WO2016006133A1 - 吸水性樹脂の製造方法、吸水性樹脂、吸水剤、吸収性物品 - Google Patents
吸水性樹脂の製造方法、吸水性樹脂、吸水剤、吸収性物品 Download PDFInfo
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- WO2016006133A1 WO2016006133A1 PCT/JP2014/079246 JP2014079246W WO2016006133A1 WO 2016006133 A1 WO2016006133 A1 WO 2016006133A1 JP 2014079246 W JP2014079246 W JP 2014079246W WO 2016006133 A1 WO2016006133 A1 WO 2016006133A1
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- C08F—MACROMOLECULAR COMPOUNDS OBTAINED BY REACTIONS ONLY INVOLVING CARBON-TO-CARBON UNSATURATED BONDS
- C08F2/00—Processes of polymerisation
- C08F2/12—Polymerisation in non-solvents
- C08F2/16—Aqueous medium
- C08F2/20—Aqueous medium with the aid of macromolecular dispersing agents
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- C08F120/00—Homopolymers 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
- C08F120/02—Monocarboxylic acids having less than ten carbon atoms; Derivatives thereof
- C08F120/04—Acids; Metal salts or ammonium salts thereof
- C08F120/06—Acrylic acid; Methacrylic acid; Metal salts or ammonium salts thereof
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- 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
- A61F13/45—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 shape
- A61F13/49—Absorbent articles specially adapted to be worn around the waist, e.g. diapers
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- 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
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- A—HUMAN NECESSITIES
- A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
- A61L—METHODS OR APPARATUS FOR STERILISING MATERIALS OR OBJECTS IN GENERAL; DISINFECTION, STERILISATION OR DEODORISATION OF AIR; CHEMICAL ASPECTS OF BANDAGES, DRESSINGS, ABSORBENT PADS OR SURGICAL ARTICLES; MATERIALS FOR BANDAGES, DRESSINGS, ABSORBENT PADS OR SURGICAL ARTICLES
- A61L15/00—Chemical aspects of, or use of materials for, bandages, dressings or absorbent pads
- A61L15/16—Bandages, dressings or absorbent pads for physiological fluids such as urine or blood, e.g. sanitary towels, tampons
- A61L15/22—Bandages, dressings or absorbent pads for physiological fluids such as urine or blood, e.g. sanitary towels, tampons containing macromolecular materials
- A61L15/24—Macromolecular compounds obtained by reactions only involving carbon-to-carbon unsaturated bonds; Derivatives thereof
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- A—HUMAN NECESSITIES
- A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
- A61L—METHODS OR APPARATUS FOR STERILISING MATERIALS OR OBJECTS IN GENERAL; DISINFECTION, STERILISATION OR DEODORISATION OF AIR; CHEMICAL ASPECTS OF BANDAGES, DRESSINGS, ABSORBENT PADS OR SURGICAL ARTICLES; MATERIALS FOR BANDAGES, DRESSINGS, ABSORBENT PADS OR SURGICAL ARTICLES
- A61L15/00—Chemical aspects of, or use of materials for, bandages, dressings or absorbent pads
- A61L15/16—Bandages, dressings or absorbent pads for physiological fluids such as urine or blood, e.g. sanitary towels, tampons
- A61L15/42—Use of materials characterised by their function or physical properties
- A61L15/60—Liquid-swellable gel-forming materials, e.g. super-absorbents
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- C08F2/00—Processes of polymerisation
- C08F2/12—Polymerisation in non-solvents
- C08F2/16—Aqueous medium
- C08F2/18—Suspension polymerisation
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- C08F2/00—Processes of polymerisation
- C08F2/32—Polymerisation in water-in-oil emulsions
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- C08F2/00—Processes of polymerisation
- C08F2/44—Polymerisation in the presence of compounding ingredients, e.g. plasticisers, dyestuffs, fillers
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- C08F4/00—Polymerisation catalysts
- C08F4/04—Azo-compounds
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- C08F6/00—Post-polymerisation treatments
- C08F6/14—Treatment of polymer emulsions
- C08F6/18—Increasing the size of the dispersed particles
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- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
- C08J3/00—Processes of treating or compounding macromolecular substances
- C08J3/24—Crosslinking, e.g. vulcanising, of macromolecules
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- C08K—Use of inorganic or non-macromolecular organic substances as compounding ingredients
- C08K3/00—Use of inorganic substances as compounding ingredients
- C08K3/18—Oxygen-containing compounds, e.g. metal carbonyls
- C08K3/20—Oxides; Hydroxides
- C08K3/22—Oxides; Hydroxides of metals
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- C08K3/34—Silicon-containing compounds
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- C08K3/00—Use of inorganic substances as compounding ingredients
- C08K3/34—Silicon-containing compounds
- C08K3/36—Silica
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- 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
- A61F2013/530481—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 having superabsorbent materials, i.e. highly absorbent polymer gel materials
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- C08F2810/00—Chemical modification of a polymer
- C08F2810/20—Chemical modification of a polymer leading to a crosslinking, either explicitly or inherently
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- C08J2333/00—Characterised by the use of homopolymers or 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 of salts, anhydrides, esters, amides, imides, or nitriles thereof; Derivatives of such polymers
- C08J2333/02—Homopolymers or copolymers of acids; Metal or ammonium salts thereof
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- C08K3/18—Oxygen-containing compounds, e.g. metal carbonyls
- C08K3/20—Oxides; Hydroxides
- C08K3/22—Oxides; Hydroxides of metals
- C08K2003/2227—Oxides; Hydroxides of metals of aluminium
Definitions
- the present invention relates to a method for producing a water-absorbing resin constituting an absorbent body suitably used for sanitary materials such as disposable diapers and sanitary products, and also relates to a water-absorbing resin, a water-absorbing agent using the water-absorbing resin, and an absorbent article.
- the acrylic acid partially neutralized salt polymer cross-linked product has excellent water absorption ability, and since it is easy to industrially obtain acrylic acid as a raw material, the quality is constant. In addition, since it can be produced at low cost and has many advantages such as being less susceptible to spoilage and deterioration, it is regarded as a preferred water-absorbent resin.
- Patent Literature 1 a method of performing reverse-phase suspension polymerization using specific amounts of specific polymer protective colloids and surfactants (Patent Literature) 1), a method in which reverse phase suspension polymerization is performed in two or more stages (see Patent Document 2), and reverse phase suspension polymerization is performed in the presence of ⁇ -1,3-glucans to obtain a water-absorbing resin.
- Patent Document 3 a method of performing a crosslinking reaction by adding a crosslinking agent to the obtained water-absorbent resin
- Patent Document 3 a method of performing reverse-phase suspension polymerization using a specific amount of a persulfate as a polymerization initiator
- Patent Document 5 a method in which a water-absorbing resin precursor is obtained by aqueous solution polymerization in the presence of phosphorous acid and / or a salt thereof, and then the water-absorbing resin precursor and a surface cross-linking agent are mixed and heated
- Patent Document 5 a method of performing a crosslinking reaction by adding a crosslinking agent to the obtained water-absorbent resin
- Patent Document 3 a method of performing reverse-phase suspension polymerization using a specific amount of a persulfate as a polymerization initiator
- Patent Document 5 a method in which a water-absorbing resin precursor is obtained by aqueous solution polymerization in the presence of phosphorous acid and / or a salt thereof, and
- the water-absorbent resin obtained by these methods does not necessarily satisfy the performance such as the high water absorption ability and the excellent water absorption speed described above, and there is still room for improvement.
- the water absorbent resin when the water absorbent resin having low diffusibility of the absorbent body is used, the water absorbent resin locally absorbs the absorbent liquid near the supply position of the absorbent liquid and swells. As the water-absorbent resin becomes dense, liquid blocking often occurs. In this case, since the diffusibility is further inhibited by the gelled water absorbent resin, the amount of the liquid to be absorbed tends to increase.
- the present invention has been proposed in view of the actual situation as described above, and has a moderate BET specific surface area for a water-absorbent resin used for sanitary materials, and improves the performance of the absorber when used as an absorber. It is an object of the present invention to provide a method for producing a water-absorbent resin, and an absorbent article using the water-absorbent resin, a water-absorbing agent containing the same, and an absorber containing the same.
- the inventors of the present invention have made extensive studies in order to solve the above-described problems.
- water-soluble ethylenically unsaturated monomer was subjected to two or more stages of reversed-phase suspension polymerization in a hydrocarbon dispersion medium in the presence of an azo compound and peroxide.
- the BET specific surface area of the secondary particles formed by agglomerating the primary particles obtained is controlled to a specific range, and as a result
- the present inventors have found that the performance of an absorbent body using the water-absorbent resin is improved and completed the present invention. That is, the present invention provides the following.
- a water-soluble ethylenically unsaturated monomer is mixed in a hydrocarbon dispersion medium in the presence of at least an azo compound, a peroxide, and an internal cross-linking agent.
- the amount of the internal crosslinking agent used in the range of 0.015 to 0.150 mmol per mole of the water-soluble ethylenically unsaturated monomer used in the polymerization of the first stage is a method for producing a water-absorbing resin characterized by controlling the BET specific surface area of secondary particles formed by agglomerating primary particles obtained by adjusting and polymerizing.
- the present invention is the amount (mol) of the internal cross-linking agent used per mol of the water-soluble ethylenically unsaturated monomer in the second and subsequent polymerizations.
- the water-absorbing resin is 90% or less of the amount (mole) of the internal cross-linking agent used in the first stage polymerization with respect to 1 mol of the water-soluble ethylenically unsaturated monomer used in the first stage polymerization. Is the method.
- the present invention provides a BET specific surface area measured by classifying secondary particles formed by agglomeration of primary particles to 300 to 400 ⁇ m. This is a method for producing a water-absorbent resin controlled to be less than 0.03 m 2 / g.
- the present invention relates to a water-absorbing resin obtained by polymerizing a water-soluble ethylenically unsaturated monomer in the presence of an internal cross-linking agent, wherein the water-absorbing resin has a physiological water absorption rate of 40 to 40. 80 seconds, the mass ratio of the particles of 150 to 850 ⁇ m occupying the ratio of the entire water absorbent resin is 85 mass% or more, the mass ratio of the particles of 300 to 400 ⁇ m is 20 mass% or more, and 300 to 400 ⁇ m.
- the water-absorbent resin is characterized in that the BET specific surface area measured by classification is less than 0.03 m 2 / g.
- the present invention is the water absorbent resin according to the invention according to (4), wherein the median particle diameter of the water absorbent resin is 200 to 600 ⁇ m.
- the present invention is a water-absorbing agent obtained by blending an inorganic fine powder with the water-absorbent resin described in the above (4) or (5).
- the present invention is an absorbent article using the absorbent body including the water-absorbent resin described in (4) or (5).
- the present invention is an absorbent article using the absorbent body containing the water-absorbing agent described in (6) above.
- a water absorbent resin having a BET specific surface area in an appropriate range can be obtained.
- the water-absorbent resin according to the present invention has a water absorption speed that is one of the factors for the diffusibility and reversion of the liquid to be absorbed in the absorber without increasing the particle diameter of the particles, and is moderate.
