JP5184030B2 - Absorbent resin particles, method for producing the same, and absorbent article - Google Patents

Description

  The present invention relates to absorbent resin particles, a production method thereof, and an absorbent article.

Conventionally, a crosslinked polymer particle having improved absorption performance by a polymerization method using a chain transfer agent such as thiol is known (Patent Document 1).
JP-A-3-179008

  Conventional cross-linked polymer particles are applied to absorbent articles such as disposable diapers, and when this absorbent article is used for a long time, the absorbent performance is insufficient, resulting in problems such as fogging. And the absorbent article of the high absorption performance which does not have such a problem and can be used for a long time is strongly desired. That is, an object of the present invention is to provide absorbent resin particles having high absorption performance.

The characteristic of the absorbent resin particles of the present invention is that the water-soluble vinyl monomer (a1) and / or the hydrolyzable vinyl monomer (a2) and the cross-linked polymer (A) having the internal cross-linking agent (a3) as essential constituent units and ,
A water-soluble vinyl monomer (a1 ′) and / or a hydrolyzable vinyl monomer (a2 ′), and a crosslinked polymer (B) having an internal crosslinking agent (a3 ′) as essential constituent units,
The water retention amount of the crosslinked polymer (A) is 30 to 55 g / g, the water retention amount of the crosslinked polymer (B) is 35 to 60 g / g,
The gist is that the difference between the water retention amount of the crosslinked polymer (A) and the water retention amount of the crosslinked polymer (B) exceeds 5 g / g.

The manufacturing method feature of the absorbent resin particles of the present invention is a method of manufacturing the above-described absorbent resin particles,
A step (1) of obtaining a crosslinked polymer (A) by copolymerizing the water-soluble vinyl monomer (a1) and / or the hydrolyzable vinyl monomer (a2) and the internal crosslinking agent (a3);
Step (2) of obtaining a crosslinked polymer (B) by copolymerizing the water-soluble vinyl monomer (a1 ′) and / or the hydrolyzable vinyl monomer (a2 ′) and the internal crosslinking agent (a3 ′); and crosslinking after mixing the crosslinking polymer polymer (a) (B), drying, steps (3) to obtain a pulverized to absorbent resin particles summarized as including the point.

  The absorbent resin particles of the present invention exhibit high absorption performance. Therefore, when this absorbent resin particle is applied to an absorbent article, there is an effect that problems such as fog do not occur even when used for a long time.

<Crosslinked polymer (A)>
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 by hydrolysis.

  The water-soluble vinyl monomer (a1) and / or the hydrolyzable vinyl monomer (a2) is not particularly limited, and for example, a water-soluble radical polymerization monomer described in JP 2005-075982 A can be used. Of these, water-soluble vinyl monomers (a1) are preferable from the viewpoint of absorption performance and the like, more preferably anionic vinyl monomers, particularly preferably a vinyl group-containing carboxylic acid (salt) having 3 to 30 carbon atoms {unsaturated mono Carboxylic acid (salt) ((meth) acrylic acid, crotonic acid, cinnamic acid and salts thereof); Unsaturated dicarboxylic acid (salt) (maleic acid, fumaric acid, citraconic acid, itaconic acid and salts thereof); And monoalkyl (carbon number 1 to 8) ester of unsaturated dicarboxylic acid (maleic acid monobutyl ester, fumaric acid monobutyl ester, maleic acid ethyl carbitol monoester, fumaric acid ethyl carbitol monoester, citraconic acid Monobutyl ester and itaconic acid glycol monoester, etc.}, preferably unsaturated monocal Phosphate (salt), most preferably acrylic acid (salt).

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.
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.

  As the internal crosslinking agent (a3), for example, an internal crosslinking agent described in JP-A-2003-225565 can be used. Of these internal cross-linking agents, an internal cross-linking agent having two or more ethylenically unsaturated groups is preferable from the viewpoint of absorption performance, and more preferably triallyl cyanurate, triallyl isocyanurate, and those having 2 to 10 carbon atoms. Poly (meth) allyl ethers of polyols, particularly preferably triallyl cyanurate, triallyl isocyanurate, tetraallyloxyethane and pentaerythritol triallyl ether, most preferably pentaerythritol triallyl ether.

  The content (mol%) of the internal crosslinking agent (a3) unit is 0.01 based on the number of moles of the water-soluble vinyl monomer (a1) unit and the hydrolyzable vinyl monomer (a2) unit from the viewpoint of absorption performance. To 1, more preferably 0.03 to 0.5, particularly preferably 0.04 to 0.2, and most preferably 0.1 to 0.15. Within this range, the absorption performance is further improved.

