WO2019188669A1

WO2019188669A1 - Water absorbent resin particles and production method therefor

Info

Publication number: WO2019188669A1
Application number: PCT/JP2019/011728
Authority: WO
Inventors: 佑介松原; 宮島　徹; 泰知松山
Original assignee: Ｓｄｐグローバル株式会社
Priority date: 2018-03-29
Filing date: 2019-03-20
Publication date: 2019-10-03
Also published as: JP2023060178A; CN111868145A; CN116769269A; CN111868145B; JP7257090B2; JPWO2019188669A1

Abstract

The present invention provides a water absorbent resin that can be supplied from a feeder in an amount with less variability in a production process. The present invention pertains to water absorbent resin particles containing a crosslinked polymer (A) containing a water-soluble vinyl monomer (a1) and a crosslinking agent (b) as essential constituent units, and fine water-insoluble silicon compound particles (c), wherein the arithmetic average of Si atomic concentrations (atomic%) as measured by scanning electron microscope-energy-dispersive X-ray spectroscopy at 20 analysis points is 0.5-5.0, and the variation coefficient of the Si atomic concentrations is 0-40%.

Description

Water-absorbent resin particles and method for producing the same

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

In hygienic materials such as paper diapers, sanitary napkins, and incontinence pads, water-absorbing resins mainly composed of hydrophilic fibers such as pulp and acrylic acid (salt) are widely used as absorbents. From the viewpoint of improving QOL (Quality Of Life) in recent years, demand for these sanitary materials has been shifting to lighter and thinner ones, and accordingly, the use of hydrophilic fibers has been desired to be reduced. . For this reason, the water-absorbing resin itself is required to have the role of liquid diffusibility and initial absorption in the absorbent body, which has been carried out by hydrophilic fibers so far. A water-absorbing resin having high liquid permeability has been required.

On the other hand, in the manufacturing process of absorbent articles such as paper diapers and sanitary napkins, when the amount of water-absorbent resin added varies, the performance of the absorbent article fluctuates. ), For example, it is desired that fluctuations in the supply amount of a screw feeder or a spring feeder are small.

By the way, as a method for improving powder flowability, a method 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, Patent Document 2 does not mention or recognize any supply amount fluctuation in the feeder, and the method does not satisfy the performance related to the supply amount fluctuation.

JP 2014-237133 A Japanese Unexamined Patent Publication No. 2016-055193

An object of the present invention is to provide a water-absorbent resin with little fluctuation in the supply amount in the feeder in the production process.

The present inventor has found that there is a relationship between the amount and distribution of the water-insoluble silicon compound fine particles used on the surface of the water-absorbent resin particles and fluctuations in the feeder supply amount of the water-absorbent resin. Accordingly, the present invention is a water-absorbent resin particle comprising the crosslinked polymer (A) having the water-soluble vinyl monomer (a1) and the crosslinking agent (b) as essential structural units and the water-insoluble silicon compound fine particles (c). The arithmetic average of the Si atom number concentration (atomic%) measured by scanning electron microscope-energy dispersive X-ray analysis at 20 analysis points is 0.5 to 5.0, and the Si atom number concentration A water-absorbent resin particle having a coefficient of variation of 0 to 40%;

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 number of Si atoms and a low coefficient of variation in the feed amount of the water-insoluble silicon compound fine particles on the surface. Reduce fluctuations in feeder supply.

The water-absorbent resin particles of the present invention include a crosslinked polymer (A) having water-soluble vinyl monomer (a1) and a crosslinking agent (b) as essential structural units, and water-insoluble silicon compound fine particles (c).

The water-soluble vinyl monomer (a1) in the present invention is not particularly limited, and known monomers, for example, at least one water-soluble substituent and an ethylenic group disclosed in paragraphs 0007 to 0023 of Japanese Patent No. 3648553 are disclosed. Vinyl monomers having a saturated group (for example, anionic vinyl monomers, nonionic vinyl monomers and cationic vinyl monomers), anionic vinyl monomers disclosed in JP-A-2003-16583, paragraphs 0009 to 0024, 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 Vinyl monomer having can be used.

Of these, anionic vinyl monomers, carboxy (salt) groups, sulfo (salt) groups, amino groups, carbamoyl groups, ammonio groups or mono-, di- or tri-alkyl ammonio groups are preferred from the standpoint of absorption performance and the like. Vinyl monomers having a 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, and 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.

As the structural unit of the crosslinked polymer (A), in addition to the water-soluble vinyl monomer (a1), other vinyl monomers (a2) copolymerizable with these can be used as the structural unit. Other vinyl monomers (a2) may be used alone or in combination of two or more.

Other vinyl monomers (a2) that can be copolymerized are not particularly limited, and are known (for example, hydrophobic vinyl monomers disclosed in paragraphs 0028 to 0029 of Japanese Patent No. 3648553, Japanese Patent Application Laid-Open No. 2003-165883). 0025 paragraph and vinyl monomer disclosed in JP-A-2005-75982, paragraph 0058, etc.) can be used. Specifically, for example, the following vinyl monomers (i) to (iii) Can be used.
(I) Aromatic ethylenic monomer having 8 to 30 carbon atoms 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.).
(Iii) alicyclic ethylenic monomer having 5 to 15 carbon atoms, 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 (a2) unit is preferably 0 to 5, more preferably 0 to 5, based on the number of moles of the water-soluble vinyl monomer (a1) unit from the viewpoint of absorption performance and the like. 3, particularly preferably 0 to 2, particularly preferably 0 to 1.5. From the viewpoint of absorption performance and the like, the content of the other vinyl monomer (a2) units is most preferably 0 mol%.

The cross-linking agent (b) 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 water-soluble substituent. A crosslinking agent having at least one functional group and having at least one ethylenically unsaturated group, and a crosslinking agent having at least two functional groups capable of reacting with a water-soluble substituent, Japanese Patent Application Laid-Open No. 2003-165883 Crosslinkers having two or more ethylenically unsaturated groups, crosslinkers having ethylenically unsaturated groups and reactive functional groups, and crosslinkers having two or more reactive substituents disclosed in paragraphs 0028 to 0031 of , The cross-linkable vinyl monomer disclosed in paragraph 0059 of JP-A-2005-75982, and stages 0015 to 0016 of JP-A-2005-95759. Crosslinking agents such as disclosed crosslinkable vinyl monomer) can be used to. Among these, from the viewpoint of absorption performance and the like, a cross-linking agent having two or more ethylenically unsaturated groups is preferable, and more preferable is poly (meth) allyl ether of a polyhydric alcohol having 2 to 40 carbon atoms, carbon number (Meth) acrylates of 2 to 40 polyhydric alcohols, (meth) acrylamides of polyhydric alcohols having 2 to 40 carbon atoms, particularly preferred are polyallyl ethers of polyhydric alcohols having 2 to 40 carbon atoms, most preferred Pentaerythritol triallyl ether. A crosslinking agent (b) may be used individually by 1 type, or may use 2 or more types together.

The content (mol%) of the crosslinking agent (b) unit is based on the total number of moles of the water-soluble vinyl monomer (a1) unit and (a1) to (a2) when the other vinyl monomer (a2) is used. 0.001 to 5 is preferable, 0.005 to 3 is more preferable, and 0.01 to 1 is particularly preferable. Within this range, the absorption performance is further improved.

