WO2015199089A1 - 吸収性樹脂およびその製造方法 - Google Patents
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- WO2015199089A1 WO2015199089A1 PCT/JP2015/068083 JP2015068083W WO2015199089A1 WO 2015199089 A1 WO2015199089 A1 WO 2015199089A1 JP 2015068083 W JP2015068083 W JP 2015068083W WO 2015199089 A1 WO2015199089 A1 WO 2015199089A1
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- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08G—MACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS
- C08G81/00—Macromolecular compounds obtained by interreacting polymers in the absence of monomers, e.g. block polymers
- C08G81/02—Macromolecular compounds obtained by interreacting polymers in the absence of monomers, e.g. block polymers at least one of the polymers being obtained by reactions involving only carbon-to-carbon unsaturated bonds
- C08G81/021—Block or graft polymers containing only sequences of polymers of C08C or C08F
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- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
- C08L33/00—Compositions 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; Compositions of derivatives of such polymers
- C08L33/04—Homopolymers or copolymers of esters
- C08L33/06—Homopolymers or copolymers of esters of esters containing only carbon, hydrogen and oxygen, which oxygen atoms are present only as part of the carboxyl radical
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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
- A61L15/26—Macromolecular compounds obtained otherwise than 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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- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
- B01J20/00—Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof
- B01J20/22—Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof comprising organic material
- B01J20/26—Synthetic macromolecular compounds
- B01J20/265—Synthetic macromolecular compounds modified or post-treated polymers
- B01J20/267—Cross-linked polymers
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- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08F—MACROMOLECULAR COMPOUNDS OBTAINED BY REACTIONS ONLY INVOLVING CARBON-TO-CARBON UNSATURATED BONDS
- C08F2/00—Processes of polymerisation
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- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08F—MACROMOLECULAR COMPOUNDS OBTAINED BY REACTIONS ONLY INVOLVING CARBON-TO-CARBON UNSATURATED BONDS
- C08F8/00—Chemical modification by after-treatment
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- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08F—MACROMOLECULAR COMPOUNDS OBTAINED BY REACTIONS ONLY INVOLVING CARBON-TO-CARBON UNSATURATED BONDS
- C08F8/00—Chemical modification by after-treatment
- C08F8/12—Hydrolysis
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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
- 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
- C08J3/246—Intercrosslinking of at least two polymers
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
- B01J2220/00—Aspects relating to sorbent materials
- B01J2220/50—Aspects relating to the use of sorbent or filter aid materials
- B01J2220/68—Superabsorbents
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- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08G—MACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS
- C08G2210/00—Compositions for preparing hydrogels
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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
- C08J2300/00—Characterised by the use of unspecified polymers
- C08J2300/14—Water soluble or water swellable polymers, e.g. aqueous gels
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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
- C08J2300/00—Characterised by the use of unspecified polymers
- C08J2300/20—Polymers characterized by their physical structure
- C08J2300/206—Star polymers
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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
- 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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- 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
- C08J2400/00—Characterised by the use of unspecified polymers
- C08J2400/20—Polymers characterized by their physical structure
- C08J2400/206—Star polymers
Definitions
- the present invention relates to a water absorbent resin that can be used for absorbent articles such as disposable diapers and sanitary napkins, so-called incontinence pads, and a method for producing the same.
- a water-absorbing resin has been used as one of constituent materials of sanitary materials that absorb sanitary cotton, disposable diapers, or other body fluids.
- a water-absorbing resin include a hydrolyzate of starch-acrylonitrile graft polymer, a neutralized product of starch-acrylic acid graft polymer, a saponified product of vinyl acetate-acrylic acid ester copolymer, and an acrylonitrile copolymer.
- examples thereof include hydrolysates of polymers or acrylamide copolymers, cross-linked products thereof, and cross-linked products of partially neutralized poly (meth) acrylic acid.
- a water-absorbing resin composed of a partially neutralized polyacrylic acid (salt) crosslinked product is often used. All of these have a crosslinked structure and are insoluble in water.
- Characteristics desired for such a water-absorbent resin include a high water absorption ratio, a high water absorption speed, an excellent suction force for sucking water from the base material, and a high liquid permeability.
- the liquid permeability of the water-absorbent resin is understood as the ability to transport the added liquid within or between the particles and distribute it three-dimensionally in the swollen state.
- the transport by capillary action through the gaps between the gel particles of the swollen water-absorbing resin is the main.
- water-absorbent resins that cannot maintain capillary voids under gel alone under load due to lack of gel stability ensure mutual separation between particles by holding these materials in a fiber matrix.
- the new generation diaper structure uses little or no fiber material to support liquid transport by the water absorbent resin. Therefore, the water-absorbent resin used therein must have sufficiently high stability in the swollen state. In order to realize high stability in the swollen state, the water-absorbent resin is required to have a swollen gel elastic modulus.
- a crosslinking agent having a plurality of functional groups capable of reacting with carboxyl groups present in the water absorbent resin is used.
- An operation is performed to form a crosslinked structure in the vicinity of the surface and increase the surface crosslinking density of the water-absorbent resin (Modern Superabsorbent Polymer Technology, 1998 1998 pp. 55-60, pp. 97-103).
- a method of adding a chain transfer agent during polymerization Japanese Patent Laid-Open No.
- the swelling gel elastic modulus is improved by a technique (Japanese Patent Publication No. 2009-53467) in which the amount of the initiator is increased.
- the mechanism for improving the swelling gel elastic modulus in these methods is considered as follows. That is, the weight average molecular weight of the main chain polymer in the water-absorbent resin can be reduced by adding a chain transfer agent during polymerization or increasing the amount of radical initiator. This reduces entanglement cross-linking of the main chain polymer. Tangled cross-linking suppresses gel swelling.
- the main chain weight average molecular weight of the water-absorbing resin obtained by these methods is not significantly different from that of ordinary water-absorbing resin, and chemical crosslinking is performed to achieve the same equilibrium absorption capacity.
- the amount of agent is not significantly different. Therefore, it is considered that many entangled crosslinks still exist in the crosslinked structure of the water-absorbent resin obtained by these techniques, and there is a great room for improvement.
- the hanging chain refers to the end portion of the main chain that is not sandwiched between the crosslinking points. Considering an extreme case, a main chain having only one cross-linking point means that the entire main chain is a hanging chain. Since hanging chains do not contribute to the swelling gel elastic modulus, in order to improve the swelling gel elastic modulus, it is better to reduce the hanging chains and increase the main chain effective for elasticity. Therefore, in order to suppress the formation of hanging chains, it is considered that the molecular weight distribution of the main chain must be narrowed to prevent the formation of extremely short main chains.
- the swelling required for the water-absorbing resin in the first place is intended to increase the swelling gel elastic modulus.
- the present inventors have found that there is a problem that the magnification is significantly reduced.
- an object of the present invention is to provide a water-absorbing resin capable of exhibiting a high swelling gel elastic modulus while maintaining a high swelling ratio and a method for producing the same.
- the present inventors have found that the water-absorbing resin having an internal cross-linked structure having a water-soluble unsaturated monomer having a dissociating group as a main component of a repeating unit of the main chain.
- the above problem is solved by controlling the value of the equilibrium swelling ratio with respect to saline, the value of the weight average molecular weight (Mw) after the predetermined hydrolysis treatment, and the molecular weight distribution (Mw / Mn) to satisfy the predetermined relationship.
- Mw weight average molecular weight
- Mn molecular weight distribution
- a water-absorbing resin having a water-soluble unsaturated monomer having a dissociating group as a main component of a repeating unit of a main chain and having an internal cross-linked structure represented by the following formula 1.
- the crosslinked structure index is 14 or more
- the weight average molecular weight (Mw) after hydrolysis is 220,000 or less
- the molecular weight distribution (Mw / Mn) after hydrolysis is 3.40 or less.
- a water-absorbent resin is provided that is characterized by:
- the hydrolysis treatment is a treatment in which 50 mg of a water-absorbent resin as a solid content is allowed to stand in 10 g of a 0.1 mol / l sodium hydroxide aqueous solution at 80 ° C. for 3 weeks, and the weight average molecular weight ( Mw) is a value measured after the processing.
- the present inventors have conventionally proposed The present inventors have found a completely different method from the method for producing a partially neutralized polyacrylic acid (salt) crosslinked product that has been widely used.
- a method for producing a water-absorbing resin having an internal cross-linked structure with a water-soluble unsaturated monomer having a dissociating group as a main component of a repeating unit of the main chain is a main component of a repeating unit of each branched chain, and the first star polymer having a first reactive functional group at the end of each branched chain;
- the second reaction which can form a chemical bond by using the water-soluble unsaturated monomer as a main component of the repeating unit of each branched chain and reacting with the first reactive functional group at the end of each branched chain. It is characterized in that it includes a reaction step of reacting a second star polymer having a functional functional group with each other.
- a water-absorbing resin capable of exhibiting a high swelling gel elastic modulus while maintaining a high swelling ratio and a method for producing the same are provided.
- Water-absorbing resin means a water-swelling, water-insoluble polymer gelling agent.
- Water swellability means that the CRC (absorption capacity under no pressure) specified by ERT441.2-02 is 5 [g / g] or more, and “water insolubility” means ERT470.
- ERT441.2-02 water-swellability
- water insolubility means ERT470.
- .Extr water-soluble content specified in 2-02 is 0 to 50% by mass.
- the shape of the water-absorbent resin is powder, particularly preferably a powder-form water-absorbent resin having a particle size and water content described later, and is referred to as water-absorbent resin particles.
- the “water-absorbing resin” in the present specification includes the water-swelling gel of the polymer gelling agent.
- EDANA European Disposables and Nonwovens Associations
- ERT is an abbreviation for a method for measuring water-absorbent resin (EDANA Recommended Test Methods), which is a European standard.
- the physical properties of the water-absorbent resin are measured in accordance with the ERT original (known document: revised in 2002). Further, when the measurement described in (a) to (d) below is performed, when the water absorbent resin is a water-swelling gel, it is preferable to perform the measurement after a drying step described later to obtain a dry polymer. .
- CRC is an abbreviation for Centrifugation Retention Capacity (centrifuge retention capacity) and means absorption capacity without pressure (hereinafter also referred to as “absorption capacity”). Specifically, after 0.200 g of the water-absorbing resin in the non-woven fabric was freely swollen for 30 minutes with respect to a large excess of 0.9 mass% sodium chloride aqueous solution (physiological saline), further using a centrifuge. Absorption capacity after draining at 250 G (unit: [g / g]).
- AAP is an abbreviation for Absorption Against Pressure, and means absorption capacity under pressure. Specifically, 0.900 g of the water-absorbent resin was swollen under a load of 2.06 kPa (0.3 psi) for 1 hour against a 0.9 mass% sodium chloride aqueous solution (physiological saline). Absorption capacity (unit: [g / g]).
- SFC SFC (Saline Flow Inducibility)
- C SFC (Saline Flow Inducibility)
- PSD is an abbreviation for Particle Size Distribution and means a particle size distribution measured by sieving.
- the mass average particle size (D50) and the particle size distribution width are measured by the same method as “Average Particle Diameter and Distribution of Particle Diameter” described in European Patent 0349240.
- X to Y indicating a range means “X or more and Y or less” including X and Y.
- t (ton) as a unit of mass means “Metric ton” (metric ton)
- ppm means “mass ppm” unless otherwise noted.
- ⁇ acid (salt) means “ ⁇ acid and / or salt thereof”
- (meth) acryl means “acryl and / or methacryl”.
- measurement is performed at room temperature (20 to 25 ° C.) and relative humidity 40 to 50% RH.
- Water-absorbent resin according to the present invention, there is provided a water-absorbent resin having a water-soluble unsaturated monomer having a dissociating group as a main component of a repeating unit of a main chain and having an internal cross-linked structure.
- the said water-absorbing resin which concerns on the said form has a crosslinked structure index
- the water-absorbing resin according to this embodiment has a water-soluble unsaturated monomer having a dissociating group as a main component of the repeating unit of the main chain.
- a certain monomer “is the main component of the repeating unit” means that the proportion of the monomer in the entire repeating unit is 50 mol% or more, unless otherwise specified.
- the “water-soluble unsaturated monomer having a dissociating group” is preferably one containing (meth) acrylic acid (salt) as the main component, and one containing acrylic acid (salt) as the main component. More preferred.
- (meth) acrylic acid salts include alkali metal salts such as sodium salt, potassium salt, lithium salt, ammonium salt, and amine salt of (meth) acrylic acid, preferably alkali metal salts, A sodium salt is preferable.
