JP2010241975A - Absorptive resin particle, and absorbing material and absorbing article containing the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an absorbing resin particle having a specific absorbing speed pattern and free from problems of conventional absorbing article (paper diaper etc.) using absorptive resin particles in which problems there occurs failure in complete absorption of liquid, and contact of unabsorbed liquid with a skin of a wearing person to cause rash etc., and to provide an absorbent article free from the problems of rash etc., by using the absorbing resin particle. <P>SOLUTION: The absorbing resin particle contains a crosslinked polymer (A) containing a water-soluble vinyl monomer (a1) and/or a hydrolyzable vinyl monomer (a2) and a crosslinking agent (b) as essential constitutional units, and has a contact angle of 20-100° between the absorbing resin particle and physiological saline. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

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

As an absorbent resin particle having an excellent absorption rate, an absorbent resin particle having a structure containing a part or all of a hydrophobic substance inside a crosslinked polymer is known (Patent Document 1).
Further, there is known an absorbent resin particle having improved powder flowability by adhering a hydrophobic substance to the surface of a crosslinked polymer (Patent Document 2).

However, with conventional absorbent resin particles and water-absorbing agents, the absorption rate over time after contact with the liquid to be absorbed (hereinafter referred to as an absorption rate pattern) is not appropriate. Specifically, the conventional absorbent resin particles have an absorption rate pattern (i) early early, medium normal, late normal (absorbent resin particles of Patent Document 1 above), (ii) early late, medium normal There is an absorptive resin particle of late ordinary (absorbent resin particle of the above-mentioned patent document 2).
When these absorbent resin particles are applied to an absorbent article (such as a paper diaper), in the absorbent body used in the absorbent article, the absorption rate of the absorbent resin is biased depending on the part of the absorbent body. It cannot be used effectively, and a problem such as blurring is likely to occur at the portion where the liquid to be absorbed remains, or the time during which the liquid that has not been absorbed in the entire absorber remains is increased.
Specifically, when the absorbent resin particles (i) are used, the liquid is rapidly absorbed at the site where the liquid to be absorbed comes into contact with the absorbent resin particles at the initial stage. However, the absorbent resin particles that have absorbed the liquid swell and become a gel, preventing the unabsorbed liquid from being diffused and absorbed in the absorber. As a result, there is a bias in the absorptivity in that the part where the liquid to be absorbed is in contact has a high absorptivity of the absorbent resin particles and the other part has a low absorptivity of the absorbent resin particles. And the time for which the liquid which was not absorbed stays in the site | part which the absorbed liquid contacted becomes long.
On the other hand, when the absorbent resin particles (ii) are used, the liquid is only gradually absorbed after contact with the absorbent resin particles at the site where the liquid to be absorbed comes into contact, and the liquid that is not absorbed is the absorbent article. As a result, the absorptivity of the absorbent resin particles tends to be equal at the site where the absorbed liquid is in contact with the other site. However, the absorption speed is generally slow, and the time during which the liquid that has not been absorbed in the entire absorber stays is increased.
And in the site | part where the liquid which was not absorbed stays long, there exists a problem that the wearer's skin which contacts the site | part tends to produce problems, such as a blur.

JP 2005-097569 A Japanese Patent Laid-Open No. 2004-261796

Absorbent articles (such as paper diapers) using conventional absorbent resin particles cannot completely absorb the liquid, and the liquid that could not be absorbed is likely to touch the wearer's skin and cause problems such as blurring. And the absorbent article which does not have such problems, such as a fog, and the absorbent resin particle which can be used for this are strongly desired.
An object of the present invention is to provide an absorbent resin particle having a specific absorption rate pattern, that is, an absorbent resin particle whose absorption rate pattern is initially slow, medium-term normal, and early late pattern. An object of the present invention is to provide an absorbent article that does not cause problems such as fogging as described above.

  As a result of intensive studies to achieve the above object, the present inventors have found that the above problems can be solved by controlling the contact angle of absorbent resin particles and physiological saline, and have reached the present invention.

  That is, the absorbent resin particles of the present invention contain a water-soluble vinyl monomer (a1) and / or a hydrolyzable vinyl monomer (a2), and a crosslinked polymer (A) having a crosslinking agent (b) as essential constituent units. The gist is that the contact angle between the absorbent resin particles and the physiological saline is 30 ° to 100 °.

