JP2006122737A - Water absorbent, and absorbing medium and absorptive article using the absorbent - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a water absorbent capable of being used for an absorptive article in which an attachment person easily senses a uncomfortable sense at urination or the like regardless of exhibiting high absorption performance even in any state (even if load is applied). <P>SOLUTION: In the water absorbent containing a cross-linking polymer (A) containing a water-soluble vinyl monomer (a1) and/or a vinyl monomer (a2) becoming (a1) by hydrolysis and an internal cross-linking agent (b) as indispensable constitution units, a gel modulus of elasticity of 30 times swelled gel obtained by absorbing 30 wt. prt. of artificial urea by 1 wt. prt. of water absorbent is 2,000-3,000 N/m<SP>2</SP>and an absorption amount of the water absorbent after 1 hour relative to saline under a load of 20 g/cm<SP>2</SP>is 7.0-16.0 g/g. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

The present invention relates to a water absorbing agent, an absorbent body using the same, and an absorbent article.

Cross-linked polymers with improved aqueous liquid absorption properties are known (Patent Documents 1, 2, and 3).
JP-A-3-179008 Japanese Patent No. 267529 European Patent Publication No. 618005A

With conventional cross-linked polymers, when applied to training diapers (pants), etc. for promoting diaper separation, there is no liquid return and the diaper surface is exposed, so it is difficult for the wearer to notice that urination has occurred. is there.
That is, the object of the present invention is to provide an absorbent article in which a wearer can easily feel discomfort during urination or the like, despite exhibiting high absorption performance in any state (however a load is applied). It is providing the water absorbing agent which can be used for.

As a result of intensive studies to achieve the above object, the present inventors have found that a water-absorbing agent having a specific gel elastic modulus and absorption amount under load can solve the above problems, and have reached the present invention.
That is, the water-absorbing agent of the present invention is characterized in that the water-soluble vinyl monomer (a1) and / or the vinyl polymer (a2) that becomes (a1) by hydrolysis and a cross-linked polymer having the internal cross-linking agent (b) as essential constituent units. In the water-absorbing agent containing (A), the gel elastic modulus of a 30-fold swollen gel obtained by absorbing 30 parts by weight of artificial urine with 1 part by weight of the water-absorbing agent is 2,000 to 3,000 N / m ² and 20 g The point is that the amount of the water-absorbing agent absorbed after 1 hour with respect to physiological saline under a load of / cm ² is 7 to 16 g / g.

  The water-absorbing agent of the present invention exhibits high absorption performance in any state (however a load is applied). Nevertheless, when this water-absorbing agent is applied to absorbent articles, the wearer can easily feel discomfort during urination.

First, the crosslinked polymer (A) will be described.
There is no particular limitation on the water-soluble vinyl monomer (a1) and / or the vinyl monomer (a2) that becomes (a1) by hydrolysis, and the water-soluble vinyl monomer and / or hydrolysis described in JP-A-2001-220415 and the like. The resulting water-soluble vinyl monomer can be used.
Among these, from the viewpoint of absorption performance, the water-soluble vinyl monomer (a1) is preferable, more preferably an anionic vinyl monomer, and particularly preferably a C3-C30 vinyl group-containing carboxylic acid (salt) {unsaturated monocarboxylic acid. Acids ((meth) acrylic acid, (meth) acrylates, crotonic acid, cinnamic acid, etc.); unsaturated dicarboxylic acids (maleic acid, maleate, fumaric acid, citraconic acid, itaconic acid, etc.); and said unsaturated Monoalkyl (carbon number 1-8) ester of 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.}, most preferably acrylic acid (salt) A.
Examples of the salt include alkali metal salts (sodium salt, potassium salt, etc.), alkaline earth metal salts (calcium salt, magnesium salt, etc.), ammonium salts {ammonium salts, tetraalkyl (alkyl group having 1 to 8 carbon atoms) ammonium salts. (Tetramethylammonium etc.) etc.} and organic amine salt etc. are mentioned. The organic amine constituting the organic amine salt includes alkylamines having 1 to 8 carbon atoms, alkanolamines having 2 to 8 carbon atoms, polyalkylene (alkylene having 1 to 8 carbon atoms) polyamine (2 to 10 amino groups). Or a derivative of a polyalkylene polyamine {a compound alkylated with an alkyl group having 1 to 8 carbon atoms, or a compound to which an alkylene oxide having 2 to 12 carbon atoms is added (average number of moles added per amino group 1 to 30 Mol)} and the like.

  When the water-soluble vinyl monomer (a1) and the vinyl monomer (a2) are used as structural units, the content weight ratio (a1 / a2) is preferably 75/25 to 99/1, and more preferably 85/15 to 95. / 5, particularly preferably 90/10 to 93/7, most preferably 91/9 to 92/8. Within this range, the absorption performance (especially the absorption amount and the absorption rate) is further improved.

As a vinyl monomer used as a structural unit of the crosslinked polymer (A), in addition to the vinyl monomers (a1) and / or (a2), other vinyl monomers (a3) copolymerizable therewith are structural units. It can be.
Examples of other copolymerizable vinyl monomers (a3) include hydrophobic vinyl monomers, but are not limited thereto.
As the other vinyl monomer (a3), the following vinyl monomers (i) to (iii) are used.

(I) an aromatic ethylenic monomer having 8 to 30 carbon atoms;
Styrene such as styrene, α-methylstyrene, vinyltoluene, dichlorostyrene and hydroxystyrene, and vinylnaphthalene.
(Ii) an aliphatic ethylenic monomer having 2 to 20 carbon atoms;
Alkenes {ethylene, propylene, butene, isobutylene, pentene, heptene, diisobutylene, octene, dodecene, octadecene, etc.}; and alkadienes {butadiene, isoprene, etc.}.
(Iii) an alicyclic ethylenic monomer having 5 to 15 carbon atoms;
Monoethylenic monomers {pinene, limonene, indene and the like}; and polyethylene monomers {cyclopentadiene, bicyclopentadiene, ethylidene norbornene, etc.} and the like.

  When the other copolymerizable vinyl monomer (a3) is used as a structural unit, the content (% by weight) of (a3) is 0.01 to based on the total weight of the vinyl monomers (a1) and (a2). 5, more preferably 0.05 to 3, particularly preferably 0.08 to 2, and most preferably 0.1 to 1.5. Within this range, the absorption performance (especially the absorption amount and the absorption rate) is further improved.

There is no limitation in particular as an internal crosslinking agent (b), The internal crosslinking agent etc. which are described in Unexamined-Japanese-Patent No. 2001-220415 can be used.
Among the internal cross-linking agents (b), from the viewpoint of absorption performance, the internal cross-linking agent (b1) having two or more ethylenically unsaturated groups is preferable, and triallyl cyanurate, triallyl isocyanurate, and carbon number are more preferable. Poly (meth) allyl ethers of 2 to 10 polyols, particularly preferably triallyl cyanurate, triallyl isocyanurate, tetraallyloxyethane and pentaerythritol triallyl ether, most preferably pentaerythritol triallyl ether.

