WO2021049631A1

WO2021049631A1 - Liquid leakage inhibitor used in absorbent containing water absorbent resin particles, and water absorbent resin particles

Info

Publication number: WO2021049631A1
Application number: PCT/JP2020/034535
Authority: WO
Inventors: 健太熊澤
Original assignee: 住友精化株式会社
Priority date: 2019-09-13
Filing date: 2020-09-11
Publication date: 2021-03-18
Also published as: JPWO2021049631A1

Abstract

The present invention relates to a liquid leakage inhibitor which contains dry silica and is used in an absorbent that contains water absorbent resin particles.

Description

Liquid leakage inhibitor and water-absorbent resin particles used for absorbers containing water-absorbent resin particles

The present invention relates to a liquid leakage inhibitor and water-absorbent resin particles used for an absorber containing water-absorbent resin particles.

Conventionally, an absorber containing water-absorbent resin particles has been used as an absorbent article for absorbing a liquid containing water as a main component such as urine. For example, Patent Document 1 below is effective for producing water-absorbent resin particles having a particle size suitable for absorbent articles such as diapers, and Patent Document 2 is effective for containing body fluids such as urine. A method of using a hydrogel-absorbing polymer having specific saline flow inducibility, performance under pressure, etc. is disclosed as a specific absorbent member.

Japanese Unexamined Patent Publication No. 6-345819 Special Table 9-510889 Gazette

In an absorbent article using a conventional absorber, the liquid to be absorbed is not sufficiently absorbed by the absorber, and a phenomenon (liquid running) in which excess liquid flows on the surface of the absorber is likely to occur, and as a result, the liquid is absorbed. There was room for improvement in terms of leakability, which leaked to the outside of the sex article.

An object of the present invention is to provide a liquid leakage inhibitor used for an absorber containing water-absorbent resin particles.

The present inventors have found that dry silica has an effect of suppressing liquid leakage of an absorber containing water-absorbent resin particles. Based on this novel finding, the present invention provides new uses for dry silica.

One aspect of the present invention relates to a liquid leakage inhibitor used for an absorber containing water-absorbent resin particles, including dry silica.

Another aspect of the present invention relates to water-absorbent resin particles containing polymer particles and the liquid leakage inhibitor arranged on the surface of the polymer particles. Another aspect of the present invention relates to an absorber containing the water-absorbent resin particles. Another aspect of the invention relates to an absorbent article comprising the absorber.

According to the present invention, it is possible to provide a liquid leakage inhibitor used for an absorber containing water-absorbent resin particles.

It is sectional drawing which shows one Embodiment of an absorbent article. It is a schematic diagram which shows an example of the measuring method of non-pressurized DW. It is a schematic diagram which shows the apparatus which simply evaluates the leak property of an absorber.

Hereinafter, some embodiments of the present invention will be described in detail. However, the present invention is not limited to the following embodiments.

In this specification, "acrylic" and "methacryl" are collectively referred to as "(meth) acrylic". Similarly, "acrylate" and "methacrylate" are also referred to as "(meth) acrylate". In the numerical range described stepwise in the present specification, the upper limit value or the lower limit value of the numerical range of one step can be arbitrarily combined with the upper limit value or the lower limit value of the numerical range of another step. In the numerical range described in the present specification, the upper limit value or the lower limit value of the numerical range may be replaced with the value shown in the examples. "A or B" may include either A or B, or both. "Water-soluble" means that it exhibits a solubility in water of 5% by mass or more at 25 ° C. The materials exemplified in the present specification may be used alone or in combination of two or more. The content of each component in the composition means the total amount of the plurality of substances present in the composition when a plurality of substances corresponding to each component are present in the composition, unless otherwise specified.

<Liquid leakage inhibitor>
The liquid leakage inhibitor used for the absorber containing the water-absorbent resin particles according to the embodiment includes dry silica. In the absorber containing the water-absorbent resin particles, the liquid leakage inhibitor containing dry silica is used as a constituent component of the water-absorbent resin particles containing the polymer particles. The dry silica may be placed on the surface of the polymer particles. Liquid leakage can be suppressed by using water-absorbent resin particles containing the liquid leakage inhibitor as the absorber.

In addition to dry silica, the liquid leakage inhibitor of the present invention includes wet silica, titanium dioxide, aluminum oxide, magnesium oxide, zinc oxide, calcium phosphate, hydrotalcite, bentonite, kaolin, talc, diatomaceous earth, zeolite and other inorganic particles. Contains nonionic surfactants, anionic surfactants, cationic surfactants, surfactants such as amphoteric surfactants, water-soluble polyvalent metal salts such as aluminum sulfate, calcium sulfate, and magnesium sulfate. You may use these compounds in combination of 2 or more types. These compounds may have hydrophilicity from the viewpoint of easily obtaining an excellent initial water absorption rate.

The content of dry silica in the liquid leakage inhibitor may be 70 to 100% by mass, 80 to 100% by mass, or 90 to 100% by mass based on the total mass of the liquid leakage inhibitor.

The dry silica according to the present invention is silica produced by a dry method, and examples thereof include fumed silica. Dry silica generally has an active hydroxyl group and is therefore hydrophilic, but the surface of the silica can be surface-treated with alkylsilane or the like to impart hydrophobicity. From the viewpoint of easily obtaining an excellent initial water absorption rate, the dry silica may have hydrophilicity.

The dry silica according to the present invention has a nanometer-sized primary particle as a constituent unit, and takes the form of a secondary particle formed by aggregating a plurality of primary particles. Further, in dry silica, a plurality of secondary particles are associated to form a secondary aggregate which is an aggregate of secondary particles. For example, the shape of the agglomerates is different between dry silica and synthetic amorphous silica other than dry silica (for example, wet silica produced by a wet method). In general, wet silica aggregates are said to have a substantially spherical aggregate structure, whereas dry silica aggregates have a chain-like aggregate structure.

The specific surface area of the dry silica according to the present invention is, for example, 50 m ² / g or more, 75 m ² / g or more, 100 m ² / g or more, 125 m ² / g or more, 150 m ² / g or more, 170 m ² / g or more, or It may be 200 m ² / g or more, 1000 m ² / g or less, 800 m ² / g or less, 600 m ² / g or less, 400 m ² / g or less, or 350 m ² / g or less. The specific surface area of the dry silica may be, for example, 50 to 1000 m ² / g, 75 to 600 m ² / g, or 100 to 400 m ² / g. The specific surface area of dry silica can be measured by the _{BET specific surface area (N 2) method.}

The bulk density of the dry silica according to the present invention may be, for example, 10 to 200 g / L. From the viewpoint that excellent water absorption characteristics can be easily obtained, the bulk density of the dry silica may be 10 g / L or more, 20 g / L or more, 30 g / L or more, or 40 g / L or more, and 200 g / L or less, 180 g / L or more. Hereinafter, it may be 150 g / L or less, 130 g / L or less, 100 g / L or less, 90 g / L or less, or 80 g / L or less. The bulk density of silica can be measured by using a pigment test method (JIS-K5101-12-1) or a powder property evaluation device described later.

The average particle size (primary average particle size) of the primary particles of the dry silica according to the present invention is 5 nm or more, 7 nm or more, 10 nm or more, or 12 nm or more from the viewpoint of handleability and adhesion to the surface of the water-absorbent resin particles. It may be 500 nm or less, 100 nm or less, 50 nm or less, 30 nm or less, or 20 nm or less. More specifically, the primary average particle size of the dry silica may be 5 nm or more and 500 nm or less, and may be 7 nm or more and 50 nm or less. The average primary particle size of silica can be measured by observation with a transmission electron microscope.

The average particle size of the secondary agglomerated particles of the dry silica according to the present invention may be 1.0 μm or more, 10 μm or more, or 20 μm or more, and 100 μm or less, 70 μm, from the viewpoint of easy handling and excellent water absorption characteristics. It may be less than or equal to 50 μm or less. From the same viewpoint, more specifically, the average particle size of the secondary agglomerated particles of the dry silica may be 1.0 μm or more and 100 μm or less, and 10 μm or more and 70 μm or less. The average particle size of the secondary agglomerated particles of silica can be measured by a dynamic light scattering method, a laser diffraction / scattering method, or a Coulter counter method.

The water content of the dry silica according to the present invention may be, for example, 10% by mass or less, 5.0% by mass or less, 3.0% by mass or less, or 2.0% by mass or less. The lower limit of the water content of the dry silica may be, for example, 0.01% by mass or more, 0.05% by mass or more, or 0.1% by mass or more. The dry silica may be fumed silica having a water content of 5% by mass or less. The water content of the dry silica can be measured by the general test method ISO787-2 for pigments and extender pigments. The water content of the dry silica in the present specification is a water content based on the total mass of the dry silica and the water in the dry silica.

