JPWO2012133734A1 - Particulate water-absorbing agent and method for producing the same - Google Patents

Abstract

Provided is a particulate water-absorbing agent excellent in handleability with a powder, and a particulate water-absorbing agent suitable for multiple uses having high absorption performance in a wide range of salt concentrations. The particulate water-absorbing agent is mainly composed of a polyacrylic acid (salt) -based water-absorbing resin, and is water-insoluble or sparingly water-soluble selected from long-chain alkyl compounds, organic polysiloxanes, and organic polymer compounds. A particulate water-absorbing agent containing 0.001 to 5% by weight of a compound (however, when a long-chain alkyl compound corresponds to a metal soap, 0.001% by weight or more and less than 1.0% by weight), and an impact test The subsequent moisture absorption blocking rate is 0 to 30 wt%, and the 20 wt% saline vertical absorption index is 1.5 to 10.0 [g / g].

Description

  The present invention is not limited to sanitary materials, but is preferably used for various applications such as civil engineering / architecture waterproofing materials, warmers for warmers, waterproofing materials for cables, etc., especially for sheet-like or tape-like applications. The present invention relates to a particulate water-absorbing agent and a method for producing the same.

  Conventionally, water-absorbing resin has been used for materials such as paper diapers, sanitary napkins, incontinence pads, and other materials intended to prevent water leakage from the ground in tunnel construction and to prevent seawater from entering the sheath due to deterioration of the sheath of the submarine cable. It is widely used as a water-absorbing agent for materials that absorb body fluid such as blood.

  In these fields, water-absorbing resins have been proposed to be used in many forms such as powder, gel, sheet, film, and fiber. Powdered water-absorbing resins are often used as particulate water-absorbing agents. Has been. The particulate water-absorbing agent is used in various forms such as a greening water retaining material, a waste liquid solidifying material, a cement water reducing material, an aromatic gel, an interior gel, a hygroscopic material, and a sandbag as it is. On the other hand, sanitary materials such as paper diapers and sanitary napkins, water-stopping tapes, disposable warmers, etc., are combined with other base materials (for example, pulp and non-woven fabric) or fixed to form a tape, It is used after being processed into a sheet or the like.

  In recent years, with the increase in the amount of water-absorbing resin used, the rate at which the water-absorbing resin is processed into a tape or sheet (production per unit time) tends to increase dramatically. In addition to the water absorption performance (for example, water absorption capacity under no pressure, water absorption capacity under pressure, water absorption speed, liquid permeability, etc.) that has been required for absorbent resins, it relates to the handling of powder in the process of manufacturing absorbent articles. Improvement of performance (powder fluidity during drying and moisture absorption) is also very important.

Therefore, techniques for adding water-insoluble inorganic compounds such as amorphous silicon dioxide and kaolin to the water-absorbent resin in order to improve the powder fluidity of the water-absorbent resin are disclosed (Patent Documents 1 to 4). . However, these techniques have a problem that the water absorption performance of the water absorbing agent under pressure (for example, absorption at a load of 20 to 50 [g / cm ² ] in 0.9% by weight saline) is lowered. In addition, in order to improve powder flowability (Anti-Caking), a technique (Patent Documents 5 to 15) for coating a water-absorbent resin surface with polysiloxane, metal soap, a specific surfactant and the like has also been proposed. In the metal soap described in Patent Document 9, powder water absorption and water absorption performance under pressure (for example, absorption at a load of 20 to 50 [g / cm ² ] in 0.9% by weight saline solution) are maintained. It is known that agents can be provided.

  Conventionally, as a basic performance of a water-absorbent resin, it is desired that the water absorption capacity under pressure is high, and many parameter patents that define the water absorption capacity under pressure have been proposed. In measuring the water absorption magnification under pressure, the main use of the water-absorbent resin was paper diapers, so physiological saline (for example, about 0.9% by weight of saline) and artificial urine of various compositions were used as the liquid to be absorbed. It is used. And the water absorption magnification is mainly evaluated, and the basis weight (the amount of water-absorbing resin per unit area at the time of measurement) is also mainly evaluated by the basis weight of about a paper diaper. The measuring method of these water-absorbing resins is also defined by JIS (Japanese Industrial Standards) and EDANA (to be described later) (Non-Patent Documents 1 to 5), and the evaluation with physiological saline is also central.

  Furthermore, many parameters whose absorption behavior is defined by artificial urine and physiological saline are also known. For example, Patent Document 16 describes excellent absorption capacity under pressure, residual monomer, water-soluble component, and foam pore size. A water absorbent resin is disclosed.

  Patent Document 17 discloses an excellent water-absorbent resin having an absorption index under pressure (PAI) and a water-soluble content of 16% by weight or less. Patent Document 18 discloses a water-absorbing resin having a water-soluble component of 1% by weight or less per minute, and having a high water absorption ratio under pressure and a high absorption efficiency of the upper and lower gel layers. Patent Document 19 discloses a water-absorbing resin having excellent water absorption capacity and vertical absorption capacity under pressure and having a soluble content of 4% by weight or less. Patent Document 20 discloses a water-absorbing resin excellent in water absorption capacity without pressure, water absorption capacity under pressure, swelling pressure after 20 minutes, water-soluble content (3.5 to 10% by weight), and maximum rewet amount. ing.

  In Patent Document 21, the diffusion absorption index indicating the maximum amount of absorption per unit time is obtained by measuring the weight of physiological saline absorbed by the absorbent composition over 60 minutes with time. The absorbent composition which is 5 [g / g / min] or more is disclosed. Patent Document 22 discloses a water-absorbing agent having a diffusion absorption ratio of 25 [g / g] or more after 60 minutes from the start of absorption, and having a water-soluble content of more than 0 and 7% by weight or less. . Patent Document 23 discloses a water-absorbing resin excellent in three of absorption capacity, gel strength, water-soluble content, and water absorption speed. Patent Document 24 discloses a water-absorbent resin having a small water-soluble content having a water absorption capacity of 20 [g / g] or more under pressure, which is obtained by polymerizing unneutralized acrylic acid and then neutralizing. .

Patent Document 25 discloses a water absorbent resin having a transport value (TW) of at least 15000 cm ³ s. Patent Document 26 discloses a water-absorbent resin that defines vertical absorption of at least 12 [g / g]. Patent Document 27 discloses a water-absorbent resin having a CAUL (Column Absorbency Under Load) of about 10 [g / g] or more.

  In Patent Document 11, a ratio between a time (t1) until the swelling volume reaches 5 ml and a time (t2) until the swelling volume reaches 40 ml by mixing a hydrophobic substance into the monomer or gel ( An absorptive resin in which t2 / t1) is 5 to 20 is disclosed.

  However, although these non-patent documents 1 to 5 and patent documents 11 and 16 to 27, etc., a lot of water absorption performance is defined by parameters, in particular, although the absorption rate under pressure in physiological saline or artificial urine has been proposed. However, a water-absorbent resin that is a particulate water-absorbing agent that is excellent in powder flowability and processed into a tape-like or sheet-like shape does not exhibit sufficient physical properties in actual use.

JP 59-80459 A JP 2000-093792 A JP 2001-137704 A International Publication No. 2000/010619 Pamphlet International Publication No. 95/033558 Pamphlet Japanese Patent Laid-Open No. 2003-082250 International Publication No. 2002/034384 Pamphlet WO97 / 37695 pamphlet European Patent Publication No. 1592750 JP-A-61-58658 International Publication No. 2010/073658 Pamphlet JP 2010-0665107 A JP-A-6-220227 JP-A-8-027278 International Publication No. 2005/077500 Pamphlet US Pat. No. 5,985,944 US Pat. No. 5,601,542 US Pat. No. 6,127,454 US Pat. No. 6,602,950 US Pat. No. 6,060,557 US Pat. No. 5,797,893 US Patent No. 5760080 US Pat. No. 4,666,975 US Pat. No. 6,187,872 US Pat. No. 7,759,422 US Pat. No. 6,297,335 U.S. Pat. No. 7,838,721

Japanese Industrial Standard (JIS) K7223-1996 Japanese Industrial Standard (JIS) K7224-1996 ERT441.2-02 (2002) ERT442.2-02 (2002) ERT470.2-02 (2002)

  The problem to be solved by the present invention is to provide a particulate water-absorbing agent that is excellent in handleability with powder, and has high absorption performance in a wide range of salt concentrations, and can be used for many purposes. And providing a particulate water-absorbing agent.

The inventors of the present invention who have studied such problems are particulate water-absorbing agents excellent in powder flowability, and as a result of examining to obtain a particulate water-absorbing agent excellent in actual use in the form of a sheet or tape, The metal soap described in Patent Document 9 provides a particulate water-absorbing agent that maintains fluidity and water absorption performance under pressure (for example, absorption at a load of 20 to 50 [g / cm ² ] in 0.9% by weight saline). Despite being able to do so, these technologies have also found the problem of reducing the water absorption performance, especially the absorption performance at the high salt concentration required for civil engineering / building waterproofing materials, cable waterproofing materials, etc. .

And in the said nonpatent literatures 1-5, the said patent documents 1-27, etc., the water absorption resin conventionally evaluated by 0.9 weight% salt solution or artificial urine, and the water absorption capacity | capacitance under pressure are according to paper diapers. With respect to the water absorbent resin that has been evaluated by the basis weight (the amount of the water absorbent resin per unit area), Patent Documents 5 to 15 improve the powder fluidity and maintain the water absorption performance, in particular, the metal soap described in Patent Document 9 particulate water-absorbing agent obtained by maintaining the fluidity and absorbency against pressure properties (e.g. absorption under a load of 20~50 [g / cm ^2] to 0.9 wt% saline) has been proposed.

  However, in the related art including Patent Documents 1 to 27, the water absorption ratio in ultra high concentration salt water (particularly 20% by weight saline) which has not been noticed at all is extremely low, and the ultra high basis weight ( The fact that the water absorption capacity under pressure at a basis weight of about 6.2 times the basis weight (to be described later), etc., was also found to be extremely reduced. And in addition to powder flowability, the absorption capacity under pressure in ultra high concentration salt water (especially 20 wt% saline) or ultra high basis weight, which has not been noticed in the past, is actually in the form of a sheet or tape. I found it important to use.

  Moreover, although it is also known in Patent Documents 1 to 4 and Patent Document 9 that the moisture absorption blocking rate (Anti-Caking) is important, the present inventors have a low moisture absorption blocking rate (high Anti-Caking) after production. It was found that even in the case of the water-absorbent resin of (), the moisture absorption blocking rate increases during actual use. And in the evaluation of the conventional moisture absorption blocking rate, it does not show a sufficient effect at the time of actual use, and the cause thereof is peeling of various Anti-Caking agents by transporting the water absorbent resin powder (for example, various transport machines such as pneumatic transport). And the moisture absorption blocking rate was found to increase. And it replaced with the conventional evaluation of the moisture absorption blocking rate, and discovered that the moisture absorption blocking rate after the impact test (modeled on conveyance) was important for actual use.

  In order to solve the above-mentioned problems, the present inventors have intensively studied. As a result, water-insoluble or poorly water-soluble compounds selected from long-chain alkyl compounds, organic polysiloxanes, and organic polymer compounds, particularly water-insoluble or poorly water-soluble long-chain alkyls. It is a particulate water-absorbing agent containing a compound or an organic polysiloxane, and it can be used in a sheet or tape form by controlling a specific moisture absorption blocking rate and a 20% by weight salt water vertical absorption index within a specific range. It became an excellent water-absorbing agent and found that the above problems could be solved.

  That is, the particulate water-absorbing agent of the present invention contains a polyacrylic acid (salt) water-absorbing resin as a main component, and is a water selected from a long-chain alkyl compound, an organic polysiloxane, and an organic polymer compound with respect to the water-absorbing resin. A particulate water-absorbing agent containing 0.001 to 5% by weight of an insoluble or hardly water-soluble compound (provided that the long-chain alkyl compound corresponds to a metal soap, 0.001% by weight or more and less than 1.0% by weight). In addition, a particulate water-absorbing agent having a moisture absorption blocking rate of 0 to 30 wt% and a 20 wt% saline vertical absorption index of 1.5 to 10.0 [g / g] is provided.

  In order to solve the above problems, the method for producing a particulate water-absorbing agent of the present invention is a method for producing a particulate water-absorbing agent mainly comprising a polyacrylic acid (salt) water-absorbing resin, wherein acrylic acid (salt) is used. A process for polymerizing an aqueous monomer solution as a main component, a water-insoluble or difficult water selected from long-chain alkyl compounds, organic polysiloxanes, and organic polymer compounds with respect to a water-absorbing resin before or after drying after the polymerization process. A step of adding 0.001 to 5% by weight of a soluble compound (however, when the long-chain alkyl compound corresponds to a metal soap, 0.001% by weight or more and less than 1.0% by weight), the long-chain alkyl compound, Provided is a method for producing a particulate water-absorbing agent which sequentially includes a step of adding a surfactant to a water-absorbing resin containing one or more of organic polysiloxane and organic polymer compound.

  According to the particulate water-absorbing agent defined in the present invention and the method for producing the same, it is possible to provide a particulate water-absorbing agent having excellent powder fluidity, which is an important factor when processed into an absorbent article. , Trouble during processing is reduced, and as a result, the productivity of the absorbent article can be improved. Furthermore, it is possible to produce and provide an absorbent article that is versatile and excellent in absorption performance.

  That is, an extremely excellent particulate water-absorbing agent capable of simultaneously improving the conflicting performances of “powder handling (powder fluidity during drying and moisture absorption)” and “absorption performance” and a method for producing the same Can be provided.

  By using the particulate water-absorbing agent obtained in the present invention for an absorbent article, it is possible to provide an absorbent article that is versatile and excellent in absorbent performance while maintaining high productivity.

FIG. 1 is a graph showing the correlation between the type and addition amount of a surfactant and the 20 wt% saline vertical absorption index. FIG. 2 is a side view schematically showing an apparatus for measuring water absorption under pressure and a 20 wt% saline vertical absorption index.

  Hereinafter, the particulate water-absorbing agent and the production method thereof according to the present invention will be described in detail. However, the scope of the present invention is not limited to these descriptions, and other than the following examples, the scope of the present invention can be changed and implemented as appropriate without departing from the spirit of the present invention.

  Specifically, the present invention is not limited to the following embodiments, and various modifications can be made within the scope shown in the claims, and obtained by appropriately combining technical means disclosed in different embodiments. Embodiments to be made are also included in the technical scope of the present invention.

[1] Definition of terms (1-1) "Water absorbent resin"
The “water-absorbing resin” in the present invention means a water-swellable water-insoluble polymer gelling agent. “Water swellability” means that the CRC (water absorption capacity under no pressure) specified by ERT442.2-02 is 5 [g / g] or more, and “water insolubility” means ERT470.2. It means that Ext (water-soluble content) specified by -02 is 0 to 50% by weight.

  The water-absorbent resin can be appropriately designed according to its use and is not particularly limited, but may be a hydrophilic cross-linked polymer obtained by cross-linking an unsaturated monomer having a carboxyl group. preferable. The total amount (100% by weight) is not limited to a form of a polymer, and may be a composition containing a surface-crosslinked polymer, an additive and the like within a range that maintains the above performance. In the present invention, the hydrophilic cross-linked polymer is a water-absorbent resin that is pulverized to form a powder, and the water-absorbent resin before surface treatment or surface cross-linking is referred to as “water-absorbent resin powder” or “water-absorbent resin precursor”. The water-absorbing resin after surface treatment or surface cross-linking is referred to as “water-absorbing resin particles”. Furthermore, in the present invention, even if the water-absorbent resin is different in shape obtained in each step (for example, a sheet shape, a fiber shape, a film shape, a gel shape, etc.), the water absorption containing additives Even a water-soluble resin composition is collectively referred to as a “water-absorbing resin”.

(1-2) “Particulate water-absorbing agent”
The “particulate water-absorbing agent” in the present invention refers to an aqueous liquid gelling agent mainly composed of a water-absorbing resin (particularly polyacrylic acid (salt) -based water-absorbing resin). In particular, in the present invention, in addition to the water-absorbing resin, a water-insoluble or hardly water-soluble compound selected from long-chain alkyl compounds, organic polysiloxanes, and organic polymer compounds described later, particularly water-insoluble or hardly water-soluble long-chain alkyl compounds or organic compounds. It is a gelling agent containing polysiloxane and optionally water (1 to 20% by weight, more preferably in the range described in (3-6)), preferably further containing a surfactant described later.

  The content of the water-absorbing resin contained in the particulate water-absorbing agent according to the present invention is preferably 60 to 99% by weight, more preferably 75 to 99% by weight, based on the whole particulate water-absorbing agent. More preferably, it is 80 to 99% by weight. The aqueous liquid is not limited to water, but may be urine, blood, feces, waste liquid, moisture or steam, ice, a mixture of water and organic solvent and / or inorganic solvent, rain water, ground water, sea water, salt water, etc. The water is not particularly limited.

(1-3) “Particles”
The “particle” in the present invention refers to a powder having fluidity, preferably Flow Rate (flow rate) defined by ERT450.2-02 or PSD (particle size distribution by sieving classification) defined by ERT420.2-02. Is a measurable powder (note that a suitable Flow Rate range is (2-2-3) and a particle size range is (3-5), which will be described later). Therefore, the “water-absorbent resin powder” and the like described in (1-1) above are “particles” in light of this definition, but in the present invention, different expressions are adopted to distinguish the presence or absence of surface crosslinking.

(1-4) “Polyacrylic acid (salt)”
The “polyacrylic acid (salt)” in the present invention optionally includes a graft component, and the repeating unit is acrylic acid and / or a salt thereof (hereinafter referred to as acrylic acid (salt)) as a main component. Means a polymer.

  Specifically, among the total monomers (excluding the internal crosslinking agent) used for polymerization, acrylic acid (salt) is essentially 50 to 100 mol%, preferably 70 to 100 mol%, more preferably 90 to 90 mol%. A polymer containing 100 mol%, particularly preferably substantially 100 mol%. Alternatively, polyacrylic acid (salt) may be obtained from a saponified product such as polyacrylonitrile or polyacrylamide. Moreover, when using a polyacrylate as a polymer, a water-soluble salt is essential, a monovalent salt is preferable as a main component of the neutralized salt, an alkali metal salt or an ammonium salt is more preferable, and an alkali metal salt is further included. Sodium salts are preferred, especially.

(1-5) “EDANA” and “ERT”
“EDANA” is an abbreviation for European Disposables and Nonwovens Associations, and “ERT” is an abbreviation for a method for measuring water-absorbent resin (EDANA Recommended Test Methods) which is a European standard (substantially world standard). is there. In the present invention, unless otherwise specified, the measurement is performed according to the ERT original (known document: revised in 2002).

(A) "CRC" (ERT441.2-02)
“CRC” is an abbreviation for Centrifugation Retention Capacity (centrifuge retention capacity) and means water absorption capacity without pressure (hereinafter also referred to as “water absorption capacity”). Specifically, after 0.200 g of the water-absorbent resin in the non-woven bag was freely swollen for 30 minutes in a large excess of 0.9 wt% sodium chloride aqueous solution, the water absorption after further draining with a centrifuge Magnification (unit: [g / g]).

(B) “AAP” (ERT442.2-02)
“AAP” is an abbreviation for Absorption Against Pressure, which means water absorption capacity under pressure. Specifically, 0.900 g of the water-absorbent resin was swollen under a load of 2.06 kPa (0.3 psi, 21 [g / cm ² ]) for 1 hour against a 0.9 wt% sodium chloride aqueous solution. It is the water absorption magnification (unit; [g / g]). In ERT442.2-02, it is written as Absorption Under Pressure, but it has substantially the same content.

(C) “PSD” (ERT420.2-02)
“PSD” is an abbreviation for Particle Size Distribution, and means a particle size distribution measured by sieving classification. The weight average particle size (D50) and the particle size distribution width are the same as those described in “(1) Average Particle Diameter and Distribution of Particle Diameter” described in European Patent No. 0349240, page 7, lines 25 to 43. taking measurement.

(1-6) “Surface treatment” and “surface crosslinking”
“Surface treatment” in the present invention is a superordinate concept including surface cross-linking, and is a treatment for adding / mixing additives to the surface of water-absorbent resin powder (water-absorbent resin precursor, base polymer), coating treatment, and unsaturated. The process which forms a core-shell structure by superposing | polymerizing a monomer etc. and the process which bridge | crosslinks the surface of a water absorbing resin powder with a surface crosslinking agent are said.

  For example, an additive such as inorganic fine particles or a surfactant is added to and mixed with the water-absorbent resin powder, and the surface is adsorbed on the surface (physical bonding) or coated. That is, radical crosslinking by a polymerization initiator when polymerizing an unsaturated monomer on the surface of the water absorbent resin powder, or physical crosslinking of the surface of the water absorbent resin by polymerization of the unsaturated monomer on the surface (polymer chains ), And performing covalent bond crosslinking or ionic bond crosslinking with a surface crosslinking agent is referred to as “surface treatment”.

  In the present invention, “surface crosslinking” refers to the surface treatment of the water-absorbent resin powder by the covalent crosslinking or ionic bonding crosslinking by the surface crosslinking agent, the irradiation of active energy rays, the radical polymerization initiator, etc. Is a cross-linking of polymer chains constituting the.

(1-7) Others In this specification, “X to Y” indicating a range means “X or more and Y or less”. Further, “t (ton)” which is a unit of weight means “Metric ton”, and unless otherwise noted, “ppm” means “ppm by weight” or “ppm by mass”. "Means. Further, in this specification, “mass” and “weight”, “mass%” and “wt%”, and “part by mass” and “part by weight” are synonymous, and there is no particular limitation on measurement of physical properties and the like. When there is not, it measures at room temperature (20-25 degreeC) / relative humidity 40-50%. Further, “˜acid (salt)” means “˜acid and / or salt thereof”, and “(meth) acryl” means “acryl and / or methacryl”.

[2] Manufacturing method of particulate water-absorbing agent The manufacturing method of the particulate water-absorbing agent of the present invention is a manufacturing method of a water-absorbing agent having a polyacrylic acid (salt) -based water-absorbing resin as a main component. ), A water-insoluble or water-resistant water selected from a long-chain alkyl compound, an organic polysiloxane, and an organic polymer compound with respect to a water-absorbing resin before or after drying after polymerization. Step of adding 0.001 to 5% by weight of a soluble compound (in the case of metal soap, 0.001% by weight or more and less than 1.0% by weight), interface with a water-absorbing resin containing a long-chain alkyl compound or an organic polysiloxane Provided is a method for producing a particulate water-absorbing agent, which sequentially includes a step of adding an activator.

  Hereinafter, (2-1) a step of polymerizing an aqueous monomer solution containing acrylic acid (salt) as a main component, (2-2) water insolubility or water resistance with respect to the water absorbent resin before or after drying after polymerization. Adding a soluble long-chain alkyl compound or organopolysiloxane in an amount of 0.001 to 5 wt% (however, 0.001 wt% or more and less than 1.0 wt% for metal soap), (2-3) long-chain alkyl The process of adding a surfactant to a water-absorbent resin containing a compound or an organic polysiloxane will be sequentially described.

(2-1) Step of polymerizing an aqueous monomer solution mainly composed of acrylic acid (salt) (unsaturated monomer)
In the present invention, one or more polyacrylic acid (salt) -based crosslinked polymers (mixtures) are used as a water-absorbing resin in order to solve the problems (objective physical properties), and acrylic acid (salt) is used as a monomer. ) Is preferably used as a main component, but monomers such as acrylamide and acrylonitrile that generate polyacrylic acid by hydrolysis after polymerization may be used, and monomers other than acrylic acid (salt) (hereinafter, (Referred to as “other monomers”) may be used as a copolymerization component. In addition, the polyacrylic acid (salt) water-absorbing resin may be a single product, or a plurality of water-absorbing resins having different neutralization rates, particle sizes, and crosslinking densities may be mixed, and if necessary, polyacrylic acid (salt) water-absorbing resin Water-absorbing resins other than resins, for example, polyamine cross-linked water-absorbing resins may be used in combination.

  The polyacrylic acid (salt) -based crosslinked polymer optionally contains a graft component, and may preferably contain 0 to 50% by weight, more preferably 0 to 40% by weight. Even if it is a coalescence, it is generically called a polyacrylic acid (salt) -based crosslinked polymer (polyacrylic acid (salt) -based water-absorbing resin).

  Although it does not specifically limit as said other monomer, For example, methacrylic acid, (anhydrous) maleic acid, fumaric acid, crotonic acid, itaconic acid, vinyl sulfonic acid, 2- (meth) acrylamido-2-methylpropane sulfone Acid, (meth) acryloxyalkanesulfonic acid and its alkali metal salt or ammonium salt, N-vinyl-2-pyrrolidone, N-vinylacetamide, (meth) acrylamide, N-isopropyl (meth) acrylamide, N, N-dimethyl Water-soluble or hydrophobic unsaturated monomers such as (meth) acrylamide, 2-hydroxyethyl (meth) acrylate, methoxypolyethylene glycol (meth) acrylate, polyethylene glycol (meth) acrylate, isobutylene and lauryl (meth) acrylate To mention Can.

  Moreover, 0-50 mol% is preferable with respect to the total number of moles of the whole unsaturated monomer, 0-30 mol% is more preferable, and the usage-amount of said other monomer is 0-10 mol%. More preferably, 0-5 mol% is especially preferable. In other words, the usage amount of acrylic acid (salt) as the main component is preferably 50 to 100 mol%, more preferably 70 to 100 mol%, based on the total number of moles of the unsaturated monomers. ~ 100 mol% is more preferable, and 95 to 100 mol% is most preferable, but from the viewpoint of the water absorption performance (CRC, AAP, etc.) of the obtained water absorbent resin and particulate water absorbent, substantially 100 mol% is most preferable. .

  In addition, when using a monomer having an acid group as an unsaturated monomer (including the above-mentioned other monomers), as a salt of the unsaturated monomer, an alkali metal salt, an alkaline earth metal salt, An ammonium salt may be used. Among these salts, monovalent salts are preferable from the viewpoint of the water-absorbing performance (CRC, AAP, etc.) of the water-absorbing resin and particulate water-absorbing agent obtained, industrial availability of unsaturated monomer salts, safety, etc. In particular, it is preferable to use monovalent metal salts, especially sodium salts or potassium salts.