- water-soluble unsaturated monomer having a dissociation group monomers other than (meth) acrylic acid (salt) include maleic acid, vinyl sulfonic acid, styrene sulfonic acid, 2- (meth) And anionic unsaturated monomers such as acrylamido-2-methylpropanesulfonic acid, 2- (meth) acryloylethanesulfonic acid, 2- (meth) acryloylpropanesulfonic acid.
- the water-absorbent resin according to the present embodiment has “a water-soluble unsaturated monomer having a dissociable group” as a main component of a repeating unit of the main chain, Not water-soluble unsaturated monomer "may be included as a repeating unit of the main chain.
- a water-soluble unsaturated monomer having a dissociable group as a main component of a repeating unit of the main chain
- Not water-soluble unsaturated monomer “may be included as a repeating unit of the main chain.
- monomers include acrylamide, methacrylamide, N-ethyl (meth) acrylamide, Nn-propyl (meth) acrylamide, N-isopropyl (meth) acrylamide, and N, N-dimethyl (meth).
- Acrylamide 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, methoxypolyethylene glycol (meth) acrylate, polyethylene glycol mono (meth) acrylate, vinylpyridine, N-vinylpyrrolidone, N-acryloylpiperidine, N Nonionic hydrophilic group-containing unsaturated monomers such as acryloylpyrrolidine and N-vinylacetamide; N, N-dimethylaminoethyl (meth) acrylate, N, N-diethylaminoethyl (meth) acrylate, N N- dimethylaminopropyl (meth) acrylate, N, N- dimethylaminopropyl (meth) acrylamide, and cationic unsaturated monomers such as those quaternary salts.
- the above-mentioned water-soluble unsaturated monomers may be used alone or in admixture of two or more.
- the proportion of the repeating unit derived from the water-soluble unsaturated monomer having a carboxylic acid (salt) group as a dissociating group in the repeating unit of the main chain is preferably 70 mol% or more More preferably, it is 80 mol% or more, more preferably 90 mol% or more (however, the upper limit is 100 mol%).
- the proportion of the repeating units of the main chain occupied by repeating units derived from acrylic acid (salt) is preferably 70 mol% or more, more preferably 80 mol% or more, and further preferably 90 mol% or more (however, the upper limit is 100 mol). %).
- the repeating unit of the main chain of the water-absorbent resin is in the range of 0 to 50 mol% acrylic acid and 100 to 50 mol% acrylate (however, the total amount of both is 100 mol% or less). Those having a range of 10 to 40 mol% acrylic acid and 90 to 60 mol% acrylate (the total amount of both being 100 mol% or less) are more preferable.
- the molar ratio of acrylate to the total amount of acrylic acid and acrylate is referred to as “neutralization rate”.
- the value of the neutralization rate is preferably 50 to 100 mol%.
- the water absorbent resin according to this embodiment is a crosslinked polymer having an internal crosslinked structure.
- the main chain of the water absorbent resin is provided. A method in which two (or more) star-shaped polymers having a functional group reactive with each other at the end of a branched chain are reacted with a water-soluble unsaturated monomer that provides a repeating unit of Is exemplified.
- the water-absorbent resin according to this embodiment has a crosslinked structure index represented by the following formula 1 of 14 or more, a weight average molecular weight after hydrolysis treatment of 220,000 or less, and The molecular weight distribution (Mw / Mn) after the decomposition treatment is 3.40 or less:
- the hydrolysis treatment is a treatment in which 50 mg of a water-absorbent resin as a solid content is allowed to stand in 10 g of a 0.1 mol / l sodium hydroxide aqueous solution at 80 ° C. for 3 weeks, and the weight average molecular weight ( Mw) is a value measured after the processing, and the operation for this measurement will be described in detail in the column of Examples described later.
- the cross-linking structure index is essential to be 14 or more, preferably 30 or more, more preferably 60 or more, still more preferably 90 or more, particularly preferably 120 or more, and most preferably. Is 170 or more.
- the upper limit value of the crosslinking structure index is not particularly limited, but is preferably 1000 or less. If the cross-linked structure index is greater than 1000, the cost for producing the water-absorbent resin may be too high.
- the weight average molecular weight (Mw) after the hydrolysis treatment described above is essential to be 220,000 or less, preferably 150,000 or less, more preferably 100,000 or less, and further preferably 50,000 or less. Especially preferably, it is 25000 or less.
- the lower limit of the weight average molecular weight (Mw) after the hydrolysis treatment is not particularly limited, but is preferably 10,000 or more.
- the weight average molecular weight (Mw) after the hydrolysis treatment is smaller than 10,000, the cost for producing the water absorbent resin may be too high.
- the molecular weight distribution (Mw / Mn) after the hydrolysis treatment described above is essential to be 3.40 or less, preferably 2.50 or less, more preferably 1.80 or less, More preferably, it is 1.45 or less, and particularly preferably 1.15 or less (however, the lower limit is 1.00).
- the cross-linking structure index is 14 or more, the weight average molecular weight (Mw) after hydrolysis is 220,000 or less, and the molecular weight distribution after hydrolysis (Mw / Mn) ) Is 3.40 or less, it was found that a water-absorbing resin capable of exhibiting a high swelling gel elastic modulus while maintaining a high swelling ratio is provided.
- the cross-linking structure index being equal to or greater than a predetermined value means that the equilibrium swelling ratio is large and the weight average molecular weight is small, indicating that there is little entanglement cross-linking.
- the narrow molecular weight distribution indicates that there are few extremely short main chains and the ratio of hanging chains is small.
- the smaller the entanglement cross-linking ratio and the higher the chemical cross-linking ratio the more it does not contribute to the elasticity of the gel. It is considered that the smaller the hanging chain, the higher the swelling gel elastic modulus.
- the weight average molecular weight after hydrolysis is 220,000 or less, and the molecular weight distribution (Mw / Mn) after hydrolysis is 3.40 or less,
- Mw / Mn molecular weight distribution
- a water-soluble unsaturated monomer that provides a repeating unit of the main chain of the water-absorbing resin is used as a main component of the repeating unit of the branched chain, and branched.
- An example is a method of reacting two (or more) star polymers having functional groups reactive with each other at the chain ends.
- a method for producing a water-absorbing resin having an internal cross-linked structure with a water-soluble unsaturated monomer having a dissociating group as a main component of a repeating unit of the main chain is provided.
- the said manufacturing method makes the said water-soluble unsaturated monomer the main component of the repeating unit of each branched chain,
- the 1st star polymer which has a 1st reactive functional group at the terminal of each branched chain, Second reactivity capable of forming a chemical bond by using the water-soluble unsaturated monomer as a main component of the repeating unit of each branched chain and reacting with the first reactive functional group at the end of each branched chain It is characterized in that it includes a reaction step of reacting the second star polymer having a functional group with each other.
- the reaction step is a step of reacting the first star polymer and the second star polymer.
- three or more star polymers may be reacted in the reaction step.
- the “star polymer” means a branched polymer having a structure in which three or more branched chains are radially extended with an atom or atomic group as a core.
- “star-shaped polymers” “New Version Polymer Dictionary” (edited by Polymer Society, Polymer Dictionary Editorial Committee, published by Asakura Shoten) and “Graduate Polymer Chemistry (KS Chemistry Special Book)” (Takuhira Nose) References such as edited and published by Kodansha may be referred to.
- the first star polymer and the second star polymer are water-soluble having a dissociating group.
- An unsaturated monomer is the main component of the repeating unit of each branched chain.
- water-soluble unsaturated monomer having a dissociating group that constitutes the main component of the repeating unit of the branched chain of the star polymer
- water-soluble unsaturated unit having a dissociating group As for the form of the water-soluble unsaturated monomer other than the “mer”, the same form as described above in the section “(2-1) Structure of the water-absorbing resin” can be adopted. Then, detailed description is abbreviate
- the number of branched chains for one core of the star polymer is not particularly limited, but is preferably 3 to 100, more preferably 3 to 10, and particularly preferably 4. is there.
- the plurality of star polymers used in the reaction process all have four branched chains, so that each star polymer has a tetrahedron structure, and as a result, internal crosslinks obtained.
- the structure is a diamond structure.
- a water-absorbing resin having such a diamond structure as an internal cross-linked structure is particularly preferable because it has higher network uniformity and a high swelling gel elastic modulus.
- the star polymer has a structure in which a polymer containing a water-soluble unsaturated monomer having a dissociating group as a branched chain as a main component of a repeating unit is bonded to a four-arm core. Is preferred.
- Each star polymer has a reactive functional group at the end of each branched chain.
- the reactive functional group present at the end of each branched chain of each star polymer reacts with the reactive functional group present at the end of each branched chain of at least one other star polymer to form a chemical bond. It must be able to be formed.
- the reactive functional group (“second reactivity" present at the end of each branched chain of the second star polymer is used.
- Functional group) react with each other at the end of each branched chain of the first star polymer (also referred to as “first reactive functional group”) to form a chemical bond. It must be possible.
- the reactive functional groups present at the ends of three or more (preferably four) branched chains constituting one star polymer may be the same as or different from each other, but are the same as each other. It is preferable that.
- first reactive functional group examples include, for example, (azide group; alkynyl group), (thiol group; alkenyl group) , (Hydrosilyl group; alkenyl group), (conjugated diene group; alkenyl group), (amino group; NHS activated ester group) and the like.
- a combination of (azide group; alkynyl group) can be preferably used.
- the method for obtaining the star polymer there is no particular limitation on the method for obtaining the star polymer, and conventionally known knowledge can be appropriately referred to.
- atoms or atomic groups constituting a core are prepared.
- the core any multifunctional compound or a compound obtained by modifying the multifunctional compound may be used.
- the polyfunctional compound include polyols such as pentaerythritol, trimethylolpropane, arabitol, and mannitol; polyamines such as triethylenetetramine.
- the valence (number of molecular chains) of the obtained star polymer is determined by the valence of atoms or atomic groups as cores prepared at this time.
- a (tetravalent) star polymer having four branched chains can be obtained.
- a modification operation of the polyfunctional compound for example, as described in the column of “Synthesis of four-armed star core” in the examples described later, a functional group (in this example, a hydroxy group) Examples include an operation in which an acyl compound is reacted with (—OH) group for esterification.
- a synthesis reaction (polymerization reaction) of the branched main chain constituting the star polymer is performed using the core prepared above.
- the polymerization reaction conventionally known techniques (radical polymerization, cationic polymerization, anionic polymerization, or chain polymerization or condensation polymerization such as living radical polymerization, living cationic polymerization, and living anion polymerization) can be used.
- radical polymerization or living radical polymerization is particularly preferable.
- the reaction is performed using a monomer component mainly composed of a water-soluble unsaturated monomer having a dissociating group.
- the dissociating group of the water-soluble unsaturated monomer having a dissociating group contained in the monomer component used in this reaction is preferably protected with a protecting group.
- a branched main chain synthesis reaction (polymerization reaction) is performed using a monomer component mainly composed of acrylic acid (salt) having a carboxy group as a dissociation group
- a carboxy group that is a dissociation group Is preferably protected using a protective group such as a tertiary butyl ester group, a methyl ester group, or an amide group.
- a protective group such as a tertiary butyl ester group, a methyl ester group, or an amide group.
- the “star polymer” used as a reaction raw material has “a water-soluble unsaturated monomer having a dissociating group” as the leading component of the repeating unit of each branched chain.
- the concept of the “water-soluble unsaturated monomer having a dissociating group” includes a monomer in which the dissociating group is protected with a protecting group as described above.
- a halogen atom such as a chlorine atom, a bromine atom, or an iodine atom
- sodium azide NaN By causing 3
- a star polymer in which the halogen atom is replaced with an azide group and an azide group is introduced at the end of each branched chain can be obtained.
- the introduction of the reactive functional group at the end of each branched chain may be carried out by two or more stages of reaction.
- the weight average molecular weight (Mw) of the star polymer thus obtained is not particularly limited, but is preferably 1000 or more, more preferably 2000 in order to obtain a water-absorbing resin having a sufficiently large equilibrium swelling ratio. It is above, More preferably, it is 5000 or more, Most preferably, it is 10,000 or more.
- the measuring method of the weight average molecular weight (Mw) of a star polymer shall be explained in full detail in the Example column mentioned later.
- Reaction conditions for reacting the first star polymer and the second star polymer (and the third, fourth,... Star polymer) in the reaction step.
- the equivalent relationship of star-shaped polymers can be appropriately set by those skilled in the art with reference to conventionally known knowledge depending on the type of reactive functional group used and the type of reaction resulting therefrom.
- the first star is obtained by performing a cycloaddition reaction in the presence of a copper catalyst.
- a chemical bond having a 1,2,3-triazole structure can be formed between the branched chain of the first polymer and the branched chain of the second star polymer.