Examples of dry silica (hydrophilic dry silica) include "Aerosil 200", "Aerosil 300", "Aerosil 380" manufactured by Nippon Aerosil Co., Ltd., and "CAB-O-SIL M-5" manufactured by Cabot Japan Co., Ltd. "CAB-O-SIL H-300", "CAB-O-SIL M-5", "CAB-O-SIL M3KD", OCI Company, Ltd. "KONASIL K-200", "KONASIL K-150", The one sold as "Leolosil QS-102" manufactured by Tokuyama Corporation can be used. These may be used alone or in combination of two or more.

<Water-absorbent resin particles>
The water-absorbent resin particles according to the present embodiment may contain polymer particles and the above-mentioned liquid leakage inhibitor arranged on the surface of the polymer particles. For example, by mixing the polymer particles and the liquid leakage inhibitor, the liquid leakage inhibitor can be arranged on the surface of the polymer particles.

The content of the liquid leakage inhibitor is 0.2 parts by mass or more, 0.35 parts by mass or more, 0.5 parts by mass or more, 1.0 parts by mass or more, or more than 100 parts by mass of the polymer particles. It may be 1.5 parts by mass or more, 5.0 parts by mass or less, 3.5 parts by mass or less, or 2.5 parts by mass or less. The content of the dry silica may be within the range described in the content of the liquid leakage inhibitor. When the content of the liquid leakage inhibitor and / or the content of the dry silica is within the above range, the liquid leakage suppression effect becomes even more excellent.

When the following water absorption rate index coefficients I and II were obtained from the 10-second value and 3-minute value of the non-pressurized DW of the water-absorbent resin particles according to one embodiment,
Water absorption rate index I = (10-second value of non-pressurized DW) x 6 [mL / g]
Water absorption rate index II = (3 minutes value of non-pressurized DW) / 3 [mL / g]
The following formula:
α = (I + II) / 2
The static suction index α calculated in 1 may be 5.0 mL / g or more.

The non-pressurized DW is the amount of the water-absorbent resin particles that have absorbed the physiological saline solution within a predetermined time after the contact with the physiological saline solution (saline solution having a concentration of 0.9% by mass) under no pressurization. It is the water absorption rate represented by. The non-pressurized DW is represented by the absorption amount (mL) per 1 g of the water-absorbent resin particles before the absorption of the physiological saline. The 10-second value and the 3-minute value of the non-pressurized DW mean the amount of absorption 10 seconds and 3 minutes after the water-absorbent resin particles come into contact with the physiological saline solution, respectively. The water absorption rate indexes I and II correspond to the values obtained by converting the 10-second value and the 3-minute value of the non-pressurized DW into the water absorption rate per minute. The static suction index α corresponds to the average value of the water absorption rate indexes I and II, and a large static suction index α means that a relatively large water absorption rate is maintained for 10 seconds to 3 minutes. To do. According to the findings of the present inventor, when the static suction index α of the water-absorbent resin particles is 5.0 mL / g or more, liquid leakage is suppressed more effectively.

When the static suction index α is large, liquid leakage due to water-absorbent resin particles tends to be suppressed more effectively. Static suction index α is 6.0 mL / g or more, 7.0 mL / g or more, 9.0 mL / g or more, 10 mL / g or more, 11 mL / g or more, 12 mL / g or more, 13 mL / g or more, 14 mL / g It may be more than or equal to 15 mL / g or more. The upper limit of the static suction index α is usually 25 mL / g or less, or 20 mL / g or less.

The water absorption rate index I may be 2 mL / g or more, 4 mL / g or more, 6 mL / g or more, or 8 mL / g or more, and may be 30 mL / g or less, or 25 mL / g or less. The water absorption rate index II may be 8 mL / g or more, 12 mL / g or more, 16 mL / g or more, 30 mL / g or less, or 25 mL / g or less. When the water absorption rate indexes I and II are within these numerical ranges, the static suction index α tends to be 5.0 mL / g.

For the water-absorbent resin particles showing a static suction index α of 5.0 mL / g or more, for example, the liquid leakage inhibitor is arranged on the polymer particles, the amount thereof is adjusted, and the surface area of the polymer particles is increased. , The crosslink density in the surface layer of the polymer particles can be adjusted, or a combination thereof can be obtained.

The water-retaining amount of the physiological saline of the water-absorbent resin particles according to the present embodiment is, for example, 20 g / g or more, 25 g / g or more, 30 g / g or more, 32 g / g or more, 34 g / g or more, 36 g / g or more. It may be 38 g / g or more, 39 g / g or more, 60 g / g or less, 55 g / g or less, 50 g / g or less, 45 g / g or less, or 42 g / g or less. The water-retaining amount of the physiological saline of the water-absorbent resin particles according to the present embodiment may be 20 to 60 g / g, 25 to 60 g / g, 30 to 55 g / g, or 32 to 55 g / g. The amount of physiological saline retained is measured by the method described in Examples described later.

Examples of the shape of the water-absorbent resin particles according to the present embodiment include a substantially spherical shape, a crushed shape, a granular shape, and a shape formed by aggregating primary particles having these shapes.

The polymer particles may be water-absorbent particles containing a polymer containing an ethylenically unsaturated monomer as a monomer unit. The ethylenically unsaturated monomer may be a water-soluble monomer, and examples thereof include (meth) acrylic acid and salts thereof, 2- (meth) acrylamide-2-methylpropanesulfonic acid and its salts. Salt, (meth) acrylamide, N, N-dimethyl (meth) acrylamide, 2-hydroxyethyl (meth) acrylate, N-methylol (meth) acrylamide, polyethylene glycol mono (meth) acrylate, N, N-diethylaminoethyl (meth) ) Acrylate, N, N-diethylaminopropyl (meth) acrylate, and diethylaminopropyl (meth) acrylamide. The ethylenically unsaturated monomer may be used alone or in combination of two or more. The proportion of the polymer containing the ethylenically unsaturated monomer as a monomer unit in the polymer particles is 50 to 100% by mass, 60 to 100% by mass, and 70 to 100% by mass based on the mass of the polymer particles. , Or 80 to 100% by mass. The polymer particles may be particles containing a (meth) acrylic acid-based polymer containing at least one of (meth) acrylic acid or (meth) acrylate as a monomer unit. The total ratio of the monomer units derived from (meth) acrylic acid or (meth) acrylate in the (meth) acrylic acid-based polymer may be 90 to 100% by mass based on the mass of the polymer. Good.

Of the polymer particles, at least the polymer in the surface layer portion may be crosslinked by the reaction with the surface cross-linking agent. The surface cross-linking agent may be, for example, a compound having two or more functional groups (reactive functional groups) having reactivity with a functional group derived from an ethylenically unsaturated monomer. Examples of the surface cross-linking agent include alkylene carbonate compounds such as ethylene carbonate and propylene carbonate; ethylene glycol, propylene glycol, 1,4-butanediol, trimethylolpropane, glycerin, polyoxyethylene glycol, polyoxypropylene glycol, and polyglycerin. Polysaccharides such as (poly) ethylene glycol diglycidyl ether, (poly) glycerin diglycidyl ether, (poly) glycerin triglycidyl ether, (poly) propylene glycol polyglycidyl ether, (poly) glycerol polyglycidyl ether and the like. Compounds; Haloepoxy compounds such as epichlorohydrin, epibromhydrin, α-methylepicrolhydrin; compounds having two or more reactive functional groups such as isocyanate compounds such as 2,4-tolylene diisocyanate and hexamethylene diisocyanate; 3-methyl- 3-Oxetane methanol, 3-ethyl-3-oxetane methanol, 3-butyl-3-oxetane methanol, 3-methyl-3-oxetane ethanol, 3-ethyl-3-oxetane ethanol, 3-butyl-3-oxetane ethanol, etc. Oxetane compounds; oxazoline compounds such as 1,2-ethylenebisoxazoline; hydroxyalkylamide compounds such as bis [N, N-di (β-hydroxyethyl)] adipamide and the like. The surface cross-linking agent may contain a polyglycidyl compound. The ratio of the polyglycidyl compound in the surface cross-linking agent is 50 to 100% by mass, 60 to 100% by mass, 70 to 100% by mass, 80 to 100% by mass, or 90 to 100% by mass based on the total mass of the surface cross-linking agent. It may be.

Even inside the polymer particles, the polymer may be internally crosslinked by self-crosslinking, cross-linking by reaction with an internal cross-linking agent, or both. From the viewpoint of ease of control of water absorption characteristics, at least a reaction by an internal cross-linking agent may be included.

The internal cross-linking agent is, for example, a compound having two or more polymerizable unsaturated groups, a compound having two or more reactive functional groups having reactivity with a functional group of an ethylenically unsaturated monomer, or a compound thereof. It can contain one or more compounds, including combinations.

