JP2012217599A - Absorbable resin particle, and absorber and absorbable article including the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide absorbable resin particles capable of being used for manufacturing an absorbable article hardly causing a problem such as the leak of a liquid or rash.SOLUTION: The absorbable resin particles (B1) include a crosslinked polymer (A1) comprising a water soluble vinyl monomer (a1) and/or a hydrolysable vinyl monomer (a2) and a crosslinking agent (b) as essential components, in which the number average number of pores per unit area to be observed by a scanning electron microscope is 1-200 pores/mmand the number average pore diameter per absorbable resin particle is 1-50 μm.

Description

  The present invention relates to absorbent resin particles, an absorbent body containing the same, and an absorbent article.

  Conventionally, a method for fixing a water-absorbent resin to a support carrier has been studied in order to improve the problem of movement and bias of the water-absorbent resin. For example, a method of embossing the absorber, a method of including a thermoplastic binder fiber in an absorber composed of a water-absorbent resin and a hydrophilic fiber, and heat-sealing the absorber, a synthetic resin having a high recovery rate from strain A method in which an absorbent body comprising a water-absorbent resin and a hydrophilic fiber is contained and the absorbent body is heat-sealed (for example, see Patent Document 1 and Patent Document 2). When it fixes to a base material, the problem of the fall of the absorption capability by the restriction | limiting of the swelling of the water absorbing resin by restraint of the binder generate | occur | produces. In particular, when the water-absorbing resin and the hydrophilic fiber are fixed with a thermoplastic binder or emulsion, there is a problem that the absorbing ability inherently possessed by the water-absorbing resin cannot be exhibited sufficiently.

JP-A-10-118114 JP-A-10-118115

  Conventional absorbent articles using absorbent resin particles (such as paper diapers) have poor entanglement between the absorbent resin particles and fibrous materials such as pulp, and the absorbent resin particles have fallen off or have moved or become uneven in the absorbent body. The absorption rate is biased and the body fluid does not diffuse efficiently into the absorber. This causes problems such as liquid leakage and occurrence of fog. The objective of this invention is providing the absorbent resin particle which can manufacture the absorbent article which does not produce the above problems.

As a result of intensive studies to achieve the above object, the present inventor has found that water-absorbent resin particles having a specific structure can solve the above problems, and have reached the present invention.
That is, the absorbent resin particle of the present invention contains a water-soluble vinyl monomer (a1) and / or a hydrolyzable vinyl monomer (a2), and a crosslinked polymer (A1) having a crosslinking agent (b) as essential constituent units. The number average number of pores per unit area observed with a scanning electron microscope is 1 to 200 / mm ² , and the number average fineness per one absorbent resin particle is Absorbent resin particles (B1) having a pore diameter of 1 to 50 μm.

  The gist of the absorbent body of the present invention is that it comprises the above-described absorbent resin particle composition and a fibrous material.

  The gist of the absorbent article of the present invention is that the absorbent article is provided.

  When the absorbent resin particles of the present invention are applied to absorbent articles (paper diapers, sanitary napkins, etc.), the absorbent resin particles in the absorbent body are not dropped and disproportionated, exhibiting excellent absorption performance, Leakage and fogging can be prevented. Furthermore, it is possible to prevent the diaper from being deformed after absorbing bodily fluids.

  The absorbent resin particle (B1) of the present invention comprises a crosslinked polymer (A1) having a water-soluble vinyl monomer (a1) and / or a hydrolyzable vinyl monomer (a2) and a crosslinking agent (b) as essential constituent units. Comprising.

  The water-soluble vinyl monomer (a1) is not particularly limited and is known {for example, a vinyl monomer disclosed in Japanese Patent No. 3648553, Japanese Patent Laid-Open No. 2003-165883, Japanese Patent Laid-Open No. 2005-75982, Japanese Patent Laid-Open No. 2005-95759}. Etc. can be used.

  The hydrolyzable vinyl monomer (a2) means a vinyl monomer that becomes a water-soluble vinyl monomer (a1) by hydrolysis, and is not particularly limited (for example, Japanese Patent No. 3648553, JP-A No. 2003-165883, The vinyl monomer etc. of Unexamined-Japanese-Patent No. 2005-75982, Unexamined-Japanese-Patent No. 2005-95759} etc. can be used. The water-soluble vinyl monomer means a vinyl monomer having a property of dissolving at least 100 g in 100 g of water at 25 ° C. The term “hydrolyzable” refers to the property of being hydrolyzed by the action of 50 ° C. water and, if necessary, the catalyst (acid or base) to make it water-soluble. Hydrolysis of the hydrolyzable vinyl monomer may be performed either during polymerization, after polymerization, or both of them, but from the viewpoint of the molecular weight of the resulting absorbent resin particles, etc., is preferable.

  Of these, water-soluble vinyl monomers (a1) are preferred from the viewpoint of absorption characteristics, etc., more preferably anionic vinyl monomers, and more preferably carboxy (salt) groups, sulfo (salt) groups, amino groups, carbamoyl groups. Vinyl monomers having an ammonio group or a mono-, di- or tri-alkyl ammonio group, then preferably vinyl monomers having a carboxy (salt) group or a carbamoyl group, particularly preferably (meth) acrylic acid (salt) and (Meth) acrylamide, next particularly preferably (meth) acrylic acid (salt), most preferably 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 an alkali metal (such as lithium, sodium and potassium) salt, an alkaline earth metal (such as magnesium and calcium) salt or an ammonium (NH ₄ ) salt. Among these salts, alkali metal salts and ammonium salts are preferable from the viewpoint of absorption characteristics and the like, more preferably alkali metal salts, and particularly preferably sodium salts.

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

  As a structural unit of the absorbent resin particles, in addition to the water-soluble vinyl monomer (a1) and the hydrolyzable vinyl monomer (a2), other vinyl monomers (a3) copolymerizable therewith can be used as the structural unit. .

Other vinyl monomers (a3) that can be copolymerized are not particularly limited and are known {for example, Japanese Patent No. 3648553, Japanese Patent Application Laid-Open No. 2003-165883, Japanese Patent Application Laid-Open No. 2005-75982, Japanese Patent Application Laid-Open No. 2005-95759. } Can be used, and the following vinyl monomers (i) to (iii) can be used.
(I) C8-C30 aromatic ethylenic monomer Styrene such as styrene, α-methylstyrene, vinyltoluene and hydroxystyrene, and halogen substituted products of styrene such as vinylnaphthalene and dichlorostyrene.
(Ii) C2-C20 aliphatic ethylene monomer Alkene [ethylene, propylene, butene, isobutylene, pentene, heptene, diisobutylene, octene, dodecene, octadecene, etc.]; and alkadiene [butadiene, isoprene, etc.], etc.
(Iii) C5-C15 alicyclic ethylene monomer Monoethylenically unsaturated monomer [pinene, limonene, indene and the like]; and polyethylene vinyl polymerizable monomer [cyclopentadiene, bicyclopentadiene, ethylidene norbornene and the like] and the like.

  When the other vinyl monomer (a3) is used as a constituent unit, the content (mol%) of the other vinyl monomer (a3) unit is that of the water-soluble vinyl monomer (a1) unit and the hydrolyzable vinyl monomer (a2) unit. Based on the number of moles, 0.01 to 5 is preferable, more preferably 0.05 to 3, then preferably 0.08 to 2, and particularly preferably 0.1 to 1.5. From the viewpoint of absorption characteristics and the like, the content of other vinyl monomer (a3) units is most preferably 0 mol%.

