WO2011040530A1 - Particulate water absorbent and method for producing same - Google Patents

Particulate water absorbent and method for producing same 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
absorbing agent
agent
step
weight
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PCT/JP2010/067086
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French (fr)
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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    • BPERFORMING OPERATIONS; TRANSPORTING
    • B01PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01JCHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J20/00Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof
    • B01J20/22Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof comprising organic material
    • B01J20/26Synthetic macromolecular compounds
    • CCHEMISTRY; METALLURGY
    • C08ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08JWORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G
    • C08J3/00Processes of treating or compounding macromolecular substances
    • C08J3/12Powdering or granulating
    • CCHEMISTRY; METALLURGY
    • C08ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08JWORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G
    • C08J3/00Processes of treating or compounding macromolecular substances
    • C08J3/12Powdering or granulating
    • C08J3/128Polymer particles coated by inorganic and organic compounds
    • CCHEMISTRY; METALLURGY
    • C08ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08JWORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G
    • C08J3/00Processes of treating or compounding macromolecular substances
    • C08J3/24Crosslinking, e.g. vulcanising, of macromolecules
    • C08J3/245Differential crosslinking of one polymer with one crosslinking type, e.g. surface crosslinking
    • BPERFORMING OPERATIONS; TRANSPORTING
    • B01PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01JCHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J2220/00Aspects relating to sorbent materials
    • B01J2220/50Aspects relating to the use of sorbent or filter aid materials
    • B01J2220/68Superabsorbents
    • CCHEMISTRY; METALLURGY
    • C08ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08JWORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G
    • C08J2300/00Characterised by the use of unspecified polymers
    • C08J2300/14Water soluble or water swellable polymers, e.g. aqueous gels
    • CCHEMISTRY; METALLURGY
    • C08ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08JWORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G
    • C08J2333/00Characterised 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
    • C08J2333/02Homopolymers or copolymers of acids; Metal or ammonium salts thereof

Abstract

Disclosed is a particulate water absorbent for an absorbent material, which is mainly composed of a polyacrylic acid (salt) water absorbent resin and exhibits excellent water absorption performance, while having excellent performance of preventing coloring over time. The particulate water absorbent has no odor and is suitable for practical use. Also disclosed is a method for producing a particulate water absorbent mainly composed of a polyacrylic acid (salt) water absorbent resin, which comprises: a step of polymerizing an aqueous monomer solution that is mainly composed of an acrylic acid (salt) that contains 10-200 ppm of a methoxyphenol; a step of drying a hydrated gel-like crosslinked polymer that is obtained by the polymerization; and a surface crosslinking step. The method for producing a particulate water absorbent is characterized by comprising a step of adding a chelating agent and an inorganic reducing agent and by satisfying the following condition (a) and/or (b). (a) The method comprises a step of adding water-insoluble inorganic fine particles. (b) In the drying step and the surface crosslinking step, the moisture content of the polymer is controlled to 3-15% by weight.

Description

Particulate water-absorbing agent and a production method thereof

The present invention is particulate water-absorbing agent as a main component of polyacrylic acid (salt) -based water absorbent resin and a method for producing the same. More particularly, it relates to a particulate water absorbing agent and a method of manufacturing absorbent bodies used in disposable diapers, sanitary napkins or the like, excellent in yellowing preventing properties, odor no, and excellent absorption ability to, the particulate water-absorbing agent as a main component of polyacrylic acid (salt) -based water absorbent resin and a method for producing the same.

Recently, water-absorbent resins have been developed which have a high degree of water absorption, paper diapers, absorbent articles such as sanitary napkins, furthermore, frequently used for agricultural or horticultural water-retaining agents, industrial water stop material or the like, mainly in disposable applications It is. As such a water-absorbent resin, have been proposed many monomers and hydrophilic polymer as a raw material, among others, polyacrylic acid (salt) -based water absorbent using acrylic acid and / or a salt thereof as a monomer resins have been used industrially most because of their high water absorbency.

Such polyacrylic acid (salt) -based water absorbent resin is a polyacrylic acid salt was neutralized before or after polymerization of acrylic acid, non-patent and patent documents 1 to 4 for such neutralization and polymerization It is disclosed in the literature 1.

The water absorption property required of the above water-absorbent resin, absorbency against non-pressure (CRC), absorbency against pressure (AAP), absorption rate (FSR / Vortex), without load liquid permeability against pressure liquid permeability , impact resistance, resistance to urine, flowability, gel strength, color, number of characteristic grain size, etc. (parameters) are known, also, numerous in various aspects among more same physical properties (e.g., absorbency against non-pressure) the provisions of the (parameter measurement method) has been proposed.

These many physical properties noted are water-absorbent resins that have been developed (particulate water absorbing agent), the number of physical properties (e.g., "absorbency against non-pressure (CRC)" and "absorbency against pressure (AAP)" even if the control etc.), in yet actual use of the absorber such as a paper diaper, and has to demonstrate sufficient performance there is a problem that it is hard to say.

The main applications of these water-absorbing agents are the sanitary materials such as paper diapers and sanitary napkins, when the powder of the water absorbing agent is complexed with a white pulp and sanitary materials, giving foreign body sensation by coloring as no initial color of the water-absorbing agent; as (aka initial color), it is required the water-absorbent resin is a white during shipment from the factory. Further, the water absorbing agent is generally a white powder, even after shipping, during its storage and transportation, when further used for sanitary materials, brown water absorbing agent from time colored (yellow and it is known to color), the thus over time the color tone of the water-absorbing agent (aka; even coloring over time), it is required even when the absorbent article during prolonged storage is white. Recently, in order to tend to use the ratio of the water-absorbent resin (wt%) increases in sanitary materials, coloring problem has become increasingly more important.

Therefore, various proposals for whiteness improvement and color protection of the water-absorbent resin has been proposed in Patent Documents 5 to 31 and the like. Specifically, as a method for controlling the polymerization inhibitor in the monomer, a technique for the methoxyphenol in acrylic acid and 10 ~ 160 ppm (Patent Document 5), the control below 0.2ppm hydroquinone in acrylic acid technology (Patent Document 6), a technique of the monomer is treated with activated carbon (Patent Document 7), techniques using tocopherol as inhibitor (Patent Document 8), as a polymerization inhibitor N- oxyl compound and manganese compound or the like the technique used (Patent Document 9), techniques using methoxyphenol and certain polyvalent metal salt (Patent documents 10 and 11) are known.

Further, as the coloring preventing agent of the water-absorbent resin, the technique (Patent Document 12) for adding a reducing agent such as hypophosphite, technique (Patent Documents 13 and 14) the addition of an anti-oxidant, a metal chelating agent and optionally other addition of a reducing agent such techniques (Patent documents 15-19) technique of adding other compounds (Patent documents 20-23) and the like are known by an organic carboxylic acid and optionally a.

Furthermore in order to prevent coloration, Patent Documents 24-26 are known as a technique that focuses on the polymerization initiator. Also includes a coloring-causing substances, techniques focusing on the iron content in aluminum and a reducing agent (Patent Document 27, 28) have also been proposed, the monomer or an acrylic acid ammonium salt, or a phosphorus atom compound or sulfur-based reducing agent is added more than once technique (Patent Document 29) are also known. Furthermore, techniques (Patent Documents 30, 31) for controlling the amount of oxygen in the drying step and the surface cross-linking step is also known.

However, even in coloring prevention method of the above Patent Documents 5 to 31 in the whiteness of the particulate water-absorbing agent obtained by the continuous polymerization, the variation is seen. Because strong demand for whiteness of the particulate water-absorbing agent, the whiteness, there is still room for improvement. Furthermore, acrylic acid, is highly increased purity of the raw materials, to mild polymerization conditions and drying conditions of the water-absorbing resin, or the conventional anti-coloring technique such use a new color protection agent, the production costs increase or decrease in productivity, there is a possibility that problems such as decrease in safety and absorption properties due to the use of anti-coloring agent may occur.

Furthermore, in addition to the coloring problem disclosed in Patent Documents 5 to 31 are known odor problem of the water-absorbent resin itself, when the water-absorbing agent to be used as sanitary materials such as paper diapers and sanitary napkins , it is required that there is no offensive smell even before use so as not to cause discomfort to the user. Recently, there if unpleasant smell or odor which is considered to be derived from the substance to be newly used As the performance of the water-absorbing agent becomes a problem.

Therefore, various odor reducing method, i.e., acrylic acid (Patent Document 32), acetic acid and propionic acid (Patent Document 33), a volatile organic solvent (Patent Document 34), a sulfur reducing agent (Patent Document 35), alcohol volatilization odor reducing covering substance (Patent Document 36) have been proposed. However, excellent anti-yellowing properties not sufficient in that it exhibits excellent absorption capacity, especially high properties by using a reducing agent, in particular, AAP (absorbency against pressure) is 20 [g / g] or more, or, SFC (saline flow conductivity) of 30 [× 10 -7 · cm 3 · s · g -1] or more, or, when the water absorption rate of 60 [sec] or less, other than the odor derived from the reducing agent, unknown cause of offensive smell that there was to be.

US Pat. No. 5210298 U.S. Patent Application Publication No. 2008/242816 Pat WO 2007/28747 pamphlet U.S. Patent Application Publication No. 2008/194863 Pat WO 2003/051940 pamphlet US Pat. No. 6444744 WO 2004/052819 pamphlet WO 2003/053482 pamphlet WO 2008/096713 pamphlet WO 2008/092843 pamphlet WO 2008/092842 pamphlet US Pat. No. 6359049 WO 2009/060062 pamphlet WO 2009/011717 pamphlet U.S. Patent Application Publication No. 2005/085604 Pat WO 2003/059961 pamphlet European Patent No. 1645596 Japanese Patent Registration No. 3107873 Publication WO 2009/005114 pamphlet WO 2008/026772 pamphlet Japanese Unexamined Patent Publication "JP 2000-327926 Patent Publication No." Japanese Unexamined Patent Publication "JP 2003-052742 Patent Publication No." Japanese Unexamined Patent Publication "JP 2005-186016 Patent Publication No." Japanese Unexamined Patent Publication "JP-A-4-331205" U.S. Patent Application Publication No. 2006/089611 Pat US Pat. No. 7528291 WO 2007/072969 pamphlet U.S. Patent Application Publication No. 2006/074160 Pat WO 2006/109882 pamphlet U.S. Patent Application Publication No. 2007/293632 Pat WO 2006/008905 pamphlet WO 2004/052949 pamphlet WO 2003/095510 pamphlet U.S. Patent Application Publication No. 2009/036855 Pat WO 2006/088115 pamphlet U.S. Patent Application Publication No. 2008/075937 Pat

Modern Superabsorbent Polymer Technology p. 39-44, etc.

The problems to be solved by the present invention, the particulate water-absorbing agent and a production method thereof as a main component of polyacrylic acid (salt) -based water absorbent resin can exhibit excellent absorption performance, further, preventing excellent coloring with time has a performance, no odor, is to provide a particulate water-absorbing agent and its method of manufacture suitable absorber in actual use. Furthermore, the problem to be solved by the present invention is excellent in urine resistance, is to provide a particulate water-absorbing agent and its method of manufacture suitable absorber in actual use.

(Particulate water-absorbing agent)
To solve the above problems, the particulate water absorbing agent of the present invention is a particulate water-absorbing agent as a main component of polyacrylic acid (salt) -based water absorbent resin, comprising: a chelating agent, and an inorganic reducing agent, the content of the chelating agent is 0.001 to 0.5 wt%, the following (1) to (3)
(1) the content of methoxyphenol is 5 ~ 60 ppm.
(2) to contain the water-insoluble inorganic fine particles.
(3) the water content is 3 to 15 wt%.
It is characterized by satisfying any one or more of the requirements.

(Method for producing a particulate water absorbing agent)
In order to solve the above problems, a manufacturing method of the particulate water-absorbing agent of the present invention, the polymerization step of the monomer aqueous solution containing as a main component an acrylic acid (salt), water-containing gel-like cross-linked heavy obtained in the polymerization a drying step of the polymer, and a surface cross-linking step, a method for producing a particulate water absorbing agent mainly containing polyacrylic acid (salt) -based water absorbent resin,
Further comprising a step of adding a chelating agent 0.001 to 0.5% by weight of the addition step and the inorganic reducing agent,
Monomer contains 10 ~ 200 ppm of methoxyphenol in to acrylic acid conversion,
The following (a) ~ (c)
(A) it includes a step of adding water-insoluble inorganic fine particles.
(B) after the drying step, and the surface cross-linking step, controlling the water content of the polymer 3 to 15% by weight.
(C) after the surface crosslinking step, performing the step of adding an inorganic reducing agent.
It is characterized by satisfying any one or more of the requirements.

(Preferred subgenus of the particulate water absorbing agent)
(Manufacturing method-Part 1 of the particulate water-absorbing agent)
As a method for producing the particulate water-absorbing agent of the present invention, a manufacturing method, the first subordinate concept of the (c) is required if the single mainly containing acrylic acid (salt) which methoxyphenol which contained 10 ~ 200 ppm a polymerization step of mer solution, and drying the hydrogel crosslinked polymer obtained by the polymerization, and the surface-crosslinking step, the particulate water-absorbing agent comprising a chelating agent 0.001-0.5 wt% of the added steps a manufacturing method, after the surface cross-linking step is characterized by performing the step of adding an inorganic reducing agent. Specific examples of the production method Part 1 in Examples 1-1 to 1-16 and Tables 1-5 below.

(Manufacturing method-Part 2 of the particulate water-absorbing agent)
As a method for producing the particulate water-absorbing agent of the present invention, a manufacturing method Part 2 of the subordinate concept of the a (b) as essential includes the step of polymerizing the monomer aqueous solution containing as a main component an acrylic acid (salt), the polymerization a drying step of the hydrogel crosslinked polymer obtained by, and a surface cross-linking step, a method for producing a particulate water absorbing agent, the addition step and the inorganic reducing chelating agent 0.001 to 0.5 wt% further comprising a step of adding agents, monomer contains 10 ~ 200 ppm of methoxyphenol in to acrylic acid conversion, and further comprising the step of adding (a) water-insoluble inorganic fine particles. Specific examples of the production method Part 2 in Examples 2-1 to 2-14 and Tables 6-7 below.

(Manufacturing Method Part 3 of the particulate water-absorbing agent)
As a method for producing the particulate water-absorbing agent of the present invention, a manufacturing method Part 3 of the subordinate concept of the a (c) as essential includes the step of polymerizing the monomer aqueous solution containing as a main component an acrylic acid (salt), the polymerization a drying step of the hydrogel crosslinked polymer obtained by, and a surface cross-linking step, a method for producing a particulate water absorbing agent, the addition step and the inorganic reducing chelating agent 0.001 to 0.5 wt% further comprising a step of adding agents, monomer contains 10 ~ 200 ppm of methoxyphenol in to acrylic acid in terms of, in the drying step and / or after the surface cross-linking step, the water content of 3-15% by weight of the polymer control is possible, even more preferably, the inorganic reducing agent, is characterized by adding to the crosslinked hydrogel polymer before drying. Specific examples of the production method, the 3 in Examples 3-1 to 3-13 and Tables 8-9 below.

According to the particulate water absorbing agent of the present invention has excellent coloring over time preventing performance, no odor, further, excellent urine resistance, provides a particulate water absorbing agent for a suitable absorber in actual use be able to.

Figure 1 is a side view showing a schematic configuration of a measuring apparatus of AAP (absorbency against pressure) according to the present embodiment. Figure 2 is a side view showing a schematic configuration of a measuring apparatus of SFC according to the present embodiment (saline flow conductivity). Figure 3 is an electron micrograph of a typical granulation particles.

It will be described below, but the present invention, the scope of the present invention should not be restricted to these descriptions, even with the addition to the following examples may be appropriately modified embodiments without departing from the spirit of the present invention.

First, define the abbreviations used below.

In this specification, a "CRC" (Centrifuge Retention Capacity) The "Centrifuge retention capacity" refers to a value obtained by a measurement method described in Examples to be described later. Also referred to as "CRC" and "absorbency against non-pressure" or simply "absorbency". Also, a "SFC" (Saline Flow Conductivity) The "saline flow conductivity" refers to a value obtained by a measurement method described in Examples to be described later. Furthermore, a "AAP" (Absorbency against Pressure) as "absorbency against pressure" to pressure of 4.83kPa or 2.0kPa refers to a value obtained by a measurement method described in Examples to be described later. Also, a "FSR" (Free Swell Rate) The "absorption rate" refers to a value obtained by a measurement method described in Examples to be described later. Furthermore, a "D50" is the (Distribution) "weight average particle size" refers to a value obtained by a measurement method described in Examples to be described later. Further, "σζ" a "logarithmic standard deviation of particle size distribution" refers to a value obtained by a measurement method described in Examples to be described later. A "FHA" (Fixed Height Absorption) "Height Absorption fixed" and refers to a value obtained by a measurement method described in Examples to be described later. Further, the "Vortex" is "water absorption rate" refers to a value obtained by a measurement method described in Examples set forth below.

In the present specification, the term "brine" refers to "an aqueous sodium chloride solution", "X ~ Y" is indicating a range, it means that it is "X or greater but Y or less", unless otherwise annotated "ppm" means "ppm by weight" or "weight ppm", "~ acid (salt)" means "~ acid and / or a salt thereof", the term "(meth) acryl", "acryl and / or means methacrylic ".

Particulate water-absorbing agent according to the present invention, the polyacrylic acid (salt) -based water absorbent resin as a main component, wherein the content of 0.001 to 0.5 wt% chelating agent, and an inorganic reducing agent, the following ( 1) is absorbing and solidifying agent of aqueous liquid which satisfies any one or more - (3).
(1) the content of methoxyphenol is 5 ~ 60 ppm,
(2) to contain the water-insoluble inorganic fine particles,
(3) the water content is 3 to 15 wt%.

The particulate water absorbing agent of the present invention, the above (1) to (3) it is essential to satisfy any one or more, of the aqueous liquid preferably any two or more, particularly preferably satisfies the three simultaneously it is a absorbing and solidifying agent, if the chelating agent and inorganic reducing agents have to be used together within the above range, low effect of preventing coloration and deterioration. In coloration and deterioration prevention, the (1) methoxyphenol and (2) water-insoluble inorganic fine particles deterioration preventing further contributes to prevention coloration. Also, the (3) moisture content affects the coloration (e.g., present Comparative Example 3-8), also contribute to the absorption rate (for example, the present embodiment 1-16) and, further also solves the odor and dust problems . Among them, in order to solve the problems of the present invention, the above (1) is preferable that the content of methoxyphenol is 5 ~ 60 ppm, further above (3) If the water content of 3 to 15% by weight, the ( 2) preferably contains a water-insoluble inorganic fine particles. That is, a chelating agent and an inorganic reducing agent in the method used in combination within the above range, the above (1) to (3) are all affect the prevention or degradation preventing coloration, in the present invention one or more of them, preferably two or more, particularly preferably selects three.

The "main component", the content of the water-absorbent resin refers to for the entire water-absorbing agent is 50 wt% or more, the content of the water absorbent resin, essential to the chelating agent and an inorganic reducing agent during the entire water absorbing agent including, for preferably a water content of 3 to 15 wt%, wherein the water-absorbing resin with less than 97 wt%, the lower limit of the water-absorbent resin 60 wt% or more, further 70% by weight or more, particularly 80 wt% or more, or even 85 wt% or more. Also, if the water content is less than 3 wt%, the content of the water-absorbent resin is less than 60 wt% 99.999% by weight, more preferably 70 wt% or more and less than 99.9 wt%, more preferably less than 80 wt% or more 99.7% by weight, particularly preferably refers to less than 90 wt% 99.5 wt%.

The particulate water absorbing agent of the present invention, comprising a polyacrylic acid (salt) -based water absorbent resin as a main component, absorbing and solidifying agent of aqueous liquid; refers to (aka gelling agents). The aqueous liquid is not limited to water, urine, blood, feces, waste liquid, moisture or steam, ice, mixture of water and an organic or inorganic solvent, rain water, ground water and the like, in particular as long as it contains water deprivation but not, preferably, the particulate water absorbing agent of the present invention, urine, and particularly human urine absorbing and solidifying agent.

Particulate water-absorbing agent according to the present invention, further, for the prevention and deterioration prevention coloration, it is preferred that the absorbing and solidifying agent of aqueous liquid containing α- hydroxy carboxylic acid compound.

Particulate water-absorbing agent according to the present invention, further, for preventing deterioration or liquid permeability improving preferably a absorbing and solidifying agent of aqueous liquid containing a polyvalent metal salt and / or a cationic polymer. Conventionally, when using a polyvalent metal salt and / or cationic polymers, coloring problems resulting water absorbing agent is likely to occur, there is no such problem in the present invention.

The particulate water absorbing agent of the present invention can exhibit excellent absorption performance, further, has excellent coloring over time preventing performance, odorless, further excellent urine resistance, suitable absorber in actual use it can provide the particulate water absorbing agent.

Hereinafter, [1] polyacrylic acid (salt) -based water absorbent resin, (2) a chelating agent, (3) inorganic reducing agent, (4) methoxy phenols, (5) water-insoluble inorganic fine particles, [6] α- hydroxy carboxylic acid compound, [7] a polyvalent metal salt and / or cationic polymer, (8) granulation, (9) the particulate water-absorbing agent, a method of manufacturing a [10] the particulate water absorbing agent, in order for [11] the water-absorbent structure explain.

[1] polyacrylic acid (salt) -based water absorbent resin (1-1) water-absorbent resin used in the particulate water absorbing agent of the monomer present invention optionally includes a graft component, the constitutional unit derived from acrylic acid a. Preferably, the water-absorbing resin has as a main component the structure unit derived from acrylic acid. This method of water-absorbent resin is not particularly limited, preferably, the water-absorbent resin is obtained by polymerizing a monomer component including acrylic acid and / or salts thereof.

Note that the constituent units derived from the monomers, for example, by the polymerization reaction, corresponds to the polymerizable double bond is opened structure of each monomer. The polymerizable double bond is open structure, for example, a structure in which a double bond between the carbon (C = C) has become a single bond (-C-C-).

In the present invention, the water-absorbing resin used in the particulate water-absorbing agent is a polymer of water-swellable water-insoluble by introducing a crosslinked structure into the polymer.

The "water-swellable", absorbency against non-pressure against saline (CRC) is 2 [g / g] or more, preferably 5 ~ 200 [g / g], and more preferably 20 ~ 100 [g / g] refers to a, the term "water-insoluble" water-soluble component of the water absorbent resin is mandatory 50 wt% or less, preferably 0 to 25 wt%, more preferably 0-15 wt%, more preferably 0 to 10 wt%, refers to substantially water-insoluble. These "water swellable (CRC)", "water-insoluble (water-soluble component)" is determined by the measurement method defined in the Examples below.

Further, the polyacrylic acid (salt) -based water absorbent resin in the present invention, acrylic acid in the total monomer (excluding a crosslinking agent) used in the polymerization and / or the total mole% mandatory to 50-100 its salt mol%, more preferably from 70 to 100 mol%, more preferably 90 to 100 mol%, particularly preferably refers to substantially 100 mol%. Note that the polyacrylic acid is not limited to polymers of acrylic acid, is a concept including a polyacrylic acid (salt) is a hydrolyzate of polyacrylonitrile or polyacrylamide, the physical properties will be described later acrylic polyacrylic acid is preferably obtained by polymerization of an acid.

The acrylic acid salt used in the present invention, lithium salts, sodium salts, alkali metal salts such as potassium salts; ammonium salts; monovalent salts of acrylic acid such as an amine salt is usually used, preferably acrylic acid alkali metal salt is used, more preferably sodium salts or potassium salts of acrylic acid. Also, the calcium salt in range with a water-swellable, polyvalent metal salts such as aluminum salts may be used in combination.

Neutralization ratio of the water-absorbent resin obtained in the present invention is preferably 10 mol% or more acid groups, less than 90 mol%, more preferably 40 mol% or more acid groups, less than 80 mol% , more preferably 50 mol% or more of the acid groups, less than 74 mol%. If the neutralization ratio is less than 10 mol%, the absorption performance, without any particular may absorbency is significantly reduced Preferably, also, if the neutralization ratio is not less than 90 mol%, the absorption performance, particularly high absorbency against pressure undesirable may water-absorbing agent can not be obtained. Also, less than 74 mol% neutralization ratio in terms of absorption performance, and more particularly preferably less than 72 mol%. That is, in the method of the present invention, tends to be colored with high neutralization rate, therefore, the upper limit of the neutralization ratio is within the above range.

The neutralization step may be performed with respect to the monomer component before polymerization, or may be made to the hydrogel crosslinked polymer during polymerization or after polymerization. Furthermore, it may be used in combination with neutralization of the neutralization and water-containing gel-like cross-linked polymer of the monomer component. Preferably neutralization is carried out with acrylic acid as a monomer component.

The water content of the water-absorbent resin obtained in the present invention (defined by the measuring method of the present application) is within the range and later in the drying step and the surface cross-linking step or the like described later, also, of the particulate water-absorbing agent as a final product the water content is preferably adjusted to 3 to 15 wt%. As a matter of course, the particulate water-absorbing agent according to the present invention, the above (1) and (2) when not satisfied the requirements of the water content of the particulate water-absorbing agent as a final product is always 3-15 It is adjusted to weight%. If the water content is higher than 15 wt%, there is a tendency that the resultant water-absorbing agent is colored, also sometimes odor and dust problems it is less than 3 wt%.

(1-2) as a monomer in the monomer present invention other than acrylic acid (salt), but using acrylic acid (salt) in the above range may be used in combination other monomers. When the monomers other than acrylic acid (salt), the amount of the monomer other than acrylic acid (salt), based on the total weight of the acrylic acid used as a main component (salt) and other monomers 0-50 mol%, preferably 0 to 30 mol%, more preferably 0 to 10 mol%. By using the monomers other than acrylic acid (salt) in the above proportions, together with the absorption characteristics of the particulate water-absorbing agent finally obtained can be further improved, to obtain a particulate water-absorbing agent even more expensive it can.

As the monomer to be used in combination other than acrylic acid (salt), for example include monomers exemplified in U.S. patent or European patent described later. Specifically, water-soluble or hydrophobic unsaturated monomers, and the like as a monomer to be used in combination. The water-soluble or hydrophobic unsaturated monomers, such as methacrylic acid, (anhydrous) maleic acid, fumaric acid, crotonic acid, itaconic acid, vinyl sulfonic acid, 2- (meth) acrylamido-2-methylpropane sulfonic acid, (meth) acryloxyalkane sulfonic acid and alkali metal salts, ammonium salts, N- vinyl-2-pyrrolidone, N- vinyl acetamide, (meth) acrylamide, N- isopropyl (meth) acrylamide, N, N- dimethyl (meth) acrylamide, 2-hydroxyethyl (meth) acrylate, methoxy polyethylene glycol (meth) acrylate, polyethylene glycol (meth) acrylate, isobutylene, lauryl (meth) acrylate. The particulate water absorbing agent of the present invention also include those copolymerizable components the water-soluble or hydrophobic unsaturated monomers.

(1-3) There is not any specific restriction on the crosslinking method used in the internal cross-linking agent present invention, for example, a method of post-crosslinking by adding a crosslinking agent after polymerization or during polymerization, a method for radical crosslinking by a radical polymerization initiator, electron can be mentioned a method in which radiation crosslinking by line or the like, operating polymerization by adding in advance a predetermined amount of the internal crosslinking agent in the monomer, method of crosslinking reaction in the polymerization simultaneously with or or after polymerization is preferred.

As the internal crosslinking agent used in the present invention, for example, N, N'-methylene bisacrylamide, (poly) ethylene glycol di (meth) acrylate, (poly) propylene glycol di (meth) acrylate, (polyoxyethylene) trimethylolpropane trimethylolpropane tri (meth) acrylate, (polyoxyethylene) glycerol tri (meth) acrylate, trimethylolpropane di (meth) acrylate, polyethylene glycol di (beta-acryloyloxy propionate), trimethylolpropane tri (beta-acryloyl oxy propionate), poly (meth) allyloxy alkane, polyethylene glycol diglycidyl ether, ethylene glycol, propylene glycol, glycerin, Butanjiru, erythritol, xylitol Sorbitol, polyethylene glycol and the like, these one or more is used. In the case of using one or more internal cross-linking agent, considering the absorption properties of the resultant water-absorbing resin or the like, to use a compound having two or more polymerizable unsaturated groups in essential at the time of polymerization preferable.

Internal crosslinking agent is preferably 0.005 to 2 mol% relative to the monomer, more preferably 0.01 to 1 mol%, more preferably 0.05 to 0.2 mol%. If the amount of the internal cross-linking agent is less than 0.005 mole%, or, if more than 2 mol%, there is a possibility that the desired absorption properties may not be obtained.

(1-4) Polymerization concentration polymerization step, if the aqueous solution of the monomer component, the concentration of the aqueous solution of the monomer component in (hereinafter, referred to as aqueous monomer solution) is the monomer type and purpose it is suitably determined by the physical properties, but are not particularly limited, preferably the physical properties is 10 to 70 wt%, more preferably 15 to 65 wt%, further more preferably from 30 to 55 wt%. The solvent other than water may be used together as necessary, the kind of solvent that can be used in combination is not particularly limited. Note Note that the monomer concentration may be a slurry of more than saturation concentration, preferably in the above range, and even more preferably not more than saturation concentration.

(1-5) Other Components In addition, upon polymerization, a water-soluble resin relative to monomer as a main component acrylic acid (salt) (e.g.,; starch, cellulose, polyvinyl alcohol) or or the water absorbent resin (or its fines), for example, 0 to 50 wt%, preferably by adding 0-20 wt%, may improve the properties of the water-absorbing resin. Further, upon polymerization, various blowing agent to the monomer (carbonate, azo compound, bubbles and the like), a surfactant, a chelating agent, a chain transfer agent such as, for example, 0 to 5 wt%, preferably 0 was added to 1% by weight, it may improve the properties of the water-absorbing resin. The above use of water-soluble resin or water-absorbent resin graft polymer (e.g.,; starch graft polymer and PVA graft polymer) gives a, which are also a polyacrylic acid (salt) -based water absorbent resin in the present invention collectively.

(1-6) reversed phase suspension polymerization in the polymerization step the invention, the aqueous solution polymerization, spray or droplets polymerization can be applied, when polymerizing the monomer aqueous solution, ease of control of the performance aspect, polymerization, it is preferably performed by aqueous solution polymerization or reversed-phase suspension polymerization. These polymerizations can also be carried out in an air atmosphere, preferably an inert gas atmosphere such as nitrogen or argon (for example, oxygen less than 1% by volume) is carried out at, also, the monomer component, the dissolved oxygen is not sufficiently substituted with inert gas (e.g., oxygen less than 1 [mg / L]) is preferably used for the polymerization after it is. In the present invention, to obtain the water-absorbent resin of high property with high productivity, the polymerization control is particularly suitable for aqueous solution polymerization was difficult, particularly preferred as the aqueous solution polymerization, the continuous belt polymerization (U.S. Pat. No. 4,893,999, described) in the first 6241928 Patent and US Patent application Publication No. 2005/215734 and the like, and continuous or batch kneader polymerization (described in U.S. Patent No. 6,987,151 No. and the second 6,710,141, etc.).