  Moreover, the absorber of this invention makes it a summary to contain the said absorbent resin particle and a fibrous material.

  The gist of the absorbent article of the present invention is that it comprises the above-described absorbent body.

The absorbent resin particles of the present invention have a specific absorption rate pattern in which the absorption rate pattern is initially low, medium-term normal, and late early.
Therefore, when the absorbent resin particles of the present invention are applied to absorbent articles (paper diapers, sanitary napkins, etc.), there is no bias in the absorption rate, and excellent absorption performance (absorption amount and absorption rate) is exhibited, causing fogging. Hateful.

Front sectional drawing which showed typically the whole apparatus for measuring the amount of absorption by the swelling volume measuring method. The side projection figure which showed typically the bottomed cylinder 1 and the disk 2 for measuring the amount of absorption by the swelling volume measuring method. The top view which showed typically the disk 2 for measuring the amount of absorption by a swelling volume measuring method.

  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 crosslinked polymer (A) may be one type or a mixture of two or more types.

  The crosslinked polymer (A) can be prepared by known aqueous solution polymerization (adiabatic polymerization, thin film polymerization, spray polymerization method, etc .; JP-A-55-133413, etc.) 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 (A) when screened as necessary is preferably 100 to 800, more preferably 200 to 700, next preferably 250 to 600, particularly preferably 300 to 500, Most preferably, 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 (McGlow 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 (A) 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 (A) is not particularly limited, and examples thereof include an irregular crushed shape, a flake shape, a pearl shape, and a rice grain shape. Among these, from the viewpoint of good entanglement with the fibrous material in the use of paper diapers and the like and no fear of dropping off from the fibrous material, an irregular crushed shape is preferable.

  The crosslinked polymer (A) 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 of the present invention preferably further contain a hydrophobic substance (C). The content (% by weight) of the hydrophobic substance (C) is preferably 0.01 to 5.0, more preferably 0.08 to 5.0, particularly preferably based on the weight of the crosslinked polymer (A). Is 0.1 to 1.1. 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, long chain fatty acids and salts thereof, long chain fatty alcohols, and these Or a mixture of two or more thereof.

  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 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.

  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, heptafluorobenzene, nonafluorofluoroxylene, tridecafluorooctylbenzene and Heptadecafluorododecylbenzene, 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, pentafluoroethanoic 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 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). .

  Among the hydrophobic substances (C), from the viewpoint of the resistance to moisture of the absorbent article, etc., long-chain fatty acids and salts thereof, and hydrophobic substances having a polysiloxane structure are preferred, particularly preferably Mg stearate, They are Ca stearate, Zn stearate and Al stearate.

  In the case where the absorbent resin particle of the present invention contains the hydrophobic substance (C), the hydrophobic substance (C) may be contained in any way, but from the viewpoint of the resistance to moisture of the absorbent article. It is preferable that a part of the hydrophobic substance (C) is present on the surface of the absorbent resin particles and the rest is present inside.

When the absorbent resin particles comprise the hydrophobic substance (C), the absorbent resin particles are preferably produced by a method including any one of the following steps (1) to (6).
(1) Step of mixing or kneading the hydrophobic substance (C) and the hydrogel of the crosslinked polymer (A) (2) After mixing or kneading of the hydrophobic substance (C) and the hydrogel of the crosslinked polymer (A) The step of mixing the crosslinked polymer prepared by drying with heating the hydrophobic substance (C) {the initial (C) and the subsequent (C) may be the same or different. The same applies to the following (3), (5), and (6). }
(3) Mixing or kneading the hydrophobic substance (C) with the hydrogel of the crosslinked polymer (A) and then drying the crosslinked polymer prepared by drying the hydrophobic substance (C). Step (4) Polymerization of the structural unit in the presence of the hydrophobic substance (C) to obtain a crosslinked polymer hydrogel (5) Polymerization of the structural unit in the presence of the hydrophobic substance (C) followed by drying Step (6) of mixing the hydrophobic substance (C) with heating to the crosslinked polymer obtained by polymerizing the structural unit in the presence of the hydrophobic substance (C), followed by drying, followed by drying. A step of mixing a hydrophobic substance (C) when surface-crosslinking the coalescence

