WO2011040530A1 - Agent hydroabsorbant particulaire et procédé de fabrication de celui-ci - Google Patents

Agent hydroabsorbant particulaire et procédé de fabrication de celui-ci Download PDF

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WO2011040530A1
WO2011040530A1 PCT/JP2010/067086 JP2010067086W WO2011040530A1 WO 2011040530 A1 WO2011040530 A1 WO 2011040530A1 JP 2010067086 W JP2010067086 W JP 2010067086W WO 2011040530 A1 WO2011040530 A1 WO 2011040530A1
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water
weight
absorbing agent
agent
particulate water
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PCT/JP2010/067086
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English (en)
Japanese (ja)
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玲子 中津留
博之 池内
貴洋 北野
邦彦 石▲崎▼
一司 鳥井
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株式会社日本触媒
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Application filed by 株式会社日本触媒 filed Critical 株式会社日本触媒
Priority to KR1020127008382A priority Critical patent/KR101887706B1/ko
Priority to JP2011534308A priority patent/JP5785087B2/ja
Priority to CN2010800434161A priority patent/CN102574100A/zh
Publication of WO2011040530A1 publication Critical patent/WO2011040530A1/fr

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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
    • 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
    • B01J20/261—Synthetic macromolecular compounds obtained by reactions only involving carbon to carbon unsaturated bonds
    • 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
    • B01J20/02—Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof comprising inorganic material
    • B01J20/0203—Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof comprising inorganic material comprising compounds of metals not provided for in B01J20/04
    • B01J20/0259—Compounds of N, P, As, Sb, Bi
    • 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
    • B01J20/02—Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof comprising inorganic material
    • B01J20/0203—Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof comprising inorganic material comprising compounds of metals not provided for in B01J20/04
    • B01J20/0262—Compounds of O, S, Se, Te
    • B01J20/0266—Compounds of S
    • 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
    • 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
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29B—PREPARATION OR PRETREATMENT OF THE MATERIAL TO BE SHAPED; MAKING GRANULES OR PREFORMS; RECOVERY OF PLASTICS OR OTHER CONSTITUENTS OF WASTE MATERIAL CONTAINING PLASTICS
    • B29B9/00—Making granules
    • B29B9/12—Making granules characterised by structure or composition
    • 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
    • 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
    • C08J3/128—Polymer particles coated by inorganic and non-macromolecular organic compounds
    • 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
    • C08J3/245—Differential crosslinking of one polymer with one crosslinking type, e.g. surface crosslinking
    • 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
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29B—PREPARATION OR PRETREATMENT OF THE MATERIAL TO BE SHAPED; MAKING GRANULES OR PREFORMS; RECOVERY OF PLASTICS OR OTHER CONSTITUENTS OF WASTE MATERIAL CONTAINING PLASTICS
    • B29B9/00—Making granules
    • B29B9/12—Making granules characterised by structure or composition
    • B29B2009/125—Micropellets, microgranules, microparticles
    • 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
    • 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

Definitions

  • the present invention relates to a particulate water-absorbing agent mainly comprising a polyacrylic acid (salt) water-absorbing resin and a method for producing the same. More specifically, the present invention relates to a particulate water-absorbing agent for absorbers used in paper diapers, sanitary napkins, and the like, and a method for producing the same, and has excellent yellowing prevention properties, no odor, and excellent absorption ability. The present invention relates to a particulate water-absorbing agent mainly composed of a polyacrylic acid (salt) -based water-absorbing resin and a method for producing the same.
  • water-absorbing resins having a high water-absorbing property have been developed, and are widely used mainly in disposable applications as absorbent articles such as paper diapers and sanitary napkins, as well as water retaining agents for agriculture and horticulture, industrial water-stopping materials, etc.
  • a water-absorbing resin many monomers and hydrophilic polymers have been proposed as raw materials.
  • polyacrylic acid (salt) -based water-absorbing using acrylic acid and / or a salt thereof as a monomer is proposed.
  • Resins are most commonly used industrially because of their high water absorption performance.
  • Such polyacrylic acid (salt) -based water-absorbing resin is obtained by neutralizing acrylic acid before or after polymerization to give a polyacrylate, and such neutralization and polymerization are disclosed in Patent Documents 1 to 4 and non-patent documents. It is disclosed in Document 1.
  • the water absorption characteristics desired for the above water-absorbing resin include: non-pressurized water absorption capacity (CRC), pressurized water absorption capacity (AAP), water absorption speed (FSR / Vortex), non-pressurized liquid permeability, pressurized liquid permeability
  • CRC non-pressurized water absorption capacity
  • AAP pressurized water absorption capacity
  • FSR / Vortex water absorption speed
  • non-pressurized liquid permeability pressurized liquid permeability
  • pressurized liquid permeability Many properties (parameters) such as impact resistance, urine resistance, fluidity, gel strength, color, particle size, etc. are known, and many more from various viewpoints among the same physical properties (for example, water absorption capacity without pressure)
  • a rule parameter measurement method
  • the water-absorbing resin (particulate water-absorbing agent) that has been developed by paying attention to these many physical properties has the above-mentioned many physical properties (for example, “absorption capacity under no pressure (CRC)” and “absorption capacity under pressure (AAP)”). Etc.), there is still a problem that it is difficult to say that the actual use of an absorbent body such as a paper diaper exhibits sufficient performance.
  • the main use of these water-absorbing agents is sanitary materials such as paper diapers and sanitary napkins. Therefore, when powdered water-absorbing agents are combined with white pulp in sanitary materials, they give a feeling of foreign matter due to coloring.
  • an initial color tone (also known as initial coloring) of the water-absorbing agent the water-absorbing resin is required to be white at the time of shipment from the factory.
  • the water-absorbing agent is generally a white powder.
  • the color of the water-absorbing agent over time also known as time-dependent coloring
  • the coloring problem has become more important.
  • Patent Documents 5 to 31, and the like various proposals for improving the whiteness of the water-absorbing resin and preventing coloring are proposed in Patent Documents 5 to 31, and the like.
  • a method for controlling the polymerization inhibitor in the monomer a technique of setting methoxyphenol in acrylic acid to 10 to 160 ppm (Patent Document 5), controlling hydroquinone in acrylic acid to 0.2 ppm or less.
  • Technology Patent Document 6
  • Patent Document 7 technology for treating monomers with activated carbon
  • Patent Document 8 technology using tocophenol as an inhibitor
  • N-oxyl compound and manganese compound as a polymerization inhibitor, etc.
  • a technique using Pt Patent Document 9
  • a technique using methoxyphenol and a specific polyvalent metal salt Patent Documents 10 and 11
  • Patent Document 12 a technique of adding a reducing agent such as hypophosphite
  • Patent Documents 13 and 14 a technique of adding an antioxidant
  • Patent Documents 15 to 19 Techniques for adding other reducing agents and the like
  • Patent Documents 20 to 23 Techniques for adding organic carboxylic acids and other compounds as necessary
  • Patent Documents 24 to 26 are known as techniques focusing on polymerization initiators for preventing coloring.
  • techniques (Patent Documents 27 and 28) that focus on the amount of iron in aluminum or a reducing agent have also been proposed as coloring-causing substances, and use an ammonium acrylate salt as a monomer or include a phosphorus atom.
  • a technique for adding a compound or a sulfur-based reducing agent a plurality of times (Patent Document 29) is also known.
  • techniques (Patent Documents 30 and 31) for controlling the amount of oxygen in the drying process and the surface crosslinking process are also known.
  • Patent Document 32 acrylic acid
  • Patent Document 33 acetic acid and propionic acid
  • Patent Document 34 volatile organic solvent
  • Patent Document 35 sulfur reducing agent
  • Patent Document 36 alcohol-based volatilization Odor reduction of substances
  • AAP water absorption capacity under pressure
  • SFC saline flow inductivity
  • the problem to be solved by the present invention is that a particulate water-absorbing agent mainly composed of a polyacrylic acid (salt) -based water-absorbing resin and a method for producing the same can exhibit excellent absorption performance, and can further prevent coloration with time.
  • the object is to provide a particulate water-absorbing agent for an absorbent material which has performance and has no odor and is suitable for practical use, and a method for producing the same.
  • the problem to be solved by the present invention is to provide a particulate water-absorbing agent for an absorbent body excellent in urine resistance and suitable for practical use, and a method for producing the same.
  • the particulate water-absorbing agent of the present invention is a particulate water-absorbing agent mainly composed of a polyacrylic acid (salt) -based water-absorbing resin, and includes a chelating agent and an inorganic reducing agent,
  • the content of the chelating agent is 0.001 to 0.5% by weight, and the following (1) to (3) (1)
  • the content of methoxyphenols is 5 to 60 ppm.
  • the water content is 3 to 15% by weight. It is characterized by satisfying any one or more of the requirements.
  • the method for producing a particulate water-absorbing agent of the present invention comprises a polymerization step of an aqueous monomer solution mainly composed of acrylic acid (salt), and a hydrogel cross-linked polymer obtained by polymerization.
  • the monomer contains 10 to 200 ppm of methoxyphenol in terms of acrylic acid,
  • (A) including a step of adding water-insoluble inorganic fine particles The water content of the polymer is controlled to 3 to 15% by weight after the drying step and in the surface cross-linking step.
  • An inorganic reducing agent addition step is performed after the surface cross-linking step. It is characterized by satisfying any one or more of the requirements.
  • the production method of the subordinate concept essentially comprising the above (c) is a simple method comprising acrylic acid (salt) containing 10 to 200 ppm of methoxyphenol as a main component.
  • a particulate water-absorbing agent comprising a polymerization step of a monomer aqueous solution, a drying step of a water-containing gel-like crosslinked polymer obtained by polymerization, a surface crosslinking step, and a step of adding 0.001 to 0.5 wt% of a chelating agent.
  • an inorganic reducing agent addition step is performed after the surface cross-linking step. Specific examples of this production method / part 1 are shown in Examples 1-1 to 1-16 and Tables 1 to 5 described later.
  • part 2 As a method for producing the particulate water-absorbing agent of the present invention, the production method of the subordinate concept essentially comprising the above (b), part 2 is a polymerization step of a monomer aqueous solution mainly composed of acrylic acid (salt), and polymerization
  • a method for producing a particulate water-absorbing agent comprising a drying step of a water-containing gel-like cross-linked polymer obtained in step 1 and a surface cross-linking step, wherein an addition step of 0.001 to 0.5 wt% of a chelating agent and inorganic reduction And a step of adding an agent, wherein the monomer contains 10 to 200 ppm of methoxyphenol in terms of acrylic acid, and (a) a step of adding water-insoluble inorganic fine particles is further included.
  • Specific examples of such production method-2 are shown in Examples 2-1 to 2-14 and Tables 6 to 7 described later.
  • part 3 is a polymerization step of a monomer aqueous solution mainly composed of acrylic acid (salt), and polymerization
  • a method for producing a particulate water-absorbing agent comprising a drying step of a water-containing gel-like cross-linked polymer obtained in step 1 and a surface cross-linking step, wherein an addition step of 0.001 to 0.5 wt% of a chelating agent and inorganic reduction And a monomer addition step, the monomer contains 10 to 200 ppm of methoxyphenol in terms of acrylic acid, and the moisture content of the polymer is 3 to 15% by weight after the drying step and / or in the surface cross-linking step. More preferably, the inorganic reducing agent is added to the hydrogel crosslinked polymer before drying. Specific examples of the production method / part 3
  • particulate water-absorbing agent suitable for practical use that has excellent anti-coloring performance over time, has no odor, and is excellent in urine resistance. be able to.
  • FIG. 1 is a side view showing a schematic configuration of a measuring apparatus for AAP (water absorption under pressure) according to the present embodiment.
  • FIG. 2 is a side view showing a schematic configuration of the SFC (saline flow conductivity) measuring apparatus according to the present embodiment.
  • FIG. 3 is an electron micrograph of typical granulated particles.
  • CRC Chiptrifuge Retention Capacity
  • SFC Seline Flow Conductivity
  • AAP Absorbency against Pressure
  • water absorption capacity under pressure is “water absorption capacity under pressure” with respect to a pressure of 4.83 kPa or 2.0 kPa, which is a value obtained by the measurement method described in the examples described later.
  • FSR Free Well Rate
  • D50 Distribution
  • ⁇ is “logarithmic standard deviation of particle size distribution”, which is a value obtained by the measurement method described in Examples described later.
  • FHA Fixed Height Absorption
  • Vortex is “water absorption rate”, which is a value obtained by the measurement method described in Examples described later.
  • saline solution means “aqueous sodium chloride solution”
  • X to Y indicating a range means “X or more and Y or less”, unless otherwise noted.
  • Ppm means “weight ppm” or “mass ppm”
  • ⁇ acid (salt) means “ ⁇ acid and / or salt thereof”
  • (meth) acryl means “acryl and / Or methacryl ".
  • the particulate water-absorbing agent according to the present invention comprises a polyacrylic acid (salt) -based water-absorbing resin as a main component, a chelating agent having a content of 0.001 to 0.5% by weight, and an inorganic reducing agent.
  • An aqueous liquid absorbent solidifying agent that satisfies at least one of (1) to (3).
  • the content of methoxyphenols is 5 to 60 ppm, (2) containing water-insoluble inorganic fine particles, (3) The water content is 3 to 15% by weight.
  • the particulate water-absorbing agent of the present invention must satisfy any one or more of the above (1) to (3), preferably an aqueous liquid satisfying any two or more, particularly preferably three simultaneously. Although it is an absorption solidifying agent, if the chelating agent and the inorganic reducing agent are not used in the above ranges, the effect of preventing coloring and deterioration is low. In preventing coloring and deterioration, the (1) methoxyphenols and the (2) water-insoluble inorganic fine particles contribute to prevention of deterioration and further prevention of coloring. In addition, the above (3) water content affects coloring (for example, Comparative Example 3-8 of the present application), contributes to the water absorption rate (for example, Example 1-16 of the present application), and further solves odor and dust problems.
  • the content of (1) methoxyphenol is preferably 5 to 60 ppm, and (3) when the water content is 3 to 15% by weight, 2) It is preferable to contain water-insoluble inorganic fine particles. That is, in the method of using a chelating agent and an inorganic reducing agent in combination within the above range, any of the above (1) to (3) has an effect on preventing coloration or preventing deterioration, and in the present invention, one or more of them, preferably Two or more, particularly preferably three are selected.
  • the “main component” means that the content of the water-absorbing resin is 50% by weight or more with respect to the entire water-absorbing agent, and the content of the water-absorbing resin requires a chelating agent and an inorganic reducing agent as essential. Since the water content is preferably 3 to 15% by weight, the water-absorbing resin is contained in less than 97% by weight, and the lower limit of the water-absorbing resin is 60% by weight or more, more preferably 70% by weight or more. It is 80% by weight or more, and further 85% by weight or more.
  • the content of the water-absorbent resin is 60% by weight or more and less than 99.999% by weight, more preferably 70% by weight or more and less than 99.9% by weight, and more preferably It means 80 wt% or more and less than 99.7 wt%, particularly preferably 90 wt% or more and less than 99.5 wt%.
  • the particulate water-absorbing agent of the present invention refers to an aqueous liquid absorbent solidifying agent (also known as a gelling agent) containing a polyacrylic acid (salt) water-absorbing resin as a main component.
  • aqueous liquid include water, urine, blood, feces, waste liquid, moisture and steam, ice, a mixture of water and an organic solvent or an inorganic solvent, rainwater, groundwater, etc.
  • the particulate water-absorbing agent of the present invention is an absorbent solidifying agent for urine, particularly human urine.
  • the particulate water-absorbing agent according to the present invention is preferably an aqueous liquid absorbing and solidifying agent containing an ⁇ -hydroxycarboxylic acid compound in order to prevent coloring and deterioration.
  • the particulate water-absorbing agent according to the present invention is preferably an aqueous liquid absorbing and solidifying agent containing a polyvalent metal salt and / or a cationic polymer in order to prevent deterioration and improve liquid permeability.
  • a polyvalent metal salt and / or a cationic polymer is used, a coloring problem of the obtained water-absorbing agent is likely to occur, but the present invention does not have such a problem.
  • the particulate water-absorbing agent according to the present invention can exhibit excellent absorption performance, has excellent anti-coloring performance over time, has no odor, and has excellent urine resistance, and is suitable for practical use.
  • the particulate water-absorbing agent can be provided.
  • the water-absorbing resin used in the particulate water-absorbing agent of the present invention optionally contains a graft component and has a structural unit derived from acrylic acid.
  • the water-absorbent resin has a structural unit derived from acrylic acid as a main component.
  • the method for producing the water-absorbing resin is not particularly limited.
  • the water-absorbing resin is obtained by polymerizing a monomer component mainly composed of acrylic acid and / or a salt thereof.
  • the structural unit derived from the monomer corresponds to, for example, a structure in which a polymerizable double bond of each monomer is opened by a polymerization reaction.
  • the structure in which a polymerizable double bond is opened is, for example, a structure in which a carbon-carbon double bond (C ⁇ C) is a single bond (—C—C—).
  • the water-absorbing resin used for the particulate water-absorbing agent is a water-swellable water-insoluble polymer in which a crosslinked structure is introduced into the polymer.
  • water swellability means that the water absorption capacity (CRC) under no pressure with respect to physiological saline is 2 [g / g] or more, preferably 5 to 200 [g / g], more preferably 20 to 100 [g. / G], and “water-insoluble” means that the water-soluble content in the water-absorbent resin is essentially 50% by weight or less, preferably 0 to 25% by weight, more preferably 0 to 15% by weight, More preferably, it means 0 to 10% by weight, which is substantially insoluble in water.
  • CRC water absorption capacity
  • water-soluble component water-soluble component
  • the polyacrylic acid (salt) -based water-absorbing resin means that the total mol% of acrylic acid and / or its salt in the total monomer (excluding the crosslinking agent) used for polymerization is essentially 50 to 100.
  • the mol% more preferably 70 to 100 mol%, still more preferably 90 to 100 mol%, particularly preferably substantially 100 mol%.
  • Polyacrylic acid is not limited to a polymer of acrylic acid, but also includes polyacrylic acid (salt), which is a hydrolyzate of polyacrylonitrile and polyacrylamide. Polyacrylic acid obtained by acid polymerization is preferred.
  • alkali metal salts such as lithium salts, sodium salts and potassium salts; ammonium salts; monovalent salts of acrylic acid such as amine salts are usually used, preferably alkali metals of acrylic acid.
  • a salt is used, and a sodium salt or potassium salt of acrylic acid is more preferable.
  • polyvalent metal salts such as calcium salt and aluminum salt, in the range which has water swelling property.
  • the neutralization rate of the water absorbent resin obtained in the present invention is preferably 10 mol% or more and less than 90 mol%, more preferably 40 mol% or more and less than 80 mol%, based on the acid groups. More preferably, it is at least 50 mol% and less than 74 mol% with respect to the acid group.
  • the neutralization rate is less than 10 mol%, the absorption performance, particularly the water absorption rate may be remarkably lowered, which is not preferable.
  • the neutralization rate is 90 mol% or more, the absorption performance, particularly the water absorption rate under pressure is high. A water absorbing agent may not be obtained, which is not preferable.
  • the neutralization rate is particularly preferably less than 74 mol%, and more preferably less than 72 mol%. That is, also in the method of the present invention, when the neutralization rate is high, the color tends to be colored. Therefore, the upper limit of the neutralization rate is set to the above range.
  • the neutralization step may be performed on the monomer component before polymerization, or may be performed on the hydrogel crosslinked polymer during or after polymerization. Furthermore, neutralization of the monomer component and neutralization of the hydrogel crosslinked polymer may be used in combination. Neutralization is preferably performed with acrylic acid as a monomer component.
  • the water content of the water-absorbing resin obtained in the present invention is within the range described later in the drying step and surface cross-linking step described later, and the particulate water-absorbing agent as the final product.
  • the moisture content is preferably adjusted to 3 to 15% by weight.
  • the particulate water-absorbing agent according to the present invention does not satisfy the requirements (1) and (2), the water content of the particulate water-absorbing agent as the final product is always 3-15. Adjusted to weight percent.
  • the water content is higher than 15% by weight, the obtained water-absorbing agent tends to be colored, and when it is less than 3% by weight, problems of odor and dust may occur.
  • acrylic acid (salt) is used in the above range as a monomer, but other monomers may be used in combination.
  • the amount of monomers other than acrylic acid (salt) used is based on the total amount of acrylic acid (salt) and other monomers used as the main component. It is 0 to 50 mol%, preferably 0 to 30 mol%, more preferably 0 to 10 mol%.
  • Examples of monomers used in combination other than acrylic acid (salt) include monomers exemplified in the following US and European patents. Specifically, examples of the monomer used in combination include water-soluble or hydrophobic unsaturated monomers. Examples of water-soluble or hydrophobic unsaturated monomers include methacrylic acid, (anhydrous) maleic acid, fumaric acid, crotonic acid, itaconic acid, vinyl sulfonic acid, 2- (meth) acrylamido-2-methylpropane sulfone.
  • the particulate water-absorbing agent according to the present invention includes those containing the water-soluble or hydrophobic unsaturated monomer as a copolymerization component.
  • the cross-linking method used in the present invention is not particularly limited.
  • a method in which a cross-linking agent is added during polymerization or post-polymerization to perform post-crosslinking a method of radical cross-linking with a radical polymerization initiator, an electron
  • the method include radiation cross-linking using a wire and the like, and a method in which a predetermined amount of an internal cross-linking agent is added to a monomer in advance to perform polymerization, and a cross-linking reaction is performed simultaneously with or after polymerization is preferable.
  • Examples of the internal crosslinking agent used in the present invention include N, N′-methylenebisacrylamide, (poly) ethylene glycol di (meth) acrylate, (poly) propylene glycol di (meth) acrylate, and (polyoxyethylene) trimethyl.
  • the internal cross-linking agent is preferably 0.005 to 2 mol%, more preferably 0.01 to 1 mol%, and still more preferably 0.05 to 0.2 mol% with respect to the monomer.
  • amount of the internal cross-linking agent used is less than 0.005 mol% or more than 2 mol%, desired absorption characteristics may not be obtained.
  • the concentration of the monomer component in this aqueous solution depends on the type of monomer and the purpose. Although it is appropriately determined depending on physical properties and is not particularly limited, it is preferably 10 to 70% by weight, more preferably 15 to 65% by weight, and still more preferably 30 to 55% by weight from the viewpoint of physical properties.
  • a solvent other than water may be used in combination as necessary, and the type of solvent that can be used in combination is not particularly limited.
  • the monomer concentration may be a slurry exceeding the saturation concentration, but is preferably in the above range, and more preferably less than the saturation concentration.
  • a water-soluble resin eg, starch, cellulose, polyvinyl alcohol
  • a water-absorbent resin or its
  • acrylic acid salt
  • 0 to 50% by weight preferably 0 to 20% by weight
  • various foaming agents carbonates, azo compounds, bubbles, etc.
  • surfactants chelating agents, chain transfer agents, and the like
  • chelating agents e.g., EDTA
  • chain transfer agents e
  • water-soluble resin or water-absorbing resin gives a graft polymer (for example; starch graft polymer or PVA graft polymer), and these are also polyacrylic acid (salt) water-absorbing resin in the present invention.
  • reverse phase suspension polymerization, aqueous solution polymerization, spraying or droplet polymerization can be applied, but from the viewpoint of performance and ease of control of polymerization when polymerizing the monomer aqueous solution, It is preferably carried out by aqueous solution polymerization or reverse phase suspension polymerization.
  • these polymerizations can be carried out in an air atmosphere, it is preferably carried out in an inert gas atmosphere such as nitrogen or argon (for example, 1% by volume or less of oxygen), and the monomer component has no dissolved oxygen. It is preferably used for the polymerization after sufficiently substituted with an active gas (for example, less than 1 [mg / L] oxygen).
  • aqueous solution polymerization in which polymerization control is difficult in order to obtain a highly productive and highly water-absorbing resin.
  • aqueous solution polymerization continuous belt polymerization (US Pat. No. 4,893,999, No. 6,241,928 and US Patent Application Publication No. 2005/215734), continuous or batch kneader polymerization (described in US Pat. No. 6,987,151, No. 6,710,141, etc.).
  • Aqueous polymerization is a method of polymerizing an aqueous monomer solution without using a dispersion solvent.
  • U.S. Pat. Nos. 4,462,001, 4,873,299, 4,286,082, 4,973,632, 4,985,518, No. 5124416, No. 5,250,640, No. 5,264,495, No. 5,145,906, No. 5,380,808, etc. European Patent Nos.
  • Monomers, crosslinking agents, polymerization initiators, and other additives described in these US patents and European patents are also applicable in the present invention.
  • Reverse phase suspension polymerization is a polymerization method in which an aqueous monomer solution is suspended in a hydrophobic organic solvent.
