JP5906010B2 - Absorbent resin particles, absorber containing the same, and absorbent article - Google Patents

Description

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

A water-absorbing agent with high liquid permeability and fast absorption rate has less moisture and return during actual use of the absorbent article, and improves the dryness of the surface of the absorbent article. It is known that it can be reduced (Patent Document 1).
In addition, an absorbent containing a viscosity modifier is excellent in the resistance to leakage of viscous liquid excrement such as loose stool and vomiting, and firmly retains the absorbed moisture. It is known to exhibit anti-fogging properties (Patent Document 2).

  However, the conventional absorbent resin particles and water-absorbing agents have a problem that even when the absorbent article can be reduced in the short-time use, the dampness is also generated in the long-time use, resulting in an unpleasant feeling.

JP 2006-057075 A JP 2005-186015 A

Absorbent articles (such as disposable diapers) that use conventional absorbent resin particles absorb liquids and solve problems such as leakage and fogging. Easy to feel uncomfortable. And the absorptive article which does not have the discomfort by such a swelling, and the absorptive resin particle which can be used for this are strongly desired.
An object of the present invention is to provide absorbent resin particles that are less likely to cause stuffiness and to provide an absorbent article that does not cause discomfort due to stuffiness as described above by using the absorbent resin particles.

  As a result of intensive studies to achieve the above object, the present inventors have found that the above problems can be solved with absorbent resin particles containing a specific nitrogen-containing compound, and have reached the present invention.

That is, the method for producing the absorbent resin particles of the present invention is a simple method in which the water-soluble vinyl monomer (a1) and / or the hydrolyzable vinyl monomer (a2) and the crosslinking agent (a3) are essential constituent monomers (a). A step (1) of obtaining a cross-linked polymer / urea composite gel by mixing a cross- linked polymer (A) obtained by copolymerizing a monomer and urea, and comprising the cross-linked polymer (A) and water. The method includes a step of mixing the hydrogel and urea, and the gist is that the amount of urea used is 5 to 40% by weight based on the total weight of (A) and urea.

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

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

The absorbent resin particles of the present invention contain a specific nitrogen-containing compound and are excellent against stuffiness.
Therefore, the absorbent resin particles of the present invention are made into absorbent articles (such as paper diapers and sanitary napkins).
When applied to, there is little stuffiness and less discomfort.

  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} 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.

The cross-linking agent (a3) is not particularly limited, and known cross-linking agents such as those disclosed in known {eg, 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} are available. Can be used.
Among these, from the viewpoint of absorption characteristics and the like, a crosslinking agent having two or more ethylenically unsaturated groups is preferable, and more preferably a poly (meth) allyl ether of a polyol having 2 to 10 carbon atoms and N, N′-methylene. Bisacrylamide, particularly preferably triallyl cyanurate, triallyl isocyanurate, tetraallyloxyethane, pentaerythritol triallyl ether and N, N'-methylenebisacrylamide, most preferably pentaerythritol triallyl ether and N, N'- Methylenebisacrylamide.

  The content (mol%) of the crosslinking agent (a3) 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.

  In addition to these monomers, the water-soluble vinyl monomer (a1) and / or the hydrolyzable vinyl monomer (a2) and the cross-linking agent (a3) are essential monomers (a). Possible other vinyl monomers (a4) can be included.

Other vinyl monomers (a4) 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 (a4) is included, the content (mol%) of the other vinyl monomer (a4) is based on the number of moles of the water-soluble vinyl monomer (a1) and the hydrolyzable vinyl monomer (a2). 0.01-5 is preferable, More preferably, it is 0.05-3, Next, Preferably it is 0.08-2, Most preferably, it is 0.1-1.5. In view of absorption performance and the like, it is most preferable not to use any other vinyl monomer (a4).

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

  A cross-linked polymer (A) is obtained by copolymerizing a water-soluble vinyl monomer (a1) and / or a hydrolyzable vinyl monomer (a2) and a monomer having the cross-linking agent (a3) as an essential constituent monomer (a). Is obtained. Examples of the copolymerization method include known aqueous solution polymerization {adiabatic polymerization, thin film polymerization, spray polymerization method, etc .; JP-A-55-133413, etc.}, and known reverse-phase suspension polymerization {Japanese Examined Patent Publication No. 54-30710, No. 56-26909 and JP-A-1-5808 etc.}.