  The content (% by weight) of the internal crosslinking agent (b) is 0.001 to 5 based on the total weight of the vinyl monomers (a1) and / or (a2) and other vinyl monomers (a3) used as necessary. Is more preferable, 0.002 to 2 is more preferable, and 0.003 to 1.6 is particularly preferable. Within this range, the absorption performance (especially the absorption amount and the absorption rate) is further improved.

The crosslinked polymer (A) is further added with additives described later {preservatives, fungicides, antibacterial agents, antioxidants, ultraviolet absorbers, colorants, fragrances, deodorants, organic fibrous materials, etc.}. It can be contained if necessary.
When these additives are contained, the content (% by weight) of the additive is preferably 0.001 to 10, more preferably 0.01 to 5, particularly preferably based on the weight of the crosslinked polymer (A). Preferably it is 0.05 to 1, most preferably 0.1 to 0.5.

The gel elastic modulus (N / m ² ) of the 30-fold swollen gel obtained by absorbing 1 part by weight of the water-absorbing agent of the present invention by 30 parts by weight of artificial urine is preferably 2,000 to 3,000, more preferably 2 , 025 to 2950, particularly preferably 2,050 to 2,900, most preferably 2,075 to 2,850. Within this range, when the water-absorbing agent of the present invention is applied to an absorbent article, more excellent resistance to leakage is exhibited.
The gel elastic modulus (N / m ² ) is a value determined by the following measurement method.
Measuring method:
Artificial urine [200 parts by weight of urea, 80 parts by weight of sodium chloride, 8 parts by weight of magnesium sulfate (7-hydrate), 3 parts by weight of calcium chloride (dihydrate), 2 parts by weight of ferric sulfate (7-hydrate), ions 9704 parts by weight of exchanged water] 60.0 g was weighed into a 100 ml beaker (inner diameter 5 cm), and in the same manner as described in JIS K7224-1996, 2.0 g of a measurement sample was precisely weighed and put into the beaker. Create a 30-fold swollen gel.
The beaker containing the 30-fold swollen gel was allowed to stand in an atmosphere of 40 ± 2 ° C. for 3 hours, and further in an atmosphere of 25 ± 2 ° C. for 0.5 hour. (For example, it measures using the card meter MAX ME-500 by ITEC Techno Engineering Co., Ltd.). The card meter conditions are as follows.
・ Pressure sensitive axis: 8mm
・ Spring: 100g ・ Load: 100g
・ Rising speed: 1 inch / 7 seconds ・ Test properties: rupture ・ Measurement time: 6 seconds ・ Measurement ambient temperature: 25 ± 2 ° C.

The absorption amount (g / g) {hereinafter, 20 absorption amount) of the water-absorbing agent of the present invention with respect to physiological saline under a load of 20 g / cm ² is preferably 7 to 16, more preferably 7.5 to 15.5, particularly preferably 8-15, most preferably 8.5-14.5. Within this range, when the water-absorbing agent of the present invention is applied to an absorbent article, the wearer can more easily feel discomfort during urination.
Moreover, 6-13 are preferable, and, as for the absorption amount (g / g) {following 40 absorption amount} with respect to the physiological saline under 40 g / cm < ² > load of the water absorbing agent of this invention, 6-13 are preferable, More preferably, 6.5. ˜12.5, particularly preferably 7 to 12, and most preferably 7.5 to 11.5. Within this range, when the water-absorbing agent of the present invention is applied to an absorbent article, the wearer can more easily feel discomfort during urination.
Further, the absorption amount (g / g) {hereinafter 60 absorption amount) of the water-absorbing agent of the present invention with respect to physiological saline under a load of 60 g / cm ² is preferably 5 to 10, more preferably 5.3. To 9.8, particularly preferably 5.6 to 9.6, and most preferably 5.9 to 9.5. Within this range, when the water-absorbing agent of the present invention is applied to an absorbent article, the wearer can more easily feel discomfort during urination.

The 20 absorption is measured at 25 ± 2 ° C. as follows.
That is, a sample of 0.10 g was weighed in a cylindrical plastic tube (inner diameter 30 mm, height 60 mm) with a nylon mesh (JIS Z8801-1: 2000) having a mesh size of 63 μm attached to the bottom, and the cylindrical plastic tube was placed vertically to make nylon. A sample is arranged on the net so as to have a substantially uniform thickness, and a weight of 29.5 mm in outer diameter × 22 mm in thickness is inserted into the cylindrical plastic tube so that a load of 20 g / cm ² is applied to the sample.
Next, a cylindrical plastic tube containing a sample and a weight in a petri dish (diameter: 120 mm) containing 60 ml of physiological saline is vertically immersed with the nylon mesh side as the bottom surface. Next, after 60 minutes, the sample and the cylindrical plastic tube containing the weight are weighed, and the weight of the physiological saline absorbed by the sample is calculated. A value obtained by multiplying the weight of the absorbed physiological saline by 10 is defined as 20 absorption (g / g).

Further, 40 absorption of the water-absorbing agent of the present invention (g / g), instead of a load of 20 g / cm ² is used the weight of the outer diameter of 29.5 mm × thickness 22mm as according to the sample, 40 g / cm ² It is measured by the same method as 20 absorption amount, except that a weight of 29.5 mm in outer diameter and 44 mm in thickness is used so that the load is applied to the sample.

Furthermore, 60 absorption of the water-absorbing agent of the present invention (g / g), instead of a load of 20 g / cm ² is used the weight of the outer diameter of 29.5 mm × thickness 22mm as according to the sample, 60 g / cm ² It is measured by the same method as 20 absorption, except that a weight with an outer diameter of 29.5 mm and a thickness of 66 mm is used so that the load is applied to the sample.

The amount of absorption (g / g) after 1 hour of the water-absorbing agent of the present invention with respect to physiological saline is preferably 50 to 75, more preferably 52 to 73, and particularly preferably 54 to 71. Within this range, when the water-absorbing agent of the present invention is applied to an absorbent article, more excellent resistance to leakage is exhibited. In addition, the absorption amount (g / g) after 1 hour with respect to the physiological saline of a water absorbing agent is a value calculated | required with the following measuring method.
Measuring method:
A tea bag (20 cm long, 10 cm wide) made of a nylon mesh (JIS Z8801-1: 2000) having a mesh size of 63 μm is charged with 1.00 g of a measurement sample, and 1,000 cc of physiological saline (salt concentration 0.9 wt%). After soaking for 1 hour without stirring, hang for 15 minutes and drain. Thereafter, the weight (k1) including the tea bag is measured, and the absorption amount is obtained from the following equation. The temperature of the physiological saline used and the measurement atmosphere is 25 ± 2 ° C.

(K2) is the weight of the tea bag measured by the same operation as described above when there is no measurement sample.

