JP2018016750A - Water-absorbing resin particle and method for producing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide water-absorbent resin particles having an excellent effect of suppressing cracking and deformation of an absorber after urination. SOLUTION: A polymer (A) containing a water-soluble vinyl monomer (a1) and / or a vinyl monomer (a2) which becomes a water-soluble vinyl monomer (a1) by hydrolysis as an essential constituent unit, and 3 polyvalent metal atoms. Water-absorbent resin particles containing a polyvalent metal salt (B) containing 0.5 to 20% by weight of the polyvalent metal salt (B) based on the weight of the water-absorbent resin particles. [Selection diagram] None

Description

  The present invention relates to water absorbent resin particles and a method for producing the same.

  At present, water-absorbent resins made mainly of hydrophilic fibers such as pulp and acrylic acid (salt) are widely used as absorbents in sanitary materials such as disposable diapers, sanitary napkins, and incontinence pads. From the viewpoint of improving QOL (quality of life) in recent years, demand for these sanitary materials has been shifting to lighter and thinner materials, and accordingly, the use of hydrophilic fibers has been desired to be reduced. . As the amount of the hydrophilic fiber used is reduced, the function of fixing the water-absorbent resin (gel) swollen by urination or the like is lowered, and there is a problem that the absorber is cracked or deformed.

As a method for suppressing cracking and deformation of the absorbent body, a method for regulating the bulk density, suppressing collision between water-absorbent resin particles, and reducing the breakability of the water-absorbent resin is already known (for example, Patent Documents). 1).
However, although this method can reduce the breakability of the water-absorbent resin particles before swelling, the shape retention of the absorbent body after swelling is not satisfactory.
Further, as a method for suppressing cracking and deformation of the absorber, a method of introducing a gel support layer inside the absorber is already known (see, for example, Patent Document 2). However, there is a problem that the diffusibility of the liquid inside the absorbent body changes and the inherent absorbability of the gel is not exhibited.

JP 2010-059254 A JP 2013-75977 A

  An object of the present invention is to provide water-absorbing resin particles having excellent shape retention properties that suppress cracking and deformation of an absorbent body after urination.

The inventor of the present invention has arrived at the present invention as a result of intensive studies to achieve the above object.
That is, the present invention relates to a polymer (A) having a water-soluble vinyl monomer (a1) and / or a vinyl monomer (a2) which becomes a water-soluble vinyl monomer (a1) by hydrolysis as an essential constituent unit, and a polyvalent metal atom. Water-absorbent resin particles containing polyvalent metal salt (B) containing 3 or more, and the polyvalent metal salt (B) contains 0.5 to 20% by weight based on the weight of the water-absorbent resin particles A method for producing water-absorbent resin particles, comprising a step of mixing particles and a solution of the polymer (A) and a polyvalent metal salt (B) containing three or more polyvalent metal atoms.

  The water-absorbent resin particles of the present invention and the water-absorbent resin particles obtained by the production method of the present invention are excellent in shape retention that suppresses cracking and deformation of the absorbent body after urination. Therefore, stable and excellent absorption performance is exhibited even in various usage situations.

  The water-absorbent resin particles of the present invention comprise a polymer (A) having a water-soluble vinyl monomer (a1) and / or a vinyl monomer (a2) that becomes a water-soluble vinyl monomer (a1) by hydrolysis as an essential constituent unit, Water-absorbent resin particles containing a polyvalent metal salt (B) containing three or more valent metal atoms.

  The water-soluble vinyl monomer (a1) in the present invention is not particularly limited, and is a known monomer, for example, at least one water-soluble substituent group disclosed in Japanese Patent No. 3648553, paragraphs 0007 to 0023 and an ethylenic group. Vinyl monomers having a saturated group (for example, anionic vinyl monomers, nonionic vinyl monomers, and cationic vinyl monomers), anionic vinyl monomers disclosed in paragraphs 0009 to 0024 of JP-A No. 2003-165883, nonionic Selected from the group consisting of a carboxylic group, a sulfo group, a phosphono group, a hydroxyl group, a carbamoyl group, an amino group and an ammonio group disclosed in paragraphs 0041 to 0051 of JP-A-2005-75982 At least one kind Vinyl monomers can be used.

  Vinyl monomer (a2) which becomes water-soluble vinyl monomer (a1) by hydrolysis [hereinafter also referred to as hydrolyzable vinyl monomer (a2). ] Is not particularly limited, and known {for example, vinyl monomers having at least one hydrolyzable substituent which becomes a water-soluble substituent by hydrolysis disclosed in paragraphs 0024 to 0025 of Japanese Patent No. 3648553, At least one hydrolyzable substituent [1,3-oxo-2-oxapropylene (—CO—O—CO—) group, acyl group and cyano disclosed in paragraphs 0052 to 0055 of JP-A-2005-75982 Vinyl monomer having a group etc.] can be used. The water-soluble vinyl monomer is a concept well known to those skilled in the art, but when expressed in terms of quantity, for example, it means a vinyl monomer that dissolves in 100 g of water at 25 ° C. The hydrolyzability in the hydrolyzable vinyl monomer (a2) means, for example, the property of being hydrolyzed by the action of water and, if necessary, a catalyst (an acid or a base) to become water-soluble. Hydrolysis of the hydrolyzable vinyl monomer (a2) may be performed either during polymerization, after polymerization, or both of them, but from the viewpoint of the absorption performance of the resulting water-absorbent resin particles, it is preferably after polymerization.

  Among these, the water-soluble vinyl monomer (a1) is preferable from the viewpoint of absorption performance and the like, and more preferably the above-mentioned anionic vinyl monomer, carboxy (salt) group, sulfo (salt) group, amino group, carbamoyl group, Vinyl monomers having an ammonio group or a mono-, di- or tri-alkylammonio group, more preferred are vinyl monomers having a carboxy (salt) group or a carbamoyl group, particularly preferred are (meth) acrylic acid (salt) and (Meth) acrylamide, particularly preferred is (meth) acrylic acid (salt), and most preferred is acrylic acid (salt).

The “carboxy (salt) group” means “carboxy group” or “carboxylate group”, and the “sulfo (salt) group” means “sulfo group” or “sulfonate group”. Moreover, (meth) acrylic acid (salt) means acrylic acid, acrylate, methacrylic acid or methacrylate, and (meth) acrylamide means acrylamide or methacrylamide. Examples of the salt include alkali metal (such as lithium, sodium and potassium) salts, alkaline earth metal (such as magnesium and calcium) salts and ammonium (NH ₄ ) salt. Among these salts, alkali metal salts and ammonium salts are preferable from the viewpoint of absorption performance and the like, more preferable are alkali metal salts, and particularly preferable are sodium salts.