Aqueous solution polymerization and is a method for polymerizing the monomer aqueous solution without using a dispersion solvent, for example, U.S. Patent No. 4,625,001, the No. 4,873,299, the No. 4,286,082, the No. 4,973,632, the No. 4,985,518, the No. 5124416, the No. 5250640, the No. 5264495, the No. 5145906, and U.S. Pat such Nos. No. 5380808, European Patent No. 0811636, the No. 0955086, the No. 0922717, the No. 1178059 It is described in European patent equal. Monomers described in these U.S. patents and European patents, crosslinking agents, polymerization initiators, can be applied in also the present invention and other additives.

The reverse phase suspension polymerization is a polymerization method for suspending the aqueous monomer solution in a hydrophobic organic solvent, for example, U.S. Patent No. 4,093,776, the No. 4,367,323, the No. 4,446,261, the No. 4,683,274, the It is described in U.S. Pat etc. No. 5,244,735.

Further, in the present invention, the time of the monomer is polymerized, to achieve the improved and coloring with time the prevention of absorption properties, which is also the object of the present invention, the total time from the time of adjusting the monomer component to the polymerization initiator the shorter preferable, these total time, preferably within 24 hours, more preferably within 12 hours, more preferably within 3 hours, particularly preferably within 1 hour.

For adjusting industrial neutralization and monomer components in large quantities tank, the residence time, that is, the total time is normally may exceed 24 hours, after adjustment of the monomer component and / or the longer the neutralized acrylic acid (the total time) is long, yellowing of the growth and the water absorbing resin of residual monomer (coloring over time) were found. Therefore, in order to shorten the residence time, preferably, the continuous neutralization and continuous monomer component adjusted to batch polymerization or continuous polymerization, more preferably the continuous polymerization is carried out.

Among the aqueous solution polymerization method, the polymerization initiation temperature of the monomer aqueous solution is 40 ° C. or higher, further 50 ° C. or more, further 60 ° C. or higher, particularly 70 ° C. or more high temperature polymerization is preferred. When applying the manufacturing method according to this high temperature polymerization invention to hydrogel obtained in (hot start polymerization), the effect of the present invention, including the particle size control can be maximized. The upper limit is below the boiling point of the aqueous solution, preferably 105 ° C. or less.

The peak temperature of the polymerization temperature is 95 ° C. or higher, more preferably 100 ° C. or higher, more preferably high temperature polymerization above 105 ° C. (boiling polymerization) are preferable. When the present invention is applied to water-containing gel obtained by such a boiling polymerization, the effect of the present invention, including the particle size control can be maximized. The upper limit is sufficient at the boiling point or less, preferably 130 ° C. or less, more preferably 120 ° C. or less.

Polymerization process in order to secure the effect of the present invention is an aqueous solution polymerization. May be neutralized in advance acrylic acid is aqueous solution polymerization, may be neutralized after polymerization, but during the polymerization in order conflicting absorbency (CRC) and improved solubles relative relationship or or after polymerization comprising the subdivision process of hydrogel polymer. Monomer as a main component acrylic acid, comprising the neutralization step of crosslinked hydrogel polymer after polymerization.

Furthermore, when mixing the reducing agent after the polymerization, the polymer gel of the viaduct sometimes mixing difficulties of high gel strength thus neutralizing agent and a reducing agent, thus, ease of uniform mixing, after polymerization a and drying it is preferable to further crosslink the previous crosslinked hydrogel polymer. Like the surface crosslinking agent described later is crosslinked, it can be used cross-linking agents which react with carboxyl groups, polyglycidyl compounds, polyhydroxy compounds such as a can be preferably used, the amount used of the monomer, preferably from 0.001 to 2 mol%, still more preferably from 0.01 to 1 mol%, particularly preferably appropriately determined in the range of 0.05 to 0.5 mol%.

The polymerization time is also not particularly limited, the kind of the hydrophilic monomer and the polymerization initiator may be appropriately determined depending on the reaction temperature and the like, 0.5 minutes usually to 3 hours, preferably 1 a minute to 1 hour.

From the viewpoint of even methoxyphenol in the resulting water-absorbing agent (especially p- methoxyphenol) Control (preferably 5 ~ 60 ppm in the water-absorbing agent), in the present invention are preferably polymerization step, methoxyphenol (especially p- methoxyphenol) acrylic acid in the monomer containing 10 ~ 200 ppm (the salt) containing 90 to 100 mol%, the monomer aqueous solution of the monomer concentration of 30 to 55% by weight, the radical polymerization initiator by 0.001 to 1 mol%, and the maximum temperature of 130 ° C. or less, preferably the polymerization time is a step of performing an aqueous solution polymerization or reversed-phase suspension polymerization under the conditions of 0.5 minutes to 3 hours, Furthermore the total mole% of acrylic acid and / or its salt of the above or below range, the concentration of the monomer component, the amount of the polymerization initiator, the polymerization temperature of the peak temperature, the polymerization time and the like.

When polymerizing the aqueous monomer solution, for example, potassium persulfate, ammonium persulfate, persulfates such as sodium persulfate, t- butyl hydroperoxide, hydroperoxide such as hydrogen peroxide, 2,2' azobis (2-amidinopropane) azo compounds such as dihydrochloride, 2-hydroxy-1-phenyl - propane-1-one, and a radical polymerization initiator such as benzoin methyl ether, further decomposition of the radical polymerization initiator redox initiators in combination with a reducing agent such as promotion to L- ascorbic acid. The amount of the polymerization initiator is usually 0.001 to 1 mol% based on the monomers, and more in the range of 0.001 to 0.5 mol%.

If polymerized in the redox initiator is preferably used in combination with persulfate or peroxide and the reducing agent, the reducing agent such as sodium sulfite, such as sodium bisulfite (heavy) sulfite (salt) , L- ascorbic acid (salt), a reducing metal such as ferrous salts (salts), amines, and the like. The amount of the reducing agent, the monomer component, usually from 0.0001 to 0.02 mol% are preferred.

Also, instead of using the polymerization initiator, radiation to the reaction system, an electron beam, the polymerization reaction may be carried out by irradiation with active energy rays such as ultraviolet rays. The radiation, electron beam, and an active energy ray polymerization initiator may be used in combination, such as ultraviolet light.

It methoxyphenol (especially p- methoxyphenol) which further to be described later is added to the monomer aqueous solution of the course of the polymerization or during polymerization of the chelating agent polymerization is preferred in that it can secure the effect of the present invention.

Reversed phase suspension polymerization in the present invention, the aqueous solution polymerization, spray polymerization or droplet polymerization can be applied, in order to secure the effect of the present invention, it is preferred that the polymerization process is an aqueous solution polymerization. May be neutralized in advance acrylic acid is aqueous solution polymerization, it may be neutralized after polymerization, but to improve the relative relationship between the conflicting absorbency (CRC) and Mizuka matter, during the polymerization or after polymerization containing hydrogel polymer that will be described later (1-7) subdivided steps.

(1-7) Gel comminution step polymerization obtained water-containing gel-like cross-linked polymer may be directly subjected to drying, but during polymerization or post polymerization, performs grain refining of water-containing gel-like crosslinked polymer it is preferable. Further grain refining using gel crusher etc., if necessary, preferably 0.1 ~ 3 mm a weight average particle diameter (defined by sieve classification), after further being comminuted to 0.5 ~ 2 mm, is dried that. The shape of polyacrylic acid (salt) -based water absorbent resin of the present invention is not particularly limited, for example, granules, powders, flakes, fibers or the like, can be in any form.

Therefore, grain refining but is carried out in a variety of ways, for example, fine particles of polymer during the above kneader polymerization, a screw type extruder having a porous structure of any shape after polymerization in the belt polymerization or tank polymerization a method of crushing by extrusion can be exemplified. Upon extrusion crushing, the addition in the form of an aqueous solution of the chelating agent described later, it is possible to further reduce the color change.

In the present invention, preferably grain refining of the crosslinked hydrogel polymer at the same time as the inorganic reducing agent is added. Mixing the water-containing gel and an inorganic reducing agent is a gel grain refining process, even by kneading, it is possible to achieve the effect of the present invention at a higher level. Further, the gel grain refining step and the polymerization step (middle), such as the case of adding an inorganic reducing agent before drying process, as described later, the odor problems in water-absorbing agent of the present invention, a water content of 3 to preferably 15 wt%, in the method of manufacturing the water-absorbing agent of the present invention is preferably controlled to a water content of the polymer in the drying step and after the surface cross-linking step 3-15 wt%.

Mixing After a reversed phase suspension polymerization of as particulate, when inorganic reducing agent (more chelating agents and α- hydroxy carboxylic acid compound described later) is added, the inorganic reducing agent is only on the surface of the water-absorbent resin It becomes a being that is, preferably internal to the inorganic reducing agent and a chelating agent and α- hydroxy carboxylic acid compound must not only on the surface of the water absorbent resin particles from the surface of the effect of the present invention are mixed. Therefore, the aqueous solution after polymerization of the polymer gel (in particular bulk gel or sheet-like gel), it is preferable to knead the inorganic reducing agent such as simultaneously with subdivision.

Incidentally, grain refining and mixing (in particular, kneading) in the kneader or a screw extruder (aka; meat chopper) are preferably used, may be used them in multiple series, also kneader and a meat chopper, etc. it may be used in combination with different devices. Screw extruder may be a single, it may be used two or more.

(1-8) Drying process in the manufacturing method of the particulate water absorbing agent of the drying process the present invention, water-containing gel obtained by the polymerization step, preferably the particulate hydrogel, more preferably, the weight average defined by sieve classification particle size of a step of drying the water-containing gel is 0.1 ~ 3 mm.

The drying method is heat drying, hot air drying, vacuum drying, fluid bed drying, infrared drying, microwave drying, drum dryer drying, azeotropic dehydration with a hydrophobic organic solvent, high humidity drying using high temperature steam, it can be employed one or more of a variety of ways. A preferred embodiment, a dew point of 40 ~ 100 ° C., more preferably a dew point can be exemplified contact drying with 50 ~ 90 ° C. gas. When using a hot-air drying, the wind velocity (wind velocity passing perpendicularly to dry the object extending horizontally) is preferably 0.01 ~ 10 [m / sec], and more preferably 0.1 to 5 [ m is in the range of / sec].

Drying temperature suitably used in the present invention is not particularly limited, for example, (preferably in the case of 100 ° C. or less carried out under reduced pressure) 50 ~ 300 ° C., preferably in the range of 100 ~ 250 ° C., more preferably 130 ~ 220 ° C., particularly preferably at a temperature range of 150 ~ 200 ℃. Drying time is usually 10 to 120 minutes, more preferably 20 to 90 minutes, more preferably 30 to 60 minutes. The drying time is less than 10 minutes, changes that occur within the polymer chain of the water absorbent resin is small, therefore believed not obtained sufficient improvement effect, therefore there may not be found effect of improving physical properties. Further, in drying time 120 minutes or more, the results or damage a water-absorbent resin, water-soluble content is increased, the effect of improving the physical properties do not also seen.

That is, in terms of control and water content adjustment methoxyphenol In the present invention, preferably drying step, the particulate water-containing gel, drying temperature 100 ~ 250 ° C., the water content in the drying time of 10 to 120 minutes 20 wt% it is preferably a step of drying to less, further drying temperature, drying time of the above or below range, a water content.

In the drying process of the present invention, the polymerization by the water content of the obtained water-containing gel-like crosslinked polymer preferably be dried to a 20% by weight or less, more preferably be dried up to 15% by weight or less, 10% it is particularly preferable to dry until the weight-percent or less. Here, the water content after drying, 2 wt% or more, 3% by weight or more, 4% by weight or more, 5% by weight or more, 6% by weight or more, preferably in the order of 7% by weight or more, the water content after drying with such a lower limit or more, it is possible to suppress the problem of odor by using a reducing agent. The water content in these ranges is preferably 2-20 wt%, more preferably 3 to 15 wt%, more preferably 5 to 15% by weight, particularly preferably from 7 to 15% by weight. Incidentally, (1-8) Drying process and later in (1-10) surface cross-linking step may be performed simultaneously and, further the water after further surface crosslinking simultaneously or surface crosslinking by adding a surface cross-linking agent in the course drying step it may be dried up rate.

In the present invention, the moisture content of more final water-absorbing agent after the drying step, the residual monomer tends to remain high moisture content, as well as bad subsequent handling properties, be used in combination chelating agents and inorganic reducing agent it has been found that that there is a high moisture content and easy coloring. Also, productivity and physical properties excessive drying and low moisture content (e.g., absorption rate) is lowered, if or use a reducing agent before drying, sometimes odor problems problems. Incidentally, Patent Document 17 (European Patent No. 1645596) and Patent Document 15 (U.S. Patent Application Publication No. 2005/0856604), does not disclose the use of certain amounts of p- methoxyphenol and water-insoluble particles. Furthermore, certain water content as the water-absorbing agent (3 to 15 wt%, still more 4 to 14 wt%, 6-12 wt%, 7-11 wt.%) Not disclose the importance of.

When adding an inorganic reducing agent before the drying step, the odor problem is found, in the present invention has solved the problems such by controlling the water content. The odor and trace components such as water-containing gel and residual monomers after polymerization rather than decomposition of mere reducing agent, a complex odor reducing agent, caused by the water content of the water-absorbent resin to a certain value or less it is estimated that it is in the present invention the water content in the drying step and later surface cross-linking step is crucial was found. In the case the moisture content after drying is too high, sometimes accompanied by a decrease in productivity in pulverization and classification to be described later, is not preferable.

(1-9) the water-absorbing resin of the present invention obtained by the pulverization step and classification step drying, grinding for Tsubukei control necessary according to the purpose, may be through processes such as classification. These methods are described, for example, in WO 2004/69915.

By drying the water-containing gel-like cross-linked polymer after polymerization, dry polymer is obtained. Dry polymer may be used as it is as a dry powder (preferably solid content of 80 wt% or more), it may also be adjusted particle size after drying if necessary. Water-absorbing resin after drying for improving physical properties of the surface cross-linking later, preferably to a specific particle size. The particle size of the polymerization, pulverization, classification, granulation, can be appropriately adjusted in the fine particle collection or the like.

(In the present embodiment, referred to as the water-absorbing resin powder substance) water-absorbent resin before surface-crosslinking The weight average particle diameter of (D50), 200 ~ 550 .mu.m, preferably 250 ~ 500 [mu] m, more preferably 300 ~ 450 [mu] m, in particular preferably it is adjusted to 350 ~ 400 [mu] m. Also, better less 150μm particles below. Based on the total weight of the dry polymer, the weight ratio of particles having a particle size of less than 150μm is usually 0 to 5 wt%, is adjusted preferably 0-3 wt%, particularly preferably 0-1 wt%. Furthermore, better less than the particle 850 .mu.m. Based on the total weight of the dry polymer, the weight ratio of Tsubukei 850μm or more particles is usually from 0 to 5 wt%, is adjusted preferably 0-3 wt%, particularly preferably 0-1 wt%. Particle size distribution logarithmic standard deviation ([sigma] [zeta]) is preferably 0.20 to 0.45, preferably 0.27 to 0.40, preferably from 0.25 to 0.37. Such particle size is preferably applied to the water-absorbent resin and the final product of the water-absorbing agent after the surface crosslinking. Therefore, preferably even after the step of adding the surface cross-linking step or after the chelating agent, inorganic reducing agent, it is applied as required classification step or crushing step.

(1-10) surface cross-linking step the particulate water-absorbing agent obtained in the present invention, after the surface crosslinking treatment step conventionally known, can be a suitable water absorbing agent more hygiene materials. The surface cross-linking, the surface layer of the water-absorbent resin: is a further providing the portion of high crosslink density (the surface near the front-rear normally several 10μm water-absorbing resin surface), radical crosslinking or surface polymerization at the surface, a surface cross-linking agent it can be formed by crosslinking reaction or the like with.

As the surface cross-linking agent which can be used in the present invention, there is provided a polyacrylate type water-absorbing functional groups and ionic bonding resin or covalent surface cross-linking agent (preferably covalent surface cross-linking agent), various of it organic or inorganic cross-linking agent can be exemplified, it is possible from the viewpoint of the physical properties and handling properties, preferably used a crosslinking agent capable of reacting with a carboxyl group. For example, polyhydric alcohol compounds, polyvalent epoxy compounds such as polyglycidyl compound, a condensate of a polyhydric amine compound or a haloepoxy compound, an oxazoline compound, a mono, di-, or poly-oxazolidinone compound, a polyvalent metal salt, alkylene carbonate compounds, oxetane compounds, can be exemplified one or two or more such cyclic urea compounds.

More specifically, U.S. Patent No. 6228930, the No. 6071976, may be mentioned compounds exemplified such as Nos. No. 6,254,990. For example, 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-cyclohexane multivalent dimethanol, etc. alcohol compounds, ethylene glycol diglycidyl ether and epoxy compounds such as glycidol, ethylene diamine, diethylene triamine, triethylene tetramine, tetraethylene pentamine, pentaethylene hexamine, polyethylene imine, polyhydric and polyamide polyamine Emissions compounds; epichlorohydrin, epibromohydrin, alpha-methyl haloepoxy compounds of epichlorohydrin or the like; oxazolidinone compound of 2-oxazolidinone, etc.; condensates of the polyvalent amine compound and the haloepoxy compound ethylene Cabo sulfonate alkylene carbonate compounds such as; oxetane compound; 2- but imidazolidinone cyclic urea compounds of the like, but is not particularly limited.

To improve the AAP and SFC Among these surface crosslinking agents, polyhydric alcohol compound as a surface cross-oxazolidinone compound, dehydration reactive crosslinking agent selected from an alkylene carbonate compound are preferably used, also, during surface crosslinking or polyvalent epoxy compounds such as polyvalent glycidyl compound as the surface cross-linking agent in order to control the surface postcrosslinking water content 3-15% by weight will be described later, it is preferably used.

The amount of the surface cross-linking agent varies depending on the compounds and combinations thereof, and the like to be used, water-absorbent resin powder 100 parts by weight, preferably in the range of 0.001 to 10 parts by weight, 0.01 in the range of parts by weight to 5 parts by weight is more preferable. In the present invention, in accordance with the surface cross-linking agent is water may be used. At this time, the amount of water used relative to the water-absorbing resin powder 100 parts by weight, preferably from 0.5 to 20 parts by weight, more preferably 0.5 to 10 parts by weight. Further, in the present invention, it is possible to use a hydrophilic organic solvent other than water.

At this time, the amount of the hydrophilic organic solvent used is relative water-absorbing resin powder 100 parts by weight, 0-10 parts by weight, preferably from 0 to 5 parts by weight. Also upon mixing of the crosslinking agent solution into the water-absorbing resin powder, a range that does not impair the effects of the present invention, for example, 0 to 10% by weight or less, preferably 0 to 5 wt%, more preferably 0-1 wt% , it may be allowed to coexist water-insoluble inorganic fine particles and a surfactant. Surfactants and amounts used are exemplified in U.S. Patent No. 7,473,739.

The mixing apparatus used in mixing the surface cross-linking agent solution, various mixers can be used, preferably, a high-speed stirring type mixer, preferably in particular high-speed stirring continuous mixer, for example, trade name Turbulizer It can be exemplified (Japan Hosokawa micron Co., Ltd.) and product names Loedige mixer (Redige Co., Ltd. of Germany), and the like.

Surface treatment in the production method of the particulate water-absorbing agent of the present invention is a step of performing surface cross-linking reaction to increase the crosslink density of the water-absorbent resin surface. To obtain the desired performance of the particulate water-absorbing agent of the present invention, the water-absorbing resin after mixing the surface cross-linking agent is preferably heat-treated, and subsequently cooling treatment if necessary.

The heating temperature of the heat treatment (heat medium temperature) is, for example, 70 - 300 ° C., preferably 120 ~ 250 ° C., more preferably 0.99 ~ 250 ° C., the heating time is preferably in the range of 1 minute to 2 hours it is. The heat treatment can be carried out using conventional dryers or heating furnaces. Here, 0.99 ~ 250 ° C., such as high-temperature surface cross-linking or polyhydric alcohols, such as (the carboxyl group of the water-absorbent resin) dewatering when using a reactive surface agent, the water after the surface cross-linked water absorbent resin is further dried the rate is less than 3%, the tendency of particular less than 1%.

In particular, in the production of water content 3 to 15 wt% of the particulate water-absorbing agent, the heating temperature (heating medium temperature more material temperature) is preferably carried out in a temperature range of 80 ~ 250 ° C., more preferably temperature range of 80 ~ 160 ° C., further the temperature range of preferably 80 ~ 120 ° C., and most preferably at a temperature range of 80 ~ 100 ° C.. If the heating time is less than 80 ° C., the surface cross-linking of the water-absorbent resin is not sufficient, absorbency against pressure and saline flow rate decreases. Polyvalent epoxy compounds such as polyvalent glycidyl compound as the surface cross-linking agent in order to control the water content of 3 to 15 wt% is preferably used. Also, if higher than 250 ° C., to produce the case and, unpleasant odors particulate water absorbing agent is colored, undesirably. Incidentally, the water content of the water-absorbing resin is not determined only by the heating temperature, heating time, pressure (vacuum) and the dew point of the reactor, to be dependent on such production volume (processing amount per unit time), their may be set as appropriate, also the material temperature of the water-absorbent resin is lower in general than the heating temperature, it is also preferable to obtain the water-absorbent agent having a predetermined water content by heating the material temperature kept below the boiling point of water.

These surface cross-linking treatment method, EP 0349240, the No. 0605150, the No. 0450923, the No. 0812873, the No. 0450924, various European patents such as Nos. No. 0668080, Japanese Patent No. 7 No. -242 709, various Japanese Patent such as Nos. No. 7-224304, US Pat. No. 5,409,771, the same No. 5,597,873, the same No. 5,385,983, the same No. 5,610,220, the same No. 5,633,316, the same No. 5,674,633, the first 5,462,972 various U.S. patents such issue, WO 99/42494, the No. 99/43720, is also described in various international patent publication such as Nos. No. 99/42496, a method in the present invention these surface crosslinking It can be applied. Also in the surface-crosslinking treatment step, after the crosslinking reaction, it may be further added a water-soluble polyvalent metal salts such as aluminum sulfate aqueous solution. These WO 2004/69915 for a method are also described in the No. 2004/69293 and the like, it is applicable to the present invention.

Incidentally, from the viewpoint of controlling the methoxyphenol, preferably the surface crosslinking step in the present invention, by mixing the surface cross-linking agent 0.001 to 10 parts by weight based on the water-absorbent resin powder 100 parts by weight after the drying step, 70 done by 1 minute to 2 hours of heat treatment at ~ 300 ° C., even at above or surface crosslinking agent and its amount below, the heating temperature and time.

Further, a polyvalent metal and / or cationic polymers described later after the surface cross-linking and simultaneously or surface cross-linking may be added. These polyvalent metal and / or cationic polymers can also act as an ion binding surface cross-linking agent, by combination with the covalent surface cross-linking agent, it is possible to further improve the liquid permeability.

Here, in the production of water content 3 to 15 wt% of the particulate water-absorbing agent, the water content of the water-absorbing resin after surface cross-linking is 3 wt% or more, 4% by weight or more, 5% by weight or more, 6 wt% or more, preferably in the order of 7% by weight or more, the moisture content of the surface crosslinking by the range, odor by using a reducing agent, an inorganic reducing agent, particularly surface-crosslinking step during or earlier it is possible to suppress the odor of the resulting water-absorbing agent in addition, as a result, it is possible to suppress the odor of the finally obtained water-absorbing agent. This effect, when the surface cross-linking step or the surface cross-linking step before, is remarkable when added to a particular drying step or post-polymerization drying step inorganic reducing agent prior, therefore, in particular moisture content in the addition of such inorganic reducing agent It is controlled. Further, as another means, the water content at the time of surface crosslinking is less than 3 wt%, for example, the surface cross-linking with the hot surface crosslinking and dehydrating reactive surface crosslinking agent of the heating medium temperature further at material temperature 0.99 ~ 250 ° C., the surface it is more preferable from the viewpoint of odor to add inorganic reducing agent after the crosslinking step.

The odor rather than decomposition of mere reducing agent, and trace components such as water-absorbing resin or its residual monomer, a complex odor reducing agent, caused by the water content of the water-absorbent resin to a certain value or less it is estimated that, water content in the drying step and the surface cross-linking step is crucial was found in the present invention. Also, in order to obtain a higher absorption capacity and higher absorbency against pressure of the water-absorbing agent, the water content of the water-absorbing resin after surface cross-linking is preferably in the above range.

Furthermore, in the case of producing the moisture content 3-15% by weight of the particulate water-absorbing agent, it is preferable to carry out surface cross-linking while maintaining the water content of the water-absorbent resin to 3 to 15 wt%, 4-14 state it is more preferable to perform the surface cross-linking while maintaining the weight%, more preferably be surface-crosslinking while holding 5 to 13 wt%, of 6-12% by weight, it was maintained at 7-11 wt% in it it is most preferable to perform the surface cross-linking. If the water content is within the above range or higher, the absorption capacity of the water-absorbent resin can be prevented from being significantly reduced. If the water content is within the above range (15 wt%) or less, coloring is further improved, it is possible to suppress the reduction in the fluidity of the handling properties of the deterioration and the powder of the water-absorbing resin.

May be further dried as necessary after surface cross-linking, the addition of water or other additives, may be adjusted water content and physical properties. Reducing agents and chelating agents is essential added in the present invention, also may be added, such as preferably added as water-insoluble inorganic fine particles after the surface crosslinking, other, relative to 100 parts by weight of the water-absorbing resin as an additive, preferably 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, antibacterial agents, deodorants, be added a polyvalent metal compound, such as good.

(1-11) in addition to other steps described above, if necessary, a granulation step, fines removal step, the water content adjustment step (for example, the present embodiment 1-16) may be provided fines recycling step or the like. Further, (1-10) after the surface cross-linking step to a chelating agent, it may be provided the step of adding an inorganic reducing agent. The (1-10) surface cross-linking step and the following [8] Various mixers used in such granulation can be used appropriately in addition.

The particulate water absorbing agent of the present invention is a particulate water-absorbing agent as a main component of polyacrylic acid (salt) -based water absorbent resin, comprising: a chelating agent, and an inorganic reducing agent, the content of the chelating agent 0.001 to 0.5 wt%, the following (1) to (3)
(1) the content of methoxyphenol is 5 ~ 60 ppm.
(2) to contain the water-insoluble inorganic fine particles.
(3) the water content is 3 to 15 wt%.
It is characterized by satisfying any one or more of the requirements.

Hereinafter, [2] a chelating agent, (3) inorganic reducing agent, for [4] methoxy phenol, and (5) water-insoluble inorganic fine particles will be described.

[2] The particulate water absorbing agent of the chelating agents present invention, for solving the problem, essential to include a chelating agent. The chelating agent of the present invention, in terms of effect, the polymer compound or a non-polymeric compound, non-polymeric compounds are preferred among them, specifically, amino polycarboxylic acid, organic polyvalent phosphoric acid, inorganic polyvalent acid , compounds selected from amino polyvalent phosphoric acid are preferred. In terms of effect, the molecular weight of the chelating agent is preferably from 100 to 5000, more preferably 200-1000. If there is no chelating agent, a poor water absorbing agent in terms of coloration and deterioration.

Here, a plurality of functional group in one molecule and a polyvalent, preferably 2 to 30, further 3 to 20, having from 4 to 10 functional groups. These chelating agents are water-soluble chelating agent, specifically, 100 g (25 ° C.) water 1g above, it is preferable and more water-soluble chelating agent which dissolves more than 10g.

Examples of the amino polycarboxylic acid, iminodiacetic acid, hydroxyethyliminodiacetic 2 acetate, nitrilotriacetic acid, nitrilotriacetic propionic acid, ethylenediaminetetraacetic acid, diethylenetriaminepentaacetic acid, triethylenetetramine 6 acid, trans-1,2-diaminocyclohexane 4 acetate, N, N-bis (2-hydroxyethyl) glycine, diaminopropanol tetraacetic acid, ethylenediamine 2 propionic acid, hydroxyethylene diamine triacetic acid, glycol ether diamine tetraacetic acid, diaminopropane tetraacetic acid, N, N'-bis (2 - hydroxybenzyl) ethylenediamine -N, N'-2 acetate, 1,6-hexamethylene diamine -N, N, N ', N'-4 acetic acid and salts thereof, and the like.

Examples of the organic polyvalent phosphoric acid, nitrilo acetate - di (methylenephosphinic acid), Nitoriroji acetate - (methylenephosphinic acid), nitriloacetic acid -β- propionic acid - methylene phosphonic acid, nitrilotris (methylene phosphonic acid), 1-hydroxy include diphosphonic acid, and as the inorganic polyvalent phosphoric include pyrophosphoric acid, tripolyphosphate and the like salts thereof.

Further, as the amino polyvalent phosphoric acid, ethylenediamine -N, N'-di (methylenephosphinic acid), ethylenediaminetetra (methylenephosphinic acid), cyclohexanediamine tetra (methylenephosphonic acid), ethylenediamine -N, N'-diacetic acid -N, N'-di (methylenephosphonic acid), ethylenediamine -N, N'-di (methylenephosphonic acid), ethylenediaminetetra (methylenephosphonic acid), polymethylene diamine tetra (methylene phosphonic acid), diethylenetriamine penta (methylene phosphonic acid) and salts thereof.

As the most preferred amino polyvalent phosphoric acid in the present invention, ethylene diamine tetra (methylene phosphonic acid) or a salt thereof. Preferable salts are monovalent salts, especially sodium salts, alkali metal salts such as potassium salts, ammonium salts, and amine salts. Further, sodium salts, potassium salts are particularly preferred as salt.

Incidentally, among these, from the viewpoint of preventing coloration, amino acid-based metal chelating agent, an amino polyvalent phosphoric acid-based metal chelating agents and salts thereof are preferably used. Especially, diethylenetriaminepentaacetic acid, triethylenetetramine 6 acid, trans-1,2-diaminocyclohexane tetraacetic acid, ethylene diamine tetra (methylenephosphinic acid), diethylenetriamine penta (methylene phosphonic acid) and salts thereof are more preferably used. Of these, ethylene diamine tetra (methylene phosphonic acid) or most preferably a salt thereof, as the salt include monovalent salts are preferred, sodium salts, alkali metal salts such as potassium salts, ammonium salts, amine salts . Sodium salts among these salts, 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 wt%, preferably 0.001 to 0.1% by weight 0.002 to 0.1% by weight Gayori , more preferably from 0.003 to 0.05 wt.%, particularly preferably 0.005 to 0.05 wt%. If the content of the chelating agent is less than 0.001 wt%, it badly the coloring with time of the particulate water-absorbing agent, since the time color of the particulate water absorbing agent deteriorates, which is not preferable. Also, if the content of the chelating agent, such as an embodiment of Patent Document 29 is more than 0.5 wt%, found that the initial coloring of the particulate water absorbing agent is increased, the initial color tone of the particulate water-absorbing agent because it may deteriorate, unfavorably. Also, because they may also deteriorate over time the color tone of the particulate water absorbing agent, which is not preferable.

Note that the coloring over time, high temperature refers to coloring of the particulate water absorbing agent, such as when long-term storage under high humidity, the initial coloring and the color tone or colored particulate water absorbing agent at the time obtained by the production They say the degree.