- reaction temperature range is preferably 0 to 100 ° C.
- reaction time range is preferably 1 minute to 96 hours.
- reaction solvents include ethers such as diethyl ether, esters such as ethyl acetate, halogenated hydrocarbons such as dichloromethane, nitriles such as acetonitrile, ketones such as acetone, organic solvents such as sulfoxides such as dimethyl sulfoxide, and water.
- An aqueous solvent such as Regarding the equivalent relationship of the reactants, the range of the second reactive functional group with respect to 1 mol equivalent of the first reactive functional group is preferably 0.80 to 1.20 mol equivalent, and most preferably 1.00 mol equivalent. It is.
- the reaction step of the manufacturing method according to the present embodiment includes branched chains of the first star polymer and the second star polymer (and the third, fourth,... Star polymers). It is preferable that the dissociation group of the water-soluble unsaturated monomer having a dissociating group is protected with a protecting group.
- the method further includes a step of deprotecting the dissociable group after the reaction step. For example, when a tertiary butyl group is used as a protecting group for a carboxy group as a dissociating group, a carboxy group as a dissociating group is liberated by performing a deprotection reaction using trifluoroacetic acid, and thus has a dissociating group.
- a water-absorbing resin having an internal cross-linked structure with a water-soluble unsaturated monomer (for example, acrylic acid) as a main component of the repeating unit of the main chain can be obtained.
- the water-absorbing resin thus obtained is subjected to a neutralization step using a base such as sodium hydrogen carbonate or sodium hydroxide to finally obtain a water-absorbing resin having a desired neutralization rate. Is possible.
- the water-absorbing resin in the form of a water-swelling gel may be used as the final object upon completion of the above-described neutralization step.
- subsequent steps such as drying, pulverization, classification, and surface cross-linking may be performed.
- each process will be briefly described.
- drying is a step of obtaining a dry polymer by drying the water-swollen gel until a desired water content is obtained.
- the water content is measured in accordance with the EDANA method (ERT430.2-02) with a sample amount of 1.0 g, a drying temperature of 180 ° C., and a drying time of 4 hours, preferably 20% by weight or less. Is 1 to 15% by weight, more preferably 2 to 10% by weight, and particularly preferably 3 to 8% by weight.
- the method for drying the water-swollen gel is not particularly limited.
- heat drying, hot air drying, vacuum drying, fluidized bed drying, infrared drying, microwave drying, drum dryer drying, azeotropic dehydration with a hydrophobic organic solvent, and the like And drying at a high humidity using high-temperature steam.
- hot air drying is preferable from the viewpoint of drying efficiency, and band drying in which hot air drying is performed on a ventilation belt is more preferable.
- the drying temperature (hot air temperature) in the hot air drying is preferably 120 to 250 ° C., more preferably 150 to 200 ° C. from the viewpoint of the color tone of the water absorbent resin and the drying efficiency.
- the drying conditions other than the drying temperature such as the speed of the hot air and the drying time, may be set as appropriate according to the moisture content and total weight of the particulate hydrous gel to be dried and the desired resin solid content, When performing band drying, various conditions described in International Publication Nos. 2006/100300, 2011/025012, 2011/025013, 2011/111657 and the like are appropriately applied.
- the dry polymer obtained in the drying step is preferably pulverized by a pulverizer.
- the pulverizer is not particularly limited.
- a roll pulverizer such as a roll mill, a hammer pulverizer such as a hammer mill, an impact pulverizer, a cutter mill, a turbo grinder, a ball mill, a flash mill, and the like are used.
- a roll mill is preferable for controlling the particle size distribution.
- the powder may be pulverized twice or more continuously, but preferably three times or more. When pulverizing twice or more, each pulverizer may be the same or different. It is also possible to use different types of pulverizers in combination.
- a sieve having a specific opening In order to control the pulverized water-absorbing resin to a specific particle size distribution, it is preferable to classify with a sieve having a specific opening.
- the classifier is not particularly limited.
- a vibration sieve unbalanced weight drive type, resonance type, vibration motor type, electromagnetic type, circular vibration type, etc.
- in-plane motion sieve horizontal motion type, horizontal circle-linear motion type
- a movable mesh screen a forced stirring screen, a mesh screen vibration screen, a wind screen, a sonic screen, and the like, preferably a vibration screen and an in-plane motion screen.
- the sieve opening is in the range of 1000 ⁇ m to 300 ⁇ m, more preferably 900 ⁇ m to 400 ⁇ m, most preferably 710 ⁇ m to 450 ⁇ m. If it is out of these ranges, the target particle size distribution may not be obtained.
- the classifier is not particularly limited, but, for example, those exemplified above are preferably used, and a fine powder type classifier (centrifugal force type, inertial force type, etc.) and the like are used.
- a fine powder type classifier centrifugal force type, inertial force type, etc.
- the shape of the water-absorbent resin obtained by the above steps is generally a single particle shape such as an irregularly crushed shape, a spherical shape, a fiber shape, a rod shape, a substantially spherical shape, a flat shape, or a structure in which they are combined. It is a grain particle shape.
- An irregularly crushed or granulated particle shape is preferable because it can be easily fixed, for example, when used in a water absorbent.
- the ratio of the particles having an irregularly crushed or granulated particle shape in the water-absorbent resin is preferably 50% or more, more preferably 70% or more, and still more preferably 90% or more in terms of the number ratio.
- the shape can be determined visually (including viewing an enlarged image with a microscope or the like).
- the number ratio does not need to be measured in total, but is obtained by sampling 10 sets of about 100 particles while changing the sampling location, and measuring the arithmetic average value of each measurement result, that is, measuring a total of about 1000 particles. Can do.
- the surface vicinity is preferably surface-crosslinked with an organic surface cross-linking agent and / or a water-soluble inorganic surface cross-linking agent which is a surface cross-linking agent. That is, it is preferable that the method for producing a water absorbent resin of the present invention includes a step of surface cross-linking the dried water absorbent resin.
- Examples of the surface cross-linking agent that can be used for the surface cross-linking treatment include an organic surface cross-linking agent and / or a water-soluble inorganic surface cross-linking agent having two or more functional groups possessed by the water-absorbing resin, in particular, a functional group capable of reacting with a carboxyl group. Is mentioned.
- a water-soluble organic surface crosslinking agent can be used.
- Epoxy compounds such as ethylenediamine, diethylenetriamine, triethylenetetramine, tetraethylenepentamine, pentaethylenehexamine, polyethyleneimine, and inorganic or organic salts thereof (for example, azetidinium salts); 2,4-tri Polyvalent isocyanate compounds such as range isocyanate and hexamethylene diisocyanate; 1,2-ethylene Polyvalent oxazoline compounds such as suxazoline; carbonic acid derivatives such as urea, thiourea, guanidine, dicyandiamide, 2-oxazolidinone; 1,3-dioxolan-2-one, 4-methyl-1,3-dioxolan-2-one, 4,5-dimethyl-1,3-dioxolan-2-one, 4,4-dimethyl-1,3-dioxolan-2-one, 4-ethyl-1,3-dioxolan-2-one, 4-hydroxymethyl -1,3
- silane coupling agents such as ⁇ -glycidoxypropyltrimethoxysilane and ⁇ -aminopropyltriethoxysilane; 3-methyl-3 -Oxetanemethanol, 3-ethyl-3-oxetanemethanol, 3-butyl-3-oxetanemethanol, 3-methyl-3-oxetaneethanol, 3-ethyl-3-oxetaneethanol, 3-butyl-3-oxetaneethanol, 3 -Oxetane compounds such as -chloromethyl-3-methyloxetane, 3-chloromethyl-3-ethyloxetane, and polyvalent oxetane compounds;
- These surface cross-linking agents may be used alone or in combination of two or more.
- polyhydric alcohols are preferred because they are highly safe and can improve the hydrophilicity of the water-absorbent resin surface.
- the amount of the surface crosslinking agent used is preferably 0.001 part by mass or more and 5 parts by mass or less with respect to 100 parts by mass of the solid content of the water absorbent resin.
- Water may be used when mixing the surface cross-linking agent and the water absorbent resin.
- the amount of water used exceeds 0.5 parts by mass, preferably 10 parts by mass or less, and more preferably in the range of 1 part by mass to 5 parts by mass with respect to 100 parts by mass of the solid content of the water absorbent resin.
- a hydrophilic organic solvent or a third substance may be used as a mixing aid.
- a hydrophilic organic solvent for example, lower alcohols such as methyl alcohol, ethyl alcohol, n-propyl alcohol, isopropyl alcohol, n-butyl alcohol, isobutyl alcohol, and t-butyl alcohol; ketones such as acetone; Ethers such as dioxane, tetrahydrofuran, methoxy (poly) ethylene glycol; amides such as ⁇ -caprolactam and N, N-dimethylformamide; sulfoxides such as dimethyl sulfoxide; ethylene glycol, diethylene glycol, propylene glycol, triethylene glycol, tetra Ethylene glycol, polyethylene glycol, 1,3-propanediol, dipropylene glycol, 2,2,4-trimethyl-1,3
- the amount of the hydrophilic organic solvent used depends on the type, particle size, water content, etc. of the water-absorbent resin, but is preferably 10 parts by mass or less, more than 0 part by mass with respect to 100 parts by mass of the solid content of the water-absorbent resin. A range of 5 parts by mass or less is more preferable.
- an inorganic acid, an organic acid, a polyamino acid, or the like shown in European Patent No. 0668080 may be present as the third substance.
- These mixing aids may act as a surface cross-linking agent, but those that do not deteriorate the water absorption performance of the water-absorbent resin after surface cross-linking are preferred.
- the water-absorbent resin according to the present invention is preferably one that has been crosslinked by mixing and heating with a surface crosslinking agent that does not contain a hydrophilic organic solvent having a boiling point of 100 ° C. or less. When the water-absorbing resin contains a hydrophilic organic solvent having a boiling point of 100 ° C.
- the presence state of the surface cross-linking agent on the surface of the water-absorbing resin changes due to vaporization of the hydrophilic organic solvent, and SFC (physiological saline flow inductive) There is a risk that the physical properties will not be fully satisfied.
- a water-soluble inorganic salt (preferably a persulfate) coexists when the water-absorbing resin and the surface cross-linking agent are mixed.
- the amount of water-soluble inorganic salt used depends on the type and particle size of the water-absorbent resin, but is preferably in the range of 0.01 to 1 part by weight with respect to 100 parts by weight of the solid content of the water-absorbent resin. The range of 0.05 parts by mass or more and 0.5 parts by mass or less is more preferable.
- the mixing method for mixing the water-absorbing resin and the surface cross-linking agent is not particularly limited.
- the surface in which the water-absorbing resin is immersed in a hydrophilic organic solvent and dissolved in water and / or the hydrophilic organic solvent as necessary examples thereof include a method of mixing a crosslinking agent, and a method of spraying or dropping a surface crosslinking agent dissolved in water and / or a hydrophilic organic solvent directly into a water-absorbent resin.
- the said heat processing temperature (heating-medium temperature) is based also on the surface crosslinking agent to be used, 40 to 250 degreeC is preferable and 150 to 250 degreeC is more preferable.
- the heat treatment temperature is less than 40 ° C., absorption characteristics such as AAP (water absorption capacity under pressure) and SFC (saline flow conductivity) may not be sufficiently improved.
- the heat treatment temperature exceeds 250 ° C., the water-absorbent resin is deteriorated, and various physical properties may be lowered.
- the heat treatment time is preferably 1 minute to 2 hours, more preferably 5 minutes to 1 hour.
- the surface cross-linking be performed in the presence of the ⁇ -hydroxycarboxylic acid (salt). Thereby, the coloring prevention effect of a water absorbing resin is acquired.
- a polyvalent metal salt to the water-absorbing resin (preferably to the particle surface), particularly at the time of surface crosslinking or after surface crosslinking.
- the addition amount of the polyvalent metal salt is preferably 0.001% by mass to 5% by mass and more preferably 0.01% by mass to 1% by mass with respect to the water absorbent resin.
- the SFC can be improved without greatly reducing the AAP of the water absorbent resin. Can do.
- a polyvalent metal salt preferably a trivalent water-soluble polyvalent metal salt
- polyvalent metal salt that can be used in the present invention are selected from, for example, Zn, Be, Mg, Ca, Sr, Al, Fe, Mn, Ti, Zr, Ce, Ru, Y, and Cr.
- Metal sulfates, nitrates, carbonates, phosphates, organic acid salts, halides (chlorides, etc.) and the like, and polyvalent metals described in JP-A-2005-11317 A salt etc. can also be mentioned.