The water retention amount (g / g) after 1 hour of the water-absorbing agent of the present invention with respect to physiological saline is preferably 30 to 65, more preferably 31 to 60, and particularly preferably 32 to 58. Within this range, when the water-absorbing agent of the present invention is applied to an absorbent article, more excellent resistance to leakage is exhibited. The water retention amount (g / g) after 1 hour with respect to the physiological saline of the water absorbing agent is a value determined by the following measurement method.
Measuring method:
A tea bag (20 cm long, 10 cm wide) made of a nylon mesh (JIS Z8801-1: 2000) having a mesh size of 63 μm is charged with 1.00 g of a measurement sample, and 1,000 cc of physiological saline (salt concentration 0.9 wt%). After soaking for 1 hour without stirring, hang for 15 minutes and drain. Thereafter, each tea bag is placed in a centrifuge, centrifuged at 150 G for 90 seconds to remove excess physiological saline, and the weight (h1) including the tea bag is measured to obtain the water retention amount from the following equation. The temperature of the physiological saline used and the measurement atmosphere is 25 ° C. ± 2 ° C.

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

The water content (% by weight) of the water-absorbing agent of the present invention is preferably 1 to 12, more preferably, based on the weight of the water-absorbing agent from the viewpoint of workability, texture, moisture resistance, etc., when applied to absorbent articles. Is from 2 to 10, particularly preferably from 4 to 8. Within this range, the water-absorbing agent is prevented from being destroyed by impact, and workability and the like are further improved.
The water content is not determined only by the drying process, but can be adjusted by the surface cross-linking process and the hydration process. The moisture content is 120 ± 5 ° C., 30 minutes {atmosphere humidity before heating 50 ± 10% RH, lamp specification 100V, 40W} heating with an infrared moisture measuring device {for example, JE400 manufactured by KETT Co., Ltd.} Calculated from the weight loss of the water-absorbing agent before and after heating.

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, and a reverse phase suspension polymerization method 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 carried out using a conventionally known solvent such as cyclohexane, normal hexane, normal heptane, toluene and xylene.

Among the polymerization forms, the solution polymerization method is preferable, and from the viewpoint of production cost, the aqueous solution polymerization method is more preferable.
Of the polymerization control methods, the adiabatic polymerization method is preferred.
That is, as the polymerization method, adiabatic solution polymerization is preferable.

  The polymerization initiation temperature (° C.) is preferably −2 to 15, more preferably −1 to 10, and particularly preferably 0 to 5. The dissolved oxygen concentration (ppm) at the start of polymerization is preferably 5 or less, more preferably 2 or less, and particularly preferably 0.5 or less. When the polymerization initiation temperature and dissolved oxygen concentration are within these ranges, the gel elastic modulus of the 30-fold swollen gel is further improved.

A polymerization initiator is preferably 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 {(i) azo initiators or (ii) peroxide initiators, ( iii) A redox initiator may be used in combination. }, More preferably (iii) redox initiator, particularly preferably from the group consisting of alkali metal sulfite, alkali metal bisulfite, ammonium sulfite, ammonium bisulfite, ferric chloride, ferric sulfate and ascorbic acid A redox initiator comprising a combination of at least one selected reducing agent and at least one oxidizing agent selected from the group consisting of alkali metal persulfate, ammonium persulfate, hydrogen peroxide and organic peroxide.

  When a polymerization initiator is used, the amount (% by weight) of the polymerization initiator used is as follows: vinyl monomer (a1) and / or (a2), other vinyl monomer (a3) used if necessary, and internal crosslinking agent (b) Is preferably 0.005 to 0.5, more preferably 0.007 to 0.4, and particularly preferably 0.009 to 0.3.

Furthermore, a complex compound can be used for the polymerization of the crosslinked polymer (A).
The complex compound is not particularly limited, and complex compounds described in International Application Pamphlet WO01-79314 and the like can be used. Among these, at least one arrangement selected from the group consisting of an iron atom, a cobalt atom, a nickel atom, a copper atom, a ruthenium atom, a rhodium atom or a palladium atom, a chlorine atom, a bromine atom, an iodine atom and a tertiary phosphine. A complex compound having a ligand, and more preferably at least one ligand selected from the group consisting of a ruthenium atom, a rhodium atom or a palladium atom, a chlorine atom, a bromine atom, an iodine atom and a tertiary phosphine; It is a complex compound having

When a complex compound is used, the amount of use (% by weight) of the complex compound is the sum of the vinyl monomers (a1) and / or (a2), other vinyl monomers (a3) used as necessary, and the internal crosslinking agent (b). Based on the weight, 5 × 10 ⁻⁷ to 2 is preferable, more preferably 10 ⁻⁶ to 1, and particularly preferably 2 × 10 ^{−5 to} 3.

  As described above, in the method for producing the water-absorbing agent of the present invention, the polymerization initiation temperature is 0 to 5 ° C., the dissolved oxygen concentration is 0.5 ppm or less, alkali metal sulfite, alkali metal bisulfite, ammonium sulfite, heavy From the group consisting of at least one reducing agent selected from the group consisting of ammonium sulfite, ferric chloride, ferric sulfate and ascorbic acid, and alkali metal persulfate, ammonium persulfate, hydrogen peroxide and organic peroxides It is particularly preferred to include an adiabatic solution polymerization step using a redox initiator consisting of a combination with at least one selected oxidizing agent.

The water-containing gel {including the crosslinked polymer (A) and water} obtained by polymerization can be crushed as necessary. The size (longest diameter) of the hydrogel after crushing 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.
The crushing can be performed by a known method, and for example, crushing can be performed using a normal apparatus such as a Bex mill, a rubber chopper, a pharma mill, a mincing machine, an impact crusher, and a roll crusher.

When using a solvent (including water) for the polymerization of the crosslinked polymer (A), the solvent can be distilled off after the polymerization.
When the solvent contains an organic solvent, the content (% by weight) of the organic solvent after the solvent is distilled off is preferably 0 to 10, more preferably 0 to 5, particularly preferably based on the weight of the crosslinked polymer (A). Preferably it is 0-3, Most preferably, it is 0-1. Within this range, the absorption performance (especially the amount of water retained) of the water-absorbing agent is further improved.
Moreover, when water is contained in the solvent, the water (% by weight) after the solvent is distilled off is preferably 0 to 20, more preferably 0 to 10, particularly preferably 0, based on the weight of the crosslinked polymer (A). ~ 5, most preferably 0-2. Within this range, the absorption performance (particularly the water retention amount) and the handling properties after drying (such as the powder flowability of the crosslinked polymer particles) are further improved.
The content and moisture of the organic solvent are determined from the weight loss of the crosslinked polymer (A) before and after heating in the same manner as in the method for measuring the water content (120 ± 5 ° C., 30 minutes).
The method of distilling off the solvent is 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 freeze drying. Ordinary methods such as drying, infrared drying, decantation and filtration may be used.

Further, the crosslinked polymer (A) can be pulverized after drying.
In the case of pulverization, the weight average particle size (μm) of the crosslinked polymer after pulverization is preferably 100 to 800, more preferably 200 to 500, and particularly preferably 300 to 400. Within this range, handling properties after pulverization (powder fluidity of the crosslinked polymer particles, etc.) are further improved.

