CN111868145B

CN111868145B - Water-absorbent resin particles and method for producing same

Info

Publication number: CN111868145B
Application number: CN201980018735.8A
Authority: CN
Inventors: 松原佑介; 宫岛徹; 松山泰知
Original assignee: SDP Global Co Ltd
Current assignee: SDP Global Co Ltd
Priority date: 2018-03-29
Filing date: 2019-03-20
Publication date: 2023-07-28
Anticipated expiration: 2039-03-20
Also published as: CN111868145A; JPWO2019188669A1; WO2019188669A1; JP7257090B2; CN116769269A; JP2023060178A

Abstract

Provided is a water-absorbent resin which has little variation in the supply amount in a feeder in a production process. The present invention relates to a water-absorbent resin particle comprising a crosslinked polymer (A) having a water-soluble vinyl monomer (a 1) and a crosslinking agent (b) as essential structural units and water-insoluble silicon compound fine particles (c), wherein the arithmetic average of the Si atomic number concentration (atomic%) at 20 points as measured by scanning electron microscope-energy dispersive X-ray analysis is 0.5 to 5.0, and the variation coefficient of the Si atomic number concentration is 0 to 40%.

Description

Water-absorbent resin particles and method for producing same

Technical Field

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

Background

As sanitary materials such as paper diapers, sanitary napkins, and incontinence pads, water-absorbent resins mainly composed of hydrophilic fibers such as pulp and acrylic acid (salt) are widely used as absorbers. In view Of recent improvement in QOL (Quality Of Life), there is a demand for these sanitary materials to be lighter and thinner, and along with this, it is desired to reduce the amount Of hydrophilic fibers. Therefore, the water-absorbent resin itself is required to have the functions of liquid diffusibility and initial absorption in the absorber which have been heretofore carried by the hydrophilic fiber, and there is a need for a water-absorbent resin having high liquid absorption under load and liquid permeability between the swollen gels.

On the other hand, in the production process of absorbent articles such as disposable diapers and sanitary napkins, if the amount of water-absorbent resin added varies, the performance of the absorbent article varies, and therefore, it is desirable that the variation in the amount of supply in the supply device (hereinafter also referred to as a feeder), for example, a screw feeder or a spring feeder, is small.

Incidentally, as a method of improving the fluidity of powder, a method of using a lubricant (patent document 1), a method of setting a specific aspect ratio and particle diameter (patent document 2), and the like are disclosed. However, with respect to the supply amount variation in the feeder, patent document 2 does not mention or recognize anything, and the method thereof cannot satisfy the performance with respect to the supply amount variation.

Prior art literature

Patent literature

Patent document 1: japanese patent laid-open publication No. 2014-237133

Patent document 2: japanese patent laid-open publication 2016-055193

Disclosure of Invention

Problems to be solved by the invention

The purpose of the present invention is to provide a water-absorbent resin which has little variation in the supply amount in a feeder in a production process.

Means for solving the problems

The present inventors have found that the amount and distribution of the water-insoluble silicon compound fine particles used on the surfaces of the water-absorbent resin particles are related to the variation in the supply amount of the water-absorbent resin to the feeder. Accordingly, the present invention relates to a water-absorbent resin particle comprising a crosslinked polymer (a) having a water-soluble vinyl monomer (a 1) and a crosslinking agent (b) as essential structural units and fine particles of a water-insoluble silicon compound (c), wherein the arithmetic average of the Si atomic number concentration (atomic%) when the number of analysis points is 20 points as measured by scanning electron microscope-energy dispersive X-ray analysis is 0.5 to 5.0, and the coefficient of variation of the Si atomic number concentration is 0 to 40%, and a method for producing the same.

ADVANTAGEOUS EFFECTS OF INVENTION

The water-absorbent resin particles of the present invention and the water-absorbent resin particles obtained by the production method of the present invention have a low coefficient of variation in the Si atomic number concentration of the water-insoluble silicon compound particles on the surface thereof, and the coefficient of variation in the amount of the filler is reduced, thereby reducing the variation in the amount of the filler supplied.

Detailed Description

The water-absorbent resin particles of the present invention comprise a crosslinked polymer (A) having a water-soluble vinyl monomer (a 1) and a crosslinking agent (b) as essential structural units and water-insoluble silicon compound fine particles (c).

The water-soluble vinyl monomer (a 1) in the present invention is not particularly limited, and a known monomer may be used, for example, a vinyl monomer having at least 1 water-soluble substituent and an ethylenically unsaturated group (for example, an anionic vinyl monomer, a nonionic vinyl monomer, and a cationic vinyl monomer) disclosed in paragraphs 0007 to 0023 of Japanese patent application publication No. 3648553, an anionic vinyl monomer, a nonionic vinyl monomer, and a cationic vinyl monomer disclosed in paragraphs 0009 to 0024 of Japanese patent application publication No. 2003-165883, and a vinyl monomer having at least one selected from the group consisting of a carboxyl group, a sulfo group, a phosphono group, a hydroxyl group, a carbamoyl group, an amino group, and an ammonium group disclosed in paragraphs 0041 to 0051 of Japanese patent application publication No. 2005-75982.

Among these, from the viewpoint of absorption performance and the like, an anionic vinyl monomer, a vinyl monomer having a carboxylic (acid salt) group, a sulfonic (acid salt) group, an amino group, a carbamoyl group, an ammonium group or a monoalkylammonium group, a dialkylammonium group or a trialkylammonium group is preferable, a vinyl monomer having a carboxylic (acid salt) group or a carbamoyl group is more preferable, (meth) acrylic acid (salt) and (meth) acrylamide are particularly preferable, and (meth) acrylic acid (salt) is particularly preferable, and acrylic acid (salt) is most preferable.

The "carboxylic (acid salt) group" means "carboxyl group" or "carboxylate group", and the "sulfonic (acid salt) group" means "sulfo group" or "sulfonate group". In addition, (meth) acrylic acid (salt) means acrylic acid, acrylic acid salt, methacrylic acid or methacrylic acid salt, and (meth) acrylamide means acrylamide or methacrylamide. Examples of the salt include alkali metal (lithium, sodium, potassium, etc.), alkaline earth metal (magnesium, calcium, etc.), and ammonium (NH) ₄ ) Salts, and the like. Among these salts, alkali metal salts and alkali metal salts are preferred from the viewpoint of absorption performance and the likeAmmonium salts, more preferably alkali metal salts, particularly preferably sodium salts.

As the structural unit of the crosslinked polymer (a), other vinyl monomers (a 2) which can be copolymerized with the water-soluble vinyl monomers (a 1) may be used as the structural unit. The other vinyl monomer (a 2) may be used alone or in combination of two or more.

The other copolymerizable vinyl monomer (a 2) is not particularly limited, and known hydrophobic vinyl monomers and the like (for example, hydrophobic vinyl monomers disclosed in paragraphs 0028 to 0029 of Japanese patent application laid-open No. 3648553, vinyl monomers disclosed in paragraph 0025 of Japanese patent application laid-open No. 2003-165883 and paragraph 0058 of Japanese patent application laid-open No. 2005-75982) can be used, and specifically, for example, vinyl monomers of the following (i) to (iii) can be used.

(i) Aromatic vinyl monomer with 8-30 carbon atoms

Styrene such as styrene, α -methylstyrene, vinyltoluene and hydroxystyrene, and halogen substituted styrenes such as vinylnaphthalene and dichlorostyrene.

(ii) Aliphatic ethylenic monomer having 2 to 20 carbon atoms

Olefins (ethylene, propylene, butene, isobutylene, pentene, heptene, diisobutene, octene, dodecene, octadecene, etc.); and diolefins (butadiene, isoprene, etc.), etc.

(iii) Alicyclic ethylenic monomer having 5 to 15 carbon atoms

Monoethylenically unsaturated monomers (pinene, limonene, indene, etc.); and polyethylenic vinyl monomers [ cyclopentadiene, dicyclopentadiene, ethylidenenorbornene, etc. ], etc.

The content (mol%) of the other vinyl monomer (a 2) unit is preferably 0 to 5, more preferably 0 to 3, particularly preferably 0 to 2, particularly preferably 0 to 1.5, based on the number of moles of the water-soluble vinyl monomer (a 1) unit, and the content of the other vinyl monomer (a 2) unit is most preferably 0 mol% from the viewpoint of absorption performance and the like.

The crosslinking agent (b) is not particularly limited, and known crosslinking agents and the like (for example, crosslinking agents having 2 or more ethylenically unsaturated groups, crosslinking agents having at least 1 functional group capable of reacting with a water-soluble substituent, crosslinking agents having at least 1 ethylenically unsaturated group, crosslinking agents having at least 2 functional groups capable of reacting with a water-soluble substituent, crosslinking agents having 2 or more ethylenically unsaturated groups, crosslinking agents having an ethylenically unsaturated group and a reactive functional group, and crosslinking agents having 2 or more reactive substituents, crosslinking monomers, which are disclosed in paragraphs 0028 to 0031 of japanese patent application laid-open No. 2003-165883, crosslinking agents having an ethylenically unsaturated group and a reactive functional group, and crosslinking monomers having 2 or more reactive substituents, which are disclosed in paragraph 9 of japanese patent application laid-open No. 2005-75982, and crosslinking monomers, which are disclosed in paragraphs 0015 to 0010016 of japanese patent application laid-open No. 2005-95759) can be used. Among these, from the viewpoint of absorption properties and the like, a crosslinking agent having 2 or more ethylenically unsaturated groups is preferable, poly (meth) allyl ether of a polyol having 2 to 40 carbon atoms, a (meth) acrylic acid ester of a polyol having 2 to 40 carbon atoms, and a (meth) acrylamide of a polyol having 2 to 40 carbon atoms are more preferable, polyallylether of a polyol having 2 to 40 carbon atoms is particularly preferable, and pentaerythritol triallylether is most preferable. The crosslinking agent (b) may be used alone or in combination of two or more.

