WO2012053121A1 - 吸水性樹脂粒子の製造方法及び吸水性樹脂粒子 - Google Patents
吸水性樹脂粒子の製造方法及び吸水性樹脂粒子 Download PDFInfo
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- WO2012053121A1 WO2012053121A1 PCT/JP2010/070905 JP2010070905W WO2012053121A1 WO 2012053121 A1 WO2012053121 A1 WO 2012053121A1 JP 2010070905 W JP2010070905 W JP 2010070905W WO 2012053121 A1 WO2012053121 A1 WO 2012053121A1
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- 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
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- 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
- C08F20/12—Esters of monohydric alcohols or phenols
- C08F20/16—Esters of monohydric alcohols or phenols of phenols or of alcohols containing two or more carbon atoms
- C08F20/18—Esters of monohydric alcohols or phenols of phenols or of alcohols containing two or more carbon atoms with acrylic or methacrylic acids
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- C08F—MACROMOLECULAR COMPOUNDS OBTAINED BY REACTIONS ONLY INVOLVING CARBON-TO-CARBON UNSATURATED BONDS
- C08F2/00—Processes of polymerisation
- C08F2/001—Multistage polymerisation processes characterised by a change in reactor conditions without deactivating the intermediate polymer
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- 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
- C08F2/00—Processes of polymerisation
- C08F2/12—Polymerisation in non-solvents
- C08F2/14—Organic medium
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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
- C08F2/18—Suspension polymerisation
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- C08F—MACROMOLECULAR COMPOUNDS OBTAINED BY REACTIONS ONLY INVOLVING CARBON-TO-CARBON UNSATURATED BONDS
- C08F2/00—Processes of polymerisation
- C08F2/32—Polymerisation in water-in-oil emulsions
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- 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
- C08F6/00—Post-polymerisation treatments
- C08F6/008—Treatment of solid polymer wetted by water or organic solvents, e.g. coagulum, filter cakes
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- C—CHEMISTRY; METALLURGY
- 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
- C08J3/12—Powdering or granulating
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- C—CHEMISTRY; METALLURGY
- 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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- C—CHEMISTRY; METALLURGY
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- C08F—MACROMOLECULAR COMPOUNDS OBTAINED BY REACTIONS ONLY INVOLVING CARBON-TO-CARBON UNSATURATED BONDS
- 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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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
- Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
- Y10T428/00—Stock material or miscellaneous articles
- Y10T428/29—Coated or structually defined flake, particle, cell, strand, strand portion, rod, filament, macroscopic fiber or mass thereof
- Y10T428/2982—Particulate matter [e.g., sphere, flake, etc.]
Definitions
- the present invention relates to a method for producing water-absorbing resin particles and water-absorbing resin particles obtained thereby. More specifically, a production method for obtaining water-absorbent resin particles having an excellent water absorption rate and a high equilibrium swelling performance by passing through specific production conditions, and having an excellent particle size and excellent handling properties, The present invention relates to a water-absorbent resin particle having excellent water-stopping performance.
- water-absorbing resin particles have been used in industrial materials such as disposable diapers, sanitary materials such as sanitary items, daily necessities such as pet sheets, agricultural and horticultural materials such as water retention materials and soil improvement materials, waterproofing materials for cables, and anti-condensation materials. Widely used in various fields.
- the water-absorbent resin particles used in such applications include hydrolysates of starch-acrylonitrile graft copolymers, neutralized starch-acrylic acid graft copolymers, vinyl acetate-acrylic esters. A saponified copolymer, a partially neutralized polyacrylic acid, and the like are known.
- the performance required for the water-absorbent resin particles includes a high water absorption amount, an excellent water absorption rate, a high swelling performance, and an appropriate medium particle size according to the application.
- the water-stop material for cables is a product in which water-absorbing resin particles are fixed between two or more liquid-permeable sheets using an adhesive or the like as necessary.
- the waterproofing material for cables is used to wind and protect the center portion of a power cable or an optical communication cable, and the cable is formed by covering the outer periphery with a material such as rubber.
- Power cables and optical communication cables absorb water to prevent external materials from deteriorating and moisture that leaks from the cracks that reach the center of the cable will lead to power loss and communication noise. At the same time, it swells to give pressure in the cable, thereby preventing water from reaching the center of the cable.
- the performance required as a water-absorbing resin for water-stopping materials used in power cables and communication cables is to prevent water from entering from the outside due to cable breakage at an early stage and to maintain the water-stopping effect over a long period of time. Therefore, it is required to be able to produce efficiently and to be excellent in handling properties as a powder during production. Therefore, the water-absorbing resin particles used for water-stopping materials have high swelling performance, high water absorption speed, moderate particle size, and good handling properties in order to realize these performances. It is required to be.
- a method for improving the swelling performance of the water absorbent resin particles a method of controlling the crosslink density of the water absorbent resin particles is conceivable.
- a method in which an aqueous acrylic acid / acrylate solution is subjected to reverse phase suspension polymerization in the presence of a surfactant of HLB 8 to 12 and then a crosslinking agent is added to perform a crosslinking reaction see Patent Document 1).
- a surfactant of HLB 8 to 12 a surfactant of HLB 8 to 12
- a crosslinking agent is added to perform a crosslinking reaction
- An object of the present invention is to provide a method for producing water-absorbing resin particles having an excellent water absorption rate and high equilibrium swelling performance, and having an appropriate particle size and excellent handling properties, and a water-absorbing resin obtained thereby To provide particles.
- the present invention relates to a method for producing water absorbent resin particles as shown below, and water absorbent resin particles obtained thereby. That is, Item 1.
- a first reverse phase suspension polymerization using a water-soluble radical polymerization initiator in a petroleum hydrocarbon dispersion medium in the presence of a surfactant having an HLB of 8 to 12, (B) and further intermediate crosslinking A step of adding an agent to perform an intermediate crosslinking reaction, (C) in a state where the surfactant is dissolved in the petroleum hydrocarbon dispersion medium, a water-soluble ethylenically unsaturated monomer is added, and an internal crosslinking agent
- a second reverse phase suspension polymerization is performed using a water-soluble radical polymerization initiator to produce a water-absorbing resin precursor, and (D) the water content of the water-absorbing resin precursor is determined.
- a method of manufacturing a water-absorbing resin particles characterized by having a step of post-crosslinking reaction Item 2.
- Production method of resin particles Item 3.
- Item 4 The water absorption according to Item 1, 2, or 3, wherein the addition ratio of the intermediate crosslinking agent is 0.0001 to 0.026 mol% with respect to the total molar amount of the water-soluble ethylenically unsaturated monomer.
- Method for producing conductive resin particles Item 5.
- Item 1, 2, 3 or 4 water-absorbent resin particles obtained using the method for producing water-absorbent resin particles according to claim 4, Item 6.
- Item 6. The water absorption according to Item 5, wherein the equilibrium swelling performance is 12 to 28 mm, the water absorption rate is 1 to 5 seconds, the physiological saline water retention capacity is 20 to 60 g / g, and the median particle size is 100 to 400 ⁇ m. Resin particles.
- the present invention is described in detail below.
- a water-soluble ethylenically unsaturated monomer is added in the absence of an internal crosslinking agent, in the presence of a surfactant having an HLB of 8 to 12, Performing a first reversed-phase suspension polymerization using a water-soluble radical polymerization initiator in a hydrocarbon dispersion medium.
- 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 applies hereinafter), 2- (meth) acrylamide-2-methylpropanesulfonic acid and / or its alkali salt, (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, and N, N-diethylaminoethyl (meth) acrylate, N, N-diethylaminopropyl (meth) acrylate, and diethylaminopropyl (meth) Amino group-containing unsaturated monomers such as acrylamide and its quaternary It can be mentioned things like, may be at least one selected from
- the water-soluble ethylenically unsaturated monomer can be usually used as an aqueous solution.
- concentration of the water-soluble ethylenically unsaturated monomer in the aqueous solution is preferably in the range of 20% by mass to the saturated concentration.
- W / O type (Water in Oil type) reversed-phase suspension state is good and it is easy to obtain a suitable particle size, and the swelling performance of the resulting water-absorbent resin particles becomes high, 30 to 45% by mass Is more preferably 35 to 45% by mass.
- the water-soluble ethylenically unsaturated monomer has an acid group such as (meth) acrylic acid or 2- (meth) acrylamido-2-methylpropanesulfonic acid
- the acid group is converted to an alkali metal salt such as an alkali metal salt.
- You may neutralize with a neutralizing agent.
- alkaline neutralizer include aqueous solutions of sodium hydroxide, potassium hydroxide, and ammonium hydroxide. These alkaline neutralizers may be used alone or in combination.
- the degree of neutralization of all acid groups by the alkaline neutralizing agent increases the swelling ability by increasing the osmotic pressure of the resulting water-absorbent resin particles, and there is a problem with safety due to the presence of the excess alkaline neutralizing agent. From the viewpoint of preventing the occurrence of this, the range of 10 to 100 mol% is preferable, the range of 30 to 90 mol% is more preferable, and the range of 50 to 80 mol% is still more preferable.
- water-soluble radical polymerization initiator 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.
- Peroxides such as cumyl peroxide, t-butyl peroxyacetate, t-butyl peroxyisobutyrate, t-butyl peroxypivalate, and hydrogen peroxide
- 2,2′-azobis [2- (N-phenylamidino) propane] dihydrochloride
- 2,2′-azobis [2- (N-allylamidino) propane] dihydrochloride
- 4,4′-azobis (4-cyano And azo compounds such as valeric acid).
- These water-soluble radical polymerization initiators may be used alone or
- the addition amount of the water-soluble radical polymerization initiator is usually 0.005 to 1 mol% with respect to the total molar amount of the water-soluble ethylenically unsaturated monomer. If the amount of the water-soluble radical polymerization initiator added is less than 0.005 mol%, it takes a long time for the polymerization reaction, which is not preferable. If the addition amount exceeds 1 mol%, a rapid polymerization reaction occurs, which is not preferable.
- the water-soluble radical polymerization initiator can also be used as a redox polymerization initiator in combination with a reducing agent such as sodium sulfite, sodium hydrogen sulfite, ferrous sulfate and L-ascorbic acid.
- a chain transfer agent may be added in order to control the swelling performance of the water absorbent resin particles.
- chain transfer agents include hypophosphites, thiols, thiolic acids, secondary alcohols, amines, and the like.
- the water-soluble ethylenically unsaturated monomer is dispersed in a petroleum hydrocarbon in the absence of an internal crosslinking agent and in the presence of a surfactant having an HLB of 8-12.
- the first feature is to perform the first reversed-phase suspension polymerization using a water-soluble radical polymerization initiator in a medium.
- aqueous solution polymerization if the polymerization reaction is carried out in the absence of an internal cross-linking agent, it is possible to improve the swelling performance of the water absorbent resin particles, particularly the equilibrium swelling performance, but the water absorbent resin precursor obtained after the polymerization is very It is difficult to obtain water-absorbing resin particles having a large particle size, good swelling performance, and suitable particle size. Met.
- the water-absorbing resin precursor can be obtained without using an internal cross-linking agent during the polymerization reaction, a lump is partially formed, or particles adhere to each other in the drying process. And tend to aggregate.
- the inventors have conducted reverse-phase suspension polymerization using a specific surfactant, petroleum-based hydrocarbon dispersion medium, and a water-soluble ethylenically unsaturated monomer aqueous solution in the absence of an internal crosslinking agent. It was found that particles having a form suitable for water-stopping material use can be obtained more easily by carrying out the above. Furthermore, it has been found that high-performance water-absorbent resin particles suitable for water-stopping materials can be obtained by performing a specific crosslinking reaction and post-crosslinking reaction on the obtained particles, and the present invention has been completed.
- the internal crosslinking agent refers to a compound that contributes to the formation of a bridge structure between polymer chains during the polymerization of monomers.
- a compound having two or more polymerizable unsaturated groups polymerizable in the water-soluble ethylenically unsaturated monomer, a functional group contained in the water-soluble ethylenically unsaturated monomer It refers to a compound having two or more functional groups capable of reacting with (for example, a carboxyl group in the case of acrylic acid) in the molecule.
- a surfactant having an HLB of 8 to 12 is used.
- a surfactant having an HLB of 8 to 12 the state of W / O type reverse phase suspension is improved, and particles having a suitable particle size can be obtained.
- the HLB of the surfactant is preferably 8.5 to 10.5.