  When either the water-soluble vinyl monomer (a1) or the hydrolyzable vinyl monomer (a2) is used as a structural unit, one kind of each may be used alone as a structural unit, and if necessary, two or more kinds may be used as a structural unit. good. The same applies when the water-soluble vinyl monomer (a1) and the hydrolyzable vinyl monomer (a2) are used as constituent units. Further, when the water-soluble vinyl monomer (a1) and the hydrolyzable vinyl monomer (a2) are used as structural units, the molar ratio [(a1) / (a2)] is preferably 75/25 to 99/1. The ratio is more preferably 85/15 to 95/5, particularly preferably 90/10 to 93/7, and most preferably 91/9 to 92/8. Within this range, the absorption performance is further improved.

  As a constituent unit of the polymer (A), in addition to the water-soluble vinyl monomer (a1) and the hydrolyzable vinyl monomer (a2), another vinyl monomer (a3) copolymerizable with these may be used as the constituent unit. it can. Other vinyl monomers (a3) may be used alone or in combination of two or more.

The other vinyl monomer (a3) is not particularly limited, and is known (for example, a hydrophobic vinyl monomer disclosed in paragraphs 0028 to 0029 of Japanese Patent No. 3648553, paragraph 0025 of Japanese Patent Laid-Open No. 2003-165883, and special features. Hydrophobic vinyl monomers and the like disclosed in paragraph 0058 of Kaikai 2005-75982 can be used. Specifically, for example, the following vinyl monomers (i) to (iii) can be used.
(I) C8-C30 aromatic ethylenic monomer Styrene such as styrene, α-methylstyrene, vinyltoluene and hydroxystyrene, and halogen substituted products of styrene such as vinylnaphthalene and dichlorostyrene.
(Ii) C2-C20 aliphatic ethylenic monomer Alkenes (ethylene, propylene, butene, isobutylene, pentene, heptene, diisobutylene, octene, dodecene, octadecene, etc.); and alkadienes (butadiene, isoprene, etc.) and the like.
(Iii) C5-C15 alicyclic ethylenic monomer Monoethylenically unsaturated monomer (such as pinene, limonene and indene); and polyethylene vinyl monomer [such as cyclopentadiene, bicyclopentadiene and ethylidene norbornene].

  The content (mol%) of the other vinyl monomer (a3) unit is based on the total number of moles of the water-soluble vinyl monomer (a1) unit and hydrolyzable vinyl monomer (a2) unit from the viewpoint of absorption performance and the like. 0 to 5 is preferable, more preferably 0 to 3, particularly preferably 0 to 2, particularly preferably 0 to 1.5. From the viewpoint of absorption performance and the like, the content of other vinyl monomer (a3) units is Most preferably, it is 0 mol%.

  The polymer (A) may be crosslinked with an internal crosslinking agent as necessary. The internal cross-linking agent is not particularly limited and is known (for example, a cross-linking agent having two or more ethylenically unsaturated groups disclosed in Japanese Patent No. 3648553, paragraphs 0031 to 0034, and a functional group capable of reacting with a water-soluble substituent. A cross-linking agent having at least one group and having at least one ethylenically unsaturated group and a cross-linking agent having at least two functional groups capable of reacting with a water-soluble substituent, Japanese Patent Application Laid-Open No. 2003-165883 To a crosslinking agent having two or more ethylenically unsaturated groups, a crosslinking agent having two or more ethylenically unsaturated groups and a reactive functional group, and a crosslinking agent having two or more reactive substituents, The crosslinkable vinyl monomer disclosed in paragraph 0059 of Kaikai 2005-75982 and paragraphs 0015-0016 of JP-A-2005-95759 The indicated cross-linking agent of the crosslinkable vinyl monomer are) it can be used. Among these, from the viewpoint of absorption performance and the like, a crosslinking agent having two or more ethylenically unsaturated groups is preferable, and more preferable is triallyl cyanurate, triallyl isocyanurate, and a poly (poly (2 to 40 carbons) polyol). Meta) allyl ethers, particularly preferred are triallyl cyanurate, triallyl isocyanurate, tetraallyloxyethane, polyethylene glycol diallyl ether and pentaerythritol triallyl ether, most preferred is pentaerythritol triallyl ether. An internal crosslinking agent may be used individually by 1 type, or may use 2 or more types together.

  As a polymerization method of the polymer (A), aqueous solution polymerization (adiabatic polymerization, thin film polymerization, spray polymerization method, etc .; JP-A-55-133413, etc.), known suspension polymerization methods and reverse phase suspension polymerization ( JP-B-54-30710, JP-A-56-26909 and JP-A-1-5808).

When aqueous solution polymerization is performed, a mixed solvent containing water and an organic solvent can be used. Examples of the organic solvent include methanol, ethanol, n-propyl alcohol, isopropyl alcohol, n-butanol, isobutyl alcohol, and t-butyl alcohol. , Isopentyl alcohol, acetone, methyl ethyl ketone, N, N-dimethylformamide, dimethyl sulfoxide, and a mixture of two or more thereof.
The amount (% by weight) of the organic solvent used is preferably 40 or less, more preferably 30 or less, based on the weight of water.

  When the suspension polymerization method or the reverse phase suspension polymerization method is employed, the polymerization may be carried out in the presence of a conventionally known dispersant or surfactant. In the case of the reverse phase suspension polymerization method, polymerization can be carried out using a hydrocarbon solvent such as xylene, normal hexane and normal heptane.

In the case of using an initiator for polymerization, an initiator for radical polymerization can be used. For example, azo compounds [azobisisobutyronitrile, azobiscyanovaleric acid, 2,2′-azobis (2-amidinopropane) hydrochloride, etc. ], Inorganic peroxides (hydrogen peroxide, ammonium persulfate, potassium persulfate, sodium persulfate, etc.), organic peroxides [benzoyl peroxide, di-t-butyl peroxide, cumene hydroperoxide, succinic acid peroxide] And di (2-ethoxyethyl) peroxydicarbonate, etc.] and redox catalyst (alkali metal sulfite or bisulfite, ammonium sulfite, ammonium bisulfite, ascorbic acid, etc., reducing agent and alkali metal persulfate, With oxidizing agents such as ammonium sulfate, hydrogen peroxide and organic peroxide And the like). These catalysts may be used alone or in combination of two or more thereof.
The amount (% by weight) of the radical polymerization initiator used is that of the water-soluble vinyl monomer (a1) and the hydrolyzable vinyl monomer (a2), when the other vinyl monomer (a3) is used (a1) to (a3). Based on the total weight, 0.0005 to 5 is preferable, and 0.001 to 2 is more preferable.

