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WO2025183162A1 - Absorbant d'eau et procédé de fabrication d'absorbant d'eau - Google Patents

Absorbant d'eau et procédé de fabrication d'absorbant d'eau

Info

Publication number
WO2025183162A1
WO2025183162A1 PCT/JP2025/007127 JP2025007127W WO2025183162A1 WO 2025183162 A1 WO2025183162 A1 WO 2025183162A1 JP 2025007127 W JP2025007127 W JP 2025007127W WO 2025183162 A1 WO2025183162 A1 WO 2025183162A1
Authority
WO
WIPO (PCT)
Prior art keywords
water
absorbing material
emulsion
absorbent
mass
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Pending
Application number
PCT/JP2025/007127
Other languages
English (en)
Japanese (ja)
Inventor
太貴 水野
亮 清水
良太 伊藤
幸次 舘
陽介 大賀
芳史 足立
博之 池内
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Nippon Shokubai Co Ltd
Original Assignee
Nippon Shokubai Co Ltd
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Nippon Shokubai Co Ltd filed Critical Nippon Shokubai Co Ltd
Publication of WO2025183162A1 publication Critical patent/WO2025183162A1/fr
Pending legal-status Critical Current
Anticipated expiration legal-status Critical

Links

Classifications

    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61F—FILTERS IMPLANTABLE INTO BLOOD VESSELS; PROSTHESES; DEVICES PROVIDING PATENCY TO, OR PREVENTING COLLAPSING OF, TUBULAR STRUCTURES OF THE BODY, e.g. STENTS; ORTHOPAEDIC, NURSING OR CONTRACEPTIVE DEVICES; FOMENTATION; TREATMENT OR PROTECTION OF EYES OR EARS; BANDAGES, DRESSINGS OR ABSORBENT PADS; FIRST-AID KITS
    • A61F13/00—Bandages or dressings; Absorbent pads
    • A61F13/15—Absorbent pads, e.g. sanitary towels, swabs or tampons for external or internal application to the body; Supporting or fastening means therefor; Tampon applicators
    • A61F13/53—Absorbent pads, e.g. sanitary towels, swabs or tampons for external or internal application to the body; Supporting or fastening means therefor; Tampon applicators characterised by the absorbing medium
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J20/00—Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof
    • B01J20/22—Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof comprising organic material
    • B01J20/26—Synthetic macromolecular compounds
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J20/00—Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof
    • B01J20/28—Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof characterised by their form or physical properties
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J20/00—Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof
    • B01J20/30—Processes for preparing, regenerating, or reactivating
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08F—MACROMOLECULAR COMPOUNDS OBTAINED BY REACTIONS ONLY INVOLVING CARBON-TO-CARBON UNSATURATED BONDS
    • C08F20/00—Homopolymers and copolymers of compounds having one or more unsaturated aliphatic radicals, each having only one carbon-to-carbon double bond, and only one being terminated by only one carboxyl radical or a salt, anhydride, ester, amide, imide or nitrile thereof
    • C08F20/02—Monocarboxylic acids having less than ten carbon atoms, Derivatives thereof
    • C08F20/04—Acids, Metal salts or ammonium salts thereof
    • C08F20/06—Acrylic acid; Methacrylic acid; Metal salts or ammonium salts thereof
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08F—MACROMOLECULAR COMPOUNDS OBTAINED BY REACTIONS ONLY INVOLVING CARBON-TO-CARBON UNSATURATED BONDS
    • C08F20/00—Homopolymers and copolymers of compounds having one or more unsaturated aliphatic radicals, each having only one carbon-to-carbon double bond, and only one being terminated by only one carboxyl radical or a salt, anhydride, ester, amide, imide or nitrile thereof
    • C08F20/02—Monocarboxylic acids having less than ten carbon atoms, Derivatives thereof
    • C08F20/10—Esters
    • C08F20/20—Esters of polyhydric alcohols or polyhydric phenols, e.g. 2-hydroxyethyl (meth)acrylate or glycerol mono-(meth)acrylate
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08F—MACROMOLECULAR COMPOUNDS OBTAINED BY REACTIONS ONLY INVOLVING CARBON-TO-CARBON UNSATURATED BONDS
    • C08F20/00—Homopolymers and copolymers of compounds having one or more unsaturated aliphatic radicals, each having only one carbon-to-carbon double bond, and only one being terminated by only one carboxyl radical or a salt, anhydride, ester, amide, imide or nitrile thereof
    • C08F20/02—Monocarboxylic acids having less than ten carbon atoms, Derivatives thereof
    • C08F20/52—Amides or imides
    • C08F20/54—Amides, e.g. N,N-dimethylacrylamide or N-isopropylacrylamide

Definitions

  • the present invention relates to a water-absorbent material and a method for producing the same.
  • sanitary materials such as disposable diapers, sanitary napkins, and so-called incontinence pads widely use mixtures containing water-absorbent resins and hydrophilic fibers such as pulp as their constituent materials for the purpose of absorbing bodily fluids.
  • water-absorbent resins and hydrophilic fibers such as pulp
  • absorbent materials with superior water-absorbing speeds as constituent materials of such materials.
  • a known water-absorbing material is a monolithic organic porous ion exchanger (water-absorbing material) consisting of a continuous skeleton and continuous pores, as described in Patent Document 1.
  • the monolithic organic porous ion exchanger is a hydrolyzate produced by hydrolyzing a crosslinked polymer of a (meth)acrylic acid ester and a compound having two or more vinyl groups in one molecule.
  • the water-absorbing polymer particles described in Patent Document 2 are known. Specifically, the water-absorbing polymer particles are produced by a method including the following steps (a) and (b).
  • step (a) a step of incorporating a first solvent into an aqueous solution of a water-soluble ethylenically unsaturated monomer in the presence of a first surfactant to obtain an O/W emulsion; and (b) a step of dispersing the O/W emulsion obtained in step (a) in a second solvent containing a second surfactant to obtain an O/W/O emulsion.
  • the monolithic organic porous ion exchanger described in Patent Document 1 is a hydrolyzate, and an excessive amount of alkaline component is used during production, resulting in 100% neutralization of the constituent (meth)acrylic acid by the alkaline component. Therefore, the alkaline component remains in the pores of the monolithic organic porous ion exchanger even after washing. Therefore, the monolithic organic porous ion exchanger has a pH value exceeding 8, which can cause, for example, rough skin in the user.
  • water-absorbing polymer particles described in Patent Document 2 leave room for improvement in terms of water absorption rate.
  • water-absorbing materials that can be used as components of sanitary materials are required to have an excellent water-separation rate in addition to an excellent water-absorption rate.
  • excellent water-separation rate means that when pressure is applied to a water-absorbing material that has absorbed an aqueous liquid and is in a swollen state, the absorbed aqueous liquid is released more easily and in greater amounts.
  • One embodiment of the present invention aims to solve the above-mentioned problems by providing a water-absorbent material that can reduce skin irritation and other issues on the user compared to conventional water-absorbent materials, and that has excellent water absorption speed and water-separation rate.
  • a water-absorbing material that is formed from a cross-linked polymer whose neutralization rate is controlled to be lower than that of conventional water-absorbing materials, and that contains an organic porous body that has a specific internal pore structure that has a water-retention capacity and bulk density within a specific range.
  • a water-absorbing material containing an organic porous body that has the specific internal pore structure can be obtained by controlling the volume ratio of the first solvent to the unsaturated monomer aqueous solution (O/W volume ratio) to 2.5 or more.
  • one embodiment of the present invention is a water-absorbing material comprising an organic porous material having a continuous skeleton and continuous pores formed by a crosslinked polymer mainly composed of structural units derived from (meth)acrylic acid (salt), Centrifuge retention capacity (CRC) is 5 to 25 g/g; The bulk density is less than 0.3 g/ml, and The water-absorbing material is one in which the neutralization rate of the crosslinked polymer is less than 70 mol %.
  • Another embodiment of the present invention is a method for producing a water-absorbing material including an organic porous material having a continuous skeleton and continuous pores formed by a crosslinked polymer containing structural units derived from (meth)acrylic acid (salt) as a main component, the method comprising: an O/W emulsion preparation step of incorporating a first solvent into an aqueous monomer solution having a neutralization rate of less than 70 mol% in the presence of a first surfactant so that the volume ratio of the first solvent to the aqueous monomer solution is 2.5 or more to obtain an O/W emulsion; an O/W/O emulsion preparation step of dispersing the O/W emulsion in a second solvent to obtain an O/W/O emulsion; and a polymerization step of polymerizing the monomers contained in the aqueous monomer solution in the O/W/O emulsion to prepare an organic porous material;
  • the method for producing a water-absorbent material includes
  • the water-absorbent material according to one embodiment of the present invention can reduce skin irritation and other issues in the user more than conventional water-absorbent materials, and is excellent in both water absorption speed and water separation rate. Furthermore, the method for manufacturing a water-absorbent material according to one embodiment of the present invention has the effect of being able to manufacture the water-absorbent material.
  • FIG. 1 is a schematic diagram showing one embodiment of an O/W/O emulsion preparation step and a polymerization step in a method for producing a water-absorbent material according to one embodiment of the present invention.
  • crosslinked polymer specifically refers to a polymer gelling agent having a water swelling capacity (CRC) of 5 g/g or more as defined by NWSP 241.0.R2(15) and a water soluble component (Ext) of 70 mass% or less as defined by NWSP 270.0.R2(15).
  • CRC water swelling capacity
  • Ext water soluble component
  • NWSP stands for "Non-Woven Standard Procedures - Edition 2015.” NWSP was jointly published by EDANA (European Disposables and Nonwovens Association) and INDA (Association of the Nonwoven Fabrics Industry) to standardize evaluation methods for nonwoven fabrics and their products in the United States and Europe, and includes standard measurement methods for water-absorbent resins. Unless otherwise specified, the physical properties of cross-linked polymers and water-absorbent materials in this specification are measured in accordance with NWSP.
