JP2012012469A - Absorptive resin particle, and absorber and absorptive article containing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To solve such a problem that, in conventional absorptive resin particles, absorption performance of the absorptive resin particles, which has been increased by virtue of modification of proximity to surfaces, is impaired as a result of destruction in the proximity to surfaces in a production process of an absorptive article because the conventional technology for controlling a water content does not sufficiently prevent the destruction in the proximity to surfaces of the absorbing resin particles.SOLUTION: The absorptive resin particle includes a crosslinked polymer (A) including a water-soluble vinyl monomer (a1) and/or a hydrolyzable vinyl monomer (a2) and a crosslinking agent (b) as indispensable constituent units and a destruction inhibitor (c), wherein the water content is 3-20%.

Description

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

As an absorbent resin particle, for example, an absorbent resin particle having a modified particle brittleness having a moisture content of 3 to 9% and a breaking stress of the particle of 30 N / m ² or more is known (Patent Document). 1).
Further, an absorptive resin in which amorphous silica particles are added, the water content is 10 to 20%, and the particle diameter retention before and after the particle collision test is 90% or more is known. (See Patent Document 2).
On the other hand, for the purpose of improving the absorption characteristics of the absorbent resin, absorption near the surface of the absorbent resin particles is heat-crosslinked with a crosslinking agent having two or more functional groups capable of reacting with acrylic acid and / or acrylate. There are absorbent resins and absorbent resins with inorganic or organic powders attached to the surface.
By the way, when the absorbent resin particles are used for absorbent articles, for example, mechanical powder transportation by a screw conveyor or a spring conveyor or powder transportation by air pressure, powder dispersion or supply by a screw feeder, etc., spraying by air pressure The absorbent article is manufactured through processes such as these.

JP-A-9-124879 Republished 2008/015980

In the manufacturing process of the above absorbent article, the surface of the absorbent resin particle is broken or the inorganic or organic powder attached to the surface is peeled off due to collision of particles, collision of particles against the wall of a machine or equipment, mechanical friction, etc. Falling occurs. As a result, the effects of surface cross-linking and adhesion of inorganic / organic powders are impaired, the absorption performance of the absorbent resin is lowered, and the performance of the absorbent article such as anti-blur and anti-moisture resistance is a problem.
That is, the conventional technology for adjusting the moisture content is not sufficient to prevent the vicinity of the surface of the absorbent resin particles from being broken, and the conventional surface of the absorbent resin particles is broken in the manufacturing process of the absorbent article. As a result, the absorption performance of the absorbent resin particles that has been improved by the modification in the vicinity of the surface is impaired.

The absorbent resin particle of the present invention comprises a crosslinked polymer (A) comprising water-soluble vinyl monomer (a1) and / or hydrolyzable vinyl monomer (a2) and crosslinking agent (b) as essential constituent units, and a breakage preventing agent. The point is that the moisture content is 3 to 20%.
The gist of the absorbent body of the present invention is that it contains the absorbent resin particles and the fibrous material.
The gist of the absorbent article of the present invention is that the absorbent body is used.

  The absorbent resin particles of the present invention are less likely to break near the surface even after being subjected to mechanical impact, and can maintain high absorption performance.

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.) or known reverse phase suspension polymerization (JP-B-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 distillation is preferably from 3 to 20, more preferably from 3.5 to 10, particularly preferably from 4 to 9, based on the weight of the crosslinked polymer. Most preferably, it is 4.5-8. Within this range, the absorption performance and the breakability of the absorbent resin particles after drying are further improved.

  In addition, the content and water content of the organic solvent are infrared moisture measuring devices {JE400 manufactured by KETT Co., Ltd .: 120 ± 5 ° C., 30 minutes, atmospheric humidity before heating 50 ± 10% RH, lamp specification 100V, It is calculated | required from the weight loss of the measurement sample before and behind heating when heated by 40W}.