As an example of a compound having two or more polymerizable unsaturated groups, (poly) ethylene glycol (in this specification, for example, "polyethylene glycol" and "ethylene glycol" are collectively referred to as "(poly) ethylene glycol". Di or tri (meth) acrylic acid esters of polyols such as (poly) propylene glycol, trimethylolpropane, glycerin polyoxyethylene glycol, polyoxypropylene glycol, and (poly) glycerin; Unsaturated polyesters obtained by reacting with unsaturated acids such as maleic acid and fumaric acid; bisacrylamides such as N, N'-methylenebis (meth) acrylamide; by reacting polyepoxide with (meth) acrylic acid. Di or tri (meth) acrylic acid esters obtained; di (meth) acrylic acid carbamil esters obtained by reacting polyisocyanates such as tolylene diisocyanate and hexamethylene diisocyanate with hydroxyethyl (meth) acrylic acid; Alylated starch; allylated cellulose; diallyl phthalate; N, N', N''-triallyl isocyanurate; divinylbenzene.

Examples of compounds having two or more reactive functional groups include glycidyl group-containing compounds such as (poly) ethylene glycol diglycidyl ether, (poly) propylene glycol diglycidyl ether, and (poly) glycerin diglycidyl ether; (poly). ) Ethylene glycol, (poly) propylene glycol, (poly) glycerin, pentaerythritol, ethylenediamine, polyethyleneimine, glycidyl (meth) acrylate.

The polymer particles may be crosslinked after polymerization. For example, by adding a cross-linking agent to the polymer and heating it, cross-linking can be performed after the polymerization. By performing cross-linking after polymerization, the degree of cross-linking of the polymer can be increased, whereby the water-absorbing characteristics of the water-absorbent resin particles can be further improved.

Examples of the cross-linking agent for performing post-polymerization cross-linking include polyols such as ethylene glycol, propylene glycol, 1,4-butanediol, trimethylolpropane, glycerin, polyoxyethylene glycol, polyoxypropylene glycol, and polyglycerin; Compounds having two or more epoxy groups such as (poly) ethylene glycol diglycidyl ether, (poly) propylene glycol diglycidyl ether, and (poly) glycerin diglycidyl ether; Haloepoxide compounds; compounds having two or more isocyanate groups such as 2,4-tolylene diisocyanate and hexamethylene diisocyanate; oxazoline compounds such as 1,2-ethylenebisoxazoline; carbonate compounds such as ethylene carbonate and propylene carbonate; Examples thereof include hydroxyalkylamide compounds such as bis [N, N-di (β-hydroxyethyl)] adipamide. Cross-linking agents for post-polymerization cross-linking are (poly) ethylene glycol diglycidyl ether, (poly) glycerin diglycidyl ether, (poly) glycerin triglycidyl ether, (poly) propylene glycol polyglycidyl ether, and polyglycerol polyglycidyl ether. It may be a polyglycidyl compound such as. These cross-linking agents may be used alone or in combination of two or more. The post-polymerization cross-linking agent may contain a polyglycidyl compound. The ratio of the polyglycidyl compound in the post-polymerization cross-linking agent is 50 to 100% by mass, 60 to 100% by mass, 70 to 100% by mass, 80 to 100% by mass, or 90 to 100% based on the total mass of the post-polymerization cross-linking agent. It may be% by mass.

The time for adding the cross-linking after the polymerization may be after the polymerization of the ethylenically unsaturated monomer used for the polymerization, and in the case of the multi-stage polymerization, it may be added after the multi-stage polymerization. In consideration of heat generation during and after polymerization, retention due to process delay, opening of the system when a cross-linking agent is added, and fluctuation of water content due to addition of water due to addition of a cross-linking agent, a cross-linking agent for post-polymerization cross-linking. May be added in the region of [water content immediately after polymerization ± 3%] from the viewpoint of water content (water content based on the mass of the water-containing gel-like polymer).

The medium particle size of the polymer particles may be 130 to 800 μm, 200 to 850 μm, 250 to 700 μm, 300 to 600 μm, or 300 to 450 μm. The polymer particles may have a desired particle size distribution at the time of being obtained by the production method described later, but the particle size distribution may be adjusted by performing an operation such as particle size adjustment using classification with a sieve. ..

The polymer particles may contain a certain amount of water in addition to the polymer of the ethylenically unsaturated monomer, and may further contain various additional components therein. Examples of additional ingredients include gel stabilizers, metal chelating agents, antibacterial agents and the like.

(Method of manufacturing water-absorbent resin particles)
The water-absorbent resin particles according to the above-exemplified embodiments can be produced, for example, by a method including a step of arranging the liquid leakage inhibitor on the surface of the polymer particles.

The polymer particles can be obtained, for example, by a method including a step of polymerizing a monomer containing an ethylenically unsaturated monomer. The polymerization method of the monomer can be selected from, for example, a reverse phase suspension polymerization method, an aqueous solution polymerization method, a bulk polymerization method, and a precipitation polymerization method. By polymerizing the ethylenically unsaturated monomer in the presence of an internal cross-linking agent, polymer particles internally cross-linked by the cross-linking agent may be obtained. Polymer particles containing inorganic particles may be obtained by polymerizing an ethylenically unsaturated monomer in the presence of inorganic particles such as silica. A part or all of the ethylene-based unsaturated monomer may form a salt such as an alkali metal salt.

In the case of the aqueous solution polymerization method, for example, the ethylenically unsaturated monomer is polymerized in a monomer aqueous solution containing an ethylenically unsaturated monomer and water to form a hydrogel polymer containing the polymer. The polymer particles can be obtained by a method including the above and drying of the hydrogel polymer. When a lumpy hydrogel polymer is formed, it may be coarsely crushed and the crude product of the hydrogel polymer may be dried. The hydrogel polymer or a crude product thereof may be dried and then pulverized, or the particles obtained by pulverization may be classified. The polymer particles used for surface cross-linking, which will be described later, may be a dried coarsely crushed product or particles obtained by further pulverizing the coarsely crushed product. The polymer particles obtained by pulverizing the coarsely crushed product may be classified, the particle size of the polymer particles may be adjusted as necessary, and then subjected to surface cross-linking.

The concentration of the ethylenically unsaturated monomer in the aqueous monomer solution may be 20% by mass or more and less than the saturated concentration, 25 to 70% by mass, or 30 to 50% by mass based on the mass of the aqueous monomer solution. Good.

The monomer aqueous solution may further contain a polymerization initiator. The polymerization initiator may be a photopolymerization initiator or a thermal radical polymerization initiator, or may be a water-soluble thermal radical polymerization initiator. The thermally radically polymerizable compound may be an azo compound, a peroxide, or a combination thereof. The amount of the polymerization initiator may be 0.00005 to 0.01 mol per 1 mol of the ethylenically unsaturated monomer.

The monomer aqueous solution may further contain the above-mentioned internal cross-linking agent. The amount of the internal cross-linking agent is 0 mmol or more, 0.001 mmol or more, 0.01 mmol or more, 0.015 mmol or more, or 0.020 mmol or more with respect to 1 mol of the ethylenically unsaturated monomer. It may be 2 mmol or less, 1 mmol or less, 0.5 mmol or less, or 0.1 mmol or less. If necessary, the aqueous monomer solution may further contain other additives such as a chain transfer agent and a thickener.

The polymerization temperature varies depending on the polymerization initiator used, but may be, for example, 0 to 130 ° C. or 10 to 110 ° C. The polymerization time may be 1 to 200 minutes or 5 to 100 minutes.

The water content of the hydrogel polymer formed by polymerization (water content based on the mass of the hydrogel polymer) is 30 to 80% by mass, 40 to 75% by mass, or 50 to 70% by mass. May be.

When a lumpy hydrogel polymer is coarsely crushed, the coarsely crushed product obtained by the coarse crushing may be in the form of particles or may have an elongated shape such that particles are connected. The minimum width of the pyroclastic material may be, for example, about 0.1 to 15 mm or 1.0 to 10 mm. The maximum width of the pyroclastic material may be about 0.1 to 200 mm or 1.0 to 150 mm. Examples of devices for crushing include kneaders (eg, pressurized kneaders, double-armed kneaders, etc.), meat choppers, cutter mills, and pharmacomills. If necessary, the lumpy hydrogel polymer may be cut before coarse crushing.

The hydrogel polymer or its crude product is dried mainly to remove water. The drying method may be a general method such as natural drying, heat drying, and vacuum drying. By further pulverizing the dried hydrogel polymer or a crude product thereof and classifying the obtained particles as necessary, polymer particles having an appropriate particle size can be obtained. The crushing method is not particularly limited, and for example, a roller mill (roll mill), a stamp mill, a jet mill, a high-speed rotary crusher (hammer mill, pin mill, rotor beater mill, etc.), or a container-driven mill (rotary mill, vibration mill, etc.). , Planet mill, etc.) can be applied. The classification method is also not particularly limited, and for example, a method using a vibrating sieve, a rotary shifter, a cylindrical stirring sieve, a blower shifter, or a low-tap type shaker can be applied.