The content (mol%) of the crosslinking agent (b) unit is preferably 0.001 to 5, more preferably 0.005 to 3, particularly preferably 0.01 to 1, based on the number of moles of the water-soluble vinyl monomer (a 1) unit (based on the total number of moles of (a 1) to (a 2) in the case of using the other vinyl monomer (a 2)). At this range, the absorption performance becomes better.

As a method for producing the crosslinked polymer (A), there can be mentioned a method in which an aqueous gel polymer (composed of a crosslinked polymer and water) obtained by a known solution polymerization (adiabatic polymerization, film polymerization, spray polymerization, etc., japanese patent application laid-open No. 55-133413, etc.), a known suspension polymerization, or a known reverse-phase suspension polymerization (Japanese patent application laid-open No. 54-30710, japanese patent application laid-open No. 56-26909, japanese patent application laid-open No. 1-5808, etc.) is dried by heating and pulverized as required. The crosslinked polymer (A) may be used alone or in a mixture of two or more.

Among the polymerization methods, the solution polymerization method is preferable, and the aqueous solution polymerization method is particularly preferable because an organic solvent or the like is not necessary, and the production cost is advantageous, and the aqueous solution adiabatic polymerization method is most preferable because a water-absorbent resin having a large water retention capacity and a small amount of water-soluble components can be obtained, and the temperature control at the time of polymerization is not necessary.

In the case of performing aqueous solution polymerization, a mixed solvent containing water and an organic solvent may be used, and examples of the organic solvent include methanol, ethanol, acetone, methyl ethyl ketone, N-dimethylformamide, dimethyl sulfoxide, and a mixture of 2 or more thereof.

In the case of performing aqueous solution polymerization, the amount (wt%) of the organic solvent is preferably 40 or less, more preferably 30 or less based on the weight of water.

In the case of using a catalyst for polymerization, conventionally known catalysts for radical polymerization can be used, and examples thereof include azo compounds [ azobisisobutyronitrile, azobiscyanovaleric acid, 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, bis (2-ethoxyethyl) peroxydicarbonate, etc. ], and redox catalysts (catalysts composed of a combination of a reducing agent such as an alkali metal sulfite or bisulfite, ammonium sulfite, ascorbic acid, etc., and an oxidizing agent such as alkali metal persulfate, ammonium persulfate, hydrogen peroxide, organic peroxide, etc.), and the like. These catalysts may be used alone or in combination of two or more thereof.

The amount (wt%) of the radical polymerization catalyst to be used is preferably 0.0005 to 5, more preferably 0.001 to 2, based on the weight of the water-soluble vinyl monomer (a 1) (based on the total weight of (a 1) to (a 2) in the case of using the other vinyl monomer (a 2)).

In the polymerization, a polymerization control agent such as a chain transfer agent may be used in combination as needed, and specific examples thereof include sodium hypophosphite, sodium phosphite, alkylmercapto alcohol, alkyl halide, thiocarbonyl compound and the like. These polymerization control agents may be used alone or in combination of two or more thereof.

The amount of the polymerization controlling agent to be used (wt%) is preferably 0.0005 to 5, more preferably 0.001 to 2, based on the weight of the water-soluble vinyl monomer (a 1) (based on the total weight of (a 1) to (a 2) in the case of using the other vinyl monomer (a 2)).

In the case of using a suspension polymerization method or an inverse suspension polymerization method as the polymerization method, the polymerization may be carried out in the presence of a conventionally known dispersing agent or surfactant, as required. In the case of the reversed-phase suspension polymerization method, polymerization can be carried out using a conventionally known hydrocarbon solvent such as xylene, n-hexane, and n-heptane.

The polymerization initiation temperature may be appropriately adjusted depending on the kind of the catalyst used, and is preferably 0 to 100 ℃, more preferably 2 to 80 ℃.

In the case where a solvent (an organic solvent, water, or the like) is used in the polymerization, the solvent is preferably distilled off after the polymerization. When the organic solvent is contained in the solvent, the content (wt%) of the organic solvent after distillation is preferably 0 to 10, more preferably 0 to 5, particularly preferably 0 to 3, and most preferably 0 to 1, based on the weight of the crosslinked polymer (a). When the amount is within this range, the absorption properties of the water-absorbent resin particles become better.

When water is contained in the solvent, the water content (% by weight) after distillation is preferably 0 to 20, more preferably 1 to 10, particularly preferably 2 to 9, and most preferably 3 to 8 based on the weight of the crosslinked polymer (a). At this range, the absorption performance becomes better.

The aqueous gel-like material (hereinafter simply referred to as aqueous gel) of the crosslinked polymer (a) can be obtained by the above polymerization method, and the crosslinked polymer (a) can be obtained by further drying the aqueous gel.

When an acid group-containing monomer such as acrylic acid or methacrylic acid is used as the water-soluble vinyl monomer (a 1), the aqueous gel may be neutralized with a base. The neutralization degree of the acid group is preferably 50 to 80 mol%. When the neutralization degree is less than 50 mol%, the adhesiveness of the resulting hydrogel polymer increases, and the workability at the time of production and use may be deteriorated. Further, the water retention capacity of the resulting water-absorbent resin particles may be lowered. On the other hand, in the case where the neutralization degree exceeds 80%, the pH of the obtained resin increases, and there is a concern about safety to human skin.

The neutralization may be performed at any stage after the polymerization of the crosslinked polymer (a) in the production of the water-absorbent resin particles, and as a preferable example, a method of neutralization in the form of an aqueous gel may be exemplified.

As the alkali for neutralization, alkali metal hydroxides such as sodium hydroxide and potassium hydroxide can be used; alkali metal carbonates such as sodium carbonate, sodium hydrogencarbonate and potassium carbonate.

The aqueous gel obtained by polymerization may be chopped as needed. The size (longest diameter) of the gel after cutting is preferably 50 μm to 10cm, more preferably 100 μm to 2cm, particularly preferably 1mm to 1cm. When the content is within this range, the drying property in the drying step is improved.

The shredding may be performed by a known method, and shredding may be performed using a shredding device (e.g., a cone mill (Bexmill), a rubber cutter (rubber cutter), a pharmaceutical mill (Pharmomill), a chopper, an impact mill, a drum mill), or the like.

The content and moisture of the organic solvent were measured by an infrared moisture meter (e.g., JE400 manufactured by KETT corporation: the weight reduction of the measurement sample was determined when the sample was heated at 120.+ -. 5 ℃ for 30 minutes, the atmospheric humidity before heating was 50.+ -.10% RH, and the lamp specifications were 100V and 40W.

As a method for removing the solvent (including water) from the aqueous gel by distillation, the following method can be applied: a method of removing (drying) by distillation with hot air at a temperature of 80 to 230 ℃, a film drying method with a drum dryer or the like heated to 100 to 230 ℃, (heating) reduced pressure drying method, freeze drying method, drying method with infrared rays, decantation, filtration, and the like.

After drying the aqueous gel to obtain the crosslinked polymer (A), further pulverization may be performed. The pulverizing method is not particularly limited, and a pulverizing device (e.g., a hammer mill, an impact mill, a drum mill, and a jet mill) or the like may be used. The crosslinked polymer after pulverization may be subjected to particle size adjustment by sieving or the like as needed.

The weight average particle diameter (μm) of the crosslinked polymer (A) which is optionally classified is preferably 100 to 800, more preferably 200 to 700, still more preferably 250 to 600, particularly preferably 300 to 500, and most preferably 350 to 450. At this range, the absorption performance becomes better.

The weight average particle diameter was measured by a method described in the Pery's Chemical Engineer's Handbook 6 th edition (Maglao-Hill book Co., 1984, page 21) using a Ro-Tap type test Sizer (i.e., takara Shuzo) with a pair of instrument (i.e., umbelliferae) and a standard sieve (JIS Z8801-1:2006). That is, JIS standard sieves were 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 trays, etc. from above. About 50g of the test particles were placed in the uppermost screen, and the mixture was vibrated for 5 minutes by a Ro-Tap type test sieve. The weight of the particles measured on each sieve and tray was measured and the total weight was set to 100% by weight, the weight fraction of the particles on each sieve was obtained, the value was plotted on a logarithmic probability paper [ the horizontal axis represents the mesh (particle size) of the sieve and the vertical axis represents the weight fraction ], and then the points were connected to each other to obtain the particle size corresponding to 50% by weight of the weight fraction, which was defined as the weight average particle size.

Further, since the smaller the content of the fine particles contained in the crosslinked polymer (a) is, the better the absorption performance is, the content (wt%) of the fine particles of 106 μm or less (preferably 150 μm or less) in the total weight of the crosslinked polymer (a) is preferably 3 or less, more preferably 1 or less. The content of the fine particles can be determined using a graph prepared when the weight average particle diameter is determined.

The shape of the crosslinked polymer (A) is not particularly limited, and examples thereof include amorphous crushed, scaly, pearl-like and rice-like ones. Among these, amorphous crushed forms are preferable in terms of good entanglement with fibrous materials and no fear of falling off from the fibrous materials in the use of paper diapers or the like.

The crosslinked polymer (a) may contain a small amount of other components such as a residual solvent and a residual crosslinking component within a range that does not impair the performance of the polymer.

