JP3205168B2 - Absorbent composition for disposable diapers - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a powdery absorbent composition suitably used for disposable diapers. More specifically, the present invention relates to an absorbent composition having not only an absorption performance but also an excellent gel elasticity after shearing and an appropriate absorption rate, and as a result, exhibiting excellent performance for a long time when applied to a disposable diaper. It is.

[0002]

2. Description of the Related Art Conventionally, a water-swellable crosslinked polymer in the form of powder, called a water-absorbent resin, has been used as an absorbent for disposable diapers. Examples of these water-absorbing resins include starch-acrylate copolymer cross-linked products, polyacrylate cross-linked products,
Acrylic acid ester-vinyl acetate copolymer crosslinked product saponified product, maleic anhydride copolymer crosslinked product, modified cellulose derivative and the like are known. Among them, starch-acrylate copolymer crosslinked product is mainly used. Products and crosslinked polyacrylates have been conventionally used for disposable diapers. However, the amount of water-absorbent resin used in conventional disposable diapers is 15% based on the total weight of the fibrous base material such as pulp and the water-absorbent resin.
The amount was as small as about 25% by weight.

[0003]

In recent years, as the thickness of disposable diapers has been reduced (increase in the amount of water-absorbent resin and decrease in the amount of pulp), the ratio of the water-absorbent resin to the fibrous base material has increased. With water-absorbing resins, it has become impossible to obtain sufficiently satisfactory disposable diaper performance. In other words, with conventional water-absorbing resins, although the absorbent performance of disposable diapers is satisfied to some extent, the elasticity of the absorbent gel after shearing is low, resulting in inferior repetitive absorption of urine. There was a problem that it was inferior or leaked. Moreover, since it was not designed for thinned paper diapers having a large ratio of water-absorbent resin / fibrous base material, the balance between the absorption capacity under pressure and the gel elasticity and the shearing force of the absorbent gel were added. In fact, no consideration has been given to stability in the condition, urinary diffusivity, and the like. In particular, in the case of a thinned paper diaper having a large ratio of the water-absorbent resin / fibrous base material, the performance of the paper diaper greatly depends on the performance of the water-absorbent resin. Therefore, considering the necessary functions as an absorbent for disposable diapers from the state where disposable diapers are actually used,
(A) absorbs urine well even under the load of the disposable diaper wearer (absorbed amount under pressure); (b) does not deform or break the absorbent gel due to the load (initial elastic modulus);
(C) Movement of the wearer (crawling, shifting the buttocks, turning over, etc.)
Absorbent gel is stable even when shear force is exerted by it, and exerts absorbency even for the next urination (elastic modulus after shearing of gel). (D) No gel blocking occurs when urine is absorbed (fine powder) At least five functions are required, such as (e) reduction of the content), and (e) an appropriate absorption rate (absorption rate, initial absorption amount under pressure) to diffuse urine widely in the disposable diaper. That is, if these functions can be imparted to the absorbent, a disposable diaper that has a good dry feeling and does not leak even when worn for a long time is realized. In particular, as the usage ratio of the absorbent to the fibrous base material increases (for example, when the ratio of the absorbent / fibrous base material exceeds 30/70 by weight), the above function is required for the absorbent. On the other hand, some proposals have been made as absorbents suitable for use in disposable diapers. For example, it has a gel capacity of at least 20 g / g for synthetic urine and the shear modulus of the hydrogel is at least 2,000 dynes / cm ²
And an ungrafted absorbent having an equilibrium extractable polymer content of 17% by weight or less (Japanese Patent Application Laid-Open No. 62-54751).
However, as the performance of the absorbent is focused only on the absorption capacity under normal pressure and the gel strength, the above-mentioned 5
Some effects can be expected for (b) and (c) of the three functions, but the other three functions cannot be said to be sufficiently satisfactory. In addition, it has a gel capacity of at least 20 g / g for synthetic urine and a mass median particle size of 4
Although there is a proposal of a slightly crosslinked absorbent gelling agent having a thickness of from 00 to 1680 μm (Japanese Patent Application Laid-Open No. 1-132802), the performance of the absorbent focuses only on the absorption capacity and the particle size under normal pressure. Therefore, although some effects can be expected for (d) of the above five functions, it cannot be said that the other four functions are sufficiently satisfied. Further, the absorption amount of physiological saline is 40 to 90 g / g, the absorption rate is 8 ml / 0.3 g or more, and the gel strength when the ion exchange water is saturated and swollen is 33 to 200 g / g.
cm ² (Japanese Patent Application Laid-Open No. 60-185804)
Japanese Patent Application Laid-Open No. 60-185805), but the performance of the absorbent is focused only on the absorption capacity under normal pressure, the liquid absorption rate and the gel strength against water. Some effects can be expected for (b) and (e) of the three functions, but the other three functions cannot be said to be sufficiently satisfactory.