Examples of the method for producing the crosslinked polymer (A) include known solution polymerization (adiabatic polymerization, thin film polymerization, spray polymerization method, etc .; JP-A-55-133413, etc.), known suspension polymerization method and reverse phase suspension. If necessary, a hydrogel polymer (consisting of a crosslinked polymer and water) obtained by suspension polymerization (Japanese Patent Publication No. Sho 54-30710, Japanese Patent Publication No. 56-26909, Japanese Patent Publication No. 1-5808, etc.) is required. It can be obtained by heat drying and grinding. The cross-linked polymer (A) may be a single type or a mixture of two or more types.

Among the polymerization methods, the solution polymerization method is preferable, and it is advantageous in terms of production cost because it is not necessary to use an organic solvent. Therefore, the aqueous solution polymerization method is particularly preferable, and the water retention amount is large and water-soluble. An aqueous solution adiabatic polymerization method is most preferred because a water-absorbing resin with a small amount of components can be obtained and temperature control during polymerization is unnecessary.

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, acetone, methyl ethyl ketone, N, N-dimethylformamide, dimethyl sulfoxide, and two or more of these. A mixture of
When aqueous solution polymerization is performed, 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.

In the case of using a catalyst for the polymerization, a conventionally known radical polymerization catalyst can be used, for example, an azo compound [azobisisobutyronitrile, azobiscyanovaleric acid and 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, etc. Oxides and di (2-ethoxyethyl) peroxydicarbonate, etc.] and redox catalysts (alkali metal sulfites or bisulfites, ammonium sulfites, ammonium bisulfites, ascorbic acids and the like, and alkali metal persulfates, Oxidation of ammonium persulfate, hydrogen peroxide and organic peroxides 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 catalyst used is 0.0005 based on the total weight of the water-soluble vinyl monomer (a1) and (a1) to (a2) when the other vinyl monomer (a2) is used. To 5 is preferable, and 0.001 to 2 is more preferable.

At the time of polymerization, a polymerization control agent such as a chain transfer agent may be used in combination, and specific examples thereof include sodium hypophosphite, sodium phosphite, alkyl mercaptan, alkyl halide, and thiocarbonyl compound. Etc. 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 0.0005 based on the total weight of the water-soluble vinyl monomer (a1) and (a1) to (a2) when the other vinyl monomer (a2) is used. To 5 is preferable, and 0.001 to 2 is more preferable.

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

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 a solvent (such as an organic solvent and water) is used for polymerization, it is preferable to distill off the solvent after polymerization. When the solvent contains an organic solvent, the content (% by weight) of the organic solvent after distillation is preferably 0 to 10, more preferably 0 to 5, particularly preferably based on the weight of the crosslinked polymer (A). Is 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, based on the weight of the crosslinked polymer (A). Most preferably, it is 3-8. Within this range, the absorption performance is further improved.

By the above polymerization method, the crosslinked polymer (A) can obtain a water-containing gel-like product containing water (hereinafter abbreviated as a water-containing gel), and the water-containing gel is further dried to obtain the crosslinked polymer (A). Obtainable.
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. Furthermore, the water retention amount of the water-absorbing resin particles obtained may decrease. 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 crosslinked polymer (A) in the production of the water-absorbent resin particles. For example, a method such as neutralization in the state of a hydrogel is preferable. Illustrated.
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 usually used.

The hydrogel obtained by polymerization can be shredded as necessary. 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 and water content of the organic solvent were measured using an infrared moisture meter [for example, JE400 manufactured by KETT Co., Ltd .: 120 ± 5 ° C., 30 minutes, atmospheric humidity before heating 50 ± 10% RH, lamp specification 100V , 40 W], from the weight loss of the measurement sample when heated.

As a method of distilling off the solvent (including water) in the hydrogel, a method of distilling (drying) with hot air at a temperature of 80 to 230 ° C., a thin film drying method using a drum dryer or the like heated to 100 to 230 ° C. (Heating) reduced pressure drying method, freeze drying method, infrared drying method, decantation, filtration and the like can be applied.

After drying the hydrogel to obtain the crosslinked polymer (A), it can be further pulverized. 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 crosslinked polymer can be adjusted in particle size by sieving or the like, if necessary.

The weight average particle diameter (μm) of the crosslinked polymer (A) screened as necessary is preferably 100 to 800, more preferably 200 to 700, next preferably 250 to 600, particularly preferably 300 to 500, most preferably Preferably it is 350-450. Within this range, the absorption performance is further improved.

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 (Mac Glow Hill Book, 1984). , Page 21). 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.

Further, since the absorption performance is better when the content of the fine particles contained in the crosslinked polymer (A) is smaller, the inclusion of fine particles of 106 μm or less (preferably 150 μm or less) in the total weight of the crosslinked polymer (A). The rate (% by weight) 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 shape of the crosslinked polymer (A) is not particularly limited, and examples thereof include an irregular 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 cross-linked polymer (A) may contain some other components such as a residual solvent and a residual cross-linking component as long as the performance is not impaired.

The water-absorbent resin particles of the present invention preferably have a structure in which the surface of the crosslinked polymer (A) is crosslinked with an 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 amount and the amount of absorption under load of the water-absorbent resin particles can be further satisfied. . Examples of the organic surface crosslinking agent (e) 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 disclosed in JP-A-61-16903, silane coupling agents described in JP-A-61-211305 and JP-A-61-252212, and JP-A-5-508425. And organic surface crosslinking agents such as polyvalent oxazoline compounds described in JP-A No. 11-240959. Of these surface cross-linking agents, from the viewpoint of economy and absorption properties, polyvalent glycidyl compounds, polyhydric alcohols and polyhydric amines are preferred, polyvalent glycidyl compounds and polyhydric alcohols are more preferred, and many are particularly preferred. Valent glycidyl compounds, most preferred are ethylene glycol diglycidyl ethers. The organic surface crosslinking agent (e) may be used alone or in combination of two or more.

In the case of surface cross-linking, the amount (% by weight) of the organic surface cross-linking agent (e) 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, and the like. From the viewpoint of absorption characteristics, etc., it 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.

Surface crosslinking of the crosslinked polymer (A) can be carried out by mixing the crosslinked polymer (A) and the organic surface crosslinking agent (e) and heating. As a mixing method of the crosslinked polymer (A) and the organic surface crosslinking agent (e), a cylindrical mixer, a screw mixer, a screw extruder, a turbulizer (registered trademark), a flexographic type vertical mixing Mixing machine, Nauter type mixer, double arm type kneader, fluid type mixer, V type mixer, minced mixer, ribbon type mixer, airflow type mixer, rotating disk type mixer, conical blender, roll mixer, etc. Examples thereof include a method of uniformly mixing the crosslinked polymer (A) and the organic surface crosslinking agent (e) using an apparatus. At this time, the organic surface cross-linking agent (e) may be diluted with water and / or an arbitrary solvent and used.

The temperature at which the cross-linked polymer (A) and the organic surface cross-linking agent (e) are mixed is not particularly limited, but is preferably 10 to 150 ° C, more preferably 20 to 100 ° C, and particularly preferably 25 to 80 ° C. is there.

After mixing the cross-linked polymer (A) and the organic surface cross-linking agent (e), heat treatment is usually performed. 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. The heating time can be appropriately set depending on the heating temperature, but is preferably 5 to 60 minutes, more preferably 10 to 40 minutes from the viewpoint of absorption performance. The water-absorbing resin obtained by surface cross-linking can be further surface cross-linked using the same or different organic surface cross-linking agent as the organic surface cross-linking agent used first.

After the surface of the crosslinked polymer (A) is crosslinked with the organic surface crosslinking agent (e), the particle size is adjusted by sieving as necessary. 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.