- surfactant examples include sorbitan fatty acid ester and (poly) glycerin fatty acid ester [(poly) means both with and without the prefix “poly”. The same shall apply hereinafter), sucrose 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 Nonionic surfactants such as castor oil, polyoxyethylene hydrogenated castor oil, alkylallyl formaldehyde condensed polyoxyethylene ether, polyoxyethylene polyoxypropylene block copolymer, polyoxyethylene polyoxypropyl alkyl ether, polyethylene glycol fatty acid ester; Fatty acid salt, alkylbenzene sulfonate, alkylmethyl taurate, polyoxyethylene alkyl Phenyl ether
- a sorbitan fatty acid ester from the viewpoint of obtaining water-absorbent resin particles having a favorable W / O-type reverse phase suspension and having a suitable particle size, and being easily available industrially, Polyglycerin fatty acid esters and sucrose fatty acid esters are preferably used, and among them, sorbitan fatty acid esters are more preferably used from the viewpoint of the water absorption rate of the water-absorbing resin particles obtained.
- These surfactants may be used alone or in combination of two or more.
- the amount of the surfactant added is the first reverse phase suspension.
- the amount is preferably 0.1 to 5 parts by weight, more preferably 0.2 to 3 parts by weight, and more preferably 0.3 to 2 parts by weight based on 100 parts by weight of the aqueous solution of the water-soluble ethylenically unsaturated monomer to be subjected to turbid polymerization. Part by mass is more preferable.
- the surfactant and the polymer protective colloid may be used in combination for the purpose of stabilizing the state of W / O type reverse phase suspension.
- the polymer protective colloid include, for example, maleic anhydride-modified polyethylene, maleic anhydride-modified polypropylene, maleic anhydride-modified ethylene / propylene copolymer, maleic anhydride-modified EPDM (ethylene-propylene-diene-terpolymer), anhydrous Maleic acid-modified polybutadiene, ethylene-maleic anhydride copolymer, ethylene-propylene-maleic anhydride copolymer, butadiene-maleic anhydride copolymer, oxidized polyethylene, ethylene-acrylic acid copolymer, ethyl cellulose, ethyl hydroxy Examples include ethyl cellulose.
- maleic anhydride-modified polyethylene maleic anhydride-modified polypropylene, maleic anhydride-modified ethylene-propylene copolymer, oxidized polyethylene, ethylene-acrylic acid copolymer Polymers are preferred.
- These polymer protective colloids may be used alone or in combination of two or more.
- the addition amount of the polymer protective colloid is selected from the viewpoint of selecting an effective addition amount that stabilizes the state of W / O-type reverse phase suspension and provides a suspension stabilization effect.
- the amount is preferably 0.1 to 5 parts by mass, more preferably 0.2 to 3 parts by mass, and more preferably 0.3 to 3 parts by mass with respect to 100 parts by mass of the aqueous solution of the water-soluble ethylenically unsaturated monomer added by suspension polymerization. 2 parts by mass is more preferable.
- Examples of the petroleum hydrocarbon dispersion medium include aliphatic hydrocarbons such as n-hexane, n-heptane, and ligroin; alicyclic hydrocarbons such as cyclopentane, methylcyclopentane, cyclohexane, and methylcyclohexane; benzene, toluene And aromatic hydrocarbons such as xylene, and the like. These may be used alone or in admixture of two or more.
- n-hexane, n-heptane and cyclohexane are preferably used from the viewpoint of industrial availability, and in particular, the W / O type reverse phase in the present invention. From the viewpoint of obtaining water-absorbing resin particles having a favorable suspended state and suitable particle diameter, and from the viewpoint of good water-absorbing performance of the water-absorbing resin particles obtained, n-heptane is more preferably used.
- the amount of the petroleum hydrocarbon dispersion medium added is 100% by mass of a water-soluble ethylenically unsaturated monomer that is subjected to reverse phase suspension polymerization from the viewpoint of appropriately removing the heat of polymerization and easily controlling the polymerization temperature.
- the amount is preferably 50 to 600 parts by mass, more preferably 100 to 550 parts by mass with respect to parts.
- the reaction temperature at the time of performing the first reverse phase suspension polymerization varies depending on the type of the water-soluble radical polymerization initiator to be used, and thus cannot be generally determined.
- the reaction temperature is preferably 20 to 110 ° C., more preferably 20 to 110 ° C. from the viewpoint of shortening the polymerization time by allowing the polymerization to proceed rapidly, removing the heat of polymerization, and performing the reaction smoothly. Is 40-90 ° C.
- the reaction time is usually 0.5 to 4 hours.
- step (B) a step of further adding an intermediate crosslinking agent to carry out an intermediate crosslinking reaction is then performed.
- the water-absorbent resin particles obtained by the first reversed-phase suspension polymerization were cross-linked, thereby adding a water-soluble ethylenically unsaturated monomer in the step (C) described later.
- the said (B) process and the (C) process mentioned later may be performed once or more, and may be performed twice or more as needed.
- Examples of the intermediate crosslinking agent used in the intermediate crosslinking reaction in the step (B) include ethylene glycol, propylene glycol, 1,4-butanediol, trimethylolpropane, glycerol, polyoxyethylene glycol, polyoxypropylene glycol, polyoxypropylene glycol, and the like.
- Polyols such as glycerin; glycidyl ether compounds such as (poly) ethylene glycol diglycidyl ether, (poly) propylene glycol diglycidyl ether, (poly) glycerin diglycidyl ether; epichlorohydrin, epibromhydrin, ⁇ -methylepichlorohydrin, etc.
- Halo epoxy compounds compounds having two or more reactive functional groups such as isocyanate compounds such as 2,4-tolylene diisocyanate and hexamethylene diisocyanate; 3-methyl 3-oxetanemethanol, 3-ethyl-3-oxetanemethanol, 3-butyl-3-oxetanemethanol, 3-methyl-3-oxetaneethanol, 3-ethyl-3-oxetaneethanol, 3-butyl-3-oxetaneethanol, etc.
- Oxetane compounds such as 1,2-ethylenebisoxazoline; carbonate compounds such as ethylene carbonate; and hydroxyalkylamide compounds such as bis [N, N-di ( ⁇ -hydroxyethyl)] adipamide.
- intermediate cross-linking agents diglycidyl ether compounds are preferable from the viewpoint of excellent reactivity, and ethylene glycol diglycidyl is particularly preferable from the viewpoint of high water solubility and good handleability as an intermediate cross-linking agent.
- Ether, propylene glycol diglycidyl ether, glycerin diglycidyl ether, and polyethylene glycol diglycidyl ether are more preferable, and ethylene glycol diglycidyl ether and propylene glycol diglycidyl ether are more preferable from the viewpoint of high water absorption performance of the resulting water-absorbent resin particles.
- These intermediate crosslinking agents may be used alone or in combination of two or more.
- the addition amount of the intermediate crosslinking agent used in the step (B) is based on the molar amount of the water-soluble ethylenically unsaturated monomer subjected to the polymerization immediately before the addition of the intermediate crosslinking agent in the step (B). 0.0001 to 0.026 mol% is preferable, 0.0005 to 0.021 mol% is more preferable, and 0.0025 to 0.015 mol% is still more preferable.
- the added amount of the intermediate crosslinking agent is less than 0.0001 mol%, the polymerized particles absorb the water-soluble ethylenically unsaturated monomer when a water-soluble ethylenically unsaturated monomer described later is added.
- the polymer is subjected to the next polymerization, so that the surface state of the water-absorbent resin particles obtained may change and the water absorption performance may be deteriorated. That is, there is a tendency that the water absorption rate becomes slow and the swelling performance becomes low. Moreover, when the addition amount of the said intermediate crosslinking agent exceeds 0.026 mol%, there exists a possibility that a crosslinking reaction may advance excessively and the water absorption performance of the water-absorbing resin particle obtained may become low.
- the “molar amount of the water-soluble ethylenically unsaturated monomer subjected to the polymerization immediately before the addition of the intermediate crosslinking agent in the step (B)” means that when the step (B) is the first time, A) means the molar amount of the water-soluble ethylenically unsaturated monomer added in the step, and when the step (B) is the second or later, the water-soluble ethylenically unsaturated monomer added in the previous step (C). It means a saturated monomer.
- the solvent for adding the intermediate crosslinking agent is not particularly limited as long as the intermediate crosslinking agent can be uniformly dispersed.
- Water may be used, and a hydrophilic organic solvent may be used. It may be used.
- the hydrophilic organic solvent include lower alcohols such as methyl alcohol, ethyl alcohol and isopropyl alcohol, ketones such as acetone and methyl ethyl ketone, ethers such as dioxane and tetrahydrofuran, and amides such as N, N-dimethylformamide.
- sulfoxides such as dimethyl sulfoxide.
- the reaction temperature of the intermediate crosslinking reaction in the step (B) is preferably 60 ° C. or higher, more preferably from 70 ° C. to the boiling point of the solvent used in the polymerization. If the reaction temperature is less than 60 ° C., the intermediate crosslinking reaction is difficult to proceed, and the water absorption performance of the resulting water absorbent resin may be lowered.
- the reaction time of the intermediate cross-linking reaction in the step (B) varies depending on the reaction temperature, the type and amount of the intermediate cross-linking agent, and cannot be determined unconditionally, but is usually preferably 1 to 200 minutes. More preferably, it is ⁇ 100 minutes, and more preferably 10-60 minutes.
- step (C) in the state where the surfactant is dissolved in the petroleum-based hydrocarbon dispersion medium, a water-soluble ethylenically unsaturated monomer is added,
- a step of producing a water-absorbing resin precursor by performing a second reverse phase suspension polymerization using a water-soluble radical polymerization initiator In the absence of an internal cross-linking agent in step (C) means that no internal cross-linking agent is added in the polymerization reaction in step (C).
- water-absorbing resin particles excellent in swelling performance can be produced with high productivity by performing reverse phase suspension polymerization a plurality of times.
- Examples of the water-soluble ethylenically unsaturated monomer used in the step (C) include (meth) acrylic acid, 2- (meth) acrylamido-2-methylpropanesulfonic acid and / or an alkali salt thereof (meta )
- Nonionic monomers such as acrylamide, N, N-dimethyl (meth) acrylamide, 2-hydroxyethyl (meth) acrylate, N-methylol (meth) acrylamide, and polyethylene glycol mono (meth) acrylate, and N , N-diethylaminoethyl (meth) acrylate, N, N-diethylaminopropyl (meth) acrylate, and amino group-containing unsaturated monomers such as diethylaminopropyl (meth) acrylamide and quaternized products thereof.
- water-soluble ethylenically unsaturated monomers (meth) acrylic acid or an alkali salt thereof, (meth) acrylamide, and N, N-dimethylacrylamide are preferred from the viewpoint of easy industrial availability.
- the water-soluble ethylenically unsaturated monomer can be usually used as an aqueous solution.
- concentration of the water-soluble ethylenically unsaturated monomer in the aqueous solution is preferably in the range of 20% by mass to the saturated concentration.
- the acid group When the water-soluble ethylenically unsaturated monomer used in the step (C) has an acid group such as (meth) acrylic acid or 2- (meth) acrylamide-2-methylpropanesulfonic acid, the acid group May be neutralized with an alkaline neutralizing agent such as an alkali metal salt.
- an alkaline neutralizing agent such as an alkali metal salt.
- alkaline neutralizer include aqueous solutions of sodium hydroxide, potassium hydroxide, and ammonium hydroxide. These alkaline neutralizing agents may be used alone or in combination of two or more.
- the degree of neutralization of all acid groups by the alkaline neutralizing agent increases the swelling ability by increasing the osmotic pressure of the resulting water-absorbent resin particles, and there is a problem with safety due to the presence of the excess alkaline neutralizing agent. From the viewpoint of preventing the occurrence of this, the range of 10 to 100 mol% is preferable, the range of 30 to 90 mol% is more preferable, and the range of 50 to 80 mol% is still more preferable.
- the amount of the water-soluble ethylenically unsaturated monomer used in the step (C) is 50 to 100 parts by mass with respect to 100 parts by mass of the water-soluble ethylenically unsaturated monomer subjected to polymerization in the step (A). 200 parts by mass is preferable, 70 to 180 parts by mass is more preferable, and 90 to 150 parts by mass is still more preferable.
- productivity with respect to the polymerization reaction time may be lowered.