Such chelating agents, the (1-6) polymerization step (1-7) gel grain refining step, (1-8) Drying process (1-9) pulverizing step and classification step, (1-10) surface crosslinking step, (1-11) other possible additives in any one or more steps, (1-6) in the polymerization step may be added to the chelating agent during monomer adjusting polymerization step before, during polymerization it may be added to the chelating agent. These (1-6) ~ (1-11) becomes the content of the water-absorbing agent usage is obtained substantially in the manufacturing process, such as, chelating agents residual monomer and water-in water-absorbing agent extract the chelating agent from the water-absorbing agent as well as matter of quantified by water or saline can be appropriately quantified like by liquid chromatography or ion chromatography I chromatography with.

Incidentally, Patent Document 29 (WO 2006/109882 pamphlet), the anti-coloring method of adding a plurality of times to a compound or a sulfur-based reducing agents containing a coloring prevention method and the phosphorus atom of using ammonium acrylate in the monomer discloses but specific moisture content of the patent document 29 present invention (3-15 wt%), let alone the specific amount of the compound containing a phosphorus atom or a sulfur based reducing agent (0.001 to 0.5% by weight There, preferably without disclosing 0.001 to 0.1 wt%), example 5, 1-hydroxyethylidene-1,1 addition of diphosphonic acid 1.0% by weight of the Patent Document 29, in example 4 also discloses a total of 2.0% by weight using 1-hydroxyethylidene-1,1-diphosphonic acid. The use of a chelating agent exceeding such 0.5 wt% also in combination of an inorganic reducing agent, as shown in Comparative Example 1-5 described below, found to give rather adverse effect on the coloring of the resultant water-absorbing agent, and it completed the present invention.

[3] inorganic reducing agent present invention to such a particulate water-absorbing agent comprises an inorganic reducing agent required, water preferably, with inorganic reducing agents, water-soluble inorganic compound or a reducing inorganic elements having reducing inorganic elements including sex organic compound. Incidentally, the "Water-soluble" means that more than 1g per 100g of water of 25 ° C., further 5g or more, dissolves especially 10g or more. If there is no chelating agent, residual monomer, a poor water absorbing agent in terms of coloration and deterioration.

Inorganic reducing agent in the present invention, distinction to be used is a reducing agent as a polymerization initiator used in the polymerization step. That is, the inorganic reducing agent means a compound having a reducing needs to have the reducing inorganic element, specifically, a compound having a reducing sulfur atom or reducing phosphorus atom. , preferably include water-soluble compound comprising a compound or a reducing phosphorus atom containing reducing sulfur atom. Therefore, even an organic compound be an inorganic compound, if it has a reducing sulfur atom or reducing phosphorus atom, regarded as inorganic reducing agents of the present invention.

The inorganic reducing agent may be an acid type, preferably a salt, more preferably a monovalent or polyvalent metal salt is a salt, a monovalent salt is more preferable. Among these inorganic reducing agent, oxygen-containing reducing inorganic compounds exemplified below, i.e., inorganic reducing agents sulfur and phosphorus is bonded to oxygen, among others oxygenated reducing inorganic salts are preferred. These inorganic reducing agents are alkyl groups, reducing inorganic atoms in organic compounds such as hydroxyalkyl groups, preferably, it may be inorganic reducing agent having a reducing sulfur atom or a phosphorus atom.

Also used in the present invention, the inorganic reducing agent having a reducing sulfur atom or reducing phosphorus atom, the oxidation number of the most stable sulfur atom +6 (positive hexavalent), oxidation of the phosphorus atoms the number is +5 (positive pentavalent), generally is less than each atom of oxidation number has a reducing +4 valent sulfur compound (e.g., sulfite, bisulfite, pyrosulfite), trivalent sulfur compounds (e.g., dithionite), +2 sulfur compounds (e.g., sulfoxylate salts), +4 valent phosphorus compound (e.g., following phosphates) + trivalent phosphorus compound (e.g., nitrous phosphate, pyrophosphoric phosphites), + 1-valent phosphorus compound (e.g., hypophosphite) are used. In these reducing inorganic compounds, reducing sulfur atom or reducing phosphorus atoms may be substituted by organic matter.

An inorganic reducing agent, as the inorganic compound containing sulfur atom is not particularly limited, for example, sodium sulfite, potassium sulfite, calcium sulfite, zinc sulfite, sulfite salts such as ammonium sulfite; sodium bisulfite, potassium bisulfite, sulfite calcium hydrogen, hydrogen sulfite salts such as ammonium bisulfite; sodium metabisulfite, potassium metabisulfite, pyrosulfite salts such as metabisulfite ammonium; sodium dithionite, potassium dithionite, ammonium dithionite, dithionite potassium three dithionite, three thione salts such as trisodium dithionite; calcium acid, dithionite, such as dithionite, zinc potassium tetrathionate, tetrathionate salts such as sodium tetrathionate, thiosulfate sodium, potassium thiosulfate, ammonium thiosulfate Thiosulfate and the like; sodium nitrite, potassium nitrite, calcium nitrite, nitrite, etc. zinc nitrite. Examples of the inorganic compounds containing phosphorus atoms, sodium hypophosphite, and the like. Among these, sulfite, bisulfite, pyrosulfite, dithionite salts are preferred, sodium sulfite, sodium bisulfite, potassium metabisulfite, sodium dithionite is preferred.

Further, an inorganic reducing agent, the water-soluble organic compound containing a sulfur atom is not particularly limited, for example, 2-hydroxy-2-sulfinate acetate sodium formaldehyde sulfoxylate, formamidine sulfinic acid, and thioglycolic acid tris ( 2-carboxyethyl) phosphine hydrochloride (TCEP), but tributylphosphine (TBP), and the like, among them, 2-hydroxy-2-sulfinate acid, 2-hydroxy-2-sulfonatoacetic acid, and / or their salts It is preferably exemplified. Preferred salts are alkali metal, and alkaline earth metal salts, Li, Na, K are preferred, especially sodium salts. 2-hydroxy-2-sulfinate acid (salt) may be used in combination with 2-hydroxy-2-sulfonatoacetic acid (salt), it may further be used in combination with the aforementioned inorganic compounds.

Preferred inorganic reducing agents, 2-hydroxy-2-sulfinate acid, an inorganic reducing agent of the present invention to have a reducing sulfur atom as a sulfinate groups, commercially available from Brueggemann Chemical (Germany Heilbron standing) BRUGGOLITE (R) FF7 as can be obtained, 2-hydroxy-2-sulfinate acid disodium salt 50-60 wt% of sodium sulfite (Na 2 SO 3) 30 ~ 35 wt% and 2-hydroxy-2- sulfonato acid disodium salt may be obtained as BRUGGOLITE (R) FF6 containing 10-15% by weight.

Inorganic reducing agent contained in the particulate water absorbing agent of the present invention is preferably 0.01 to 1.0 wt%, more preferably 0.05 to 1.0% by weight, 0.05 to 0.5 wt% particularly preferred. When the content of the inorganic reducing agent is 0.01 wt% or more, it is possible to suppress the coloring with time of the particulate water-absorbing agent. Further, when the content of the inorganic reducing agent is 1.0 wt% or less, it is possible to suppress the odor of the particulate water-absorbing agent, in particular, the effect of the odor after the particulate water-absorbing agent has absorbed an aqueous liquid it is possible to suppress.

Incidentally, the inorganic reducing agent is the (1-6) polymerization step (1-7) gel grain refining step, (1-8) Drying process (1-9) pulverizing step and classification step, (1-10) surface cross-linking step, (1-11) other steps (such as the addition step after the surface cross-linking) can be added in any one or more of, but may be added at the time of polymerization initiation is (1-6) polymerization process, in general the reducing agent is consumed, preferably during the polymerization, more preferably be added after the polymerization step, the manufacturing process may be added, including the amount of reducing agent consumed in the particular process or drying process. The amount of the inorganic reducing agent in the resulting water absorbing agent drying step after, especially if the addition of the inorganic reducing agent after surface crosslinking, the content of the water-absorbing agent usage is obtained substantially in the manufacturing process but drying step prior to chelator residual monomer and extractable polymer quantitative liquid chromatography or ion chromatography to extract a chelating agent from the water-absorbing agent as well with water and saline in the inorganic water-absorbing agent to be added It can be appropriately quantified, and the like. These (1-6) ~ (1-11), but usage at each manufacturing step, such as is in substantially resulting water-absorbing agent, in the water-absorbing agent chelating agent of residual monomer and extractable polymer appropriately be quantified such as liquid chromatography or ion chromatography to extract a chelating agent from the water-absorbing agent as well as quantitatively by water or saline.

Inorganic reducing agents of the present invention is preferably from the viewpoint of odor being added after the surface crosslinking treatment step. As in Patent Document 5, without controlling the specific water content of the present invention (3-15 wt%), as addition of an inorganic reducing agent a surface-crosslinking treatment step or before that, the resulting particulate water-absorbing agent There after unfavorable may have off-flavors, especially obtained particulate water absorbing agent has absorbed aqueous liquid, undesirably generate off-flavors. Such odor is not limited to odor mere inorganic reducing agent, a surface cross-linking step, it is estimated that the odor by-produced in surface cross-linking step, especially aiming at high SFC and high AAP.

That is, the method of manufacturing the water-absorbing agent present invention, the production method thereof 3 subordinate concepts to the (c) Required method for producing a particulate water absorbing agent of the present invention (Part 3), acrylic acid (salt) mainly comprising a polymerization step of an aqueous monomer solution containing as a main component, a drying step of the hydrogel crosslinked polymer obtained by polymerizing, and a surface cross-linking step, polyacrylic acid (salt) -based water absorbent resin a method for producing a particulate water absorbing agent to, further comprising, a monomer methoxyphenol to acrylic acid and adding step of the chelating agent 0.001 to 0.5% by weight of the addition step and the inorganic reducing agent contains 10 ~ 200 ppm in terms of after the drying step, and the surface cross-linking step, controlling the water content of the polymer 3 to 15 wt%, more preferably, the inorganic reducing agent, before drying shaped hydrogel It is added to the crosslinked polymer, the particulate water-absorbing agent It is a manufacturing method (third manufacturing method).

[4] The particulate water absorbing agent of the methoxy phenol present invention, if that does not satisfy the requirements of the above (2) and (3), which will contain 5 ~ 60 ppm of methoxyphenol, (2) and even if it meets one of the requirements of (3), preferably contains a methoxyphenol, and more preferably contains 5 ~ 60 ppm of methoxyphenol.

The methoxy phenols, specifically, o, m, p-methoxyphenol and further a methyl group them, t- butyl group, one or methoxyphenol having two or more substituents such as a hydroxyl group is illustrated, particularly preferably, p- methoxyphenol in the present invention use, are used in particular the (1-6) polymerization process.

p- methoxyphenol is preferably contained in the acrylic acid is a monomer main component a polyacrylic acid (salt) -based water absorbent resin of the present invention. The content of methoxyphenol in the particulate water-absorbing agent (especially p- methoxyphenol) of the present invention is more preferably 5 ~ 50 ppm, more preferably 6 ~ 50 ppm, particularly preferably 7 ~ 40 ppm, and most preferably 8 ~ 30 ppm . The (1-6) in the polymerization step, urine by controlled within ranges described in the section methoxy content of phenol (10 ~ 200 ppm) further below (10-1) acrylic acid, polymerization control with since the gel stability during use, such as sex increases even more preferred.

If the content of the methoxyphenol is less than 5 ppm, i.e., if the removal of p- methoxyphenol as a polymerization inhibitor by purification such as distillation, there is a risk that polymerization occurs before starting a deliberately polymerizing only Narazu is not preferable because the weatherability is deteriorated in the particulate water-absorbing agent of the present invention obtained acrylic acid (salt) as a main raw material. Also, if the content of the methoxyphenol is more than 60 ppm, not preferable because problems such as the polymerization reaction of the polymerizable delay etc. can not be controlled is generated, is not preferable because the particulate water absorbing agent of the present invention is colored.

The particulate water absorbing agent methoxyphenol in (5 ~ 60 ppm), the above polymerization of a monomer aqueous solution containing as a main component an acrylic acid (salt) for 10 ~ 200 ppm containing methoxyphenol (concentration of the of the present invention, temperature, after polymerization initiator, etc.), coordinate polymerization obtained in drying the crosslinked hydrogel polymer under the conditions of preferred ranges described above (the above temperature, time, wind speed, by going through a process of solids, etc.) can do. Generally p- methoxyphenol as a polymerization inhibitor in acrylic acid is also known to be used in an amount of 200 ppm, also distillation of acrylic acid (boiling point 143 ° C.) during the polymerization of the water-absorbing resin (e.g., U.S. Patent No. 6,388,000 No.) treated with activated charcoal acrylic acid salt or (Patent Document 7) it is also well known that, according distillation in purification p- methoxyphenol is substantially removed from the acrylic acid, therefore, of the present invention p- methoxyphenol It is not become a.

Incidentally, Patent Patent Document 17 (EP 1645596), the oxygen-containing reducing inorganic salt, an aminocarboxylic acid chelating agent and a water absorbent resin composition containing an organic antioxidant disclosed, prevent organic oxidizing (claim 7 of Patent Patent Document 17, examples 1 wt% in 6 used) alkyl hydroxy anisole as an example of the agent are disclosed and the alkyl hydroxy anisole does not exhibit a sufficient effect as compared to the p- methoxyphenol.

Furthermore, the anti-coloring technique with a reducing agent such as described in Patent Document 12 and Patent Document 15 to 19 in combination with a chelating agent and an inorganic reducing agent, the more specific content of methoxyphenol (especially p- main Toshi phenol) control does not disclose the problems and effects described in the present application due to (in particular uniformly small amount contained in the inside of the water absorbing resin used in the polymerization) is.

Similarly, as described in Patent Document 15 and the examples 5, the case of adding an inorganic reducing agent before drying, requiring attention for odor generated by the final water content after surface crosslinking. Patent Document 5 discloses the polymerization of the water-absorbent resin in p- main tosylate phenol 10 ~ 160 ppm but, p- main tosyl phenol discloses including patent Documents 10 and 11, in combination and preferably the final moisture of the present chelating agent and a reducing agent It does not disclose the rate. Furthermore, these patent documents disclose the use of a polymerization time of p- methoxyphenol, p- methoxyphenol also consumed during the polymerization or during drying, because it does not disclose a control method of the present invention, the resulting final product not disclose p- main Toshi phenol content in. Further, Non-Patent Document 1; and wherein the (The Modern Superaborbent Polymer Technology 1998 years) of eight in Table 5,2 of page41 manufacturing location A ~ remaining p- main tosylate phenolic water absorbent resin from H (MEHQ) and, MEHQ is disclosed a water-absorbent resin of 16 ~ 151 ppm, but non-patent document 1 neither discloses the use of chelating agents and inorganic reducing agent to a specific MEHQ (5 ~ 60ppm) of the present invention.

[5] The particulate water absorbing agent of the water-insoluble inorganic fine particles present invention, if that does not satisfy the requirements of the above (1) and (3), which will contain a water-insoluble inorganic fine particles, (1) and ( even if it meets one of the requirements 3), from the viewpoint of flowability of the liquid permeability (SFC) improvement and moisture absorption during, water-insoluble inorganic fine particles, it is preferred particularly that includes a white water-insoluble inorganic fine particles . Here, by the addition of white water-insoluble inorganic fine particles, a white resulting water-absorbing resin is further improved, Further, the gel strength of the water-absorbing resin is preferably improved. Etc. Patent Patent Documents 15-17, does not disclose the p- methoxyphenol and white combination of water-insoluble inorganic fine particles traces. Here, the whiteness of the water-insoluble inorganic fine particles L, a, b in 70 above, ± 5 within a range within ± 10, preferably 80 or more, ± 3 within, ± 7, preferably within 90 above, ± 2 within is within ± 5, white (preferably 5 or more L, more is 7 or higher) than the water-absorbent resin before mixing the insoluble inorganic fine particles are used. In particular the water content of 3 to 15 wt% in the water absorbing agent, if further the above range, in order to solve the problem of the present invention, water-insoluble inorganic fine particles are preferably used in combination.

The water-insoluble inorganic fine particles, average particle diameter measured by a Coulter counter method, preferably the 0.001 ~ 200 [mu] m, more preferably 0.005 ~ 50 [mu] m, more preferably in the range of 0.01 ~ 10 [mu] m particles , preferably hydrophilic fine particles include silica metal oxide such as (silicon dioxide) or titanium oxide, zinc and silicon, or a composite hydrous oxide (e.g., including zinc and aluminum, WO 2005/010102 illustrated) No. silicate such as natural zeolite or synthetic zeolite (salt), kaolin, talc, clay, bentonite, calcium phosphate, barium phosphate, silicic acid or a salt thereof, clay, diatomaceous earth, silica gel, zeolite, bentonite, hydroxyapatite, hydro hydrotalcite, vermiculite, perlite, Isola Door, activated clay, silica sand, quartzite, strontium ore, fluorite, bauxite, and the like. Further, more preferably these silicon dioxide and silicic acid (salt), silicon dioxide and silicic acid (salt) is more preferable.

But not the silicon dioxide is particularly limited, it is preferably a fumed silica amorphous prepared by a dry method. Such as silicon dioxide, it referred to as quartz is not preferable because it can cause health problems.

Water-insoluble inorganic fine particles contained in the particulate water absorbing agent of the present invention is preferably in the range of 0.05 to 1.0 wt%, more preferably 0.05 to 0.8 wt%, more preferably from 0.05 to 0.7 wt%, particularly preferably from 0.1 to 0.5 wt%. When the content of water-insoluble inorganic fine particles 0.05% by weight or more, it is possible to suppress the deterioration of the urine resistance of the particulate water-absorbing agent. If it is 1.0% by weight or less content of the water-insoluble inorganic fine particles, it is possible to suppress a decrease in absorbency against pressure of the particulate water-absorbing agent.

Water-absorbing resin of the above-mentioned [1], [2] in addition to a chelating agent to [5] the water-insoluble inorganic fine particles, the following [6] α- hydroxy carboxylic acid compound, [7] a polyvalent metal salt and / or cationic it is also preferred to include a polymer, it may also have (8) granulation.

[6] α- hydroxy carboxylic acid compound particulate water absorbing agent of the present invention, further anti-coloring and deterioration prevention (weather resistance, urine resistance) from the viewpoint of, reducing sulfur compounds described above (e.g., 2-hydroxy - 2-sulfinate acetate) Besides, preferably containing α- hydroxy carboxylic acid compound, and more preferably contains non-reducing α- hydroxy carboxylic acid compound. Here, the non-reducing α- hydroxy carboxylic acid compound, refer reducing inorganic elements (e.g., reducing sulfur, sulfinate, etc. group) having no hydroxycarboxylic acid compound. In particular, when meeting high AAP and high SFC, or, if it contains a polyvalent metal salt and / or polyamine polymer, preferably contains α- hydroxy carboxylic acid compounds from prevention and deterioration prevention coloration, surface cross-linking step or it it is preferable to mix in later.

The obtained may α- hydroxy carboxylic acid compound used in the present invention, means a carboxylic acid or salt thereof having both a hydroxyl group in the molecule, a hydroxy carboxylic acid compound having a hydroxyl group at the α-position. The α- hydroxy carboxylic acid compound is preferably non-polymeric α- hydroxy carboxylic acids, ease of addition, from the viewpoint of the addition effect, the molecular weight is preferably 40-2,000, and more preferably 60 to 1000, particularly preferably in the range of 100-500, it is preferably water-soluble. Such α- hydroxy carboxylic acid compounds, glycolic acid, tartaric acid, lactic acid (salt), citric acid (salt), malic acid (salt), isocitrate (salt), glyceric acid (salt), poly α- hydroxy acrylate (salt), and the like. Among them, lactic acid (salt), malic acid (salt) are preferred, lactic acid (salt) are more preferable.

The salt of α- hydroxy carboxylic acid is not particularly limited, as the salt used is mono- salt or polyvalent salt, preferably a monovalent salt-trivalent salt, specifically, sodium salt , potassium salt, calcium salt, magnesium salt, preferably an aluminum salt, a sodium salt is more preferable. Also, groups of α- hydroxy carboxylic acid may be substituted in the 100% salt, it may be partially substituted.

These α- hydroxy carboxylic acid compound, cost-per-Four terms of performance, the content of the particulate water absorbing agent is preferably in the range of 0.05-1.0 wt%, more preferably from 0.05 to 0.5 wt%, more preferably in the range of 0.1 to 0.5 wt%. Further, a specific range of methoxyphenol, the particulate water absorbing agent of the present invention comprising a chelating agent and an inorganic reducing agent, it is possible to further enhance the aforementioned effect of the present invention by including the further α- hydroxy carboxylic acid compound.

[7] The particulate water absorbing agent of the polyvalent metal salt and / or a cationic polymer present invention, the water absorption rate (Vortex) improved from the viewpoint of flowability during liquid permeability (SFC) improvement and hygroscopic polyvalent metal preferably further comprises a salt and / or a cationic polymer.

Examples of the polyvalent metal salt, a polyvalent metal organic acid salt or inorganic acid salt, aluminum, zirconium, iron, titanium, calcium, magnesium, polyvalent metal salts of zinc or the like. Polyvalent metal salt is water-soluble, water-insoluble either good, preferably water-soluble polyvalent metal salt, 25 ° C. water to 2 wt% or more, water-soluble polyvalent metal to further dissolution of more than 5 wt% salt can be used. Specifically, for example, aluminum chloride, polyaluminum chloride, aluminum sulfate, aluminum nitrate, potassium bis aluminum sulfate, sodium bis aluminum sulfate, potassium alum, ammonium alum, sodium alum, sodium aluminate, calcium chloride, calcium nitrate, chloride magnesium, magnesium sulfate, magnesium nitrate, zinc chloride, zinc sulfate, zinc nitrate, zirconium chloride, zirconium sulfate, inorganic salts such as zirconium nitrate, their multivalent metal lactate, be exemplified organic acid salts such as acetate can.

Further, it is preferable to also use a salt having these crystal water from the viewpoint of solubility of the absorption liquid such as urine. Particularly preferred are aluminum compounds, among others, aluminum chloride, polyaluminum chloride, aluminum sulfate, aluminum nitrate, potassium bis aluminum sulfate, sodium bis aluminum sulfate, potassium alum, ammonium alum, sodium alum, sodium aluminate are preferable, aluminum sulfate are particularly preferred, aluminum sulfate 18-hydrate, powder of hydrous crystals of aluminum sulfate 14-18 water salts can be most suitably used. These may be used singly or in combination of two or more kinds.

As the cationic polymer is a cationic polymer having an amino group, furthermore are water soluble cationic polymer, preferably, 2% by weight or more 25 ° C. water, water-soluble further dissolving 5 wt% or more it is a polymer. For example, polyalkylene imines such as polyethylene imine, polyether polyamines, polyether amine, polyvinyl amine, polyalkyl amines, polyallylamine, polydiallylamine, poly (N- alkyl allylamine), monoallylamine - diallylamine copolymer, N- alkyl allylamine - monoallylamine copolymers, monoallylamine - dialkyl diallyl ammonium salts, copolymers, diallylamine - dialkyl diallyl ammonium salt, a copolymer, polyethylene polyamine, polypropylene polyamine, polyamidine like; salts thereof preferably. Further, modified cationic polymers described in WO 2009/041727 may be mentioned more preferably.

The weight average molecular weight of the cationic polymer is preferably 5,000 or more, more preferably 10000 or more, and still more preferably 30000 or more. Weight average molecular weight may not be obtained the effect of expected to be less than 5000. Further, there is no upper limit particularly limited weight average molecular weight of the cationic polymer is preferably 1,000,000 or less, more preferably 500,000 or less. The weight average molecular weight of the cationic polymer compound, by 1,000,000 or less, viscosity becomes low, preferable because of excellent handling and mixing properties. The weight average molecular weight, GPC, viscosity measurements, can be determined by known methods of static light scattering or the like.

Surface crosslinking with the polyvalent metal, WO 2007/121037, the No. 2008/09843, the No. 2008/09842, U.S. Patent No. 7,157,141, the No. 6,605,673, the No. 6,620,889, U.S. Patent Application Publication No. 2005/0288182, the No. 2005/0070671, the No. 2007/0106013, are shown in Nos. No. 2006/0073969. Further, the polyamine polymer in addition to the organic surface cross-linking agent, may be improved liquid permeability or the like by using in particular the weight average molecular weight from 5000 to 1,000,000 approximately polyamine polymer simultaneously or separately.

Polyamine polymer used, for example, U.S. Pat. No. 7,098,284, WO 2006/082188, the No. 2006/082189, the No. 2006/082197, the No. 2006/111402, the No. 2006/111403 It is illustrated such as Nos. No. 2006/111404.

The amount of the particulate water-absorbing agent polyvalent metal salts and / or cationic polymers are included in the present invention, with respect to the particulate water-absorbing agent 100 parts by weight, 0-5 parts by weight, preferably from 0.001 to 3 wt. parts, more preferably from 0.01 to 2 parts by weight. When the content of the polyvalent metal salt and / or a cationic polymer is more than 5 parts by weight, absorption performance, without any particular may absorbency is significantly reduced Preferably, also, it may cause coloring undesirable.

[8] The particulate water absorbing agent of the granulation present invention is preferably a granulated product. By a granulated product, the amount of dust contained in the particulate water-absorbing agent is reduced.

To obtain a particulate water absorbing agent of the present invention, preferably, it is granulated during or after polymerization. By being granulated, further excellent in water absorption speed and particle size, an excellent water-absorbing agent in actual use as a paper diaper.

Here, the granulation, and by combining a plurality of the particulate water absorbent resin means that a single large particle state of, as long as the final binding particles, binding time may be a hydrogel, dried may be a thing may be a monomeric, linkage particles in point contact may be in surface contact, there may the interface between the particles, is by the binding between particles, even if the interface is not completely eliminated good, preferably it is granulated particles having a surface in terms of absorption rate.

Before granulation of the water-absorbing resin used in the present invention, (particle size less than 150 [mu] m) fines only may be a fine powder, but may be a mixture of particles having a larger particle diameter than the fine, granulated before water particle size of sexual resin preferably has a weight average particle diameter of 500μm or less, it is preferred for to improve the performance such as water-absorption rate and capillary absorption capacity is 400μm or less. The granulation of the present invention by settled a plurality of water-absorbent resin particles, between bound particles or having a surface, refers to the water-absorbent resin particles which eliminates the interface between the particles, usually, the weight average particle diameter increased (e.g. 1.01 to 10 times), and / or reduction of fines (e.g., 150 [mu] m flowthrough, further reduction of 106 [mu] m) can be defined even.

Also, during the granulation prior to the water-absorbent resin, the ratio of the particle size is less than 300μm particles, relative to the water absorbent resin is preferably 10 wt% or more, more preferably 30 wt% or more , further preferably 50 wt% or more. Can such water-absorbent resin having a particle diameter obtained by reversed phase suspension polymerization (in particular two-stage polymerization), others, those that have been pulverized water-absorbent resin obtained by aqueous solution polymerization, or in sieved them it can be obtained preferably by adjusting the particle size. Alternatively, it is also possible to use those granulated grain size adjusted water-absorbent resin fine powder of the following particle size 300 [mu] m, the granulation of the fine powder in irregularly pulverized shaped particles of the primary particles obtained by pulverizing one it may be used parts mixed water-absorbing resin. Absorption properties such as absorption rate, a capillary absorption capacity when mixed some granules of the water-absorbent resin can be obtained water absorbent resin composition of the present invention more excellent. Mixing amount of the granulated product of the fine powder is preferably 5 wt% or more, more preferably 10 wt% or more, more preferably 15 wt% or more.

As the granulation method, the method is not particularly limited if the larger particles by combining a plurality of polymerization particles, granulation by reverse phase suspension, i.e., aggregation during reversed phase polymerization (EP 0695762 , U.S. Patent No. 4,732,968), or two-stage polymerization (EP 0807646), or it can be carried out in the reverse-phase granulation (U.S. Pat. No. 4,732,968) with an inert inorganic additive after polymerization. By granulating, further excellent water-absorbing agent in actual use of the paper diaper can be obtained. The electron micrographs of typical granulated particles shown in FIG.

Further, as the granulation method other than reverse phase suspension polymerization, in order to obtain the particulate water absorbing agent of the present invention, the method for manufacturing the fine granules, a known technique for reproducing fine powder can be used.

For example, a method of drying by mixing a fine powder of hot water the water absorbing resin (U.S. Pat. No. 6,228,930), a method of polymerizing mixed with the aqueous monomer solution fine powder of the water-absorbent resin (U.S. Pat. No. 5,264,495) the method of granulation on a particular surface pressure or water is added to the fine powder of the water-absorbent resin (EP 844270), the fine powder of the water absorbent resin to form a largely amorphous gel moistened dried and ground method (U.S. Pat. No. 4,950,692), a method of mixing the fines with polymer gel of absorbent resin (U.S. Pat. No. 5,478,879) or the like can be used, preferably mixed with fine powder of the hot water and the water-absorbent resin method of drying is used with. Incidentally, the particle diameter represented by sieve size as classified. The granulation water is used as the binder, the water may contain the chelating agent and a reducing inorganic material.

Furthermore, after the surface cross-linking treatment, the addition of the aqueous liquid is heated while maintaining the water content of 1-10 wt%, including the granulation step of granulating necessary, it is adjusted to a specific particle size as powder. The aqueous liquid is added, water alone may be, or, chelating agents or inorganic reducing agents of the present invention, or plant extracts, antimicrobial agents, water-soluble polymer may contain inorganic salts. The content thereof, the concentration of the aqueous solution is from 0.001 to 50 wt%, more preferably from 0.001 to 30 wt%, and most preferably in the range of 0.01 to 10 wt%. Granulation in the present invention is preferably a method of mixing spraying or dropping the water absorbing resin and the aqueous liquid, a method of spraying is more preferable. Droplet size to be sprayed is preferably in the range of 0.1 ~ 300 [mu] m in average particle size, more preferably in the range of 0.1 ~ 200 [mu] m. The granulator used in the granulation, it is preferable that with a large mixing force.

Specifically, agitation granulation method, tumbling granulation method, a compression granulation method and fluidized bed granulation method and the like are exemplified, it can be carried out preferably by any method. Among them, stirring granulation method is more preferable in view of such convenience. When carrying out these methods, except that as the water supply may be carried out by steam, such as devices and operating conditions can be applied to conventional similar techniques. In the present invention, for performing the water supply by supplying steam into the apparatus, the apparatus used comprises a nozzle or the like capable of injecting steam, further high sealing property so that the supply of water vapor can be smoothly it is desirable that the device can be adjusted in the internal pressure.

For example, if carried out by stirring granulation method, the agitation device which can be used have continuous and batch, there is a vertical and horizontal, respectively. The vertical continuous stirrer, a spiral pin mixer (manufactured by Pacific Ocean Machinery & Engineering Co., Ltd.), flow jet mixer and Shugi granulation system (Konaken Pautekkusu Corporation). Examples of horizontal continuous stirring device, Ann New color layer mixer (manufactured by Doraisuberuke Co.) and (manufactured by List Co.) biaxial mixer, and the like.