  • the residence time that is, the total time is usually more than 24 hours, but after adjusting the monomer components and / or The longer the time after neutralization of acrylic acid (the above-mentioned total time), the greater the residual monomer and the yellowing phenomenon (coloring with time) of the water absorbent resin. Therefore, in order to shorten the residence time, preferably, batch polymerization or continuous polymerization is performed with continuous neutralization and continuous monomer component adjustment, and more preferably continuous polymerization is performed.
  • the polymerization start temperature of the monomer aqueous solution is 40 ° C. or higher, more preferably 50 ° C. or higher, further 60 ° C. or higher, and particularly 70 ° C. or higher.
  • the production method according to the present invention is applied to the hydrous gel obtained by such high temperature polymerization (high temperature initiation polymerization), the effects of the present invention including particle size control can be maximized.
  • the upper limit is not higher than the boiling point of the aqueous solution, preferably not higher than 105 ° C.
  • high temperature polymerization in which the peak temperature of the polymerization temperature is 95 ° C. or higher, more preferably 100 ° C. or higher, and further preferably 105 ° C. or higher is preferable.
  • the present invention is applied to a hydrogel obtained by such boiling polymerization, the effects of the present invention including particle size control can be maximized.
  • the upper limit of the boiling point is sufficient, preferably 130 ° C. or less, more preferably 120 ° C. or less.
  • the polymerization process is aqueous polymerization in order to further exhibit the effects of the present invention.
  • acrylic acid may be neutralized in advance, or may be neutralized after polymerization, but in order to improve the relative relationship between the opposite water absorption capacity (CRC) and the soluble content,
  • a fragmentation step of the hydrogel polymer is included after the polymerization.
  • the monomer contains acrylic acid as a main component, and includes a neutralization step of the hydrogel crosslinked polymer after polymerization.
  • a crosslinking agent that reacts with a carboxyl group can be used in the same manner as the surface crosslinking agent described later, and a polyglycidyl compound, a polyhydroxy compound, and the like can be suitably used.
  • the polymerization time is not particularly limited, and may be appropriately determined according to the kind of the hydrophilic monomer or polymerization initiator, the reaction temperature, etc., but is usually 0.5 minutes to 3 hours, preferably 1 Min to 1 hour.
  • the polymerization step is preferably performed with methoxyphenols.
  • methoxyphenols especially p-methoxyphenol
  • a monomer aqueous solution containing 90 to 100 mol% of acrylic acid (salt) in a monomer containing 10 to 200 ppm and having a monomer concentration of 30 to 55% by weight is used as a radical polymerization initiator.
  • it is a step in which aqueous solution polymerization or reverse phase suspension polymerization is carried out under the condition that the maximum temperature is 130 ° C.
  • the polymerization time is 0.5 minutes to 3 hours by 0.001 to 1 mol%.
  • persulfates such as potassium persulfate, ammonium persulfate and sodium persulfate, hydroperoxides such as t-butyl hydroperoxide and hydrogen peroxide, 2,2′- Azo compounds such as azobis (2-amidinopropane) dihydrochloride, radical polymerization initiators such as 2-hydroxy-1-phenyl-propan-1-one and benzoin methyl ether, and further decomposition of these radical polymerization initiators
  • a redox initiator or the like that is used in combination with a reducing agent such as L-ascorbic acid that promotes is used.
  • the amount of the polymerization initiator used is usually in the range of 0.001 to 1 mol%, more preferably 0.001 to 0.5 mol%, based on the monomer.
  • a persulfate or peroxide in combination with the reducing agent.
  • the reducing agent include (heavy) sulfites (salts) such as sodium sulfite and sodium bisulfite. , L-ascorbic acid (salt), reducing metals (salts) such as ferrous salts, amines and the like.
  • the amount of these reducing agents used is usually preferably 0.0001 to 0.02 mol% with respect to the monomer component.
  • the polymerization reaction may be carried out by irradiating the reaction system with active energy rays such as radiation, electron beam, and ultraviolet rays.
  • active energy rays such as radiation, electron beam, and ultraviolet rays.
  • methoxyphenols described below particularly p-methoxyphenol
  • a chelating agent are added to the monomer aqueous solution during the polymerization or in the middle of the polymerization to polymerize the effect of the present invention.
  • the polymerization step is preferably aqueous solution polymerization in order to further exert the effects of the present invention.
  • acrylic acid may be neutralized in advance or may be neutralized after polymerization.
  • the hydrogel polymer includes a (1-7) fragmentation step described later.
  • the hydrogel crosslinked polymer obtained by polymerization may be dried as it is, but the hydrogel crosslinked polymer is refined during or after the polymerization. It is preferable. Further, if necessary, it is finely divided using a gel crusher, etc., preferably 0.1 to 3 mm, more preferably 0.5 to 2 mm in weight average particle diameter (specified by sieve classification), and then dried.
  • the shape of the polyacrylic acid (salt) water-absorbing resin of the present invention is not particularly limited, and can be any form such as granules, powders, flakes, fibers, and the like.
  • fine graining is carried out by various methods. For example, from a screw type extruder having a porous structure of an arbitrary shape after the fine graining at the time of polymerization in the kneader polymerization or the polymerization by belt polymerization or tank polymerization.
  • the method of extruding and crushing can be exemplified. In extrusion crushing, it is also possible to further reduce the color change by adding a chelating agent described later in the form of an aqueous solution.
  • an inorganic reducing agent is preferably added at the same time as the hydrated gel-like crosslinked polymer is refined.
  • the effect of the present invention can be achieved at a higher level by mixing and further kneading the hydrogel and the inorganic reducing agent.
  • the water content of the water-absorbing agent of the present invention is 3 to 15% by weight is preferable, and in the method for producing a water-absorbing agent of the present invention, the water content of the polymer is preferably controlled to 3 to 15% by weight after the drying step and in the surface cross-linking step.
  • an inorganic reducing agent furthermore, a chelating agent or an ⁇ -hydroxycarboxylic acid compound described later
  • the inorganic reducing agent is mixed only on the surface of the water absorbent resin.
  • an inorganic reducing agent and, if necessary, a chelating agent and an ⁇ -hydroxycarboxylic acid compound are mixed not only on the surface of the water-absorbent resin particles but also inside. Therefore, it is preferable to knead the inorganic reducing agent and the like at the same time as the fragmentation of the polymer gel (particularly a bulk gel or sheet gel) after aqueous solution polymerization.
  • a kneader or a screw-type extruder is preferably used for fine graining and mixing (especially kneading), and a plurality of them may be used in series, or a kneader and a meat chopper, etc. Different devices may be used in combination.
  • One screw type extruder may be used, or two or more screw extruders may be used.
  • the drying step in the method for producing a particulate water-absorbing agent of the present invention is a water-containing gel obtained by a polymerization step, preferably a particulate water-containing gel, and more preferably a weight average defined by sieving classification.
  • the hydrogel having a particle diameter of 0.1 to 3 mm is dried.
  • Drying methods include heat drying, hot air drying, vacuum drying, fluidized bed drying, infrared drying, microwave drying, drum dryer drying, azeotropic dehydration with hydrophobic organic solvents, high humidity drying using high temperature steam, etc.
  • One type or two or more types of various methods can be employed.
  • contact drying with a gas having a dew point of 40 to 100 ° C., more preferably a dew point of 50 to 90 ° C. can be exemplified.
  • the wind speed (the speed of the wind passing perpendicularly to the drying object spreading horizontally) is preferably 0.01 to 10 [m / sec], more preferably 0.1 to 5 [m / sec]. m / sec].
  • the drying temperature suitably used in the present invention is not particularly limited, but is, for example, in the range of 50 to 300 ° C. (preferably carried out under reduced pressure when 100 ° C. or lower), preferably 100 to 250 ° C., more preferably The temperature range is 130 to 220 ° C, particularly preferably 150 to 200 ° C.
  • the drying time is usually 10 to 120 minutes, more preferably 20 to 90 minutes, still more preferably 30 to 60 minutes. If the drying time is less than 10 minutes, the change that occurs in the polymer chain inside the water-absorbent resin is small, so that it is considered that a sufficient improvement effect cannot be obtained, and therefore the improvement effect of various physical properties may not be seen. On the other hand, if the drying time is 120 minutes or longer, the water-absorbent resin is damaged, resulting in an increase in water-soluble content and no improvement in physical properties.
  • the drying step is preferably performed in such a way that the particulate water-containing gel has a water content of 20% by weight at a drying temperature of 100 to 250 ° C. and a drying time of 10 to 120 minutes. It is preferable to be a step of performing the following drying, and further, the drying temperature, the drying time, and the moisture content within the above or the following ranges.
  • the water content of the water-containing gel-like crosslinked polymer obtained by the above polymerization is preferably dried to 20% by weight or less, more preferably 15% by weight or less, and more preferably 10%. It is particularly preferred to dry to weight percent or less.
  • the moisture content after drying is preferably 2% by weight or more, 3% by weight or more, 4% by weight or more, 5% by weight or more, 6% by weight or more, and 7% by weight or more in order. By setting it as more than such a lower limit, the problem of the odor by using a reducing agent can be suppressed.
  • the water content is preferably 2 to 20% by weight, more preferably 3 to 15% by weight, still more preferably 5 to 15% by weight, and particularly preferably 7 to 15% by weight.
  • the (1-8) drying step and the (1-10) surface cross-linking step described later may be carried out simultaneously, and a surface cross-linking agent is added during the drying step to further simultaneously with or after the surface cross-linking. You may dry up to rate.
  • the moisture content of the final water-absorbing agent after the drying step is likely to remain when the moisture content is high, and not only the subsequent handleability is poor, but also a chelating agent and an inorganic reducing agent may be used in combination. It was found that when the water content was high, it was easy to color. In addition, when the moisture content is low, productivity and physical properties (for example, water absorption rate) may be reduced due to excessive drying, or a problem of odor may occur when a reducing agent is used before drying.
  • Patent Document 17 European Patent No. 1645596
  • Patent Document 15 US Patent Application Publication No. 2005/0856504
  • This odor is not a simple decomposition of the reducing agent, but rather a complex odor of trace components such as water-containing gel after polymerization and residual monomers and the reducing agent, and is caused by keeping the water content of the water-absorbing resin below a certain level.
  • the water content in the drying step and the surface cross-linking step described later is extremely important.
  • productivity may be reduced in the pulverization and classification described below, which is not preferable.
  • Pulverization Step / Classification Step The water-absorbent resin of the present invention obtained by drying may be subjected to steps such as pulverization and classification for particle size control as required according to the purpose. These methods are described in, for example, International Publication No. 2004/69915.
  • a dried polymer can be obtained by drying the hydrogel crosslinked polymer after polymerization.
  • the dry polymer may be used as it is as a dry powder (preferably with a solid content of 80% by weight or more), and the particle size may be adjusted after drying if necessary.
  • the water-absorbent resin after drying is preferably made to have a specific particle size in order to improve physical properties by surface cross-linking described later.
  • the particle size can be appropriately adjusted by polymerization, pulverization, classification, granulation, fine powder recovery and the like.
  • the weight average particle diameter (D50) of the water-absorbent resin before surface cross-linking is 200 to 550 ⁇ m, preferably 250 to 500 ⁇ m, more preferably 300 to 450 ⁇ m, especially Preferably, it is adjusted to 350 to 400 ⁇ m. Also, the fewer the particles less than 150 ⁇ m, the better.
  • the weight ratio of particles having a particle diameter of less than 150 ⁇ m to the weight of the whole dry polymer is usually adjusted to 0 to 5% by weight, preferably 0 to 3% by weight, particularly preferably 0 to 1% by weight. Furthermore, the smaller the particles of 850 ⁇ m or more, the better.
  • the weight ratio of particles having a particle size of 850 ⁇ m or more with respect to the total weight of the dry polymer is usually adjusted to 0 to 5% by weight, preferably 0 to 3% by weight, particularly preferably 0 to 1% by weight.
  • the logarithmic standard deviation ( ⁇ ) of the particle size distribution is preferably 0.20 to 0.45, preferably 0.27 to 0.40, and preferably 0.25 to 0.37.
  • Such a particle size is preferably applied also to the water-absorbing resin after surface cross-linking and the water-absorbing agent of the final product. Therefore, preferably, a classification step and a crushing step are applied as necessary after the surface cross-linking step and after the addition of the chelating agent / inorganic reducing agent.
  • the particulate water-absorbing agent obtained in the present invention can be made a water-absorbing agent more suitable for hygiene materials through a conventionally known surface cross-linking treatment step.
  • Surface cross-linking means that a portion having a higher cross-linking density is provided in the surface layer of the water-absorbent resin (near the surface: usually around several tens of ⁇ m from the surface of the water-absorbent resin). It can be formed by a crosslinking reaction or the like.
  • Examples of the surface cross-linking agent that can be used in the present invention include a surface cross-linking agent (preferably a covalent cross-linking surface cross-linking agent) that is ion-bonding or covalent-bonding with a functional group of a polyacrylic acid-based water absorbent resin,
  • the organic or inorganic crosslinking agent can be exemplified, but a crosslinking agent capable of reacting with a carboxyl group can be preferably used from the viewpoint of physical properties and handleability.
  • polyhydric alcohol compounds polyvalent epoxy compounds represented by polyvalent glycidyl compounds, polyvalent amine compounds or condensates thereof with haloepoxy compounds, oxazoline compounds, mono-, di- or polyoxazolidinone compounds, polyvalent metal salts,
  • polyhydric alcohol compounds polyvalent epoxy compounds represented by polyvalent glycidyl compounds, polyvalent amine compounds or condensates thereof with haloepoxy compounds, oxazoline compounds, mono-, di- or polyoxazolidinone compounds, polyvalent metal salts,
  • One type or two or more types such as an alkylene carbonate compound, an oxetane compound, and a cyclic urea compound can be exemplified.
  • compounds exemplified in U.S. Pat. Nos. 6,228,930, 6071976, and 6254990 can be exemplified.
  • mono, di, tri, tetra or polyethylene glycol monopropylene glycol, 1,3-propanediol, dipropylene glycol, 2,3,4-trimethyl-1,3-pentanediol, polypropylene glycol, glycerin, polyglycerin , 2-butene-1,4-diol, 1,4-butanediol, 1,3-butanediol, 1,5-pentanediol, 1,6-hexanediol, 1,2-cyclohexanedimethanol, etc.
  • Alcohol compounds such as ethylene glycol diglycidyl ether and glycidol; polyvalent amines such as ethylenediamine, diethylenetriamine, triethylenetetramine, tetraethylenepentamine, pentaethylenehexamine, polyethyleneimine, and polyamidepolyamine Haloepoxy compounds such as epichlorohydrin, epibromohydrin, ⁇ -methylepichlorohydrin; condensates of the above polyvalent amine compounds and haloepoxy compounds; oxazolidinone compounds such as 2-oxazolidinone; ethylene carbonate Examples thereof include, but are not particularly limited to, alkylene carbonate compounds such as: oxetane compounds; cyclic urea compounds such as 2-imidazolidinone.
  • a dehydration-reactive cross-linking agent selected from a polyhydric alcohol compound, an oxazolidinone compound, and an alkylene carbonate compound is preferably used as the surface cross-linking agent.
  • a polyvalent epoxy compound typified by a polyvalent glycidyl compound is preferably used as the surface cross-linking agent in order to control the water content 3 to 15% by weight described later after the surface cross-linking.
  • the amount of the surface cross-linking agent used is preferably in the range of 0.001 to 10 parts by weight with respect to 100 parts by weight of the water-absorbent resin powder, although it depends on the compounds used and combinations thereof. More preferably within the range of 5 to 5 parts by weight.
  • water can be used in accordance with the surface cross-linking agent.
  • the amount of water used is preferably in the range of 0.5 to 20 parts by weight, more preferably 0.5 to 10 parts by weight with respect to 100 parts by weight of the water absorbent resin powder.
  • a hydrophilic organic solvent can be used in addition to water.
  • the amount of the hydrophilic organic solvent used is 0 to 10 parts by weight, preferably 0 to 5 parts by weight, with respect to 100 parts by weight of the water-absorbent resin powder. Further, when mixing the crosslinking agent solution into the water-absorbent resin powder, the amount is within a range not hindering the effect of the present invention, for example, 0 to 10% by weight or less, preferably 0 to 5% by weight, more preferably 0 to 1% by weight. Water-insoluble inorganic fine particles and surfactants may coexist. Surfactants used and the amounts used are exemplified in US Pat. No. 7,473,739.
  • a high-speed stirring type mixer particularly a high-speed stirring type continuous mixer is preferable.
  • a trade name turbulizer Mobulizer by Hosokawa Micron Co., Ltd. in Japan
  • the brand name Redige Mixer made by Redige, Germany.
  • the surface treatment in the method for producing a particulate water-absorbing agent of the present invention is a step of performing a surface cross-linking reaction for increasing the cross-linking density of the water-absorbent resin surface.
  • the water-absorbent resin after mixing the surface cross-linking agent is preferably subjected to a heat treatment, and if necessary, a cooling treatment is thereafter performed.
  • the heating temperature (heating medium temperature) of the heat treatment is, for example, 70 to 300 ° C., preferably 120 to 250 ° C., more preferably 150 to 250 ° C., and the heating time is preferably in the range of 1 minute to 2 hours. It is.
  • the heat treatment can be performed using a normal dryer or a heating furnace.
  • a dehydration reactive surface agent such as a high-temperature surface cross-link such as 150 to 250 ° C. or a polyhydric alcohol
  • the water-absorbing resin is further dried and the water content after surface cross-linking The rate tends to be less than 3%, particularly less than 1%.
  • the heating temperature is preferably performed in the temperature range of 80 to 250 ° C., more preferably A temperature range of 80 to 160 ° C., more preferably a temperature range of 80 to 120 ° C., and most preferably a temperature range of 80 to 100 ° C.
  • the heating time is less than 80 ° C., the surface cross-linking of the water-absorbent resin is not sufficient, and the water absorption magnification and saline flow induction rate under pressure are lowered.
  • a polyvalent epoxy compound typified by a polyvalent glycidyl compound is preferably used as a surface crosslinking agent.
  • a polyvalent epoxy compound typified by a polyvalent glycidyl compound is preferably used as a surface crosslinking agent.
  • the temperature is higher than 250 ° C., it is not preferable because the particulate water-absorbing agent is colored or an unpleasant odor is generated.
  • the water content of the water-absorbent resin is not only determined by the heating temperature, but also depends on the heating time, the pressure (decompression) of the reactor, the dew point, and the production amount (processing amount per unit time). What is necessary is just to set suitably, and since the material temperature of water-absorbing resin is generally lower than heating temperature, it is also preferable to obtain the water-absorbing agent with a predetermined water content by heating the material temperature below the boiling point of water.
  • a water-soluble polyvalent metal salt such as an aluminum sulfate aqueous solution may be added after the crosslinking reaction.
  • the surface cross-linking step is preferably performed by mixing 0.001 to 10 parts by weight of the surface cross-linking agent with respect to 100 parts by weight of the water absorbent resin powder after the drying step. It is carried out by heat treatment at ⁇ 300 ° C. for 1 minute to 2 hours, and further includes the above or the following surface cross-linking agent and its amount, heating temperature and time.
  • a polyvalent metal and / or a cationic polymer described later may be added simultaneously with the surface crosslinking or after the surface crosslinking.
  • These polyvalent metals and / or cationic polymers can also act as an ion-bonding surface cross-linking agent, and the liquid permeability can be further improved by the combined use with the above-mentioned covalent-bonding surface cross-linking agent.
  • the water content of the water-absorbent resin after surface crosslinking is 3% by weight or more, 4% by weight or more, 5% by weight or more, 6% It is preferable in the order of not less than 7% by weight and not less than 7% by weight, and by setting the moisture content of the surface crosslinking within such a range, the odor due to the use of the reducing agent, especially the inorganic reducing agent during or before the surface crosslinking step can be reduced.
  • the odor of the obtained water absorbing agent at the time of addition can be suppressed, and as a result, the odor of the water absorbing agent finally obtained can be further suppressed.
  • the water content at the time of surface cross-linking is less than 3% by weight, for example, high-temperature surface cross-linking at a heat medium temperature or a material temperature of 150 to 250 ° C. or surface cross-linking with a dehydration-reactive surface cross-linking agent. It is more preferable from the viewpoint of odor to add an inorganic reducing agent after the crosslinking step.
  • This odor is not a simple decomposition of the reducing agent, but a complex odor of a trace amount component such as the water-absorbing resin or its residual monomer and the reducing agent, and is caused by keeping the water content of the water-absorbing resin below a certain level.
  • the water content in the drying step and the surface cross-linking step is extremely important.
  • the water content of the water-absorbing resin after surface crosslinking is preferably within the above range.
  • a particulate water-absorbing agent having a water content of 3 to 15% by weight it is preferable to carry out surface crosslinking while maintaining the water content of the water-absorbing resin at 3 to 15% by weight. More preferably, surface cross-linking is carried out while maintaining at 5% by weight, and still more preferably surface cross-linking is carried out while maintaining at 5 to 13% by weight, with the state maintained at 6 to 12% by weight and 7 to 11% by weight. Most preferably, surface cross-linking is performed. If the water content is not less than the above range, it is possible to avoid a significant decrease in the absorption capacity of the water absorbent resin. If the water content is not more than the above range (15% by weight), the coloring is further improved, and the deterioration of the handleability of the water-absorbent resin and the decrease in the fluidity of the powder can be suppressed.
  • Further drying may be performed after the surface cross-linking as necessary, and water content and other physical properties may be adjusted by adding water and other additives.
  • the reducing agent and chelating agent that are essentially added in the present invention may be added after the surface crosslinking, and the water-insoluble inorganic fine particles that are preferably added may be added. May be added 0.001 to 20 parts by weight, more preferably 0.01 to 10 parts by weight, particularly preferably 0.1 to 5 parts by weight of an antibacterial agent, deodorant, polyvalent metal compound, and the like. Good.
  • a granulation step a fine powder removal step, a moisture content adjustment step (for example, Example 1-16 of the present application), a fine powder recycling step, and the like may be provided.
  • a step of adding a chelating agent and an inorganic reducing agent may be provided after the (1-10) surface crosslinking step.
  • various mixers used in the above (1-10) surface cross-linking step and the following [8] granulation can be appropriately used.
  • the particulate water-absorbing agent of the present invention is a particulate water-absorbing agent mainly composed of a polyacrylic acid (salt) -based water-absorbing resin, including a chelating agent and an inorganic reducing agent, and the content of the chelating agent is 0.001 to 0.5% by weight, and the following (1) to (3) (1)
  • the content of methoxyphenols is 5 to 60 ppm.
  • the water content is 3 to 15% by weight. It is characterized by satisfying any one or more of the requirements.
  • the particulate water-absorbing agent of the present invention essentially contains a chelating agent in order to solve the problem.
  • a chelating agent of the present invention a polymer compound or a non-polymer compound, particularly a non-polymer compound is preferable from the viewpoint of effects, and specifically, an amino polyvalent carboxylic acid, an organic polyvalent phosphoric acid, an inorganic polyvalent phosphoric acid. A compound selected from aminopolyphosphoric acid is preferred.
  • the chelating agent preferably has a molecular weight of 100 to 5,000, more preferably 200 to 1,000. When there is no chelating agent, the water absorbing agent is inferior in terms of coloring and deterioration.
  • polyvalent has a plurality of the functional groups in one molecule, preferably 2 to 30, more preferably 3 to 20, and 4 to 10 functional groups.
  • chelating agents are preferably water-soluble chelating agents, specifically, water-soluble chelating agents that dissolve in 1 g or more, more preferably 10 g or more, in 100 g (25 ° C.) of water.
  • amino polycarboxylic acid examples include iminodiacetic acid, hydroxyethyliminodiacetic acid, nitrilotriacetic acid, nitrilotripropionic acid, ethylenediaminetetraacetic acid, diethylenetriaminepentaacetic acid, triethylenetetraminehexaacetic acid, trans-1,2-diaminocyclohexane.
  • organic polyvalent phosphoric acid examples include nitriloacetic acid-di (methylenephosphinic acid), nitriloacetic acid- (methylenephosphinic acid), nitriloacetic acid- ⁇ -propionic acid-methylenephosphonic acid, nitrilotris (methylenephosphonic acid), 1-hydroxy Examples thereof include ethylidene diphosphonic acid, and examples of the inorganic polyvalent phosphoric acid include pyrophosphoric acid, tripolyphosphoric acid and salts thereof.
  • the amino polyvalent phosphoric acid includes ethylenediamine-N, N′-di (methylenephosphinic acid), ethylenediaminetetra (methylenephosphinic acid), cyclohexanediaminetetra (methylenephosphonic acid), ethylenediamine-N, N′-diacetic acid.
  • the most preferred amino polyvalent phosphoric acid in the present invention includes ethylenediaminetetra (methylenephosphonic acid) or a salt thereof.