- the addition amount of the water-soluble ethylenically unsaturated monomer used in the polymerization reaction operation in the step (C) exceeds 200 parts by mass, the productivity for the polymerization reaction time is high, but the water solubility used for the polymerization reaction is high.
- the amount of the ethylenically unsaturated monomer may increase, making it difficult to control the polymerization reaction.
- the surfactant is dissolved in the petroleum hydrocarbon dispersion medium in the reaction mixture after the intermediate crosslinking reaction in the step (B) is completed. It is necessary to add in the state.
- the water-soluble ethylenically unsaturated monomer is added in a state where the surfactant is not dissolved in the petroleum hydrocarbon dispersion medium, the water-soluble ethylenically unsaturated monomer added by the polymerized particles is absorbed. Then, they are aggregated and integrated (agglomerated).
- the “state in which the surfactant is dissolved in the petroleum hydrocarbon dispersion medium” can be created, for example, by controlling the temperature of the reaction mixture after the intermediate crosslinking reaction is completed.
- the temperature of the reaction mixture varies depending on the type of the surfactant and cannot be determined unconditionally. For example, it is preferably 40 to 65 ° C., more preferably 50 to 60 ° C.
- the temperature of the reaction mixture is less than 40 ° C., the surfactant is precipitated, so that the surfactant effect is lowered, and the polymerized particles absorb the water-soluble ethylenically unsaturated monomer added, and aggregate and integrate. May become agglomerated (agglomerated).
- the temperature of the reaction mixture exceeds 65 ° C., there is a risk that a polymerization reaction occurs when the water-soluble ethylenically unsaturated monomer is added, such being undesirable.
- water-soluble radical polymerization initiator used in the step (C) examples include persulfates such as potassium persulfate, ammonium persulfate, and sodium persulfate, methyl ethyl ketone peroxide, methyl isobutyl ketone peroxide, di-t- Peroxides such as butyl peroxide, t-butyl cumyl peroxide, t-butyl peroxyacetate, t-butyl peroxyisobutyrate, t-butyl peroxypivalate, and hydrogen peroxide; 2′-azobis [2- (N-phenylamidino) propane] dihydrochloride, 2,2′-azobis [2- (N-allylamidino) propane] dihydrochloride, 2,2′-azobis ⁇ 2- [ 1- (2-hydroxyethyl) -2-imidazolin-2-yl] propane ⁇ dihydrochloride, 2,2′-azobi ⁇ 2-Methy
- the amount of the water-soluble radical polymerization initiator used in the step (C) varies depending on the type of polymerization initiator and the reaction conditions, and thus cannot be determined unconditionally, but is usually added in the step (A).
- the amount is 0.005 to 1 mol% based on the molar amount of the water-soluble ethylenically unsaturated monomer. If the amount of the water-soluble radical polymerization initiator added is less than 0.005 mol%, it takes a long time for the polymerization reaction, which is not preferable. If the amount of the water-soluble radical polymerization initiator added exceeds 1 mol%, an abrupt polymerization reaction occurs, which is not preferable.
- the water-soluble radical polymerization initiator can also be used as a redox polymerization initiator in combination with a reducing agent such as sodium sulfite, sodium hydrogen sulfite, ferrous sulfate, and L-ascorbic acid.
- a reducing agent such as sodium sulfite, sodium hydrogen sulfite, ferrous sulfate, and L-ascorbic acid.
- the polymerization reaction is performed in the absence of an internal crosslinking agent from the viewpoint of enhancing the swelling performance of the water-absorbent resin particles, particularly the equilibrium swelling performance.
- a chain transfer agent from a viewpoint of controlling the swelling performance of the water absorbent resin particle obtained.
- chain transfer agents include hypophosphites, thiols, thiolic acids, secondary alcohols, amines, and the like.
- the reaction temperature varies depending on the type of the water-soluble radical polymerization initiator to be used, and thus cannot be determined unconditionally. Usually, the reaction temperature is preferably 20 to 110 ° C.
- the reaction time is usually 0.5 to 4 hours.
- the water-absorbent resin precursor obtained through the steps (A) to (C) can be obtained in various forms such as a spherical shape, a granular shape, a crushed shape, a confetti shape, and an aggregate thereof.
- the water-absorbent resin precursor is preferably obtained in the form of granules. A granular shape having uniform irregularities on the surface is more preferable.
- amorphous silica can be added to form aggregated particles.
- the amorphous silica include dry silica and wet silica. Among these amorphous silicas, wet silica is preferably used.
- the addition amount of the amorphous silica is preferably 0.0001 to 100 parts by mass with respect to the total mass of the water-soluble ethylenically unsaturated monomer subjected to polymerization in the steps (A) and (C). The amount is 1 part by mass, more preferably 0.001 to 0.5 part by mass, and still more preferably 0.01 to 0.2 part by mass.
- the total mass of the water-soluble ethylenically unsaturated monomer component constituting the water-absorbing resin precursor is calculated from the total mass of the water-soluble ethylenically unsaturated monomer used in the polymerization reaction, from the theoretical polymer solids. As a minute, it can be obtained by calculation.
- the water content of the water-absorbent resin precursor is then compared with the water-soluble ethylenically unsaturated monomer component constituting the water-absorbent resin precursor. After adjusting to 30 to 100% by mass, a post-crosslinking reaction step is performed.
- a method of adjusting the water content of the water-absorbent resin precursor to 30 to 100% by mass with respect to the water-soluble ethylenically unsaturated monomer component constituting the water-absorbent resin precursor (hereinafter simply referred to as primary drying).
- the water-absorbent resin precursor is dispersed in a petroleum-based hydrocarbon dispersion medium and dehydrated by azeotropic distillation by heating from the outside, or the water-absorbent resin by decantation. Examples thereof include a method of taking out the precursor and drying it under reduced pressure, a method of filtering the water-absorbent resin precursor with a filter and drying it under reduced pressure.
- a method in which a water-absorbent resin precursor obtained by polymerization is dispersed in a petroleum hydrocarbon dispersion medium and dehydrated by azeotropic distillation is preferred because of its simplicity in the production process.
- a post-crosslinking agent is added to the obtained water-absorbent resin precursor to perform a post-crosslinking reaction.
- a post-crosslinking agent is added to the obtained water-absorbent resin precursor to perform a post-crosslinking reaction.
- a compound having in the molecule two or more functional groups capable of reacting with a functional group contained in the water-soluble ethylenically unsaturated monomer for example, a carboxyl group in the case of acrylic acid
- a water-soluble compound for example, polyols such as ethylene glycol, propylene glycol, 1,4-butanediol, trimethylolpropane, glycerin, polyoxyethylene glycol, polyoxypropylene glycol, polyglycerin, etc.
- Glycidyl ether compounds such as (poly) ethylene glycol diglycidyl ether, (poly) propylene glycol diglycidyl ether, (poly) glycerin diglycidyl ether; haloepoxy such as epichlorohydrin, epibromohydrin, ⁇ -methylepichlorohydrin Compound: Compound having two or more reactive functional groups such as isocyanate compounds such as 2,4-tolylene diisocyanate and hexamethylene diisocyanate; 3-methyl-3-oxetanemethanol, 3-ethyl-3-oxetanemethanol, 3- Oxetane compounds such as butyl-3-oxetanemethanol, 3-methyl-3-oxetaneethanol, 3-ethyl-3-oxetaneethanol, 3-butyl-3-oxetaneethanol; oxazoline compounds such as 1,2-ethylenebisoxazoline; And carbonate compounds such as ethylene carbonate
- diglycidyl ether compounds are preferred from the viewpoint of excellent reactivity, and ethylene glycol diglycidyl ether is particularly preferred from the viewpoint of high water solubility and good handleability as a crosslinking agent.
- Propylene glycol diglycidyl ether, glycerin diglycidyl ether, and polyethylene glycol diglycidyl ether are more preferable, and ethylene glycol diglycidyl ether and propylene glycol diglycidyl ether are more preferable from the viewpoint of high swelling performance of the water-absorbent resin particles obtained.
- the post-crosslinking agent may be the same as or different from the intermediate crosslinking agent.
- the amount of the post-crosslinking agent added is preferably 0.001 to 3 mol%, preferably 0.005 to 2%, based on the total molar amount of the water-soluble ethylenically unsaturated monomer constituting the water absorbent resin precursor.
- the mol% is more preferable, 0.01 to 1 mol% is more preferable, and 0.02 to 0.5 mol% is particularly preferable. If the amount of the post-crosslinking agent added relative to the total molar amount of the water-soluble ethylenically unsaturated monomer is less than 0.001 mol%, the surface of the water-absorbent resin particles tends to have a viscosity during water absorption because the crosslinking is weak.
- the initial swelling performance tends to be low, and if it exceeds 3 mol%, the water retention amount of the resulting water-absorbent resin particles is lowered, and the swelling performance may be lowered accordingly.
- the total molar amount of the water-soluble ethylenically unsaturated monomer component constituting the water-absorbent resin precursor is the same as that of the water-soluble ethylenically unsaturated monomer used in the steps (A) and (C). It can be obtained by calculation from the total molar amount.
- the mixing of the water absorbent resin precursor and the post-crosslinking agent is performed after adjusting the water content of the water absorbent resin precursor to a specific range.
- the post-crosslinking reaction can proceed more suitably by controlling the moisture content during the reaction between the water absorbent resin precursor and the post-crosslinking agent.
- the water content of the water-absorbent resin precursor in the post-crosslinking step is 30 to 100% by mass, preferably 30 to 90% by mass, based on the water-soluble ethylenically unsaturated monomer component constituting the water-absorbent resin precursor. More preferably, it is 35 to 80% by mass.
- the moisture content is less than 30% by mass, the post-crosslinking agent is not uniformly dispersed in the water absorbent resin precursor.
- the moisture content exceeds 100% by mass, it becomes difficult to crosslink the surface layer of the water-absorbent resin precursor, and performance such as swelling performance is deteriorated.
- the moisture content is post-crosslinked to an amount obtained by subtracting the amount of moisture extracted outside by the primary drying step from the amount of moisture contained in the monomer aqueous solution before polymerization (the amount of moisture in the primary dry gel).
- the water-soluble ethylenically unsaturated monomer constituting the water-absorbent resin precursor after calculating the water content of the water-absorbent resin precursor by adding the amount of water used as necessary when adding the agent It can obtain
- the mass of the water-soluble ethylenically unsaturated monomer component constituting the water-absorbent resin precursor is the total mass of the water-soluble ethylenically unsaturated monomer used in the steps (A) and (C). From the above, the theoretical polymer solid content can be obtained by calculation.
- the amount of water used as needed when adding the post-crosslinking agent relative to the amount of water in the primary dry gel is such that the post-crosslinking agent is made uniform while rationally shortening the drying step and improving the economics of the process. From the viewpoint of dispersion, 100: 0 to 60:40 is preferable, 99: 1 to 70:30 is more preferable, 98: 2 to 80:20 is still more preferable, and 98: 2 to 90:10 is even more preferable.
- water or a hydrophilic organic solvent may be used as a solvent for uniformly dispersing the post-crosslinking agent.
- the hydrophilic organic solvent include lower alcohols such as methyl alcohol, ethyl alcohol and isopropyl alcohol, ketones such as acetone and methyl ethyl ketone, ethers such as dioxane and tetrahydrofuran, amides such as N, N-dimethylformamide, And sulfoxides such as dimethyl sulfoxide. Each of these may be used alone, or may be mixed with water or used in combination of two or more as required.
- the reaction temperature when the water-absorbing resin precursor is post-crosslinked with a post-crosslinking agent is preferably 60 ° C. or higher, more preferably 70 to 200 ° C., and still more preferably 80 to 150 ° C. If the reaction temperature is less than 60 ° C., the post-crosslinking reaction is difficult to proceed, and the reaction tends to require an excessive amount of time. If the reaction temperature exceeds 200 ° C., the resulting water-absorbent resin particles are decomposed or the water-absorbent resin There is a risk of coloring the particles.
- the post-crosslinking reaction time varies depending on the reaction temperature, the type and amount of the post-crosslinking agent, and cannot be determined unconditionally, but is usually 1 to 300 minutes, preferably 5 to 200 minutes.
- water-absorbing resin particles having high swelling performance can be obtained by the method of the present invention. It is considered that, by subjecting the water absorbent resin precursor adjusted to a specific moisture content to a post-crosslinking reaction under specific conditions, the crosslink density balance between the surface vicinity and the inside of the water absorbent resin particles is most suitable.