The vertical batch type stirring device, a Henschel mixer (manufactured by Mitsui Mining Co., Ltd.) and Turbo hair mixer (Moritz Corporation). Examples of the horizontal batch stirrer, Loedige Mixer (Redige Co.) , multi-flux mixer (manufactured by Gerikke Co.) and (manufactured by Pacific Ocean Machinery & Engineering Co., Ltd.) pro sure mixer and the like.

Further, as the granulation apparatus of the above, for example, cylindrical mixer, a double wall conical mixer, high-speed stirring type mixer, V-shaped mixer, a ribbon type mixer, screw type mixer, double-arm type kneader , pulverizing type kneaders, rotary mixers, airflow type mixer, a turbulizer, a batch type Lodige mixer, a continuous type Lödige mixer or the like are preferable.

In the case of granulating after the surface cross-linking, after mixing the aqueous liquid, to be heated while maintaining the water content preferred. Was added an aqueous solution of a chelating agent or an inorganic reducing agent in this step, preferably it is added to the granulation and simultaneous chelating agent or an inorganic reducing agent. In general, the addition of water to the water-absorbent resin, but tack occurs when heated while maintaining the water content in a short time it is not tacky, the fluidity of the powder is recovered, simplify the manufacturing process , it is possible to shorten the time required.

In the present invention call this heating step and the curing step. Granulation rate and granulation in terms of strength, (defined by loss on drying 3 hours at 180 ° C.) water content at the time of heat treatment is preferably 1 to 10 wt%, more preferably from 2 to 8% by weight, more preferably 2 It is heated while maintaining the .5 to 6 wt%. Heating the heat medium heated air or the like, in which the heating temperature (heating medium temperature or material temperature) is preferably in the range of 40 ~ 120 ° C., in the range of more preferably 50 ~ 100 ° C., the heating time is , in the range of 1 minute to 2 hours it is preferred. A suitable combination example of heating temperature and heating time is 0.1 to 1.5 hours at 60 ° C., from 0.1 to 1 hour at 100 ° C..

[9] The particulate water absorbing agent of the particulate water-absorbing agent present invention is a particulate water-absorbing agent as a main component of polyacrylic acid (salt) -based water absorbent resin, comprising: a chelating agent, and an inorganic reducing agent, the content of the chelating agent is 0.001 to 0.5 wt%, is characterized by satisfying any one or more of the requirements of the following constituent elements (1) to (3).
(1) the content of methoxyphenol is 5 ~ 60 ppm.
(2) to contain the water-insoluble inorganic fine particles.
(3) the water content is 3 to 15 wt%.

That is, as the water-absorbing agent as essential (1), a novel water-absorbing agent of the present invention (first water-absorbing agent) is shown in the Examples below, polyacrylic acid (salt) -based mainly of water-absorbing resin a particulate water-absorbing agent and a chelating agent, and a inorganic reducing agent, a content of the chelating agent is 0.001 to 0.5 wt%, methoxyphenol (especially p- methoxyphenol) the content of it is 5 ~ 60ppm. The novel water-absorbing agent of the present invention shown in Examples described later, preferably, absorbency against non-pressure (CRC) is 25 [g / g] or more, absorbency against pressure (AAP4.83kPa) is 20 [g / in g] or more, saline flow conductivity (SFC) is 30 [× 10 -7 · cm 3 · s · g -1] or more. Such water-absorbing agent is preferably a water absorption rate (FSR) is 0.2 [g / g / sec] or more high water absorption speed, meeting the particle size below. Further, the water-absorbing agent preferably further comprises an α- hydroxy carboxylic acid compound. Moreover, further comprising a polyvalent metal salt and / or a cationic polymer. These water-absorbing agent, the initial and for temporal high coloring without any white in liquid permeability (SFC) or absorbency against pressure (AAP) is also a high liquid distribution and less back be used in a diaper of the high concentration less pulp the amount (Re-wet) of, without coloring problems derived from water-absorbing agent, provide good disposable diapers.

Further, as a water-absorbing agent as essential above (2), a novel water-absorbing agent of the present invention shown in Examples below (the second water-absorbing agent), polyacrylic acid (salt) -based water absorbent resin primary a particulate water-absorbing agent as a component, and a chelating agent, and a inorganic reducing agent, the content of the chelating agent is 0.001 to 0.5 wt%, containing water-insoluble inorganic fine particles. The water-absorbing agent containing the methoxyphenol (especially p- methoxyphenol) is arbitrary, but may be 0 ~ 200 ppm, preferably, the (1) and novel water-absorbing agent of the present invention (first water-absorbing agent) is similar to the 5 ~ 60 ppm range and weather resistance and coloring is further improved. The novel water-absorbing agent of the present invention (second water-absorbing agent) can be a water content similar to the first water-absorbing agent is less than 3 wt%, but preferably satisfies (3), the range of 3 to 15 wt% is there. The novel water-absorbing agent of the present invention shown in Examples described later, preferably, absorbency against non-pressure (CRC) is 25 [g / g] or more, absorbency against pressure (AAP2.0kPa) is 25 [g / in g] or more, the water absorption rate (Vortex) is less than 60 seconds.

Further, as a water-absorbing agent as essential above (3), a novel water-absorbing agent of the present invention shown in example (a third water-absorbing agent), polyacrylic acid (salt) -based water absorbent resin primary a particulate water-absorbing agent as a component, and a chelating agent, and a inorganic reducing agent, the content of the chelating agent is 0.001 to 0.5 wt%, with moisture content of 3 to 15 wt% is there. The water-absorbing agent containing the methoxyphenol (especially p- methoxyphenol) is arbitrary, but may be 0 ~ 200 ppm, preferably, the (1) and novel water-absorbing agent of the present invention (first water-absorbing agent) is similar to the 5 ~ 60 ppm range and weather resistance and coloring is further improved. The novel water-absorbing agent of the present invention (third water-absorbing agent) is preferably that containing the (1) and novel water-absorbing agent (first water-absorbing agent) as well as water-insoluble inorganic fine particles of the present invention, urine resistance is further improved. The novel water-absorbing agent of the present invention shown in Examples described later, preferably, absorbency against non-pressure (CRC) is 25 [g / g] or more, absorbency against pressure (AAP2.0kPa) is 25 [g / in g] or more, the residual monomer is 500ppm or less. The water-absorbing agent is also preferably further comprises a α- hydroxy carboxylic acid compound. Moreover, further comprising a polyvalent metal salt and / or a cationic polymer.

The novel water-absorbing agent of the present invention (in particular the first water-absorbing agent, more second and third water-absorbing agent), alpha-hydroxy carboxylic acid (salt shown in the above "(6) alpha-hydroxy carboxylic acid compound" ) and / or preferably includes a polyvalent metal salt and / or cationic polymers such as described in "(7) polyvalent metal salt and / or cationic polymers", which are the "[1] polyacrylic acid ( It is integral with the polyacrylic acid (salt) -based water absorbent resin shown in salt) -based water absorbent resin ".

Incidentally, the particulate water absorbing agent of the present invention, among the physical properties exemplified below, for favorably used white high density diapers, liquid permeability (SFC) and the absorption capacity under load (AAP), more preferably absorption rate and the residual monomer is also important, absorbency against pressure (AAP) is 20 [g / g] or more, saline flow conductivity (SFC) is 30 [× 10 -7 · cm 3 · s · g -1 ] above, the water absorption rate (Vortex) is 60 seconds or less, the residual monomer is 500ppm or less, more preferably satisfy any one of the requirements.

The more preferred range of these physical properties are shown below.

Absorption capacity without load (CRC) is 25 [g / g] or more, absorbency against pressure (AAP4.83kPa) is 20 [g / g] or more, saline flow conductivity (SFC) is 30 [× 10 -7 is · cm 3 · s · g -1 ] or more. Moreover, absorption capacity without load (CRC) is 25 [g / g] or more, absorbency against pressure (AAP2.0kPa) is at 25 [g / g] or more, the water absorption rate (Vortex) is less than 60 seconds. The water absorbing agent further satisfies the following.

(A) Fe
Further, the particulate water absorbing agent of the present invention, in terms of their color protection, preferred Fe content (as in terms of Fe 2 O 3 value) is 1ppm or less, more preferably 0.1ppm or less, particularly preferably 0.02ppm or less it is. Fe content in the raw material of the Fe content water-absorbent resin to the control of, in particular base appropriately purified to be used for neutralization, for example, by removing NaOH, the Fe of Na 2 CO 3), can be controlled is there. Fe content may be measured in the raw material may be measured in the final water-absorbing agent.

Note that the "as calculated as Fe 2 O 3 value" iron iron alone or a compound containing (Fe 2 O 3 and their iron salt, iron hydroxide, iron complex, etc.) the absolute amount of Fe in, Fe 2 O 3 is to be expressed as an iron compound represented by (molecular weight 159.7) is the weight obtained by oxidizing all counters Fe, as Fe content, iron content is at 55.85 × 2 / 159.7 unambiguously calculated molecular weight (Fe in Fe 2 O 3).

That is, from the base a major used for neutralization, preferably, the particulate water absorbing agent of the present invention is iron (Fe) is 2ppm or less, and more preferably 1.5ppm or less, more preferably 1ppm or less, particularly preferably 0.5ppm are included below, the lower limit is preferably 0.001 ppm, more preferably from 0.01 ppm.

For example, when Fe is (if obtaining the Fe amount from the amount of Fe 2 O 3, the calculated is as the amount of Fe 2 O 3 × 55.85 × 2 / 159.7) 10 neutralized in ppm NaOH, CH 2 = CHCOOH (molecular weight 72) + NaOH (molecular weight 40, Fe is about 7 ppm) than → CH 2 = CHCOONa (94) , the sodium polyacrylate obtained, neutralization ratio 75 mol% of sodium acrylate (molecular weight 88. in 55), the 7ppm × 40 / 88.55 = Fe content of about 3 ppm. Iron of such predetermined amount to accelerate the decomposition of the water-absorbent resin at the time of disposal after use, the excess iron is undesirable cause coloration before degradation and the use of time of use.

Control of iron content is mainly performed by the control of the base (especially sodium hydroxide) used for neutralization, and other raw materials (acrylic acid, crosslinking agent, water, etc.) the control of the minor iron, furthermore the polymerization apparatus or monomers piping of apparatus or piping of the resin coat various water-absorbent resins, glass coating, performed in stainless steel control. Incidentally, the iron content in the in basic and water-absorbent resin, for example, can be quantified by ICP emission spectroscopic analysis method described in JIS K1200-6, by reference quantification method, refer to WO 2008/090961 can.

(B) the particulate water-absorbing agent of the particle shape present invention particles (water-absorbing agent Part 1 - water absorbing agent No. 3) shape is not limited to a particular shape, spherical, substantially spherical, (a pulverized product) amorphous crushing, rod, polyhedral, sausages (e.g., U.S. Pat. No. 4,973,632), particles with wrinkles (for example, U.S. Pat. No. 5,744,564), and the like. They may even primary particles (single particle), may be a granulated particle, or a mixture thereof. The particle may be a foamed porous. Preferred particles, irregularly pulverized primary particles or granules and the like. By granulated comprise micronized alone or fines, dust can also be reduced, the proportion of the surface is increased further to particle size, preferably improved water absorption rate.

(C) a particle size water-absorbing agent of the present invention (Part 3 water absorbent Part 1 water-absorbing agent) is a particulate from water absorbing properties, it is preferable that weight average particle diameter (D50) is in the range of 200 ~ 600 .mu.m, 200 more preferably ~ in the range of 550 .mu.m, more preferably in the range of 250 ~ 500 [mu] m. Also, the better JIS standard sieve 150μm particles below is small, its content is usually 0-5% by weight, preferably 0 to 3% by weight, particularly preferably 0 to 1 wt%. Furthermore, the better JIS standard sieve 850μm or more of the particles less, its content is usually 0-5% by weight, preferably 0 to 3% by weight, particularly preferably 0 to 1 wt%.

Bulk specific gravity of the water-absorbing agent of the present invention (defined in U.S. Pat. No. 6,562,879) 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 and classification, and the like.

(D) Other additives Furthermore, in accordance with the intended function, in order to impart various functions, with respect to the water-absorbing agent of the present invention, surfactants, oxidizing agents, water-insoluble inorganic or organic powder such as metal soaps, deodorants, antimicrobial agents, the pulp and thermoplastic fibers, 0 to 3% by weight, preferably may be added 0-1% by weight. As the surfactant, surfactants of WO 2005/075070 Patent described is preferably exemplified.

(E) water content of the water content particulate water absorbing agent of the present invention (water-absorbing agent Part 1 - water absorbing agent No. 3) is, for example, 0.5 to 16% by weight, (mandatory in the water absorbing agent No. 2) 3 preferably to 15 wt%, more preferably a 4 to 14 wt%, more preferably 5-13 wt%, in particular 6-12% by weight, a further 7-11% by weight. The water content as an example of the adjustment method, the predetermined moisture content of the drying and surface crosslinking is controlled by further adding or drying of water necessary. Water content 0.5% by weight or more, especially if 3% by weight or more, absorption rate (Vortex / FSR) is improved, problems or odor, reduction in the absorption rate, lowering of the impact resistance, the dusting hardly cause such, if the water content is 15 wt% or less, coloration is suppressed, it is possible to suppress a decrease in tackiness and absorbency particles. The water content of the water-absorbing agent is low and the water absorption rate (Vortex / FSR) is decreased, (especially if the surface cross-linking step or earlier) timing of addition of inorganic reducing agents have odor problems, also when high water content tend to coloration problem occurs, therefore, it is preferably the above water content.

(F) absorbency against non-pressure (CRC)
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, still more preferably at 25 [g / g] or more . The upper limit of the CRC is not particularly limited, preferably at 70 [g / g] or less, and more preferably not more than 50 [g / g], still more preferably 40 [g / g] or less. If the CRC is less than 5 [g / g], the case of using the particulate water absorbing agent in the water-absorbent structure, the absorption amount is too small, not suitable for use of the sanitary materials such as diapers. Further, CRC is larger than 70 [g / g], sometimes absorbency against pressure (AAP) and liquid permeability (SFC) is lowered, the particulate water-absorbing agent is used in paper diapers or the like water-absorbent structure If, it may become impossible to obtain a water absorbing agent which is excellent in liquid acquisition rate into the absorbent core. CRC can be controlled by such as an internal-crosslinking agent and surface cross-linking agents described above.

(G) absorbency against pressure (AAP)
AAP of the particulate water-absorbing agent used in the present invention (2.0 kPa further 4.83 kPa) is, 20 [g / g] or more, preferably 22 [g / g] or more, more preferably 23 [g / and the g] or more, still more preferably 24 [g / g] or more, and most preferably 25 [g / g] or more. The upper limit of the AAP is not particularly limited, is preferably 30 [g / g] or less. If AAP is 20 [g / g] or more, when using a particulate water absorbing agent in the water-absorbent structure, the liquid when applied pressure to the water absorbent core back (aka rewet: referred to as Re-Wet) is less it is possible to obtain a water-absorbing agent. AAP can be controlled by the surface cross-linking and particle size like the above.

The load condition of the AAP, the type of the resultant particulate water-absorbing agent, may be selected as appropriate 4.83kPa or 2.0 kPa, if Shimese the above range, it may be in either the load conditions, but preferably, 2.0kPa further satisfies the AAP under a load of 4.83 kPa.

(H) saline flow conductivity (SFC)
SFC of the particulate water-absorbing agent used in the present invention is preferably not 30 [× 10 -7 · cm 3 · s · g -1] or more, more preferably 50 [× 10 -7 · cm 3 · s · and the g -1] or more, still more preferably 70 [× 10 -7 · cm 3 · s · g -1] or more, particularly preferably 80 [× 10 -7 · cm 3 · s · g -1] or more. If the SFC 30 [× 10 -7 · cm 3 · s · g -1] or more, it is possible to further improve the liquid permeability, the use of the particulate water absorbing agent in the water-absorbent structure, the water absorbent core it is possible to obtain the water-absorbent agent excellent in uptake rate of the liquid. The upper limit of SFC is not particularly specified, preferably 3000 [× 10 -7 · cm 3 · s · g -1] or less, more preferably 2000 [× 10 -7 · cm 3 · s · g -1] less. If the SFC 3000 [× 10 -7 · cm 3 · s · g -1] or less, it is possible when using the particulate water absorbing agent in the water-absorbent structure, to suppress the leakage in the water absorbent core. SFC above surface crosslinking and particle size, control of the above-mentioned range of CRC, can be controlled with the polyvalent metal salt or a polyamine polymer described in "(7) polyvalent metal salt and / or cationic polymer" and the like. In the present specification sometimes referred saline flow conductivity (SFC) liquid permeability or liquid permeability and (SFC).

(I) water absorption rate that 1 (FSR)
Particulate water-absorbing agent according to the present invention, FSR is preferably 0.1 [g / g / sec] or higher, more preferably 0.15 [g / g / sec] or higher, more preferably 0. 20 [g / g / sec] or higher, and most preferably 0.25 [g / g / sec] or higher. Upper limit of FSR is not particularly specified, an excessive superabsorbent speed (Vortex or FSR) is because there is a risk of impairing liquid permeability (eg SFC) or liquid diffusibility, preferably 5.0 [g / g / sec] or less, more preferably 3.0 [g / g / sec] or less. If the FSR 0.05 [g / g / sec] or higher, for example, when using a particulate water absorbing agent in the water-absorbent structure, and more prevents the liquid is caused to liquid leakage without being sufficiently absorbed be able to. FSR can be controlled by the particle size and foaming polymerization.

(J) water absorption rate that 2 (Vortex)
Particulate water-absorbing agent according to the present invention, Vortex is preferably not more than 60 seconds, more preferably not more than 55 seconds, more preferably not more than 50 seconds, and most preferably no more than 40 seconds. The lower limit of Vortex is not specified particularly, but is preferably 10 seconds or more. If Vortex is less than 60 seconds, for example, when using a particulate water absorbing agent in the water-absorbent structure, it is possible to further suppress the liquid is caused to liquid leakage without being sufficiently absorbed. Vortex can be controlled by the particle size and foaming polymerization.

(K) water-soluble component (Extr)
Particulate water-absorbing agent according to the present invention, the water soluble content of 50 wt% to mandatory or less, preferably 35 wt% or less, more preferably 25 wt%, more preferably is 15 wt% or less . If extractable polymer is 35 wt% or less, the gel strength is stronger, and excellent by liquid permeability. Also, when using a particulate water absorbing agent in the water-absorbent structure, the return of the liquid when pressure is applied to the water-absorbent structure (called rewetting: Re-Wet) can be obtained less water absorbent. Water-soluble component can be controlled by the internal cross-linking agent described above.

The particulate water-absorbing agent according to (l) the residual monomers present invention, from the viewpoint of safety, a residual monomer 500ppm or less, preferably 400ppm or less, more preferably controlled to 300ppm or less. Residual monomer in addition to the polymerization or drying, inorganic reducing agents, in particular reduced by the use of inorganic reducing agent having a sulfur element. Water-absorbing agent of the present invention Discontinue more residual monomers is small, even when the water absorbing agent used at high concentrations (increasing usage) in disposable diapers, less preferred eluting residual monomer in the paper diaper.

(M) Initial color tone (aka; initial color)
Particulate water-absorbing agent according to the present invention, which can be suitably used for sanitary materials for such as paper diapers, it is preferable that the white powder. Particulate water-absorbing agent according to the present invention is a Hunter Lab color system measured by spectroscopic color difference meter of the particulate water-absorbing agent particulate water absorbing agent after production, L value (Lightness) of at least 88, more 89 or more, preferably preferably it exhibits 90 or more. The upper limit of the L value is usually 100, problems with color in the product, such as 88 if sanitary material powder does not occur. Further, b values ​​0 to 12, preferably 0 to 10, further 0 to 9, a value -3 to 3, preferably -2 to 2, further to the -1 to 1.

Note that the initial color tone, is a color tone after production particulate water-absorbing agent, typically it is color measured before the factory shipment. Further, for example, 30 ° C. or less, after manufacture if stored in an atmosphere of RH 50% relative humidity is a value measured within 1 year.

(N) time tone (aka; coloring with time)
Particulate water-absorbing agent according to the present invention, which can be suitably used for sanitary materials for such as paper diapers, this time, to maintain a significantly clean white state even during long-term storage conditions at high humidity and temperature conditions it is preferable. The long-term storage conditions, as long-term storage color stability accelerated test, including the examples described below, after exposure particulate water absorbing agent temperature 70 ± 1 ° C., in an atmosphere of RH relative humidity 65 ± 1% 7 day water it can be examined by measuring the Hunter Lab color system of L value (Lightness) by spectroscopic color difference meter of agents. Particulate water-absorbing agent according to the present invention is a Hunter Lab color system measured by spectroscopic color difference meter of the long-term storage color stability accelerated test after the water-absorbing agent, L value (Lightness) of at least 80 or more, further 81 or more , still more 82 or more, it is particularly preferable to indicate the 83 or more. The upper limit of the L value is usually 100, if the L values ​​after accelerated test 80 or more, a level that substantially problem does not occur even in long-term storage conditions at high humidity and temperature conditions. Further, b values ​​0-15, preferably 0-12, further 0 to 10, a value -3 to 3, preferably -2 to 2, further to the -1 to 1.

[10] method for producing a particulate water absorbing agent of the manufacturing method of the present invention of the particulate water-absorbing agent, for example, carried out by the method described in the above [1] to [8].

Specifically, the polymerization step of the monomer aqueous solution containing as a main component an acrylic acid (salt) containing 10 ~ 200 ppm of methoxyphenol, and drying the hydrogel crosslinked polymer obtained by polymerizing, surface and a crosslinking step, a method for producing a polyacrylic acid (salt) -based particulate water-absorbing agent further comprises a step of adding a chelating agent 0.001 to 0.5% by weight of the addition step and the inorganic reducing agent, monomer contains 10 ~ 200 ppm of methoxyphenol in to acrylic acid in terms of a production method that satisfies one or more of the following (a) ~ (c).
(A) further comprises a step of adding water-insoluble inorganic fine particles.
(B) after the drying step, and the surface cross-linking step, controlling the water content of the polymer 3 to 15% by weight.
(C) after the surface crosslinking step, performing the step of adding an inorganic reducing agent.

By the above production method has excellent absorption performance and coloring over time preventing performance, very little odor More surprisingly, excellent urine resistance is obtained a particulate water absorbing agent for a suitable absorber in actual use be able to.

The method for producing a particulate water absorbing agent of the present invention, the above-mentioned [1], [2 "chelating agent mentioned in the like, the polymerization before or during the polymerization of the aqueous monomer solution to the particulate water-absorbing agent obtained by adding it is preferably a production process.

The method for producing a particulate water absorbing agent of the present invention, the above-mentioned [1], [3 "inorganic reducing agent mentioned in the like, obtained by adding to the crosslinked hydrogel polymer before the drying of the particulate water-absorbing agent it is preferably a production process.

Method for producing a particulate water absorbing agent of the present invention further comprises a step of adding to the [6 "mentioned like α- hydroxy carboxylic acid (salt) is preferably a method for producing a particulate water absorbing agent.

Method for producing a particulate water absorbing agent of the present invention preferably further is method for producing a particulate water absorbing agent comprising the step of adding a polyvalent metal salt and / or cationic polymers mentioned above [7 "and the like.

Method for producing a particulate water absorbing agent of the present invention preferably further is method for producing a particulate water absorbing agent comprising a granulation step described above [8 "or the like.

Moreover, method for producing a particulate water absorbing agent of the present invention, as an example, is performed by the method described in the above [1] to [8]. More specifically, the polymerization step comprises 90 to 100 mol% of acrylic acid (salt) in the monomer, the monomer aqueous solution of the monomer concentration of 30 to 55% by weight, the radical polymerization initiator 0. by 001-1 mol%, and the maximum temperature of 130 ° C. or less, under the conditions the polymerization time is 0.5 minutes to 3 hours, a step of performing an aqueous solution polymerization or reversed-phase suspension polymerization, neutralization step, Fe content is made with a base which is 0 ~ 10 (× 55.85 × 2 / 159.7) ppm, drying step, the particulate water-containing gel, the drying time of 10 to 120 minutes at a drying temperature 100 ~ 250 ° C. dried to a moisture content 20% by weight Te is a process, the surface cross-linking step is dried 70 to a mixture of surface crosslinking agent 0.001 to 10 parts by weight based on the water-absorbent resin powder 100 parts by weight of the post-process 300 ℃ place in the heat treatment of 1 minute to 2 hours, the resulting particulate Manufacturing method of a methoxyphenol content of the water-absorbing agent and 5 ~ 60 ppm, and the like. Control of methoxyphenol content of the resultant particulate water-absorbing agent can be carried out by methods or later method of the above.

Methoxyphenol described above in the manufacturing method of the particulate water-absorbing agent of the present invention, the production step of the particulate water-absorbing agent, may be added at any time, the aforementioned is used as the main component of the monomer preferably contained in acrylic acid, it is preferable to appropriately adjust the content in the purification step of the acrylic acid.

In the method for producing a particulate water absorbing agent of the present invention, methoxy phenols preferably used acrylic acid containing 10 ~ 200 ppm.

(10-1) The method for producing acrylic acid used in the acrylic acid present invention, propylene and / or gas-phase catalytic oxidation of acrolein, ethylene cyanohydrin process, high pressure Reppe process, improved Reppe process, ketene process , acrylonitrile hydrolysis method or the like are known as an industrial production method, among others propylene and / or gas phase oxidation of acrolein is most frequently employed. Then, in the present invention, acrylic acid obtained in such a gas phase oxidation process is preferably used.

In the method for producing a particulate water absorbing agent according to the present invention, versus acrylic acid in terms of value, monomer methoxyphenol which contained 10 ~ 200 ppm it is preferably used. Main component of the monomer may be acrylic acid, it may be an acrylic acid and acrylic acid salt. As the methoxy phenols, specifically, o, m, p-methoxyphenol and further a methyl group them, t- butyl group, one or methoxyphenol having two or more substituents, such as hydroxyl There are exemplified, particularly preferably, p- methoxyphenol is used in the present invention.

The content of methoxyphenol is in to acrylic acid in terms of value, preferably 10 ~ 120 ppm, preferably 10 ~ 90 ppm, more preferably 20 ~ 90 ppm. Equal to or less than the content of p- methoxyphenol 200 ppm, it is possible to suppress the coloration of the resulting water-absorbent resin (yellowing / yellowing). Also, p- when the content of methoxyphenol is less than 10 ppm, i.e., if the removal of p- methoxyphenol as a polymerization inhibitor by purification such as distillation, the risk of polymerization occurs before starting intentionally polymerization there not only is not preferable because the weather resistance of the water-absorbent resin or water-absorbing agent obtained acrylic acid (salt) as a main raw material as described above is deteriorated.

Incidentally, methoxyphenol during polymerization when referenced to the acrylic acid (molecular weight 72), acrylate obtained by neutralizing the required molecular weight increase (e.g., molecular weight 75 mole% neutralized sodium salt 88 .5), and other, because the components listed in the above [2] to [7] also added, the content of relatively methoxyphenol is reduced. Moreover, in view also consumed during the polymerization, in the present invention, relative to the content 10 ~ 200 ppm of methoxyphenol in the polymerization before acrylates, methoxyphenol in polyacrylate obtained is a 5 ~ 60 ppm Become.

The method of the particulate water absorbing agent produced the present invention, it is a manufacturing method of the particulate water-absorbing agent passing through the polymerization of the monomer aqueous solution acrylic acid 10 ~ 200 ppm containing methoxyphenol (especially p- main Toshi phenol) preferable. Further, the polymerization process (density, initiator, temperature) and drying (temperature, time, solids, air volume, etc.) by going through a predetermined amount of methoxyphenol is consumed, resulting the range of methoxyphenol ( particularly p- methoxyphenol) containing at 5 ~ 60 ppm, can be obtained particulate water-absorbing agent uniformly contained within particular polymer.

That is, in the manufacturing method of the present invention, methoxyphenol content by using a monomer of 10 ~ 200 ppm, the methoxyphenol of the water-absorbent resin obtained by the radical polymerization, and drying and 5 ~ 60 ppm it may be a manufacturing method.

The control method of the main tosylate phenol in the water-absorbent resin is limited to above example is not the sole, other following methods can be exemplified as a technique may be used in combination thereof.

Process Part 2; After polymerization the main tosylate phenols absence or the water absorbent resin is less than 10ppm, the method further adding a predetermined amount of main tosylate phenols after drying.

Preparation Part 3; after to the water-absorbent resin with a monomer containing excessive main tosylate phenol polymerization, a method of removing by washing a predetermined amount of main tosylate phenols before drying. The water or hydroalcoholic mixtures can be used for cleaning.

Further, the monomer used in the present invention may be used a polymerization inhibitor other than p- methoxyphenol in the manufacturing process, it may be the polymerization inhibitor in combination with p- methoxyphenol.

Examples of the polymerization inhibitor other than p- methoxyphenol, for example, phenothiazine, hydroquinone, copper salts, manganese acetate, methylene blue and the like are effective. However, unlike these polymerization inhibitors methoxyphenol, to inhibit polymerization, ultimately the better small, p- methoxyphenol and when used in combination, the concentration in the monomer is preferably from 0.01 ~ 10 ppm .

Further, in order to solve the problem (coloring preventing) of the present invention, the water content in the acrylic acid may more small, usually, 1000 ppm or less, preferably 750ppm or less, more preferably 500ppm or less, more preferably 300ppm or less, particularly preferably 200ppm or less, 100ppm or less, 80ppm or less, preferably in the following order 50ppm. Water is preferably as small but, 1 ppm order of dewatering costs, even at sufficiently be about 5 ppm. To obtain an acrylic acid such low moisture, or to adjust to a predetermined amount of moisture is repeated distillation or crystallization was purified acrylic acid, and or by contacting the acrylic acid with an inorganic or organic dehydrating agent, good them to water a predetermined amount. If the water content in the monomer is more than 1000 ppm, there is a tendency that coloring of the resultant water-absorbing resin (in particular coloring with time) is worsened.

The main component of the monomer is acrylic acid and / or acrylic acid salt, in these acrylic acid and acrylic acid salt, the molecular weight is different. The difference in the molecular weight in consideration, in the present invention, in terms of value to acrylic acid is defined. The pair acrylic acid converted value, when the salt of acrylic acid was calculated as a non-neutralized acrylic acid all equimolar, a content ratio of the weight of the minor component relative to the weight of acrylic acid (weight ratio). That is, for example, sodium acrylate after the neutralization (molecular weight 94) are in terms of weight of acrylic acid (molecular weight 72), the weight in p- methoxyphenol such as the minor component of the converted acrylic acid (94 converted to 72) such proportion (weight ratio) is defined. In the particulate water absorbing agent after the polymerization, if the acrylic acid salt of partial neutralization or complete neutralization is in the polymer, to acrylic acid in terms of value, partially neutralized or completely neutralized polyacrylate all such in terms that the polyacrylic acid molar unneutralized can be calculated. The above partial neutralization is meant that the neutralization ratio is less than 100 mol% greater than 0 mol%. The above and complete neutralization means that neutralization rate of 100 mol%. The above unneutralized means neutralization ratio is 0 mol%.

Note that determination of the component can be carried out by liquid chromatography or gas chromatography.