- the polyvalent metal salts it is most preferable to use a trivalent water-soluble metal salt.
- the trivalent water-soluble polyvalent metal salt include aluminum chloride, polyaluminum chloride, aluminum sulfate, aluminum nitrate, potassium aluminum sulfate, sodium aluminum sulfate, potassium alum, ammonium alum, sodium alum, sodium aluminate, and chloride.
- examples thereof include iron (III), cerium (III) chloride, ruthenium (III) chloride, yttrium chloride (III), chromium chloride (III) and the like.
- a salt having water of crystallization from the viewpoint of the solubility of an absorbing solution such as urine.
- aluminum compounds among which aluminum chloride, polyaluminum chloride, aluminum sulfate, aluminum nitrate, potassium aluminum bissulfate, sodium aluminum bissulfate, potassium alum, ammonium alum, sodium alum, sodium aluminate are preferred, aluminum sulfate Is particularly preferable, and an aqueous solution of aluminum sulfate (preferably a solution having an aluminum sulfate concentration of 90% or more of the saturation concentration) can be most suitably used. These may be used alone or in combination of two or more.
- a chelating agent from the viewpoints of the color tone (coloring prevention) and deterioration prevention of the obtained water-absorbent resin.
- the chelating agent specifically, the compounds disclosed in “[2] chelating agent” of WO 2011/040530 and the amount used thereof are applied to the present invention.
- additives other than the above-mentioned additives can be added in order to add various functions to the water absorbent resin.
- additives include surfactants, compounds having phosphorus atoms, oxidizing agents, organic reducing agents, water-insoluble inorganic fine particles, organic powders such as metal soaps, deodorants, antibacterial agents, pulp and thermoplastics. Examples thereof include fibers.
- the surfactant is a compound disclosed in International Publication No. 2005/077500, and the water-insoluble inorganic fine particles are disclosed in International Publication No. 2011/040530 “[5] Water-insoluble inorganic fine particles”. Each of these compounds is applied to the present invention.
- the amount of the additive used is appropriately determined depending on the application and is not particularly limited, but is preferably 0.001% by mass or more and 3% by weight with respect to 100 parts by weight of the water absorbent resin powder. Hereinafter, it is more preferably 0.01% by weight or more and 1% by weight or less. Moreover, this additive can also be added at a process different from the said process.
- the CRC of the water absorbent resin according to the present invention is usually 5 (g / g) or more, preferably 15 (g / g) or more, and more preferably 25 (g / g) or more.
- the upper limit of CRC is not particularly limited, it is preferably 70 (g / g) or less, more preferably 50 (g / g) or less, and further preferably 40 (g / g) or less.
- the CRC is less than 5 (g / g)
- the water-absorbent resin is used for the water-absorbing body, the amount of absorption is too small and it is not suitable for the use of sanitary materials such as diapers.
- the AAP of the water-absorbent resin according to the present invention is preferably 20 (g / g) or more, more preferably 22 (g / g) or more, and further preferably 23 (g / g) or more. Preferably it is 24 (g / g) or more.
- the upper limit of CRC is not particularly limited, it is preferably 30 (g / g) or less.
- the SFC (saline flow conductivity) of the water-absorbent resin of the present invention is preferably 50 ( ⁇ 10 ⁇ 7 ⁇ cm 3 ⁇ s ⁇ g ⁇ 1 ) or more, more preferably 60 ( ⁇ 10 ⁇ 7 ⁇ cm 3).
- ⁇ S ⁇ g ⁇ 1 ) or more more preferably 70 ( ⁇ 10 ⁇ 7 ⁇ cm 3 ⁇ s ⁇ g ⁇ 1 ) or more, particularly preferably 80 ( ⁇ 10 ⁇ 7 ⁇ cm 3 ⁇ s ⁇ g ⁇ 1 ) or more It is.
- the upper limit is not particularly limited, but is preferably 3000 ( ⁇ 10 ⁇ 7 ⁇ cm 3 ⁇ s ⁇ g ⁇ 1 ) or less, more preferably 2000 ( ⁇ 10 ⁇ 7 ⁇ cm 3 ⁇ s ⁇ g ⁇ 1 ) or less. is there. If it is less than the SFC is 50 ( ⁇ 10 -7 ⁇ cm 3 ⁇ s ⁇ g -1), due to the low liquid permeable body fluids such as urine or blood, is not suitable as an absorber of sanitary goods such as paper diapers . In addition, when the SFC exceeds 3000 ( ⁇ 10 ⁇ 7 ⁇ cm 3 ⁇ s ⁇ g ⁇ 1 ), body fluid such as urine and blood may not be sufficiently absorbed and liquid leakage may occur. Not suitable as an absorbent material for sanitary goods such as diapers. SFC can be controlled by particle size, surface cross-linking agent, polyvalent metal salt, cationic polymer, and the like.
- the water-absorbent resin according to the present invention has a water-soluble component (water-soluble component) amount of preferably 0 to 35% by mass, more preferably 0 to 25% by mass, and further preferably 0 to 15% by mass. It is. When the amount of water-soluble component (water-soluble component) exceeds 35% by mass, the gel strength may be weak and the liquid permeability may be poor. Further, when a water absorbent resin is used for the water absorbent body, there is a possibility that it is impossible to obtain a water absorbent resin with little liquid return (commonly called Re-Wet) when pressure is applied to the water absorbent body.
- Re-Wet liquid return
- the water absorbent resin according to the present invention preferably has a mass average particle size (D50) of 200 to 600 ⁇ m. More preferably, it is 300 to 500 ⁇ m.
- D50 mass average particle size of the water-absorbent resin
- the mass average particle diameter (D50) of the water-absorbent resin is out of the range of 200 to 600 ⁇ m, the liquid permeability and diffusibility can be remarkably reduced, or the absorption rate can be greatly reduced.
- a water-absorbent resin is used in, for example, a diaper, there is a risk of causing liquid leakage.
- the logarithmic standard deviation ( ⁇ ) of the particle size distribution is preferably 0.20 to 0.50, and more preferably 0.30 to 0.40. If it is out of this range, the liquid permeability is lowered, and there is a possibility that the liquid uptake speed into the water absorbing body is remarkably deteriorated.
- the ratio of particles having a size capable of passing through a sieve having an aperture of 150 ⁇ m and the ratio of particles having a size of 850 ⁇ m or more are preferably 0 to 5% by mass, and 0 to 3% by mass. More preferably.
- each step in each example is carried out at a substantially normal pressure ( ⁇ 5% of atmospheric pressure, more preferably within 1%). In the same step, pressure by intentional pressurization or reduced pressure is used. It was carried out without any changes.
- equilibrium swelling gel a dispersion of a gel in an equilibrium swelling state
- this cylinder was placed on 5 sheets of filter paper (Advantec No2, 150 mm in diameter) and allowed to stand for 5 minutes in an environment of room temperature 15-30 ° C. and 30-90% humidity. After that, this filter is placed on 5 sheets of new filter paper (Advantec No2, 150mm in diameter), and left at room temperature 15-30 ° C, 30-90% humidity for 5 minutes, then drained. A predetermined weight (mass W1) was weighed from the gel.
- the polymer solid content of the equilibrium swollen gel (mass W1) can be determined by loss on drying. At that time, the solid content NaCl in the gel was first removed by the following method. That is, the gel thus weighed (mass W1) was transferred into a polypropylene container (manufactured by Tokyo Glass Instrument Co., Ltd.) having a capacity of 250 ml, immersed in 200 ml of pure water (temperature 21 to 25 ° C.), capped, Allowed to stand for 48 hours.
- a polypropylene container manufactured by Tokyo Glass Instrument Co., Ltd.
- the liquid in the polypropylene container was removed, 200 ml of pure water (temperature 21 to 25 ° C.) was added again, the lid was capped, and the mixture was allowed to stand for 48 hours. Thereafter, the liquid in the polypropylene container was removed, 200 ml of pure water (temperature 21 to 25 ° C.) was added again, the lid was capped, and the mixture was allowed to stand for 48 hours.
- the pure water swelling gel obtained by removing NaCl was placed on an aluminum cup (mass W0) having a bottom diameter of about 5 cm.
- mass W0 The major axis of the obtained pure water swelling gel was larger than 3 mm, it was chopped with scissors until the major axis became about 3 mm.
- the elastic modulus (G n ) under each load was measured. Deviation between measured value (G m ) of elastic modulus under load of (0.34 + 0.68 ⁇ m) N and measured value of elastic modulus (G m-1 ) under the immediately preceding load, elasticity under the immediately following load When the deviation from the measured value of the rate (G m + 1 ) was within 5%, G m was taken as the elastic modulus of the gel.
- Example preparation In a 120 ml polypropylene container (manufactured by Tokyo Glass Instrument Co., Ltd.), the gel that had reached an equilibrium swelling state in a 0.9 wt% sodium chloride aqueous solution was weighed (50 ⁇ physiological saline equilibrium swelling ratio) mg. To this was added 10 g of a 0.1 mol / l sodium hydroxide aqueous solution, the lid was covered, and the mixture was allowed to stand in an airless dryer (ADVANTEC DRV320DA) at 80 ° C. for 3 weeks. After 3 weeks, the gel was hydrolyzed into a solution.
- ADVANTEC DRV320DA airless dryer
- the solution thus obtained was diluted 4-fold with the following eluent and passed through a filter (GL Science Disc, aqueous 25A, pore size 0.2 ⁇ m, manufactured by GL Sciences Inc.). GPC measurement of this solution was performed under the following conditions.
- the measurement apparatus and measurement conditions were as follows.
- Viscotek OmniSEC3.1 registered trademark
- Viscotek OmniSEC3.1 registered trademark
- DP viscometer
- Mw weight average molecular weight
- Mn number average molecular weight
- Mw / Mn molecular weight distribution
- IV Intrinsic viscosity
- Measuring instrument HLC-8120 (manufactured by Tosoh Corporation) Column: G5000HXL (manufactured by Tosoh Corp.) and GMHXL-L (manufactured by Tosoh Corp.) connected in series
- Eluent Tetrahydrofuran Standard curve standard: Polystyrene
- the resulting solution was dried under reduced pressure at 1 mmHg for 5 hours at room temperature to obtain a crude product of a four-armed star polymer (1-Br) having a chemical structure represented by the following chemical formula B.
- a solution of this crude product dissolved in 100 ml of diethyl ether was transferred to a separatory funnel, and 100 ml of pure water was added and shaken.
- the collected organic layer was transferred to a separatory funnel, and 100 ml of pure water was added again and shaken.
- the obtained organic layer was dried under reduced pressure at 1 mmHg for 5 hours at room temperature to obtain a solid four-armed star polymer (1-Br).
- the chemical structure of the obtained product was confirmed by proton NMR measurement using deuterated chloroform as a solvent.
- As a characteristic peak a peak derived from hydrogen on carbon having a bromine functional group, which appears at a chemical shift of 4.1 ppm, can be mentioned.
- the four-armed star polymer (1-N 3 ) obtained as described above had a weight average molecular weight Mw of 12,550 and a molecular weight distribution Mw / Mn of 1.15.
- the chemical structure of the obtained product was confirmed by proton NMR measurement using deuterated chloroform as a solvent.
- a characteristic peak a peak derived from hydrogen on the 1,2,3-triazole ring, which appeared at the position of chemical shift of 7.5 ppm, a position of 1,2,3-, which appeared at the position of chemical shift of 5.2 ppm
- Examples include a peak derived from hydrogen on carbon having a triazole ring, and a peak derived from hydrogen of a trimethylsilyl group appearing at a chemical shift position of 0.1 ppm.
- a four-armed star polymer (1-H alkyne) having a chemical structure represented by the following chemical formula F A crude product was obtained. A solution of this crude product dissolved in 100 ml of diethyl ether was transferred to a separatory funnel, and 100 ml of pure water was added and shaken. The collected organic layer was transferred to a separatory funnel, and 100 ml of pure water was added again and shaken. The obtained organic layer was dried under reduced pressure at 1 mmHg for 5 hours at room temperature, and the resulting solid was washed with 50 ml of hexane three times to obtain a solid four-armed star polymer (1-H alkyne).
- acetone-swelled gel was taken out from a glass beaker, allowed to stand at room temperature in the atmosphere for 24 hours and dried, and a cylindrical polytertiary butyl acrylate cross-linked product having a chemical structure represented by the following chemical formula G (1- tBA gel) was obtained.
- the crosslinked polyacrylic acid produced by such deprotection reaction of tertiary butyl group was taken out from the glass beaker and immersed in 30 ml of pure water in another 50 ml glass beaker.
- the glass beaker is placed on a shaking table, shaken at a speed of 60 revolutions per minute for 18 hours to wash away remaining trifluoroacetic acid, and has a chemical structure represented by the following chemical formula H.