There are no particular limitations on the crosslinking agent (b), and known crosslinking agents such as those disclosed in known {eg, Japanese Patent No. 3648553, Japanese Patent Laid-Open No. 2003-165883, Japanese Patent Laid-Open No. 2005-75982, Japanese Patent Laid-Open No. 2005-95759}, and the like. Can be used.
Among these, from the viewpoint of absorption characteristics, etc., a crosslinking agent having two or more ethylenically unsaturated groups is preferable, more preferably a poly (meth) allyl ether of a polyol having 2 to 10 carbon atoms, particularly preferably triallylsia. Nurate, triallyl isocyanurate, tetraallyloxyethane and pentaerythritol triallyl ether, most preferably pentaerythritol triallyl ether.

  The content (mol%) of the crosslinking agent (b) unit is preferably 0.001 to 5, more preferably, based on the number of moles of the water-soluble vinyl monomer (a1) unit and the hydrolyzable vinyl monomer (a2) unit. Is 0.005 to 3, particularly preferably 0.01 to 1. Within this range, the absorption characteristics are further improved.

  The cross-linked polymer (A1) may be one type or a mixture of two or more types.

  The cross-linked polymer (A1) can be prepared by known aqueous solution polymerization {adiabatic polymerization, thin film polymerization, spray polymerization method, etc .; JP-A-55-133413, etc.} or known reverse-phase suspension polymerization {Japanese Examined Patent Publication No. 54-30710. Gazette, JP-A-56-26909 and JP-A-1-5808, etc.}. Among the polymerization methods, the solution polymerization method is preferable, and an aqueous solution polymerization method is particularly preferable because it is not necessary to use an organic solvent and is advantageous in terms of production cost.

  Water-containing gel obtained by polymerization {consists of a crosslinked polymer and water. } 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 shredded using a normal shredding device {for example, a bex mill, rubber chopper, pharma mill, mincing machine, impact crusher and roll crusher}. .

  When using a solvent (organic solvent, water, etc.) for the polymerization, it is preferable to distill off the solvent after the polymerization. When the solvent contains an organic solvent, the content (% by weight) of the organic solvent after the distillation is preferably 0 to 10, more preferably 0 to 5, particularly preferably 0, based on the weight of the absorbent resin particles. ~ 3, most preferably 0-1. It is. Within this range, the absorption performance (particularly the water retention amount) of the absorbent resin particles is further improved.

  When water is contained in the solvent, the water content (% by weight) after the distillation is preferably 0 to 20, more preferably 1 to 10, particularly preferably 2 to 9, most preferably based on the weight of the crosslinked polymer. 3-8. Within this range, the absorption performance and the breakability of the absorbent resin particles after drying are further improved.

  In addition, the content and moisture of the organic solvent are an infrared moisture meter {JE400 manufactured by KETT Co., Ltd .: 120 ± 5 ° C., 30 minutes, atmospheric humidity before heating 50 ± 10% RH, lamp specification 100V, 40W } Is obtained from the weight loss of the measurement sample before and after heating.

  As a method of distilling off the solvent (including water), 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 heated to 100 to 230 ° C., (heating ) Vacuum drying, freeze drying, infrared drying, decantation, filtration, etc. can be applied.

  The crosslinked polymer can be pulverized after drying. The pulverization method is not particularly limited, and a normal pulverizer (for example, a hammer-type pulverizer, an impact-type pulverizer, a roll-type pulverizer, and a shet airflow-type 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 (A1) when sieved as necessary is preferably 100 to 800, more preferably 200 to 700, next preferably 250 to 600, particularly preferably 300 to 500, Most preferably, it is 350-450. Within this range, the absorption performance is further improved.

  In addition, the weight average particle diameter 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 Company, 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 the 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 {the horizontal axis is the sieve aperture (particle size ), The vertical axis is plotted in the weight fraction}, a line connecting the points is drawn, and the particle diameter corresponding to the weight fraction of 50% by weight is obtained, and this is defined as the weight average particle diameter.

  Further, since the absorption performance is better when the content of fine particles is smaller, the content of fine particles of 106 μm or less (preferably 150 μm or less) in the total particles is preferably 3% by weight or less, more preferably 1% by weight or less. It is. The content of the fine particles can be determined using a plot created when determining the above weight average particle diameter.

  The apparent density (g / ml) of the crosslinked polymer (A1) is preferably 0.54 to 0.70, more preferably 0.56 to 0.65, and particularly preferably 0.58 to 0.60. Within this range, the absorption performance is further improved. The apparent density is measured at 25 ° C. according to JIS K7365: 1999.

  The shape of the crosslinked polymer (A1) 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 crosslinked polymer (A1) can be subjected to a surface crosslinking treatment with a surface crosslinking agent, if necessary. As the surface cross-linking agent, known {Japanese Patent Laid-Open Nos. 59-189103, 58-180233, 61-16903, 61-21305, 61-252212 are known. , JP-A-51-136588, JP-A-61-257235, etc.} surface crosslinking agent {polyvalent glycidyl, polyhydric alcohol, polyvalent amine, polyvalent aziridine, polyvalent isocyanate, silane coupling Agents and polyvalent metals, etc.} can be used. Of these surface cross-linking agents, from the viewpoint of economy and absorption properties, polyvalent glycidyl, polyhydric alcohol and polyvalent amine are preferable, more preferably polyvalent glycidyl and polyhydric alcohol, particularly preferably polyvalent glycidyl, most preferably Preferred is ethylene glycol diglycidyl ether.

  In the case of surface cross-linking treatment, the amount (% by weight) of the surface cross-linking agent is not particularly limited because it can be variously changed depending on the type of surface cross-linking agent, the conditions for cross-linking, the target performance, etc. From the viewpoint of the above, based on the weight of the water-soluble vinyl monomer (a1), the hydrolyzable vinyl monomer (a2) and the crosslinking agent (b), 0.001 to 3 is preferable, more preferably 0.005 to 2, Most preferably, it is 0.01-1.

  In the case of performing the surface cross-linking treatment, the method of the surface cross-linking treatment is known {for example, the method of Japanese Patent No. 3648553, JP-A No. 2003-165883, JP-A No. 2005-75982, JP-A No. 2005-95759}. Is applicable.

The absorbent resin particles (B1) preferably further contain a hydrophobic substance (C). The content (% by weight) of the hydrophobic substance (C) in (B1) is preferably 0.01 to 10.0 based on the weight of the crosslinked polymer (A1) contained in the absorbent resin particles (B1). More preferably, it is 0.02 to 1.0, and particularly preferably 0.03 to 0.1. This range is preferable because the anti-absorbent article is excellent in anti-fogging property.
The hydrophobic substance (C) includes a hydrophobic substance (C1) containing a hydrocarbon group, a hydrophobic substance (C2) containing a hydrocarbon group having a fluorine atom, and a hydrophobic substance (C3) having a polysiloxane structure. Etc. are included.

  Hydrophobic substances (C1) containing hydrocarbon groups include polyolefin resins, polyolefin resin derivatives, polystyrene resins, polystyrene resin derivatives, waxes, long-chain fatty acid esters, compounds composed of a hydrophobic part and a hydrophilic part, and two types thereof. The above mixtures and the like are included.

  As the polyolefin resin, an olefin having 2 to 4 carbon atoms {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) And polymers having an average molecular weight of 1,000 to 1,000,000 {for example, 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—) or the like 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, carbana wax, beef tallow, etc.).

  As long-chain fatty acid esters, 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. Of these, sucrose stearate monoester, sucrose stearate diester, and sucrose stearate triester are preferable from the viewpoint of the resistance to moisture of the absorbent article, and more preferably sucrose stearate monoester and sucrose. Stearic acid diester.

  Examples of the compound composed of a hydrophobic part and a hydrophilic part include long-chain fatty acids and salts thereof, and long-chain aliphatic alcohols.

  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, behenic acid, etc.), and salts thereof include zinc, calcium, Examples thereof include salts with magnesium or aluminum (hereinafter abbreviated as Zn, Ca, Mg, Al) {for example, palmitic acid Ca, palmitic acid Al, stearic acid Ca, stearic acid Mg, stearic acid Al, etc.}. From the viewpoint of the moisture resistance of the absorbent article, Zn stearate, Ca stearate, Mg stearate, and Al stearate are preferable, and Mg stearate is more preferable.