At the time of polymerization, a polymerization control agent typified by a chain transfer agent may be used as necessary. Specific examples thereof include sodium hypophosphite, sodium phosphite, alkyl mercaptans, alkyl halides. And thiocarbonyl compounds. These polymerization control agents may be used alone or in combination of two or more thereof.
The amount (% by weight) of the polymerization control agent used is that of the water-soluble vinyl monomer (a1) and the hydrolyzable vinyl monomer (a2), in the case of using other vinyl monomers (a3) (a1) to (a3), Based on the total weight, 0.0005 to 5 is preferable, and 0.001 to 2 is more preferable.

  The polymerization start temperature can be appropriately adjusted depending on the type of catalyst used, but is preferably 0 to 100 ° C, more preferably 2 to 80 ° C.

  When using a solvent (such as an organic solvent and water) for the polymerization, the solvent is preferably distilled off after the polymerization. When the solvent contains an organic solvent, the content (% by weight) of the organic solvent after the distillation is preferably 0 to 10, more preferably 0 to 5, particularly preferably based on the weight of the polymer (A). 0-3, most preferably 0-1. Within this range, the absorption performance of the water-absorbent resin particles is further improved.

  When water is contained in the solvent, the water content (% by weight) after the distillation is preferably 0 to 20, more preferably 1 to 10, particularly preferably 2 to 9, most preferably based on the weight of the polymer (A). Preferably it is 3-8. Within this range, the absorption performance is further improved.

  The polymer (A) can be obtained by polymerizing a monomer composition having the water-soluble vinyl monomer (a1) and / or the hydrolyzable vinyl monomer (a2) as essential constituent components. Preferred is an aqueous solution polymerization method that does not require the use of an organic solvent or the like and is advantageous in terms of production cost, and more preferred is an aqueous liquid absorbent resin that has a large amount of water retention and a small amount of water-soluble components, An aqueous solution adiabatic polymerization method that does not require temperature control during polymerization is most preferable.

A water-containing gel (hereinafter abbreviated as water-containing gel) can be obtained by the above-described polymerization method, and the polymer (A) is obtained by further crosslinking the surface of the particulate polymer obtained by drying the water-containing gel as necessary. You can also get
When an acid group-containing monomer such as acrylic acid or methacrylic acid is used as the water-soluble vinyl monomer (a1), the hydrogel may be neutralized with a base. The neutralization degree of the acid group is preferably 50 to 80 mol%. When the degree of neutralization is less than 50 mol%, the resulting water-containing gel polymer has high tackiness, and the workability during production and use may deteriorate. Further, the water retention amount of the obtained aqueous liquid absorbent resin may be reduced. On the other hand, when the degree of neutralization exceeds 80%, the pH of the obtained resin becomes high, and there is a concern that the safety of human skin may be concerned.
The neutralization may be performed at any stage after the polymerization of the monomer composition in the production of the water-absorbent resin particles. For example, a method of neutralizing in the state of a hydrous gel is exemplified as a preferred example. .
As the base to be neutralized, alkali metal hydroxides such as sodium hydroxide and potassium hydroxide, and alkali metal carbonates such as sodium carbonate, sodium hydrogen carbonate and potassium carbonate can be used.

  The water-containing gel obtained by polymerization can be shredded as necessary before drying. The size (longest diameter) of the gel after chopping is preferably 50 μm to 10 cm, more preferably 100 μm to 2 cm, and particularly preferably 1 mm to 1 cm. Within this range, the drying property in the drying process is further improved.

  Shredding can be performed by a known method, and can be performed using a shredding device (for example, a bex mill, rubber chopper, pharma mill, mincing machine, impact pulverizer, and roll pulverizer).

  In addition, the content of the organic solvent and the water content are as follows: Infrared moisture meter [JE400 manufactured by KETT Co., Ltd .: 120 ± 5 ° C., 30 minutes, atmospheric humidity before heating 50 ± 10% RH, lamp specification 100V, 40W] is obtained from the weight loss of the measurement sample when heated.

  As a method of distilling off the solvent (including water) of the hydrogel and drying it, a method of distilling (drying) with hot air at a temperature of 80 to 230 ° C., a drum dryer heated to 100 to 230 ° C., etc. A thin film drying method, a (heating) vacuum drying method, a freeze drying method, a drying method using infrared rays, decantation, filtration, and the like can be applied. Moreover, although it does not specifically limit about drying time, From a viewpoint of deterioration of the gel by overdrying, 0 to 3 hours are preferable and 0 to 30 minutes are still more preferable.

The shape and particle size of the polymer (A) can be controlled by pulverization and classification as required. Examples of the shape of the polymer (A) include an irregularly crushed shape, a flake shape, a pearl shape, and a rice grain shape. Among these, from the viewpoint of good entanglement with the fibrous material in the use of paper diapers and the like and no fear of dropping off from the fibrous material, an irregular crushed shape is preferable.
The pulverization method is not particularly limited, and a pulverizer (for example, a hammer pulverizer, an impact pulverizer, a roll pulverizer, and a shet airflow pulverizer) can be used. The pulverized polymer can be adjusted in particle size by sieving if necessary.

The weight average particle diameter (μm) of the polymer (A) is preferably 100 to 800, more preferably 200 to 700, next preferably 250 to 600, particularly preferably 300 to 500, and most preferably 350 to 450. is there. Within this range, the breakage resistance and absorption performance of the water-absorbent resin particles are further improved.
From the viewpoint of absorption performance, the content (% by weight) of fine particles of 106 μm or less (preferably 150 μm or less) in the total weight of the polymer (A) is preferably 3 or less, and more preferably 1 or less. The content of the fine particles can be determined using a graph created when determining the above-mentioned weight average particle diameter.