  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, and the like 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 (Mac Glow Hill Book, 1984). , Page 21). That is, JIS standard sieves are combined in the order of 1000 μm, 850 μm, 710 μm, 500 μm, 425 μm, 355 μm, 250 μm, 150 μm, 125 μm, 75 μm and 45 μm, and a tray from the top. About 50 g of the measured particles are put in the uppermost screen and shaken for 5 minutes with a low-tap test sieve shaker. Weigh the measured particles on each sieve and 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 cross-linked polymer (A) may be surface-crosslinked with a surface cross-linking agent as necessary. Examples of the surface cross-linking agent include polyvalent glycidyl described in JP-A No. 59-189103 and JP-A No. 58-180233. And polyhydric alcohols, polyhydric amines, polyhydric aziridines and polyhydric isocyanates described in JP-A No. 61-16903 and JP-A No. 61-212305 or JP-A No. 61-252212. And the polyvalent metals described in JP-A Nos. 51-136588 and 61-257235, and the like. Of these surface cross-linking agents, polyvalent glycidyl, polyvalent amine and silane coupling agent are preferable from the viewpoint of absorption characteristics and breakability of absorbent resin particles, more preferably polyvalent glycidyl and silane coupling agent, Polyvalent glycidyl is preferred. Among polyvalent glycidyl, ethylene glycol diglycidyl ether and glycerin diglycidyl ether are preferable, and ethylene glycol diglycidyl ether is particularly preferable.

  The content (% by weight) of the surface crosslinking agent is preferably from 0.01 to 0.10, more preferably from 0.03 to 0.00, based on the weight of the crosslinked polymer (A) from the viewpoint of absorption performance and the like. 8, particularly preferably 0.05 to 0.06.

  When performing surface crosslinking, the surface crosslinking method may be a known method {for example, the method disclosed in JP-A No. 13-2935, JP-A No. 2003-147005, or JP-A No. 2003-165883}. Can do.

  The surface crosslinking may be performed by repeating the above surface crosslinking twice or more. That is, the absorbent resin particles obtained by surface cross-linking with a surface cross-linking agent can be subjected to additional surface cross-linking with the same or different surface cross-linking agents. The content of the additional surface crosslinking agent, the treatment method, the treatment temperature, the treatment time, etc. are the same as in the above case.

  The anti-breaking agent (c) includes a liquid at 40 ° C. The viscosity (mPa · s) at 40 ° C. of the anti-breaking agent (c) is preferably 10 to 4000, more preferably 100 to 3000, and particularly preferably 500 to 2000. Within this range, the breakage prevention property of the absorbent resin is further improved.

The SP value of the anti-breaking agent (c) is preferably 7 to 18, more preferably 8 to 17, particularly preferably 10 to 16. Within this range, the breakage prevention property of the absorbent resin is further improved. The SP value is generally used as a factor expressing the polarity of the compound. In the present invention, the SP value of the solvent described in Polymer Handbook 3rd edition (issued by WILEY INTERSCIENCE) VII-527 to 539 [( cal / cm ³ ) ^1/2 ], and for substances not listed in this table, the Hoy cohesive energy described in VII-525 in the Small formula of VII-524 of the same handbook The value δ [(cal / cm ³ ) ^1/2 ] derived by substituting constants shall be applied.

  The boiling point of the anti-breaking agent (c) is preferably 80 to 400 ° C, more preferably 90 to 350 ° C, particularly preferably 100 to 300 ° C. Within this range, the breakage prevention property of the absorbent resin is further improved.

  Examples of the anti-breaking agent (c) include C2-C10 polyhydric (2-6 valent) alcohol (c1), oxyethylene-containing compound (c2), oxypropylene-containing compound (c3) and ester (c4). included.

  Examples of the polyvalent (2-6 valent) alcohol (c1) having 2 to 10 carbon atoms include ethylene glycol, diethylene glycol, propylene glycol, glycerin, pentaerythritol, 1,4-butanediol, 1,6-hexanediol, 1, Examples include 10-decanediol, diglycerin, and triglycerin.