The water-absorbent resin particles of the present invention include water-insoluble silicon compound fine particles (c). Examples of the water-insoluble silicon compound fine particles (c) include silicon dioxide such as fumed silica, wet silica, colloidal silica, and modified silica, and silicate fine particles such as talc, kaolin, zeolite, and montmorillonite. Fumed silica and colloidal silica are preferable from the viewpoints of properties, ease of handling, and absorption performance. (C) may be used individually by 1 type, and may use 2 or more types together.

The water-insoluble silicon compound fine particles (c) in the present invention are preferably spherical or irregular 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 is improved. The average primary particle diameter of the water-insoluble silicon compound fine particles (c) is preferably 2 to 80 nm, more preferably 3 to 60 nm, and particularly preferably 5 to 50 nm. If the average primary particle diameter is less than 1 nm, the absorption characteristics under load of the water-absorbent resin particles may be deteriorated. Moreover, when larger than 100 nm, the liquid permeability of a water-absorbent resin particle may deteriorate.

The average primary particle diameter of the water-insoluble silicon compound fine particles (c) may be measured by a conventionally known method. For example, individual particles of 100 or more particles from a 50,000-fold image with a transmission electron microscope are used. A method of measuring the particle diameter from the average of the longest diameter and the shortest diameter of the particle, obtaining an arithmetic average value thereof, a method using a scattering type particle size distribution measuring apparatus using dynamic light scattering or laser diffraction, and a spherical particle. In some cases, a method of calculating from the specific surface area by the BET method may be used. When using a commercial product, the catalog value can be used instead. In addition, when there is a significant difference depending on the measurement method when obtaining by measurement, the method using the transmission electron microscope described above is used.

The water absorbent resin particles of the present invention can be obtained by mixing the crosslinked polymer (A) and the water-insoluble silicon compound fine particles (c). The mixing method includes a cylindrical mixer, a screw mixer, a screw extruder, a turbulizer (registered trademark), a flexo-mix vertical mixer, a nauter mixer, a double-arm kneader, and a fluid mixer. , V-type mixers, minced mixers, ribbon-type mixers, air-flow-type mixers, rotary disk-type mixers, conical blenders, roll mixers, and other known mixing devices. From the viewpoint that the variation coefficient of the atomic number concentration is low, a vertical mixer having a cylindrical mixing layer and rotating around a central axis is preferable. Note that the vertical type means that the rotation axis is in the vertical direction (vertical direction) and the horizontal type means that the rotation axis is in the horizontal direction. As a representative example of the vertical type mixer, a flexo-mix type vertical type mixer (for example, a trade name) : Flexomix FX, Flexomix FXD: both manufactured by Hosokawa Micron Corporation), and a typical example of a horizontal mixer is Turbulizer (registered trademark). The flexo-mix type vertical mixer has a high turbulent mixing effect and is considered to increase the uniformity because the mixing is performed quickly. In a horizontal mixer, water-absorbing resin particles tend to accumulate in the lower part of the mixing tank, and mixing tends to be uneven. It is considered that the water-insoluble silicon compound fine particles (c) are difficult to spread on the surface of the crosslinked polymer (A) and can be uniformly mixed on the surface by mixing at high speed and turbulent flow.

Rotational speed at the time of mixing in the flexo-mix type vertical mixer is preferably 1000 to 4000 rpm, more preferably 2000 to 3000 rpm. If it is lower than 1000 rpm, uniform mixing cannot be performed, and if it is higher than 4000 rpm, the water-absorbent resin particles may be broken by impact and fine powder may be generated.

The feed amount of the water-absorbent resin particles to the flexographic type vertical mixer is preferably in a range not exceeding the processing capacity according to the model. For example, flexographic mix FXD100 is 50 to 100 kg / h. If it is lower than 50 kg / h, the amount of processing per unit time is small and inefficient, and if it exceeds 100 kg, troubles such as blockage occur.

For mixing the crosslinked polymer (A) and the water-insoluble silicon compound fine particles (c), it is preferable to add the water-insoluble silicon compound fine particles (c) while stirring the crosslinked polymer (A). The added water-insoluble silicon compound fine particles (c) may be added simultaneously with water and / or a 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 can be added. From the viewpoint, it is preferable to add a dispersion, and it is more preferable to add an aqueous dispersion. When adding a dispersion liquid, it is preferable to add by spraying or dripping.

When the dispersion of water-insoluble silicon compound fine particles (c) is used, the content of the water-insoluble silicon compound fine particles (c) contained in the dispersion is preferably 5 to 70% by weight based on the total weight of the dispersion. More preferably, it is 10 to 60% by weight.

The dispersion of the water-insoluble silicon compound fine particles (c) may be a dispersion obtained by directly granulating a raw material by reacting with water and / or a solvent by a conventionally known method. A dispersion obtained by mechanical dispersion in a solvent may also be used.
From the viewpoint of the stability of the dispersion, it is preferable to use a dispersion obtained by directly granulating raw materials in water and / or a solvent. The dispersion of water-insoluble silicon compound fine particles (c) can be obtained as a commercial product as an aqueous colloidal solution (sol).
In addition, additives, such as arbitrary stabilizers, may be contained in the dispersion liquid as needed. Examples of stabilizers include commercially available surfactants and dispersants, commercially available acid compounds [phosphoric acid (salt), boric acid (salt), alkali metal (salt) and alkaline earth metal (salt), hydroxycarboxylic Acid (salt), fatty acid (salt), etc.].

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

After the crosslinked polymer (A) and the water-insoluble silicon compound fine particles (c) are mixed, a heat treatment may be further performed. The heating temperature is preferably 25 to 180 ° C., more preferably 30 to 175 ° C., and particularly preferably 35 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. Moreover, when not heating, the water and solvent used together will remain excessively in the water-absorbent resin, and the absorption performance may deteriorate. 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 amount of water and solvent remaining in the water-absorbent resin can be obtained by the heat loss method in accordance with JIS K0067-1992 (chemical product weight loss and residue test method).

In the case of heating after mixing the crosslinked polymer (A) and the water-insoluble silicon compound fine particles (c), 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, it is 10 to 40 minutes. The water-absorbent resin obtained by mixing the crosslinked polymer (A) and the water-insoluble silicon compound fine particles (c) is the same or different from the water-insoluble silicon compound fine particles used initially, Further surface treatment is possible.

The water-absorbent resin particles of the present invention may be used after mixing the crosslinked polymer (A) and the water-insoluble silicon compound fine particles (c), and sieving 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.

In the water absorbent resin particles of the present invention, the content of the water-insoluble silicon compound fine particles (c) can be adjusted according to the use of the water absorbent resin particles, but based on the weight of the crosslinked polymer (A), The content 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. If it is more than this range, dust will be peeled off from the surface of the water-absorbent resin, and if it is less than this range, moisture absorption blocking tends to occur.

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

In the present invention, the Si atom number concentration on the surface of the water-absorbent resin particles measured by scanning electron microscope-energy dispersive X-ray analysis is determined by measuring 20 random 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 the portion from the portion where the water-absorbent resin particles are exposed to the outside air to the inside of about 1 μm. Show.

In the measurement by scanning electron microscope-energy dispersive X-ray analysis, the electron beam is squeezed under the conditions of an acceleration voltage of 15 eV and a magnification of 100 times, and the intensity of characteristic X-rays observed for each element is detected. The composition of the measured electron beam irradiation region (the surface of the water-absorbent resin particles) can be determined. Since the Si atom number concentration on the surface of the water-absorbent resin particles may vary depending on individual water-absorbent resin particles, it is preferable to measure 20 random water-absorbent resin particles and obtain the arithmetic average value.