  Moreover, when using acrylic acid (salt) as an unsaturated monomer, the ratio of acrylic acid and acrylate is 0-50 mol% of acrylic acid and 100-50 mol% of acrylate (however, the total of both) Is preferably 100 mol% or less), more preferably 10 to 40 mol% of acrylic acid and 90 to 60 mol% of acrylate. That is, the “neutralization ratio”, which is the molar ratio of acrylate to the total amount of acrylic acid and acrylate, is preferably 50 to 100 mol%, more preferably 60 to 90 mol%.

  In order to form the acrylate, neutralize acrylic acid in the monomer state before polymerization, neutralize in the polymer state during or after polymerization, or use these operations in combination. Is mentioned. Further, acrylic acid (salt) may be formed by mixing acrylic acid and acrylate.

(Internal crosslinking agent)
If the water-absorbent resin in the present invention has the “water swellability” and “water insolubility” defined in (1-1) above, a crosslinked structure (surface crosslinking (secondary crosslinking) described later) is provided therein. Is considered to have internal cross-linking. Therefore, although it can be obtained by self-crosslinking of an unsaturated monomer, a water-absorbing resin obtained by copolymerization or reaction of an unsaturated monomer and an internal crosslinking agent is preferable. Examples of the internal cross-linking agent include compounds having two or more polymerizable unsaturated groups or two or more reactive groups in one molecule.

  Although it does not specifically limit as said internal crosslinking agent, For example, N, N'-methylenebis (meth) acrylamide, (poly) ethylene glycol di (meth) acrylate, (poly) propylene glycol di (meth) acrylate, trimethylolpropane Tri (meth) acrylate, glycerin tri (meth) acrylate, glycerin acrylate methacrylate, ethylene oxide modified trimethylolpropane tri (meth) acrylate, pentaerythritol hexa (meth) acrylate, triallyl cyanurate, triallyl isocyanurate, triallyl phosphate , Triallylamine, poly (meth) allyloxyalkane, (poly) ethylene glycol diglycidyl ether, glycerol diglycidyl ether, ethylene glycol Polyethylene glycol, propylene glycol, glycerol, pentaerythritol, ethylenediamine, ethylene carbonate, propylene carbonate, polyethylenimine, and glycidyl (meth) acrylate. These internal crosslinking agents may be used alone or in combination of two or more. In consideration of the water absorption performance of the water-absorbing resin and the particulate water-absorbing agent, it is preferable to use an internal cross-linking agent having two or more polymerizable unsaturated groups during the polymerization. The internal cross-linking agent may be added all at once to the reaction system, or may be added separately. Moreover, what is necessary is just to add to the reaction system before superposition | polymerization of an unsaturated monomer, after superposition | polymerization, after superposition | polymerization, or after neutralization.

  The amount of the internal cross-linking agent used is appropriately determined according to the desired 1-hour soluble content, water absorption capacity (CRC), etc., but the monomer excluding the internal cross-linking agent (unsaturated monomer as a whole) Is preferably 0.001 to 2 mol%, more preferably 0.005 to 0.5 mol%, still more preferably 0.01 to 0.2 mol%, and 0.03 to 0.15 mol%. Particularly preferred. If the amount used is less than 0.001 mol% or exceeds 2 mol%, the water absorbing performance of the resulting water absorbent resin and particulate water absorbing agent cannot be obtained sufficiently, such being undesirable.

(Polymerization initiator)
The polymerization initiator used in the polymerization step of the present invention is appropriately selected depending on the polymerization form and is not particularly limited, and examples thereof include a photodegradable polymerization initiator, a thermal decomposition polymerization initiator, and a redox polymerization initiator. It is done.

  Examples of the photodegradable polymerization initiator include benzoin derivatives, benzyl derivatives, acetophenone derivatives, benzophenone derivatives, azo compounds, and the like. Examples of the thermal decomposition polymerization initiator include persulfates such as sodium persulfate, potassium persulfate, and ammonium persulfate; peroxides such as hydrogen peroxide, t-butyl peroxide, and methyl ethyl ketone peroxide; 2 , 2′-azobis (2-amidinopropane) dihydrochloride, 2,2′-azobis [2- (2-imidazolin-2-yl) propane] dihydrochloride, and the like. Furthermore, examples of the redox polymerization initiator include a system in which a reducing compound such as L-ascorbic acid or sodium bisulfite is used in combination with the persulfate or peroxide. Moreover, combined use with the said photodegradable polymerization initiator and a thermal decomposition type polymerization initiator is also mentioned as a preferable form.

  The amount of these polymerization initiators used is preferably 0.001 to 2 mol% and more preferably 0.01 to 0.1 mol% with respect to the monomer. When the amount used exceeds 2 mol%, it is difficult to control the polymerization, and when the amount used is less than 0.001 mol%, the amount of residual monomer increases, which is not preferable.

(Polymerization method)
The polymerization method of the unsaturated monomer in the present invention is not particularly limited, and can be carried out by bulk polymerization or precipitation polymerization which is substantially solvent-free, but the obtained water-absorbing resin and particulate water-absorbing agent can be used. From the viewpoint of water absorption performance, further water absorption performance of the hydrogel crosslinked polymer, other ease of polymerization control, etc., a polymerization method in which an unsaturated monomer is used as an aqueous solution, particularly spray polymerization, droplet polymerization, aqueous solution Polymerization and reverse phase suspension polymerization are preferably employed. In addition, the unsaturated monomer mentioned above shall contain another monomer and an internal crosslinking agent.

  When the unsaturated monomer is an aqueous solution, the monomer concentration in the aqueous solution is appropriately determined depending on the temperature of the aqueous solution and the type of the monomer, and is not particularly limited, but is preferably 10 to 70% by weight, and 20 to 60% by weight. % Is more preferable.

  Polymerization of the unsaturated monomer is initiated by addition of the polymerization initiator, irradiation with active energy rays such as ultraviolet rays, electron beams and γ rays, or a combination thereof. The polymerization temperature may be appropriately selected according to the type of polymerization initiator and active energy ray to be used, and is not particularly limited, but is preferably 15 to 130 ° C and more preferably 20 to 120 ° C. If the reaction temperature (reaction start temperature or reaction peak temperature) is out of the above range, the amount of residual monomer in the resulting water-absorbent resin increases or the self-crosslinking reaction proceeds excessively, and the water-absorbent resin and particulate water-absorbing agent Since water absorption performance falls, it is not preferred.

  The reverse phase suspension polymerization is a method in which an aqueous monomer solution is suspended in a hydrophobic organic solvent for polymerization. For example, U.S. Pat. Nos. 4,093,776, 4,367,323, 4,446,261, Nos. 4,683,274 and 5,244,735.

  The aqueous solution polymerization is a method of polymerizing an aqueous monomer solution without using a dispersion solvent. For example, U.S. Pat. Nos. 4,462,001, 4,873,299, 4,286,682, 4,973,632, and 4,985,518. No. 5,124,416, No. 5,250,640, No. 5,264,495, No. 5,145,906, No. 5,380808, etc., and European Patent Nos. 081636, 09555086, 0922717, etc. . It should be noted that a solvent other than water may be used in combination as necessary, and the type thereof is not particularly limited. Therefore, the water-absorbent resin of the present invention can be obtained by applying the unsaturated monomer, the polymerization initiator, and the like to the polymerization methods disclosed in the above patent documents.

(2-1-2) Fine-graining step The gel during or after polymerization is finely divided with a kneader, meat chopper, or the like as necessary for heat removal during polymerization or drying efficiency. The weight average particle diameter (D50) of the hydrogel is preferably 0.5 to 4 mm, more preferably 0.3 to 3 mm, and even more preferably 0.5 to 2 mm. The weight average particle diameter can be measured using the wet classification method described in paragraph [0091] of JP-A No. 2000-63527.

(2-1-2) Drying step The drying method in the present invention is not particularly limited as long as the desired moisture content can be obtained, and various methods can be employed. Specific examples include heat drying, hot air drying, vacuum drying, infrared drying, microwave drying, azeotropic dehydration drying with a hydrophobic organic solvent, and high humidity drying using high-temperature steam.

  As drying temperature, 60-250 degreeC is preferable, 100-220 degreeC is more preferable, 120-200 degreeC is further more preferable. The drying time may be appropriately selected within the range of 1 minute to 5 hours, preferably 10 minutes to 2 hours.

  The moisture content (% by weight) of the dried polymer after drying is determined from loss on drying (1 g of powder or particles is dried at 180 ° C. for 3 hours). The resin solid content after drying (100-water content) is preferably 80% by weight or more, more preferably 85 to 99% by weight, and still more preferably 90 to 98% by weight.

  The “moisture content” in the present invention refers to the amount of water contained in the particulate water-absorbing agent, and the weight loss when 1 g of the particulate water-absorbing agent is dried at 180 ° C. for 3 hours is based on the weight before drying. This is a numerical value expressed as a ratio (% by weight).

(2-1-3) Grinding step, classification step When the polymerization step is reverse phase suspension polymerization, the particle size is controlled at the time of polymerization, so the pulverization step is optional. The aggregate may be crushed (operation for loosening the aggregate). Moreover, when the said polymerization process is aqueous solution polymerization, although the grinding | pulverization process after drying can also be abbreviate | omitted at the time of superposition | polymerization or the degree of gel crushing after superposition | polymerization, Preferably grinding | pulverization and classification are performed further.

  That is, the dry polymer obtained in the drying step can be used as a water-absorbent resin powder as it is, but in order to obtain the particulate water-absorbing agent of the present invention, it is preferable to control to a specific particle size by pulverization and classification. . The particle size control is not limited to pulverization and classification, and can be appropriately performed in each step such as fine powder collection and granulation in addition to polymerization. Hereinafter, the particle size is defined by a standard sieve (JIS Z8801-1 (2000)).

  The preferable particle size is omitted because it will be described later in (3-5), but for the purpose of improving the 20 wt% saline vertical absorption index, moisture absorption blocking rate and other physical properties described later in (3-1) and later. The weight average particle diameter (D50) of the water-absorbent resin before surface crosslinking is 250 μm to 450 μm, the content of particles having a particle diameter of less than 150 μm is 0 to 5% by weight, and the logarithmic standard deviation (σζ) is 0 to 0.45. Furthermore, it is preferable that the particle size described later in (3-5) is controlled before surface crosslinking. The classification step is preferably provided before the surface cross-linking, and if necessary, a classification step (second classification step) is preferably further provided after the surface cross-linking to control the particle size.

(2-1-4) Surface cross-linking step A water-absorbent resin powder is obtained through each of the above steps. Thereafter, the surface of the water-absorbent resin powder is further cross-linked (secondary cross-linking with respect to the internal cross-linking which is primary cross-linking). (Subsequent cross-linking) treatment to obtain water-absorbing resin particles increases the cross-linking density in the vicinity of the resin surface, and various physical properties of the water-absorbing resin particles and the particulate water-absorbing agent are, in particular, water absorption capacity under pressure (AAP) and 20 weight. % Saline vertical absorption index is improved. That is, the present invention preferably includes a step of further surface cross-linking the dried water-absorbent resin. The water absorbent resin in the water absorbent is preferably surface-crosslinked.

  When performing surface crosslinking in the present invention, before or after the step of adding a water-insoluble or poorly water-soluble compound selected from long-chain alkyl compounds, organic polysiloxanes, and organic polymer compounds, particularly long-chain alkyl compounds or organic polysiloxanes. However, it is preferable to add a surfactant to the surface-crosslinking step, the step of adding a long-chain alkyl compound or an organic polysiloxane, or the water-absorbing resin containing the long-chain alkyl compound or the organic polysiloxane. Steps are included in sequence.

(Surface cross-linking agent)
The surface cross-linking agent used in the present invention is not particularly limited as long as it is a surface cross-linking agent that improves the properties of the resulting water-absorbent resin particles and particulate water-absorbing agent. Covalent bonds or ionic bonds, particularly surface cross-linking agents (organic surface cross-linking agents) that are covalently bonded are preferred, such as polyhydric alcohol compounds, epoxy compounds, polyvalent amine compounds, condensates of polyvalent amine compounds and haloepoxy compounds, oxazolines. Examples thereof include compounds, monooxazolidinone compounds, dioxazolidinone compounds, polyoxazolidinone compounds, polyvalent metal salts, and alkylene carbonate compounds. These surface cross-linking agents may be used alone or in combination of two or more.

  More specifically, organic surface crosslinking agents disclosed in US Pat. Nos. 6,228,930, 6071976, 6254990 and the like can be mentioned. That is, monoethylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, 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 Polyhydric alcohol compounds such as dimethanol; Epoxy compounds such as ethylene glycol diglycidyl ether and glycidol; Ethylenediamine, diethylenetriamine, triethylenetetramine, tetraethylenepentamine, pentae Polyvalent amine compounds such as lenhexamine, polyethyleneimine and polyamide polyamine; haloepoxy compounds such as epichlorohydrin, epibromohydrin and α-methylepichlorohydrin; condensates of the polyvalent amine compounds and the haloepoxy compounds An oxazolidinone compound such as 2-oxazolidinone; an alkylene carbonate compound such as ethylene carbonate;

(Ion-binding surface cross-linking agent)
In addition to the organic surface crosslinking agent, a polyvalent metal salt, a polyamine polymer, or the like can be used as the ion binding surface crosslinking agent. Furthermore, liquid permeability etc. can also be improved by using an inorganic surface crosslinking agent other than the said organic surface crosslinking agent. In this case, the inorganic surface cross-linking agent used is preferably a divalent or higher, more preferably a trivalent or tetravalent polyvalent metal salt (organic salt or inorganic salt) or hydroxide. Examples of the salt include International Publication Nos. 2007/121037, 2008/09843, 2008/09842, U.S. Pat. Nos. 7,157,141, 6,605,673, and 6620889, and U.S. Patent Application Publication No. 2005/0288182. No., 2005/0070671, 2007/0106013, 2006/0073969, and the like. More specifically, examples include aluminum and zirconium, and examples include aluminum lactate and aluminum sulfate. The inorganic surface crosslinking agent is used simultaneously with or separately from the organic surface crosslinking agent.

  Moreover, a liquid permeability etc. can also be improved by using a polyamine polymer, especially a polyamine polymer with a weight average molecular weight of about 5000 to 1 million simultaneously or separately with the organic surface crosslinking agent. In this case, the polyamine polymer used is, for example, US Pat. No. 7098284, International Publication Nos. 2006/082188, 2006/082189, 2006/082197, 2006/111402, and 2006. / 111403, 2006/111404, and the like.

(Amount of surface cross-linking agent used)
Among the various surface cross-linking agents described above, in order to improve the physical properties of the water-absorbent resin particles as much as possible, it is preferable to use a covalently-bonded surface cross-linking agent, and further prevent a decrease in water content during the surface treatment. Therefore, an epoxy compound, a haloepoxy compound, and an oxazolidinone compound that react at a low temperature are more preferable, and at least an epoxy compound and a haloepoxy compound are more preferable. Particularly preferably, an alkylene carbonate or a polyhydric alcohol is used in combination.

  Further, when a dehydration-reactive surface cross-linking agent selected from alkylene carbonate and polyhydric alcohol is used, the water content decreases more remarkably because surface cross-linking, particularly dehydration esterification reaction with polyacrylic acid, is performed at a high temperature. Therefore, water is appropriately added after the surface crosslinking to adjust the water content to be described later. In addition, when using a polyhydric alcohol as a dehydration-reactive surface cross-linking agent, a polyhydric alcohol having 2 to 10 carbon atoms is preferable, a polyhydric alcohol having 3 to 8 is more preferable, and a diol is particularly preferable.

  The amount of the surface cross-linking agent used depends on the type of surface cross-linking agent used, the combination of the water-absorbent resin powder and the surface cross-linking agent, etc., but preferably 0 0.001 to 10 parts by weight, more preferably 0.01 to 5 parts by weight.

(Water and solvent and the amount used)
In the surface cross-linking treatment, it is preferable to use water together with the surface cross-linking agent. The amount of water used at this time depends on the water content of the water-absorbent resin powder, but is usually preferably 0.5 to 20 parts by weight with respect to 100 parts by weight of the water-absorbent resin powder. 10 parts by weight is more preferable. When mixing the surface cross-linking agent or its aqueous solution, a hydrophilic organic solvent or a third substance may be used as a mixing aid.

  Examples of the hydrophilic organic solvent (particularly water-soluble organic solvent) include lower alcohols such as methyl alcohol, ethyl alcohol, n-propyl alcohol, isopropyl alcohol, n-butyl alcohol, isobutyl alcohol, and t-butyl alcohol; Ketones such as acetone; Ethers such as dioxane, tetrahydrofuran and methoxy (poly) ethylene glycol; Amides such as ε-caprolactam and N, N-dimethylformamide; Sulphoxides such as dimethyl sulfoxide; Ethylene glycol, diethylene glycol and propylene glycol , Triethylene glycol, tetraethylene glycol, polyethylene glycol, 1,3-propanediol, dipropylene glycol, 2,2,4-trimethyl-1,3-pentanedi , Polypropylene glycol, glycerin, polyglycerin, 2-butene-1,4-diol, 1,3-butanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, 1 , 2-cyclohexanedimethanol, 1,2-cyclohexanol, trimethylolpropane, diethanolamine, triethanolamine, polyoxypropylene, oxyethylene-oxypropylene block copolymers, polyhydric alcohols such as pentaerythritol, sorbitol, etc. It is done. The polyhydric alcohol is classified as a surface crosslinking agent when it reacts with the water-absorbent resin, and is classified as a hydrophilic organic solvent when it does not react. The presence or absence of the reaction can be easily discriminated by the residual amount of polyhydric alcohol or the increased amount of ester (IR analysis or the like).

  The amount of the hydrophilic organic solvent used is preferably 10 parts by weight or less with respect to 100 parts by weight of the solid content of the water-absorbent resin powder, although it depends on the type, particle size, water content and the like of the water-absorbent resin powder. More preferably, it is 1 to 5 parts by weight.

(Other auxiliaries)
As other auxiliaries (third substances), inorganic acids, organic acids, polyamino acids and the like described in EP 0668080 and surfactants described later may be present.

  In order to mix the water-absorbent resin powder and the surface cross-linking agent more uniformly, non-cross-linkable water-soluble inorganic bases (preferably alkali metal salts, ammonium salts, alkali metal hydroxides, and ammonia or hydroxide thereof) Product) and non-reducing alkali metal salt pH buffer (preferably hydrogen carbonate, dihydrogen phosphate, hydrogen phosphate, etc.) are allowed to coexist when the water absorbent resin powder and the surface cross-linking agent are mixed. May be.

  Although these usage-amounts are based also on the kind of water-absorbent resin powder, a particle size, etc., 0.005-10 weight part is preferable with respect to solid content of 100 weight part of water-absorbent resin powder, 0.05-5 Part by weight is more preferred.

(Physical properties after surface crosslinking)
The surface crosslinking is preferably controlled within the range of AAP to be described later, but the surface water absorption step (AAP) under a load of 2.06 kPa is controlled to 20 [g / g] or more by the surface crosslinking step. The preferred water absorption capacity under non-pressure after surface crosslinking (CRC) is in the range described later in (3-11), and the preferred water absorption capacity under pressure (AAP) after surface crosslinking is described later in (3-11). The reaction time, reaction temperature, type of surface cross-linking agent, amount of use thereof, and the like may be appropriately adjusted to such a range.

(Method for adding surface cross-linking agent)
The surface cross-linking agent can be added by various techniques. For example, when the water-absorbing resin powder is obtained by aqueous solution polymerization, the water-absorbing resin powder during or after the drying step, particularly the water-absorbing resin powder whose particle size is controlled through the above (2-1-3). On the other hand, a method of premixing the surface cross-linking agent with water and / or a hydrophilic organic solvent as needed and dropping and mixing it with the water-absorbent resin powder is preferable, and a spraying method is more preferable. The size of the droplets to be sprayed is preferably from 0.1 to 300 μm, more preferably from 1 to 200 μm, as an average droplet diameter.

  As a mixing device used when mixing the water-absorbent resin powder, the surface cross-linking agent, water or a hydrophilic organic solvent, a mixing device having a large mixing force in order to uniformly and reliably mix these compounds. An apparatus is preferred. Examples of such a mixing apparatus include a cylindrical mixer, a double wall conical mixer, a high-speed stirring mixer, a V-shaped mixer, a ribbon mixer, a screw mixer, a double-arm kneader, Pulverization type kneaders, rotary mixers, airflow type mixers, turbulizers, batch-type Redige mixers, continuous-type Redige mixers, and the like are preferably used.

(Heat treatment)
After the surface cross-linking agent (preferably an aqueous solution thereof) and the water absorbent resin powder are mixed, heat treatment is preferably performed. Conditions for performing the heat treatment are appropriately set according to the crosslinking agent. For example, in the case of an epoxy crosslinking agent such as a glycidyl ether compound or an ion-reactive crosslinking agent, the temperature of the water-absorbent resin powder or the heat used for the heat treatment. The temperature of the medium is preferably 60 to 250 ° C, more preferably 60 to 150 ° C, still more preferably 80 to 120 ° C. The heating time for the heat treatment is preferably 1 minute to 2 hours. Preferable examples of the combination of the heating temperature and the heating time include 0.1 to 1.5 hours at 180 ° C. and 0.1 to 1 hour at 100 ° C.

  In the case where a dehydration-reactive surface cross-linking agent such as oxazolidinone, alkylene carbonate or polyhydric alcohol is used as the surface cross-linking agent, the temperature of the water absorbent resin powder or the temperature of the heat medium used for the heat treatment is preferably 100 to 250. ° C, more preferably 150 to 250 ° C, and still more preferably 170 to 210 ° C. When alkylene carbonate or polyhydric alcohol is used as the surface cross-linking agent and heating is performed within the temperature range, from the viewpoint of the powdering rate described later in (3-7) after surface cross-linking, preferably (3- In 6), the water content of the particulate water-absorbing agent described later is adjusted.

  Further, when the water-absorbing resin powder is obtained by reverse phase suspension polymerization, during the azeotropic dehydration after the completion of the polymerization and / or after the azeotropic dehydration, for example, the water content of the hydrogel is 50% by weight or less, When it is preferably 40% by weight or less, more preferably 30% by weight or less (the lower limit is preferably 5% by weight or more, more preferably 10% by weight or more, particularly preferably 15% by weight or more). The surface-crosslinked water-absorbent resin particles can be obtained by dispersing the surface cross-linking agent, preferably a glycidyl ether compound, in the hydrophobic organic solvent used in (1).

(Moisture content after surface crosslinking)
In the above-described surface cross-linking, particularly dehydration-reactive surface cross-linking agent (dehydration-reactive cross-linking agent) or high-temperature surface cross-linking (eg, 150 to 250 ° C.), the water-absorbing resin obtained has high physical properties (particularly high AAP). Most of the water in the water-absorbing resin existing after the drying step and the water added to the water-absorbing resin as a solvent for the crosslinking agent are removed. For this reason, the water content of the water-absorbent resin after the surface crosslinking reaction is usually as low as 0 to 5% by weight, further 0 to 3% by weight, and further 0 to 1% by weight. Therefore, generally high water absorption and high water content are not compatible. Therefore, in the prior art, a technique of adding water after high-temperature surface cross-linking has also been proposed. However, when water is added, adhesion between water-absorbing resin particles is expressed, and it can be stably produced in the production process. Have difficulty.

  That is, such a low water content water-absorbing resin has a problem of impact resistance stability, and a technique of adding about several percent of water to the water-absorbing resin after surface crosslinking (also known as rehumidification) has been proposed. However, when water is added, an adhesive force is generated between the particles, and when the amount of water added increases, the load on the mixer increases and the mixing device often stops, and mixing aids (eg, inorganic salts) Addition has a problem that the physical properties of the water-absorbent resin (for example, water absorption capacity under pressure) are lowered.

  In order to solve such a problem, in the production method of the present invention, a water-insoluble or poorly water-soluble compound selected from a long-chain alkyl compound, an organic polysiloxane, and an organic polymer compound, particularly a fatty acid (salt) is an essential component, and the compound The water content of the water-absorbent resin or the particulate water-absorbing agent can be adjusted to a predetermined range (preferably 5 to 20% by weight) by adding water at the same time or after the addition. Therefore, in the present invention, a predetermined amount of water is added to the surface-crosslinked water-absorbing resin having a low water content (0 to 5% by weight, further 0 to 3% by weight, further 0 to 1% by weight) (rehumidification). However, it is preferable because uniform water mixing can be performed, and the deterioration of physical properties after surface crosslinking (derived from rehumidification) is substantially small. The addition of water at the same time as the addition of the compound refers to the addition of the compound powder and water to the water-absorbent resin at the same time as well as addition in the form of an aqueous dispersion or an aqueous solution.

(2-2) Step of adding a water-insoluble or poorly water-soluble compound selected from a long-chain alkyl compound, an organic polysiloxane, and an organic polymer compound, in particular, a step of adding a long-chain alkyl compound or an organic polysiloxane In the production method of the present invention, 0.001 to 5% by weight of a water-insoluble or poorly water-soluble compound selected from a long-chain alkyl compound, an organic polysiloxane, and an organic polymer compound with respect to the water-absorbing resin before or after drying after polymerization (in the case of metal soap, however) 0.001% by weight or more and less than 1.0% by weight) is further included.

  In the present invention, a long-chain alkyl compound or an organic polysiloxane is preferably added as a water-insoluble or hardly water-soluble compound, and a fatty acid (salt) is preferably added as a long-chain alkyl compound. This will be described in more detail below.

  Hereinafter, although description of water-insoluble or poorly water-soluble organic polymer compounds such as (2-2-1) to (2-2-3) is omitted as necessary, water-insoluble or poorly water-soluble long-chain alkyl compounds or organic compounds are omitted. It can be applied in the same manner as polysiloxane. Further, in long-chain alkyl compounds and organic polysiloxanes, water insolubility or poor water solubility is essential, but such description is also omitted if necessary.