- This is a water-absorbent resin having a BET specific surface area in a wide range.
- a method for producing a water absorbent resin according to the present invention is a method for producing a water absorbent resin by subjecting a water-soluble ethylenically unsaturated monomer to reverse phase suspension polymerization in a hydrocarbon dispersion medium, in the presence of an internal crosslinking agent. And reverse-phase suspension polymerization in the presence of an azo compound and a peroxide. This will be described in more detail below.
- water-soluble ethylenically unsaturated monomer examples include (meth) acrylic acid (in the present specification, “acryl” and “methacryl” are collectively referred to as “(meth) acryl”; the same shall apply hereinafter) and 2- (meth) acrylamide-2-methylpropanesulfonic acid and salts thereof; (meth) acrylamide, N, N-dimethyl (meth) acrylamide, 2-hydroxyethyl (meth) acrylate, N-methylol (meth) Nonionic monomers such as acrylamide and polyethylene glycol mono (meth) acrylate; amino groups such as N, N-diethylaminoethyl (meth) acrylate, N, N-diethylaminopropyl (meth) acrylate and diethylaminopropyl (meth) acrylamide Examples thereof include unsaturated monomers and
- water-soluble ethylenically unsaturated monomers (meth) acrylic acid or a salt thereof, (meth) acrylamide, and N, N-dimethylacrylamide are preferable from the viewpoint of industrial availability. , (Meth) acrylic acid and salts thereof are more preferred.
- these water-soluble ethylenically unsaturated monomers may be used independently and may be used in combination of 2 or more types.
- acrylic acid and its salts are widely used as raw materials for water-absorbing resins, and these acrylic acid partial neutralized salts are used by copolymerizing the other water-soluble ethylenically unsaturated monomers described above.
- the partially neutralized acrylic acid salt is preferably used as a main water-soluble ethylenically unsaturated monomer in an amount of 70 to 100 mol% based on the total water-soluble ethylenically unsaturated monomer.
- the water-soluble ethylenically unsaturated monomer is dispersed in a hydrocarbon dispersion medium in an aqueous solution state and subjected to reverse phase suspension polymerization.
- the dispersion efficiency in the hydrocarbon dispersion medium can be increased.
- the concentration of the water-soluble ethylenically unsaturated monomer in this aqueous solution is preferably in the range of 20% by mass to below the saturated concentration.
- the monomer concentration is more preferably 55% by mass or less, further preferably 50% by mass or less, and further preferably 45% by mass or less.
- the concentration of the water-soluble ethylenically unsaturated monomer is more preferably 25% by mass or more, further preferably 28% by mass or more, and 30% by mass. More preferably, it is more than the above.
- the acid group is previously alkaline if necessary. You may use what was neutralized with the neutralizing agent.
- alkaline neutralizer include alkali metal salts such as sodium hydroxide, sodium carbonate, sodium hydrogen carbonate, potassium hydroxide, and potassium carbonate; ammonia and the like. These alkaline neutralizers may be used in the form of an aqueous solution in order to simplify the neutralization operation.
- the alkaline neutralizer mentioned above may be used independently, and may be used in combination of 2 or more types.
- the degree of neutralization of the water-soluble ethylenically unsaturated monomer with the alkaline neutralizing agent is 10 to 100 mol% as the degree of neutralization for all acid groups of the water-soluble ethylenically unsaturated monomer. It is preferably 30 to 90 mol%, more preferably 40 to 85 mol%, still more preferably 50 to 80 mol%.
- hydrocarbon dispersion medium examples include those having 6 to 8 carbon atoms such as n-hexane, n-heptane, 2-methylhexane, 3-methylhexane, 2,3-dimethylpentane, 3-ethylpentane, and n-octane.
- Aliphatic hydrocarbons cyclohexane, methylcyclohexane, cyclopentane, methylcyclopentane, trans-1,2-dimethylcyclopentane, cis-1,3-dimethylcyclopentane, trans-1,3-dimethylcyclopentane, etc.
- Aromatic hydrocarbons such as benzene, toluene and xylene.
- hydrocarbon dispersion media n-hexane, n-heptane, and cyclohexane are particularly preferably used because they are easily available industrially, have stable quality, and are inexpensive.
- These hydrocarbon dispersion media may be used alone or in combination of two or more.
- a suitable result can be obtained by using a commercially available product such as Exol heptane (manufactured by ExxonMobil: containing 75 to 85% by mass of hydrocarbon of heptane and its isomer). be able to.
- the amount of the hydrocarbon dispersion medium used is that from the viewpoint of uniformly dispersing the water-soluble ethylenically unsaturated monomer and facilitating control of the polymerization temperature, the first stage water-soluble ethylenically unsaturated monomer
- the amount is preferably 100 to 1500 parts by mass, more preferably 200 to 1400 parts by mass with respect to 100 parts by mass.
- the reverse phase suspension polymerization is performed in two or more stages, and the above-mentioned first stage polymerization means the first stage polymerization reaction in the multistage polymerization (the same applies hereinafter). .
- a dispersion stabilizer In the reverse phase suspension polymerization, a dispersion stabilizer can be used in order to improve the dispersion stability of the water-soluble ethylenically unsaturated monomer in the hydrocarbon dispersion medium. As the dispersion stabilizer, a surfactant can be used.
- surfactant examples include sucrose fatty acid ester, polyglycerin fatty acid ester, sorbitan fatty acid ester, polyoxyethylene sorbitan fatty acid ester, polyoxyethylene glycerin fatty acid ester, sorbitol fatty acid ester, polyoxyethylene sorbitol fatty acid ester, polyoxyethylene Alkyl ether, polyoxyethylene alkylphenyl ether, polyoxyethylene castor oil, polyoxyethylene hydrogenated castor oil, alkylallyl formaldehyde condensed polyoxyethylene ether, polyoxyethylene polyoxypropylene block copolymer, polyoxyethylene polyoxypropyl alkyl ether, Polyethylene glycol fatty acid ester, alkyl glucoside, N-alkyl gluconami , Polyoxyethylene fatty acid amides, polyoxyethylene alkyl amines, phosphoric esters of polyoxyethylene alkyl ethers, can be used phosphoric acid ester of polyoxyethylene alkyl ary
- sorbitan fatty acid ester sorbitan fatty acid ester, polyglycerin fatty acid ester, and sucrose fatty acid ester are preferably used from the viewpoint of dispersion stability of the monomer.
- These surfactants may be used alone or in combination of two or more.
- the amount of the surfactant used is preferably 0.1 to 30 parts by mass, preferably 0.3 to 20 parts per 100 parts by mass of the water-soluble ethylenically unsaturated monomer in the first stage. More preferably, it is part by mass.
- a polymer dispersant may be used in combination with the surfactant described above.
- polymeric dispersant examples include maleic anhydride-modified polyethylene, maleic anhydride-modified polypropylene, maleic anhydride-modified ethylene / propylene copolymer, maleic anhydride-modified EPDM (ethylene / propylene / diene / terpolymer), and anhydrous.
- maleic acid-modified polybutadiene maleic anhydride / ethylene copolymer, maleic anhydride / propylene copolymer, maleic anhydride / ethylene / propylene copolymer, maleic anhydride / butadiene copolymer, polyethylene, polypropylene, ethylene / propylene
- the copolymer include oxidized polyethylene, oxidized polypropylene, oxidized ethylene / propylene copolymer, ethylene / acrylic acid copolymer, ethyl cellulose, and ethyl hydroxyethyl cellulose.
- polymeric dispersants in particular, from the viewpoint of dispersion stability of the monomer, 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, oxidized ethylene / propylene copolymer It is preferable to use a polymer. These polymer dispersants may be used alone or in combination of two or more.
- the amount of the polymeric dispersant used is preferably 0.1 to 30 parts by mass, and preferably 0.3 to 20 parts per 100 parts by mass of the water-soluble ethylenically unsaturated monomer in the first stage. More preferably, it is part by mass.
- Internal cross-linking agent In the method for producing a water absorbent resin according to the present invention, in the presence of the internal cross-linking agent, the amount of the internal cross-linking agent used during the first stage polymerization is adjusted to a specific range, and a water-soluble ethylenically unsaturated monomer. It is characterized by conducting reverse phase suspension polymerization of the body.
- Examples of the internal crosslinking agent include those capable of crosslinking the polymer of the water-soluble ethylenically unsaturated monomer to be used.
- (poly) ethylene glycol [“(poly)” is prefixed with “poly”. It means the case with and without. The same shall apply hereinafter), (poly) propylene glycol, 1,4-butanediol, trimethylolpropane, diols such as (poly) glycerin, polyols such as triol, and (meth) acrylic acid, maleic acid, fumaric acid, etc.
- Unsaturated polyesters obtained by reacting with acids bisacrylamides such as N, N-methylenebisacrylamide; di (meth) acrylates or tris obtained by reacting polyepoxides with (meth) acrylic acid (Meth) acrylic acid esters; di (meth) acrylic acid carbamyl esters obtained by reacting polyisocyanates such as tolylene diisocyanate and hexamethylene diisocyanate with hydroxyethyl (meth) acrylate; allylated starch, allyl Cellulose, diallyl phthalate, N, Compounds having two or more polymerizable unsaturated groups such as', N ′′ -triallyl isocyanate, divinylbenzene; (poly) ethylene glycol diglycidyl ether, (poly) propylene glycol diglycidyl ether, (poly) glycerin diglycidyl Polyglycidyl compounds such as diglycidyl compounds such as ether and t
- polyglycidyl compounds are preferably used, diglycidyl ether compounds are more preferably used, (poly) ethylene glycol diglycidyl ether, (poly) propylene glycol diglycidyl ether, (poly) glycerin. It is particularly preferred to use diglycidyl ether.
- diglycidyl ether compounds may be used alone or in combination of two or more.
- the amount of the internal cross-linking agent used in the first stage polymerization is selected from the viewpoint that the obtained polymer exhibits excellent water absorption performance by appropriate cross-linking.
- the amount is 0.015 mmol or more, preferably 0.020 mmol or more, and more preferably 0.025 mmol or more with respect to 1 mol of the saturated monomer.
- the amount of the internal crosslinking agent used in the first stage polymerization is 0.150 mmol or less relative to 1 mol of the water-soluble ethylenically unsaturated monomer used in the first stage polymerization. It is preferably 120 mmol or less, and more preferably 0.100 mmol or less.
- the amount of the internal crosslinking agent used in the first stage polymerization is 0.015 to 0.150 mmol with respect to 1 mol of the water-soluble ethylenically unsaturated monomer in the first stage polymerization. 0.020 to 0.120 mmol, and more preferably 0.025 to 0.100 mmol.
- the amount (mole) of the internal crosslinking agent used in 1 mol of the water-soluble ethylenically unsaturated monomer in the second and subsequent stages is used in the first stage polymerization of the internal crosslinking agent used in the first stage polymerization.
- the amount used (mol) is preferably 90% or less of the amount (mol) used relative to 1 mol of the water-soluble ethylenically unsaturated monomer, more preferably 10-85%.