The arithmetic average of the Si atom number concentration (atomic%) measured by scanning electron microscope-energy dispersive X-ray analysis at an analysis point of 20 of the present invention is 0.5 to 5.0, and is a water-insoluble silicon compound It can adjust with content and addition method of microparticles | fine-particles (c). From the viewpoint of suppressing fluctuations in the feed amount and absorption performance, 1.0 to 2.5 is preferable. When the amount is more than 5.0, dust is peeled off from the surface of the water-absorbent resin, and when the amount is less than 0.5, moisture absorption is easily blocked.

Since the water-insoluble silicon compound fine particles (c) adhere to the water-absorbent resin particles with a force acting on the powder such as van der Waals force, it is difficult to control the amount of adhesion after adhesion, and turbulent mixing From the viewpoint of adjusting the average Si atom number concentration, it is preferable to mix uniformly.

In the water-absorbent resin particles of the present invention, the variation coefficient of the Si atom number concentration measured by scanning electron microscope-energy dispersive X-ray analysis at an analysis point of 20 depends on the method of adding the water-insoluble silicon compound fine particles (c). Although controlled, it is 0 to 40%. From the viewpoint of feed amount control and production efficiency, it is preferably 1 to 30%, more preferably 1 to 25%, and particularly preferably 10 to 25%. The variation coefficient of the Si atom number concentration is an index of the uniformity of Si atoms on the surface of the water-absorbent resin particles, and the lower the value, the more uniformly Si atoms, that is, the water-insoluble silicon compound fine particles (c) are added. If the coefficient of variation exceeds 40%, the feed amount 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) and the water-insoluble silicon compound fine particles (c). The surface of the crosslinked polymer (A) is an organic surface crosslinking agent ( In the case of having a structure crosslinked by e), the water-insoluble silicon compound fine particles (c) may be added at any stage before or after the surface crosslinking with the organic surface crosslinking agent (e). 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 cross-linking agent (e), and the water-insoluble silicon compound fine particles (c) are added to the organic surface cross-linking agent ( More preferably, it is added simultaneously with the addition of e).

The water absorbent resin particles of the present invention may further contain a polyhydric alcohol (f) having 4 or less carbon atoms. Examples of the polyhydric alcohol (f) having 4 or less carbon atoms include ethylene glycol, propylene glycol, 1,3-propanediol, glycerin, 1,4-butanediol and the like. Of these, propylene glycol and glycerin are preferable from the viewpoint of safety and availability, and propylene glycol is more preferable. (F) may be used individually by 1 type, and may use 2 or more types together.

The use amount (% by weight) of the polyhydric alcohol (f) having 4 or less carbon atoms is preferably 0.05 to 5 based on the weight of the cross-linked polymer (A) from the viewpoint of absorption performance and liquid permeability. Preferably it is 0.1 to 3, particularly preferably 0.2 to 2.

In the case of containing a polyhydric alcohol (f) having 4 or less carbon atoms, it may be added in any step, but from the viewpoint of uniformity of Si atoms, the water-insoluble silicon compound fine particles (c) and the organic surface crosslinking agent (e) Are preferably added simultaneously. By using (f), the wettability and permeability of the additive liquid with respect 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), a hydrophobic substance (g1) containing a hydrocarbon group, a hydrophobic substance (g2) containing a hydrocarbon group having a fluorine atom, and a hydrophobic substance (g3) having a polysiloxane structure Etc. are included.

Hydrophobic substances (g1) containing hydrocarbon groups 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 two or more thereof are included.

The polyolefin resin has a C2-4 olefin {ethylene, propylene, isobutylene, isoprene, etc.} as an essential constituent monomer (the olefin content is at least 50% by weight based on the weight of the polyolefin resin). Examples thereof include polymers having an average molecular weight of 1,000 to 1,000,000 {eg, polyethylene, polypropylene, polyisobutylene, poly (ethylene-isobutylene), isoprene, etc.}.

Examples of the polyolefin resin derivative include polymers having a weight average molecular weight of 1,000 to 1,000,000 introduced by introducing a carboxyl group (—COOH), 1,3-oxo-2-oxapropylene (—COOCO—), etc. into a polyolefin resin {for example, polyethylene heat Degradation, polypropylene thermal degradation, maleic acid modified polyethylene, chlorinated polyethylene, maleic acid modified polypropylene, ethylene-acrylic acid copolymer, ethylene-maleic anhydride copolymer, isobutylene-maleic anhydride copolymer, maleation Polybutadiene, ethylene-vinyl acetate copolymer, and maleated product of ethylene-vinyl acetate copolymer}.

As the polystyrene resin, a polymer having a weight average molecular weight of 1,000 to 1,000,000 can be used. *

As the polystyrene resin derivative, a polymer having a weight average molecular weight of 1,000 to 1,000,000 (for example, styrene-containing styrene as an essential constituent monomer (the content of styrene is at least 50% by weight based on the weight of the polystyrene derivative)). Maleic anhydride copolymer, styrene-butadiene copolymer, styrene-isobutylene copolymer, etc.}.

Examples of the wax include waxes having a melting point of 50 to 200 ° C. (for example, paraffin wax, beeswax, carnauba wax, beef tallow, etc.).

Long chain fatty acid esters 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, oleic acid) Ethyl, glycerin lauric acid monoester, glycerin stearic acid monoester, glycerin oleic acid monoester, pentaerythritol lauric acid monoester, pentaerythritol stearate monoester, pentaerythritol oleic acid monoester, sorbit lauric acid monoester, Sorbit stearic acid monoester, sorbit oleic acid monoester, sucrose palmitic acid monoester, sucrose palmitic acid diester, sucrose palmitic acid triester, sucrose stearic acid monoester Ester, sucrose stearic acid diester, sucrose stearic acid triester, and beef tallow} and the like.

Examples of long-chain fatty acids and salts thereof include fatty acids having 8 to 30 carbon atoms (for example, lauric acid, palmitic acid, stearic acid, oleic acid, dimer acid, and behenic acid), and salts thereof include zinc, calcium, Examples thereof include salts with magnesium or aluminum (hereinafter abbreviated as Zn, Ca, Mg, Al, respectively) {for example, palmitic acid Ca, palmitic acid Al, stearic acid Ca, stearic acid Mg, stearic acid Al, etc.}.

Examples of the long-chain aliphatic alcohol include aliphatic alcohols having 8 to 30 carbon atoms (for example, lauryl alcohol, palmityl alcohol, stearyl alcohol, oleyl alcohol, etc.). From the viewpoint of the moisture resistance of the absorbent article, palmityl alcohol, 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, ammonia, or a primary amine having 1 to 7 carbon atoms. And amidated product of a long chain fatty acid having 8 to 30 carbon atoms, 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 Examples thereof include amidated products of secondary amines having two aliphatic hydrocarbon groups having 1 to 7 carbon atoms and long chain fatty acids having 8 to 30 carbon atoms.

As an amidation 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, a compound obtained by reacting a primary amine and a carboxylic acid 1: 1 is used. : Divided into those reacted in 2. Examples of the product reacted at 1: 1 include acetic acid N-octylamide, acetic acid N-hexacosylamide, heptacosanoic acid N-octylamide, heptacosanoic acid N-hexacosylamide and the like. Examples of those reacted at 1: 2 include diacetate N-octylamide, diacetate N-hexacosylamide, diheptacosanoic acid N-octylamide, and diheptacosanoic acid N-hexacosylamide. In the case where the primary amine and the carboxylic acid are reacted at 1: 2, the carboxylic acid used may be the same or different.