- a water-swelling gel (1-AA gel) of a crosslinked polyacrylic acid was obtained.
- the obtained partially neutralized polyacrylic acid crosslinked crosslinked gel (water absorbent resin 1) was transferred into a 250 ml polypropylene container, immersed in 200 ml of a 0.9 wt% sodium chloride aqueous solution, and allowed to stand for 48 hours. Thereafter, the aqueous solution in the polypropylene container was removed, and 200 ml of a 0.9 wt% sodium chloride aqueous solution was added again, and the mixture was allowed to stand for 48 hours. Thereafter, the aqueous solution in the polypropylene container was removed, and 200 ml of a 0.9 wt% sodium chloride aqueous solution was added again, and the mixture was allowed to stand for 48 hours.
- the equilibrium swelling ratio of the partially neutralized polyacrylic acid crosslinked swelling gel (water-absorbent resin 1) in an equilibrium swelling state in 0.9% by weight sodium chloride aqueous solution is 24.8 g / g, and the elastic modulus is 24,276 Pa. Met. Further, after hydrolysis, the weight average molecular weight Mw was 7,355, and the molecular weight distribution Mw / Mn was 1.06. These results are shown in Table 1 below.
- the four-armed star polymer (2-N 3 ) obtained as described above had a weight average molecular weight Mw of 17,029 and a molecular weight distribution Mw / Mn of 1.11.
- the equilibrium swelling ratio of the partially neutralized polyacrylic acid crosslinked swelling gel (water absorbent resin 2), which was in an equilibrium swelling state in this 0.9% by weight aqueous sodium chloride solution, was 38.4 g / g, and its elastic modulus was 8,272 Pa. Met. Further, after hydrolysis, the weight average molecular weight Mw was 10,473, and the molecular weight distribution Mw / Mn was 1.11. These results are shown in Table 1 below.
- the four-armed star polymer (3-N 3 ) obtained as described above had a weight average molecular weight Mw of 25,585 and a molecular weight distribution Mw / Mn of 1.11.
- the equilibrium swelling ratio of the partially neutralized polyacrylic acid crosslinked swollen gel (water-absorbent resin 3) in the 0.9% by weight sodium chloride aqueous solution is 42.5 ⁇ ⁇ ⁇ ⁇ ⁇ ⁇ ⁇ g / g and the elastic modulus is 7,606 Pa. Met. Further, after hydrolysis, the weight average molecular weight Mw was 14,316, and the molecular weight distribution Mw / Mn was 1.11. These results are shown in Table 1 below.
- the four-armed star polymer (4-N 3 ) obtained as described above had a weight average molecular weight Mw of 45,728 and a molecular weight distribution Mw / Mn of 1.16.
- the equilibrium swelling ratio of the partially neutralized polyacrylic acid crosslinked swelling gel (water-absorbent resin 4) in an equilibrium swelling state in 0.9% by weight sodium chloride aqueous solution is 80.4 g / g, and the elastic modulus is 1,308 Pa. Met. Further, after hydrolysis, the weight average molecular weight Mw was 24,725, and the molecular weight distribution Mw / Mn was 1.14. These results are shown in Table 1 below.
- reaction solution was immediately transferred to the following reaction vessel substituted with nitrogen gas using a syringe and allowed to stand in a dryer at 60 ° C. for 18 hours to obtain a disk-shaped gel.
- the reaction vessel is obtained by sandwiching silicon rubber having a circular hole between two glass plates and fastening the periphery with a clip.
- a part (2.0 g) of this gel was cut into a strip shape, transferred to a 780 ml polypropylene container with a lid (manufactured by Entec), immersed in 400 ml of a 0.9 wt% sodium chloride aqueous solution, and allowed to stand for 48 hours. did. Thereafter, the aqueous solution in the polypropylene container was removed, and 400 ml of 0.9 wt% sodium chloride aqueous solution was added again, and the mixture was allowed to stand for 48 hours. Thereafter, the aqueous solution in the polypropylene container was removed, and 400 ml of 0.9 wt% sodium chloride aqueous solution was added again, and the mixture was allowed to stand for 48 hours.
- a partially neutralized polyacrylic acid crosslinked crosslinked gel (comparative water-absorbing resin 1) of this comparative example, which was in an equilibrium swollen state in a 0.9 wt% sodium chloride aqueous solution, was obtained.
- the elastic modulus was 7,867 Pa.
- the weight average molecular weight (Mw) was 1,460,000, and the molecular weight distribution (Mw / Mn) was 1.69.
- Comparative Example 2 In the part of this comparative example, which was in an equilibrium swollen state in a 0.9 wt% sodium chloride aqueous solution in the same manner as in Comparative Example 1 except that the amount of polyethylene glycol diacrylate was 0.058 g and the amount of pure water was 21.836 g. A swollen gel (comparative water-absorbing resin 2) of a crosslinked polyacrylic acid was obtained.
- Comparative Example 3 In the part of this comparative example, which was in an equilibrium swollen state in a 0.9 wt% sodium chloride aqueous solution in the same manner as in Comparative Example 1 except that the amount of polyethylene glycol diacrylate was 0.043 g and the amount of pure water was 21.851 g. A swollen gel (comparative water-absorbing resin 3) of a cross-linked Japanese polyacrylic acid was obtained.
- Comparative Example 4 In the part of this comparative example, which was in an equilibrium swollen state in a 0.9 wt% sodium chloride aqueous solution in the same manner as in Comparative Example 1 except that the amount of polyethylene glycol diacrylate was 0.028 g and the amount of pure water was 21.866 g. A swollen gel (comparative water-absorbing resin 4) of a cross-linked polyacrylic acid was obtained.
- the equilibrium swelling ratio of the partially neutralized polyacrylic acid cross-linked swelling gel of this comparative example (comparative water absorbent resin 4), which was in an equilibrium swelling state in this 0.9% by weight sodium chloride aqueous solution, was 65.5 g / g.
- the elastic modulus was 980 Pa.
- the weight average molecular weight (Mw) was 1,340,000, and the molecular weight distribution (Mw / Mn) was 1.56.
- Comparative Example 5 0.9 wt% chloride in the same manner as in Comparative Example 1 except that the amount of 10 wt% sodium persulfate aqueous solution was 3.250 g, the amount of 0.1 wt% L-ascorbic acid aqueous solution was 2.420 g, and the amount of pure water was 17.170 g.
- a swollen gel (comparative water-absorbing resin 5) of a partially neutralized polyacrylic acid crosslinked body of this comparative example that was in an equilibrium swollen state in an aqueous sodium solution was obtained.
- Comparative Example 6 Comparative example except that the amount of pure water was 17.170 g, and 2.970 g of a 10% by weight sodium persulfate pentahydrate aqueous solution was added simultaneously with a 10% by weight sodium persulfate aqueous solution and a 0.1% by weight L-ascorbic acid aqueous solution.
- a swollen gel comparative example 6 of a partially neutralized polyacrylic acid crosslinked body of this comparative example, which was in an equilibrium swollen state in a 0.9 wt% sodium chloride aqueous solution, was obtained.
- the equilibrium swelling ratio of the partially neutralized polyacrylic acid cross-linked swelling gel of this comparative example (comparative water absorbent resin 6) in the 0.9% by weight aqueous sodium chloride solution was 33.1 g / g, The elastic modulus was 8,421Pa. Further, after hydrolysis, the weight average molecular weight (Mw) was 1,116,000, and the molecular weight distribution (Mw / Mn) was 1.49. These results are shown in Table 1 below.
- This gel was transferred into a 780 ml polypropylene container (manufactured by Entec) with a lid, immersed in a mixed solution of 8 ml of 2 mol / l hydrochloric acid aqueous solution and 192 ml of 0.9 wt% sodium chloride aqueous solution, and allowed to stand for 72 hours. Thereafter, the aqueous solution in the polypropylene container was removed, 200 ml of 0.9 wt% sodium chloride aqueous solution was added, and the mixture was allowed to stand for 48 hours.
- the equilibrium swelling ratio of the partially neutralized polyacrylic acid cross-linked swelling gel of this comparative example (comparative water absorbent resin 7) in the 0.9% by weight sodium chloride aqueous solution was 51.8 ⁇ ⁇ ⁇ ⁇ ⁇ ⁇ ⁇ g / g
- the elastic modulus was 3149Pa.
- the weight average molecular weight (Mw) after hydrolysis was 239,600
- the molecular weight distribution (Mw / Mn) was 3.48.
- the water-absorbent resins of Examples 1 to 4 according to the present invention show higher swelling gel elastic modulus than the water-absorbent resin according to the comparative example showing the equivalent equilibrium swelling ratio. I understand that.
- Mw weight average molecular weight
- the crosslinked structure index decreases.
- the water-absorbent resin synthesized by using a star polymer having a higher molecular weight having a reactive functional group at the end as a starting material has a higher weight after hydrolysis. It is believed to exhibit an average molecular weight (Mw) and a smaller cross-linked structure index.
- the water-absorbing resin thus obtained also has a high swelled gel elastic modulus as compared with the water-absorbing resin according to the comparative example which has less entanglement and hanging chains and shows the same equilibrium swelling ratio, as in Examples 1 to 4. It is considered a thing. That is, the water-absorbent resin according to the comparative example, which is a water-absorbent resin having a larger weight average molecular weight (Mw) after hydrolysis than that of Examples 1 to 4 and a small cross-linked structure index, and showing an equivalent equilibrium swelling ratio, In comparison, it is considered possible to obtain a water-absorbing resin exhibiting a high swelling gel elastic modulus.
- Mw weight average molecular weight
- a cross-linked structure index value of 14 or more (preferably 170 or more), a weight average molecular weight after hydrolysis of 220,000 or less (Mw), and a molecular weight distribution (Mw / Mn) of 3.40 or less Therefore, it can be expected that a higher swelling gel elastic modulus is exhibited as compared with the water absorbent resin according to the comparative example showing the equivalent equilibrium swelling ratio. From this, the water-absorbent resin according to the present invention exhibits excellent liquid permeability even under a load as compared with a water-absorbent resin composed of a conventional partially neutralized polyacrylic acid (salt) crosslinked body. It can be said.