- the drying step may be performed by removing moisture, organic solvent, and the like by distillation by adding energy such as heat from the outside (
- this drying step is also referred to as secondary drying).
- secondary drying By performing such secondary drying, powdery water-absorbing resin particles are obtained.
- the method of secondary drying is not particularly limited.
- the mixture of resin particles after being dispersed in a petroleum hydrocarbon dispersion medium and then subjected to a crosslinking reaction is distilled to simultaneously remove moisture and the petroleum hydrocarbon dispersion medium.
- examples thereof include a method of removing, a method of taking out resin particles by decantation and drying under reduced pressure, and a method of separating resin particles by a filter and drying under reduced pressure.
- a method of simultaneously removing moisture and petroleum hydrocarbon dispersion medium by distilling a mixture of resin particles after being dispersed in a petroleum hydrocarbon dispersion medium and subjected to a crosslinking reaction is preferable.
- water-absorbing resin particles of the present invention By using the method for producing water-absorbing resin particles of the present invention, water-absorbing resin particles having both excellent water absorption speed and high equilibrium swelling performance, moderate particle size and good handling properties can be obtained. Such water-absorbing resin particles are also one aspect of the present invention.
- the water-absorbent resin particles of the present invention preferably have an equilibrium swelling performance of 10 to 28 mm. By having such a high swelling performance, after preventing initial flooding due to cracks in the cable external material, it maintains a long-term flood prevention effect and exhibits an appropriate swelling pressure that does not promote cable material degradation. can do. Further, the equilibrium swelling performance is more preferably 11 to 24 mm, further preferably 12 to 20 mm, and particularly preferably 13 to 18 mm.
- the water absorbent resin particles of the present invention preferably have a physiological saline water absorption rate of 1 to 10 seconds. By having such an excellent water absorption speed, it is possible to prevent water from entering due to cable cracks more quickly.
- the water absorption speed is more preferably 1 to 8 seconds, and further preferably 1 to 5 seconds.
- the water absorbent resin particles of the present invention preferably have a median particle size of 100 to 400 ⁇ m. By having such a median particle size, it is possible to maintain good handling properties as a powder during the production of the water-stopping material and to make the water-stopping material thin.
- the median particle diameter is more preferably 120 to 350 ⁇ m, and further preferably 130 to 300 ⁇ m.
- the physiological saline water retention capacity of the water-absorbent resin particles of the present invention is not particularly limited, but it is preferably 20 to 60 g / g, more preferably 25 to 55 g / g because it is preferable to absorb more water.
- the equilibrium swelling performance, physiological saline water absorption rate, physiological saline water retention capacity, and median particle size of the water-absorbent resin particles of the present invention are all values measured by the measurement methods described in the examples described later. .
- the water-absorbent resin particles of the present invention may further contain additives such as heat-resistant stabilizers, antioxidants and antibacterial agents.
- the amount of the additive varies depending on the use of the water-absorbent resin particles, the kind of the additive, etc., but the total mass of the water-soluble ethylenically unsaturated monomer added in the steps (A) and (C) is 100.
- the amount is preferably 0.001 to 10 parts by mass, more preferably 0.01 to 5 parts by mass, and still more preferably 0.1 to 2 parts by mass with respect to parts by mass.
- the total mass of the water-soluble ethylenically unsaturated monomer component constituting the water-absorbing resin precursor is calculated from the total mass of the water-soluble ethylenically unsaturated monomer used in the polymerization reaction, from the theoretical polymer solids. As a minute, it can be obtained by calculation.
- Example 1 (First reverse phase suspension polymerization) A round bottom cylinder with an inner diameter of 100 mm, equipped with a reflux condenser, a dropping funnel, a nitrogen gas introduction pipe, and a stirring blade (a fluororesin coated on the surface) having two inclined paddle blades with a blade diameter of 50 mm as a stirrer A type separable flask was prepared. To this flask, 360 g of n-heptane was taken, and 1.47 g of sorbitan monolaurate (trade name: Nonion LP-20R, manufactured by NOF Corporation) having an HLB of 8.6 as a surfactant was added up to 50 ° C.
- sorbitan monolaurate trade name: Nonion LP-20R, manufactured by NOF Corporation
- the mass of the water-soluble ethylenically unsaturated monomer in this monomer aqueous solution was 91.0 g, and the water content was 148.6 g.
- the rotation speed of the stirrer was set to 450 r / min, the monomer aqueous solution for the first polymerization was added to the separable flask, the system was replaced with nitrogen gas for 30 minutes, and then placed in a 70 ° C. water bath. The temperature was increased by immersion, and the first reverse phase suspension polymerization was performed for 1 hour.
- the rotation speed of the stirrer was set to 1000 r / min, and the reaction mixture after completion of the intermediate crosslinking reaction was cooled to 60 ° C. (in a state where sorbitan monolaurate was dissolved in n-heptane)
- the monomer aqueous solution for the second polymerization adjusted to 14 ° C. was dropped into the system, and the system was stirred for 30 minutes at the rotational speed while maintaining the system temperature (47 ° C.) when the dropping was completed.
- the inside of the system was replaced with nitrogen gas, and then the temperature was increased by immersing in a 70 ° C. water bath, and the second reverse phase suspension polymerization was performed for 1 hour to obtain a water absorbent resin precursor.
- Example 2 As an intermediate crosslinking agent to be added in the (intermediate crosslinking reaction) of Example 1, instead of 0.41 g (0.000047 mol) of a 2% by mass ethylene glycol diglycidyl ether aqueous solution, a 2% by mass ethylene glycol diglycidyl ether aqueous solution. Using 1.24 g (0.00014 mol) and further in the (post-crosslinking reaction) of Example 1, water and n-heptane were azeotroped to reduce the amount of water extracted from the system from 197.3 g.
- Example 3 In Example 1 (second reversed phase suspension polymerization), the cooling temperature of the reaction mixture after completion of the intermediate crosslinking reaction was changed from 60 ° C. to 50 ° C., and the temperature inside the system when dripping was completed was changed. Except that the temperature was changed from 47 ° C. to 41 ° C., the same operation as in Example 1 was performed (the water content with respect to the water-soluble ethylenically unsaturated monomer component constituting the water-absorbent resin precursor was 41% by mass), granule 189.5 g of a water-absorbent resin particle was obtained.
- Example 4 (First reverse phase suspension polymerization) A round bottom cylinder with an inner diameter of 100 mm, equipped with a reflux condenser, a dropping funnel, a nitrogen gas introduction pipe, and a stirring blade (a fluororesin coated on the surface) having two inclined paddle blades with a blade diameter of 50 mm as a stirrer A type separable flask was prepared. To this flask, 400 g of n-heptane was taken, and 1.30 g of sorbitan monolaurate (manufactured by NOF Corporation, trade name: Nonion LP-20R) having an HLB of 8.6 as a surfactant was added, up to 50 ° C.
- sorbitan monolaurate manufactured by NOF Corporation, trade name: Nonion LP-20R
- the mass of the water-soluble ethylenically unsaturated monomer in this monomer aqueous solution was 80.2 g, and the water content was 130.9 g.
- the rotation speed of the stirrer was set to 450 r / min, the monomer aqueous solution for the first polymerization was added to the separable flask, the system was replaced with nitrogen gas for 30 minutes, and then placed in a 70 ° C. water bath. The temperature was increased by immersion, and the first reverse phase suspension polymerization was performed for 1 hour.
- the rotation speed of the stirrer was set to 1000 r / min, and the reaction mixture after completion of the intermediate crosslinking reaction was cooled to 60 ° C. (in a state where sorbitan monolaurate was dissolved in n-heptane)
- the monomer aqueous solution for the second polymerization adjusted to 14 ° C. was dropped into the system, and the system was stirred for 30 minutes at the rotation speed while maintaining the system temperature (50 ° C.) when the dropping was completed.
- the inside of the system was replaced with nitrogen gas, and then the temperature was increased by immersing in a 70 ° C. water bath, and a second reverse phase suspension polymerization was performed for 1 hour to obtain a water-absorbing resin particle precursor.
- Example 5 To the liquid containing the water-absorbent resin precursor obtained after the (second-time reversed-phase suspension polymerization) in Example 1, an amorphous silica powder (manufactured by Tokuyama Soda Co., Ltd., trade name: Toxeal P) Except for adding 0.04 g, the same operation as in Example 1 was performed to obtain 188.6 g of granular water-absorbent resin particles in which the particles were aggregated.
- an amorphous silica powder manufactured by Tokuyama Soda Co., Ltd., trade name: Toxeal P
- Example 6 In Example 1 (post-crosslinking reaction), the amount of water withdrawn out of the system was changed from 197.3 g to 120.8 g by azeotropic distillation of water and n-heptane. Except that instead of 7.36 g (0.000845 mol) of a 2% by mass ethylene glycol diglycidyl ether aqueous solution, it was changed to 1.84 g (0.000211 mol) of a 2% by mass ethylene glycol diglycidyl ether aqueous solution. Then, the same operation as in Example 1 was performed, and the water-absorbing ethylenically unsaturated monomer component constituting the water-absorbing resin precursor was 80% by mass. Obtained.
- Example 7 In Example 1 (post-crosslinking reaction), the amount of water withdrawn out of the system was changed from 197.3 g to 159.0 g by azeotropically boiling water and n-heptane. Except that 7.36 g (0.000845 mol) of a 2% by weight aqueous ethylene glycol diglycidyl ether solution was replaced with 3.68 g (0.000423 mol) of a 2% by weight aqueous ethylene glycol diglycidyl ether solution. Then, the same operation as in Example 1 was performed, and the water-absorbing ethylenically unsaturated monomer component constituting the water-absorbing resin precursor was 60% by mass. 191.3 g of granular water-absorbing resin particles Obtained.
- the rotation rate of the stirrer was set to 700 r / min, the monomer aqueous solution was added to the separable flask, the inside of the system was replaced with nitrogen gas for 30 minutes, and then immersed in a 70 ° C. water bath to raise the temperature. Reverse phase suspension polymerization was carried out for 1 hour.
- the rotation rate of the stirrer was set to 700 r / min, the monomer aqueous solution was added to the separable flask, the inside of the system was replaced with nitrogen gas for 30 minutes, and then immersed in a 70 ° C. water bath to raise the temperature. Reverse phase suspension polymerization was carried out for 1 hour to obtain a water-absorbing resin precursor.
- the mass of the water-soluble ethylenically unsaturated monomer in this monomer aqueous solution was 91.0 g, and the water content was 148.6 g.
- the rotation speed of the stirrer was set to 450 r / min, the monomer aqueous solution for the first polymerization was added to the separable flask, the system was replaced with nitrogen gas for 30 minutes, and then placed in a 70 ° C. water bath. The temperature was increased by immersion, and the first reverse phase suspension polymerization was performed for 1 hour.
- the rotation speed of the stirrer was set to 1000 r / min, and the reaction mixture after completion of the intermediate crosslinking reaction was cooled to 60 ° C. (in a state where sorbitan monolaurate was dissolved in n-heptane)
- the monomer aqueous solution for the second polymerization adjusted to 14 ° C. was dropped into the system, and the system was stirred for 30 minutes at the rotational speed while maintaining the system temperature (47 ° C.) when the dropping was completed.
- the inside of the system was replaced with nitrogen gas, and then the temperature was increased by immersing in a 70 ° C. water bath, and a second reverse phase suspension polymerization was performed for 1 hour to obtain a water-absorbing resin particle precursor.
- Example 4 After completion of (first reverse phase suspension polymerization) in Example 1, the same operation as in Example 1 was performed, except that ethylene glycol diglycidyl ether was not added as an intermediate crosslinking agent. However, when the monomer aqueous solution for the second polymerization was dropped into the system, the stirring load of the stirrer increased and the stirring became impossible, so the subsequent steps were canceled.
- the rotation speed of the stirrer was set to 700 r / min, the monomer aqueous solution for the first polymerization was added to the separable flask, the system was replaced with nitrogen gas for 30 minutes, and then placed in a 70 ° C. water bath. The temperature was increased by immersion, and the first reverse phase suspension polymerization was performed for 1 hour.
- the rotation speed of the stirrer was set to 1000 r / min, and the reaction mixture after completion of the intermediate crosslinking reaction was cooled to 50 ° C. (a state where the sucrose fatty acid ester was dissolved in n-heptane),
- the monomer aqueous solution for the second polymerization adjusted to 14 ° C. is dropped into the system, and stirring is performed for 30 minutes at the rotation speed while maintaining the system temperature (47 ° C.) when the dropping is completed.