(10-2) neutralizer The neutralizer such as sodium hydroxide or sodium carbonate used for neutralization of the monomers and polymers in the present invention (base), the smaller the amount of iron preferably, the content (as terms of Fe 2 O 3 value) is usually from 0 ~ 10.0 ppm relative to base solids, preferably 0.2 ~ 5.0 ppm, more preferably of 0.5 ~ 5.0 ppm It is included in the range. When the content of iron is less than 0.01 ppm, not only before the polymerization initiator addition there is a risk that polymerization occurs, even with the addition of initiator is also possible that polymerization is slow reversed. Such iron may be a Fe ion, but preferably from the viewpoint of effects trivalent iron, in particular Fe 2 O 3. Incidentally, Fe amount in the above range, the molecular weight ratio of iron and iron oxide (55.85 × 2 / 159.7 (Fe in Fe 2 O 3)) in unambiguously calculated.

The absolute amount of Fe regardless of the type of counter anions in the present invention is important, oxides wherein counter anion the amount of Fe and in terms of Fe 2 O 3 (e.g., Fe (II) or Fe (III), sulfates, hydrochlorides, regardless hydroxides), which the Fe 2 O 3 is an oxide of Fe (III), the Fe (molecular weight 55.85) and the molecular weight of Fe 2 O 3 ( from 159.7), preferably the amount of Fe in the base of the present invention (Fe conversion) becomes 0 ~ 7.0 ppm.

When the content of iron is less than 0.01 ppm, not only the polymerization occurs danger before the polymerization initiator addition, even with the addition of initiator is also possible that polymerization is slow reversed. The iron used in the present invention may be a Fe ion, but preferably from the viewpoint of the effect is a trivalent iron, in particular Fe 2 O 3 or iron hydroxide.

That is, in the present invention, preferably the neutralization step, made at the Fe content (Fe equivalent) of 0 ~ 7.0 ppm of bases (in particular NaOH or sodium carbonate is controlled to the Fe content), more preferably the in the range of Fe content.

(10-3) The method of adding the inorganic reducing agent in the production method of the particulate water-absorbing agent of the addition method the present invention an inorganic reducing agent, the (1-6) polymerization step (1-7) Gel comminution step, (1-8) drying process (1-9) pulverizing step and classification step can be added (1-10) surface cross-linking step, the (1-11) or one of the other steps, is particularly limited Although not, powdery, solution, emulsion, or, it is preferred to be added as a suspension, it is preferable to be added as a solution, it is more preferably added as an aqueous solution.

If an inorganic reducing agent in the production method of the particulate water-absorbing agent of the present invention is added in powder form, preferably has an average particle size of the powder particles is 0.001 ~ 850 .mu.m, it is 0.01 ~ 600 .mu.m more preferably, more preferably 0.05 ~ 300 [mu] m. The average particle size can be measured as a volume average particle diameter by laser. An example of a laser is described in U.S. Patent Application Publication No. 2004/0110006.

As the solvent used in the case of the inorganic reducing agent in the production method of the particulate water-absorbing agent of the present invention is added in solution, it is not particularly limited, for example, water; ethanol, methanol, propylene glycol, glycerin It can be suitably used polyethylene glycol, and the like; alcohols. Among these it is preferable to use a mixed solution of water or water and an alcohol, and most preferably added as an aqueous solution. The concentration of the inorganic reducing agent such solution is appropriately determined, it may be a dispersion or a supersaturated solution which exceeds the saturation concentration, but the solution of the following ranges, in particular an aqueous solution, the upper limit is the saturation concentration.

Further, Examples of the dispersion medium used in the case of the inorganic reducing agent is mixed in suspension, but are not particularly limited, for example, water; ethanol, methanol, propylene glycol, glycerin, polyethylene it can be used glycol suitably. Further, it is preferred that such concentration of the inorganic reducing agent in the dispersion is 1 to 100 wt%, and more preferably 10 to 100 wt%. Further, as a dispersing agent, further water-soluble polymer, a surfactant or the like may be added.

Further, the inorganic reducing agent addition to the solution or suspension, together with emulsifiers, for example, as an emulsion in water, may be mixed with the water absorbent resin. As a dispersion medium for such a case, it is not particularly limited, for example, can be preferably used water.

As the emulsifier, is not particularly limited, nonionic surfactants, may be used cationic surfactants. Further, it is preferred that such concentration of the inorganic reducing agent emulsion liquid is 1 to 90 wt%, and more preferably 10 to 90 wt%.

Furthermore, in the method for producing a particulate water absorbing agent according to the present invention, the inorganic reducing agent is more preferably added as an aqueous solution. Further, it is preferred that such concentration of the inorganic reducing agent in the aqueous solution is from 0.01 to 90 wt%, more preferably more preferably 0.5 to 60 wt%, 1-90 wt% , particularly preferably 10 to 60 wt%, and most preferably 10 to 90 wt%. The upper limit may be a dispersion or supersaturated solution within the range, the upper limit is the saturation concentration.

The addition of the particulate water-absorbing agent of the manufacturing method inorganic reducing agents in the present invention, prior to polymerization of the monomer solution, water-containing gel-like crosslinked product of the polymerization during or after polymerization, the surface cross-linking step before, after the surface cross-linking step either may be conducted at a time but, during the polymerization, hydrogel cross-linked polymer after polymerization (i.e., crosslinked hydrogel polymer before drying), or it is more preferably added after the surface crosslinking step.

When adding an inorganic reducing agent to the crosslinked hydrogel polymer after polymerization, or a water-containing gel-like cross-linked polymer after polymerization addition of an inorganic reducing agent in the process of grain refining, grain refining has been after polymerization it is preferable to mix adding an inorganic reducing agent to the hydrogel crosslinked polymer. During surface crosslinking, or, in the case of performing the addition of an inorganic reducing agent before surface crosslinking as in Patent Document 15, if not controlled water content between 3 and 15 wt% as in the present invention, the particulate water absorbing agent coloring not only, the odor becomes stronger.

Further, after the surface cross-linking step, the timing for performing the adding step, is not particularly limited, the polyvalent metal salt and / or cationic polymer, prior to addition, added simultaneously or either after addition it may be added at the time. Furthermore, the α- hydroxy carboxylic acid compound, prior to addition, may be added at any time of the addition simultaneously with or after the addition.

Inorganic reducing agent in the method for producing a particulate water absorbing agent of the present invention, after the addition, or simultaneously the polyacrylic acid (salt) -based be mixed with the water-absorbing resin is preferably an addition. Specific mixing method of adding or mixing is not particularly limited, can be mixed with a known crushing device and pulverized device and a stirring device.

Such crushing equipment and grinding equipment, a kneader or a screw extruder having a porous structure of any shape (aka; meat chopper) can be exemplified. Incidentally, may be used according crushing device by a plurality series, also kneader and a meat chopper or the like, may be used in combination with different devices. Screw extruder may be a single, it may be used two or more. Such stirring apparatus include cylinder type mixers, screw type mixers, screw type extruders, turbulizer, Nauta type mixers, V-type mixer, double-arm type kneaders, flow type mixers, mixing the air flow type machine, rotary disk type mixers, roll mixers, tumbling type mixer, Lödige mixer, a paddle blender, a ribbon mixer, a rotary blender, a jar tumbler, plow jar mixer can be suitably used mortar mixer. Further, such a stirring device is equipped with a polyacrylic acid (salt) -based water absorbent resin after the surface cross-linking, and the inorganic reducing agent, a heating device for heating the mixture optionally containing a said other additives it may be, may be provided with a cooling device for cooling the mixture was heated by a heating device. Although not particularly limited times to agitate by the stirring device, preferably 60 minutes or less, and more preferably not more than 30 minutes.

(10-4) In the above chelating agent in the production method of the particulate water-absorbing agent of the addition method the invention of the chelating agent, the (1-6) Polymerization Step - (1-10) surface cross-linking step and (1-11) including other steps, it may be added at any time of the particulate water-absorbing agent manufacturing process, in the (1-6) polymerization process, is preferably added to the aqueous monomer solution prior to polymerization or during polymerization . When added to the aqueous monomer solution prior to polymerization or during polymerization, for the chelating agent can be included in the uniform by the particulate water absorbing agent, particularly preferred in that it can effectively prevent the coloring over time.

In the above (1-6) polymerization step, the case of adding a chelating agent to the polymerization prior to the monomer solution, and to line mixing with a monomer feed line to the polymerization reactor, to be stirred and mixed in a reaction-flight preferable. Also, when added to the course of the polymerization, after the start of the polymerization reaction, while until the polymerization reaction reaches a peak temperature, or, it is preferred that polymer from the polymerization reactor is added until it is discharged. Adding a chelating agent to the aqueous monomer solution during polymerization or during polymerization can uniformly added to the particulate water absorbing agent of the present invention the chelating agent is preferable in that it is possible to further exerted the effects of the present invention.

(10-5) in the method for producing a particulate water absorbing agent of the addition method the present invention the water-insoluble inorganic fine particles, the above water-insoluble inorganic fine particles, wherein (1-6) Polymerization Step - (1-10) surface cross-linking step Ya (1-11), including other steps, may be added at any time of the particulate water-absorbing agent manufacturing process, preferably added after the (1-10) surface cross-linking step. That is, the water-insoluble inorganic fine particles added simultaneously with the surface crosslinking agent mentioned above or crosslinking the water-absorbent resin surface, after crosslinking the water-absorbent resin surface with a surface crosslinking agent mentioned above, it is preferable to add a water-insoluble inorganic fine particles . In particular, by adding a surface treatment of the water-insoluble inorganic fine particles to the water-absorbing resin after surface cross-linking by surface cross-linking agent, the desired absorption properties, particularly high liquid permeation properties are achieved. The water-insoluble inorganic fine particles may be added respectively at the same time as the above-mentioned α- hydroxy carboxylic acid compound, it is preferable or added as a pre-blended mixture with α- hydroxy carboxylic acid compound.

(10-6) in the addition method method for producing a particulate water absorbing agent of the present invention the α- hydroxy carboxylic acid compound, the α- hydroxy carboxylic acid compound mentioned above, the (1-6) Polymerization Step - (1-10) including surface cross-linking step and (1-11) other steps, may be added at any point in the production step of the particulate water-absorbing agent, in consideration of the effect of the term color stability, the polymerizable monomer may be previously be contained, it is preferable that the above-mentioned polymerization reaction is added in subsequent step after completion. As a method for the polymerization reaction is added in a subsequent step after completion of a method of adding to the polymerization after the hydrogel polymer, a method of adding to the dried product after the drying step, a method of adding a surface-crosslinking treatment step or thereafter preferable.

The method of adding the particulate in the method of manufacturing the water-absorbing agent, alpha-hydroxy carboxylic acid compounds of the present invention include, but are not limited to, powder, solution, it is preferable to add as an emulsion, or suspension it is more preferable to be added as a solution, it is more preferably added as an aqueous solution. Furthermore, the α- hydroxy carboxylic acid compound, mentioned above, chelating agents, polyvalent metal salts and / or cationic polymers, may be added respectively at the same time as the water-insoluble inorganic fine particles were mixed in advance each of these components it may be added as a mixture.

(10-7) in the method for producing a particulate water absorbing agent of the addition method the present invention polyvalent metal salts and / or cationic polymers, multivalent metal salt and / or cationic polymers described above, the (1-6) including polymerization step ~ (1-10) surface cross-linking step and (1-11) other steps, may be added at any point in the production step of the particulate water-absorbing agent is preferably added during the surface treatment .

That is, in the (1-10) surface cross-linking step, or a method of crosslinking the water-absorbent resin surface is added simultaneously with the polyvalent metal salt and / or a cationic polymer the aforementioned surface cross-linking agent, the surface crosslinking agent described above after crosslinking the water-absorbent resin surface, a second surface cross-linking step, a method of adding a polyvalent metal salt and / or cationic polymers are preferred. Polyvalent metal salt and / or cationic polymer is reactive with the functional groups of the polyacrylic acid water absorbent resins, particularly ion binding (first or second) surface cross-linking agent, further improve the physical properties of the resultant water-absorbing agent make. In particular, the water-absorbing resin after surface cross-linking by surface cross-linking agent, by surface treatment by adding a polyvalent metal salt and / or cationic polymer, the desired absorption properties, particularly high liquid passing property (SFC) is achieved It is. Incidentally, the polyvalent metal salt and / or cationic polymer, respectively or simultaneously added with the aforementioned α- hydroxy carboxylic acid compound, it is preferable or added as a pre-blended mixture with α- hydroxy carboxylic acid compound. Conventionally, achieved using the polyvalent metal salt and / or cationic polymers was sometimes cause coloring of the water-absorbent resin, but no problem in the present invention, the physical properties improve by polyvalent metal salt and / or a cationic polymer to.

(10-8) drying after addition addition, the (10-3) after the addition step to (10-7) may be dried and the resulting mixture. Here, drying is 50% or more time in the time required for the drying process, through more preferably substantially all of the drying process, preferably it is preferably carried out at a temperature range of less than 100 ° C. or higher 40 ° C.. By drying at such a temperature range, the water-absorbing agent is not damaged by heat, does not adversely affect the properties of the water-absorbing agent obtained.

The drying temperature is defined by a heat medium temperature, if that can not be defined in a microwave or the like heat medium temperature is defined by the material temperature. The drying method, the drying temperature is not particularly limited so long as it is within the above range, hot air drying, airless drying, reduced pressure drying, infrared drying, can be suitably used microwave drying. Range of drying temperature is more preferably 40 ℃ ~ 100 ℃, more preferably at a temperature range of 50 ℃ ~ 90 ℃. The drying may be dried at a constant temperature, it may be dried by changing the temperature, but virtually all of the drying step can be made so that the water content to be described later and in the temperature range of the It is preferred.

Drying time, the surface area of ​​the water-absorbing agent, water content, and depending on the type of the dryer, is appropriately selected such that moisture content of interest. Drying time is usually 10 to 120 minutes, more preferably 20 to 90 minutes, more preferably 30 to 60 minutes. The drying time is less than 10 minutes, drying is not sufficient, there is a case handling property insufficient. Further, in drying time 120 minutes or more, the results or damage a water-absorbing agent by excessive drying, odor (estimated also complex inorganic reducing agent and water-absorbing resin) may be generated, water soluble fraction rise to or happened, there is a case in which the effect of improving the physical properties not be seen. This drying step may be adjusted such that the moisture content of the particulate water absorbing agent of the present invention is 5 wt% or less.

Preferably from 3 to 15 wt% as a water content after drying, more preferably 4 to 14 wt%, more preferably 5-13 wt%, in particular 6-12% by weight, a further 7-11% by weight. The water content as an example of the adjustment method, the method described above is illustrated.

Patent Document 17 (EP 1645596), the water absorbent having the water-oxygen-containing reducing inorganic salt, the coloring resistance which comprises the aminocarboxylic acid metal chelating agent and an organic antioxidant It discloses a resin composition, but to use a certain amount of p- methoxyphenol and water-insoluble particles is not disclosed, the importance of the water content of the resulting water-absorbent resin composition is not described. Uses a 80% by weight of acrylic acid (92g + 119.1g) and 30 wt% NaOH aqueous solution (102.2 g + 132.2 g) water-absorbent resin 214.4g obtained and as a monomer in production example in Example of Patent Document 17 Te, oxygen-containing reducing inorganic salt in example 1-7, to obtain a water-absorbent resin composition aminocarboxylic acid metal chelating agent and an organic antioxidant is mixed without solvent. Therefore, in Patent Document 17, the water content of the water-absorbing resin from a raw material of the water-absorbent resin (g) and yield (212.2g) is obtained by the calculation and 17 wt%, thus, Patent Document 17 present preferred moisture content 3-15% by weight, still more 4 to 14 wt%, 5-13 wt%, 6-12 wt.%, not disclose 7-11 wt%. The Patent Document 17 Suruga disclose an alkyl hydroxy anisole (such as butyl) as an organic antioxidant (paragraph [0019] [0020] Example 6), does not disclose a small amount of p- methoxyphenol.

[11) water absorber according to the water-absorbent structure present invention includes a particulate water absorbing agent of the present invention. By combining the particulate water-absorbing agent of the present invention with a suitable material, for example, it may be a suitable absorbent core as an absorbent layer for sanitary materials. The following describes the water-absorbent structure of the present invention. Water-absorbing agent of the present invention is white, liquid permeability, absorbency against pressure, water absorption rate is high, since less residual monomer, the high concentration water body can be suitably used especially diapers.

In the present invention, the water-absorbent structure, blood, body fluids, a composition for use in sanitary materials to absorb urine and the like, is that of the molded composition comprising particulate water-absorbing agent and other materials. Here, as the sanitary materials include, for example, paper diapers, sanitary napkins, incontinence pads, medical pads, and the like. Other materials used in the absorbent core include cellulose fibers.

Specific examples of such cellulose fibers, for example, mechanical pulp from wood, chemical pulp, semichemical pulp, wood pulp fibers such as dissolving pulp; rayon, acetate or the like artificial cellulose fibers and the like. More preferred cellulose fibers are wood pulp fibers. Also these cellulose fibers are nylon, may partially contain synthetic fibers such as polyester.

When using the particulate water absorbing agent of the present invention as part of the absorbent core, the content of the particulate water absorbing agent contained in the water absorbent core is preferably 20 wt% or more, more preferably 30 wt% or more, more preferably in the range of more than 50 wt%. Weight of the particulate water-absorbing agent of the present invention contained in the water-absorbent structure is less than 20 wt%, there is a possibility that sufficient absorption effect can not be obtained.

To produce the water-absorbent structure using the particulate water absorbing agent and the cellulose fibers according to the present invention, for example, paper made of a cellulose fiber, sprayed with the water absorbing agent to the mat, and these paper if necessary, with mat how to clamping, it can be appropriately selected and a method of blending uniformly the cellulose fibers and water-absorbing agent, a known means for obtaining water-absorbent structure. As a more preferred method, after the particulate water absorbing agent and the cellulose fibers dry 混含 include a method of compressing. By this method, it is possible to suppress significantly the dropping of the particulate water-absorbing agent from the cellulose fibers. Compression is preferably carried out under heating, its temperature range is, for example, 50 ~ 200 ° C..

Particulate water-absorbing agent according to the present invention, when used in the water absorbent core, because of its excellent physical properties, faster uptake of liquid, also, the residual amount of the water-absorbing body surface of the liquid is small, a very good absorbent core can get.

Particulate water-absorbing agent according to the present invention, because it has excellent water absorption properties, can be used as a water-absorbing water-retaining agent of various applications. Specifically, for example, paper diapers, sanitary napkins, incontinence pads, water water retaining agents for absorbent articles such as medical pads; sphagnum moss alternative, soil amendment modifiers, water retention agents, agricultural and horticultural agricultural chemicals efficacy duration agents use a water retention agent; interior wall material for condensation prevention agent, architectural water retaining agents such as cement additive; release control agents, wet ice, disposable body warmer, sludge coagulants, food freshness holding agent, an ion-exchange column material, sludge or oil dehydrating agents, drying agents, it can be used in the humidity control materials. Above all, the water absorbing agent according to the present invention, paper diapers, such as sanitary napkins, feces, particularly preferably used in absorbing sanitary materials urine or blood.

Water absorber according to the present invention, paper diapers, sanitary napkins, incontinence pads, when used for sanitary materials such as medical pads, (a) a liquid permeable top sheet disposed adjacent to the body of the wearer , away from the body (b) the wearer, is disposed adjacent to the wearer's garment, disposed impermeable backsheet, and (c) between the topsheet and the backsheet to the liquid water-absorbent structure, is preferably used in comprising at configure. The water-absorbent structure may be two or more layers may be used with a pulp layer or the like.

As described above, the particulate water-absorbing agent according to the present invention can be rephrased in the following manner.

(1) A particulate water-absorbing agent as a main component of polyacrylic acid (salt) -based water absorbent resin, methoxy phenols 5 ~ 60 ppm, characterized in that it comprises a chelating agent and an inorganic reducing agent, polyacrylic particulate water-absorbing agent as a main component an acid (salt) -based water absorbent resin.

(2) A particulate water-absorbing agent as a main component of polyacrylic acid (salt) -based water absorbent resin, chelating agent, characterized in that it comprises an inorganic reducing agent and water-insoluble inorganic fine particles, polyacrylic acid (salt particulate water-absorbing agent as a main component) -based water absorbent resin.

(3) A surface cross-linked polyacrylic acid (salt) -based water absorbent resin is particulate water-absorbing agent as a main component, inorganic reducing agent and chelating agent, p- methoxy includes phenol, water content 3-15 by weight%, particulate water-absorbing agent as a main component of polyacrylic acid (salt) -based water absorbent resin.

Similarly, method for producing a particulate water absorbing agent of the present invention can be paraphrased as follows.

(1) a polymerization step of the monomer aqueous solution containing as a main component an acrylic acid (salt) which methoxyphenol which contained 10 ~ 200 ppm, the drying step of the hydrogel crosslinked polymer obtained by polymerizing, surface cross-linking step If, comprising the step of adding a chelating agent, a method for producing a particulate water absorbing agent,
After surface cross-linking step, and carrying out the addition process of the inorganic reducing agent, method for producing a particulate water absorbing agent.

(2) including a step of polymerizing the monomer aqueous solution containing as a main component an acrylic acid (salt), and a drying step of the resultant crosslinked hydrogel polymer by polymerization, a method for producing a particulate water absorbing agent ,
Surface cross-linking step, the step of adding a chelating agent, characterized in that it comprises a step of adding an inorganic reducing agent and water-insoluble inorganic fine particles, method for producing a particulate water absorbing agent.

(3) a polymerization step of the monomer aqueous solution containing as a main component an acrylic acid (salt) which methoxyphenol which contained 10 ~ 200 ppm, the drying step of the hydrogel crosslinked polymer obtained by polymerizing, surface cross-linking step If, as a main component of polyacrylic acid (salt) -based water absorbent resin containing a step of adding an inorganic reducing agent and a chelating agent, a method for producing a particulate water absorbing agent,
And controlling the water content of the polymer 3 to 15 wt% in the drying step and the surface cross-linking step, the manufacturing method of the particulate water-absorbing agent as a main component of polyacrylic acid (salt) -based water absorbent resin.

The present invention is not limited to the above embodiments, and various modifications are possible within the scope of the claims, embodiments obtained by appropriately combining technical means disclosed in different embodiments for also included in the technical scope of the present invention.

(Preferred subgenus of the particulate water absorbing agent)
(Manufacturing method-Part 1 of the particulate water-absorbing agent)
As a method for producing the particulate water-absorbing agent of the present invention, a manufacturing method, the first subordinate concept of the (c) is required if the single mainly containing acrylic acid (salt) which methoxyphenol which contained 10 ~ 200 ppm a polymerization step of mer solution, and drying the hydrogel crosslinked polymer obtained by the polymerization, and the surface-crosslinking step, the particulate water-absorbing agent comprising a chelating agent 0.001-0.5 wt% of the added steps a manufacturing method, after the surface cross-linking step is characterized by performing the step of adding an inorganic reducing agent. Specific examples of the production method Part 1 in Examples 1-1 to 1-16 and Tables 1-5 below.

(Manufacturing method-Part 2 of the particulate water-absorbing agent)
As a method for producing the particulate water-absorbing agent of the present invention, a manufacturing method Part 2 of the subordinate concept of the a (b) as essential includes the step of polymerizing the monomer aqueous solution containing as a main component an acrylic acid (salt), the polymerization a drying step of the hydrogel crosslinked polymer obtained by, and a surface cross-linking step, a method for producing a particulate water absorbing agent, the addition step and the inorganic reducing chelating agent 0.001 to 0.5 wt% further comprising a step of adding agents, monomer contains 10 ~ 200 ppm of methoxyphenol in to acrylic acid conversion, and further comprising the step of adding (a) water-insoluble inorganic fine particles. Specific examples of the production method Part 2 in Examples 2-1 to 2-14 and Tables 6-7 below.

(Manufacturing Method Part 3 of the particulate water-absorbing agent)
As a method for producing the particulate water-absorbing agent of the present invention, a manufacturing method Part 3 of the subordinate concept of the a (c) as essential includes the step of polymerizing the monomer aqueous solution containing as a main component an acrylic acid (salt), the polymerization a drying step of the hydrogel crosslinked polymer obtained by, and a surface cross-linking step, a method for producing a particulate water absorbing agent, the addition step and the inorganic reducing chelating agent 0.001 to 0.5 wt% further comprising a step of adding agents, monomer contains 10 ~ 200 ppm of methoxyphenol in to acrylic acid in terms of, in the drying step and / or after the surface cross-linking step, the water content of 3-15% by weight of the polymer control is possible, even more preferably, the inorganic reducing agent, is characterized by adding to the crosslinked hydrogel polymer before drying. Specific examples of the production method, the 3 in Examples 3-1 to 3-13 and Tables 8-9 below.

The present invention will be described below according to examples, the present invention is not intended to be construed limited to the embodiments. Moreover, various physical properties described in the scope and embodiments of the claimed invention was determined according to the following measuring method. Note that the following measurement method is describes a particulate water absorbing agent, it is also measured replaced the particulate water absorbing agent with the water-absorbing resin for a water-absorbent resin. Furthermore, electrical equipment used in the examples, with 200V or 100 V, and was used under the conditions of 60 Hz. Further, the particulate water-absorbing agent, unless otherwise specified, 25 ° C. ± 2 ° C., was used under the conditions of RH 50% relative humidity. Illustrated reagents and instruments by the following measurement methods and embodiments may be replaced with an appropriate equivalent.

Incidentally, the particulate water absorbing agent of the present invention includes an inorganic reducing agent required, below, a surface-crosslinked water-absorbent resin, the prior addition of an inorganic reducing agent the water-absorbing resin, the particulate water-absorbing agent precursor sometimes referred to as (see, examples 1-1 to 1-8, Comparative examples 1-3 and 1-4, etc.).

[Method of evaluating the physical properties]
[CRC]
After the particulate water absorbing agent 0.2g was uniformly placed sealed bag made of nonwoven fabric (60 × 60mm), 25 ± 3 0.9 wt% sodium chloride aqueous solution adjusted in ° C. (aka; saline) into 500g soaked. After 60 minutes, the bag was pulled up, after 3 minutes drained 250G using a centrifugal separator, and weighed W1 [g] of the bag. The same operation is performed without putting a particulate water-absorbing agent, it was determined by weight W2 [g] at that time. It was calculated CRC (absorbency against non-pressure) according to the following equation.

Figure JPOXMLDOC01-appb-M000001

[Water-soluble component]
Lidded plastic container having a capacity of 250 ml, put a 0.90 wt% aqueous solution of sodium chloride 184.3g and the particulate water absorbing agent 1.00 g, subjected to stirring for 16 hours, extract the extractable polymer in the particulate water-absorbing agent did. The extract a filter paper (ADVANTEC Toyo Co., product name: JIS P 3801, No.2, thickness 0.26 mm, diameter of retained particles 5 [mu] m) was filtered using a measuring 50.0g of the resulting filtrate It was a solution.

Then, titrated until pH10 with 0.1N NaOH aqueous solution, then, titration was carried out until the pH2.7 with 0.1N aqueous HCl. Titer ([NaOH] ml, [HCl] ml) at this time was determined. Further, the same titration operations, performed for only 0.90 wt% aqueous solution of sodium chloride 184.3 g, empty titration amounts ([bNaOH] ml, [bHCl] ml) was determined.

For particulate water absorbing agent of the present invention, the average molecular weight of the monomer, based on the titration amounts obtained by the above operation, the water-soluble component in the particulate water-absorbing agent can be calculated by the following equation 2 . Incidentally, when the average molecular weight of the monomer is unknown, the average molecular weight of the monomer by using a neutralization ratio obtained by the titration can be calculated. The neutralization ratio is calculated by the following equation (3).

Figure JPOXMLDOC01-appb-M000002

Figure JPOXMLDOC01-appb-M000003

[Residual monomer]
Residual monomers contained in the particulate water absorbing agent of the present invention (residual acrylic acid (salt)), except for changing the stirring time in the measurement method described above [water-soluble component] in 2 hours 16 hours, the same operation obtained by analyzing the filtrate obtained by performing. Specifically, the filtrate obtained by the manipulation, by high-performance liquid chromatographic analysis, it is possible to determine the residual monomer in the particulate water-absorbing agent. Incidentally, the residual monomer is expressed in ppm (vs. particulate water-absorbing agent).

[AAP]
Absorbency against pressure (AAP) represents an absorbency of 60 minutes 4.83kPa or 2.0kPa 0.90 wt% saline. Incidentally, AAP may also be referred to as absorbency against pressure at 4.83kPa or 2.0 kPa.

Using the apparatus shown in FIG. 1, the bottom of a plastic supporting cylinder 100 having an inner diameter of 60 mm, a stainless steel 400-mesh metal gauze 101 (aperture 38 [mu] m) was fused at room temperature (20 ~ 25 ° C.), humidity 50 RH% condition under was uniformly sprayed particulate water absorbing agent 0.900g onto net-, thereon, with respect to the particulate water-absorbing agent, 4.83 kPa of (0.7 psi) or 2.0 kPa (0.3 psi) it is adjusted to be able to apply a load uniformly, placed outside diameter does not occur a gap between the slightly smaller supporting cylinder than 60 mm, and a piston 103 and a load 104 that vertical movement is not impeded in this order and weighed Wa [g] of the set of measurement apparatus.

Glass filter 106 having a diameter of 90mm to the inside of the petri dish 105 having a diameter of 150 mm (produced by Sogo Rikagaku Glass Seisakusho Ltd., pore diameter: 100 ~ 120 [mu] m) Place the 0.90 wt% aqueous solution of sodium chloride 108 (20 ~ 25 ℃) It was added up to the same level as the upper surface of the glass filter. Thereon, the filter paper 107 having a diameter of 90 mm (ADVANTEC Toyo Co., Ltd., product name: JIS P 3801, No.2, thickness 0.26 mm, diameter of retained particles 5 [mu] m) placed one sheet, so the surface is wetted all, and an excess of liquid was removed.

Place the above set of measurement apparatus on the wet filter paper above and the liquid was absorbed under load. After one hour, lifting the set of measurement apparatus was measured and its weight Wb [g]. Then, Wa, from Wb, was calculated AAP [g / g] according to the following equation.

Figure JPOXMLDOC01-appb-M000004

[SFC]
SFC (saline flow conductivity) is a value showing liquid permeability upon swelling of the water-absorbent resin particles or water-absorbing agent. And shown to have high liquid permeability as the value of the SFC is high. U.S. Patent saline flow conductivity of the 5849405 Pat described (SFC) was performed according to Test.

Using the apparatus shown in FIG. 2, the uniformly charged particulate water absorbing agent in the container 40 0.900 [g] under a pressure of 2.07 kPa (0.3 psi) with artificial urine and allowed to swell for 60 minutes It was recorded the height of the gel layer of a gel 44. Then under pressure of 2.07 kPa, 0.69 wt% aqueous sodium chloride solution 33 was passed through a gel 44 swollen from a tank 31 under a constant hydrostatic pressure. This SFC test was performed at room temperature (20 ~ 25 ℃). Using a computer and a scale, the amount of liquid passing through the gel layer was recorded for 10 min at 20 second intervals as a function of time.