  • crosslinked polymer is not limited to a composition in which the total amount (100% by mass) is the crosslinked polymer alone, but may also refer to a composition that contains additives and is generally referred to as a "water-absorbent resin composition.” Furthermore, in this specification, the term “crosslinked polymer” may also include a crosslinked polymer that is in a hydrous gel state with water trapped inside.
  • water-absorbing material refers to a material that has a continuous skeleton formed primarily of a crosslinked polymer and continuous pores, and that has the ability to absorb and retain a solution (liquid).
  • a solution liquid
  • it can be used as an absorbent in combination with a particulate superabsorbent polymer, commonly known as a water-absorbent resin, which has excellent water-absorbing properties.
  • the water-absorbing material of the present invention is characterized by temporarily retaining the liquid and transferring it to the superabsorbent polymer.
  • the solution (liquid) is not limited to water, but can be any liquid.
  • Liquids that can be absorbed by the water-absorbing material according to one embodiment of the present invention include, for example, urine, menstrual blood, sweat, saline solution, oil, organic solvents, and waste liquid.
  • the water-absorbing material described herein may be a particulate (powdered) water-absorbing material, i.e., a water-absorbing material generally referred to as a "particulate water-absorbing material.” Because the particulate water-absorbing material contains a cross-linked polymer as its primary component, it corresponds to a particulate cross-linked polymer.
  • the concept of "particulate water-absorbing material” encompasses both a single grain of particulate water-absorbing material and an aggregate of multiple particulate water-absorbing materials. In this specification, "particulate” means having a particle shape.
  • the water-absorbing material contains a cross-linked polymer (also called a particulate cross-linked polymer) as its main component.
  • the water-absorbing material contains 60 to 100% by mass, preferably 70 to 95% by mass, and more preferably 75 to 90% by mass of the cross-linked polymer.
  • the remainder of the water-absorbing material may optionally contain water and/or additives (inorganic fine particles, polyvalent metal cations, etc.).
  • the upper limit of the cross-linked polymer content in the water-absorbent material is, for example, 100 mass%, 90 mass%, 80 mass%, or 70 mass%.
  • the water-absorbent material further contains 5 to 30 mass% of components other than the cross-linked polymer, particularly water and/or additives (inorganic fine particles, polyvalent metal cations, etc.).
  • the preferred water content of the water-absorbing material is 0.2 to 30% by mass.
  • a composition containing a crosslinked polymer in which components such as water and/or additives are integrated with and/or mixed with the crosslinked polymer is also encompassed in the "particulate water-absorbing material.”
  • the "water content” is a numerical value indicating the ratio of the mass of water contained in the measurement object to the mass of the entire measurement object, more specifically, the mass of the entire measurement object in a water-containing state, and can be calculated based on the following formula (2).
  • the measurement object include the water-absorbing material, the organic porous material described below, the crosslinked polymer described below, and the hydrogel described below, and the water content can be calculated in the same manner.
  • a water-absorbing material according to one embodiment of the present invention is a water-absorbing material comprising an organic porous material having a continuous skeleton formed by a cross-linked polymer whose main component is a structural unit derived from (meth)acrylic acid (salt) and continuous pores, and has a centrifuge retention capacity (CRC) of 5 to 25 g/g, a bulk specific gravity of less than 0.3 g/ml, and a neutralization rate of the cross-linked polymer of less than 70 mol%.
  • CRC centrifuge retention capacity
  • the neutralization rate of the cross-linked polymer is less than 70 mol %. Therefore, the water-absorbing material of the present invention is controlled to be weakly acidic, and can, for example, reduce skin irritation and other issues experienced by users of the water-absorbing material compared to conventional water-absorbing materials.
  • the water-absorbing material of the present invention contains an organic porous material having a continuous skeleton formed by a cross-linked polymer and continuous pores, so when it absorbs liquids such as water, the liquid is retained within the cross-linked polymer and the continuous pores.
  • the CRC refers to the amount of liquid remaining in the water-absorbent material after a specific centrifugal force (pressure) is applied to the water-absorbent material in a swollen state after absorbing the liquid, causing some of the liquid to be released.
  • pressure pressure
  • the liquid that was held inside the interconnected pores is mainly released from the water-absorbent material in a swollen state. Therefore, the CRC is mainly the amount of liquid held in the cross-linked polymer of the water-absorbent material in a swollen state.
  • the bulk density is a parameter that represents the mass per unit volume of the water-absorbent material. This mass is mainly the mass of the cross-linked polymer that constitutes the water-absorbent material per unit volume. Therefore, the bulk density is a parameter that represents the ratio of the portion of the entire water-absorbent material that is occupied by the continuous skeleton to the portion that is occupied by the continuous pores. In other words, a low bulk density means that the portion of the entire water-absorbent material that is occupied by the continuous skeleton is small, and the portion that is occupied by the continuous pores is large.
  • the water-absorbent material of the present invention has a CRC of 25 g/g or less and a bulk density controlled to less than 0.3 g/ml. Therefore, the water-absorbent material of the present invention has a structure in which a large proportion of the interconnected pores is occupied. This structure makes it easier to absorb the liquid and easier to release the liquid when centrifugal force (pressure) is applied. Therefore, the water-absorbent material of the present invention has excellent water absorption speed and water separation rate.
  • the water-absorbent material of the present invention has a CRC of 5 g/g or more. This means that the water-absorbent material of the present invention contains a portion occupied by a predetermined amount of the continuous skeleton. Therefore, the water-absorbent material of the present invention has a predetermined water-absorbing performance.
  • the water-absorbent material of the present invention can reduce skin irritation and other issues experienced by users more than conventional water-absorbent materials, and is excellent in both water absorption speed and water separation rate.
  • Patent Document 2 states that water-absorbing materials containing organic porous materials with low bulk density lack mechanical strength.
  • the mechanical strength of the water-absorbing material of the present invention was confirmed by placing the water-absorbing material and glass beads in a glass container and shaking it (damage test). It was confirmed that the water-absorbing material of the present invention has sufficient mechanical strength for use as a water-absorbing material. This method is a technique for simulating mechanical damage that occurs during manufacturing processes in chemical plants, etc.
  • (meth)acrylic acid (salt) means (meth)acrylic acid and/or its salt.
  • “monomer composition containing a (meth)acrylic acid (salt)-based monomer” means a monomer composition containing 50 mol% or more of (meth)acrylic acid (salt) relative to the total monomers excluding the crosslinking agent.
  • the crosslinked polymer contained in the water-absorbing material of the present invention is a crosslinked polymer that contains 50 mol% or more of structural units derived from (meth)acrylic acid (salt) relative to the total structural units constituting the poly(meth)acrylic acid (salt)-based crosslinked polymer, and is a crosslinked polymer that optionally contains structural units derived from an internal crosslinking agent.
  • the crosslinked polymer is a crosslinked polymer in which, based on the constituent monomers excluding the internal crosslinking agent, 50 mol % or more, preferably 70 mol % or more, and more preferably 90 mol % or more is (meth)acrylic acid (salt). Furthermore, the crosslinked polymer is a crosslinked polymer in which, based on the constituent monomers excluding the internal crosslinking agent, 100 mol % or less, and more preferably essentially 100 mol % is (meth)acrylic acid (salt).
  • the cross-linked polymer contained in the water-absorbing material of the present invention may be, for example, particulate.
  • the particulate cross-linked polymer may have one or more shapes selected from the group consisting of irregularly pulverized (irregular), spherical, fibrous, rod-like, approximately spherical, and flat.
  • the cross-linked polymer be spherical particles, taking into account damage during the manufacturing process and reduced productivity due to the generation of fine powder.
  • the particulate cross-linked polymer is referred to as a particulate cross-linked polymer whether it is a single particle or an aggregate of multiple particles.
  • the cross-linked polymer is porous.
  • the term "monomer composition” refers to raw material components that form the crosslinked polymer, and refers to a composition that contains (meth)acrylic acid (salt) as the main monomer component, as well as a monomer other than (meth)acrylic acid (salt), and an internal crosslinking agent as an optional component.
  • the raw material components that form the crosslinked polymer are referred to as the monomer composition.
  • a monomer containing an acid group is preferred among monomers having an unsaturated double bond (ethylenically unsaturated monomers).
  • monomers having an unsaturated double bond include anionic unsaturated monomers and/or salts thereof, such as maleic acid (anhydride), fumaric acid, crotonic acid, itaconic acid, cinnamic acid, vinyl sulfonic acid, allyl toluene sulfonic acid, vinyl toluene sulfonic acid, styrene sulfonic acid, 2-(meth)acrylamido-2-methylpropanesulfonic acid, 2-(meth)acryloylethanesulfonic acid, 2-(meth)acryloylpropanesulfonic acid, and 2-hydroxyethyl (meth)acryloyl phosphate.
  • anionic unsaturated monomers and/or salts thereof such as maleic acid (anhydride), fumaric acid, crotonic acid, it
  • the salt may be one or more salts selected from the group consisting of alkali metal salts, ammonium salts, and amine salts. Sodium salts, potassium salts, lithium salts, or ammonium salts are more preferred, and sodium salts are particularly preferred.
  • the neutralization rate of the crosslinked polymer contained in the water-absorbing material of the present invention can be controlled by the neutralization rate of the monomer composition. It may also be adjusted by adding a neutralizing agent to the crosslinked polymer or the water-absorbing material after the polymerization process.
  • the neutralization rate is the ratio (unit: mol%) of the number of moles of neutralized monomers to the number of moles of all monomers (excluding the internal crosslinking agent) that make up the crosslinked polymer.