As the oxyethylene-containing compound (c2), an ethylene oxide 1-8 mol adduct (c21) of alcohol can be used.
The addition number (mole) of ethylene oxide is preferably from 1 to 8, more preferably from 1 to 6, particularly preferably from 1 to 4, and most preferably from 1 to 3, and most preferably from the viewpoint of absorption performance. Is 1 or 2.
Examples of the alcohol include polyvalent (2 to 5 valent) alcohols having 6 to 10 carbon atoms, polyvalent (2 to 6 valent) alcohols having 2 to 5 carbon atoms, and the like.
Examples of the polyhydric (2-5 pentavalent) alcohol having 6 to 10 carbon atoms include 1,6-hexanediol, 1,10-decanediol, diglycerin, and triglycerin.
Examples of the polyhydric (2-6 valent) alcohol having 2 to 5 carbon atoms include ethylene glycol, diethylene glycol, propylene glycol, glycerin, pentaerythritol and 1,4-butanediol.

As the oxypropylene-containing compound (c3), there can be used a propylene oxide 1-20 mol adduct (c31) of alcohol and a propylene oxide 1-20 mol adduct (c32) of the above oxyethylene-containing compound.
The addition number (mol) of propylene oxide is preferably 1 to 20, more preferably 2 to 18, particularly preferably 3 to 17, and most preferably 4 to 16, most preferably in one molecule from the viewpoint of absorption performance. Preferably it is 5-15.
Examples of the alcohol include monohydric alcohols having 1 to 9 carbon atoms in addition to the above alcohols.
Examples of the monohydric alcohol having 1 to 9 carbon atoms include methanol, ethanol, n-propyl alcohol, isopropyl alcohol, n-butyl alcohol, isobutyl alcohol, sec-butyl alcohol, tert-butyl alcohol, n-hexanol, and n-pentanol. , 2-ethylhexanol, n-octanol and the like.

As the ester (c4), an organic acid {monovalent carboxylic acid, polyvalent (2-6 valent) carboxylic acid, etc.} or inorganic acid {sulfuric acid, phosphoric acid, etc.}, the aforementioned monohydric alcohol, polyvalent (2- Hexavalent alcohols, ester compounds of alcohols with ethylene oxide adducts or alcohol propylene oxide adducts, and the like can be used.
Specific examples of (c4) include butyl acetate and ethylene glycol acetic acid diester.
These ester compounds are not limited as long as they have at least one ester bond, and (c4) includes a carboxylate group {alkali metal (sodium, potassium, etc.) ions etc. as counter ions}. You may go out.

  Among these anti-breaking agents (c), from the viewpoint of anti-breaking properties, polyvalent (2-6 valent) alcohols (c1) and oxyethylene-containing compounds (c2) having 2 to 10 carbon atoms are preferable, and more preferably (C1) is preferred.

  The content of the anti-breaking agent (c) is preferably 0.1 to 1.0% by weight, more preferably 0.15 to 0.95, particularly preferably 0, based on the weight of the crosslinked polymer (A). .2 to 0.9, most preferably 0.3 to 0.8. Within this range, the breakage prevention property of the absorbent resin is further improved.

  The anti-breaking agent (c) can be used in a form dissolved and / or emulsified in water and / or a volatile solvent. 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.) and C3-C5 esters (ethyl formate, ethyl acetate, isopropyl acetate, diethyl carbonate, etc.) and the like. When using water and / or a volatile solvent, from the viewpoint of dryness (ease of volatilization), the amount (% by weight) of these used is 1 to 900 based on the weight of the anti-breaking agent (c). More preferably, it is 5-700, Most preferably, it is 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.

As a method of incorporating the breakage preventive agent (c) into the absorbent resin particles, it is preferable to attach (c) to part or all of the surface of the crosslinked polymer (A) from the viewpoint of breakage prevention. A method of spraying (c) onto the polymer (A) and a method of dipping the crosslinked polymer (A) into (c) can be mentioned.
Examples of a mixing device applicable to spraying or dipping include a nauter mixer and a turbulizer.