  In any step of (1) to (3), as the hydrophobic substance (C), a pulverized product of the hydrophobic substance (C) film, a bead, a rod, or a fiber 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 {for example, GE Toshiba Silicones, Inc .: Tospearl 120 (amorphous silicone resin fine powder, volume average particle size 2 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 (A) and the hydrophobic substance (C) is not limited as long as it is mixed so that a part of the hydrophobic substance (C) exists on the surface of the crosslinked polymer (A). .
However, the hydrophobic substance (C) is not a dried product of the crosslinked polymer (A), but is mixed with the hydrous gel of (A) or the polymer solution before polymerizing (A). From the viewpoint of being uniformly contained in (A), it is preferably mixed with the hydrogel of (A). In addition, it is preferable to mix uniformly so that mixing may be carried out.

  When the cross-linked polymer (A) is obtained by the aqueous solution polymerization method, the timing of mixing or kneading the hydrophobic substances (C) and (A) is not particularly limited, but during the polymerization step {in the presence of (C) , (A)}, immediately after the polymerization step, during crushing (minching) of the hydrogel, during drying of the hydrogel, after drying of the hydrogel, and the like. Among these, from the viewpoint of the anti-moisture resistance of the absorbent article, (C) is preferably kneaded immediately after the polymerization step and during the hydrated gel crushing (minced) step, more preferably the hydrated gel crushed (minced). ) Kneading during the process.

When the crosslinked polymer (A) is obtained by the reverse phase suspension polymerization method or emulsion polymerization, the timing of mixing the hydrophobic substance (C) and (A) is not particularly limited, but during the polymerization process {(C) In the presence of (1), immediately after the polymerization step, during the dehydration step (in 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 addition, when two or more types of hydrophobic substances (C) are used, from the viewpoint of anti-fogging properties of the absorbent article, the timing of mixing one of the hydrophobic substances (C) is to crush the hydrous gel (mince). The timing of mixing the other is preferably during the step of surface cross-linking after drying the hydrogel or after the surface cross-linking of the dried hydrogel, more preferably after the cross-linking of the dry hydrogel is there.

  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 steps (2) and (5), when the hydrophobic substance (C) is mixed with the crosslinked polymer while heating, the mixing temperature (° C.) is 150 ° C. or less, and the hydrophobic substance (C) It is preferable that it is melting | fusing point of + hydrophobic substance (C) +50 degreeC, More preferably, it is melting | fusing point of hydrophobic substance (C)-melting point of hydrophobic substance (C) +30 degreeC. Within this range, the hydrophobic substance (C) is uniformly present on the surface, and the anti-fogging property is further improved.

  In the method for producing the crosslinked polymer (A) in the presence of the hydrophobic substance (C), (C) is dissolved or emulsified (dispersed) in the polymer solution of the crosslinked polymer (A), (A) can also be manufactured, precipitating (C) with progress of superposition | polymerization of A). The polymerization method is the same as in the case of the crosslinked polymer (A) 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, it is preferable not to use an emulsifier). 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 (A) can be adopted.

When a solvent (including an organic solvent and / or water) is used for production of the absorbent resin particles, 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. It is. 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 moisture and the method for distilling off the solvent are the same as in the case of the crosslinked polymer (A).

The absorbent resin particles 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 (A).

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 (A) can be employed.

  The apparent density (g / ml) of the absorbent resin particles of the present invention 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 (A).

  The shape of the absorbent resin particles is not particularly limited, and examples thereof include an irregularly crushed shape, a flake shape, a pearl shape, and a rice grain shape. Among these, from the viewpoint of good entanglement with the fibrous material in the use of paper diapers and the like and no fear of dropping off from the fibrous material, an irregular crushed shape is preferable.

  The absorbent resin particles 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. 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 of the present invention may contain other additives (for example, known preservatives, fungicides, antibacterial agents, antioxidants, ultraviolet rays (for example, JP 2003-225565 A, JP 2006-131767 A). Absorbers, colorants, fragrances, deodorants, inorganic powders, organic fibrous materials, etc.}. When these additives are contained, the content (% by weight) of the additive is preferably 0.01 to 5, more preferably 0.08 to 5, particularly preferably based on the weight of the crosslinked polymer (A). Preferably it is 0.1-3, Most preferably, it is 0.1-0.5.

