JP2009114414A - Water absorbing resin particle, absorber and absorptive article - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide water absorbing resin particles which absorb water and can easily release water after a definite period of time. <P>SOLUTION: The water absorbing resin particles comprise as essential monomers a water-soluble vinyl monomer (a1) and/or a hydrolyzable vinyl monomer (a2) and ketimine obtained from vinyl ketone and polyamine. It is preferable that the content of ketimine (b) unit should be 0.0005-3 mol% based on the number of moles of water-soluble vinyl monomer (a1) unit and hydrolyzable vinyl monomer (a2) unit. It is preferable that vinyl ketone should be isopropyl vinyl ketone, isobutyl vinyl ketone, t-butyl vinyl ketone, isopropenyl isopropyl ketone, isopropenyl isobutyl ketone, or isopropenyl t-butyl ketone. It is preferable that polyamine should be aliphatic diamine or aliphatic triamine. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to water-absorbing resin particles, an absorbent body using the same, and an absorbent article.

Water-absorbing resin particles obtained by copolymerizing acrylic acid and N, N′-methylenebisacrylamide and partially neutralizing this with sodium hydroxide are known {Patent Documents 1 to 3}.
JP 2006-110545 A JP 2006-122737 A JP 2006-206777 A

  However, the conventional water-absorbent resin particles do not release water even if they are subjected to some load once they absorb water, so they may be disposed of in a state of containing a large amount of water after use. There is a problem that environmental load is large. That is, an object of the present invention is to provide water-absorbing resin particles that can absorb water and can be easily separated after a certain time.

  The water-absorbent resin particles of the present invention are characterized in that water-soluble vinyl monomer (a1) and / or hydrolyzable vinyl monomer (a2) and ketimine (b) obtained from vinyl ketone and polyamine are essential monomers. Is the gist.

  The water-absorbent resin particles of the present invention can easily separate water after a certain time after absorbing water. Therefore, when the water-absorbent resin particles of the present invention are applied to an absorbent article, the absorbent article after use can easily separate water after a certain time, and is necessary when the absorbent article is incinerated. Energy can be reduced.

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 hydrolyzable vinyl monomer means a vinyl monomer that becomes a water-soluble vinyl monomer (a1) by hydrolysis.
The water-soluble vinyl monomer (a1) and / or the hydrolyzable vinyl monomer (a2) is not particularly limited, and for example, a vinyl monomer (VM) described in JP-A-2005-075982 can be used. Of these, water-soluble vinyl monomers (a1) are preferable from the viewpoint of absorption performance and the like, more preferably vinyl monomers having a carboxy group, a sulfo group and / or a carbamoyl group, and particularly preferably (meth) acrylic acid (salt). And (meth) acrylamide. In addition, (meth) acrylic acid (salt) means (meth) acrylic acid and / or (meth) acrylate.

  Each of the water-soluble vinyl monomer (a1) and / or the hydrolyzable vinyl monomer (a2) may be a single structural unit or two or more structural units.

  Of the water-soluble vinyl monomer (a1) and the hydrolyzable vinyl monomer (a2), the water-soluble vinyl monomer (a1) is preferable from the viewpoint of absorption performance and the like, and more preferably (a1) is used alone as a structural unit. It is.

  When both the water-soluble vinyl monomer (a1) and the hydrolyzable vinyl monomer (a2) are used as constituent units, the molar ratio {(a1) / (a2)} of these vinyl monomer units is 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.

  Ketimine (b) is obtained from vinyl ketone and polyamine by known methods {for example, JP-A-8-120041, JP-A-8-176104, JP-A-11-508557, JP-A-2007-169498. JP, 2007-84497, A}. In the reaction of vinyl ketone and polyamine, measures for preventing polymerization {for example, dry air is bubbled. } Is preferable.

  Vinyl ketones include ketones with an ethylenic double bond, such as methyl vinyl ketone, ethyl vinyl ketone, isopropyl vinyl ketone, isobutyl vinyl ketone, t-butyl vinyl ketone, isopropenyl methyl ketone, isopropenyl ethyl ketone, isopropenyl ethyl ketone, Examples include propenyl isopropyl ketone, isopropenyl isobutyl ketone and isopropenyl t-butyl ketone.