The crosslinked polymer particles (A) can further contain other vinyl monomers that can be copolymerized as structural units. {It is preferable not to include other vinyl monomers as structural units. }.
The other vinyl monomer 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 other vinyl monomer is used as the constituent unit, the content (mol%) of the other vinyl monomer unit is selected from the water-soluble vinyl monomer (a1) unit and hydrolyzable vinyl monomer (a2) unit from the viewpoint of absorption performance. Based on the total number of moles, 0.01 to 30 is preferable, 0.05 to 20 is more preferable, and 0.1 to 15 is particularly preferable.

  The water retention amount (g / g) of the crosslinked polymer (A) is preferably 35 to 60, more preferably 40 to 55, and particularly preferably 45 to 50.

  The amount of water retained was measured by drying the measurement sample {crosslinked polymer} at 150 ° C. for 1 hour with a circulating dryer to reduce the water content to 3% by weight or less, pulverizing it with a juicer mixer, and adjusting the particle size to 250 to 500 μm. A sample of 1.00 g was placed in a tea bag (20 cm long, 10 cm wide) made of a nylon net having a mesh size of 63 μm, and placed in 1,000 ml of physiological saline (saline concentration 0.9 wt%) for 1 hour without stirring. After soaking, hang for 15 minutes to drain water, place the tea bag in a centrifuge, centrifuge at 150G for 90 seconds to remove excess saline, measure the weight (S1) including the tea bag, It is obtained from the following formula. In addition, the temperature of the physiological saline used and measurement atmosphere is 25 degreeC +/- 2 degreeC. In the following formula, (S0) is the weight of the tea bag measured by performing the same operation as described above without a measurement sample.

(Water content) = (S1)-(S0)

  The smaller the crosslinking density of the crosslinked polymer (A), the higher the water retention amount of the crosslinked polymer (A). Reduction of the crosslinking density can be achieved by reducing the amount of the internal crosslinking agent used and decreasing the polymerization concentration. Of these, it is effective to reduce the amount of the internal crosslinking agent used. Further, the water retention amount of the crosslinked polymer (A) can also be increased by increasing the ion concentration {for example, increasing the amount of vinyl group-containing carboxylate, unsaturated dicarboxylate, etc. used}. . Furthermore, to increase the molecular weight of the crosslinked polymer (A) {reducing the amount of the reaction catalyst, lowering the reaction temperature, and reducing or not using the chain transfer agent}, the crosslinked polymer ( The water retention amount of A) can be increased.

  On the other hand, reducing the water retention amount of the crosslinked polymer can be achieved by the reverse method described above.

  Among these methods, to adjust the water retention amount of the crosslinked polymer (A), it is effective to adjust the crosslinking density and the ion concentration, and it is more effective to adjust the crosslinking density. It is particularly effective to adjust the use amount of the internal cross-linking agent and the polymerization concentration, and it is most effective to adjust the use amount of the internal cross-linking agent.

As a polymerization form of the crosslinked polymer (A), a conventionally known method can be used, and a solution polymerization method, an emulsion polymerization method, a suspension polymerization method, a reverse phase suspension polymerization method, and the like can be applied. Further, the shape of the polymerization solution at the time of polymerization may be a thin film, a spray, 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 carried out using a conventionally known solvent such as cyclohexane, normal hexane, normal heptane, toluene and xylene.
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.

  A polymerization initiator can be used for the polymerization of the crosslinked polymer (A). 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.

(I) As the azo initiator, azobisisobutyronitrile, azobiscyanovaleric acid and its salt, 2,2′-azobis (2-amidinopropane) hydrochloride and 2,2′-azobis (2-methyl-) N- (2-hydroxyethyl) propionamide and the like can be mentioned.

(Ii) Peroxide initiators include inorganic peroxides [hydrogen peroxide, ammonium persulfate, potassium persulfate, sodium persulfate, etc.], organic peroxides [benzoyl peroxide, di-t-butyl peroxide] , Cumene hydroperoxide, succinic acid peroxide, di (2-ethoxyethyl) peroxydicarbonate, etc.].

(Iii) As a redox initiator, at least one reducing agent such as alkali metal sulfite, alkali metal bisulfite, ammonium sulfite, ammonium bisulfite, ferric chloride, ferric sulfate, and ascorbic acid; Examples thereof include those comprising a combination of at least one oxidizing agent such as alkali metal persulfate, ammonium persulfate, hydrogen peroxide and organic peroxide.

(Iv) As an organic halogen compound initiator, 1 to 10 halogen atoms, 1 to 1 carbon atoms selected from the group consisting of alkyl halides, halogenated alkyl phenyl ketones, halogenated alkyl carboxylic acids and halogenated alkyl carboxylic acid alkyl esters 15 organic halogen compounds are used, and tetrachloromethane, trichlorobromomethane, trichloroiodomethane, dichloromethylphenylketone, 1-bromo-1-methylethylcarboxylic acid, and alkyl group having 1 to 12 carbon atoms 1-bromo. -1-methylethylcarboxylic acid alkyl esters (methyl 1-bromo-1-methylethylcarboxylate, ethyl 1-bromo-1-methylethylcarboxylate, octyl 1-bromo-1-methylethylcarboxylate and 1-bromo- 1-methylethylcarboxylic acid Glycoluril), and the like.