  The contact angle (°) of the absorbent resin particles of the present invention with physiological saline is 20 ° to 100 °, preferably 25 ° to 80 °, more preferably 30 ° to 60 °. When the contact angle is less than 20 °, when the absorbent resin particles are used for absorbent articles (diapers, etc.), the initial absorption rate is too fast and spot absorption is performed, resulting in poor anti-blurring property. If it exceeds 100 °, the absorption speed is too slow and the anti-fogging property is deteriorated. The contact angle between the absorbent resin particles and physiological saline is measured by the following method.

<Measurement method of contact angle between absorbent resin particles and physiological saline>
The particle size was adjusted to a plastic petri dish with an inner diameter of 8.5 cm and a height of 1.2 cm placed on a horizontal table (particles having a particle diameter of 500 to 710 μm were 20% by weight, particles having a particle diameter of 300 to 500 μm were 55% by weight. %, Particles having a particle diameter of 150 to 300 μm are 25 wt%) are poured into the petri dish so that the particles overflow. Next, a horizontal surface formed of absorbent resin particles on the upper side of the petri dish is produced by scraping along the upper side of the petri dish using a bar having a flat bottom surface. One drop (about 0.02 g) of physiological saline is dropped using a dropper at the center of the horizontal surface of the absorbent resin particles. The time measurement is started from the time when the absorbent resin particles and the physiological saline are in contact with each other, and the contact angle between the horizontal surface of the absorbent resin particles and the physiological saline after 0.2 seconds is defined as the contact angle. The contact angle was measured using a video image taken from the side of the horizontal surface of the absorbent resin particles in which the physiological saline is dripped onto the center of the horizontal surface. Do it. The contact angle is determined using the θ / 2 method. In addition, when the dropped droplet is absorbed by the absorbent resin and no droplet exists on the horizontal surface after 0.2 seconds, the contact angle is set to 0 °.
The θ / 2 method is a known method, and an angle between a straight line connecting one of the left and right end points of the droplet and the vertex of the droplet and the horizontal surface is θ / 2, In this method, the contact angle is obtained by doubling the θ / 2 value.
The measurement is performed in a room at 25 ± 2 ° C. and humidity 50 ± 10%.

  The contact angle between the absorbent resin particles and physiological saline can be controlled by adjusting the amount of the hydrophobic substance (C) present on the surface of the absorbent resin particles. When the contact angle is small, the contact angle can be increased by increasing the amount of (C) present on the surface by increasing the amount of the hydrophobic substance (C) mixed with the absorbent resin particles. If the contact angle is large, the contact angle is increased by reducing the amount of (C) present on the surface by a method such as reducing the amount of the hydrophobic substance (C) mixed with the absorbent resin particles. be able to.

In the swelling volume measurement method for physiological saline per gram of the absorbent resin particles of the present invention, the time until the swelling volume reaches 5 ml (initial absorption rate, t1) is preferably 20 seconds to 60 seconds, Preferably, it is 20 seconds to 50 seconds, and most preferably 30 seconds to 40 seconds. Moreover, it is preferable that the time until the swelling volume reaches 20 ml (mid-term absorption rate, t2) is 60 seconds to 150 seconds. The time until the swelling volume reaches 40 ml (late absorption rate t3) is preferably 150 to 600, more preferably 150 to 500, and most preferably 150 to 400. Within these ranges, the anti-fogging property of the absorbent article is further improved.
Adjusting the content of the hydrophobic substance (C), the contact angle between the absorbent resin particles and physiological saline, the apparent density of the absorbent resin particles, the weight average particle diameter of the absorbent resin particles, and the like to the above preferred ranges. Thus, the amount of absorption by the swelling volume measurement method can be adjusted to a preferred range.

  The swelling volume measurement method is a measurement method performed using the apparatus shown in FIG. 1 in a room at 25 ± 2 ° C. and a humidity of 50 ± 10%. The temperature of the physiological saline used is 25 ° C. ± 2 ° C.