In the case of the reverse phase suspension polymerization method, for example, an interface between a hydrocarbon dispersion medium and a monomer aqueous solution containing an ethylenically unsaturated monomer, a radical polymerization initiator, water, etc. dispersed in the hydrocarbon dispersion medium. In a suspension containing an activator, an ethylenically unsaturated monomer is polymerized to form a particulate hydrogel polymer containing the polymer, and hydrocarbon dispersion from the suspension. Polymer particles can be obtained by methods involving removing the medium and water.

The hydrocarbon dispersion medium may contain at least one compound selected from the group consisting of chain aliphatic hydrocarbons having 6 to 8 carbon atoms and alicyclic hydrocarbons having 6 to 8 carbon atoms. Hydrocarbon dispersion media include chain aliphatic hydrocarbons such as n-hexane, n-heptane, 2-methylhexane, 3-methylhexane, 2,3-dimethylpentane, 3-ethylpentane, and n-octane; cyclohexane. , Methylcyclohexane, cyclopentane, methylcyclopentane, trans-1,2-dimethylcyclopentane, cis-1,3-dimethylcyclopentane, trans-1,3-dimethylcyclopentane and other alicyclic hydrocarbons; benzene, Examples include aromatic hydrocarbons such as toluene and xylene. The hydrocarbon dispersion medium may be used alone or in combination of two or more. The amount of the hydrocarbon dispersion medium may be 30 to 1000 parts by mass, 40 to 500 parts by mass, or 50 to 300 parts by mass with respect to 100 parts by mass of the aqueous monomer solution containing the monomer.

Examples of thermal radical polymerization initiators include persulfates, peroxides, and azo compounds. The amount of the radical polymerization initiator may be 0.00005 to 0.01 mol per 1 mol of the ethylenically unsaturated monomer.

The suspension for reverse phase suspension polymerization may further contain the above-mentioned internal cross-linking agent. The internal cross-linking agent is usually added to a monomer aqueous solution containing an ethylene-based unsaturated monomer. The amount of the internal cross-linking agent is 0 mmol or more, 0.001 mmol or more, 0.01 mmol or more, 0.015 mmol or more, or 0.020 mmol or more with respect to 1 mol of the ethylenically unsaturated monomer. It may be 2 mmol or less, 1 mmol or less, 0.5 mmol or less, or 0.1 mmol or less.

Suspensions for reverse phase suspension polymerization usually further contain a surfactant. The surfactant may be a nonionic surfactant, an anionic surfactant or the like. Examples of nonionic surfactants include sorbitan fatty acid ester and (poly) glycerin fatty acid ester (“(poly)” means both with and without the prefix “poly”. The same applies hereinafter.), Sucrose fatty acid ester, polyoxyethylene sorbitan fatty acid ester, polyoxyethylene glycerin fatty acid ester, sorbitol fatty acid ester, polyoxyethylene sorbitol fatty acid ester, polyoxyethylene alkyl ether, polyoxyethylene alkyl phenyl ether, polyoxy. Examples thereof include ethylene castor oil, polyoxyethylene cured castor oil, alkylallyl formaldehyde condensed polyoxyethylene ether, polyoxyethylene polyoxypropylene block copolymer, polyoxyethylene polyoxypropyl alkyl ether, polyethylene glycol fatty acid ester and the like. Examples of anionic surfactants include fatty acid salts, alkylbenzene sulfonates, alkylmethyl taur phosphates, polyoxyethylene alkylphenyl ether sulfates, polyoxyethylene alkyl ether sulfonates, and phosphorus in polyoxyethylene alkyl ethers. Examples thereof include acid esters and phosphoric acid esters of polyoxyethylene alkyl allyl ethers. The surfactant may be used alone or in combination of two or more. The amount of the surfactant may be 0.05 to 10 parts by mass, 0.08 to 5 parts by mass, or 0.1 to 3 parts by mass with respect to 100 parts by mass of the aqueous monomer solution.

The suspension for reverse phase suspension polymerization may further contain a polymer-based dispersant. Examples of polymer dispersants include maleic anhydride-modified polyethylene, maleic anhydride-modified polypropylene, maleic anhydride-modified ethylene / propylene copolymer, maleic anhydride-modified EPDM (ethylene / propylene / diene / terpolymer), and anhydrous. Maleic acid-modified polybutadiene, maleic anhydride / ethylene copolymer, maleic anhydride / propylene copolymer, maleic anhydride / ethylene / propylene copolymer, maleic anhydride / butadiene copolymer, polyethylene, polypropylene, ethylene / propylene Examples thereof include copolymers, oxidized polyethylene, oxidized polypropylene, oxidized ethylene / propylene copolymers, ethylene / acrylic acid copolymers, ethyl cellulose, ethyl hydroxyethyl cellulose and the like. The polymer-based dispersant may be used alone or in combination of two or more. The amount of the polymer-based dispersant may be 0.05 to 10 parts by mass, 0.08 to 5 parts by mass, or 0.1 to 3 parts by mass with respect to 100 parts by mass of the aqueous monomer solution.

The suspension for reverse phase suspension polymerization may contain other components such as a chain transfer agent and a thickener, if necessary. The temperature of the polymerization reaction varies depending on the radical polymerization initiator used, but may be, for example, 20 to 150 ° C. or 40 to 120 ° C. The reaction time is usually 0.5-4 hours. The reverse phase suspension polymerization may be carried out in a plurality of times.

After the polymerization, the polymer particles can be obtained by removing the hydrocarbon dispersion medium and water from the suspension containing the hydrogel polymer and the hydrocarbon dispersion medium. For example, azeotropic distillation, decantation, filtration, vacuum drying, or a combination thereof can remove the hydrocarbon dispersion medium and water. Water, hydrocarbon dispersion medium, or both may remain in the polymer particles to some extent.

The method for producing water-absorbent resin particles further includes a step of surface-crosslinking the polymer particles by heating a reaction mixture containing the polymer particles and an aqueous solution of a surface-crosslinking agent containing water and a surface-crosslinking agent. Good.

The surface cross-linking agent aqueous solution contains water and a surface cross-linking agent dissolved in water. The aqueous surface cross-linking agent solution may further contain a hydrophilic organic solvent. The organic solvent may be, for example, an alcohol such as 2-propanol, ethanol or methanol. The ratio of water to the total amount of water and the organic solvent is 100% by mass or less, and may be 50% by mass or more, 60% by mass or more, 70% by mass or more, 80% by mass or more, or 90% by mass or more. ..

The polymer particles can be surface-crosslinked by mixing the polymer particles and the aqueous surface cross-linking agent solution and heating the reaction mixture formed with stirring, if necessary. The heating temperature for surface cross-linking may be appropriately adjusted so that the surface cross-linking proceeds, for example, 70 to 300 ° C., 100 to 270 ° C., 120 to 250 ° C., 150 to 220 ° C., or 170 to 200 ° C. You may. The reaction time for surface cross-linking may be, for example, 1 to 200 minutes, 10 to 100 minutes, 20 to 80 minutes, 30 to 70 minutes, 40 to 60 minutes, or 5 to 100 minutes. The surface cross-linking step may be carried out twice or more.

Water and hydrocarbon dispersion medium are removed from the polymer particles after surface cross-linking, if necessary. The polymer particles after surface cross-linking may be further treated by drying, grinding, classification or a combination thereof.

The method for producing the water-absorbent resin particles may include a step of arranging the liquid leakage inhibitor after surface cross-linking.

<Absorbent>
The absorber according to one embodiment contains the water-absorbent resin particles according to this embodiment. The absorber according to the present embodiment can contain a fibrous substance, for example, a mixture containing water-absorbent resin particles and the fibrous substance. The structure of the absorber may be, for example, a structure in which the water-absorbent resin particles and the fibrous material are uniformly mixed, and the water-absorbent resin particles are sandwiched between the fibrous material formed in a sheet or layer. It may be a configuration or another configuration.

Examples of the fibrous material include finely pulverized wood pulp; cotton; cotton linter; rayon; cellulosic fibers such as cellulose acetate; synthetic fibers such as polyamide, polyester and polyolefin; and a mixture of these fibers. The fibrous material may be used alone or in combination of two or more. As the fibrous material, hydrophilic fibers can be used.

The mass ratio of the water-absorbent resin particles in the absorber is 40% by mass or more, 45% by mass or more, 50% by mass or more, 55% by mass or more, and 60% by mass or more with respect to the total of the water-absorbent resin particles and the fibrous material. , 65% by mass or more, or 70% by mass. The mass ratio of the water-absorbent resin particles in the absorber is 100% by mass or less, 95% by mass or less, 90% by mass or less, 85% by mass or less, or 80 with respect to the total of the water-absorbent resin particles and the fibrous material. It may be% by mass. The mass ratio of the water-absorbent resin particles in the absorber may be 40 to 100% by mass, 50 to 95% by mass, or 60 to 90% by mass with respect to the total of the water-absorbent resin particles and the fibrous material.