  The content (% by weight) of the cross-linked polymer (A) is 60 to 95 based on the weight of the cross-linked polymer (A) and the nitrogen-containing compound (B). ~ 90.

<Nitrogen-containing compound (B) represented by general formula (1)>
The nitrogen-containing compound (B) is represented by the general formula (1). The nitrogen-containing compound (B) includes a salt thereof.

R < ¹ > -R < ⁴ > in General formula (1) represents hydrogen, a hydroxyl group, an amino group, a nitrile group, an alkyl group, an alkenyl group, or an aryl group. In the alkyl group, alkenyl group or aryl group, the hydrogen atom of these groups may be substituted with a hydroxyl group, a carboxyl group, an amino group, a nitrile group or a halogen atom.
The number of carbon atoms of the alkyl group, alkenyl group or aryl group is preferably 1 to 10, more preferably 1 to 6, from the viewpoint of preventing stuffiness.
The alkyl group and alkenyl group include those having a linear structure or a branched structure. In the alkyl group, alkenyl group or aryl group, when the hydrogen atom is substituted, examples of the substituent include a hydroxyl group, a carboxyl group, an amino group, a nitrile group, and a halogen atom. Group, carboxyl group and amino group are preferred.

  Specific examples of the nitrogen-containing compound represented by the general formula (1) include urea, 1-methylurea, hydroxyurea, 1,1-dimethylurea, 1,3-dimethylurea, carbohydrazide, semicarbazide hydrochloride, and the like. Is mentioned. As (B), urea is preferable from the viewpoint of preventing stuffiness.

  The solubility of (B) in water at 25 ° C. is preferably 0.1 to 500 g / 100 ml, more preferably 1 to 500 g / 100 ml, and still more preferably 10 to 500 g / 100 ml. Within this range, the absorption performance is further improved.

  The content (% by weight) of (B) is 5 to 40 based on the total weight of the cross-linked polymers (A) and (B), and is preferably 10 to 20 from the viewpoint of being less likely to cause stuffiness. . When the content of (B) is less than 5, stuffiness is likely to occur, and when it exceeds 40, the absorption performance is deteriorated.

  The absorbent resin particles of the present invention can be easily obtained by the production method of the present invention described below.

A water-soluble vinyl monomer (a1) and / or a hydrolyzable vinyl monomer (a2) and a monomer having a crosslinking agent (a3) as an essential constituent monomer (a) are copolymerized to obtain a crosslinked polymer (A). (1) After obtaining (A) and a nitrogen-containing compound (B) to obtain a crosslinked polymer / nitrogen-containing compound composite gel (A / B) or water-soluble vinyl monomer (a1) and / or Alternatively, the monomer having the hydrolyzable vinyl monomer (a2) and the crosslinking agent (a3) as the essential constituent monomer (a) and the nitrogen-containing compound (B) are mixed and then copolymerized to crosslink. Comprising a step (2) of obtaining a polymer / nitrogen-containing compound composite gel (A / B).

  In the production method of the present invention, the nitrogen-containing compound (B) is preferably solid.

<Step (1)>
In step (1), after obtaining the crosslinked polymer (A) obtained by the above-mentioned method, the crosslinked polymer (A) and the nitrogen-containing compound (B) are mixed to form a crosslinked polymer / nitrogen-containing compound composite. This is a step of obtaining a body gel (A / B).

  The method of mixing the crosslinked polymer (A) and the nitrogen-containing compound (B) includes a method of mixing the crosslinked polymer (A), a water-containing gel composed of water, and the nitrogen-containing compound (B).

  The use amount (% by weight) of the nitrogen-containing compound (B) (amount not containing a solvent such as water) is based on the weight of the crosslinked polymer (A) and the nitrogen-containing compound (B), from the viewpoint of occurrence of stuffiness. 5 to 40, preferably 10 to 20.

  When using the hydrogel which consists of a crosslinked polymer (A) and water, you may use this hydrogel after shredding as needed. When chopping, 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 from the viewpoint of the drying property of the gel.

  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}. .