  Of these, (i) azo initiators, (ii) peroxide initiators and (iii) redox initiators are preferred, and (i) azo initiators and (ii) peroxide initiators are more preferred. And (iii) redox initiator.

  When the polymerization initiator is used, the amount (% by weight) of the polymerization initiator used is the water-soluble vinyl monomer (a1), the hydrolyzable vinyl monomer (a2) and the internal cross-linking agent (a3), and other used if necessary. Is preferably 0.005 to 0.5, more preferably 0.007 to 0.4, and particularly preferably 0.009 to 0.3, based on the total weight of the vinyl monomers (a3).

<Crosslinked polymer (B)>
The water-soluble vinyl monomer (a1 ′), hydrolyzable vinyl monomer (a2 ′), internal cross-linking agent (a3 ′), polymerization method and preferred ranges thereof are the same as those for the cross-linked polymer (A). The method for adjusting the amount of water retention is the same as in the case of the crosslinked polymer (A).

  However, the content (mol%) of the internal crosslinking agent (a3 ′) unit is based on the number of moles of the water-soluble vinyl monomer (a1 ′) unit and the hydrolyzable vinyl monomer (a2 ′) unit from the viewpoint of absorption performance. 0.005-0.8 is more preferable, 0.01-0.4 is more preferable, 0.03-0.2 is particularly preferable, and 0.05-0.08 is most preferable. Within this range, the absorption performance is further improved.

  The water retention amount (g / g) of the crosslinked polymer (B) is preferably 40 to 65, more preferably 45 to 60, and particularly preferably 50 to 55.

  The difference between the water retention amount of the crosslinked polymer (A) and the water retention amount of the crosslinked polymer (B) is more than 5 g / g, more preferably 5 to 20, particularly preferably 7 to 15, most preferably Preferably it is 8-10. Within this range, the absorption performance is further improved.

  The content (% by weight) of the crosslinked polymer (A) is preferably 20 to 80, more preferably 40 to 60, particularly preferably based on the total weight of the crosslinked polymer (A) and the crosslinked polymer (B). Is 45-55.

  The content (% by weight) of the crosslinked polymer (B) is preferably 20 to 80, more preferably 40 to 60, particularly preferably based on the total weight of the crosslinked polymer (A) and the crosslinked polymer (B). Is 45-55.

  If the absorptive resin particle of this invention contains a crosslinked polymer (A) and a crosslinked polymer (B), there will be no restriction | limiting in a manufacturing method, For example, it is easily obtained by the following method.

<1> Step (1) of obtaining a crosslinked polymer (A) by copolymerizing the water-soluble vinyl monomer (a1) and / or the hydrolyzable vinyl monomer (a2) and the internal crosslinking agent (a3);
Step (2) of obtaining a crosslinked polymer (B) by copolymerizing the water-soluble vinyl monomer (a1 ′) and / or the hydrolyzable vinyl monomer (a2 ′) and the internal crosslinking agent (a3 ′); and crosslinking A method comprising a step (3) of mixing the polymer (A) and the crosslinked polymer (B), and then drying and pulverizing to obtain absorbent resin particles;

<2> A water-soluble vinyl monomer (a1) and / or a hydrolyzable vinyl monomer (a2) and an internal cross-linking agent (a3) are copolymerized to obtain a cross-linked polymer (A), and then dried and pulverized. A step (1) of obtaining crosslinked polymer particles (AA);
In the presence of the crosslinked polymer particles (AA), a water-soluble vinyl monomer (a1 ′) and / or a hydrolyzable vinyl monomer (a2 ′) and an internal crosslinking agent (a3 ′) are copolymerized to form a crosslinked polymer composite. After obtaining (AAB), a method comprising the step (2) of drying and pulverizing to obtain absorbent resin particles;

<3> A step of obtaining crosslinked polymer particles (AAA) by subjecting the water-soluble vinyl monomer (a1) and / or hydrolyzable vinyl monomer (a2) and the internal crosslinking agent (a3) to reverse phase suspension polymerization (1). );
In the presence of the crosslinked polymer particles (AAA), a water-soluble vinyl monomer (a1 ′) and / or a hydrolyzable vinyl monomer (a2 ′) and an internal crosslinking agent (a3 ′) are copolymerized to form a crosslinked polymer composite. After obtaining (AAAB), a method comprising the step (2) of obtaining absorbent resin particles by drying and pulverization

  Among these methods, the method <1> or <2> is preferable, and the method <1> is more preferable.

  As a device for mixing the cross-linked polymer (A) and the cross-linked polymer (B), a known mixing / kneading device can be used, for example, a bex mill, a rubber chopper, a pharma mill, a mincing machine, an impact pulverizer. And a roll type pulverizer, a homomixer, a biomixer and an SV mixer. Among these, from the viewpoint of mixing properties and the like, a bex mill, a rubber chopper, a pharma mill, and a mincing machine are preferable, and a minching machine is more preferable.