  • the salt include monovalent salts, particularly alkali metal salts such as sodium salt and potassium salt, ammonium salts, and amine salts.
  • alkali metal salts such as sodium salt and potassium salt, ammonium salts, and amine salts.
  • a sodium salt and potassium salt are especially preferable.
  • aminocarboxylic acid metal chelating agents amino polyvalent phosphoric acid metal chelating agents, and salts thereof are preferably used from the viewpoint of preventing coloring.
  • diethylenetriaminepentaacetic acid triethylenetetraminehexaacetic acid, trans-1,2-diaminocyclohexanetetraacetic acid, ethylenediaminetetra (methylenephosphinic acid), diethylenetriaminepenta (methylenephosphonic acid) and salts thereof are more preferably used.
  • ethylenediaminetetra (methylenephosphonic acid) or a salt thereof is most preferable, and the salt is preferably a monovalent salt, and examples thereof include alkali metal salts such as sodium salts and potassium salts, ammonium salts, and amine salts. . Of these salts, sodium salts and potassium salts are particularly preferred.
  • the content of the chelating agent in the particulate water-absorbing agent of the present invention is 0.001 to 0.5% by weight, preferably 0.001 to 0.1% by weight, more preferably 0.002 to 0.1% by weight. Preferably, 0.003 to 0.05% by weight is more preferable, and 0.005 to 0.05% by weight is particularly preferable.
  • the content of the chelating agent is less than 0.001% by weight, coloration with time of the particulate water-absorbing agent becomes severe, and color tone with time of the particulate water-absorbing agent deteriorates, which is not preferable.
  • the coloration with time refers to the coloration of the particulate water-absorbing agent when stored for a long period of time at high temperature and high humidity
  • the initial coloring refers to the color tone or coloring of the particulate water-absorbing agent as obtained at the time of manufacture. Say degree.
  • Such chelating agents include the above (1-6) polymerization step, (1-7) gel granulation step, (1-8) drying step, (1-9) pulverization step / classification step, (1-10) surface It can be added to any one or more of the crosslinking step, (1-11) and other steps.
  • a chelating agent may be added at the time of monomer preparation before the polymerization step.
  • a chelating agent may be added.
  • the amount used in each production step such as (1-6) to (1-11) is substantially the content in the obtained water-absorbing agent, but the chelating agent in the water-absorbing agent contains residual monomers and water.
  • the chelating agent can be extracted from the water-absorbing agent with water or physiological saline, and can be appropriately determined by liquid chromatography, ion chromatography, or the like.
  • Patent Document 29 (WO 2006/109882 pamphlet) describes a coloring prevention method using ammonium acrylate as a monomer, and a coloring prevention method in which a compound containing a phosphorus atom or a sulfur-based reducing agent is added a plurality of times.
  • Patent Document 29 discloses not only the specific water content (3 to 15% by weight) of the present invention but also a specific addition amount (0.001 to 0.5% by weight) of a compound containing a phosphorus atom or a sulfur-based reducing agent. And preferably 0.001 to 0.1% by weight).
  • 1-hydroxyethylidene-1,1-diphosphonic acid was added in an amount of 1.0% by weight.
  • the particulate water-absorbing agent according to the present invention essentially contains an inorganic reducing agent, preferably a water-soluble inorganic compound having a reducing inorganic element or a water-soluble compound having a reducing inorganic element as the inorganic reducing agent.
  • an inorganic reducing agent preferably a water-soluble inorganic compound having a reducing inorganic element or a water-soluble compound having a reducing inorganic element as the inorganic reducing agent.
  • the “water-soluble” means that 1 g or more, further 5 g or more, particularly 10 g or more is dissolved in 100 g of water at 25 ° C. When there is no chelating agent, it becomes a water-absorbing agent inferior in terms of residual monomer, coloring and deterioration.
  • the inorganic reducing agent in the present invention is used separately from the reducing agent as the polymerization initiator used in the polymerization step. That is, the inorganic reducing agent refers to a compound having a reducing property, as long as it has a reducing inorganic element, and specifically includes a compound having a reducing sulfur atom or a reducing phosphorus atom. And preferably a compound containing a reducing sulfur atom or a water-soluble compound containing a reducing phosphorus atom. Therefore, even if it is an inorganic compound or an organic compound, if it has a reducing sulfur atom or a reducing phosphorus atom, it is regarded as the inorganic reducing agent of the present invention.
  • the inorganic reducing agent may be in the acid form, but is preferably in the salt form, and the salt is more preferably a monovalent or polyvalent metal salt, and more preferably a monovalent salt.
  • oxygen-containing reducing inorganic compounds exemplified below, that is, inorganic reducing agents in which sulfur or phosphorus is combined with oxygen, among which oxygen-containing reducing inorganic salts are preferable.
  • These inorganic reducing agents may be inorganic reducing agents having a reducing inorganic atom, preferably a reducing sulfur atom or phosphorus atom, in an organic compound such as an alkyl group or a hydroxyalkyl group.
  • the inorganic reducing agent having a reducing sulfur atom or a reducing phosphorus atom used in the present invention the most stable oxidation number of the sulfur atom is +6 (positive hexavalent), and the oxidation of the phosphorus atom.
  • the number is +5 (positive pentavalent), but in general, each atom having an oxidation number of less than that has reducibility, and a + 4-valent sulfur compound (for example, sulfite, bisulfite, pyrosulfite), + Trivalent sulfur compounds (eg dithionite), +2 valent sulfur compounds (eg sulfoxylate), +4 valent phosphorus compounds (eg hypophosphates), +3 valent phosphorus compounds (eg suboxides) Phosphates, pyrophosphites), +1 valent phosphorus compounds (eg hypophosphites) are used.
  • the reducing sulfur atom or the reducing phosphorus atom may be substituted with an organic substance.
  • the inorganic reducing agent-containing inorganic compound that is an inorganic reducing agent is not particularly limited.
  • sulfites such as sodium sulfite, potassium sulfite, calcium sulfite, zinc sulfite, and ammonium sulfite
  • sodium bisulfite, potassium bisulfite, sulfite Bisulfites such as calcium hydrogen and ammonium bisulfite
  • pyrosulfites such as sodium pyrosulfite, potassium pyrosulfite and ammonium pyrosulfite
  • sodium dithionite, potassium dithionite, ammonium dithionite, dithione Dithionites such as calcium oxide and zinc dithionite
  • Trithionates such as potassium trithionate and sodium trithionate
  • Tethionates such as potassium tetrathionate and sodium tetrathionate
  • sulfite, bisulfite, pyrosulfite, and dithionite are preferable, and sodium sulfite, sodium bisulfite, potassium pyrosulfite, and sodium dithionite are more preferable.
  • the water-soluble organic compound containing a sulfur atom which is an inorganic reducing agent, is not particularly limited.
  • 2-hydroxy-2-sulfinate acetic acid sodium formaldehyde sulfoxylate, formamidine sulfinic acid and thioglycolic acid tris 2-carboxyethyl) phosphine hydrochloride (TCEP), tributylphosphine (TBP), etc., among which 2-hydroxy-2-sulfinate acetic acid, 2-hydroxy-2-sulfonatoacetic acid, and / or their salts
  • TCEP 2-carboxyethyl) phosphine hydrochloride
  • TBP tributylphosphine
  • 2-hydroxy-2-sulfinate acetic acid, 2-hydroxy-2-sulfonatoacetic acid, and / or their salts Preferably exemplified.
  • Preferred salts are alkali metal and alkaline earth metal salts, with Li, Na and K being preferred, and sodium salt being particularly preferred.
  • 2-Hydroxy-2-sulfinate acetic acid (salt) may be used in combination with 2-hydroxy-2-sulfonatoacetic acid (salt), and may further be used in combination with the aforementioned inorganic compound.
  • 2-hydroxy-2-sulfinate acetic acid is an inorganic reducing agent of the present invention because it has a reducing sulfur atom as a sulfinate group, and BRUGGOLITE commercially available from Brueggemann Chemical (Heilbron, Germany).
  • BRUGGOLITE commercially available from Brueggemann Chemical (Heilbron, Germany).
  • R Available as FF7, 50-60 wt% 2-hydroxy-2-sulfinate acetic acid disodium salt, 30-35 wt% sodium sulfite (Na 2 SO 3 ) and 2-hydroxy-2- It can be obtained as BRUGGOLITE® FF6 containing 10-15% by weight of sulfonatoacetic acid disodium salt.
  • the inorganic reducing agent contained in the particulate water-absorbing agent of the present invention is preferably 0.01 to 1.0% by weight, more preferably 0.05 to 1.0% by weight, and 0.05 to 0.5% by weight. Particularly preferred. If content of the said inorganic reducing agent is 0.01 weight% or more, the coloring with time of a particulate water absorbing agent can be suppressed. Moreover, if content of the said inorganic reducing agent is 1.0 weight% or less, the odor of a particulate water absorbing agent can be suppressed, especially the odor after a particulate water absorbing agent absorbs an aqueous liquid is effective. Can be suppressed.
  • the inorganic reducing agent is the above (1-6) polymerization step, (1-7) gel granulation step, (1-8) drying step, (1-9) pulverization step / classification step, (1-10) It can be added to any one or more of the surface cross-linking step, (1-11) and other steps (addition step after surface cross-linking, etc.).
  • (1-6) In the polymerization step it may be added at the start of polymerization. Since the reducing agent is consumed, it is preferably added during the polymerization, further after the polymerization step, and may be added including the amount of the reducing agent consumed in the production step, particularly the step or the drying step.
  • the amount of the inorganic reducing agent in the resulting water-absorbing agent is the content in the water-absorbing agent obtained substantially after the drying step, particularly if the inorganic reducing agent after surface crosslinking is added.
  • the chelating agent in the inorganic water-absorbing agent added before the drying step is extracted from the water-absorbing agent with water or physiological saline as in the determination of residual monomers and water-soluble components, and liquid chromatography or ion chromatography. It can be quantified as appropriate.
  • the amount used in each production step such as (1-6) to (1-11) is substantially in the obtained water-absorbing agent, but the chelating agent in the water-absorbing agent is the residual monomer or water-soluble component.
  • the chelating agent can be extracted from the water-absorbing agent with water or physiological saline, and quantified appropriately by liquid chromatography, ion chromatography, or the like.
  • the inorganic reducing agent of the present invention is preferably added after the surface crosslinking treatment step from the viewpoint of odor.
  • the resulting particulate water-absorbing agent May have an unpleasant odor, which is not preferable.
  • the obtained particulate water-absorbing agent absorbs an aqueous liquid and generates an unpleasant odor.
  • Such odors are not limited to simple odors of inorganic reducing agents, but are presumed to be by-products in the surface cross-linking process, particularly in the surface cross-linking process aiming at high SFC and high AAP.
  • the manufacturing method of the water-absorbing agent of the present invention is the manufacturing method No. 3 of the subordinate concept in which (c) is essential, and the manufacturing method of the particulate water-absorbing agent of the present invention (No. 3) is acrylic acid (salt).
  • the main component is a polyacrylic acid (salt) water-absorbing resin, which includes a polymerization step of an aqueous monomer solution mainly containing water, a drying step of a hydrogel crosslinked polymer obtained by polymerization, and a surface crosslinking step And a step of adding 0.001 to 0.5% by weight of a chelating agent and a step of adding an inorganic reducing agent, wherein the monomer is a methoxyphenol compound with respect to acrylic acid.
  • the water content of the polymer is controlled to 3 to 15% by weight after the drying step and in the surface cross-linking step, more preferably, the inorganic reducing agent is added to the water-containing gel before drying.
  • Particulate water absorption added to the cross-linked polymer A method for producing (third manufacturing method).
  • Methoxyphenols When the particulate water-absorbing agent of the present invention does not satisfy the requirements (2) and (3), it contains 5 to 60 ppm of methoxyphenols. Even if it satisfies the requirement of either (3), it preferably contains methoxyphenols, and more preferably contains 5 to 60 ppm of methoxyphenols.
  • methoxyphenols include o, m, p-methoxyphenol and methoxyphenols having one or more substituents such as a methyl group, a t-butyl group, and a hydroxyl group.
  • p-methoxyphenol is used in the present invention, particularly in the (1-6) polymerization step.
  • p-methoxyphenol is contained in acrylic acid which is a main monomer component constituting the polyacrylic acid (salt) water-absorbing resin of the present invention.
  • the content of methoxyphenols (particularly p-methoxyphenol) in the particulate water-absorbing agent of the present invention is more preferably 5 to 50 ppm, further preferably 6 to 50 ppm, particularly preferably 7 to 40 ppm, and most preferably 8 to 30 ppm. .
  • the content of methoxyphenols (10 to 200 ppm) is further controlled within the range described in the section of (10-1) acrylic acid, which will be described later. Since the gel stability at the time of use of property etc. increases further, it is preferable.
  • the content of the methoxyphenol is less than 5 ppm, that is, when p-methoxyphenol, which is a polymerization inhibitor, is removed by purification such as distillation, there is only a risk that polymerization will occur before intentionally starting the polymerization.
  • the weather resistance of the particulate water-absorbing agent of the present invention obtained using acrylic acid (salt) as a main raw material is not preferable.
  • the content of the methoxyphenol exceeds 60 ppm, it is not preferable because problems such as a polymerization reaction such as polymerization delay cannot be controlled, and the particulate water-absorbing agent of the present invention is colored, which is not preferable.
  • the methoxyphenols (5 to 60 ppm) in the particulate water-absorbing agent of the present invention are obtained by polymerizing an aqueous monomer solution mainly containing acrylic acid (salt) containing 10 to 200 ppm of methoxyphenols (the above concentration, Temperature, polymerization initiator, etc.) and then adjusting the water-containing gel-like cross-linked polymer obtained by polymerization through the above-mentioned preferable range of conditions (the above temperature, time, wind speed, solid content, etc.). can do.
  • p-methoxyphenol is generally used in an amount of 200 ppm as a polymerization inhibitor for acrylic acid, and acrylic acid (boiling point 143 ° C.) is purified by distillation during polymerization of a water-absorbing resin (for example, US Pat. No. 6,388,000). And the treatment of acrylates with activated carbon (Patent Document 7), p-methoxyphenol is substantially removed from acrylic acid by such distillation purification, and thus the p-methoxyphenol of the present invention is used. It cannot be.
  • Patent Document 17 discloses a water-absorbing resin composition containing an oxygen-containing reducing inorganic salt, an aminocarboxylic acid chelating agent, and an organic antioxidant, and provides an organic antioxidant.
  • an agent alkylhydroxyanisole is disclosed (used in claim 7 of Patent Literature 17, 1% by weight in Example 6).
  • alkylhydroxyanisole does not exhibit a sufficient effect as compared with p-methoxyphenol.
  • Patent Document 15 discloses the polymerization of a water-absorbing resin at 10 to 160 ppm of p-methosphenol.
  • Patent Documents 10 and 11 which disclose p-methosylphenol, the combined use of the present chelating agent and reducing agent and the preferred final water content The rate is not disclosed.
  • Non-Patent Document 1 The Modern Superpolymer Polymer Technology; 1998), the remaining p-methiphenol (MEHQ) in the water-absorbent resin from eight production locations A to H is described.
  • MEHQ p-methiphenol
  • Non-Patent Document 1 also does not disclose the use of a chelating agent and an inorganic reducing agent in the specific MEHQ (5 to 60 ppm) of the present invention.
  • the particulate water-absorbing agent of the present invention contains water-insoluble inorganic fine particles when the requirements (1) and (3) are not satisfied. Even in the case of satisfying any of the requirements of 3), it is preferable to contain water-insoluble inorganic fine particles, particularly white water-insoluble inorganic fine particles, from the viewpoint of improving liquid permeability (SFC) and fluidity at the time of moisture absorption. .
  • SFC liquid permeability
  • Patent documents 15 to 17 do not disclose the combined use of a trace amount of p-methoxyphenol and white water-insoluble inorganic fine particles.
  • the whiteness of the water-insoluble inorganic fine particles is in the range of 70 or more, within ⁇ 5, or ⁇ 10 in terms of L, a, and b, preferably 80 or more, within ⁇ 3, or within ⁇ 7, preferably 90.
  • insoluble inorganic fine particles that are within ⁇ 2 and within ⁇ 5 and are whiter than the water-absorbent resin before mixing preferably, L is 5 or more, and 7 or more
  • water-insoluble inorganic fine particles are preferably used in combination in order to solve the problems of the present invention.
  • the water-insoluble inorganic fine particles are fine particles having an average particle size measured by a Coulter counter method of preferably 0.001 to 200 ⁇ m, more preferably 0.005 to 50 ⁇ m, and still more preferably 0.01 to 10 ⁇ m.
  • it is a hydrophilic fine particle, for example, a metal oxide such as silica (silicon dioxide) or titanium oxide, a composite hydrous oxide containing zinc and silicon, or zinc and aluminum (for example, WO 2005/010102).
  • Silicic acid such as natural zeolite and synthetic zeolite, kaolin, talc, clay, bentonite, calcium phosphate, barium phosphate, silicic acid or its salt, clay, diatomaceous earth, silica gel, zeolite, bentonite, hydroxyapatite, hydro Talsite, vermiculite, perlite, iso Ito, activated clay, silica sand, quartzite, strontium ore, fluorite, bauxite, and the like. Of these, silicon dioxide and silicic acid (salt) are more preferred, and silicon dioxide and silicic acid (salt) are even more preferred.
  • the silicon dioxide is not particularly limited, but is preferably amorphous fumed silica produced by a dry method. Silicon dioxide or the like called quartz is not preferable because it may cause health problems.
  • the water-insoluble inorganic fine particles contained in the particulate water-absorbing agent of the present invention are preferably in the range of 0.05 to 1.0% by weight, more preferably 0.05 to 0.8% by weight, still more preferably 0.05 to It is 0.7% by weight, particularly preferably in the range of 0.1 to 0.5% by weight.
  • the content of the water-insoluble inorganic fine particles is 0.05% by weight or more, deterioration of the urine resistance of the particulate water-absorbing agent can be suppressed.
  • the content of the water-insoluble inorganic fine particles is 1.0% by weight or less, it is possible to suppress a decrease in the water absorption capacity under pressure of the particulate water-absorbing agent.
  • the water-absorbing resin of [1] above includes the following [6] ⁇ -hydroxycarboxylic acid compound, [7] polyvalent metal salt and / or cationic property It is also preferable to contain a polymer, and [8] may be granulated.
  • the particulate water-absorbing agent of the present invention has the above-described reducing sulfur compound (for example, 2-hydroxy-) from the viewpoint of further prevention of coloring and deterioration (weather resistance, urine resistance) and the like.
  • reducing sulfur compound for example, 2-hydroxy-
  • an ⁇ -hydroxycarboxylic acid compound is preferably included, and a non-reducing ⁇ -hydroxycarboxylic acid compound is more preferable.
  • the non-reducing ⁇ -hydroxycarboxylic acid compound refers to a hydroxycarboxylic acid compound having no reducing inorganic element (for example, reducing sulfur, sulfinate group, etc.).
  • the ⁇ -hydroxycarboxylic acid compound that can be used in the present invention is a carboxylic acid having a hydroxyl group in the molecule or a salt thereof, and is a hydroxycarboxylic acid compound having a hydroxyl group at the ⁇ -position.
  • the ⁇ -hydroxycarboxylic acid compound is preferably a non-polymeric ⁇ -hydroxycarboxylic acid, and its molecular weight is preferably 40 to 2000, more preferably 60 to 1000, and particularly preferably from the viewpoint of ease of addition and effect of addition. It is in the range of 100 to 500 and is preferably water-soluble.
  • ⁇ -hydroxycarboxylic acid compounds examples include glycolic acid, tartaric acid, lactic acid (salt), citric acid (salt), malic acid (salt), isocitric acid (salt), glyceric acid (salt), poly ⁇ -hydroxyacrylic acid (Salt) etc. are mentioned. Among them, lactic acid (salt) and malic acid (salt) are preferable, and lactic acid (salt) is more preferable.
  • the salt of ⁇ -hydroxycarboxylic acid is not particularly limited.
  • a monovalent salt or a polyvalent salt is used, preferably a monovalent salt to a trivalent salt, specifically, a sodium salt.
  • Potassium salt, calcium salt, magnesium salt and aluminum salt are preferable, and sodium salt is more preferable.
  • the acid group of ⁇ -hydroxycarboxylic acid may be substituted with 100% salt or may be partially substituted.
  • the content of these ⁇ -hydroxycarboxylic acid compounds in the particulate water-absorbing agent is preferably in the range of 0.05 to 1.0% by weight, more preferably 0.05 to 0.5%. % By weight, more preferably in the range of 0.1 to 0.5% by weight.
  • the particulate water-absorbing agent of the present invention containing a specific range of methoxyphenol, a chelating agent and an inorganic reducing agent further contains an ⁇ -hydroxycarboxylic acid compound, the aforementioned effects of the present invention can be further enhanced.
  • the particulate water-absorbing agent of the present invention is a polyvalent metal from the viewpoint of improving water absorption rate (Vortex), improving liquid permeability (SFC), fluidity at the time of moisture absorption, etc. It is preferable to further contain a salt and / or a cationic polymer.
  • the polyvalent metal salt is an organic acid salt or inorganic acid salt of a polyvalent metal, and polyvalent metal salts such as aluminum, zirconium, iron, titanium, calcium, magnesium, and zinc are preferable.
  • the polyvalent metal salt may be either water-soluble or water-insoluble, but is preferably a water-soluble polyvalent metal salt. Salt can be used.
  • aluminum chloride polyaluminum chloride, aluminum sulfate, aluminum nitrate, potassium bissulfate aluminum, sodium bissulfate aluminum, potassium alum, ammonium alum, sodium alum, sodium aluminate, calcium chloride, calcium nitrate, chloride
  • Illustrate inorganic acid salts such as magnesium, magnesium sulfate, magnesium nitrate, zinc chloride, zinc sulfate, zinc nitrate, zirconium chloride, zirconium sulfate and zirconium nitrate, and organic acid salts such as lactates and acetates of these polyvalent metals. Can do.
  • a salt having water of crystallization from the viewpoint of solubility in 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
  • water-containing crystal powders such as aluminum sulfate 18 hydrate and aluminum sulfate 14-18 hydrate. These may be used alone or in combination of two or more.
  • the cationic polymer is a cationic polymer having an amino group, more preferably a water-soluble cationic polymer, and preferably has a water solubility of 2% by weight or more, more preferably 5% by weight or more in water at 25 ° C. It is a polymer.
  • polyalkyleneimine such as polyethyleneimine, polyether polyamine, polyetheramine, polyvinylamine, polyalkylamine, polyallylamine, polydiallylamine, poly (N-alkylallylamine), monoallylamine-diallylamine copolymer, N-alkyl Allylamine-monoallylamine copolymer, monoallylamine-dialkyldiallylammonium salt / copolymer, diallylamine-dialkyldiallylammonium salt / copolymer, polyethylene polyamine, polypropylene polyamine, polyamidine, etc .; these salts are preferred.
  • the modified cationic polymer described in International Publication No. 2009/041727 is more preferable.
  • the weight average molecular weight of the cationic polymer is preferably 5000 or more, more preferably 10,000 or more, and further preferably 30000 or more. If the weight average molecular weight is less than 5000, the expected effect may not be obtained.
  • the upper limit of the weight average molecular weight of the cationic polymer is not particularly limited, but is preferably 1,000,000 or less, and more preferably 500,000 or less. It is preferable that the cationic polymer compound has a weight average molecular weight of 1,000,000 or less because the viscosity becomes low and the handling property and mixing property are excellent.
  • the weight average molecular weight can be measured by a known method such as GPC, viscosity measurement, or static light scattering.
  • a polyamine polymer particularly a polyamine polymer having a weight average molecular weight of about 5,000 to 1,000,000 may be used simultaneously or separately to improve liquid permeability.
  • the polyamine polymer used is, for example, US Pat. No. 7098284, WO 2006/082188, 2006/082189, 2006/082197, 2006/111402, and 2006/111403. No. 2006/111404 and the like.
  • the amount of the polyvalent metal salt and / or cationic polymer used in the particulate water-absorbing agent of the present invention is 0 to 5 parts by weight, preferably 0.001 to 3 parts by weight per 100 parts by weight of the particulate water-absorbing agent. Parts, more preferably in the range of 0.01 to 2 parts by weight.
  • the content of the polyvalent metal salt and / or the cationic polymer is more than 5 parts by weight, the absorption performance, particularly the water absorption ratio may be remarkably lowered, and coloring may be caused.
  • the particulate water-absorbing agent of the present invention is preferably a granulated product. By being a granulated product, the amount of dust contained in the particulate water-absorbing agent is reduced.
  • the particulate water-absorbing agent of the present invention is preferably granulated during or after polymerization.
  • the water absorption agent is further excellent in water absorption speed and particle size, and is excellent in actual use as a paper diaper.