  The weight average particle size was measured using a low-tap test sieve shaker and a standard sieve (JIS Z8801-1: 2006), Perry's Chemical Engineers Handbook, 6th edition (McGlow Hill Book Campany, 1984, 21). Page). That is, JIS standard sieves are combined in the order of 1000 μm, 850 μm, 710 μm, 500 μm, 425 μm, 355 μm, 250 μm, 150 μm, 125 μm, 75 μm and 45 μm, and a tray from the top. About 50 g of the measured particles are put in the uppermost screen and shaken for 5 minutes with a low-tap test sieve shaker. Weigh the measured particles on each sieve and pan, and calculate the weight fraction of the particles on each sieve with the total as 100% by weight. This value is the logarithmic probability paper [horizontal axis is sieve aperture (particle size ), The vertical axis is plotted in the weight fraction], and then a line connecting the points is drawn to obtain the particle diameter corresponding to the weight fraction of 50% by weight, which is defined as the weight average particle diameter.

  The polymer (A) may contain some other components such as a residual solvent and a residual crosslinking component as long as the performance is not impaired.

  The polymer (A) of the present invention can have a structure in which the surface is crosslinked with a surface crosslinking agent (d). By cross-linking the surface of the polymer (A), the gel strength of the water-absorbent resin particles can be improved, and the desired water retention amount and the absorption amount under load of the water-absorbent resin particles can be satisfied. Examples of the surface cross-linking agent (d) include known polyvalent glycidyl compounds, polyvalent amines, polyvalent aziridine compounds and polyvalent isocyanate compounds described in JP 59-189103 A, JP 58-180233 A. And polyhydric alcohols described in JP-A-61-16903, silane coupling agents described in JP-A-61-211305 and JP-A-61-252212, and JP-A-5-508425. Alkylene carbonate, polyvalent oxazoline compounds described in JP-A No. 11-240959, and surface cross-linking agents such as polyvalent metals described in JP-A Nos. 51-136588 and 61-257235 can be used. Of these surface cross-linking agents, from the viewpoint of economy and absorption characteristics, polyvalent glycidyl compounds, polyhydric alcohols and polyvalent Mines are preferred, more preferred are polyvalent glycidyl compounds and polyhydric alcohols, particularly preferred are polyvalent glycidyl compounds, and most preferred are ethylene glycol diglycidyl ethers. Two or more types may be used in combination, and in the case of using two or more types in combination, two types in which the surface cross-linking agents are not reactive are selected from the viewpoint of breakage resistance of the water-absorbent resin particles. It is preferable to do.

  The amount (% by weight) of the surface cross-linking agent (d) is not particularly limited because it can be variously changed depending on the type of surface cross-linking agent, the conditions for cross-linking, the target performance, etc. From the viewpoint of absorption characteristics, etc. The amount is preferably 0.001 to 3, more preferably 0.005 to 2, and particularly preferably 0.01 to 1.5 with respect to 100 parts by weight of the water absorbent resin.

  The surface crosslinking of the polymer (A) can be performed by mixing the polymer (A) and the surface crosslinking agent (d) and heating as necessary. As a mixing method of the polymer (A) and the surface cross-linking agent (d), a cylindrical mixer, a screw mixer, a screw extruder, a turbulator, a nauter mixer, a double-arm kneader, a fluid type Polymer (A) using a mixing device such as a mixer, a V-type mixer, a minced mixer, a ribbon-type mixer, a fluid-type mixer, an airflow-type mixer, a rotating disk-type mixer, a conical blender, and a roll mixer And a method of uniformly mixing the surface crosslinking agent (d). At this time, the surface crosslinking agent (d) may be used after diluted with water and / or an arbitrary solvent.

  Although the temperature at the time of mixing a polymer (A) and a surface crosslinking agent (d) is not specifically limited, 10-150 degreeC is preferable, More preferably, it is 20-100 degreeC, Especially preferably, it is 25-80 degreeC.

  After mixing the polymer (A) and the surface cross-linking agent (d), the surface-crosslinked polymer (A) can be obtained by performing a heat treatment. The heating temperature is preferably 100 to 180 ° C., more preferably 110 to 175 ° C., and particularly preferably 120 to 170 ° C. from the viewpoint of breakage resistance of the resin particles. Heating at 180 ° C. or lower is advantageous in terms of equipment because indirect heating using steam is possible, and absorption performance may deteriorate at heating temperatures below 100 ° C. Moreover, although heating time can be suitably set with heating temperature, from a viewpoint of absorption performance, Preferably it is 5 to 60 minutes, More preferably, it is 10 to 40 minutes. The surface-crosslinked polymer (A) can be further surface-crosslinked using the same or different surface cross-linking agent as the surface cross-linking agent used first.

  The polymer (A) is sieved as necessary to adjust the particle size. The average particle size of the obtained particles is preferably 100 to 600 μm, more preferably 200 to 500 μm. The content of fine particles is preferably small, the content of particles of 100 μm or less is preferably 3% by weight or less, and the content of particles of 150 μm or less is more preferably 3% by weight or less.

  In the water-absorbent resin particles of the present invention, the polymer (A) may be further treated with a hydrophobic substance, and the method described in JP2013-231199A can be used as a method of treating with a hydrophobic substance. .

  The water-absorbent resin particles of the present invention preferably have a polyvalent metal salt (B) on the resin particle surface. The polyvalent metal salt (B) contains 3 or more polyvalent metal atoms in one molecule, and examples of the polyvalent metal atom include calcium, magnesium, iron, aluminum, cobalt, nickel, copper and the like. Examples of the polyvalent metal salt (B) containing 3 or more polyvalent metal atoms in one molecule include polyferric sulfate, polyaluminum chloride, polyaluminum acetate, polyaluminum hydroxide, and polyaluminum sulfate silicate. . Of these, polyferric sulfate and polyaluminum chloride are preferred, and polyaluminum chloride is more preferred. The water-absorbent resin particles of the present invention have a polyvalent metal salt containing 3 or more polyvalent metal atoms in one molecule, and thus can suppress cracks and the like of the water absorbent after water absorption. This is presumed that by containing three or more polyvalent metal atoms in one molecule, it interacts with the gel at multiple points, and the shape retention of the absorbent after swelling is drastically improved.

  The polyvalent metal salt (B) is 0.5 to 20% by weight, preferably 1.0 to 10.0% by weight, based on the weight of the water-absorbent resin particles, from the viewpoint of breakage resistance of the particles after water absorption. %, More preferably 1.5 to 8.0% by weight. When the content of the polyvalent metal salt (B) is less than 0.5% by weight, the particle surface is not sufficiently covered, and the effect of improving the shape retention of the absorbent after swelling is low. On the other hand, if it exceeds 20% by weight, the gel swelling inhibition effect is great, and the absorption performance is deteriorated. Moreover, also when it has a polyvalent metal salt (B) on the resin particle surface, it is preferable that the polyvalent metal salt (B) which exists on the resin particle surface is the above-mentioned quantity range. Here, the resin particle surface refers to the surface or the vicinity of the surface, and means a surface layer part having a thickness of several tens of μm or less or a surface layer part having a thickness of 1/10 or less.