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

  The usage-amount (weight%) of a crosslinked polymer (A) is 60-95 based on the weight of a crosslinked polymer (A) and a nitrogen-containing compound (B), Preferably it is 80-90. Within this range, the occurrence of stuffiness is further improved.

  As a mixing device of the crosslinked polymer (A) and the nitrogen-containing compound (B), a known device {double-arm kneader, internal mixer (Banbury mixer), self-cleaning mixer, gear compounder, screw-type extruder , Screw type kneader, pulverizing type kneader, minced machine, cylindrical mixer, V-shaped mixer, ribbon type mixer, screw type mixer, double arm type mixer, groove type mixer, vertical type mixer, tar A bulletizer, a Nauter type mixer, a fluid type mixer, an airflow type mixer, a rotating disk type mixer, a conical blender, a roll mixer, etc.} can be used. These can be used in combination.

  The mixing temperature (° C.) of the crosslinked polymer (A) and the nitrogen-containing compound (B) is preferably 0 to 150, more preferably 5 to 130, and particularly preferably 10 to 100. Within this range, it becomes easier to mix evenly and the absorption performance is further improved.

<Step (2)>
Mixing the water-soluble vinyl monomer (a1) and / or the hydrolyzable vinyl monomer (a2) and the monomer having the crosslinking agent (a3) as an essential constituent monomer (a) with the nitrogen-containing compound (B) The method is not particularly limited as long as it can be uniformly mixed.

  As a mixing device of the monomer and the nitrogen-containing compound (B), a known device {a double arm type kneader, an internal mixer (Banbury mixer), a self-cleaning type mixer, a gear compounder, a screw type extruder, a screw type Kneaders, pulverizing kneaders, mincing machines, cylindrical mixers, V-shaped mixers, ribbon-type mixers, screw-type mixers, double-armed mixers, groove-type mixers, vertical mixers, turbulizers, Nauter type mixer, fluid type mixer, airflow type mixer, rotary disk type mixer, conical blender, roll mixer, etc.} can be used. A plurality of these may be combined.

  The use amount (% by weight) of the nitrogen-containing compound (B) is preferably 5 to 40 based on the weight of the essential constituent monomer (a) and the nitrogen-containing compound (B), from the viewpoint of occurrence of stuffiness. Preferably it is 10-20.

  The use amount (% by weight) of the essential constituent monomer (a) is preferably 60 to 95 from the viewpoint of occurrence of stuffiness based on the weight of the essential constituent monomer (a) and the nitrogen-containing compound (B). More preferably, it is 80-90.

  0-150 are preferable, as for the mixing temperature (degreeC) of a monomer and a nitrogen-containing compound (B), More preferably, it is 5-130, Most preferably, it is 10-100. Within this range, it becomes easier to mix evenly and the absorption performance is further improved.

  After mixing with the nitrogen-containing compound (B), a monomer having the water-soluble vinyl monomer (a1) and / or the hydrolyzable vinyl monomer (a2) and the crosslinking agent (a3) as an essential constituent monomer (a) Examples of the copolymerization method include known aqueous solution polymerization {adiabatic polymerization, thin film polymerization, spray polymerization method, etc .; Japanese Patent Laid-Open No. 55-133413}, and known reverse phase suspension polymerization {Japanese Patent Publication No. 54-30710, No. 56-26909 and JP-A-1-5808 etc.}.

The crosslinked polymer / nitrogen-containing compound composite gel (A / B) obtained in the step (1) or (2) can lead to absorbent resin particles by post-treatment.
Post-processing includes shredding, solvent evaporation (drying), pulverization, particle size adjustment, surface crosslinking, and mixing of additives. These post-processing may be performed in combination, or only one of them may be performed. Moreover, there is no restriction | limiting in the order of post-processing, Although it determines suitably, said order is preferable from a viewpoint of absorption performance. In addition, it is preferable to include drying from a viewpoint of absorption performance among these post-processing. Moreover, when employ | adopting aqueous solution polymerization, it is preferable that a grinding | pulverization is further included from a viewpoint of absorption performance.

<Shred>
Shredding can be performed by a known method, and can be shredded using a known shredding device {for example, a bex mill, rubber chopper, pharma mill, mincing machine, impact crusher and roll crusher}. .