  Of these vinyl ketones, isopropyl vinyl ketone, isobutyl vinyl ketone, t-butyl vinyl ketone, isopropenyl isopropyl ketone, isopropenyl isobutyl ketone, and isopropenyl t-butyl ketone are preferable, and more preferably, from the viewpoint of ease of water separation and the like. Isobutyl vinyl ketone, t-butyl vinyl ketone, isopropenyl isobutyl ketone and isopropenyl t-butyl ketone, particularly preferably t-butyl vinyl ketone and isopropenyl t-butyl ketone.

  Examples of the polyamine include amines having at least two primary amino groups, and aliphatic amines and aromatic amines can be used.

  Examples of the aliphatic diamine include 1,2-ethylenediamine, 1,3-propylenediamine, 1,4-butylenediamine, 1,6-hexamethylenediamine {1,6-hexylenediamine}, 1,2-diaminocyclohexane, 1,4-diaminocyclohexane and polyetheramine {eg, polyetheramine from Huntsman International LLC, “JEFFAMINE” is a registered trademark of Huntsman Petrochemical Corporation. } Etc. are mentioned.

  Examples of the aliphatic triamine include diethylenetriamine, dipropylenetriamine, and 1,3,6-triaminohexane.

  Aromatic diamines include o-, m- or p-phenylenediamine and o-, m- or p-xylylenediamine.

  Examples of the aromatic triamine include 1,3,5-triaminobenzene and 1,2,4-triaminobenzene.

  Of these polyamines, aliphatic diamines and aliphatic triamines are preferred, aliphatic diamines are more preferred, 1,2-ethylenediamine, 1,3-propylenediamine, 1,4-butylenediamine, 1,6- Hexamethylenediamine, 1,2-diaminocyclohexane and 1,4-diaminocyclohexane, most preferably 1,2-ethylenediamine and 1,6-hexamethylenediamine.

  The content (mol%) of the ketimine (b) unit is preferably 0.0005 to 3, more preferably based on the number of moles of the water-soluble vinyl monomer (a1) unit and the hydrolyzable vinyl monomer (a2) unit. 0.003 to 1, particularly preferably 0.02 to 0.6. Within this range, it becomes easier to separate water.

  Ketimine (b) has at least two vinyl groups corresponding to the number of amino groups of the polyamine, and ketimine (b) acts as an internal crosslinking agent. And when the water-absorbent resin particles of the present invention absorb water, the> C = N-bond of the ketimine (b) unit is gradually hydrolyzed, and the monoketimine unit obtained from the vinyl ketone unit, 1 mol of polyamine and 1 mol of vinyl ketone. And / or polyamines. If it does so, since many crosslinked structures of a water-absorbent resin particle are lost, it will water-separate. Therefore, when the water-absorbent resin particles of the present invention are applied to an absorbent article, the absorbent article after use can easily separate water after a certain time, and is necessary when the absorbent article is incinerated. Energy can be reduced.

The water-absorbent resin particles of the present invention may contain a normal internal crosslinking agent (c) as a structural unit.
Examples of the internal cross-linking agent (c) include known internal cross-linking agents {for example, Patent Documents 1 to 3}, and the like. The internal cross-linking agent (c1) having two or more ethylenically unsaturated bonds, at least one functional group capable of reacting with the water-soluble substituent of a1) {carboxy group, sulfo group, carbamoyl group, etc.} and / or the water-soluble substituent formed by hydrolysis of the hydrolyzable vinyl monomer (a2) And an internal cross-linking agent (c2) having at least one ethylenically unsaturated bond, and water-soluble substituents of the water-soluble vinyl monomer (a1) and / or hydrolysis of the hydrolyzable vinyl monomer (a2) An internal cross-linking agent (c3) having at least two functional groups capable of reacting with a water-soluble substituent can be used.