In order to improve the morphological retention before and during use of the absorber, the fibers may be adhered to each other by adding an adhesive binder to the fibrous material. Examples of the adhesive binder include heat-sealing synthetic fibers, hot melt adhesives, and adhesive emulsions. The adhesive binder may be used alone or in combination of two or more.

Examples of the heat-bondable synthetic fiber include a total fusion type binder such as polyethylene, polypropylene, and an ethylene-propylene copolymer; a side-by-side of polypropylene and polyethylene, and a non-total fusion type binder having a core-sheath structure. In the above-mentioned non-total fusion type binder, only the polyethylene portion can be heat-sealed.

Examples of the hot melt adhesive include ethylene-vinyl acetate copolymer, styrene-isoprene-styrene block copolymer, styrene-butadiene-styrene block copolymer, styrene-ethylene-butylene-styrene block copolymer, and styrene-ethylene-propylene-styrene block copolymer. , A mixture of a base polymer such as amorphous polypropylene and a tackifier, a plasticizer, an antioxidant and the like.

Examples of the adhesive emulsion include polymers of at least one monomer selected from the group consisting of methyl methacrylate, styrene, acrylonitrile, 2-ethylhexyl acrylate, butyl acrylate, butadiene, ethylene, and vinyl acetate.

The absorber according to the present embodiment may contain a deodorant, an antibacterial agent, a fragrance and the like.

The shape of the absorber according to the present embodiment is not particularly limited, and may be, for example, a sheet shape. The thickness of the absorber (for example, the thickness of the sheet-shaped absorber) may be, for example, 0.1 to 20 mm and 0.3 to 15 mm.

<Absorbable article>
The absorbent article according to the present embodiment includes an absorber according to the present embodiment. The absorbent article according to the present embodiment is a core wrap that retains the shape of the absorber; a liquid permeable sheet that is arranged on the outermost side of the side where the liquid to be absorbed enters; Examples thereof include a liquid permeable sheet arranged on the outermost side on the opposite side. Examples of absorbent articles include diapers (for example, paper diapers), toilet training pants, incontinence pads, sanitary materials (sanitary napkins, tampons, etc.), sweat pads, pet sheets, toilet members, animal excrement treatment materials, and the like. ..

FIG. 1 is a cross-sectional view showing an example of an absorbent article. The absorbent article 100 shown in FIG. 1 includes an absorbent body 10, core wraps 20a and 20b, a liquid permeable sheet 30, and a liquid permeable sheet 40. In the absorbent article 100, the liquid permeable sheet 40, the core wrap 20b, the absorbent body 10, the core wrap 20a, and the liquid permeable sheet 30 are laminated in this order. In FIG. 1, there is a portion shown so that there is a gap between the members, but the members may be in close contact with each other without the gap.

The absorber 10 has a water-absorbent resin particle 10a according to the present embodiment and a fiber layer 10b containing a fibrous material. The water-absorbent resin particles 10a are dispersed in the fiber layer 10b.

The core wrap 20a is arranged on one side of the absorber 10 (upper side of the absorber 10 in FIG. 1) in contact with the absorber 10. The core wrap 20b is arranged on the other side of the absorber 10 (lower side of the absorber 10 in FIG. 1) in contact with the absorber 10. The absorber 10 is arranged between the core wrap 20a and the core wrap 20b. Examples of the core wraps 20a and 20b include tissues, non-woven fabrics and the like. The core wrap 20a and the core wrap 20b have, for example, a main surface having the same size as the absorber 10.

The liquid permeable sheet 30 is arranged on the outermost side on the side where the liquid to be absorbed enters. The liquid permeable sheet 30 is arranged on the core wrap 20a in contact with the core wrap 20a. Examples of the liquid permeable sheet 30 include non-woven fabrics made of synthetic resins such as polyethylene, polypropylene, polyester and polyamide, and porous sheets. The liquid permeable sheet 40 is arranged on the outermost side of the absorbent article 100 on the opposite side of the liquid permeable sheet 30. The liquid impermeable sheet 40 is arranged under the core wrap 20b in contact with the core wrap 20b. Examples of the liquid impermeable sheet 40 include a sheet made of a synthetic resin such as polyethylene, polypropylene, and polyvinyl chloride, and a sheet made of a composite material of these synthetic resins and a non-woven fabric. The liquid permeable sheet 30 and the liquid permeable sheet 40 have, for example, a main surface wider than the main surface of the absorber 10, and the outer edges of the liquid permeable sheet 30 and the liquid permeable sheet 40 are It extends around the absorber 10 and the core wraps 20a, 20b.

The magnitude relationship between the absorbent body 10, the core wraps 20a and 20b, the liquid permeable sheet 30, and the liquid permeable sheet 40 is not particularly limited, and is appropriately adjusted according to the use of the absorbent article and the like. Further, the method of retaining the shape of the absorber 10 using the core wraps 20a and 20b is not particularly limited, and as shown in FIG. 1, the absorber may be wrapped by a plurality of core wraps, and the absorber is wrapped by one core wrap. But it may be.

According to the present embodiment, it is possible to provide a liquid absorbing method using an absorber or an absorbent article according to the present embodiment. The liquid absorbing method according to the present embodiment includes a step of bringing the liquid to be absorbed into contact with the absorber or the absorbent article according to the present embodiment.

<Method of suppressing liquid leakage from absorber and use of dry silica (application)>
According to this embodiment, it is possible to suppress liquid leakage of the absorber containing the water-absorbent resin particles. The method for suppressing liquid leakage of an absorber containing water-absorbent resin particles according to the present embodiment includes a step of incorporating dry silica as a liquid leakage inhibitor into the water-absorbent resin particles. The step of containing the dry silica may be a step of containing the dry silica by mixing the polymer particles described above with the dry silica.

As an embodiment of the present invention, the use or application of dry silica for suppressing liquid leakage of an absorber containing water-absorbent resin particles is provided. As another embodiment of the present invention, the use or application of dry silica for producing a liquid leakage inhibitor used for an absorber containing water-absorbent resin particles is provided.

Hereinafter, the present invention will be described in more detail with reference to examples. However, the present invention is not limited to these examples.

<Preparation of silica as a liquid leakage inhibitor>
(Dry silica A)
The specific surface area is 200 ± 5 m ² / g, the bulk density is 33 g / L, the water content is 1.0% or less, the primary average particle size is 7 to 20 nm, and the average particle size of the secondary aggregate is 30 to 50 μm. Dry silica (Cabot Japan Co., Ltd., product name: M-5) was prepared. This was designated as dry silica A.

(Dry silica B)
The specific surface area is 300 ± 5 m ² / g, the bulk density is 40 g / L, the water content is 1.0% or less, the primary average particle size is 7 to 20 nm, and the average particle size of the secondary aggregate is 30 to 50 μm. Dry silica (Cabot Japan Co., Ltd., product name: H300) was prepared. This was designated as dry silica B.

(Dry silica C)
The specific surface area is 200 ± 5 m ² / g, the bulk density is 54 g / L, the water content is 1.0% or less, the primary average particle size is 7 to 20 nm, and the average particle size of the secondary aggregate is 30 to 50 μm. Dry silica (Cabot Japan Co., Ltd., product name: M3KD) was prepared. This was designated as dry silica C.

(Dry silica D)
Dry silica (Japan) with a specific surface area of 200 m ² / g, a bulk density of 31 g / L, a water content of 1.5% or less, a primary average particle size of 12 nm, and an average particle size of secondary aggregates of 1 to 10 μm. Aerosil Co., Ltd., product name: Aerosil 200) was prepared. This was designated as dry silica D.

(Dry silica E)
A dry silica (OCI Company, Ltd., product name: KONASIL K-200) having a specific surface area of 216 m ² / g, a bulk density of 41 g / L, a water content of 0.1%, a primary average particle size of 12 nm, and a dry silica (manufactured by OCI Company, Ltd.) was prepared. .. This was designated as dry silica E.

(Dry silica F)
A dry silica (OCI Company, Ltd., product name: KONASIL K-150) having a specific surface area of 155 m ² / g, a bulk density of 47 g / L, a water content of 0.1%, a primary average particle size of 14 nm, and a dry silica (manufactured by OCI Company, Ltd.) was prepared. .. This was designated as dry silica F.

(Dry silica G)
A dry silica (manufactured by Tokuyama Corporation, product name: Leoloseal QS-102) having a specific surface area of 200 m ² / g, a bulk density of 35 g / L, a water content of 1.5% or less, and a primary average particle diameter of 12 nm was prepared. .. This was designated as dry silica G.

(Wet silica)
Wet silica (specific surface area 190 m ² / g, bulk density 100 g / L, moisture content 6.1%, primary average particle size 10-30 nm, average particle size of secondary aggregates 9.8 μm) OSC (Oriental Silkas Corporation), product name: Toxile NPS) was prepared.