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Abstract
Description
(1-1)吸水性樹脂
本明細書において、「吸水性樹脂」とは、水膨潤性水不溶性の高分子ゲル化剤を意味する。なお、「水膨潤性」とは、ERT441.2-02で規定するCRC(無加圧下吸収倍率)が5[g/g]以上であることをいい、また、「水不溶性」とは、ERT470.2-02で規定するExtr(水可溶分)が0~50質量%であることをいう。ここで、吸水性樹脂の形状としては粉末状、特に好ましくは後述の粒度や含水率を有する粉末状の吸水性樹脂がよく、吸水性樹脂粒子と称する。なお、本明細書における「吸水性樹脂」には、上記高分子ゲル化剤の水膨潤ゲルも含むものとする。
「EDANA」は、欧州不織布工業会(European Disposables and Nonwovens Associations)の略称であり、「ERT」は、欧州標準である吸水性樹脂の測定方法(EDANA Recommended Test Methods)の略称である。なお、本発明では、特に断りのない限り、ERT原本(公知文献:2002年改定)に準拠して、吸水性樹脂の物性を測定する。また、以下(a)~(d)に述べる測定を行う際、吸水性樹脂が水膨潤ゲルである場合には、後述する乾燥工程を経て、乾燥重合体とした上で測定を行うことが好ましい。
「CRC」は、Centrifuge Retention Capacity(遠心分離機保持容量)の略称であり、無加圧下吸収倍率(以下、「吸収倍率」と称することもある)を意味する。具体的には、不織布中の吸水性樹脂0.200gを、大過剰の0.9質量%塩化ナトリウム水溶液(生理食塩水)に対して30分間自由膨潤させた後、更に遠心分離機を用いて250Gで水切りした後の吸収倍率(単位;[g/g])である。
「AAP」は、Absorption Against Pressureの略称であり、加圧下吸収倍率を意味する。具体的には、吸水性樹脂0.900gを、0.9質量%塩化ナトリウム水溶液(生理食塩水)に対して1時間、2.06kPa(0.3psi)での荷重下で膨潤させた後の吸収倍率(単位;[g/g])である。
「SFC(生理食塩水流れ誘導性)」は、2.07kPa荷重下での吸水性樹脂に対する0.69重量%塩化ナトリウム水溶液の通液性をいい、米国特許第5669894号に開示される
SFC試験方法に準拠して測定される。
「PSD」とは、Particle Size Distributionの略称であり、篩分級により測定される粒度分布を意味する。なお、質量平均粒子径(D50)及び粒子径分布幅は欧州特許0349240号に記載された「Average Particle Diameter and Distribution of Particle Diameter」と同様の方法で測定する。
本明細書において、範囲を示す「X~Y」は、XおよびYを含む「X以上Y以下」であることを意味する。また、質量の単位である「t(トン)」は、「Metric ton(メトリック トン)」であることを意味し、更に、特に注釈のない限り、「ppm」は「質量ppm」を意味する。また、「~酸(塩)」は「~酸および/またはその塩」を意味し、「(メタ)アクリル」は「アクリルおよび/またはメタクリル」を意味する。また、物性等の測定に関しては、特に断りのない限り、室温(20~25℃)、相対湿度40~50%RHで測定する。
本発明の一形態によれば、解離基を有する水溶性不飽和単量体を主鎖の繰り返し単位の主成分とし、内部架橋構造を有する吸水性樹脂が提供される。そして、当該形態に係る前記吸水性樹脂は、後述する数式1で表される架橋構造指数が14以上であり、かつ加水分解処理後の重量平均分子量(Mw)が220000以下であり、かつ加水分解処理後の分子量分布(Mw/Mn)が3.40以下である点に特徴を有するものである。
本形態に係る吸水性樹脂は、解離基を有する水溶性不飽和単量体を主鎖の繰り返し単位の主成分とするものである。ここで、本明細書において、ある単量体が「繰り返し単位の主成分である」とは、当該単量体の繰り返し単位全体に占める割合が50mol%以上であることを意味し、特記しない限り、好ましくは70mol%以上、より好ましくは90mol%以上、さらに好ましくは95mol%以上、特に好ましくは98mol%以上、最も好ましくは99mol%以上である。
本形態に係る吸水性樹脂は、下記数式1で表される架橋構造指数が14以上であり、かつ加水分解処理後の重量平均分子量が220000以下であり、かつ加水分解処理後の分子量分布(Mw/Mn)が3.40以下であることを特徴とするものである:
(3-1)概要
本発明の他の形態によれば、上述した〔2〕本発明に係る吸水性樹脂の製造方法の一例もまた、提供される。すなわち、上述した〔2〕本発明に係る吸水性樹脂に係る発明の技術的範囲は、以下に詳述する製造方法によって製造されたもののみには限定されない。
反応工程では、第1の星型ポリマーと第2の星型ポリマーとを反応させる工程である。なお、場合によっては、反応工程において3種以上の星型ポリマーを反応させてもよい。ここで、「星型ポリマー」とは、原子または原子団をコアとし、3本以上の分岐鎖が放射状に延びた構造を有する分岐ポリマーを意味する。なお、「星型ポリマー」については、「新版高分子辞典」(高分子学会、高分子辞典編集委員会編集、朝倉書店刊)や「大学院高分子化学(KS化学専門書)」(野瀬卓平ら編集、講談社刊)などの文献が参照されうる。
本形態に係る製造方法では、例えば上述した中和工程の終了とともに、水膨潤ゲルの状態の吸水性樹脂を最終目的物としてもよいが、場合によっては、従来公知の吸水性樹脂と同様に、乾燥、粉砕、分級、表面架橋等の後工程を実施してもよい。以下、各工程について簡単に説明する。
上記反応工程(および中和工程)で得られた吸水性樹脂が水膨潤ゲルである場合、当該吸水性樹脂は、乾燥し、乾燥の前および/または後で通常粉砕されて乾燥重合体としてもよい。なお、本明細書において、「乾燥」とは、水膨潤ゲルを所望する含水率となるまで乾燥させて乾燥重合体を得る工程である。該含水率は、EDANA法(ERT430.2-02)に準拠して、試料量を1.0g、乾燥温度を180℃、乾燥時間を4時間として測定され、好ましくは20重量%以下、より好ましくは1~15重量%、更に好ましくは2~10重量%、特に好ましくは3~8重量%である。
上記乾燥工程で得られた乾燥重合体は粉砕機によって粉砕されることが好ましい。粉砕機は特に限定されないが、例えばロールミルのようなロール式粉砕機、ハンマーミルのようなハンマー式粉砕機、衝撃式粉砕機、カッターミル、ターボグラインダー、ボールミル、フラッシュミルなどが用いられる。この中でも、粒度分布を制御するためにはロールミルが好ましい。粒度分布を制御するため連続して2回以上粉砕しても良いが、好ましくは3回以上である。2回以上粉砕する場合には、それぞれの粉砕機は同じであっても違っていても良い。違う種類の粉砕機を組み合わせて使うことも可能である。
本発明に係る吸水性樹脂は、その表面近傍が表面架橋剤である有機表面架橋剤および/または水溶性無機表面架橋剤によって表面架橋されていることが好ましい。すなわち、本発明の吸水性樹脂の製造方法は、乾燥後の吸水性樹脂を表面架橋する工程を含むことが好ましい。
本発明に係る吸水性樹脂の製造方法は、多価金属塩を吸水性樹脂に添加(好ましくは粒子表面に添加)する工程、特に表面架橋時または表面架橋後に添加することが好ましい。多価金属塩の添加量は、吸水性樹脂に対し、好ましくは0.001質量%以上5質量%以下、より好ましくは0.01質量%以上1質量%以下である。
ポリプロピレン製容器中で、(膨潤ゲル1.6~20gが得られる量の)吸水性樹脂を過剰(吸水性樹脂の1000倍以上の重量)の0.9重量%塩化ナトリウム水溶液(温度21~25℃)中に浸け、48時間静置する。その後、ポリプロピレン製容器中の水溶液を除き、再び過剰の0.9重量%塩化ナトリウム水溶液を加え、48時間静置する。この後、ポリプロピレン製容器中の水溶液を除き、再度過剰の0.9重量%塩化ナトリウム水溶液を加え、48時間静置することにより、平衡膨潤状態のゲル(以下、平衡膨潤ゲル)の分散液が得られる。
0.9重量%食塩水に対する平衡膨潤倍率(g/g) = W1/W-1
ただし、式中の平衡膨潤ゲルの質量W1およびポリマー固形分Wは下記で求められる。
ERT442.2-02記載の、AAP測定用の、底部に目開き36μm(400meshに相当)のワイヤーメッシュを有する樹脂製のシリンダー(内径6cmで高さ5cm。)に、上記得られた平衡膨潤ゲルの分散液の全量を入れ、さらに自然ろ過による水切りを5分間行った。ろ過後、さらに、ゲルが粒子状である場合にはシリンダー底面をすべて覆うように平面状に圧縮することなくスパチュラで均して入れ、シリンダー底面をすべて覆えない塊状ゲルである場合にはシリンダー底面に対して塊状ゲルの接触底面積が最大となるような入れ方で入れた。その後、さらなる水切りのために、このシリンダーをろ紙(Advantec No2、直径150mm)を5枚重ねた上に置き、室温15~30℃、30~90%の湿度の環境下で5分間静置した。その後、新たにろ紙(Advantec No2、直径150mm)を5枚重ねた上に、このシリンダーを置き、室温15~30℃、30~90%の湿度の環境下で5分間静置した後、水切りされたゲルから所定の重量(質量W1)を量り取った。
平衡膨潤ゲル(質量W1)のポリマー固形分は乾燥減量で求められるが、その際にまずゲル中の固形分NaClを以下の手法で除去した。すなわち、こうして量り取ったゲル(質量W1)を容量250 mlのポリプロピレン製容器(東京硝子器械株式会社製)中に移し、200 mlの純水(温度21~25℃)に浸けてフタをし、48時間静置した。この後、ポリプロピレン製容器中の液体を除き、再び200 ml(温度21~25℃)の純水を加えてフタをし、48時間静置した。この後、ポリプロピレン製容器中の液体を除き、再度200 ml(温度21~25℃)の純水を加えてフタをし、48時間静置した。
(試料調製)
0.9重量%塩化ナトリウム水溶液中で平衡膨潤状態に達したゲルをステンレス製のバット(20cm×12.5cm×7cm)中に移した。鋼製のポンチ(POSK25高級ベルトポンチ25mm、トラスコ中山株式会社製)を用いて、ゲルを直径25mmの円柱状にくり抜いた。このゲルの弾性率を、以下の条件でのずり試験により測定した。
測定機器:MCR 301(Anton Paar社製)
治具:アルミ製プレート直径25mm
歪み:0.01%
周波数:1 Hz
測定方法:まず、0.34Nの荷重下で上記の条件でゲルにずりをかけ、5分間、10秒毎に貯蔵弾性率を測定した。測定開始から120秒~300秒の貯蔵弾性率の平均値を、0.34Nの荷重下での弾性率(G0)とした。その後、ゲルにかける荷重を段階的に0.68Nずつ増していき、(すなわち、荷重を(0.34 + 0.68×n)N (n=1,2,3,…m-1,m,m+1,…)とした。)各々の荷重下における弾性率(Gn)を測定した。(0.34 + 0.68×m)Nの荷重下での弾性率の測定値(Gm)と、直前の荷重下における弾性率の測定値(Gm-1)とのずれ、直後の荷重下における弾性率の測定値(Gm+1)とのずれがともに5%以内となった時点で、Gmをそのゲルの弾性率とした。
(試料調製)
容量120mlのポリプロピレン製容器(東京硝子器械株式会社製)中に、0.9重量%塩化ナトリウム水溶液中で平衡膨潤状態に達したゲルを、(50 × 生理食塩水平衡膨潤倍率)mg量り取った。これに10gの0.1mol/lの水酸化ナトリウム水溶液を加えてフタをし、80℃の無風乾燥機(ADVANTEC DRV320DA)中に3週間静置した。3週間後、ゲルは加水分解されて溶液状になっていた。
ビスコテック社製TDA302(登録商標)を用いて、測定を行った。装置構成としては、サイズ排除クロマトグラフィー、屈折率検出器、光散乱検出器、およびキャピラリー粘度計を搭載した装置である。測定装置および測定条件は以下の通りとした。
ガードカラム:OHpak SB-G(昭和電工株式会社製)
カラム:OHpak SB-806MHQ(昭和電工株式会社製)を2本直列につないで使用した
検出器:ビスコテック社製TDA302(系内温度は30℃で保持)
溶離液:リン酸2水素ナトリウム2水和物60mM・リン酸水素2ナトリウム12水和物20mM・アジ化ナトリウム400ppm水溶液(pH6.35~6.38)
流速:0.5ml/min
注入量:100μl