  The mixing temperature (° C.) is preferably 20 to 100, more preferably 40 to 90, and particularly preferably 50 to 80. Within this range, (c) can easily be impregnated uniformly on the surface, and the breakage preventing property of the absorbent resin is further improved.

The absorbent resin particles of the present invention preferably further contain a hydrophobic substance (d). The content (% by weight) of the hydrophobic substance (d) is preferably 0.001 to 10.0, more preferably 0.08 to 5.0, particularly preferably based on the weight of the crosslinked polymer (A). Is 0.1 to 1.0. This range is preferable because the anti-absorbent article is excellent in anti-fogging property.
In the present invention, a substance corresponding to the breakage preventing agent (c) is handled as a breakage preventing agent and is not included in the hydrophobic substance (d).

  As the hydrophobic substance (d), a hydrophobic substance (d1) containing a hydrocarbon group, a hydrophobic substance (d2) containing a hydrocarbon group having a fluorine atom, and a hydrophobic substance (d3) having a polysiloxane structure Etc. are included.

  Examples of the hydrophobic substance (d1) containing a hydrocarbon group include a polyolefin resin, a polyolefin resin derivative, a polystyrene resin, a polystyrene resin derivative, a wax, a compound composed of a hydrophobic part and a hydrophilic part, and a mixture of two or more thereof. 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.).

  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 10 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 to 300 ° C, more preferably 60 to 200 ° C, and particularly preferably 80 to 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 >.

  Examples of the hydrophobic substance (d2) containing a hydrocarbon group having a fluorine atom include perfluoroalkane, perfluoroalkene, perfluoroaryl, perfluoroalkyl ether, perfluoroalkyl carboxylic acid, perfluoroalkyl alcohol, and those 2 A mixture of seeds or more is included.

  Examples of the perfluoroalkane include alkanes having 4 to 42 fluorine atoms and 1 to 20 carbon atoms (for example, trifluoromethane, pentafluoroethane, pentafluoropropane, tridecafluorooctane, heptadecafluorododecane, etc.).

  Examples of the perfluoroalkene include alkenes having 4 to 42 fluorine atoms and 2 to 20 carbon atoms (for example, trifluoroethylene, pentafluoropropene, tridecafluorooctene, heptadecafluorododecene, etc.).

  Examples of perfluoroaryl include aryl having 4 to 42 fluorine atoms and 6 to 20 carbon atoms {for example, trifluorobenzene, tridecafluorooctylbenzene, heptadecafluorododecylbenzene, etc.}.

  Examples of the perfluoroalkyl ether include ethers having 2 to 82 fluorine atoms and 2 to 40 carbon atoms (for example, ditrifluoromethyl ether, ditridecafluorooctyl ether, diheptadecafluorododecyl ether, etc.).

  Perfluoroalkyl carboxylic acids include carboxylic acids having 3 to 41 fluorine atoms and 1 to 21 carbon atoms {for example, pentafluoroethanoic acid, tridecafluorooctanoic acid, heptadecafluorododecanoic acid and their metals (alkali metal and Alkaline earth metal etc.) salt etc.}.

  Examples of perfluoroalkyl alcohols include alcohols having 3 to 41 fluorine atoms and 1 to 20 carbon atoms (for example, pentafluoroethanol, nonaflufluorohexanol, tridecafluorooctanol, heptadecafluorododecanol, etc.) and ethylene of this alcohol. Examples include oxides (1 to 20 moles per mole of alcohol) adduct.

  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 (d3) 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-22-6266 {side chain, oxyethylene and oxypropylene}

FZ-2110 {both ends, oxyethylene and oxypropylene}, FZ-2122 {both ends, oxyethylene and oxypropylene}, FZ-2154 {both ends, oxyethylene and oxypropylene}, manufactured by Toray Dow Corning Co., Ltd. FZ-2203 {both ends, oxyethylene 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.
* Shin-Etsu Chemical Co., Ltd. X-22-343 {side chain, 525}, X-22-163C {both ends, 2700}, X-22-169AS {both ends, 500}, X-22-173DX {single Terminal, 4500}, X-22-9002 {Side chain, both ends, 5000}

-FZ-3720 {side chain, 1200}, FZ-3736 {side chain, 5000}, BY 16-855D {side chain, 180}, BY 16-8 {side chain, 3700} manufactured by Toray Dow Corning Co., Ltd.