The specific surface area is a value measured by the BET specific surface area (N ₂ ) method, the water content is a value measured by the general test method ISO787-2 for pigments and extender pigments, and the primary average particles are transmitted electrons. It is a value measured by observation with a microscope, and the average particle size of the secondary aggregate is a value measured by a laser diffraction / scattering method.

The bulk density of silica as a liquid leakage inhibitor was measured by the following procedure using a powder property evaluation device (manufactured by Hosokawa Micron Co., Ltd., model number: PT-X). The bulk density was measured at room temperature (25 ° C ± 2 ° C).

First, the mass W ₀ of an empty container (cup XS-18, inner diameter 5.0 cm, height 5.0 cm, volume 100 cm ³ ) was measured. Next, about 120 mL of silica was put into the container using the scoop XS-12 attached to the device. After charging, the blade XS-13 was used to scrape off the silica protruding from the upper part of the container. Subsequently, the mass was measured W ₁ of the vessel containing the silica. Based on the mass W ₀ and the mass W ₁ , the bulk density was calculated from the following formula. The bulk density was measured three times in total, and the average value was obtained as the bulk density of silica.
Bulk density of silica [g / L] = (W ₁ [g] -W ₀ [g]) / 100 [cm ³ ] x 1000

<Preparation of polymer particles>
Manufacturing example 1
First-stage polymerization reaction A reflux cooler, a dropping funnel, a nitrogen gas introduction pipe, and a stirring blade having four inclined paddle blades with a blade diameter of 5 cm in two stages as a stirrer, with an inner diameter of 11 cm and an internal volume of 2 L. A round-bottomed cylindrical separable flask was prepared. In this flask, 293 g of n-heptane and 0.736 g of a maleic anhydride-modified ethylene-propylene copolymer (Mitsui Chemicals, Inc., High Wax 1105A) as a polymer-based dispersant were placed. The reaction solution in the flask was heated to 80 ° C. with stirring to dissolve the polymer-based dispersant in n-heptane. Then, the reaction solution was cooled to 50 ° C.

92.0 g (1.03 mol) of an acrylic acid aqueous solution having a concentration of 80.5 mass% was placed in a beaker having an internal volume of 300 mL. While cooling the beaker from the outside, 147.7 g of a sodium hydroxide aqueous solution having a concentration of 20.9 mass% was added dropwise to the acrylic acid aqueous solution, thereby neutralizing 75 mol% of acrylic acid. Next, 0.092 g of hydroxylethyl cellulose (Sumitomo Seika Co., Ltd., HECAW-15F) as a thickener and 2,2'-azobis (2-amidinopropane) dihydrochloride as a water-soluble radical polymerization initiator were added to an aqueous acrylic acid solution. The first step is to dissolve 0.092 g (0.339 mmol), 0.018 g (0.067 mmol) of potassium persulfate, and 0.010 g (0.057 mmol) of ethylene glycol diglycidyl ether as an internal cross-linking agent. A monomer aqueous solution of the above was prepared.

The first-stage monomer aqueous solution was added to the above-mentioned reaction solution in the separable flask, and the reaction solution was stirred for 10 minutes. Next, a surfactant solution containing 6.62 g of n-heptane and 0.736 g of sucrose stearic acid ester (HLB: 3, Mitsubishi Chemical Foods Co., Ltd., Ryoto Sugar Ester S-370) was added to the reaction solution, and the mixture was stirred. The inside of the system was sufficiently replaced with nitrogen while stirring the reaction solution at a blade rotation speed of 550 rpm. Then, the polymerization reaction was allowed to proceed over 60 minutes while heating the separable flask in a water bath at 70 ° C. By this polymerization reaction, a first-stage polymerization slurry liquid containing a hydrogel-like polymer was obtained.

Second-stage polymerization reaction 128.8 g (1.44 mol) of an acrylic acid aqueous solution having a concentration of 80.5% by mass was placed in a beaker having an internal volume of 500 mL. While cooling the beaker from the outside, 159.0 g of a sodium hydroxide aqueous solution having a concentration of 27% by mass was added dropwise to the acrylic acid aqueous solution, thereby neutralizing 75 mol% of acrylic acid. Next, 0.129 g (0.476 mmol) of 2,2'-azobis (2-amidinopropane) dihydrochloride and 0.026 g (0.096 mmol) of potassium persulfate were dissolved in an aqueous acrylic acid solution. A second-stage monomer aqueous solution was prepared.

The first-stage polymerized slurry liquid in the separable flask was cooled to 25 ° C. while stirring at a stirring blade rotation speed of 1000 rpm. The whole amount of the aqueous monomer solution of the second stage was added thereto, and then the inside of the system was replaced with nitrogen over 30 minutes. Then, the polymerization reaction was allowed to proceed over 60 minutes while heating the separable flask in a water bath at 70 ° C. As a cross-linking agent for post-polymerization cross-linking, 0.580 g (0.067 mmol) of a 2% by mass ethylene glycol diglycidyl ether aqueous solution was added to obtain a hydrogel polymer.

0.265 g of a diethylenetriamine-5 sodium acetate aqueous solution having a concentration of 45% by mass was added to the reaction solution containing the hydrogel polymer under stirring. Then, the flask was immersed in an oil bath set at 125 ° C., and 239.0 g of water was extracted from the system by azeotropic distillation of n-heptane and water. Then, 4.42 g (0.507 mmol) of an ethylene glycol diglycidyl ether aqueous solution having a concentration of 2% by mass was added to the reaction solution as a surface cross-linking agent, and the cross-linking reaction with the surface cross-linking agent was allowed to proceed at 83 ° C. for 2 hours. It was.

From the reaction solution after the surface cross-linking reaction, n-heptane and water were distilled off by heating at 125 ° C. to obtain a reaction product. The obtained reaction product was passed through a sieve having an opening of 850 μm to obtain 228.3 g of polymer particles. The medium particle size of the polymer particles was 364 μm. If necessary, polymerization was carried out multiple times in the same manner.

Manufacturing example 2
The water-soluble radical polymerization initiator in the first-stage polymerization reaction was changed to 0.0736 g (0.272 mmol) of potassium persulfate without using 2,2'-azobis (2-amidinopropane) dihydrochloride. , The water-soluble radical polymerization initiator in the second-stage polymerization reaction was changed to 0.090 g (0.333 mmol) of potassium persulfate without using 2,2'-azobis (2-amidinopropane) dihydrochloride. As a result, 0.0116 g (0.067 mmol) of ethylene glycol diglycidyl ether was used as the internal cross-linking agent, no cross-linking agent was added for post-polymerization cross-linking, and water content after the second stage polymerization. In the gel-like polymer, 230.6 g of polymer particles were obtained in the same manner as in Production Example 1 except that 256.1 g of water was extracted from the system by co-boiling distillation. The medium particle size of the polymer particles was 349 μm.

Manufacturing example 3
The amount of ethylene glycol diglycidyl ether as an internal cross-linking agent in the first-stage polymerization reaction was changed to 0.0046 g (0.026 mmol), and ethylene was used as an internal cross-linking agent in the preparation of the second-stage aqueous solution. 0.0116 g (0.067 mmol) of glycol diglycidyl ether was used, no cross-linking agent was added for post-polymerization cross-linking, and co-boiling was performed in the second-stage post-polymerization hydrogel polymer. Manufactured except that 219.2 g of water was extracted from the system by distillation and the amount of ethylene glycol diglycidyl ether aqueous solution having a concentration of 2% by mass as a surface cross-linking agent was changed to 6.62 g (0.760 mmol). 226.1 g of polymer particles were obtained in the same procedure as in Example 1. The medium particle size of the polymer particles was 356 μm.

Manufacturing example 4
The amount of ethylene glycol diglycidyl ether as an internal cross-linking agent in the first-stage polymerization reaction was changed to 0.0046 g (0.026 mmol), and as an internal cross-linking agent in the preparation of the second-stage aqueous solution. 0.0116 g (0.067 mmol) of ethylene glycol diglycidyl ether was used, no cross-linking agent was added for post-polymerization cross-linking, and both were used in the second-stage post-polymerization hydrogel polymer. 220.2 g of polymer particles were obtained in the same procedure as in Production Example 1 except that 234.2 g of water was extracted from the system by boiling distillation. The medium particle size of the polymer particles was 355 μm.
Production example 5
The amount of ethylene glycol diglycidyl ether as an internal cross-linking agent in the first-stage polymerization reaction was changed to 0.0368 g (0.211 mmol). In the preparation of the second-stage aqueous solution, ethylene was used as an internal cross-linking agent. The use of 0.0515 g (0.296 mmol) of glycol diglycidyl ether, no addition of a cross-linking agent for post-polymerization cross-linking, and co-boiling in the water-containing gel-like polymer after the second stage polymerization. 221.8 g of polymer particles were obtained in the same procedure as in Production Example 1 except that 286.9 g of water was extracted from the system by distillation. The medium particle size of the polymer particles was 396 μm.