  Among these internal cross-linking agents (c), from the viewpoint of absorption performance and the like, an internal cross-linking agent (c1) having two or more ethylenically unsaturated bonds is preferable, and more preferably a poly (poly (2-10) having 2 to 10 carbon atoms. Meta) allyl ethers, particularly preferably triallyl cyanurate, triallyl isocyanurate, tetraallyloxyethane and pentaerythritol triallyl ether, most preferably pentaerythritol triallyl ether.

  When the internal cross-linking agent (c) is included as a constituent unit, the content (mol%) of the internal cross-linking agent (c) unit is determined from the viewpoint of absorption performance and the like, from the viewpoint of absorption performance and the like. (A2) Based on the number of moles of the unit, 0.00001 to 0.01 is preferable, 0.00005 to 0.001 is more preferable, and 0.0001 to 0.0005 is particularly preferable.

  The water-absorbent resin particles of the present invention can further contain a copolymerizable other vinyl monomer (a3) as a constituent unit {preferably not containing the other vinyl monomer (a4) as a constituent unit. }.

  The other vinyl monomer (a4) is not limited as long as it is a monomer that can be copolymerized with the water-soluble vinyl monomer (a1) and the like, and examples thereof include a vinyl monomer described in JP-A-2003-225565.

  When the other vinyl monomer (a4) is used as a constituent unit, the content (mol%) of the other vinyl monomer (a4) unit is selected from the viewpoint of absorption performance and the like. a2) Based on the number of moles of the unit, 0.01 to 30 is preferable, more preferably 0.05 to 20, and particularly preferably 0.1 to 15.

  As a polymerization form for obtaining water-absorbent resin particles, conventionally known methods {for example, Patent Documents 1 to 3} can be used, such as solution polymerization method, emulsion polymerization method, suspension polymerization method, reverse phase suspension. A turbid polymerization method or the like can be applied. Further, the shape of the polymerization solution at the time of polymerization may be a thin film shape, a spray shape, or the like. As a polymerization control method, an adiabatic polymerization method, a temperature control polymerization method, an isothermal polymerization method, or the like can be applied.

  When suspension polymerization or reverse phase suspension polymerization is applied as the polymerization method, conventionally known dispersants (such as sucrose ester, phosphate ester and sorbitan ester) and protective colloid (Poval, α) -Olefin-maleic anhydride copolymer, polyethylene oxide, etc.) can be used. In the case of the reverse phase suspension polymerization method, polymerization can be performed using a conventionally known hydrophobic solvent {cyclohexane, normal hexane, normal heptane, toluene, xylene and the like}.

  Among the polymerization methods, a solution polymerization method is preferable, a solution polymerization method using a hydrophobic solvent is more preferable, and a solution polymerization method using normal heptane is particularly preferable.

  In order to obtain water-absorbing resin particles, a polymerization initiator can be used for the polymerization. The polymerization initiator is not particularly limited and conventionally known ones can be used. (I) An azo initiator, (ii) a peroxide initiator, (iii) a redox initiator, and (iv) an organic halogen compound start An agent can be used.

  When the polymerization initiator is used, the amount (% by weight) of the polymerization initiator used is the water-soluble vinyl monomer (a1), hydrolyzable vinyl monomer (a2) and ketimine (b), and other vinyls used as necessary. Based on the weight of the monomer (a3) and / or the internal crosslinking agent (c), 0.005 to 3.0 is preferable, more preferably 0.007 to 1.5, and particularly preferably 0.009 to 1.0. It is.

  The gel {including the water-absorbent resin particle precursor and the solvent} obtained by polymerization can be shredded as necessary. The size (longest diameter) of the gel after chopping is preferably 50 μm to 10 cm, more preferably 100 μm to 2 cm, and particularly preferably 1 mm to 1 cm. Within this range, the drying property in the drying process is further improved.

  Shredding can be performed by a known method, and can be 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 (including water) 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 10 to 0.01, more preferably 5 to 0.05, based on the weight of the water absorbent resin particles. Particularly preferred is 3 to 0.1, and most preferred is 1 to 0.5. Within this range, the absorption performance is further improved.