  • the water-absorbent material of the present invention has a low neutralization rate of less than 70 mol%, which, as mentioned above, can reduce skin irritation and other issues in users of the water-absorbent material compared to conventional water-absorbent materials. From this perspective, it is preferable that the neutralization rate be 65 mol% or less.
  • the neutralization rate is preferably 30 mol% or greater, and more preferably 40 mol% or greater.
  • the monomer composition may contain, as necessary, a "hydrophilic or hydrophobic unsaturated monomer (hereinafter referred to as "other monomer”)" in addition to the aforementioned “(meth)acrylic acid (salt)” and “monomer other than (meth)acrylic acid (salt).”
  • other monomer a hydrophilic or hydrophobic unsaturated monomer
  • Examples of such other monomers include mercaptan group-containing unsaturated monomers; phenolic hydroxyl group-containing unsaturated monomers; amide group-containing unsaturated monomers such as N-vinyl-2-pyrrolidone, N-vinylacetamide, (meth)acrylamide, N-isopropyl(meth)acrylamide, N-ethyl(meth)acrylamide, and N,N-dimethyl(meth)acrylamide; and amino group-containing unsaturated monomers such as N,N-dimethylaminoethyl(meth)acrylate, N,N-dimethylaminopropyl(meth)acrylate, and N,N-dimethylaminopropyl(meth)acrylamide.
  • One or more of the above-mentioned other monomers can be used.
  • the amount of other monomers used should be sufficient so long as it does not impair the physical properties of the resulting water-absorbing material; specifically, it should be 50 mol % or less, and more preferably 20 mol % or less, of the monomer composition excluding the internal crosslinking agent.
  • the crosslinked polymer is crosslinked.
  • the crosslinking may be a self-crosslinking type that does not use a crosslinking monomer.
  • the crosslinked polymer is preferably internally crosslinked by an internal crosslinking agent.
  • the internal crosslinking agent is preferably at least one selected from the group consisting of polyfunctional acrylate crosslinking agents, acrylamide crosslinking agents, and glycidyl ether crosslinking agents.
  • the internal crosslinking agent examples include N,N'-methylenebis(meth)acrylamide, (poly)ethylene glycol di(meth)acrylate, (poly)propylene glycol di(meth)acrylate, trimethylolpropane di(meth)acrylate, trimethylolpropane tri(meth)acrylate, glycerin tri(meth)acrylate, glycerin acrylate methacrylate, ethylene oxide-modified trimethylolpropane tri(meth)acrylate, pentaerythritol tetra(meth)acrylate, dipentaerythritol hexa(meth)acrylate, triallyl cyanurate, triallyl isocyanurate, triallyl phosphate, triallylamine, poly(meth)allyloxyalkane, (poly)ethylene glycol diglycidyl ether, glycerol diglycidyl ether, ethylene glycol, polyethylene glycol, propy
  • an internal crosslinking agent having two or more polymerizable unsaturated groups is preferably selected.
  • polymerizable unsaturated group examples include allyl groups and (meth)acrylate groups. Of the polymerizable unsaturated groups, (meth)acrylate groups are preferred.
  • internal crosslinking agents having two or more polymerizable unsaturated groups with a (poly)alkylene glycol structure can be used, such as polyethylene glycol di(meth)acrylate.
  • the number of alkylene glycol units in the internal crosslinking agent is preferably 1 or more, more preferably 2 or more, even more preferably 4 or more, and particularly preferably 6 or more.
  • the number of alkylene glycol units is preferably 100 or less, more preferably 50 or less, even more preferably 20 or less, and particularly preferably 10 or less.
  • the content of the internal crosslinking agent is preferably 0.001 mol% or more, more preferably 0.01 mol% or more, and even more preferably 0.1 mol% or more, based on the portion of the monomer composition excluding the internal crosslinking agent. Furthermore, the content of the internal crosslinking agent is preferably 10 mol% or less, more preferably 7 mol% or less, and even more preferably 5 mol% or less, based on the portion of the monomer composition excluding the internal crosslinking agent.
  • the content of the internal crosslinking agent When the content of the internal crosslinking agent is within the above range, the water absorption performance of the crosslinked polymer and the water absorbent material of the present invention can be controlled within the desired range. On the other hand, when the content of the internal crosslinking agent is outside the above range, the gel strength of the crosslinked polymer decreases, which may result in an increase in the water-soluble content of the crosslinked polymer or a decrease in the absorption capacity of the crosslinked polymer and the water absorbent material of the present invention.
  • the crosslinked polymer may be surface-crosslinked to provide a surface-crosslinked layer.
  • the surface-crosslinked layer may be formed on the surface of the crosslinked polymer by surface crosslinking using a surface crosslinking agent described in U.S. Pat. No. 7,183,456, for example.
  • At least one surface crosslinking agent is selected from these surface crosslinking agents, taking into consideration reactivity and the like.
  • a surface crosslinking agent having two or more functional groups that react with a carboxyl group and that form a covalent bond is preferably selected.
  • Examples of the surface cross-linking agent include ethylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, polyethylene glycol, propylene glycol, dipropylene glycol, polypropylene glycol, 1,3-propanediol, 1,2-butanediol, 1,3-butanediol, 1,4-butanediol, 2,3-butanediol, 1,2-pentanediol, 1,3-pentanediol, 1,4-pentanediol, 1,5-pentanediol, 2,3-pentanediol, and 2,4-pentanediol.
  • polyhydric alcohol compounds such as 1,2-hexanediol, 1,3-hexanediol, 1,4-hexanediol, 1,5-hexanediol, 1,6-hexanediol, 2,3-hexanediol, 2,4-hexanediol, glycerin, polyglycerin, diethanolamine, and triethanolamine; polyvalent amine compounds such as ethylenediamine, diethylenetriamine, triethylenetetramine, tetraethylenepentamine, pentaethylenehexamine, polyallylamine, and polyethyleneimine; haloepoxy compounds; polyvalent amination compounds condensation products of a copolymer with a haloepoxy compound; oxazoline compounds such as 1,2-ethylenebisoxazoline; oxazolidinone compounds; 1,3-dioxolan-2-one (ethylene carbonate), 4-methyl-1,3-dioxolan-2-
  • the organic porous body of the present invention has a continuous skeleton formed by the crosslinked polymer and continuous pores.
  • the organic porous body is an organic porous body formed from the crosslinked polymer, and may be in the form of particles. Therefore, the organic porous body may be the crosslinked polymer in the form of particles.
  • the thickness of the continuous skeleton of the organic porous material in a dry state is preferably 0.1 ⁇ m or more, more preferably 0.5 ⁇ m or more, and even more preferably 1 ⁇ m or more. If the thickness is equal to or greater than the lower limit, the strength of the organic porous material and the water-absorbing material of the present invention itself can be improved.
  • the thickness is preferably 100 ⁇ m or less, more preferably 50 ⁇ m or less, and even more preferably 10 ⁇ m or less.
  • the speed at which the water-absorbing material of the present invention absorbs liquids such as water can be improved.
  • the pore structure of the organic porous material is an open-cell structure
  • the cross section of the skeleton that appears in a test piece for electron microscope measurement of the water-absorbent material of the present invention is used as the thickness evaluation point.
  • the open-cell structure is a structure in which bubble-like macropores overlap each other.
  • the average diameter of the interconnected pores of the organic porous material in a dry state is preferably 0.1 ⁇ m or more, more preferably 1.0 ⁇ m or more, and even more preferably 2.0 ⁇ m or more.
  • the speed at which the water-absorbing material of the present invention absorbs liquids such as water can be improved.
  • the average diameter of the interconnected pores of the organic porous material in a dry state is preferably 1000 ⁇ m or less, more preferably 100 ⁇ m or less, and even more preferably 50 ⁇ m or less.
  • the strength of the organic porous material and the water-absorbing material of the present invention itself can be improved.
  • the sample used to measure the thickness of the continuous skeleton and the average diameter of the continuous pores is the water-absorbing material of the present invention, which has been dried in a vacuum dryer at 50°C for 18 hours or more. The final pressure reached is 0 Torr.
  • the water-absorbent material of the present invention can be produced by a method for producing a water-absorbent material according to one embodiment of the present invention, which will be described later. Therefore, the water-absorbent material can contain a surfactant due to the surfactant remaining in the water-absorbent material.
  • the surfactant may be, for example, one of the surfactants listed as specific examples of the "first surfactant” and "second surfactant” described below.
  • the surfactant may be a single type or a mixture of two or more types.
  • the upper limit of the surfactant content is preferably 15 parts by mass or less, and more preferably 10 parts by mass or less, per 100 parts by mass of the cross-linked polymer.
  • the lower limit of the surfactant content is not particularly limited, but can be, for example, 0.045 parts by mass or more, and preferably 0.090 parts by mass or more, per 100 parts by mass of the cross-linked polymer.
  • the water-absorbing material of the present invention may contain a chelating agent.
  • the chelating agent may be, for example, a polycarboxylic acid and its salt.
  • the chelating agent is preferably a chelating agent having high ion-sequestering and chelating ability for Fe or Cu.
  • the chelating agent is a chelating agent having a stability constant for Fe ions of 10 or more, preferably 20 or more, and more preferably an aminopolycarboxylic acid and its salt.
  • the aminopolycarboxylic acid and its salt may be a polymer.
  • aminopolycarboxylic acids and their salts are aminocarboxylic acids and their salts having a lower limit of 3 or more, preferably 4 or more, more preferably 5 or more, and an upper limit of usually 100 or less, more preferably 20 or less, of carboxyl groups.
  • polycarboxylic acids examples include diethylenetriaminepentaacetic acid, triethylenetetraaminehexaacetic acid, cyclohexane-1,2-diaminetetraacetic acid, N-hydroxyethylethylenediaminetriacetic acid, ethylene glycol diethyl ether diaminetetraacetic acid, ethylenediaminetetrapropionic acid, N-alkyl-N'-carboxymethylaspartic acid, and N-alkenyl-N'-carboxymethylaspartic acid, as well as alkali metal salts, alkaline earth metal salts, ammonium salts, and amine salts thereof.