Production example 6
In the hydrogel polymer after the second stage polymerization, 227.7 g of polymer particles were obtained in the same manner as in Production Example 1 except that 228.7 g of water was extracted from the system by azeotropic distillation. It was. The medium particle size of the polymer particles was 380 μm.

Production example 7
In the hydrogel polymer after the second stage polymerization, 221.7 g of polymer particles were obtained in the same manner as in Production Example 1 except that 253.3 g of water was extracted from the system by azeotropic distillation. It was. The medium particle size of the polymer particles was 356 μm.

Production Example 8
In the hydrogel polymer after the second stage polymerization, 215.5 g of polymer particles were obtained in the same manner as in Production Example 1 except that 261.5 g of water was extracted from the system by azeotropic distillation. It was. The medium particle size of the polymer particles was 377 μm.

Manufacturing example 9
The water-soluble radical polymerization initiator in the first-stage polymerization reaction was changed to 0.0736 g (0.272 mmol) of potassium persulfate without using 2,2'-azobis (2-amidinopropane) dihydrochloride. , The water-soluble radical polymerization initiator in the second-stage polymerization reaction was changed to 0.090 g (0.333 mmol) of potassium persulfate without using 2,2'-azobis (2-amidinopropane) dihydrochloride. In the same manner as in Production Example 1, 226.4 g of polymer particles was obtained in the same manner as in Production Example 1, except that 256.1 g of water was extracted from the system by radical distillation. The medium particle size of the polymer particles was 417 μm.

<Preparation of water-absorbent resin particles>
Example 1
30 g of the polymer particles obtained in Production Example 1 and 0.15 g of dry silica A (Cabot Japan Co., Ltd., M-5) were mixed to obtain water-absorbent resin particles containing dry silica.

Example 2
Water-absorbent resin particles of Example 2 were obtained in the same manner as in Example 1 except that the amount of dry silica A (Cabot Japan Co., Ltd., M-5) added was changed to 0.6 g.

Example 3
The water-absorbent resin particles of Example 3 were obtained in the same manner as in Example 1 except that the dry silica was changed to dry silica B (H300 manufactured by Cabot Japan Co., Ltd.) instead of M-5 manufactured by Cabot Japan Co., Ltd. ..

Example 4
The water-absorbent resin particles of Example 2 were obtained in the same manner as in Example 3 except that the amount of dry silica B (Cabot Japan Co., Ltd., H300) added was changed to 0.06 g.

Example 5
The water-absorbent resin particles of Example 5 were obtained in the same manner as in Example 3 except that the amount of dry silica B (Cabot Japan Co., Ltd., H300) added was changed to 0.3 g.

Example 6
The water-absorbent resin particles of Example 6 were obtained in the same manner as in Example 1 except that the dry silica was changed to dry silica C (M3KD manufactured by Cabot Japan Co., Ltd.) instead of M-5 manufactured by Cabot Japan Co., Ltd. ..

Example 7
The water-absorbent resin particles of Example 7 were obtained in the same manner as in Example 1 except that the dry silica was changed to dry silica D (Aerosil 200 manufactured by Nippon Aerosil Co., Ltd.) instead of M-5 manufactured by Cabot Japan Co., Ltd. It was.

Example 8
The water-absorbent resin particles of Example 8 were obtained in the same manner as in Example 7 except that the amount of dry silica D (Nippon Aerosil Co., Ltd., Aerosil 200) added was changed to 0.06 g.

Example 9
Water-absorbent resin particles of Example 9 were obtained in the same manner as in Example 7 except that the amount of dry silica D (Nippon Aerosil Co., Ltd., Aerosil 200) added was changed to 0.3 g.

Example 10
30 g of the polymer particles obtained in Production Example 6 and 0.24 g of dry silica A (Cabot Japan Co., Ltd., M-5) were mixed to obtain water-absorbent resin particles of Example 10.

Example 11
The water-absorbent resin particles of Example 11 were obtained in the same manner as in Example 10 except that the polymer particles obtained in Production Example 6 were replaced with the polymer particles obtained in Production Example 7.

Example 12
The water-absorbent resin particles of Example 12 were obtained in the same manner as in Example 10 except that the polymer particles obtained in Production Example 6 were replaced with the polymer particles obtained in Production Example 8.

Example 13
Example 13 in the same manner as in Example 1 except that the dry silica A (M-5 manufactured by Cabot Japan Co., Ltd.) was replaced with the dry silica E (OCI Company, Ltd, KONASIL K-200) as the dry silica. Water-absorbent resin particles were obtained.

Example 14
The water-absorbent resin particles of Example 14 were obtained in the same manner as in Example 13 except that the polymer particles obtained in Production Example 1 were replaced with the polymer particles obtained in Production Example 8.

Example 15
Example 15 in the same manner as in Example 1 except that the dry silica A (M-5 manufactured by Cabot Japan Co., Ltd.) was replaced with the dry silica F (OCI Company, Ltd, KONASIL K-150) as the dry silica. Water-absorbent resin particles were obtained.

Example 16
The water-absorbent resin particles of Example 16 were obtained in the same manner as in Example 15 except that the polymer particles obtained in Production Example 1 were replaced with the polymer particles obtained in Production Example 8.

Example 17
Example 17 in the same manner as in Example 1 except that the dry silica A (M-5 manufactured by Cabot Japan Co., Ltd.) was replaced with the dry silica G (Reoloseal QS-102 manufactured by Tokuyama Corporation) as the dry silica. Water-absorbent resin particles were obtained.

Example 18
The water-absorbent resin particles of Example 18 were obtained in the same manner as in Example 1 except that the polymer particles obtained in Production Example 1 were replaced with the polymer particles obtained in Production Example 9.

Comparative Example 1
30 g of the polymer particles obtained in Production Example 2 and 0.03 g of wet silica (OSC, Toxil NP-S) were mixed to obtain water-absorbent resin particles containing wet silica.

Comparative Example 2
30 g of the polymer particles obtained in Production Example 3 and 0.06 g of wet silica (OSC, Toxil NP-S) were mixed to obtain water-absorbent resin particles containing wet silica.

Comparative Example 3
30 g of the polymer particles obtained in Production Example 4 and 0.06 g of wet silica (OSC, Toxil NP-S) were mixed to obtain water-absorbent resin particles containing wet silica.

Comparative Example 4
30 g of the polymer particles obtained in Production Example 5 and 0.06 g of wet silica (OSC, Toxil NP-S) were mixed to obtain water-absorbent resin particles containing wet silica.

Comparative Example 5
30 g of the polymer particles obtained in Production Example 1 and 0.06 g of wet silica (OSC, Toxile NP-S) were mixed with the polymer particles to obtain water-absorbent resin particles containing the wet silica.

Comparative Example 6
The polymer particles obtained in Production Example 1 without adding dry silica A (Cabot Japan Co., Ltd., M-5) were used as the water-absorbent resin particles of Comparative Example 6.

2. Evaluation <Saline water retention>
The physiological saline water retention amount (room temperature, 25 ° C. ± 2 ° C.) of the water-absorbent resin particles was measured by the following procedure. First, a cotton bag (Membroad No. 60, width 100 mm x length 200 mm) weighing 2.0 g of water-absorbent resin particles was placed in a 500 mL beaker. Pour 500 g of 0.9 mass% sodium chloride aqueous solution (physiological saline) into a cotton bag containing water-absorbent resin particles at a time so that mamaco cannot be formed, tie the upper part of the cotton bag with a rubber ring, and let it stand for 30 minutes. The water-absorbent resin particles were swollen with. After 30 minutes, the cotton bag is dehydrated for 1 minute using a dehydrator (manufactured by Kokusan Co., Ltd., product number: H-122) set to have a centrifugal force of 167 G, and the cotton bag containing the swelling gel after dehydration. The mass Wa (g) of was measured. The same operation was performed without adding the water-absorbent resin particles, the empty mass Wb (g) of the cotton bag when wet was measured, and the amount of physiological saline water retained was calculated from the following formula.
Saline water retention (g / g) = [Wa-Wb] /2.0

<Medium particle size>
50 g of polymer particles (or water-absorbent resin particles) were used for measuring the medium particle size.

From the top, JIS standard sieves have a mesh size of 850 μm, a mesh size of 500 μm, a mesh size of 425 μm, a mesh size of 300 μm, a mesh size of 250 μm, a mesh size of 180 μm, a mesh size of 150 μm, Combined in the order of the saucer.

Polymer particles (or water-absorbent resin particles) were placed in the best combined sieve and shaken for 20 minutes according to JIS Z8815 (1994) using a low-tap shaker to classify. After classification, the mass of the polymer particles (or water-absorbent resin particles) remaining on each sieve was calculated as a mass percentage with respect to the total amount, and the particle size distribution was determined. By integrating on the sieve in order from the one with the largest particle size with respect to this particle size distribution, the relationship between the mesh size of the sieve and the integrated value of the mass percentage of the polymer particles (or water-absorbent resin particles) remaining on the sieve is logarithmic. Plotted on probability paper. By connecting the plots on the probability paper with a straight line, the particle size corresponding to the cumulative mass percentage of 50% by mass was defined as the medium particle size.