(2-2-1) Method of addition The above long-chain alkyl compound or organic polysiloxane (and water-insoluble or poorly water-soluble organic polymer compound, hereinafter omitted) is (1) dissolved in warm water or an organic solvent as a solution. A method of adding, (2) a method of dry blending as a powder, (3) a method of dry blending as a powder, and then heating and fixing to a melting point or higher, and (4) a suspension as an aqueous dispersion of fine powder (5) If the long-chain alkyl compound or the organic polysiloxane is in a liquid state at room temperature or warm, it absorbs water. A method of directly adding to the functional resin can also be employed. More preferably, a compound having a melting point or Tg in the following range may be melted and mixed.

  The “aqueous dispersion” is a long-chain alkyl compound or organic polysiloxane that is uniformly dispersed in water using a dispersion stabilizer and has fluidity. Examples of the form include slurry, suspension, and emulsified liquid. The upper limit of the viscosity is about 10,000 cps (25 ° C.). However, even if the viscosity is low, there is no problem and the viscosity may be substantially the same as that of water.

  Furthermore, when the long-chain alkyl compound or the organic polysiloxane is produced in an aqueous dispersion state, it can be used as it is without being dried, or it can be used after being concentrated or diluted to some extent. Among these, the method of adding in the form of an aqueous dispersion or a solution is preferable to the dry blend method in which deterioration of the working environment due to dust and the risk of dust explosion are a concern. However, the preferred addition method varies depending on the form of the long-chain alkyl compound or organic polysiloxane used.

(Mixing device)
In the present invention, an apparatus for mixing the water-absorbing resin with a long-chain alkyl compound or organic polysiloxane, a chelating agent, a surfactant (or a solution or dispersion thereof) is not particularly limited. Type mixer, screw type mixer, screw type extruder, turbulizer, nauter type mixer, V type mixer, ribbon type mixer, double arm type kneader, fluid type mixer, air flow type mixer, rotating disk Examples thereof include a type mixer, a roll mixer, a rolling mixer, and a Redige mixer. Moreover, as a mixing form, although a continuous type, a batch type, or these combined use is employable, continuous mixing is more preferable from a viewpoint of production efficiency.

  As the mixing device, a rotary mixer is generally used, and the number of rotations is not particularly limited as long as the water-absorbent resin is not damaged, and is preferably 5 to 3000 rpm, preferably 10 to 500 rpm. Is more preferable, and 15-300 rpm is still more preferable. When the said rotation speed exceeds 3000 rpm, since the dust of a water absorbing resin generate | occur | produces and water absorption performance falls, it is unpreferable. On the other hand, when the rotational speed is less than 5 rpm, the mixing property is insufficient and the intended effect of improving the hygroscopic fluidity cannot be obtained.

  Moreover, especially the powder temperature of the water absorbing resin at the time of mixing is although it does not restrict | limit, Room temperature-120 degreeC is preferable, 50-100 degreeC is more preferable, 50-80 degreeC is further more preferable. When the said powder temperature exceeds 120 degreeC, since the added water evaporates and in order to obtain the target moisture content, a lot of water is needed, and also the load of a mixing apparatus increases, which is not preferable.

  The mixing time is not particularly limited, but is preferably 1 second to 20 minutes, more preferably 10 seconds to 10 minutes, and further preferably 20 seconds to 5 minutes. When the mixing time exceeds 20 minutes, it is not possible to obtain an effect commensurate with it, and conversely promote the powdering of the water-absorbent resin, and the amount of fine powder (fine particles passing through a sieve having an opening of 150 μm) and Since the amount of dust increases, it is not preferable.

(2-2-2) Addition time The addition of the long-chain alkyl compound or organic polysiloxane (and water-insoluble or poorly water-soluble organic polymer compound, hereinafter omitted) exhibits the effects of the present invention. As long as it can be added at any stage of the production process of the water-absorbent resin or the particulate water-absorbing agent, it is preferably any one of the following steps (A) to (F) or a plurality of steps. Preferably, it can be added in any one or a plurality of steps of the following step (D), step (E) and step (F).

  Step (A): A step of preparing an aqueous monomer solution mainly composed of acrylic acid (salt).

  Step (B): A step of adding a polymerization initiator to the aqueous monomer solution obtained in the step (A) or irradiating active energy rays such as ultraviolet rays to cross-link the aqueous monomer solution.

  Step (C): a step of crushing the hydrogel crosslinked polymer obtained in step (B) and neutralizing at the same time as crushing or after crushing, if necessary.

  Step (D): A step of drying the hydrogel after the steps (A) to (C) and obtaining water-absorbent resin powder through pulverization and classification as necessary.

  Step (E): A step of surface cross-linking the water-absorbent resin powder obtained in Step (D).

  Step (F): Step of obtaining a product by adding water or an aqueous solution and granulating after surface cross-linking in step (E).

  In addition, in the manufacturing method of the particulate water-absorbing agent according to the present invention, the polymerization step and the drying step are essential steps, but the above steps (A) to (F) are not necessarily essential steps. In addition, there may be other steps such as a deaeration step, a granulation step, and other modifier addition steps.

(2-2-3) “Curing” and “Curing process”
In the above addition, a long-chain alkyl compound or organic polysiloxane (and a water-insoluble or poorly water-soluble organic polymer compound, hereinafter omitted), a surfactant, a chelating agent, etc. are added to the water-absorbent resin as an aqueous solution or aqueous dispersion. In this case, the water-absorbing resin becomes a wet wet product due to the action of water, but then becomes a dry dry product by absorbing water. Here, it is sometimes referred to as “curing” or “curing step” for abbreviated that the particle surface is dried by standing or heating for a predetermined time and the particles are lightly aggregated. Further, the aggregated particles may be referred to as “cured product”. Therefore, when water is used to add a long-chain alkyl compound or organic polysiloxane, a surfactant, a chelating agent, etc., it is preferably heated at a predetermined temperature (for example, 40 to 150 ° C.), or at a room temperature for a predetermined time or in a heated state. Is allowed to pass through the curing step (for example, 1 minute to 3 hours). It is preferable because the water-absorbent resin fine powder can be reduced by agglomeration (also known as granulation) in the curing step.

  The fluidity of the dried (Dry) water-absorbent resin powder after curing can be defined by the Flow-Rate specified by ERT450.2-02, and the lightly agglomerated water-absorbent resin powder is crushed and classified as necessary. Thus, for example, it is preferable that the water absorbent resin powder (particulate water absorbing agent) is 30 [g / s] or less, further 20 [g / s] or less, and further 15 [g / s] or less. The wet water-absorbent resin powder after the addition of the aqueous dispersion may be left for a predetermined time or heated (or dried by heating) until it falls within the Flow-Rate range, and further crushed and classified as necessary.

(2-2-4) Addition amount of water-insoluble or poorly water-soluble compound selected from long-chain alkyl compounds, organic polysiloxanes, and organic polymer compounds, particularly addition amounts of long-chain alkyl compounds, organic polysiloxanes, etc. The content of the long-chain alkyl compound or organic polysiloxane (and water-insoluble or poorly water-soluble organic polymer compound, hereinafter omitted) contained in the particulate water-absorbing agent and / or the amount added to the water-absorbing resin is 0.001-5 weight% is preferable with respect to acrylic acid (salt) type water-absorbing resin, 0.002-3 weight% is more preferable, 0.01-2 weight% is further more preferable, 0.05-1 weight% % (Further 0.9% by weight, especially 0.8% by weight, especially 0.6% by weight) is particularly preferred.

  It is preferable to make the content and / or addition amount within the above range because the moisture absorption fluidity is drastically improved and the load on the mixer in the granulation step is greatly reduced. However, when using a metal soap, as will be described later in (2-7), the upper limit is preferably less than 1.0% by weight and more preferably 0.9% by weight or less from the viewpoint of effects and dust. In particular, it is more preferably 0.8% by weight or less, particularly 0.6% by weight or less.

  When the long-chain alkyl compound or organic polysiloxane is added as an aqueous dispersion, the amount of water added is preferably 3 to 25% by weight, more preferably 3 to 20% by weight, based on the water-absorbent resin. 5 to 10% by weight is more preferable. Furthermore, about the dispersion stabilizer added simultaneously or separately with a fatty acid (salt), 0.0001 to 1 weight% is preferable with respect to a water absorbing resin, and 0.0001 to 0.5 weight% is more preferable. That is, when the particulate water-absorbing agent according to the present invention is obtained by adding a long-chain alkyl compound or an organic polysiloxane and water to a water-absorbing resin, the preferred addition amount thereof is a long amount relative to the water-absorbing resin. The chain alkyl compound or organic polysiloxane is 0.001 to 5% by weight, water is 3 to 25% by weight, and the dispersion stabilizer is 0.0001 to 1% by weight.

  Further, when the long-chain alkyl compound or organic polysiloxane is added as an aqueous dispersion, the concentration of the long-chain alkyl compound or organic polysiloxane contained in the aqueous dispersion is preferably 1 to 90% by weight, and 1 to 60% by weight. % Is more preferable, 1 to 40% by weight is further preferable, and the concentration of the dispersion stabilizer contained in the aqueous dispersion is preferably 0 to 10% by weight, more preferably 0 to 5% by weight, and 0 to 3% by weight. % Is more preferable.

  Moreover, when adding the said long-chain alkyl compound or organic polysiloxane as a (water) solution, the mixed solution of water or water, and an organic solvent is used as a solvent. In this case, the amount of added water or a mixed solvent of water and an organic solvent is preferably 3 to 25% by weight, more preferably 3 to 20% by weight, and more preferably 5 to 10% by weight with respect to the water absorbent resin. Further preferred. Further, the concentration of the fatty acid (salt) contained in the (water) solution is preferably 1 to 90% by weight, more preferably 1 to 60% by weight, and further preferably 1 to 40% by weight. The solvent may be removed by drying if necessary.

  Thus, a long-chain alkyl compound or organic polysiloxane, water, a dispersion stabilizer, or an aqueous dispersion or (water) solution of a long-chain alkyl compound or organic polysiloxane is added within the above range, and the water content described later By controlling so that it may become a rate, the impact-resistant stability and pulverization rate of a particulate water-absorbing agent improve dramatically.

(2-2-5) Long-chain alkyl compound, organic polysiloxane, organic polymer compound In the particulate water-absorbing agent and method for producing the same according to the present invention, a long-chain alkyl compound, organic polysiloxane, or organic polymer compound is selected. A water-insoluble or poorly water-soluble compound is essential. By using a long-chain alkyl compound or an organic polysiloxane, the moisture absorption blocking rate described later in (3-2) can be controlled to be low, and unlike conventional inorganic fine particles (for example, silica fine powder powder), Since there is almost no drop in the water absorption capacity under pressure (AAP), both the moisture absorption blocking rate and the water absorption capacity under pressure (AAP) can be achieved.

  Hereinafter, the long-chain alkyl compound or the organic polysiloxane will be further described.

(Insoluble or sparingly soluble in water)
The long-chain alkyl compound or organic polysiloxane according to the present invention (and water-insoluble or poorly water-soluble organic polymer compound, hereinafter omitted) is preferably insoluble or hardly soluble, and the solubility in deionized water is, for example, , 0 to 10 [g / L] is preferable, 0 to 5 [g / L] is more preferable, 0 to 2 [g / L] is more preferable to 1 L of deionized water at 20 ± 1 ° C. 1 [g / L], more preferably 0 to 0.5 [g / L] is particularly preferable. When the solubility exceeds 10 [g / L], a long-chain alkyl compound or an organic polysiloxane may be eluted in urine or blood, which is not preferable.

(Long chain alkyl)
Among these long-chain alkyl compounds, organic polysiloxanes, and organic polymer compounds, 90% by weight or more is preferably a compound having a long-chain hydrocarbon chain (long-chain alkyl) having 8 to 30 carbon atoms. Is more preferably 10-25, and still more preferably 12-20. When the number of carbon atoms is 7 or less, the effect of improving the powder fluidity at the time of moisture absorption decreases, which is not preferable. Moreover, when the said carbon number is 31 or more, since acquisition is difficult and there exists a possibility that the absorption performance of the particulate water absorbing agent in high salt concentration may fall, it is not preferable. The long-chain alkyl compound is preferably a non-polymer compound, and the following compounds can be suitably used.
(Organic polysiloxane)
The organic polysiloxane according to the present invention is a general term for compounds having a siloxane bond (Si—O—Si) in the main skeleton, and the main skeleton (silicone chain) may have a linear structure, a branched structure, or a cyclic structure. Is an organic polysiloxane having a linear structure or a branched structure, more preferably a methyl group, a phenyl group, or the like at the terminal or side chain (lateral branch) such as dimethylsiloxane, methylphenylsiloxane, methylhydrogensiloxane, etc. An organic polysiloxane having an organic group, preferably an alkyl group, more preferably a methyl group, is used. More preferably, a substituent other than an alkyl group is separately added to the side chain, one end, both ends, the side chain and both ends. The modified polysiloxane is used.

  The organic polysiloxanes introduced with substituents include amino modification, monoamine modification, diamine modification, epoxy modification, cycloaliphatic epoxy modification, carbinol modification, mercapto modification, carbosyl modification, amino polyether modification, epoxy polyether modification, epoxy "Organic polysiloxanes with reactive organic groups" such as aralkyl modification; polyether modification, methoxy polyether modification, aralkyl modification, fluoroalkyl modification, long chain alkyl modification, higher fatty acid ester modification, higher fatty acid amide modification, phenol modification And “organopolysiloxane having a non-reactive organic group introduced” such as long-chain alkyl / aralkyl modification.

  In general, a molecule having a linear structure having a siloxane bond number of 2000 or less exhibits oil properties, and a molecule having a linear structure having a siloxane bond number of 5000 to 10,000 shows rubber properties. A relatively low-molecular-weight monomer having a main monomer bond number of 10 (or 20) or less is sometimes called polysiloxane or simply siloxane. In the present invention, the main skeleton has a siloxane bond (Si—O—). The compounds having Si) are collectively called organic polysiloxane.

(Functional group)
Furthermore, the long-chain alkyl compound or the long-chain hydrocarbon chain of the organic polysiloxane used in the present invention is not particularly limited, and may be a saturated hydrocarbon chain or an unsaturated hydrocarbon chain. However, when a long-chain hydrocarbon chain having an unsaturated bond is used, problems such as color deterioration and odor will occur if the resulting particulate water-absorbing agent is subjected to heat or oxidation during storage. More preferred.

  The long-chain alkyl compound preferably has a carbon number within the above range, specifically, a saturated or unsaturated fatty acid, aliphatic alcohol, aliphatic amine, aliphatic amino acid, aliphatic amide is preferable, Fatty acids are more preferred. The acid group may be a salt. Among these, a long-chain alkyl compound is preferable, and a long-chain alkyl compound that has a hydrophilic functional group and is solid or liquid at room temperature. That is, in the present invention, as the long-chain alkyl compound, preferably a long-chain alkylcarboxylic acid or a salt or ester thereof, a long-chain alkylamide is used, or a fatty acid, a salt or ester thereof, or a fatty acid amide is used. Fatty acids and their salts or esters, especially fatty acids and their salts are used. Further, the long-chain alkyl compound has the above-mentioned number of carbon atoms, preferably solid at normal temperature, and further has a melting point described later.

  Further, organic polysiloxanes are preferable, and organic polysiloxanes having a hydrophilic functional group that are solid or liquid at room temperature are preferable, and liquid organic polysiloxanes are more preferable.

  A preferred functional group is a hydrophilic functional group, and among them, at least one hydrophilic functional group among a hydroxyl group, a carboxyl group, a sulfonic acid group, a phosphoric acid group, an amino group, an imino group, and an amide group.

  One or more functional groups may be present in the molecule, or a plurality of different functional groups may be present. In the case of a non-polymeric compound, it preferably has 1 to 3, more preferably 1 to 2, and still more preferably one functional group in the molecule. In particular, a long-chain alkyl compound or an organic polysiloxane in which the hydrophilic functional group is a carboxyl group is used.

  90% by weight or more of the long-chain alkyl compound has a long-chain hydrocarbon chain having 8 to 30 carbon atoms. The acid group may be unneutralized, may be a monovalent salt, may be a polyvalent metal salt, and the polyvalent metal salt is one or more compounds selected from barium, calcium, magnesium, aluminum, and zinc salts It may be. The hydrophilic functional group may be a monovalent salt of an acid group, specifically, an alkali metal salt or an ammonium salt.

(Powder or liquid)
These compounds further coat the surface of the water-absorbent resin. The compound may be coated with a water-absorbent resin as a powder, and when the compound is liquid or solution, the compound may be coated with a water-absorbent resin as a film.

  In order to solve the problem, the long-chain alkyl compound or the organopolysiloxane is liquid or solid at room temperature. In particular, in the case of the long-chain alkyl compound, the long-chain alkyl compound is solid at room temperature, and is further in a water-insoluble or hardly water-soluble powder form. More preferably. The particle diameter of these compounds is not particularly limited, but the median diameter is more than 0, preferably less than 100 μm, more preferably 0.01 μm or more and less than 50 μm, further preferably 0.01 μm or more and less than 10 μm.

  In general, the particle diameter of the long-chain alkyl compound or organic polysiloxane is preferably smaller than the weight average particle diameter (D50) of the water-absorbent resin. The “median diameter” refers to a particle diameter corresponding to 50% of the cumulative distribution curve. A cumulative curve is obtained when the entire particle is regarded as one group and the total volume is 100%. % Particle diameter (cumulative average diameter). The median diameter is measured by dispersing metal soap in a solvent such as methyl alcohol using a particle size distribution measuring device such as LS-920 manufactured by Horiba, Ltd.

(Melting point)
The melting point of the long-chain alkyl compound (or organic polysiloxane) according to the present invention (or Tg of the organic polymer compound) is preferably 20 to 350 ° C, more preferably 40 to 350 ° C, still more preferably 50 to 350 ° C, 60-350 degreeC is still more preferable, 70-350 degreeC is especially preferable, and 80-350 degreeC is the most preferable. The organic polysiloxane may be solid at room temperature, but a compound that is liquid at room temperature is preferably used. When the melting point is less than 20 ° C. for a long-chain alkyl compound or the like, the powder fluidity of the resulting particulate water-absorbing agent is deteriorated and handling properties are lowered, which is not preferable. Moreover, when handling a particulate water-absorbing agent industrially, in order to prevent moisture absorption of a particulate water-absorbing agent, it is preferable to heat and heat a hopper, a transportation pipe, a fixed amount feeder, etc., and heat-and-heat at 30-80 degreeC. A compound having a melting point or Tg in the above range may be melted and mixed.

(2-2-6) Specific long-chain alkyl compound or organic polysiloxane In the present invention, as the long-chain alkyl compound or organic polysiloxane, the above (2-2-4) and (2-2-5) are preferable. A compound having a melting point (or Tg), carbon number, functional group, powder or liquid, long-chain alkyl, or insoluble or hardly soluble in water is used. Specific examples of the compound include long-chain alkyl compounds or organic polysiloxanes. Further, the long-chain alkyl compounds are preferably the following (a) fatty acids and salts thereof, and the organic polysiloxanes are liquid. The organopolysiloxane is preferred.

  Hereinafter, although the long-chain alkyl compound or organic polysiloxane which can be used concretely is illustrated, it is not specifically limited.

(A) Fatty acid and its salt Specifically, as the fatty acid, linear or octylic acid, octynic acid, decanoic acid, lauric acid, myristic acid, palmitic acid, oleic acid, stearic acid, bovine fatty acid, castor fatty acid, etc. Examples include branched chain fatty acids; petroleum acids such as benzoic acid, naphthenic acid, naphthoic acid, and naphthoxyacetic acid; and polymer acids such as poly (meth) acrylic acid and polysulfonic acid. Among these, long chain fatty acids such as octylic acid, octoic acid, decanoic acid, lauric acid, myristic acid, palmitic acid, oleic acid, stearic acid, bovine fatty acid, castor hardened fatty acid are preferable, octylic acid, decanoic acid, lauric acid, Long chain saturated fatty acids having no unsaturated bond such as myristic acid, palmitic acid, stearic acid are more preferable, and long chain saturated fatty acids having 12 to 20 carbon atoms such as lauric acid, myristic acid, palmitic acid, stearic acid are most preferable. .

  The salt of the fatty acid (salt) in the present invention is preferably a metal salt or an ammonium salt, more preferably a divalent or higher polyvalent metal salt or an alkali metal salt, and even more preferably a divalent or higher polyvalent metal salt. . As the alkali metal salt, sodium salt and potassium salt are particularly preferable, and sodium salt is most preferable. The divalent or higher polyvalent metal salt is not particularly limited as long as it is an alkaline earth metal salt, a transition metal salt or the like, but from the viewpoint of availability, barium salt, calcium salt, magnesium salt, aluminum salt Zinc salts are preferable, and calcium salts, magnesium salts, aluminum salts, and zinc salts are more preferable. In the present invention, such a polyvalent metal salt of a fatty acid is sometimes referred to as “metal soap”.

  Specific examples of the fatty acid salts are preferably sodium myristate, sodium palmitate, sodium laurate, sodium stearate, potassium myristate, potassium palmitate, potassium laurate, potassium stearate, calcium laurate, laurin Magnesium oxide, zinc laurate, aluminum laurate, barium laurate, calcium myristate, magnesium myristate, zinc myristate, aluminum myristate, barium myristate, calcium palmitate, magnesium palmitate, zinc palmitate, aluminum palmitate , Barium palmitate, calcium stearate, magnesium stearate, zinc stearate, aluminum stearate, steer Barium phosphate and the like, it can be combined foil and an optional organic acid and a metal salt in limited thereto. Furthermore, the said fatty acid (salt) may use together 1 type, or 2 or more types.

Further, polyvalent metal salts of the above fatty acids (metal soaps) may be partially hydroxides, as its structural formula is represented by (organic ^{acid) xM n + (OH) n} -x , etc. It may have a salt structure. M ^{n +} represents an n-valent metal ion species, and x represents an integer of 1 to n (n ≧ 2).

  The fatty acid (salt) according to the present invention may be a fatty acid or a fatty acid salt as its form, but is preferably a fatty acid salt. In addition, it is not necessary for all of the acid groups to be a salt, and a small amount of an organic acid or an excess salt may be contained, but preferably a salt in which 90 mol% or more of the acid groups (carboxyl groups) are neutralized. More preferably 95 to 105 mol%, further preferably 98 to 102 mol%, particularly preferably 99 to 101 mol% of a neutralized salt.

  The melting point of the fatty acid (salt) may be actually measured, or may be a value described in the Chemical Dictionary (Edited by the Chemical Dictionary, published by Kyoritsu Publishing Co., Ltd.). For example, in the aforementioned chemical dictionary, it is described that zinc stearate: 120 to 130 ° C., aluminum stearate; 103 ° C., calcium stearate; 180 ° C., magnesium stearate; These fatty acids (salts) are preferably applied because they have an optimum melting point for the present invention. Furthermore, since it is possible to adjust the melting point to a desired melting point in a wide range by appropriately selecting a fatty acid (salt), it is preferable to select a fatty acid (salt) having a melting point higher than the use temperature in actual use. .

(A ′) Fatty Acid Ester Further, with respect to the above fatty acid, esters of these carboxylic acids, particularly esters with monohydric or polyhydric alcohols can also be suitably used. Specifically, for example, methyl esters, ethyl esters, polyethylene glycol esters, glycerin esters and the like of these carboxylic acids can be used.

(B) Aliphatic alcohol (aliphatic dihydric alcohol)
Examples of the aliphatic dihydric alcohol include saturated aliphatic dihydric alcohols, meso-2,3-butanediol (melting point: 34.4 ° C.), tetramethylethylene glycol (melting point: 38 ° C.), and hexahydrates thereof. (Melting point 46-47 ° C), hexamethyltrimethylene glycol (melting point 126-128 ° C), 2,2-dimethyl-1,3-butanediol (melting point 10 ° C), 2,2-dimethyl-1,3-pentane Diol (melting point 60-63 ° C.), 2,2,4-trimethyl-1,3-pentanediol (melting point 52 ° C.), 1,4-butanediol (melting point 19 ° C.), 2,5-hexanediol (melting point 43 -44 ° C), 1,6-hexanediol (melting point 42 ° C), 1,8-octanediol (melting point 60 ° C), 1,9-nonanediol (melting point 45 ° C), 1,10-decanediol ( 72-74 ° C), 1,11-undecanediol (melting point 62-62.5 ° C), 1,12-dodecanediol (melting point 79-79.5 ° C), 1,13-tridecanediol (melting point 76.76 ° C). 4-76.6 ° C), 1,14-tetradecanediol (melting point 83-85 ° C), 1,12-octadecanediol (melting point 66-67 ° C), 1,18-octadecanediol (melting point 96-98 ° C), etc. Is mentioned.

(Unsaturated glycol)
Examples of the unsaturated glycol include cis-2,5-dimethyl-3-hexene-2,5-diol (melting point 69 ° C.), cis-2,5-dimethyl-3-hexene-2,5-diol (melting point 77). ° C), meso-2,6-octadiene-4,5-diol (melting point: 23-24 ° C), racemic-2,6-octadiene-4,5-diol (melting point: 48 ° C), and the like.

(Polyethylene glycol)
Semi-solid, waxy or waxy solid polyethylene glycol at room temperature includes PEG 600 (melting point 15 to 25 ° C.), PEG 1000 (melting point 35 to 40 ° C.), PEG 3000 to 4000 (melting point 53 to 56 ° C.), PEG 5000 to 7000 ( Melting point 58-62 ° C.).

(Saturated trihydric alcohol)
Examples of the saturated trihydric alcohol include glycerin (melting point: 18 ° C.), 2-methyl-2,3,4-butanetriol (melting point: 49 ° C.), 2,3,4-hexanetriol (melting point: 47 ° C.), 2,4 -Dimethyl-2,3,4-hexanetriol (melting point: 75 ° C.), dimethylpentaneglycerol (melting point: 83 ° C.), 2,4-dimethyl-2,3,4-pentanetriol (melting point: 99 ° C.) and the like.

(Saturated tetrahydric alcohol)
Examples of the saturated tetrahydric alcohol include 1,2,4,5-hexanetetrol (melting point 88 ° C.), 1,2,5,6-hexanetetrol (melting point 96 ° C.) and the like.