  The mixing temperature (° C.) of the crosslinked polymer (A) and the crosslinked polymer (B) is preferably 60 to 120, more preferably 80 to 100, and most preferably 85 to 95 from the viewpoint of reducing the apparatus load. .

  In mixing, the water content (% by weight) of the crosslinked polymer (A) and the crosslinked polymer (B) is preferably 10 to 90, more preferably 30 to 80, and particularly preferably 40, from the viewpoint of mixing properties. ~ 70, most preferably 50-60.

  The moisture (%) was heated by an infrared moisture measuring device {JE400 manufactured by KETT Co., Ltd .: 120 ± 5 ° C., 30 minutes, ambient humidity 50 ± 10% RH before heating, lamp specification 100V, 40W}. It is obtained from the weight loss of the measurement sample before and after heating.

  In the presence of the crosslinked polymer particles (AA) or the crosslinked polymer particles (AAA), the water-soluble vinyl monomer (a1 ′) and / or the hydrolyzable vinyl monomer (a2 ′) and the internal crosslinking agent (a3 ′) are used together. As a method of polymerizing to obtain a crosslinked polymer composite, a known polymerization method can be applied except that the presence of the crosslinked polymer particles (AA) or the crosslinked polymer particles (AAA).

  Drying of the cross-linked polymer (A) and the mixture of the cross-linked polymer (B) or the cross-linked polymer complex can be carried out by a known method {heat drying, hot air drying, vacuum drying, infrared drying, microwave drying, hydrophobic organic solvent and Azeotropic dehydration, high-humidity drying using high-temperature steam, etc.} can be applied. The drying temperature is preferably about 150 to 250 ° C.

  Prior to drying, the mixture of the crosslinked polymer (A) and the crosslinked polymer (B) or the crosslinked polymer composite may be shredded. By cutting, the drying efficiency can be improved, and the pulverization efficiency when pulverizing after drying can also be improved. When cutting, the size (maximum length) after shredding is preferably 50 μm to 10 cm, more preferably 100 μm to 2 cm, and particularly preferably 1 mm to 1 cm. Shredding can be performed by a known method, and for example, usual apparatuses such as a Bex mill, a rubber chopper, a pharma mill, a mincing machine, an impact pulverizer, and a roll pulverizer can be used.

  The drying temperature is the temperature of the heat medium when oil or steam is used as the heat medium, and the temperature of the material (the material to be dried) when drying by far infrared rays or the like. Further, the drying temperature may be changed stepwise. The drying time depends on the surface area of the material to be dried, moisture, the type of dryer, and the like, and may be selected so as to achieve the desired moisture. For example, it is preferably about 10 to 180 minutes, more preferably 30 to 120. About a minute.

  After drying, the water-absorbent resin particles of the present invention can be obtained by pulverization and / or particle size adjustment by a known method or the like.

  100-800 are preferable, as for the weight average particle diameter (micrometer) of the absorptive resin particle | grains of this invention, More preferably, it is 200-500, Most preferably, it is 300-400. Within this range, the absorption performance and handling properties (such as powder fluidity of the absorbent resin particles) are further improved. In addition, the weight average particle size is obtained by measuring the particle size distribution of the measurement sample, and using logarithmic probability paper {horizontal axis: particle size, vertical axis: cumulative content (wt%)}, the relationship between the cumulative content and the particle size. It is obtained by plotting and determining the particle size corresponding to a cumulative content of 50% by weight. 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 content of fine particles in the absorbent resin particles of the present invention is preferably smaller from the viewpoint of absorption performance, etc., and the content of fine particles of 150 μm or less (preferably 106 μm) or less in the total particles of the absorbent resin particles, It is preferably 3% by weight or less, and more preferably 1% 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 absorbent resin particles is not particularly limited, and examples thereof include an irregularly crushed shape, a flake shape, a pearl shape, and a rice grain shape. Among these, from the viewpoint of good entanglement with a fibrous material when applied to a paper diaper and the like and no fear of dropping off from the fibrous material, an amorphous crushed shape is preferable.

  The absorbent resin particles of the present invention can be subjected to surface crosslinking by a known method or the like, if necessary. As a crosslinking agent (surface crosslinking agent) for performing surface crosslinking, the same as the internal crosslinking agent (a3) can be used. As the surface crosslinking agent, from the viewpoint of absorption performance and the like, the water-soluble substituent {carboxy group, sulfo group, carbamoyl group, etc.) and / or hydrolyzable vinyl monomer (a2, a1 ′) of the water-soluble vinyl monomer (a1, a1 ′) a crosslinking agent 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 diglycidyl ether. Most preferred is ethylene glycol diglycidyl ether.