The apparatus shown in FIG. 1 comprises an acrylic bottomed cylinder 1 and an acrylic disk 2.
The bottomed cylinder 1 is a bottomed cylinder having a bottom at one opening of a cylinder having an inner diameter of 81 mm and a length of 35 mm, and the other one being open.
The acrylic disk 2 is a disk having an outer diameter of 80.5 mm and a thickness of 12 mm. The disk 2 has a circular recess having a diameter of 70.5 mm and a depth of 4 mm at a position where the center of the disk coincides with the center of the circle. In the disk 2, a circular cylinder having a length of 13 mm and an outer diameter of 15 mm as a handle is located at a position where the center of the disk 2 coincides with the center of the bottom surface of the cylinder.
Furthermore, the disk 2 is made up of 64 holes having a diameter of 2 mm that are radially formed (see FIG. 3). The hole of the disk 2 will be described. There are five holes each having a diameter of 2 mm at equal intervals of 5 mm between the position of 10 mm from the center of the disk and the position of 30 mm on the bisector of the disk (total of 40 holes). In addition, three holes with a diameter of 2 mm are present at equal intervals of 5 mm on a bisector inclined at 22.5 ° from the above-mentioned bisector, between 20 mm and 30 mm from the center of the disk. 24 in total).
The weight of the disk 2 is 60 g ± 5 g.

<Measurement method of swelling volume>
2.5 g of a measurement sample (moisture content of 8% or less) sieved to a particle diameter of 150 to 850 μm is placed in a vertically standing cylinder 1 so as to have a substantially uniform thickness at the bottom of the bottomed cylinder 1. 2 is placed so that the handle of the cylinder is on top, and the distance from the bottom surface of the cylinder to the top surface of the handle of the disk is measured using a thickness meter (for example, Digimatic Indicator ID-F150 manufactured by Mitutoyo). At this time, the weight of the measuring rod of the digimatic indicator is 140 g ± 10 g, and the pressure applied to the absorbent resin particles is 3.9 ± 0.3 g / cm ² because the weight of the measuring rod and the disk 2 is applied. Next, the display of the thickness of the Digimatch indicator is set to zero. Subsequently, 120 ml of physiological saline is introduced into the bottomed cylinder 1 within 2 seconds. The time for starting the charging is set to 0, and the distance H (cm) at which the disk 2 is intermittently raised is recorded. The absorption amount of the absorbent resin particles after the elapse of a predetermined time from the start of water absorption is determined by the following formula.

The same measurement is performed 5 times, and the average value is taken as the measured value. The means for measuring the distance by which the disk 2 is raised is not particularly limited as long as the pressure applied to the absorbent resin particles at the time of measurement is 3.9 ± 0.3 g / cm ² .

  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 to the fiber (weight of absorbent resin particle / weight of fiber) is preferably 40/60 to 70/30, More preferably, it is 50 / 50-60 / 40.

  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”. In addition, the absorption amount by the swelling volume measuring method of an absorptive resin particle, the amount of water retention, and the contact angle with the physiological saline were measured by the method mentioned 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 1.9 parts of the substance (C-1) {Tospearl 120 (amorphous silicone resin fine powder, volume average particle size 2 μm)} were added and mixed to obtain a chopped gel (2). Further, the chopped gel (2) was dried with a ventilation band dryer {150 ° C., wind speed 2 m / sec} to obtain a dried product. After the dried product was pulverized with a juicer mixer (Osterizer BLENDER manufactured by Oster), dried particles were obtained by adjusting the particle size to 150 to 710 μm using a sieve having an opening of 150 and 710 μm. 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 were added while being sprayed and mixed, and the mixture was allowed to stand at 150 ° C. for 30 minutes for surface crosslinking to obtain dry resin particles. To this dry resin particle, 0.01 part of a hydrophobic substance (C-2) {stearic acid, particle diameter of about 1 mm} was added, and a bench kneader (PNV-1 manufactured by HITACHI) was used at 80 ° C. for 30 minutes. Absorbing resin particles (1) were obtained by stirring. The weight average particle diameter of the absorbent resin particles (1) was 400 μm, and the apparent density was 0.58 g / ml. Moreover, the contact angle of the absorbent resin particles with physiological saline was 30 °.

<Example 2>
In the same manner as in Example 1 except that the “hydrophobic substance (C-2) 0.01 part” was changed to “hydrophobic substance (C-2) 0.03 part” in Example 1, the present invention Absorbent resin particles (2) were obtained. The weight average particle diameter of the absorbent resin particles (2) was 400 μm, and the apparent density was 0.58 g / ml. Moreover, the contact angle of the absorbent resin particles with physiological saline was 40 °.