- “in the presence of an azo compound and a peroxide” does not necessarily mean that the azo compound and the peroxide coexist at the start of the polymerization reaction. It means a state in which the other compound is present while the monomer conversion by cleavage is less than 10%, but both of them in an aqueous solution containing a water-soluble ethylenically unsaturated monomer before the start of the polymerization reaction. It is preferable that they coexist with each other.
- the azo compound and the peroxide may be added to the polymerization reaction system through separate flow paths, or may be sequentially added to the polymerization reaction system through the same flow path.
- the form of the azo compound and peroxide used may be a powder or an aqueous solution.
- examples of the azo compound include 1- ⁇ (1-cyano-1-methylethyl) azo ⁇ formamide, 2,2′-azobis [2- (N-phenylamidino) propane] dihydrochloride, 2,2'-azobis ⁇ 2- [N- (4-chlorophenyl) amidino] propane ⁇ dihydrochloride, 2,2'-azobis ⁇ 2- [N- (4-hydroxyphenyl) amidino] propane ⁇ dihydrochloride 2,2′-azobis [2- (N-benzylamidino) propane] dihydrochloride, 2,2′-azobis [2- (N-allylamidino) propane] dihydrochloride, 2,2′-azobis ( 2-amidinopropane) dihydrochloride, 2,2'-azobis ⁇ 2- [N- (2-hydroxyethyl) amidino] propane ⁇ dihydrochloride, 2,2'-azobis [2- (5-methyl-2 -Imidazolin-2-yl) prop
- peroxide examples include persulfates such as potassium persulfate, ammonium persulfate, and sodium persulfate; methyl ethyl ketone peroxide, methyl isobutyl ketone peroxide, di-t-butyl peroxide, t-butyl cumyl peroxide, t And peroxides such as -butyl peroxyacetate, t-butyl peroxyisobutyrate, t-butyl peroxypivalate, and hydrogen peroxide.
- persulfates such as potassium persulfate, ammonium persulfate, and sodium persulfate
- methyl ethyl ketone peroxide methyl isobutyl ketone peroxide
- di-t-butyl peroxide di-t-butyl peroxide
- t-butyl cumyl peroxide t
- t And peroxides such as -butyl per
- potassium persulfate, ammonium persulfate, sodium persulfate, and hydrogen peroxide are preferably used from the viewpoint of obtaining a water-absorbing resin having excellent water absorption performance. It is more preferable to use ammonium sulfate or sodium persulfate. These peroxides may be used alone or in combination of two or more.
- the amount of the azo compound and the peroxide used is preferably 0.00005 mol or more per 1 mol of the water-soluble ethylenically unsaturated monomer from the viewpoint of shortening the polymerization reaction time. More preferably, it is 0.0001 mol or more. Moreover, from a viewpoint of preventing a rapid polymerization reaction, it is preferable that it is 0.005 mol or less with respect to 1 mol of water-soluble ethylenically unsaturated monomers, and it is more preferable that it is 0.001 mol or less.
- the amount of the azo compound and peroxide used is preferably 40% by weight or more of the total amount of the azo compound and peroxide used, and preferably 50% by weight or more. It is more preferable to set it as a ratio, it is more preferable to set it as the ratio which is 60 mass% or more, and it is more preferable to set it as the ratio which is 70 mass% or more.
- the proportion of the azo compound is preferably 95% by mass or less, more preferably 90% by mass or less, of the total amount of the azo compound and peroxide used, more preferably 85% by mass or less. It is more preferable to set it as the ratio which is, and it is still more preferable to set it as the ratio which is 80 mass% or less. Further, the mass ratio range (azo compound: peroxide) is preferably 8:12 to 19: 1.
- reverse phase suspension polymerization may be performed by adding other components to the water-soluble ethylenically unsaturated monomer as desired.
- a chain transfer agent, a thickener, and other various additives can be added.
- the water-soluble ethylenically unsaturated monomer may be polymerized in the presence of a chain transfer agent.
- examples of the chain transfer agent include thiols such as ethanethiol, propanethiol, and dodecanethiol; thiolic acids such as thioglycolic acid, thiomalic acid, dimethyldithiocarbamic acid, diethyldithiocarbamic acid, and salts thereof; and isopropanol Secondary salts of phosphorous acid, orthophosphoric acid salts such as phosphorous acid, disodium phosphite, dipotassium phosphite, diammonium phosphite, sodium hydrogen phosphite, potassium hydrogen phosphite, Phosphorous acid compounds such as acid salts of phosphorous acid such as ammonium hydrogenphosphate; orthophosphoric acid salts such as phosphoric acid, sodium phosphate, potassium phosphate, ammonium phosphate, sodium dihydrogen phosphate, diphosphate Potassium hydrogen, ammonium dihydrogen phosphate, disodium hydrogen
- Examples thereof include phosphoric acid compounds; pyrophosphoric acid, tripolyphosphoric acid, polyphosphoric acid and salts thereof; trimethyl phosphate, nitrilotrimethylene triphosphonic acid, and the like.
- chain transfer agents may be used alone or in combination of two or more. Moreover, you may use the hydrate as a chain transfer agent.
- the amount of the chain transfer agent used is preferably 0.00001 to 0.0005 mol, and preferably 0.000025 to 0.00012 mol, with respect to 1 mol of the water-soluble ethylenically unsaturated monomer. More preferred.
- reverse phase suspension polymerization may be performed by adding a thickener to an aqueous solution containing a water-soluble ethylenically unsaturated monomer.
- a thickener By adjusting the aqueous solution viscosity by adding a thickener as described above, it is also possible to control the median particle diameter obtained in the reverse phase suspension polymerization.
- the thickener for example, hydroxyethyl cellulose, hydroxypropyl cellulose, methyl cellulose, carboxymethyl cellulose, polyacrylic acid, polyacrylic acid (partial) neutralized product, polyethylene glycol, polyacrylamide, polyethyleneimine, dextrin, alginic acid Sodium, polyvinyl alcohol, polyvinyl pyrrolidone, polyethylene oxide and the like can be used.
- polymerization is the same, there exists a tendency for the median particle diameter of the particle
- Reverse phase suspension polymerization In carrying out the reverse phase suspension polymerization, for example, an aqueous monomer solution containing a water-soluble ethylenically unsaturated monomer is used as a hydrocarbon dispersion medium in the presence of a surfactant and / or a polymeric dispersant. Disperse. At this time, as long as the polymerization reaction is not started, the addition time of the surfactant and the polymer dispersant may be before or after the dispersion of the monomer aqueous solution.
- reverse-phase suspension polymerization is performed in two or more stages.
- a water absorbent resin containing secondary particles in which primary particles are aggregated is produced by performing polymerization in two or more stages. It is more preferable to carry out in 2 to 3 stages from the viewpoint of increasing productivity.
- a water-soluble ethylenically unsaturated monomer is added to the reaction mixture obtained in the first-stage polymerization reaction after the first-stage reverse-phase suspension polymerization.
- the body can be added and mixed to carry out reverse phase suspension polymerization of the second and subsequent stages in the same manner as in the first stage.
- the reverse phase suspension polymerization in each stage after the second stage in addition to the water-soluble ethylenically unsaturated monomer, the internal crosslinking agent, the azo compound and the peroxide described above are added to each of the second stage and subsequent stages.
- the reaction temperature of the polymerization reaction is from 20 to 110 ° C. from the viewpoint of allowing the polymerization to proceed rapidly and shortening the polymerization time, thereby improving the economy and easily removing the heat of polymerization to allow the reaction to proceed smoothly. It is preferable that the temperature is 40 to 90 ° C.
- the reaction time is preferably 0.5 to 4 hours.
- the stirring operation of the monomer aqueous solution can be performed using various known stirring blades.
- a stirring blade for example, a propeller blade, a paddle blade, an anchor blade, a turbine blade, a fiddler blade, a ribbon blade, a full zone blade (manufactured by Shinko Pantech Co., Ltd.), a max blend blade (Sumitomo Heavy Industries, Ltd.) Product), Supermix wing (manufactured by Satake Chemical Machinery Co., Ltd.) and the like.
- the primary particles obtained in the first-phase reversed-phase suspension polymerization By controlling the median particle size, it is possible to efficiently control the BET specific surface area of the secondary particles formed by aggregation of the primary particles. If the stirring blades are of the same type, the median particle diameter of the primary particles obtained tends to decrease as the stirring speed is increased.
- Post-crosslinking step> in the method for producing a water-absorbing resin according to the present invention, as described above, the water-soluble ethylenically unsaturated monomer is reversed in the presence of an internal crosslinking agent and in the presence of an azo compound and a peroxide.
- Post-crosslinking with a post-crosslinking agent is preferred for a hydrogel having an internal cross-linked structure obtained by phase suspension polymerization.
- the cross-linking density near the surface of the water-absorbent resin is increased, and the water absorption capacity under load, the water absorption speed, It is possible to obtain a water-absorbent resin particularly improved for hygiene material applications with improved performance such as gel strength.
- examples of the post-crosslinking agent include compounds having two or more reactive functional groups.
- polyols such as ethylene glycol, propylene glycol, 1,4-butanediol, trimethylolpropane, glycerin, polyoxyethylene glycol, polyoxypropylene glycol, polyglycerin; (poly) ethylene glycol diglycidyl ether, (poly) Polyglycidyl compounds such as glycerin diglycidyl ether, (poly) glycerin triglycidyl ether, trimethylolpropane triglycidyl ether, (poly) propylene glycol polyglycidyl ether, (poly) glycerol polyglycidyl ether; epichlorohydrin, epibromohydrin, Haloepoxy compounds such as ⁇ -methylepichlorohydrin; isoforms such as 2,4-tolylene diisocyanate and he
- post-crosslinking agents (poly) ethylene glycol diglycidyl ether, (poly) glycerin diglycidyl ether, (poly) glycerin triglycidyl ether, trimethylolpropane triglycidyl ether, (poly) propylene glycol polyglycidyl ether, ( Polyglycidyl compounds such as poly) glycerol polyglycidyl ether are particularly preferred. These post-crosslinking agents may be used alone or in combination of two or more.
- the amount of the post-crosslinking agent used is preferably 0.00001 to 0.01 mol, preferably 0.00005 to 0.005 mol, based on 1 mol of the total amount of the water-soluble ethylenically unsaturated monomer used in the polymerization.
- the amount is more preferably 005 mol, and further preferably 0.0001 to 0.002 mol.
- the post-crosslinking agent may be added as it is or may be added as an aqueous solution, but if necessary, it may be added as a solution using a hydrophilic organic solvent as a solvent.
- a hydrophilic organic solvent include lower alcohols such as methyl alcohol, ethyl alcohol, n-propyl alcohol and isopropyl alcohol; ketones such as acetone and methyl ethyl ketone; ethers such as diethyl ether, dioxane and tetrahydrofuran; N, N Amides such as dimethylformamide; sulfoxides such as dimethyl sulfoxide.
- These hydrophilic organic solvents may be used alone or in combination of two or more or as a mixed solvent with water.