  When shredding, the size (longest diameter) of the composite gel (A / B) after shredding 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, in addition to being easier to handle, when the solvent is subsequently distilled off, the solvent is further easily distilled off, and when pulverizing thereafter, the pulverization is further facilitated.

<Solvent evaporation (drying)>
In the step (1) or (2), when a solvent (such as an organic solvent and water) is used, it is preferable to distill off the solvent from the viewpoint of absorption performance.
When the solvent contains an organic solvent, the content (% by weight) of the organic solvent after the distillation is preferably 0 to 10, more preferably 0 to 5, particularly preferably 0, based on the weight of the absorbent resin particles. ~ 3, most preferably 0-1. Within this range, the absorption performance is further improved.

When water is contained in the solvent, the water content (% by weight) after distillation is preferably 0 to 25, more preferably 1 to 20, particularly preferably 2 to 17, most preferably based on the weight of the absorbent resin particles. Is 3-15. Within this range, the absorption performance and breakage resistance of the absorbent resin particles are further improved.

  In addition, the content and moisture of the organic solvent are an infrared moisture measuring device {JE400 manufactured by Kett Science Laboratory 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, etc. can be applied.
Prior to the solvent distillation, the solvent can be removed by decantation, centrifugation, filtration, or the like.

<Crushing>
The pulverization is preferably performed after distilling off the solvent from the viewpoint of absorption performance.
The pulverization method is not particularly limited, and can be pulverized by a known pulverizer (for example, a hammer pulverizer, an impact pulverizer, a roll pulverizer, and a jet airflow pulverizer).

<Granularity control>
The size of the pulverized particles is adjusted by sieving or the like as necessary.
The weight average particle diameter (μm) of the pulverized particles is preferably 100 to 800, more preferably 200 to 500, and particularly preferably 350 to 450. Within this range, the absorption performance is further improved. Therefore, it is preferable to adjust the particle size so as to be in this range.

  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.

<Surface cross-linking>
The cut chopped gel or the pulverized particles can be subjected to surface cross-linking treatment with a surface cross-linking agent, if necessary.
As the surface crosslinking agent, known {for example, JP 59-189103, JP 58-180233, JP 61-16903, JP 61-2111305, JP 61-252212, Surface cross-linking agents {polyvalent glycidyl, polyhydric alcohol, polyvalent amine, polyvalent aziridine, polyvalent isocyanate, silane coupling agent and polyvalent metal of JP-A-51-136588 and JP-A-61-257235} Etc.} can be used. Of these surface cross-linking agents, from the viewpoint of economy and absorption performance, polyvalent glycidyl, polyhydric alcohol and polyvalent amine are preferable, more preferably polyvalent glycidyl and polyhydric alcohol, particularly preferably polyvalent glycidyl, Preferred is ethylene glycol diglycidyl ether.

  In the case of surface cross-linking, the amount (% by weight) of the surface cross-linking agent is not particularly limited because it can be changed variously depending on the type of surface cross-linking agent, cross-linking conditions, target performance, etc. From a viewpoint etc., based on the weight of an essential constituent monomer (a), 0.001-3 are preferable, More preferably, it is 0.005-2, Most preferably, it is 0.01-1.

  In the case of surface crosslinking, a known method {for example, 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} can be applied.

<Mixing of additives>
For shredded gels, dry particles, pulverized particles or surface cross-linked particles, other additives (for example, known preservatives, fungicides, antibacterial agents (for example, JP-A No. 2003-225565 and JP-A No. 2006-131767)) Agent, antioxidant, ultraviolet absorber, colorant, fragrance, deodorant, inorganic powder, organic fibrous material, etc.}.
When other additives are mixed, the mixing method is not limited as long as uniform mixing is possible, and a known mixing method can be applied.

  The content (% by weight) of other additives is preferably 10 or less, more preferably 8 or less, and then preferably 5 or less, based on the total weight of (A) and (B). Preferably it is 3 or less, and most preferably 1 or less. Within this range, the absorption performance is good.

  The shape of the absorbent resin particle of the present invention 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, when applied to a paper diaper or the like, from the viewpoint of good entanglement with the fibrous material, no fear of dropping off from the fibrous material, and from the viewpoint of absorption performance, an irregularly crushed shape and a pearl shape are preferable.