Examples of amidated products of ammonia or primary amines having 1 to 7 carbon atoms and long chain fatty acids having 8 to 30 carbon atoms include those obtained by reacting ammonia or primary amines with carboxylic acids in a 1: 1 ratio. Divided into reacted products. Nonionic acid amide, nonanoic acid methylamide, nonanoic acid N-heptylamide, heptacosanoic acid amide, heptacosanoic acid N-methylamide, heptacosanoic acid N-heptylamide and heptacosanoic acid N-hexacosylamide Etc. The ones reacted in 1: 2 include dinonanoic acid amide, dinonanoic acid N-methylamide, dinonanoic acid N-heptylamide, dioctadecanoic acid amide, dioctadecanoic acid N-ethylamide, dioctadecanoic acid N-heptylamide, diheptacosanoic acid amide And diheptacosanoic acid N-methylamide, diheptacosanoic acid N-heptylamide, and diheptacosanoic acid N-hexacosylamide. In addition, as a thing which ammonia or primary amine and carboxylic acid reacted by 1: 2, the carboxylic acid to be used may be the same or different.

Examples of amidated products 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-methylhexacosyl acetate Amide, acetic acid N-octylhexacosylamide, acetic acid N-dihexacosylamide, heptacosanoic acid N-methyloctylamide, heptacosanoic acid N-methylhexacosylamide, heptacosanoic acid N-octylhexacosylamide and heptacosane Examples include acid N-dihexacosylamide.

Examples of amidated products of secondary amines having two aliphatic hydrocarbon groups having 1 to 7 carbon atoms and long chain fatty acids having 8 to 30 carbon atoms include nonanoic acid N-dimethylamide, nonanoic acid N-methylheptylamide, Nonanoic acid N-diheptylamide, heptacosanoic acid N-dimethylamide, heptacosanoic acid N-methylheptylamide, heptacosanoic acid N-diheptylamide and the like can be mentioned.

Examples of the hydrophobic substance (g2) containing a hydrocarbon group having a fluorine atom include perfluoroalkane, perfluoroalkene, perfluoroaryl, perfluoroalkyl ether, perfluoroalkyl carboxylic acid, perfluoroalkyl alcohol, and those 2 A mixture of seeds or more is included.

Examples of the hydrophobic substance (g3) having a polysiloxane structure include polydimethylsiloxane, polyether-modified polysiloxane {polyoxyethylene-modified polysiloxane and poly (oxyethylene / oxypropylene) -modified polysiloxane, etc.}, carboxy-modified polysiloxane, Epoxy-modified polysiloxane, amino-modified polysiloxane, alkoxy-modified polysiloxane and the like, and mixtures thereof 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. Within this range, the blocking resistance during initial swelling is further improved. The HLB value means a hydrophilic-hydrophobic balance (HLB) value, and is determined by the Oda method (new introduction to surfactants, page 197, Takehiko Fujimoto, published by Sanyo Chemical Industries, Ltd., published in 1981). .

Of the hydrophobic substances (g), from the viewpoint of blocking resistance at the time of initial swelling, a hydrophobic substance (g1) containing a hydrocarbon group is preferred, more preferably a long-chain fatty acid ester, a long-chain fatty acid and a salt thereof, Long chain aliphatic alcohols and long chain aliphatic amides, more preferably sorbite stearate, sucrose stearate, stearic acid, Mg stearate, Ca stearate, Zn stearate and Al stearate, particularly preferably Sucrose stearate and Mg stearate, most preferably sucrose stearate.

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

When the hydrophobic substance (g) is contained, it may be added in any step, but it is preferably added before the addition of the water-insoluble silicon compound fine particles (c) from the viewpoint of absorption performance. In the case where the surface of A) has a structure crosslinked with the organic surface crosslinking agent (e), the hydrophobic substance (g) is further added before the surface crosslinking with the organic surface crosslinking agent (e). preferable.

The water-absorbent resin particles of the present invention may contain, as necessary, additives (for example, known preservatives, fungicides, antibacterial agents, oxidation agents (described in JP-A No. 2003-225565 and JP-A No. 2006-131767, etc.)) An inhibitor, an ultraviolet absorber, a chelating agent, a colorant, a fragrance, a deodorant, a liquid permeability improver, and an organic fibrous material). When these additives are contained, the content (% by weight) of the additive is preferably 0.001 to 10, more preferably 0.01 to 5, particularly preferably based on the weight of the crosslinked polymer (A). Preferably it is 0.05 to 1, most preferably 0.1 to 0.5.

The production method of the present invention is a method for producing the water-absorbent resin particles of the present invention, wherein the crosslinked polymer (A) having water-soluble vinyl monomer (a1) and crosslinking agent (b) as essential structural units and water-insoluble. A mixing step of mixing the silicon compound fine particles (c) with a vertical mixer by turbulent mixing; In the mixing step, the mixing is preferably performed by turbulent mixing using a flexographic type vertical mixer. At that time, when the surface of the crosslinked polymer (A) has a structure crosslinked by an organic surface crosslinking agent (e), the crosslinked polymer (A) is preferably the water-insoluble silicon compound fine particles (c) or The aqueous colloidal solution of the water-insoluble silicon compound fine particles (c) and the surface cross-linking agent are added simultaneously. Specific examples of the water-insoluble silicon compound fine particles (c) or the aqueous colloidal liquid of the water-insoluble silicon compound fine particles (c) are as described above. The addition amount and addition method thereof are also as described above. From the viewpoint of liquid permeability, an aqueous colloidal solution of water-insoluble silicon compound fine particles (c), an organic surface crosslinking agent (e It is more preferable that the polyhydric alcohol having 4 or less carbon atoms is simultaneously added by spraying while being mixed by a flexographic type vertical mixer, and then heat-treated.

The water retention amount (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) will be described later. 25 to 55 is preferable, 30 to 50 is more preferable, and 35 to 45 is particularly preferable. If the water retention amount is lower than this range, the diaper absorption amount is low, and if it is higher than this range, the absorption amount under load is low. The amount of water retention can be appropriately adjusted by the amount (% by weight) used 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 / 143737, etc., and is preferably 5 to 300 from the viewpoint of the diaper absorption rate, 10 to 280 is more preferable, and 15 to 250 is particularly preferable. It is empirically known that the gel flow rate conflicts with the water retention amount, and there are cases where a high water retention amount is required and a high gel flow rate is required depending on the configuration 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. . Within this range, the anti-fogging property of the absorbent article is further improved. The apparent density of the water absorbent resin particles is measured at 25 ° C. according to JIS K7365: 1999.

The moisture absorption blocking rate of the water-absorbent resin particles of the present invention can be measured by the method described later, and is preferably 0 to 50%, more preferably 0 to 30%, and particularly preferably 0 to 20%. Within this range, blocking problems are unlikely to occur regardless of the work environment.

An absorbent body can be obtained using the water-absorbent resin particles of the present invention. As the absorber, water-absorbing resin particles may be used alone or may be used together with other materials as an absorber.
Examples of other materials include fibrous materials. The structure and production method of the absorbent when used together with the fibrous material are the same as those known (JP 2003-225565 A, JP 2006-131767 A, JP 2005-097569 A, etc.). is there.

Preferred as the fibrous material are cellulose fibers, organic synthetic fibers, and a mixture of cellulose fibers and organic synthetic fibers.

Examples of the cellulosic fibers include natural fibers such as fluff pulp, and cellulosic chemical fibers such as viscose rayon, acetate, and cupra. There are no particular restrictions on the raw materials (conifers, hardwoods, etc.), production methods (chemical pulp, semi-chemical pulp, mechanical pulp, CTMP, etc.), bleaching methods, etc. of this cellulose-based natural fiber.