  • the granulation means that a plurality of particulate water-absorbing resins are combined to form one large particle state, and as long as it finally becomes a combined particle, a water-containing gel may be used at the time of bonding, It may be a product, a monomer, a point contact or a surface contact between the bonded particles, and there may be an interface between the particles. Depending on the bond between the particles, the interface may be completely extinguished. Although it is good, it is preferably a granulated particle having an interface from the viewpoint of water absorption speed.
  • the water-absorbing resin before granulation used in the present invention may be only fine powder (having a particle size of less than 150 ⁇ m), or may be a mixture of fine powder and particles having a particle diameter larger than the fine powder.
  • the particle diameter of the conductive resin is preferably a weight average particle diameter of 500 ⁇ m or less, and more preferably 400 ⁇ m or less in order to improve performance such as the water absorption rate and the capillary absorption capacity.
  • the granulation of the present invention refers to water-absorbing resin particles having a plurality of water-absorbing resin particles settled and having an interface between bonded particles or having no interface between particles, and usually having a weight average particle diameter. It can also be defined by an increase (eg, 1.01 to 10 times) and / or a reduction in fines (eg, a 150 ⁇ m pass through, or even a 106 ⁇ m decrease).
  • the ratio of particles having a particle size of less than 300 ⁇ m is preferably 10% by weight or more, more preferably 30% by weight or more based on the water absorbent resin. 50% by weight or more is more preferable.
  • a water-absorbing resin having such a particle size can be obtained by reverse-phase suspension polymerization (particularly two-stage polymerization), or a pulverized water-absorbing resin obtained by aqueous solution polymerization, or these can be sieved. It can preferably be obtained by adjusting the particle size.
  • a water-absorbent resin fine powder having a particle diameter of 300 ⁇ m or less may be granulated and adjusted in particle size, and the granulated product of fine powder may be added to the irregularly pulverized primary particles obtained by pulverization.
  • a partially mixed water-absorbing resin may be used.
  • the water-absorbent resin composition of the present invention can be obtained which has more excellent absorption characteristics such as water absorption rate and capillary absorption capacity.
  • the mixing amount of the granulated fine powder is preferably 5% by weight or more, more preferably 10% by weight or more, and further preferably 15% by weight or more.
  • the method is not particularly limited as long as a plurality of polymer particles are combined to form a large particle.
  • Granulation in reverse phase suspension that is, aggregation during reverse phase polymerization (European Patent No. 0695762) , U.S. Pat. No. 4,732,968), or two-stage polymerization (European Patent No. 0807646), or reverse phase granulation by adding an inert inorganic substance after polymerization (U.S. Pat. No. 4,732,968).
  • a water-absorbing agent that is even better for actual use in paper diapers can be obtained.
  • An electron micrograph of typical granulated particles is shown in FIG.
  • a known technique for regenerating fine powder can be used as a method for producing a fine powder granulated product in order to obtain the particulate water-absorbing agent of the present invention.
  • a method in which warm water and fine water absorbent resin powder are mixed and dried (US Pat. No. 6,228,930), or a method in which the fine water absorbent resin powder is mixed with an aqueous monomer solution and polymerized (US Pat. No. 5,264,495).
  • a method of adding water to fine powder of water-absorbent resin and granulating it at a specific surface pressure or higher (European Patent No. 844270), sufficiently drying the fine powder of water-absorbent resin to form an amorphous gel, and drying and grinding The method (US Pat. No. 4,950,692), the method of mixing fine powder of water-absorbent resin and polymer gel (US Pat. No. 5,478,879), etc.
  • the hot water and fine powder of water-absorbent resin are mixed Then, a drying method is used.
  • the particle diameter is indicated by the sieve diameter to be classified.
  • water is used as a binder, and the water may contain the chelating agent or a reducing inorganic substance.
  • a granulated step of adding an aqueous liquid and heating while maintaining a water content of 1 to 10% by weight and adjusting the size as necessary is adjusted to a specific particle size as a powder.
  • the aqueous liquid to be added may be water alone, or may contain the chelating agent or inorganic reducing agent of the present invention, or a plant component, antibacterial agent, water-soluble polymer, inorganic salt and the like.
  • the concentration of the aqueous solution is 0.001 to 50% by weight, more preferably 0.001 to 30% by weight, and most preferably 0.01 to 10% by weight.
  • granulation is preferably performed by spraying or dropping and mixing an aqueous liquid onto the water-absorbent resin, and more preferably by spraying.
  • the size of the droplets to be sprayed is preferably in the range of 0.1 to 300 ⁇ m, more preferably in the range of 0.1 to 200 ⁇ m, in terms of average particle diameter.
  • the granulator used for granulation is preferably one having a large mixing force.
  • agitation type granulation method rolling type granulation method, compression type granulation method, fluidized bed granulation method and the like, and any method can be preferably used.
  • the stirring granulation method is more preferable in terms of simplicity and the like.
  • a conventionally known similar technique can be applied to the apparatus, operating conditions, etc., except that the water supply can be performed with water vapor.
  • the apparatus to be used since water is supplied by supplying water vapor into the apparatus, the apparatus to be used is equipped with a nozzle or the like that can inject water vapor, and has a high sealing performance so that water vapor can be supplied smoothly.
  • a device capable of adjusting the internal pressure is desirable.
  • the stirring type granulation method when carrying out by the stirring type granulation method, there are a continuous type and a batch type as stirring devices that can be used, and there are a vertical type and a horizontal type, respectively.
  • the vertical continuous stirring device include a spiral pin mixer (manufactured by Taiheiyo Kiko Co., Ltd.), a flow jet mixer and a Shugi type granulation system (manufactured by Gakken Powtex Co., Ltd.).
  • the horizontal continuous stirring device examples include an annular layer mixer (Drysberge) and a biaxial mixer (List).
  • vertical batch stirrers examples include Henschel mixers (Mitsui Mining Co., Ltd.) and turbo shear mixers (Moritz Corp.), and horizontal batch stirrers include Redige mixers (Ladyge Corp.). And a multi-flux mixer (manufactured by Gericke) and a proscher mixer (manufactured by Taiheiyo Kiko).
  • examples of the granulating apparatus include a cylindrical mixer, a double wall cone mixer, a high-speed stirring mixer, a V-shaped mixer, a ribbon mixer, a screw mixer, and a double-arm kneader.
  • Pulverization type kneaders, rotary mixers, airflow type mixers, turbulizers, batch-type Redige mixers, continuous-type Redige mixers, and the like are suitable.
  • aqueous liquid when granulating after surface cross-linking, it is preferable that after the aqueous liquid is mixed, heat treatment is performed while maintaining the moisture content. It is also preferable to add a chelating agent or an inorganic reducing agent as an aqueous solution in this step, and add the chelating agent or the inorganic reducing agent simultaneously with granulation.
  • a chelating agent or an inorganic reducing agent as an aqueous solution in this step, and add the chelating agent or the inorganic reducing agent simultaneously with granulation.
  • this heating process is called a curing process.
  • the moisture content (specified by loss on drying at 180 ° C. for 3 hours) is preferably 1 to 10% by weight, more preferably 2 to 8% by weight, even more preferably 2 during heat treatment. Heated while maintaining 5 to 6% by weight.
  • a heating medium such as hot air is used for heating, and the heating temperature (heating medium temperature or material temperature) is preferably in the range of 40 to 120 ° C., more preferably in the range of 50 to 100 ° C., and the heating time is A range of 1 minute to 2 hours is preferable.
  • Preferable examples of the combination of heating temperature and heating time are 0.1 to 1.5 hours at 60 ° C. and 0.1 to 1 hour at 100 ° C.
  • the particulate water-absorbing agent of the present invention is a particulate water-absorbing agent mainly comprising a polyacrylic acid (salt) -based water-absorbing resin, and includes a chelating agent and an inorganic reducing agent,
  • the content of the chelating agent is 0.001 to 0.5% by weight and satisfies any one or more of the following constituent requirements (1) to (3).
  • the content of methoxyphenols is 5 to 60 ppm.
  • the water content is 3 to 15% by weight.
  • the novel water-absorbing agent (first water-absorbing agent) of the present invention which is also shown in Examples described later, is mainly composed of a polyacrylic acid (salt) -based water-absorbing resin.
  • a particulate water-absorbing agent comprising a chelating agent and an inorganic reducing agent, the content of the chelating agent being 0.001 to 0.5% by weight, and methoxyphenols (particularly p-methoxyphenol) The content of is 5 to 60 ppm.
  • the novel water-absorbing agent of the present invention also shown in the examples described below preferably has an absorption capacity without load (CRC) of 25 [g / g] or more and a water absorption capacity under pressure (AAP of 4.83 kPa) of 20 [g / g. g] or more, and the saline flow conductivity (SFC) is 30 [ ⁇ 10 ⁇ 7 ⁇ cm 3 ⁇ s ⁇ g ⁇ 1 ] or more.
  • Such a water-absorbing agent preferably has a high water absorption rate of a water absorption rate (FSR) of 0.2 [g / g / sec] or more and satisfies the following particle size.
  • FSR water absorption rate
  • such a water absorbing agent preferably further contains an ⁇ -hydroxycarboxylic acid compound.
  • a polyvalent metal salt and / or a cationic polymer are further included.
  • These water-absorbing agents are white without initial and aging coloring, and have high liquid permeability (SFC) and absorption capacity under pressure (AAP). Therefore, even when used in high-concentration diapers with low pulp, high liquid diffusion and low return. A good disposable diaper is provided without coloring problems due to the amount of (Re-wet) water-absorbing agent.
  • the novel water-absorbing agent (second water-absorbing agent) of the present invention shown in Examples described later is mainly a polyacrylic acid (salt) -based water-absorbing resin.
  • Such a water-absorbing agent may optionally contain methoxyphenols (particularly p-methoxyphenol), and may be 0 to 200 ppm, preferably (1) and the novel water-absorbing agent of the present invention (first water-absorbing agent).
  • the novel water-absorbing agent (second water-absorbing agent) of the present invention may have a water content of less than 3% by weight, like the first water-absorbing agent, but preferably satisfies (3) and falls within the range of 3 to 15% by weight. is there.
  • the novel water-absorbing agent of the present invention also shown in the examples described below preferably has an absorption capacity without load (CRC) of 25 [g / g] or more and a water absorption capacity under pressure (AAP of 2.0 kPa) of 25 [g / g. g] and the water absorption rate (Vortex) is 60 seconds or less.
  • the novel water-absorbing agent (third water-absorbing agent) of the present invention shown in the examples described later is mainly a polyacrylic acid (salt) -based water-absorbing resin.
  • a particulate water-absorbing agent as a component, comprising a chelating agent and an inorganic reducing agent, wherein the content of the chelating agent is 0.001 to 0.5% by weight, and the water content is 3 to 15% by weight. is there.
  • Such a water-absorbing agent may optionally contain methoxyphenols (particularly p-methoxyphenol), and may be 0 to 200 ppm, preferably (1) and the novel water-absorbing agent of the present invention (first water-absorbing agent).
  • the novel water-absorbing agent (third water-absorbing agent) of the present invention preferably contains water-insoluble inorganic fine particles in the same manner as (1) and the novel water-absorbing agent (first water-absorbing agent) of the present invention. Urine resistance is further improved.
  • the novel water-absorbing agent of the present invention also shown in the examples described below preferably has an absorption capacity without load (CRC) of 25 [g / g] or more and a water absorption capacity under pressure (AAP of 2.0 kPa) of 25 [g / g. g] or more and the residual monomer is 500 ppm or less.
  • Such a water-absorbing agent preferably further contains an ⁇ -hydroxycarboxylic acid compound.
  • a polyvalent metal salt and / or a cationic polymer are further included.
  • novel water-absorbing agents are the ⁇ -hydroxycarboxylic acids (salts) shown in the above “[6] ⁇ -hydroxycarboxylic acid compound”.
  • liquid permeability SFC
  • absorption capacity under pressure AAP
  • SFC saline flow conductivity
  • Absorption capacity under no pressure is 25 [g / g] or more
  • Absorption capacity under pressure (AAP 4.83 kPa) is 20 [g / g] or more
  • Saline flow conductivity is 30 [ ⁇ 10 ⁇ 7 ⁇ Cm 3 ⁇ s ⁇ g -1 ] or more.
  • the absorption capacity without load is 25 [g / g] or more
  • the absorption capacity under pressure is 25 [g / g] or more
  • the water absorption speed (Vortex) is 60 seconds or less.
  • the water absorbing agent further satisfies the following.
  • the particulate water-absorbing agent of the present invention has a preferable Fe content (as a value converted to Fe 2 O 3 ) of 1 ppm or less, more preferably 0.1 ppm or less, particularly preferably 0.02 ppm or less from the viewpoint of preventing coloring. It is.
  • the amount of Fe can be controlled by appropriately purifying the amount of Fe in the raw material of the water-absorbent resin, particularly the base used for neutralization, and removing, for example, Fe of NaOH, Na 2 CO 3 ). is there.
  • the amount of Fe may be measured in the raw material or with the final water-absorbing agent.
  • the molecular weight (Fe in Fe 2 O 3 ) can be uniquely calculated.
  • the particulate water-absorbing agent of the present invention has an iron (Fe) content of 2 ppm or less, more preferably 1.5 ppm or less, still more preferably 1 ppm or less, particularly preferably.
  • the lower limit is preferably 0.001 ppm, more preferably 0.01 ppm.
  • the amount of iron is controlled mainly by controlling the base used for neutralization (especially caustic soda).
  • the amount of raw materials (acrylic acid, cross-linking agent, water, etc.) is controlled, and polymerization equipment, monomer piping, etc.
  • Various water-absorbing resin devices and piping resin coating, glass coating, and stainless steel control can be used.
  • the amount of iron in the base and the water-absorbing resin can be quantified by, for example, the ICP emission spectroscopic method described in JIS K1200-6, and refer to International Publication No. 2008/090961 as a reference for the quantification method. Can do.
  • the shape of the particles of the particulate water-absorbing agent (water-absorbing agent 1 to water-absorbing agent 3) of the present invention is not limited to a specific shape, and is spherical, substantially spherical, or pulverized. Examples thereof include a crushed shape, a rod shape, a polyhedron shape, a sausage shape (for example, U.S. Pat. No. 4,973,632), and particles having ridges (for example, U.S. Pat. No. 5,744,564). They may be single particles, granulated particles, or a mixture thereof. The particles may be foamed porous. Preferable particles include irregularly pulverized primary particles or granules. Granulation containing fine powder alone or fine powder is preferable because dust can be reduced, the ratio of the surface to the particle diameter is increased, and the water absorption speed is improved.
  • the water-absorbing agent (water-absorbing agent 1 to water-absorbing agent 3) of the present invention is preferably in the form of particles due to its water-absorbing properties, and the weight average particle diameter (D50) is preferably in the range of 200 to 600 ⁇ m. It is more preferably in the range of ⁇ 550 ⁇ m, still more preferably in the range of 250 to 500 ⁇ m. Further, the smaller the particle size of the JIS standard sieve is less than 150 ⁇ m, the better.
  • the content is usually 0 to 5% by weight, preferably 0 to 3% by weight, particularly preferably 0 to 1% by weight. Further, the smaller the number of particles of JIS standard sieve 850 ⁇ m or more, the better.
  • the content thereof is usually 0 to 5% by weight, preferably 0 to 3% by weight, particularly preferably 0 to 1% by weight.
  • the bulk specific gravity (specified in US Pat. No. 6,562,879) of the water-absorbing agent of the present invention is 0.30 to 0.90, preferably 0.50 to 0.80, more preferably 0.60 to 0.75.
  • the particle size can be controlled by the above pulverization or classification.
  • water-insoluble inorganic or organic powders such as surfactants, oxidizing agents, metal soaps, etc.
  • Deodorizers, antibacterial agents, pulp, thermoplastic fibers, etc. may be added in an amount of 0 to 3% by weight, preferably 0 to 1% by weight.
  • surfactant a surfactant described in International Publication No. 2005/077500 is preferably exemplified.
  • the water content of the particulate water-absorbing agent of the present invention is, for example, 0.5 to 16% by weight (essentially in water-absorbing agent 2) 3 Is preferably 15 to 15% by weight, more preferably 4 to 14% by weight, still more preferably 5 to 13% by weight, particularly 6 to 12% by weight, and further 7 to 11% by weight.
  • the water content is controlled by drying and surface cross-linking with the above-mentioned predetermined water content, and if necessary, adding or drying water.
  • the water content is 0.5% by weight or more, especially 3% by weight or more, the water absorption rate (Vortex / FSR) is further improved, causing odor problems, lowering the water absorption rate, lowering impact resistance, and generating dust. If the water content is 15% by weight or less, coloring is also suppressed, and it is possible to suppress the adhesion of the particles and the decrease in water absorption. If the water content of the water-absorbing agent is low, the water absorption rate (Vortex / FSR) decreases, and there is a problem of odor when the inorganic reducing agent is added (especially if it is at or before the surface cross-linking step), and if the water content is high Coloring problems tend to occur. Therefore, the water content is preferably set to the above-mentioned content.
  • the CRC of the particulate water-absorbing agent used in the present invention is preferably 5 [g / g] or more, more preferably 15 [g / g] or more, and further 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 still more preferably 40 [g / g] or less.
  • the CRC is less than 5 [g / g]
  • the particulate water-absorbing agent 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.
  • CRC when CRC is larger than 70 [g / g], the water absorption capacity under pressure (AAP) and liquid permeability (SFC) may decrease, and the particulate water-absorbing agent is used for water absorbent bodies such as paper diapers. In some cases, it may not be possible to obtain a water-absorbing agent excellent in the rate of liquid uptake into the water-absorbing body.
  • CRC can be controlled by the internal cross-linking agent and surface cross-linking agent described above.
  • the AAP (2.0 kPa or 4.83 kPa) of the particulate water-absorbing agent used in the present invention is 20 [g / g] or more, preferably 22 [g / g] or more, more preferably 23 [g / g. g] or more, more preferably 24 [g / g] or more, and most preferably 25 [g / g] or more.
  • the upper limit value of AAP is not particularly limited, but is preferably 30 [g / g] or less.
  • AAP is 20 [g / g] or more
  • a particulate water-absorbing agent when used for the water-absorbing body, there is less return of the liquid when the pressure is applied to the water-absorbing body (commonly known as Re-Wet).
  • a water absorbing agent can be obtained.
  • AAP can be controlled by the above surface cross-linking and particle size.
  • the AAP load condition may be appropriately selected from 4.83 kPa or 2.0 kPa depending on the type of the particulate water-absorbing agent to be obtained, and any load condition may be used as long as the above numerical range is shown.
  • the above AAP is satisfied with a load of 2.0 kPa or even 4.83 kPa.
  • the SFC of the particulate water-absorbing agent used in the present invention is preferably 30 [ ⁇ 10 ⁇ 7 ⁇ cm 3 ⁇ s ⁇ g ⁇ 1 ] or more, more preferably 50 [ ⁇ 10 ⁇ 7 ⁇ cm 3 ⁇ s ⁇ g ⁇ 1 ] or more, more preferably 70 [ ⁇ 10 ⁇ 7 ⁇ cm 3 ⁇ s ⁇ g ⁇ 1 ] or more, and particularly preferably 80 [ ⁇ 10 ⁇ 7 ⁇ cm 3 ⁇ s ⁇ g ⁇ 1 ]. That's it.
  • the liquid permeability can be further improved, and when the particulate water-absorbing agent is used for the water-absorbing body, It is possible to obtain a water-absorbing agent that is superior in the liquid uptake rate.
  • the upper limit of SFC is not particularly specified, but is preferably 3000 [ ⁇ 10 ⁇ 7 ⁇ cm 3 ⁇ s ⁇ g ⁇ 1 ] or less, more preferably 2000 [ ⁇ 10 ⁇ 7 ⁇ cm 3 ⁇ s ⁇ g ⁇ 1 ]. It is as follows.
  • SFC When the SFC is 3000 [ ⁇ 10 ⁇ 7 ⁇ cm 3 ⁇ s ⁇ g ⁇ 1 ] or less, liquid leakage at the water absorbent can be suppressed when the particulate water absorbent is used for the water absorbent.
  • SFC can be controlled by the above-mentioned surface cross-linking and particle size, control of CRC to the above-mentioned range, and the polyvalent metal salt and polyamine polymer shown in the above “[7] Polyvalent metal salt and / or cationic polymer”.
  • saline flow conductivity (SFC) may be expressed as liquid permeability or liquid permeability (SFC).
  • the particulate water-absorbing agent according to the present invention has an FSR of preferably 0.1 [g / g / sec] or more, more preferably 0.15 [g / g / sec] or more, and still more preferably 0.8. It is 20 [g / g / sec] or more, and most preferably 0.25 [g / g / sec] or more.
  • an excessively high water absorption rate (Vortex and FSR) is liable to impair liquid permeability (for example, SFC) and liquid diffusibility, and is preferably 5.0 [g / g / sec] or less, and more preferably 3.0 [g / g / sec] or less.
  • the FSR is 0.05 [g / g / sec] or more, for example, when a particulate water-absorbing agent is used for the water-absorbing body, the liquid is not sufficiently absorbed and liquid leakage is further suppressed. be able to.
  • the FSR can be controlled by the above particle size and foam polymerization.
  • Vortex is preferably 60 seconds or less, more preferably 55 seconds or less, still more preferably 50 seconds or less, and most preferably 40 seconds or less.
  • the lower limit of Vortex is not particularly specified, but is preferably 10 seconds or longer. If Vortex is 60 seconds or less, for example, when a particulate water-absorbing agent is used for the water-absorbing body, it is possible to further prevent liquid from being sufficiently absorbed and causing liquid leakage.
  • Vortex can be controlled by the above particle size, foam polymerization and the like.
  • the water-soluble component is essentially 50% by weight or less, preferably 35% by weight or less, more preferably 25% by weight or less, and further preferably 15% by weight or less. .
  • the water-soluble content is 35% by weight or less, the gel strength is stronger and the liquid permeability is more excellent.
  • a water-absorbing agent with less liquid return commonly called Re-Wet
  • the water-soluble component can be controlled by the above internal cross-linking agent.
  • the residual monomer is controlled to 500 ppm or less, preferably 400 ppm or less, more preferably 300 ppm or less from the viewpoint of safety.
  • Residual monomers can be reduced by using an inorganic reducing agent, particularly an inorganic reducing agent having elemental sulfur, in addition to the polymerization and drying.
  • the water-absorbing agent of the present invention is preferred because it has less residual monomer, and even when the water-absorbing agent is used in paper diapers at a high concentration (increase the amount used), the amount of residual monomers eluting in the paper diaper is small.
  • the particulate water-absorbing agent according to the present invention can be suitably used for sanitary materials such as paper diapers, and is preferably a white powder.
  • the particulate water-absorbing agent according to the present invention has an L value (Lightness) of at least 88, more preferably 89 or more, in Hunter Lab color system measurement using a spectral color difference meter of the particulate water-absorbing agent after production of the particulate water-absorbing agent. Preferably represents 90 or more.
  • the upper limit of the L value is normally 100. However, if the powder is 88, there is no problem with color tone in products such as sanitary materials.
  • the b value is 0 to 12, preferably 0 to 10, more preferably 0 to 9, and the a value is -3 to 3, preferably -2 to 2, and more preferably -1 to 1.
  • the initial color tone is a color tone after the production of the particulate water-absorbing agent, but is generally a color tone measured before factory shipment. Further, for example, if stored in an atmosphere of 30 ° C. or lower and a relative humidity of 50% RH, the value is measured within one year after production.
  • the particulate water-absorbing agent according to the present invention can be suitably used for sanitary materials such as paper diapers, and in that case, a remarkably clean white state is maintained even in a long-term storage state under high humidity and temperature conditions. It is preferable.
  • the long-term storage state is a long-term storage color stability promotion test, including the examples described later, and water absorption after the particulate water-absorbing agent has been exposed to an atmosphere having a temperature of 70 ⁇ 1 ° C. and a relative humidity of 65 ⁇ 1% RH for 7 days. It can be examined by measuring the L value (Lightness) of the Hunter Lab color system using a spectral color difference meter of the agent.
  • the particulate water-absorbing agent according to the present invention has an L value (Lightness) of at least 80, more preferably 81 or more in Hunter Lab color system measurement by a spectral color difference meter of the water-absorbing agent after the long-term storage color stability promotion test. Further, it is preferable to show 82 or more, particularly 83 or more.
  • the upper limit of the L value is usually 100, but if the L value after the accelerated test is 80 or more, it is a level at which no substantial problem occurs even in a long-term storage state under high humidity and temperature conditions.
  • the b value is 0 to 15, preferably 0 to 12, more preferably 0 to 10, and the a value is -3 to 3, preferably -2 to 2, and more preferably -1 to 1.
  • Manufacturing method of particulate water-absorbing agent The manufacturing method of the particulate water-absorbing agent of the present invention is performed by the method described in the above [1] to [8] as an example.