The water-absorbent resin particles of the present invention preferably have a structure in which the surface of the crosslinked polymer (A) is crosslinked by the organic surface crosslinking agent (e). By crosslinking the surface of the crosslinked polymer (a), the gel strength of the water-absorbent resin particles can be improved, and the desired water retention capacity and absorption capacity under load of the water-absorbent resin particles can be further satisfied. As the organic surface crosslinking agent (e), known organic surface crosslinking agents and the like (polyglycidyl compounds described in JP-A-59-189103, polyamines, polyazacycloalkane compounds, polyisocyanate compounds and the like, polyols of JP-A-58-180233 and JP-A-61-16903, silane coupling agents described in JP-A-61-211305 and JP-A-61-252212, alkylene carbonate described in JP-A-5-508425, polyvalent oxazoline compounds described in JP-A-11-240959 and the like) can be used. Among these surface crosslinking agents, polyglycidyl compounds, polyols and polyamines are preferred from the viewpoints of economy and absorption characteristics, polyglycidyl compounds and polyols are more preferred, polyglycidyl compounds are particularly preferred, and ethylene glycol diglycidyl ether is most preferred. The organic surface cross-linking agent (e) may be used alone or in combination of two or more.

In the case of performing surface crosslinking, the amount (wt%) of the organic surface crosslinking agent (e) is not particularly limited, as it varies depending on the kind of the surface crosslinking agent, the condition under which the crosslinking is performed, the target performance, etc., but is preferably 0.001 to 3, more preferably 0.005 to 2, particularly preferably 0.01 to 1.5, based on the weight of the water-absorbent resin particles, etc., from the viewpoint of absorption characteristics.

The surface crosslinking of the crosslinked polymer (a) can be carried out by mixing the crosslinked polymer (a) with an organic surface crosslinking agent (e) and heating. Examples of the method for mixing the crosslinked polymer (a) with the organic surface crosslinking agent (e) include a method in which the crosslinked polymer (a) and the organic surface crosslinking agent (e) are uniformly mixed using a mixing device such as a barrel type mixer, a screw type extruder, a high-speed paddle type mixer (registered trademark), a flexmix type vertical mixer, a nodus type mixer, a double arm type kneader, a flow type mixer, a V type mixer, a chopper mixer, a ribbon mixer, a gas flow type mixer, a rotating disc type mixer, a conical mixer, a drum mixer, or the like. In this case, the organic surface cross-linking agent (e) may be diluted with water and/or any solvent.

The temperature at which the crosslinked polymer (A) and the organic surface crosslinking agent (e) are mixed is not particularly limited, but is preferably 10 to 150 ℃, more preferably 20 to 100 ℃, and particularly preferably 25 to 80 ℃.

After mixing the crosslinked polymer (A) with the organic surface crosslinking agent (e), a heat treatment is generally performed. The heating temperature is preferably 100 to 180 ℃, more preferably 110 to 175 ℃, particularly preferably 120 to 170 ℃, from the viewpoint of the fracture resistance of the resin particles. If the temperature is 180 ℃ or lower, indirect heating can be performed by using steam, which is advantageous in terms of equipment; at heating temperatures less than 100 ℃, the absorption properties may deteriorate. The heating time may be set as appropriate according to the heating temperature, and is preferably 5 to 60 minutes, more preferably 10 to 40 minutes, from the viewpoint of the absorption performance. The water-absorbent resin obtained by surface crosslinking may be further surface crosslinked using an organic surface crosslinking agent of the same kind or different kind from the organic surface crosslinking agent used initially.

The surface of the crosslinked polymer (A) is crosslinked with an organic surface crosslinking agent (e), and then, if necessary, the crosslinked polymer (A) is subjected to screening to adjust the particle size. The average particle diameter of the obtained particles is preferably 100 to 600. Mu.m, more preferably 200 to 500. Mu.m. The content of the fine particles is preferably a small amount, preferably a content of particles of 100 μm or less is 3% by weight or less, more preferably a content of particles of 150 μm or less is 3% by weight or less.

The water-absorbent resin particles of the present invention contain water-insoluble silicon compound fine particles (c). Examples of the fine particles (c) of the water-insoluble silicon compound include silica such as fumed silica, wet silica, colloidal silica, and modified silica; silicate fine particles such as talc, kaolin, zeolite and montmorillonite are preferable from the viewpoints of easiness of obtaining, easiness of handling and absorption performance. (c) One kind may be used alone, or two or more kinds may be used in combination.

The water-insoluble silicon compound fine particles (c) in the present invention are preferably spherical or amorphous particles having an average primary particle diameter of 1 to 100 nm. When the particles are spherical or amorphous, the powder flowability of the water-absorbent resin particles becomes good. The average primary particle diameter of the water-insoluble silicon compound fine particles (c) is preferably 2 to 80nm, more preferably 3 to 60nm, particularly preferably 5 to 50nm. When the average primary particle diameter is less than 1nm, there is a possibility that the absorption characteristics of the water-absorbent resin particles under load may be deteriorated. When the particle diameter is larger than 100nm, the liquid permeability of the water-absorbent resin particles may be deteriorated.

The average primary particle diameter of the water-insoluble silicon compound particles (c) may be measured by a conventionally known method, and examples thereof include the following methods: a method of calculating an arithmetic average value of 100 or more particles from the average measured particle diameters of the longest and shortest diameters of the particles using a 5-ten thousand-fold image of a transmission electron microscope; a method using a scattering particle size distribution measuring apparatus using dynamic light scattering or laser diffraction; in the case of spherical particles, the specific surface area by the BET method is calculated. In the case of using a commercial product, the commercial product may be replaced with a catalogue value. When there is a significant difference in measurement methods in the measurement, the above-described method using a transmission electron microscope is adopted.

The water-absorbent resin particles of the present invention can be obtained by mixing the crosslinked polymer (A) with the water-insoluble silicon compound fine particles (c). Examples of the mixing method include a method of uniformly mixing using a known mixing device such as a cylindrical mixer, a screw extruder, a high-speed paddle mixer (turbo) (registered trademark), a flexmix type vertical mixer, a nodavi mixer, a double-arm kneader, a flow mixer, a V-type mixer, a chopper mixer, a ribbon mixer, an air-flow mixer, a rotating disk mixer, a conical mixer, and a drum mixer, and a vertical mixer having a cylindrical mixed layer and rotating around a central axis is preferable in terms of reduction in the coefficient of variation in the concentration of Si atoms. The vertical type means that the rotation axis is in the up-down direction (vertical direction), the horizontal type means that the rotation axis is in the horizontal direction, and a typical example of the vertical mixer is a flexmix type vertical mixer (for example, trade names: flexmix FX, flexmix FXD: manufactured by Hosokawa Micron corporation), and a typical example of the horizontal mixer is a high-speed paddle mixer (turbo mixer) (registered trade name). It is considered that the flexmix type vertical mixer has a high turbulent mixing effect and can perform mixing rapidly, thereby improving uniformity. In the case of the horizontal mixer, the water-absorbent resin particles are likely to be stored in the lower part of the mixing tank, and the mixing tends to be uneven. The water-insoluble silicon compound particles (c) are considered to be hardly spread on the surface of the crosslinked polymer (a), and can be uniformly mixed on the surface by high-speed and turbulent mixing.

The rotation speed at the time of mixing by a flexmix type vertical mixer is preferably 1000 to 4000rpm, more preferably 2000 to 3000rpm. If the speed is less than 1000rpm, the mixing is not uniform, and if the speed is more than 4000rpm, the water-absorbent resin particles may be broken by impact, and fine powder may be generated.

The amount of the water-absorbent resin particles fed to the flexmix vertical mixer is preferably not more than the range of the handling capacity corresponding to the model. For example, in the case of Flexomix FXD100, 50 to 100kg/h. If the amount is less than 50kg/h, the throughput per unit time is small and the efficiency is low, and if it exceeds 100kg, clogging and the like are caused.

The mixing of the crosslinked polymer (A) with the water-insoluble silicon compound fine particles (c) is preferably carried out by adding the water-insoluble silicon compound fine particles (c) to the crosslinked polymer (A) under stirring. The added water-insoluble silicon compound particles (c) may be added simultaneously with water and/or solvent. When the water-insoluble silicon compound fine particles (c) are added simultaneously with water and/or a solvent, a dispersion in which the water-insoluble silicon compound fine particles (c) are dispersed in water and/or a solvent may be added, and from the viewpoint of workability, the dispersion is preferably added, and further, the aqueous dispersion is preferably added. In the case of adding the dispersion, it is preferable to add the dispersion by spraying or dripping.

In the case of using the dispersion of the water-insoluble silicon compound fine particles (c), the content of the water-insoluble silicon compound fine particles (c) contained in the dispersion is preferably 5 to 70% by weight, more preferably 10 to 60% by weight, relative to the total weight of the dispersion.

As the dispersion of the water-insoluble silicon compound fine particles (c), a dispersion obtained by reacting the raw materials in water and/or a solvent by a conventionally known method and directly granulating the resultant mixture may be used, or a dispersion obtained by mechanically dispersing fine particles in water and/or a solvent may be used.

From the viewpoint of stability of the dispersion, it is preferable to use a dispersion obtained by reacting the raw materials in water and/or a solvent and directly granulating the resultant. The dispersion of the water-insoluble silicon compound fine particles (c) can be obtained as an aqueous colloidal solution (sol) as a commercial product.

The dispersion may contain any additive such as a stabilizer, if necessary. Examples of the stabilizer include a commercially available surfactant or dispersant, and a commercially available acid compound [ phosphoric acid (salt), boric acid (salt), alkali metal (salt) and alkaline earth metal (salt), hydroxycarboxylic acid (salt), fatty acid (salt), and the like ].