  The water absorbent resin of the present invention can be obtained by mixing the polymer (A) and the polyvalent metal salt (B). As a mixing method, a cylindrical mixer, a screw type mixer, a screw type extruder, a turbulizer, a nauter type mixer, a double arm type kneader, a fluid type mixer, a V type mixer, a minced mixer, a ribbon type The method of uniformly mixing using well-known mixing apparatuses, such as a mixer, a fluid-type mixer, an airflow type mixer, a rotary disk type mixer, a conical blender, and a roll mixer, is mentioned.

  In mixing the polymer (A) and the polyvalent metal salt (B), it is preferable to add the polyvalent metal salt (B) under stirring of the polymer (A). You may add the polyvalent metal salt (B) added simultaneously with water and / or a solvent. When the polyvalent metal salt (B) is added simultaneously with water and / or a solvent, a solution in which the polyvalent metal salt (B) is dissolved in water and / or a solvent or the polyvalent metal salt (B) is mixed with water and / or a solvent. It is preferable to add a solution from the viewpoint of workability and the like, and it is more preferable to add a solution dissolved in water. When adding a solution or a dispersion, it is preferable to add by spraying or dripping.

  When an aqueous solution in which the polyvalent metal salt (B) is dissolved in water is used, the content of the polyvalent metal salt (B) contained in the aqueous solution is based on the total weight of the aqueous solution from the viewpoint of shape retention of the absorber after water absorption. 5 to 70% by weight is preferable, and more preferably 10 to 60% by weight. When the concentration is lower than the above range, the polyvalent metal salt penetrates into the polymer and the shape retention is lowered. When the concentration is higher, the polymer becomes non-uniform.

  The type of solvent is not particularly limited, but polyhydric alcohols (ethylene glycol, propylene glycol, 1,4-butanediol, etc.) are preferably used, and the solvent may be used alone or in combination of two or more. May be.

  100-140 degreeC is preferable and, as for the temperature at the time of mixing a polymer (A) and a polyvalent metal salt (B), More preferably, it is 100-120 degreeC.

  In the case of heating after mixing the polymer (A) and the polyvalent metal salt (B), the heating time can be appropriately set depending on the heating temperature, but from the viewpoint of absorption performance, preferably 5 to 60 minutes, more preferably Is 10 to 40 minutes. The water-absorbent resin obtained by mixing the polymer (A) and the polyvalent metal salt (B) is further surface-treated using the same or different polyvalent metal salt as the polyvalent metal salt used first. It is also possible.

  The water-absorbent resin particles of the present invention may be used after the polymer (A) and the polyvalent metal salt (B) are mixed and sieved to adjust the particle size. The average particle size of the particles obtained by adjusting the particle size is preferably 100 to 600 μm, more preferably 200 to 500 μm. The content of fine particles is preferably small, the content of particles of 100 μm or less is preferably 3% by weight or less, and the content of particles of 150 μm or less is more preferably 3% by weight or less.

  The water-absorbent resin particles of the present invention may further contain water-insoluble inorganic particles (f). By containing the water-insoluble inorganic particles (f), the surface of the particles contained in the water-absorbent resin particles is surface-treated with the water-insoluble inorganic particles (f), so that the water-absorbent resin particles have blocking resistance and liquid permeability. improves.

  Examples of the water-insoluble inorganic particles (f) include colloidal silica, fumed silica, clay and talc. Colloidal silica and silica are preferable and more preferable from the viewpoints of availability, ease of handling, and absorption performance. Is colloidal silica. One type of water-insoluble inorganic particles (f) may be used alone, or two or more types may be used in combination.

  The use amount (parts by weight) of the water-insoluble inorganic particles (f) is preferably from 0.01 to 5, more preferably from 0.05 to 1, particularly preferably from 100 parts by weight of the water absorbent resin from the viewpoint of absorption performance. Is 0.1 to 0.5.

  When the water-insoluble inorganic particles (f) are contained, it is preferable to mix the water-absorbing resin particles and the water-insoluble inorganic particles (f), and the mixing is performed in the same manner as the mixing of the polyvalent metal salt (B). The conditions are the same.

  The water-absorbent resin particles after mixing the water-insoluble inorganic particles (f) may be used after adjusting the particle size, and the particle size adjustment is performed in the same manner as the particle size adjustment performed after mixing the polyvalent metal salt (B). The same applies to the particle size after particle size adjustment.

  The water-absorbent resin particles of the present invention may be added with additives (for example, known preservatives, fungicides, antibacterial agents, oxidation agents (for example, described in JP-A-2003-225565 and JP-A-2006-131767, etc.) An inhibitor, an ultraviolet absorber, a colorant, a fragrance, a deodorant, a liquid permeability improver (for example, sodium aluminum sulfate 12 hydrate, etc.) and an organic fibrous material) can also be included. When these additives are contained, the content (% by weight) of the additives is preferably 0.001 to 10, more preferably 0.01 to 5, particularly preferably based on the weight of the polymer (A). Is 0.05 to 1, most preferably 0.1 to 0.5.

  The production method of the present invention includes a step of mixing the polymer (A) and a solution of a polyvalent metal salt (B) containing 3 or more polyvalent metal atoms. In the step of mixing the polymer (A) and the polyvalent metal salt (B) solution, the polymer (A) and the polyvalent metal salt (B) solution are mixed using the known mixing device. Can be done. The temperature during mixing is preferably 100 to 140 ° C, more preferably 100 to 120 ° C. By setting it as the solution of a polyvalent metal salt (B), a polymer (A) and a polyvalent metal salt (B) can be mixed uniformly, and quality is stabilized. It is preferable that after the surface of the polymer (A) is crosslinked with a surface crosslinking agent (d), a solution of the polyvalent metal salt (B) is mixed. The production method of the present invention is suitable for obtaining the water-absorbent resin particles of the present invention.

The water content of the water-absorbent resin of the present invention is preferably controlled to 1 to 10% by weight, more preferably 2 to 9% by weight, and particularly preferably 3 to 8% by weight from the viewpoint of breakage resistance.
The apparent density (g / ml) of the water-absorbent resin particles of the present invention is preferably 0.52 to 0.70, more preferably 0.54 to 0.68, and particularly preferably 0.56 to 0.66. . Within this range, the function of fixing the water-absorbent resin (gel) swollen due to urination of the absorbent article is further improved. The apparent density of the water absorbent resin particles is measured at 25 ° C. in accordance with JIS K7365: 1999.