Examples of organic synthetic fibers include polypropylene fibers, polyethylene fibers, polyamide fibers, polyacrylonitrile fibers, polyester fibers, polyvinyl alcohol fibers, polyurethane fibers, and heat-fusible composite fibers (the above fibers having different melting points). And a fiber obtained by compounding at least two of the above into a sheath core type, an eccentric type, a parallel type, and the like, a fiber obtained by blending at least two kinds of the above fibers, and a fiber obtained by modifying the surface layer of the above fibers).

Among these fibrous materials, preferred are cellulose-based natural fibers, polypropylene-based fibers, polyethylene-based fibers, polyester-based fibers, heat-fusible conjugate fibers, and mixed fibers thereof, and more preferable are obtained. The fluff pulp, the heat-fusible conjugate fiber, and the mixed fiber thereof are preferable in that the water-absorbing agent has excellent shape retention after water absorption.

The length and thickness of the fibrous material are not particularly limited and can be suitably used as long as the length is 1 to 200 mm and the thickness is in the range of 0.1 to 100 denier. The shape is not particularly limited as long as it is fibrous, and examples thereof include a thin cylindrical shape, a split yarn shape, a staple shape, a filament shape, and a web shape.

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

An absorbent article can be obtained using the water absorbent resin of the present invention. Specifically, the absorber is used. The absorbent article is applicable not only to sanitary articles such as paper diapers and sanitary napkins, but also to various uses such as absorption of various aqueous liquids described below, use as a retention agent, and use as a gelling agent. The manufacturing method and the like of the absorbent article are the same as known ones (described in JP 2003-225565 A, JP 2006-131767 A, JP 2005-097569 A, etc.).

Hereinafter, 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 indicate parts by weight and% indicates% by weight. The water retention amount of the water absorbent resin particles with respect to physiological saline, the absorption amount under load, the moisture absorption blocking rate, the surface Si amount, the variation coefficient of the surface Si amount, the feed amount and the variation coefficient of the feed amount 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 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, and the weight (h1) including the tea bag was measured to obtain the water retention amount from the following formula. In addition, the temperature of the used physiological saline and measurement atmosphere was 25 degreeC +/- 2 degreeC.
Water retention amount (g / g) = (h1) − (h2)
In addition, (h2) is the weight of the tea bag measured by the same operation as described above when there is no measurement sample.

<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 μm mesh (JIS Z8801-1: 2006) nylon net attached to the bottom, 250-500 μm 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: 210.6 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 weight (M2) of the entire cylindrical plastic tube was weighed, and the absorbed amount under load 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 moisture absorption blocking rate>
10 g of the measurement sample passed through a 850 μm wire mesh (JIS Z8801-1: 2001) is uniformly placed in a 5 cm diameter aluminum cylindrical dish and placed in a constant temperature and humidity chamber of 40 ± 1 ° C. and relative humidity of 80 ± 5%. And left for 3 hours. After measuring the total weight (a) of the measurement sample after standing for 3 hours, the sample was tapped five times with a wire mesh (JIS Z8801-1: 2001) having an opening of 1400 μm, blocked by moisture absorption and having an opening of 1400 μm. The weight (b) of the resin particles remaining on the wire mesh was measured, and the moisture absorption blocking rate was determined from the following formula.
Moisture absorption blocking rate (%) = (b / a) × 100

<Measuring method of average Si atom number concentration and variation coefficient of Si atom number concentration>
Fix 10 or more measurement samples that have been screened to a range of 250-500μm using a 30-mesh screen and a 60-mesh screen on a sample table with carbon tape, so that the particles do not overlap each other. It was set in a field emission type scanning electron microscope “Quanta FEG250 FEG” manufactured by FEI and equipped with a line analysis (EDS analysis) apparatus OctaneElite. The acceleration voltage was 15 eV, the magnification was 100 times, one particle was displayed on the screen, and the range within the particle was subjected to EDS analysis by surface analysis.
20 samples are randomly measured for one type of measurement sample, and the arithmetic average value of the detected number of Si atoms% (atomic%) is taken as the average of the Si atom number concentration of the measured sample, and the standard deviation of the number of Si atoms% The value obtained by dividing the value by the average value was taken as the variation coefficient of the Si atom number concentration.

<Measuring method of feed amount and variation coefficient of feed amount>
500 g of a measurement sample was placed in a hopper of an accurate feeder (model 100, shaft: spring type, manufactured by Kuma Engineering Co., Ltd.). An electronic balance with a metal tray placed on the tip of the sample supply port was set, FeedRate was set to 900, and sample supply was started. The supply amount was recorded every 10 seconds from the time when the integrated supply amount to the tray reached 50 g, and the feed amount was recorded for 200 seconds. A value obtained by converting the amount supplied for 200 seconds per minute is the feed amount (g / min), and a value obtained by dividing the standard deviation of the supply amount every 10 seconds by the average value is defined as a variation coefficient of the feed amount. .

<Example 1>
Acrylic acid (a1-1) {Mitsubishi Chemical Corporation, purity 100%} 131 parts, Cross-linking agent (b-1) {Pentaerythritol triallyl ether, Osaka Soda Co., Ltd.} 0.44 parts and deionized water 362 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, 0.5 part of 1% aqueous hydrogen peroxide solution, 1 part of 2% aqueous ascorbic acid solution and 2% 2,2′-azobisamidinopropane Polymerization was initiated by adding and mixing 1 part of an aqueous dihydrochloride solution. After the temperature of the mixture reached 80 ° C., a water-containing gel was obtained by polymerization at 80 ± 2 ° C. for about 5 hours.

Next, this water-containing gel was shredded with a mincing machine (12VR-400K manufactured by ROYAL), and mixed and neutralized by adding 108 parts of a 48.5% aqueous sodium hydroxide solution to neutralize the gel (degree of neutralization: 72%). Further, the neutralized hydrogel was dried with a ventilation dryer {200 ° C., wind speed 2 m / sec} to obtain a dried product. The dried product was 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 a crosslinked polymer (A-1).

Subsequently, 100 parts of the resulting crosslinked polymer (A-1) was stirred at high speed (Flexomix FXD100 manufactured by Hosokawa Micron Corporation: rotation speed 3000 rpm, feed rate 50 kg / h), and water-insoluble silicon compound fine particles (c) were added thereto. Klebosol 30cal25 (Merck colloidal silica, solid content 30%, average primary particle size 25 nm) 1.0 part, ethylene glycol diglycidyl ether 0.1 part as organic surface crosslinking agent (e), carbon number 4 or less A liquid obtained by mixing 1.0 part of propylene glycol as a monohydric alcohol (f) and 1.6 parts of water is spray-added from a spray nozzle and mixed uniformly, and then heated at 130 ° C. for 30 minutes to obtain the water absorption Resin particles (P-1) were obtained. The apparent density of (P-1) was 0.58 g / ml.

<Example 2>
While 100 parts of the crosslinked polymer (A-1) obtained in the same manner as in Example 1 was stirred at high speed (Flexomix FXD100 manufactured by Hosokawa Micron Corporation: rotation speed 3000 rpm, feed rate 50 kg / h) From a spray nozzle, a solution obtained by mixing 0.1 part of ethylene glycol diglycidyl ether as the agent (e), 1.0 part of propylene glycol as the polyhydric alcohol (f) having 4 or less carbon atoms, and 1.6 parts of water After spray addition, uniform mixing, heating at 130 ° C. for 30 minutes, cooling to room temperature, water-insoluble silicon compound while further stirring at high speed (Flexomix FXD100 manufactured by Hosokawa Micron Corporation: rotation speed 3000 rpm, feed rate 50 kg / h) Klebosol 30cal25 as a fine particle (c) Sprayed with a mixture of 1.0 part of mosquito, solid content 30%, average primary particle size 25 nm), 0.5 part of propylene glycol as polyhydric alcohol (f) having 4 or less carbon atoms, and 0.5 part of water After spray addition from a nozzle and mixing uniformly, the mixture was heated at 80 ° C. for 30 minutes to obtain water-absorbent resin particles (P-2) of the present invention. The apparent density of (P-2) was 0.58 g / ml.