The temperature at which the crosslinked polymer (A) is mixed with the water-insoluble silicon compound fine particles (c) is preferably 10 to 150 ℃, more preferably 20 to 100 ℃, particularly preferably 25 to 80 ℃, from the viewpoint of absorption performance.

After mixing the crosslinked polymer (A) with the water-insoluble silicon compound fine particles (c), further heat treatment may be performed. The heating temperature is preferably 25 to 180 ℃, more preferably 30 to 175 ℃, particularly preferably 35 to 170 ℃, from the viewpoint of the fracture resistance of the resin particles. If the heating is performed at 180 ℃ or lower, indirect heating can be performed by using steam, which is advantageous in terms of equipment. In addition, if heating is not performed, water and solvent used in combination remain excessively in the water-absorbent resin, and the absorption performance may be deteriorated. The amount of water and solvent remaining in the water-absorbent resin is preferably 1 to 10 parts by weight per 100 parts by weight of the water-absorbent resin. The amounts of water and solvent remaining in the water-absorbent resin can be obtained by a heating loss method according to JIS K0067-1992 (chemical loss and residue test method).

When the crosslinked polymer (a) is mixed with the water-insoluble silicon compound fine particles (c) and then heated, the heating time can be set as appropriate according to the heating temperature, and is preferably 5 to 60 minutes, more preferably 10 to 40 minutes, from the viewpoint of the absorption performance. The water-absorbent resin obtained by mixing the crosslinked polymer (A) with the water-insoluble silicon compound fine particles (c) may be further surface-treated with water-insoluble silicon compound fine particles of the same kind or different kind from the water-insoluble silicon compound fine particles used initially.

The water-absorbent resin particles of the present invention can be used by mixing the crosslinked polymer (A) with the water-insoluble silicon compound fine particles (c), followed by screening to adjust the particle size. The average particle diameter of the particles obtained by adjusting the particle size is preferably 100 to 600. Mu.m, more preferably 200 to 500. Mu.m. The content of the fine particles is preferably a small amount, preferably a content of particles of 100 μm or less is 3% by weight or less, and more preferably a content of particles of 150 μm or less is 3% by weight or less.

The content of the water-insoluble silicon compound fine particles (c) in the water-absorbent resin particles of the present invention can be adjusted according to the use of the water-absorbent resin particles, and is preferably 0.01 to 1% by weight, more preferably 0.02 to 0.8% by weight, and particularly preferably 0.05 to 0.5% by weight, based on the weight of the crosslinked polymer (A). When the amount is more than this range, the water-absorbent resin surface is peeled off to generate detached dust, and when the amount is less than this range, moisture absorption blocking is likely to occur.

In the water-absorbent resin particles of the present invention, the arithmetic average of the Si atomic number concentration (atomic%) can be adjusted by the content of the water-insoluble silicon compound fine particles (c) and the addition method.

The Si atomic number concentration of the surface of the water-absorbent resin particles obtained by the scanning electron microscope-energy-dispersive X-ray analysis measurement in the present invention can be determined by randomly measuring 20 water-absorbent resin particles. The surface of the water-absorbent resin particles is a surface observed by a scanning electron microscope-energy-dispersive X-ray analysis, and represents a portion ranging from a portion of the water-absorbent resin particles exposed to the outside air to about 1 μm inside.

In the measurement by the scanning electron microscope-energy dispersion type X-ray analysis, the electron beam was focused and irradiated at an acceleration voltage of 15eV and a magnification of 100 times, and the intensity of the characteristic X-rays observed for each element was detected, whereby the composition of the electron beam irradiation region (the surface of the water-absorbent resin particles) to be measured was obtained. Since the Si atom number concentration on the surface of the water-absorbent resin particles may vary depending on the respective water-absorbent resin particles, it is preferable to measure 20 water-absorbent resin particles randomly and calculate the Si atom number concentration as an arithmetic average value.

The arithmetic average of the Si atomic number concentration (atomic%) measured by the scanning electron microscope-energy dispersive X-ray analysis at 20 points in the analysis point of the present invention is 0.5 to 5.0, and the content and the addition method of the water-insoluble silicon compound particles (c) can be adjusted. From the viewpoint of suppressing the variation in the amount of the additive to be fed and the absorption performance, it is preferably 1.0 to 2.5. If the amount is more than 5.0, the water-absorbent resin surface is peeled off to generate detached dust, while if it is less than 0.5, hygroscopic blocking is likely to occur.

The water-insoluble silicon compound particles (c) adhere to the water-absorbent resin particles by a force acting on the powder such as van der Waals force, and therefore it is difficult to control the amount of adhesion after the adhesion, and it is preferable to uniformly mix them by turbulent mixing or the like in terms of adjusting the average value of the Si atomic number concentration.

In the water-absorbent resin particles of the present invention, the coefficient of variation of the Si atomic number concentration measured by a scanning electron microscope-energy-dispersive X-ray analysis at 20 points in analysis can be controlled to 0 to 40% by the method of adding the water-insoluble silicon compound particles (c). From the viewpoints of control of the amount of the additive to be added and production efficiency, it is preferably 1 to 30%, more preferably 1 to 25%, particularly preferably 10 to 25%. The coefficient of variation in the Si atom number concentration is an index of uniformity of Si atoms on the surface of the water-absorbent resin particles, and a lower coefficient of variation indicates that Si atoms, that is, the water-insoluble silicon compound particles (c), are added more uniformly. If the coefficient of variation exceeds 40%, the amount of the additive varies, and the performance of the absorbent article varies, which is not preferable.

The water-absorbent resin particles of the present invention can be obtained by mixing the crosslinked polymer (a) with the water-insoluble silicon compound fine particles (c), and in the case where the surface of the crosslinked polymer (a) has a structure crosslinked by the organic surface crosslinking agent (e), the addition of the water-insoluble silicon compound fine particles (c) may be performed at any stage before and after the surface crosslinking by the organic surface crosslinking agent (e), and from the viewpoint of uniformity, the water-insoluble silicon compound fine particles (c) are preferably added simultaneously with or before the addition of the organic surface crosslinking agent (e), and further preferably the water-insoluble silicon compound fine particles (c) are added simultaneously with the addition of the organic surface crosslinking agent (e).

The water-absorbent resin particles of the present invention may further contain a polyol (f) having 4 or less carbon atoms. Examples of the polyol (f) having 4 or less carbon atoms include ethylene glycol, propylene glycol, 1, 3-propanediol, glycerin, and 1, 4-butanediol. Among these, propylene glycol and glycerin are preferable, and propylene glycol is more preferable, from the viewpoints of safety and ease of acquisition. (f) One kind may be used alone, or two or more kinds may be used in combination.

The amount (wt%) of the polyol (f) having 4 or less carbon atoms is preferably 0.05 to 5, more preferably 0.1 to 3, and particularly preferably 0.2 to 2, based on the weight of the crosslinked polymer (a), from the viewpoints of absorption performance and liquid permeability.

When the polyol (f) having 4 or less carbon atoms is contained, the addition may be performed in any step, and from the viewpoint of uniformity of Si atoms, it is preferable to add the water-insoluble silicon compound fine particles (c) and the organic surface crosslinking agent (e) at the same time. By using (f), wettability and permeability of the additive solution to the crosslinked polymer (a) can be improved, and Si atoms can be made uniform.

The water-absorbent resin particles of the present invention may further contain a hydrophobic substance (g). As the hydrophobic substance (g), there is included: a hydrophobic substance (g 1) containing a hydrocarbon group, a hydrophobic substance (g 2) containing a hydrocarbon group having a fluorine atom, a hydrophobic substance (g 3) having a polysiloxane structure, and the like.

Examples of the hydrophobic substance (g 1) containing a hydrocarbon group include polyolefin resins, polyolefin resin derivatives, polystyrene resins, polystyrene resin derivatives, waxes, long-chain fatty acid esters, long-chain fatty acids and salts thereof, long-chain aliphatic alcohols, long-chain aliphatic amides, and mixtures of 2 or more thereof.

The polyolefin resin may be a polymer { for example, polyethylene, polypropylene, polyisobutylene, poly (ethylene-isobutylene), isoprene, etc. }, which has a weight average molecular weight of 1000 to 100 ten thousand and contains an olefin { ethylene, propylene, isobutylene, isoprene, etc. } having 2 to 4 carbon atoms as an essential constituent monomer (the content of the olefin is at least 50 wt.% based on the weight of the polyolefin resin).

Examples of the polyolefin resin derivative include polymers { for example, polyethylene thermal degradation products, polypropylene thermal degradation products, maleic acid-modified polyethylene, chlorinated polyethylene, maleic acid-modified polypropylene, ethylene-acrylic acid copolymers, ethylene-maleic anhydride copolymers, isobutylene-maleic anhydride copolymers, maleated polybutadiene, ethylene-vinyl acetate copolymers, and maleated products of ethylene-vinyl acetate copolymers }, each having a weight average molecular weight of 1000 to 100 tens of thousands, which are obtained by introducing a carboxyl group (-COOH), a 1, 3-oxo-2-oxapropylene group (-COOCO-) or the like into a polyolefin resin.

The polystyrene resin may be a polymer having a weight average molecular weight of 1000 to 100 ten thousand.

The polystyrene resin derivative may be a polymer { for example, a styrene-maleic anhydride copolymer, a styrene-butadiene copolymer, a styrene-isobutylene copolymer, etc. }, which has a weight average molecular weight of 1000 to 100 ten thousand and is formed from styrene as an essential constituent monomer (the content of styrene is at least 50% by weight based on the weight of the polystyrene derivative).