- the post-crosslinking agent may be added after the polymerization reaction of the water-soluble ethylenically unsaturated monomer is almost completed. It is preferably added in the presence of water in the range of 400 parts by weight, more preferably in the presence of water in the range of 5 to 200 parts by weight, and added in the presence of water in the range of 10 to 100 parts by weight. Is more preferable, and it is even more preferable to add in the presence of water in the range of 20 to 60 parts by mass.
- the amount of moisture means the total amount of moisture contained in the polymerization reaction system and moisture used as necessary when adding the post-crosslinking agent.
- the reaction temperature in the post-crosslinking reaction is preferably 50 to 250 ° C., more preferably 60 to 180 ° C., further preferably 60 to 140 ° C., and particularly preferably 70 to 120 ° C. preferable.
- the reaction time for the post-crosslinking reaction is preferably 1 to 300 minutes, more preferably 5 to 200 minutes.
- a drying step of removing water, hydrocarbon dispersion medium, and the like by distillation by adding energy such as heat from the outside. May be included.
- dehydration is performed from a hydrous gel after reversed-phase suspension polymerization
- water and the hydrocarbon dispersion medium are temporarily removed from the system by azeotropic distillation by heating the system in which the hydrogel is dispersed in the hydrocarbon dispersion medium. Distill off. At this time, if only the distilled hydrocarbon dispersion medium is returned to the system, continuous azeotropic distillation is possible.
- the temperature in the system during drying is maintained below the azeotropic temperature of the hydrocarbon dispersion medium, which is preferable from the standpoint that the resin is hardly deteriorated. Subsequently, water and hydrocarbon dispersion medium are distilled off to obtain water-absorbent resin particles.
- the treatment conditions of the drying step after the polymerization and adjusting the amount of dehydration it is possible to control various performances of the resulting water-absorbent resin.
- the drying treatment by distillation may be performed under normal pressure or under reduced pressure. Moreover, you may carry out under airflow, such as nitrogen, from a viewpoint of improving drying efficiency.
- the drying temperature is preferably 70 to 250 ° C., more preferably 80 to 180 ° C., further preferably 80 to 140 ° C., and more preferably 90 to A temperature of 130 ° C. is particularly preferable.
- the drying temperature is preferably 40 to 160 ° C., more preferably 50 to 110 ° C.
- the drying step by distillation described above is performed after the completion of the cross-linking step. Like that. Or you may make it perform a post-crosslinking process and a drying process simultaneously.
- a chelating agent such as a chelating agent, a reducing agent, an oxidizing agent, an antibacterial agent, and a deodorizing agent after superposition
- polymerization during drying, or after drying with respect to a water absorbing resin as needed.
- the water-absorbent resin according to the present invention is obtained by the above-described method, specifically, obtained by polymerizing while adjusting the amount of the internal crosslinking agent during the first stage polymerization, The BET specific surface area is controlled in an appropriate range, and the absorbent article using the water absorbent resin has excellent absorption performance.
- the water-absorbent resin according to the present invention is a water-absorbent resin obtained by polymerizing a water-soluble ethylenically unsaturated monomer in the presence of an internal cross-linking agent, and includes a physiological salt of the water-absorbent resin.
- the water absorption rate is 40 to 80 seconds
- the mass proportion of particles of 150 to 850 ⁇ m in the proportion of the entire water absorbent resin is 85 mass% or more
- the mass proportion of particles of 300 to 400 ⁇ m is 20 mass% or more.
- the BET specific surface area of the particles measured by classification to 300 to 400 ⁇ m is less than 0.03 m 2 / g.
- the “water absorption rate” of a water absorbent resin is a property that affects the characteristics required of such an absorbent when the absorbent is formed by combining the water absorbent resin and hydrophilic fibers. For example, the diffusibility of the liquid to be absorbed to the entire absorber tends to be excellent by appropriately reducing the water absorption rate.
- the water absorption rate of this water absorbing resin can be measured as a physiological saline water absorption rate based on the following method.
- the measurement of the water absorption rate is performed in a room adjusted to 25 ° C. ⁇ 1 ° C. and in a room temperature adjusted to 25 ⁇ 0.2 ° C. in a room temperature adjusted to 25 ⁇ 0.2 ° C., as described in Examples below.
- the time can be made the water absorption speed of the water absorbent resin.
- the physiological saline water absorption speed is 40 to 80 seconds.
- a water-absorbent resin is used for the absorber, it is preferably 42 seconds or longer, more preferably 45 seconds or longer, from the viewpoint that the absorber has good diffusibility.
- the mass ratio of particles of 150 to 850 ⁇ m in the total ratio is 85 mass% or more, and more preferably 90 mass% or more. Further, the mass ratio of 300 to 400 ⁇ m particles in the total ratio is 20 mass% or more, more preferably 25 mass% or more, and further preferably 30 mass% or more.
- the water-absorbent resin according to the present invention preferably has a median particle size of 200 to 600 ⁇ m, more preferably 200 to 500 ⁇ m, and further preferably 250 to 450 ⁇ m.
- the water-absorbing resin is not limited to those composed only of secondary particles in which primary particles are aggregated, and may include single particles (primary particles).
- Examples of the shape of the primary particles include a substantially spherical shape, an irregular crushed shape, and a plate shape.
- a substantially spherical single particle shape having a smooth surface shape such as a true spherical shape, an elliptical spherical shape, etc. can be mentioned. Since the surface shape is smooth, the fluidity as a powder is increased, and the aggregated particles are easily packed closely, so that they are not easily broken even under impact and have a high particle strength. Become.
- the BET specific surface area of the particles measured by classifying to 300 to 400 ⁇ m is less than 0.03 m 2 / g. Further, BET specific surface area is preferably not more than 0.028 m 2 / g, more preferably at most 0.026m 2 / g. Further, the BET specific surface area is preferably 0.010 m 2 / g or more. When the BET specific surface area is in such a range, the absorption performance when used in an absorbent article can be improved.
- the BET specific surface area was measured by adjusting the water-absorbing resin to a particle diameter that passed through a sieve having an opening of 400 ⁇ m and retained on the sieve having an opening of 300 ⁇ m, as described in the examples below.
- This sample was dried at 100 ° C. for 16 hours under the degassing conditions of heating and evacuation, and then heated by a method using krypton gas as an adsorption gas with a specific surface area measurement device (AUTOSORB-1, manufactured by Cantachrome).
- AUTOSORB-1 a specific surface area measurement device
- the BET specific surface area of the water absorbent obtained by adding an additive such as inorganic fine powder to the water absorbent resin is measured, the result is that the additive attached to the surface of the water absorbent resin has a very large BET specific surface area.
- the water-absorbent resin is measured in a state before the additive is added, or in the case of the water-absorbing agent, it adheres to the surface. It is desirable to perform the measurement after removing the additive by washing.
- the water-absorbent resin according to the present invention preferably has a physiological saline water retention capacity of 30 g / g or more.
- the physiological saline water retention capacity indicates the mass of physiological saline that can be absorbed by the water absorbent resin per unit mass, and represents the degree of absorption capacity of the liquid of the water absorbent resin.
- the physiological saline water retention capacity is more preferably 35 g / g or more, and further preferably 40 g / g or more.
- an upper limit of the physiological saline water retention capacity it is preferable that it is 60 g / g or less.
- the physiological saline water absorption capacity under a load of 4.14 kPa is preferably 16 ml / g or more, more preferably 18 ml / g or more, and 20 ml / g or more. More preferably it is.
- an upper limit of the physiological saline water absorption ability under a 4.14kPa load it is preferable that it is 50 ml / g or less.
- the above-mentioned water-absorbent resin has a physiological saline water retention capacity, a physiological saline water absorption capacity under a load of 4.14 kPa, a physiological saline water absorption speed, a median particle diameter, and a BET specific surface area. It can be measured by the described measuring method.
- additives depending on the purpose can be blended to make a water-absorbing agent.
- additives include inorganic fine powders, surfactants, oxidizing agents, reducing agents, metal chelating agents, radical chain inhibitors, antioxidants, antibacterial agents, and deodorants.
- inorganic fine powders include hydrophilic silica, hydrophobic silica, talc, zeolite, aluminum oxide powder and the like.
- the water-absorbent resin according to the present invention constitutes an absorbent body used for sanitary materials such as sanitary goods and disposable diapers, and is suitably used for absorbent articles including the absorbent body.
- the absorbent body using the water-absorbent resin is composed of, for example, a water-absorbent resin and hydrophilic fibers.
- the structure of the absorber is a mixed dispersion obtained by mixing the water-absorbent resin and the hydrophilic fiber so as to have a uniform composition, and a sandwich in which the water-absorbent resin is sandwiched between layered hydrophilic fibers. Examples include a structure, a structure in which a water-absorbing resin and a hydrophilic fiber are wrapped with a tissue.
- the absorbent body may contain other components, for example, an adhesive binder such as a heat-fusible synthetic fiber, a hot melt adhesive, and an adhesive emulsion for enhancing the shape retention of the absorbent body. .
- the content of the water-absorbing resin in the absorber is preferably 5 to 95% by mass, more preferably 20 to 90% by mass, and further preferably 30 to 80% by mass.
- the content of the water-absorbent resin is less than 5% by mass, the absorption capacity of the absorber is lowered, which may cause liquid leakage and reversion.
- the content of the water-absorbing resin exceeds 95% by mass, the cost of the absorber increases and the feel of the absorber becomes harder.
- hydrophilic fibers include cellulose fibers such as cotton-like pulp, mechanical pulp, chemical pulp, and semi-chemical pulp obtained from wood, synthetic cellulose fibers such as rayon and acetate, and polyamides, polyesters, and polyolefins that have been hydrophilized. Examples thereof include fibers made of resin.
- the absorbent body using the water absorbent resin between a liquid permeable sheet (top sheet) through which liquid can pass and a liquid impermeable sheet (back sheet) through which liquid cannot pass. It can be set as an absorbent article.
- the liquid permeable sheet is disposed on the side in contact with the body, and the liquid impermeable sheet is disposed on the opposite side in contact with the body.
- liquid permeable sheet examples include air-through type, spunbond type, chemical bond type, needle punch type nonwoven fabrics and porous synthetic resin sheets made of fibers such as polyethylene, polypropylene, and polyester.
- liquid impermeable sheet examples include synthetic resin films made of resins such as polyethylene, polypropylene, and polyvinyl chloride.
- Physiological saline water retention capacity A cotton bag (Membroad No. 60, width 100 mm ⁇ length 200 mm) weighing 2.0 g of the water-absorbing resin was placed in a 500 mL beaker. Pour 500 g of 0.9 mass% sodium chloride aqueous solution (saline) into a cotton bag containing a water-absorbent resin at once so that no mako can be made, and tie the upper part of the cotton bag with a rubber band and let it stand for 30 minutes. The water absorbent resin was swollen.
- the cotton bag was dehydrated for 1 minute using a dehydrator (manufactured by Kokusan Centrifuge Co., Ltd., product number: H-122) set to have a centrifugal force of 167 G, and contained a swollen gel after dehydration.