- the inside of the system was replaced with nitrogen gas, and then the temperature was increased by immersing in a 70 ° C. water bath, and the second reverse phase suspension polymerization was performed for 1 hour to obtain a water absorbent resin precursor.
- Example 6 As an intermediate crosslinking agent to be added in the (intermediate crosslinking reaction) of Example 1, instead of 0.41 g (0.000047 mol) of a 2% by mass ethylene glycol diglycidyl ether aqueous solution, a 2% by mass ethylene glycol diglycidyl ether aqueous solution. 1.24 g (0.00014 mol) was used. Further, in Example 1 (second-phase reversed-phase suspension polymerization), the cooling temperature of the reaction mixture after completion of the intermediate crosslinking reaction was changed from 60 ° C. to 30 ° C., and the temperature inside the system when the dropping was completed The same operation as in Example 1 was performed except that the temperature was changed from 47 ° C. to 28 ° C.
- the mass of the water-soluble ethylenically unsaturated monomer in this monomer aqueous solution was 91.0 g, and the water content was 148.6 g.
- the rotation speed of the stirrer was set to 450 r / min, the monomer aqueous solution for the first polymerization was added to the separable flask, the system was replaced with nitrogen gas for 30 minutes, and then placed in a 70 ° C. water bath. The temperature was increased by immersion, and the first reverse phase suspension polymerization was performed for 1 hour.
- the number of revolutions of the stirrer was set to 1000 r / min, and the reaction mixture after completion of the first reverse-phase suspension polymerization reaction was 60 ° C.
- the second monomer aqueous solution for polymerization adjusted to 14 ° C. was dropped into the system, and the dropping was completed.
- the system temperature 47 ° C.
- the system was agitated for 30 minutes at the same time as the system was replaced with nitrogen gas, and then immersed in a 70 ° C. water bath to raise the temperature. Phase suspension polymerization was carried out for 1 hour to obtain a water absorbent resin precursor.
- Example 8 In Example 1 (post-crosslinking reaction), except that the amount of water withdrawn out of the system was changed from 197.3 g to 71.6 g by azeotropic distillation of water and n-heptane. The same operation was performed to obtain 191.0 g of granular water-absorbent resin particles (the water content with respect to the water-soluble ethylenically unsaturated monomer component constituting the water-absorbent resin precursor was 110% by mass).
- the cotton bag was dehydrated using H-122) for 1 minute, and the weight Wa (g) of the cotton bag containing the swollen gel after dehydration was measured.
- the same operation was performed without adding the water-absorbent resin particles, the empty mass Wb (g) when the cotton bag was wet was measured, and the water retention capacity was calculated from the following equation.
- Water retention capacity of water-absorbent resin particles (g / g) [Wa-Wb] (g) / mass of water-absorbent resin particles (g)
- the mass of the water-absorbent resin particles remaining on each sieve is calculated as a percentage by mass with respect to the total amount, and by integrating in order from the larger particle diameter, the water-absorbent resin particles remaining on the sieve and the sieve
- the relationship between the mass percentage and the integrated value 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% by mass was defined as the median particle diameter.
- the swelling performance measuring device X shown in FIG. 1 includes a moving distance measuring device 1, a concave circular cup 2 (height 30 mm, inner diameter 80.5 mm), and a plastic convex circular cylinder 3 (outer diameter 80 mm, water-absorbing resin particles). 60 through holes 7 having a diameter of 2 mm are equally provided on the contact surface) and the nonwoven fabric 4.
- the swelling performance measuring apparatus X can measure the displacement of the distance by the laser beam 6 in units of 0.01 mm.
- the concave circular cup 2 can uniformly spread a predetermined amount of water-absorbing resin particles.
- the convex circular cylinder 3 can uniformly apply a load of 90 g to the water absorbent resin particles 5.
- a sample (water-absorbent resin particles 5) 0.1 g is uniformly sprayed on the concave circular cup 2, and the nonwoven fabric 4 is laid thereon.
- the convex circular cylinder 3 is placed gently on the nonwoven fabric 4 and installed so that the laser beam 6 of the sensor of the moving distance measuring device 1 comes to the center of the cylinder. 130 g of ion-exchanged water previously adjusted to 20 ° C.
- the moving distance of the convex circular cylinder 3 10 minutes after the start of water absorption was defined as the equilibrium swelling performance.
- each of the water-absorbent resin particles obtained in Examples 1 to 7 has an excellent water absorption rate and high equilibrium swelling performance, and has a moderate median particle size. Recognize. On the other hand, it can be seen that the water-absorbent resin particles obtained in the comparative example have insufficient water absorption speed and swelling performance.
- the water-absorbent resin particles of the present invention are used for sanitary materials such as disposable diapers, sanitary products, pet sheets, agricultural and horticultural materials such as water retention materials and soil improvement materials, water-stopping materials for power and communication cables, and anti-condensation materials. It can be used in various fields such as for industrial materials, and is particularly suitable for industrial materials such as water / waterstop materials for power / communication cables.
Abstract
Description
また、高い吸水量及び高い膨潤性能を有し、かつ、粒径の小さい吸水性樹脂粒子を製造する方法としては、例えば、水溶性エチレン性不飽和単量体を逆相懸濁重合させる方法において、1段目の重合後、界面活性剤及び/又は高分子保護コロイドが炭化水素系溶媒に溶解している状態で、2段目に用いる水溶性エチレン性不飽和単量体を添加して、重合する方法(特許文献2参照)が提案されている。
また、特許文献2に開示されている方法により得られる吸水性樹脂粒子は、粒子径が小さいため、ハンドリング性が低いという問題があった。
本発明の目的は、優れた吸水速度及び高い平衡膨潤性能を有し、かつ、粒径が適度な大きさでハンドリング性に優れた吸水性樹脂粒子の製造方法、及びそれにより得られる吸水性樹脂粒子を提供することにある。
即ち、
