples 1, 2, and 5 are excellent in terms of dust generation, with Example 1 being particularly excellent.

Reference Signs List 1 burette part 3 clamp 4 measurement part 5 conduit 10a water-absorbent polymer particles 11 stand 13 measurement stand 13a through hole 21 burette tube 22 cock 23 rubber stopper 24 cock 25 air introduction tube 31 cylinder 32 polyamide mesh 33 weight 50 saline solution

Claims

A water-absorbing resin composition comprising an antibacterial metal-containing deodorant, a porous deodorant, and water-absorbing polymer particles,
the ratio (X/Y) of the content X (parts by mass) of the porous deodorant to the content Y (parts by mass) of the antibacterial metal-containing deodorant is 0.8 or more;
A water absorbent resin composition, wherein the sum (x+y) of a content rate x (mass%) of the porous deodorant and a content rate y (mass%) of the antibacterial metal-containing deodorant in the entire water absorbent resin composition is 0.10 mass% or more.
The water-absorbent resin composition according to claim 1, wherein the sum (x+y) of the content x (mass%) and the content y (mass%) is 0.50 mass% or less.
The water-absorbent resin composition according to claim 1 or 2, wherein the antibacterial metal contained in the antibacterial metal-containing deodorant contains at least one selected from the group consisting of silver, copper, zinc, bismuth, cobalt, aluminum, and nickel.
The water-absorbent resin composition according to claim 1 or 2, wherein the antibacterial metal-containing deodorant contains at least one selected from the group consisting of silver powder, silver chloride (I), silver oxide (I), and a substance carrying at least one of silver ions and zinc ions.
The water-absorbent resin composition according to claim 1 or 2, wherein the porous deodorant contains at least one selected from the group consisting of activated carbon, silicon dioxide, and silicates.
The water-absorbent resin composition according to claim 1 or 2, wherein the antibacterial metal-containing deodorant has a median particle diameter of 0.1 μm to 100 μm, and the porous deodorant has a median particle diameter of 1 μm to 100 μm.
An absorbent article comprising an antibacterial metal-containing deodorant, a porous deodorant, and water-absorbing polymer particles,
the ratio (X/Y) of the content X (parts by mass) of the porous deodorant to the content Y (parts by mass) of the antibacterial metal-containing deodorant is 0.8 or more;
The sum (x+y) of the content x (mass%) of the porous deodorant and the content y (mass%) of the antibacterial metal-containing deodorant based on the total amount of the antibacterial metal-containing deodorant, the porous deodorant, and the water-absorbent polymer particles is 0.10 mass% or more.