(Aliphatic monohydric alcohol)
The aliphatic monohydric alcohol that is solid at room temperature is a saturated aliphatic monohydric alcohol, lauryl alcohol (melting point: 24 ° C.), myristyl alcohol (melting point: 38 ° C.), cetyl alcohol (49 ° C.), stearyl alcohol (melting point: 58.degree. 5 ° C.), neopentyl alcohol (melting point 52-53 ° C.), n-eicosyl alcohol (melting point 63.5 ° C.), n-hexacosyl alcohol (melting point 79.5 ° C.), and unsaturated aliphatic monovalent Examples include 2,4-pentadiin-1-ol (melting point: 26 to 28 ° C.) which is alcohol.

(C) Aliphatic amine Examples of the aliphatic amine that is solid at room temperature include diamine compounds such as ethylenediamine (melting point 8.5 ° C), tetramethylenediamine (melting point 27 ° C), hexamethylenediamine (melting point 42 ° C), hepta. Examples include methylene diamine (melting point: 28 to 29 ° C.), octamethylene diamine (melting point: 52 ° C.), nonamethylene diamine (melting point: 37.5 ° C.), and the like.

(D) Aliphatic amino alcohol As aliphatic amino alcohol solid at room temperature, diisopropanolamine (melting point: 43 ° C), triisopropanolamine (melting point: 57.2 ° C), 1-aminopentan-5-ol (melting point: 36 ° C) ) And the like.

(E) Aliphatic ether Examples of the aliphatic ether that is solid at room temperature include dicetyl ether (melting point: 55 ° C.), isoamyl cetyl ether (melting point: 30 ° C.), and the like.

(F) Aliphatic sulfonic acid As the aliphatic sulfonic acid that is solid at normal temperature, n-pentanesulfonic acid (melting point: 15.9 ° C.) and n-hexanesulfonic acid (melting point: 16.1 ° C.), which are alkanesulfonic acid compounds. N-nonanesulfonic acid (melting point 46 ° C.), n-decanesulfonic acid (melting point 46.5 ° C.), n-undecanesulfonic acid (melting point 52 ° C.), n-dodecanesulfonic acid (melting point 58 ° C.), and the like. .

(G) Aliphatic ketone Solid aliphatic ketones at room temperature include di-n-hexyl ketone (melting point: 31 ° C.), di-n-heptyl ketone (melting point: 41 ° C.), and methyl-n-nonyl ketone (melting point: 15 ° C.). Methyl-n-decyl ketone (melting point 21 ° C.), methyl-n-undecyl ketone (melting point 29 ° C.), methyl-n-dodecyl ketone (melting point 34 ° C.), methyl-n-tridecyl ketone (melting point 39 ° C.), etc. Is mentioned.

(H) Polyvalent amine compound As the polyvalent amine compound, diamine compounds such as ethylenediamine (melting point 8.5 ° C), tetramethylenediamine (melting point 27 ° C), hexamethylenediamine (melting point 42 ° C), heptamethylenediamine ( Melting point 28-29 ° C), octamethylenediamine (melting point 52 ° C), nonamethylenediamine (melting point 37.5 ° C), and the like.

(I) Unsubstituted long-chain alkyl compound Examples of the unsubstituted long-chain alkyl compound include higher aliphatic hydrocarbons such as n-dodecane, n-hexadecane, and n-heptadecane.

(J) Amide compound Examples of the amide compound include higher fatty acid amides such as lauric acid amide, oleic acid amide, and erucic acid amide.

(K) Organic polymer compound With respect to the long-chain alkyl compound that is a non-polymer compound such as the above (a) to (j), a water-insoluble or hardly water-soluble organic polymer compound is preferably a thermoplastic polymer. Used, for example, polyethylene, polystyrene, ethylene / alkyl methacrylic acid copolymer (EMA), polypropylene, polyurethane, ethylene / acrylic acid copolymer (EAA), ethylene / vinyl acetate copolymer, oxidation-modified polyethylene, maleic anhydride-modified polyethylene, Polyolefins such as maleic anhydride-modified polybutadiene and maleic anhydride-modified EPDM (ethylene, propylene, diene, terpolymer); polyamides such as nylon; polyesters such as polyethylene terephthalate; cellulose acetate, cellulose propionate And cellulose derivatives such as cellulose butyrate, ethyl cellulose, benzyl cellulose, and ethyl hydroxyethyl cellulose.

(Organic polysiloxane)
In the present invention, the organic polysiloxane is a solid or liquid at room temperature as a water-insoluble or poorly water-soluble organic silicone polymer with respect to the long-chain alkyl compound that is a non-polymer compound such as the above (a) to (j). Preferably, it may be liquid at normal temperature, and as described above, it may be an organic polysiloxane that is not reactive with the water-absorbing resin, or may be a reactive organic polysiloxane, preferably a modified polysiloxane. Is used. The organic polysiloxane may be a compound that acts as a surfactant by containing a hydrophilic group such as polyoxyethylene. The preferred solubility, degree of polymerization, and functional group of the organic polysiloxane in water are as described above.

  Non-reactive organopolysiloxanes include, for example, dimethyl silicone oil, methyl hydrogen silicone oil, methyl phenyl silicone oil, cyclic dimethyl silicone oil, polyether modified silicone oil, carboxyl modified silicone oil, alkyl modified silicone oil, alkoxy Examples include modified silicone oil. Two or more of these can be used in combination. An organic polysiloxane in the form of an emulsion obtained by emulsifying these in water can also be suitably used in the present invention. Dimethyl silicone oil and polyether-modified silicone oil (polyoxyalkylene-modified silicone compound) are more preferable.

  Examples of the reactive organic polysiloxane include silicone oils having at least one functional group that reacts with a carboxylic acid (salt) group. Specifically, amino-modified silicone oil, epoxy-modified silicone oil, carbinol-modified Examples thereof include silicone oil, phenol-modified silicone oil, mercapto-modified silicone oil, and the like. More preferred are amino-modified silicone oils and epoxy-modified silicone oils that can react with carboxylic acid (salt) groups at relatively low temperatures. Particularly preferred organic polysiloxanes having reactivity are amino-modified silicone oils in that they can react with carboxylic acid (salt) groups at room temperature.

As an amino-modified silicone oil, -R1NR2R3 (wherein R1 is an alkylene group having 1 to 12 carbon atoms, R2, R3 is H or an alkyl group having 1 to 12 carbon atoms) at the terminal and / or in the molecule of the silicone polymer molecule. Examples include amino-modified silicone oils having the indicated groups. In the alkylene group and / or alkyl group, one or more hydrogen atoms may be substituted with an OH group, a COOH group, an NH ₂ group, or the like. When the number of carbon atoms is 2 or more, a carbon-carbon bond An ether bond containing an oxygen atom may be included in between.

  Examples of the epoxy-modified silicone oil include an epoxy-modified silicone oil having a group represented by —RX (where R is an alkylene group having 1 to 12 carbon atoms, X is an epoxy group) in the terminal and / or molecule of the silicone polymer molecule. Is exemplified. In the alkylene group, one or more hydrogen atoms may be substituted with an OH group, a COOH group, or the like. When the number of carbon atoms is 2 or more, an ether containing an oxygen atom between carbon-carbon bonds. Bonds may be included.

  When the polyoxyalkylene-modified silicone compound is used in the present invention, specifically, for example, polyoxyethylene-modified dimethylpolysiloxane, polyoxyethylene / polyoxypropylene block or random copolymer-modified dimethylpolysiloxane, A dimethylpolysiloxane modified with polyoxyethylene having an alkyl group having 1 to 12 carbon atoms at the terminal, or a block or random copolymer of polyoxyethylene / polyoxypropylene having an alkyl group having 1 to 12 carbon atoms at the terminal Examples thereof include modified dimethylpolysiloxane, the above-mentioned polyoxyalkylene-modified products of dimethylpolysiloxane derivatives having amino groups, epoxy groups and the like at the terminals and / or inside the molecules of dimethylpolysiloxane. More preferably, it is polyoxyethylene-modified dimethylpolysiloxane, polyoxyethylene / polyoxypropylene block or random copolymer-modified dimethylpolysiloxane, and more preferably polyoxyethylene-modified dimethylpolysiloxane because it can be obtained industrially at low cost. Oxyethylene-modified dimethylpolysiloxane. The ratio of the oxyethylene group to the oxypropylene group is not particularly limited as long as the content of the polyoxyethylene group is within the above range, but is usually (100 to 50): (0 to 50), preferably (100 to 60): (0 to 40).

  The number of reactive functional groups of the organic polysiloxane having reactivity may be usually one or more in one molecule of silicone oil. However, it is preferable to have two or more reactive functional groups for the purpose of crosslinking the vicinity of the surface of the resin particles. Furthermore, the number of a preferable reactive functional group is 2-20 from a viewpoint of performing efficient bridge | crosslinking. Moreover, as a position of a reactive functional group, any of the terminal of a silicone polymer molecule, a side chain, or both of a terminal and a side chain may be sufficient.

  The organic polysiloxane may be liquid at normal temperature, and the molecular weight is not particularly limited, but is preferably 1000 or more, more preferably 3000 or more. The upper limit of the molecular weight of the organic polysiloxane is not particularly limited, but is usually about 1 million, more preferably about 100,000, and further preferably about 20,000. It is preferable to use an organic polysiloxane having a molecular weight of 1000 or more because there is no possibility that the moisture absorption blocking rate and the dustiness will deteriorate over time. If the molecular weight or degree of polymerization is low, it may have to be used in large quantities. On the other hand, if the molecular weight or degree of polymerization is too high, the viscosity or melting point will not be too high and uniform processing will be easy. There is also.

  The surface tension is not particularly limited, but is preferably 18 to 30 [dyne / cm], more preferably 20 to 26 [dyne / cm]. The viscosity is not particularly limited as long as it is liquid at normal temperature, but it is preferably 10 to 20000 centistokes [cst] at normal temperature (25 ° C.), and particularly preferably, it is not necessary to dilute with solvents and absorbs water. 30 to 1000 [cst] in that mixing with a functional resin is easy.

  Organopolysiloxanes also use linear dimethylpolysiloxanes as the base polymer, and their end groups can be blocked in different ways (“Chemieund Technology des Kalthaertenden Siliconcoattchus” [“Chemistry and Technoltechnoltechnol technol technol”). 48-64, SILICONE-Chemieund Technology [SILICONES-Chemistry and technology], [Symposium, April 28, 1989], Vulcan Publishing, Essen).

(2-2-7) Dispersion stabilizer In the particulate water-absorbing agent of the present invention and the method for producing the same, when a long-chain alkyl compound or an organic polysiloxane is used as an aqueous dispersion, it is stable in a colloidal form without being aggregated in water. It is preferable to use a dispersion stabilizer in order to disperse mechanically. The dispersion stabilizer is not particularly limited as long as it is a dispersion stabilizer that has been conventionally used for stably dispersing water-insoluble fine particles in water, and examples thereof include water-soluble polymers and hydrophilic properties described below. Organic solvents, surfactants and the like can be mentioned, among which surfactants are preferably used.

(Water-soluble polymer)
In the present invention, the aqueous polymer as the dispersion stabilizer is not particularly limited, and examples thereof include polyvinyl alcohol, starch, (carboxy) methylcellulose, hydroxyethylcellulose, polyacrylic acid (salt) and the like. These water-soluble polymers are preferably dissolved in water (25 ° C.) by 1% by weight or more, more preferably 5% by weight or more, and further preferably 10% by weight or more. The molecular weight is preferably 500 to 50 million, more preferably 1000 to 5 million, and still more preferably 10,000 to 1 million.

(Hydrophilic organic solvent)
In the present invention, the hydrophilic organic solvent as the dispersion stabilizer is not particularly limited, and examples thereof include hydrophilic organic solvents used in combination in the above-described surface crosslinking step. Specifically, ethylene glycol, diethylene glycol, Propylene glycol, triethylene glycol, tetraethylene glycol, polyethylene glycol, 1,3-propanediol, dipropylene glycol, 2,2,4-trimethyl-1,3-pentanediol, polypropylene glycol, glycerin, polyglycerin, 2- Butene-1,4-diol, 1,3-butanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, 1,2-cyclohexanedimethanol, 1,2-cyclohexanol , Trimethylolpropane, die Noruamin, triethanolamine, polyoxyethylene propane, oxyethylene / oxypropylene block copolymer, pentaerythritol, and polyhydric alcohols sorbitol and the like. The polyhydric alcohol preferably has 2 to 10 carbon atoms, and more preferably has 3 to 8 carbon atoms. In these polyhydric alcohols, a part of the hydroxyl groups may be alkoxylated (for example, methoxypolyethylene glycol). Among the polyhydric alcohols, ethylene glycol, propylene glycol, propanediol, pentanediol, hexanediol, glycerin, and trimethylolpropane are more preferable. These may use only 1 type and may use 2 or more types together.

(Surfactant)
When a surfactant is used as a dispersion stabilizer, for example, when a fatty acid (salt) is used, the method disclosed in JP-A-59-219400 and JP-B-4-7260 is used. An aqueous dispersion of (salt) can be produced. Furthermore, commercially available dispersions such as zinc stearate N (Nippon Oil Co., Ltd.), Hydrin Z-7-30, Hydrin O-128 (Chukyo Oil & Fats Co., Ltd.), Fukodisper ZD and Fukodisper C (ADEKA Chemical Supply Co., Ltd.) The body can be used as it is.

(2-3) Surfactant addition step The present invention provides a surfactant for a water-absorbing resin containing a long-chain alkyl compound or an organic polysiloxane (and a water-insoluble or poorly water-soluble organic polymer compound, hereinafter omitted). It is a manufacturing method of the particulate water absorbing agent including the process of adding an agent.

  By adding a surfactant to a water-absorbing resin containing a long-chain alkyl compound or an organic polysiloxane, the 20 wt% saline vertical absorption index of the present invention described later in (3-1) is improved. Was found. The surfactant must be further added after the addition of the long-chain alkyl compound or the organic polysiloxane, and the addition order is simultaneous (simultaneous addition with the surfactant) or reverse (long-chain after the addition of the surfactant). If an alkyl compound or an organic polysiloxane is added), the effect of improving the 20 wt% saline vertical absorption index of the present invention is not substantially observed, and the order of addition is important in the method for producing the particulate water-absorbing agent. It was found that

  In addition, as will be described later in (2-7), the prior application PCT / JP2010 / 066957 (PCT application date; September 29, 2010) discloses simultaneous addition of metal soap and surfactant. In the present invention, however, it was found that the 20 wt% saline vertical absorption index, which is a novel parameter not disclosed in the previous PCT application, is improved in the order of addition.

  Even if a surfactant is added to a water-absorbing resin containing a long-chain alkyl compound or an organic polysiloxane, other physical properties such as CRC and (3-12) described later in (3-11) can be obtained. Even in AAP described later, the improvement effect was not substantially observed, and it was found that it contributes specifically to the 20 wt% saline vertical absorption index.

(Addition amount)
From the viewpoint of improving the 20 wt% saline vertical absorption index, the addition amount of the surfactant is preferably in the range of 0.001 to 1.0 wt% with respect to the polyacrylic acid (salt) water absorbent resin, Furthermore, the range of 0.002 to 0.5% by weight, further 0.003 to 0.2% by weight, further 0.004 to 0.1% by weight, and further 0.005 to 0.05% by weight. Particularly preferred.

  Such a surfactant is preferably used also in the step of adding the long-chain alkyl compound or the organic polysiloxane, and the amount used is similarly in the range of 0.001 to 1.0% by weight, more preferably in the above range. is there.

  Depending on the type and addition amount of the surfactant, the surface tension (N / m) of the resulting particulate water-absorbing agent is excessively reduced, and the amount of liquid returned from the absorbent article (especially paper diapers) (Re -Wet "rewetting") may be increased. Therefore, more preferably, the surface tension of the particulate water-absorbing agent (as defined in US Pat. No. 7,473,739) is 20 (N / m) or more, further 30 (N / m) or more, and further 40 (N / m). ), And further, the type and amount of the surfactant may be selected so as to be in the range of 50 (N / m) or more. The upper limit is about 73 (N / m).

(solution)
The surfactant may be added as it is, but from the viewpoint of physical properties, it is added as a solution, particularly an aqueous solution. By adding it as a solution, it becomes a film-form surfactant on the surface of the water-absorbent resin, and includes the case where the powder compound or liquid compound described in (2-2) is used. It is preferable because the water vertical absorption index is further improved. When the surfactant is added as a solution, the amount of water added is preferably 3 to 25% by weight, more preferably 3 to 20% by weight, and even more preferably 5 to 10% by weight with respect to the water absorbent resin. . Further, when the surfactant is added as a solution, the concentration of the surfactant contained in the solution is preferably 1 to 90% by weight, more preferably 1 to 60% by weight, still more preferably 1 to 40% by weight, and The concentration of the other dispersion stabilizer contained in the solution is preferably 0 to 10% by weight, more preferably 0 to 5% by weight, and still more preferably 0 to 3% by weight. After adding these surfactants and other dispersion stabilizers, the water-absorbent resin may be heated or dried as necessary, or adjusted to a predetermined moisture content (%), as described later. Good.

(Surfactant)
In the present invention, the surfactant as the dispersion stabilizer is not particularly limited, but for example, polyoxyalkylene alkyl such as polyoxyethylene lauryl ether, polyoxyethylene cetyl ether, polyoxyethylene stearyl ether, polyoxyethylene oleyl ether, etc. Ethers; polyoxyalkylene alkyl phenyl ethers such as polyoxyethylene octyl phenyl ether and polyoxyethylene nonyl phenyl ether; polyoxyalkylene alkyl amino ethers such as polyoxyethylene lauryl amino ether and polyoxyethylene stearyl amino ether; sorbitan monolaurate Sorbitan fatty acid esters such as sorbitan monopalmitate, sorbitan monostearate, sorbitan monooleate, poly Polyoxyalkylene sorbitan fatty acid esters such as xylethylene sorbitan monolaurate, polyoxyethylene sorbitan monopalmitate, polyoxyethylene sorbitan monostearate, polyoxyethylene sorbitan monooleate; polyethylene glycol monolaurate, polyethylene glycol monooleate , Polyalkylene glycol fatty acid esters such as polyethylene glycol monostearate, polyethylene glycol dilaurate, and polyethylene glycol distearate; nonionic surfactants typified by glycerin fatty acid esters such as lauric acid monoglyceride, stearic acid monoglyceride, and oleic acid monoglyceride Is used.

  In addition, for example, polyoxyethylene lauryl ether sodium sulfate, polyoxyethylene octyl phenyl ether sodium sulfate, polyoxyethylene nonyl ether sodium sulfate, lauryl sulfate triethanolamine, sodium lauryl sulfate, potassium lauryl sulfate, ammonium lauryl sulfate, and the like. Salts: sulfonic acid salts such as sodium dodecylbenzenesulfonate, sodium alkylnaphthalenesulfonate, sodium dialkylsulfosuccinate; anionic surfactants typified by phosphate ester salts such as potassium alkylphosphate are used.

  Further, for example, a cationic surfactant represented by a quaternary ammonium salt such as lauryltrimethylammonium chloride, stearyltrimethylammonium chloride, cetyltrimethylammonium chloride is used.

  Among these surfactants, nonionic surfactants or anionic surfactants are preferable, and these surfactants may be used alone or in combination of two or more. In particular, from the viewpoint of improving the 20 wt% saline vertical absorption index, the surfactant preferably has a polyoxyethylene unit. In addition, by using or containing the surfactant, process damage due to the transport of the resin particles can be reduced, and physical properties can be maintained high even during actual use.

(Mixing method)
For the mixing of the surfactant, the addition method described in the above (2-2-1) and the mixing device thereof can be used as appropriate. If necessary, the curing step described in the above (2-2-3) and the classification step may be provided.

(2-4) Chelating agent addition step (optional)
In the particulate water-absorbing agent and the method for producing the same according to the present invention, a chelating agent is preferably used. Preferably, the production method further includes a step of adding a chelating agent.

  The chelating agent is not particularly limited as long as the effects of the present invention on coloration with time, increase rate of deteriorated soluble matter, etc. are exhibited, but a water-soluble organic chelating agent is preferable from the viewpoint of availability and handling properties. From the viewpoint of cost-effectiveness, a water-soluble organic chelating agent having a nitrogen atom and / or a phosphorus atom or a water-soluble organic chelating agent having an α-hydroxycarboxylic acid structure is more preferred, and an amino polyvalent carboxylic acid (salt), organic More preferred are water-soluble organic chelating agents selected from polyvalent phosphoric acid (salt), aminopolyvalent phosphoric acid (salt), and α-hydroxycarboxylic acid (salt). Organic polyvalent phosphoric acid (salt), aminopolyvalent phosphorous A water-soluble organic chelating agent selected from acids (salts) and α-hydroxycarboxylic acids (salts) is particularly preferred.

  “Chelating agent” refers to a compound that captures metal ions such as transition metal ions. In the present invention, the weight average molecular weight is preferably 100 from the viewpoint of the effect on polymerization and the physical properties of the resulting particulate water-absorbing agent. An organic chelating agent that is a water-soluble non-polymeric compound of ˜5000, more preferably 100˜2000, even more preferably 100˜1000, particularly preferably 100˜500 is used. When the weight average molecular weight exceeds 5,000, for example, the viscosity of the unsaturated monomer aqueous solution may increase depending on the timing of addition of the chelating agent.

  The solubility of the chelating agent that can be used in the present invention in deionized water is preferably 1 g or more, more preferably 5 g or more, and even more preferably 10 g or more with respect to 100 g of deionized water at 20 ± 1 ° C. 20 g or more is particularly preferable.

(Amino polyvalent carboxylic acid (salt), organic polyvalent phosphoric acid (salt), amino polyvalent phosphoric acid (salt))
As described above, amino polyvalent carboxylic acid (salt), organic polyvalent phosphoric acid (salt), and amino polyvalent phosphoric acid (salt) are preferable examples of the chelating agent of the present invention. Alternatively, an amino polyvalent carboxylic acid (salt) having two or more, preferably three or more, more preferably 3 to 100, further preferably 3 to 20, and particularly preferably 3 to 10 phosphate groups in the molecule. ), Organic polyvalent phosphoric acid (salt) or amino polyvalent phosphoric acid (salt).

  The amino polyvalent carboxylic acid (salt) in the present invention is not particularly limited. For example, iminodiacetic acid, hydroxyethyliminodiacetic acid, nitrilotriacetic acid, nitrilotripropionic acid, ethylenediaminetetraacetic acid, hydroxyethylenediaminetriacetic acid, hexa Methylenediaminetetraacetic acid, diethylenetriaminepentaacetic acid, triethylenetetraminehexaacetic acid, trans-1,2-diaminocyclohexanetetraacetic acid, bis (2-hydroxyethyl) glycine, diaminopropanoltetraacetic acid, ethylenediamine-2-propionic acid, glycol ether diamine Tetraacetic acid, bis (2-hydroxybenzyl) ethylenediaminediacetic acid, ethylenediaminedisuccinic acid, L-glutamic acid diacetic acid, 3-hydroxy-2,2'-iminodisuccinic acid, glycol ether Tetraacetic acid, and methyl glycine diacetic acid and the like salts thereof.

  The organic polyvalent phosphoric acid (salt) or amino polyvalent phosphoric acid (salt) in the present invention is not particularly limited, and examples thereof include hydroxyethylene diphosphate, ethylenediamine-N, N′-di (methylenephosphinic acid), Ethylenediaminetetra (methylphosphinic acid), nitriloacetic acid-di (methylenephosphinic acid), nitriloacetic acid- (methylenephosphinic acid), nitriloacetic acid-6-propionic acid-methylenephosphonic acid, nitrilotris (methylenephosphonic acid), cyclohexanediaminetetra (Methylenephosphonic acid), ethylenediamine-N, N′-diacetic acid-N, N′-di (methylenephosphonic acid), ethylenediamine-N, N′-di (methylenephosphonic acid), ethylenediaminetetra (methylenephosphonic acid), Polymethylenediaminetetra (methylenediamine Acid), diethylenetriamine penta (methylene phosphonic acid), 1-hydroxyethylidene-diphosphonic acid and salts thereof. Among these, one or more kinds can be used. Further, from the viewpoint of water solubility, preferable examples of the salt include alkali metal salts such as sodium salt and potassium salt, ammonium salt, and amine salt.

  Among the above-described chelating agents, amino polyvalent phosphoric acid (salt) having an aminophosphonic acid group is most preferable from the viewpoint of water absorption characteristics (water absorption capacity, increase rate of deteriorated soluble matter, coloration with time, etc.).

(Α-hydroxycarboxylic acid (salt))
As the water-soluble organic chelating agent of the present invention, α-hydroxycarboxylic acid can also be mentioned as a preferred example. Hydroxycarboxylic acid refers to a carboxylic acid having a hydroxyl group in the molecule. In the present invention, α-hydroxycarboxylic acid having a hydroxyl group bonded to carbon at the α-position is preferably used. Among these, α-hydroxycarboxylic acids such as non-polymeric α-hydroxycarboxylic acids are preferable, and aliphatic α-hydroxycarboxylic acids having no cyclic structure or unsaturated group are more preferable. Use of an aromatic α-hydroxycarboxylic acid or an aliphatic α-hydroxycarboxylic acid having a cyclic structure or an unsaturated group is not preferred because these themselves are colored by an oxidation reaction or the like.

  The α-hydroxycarboxylic acid (salt) in the present invention is not particularly limited. For example, lactic acid (salt), citric acid (salt), malic acid (salt), isocitric acid (salt), glyceric acid (salt), Examples thereof include tartaric acid (salt) and D-form, L-form, meso-form and the like thereof. Of these, α-hydroxymonocarboxylic acid such as lactic acid or the like, or preferably two or more, more preferably 2 to 10, more preferably 2 to 6, more preferably 2 or more carboxyl groups in the molecule. Is an α-hydroxy polyvalent carboxylic acid having 2-4. As the α-hydroxy polyvalent carboxylic acid, malic acid (salt), citric acid (salt), isocitric acid (salt), and tartaric acid (salt) are particularly preferably used from the viewpoint of water absorption characteristics and coloring improvement.

  When α-hydroxycarboxylate is used, monovalent salts are preferable from the viewpoint of solubility in water, and alkali metal salts such as lithium, potassium and sodium, ammonium salts, monovalent amine salts and the like are more preferable. . Further, when α-hydroxy polyvalent carboxylic acid is used as a salt, all the carboxyl groups may be used as a salt, or only a part may be used as a salt.