  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.

The melting point of the compound composed of the hydrophobic part and the hydrophilic part is preferably 50 ° C. to 300 ° C., more preferably 60 ° C. to 200 ° C., particularly preferably 80 ° C. to 80 ° C. from the viewpoint of the moisture resistance of the absorbent article. 160 ° C.
Moreover, it is preferable that the dissociation degree of the compound which consists of a hydrophobic part and a hydrophilic part is 1 * 10 < ^-3 > -1 * 10 < ^-20 > from a viewpoint of absorption performance.

  Examples of the hydrophobic substance (C2) 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.

  As perfluoroalkanes, alkanes having 4 to 42 fluorine atoms and 1 to 20 carbon atoms {for example, trifluoromethane, pentafluoroethane, pentafluoropropane, heptafluoropropane, heptafluorobutane, nonafluorofluorohexane, tridecafluoro Octane and heptadecafluorododecane, etc.}.

  The perfluoroalkene includes alkenes having 4 to 42 fluorine atoms and 2 to 20 carbon atoms (for example, trifluoroethylene, pentafluoropropene, trifluoropropene, heptafluorobutene, nonafluorofluorohexene, tridecafluorooctene and hepta Decafluorododecene etc.}.

  Perfluoroaryl includes aryl having 4 to 42 fluorine atoms and 6 to 20 carbon atoms {for example, trifluorobenzene, pentafluorotoluene, trifluoronaphthalene, hexafluorobenzene, tetrafluoroxylene, tridecafluorooctylbenzene, and hepta. Decafluorododecylbenzene, etc.}.

  Examples of perfluoroalkyl ether include ethers having 2 to 82 fluorine atoms and 2 to 40 carbon atoms (for example, ditrifluoromethyl ether, dipentafluoroethyl ether, dipentafluoropropyl ether, diheptafluoropropyl ether, diheptafluoro). Butyl ether, dinonafluorofluorohexyl ether, ditridecafluorooctyl ether, diheptadecafluorododecyl ether, etc.}.

  Examples of perfluoroalkylcarboxylic acids include carboxylic acids having 3 to 41 fluorine atoms and 1 to 21 carbon atoms (for example, trifluoroethanoic acid, pentafluoropropanoic acid, heptafluoropropanoic acid, heptafluorobutanoic acid, nonafluorofluorohexane). Acid, tridecafluorooctanoic acid, heptadecafluorododecanoic acid, and salts of these metals (alkali metal and alkaline earth metal etc.), etc.}.

  Perfluoroalkyl alcohols include alcohols having 3 to 41 fluorine atoms and 1 to 20 carbon atoms (for example, pentafluoroethanol, pentafluoropropanol, heptafluoropropanol, heptafluorobutanol, nonaflufluorohexanol, tridecafluorooctanol and Heptadecafluorododecanol and the like} and ethylene oxide (1 to 20 mol per 1 mol of alcohol) adduct of this alcohol.

  Examples of the mixture of two or more of these include a mixture of perfluoroalkylcarboxylic acid and perfluoroalkyl alcohol {for example, a mixture of pentafluoroethanoic acid and pentafluoroethanol, etc.}.

  Examples of the hydrophobic substance (C3) 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 position of the organic group (modified group) of the modified silicone {polyether-modified polysiloxane, carboxy-modified polysiloxane, epoxy-modified polysiloxane, amino-modified polysiloxane, etc.} is not particularly limited, but the side chain of polysiloxane, polysiloxane Both ends of the polysiloxane, one end of the polysiloxane, and both the side chain and both ends of the polysiloxane may be used. Among these, from the viewpoint of absorption characteristics and the like, both the side chain of polysiloxane and the side chain and both ends of polysiloxane are preferred, and both the side chain and both ends of polysiloxane are more preferred.

  Examples of the organic group (modified group) of the polyether-modified polysiloxane include a group containing a polyoxyethylene group or a poly (oxyethylene / oxypropylene) group. The content (pieces) of oxyethylene groups and / or oxypropylene groups contained in the polyether-modified polysiloxane is preferably 2 to 40, more preferably 5 to 30, particularly preferably per molecule of the polyether-modified polysiloxane. 7-20, most preferably 10-15. Within this range, the absorption characteristics are further improved. Moreover, when it contains an oxyethylene group and an oxypropylene group, the content (% by weight) of the oxyethylene group is preferably 1 to 30, more preferably 3 to 25, and particularly preferably 5 based on the weight of the polysiloxane. ~ 20. Within this range, the absorption characteristics are further improved.

The polyether-modified polysiloxane can be easily obtained from the market. For example, the following products {modified position, type of oxyalkylene} can be preferably exemplified.
* Shin-Etsu Chemical Co., Ltd. KF-945 {side chain, oxyethylene and oxypropylene}, KF-6020 {side chain, oxyethylene and oxypropylene}, X-22-6191 {side chain, oxyethylene and oxypropylene} X-22-4922 {side chain, oxyethylene and oxypropylene}, X-22-4272 {side chain, oxyethylene and oxypropylene}, X-22-6266 {side chain, oxyethylene and oxypropylene}

FZ-2110 {both ends, oxyethylene and oxypropylene}, FZ-2122 {both ends, oxyethylene and oxypropylene}, FZ-7006 {both ends, oxyethylene and oxypropylene}, manufactured by Toray Dow Corning Co., Ltd. FZ-2166 {both ends, oxyethylene and oxypropylene}, FZ-2164 {both ends, oxyethylene and oxypropylene}, FZ-2154 {both ends, oxyethylene and oxypropylene}, FZ-2203 {both ends, oxy Ethylene and oxypropylene} and FZ-2207 {both ends, oxyethylene and oxypropylene}

  The organic group (modified group) of the carboxy-modified polysiloxane includes a group containing a carboxy group, and the organic group (modified group) of the epoxy-modified polysiloxane includes a group containing an epoxy group. Examples of the organic group (modified group) of polysiloxane include groups containing amino groups (1, 2, and tertiary amino groups). The organic group (modified group) content (g / mol) of these modified silicones is preferably 200 to 11000, more preferably 600 to 8000, and particularly preferably 1000 to 4000 as carboxy equivalent, epoxy equivalent or amino equivalent. It is. Within this range, the absorption characteristics are further improved. The carboxy equivalent is measured according to “16. Total acid value test” of JIS C2101: 1999. Moreover, an epoxy equivalent is calculated | required based on JISK7236: 2001. The amino equivalent is measured according to “8. Potentiometric titration method (base number / hydrochloric acid method)” of JIS K2501: 2003.

The carboxy-modified polysiloxane can be easily obtained from the market. For example, the following products {modified position, carboxy equivalent (g / mol)} can be preferably exemplified.
* Shin-Etsu Chemical Co., Ltd. X-22-3701E {side chain, 4000}, X-22-162C {both ends, 2300}, X-22-3710 {single end, 1450}

-BY 16-880 {side chain, 3500}, BY 16-750 {both ends, 750}, BY 16-840 {side chain, 3500}, SF8418 {side chain, 3500} manufactured by Toray Dow Corning Co., Ltd.