Flow rate passing through the swollen gel 44 (mainly between particles thereof) Fs (T) is divided by the weight gain [g] elapsed time [s]; it was determined in the units g / s] be. The time when the constant hydrostatic pressure and a stable flow rate had been obtained was set as Ts, using only data obtained in the course of Ts and 10 minutes on the flow rate calculated using the flow rate obtained in the course of Ts and 10 minutes the value of fs (T = 0), that is to calculate the first flow rate through the gel layer. Fs (T = 0) was calculated by extrapolating the results of a least square method Fs (T) versus time T = 0.

Figure JPOXMLDOC01-appb-M000005

here,
Fs (t = 0): flow rate [g / s]
L0: the gel layer height [cm]
[rho: the density of the aqueous sodium chloride solution (1.003 [g / cm 3] )
A: the upper side of the gel layer area of the cell 41 (28.27 [cm 2])
[Delta] P: hydrostatic pressure applied to the gel layer (4920 [dyn / cm 2] )
It is.

For SFC measurement apparatus shown in FIG. 2 will be described in detail.

The tank 31, the glass tube 32 was inserted, the lower end of the glass tube 32 can maintain a 0.69 wt% aqueous sodium chloride solution 33 from the bottom of the swollen gel 44 in the cell 41, at a height of 5cm above It was arranged to. 0.69 wt% aqueous sodium chloride solution 33 in the tank 31 was supplied to the cell 41 through the L-shaped tube 34 with a cock 35. Under the cell 41, a container 48 for collecting the passed liquid was disposed, collecting container 48 was placed on an even balance 49. The inner diameter of the cell 41 is 6 cm, stainless steel wire mesh 42 of the mesh 38μm was installed on the bottom surface. At the bottom of the piston 46, there is sufficient holes 47 for passing the liquid, the particulate water absorbing agent in a bottom portion, or its swollen gel, permeable glass filter 45 do not enter the hole 47 is attached It had been. The cell 41 was placed on a stand to put the cell, base surface in contact with the cell was positioned on the stainless metal gauze 43 which did not prevent the liquid from passing through.

Incidentally, the artificial urine, the pure water 994.25 [g], calcium chloride dihydrate 0.25 [g], potassium chloride 2.0 [g], magnesium chloride hexahydrate 0.50 [g] , sodium sulfate 2.0 [g], 2 hydrogen ammonium 0.85 phosphate [g], and was used plus hydrogen phosphate diammonium 0.15 [g].

[Absorption rate that 1 (FSR)]
The FSR (absorption rate), is indicative of the speed of absorbing the liquid of the water-absorbing agent. Water absorption rate is preferably to exhibit high values. By using the water absorption speed is high water-absorbing agent in the water-absorbent structure, it is possible to obtain an excellent water absorber water absorption rate of the liquid. Absorption rate is measured by the following method.

To accurately weighed particulate water absorbing agent 1.000 ± 0.0005 [g] to the fourth decimal place (Wc [g]), a glass beaker 25 ml (diameter 32 ~ 34 mm, height 50 mm), the particles the upper surface of Jo water-absorbing agent was placed so that the horizontal. If necessary, carefully perform treatment such tapping the beaker, to level the particulate water absorbing agent. Then, weighed 0.9 wt% aqueous sodium chloride solution 20ml was adjusted to 23 ± 2.0 ° C. in a glass beaker 50 ml, was weighed of the aqueous solution to the fourth decimal place (Wd [g]).

Next, the 0.9 wt% aqueous sodium chloride solution, poured quickly 25ml beaker containing the particulate water-absorbing agent, as a starting point a moment when sodium chloride aqueous solution and the particulate water absorbing agent is in contact, and starts time measurement. The liquid level in the beaker poured salt sodium solution, viewed from an angle of about 20 °, the liquid surface was measured time (Th [sec]) from the aqueous solution to replace the particulate water-absorbing agent. Then, the weight of aqueous sodium chloride solution adhering to the beaker after pouring aqueous sodium chloride solution (beaker residual amount) (We [g]) was measured to the fourth decimal place. By the following equation was determined FSR (water absorption rate) [g / g / sec]. Incidentally, it measured 3 times on one sample, and the average value was used as the representative value.

Figure JPOXMLDOC01-appb-M000006

[Absorption rate that 2 (Vortex)]
Preconditioned 0.90 wt% aqueous sodium chloride solution (saline) 1.000 Food Blue No. 1 is a food additive in parts by weight (CAS Number: 3844-45-9) was added 0.02 part by weight , it was adjusted to a liquid temperature 30 ° C.. Physiological saline 50ml The trunk diameter 55 mm, weighing the beaker 100ml Height 70 mm (e.g. SOGO LABORATORY GLASS WORKS is compliant with JISR-3503 to sell beaker), length 40 mm, the thickness 8mm cylindrical Teflon (registered trademark) magnetic stirrer (e.g., SOGO LABORATORY S type glass Seisakusho sold) in in stirring conditions of 600 rpm, examples below or obtained in Comparative example particulate water absorbing agent 2.0g It was charged, to measure the water absorption rate (in seconds). Start, end point, according to the criteria described in JIS K 7224 (1996 fiscal) "absorption rate test method commentary superabsorbent resin" particulate water absorbing agent to the liquid absorbing saline in gelation saline measures the time to time rotation until covering the stirrer chip to rotate (covered with V-shaped when viewed from a cross-sectional), is evaluated as absorption rate (seconds).

[Weight average particle diameter (D50), logarithmic standard deviation of particle size distribution ([sigma] [zeta]) and 150μm particles below]
Weight average particle diameter (D50) was measured according to the method described in WO 2004/069404 pamphlet. A predetermined amount of the particulate water absorbing agent mesh 850μm, 710μm, 600μm, 500μm, 425μm, 300μm, 212μm, 150μm, 106μm, 45μm of JIS standard sieves (JIS Z8801-1 (2000)), or those JIS standard sieve It sieved using a corresponding sieve was plotted and a residual percentage R on a logarithmic probability paper. Thus, reading the particle diameter corresponding to R = 50 wt% as the weight average particle diameter (D50).

Logarithmic standard deviation of particle size distribution ([sigma] [zeta]) is represented by the following formula, it means a narrow particle size distribution as the value of [sigma] [zeta] is small.

Figure JPOXMLDOC01-appb-M000007

here,
X1: R = 84.1 particle size equivalent to [wt%] X2: a particle diameter corresponding to R = 15.9 [wt%].

The 150μm particles below [wt%] as defined by the standard sieve classification, the weight of particles passing through a mesh opening 150μm of JIS standard sieves (JIS Z8801-1 (2000)), to the total weight of the particulate water-absorbing agent a ratio [wt%]. In the present specification, simply referred to as "150 [mu] m particles below [wt%] or" 150 [mu] m pass [%] ".

[Coloration evaluation of the particulate water-absorbing agent (Hunter Lab color system / L value)]
Colored evaluation of the particulate water-absorbing agent was performed using a HunterLab Co. LabScan (TM) XE. Setting conditions of the measurement, reflection measurement is selected, the inner diameter 30 mm, is used a powder-paste sample container height 12 mm, standard round white board for powder-paste as the standard No. 2 is used, 30Fai floodlight pipe were used. It was filled with the particulate water absorbing agent of from about 5g to the sample container for equipped. This filling has been to fill the equipped sample vessel 60% approximately. Under the conditions of room temperature (20 ~ 25 ° C.) and humidity 50 RH%, L values ​​of the surface at the spectroscopic color difference meter: was measured (Lightness lightness index). This value, the "lightness index before exposure" is a white greater the value.

Further, by the same measuring method of the same apparatus, capable of measuring simultaneously the object color a in other measure, b (chromaticity) also. a / b The smaller, indicating that the closer to the substantially white in low color. Immediately after the production of the particulate water-absorbing agent, or, 30 ° C. or less, the following conditions relative humidity of 50% RH, the coloring evaluation period stored particulate water absorbing agent within one year is the initial color.

Subsequently, by filling the particulate water-absorbing agent of from about 5g to the paste container for a specimen, 70 ± 1 ° C., relative humidity of 65 ± 1% of the atmosphere adjusted constant temperature constant humidity chamber (ESPEC Co. small environmental test chambers, format SH-641) paste sample container filled with particulate water-absorbing agent were exposed for 7 days in a. This exposure is 7 days coloring acceleration test. After exposure was measured L value of the surface (Lightness) a / b value by the above spectroscopic color difference meter. This measurement, the coloring with time after the accelerated test.

[Odor Test]
Put particulate water-absorbing agent 1 part by weight beaker 100 ml, was added to 0.9 wt% aqueous sodium chloride solution 20 parts by weight, and allowed to stand for 1 hour in a sealed 37 ° C. The beaker with the film. This was followed by an odor sensory test by the subject 10 adults. Evaluation method, no unpleasant odor, ○ what is determined to be odor usable for sanitary materials such as diapers, there are unpleasant odors, judged to be unusable odor for sanitary materials such as diapers It was × what is. In particular, it was ×× things unpleasant odor is strong.

[Moisture content]
In an aluminum cup of about 50mm size of the bottom diameter, weighed particulate water absorbing agent 1.00 [g], was measured the total weight of the particulate water-absorbing agent and the aluminum cup W8 [g]. And then dried by standing for 3 hours in an oven at ambient temperature 180 ° C.. Three hours after the oven fetches the particulate water absorbing agent and the aluminum cup from, and cooled to room temperature in a desiccator. Thereafter, calculated on the total weight of the particulate water-absorbing agent and the aluminum cup after drying W9 [g], it was calculated water content according to the following equation Equation 8.

Figure JPOXMLDOC01-appb-M000008

[Accelerated weather resistance test (gel deterioration test Part 1)
Inner diameter particulate water absorbing agent 3.0 g 7.0 cm, placed in a quartz-made separable flask of height 14.0 cm, deionized water was added 57.0 g. Thereafter, while stirring the metal halide lamp 20 times swollen gel particles in the separable flask to (60 g) from the center of the axis to the tip is 3.0 cm, a stirring blade having four flat blades of width 1.0 cm (Ushio electric Ltd., UVL-1500M2-N1) ultraviolet irradiation apparatus fitted with a (same, with a UV-152 / 1MNSC3-AA06) , the irradiation intensity 60 [mW / cm 2] for 1 minute, and irradiated with ultraviolet rays at room temperature, to obtain a water-containing gel-like water-absorbing agent underwent accelerated weather resistance test.

Then, the lid plastic container having a capacity of 250 ml, put a 0.90 wt% aqueous solution of sodium chloride 184.3g and the hydrogel water-absorbing agent 2.00 g, subjected to 16 hours at bending Ne stirrer, water-containing gel-like water to extract the soluble fraction of the agent. The extract was filtrated with a filter paper (ADVANTEC Toyo Co., product name: JIS P 3801, No.2, thickness 0.26 mm, diameter of retained particles 5 [mu] m) was filtered using a 5.0g of the resulting filtrate 0 the mixed solution of .90 wt% aqueous solution of sodium chloride 45.0g was measured solution.

Then, titrated until pH10 with 0.1N NaOH aqueous solution, then, titration was carried out until the pH2.7 with 0.1N aqueous HCl. Titer ([NaOH] ml, [HCl] ml) at this time was determined. Further, the same titration operations, performed for only 0.90 wt% aqueous solution of sodium chloride 184.3 g, empty titration amounts ([bNaOH] ml, [bHCl] ml) was determined.

For hydrogel water-absorbing agent of the present invention, the average molecular weight of the monomer, based on the titration amounts obtained by the above operation, soluble component of the water-containing gel-like water-absorbing agent can be calculated by the following equation (9) . Incidentally, when the average molecular weight of the monomer is unknown, the average molecular weight of the monomer by using a neutralization ratio obtained by the titration can be calculated. The neutralization ratio is calculated by the following equation 10.

Figure JPOXMLDOC01-appb-M000009

Figure JPOXMLDOC01-appb-M000010

Deterioration rate from solubles solubles and the hydrogel water-absorbing agent of the particulate water-absorbing agent, is calculated by the following equation (11).

Figure JPOXMLDOC01-appb-M000011

[Urine resistance test (gel deterioration test Part 2)
Put particulate water-absorbing agent 1 part by weight to 250ml with lid plastic container (Teraoka made pack Ace Co.) was added to simulated artificial urine 25 parts by weight, the sealing to the particulate water-absorbing agent at a predetermined temperature and time It was allowed to deteriorate. Then, when you stand down for 10 minutes a plastic container with 250ml lid to the side, swollen gel was evaluated whether the flow. In the present study, it was conducted by the following two aging conditions.

(1) urine resistance test (L- ascorbic acid concentration Normal) (gel deterioration test thereof 2-1)
[Gel degradation conditions (1)]
Simulated artificial urine: L-ascorbic acid 0.005 wt% concentration of saline degradation temperature: 37 ° C.
Degradation time: 24 hours (2) urine resistance test (1000 times L- ascorbic acid) (Gel deterioration test thereof 2-2)
[Gel deterioration condition (2)]
Simulated artificial urine: L-ascorbic acid 5% strength by weight saline degradation temperature: 90 ° C.
Deterioration time: 1 hour [Dust Measurement]
Using the Seishin Enterprise Co. Heubach Dustmeter 2000, to measure the amount of dust from the particulate water-absorbing agent under the following conditions.

Measurement conditions the working environment: 18 ~ 22 ℃ / 45 ~ 55RH%
Sample: 100.00g
Format: Type (I) (horizontal)
Rotat. : 30 [R / min]
Airflow: 20.0 [L / min]
Time: 60min (set upper limit 30 Bun'yue, performed twice for 30 minutes)
Capture filter: filter paper (ADVANTEC made GC90)
By measuring the measured weight increase of the filter paper after 10 minutes [mg], it was determined amount of the dust from the particulate water-absorbing agent from the following equation.

Figure JPOXMLDOC01-appb-M000012

[P- methoxyphenol contained in the particulate water-absorbing agent]
p- methoxyphenol contained in the particulate water absorbing agent of the present invention, except for changing the stirring time in the evaluation method of the above-mentioned [soluble content] to 1 hour to 16 hours, the filtrate obtained by the same procedure It is found by analysis. Specifically, the filtrate obtained by the manipulation, by high-performance liquid chromatographic analysis, it is possible to obtain the p- methoxy phenol in the particulate water-absorbing agent. Incidentally, p- methoxyphenol, expressed in ppm (vs. particulate water-absorbing agent).

[Reducing agent contained in the particulate water-absorbing agent (sodium hydrogen sulfite)
As the reducing agent contained in the particulate water absorbing agent of the present invention, it illustrates a method of measuring sodium bisulfite. Beaker 200ml putting pure water 50g and the particulate water absorbing agent 0.5g to stand for 1 hour. Then, methanol was added to 50 g, is added a solution 2.5g were dissolved malachite green 2mmol eluent below. The solution was stirred for about 30 minutes, filtered, determine the amount of the reducing agent contained in the particulate water-absorbing agent by analyzing the filtrate by high performance liquid chromatography. Incidentally, eluent is adjusted with methanol 400 ml, n-hexane 6ml, 0.0M-2-N-morpholino-ethanesulfonic acid, the ratio in the sodium salt 100 ml. A calibration curve can be created by analyzing a spiked with a reducing agent to the particulate water-absorbing agent which does not contain a reducing agent.

[Chelating agents contained in the particulate water-absorbing agent]
Chelating agents contained in the particulate water absorbing agent of the present invention, except for changing the stirring time in the evaluation method of the above-mentioned [soluble content] to 1 hour to 16 hours, to analyze the filtrate obtained by the same procedure It can be found by. Specifically, the filtrate obtained by the manipulation, by high-performance liquid chromatographic analysis, it is possible to obtain the chelating agent in the particulate water-absorbing agent. Incidentally, the chelating agent amounts, expressed in ppm (vs. particulate water-absorbing agent). A calibration curve can be created by analyzing a spiked with chelating agent to the particulate water absorbing agent without the chelating agent.

[Example 1-1]
Using the apparatus shown in FIG. 3 described in U.S. Patent No. 7,265,190, according to the following were prepared crosslinked hydrogel polymer.

First, p-35.2 parts by weight of acrylic acid content was adjusted to 70ppm of methoxyphenol, 11.7 parts by weight 48 wt% sodium hydroxide aqueous solution, polyethylene glycol diacrylate (average ethylene oxide unit number: n = 9) 0.23 parts by weight, 1 wt% diethylenetriamine pentaacetic acid trisodium as a chelating agent (abbreviation: DTPA · 3Na) aqueous solution 0.22 parts by weight, and a monomer aqueous solution having a composition of deionized water 33.6 parts by weight (1 -1) was produced.

Then, the monomer aqueous solution was adjusted to 40 ° C. The (1-1), was fed continuously to the polymerization process using a metering pump. Before introducing the belt polymerizer, 48 wt% sodium hydroxide aqueous solution (iron content 0.7 ppm (vs. NaOH solids)) was continuously mixed at line mixing 17.7 parts by weight. At this time, the heat of neutralization, the monomer temperature increased to 86 ° C..

Then, 4 wt% aqueous solution of sodium persulfate 1.38 parts by weight of continuous mixing at line mixing, resulting continuous mixture (1-1), on a plane belt having weirs at both ends, a thickness of about 7. It was supplied so as to 5mm. Continuously for 3 minutes polymerization to obtain water-containing gel-like crosslinked polymer (1-1).

It was then subdivided into approximately 1.5mm above hydrogel crosslinked polymer (1-1) a meat chopper with a pore diameter of 22 mm. The fragmented gel, loaded spread over the porous plate moving in a continuous ventilation band drier, and dried for 30 minutes at 185 ° C., to obtain dried polymer (1-1). The resulting dried polymer (1-1) was ground in a roll mill, mesh opening 710 .mu.m and by sieving in a sieving device having a metal sieve screen of 175 .mu.m, the 175 ~ 710 .mu.m water-absorbing resin powder (1 -1) was obtained.

The obtained water-absorbing resin powder (1-1) 100 parts by weight, 0.3 part by weight of 1,4-butanediol, propylene glycol 0.6 parts by weight, the mixing of deionized water 3.0 parts by weight after mixing the surface cross-linking agent comprising a liquid uniformly, by heating the mixture for 40 minutes at 208 ° C., to obtain a surface cross-linked water-absorbing resin powder (1-1).

The resulting surface crosslinked water-absorbent resin powder (1-1) was cooled, the surface cross-linked water absorbent resin powder (1-1) with respect to 100 parts by weight, 30 wt% aqueous sodium bisulfite 1.66 weight parts were added and mixed to obtain a particulate water absorbing agent precursor (1-1). Then, the resultant particulate water absorbing agent precursor (1-1) was left in a 60 ° C. in a hot air drier for 30 minutes, then, by pass through a JIS standard sieve 710 .mu.m, the particulate water-absorbing agent ( 1-1) was obtained. The water content of the obtained particulate water absorbing agent (1-1) was 1.8 wt%. Obtained particulate water absorbing agent properties of (1-1) described in Table 1.

[Example 1-2]
Except for changing the addition amount of 30 wt% aqueous sodium bisulfite solution of Example 1-1 according to 3.33 parts by weight 1.66 parts by weight, in the same manner as in Example 1-1 particulate water-absorbing agent ( 1-2) was obtained. Obtained particulate water absorbing agent properties of (1-2) described in Table 1.

[Example 1-3]
Example 1-1 was changed to 0.166 parts by weight 1.66 parts by weight of the added amount of 30 wt% aqueous sodium bisulfite according water absorbing agent obtained in the same manner as in Example 1-1 to 100 parts by weight, further 50 wt% sodium lactate aqueous solution was mixed 0.6 parts by weight added to give a particulate water absorbing agent precursor (1-3). Then, the resultant particulate water absorbing agent precursor (1-3) was left in a 60 ° C. in a hot air drier for 30 minutes, then, by pass through a JIS standard sieve 710 .mu.m, the particulate water-absorbing agent ( 1-3) was obtained. The water content of the obtained particulate water absorbing agent (1-3) was 2.0 wt%. Obtained particulate water absorbing agent properties of (1-3) described in Table 1-1.

[Example 1-4]
In Examples 1-3, the amount of 30 wt% aqueous solution of sodium hydrogen sulfite was changed to 1.66 parts by weight 0.166 part by weight, and the amount of 50 wt% sodium lactate aqueous solution from 0.6 parts by weight it was changed to 0.1 part by weight, to obtain a particulate water absorbing agent in the same manner as in example 1-3 (1-4). Obtained particulate water absorbing agent properties of (1-4) described in Table 1-1.

[Example 1-5]
In Example 1-3, except for changing the addition amount of 30 wt% aqueous sodium bisulfite solution to 1.66 parts by weight 0.166 part by weight, the particulate water-absorbing in the same manner the same as Example 1-3 It was obtained agent (1-5). Obtained particulate water absorbing agent properties of (1-5) described in Table 1.

[Example 1-6]
To the surface cross-linked water absorbent resin powder (1-1) 100 parts by weight in Example 1-1, were added and mixed 0.33 parts by weight of 30 wt% aqueous sodium bisulfite, further aqueous aluminum sulfate solution (aluminum oxide basis in 8 wt%) 0.9 parts by weight, 60 wt% sodium lactate aqueous solution 0.30 parts by weight, and by uniformly mixing the mixture 1.22 parts by weight of propylene glycol 0.02 parts by weight, particulate to give water-absorbing agent precursor (1-6). Then, the resultant particulate water absorbing agent precursor (1-6) was left in a 60 ° C. in a hot air drier for 30 minutes, then, by pass through a JIS standard sieve 710 .mu.m, the particulate water-absorbing agent ( 1-6) was obtained. Obtained particulate water absorbing agent properties of (1-6) described in Table 1.

[Example 1-7]
Using the apparatus shown in FIG. 3 described in U.S. Patent No. 7,265,190, according to the following were prepared crosslinked hydrogel polymer.

First, p-35.2 parts by weight of acrylic acid content was adjusted to 70ppm of methoxyphenol, 11.7 parts by weight 48 wt% sodium hydroxide aqueous solution, polyethylene glycol diacrylate (average ethylene oxide unit number: n = 9) 0.23 parts by weight, 31% ethylene diamine tetra (methylene phosphonic acid) pentasodium (abbreviation: EDTMPA · 5Na) aqueous solution 0.03 parts by weight, and a monomer aqueous solution having a composition ratio of deionized water 33.6 parts by weight ( 1-7) was prepared.

Then, the monomer aqueous solution was adjusted to 40 ° C. The (1-7), was fed continuously to the polymerization process using a metering pump. Before introducing the belt polymerizer was continuously mixed 17.7 parts by weight 48 wt% aqueous solution of sodium hydroxide at line mixing. At this time, the heat of neutralization, the monomer temperature increased to 86 ° C.. Then, 4 wt% aqueous solution of sodium persulfate 1.38 parts by weight of continuous mixing at line mixing, resulting continuous mixture (1-7), on a plane belt having weirs at both ends, a thickness of about 7. It was supplied so as to 5mm. Continuously for 3 minutes polymerization to obtain water-containing gel-like crosslinked polymer (1-7).

It was then subdivided into approximately 1.5mm above hydrogel crosslinked polymer (1-7) a meat chopper with a pore diameter of 22 mm. The fragmented gel, loaded spread over the porous plate moving in a continuous ventilation band drier, and dried for 30 minutes at 185 ° C., to obtain dried polymer (1-7). After grinding the resulting dried polymer (1-7) in a roll mill, by sieving in a sieving device having a mesh opening 710 .mu.m and a metal sieve screen of 175 .mu.m, the water-absorbing resin powder of particle size of 175 ~ 710 .mu.m to give the body (1-7).

The obtained water-absorbing resin powder (1-7) 100 parts by weight of 1,4-butanediol 0.3 parts by weight, 0.6 parts by weight of propylene glycol, and deionized water 3.0 parts by weight after mixture was mixed a surface crosslinking agent uniformly made of, by heating the mixture for 40 minutes at 208 ° C., to obtain a surface cross-linked water-absorbing resin powder (1-7).

The resulting surface crosslinked water-absorbent resin powder (1-7) was cooled, the surface cross-linked water absorbent resin powder (1-7) with respect to 100 parts by weight, 30 wt% aqueous sodium bisulfite 1.66 weight parts, 30 (8% by weight aluminum oxide basis)% by weight aqueous solution of aluminum sulfate 0.9 parts by weight, 60 wt% sodium lactate aqueous solution 0.30 parts by weight, and a mixture of propylene glycol 0.03 parts by weight 1.23 It was obtained particulate water absorbing agent precursor (1-7) by uniformly adding a mixture of parts by weight. Then, the resultant particulate water absorbing agent precursor (1-7) was left in a 60 ° C. in a hot air drier for 30 minutes, then, by pass through a JIS standard sieve 710 .mu.m, the particulate water-absorbing agent ( 1-7) was obtained. Obtained particulate water absorbing agent properties of (1-7) described in Table 1.

[Example 1-8]
Commercially available acrylic acid (Wako Pure Chemical, special grade reagent; p-methoxyphenol 200ppm containing) obtained in gas-phase catalytic oxidation and then fed into the bottom of the high boiling impurities separation column having Museki perforated plate 50 stages, distilling the reflux ratio as 1, by further re-distillation to obtain 99% by weight of acrylic acid and traces of impurities (mainly water) purified acrylic acid consisting of (1-8). p- methoxyphenol content in the purified acrylic acid (1-8) was ND (less than 1 ppm).

In purified acrylic acid (1-8) a p- methoxyphenol to give the adjustment acrylic acid (1-8) by adding 15 ppm.

Using the apparatus shown in FIG. 3 described in U.S. Patent No. 7,265,190, according to the following were prepared crosslinked hydrogel polymer.

First, the adjusting acrylic acid (1-8) 35.2 parts by weight, 48 wt% sodium hydroxide aqueous solution (iron content 0.7 ppm (vs. NaOH solids)) 11.7 parts by weight of polyethylene glycol diacrylate (average ethylene oxide number of units: n = 9) 0.23 parts by weight, 31 wt% ethylenediaminetetra (methylene phosphonic acid) pentasodium (abbreviation: EDTMPA · 5Na) aqueous solution 0.03 parts by weight of deionized water 33.6 parts by weight to prepare a monomer solution having a composition ratio of (1-8).

Then, the monomer aqueous solution (1-8) was adjusted to 40 ° C., was continuously fed with a metering pump. The aqueous monomer solution (1-8) was continuously mixed 17.7 parts by weight 48 wt% aqueous solution of sodium hydroxide at line mixing. At this time, the heat of neutralization, the temperature of the monomer was increased to 86 ° C.. It was then continuously mixed 4 wt% aqueous solution of sodium persulfate 1.38 part by weight line mixing. The continuous mixture obtained by this line mixing (1-8), on a plane belt having weirs at both ends, and supplies so as to have a thickness of about 7.5 mm, subjected to continuous 3 minutes polymerization, water gel-like crosslinked polymer (1-8) was obtained.

It was then subdivided into approximately 1.5mm above hydrogel crosslinked polymer (1-8) a meat chopper with a pore diameter of 22 mm. The fragmented gel, loaded spread over the porous plate moving in a continuous ventilation band drier, and dried for 30 minutes at 185 ° C., to obtain dried polymer (1-8). The resulting dried polymer (1-8) was ground in a roll mill, mesh opening 710 .mu.m and by sieving in a sieving device having a metal sieve screen of 175 .mu.m, the 175 ~ 710 .mu.m water-absorbing resin powder (1 -8) was obtained.

The obtained water-absorbing resin powder (1-8) 100 parts by weight of 1,4-butanediol 0.3 parts by weight, 0.6 parts by weight of propylene glycol, and deionized water 3.0 parts by weight after mixture was mixed a surface crosslinking agent uniformly made of, by heating the mixture for 40 minutes at 208 ° C., to obtain a surface cross-linked water-absorbing resin powder (1-8).

The resulting surface crosslinked water-absorbent resin powder (1-8) was cooled, the surface cross-linked water absorbent resin powder (1-8) with respect to 100 parts by weight, 30 wt% aqueous sodium bisulfite 1.66 weight (8% by weight aluminum oxide basis) 0.9 parts by weight of parts and an aqueous solution of aluminum sulfate, 60 wt% sodium lactate aqueous solution 0.50 parts by weight, and the mixture 1.44 parts by weight of propylene glycol 0.04 parts by weight It was obtained particulate water absorbing agent precursor (1-8) by uniformly added and mixed. Then, the resultant particulate water absorbing agent precursor (1-8) was left in a 60 ° C. in a hot air drier for 30 minutes, then, by pass through a JIS standard sieve 710 .mu.m, the particulate water-absorbing agent ( 1-8) was obtained. Obtained particulate water absorbing agent properties of (1-8) described in Table 1.

[Example 1-9]
The p- methoxyphenol in Example 1-8 purified acrylic acid described (1-8) to obtain an adjustment acrylic acid (1-9) by adding 200 ppm.

Except for using adjustment acrylic acid (1-9) in place of the adjusting acrylic acid (1-8), the surface cross-linked water absorbent resin powders by performing surface crosslinking treatment of the same polymerization as in Example 1-8 (1-9) was obtained.

The resulting surface crosslinked water-absorbent resin powder (1-9) was cooled, the surface cross-linked water absorbent resin powder (1-9) with respect to 100 parts by weight, 30 wt% aqueous sodium bisulfite 1.66 weight parts were added and mixed to obtain a particulate water absorbing agent precursor (1-9). Then, the resultant particulate water absorbing agent precursor (1-9) was left in a 60 ° C. in a hot air drier for 30 minutes, then, by pass through a JIS standard sieve 710 .mu.m, the particulate water-absorbing agent ( 1-9) was obtained. The water content of the obtained particulate water absorbing agent (1-9) was 1.8 wt%. Obtained particulate water absorbing agent properties of (1-9) described in Table 1.

[Comparative Example 1-1]
Without using the chelating agent, also except for changing the addition amount of 30 wt% aqueous sodium bisulfite solution to 0.166 parts by weight 1.66 parts by weight In the same manner as described in Example 1-1 thereby obtaining a comparative particulate water absorbing agent (1-1). The resultant comparative particulate water absorbing agent properties of (1-1) described in Table 1.

[Comparative Example 1-2]
Except for not using 30 wt% aqueous sodium bisulfite solution, was obtained in the same manner as in the method of Example 1-1 described comparative particulate water-absorbing agent (1-2). The resultant comparative particulate water absorbing agent properties of (1-2) described in Table 1.

[Comparative Example 1-3]
The comparative comparative particulate water-absorbing agent obtained in Example 1-2 (1-2) 100 parts by weight, (8% by weight aluminum oxide basis) aqueous solution of aluminum sulfate 0.9 parts by weight, 60 wt% sodium lactate solution 0.30 parts by weight, and the mixture 1.22 parts by weight of propylene glycol 0.02 parts by homogeneously mixed to obtain comparative particulate water absorbing agent precursor (1-3).

Then, compare the obtained particulate water absorbing agent precursor (1-3) was left in a 60 ° C. in a hot air drier for 30 minutes, by then, to pass through a JIS standard sieve 710 .mu.m, comparative particulate water-absorbing It was obtained agent (1-3). The resultant comparative particulate water absorbing agent properties of (1-3) described in Table 1.