  In the case of surface cross-linking, the content (% by weight) of the surface cross-linking agent is preferably 0.001 to 7, more preferably 0.002 based on the weight of the cross-linked polymer (A) and the cross-linked polymer (B). ~ 5, particularly preferably 0.003-4. In this range, the absorption performance is further improved.

  When applied to absorbent articles, the water content (% by weight) of the absorbent resin particles of the present invention is preferably 1 to 15, more preferably 2 to 12, particularly preferably from the viewpoints of workability, texture, moisture resistance and the like. Is 4-10. Within this range, the absorbent resin particles are prevented from being destroyed by impact, and workability and the like are further improved. The moisture is not determined only by the drying process, but is adjusted by a surface cross-linking process and a hydration process that are performed as necessary.

The absorbent resin particles of the present invention can contain known additives. Examples of additives that can be used include antiseptics, fungicides, antibacterial agents, antioxidants, ultraviolet absorbers, colorants, fragrances, deodorants, and organic fibrous materials.
When the additive is contained, the total content (% by weight) of the additive varies depending on the use, but is preferably 10 ^{−6 to} 20 based on the weight of the crosslinked polymer (A) and the crosslinked polymer (B). More preferably, it is 10 ^<-5 > ^-10, Most preferably, it is 10 ^<-4 > ^-5 . Within this range, the additive properties can be effectively imparted without deteriorating the absorption performance.
When a known additive is contained, the additive can be added at any stage.

  When the absorbent resin particles of the present invention are applied to an absorbent body, an absorbent article having excellent absorption performance can be easily produced.

  As a method of applying the absorbent resin particles to the absorbent body, a normal method can be applied. For example, (1) a method of dispersing absorbent resin particles between layers of fibrous materials; (2) fibrous materials And (3) a method of sandwiching the absorbent resin particles with a fibrous material, if necessary, with two or more water-absorbing papers or nonwoven fabrics.

  When the 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 total weight of the absorbent resin particles and the fibrous material. Within this range, the absorbent performance of the obtained absorbent body is further improved.

  The absorbent body using the absorbent resin particles of the present invention can be used even if it absorbs liquid {absorbed liquid (body fluid such as sweat, urine and blood, and water such as seawater, groundwater and muddy water)}. Therefore, when applied to sanitary goods such as disposable diapers and sanitary napkins, it exhibits not only excellent absorption performance but also excellent characteristics that the liquid to be absorbed is difficult to reverse even under pressure.

  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. Furthermore, even among paper diapers, the surface dryness value measured by the SDME method is 65% or more (preferably 70% or more, more preferably 80% or more, particularly preferably 90% or more), which is suitable for paper diapers. Yes.

<Surface dryness value by SDME method>
The surface dryness value by the SDME method is measured by the following procedure using an SDME (Surface Dryness Measurement Equipment) tester (manufactured by WK system).
A paper diaper (artificial urine enough to cover the paper diaper (0.03% by weight of calcium chloride, 0.08% by weight of magnesium sulfate, 0.8% by weight of sodium chloride and 99.% of ion-exchanged water). 09% by weight) and left on top for 60 minutes to set a 0% dryness value, and then set the detector of the SDME tester to a dry paper diaper (paper diaper was heated at 80 ° C. for 2 hours) Set 100% dryness and calibrate the SDME tester.

  Next, a metal ring (inner diameter 70 mm, outer diameter 80 mm length 50 mm, weight 300 g) is set at the center of the paper diaper to be measured, and 80 ml of artificial urine is injected. Immediately after injection, the metal ring is removed, and an SDME detector is set in contact with the paper diaper at the center of the paper diaper, and measurement is started. The value 3 minutes after the start of measurement is taken as the surface dryness value by SDME.

  The absorbent resin particles of the present invention are not only used for sanitary products as described above, but also pet urine absorbents, urine gelling agents for portable toilets, freshness preservation agents such as fruits and vegetables, drip absorbents for meat and seafood, cold insulation agents, It is also useful for various applications such as disposable body warmers, battery gelling agents, water retention agents such as plants and soil, anti-condensation agents, water-stopping materials and packing materials, and artificial snow.

  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, parts indicate parts by weight and% indicates% by weight.

<Production Example 1>
88 parts (0.936 moles) sodium acrylate, 22.85 parts (0.317 moles) acrylic acid, 0.4 parts (0.0026 moles) N, N′-methylenebisacrylamide and deionized water While stirring and mixing 293, the temperature was maintained at 1 to 2 ° C., and nitrogen was introduced into the mixed solution to make the dissolved oxygen concentration in the mixed solution 0.5 ppm or less. Subsequently, 0.3 part of 1% hydrogen peroxide aqueous solution, 0.8 part of 0.2% ascorbic acid aqueous solution and 0.8 part of 2% 2,2′-azobisamidinopropane dihydrochloride aqueous solution were added to this mixed solution. Was added and mixed to start polymerization, and after the reaction solution reached 80 ° C., polymerization was performed at a polymerization temperature of 80 ± 2 ° C. for about 5 hours to obtain a crosslinked polymer (1). The water retention amount of the crosslinked polymer (1) was 45 (g / g).