  • polycarboxylic acids diethylenetriaminepentaacetic acid, triethylenetetraaminehexaacetic acid, N-hydroxyethylethylenediaminetriacetic acid, and their salts are most preferred.
  • One or more of the polycarboxylic acids can be used.
  • the content of the chelating agent, particularly the amino polycarboxylic acid is a trace component, typically 0.00001 to 10 parts by mass, preferably 0.0001 to 1 part by mass, and more preferably 0.01 to 0.5 parts by mass, per 100 parts by mass of the crosslinked polymer.
  • the inclusion of a chelating agent provides sufficient effects and/or additional functions, while maintaining the absorbent performance of the water-absorbing material.
  • the water-absorbing material of the present invention may contain inorganic fine particles, particularly water-insoluble inorganic fine particles, to prevent blocking during moisture absorption.
  • the inorganic fine particles include one or more selected from the group consisting of metal oxides such as silicon dioxide and titanium oxide, silicic acid (salts) such as natural zeolite and synthetic zeolite, kaolin, talc, clay, and bentonite.
  • metal oxides such as silicon dioxide and titanium oxide
  • silicic acid (salts) such as natural zeolite and synthetic zeolite, kaolin, talc, clay, and bentonite.
  • silicon dioxide and silicic acid (salts) are preferred, with silicon dioxide and silicic acid (salts) having an average particle size measured by the Coulter Counter method of 0.001 to 200 ⁇ m being even more preferred.
  • the water-absorbing material of the present invention may be imparted with deodorizing properties by incorporating zeolite, with zeolite having a SiO
  • the content of the inorganic fine particles is typically in the range of 0 to 10 parts by mass, preferably 0.001 to 5 parts by mass, and more preferably 0.002 to 3 parts by mass, per 100 parts by mass of the crosslinked polymer.
  • the sufficient effects and/or additional functions of the inorganic fine particles can be obtained, and the absorption performance of the water-absorbing material can be maintained.
  • the water-absorbing material of the present invention may contain additives other than the surfactant, the chelating agent, and the inorganic fine particles, to the extent that the object of the present invention is not impaired.
  • the other additives mentioned above may include plant components, polyvalent metal salts of organic acids, complex hydrous oxides, reducing substances, antibacterial agents, deodorants, water-soluble polymers, water-insoluble polymers, water, organic fine particles, reducing agents, oxidizing agents, and inorganic salts.
  • the content of the other additives varies depending on the purpose and additional function.
  • the content of each additive is typically in the range of 0 to 10 parts by mass, preferably 0.001 to 5 parts by mass, and more preferably 0.002 to 3 parts by mass, per 100 parts by mass of the crosslinked polymer.
  • One or more types of the additives can be used.
  • the full effects and/or additional functions of the additives can be obtained, while the absorbent performance of the water-absorbing material can be maintained.
  • CRC Centrifuge holding capacity
  • the CRC refers to the water absorption capacity (unit: g/g) after 0.2 g of the water-absorbing material is placed in a nonwoven bag, immersed in a large excess of 0.9% by mass sodium chloride aqueous solution for 30 minutes to allow free swelling, and then drained using a centrifuge (250 G).
  • the CRC can be measured, for example, by the method shown in the Examples.
  • the CRC of the water-absorbent material of the present invention is 25 g/g or less, preferably 23 g/g or less, and more preferably 20 g/g or less.
  • the CRC is 5 g/g or more, preferably 7 g/g or more, and more preferably 10 g/g or more. It is preferable that the CRC is equal to or greater than the lower limit from the viewpoint of maintaining the water absorption performance, such as the water absorption rate, of the water-absorbent material of the present invention.
  • the CRC value can be controlled by adjusting the water absorption capacity of the crosslinked polymer by changing the type and amount of the internal crosslinking agent, surface crosslinking agent, etc.
  • the bulk specific gravity of the water-absorbent material of the present invention is a parameter representing the mass per unit volume.
  • the bulk specific gravity is the mass (unit: [g/mL]) of the water-absorbent material when the water-absorbent material is allowed to fall freely into a 10 mL container and filled therewith.
  • the bulk density is less than 0.3 g/mL, preferably 0.27 g/mL or less, more preferably 0.25 g/mL or less, even more preferably 0.20 g/mL or less, and even more preferably 0.17 g/mL or less.
  • the bulk density being equal to or less than the upper limit means that the water-absorbing material of the present invention has a structure in which the interconnected pores are large and/or numerous, and as a result, both the water absorption rate and the water syneresis rate of the water-absorbing agent are improved.
  • the bulk specific gravity is preferably 0.05 g/mL or more, and more preferably 0.07 g/mL or more. Having the bulk specific gravity equal to or greater than the lower limit is preferable from the viewpoint of maintaining the water absorption performance, such as CRC, of the water-absorbent material of the present invention.
  • the water absorption rate of the water absorbent material of the present invention is expressed, for example, as a value measured by a method generally called the Vortex method (water absorption rate (Vortex): unit [seconds]).
  • the water absorption rate (Vortex) value of the water absorbent material of the present invention is preferably a small value, specifically, preferably 10 seconds or less, more preferably 7 seconds or less, even more preferably 5 seconds or less, and particularly preferably 2 seconds or less.
  • the water absorption rate (Vortex) value can be measured, for example, by the method described in the examples.
  • the free swelling capacity (FSC) of the water absorbent material of the present invention is an abbreviation for Free Swell Capacity, and refers to the water absorption capacity of the water absorbent material when suspended under no pressure. In this specification, FSC is measured in accordance with NWSP 240.0. R2(15).
  • the FSC value of the water absorbent material can be controlled by changing the type and amount of the internal crosslinking agent and surface crosslinking agent, etc., to adjust the water absorption capacity of the crosslinked polymer.
  • the FSC value is preferably 35 g/g or more, more preferably 40 g/g or more, and even more preferably 50 g/g or more. Furthermore, the FSC value is preferably 150 g/g or less, more preferably 120 g/g or less, and even more preferably 100 g/g or less. By ensuring that the FSC value is within the above range, the water absorption rate and water syneresis rate of the water-absorbent material of the present invention can be further improved.
  • a high value of the water syneresis rate means that the water absorbent material in a swollen state is more likely to release the liquid it has absorbed, and has an excellent water syneresis rate.
  • the value of the water syneresis rate can usually be 95% or less.
  • the pH of the water-absorbing material of the present invention is controlled to a range showing weak acidity, specifically, it may be in the range of 4.5 to 6.5, and preferably in the range of 5.0 to 6.0.
  • the pH can be controlled by adjusting the neutralization rate of the monomer composition, which is the raw material, to be within the above-mentioned range.
  • the pH can be measured by the method described in the Examples.
  • the water-absorbing material of the present invention is porous and may be particulate. Its mass-average particle diameter (D50) is preferably 100 ⁇ m or more and 1000 ⁇ m or less, more preferably 300 ⁇ m or more and 800 ⁇ m or less, and even more preferably 400 ⁇ m or more and 700 ⁇ m or less.
  • the mass-average particle diameter (D50) refers to the particle diameter of a standard sieve with a fixed mesh size, corresponding to 50% by mass of the total particles, as described in U.S. Patent No. 5,051,259. The D50 can be measured, for example, by the method described in the Examples.
  • the water-absorbent material of the present invention can be produced, for example, by a method for producing a water-absorbent material according to one embodiment of the present invention, which will be described later.
  • the water-absorbing material of the present invention is an organic porous material having a continuous skeleton and continuous pores formed primarily from a crosslinked polymer, and therefore has the ability to absorb and retain solutions (liquids). Therefore, it can be used in absorbents for hygiene products, and as mentioned above, it can be used in combination with existing superabsorbent polymers with excellent water-absorbing performance, such as water-absorbent resins. Furthermore, because the water-absorbing material of the present invention is a particulate porous material, it can be easily mixed with a particulate superabsorbent polymer (water-absorbent resin) to form a composition and used in absorbents, etc. Such a composite absorbent material containing the water-absorbing material of the present invention and water-absorbent resin particles is also included in the present invention.
  • a method for producing a water-absorbing material according to one embodiment of the present invention is a method for producing a water-absorbing material comprising an organic porous material having a continuous skeleton formed by a crosslinked polymer mainly composed of structural units derived from (meth)acrylic acid (salt) and continuous pores, and comprises the following steps: an O/W emulsion preparation step of incorporating a first solvent into an aqueous monomer solution having a neutralization rate of less than 70 mol% in the presence of a first surfactant so that the volume ratio of the first solvent to the aqueous monomer solution is 2.5 or more to obtain an O/W emulsion; an O/W/O emulsion preparation step of dispersing the O/W emulsion in a second solvent to obtain an O/W/O emulsion; and a polymerization step of polymerizing the monomers contained in the a
  • Water-absorbent material are used for the terms “crosslinked polymer,” “organic porous material,” and “water-absorbent material.”
  • the present invention aims to provide a water-absorbent material that can reduce skin irritation and other issues in the user compared to conventional water-absorbent materials, and that has excellent water absorption speed and water-separation rate.
  • the inventors have discovered that the water-retention capacity and bulk density of the water-absorbent material produced by the manufacturing method of the present invention are controlled within specific ranges, and that this water-absorbent material can solve the above-mentioned problems.
  • the inventors have discovered that by making the neutralization rate of the monomer lower than that of conventional monomers, it is possible to prepare an O/W emulsion having an O/W volume ratio of 2.5 or more, and to produce a water-absorbent material that can solve the above-mentioned problems.
  • the neutralization rate of the monomer here corresponds to the neutralization rate of the cross-linked polymer that constitutes the water-absorbent material being produced.