- the mass Wa (g) of the cotton bag was measured. The same operation was performed without adding the water-absorbent resin, the empty mass Wb (g) when the cotton bag was wet was measured, and the physiological saline water retention capacity was calculated from the following equation.
- Physiological saline water retention capacity [Wa-Wb] (g) / mass of water absorbent resin (g)
- the 1 includes a burette unit 1, a conduit 2, a measurement table 3, and a measurement unit 4 placed on the measurement table 3.
- a rubber stopper 14 is connected to the upper part of the burette 10
- an air introduction pipe 11 and a cock 12 are connected to the lower part
- a cock 13 is attached to the upper part of the air introduction pipe 11.
- a conduit 2 is attached from the burette unit 1 to the measuring table 3, and the diameter of the conduit 2 is 6 mm.
- a hole with a diameter of 2 mm is opened at the center of the measuring table 3 and the conduit 2 is connected.
- the measuring unit 4 includes a cylinder 40, a nylon mesh 41 attached to the bottom of the cylinder 40, and a weight 42.
- the inner diameter of the cylinder 40 is 2.0 cm.
- the nylon mesh 41 is formed to 200 mesh (aperture 75 ⁇ m). A predetermined amount of the water absorbent resin 5 is uniformly dispersed on the nylon mesh 41.
- the weight 42 has a diameter of 1.9 cm and a mass of 119.6 g. The weight 42 is placed on the water absorbent resin 5 so that a load of 4.14 kPa can be uniformly applied to the water absorbent resin 5.
- the cock 12 and the cock 13 of the burette unit 1 are closed, and physiological saline adjusted to 25 ° C. is introduced from the upper part of the burette 10. Then, the cock 12 and the cock 13 of the burette part 1 were opened. Next, the height of the measurement table 3 was adjusted so that the tip of the conduit 2 at the center of the measurement table 3 and the air introduction port of the air introduction tube 11 had the same height.
- the amount of decrease in physiological saline in the burette 10 (the amount of physiological saline absorbed by the water absorbent resin 5) Wc (mL) was continuously read from the time when the water absorbent resin 5 began to absorb water.
- the physiological saline water-absorbing ability under the 4.14 kPa load of the water-absorbing resin after 60 minutes from the start of water absorption was determined by the following equation.
- the water-absorbing resin was put into the combined uppermost sieve and classified by shaking for 20 minutes using a low-tap shaker. After classification, the mass of the water-absorbent resin remaining on each sieve was calculated as a mass percentage with respect to the total amount to obtain a particle size distribution. With respect to this particle size distribution, the sieve screen was integrated in order from the largest particle size, and the relationship between the sieve opening and the integrated value of the mass percentage of the water absorbent resin remaining on the sieve was plotted on a logarithmic probability paper. By connecting the plots on the probability paper with a straight line, the particle diameter corresponding to an integrated mass percentage of 50 mass% was defined as the median particle diameter.
- the ratio of the water-absorbing resin having a particle diameter of 300 to 400 ⁇ m is the ratio of the water-absorbing resin remaining on the sieve having an opening of 300 ⁇ m.
- the presence of the water-absorbing resin having a particle diameter of 150 to 850 ⁇ m is present.
- the ratio is a numerical value obtained by adding all the ratios of the water-absorbing resin remaining on the sieves having openings of 150 ⁇ m, 250 ⁇ m, 300 ⁇ m, 400 ⁇ m, 500 ⁇ m, and 600 ⁇ m.
- the water-absorbent resin to be measured was adjusted to a particle diameter that passed through a sieve having an opening of 400 ⁇ m and held on the sieve having an opening of 300 ⁇ m, and used for the measurement of the specific surface area.
- 10 g of the sample after classification is dispersed in 100 g of ethanol, washed for 5 minutes with an ultrasonic cleaner (US-103, manufactured by SND Co., Ltd.), and then filtered through a sieve having an opening of 300 ⁇ m. did.
- the same washing operation was performed two more times to obtain a measurement sample that had been washed three times in total. This sample was dried at 100 ° C. for 16 hours under a degassing condition of heat evacuation.
- an adsorption isotherm is measured at a temperature of 77K by a method using krypton gas as an adsorption gas with a specific surface area measuring device (AUTOSORB-1, manufactured by Cantachrome), and a specific surface area is obtained from a multipoint BET plot to obtain water absorption.
- AUTOSORB-1 a specific surface area measuring device
- Example 1 As a reflux condenser, a dropping funnel, a nitrogen gas introduction pipe, and a stirrer having a stirrer blade having two inclined paddle blades with a blade diameter of 50 mm in two stages, an inner diameter of 110 mm, a 2 L round bottom cylinder A type separable flask was prepared.
- n-heptane 300 g was taken as a hydrocarbon dispersion medium, 0.74 g of sucrose stearate ester of HLB3 (Mitsubishi Chemical Foods Co., Ltd., Ryoto Sugar Ester S-370) as a surfactant, and polymer dispersion 0.74 g of maleic anhydride-modified ethylene / propylene copolymer (Mitsui Chemicals, High Wax 1105A) was added as an agent, and the temperature was raised to 80 ° C. while stirring to dissolve the surfactant, and then up to 50 ° C. Cooled down.
- the monomer aqueous solution prepared as described above was added to the separable flask and the system was sufficiently replaced with nitrogen, and then the flask was immersed in a 70 ° C. water bath and raised.
- the polymerization slurry liquid of the 1st step was obtained by heating and performing polymerization for 60 minutes.
- the inside of the above-described separable flask system is cooled to 27 ° C., and then the entire amount of the second-stage monomer aqueous solution is changed to the first-stage polymerization slurry liquid.
- the flask was again immersed in a 70 ° C. water bath to raise the temperature, and the second stage polymerization was carried out for 30 minutes.
- the dried product was passed through a sieve having an opening of 1000 ⁇ m to obtain 233.4 g of a water absorbent resin having a form of secondary particles in which spherical primary particles were aggregated.
- the water absorbent resin thus obtained was evaluated according to the various test methods described above.
- the obtained water-absorbent resin had a mass ratio of particles of 150 to 850 ⁇ m in the total proportion of 98.2% by mass and a mass ratio of particles of 300 to 400 ⁇ m was 39.4% by mass. .
- Example 2 In Example 2, the same operation as in Example 1 was performed except that the 2% aqueous solution of ethylene glycol diglycidyl ether added as a post-crosslinking agent was changed to 6.62 g (0.761 mmol). 232.9 g of a water-absorbing resin having a form of secondary particles in which the particles were aggregated was obtained. The water absorbent resin thus obtained was evaluated according to the various test methods described above.
- the obtained water-absorbent resin had a mass ratio of 150 to 850 ⁇ m particles in the total proportion of 97.8% by mass and a mass ratio of 300 to 400 ⁇ m particles of 36.5% by mass. .
- Example 3 In Example 3, ethylene glycol diglycidyl ether was changed to 0.0202 g (0.116 mmol) as an internal cross-linking agent to be added to the first stage monomer, and the stirring rotation speed of the stirrer was 500 rpm. Except for the polymerization of the eyes, the same operation as in Example 1 was performed to obtain 231.0 g of a water-absorbent resin having a form of secondary particles in which spherical primary particles were aggregated. The water absorbent resin thus obtained was evaluated according to the various test methods described above.
- the obtained water-absorbent resin had a mass ratio of 150 to 850 ⁇ m particles in the total proportion of 90.7% by mass and a mass ratio of 300 to 400 ⁇ m particles of 24.2% by mass. .
- Example 4 In Example 4, the same operation as in Example 1 was performed except that ethylene glycol diglycidyl ether was changed to 0.0202 g (0.116 mmol) as an internal cross-linking agent added to the first stage monomer. Then, 232.1 g of a water-absorbing resin having the form of secondary particles in which spherical primary particles were aggregated was obtained. The water absorbent resin thus obtained was evaluated according to the various test methods described above.
- the obtained water-absorbing resin had a mass ratio of 150 to 850 ⁇ m particles in the total proportion of 97.9% by mass, and a mass ratio of 300 to 400 ⁇ m particles was 32.6% by mass. .
- Example 5 In Example 5, the internal crosslinking agent species was changed to polyethylene glycol diglycidyl ether (Nagase ChemteX Corporation, EX-861), and 0.0405 g of polyethylene glycol diglycidyl ether added to the first stage monomer was used. (0.0369 mmol), except that the polyethylene glycol diglycidyl ether added to the second stage monomer was 0.0116 g (0.0106 mmol), the same operation as in Example 1, 233.8 g of a water-absorbent resin having a secondary particle form in which spherical primary particles were aggregated was obtained. The water absorbent resin thus obtained was evaluated according to the various test methods described above.
- the obtained water-absorbent resin had a mass ratio of 150 to 850 ⁇ m particles in the total proportion of 95.8 mass% and a mass ratio of 300 to 400 ⁇ m particles of 31.3 mass%. .
- Example 6 polyethylene glycol diglycidyl ether (Nagase ChemteX Corporation, EX-861) was changed to 0.0810 g (0.0737 mmol) as an internal crosslinking agent to be added to the first-stage monomer. Except for the above, the same operation as in Example 5 was performed to obtain 232.9 g of a water-absorbent tree having a form of secondary particles in which spherical primary particles were aggregated. The water absorbent resin thus obtained was evaluated according to the various test methods described above.
- the obtained water-absorbent resin had a mass ratio of particles of 150 to 850 ⁇ m in the total proportion of 95.8% by mass, and a mass ratio of particles of 300 to 400 ⁇ m was 25.5% by mass. .
- Example 7 polyethylene glycol diglycidyl ether (Nagase ChemteX Corporation, EX-861) was changed to 0.0639 g (0.0581 mmol) as an internal crosslinking agent to be added to the first stage monomer, The same operation as in Example 5 was performed except that the first stage polymerization was performed with the stirring rotation speed of the stirrer being 650 rpm, and 231.7 g of the water absorbent resin having the form of secondary particles in which spherical primary particles were aggregated. Got. The water absorbent resin thus obtained was evaluated according to the various test methods described above.
- the obtained water-absorbent resin had a mass ratio of 150 to 850 ⁇ m particles in the total proportion of 94.5% by mass, and a mass ratio of 300 to 400 ⁇ m particles was 29.8% by mass. .
- Comparative Example 1 In Comparative Example 1, reverse-phase suspension polymerization was performed using only a peroxide alone to produce a water-absorbent resin.
- a round bottom cylinder having an inner diameter of 110 mm and a 2 L capacity provided with a reflux condenser, a dropping funnel, a nitrogen gas introduction pipe, and a stirring blade having two bladed paddle blades with a blade diameter of 50 mm in two stages as a stirrer.
- a type separable flask was prepared, 300 g of n-heptane was taken as a hydrocarbon dispersion medium, and sucrose stearate ester of HLB3 as a surfactant (Mitsubishi Chemical Foods Co., Ltd., Ryoto Sugar Ester S-370) 0.74 g, 0.74 g of maleic anhydride-modified ethylene / propylene copolymer (Mitsui Chemicals, High Wax 1105A) as a polymeric dispersant was added, and the temperature was raised to 80 ° C. with stirring, the surfactant. Was dissolved and then cooled to 50 ° C.