項1.水溶性エチレン性不飽和単量体を逆相懸濁重合して吸水性樹脂粒子を製造する方法であって、(A)水溶性エチレン性不飽和単量体を、内部架橋剤の非存在下、HLBが8~12の界面活性剤の存在下、石油系炭化水素分散媒中で水溶性ラジカル重合開始剤を用いて第一回目の逆相懸濁重合を行う工程、(B)更に中間架橋剤を加えて中間架橋反応を行う工程、(C)前記界面活性剤が石油系炭化水素分散媒に溶解している状態で、水溶性エチレン性不飽和単量体を添加し、内部架橋剤の非存在下、水溶性ラジカル重合開始剤を用いて第二回目の逆相懸濁重合を行い、吸水性樹脂前駆体を作製する工程、及び、(D)前記吸水性樹脂前駆体の水分率を、前記吸水性樹脂前駆体を構成する水溶性エチレン性不飽和単量体成分に対して30~100質量%に調整した後、後架橋反応させる工程を有することを特徴とする吸水性樹脂粒子の製造方法、
項2.HLBが8~12の界面活性剤は、ソルビタン脂肪酸エステル、ポリグリセリン脂肪酸エステル、及び、ショ糖脂肪酸エステルからなる群より選ばれる少なくとも1種の化合物であることを特徴とする項1記載の吸水性樹脂粒子の製造方法、
項3.中間架橋剤が、グリシジルエーテル化合物であることを特徴とする項1又は2記載の吸水性樹脂粒子の製造方法、
項4.中間架橋剤の添加割合が、水溶性エチレン性不飽和単量体の総モル量に対して、0.0001~0.026モル%であることを特徴とする項1、2又は3記載の吸水性樹脂粒子の製造方法、
項5.項1、2、3又は4記載の吸水性樹脂粒子の製造方法を用いて得られることを特徴とする吸水性樹脂粒子、
項6.平衡膨潤性能が12~28mm、吸水速度が1~5秒、生理食塩水保水能が20~60g/g、及び、中位粒径が100~400μmであることを特徴とする項5記載の吸水性樹脂粒子、である。
以下に本発明を詳細に説明する。
なお、前記水溶性ラジカル重合開始剤は、亜硫酸ナトリウム、亜硫酸水素ナトリウム、硫酸第一鉄及びL-アスコルビン酸等の還元剤を併用して、レドックス重合開始剤として用いることもできる。
水溶液重合では、内部架橋剤の非存在下で重合反応を行うと、吸水性樹脂粒子の膨潤性能、特に平衡膨潤性能を高めることが可能となるが、重合後に得られる吸水性樹脂前駆体が非常に粘調で、裁断が困難となるため、後工程の乾燥工程や粉砕工程で多大な負荷が掛かり、膨潤性能が良好で、かつ、適度な粒子径を有する吸水性樹脂粒子を得ることは困難であった。
また、従来の逆相懸濁重合では、重合反応時に内部架橋剤を使用しなくても吸水性樹脂前駆体が得られるものの、部分的に塊状物が生成したり、乾燥工程において粒子同士が粘着して凝集したりする傾向があった。
本発明者らは、鋭意検討した結果、内部架橋剤の非存在下、特定の界面活性剤、石油系炭化水素分散媒、水溶性エチレン性不飽和単量体水溶液を用いて逆相懸濁重合を行うことで、止水材用途に好適な形態の粒子がより簡便に得られることを見出した。更に、得られた粒子に特定の架橋反応、後架橋反応を行うことで、止水材用途に好適な高性能の吸水性樹脂粒子が得られることを見出し、本発明の完成に至った。
なお、本発明において、内部架橋剤とは、単量体の重合中に高分子鎖間の橋架け構造を形成するのに寄与する化合物のことをいう。具体的には、前記水溶性エチレン性不飽和単量体と重合可能な重合性不飽和基を分子内に2個以上有する化合物、前記水溶性エチレン性不飽和単量体中に含まれる官能基(例えば、前記アクリル酸の場合はカルボキシル基)と反応しうる官能基を分子内に2個以上有する化合物等のことをいう。
なお、前記(B)工程及び後述する(C)工程は、1回以上行い、必要により2回以上行ってもよい。
これらの中間架橋剤のなかでも、反応性に優れている観点から、ジグリシジルエーテル化合物が好ましく、なかでも、水溶性が高く、中間架橋剤としてのハンドリング性が良いという観点から、エチレングリコールジグリシジルエーテル、プロピレングリコールジグリシジルエーテル、グリセリンジグリシジルエーテル、ポリエチレングリコールジグリシジルエーテルがより好ましく、得られる吸水性樹脂粒子の吸水性能が高いという観点から、エチレングリコールジグリシジルエーテル、プロピレングリコールジグリシジルエーテルが更に好ましい。これらの中間架橋剤は、それぞれ単独で用いてもよく、2種以上を組み合わせて使用してもよい。
なお、「前記(B)工程の中間架橋剤を添加する直前の重合に付した水溶性エチレン性不飽和単量体のモル量」とは、(B)工程が1回目の場合は、前記(A)工程において添加した水溶性エチレン性不飽和単量体のモル量を意味し、(B)工程が2回目以降の場合は、1回前の(C)工程において添加した水溶性エチレン性不飽和単量体を意味する。
前記(B)工程における中間架橋反応の反応時間は、反応温度、前記中間架橋剤の種類及び添加量等によって異なるので一概には決定することができないが、通常、1~200分間が好ましく、5~100分間がより好ましく、10~60分間が更に好ましい。
なお、本(C)工程における内部架橋剤の非存在下とは、(C)工程の重合反応において内部架橋剤を添加しないことを意味する。
本発明では、逆相懸濁重合を複数回行うことで、膨潤性能に優れた吸水性樹脂粒子を生産性高く製造することができる。
前記水溶性エチレン性不飽和単量体は、通常、水溶液として用いることができる。前記水溶液における水溶性エチレン性不飽和単量体の濃度は、20質量%~飽和濃度の範囲であることが好ましい。また、W/O型(Water in Oil型)逆相懸濁の状態が良好で好適な粒径を得やすく、得られる吸水性樹脂粒子の膨潤性能が高くなるという観点から、30~45質量%がより好ましく、35~45質量%であることが更に好ましい。
「前記界面活性剤が石油系炭化水素分散媒に溶解している状態」は、例えば、前記中間架橋反応が終了した反応混合物の温度を制御することにより、作り出すことができる。前記反応混合物の温度は、前記界面活性剤の種類により異なるので一概には決定することができないが、例えば、好ましくは40~65℃であり、より好ましくは50~60℃である。反応混合物の温度が40℃未満であると、界面活性剤が析出することにより界面活性効果が低くなり、重合した粒子が添加した水溶性エチレン性不飽和単量体を吸収し、凝集して一体化(塊状化)することがある。また、反応混合物の温度が65℃を超えると、水溶性エチレン性不飽和単量体を添加している際に重合反応が起こる等の危険があるので好ましくない。
なお、前記水溶性ラジカル重合開始剤は、亜硫酸ナトリウム、亜硫酸水素ナトリウム、硫酸第一鉄、及びL-アスコルビン酸等の還元剤を併用して、レドックス重合開始剤として用いることもできる。
また、得られる吸水性樹脂粒子の膨潤性能を制御する観点から、連鎖移動剤を使用してもよい。このような連鎖移動剤としては、例えば、次亜リン酸塩類、チオール類、チオール酸類、第2級アルコール類、アミン類等が挙げられる。
前記(C)工程において、反応温度は、使用する水溶性ラジカル重合開始剤の種類によって異なるので、一概には決定することができない。通常、該反応温度は、重合を迅速に進行させることで重合時間を短くする観点、重合熱を除去することが容易である観点、円滑に反応を行う観点から、好ましくは20~110℃であり、より好ましくは40~90℃である。反応時間は、通常、0.5~4時間である。
非晶質シリカの添加量としては、前記(A)工程及び(C)工程において重合に付した水溶性エチレン性不飽和単量体の総質量100質量部に対して、好ましくは0.0001~1質量部、より好ましくは0.001~0.5質量部、更に好ましくは0.01~0.2質量部である。
なお、前記吸水性樹脂前駆体を構成する水溶性エチレン性不飽和単量体成分の総質量は、重合反応に用いた水溶性エチレン性不飽和単量体の総質量から、理論上のポリマー固形分として、計算により求めることができる。
これらの後架橋剤のなかでも、反応性に優れている観点から、ジグリシジルエーテル化合物が好ましく、なかでも、水溶性が高く、架橋剤としてのハンドリング性が良いという観点から、エチレングリコールジグリシジルエーテル、プロピレングリコールジグリシジルエーテル、グリセリンジグリシジルエーテル、ポリエチレングリコールジグリシジルエーテルがより好ましく、得られる吸水性樹脂粒子の膨潤性能が高いという観点から、エチレングリコールジグリシジルエーテル、プロピレングリコールジグリシジルエーテルがさらに好ましい。
なお、前記後架橋剤は、前記中間架橋剤と同じものであってもよく、異なるものであってもよい。
なお、前記吸水性樹脂前駆体を構成する水溶性エチレン性不飽和単量体成分の総モル量は、前記(A)工程及び(C)工程で用いた水溶性エチレン性不飽和単量体の総モル量から、計算により求めることができる。
なお、前記水分率は、重合前の単量体水溶液に含まれる水分量から、1次乾燥工程により外部に抽出された水分量を差し引いた量(1次乾燥ゲルの水分量)に、後架橋剤を添加する際に必要に応じて用いられる水分量を合計することにより、吸水性樹脂前駆体の水分量を算出した後、吸水性樹脂前駆体を構成する水溶性エチレン性不飽和単量体成分の質量に対する吸水性樹脂前駆体の水分量の割合を算出することによって求めることできる。
なお、前記吸水性樹脂前駆体を構成する水溶性エチレン性不飽和単量体成分の質量は、前記(A)工程及び(C)工程で用いた水溶性エチレン性不飽和単量体の総質量から、理論上のポリマー固形分として、計算により求めることができる。
1次乾燥ゲルの水分量に対する、後架橋剤を添加する際に必要に応じて用いられる水分量は、乾燥工程を合理的に短縮してプロセスの経済性を高めつつ、後架橋剤を均一に分散させる観点から、100:0~60:40が好ましく、99:1~70:30がより好ましく、98:2~80:20が更に好ましく、98:2~90:10がより更に好ましい。
前記後架橋の反応時間は、反応温度、後架橋剤の種類及び量等によって異なるので一概には決定することができないが、通常、1~300分間、好ましくは5~200分間である。
前記添加剤の量は、吸水性樹脂粒子の用途、添加剤の種類等によって異なるが、前記(A)工程及び(C)工程において添加された水溶性エチレン性不飽和単量体の総質量100質量部に対して、好ましくは0.001~10質量部、より好ましくは0.01~5質量部、更に好ましくは0.1~2質量部である。
なお、前記吸水性樹脂前駆体を構成する水溶性エチレン性不飽和単量体成分の総質量は、重合反応に用いた水溶性エチレン性不飽和単量体の総質量から、理論上のポリマー固形分として、計算により求めることができる。
(第一回目の逆相懸濁重合)
還流冷却器、滴下ロート、窒素ガス導入管、撹拌機として翼径50mmの4枚傾斜パドル翼を2段で有する撹拌翼(フッ素樹脂を表面にコートしたもの)を備えた内径100mm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n-ヘプタン360gをとり、界面活性剤としてのHLBが8.6のソルビタンモノラウレート(日油株式会社製、商品名:ノニオンLP-20R)1.47gを添加し、50℃まで昇温して界面活性剤を溶解したのち、内温を47℃まで冷却した。
一方、500mL容の三角フラスコに80.5質量%のアクリル酸水溶液92g(1.03モル)を入れ、これを氷冷しながら20.9質量%の水酸化ナトリウム水溶液147.6gを滴下して75モル%の中和を行ったのち、過硫酸カリウム0.101g(0.00037モル)を加えて溶解し、第一回目の重合用の単量体水溶液を調製した。なお、この単量体水溶液における水溶性エチレン性不飽和単量体の質量は91.0g、水分量は148.6gであった。
撹拌機の回転数を450r/minとして、前記第一回目の重合用の単量体水溶液を前記セパラブルフラスコに添加して、系内を窒素ガスで30分間置換した後、70℃の水浴に浸漬して昇温し、第一回目の逆相懸濁重合を1時間行った。
第一回目の逆相懸濁重合反応の終了後、得られた反応混合物に、中間架橋剤として2質量%のエチレングリコールジグリシジルエーテル水溶液0.41g(0.000047モル)を添加して、75℃で30分間、中間架橋反応を行った。
次に、前記第一回目の重合用の単量体とは別に、500mL容の三角フラスコに80.5質量%のアクリル酸水溶液92g(1.03モル)を入れ、これを氷冷しながら26.9質量%の水酸化ナトリウム水溶液114.7gを滴下して75モル%の中和を行ったのち、過硫酸カリウム0.101g(0.00037モル)を加えて溶解し、第二回目の重合用の単量体水溶液を調製した。なお、この単量体水溶液における水溶性エチレン性不飽和単量体の質量は91.0g、水分量は115.7gであった。
前記中間架橋反応の終了後、撹拌機の回転数を1000r/minとして、中間架橋反応終了後の反応混合物を60℃に冷却し(ソルビタンモノラウレートが、n-ヘプタンに溶解している状態)、14℃に調整した前記第二回目の重合用の単量体水溶液を系内に滴下し、滴下が終了したときの系内温度(47℃)に保ちながら、前記回転数で30分間攪拌を行うと同時に系内を窒素ガスで置換した後、70℃の水浴に浸漬して昇温し、第二回目の逆相懸濁重合を1時間行い、吸水性樹脂前駆体を得た。
得られた吸水性樹脂前駆体を含有する液体を、120℃の油浴を使用して昇温し、水とn-ヘプタンとを共沸することにより、n-ヘプタンを還流しながら、197.3gの水を系外へ抜き出した後、後架橋剤として2質量%のエチレングリコールジグリシジルエーテル水溶液7.36g(0.00085モル)を添加した。このときの水分量は74.6gであり、吸水性樹脂前駆体を構成する水溶性エチレン性不飽和単量体成分に対する水分率は、41質量%であった。後架橋剤混合物を調製後、80℃で2時間保持した。その後、n-へプタンを蒸発させて乾燥することによって、顆粒状の吸水性樹脂粒子を190.5g得た。
実施例1の(中間架橋反応)において添加する中間架橋剤として、2質量%のエチレングリコールジグリシジルエーテル水溶液0.41g(0.000047モル)に代えて、2質量%のエチレングリコールジグリシジルエーテル水溶液1.24g(0.00014モル)を用い、更に実施例1の(後架橋反応)において、水とn-ヘプタンとを共沸することにより、系外に抜き出す水の量を、197.3gから198.1gに変更した(吸水性樹脂前駆体を構成する水溶性エチレン性不飽和単量体成分に対する水分率は、41質量%)以外は、実施例1と同様の操作を行い、顆粒状の吸水性樹脂粒子を188.5g得た。