<Example 3>
In the same manner as in Example 1, except that 0.01 part of “hydrophobic substance (C-2)” was changed to “0.1 part of hydrophobic substance (C-2)” in Example 1, the present invention Absorbent resin particles (3) were obtained. The weight average particle diameter of the absorbent resin particles (3) was 400 μm, and the apparent density was 0.58 g / ml. Moreover, the contact angle of the absorbent resin particles with physiological saline was 60 °.

<Example 4>
In Example 1, except that “1.9 parts of hydrophobic substance (C-1)” was changed to “0.19 parts of hydrophobic substance (C-1)”, the present invention was similar to Example 1. Absorbent resin particles (4) were obtained. The weight average particle diameter of the absorbent resin particles (4) was 400 μm, and the apparent density was 0.60 g / ml. Moreover, the contact angle of the absorbent resin particles with physiological saline was 30 °.

<Example 5>
In Example 1, 1.9 parts of “hydrophobic substance (C-1)” was changed to “1.9 parts of hydrophobic substance (C-3) {Mg stearate}”, and hydrophobic substance (C -2) and the absorbent resin particles (5) of the present invention in the same manner as in Example 1 except that the operation of stirring at 80 ° C. for 30 minutes using a bench kneader was not performed. Got. The weight average particle diameter of the absorbent resin particles (5) was 400 μm, and the apparent density was 0.60 g / ml. Moreover, the contact angle of the absorbent resin particles with physiological saline was 60 °.

<Example 6>
In Example 5, except that “1.9 parts of hydrophobic substance (C-3)” was changed to “5.7 parts of hydrophobic substance (C-3)”, the present invention was carried out in the same manner as in Example 5. Absorbent resin particles (6) were obtained. The weight average particle diameter of the absorbent resin particles (6) was 400 μm, and the apparent density was 0.60 g / ml. The contact angle of the absorbent resin particles with physiological saline was 80 °.

<Example 7>
Preparatory Step 145.4 parts of acrylic acid was diluted with 9.4 parts of water and neutralized by adding 242.3 parts of 25% aqueous sodium hydroxide while cooling to 20-30 ° C. After 0.09 part of ethylene glycol diglycidyl ether (manufactured by Nagase Kasei Kogyo Co., Ltd., Denacol EX-810), 0.0146 part of sodium hypophosphite monohydrate, and potassium persulfate are uniformly dissolved in this solution. A monomer aqueous solution (1) was obtained by adding 1.45 parts of a hydrophobic substance (C-1).
Next, in a reaction vessel equipped with a stirrer, a reflux condenser, a thermometer, and a nitrogen gas introduction tube, 624 parts of cyclohexane is added and 1.56 parts of sorbitan monostearate is added and dissolved therein, followed by stirring. While replacing with nitrogen.

・ Process (1)
Subsequently, after the temperature in the reaction vessel was raised to 70 ° C., 397 parts of the monomer aqueous solution (1) was added dropwise at 6.6 parts / min over 60 minutes while maintaining the temperature at 70 ° C. Thereafter, aging was performed at 75 ° C. for 30 minutes to obtain an aqueous solution containing the absorbent resin precursor (1).

・ Process (2)
Thereafter, the water content of the aqueous solution containing the absorbent resin precursor (1) is about 20% by azeotropic distillation of water and cyclohexane (infrared moisture meter (FD-100 type, manufactured by Kett, 180 ° C., 20 minutes). When the stirring was stopped after cooling to 30 ° C., the resin particles settled, and the resin particles and cyclohexane were separated by decantation. The resin particles were dried until the water content was 20% or less, and 0.013 part of a 1% aqueous solution of ethylene glycol diglycidyl ether (manufactured by Nagase Kasei Kogyo Co., Ltd., Denacol EX-810) was sprayed on the resin particles at 80 parts. The surface cross-linking reaction was carried out for 1 hour, followed by further drying at 110 ° C. to obtain a powdery absorbent resin.The powdery absorbent resin particles were combined with a hydrophobic substance (C-2). {Stearic acid, particle diameter of about 1 mm} 0.024 part was added and stirred for 30 minutes at 80 ° C. using a bench kneader (PNV-1 manufactured by HITACHI), whereby the absorbent resin particles (7 The weight average particle diameter of the absorbent resin particles (7) was 400 μm, the apparent density was 0.60 g / ml, and the contact angle of the absorbent resin particles with physiological saline was 40. °.