  When water is contained in the solvent, the water content (% by weight) after distillation is preferably 0 to 20, more preferably 0 to 10, particularly preferably 0 to 5, most preferably based on the weight of the water absorbent resin particles. Is 0-2. Within this range, the absorption performance and handling properties after drying (powder fluidity of water-absorbent resin particles, etc.) 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, a method of distilling (drying) with hot air at a temperature of 80 to 230 ° C., a thin film drying method using a drum dryer or the like heated to 100 to 230 ° C., a (heating) vacuum drying method, a freezing A drying method, an infrared drying method, decantation, filtration, or the like can be applied.

The water absorbent resin particles of the present invention 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 water-absorbing resin particles can be adjusted in particle size by sieving if necessary.

  100-800 are preferable, as for the weight average particle diameter (micrometer) of the water absorbing resin particle | grains of this invention, More preferably, it is 200-500, Most preferably, it is 300-400. Within this range, handling properties after pulverization (powder fluidity of water-absorbent resin particles, etc.) are further improved.

  For the weight average particle size, measure the particle size distribution of the measurement sample, and plot the relationship between the cumulative content and the particle size on the log probability paper {horizontal axis: particle size, vertical axis: cumulative content (wt%)}. The particle size corresponding to a cumulative content of 50% by weight is obtained. The particle size distribution is measured in accordance with JIS Z8815-1994. For example, sieves with an inner diameter of 150 mm and a depth of 45 mm {openings: 710 μm, 500 μm, 300 μm, 150 μm and 106 μm} are used with a narrow opening sieve. Overlay, put 50 g of measurement sample on top of 710 μm sieve with widest opening, sieve for 10 minutes with sieve shaker, measure weight of measurement sample remaining on each sieve, It is measured by determining the weight percent of the measurement sample remaining on each sieve based on the weight of the measurement sample.

  The water-absorbent resin particles of the present invention preferably have a small content of fine particles, and the content of fine particles of 106 μm or less in the total particles is preferably 3% by weight or less, more preferably 150 μm or less in the total particles. The content of the fine particles is 3% by weight or less.

  The content of the fine particles can be determined using a plot created when determining the above weight average particle diameter.

  The shape of the water-absorbent resin particles of the present invention is not particularly limited, and examples thereof include ordinary shapes {for example, irregularly crushed shapes, flake shapes, pearl shapes, and rice grains}. 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 water-absorbent resin particles of the present invention 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 (c) can be used. As the surface cross-linking agent, water-soluble substituents {carboxy group, sulfo group, carbamoyl group, etc.) of water-soluble vinyl monomer (a1) and / or hydrolyzable vinyl monomer ( The crosslinking agent (c3) having at least two functional groups capable of reacting with water-soluble substituents generated by hydrolysis of a2) is preferred, more preferably polyvalent glycidyl, particularly preferably ethylene glycol diglycidyl ether and glycerin di. Glycidyl ether, most preferably ethylene glycol diglycidyl ether.

  In the case of surface cross-linking, the content (% by weight) of the surface cross-linking agent is selected from water-soluble vinyl monomer (a1), hydrolyzable vinyl monomer (a2) and ketimine (b), and internal cross-linking agent (c) used as necessary. And / or 0.001-7 are preferable based on the weight of another vinyl monomer (a3), More preferably, it is 0.002-5, Most preferably, it is 0.003-4. 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.).

  In the water-absorbent resin particles of the present invention, an additive {preservative, An antifungal agent, an antibacterial agent, an antioxidant, an ultraviolet absorber, a colorant, a fragrance, a deodorant, an organic fibrous material, and a mixture thereof can be added.

When these additives are contained, the content (% by weight) of the additives varies depending on the use, but is preferably 10 ^{−6 to} 20 and more preferably 10 ⁻⁵ to 10 based on the weight of the water-absorbent resin particles. , particularly preferably ^10-4 to 5. Within this range, the effect of the additive can be imparted without reducing the absorption performance of the water-absorbent resin particles.