実施例1の(第二回目の逆相懸濁重合)において、中間架橋反応終了後の反応混合物の冷却温度を60℃から50℃に変更し、かつ、滴下が終了したときの系内温度を47℃から41℃に変更した以外は、実施例1と同様の操作を行い(吸水性樹脂前駆体を構成する水溶性エチレン性不飽和単量体成分に対する水分率は、41質量%)、顆粒状の吸水性樹脂粒子を189.5g得た。
(第一回目の逆相懸濁重合)
還流冷却器、滴下ロート、窒素ガス導入管、撹拌機として翼径50mmの4枚傾斜パドル翼を2段で有する撹拌翼(フッ素樹脂を表面にコートしたもの)を備えた内径100mm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n-ヘプタン400gをとり、界面活性剤としてのHLBが8.6のソルビタンモノラウレート(日油株式会社製、商品名:ノニオンLP-20R)1.30gを添加し、50℃まで昇温して界面活性剤を溶解したのち、内温を47℃まで冷却した。
一方、500mL容の三角フラスコに80.5質量%のアクリル酸水溶液81g(0.91モル)を入れ、これを氷冷しながら20.9質量%水酸化ナトリウム水溶液130.0gを滴下して75モル%の中和を行ったのち、過硫酸カリウム0.0892g(0.00033モル)を加えて溶解し、第一回目の重合用の単量体水溶液を調製した。なお、この単量体水溶液における水溶性エチレン性不飽和単量体の質量は80.2g、水分量は130.9gであった。
撹拌機の回転数を450r/minとして、前記第一回目の重合用の単量体水溶液を前記セパラブルフラスコに添加して、系内を窒素ガスで30分間置換した後、70℃の水浴に浸漬して昇温し、第一回目の逆相懸濁重合を1時間行った。
第一回目の逆相懸濁重合反応の終了後、得られた反応混合物に、中間架橋剤として2質量%のエチレングリコールジグリシジルエーテル水溶液0.36g(0.000041モル)を添加して、75℃で30分間、中間架橋反応を行った。
次に、前記第一回目の重合用の単量体とは別に、500mL容の三角フラスコに80.5質量%のアクリル酸水溶液81g(0.91モル)を入れ、これを氷冷しながら26.9質量%の水酸化ナトリウム水溶液101.0gを滴下して75モル%の中和を行ったのち、過硫酸カリウム0.0892g(0.00033モル)を加えて溶解し、第二回目の重合用の単量体水溶液を調製した。なお、この単量体水溶液における水溶性エチレン性不飽和単量体の質量は80.2g、水分量は101.9gであった。
前記中間架橋反応の終了後、撹拌機の回転数を1000r/minとして、中間架橋反応終了後の反応混合物を60℃に冷却し(ソルビタンモノラウレートが、n-ヘプタンに溶解している状態)、14℃に調整した前記第二回目の重合用の単量体水溶液を系内に滴下し、滴下が終了したときの系内温度(50℃)に保ちながら、前記回転数で30分間攪拌を行うと同時に系内を窒素ガスで置換した後、70℃の水浴に浸漬して昇温し、第二回目の逆相懸濁重合を1時間行い、吸水性樹脂粒子前駆体を得た。
得られた吸水性樹脂前駆体を含有する液体を、120℃の油浴を使用して昇温し、水とn-ヘプタンを共沸することにより、n-ヘプタンを還流しながら、181.8gの水を系外へ抜き出した後、後架橋剤として2質量%のエチレングリコールジグリシジルエーテル水溶液6.48g(0.00074モル)を添加した。このときの水分量は、57.6gであり、吸水性樹脂前駆体を構成する水溶性エチレン性不飽和単量体成分に対する水分率は35.9質量%であった。後架橋剤混合物を調製後、80℃で2時間保持した。その後、n-へプタンを蒸発させて乾燥することによって、顆粒状の吸水性樹脂粒子を164.7g得た。
実施例1の(第二回目の逆相懸濁重合)を行った後に得られる吸水性樹脂前駆体を含有する液体に、非晶質シリカ粉末(徳山ソーダ株式会社製、商品名:トクシールP)0.04gを添加した以外は、実施例1と同様の操作を行い、粒子が凝集した顆粒状の吸水性樹脂粒子188.6gを得た。
実施例1の(後架橋反応)において、水とn-ヘプタンとを共沸することにより、系外に抜き出す水の量を、197.3gから120.8gに変更した、更に添加する後架橋剤として、2質量%のエチレングリコールジグリシジルエーテル水溶液7.36g(0.000845モル)に代えて、2質量%のエチレングリコールジグリシジルエーテル水溶液1.84g(0.000211モル)に変えた、以外は、実施例1と同様の操作を行い、(吸水性樹脂前駆体を構成する水溶性エチレン性不飽和単量体成分に対する水分率は、80質量%)顆粒状の吸水性樹脂粒子を191.1g得た。
実施例1の(後架橋反応)において、水とn-ヘプタンとを共沸することにより、系外に抜き出す水の量を、197.3gから159.0gに変更した、更に添加する後架橋剤として、2質量%のエチレングリコールジグリシジルエーテル水溶液7.36g(0.000845モル)に代えて、2質量%のエチレングリコールジグリシジルエーテル水溶液3.68g(0.000423モル)に変えた、以外は、実施例1と同様の操作を行い、(吸水性樹脂前駆体を構成する水溶性エチレン性不飽和単量体成分に対する水分率は、60質量%)顆粒状の吸水性樹脂粒子を191.3g得た。
(逆相懸濁重合)
還流冷却器、滴下ロート、窒素ガス導入管、撹拌機として翼径50mmの4枚傾斜パドル翼を2段で有する撹拌翼(フッ素樹脂を表面にコートしたもの)を備えた内径100mm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n-ヘプタン453gをとり、界面活性剤としてのHLBが8.6のソルビタンモノラウレート(日油株式会社製、商品名:ノニオンLP-20R)1.90gを添加し、50℃まで昇温して界面活性剤を溶解したのち、内温を47℃まで冷却した。
一方、500mL容の三角フラスコに80.5質量%のアクリル酸水溶液48.5g(0.54モル)を入れ、これを氷冷しながら22.6質量%の水酸化ナトリウム水溶液76.7gを滴下して80モル%の中和を行ったのち、過硫酸カリウム0.13g(0.00037モル)を加えて溶解し、単量体水溶液を調製した。なお、この単量体水溶液における水溶性エチレン性不飽和単量体の質量は48.6g、水分量は76.6gであった。
撹拌機の回転数を700r/minとして、前記単量体水溶液を前記セパラブルフラスコに添加して、系内を窒素ガスで30分間置換した後、70℃の水浴に浸漬して昇温し、逆相懸濁重合を1時間行った。
逆相懸濁重合反応の終了後、得られた反応混合物に、後架橋剤として2質量%のエチレングリコールジグリシジルエーテル水溶液5.0g(0.00057モル)を添加した。このときの水分量は、81.5gであり、吸水性樹脂前駆体を構成する水溶性エチレン性不飽和単量体成分に対して167.9質量%であった。その後、75℃で30分間、後架橋反応を行った。
次いで、得られた反応液を120℃の油浴を使用して昇温し、水とn-ヘプタンを共沸することにより、n-ヘプタンを還流しながら、65.0gの水を系外へ抜き出し、その後、n-へプタンを蒸発させて乾燥することによって、顆粒状の吸水性樹脂粒子50.0gを得た。
(逆相懸濁重合)
還流冷却器、滴下ロート、窒素ガス導入管、撹拌機として翼径50mmの4枚傾斜パドル翼を2段で有する撹拌翼(フッ素樹脂を表面にコートしたもの)を備えた内径100mm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n-ヘプタン453gをとり、界面活性剤としてのHLBが8.6のソルビタンモノラウレート(日油株式会社製、商品名:ノニオンLP-20R)1.104gを添加し、50℃まで昇温して界面活性剤を溶解したのち、内温を47℃まで冷却した。
一方、500mL容の三角フラスコに80.5質量%のアクリル酸水溶液92g(1.03モル)を入れ、これを氷冷しながら20.9質量%の水酸化ナトリウム水溶液147.6gを滴下して75モル%の中和を行ったのち、過硫酸カリウム0.101g(0.00037モル)を加えて溶解し、単量体水溶液を調製した。なお、この単量体水溶液における水溶性エチレン性不飽和単量体の質量は91.0g、水分量は148.6gであった。
撹拌機の回転数を700r/minとして、前記単量体水溶液を前記セパラブルフラスコに添加して、系内を窒素ガスで30分間置換した後、70℃の水浴に浸漬して昇温し、逆相懸濁重合を1時間行い、吸水性樹脂前駆体を得た。
得られた吸水性樹脂前駆体を含有する液体を、120℃の油浴を使用して昇温し、水とn-ヘプタンを共沸することにより、n-ヘプタンを還流しながら、125.8gの水を系外へ抜き出した後、後架橋剤として2質量%のエチレングリコールジグリシジルエーテル水溶液5.52g(0.00063モル)を添加した。このときの水分量は、28.2gであり、吸水性樹脂前駆体を構成する水溶性エチレン性不飽和単量体成分に対して31質量%であった。後架橋剤を添加後、80℃で2時間保持した。その後、n-へプタンを蒸発させて乾燥することによって、顆粒状の吸水性樹脂粒子を94.5g得た。
(第一回目の逆相懸濁重合)
還流冷却器、滴下ロート、窒素ガス導入管、撹拌機として翼径50mmの4枚傾斜パドル翼を2段で有する撹拌翼(フッ素樹脂を表面にコートしたもの)を備えた内径100mm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n-ヘプタン360gをとり、界面活性剤としてのHLBが8.6のソルビタンモノラウレート(日油株式会社製、商品名:ノニオンLP-20R)1.47gを添加し、50℃まで昇温して界面活性剤を溶解したのち、内温を47℃まで冷却した。
一方、500mL容の三角フラスコに80.5質量%のアクリル酸水溶液92g(1.03モル)を入れ、これを氷冷しながら20.9質量%の水酸化ナトリウム水溶液147.6gを滴下して75モル%の中和を行ったのち、過硫酸カリウム0.101g(0.00037モル)を加えて溶解し、第一回目の重合用の単量体水溶液を調製した。なお、この単量体水溶液における水溶性エチレン性不飽和単量体の質量は91.0g、水分量は148.6gであった。
撹拌機の回転数を450r/minとして、前記第一回目の重合用の単量体水溶液を前記セパラブルフラスコに添加して、系内を窒素ガスで30分間置換した後、70℃の水浴に浸漬して昇温し、第一回目の逆相懸濁重合を1時間行った。
第一回目の逆相懸濁重合反応の終了後、得られた反応混合物に、中間架橋剤として2質量%のエチレングリコールジグリシジルエーテル水溶液5.0g(0.00057モル)を添加して、75℃で30分間、中間架橋反応を行った。
次に、前記第一回目の重合用の単量体とは別に、500mL容の三角フラスコに80.5質量%のアクリル酸水溶液92g(1.03モル)を入れ、これを氷冷しながら20.9質量%の水酸化ナトリウム水溶液147.6gを滴下して75モル%の中和を行ったのち、過硫酸カリウム0.101g(0.00037モル)を加えて溶解し、第二回目の重合用の単量体水溶液を調製した。なお、この単量体水溶液における水溶性エチレン性不飽和単量体の質量は91.0g、水分量は148.6gであった。
前記中間架橋反応の終了後、撹拌機の回転数を1000r/minとして、中間架橋反応終了後の反応混合物を60℃に冷却し(ソルビタンモノラウレートが、n-ヘプタンに溶解している状態)、14℃に調整した前記第二回目の重合用の単量体水溶液を系内に滴下し、滴下が終了したときの系内温度(47℃)に保ちながら、前記回転数で30分間攪拌を行うと同時に系内を窒素ガスで置換した後、70℃の水浴に浸漬して昇温し、第二回目の逆相懸濁重合を1時間行い、吸水性樹脂粒子前駆体を得た。
得られた吸水性樹脂粒子前駆体を含む反応混合物に、後架橋剤として2質量%のエチレングリコールジグリシジルエーテル水溶液5.0g(0.00057モル)を添加した。このときの水分量は、163.6gであり、吸水性樹脂前駆体を構成する水溶性エチレン性不飽和単量体成分に対して169.5質量%であった。その後、75℃で30分間、後架橋反応を行った。
次いで、120℃の油浴を使用して昇温し、水とn-ヘプタンを共沸することにより、n-ヘプタンを還流しながら、125.0gの水を系外へ抜き出し、その後、n-へプタンを蒸発させて乾燥することによって、顆粒状の吸水性樹脂粒子を190.7g得た。
実施例1の(第一回目の逆相懸濁重合)の終了後に、中間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添加しなかった以外は、実施例1と同様の操作を行った。
しかしながら、第二回目の重合用の単量体水溶液を系内に滴下している際に、攪拌機の攪拌負荷が大きくなり、攪拌できない状態になったので、以降の工程をとりやめた。
(第一回目の逆相懸濁重合)
還流冷却器、滴下ロート、窒素ガス導入管、撹拌機として翼径50mmの4枚傾斜パドル翼を2段で有する撹拌翼を備えた内径100mm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n-ヘプタン340gをとり、界面活性剤としてHLBが3.0のショ糖脂肪酸エステル(三菱化学フーズ株式会社製、商品名:S-370)0.92gを添加し、80℃まで昇温して界面活性剤を溶解させたのち、内温を35℃にした。
一方、500mL容の三角フラスコに80.5質量%のアクリル酸水溶液92g(1.03モル)を入れ、氷冷しながら20.9質量%の水酸化ナトリウム水溶液147.6gを滴下して75モル%の中和を行ったのち、過硫酸カリウム0.092g(0.00034モル)を加えて溶解し、第一回目の重合用の単量体水溶液を調製した。なお、この単量体水溶液における水溶性エチレン性不飽和単量体の質量は91.0g、水分量は148.6gであった。
撹拌機の回転数を700r/minとして、前記第一回目の重合用の単量体水溶液を前記セパラブルフラスコに添加して、系内を窒素ガスで30分間置換した後、70℃の水浴に浸漬して昇温し、第一回目の逆相懸濁重合を1時間行った。