(Method of adding chelating agent)
As the addition method of the chelating agent in the present invention, the addition method described in the above (2-2-1) and the mixing device thereof can be used as appropriate. Specifically, the above-described (1) dissolved in warm water or an organic solvent. And (2) a method of dry blending as a powder, and (4) a method of adding as an aqueous dispersion of fine powder as a suspension. Among these, the method of adding in the form of a solution or an aqueous dispersion is preferable from the viewpoint of fixing to a particulate water-absorbing agent.

  In addition, as for the addition time of the chelating agent, it can be added at any stage of the production process of the water-absorbent resin or the particulate water-absorbing agent, as long as the effect of the present invention is manifested, similar to the above-mentioned time. Is any one or a plurality of steps from the step (A) to the step (F), more preferably the step (A), step (B), step (C), step (E), step (F). ) In any one or a plurality of steps.

(Amount of chelating agent added)
The content of the chelating agent contained in the particulate water-absorbing agent according to the present invention and / or the addition amount of the chelating agent added to the water-absorbing resin is an effect on the coloration with time and the rate of increase in the deteriorated soluble content of the present invention. However, 0.001 to 5% by weight is preferable with respect to the polyacrylic acid (salt) water-absorbing resin, 0.0025 to 5% by weight is more preferable, and 0.005 to 3 is preferable. More preferred is weight percent.

  However, since the necessary amount for obtaining the effect of the present invention varies depending on the type of chelating agent, more specifically, from the viewpoint of cost, organic polyvalent phosphoric acid (salt), amino polyvalent phosphoric acid (salt) In some cases, since the effect is exhibited even in a small amount, 0.001 to 0.5% by weight is sufficient with respect to the polyacrylic acid (salt) water-absorbing resin, and more preferably 0.001 to 0.4%. 1% by weight, more preferably 0.005 to 0.1% by weight is sufficient. In the case of α-hydroxycarboxylic acid (salt) and amino polyvalent carboxylic acid (salt), 0.01 to 5% by weight is preferable with respect to the polyacrylic acid (salt) -based water absorbent resin. 05 to 5% by weight is more preferable, 0.1 to 3% by weight is further preferable, and 0.2 to 3% by weight is particularly preferable.

  Moreover, although the ratio (weight ratio) of a fatty acid (salt) and a chelating agent is also set appropriately, for example, the chelating agent is in the range of 3000 to 0.1 with respect to the fatty acid (salt) 100. Among them, in the case of organic polyvalent phosphoric acid (salt) and amino polyvalent phosphoric acid (salt), the chelating agent is 100 to 0.1, more preferably 50 to 1, and further 30 to 3 with respect to 100 fatty acid (salt). It is a range. In the case of α-hydroxycarboxylic acid (salt) and amino polyvalent carboxylic acid (salt), the chelating agent is 3000 to 1, more preferably 2000 to 5, more preferably 1000 to 10, more preferably 500 to 100 fatty acid (salt). It is in the range of -20, and further 250-20. Excessive use of the chelating agent may cause an increase in cost and a decrease in water absorption ratio due to a decrease in the amount of water-absorbing resin in the particulate water-absorbing agent.

(2-5) Water addition step (optional) and method for adjusting water content The water content of the particulate water-absorbing agent according to the present invention is 1 to 20% by weight, more preferably 5 to 20% by weight, preferably 5 -18% by weight, more preferably 6-18% by weight, still more preferably 7-15% by weight, and particularly preferably 8-13% by weight.

  By adjusting the moisture content of the particulate water-absorbing agent within the above range, the powdering rate, moisture-absorbing fluidity, water-absorbing performance (AAP), which will be described later, are improved, and impact resistance (abrasion resistance) is excellent. A particulate water-absorbing agent can be obtained. Furthermore, it becomes possible to suppress the charging of the particulate water-absorbing agent, and the handleability of the powder is remarkably improved. In addition, when the water content is less than 1% by weight, sufficient impact resistance stability cannot be obtained, and when the water content exceeds 20% by weight, water absorption performance (CRC, AAP, etc.) and moisture absorption fluidity can be obtained. Since it causes a decrease, it is not preferable.

  The method for adjusting the water content is not particularly limited. For example, when a fatty acid (salt) or a chelating agent is added in an aqueous dispersion or (water) solution, the water content is added depending on the water content of the water absorbent resin to be used. The amount may be adjusted as appropriate, and water may be further added to the particulate water-absorbing agent after adding an aqueous dispersion of fatty acid (salt) or chelating agent or (water) solution. Furthermore, as another adjustment method, after adding water, a fatty acid (salt), and a chelating agent within the above-mentioned range to the water-absorbent resin, adjustment can be performed by drying by heating or drying under reduced pressure. When the moisture content is adjusted by heat drying or the like, the penetration of water into the water-absorbent resin is promoted, and the surface can be dried and rapidly formed into particles.

  In the method for producing a particulate water-absorbing agent according to the present invention, the water-absorbent resin immediately after the addition of an aqueous dispersion or (water) solution of a fatty acid (salt) or a chelating agent, or water alone is wet only with water. Or gelled, resulting in poor fluidity. However, since water existing on the surface of the water-absorbent resin is absorbed and diffused inside the water-absorbent resin after a certain period of time, the particles again have fluidity. Therefore, in the present invention, the wet water-absorbent resin may be allowed to stand for a certain period of time in order to promote the diffusion of water into the interior, or may be heated or partially dried while maintaining the moisture content. .

  When the moisture content is adjusted by the heat drying, the heating temperature is preferably 200 ° C. or less, preferably 30 to 100 ° C., more preferably 50 to 90 ° C., and further preferably 60 to 80 ° C. The heating time is preferably 1 second to 3 hours, more preferably 1 minute to 1 hour, and is appropriately determined within the above range.

  In addition, the water-absorbing agent that has been particulated by heat drying can be used as it is, but operations such as crushing and classification may be performed as necessary. In particular, the water-absorbent resin powder that has become wet by the addition of water may have a dry surface and agglomerate particles due to the diffusion or drying of water from the resin surface to the inside. In this case, although it depends on the degree of aggregation, it may be classified by crushing (operation for mechanically loosening the aggregation) as necessary. These crushing and classifying operations are optional and are performed as necessary. Examples of the crushing apparatus and classifying apparatus that can be used are exemplified in the granulation method described in US Pat. Nos. 4,734,478 and 5,369,148. Has been.

(2-6) Particle size adjustment step (granulation step, granulation step, fine powder recovery step) (optional)
In the method for producing a particulate water-absorbing agent of the present invention, in order to adjust the particulate water-absorbing agent to a particle size described later in (7-6), a granulation step, a sizing step, a fine powder collection step, etc., as necessary. You may perform a particle size adjustment process suitably. In addition, as a particle size adjustment process, the process currently disclosed by US Patent Application Publication No. 2004/181031, 2004/242761, 2006/247351 etc. is employable, for example.

(2-7) Addition step of insoluble inorganic fine particles, polyvalent metal salt, inorganic reducing agent, etc. (optional)
In addition, an addition step of adding insoluble inorganic fine particles, polyvalent metal salt, inorganic reducing agent, and the like, which will be described later in (3-15), may be included. Among them, the addition of an inorganic reducing agent can suppress the coloration of the particulate water-absorbing agent over time and deterioration due to urine at a higher level, and reduce the residual monomer amount.

(2-8) Difference from the unpublished PCT / JP2010 / 66957 which is the prior application (see; Comparative Examples 5 to 8 in the present specification)
In an unpublished PCT / JP2010 / 66957 (PCT application date; September 29, 2010), which is a prior application by the present applicant, an aqueous dispersion of a surfactant and a metal soap is added to the water-absorbent resin. And a method for producing the same (see; claims 8 to 20, claims 21 to 30, Examples 1 to 16, Tables 1 to 3, etc.) are disclosed.

  Specifically, Examples 10, 11, 15, and 16 of the above-mentioned PCT application as a prior application include 100 parts by weight of a water absorbent resin and 1.0 part by weight of a metal soap and 0.1 part by weight of a surfactant. A water-absorbing agent obtained by adding an aqueous dispersion is disclosed.

  The above-mentioned PCT application, which is a prior application, discloses adding an aqueous dispersion of a surfactant and a metal soap to the water-absorbent resin, that is, simultaneous addition of the surfactant and the metal soap, and the amount thereof is also disclosed. Metal soap is 0.001-5 weight part. However, the PCT application does not disclose the subject of the present application or the new parameters (20% by weight saline vertical absorption index, moisture absorption blocking rate after impact test), but also adds a surfactant after the addition of metal soap. The addition order essential for the production method of the present invention is not disclosed. As described in (2-3) above, in the present invention, in the addition order, the 20 wt% saline vertical absorption index, which is a novel parameter that is not disclosed in the previous PCT application, is improved. Was found.

  In the PCT application, which is a prior application, it is disclosed that metal soap is used in the range of 0.001 to 5 parts by weight. In Examples 10, 11, 15, and 16, the amount of metal soap is 1. It is disclosed that it is 0 part by weight. However, in solving the problems of the present invention, when the amount of metal soap used is 1.0 part by weight or more, the 20% by weight saline vertical absorption index is decreased, and further, the moisture absorption blocking ratio is improved by addition. Appropriate effect is not seen. Therefore, it is not only disadvantageous in terms of cost, but also a problem of dust may occur when the metal soap powder is peeled off or detached from the particulate water-absorbing agent.

  Therefore, in order to solve the problem in the present invention, as a difference from the PCT application, the addition order and the addition amount of metal soap are defined, and the long chain described in (2-2-3) above The addition amount of the alkyl compound or the organic polysiloxane is set within the above-described range.

  In addition, the result of the additional test of the said PCT application which discloses simultaneous addition of surfactant and metal soap is shown as Comparative Examples 5 to 8 described later. In these Comparative Examples 5 to 8, the moisture absorption blocking rate and There is a problem with dust. On the other hand, the problem which concerns in Examples 1-17 of this invention does not arise.

(2-9) Differences from the unpublished Japanese Patent Application No. 2011-171169, which is a prior application, to the unpublished Japanese Patent Application No. 2011-171169 (the filing date; January 28, 2011) In addition, a water absorbing agent obtained by adding a fatty acid (salt) such as metal soap and a chelating agent to a water absorbing resin and a method for producing the same are disclosed.

  Similar to PCT / JP2010 / 66957 described in the above (2-8), the above-mentioned Japanese Patent Application No. 2011-171169, which is a prior application, is also subject to the present application and new parameters (20 wt% saline vertical absorption index, after impact test). In addition, the addition order essential in the production method of the present invention in which a surfactant is added after addition of a fatty acid (salt) is not disclosed. As described in (2-3) above, in the present invention, in the addition order, the 20 wt% saline vertical absorption index, which is a novel parameter that is not disclosed in the prior application, is improved. It was found.

(2-10) Differences from other Patent Documents 1 to 27, especially Patent Document 9 (Reference: Comparative Example 2 of the present specification)
Other problems of Patent Documents 1 to 27 are as described in the background art above, and Patent Documents 1 to 27 also include the problems of the present application and new parameters (20 wt% saline vertical absorption index, moisture absorption blocking after impact test). In addition, the addition order essential in the production method of the present invention in which a surfactant is added after addition of a fatty acid (salt) such as metal soap is not disclosed.

In particular, in the metal soap described in Patent Document 9 (European Patent Publication No. 1592750), fluidity and water absorption performance under pressure (for example, absorption at a load of 20 to 50 g / cm ² in 0.9 wt% saline solution) were maintained. It is known that particulate water-absorbing agents can be provided. However, in the method described in Patent Document 9, even if the water absorption performance under pressure (for example, absorption at a load of 20 to 50 g / cm ² in 0.9% by weight saline solution) is high, the particulate water absorbing agent of the present invention. Was found to have a low 20 wt% saline vertical absorption index, which is an essential new parameter.

  In addition, the result of the follow-up test of Patent Document 9 in which the addition of only metal soap is disclosed is shown as Comparative Example 2 to be described later. In Comparative Example 2, the 20% by weight saline vertical absorption index is low. Has occurred. On the other hand, the problem which concerns in Examples 1-17 of this invention does not arise. Therefore, in the present invention, both a good “20 wt% saline vertical absorption index (1.5 to 10 g / g)” and a good “moisture absorption blocking ratio after impact test (0 to 30%)” are compatible. A novel particulate water-absorbing agent can be provided.

[3] Particulate water-absorbing agent The particulate water-absorbing agent of the present invention obtained by taking the above production method as an example is a particulate water-absorbing agent mainly composed of a polyacrylic acid (salt) -based water-absorbing resin, and has a moisture absorption blocking rate. 0 to 40% (more preferably 0 to 30%), and 20% by weight normal saline water absorption index is 1.5 to 10.0 [g / g]. Furthermore, the particulate water-absorbing agent of the present invention contains a polyacrylic acid (salt) -based water-absorbing resin as a main component, and water selected from long-chain alkyl compounds, organic polysiloxanes, and organic polymer compounds with respect to the water-absorbing resin. A particulate water-absorbing agent containing 0.001 to 5% by weight of an insoluble or poorly water-soluble compound (however, 0.001 or more and less than 1.0% by weight for metal soap), having a moisture absorption blocking rate of 0 to 30%, and The 20 wt% saline vertical absorption index is 1.5 to 10.0 [g / g].

That is, a water-absorbing resin that has been conventionally evaluated with 0.9% by weight saline solution or artificial urine, or a basis weight (amount of water-absorbing resin per unit area, for example, (5 -2), with respect to the water-absorbing resin evaluated in AAP (spreading 0.9 g of water-absorbing resin in a range of 60 mm in diameter)), Patent Documents 5 to 15 further improve powder fluidity and water absorption performance. Water-absorbing resin, particularly in Patent Document 9, by adding metal soap, powder flowability and water-absorbing performance under pressure (for example, a load of 20 to 50 [g / cm to 0.9 wt% saline) ^[2 ] has been proposed.

  However, in the related art, the water absorption ratio in extremely high-concentration salt water (particularly 20% by weight saline solution) that has not been noticed at all is extremely low. Water absorption capacity under pressure (20% by weight saline vertical absorption index) at a high basis weight (spraying 10 g of water-absorbing resin in a range of 25.4 mm in diameter. Basis weight about 6.2 times that of AAP) is extremely reduced. I found the facts. In addition to powder flowability, the addition of ultra-high-concentration salt water (especially 20% by weight saline) and ultra-high basis weight (basis weight about 6.2 times that of AAP), which has not been noticed in the past. It has been found that the reduced water absorption is important during actual use in the form of a sheet or tape.

  Moreover, although it is also known in the above-mentioned patent documents that the moisture absorption blocking rate (Anti-Caking) is important, the present inventors are a water absorption resin having a low moisture absorption blocking rate (high Anti-Caking) after production. Even if it exists, the fact that the moisture absorption blocking rate rose at the time of actual use was discovered. And in the evaluation of the conventional moisture absorption blocking rate, it does not show a sufficient effect at the time of actual use, and the cause thereof is peeling of various Anti-Caking agents by transporting the water absorbent resin powder (for example, various transport machines such as pneumatic transport). And the moisture absorption blocking rate was found to increase. And it replaced with the conventional evaluation of the moisture absorption blocking rate, discovered that the moisture absorption blocking rate after an impact test (modeling conveyance) was important for actual use, and completed this invention. Hereinafter, the preferable 20 wt% saline vertical absorption index, the moisture absorption blocking rate after the impact test, and the like will be further described.

(3-1) 20% by weight saline vertical absorption index As an example of means for achieving the above production method, a water-insoluble or poorly water-soluble compound selected from long-chain alkyl compounds, organic polysiloxanes, and organic polymer compounds is added. Further, as an example of means for achieving the addition of the surfactant after the addition of the long-chain alkyl compound or the organic polysiloxane, the 20 wt% saline vertical absorption index of the particulate water-absorbing agent according to the present invention is 1. 5 [g / g] or more. The measurement method will be described later in (5-3), but compared to the conventional water absorption capacity under pressure (AAP), which has been evaluated with the basis weight of paper diapers, 0.9% by weight saline and artificial urine, The 20 wt% saline vertical absorption index of the present invention is that the salt concentration of the absorbing solution is about 22 times, and the basis weight of the water absorbing agent at the time of measurement (water absorbing agent amount per unit area) is about 6.2 times. The idea is fundamentally different from conventional measurement methods.

  The 20 wt% saline vertical absorption index in the present invention is preferably 1.5 [g / g] or more, more preferably 2.0 [g / g] or more, and further preferably 3.0 [g / g] or more. 4.0 [g / g] or more is even more preferable, 5.0 [g / g] or more is particularly preferable, and 6.0 [g / g] or more is most preferable. The upper limit is preferably higher, but 15 [g / g] or less, more preferably 10 [g / g] or less is sufficient from the balance with other physical properties and costs.

  When the 20 wt% saline vertical absorption index is less than 1.5 [g / g], the conventional well-known physical properties, for example, 0.9 wt% saline or artificial urine, It has been found that even when the water absorption capacity under pressure (AAP) is about the same, when the particulate water-absorbing agent is used in the form of a sheet or tape, it is inferior in water absorption characteristics during actual use.

(3-2) Moisture absorption fluidity after impact test (moisture absorption blocking rate)
The moisture absorption blocking rate (after the impact test) of the particulate water-absorbing agent according to the present invention is preferably 0 to 40% by weight, more preferably 0 to 30% by weight, further preferably 0 to 20% by weight, and 0 to 5% by weight. % Is particularly preferable, and 0 to 2% by weight is most preferable. Although the measurement method will be described later in (5-9), it is fundamentally different from the conventional measurement method because it is an evaluation after the impact test compared to the conventional moisture absorption blocking rate.

  If the moisture absorption blocking rate after the impact test exceeds 20% by weight, even if the moisture absorption blocking rate after the production of the water absorbing agent is excellent, the anti-caking agent may be detached due to the transportation of the particulate water absorbing agent, etc. Poor handling of particulate water-absorbing agent in the environment. Therefore, in a manufacturing apparatus such as a thin absorbent body for sanitary materials, aggregation or clogging of the particulate water absorbing agent occurs in the transfer pipe or the like, or the hydrophilic fiber and the particulate water absorbing agent are mixed uniformly. This may cause a problem that it cannot be performed.

  By adjusting the use of a long-chain alkyl compound or an organic polysiloxane in a state where the particle size of the water-absorbent resin is controlled, a moisture absorption blocking ratio within the above range can be achieved.

(3-3) Long-chain alkyl compounds or organic polysiloxanes Examples and contents of long-chain alkyl compounds or organic polysiloxanes (and water-insoluble or poorly water-soluble organic polymers, hereinafter omitted) are as described in (2-2 -3) and (2-2-4) above.

  That is, a more preferable long-chain alkyl compound is a solid or liquid long-chain alkyl compound having a hydrophilic functional group at room temperature, and a more preferable organic polysiloxane is a solid or liquid organic polysiloxane having a hydrophilic functional group. is there. Further, a more preferred hydrophilic functional group is at least one of a hydroxyl group, a carboxyl group, a sulfonic acid group, a phosphoric acid group, an amino group, an imino group, and an amide group, and particularly preferably a carboxy group. 90% by weight or more of the long-chain alkyl compound preferably has a long-chain hydrocarbon chain having 8 to 30 carbon atoms.

  Further, more preferred hydrophilic functional group is an acid group polyvalent metal salt, and furthermore, the polyvalent metal salt is one or more compounds selected from barium salt, calcium salt, magnesium salt, aluminum salt, zinc salt It is. Or a more preferable hydrophilic functional group is an alkali metal salt of an acid group.

(3-4) Surfactant Since the surfactant is used in the above production method, the particulate water-absorbing agent further contains a surfactant. Content of the said surfactant is 0.001-1.0 weight% with respect to polyacrylic acid (salt) type water absorbing resin, and also is the range as described in said (2-3). Preferred surfactants are as described in (2-3) above, and it is preferable that the surfactant has a polyoxyethylene unit, particularly from the viewpoint of improving the 20 wt% saline vertical absorption index. In addition, the use or inclusion of a surfactant can reduce process damage due to particle conveyance, and can maintain high physical properties even during actual use.

(3-5) Particle size Among the particulate water-absorbing agent according to the present invention, the proportion of the particulate water-absorbing agent having a particle diameter (specified by a standard sieve) of 150 μm or more and less than 850 μm is 95-100. % By weight is preferable, 97 to 100% by weight is more preferable, 98 to 100% by weight is further preferable, and 99 to 100% by weight is particularly preferable. In particular, from the viewpoint of liquid permeability, the amount of the particulate water-absorbing agent according to the present invention is preferably 0 to 5% by weight, more preferably 0 to 3% by weight, even more preferably 150 μm passing material (corresponding to less than 150 μm). Is controlled to 0 to 2% by weight, particularly preferably 0 to 1% by weight.

  Furthermore, the weight average particle diameter (D50) of the particulate water-absorbing agent is preferably 250 to 450 μm, more preferably 300 to 450 μm, and further preferably 325 to 425 μm. Moreover, regarding the particle size distribution of the particulate water-absorbing agent, the logarithmic standard deviation (σζ) serving as an index of uniformity is preferably 0 to 0.45, more preferably 0 to 0.425, and most preferably 0 to 0.40. .

  When the proportion of the particulate water-absorbing agent having a particle diameter of 850 μm or more exceeds 5% by weight with respect to all particles, a foreign material sensation may be produced or the touch may be deteriorated when sanitary materials such as paper diapers are manufactured. It is not preferable because it gives the user an unpleasant feeling. Further, when the proportion of the particulate water-absorbing agent having a particle diameter of less than 150 μm exceeds 5% by weight with respect to all particles, or when the logarithmic standard deviation (σζ) exceeds 0.45, the water absorption capacity under pressure Many problems occur, such as drastic decrease in moisture and fluidity of moisture absorption, deterioration of working environment due to dust generated during the manufacture of sanitary materials such as paper diapers, and increased segregation due to wide particle size distribution. It is not preferable.

  The particle size of the particulate water-absorbing agent can be defined by the method described later in (5-4), and may be controlled by the water-absorbing resin production process or by the particulate water-absorbing agent production process. Good. The control method can be appropriately performed by pulverization, classification, granulation, preparation of the particle size after classification, and the like. Such particle size control is preferably performed in a classification step before the surface crosslinking (first classification step) or the like, and further performed in a classification step after the surface crosslinking (second classification step) to control the particle size. Specific particle size control can be performed by the steps described in U.S. Patent Application Publication Nos. 2004/181031, 2004/242761, 2006/247351, and the like.

(3-6) Water content The water content of the particulate water-absorbing agent is 1 to 20% by weight, more preferably 5 to 20% by weight, preferably 5 to 18% by weight, more preferably 6 to 18% by weight, Preferably it is 7 to 15 weight%, Most preferably, it is 8 to 13 weight%. The water content of the particulate water-absorbing agent can be defined by the method described later in (5-5) (loss on drying at 180 ° C. for 3 hours).

  By adjusting the water content of the particulate water-absorbing agent within the above range, the moisture absorption fluidity described in (3-2) above, the 20 wt% saline vertical absorption index described in (3-1), and Moreover, it leads also to the improvement of the powdering rate described in the following (3-7), and a particulate water-absorbing agent excellent in impact resistance (abrasion resistance) can be obtained. Furthermore, it becomes possible to suppress the charging of the particulate water-absorbing agent, and the handleability of the powder is remarkably improved. When the water content is less than 1% by weight, sufficient impact resistance stability cannot be obtained. When the water content exceeds 20% by weight, water absorption performance (CRC, AAP, etc.) and moisture absorption flow are not obtained. This is not preferable because it causes a decrease in the property.

  The method for adjusting the water content is not particularly limited. For example, when a fatty acid (salt) or a chelating agent is added in an aqueous dispersion or (water) solution, the water content is added depending on the water content of the water absorbent resin to be used. The amount may be adjusted as appropriate, and water may be further added to the particulate water-absorbing agent after adding an aqueous dispersion of fatty acid (salt) or chelating agent or (water) solution. Furthermore, as another adjustment method, after adding water, a fatty acid (salt), and a chelating agent within the above-mentioned range to the water-absorbent resin, adjustment can be performed by drying by heating or drying under reduced pressure. When the moisture content is adjusted by heat drying or the like, the penetration of water into the water-absorbent resin is promoted, and the surface can be dried and rapidly formed into particles.

(3-7) Powdering rate The powdering rate of the particulate water-absorbing agent according to the present invention (increase in 150 μm passing material after impact test) is preferably 0 to 1.0% by weight, and 0 to 0.8% by weight. % Is more preferable, and 0 to 0.6% by weight is more preferable. When the above-mentioned pulverization rate exceeds 1.0% by weight, liquid permeability may be reduced due to dust generated during transportation or use of the particulate water-absorbing agent (for example, during processing into sanitary materials) This is not preferable because it may cause deterioration. The water content of the particulate water-absorbing agent can be defined by the method described later in (5-5).

  The control of the pulverization rate can be performed by the control of the moisture content, etc., and can be performed by setting the moisture content to a predetermined value or more, particularly within the range described in (3-6) above.

(3-8) Surface cross-linking In order to improve the 20 wt% saline vertical absorption index, etc., in the present invention, preferably, the above-described method in the particulate water-absorbing agent is performed by the method described in (2-1-4) above. Surface cross-linking is applied to the polyacrylic acid (salt) water-absorbing resin.

(3-9) Chelating agent The particulate water-absorbing agent preferably further contains a chelating agent in order to suppress the increase amount and the rate of increase of the deteriorated soluble component described in the following (3-10) and to prevent coloring. The content of the chelating agent is 0.001 to 5.0% by weight with respect to the polyacrylic acid (salt) water-absorbing resin, and is further in the range described in (2-4) above. A preferable chelating agent is the compound described in the above (2-4), and the chelating agent is a water-soluble organic chelating agent having a nitrogen atom and / or a phosphorus atom, or the chelating agent is an α-hydroxycarboxylic acid. (Salt).

  By using such a chelating agent, the amount of increase in the degradation soluble content in the degradation acceleration test can be set to 0 to 15% by weight, and further within the following range (3-10).