<Production Example 2>
Except that N, N′-methylenebisacrylamide was changed from “0.4 part (0.0026 mol part)” to “0.3 part (0.0019 mol part)”, in the same manner as in Production Example 1, A crosslinked polymer (2) was obtained. The water retention amount of the crosslinked polymer (2) was 50 (g / g).

<Production Example 3>
Crosslinking in the same manner as in Production Example 1 except that N, N′-methylenebisacrylamide was changed from “0.4 part (0.0026 mol part)” to “0.2 part (0.0013 mol part)”. A polymer (3) was obtained. The water retention amount of the crosslinked polymer (3) was 55 (g / g).

<Production Example 4>
Crosslinking in the same manner as in Production Example 1 except that N, N′-methylenebisacrylamide was changed from “0.4 part (0.0026 mol part)” to “0.15 part (0.00097 mol part)”. A polymer (4) was obtained. The water retention amount of the crosslinked polymer (4) was 60 (g / g).

<Production Example 5>
Crosslinking in the same manner as in Production Example 1 except that N, N′-methylenebisacrylamide was changed from “0.4 part (0.0026 mol part)” to “0.1 part (0.00065 mol part)”. A polymer (5) was obtained. The water retention amount of the crosslinked polymer (5) was 65 (g / g).

<Production Example 6>
Crosslinking in the same manner as in Production Example 1 except that N, N′-methylenebisacrylamide was changed from “0.4 part (0.0026 mol part)” to “0.45 part (0.0029 mol part)”. A polymer (6) was obtained. The water retention amount of the crosslinked polymer (6) was 40 (g / g).

<Production Example 7>
Crosslinking in the same manner as in Production Example 1 except that N, N′-methylenebisacrylamide was changed from “0.4 part (0.0026 mol part)” to “0.5 part (0.0032 mol part)”. A polymer (7) was obtained. The water retention amount of the crosslinked polymer (7) was 35 (g / g).

<Example 1>
20 parts of the crosslinked polymer (1) obtained in Production Example 1 and 80 parts of the crosslinked polymer (2) obtained in Production Example 2 were added to a mincing machine (eyepiece hole diameter: 6 mm, 12VR-400K manufactured by Iizuka Kogyo Co., Ltd.). The mixture was mixed at 90 ° C. for 5 minutes, and then dried with a vent type band dryer (135 ° C., 2.0 m / sec; manufactured by Inoue Metal Industry Co., Ltd.) to obtain a dry polymer. This dried polymer was pulverized with a juicer mixer (National MX-X53, manufactured by Matsushita Electric Industrial Co., Ltd.) and adjusted to a particle size range of 150 to 710 μm using a sieve having openings of 150 and 710 μm. 5.5 parts of 1% water / methanol mixed solution of ethylene glycol diglycidyl ether (weight ratio of water / methanol = 60/40) while stirring at high speed (made by Hosokawa Micron High Speed Stirring Turbulizer Mixer: 2,000 rpm) The mixture was added and mixed while spraying, left standing at 140 ° C. for 30 minutes, and heat-crosslinked (surface cross-linked) to obtain absorbent resin particles (1) of the present invention.

<Example 2>
The crosslinked polymer (1) obtained in Production Example 1 was changed from “20 parts” to “80 parts”, and the crosslinked polymer (2) obtained in Production Example 2 was changed from “80 parts” to “20 parts”. Absorbent resin particles (2) of the present invention were obtained in the same manner as in Example 1 except that the above was changed.

<Example 3>
The crosslinked polymer (1) obtained in Production Example 1 was changed from “20 parts” to “40 parts”, and the crosslinked polymer (2) obtained in Production Example 2 was changed from “80 parts” to “60 parts”. Absorbent resin particles (3) of the present invention were obtained in the same manner as in Example 1 except that the above was changed.

<Example 4>
The crosslinked polymer (1) obtained in Production Example 1 was changed from “20 parts” to “60 parts”, and the crosslinked polymer (2) obtained in Production Example 2 was changed from “80 parts” to “40 parts”. Absorbent resin particles (4) of the present invention were obtained in the same manner as in Example 1 except that the above was changed.

<Example 5>
The crosslinked polymer (1) obtained in Production Example 1 was changed from “20 parts” to “50 parts”, and the crosslinked polymer (2) obtained in Production Example 2 was changed from “80 parts” to “50 parts”. Absorbent resin particles (5) of the present invention were obtained in the same manner as in Example 1 except that the above was changed.

<Example 6>
The crosslinked polymer (1) obtained in Production Example 1 was changed from “20 parts” to “50 parts”, and “Crosslinked polymer (2) obtained in Production Example 2 80 parts” was changed to “Production Example (3). Absorbent resin particles (6) of the present invention were obtained in the same manner as in Example 1 except that the cross-linked polymer (3) obtained in (1) was changed to 50 parts.