  The water retention amount (g / g) of the water-absorbent resin particles of the present invention can be measured by the method described later, and is preferably 36 or more, more preferably 37 or more, and still more preferably 38 or more from the viewpoint of shape retention. preferable. In addition, the upper limit is preferably 55 or less, more preferably 53 or less, and even more preferably 51 or less, from the viewpoint of the amount of absorption under load. The water retention amount can be appropriately adjusted by the amount (% by weight) of the surface cross-linking agent (d) used.

  The absorbed amount under load (g / g) of the water-absorbent resin particles of the present invention can be measured by the method described later, and is preferably 5 or more, more preferably 10 or more, and particularly preferably 13 or more from the viewpoint of water absorption performance. preferable. The upper limit is preferably 30 or less, more preferably 27 or less, and particularly preferably 24 or less, from the viewpoint of shape retention.

The water-absorbent resin particles of the present invention constitute an absorbent used for sanitary materials such as disposable diapers, sanitary napkins, incontinence pads, medical pads, etc., and are suitably used for absorbent articles containing the absorbent. It is done.
The water absorbent body using the water absorbent resin particles of the present invention is excellent in absorption amount, excellent in liquid uptake speed, excellent in dry touch under pressure after absorption, and suppresses cracking and deformation of the absorbent body. Can do.

  The absorber using the water absorbent resin particles of the present invention is composed of, for example, water absorbent resin particles and hydrophilic fibers. Specific examples of the hydrophilic fiber include wood pulp fibers such as mechanical pulp, chemical pulp, semi-chemical pulp, and dissolved pulp from wood, and artificial cellulose fibers such as rayon and acetate. A preferred hydrophilic fiber is wood pulp fiber. These hydrophilic fibers may partially contain synthetic fibers such as nylon and polyester.

  The content of the water-absorbent resin particles in the absorber is preferably 5 to 95% by mass, more preferably 20 to 90% by mass, and 30 to 80% by mass from the viewpoint of light weight and thin film formation. More preferably it is.

  As the constitution of the absorbent body, the water-absorbent resin particles are sandwiched between the mixed dispersion obtained by mixing the water-absorbent resin particles and the hydrophilic fibers so as to have a uniform composition, and the layered hydrophilic fibers. And a sandwich structure, a structure in which water-absorbent resin particles and hydrophilic fibers are wrapped with a tissue, and the like. The absorbent body may contain other components, for example, an adhesive binder such as a heat-fusible synthetic fiber, a hot melt adhesive, and an adhesive emulsion for enhancing the shape retention of the absorbent body. .

  Also, the absorbent body using the water-absorbent resin particles is held between a liquid-permeable sheet (top sheet) through which liquid can pass and a liquid-impermeable sheet (back sheet) through which liquid cannot pass. Thus, an absorbent article can be obtained. The liquid permeable sheet is disposed on the side in contact with the body, and the liquid impermeable sheet is disposed on the opposite side in contact with the body.

  Examples of the liquid permeable sheet include air-through type, spun bond type, chemical bond type, needle punch type nonwoven fabrics and porous synthetic resin sheets made of fibers such as polyethylene, polypropylene, and polyester. Examples of the liquid impermeable sheet include synthetic resin films made of resins such as polyethylene, polypropylene, and polyvinyl chloride.

  Hereinafter, although an example and a comparative example explain the present invention further, the present invention is not limited to these. Hereinafter, unless otherwise specified, parts indicate parts by weight and% indicates% by weight. In addition, the water retention amount with respect to the physiological saline of the water absorbing resin, the absorption amount under load, the apparent density, the gel strength, and the shape retention of the absorber were measured by the following methods.

<Measurement method of water retention amount>
1.00 g of a measurement sample is placed in a tea bag (20 cm long, 10 cm wide) made of a nylon net having a mesh size of 63 μm (JIS Z8801-1: 2006) and in 1,000 ml of physiological saline (saline concentration 0.9%). The sample was immersed for 1 hour without stirring and then pulled up, suspended for 15 minutes and drained. Thereafter, each tea bag was placed in a centrifuge, centrifuged at 150 G for 90 seconds to remove excess physiological saline, the weight (h1) including the tea bag was measured, and the water retention amount was determined from the following equation. In addition, the temperature of the used physiological saline and measurement atmosphere was 25 degreeC +/- 2 degreeC. (H2) is the weight of the tea bag measured by the same operation as described above when there is no measurement sample.
Water retention amount (g / g) = (h1)-(h2)

<Measurement method of absorption under load>
Using a 30-mesh sieve and a 60-mesh sieve in a cylindrical plastic tube (inner diameter: 25 mm, height: 34 mm) with a 63 m mesh (JIS Z8801-1: 2006) nylon net attached to the bottom, 250-500 m Weighing 0.16 g of the measurement sample screened in the range, aligning the cylindrical plastic tube vertically and adjusting the measurement sample to a substantially uniform thickness on a nylon mesh, and then weighing on the measurement sample (weight: 200 g, outer diameter: 24.5 mm). After measuring the weight (M1) of the entire cylindrical plastic tube, a cylindrical plastic containing a measurement sample and a weight in a petri dish (diameter: 12 cm) containing 60 ml of physiological saline (salt concentration 0.9%). The tube was set up vertically and immersed with the nylon mesh side as the bottom surface and allowed to stand for 60 minutes. After 60 minutes, the cylindrical plastic tube was pulled up from the petri dish, and the slant was tilted to collect the water adhering to the bottom in one place and dropped as water droplets. The total weight (M2) of the cylindrical plastic tube was weighed, and the amount of absorption under pressure was determined from the following equation. In addition, the temperature of the used physiological saline and measurement atmosphere was 25 degreeC +/- 2 degreeC.
Absorption under load (g / g) = {(M2)-(M1)} / 0.16

<Measurement method of apparent density>
It measured based on JISK7365: 1999.