By applying the water-absorbent resin particles of the present invention to an absorbent body, it is possible to produce an absorbent article in which the absorbent liquid can be easily separated after use.
As a method of applying the absorbent resin particles to the absorbent body, a normal method can be applied. For example, (1) a method in which water-absorbing resin particles are dispersed between fibrous layers; (2) a fibrous material And (3) a method of sandwiching water-absorbing resin particles with a fibrous material, if necessary, using two or more water-absorbing papers and nonwoven fabrics.

  When the water-absorbent resin particles of the present invention are applied to an absorbent body, the content (% by weight) of the water-absorbent resin particles of the present invention can be variously changed according to the type and size of the absorbent body and the target absorption performance. However, it is preferably 30 to 95, more preferably 40 to 94, and particularly preferably 50 to 93, based on the weight of the water absorbent resin particles and the fibrous material. Within this range, the absorbent performance of the obtained absorbent body is further improved.

As an absorbent article, an absorbent article provided with an absorber, a liquid permeable sheet, and a breathable back sheet is preferable, and more preferably an absorbent article as a sanitary article.
Hygiene products include paper diapers (children's disposable diapers and adult disposable diapers, etc.), napkins (such as sanitary napkins), paper towels, pads (such as incontinence pads and surgical underpads), and pet sheets (pet urine absorbing sheets). Etc. Of these hygiene articles, they are more suitable for disposable diapers.

  Hereinafter, although an example and a comparative example explain the present invention further, the present invention is not limited to these. Hereinafter, unless otherwise specified, “part” means “part by weight” and “%” means “% by weight”.

<Production Example 1>
Methyl t-butyl ketone 100 parts (1 mole part), dimethylamine hydrochloride 95 parts (1.2 mole parts) and paraformaldehyde 38 parts (1 mole part) were dissolved in refluxed ethanol 120 parts, and hydrochloric acid 1.2. The reaction mixture was cooled for 10 hours while refluxing ethanol, and the reaction mixture was cooled in an ice bath, and the deposited precipitate was filtered off by suction filtration, followed by N, N-dimethyl-4,4-dimethylpentane. -3-one-1-amine hydrochloride was obtained. This was recrystallized twice in ethanol, then dissolved in 160 parts of water, slowly heated to 100-103 ° C. and concentrated to separate the organic layer and water tank. The organic layer was extracted with diethyl ether, dried over calcium chloride, the ether was distilled off, and distilled under reduced pressure (60 ° C., 13.7 kPa) to obtain t-butyl vinyl ketone { ¹ H-NMR (100 MHz ): Δ 1.14 (s, 9H, CH ₃ ), δ 5.60 (d, 1H, CH), δ 6.24 (d, 1H, CH ₂ ), δ 6.78 (d, 1H, CH ₂ )}.

  In a flask equipped with a stirrer, a heating device, a dropping funnel, a thermometer, a Dean-Stark water separator, and an air introduction tube, 1,2-ethylenediamine 60 parts (1 mole part), t-butyl vinyl ketone 220 parts (2 .2 mol parts) and 500 ml of hexane, heated to 75 ° C. while bubbling dry air, and refluxed until 36 parts (2 mol parts) of water was generated and separated to obtain crude ketimine . The crude ketimine was distilled off hexane and unreacted t-butyl vinyl ketone at 50 to 80 ° C. and 2 to 8 Pa to obtain ketimine (b1).

<Production Example 2>
2,2-dimethyl-3-pentanone 114 parts (1 mol part), N, N-dimethylmethyleneimonium chloride {(CH ₃ ) ₂ N ⁺ = CH ₂ Cl ⁻ } 112.2 parts (1.2 mol part) ) And 1000 parts of acetonitrile while refluxing, the mixture was reacted for 5 hours, cooled to about 25 ° C., 170.4 parts (1.2 mole parts) of methyl iodide and 500 parts of methanol were added, and the mixture was heated at 25 ° C. for 3 hours. Reaction was performed, and acetonitrile was distilled off to obtain a quaternary ammonium salt {N, N, N-trimethyl-2,4,4-trimethyl-3-carbonylpentylammonium iodine salt}. Subsequently, this quaternary ammonium salt was added to 1000 parts of a 5% aqueous sodium hydroxide solution, and t-butylisopropenyl ketone was distilled under reduced pressure {70 ° C., 10.7 kPa, ¹ H while heating {while Hofmann decomposition}. -NMR (90 MHz): δ 1.23 (s, 9H, C ₃ H ₉ ), δ 1.90 (t, 3H, CH ₃ ), δ 5.39 (m, 2H, βCH ₂ )}, ¹³ C-NMR ( 20 MHz) {δ20.55 (CH ₃ ), δ27.29 (C ₄ H ₉ ), δ117.48 (βCH ₂ ), δ208.7 (C═O)}.