The epoxy-modified polysiloxane can be easily obtained from the market. For example, the following products {modified position, epoxy equivalent} can be preferably exemplified.
・ X-22-343 {side chain, 525}, KF-101 {side chain, 350}, KF-1001 {side chain, 3500}, X-22-2000 {side chain, 620} manufactured by Shin-Etsu Chemical Co., Ltd. X-22-2046 {side chain, 600}, KF-102 {side chain, 3600}, X-22-4741 {side chain, 2500}, KF-1002 {side chain, 4300}, X-22-3000T {Side chain, 250}, X-22-163 {both ends, 200}, KF-105 {both ends, 490}, X-22-163A {both ends, 1000}, X-22-163B {both ends, 1750}, X-22-163C {both ends, 2700}, X-22-169AS {both ends, 500}, X-22-169B {both ends, 1700}, X-22-173DX {single end, 4500} , X-22-9002 { Side chain, both ends, 5000}

-FZ-3720 {side chain, 1200}, BY 16-839 {side chain, 3700}, SF 8411 {side chain, 3200}, SF 8413 {side chain, 3800}, SF 8421 {manufactured by Toray Dow Corning Co., Ltd. Side chain, 11000}, BY 16-876 {side chain, 2800}, FZ-3736 {side chain, 5000}, BY 16-855D {side chain, 180}, BY 16-8 {side chain, 3700}

The amino-modified silicone can be easily obtained from the market. For example, the following products {modified position, amino equivalent} can be preferably exemplified.
-Shin-Etsu Chemical Co., Ltd. KF-865 {side chain, 5000}, KF-864 {side chain, 3800}, KF-859 {side chain, 6000}, KF-393 {side chain, 350}, KF-860 {Side Chain, 7600}, KF-880 {Side Chain, 1800}, KF-8004 {Side Chain, 1500}, KF-8002 {Side Chain, 1700}, KF-8005 {Side Chain, 11000}, KF-867 {Side Chain, 1700}, X-22-3820W {Side Chain, 55000}, KF-869 {Side Chain, 8800}, KF-861 {Side Chain, 2000}, X-22-3939A {Side Chain, 1500} , KF-877 {side chain, 5200}, PAM-E {both ends, 130}, KF-8010 {both ends, 430}, X-22-161A {both ends, 800}, X-22-161B {both Terminal 1500 }, KF-8012 {both ends, 2200}, KF-8008 {both ends, 5700}, X-22-1660B-3 {both ends, 2200}, KF-857 {side chain, 2200}, KF-8001 { Side chain, 1900}, KF-862 {side chain, 1900}, X-22-9192 {side chain, 6500}

-FZ-3707 {side chain, 1500}, FZ-3504 {side chain, 1000}, BY 16-205 {side chain, 4000}, FZ-3760 {side chain, 1500}, FZ manufactured by Toray Dow Corning Co., Ltd. -3705 {side chain, 4000}, BY 16-209 {side chain, 1800}, FZ-3710 {side chain, 1800}, SF 8417 {side chain, 1800}, BY 16-849 {side chain, 600}, BY 16-850 {side chain, 3300}, BY 16-879B {side chain, 8000}, BY 16-892 {side chain, 2000}, FZ-3501 {side chain, 3000}, FZ-3785 {side chain, 6000}, BY 16-872 {side chain, 1800}, BY 16-213 {side chain, 2700}, BY 16-203 {side chain, 1900}, BY 16-898 {side chain, 2900 BY 16-890 {side chain, 1900}, BY 16-893 {side chain, 4000}, FZ-3789 {side chain, 1900}, BY 16-871 {both ends, 130}, BY 16-853C {both Terminal 360}, BY 16-853U {both ends, 450}

  Examples of these mixtures include a mixture of polydimethylsiloxane and carboxyl-modified polysiloxane, a mixture of polyether-modified polysiloxane and amino-modified polysiloxane, and the like.

The viscosity (mPa · s, 25 ° C.) of the hydrophobic substance having a polysiloxane structure is preferably 10 to 5000, more preferably 15 to 3000, and particularly preferably 20 to 1500. Within this range, the absorption characteristics are further improved. The viscosity is JIS Z8803-1991 “Viscosity of liquid”. Cone and cone-measured according to the viscosity measurement method using a flat plate rotational viscometer {for example, E-type viscometer with temperature adjusted to 25.0 ± 0.5 ° C. (RE80L, Toki Sangyo Co., Ltd., radius 7 mm) , Angle 5.24 × 10 ⁻² rad cone). }

  The HLB value of the hydrophobic substance (C) is preferably from 1 to 10, more preferably from 3 to 8, particularly preferably from 5 to 7. Within this range, the moisture resistance of the absorbent article 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, Sanyo Chemical Industries, Ltd., published in 1981). .

  Of these hydrophobic substances (C), a compound comprising a hydrophobic part and a hydrophilic part is preferred from the viewpoint of the resistance to moisture of the absorbent article, etc., more preferably long-chain fatty acids and salts thereof, and particularly preferably stearin. It is at least one selected from the group consisting of acid Mg, Ca stearate, Zn stearate, Al stearate, and stearates.

  When the absorbent resin particles (B1) contain (C), if the absorbent resin particles have a structure containing part or all of (C) inside, the hydrophobic substance (C) However, it is preferable that a part of the hydrophobic substance (C) is present on the surface of the absorbent resin particles from the viewpoint of the moisture resistance of the absorbent article.

  The structure in which the absorbent resin particles contain part or all of the hydrophobic substance (C) in the interior is obtained by combining the absorbent resin particles with the water content of (1) the hydrophobic substance (C) and the crosslinked polymer (A1). It can be produced by a method of mixing and kneading with a gel or (2) a method of obtaining a water-containing gel of a crosslinked polymer (A1) by polymerizing structural units in the presence of a hydrophobic substance (C).

In the method (1), as the hydrophobic material (C), a material obtained by processing the hydrophobic material (C) into a pulverized product, bead, rod or fiber of a film can be used. The volume average particle size (μm) of the pulverized film is preferably 5 to 50, more preferably 7 to 30, and particularly preferably 10 to 20. The volume average particle diameter (μm) of the beads is preferably 0.5 to 100, more preferably 1 to 30, and particularly preferably 2 to 20. The rod-like length (μm) is preferably 5 to 50, more preferably 7 to 30, particularly preferably 10 to 20, and the diameter (μm) is preferably 0.5 to 50, more preferably 1 to 1. 30, particularly preferably 2-15. The fibrous length (μm) is preferably 5 to 50, more preferably 7 to 30, particularly preferably 10 to 20, and the diameter (μm) is preferably 0.5 to 50, more preferably 1. -30, particularly preferably 2-15. Within these ranges, the moisture resistance of the absorbent article is further improved.

When the hydrophobic substance (C1) containing a hydrocarbon group is used, beads such as Mg stearate beads, polystyrene beads and polyethylene beads, and polyethylene films (for example, Tamapoly, SE625M, UB-1) and polystyrene are used. Examples thereof include pulverized products (volume average particle size 20 to 50 μm) of films such as films (for example, manufactured by Asahi Kasei Corporation: OPS). When using a hydrophobic substance (C3) containing polysiloxane, silicone beads {eg, GE Toshiba Silicones, Inc .: Tospearl 240 (amorphous silicone resin fine powder, volume average particle size 4 μm), Tospearl 3120 (true spherical shape) Silicone resin fine powder, volume average particle size 12 μm), Tospearl 145 (true spherical silicone resin fine powder, volume average particle size 4.5 μm), etc.}. When using a hydrophobic substance (C2) containing a hydrocarbon group having a fluorine atom, a fluorine film {eg, Asahi Glass Co., Ltd .: FLUON PTFE (polytetrafluoroethylene film), FLUON PFA (tetrafluoroethylene and Perfluoroethylene copolymer film), FLUON AFLAS (tetrafluoroethylene and propylene copolymer film), etc.} pulverized product (volume average particle size of 20 to 50 μm).
Of these, beads are preferable from the viewpoint of the anti-moisture property of the absorbent article, and more preferably Mg stearate beads.