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-857 {side chain, 2200}, KF-8001 {side chain, 1900}, KF-862 {side chain, 1900}, X-22 -919
2 {side chain, 6500}

-FZ-3707 {Side chain, 1500}, BY 16-203 {Side chain, 1900}, BY 16-898 {Side chain, 2900}, BY 16-890 {Side chain, 1900} manufactured by Toray Dow Corning Co., Ltd. BY 16-893 {side chain, 4000}, FZ-3789 {side chain, 1900}, BY 16-871 {both ends, 130}, BY 16-853C {both ends, 360}, BY 16-853U {both End, 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 (d) 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 (d), 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. Acid Mg, Ca stearate, Zn stearate, Al stearate.

  If the absorbent resin particle of the present invention has a structure comprising part or all of the hydrophobic substance (d) inside the absorbent resin particle, how the hydrophobic substance (d) is contained. However, it is preferable that a part of the hydrophobic substance (d) 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 a part or all of the hydrophobic substance (d) in the interior of the absorbent resin particles includes (1) water content of the hydrophobic substance (d) and the crosslinked polymer (A). It can be produced by a method of mixing and kneading with a gel, or (2) a method of obtaining a hydrous gel of a crosslinked polymer (A) by polymerizing structural units in the presence of a hydrophobic substance (d).

In the method (1), as the hydrophobic substance (d), a material obtained by processing the hydrophobic substance (d) 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 (d1) 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 (d3) containing polysiloxane, silicone beads {for example, GE Toshiba Silicones Co., Ltd .: 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 45 μm), etc.}. When using a hydrophobic substance (d2) containing a hydrocarbon group having a fluorine atom, a fluorine film {for example, 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 (d) is not limited as long as the hydrophobic substance (d) is mixed so that it exists inside the crosslinked polymer (A).
However, the hydrophobic substance (d) is preferably not mixed with the dried polymer of the crosslinked polymer (A) but with the hydrogel of (A) or the polymerization solution of (A), more preferably of (A). 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 (A) is obtained by the aqueous solution polymerization method, the timing for mixing and kneading the hydrophobic substances (d) and (A) 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. Further, when the hydrophobic substance (d) is a long-chain fatty acid salt, the long-chain fatty acid and the metal hydroxide may be mixed or separately.

  When the crosslinked polymer (A) is obtained by the reverse phase suspension polymerization method or emulsion polymerization, the timing for mixing the hydrophobic substance (d) and (A) is not particularly limited, but during the polymerization step {(d) In the presence of (A)}, immediately after the polymerization step, during the dehydration step (in the step of dehydrating to a water content of around 10% by weight), immediately after the dehydration step, and after the dehydration step, the step of separating and distilling off the organic solvent For example, 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 for producing the crosslinked polymer (A) in the presence of the hydrophobic substance (d), the hydrophobic substance (d) is dissolved or emulsified (dispersed) in the polymer solution of the crosslinked polymer (A), It can be carried out while precipitating (d) as the polymerization of (A) proceeds. The polymerization method is the same as that for the crosslinked polymer (A) except that the polymerization is performed in the presence of the hydrophobic substance (d).

The hydrophobic substance (d) 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 (d). 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 (d) can be shredded 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.

The absorbent resin particles of the present invention can further contain an inorganic powder (e) on the surface. Examples of the inorganic powder (e) include hydrophilic inorganic particles (e1) and hydrophobic inorganic particles (e2).
Examples of the hydrophilic inorganic particles (e1) include particles of glass, silica gel, silica, clay and the like.
Examples of the hydrophobic inorganic particles (e2) include particles of carbon fiber, kaolin, talc, mica, bentonite, sericite, asbestos, shirasu, and the like.
Of these, hydrophilic inorganic particles (e1) are preferred, and silica is most preferred.