The weight average particle diameter plots each particle size distribution of the crosslinked polymer on logarithmic probability paper (logarithm of particle diameter on the horizontal axis and content based on weight on the vertical axis) and occupies 50% by weight of the total weight. According to the method for determining the particle size.
The particle size distribution was measured in accordance with JIS Z8815-1994, and 710 μm, 500 μm, 300 μm, 150 μm and 106 μm aperture sieves having an inner diameter of 150 mm and a depth of 45 mm were stacked on top of each other with a narrow aperture sieve. Place 50 g of the measurement sample on the 710 μm sieve with the widest opening at the top, sieve for 10 minutes with a sieve vibrator, measure the weight of the measurement sample remaining on each sieve, Measured by determining the weight percent of the measurement sample remaining on each sieve based on weight.

The smaller the content of fine particles, the better the absorption performance. The content of fine particles of 106 μm or less in the total particles is preferably 3% by weight or less, and more preferably the content of fine particles of 150 μm or less in the total particles is 3% by weight. It is as follows.
The content of the fine particles can be determined using a plot created when determining the above weight average particle diameter.

The pulverization method is not particularly limited, and usual devices such as a hammer pulverizer, an impact pulverizer, a roll pulverizer, and a shet airflow pulverizer can be used.
The obtained pulverized product is sieved as necessary to adjust the particle size.
The shape of the crosslinked polymer particles is not particularly limited, and examples thereof include an irregularly crushed shape, a flake shape, a pearl shape, and a rice grain shape. Among these, from the viewpoint of good entanglement with the fibrous material for use in paper diapers and the like and no fear of dropping off from the fibrous material, an irregular crushed shape is preferable.

The cross-linked polymer can be subjected to surface cross-linking as required, and surface cross-linking is particularly effective for improving the gel elastic modulus of the 30-fold swollen gel of the water-absorbing agent when it is low (less than 2000 N / m ² ). It is effective.
As the crosslinking agent (surface crosslinking agent) for performing the surface crosslinking, the same as the internal crosslinking agent (b) can be used. As the surface cross-linking agent, from the viewpoint of the absorption performance of the water-absorbing agent, etc., a hydrophilic substituent (carboxy group, hydroxyl group, etc.) of the water-soluble vinyl monomer (a1) and / or hydrophilicity generated by hydrolysis of the vinyl monomer (a2). Preferred is a crosslinking agent (b3) having at least two functional groups capable of reacting with a functional substituent, more preferably a compound having a polyvalent metal and a plurality of glycidyl groups, 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 the total weight of the vinyl monomers (a1) and / or (a2), the internal cross-linking agent (b) and other vinyl monomers (a3) used as necessary. Is preferably from 0.0001 to 7, more preferably from 0.0002 to 5, particularly preferably from 0.0003 to 4.
When the content (% by weight) of the surface cross-linking agent is below the above range, it is difficult to improve the gel elastic modulus of the 30-fold swollen gel of the water-absorbing agent. Although the rate is improved, the absorption amount of the water-absorbing agent after 1 hour with respect to physiological saline under load (20 absorption amount, 40 absorption amount, 60 absorption amount) tends to be too high, and the water absorption agent is used as an absorbent article. When applied, the wearer tends to be less likely to feel discomfort during urination. Therefore, within this range, even when the gel elastic modulus of the 30-fold swollen gel of the water-absorbing agent is low, the surface cross-linking treatment can be performed in any state (however under load). When it is applied to an absorbent article, it can make it easier for the wearer to feel discomfort when urinating.
The surface crosslinking can be achieved by a normal method, such as a method of spraying or impregnating a crosslinked polymer with an aqueous solution containing a surface crosslinking agent, followed by heat treatment (100 to 200 ° C.).

It is preferable that the water-absorbing agent of the present invention further includes a diffusion penetrant as a constituent component. When the diffusion penetrant is included, the absorption performance (absorption amount and absorption rate) is further improved, and higher absorption performance is easily exhibited in any state (however a load is applied).
The diffusion penetrant is an additive for improving the diffusibility and penetrability of the liquid inside the water-absorbing agent, and is a conventionally known surfactant or the like (for example, “the latest technology of water-soluble polymer” CMC Publishing, May 2000). Or “surfactant applied technology” described in CMC publication December 2002). When the crosslinked polymer (A) is obtained by aqueous solution polymerization, surfactants (anionic surfactants, nonionic surfactants, cationic surfactants and amphoteric surfactants) are used as diffusion penetrants. These may be used alone or in combination of two or more.

  Examples of the anionic surfactant include ether carboxylic acids having 12 to 300 carbon atoms or salts thereof, {polyoxyethylene (degree of polymerization 1 to 5) sodium lauryl ether acetate and polyoxyethylene (degree of polymerization 1 to 5) lauryl sulfosuccinic acid. 2 sodium, etc.}, C12-300 alkyl (ether) sulfate ester salt {sodium lauryl sulfate, polyoxyethylene (degree of polymerization 1-5) sodium lauryl sulfate, polyoxyethylene (degree of polymerization 1-5) lauryl sulfate tri Ethanolamine and polyoxyethylene (degree of polymerization 1-5) coconut oil fatty acid monoethanolamide sodium sulfate, etc.}, C12-24 alkyl (or alkylphenyl) sulfonate {sodium dodecylbenzenesulfonate, diethylhexylsulfosuccinate Acid sodium etc.}, Alkyl (ether) phosphate ester salt having 12 to 300 prime atoms {sodium lauryl phosphate and polyoxyethylene (degree of polymerization 1 to 100) sodium lauryl ether phosphate}, fatty acid salt having 12 to 24 carbon atoms {sodium laurate and Lauric acid triethanolamine, etc.}, acylated amino acid salt {coconut oil fatty acid methyl taurine sodium, coconut oil fatty acid sarcosine sodium, coconut oil fatty acid sarcosine triethanolamine, N-coconut oil fatty acid acyl-L-glutamic acid triethanolamine, N- Palm oil fatty acid acyl-sodium L-glutamate and sodium lauroylmethyl-β-alanine} and other anionic surfactants {polyoxyethylene sulfosuccinate (degree of polymerization 1-5) disodium lauroylethanolamide, etc. } Etc. are mentioned.