The mixing method of the crosslinked polymer (A1) and the hydrophobic substance (C) is not limited as long as the hydrophobic substance (C) is mixed so as to exist inside the crosslinked polymer (A1).
However, the hydrophobic substance (C) is preferably not mixed with the dried polymer of the crosslinked polymer (A1) but with the hydrogel (A1) or the polymerization solution (A1), and more preferably (A1). To be mixed with hydrous gel. In addition, it is preferable to mix uniformly so that mixing may be carried out.
When the crosslinked polymer (A1) is obtained by the aqueous solution polymerization method, the timing for mixing and kneading the hydrophobic substances (C) and (A1) is not particularly limited, but during the polymerization process, immediately after the polymerization process, Examples thereof include crushing (minching) and drying of the hydrogel. Among these, from the viewpoint of the anti-moisture resistance of the absorbent article, it is preferable to be immediately after the polymerization step and during the water-containing gel crushing (mincing) step, and more preferably during the water-containing gel crushing (mincing) step. When the hydrophobic substance (C) is a long-chain fatty acid salt, the long-chain fatty acid and the metal hydroxide may be mixed or individually added.

  When the crosslinked polymer (A1) is obtained by the reverse phase suspension polymerization method or emulsion polymerization, the timing of mixing the hydrophobic substance (C) and (A1) is not particularly limited, but during the polymerization process {(C) In the presence of (A1)}, immediately after the polymerization step, during the dehydration step (during the step of dehydrating to about 10% by weight of water), immediately after the dehydration step, during the step of separating and distilling off the organic solvent used in the polymerization And during the drying of the hydrogel. Among these, from the viewpoint of the anti-moisture resistance of the absorbent article, it is preferable during the polymerization step, immediately after the polymerization step, during the dehydration step, immediately after the dehydration step, and during the step of separating and distilling off the organic solvent used for the polymerization. Is immediately after the polymerization step during the polymerization step.

  In the case of mixing during the drying of the hydrogel, a normal apparatus such as a bex mill, rubber chopper, pharma mill, mincing machine, impact pulverizer, and roll pulverizer can be used. When mixing in the polymerization solution, a device having a relatively high stirring force such as a homomixer or a biomixer can be used. Moreover, when mixing in drying of a hydrogel, kneading apparatuses, such as SV mixer, can also be used.

  The mixing temperature (° C.) is preferably 20 to 100, more preferably 40 to 90, and particularly preferably 50 to 80. Within this range, it becomes easier to mix evenly and the absorption characteristics are further improved.

  In the method (2) for producing the crosslinked polymer (A1) in the presence of the hydrophobic substance (C), the hydrophobic substance (C) is dissolved or emulsified (dispersed) in the polymer solution of the crosslinked polymer (A1). In addition, it can be carried out while precipitating (C) as the polymerization of (A1) proceeds. The polymerization method is the same as in the case of the crosslinked polymer (A1) except that the polymerization is performed in the presence of the hydrophobic substance (C).

The hydrophobic substance (C) can also be used in a form dissolved and / or emulsified in water and / or a volatile solvent (however, no emulsifier is used). The volatile solvent preferably has a vapor pressure (Pa) at 20 ° C. of 0.13 to 5.3, more preferably 0.15 to 4.5, particularly preferably, from the viewpoint of easy removal. Is from 0.23 to 3.8.
Examples of the volatile solvent include alcohols having 1 to 3 carbon atoms (such as methanol, ethanol and isopropyl alcohol), hydrocarbons having 5 to 8 carbon atoms (such as pentane, hexane, cyclohexane and toluene), and ethers having 2 to 4 carbon atoms ( Dimethyl ether, diethyl ether, tetrahydrofuran, etc.), C3-C4 ketones (acetone, methyl ethyl ketone, etc.), C3-C5 esters (ethyl formate, ethyl acetate, isopropyl acetate, diethyl carbonate, etc.) and the like. When water and / or a volatile solvent is used, the amount (% by weight) of these used is preferably 1 to 900, more preferably 5 to 700, particularly preferably based on the weight of the hydrophobic substance (C). 10-400. When water and a volatile solvent are used, the amount (% by weight) of water used is preferably from 50 to 98, more preferably from 60 to 95, particularly preferably from 70 to 90, based on the weight of water and the volatile solvent. It is.

The water-containing gel containing the hydrophobic substance (C) can be chopped as necessary. The size (longest diameter) of the hydrogel particles 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.
As the shredding method, the same method as in the case of the crosslinked polymer (A1) can be adopted.

When a solvent (including an organic solvent and / or water) is used for production of the absorbent resin particles (B1), the solvent can be distilled off after polymerization.
When the solvent contains an organic solvent, the content (% by weight) of the organic solvent after the distillation is preferably 0 to 10, more preferably 0 to 5, particularly preferably 0, based on the weight of the absorbent resin particles. ~ 3, most preferably 0-1. Within this range, the absorption performance (particularly the water retention amount) of the absorbent resin particles is further improved.

Moreover, 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 absorbent resin particles. Most preferably, it is 3-8. Within this range, the absorption performance (particularly the water retention amount) and the breakability of the absorbent resin particles after drying are further improved.
In addition, the content of the organic solvent and the method for measuring the water content and the method for distilling off the solvent are the same as in the case of the crosslinked polymer (A1).

The absorbent resin particles (B1) can be pulverized. When the absorbent resin particles contain a solvent, the solvent is preferably pulverized after being distilled off (dried).
When pulverizing, the weight average particle size (μm) after pulverization is preferably 100 to 800, more preferably 200 to 700, next preferably 250 to 600, particularly preferably 300 to 500, and most preferably 350 to 450. It is. Within this range, handling properties after pulverization (powder fluidity of absorbent resin particles and the like) and anti-fogging properties of the absorbent article are further improved. In addition, a weight average particle diameter can be measured like the case of a crosslinked polymer (A1).

The smaller the content of fine particles, the better the absorption performance. The content of fine particles of 106 μm or less in the total particles is preferably 3% by weight or less, and more preferably the content of fine particles of 150 μm or less in the total particles is 3% by weight. It is as follows. The content of the fine particles can be determined using a plot created when determining the above weight average particle diameter.
For pulverization and particle size adjustment, the same method as in the case of the crosslinked polymer (A1) can be employed.

  The apparent density (g / ml) of the absorbent resin particles (B1) is preferably 0.54 to 0.70, more preferably 0.56 to 0.65, and particularly preferably 0.58 to 0.60. . Within this range, the anti-fogging property of the absorbent article is further improved. The apparent density can be measured in the same manner as in the case of the crosslinked polymer (A1).

  The shape of the absorbent resin particles (B1) 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 absorbent resin particles (B1) can be subjected to surface crosslinking as necessary. As the crosslinking agent (surface crosslinking agent) for performing the surface crosslinking, the same as the internal crosslinking agent (b) can be used. As the surface cross-linking agent, from the viewpoint of the absorption performance of the absorbent resin particles, the water-soluble substituent of the water-soluble vinyl monomer (a1) and / or the water-soluble substituent generated by hydrolysis of the vinyl monomer (a2) is reacted. The cross-linking agent (b3) having at least two functional groups that can be used is preferable, more preferably polyvalent glycidyl, particularly preferably ethylene glycol diglycidyl ether and glycerin diglycidyl ether, and most preferably ethylene glycol diglycidyl ether.

  In the case of surface cross-linking, the content (% by weight) of the surface cross-linking agent is the total weight of the vinyl monomers (a1) and / or (a2), the internal cross-linking agent (b) and other vinyl monomers (a3) used as necessary. Is preferably 0.001 to 7, more preferably 0.002 to 5, particularly preferably 0.003 to 4. That is, in this case, the upper limit of the content (% by weight) of the surface cross-linking agent is preferably 7 based on the total weight of (a1) and / or (a2), (b) and (a3), more preferably 5, particularly preferably 4. Similarly, the lower limit is preferably 0.001, more preferably 0.002, and particularly preferably 0.003. In this range, the absorption performance is further improved. Surface cross-linking can be achieved by a method of spraying or impregnating absorbent particles with an aqueous solution containing a surface cross-linking agent, followed by heat treatment (100 to 200 ° C.).