<Example 3>
While 100 parts of the crosslinked polymer (A-1) obtained in the same manner as in Example 1 was stirred at high speed (Flexomix FXD100 manufactured by Hosokawa Micron Corporation: rotation speed 3000 rpm, feed rate 50 kg / h) From a spray nozzle, a solution obtained by mixing 0.1 part of ethylene glycol diglycidyl ether as the agent (e), 1.0 part of propylene glycol as the polyhydric alcohol (f) having 4 or less carbon atoms, and 1.6 parts of water After spray addition, uniform mixing, heating at 130 ° C. for 30 minutes, cooling to room temperature, water-insoluble silicon compound while further stirring at high speed (Flexomix FXD100 manufactured by Hosokawa Micron Corporation: rotation speed 3000 rpm, feed rate 50 kg / h) Aerosil 200 as fine particles (c) (Humedosil manufactured by Nippon Aerosil Co., Ltd.) The average primary particle size of 12 nm) is sprayed from a spray nozzle by dispersing 0.1 part of propylene glycol as a polyhydric alcohol (f) having 4 or less carbon atoms and 0.5 part of water. After the addition and uniform mixing, the mixture was heated at 80 ° C. for 30 minutes to obtain the water-absorbent resin particles (P-3) of the present invention. The apparent density of (P-3) was 0.59 g / ml.

<Example 4>
From Example 1, 0.1 part of ethylene glycol diglycidyl ether as the organic surface crosslinking agent (e) is 0.03 part, and 1.0 part of propylene glycol as the polyhydric alcohol (f) having 4 or less carbon atoms is 0. The water-absorbent resin particles (P-4) of the present invention were obtained in the same manner except that 1.6 parts of water was changed to 0.80 parts at 60 parts. The apparent density of (P-4) was 0.58 g / ml.

<Example 5>
From Example 1, 1.0 part of Klebosol 30cal25 (colloidal silica manufactured by Merck Co., Ltd., solid content 30%, average primary particle size 25 nm) as water-insoluble silicon compound fine particles (c) was changed to 0.17 part, and an organic surface crosslinking agent (e ) 0.1 part of ethylene glycol diglycidyl ether as 0.01), 1.0 part of propylene glycol as polyhydric alcohol (f) having 4 or less carbon atoms, 0.30 part, 1.6 parts of water The water-absorbent resin particles (P-5) of the present invention were obtained in the same manner except that was changed to 0.30 part. The apparent density of (P-5) was 0.59 g / ml.

<Example 6>
The same procedure as in Example 1 except that 1.0 part of Klebosol 30cal25 (Merck colloidal silica, solid content 30%, average primary particle size 25 nm) as water-insoluble silicon compound fine particles (c) was changed to 1.5 parts. Inventive water-absorbing resin particles (P-6) were obtained. The apparent density of (P-6) was 0.58 g / ml.

<Example 7>
(P-1) Put 100 parts by weight in a plastic bag and add 0.1 part Aerosil 200 (fumed silica manufactured by Nippon Aerosil Co., Ltd., average primary particle size 12 nm) as water-insoluble silicon compound fine particles (c). Then, the water-absorbent resin particles (P-7) of the present invention were obtained. The apparent density of (P-7) was 0.57 g / ml.

<Example 8>
Acrylic acid (a1-1) {manufactured by Mitsubishi Chemical Corporation, purity 100%} 155 parts, crosslinking agent (b-1) {pentaerythritol triallyl ether, Osaka Soda Co., Ltd.} 0.54 parts and deionized water 335 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, 0.6 part of 1% aqueous hydrogen peroxide solution, 1.2 parts of 2% aqueous ascorbic acid solution and 2% 2,2′-azobis Polymerization was initiated by adding and mixing 8 parts of an amidinopropane dihydrochloride aqueous solution. After the temperature of the mixture reached 90 ° C., a water-containing gel was obtained by polymerization at 90 ± 2 ° C. for about 5 hours.

Next, this water-containing gel is shredded with a mincing machine (12 VR-400K manufactured by ROYAL), and then mixed and neutralized by adding 128 parts of 48.5% aqueous sodium hydroxide solution to neutralize the gel (degree of neutralization: 72%). Further, the neutralized hydrogel was dried with a ventilation dryer {150 ° C., wind speed 2 m / sec} to obtain a dried product. The dried product was 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 a crosslinked polymer (A-2).

Next, 100 parts of the resulting crosslinked polymer (A-2) was stirred at high speed (Flexomix FXD100 manufactured by Hosokawa Micron Corporation: rotation speed 3000 rpm, feed rate 50 kg / h). Klebosol 30cal25 (Merck colloidal silica, solid content 30%, average primary particle size 25 nm) 1.0 part, 0.12 part of ethylene glycol diglycidyl ether as organic surface crosslinking agent (e), carbon number 4 or less A solution obtained by mixing 1.6 parts of propylene glycol as a monohydric alcohol (f) and 2.3 parts of water is sprayed from a spray nozzle and mixed uniformly, and then heated at 140 ° C. for 30 minutes to absorb the water absorption of the present invention. Resin particles (P-8) were obtained. The apparent density of (P-8) was 0.60 g / ml.

<Comparative Example 1>
100 parts of the crosslinked polymer (A-1) obtained in the same manner as in Example 1 was stirred at a high speed (high speed stirring turbulizer manufactured by Hosokawa Micron Co., Ltd. (registered trademark, the same applies hereinafter): rotational speed 2000 rpm, feed speed 50 kg / h) However, 1.0 part of Klebosol 30cal25 (Merck colloidal silica, solid content 30%, average primary particle size 25 nm) as water-insoluble silicon compound fine particles (c), and ethylene glycol as an organic surface cross-linking agent (e) A solution prepared by mixing 0.1 part of diglycidyl ether, 1.0 part of propylene glycol as polyhydric alcohol (f) having 4 or less carbon atoms, and 1.6 parts of water was added and mixed. Heating for a minute gave comparative water-absorbent resin particles (R-1). The apparent density of (R-1) was 0.57 g / ml.

<Comparative example 2>
While 100 parts of the crosslinked polymer (A-1) obtained in the same manner as in Example 1 was used (high-speed stirring turbulizer manufactured by Hosokawa Micron Co., Ltd .: rotation speed 2000 rpm, feed rate 50 kg / h) A mixture of ethylene glycol diglycidyl ether 0.1 part as agent (e), propylene glycol 1.0 part as polyhydric alcohol (f) having 4 or less carbon atoms, and water 1.6 parts, After uniform mixing, the mixture was heated at 130 ° C. for 30 minutes, cooled to room temperature, and further water-insoluble silicon compound fine particles (high-speed stirring turbulizer manufactured by Hosokawa Micron Corporation: rotation speed 2000 rpm, feed rate 50 kg / h) c) Klebosol 30cal25 (Merck colloidal silica, solid content 30%, average primary particle size 25n) ) After mixing a liquid in which 1.0 part, 0.5 part of propylene glycol as a polyhydric alcohol (f) having 4 or less carbon atoms, and 0.5 part of water were mixed, the mixture was heated at 80 ° C. for 30 minutes for comparison. Water-absorbent resin particles (R-2) for use were obtained. The apparent density of (R-2) was 0.58 g / ml.