  • Figure 1 is a schematic diagram showing one embodiment of the O/W/O emulsion preparation step and polymerization step of the manufacturing method of the present invention.
  • the leftmost diagram in Figure 1 shows an O/W emulsion prepared in the O/W emulsion preparation step of the manufacturing method of the present invention.
  • the O/W emulsion has a first solvent 1 dispersed in an aqueous monomer solution 2, and the volume ratio of first solvent 1 to aqueous monomer solution 2 (O/W volume ratio) is 2.5 or greater.
  • the O/W emulsion prepared in the O/W emulsion preparation step is added to the second solvent 3 and emulsified. This results in the preparation of an O/W/O emulsion in which the O/W emulsion 4 is dispersed in the second solvent 3.
  • the first solvent is dispersed in the aqueous monomer solution. Furthermore, the O/W volume ratio in O/W emulsion 4 is the same as the O/W volume ratio in the O/W emulsion prepared in the O/W emulsion preparation step.
  • the monomers contained in the aqueous monomer solution in the O/W emulsion 4 are polymerized to form a crosslinked polymer.
  • the crosslinked polymer then forms the continuous skeleton that constitutes the organic porous material 5 prepared in the polymerization step.
  • the area where the first solvent is present becomes the continuous pores that constitute the organic porous material 5. Therefore, as shown in the rightmost diagram in Figure 1, the polymerization step prepares an organic porous material that has a continuous skeleton formed by the crosslinked polymer and a structure in which continuous pores are dispersed within.
  • the manufacturing method of the present invention produces a water-absorbing material that includes an organic porous material having the continuous skeleton and the continuous pores.
  • the organic porous material 5 in Figure 1 can be a water-absorbing material.
  • an aqueous monomer solution with a neutralization rate of less than 70 mol% is used as a raw material.
  • the neutralization rate of the aqueous monomer solution is the ratio (unit: mol%) of the number of moles of neutralized monomer to the number of moles of all monomers (excluding internal crosslinking agents) in the aqueous monomer solution containing the monomer composition, and is the neutralization rate of the crosslinked polymer obtained from the aqueous monomer solution. Therefore, the water-absorbing material manufactured by the manufacturing method of the present invention is controlled to be weakly acidic, and can, for example, cause less skin irritation and other problems to users of the water-absorbing material than conventional water-absorbing materials.
  • the manufacturing method of the present invention can produce a water-absorbent material containing an organic porous material without undergoing hydrolysis. Therefore, the manufacturing method of the present invention does not require the use of excess alkali, which is essential for hydrolysis. Therefore, according to the manufacturing method of the present invention, a water-absorbent material containing an organic porous material can be produced while arbitrarily adjusting the neutralization rate to a small value of less than 70 mol%, and as a result, as mentioned above, it is possible to reduce skin roughness and other problems in users of the water-absorbent material.
  • the continuous pores of the organic porous material 5 are formed in areas where the first solvent dispersed in the O/W emulsion 4 is present.
  • the O/W volume ratio in the O/W emulsion 4 is 2.5 or more. Therefore, the proportion of continuous pores in the organic porous material 5 is large. In other words, in the organic porous material 5, the portion of the entire water-absorbent material occupied by the continuous skeleton is small, and the portion occupied by the continuous pores is large.
  • Water-absorbent material when the interconnected pores account for a large proportion of the material, the material is more likely to absorb the liquid and more likely to release the liquid when centrifugal force (pressure) is applied. Therefore, a water-absorbent material containing organic porous material 5 has improved water absorption speed and water separation rate.
  • the manufacturing method of the present invention can reduce skin irritation and other issues experienced by users of the water-absorbent material compared to conventional water-absorbent materials, and can produce a water-absorbent material that has excellent water absorption speed and water-separation rate.
  • an O/W emulsion having an O/W volume ratio adjusted to 2.5 or greater is prepared by using an aqueous monomer solution with a neutralization rate of less than 70 mol% as a raw material.
  • the O/W emulsion is then dispersed in a second solvent to form an O/W/O emulsion, where the monomers contained in the aqueous monomer solution are polymerized to produce a water-absorbing material containing an organic porous material.
  • particle size is controlled at the O/W/O emulsion stage to produce a water-absorbing material containing an organic porous material.
  • the manufacturing method of the present invention can produce a water-absorbing material having a predetermined particle size without crushing the resulting organic porous material. It is known that crushing an organic porous material results in a large amount of fine powder being produced as a by-product, reducing productivity. Therefore, the manufacturing method of the present invention can produce a water-absorbing material having a predetermined particle size while avoiding the reduction in productivity caused by the by-production of a large amount of fine powder.
  • the O/W emulsion preparation step of the production method of the present invention is a step of obtaining an O/W emulsion by incorporating a first solvent into an aqueous monomer solution having a neutralization rate of less than 70 mol % in the presence of a first surfactant so that the volume ratio of the first solvent to the aqueous monomer solution is 2.5 or more.
  • the aqueous monomer solution is an aqueous solution containing monomers that are raw materials for the water-absorbing material to be produced, and optionally an internal cross-linking agent, etc.
  • the concentration of the monomers in the aqueous monomer solution is usually preferably 30% by mass to the saturated concentration, more preferably 35 to 45% by mass, based on the total mass of the aqueous monomer solution.
  • the water used in the aqueous monomer solution is not particularly limited, and examples thereof include tap water, distilled water, and ion-exchanged water.
  • the production method of the present invention may also include a monomer aqueous solution preparation step, prior to the O/W emulsion preparation step, of preparing the monomer aqueous solution.
  • This step involves dissolving the monomer and, optionally, an internal crosslinking agent, etc., in water to prepare the monomer aqueous solution.
  • This step may also include adjusting the neutralization rate of the monomer aqueous solution.
  • Known methods can be used to adjust the neutralization rate.
  • one such method is to neutralize the acid group of (meth)acrylic acid (salt), which is the main component of the monomer in the production method of the present invention, using a compound containing an alkali metal.
  • the alkali metal include lithium, sodium, and potassium. Of these alkali metals, sodium and potassium are preferred.
  • One or more of the alkali metals can be used.
  • the acid groups can be neutralized by, for example, adding dropwise an aqueous solution of a compound containing an alkali metal, such as sodium hydroxide and/or potassium hydroxide, to the monomer or an aqueous solution containing the monomer, and mixing.
  • concentration of the compound containing an alkali metal in the aqueous solution is not particularly limited, but is typically about 20 to 50% by mass.
  • the monomer and internal cross-linking agent in the aqueous monomer solution can be found in the ⁇ Monomer> and ⁇ Internal cross-linking agent> sections of [2-1. Cross-linked polymer] in [2. Water-absorbing material]. Note that the "neutralization rate of cross-linked polymer" in the ⁇ Monomer> section corresponds to the "neutralization rate of aqueous monomer solution,” and the "content” corresponds to the "amount used" in the production method of the present invention.
  • a preferred example of the aqueous monomer solution is an aqueous monomer solution containing an internal crosslinking agent, wherein the internal crosslinking agent is at least one selected from the group consisting of a polyfunctional acrylate crosslinking agent, an acrylamide crosslinking agent, and a glycidyl ether crosslinking agent.
  • the polymerization initiator can be added to one or more of the aqueous monomer solution, the O/W emulsion, and the O/W/O emulsion at any time before the polymerization step.
  • the polymerization initiator is preferably added to the aqueous monomer solution in advance to ensure uniform dispersion.
  • a water-soluble radical polymerization initiator can be used as the polymerization initiator.
  • examples include persulfates such as potassium persulfate, sodium persulfate, and ammonium persulfate; azo polymerization initiators such as 2,2'-azobis(2-amidinopropane) dihydrochloride and 2,2'-azobis(2-(2-imidazolin-2-yl)propane) dihydrochloride; and hydrogen peroxide.
  • the polymerization initiators that can be used in the production method of the present invention are not limited to the exemplified polymerization initiators.
  • the polymerization initiator is preferably an azo initiator and/or a persulfate. One or more types of polymerization initiators can be used.
  • the amount of polymerization initiator used is usually preferably 0.05 to 10 millimoles per mole of total monomers contained in the aqueous monomer solution.
  • the first surfactant used in the O/W emulsion preparation step is not particularly limited as long as it can prepare the O/W emulsion.
  • the first surfactant include nonionic surfactants such as polyoxyethylene-polyoxypropylene copolymer, polyoxyethylene alkyl ether, polyoxypropylene alkyl ether, hydrophobically modified polyether urethane, hydrophobically modified polyester urethane, polyoxyethylene glycerin monostearate, polyoxyethylene glycerin monoisostearate, rosin ester, and polyoxyethylene rosin ester; and anionic surfactants such as sodium lauryl sulfate and polyoxyethylene sodium lauryl sulfate.
  • the first surfactant is preferably a polyoxyethylene-polyoxypropylene copolymer.
  • One or more types of first surfactants can be used.
  • a polyoxyethylene-polyoxypropylene copolymer as the first surfactant is preferable because it has the advantage of improving stability during polymerization in the polymerization step described below and allowing the formation of a large number of interconnected pores.
  • a polyoxyethylene-polyoxypropylene-polyoxyethylene block copolymer can be used as the polyoxyethylene-polyoxypropylene copolymer.
  • the weight average molecular weight of the polyoxyethylene-polyoxypropylene-polyoxyethylene block copolymer is preferably 3,000 or more, more preferably 5,000 or more, from the viewpoints of improving stability during polymerization in the polymerization step described below and forming a large number of interconnected pores. Furthermore, from the viewpoints of improving water solubility and workability, the weight average molecular weight is preferably 100,000 or less, more preferably 30,000 or less. From these viewpoints, the weight average molecular weight is preferably 3,000 to 100,000, more preferably 5,000 to 30,000.