<Method for measuring gel strength> Artificial urine [200 parts by weight of urea, 80 parts by weight of sodium chloride, 8 parts by weight of magnesium sulfate (7-hydrate), 3 parts by weight of calcium chloride (7-hydrate), ferric sulfate (7 water) Salt) 2 parts by weight, ion-exchanged water 9704 parts by weight] Weigh 60.0 g into a 100 ml beaker (inner diameter 5 cm), and precisely weigh 2.0 g of the measurement sample in the same manner as described in JIS K7224-1996. Was put into the beaker to prepare a 30-fold swollen gel. The beaker containing the 30-fold swollen gel was allowed to stand in an atmosphere of 40 ± 2 ° C. for 3 hours, and further in an atmosphere of 25 ± 2 ° C. for 0.5 hour. (For example, it was manufactured by ITEC Techno Engineering Co., Ltd. using a card meter / Max ME-500). The card meter conditions are as follows.・ Pressure sensitive axis: 8 mm ・ Spring: 100 g ・ Load: 100 g ・ Raising speed: 1 inch / 7 seconds ・ Test properties: rupture ・ Measurement time: 6 seconds ・ Measurement ambient temperature: 25 ± 2 ° C.

<Preparation of Absorbent Article> After 100 parts of fluff pulp and 100 parts of an evaluation sample {water-absorbing resin particles} were mixed with an airflow type mixing device {Pad former manufactured by Autech Co., Ltd.} to obtain a mixture, This mixture was uniformly laminated on an acrylic plate (thickness 4 mm) so as to have a basis weight of about 500 g / m ^2, and pressed at a pressure of 5 Kg / cm ² for 30 seconds to obtain an absorber. The absorbent body is cut into a 14 cm × 36 cm rectangle, and water absorbent paper (basis weight: 15.5 g / m ² , manufactured by Advantech Co., Ltd., filter paper No. 2) having the same size as the absorbent body is arranged above and below each. An absorbent article was prepared by disposing a polyethylene sheet (polyethylene film UB-1 manufactured by Tamapoly Co., Ltd.) on the back surface and a non-woven fabric (basis weight 20 g / m ² , Eltas Guard manufactured by Asahi Kasei Co., Ltd.) on the surface.

<Shape retention evaluation method>
The obtained absorbent article was cut into a 3 cm × 8 cm rectangle, and 12 g of physiological saline was added. One minute after the addition, the absorbent article cut into a sample bag with a chuck (manufactured by Production Nippon Co., Ltd., Unipack D-4) was put, and the inside was filled with nitrogen gas and sealed. The sample bag containing the absorbent article was shaken up and down 30 times at a speed of 30 cm / second and with an amplitude of 30 cm, and the degree of dropping of the water absorbent resin particles inside the absorbent body after the test from the hydrophilic fibers was evaluated in four stages. .
A: No dropout of water-absorbent resin particles B: Some of the water-absorbent resin particles (less than 1/5) dropped off Δ: 1/5 or more of the absorbent resin particles dropped off x: The cut absorbent article collapsed

<Production Example 1>
Acrylic acid (a1-1) {Mitsubishi Chemical Co., Ltd., purity 100%} 270 parts, Crosslinker (b-1) {Pentaerythritol triallyl ether, manufactured by Daiso Corporation} 0.98 parts and ion-exchanged water 712 The part was kept at 3 ° C. with stirring and mixing. After flowing nitrogen into this mixture to reduce the dissolved oxygen amount to 1 ppm or less, 1.1 parts of 1% aqueous hydrogen peroxide solution, 2.0 parts of 2% aqueous ascorbic acid solution, and 2% 2,2′-azobis Polymerization was initiated by adding and mixing 13.5 parts of an amidinopropane dihydrochloride aqueous solution. After the temperature of the mixture reached 80 ° C., it was aged at 80 ± 2 ° C. for about 5 hours to obtain a water-containing gel.

  Next, while this hydrated gel was shredded with a mincing machine (12VR-400K manufactured by ROYAL), 220 parts of 49% sodium hydroxide aqueous solution was added and mixed and neutralized to obtain a neutralized gel. Further, the neutralized water-containing gel was air-dried using a ventilation dryer (manufactured by Inoue Metal) under the conditions of a supply temperature of 150 ° C. and a wind speed of 1.5 m / sec until the water content became 4% to obtain a dried product. It was. The dried product is pulverized with a juicer mixer (Osterizer BLENDER manufactured by Oster), and then sieved to adjust the particle size to a particle size range of 710 to 150 μm to obtain resin particles (A-1) containing a crosslinked polymer. It was.

  Subsequently, 100 parts of the obtained resin particles (A-1) were stirred at a high speed (high-speed stirring turbulizer manufactured by Hosokawa Micron: rotation speed: 2000 rpm), and ethylene glycol diglycidyl ether 0 as a surface cross-linking agent (d) was added thereto. .. 12 parts, 1.0 part of propylene glycol, 1.0 part of Klebosol 30cal25 (colloidal silica manufactured by AZ Materials) as water-insoluble inorganic fine particles (f) and 1.7 parts of ion-exchanged water, and liquid flow A mixture of sodium aluminum sulfate dodecahydrate 0.6 part, propylene glycol 0.6 part and ion-exchanged water 1.5 part as a property improver was added at the same time and mixed uniformly. Heating was performed for minutes to obtain surface-crosslinked resin particles (A-2).

<Production Example 2>
Production Example 1 except that the surface crosslinking agent (d) used for 100 parts of the obtained resin particles (A-1) was changed to 0.16 parts of ethylene glycol diglycidyl ether and 1.4 parts of propylene glycol, respectively. The same surface-crosslinked resin particles (A-3) were obtained.

<Production Example 3>
Production Example 1 except that the surface cross-linking agent (d) used for 100 parts of the obtained resin particles (A-1) was changed to 0.01 parts of ethylene glycol diglycidyl ether and 0.5 parts of propylene glycol, respectively. The same surface-crosslinked resin particles (A-4) as in Example 1 were obtained.

<Example 1>
While stirring 100 parts of the resin particles (A-2) obtained in Production Example 1 at high speed (high-speed stirring turbulizer manufactured by Hosokawa Micron: rotation speed 2000 rpm), an aqueous polyferric sulfate solution as a polyvalent metal salt (B) (Nankai Chemical Co., Ltd., 11% by weight of total iron) 5.0 parts was added and mixed uniformly. Then, it heated at 80 degreeC for 30 minute (s), and obtained the water absorbing resin particle (P-1) of this invention.

<Example 2>
While stirring 100 parts of the resin particles (A-2) obtained in Production Example 1 at high speed (high speed stirring turbulizer manufactured by Hosokawa Micron: rotation speed 2000 rpm), a polyaluminum chloride aqueous solution (Nankai) as a polyvalent metal salt (B) Chemical Co., Ltd. (10% by weight aluminum oxide) (5.0 parts) was added and mixed uniformly. Then, it heated at 80 degreeC for 30 minute (s), and obtained the water absorbing resin particle (P-2) of this invention.