本測定に使用する純水としては、十分に不純物を取り除いたものを使用した。また、測定は十分な量の溶媒を装置に流し、検出器のベースラインが安定した状態で行った。特に、光散乱検出器でのノイズピークが無い状態で測定を行った。
以下の装置および条件によりGPC測定を行った。
カラム:G5000HXL(東ソー社製)、GMHXL-L(東ソー社製)を2本直列につないで使用した
溶離液:テトラヒドロフラン
検量線用標準物質:ポリスチレン
測定方法:溶離液に測定対象物の固形分が0.3質量%となるように溶解し、フィルターにてろ過したものを測定した。測定は十分な量の溶媒を装置に流し、検出器のベースラインが安定した状態で行った。
(4腕状の星型コアの合成)
先行技術文献(J. Am. Chem. Soc., 2006, 128, 14599-14605)のScheme 1(14601頁)に記載の方法で、下記化学式Aで表される化学構造を有する4腕状の星型コアを合成した。
撹拌子を入れた、窒素で満たされた50mlナスフラスコ中で、臭化銅(I)80 mg、臭化銅(II)6 mgをアセトン2.0 g、ターシャリーブチルアクリレート14.1 gに溶解させた。そこにペンタメチルジエチレントリアミン107 mgを加え、室温下で5分間撹拌した後、上記で合成した4腕状の星型コア 0.2 gを加え、反応液とした。この反応液を50℃の油浴中で1.5時間加熱撹拌した。得られた溶液を室温下、1mmHgで5時間減圧乾燥し、下記化学式Bで表される化学構造を有する4腕状の星型ポリマー(1-Br)の粗生成物を得た。この粗生成物をジエチルエーテル100mlに溶解させた溶液を分液ロートに移し、純水100mlを加えて振り混ぜた。回収した有機層を分液ロートに移し、再び純水100mlを加えて振り混ぜた。得られた有機層を室温下、1mmHgで5時間減圧乾燥することにより、固体の4腕状の星型ポリマー(1-Br)を得た。得られた生成物の化学構造は、重クロロホルムを溶媒に用いるプロトンNMR測定により確認した。特徴的なピークとして、4.1ppmの化学シフトの位置に現れた、臭素官能基を有する炭素上の水素に由来するピークが挙げられる。
撹拌子を入れた、窒素で満たされた50mlナスフラスコ中で、上記で合成した4腕状の星型ポリマー(1-Br) 2.0 gとアジ化ナトリウム 156 mgとを、ジメチルホルムアミド10 mlに溶解させ、反応液とした。この反応液を室温下で18時間撹拌した後、50℃の湯浴中、1mmHgで5時間減圧乾燥し、下記化学式Cで表される化学構造を有する4腕状の星型ポリマー(1-N3)の粗生成物を得た。この粗生成物をジエチルエーテル100mlに溶解させた溶液を分液ロートに移し、純水100mlを加えて振り混ぜた。回収した有機層を分液ロートに移し、再び純水100mlを加えて振り混ぜた。得られた有機層を室温下、1mmHgで5時間減圧乾燥することにより、固体の4腕状の星型ポリマー(1-N3)を得た。得られた生成物の化学構造は、重クロロホルムを溶媒に用いるプロトンNMR測定により確認した。特徴的なピークとして、3.7ppmの化学シフトの位置に現れた、アジド官能基を有する炭素上の水素に由来するピークが挙げられる。
(ジアルキンの合成)
先行技術文献(J. Am. Chen. Soc. 2007, 129, 12916-12917)に記載の方法で、下記化学式Dで表される化学構造を有するジアルキンを得た。具体的には、同文献のSupporting Information(S2)に記載されているように、2-(プロパン-2-イニル)マロン酸ジメチル(1.0 mmol)のテトラヒドロフラン溶液を0℃にてNaH (1.5 mmol)で処理し、室温にて撹拌を30分間継続した後、アルキル化剤として(3-ブロモプロパン-1-イニル)トリメチルシラン(1.5 mmol)を添加して、反応を進行させた。
撹拌子を入れた、窒素で満たされた50mlナスフラスコ中で、上記で合成した4腕状の星型ポリマー(1-N3) 1.0 g、上記で合成したジアルキン 134.6 mg、臭化銅(I)57.4 mg をジメチルホルムアミド10 mlに溶解させた。そこにペンタメチルジエチレントリアミン76.8 mgを加え、反応液とした。この反応液を室温下で18時間撹拌した後、50℃の湯浴中、1mmHgで5時間減圧乾燥し、下記化学式Eで表される化学構造を有する4腕状の星型ポリマー(1-Siアルキン)の粗生成物を得た。この粗生成物をジエチルエーテル100mlに溶解させた溶液を分液ロートに移し、純水100mlを加えて振り混ぜた。回収した有機層を分液ロートに移し、再び純水100mlを加えて振り混ぜた。得られた有機層を室温下、1mmHgで5時間減圧乾燥し、生じた固体をヘキサン50mlで3回洗浄することにより、固体の4腕状の星型ポリマー(1-Siアルキン)を得た。得られた生成物の化学構造は、重クロロホルムを溶媒に用いるプロトンNMR測定により確認した。特徴的なピークとして、7.5ppmの化学シフトの位置に現れた、1,2,3-トリアゾール環上の水素に由来するピーク、5.2ppmの化学シフトの位置に現れた、1,2,3-トリアゾール環を有する炭素上の水素に由来するピーク、0.1ppmの化学シフトの位置に現れた、トリメチルシリル基の水素に由来するピークが挙げられる。
撹拌子を入れた、窒素で満たされた50mlナスフラスコ中で、上記で合成した4腕状の星型ポリマー(1-Siアルキン) 1.0 gをテトラヒドロフラン10 mlに溶解させ、0℃に冷やした。そこにテトラブチルアンモニウムフルオリドの1 mol/Lテトラヒドロフラン溶液 1.4 mlを加え、反応液とした。この反応液を室温にもどし、18時間撹拌した後、室温下、1mmHgで5時間減圧乾燥し、下記化学式Fで表される化学構造を有する4腕状の星型ポリマー(1-Hアルキン)の粗生成物を得た。この粗生成物をジエチルエーテル100mlに溶解させた溶液を分液ロートに移し、純水100mlを加えて振り混ぜた。回収した有機層を分液ロートに移し、再び純水100mlを加えて振り混ぜた。得られた有機層を室温下、1mmHgで5時間減圧乾燥し、生じた固体をヘキサン50mlで3回洗浄することにより、固体の4腕状の星型ポリマー(1-Hアルキン)を得た。得られた生成物の化学構造は、重クロロホルムを溶媒に用いるプロトンNMR測定により確認した。上述の1-Siアルキンの場合と同様に、特徴的なピークとして、1,2,3-トリアゾール環上の水素に由来するピークが7.5ppmの化学シフトの位置に、1,2,3-トリアゾール環を有する炭素上の水素に由来するピークが5.2ppmの化学シフトの位置にそれぞれ現れた。その一方で、0.1ppmの化学シフトの位置にピークは現れなかったことから、トリメチルシリル基の脱保護反応の進行が確認された。
撹拌子を入れた、窒素で満たされたガラスバイアル中で上記で合成した4腕状の星型ポリマー(1-N3) 92.0 mgと上記で合成した4腕状の星型ポリマー(1-Hアルキン)100.0 mgとをアセトン533.0 μlに溶解させ、0℃に冷やした。ここに、別のガラスバイアル中で臭化銅(I)5.7 mg、ペンタメチルジエチレントリアミン7.7 mgをメタノール133.0 μlに溶解させて得た溶液を加え、反応液とした。この反応液を30秒間撹拌した後、バイアル中から撹拌子を取り出し、室温下で静置したところ、30分程度で反応液は固まり、ゲルとなった。その後、ガラスバイアルを室温下で18時間静置した。生成したゲルをガラスバイアルから取り出した。50mlガラスビーカー中で、得られたゲルを30mlのアセトンに浸けた。このガラスビーカーを振とう台の上に置き、毎分60回転の速さで24時間振とうし、残存している銅を洗い出した。得られたアセトン膨潤ゲルをガラスビーカーから取り出し、大気中室温で24時間静置して乾燥し、下記化学式Gで表される化学構造を有する、円柱状のポリターシャリーブチルアクリレート架橋体(1-tBAゲル)を得た。
50mlガラスビーカー中に、上記で合成したポリターシャリーブチルアクリレート架橋体(1-tBAゲル)を移し、ジクロロメタン12ml、トリフルオロ酢酸3mlの混合液に浸けた。このガラスビーカーを振とう台の上に置き、毎分60回転の速さで24時間振とうした。この際、当該架橋体は一旦混合液を吸液して膨潤するが、徐々にトリフルオロ酢酸によるターシャリーブチル基の脱保護反応が進行することにより再び混合液を吐き出して収縮した。このようなターシャリーブチル基の脱保護反応により生じたポリアクリル酸架橋体をガラスビーカーから取り出し、別の50mlガラスビーカー中で30mlの純水に浸けた。このガラスビーカーを振とう台の上に置き、毎分60回転の速さで18時間振とうして残存しているトリフルオロ酢酸を洗い出し、下記化学式Hで表される化学構造を有する、円柱状のポリアクリル酸架橋体の水膨潤ゲル(1-AAゲル)を得た。
酸架橋体の膨潤ゲル(吸水性樹脂1)の合成)
120mlのポリプロピレン製容器(東京硝子器械株式会社製)中で94.5 mgの炭酸水素ナトリウムを30 mlの0.9重量%塩化ナトリウム水溶液に溶解させ、この溶液に上記で合成したポリアクリル酸架橋体の水膨潤ゲル(1-AAゲル)を浸けて、72時間静置した。得られた部分中和ポリアクリル酸架橋体の膨潤ゲル(吸水性樹脂1)を250mlのポリプロピレン製容器中に移し、200 mlの0.9重量%塩化ナトリウム水溶液に浸け、48時間静置した。この後、ポリプロピレン製容器中の水溶液を除き、再び200 mlの0.9重量%塩化ナトリウム水溶液を加え、48時間静置した。この後、ポリプロピレン製容器中の水溶液を除き、再度200 mlの0.9重量%塩化ナトリウム水溶液を加え、48時間静置した。こうして、0.9重量%塩化ナトリウム水溶液中で平衡膨潤状態となった、部分中和ポリアクリル酸架橋体の膨潤ゲル(吸水性樹脂1)を得た。この膨潤ゲル(吸水性樹脂1)は下記化学式Iで表される化学構造を有するものである。
(4腕状の星型ポリマー(2-Br)の合成)
ターシャリーブチルアクリレートの量を17.6 gとし、反応時間を2時間とした以外は実施例1における「4腕状の星型ポリマー(1-Br)の合成」と同様にして、上記化学式Bにおいてn=30の化学構造を有する固体の4腕状の星型ポリマー(2-Br)を得た。
4腕状の星型ポリマー(1-Br)に代えて上記で合成した4腕状の星型ポリマー(2-Br)を用い、アジ化ナトリウム(NaN3)の量を110 mgとした以外は実施例1における「4腕状の星型ポリマー(1-N3)の合成」と同様にして、上記化学式Cにおいてn=30の化学構造を有する固体の4腕状の星型ポリマー(2-N3)を得た。
4腕状の星型ポリマー(1-N3)に代えて上記で合成した4腕状の星型ポリマー(2-N3)を用い、ジアルキンの量を 89.7 mg、臭化銅(I)の量を38.1 mg、ペンタメチルジエチレントリアミンの量を 51.2 mgとした以外は実施例1における「4腕状の星型ポリマー(1-Siアルキン)の合成」と同様にして、上記化学式Eにおいてn=30の化学構造を有する固体の4腕状の星型ポリマー(2-Siアルキン)を得た。
4腕状の星型ポリマー(1-Siアルキン)に代えて上記で合成した4腕状の星型ポリマー(2-Siアルキン)を用い、テトラブチルアンモニウムフルオリドの1 mol/Lテトラヒドロフラン溶液の量を1.0 mlとした以外は実施例1における「4腕状の星型ポリマー(1-Hアルキン)の合成」と同様にして、上記化学式Fにおいてn=30の化学構造を有する固体の4腕状の星型ポリマー(2-Hアルキン)を得た。
4腕状の星型ポリマー(1-N3)92.0 mgに代えて上記で合成した4腕状の星型ポリマー(2-N3) 94.8 mgを用い、4腕状の星型ポリマー(1-Hアルキン)に代えて上記で合成した4腕状の星型ポリマー(2-Hアルキン)を用い、臭化銅(I)の量を3.8 mg、ペンタメチルジエチレントリアミンの量を4.8 mgとした以外は実施例1における「ポリターシャリーブチルアクリレート架橋体(1-tBAゲル)の合成」と同様にして、上記化学式Gにおいてn=30の化学構造を有する円柱状のポリターシャリーブチルアクリレート架橋体(2-tBAゲル)を得た。
ポリターシャリーブチルアクリレート架橋体(1-tBAゲル)に代えて上記で合成したポリターシャリーブチルアクリレート架橋体(2-tBAゲル)を用いた以外は実施例1における「ポリアクリル酸架橋体の水膨潤ゲル(1-AAゲル)の合成」と同様にして、上記化学式Hにおいてn=30の化学構造を有する円柱状のポリアクリル酸架橋体の水膨潤ゲル(2-AAゲル)を得た。