(3-10) Increase amount and increase rate of deteriorated soluble component and adjustment method thereof The particulate water-absorbing agent according to the present invention is characterized by an increase amount and an increase rate of deteriorated soluble component in the deterioration promotion test. In addition, the specific measurement method regarding the increase amount and increase rate of a deterioration acceleration test and a deterioration soluble part is later mentioned in (5-7).

  0-15% by weight is preferable, 0-13% by weight is more preferable, 0-11% by weight is further preferable, and 0-10% by weight is increased in the deterioration promotion test of the particulate water-absorbing agent of the present invention. Weight percent is particularly preferred.

  Moreover, the increase rate (times) of the deterioration soluble part in the deterioration acceleration test of the particulate water-absorbing agent of the present invention is 1.0 to 4.0, preferably 1.0 to 3.5, 1.0 to 3.0 is more preferable, 1.0 to 2.5 is more preferable, and 1.0 to 2.0 is particularly preferable.

  By setting the increase amount (%) and increase rate (times) of the degradation soluble component within the above range, the water absorption performance as designed can be maintained even in an environment where the particulate water absorbent may be deteriorated. For example, even when the particulate water-absorbing agent is used as a paper diaper for a long time, the absorption performance of the paper diaper is not lowered, and troubles such as urine leakage and rough skin can be reduced. On the other hand, when the increase amount and the rate of increase of the deteriorated soluble component are out of the above ranges, the water absorption performance deteriorates over time in an environment where the particulate water absorbing agent may be deteriorated. For example, the particulate water absorbing agent is removed from a paper diaper. When used for a long time, the absorption performance of paper diapers is lowered, and troubles such as urine leakage and rough skin are increased.

  The method for adjusting the amount of increase (%) and rate of increase (times) of the above-mentioned deteriorated soluble component is adjusted by appropriately setting the one-hour soluble component or the amount (addition amount) of the internal crosslinking agent and / or chelating agent. can do. If the amount of the internal cross-linking agent is large, the amount of the chelating agent needs to be decreased. Conversely, if the amount of the internal cross-linking agent is small, the amount of the chelating agent needs to be increased. Similarly, it is necessary to reduce the amount of chelating agent when the amount of soluble component for one hour is large, and conversely, when the amount of soluble component for one hour is small, the amount of chelating agent must be increased.

(3-11) Absorption capacity without pressure (CRC)
The water absorption capacity without load (CRC) of the particulate water-absorbing agent according to the present invention is preferably 10 [g / g] or more, more preferably 15 [g / g] or more, and further preferably 25 [g / g] or more. 28 [g / g] or more is even more preferable, 30 [g / g] or more is particularly preferable, and 33 [g / g] or more is most preferable. The upper limit is not particularly limited, but is preferably 60 [g / g] or less, more preferably 55 [g / g] or less, further preferably 50 [g / g] or less, and 45 [g / g] or less. Is particularly preferred. CRC can be defined by the method described later in (5-1), and can be appropriately adjusted by the amount of the crosslinking agent and the ratio of surface crosslinking during the polymerization described in (2-1).

  The upper and lower limits of the CRC can be appropriately selected within this range. For example, 10 to 60 [g / g], further 15 to 50 [g / g], particularly 25 (28, 30, 33) to 45 [g / g]. ] Is controlled within the range. When the CRC is less than 10 [g / g], the amount of water absorption is small when used in the absorbent body, and it is not suitable for the use of sanitary materials such as paper diapers. On the other hand, when the CRC exceeds 60 [g / g], there is a possibility that a particulate water-absorbing agent having an excellent liquid uptake rate into the absorber cannot be obtained.

(3-12) Absorption capacity under pressure (AAP)
In the particulate water-absorbing agent according to the present invention, a significant reduction in physical properties (due to damage, rehumidification, etc.) is suppressed by the addition of a long-chain alkyl compound or an organic polysiloxane, so that a high water absorption capacity under pressure is obtained.

  The water absorption capacity under load (AAP) of the particulate water-absorbing agent according to the present invention is preferably 10 [g / g] or more, more preferably 15 [g / g] or more under a pressure (under load) of 2.06 kPa. 18 [g / g] or more is more preferable, 20 [g / g] or more is further more preferable, 25 [g / g] or more is particularly preferable, and 28 [g / g] or more is most preferable. The upper limit is not particularly limited, but is preferably 50 [g / g] or less, and more preferably 40 [g / g] or less from the viewpoint of ease of production and balance with other physical properties. When the AAP is less than 10 [g / g], when a particulate water-absorbing agent is used for the absorber, the return amount of the liquid when the pressure is applied to the absorber (referred to as Re-Wet (rewetting)) is small. Absorber may not be obtained.

  AAP can be defined by the method described later in (5-2), and can be appropriately adjusted by the ratio of surface cross-linking described in (2-1-4) above.

(3-13) Soluble content The 1 hour soluble content of the particulate water-absorbing agent according to the present invention is preferably 25% by weight or less, more preferably 23% by weight or less, further preferably 20% by weight or less, and 18% by weight. The following is particularly preferable, and 15% by weight or less is most preferable. The lower limit is 0% by weight. When the 1-hour soluble component exceeds 25% by weight, the liquid take-up speed becomes slow or the water absorption rate decreases when used for an absorber. Is not preferable. The soluble component can be defined by the method described later in (5-6), and can be appropriately adjusted by the amount of the crosslinking agent and the ratio of surface crosslinking during the polymerization described in (2-1).

(3-14) Other components contained in particulate water-absorbing agent The particulate water-absorbing agent of the present invention comprises the above-described components (water-absorbing resin, long-chain alkyl compound or organic polysiloxane, surfactant, preferably chelating agent). In addition to water and water), insoluble inorganic fine particles, polyvalent metal salts, inorganic reducing agents, and the like may be included to impart various performances. Among these, addition of an inorganic reducing agent can suppress the coloring and deterioration of the particulate water-absorbing agent over time at a higher level.

  The inorganic reducing agent refers to a compound having a reducing inorganic element. Specifically, it is a compound having a reducing sulfur atom or phosphorus atom, and the compound corresponds to an inorganic compound or an organic compound. The inorganic reducing agent may be acid type or salt type, but is preferably salt type, more preferably monovalent or polyvalent metal salt, and more preferably monovalent salt. Among these inorganic reducing agents, an oxygen-containing reducing inorganic compound, that is, an inorganic reducing agent in which sulfur or phosphorus is combined with oxygen is preferable, and an oxygen-containing reducing inorganic salt is more preferable.

  The addition amount of the insoluble inorganic fine particles, the polyvalent metal salt, or the inorganic reducing agent depends on the combination with various components contained in the particulate water-absorbing agent, but is 0 to 6 weights with respect to 100 parts by weight of the water-absorbing resin. Part by weight, more preferably 0.001 to 5 parts by weight, particularly preferably 0.01 to 3 parts by weight, and most preferably 0.01 to 1 part by weight. When the addition amount is out of the above range, it is difficult to prevent a decrease in water absorption performance when receiving damage, which is not preferable.

  The mixing operation of the water-absorbent resin and the insoluble inorganic fine particles, the polyvalent metal salt, or the inorganic reducing agent is not particularly limited, and may be performed simultaneously with the addition or separately as described above. Moreover, about the addition method, what is called wet mixing method etc. which suspend and add in water etc. may be employ | adopted, and the dry blend method of mixing powders may be employ | adopted.

[4] Absorber, Absorbent Article The particulate water-absorbing agent of the present invention is used for various purposes for the purpose of water absorption, and particularly used for processing into a sheet or tape. Processing of the particulate water-absorbing agent is performed by means of compression, suction, adhesion, etc., using another base material or adhesive as necessary. Specifically, the particulate water-absorbing agent is preferably processed to have a thickness (Z-axis direction) of 5 mm or less, and further about 0.1 to 4 mm and 0.3 to 3 mm. The direction and the planar shape are appropriately selected according to the purpose. For example, the area is 10 cm ^{2 to} 100 m ² and the length is about 1 cm to 1000 m. Furthermore, after processing into a sheet form and a tape form, you may cut | judge at the time of use. The absorbent body of the present invention processed into a sheet form or a tape form is used for absorbent articles (final consumer goods) such as water-stopping rubber, water-stopping tape, kitchen sheets, pet sheets, hemostatic sheets, paper diapers and napkins. Can be used. Further, since the particulate water-absorbing agent of the present invention is excellent in impact resistance and hygroscopic fluidity, when used in an absorbent body or absorbent article, trouble reduction in the manufacturing process of the absorbent article and improvement of the working environment can be achieved. In addition, the reduction in water absorption performance due to damage can be suppressed, and the original performance of the particulate water absorbing agent can be sufficiently exhibited in an absorbent article or the like.

  In addition, the particulate water-absorbing agent of the present invention has high water absorption performance (CRC, AAP, etc.), excellent color tone with time, and excellent urine resistance as evaluated by the rate of increase in degraded soluble content. Therefore, since coloring with time and deterioration of water absorption performance of absorbent articles and the like can be suppressed, problems such as liquid (urine) leakage and rough skin do not occur even after processing into a sheet or tape.

  The absorbent body and absorbent article of the present invention comprise the particulate water-absorbing agent of the present invention, and the “absorber” referred to here is an absorption molded mainly with the particulate water-absorbing agent and hydrophilic fibers. Say the material.

  The present invention provides an absorbent body, particularly a sheet-like absorbent body, which is molded containing 20 to 100% by weight of a particulate water-absorbing agent and 80 to 0% by weight of hydrophilic fibers. The absorber means a structure substantially consisting of a hydrophilic or water-absorbing material capable of absorbing liquid (particularly 90 to 100% by weight), and the content of the particulate water-absorbing agent in the absorber. (Core concentration; content with respect to the total weight of the particulate water-absorbing agent and the hydrophilic fiber) is preferably 20 to 100% by weight, more preferably 25 to 90% by weight, further preferably 30 to 80% by weight, and 40 to 80%. Weight percent is most preferred. The higher the content, the more easily the water absorption performance of the absorbent body or absorbent article is affected by the water absorption performance of the particulate water absorbing agent.

  Hereinafter, the present invention will be described in more detail with reference to Examples and Comparative Examples. The technical contents shown in each embodiment can be used in appropriate combination with the technical contents shown in another embodiment.

  All electric devices used in the examples and comparative examples are used under the conditions of 100 V and 60 Hz. Unless otherwise specified, each of the electric devices is used under the conditions of room temperature (25 ° C. ± 2 ° C.) and relative humidity of 50% RH. Physical properties were measured.

  In addition, each physical property of the particulate water-absorbing agent of the present invention is defined by each evaluation method shown below. Further, for convenience, “wt%” may be described as “wt%” and “liter” as “L”. Furthermore, in this specification, “0.90 wt% sodium chloride aqueous solution” may be referred to as “physiological saline”, but both are treated as the same. Furthermore, in the following (5-1) to (5-11), for convenience, it is described as “particulate water absorbent”, but when measuring about “water absorbent resin powder” or “water absorbent resin particles”, etc., “Particulate water-absorbing agent” is read as “water-absorbing resin powder” or “water-absorbing resin particles”.

(5-1) Absorption capacity without pressure (CRC)
The measurement of water absorption capacity without load (CRC) of the particulate water-absorbing agent according to the present invention was performed according to ERT441.2-02.

  That is, 0.200 g (weight W0 [g]) of the particulate water-absorbing agent is uniformly put into a non-woven bag (85 mm × 60 mm) and heat-sealed, and then the temperature is adjusted to 25 ± 3 ° C. and excessively large (normally 500 ml) Of 0.9 wt% sodium chloride aqueous solution. After 30 minutes, the bag was pulled up and drained using a centrifuge (Centrifuge manufactured by Kokusan Co., Ltd .: Model H-122) under conditions of 250 G for 3 minutes. Thereafter, the weight of the bag (W1 [g]) was measured.

The same operation was performed without adding the particulate water-absorbing agent, and the weight of the bag (W2 [g]) at that time was measured. From the obtained W0 [g], W1 [g], and W2 [g], the following equation CRC [g / g] = {(W1-W2) / W0} -1
The water absorption capacity (CRC) was calculated under no pressure.

(5-2) Absorption capacity under pressure (AAP)
The water absorption capacity under load (AAP) of the particulate water-absorbing agent according to the present invention was measured according to ERT442.2-02.

That is, 0.9 g (weight W3 [g]) of the particulate water-absorbing agent was put into a measuring device (see FIG. 2), and the weight (W4 [g]) of the measuring device set was measured. Next, 0.90 wt% sodium chloride aqueous solution was absorbed into the particulate water-absorbing agent under a pressure of 2.06 kPa. After 1 hour, the weight (W5 [g]) of the measuring device set was measured. From the obtained W3 [g], W4 [g], and W5 [g], the following formula AAP [g / g] = (W5-W4) / W3
The water absorption capacity under pressure (AAP) was calculated.

  In the measuring apparatus shown in FIG. 2, a glass filter 106, a filter paper 107, and a plastic support cylinder 100 having an inner diameter of 60 mm are placed in this order in a Petri dish 105, and a stainless steel 400 mesh wire net 101 is placed in the support cylinder 100. A piston 103 and a weight 104 for applying a load are inserted. Then, a particulate water-absorbing agent is put on the wire net 101, and after placing the piston 103 and the weight 104 on the particulate water-absorbing agent, 0.90% by weight (or 20% by weight) sodium chloride is placed on the Petri dish 105. The measurement is started by putting the aqueous solution 108 so that the filter paper 107 is not immersed. That is, the measurement is continued for one hour after the 0.90 wt% (or 20 wt%) sodium chloride aqueous solution 108 sucked up by the glass filter 106 wets the filter paper 107. During the measurement, the particulate water-absorbing agent absorbs 0.90% by weight (or 20% by weight) of the sodium chloride aqueous solution 108 to become the swollen gel 102, and pushes up the piston 103 and the weight 104. Therefore, during the measurement, the swelling gel 102 (particulate water absorbing agent) is always loaded with the piston 103 and the weight 104, and 0.90 wt% (or 20 wt%) of chloride under a pressure of 2.06 kPa. The sodium aqueous solution 108 is absorbed.

(5-3) 20 wt% saline vertical absorption index The measurement of the 20 wt% saline vertical absorption index of the particulate water-absorbing agent according to the present invention is the water absorption capacity under pressure (AAP) described in (5-2) above. The measurement conditions were partially changed.

  That is, the amount of the particulate water-absorbing agent used is 0.9 g to 1.0 g, the inner diameter of the support cylinder 100 of the measuring device is 60 mm to 25.4 mm, and the concentration of the sodium chloride aqueous solution is 0.9 wt% to 20 wt%. %, The absorption time under pressure (AAP) was measured by changing the absorption time from 1 hour to 30 minutes. In addition, by changing the inner diameter of the support cylinder 100 to 25.4 mm, the basis weight (amount of water absorbing agent per unit area) was increased by about 6.2 times.

(5-4) Weight average particle diameter (D50) and logarithmic standard deviation of particle size distribution (σζ)
The weight average particle diameter (D50) and logarithmic standard deviation (σζ) of the particle size distribution of the particulate water-absorbing agent according to the present invention were measured according to the measurement method disclosed in European Patent No. 0349240.

That is, using a sieve corresponding to a JIS standard sieve (JIS Z8801-1 (2000)) having an opening of 850 μm, 710 μm, 600 μm, 500 μm, 420 μm, 300 μm, 212 μm, 150 μm, 106 μm, 45 μm, or JIS standard sieve, 10 g of the particulate water-absorbing agent was classified. After classification, the weight of each sieve was measured, and the residual percentage R of each particle size was plotted on logarithmic probability paper. The particle diameter corresponding to R = 50% by weight was read as the weight average particle diameter (D50). The logarithmic standard deviation (σζ) of the particle size distribution is expressed by the following equation: σζ = 0.5 × ln (X2 / X1)
Calculated according to

  Here, X1 indicates a particle diameter corresponding to R = 84.1% by weight, and X2 indicates a particle diameter corresponding to R = 15.9% by weight. Note that the smaller the value of σζ, the narrower the particle size distribution.

(5-5) Moisture content The moisture content of the particulate water-absorbing agent according to the present invention was measured according to ERT430.2-02 (however, only the sample weight and the drying temperature were changed).

That is, 1.000 g (weight W6 [g]) of the particulate water-absorbing agent was weighed into an aluminum cup (weight W7 [g]) having a bottom diameter of 5 cm, and then left standing in a windless dryer at 180 ° C. Dried. After the elapse of 3 hours, the total weight (W8 [g]) of the sample was measured, and the following formula: moisture content [wt%] = [{W6- (W8-W7)} / W6] × 100
The water content was calculated according to

(5-6) 1-hour soluble component The “1-hour soluble component” in the present invention is an Ext (water soluble component) measurement method defined in ERT470.2-02, and the extraction time is changed to 1 hour. It refers to the water-soluble matter obtained as described above.

  That is, 200.0 g of 0.90 wt% sodium chloride aqueous solution was weighed into a plastic container with an inner lid and an outer lid having a capacity of 250 ml containing a 35 mm-long rotor, and then 1.00 g of a particulate water-absorbing agent was added to the above. It was added to the aqueous solution and sealed with an inner lid and an outer lid. Then, it stirred for 1 hour (about 500 rpm) using the stirrer at room temperature. By the above operation, the water-soluble component of the particulate water-absorbing agent was extracted.

  After stirring, the extract, which is the above aqueous solution, was filtered using a filter paper (manufactured by ADVANTEC Toyo Co., Ltd .; product name: JIS P 3801 No.2 / thickness 0.26 mm, reserved particle diameter 5 μm), and obtained. The filtrate 50.0 g was used as a measurement liquid. Subsequently, after titrating the said measuring liquid with 0.1N-NaOH aqueous solution until it became pH10, it titrated with 0.1N-HCl aqueous solution until it became pH2.7. The titer at this time was determined as [NaOH] ml and [HCl] ml.

  In addition, the same operation was performed using only 200.0 g of a 0.90% by weight sodium chloride aqueous solution without adding a particulate water-absorbing agent, and the empty titration amounts ([b1NaOH] ml and [b1HCl] ml) were obtained.

From the above titration amount and monomer average molecular weight, the following formula: 1 hour soluble content [% by weight] = 0.1 × (monomer average molecular weight) × 200 × 100 × ([HCl] − [b1HCl]) / 1000 / 1.0 / 50.0
According to the calculation, the soluble component for 1 hour was calculated. When the average molecular weight of the monomer is unknown, neutralization rate [mol%] = {1-([NaOH]-[b1NaOH]) / ([HCl]-[b1HCl])} × 100
The monomer average molecular weight was calculated using the neutralization rate calculated according to

(5-7) Degradable soluble matter (degradation acceleration test, increase amount of degradable soluble component, rate of increase of degradable soluble component)
The “degradable soluble component” in the present invention is an Ext (water soluble component) measuring method defined by ERT470.2-02, and a 0.90 wt% sodium chloride aqueous solution is replaced with a 0.90 wt% sodium chloride aqueous solution. It is changed to an aqueous solution (deterioration test solution) in which L-ascorbic acid is mixed, and the water-soluble component when stirred for 1 hour after standing at 60 ° C. for 2 hours. This test is called “degradation acceleration test”, and the difference between the obtained degradation soluble component and the one-hour soluble component calculated in (5-6) above is defined as “increase amount of degradation soluble component”. The ratio between the soluble content and the 1-hour soluble content calculated in (5-6) above is referred to as “increase rate of the deteriorated soluble content”.

  That is, an aqueous solution (deterioration test solution) containing 0.05% by weight of L-ascorbic acid and 0.90% by weight of sodium chloride in a plastic container with an inner lid and an outer lid with a capacity of 250 ml containing a 35 mm long rotor. / L-ascorbic acid 0.10 g and a 0.90 wt% sodium chloride aqueous solution 199.90 g) 200.0 g was weighed, and then particulate water-absorbing agent 1.00 g was added to the above aqueous solution. The cap was sealed with an outer lid. Then, it left still for 2 hours to the thermostat adjusted to 60 +/- 2 degreeC. After 2 hours, the container was taken out from the incubator and stirred at room temperature for 1 hour using a stirrer (about 500 rpm). By the above operation, the water-soluble component of the particulate water-absorbing agent was extracted.

  After stirring, the extract, which is the above aqueous solution, was filtered using a filter paper (manufactured by ADVANTEC Toyo Co., Ltd .; product name: JIS P 3801 No.2 / thickness 0.26 mm, reserved particle diameter 5 μm), and obtained. The filtrate 50.0 g was used as a measurement liquid. Subsequently, after titrating the said measuring liquid with 0.1N-NaOH aqueous solution until it became pH10, it titrated with 0.1N-HCl aqueous solution until it became pH2.7. The titer at this time was determined as [NaOH] ml and [HCl] ml.

  In addition, the same operation was performed using only 200.0 g of the deterioration test solution without adding the particulate water-absorbing agent, and the empty droplet quantification ([b2NaOH] ml and [b2HCl] ml) was obtained.

From the above titration amount and monomer average molecular weight: Degradable soluble content [wt%] = 0.1 × monomer average molecular weight × 200 × 100 × ([HCl] − [b2HCl]) / 1000 / 1.0 /50.0
The degradation soluble content was calculated according to In addition, when the monomer average molecular weight was unknown, the monomer average molecular weight was calculated using the neutralization rate calculated in the above (5-6).

Moreover, the increase amount of a degradation soluble component is the following formula. Increase amount of a degradation soluble component [weight%] = (degradation soluble component)-(1 hour soluble component)
The increase rate of the deteriorated soluble component is calculated as follows: The increase rate of the deteriorated soluble component [-] = (degradable soluble component) / (1 hour soluble component)
Calculated according to

(5-8) Dusting rate
The “powdering rate” in the present invention refers to a physical property value for evaluating the amount of fine powder generated when a particulate water-absorbing agent is used, and can be determined by the following method.

That is, for the particulate water-absorbing agent, the particle size distribution was measured in accordance with the method described in (5-4) above, and the following formula: Particle content [wt%] with a particle size of less than 150 μm = (Weight) / (weight of water-absorbing resin or particulate water-absorbing agent)
Thus, the content of particles having a particle size of less than 150 μm was determined.

Separately from this, in the P / S test (impact test) specified in (5-10) below, the same operation was performed except that the shaking time was changed from 30 minutes to 60 minutes, causing damage. A particulate water-absorbing agent was obtained. And about the obtained particulate water-absorbing agent, the particle size distribution was measured according to the method as described in said (5-4), and the particle content rate with a particle size of less than 150 micrometers was calculated | required according to the said formula. Next, the following formula: Pulverization rate [% by weight] = (Particle content less than 150 μm particle size after P / S test) − (Particle content less than 150 μm particle size before P / S test)
Thus, the powdering rate of the particulate water-absorbing agent was determined. The lower the value of the powdering rate, the better the particulate water-absorbing agent is in impact resistance stability.

(5-9) Hygroscopic fluidity after impact test (Hygroscopic blocking rate / 60 minutes value)
“Hygroscopic fluidity” in the present invention is an abbreviation for “powder fluidity after moisture absorption” after the impact test. After the impact test (shaking for 10 minutes), the particulate water-absorbing agent is heated to a temperature of 25 ° C. and a relative humidity. The physical property value evaluated for fluidity as blocking, caking, or powder when left under a condition of 90% RH, and judged by “moisture absorption blocking rate”.

  In the present invention, assuming a process damage when processed into an absorbent article, in the P / S test (impact test) defined in the following (5-10), the shaking time is from 30 minutes. Except for changing to 10 minutes, the same operation was performed, and the moisture absorption blocking rate was measured by the following procedure for the particulate water-absorbing agent damaged by the P / S test (shaking for 10 minutes).

  That is, about 2 g of a particulate water-absorbing agent is uniformly sprayed on an aluminum cup having a diameter of 52 mm, and then a thermo-hygrostat (manufactured by Tabay Espec Co., Ltd .; PLATINOUS LUCIFER PL) adjusted to a temperature of 25 ° C. and a relative humidity of 90 ± 5% RH. -2G) for 1 hour (60 minutes).

  Thereafter, the particulate water-absorbing agent in the aluminum cup was gently transferred onto a JIS standard sieve (The IIDA TESTING SIEVE / inner diameter 80 mm) having an opening of 2000 μm (8.6 mesh), and a low-tap type sieve shaker (Iida Co., Ltd.). Using an ES-65 type sieve shaker / rotational speed of 230 rpm and impact number of 130 rpm, classification was performed for 5 seconds under conditions of a temperature of 20 to 25 ° C. and a relative humidity of 50% RH.

Next, the weight of the particulate water-absorbing agent (weight W9 [g]) remaining on the JIS standard sieve and the particulate water-absorbing agent (weight W10 [g]) that passed through the JIS standard sieve were measured. [Weight%] = {W9 / (W9 + W10)} × 100
Thus, the moisture absorption fluidity (moisture absorption blocking rate) was calculated. The moisture absorption blocking rate indicates that the lower the value (closer to 0%), the better the particulate water-absorbing agent is in the moisture absorption fluidity.

(5-10) Paint shaker test (P / S test (shaking for 30 minutes))
The “paint shaker test (P / S test)” in the present invention refers to a test in which the particulate water-absorbing agent is subjected to process damage equivalent to actual equipment (corresponding to process damage received in an actual manufacturing plant). This is a test that reproduces the energy equivalent to the energy actually received by the particulate water-absorbing agent by pneumatic transportation at the laboratory scale.

  That is, a glass container having a diameter of 6 cm, a height of 11 cm, and an internal volume of 225 ml (preferably, a mayonnaise bottle manufactured by Yamamura Glass Co., Ltd., trade name: A-29 or equivalent), 30 g of a particulate water-absorbing agent and a glass having a diameter of 6 mm. 10 g of beads (soda-lime glass beads for precision fraction filling) are put in, and after the resinous inner lid (material: polyethylene) and outer lid (material: polypropylene) for the container, paint shaker (Toyo Seisakusho) Product No. 488) and shaken at 800 [cycle / min] (CPM) for 30 minutes. Thereafter, the glass beads were removed with a JIS standard sieve having an opening of 2 mm to obtain a damaged particulate water-absorbing agent. For the paint shaker device (P / S tester), glass container, and other conditions, reference can be made to JP-A-9-235378 (specifications and FIGS. 12 to 15).