  The shape of the hydrophilic inorganic particles (e1) and the hydrophobic inorganic particles (e2) may be any of an irregular shape (crushed shape), a true spherical shape, a film shape, a rod shape, a fiber shape, etc., 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 (e) is preferably 0.01 to 3.0, more preferably 0.05 to 1.0, and then preferably based on the weight of the crosslinked polymer (A). Is 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.

If necessary, additives can be added to the absorbent resin particles of the present invention at any stage {polymerization step, drying step, surface cross-linking step and / or before and after these steps}.
Examples of additives include known additives (for example, Japanese Patent Application Laid-Open No. 2003-225565) {preservatives, fungicides, antioxidants, ultraviolet absorbers, colorants, deodorants, organic fibrous materials, etc.} These can be used, and one or more of these may be used in combination.

In the method for measuring the swelling volume with respect to physiological saline per gram of the absorbent resin particles of the present invention, the ratio of the time until the swelling volume reaches 5 ml (t1) and the time until the swelling volume reaches 40 ml (t2) (t2 / t1) is from 5 to 20, preferably from 5 to 15, and most preferably from 5 to 10. Further, t1 is preferably 20 to 60 seconds, more preferably 20 to 50 seconds, and most preferably 30 to 40 seconds.
By adjusting the content of the hydrophobic substance (d), the apparent density of the absorbent resin particles, the weight average particle diameter of the absorbent resin particles, etc. to the above preferred ranges, the amount of absorption by the swelling volume measurement method is adjusted to the preferred range. it can.

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.
Further, the disk 2 is made up of 64 holes having a diameter of 2 mm radially (see FIG. 5). 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>
2.50 g of a measurement sample (moisture content of 8.0% or less) sieved to a particle size of 150 to 850 μm is weighed in a vertically standing cylinder 1 with a bottom plate, and a uniform thickness is obtained at the bottom of the cylinder 1 with a bottom plate. The disc 2 is placed so that the column handle is facing upward, and the distance from the bottom surface of the cylinder to the top surface of the disc handle is measured using a thickness meter (for example, Digimatic Indicator ID-F150 manufactured by Mitutoyo). taking measurement. At this time, the pressure applied to the absorbent resin particles is 3.9 ± 0.3 g / cm ² due to the weight (140 g ± 10 g) of the measuring rod of the digimatic indicator and the weight of the disc 2 with handle. 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 at which the disk is started is set to 0, and the distance H (cm) at which the disk 2 has risen as time elapses from the start of charging is recorded as continuous data. By calculating the swelling volume (ml) per 1 g of the absorbent resin particles according to the following formula, data of the swelling volume change with time is obtained. From this data, the time (t1) until the swelling volume reaches 5 ml and the time (t2) until the swelling volume reaches 40 ml are determined. The same measurement is performed 5 times, and the average value is taken as the measured value.

  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 pressure absorption amount (g / g) of the absorbent resin particles of the present invention is preferably from 8 to 35, more preferably from 9 to 25, particularly preferably from 10 to 20, from the viewpoint of the moisture resistance of the absorbent article. is there. The pressure absorption amount of the absorbent resin particles is measured by the following method.

<Pressure absorption amount>
Place 0.160 g of the absorbent resin in a plastic cylinder (inner diameter 25 mm, height 30 mm) with a 250 mesh nylon net on the bottom, and evenly smooth it. Place a 200g weight that goes up and down in the cylinder. The load at this time corresponds to about 40 g / cm ² . A plastic cylinder containing an absorbent resin and a weight is immersed in a petri dish (diameter: 12 cm) containing 60 ml of physiological saline with the nylon mesh side facing down and left to stand. The mass by which the absorbent resin absorbed physiological saline increased was measured after 60 minutes, and the value was converted to a value per 1 g of absorbent resin to obtain a pressure absorption amount at 40 g / cm ² .

  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 water retention amount, and the pressure absorption amount were measured by the method mentioned above.