  Except for changing “t-butyl vinyl ketone 220 parts (2.2 mol parts)” to “t-butyl isopropenyl ketone 277.2 parts (2.2 mol parts)”, in the same manner as in Production Example 1, Ketimine (b2) was obtained.

<Production Example 3>
Ketimine (b3) was prepared in the same manner as in Production Example 1 except that “1,2-ethylenediamine 60 parts (1 mole part)” was changed to “1,6-hexamethylenediamine 116 parts (1 mole part)”. Obtained.

<Example 1>
Normal heptane {bubbled with nitrogen gas so that the dissolved oxygen was 0.5 ppm or less} was refluxed with stirring while adding 300 parts of benzoyl peroxide, 50 parts of acrylic acid (0.69). Mole part), sodium acrylate 15 parts (0.16 mole part), ketimine (b1) 0.25 part (0.001 mole part), vinyl acetate 0.03 part (0.00035 mole part) and normal heptane 200 A mixed solution consisting of parts was added dropwise over 1 hour. Furthermore, after stirring at 110 ° C. for 10 minutes under reflux, the mixture was cooled to about 25 ° C., and the precipitated polymer was separated by suction filtration. The polymer was washed with normal heptane, sandwiched with filter paper to remove the solvent, and then dried in a vacuum oven {2-8 Pa, 100 ° C.} to obtain a dried product. The dried product is pulverized with a juicer mixer (MX-X53, Matsushita Electric Industrial Co., Ltd.), adjusted to a particle size of 250 to 600 μm using a sieve having an opening of 600 and 250 μm, and the water absorbent resin particles ( 1) was obtained.

<Example 2>
The water absorption of the present invention was the same as in Example 1 except that ketimine (b1) was changed from “0.25 part (0.001 mol part)” to “0.05 part (0.0002 mol part)”. Resin particles (2) were obtained.

<Example 3>
The water absorption of the present invention was the same as in Example 1 except that ketimine (b1) was changed from “0.25 part (0.001 mol part)” to “1.25 parts (0.005 mol part)”. Resin particles (3) were obtained.

<Example 4>
In the same manner as in Example 1, except that “ketimine (b1) 0.25 part (0.001 mol part)” was changed to “ketimine (b2) 0.28 part (0.001 mol part)”. The water-absorbent resin particles (4) of the invention were obtained.

<Example 5>
In the same manner as in Example 1, except that “ketimine (b1) 0.25 part (0.001 mol part)” was changed to “ketimine (b3) 0.3 part (0.001 mol part)”. The water-absorbent resin particles (5) of the invention were obtained.

<Example 6>
“Ketimine (b1) 0.25 part (0.001 mol part)” is replaced with “ketimine (b1) 0.24 part (0.00097 mol part) and internal crosslinking agent (c1) {N, N′-methylenebisacrylamide”. } 0.0001 part (6.5 × 10 ⁻⁷ mol part) ”, in the same manner as in Example 1, to obtain water-absorbent resin particles (6) of the present invention.

<Example 7>
“Ketimine (b1) 0.25 part (0.001 mol part)” is replaced with “ketimine (b1) 0.24 part (0.00097 mol part) and internal crosslinking agent (c1) 0.005 part (3.2 × The water-absorbent resin particles (7) of the present invention were obtained in the same manner as in Example 1 except that the content was changed to “10 ⁻⁵ mol part”.