  • a polymerization step of an aqueous monomer solution mainly composed of acrylic acid (salt) containing 10 to 200 ppm of methoxyphenols a drying step of a hydrogel crosslinked polymer obtained by polymerization, a surface
  • a method of producing a polyacrylic acid (salt) -based particulate water-absorbing agent comprising a crosslinking step further comprising a step of adding 0.001 to 0.5% by weight of a chelating agent and a step of adding an inorganic reducing agent,
  • the monomer contains methoxyphenols in an amount of 10 to 200 ppm in terms of acrylic acid and satisfies one or more of the following (a) to (c).
  • the method further includes a step of adding water-insoluble inorganic fine particles.
  • the water content of the polymer is controlled to 3 to 15% by weight after the drying step and in the surface cross-linking step.
  • An inorganic reducing agent addition step is performed after the surface cross-linking step.
  • the method for producing the particulate water-absorbing agent of the present invention is a particulate water-absorbing agent obtained by adding the chelating agent mentioned in the above [1], [2] or the like to a monomer aqueous solution before or during polymerization.
  • a production method is preferred.
  • the method for producing the particulate water-absorbing agent of the present invention is a particulate water-absorbing agent obtained by adding the inorganic reducing agent mentioned in the above [1], [3] etc. to the hydrogel crosslinked polymer before drying.
  • a production method is preferred.
  • the method for producing a particulate water-absorbing agent of the present invention is preferably a method for producing a particulate water-absorbing agent further comprising the step of adding the ⁇ -hydroxycarboxylic acid (salt) mentioned in [6] above.
  • the method for producing a particulate water-absorbing agent of the present invention is preferably a method for producing a particulate water-absorbing agent further comprising the step of adding the polyvalent metal salt and / or the cationic polymer mentioned in [7] above.
  • the method for producing a particulate water-absorbing agent of the present invention is preferably a method for producing a particulate water-absorbing agent further including the granulation step described in [8] above.
  • the method for producing the particulate water-absorbing agent of the present invention is performed by the methods described in [1] to [8] above as an example. More specifically, in the polymerization step, a monomer aqueous solution containing 90 to 100% by weight of acrylic acid (salt) in the monomer and having a monomer concentration of 30 to 55% by weight is converted to a radical polymerization initiator 0. 001 to 1 mol% is a step in which aqueous solution polymerization or reverse phase suspension polymerization is performed under conditions where the maximum temperature is 130 ° C.
  • the drying step is performed with the particulate hydrogel at a drying temperature of 100 to 250 ° C. and a drying time of 10 to 120 minutes.
  • the surface crosslinking step is performed by mixing 0.001 to 10 parts by weight of a surface crosslinking agent with respect to 100 parts by weight of the water absorbent resin powder after the drying step.
  • Particulate obtained by heat treatment at °C for 1 minute to 2 hours A production method in which the methoxyphenol content of the water-absorbing agent is 5 to 60 ppm can be mentioned. Control of the methoxyphenol content of the obtained particulate water-absorbing agent can be performed by the method described above or the method described later.
  • the aforementioned methoxyphenols in the method for producing the particulate water-absorbing agent of the present invention may be added at any point in the production step of the particulate water-absorbing agent, but the aforementioned methoxyphenols used as the main component of the monomer. It is preferable that it is contained in acrylic acid, and it is preferable to adjust content suitably in the purification process of acrylic acid.
  • acrylic acid containing 10 to 200 ppm of methoxyphenols it is preferable to use acrylic acid containing 10 to 200 ppm of methoxyphenols.
  • Acrylic acid As a method for producing acrylic acid used in the present invention, propylene and / or acrolein catalytic gas phase oxidation method, ethylene cyanohydrin method, high-pressure repe method, improved repe method, ketene method
  • the acrylonitrile hydrolysis method is known as an industrial production method, and among them, the gas phase oxidation method of propylene and / or acrolein is most often employed. And in this invention, the acrylic acid obtained by this vapor phase oxidation method is used suitably.
  • a monomer containing 10 to 200 ppm of methoxyphenol in terms of acrylic acid is preferably used.
  • the main component of this monomer may be acrylic acid, and may be acrylic acid and acrylate.
  • the methoxyphenols include o, m, p-methoxyphenol, and methoxyphenols having one or more substituents such as a methyl group, a t-butyl group, and a hydroxyl group.
  • p-methoxyphenol is used in the present invention.
  • the content of methoxyphenols is preferably 10 to 120 ppm, preferably 10 to 90 ppm, more preferably 20 to 90 ppm in terms of acrylic acid.
  • the content of p-methoxyphenol is 200 ppm or less, coloring (yellowing / yellowing) of the obtained water absorbent resin can be suppressed.
  • the content of p-methoxyphenol is less than 10 ppm, that is, when p-methoxyphenol, which is a polymerization inhibitor, is removed by purification such as distillation, there is a risk that polymerization will occur before intentionally starting the polymerization. Not only that, but the weather resistance of the water-absorbing resin or water-absorbing agent obtained using acrylic acid (salt) as the main raw material as described above is not preferable.
  • the methoxyphenol at the time of polymerization is based on acrylic acid (molecular weight 72)
  • the acrylic acid salt obtained by neutralization if necessary has an increased molecular weight (for example, a molecular weight of 88 mol for 75 mol% neutralized sodium salt).
  • the content of methoxyphenols is relatively reduced.
  • the content of methoxyphenols in the acrylate before polymerization is 10 to 200 ppm
  • methoxyphenols in the obtained polyacrylate is 5 to 60 ppm. Become.
  • the method for producing a particulate water-absorbing agent of the present invention is a method for producing a particulate water-absorbing agent through polymerization of an aqueous monomer solution in which acrylic acid contains 10 to 200 ppm of methoxyphenols (particularly p-methosphenol). preferable. Furthermore, a predetermined amount of methoxyphenol is consumed through the polymerization step (concentration, initiator, temperature) and drying step (temperature, time, solid content, air volume, etc.), and methoxyphenol in the above-mentioned range ( In particular, a particulate water-absorbing agent containing 5 to 60 ppm of p-methoxyphenol, in particular uniformly contained inside the polymer can be obtained.
  • the methoxyphenol of the water absorbent resin obtained by the radical polymerization step and the drying step is set to 5 to 60 ppm. It may be a manufacturing method.
  • the method for controlling methosylphenol in the water-absorbent resin is not limited to the above example, and other methods can be exemplified as follows, and these may be used in combination.
  • Production method 2 A method in which a predetermined amount of methosphenols is added after polymerization of the water-absorbent resin in the absence of methosylphenols or less than 10 ppm, and further after drying.
  • Manufacturing method 3 A method of removing a predetermined amount of methosphenols by washing before drying after polymerization into a water-absorbing resin with a monomer containing excessive methosylphenols.
  • water or a hydroalcoholic liquid mixture can be used for washing.
  • a polymerization inhibitor other than p-methoxyphenol may be used in the production process, or the polymerization inhibitor may be used in combination with p-methoxyphenol.
  • polymerization inhibitors other than p-methoxyphenol for example, phenothiazine, hydroquinone, copper salt, manganese acetate, methylene blue and the like are effective. However, unlike methoxyphenol, these polymerization inhibitors inhibit the polymerization, so the final amount is better.
  • concentration in the monomer is preferably 0.01 to 10 ppm. .
  • the amount of water in acrylic acid is preferably as small as possible, and is usually 1000 ppm or less, preferably 750 ppm or less, more preferably 500 ppm or less, more preferably 300 ppm or less, particularly preferably. Is preferably in the order of 200 ppm or less, 100 ppm or less, 80 ppm or less, 50 ppm or less. Less moisture is preferable, but about 1 ppm or even about 5 ppm is sufficient from the dehydration cost.
  • Moisture may be a predetermined amount.
  • the amount of water in the monomer exceeds 1000 ppm, the coloring (particularly coloring with time) of the resulting water-absorbent resin tends to deteriorate.
  • the main component of the monomer is acrylic acid and / or acrylate, but the molecular weight is different between acrylic acid and acrylate.
  • the value in terms of acrylic acid is defined in the present invention.
  • the value in terms of acrylic acid is the content ratio (weight ratio) of the above-mentioned trace component weight to the weight of acrylic acid when all acrylates are converted to be equimolar unneutralized acrylic acid. That is, for example, the neutralized sodium acrylate (molecular weight 94) is converted to acrylic acid (molecular weight 72) by weight, and the above trace components such as p-methoxyphenol are converted into acrylic acid (94 converted to 72) by weight.
  • the content ratio (weight ratio) and the like are defined.
  • the conversion value for acrylic acid is all partially neutralized or completely neutralized polyacrylate, etc. It can be calculated in terms of moles of unneutralized polyacrylic acid.
  • the partial neutralization means that the neutralization rate is more than 0 mol% and less than 100 mol%.
  • the said complete neutralization means that the neutralization rate is 100 mol%.
  • the said non-neutralized means that the neutralization rate is 0 mol%.
  • the above components can be quantified by liquid chromatography or gas chromatography.
  • the neutralizing agent (base) such as caustic soda or sodium carbonate used for neutralization of the monomer or polymer in the present invention is preferably as the iron content is small, and the content thereof (As converted to Fe 2 O 3 ) is usually in the range of 0 to 10.0 ppm, preferably 0.2 to 5.0 ppm, more preferably 0.5 to 5.0 ppm relative to the base solid content. Included in range.
  • the iron content is less than 0.01 ppm, not only does the polymerization occur before the polymerization initiator is added, but there is a possibility that the polymerization may be delayed even if the initiator is added.
  • Such iron may be Fe ions, but from the viewpoint of effects, trivalent iron, particularly Fe 2 O 3 is preferred.
  • the amount of Fe can be uniquely calculated within the above range by the molecular weight ratio of iron and iron oxide (55.85 ⁇ 2 / 159.7 (Fe in Fe 2 O 3 )).
  • the absolute amount of Fe is important regardless of the type of counter anion.
  • the amount of Fe is expressed as a counter anion (for example, an oxide of Fe (II) or Fe (III), Regardless of sulfate, hydrochloride, hydroxide, etc.), Fe 2 O 3 is an oxide of Fe (III), and the molecular weight of the Fe (molecular weight 55.85) and Fe 2 O 3 ( 159.7), the preferable amount of Fe (in terms of Fe) in the base of the present invention is 0 to 7.0 ppm.
  • the iron used in the present invention may be Fe ions, but from the viewpoint of effects, trivalent iron, particularly Fe 2 O 3 or iron hydroxide is preferred.
  • the neutralization step is preferably performed with a base having an Fe content (Fe conversion) of 0 to 7.0 ppm (particularly NaOH or sodium carbonate controlled to the Fe content), and more preferably It is the range of Fe content.
  • the method for adding the inorganic reducing agent in the method for producing the particulate water-absorbing agent of the present invention includes the above (1-6) polymerization step, (1-7) gel refining step, It can be added to any one or more of (1-8) drying step, (1-9) pulverization step / classification step, (1-10) surface cross-linking step, and (1-11) other step, and is particularly limited. Although not a thing, it is preferable to add as a powder form, a solution, an emulsion, or a suspension, it is preferable to add as a solution, and it is more preferable to add as an aqueous solution.
  • the average particle diameter of the powder particles is preferably 0.001 to 850 ⁇ m, and preferably 0.01 to 600 ⁇ m. More preferably, it is 0.05 to 300 ⁇ m.
  • an average particle diameter can be measured as a volume average particle diameter with a laser. An example of a laser is described in US Patent Application Publication No. 2004/0110006.
  • the solvent used when the inorganic reducing agent in the method for producing the particulate water-absorbing agent of the present invention is added as a solution is not particularly limited, and examples thereof include water; ethanol, methanol, propylene glycol, glycerin, and the like. Alcohols such as polyethylene glycol and the like can be preferably used. Among them, it is preferable to use water or a mixed solution of water and alcohols, and most preferably, it is added as an aqueous solution. Further, the concentration of the inorganic reducing agent in such a solution is appropriately determined and may be a dispersion or supersaturated solution exceeding the saturated concentration, but the following range is a solution, particularly an aqueous solution, and the upper limit is the saturated concentration.
  • the dispersion medium used when the inorganic reducing agent is mixed in a suspension is not particularly limited.
  • water; alcohols such as ethanol, methanol, propylene glycol, and glycerin; polyethylene Glycol or the like can be preferably used.
  • the concentration of the inorganic reducing agent in the dispersion is preferably 1 to 100% by weight, and more preferably 10 to 100% by weight.
  • the inorganic reducing agent may be mixed with a water-absorbing resin as an emulsion in water, for example, together with an emulsifier.
  • the dispersion medium in such a case is not particularly limited, but water or the like can be suitably used, for example.
  • the emulsifier is not particularly limited, but a nonionic surfactant, a cationic surfactant, or the like may be used.
  • concentration of the inorganic reducing agent in the emulsion is preferably 1 to 90% by weight, more preferably 10 to 90% by weight.
  • the inorganic reducing agent is added as an aqueous solution.
  • concentration of the inorganic reducing agent in the aqueous solution is preferably 0.01 to 90% by weight, more preferably 0.5 to 60% by weight, and still more preferably 1 to 90% by weight. It is particularly preferably 10 to 60% by weight, and most preferably 10 to 90% by weight.
  • the upper limit may be a dispersion or a supersaturated solution within the above range, but the upper limit is a saturated concentration.
  • the addition of the inorganic reducing agent in the method for producing the particulate water-absorbing agent of the present invention may be any of the monomer solution before polymerization, the hydrogel crosslinked product during or after polymerization, before the surface crosslinking step, after the surface crosslinking step. Although it may be carried out at a time, it is more preferable to add during the polymerization, the hydrogel crosslinked polymer after polymerization (that is, the hydrogel crosslinked polymer before drying) or after the surface crosslinking step.
  • an inorganic reducing agent is added in the step of finely granulating the hydrogel crosslinked polymer after polymerization, or after the finely polymerized polymerization It is preferable to add and mix an inorganic reducing agent to the hydrogel crosslinked polymer.
  • an inorganic reducing agent is added at the time of surface crosslinking or before surface crosslinking as in Patent Document 15, unless the water content is controlled to 3 to 15% by weight as in the present invention, the particulate water absorbing agent is colored. Not only does it become odorous,
  • timing of the addition step after the surface cross-linking step is not particularly limited, and any of the polyvalent metal salt and / or cationic polymer before, at the same time as, or after the addition. You may add at the time. Further, the ⁇ -hydroxycarboxylic acid compound may be added before, simultaneously with, or after the addition.
  • the inorganic reducing agent in the method for producing the particulate water-absorbing agent of the present invention is preferably mixed with the polyacrylic acid (salt) water-absorbing resin after addition or simultaneously with the addition.
  • the specific mixing method to add or mix is not specifically limited, It can mix using a well-known crushing apparatus, a grinding
  • Examples of the crushing apparatus and crushing apparatus include a kneader and a screw type extruder (also known as meat chopper) having an arbitrarily shaped porous structure.
  • a plurality of such crushing devices may be used in series, or different devices such as a kneader and a meat chopper may be used in combination.
  • One screw type extruder may be used, or two or more screw extruders may be used.
  • Examples of such a stirring device include a cylindrical mixer, a screw mixer, a screw extruder, a turbulator, a nauter mixer, a V mixer, a double-arm kneader, a fluid mixer, and an airflow mixer.
  • the stirring device includes a heating device that heats a mixture containing the polyacrylic acid (salt) water-absorbing resin after surface crosslinking, the inorganic reducing agent, and, if necessary, the other additives. You may provide the cooling device which cools the said mixture heated with the heating apparatus.
  • the time which stirs with the said stirring apparatus is not specifically limited, Preferably it is 60 minutes or less, More preferably, it is 30 minutes or less.
  • the aforementioned chelating agent in the method for producing a particulate water-absorbing agent of the present invention comprises the above (1-6) polymerization step to (1-10) surface crosslinking step and (1-11) It may be added at any point in the particulate water-absorbing agent production process including other processes, but it is preferably added to the monomer aqueous solution before or during polymerization in the (1-6) polymerization process. .
  • the chelating agent can be more uniformly contained in the particulate water-absorbing agent, and therefore, it is particularly preferable in that coloring with time can be effectively prevented.
  • the chelating agent it is preferable to add the chelating agent to the monomer aqueous solution during the polymerization or in the middle of the polymerization because the chelating agent can be uniformly added to the particulate water-absorbing agent of the present invention, and the effects of the present invention can be further exhibited.
  • water-insoluble inorganic fine particles simultaneously with the surface cross-linking agent to cross-link the surface of the water-absorbent resin, or to add water-insoluble inorganic fine particles after cross-linking the surface of the water-absorbent resin with the surface cross-linking agent.
  • water-insoluble inorganic fine particles are preferably added simultaneously with the above-mentioned ⁇ -hydroxycarboxylic acid compound or added as a mixture previously mixed with the ⁇ -hydroxycarboxylic acid compound.
  • the ⁇ -hydroxycarboxylic acid compound described above is the above (1-6) polymerization step to (1-10). It may be added at any point in the production process of the particulate water-absorbing agent, including the surface crosslinking step and (1-11) other steps. It may be contained in advance, and is preferably added in a subsequent step after completion of the polymerization reaction described above.
  • a method of adding in the latter step after the completion of the polymerization reaction there are a method of adding to the hydrogel polymer after polymerization, a method of adding to the dried product after the drying step, a surface cross-linking treatment step or a method of adding after that. preferable.
  • the method for adding the ⁇ -hydroxycarboxylic acid compound in the method for producing a particulate water-absorbing agent of the present invention is not particularly limited, but it is preferably added as a powder, a solution, an emulsion, or a suspension. More preferably, it is added as a solution, and more preferably as an aqueous solution. Furthermore, the ⁇ -hydroxycarboxylic acid compound may be added simultaneously with the above-described chelating agent, polyvalent metal salt and / or cationic polymer and water-insoluble inorganic fine particles, or previously mixed with each of these components. It may be added as a mixture.
  • the polyvalent metal salt and / or cationic polymer described above is the above (1-6). It may be added at any point in the production step of the particulate water-absorbing agent, including the polymerization step to (1-10) surface cross-linking step and (1-11) other steps, but is preferably added during the surface treatment. .
  • a method in which a polyvalent metal salt and / or a cationic polymer is added simultaneously with the above-mentioned surface cross-linking agent to cross-link the water-absorbent resin surface A method of adding a polyvalent metal salt and / or a cationic polymer as the second surface cross-linking step after cross-linking the water-absorbent resin surface is preferred.
  • the polyvalent metal salt and / or cationic polymer reacts with the functional group of the polyacrylic acid-based water-absorbing resin, particularly as a surface cross-linking agent that ionically bonds (first or second), and further improves the properties of the resulting water-absorbing agent.
  • a polyvalent metal salt and / or a cationic polymer to the water-absorbing resin after surface crosslinking with a surface crosslinking agent, surface treatment is achieved, achieving desired water absorption characteristics, especially high liquid flow characteristics (SFC).
  • SFC liquid flow characteristics
  • the polyvalent metal salt and / or the cationic polymer are preferably added simultaneously with the above-mentioned ⁇ -hydroxycarboxylic acid compound or added as a mixture previously mixed with the ⁇ -hydroxycarboxylic acid compound.
  • the use of a polyvalent metal salt and / or a cationic polymer sometimes caused coloring of the water-absorbent resin.
  • the present invention there is no problem, and the physical properties are improved by the polyvalent metal salt and / or the cationic polymer. To do.
  • the resulting mixture may be dried.
  • the drying is preferably performed in a temperature range of 40 ° C. or more and less than 100 ° C. through 50% or more of the time required for the drying step, more preferably through substantially all the drying steps.
  • the drying temperature is specified by the heating medium temperature, but if it cannot be specified by the heating medium temperature such as microwave, it is specified by the material temperature.
  • the drying method is not particularly limited as long as the drying temperature is within the above range, and hot air drying, airless drying, reduced pressure drying, infrared drying, microwave drying and the like can be suitably used.
  • the range of the drying temperature is more preferably 40 ° C. to 100 ° C., still more preferably 50 ° C. to 90 ° C.
  • the drying may be performed at a constant temperature or may be performed by changing the temperature, but substantially all the drying steps are performed within the above temperature range and the moisture content described later. Is preferred.
  • the drying time depends on the surface area of the water-absorbing agent, the moisture content, and the type of the dryer, and is appropriately selected so as to achieve the desired moisture content.
  • the drying time is usually 10 to 120 minutes, more preferably 20 to 90 minutes, still more preferably 30 to 60 minutes. If the drying time is less than 10 minutes, the drying may not be sufficient and the handleability may not be sufficient. In addition, if the drying time is 120 minutes or more, the water-absorbing agent may be damaged by excessive drying, resulting in an odor (presumed to be a composite of an inorganic reducing agent and a water-absorbing resin) or a water-soluble amount. In some cases, there is no improvement in physical properties.
  • the water content of the particulate water-absorbing agent of the present invention may be adjusted to 5% by weight or less.
  • the water content after drying is preferably 3 to 15% by weight, more preferably 4 to 14% by weight, still more preferably 5 to 13% by weight, particularly 6 to 12% by weight, and further 7 to 11% by weight.
  • the method mentioned above is illustrated as an example of the adjustment method of the moisture content.
  • Patent Document 17 discloses a water-absorbing water-resistant resin comprising a water-absorbing resin, an oxygen-containing reducing inorganic salt, an aminocarboxylic acid metal chelating agent and an organic antioxidant. Although the resin composition is disclosed, the use of a specific amount of p-methoxyphenol or water-insoluble fine particles is not disclosed, and the importance of the water content of the obtained water-absorbing resin composition is not described. In Examples of Patent Document 17, 214.4 g of a water-absorbing resin obtained by using 80 wt% acrylic acid (92 g + 119.1 g) and 30 wt% NaOH aqueous solution (102.2 g + 132.2 g) as monomers in the production example was used.
  • Example 1-7 the water-absorbing resin composition was obtained by mixing the oxygen-containing reducing inorganic salt, the aminocarboxylic acid metal chelating agent and the organic antioxidant without a solvent. Therefore, in Patent Document 17, the water content of the water-absorbent resin is calculated as 17% by weight from the raw material (g) and the yield (212.2 g) of the water-absorbent resin. 3 to 15% by weight, further 4 to 14% by weight, 5 to 13% by weight, 6 to 12% by weight and 7 to 11% by weight are not disclosed.
  • Patent Document 17 discloses alkylhydroxyanisole (such as butyl) as an organic antioxidant (paragraphs [0019] [0020] [Example 6]), but does not disclose a trace amount of p-methoxyphenol.
  • the water-absorbing body according to the present invention includes the particulate water-absorbing agent according to the present invention.
  • an appropriate material for example, a water-absorbing body suitable as an absorbent layer for sanitary materials can be obtained.
  • the water absorbing body of the present invention will be described. Since the water-absorbing agent of the present invention is white, has high liquid permeability, water absorption capacity under pressure, high water absorption speed, and little residual monomer, it can be suitably used for high-concentration water-absorbing bodies, particularly diapers.
  • the water absorbent is a composition used for a sanitary material that absorbs blood, body fluid, urine and the like, and is a molded composition made of a particulate water absorbent and other materials.
  • the sanitary material include paper diapers, sanitary napkins, incontinence pads, medical pads, and the like.
  • cellulose fibers can be exemplified.
  • cellulose fibers include, for example, wood pulp fibers such as mechanical pulp, chemical pulp, semi-chemical pulp, and dissolved pulp from wood; artificial cellulose fibers such as rayon and acetate. More preferred cellulose fibers are wood pulp fibers. These cellulose fibers may partially contain synthetic fibers such as nylon and polyester.
  • the content of the particulate water-absorbing agent contained in the water-absorbing body is preferably 20% by weight or more, more preferably 30% by weight. More preferably, it is in the range of 50% by weight or more.
  • the weight of the particulate water-absorbing agent of the present invention contained in the water-absorbing body is less than 20% by weight, a sufficient absorption effect may not be obtained.
  • the above-mentioned water-absorbing agent is sprayed on a paper, mat, etc. made of cellulose fiber, and if necessary, with these paper, mat, etc.
  • Known means for obtaining a water-absorbing body such as a sandwiching method and a method of uniformly blending cellulose fibers and a water-absorbing agent, can be appropriately selected.
  • a method in which a particulate water-absorbing agent and cellulose fiber are dry mixed and then compressed can be mentioned. By this method, it is possible to remarkably suppress the dropping of the particulate water-absorbing agent from the cellulose fiber.
  • the compression is preferably performed under heating, and the temperature range is, for example, 50 to 200 ° C.
  • the particulate water-absorbing agent according to the present invention is excellent in various physical properties when used in a water-absorbing body, so that the liquid can be taken up quickly, and the remaining amount of liquid on the surface of the water-absorbing body is small. can get.
  • the particulate water-absorbing agent according to the present invention has excellent water-absorbing properties, it can be used as a water-absorbing water-retaining agent for various applications.