[Comparative Example 1-4]
Example 1-1 except for changing the content of acrylic acid in the p- methoxyphenol according from 70ppm to 270ppm, the Example 1-1 Similarly to compare the surface-crosslinked water-absorbent resin powder obtained by the (1 -4) with respect to 100 parts by weight, the 0.166 parts by weight of 30 wt% aqueous sodium bisulfite was added uniformly mixed to obtain comparative particulate water absorbing agent precursor (1-4). Then, compare the obtained particulate water absorbing agent precursor (1-4) was left in a 60 ° C. in a hot air drier for 30 minutes, by then, to pass through a JIS standard sieve 710 .mu.m, comparative particulate water-absorbing It was obtained agent (1-4). The resultant comparative particulate water absorbing agent properties of (1-4) described in Table 1.

[Comparative Example 1-5]
Show more comparative examples of the chelating agent with reference to Patent Documents 29 and their Examples 4 and 5. That is, 1 wt% diethylenetriamine pentaacetic acid trisodium (abbreviation: DTPA · 3Na) the amount of the aqueous solution to 25.8 parts by weight and 0.22 parts by weight, the amount of deionized water from 33.6 parts by weight 8. 0 change in weight, except that further change the amount of 30 wt% aqueous sodium bisulfite solution to 3.33 parts by weight 1.66 parts by weight, the procedure of example 1-1, a chelating agent 6000ppm and inorganic reducing agents comparative particulate water-absorbing agent containing 1.0 wt% was obtained (1-5). The water content of the resultant comparative particulate water-absorbing agent (1-5) was 1.9 wt%. The resultant comparative particulate water absorbing agent properties of (1-5) described in Table 1.

[Example 1-10]
Adjusting acrylic acid in Example 1-7, except for changing in Example 1-9 adjusting acrylic acid described (1-9), the particulate water-absorbing agent by the same manner as in Example 1-7 (1 -10) was obtained. Obtained particulate water absorbing agent properties of (1-10) are listed in Table 1.

[Example 1-11]
Adjusting acrylic acid in Example 1-7 described, was changed to Example 1-8 adjusting acrylic acid described (1-8), the particulate water-absorbing agent by the same manner as in Example 1-7 ( 1-11) was obtained. Obtained particulate water absorbing agent properties of (1-11) are listed in Table 1.

[Example 1-12]
31 wt% ethylenediaminetetra (methylene phosphonic acid) pentasodium (abbreviation: EDTMPA · 5Na) was changed to 0.07 parts by weight amount of 0.03 parts by weight of an aqueous solution, in the same manner as in Example 1-11 It was obtained particulate water absorbing agent (1-12) by. Obtained particulate water absorbing agent properties of (1-12) are listed in Table 1.

[Example 1-13]
The deterioration rate obtained as a result of performing the weathering test for Examples 1-1 wherein the particulate water-absorbing agent (1-1) described in Table 2.

[Comparative Example 1-6]
Instead the content of examples 1-1 according p- methoxyphenol in acrylic acid was adjusted to 70 ppm, the p- methoxyphenol obtained in Example 1-8 in purified acrylic acid (1-8) of the ND p- methoxyphenol except for using 1ppm comparable acrylate obtained by adding (1-6) to performs similarly polymerizing method described in example 1-1, comparative particulate water-absorbing agent (1 -6) was obtained. The resultant comparative particulate water-absorbing agent (1-6) p-methoxyphenol was ND (less than 1 ppm). The resultant comparative particulate water-absorbing agent The results of the weathering test using a (1-6) described in Table 2.

[Example 1-14]
Particulate water-absorbing agent (1-1), (1-8), describes the remaining p- methoxyphenol, remaining chelating agent, a result of measuring the remaining sodium bisulfite in Table 3 (1-9).

[Comparative Example 1-7]
Comparative particulate water-absorbing agent (1-4) are described in Table 3 remaining p- methoxyphenol, remaining chelating agent, a result of measuring the remaining sodium bisulfite (1-5).

Figure JPOXMLDOC01-appb-T000013

Figure JPOXMLDOC01-appb-T000014

Figure JPOXMLDOC01-appb-T000015

[Comparative Example 1-8]
As described above, Patent Document 17 (EP 1645596) do not disclose water-insoluble inorganic fine particles, the specific amount of p- methoxyphenol, certain moisture content (3-15 wt%). Also JP 17 as an organic antioxidant discloses such (such as butyl) alkyl hydroxy anisole (paragraph [0019] Example 6). Therefore, in order to show the significance of the present invention, according to Patent Documents 17 and Example 6 of its corresponding Japanese Patent Registration No. 3940103 publication, thereby obtaining a comparative particulate water absorbing agent (1-8).

Specifically, the polyethylene container having a capacity of 2L, 100 parts by weight of the water-absorbent resin obtained in Production Example of the registered patent publications, 3 parts by weight of sodium nitrite, hydroxyethylene diamine triacetic acid trisodium (particle diameter 106μm or less of the particles the proportion of 89% by weight of one) 1.5 parts by weight were charged butylhydroxyanisole 1 part by weight of the disclosed in Patent Document 17, and mixed for 1 hour in a mixer equipped with a stirring blade, comparative particulate water-absorbing agent ( 1-8) was obtained.

Obtained comparative particulate water-absorbing agent (1-8) was 0.9 wt% aqueous sodium chloride solution to 1.0 g (aka; saline) 19.0 g was added and allowed to swell to 20 times. Then placed bulging moistened allowed comparative particulate water absorbing agent (1-8) in the lid plastic container having a capacity of 120 ml, by standing for 3 hours in an oven at ambient temperature 37 ° C., swelling comparative particulate water-absorbing agent ( 1-8) was obtained. 20 times swollen gel of the comparative particulate water-absorbing agent obtained according to the Patent Document 17 (1-8) was colored yellow.

Subsequently, color tone of 20 times swollen gel of the comparative particulate water-absorbing agent (1-8) (initial color tone) was measured using a Hunter Lab Inc. LabScanXE. The measurement results are shown in Table 4.

Incidentally, color measurement was carried out by filling the test substance white propylene steel container having a diameter of 5.0 cm, height 1.2 cm. Further, the color tone of white propylene container made of the foregoing as blank, L value: 54.73, a value: 0.16, b values ​​were: -0.50.

Further, the powder of Patent Document 17 Comparative particulate water-absorbing agent according to (butylhydroxyanisole 1 part by weight) (1-8), in the same manner as in Example 1-1 to 1-12 and Table 2 for 7 days colored accelerated test (70 ℃, RH65%) were subjected to, the particulate water absorbing agent of the present invention for maintaining a substantially white, comparative particulate water-absorbing agent (1-8) was colored orange. It was measured tone (time tone) as well. The measurement results are shown in Table 5. Further, comparative particulate water-absorbing agent after coloring acceleration test 7 days (1-8) had emanated odor.

[Example 1-15]
For particulate water absorbing agent obtained in Example 1-1 (1-1), and in the same operation as in Comparative Example 1-8, 20 times swollen gel of the particulate water-absorbing agent (1-1) (1 -15) was obtained. The resulting swollen particulate water-absorbing agent (1-15) is 20 times swollen gel in Patent Document 17 above comparative particulate water-absorbing agent according to (butylhydroxyanisole 1 part by weight) (1-8) is turned yellow whereas, 20 times swollen gel of the particulate water-absorbing agent (1-1)) (1-15) remained clear hydrogel.

The color tone of 20 times swollen gel of particulate water absorbing agent (1-1) (1-15) was measured in the same manner as in Comparative Example 1-8. The measurement results are shown in Table 4.

[Example 1-16]
For water content 1.8 wt% of the particulate water-absorbing agent obtained in Example 1-1 (1-1), was measured water absorption rate (FSR), 0.23 [g / g / sec] met It was. To investigate the effect of moisture content, the particulate water absorbing agent (1-1) in the addition of 10% by weight of water, dried under reduced pressure for a further 80 ° C., water content 3.9% by weight of the particulate water-absorbing agent ( 1-15) was obtained.

Water absorption speed of the resultant water content of 3.9 wt% of the particulate water-absorbing agent (1-15) (FSR) is 0.27 [g / g / sec], increase the moisture content, particularly water content 3 with to 15 wt%, it can be seen that the improved water absorption rate of the water-absorbing agent. Hereinafter, a method of manufacturing a water absorbing agent to water content 3 to 15% by weight, described in Examples 3-1 to 3-13.

Figure JPOXMLDOC01-appb-T000016

Figure JPOXMLDOC01-appb-T000017

(Summary)
Above Examples 1-1 to 1-16 and Tables 1-5 is a process for producing 1 that of the particulate water-absorbing agent of the present invention, the methoxyphenol a 10 ~ 200 ppm containing to acrylic acid (salt) comprising a polymerization step of an aqueous monomer solution containing as a main component, a drying step of the hydrogel crosslinked polymer obtained by the polymerization, and the surface-crosslinking step, the chelating agent 0.001-0.5 wt% of the added steps a method for producing a particulate water absorbing agent after the surface cross-linking step, and carrying out the addition process of the inorganic reducing agent, a method for producing a particulate water absorbing agent.

As in the above Examples 1-1 to 1-13, the water absorbing agent according to the present invention is excellent in temporal color tone and initial color tone, after the surface crosslinking step, by performing the step of adding an inorganic reducing agent, 3 wt% even at low moisture content of less than 3 wt% of low moisture content and high temperature surface crosslinking (150 ~ 250 ℃) below, the resultant water-absorbing agent had no unpleasant odor. From this odor rather odor simply use the raw material (in particular inorganic reducing agent), a complex odor in the manufacturing process water absorbing resin and an inorganic reducing agent, the occurrence can not be expected, new according the present invention found the problem, it was resolved to above. In Comparative Examples 1-1 to 1-3 containing only one of the chelating agents and inorganic reducing agents, methoxyphenol amount with time color was bad even within the range of 5 - 60 ppm. Comparative Example methoxyphenol amount is outside the range of 5 ~ 60 ppm 1-4 (82 ppm in the water-absorbing agent), Comparative Example 1-6 in (at 1ppm with acrylic acid, ND in the obtained water-absorbing agent) over time tones bad, or poor weather resistance (see after the accelerated test of Table 2 solubles). Furthermore, the particular moisture content of Patent Document 29 present invention (3-15 wt%) is let alone specific amount of the compound containing a phosphorus atom or a sulfur based reducing agent (0.001 to 0.5 wt%, 0 .001 not disclose to 0.1 wt%), example 5, 1-hydroxyethylidene-1,1 addition of diphosphonic acid 1.0% by weight of the Patent Document 29, in example 4 also 1-hydroxyethylidene- It discloses the use of 1,1-diphosphonic acid total 2.0 wt% but, as shown in Comparative example 1-5, an example of using a chelating agent in excess of such 0.5% by weight of the water absorbing agent obtained rather it found that adversely affect the coloring, and solve it in water content control to a specific range. Furthermore, as shown in Examples 1-16, a specific amount of water in the water-absorbing agent is preferably from improvement in absorption rate.

That is, as shown in the above examples, the novel water-absorbing agent of the present invention is a particulate water-absorbing agent as a main component of polyacrylic acid (salt) -based water absorbent resin, a chelating agent, and an inorganic reducing agent It comprises a content of the chelating agent is 0.001 to 0.5 wt%, the content of methoxyphenol is 5 ~ 60 ppm. The novel water-absorbing agent of the present invention shown in the above embodiment, preferably, the absorption capacity without load (CRC) is 25 [g / g] or more, absorbency against pressure (AAP4.83kPa) is 20 [g / g] or more, it is the saline flow conductivity (SFC) is 30 [× 10 -7 · cm 3 · s · g -1] or more. Although not listed in the table, the water-absorbing agent is in the range of FSR 0.25 before and after (± 0.02) [g / g / sec], also residual monomer also 400ppm or less, the weight average particle diameter ( D50) it was also about 360 ~ 380μm. Further, the water-absorbing agent preferably further comprises an α- hydroxy carboxylic acid compound. Moreover, further comprising a polyvalent metal salt and / or a cationic polymer. These water absorbing agent initially and over time coloring without any white in liquid permeability (SFC) and the absorbency against pressure (AAP) for even higher, high liquid diffusion and low return be used in low pulp high concentration diapers the amount (Re-wet) of, without coloring problems derived from water-absorbing agent, provide good disposable diapers.

[Example 2-1]
In a kneader equipped with two sigma-type blades, sodium acrylate was neutralized iron in NaOH containing 0.7 ppm, of acrylic acid and water, the concentration of the monomer is 38 wt%, neutralization ratio of 75 mol% the aqueous monomer solution was prepared of. Incidentally, acrylic acid, was used to adjust the content of p- methoxyphenol to 70 ppm. This aqueous monomer solution, as an internal cross-linking agent, polyethylene glycol diacrylate (average ethylene glycol unit: 9) were dissolved at a 0.045 mole% (vs. monomer).

Then, blowing nitrogen gas into the aqueous monomer solution, while reducing the dissolved oxygen of the monomer in the aqueous solution, the whole reaction vessel was replaced with nitrogen. Subsequently, after adjusting the temperature of the aqueous monomer solution to 22 ° C. while rotating the two sigma type blades, 0.12 sodium persulfate as a polymerization initiator [g / mol] (to monomer), L-ascorbic acid was added in an amount of 0.005 [g / mol] (relative to the monomer).

Since the monomer solution became cloudy immediately polymerization has started, and stop the rotation of the blades. Obtained after the polymerization temperature reached 50 ° C., the blade was rotated again, and stirring continued under polymerization in a kneader, hydrogel crosslinked polymer having a weight average particle size of about 2mm after about 50 minutes (2-1) It was.

The obtained hydrogel crosslinked polymer (2-1), and dried at about 60 minutes a hot air dryer at 170 ° C.. The dried product was pulverized with a roll mill pulverizer, mesh opening 850μm and 150μm sieve Ide and classified (sieve of vertical removal), water content 3 wt%, the weight average particle diameter of 370μm water-absorbent resin particles (2 1) was obtained. The resulting water-absorbent resin particles (2-1), the particle diameter of particles larger than 850μm are not substantially contain and fines of less than 150μm were contained 2 wt%.

The obtained water-absorbent resin particles (2-1) 100 parts by weight, 0.025 parts by weight of ethylene glycol diglycidyl ether, 0.3 part by weight of 1,4-butanediol, propylene glycol 0.5 part by weight, obtained were uniformly mixed surface crosslinking agent consisting of a mixture of deionized water 3.0 parts by weight, by the mixture is heated for 40 minutes at 208 ° C., the surface cross-linked water absorbent resin powder (2-1) It was.

The resulting surface cross-linked water-absorbing resin powder (2-1) was cooled, the surface cross-linked water absorbent resin powder (2-1) with respect to 100 parts by weight, 30 wt% aqueous sodium bisulfite 1.66 weight parts and adding and mixing 45 wt% diethylenetriamine pentaacetic sodium acetate aqueous solution 0.44 parts by weight, to give a particulate water absorbing agent precursor (2-1). Then, the resultant particulate water absorbing agent precursor (2-1) was left in a 60 ° C. in a hot air drier for 30 minutes, then allowed to pass through a JIS standard sieve 810Myuemu. Furthermore, with respect to surface cross-linked water-absorbing resin powder (2-1) 100 parts by weight of silica as a white water-insoluble inorganic fine particles (trade name: Aerosil 200CF-5, manufactured by Nippon Aerosil Co., Ltd.) and 0.3 parts by weight by adding and mixing, to give a particulate water absorbing agent (2-1). Obtained particulate water absorbing agent properties of (2-1) described in Table 6. Incidentally, silica L, a, b are respectively 93.6, -0.8, a -3.6, was a white than the water-absorbing resin.

[Example 2-2]
In Example 2-1, except that the amount of silica to surface-crosslinked water-absorbing resin powder (2-1) 100 parts by weight was changed to 1.0 parts by weight 0.3 parts by weight, Example 2 1 and was obtained particulate water absorbing agent (2-2) in a similar manner. Obtained particulate water absorbing agent properties of (2-2) described in Table 6.

[Example 2-3]
In Example 2-1, except that the amount of silica to surface-crosslinked water-absorbing resin powder (2-1) 100 parts by weight was changed to 0.5 parts by weight 0.3 parts by weight, Example 2 1 and was obtained particulate water absorbing agent (2-3) in a similar manner. Obtained particulate water absorbing agent properties of (2-3) described in Table 6.

[Example 2-4]
In Example 2-1, except that the amount of silica to surface-crosslinked water-absorbing resin powder (2-1) 100 parts by weight was changed to 0.05 part by weight to 0.3 parts by weight, Example 2 1 and was obtained particulate water absorbing agent (2-4) in a similar manner. Obtained particulate water absorbing agent properties of (2-4) described in Table 6.

[Example 2-5]
In Example 2-1, the surface cross-linked water absorbent resin powder (2-1) was changed to 0.022 parts by weight 0.44 parts by weight of the added amount of 45 wt% diethylenetriamine pentaacetic acid sodium aqueous solution for 100 parts by weight except, to obtain a particulate water absorbing agent in the same manner as in example 2-1 (2-5). Obtained particulate water absorbing agent properties of (2-5) described in Table 6.

[Example 2-6]
In Example 2-1, the surface cross-linked water absorbent resin powder (2-1) was changed to 2.2 parts by weight 0.44 parts by weight of the added amount of 45 wt% diethylenetriamine pentaacetic acid sodium aqueous solution for 100 parts by weight except, to obtain a particulate water absorbing agent in the same manner as in example 2-1 (2-6). Obtained particulate water absorbing agent properties of (2-6) described in Table 6.

[Example 2-7]
36.8 parts by weight of acrylic acid content was adjusted to 70ppm of p- methoxyphenol, 12.2 parts by weight 48 wt% sodium hydroxide aqueous solution, polyethylene glycol diacrylate (average ethylene oxide unit number: n = 9) 0. 08 parts by weight, 1 wt% diethylenetriamine pentaacetic acid trisodium (abbreviation: DTPA · 3Na) Preparation aqueous 0.42 parts by weight, and a monomer aqueous solution having a composition of deionized water 30.3 parts by weight (2-2) did.

Then, the monomer aqueous solution was adjusted to 40 ° C. The (2-2), was fed continuously to the polymerization process using a metering pump. Before introducing the belt polymerizer was continuously mixed 18.5 parts by weight 48 wt% aqueous solution of sodium hydroxide at line mixing. At this time, the heat of neutralization, the monomer temperature increased to 86 ° C.. Then, 4 wt% aqueous solution of sodium persulfate 1.66 parts by weight of continuous mixing at line mixing, resulting continuous mixture (2-2), on a plane belt having weirs at both ends, a thickness of about 7. It was supplied so as to 5mm. Continuously for 3 minutes polymerization to obtain water-containing gel-like crosslinked polymer (2-2).

It was then subdivided into approximately 1.5mm above hydrogel crosslinked polymer (2-2) a meat chopper with a pore diameter of 22 mm. The fragmented gel, loaded spread over the porous plate moving in a continuous ventilation band drier, and dried for 30 minutes at 185 ° C., to obtain dried polymer (2-2). After grinding the resulting dried polymer (2-2) in a roll mill, mesh opening 850μm and 150μm sieve Ide and classified (sieve of vertical removal), water content 3 wt%, the weight-average water absorption of the particle diameter 370μm to obtain resin particles (2-2). The resulting water-absorbent resin particles (2-2), the particle diameter of particles larger than 850μm are not substantially contain and fines of less than 150μm were contained 2 wt%.

The obtained water-absorbent resin particles (2-2) 100 parts by weight of 1,4-butanediol 0.3 parts by weight, 0.5 parts by weight of propylene glycol, and mixtures of deionized water 3.0 parts by weight after mixing the surface cross-linking agent comprising a liquid uniformly, by heating the mixture for 40 minutes at 208 ° C., to obtain a surface cross-linked water-absorbing resin powder (2-2).

The resulting surface cross-linked water-absorbing resin powder (2-2) was cooled, the surface cross-linked water absorbent resin powder (2-2) with respect to 100 parts by weight, 30 wt% aqueous sodium bisulfite 1.66 weight parts and adding and mixing 45 wt% diethylenetriamine pentaacetic sodium acetate aqueous solution 0.44 parts by weight, to give a particulate water absorbing agent precursor (2-2). Then, the resultant particulate water absorbing agent precursor (2-2) was left in a 60 ° C. in a hot air drier for 30 minutes, then allowed to pass through a JIS standard sieve 810Myuemu. Furthermore, with respect to surface cross-linked water-absorbing resin powder (2-2) 100 parts by weight of silica (trade name: Aerosil 200CF-5, manufactured by Nippon Aerosil Co., Ltd.) by admixing 0.3 part by weight, the particles give Jo water absorbing agent (2-7). Obtained particulate water absorbing agent properties of (2-7) described in Table 6.

[Example 2-8]
In Example 2-1, except that the addition amount of the surface cross-linked water absorbent resin powder (2-1) 30 wt% aqueous sodium bisulfite solution for 100 parts by weight was changed to 0.22 parts by weight 1.66 parts by weight It was obtained a particulate water absorbing agent in the same manner as in example 2-1 (2-8). Obtained particulate water absorbing agent properties of (2-8) described in Table 6.

[Example 2-9]
In Example 2-1, except for changing the addition amount of 30 wt% aqueous sodium bisulfite solution for surface crosslinking water-absorbing resin powder (2-1) 100 parts by weight 22 parts by weight 1.66 parts by weight, to obtain a particulate water absorbing agent (2-9) in the same manner as in example 2-1. Obtained particulate water absorbing agent properties of (2-9) described in Table 6.

[Example 2-10]
To the surface cross-linked water absorbent resin powder (2-1) 100 parts by weight in Example 2-1, further except that water was added 3 parts by weight, the particulate water in the same manner as in Example 2-1 It was obtained agent (2-10). Obtained particulate water absorbing agent properties of (2-10) are listed in Table 6.

[Example 2-11]
To the surface cross-linked water absorbent resin powder (2-1) 100 parts by weight in Example 2-1, further 1.8 parts 50 wt% aqueous solution of aluminum sulfate, 0.55 parts by weight of 60% sodium lactate aqueous solution, and except for adding a mixed solution of propylene glycol 0.05 parts by weight, to obtain a particulate water absorbing agent in the same manner as in example 2-1 (2-11). Obtained particulate water absorbing agent properties of (2-11) are listed in Table 6.

[Example 2-12]
In Example 2-1, a polyethylene glycol diacrylate (average ethylene glycol unit: 9) the amount of the 0.023 mol% to 0.035 mol% (relative to the monomer), the water-absorbing resin particles (2- the weight average particle diameter of 1) and classified as a 350 .mu.m, further was changed to 35 minutes to heat treatment conditions in the surface crosslinking step in 40 minutes 200 ° C. at 208 ° C., as in example 2-1 It was obtained particulate water absorbing agent (2-12) in a similar manner. Obtained particulate water absorbing agent properties of (2-12) are listed in Table 6.

[Comparative Example 2-1]
Except that was not performed addition of 45 wt% diethylenetriamine pentaacetic sodium acetate aqueous solution 0.22 parts by weight, was obtained in the same manner as in the method of Example 2-1 described comparative particulate water-absorbing agent (2-1). The resultant comparative particulate water absorbing agent properties of (2-1) described in Table 6.

[Comparative Example 2-2]
Except for changing to what was not performed addition of 30 wt% aqueous sodium bisulfite 1.66 parts by weight, the amount of silica to 0.5 part by weight from 0.3 parts by weight, in Example 2-1 described to give way and the same way a comparative particulate water absorbing agent (2-2). The resultant comparative particulate water absorbing agent properties of (2-2) described in Table 6.

[Comparative Example 2-3]
Silica (trade name: Aerosil 200CF-5, manufactured by Nippon Aerosil Co., Ltd.) except that was not carried out the addition of 0.5 part by weight, in the same manner as in Comparative Example 2-2 Comparative particulate water absorbing agent (2-3) It was obtained. The resultant comparative particulate water absorbing agent properties of (2-3) described in Table 6.

[Example 2-13]
In Example 2-1, the silica (trade name: Aerosil 200CF-5, manufactured by Nippon Aerosil Co., Ltd.) except for not adding 0.3 part by weight were performed in the same manner as in Example 2-1, the particulate water-absorbing agent ( 2-13) was obtained. Obtained particulate water absorbing agent properties of (2-13) are listed in Table 6.

It was improved to AAP Example 2-1 (28 [g / g]) from 31 [g / g] (Example 2-13), on the contrary, Vortex (absorption rate) of 50 seconds (Example 2 decreased from 1) to 64 seconds (example 2-13), further, urine resistance (deterioration component 1000 times) becomes "Yes flow (example 2-13)". No disclosure in Patent Document 17, it can be seen the water-insoluble inorganic fine particles is important to the urine resistance and water absorption rate (Vortex).

[Example 2-14]
In Example 2-1, except for not adding p- methoxyphenol in acrylic acid at the time of polymerization it was performed in the same manner as in Example 2-1 to provide a particulate water absorbing agent (2-14). Obtained particulate water absorbing agent properties of (2-14) are listed in Table 6. EXAMPLE 2-1 against deterioration rate 17.6% of (acrylic acid p- methoxyphenol 70 ppm), Example 2-1 (in 0ppm acrylic acid, 0ppm in the water-absorbing agent) In the deterioration rate 27. 3%, as in Table 2, when the p- methoxyphenol does not meet the present application, weather resistance is lowered. Incidentally, The results are shown in Table 7. No disclosed in, Patent Document 17, it can be seen traces of p- methoxyphenol is important weather resistance.

Figure JPOXMLDOC01-appb-T000018

Figure JPOXMLDOC01-appb-T000019

(Summary)
Examples 2-1 to 2-14 and Tables 6-7 is a process for producing 2 that of the particulate water-absorbing agent of the present invention, the polymerization process of the monomer aqueous solution containing as a main component an acrylic acid (salt) When the drying step of the resultant crosslinked hydrogel polymer by polymerization, and a surface cross-linking step, a method for producing a particulate water absorbing agent mainly containing polyacrylic acid (salt) -based water absorbent resin further comprising a step of adding a chelating agent 0.001 to 0.5% by weight of the addition step and the inorganic reducing agent, monomer contains 10 ~ 200 ppm of methoxyphenol in to acrylic acid in terms of, (a) water further comprising the step of adding the insoluble inorganic fine particles, a method for producing a particulate water absorbing agent (second manufacturing method).

As in the above Examples 2-1 to 2-12, the water absorbing agent according to the present invention, coloring over time preventing property, urine resistance, excellent absorption rate. In Comparative Examples 2-1 to 2-3 with the addition only one of the chelating agents and inorganic reducing agents, aging tone is poor. Only one of the water-insoluble inorganic fine particles and the chelating agent was added, Comparative Example 2-1 and 2-3, poor urine resistance. In Comparative Example 2-3 not containing water-insoluble inorganic fine particles (silica) is slower absorption rate. Regard water content, a water content of 4.1 wt% in amount of dust 6mg of Example 2-10, the dust amount 21mg in moisture content 2.0% by weight of Examples 2-1, the water of Comparative Example 2-3 compared to the amount of dust 40mg of at the rate 1.7%, dramatically dust amount is reduced in water content 3.0% by weight or more.

Above, the novel water-absorbing agent of the present invention shown in the above embodiment (the second water-absorbing agent) is a particulate water-absorbing agent as a main component of polyacrylic acid (salt) -based water absorbent resin, chelating agent When, and a inorganic reducing agent, the content of the chelating agent is 0.001 to 0.5 wt%, containing water-insoluble inorganic fine particles. The novel water-absorbing agent of such present invention of the above embodiment, preferably, the absorption capacity without load (CRC) is 25 [g / g] or more, absorbency against pressure (AAP2.0kPa) is 25 [g / g] or more, Vortex (absorption rate) is less than 60 seconds. Although the water-absorbing agent containing the methoxyphenol (especially p- methoxyphenol) is arbitrary, the (1) and novel water-absorbing agent (first water-absorbing agent) as well as of 5 ~ 60 ppm scope of the present invention ( in the above embodiment are approximately 10ppm longitudinal), weather resistance and coloring is further improved. The novel water-absorbing agent of the present invention (second water-absorbing agent) can be a water content similar to the first water-absorbing agent is less than 3 wt%, but preferably satisfies (3), the range of 3 to 15 wt% is there. These water absorbing agent initially and over time colored without white high absorption rate (Vortex) also for high absorption capacity under a load (AAP), high liquid diffusion and less used in low pulp high concentration diapers return amount (Re-wet) of, without coloring problems from the water-absorbing agent, provide good disposable diapers.

[Production Example 3-1]
Commercially available acrylic acid (Wako Pure Chemical, special grade reagent; p-methoxyphenol 200ppm containing) obtained in gas-phase catalytic oxidation and then fed into the bottom of the high boiling impurities separation column having Museki perforated plate 50 stages, distilling the reflux ratio as 1, by further re-distillation to obtain an impurity of less than 99% of acrylic acid and traces (mainly water) consisting of purified acrylic acid (3-1). p- methoxyphenol content in the purified acrylic acid (3-1) was ND (less than 1 ppm). ND refers to content for purified acrylic acid (3-1) means that less than 1 ppm.

To obtain purified acrylic acid (3-1) in p- methoxyphenol adjusting acrylic acid by the addition of 70 ppm (3-1).

[Comparative Example 3-1]
Sigma type blades in a reactor formed by attaching a lid to a jacketed stainless twin-arm kneader of 10 liters in 2 inborn, adjusting acrylic acid obtained in Production Example 3-1 (3-1) 408 .4G, the adjustment acrylic acid obtained in production example 3-1 (3-1) was diluted with pure water, neutralized with aqueous sodium hydroxide (iron content 0.7 ppm (vs. NaOH solids)) obtained in 37 wt% sodium acrylate aqueous solution 4321.9G, pure water 724.2G, and was a reaction solution of polyethylene glycol diacrylate (molecular weight 523) 4.74 g.

Then the reaction solution under a nitrogen gas atmosphere, was degassed for 30 minutes. Subsequently, when the reaction solution was added with stirring 10% by weight aqueous solution of sodium persulfate 29.5g and 0.1 wt% L-ascorbic acid solution 11.3g, the polymerization was initiated after approximately 25 seconds. Then, while grinding the generated gel, subjected to polymerization at 25 ° C. or higher 95 ° C. or less, the polymerization was taken out after 30 minutes from the start crosslinked hydrogel polymer (C1-a). The obtained hydrogel crosslinked polymer particle has a diameter subdivided into more than about 5 mm. Incidentally, the solid content of the hydrogel crosslinked polymer (C1-a) (180 ℃, calculated from loss on drying for 3 hours) was 37.5 wt%.

Spread hydrogel crosslinked polymer (C1-a) on a 50-mesh metal net and dried with hot air for 65 minutes at 170 ° C., the dried product was pulverized with a roll mill, further classified with a mesh opening JIS standard sieve of 850μm by filled out to yield a weight-average particle diameter (D50) 371μm, irregularly pulverized shaped water absorbent resin particles of the logarithmic standard deviation ([sigma] [zeta]) 0.34 of particle size distribution (C1-c). Centrifuge retention capacity of the water-absorbing resin particles (C1-c) (CRC) is 46 (g / g), water-soluble component was 18 wt%.

The resulting water-absorbent resin particles (C1-c) 0.027 parts by weight of ethylene glycol diglycidyl ether 100 parts by weight, 0.3 part by weight of 1,4-butanediol, 1,2-propylene glycol 0.5 part by weight , and after mixing the surface cross-linking agent uniformly made from a mixture of pure water 2.8 parts by weight, the mixture was heated for 60 minutes at 180 ° C.. Thereafter, beating resulting particles to pass through a JIS standard sieve having a mesh opening 850 .mu.m, the surface was obtained by the comparative particulate water absorbing agent (3-1) crosslinking. Comparative particulate water absorbing agent analysis results of (3-1) described in Table 8 and Table 9.