The absorbent resin particles (B1) can further have an inorganic powder (D) attached to the particle surface. The inorganic powder (D) includes hydrophilic inorganic particles (d1) and hydrophobic inorganic particles (d2).
Examples of the hydrophilic inorganic particles (d1) include particles such as glass, silica gel, silica, and clay.
Examples of the hydrophobic inorganic particles (d2) include particles such as carbon fiber, kaolin, talc, mica, bentonite, sericite, asbestos, and shirasu.
Of these, hydrophilic inorganic particles (d1) are preferred, and silica is most preferred.

  The shape of the hydrophilic inorganic particles (d1) and the hydrophobic inorganic particles (d2) may be any of an irregular shape (crushed shape), a true spherical shape, a film shape, a rod shape, and a fibrous shape, but the irregular shape (crushed shape). Alternatively, a true spherical shape is preferable, and a true spherical shape is more preferable.

  The content (% by weight) of the inorganic powder (D) in (B1) is preferably 0.01 to 3.0 based on the weight of the crosslinked polymer (A1) contained in the absorbent resin particles (B1). More preferably, it is 0.05 to 1.0, next preferably 0.1 to 0.8, particularly preferably 0.2 to 0.7, and most preferably 0.3 to 0.6. Within this range, the anti-fogging property of the absorbent article is further improved.

  For the absorbent resin particles (B1), other additives (for example, known preservatives, fungicides, antibacterial agents, antioxidants, ultraviolet rays (for example, JP 2003-225565 A, JP 2006-131767 A, etc.) An absorbent, a colorant, a fragrance, a deodorant, an organic fibrous material, etc.}. When these additives are contained, the content (% by weight) of the additives is preferably 0.001 to 10, more preferably 0.01 to 5, particularly preferably based on the weight of the crosslinked polymer (A1). Preferably it is 0.05 to 1, most preferably 0.1 to 0.5.

The number average number of pores per unit area observed with the scanning electron microscope of the absorbent resin particles (B1) of the present invention is 1 to 200 / mm ² , and is a viewpoint of entanglement with the fibrous material. To preferably 5 to 150 pieces / mm ² , more preferably 10 to 100 pieces / mm ² . If the number is less than 1, the entanglement with the fibrous material is deteriorated, and if it exceeds 200, the absorption performance in the absorbent body is deteriorated.
In addition, the number average number of pores per unit area observed with the scanning electron microscope of the absorbent resin particles (B1) is obtained by the following method.
<Method for measuring number average number of pores>
The number of pores per unit area is determined from the number of pores for 30 particles using a photograph with a magnification of 50 to 100 times obtained with a scanning electron microscope, and the number is averaged.

  The absorbent resin particles in the above range include, for example, a gas-permeable band containing a chopped gel containing the hydrophobic substance (C) in an amount of 0.01 to 10.0% by weight based on the weight of the crosslinked polymer (A1). It is obtained by drying with a dryer {130 ° C. to 230 ° C., wind speed 2 m / sec to 10 m / sec}.

The number average pore diameter per absorbent resin particle of the absorbent resin particle (B1) of the present invention is 1 to 50 μm, preferably 3 to 40 μm, more preferably from the viewpoint of entanglement with the fibrous material. 5 to 30 μm. If it is less than 1 μm or more than 50 μm, the entanglement with the fibrous material becomes worse.
In addition, the number average pore diameter of the absorbent resin particles (B1) is obtained by the following method.
<Measurement method of number average pore diameter>
Calculation is performed by using a photograph with a magnification of 50 to 100 times obtained by a scanning electron microscope to average the pore diameters of 30 particles.
The absorbent resin particles in the above range include, for example, a gas-permeable band containing a chopped gel containing the hydrophobic substance (C) in an amount of 0.01 to 10.0% by weight based on the weight of the crosslinked polymer (A1). It is obtained by drying with a dryer {130 ° C. to 230 ° C., wind speed 2 m / sec to 10 m / sec}.

In the absorbent resin particles (B1) of the present invention, the ratio of the maximum pore diameter of the absorbent resin particles (B1) to the particle diameter of (B1) (maximum pore diameter / resin particle diameter) is a fibrous material. From the viewpoint of entanglement, 0.001 to 0.3 is preferable, and 0.005 to 0.25 μm is more preferable.
In addition, the ratio between the maximum pore diameter of the absorbent resin particles (B1) and the particle diameter of (B1) is obtained by the following method.
<Measuring method of ratio of maximum pore diameter of absorbent resin particle (B1) and maximum particle diameter of (B1)>
Using a photograph with a magnification of 50 to 100 times obtained with a scanning electron microscope, the ratio of the maximum pore diameter of 30 particles to the particle diameter of (B1) is calculated and obtained by number averaging.
The absorbent resin particles in the above range include, for example, a gas-permeable band containing a chopped gel containing the hydrophobic substance (C) in an amount of 0.01 to 10.0% by weight based on the weight of the crosslinked polymer (A1). It is obtained by drying with a dryer {130 ° C. to 230 ° C., wind speed 2 m / sec to 10 m / sec}.

  The water retention amount (g / g) of the absorbent resin particles of the present invention is preferably from 28 to 45, more preferably from 32 to 40, particularly preferably from 34 to 38, from the viewpoint of anti-fogging properties of the absorbent article. The water retention amount of the absorbent resin particles is measured by the following method.

<Measurement method of water retention amount of absorbent resin particles>
1.00 g of a measurement sample is put into 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% by weight). After being immersed in the inside for 1 hour without stirring, it was suspended for 15 minutes and drained. Thereafter, each tea bag is placed in a centrifuge, centrifuged at 150 G for 90 seconds to remove excess physiological saline, and the weight (h1) including the tea bag is measured to obtain the water retention amount from the following equation. In addition, the temperature of the used physiological saline and measurement atmosphere shall be 25 degreeC +/- 2 degreeC.
The weight of the tea bag after centrifugal dehydration is measured (h2) in the same manner as above except that no measurement sample is used.

  Water retention amount (g / g) = (h1)-(h2)

  The absorbent resin particles of the present invention can be used as an absorbent body together with a fibrous material. The structure and manufacturing method of the absorber are the same as those known in the art (Japanese Patent Laid-Open Nos. 2003-225565, 2006-131767, and 2005-097569, etc.). Moreover, it is preferable that this absorber comprises absorbent articles {paper diapers, sanitary napkins, etc.}. The manufacturing method and the like of the absorbent article are the same as known ones (Japanese Unexamined Patent Publication Nos. 2003-225565, 2006-131767, and 2005-097569, etc.).

  When the absorbent resin particle of the present invention is used as an absorbent body together with a fibrous material, the weight ratio of the absorbent resin particle composition to the fiber (weight of absorbent resin particle composition / weight of fiber) 40/60 to 70 / 30 is preferable, and more preferably 50/50 to 60/40.

  In the absorbent body of the present invention, the dropout rate of the absorbent resin particles after the vibration test is preferably 30% or less, more preferably 10% or less, from the viewpoint of absorption performance. In order to make this range, (B1) of the present invention described above may be used.

  Hereinafter, although an example and a comparative example explain the present invention further, the present invention is not limited to these. Unless otherwise specified, “part” means “part by weight” and “%” means “% by weight”. The absorption amount, water retention amount, and gel strength by the swelling volume measurement method of the absorbent resin particles were measured by the methods described above.