<Example 7>
The cross-linked polymer (1) obtained in Production Example 1 was changed from “20 parts” to “45 parts” and “Cross-linked polymer (2) obtained in Production Example 2 80 parts” was changed to “Production Example (4). The absorbent resin particles (7) of the present invention were obtained in the same manner as in Example 1 except that the crosslinked polymer (4) obtained in (1) was changed to 55 parts.

<Example 8>
The cross-linked polymer (1) obtained in Production Example 1 was changed from “20 parts” to “55 parts” and “Cross-linked polymer (2) obtained in Production Example 2 80 parts” was changed to “Production Example (5). Absorbent resin particles (8) of the present invention were obtained in the same manner as in Example 1, except that the cross-linked polymer (5) obtained in (1) was changed to 45 parts.

<Example 9>
“20 parts of the crosslinked polymer (1) obtained in Production Example 1” was changed to “50 parts of the crosslinked polymer (6) obtained in Production Example 6” and the crosslinked polymer obtained in Production Example 2 (2 ) Was changed from “80 parts” to “50 parts” in the same manner as in Example 1 to obtain absorbent resin particles (9) of the present invention.

<Example 10>
“20 parts of the crosslinked polymer (1) obtained in Production Example 1” was changed to “50 parts of the crosslinked polymer (7) obtained in Production Example 7” and the crosslinked polymer obtained in Production Example 2 (2 ) Was changed from “80 parts” to “50 parts” in the same manner as in Example 1 to obtain absorbent resin particles (10) of the present invention.

<Example 11>
“20 parts of the crosslinked polymer (1) obtained in Production Example 1” was changed to “45 parts of the crosslinked polymer (4) obtained in Production Example 4” and the crosslinked polymer obtained in Production Example 2 (2 ) Was changed from “80 parts” to “55 parts” in the same manner as in Example 1 to obtain absorbent resin particles (11) of the present invention.

<Example 12>
“20 parts of the crosslinked polymer (1) obtained in Production Example 1” was changed to “45 parts of the crosslinked polymer (3) obtained in Production Example 3” and “the crosslinked polymer obtained in Production Example 2 ( The absorbent resin particles (12) of the present invention were obtained in the same manner as in Example 1 except that “2) 80 parts” was changed to “55 parts of the crosslinked polymer obtained in Production Example 5 (5)”.

<Comparative Example 1>
After 100 parts of the crosslinked polymer (1) obtained in Production Example 1 was stirred at 90 ° C. for 5 minutes with a mincing machine (diameter hole diameter: 6 mm, 12VR-400K manufactured by Iizuka Kogyo Co., Ltd.), a ventilation type band dryer ( Drying was performed at 135 ° C., 2.0 m / sec; manufactured by Inoue Metal Industry Co., Ltd., to obtain a dry polymer. This dried polymer was pulverized with a juicer mixer (National MX-X53, manufactured by Matsushita Electric Industrial Co., Ltd.) and adjusted to a particle size range of 150 to 710 μm using a sieve having openings of 150 and 710 μm. 5.5 parts of a 1 wt% water / methanol mixed solution (water / methanol weight ratio = 60/40) of ethylene glycol diglycidyl ether while stirring at high speed (high-speed stirring turbulizer mixer: 2,000 rpm) Was added and mixed while spraying, and the mixture was allowed to stand at 140 ° C. for 30 minutes and subjected to heat crosslinking (surface crosslinking) to obtain comparative absorbent resin particles (H1).

<Comparative example 2>
Absorbent resin particles for comparison in the same manner as in Comparative Example 1 except that the “crosslinked polymer (1) obtained in Production Example 1” was changed to “crosslinked polymer (2) obtained in Production Example 2”. (H2) was obtained.

<Comparative Example 3>
Absorbent resin particles for comparison in the same manner as in Comparative Example 1 except that the “crosslinked polymer (1) obtained in Production Example 1” was changed to “crosslinked polymer (3) obtained in Production Example 3”. (H3) was obtained.

  About the absorptive resin particle obtained by the Example and the comparative example, the water retention amount and the absorption amount under load were measured, and it showed in Table 1.

<Measurement method of absorption under load>
Weigh 0.1 g of measurement sample in a cylindrical plastic tube (inner diameter 30 mm, height 60 mm) with a nylon mesh of 63 μm (conforming to JIS Z8801-1: 2001) pasted on the bottom, and make the plastic tube vertical. A measurement sample was arranged on a nylon net so as to have a substantially uniform thickness, and a weight of 29.5 mm × 22 mm in outer diameter was placed on the measurement sample so as to obtain a load of 40 g / cm ² . In a petri dish (diameter: 12 cm) containing 60 ml of physiological saline (salt concentration 0.9%), place a plastic tube containing a measurement sample and a weight vertically, immerse the nylon mesh side on the bottom, and let it stand, After 60 minutes, the plastic tube containing the sample and the weight is weighed, and the weight of the measurement sample that has absorbed physiological saline is calculated. The value 10 times the increased weight is the absorbed amount under load with respect to physiological saline (g / G). The physiological saline used and the temperature of the measurement atmosphere were 25 ° C. ± 2 ° C.