ポリアクリル酸架橋体の水膨潤ゲル(1-AAゲル)に代えて上記で合成したポリアクリル酸架橋体の水膨潤ゲル(2-AAゲル)を用いた以外は実施例1における「0.9重量%塩化ナトリウム水溶液中で平衡膨潤状態となった、部分中和ポリアクリル酸架橋体の膨潤ゲル(吸水性樹脂1)の合成」と同様にして、0.9重量%塩化ナトリウム水溶液中で平衡膨潤状態となった、部分中和ポリアクリル酸架橋体の膨潤ゲル(吸水性樹脂2)を得た。この膨潤ゲル(吸水性樹脂2)は上記化学式Iにおいてn=30の化学構造を有するものである。
(4腕状の星型ポリマー(3-Br)の合成)
ターシャリーブチルアクリレートの量を28.2 gとし、反応時間を2時間とした以外は実施例1における「4腕状の星型ポリマー(1-Br)の合成」と同様にして、上記化学式Bにおいてn=40の化学構造を有する固体の4腕状の星型ポリマー(3-Br)を得た。
4腕状の星型ポリマー(1-Br)に代えて上記で合成した4腕状の星型ポリマー(3-Br)を用い、アジ化ナトリウム(NaN3)の量を83 mgとした以外は実施例1における「4腕状の星型ポリマー(1-N3)の合成」と同様にして、上記化学式Cにおいてn=40の化学構造を有する固体の4腕状の星型ポリマー(3-N3)を得た。
4腕状の星型ポリマー(1-N3)に代えて上記で合成した4腕状の星型ポリマー(3-N3)を用い、ジアルキンの量を 67.3 mg、臭化銅(I)の量を28.6 mg、ペンタメチルジエチレントリアミンの量を 38.4 mgとした以外は実施例1における「4腕状の星型ポリマー(1-Siアルキン)の合成」と同様にして、上記化学式Eにおいてn=40の化学構造を有する固体の4腕状の星型ポリマー(3-Siアルキン)を得た。
4腕状の星型ポリマー(1-Siアルキン)に代えて上記で合成した4腕状の星型ポリマー(3-Siアルキン)を用い、テトラブチルアンモニウムフルオリドの1 mol/Lテトラヒドロフラン溶液の量を0.8 mlとした以外は実施例1における「4腕状の星型ポリマー(1-Hアルキン)の合成」と同様にして、上記化学式Fにおいてn=40の化学構造を有する固体の4腕状の星型ポリマー(3-Hアルキン)を得た。
4腕状の星型ポリマー(1-N3)92.0 mgに代えて上記で合成した4腕状の星型ポリマー(3-N3) 96.1 mgを用い、4腕状の星型ポリマー(1-Hアルキン)に代えて上記で合成した4腕状の星型ポリマー(3-Hアルキン)を用い、臭化銅(I)の量を3.0 mg、ペンタメチルジエチレントリアミンの量を3.6 mgとした以外は実施例1における「ポリターシャリーブチルアクリレート架橋体(1-tBAゲル)の合成」と同様にして、上記化学式Gにおいてn=40の化学構造を有する円柱状のポリターシャリーブチルアクリレート架橋体(3-tBAゲル)を得た。
ポリターシャリーブチルアクリレート架橋体(1-tBAゲル)に代えて上記で合成したポリターシャリーブチルアクリレート架橋体(3-tBAゲル)を用いた以外は実施例1における「ポリアクリル酸架橋体の水膨潤ゲル(1-AAゲル)の合成」と同様にして、上記化学式Hにおいてn=40の化学構造を有する円柱状のポリアクリル酸架橋体の水膨潤ゲル(3-AAゲル)を得た。
ポリアクリル酸架橋体の水膨潤ゲル(1-AAゲル)に代えて上記で合成したポリアクリル酸架橋体の水膨潤ゲル(3-AAゲル)を用いた以外は実施例1における「0.9重量%塩化ナトリウム水溶液中で平衡膨潤状態となった、部分中和ポリアクリル酸架橋体の膨潤ゲル(吸水性樹脂1)の合成」と同様にして、0.9重量%塩化ナトリウム水溶液中で平衡膨潤状態となった、部分中和ポリアクリル酸架橋体の膨潤ゲル(吸水性樹脂3)を得た。この膨潤ゲル(吸水性樹脂3)は上記化学式Iにおいてn=40の化学構造を有するものである。
(4腕状の星型ポリマー(4-Br)の合成)
臭化銅(I)の量を40 mg、臭化銅(II)の量を3 mg、ターシャリーブチルアクリレートの量を28.2 g、ペンタメチルジエチレントリアミンの量を54 mg、4腕状の星型コアの量を0.1 gとし、反応時間を2時間とした以外は実施例1における「4腕状の星型ポリマー(1-Br)の合成」と同様にして、上記化学式Bにおいてn=80の化学構造を有する固体の4腕状の星型ポリマー(4-Br)を得た。
4腕状の星型ポリマー(1-Br)に代えて上記で合成した4腕状の星型ポリマー(4-Br)を用い、アジ化ナトリウム(NaN3)の量を41 mgとした以外は実施例1における「4腕状の星型ポリマー(1-N3)の合成」と同様にして、上記化学式Cにおいてn=80の化学構造を有する固体の4腕状の星型ポリマー(4-N3)を得た。
4腕状の星型ポリマー(1-N3)に代えて上記で合成した4腕の星型ポリマー(4-N3)を用い、ジアルキンの量を 33.6 mg、臭化銅(I)の量を14.3 mg 、ペンタメチルジエチレントリアミンの量を 19.2 mgとした以外は実施例1における「4腕状の星型ポリマー(1-Siアルキン)の合成」と同様にして、上記化学式Eにおいてn=80の化学構造を有する固体の4腕状の星型ポリマー(4-Siアルキン)を得た。
4腕状の星型ポリマー(1-Siアルキン)に代えて上記で合成した4腕状の星型ポリマー(4-Siアルキン)を用い、テトラブチルアンモニウムフルオリドの1 mol/Lテトラヒドロフラン溶液の量を0.4 mlとした以外は実施例1における「4腕状の星型ポリマー(1-Hアルキン)の合成」と同様にして、上記化学式Fにおいてn=80の化学構造を有する固体の4腕状の星型ポリマー(4-Hアルキン)を得た。
4腕状の星型ポリマー(1-N3)92.0 mgに代えて上記で合成した4腕状の星型ポリマー(4-N3) 98.0 mgを用い、4腕状の星型ポリマー(1-Hアルキン)に代えて上記で合成した4腕状の星型ポリマー(4-Hアルキン)を用い、臭化銅(I)の量を1.5 mg、ペンタメチルジエチレントリアミンの量を1.8 mgとした以外は実施例1における「ポリターシャリーブチルアクリレート架橋体(1-tBAゲル)の合成」と同様にして、上記化学式Gにおいてn=80の化学構造を有する円柱状のポリターシャリーブチルアクリレート架橋体(4-tBAゲル)を得た。
ポリターシャリーブチルアクリレート架橋体(1-tBAゲル)に代えて上記で合成したポリターシャリーブチルアクリレート架橋体(4-tBAゲル)を用いた以外は実施例1における「ポリアクリル酸架橋体の水膨潤ゲル(1-AAゲル)の合成」と同様にして、上記化学式Hにおいてn=80の化学構造を有する円柱状のポリアクリル酸架橋体の水膨潤ゲル(4-AAゲル)を得た。
ポリアクリル酸架橋体の水膨潤ゲル(1-AAゲル)に代えて上記で合成したポリアクリル酸架橋体の水膨潤ゲル(4-AAゲル)を用いた以外は実施例1における「0.9重量%塩化ナトリウム水溶液中で平衡膨潤状態となった、部分中和ポリアクリル酸架橋体の膨潤ゲル(吸水性樹脂1)の合成」と同様にして、0.9重量%塩化ナトリウム水溶液中で平衡膨潤状態となった、部分中和ポリアクリル酸架橋体の膨潤ゲル(吸水性樹脂4)を得た。この膨潤ゲル(吸水性樹脂4)は上記化学式Iにおいてn=80の化学構造を有するものである。
容量250mlのポリプロピレン製容器(東京硝子器械株式会社製)中で、48質量%水酸化ナトリウム水溶液17.170gと、5℃に冷やした純水21.750gとを入れ、撹拌した。そこにポリエチレングリコールジアクリレート(分子量(Mw)523)0.144gとアクリル酸19.800gとの混合液をゆっくりと加え、反応液とした。次にこの反応液を窒素ガス雰囲気下で、20分間脱気した。続いて、反応液に10質量%過硫酸ナトリウム水溶液0.650gおよび0.1質量%L-アスコルビン酸水溶液0.484gを撹拌しながら添加した。得られた反応液を、シリンジを用いてすみやかに、窒素ガスで置換した下記の反応容器に移し、60℃の乾燥機中で18時間静置し、ディスク状ゲルを得た。上記反応容器とは、円形の空孔を有するシリコンゴムを2枚のガラス板の間に挟み、周囲をクリップで留めたものである。
ポリエチレングリコールジアクリレートの量を0.058g、純水の量を21.836gとした以外は比較例1と同様にして、0.9重量%塩化ナトリウム水溶液中で平衡膨潤状態となった、本比較例の部分中和ポリアクリル酸架橋体の膨潤ゲル(比較吸水性樹脂2)を得た。
ポリエチレングリコールジアクリレートの量を0.043g、純水の量を21.851gとした以外は比較例1と同様にして、0.9重量%塩化ナトリウム水溶液中で平衡膨潤状態となった、本比較例の部分中和ポリアクリル酸架橋体の膨潤ゲル(比較吸水性樹脂3)を得た。
ポリエチレングリコールジアクリレートの量を0.028g、純水の量を21.866gとした以外は比較例1と同様にして、0.9重量%塩化ナトリウム水溶液中で平衡膨潤状態となった、本比較例の部分中和ポリアクリル酸架橋体の膨潤ゲル(比較吸水性樹脂4)を得た。
10質量%過硫酸ナトリウム水溶液の量を3.250g、0.1質量%L-アスコルビン酸水溶液の量を2.420g、純水の量を17.170gとした以外は比較例1と同様にして、0.9重量%塩化ナトリウム水溶液中で平衡膨潤状態となった、本比較例の部分中和ポリアクリル酸架橋体の膨潤ゲル(比較吸水性樹脂5)を得た。
純水の量を17.170gとし、10質量%過硫酸ナトリウム水溶液、0.1質量%L-アスコルビン酸水溶液と同時に10質量%亜リン酸水素2ナトリウム5水和物水溶液2.970gを添加した以外は比較例1と同様にして、0.9重量%塩化ナトリウム水溶液中で平衡膨潤状態となった、本比較例の部分中和ポリアクリル酸架橋体の膨潤ゲル(比較吸水性樹脂6)を得た。
容量120mlのポリプロピレン製容器中で、0.111gのエチレングリコールジグリシジルエーテル (Denacol EX-810、ナガセケムテックス製)に20.00g の30質量%ポリアクリル酸ナトリウム水溶液(DL522、日本触媒製)を加えて、スパチュラで撹拌し溶解させた。その後パックエースにふたをし、3時間静置して溶液中の気泡をなくした。このポリプロピレン製容器を80℃のオーブンに入れ、12時間静置し、ディスク状ゲルを得た。
上述した先行技術文献の1つである特表2009-531467号公報の実施例および比較例には、種々の吸水性樹脂のCRCおよび加水分解後重量平均分子量(Mw)が記載されている。これらのうち、以下の数式2で示す「参考架橋構造指数」が最も高い吸水性樹脂では、CRCは28.3(g/g)であり、加水分解後重量平均分子量(Mw)は221,634であり、分子量分布(Mw/Mn)は1.95であった。この吸水性樹脂を比較吸水性樹脂8とし、これらの結果を下記の表1に示す。
Claims (10)
- 前記繰り返し単位の90mol%以上が、解離基としてカルボン酸(塩)基を有する水溶性不飽和単量体由来の繰り返し単位である、請求項1に記載の吸水性樹脂。
- 前記繰り返し単位の90mol%以上が、アクリル酸(塩)由来の繰り返し単位である、請求項1または2に記載の吸水性樹脂。
- 中和率が50~100mol%である、請求項1~3のいずれか1項に記載の吸水性樹脂。
- 解離基を有する水溶性不飽和単量体を主鎖の繰り返し単位の主成分とし、内部架橋構造を有する吸水性樹脂の製造方法であって、
前記水溶性不飽和単量体を各分岐鎖の繰り返し単位の主成分とし、各分岐鎖の末端に第1の反応性官能基を有する第1の星型ポリマーと、
前記水溶性不飽和単量体を各分岐鎖の繰り返し単位の主成分とし、各分岐鎖の末端に前記第1の反応性官能基と互いに反応して化学結合を形成しうる第2の反応性官能基を有する第2の星型ポリマーと、を互いに反応させる反応工程を含むことを特徴とする、吸水性樹脂の製造方法。 - 前記第1の星型ポリマーおよび前記第2の星型ポリマーのそれぞれにおいて、前記分岐鎖の繰り返し単位の90mol%以上が、アクリル酸(塩)由来の繰り返し単位である、請求項5に記載の吸水性樹脂の製造方法。
- 前記第1の星型ポリマーおよび前記第2の星型ポリマーが、4腕のコアに分岐鎖として前記水溶性不飽和単量体を繰り返し単位の主成分とする重合体が結合した構造を有する、請求項5または6に記載の吸水性樹脂の製造方法。
- 前記第1の反応性官能基がアジド基であり、前記第2の反応性官能基がアルキニル基である、請求項5~7のいずれか1項に記載の吸水性樹脂の製造方法。
- 前記第1の星型ポリマーおよび前記第2の星型ポリマーの前記分岐鎖を構成する前記水溶性不飽和単量体の前記解離基を保護基により保護した状態で前記反応工程を行い、前記反応工程終了後に前記解離基を脱保護する工程をさらに含む、請求項5~8のいずれか1項に記載の吸水性樹脂の製造方法。
- 前記解離基を中和する工程をさらに含む、請求項5~9のいずれか1項に記載の吸水性樹脂の製造方法。
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