Examples of the wax include waxes having a melting point of 50 to 200 ℃ (e.g., paraffin wax, beeswax, carnauba wax, tallow, etc.).

As the long-chain fatty acid ester, examples thereof include esters of fatty acids having 8 to 30 carbon atoms and alcohols having 1 to 12 carbon atoms { for example, methyl laurate, ethyl laurate, methyl stearate, ethyl stearate, methyl oleate, ethyl oleate, glycerol monolaurate, glycerol monostearate, glycerol monooleate, pentaerythritol monolaurate, pentaerythritol monostearate, sorbitol monolaurate, sucrose palmitate, sucrose stearate monoester, sucrose stearate diester, sucrose stearate triester, tallow, and the like }.

Examples of the long-chain fatty acid and its salt include fatty acids { having 8 to 30 carbon atoms, such as lauric acid, palmitic acid, stearic acid, oleic acid, dimer acid, and behenic acid }, and examples of the salt include salts { such as Ca palmitate, al palmitate, ca stearate, mg stearate, al stearate }, with zinc, calcium, magnesium, or aluminum (hereinafter, abbreviated as Zn, ca, mg, al).

Examples of the long-chain aliphatic alcohol include aliphatic alcohols having 8 to 30 carbon atoms { e.g., lauryl alcohol, palmityl alcohol, stearyl alcohol, oleyl alcohol, etc. }. From the viewpoint of leakage resistance of the absorbent article, etc., palmitol, stearyl alcohol, and oleyl alcohol are preferable, and stearyl alcohol is more preferable.

Examples of the long-chain aliphatic amide include an amidated product of a long-chain aliphatic primary amine having 8 to 30 carbon atoms and a carboxylic acid having a hydrocarbon group having 1 to 30 carbon atoms, an amidated product of ammonia or a primary amine having 1 to 7 carbon atoms and a long-chain fatty acid having 8 to 30 carbon atoms, an amidated product of a long-chain aliphatic secondary amine having at least one aliphatic chain having 8 to 30 carbon atoms and a carboxylic acid having 1 to 30 carbon atoms, and an amidated product of a secondary amine having two aliphatic hydrocarbon groups having 1 to 7 carbon atoms and a long-chain fatty acid having 8 to 30 carbon atoms.

The amidation products of a long-chain aliphatic primary amine having 8 to 30 carbon atoms and a carboxylic acid having a hydrocarbon group having 1 to 30 carbon atoms are classified into those obtained by reacting a primary amine with a carboxylic acid in a ratio of 1:1 and those obtained by reacting a primary amine with a carboxylic acid in a ratio of 1:2. Examples of the reaction product obtained in the 1:1 reaction include N-octylamide acetate, N-hexacosamide acetate, N-octylamide eicosanoate, and N-hexacosamide eicosanoate. Examples of the reaction product obtained by the 1:2 reaction include N-octylamide diacetate, N-hexacosamide diacetate, N-octylamide di (heptacosanoic acid) and N-hexacosamide di (heptacosanoic acid). In the case of a substance obtained by reacting a primary amine with a carboxylic acid in a ratio of 1:2, the carboxylic acid used may be the same or different.

The amidation products of ammonia or a primary amine having 1 to 7 carbon atoms and a long-chain fatty acid having 8 to 30 carbon atoms are classified into those obtained by reacting ammonia or a primary amine with a carboxylic acid in a ratio of 1:1 and those obtained by reacting 1:2. Examples of the reaction product obtained in the 1:1 reaction include pelargonic acid amide, pelargonic acid methyl amide, pelargonic acid N-heptyl amide, eicosanoic acid N-methyl amide, eicosanoic acid N-heptyl amide, and eicosanoic acid N-hexacosamide. Examples of the substances obtained by the 1:2 reaction include dipelargonamide, dipelargonamide N-methyl, dipelargonamide N-heptyl, dioctadecanoamide, dioctadecanoate N-ethyl, dioctadecanoate N-heptyl, dioctadecanoate amide, dioctadecanoate N-methyl, dioctadecanoate N-heptyl, and dioctadecanoate N-hexacosamide. The carboxylic acid used may be the same or different as the one obtained by reacting ammonia or a primary amine with a carboxylic acid at a ratio of 1:2.

Examples of the amidation product of a long-chain aliphatic secondary amine having at least one aliphatic chain having 8 to 30 carbon atoms and a carboxylic acid having 1 to 30 carbon atoms include N-methyloctylamide acetate, N-methylhexacosanamide acetate, N-octylhexacosanamide acetate, N-di (hexacosanyl) amide acetate, N-methyloctylamide heptacosanate, N-methylhexacosanamide heptacosanate, N-octylhexacosanamide heptacosanate, and N-di (hexacosanyl) amide heptacosanate.

Examples of the amidation product of a secondary amine having two aliphatic hydrocarbon groups having 1 to 7 carbon atoms and a long-chain fatty acid having 8 to 30 carbon atoms include N-dimethylamide nonanoate, N-methylheptanylamide nonanoate, N-diheptylamide nonanoate, N-dimethylamide eicosanoate, N-methylheptanylamide eicosanoate and N-diheptylamide eicosanoate.

Examples of the hydrophobic substance (g 2) containing a hydrocarbon group having a fluorine atom include perfluoroalkanes, perfluoroalkenes, perfluoroaromatics, perfluoroalkyl ethers, perfluoroalkyl carboxylic acids, perfluoroalkyl alcohols, and mixtures of 2 or more thereof.

As the hydrophobic substance (g 3) having a polysiloxane structure, polydimethyl siloxane, polyether-modified polysiloxane { polyoxyethylene-modified polysiloxane and poly (ethylene oxide-propylene oxide) -modified polysiloxane, etc. }, carboxyl-modified polysiloxane, epoxy-modified polysiloxane, amino-modified polysiloxane, alkoxy-modified polysiloxane, etc., and mixtures thereof, etc., are included.

The HLB value of the hydrophobic substance (g) is preferably 1 to 10, more preferably 2 to 8, particularly preferably 3 to 7. When the amount is within this range, the blocking resistance at the time of initial swelling becomes better. The HLB value is a hydrophilic-hydrophobic balance (HLB) value, and was obtained by the Kogyo method (New surfactant was published by Sanyo chemical industry Co., ltd., published in 1981), page 197, vine Wu Yan.

Among the hydrophobic substances (g), the hydrophobic substance (g 1) containing a hydrocarbon group is preferable from the viewpoint of blocking resistance at the time of initial swelling, more preferable are long-chain fatty acid esters, long-chain fatty acids and salts thereof, long-chain fatty alcohols and long-chain fatty amides, further preferable are sorbitol stearate, sucrose stearate, stearic acid, mg stearate, ca stearate, zn stearate and Al stearate, particularly preferable are sucrose stearate and Mg stearate, and most preferable are sucrose stearate.

The amount (wt%) of the hydrophobic substance (g) is preferably 0.001 to 1, more preferably 0.005 to 0.5, and particularly preferably 0.01 to 0.3, based on the weight of the crosslinked polymer (a), from the viewpoints of absorption performance and blocking resistance at the time of initial swelling.

In the case where the hydrophobic substance (g) is contained, it may be added in an optional step, and from the viewpoint of the absorption performance, it is preferable to add the hydrophobic substance (g) before the addition of the water-insoluble silicon compound fine particles (c), and in the case where the surface of the crosslinked polymer (a) has a structure crosslinked by the organic surface crosslinking agent (e), it is more preferable to add the hydrophobic substance (g) before the surface crosslinking by the organic surface crosslinking agent (e).

The water-absorbent resin particles of the present invention may contain additives (for example, preservatives, mildewcides, antibacterial agents, antioxidants, ultraviolet absorbers, chelating agents, colorants, fragrances, deodorants, liquid permeability improvers, organic fibrous materials, and the like, which are known (described in Japanese patent laid-open publication No. 2003-225565 and Japanese patent laid-open publication No. 2006-131767, etc.) as needed. In the case of containing these additives, the content (wt%) of the additives is preferably 0.001 to 10, more preferably 0.01 to 5, particularly preferably 0.05 to 1, most preferably 0.1 to 0.5, based on the weight of the crosslinked polymer (A).

The production method of the present invention is a production method of the water-absorbent resin particles of the present invention, comprising the following mixing steps: the crosslinked polymer (A) having the water-soluble vinyl monomer (a 1) and the crosslinking agent (b) as essential structural units and the water-insoluble silicon compound fine particles (c) are mixed by turbulent mixing using a vertical mixer. In the above-described mixing step, the mixing is preferably performed by turbulent mixing using a flexmix type vertical mixer. In this case, when the surface of the crosslinked polymer (a) has a structure crosslinked by the organic surface crosslinking agent (e), the crosslinked polymer (a) is preferably added together with the water-insoluble silicon compound fine particles (c) or the aqueous colloidal fluid of the water-insoluble silicon compound fine particles (c) and the surface crosslinking agent. Specific examples of the water-insoluble silicon compound fine particles (c) or the aqueous colloidal solution of the water-insoluble silicon compound fine particles (c) are as described above. As described above, the amount of the water-insoluble silicon compound particles (c) to be added, the organic surface cross-linking agent (e), and the polyol having 4 or less carbon atoms are preferably mixed by a flexmix type vertical mixer, and then the mixture is sprayed onto the cross-linked polymer (a) and then heat-treated.