  Nonionic surfactants include aliphatic alcohol (C12-24) alkylene oxide (C2-5) adduct (degree of polymerization 1-5) {lauryl alcohol ethylene oxide addition (polymerization degree 3), oleyl Alcohol ethylene oxide addition (polymerization degree 3) and MacCo alcohol ethylene oxide addition (polymerization degree 3) etc.}, polyoxyalkylene (carbon number 2-8, polymerization degree 1-5) higher fatty acid (carbon number 12-24) Esters {polyethylene glycol monostearate (polymerization degree 3) and polyethylene glycol distearate (polymerization degree 3), etc.}, polyvalent (2 to 10 valent) alcohol fatty acid (carbon number 8 to 24) ester {glyceryl monostearate, mono Ethylene glycol stearate, sorbitan lauric acid (mono / di) ester, Rubitan palmitic acid (mono / di) ester, sorbitan stearic acid (mono / di) ester, sorbitan oleic acid (mono / di) ester, sorbitan coconut oil (mono / di) ester, etc.}, polyoxyalkylene (2 carbon atoms) -8, degree of polymerization 1-5) polyvalent (2-10 valent) alcohol higher fatty acid (carbon number 8-24) ester {polyoxyethylene (degree of polymerization 2) sorbitan lauric acid (mono / di) ester, polyoxyethylene (Degree of polymerization 2) sorbitan palmitic acid (mono / di) ester, polyoxyethylene (degree of polymerization 3) sorbitan stearic acid (mono / di) ester, polyoxyethylene (degree of polymerization 3) sorbitan oleic acid (mono / di) ester , Polyoxyethylene (degree of polymerization 2) lauric acid (mono / di) ester, polyoxyethylene (heavy Degree 3) stearic acid (mono / di) ester, polyoxyethylene (degree of polymerization 3) oleic acid (mono / di) ester, dioleic acid methyl glucoside, etc.}, fatty acid alkanolamide {1: 1 type coconut oil fatty acid diethanolamide, 1: 1 type lauric acid diethanolamide, etc.], polyoxyalkylene (carbon number 2-8, polymerization degree 1-5) alkyl (carbon number 1-22) phenyl ether {polyoxyethylene (degree of polymerization 2) nonylphenyl ether, etc. }, Polyoxyalkylene (carbon number 2-8, degree of polymerization 1-5) alkyl (carbon number 8-24) amino ether, alkyl (carbon number 8-24) dialkyl (carbon number 1-6) amine oxide {lauryldimethyl Amine oxide etc.}. In the above, (mono / di) ester means monoester or diester. The same applies to the following.

  Cationic surfactants include quaternary ammonium salts {stearyltrimethylammonium chloride, behenyltrimethylammonium chloride, distearyldimethylammonium chloride and ethyl lanolin sulfate fatty acid aminopropylethyldimethylammonium} and amine salts {diethylaminoethylamide stearate. Lactate, dilaurylamine hydrochloride, oleylamine lactate, etc.}.

  Amphoteric surfactants include betaine-type amphoteric surfactants {coconut oil fatty acid amidopropyldimethylaminoacetic acid betaine, lauryldimethylaminoacetic acid betaine, 2-alkyl-N-carboxymethyl-N-hydroxyethylimidazolinium betaine, laurylhydroxy Sulfobetaine and lauroylamidoethylhydroxyethylcarboxymethylbetaine hydroxypropyl phosphate sodium etc.} and amino acid type amphoteric surfactant {sodium β-laurylaminopropionate etc.} and the like.

  Among these diffusion penetrants, an anionic surfactant and a nonionic surfactant are used from the viewpoint that the absorbent article exhibits high absorption performance in any state (however a load is applied). Preferably, alkyl (ether) sulfate ester salt, alkyl (or alkylphenyl) sulfonate salt, alkyl (ether) phosphate ester salt, fatty acid salt and polyhydric alcohol fatty acid ester, particularly preferably sodium lauryl sulfate, Sodium lauryl phosphate, sodium dodecylbenzenesulfonate, sodium diethylhexylsulfosuccinate, sodium lauryl phosphate, sodium laurate, sorbitan lauric acid (mono / di) ester, sorbitan palmitic acid (mono / di) ester, sorbitan stearin (Mono / di) ester, sorbitan oleic acid (mono / di) ester and sorbitan coconut oil (mono / di) ester, sorbitan lauric acid (mono / di) ester, most preferably sodium dodecylbenzenesulfonate, diethylhexylsulfosucci Sodium acid.

  When the crosslinked polymer (A) is obtained by emulsion polymerization or reverse phase suspension polymerization, the diffusion penetrant is a surfactant (emulsifier / dispersant) used during emulsion polymerization or reverse phase suspension polymerization. The same surfactant as) is not preferred. This is because even if such a same surfactant is used as a diffusion penetrating agent, it is considered that the diffusibility and penetrability of the liquid are hardly improved inside the water absorbing agent. In this case, an anionic surfactant and a cationic surfactant that are different from the surfactant used in emulsion polymerization or reverse phase suspension polymerization are preferred, and a different anionic surfactant is more preferred. The different anionic surfactants are preferably the same as those exemplified in the aqueous solution polymerization.

  The HLB value of the diffusion penetrant is preferably 5 to 12, more preferably 6 to 11, particularly preferably 7 to 10, and most preferably 8 to 9. In this range, the absorbent article obtained by using this exhibits even higher absorption performance in any state (however a load is applied).

  When the diffusion penetrant is contained, the content (% by weight) of the diffusion penetrant is preferably 0.001 to 3, more preferably 0.005 to 1, especially based on the weight of the crosslinked polymer (A). Preferably it is 0.07-0.5, Most preferably, it is 0.1-0.3. Within this range, the absorbent article obtained by containing this exhibits even higher absorption performance in any state (however a load is applied).

In the case of the aqueous solution polymerization method, the timing of adding the diffusion penetrant is not particularly limited, and examples thereof include during the polymerization step, immediately after the polymerization step, during crushing (minching) of the hydrogel and during drying of the hydrogel. Among these, from the viewpoint of the anti-moisture resistance of the absorbent article, it is preferably immediately after the polymerization step and during the crushing (mincing) step of the hydrogel, and more preferably immediately after the polymerization step.
In the case of the reverse phase suspension polymerization method or emulsion polymerization, the diffusion penetrant was added immediately after the polymerization step, during the dehydration step (during the step of dehydrating to about 10% by weight of water), immediately after the dehydration step, and used for the polymerization. Examples include the step of separating and distilling the organic solvent and the drying of the hydrogel. Among these, from the viewpoint of the resistance to absorption of the absorbent article and the stability during polymerization, immediately after the polymerization process, during the dehydration process, immediately after the dehydration process and during the process of separating and distilling the organic solvent used for the polymerization are preferable. More preferably, it is immediately after the polymerization step, during the dehydration step, immediately after the dehydration step, and during the step of separating and distilling the organic solvent used for the polymerization.

In the water-absorbing agent of the present invention, if necessary, additives at any stage {polymerization step of cross-linked polymer (A), crushing step, drying step, crushing step, surface cross-linking step and / or before and after these steps, etc.) Can be added.
As additives, antiseptics, fungicides, antibacterial agents, antioxidants, ultraviolet absorbers, colorants, fragrances, deodorants, organic fibrous materials, etc. can be used. May be.

Examples of the preservative include preservatives such as salicylic acid, sorbic acid, dehydroacetic acid and methylnaphthoquinone, and bactericides such as chloramine B and nitrofurazone.
Examples of fungicides include butyl p-oxybenzoate.
Examples of the antibacterial agent include benzalkonium chloride salt and chlorhexidine gluconate.