  • the polyoxyethylene content of the polyoxyethylene-polyoxypropylene-polyoxyethylene block copolymer is preferably 40% by mass or more, and more preferably 45% by mass or more.
  • the O/W/O emulsion can be maintained in a good emulsified state, making it easier to form continuous pores inside the particles.
  • the content is preferably 90% by mass or less, and more preferably 85% by mass or less. From these viewpoints, the content is preferably 40 to 90% by mass, and more preferably 45 to 85% by mass.
  • Polyoxyethylene-polyoxypropylene-polyoxyethylene block copolymers are readily available industrially. Representative examples include the "ADEKA PLURONIC” (registered trademark) series manufactured by Asahi Denka Kogyo Co., Ltd., the "PLURONIC” (registered trademark) series manufactured by BASF, and the "NEUPOL” (registered trademark) series manufactured by Sanyo Chemical Industries, Ltd. These polyoxyethylene-polyoxypropylene-polyoxyethylene block copolymers may be used alone or in combination of two or more types.
  • the amount of the first surfactant used is preferably 0.1 parts by mass or more, and more preferably 0.5 parts by mass or more, per 100 parts by mass of the aqueous monomer solution, from the viewpoint of facilitating dispersion of the first solvent in the aqueous monomer solution. Furthermore, adding an excessive amount of the first surfactant tends to result in a commensurate effect being less than economical, so the amount of the first surfactant used is preferably 15 parts by mass or less, and more preferably 10 parts by mass or less, per 100 parts by mass of the aqueous monomer solution.
  • the amount of the first surfactant used is preferably 0.1 to 15 parts by mass, and more preferably 0.5 to 10 parts by mass, per 100 parts by mass of the aqueous monomer solution.
  • the destination or timing of addition of the first surfactant there are no particular limitations on the destination or timing of addition of the first surfactant, as long as it is used during the preparation of the O/W emulsion.
  • the first solvent used in the O/W emulsion preparation step is not particularly limited as long as it is a hydrophobic organic solvent and can be dispersed in the aqueous monomer solution to obtain an O/W emulsion.
  • the phrase "the first solvent is dispersed in the aqueous monomer solution" means that the first solvent is contained in the aqueous monomer solution.
  • the first solvent is preferably a hydrocarbon organic solvent, such as one or more solvents selected from the group consisting of n-pentane, n-hexane, n-heptane, n-octane, cyclohexane, and methylcyclohexane.
  • n-pentane n-hexane
  • n-heptane n-octane
  • cyclohexane cyclohexane
  • methylcyclohexane methylcyclohexane.
  • one or more solvents selected from the group consisting of n-hexane, n-heptane, and cyclohexane are more preferred because they are easily available industrially, have stable quality, and are relatively inexpensive.
  • the O/W volume ratio in the O/W emulsion preparation step is 2.5 or more, where the O/W volume ratio is the volume (mL) of the first solvent/the volume (mL) of the aqueous monomer solution in the O/W emulsion.
  • the O/W volume ratio is preferably 2.5 or more, more preferably 2.8 or more, even more preferably 3.0 or more, even more preferably 3.2 or more, and even more preferably 5.0 or more. Furthermore, when the O/W volume ratio is a specific value or less, the emulsification is stabilized, the aqueous monomer solution can sufficiently encapsulate the first solvent, and the O/W emulsion can be successfully prepared. From this viewpoint, the O/W volume ratio is preferably 15.0 or less, and more preferably 10.0 or less.
  • the viscosity of the aqueous monomer solution at 25°C is preferably 500 mPa ⁇ s or more, more preferably 1000 mPa ⁇ s or more, from the viewpoint of increasing the porosity of the particles obtained by stabilizing the O/W emulsion.
  • the viscosity of the aqueous monomer solution can be adjusted, for example, using a polymeric thickener.
  • Preferably used polymeric thickeners include, for example, hydroxyethyl cellulose, carboxymethyl cellulose, guar gum, gum arabic, glucomannan, dextrin, polyvinyl alcohol, polyethylene oxide, and partially neutralized polyacrylic acid. This is because these polymeric thickeners can impart a relatively high viscosity to the aqueous monomer solution even when used in small amounts.
  • One or more types of polymeric thickeners can be used.
  • the method for preparing the O/W emulsion in the O/W emulsion preparation step is not particularly limited, and examples of the method include a method of mixing the aqueous monomer solution with a first surfactant and gradually adding a first solvent to the resulting mixture while stirring it.
  • the liquid temperature of the aqueous monomer solution when preparing the O/W emulsion is preferably 30°C or less, more preferably 15 to 25°C, from the viewpoint of the stability of the O/W emulsion.
  • a stirring device or the like may be used when preparing the O/W emulsion.
  • the stirring device may be, for example, a device capable of finely emulsifying, such as a homomixer, or a general stirring blade such as a paddle, propeller, or screw type. With either stirring device, the number and size of pores in the resulting particles can be appropriately adjusted by adjusting the stirring speed, etc.
  • the O/W/O emulsion preparation step of the production method of the present invention is a step of dispersing the O/W emulsion prepared in the O/W emulsion preparation step in a second solvent to obtain an O/W/O emulsion.
  • the second solvent contains a second surfactant.
  • the second solvent used in the O/W/O emulsion preparation step is a dispersion medium for the O/W emulsion.
  • the second solvent is a hydrophobic organic solvent and is not particularly limited as long as it can disperse the O/W emulsion to obtain an O/W/O emulsion.
  • the second solvent is preferably a hydrocarbon organic solvent, such as one or more solvents selected from the group consisting of n-pentane, n-hexane, n-heptane, n-octane, cyclohexane, and methylcyclohexane. Of these, one or more solvents selected from the group consisting of n-hexane, n-heptane, and cyclohexane are more preferred because they are easily available industrially, have stable quality, and are relatively inexpensive.
  • the first solvent and the second solvent may be the same type, or different types. It is preferable that the first solvent and the second solvent are the same type, as this makes it easier to reuse the solvent recovered in the drying process described below.
  • the second surfactant examples include sucrose fatty acid esters, (poly)glycerin 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, alkylaryl formaldehyde 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
  • the second surfactant is preferably at least one selected from the group consisting of sucrose fatty acid esters, sorbitan fatty acid esters, sorbitol fatty acid esters, and polyglycerin fatty acid esters, with sucrose fatty acid esters being more preferred due to their superior safety.
  • the amount of the second surfactant used is preferably 0.5 parts by mass or more, more preferably 1 part by mass or more, per 100 parts by mass of the aqueous monomer solution, from the viewpoint of ensuring stability during polymerization in the polymerization step described below. Furthermore, the amount of the second surfactant used is preferably 10 parts by mass or less, more preferably 5 parts by mass or less, per 100 parts by mass of the aqueous monomer solution. This is because adding an excessive amount of the second surfactant does not provide a commensurate effect and tends to be uneconomical. From these viewpoints, the amount of the second surfactant is preferably 0.5 to 10 parts by mass, more preferably 1 to 5 parts by mass, per 100 parts by mass of the aqueous monomer solution.
  • the method for preparing the O/W/O emulsion in the O/W/O emulsion preparation step is not particularly limited.
  • the method may include adding the O/W emulsion to the second solvent while stirring the emulsion by a liquid-transfer device such as a tube pump.
  • the device used for stirring is not particularly limited, and for example, a paddle-type stirring blade used for stirring in a flask can be used.
  • the polymerization step in the production method of the present invention is a step of preparing an organic porous material by polymerizing the monomers contained in the aqueous monomer solution in the O/W/O emulsion prepared in the O/W/O emulsion preparation step.
  • the reaction temperature at which the monomer polymerization reaction is carried out in the polymerization step cannot be determined in general terms, as it differs depending on factors such as the type of polymerization initiator used.
  • the reaction temperature is preferably 40 to 100°C, more preferably 50 to 80°C, from the viewpoint of promoting rapid polymerization and shortening the polymerization time, thereby improving economic efficiency, while also conducting the polymerization reaction without boiling the first or second organic solvent.
  • Suitable polymer dispersion stabilizers include maleic anhydride-modified polyethylene, maleic anhydride-modified polypropylene, maleic anhydride-modified ethylene-propylene copolymer, maleic anhydride-modified ethylene-propylene-diene terpolymer (EPDM), 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
  • polymer dispersion stabilizers include 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.
  • the polymer dispersion stabilizer may be one type, or a mixture of two or more types. Furthermore, these polymer dispersion stabilizers may be used in combination with the second surfactant.
  • the amount of the polymer dispersion stabilizer used is preferably 0.5 parts by mass or more, and more preferably 1 part by mass or more, per 100 parts by mass of the aqueous monomer solution. Furthermore, the amount of the polymer dispersion stabilizer used is preferably 10 parts by mass or less, and more preferably 5 parts by mass or less, per 100 parts by mass of the aqueous monomer solution. Adding an excessive amount of the polymer dispersion stabilizer may not provide a commensurate effect and may even be uneconomical.
  • the reaction time for the polymerization reaction is not particularly limited, but is usually about 0.5 to 3 hours.
  • the organic porous material is usually obtained in the form of hydrogel particles by the polymerization step.
  • the manufacturing method of the present invention may include a post-crosslinking step in which a post-crosslinking reaction is carried out on the organic porous material obtained by the polymerization step.
  • the post-crosslinking step post-crosslinks, i.e., surface-crosslinks, the crosslinked polymer constituting the organic porous material.
  • the post-crosslinking step yields an organic porous material formed from the surface-crosslinked crosslinked polymer and the continuous pores.
  • the organic porous material obtained by the post-crosslinking step is also referred to as the "organic porous material after surface-crosslinking.”
  • post-crosslinking agent a crosslinking agent capable of reacting with the reactive group in the crosslinked polymer can be used.