<Example 1>
Acrylic acid (a1-1) as a water-soluble vinyl monomer {Mitsubishi Chemical Corporation, purity 100%} 155 parts (2.15 mol parts), Pentaerythritol triallyl ether (b1) as a cross-linking agent {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., a water-containing gel was obtained by polymerization at 90 ± 2 ° C. for about 5 hours.
Next, while chopping 502.27 parts of this hydrogel with a mincing machine (12VR-400K manufactured by ROYAL), add and mix 128.42 parts of 48.5% sodium hydroxide aqueous solution, and subsequently stearin as a hydrophobic substance. 1.9 parts of acid Mg (d1) {volume average particle size 8 μm} was added and mixed to obtain a chopped gel. Further, the chopped gel 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 crosslink the surface to obtain absorbent resin particles. While further 100 parts of the absorbent resin particles were stirred at a high speed (high speed stirring turbulizer manufactured by Hosokawa Micron: rotation speed 2000 rpm), 0.5 parts of propylene glycol (c1) was added as a breakage preventing agent by spraying on the surface. The impregnated resin particles (1) of the present invention were obtained by impregnation. The weight average particle diameter of the absorbent resin particles (1) was 395 μm, the apparent density was 0.58 g / ml, and the water content was 6%.

<Example 2>
Absorbent resin particles (2) of the present invention were obtained in the same manner as in Example 1 except that “0.5 part of propylene glycol (c1)” was changed to “0.2 part of propylene glycol (c1)”. . The weight average particle diameter of the absorbent resin particles (2) was 390 μm, the apparent density was 0.58 g / ml, and the water content was 6%.

<Example 3>
Absorbent resin particles (3) of the present invention were obtained in the same manner as in Example 1 except that “0.5 part of propylene glycol (c1)” was changed to “1.0 part of propylene glycol (c1)”. . The weight average particle diameter of the absorbent resin particles (3) was 400 μm, the apparent density was 0.58 g / ml, and the water content was 6%.

<Example 4>
Absorbent resin particles of the present invention in the same manner as in Example 1 except that “0.5 part of propylene glycol (c1)” was changed to “0.5 part of ethylene glycol ethylene oxide 2-mol adduct (c2)” (4) was obtained. The weight average particle diameter of the absorbent resin particles (4) was 395 μm, the apparent density was 0.58 g / ml, and the water content was 6%.

<Example 5>
Absorbent resin particles of the present invention in the same manner as in Example 1 except that "0.5 parts of propylene glycol (c1)" was changed to "0.5 parts of butyl alcohol propylene oxide 12-mol adduct (c3)" (5) was obtained. The weight average particle diameter of the absorbent resin particles (5) was 405 μm, the apparent density was 0.60 g / ml, and the water content was 6%.

<Example 6>
Absorbing resin particles (1) of Example 1 0.6 parts of Aerosil 200PE (Nippon Aerosil Co., Ltd.) (e1) as hydrophilic inorganic particles are added and mixed, and the absorbing resin particles (6) of the present invention are mixed. Got. The weight average particle diameter of the absorbent resin particles (6) was 390 μm, the apparent density was 0.57 g / ml, and the water content was 6%.

<Example 7>
Absorbent resin particles (7) of the present invention were obtained in the same manner as in Example 1 except that “1.9 parts of Mg (d1) stearate as a hydrophobic substance” was not used. The weight average particle diameter of the absorbent resin particles (7) was 405 μm, the apparent density was 0.60 g / ml, and the water content was 6%.

<Example 8>
The present invention was carried out in the same manner as in Example 1 except that “0.5 part of propylene glycol (c1)” was changed to “mixed solution of 0.5 part of propylene glycol (c1) and 5 parts of {ion exchange water}”. Absorbent resin particles (8) were obtained. The weight average particle diameter of the absorbent resin particles (8) was 410 μm, the apparent density was 0.60 g / ml, and the water content was 10%.

<Comparative Example 1>
Comparative absorbent resin particles (1) were obtained in the same manner as in Example 1 except that “0.5 parts of propylene glycol (c1)” was not added. The weight average particle diameter of the comparative absorbent resin particles (1) was 390 μm, the apparent density was 0.58 g / ml, and the water content was 6%.