<Example 8>
In Example 7, the “hydrophobic substance (C-1) 1.45 parts” was changed to “hydrophobic substance (C-3) 1.45 parts”, and the “hydrophobic substance (C-2) was changed to Absorbent resin particles (8) of the present invention were obtained in the same manner as in Example 7 except that they were not used, and the weight average particle diameter of the absorbent resin particles (8) was 400 μm and the apparent density was 0. The contact angle between the absorbent resin particles and the physiological saline was 60 °.

<Example 9>
In Example 1, "155 parts (2.15 parts by mole) of water-soluble vinyl monomer (a1-1), 0.6225 parts (0.0024 parts by mole) of crosslinking agent (b1) and 340.27 parts of deionized water""Water-soluble vinyl monomer (a1-1) 155 parts (2.15 mole parts), crosslinking agent (b1) 0.6225 parts (0.0024 mole parts), hydrophobic substance (C-3) 1.55 parts And deionized water 335.541 parts "and the absorptivity of the present invention was the same as in Example 1 except that" hydrophobic substance (C-2) 0.019 part "was not used. Resin particles (9) were obtained. The weight average particle diameter of the absorbent resin particles (9) was 400 μm, and the apparent density was 0.59 g / ml. Moreover, the contact angle of the absorbent resin particles with physiological saline was 60 °.

<Comparative Example 1>
A solution prepared by dissolving 0.004 parts of amino-modified silicone (Shin-Etsu Chemical Co., Ltd. product: KF354) in 80 parts of methanol was added to 40 parts of clay (manufactured by ROCKWOODS ADDIIVES LIMITEDD: LAPONITE 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, 293 parts of deionized water, and 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 (1) was obtained.
7.6 parts of the material particles (F) and 0.3 part of the surfactant (1) (Sanyo Kasei Kogyo Co., Ltd .: Sanmorin OT70) are added to 300 parts of the hydrous gel (1). After kneading at 6 mm, 12 VR-400K manufactured by Iizuka Kogyo Co., Ltd. for 5 minutes at 25 ° C., the mixture was dried with an aeration-type 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 390 μm, and the apparent density was 0.55 g / ml. Moreover, the contact angle of the absorbent resin particles with physiological saline was 0 °.

<Comparative example 2>
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 bring 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 an aqueous solution of 2-methyl-N- (2-hydroxyethyl) -propionamide] 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, while adding 502.27 parts of this hydrous gel (1) with a mincing machine (12VR-400K, manufactured by ROYAL), 128.42 parts of 48.5% sodium hydroxide aqueous solution was added and mixed to obtain a chopped gel. (2) was obtained. Further, the chopped gel (2) was dried with a ventilation band dryer {150 ° C., wind speed 2 m / sec} to obtain a dried product. After the dried product was pulverized with a juicer mixer (Osterizer BLENDER manufactured by Oster), dried particles were obtained by adjusting the particle size to 150 to 710 μm using a sieve having an opening of 150 and 710 μm. 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 the mixture was allowed to stand at 150 ° C. for 30 minutes to crosslink the surface to obtain comparative absorbent resin particles (H2). The weight average particle diameter of the absorbent resin particles (H2) was 400 μm, and the apparent density was 0.61 g / ml. Moreover, the contact angle of the absorbent resin particles with physiological saline was 0 °.

<Comparative Example 3>
Bench type kneader (PNV-1 manufactured by HITACHI) by adding 19 parts of hydrophobic substance (C-2) {stearic acid, particle diameter of about 1 mm} to the absorbent resin particles (H2) obtained in Comparative Example 2 For 30 minutes at 80 ° C. to obtain comparative absorbent resin particles (H3). The weight average particle diameter of the absorbent resin particles (H3) was 400 μm, and the apparent density was 0.61 g / ml. Further, the contact angle of the absorbent resin particles with physiological saline was 110 °.