  • water absorbent water retention agents for absorbent articles such as paper diapers, sanitary napkins, incontinence pads, medical pads; horticultural horticulture such as moss substitutes, soil modification improvers, water retention agents, agricultural chemical efficacy sustaining agents Water retention agent for building walls; anti-condensation agent for interior wall material, cement additive, etc .; release control agent, cold insulation agent, disposable warmer, sludge coagulant, food freshness retention agent, ion exchange column material, sludge or oil It can be used as a dehydrating agent, desiccant, humidity adjusting material, etc.
  • the water-absorbing agent according to the present invention is particularly preferably used for sanitary materials for absorbing feces, urine or blood, such as paper diapers and sanitary napkins.
  • the water absorbent according to the present invention is used for sanitary materials such as paper diapers, sanitary napkins, incontinence pads, medical pads, etc., (a) a liquid-permeable top sheet disposed adjacent to the wearer's body (B) a liquid impervious backsheet disposed far from the wearer's body and adjacent to the wearer's clothing; and (c) disposed between the topsheet and the backsheet. It is preferable to be used in a configuration comprising a water absorbent. Two or more water absorbent bodies may be used, or a water absorbent body may be used together with a pulp layer or the like.
  • the particulate water-absorbing agent according to the present invention can be rephrased as follows.
  • a polyacrylic acid (salt) characterized in that it is a particulate water-absorbing agent composed mainly of a polyacrylic acid (salt) -based water-absorbing resin and contains a chelating agent, an inorganic reducing agent and water-insoluble inorganic fine particles.
  • a particulate water-absorbing agent mainly composed of a water-absorbing resin.
  • a particulate water-absorbing agent mainly composed of a surface-crosslinked polyacrylic acid (salt) -based water-absorbing resin, comprising an inorganic reducing agent, a chelating agent and p-methoxyphenol, and having a water content of 3 to 15
  • a particulate water-absorbing agent comprising, as a main component, a polyacrylic acid (salt) -based water-absorbing resin in weight percent.
  • the method for producing the particulate water-absorbing agent of the present invention can be rephrased as follows.
  • a method for producing a particulate water-absorbing agent comprising the step of adding a chelating agent, A method for producing a particulate water-absorbing agent, wherein an inorganic reducing agent addition step is performed after the surface cross-linking step.
  • a method for producing a particulate water-absorbing agent comprising a polymerization step of an aqueous monomer solution containing acrylic acid (salt) as a main component and a drying step of a hydrogel crosslinked polymer obtained by polymerization.
  • a method for producing a particulate water-absorbing agent comprising a surface crosslinking step, a chelating agent addition step, an inorganic reducing agent and a water-insoluble inorganic fine particle addition step.
  • a method for producing a particulate water-absorbing agent comprising, as a main component, a polyacrylic acid (salt) -based water-absorbing resin including an inorganic reducing agent and a chelating agent addition step
  • a method for producing a particulate water-absorbing agent comprising a polyacrylic acid (salt) water-absorbing resin as a main component, wherein the water content of the polymer is controlled to 3 to 15% by weight in the drying step and the surface cross-linking step.
  • the production method of the subordinate concept essentially comprising the above (c) is a simple method comprising acrylic acid (salt) containing 10 to 200 ppm of methoxyphenol as a main component.
  • a particulate water-absorbing agent comprising a polymerization step of a monomer aqueous solution, a drying step of a water-containing gel-like crosslinked polymer obtained by polymerization, a surface crosslinking step, and a step of adding 0.001 to 0.5 wt% of a chelating agent.
  • an inorganic reducing agent addition step is performed after the surface cross-linking step. Specific examples of this production method / part 1 are shown in Examples 1-1 to 1-16 and Tables 1 to 5 described later.
  • part 2 As a method for producing the particulate water-absorbing agent of the present invention, the production method of the subordinate concept essentially comprising the above (b), part 2 is a polymerization step of a monomer aqueous solution mainly composed of acrylic acid (salt), and polymerization
  • a method for producing a particulate water-absorbing agent comprising a drying step of a water-containing gel-like cross-linked polymer obtained in step 1 and a surface cross-linking step, wherein an addition step of 0.001 to 0.5 wt% of a chelating agent and inorganic reduction And a step of adding an agent, wherein the monomer contains 10 to 200 ppm of methoxyphenol in terms of acrylic acid, and (a) a step of adding water-insoluble inorganic fine particles is further included.
  • Specific examples of such production method-2 are shown in Examples 2-1 to 2-14 and Tables 6 to 7 described later.
  • part 3 is a polymerization step of a monomer aqueous solution mainly composed of acrylic acid (salt), and polymerization
  • a method for producing a particulate water-absorbing agent comprising a drying step of a water-containing gel-like cross-linked polymer obtained in step 1 and a surface cross-linking step, wherein an addition step of 0.001 to 0.5 wt% of a chelating agent and inorganic reduction And a monomer addition step, the monomer contains 10 to 200 ppm of methoxyphenol in terms of acrylic acid, and the moisture content of the polymer is 3 to 15% by weight after the drying step and / or in the surface cross-linking step. More preferably, the inorganic reducing agent is added to the hydrogel crosslinked polymer before drying. Specific examples of the production method / part 3
  • the present invention will be described in accordance with examples, but the present invention is not limited to the examples and is not to be interpreted.
  • Various physical properties described in the claims and examples of the present invention were determined according to the following measurement methods.
  • the following measuring method describes the particulate water-absorbing agent
  • the water-absorbing resin is measured by replacing the particulate water-absorbing agent with the water-absorbing resin.
  • the electric equipment used in the examples was 200V or 100V, and was used under conditions of 60 Hz.
  • the particulate water-absorbing agent was used under conditions of 25 ° C. ⁇ 2 ° C. and a relative humidity of 50% RH unless otherwise specified.
  • the reagents and instruments exemplified in the following measurement methods and examples may be appropriately replaced with equivalent products.
  • the particulate water-absorbing agent of the present invention essentially contains an inorganic reducing agent.
  • the surface-crosslinked water-absorbing resin, the water-absorbing resin before adding the inorganic reducing agent, the particulate water-absorbing agent precursor are reference; Examples 1-1 to 1-8, Comparative Examples 1-3, 1-4, etc.).
  • titration was performed with 0.1N NaOH aqueous solution until pH 10 was reached, and then titration was performed with 0.1N HCl aqueous solution until pH 2.7 was reached. At this time, titration amounts ([NaOH] ml, [HCl] ml) were determined. In addition, the same titration operation was performed on only 184.3 g of a 0.90% by weight sodium chloride aqueous solution, and empty titration amounts ([bNaOH] ml, [bHCl] ml) were obtained.
  • the water-soluble content in the particulate water-absorbing agent can be calculated by the following formula 2 based on the average molecular weight of the monomer and the titration amount obtained by the above operation. .
  • the average molecular weight of the monomer can be calculated using the neutralization rate obtained by titration. This neutralization rate is calculated by the following formula 3.
  • the residual monomer (residual acrylic acid (salt)) contained in the particulate water-absorbing agent of the present invention is the same operation except that the stirring time in the measurement method of [Water-soluble content] is changed from 16 hours to 2 hours. It is calculated
  • AAP Absorptive power against pressure indicates a water absorption capacity of 60 minutes at 4.83 kPa or 2.0 kPa with respect to 0.90 wt% saline. AAP is sometimes referred to as water absorption capacity under pressure at 4.83 kPa or 2.0 kPa.
  • a stainless steel 400 mesh wire mesh 101 (mesh size 38 ⁇ m) is fused to the bottom of a plastic support cylinder 100 having an inner diameter of 60 mm, and the conditions are room temperature (20 to 25 ° C.) and humidity 50 RH%.
  • 0.900 g of the particulate water-absorbing agent is evenly dispersed on the net, and on that, 4.83 kPa (0.7 psi) or 2.0 kPa (0.3 psi) with respect to the particulate water-absorbing agent.
  • the piston 103 and the load 104 which are adjusted so that the load can be applied uniformly and whose outer diameter is slightly smaller than 60 mm and does not cause a gap with the support cylinder and do not hinder the vertical movement, are placed in this order.
  • the weight Wa [g] of this measuring device set was measured.
  • a glass filter 106 having a diameter of 90 mm (manufactured by Mutual Science Glass Co., Ltd., pore diameter: 100 to 120 ⁇ m) is placed inside a petri dish 105 having a diameter of 150 mm, and a 0.90 wt% sodium chloride aqueous solution 108 (20 to 25 ° C.). Was added to the same level as the upper surface of the glass filter.
  • a sheet of filter paper 107 having a diameter of 90 mm (manufactured by ADVANTEC Toyo Co., Ltd., product name: JIS P 3801, No. 2, thickness 0.26 mm, reserved particle diameter 5 ⁇ m) is placed so that the entire surface is wetted, and Excess liquid was removed.
  • the above measuring device set was placed on the wet filter paper, and the liquid was absorbed under load. After 1 hour, the measuring device set was lifted and its weight Wb [g] was measured. And AAP [g / g] was computed from Wa and Wb according to the following formula.
  • SFC saline solution inductivity
  • the particulate water-absorbing agent 0.900 [g] uniformly placed in the container 40 is swollen for 60 minutes in an artificial urine under a pressure of 2.07 kPa (0.3 psi).
  • the height of the gel layer of gel 44 was recorded.
  • a 0.69 wt% sodium chloride aqueous solution 33 was passed through the gel 44 swollen from the tank 31 with a constant hydrostatic pressure.
  • This SFC test was conducted at room temperature (20-25 ° C.). Using a computer and a balance, the amount of liquid passing through the gel layer at 20 second intervals as a function of time was recorded for 10 minutes.
  • the flow velocity Fs (T) passing through the swollen gel 44 was determined by dividing the increased weight [g] by the elapsed time [s] [unit: g / s]. Let Ts be the time at which a constant hydrostatic pressure and a stable flow rate were obtained, use only the data obtained between Ts and 10 minutes for the flow rate calculation, and use the flow rate obtained between Ts and 10 minutes.
  • the value of Fs (T 0), ie the initial flow rate through the gel layer, was calculated.
  • Fs (t 0): flow rate [g / s] L0: Gel layer height [cm] ⁇ : Density of aqueous sodium chloride solution (1.003 [g / cm 3 ]) A: Area above the gel layer in the cell 41 (28.27 [cm 2 ]) ⁇ P: hydrostatic pressure applied to the gel layer (4920 [dyn / cm 2 ]) It is.
  • a glass tube 32 is inserted into the tank 31, and the lower end of the glass tube 32 can maintain a 0.69 wt% sodium chloride aqueous solution 33 at a height of 5 cm above the bottom of the swollen gel 44 in the cell 41.
  • a 0.69 wt% sodium chloride aqueous solution 33 in the tank 31 was supplied to the cell 41 through an L-shaped tube 34 with a cock 35.
  • a container 48 for collecting the passed liquid is disposed, and the collection container 48 is installed on an upper pan balance 49.
  • the cell 41 had an inner diameter of 6 cm, and a stainless steel wire mesh having an opening of 38 ⁇ m was installed on the bottom surface.
  • a glass filter 45 with good permeability is attached at the bottom so that the particulate water-absorbing agent or its swollen gel does not enter the hole 47. It was.
  • the cell 41 was placed on a table on which the cell was placed, and the surface of the table in contact with the cell was placed on a stainless steel wire mesh 43 that did not prevent liquid permeation.
  • the FSR water absorption rate
  • the water absorption rate is an index of the rate of absorbing the liquid of the water absorbing agent.
  • the water absorption rate is preferably high.
  • the particulate water-absorbing agent 1.000 ⁇ 0.0005 [g] is accurately weighed to 4 digits after the decimal point (Wc [g]), and the particles are placed in a 25 ml glass beaker (diameter 32 to 34 mm, height 50 mm).
  • the water-absorbing agent was placed so that the upper surface thereof was horizontal. If necessary, take measures such as tapping the beaker carefully to level the particulate water-absorbing agent.
  • 20 ml of a 0.9 wt% sodium chloride aqueous solution adjusted to 23 ⁇ 2.0 ° C. was weighed into a 50 ml glass beaker, and the weight of the aqueous solution was measured to 4 digits after the decimal point (Wd [g]).
  • the 0.9 wt% sodium chloride aqueous solution was quickly poured into a 25 ml beaker containing a particulate water-absorbing agent, and time measurement was started from the moment when the sodium chloride aqueous solution and the particulate water-absorbing agent contacted each other.
  • the liquid level in the beaker into which the sodium chloride aqueous solution was poured was visually observed from an angle of about 20 °, and the time (Th [sec]) until the liquid level was replaced from the aqueous solution by the particulate water-absorbing agent was measured.
  • the weight (We [g]) of the sodium chloride aqueous solution (beaker remaining amount) adhering to the beaker after pouring the sodium chloride aqueous solution was measured to 4 digits after the decimal point.
  • FSR water absorption rate [g / g / sec] was determined by the following equation. In addition, it measured 3 times about one sample, and made the average value the representative value.
  • the weight average particle diameter (D50) was measured according to the method described in International Publication No. 2004/066944 pamphlet.
  • a predetermined amount of the particulate water-absorbing agent is applied to a JIS standard sieve (JIS Z8801-1 (2000)) having openings of 850 ⁇ m, 710 ⁇ m, 600 ⁇ m, 500 ⁇ m, 425 ⁇ m, 300 ⁇ m, 212 ⁇ m, 150 ⁇ m, 106 ⁇ m, 45 ⁇ m, or these JIS standard sieves.
  • the logarithmic standard deviation ( ⁇ ) of the particle size distribution is expressed by the following formula, and the smaller the value of ⁇ , the narrower the particle size distribution.
  • the particles [% by weight] defined by the standard sieve classification are less than 150 ⁇ m with respect to the weight of particles passing through a JIS standard sieve (JIS Z8801-1 (2000)) having an opening of 150 ⁇ m and the total weight of the particulate water-absorbing agent. It is a ratio [% by weight]. In the present specification, it is also simply referred to as “particles less than 150 ⁇ m [wt%]” or “150 ⁇ m pass [%]”.
  • the L value (Lightness: lightness index) of the surface was measured with the spectral color difference meter. This value is defined as “brightness index before exposure”, and the higher the value, the whiter the color.
  • the object colors a and b (chromaticity) of other scales can be measured simultaneously by the same measuring method of the same apparatus.
  • the coloring evaluation result of the particulate water-absorbing agent stored for a period of one year or less is used as the initial color tone.
  • the above-mentioned paste sample container was filled with about 5 g of a particulate water-absorbing agent and adjusted to an atmosphere of 70 ⁇ 1 ° C. and a relative humidity of 65 ⁇ 1% (Espec Co., Ltd. small environmental tester, A paste sample container filled with particulate water-absorbing agent in type SH-641) was exposed for 7 days. This exposure is a 7 day color acceleration test. After the exposure, the L value (Lightness) a / b value of the surface was measured with the spectral color difference meter. This measured value is defined as coloration with time after the acceleration test.
  • Particulate water-absorbing agent 1.00 [g] was weighed into an aluminum cup having a bottom size of about 50 mm in diameter, and the total weight W8 [g] of the particulate water-absorbing agent and the aluminum cup was measured. Then, it was left to stand in an oven with an atmospheric temperature of 180 ° C. for 3 hours and dried. After 3 hours, the particulate water-absorbing agent and the aluminum cup were taken out of the oven and cooled to room temperature in a desiccator. Thereafter, the total weight W9 [g] of the particulate water-absorbing agent and the aluminum cup after drying was determined, and the water content was determined according to the following equation (8).
  • titration was performed with 0.1N NaOH aqueous solution until pH 10 was reached, and then titration was performed with 0.1N HCl aqueous solution until pH 2.7 was reached. At this time, titration amounts ([NaOH] ml, [HCl] ml) were determined. In addition, the same titration operation was performed on only 184.3 g of a 0.90% by weight sodium chloride aqueous solution, and empty titration amounts ([bNaOH] ml, [bHCl] ml) were obtained.
  • the soluble content of the water-containing gel-like water-absorbing agent can be calculated by the following equation 9 based on the average molecular weight of the monomer and the titration amount obtained by the above operation.
  • the average molecular weight of the monomer can be calculated using the neutralization rate obtained by titration. This neutralization rate is calculated by the following formula 10.
  • the deterioration rate is calculated by the following equation 11 from the soluble part of the particulate water-absorbing agent and the soluble part of the hydrogel water-absorbing agent.
  • [Urine resistance test] (Gel degradation test 2) Put 1 part by weight of the particulate water-absorbing agent into a 250 ml plastic container with a lid (Pack Ace made by Terraoka Co., Ltd.), add 25 parts by weight of simulated artificial urine, and then seal the particulate water-absorbing agent at a predetermined temperature and time. Deteriorated. Thereafter, it was evaluated whether the swollen gel flows when the 250 ml lidded plastic container is laid down and left for 10 minutes. In this test, the following two deterioration conditions were used.
  • Urine resistance test normal L-ascorbic acid concentration
  • Gel degradation test 2-1 [Gel degradation condition (1)] Simulated artificial urine: L-ascorbic acid 0.005 wt% physiological saline Deterioration temperature: 37 ° C Deterioration time: 24 hours (2) Urine resistance test (L-ascorbic acid 1000 times) (Gel degradation test 2-2) [Gel degradation condition (2)] Simulated artificial urine: L-ascorbic acid 5% by weight physiological saline Deterioration temperature: 90 ° C Deterioration time: 1 hour [Dust measurement] The amount of dust from the particulate water-absorbing agent was measured under the following conditions using a Hebach Dustmeter 2000 manufactured by Seishin Corporation.
  • the p-methoxyphenol contained in the particulate water-absorbing agent of the present invention is obtained by subjecting a filtrate obtained by carrying out the same operation except that the stirring time in the evaluation method for [soluble matter] is changed from 16 hours to 1 hour. It is required by analyzing. Specifically, p-methoxyphenol in the particulate water-absorbing agent can be obtained by analyzing the filtrate obtained by this operation by high performance liquid chromatography. Note that p-methoxyphenol is expressed in ppm (vs. particulate water absorbing agent).
  • reducing agent contained in particulate water-absorbing agent sodium hydrogen sulfite
  • a method for measuring sodium bisulfite is exemplified. In a 200 ml beaker, 50 g of pure water and 0.5 g of a particulate water-absorbing agent are placed and left for 1 hour. Next, after adding 50 g of methanol, 2.5 g of a solution obtained by dissolving 2 mmol of malachite green in an eluent described later is added.
  • the solution is stirred for about 30 minutes and then filtered, and the amount of the reducing agent contained in the particulate water-absorbing agent is determined by analyzing the filtrate by high performance liquid chromatography.
  • the eluent is adjusted in a ratio of 400 ml of methanol, 6 ml of n-hexane, 100 ml of 0.0M-2-N-morpholino-ethanesulfonic acid, sodium salt.
  • a calibration curve can be created by analyzing a particulate water-absorbing agent that does not contain a reducing agent and spiked with the reducing agent.
  • the chelating agent contained in the particulate water-absorbing agent of the present invention is analyzed for the filtrate obtained by performing the same operation except that the stirring time in the above-mentioned evaluation method of [soluble matter] is changed from 16 hours to 1 hour. It is required by that.
  • the chelating agent in the particulate water-absorbing agent can be obtained by analyzing the filtrate obtained by the operation by high performance liquid chromatography.
  • the amount of chelating agent is expressed in ppm (vs. particulate water absorbing agent).
  • the calibration curve can be prepared by analyzing a particulate water-absorbing agent that does not contain a chelating agent and spiked with the chelating agent.
  • Example 1-1 Using the apparatus shown in FIG. 3 described in US Pat. No. 7,265,190, a hydrogel crosslinked polymer was produced according to the following.
  • the monomer aqueous solution (1-1) adjusted to 40 ° C. was continuously supplied to the polymerization step using a metering pump.
  • 17.7 parts by weight of a 48 wt% aqueous sodium hydroxide solution (iron content 0.7 ppm (based on NaOH solid content)) was continuously mixed by line mixing.
  • the monomer temperature rose to 86 ° C. due to heat of neutralization.
  • the water-containing gel-like crosslinked polymer (1-1) was subdivided into about 1.5 mm with a meat chopper having a pore diameter of 22 mm.
  • the fragmented gel was spread and placed on a moving perforated plate of a continuous ventilation band dryer, and dried at 185 ° C. for 30 minutes to obtain a dried polymer (1-1).
  • the obtained dried polymer (1-1) is pulverized with a roll mill and then sieved with a sieving apparatus having a mesh screen having openings of 710 ⁇ m and 175 ⁇ m, whereby a water-absorbing resin powder of 175 to 710 ⁇ m (1 -1) was obtained.
  • Example 1-2 A particulate water-absorbing agent (in the same manner as in Example 1-1) except that the addition amount of the 30 wt% sodium hydrogen sulfite aqueous solution described in Example 1-1 was changed from 1.66 parts by weight to 3.33 parts by weight. 1-2) was obtained. Table 1 shows the physical properties of the obtained particulate water-absorbing agent (1-2).
  • Example 1-3 A water-absorbing agent obtained in the same manner as in Example 1-1 except that the addition amount of the 30% by weight sodium hydrogen sulfite aqueous solution described in Example 1-1 was changed from 1.66 parts by weight to 0.166 parts by weight. To 100 parts by weight, 0.6 part by weight of a 50% by weight aqueous sodium lactate solution was further added and mixed to obtain a particulate water-absorbing agent precursor (1-3). Next, the obtained particulate water-absorbing agent precursor (1-3) was left in a hot air dryer at 60 ° C. for 30 minutes, and then passed through a JIS standard sieve having a mesh opening of 710 ⁇ m. 1-3) was obtained. The water content of the obtained particulate water-absorbing agent (1-3) was 2.0% by weight. Table 1-1 shows the physical properties of the obtained particulate water-absorbing agent (1-3).
  • Example 1-4 In Example 1-3, the addition amount of the 30 wt% sodium hydrogen sulfite aqueous solution was changed from 0.166 parts by weight to 1.66 parts by weight, and the addition amount of the 50 wt% sodium lactate aqueous solution was changed from 0.6 parts by weight.
  • a particulate water-absorbing agent (1-4) was obtained in the same manner as in Example 1-3, except that the amount was changed to 0.1 parts by weight.
  • Table 1-1 shows the physical properties of the resulting particulate water-absorbing agent (1-4).
  • Example 1-5 In the same manner as in Example 1-3, except that the addition amount of the 30 wt% aqueous sodium hydrogen sulfite solution in Example 1-3 was changed from 0.166 parts by weight to 1.66 parts by weight. Agent (1-5) was obtained. Table 1 shows the physical properties of the obtained particulate water-absorbing agent (1-5).
  • Example 1-6 To 100 parts by weight of the surface-crosslinked water-absorbing resin powder (1-1) in Example 1-1, 0.33 parts by weight of a 30% by weight sodium hydrogen sulfite aqueous solution was added and mixed, and an aqueous aluminum sulfate solution (in terms of aluminum oxide) 8 wt%) 0.9 part by weight, 60% by weight sodium lactate aqueous solution 0.30 part by weight, and propylene glycol 0.02 part by weight mixed liquid 1.22 parts by weight is uniformly mixed to form particles A water-absorbing agent precursor (1-6) was obtained. Next, the obtained particulate water-absorbing agent precursor (1-6) was left in a hot air dryer at 60 ° C. for 30 minutes, and then passed through a JIS standard sieve having a mesh opening of 710 ⁇ m. 1-6) was obtained. Table 1 shows the physical properties of the resulting particulate water-absorbing agent (1-6).
  • Example 1-7 Using the apparatus shown in FIG. 3 described in US Pat. No. 7,265,190, a hydrogel crosslinked polymer was produced according to the following.
  • the monomer aqueous solution (1-7) adjusted to 40 ° C. was continuously supplied to the polymerization step using a metering pump.
  • a metering pump Prior to introduction into the belt polymerization machine, 17.7 parts by weight of a 48% by weight aqueous sodium hydroxide solution was continuously mixed by line mixing. At this time, the monomer temperature rose to 86 ° C. due to heat of neutralization.
  • 1.38 parts by weight of a 4% by weight aqueous sodium persulfate solution was continuously mixed by line mixing, and the resulting continuous mixture (1-7) was placed on a flat belt having weirs at both ends to a thickness of about 7. It supplied so that it might be set to 5 mm. Polymerization was continuously carried out for 3 minutes to obtain a hydrogel crosslinked polymer (1-7).
  • the hydrogel crosslinked polymer (1-7) was subdivided into about 1.5 mm with a meat chopper having a pore diameter of 22 mm.
  • the fragmented gel was spread and placed on a moving perforated plate of a continuous ventilation band dryer, and dried at 185 ° C. for 30 minutes to obtain a dried polymer (1-7).