  Antioxidants include triethylene glycol-bis- [3- (3-tert-butyl-5-methyl-4-hydroxyphenyl) propionate], 1,6-hexanediol-bis [3- (3,5- Di-t-butyl-4-hydroxyphenyl) propionate], octadecyl-3- (3,5-di-t-butyl-4-hydroxyphenylpropionate) and 3,5-di-t-butyl-4-hydroxybenzyl Examples include hindered phenol antioxidants such as phosphonate-diethyl ester and amine antioxidants such as n-butylamine, triethylamine and diethylaminomethyl methacrylate.

  Examples of the ultraviolet absorber include 2- (5-methyl-2-hydroxyphenyl) benzotriazole, 2- (3,5-di-tert-butyl-2-hydroxyphenyl) benzotriazole, 2- (3,5-di Benzotriazole ultraviolet absorbers such as -t-butyl-2-hydroxyphenyl) -5-chlorobenzotriazole and 2- (3,5-di-t-amyl-2-hydroxyphenyl) benzotriazole; 2- (4 , 6-Diphenyl-1,3,5-triazin-2-yl) -5-[(hexyl) oxy] -phenol and other triazine-based UV absorbers; 2-hydroxy-4-n-octyloxybenzophenone and other benzophenones And oxalic acid anilide ultraviolet absorbers such as 2-ethoxy-2′-ethyloxalic acid bisanilide, etc. That.

Examples of the colorant include inorganic pigments such as titanium oxide and ferrite, organic pigments such as azo lake, benzimidazolone and phthalocyanine, and dyes such as nigrosine and aniline.
As a fragrance | flavor, natural fragrance | flavors, such as a fragrance | flavor, abies oil, and turpentine oil, and synthetic fragrance | flavors, such as menthol, citral, p-methylacetophenone, and floral, etc. are mentioned.
Examples of the deodorant include zeolite, silica, flavonoid, cyclodextrin and the like.

When these additives are added, the addition amount (% by weight) varies depending on the use, but is preferably 10 ^{−6 to} 20, more preferably 10 ⁻⁵ to 10, particularly preferably based on the weight of the water-absorbing agent. 10 ^{−4 to} 5. Within this range, an antibacterial action or the like can be imparted without reducing the absorption performance of the water-absorbing agent.

By applying the water-absorbing agent of the present invention to various absorbers, an absorbent article having excellent absorption performance can be produced. The absorber contains the water-absorbing agent of the present invention and a fibrous material.
As a method of applying a water-absorbing agent to the absorber, (1) a method in which the water-absorbing agent is dispersed between layers of fibrous materials such as pulp arranged in layers; (2) pulp and heat-fusible fibers (3) A method of sandwiching a water absorbent together with a fibrous material, if necessary, using two or more water absorbent papers or nonwoven fabrics.

  As the fibrous material, fibrous materials conventionally used for absorbent articles such as various fluff pulps and cotton-like pulps can be used. There are no particular restrictions on the raw materials (such as conifers and hardwoods), production methods {craft pulp, chemical pulp, semi-chemical pulp, chemithermomechanical pulp (CTMP), etc.}, bleaching methods, and the like. As the fibrous material, in addition to the organic fibrous material described above, a synthetic fiber that does not swell in water can be used alone or in combination with the above fluff pulp or cotton pulp, if necessary. Examples of synthetic fibers include polyolefin fibers (polyethylene fibers and polypropylene fibers, etc.), polyester fibers (polyethylene terephthalate fibers, etc.), polyolefin / polyester composite fibers, polyamide fibers, and polyacrylonitrile fibers.

The length and thickness of the fibrous material are not particularly limited, but usually, the length is preferably 1 to 200 mm, and the thickness is preferably 0.1 to 100 denier (0.11 to 110 dtex).
The shape is not particularly limited as long as it is fibrous, and examples thereof include a web shape, a thin cylindrical shape, a cut split yarn shape, a staple shape, and a filament shape.

  The amount (% by weight) of the water-absorbing agent of the present invention to the absorber can be variously changed according to the type and size of the absorber and the target absorption performance, but the total weight of the water-absorbing agent and the fibrous material can be changed. Based on this, 20 to 95 are preferable, more preferably 25 to 90, and particularly preferably 30 to 80. Within this range, the resulting absorbent exhibits even higher absorption performance in any state (however a load is applied).

The absorbent body using the water-absorbing agent of the present invention exhibits excellent absorbability with respect to liquids to be absorbed (body fluids such as sweat, urine and blood, and water such as seawater, groundwater and muddy water). Suitable for sanitary goods such as napkins.
Therefore, by using the water-absorbing agent of the present invention, an absorbent article that exhibits high absorption performance in any state (however a load is applied) can be easily manufactured. That is, even when the user is sitting or lying down, the amount of absorption and the absorption speed do not decrease, and as a result, problems such as leakage are extremely unlikely to occur. Nevertheless, the wearer can easily feel discomfort when urinating.

It is preferable that the absorbent article which arrange | positions the absorber using the water absorbing agent of this invention is equipped with an absorber, a liquid-permeable sheet, and a breathable back sheet. And such an absorbent article is suitable as sanitary goods.
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. Among these sanitary goods, it is suitable for paper diapers. Furthermore, among the paper diapers, it is most suitable for a paper diaper for promoting diaper separation (for training).

  The surface dryness value (%) measured by the SDME method of the absorbent article is preferably 30 to 70, more preferably 35 to 65, and particularly preferably 40 to 60. Below this range, it means that there is a large amount of liquid to be absorbed present on the surface of the absorbent article, that is, the liquid to be absorbed is easy to leak. On the other hand, if it exceeds this range, it means that there is almost no liquid to be absorbed on the surface of the absorbent article, and it means that it is difficult for the wearer to feel uncomfortable when urinating when applied to training paper diapers etc. To do. Therefore, the above range is preferable from the viewpoint of worrying about moles and discomfort of the wearer during urination.

<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).
Place the detector of the SDME tester on a sufficiently moistened absorbent article (soaked in artificial urine that covers the absorbent article and let stand for 60 minutes), set the 0% dryness value, then The SDME tester detector is placed on a dry absorbent article (the absorbent article is dried by heating at 80 ° C. for 2 hours), 100% dryness is set, and the SDME tester is calibrated.
Next, a metal ring (inner diameter 70 mm, outer diameter 80 mm length 50 mm, weight 300 g) is set in the center of the absorbent article 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 absorbent article in the center of the absorbent article, and measurement is started. The value 1 minute after the start of measurement is taken as the surface dryness value by SDME.

  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.

<Example 1>
In a glass reaction vessel, 77 parts of sodium acrylate, 22.85 parts of acrylic acid, 0.3 part of N, N′-methylenebisacrylamide and 293 parts of deionized water, 0.001 part of dichlorotris (triphenylphosphine) ruthenium The contents were kept at 2 ° C. while stirring and mixing.
After flowing nitrogen into the contents to make the dissolved oxygen amount 0.5 ppm or less, 0.3 part of 1% aqueous solution of hydrogen peroxide, 0.8 part of 0.2% aqueous solution of ascorbic acid and 2,2′- By adding and mixing 0.8 part of a 2% aqueous solution of azobisamidinopropane dihydrochloride to start polymerization, the reaction liquid reached 80 ° C., and then polymerized at a polymerization temperature of 80 ± 2 ° C. for about 5 hours. Then, a hydrogel polymer (AA-1) comprising the crosslinked polymer (A1) was obtained. The water content (120 ± 5 ° C. × 30 minutes) was 74.6%.