- the aqueous monomer solution prepared as described above was added to the separable flask and the system was sufficiently replaced with nitrogen, and then the flask was immersed in a 70 ° C. water bath and raised.
- the polymerization slurry liquid of the 1st step was obtained by heating and performing polymerization for 60 minutes.
- the inside of the above-described separable flask system is cooled to 25 ° C., and then the entire amount of the second-stage monomer aqueous solution is mixed with the first-stage polymerization slurry.
- the flask was again immersed in a 70 ° C. water bath to raise the temperature, and the second stage polymerization was carried out for 30 minutes.
- the dried product was passed through a sieve having an opening of 1000 ⁇ m to obtain 234.5 g of a water-absorbent resin in a form in which spherical particles were aggregated.
- the water absorbent resin thus obtained was evaluated according to the various test methods described above.
- the obtained water-absorbent resin had a mass ratio of 150 to 850 ⁇ m particles in the total proportion of 98.1% by mass and a mass ratio of 300 to 400 ⁇ m particles of 36.9% by mass. .
- Comparative Example 2 In Comparative Example 2, ethylene glycol diglycidyl ether was changed to 0.0156 g (0.090 mmol) as an internal cross-linking agent to be added to the first stage monomer and added to the second stage monomer. Change ethylene glycol diglycidyl ether to 0.0155 g (0.089 mmol) as an internal crosslinking agent, and change 2% aqueous solution of ethylene glycol diglycidyl ether added as a post-crosslinking agent to 6.62 g (0.761 mmol). Except for this, the same operation as in Comparative Example 1 was performed to obtain 233.6 g of a water-absorbent resin having a form of secondary particles in which spherical primary particles were aggregated. The water absorbent resin thus obtained was evaluated according to the various test methods described above.
- the obtained water-absorbing resin had a mass ratio of 150 to 850 ⁇ m particles in the total proportion of 93.9% by mass, and a mass ratio of 300 to 400 ⁇ m particles was 34.7% by mass. .
- Comparative Example 3 In Comparative Example 3, ethylene glycol diglycidyl ether was changed to 0.0101 g (0.058 mmol) as an internal cross-linking agent to be added to the first stage monomer, and the stirring speed of the stirrer was changed to 500 rpm. The eye was polymerized. Then, the same operation as in Comparative Example 1 was performed except that ethylene glycol diglycidyl ether was changed to 0.0116 g (0.067 mmol) as an internal crosslinking agent to be added to the second-stage monomer. As a result, 231.8 g of a water-absorbent resin having a form of secondary particles in which primary particles were aggregated was obtained. The water absorbent resin thus obtained was evaluated according to the various test methods described above.
- the obtained water-absorbent resin had a mass ratio of 150 to 850 ⁇ m particles in the total ratio of 98.0% by mass and a mass ratio of 300 to 400 ⁇ m particles of 40.7% by mass. .
- Comparative Example 4 In Comparative Example 4, ethylene glycol diglycidyl ether was changed to 0.0276 g (0.1584 mmol) as an internal cross-linking agent to be added to the first stage monomer, and the stirring speed of the stirrer was changed to 500 rpm. Except that the eye polymerization was performed, the same operation as in Example 2 was performed to obtain 232.9 g of a water absorbent resin having a form of secondary particles in which spherical primary particles were aggregated. The water absorbent resin thus obtained was evaluated according to the various test methods described above.
- the obtained water-absorbent resin had a mass ratio of 150 to 850 ⁇ m particles in the total proportion of 97.2% by mass and a mass ratio of 300 to 400 ⁇ m particles of 36.4% by mass. .
- Table 1 shows the evaluation results of the water-absorbent resins obtained in Examples 1 to 7 and Comparative Examples 1 to 4. Table 1 also shows the polymerization conditions in each example and comparative example.
- water-absorbing resins having a controlled BET specific surface area were obtained by the water-absorbing resin production methods of Examples 1 to 7.
- a polyethylene-polypropylene air-through porous liquid permeable sheet made of polyethylene-polypropylene having the same size as the absorber and having a basis weight of 22 g / m 2 is arranged on the upper surface of the absorbent body, and the polyethylene liquid having the same size and the same basis weight is placed on the liquid surface.
- Example 9 to 11 and Comparative Examples 5 to 7 In Examples 9 to 11 and Comparative Examples 5 to 6, instead of the water-absorbent resin obtained in Example 1, they were obtained in Examples 2, 4, 6 and Comparative Examples 1, 3, 4 respectively. Except having used the obtained water absorbing resin, operation similar to Example 8 was performed and the absorbent article was obtained. In addition, the obtained absorbent article was made into the absorbent article of Example 9,10,11 and Comparative Example 5,6,7 in order, respectively.
- the total time for the first to third times was defined as the total penetration time.
- it can be said that it is so preferable as an absorbent article that penetration time is short.
- the mass (Wd (g), about 50 g) is measured in advance in the vicinity of the test liquid charging position on the absorbent article 120 minutes after the start of the first test liquid charging in the above-described measurement of the permeation time.
- a 10 cm square filter paper was placed, and a weight of 5 kg with a bottom surface of 10 cm ⁇ 10 cm was placed thereon. After loading for 5 minutes, the mass of the filter paper (We (g)) was measured, and the increased mass was taken as the reversal amount (g). In addition, it can be said that it is preferable as an absorbent article, so that the amount of reversion is small.