  • the obtained dried polymer (1-7) is pulverized with a roll mill and then sieved with a sieving machine having a metal sieve mesh having openings of 710 ⁇ m and 175 ⁇ m, whereby a water absorbent resin powder having a particle size of 175 to 710 ⁇ m.
  • a body (1-7) was obtained.
  • Example 1-8 Supplying commercially available acrylic acid obtained by gas phase catalytic oxidation (Wako Pure Chemicals, reagent special grade; containing 200 ppm of p-methoxyphenol) to the bottom of a high-boiling-point impurity separation tower having 50 plates of non-weired perforated plates, Distillation was carried out at a reflux ratio of 1, followed by redistillation to obtain purified acrylic acid (1-8) comprising 99% by weight or more of acrylic acid and a trace amount of impurities (mainly water). The amount of p-methoxyphenol in purified acrylic acid (1-8) was ND (less than 1 ppm).
  • Acrylic acid (1-8) was obtained by adding 15 ppm of p-methoxyphenol to purified acrylic acid (1-8).
  • the monomer aqueous solution (1-8) was adjusted to 40 ° C. and continuously fed with a metering pump.
  • a metering pump To this monomer aqueous solution (1-8), 17.7 parts by weight of 48% by weight sodium hydroxide aqueous solution was continuously mixed by line mixing. At this time, the temperature of the monomer rose to 86 ° C. due to heat of neutralization.
  • 1.38 parts by weight of a 4% by weight aqueous sodium persulfate solution was continuously mixed by line mixing.
  • the continuous mixture (1-8) obtained by this line mixing was supplied onto a flat belt having weirs at both ends so that the thickness was about 7.5 mm, and polymerization was continuously carried out for 3 minutes. A gel-like crosslinked polymer (1-8) was obtained.
  • the hydrogel crosslinked polymer (1-8) was subdivided into about 1.5 mm with a meat chopper having a pore diameter of 22 mm. This fragmented gel was spread and placed on a moving perforated plate of a continuous ventilation band dryer, and dried at 185 ° C. for 30 minutes to obtain a dried polymer (1-8).
  • the obtained dried polymer (1-8) was pulverized with a roll mill, and then sieved with a sieving apparatus having a metal sieve mesh having openings of 710 ⁇ m and 175 ⁇ m, whereby a 175 to 710 ⁇ m water absorbent resin powder (1 -8) was obtained.
  • the obtained particulate water-absorbing agent precursor (1-8) was left in a hot air dryer at 60 ° C. for 30 minutes, and then passed through a JIS standard sieve having a mesh opening of 710 ⁇ m. 1-8) was obtained.
  • Table 1 shows the physical properties of the obtained particulate water-absorbing agent (1-8).
  • Example 1-9 The adjusted acrylic acid (1-9) was obtained by adding 200 ppm of p-methoxyphenol to the purified acrylic acid (1-8) described in Example 1-8.
  • Example 1-1 A chelating agent was not used, and the same procedure as described in Example 1-1 was performed except that the addition amount of the 30% by weight aqueous sodium hydrogen sulfite solution was changed from 1.66 parts by weight to 0.166 parts by weight. A comparative particulate water-absorbing agent (1-1) was obtained. Table 1 shows the physical properties of the obtained comparative particulate water-absorbing agent (1-1).
  • Comparative Example 1-2 A comparative particulate water-absorbing agent (1-2) was obtained in the same manner as described in Example 1-1 except that the 30 wt% aqueous sodium hydrogen sulfite solution was not used. Table 1 shows the physical properties of the obtained comparative particulate water-absorbing agent (1-2).
  • Comparative Example 1-3 With respect to 100 parts by weight of the comparative particulate water-absorbing agent (1-2) obtained in Comparative Example 1-2, 0.9 part by weight of an aqueous aluminum sulfate solution (8% by weight in terms of aluminum oxide) and 60% by weight aqueous sodium lactate solution By uniformly mixing 1.22 parts by weight of a mixed solution consisting of 0.30 parts by weight and 0.02 parts by weight of propylene glycol, a comparative particulate water-absorbing agent precursor (1-3) was obtained.
  • the comparative particulate water-absorbing agent precursor (1-3) thus obtained is left in a hot air dryer at 60 ° C. for 30 minutes, and then passed through a JIS standard sieve having a mesh opening of 710 ⁇ m. Agent (1-3) was obtained.
  • Table 1 shows the physical properties of the obtained comparative particulate water-absorbing agent (1-3).
  • Comparative Example 1-4 Comparative surface-crosslinked water-absorbing resin powder (1) obtained in the same manner as in Example 1-1 except that the content of p-methoxyphenol in acrylic acid described in Example 1-1 was changed from 70 ppm to 270 ppm. -4) To 100 parts by weight, 0.166 parts by weight of a 30% by weight aqueous sodium hydrogen sulfite solution was uniformly added and mixed to obtain a comparative particulate water-absorbing agent precursor (1-4). Next, the obtained comparative particulate water-absorbing agent precursor (1-4) is left in a hot air drier at 60 ° C. for 30 minutes, and then passed through a JIS standard sieve having a mesh opening of 710 ⁇ m. Agent (1-4) was obtained. Table 1 shows the physical properties of the comparative particulate water-absorbing agent (1-4).
  • Example 1-5 The comparative example with many chelating agents is shown with reference to Patent Document 29 and Examples 4 and 5 thereof. That is, the addition amount of a 1% by weight diethylenetriaminepentaacetic acid trisodium acetate (abbreviation: DTPA ⁇ 3Na) aqueous solution is 0.22 to 25.8 parts by weight, and the addition amount of deionized water is 33.6 to 8. The same procedure as in Example 1-1 was carried out except that the amount was changed to 0 wt. And the addition amount of the 30 wt.% Sodium hydrogen sulfite aqueous solution was changed from 1.66 wt.
  • DTPA ⁇ 3Na diethylenetriaminepentaacetic acid trisodium acetate
  • a comparative particulate water-absorbing agent (1-5) containing 6000 ppm and 1.0% by weight of an inorganic reducing agent was obtained.
  • the obtained comparative particulate water-absorbing agent (1-5) had a water content of 1.9% by weight.
  • Table 1 shows the physical properties of the comparative particulate water-absorbing agent (1-5).
  • Example 1-10 A particulate water-absorbing agent (1) was obtained in the same manner as in Example 1-7, except that the adjusted acrylic acid in Example 1-7 was changed to the adjusted acrylic acid (1-9) described in Example 1-9. -10) was obtained. Table 1 shows the physical properties of the obtained particulate water-absorbing agent (1-10).
  • Example 1-11 A particulate water-absorbing agent (Example 1-7) was prepared in the same manner as in Example 1-7, except that the prepared acrylic acid described in Example 1-7 was changed to the adjusted acrylic acid (1-8) described in Example 1-8. 1-11) was obtained. Table 1 shows the physical properties of the obtained particulate water-absorbing agent (1-11).
  • Example 1-12 Example 1-11, except that the addition amount of 31 wt% ethylenediaminetetra (methylenephosphonic acid) 5 sodium (abbreviation: EDTMPA ⁇ 5Na) aqueous solution was changed from 0.03 parts by weight to 0.07 parts by weight. As a result, a particulate water-absorbing agent (1-12) was obtained. Table 1 shows the physical properties of the obtained particulate water-absorbing agent (1-12).
  • Table 2 shows the deterioration rates obtained as a result of the weather resistance test performed on the particulate water-absorbing agent (1-1) described in Example 1-1.
  • Example 1-6 In place of acrylic acid with the p-methoxyphenol content adjusted to 70 ppm described in Example 1-1, p-methoxyphenol obtained in Example 1-8 was converted to ND purified acrylic acid (1-8). Polymerization was carried out in the same manner as in Example 1-1 except that comparative adjusted acrylic acid (1-6) obtained by adding 1 ppm of p-methoxyphenol was used, and a comparative particulate water absorbing agent (1 -6) was obtained. The obtained comparative particulate water-absorbing agent (1-6) had p-methoxyphenol of ND (less than 1 ppm). Table 2 shows the results of a weather resistance test using the obtained comparative particulate water-absorbing agent (1-6).
  • Table 3 shows the results obtained by measuring the residual p-methoxyphenol, residual chelating agent, and residual sodium bisulfite in the particulate water-absorbing agents (1-1), (1-8) and (1-9).
  • Table 3 shows the results of measuring the residual p-methoxyphenol, the residual chelating agent, and the residual sodium hydrogen sulfite of the comparative particulate water-absorbing agents (1-4) and (1-5).
  • Patent Document 17 European Patent No. 1645596 does not disclose water-insoluble inorganic fine particles, a specific amount of p-methoxyphenol, and a specific water content (3 to 15% by weight).
  • Patent Document 17 discloses alkylhydroxyanisole (such as butyl) as an organic antioxidant (paragraph [0019] [Example 6]). Therefore, in order to show the significance of the present invention, a comparative particulate water-absorbing agent (1-8) was obtained according to Example 6 of Patent Document 17 and corresponding Japanese Patent No. 3940103.
  • the color tone (initial color tone) of the 20-fold swollen gel of the comparative particulate water-absorbing agent (1-8) was measured using LabScan XE manufactured by Hunter Lab. Table 4 shows the measurement results.
  • the color tone measurement was performed by filling a test substance into a white propylene container having a diameter of 5.0 cm and a height of 1.2 cm.
  • the color tone of the white propylene container described above as a blank was L value: 54.73, a value: 0.16, and b value: -0.50.
  • the powder of the comparative particulate water-absorbing agent (1-8) according to Patent Document 17 (1 part by weight of butylhydroxyanisole) was colored for 7 days as in Examples 1-1 to 1-12 and Table 2 thereof.
  • An accelerated test 70 ° C., RH 65% was conducted.
  • the particulate water-absorbing agent of the present invention maintained a substantially white color, whereas the comparative particulate water-absorbing agent (1-8) was colored orange.
  • the color tone (color tone with time) was measured. Table 5 shows the measurement results.
  • the comparative particulate water-absorbing agent (1-8) after the 7-day coloring acceleration test had a strange odor.
  • Example 1-15 The particulate water-absorbing agent (1-1) obtained in Example 1-1 was treated in the same manner as in Comparative Example 1-8, whereby a 20-fold swelling gel (1) of the particulate water-absorbing agent (1-1) was obtained. -15) was obtained. In the obtained swollen particulate water-absorbing agent (1-15), the 20-fold swollen gel of the comparative particulate water-absorbing agent (1-8) according to Patent Document 17 (1 part by weight of butylhydroxyanisole) turns yellow. On the other hand, the 20-fold swollen gel (1-15) of the particulate water-absorbing agent (1-1) remained a transparent water-containing gel.
  • Example 1-16 The water absorption rate (FSR) of the particulate water-absorbing agent (1-1) having a water content of 1.8% by weight obtained in Example 1-1 was measured to be 0.23 [g / g / sec]. It was. In order to investigate the influence of the water content, 10% by weight of water was added to the particulate water-absorbing agent (1-1) and further dried at 80 ° C. under reduced pressure to obtain a particulate water-absorbing agent having a water content of 3.9% by weight ( 1-15) was obtained.
  • FSR water absorption rate
  • the water absorption rate (FSR) of the obtained particulate water-absorbing agent (1-15) having a water content of 3.9% by weight is 0.27 [g / g / sec], which improves the water content, especially the water content It can be seen that the water absorption rate of the water absorbing agent is improved by setting the content to 3 to 15% by weight.
  • a method for producing a water-absorbing agent having a water content of 3 to 15% by weight will be described in Examples 3-1 to 3-13.
  • Examples 1-1 to 1-16 and Tables 1 to 5 relate to the production method 1 of the particulate water-absorbing agent of the present invention, and acrylic acid (salt) containing 10 to 200 ppm of methoxyphenols.
  • a polymerization step of a monomer aqueous solution as a main component, a drying step of a hydrogel crosslinked polymer obtained by polymerization, a surface crosslinking step, and a step of adding 0.001 to 0.5% by weight of a chelating agent are included.
  • a method for producing a particulate water-absorbing agent comprising the step of adding an inorganic reducing agent after the surface cross-linking step.
  • the water-absorbing agent according to the present invention is excellent in color tone with time and initial color tone, and is 3% by weight by adding an inorganic reducing agent after the surface crosslinking step. Even with a low water content of less than 3% or a low water content of less than 3% by high-temperature surface crosslinking (150 to 250 ° C.), the obtained water-absorbing agent had no unpleasant odor. Such odor is not simply the odor of the raw material used (particularly, the inorganic reducing agent), but is a composite odor in the manufacturing process of the water-absorbing resin, the inorganic reducing agent, and was not expected to occur. I found a new problem and solved it above.
  • Comparative Examples 1-1 to 1-3 containing only one of the chelating agent and the inorganic reducing agent the color tone with time was poor even when the amount of methoxyphenol was in the range of 5 to 60 ppm.
  • Comparative Example 1-4 (82 ppm in the water-absorbing agent) in which the amount of methoxyphenol is outside the range of 5 to 60 ppm
  • Comparative Example 1-6 (1 ppm with acrylic acid and ND in the obtained water-absorbing agent), the color tone with time Poor or weather resistance (see soluble content after accelerated test in Table 2).
  • Patent Document 29 describes the specific water content (3 to 15% by weight) of the present invention as well as the specific addition amount (0.001 to 0.5% by weight of a compound containing a phosphorus atom or a sulfur-based reducing agent, 0% .001 to 0.1% by weight), in Example 5 of Patent Document 29, 1.0% by weight of 1-hydroxyethylidene-1,1-diphosphonic acid was added, and in Example 4, 1-hydroxyethylidene was also used.
  • Example 4 1-hydroxyethylidene was also used.
  • the use of a total of 2.0% by weight of 1,1-diphosphonic acid is disclosed, as shown in Comparative Example 1-5, an example of using such a chelating agent exceeding 0.5% by weight is the use of the obtained water-absorbing agent. We found that it adversely affects coloring, and solved it by controlling the moisture content within a specific range.
  • the specific water content in the water-absorbing agent is preferable from the viewpoint of improving the water absorption rate.
  • the novel water-absorbing agent of the present invention is a particulate water-absorbing agent mainly composed of a polyacrylic acid (salt) -based water-absorbing resin, and includes a chelating agent, an inorganic reducing agent,
  • the content of the chelating agent is 0.001 to 0.5% by weight, and the content of methoxyphenols is 5 to 60 ppm.
  • the novel water-absorbing agent of the present invention shown in the above examples preferably has an absorption capacity without load (CRC) of 25 [g / g] or more and an absorption capacity under pressure (AAP of 4.83 kPa) of 20 [g / g].
  • the saline flow conductivity is 30 [ ⁇ 10 ⁇ 7 ⁇ cm 3 ⁇ s ⁇ g ⁇ 1 ] or more.
  • the water-absorbing agent has an FSR in the range of about 0.25 ( ⁇ 0.02) [g / g / sec], the residual monomer is 400 ppm or less, and the weight average particle diameter ( D50) was also about 360 to 380 ⁇ m.
  • the water absorbing agent preferably further contains an ⁇ -hydroxycarboxylic acid compound.
  • a polyvalent metal salt and / or a cationic polymer are further included.
  • Example 2-1 In a kneader equipped with two sigma-type blades, the monomer concentration is 38% by weight and the neutralization rate is 75% by mole consisting of sodium acrylate neutralized with NaOH containing 0.7 ppm of iron, acrylic acid and water.
  • a monomer aqueous solution was prepared. Acrylic acid having a p-methoxyphenol content adjusted to 70 ppm was used.
  • polyethylene glycol diacrylate (average number of ethylene glycol units: 9) was dissolved as an internal cross-linking agent so as to be 0.045 mol% (with respect to the monomer).
  • the obtained hydrogel crosslinked polymer (2-1) was dried with a hot air dryer at 170 ° C. for about 60 minutes. Next, the dried product was pulverized with a roll mill pulverizer, classified with a sieve having an opening of 850 ⁇ m and 150 ⁇ m (the top and bottom of the sieve were removed), and water-absorbing resin particles having a water content of 3% by weight and a weight average particle diameter of 370 ⁇ m (2- 1) was obtained.
  • the obtained water-absorbing resin particles (2-1) contained substantially no particles having a particle diameter of 850 ⁇ m or more and 2% by weight of fine particles having a particle diameter of less than 150 ⁇ m.
  • the obtained surface cross-linked water-absorbent resin powder (2-1) After cooling the obtained surface cross-linked water-absorbent resin powder (2-1), 30% by weight aqueous sodium hydrogen sulfite solution 1.66 wt. Per 100 parts by weight of the surface cross-linked water-absorbent resin powder (2-1). And 0.44 parts by weight of 45 wt% diethylenetriaminepentasodium acetate aqueous solution were added and mixed to obtain a particulate water-absorbing agent precursor (2-1). Next, the obtained particulate water-absorbing agent precursor (2-1) was left in a hot air dryer at 60 ° C. for 30 minutes, and then passed through a JIS standard sieve having an opening of 810 ⁇ m.
  • silica trade name: Aerosil 200CF-5, manufactured by Nippon Aerosil Co., Ltd.
  • a particulate water-absorbing agent (2-1) was obtained.
  • Table 6 shows the physical properties of the obtained particulate water-absorbing agent (2-1). Note that L, a, and b of silica were 93.6, -0.8, and -3.6, respectively, which were whiter than the water-absorbent resin.
  • Example 2-2 Except that the amount of silica added to 100 parts by weight of the surface-crosslinked water-absorbent resin powder (2-1) in Example 2-1 was changed from 0.3 part by weight to 1.0 part by weight, Example 2- In the same manner as in Example 1, a particulate water-absorbing agent (2-2) was obtained. Table 6 shows the physical properties of the obtained particulate water-absorbing agent (2-2).
  • Example 2-3 Except that the amount of silica added to 100 parts by weight of the surface-crosslinked water-absorbing resin powder (2-1) in Example 2-1 was changed from 0.3 parts by weight to 0.5 parts by weight, Example 2- In the same manner as in Example 1, a particulate water-absorbing agent (2-3) was obtained. Table 6 shows the physical properties of the obtained particulate water-absorbing agent (2-3).
  • Example 2 was the same as Example 2 except that the amount of silica added to 100 parts by weight of the surface-crosslinked water-absorbing resin powder (2-1) was changed from 0.3 parts by weight to 0.05 parts by weight. In the same manner as in Example 1, a particulate water-absorbing agent (2-4) was obtained. Table 6 shows the physical properties of the particulate water-absorbing agent (2-4).
  • Example 2-5 In Example 2-1, the addition amount of 45 wt% diethylenetriamine pentasodium acetate aqueous solution was changed from 0.44 parts by weight to 0.022 parts by weight with respect to 100 parts by weight of the surface crosslinked water absorbent resin powder (2-1). Except for the above, a particulate water-absorbing agent (2-5) was obtained in the same manner as in Example 2-1. Table 6 shows the physical properties of the resulting particulate water-absorbing agent (2-5).
  • Example 2-6 In Example 2-1, the addition amount of 45 wt% diethylenetriamine pentasodium acetate aqueous solution was changed from 0.44 parts by weight to 2.2 parts by weight with respect to 100 parts by weight of the surface crosslinked water absorbent resin powder (2-1). Except for the above, a particulate water-absorbing agent (2-6) was obtained in the same manner as in Example 2-1. Table 6 shows the physical properties of the particulate water-absorbing agent (2-6) so obtained.
  • the monomer aqueous solution (2-2) adjusted to 40 ° C. was continuously supplied to the polymerization step using a metering pump.
  • a metering pump Prior to introduction into the belt polymerization machine, 18.5 parts by weight of a 48% by weight aqueous sodium hydroxide solution was continuously mixed by line mixing. At this time, the monomer temperature rose to 86 ° C. due to heat of neutralization.
  • 1.66 parts by weight of a 4% by weight sodium persulfate aqueous solution was continuously mixed by line mixing, and the obtained continuous mixture (2-2) was formed on a flat belt having weirs at both ends to a thickness of about 7. It supplied so that it might be set to 5 mm. Polymerization was carried out continuously for 3 minutes to obtain a hydrogel crosslinked polymer (2-2).
  • the hydrogel crosslinked polymer (2-2) was subdivided into about 1.5 mm with a meat chopper having a pore diameter of 22 mm. This fragmented gel was spread and placed on a moving perforated plate of a continuous ventilation band dryer, and dried at 185 ° C. for 30 minutes to obtain a dried polymer (2-2).
  • the obtained dried polymer (2-2) was pulverized with a roll mill, and then classified with a sieve having an opening of 850 ⁇ m and 150 ⁇ m (the top and bottom of the sieve were removed), and the water absorption was 3% by weight and the weight average particle diameter was 370 ⁇ m.
  • Resin particles (2-2) were obtained.
  • the obtained water-absorbing resin particles (2-2) contained substantially no particles having a particle diameter of 850 ⁇ m or more and 2% by weight of fine particles having a particle size of less than 150 ⁇ m.
  • the obtained surface cross-linked water-absorbent resin powder (2-2) After cooling the obtained surface cross-linked water-absorbent resin powder (2-2), 1.66 wt.% Of a 30 wt% sodium hydrogen sulfite aqueous solution is added to 100 parts by weight of the surface cross-linked water-absorbent resin powder (2-2). And 0.44 parts by weight of 45 wt% diethylenetriaminepentasodium acetate aqueous solution were added and mixed to obtain a particulate water-absorbing agent precursor (2-2). Next, the obtained particulate water-absorbing agent precursor (2-2) was left in a hot air dryer at 60 ° C. for 30 minutes, and then passed through a JIS standard sieve having an opening of 810 ⁇ m.
  • Example 2-8 In Example 2-1, except that the addition amount of 30 wt% sodium hydrogen sulfite aqueous solution was changed from 1.66 parts by weight to 0.22 parts by weight with respect to 100 parts by weight of the surface crosslinked water absorbent resin powder (2-1). Gave a particulate water-absorbing agent (2-8) in the same manner as in Example 2-1. Table 6 shows the physical properties of the resulting particulate water-absorbing agent (2-8).
  • Example 2-9 In Example 2-1, except that the addition amount of the 30 wt% sodium hydrogen sulfite aqueous solution was changed from 1.66 parts by weight to 22 parts by weight with respect to 100 parts by weight of the surface crosslinked water absorbent resin powder (2-1). A particulate water-absorbing agent (2-9) was obtained in the same manner as in Example 2-1. Table 6 shows the physical properties of the particulate water-absorbing agent (2-9) so obtained.
  • Example 2-10 In the same manner as in Example 2-1, except that 3 parts by weight of water was further added to 100 parts by weight of the surface-crosslinked water-absorbing resin powder (2-1) in Example 2-1. Agent (2-10) was obtained. Table 6 shows the physical properties of the particulate water-absorbing agent (2-10) so obtained.
  • Example 2-11 For 100 parts by weight of the surface-crosslinked water-absorbent resin powder (2-1) in Example 2-1, 1.8 parts by weight of 50% by weight aluminum sulfate aqueous solution, 0.55 parts by weight of 60% sodium lactate aqueous solution, A particulate water-absorbing agent (2-11) was obtained in the same manner as in Example 2-1, except that a mixed solution of 0.05 part by weight of propylene glycol was added. Table 6 shows the physical properties of the particulate water-absorbing agent (2-11).
  • Example 2-12 In Example 2-1, the addition amount of polyethylene glycol diacrylate (average number of ethylene glycol units: 9) was changed from 0.035 mol% (monomer) to 0.023 mol%, and water-absorbing resin particles (2- Classification was performed so that the weight average particle diameter of 1) was 350 ⁇ m, and the heat treatment conditions in the surface crosslinking step were changed from 208 ° C. for 40 minutes to 200 ° C. for 35 minutes, as in Example 2-1. In the same manner, a particulate water absorbing agent (2-12) was obtained. Table 6 shows the physical properties of the particulate water-absorbing agent (2-12) so obtained.
  • Comparative Example 2-1 A comparative particulate water-absorbing agent (2-1) was obtained in the same manner as in Example 2-1 except that 0.22 parts by weight of 45% by weight diethylenetriaminepentasodium acetate aqueous solution was not added. Table 6 shows the physical properties of the comparative particulate water-absorbing agent (2-1).
  • Example 2-1 except that 1.66 parts by weight of 30% by weight aqueous sodium hydrogen sulfite solution was not added and the addition amount of silica was changed from 0.3 parts by weight to 0.5 parts by weight
  • a comparative particulate water-absorbing agent (2-2) was obtained.
  • Table 6 shows the physical properties of the comparative particulate water-absorbing agent (2-2).
  • Comparative Example 2-3 Comparative particulate water-absorbing agent (2-3) in the same manner as Comparative Example 2-2, except that 0.5 part by weight of silica (trade name: Aerosil 200CF-5, manufactured by Nippon Aerosil Co., Ltd.) was not added. Got. Table 6 shows the physical properties of the comparative particulate water-absorbing agent (2-3).