  The weight average particle diameter (μm) of the absorbent resin particles of the present invention 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.

  The apparent density (g / ml) of the absorbent resin particles of the present invention is preferably 0.54 to 0.70, more preferably 0.56 to 0.65, and particularly preferably 0.58 to 0.63. . Within this range, the absorption performance is further improved. The apparent density is measured at 25 ° C. according to JIS K7365: 1999.

By applying the absorbent resin particles of the present invention to various absorbers, absorbent articles having excellent absorption performance can be produced. Absorbers and absorbent articles are produced by known methods (for example, JP-A-2003-225565, JP-A-2006-131767, JP-A-2005-097569, JP-A-2005-186016).
Absorbent articles include sanitary products {paper diapers (children's disposable diapers, adult disposable diapers, etc.), napkins (sanitary napkins, etc.), vomiting absorption etiquette bags, paper towels, pads (incontinence pads and surgical underpads) Etc.) and pet sheets (pet urine absorption sheets, heat insulation sheets, etc.)} and various household and industrial absorption sheets {freshness maintenance sheets, drip absorption sheets, paddy rice seedling sheets, concrete curing sheets and cables, etc. Running prevention sheet, etc.}.
Among these, the absorbent resin particles of the present invention are suitable for sanitary goods from the viewpoint of absorption performance, and are further suitable for paper diapers, pads and sanitary napkins, especially paper diapers and sanitary napkins.

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>
A glass reaction vessel with a capacity of 1 liter was charged with 77 g of sodium acrylate, 22.7 g of acrylic acid, 0.3 g of N, N′-methylenebisacrylamide and 295 g of deionized water, and the temperature of the contents was adjusted to 3 while stirring and mixing. Kept at ℃. After flowing nitrogen into the contents to make the dissolved oxygen amount 1 ppm or less, 1 g of 1% aqueous solution of hydrogen peroxide, 1.2 g of 0.2% aqueous solution of ascorbic acid and 2,2′-azobisamidinopropane dihydro A hydrated gel polymer (A1) was obtained by adding and mixing 2.8 g of a 2% aqueous solution of chloride to initiate polymerization and polymerizing for about 5 hours.

<Production Example 2>
A glass reaction vessel with a capacity of 1 liter is charged with 77 g of sodium acrylate, 22.7 g of acrylic acid, 0.3 g of N, N′-methylenebisacrylamide, 5.26 g of urea and 295 g of deionized water while stirring and mixing. The temperature of the object was kept at 3 ° C. After flowing nitrogen into the contents to make the dissolved oxygen amount 1 ppm or less, 1 g of 1% aqueous solution of hydrogen peroxide, 1.2 g of 0.2% aqueous solution of ascorbic acid and 2,2′-azobisamidinopropane dihydro 2.8 g of a 2% aqueous solution of chloride was added and mixed to initiate polymerization, and polymerization was carried out for about 5 hours to obtain a hydrogel polymer (A2).

<Example 1>
5.26 g of urea was added to the hydrogel polymer (A1) obtained in Production Example 1 and mixed uniformly with an internal mixer, and then air-flowing band drying under conditions of 150 ° C. and wind speed of 2.0 m / sec. It dried with the machine (made by Inoue Metal Industry). The obtained dried product was pulverized and adjusted to a particle size of 30 to 60 mesh to obtain a water absorbing agent. 2 g of a 10% water / methanol mixed solution of ethylene glycol diglycidyl ether (water / methanol = 70/30) was added and mixed while stirring 100 g of this water-absorbing agent, followed by heat crosslinking at 140 ° C. for 30 minutes. Crosslinked absorbent resin particles (1) were obtained.

<Example 2>
Absorbent resin particles (2) were obtained in the same manner as in Example 1, except that "5.26 g of urea was added" to "11.11 g of urea was added".

<Example 3>
Absorbent resin particles (3) were obtained in the same manner as in Example 1 except that “5.26 g of urea was added” to “25 g of urea was added”.

<Example 4>
Absorbent resin particles (4) were obtained in the same manner as in Example 1 except that "5.26 g of urea was added" to "66.67 g of urea" was changed.