<Comparative example 4>
Absorbent resin particles (H4) for comparison were obtained according to Example 1 of JP2007-291351. The weight average particle diameter of the absorbent resin particles (H4) was 400 μm, and the apparent density was 0.70 g / ml. Moreover, the contact angle of the absorbent resin particles with physiological saline was 5 °.

  About the absorptive resin particles obtained in Examples 1 to 9 and Comparative Examples 1 to 4, measured physical properties {weight average particle diameter, apparent density}, content of hydrophobic substance (C) and evaluation results {water retention amount Table 1 shows the contact angle with physiological saline and the method for measuring the swelling volume. In addition, content (%) of hydrophobic substance (C) shows content (weight%) based on the weight of a crosslinked polymer (A).

The absorbent resin particles (Examples 1 to 9) of the present invention have a contact angle within a range of 20 ° to 100 °, and are appropriate contact angles. On the other hand, the absorbent resin particles of the comparative example have a contact angle that is not within this range and is not an appropriate contact angle.
As can be seen from Table 1, the absorbent resin particles (Examples 1 to 9) of the present invention have values in the range of t1 from 20 seconds to 60 seconds, t2 from 60 seconds to 150 seconds, and t3 from 150 to 600 seconds. The absorption rate pattern is appropriate. On the other hand, t1 and t3 are not in the above range in Comparative Example 1, t1 is not in the above range in Comparative Example 2, t2 and t3 are not in the above range in Comparative Examples 3 and 4, and the absorption rate pattern is not appropriate. .
Subsequently, when the absorption rate pattern was appropriate, it was evaluated what absorption characteristics were exhibited when applied to an absorbent article. Using the absorbent resin particles obtained in Examples 1 to 9 and Comparative Examples 1 to 4, absorbent articles (paper diapers) were prepared as follows, and the surface dryness value by the SDME method was evaluated. Are shown in Table 2.

<Preparation 1 of absorbent article (paper diaper)>
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.

<Preparation 2 of absorbent article (paper diaper)>
Preparation of absorbent article (paper diaper) 1 except that “100 parts fluff pulp and 100 parts evaluation sample {absorbent resin particles}” were changed to “80 parts fluff pulp and 120 parts evaluation sample {absorbent resin particles}” The paper diaper (2) was adjusted in the same manner as described above. The weight ratio of absorbent resin particles to fibers (weight of absorbent resin particles / weight of fiber) was 60/40.

<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 (1-1) {center}, the surface dryness value (1-2) {left}, and the surface dryness value (1-3) {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 article using the absorbent resin particles of the present invention has a surface dryness value (1-1), (1- 2) and (1-3) were excellent with no bias. That is, the absorbent resin particles of the present invention had a specific absorption rate pattern and excellent absorption characteristics when applied to absorbent articles. Therefore, even if an absorbent article to which the absorbent resin particles of the present invention are applied is used, it is easily predicted that there is no concern about blurring or the like.

  The absorbent resin particles of the present invention can be applied to an absorbent body containing absorbent resin particles and a fibrous material, and absorbent articles {paper diapers, sanitary napkins, and medical blood retaining bodies comprising the absorbent body. It is useful for the agent}. 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.

DESCRIPTION OF SYMBOLS 1 Bottomed cylinder 2 Disc 3 Absorbent resin particle 4 Digimatic indicator thickness measurement bar 5 Digimatic indicator thickness display 6 Digimatic indicator base

Claims (8)

A water-soluble vinyl monomer (a1) and / or a hydrolyzable vinyl monomer (a2), and a cross-linked polymer (A) having a cross-linking agent (b) as an essential constituent unit, absorbent resin particles and physiological saline Absorbent resin particles having a contact angle of 20 ° to 100 °. Furthermore, the absorptive resin particle of Claim 1 which contains 0.01-5.0 weight% of hydrophobic substances (C) based on the weight of a crosslinked polymer (A). The absorbent resin particle according to claim 2, 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 2 or 3, wherein the hydrophobic substance (C) is a long-chain fatty acid (salt). The absorbent resin particle according to any one of claims 2 to 4, wherein the hydrophobic substance (C) is Mg stearate or stearic acid. The absorbent resin particle according to any one of claims 1 to 5, wherein the absorbent resin particle has an irregular crushed shape. An absorbent comprising the absorbent resin particles according to any one of claims 1 to 6 and a fibrous material. An absorbent article using the absorber according to claim 7.

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