- the absorbent article using the water-absorbent resin having an appropriate BET specific surface area and water absorption speed of the example was superior in performance of the permeation time and the amount of reversal compared to the comparative example.
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Abstract
Description
本発明に係る吸収性樹脂の製造方法について説明する。
[水溶性エチレン性不飽和単量体]
水溶性エチレン性不飽和単量体としては、例えば、(メタ)アクリル酸(本明細書においては、「アクリ」及び「メタクリ」を合わせて「(メタ)アクリ」と表記する。以下同様)及びその塩;2-(メタ)アクリルアミド-2-メチルプロパンスルホン酸及びその塩;(メタ)アクリルアミド、N,N-ジメチル(メタ)アクリルアミド、2-ヒドロキシエチル(メタ)アクリレート、N-メチロール(メタ)アクリルアミド、ポリエチレングリコールモノ(メタ)アクリレート等の非イオン性単量体;N,N-ジエチルアミノエチル(メタ)アクリレート、N,N-ジエチルアミノプロピル(メタ)アクリレート、ジエチルアミノプロピル(メタ)アクリルアミド等のアミノ基含有不飽和単量体及びその4級化物等が挙げられる。これらの水溶性エチレン性不飽和単量体の中でも、工業的に入手が容易であること等の観点から、(メタ)アクリル酸又はその塩、(メタ)アクリルアミド、N,N-ジメチルアクリルアミドが好ましく、(メタ)アクリル酸及びその塩がより好ましい。なお、これらの水溶性エチレン性不飽和単量体は、単独で用いてもよく、2種類以上を組み合わせて用いてもよい。
炭化水素分散媒としては、例えば、n-ヘキサン、n-ヘプタン、2-メチルヘキサン、3-メチルヘキサン、2,3-ジメチルペンタン、3-エチルペンタン、n-オクタン等の炭素数6~8の脂肪族炭化水素;シクロヘキサン、メチルシクロヘキサン、シクロペンタン、メチルシクロペンタン、trans-1,2-ジメチルシクロペンタン、cis-1,3-ジメチルシクロペンタン、trans-1,3-ジメチルシクロペンタン等の脂環族炭化水素;ベンゼン、トルエン、キシレン等の芳香族炭化水素等が挙げられる。これらの炭化水素分散媒の中でも、特に、工業的に入手が容易であり、品質が安定しており且つ安価である点で、n-ヘキサン、n-ヘプタン、シクロヘキサンが好適に用いられる。これらの炭化水素分散媒は、単独で用いてもよく、2種類以上を組み合わせて用いてもよい。なお、炭化水素分散媒の混合物の例としては、エクソールヘプタン(エクソンモービル社製:ヘプタン及びその異性体の炭化水素75~85質量%含有)等の市販品を用いても好適な結果を得ることができる。
(界面活性剤)
逆相懸濁重合では、水溶性エチレン性不飽和単量体の炭化水素分散媒中での分散安定性を向上させるために、分散安定剤を用いることもできる。その分散安定剤としては、界面活性剤を用いることができる。
また、逆相懸濁重合で用いられる分散安定剤としては、前述した界面活性剤と共に、高分子系分散剤を併せて用いてもよい。
本発明に係る吸水性樹脂の製造方法では、内部架橋剤の存在下、その1段目の重合時に用いる内部架橋剤の使用量を特定の範囲に調整して、水溶性エチレン性不飽和単量体の逆相懸濁重合を行うことに特徴がある。
本発明に係る吸水性樹脂の製造方法では、水溶性エチレン性不飽和単量体に対して、アゾ系化合物と過酸化物との存在下において逆相懸濁重合を行うことを特徴とする。
具体的に、アゾ系化合物としては、例えば、1-{(1-シアノ-1-メチルエチル)アゾ}ホルムアミド、2,2’-アゾビス[2-(N-フェニルアミジノ)プロパン]二塩酸塩、2,2’-アゾビス{2-[N-(4-クロロフェニル)アミジノ]プロパン}二塩酸塩、2,2’-アゾビス{2-[N-(4-ヒドロキシフェニル)アミジノ]プロパン}二塩酸塩、2,2’-アゾビス[2-(N-ベンジルアミジノ)プロパン]二塩酸塩、2,2’-アゾビス[2-(N-アリルアミジノ)プロパン]二塩酸塩、2,2’-アゾビス(2-アミジノプロパン)二塩酸塩、2,2’-アゾビス{2-[N-(2-ヒドロキシエチル)アミジノ]プロパン}二塩酸塩、2,2’-アゾビス[2-(5-メチル-2-イミダゾリン-2-イル)プロパン]二塩酸塩、2,2’-アゾビス[2-(2-イミダゾリン-2-イル)プロパン]二塩酸塩、2,2’-アゾビス[2-(4,5,6,7-テトラヒドロ-1H-1,3-ジアゼピン-2-イル)プロパン]二塩酸塩、2,2’-アゾビス[2-(5-ヒドロキシ-3,4,5,6-テトラヒドロピリミジン-2-イル)プロパン]二塩酸塩、2,2’-アゾビス{2-[1-(2-ヒドロキシエチル)-2-イミダゾリン-2-イル]プロパン}二塩酸塩、2,2’-アゾビス[2-(2-イミダゾリン-2-イル)プロパン]、2,2’-アゾビス{2-メチル-N-[1,1-ビス(ヒドロキシメチル)-2-ヒドロキシエチル]プロピオンアミド}、2,2’-アゾビス{2-メチル-N-[1,1-ビス(ヒドロキシメチル)エチル]プロピオンアミド}、2,2’-アゾビス[2-メチル-N-(2-ヒドロキシエチル)プロピオンアミド]、2,2’-アゾビス(2-メチルプロピオンアミド)二塩酸塩、4,4’-アゾビス-4-シアノバレイン酸、2,2’-アゾビス[2-(ヒドロキシメチル)プロピオニトリル]、2,2’-アゾビス[2-(2-イミダゾリン-2-イル)プロパン]二硫酸塩二水和物、2,2’-アゾビス[N-(2-カルボキシエチル)-2-メチルプロピオンアミジン]四水和物、2,2’-アゾビス[2-メチル-N-(2-ヒドロキシエチル)プロピオンアミド]等のアゾ化合物が挙げられる。これらの中でも、2,2’-アゾビス(2-アミジノプロパン)二塩酸塩、2,2’-アゾビス{2-[1-(2-ヒドロキシエチル)-2-イミダゾリン-2-イル]プロパン}二塩酸塩、2,2’-アゾビス[N-(2-カルボキシエチル)-2-メチルプロピオンアミジン]四水和物が、重合温度等の重合反応の調整の容易さや、優れた吸水性能を有する吸水性樹脂が得られるという点から特に好ましい。これらアゾ系化合物は、単独で用いてもよく、2種類以上を組み合わせて用いてもよい。
過酸化物としては、例えば、過硫酸カリウム、過硫酸アンモニウム、過硫酸ナトリウム等の過硫酸塩類;メチルエチルケトンパーオキシド、メチルイソブチルケトンパーオキシド、ジ-t-ブチルパーオキシド、t-ブチルクミルパーオキシド、t-ブチルパーオキシアセテート、t-ブチルパーオキシイソブチレート、t-ブチルパーオキシピバレート、過酸化水素等の過酸化物が挙げられる。これらの過酸化物の中でも、優れた吸水性能を有する吸水性樹脂が得られる観点から、過硫酸カリウム、過硫酸アンモニウム、過硫酸ナトリウム、過酸化水素を用いることが好ましく、さらに、過硫酸カリウム、過硫酸アンモニウム、過硫酸ナトリウムを用いることがより好ましい。これらの過酸化物は、単独で用いてもよく、2種類以上を組み合わせて用いてもよい。
アゾ系化合物と過酸化物の使用量としては、重合反応の時間を短縮するという観点から、水溶性エチレン性不飽和単量体1モルに対して0.00005モル以上であることが好ましく、0.0001モル以上であることがより好ましい。また、急激な重合反応を防ぐという観点から、水溶性エチレン性不飽和単量体1モルに対して0.005モル以下であることが好ましく、0.001モル以下であることがより好ましい。
本発明に係る吸水性樹脂の製造方法では、所望によりその他の成分を、水溶性エチレン性不飽和単量体に添加して逆相懸濁重合を行うようにしてもよい。その他の成分としては、連鎖移動剤、増粘剤、その他各種の添加剤等を添加することができる。
本発明に係る吸水性樹脂の製造方法では、吸水性樹脂の吸水性能を制御するために、連鎖移動剤の存在下に水溶性エチレン性不飽和単量体の重合を行うようにしてもよい。
また、本発明に係る吸水性樹脂の製造方法では、水溶性エチレン性不飽和単量体を含む水溶液に対して増粘剤を添加して逆相懸濁重合を行うようにしてもよい。このように増粘剤を添加して水溶液粘度を調整することによって、逆相懸濁重合において得られる中位粒子径を制御することも可能である。
逆相懸濁重合を行うにあたっては、例えば、界面活性剤及び/又は高分子系分散剤の存在下に、水溶性エチレン性不飽和単量体を含む単量体水溶液を、炭化水素分散媒に分散させる。このとき、重合反応を開始する前であれば、界面活性剤や高分子系分散剤の添加時期は、単量体水溶液分散の前後どちらであってもよい。
次に、本発明に係る吸水性樹脂の製造方法においては、前述したように内部架橋剤の存在下、アゾ系化合物と過酸化物との存在下において水溶性エチレン性不飽和単量体を逆相懸濁重合して得られた内部架橋構造を有する含水ゲル状物に対して後架橋剤で後架橋すること(後架橋反応)が好ましい。このように、重合後以降に、内部架橋構造を有する含水ゲル状物に対して後架橋反応を施すことによって、吸水性樹脂の表面近傍の架橋密度を高めて、荷重下吸水能、吸水速度、ゲル強度等の諸性能を高めた、衛生材料用途に特に好適な吸水性樹脂を得ることが可能である。
本発明に係る吸水性樹脂の製造方法においては、前述した逆相懸濁重合を行った後、熱等のエネルギーを外部から加えることで、水、炭化水素分散媒等を蒸留により除去する乾燥工程を含んでいてもよい。逆相懸濁重合後の含水ゲルから脱水を行う場合、炭化水素分散媒中に含水ゲルが分散している系を加熱することで、水と炭化水素分散媒を共沸蒸留により系外に一旦留去する。このとき、留去した炭化水素分散媒のみを系内へ返送すると、連続的な共沸蒸留が可能である。その場合、乾燥中の系内の温度が、炭化水素分散媒の共沸温度以下に維持されるため、樹脂が劣化しにくい等の観点から好ましい。引き続き、水及び炭化水素分散媒を留去することにより、吸水性樹脂の粒子が得られる。この重合後における乾燥工程の処理条件を制御して脱水量を調整することにより、得られる吸水性樹脂の諸性能を制御することが可能である。
次に、本発明に係る吸水性樹脂について説明する。本発明に係る吸水性樹脂は、前述した方法により得られるものであり、具体的には、1段目の重合時に内部架橋剤の使用量を調整しながら重合して得られるものであって、そのBET比表面積が適度な範囲に制御され、その吸水性樹脂を用いた吸収性物品は優れた吸収性能を有する。
本発明に係る吸水性樹脂は、例えば生理用品、紙おむつ等の衛生材料に用いられる吸収体を構成するものであり、その吸収体を含む吸収性物品に好適に用いられる。
以下、実施例及び比較例を示して本発明をより詳細に説明するが、本発明は以下の実施例等により何ら限定されるものではない。
[吸水性樹脂の評価試験]
下記の実施例1~7、及び、比較例1~4にて得られる吸水性樹脂について、下記に示す各種の試験に供して評価した。以下、各評価試験方法について説明する。
吸水性樹脂2.0gを量り取った綿袋(メンブロード60番、横100mm×縦200mm)を500mL容のビーカー内に設置した。吸水性樹脂の入った綿袋中に0.9質量%塩化ナトリウム水溶液(生理食塩水)500gをママコができない様に一度に注ぎ込み、綿袋の上部を輪ゴムで縛り、30分静置させることで吸水性樹脂を膨潤させた。30分経過後の綿袋を、遠心力が167Gとなるよう設定した脱水機(国産遠心機株式会社製、品番:H-122)を用いて1分間脱水し、脱水後の膨潤ゲルを含んだ綿袋の質量Wa(g)を測定した。吸水性樹脂を添加せずに同様の操作を行い、綿袋の湿潤時の空質量Wb(g)を測定し、以下の式から生理食塩水保水能を算出した。
図1に概略構成を示した測定装置Xを用いて、吸水性樹脂の4.14kPa荷重下での生理食塩水吸水能を測定した。
生理食塩水吸水速度は、25℃±1℃に調節した室内で行った。恒温水槽にて25±0.2℃の温度に調整した生理食塩水50±0.1gをマグネチックスターラーバー(8mmφ×30mmのリング無し)で600rpmに攪拌して渦を発生させた。得られた吸水性樹脂2.0±0.002gを、その生理食塩水中に一度に添加し、吸水性樹脂の添加後から渦が消失し、液面が平坦になるまでの時間(秒)を測定し、当該時間を吸水性樹脂の生理食塩水吸水速度とした。
吸水性樹脂50gに、滑剤として、0.25gの非晶質シリカ(エボニックデグサジャパン株式会社製、カープレックス#80)を混合した。
測定する吸水性樹脂を、目開き400μmの篩を通過し、目開き300μmの篩上に保持される粒子径に調整したものを比表面積の測定に用いた。次に、この分級後のサンプル10gを、エタノール100gの中に分散させ、超音波洗浄機(US-103、株式会社エスエヌディ製)で5分間洗浄を行った後、目開き300μmの篩で濾別した。同様の洗浄操作をあと2回実施し、合計3回の洗浄を実施した測定用試料を得た。この試料を100℃、16時間加熱真空排気の脱気条件で乾燥した。その後、比表面積測定装置(AUTOSORB-1,カンタクローム社製)により、吸着ガスとしてクリプトンガスを用いる方法で温度77Kにて吸着等温線を測定し、多点BETプロットから比表面積を求め、吸水性樹脂のBET比表面積とした。
[実施例1]
実施例1では、還流冷却器、滴下ロート、窒素ガス導入管、並びに、攪拌機として、翼径50mmの4枚傾斜パドル翼を2段で有する攪拌翼を備えた内径110mm、2L容の丸底円筒型セパラブルフラスコを準備した。このフラスコに、炭化水素分散媒としてn-ヘプタン300gをとり、界面活性剤としてHLB3のショ糖ステアリン酸エステル(三菱化学フーズ株式会社、リョートーシュガーエステルS-370)0.74g、高分子系分散剤として無水マレイン酸変性エチレン・プロピレン共重合体(三井化学株式会社、ハイワックス1105A)0.74gを添加し、攪拌しつつ80℃まで昇温して界面活性剤を溶解した後、50℃まで冷却した。