<Example 13>
About 100 parts by weight of a mixture obtained by mixing 100 parts of fluff pulp and 100 parts of the absorbent resin particles (1) of the present invention obtained in Example 1 with an airflow 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 40 cm × 30 cm rectangle and sandwiched between two sheets of water absorbent paper (basis weight: 15.5 g / m2: Advantech, filter paper No. 2) of the same size (14 cm × 36 cm) After that, a polyethylene sheet (polyethylene film UB-1, manufactured by Tamapoly Co., Ltd., 14 cm × 36 cm) is arranged 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 arranged on the surface. Thus, an absorbent article (1) of the present invention was prepared.

<Examples 14 to 24>
Except having changed "absorbent resin particle (1)" into "any of the absorbent resin particles (2)-(12)", it carried out similarly to Example 13, and the absorber (K2)- (K12) was prepared, and absorbent articles (2) to (12) of the present invention were further prepared.

<Comparative Examples 4-6>
Except that the “absorbent resin particles (1)” was changed to “any of the absorbent resin particles (H1) to (H3)”, in the same manner as in Example 13, the comparative absorber (HK1) to (HK3) was prepared, and comparative absorbent articles (H1) to (H3) were prepared.

  About the absorbent article obtained by the Example and the comparative example, the surface dryness value (%) by SDME method was measured, and it showed in Table 2.

As can be seen from Tables 1 and 2, the absorbent resin particles (1) to (12) prepared in Examples 1 to 12 have improved absorption performance (water retention amount, absorption amount under load), and absorbency using these. The article was remarkably superior in surface dryness value by the SDME method. Therefore, it can be estimated that the discomfort felt on the skin when the absorbent article is worn can be significantly reduced.
On the other hand, it was clear that the comparative absorbent resin particles (H1) to (H3) have low absorption performance, and the absorbent articles using these have extremely poor surface dryness values by the SDME method.

Claims (7)

A crosslinked polymer (A) having the water-soluble vinyl monomer (a1) and / or the hydrolyzable vinyl monomer (a2), and the internal crosslinking agent (a3) as essential constituent units;
A water-soluble vinyl monomer (a1 ′) and / or a hydrolyzable vinyl monomer (a2 ′), and a crosslinked polymer (B) having an internal crosslinking agent (a3 ′) as essential constituent units,
The water retention amount of the crosslinked polymer (A) is 30 to 55 g / g, the water retention amount of the crosslinked polymer (B) is 35 to 60 g / g,
Absorbent resin particles, wherein the difference between the water retention amount of the crosslinked polymer (A) and the water retention amount of the crosslinked polymer (B) exceeds 5 g / g. Based on the total weight of the crosslinked polymer (A) and the crosslinked polymer (B), the content of the crosslinked polymer (A) is 20 to 80% by weight, and the content of the crosslinked polymer (B) is 20 to 80% by weight. The absorbent resin particle according to claim 1 , which is%. A method for producing the absorbent resin particles according to claim 1 or 2,
A step (1) of obtaining a crosslinked polymer (A) by copolymerizing the water-soluble vinyl monomer (a1) and / or the hydrolyzable vinyl monomer (a2) and the internal crosslinking agent (a3);
Step (2) of obtaining a crosslinked polymer (B) by copolymerizing the water-soluble vinyl monomer (a1 ′) and / or the hydrolyzable vinyl monomer (a2 ′) and the internal crosslinking agent (a3 ′); and crosslinking after mixing the crosslinking polymer polymer (a) (B), drying, method of manufacturing an absorbent resin particles to step (3) to obtain a pulverized to absorbent resin particles, characterized in including it. The amount of the internal crosslinking agent (a3) used is 0.01 to 1 based on the number of moles of the water-soluble vinyl monomer (a1) unit and the hydrolyzable vinyl monomer (a2) unit, and the internal crosslinking agent (a3 ′) The production method according to claim 3 , wherein the amount of is 0.005 to 0.8 based on the number of moles of the water-soluble vinyl monomer (a1 ′) unit and the hydrolyzable vinyl monomer (a2 ′) unit. Based on the total weight of the crosslinked polymer (A) and the crosslinked polymer (B), the mixed amount of the crosslinked polymer (A) is 20 to 80% by weight, and the mixed amount of the crosslinked polymer (B) is 20 to 80% by weight. The manufacturing method according to claim 3 or 4 , which is%. An absorbent body comprising the absorbent resin particles according to claim 1 or 2 and a fibrous substance. An absorbent article comprising the absorbent body according to claim 6 .