(5-11) Evaluation test with water-absorbing sheet Using the particulate water-absorbing agent 8.4 [g] and the wood pulverized pulp 12.6 [g] obtained in this example, 12 cm × 38 cm, thickness of about 5 mm An absorbent sheet (core concentration: 40% by weight) was prepared. Next, the absorbent sheet was spread on a flat surface, and a resin cylinder (inner diameter 25 mm, internal volume 60.3 [g / cm ² ]) was placed in the center of the sheet. Subsequently, 60 ml of a 0.9% by weight aqueous sodium chloride solution was quickly poured into the cylinder, and the time [seconds] from the injection until the liquid in the cylinder was absorbed by the absorbent sheet and disappeared was measured. Then, injection of 60 ml of 0.9 wt% sodium chloride aqueous solution was performed three times in total, and each absorption amount (absorption amount per minute) was expressed by the following equation: absorption amount [g] = {60 [g] / (inside cylinder Time until the liquid of the liquid disappears) [seconds]} × 60 [seconds]
Calculated according to

[Production Example 1]
Polyethylene glycol diacrylate (molecular weight 523) 2.28 g (0.02 mol%: monomer) was dissolved in 5500 g (monomer concentration 35 wt%) of an aqueous sodium acrylate solution having a neutralization rate of 75 mol%. After obtaining the monomer aqueous solution (a), it was deaerated under a nitrogen gas atmosphere for 30 minutes.

  Next, the monomer aqueous solution (a) is charged into a reactor formed by attaching a lid to a double-arm jacketed stainless steel kneader having two sigma type blades with an internal volume of 10 L, and the liquid temperature is set to 30. Nitrogen gas was blown into the reactor while maintaining the temperature, and nitrogen gas substitution was performed so that dissolved oxygen in the system (monomer aqueous solution (a)) became 1 ppm or less.

  Subsequently, 24.6 g of a 10% by weight aqueous sodium persulfate solution and 21.8 g of a 0.2% by weight aqueous L-ascorbic acid solution were separately added while stirring the monomer aqueous solution (a). Polymerization started about 1 minute after the addition was completed. Then, the resulting hydrogel crosslinked polymer (a) was polymerized at 30 to 90 ° C. while pulverizing, and the hydrogel crosslinked polymer (a) was taken out from the reactor after 60 minutes from the start of polymerization. The obtained hydrogel crosslinked polymer (a) had a diameter of about 5 mm.

  The finely divided hydrogel crosslinked polymer (a) is spread on a wire mesh having an opening of 300 μm (50 mesh), dried with hot air at 180 ° C. for 45 minutes, pulverized with a roll mill, and further opened. Classification was carried out with 850 μm and 150 μm JIS standard sieves. By this series of operations, a water absorbent resin powder (a) having a particle size of 150 μm or more and less than 850 μm was obtained. The CRC of the water absorbent resin powder (a) (absorption capacity under no pressure) was 53.0 [g / g].

  Next, a surface treatment agent comprising 0.02 parts by weight of ethylene glycol diglycidyl ether, 1.5 parts by weight of propylene glycol and 3.0 parts by weight of water is uniformly applied to 100 parts by weight of the water absorbent resin powder (a). And heated at 100 ° C. for 45 minutes. Thereafter, a paint shaker test (shaking for 30 minutes) was performed, and the particles were sized as a passing product of a JIS standard sieve having an opening of 850 μm, whereby water-absorbent resin particles (A1) having a crosslinked surface were obtained.

[Production Example 2]
Surface comprising 0.015 parts by weight of ethylene glycol diglycidyl ether, 1.5 parts by weight of propylene glycol and 3.5 parts by weight of water with respect to 100 parts by weight of the water-absorbent resin powder (a) obtained in Production Example 1 above. The treating agent was mixed uniformly and heat-treated at 100 ° C. for 45 minutes. Thereafter, a paint shaker test (shaking for 30 minutes) was performed, and the particles were sized as a passing product of a JIS standard sieve having an opening of 850 μm, thereby obtaining water-absorbent resin particles (A2) having a crosslinked surface.

[Production Example 3]
With respect to 100 parts by weight of the water-absorbent resin powder (a) obtained in Production Example 1, 0.03 part by weight of ethylene glycol diglycidyl ether, 0.32 part by weight of 1,4-butanediol, 0.5 parts of propylene glycol A surface treatment agent consisting of parts by weight and 3.0 parts by weight of water was uniformly mixed and heat-treated at 180 ° C. for 45 minutes. Thereafter, a paint shaker test (shaking for 30 minutes) was performed, and the particles were sized as a passing product of a JIS standard sieve having an opening of 850 μm, thereby obtaining water-absorbing resin particles (A3) having a crosslinked surface.

[Production Example 4]
5.7 g (0.05 mol%: monomer) of polyethylene glycol diacrylate (molecular weight 523) was dissolved in 5500 g of sodium acrylate aqueous solution (monomer concentration 35 wt%) having a neutralization rate of 75 mol%. After obtaining the monomer aqueous solution (a4), it was degassed for 30 minutes in a nitrogen gas atmosphere.

  Next, the monomer aqueous solution (a4) was charged into a reactor formed by attaching a lid to a double-arm jacketed stainless steel kneader having two sigma-type blades with an internal volume of 10 L, and the liquid temperature was 30. Nitrogen gas was blown into the reactor while maintaining the temperature, and nitrogen gas substitution was performed so that dissolved oxygen in the system (monomer aqueous solution (a4)) was 1 ppm or less.

  Subsequently, 24.6 g of a 10% by weight sodium persulfate aqueous solution and 21.8 g of a 0.2% by weight L-ascorbic acid aqueous solution were separately added while stirring the monomer aqueous solution (a4). Polymerization started about 1 minute after the addition was completed. Then, the produced hydrogel crosslinked polymer (a4) was polymerized at 30 to 90 ° C. while pulverizing, and the hydrogel crosslinked polymer (a4) was taken out from the reactor after 60 minutes from the start of polymerization. The obtained hydrogel crosslinked polymer (a4) had a diameter of about 5 mm.

  The finely divided hydrogel crosslinked polymer (a4) is spread on a wire mesh with an opening of 300 μm (50 mesh), dried with hot air at 180 ° C. for 45 minutes, and then pulverized with a roll mill. Classification was carried out with 850 μm and 150 μm JIS standard sieves. By this series of operations, a water absorbent resin powder (a4) having a particle diameter of 150 μm or more and less than 850 μm was obtained. The water absorbent resin powder (a4) had a CRC (water absorption capacity under no pressure) of 42.0 [g / g].

  Next, a surface treatment agent comprising 0.04 parts by weight of ethylene glycol diglycidyl ether, 1.5 parts by weight of propylene glycol and 3.0 parts by weight of water is uniformly applied to 100 parts by weight of the water absorbent resin powder (a4). And heated at 100 ° C. for 45 minutes. Thereafter, a paint shaker test (shaking for 30 minutes) was performed, and the particles were sized as a passing product of a JIS standard sieve having an opening of 850 μm, thereby obtaining water-absorbing resin particles (A4) having a crosslinked surface.

[Production Example 5]
The dried product (hydrogel-dried hydrogel crosslinked polymer (a)) obtained in Production Example 1 was pulverized with a roll mill and further classified only with a JIS standard sieve having an opening of 850 μm. By this series of operations, a water absorbent resin powder (a5) having a particle size of less than 850 μm was obtained. And except the said operation, operation similar to manufacture example 1 was performed and the water absorbent resin particle (A5) by which the surface was bridge | crosslinked was obtained.

[Example 1]
Zinc stearate aqueous dispersion (manufactured by ADEKA Chemical Supply Co., Ltd .; trade name FPCODISPER ZD (registered trademark) / solid content 42.5% by weight, including surfactant) 0.706 parts by weight and water 6.254 parts by weight Then, 0.04 part by weight of ethylenediaminetetra (methylenephosphonic acid) 5 sodium (hereinafter abbreviated as “EDTMP · 5Na”) was added to prepare dispersion (1).

  Next, 7 parts by weight of the dispersion (1) (substantial addition amount: 0.3 parts by weight of zinc stearate, EDTMP · 5Na0) with respect to 100 parts by weight of the water-absorbent resin particles (A1) obtained in Production Example 1. .04 parts by weight, 6.66 parts by weight of water) was added with stirring and mixed for 1 minute. Then, after transferring to a bag with a chuck, sealing, and curing at 80 ° C. for 1 hour, the cured product was crushed until it passed through a JIS standard sieve having an opening of 850 μm to obtain water absorbent resin particles (B1). .

  Further, a surfactant aqueous solution (1) comprising 0.1 part by weight of polyoxyethylene alkyl ether (manufactured by Nippon Shokubai Co., Ltd .; Softanol 90 (registered trademark) / solid content of 100% by weight) and 2.0 parts by weight of water was prepared. did. Then, 2.1 parts by weight of the surfactant aqueous solution (1) was added to 100 parts by weight of the water-absorbent resin particles (B1) with stirring, and mixed for 1 minute. After that, it was transferred to a bag with a chuck (produced by Nihon Co., Ltd .; Unipack (registered trademark)), sealed, cured at 80 ° C. for 1 hour, and then cured until it passed through a JIS standard sieve having an opening of 850 μm. The product was crushed (sized) to obtain a particulate water-absorbing agent (1). Table 1 shows various performances of the obtained particulate water-absorbing agent (1).

[Example 2]
In Example 1, the amount of polyoxyethylene alkyl ether was changed to 0.05 parts by weight to prepare a surfactant aqueous solution (2), and the surfactant was added to 100 parts by weight of the water-absorbent resin particles (B1). Except for adding 2.05 parts by weight of the aqueous agent solution (2), the same operation as in Example 1 was performed to obtain a particulate water-absorbing agent (2). Table 1 shows various performances of the obtained particulate water-absorbing agent (2).

[Example 3]
In Example 1, the surfactant aqueous solution (3) was prepared by changing the amount of polyoxyethylene alkyl ether to 0.01 parts by weight, and the surfactant was added to 100 parts by weight of the water-absorbent resin particles (B1). Except for adding 2.01 parts by weight of the aqueous agent solution (3), the same operation as in Example 1 was performed to obtain a particulate water-absorbing agent (3). Various performances of the obtained particulate water-absorbing agent (3) are shown in Tables 1, 3 and 4.

[Example 4]
In Example 1, the amount of polyoxyethylene alkyl ether was changed to 0.005 parts by weight to prepare an aqueous surfactant solution (4), and the surfactant was used with respect to 100 parts by weight of the water-absorbent resin particles (B1). Except for adding 2.005 parts by weight of the aqueous agent solution (4), the same operation as in Example 1 was performed to obtain a particulate water-absorbing agent (4). Table 1 shows various performances of the obtained particulate water-absorbing agent (4).

[Example 5]
In Example 3, the water-absorbent resin particles (A2) obtained in Production Example 2 were used in place of the water-absorbent resin particles (A1). Agent (5) was obtained. Table 1 shows various performances of the obtained particulate water-absorbing agent (5).

[Example 6]
Calcium stearate aqueous dispersion (manufactured by ADEKA Chemical Supply Co., Ltd .; trade name EFCODISPER C (registered trademark) / solid content 50% by weight, including surfactant) 0.6 part by weight and 6.36 parts by weight of water were mixed Then, dispersion liquid (6) was created by adding EDTMP · 5Na 0.04 part by weight.

  Next, 7 parts by weight of the dispersion liquid (6) (substantial addition amount: 0.3 parts by weight of calcium stearate, EDTMP · 5Na, 0.1% by weight) with respect to 100 parts by weight of the water-absorbent resin particles (A1) obtained in Production Example 1. 04 parts by weight and 6.66 parts by weight of water) were added with stirring and mixed for 1 minute. Then, after transferring to a bag with a chuck, sealing, and curing at 80 ° C. for 1 hour, the cured product was crushed until passing through a JIS standard sieve having an opening of 850 μm to obtain water absorbent resin particles (B6). .

  Furthermore, a surfactant aqueous solution (6) comprising 0.01 part by weight of polyoxyethylene alkyl ether and 2.0 parts by weight of water was prepared. Then, 2.01 parts by weight of the surfactant aqueous solution (6) was added to 100 parts by weight of the water-absorbent resin particles (B6) with stirring, and mixed for 1 minute. Thereafter, the product was transferred to a bag with a chuck, sealed, and cured at 80 ° C. for 1 hour, and then the cured product was crushed until it passed through a JIS standard sieve having an opening of 850 μm to obtain a particulate water-absorbing agent (6). . Table 1 shows various performances of the obtained particulate water-absorbing agent (6).

[Example 7]
In Example 1, instead of polyoxyethylene alkyl ether, polyoxyethylene sorbitan monostearate (manufactured by Kao Corporation; Rheodor TW-S120V (registered trademark) / solid content 100 wt%) was used, and the polyoxyethylene sorbitan was used. A surfactant aqueous solution (7) comprising 0.1 part by weight of monostearate and 2.0 parts by weight of water was prepared, and the surfactant aqueous solution (7) was added to 100 parts by weight of the water-absorbent resin particles (B1). Except for adding 2.1 parts by weight, the same operation as in Example 1 was performed to obtain a particulate water-absorbing agent (7). Table 1 shows various performances of the obtained particulate water-absorbing agent (7).

[Example 8]
In Example 7, the surfactant aqueous solution (8) was prepared by changing the amount of polyoxyethylene sorbitan monostearate to 0.05 parts by weight, and 100 parts by weight of the water absorbent resin particles (B1) Except for adding 2.05 parts by weight of aqueous surfactant solution (8), the same operation as in Example 7 was performed to obtain a particulate water-absorbing agent (8). Table 1 shows various performances of the obtained particulate water-absorbing agent (8).

[Example 9]
In Example 7, the surfactant aqueous solution (9) was prepared by changing the amount of polyoxyethylene sorbitan monostearate to 0.01 parts by weight, and the water-absorbent resin particles (B1) 100 parts by weight A particulate water-absorbing agent (9) was obtained in the same manner as in Example 7 except that 2.01 parts by weight of the aqueous surfactant solution (9) was added. Table 1 shows various performances of the obtained particulate water-absorbing agent (9).

[Example 10]
In Example 7, the surfactant aqueous solution (10) was prepared by changing the amount of polyoxyethylene sorbitan monostearate to 0.005 parts by weight, and 100 parts by weight of the water absorbent resin particles (B1) A particulate water-absorbing agent (10) was obtained in the same manner as in Example 7, except that 2.005 parts by weight of the surfactant aqueous solution (10) was added. Table 1 shows various performances of the obtained particulate water-absorbing agent (10).

[Example 11]
In Example 1, instead of polyoxyethylene alkyl ether, sodium polyoxyethylene lauryl sulfate (manufactured by Kao Corporation; Emar 20C / solid content 25% by weight) was used, and 0.4 part by weight of sodium polyoxyethylene lauryl sulfate was used. And a surfactant aqueous solution (11) composed of 1.7 parts by weight of water and 2.1 parts by weight (substantially added) of the surfactant aqueous solution (11) with respect to 100 parts by weight of the water-absorbent resin particles (B1). Amount: sodium polyoxyethylene lauryl sulfate 0.1 parts by weight, water 2 parts by weight) was added in the same manner as in Example 1 to obtain a particulate water-absorbing agent (11). Table 1 shows various performances of the obtained particulate water-absorbing agent (11).

[Example 12]
In Example 11, a surfactant aqueous solution (12) comprising 0.04 parts by weight of sodium polyoxyethylene lauryl sulfate and 1.97 parts by weight of water was prepared by changing the amount of sodium polyoxyethylene lauryl sulfate and water. The surfactant aqueous solution (12) is 2.01 parts by weight per 100 parts by weight of the water-absorbent resin particles (B1) (substantially added amount: 0.01 parts by weight of sodium polyoxyethylene lauryl sulfate, 2 parts by weight of water). Except that was added, the same operation as in Example 11 was performed to obtain a particulate water-absorbing agent (12). Table 1 shows various performances of the obtained particulate water-absorbing agent (12).

[Example 13]
In Example 11, an aqueous surfactant solution (13) comprising 0.02 parts by weight of polyoxyethylene sodium lauryl sulfate and 1.985 parts by weight of water was prepared by changing the amount of sodium polyoxyethylene lauryl sulfate and water. The surfactant aqueous solution (13) is 2.005 parts by weight with respect to 100 parts by weight of the water-absorbent resin particles (B1) (substantially added amount: 0.005 parts by weight of sodium polyoxyethylene lauryl sulfate, 2 parts by weight of water). Except that was added, the same operation as in Example 11 was performed to obtain a particulate water-absorbing agent (13). Table 1 shows various performances of the obtained particulate water-absorbing agent (13).

[Example 14]
In Example 1, sodium lauryl sulfate (manufactured by Kao Corporation; Emar 2F paste / solid content 30% by weight) was used instead of polyoxyethylene alkyl ether, 0.33 part by weight of sodium lauryl sulfate and 1.77 of water. A surfactant aqueous solution (14) consisting of parts by weight was prepared, and 2.1 parts by weight of the surfactant aqueous solution (14) (substantial addition amount: sodium lauryl sulfate) per 100 parts by weight of the water-absorbent resin particles (B1). Except for the addition of 0.1 part by weight and 2 parts by weight of water, the same operation as in Example 1 was performed to obtain a particulate water-absorbing agent (14). Table 1 shows various performances of the obtained particulate water-absorbing agent (14).

[Example 15]
In Example 1, instead of polyoxyethylene alkyl ether, polyoxyethylene alkyl ether sulfosuccinic acid half ester salt (manufactured by Nippon Shokubai Co., Ltd .; Softanol MES-3 / solid content 35% by weight) is used. A surfactant aqueous solution (15) composed of 0.29 parts by weight of ether sulfosuccinic acid half ester salt and 1.81 parts by weight of water was prepared, and the surfactant aqueous solution was added to 100 parts by weight of the water absorbent resin particles (B1). (15) The same operation as in Example 1 was performed except that 2.1 parts by weight (substantial addition amount: 0.1 part by weight of polyoxyethylene alkyl ether sulfosuccinic acid half ester salt, 2 parts by weight of water) was added. And a particulate water-absorbing agent (15) was obtained. Table 1 shows various performances of the obtained particulate water-absorbing agent (15).

[Example 16]
In Example 1, instead of polyoxyethylene alkyl ether, lauryl betaine (manufactured by Kao Corporation; Amphital 20BS / solid content 31% by weight) was used, and from 0.32 parts by weight of the lauryl betaine and 1.78 parts by weight of water. A surfactant aqueous solution (16) is prepared, and 2.1 parts by weight of the surfactant aqueous solution (16) (substantially added amount: 0.1% by weight of lauryl betaine) with respect to 100 parts by weight of the water absorbent resin particles (B1). Except for the addition of 2 parts by weight of water), the same operation as in Example 1 was performed to obtain a particulate water-absorbing agent (16). Table 1 shows various performances of the obtained particulate water-absorbing agent (16).

[Example 17]
The same operation as in Example 12 was performed to prepare a surfactant aqueous solution (12). In Example 1, the dispersion (1) containing the zinc stearate aqueous dispersion was added to the water-absorbent resin particles (A1), mixed for 1 minute, and then transferred to a bag with a chuck without performing a curing operation. A particulate water-absorbing agent (17) was obtained in the same manner as in Example 1 except that the surfactant aqueous solution (12) was added to the mixture. Table 1 shows various performances of the obtained particulate water-absorbing agent (17).

[Example 18]
Zinc stearate aqueous dispersion (manufactured by ADEKA Chemical Supply Co., Ltd .; trade name FPCODISPER ZD (registered trademark) / solid content 42.5% by weight, including surfactant) 0.353 parts by weight and water 6.725 parts by weight After mixing, 0.04 part by weight of EDTMP · 5Na was added to prepare a dispersion (18).

  Next, 7 parts by weight of the dispersion (18) (substantially added amount: 0.15 parts by weight of zinc stearate, EDTMP · 5Na0) with respect to 100 parts by weight of the water-absorbent resin particles (A1) obtained in Production Example 1. 0.04 parts by weight, 6.76 parts by weight of water) was added with stirring and mixed for 1 minute. Then, after transferring to a bag with a chuck and sealing, and curing at 80 ° C. for 1 hour, the cured product was disintegrated until it passed through a JIS standard sieve having an opening of 850 μm to obtain water-absorbing resin particles (B18). .

  Further, a surfactant aqueous solution (18) composed of 0.4 parts by weight of sodium polyoxyethylene lauryl sulfate (manufactured by Kao Corporation; Emar 20C / solid content 25% by weight) and 1.867 parts by weight of water was prepared to absorb water. With respect to 100 parts by weight of the resin particles (B18), 2.1 parts by weight of the surfactant aqueous solution (18) (substantially added amount: 0.1 parts by weight of sodium polyoxyethylene lauryl sulfate, 2 parts by weight of water) is stirred. And added for 1 minute. Thereafter, the product was transferred to a bag with a chuck, sealed, and cured at 80 ° C. for 1 hour, and then the cured product was crushed until it passed through a JIS standard sieve having an opening of 850 μm to obtain a particulate water-absorbing agent (18). . Table 1 shows various performances of the obtained particulate water-absorbing agent (18).

[Example 19]
In Example 1, the water-absorbent resin particles (A3) obtained in Production Example 3 were used in place of the water-absorbent resin particles (A1) obtained in Production Example 1, and the same operations as in Example 1 were performed. Operation was performed to obtain a particulate water-absorbing agent (19). Table 1 shows various performances of the obtained particulate water-absorbing agent (19).

[Example 20]
In Example 1, the water-absorbent resin particles (A5) obtained in Production Example 5 were used in place of the water-absorbent resin particles (A1) obtained in Production Example 1, and the same operations as in Example 1 were used. Operation was performed to obtain a particulate water-absorbing agent (20). Table 1 shows various performances of the obtained particulate water-absorbing agent (20).

[Example 21]
A mixed solution (21) of 0.5 parts by weight of epoxy-modified silicone (manufactured by Shin-Etsu Chemical Co., Ltd .; KF101) and 4.5 parts by weight of methanol was prepared.

  Next, with respect to 100 parts by weight of the water-absorbent resin particles (A1) obtained in Production Example 1, 5.0 parts by weight of the mixed solution (21) was added with stirring and mixed for 1 minute, and then 150 ° C. For 20 minutes. Thereafter, the mixture was pulverized until it passed through a JIS standard sieve having an opening of 850 μm to obtain water absorbent resin particles (B21).

  Subsequently, a dispersion liquid (21) composed of 0.04 part by weight of diethylenetriaminepentaacetic acid pentasodium, 0.05 part by weight of polyoxyethylene alkyl ether and 2.91 parts by weight of water was prepared.

  Then, with respect to 100 parts by weight of the water-absorbent resin particles (B21), 3.0 parts by weight of the dispersion (21) was added with stirring and cured at 80 ° C. for 1 hour, and then a JIS standard having an opening of 850 μm. The cured product was pulverized until passing through a sieve to obtain a particulate water-absorbing agent (21). Table 1 shows various performances of the obtained particulate water-absorbing agent (21).

[Example 22]
In Example 21, the same operation as in Example 21 was performed except that a mixed solution (22) was prepared using amino-modified silicone (manufactured by Shin-Etsu Chemical Co., Ltd .; KF808) instead of epoxy-modified silicone. While obtaining the water absorbing resin particle (B22), the particulate water-absorbing agent (22) was obtained. Table 1 shows various performances of the obtained particulate water-absorbing agent (22).

[Example 23]
To 100 parts by weight of the water-absorbent resin particles (A1) obtained in Production Example 1, 1.0 part by weight of a polyethylene emulsion (manufactured by Mitsui Chemicals, Inc .; Chemipearl WP100) was added with stirring and mixed for 1 minute. After that, it was transferred to a bag with a chuck (produced by Nihon Co., Ltd .; Unipack (registered trademark)), sealed, cured at 80 ° C. for 1 hour, and then cured until it passed through a JIS standard sieve having an opening of 850 μm. The product was pulverized (sized) to obtain water-absorbing resin particles (B23).

  Next, with respect to 100 parts by weight of the water-absorbent resin particles (B23), 3.0 parts by weight of the dispersion (21) prepared in Example 21 was added with stirring and cured at 80 ° C. for 1 hour. The cured product was pulverized until it passed through a JIS standard sieve having an opening of 850 μm to obtain a particulate water-absorbing agent (23). Table 1 shows various performances of the obtained particulate water-absorbing agent (23).

[Example 24]
In Production Example 4, after 60 minutes from the start of polymerization, 15.4 g of magnesium stearate (manufactured by Wako Pure Chemical Industries, Ltd.) was added to the hydrogel crosslinked polymer (a4) and mixed for 1 minute in the reactor. Except having done, operation similar to operation of manufacture example 4 was performed, and the water absorbing resin particle (B24) was obtained. In Patent Document 11, mixing of magnesium stearate into a gel is described.

  Next, to 100 parts by weight of the water-absorbent resin particles (B24), 3.0 parts by weight of the dispersion (21) prepared in Example 21 (not described in Patent Document 11) is added with stirring. After curing at 80 ° C. for 1 hour, the cured product was pulverized until it passed through a JIS standard sieve having an opening of 850 μm to obtain a particulate water-absorbing agent (24). Table 1 shows various performances of the obtained particulate water-absorbing agent (24).

[Example 25]
In Example 24, except that 57.75 g of sucrose stearate (manufactured by Mitsubishi Chemical Foods, Inc .; S770) was added instead of magnesium stearate, the same operation as in Example 24 was performed, and particulate water absorption Agent (25) was obtained. Table 1 shows various performances of the obtained particulate water-absorbing agent (25).

[Example 26]
In Example 24, except that 57.75 g of palmitic acid (manufactured by Wako Pure Chemical Industries, Ltd.) was added instead of magnesium stearate, the same operation as in Example 24 was performed, and the particulate water absorbing agent (26) Got. Table 1 shows various performances of the obtained particulate water-absorbing agent (26).

[Example 27]
Zinc stearate aqueous dispersion (manufactured by ADEKA Chemical Supply Co., Ltd .; trade name: EFCODISPER ZD (registered trademark) / solid content 42.5% by weight, including surfactant) 0.71 part by weight and water 6.29 parts by weight Parts were mixed to prepare dispersion (27).