  • post-crosslinking agent examples include polyols such as ethylene glycol, propylene glycol, trimethylolpropane, glycerin, (poly)oxyethylene glycol, polyoxypropylene glycol, and polyglycerin; ether compounds with two or more glycidyl groups such as (poly)ethylene glycol diglycidyl ether, (poly)propylene glycol diglycidyl ether, and (poly)glycerin triglycidyl ether; and compounds with two or more reactive functional groups such as haloepoxy compounds such as epichlorohydrin, epibromohydrin, and ⁇ -methylepichlorohydrin. These can be used alone or in combination of two or more.
  • (poly)ethylene glycol diglycidyl ether is preferred.
  • the amount of post-crosslinking agent used cannot be determined in general terms, as it varies depending on the water content of the crosslinked polymer and the processing temperature. Note that the water content of the crosslinked polymer is the same as the water content of the organic porous material.
  • the post-crosslinking agent may be added at any time after the polymerization reaction is complete.
  • the addition time is preferably when the water content of the crosslinked polymer is 10% by mass or more, and more preferably when it is 20% by mass or more.
  • the addition time is preferably when the water content of the crosslinked polymer is 80% by mass or less, and more preferably when it is 65% by mass or less.
  • the post-crosslinking agent is preferably added when the water content of the crosslinked polymer is 10 to 80% by mass, and more preferably when it is 20 to 65% by mass.
  • the post-crosslinking step may include a dehydration treatment for removing water from the crosslinked polymer to adjust its water content before adding the post-crosslinking agent to the crosslinked polymer.
  • a known method may be used as the dehydration method. For example, a method of distilling off water and a hydrophobic organic solvent using an azeotropic distillation column may be used.
  • the water content and solid content in the hydrogel i.e., the solid content of the crosslinked polymer, can be calculated from the amounts of raw material compounds such as monomers charged in the polymerization reaction and the amount of water removed in the dehydration and drying processes described below.
  • the post-crosslinking reaction in the post-crosslinking step can be carried out, for example, by adding a solution of a post-crosslinking agent to a hydrogel adjusted to a predetermined water content obtained by subjecting a hydrogel after completion of the polymerization reaction to the dehydration treatment.
  • the solution of the post-crosslinking agent is, for example, a solution in which the post-crosslinking agent is dissolved in water or alcohol, and the concentration of the post-crosslinking agent is 0.5 to 50% by mass.
  • drying may be carried out immediately after adding the post-crosslinking agent solution, and it is more preferable to maintain the internal temperature at 50 to 90°C for 0.5 to 6 hours to promote the post-crosslinking reaction.
  • the internal temperature refers to the temperature of the hydrogel after adding the post-crosslinking agent solution, i.e., the temperature of the mixture of the post-crosslinking agent solution and the hydrogel.
  • the production method of the present invention may include a drying step of removing water and the hydrophobic organic solvent from the organic porous material obtained by the polymerization step or the surface-crosslinked organic porous material obtained by the post-crosslinking step.
  • Known methods can be used to remove the water and hydrophobic organic solvent. Examples of such methods include distilling off the water and hydrophobic organic solvent using an azeotropic distillation column, filtration, and drying under reduced pressure. Only one method may be used, or two or more methods may be combined. By carrying out the drying step, a water-absorbing material with a low moisture content and in a dry state can be successfully produced.
  • the production method of the present invention may include a chelating agent mixing step of mixing the aqueous monomer solution or the organic porous material with a chelating agent.
  • the organic porous material may be the organic porous material obtained in the polymerization step, or may be a surface-crosslinked organic porous material obtained after the post-crosslinking step.
  • the type and amount of chelating agent used in the chelating agent mixing step are not particularly limited, and the description regarding the type and content of chelating agent shown in [2. Water-absorbing material], section [2-4. Chelating agent] above can be used.
  • the production method of the present invention may include an inorganic fine particle mixing step of mixing the organic porous material with inorganic fine particles.
  • the organic porous material may be the organic porous material obtained in the polymerization step, or may be a surface-crosslinked organic porous material obtained after the post-crosslinking step.
  • the type and amount of inorganic fine particles used in the inorganic fine particle addition step are not particularly limited, and the description regarding the type and content of inorganic fine particles shown in [2. Water-absorbing material] section [2-5. Inorganic fine particles] above can be used.
  • the production method of the present invention may include a step of mixing the organic porous material with other additives.
  • the organic porous material may be the organic porous material obtained in the polymerization step, or may be a surface-crosslinked organic porous material obtained after the post-crosslinking step.
  • the production method of the present invention may include a recovery step of separating and recovering fine powder from the produced organic porous material.
  • the separated fine powder may be added to each step, such as the O/W emulsion preparation step and the O/W/O emulsion preparation step, for reuse.
  • One embodiment of the present invention may include the inventions set forth in [1] to [13] below.
  • a water-absorbing material comprising an organic porous material having a continuous skeleton formed by a crosslinked polymer mainly composed of structural units derived from (meth)acrylic acid (salt) and continuous pores, Centrifuge retention capacity (CRC) is 5 to 25 g/g; The bulk density is less than 0.3 g/ml, and A water-absorbing material, wherein the neutralization rate of the crosslinked polymer is less than 70 mol %.
  • Water separation rate [%] ⁇ (FSC [g/g] - CRC [g/g])/FSC [g/g] ⁇ x 100... (1)
  • [5] The water-absorbing material according to any one of [1] to [4], wherein the water-absorbing material contains a chelating agent.
  • a method for producing a water-absorbing material comprising an organic porous material having a continuous skeleton formed by a crosslinked polymer mainly composed of structural units derived from (meth)acrylic acid (salt) and continuous pores, an O/W emulsion preparation step of incorporating a first solvent into an aqueous monomer solution having a neutralization rate of less than 70 mol% in the presence of a first surfactant so that the volume ratio of the first solvent to the aqueous monomer solution is 2.5 or more to obtain an O/W emulsion; an O/W/O emulsion preparation step of dispersing the O/W emulsion in a second solvent to obtain an O/W/O emulsion; and a polymerization step of polymerizing the monomers contained in the aqueous monomer solution in the O/W/O emulsion to prepare an organic porous material;
  • a method for producing a water-absorbing material comprising:
  • the aqueous monomer solution contains a polymerization initiator, The method for producing a water-absorbing material according to [7], wherein the polymerization initiator is an azo-based initiator and/or a persulfate.
  • the aqueous monomer solution contains an internal crosslinking agent
  • a composite absorbent body comprising the water-absorbing material described in any one of [1] to [6] and water-absorbent resin particles.
  • CRC ⁇ Centrifuge holding capacity
  • ⁇ Bulk specific gravity> The water-absorbing material was poured into a cylindrical plastic container with a volume of 10 mL (inner diameter 2.5 cm) until it was piled high and spilled outside the container, and then the water-absorbing material was leveled off at the top of the container using a flat leveling rod. During this process, the container was worked on with as little vibration as possible to prevent the water-absorbing material from being packed tightly inside the container. Thereafter, the weight of the water-absorbing material packed into the container was calculated from the change (difference) in the weight of the container before and after filling it with the water-absorbing material. The bulk specific gravity (unit: g/mL) of the water-absorbing material was calculated by dividing this weight by the volume (10 mL) of the container.
  • a food additive was added to 1,000 parts by weight of a 0.90 wt % aqueous sodium chloride solution (physiological saline), and the liquid temperature was adjusted to 30° C. 50 ml of the physiological saline was measured and placed in a 100 m
  • the endpoint of the water absorption rate measurement was determined in accordance with the standards set forth in JIS K 7224-1996, "Explanation of Test Method for Water Absorption Rate of Super Absorbent Resins," and the time (vortex: seconds) until the sample absorbed the saline solution and covered the stirrer tip with the test liquid was measured as the water absorption rate (seconds).
  • FSC Free Swelling Ratio
  • ⁇ Separation rate> Using the CRC and FSC of the water-absorbent material, the water syneresis rate of the water-absorbent material was calculated based on the following formula (1).
  • Water separation rate [%] ⁇ (FSC [g/g] - CRC [g/g])/FSC [g/g] ⁇ x 100... (1) ⁇ pH>
  • the pH of the water-absorbing material was measured in accordance with NWSP 200.0. R2 (15). Specifically, 100 ml of a 0.90% by mass sodium chloride aqueous solution at 23 ° C was weighed into a beaker.
  • 0.5 g of water-absorbing material was added to the sodium chloride aqueous solution while stirring the sodium chloride aqueous solution in the beaker at 150 rpm using a cylindrical stirrer having a length of 40 mm and a diameter (diameter of the cross section perpendicular to the length of the cylinder) of 8 mm. Subsequently, the sodium chloride aqueous solution was stirred for 10 minutes to allow the water-absorbing material to swell. Thereafter, a pH electrode was inserted into the sodium chloride aqueous solution, and the pH was read when the value stabilized.
  • Mass average particle diameter (D50) The mass-average particle diameter (D50) of the water-absorbing material was measured in accordance with "(3) Mass-Average Particle Diameter (D50) and Logarithmic Standard Deviation ( ⁇ ) of Particle Diameter Distribution" described in columns 27 and 28 of U.S. Pat. No. 7,638,570.
  • the samples before and after the damage test were sieved through a JIS standard sieve with 150 ⁇ m openings, and the ratio of the fine powder that passed through the sieve to the test sample was taken as the amount of fine powder (wt%), and the increase in the amount of fine powder before and after the test (amount of fine powder after the test - amount of fine powder before the test) was calculated.
  • Example 1 Preparation of O/W Emulsion A 1000 mL four-neck separable flask (1) (hereinafter referred to as "flask (1)") equipped with a stirrer, a dropping funnel, a fluororesin tube for nitrogen gas injection, and a thermometer was prepared. 16.85 g of acrylic acid, 39.63 g of a 37% by mass aqueous solution of sodium acrylate, and 2.00 g of methylenebisacrylamide were charged into the flask (1). The neutralization rate of the acrylic acid (salt) was 40 mol%. Subsequently, 0.64 g of hydroxyethyl cellulose was added to the flask (1) and stirred.