0.4 part of diffusion penetrant 1 (Sanyo Kasei Kogyo Co., Ltd .: Sanmorin OT70, an anionic surfactant) is added to 400 parts of the hydrogel polymer (AA-1), and a mincing machine (hole diameter of the eye plate: 6 mm). , 12VR-400K manufactured by Iizuka Kogyo Co., Ltd.) and kneaded at 25 ° C. for 5 minutes, and then dried with an aeration-type band dryer under conditions of 135 ° C. and a wind speed of 2.0 m / sec to obtain a dried polymer product.
This polymer dried product was pulverized with a commercially available juicer mixer, adjusted to a particle size of 250 to 600 μm using a sieve having an opening of 600 and 250 μm, and then 100 parts of this polymer was stirred at high speed (high speed stirring turbulizer manufactured by Hosokawa Micron). 1 part of a 1% water / methanol mixed solution of ethylene glycol diglycidyl ether (weight ratio of water / methanol = 60/40) was added while being sprayed and mixed at 140 ° C. for 30 minutes. The water-absorbing agent (1) of the present invention was obtained by standing and heating and crosslinking.

<Example 2>
The water-absorbing agent of the present invention was the same as in Example 1 except that 1 part of a 1% water / methanol mixed solution of ethylene glycol diglycidyl ether (water / methanol weight ratio = 60/40) was changed to 3 parts. (2) was obtained.

<Example 3>
The water-absorbing agent of the present invention was obtained in the same manner as in Example 1 except that 1 part of a 1% water / methanol mixed solution of ethylene glycol diglycidyl ether (weight ratio of water / methanol = 60/40) was changed to 2 parts. (3) was obtained.

<Example 4>
In the same manner as in Example 1, except that 1 part of a 1% water / methanol mixed solution of ethylene glycol diglycidyl ether (water / methanol weight ratio = 60/40) was changed to 2.8 parts. A water absorbing agent (4) was obtained.

<Example 5>
In the same manner as in Example 1, except that 1 part of a 1% water / methanol mixed solution of ethylene glycol diglycidyl ether (water / methanol weight ratio = 60/40) was changed to 2.5 parts. A water absorbing agent (5) was obtained.

<Example 6>
Diffusion penetrant 1 (Sanyo Kasei Kogyo Co., Ltd .: Sanmorin OT70) was changed to Diffusion penetrant 2 (Sanyo Kasei Kogyo Co., Ltd .: NAROACTY ID50, nonionic surfactant) in the same manner as in Example 1. The water-absorbing agent (6) of the present invention was obtained.

<Example 7>
Diffusion penetrant 1 (Sanyo Kasei Kogyo Co., Ltd .: Sanmorin OT70) was changed to Diffusion penetrant 3 (Sanyo Kasei Kogyo Co., Ltd .: NAROACTY N-85, nonionic surfactant). Thus, the water-absorbing agent (7) of the present invention was obtained.

<Example 8>
A water-absorbing agent (8) of the present invention was obtained in the same manner as in Example 1 except that the diffusion penetrant 1 (Sanyo Kasei Kogyo Co., Ltd .: Sanmorin OT70) was not used.

<Comparative Example 1>
1 part of 1% water / methanol mixed solution of ethylene glycol diglycidyl ether (weight ratio of water / methanol = 60/40) was mixed with 10% water / methanol mixed solution of ethylene glycol diglycidyl ether (weight ratio of water / methanol). = 60/40) A comparative water-absorbing agent (9) was obtained in the same manner as in Example 1 except for changing to 5 parts.

<Comparative example 2>
1 part of a 1% water / methanol mixed solution (water / methanol weight ratio = 60/40) of ethylene glycol diglycidyl ether was mixed with a 1% water / methanol mixed solution of ethylene glycol diglycidyl ether (water / methanol weight ratio). = 30/70) A comparative water-absorbing agent (10) was obtained in the same manner as in Example 1 except that it was changed to 1 part.

<Comparative Example 3>
1 part of 1% water / methanol mixed solution of ethylene glycol diglycidyl ether (weight ratio of water / methanol = 60/40) was mixed with 10% water / methanol mixed solution of ethylene glycol diglycidyl ether (weight ratio of water / methanol). = 30/70) A comparative water absorbing agent (11) was obtained in the same manner as in Example 1 except for changing to 7 parts.

<Comparative example 4>
In a glass reaction vessel, 77 parts of sodium acrylate, 22.85 parts of acrylic acid, 0.01 part of N, N′-methylenebisacrylamide and 293 parts of deionized water, 0.001 part of dichlorotris (triphenylphosphine) ruthenium The contents were kept at 7 ° C. while stirring and mixing.
After flowing nitrogen into the contents to make the dissolved oxygen amount 5 ppm, 0.3 part of 1% aqueous solution of hydrogen peroxide, 0.8 part of 0.2% aqueous solution of ascorbic acid and 2,2′-azobisamidino By adding and mixing 0.8 parts of a 2% aqueous solution of propanedihydrochloride to initiate polymerization, the reaction solution reached 85 ° C., and then polymerized at a polymerization temperature of 85 ± 2 ° C. for about 5 hours, thereby allowing crosslinking polymerization. A hydrogel polymer (AA-2) comprising the coalescence (A1) was obtained. The water content (120 ± 5 ° C. × 30 minutes) was 75.1%.
0.4 parts of a diffusion penetrant 1 (Sanyo Kasei Kogyo Co., Ltd .: Sanmorin OT70, an anionic surfactant) is added to 400 parts of a hydrogel polymer (AA-2), and a mincing machine (hole diameter of the eye plate: 6 mm). , 12VR-400K manufactured by Iizuka Kogyo Co., Ltd.) and kneaded at 25 ° C. for 5 minutes, and then dried with an aeration-type band dryer under conditions of 135 ° C. and a wind speed of 2.0 m / sec to obtain a dried polymer product.
This polymer dried product was pulverized with a commercially available juicer mixer, adjusted to a particle size of 250 to 600 μm using a sieve having an opening of 600 and 250 μm, and then 100 parts of this polymer was stirred at high speed (high speed stirring turbulizer manufactured by Hosokawa Micron). 1 part of a 1% water / methanol mixed solution of ethylene glycol diglycidyl ether (weight ratio of water / methanol = 60/40) was added while being sprayed and mixed at 140 ° C. for 30 minutes. The water absorbing agent (12) for a comparison was obtained by standing still and carrying out heat crosslinking.

About the water-absorbing agent (1) to (8) of the present invention and the comparative water-absorbing agents (9) to (12), 30 times gel elastic modulus, 20 absorption amount, 40 absorption amount, 60 absorption amount, absorption amount and water retention amount The results are shown in Table 1.