< Reference Example 5>
The water-containing gel polymer (A2) obtained in Production Example 2 was shredded to a size of 3 to 7 mm with an internal mixer, and then dried with a ventilation band dryer under conditions of 150 ° C. and a wind speed of 2.0 m / sec. . The obtained dried product was pulverized and adjusted to a particle size of 30 to 60 mesh to obtain a water absorbing agent. 2 g of a 10% water / methanol mixed solution of ethylene glycol diglycidyl ether (water / methanol = 70/30) was added and mixed while stirring 100 g of this water-absorbing agent, followed by heating and crosslinking at 140 ° C. for 30 minutes. Crosslinked absorbent resin particles (5) were obtained.

<Comparative Example 1>
The hydrogel polymer ( A1 ) obtained in Production Example 1 is shredded to a size of 3 to 7 mm with an internal mixer, and then dried with a ventilated band dryer under conditions of 150 ° C. and a wind speed of 2.0 m / sec. did. The obtained dried product was pulverized and adjusted to a particle size of 30 to 60 mesh to obtain a water absorbing agent. 2 g of a 10% water / methanol mixed solution of ethylene glycol diglycidyl ether (water / methanol = 70/30) was added and mixed while stirring 100 g of this water-absorbing agent, followed by heating and crosslinking at 140 ° C. for 30 minutes. Cross-linked comparative absorbent resin particles (H1) were obtained. In addition, this comparative example 1 is a thing corresponded to the comparative example 2 of Unexamined-Japanese-Patent No. 2002-282687.

< Reference Comparative Example 2>
After the hydrogel polymer (A1) obtained in Production Example 1 was shredded to a size of 3 to 7 mm with an internal mixer, 5 g of urea (B) was added and further mixed uniformly with the internal mixer. Except for the above, absorbent resin particles (H2) were obtained in the same manner as in Example 1. In addition, this reference comparative example 2 is a thing corresponded to Example 5 of Unexamined-Japanese-Patent No. 2002-282687.

  Using the absorbent resin particles obtained in Examples 1 to 5 and Comparative Examples 1 and 2, an absorber and an absorbent article (paper diaper) were prepared as follows, and the absorption time and humidity increase rate (Mule's The results are shown in Table 2.

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

<Absorption time measurement method>
Set a metal ring (inner diameter 70 mm, length 50 mm) in the center of the paper diaper to be measured, inject 100 ml of physiological saline, and then absorb the physiological saline until it is absorbed {Glossiness due to physiological saline cannot be confirmed Until {} is measured. The physiological saline and measurement atmosphere were 25 ± 3 ° C. and 65 ± 5% RH.
<Humidity rise measurement method: evaluation of moisture>
The humidity in the auto dry desiccator (manufactured by AZ ONE: UVOH400SA) is adjusted to 36 ± 1% (T0) and the temperature is adjusted to 28 ± 1 ° C. After measuring the absorption time of the paper diaper with the above absorption time measurement method, immediately put the paper diaper in the auto dry desiccator, close the lid and seal it, stop the humidity control device, put the paper diaper in the auto dry desiccator The humidity (T1) after 15 minutes is measured. The disposable diaper is placed beside the hygrometer, and the humidity increase rate is obtained by the following formula.

(T1-T0) / T0 = humidity increase rate

  As can be seen from Table 1, the absorbent article using the absorbent resin particles of the present invention had a low rate of increase in humidity and was excellent in preventing swelling as compared with an absorbent article using comparative absorbent resin particles.

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 fish, seafood, disposable warmer, gelling agent for batteries,
It can also be used in various applications such as soil water retention agents, anti-condensation agents, water-stopping agents, packing agents and artificial snow.

Claims (2)

  A cross-linked polymer (A) obtained by copolymerizing a water-soluble vinyl monomer (a1) and / or a hydrolyzable vinyl monomer (a2) and a monomer having a cross-linking agent (a3) as an essential constituent monomer (a) ) And urea to obtain a crosslinked polymer / urea composite gel (1), comprising the step of mixing the crosslinked polymer (A), a hydrous gel comprising water and urea, The manufacturing method of the absorbent resin particle whose usage-amount of urea is 5 to 40 weight% based on the total weight of (A) and urea.   The production method according to claim 1, wherein urea is in a solid form.