<Example 1>
Water-soluble vinyl monomer (a1-1) {acrylic acid, manufactured by Mitsubishi Chemical Corporation, purity 100%} 155 parts (2.15 mole parts), crosslinking agent (b1) {pentaerythritol triallyl ether, manufactured by Daiso Corporation } 0.6225 parts (0.0024 mole part) and 340.27 parts deionized water were kept at 3 ° C. with stirring and mixing. Nitrogen was introduced into the mixture to reduce the dissolved oxygen amount to 1 ppm or less, and then 0.62 part of 1% aqueous hydrogen peroxide solution, 1.1625 part of 2% aqueous ascorbic acid solution and 2% 2,2′-azobis [ 2.325 parts of 2-methyl-N- (2-hydroxyethyl) -propionamide] aqueous solution was added and mixed to initiate polymerization. After the temperature of the mixture reached 90 ° C., polymerization was carried out at 90 ± 2 ° C. for about 5 hours to obtain a hydrogel (1).
Next, hydrated this hydrogel (1) 502.27 parts with a mincing machine (12VR-400K manufactured by ROYAL), added and mixed 128.42 parts of 48.5% sodium hydroxide aqueous solution, followed by hydrophobicity 0.19 part of the substance (C-1) {Mg stearate, volume average particle size 8 μm} was added and mixed to obtain a chopped gel (1). Further, the chopped gel (1) was dried with a ventilation type band 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 Co., Ltd.), and then adjusted to a particle size of 150 to 710 μm using a 150 and 710 μm sieve to obtain dried particles. While stirring 100 parts of the dry particles (high-speed stirring turbulizer manufactured by Hosokawa Micron: rotation speed 2000 rpm), a 2% water / methanol mixed solution of ethylene glycol diglycidyl ether (water / methanol weight ratio = 70/30). 5 parts of was added while being sprayed and mixed, and left to stand at 150 ° C. for 30 minutes to cross-link the surface to obtain absorbent resin particles (B1-1). The weight average particle diameter of the absorbent resin particles (B1-1) was 395 μm, and the apparent density was 0.58 g / ml. When the surface shape was observed with a scanning electron microscope (SEM), the average number of pores per unit area was 33 / mm ² , and the number average pore size per absorbent resin particle was 30 μm. The ratio of the maximum pore diameter of the absorbent resin particles (B1-1) to the maximum particle diameter of (B1) (maximum pore diameter / resin particle diameter) was 0.25.

<Example 2>
Absorbent resin particles (B1-2) were obtained in the same manner as in Example 1 except that the “band dryer 150 ° C.” was changed to “230 ° C.”. The weight average particle diameter of the absorbent resin particles (B1-2) was 395 μm, and the apparent density was 0.56 g / ml. The average number of pores per unit area was 150 / mm ² , and the number average pore diameter per absorbent resin particle was 5 μm. The ratio of the maximum pore diameter of the absorbent resin particles (B1-2) to the maximum particle diameter of (B1-2) (maximum pore diameter / resin particle diameter) was 0.01.

<Example 3>
Absorbent resin particles (B1-3) were obtained in the same manner as in Example 1 except that “band dryer wind speed 2 m / s” was changed to “5 m / s”. The weight average particle diameter of the absorbent resin particles (B1-3) was 395 μm, and the apparent density was 0.56 g / ml. The average number of pores per unit area was 180 / mm ² , and the number average pore diameter per absorbent resin particle was 3 μm. The ratio of the maximum pore diameter of the absorbent resin particles (B1-3) to the maximum particle diameter of (B1-3) (maximum pore diameter / resin particle diameter) was 0.005.

<Example 4>
In the same manner as in Example 1, except that “hydrophobic substance (C-1) 0.19 part” was changed to “hydrophobic substance (C-1) 0.09 part”, absorbent resin particles (B1- 4) was obtained. The weight average particle diameter of the absorbent resin particles (3) was 410 μm, and the apparent density was 0.60 g / ml. The average number of pores per unit area was 110 / mm ² , and the number average pore diameter per absorbent resin particle was 20 μm. The ratio of the maximum pore diameter of the absorbent resin particles (B1-4) to the maximum particle diameter of (B1) (maximum pore diameter / resin particle diameter) was 0.10.

<Example 5>
“Hydrophobic substance (C-1) 0.19 part” is changed to “Hydrophobic substance (C-6) {Stearic acid sucrose ester (HLB = 3.0, manufactured by Mitsubishi Chemical Foods)} 0.19 part”. Absorbent resin particles (B1-5) were obtained in the same manner as in Example 1 except for the change. The weight average particle diameter of the absorbent resin particles (B1-5) was 390 μm, and the apparent density was 0.58 g / ml. The average number of pores per unit area was 45 / mm ² , and the number average pore diameter per absorbent resin particle was 8 μm. The ratio of the maximum pore diameter of the absorbent resin particles (B1-5) to the maximum particle diameter of (B1) (maximum pore diameter / resin particle diameter) was 0.015.

<Example 6>
"0.19 part of hydrophobic substance (C-1)" was changed to "hydrophobic substance (C-7) {glyceryl stearate (HLB = 3.8, manufactured by Kao Corporation)} 0.19 part" Except that, the absorbent resin particles (B1-6) were obtained in the same manner as in Example 1. The weight average particle diameter of the absorbent resin particles (B1-6) was 390 μm, and the apparent density was 0.58 g / ml. The average number of pores per unit area was 40 / mm ² , and the number average pore diameter per absorbent resin particle was 9 μm. The ratio of the maximum pore diameter of the absorbent resin particles (B1-6) to the maximum particle diameter of (B1) (maximum pore diameter / resin particle diameter) was 0.02.

<Example 7>
"Water-soluble vinyl monomer (a1-1) 155 parts (2.15 mole parts), crosslinking agent (b1) 0.6225 parts (0.0024 mole parts) and deionized water 340.27 parts" 155 parts (2.15 mole parts) of monomer (a1-1), cross-linking agent (b1) (0.0024 mole parts), 0.19 part of hydrophobic substance (C-1) 335.541 parts of deionized water " Absorbent resin particles (B1-7) were obtained in the same manner as in Example 1, except that the change was not made and "0.19 part of the hydrophobic substance (C-1)" was not used. The weight average particle diameter of the absorbent resin particles (B1-7) was 395 μm, and the apparent density was 0.59 g / ml. The average number of pores per unit area was 25 / mm ² , and the number average pore diameter per absorbent resin particle was 15 μm. The ratio of the maximum pore diameter of the absorbent resin particles (B1-7) to the maximum particle diameter of (B1) (maximum pore diameter / resin particle diameter) was 0.03.

<Comparative Example 1>
A solution prepared by dissolving 0.004 part of amino-modified silicone (Shin-Etsu Chemical Co., Ltd. product: KF354) in 80 parts of methanol was added to 40 parts of clay (ROCKWOOD ADDIIVES LIMITEDED: LAPONIPE XLG) and stirred at 25 ° C. for 2 minutes. Then, it dried at 60 degreeC * 1 hour, and obtained the material particle (F). The volume average particle diameter of the material particles (F) was 80 μm.

Next, in a glass reaction vessel, 77 parts of sodium acrylate, 22.85 parts of acrylic acid, 0.15 part of N, N′-methylenebisacrylamide and 293 parts of deionized water, dichlorotris (triphenylphosphine) ruthenium 0 0.001 part was charged, and the temperature of the contents was kept at 3 ° C. while stirring and mixing. After flowing nitrogen into the contents to make the dissolved oxygen amount 1 ppm or less, 0.3 part of 1% aqueous solution of hydrogen peroxide, 0.8 part of 0.2% aqueous solution of ascorbic acid and 2,2′-azobis Polymerization is started by adding and mixing 0.8 parts of a 2% aqueous solution of amidinopropane dihydrochloride, and after the reaction solution reaches 80 ° C., it is polymerized at a polymerization temperature of 80 ± 2 ° C. for about 5 hours. Gel (2) was obtained.
To 300 parts of hydrogel (2), 30 parts of material particles (F) and surfactant (1) (Sanyo Kasei Kogyo Co., Ltd .: Sanmorin OT70) 0.3 parts are added, and a mincing machine (hole diameter of the eye plate: 6 mm, After kneading for 5 minutes at 25 ° C. with 12VR-400K manufactured by Iizuka Kogyo Co., Ltd., it was dried with an air-flowing band dryer under conditions of 135 ° C. and a wind speed of 2.0 m / sec to obtain a dried polymer product.
The polymer dried product was pulverized with a juicer mixer (Osterizer BLENDER manufactured by Oster) and adjusted to a particle size of 150 to 710 μm using 150 and 710 μm sieves. 2 parts of a 10% water / methanol mixed solution of ethylene glycol diglycidyl ether (water / methanol weight ratio = 70/30) was added while being sprayed and mixed while the high-speed stirring turbulizer was rotated at 2000 rpm. Absorbent resin particles (H1) for comparison were obtained by allowing to stand at 140 ° C. for 30 minutes and crosslinking by heating. The weight average particle diameter of the absorbent resin particles (H1) was 395 μm, and the apparent density was 0.55 g / ml. The average number of pores per unit area was 0 / mm ² .