<Comparative example 2>
Dry body particles were obtained in the same manner as in Example 1. 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 40 minutes to crosslink the surface to obtain comparative absorbent resin particles. While further 100 parts of the absorbent resin particles were stirred at a high speed (high speed stirring turbulizer manufactured by Hosokawa Micron: rotation speed 2000 rpm), 0.5 parts of propylene glycol (c1) was added as a breakage preventing agent by spraying on the surface. A comparative absorbent resin particle (2) was obtained by impregnation. The weight average particle diameter of the comparative absorbent resin particles (2) was 390 μm, the apparent density was 0.58 g / ml, and the water content was 1%.

<Comparative Example 3>
In the same manner as in Example 1 except that “0.5 part of propylene glycol (c1)” was changed to “mixed solution of 0.5 part of propylene glycol (c1) and 25 parts of {ion exchange water}”. Absorbent resin particles (3) were obtained. The weight average particle diameter of the comparative absorbent resin particles (3) was 390 μm, the apparent density was 0.58 g / ml, and the water content was 25%.

<Fracture test method>
A 100 g sample of absorbent resin particles was placed in a ball mill (5 poles) and rotated at 150 rpm for 15 minutes.
With respect to the absorbent resin particles after the treatment with this ball mill, the amount of absorption, the amount of water retained, and the amount of pressure absorption were measured by a swelling volume measurement method.

  About the absorptive resin particles obtained in Examples 1 to 8 and Comparative Examples 1 to 3, the measured physical properties {weight average particle diameter, apparent density} and performance evaluation results {absorption amount by swollen volume measurement method, water retention amount, Table 1 shows the pressure absorption amount. In addition,% shows content (weight%) based on the weight of a crosslinked polymer (A). Table 2 shows the performance evaluation results {absorption amount, water retention amount, pressure absorption amount by swelling volume measurement method) after the breakability test.

  From the results of Table 1 and Table 2, the absorbent resin particles (1) to (8) of the present invention obtained in Examples 1 to 8 are comparative absorbent resin particles (1) to Comparative Examples 1 to 3. Compared with (3), there is no significant difference in the performance before the breakability test, but there is a large difference in the absorption performance after the breakability test {absorption amount by the swollen volume measurement method, pressure absorption amount}. A dramatic improvement in breakability is observed.

  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 (10)

An absorption comprising 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 essential constituent units, and a breakage preventing agent (c). Absorbent resin particles having a water content of 3 to 20%. The absorbent resin particle according to claim 1, wherein the breakage inhibitor (c) has an SP value of 7 to 18, a boiling point of 80 to 400 ° C, and (c) is liquid at 40 ° C. The absorbent resin particle according to claim 1 or 2, wherein the content of the breakage inhibitor (c) is 0.1 to 1.0% by weight based on the weight of the crosslinked polymer (A). In the swelling volume measurement method, the ratio (t2 / t1) between the time (t1) until the swelling volume reaches 5 ml and the time (t2) until the swelling volume reaches 40 ml with respect to physiological saline per 1 g of the absorbent resin particles. The absorbent resin particle according to any one of claims 1 to 3, wherein The absorbent resin particles according to any one of claims 1 to 4, wherein, in the swelling volume measurement method, a time (t1) until the swelling volume reaches 5 ml is 20 to 60 seconds. Furthermore, the absorptive resin particle in any one of Claims 1-5 formed by containing 0.001-10.0 weight% of hydrophobic substances (d) based on the weight of a crosslinked polymer (A). The absorbent resin particle according to claim 6, wherein a part of the hydrophobic substance (d) is present on the surface of the absorbent resin particle. Furthermore, the absorptive resin particle in any one of Claims 1-7 which contains 0.01-3.0% of inorganic powder (e) on the surface based on the weight of a crosslinked polymer (A). An absorbent comprising the absorbent resin particles according to any one of claims 1 to 8 and a fibrous material. An absorbent article using the absorber according to claim 9.

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