  • Aqueous solution A was prepared by dissolving 2.27 g of polyoxyethylene-polyoxypropylene copolymer (manufactured by Asahi Denka Kogyo Co., Ltd., trade name: Adeka Pluronic F-108, mass average molecular weight: 15,500) in 21.61 g of ion-exchanged water. Furthermore, aqueous solution B was prepared by dissolving 0.05 g of 2,2'-azobis(2-methylpropionamidine) dihydrochloride in 2.59 g of ion-exchanged water.
  • Aqueous solution A and aqueous solution B were added to the flask (1), mixed, and dissolved to prepare an aqueous monomer solution.
  • 433.3 g (646 mL) of n-heptane was added dropwise to the aqueous monomer solution at a flow rate of 11 mL/min.
  • flask (2) Preparation of O/W/O Emulsion A 2000 mL four-neck separable flask (2) (hereinafter referred to as "flask (2)") equipped with a stirrer, a reflux condenser, a fluororesin tube for nitrogen gas injection, and a thermometer was prepared, and 670 g (1000 mL) of n-heptane was poured into the flask (2).
  • sucrose fatty acid ester manufactured by Mitsubishi Chemical Foods Corporation, product name: S-370
  • maleic anhydride-modified polyethylene manufactured by Mitsui Chemicals, Inc., product name: HI-WAX1105A
  • the solvent was removed from the slurry by filtering using a sieve with 125 ⁇ m openings to obtain a filtrate.
  • the filtrate was dried under reduced pressure at 60°C for 2 hours to produce 35 g of an organic porous material with a mass average particle size of 554 ⁇ m.
  • This organic porous material was designated Water Absorbent Material 1.
  • Example 2 Except for the changes shown in (i) and (ii) below, an organic porous material was produced by the same method as in Example 1.
  • the neutralization rate of the acrylic acid (salt) used in Example 2 was 50 mol %.
  • the produced organic porous material had a mass average particle diameter of 524 ⁇ m and a mass of 34 g.
  • This organic porous material was designated water absorbent material 2.
  • Example 3 Except for the changes shown in (iii) and (iv) below, an organic porous material was produced by the same method as in Example 2.
  • the neutralization rate of the acrylic acid (salt) used in Example 3 was 50 mol %, the same as in Example 2.
  • the produced organic porous material had a mass average particle diameter of 542 ⁇ m and a mass of 34 g.
  • This organic porous material was designated water absorbent material 3.
  • Example 4 Except for the changes shown in (v) and (vi) below, an organic porous material was produced by the same method as in Example 2.
  • the neutralization rate of the acrylic acid (salt) used in Example 4 was 50 mol%, the same as in Example 2.
  • the produced organic porous material had a mass average particle diameter of 478 ⁇ m and a mass of 33 g. This organic porous material was designated water absorbent material 4.
  • Example 5 Except for the changes shown in (vii) and (viii) below, an organic porous material was produced by the same method as in Example 1.
  • the neutralization rate of the acrylic acid (salt) used in Example 5 was 60 mol %.
  • the produced organic porous material had a mass average particle diameter of 488 ⁇ m and a mass of 35 g. This organic porous material was designated water absorbent material 5.
  • Example 6 The organic porous material obtained in Example 2 was subjected to the following steps (ix) and (x) to prepare an organic porous material.
  • (ix) 1.0 part by mass of pure water and 0.01 part by mass of diethylenetriaminepentaacetic acid trisodium salt (DTPA 3Na) were uniformly mixed with 100 parts by mass of the organic porous material obtained in Example 2.
  • the mixture was then heat-treated at 60°C for 45 minutes in a windless environment and crushed until it passed through a JIS standard sieve with an opening of 850 ⁇ m.
  • the produced organic porous material had a mass average particle diameter of 520 ⁇ m. This organic porous material was designated as water absorbent material 6.
  • the aqueous monomer solution and n-heptane did not emulsify during preparation of the O/W emulsion, resulting in phase separation, making it impossible to produce an organic porous material.
  • the resulting emulsion was quickly transferred to a reaction vessel, sealed, and left to stand at 60°C for 24 hours to polymerize the monomers in the emulsion.
  • the contents of the reaction vessel were removed and roughly crushed into 1 cm cubes.
  • the contents were then extracted with methanol to obtain an extract.
  • the extract was then dried under reduced pressure to obtain a dried product.
  • the resulting dried material was immersed in dichloroethane containing zinc bromide, then stirred at 40°C for 24 hours.
  • the dried material was then contacted with methanol, 4% hydrochloric acid, 4% aqueous sodium hydroxide solution, and water, in that order, to hydrolyze the dried material.
  • the resulting hydrolyzed material was dried, pulverized, and classified to obtain an organic porous material with a mass average particle size in the range of 500 to 850 ⁇ m.
  • This organic porous material was designated Comparative Water Absorbent Material 1.
  • the methods for producing the water-absorbent materials of Examples 1 to 6 have a neutralization rate of less than 70 mol% for the aqueous monomer solution and an O/W volume ratio of 2.5 or more for the O/W emulsion, satisfying the requirements for the production method of the present invention. Therefore, the methods for producing the water-absorbent materials of Examples 1 to 6 fall under the production method of the present invention.
  • the water-absorbent material of the present invention can be produced using the manufacturing method of the present invention.
  • Water Absorbent Materials 1 to 6 have a pH of 4.7 to 5.6, making them weakly acidic. This shows that Water Absorbent Materials 1 to 6 are better able to reduce skin irritation and other issues for users than conventional water absorbent materials. Furthermore, Water Absorbent Materials 1 to 6 have sufficiently small Vortex values and sufficiently high water release rates, making them excellent in both water absorption speed and water release rate.
  • the water-absorbent material of the present invention can reduce skin irritation and other issues in users more than conventional water-absorbent materials, and is superior in both water absorption speed and water separation rate. It was also found that the manufacturing method of the present invention can be used to manufacture the water-absorbent material.
  • Comparative Example 1 shows that with the manufacturing method of the present invention, by adjusting the neutralization rate of the aqueous monomer solution to less than 70 mol%, it is possible to produce a water-absorbent material even when the O/W volume ratio is 2.5 or higher.
  • the present invention can be preferably used in applications requiring less skin irritation and other issues for users than conventional absorbent materials, as well as high water absorption speed and high water release rate.
  • applications include use as a substitute for hydrophilic fibers such as pulp that are conventionally used in sanitary materials such as disposable diapers and sanitary napkins, incontinence pads such as absorbent shorts/pads, and breast pads, or as a water-absorbent polymer in the above-mentioned sanitary materials.
  • soil water retention agents include, for example, soil water retention agents, seedling raising sheets, seed coating materials, anti-condensation sheets, drip absorbents, freshness-preserving materials, disposable warmers, cooling bandanas, ice packs, medical waste liquid solidifying agents, soil surplus solidifying agents, water-damage preventing waste liquid gelling agents, water-absorbing sandbags, portable disaster toilets, compresses, thickeners for cosmetics, water-stopping materials for electrical and electronic materials and communication cables, gasket packing, sustained-release agents for fertilizers, various sustained-release agents (air disinfectants, air fresheners, etc.), pet sheets, cat litter, wound protection dressings, anti-condensation building materials, and oil moisture removers.

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  • Polymers & Plastics (AREA)
  • Analytical Chemistry (AREA)
  • Engineering & Computer Science (AREA)
  • Epidemiology (AREA)
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  • Heart & Thoracic Surgery (AREA)
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  • Solid-Sorbent Or Filter-Aiding Compositions (AREA)
  • Absorbent Articles And Supports Therefor (AREA)

Abstract

L'invention concerne un absorbant d'eau comprenant : un squelette continu qui est formé à partir d'un polymère réticulé ayant, en tant que composant principal, une unité structurale dérivée d'un acide (méth)acrylique (sel) et des pores continus. L'absorbant d'eau présente une capacité de rétention centrifuge (CRC) de 5 à 25 g/g et une densité apparente inférieure à 0,3 g/ml. Le taux de neutralisation du polymère réticulé est inférieur à 70 % en moles. Ledit absorbant d'eau peut mieux réduire la rugosité de la peau et similaire d'un utilisateur par rapport aux absorbants d'eau classiques, et présente une excellente vitesse d'absorption d'eau et un excellent taux de séparation d'eau.
PCT/JP2025/007127 2024-02-29 2025-02-28 Absorbant d'eau et procédé de fabrication d'absorbant d'eau Pending WO2025183162A1 (fr)

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Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS62106902A (ja) * 1985-11-02 1987-05-18 Lion Corp 多孔性ポリマ−の製造方法
JP2001011106A (ja) * 1999-06-30 2001-01-16 Mitsubishi Chemicals Corp 高吸水性樹脂の製造方法
JP2017185485A (ja) * 2016-03-31 2017-10-12 株式会社日本触媒 吸水剤及びその製造方法
JP2022175087A (ja) * 2021-05-12 2022-11-25 株式会社日本触媒 ポリ（メタ）アクリル酸（塩）系吸水性樹脂、及び吸収体

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS62106902A (ja) * 1985-11-02 1987-05-18 Lion Corp 多孔性ポリマ−の製造方法
JP2001011106A (ja) * 1999-06-30 2001-01-16 Mitsubishi Chemicals Corp 高吸水性樹脂の製造方法
JP2017185485A (ja) * 2016-03-31 2017-10-12 株式会社日本触媒 吸水剤及びその製造方法
JP2022175087A (ja) * 2021-05-12 2022-11-25 株式会社日本触媒 ポリ（メタ）アクリル酸（塩）系吸水性樹脂、及び吸収体

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