The water retention capacity (g/g) of the water-absorbent resin particles of the present invention and the water-absorbent resin particles obtained by the production method of the present invention (hereinafter referred to as the water-absorbent resin particles of the present invention without distinguishing them) can be measured by the method described later, and is preferably 25 to 55, more preferably 30 to 50, and particularly preferably 35 to 45. If the water retention amount is less than this range, the absorption amount of the diaper decreases, and if it is more than this range, the absorption amount under load decreases. The water retention amount can be appropriately adjusted by the amounts (wt%) of the crosslinking agent (b) and the organic surface crosslinking agent (e).

The gel flow rate (ml/min) of the water-absorbent resin particles of the present invention can be measured by the method disclosed in WO2016/143736 or the like, and is preferably 5 to 300, more preferably 10 to 280, and particularly preferably 15 to 250, from the viewpoint of the absorption rate of the diaper. It is empirically found that the gel flow rate is opposite to the water retention amount, and that the high water retention amount and the high gel flow rate are required depending on the structure of the diaper.

The apparent density (g/ml) of the water-absorbent resin particles of the present invention is preferably 0.50 to 0.80, more preferably 0.52 to 0.75, and particularly preferably 0.54 to 0.70. When the content is within this range, the skin irritation resistance of the absorbent article becomes better. The apparent density of the water-absorbent resin particles was measured at 25℃in accordance with JIS K7365:1999.

The moisture absorption blocking ratio of the water-absorbent resin particles of the present invention can be measured by the method described below, and is preferably 0 to 50%, more preferably 0 to 30%, particularly preferably 0 to 20%. When the content is within this range, the problem of blocking is difficult to occur, independent of the working environment.

The absorbent body can be obtained using the water-absorbent resin particles of the present invention. The absorbent material may be formed by using the water-absorbent resin particles alone or by using the water-absorbent resin particles together with other materials.

As the other material, a fibrous material or the like can be mentioned. The structure and the manufacturing method of the absorber when used together with the fibrous material are the same as those of the known absorber (Japanese patent application laid-open No. 2003-225565, japanese patent application laid-open No. 2006-131767, japanese patent application laid-open No. 2005-097569, etc.).

The fibrous material is preferably cellulose fibers, organic synthetic fibers, or a mixture of cellulose fibers and organic synthetic fibers.

Examples of the cellulose-based fibers include natural fibers such as fluff pulp, cellulose-based chemical fibers such as viscose rayon, acetate, and cuprammonium rayon. The raw material (needle-leaved tree, broad-leaved tree, etc.), the production method (chemical pulp, semi-chemical pulp, mechanical pulp, CTMP, etc.), the bleaching method, etc. of the cellulose-based natural fiber are not particularly limited.

Examples of the organic synthetic fibers include polypropylene fibers, polyethylene fibers, polyamide fibers, polyacrylonitrile fibers, polyester fibers, polyvinyl alcohol fibers, polyurethane fibers, and hot-melt adhesive composite fibers (fibers in which at least 2 of the fibers having different melting points are composited with a core-sheath type, a core-shift type, a side-by-side type, or the like, fibers in which at least 2 of the fibers are mixed, and fibers in which a surface layer of the fibers is modified).

Among these fibrous materials, cellulose-based natural fibers, polypropylene-based fibers, polyethylene-based fibers, polyester-based fibers, hot-melt adhesive composite fibers, and mixed fibers thereof are preferable, and from the viewpoint of excellent shape retention of the obtained water absorbing agent after water absorption, fluff pulp, hot-melt adhesive composite fibers, and mixed fibers thereof are more preferable.

The length and thickness of the fiber are not particularly limited, and may be suitably used as long as the length is 1 to 200mm and the thickness is 0.1 to 100 denier. The shape is not particularly limited as long as it is fibrous, and a thin cylindrical shape, split filaments, short fibers, filaments, net shape, and the like can be exemplified.

When the water-absorbent resin particles are formed into an absorbent body together with the fibrous material, the weight ratio of the water-absorbent resin particles to the fibers (weight of the water-absorbent resin particles/weight of the fibers) is preferably 40/60 to 90/10, more preferably 70/30 to 80/20.

The water-absorbent resin of the present invention can be used to obtain an absorbent article. Specifically, the absorber described above is used. The absorbent article can be used not only as a sanitary article such as a disposable diaper or a sanitary napkin, but also as an article used for various purposes such as an absorbent or retention agent for various aqueous liquids and a gelling agent as described later. The method for producing the absorbent article is similar to known methods (methods described in Japanese patent application laid-open No. 2003-225565, japanese patent application laid-open No. 2006-131767, japanese patent application laid-open No. 2005-097569, and the like).

Examples

The present invention will be further described with reference to examples and comparative examples, but the present invention is not limited thereto. Hereinafter, unless otherwise specified, parts means parts by weight and% means% by weight. The water retention capacity, the absorption capacity under load, the moisture absorption blocking ratio, the surface Si amount, the coefficient of variation of the surface Si amount, the amount of addition, and the coefficient of variation of the amount of addition of the water-absorbent resin particles with respect to physiological saline were measured by the following methods.

< method for measuring Water retention >

A teabag (length 20cm, width 10 cm) made of nylon mesh with mesh opening of 63 μm (JIS Z8801-1:2006) was filled with 1.00g of a measurement sample, immersed in 1,000ml of physiological saline (salt concentration 0.9%) without stirring for 1 hour, lifted, and suspended for 15 minutes to remove water. Thereafter, the mixture was placed in a centrifugal separator together with the tea bag, and centrifugal dehydration was carried out at 150G for 90 seconds to remove the remaining physiological saline, and the weight (h 1) including the tea bag was measured to determine the water retention amount by the following formula. The temperature of the physiological saline and the measurement atmosphere used was 25.+ -. 2 ℃.

Water retention (g/g) = (h 1) - (h 2)

The weight of the tea bag (h 2) was measured by the same procedure as described above without the measurement sample.

< method for measuring absorption under load >

A measuring sample of 0.16g was weighed in a cylindrical plastic tube (inner diameter: 25mm, height: 34 mm) having a mesh of 63 μm (JIS Z8801-1:2006) adhered to the bottom surface, and sieved to a range of 250 to 500 μm using a 30 mesh sieve and a 60 mesh sieve, the cylindrical plastic tube was set so as to be perpendicular, and the measuring sample was adjusted so as to have a substantially uniform thickness on the nylon mesh, and then a weight (weight: 210.6g, outer diameter: 24.5 mm) was placed on the measuring sample. After measuring the weight (M1) of the whole cylindrical plastic tube, the cylindrical plastic tube with the measurement sample and weight added thereto was vertically set up in a plate (diameter: 12 cm) with 60ml of physiological saline (salt concentration: 0.9%) added thereto, and the nylon net side was immersed with the nylon net side as the bottom, and allowed to stand for 60 minutes. After 60 minutes, the cylindrical plastic tube was lifted from the dish and tilted, and the water attached to the bottom was collected in one place and dropped as a water droplet, thereby removing the excess water, and then the weight (M2) of the entire cylindrical plastic tube to which the measurement sample and the weight were added was measured, and the absorption under load was determined by the following formula. The temperature of the physiological saline and the measurement atmosphere used was 25.+ -. 2 ℃.

Absorption under load (g/g) = { (M2) - (M1) }/0.16

< measurement of moisture absorption blocking Rate >

10g of a measurement sample having passed through a metal mesh having a mesh opening of 850 μm (JIS Z8801-1:2001) was placed uniformly in an aluminum cylindrical dish having a diameter of 5cm, and the mixture was allowed to stand in a constant temperature and humidity tank having a relative humidity of 80.+ -. 5% at 40.+ -. 1 ℃ for 3 hours. The total weight (a) of the measurement sample after 3 hours of standing was measured, and then it was tapped 5 times with a metal mesh (JIS Z8801-1:2001) having a mesh opening of 1400 μm to screen, and the weight (b) of the resin particles adhered by moisture absorption and remaining on the metal mesh having a mesh opening of 1400 μm was measured, whereby the moisture absorption blocking ratio was determined by the following formula.

Moisture absorption blocking ratio (%) = (b/a) ×100

< average of Si atomic number concentration and method for measuring coefficient of variation of Si atomic number concentration >

The measurement sample 10 particles or more, which were sieved to a range of 250 to 500 μm using a 30-mesh sieve and a 60-mesh sieve, were fixed to a sample stage to which a carbon tape was attached so that the particles did not overlap each other, and were set on a field emission scanning electron microscope "QuantaFEG250FEG" manufactured by FEI company, which was attached to an energy dispersive X-ray analysis (EDS analysis) device OctaneElite manufactured by Ametech company. The acceleration voltage was set to 15eV and the magnification was set to 100 times, so that 1 particle was displayed on the screen, and EDS analysis was performed on the range within the particle by surface analysis.

Each measurement sample was randomly measured in 20 particles, the arithmetic average of the detected Si atomic number% (atomic%) was used as the average of the Si atomic number concentrations of the measurement samples, and the standard deviation of the Si atomic number% was divided by the average to obtain a variation coefficient of the Si atomic number concentrations.

< method for measuring feed amount and coefficient of variation of feed amount >

500g of the measurement sample was charged into a hopper of an AccuRate feeder (model 100, shaft: spring type, manufactured by KUMA engineering Co.). An electronic balance with a metal tray placed on the front end of the sample supply port was set to 900 to start sample supply. The supply amount was recorded every 10 seconds from the time when the cumulative supply amount to the tray reached 50g, and the 200-second charge amount was recorded. The amount supplied during 200 seconds was converted into a value per 1 minute as the amount of charge (g/min), and a value obtained by dividing the standard deviation of the amount supplied per 10 seconds by the average value was used as the coefficient of variation of the amount of charge.