[Example 3-1]
By polymerizing in the same manner as in Comparative Example 3-1 was obtained hydrogel crosslinked polymer (1-a). While adding 0.375 wt% aqueous sodium bisulfite solution feed rate 30 [g / min], meat with resultant hydrogel polymer (1-a) the feed rate 600 [g / min] chopper (MEAT -CHOPPER TYPE: 12VR-400KSOX Iizuka industry Co., die hole diameter: 11 mm, hole number: 10, reground die thickness 8 mm), hydrogel crosslinked polymer (1-a) to a uniform aqueous solution of sodium hydrogensulfite by mixing (500 ppm with a reducing agent) to give comminuted water-containing gel-like crosslinked polymer (1-b).

Spread the comminuted water-containing gel-like crosslinked polymer (1-b) on a 50-mesh metal net and a 65 minute hot air drying at 170 ° C., the dried product was pulverized with a roll mill, further mesh opening 850μm of classified with a JIS standard sieve, by filled out to yield a weight-average particle diameter (D50) 371μm, irregularly pulverized shaped water absorbent resin particles of the logarithmic standard deviation ([sigma] [zeta]) 0.34 of particle size distribution (1-c) . Centrifuge retention capacity of the water-absorbent resin particles (1-c) (CRC) is 46 (g / g), water-soluble component was 18 wt%.

The resulting water-absorbent resin particles (1-c) 0.020 parts by weight of ethylene glycol diglycidyl ether 100 parts by weight, 1.5 parts by weight of 1,2-propylene glycol, a mixed solution of pure water 3.5 parts by weight after uniformly mixing the surface cross-linking agent comprising, homogeneously spread mixture in a stainless steel vat, and sealing the entire vat made of polyethylene back, was heat treated at 100 ° C. 40 min. Thereafter, beating resulting particles to pass through a JIS standard sieve having a mesh opening 850 .mu.m, the surface was obtained water-absorbent resin particles to crosslink the (1-d).

The resulting water-absorbent resin particles (1-d) 0.5 wt% ethylenediaminetetra to 100 parts by weight (methylene phosphonic acid) pentasodium (abbreviation: EDTMPA · 5Na) aqueous solution were mixed 1.0 part by weight additives, particulate to obtain a water absorbing agent (3-1). The analytical results of the particulate water-absorbing agent (3-1) described in Table 8 and Table 9.

[Example 3-2]
Except for changing the feed rate of 0.375 wt% aqueous sodium bisulfite solution from 30 [g / min] to 12 [g / min] in the same manner as in Example 3-1, the particulate water-absorbing agent (3-2 ) was obtained. The analytical results of the particulate water-absorbing agent (3-2) described in Table 8 and Table 9.

[Example 3-3]
0.5 wt% ethylenediaminetetra (methylene phosphonic acid) pentasodium (abbreviation: EDTMPA · 5Na) aqueous solution of 2.5 wt %% ethylenediaminetetra (methylenephosphonic acid) pentasodium (abbreviation: EDTMPA · 5Na) was changed to an aqueous solution, the addition amount, except that the 2.0 parts by weight per 100 parts by weight of the water-absorbent resin particles in the same manner as in example 3-1, to obtain a water-absorbent resin particles (3-e). The resulting water-absorbent resin particles (3-e) silica gel To 100 parts by weight (trade name: Aerosil 200, Nippon Aerosil Co., Ltd.) by mixing 0.3 part by weight additives, particulate water-absorbing agent (3-3) It was obtained. The analytical results of the particulate water-absorbing agent (3-3) described in Table 8 and Table 9.

[Example 3-4]
0.5 wt% ethylenediaminetetra (methylene phosphonic acid) pentasodium (abbreviation: EDTMPA · 5Na) aqueous solution of 2.5 wt% ethylenediaminetetra (methylene phosphonic acid) pentasodium (abbreviation: EDTMPA · 5Na) was changed to an aqueous solution, the the doping concentrations was except that the 4.0 parts by weight per 100 parts by weight of the water-absorbent resin particles in the same manner as in example 3-1, the particulate water absorbing agent (3-4). The analytical results of the particulate water-absorbing agent (3-4) described in Table 8 and Table 9.

[Example 3-5]
The concentration of 0.375 wt% aqueous solution of sodium hydrogen sulfite was changed to 0.1 wt%, and change the feed rate from 30 [g / min] to 22.5 [g / min], 0.5 wt% ethylenediamine tetra (methylene phosphonic acid) pentasodium (abbreviation: EDTMPA · 5Na) aqueous solution of 2.5 parts by weight ethylene diamine tetra (methylene phosphonic acid) pentasodium (abbreviation: EDTMPA · 5Na) was changed to an aqueous solution, the amount added, the water-absorbing except that the 2.0 parts by weight relative to the resin particles 100 parts by weight in the same manner as in example 3-1, to give a particulate water absorbing agent (3-5). The analytical results of the particulate water-absorbing agent (3-5) described in Table 8 and Table 9.

[Example 3-6]
The feed rate of 0.375 wt% aqueous sodium bisulfite was changed from 30 [g / min] to 60 [g / min], 0.5 wt% ethylenediaminetetra (methylene phosphonic acid) pentasodium (abbreviation: EDTMPA · 5Na ) the amount of the aqueous solution, except for changing to 4.0 parts by weight per 100 parts by weight of the water-absorbent resin particles in the same manner as in example 3-1, to give a particulate water absorbing agent (3-6) It was. The analytical results of the particulate water-absorbing agent (3-6) described in Table 8 and Table 9.

[Example 3-7]
The concentration of 0.375 wt% aqueous solution of sodium hydrogen sulfite was changed to 3.75 wt%, except for changing the feed rate from 60 [g / min] to 30 [g / min] Example 3-6 It was obtained in the same manner particulate water absorbing agent (3-7). The analytical results of the particulate water-absorbing agent (3-7) described in Table 8 and Table 9.

[Example 3-8]
Except for changing the feed rate of 3.75 wt% aqueous sodium bisulfite solution from 30 [g / min] to 60 [g / min] in the same manner as in Example 3-7, the particulate water-absorbing agent (3-8 ) was obtained. The analytical results of the particulate water-absorbing agent (3-8) described in Table 8 and Table 9.

[Example 3-9]
To obtain an adjustment acrylic acid (3-2) by changing the amount added of Production Example 3-1 p-methoxyphenol for purifying acrylic acid according from 70ppm to 10 ppm.

Except for using adjustment acrylic acid (3-2) is a surface in the same manner as in Example 3-1 to obtain a water-absorbent resin particles crosslinked (9-d).

The resulting water-absorbent resin particles (9-d) to 100 parts by weight of 0.5 wt% ethylenediaminetetra (methylene phosphonic acid) pentasodium (abbreviation: EDTMPA · 5Na) aqueous solution were mixed 4.0 parts by weight additives, water-absorbing to obtain resin particles (9-e).

The resulting water-absorbent resin particles (9-e) silica gel To 100 parts by weight (trade name: Aerosil 200, Nippon Aerosil Co., Ltd.) by mixing 0.3 part by weight additives, particulate water-absorbing agent (3-9) It was obtained. The analytical results of the particulate water-absorbing agent (3-9) described in Table 8 and Table 9. Incidentally, the deterioration rate by the accelerated weather resistance test of the particulate water-absorbing agent (3-9) was 12%.

[Example 3-10]
To obtain an adjustment acrylic acid (3-3) by changing the amount added of Production Example 3-1 p-methoxyphenol for purifying acrylic acid according from 70ppm to 200 ppm.

Except for using adjustment acrylic acid (3-3) is a surface in the same manner as in Example 3-1 to obtain a water-absorbent resin particles crosslinked (10-d).

The resulting water-absorbent resin particles (10-d) 1 wt% ethylenediaminetetra (methylene phosphonic acid) in 100 parts by weight of pentasodium (abbreviation: EDTMPA · 5Na) aqueous solution were mixed 2.0 parts by weight additives, water-absorbing resin particles It was obtained (10-e).

The resulting water-absorbent resin particles (10-e) on silica gel to 100 parts by weight (trade name: Aerosil 200, Nippon Aerosil Co., Ltd.) by mixing 0.3 part by weight additives, particulate water-absorbing agent (3-10) It was obtained. The analytical results of the particulate water-absorbing agent (3-10) are listed in Table 8 and Table 9.

[Example 3-11]
The concentration of 0.375 wt% aqueous solution of sodium hydrogen sulfite was changed to 1 wt%, and change the feed rate of 30 [g / min] from 45 [g / min], 1 wt% ethylenediaminetetra (methylene phosphonic acid) 5 sodium (abbreviation: EDTMPA · 5Na) the amount of the aqueous solution, and 5.0 parts by weight per 100 parts by weight of the water-absorbent resin particles, further, 15 wt% sodium lactate aqueous solution with respect to 100 parts by weight of the water-absorbent resin particles except for adding 2 parts by weight in the same manner as in example 3-1, to give a particulate water absorbing agent (3-11). The analytical results of the particulate water-absorbing agent (3-11) are listed in Table 8 and Table 9.

[Example 3-12]
The concentration of 0.375 wt% aqueous solution of sodium hydrogen sulfite was changed to 1 wt%, and change the feed rate of 30 [g / min] from 45 [g / min], 1 wt% ethylenediaminetetra (methylene phosphonic acid) 5 sodium (abbreviation: EDTMPA · 5Na) the amount of the aqueous solution, and 5.0 parts by weight per 100 parts by weight of the water-absorbent resin particles, further, 25 wt% aqueous solution of aluminum sulfate per 100 parts by weight of the water-absorbent resin particles except for adding 2 parts by weight and 15% by weight sodium lactate solution 2 parts by weight in the same manner as in example 3-1, to give a particulate water absorbing agent (3-12). The analytical results of the particulate water-absorbing agent (3-12) are listed in Table 8 and Table 9.

[Example 3-13]
The water-absorbing resin particles (3-11) 100 parts by weight in Example 3-11, wherein the silica (trade name: Aerosil 200, Nippon Aerosil Co., Ltd.) by adding and mixing 0.5 part by weight, the particulate water-absorbing agent (3-13) was obtained. The analytical results of the particulate water-absorbing agent (3-13) are listed in Table 8 and Table 9.

[Comparative Example 3-2]
By polymerizing in the same manner as in Comparative Example 3-1 was obtained hydrogel crosslinked polymer (C2-a). While adding 0.1% aqueous sodium hydrogen sulfite solution feed rate 18 [g / min], meat with resultant hydrogel polymer (C2-a) feed rate 600 [g / min] Chopper (MEAT- CHOPPER TYPE: 12VR-400KSOX Iizuka industry Co., die hole diameter: 11 mm, hole number: 10, reground die thickness 8 mm), hydrogel crosslinked polymer (C2-a) the aqueous solution of sodium hydrogen sulfite uniformly in mixing by obtain comminuted water-containing gel-like crosslinked polymer (C2-b).

Spread the comminuted water-containing gel-like crosslinked polymer (C2-b) on a 50-mesh metal net and a 65 minute hot air drying at 170 ° C., the dried product was pulverized with a roll mill, further mesh opening 850μm of classified with a JIS standard sieve, by filled out to yield a weight-average particle diameter (D50) 371μm, irregularly pulverized shaped water absorbent resin particles of the logarithmic standard deviation ([sigma] [zeta]) 0.34 of particle size distribution (1-c) . Centrifuge retention capacity of the water-absorbing resin particles (C2-c) (CRC) is 46 (g / g), water-soluble component was 18 wt%.

The resulting water-absorbent resin particles (C2-c) 0.027 parts by weight of ethylene glycol diglycidyl ether 100 parts by weight, 0.3 part by weight of 1,4-butanediol, 1,2-propylene glycol 0.5 part by weight after mixing the surface cross-linking agent comprising a mixed liquid of pure water 2.8 parts by uniformly and the mixture was heated for 60 minutes at 180 ° C.. Thereafter, beating resulting particles to pass through a JIS standard sieve having a mesh opening 850 .mu.m, the surface was obtained by the comparative particulate water absorbing agent (3-2) crosslinking. Comparative particulate water absorbing agent analysis results of (3-2) described in Table 8 and Table 9.

[Comparative Example 3-3]
Comparative water absorbing resin particles (3-1) 0.05% by weight ethylenediaminetetraacetic to 100 parts by weight (methylene phosphonic acid) pentasodium (abbreviation: EDTMPA · 5Na) aqueous solution by mixing 1.0 part by weight additives, comparative particulate give Jo water absorbing agent (3-3). Comparative particulate water absorbing agent analysis results of (3-3) described in Table 8 and Table 9.

[Comparative Example 3-4]
The concentration of 0.375 wt% aqueous solution of sodium hydrogen sulfite was changed to 30 wt%, except for changing the feed rate from 60 [g / min] to 26.25 [g / min] similarly to Example 3-1 It performs operations to obtain fragmented compared hydrogel cross-linked polymer (C4-b).

Fragmented compared hydrogel cross-linked polymer (C4-b) spread on a 50-mesh metal net and dried with hot air for 65 minutes at 170 ° C., the dried product was pulverized with a roll mill, further mesh opening 850μm of classified with a JIS standard sieve, obtained by formulating a weight average particle diameter (D50) 371μm, irregular pulverized shaped comparative water absorbing resin particles of the logarithmic standard deviation ([sigma] [zeta]) 0.34 of particle size distribution (C4-c) It was. Centrifuge retention capacity of the comparative water absorbing resin particles (C4-c) (CRC) is 44 [g / g], water-soluble component was 16 wt%.

The resulting comparative water-absorbent resin particles (C4-c) 0.027 parts by weight of ethylene glycol diglycidyl ether 100 parts by weight, 0.3 part by weight of 1,4-butanediol, 1,2-propylene glycol 0.5 wt parts and were uniformly mixed surface crosslinking agent comprising a mixed liquid of pure water 2.8 parts by weight, the mixture was heated for 60 minutes at 180 ° C.. Thereafter, beating resulting particles to pass through a JIS standard sieve having a mesh opening 850 .mu.m, the surface was obtained by the comparative particulate water absorbing agent (3-4) crosslinking. Comparative particulate water absorbing agent analysis results of (3-4) described in Table 8 and Table 9.

[Comparative Example 3-5]
The concentration of the aqueous solution of sodium hydrogen sulfite was changed from 0.375 wt% to 30 wt%, and change the feed rate from 60 [g / min] to 45 [g / min], ethylene diamine tetra (methylene phosphonic acid) pentasodium (abbreviation: EDTMPA · 5Na) but without the addition of the aqueous solution in the same manner as in example 3-1, thereby obtaining a comparative particulate water absorbing agent (3-5).

[Comparative Example 3-6]
Production Example 3-1, for refining acrylic acid, p- methoxyphenol of adding an amount to obtain an adjustment acrylic acid (3-6) by changing from 70ppm to 1 ppm. Except for using adjustment acrylic acid (3-6) was obtained in Example 3-1, wherein a fragmented compared crosslinked hydrogel polymer in the same manner (C6-b).

Spread the fragmented compared hydrogel cross-linked polymer (C6-b) on a 50-mesh metal net and dried with hot air for 65 minutes at 170 ° C., the dried product was pulverized with a roll mill, open more eyes 850μm classified with a JIS standard sieve, by formulating a weight average particle diameter (D50) 371μm, irregular pulverized shaped comparative water absorbing resin particles of the logarithmic standard deviation ([sigma] [zeta]) 0.34 of particle size distribution (C6-c) Obtained. Centrifuge retention capacity of the comparative water absorbing resin particles (C6-c) (CRC) is 50 [g / g], water-soluble component was 24 wt%.

The obtained comparative water-absorbent resin particles (C6-c) 100 parts by weight, 0.027 parts by weight of ethylene glycol diglycidyl ether, 0.3 part by weight of 1,4-butanediol, 1,2-propylene glycol 0.5 parts, and after uniformly mixed surface crosslinking agent comprising a mixed liquid of pure water 2.8 parts by weight, the mixture was heated for 60 minutes at 180 ° C.. Thereafter, beating resulting particles to pass through a JIS standard sieve having a mesh opening 850 .mu.m, to obtain surface comparative water absorbing resin particles are crosslinked with (C6-d).

The obtained comparative water-absorbent resin particles (C6-d) 100 parts by weight, 5 wt% ethylenediaminetetra (methylene phosphonic acid) pentasodium (abbreviation: EDTMPA · 5Na) aqueous solution was mixed 0.4 parts by weight of additives, comparative water to obtain a sexual resin particles (C6-e).

The resulting comparative water-absorbent resin particles (6-e) silica gel To 100 parts by weight (trade name: Aerosil 200, Nippon Aerosil Co., Ltd.) by mixing 0.3 part by weight additives, comparative particulate water-absorbing agent (3 6) was obtained.

Comparison deterioration rate due to the accelerated weather resistance test of the particulate water-absorbing agent (3-6) is 24%, were weatherproof poor particulate water absorbing agent.

[Comparative Example 3-7]
Production Example 3-1 to obtain an adjustment acrylic acid (3-7) The amount added of p- methoxyphenol to purified acrylic acid by changing from 70ppm to 270 ppm. Except for using adjustment acrylic acid (3-7) got Similarly comparative particulate water-absorbing agent as in Comparative Example 3-6 (3-7).

[Comparative Example 3-8]
Relationship coloration water content below. That is, the embodiment except that changes the concentration of 0.375 wt% aqueous sodium bisulfite solution to 0.1 wt%, and further change its feed rate to 30 [g / min] from 22.5 [g / min] in the same manner as the example 3-1, to obtain surface water-absorbent resin particles to crosslink the (C8-d).

The resulting water-absorbing resin particles (C8-d) 100 parts by weight, 0.5 wt% ethylenediaminetetra (methylene phosphonic acid) pentasodium (abbreviation: EDTMPA · 5Na) aqueous solution were mixed 1.0 part by weight of additives, further by mixing deionized water is added 13 parts by weight, to obtain a moisture content 17% by weight of the comparative particulate water absorbing agent (3-8). Comparative particulate water absorbing agent analysis results of (3-8) described in Table 8 and Table 9. Incidentally, moisture content 17% by weight of the comparative particulate water-absorbing agent (3-8), as shown in Table, bad coloration than the water content of the water-absorbing agent of the present invention, tends to lump agglomerated particles , were those poor handling properties.

Figure JPOXMLDOC01-appb-T000020

Figure JPOXMLDOC01-appb-T000021

(Summary)
Above, the Examples 3-1 to 3-13 and Table 8, Table 9 relates to a manufacturing method thereof 3 of the particulate water-absorbing agent of the present invention, a single composed mainly of acrylic acid (salt) a polymerization step of mer solution, and drying the hydrogel crosslinked polymer obtained by polymerizing, and a surface cross-linking step, polyacrylic acid (salt) -based particulate water-absorbing agent to the water absorbent resin as a main component the method of manufacturing further comprises, 10 ~ 200 ppm containing monomer methoxy phenol with respect to acrylic acid in terms of the step of adding a chelating agent 0.001 to 0.5% by weight of the addition step and the inorganic reducing agent and, after the drying step, and the surface cross-linking step, controlling the water content of the polymer 3 to 15 wt%, more preferably, the inorganic reducing agent is added to the crosslinked hydrogel polymer before drying .

As in the above Examples 3-1 to 3-13, the particulate water-absorbing agent according to the present invention, the water content include a chelating agent and an inorganic reducing agent is 3 to 15 wt%, by such a configuration, time tone and excellent initial color tone, there was no unpleasant odor. Time tone Comparative Examples 3-1 to 3-3 containing only one of the chelating agents and inorganic reducing agent is poor. Further, Comparative Examples 3-4 and 3-5 is larger the amount added only reducing agent, odor was very strong particulate water absorbing agent. Comparative Example methoxyphenol amount is outside the range of 5 ~ 60 ppm in 10 ~ 200 ppm, or water-absorbing agent in the acrylic acid 3-6 (1 ppm in the acrylic acid), the deterioration rate is high weather resistance is poor particulate water-absorbing agent met. In Comparative Example 3-7 (270 ppm in acrylic acid) is worse initial color and odor occurs. Such odor, rather than reducing agent itself odor is believed to be odor-products from the surface cross-linking. Further, the water content, Comparative Example 3-8 poor coloring compared to water absorbing agent (water content 17 wt%) In the present invention, also, urine resistance (1000-fold degraded component) was also inferior. Further, the production method of the present invention is degraded, in terms of resolving the odor and coloration problems, residual monomer 400ppm or less, more 300ppm or less and low.

Above, the novel water-absorbing agent of the present invention, also shown in the above embodiment (a third water-absorbing agent) is a particulate water-absorbing agent as a main component of polyacrylic acid (salt) -based water absorbent resin, chelating agent When, and a inorganic reducing agent, the content of the chelating agent is 0.001 to 0.5 wt%, a water content of 3 to 15 wt%. The novel water-absorbing agent of the present invention, also shown in the above embodiment, preferably, the absorption capacity without load (CRC) is 25 [g / g] or more, absorbency against pressure (AAP2.0kPa) is 25 [g in / g] or more, the residual monomer is 500ppm or less. The water-absorbing agent containing the methoxyphenol (especially p- methoxyphenol) is arbitrary, but may be 0 ~ 200 ppm, preferably, the (1) and novel water-absorbing agent of the present invention (first water-absorbing agent) and is similar to the 5 ~ 60 ppm range (above examples 3-1 to about 10ppm longitudinal at 3-8), weather resistance and coloring is further improved. The novel water-absorbing agent of the present invention (third water-absorbing agent) is preferably that containing the (1) and novel water-absorbing agent (first water-absorbing agent) as well as water-insoluble inorganic fine particles of the present invention, urine resistance is further improved. The water-absorbing agent is also preferably further comprises a α- hydroxy carboxylic acid compound. Moreover, further comprising a polyvalent metal salt and / or a cationic polymer.

These water absorbing agent initially and white without aging the colored residual monomers is small and absorption rate (Vortex) is high, since high absorption capacity under a load (AAP), be used in low pulp high concentration diapers high liquid diffusion and small return amount (Re-wet) of, without coloring problems derived from water-absorbing agent, provide good disposable diapers.

Particulate water-absorbing agent obtained by the production method according to the present invention is suitable as disposable diapers, sanitary napkins, the sanitary materials such as incontinence pads.

Holes 48 collecting container 31 tank 32 glass tube 33 0.69 wt% saline 34 cock L-shaped tube 35 cock 40 container 41 cell 42 of stainless steel wire mesh 43 of stainless steel wire mesh 44 swollen gel 45 glass filter 46 piston 47 in the piston 49 upper tray balance 100 plastic supporting cylinder 101 stainless steel 400 mesh metal gauze 102 swollen gel 103 piston 104 load (weight)
105 Petri dish 106 glass filter 107 filter paper 108 0.90 wt% saline

Claims (39)

  1. A particulate water-absorbing agent as a main component of polyacrylic acid (salt) -based water absorbent resin,
    It includes a chelating agent, and an inorganic reducing agent,
    The content of the chelating agent is 0.001 to 0.5 wt%,
    Particulate water-absorbing agent and satisfies the following (1) any one or more of the requirements to (3).
    (1) the content of methoxyphenol is 5 ~ 60 ppm.
    (2) to contain the water-insoluble inorganic fine particles.
    (3) the water content is 3 to 15 wt%.
  2. (1) satisfy any two or more of the requirements to (3), the particulate water absorbing agent according to claim 1.
  3. Satisfying all of the above (1) to (3), the particulate water absorbing agent according to claim 1 or 2.
  4. The content of the chelating agent is 0.001 to 0.1 wt%, particulate water-absorbing agent according to any one of claims 1-3.
  5. The content of methoxyphenol is 5 ~ 60 ppm, the particulate water absorbing agent according to any one of claims 1-4.
  6. The chelating agent, an amino polycarboxylic acid, an organic polyvalent phosphoric acid, inorganic polyvalent phosphoric acid, and at least one compound selected from the group consisting of amino multivalent acid, any of claims 1 to 5, 1 particulate water-absorbing agent according to claim.
  7. The content of the inorganic reducing agent is from 0.01 to 1.0 wt%, particulate water-absorbing agent according to any one of claims 1-6.
  8. The inorganic reducing agent, a water-soluble inorganic compound having reducing inorganic elements, particulate water-absorbing agent according to any one of claims 1 to 7.
  9. The inorganic reducing agent, a water-soluble organic compound having a reducing inorganic elements, particulate water-absorbing agent according to any one of claims 1 to 7.
  10. The inorganic reducing agent, sulfite, bisulfite, a pyrosulfite, and at least one compound selected from the group consisting of Ani dithionite salt, according to any one of claims 1 to 9 particulate water-absorbing agent.
  11. They comprise water-insoluble inorganic fine particles,
    The content of the water-insoluble inorganic fine particles is 0.05 to 1.0 wt%, particulate water-absorbing agent according to any one of claims 1 to 10.
  12. The water-insoluble inorganic fine particles are silica, particulate water-absorbing agent according to claim 11.
  13. Further α- hydroxy carboxylic acid compounds include, particulate water-absorbing agent according to any one of claims 1 to 12.
  14. The α- hydroxy carboxylic acid compound, lactate (salt), and at least one compound selected from the group consisting of malic acid (salt), the particulate water absorbing agent according to claim 13.
  15. Further comprising a polyvalent metal salt and / or cationic polymer, the particulate water absorbing agent according to any one of claims 1 to 14.
  16. The iron content is 2ppm or less, the particulate water absorbing agent according to any one of claims 1 to 15.
  17. The polyacrylic acid (salt) -based water absorbent resin is granulated, the particulate water absorbing agent according to any one of claims 1 to 16.
  18. The following (4) to further satisfy one of the requirements of (7), the particulate water absorbing agent according to any one of claims 1 to 17.
    (4) absorbency against pressure (AAP4.83KPa) or absorbency against pressure (AAP2.0KPa) is 20 [g / g] or more (5) saline flow conductivity (SFC) is 30 [× 10 -7 · cm 3 · s · g -1] or (6) absorption rate (Vortex) is 60 seconds or less, or absorption rate (FSR) is 0.20 [g / g / sec] or higher (7) residual monomer 500ppm or less
  19. Absorption capacity without load (CRC) is 25 [g / g] or more, absorbency against pressure (AAP4.83kPa) in the 20 [g / g] or more, saline flow conductivity (SFC) is 30 [× 10 - is 7 · cm 3 · s · g -1] or more, the particulate water absorbing agent according to any one of claims 1 to 17.
  20. Absorption capacity without load (CRC) is 25 [g / g] or more, absorbency against pressure (AAP2.0KPa) in the 25 [g / g] or more, Vortex (absorption rate) is less than 60 seconds, claim particulate water-absorbing agent according to any one of 1-17.
  21. A polymerization step of the monomer aqueous solution containing as a main component an acrylic acid (salt), comprising the step of drying the hydrogel crosslinked polymer obtained by polymerization, and the surface-crosslinking step, polyacrylic acid (salt) -based water the rESIN a method for producing a particulate water absorbing agent as a main component,
    Further comprising a step of adding a chelating agent 0.001 to 0.5% by weight of the addition step and the inorganic reducing agent,
    Methoxyphenol of the monomer in the aqueous solution contains 10 ~ 200 ppm versus acrylic acid in terms of,
    The following (a) ~ and satisfies any one or more of the requirements of (c), the production method of the particulate water-absorbing agent as a main component of polyacrylic acid (salt) -based water absorbent resin.
    (A) further comprises a step of adding water-insoluble inorganic fine particles.
    (B) after the drying step, and the surface cross-linking step, controlling the water content of the polymer 3 to 15% by weight.
    (C) after the surface crosslinking step, by performing the addition of the inorganic reducing agent.
  22. Satisfy any two or more of the above requirements (a) ~ (c), The method according to claim 21.
  23. It satisfies the above (a) and (b), The method according to claim 21 or 22.
  24. Satisfying all of the above (a) ~ (c), The method according to claim 21 or 22.
  25. A polymerization step of the monomer aqueous solution containing as a main component an acrylic acid (salt) containing methoxyphenol 10 to 200 weight ppm, the drying step of the hydrogel crosslinked polymer obtained by the polymerization, and the surface-crosslinking step a method for producing a particulate water absorbing agent including a step of adding a chelating agent,
    Performing the addition process of the (c) inorganic reducing agent after the surface crosslinking step, the manufacturing method according to any one of claims 21-24.
  26. The methoxyphenol contained in aqueous monomer solution is p- methoxyphenol, containing pairs 10 ~ 120 ppm in acrylic acid conversion method according to any one of claims 21-25.
  27. The chelating agent is added to the aqueous monomer solution prior to polymerization or during polymerization method according to any one of claims 21 to 26.
  28. The inorganic reducing agent is added to the crosslinked hydrogel polymer before the drying method according to any one of claims 21-27.
  29. The inorganic reducing agent, a water-soluble inorganic compound having reducing inorganic elements, method according to any one of claims 21-28.
  30. The inorganic reducing agent, a water-soluble organic compound having a reducing inorganic elements, method according to any one of claims 21-29.
  31. The inorganic reducing agent is a compound having a reducing sulfur atom or a reducing phosphorus atom, the production method according to any one of claims 21-30.
  32. Further step of adding α- hydroxy carboxylic acid compound comprises The process of claim 21-31 any one.
  33. Polyvalent metal further comprising the step of adding salt and / or cationic polymer, the production method according to any one of claims 21-32.
  34. Further comprising a granulation step, the manufacturing method according to any one of claims 21-33.
  35. It is a process in which the polymerization step is carried out with an aqueous solution polymerization process according to any one of claims 21-34.
  36. After the polymerization or polymerization, further comprising a gel grain refining step for grain refining of hydrogel crosslinked polymer, the production method according to any one of claims 21-35.
  37. Adding an inorganic reducing agent at the same time as grain refining of the hydrogel crosslinked polymer, the production method according to claim 36.
  38. Is the surface the surface cross-linking agent is a polyvalent epoxy compound used in the crosslinking step, the manufacturing method according to any one of claims 21-37.
  39. Further comprising a neutralization step,
    Said polymerization step comprises 90 to 100 mol% of acrylic acid (salt) in the monomer, the monomer concentration 30 to 55% by weight of the aqueous monomer solution, a radical polymerization initiator 0.001 to 1 mole% by, and the maximum temperature of 130 ° C. or less, under the conditions the polymerization time is 0.5 minutes to 3 hours, a step of performing an aqueous solution polymerization or reversed-phase suspension polymerization,
    The neutralization step, Fe content is made in the base of 0 ~ 7 ppm,
    The drying step, and a particulate, the resultant crosslinked hydrogel polymer by polymerization, be a step of drying to a moisture content 20% by weight in the dry time of 10 to 120 minutes at a drying temperature 100 ~ 250 ° C. ,
    The surface cross-linking step, with respect to the water-absorbent resin powder 100 parts by weight after the drying step is completed, a mixture of surface crosslinking agent 0.001 to 10 parts by weight, performing 1 minute to 2 hours of heat treatment at 70 ~ 300 ° C. It is a process,
    Methoxy phenols content of the resultant particulate water-absorbing agent and 5 ~ 60 ppm, The method according to any one of claims 21-38.
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