実施例2では、後架橋剤として添加するエチレングリコールジグリシジルエーテルの2%水溶液を6.62g(0.761ミリモル)に変更したこと以外は、実施例1と同様の操作を行い、球状の一次粒子が凝集した二次粒子の形態を有する吸水性樹脂232.9gを得た。このようにして得られた吸水性樹脂を、前述の各種試験方法に従って評価した。
実施例3では、第1段目の単量体に添加する内部架橋剤としてエチレングリコールジグリシジルエーテルを0.0202g(0.116ミリモル)に変更し、攪拌機の攪拌回転数を500rpmとして第1段目の重合を行った以外は、実施例1と同様の操作を行い、球状の一次粒子が凝集した二次粒子の形態を有する吸水性樹脂231.0gを得た。このようにして得られた吸水性樹脂を、前述の各種試験方法に従って評価した。
実施例4では、第1段目の単量体に添加する内部架橋剤としてエチレングリコールジグリシジルエーテルを0.0202g(0.116ミリモル)に変更したこと以外は、実施例1と同様の操作を行い、球状の一次粒子が凝集した二次粒子の形態を有する吸水性樹脂232.1gを得た。このようにして得られた吸水性樹脂を、前述の各種試験方法に従って評価した。
実施例5では、内部架橋剤種をポリエチレングリコールジグリシジルエーテル(ナガセケムテックス株式会社、EX-861)に変更し、第1段目の単量体に添加するポリエチレングリコールジグリシジルエーテルを0.0405g(0.0369ミリモル)とし、第2段目の単量体に添加するポリエチレングリコールジグリシジルエーテルを0.0116g(0.0106ミリモル)としたこと以外は、実施例1と同様の操作を行い、球状の一次粒子が凝集した二次粒子の形態を有する吸水性樹脂233.8gを得た。このようにして得られた吸水性樹脂を、前述の各種試験方法に従って評価した。
実施例6では、第1段目の単量体に添加する内部架橋剤としてポリエチレングリコールジグリシジルエーテル(ナガセケムテックス株式会社、EX-861)を0.0810g(0.0737ミリモル)に変更したこと以外は、実施例5と同様の操作を行い、球状の一次粒子が凝集した二次粒子の形態を有する吸水性樹232.9gを得た。このようにして得られた吸水性樹脂を、前述の各種試験方法に従って評価した。
実施例7では、第1段目の単量体に添加する内部架橋剤としてポリエチレングリコールジグリシジルエーテル(ナガセケムテックス株式会社、EX-861)を0.0639g(0.0581ミリモル)に変更し、攪拌機の攪拌回転数を650rpmとして第1段目の重合を行った以外は、実施例5と同様の操作を行い、球状の一次粒子が凝集した二次粒子の形態を有する吸水性樹脂231.7gを得た。このようにして得られた吸水性樹脂を、前述の各種試験方法に従って評価した。
比較例1では、過酸化物のみを単独で用いて逆相懸濁重合を行い、吸水性樹脂を作製した。
比較例2では、第1段目の単量体に添加する内部架橋剤としてエチレングリコールジグリシジルエーテルを0.0156g(0.090ミリモル)に変更し、第2段目の単量体に添加する内部架橋剤としてエチレングリコールジグリシジルエーテルを0.0155g(0.089ミリモル)に変更し、後架橋剤として添加するエチレングリコールジグリシジルエーテルの2%水溶液を6.62g(0.761ミリモル)に変更したこと以外は、比較例1と同様の操作を行い、球状の一次粒子が凝集した二次粒子の形態を有する吸水性樹脂233.6gを得た。このようにして得られた吸水性樹脂を、前述の各種試験方法に従って評価した。
比較例3では、第1段目の単量体に添加する内部架橋剤としてエチレングリコールジグリシジルエーテルを0.0101g(0.058ミリモル)に変更し、攪拌機の攪拌回転数を500rpmとして第1段目の重合を行った。そして、第2段目の単量体に添加する内部架橋剤としてエチレングリコールジグリシジルエーテルを0.0116g(0.067ミリモル)に変更したこと以外は、比較例1と同様の操作を行い、球状の一次粒子が凝集した二次粒子の形態を有する吸水性樹脂231.8gを得た。このようにして得られた吸水性樹脂を、前述の各種試験方法に従って評価した。
比較例4では、第1段目の単量体に添加する内部架橋剤としてエチレングリコールジグリシジルエーテルを0.0276g(0.1584ミリモル)に変更し、攪拌機の攪拌回転数を500rpmとして第1段目の重合を行ったこと以外は、実施例2と同様の操作を行い、球状の一次粒子が凝集した二次粒子の形態を有する吸水性樹脂232.9gを得た。このようにして得られた吸水性樹脂を、前述の各種試験方法に従って評価した。
[吸水性樹脂の評価結果]
下記表1に、実施例1~7、及び、比較例1~4にて得られた吸水性樹脂の評価結果を示す。なお、表1には、各実施例、比較例における重合条件も併せて示す。
次に、実施例1、2、4、6及び比較例1、3、4で得られた吸水性樹脂を用いて、後述の方法により吸収体及び吸収性物品を作製し、評価した。
[実施例8]
実施例1で得られた吸水性樹脂12gと解砕パルプ(レオニア社製レイフロック)12gを用い、空気抄造によって均一混合することにより、40cm×12cmの大きさのシート状の吸収体コアを作製した。次に、吸収体コアの上下を、吸収体コアと同じ大きさで、坪量16g/m2の2枚のティッシュペーパーではさんだ状態で、全体に196kPaの荷重を30秒間加えてプレスすることにより吸収体を作製した。さらに吸収体の上面に、吸収体と同じ大きさで、坪量22g/m2のポリエチレン-ポリプロピレン製エアスルー型多孔質液体透過性シートを配置し、同じ大きさ、同じ坪量のポリエチレン製液体不透過性シートを吸収体の下面に配置して、吸収体を挟みつけることにより、吸水性樹脂の坪量が250g/m2、親水性繊維の坪量が250g/m2の吸収性物品とした。
実施例9~11、及び、比較例5~6では、実施例1で得られた吸水性樹脂に代えて、それぞれ、実施例2、4、6、及び、比較例1、3、4で得られた吸水性樹脂を用いたこと以外は、実施例8と同様の操作を行い、吸収性物品を得た。なお、得られた吸収性物品をそれぞれ順に、実施例9、10、11、及び、比較例5、6、7の吸収性物品とした。
試験液として、イオン交換水に、NaCl:0.780質量%、CaCl2:0.022質量%、MgSO4:0.038質量%となるように配合して溶解させ、さらに少量の青色1号を配合したものを調製した。
先ず、水平の台上に吸収性物品を置いた。吸収性物品の中心部に、内径3cmの液投入用シリンダーを具備した測定器具を置き、80mLの試験液をそのシリンダー内に一度に投入するとともに、ストップウォッチを用いて、試験液がシリンダー内から完全に消失するまでの時間を測定し、1回目の浸透時間(秒)とした。
前述した浸透時間の測定における1回目の試験液投入開始から120分後、吸収性物品上の試験液投入位置付近に、予め質量(Wd(g)、約50g)を測定しておいた10cm四方とした濾紙を置き、その上に底面が10cm×10cmの質量5kgの重りを載せた。5分間の荷重後、濾紙の質量(We(g))を測定し、増加した質量を逆戻り量(g)とした。なお、逆戻り量が小さいほど、吸収性物品として好ましいと言える。
前述した逆戻り量の測定後5分以内に、試験液が浸透した吸収性物品の長手方向の拡がり寸法(cm)を測定した。なお、小数点以下の数値は四捨五入した。
次に、下記表2に、実施例8~11、及び、比較例5~7で得られた吸収性物品の評価結果を示す。
1 ビュレット部
2 導管
3 測定台
4 測定部
5 吸水性樹脂
Claims (8)
- 水溶性エチレン性不飽和単量体を炭化水素分散媒中で、少なくともアゾ系化合物、過酸化物、及び内部架橋剤の存在下で2段以上の逆相懸濁重合を行うに際し、
1段目の重合時における内部架橋剤の使用量を、1段目の重合時に使用する水溶性エチレン性不飽和単量体1モル当たり0.015~0.150ミリモルの範囲で調整して重合を行うことによって、得られる一次粒子が凝集して形成された二次粒子のBET比表面積を制御することを特徴とする吸水性樹脂の製造方法。 - 2段目以降の重合時における、前記内部架橋剤の前記水溶性エチレン性不飽和単量体1モル当たりの使用量(モル)が、前記1段目の重合時に用いる内部架橋剤の1段目の重合時に使用する水溶性エチレン性不飽和単量体1モルに対する使用量(モル)の90%以下である請求項1記載の吸水性樹脂の製造方法。
- 一次粒子が凝集して形成された二次粒子の、300~400μmに分級して測定したBET比表面積を、0.03m2/g未満に制御する請求項1又は2に記載の吸水性樹脂の製造方法。
- 水溶性エチレン性不飽和単量体を内部架橋剤の存在下で重合させることにより得られる吸水性樹脂であって、
当該吸水性樹脂の生理食塩水吸水速度が40~80秒であり、
当該吸水性樹脂全体の割合に占める150~850μmの粒子の質量割合が85質量%以上であり、300~400μmの粒子の質量割合が20質量%以上であり、
300~400μmに分級して測定したBET比表面積が0.03m2/g未満である
ことを特徴とする吸水性樹脂。 - 当該吸水性樹脂の中位粒子径が、200~600μmである請求項4に記載の吸水性樹脂。
- 請求項4又は5に記載の吸水性樹脂に無機微粉末を配合してなる吸水剤。
- 請求項4又は5に記載の吸水性樹脂を含む吸収体を用いてなる吸収性物品。
- 請求項6に記載の吸水剤を含む吸収体を用いてなる吸収性物品。
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- 2014-11-04 US US14/787,716 patent/US9873755B2/en active Active
- 2014-11-04 MX MX2017000345A patent/MX2017000345A/es unknown
- 2014-11-04 BR BR112017000530-1A patent/BR112017000530B1/pt active IP Right Grant
- 2014-11-04 EP EP14882127.5A patent/EP2993191B1/en active Active
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CN108137743A (zh) * | 2016-02-24 | 2018-06-08 | 株式会社Lg化学 | 用于基于丙烯酸的聚合物的制备方法 |
EP3333200A4 (en) * | 2016-02-24 | 2018-11-14 | LG Chem, Ltd. | Method for preparing acrylic acid-based polymer |
US10745500B2 (en) | 2016-02-24 | 2020-08-18 | Lg Chem, Ltd. | Preparation method for acrylic acid-based polymer |
JPWO2018180864A1 (ja) * | 2017-03-29 | 2020-02-06 | 住友精化株式会社 | 吸水性樹脂 |
JP7194101B2 (ja) | 2017-03-29 | 2022-12-21 | 住友精化株式会社 | 吸水性樹脂 |
WO2019074099A1 (ja) * | 2017-10-12 | 2019-04-18 | 住友精化株式会社 | 吸水性樹脂及び吸収性物品 |
JPWO2019074099A1 (ja) * | 2017-10-12 | 2020-11-05 | 住友精化株式会社 | 吸水性樹脂及び吸収性物品 |
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WO2020184387A1 (ja) * | 2019-03-08 | 2020-09-17 | 住友精化株式会社 | 吸水性樹脂粒子及びその製造方法、吸収体、並びに吸収性物品 |
WO2020218166A1 (ja) * | 2019-04-23 | 2020-10-29 | 住友精化株式会社 | 吸水性樹脂粒子 |
Also Published As
Publication number | Publication date |
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US20170107313A1 (en) | 2017-04-20 |
EP2993191A4 (en) | 2016-05-18 |
CN105517660B (zh) | 2017-05-31 |
TWI542599B (zh) | 2016-07-21 |
EP2993191B1 (en) | 2022-08-24 |
KR20160017649A (ko) | 2016-02-16 |
SA517380670B1 (ar) | 2021-06-15 |
EP2993191A1 (en) | 2016-03-09 |
BR112017000530A2 (pt) | 2017-11-14 |
KR101641656B1 (ko) | 2016-07-21 |
US9873755B2 (en) | 2018-01-23 |
JP2016028117A (ja) | 2016-02-25 |
CA2951468C (en) | 2018-06-05 |
JP5689204B1 (ja) | 2015-03-25 |
TW201607961A (zh) | 2016-03-01 |
CN105517660A (zh) | 2016-04-20 |
BR112017000530B1 (pt) | 2020-11-17 |
SG11201700193RA (en) | 2017-03-30 |
MX2017000345A (es) | 2017-08-25 |
CA2951468A1 (en) | 2016-01-14 |
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