Example 1 ]

Acrylic acid (a 1-1) { Mitsubishi chemical Co., ltd., purity 100% }131 parts, crosslinking agent (b-1) { pentaerythritol triallyl ether, OSAKA SODA CO., LTD. Manufactured }0.44 parts, and deionized water 362 parts were stirred and mixed, and kept at 3 ℃. After nitrogen was introduced into the mixture so that the amount of dissolved oxygen was 1ppm or less, 0.5 part of a 1% hydrogen peroxide solution, 1 part of a 2% aqueous ascorbic acid solution, and 1 part of a 2%, 2' -azobis amidinopropane dihydrochloride aqueous solution were mixed and added to initiate polymerization. After the temperature of the mixture reached 80 ℃, polymerization was carried out at 80±2 ℃ for about 5 hours, thereby obtaining an aqueous gel.

Then, the aqueous gel was cut by a chopper (12 VR-400K manufactured by ROYAL Co.) and 108 parts of 48.5% aqueous sodium hydroxide solution was added thereto to mix and neutralize the aqueous gel, thereby obtaining a neutralized gel (neutralization degree: 72%). The neutralized aqueous gel was further dried using a vent dryer {200 ℃ C., wind speed 2 m/s }, to obtain a dried body. The dried product was crushed by a juice mixer (OSTERIZER BLENDER manufactured by Oster Co.) and then sieved to adjust the mesh size to a range of 710 to 150 μm, thereby obtaining a crosslinked polymer (A-1).

Next, while 100 parts of the resulting crosslinked polymer (A-1) was stirred at a high speed (Flexomix FXD100, hosokawa Micron, inc. at a rotation speed of 3000rpm and a feed rate of 50 kg/h), a liquid was spray-added thereto by mixing 1.0 part of Klebosol30cal25 (colloidal silica, solid content 30% and average primary particle diameter 25nm, manufactured by Merck, inc.) as water-insoluble silicon compound fine particles (c), 0.1 part of ethylene glycol diglycidyl ether as an organic surface crosslinking agent (e), 1.0 part of propylene glycol as a polyol (f) having 4 or less carbon atoms, and 1.6 parts of water, and then, heating at 130℃for 30 minutes, to obtain water-absorbent resin particles (P-1) of the present invention. The apparent density of (P-1) was 0.58g/ml.

Example 2 ]

While 100 parts of the crosslinked polymer (A-1) obtained in the same manner as in example 1 was stirred at a high speed (FlexomiFXD 100 manufactured by Hosokawa Micron: 3000rpm, 50 kg/h) and 1.0 part of ethylene glycol diglycidyl ether as the organic surface crosslinking agent (e), 1.0 part of propylene glycol as the polyol (f) having 4 or less carbon atoms, and 1.6 parts of water were added thereto by spraying from a nozzle, and after uniformly mixing, the mixture was heated at 130℃for 30 minutes, cooled to room temperature, and then further stirred at a high speed (FlexomiFXD 100 manufactured by Hosokawa Micron: 3000rpm, 50 kg/h), klebosol30 (colloidal silica manufactured by merck corporation, solid content 30%, average primary particle diameter 25 nm) as the water-insoluble silicon compound fine particles (c) was added thereto by spraying from a nozzle, and after uniformly mixing the mixture with 0.5 parts of propylene glycol as the polyol (f) having 4 or less carbon atoms and 0.5 parts of water, the water-absorbent resin was obtained by uniformly mixing the mixture, and then heating the mixture to obtain water-absorbent resin particles (2 minutes, after which the water-absorbent resin particles were mixed. The apparent density of (P-2) was 0.58g/ml.

Example 3 ]

While 100 parts of the crosslinked polymer (A-1) obtained in the same manner as in example 1 was stirred at a high speed (FlexomiFXD 100 manufactured by Hosokawa Micron: 3000rpm, 50 kg/h) and 0.1 part of ethylene glycol diglycidyl ether as the organic surface crosslinking agent (e), 1.0 part of propylene glycol as the polyol (f) having 4 or less carbon atoms, and 1.6 parts of water were added thereto by spraying from a nozzle, and after mixing uniformly, the mixture was heated at 130℃for 30 minutes, cooled to room temperature, and then further stirred at a high speed (FlexomiFXD 100 manufactured by Hosokawa Micron: 3000rpm, 50 kg/h), 0.1 part of Aerosil200 (produced by NIPPON AEROSIL) as the water-insoluble silicon compound fine particles (c) (silica, average primary particle diameter 12 nm) was added by spraying from a nozzle, and after mixing uniformly, the mixture was heated at 0.5 part of propylene glycol as the polyol (f) having 4 or less carbon atoms with 0.5 parts of water, and then mixed uniformly, the resultant resin was heated at 80 minutes, to obtain water-absorbent resin particles. The apparent density of (P-3) was 0.59g/ml.

Example 4 ]

The water-absorbent resin particles (P-4) of the present invention were obtained in the same manner as in example 1 except that 0.1 part of ethylene glycol diglycidyl ether as the organic surface-crosslinking agent (e) was changed to 0.03 part, 1.0 part of propylene glycol as the polyol (f) having 4 or less carbon atoms was changed to 0.60 part, and 1.6 parts of water was changed to 0.80 part. The apparent density of (P-4) was 0.58g/ml.

Example 5 ]

The water-absorbent resin particles (P-5) of the present invention were obtained in the same manner as in example 1, except that 1.0 part of Klebosol30cal25 (colloidal silica, 30% of solid content, 25nm average primary particle diameter, manufactured by Merck Co.) as the water-insoluble silicon compound fine particles (c) was changed to 0.17 part, 0.1 part of ethylene glycol diglycidyl ether as the organic surface cross-linking agent (e) was changed to 0.01 part, 1.0 part of propylene glycol as the polyol (f) having 4 or less carbon atoms was changed to 0.30 part, and 1.6 parts of water was changed to 0.30 part. The apparent density of (P-5) was 0.59g/ml.

Example 6 ]

Water-absorbent resin particles (P-6) of the present invention were obtained in the same manner as in example 1 except that 1.0 part of Klebosol30cal25 (colloidal silica, solid content 30% and average primary particle diameter 25nm manufactured by Merck Co.) as the water-insoluble silicon compound fine particles (c) was changed to 1.5 parts. The apparent density of (P-6) was 0.58g/ml.

Example 7 ]

100 parts by weight of (P-1) were put into a plastic bag, and 0.1 part by weight of Aerosil200 (fumed silica, 12nm average primary particle diameter, manufactured by NIPPON AEROSIL Co., ltd.) as the water-insoluble silicon compound fine particles (c) was added and kneaded, whereby the water-absorbent resin particles (P-7) of the present invention were obtained by thorough mixing. The apparent density of (P-7) was 0.57g/ml.

Example 8 ]

Acrylic acid (a 1-1) { Mitsubishi chemical Co., ltd., purity 100% }155 parts, a crosslinking agent (b-1) { pentaerythritol triallyl ether, OSAKA SODA CO., LTD. Manufactured }0.54 parts, and deionized water 335 parts were stirred and mixed, and kept at 3 ℃. After nitrogen was introduced into the mixture so that the amount of dissolved oxygen was 1ppm or less, 0.6 part of a 1% hydrogen peroxide solution, 1.2 parts of a 2% aqueous ascorbic acid solution, and 8 parts of a 2%, 2' -azobis amidinopropane dihydrochloride aqueous solution were mixed and polymerized. After the temperature of the mixture reached 90 ℃, polymerization was carried out at 90±2 ℃ for about 5 hours, thereby obtaining an aqueous gel.

Next, the aqueous gel was cut by a chopper (12 VR-400K manufactured by ROYAL Co.) and 128 parts of 48.5% aqueous sodium hydroxide solution was added thereto to mix and neutralize the aqueous gel, thereby obtaining a neutralized gel (neutralization degree: 72%). The neutralized aqueous gel was further dried using a vent dryer {150 ℃ C., wind speed 2 m/s }, to obtain a dried body. The dried product was crushed by a juice mixer (OSTERIZER BLENDER manufactured by Oster Co.) and then sieved to adjust the mesh size to a range of 710 to 150 μm, thereby obtaining a crosslinked polymer (A-2).

Next, while 100 parts of the resulting crosslinked polymer (A-2) was stirred at a high speed (FlexomixFXD 100 manufactured by Hosokawa Micron: rotation speed 3000rpm, feed rate 50 kg/h), a liquid obtained by mixing 1.0 part of Klebosol30cal25 (colloidal silica manufactured by Merck) as water-insoluble silicon compound fine particles (c) (solid content 30% by Merck) with 0.12 part of ethylene glycol diglycidyl ether as an organic surface crosslinking agent (e), 1.6 parts of propylene glycol as a polyol (f) having 4 or less carbon atoms, and 2.3 parts of water was sprayed from a nozzle, and then, the mixture was uniformly mixed, and heated at 140℃for 30 minutes to obtain water-absorbent resin particles (P-8) of the present invention. The apparent density of (P-8) was 0.60g/ml.

Comparative example 1 ]

A liquid obtained by mixing 100 parts of the crosslinked polymer (A-1) obtained in the same manner as in example 1 (Hosokawa Micron Co., ltd., high-speed stirring paddle mixer (registered trademark: the same shall apply hereinafter) at a rotation speed of 2000rpm and a feed rate of 50 kg/h) with 1.0 part of Klebosol30cal25 (colloidal silica, solid content 30% and average primary particle diameter 25nm, manufactured by merck Co., ltd.) as the water-insoluble silicon compound fine particles (c), 0.1 part of ethylene glycol diglycidyl ether as the organic surface crosslinking agent (e), 1.0 part of propylene glycol as the polyol (f) having 4 or less, and 1.6 parts of water was added thereto, and after mixing, the mixture was heated at 130℃for 30 minutes, to obtain water-absorbent resin particles (R-1) for comparison. The apparent density of (R-1) was 0.57g/ml.