<Comparative Example 1>
While stirring and mixing 81.8 parts (1.14 mole part) of acrylic acid, 0.3 part (0.0019 mole part) of N, N′-methylenebisacrylamide and 241 parts of deionized water, the temperature was adjusted to 1 to The temperature was kept at 2 ° C., and nitrogen was allowed to flow into the mixed solution so that the amount of dissolved oxygen in the mixed solution was 0.5 ppm or less. Subsequently, 1 part of a 1% aqueous hydrogen peroxide solution, 1.2 parts of a 0.2% ascorbic acid aqueous solution and 2.8 parts of a 2% 2,2′-azobisamidinopropane dihydrochloride aqueous solution are added to the mixture. Polymerization was started by mixing, and after the reaction temperature reached 70 ° C., polymerization was performed at a polymerization temperature of 75 ± 5 ° C. for about 8 hours to obtain a water-containing resin (gel). This water-containing resin (gel) was chopped to a size of 3 to 7 mm with an internal mixer to obtain a chopped gel, and then 67.5 parts of a 48 wt% aqueous sodium hydroxide solution was added to 325 parts of the chopped gel. This was added to neutralize 72 equivalent% of the carboxy group to obtain a neutralized chopped gel. In addition, the neutralization degree of the neutralized chopped gel calculated from the acid value measured according to JIS K0113-1997 (using 0.1 N potassium hydroxide aqueous solution as a titrant, potentiometric titration method, inflection point method) Was 70.1 equivalent%.

  Next, this neutralized chopped gel is laminated to a thickness of about 5 cm on a stainless steel tray that is 20 cm long × 20 cm wide × 10 cm high, has no top plate, and has a 4 mm mesh wire mesh on the bottom plate. And it dried with the ventilation type | mold band dryer (made by Inoue Metal) on the conditions of 150 degreeC and the wind speed of 2.0 m / s, and obtained the dry polymer. The dried polymer is pulverized with a juicer mixer (MX-X53, Matsushita Electric Industrial Co., Ltd.), adjusted to a particle size of 250 to 600 μm using a sieve having openings of 600 and 250 μm, and water-absorbent resin particles for comparison (H1) was obtained.

<Comparative example 2>
The same as Comparative Example 1 except that “N, N′-methylenebisacrylamide 0.3 part (0.0019 mol part)” was changed to “ethylene glycol diacrylate 0.32 part (0.0019 mol part)”. Thus, water-absorbing resin particles (H2) for comparison were obtained.

<Comparative Example 3>
Comparative Example 1 except that “N, N′-methylenebisacrylamide 0.3 part (0.0019 mol part)” was changed to “trimethylolpropane triacrylate 0.13 part (0.0013 mol part)”. Similarly, comparative water-absorbing resin particles (H3) were obtained.

  For the water-absorbent resin particles obtained in Examples 1 to 7 and Comparative Examples 1 to 3, the water retention amount after 1 hour, the water retention amount after 4 hours, and the water retention amount after 10 hours were measured, and these results are shown in Table 1. .

<Water retention after 1 hour>
A measurement sample (1.00 g) was placed in a tea bag (20 cm long, 10 cm wide) made of a nylon mesh (JIS Z8801-1: 2000) having a mesh opening of 63 μm, and the tea bag was filled with physiological saline (salt concentration: 0.9% by weight). ) After being immersed in 1,000 ml without stirring for 1 hour, it was suspended for 15 minutes to drain water. Thereafter, each tea bag was placed in a centrifuge, centrifuged at 150 G for 90 seconds to remove excess physiological saline, and the weight (h1) including the tea bag was measured to obtain the water retention amount from the following formula. In addition, the temperature of the used physiological saline and measurement atmosphere is 25 degreeC +/- 2 degreeC.

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

(H2) is the weight of the tea bag measured by the same operation as described above when there is no measurement sample.

<Water retention after 4 hours>
The amount of water retained was determined in the same manner as the amount of water retained for 1 hour, except that the time of immersion in physiological saline was changed from “1 hour” to “4 hours”.

<Water retention after 10 hours>
The amount of water retained was determined in the same manner as the amount of water retained for 1 hour, except that the time of immersion in physiological saline was changed from “1 hour” to “10 hours”.