<Unpressurized DW>
The non-pressurized DW of the water-absorbent resin particles was measured using the measuring device shown in FIG. The measurement was carried out 5 times for one type of water-absorbent resin particles, and the average value of the measured values at three points excluding the minimum value and the maximum value was obtained.
The measuring device has a burette portion 1, a conduit 5, a measuring table 13, a nylon mesh sheet 15, a frame 11, and a clamp 3. The burette portion 1 includes a burette tube 21 on which a scale is described, a rubber stopper 23 for sealing the upper opening of the burette tube 21, a cock 22 connected to the tip of the lower portion of the burette tube 21, and a lower portion of the burette tube 21. It has an air introduction pipe 25 and a cock 24 connected to the burette. The burette portion 1 is fixed by a clamp 3. The flat plate-shaped measuring table 13 has a through hole 13a having a diameter of 2 mm formed in the central portion thereof, and is supported by a frame 11 having a variable height. The through hole 13a of the measuring table 13 and the cock 22 of the burette portion 1 are connected by a conduit 5. The inner diameter of the conduit 5 is 6 mm.

The measurement was performed in an environment with a temperature of 25 ° C and a humidity of 60 ± 10%. First, the cock 22 and the cock 24 of the burette portion 1 were closed, and 0.9 mass% saline solution 50 adjusted to 25 ° C. was put into the burette tube 21 through the opening at the upper part of the burette tube 21. The concentration of 0.9% by mass of the saline solution is a concentration based on the mass of the saline solution. After sealing the opening of the burette tube 21 with the rubber stopper 23, the cock 22 and the cock 24 were opened. The inside of the conduit 5 was filled with 0.9% by mass saline solution 50 to prevent air bubbles from entering. The height of the measuring table 13 was adjusted so that the height of the water surface of the 0.9% by mass saline solution that reached the inside of the through hole 13a was the same as the height of the upper surface of the measuring table 13. After the adjustment, the height of the water surface of the 0.9 mass% saline solution 50 in the burette tube 21 was read by the scale of the burette tube 21, and the position was set as the zero point (reading value at 0 seconds).

A nylon mesh sheet 15 (100 mm × 100 mm, 250 mesh, thickness about 50 μm) was laid in the vicinity of the through hole 13a on the measuring table 13, and a cylinder having an inner diameter of 30 mm and a height of 20 mm was placed in the center thereof. 1.00 g of water-absorbent resin particles 10a were uniformly sprayed on this cylinder. Then, the cylinder was carefully removed to obtain a sample in which the water-absorbent resin particles 10a were dispersed in a circle in the central portion of the nylon mesh sheet 15. Next, the nylon mesh sheet 15 on which the water-absorbent resin particles 10a were placed was quickly moved so that the center thereof was at the position of the through hole 13a so that the water-absorbent resin particles 10a did not dissipate, and the measurement was started. .. The time when the air bubbles were first introduced from the air introduction pipe 25 into the burette pipe 21 was defined as the start of water absorption (0 seconds).

The amount of decrease in the 0.9% by mass saline solution 50 in the bullet tube 21 (that is, the amount of the 0.9% by mass saline solution absorbed by the water-absorbent resin particles 10a) is sequentially read in units of 0.1 mL, and the water-absorbent resin particles are read. 10 seconds, 1 minute, 3 minutes, 5 minutes, and 10 minutes after the start of water absorption of 10a, the weight loss Wc (g) of 0.9% by mass saline solution was read. From Wc, the 10-second value, 1-minute value, 3-minute value, 5-minute value, and 10-minute value of the non-pressurized DW were obtained by the following formula. The non-pressurized DW is the amount of water absorbed per 1.00 g of the water-absorbent resin particles 10a.
Unpressurized DW value (mL / g) = Wc / 1.00

<Simple evaluation of leakability in absorber>
(1) Preparation of artificial urine Sodium chloride, calcium chloride and magnesium sulfate were dissolved in ion-exchanged water at the following concentrations. A small amount of Blue No. 1 was added to the obtained solution to obtain artificial urine colored blue. The obtained artificial urine was used as a test solution for evaluating leakability. The following concentrations are based on the total mass of artificial urine.
Artificial urine composition NaCl: 0.780% by mass
CaCl ₂ : 0.022% by mass
0054 ₄ : 0.038% by mass
Blue No. 1: 0.002% by mass

(2) Leakage test FIG. 3 is a schematic view showing an apparatus for simply evaluating the leakability of an absorber. Using the apparatus shown in FIG. 3, the liquid leakage property of the test absorber was evaluated by the following procedures i), ii), iii), iv) and v).
i) A strip-shaped adhesive tape (manufactured by Diatex Co., Ltd., Piolan tape) having a length of 15 cm and a width of 5 cm is placed on a laboratory table so that the adhesive surface faces up, and the water-absorbent resin particles 3 are placed on the adhesive surface. .0 g was evenly sprayed. A stainless steel roller (mass 4.0 kg, diameter 10.5 cm, width 6.0 cm) is placed on top of the sprayed water-absorbent resin particles, and the roller is reciprocated three times between both ends in the longitudinal direction of the adhesive tape. It was. As a result, a water-absorbing layer made of water-absorbent resin particles was formed on the adhesive surface of the adhesive tape (test absorber).
ii) The adhesive tape was lifted upright to remove excess water-absorbent resin particles from the water-absorbent layer. Again, the roller was placed on the water absorption layer and reciprocated three times between both ends of the adhesive tape in the longitudinal direction.
iii) In a room at a temperature of 25 ± 2 ° C., an acrylic resin plate 45 having _{a rectangular flat main surface S 1} _{having a length of 30 cm and a width of 55 cm is arranged in a width direction parallel to a horizontal plane S 0} , and the main surface S ₁ And the horizontal plane S ₀ were fixed so as to form 30 degrees. The main surface S ₁ of the fixed acrylic plate 45, the adhesive tape (test absorber) 46 water-absorbing layer is formed, the water-absorbing layer is exposed, its longitudinal direction with respect to the width direction of the acrylic resin plate 45 It was pasted in a vertical orientation.
iv) Using a micropipette 47 (Pipetteman Neo P1000N manufactured by MS Equipment Co., Ltd.), 0.25 mL of the test solution at a liquid temperature of 25 ° C. was applied from a height of about 1 cm from the surface at a position about 1 cm from the upper end of the water absorption layer. All were injected within 1 second.
v) Thirty seconds after the start of injection of the test solution 55, the maximum value of the moving distance of the test solution 55 injected into the water absorption layer was read and recorded as the diffusion distance D. The diffusion distance D is a distance on the main surface connecting the dropping point (injection point) and the longest reaching point with a straight line in the direction perpendicular to the short side of the acrylic resin plate 45.

3. 3. Results The evaluation results are shown in Tables 1 and 2. A diffusion distance of "14 *" indicates that the test solution leaked from the lower part of the water absorption layer. The addition amount in Tables 1 and 2 indicates the addition amount of silica with respect to 100 parts by mass of the polymer particles.

As shown in Tables 1 and 2, when dry silica as a liquid leakage inhibitor was contained, liquid leakage was suppressed.

1 ... Burette part, 3 ... Clamp, 5 ... Conduit, 10 ... Absorbent, 10a ... Water-absorbent resin particles, 10b ... Fiber layer, 11 ... Stand, 13 ... Measuring table, 13a ... Through hole, 15 ... Nylon mesh sheet, 20a, 20b ... core wrap, 21 ... burette tube, 22 ... cock, 23 ... rubber stopper, 24 ... cock, 25 ... air introduction tube, 50 ... 0.9% by mass saline solution, 30 ... liquid permeable sheet, 40 ... liquid Impermeable sheet, 45 ... acrylic resin plate, 46 ... test absorber, 47 ... micropipette, 55 ... test solution, 100 ... absorbent article.

Claims

A liquid leakage inhibitor used for absorbers containing water-absorbent resin particles, including dry silica.
The liquid leakage inhibitor according to claim 1, wherein the dry silica has a bulk density of 10 to 200 g / L.
A water-absorbent resin particle containing the polymer particles and the liquid leakage inhibitor according to claim 1 or 2 arranged on the surface of the polymer particles.
The water-absorbent resin particles according to claim 3, wherein the water-absorbent resin particles have a static suction index α of 5.0 mL / g or more calculated by the following formula.
Formula: α = (I + II) / 2
here,
Water absorption rate index I = (10-second value of non-pressurized DW) x 6 [mL / g]
Water absorption rate index II = (3 minutes value of non-pressurized DW) / 3 [mL / g]
Is.
An absorber containing the water-absorbent resin particles according to claim 3 or 4.
An absorbent article comprising the absorber according to claim 5.