<Example 9>
A mixture obtained by mixing 100 parts of fluff pulp and 100 parts of the water-absorbing agent (1) of the present invention obtained in Example 1 with an airflow type mixing device is uniformly laminated so as to have a basis weight of about 400 g / m ² . Pressing was performed at a pressure of 5 kg / cm ² for 30 seconds to obtain an absorber (B1).
The obtained absorbent body (B1) is cut into a 14 cm × 36 cm rectangle, water absorbent paper having the same size as the absorbent body (basis weight 15.5 g / m ² ) is placed on each of the upper and lower sides, and further on a commercially available paper diaper The disposable diaper (1) was created by arrange | positioning the polyethylene sheet currently used on the back surface and the nonwoven fabric made from polyethylene (basis weight 20.0g / m < ² >) on the surface.

<Examples 10 to 16>
Absorbers (B2) to (B8) are prepared in the same manner as in Example 9 except that the water absorbent (1) is changed to the water absorbent (2) to (8), and further the paper diapers (2) to (8) )created.

<Comparative Examples 5-8>
Comparative absorbents (B9) to (B12) were prepared in the same manner as in Example 9, except that the water absorbent (1) was changed to the water absorbents (9) to (12) obtained in Comparative Examples 1 to 4. Comparative paper diapers (9) to (12) were prepared.

  For the produced paper diapers (1) to (12), the amount of absorption until leakage and surface dryness were measured by the following method, and the surface dryness value by SDME was measured by the above method, and the measurement results are shown in Table 2.

<Absorption amount until leakage>
After placing a paper diaper (140 mm x 360 mm) on an acrylic board (140 mm x 360 mm, weight 0.5 kg), one end (upper end) of the short side (140 mm) of the paper diaper is fixed to the acrylic board with gum tape (paper diaper and gum tape) The acrylic plate is fixed in a state of being inclined at 45 degrees so that one end (upper end) to which the diaper is fixed becomes the upper portion. Next, artificial urine was introduced at a rate of 100 g / min for 30 minutes from the upper end to a portion of 30 mm from the upper end (330 mm from the other end (lower end)) and 70 mm from both ends of the long side. Then, after being left in an atmosphere of 40 ± 2 ° C. for 3 hours and further in an atmosphere of 25 ° C. ± 2 ° C. for 0.5 hour, it was continuously 30 mm from the upper end {330 mm from the other end (lower end)} Artificial urine is introduced at a rate of 100 g / min from each end of the side at a rate of 100 g / min, the end point is the time when the artificial urine leaks from the lower end of the disposable diaper, and the amount of artificial urine input up to the end point is obtained. The amount of absorption until leakage was used.

<Dry surface>
Using the paper diaper after measuring the amount of absorption until leakage, the dry feeling on the surface of the paper diaper was determined by touching with 10 panelists and evaluated in the following four stages. The average of 10 persons was calculated | required and it was set as the surface dry feeling.

◎: Feeling damp (when you feel discomfort)
×: No squeaky feeling (state in which uncomfortable feeling is not felt)
XX: Over wet condition

As can be seen from Table 2, the disposable diapers (1) to (8) prepared in Examples 9 to 16 have a high value of absorption up to the moisture, and thus feel wet without being worried about the moisture. (Pleasant feeling state) It had a surface dry feeling and the SDME surface dryness was 50-57.
On the other hand, the disposable diaper (9) prepared in Comparative Example 5 has a high value of absorption up to the mole, and there is no concern about the mole, but it has a surface dry feeling with no squeezing feeling and an SDME surface dryness of 95. It was.
Moreover, the paper diapers (10) to (12) created in Comparative Examples 6 to 8 have a small amount of absorption up to the mole and are easy to mole. Moreover, the paper diaper (11) prepared in Comparative Example 7 had a surface dry feeling with no squeezing feeling, and the SDME surface dryness was 80. Moreover, the paper diaper (10) or (12) created in Comparative Example 6 or 8 had a surface dry feeling in a wet state exceeding the wetness, and the SDME surface dryness was 15 or 20.
From the above results, it can be seen that the absorbent article (paper diaper) using the water-absorbing agent of the present invention can easily feel discomfort during urination or the like even though there is no concern about leakage. On the other hand, in the comparative paper diaper (Comparative Example 5) where there is no concern about leakage, it can be seen that the wearer cannot feel discomfort during urination. It can be seen that other examples of the comparative diapers are easy to learn.

In the absorbent article to which the water-absorbing agent of the present invention is applied, the liquid to be absorbed (body fluid such as urine and blood) is difficult to leak. The water-absorbing agent of the present invention includes, in particular, paper diapers (such as children's diapers and adult paper diapers), napkins (such as sanitary napkins), paper towels, pads (such as incontinence pads and surgical underpads), and pet sheets (pets). It is suitable for sanitary goods such as urine absorbing sheets), and is also suitable for disposable diapers and training diapers (pants) for promoting diaper separation.
The water-absorbing agent of the present invention is not only a sanitary product, but also a pet urine absorbent, a urine gelling agent for portable toilets, a freshness-preserving agent such as fruits and vegetables, a drip absorbent for meats and seafood, a cold preservation agent, a disposable body warmer, a battery It is also useful for various applications such as water gelling agents, water retention agents such as plants and soil, anti-condensation agents, water-stopping materials and packing materials, and artificial snow.

Claims (6)

In the water-absorbing agent containing the water-soluble vinyl monomer (a1) and / or the vinyl monomer (a2) which becomes (a1) by hydrolysis and the crosslinked polymer (A) having the internal crosslinking agent (b) as essential constituent units,
The gel elastic modulus of the 30-fold swollen gel obtained by absorbing 1 part by weight of the water-absorbing agent is 30 parts by weight of artificial urine is 2,000 to 3,000 N / m ² ,
A water-absorbing agent, wherein the amount of water-absorbing agent absorbed after 1 hour with respect to physiological saline under a load of 20 g / cm ² is 7 to 16 g / g. The water-absorbing agent according to claim 1, wherein the absorbed amount after 1 hour with respect to physiological saline under a load of 40 g / cm ² is 6 to 13 g / g. The water-absorbing agent according to claim 1 or 2, wherein the absorbed amount after 1 hour with respect to physiological saline under a load of 60 g / cm ² is 5 to 10 g / g. The absorber containing the water absorbing agent of Claims 1-3 and a fibrous material. An absorbent article comprising the absorber according to claim 4. A method for producing the water-absorbing agent according to claim 1,
The polymerization start temperature is 0 to 5 ° C., and the dissolved oxygen concentration is 0.5 ppm or less. From alkali metal sulfite, alkali metal bisulfite, ammonium sulfite, ammonium bisulfite, ferric chloride, ferric sulfate and ascorbic acid A redox initiator comprising a combination of at least one reducing agent selected from the group consisting of and at least one oxidizing agent selected from the group consisting of alkali metal persulfates, ammonium persulfate, hydrogen peroxide and organic peroxides. A method for producing a water-absorbing agent, comprising an adiabatic solution polymerization step using