<Example 8>
A basis weight of about 100 parts of fluff pulp and 100 parts of the water-absorbent resin particles (1) of the present invention obtained in Example 1 were mixed with an airflow type mixing device {pad former manufactured by Autech Co., Ltd.}. It is uniformly laminated on a sheet made of nylon net (mesh conforming to JIS Z8801-1: 2000) with a mesh size of 63 μm so as to be 400 g / m ^2, and pressed at a pressure of 5 kg / cm ² for 30 seconds. The absorber (K1) of the present invention was obtained.
The absorbent body (K1) is cut into a rectangle of 14 cm × 36 cm, and the same size (14 cm × 36 cm) of water-absorbing paper (basis weight 15.5 g / m ² : filter paper No. 2 manufactured by Advantech) After sandwiching, a polyethylene sheet (polyethylene film UB-1, manufactured by Tamapoly Co., Ltd., 14 cm × 36 cm) is placed on the back surface, and a non-woven fabric (basis weight 20.0 g / m ² , 14 cm × 36 cm: Eltas guard manufactured by Asahi Kasei Co., Ltd.) is placed on the surface. By doing this, the absorbent article (1) of this invention was created.

<Examples 9 to 14>
Except having changed "water-absorbent resin particle (1)" into "any of water-absorbent resin particle (2)-(7)", it carried out similarly to Example 8, and the absorber (K2)- (K7) was prepared, and absorbent articles (2) to (7) of the present invention were further prepared.

<Comparative Examples 4-6>
Absorbent for comparison (HK1) to Example 8 except that “water absorbent resin particles (1)” were changed to “any of water absorbent resin particles (H1) to (H3)”. (HK3) was prepared, and comparative absorbent articles (H1) to (H3) were prepared.

  The absorbent articles obtained in Examples and Comparative Examples were measured for 1 hour diaper water retention, 4 hour diaper water retention and 10 hour diaper water retention, and are shown in Table 2.

<1 hour diaper water retention>
The evaluation sample {absorbent article} is immersed in 20 liters of physiological saline (salt concentration 0.9% by weight) without stirring for 1 hour, then suspended for 15 minutes, placed in a centrifuge, and centrifuged at 75 G for 90 seconds. The excess physiological saline was removed by dehydration, the weight (h1; unit g) was measured, and the water retention amount was determined from the following formula. In addition, the temperature of the used physiological saline and measurement atmosphere is 25 degreeC +/- 2 degreeC.

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

(H2) is the weight (g) of the evaluation sample immediately before being immersed in physiological saline.

<4 hour diaper water retention>
The amount of water retained was determined in the same manner as the amount of water retained for 1 hour, except that the time of immersion in physiological saline was changed from “1 hour” to “4 hours”.

<10 hours diaper water retention>
The amount of water retained was determined in the same manner as the amount of water retained for 1 hour, except that the time of immersion in physiological saline was changed from “1 hour” to “10 hours”.

  As shown in Table 2, when the water absorbent resin particles of the present invention were used, water could be removed in a short time. On the other hand, when comparative water-absorbent resin particles were used, water could hardly be removed even after 10 hours.

Claims (6)

A water-soluble vinyl monomer (a1) and / or a hydrolyzable vinyl monomer (a2);
A water-absorbent resin particle comprising ketimine (b) obtained from vinyl ketone and polyamine as essential monomers. The water absorption according to claim 1, wherein the content of the ketimine (b) unit is 0.0005 to 3 mol% based on the number of moles of the water-soluble vinyl monomer (a1) unit and the hydrolyzable vinyl monomer (a2) unit. Resin particles. The water-absorbent resin particles according to claim 1 or 2, wherein the vinyl ketone is isopropyl vinyl ketone, isobutyl vinyl ketone, t-butyl vinyl ketone, isopropenyl isopropyl ketone, isopropenyl isobutyl ketone or isopropenyl t-butyl ketone. The water-absorbent resin particles according to any one of claims 1 to 3, wherein the polyamine is an aliphatic diamine or an aliphatic triamine. An absorbent comprising the water-absorbent resin particles according to any one of claims 1 to 4 and fibers. An absorbent article comprising the absorbent body according to claim 5.