Comparative example 2 ]

A liquid obtained by mixing 100 parts of the crosslinked polymer (A-1) obtained in the same manner as in example 1 with 0.1 part of ethylene glycol diglycidyl ether as the organic surface crosslinking agent (e), 1.0 part of propylene glycol as the polyol (f) having 4 or less carbon atoms and 1.6 parts of water was uniformly mixed while stirring at a high speed (a high-speed stirring paddle mixer manufactured by Hosokawa Micron, inc. at a rotational speed of 2000rpm, a charging speed of 50 kg/h), and after cooling to room temperature, a liquid obtained by mixing 1.5 parts of propylene glycol as the polyol (f) having 4 or less carbon atoms and 0.5 part of water as the polyol (f) was heated at a temperature of 130℃for 30 minutes, and then, after further stirring at a high speed (a high-speed stirring paddle mixer manufactured by Hosokawa Micron, inc. at a rotational speed of 2000rpm, a charging speed of 50 kg/h), klebosol30cal25 (manufactured by Merck, colloidal silica, solid content 30%, average primary particle diameter 25 nm) as the water-insoluble silicon compound particles (c) was mixed, and then, water-absorbent resin particles were obtained by mixing at a high-speed (R) for 30 minutes. The apparent density of (R-2) was 0.58g/ml.

Comparative example 3 ]

A liquid obtained by mixing 100 parts of the crosslinked polymer (A-1) obtained in the same manner as in example 1 with 0.1 part of ethylene glycol diglycidyl ether as the organic surface crosslinking agent (e), 1.0 part of propylene glycol as the polyol (f) having 4 or less carbon atoms and 1.6 parts of water was uniformly mixed while stirring at a high speed (a high-speed stirring paddle mixer manufactured by Hosokawa Micron, inc. at a rotational speed of 2000rpm, a charging speed of 50 kg/h), and 0.1 part of Aerosil200 (NIPPON AESIL, inc. at a primary particle diameter of 12 nm), 0.5 part of propylene glycol as the polyol (f) having 4 or less carbon atoms and 0.5 part of water were mixed with each other, heated at 130℃for 30 minutes, cooled to room temperature, and then stirred at a high speed (a high-speed stirring paddle mixer manufactured by Hosokawa Micron, inc. at a rotational speed of 2000rpm, a charging speed of 50 kg/h), and then heated at a high speed of 80℃for 30 minutes was mixed with water-absorbent resin particles obtained by mixing the Aerosil200 (NIPPON AESIL SIL, inc. as the gas phase silica particle (c). The apparent density of (R-3) was 0.59g/ml.

Comparative example 4 ]

A liquid obtained by mixing 100 parts of the crosslinked polymer (A-1) obtained in the same manner as in example 1 with 0.1 part of ethylene glycol diglycidyl ether as the organic surface crosslinking agent (e), 1.0 part of propylene glycol as the polyol (f) having 4 or less carbon atoms and 1.6 parts of water was added thereto while stirring at a high speed (a high-speed stirring paddle mixer manufactured by Hosokawa Micron, inc.: 2000rpm, 50 kg/h), and after uniformly mixing, the mixture was heated at 130℃for 30 minutes, cooled to room temperature, and then stirred at a high speed (a high-speed stirring paddle mixer manufactured by Hosokawa Micron, inc.: 2000rpm, 50 kg/h), while mixing Aerosil200 (produced by NIPPON AEROSIL, inc.: having an average primary particle diameter of 12 nm) as the water-insoluble silicon compound particles (c) was further heated at 80℃for 0.7 parts, to obtain water-absorbent resin particles (R-4) for comparison. The apparent density of (R-4) was 0.59g/ml.

Comparative example 5 ]

A liquid obtained by mixing 100 parts of the crosslinked polymer (A-1) obtained in the same manner as in example 1 with 0.1 part of ethylene glycol diglycidyl ether as the organic surface crosslinking agent (e), 1.0 part of propylene glycol as the polyol (f) having 4 or less carbon atoms and 1.6 parts of water was added thereto while stirring at a high speed (a high-speed stirring paddle mixer manufactured by Hosokawa Micron, inc.: 2000rpm, 50 kg/h), and after uniformly mixing, the mixture was heated at 130℃for 30 minutes, cooled to room temperature, and then stirred at a high speed (a high-speed stirring paddle mixer manufactured by Hosokawa Micron, inc.: 2000rpm, 50 kg/h), while mixing Klebosol30cal25 (colloidal silica manufactured by Merck, solid content 30%, average primary particle diameter 25 nm) as the water-insoluble silicon compound particles (c), and thereafter heating at 80℃for 0.1 part for 30 minutes, to obtain water-absorbent resin particles (R-5) for comparison. The apparent density of (R-5) was 0.58g/ml.

Comparative example 6 ]

Comparative water-absorbent resin particles (R-6) were obtained in the same manner as in example 1 except that Klebosol30cal25 as the water-insoluble silicon compound fine particles (c) was not used. The apparent density of (r=6) was 0.60g/ml.

TABLE 1

From the results shown in Table 1, the amounts of water held in examples 1 to 3, 6, and 7 and comparative example were all good, and no significant difference was observed, but the variation coefficient of the Si atomic number concentration in examples was low, and the variation coefficient of the amount of the feed was low, which was good. In examples and comparative examples, the mixing method was changed, and the coefficient of variation of the Si atomic number concentration was changed. On the other hand, in comparative examples 1 to 4 in which the coefficient of variation in the Si atomic number concentration is high, the coefficient of variation in the feed amount is increased, and it can be said that it is important to reduce the coefficient of variation in the Si atomic number concentration. In comparative examples 5 and 6, the Si atom number concentration was low, and the moisture absorption blocking rate was high. Further, as shown in examples 4, 5 and 8, the water-absorbent particles of the present invention can reduce the variation coefficient of the amount of addition by reducing the variation coefficient of the Si atomic number concentration even in a wide water retention region.

The water-absorbent resin particles of the present invention are suitable for sanitary products such as disposable diapers (e.g., child diapers and adult diapers), sanitary napkins (e.g., menstrual napkins), tissues, pads (e.g., incontinence pads and surgical pads), and pet pads (e.g., pet pads), and are particularly suitable for disposable diapers, because the amount of the water-absorbent resin particles to be fed varies little in a feeder (feeder) in a production process, and the production is stable when the water-absorbent resin particles are applied to the production of various absorbers. The water-absorbent resin particles of the present invention are useful not only for sanitary products, but also for various applications such as pet urine absorbent, urine gelling agent for portable toilets, antistaling agent for vegetables and fruits, drip absorbent for meats and aquatic products, cold-retaining agent, disposable heating furnace, battery gelling agent, water-retaining agent for plants and soil, condensation inhibitor, water-blocking material, sealing material, and artificial snow.

Claims

1. A water-absorbent resin particle comprising a crosslinked polymer (A) having a water-soluble vinyl monomer (a 1) and a crosslinking agent (b) as essential structural units and water-insoluble silicon compound fine particles (c), wherein the arithmetic average of Si atomic number concentrations at 20 points as measured by scanning electron microscope-energy dispersive X-ray analysis is 0.5 to 5.0, the variation coefficient of Si atomic number concentrations is 0 to 40%, the unit of Si atomic number concentrations is atomic%,

the water-insoluble silicon compound particles (c) are spherical or amorphous particles having an average primary particle diameter of 1nm to 100nm,

the water-absorbent resin particles are obtained by a production method comprising the following mixing step,

in the mixing step, a crosslinked polymer (A) having a water-soluble vinyl monomer (a 1) and a crosslinking agent (b) as essential structural units is mixed with water-insoluble silicon compound particles (c) by turbulent mixing using a vertical mixer,

in the mixing step, turbulent mixing is performed by using a Flexomix type vertical mixer, and the rotational speed at the time of mixing by using the Flexomix type vertical mixer is 1000rpm to 4000rpm.

2. The water-absorbent resin particles according to claim 1, wherein the content of the water-insoluble silicon compound fine particles (c) is 0.01 to 1% by weight based on the weight of the crosslinked polymer (a).

3. The water-absorbent resin particles according to claim 1, wherein the surface of the crosslinked polymer (A) has a structure crosslinked by the organic surface crosslinking agent (e).

4. The water-absorbent resin particles according to claim 1, wherein the water-absorbent resin particles further contain a polyol (f) having 4 or less carbon atoms.

5. The water-absorbent resin particles according to claim 1, wherein the water retention capacity of the water-absorbent resin particles is 25g/g to 55g/g.

6. A process for producing the water-absorbent resin particles according to any one of claims 1 to 5, comprising the following mixing steps: mixing the crosslinked polymer (A) having the water-soluble vinyl monomer (a 1) and the crosslinking agent (b) as essential structural units with the water-insoluble silicon compound fine particles (c) by turbulent mixing using a vertical mixer,

7. The method for producing water-absorbent resin particles according to claim 6, wherein the content of the water-insoluble silicon compound fine particles (c) is 0.01 to 1% by weight based on the weight of the crosslinked polymer (A).

8. The method for producing water-absorbent resin particles according to claim 6 or 7, wherein a dispersion of the water-insoluble silicon compound fine particles (c) in water and/or a solvent is added by spraying.

9. An absorbent body comprising the water-absorbent resin particles according to any one of claims 1 to 5.

10. The absorbent according to claim 9, wherein the absorbent further comprises fibers.

11. An absorbent article comprising the absorber according to claim 9 or 10.