  • Example 2-13 In Example 2-1, the same procedure as in Example 2-1 was performed except that 0.3 part by weight of silica (trade name: Aerosil 200CF-5, manufactured by Nippon Aerosil Co., Ltd.) was not added. 2-13) was obtained. Table 6 shows the physical properties of the particulate water-absorbing agent (2-13) so obtained.
  • silica trade name: Aerosil 200CF-5, manufactured by Nippon Aerosil Co., Ltd.
  • Example 2-1 Although the AAP (28 [g / g]) in Example 2-1 was improved to 31 [g / g] (Example 2-13), the Vortex (water absorption rate) was 50 seconds (Example 2- 1) to 64 seconds (Example 2-13), and further, urine resistance (1000 times the amount of deteriorated component) became “flowing (Example 2-13)”. It can be seen that water-insoluble inorganic fine particles not disclosed in Patent Document 17 and the like are important for urine resistance and water absorption rate (Vortex).
  • Example 2-14 In Example 2-1, a particulate water absorbing agent (2-14) was obtained in the same manner as in Example 2-1, except that p-methoxyphenol was not added to the acrylic acid during polymerization.
  • Table 6 shows the physical properties of the particulate water-absorbing agent (2-14).
  • the deterioration rate of Example 2-1 70 ppm of p-methoxyphenol in acrylic acid
  • that of Example 2-1 (0 ppm in acrylic acid and 0 ppm in the water absorbent) was 27.
  • Table 2 when p-methoxyphenol did not satisfy the present application, the weather resistance was lowered.
  • Table 7 It can be seen that a small amount of p-methoxyphenol which is not disclosed in Patent Document 17 is important for weather resistance.
  • Examples 2-1 to 2-14 and Tables 6 to 7 relate to the production method 2 of the particulate water-absorbing agent of the present invention, and a polymerization step of an aqueous monomer solution mainly composed of acrylic acid (salt) And a method for producing a particulate water-absorbing agent comprising a polyacrylic acid (salt) water-absorbing resin as a main component, comprising a drying step of a hydrogel crosslinked polymer obtained by polymerization and a surface crosslinking step.
  • the water-absorbing agent according to the present invention is excellent in anti-coloring property, urine resistance, and absorption rate.
  • Comparative Examples 2-1 to 2-3 in which only one of the chelating agent and the inorganic reducing agent is added, the color tone with time is poor.
  • Comparative Examples 2-1 and 2-3 to which only one of the water-insoluble inorganic fine particles and the chelating agent is added have poor urine resistance.
  • Comparative Example 2-3 not containing water-insoluble inorganic fine particles (silica) has a low absorption rate.
  • the dust content was 6 mg at a water content of 4.1% by weight in Example 2-10, the dust content was 21 mg at a water content of 2.0% by weight in Example 2-1, and the water content of Comparative Example 2-3. Compared with the dust amount of 40 mg at a rate of 1.7%, the dust amount is drastically reduced at a moisture content of 3.0% by weight or more.
  • the novel water-absorbing agent (second water-absorbing agent) of the present invention shown in the above examples is a particulate water-absorbing agent mainly composed of a polyacrylic acid (salt) -based water-absorbing resin, and is a chelating agent. And an inorganic reducing agent, the content of the chelating agent is 0.001 to 0.5% by weight, and contains water-insoluble inorganic fine particles.
  • the novel water-absorbing agent of the present invention according to the above-mentioned embodiment preferably has an absorption capacity without load (CRC) of 25 [g / g] or more and a water absorption capacity under pressure (AAP of 2.0 kPa) of 25 [g / g].
  • the Vortex water absorption rate is 60 seconds or less.
  • a water-absorbing agent may optionally contain methoxyphenols (particularly p-methoxyphenol), but in the range of 5 to 60 ppm as in the case of (1) and the novel water-absorbing agent (first water-absorbing agent) of the present invention ( In the above embodiment, the weather resistance and coloring are further improved.
  • the novel water-absorbing agent (second water-absorbing agent) of the present invention may have a water content of less than 3% by weight, like the first water-absorbing agent, but preferably satisfies (3) and falls within the range of 3 to 15% by weight. is there.
  • These water-absorbing agents are white without initial and coloration, have high water absorption rate (Vortex), and high absorption capacity under pressure (AAP). Therefore, even when used in high-concentration paper diapers with little pulp, high liquid diffusion and little The return amount (Re-wet) provides a good paper diaper without the problem of coloring due to the water-absorbing agent.
  • Acrylic acid (3-1) was obtained by adding 70 ppm of p-methoxyphenol to purified acrylic acid (3-1).
  • [Comparative Example 3-1] Prepared acrylic acid (3-1) 408 obtained in Production Example 3-1 in a reactor formed by attaching a cover to a jacketed stainless steel double-arm kneader with two sigma blades and an internal volume of 10 liters .4 g, the prepared acrylic acid (3-1) obtained in Production Example 3-1 was diluted with pure water and neutralized with an aqueous sodium hydroxide solution (iron content 0.7 ppm (vs. NaOH solid content)). The 3721.9 g of 37 wt% sodium acrylate aqueous solution obtained in the above, 724.2 g of pure water, and 4.74 g of polyethylene glycol diacrylate (molecular weight 523) were dissolved to obtain a reaction solution.
  • this reaction solution was degassed for 30 minutes in a nitrogen gas atmosphere. Subsequently, 29.5 g of a 10 wt% sodium persulfate aqueous solution and 11.3 g of a 0.1 wt% L-ascorbic acid aqueous solution were added to the reaction solution with stirring. Polymerization started after about 25 seconds. Then, polymerization was performed at 25 ° C. or more and 95 ° C. or less while pulverizing the generated gel, and a hydrous gel-like crosslinked polymer (C1-a) was taken out 30 minutes after the start of the polymerization. The obtained hydrogel crosslinked polymer was subdivided to have a diameter of about 5 mm or less. The solid content of the hydrogel crosslinked polymer (C1-a) (calculated from loss on drying at 180 ° C. for 3 hours) was 37.5% by weight.
  • the hydrogel crosslinked polymer (C1-a) is spread on a 50-mesh wire mesh, dried with hot air at 170 ° C. for 65 minutes, the dried product is pulverized using a roll mill, and further classified with a JIS standard sieve having an opening of 850 ⁇ m.
  • amorphous crushed water-absorbent resin particles (C1-c) having a weight average particle diameter (D50) of 371 ⁇ m and a logarithmic standard deviation of particle size distribution ( ⁇ ) of 0.34 were obtained.
  • the centrifuge retention capacity (CRC) of the water-absorbent resin particles (C1-c) was 46 (g / g), and the water-soluble content was 18% by weight.
  • Example 3-1 Polymerization was conducted in the same manner as in Comparative Example 3-1, thereby obtaining a hydrogel crosslinked polymer (1-a). While adding a 0.375 wt% aqueous sodium hydrogen sulfite solution at a feed rate of 30 [g / min], the obtained hydrogel polymer (1-a) was fed at a feed rate of 600 [g / min] with a meat chopper (MEAT). -CHOPPER TYPE: 12VR-400KSOX Iizuka Kogyo Co., Ltd., die hole diameter: 11mm, hole number: 10, die thickness 8mm) By mixing (500 ppm with a reducing agent), a finely divided hydrogel crosslinked polymer (1-b) was obtained.
  • MEAT meat chopper
  • This finely divided hydrogel crosslinked polymer (1-b) is spread on a 50 mesh wire net, dried with hot air at 170 ° C. for 65 minutes, and the dried product is pulverized using a roll mill, and further has an opening of 850 ⁇ m.
  • amorphous crushed water-absorbent resin particles (1-c) having a weight average particle diameter (D50) of 371 ⁇ m and a logarithmic standard deviation of particle size distribution ( ⁇ ) of 0.34 were obtained.
  • the water-absorbent resin particles (1-c) had a centrifuge retention capacity (CRC) of 46 (g / g) and a water-soluble content of 18% by weight.
  • Example 3-2 In the same manner as in Example 3-1, except that the feed rate of the 0.375 wt% sodium hydrogen sulfite aqueous solution was changed from 30 [g / min] to 12 [g / min], the particulate water absorbing agent (3-2 ) The analysis results of the particulate water-absorbing agent (3-2) are shown in Tables 8 and 9.
  • Example 3-3 0.5 wt% ethylenediaminetetra (methylenephosphonic acid) 5 sodium (abbreviation: EDTMPA ⁇ 5Na) aqueous solution was changed to 2.5 wt% ethylenediaminetetra (methylenephosphonic acid) 5 sodium (abbreviation: EDTMPA ⁇ 5Na) aqueous solution, Water-absorbing resin particles (3-e) were obtained in the same manner as in Example 3-1, except that the addition amount was 2.0 parts by weight with respect to 100 parts by weight of the water-absorbing resin particles.
  • Example 3-4 0.5 wt% ethylenediaminetetra (methylenephosphonic acid) 5 sodium (abbreviation: EDTMPA ⁇ 5Na) aqueous solution was changed to 2.5 wt% ethylenediaminetetra (methylenephosphonic acid) 5 sodium (abbreviation: EDTMPA ⁇ 5Na) aqueous solution,
  • a particulate water-absorbing agent (3-4) was obtained in the same manner as in Example 3-1, except that the addition amount was 4.0 parts by weight with respect to 100 parts by weight of the water-absorbent resin particles.
  • the analysis results of the particulate water absorbing agent (3-4) are shown in Tables 8 and 9.
  • Example 3-5 The concentration of the 0.375 wt% sodium hydrogen sulfite aqueous solution was changed to 0.1 wt%, the feed rate was changed from 30 [g / min] to 22.5 [g / min], and 0.5 wt% ethylenediamine Tetra (methylenephosphonic acid) 5 sodium (abbreviation: EDTMPA ⁇ 5Na) aqueous solution was changed to 2.5 parts by weight ethylenediaminetetra (methylenephosphonic acid) 5 sodium (abbreviation: EDTMPA ⁇ 5Na) aqueous solution, and the amount added was
  • a particulate water-absorbing agent (3-5) was obtained in the same manner as in Example 3-1, except that the amount was 2.0 parts by weight with respect to 100 parts by weight of the resin particles.
  • the analysis results of the particulate water absorbing agent (3-5) are shown in Tables 8 and 9.
  • Example 3-6 The feed rate of the 0.375 wt% sodium hydrogen sulfite aqueous solution was changed from 30 [g / min] to 60 [g / min], and 0.5 wt% ethylenediaminetetra (methylenephosphonic acid) 5 sodium (abbreviation: EDTMPA ⁇ 5Na )
  • EDTMPA ⁇ 5Na ethylenediaminetetra (methylenephosphonic acid) 5 sodium
  • Example 3-7 Example 3-6 except that the concentration of the 0.375 wt% sodium hydrogen sulfite aqueous solution was changed to 3.75 wt% and the feed rate was changed from 60 [g / min] to 30 [g / min]. Similarly, a particulate water-absorbing agent (3-7) was obtained. The analysis results of the particulate water absorbing agent (3-7) are shown in Tables 8 and 9.
  • Example 3-8 A particulate water-absorbing agent (3-8) was prepared in the same manner as in Example 3-7 except that the feed rate of the 3.75 wt% aqueous sodium hydrogen sulfite solution was changed from 30 [g / min] to 60 [g / min]. ) The analysis results of the particulate water absorbing agent (3-8) are shown in Tables 8 and 9.
  • Modified acrylic acid (3-2) was obtained by changing the amount of p-methoxyphenol added to the purified acrylic acid described in Production Example 3-1 from 70 ppm to 10 ppm.
  • a water-absorbing resin particle (9-d) having a cross-linked surface was obtained in the same manner as in Example 3-1, except that the prepared acrylic acid (3-2) was used.
  • a particulate water-absorbing agent (3-9) Got By adding 0.3 parts by weight of silica gel (trade name: Aerosil 200, manufactured by Nippon Aerosil Co., Ltd.) to 100 parts by weight of the obtained water-absorbent resin particles (9-e), a particulate water-absorbing agent (3-9) Got.
  • the analysis results of the particulate water absorbing agent (3-9) are shown in Tables 8 and 9.
  • the deterioration rate of the particulate water-absorbing agent (3-9) according to the weather resistance promotion test was 12%.
  • Adjusted acrylic acid (3-3) was obtained by changing the amount of p-methoxyphenol added to the purified acrylic acid described in Production Example 3-1 from 70 ppm to 200 ppm.
  • a water-absorbing resin particle (10-d) having a cross-linked surface was obtained in the same manner as in Example 3-1, except that the prepared acrylic acid (3-3) was used.
  • Example 3-11 The concentration of the 0.375 wt% sodium hydrogen sulfite aqueous solution was changed to 1 wt%, the feed rate was changed from 30 [g / min] to 45 [g / min], and 1 wt% ethylenediaminetetra (methylenephosphonic acid)
  • the addition amount of 5 sodium (abbreviation: EDTMPA ⁇ 5Na) aqueous solution is 5.0 parts by weight with respect to 100 parts by weight of the water absorbent resin particles, and further 15% by weight sodium lactate aqueous solution with respect to 100 parts by weight of the water absorbent resin particles.
  • a particulate water-absorbing agent (3-11) was obtained in the same manner as in Example 3-1, except that 2 parts by weight were added.
  • the analysis results of the particulate water absorbing agent (3-11) are shown in Tables 8 and 9.
  • Example 3-12 The concentration of the 0.375 wt% sodium hydrogen sulfite aqueous solution was changed to 1 wt%, the feed rate was changed from 30 [g / min] to 45 [g / min], and 1 wt% ethylenediaminetetra (methylenephosphonic acid)
  • the addition amount of 5 sodium (abbreviation: EDTMPA ⁇ 5Na) aqueous solution is 5.0 parts by weight with respect to 100 parts by weight of the water-absorbent resin particles, and further 25% by weight aluminum sulfate aqueous solution with respect to 100 parts by weight of the water-absorbent resin particles
  • a particulate water-absorbing agent (3-12) was obtained in the same manner as in Example 3-1, except that 2 parts by weight and 2 parts by weight of a 15% by weight aqueous sodium lactate solution were added.
  • the analysis results of the particulate water absorbing agent (3-12) are shown in Tables 8 and 9.
  • Example 3-13 A particulate water-absorbing agent is obtained by adding and mixing 0.5 parts by weight of silica (trade name: Aerosil 200, manufactured by Nippon Aerosil Co., Ltd.) with 100 parts by weight of the water-absorbent resin particles (3-11) described in Example 3-11. (3-13) was obtained. The analysis results of the particulate water absorbing agent (3-13) are shown in Tables 8 and 9.
  • This finely divided hydrogel crosslinked polymer (C2-b) is spread on a 50 mesh wire net, dried with hot air at 170 ° C. for 65 minutes, the dried product is pulverized using a roll mill, and further has an opening of 850 ⁇ m.
  • amorphous crushed water-absorbent resin particles (1-c) having a weight average particle diameter (D50) of 371 ⁇ m and a logarithmic standard deviation of particle size distribution ( ⁇ ) of 0.34 were obtained.
  • the centrifuge retention capacity (CRC) of the water-absorbent resin particles (C2-c) was 46 (g / g), and the water-soluble content was 18% by weight.
  • Comparative water-absorbent resin particles (3-1) 100 parts by weight of 0.05 wt% ethylenediaminetetra (methylenephosphonic acid) 5 sodium (abbreviation: EDTMPA ⁇ 5Na) aqueous solution was added and mixed to give comparative particles A water-absorbing agent (3-3) was obtained.
  • the analysis results of the comparative particulate water-absorbing agent (3-3) are shown in Tables 8 and 9.
  • Example 3-4 Example 3-1 except that the concentration of the 0.375% by weight sodium hydrogen sulfite aqueous solution was changed to 30% by weight and the feed rate was changed from 60 [g / min] to 26.25 [g / min].
  • the comparative hydrous gel-like crosslinked polymer (C4-b) was obtained by performing the above operations.
  • the subdivided comparative hydrogel crosslinked polymer (C4-b) was spread on a 50-mesh wire mesh, dried with hot air at 170 ° C. for 65 minutes, the dried product was pulverized using a roll mill, and further opened with an opening of 850 ⁇ m.
  • a comparatively pulverized comparative water-absorbent resin particle (C4-c) having a weight average particle diameter (D50) of 371 ⁇ m and a logarithmic standard deviation of particle size distribution ( ⁇ ) of 0.34 is obtained. It was.
  • the comparative water absorbent resin particles (C4-c) had a centrifuge retention capacity (CRC) of 44 [g / g] and a water-soluble content of 16% by weight.
  • 100 parts by weight of the obtained comparative water-absorbent resin particles (C4-c) are 0.027 parts by weight of ethylene glycol diglycidyl ether, 0.3 parts by weight of 1,4-butanediol, 0.5 parts by weight of 1,2-propylene glycol.
  • a surface cross-linking agent composed of 2.8 parts by weight of pure water were uniformly mixed, and then the mixture was heat-treated at 180 ° C. for 60 minutes. Thereafter, the obtained particles were pulverized until they passed through a JIS standard sieve having an opening of 850 ⁇ m to obtain a comparative particulate water-absorbing agent (3-4) having a crosslinked surface.
  • the analysis results of the comparative particulate water absorbing agent (3-4) are shown in Tables 8 and 9.
  • modified acrylic acid (3-6) was obtained by changing the amount of p-methoxyphenol added to purified acrylic acid from 70 ppm to 1 ppm.
  • a comparative hydrogel crosslinked polymer (C6-b) was obtained in the same manner as described in Example 3-1, except that the modified acrylic acid (3-6) was used.
  • This subdivided comparative hydrogel crosslinked polymer (C6-b) was spread on a 50-mesh wire mesh, dried with hot air at 170 ° C. for 65 minutes, the dried product was pulverized using a roll mill, and further opened with an opening of 850 ⁇ m.
  • non-uniformly crushed comparative water-absorbent resin particles (C6-c) having a weight average particle size (D50) of 371 ⁇ m and a logarithmic standard deviation of particle size distribution ( ⁇ ) of 0.34 are obtained. Obtained.
  • the comparative water absorbent resin particles (C6-c) had a centrifuge retention capacity (CRC) of 50 [g / g] and a water-soluble content of 24% by weight.
  • silica gel (trade name: Aerosil 200, manufactured by Nippon Aerosil Co., Ltd.) to 100 parts by weight of the obtained comparative water-absorbing resin particles (6-e), a comparative particulate water-absorbing agent (3- 6) was obtained.
  • the deterioration rate of the comparative particulate water-absorbing agent (3-6) by the weather resistance promotion test was 24%, and it was a particulate water-absorbing agent having poor weather resistance.
  • modified acrylic acid (3-7) was obtained by changing the amount of p-methoxyphenol added to the purified acrylic acid from 70 ppm to 270 ppm.
  • a comparative particulate water-absorbing agent (3-7) was obtained in the same manner as in Comparative Example 3-6 except that adjusted acrylic acid (3-7) was used.
  • Example 3-8 The relationship between water content and coloring is shown below. That is, it was carried out except that the concentration of the 0.375 wt% sodium hydrogen sulfite aqueous solution was changed to 0.1 wt% and the feed rate was changed from 30 [g / min] to 22.5 [g / min]. The same operation as in Example 3-1 was performed to obtain water-absorbing resin particles (C8-d) having a crosslinked surface.
  • the comparative particulate water-absorbing agent (3-8) having a water content of 17% by weight is poorly colored as compared with the water-absorbing agent having the water content of the present invention, and the particles tend to aggregate and form a lump. The handling was poor.
  • Example 3-1 to Example 3-13 and Tables 8 and 9 relate to the production method 3 of the particulate water-absorbing agent of the present invention, and the simple substance mainly composed of acrylic acid (salt).
  • a particulate water-absorbing agent mainly composed of a polyacrylic acid (salt) -based water-absorbing resin comprising a polymerization step of a monomer aqueous solution, a drying step of a hydrogel crosslinked polymer obtained by polymerization, and a surface crosslinking step
  • the method further comprises a step of adding 0.001 to 0.5% by weight of a chelating agent and a step of adding an inorganic reducing agent, and the monomer contains 10 to 200 ppm of methoxyphenol in terms of acrylic acid.
  • the water content of the polymer is controlled to 3 to 15% by weight, and more preferably, the inorganic reducing agent is added to the water-containing gel-like cross-linked polymer before drying.
  • the particulate water-absorbing agent according to the present invention contains a chelating agent and an inorganic reducing agent and has a water content of 3 to 15% by weight.
  • the initial color tone was excellent and there was no unpleasant odor.
  • Comparative Examples 3-1 to 3-3 containing only one of a chelating agent and an inorganic reducing agent, the color tone with time was poor.
  • Comparative Examples 3-4 and 3-5 which contain only a reducing agent and a large amount thereof, were particulate water-absorbing agents having a very strong odor.
  • Comparative Example 3-6 (1 ppm in acrylic acid) in which the amount of methoxyphenol is outside the range of 10 to 200 ppm in acrylic acid or 5 to 60 ppm in water absorbing agent is a particulate water absorbing agent having a high deterioration rate and poor weather resistance Met.
  • Comparative Example 3-7 270 ppm in acrylic acid
  • the initial coloring was poor and odor was generated.
  • Such an odor is considered to be an odor derived from by-products in the surface crosslinking rather than the odor of the reducing agent itself.
  • Comparative Example 3-8 water content 17% by weight
  • coloring was worse than the water-absorbing agent of the present invention, and urine resistance (1000 times deteriorated component) was also inferior.
  • the manufacturing method of the present invention solves the problems of deterioration, odor and coloring, and the residual monomer is as low as 400 ppm or less, and further as 300 ppm or less.
  • the novel water-absorbing agent (third water-absorbing agent) of the present invention is a particulate water-absorbing agent mainly composed of polyacrylic acid (salt) -based water-absorbing resin, and is a chelating agent. And an inorganic reducing agent, the content of the chelating agent is 0.001 to 0.5% by weight, and the water content is 3 to 15% by weight.
  • the novel water-absorbing agent of the present invention shown in the above-mentioned examples preferably has an absorption capacity without load (CRC) of 25 [g / g] or more and an absorption capacity under load (AAP of 2.0 kPa) of 25 [g. / G] and the residual monomer is 500 ppm or less.
  • Such a water-absorbing agent may optionally contain methoxyphenols (particularly p-methoxyphenol), and may be 0 to 200 ppm, preferably (1) and the novel water-absorbing agent of the present invention (first water-absorbing agent). Similarly, the range of 5 to 60 ppm (about 10 ppm in the above Examples 3-1 to 3-8) is further improved in weather resistance and coloring.
  • the novel water-absorbing agent (third water-absorbing agent) of the present invention preferably contains water-insoluble inorganic fine particles in the same manner as (1) and the novel water-absorbing agent (first water-absorbing agent) of the present invention. Urine resistance is further improved.
  • Such a water-absorbing agent preferably further contains an ⁇ -hydroxycarboxylic acid compound.
  • a polyvalent metal salt and / or a cationic polymer are further included.
  • water-absorbing agents are white without any initial or aging coloring, little residual monomer, high water absorption rate (Vortex), high absorption capacity under pressure (AAP), so even if used in high-concentration paper diapers with little pulp Provided a good paper diaper with high liquid diffusion and low return (Re-wet), without coloring problems due to the water-absorbing agent.
  • the particulate water-absorbing agent obtained by the production method according to the present invention is suitable for sanitary materials such as paper diapers, sanitary napkins and incontinence pads.

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Abstract

L'invention concerne un agent hydroabsorbant particulaire contenant en tant que composant principal une résine hydroabsorbante à base d'acide polyacrylique (sel), plus particulièrement l'invention concerne un agent hydroabsorbant particulaire pour corps absorbant, adapté à un usage pratique, inodore, montrant d'excellentes propriétés d'absorption et possédant également d'excellentes propriétés empêchant une coloration avec le temps. Le procédé de fabrication de l'agent hydroabsorbant particulaire contenant en tant que composant principal une résine hydroabsorbante à base d'acide polyacrylique (sel), comprend : une étape de polymérisation d'une solution aqueuse de monomère contenant en tant que composant principal un acide polyacrylique (sel) qui renferme 10 à 200ppm de méthoxyphénol; une étape de séchage du polymère réticulé de type gel aqueux obtenu par polymérisation; et une étape de réticulation de surface. Le procédé de fabrication de l'invention est caractéristique en ce qu'il comporte une étape d'addition d'un chélateur et d'un agent réducteur, et en ce qu'il satisfait les conditions (a) et / ou (b) suivantes : (a) comporter une étape d'addition de microparticules inorganiques insolubles dans l'eau; (b) maintenir la teneur en eau du polymère entre 3 et 15% en poids, lors des étapes de séchage et de réticulation de surface.
PCT/JP2010/067086 2009-09-30 2010-09-30 Agent hydroabsorbant particulaire et procédé de fabrication de celui-ci WO2011040530A1 (fr)

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