第一回目の逆相懸濁重合反応の終了後、得られた反応混合物に、中間架橋剤として2質量%のエチレングリコールジグリシジルエーテル水溶液0.41g(0.000047モル)を添加して、75℃で30分間、中間架橋反応を行った。
次に、前記第一回目の重合用の単量体とは別に、500mL容の三角フラスコに80.5質量%のアクリル酸水溶液92g(1.03モル)を入れ、これを氷冷しながら20.9質量%の水酸化ナトリウム水溶液147.6gを滴下して75モル%の中和を行ったのち、過硫酸カリウム0.092g(0.00034モル)を加えて溶解し、第二回目の重合用の単量体水溶液を調製した。なお、この単量体水溶液における水溶性エチレン性不飽和単量体の質量は91.0g、水分量は148.6gであった。
中間架橋反応の終了後、撹拌機の回転数を1000r/minとして、中間架橋反応終了後の反応混合物を50℃に冷却し(ショ糖脂肪酸エステルが、n-ヘプタンに溶解している状態)、14℃に調整した前記第二回目の重合用の単量体水溶液を系内に滴下し、滴下が終了したときの系内温度(47℃)に保ちながら、前記回転数で30分間攪拌を行うと同時に系内を窒素ガスで置換した後、70℃の水浴に浸漬して昇温し、第二回目の逆相懸濁重合を1時間行い、吸水性樹脂前駆体を得た。
得られた吸水性樹脂前駆体を含有する液体を、120℃の油浴を使用して昇温し、水とn-ヘプタンを共沸することにより、n-ヘプタンを還流しながら、250.0gの水を系外に抜き出した後、後架橋剤として2質量%のエチレングリコールジグリシジルエーテル水溶液5.5g(0.000631モル)を添加した。このときの水分量は、52.9gであり、吸水性樹脂前駆体を構成する水溶性エチレン性不飽和単量体成分に対する水分率は29.1質量%であった。後架橋剤を添加後、80℃で2時間保持した。その後、n-ヘプタンと水とを加熱留去することにより、真球状の吸水性樹脂粒子191.1gを得た。
実施例1の(中間架橋反応)において添加する中間架橋剤として、2質量%のエチレングリコールジグリシジルエーテル水溶液0.41g(0.000047モル)に代えて、2質量%のエチレングリコールジグリシジルエーテル水溶液1.24g(0.00014モル)を用いた。更に実施例1の(第二回目の逆相懸濁重合)において、中間架橋反応終了後の反応混合物の冷却温度を60℃から30℃に変更し、かつ、滴下が終了したときの系内温度を47℃から28℃になった以外は、実施例1と同様の操作を行った。(第二回目の重合用の単量体水溶液を系内に滴下する際、ソルビタンモノラウレートはn-ヘプタンに未溶解の状態であった。)
しかしながら、第二回目の重合用の単量体水溶液を系内に滴下している際に、攪拌機の攪拌負荷が大きくなり、攪拌できない状態になったので、以降の工程をとりやめた。
(第一回目の逆相懸濁重合)
還流冷却器、滴下ロート、窒素ガス導入管、撹拌機として翼径50mmの4枚傾斜パドル翼を2段で有する撹拌翼(フッ素樹脂を表面にコートしたもの)を備えた内径100mm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n-ヘプタン360gをとり、界面活性剤としてのHLBが8.6のソルビタンモノラウレート(日油株式会社製、商品名:ノニオンLP-20R)1.47gを添加し、50℃まで昇温して界面活性剤を溶解したのち、内温を47℃まで冷却した。
一方、500mL容の三角フラスコに80.5質量%のアクリル酸水溶液92g(1.03モル)を入れ、これを氷冷しながら20.9質量%の水酸化ナトリウム水溶液147.6gを滴下して75モル%の中和を行ったのち、過硫酸カリウム0.101g(0.00037モル)とエチレングリコールジグリシジルエーテル0.0082g(0.000047モル)を加えて溶解し、第一回目の重合用の単量体水溶液を調製した。なお、この単量体水溶液における水溶性エチレン性不飽和単量体の質量は91.0g、水分量は148.6gであった。
撹拌機の回転数を450r/minとして、前記第一回目の重合用の単量体水溶液を前記セパラブルフラスコに添加して、系内を窒素ガスで30分間置換した後、70℃の水浴に浸漬して昇温し、第一回目の逆相懸濁重合を1時間行った。
次に、前記第一回目の重合用の単量体とは別に、500mL容の三角フラスコに80.5質量%のアクリル酸水溶液92g(1.03モル)を入れ、これを氷冷しながら26.9質量%の水酸化ナトリウム水溶液114.7gを滴下して75モル%の中和を行ったのち、過硫酸カリウム0.101g(0.00037モル)を加えて溶解し、第二回目の重合用の単量体水溶液を調製した。なお、この単量体水溶液における水溶性エチレン性不飽和単量体の質量は91.0g、水分量は115.7gであった。
第一回目の逆相懸濁重合反応の終了後(架橋反応の終了後)、撹拌機の回転数を1000r/minとして、第一回目の逆相懸濁重合反応終了後の反応混合物を60℃に冷却し(ソルビタンモノラウレートが、n-ヘプタンに溶解している状態)、14℃に調整した前記第二回目の重合用の単量体水溶液を系内に滴下し、滴下が終了したときの系内温度(47℃)に保ちながら、前記回転数で30分間攪拌を行うと同時に系内を窒素ガスで置換した後、70℃の水浴に浸漬して昇温し、第二回目の逆相懸濁重合を1時間行い、吸水性樹脂前駆体を得た。
得られた吸水性樹脂前駆体を含有する液体を、120℃の油浴を使用して昇温し、水とn-ヘプタンを共沸することにより、n-ヘプタンを還流しながら、196.9gの水を系外へ抜き出した後、後架橋剤として2質量%のエチレングリコールジグリシジルエーテル水溶液7.36g(0.00085モル)を添加した。このときの水分量は74.6gであり、吸水性樹脂前駆体を構成する水溶性エチレン性不飽和単量体成分に対して37質量%であった。後架橋剤混合物を調製後、80℃で2時間保持した。その後、n-へプタンを蒸発させて乾燥することによって、顆粒状の吸水性樹脂粒子を190.5g得た。
実施例1の(後架橋反応)において、水とn-ヘプタンとを共沸することにより、系外に抜き出す水の量を、197.3gから71.6gに変更した以外は、実施例1と同様の操作を行い、(吸水性樹脂前駆体を構成する水溶性エチレン性不飽和単量体成分に対する水分率は、110質量%)顆粒状の吸水性樹脂粒子を191.0g得た。
実施例及び比較例で得られた吸水性樹脂粒子について、以下の評価を行った。結果を表1に示した。
500mL容のビーカーに、0.9質量%食塩水(生理食塩水)500gを量り取り、600r/minで撹拌させながら、吸水性樹脂粒子2.0gを、ママコが発生しないように分散させた。前記回転数で撹拌させた状態で30分間放置し、吸水性樹脂粒子を十分に膨潤させた。その後、綿袋(メンブロード60番、横100mm×縦200mm)中に注ぎ込み、綿袋の上部を輪ゴムで縛り、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)を用いて綿袋を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。吸水性樹脂粒子を添加せずに同様の操作を行ない、綿袋の湿潤時の空質量Wb(g)を測定し、以下の式から保水能を算出した。
吸水性樹脂粒子の生理食塩水保水能(g/g)=[Wa-Wb](g)/吸水性樹脂粒子の質量(g)
本試験は、25℃±1℃に調節された室内で行った。100mL容のビーカーに、生理食塩水50±0.1gを量りとり、マグネチックスターラーバー(8mmφ×30mmのリング無し)を投入し、ビーカーを恒温水槽に浸漬して、液温を25±0.2℃に調節した。次に、マグネチックスターラー上にビーカーを置いて、回転数600r/minとして、生理食塩水に渦を発生させた後、吸水性樹脂粒子2.0±0.002gを、前記ビーカーに素早く添加し、ストップウォッチを用いて、吸水性樹脂粒子の添加後から液面の渦が収束する時点までの時間(秒)を測定し、吸水性樹脂粒子の吸水速度とした。
吸水性樹脂粒子100gに、滑剤として、0.5gの非晶質シリカ(エボニックデグサジャパン株式会社製、商品名:Sipernat 200)を混合した。
上記吸水性樹脂粒子を、JIS標準篩の目開250μmの篩を用いて通過させ、その通過量が50質量%以上の場合には(A)の篩の組み合わせを、その通過量が50質量%未満の場合には(B)の篩の組み合わせを用いて中位粒径を測定した。
(A)JIS標準篩を上から、目開き425μmの篩、目開き250μmの篩、目開き180μmの篩、目開き150μmの篩、目開き106μmの篩、目開き75μmの篩、目開き45μmの篩及び受け皿の順に組み合わせた。
(B)JIS標準篩を上から、目開き850μmの篩、目開き600μmの篩、目開き500μmの篩、目開き425μmの篩、目開き300μmの篩、目開き250μmの篩、目開き150μmの篩及び受け皿の順に組み合わせた。
組み合わせた最上の篩に、前記吸水性樹脂粒子を入れ、ロータップ式振とう器を用いて20分間振とうさせて分級した。
分級後、各篩上に残った吸水性樹脂粒子の質量を全量に対する質量百分率として計算し、粒子径の大きい方から順に積算することにより、篩の目開きと篩上に残った吸水性樹脂粒子の質量百分率の積算値との関係を対数確率紙にプロットした。確率紙上のプロットを直線で結ぶことにより、積算質量百分率50質量%に相当する粒子径を中位粒径とした。
吸水開始から10分後の平衡膨潤性能を、膨潤性能測定装置を用いて測定した。膨潤性能測定装置の概略説明図を図1に示す。図1に示した膨潤性能測定装置Xは、移動距離測定装置1と凹型円形カップ2(高さ30mm、内径80.5mm)、プラスチック製の凸型円形シリンダー3(外径80mm、吸水性樹脂粒子との接触面に直径2mmの貫通孔7が均等に60個配設)及び不織布4からなっている。膨潤性能測定装置Xは、レーザー光6により距離の変位を0.01mm単位で測定することができるようになっている。凹型円形カップ2は、所定量の吸水性樹脂粒子を均一に散布することができるようになっている。凸型円形シリンダー3は、吸水性樹脂粒子5に対して90gの荷重を均一に加えることができるようになっている。
凹型円形カップ2に試料(吸水性樹脂粒子5)0.1gを均一に散布し、その上に不織布4を敷く。凸型円形シリンダー3を不織布4の上に静かにのせ、移動距離測定装置1のセンサーのレーザー光6がシリンダーの中央部にくるように設置する。予め20℃に調節したイオン交換水130gを凹型円形カップ2内に投入し、吸水性樹脂粒子5が膨潤して凸型円形シリンダー3を押し上げた距離を測定する。吸水開始から10分後における凸型円形シリンダー3の移動距離を平衡膨潤性能とした。
2 凹型円形カップ
3 凸型円形シリンダー
4 不織布
5 吸水性樹脂粒子
6 レーザー光
7 貫通孔
X 膨潤性能測定装置
Claims (6)
- 水溶性エチレン性不飽和単量体を逆相懸濁重合して吸水性樹脂粒子を製造する方法であって、
(A)水溶性エチレン性不飽和単量体を、内部架橋剤の非存在下、HLBが8~12の界面活性剤の存在下、石油系炭化水素分散媒中で水溶性ラジカル重合開始剤を用いて第一回目の逆相懸濁重合を行う工程、
(B)更に中間架橋剤を加えて中間架橋反応を行う工程、
(C)前記界面活性剤が石油系炭化水素分散媒に溶解している状態で、水溶性エチレン性不飽和単量体を添加し、内部架橋剤の非存在下、水溶性ラジカル重合開始剤を用いて第二回目の逆相懸濁重合を行い、吸水性樹脂前駆体を作製する工程、及び、
(D)前記吸水性樹脂前駆体の水分率を、前記吸水性樹脂前駆体を構成する水溶性エチレン性不飽和単量体成分に対して30~100質量%に調整した後、後架橋反応させる工程を有する
ことを特徴とする吸水性樹脂粒子の製造方法。 - HLBが8~12の界面活性剤は、ソルビタン脂肪酸エステル、ポリグリセリン脂肪酸エステル、及び、ショ糖脂肪酸エステルからなる群より選ばれる少なくとも1種の化合物であることを特徴とする請求項1記載の吸水性樹脂粒子の製造方法。
- 中間架橋剤が、グリシジルエーテル化合物であることを特徴とする請求項1又は2記載の吸水性樹脂粒子の製造方法。
- 中間架橋剤の添加割合が、水溶性エチレン性不飽和単量体の総モル量に対して、0.0001~0.026モル%であることを特徴とする請求項1、2又は3記載の吸水性樹脂粒子の製造方法。
- 請求項1、2、3又は4記載の吸水性樹脂粒子の製造方法を用いて得られることを特徴とする吸水性樹脂粒子。
- 平衡膨潤性能が12~28mm、吸水速度が1~5秒、生理食塩水保水能が20~60g/g、及び、中位粒径が100~400μmであることを特徴とする請求項5記載の吸水性樹脂粒子。
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Also Published As
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CA2814797A1 (en) | 2012-04-26 |
TWI485163B (zh) | 2015-05-21 |
KR20130140723A (ko) | 2013-12-24 |
CA2814797C (en) | 2017-07-18 |
US8951637B2 (en) | 2015-02-10 |
AU2010362811B2 (en) | 2015-05-07 |
US20130260151A1 (en) | 2013-10-03 |
CN103154043B (zh) | 2015-04-22 |
EP2631251A4 (en) | 2015-08-19 |
AU2010362811A1 (en) | 2013-05-23 |
CN103154043A (zh) | 2013-06-12 |
TW201217401A (en) | 2012-05-01 |
KR101715443B1 (ko) | 2017-03-10 |
JPWO2012053121A1 (ja) | 2014-02-24 |
EP2631251B1 (en) | 2019-01-23 |
ES2715966T3 (es) | 2019-06-07 |
JP5658759B2 (ja) | 2015-01-28 |
EP2631251A1 (en) | 2013-08-28 |
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