<Comparative 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 (a high-speed stirring turbulator manufactured by Hosokawa Micron Co., Ltd .: rotation speed 2000 rpm, feed speed 50 kg / h), Add a mixture of ethylene glycol diglycidyl ether 0.1 part as surface cross-linking agent (e), propylene glycol 1.0 part as polyhydric alcohol (f) having 4 or less carbon atoms, and water 1.6 parts. After homogeneous mixing, heating at 130 ° C. for 30 minutes, cooling to room temperature, and further water-insoluble silicon compound with high-speed stirring (high-speed stirring turbulizer manufactured by Hosokawa Micron Co., Ltd .: rotation speed 2000 rpm, feed rate 50 kg / h) Aerosil 200 as fine particles (c) (fumed silica manufactured by Nippon Aerosil Co., Ltd., average primary particle size 12 nm) And a liquid obtained by mixing 0.5 part of propylene glycol as polyhydric alcohol (f) having 4 or less carbon atoms and 0.5 part of water, and then heating at 80 ° C. for 30 minutes to obtain a water absorption for comparison. Resin particles (R-3) were obtained. The apparent density of (R-3) was 0.59 g / ml.

<Comparative example 4>
While 100 parts of the crosslinked polymer (A-1) obtained in the same manner as in Example 1 was stirred at a high speed (a high-speed stirring turbulator manufactured by Hosokawa Micron Co., Ltd .: rotation speed 2000 rpm, feed speed 50 kg / h), Add a mixture of ethylene glycol diglycidyl ether 0.1 part as surface cross-linking agent (e), propylene glycol 1.0 part as polyhydric alcohol (f) having 4 or less carbon atoms, and water 1.6 parts. After homogeneous mixing, heating at 130 ° C. for 30 minutes, cooling to room temperature, and further water-insoluble silicon compound with high-speed stirring (high-speed stirring turbulizer manufactured by Hosokawa Micron Co., Ltd .: rotation speed 2000 rpm, feed rate 50 kg / h) Aerosil 200 as fine particles (c) (fumed silica manufactured by Nippon Aerosil Co., Ltd., average primary particle size 12 nm) After mixing the parts, by heating 80 ° C. 30 minutes to obtain water absorbing resin particles for comparison (R-4). The apparent density of (R-4) was 0.59 g / ml.

<Comparative Example 5>
While 100 parts of the crosslinked polymer (A-1) obtained in the same manner as in Example 1 was stirred at a high speed (a high-speed stirring turbulator manufactured by Hosokawa Micron Co., Ltd .: rotation speed 2000 rpm, feed speed 50 kg / h), Add a mixture of ethylene glycol diglycidyl ether 0.1 part as surface cross-linking agent (e), propylene glycol 1.0 part as polyhydric alcohol (f) having 4 or less carbon atoms, and water 1.6 parts. After homogeneous mixing, heating at 130 ° C. for 30 minutes, cooling to room temperature, and further water-insoluble silicon compound with high-speed stirring (high-speed stirring turbulizer manufactured by Hosokawa Micron Co., Ltd .: rotation speed 2000 rpm, feed rate 50 kg / h) Klebosol 30cal25 as fine particles (c) (Merck colloidal silica, solid content 30%, average primary particles) 25 nm) were mixed with 0.1 parts by heating 80 ° C. 30 minutes to obtain water absorbing resin particles for comparison (R-5). The apparent density of (R-5) was 0.58 g / ml.

<Comparative Example 6>
Comparative water-absorbing resin particles (R-6) were obtained in the same manner as in Example 1, except that Klebosol 30cal25 as the water-insoluble silicon compound fine particles (c) was not used. The apparent density of (R = 6) was 0.60 g / ml.

From the results of Table 1, the water retention amount is good and no significant difference is seen through Examples 1 to 3, 6, 7 and Comparative Examples, but the Examples have a low coefficient of variation in the number of Si atoms, and the feed amount The coefficient of variation was low and good. The variation method of the Si atom number concentration was changed by changing the mixing method between the example and the comparative example. On the other hand, in Comparative Examples 1 to 4 where the variation coefficient of the Si atom number concentration is high, the variation coefficient of the feed amount is high, and lowering the variation coefficient of the Si atom number concentration lowers the variation coefficient of the feed amount. It is particularly important. Comparative Examples 5 and 6 have a low Si atom number concentration and a high moisture absorption blocking rate. Furthermore, as shown in Examples 4, 5, and 8, the water-absorbing fine particles of the present invention can reduce the variation coefficient of the feed amount by reducing the variation coefficient of the Si atom number concentration even in a wide water retention range. .

Since the water-absorbent resin particles of the present invention have little fluctuation in the amount of feed in a supply device (feeder) in the production process, when applied to the production of various absorbers, production is stable. Suitable for hygiene items such as adult paper diapers, napkins (sanitary napkins, etc.), paper towels, pads (pads for incontinence, surgical underpads, etc.) and pet sheets (pet urine absorbing sheets). Ideal for disposable diapers. The water-absorbent resin particles of the present invention are not only sanitary products, but also pet urine absorbents, urine gelling agents for portable toilets, freshness preservation agents such as fruits and vegetables, meat and seafood drip absorbents, cold insulation agents, disposable warmers It is also useful for various uses such as battery gelling agents, water retention agents for plants and soil, anti-condensation agents, water-stopping materials and packing materials, and artificial snow.

Claims

A water-absorbent resin particle comprising a crosslinked polymer (A) having a water-soluble vinyl monomer (a1) and a crosslinking agent (b) as essential constituent units, and water-insoluble silicon compound fine particles (c), wherein the scanning electron The arithmetic mean of Si atom number concentration (atomic%) measured by microscope-energy dispersive X-ray analysis at 20 analysis points is 0.5 to 5.0, and the variation coefficient of Si atom number concentration is 0 to Water-absorbent resin particles that are 40%.
The water-absorbent resin particles according to claim 1, wherein the water-insoluble silicon compound fine particles (c) are spherical or amorphous particles having an average primary particle diameter of 1 to 100 nm.
The water-absorbent resin particles according to claim 1 or 2, 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).
The water-absorbent resin particle according to any one of claims 1 to 3, wherein the surface of the crosslinked polymer (A) has a structure crosslinked by an organic surface crosslinking agent (e).
The water-absorbent resin particles according to any one of claims 1 to 4, further comprising a polyhydric alcohol (f) having 4 or less carbon atoms.
The water-absorbent resin particles according to any one of claims 1 to 5, wherein the water retention amount is 25 to 55 g / g.
A method for producing the water-absorbent resin particles according to any one of claims 1 to 6, wherein the crosslinked polymer (A) comprises the water-soluble vinyl monomer (a1) and the crosslinking agent (b) as essential constituent units, A method for producing water-absorbing resin particles, comprising a mixing step of mixing water-insoluble silicon compound fine particles (c) by turbulent mixing with a vertical mixer.
The method for producing water-absorbent resin particles according to claim 7, 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).
The method for producing water-absorbent resin particles according to claim 7 or 8, wherein the dispersion of water-insoluble silicon compound fine particles (c) dispersed in water and / or a solvent is sprayed and added.
The method for producing water-absorbent resin particles according to any one of claims 7 to 9, wherein the mixing step is performed by turbulent mixing using a flexographic type vertical mixer.
An absorbent comprising the water-absorbent resin particles according to any one of claims 1 to 6.
Furthermore, the absorber of Claim 11 formed by containing a fibrous material.
An absorbent article comprising the absorber according to claim 11 or 12.