<Comparative example 2>
“Material part (E) 30 parts” was changed to “silicone beads (Toshiba Silicone Corp .: Tospearl average particle size 2 μm) 30 parts” and “Surfactant (1) (Sanyo Chemical Industries, Ltd .: Sanmorin OT70) ) 0.3 parts "was changed to" Surfactant (2) (Sanyo Kasei Kogyo Co., Ltd .: NAROACTY ID50) 0.3 parts "in the same manner as Comparative Example 1 except that the absorbent resin particles for comparison were used. (H2) was obtained. The weight average particle diameter of the absorbent resin particles (H2) was 400 μm, and the apparent density was 0.55 g / ml. The average number of pores per unit area was 0 / mm ² .

  About the absorptive resin particles obtained in Examples 1 to 7 and Comparative Examples 1 and 2, the measured physical properties {number average number of pores, number average pore diameter, maximum pore diameter / resin particle diameter, weight average Table 1 shows the particle diameter, the apparent density} and the performance evaluation result {water retention amount}.

  Subsequently, when the absorbent resin particle composition of this example was applied to an absorbent article, it was evaluated what absorption characteristics were exhibited. Using the absorbent resin particles obtained in Examples 1 to 7 and Comparative Examples 1 and 2, absorbent articles (paper diapers) were prepared as follows, and surface dryness by the SDME method after a drop test was performed. The values were evaluated and the results are shown in Table 2.

<Preparation of absorbent articles (paper diapers)>
100 parts of fluff pulp and 100 parts of an evaluation sample {absorbent resin particles} were mixed with an airflow type mixing apparatus {Pad former manufactured by Autech Co., Ltd.} to obtain a mixture. laminated on m ² and so as to uniformly acrylic plate (thickness 4 mm), and pressed for 30 seconds at a pressure of 5 kg / cm ^2, to obtain absorbent body (1). This absorbent body (1) is cut into a 10 cm × 40 cm rectangle, and water absorbent paper (basis weight 15.5 g / m ² , manufactured by Advantech, filter paper No. 2) having the same size as the absorbent body is arranged above and below each. Further, a paper diaper (1) was prepared by disposing a polyethylene sheet (polyethylene film UB-1 manufactured by Tamapoly Co., Ltd.) on the back surface and a non-woven fabric (basis weight 20 g / m ² , Eltas Guard manufactured by Asahi Kasei Co., Ltd.) on the surface. The weight ratio of the absorbent resin particles to the fibers (weight of the absorbent resin particles / weight of the fibers) was 50/50.

<Absorption resin particle dropout test using low tap test sieve shaker>
Using a low-tap test sieve shaker and a standard sieve (JIS Z8801-1: 2006), that is, place the absorbent on a 850 μm sieve and shake for 5 minutes on a low-tap test sieve shaker. The drop-off rate was determined from the weight of the absorbent resin particles dropped into the tray.

<Surface dryness value by SDME method>
A disposable diaper {artificial urine (0.03% by weight of potassium chloride, 0.08% by weight of magnesium sulfate, 0.88% by weight of sodium sulfate, 0.8% by weight of sodium chloride) in which the detector of the SDME (Surface Dryness Measurement Equipment) tester (manufactured by WK system) is sufficiently moistened. % And deionized water 99.09% by weight) and a paper diaper was soaked for 60 minutes. }, A 0% dryness value was set, and then the detector of the SDME tester was prepared by drying a paper diaper {paper diaper at 80 ° C. for 2 hours by heating. } Was set to 100% dryness, and the SDME tester was calibrated. Next, set a metal ring (inner diameter 70 mm, length 50 mm) in the center of the paper diaper to be measured, inject 80 ml of artificial urine, and absorb the artificial urine {until no gloss can be confirmed by artificial urine}, immediately Remove the metal ring, place three SDME detectors on the center of the paper diaper and its left and right sides (three locations at equal intervals of 10 cm from the end of the 40 cm paper diaper), and start measuring the surface dryness value, 5 minutes after the start of the measurement Were the surface dryness value (1) {center}, the surface dryness value (2) {left}, and the surface dryness value (3) {right}, respectively.
The artificial urine, measurement atmosphere, and standing atmosphere were 25 ± 5 ° C. and 65 ± 10% RH.

  As can be seen from Table 2, the absorbent articles using the absorbent resin particles of the present invention have surface dryness values (1), (2), () as compared to absorbent articles using comparative absorbent resin particles. 3) There was no bias and high dryness. That is, when the absorbent resin particles of the present invention are applied to absorbent articles, they have excellent absorption characteristics because they have good entanglement with the pulp and are not unevenly distributed in the absorbent body after the vibration test.

  The absorbent resin particle composition of the present invention can be applied to an absorbent comprising the absorbent resin particle composition and a fibrous material, and an absorbent article {paper diaper, sanitary napkin and It is useful for medical blood retention agents. In addition, pet urine absorbent, urine gelling agent for portable toilets, freshness preservation agent for fruits and vegetables, drip absorbent for meat and seafood, cooler, disposable warmer, battery gelling agent, water retention agent for plants and soil, dew condensation It can also be used in various applications such as inhibitors, water-stopping agents, packing agents and artificial snow.

Claims (10)

Absorbent resin particles comprising a water-soluble vinyl monomer (a1) and / or a hydrolyzable vinyl monomer (a2), and a crosslinked polymer (A1) having a crosslinking agent (b) as essential constituent units, and scanning type Absorbent resin particles having a number average number of pores per unit area of 1 to 200 / mm ² observed with an electron microscope and a number average pore diameter of 1 to 50 μm per absorbent resin particle (B1). The average of the ratio of the maximum pore diameter of the absorbent resin particles (B1) to the particle diameter of (B1) (maximum pore diameter / resin particle diameter) is 0.001 to 0.3. The absorbent resin particle as described. The absorbent resin according to claim 1 or 2, wherein the absorbent resin particles (B1) contain 0.01 to 10.0% by weight of the hydrophobic substance (C) based on the weight of the crosslinked polymer (A1). particle. The absorbent resin particle according to claim 3, wherein a part of the hydrophobic substance (C) is present on the surface of the absorbent resin particle. The absorbent resin particle according to claim 3 or 4, wherein the hydrophobic substance (C) comprises a hydrophobic part and a hydrophilic part, and has a melting point of 50C to 300C. Absorbent resin particles according to any one of claims 1 to 5, wherein the shape of the absorbent resin particles (B1) is irregularly crushed. The absorbent resin particle according to any one of claims 1 to 6, wherein an apparent density (g / ml) of the absorbent resin particle (B1) is 0.54 to 0.70. An absorbent comprising the absorbent resin particles according to any one of claims 1 to 7 and a fibrous material. The absorbent body according to claim 8, wherein a dropout rate of the absorbent resin particles after the vibration test is 30% or less. An absorbent article using the absorbent body according to claim 8 or 9.