<Example 3>
In Example 2, the same operation as in Example 2 was performed except that the resin particles (A-2) were changed to resin particles (A-3) to obtain the water-absorbing resin particles (P-3) of the present invention. It was.

<Example 4>
In Example 2, the same operation as in Example 2 was performed except that the resin particles (A-2) were changed to resin particles (A-4) to obtain the water-absorbing resin particles (P-4) of the present invention. It was.

<Example 5>
In Example 1, except having changed the resin particle (A-2) into the resin particle (A-1), operation similar to Example 1 is performed and the water absorbing resin particle (P-5) of this invention is obtained. It was.

<Comparative Example 1>
The resin particles (A-2) obtained in Production Example 1 were directly used as comparative water-absorbing resin particles (R-1).

<Comparative example 2>
While stirring 100 parts of the resin particles (A-2) obtained in Production Example 1 at high speed (high-speed stirring turbulizer manufactured by Hosokawa Micron: rotation speed: 2000 rpm), an aqueous polyaluminum chloride solution (manufactured by Nankai Chemical Co., Ltd.) 30.0 Part was added and mixed uniformly. Thereafter, the mixture was heated at 80 ° C. for 30 minutes to obtain comparative water absorbent resin particles (R-2).

<Comparative Example 3>
While stirring 100 parts of the resin particles (A-2) obtained in Production Example 1 at a high speed (high speed stirring turbulizer manufactured by Hosokawa Micron: rotation speed 2000 rpm), 5.0 parts of sodium aluminum sulfate 12 hydrate and ions A mixed solution obtained by mixing 3.0 parts of exchange water was mixed uniformly. Thereafter, the mixture was heated at 80 ° C. for 30 minutes to obtain comparative water-absorbent resin particles (R-3).

<Comparative Example 4>
In Comparative Example 2, the same operation as in Comparative Example 2 was performed except that 15.0 parts of polyaluminum chloride aqueous solution (manufactured by Nankai Chemical Co., Ltd.) was changed to 0.4 parts, and comparative water absorbent resin particles (R -4) was obtained.

  Performance evaluation results for the water absorbent resin particles (P-1) to (P-5) of Examples 1 to 5 and the water absorbent resin particles (R-1) to (R-4) of Comparative Examples 1 to 4 (retention) Water amount, absorption amount under load, apparent density, gel strength). The results are shown in Table 1.

<Preparation of absorber>
After mixing 100 parts of fluff pulp and 100 parts of the water-absorbent resin particles (P-1) obtained in Example 1 with an airflow type mixing device {Pad former manufactured by Autech Co., Ltd.}, a mixture was obtained. This mixture was uniformly laminated on an acrylic plate (thickness 4 mm) so as to have a basis weight of about 500 g / m ^2, and pressed at a pressure of 5 Kg / cm ² for 30 seconds to obtain an absorber. The absorbent body is cut into a 14 cm × 36 cm rectangle, and water absorbent paper (basis weight: 15.5 g / m ² , manufactured by Advantech Co., Ltd., filter paper No. 2) having the same size as the absorbent body is arranged above and below each. An absorbent article was prepared by disposing a polyethylene sheet (polyethylene film UB-1 manufactured by Tamapoly Co., Ltd.) on the back surface and a non-woven fabric (basis weight 20 g / m ² , Eltas Guard manufactured by Asahi Kasei Co., Ltd.) on the surface.

  The water-absorbent resin particles (P-1) were replaced with the water-absorbent resin particles (P-2) to (P-5) of Examples 2 to 5 and the water-absorbent resin particles (R-1) to (R) of Comparative Examples 1 to 4. Except for changing to -4), the absorbent body and the absorbent article were respectively adjusted in the same manner as described above. Table 1 shows the shape retention evaluation results for the obtained absorbent article.

From the comparison between Example 1 and Comparative Example 1, the shape retention of the absorber is improved by containing the polyvalent metal salt (B). From Comparative Examples 2 and 4, it can be seen that if the content of the polyvalent metal salt (B) is not appropriate, the water absorption performance of the water retention amount and the water absorption amount under load is inferior. Moreover, it turns out that the comparative example 3 using the polyvalent metal salt containing only two polyvalent metal atoms is inferior in the shape retention of the absorber.
In the absorbent resin particles described in the present invention, since the polyvalent metal salt (B) is unevenly distributed on the particle surface and does not inhibit the swelling of the gel, the absorbency using the absorbent resin particles of the present invention It can be seen that the article has excellent absorption performance and excellent shape retention that suppresses cracking and deformation of the absorber.

Claims (10)

  A polymer (A) having a water-soluble vinyl monomer (a1) and / or a vinyl monomer (a2) which becomes a water-soluble vinyl monomer (a1) by hydrolysis as an essential constituent unit, and a polyvalent metal atom containing three or more polyvalent metal atoms Water-absorbing resin particles containing a valent metal salt (B), and containing 0.5 to 20% by weight of the polyvalent metal salt (B) based on the weight of the water-absorbing resin particles.   The water-absorbent resin particles according to claim 1, wherein the water retention amount of 0.9% by weight saline is 36 to 55 g / g per unit weight.   The water-absorbent resin particles according to claim 1 or 2, having an apparent density of 0.52 to 0.70 g / ml.   The water-absorbent resin particles according to any one of claims 1 to 3, wherein the polyvalent metal salt (B) is polyferric sulfate or polyaluminum chloride.   The water-absorbent resin particles according to any one of claims 1 to 4, further comprising water-insoluble inorganic particles (f).   The water-absorbent resin particles according to claim 5, comprising two or more kinds of water-insoluble inorganic particles (f).   A polymer (A) having a water-soluble vinyl monomer (a1) and / or a vinyl monomer (a2) which becomes a water-soluble vinyl monomer (a1) by hydrolysis as an essential constituent unit, and a polyvalent metal atom containing three or more polyvalent metal atoms A method for producing water-absorbent resin particles, comprising a step of mixing a solution of a valent metal salt (B).   The manufacturing method of Claim 7 which mixes the solution of the said polyvalent metal salt (B) at 100-140 degreeC after bridge | crosslinking the surface of the said polymer (A) with the surface crosslinking agent (d).   The absorber containing the water absorbing resin particle in any one of Claims 1-6.   An absorbent article using the absorbent body according to claim 9.