  Next, 7 parts by weight of the dispersion (27) was added to 100 parts by weight of the water-absorbent resin particles (A1) obtained in Production Example 1 with stirring, and mixed for 1 minute. After that, it was transferred to a bag with a chuck (produced by Nihon Co., Ltd .; Unipack (registered trademark)), sealed, cured at 80 ° C. for 1 hour, and then unwound until it passed through a JIS standard sieve with an opening of 850 μm. By crushing (sizing), water-absorbing resin particles (B27) were obtained.

  Further, 2.05 parts by weight of the aqueous surfactant solution (2) prepared in Example 2 was added to 100 parts by weight of the water-absorbent resin particles (B27) with stirring, and mixed for 1 minute. After that, it was transferred to a bag with a chuck (produced by Nihon Co., Ltd .; Unipack (registered trademark)), sealed, cured at 80 ° C. for 1 hour, and then cured until it passed through a JIS standard sieve having an opening of 850 μm. The product was crushed to obtain a particulate water-absorbing agent (27). Various performances of the obtained particulate water-absorbing agent (27) are shown in Tables 1 and 4.

[Comparative Example 1]
Except not using a zinc stearate aqueous dispersion, operation similar to the operation of Example 1 was performed, and the comparison dispersion liquid (1) was created. That is, the comparative dispersion liquid (1) consists of 0.04 parts by weight of EDTMP · 5Na and 6.96 parts by weight of water.

  Next, 7.0 parts by weight of the comparative dispersion (1) was added to 100 parts by weight of the water-absorbent resin particles (A1) obtained in Production Example 1 with stirring, and mixed for 1 minute. After that, it was transferred to a bag with a chuck, sealed, and cured at 80 ° C. for 1 hour, and then the cured product was crushed until it passed through a JIS standard sieve having an opening of 850 μm to obtain a comparative particulate water-absorbing agent (1). It was. Table 2 shows various performances of the obtained comparative particulate water-absorbing agent (1).

[Comparative Example 2]
A comparative example corresponding to Patent Document 9 in which a technique for adding only metal soap to a water absorbent resin is disclosed is shown below.

  That is, in Example 1, except for not adding the aqueous surfactant solution, the same operation as in Example 1 was performed to obtain a comparative particulate water-absorbing agent (2). Table 2 shows various performances of the obtained comparative particulate water-absorbing agent (2).

[Comparative Example 3]
Comparative examples corresponding to Patent Documents 1 to 4 in which techniques for adding water-insoluble inorganic fine particles to a water-absorbent resin are disclosed are shown below.

  That is, with respect to 100 parts by weight of the comparative particulate water-absorbing agent (1) obtained in Comparative Example 1, 0.3 part by weight of silica (manufactured by Nippon Aerosil Co., Ltd .; Aerosil 200CF-5) was added to form a comparative particulate. A water absorbing agent (3) was obtained. Table 2 shows various performances of the obtained comparative particulate water-absorbing agent (3).

[Comparative Example 4]
In Example 1, instead of preparing the surfactant aqueous solution (1), a comparative aqueous solution (4) comprising 0.1 part by weight of aluminum sulfate.16 hydrate and 2.0 parts by weight of water was prepared. Then, a comparative particulate water-absorbing agent was obtained by performing the same operation as in Example 1 except that 2.1 parts by weight of the comparative aqueous solution (4) was added to 100 parts by weight of the water-absorbing resin particles (B1). (4) was obtained. Table 2 shows various performances of the obtained comparative particulate water-absorbing agent (4).

[Comparative Example 5]
Comparative example corresponding to PCT / JP2010 / 66957, which is a prior application disclosing simultaneous addition of metal soap and surfactant in an aqueous dispersion, that is, comparison corresponding to simultaneous addition of metal soap and surfactant Examples (Comparative Examples 5 to 8) are shown below.

  That is, instead of preparing the surfactant aqueous solution (1) in Example 1, after mixing 2.353 parts by weight of a zinc stearate aqueous dispersion and 4.207 parts by weight of water, 0.04 parts by weight of EDTMP · 5Na. Then, 0.4 part by weight of sodium polyoxyethylene lauryl sulfate (manufactured by Kao Corporation; Emar 20C / solid content 25% by weight) was added to prepare a comparative dispersion (5).

  Next, 7.0 parts by weight of the comparative dispersion (5) (substantially added) instead of the aqueous surfactant solution (1) with respect to 100 parts by weight of the water-absorbent resin particles (A1) obtained in Production Example 1. Example 1 except that 1.0 part by weight of zinc stearate, 0.04 part by weight of EDTMP · 5Na, 0.1 part by weight of sodium polyoxyethylene lauryl sulfate, 5.86 parts by weight of water) was added with stirring. The same operation as that of No. 1 was performed to obtain a comparative particulate water-absorbing agent (5). Table 2 shows various performances of the obtained comparative particulate water-absorbing agent (5).

[Comparative Example 6]
In Comparative Example 5, instead of preparing the comparative dispersion (5), 0.706 parts by weight of zinc stearate aqueous dispersion and 6.134 parts by weight of water were mixed, and then 0.04 part by weight of EDTMP · 5Na and polyoxy Comparative dispersion (6) was prepared by adding 0.12 parts by weight of sodium ethylene lauryl sulfate.

  Next, 7.0 parts by weight of the comparative dispersion (6) (substantial addition amount) instead of the comparative dispersion (5) with respect to 100 parts by weight of the water-absorbent resin particles (A1) obtained in Production Example 1. Comparative Example 5 except that 0.3 parts by weight of zinc stearate, 0.04 parts by weight of EDTMP · 5Na, 0.03 parts by weight of sodium polyoxyethylene lauryl sulfate, and 6.63 parts by weight of water) were added with stirring. The same operation as the operation was performed to obtain a comparative particulate water-absorbing agent (6). Table 2 shows various performances of the obtained comparative particulate water-absorbing agent (6).

[Comparative Example 7]
In Comparative Example 5, instead of preparing the comparative dispersion liquid (5), 0.706 parts by weight of zinc stearate aqueous dispersion and 6.214 parts by weight of water were mixed, and then 0.04 part by weight of EDTMP · 5Na and polyoxy Comparative dispersion (7) was prepared by adding 0.04 part by weight of sodium ethylene lauryl sulfate.

  Next, 7.0 parts by weight of the comparative dispersion (7) (substantial addition amount) instead of the comparative dispersion (5) with respect to 100 parts by weight of the water-absorbent resin particles (A1) obtained in Production Example 1 Comparative Example 5 except that 0.3 parts by weight of zinc stearate, 0.04 parts by weight of EDTMP · 5Na, 0.01 parts by weight of sodium polyoxyethylene lauryl sulfate, and 6.65 parts by weight of water) were added with stirring. The same operation as the operation was performed to obtain a comparative particulate water-absorbing agent (7). Table 2 shows various performances of the obtained comparative particulate water-absorbing agent (7).

[Comparative Example 8]
In Comparative Example 5, instead of preparing the comparative dispersion liquid (5), 0.706 parts by weight of zinc stearate aqueous dispersion and 6.214 parts by weight of water were mixed, and then 0.04 part by weight of EDTMP · 5Na and polyoxy Comparative dispersion (8) was prepared by adding 0.02 part by weight of sodium ethylene lauryl sulfate.

  Next, 7.0 parts by weight of the comparative dispersion (8) (substantial addition amount) instead of the comparative dispersion (5) with respect to 100 parts by weight of the water-absorbent resin particles (A1) obtained in Production Example 1. Comparative Example 5 except that 0.3 parts by weight of zinc stearate, 0.04 parts by weight of EDTMP · 5Na, 0.005 parts by weight of sodium polyoxyethylene lauryl sulfate, and 6.65 parts by weight of water) were added with stirring. The same operation as the operation was performed to obtain a comparative particulate water-absorbing agent (8). Table 2 shows various performances of the obtained comparative particulate water-absorbing agent (8).

[Comparative Example 9]
Zinc stearate aqueous dispersion (manufactured by ADEKA Chemical Supply Co., Ltd .; trade name FPCODISPER ZD (registered trademark) / solid content 42.5% by weight, including surfactant) 0.71 part by weight and water 6.29 parts by weight Was mixed to prepare a comparative dispersion liquid (9).

  Next, 7 parts by weight of the comparative dispersion (9) was added to 100 parts by weight of the water-absorbent resin particles (A1) obtained in Production Example 1 with stirring, and mixed for 1 minute. After that, it was transferred to a bag with a chuck, sealed, cured at 80 ° C. for 1 hour, and then the cured product was crushed until it passed through a JIS standard sieve having an opening of 850 μm to obtain a comparative particulate water-absorbing agent (9). It was. Various performances of the obtained comparative particulate water-absorbing agent (9) are shown in Tables 2 and 3.

[Comparative Example 10]
Zinc stearate aqueous dispersion (manufactured by ADEKA Chemical Supply Co., Ltd .; trade name FPCODISPER ZD (registered trademark) / solid content 42.5% by weight, including surfactant) 0.235 parts by weight and water 6.725 parts by weight Then, 0.04 parts by weight of EDTMP · 5Na was added to prepare a comparative dispersion (10).

  Next, with respect to 100 parts by weight of the water-absorbent resin particles (A1) obtained in Production Example 1, 7 parts by weight of the comparative dispersion (10) (substantial addition amount: 0.1 parts by weight of zinc stearate, EDTMP · 5Na 0.04 parts by weight, water 6.76 parts by weight) was added with stirring and mixed for 1 minute. After that, it was transferred to a bag with a chuck, sealed, cured at 80 ° C. for 1 hour, and then the cured product was crushed until it passed through a JIS standard sieve having an opening of 850 μm to obtain a comparative particulate water-absorbing agent (10). It was. Table 2 shows various performances of the obtained comparative particulate water-absorbing agent (10).

[Comparative Example 11]
In Comparative Example 10, the same operation as in Comparative Example 10 was performed except that the water absorbent resin particles (A5) obtained in Production Example 5 were used in place of the water absorbent resin particles (A1), and the comparative particulate form A water absorbing agent (11) was obtained. Table 2 shows various performances of the obtained comparative particulate water-absorbing agent (11).

[Comparative Example 12]
A method corresponding to Example 2 described in Patent Document 5 (and corresponding patent No. 3169133) relating to water-absorbing resin particles treated with organopolysiloxane is shown below.

  The water-absorbent resin particles (B23) in Example 23, that is, the water-absorbent resin particles (B23) before adding the dispersion liquid (21) were used as the comparative particulate water-absorbing agent (12). Table 2 shows various performances of the comparative particulate water-absorbing agent (12).

[Comparative Example 13]
A method corresponding to Example 1 described in Patent Document 5 (and corresponding patent No. 3169133) relating to water-absorbing resin particles treated with organopolysiloxane is shown below.

  The water-absorbent resin particles (B24) in Example 24, that is, the water-absorbent resin particles (B24) before adding the dispersion liquid (21) were used as the comparative particulate water-absorbing agent (13). Table 2 shows various performances of the comparative particulate water-absorbing agent (13).

（まとめ）表１〜３
表２に示すように、特許文献９に相当する比較例２（ステアリン酸亜鉛を添加）の比較粒子状吸水剤（２）や、特許文献５に相当する比較例１２、１３の比較粒子状吸水剤（１２）（１３）は、衝撃試験後の吸湿流動性（吸湿ブロッキング率）、即ち、取り扱い性は良好であるものの、２０重量％食塩水垂直吸収指数が低い。また、比較例１（添加剤無し）および比較例３（シリカを添加）の比較粒子状吸水剤（１），（３）は、２０重量％食塩水垂直吸収指数は高いものの、衝撃試験後の吸湿流動性が悪い。

(Summary) Tables 1-3
As shown in Table 2, the comparative particulate water-absorbing agent (2) of Comparative Example 2 (added with zinc stearate) corresponding to Patent Document 9 and the comparative particulate water-absorbing water of Comparative Examples 12 and 13 corresponding to Patent Document 5 Agents (12) and (13) have good moisture-absorbing fluidity (moisture-absorbing blocking rate) after the impact test, that is, good handleability, but have a low 20 wt% saline vertical absorption index. Comparative particulate water-absorbing agents (1) and (3) of Comparative Example 1 (no additive) and Comparative Example 3 (added silica) had a high 20 wt% saline vertical absorption index, but after the impact test. Hygroscopic fluidity is poor.

  On the other hand, as shown in Table 1, Examples 1 to 23 of the present invention (one of zinc stearate, calcium stearate, modified silicone, magnesium stearate, sucrose stearate, palmitic acid, polyethylene emulsion) The particulate water-absorbing agents (1) to (23) related to the addition of a surfactant have a high 20 wt% saline vertical absorption index in addition to good hygroscopic fluidity after the impact test. Therefore, it can be seen that the balance between the handleability and the absorption performance of the powder is excellent. That is, it can be seen that an excellent particulate absorbent can be obtained by the production method of the present invention. Moreover, in Examples 24-26, although the hydrophobic substance of patent document 11 is used, the outstanding water absorbing agent which is not described in patent document 11 is manufactured by the manufacturing method which concerns on this invention. It can be seen that it can be provided.

  Further, the comparative particulate water absorbing agent (4) of Comparative Example 4 (added with zinc stearate and aluminum sulfate) to which no surfactant is added has a low 20 wt% saline vertical absorption index. It turns out that the manufacturing method of this invention added later is effective.

  And as a kind of surfactant, it turns out that any of nonionicity (Examples 1-10) and ionicity (Examples 11-17) may be sufficient.

  The structure of the surfactant is that the particulate water-absorbing agent (14) of Example 14 (added sodium lauryl sulfate) is better than the particulate water-absorbing agent (11) of Example 11 (added sodium polyoxyethylene lauryl ether sulfate). Since the 20% by weight saline vertical absorption index is lower, it can be seen that a structure having polyoxyethylene units is more preferable.

  In addition, from the results of Example 19, it can be seen that an increase in the amount of passing through 150 μm passing through a JIS standard sieve having an opening of 150 μm (for example, more than 5%) adversely affects the blocking rate and the 20 wt% saline vertical absorption index. . Furthermore, it can be seen from the results of Example 20 that a decrease in moisture content (for example, less than 5%) adversely affects the powdering rate.

  And as shown in FIG. 1, the addition amount of surfactant is 0.01-0.05 weight part with the big improvement effect of a 20 weight% salt water perpendicular | vertical absorption index with respect to 100 weight part of water absorbent resin particles. It can be seen that the degree is preferred. It can also be seen that even if the addition amount is more than 0.1 parts by weight, it is difficult to obtain a further improvement effect of the 20 wt% saline vertical absorption index.

  Furthermore, regarding the method of adding the surfactant, from Comparative Examples 5 and 6 corresponding to the prior application PCT / JP2010 / 66957, when zinc stearate and the surfactant were added simultaneously, the amount of surfactant added It can be seen that although the effect of improving the 20 wt% saline vertical absorption index is high, the hygroscopic fluidity deteriorates.

  That is, as in Examples 1 to 8, it can be seen that by adding a surfactant after the addition of zinc stearate, the balance between handleability and absorption performance is excellent, and the effects of both can be maximized.

  In Comparative Example 5, if the amount of zinc stearate used is increased, even when zinc stearate and a surfactant are added at the same time, the comparative particulate form is excellent in hygroscopic fluidity and 20 wt% saline vertical absorption index. Although the water-absorbing agent (5) can be obtained, excessive addition of zinc stearate is required, resulting in a problem that the production cost is increased and a large amount of zinc stearate is peeled off from the water-absorbent resin. If a large amount of zinc stearate is peeled off from the water-absorbent resin, a large amount of zinc stearate will adhere to the device for processing absorbent articles, and contamination may occur when other products are produced with this device (of zinc stearate). ) Work environment deteriorates due to intense dusting (dust generation). Therefore, excessive addition of additives is not a suitable means for practical use.

  As shown in Table 3, from the comparison between Example 3 and Comparative Example 9, the increase amount (%) of the deteriorated soluble component and the increase rate (%) of the deteriorated soluble component are controlled to be low by using the chelating agent. It can be seen that deterioration due to urine is substantially not observed (excellent urine resistance).

[Example 28]
Using the particulate water-absorbing agent (3) obtained in Example 3, the evaluation test using the water-absorbing sheet described in the above (5-11) was performed. The results are shown in Table 5.

[Comparative Example 14]
Using the comparative particulate water-absorbing agent (2) obtained in Comparative Example 2, the evaluation test using the water-absorbing sheet described in the above (5-11) was performed. The results are shown in Table 5.

（まとめ）
表５に示すように、従来は重要であると考えられていた無加圧下吸水倍率（ＣＲＣ）および加圧下吸水倍率（ＡＡＰ）が同等の粒子状吸水剤（３）および比較粒子状吸水剤（２）において、吸水シートでの試験評価では、本発明の粒子状吸水剤（実施例３）の方が高い吸水量を示す結果が得られた。

(Summary)
As shown in Table 5, the particulate water-absorbing agent (3) and the comparative particulate water-absorbing agent (CRC) and the comparative particulate water-absorbing agent (CRC) having the same water absorption capacity under pressure (CRC) and water absorption capacity under pressure (AAP), which were conventionally considered important, In 2), in the test evaluation with the water-absorbing sheet, the particulate water-absorbing agent of the present invention (Example 3) showed a higher water absorption.

  The particulate water-absorbing agent (Example 3) of the present invention has a 20% by weight normal saline absorption index higher than that of the comparative particulate water-absorbing agent (2). In addition to the conventional non-pressurized water absorption capacity (CRC) and pressurized water absorption capacity (AAP), it was found that the 20 wt% saline vertical absorption index is also important for the performance of the agent.

[Example 29]
In the evaluation of the above (5-9) hygroscopic fluidity (hygroscopic blocking rate) using the particulate water-absorbing agents (1) to (16) obtained in Examples 1 to 16, P / given by assuming process damage The shaking time on the S tester was changed to 0 minutes, 10 minutes, and 30 minutes. However, at any shaking time, the moisture absorption blocking rate was 0% and was stable.

  Therefore, it can be seen that the particulate water-absorbing agent maintains a stable moisture absorption blocking rate and can be widely used regardless of the change (large or small) and the presence or absence of process damage.

[Comparative Example 15]
0.3 parts by weight of silica (manufactured by Nippon Aerosil Co., Ltd .; Aerosil 200CF-5) obtained in Comparative Example 3 corresponding to Patent Documents 1 to 4 in which a technique for adding water-insoluble inorganic fine particles to a water-absorbent resin was disclosed Using the comparative particulate water-absorbing agent (3) to which was added, a test similar to the test of Example 20 was performed, and the shaking time was changed to 0 minutes, 10 minutes, and 30 minutes. Then, with an increase in shaking time (corresponding to an increase in process damage), the moisture absorption blocking rate deteriorated to 0%, 50%, and 90%.

  Therefore, it can be seen that the particulate water-absorbing agents corresponding to Patent Documents 1 to 4 are difficult to use stably because the hygroscopic fluidity decreases due to an increase in process damage.

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

  The method for producing a particulate water-absorbing agent according to the present invention is suitable for producing a particulate water-absorbing agent mainly composed of a water-absorbing resin having high physical properties. The particulate water-absorbing agent according to the present invention is not limited to sanitary materials, but is used for various applications such as civil engineering / architectural water-stopping materials, warmers for cairo, and water-stopping materials for cables. The particulate water-absorbing agent according to the present invention is particularly preferably used for sheet-like or tape-like applications, and can be widely used in various industries.

DESCRIPTION OF SYMBOLS 100 Support cylinder 101 Wire net 102 Swelling gel 103 Piston 104 Weight 105 Petri dish 106 Glass filter 107 Filter paper 108 0.90 weight% (or 20 weight%) Sodium chloride aqueous solution

Claims (32)

A water-insoluble or sparingly water-soluble compound selected from a long-chain alkyl compound, an organic polysiloxane, and an organic polymer compound, containing a polyacrylic acid (salt) -based water-absorbing resin as a main component. A particulate water-absorbing agent containing 5% by weight (however, when a long-chain alkyl compound corresponds to a metal soap, 0.001% by weight or more and less than 1.0% by weight),
Particulate water absorption, wherein the moisture absorption blocking rate after impact test is 0 to 30% by weight, and the 20% by weight normal saline water absorption index is 1.5 to 10.0 [g / g]. Agent.   The particulate water-absorbing agent according to claim 1, wherein 90% by weight or more of the long-chain alkyl compound has a hydrocarbon chain having 8 to 30 carbon atoms.   The particulate water-absorbing agent according to claim 1 or 2, wherein the long-chain alkyl compound is a solid or liquid compound having a hydrophilic functional group at room temperature.   The particulate water-absorbing agent according to claim 1 or 2, wherein the organic polysiloxane is a solid or liquid compound having a hydrophilic functional group at room temperature.   The particulate water absorption according to claim 3 or 4, wherein the hydrophilic functional group is at least one functional group selected from a hydroxyl group, a carboxyl group, a sulfonic acid group, a phosphoric acid group, an amino group, an imino group, and an amide group. Agent.   The particulate water-absorbing agent according to claim 5, wherein the hydrophilic functional group is a carboxyl group or an amino group.   The particulate water-absorbing agent according to claim 6, wherein the hydrophilic functional group is a polyvalent metal salt of an acid group.   The particulate water-absorbing agent according to claim 7, wherein the polyvalent metal salt is one or more compounds selected from barium salts, calcium salts, magnesium salts, aluminum salts, and zinc salts.   The particulate water-absorbing agent according to claim 6, wherein the hydrophilic functional group is an alkali metal salt of an acid group.   Furthermore, the particulate water absorbing agent as described in any one of Claims 1-9 containing surfactant.   The particulate water-absorbing agent according to claim 10, wherein the content of the surfactant is 0.001 to 1.0% by weight with respect to the polyacrylic acid (salt) water-absorbing resin.   The particulate water-absorbing agent according to claim 10 or 11, wherein the surfactant is a compound having a polyoxyethylene unit.   Furthermore, the particulate water absorbing agent as described in any one of Claims 1-12 containing a chelating agent.   The particulate water-absorbing agent according to claim 13, wherein the content of the chelating agent is 0.001 to 5.0% by weight with respect to the polyacrylic acid (salt) -based water-absorbing resin.   The particulate water-absorbing agent according to claim 13 or 14, wherein the chelating agent is a water-soluble organic compound having a nitrogen atom and / or a phosphorus atom.   The particulate water-absorbing agent according to claim 13 or 14, wherein the chelating agent is α-hydroxycarboxylic acid (salt).   The particulate water-absorbing agent according to any one of claims 1 to 16, wherein the polyacrylic acid (salt) -based water-absorbent resin is a water-absorbent resin particle subjected to surface crosslinking.   The particulate water-absorbing agent according to any one of claims 1 to 17, wherein an increase amount of the deterioration soluble component in the deterioration acceleration test is 0 to 15% by weight.   The particulate water absorbing agent according to any one of claims 1 to 18, wherein a water absorption capacity under load (AAP) under a load of 2.06 kPa is 20 [g / g] or more.   The particulate water-absorbing agent according to any one of claims 1 to 19, wherein the water content is 1 to 20% by weight.   The particulate water-absorbing agent according to any one of claims 1 to 20, wherein a powdering rate in an impact test is 1.0% by weight or less.   The weight average particle diameter (D50) is 250 to 450 μm, the content of particles having a particle diameter of less than 150 μm is 0 to 5% by weight, and the logarithmic standard deviation (σζ) is 0 to 0.45. The particulate water-absorbing agent according to any one of the above.   An absorbent body comprising 20 to 80 wt% of the particulate water-absorbing agent according to any one of claims 1 to 22 and 80 to 20 wt% of a hydrophilic fiber. A method for producing a particulate water-absorbing agent comprising a polyacrylic acid (salt) water-absorbing resin as a main component,
A process for polymerizing an aqueous monomer solution mainly composed of acrylic acid (salt), a long-chain alkyl compound, an organic polysiloxane, or an organic polymer compound for a water-absorbing resin before or after drying after the polymerization process. Adding 0.001 to 5% by weight of a selected water-insoluble or hardly water-soluble compound (provided that the long-chain alkyl compound corresponds to a metal soap, 0.001% by weight or more and less than 1.0% by weight); A particulate water-absorbing agent characterized by comprising a step of sequentially adding a surfactant to a water-absorbing resin containing any one or more of the long-chain alkyl compound, organic polysiloxane, and organic polymer compound. Production method.   The production method according to claim 24, wherein the amount of the surfactant added is 0.001 to 1.0% by weight with respect to the polyacrylic acid (salt) -based water absorbent resin.   The production method according to claim 24 or 25, wherein a surfactant is also added in the step of adding any one or more of the long-chain alkyl compound, organic polysiloxane, and organic polymer compound.   The manufacturing method according to any one of claims 24 to 26, further comprising a step of surface cross-linking the water-absorbent resin after drying.   The step of surface cross-linking the dried water-absorbent resin, and adding one or more of a long-chain alkyl compound, organic polysiloxane, and organic polymer compound to the surface-crosslinked water-absorbent resin 28. The method according to any one of claims 24 to 27, further comprising a step of sequentially adding a surfactant to the water-absorbent resin containing any one or more of the step, the long-chain alkyl compound, the organic polysiloxane, and the organic polymer compound. The manufacturing method according to one item.   The production method according to any one of claims 24 to 28, further comprising a step of adding a chelating agent.   The weight average particle diameter (D50) of the water-absorbent resin before surface crosslinking is 250 to 450 μm, the content of particles having a particle diameter of less than 150 μm is 0 to 5% by weight, and the logarithmic standard deviation (σζ) is 0 to 0.45. The manufacturing method according to any one of claims 24 to 29.   The manufacturing method as described in any one of Claims 24-30 whose water absorption capacity | capacitance (AAP) under pressure in 2.06 kPa load of the surface-crosslinked water absorbent resin is 20 [g / g] or more.   The water content of the water-absorbent resin after the step of adding a surfactant to the water-absorbent resin containing any one or more of a long-chain alkyl compound, an organic polysiloxane, and an organic polymer compound is 1 to 20% by weight. The manufacturing method according to any one of claims 24 to 31, wherein

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