[0004]

In view of the above problems, the present inventors have made intensive studies on absorbents for disposable diapers, particularly thinned disposable diapers in which an absorbent is used at a high concentration. It has been found that a desired absorbent can be obtained by mixing a hydrophilic silicon dioxide fine powder having a specific property with a carboxylic acid group-containing water-absorbent resin particle having a multiple cross-linking structure, and further controlling the particle size distribution. Reached the present invention.

That is, the present invention relates to a powdery absorbent composition used as a paper diaper together with a fibrous base material,
Acrylate and acrylic acid are the main monomer components of the polymer, and at least two double bonds copolymerizable with the monomer are present.
Water-absorbent resin particles (A) having a structure crosslinked by a first crosslinking agent (a) having at least two functional groups capable of covalently bonding to a carboxylic acid group and a second crosslinking agent (b) having at least two functional groups.
Wherein (A) is a unit of acrylic acid and acrylate
The polymer mixture is polymerized with (a), and the resulting water-containing gel
Reacting the carboxylic acid groups in the polymer in (b)
And (A) a hydrophilic silicon dioxide fine powder (B) having a specific surface area of 50 to 450 m 2 / mg and a hydrophilicity of 70% or more.
(B) a mixing ratio of 0.05 to 5 parts by weight with respect to 00 parts by weight, and a content of a particle size larger than 850 μm is 1
0% by weight or less, content of particle size smaller than 150μ is 10
Use and with fibrous substrates as paper diapers; diapers absorbent composition having a particle size distribution by weight or less%
Powdery absorbent composition comprising acrylate and
Acrylic acid is the main monomer component of the polymer, and
First crosslink having at least two polymerizable double bonds
A small number of functional groups capable of covalently bonding with the agent (a) and the carboxylic acid group;
Structure crosslinked with at least two second crosslinking agents (b)
Water-absorbent resin particles (A) having the formula (A):
Acrylic acid is polymerized with (a), and the resulting hydrous gel is obtained.
Carboxylic acid group in toluene-based polymer
And the carboxylic acid groups in the polymer are further reacted in (b).
Obtained by cross-linking substantially uniformly by
And a specific surface area of 50 to 450 m2 / mg and a degree of hydrophilicity of 7
0% or more of hydrophilic silicon dioxide fine powder (B)
(A) 100 parts by weight, (B) 0.05 to 5 weights
Particle size in a mixing ratio of parts by weight and greater than 850μ
Having a particle size of 10% by weight or less and smaller than 150μ
Paper diapers having a particle size distribution with a content of 10% by weight or less
It is an absorbent composition .

In the present invention, the salts of acrylic acid include:
Alkali metal salts (eg, sodium salt, potassium salt, lithium salt), ammonium salts, amine salts (eg, alkylamine salts such as methylamine salt and trimethylamine salt; alkanolamine salts such as triethanolamine salt and diethanolamine salt). Can be Among these, preferred salts are alkali metal salts, and more preferred salts are sodium and potassium salts.

When a mixture of acrylic acid and acrylate is used as the monomer, the molar ratio of acrylic acid to acrylate is usually (10-40) :( 60-90), preferably (20-35). : (80 to 65). When the molar ratio of acrylic acid is less than 10, pH of the resulting water-absorbent resin
Becomes alkaline, while if it exceeds 40, the pH becomes acidic, and in either case, it is not preferable from the viewpoint of safety for human skin, and thus it is not suitable as a component of the absorbent composition for disposable diapers.

When acrylic acid is used as a monomer, it is usual that the carboxylic acid group in the polymer is partially neutralized with an alkaline substance after polymerization. Alkaline substances used for this neutralization include alkali metal compounds (such as sodium hydroxide and potassium hydroxide), alkali metal carbonates (such as sodium carbonate and sodium bicarbonate), ammonia,
Examples include amine compounds (alkylamines such as methylamine and trimethylamine; alkanolamines such as triethanolamine and diethanolamine) and two or more of these. The degree of neutralization is usually 60 to 90 mol%, preferably 65 to 80 mol%. Neutralization degree 60
When the amount is less than 90 mol%, the pH of the resulting water-absorbent resin becomes acidic. On the other hand, when the amount exceeds 90 mol%, the pH becomes alkaline, and in any case, it is not preferable in terms of safety to human skin. It is not suitable as a component of the absorbent composition.

In the present invention, examples of the first crosslinking agent (a) having at least two double bonds copolymerizable with the monomer include the following. Bis (meth) acrylamide: N, N′-alkylene (C ₁ -C ₆ ) bis (meth) acrylamide
N'-methylenebisacrylamide and the like. Di- or polyester of polyols and unsaturated mono- or polycarboxylic acids: di- or tri- (meth) acrylic acid of polyols [ethylene glycol, trimethylolpropane, glycerin, polyoxyethylene glycol, polyoxypropylene glycol, etc.] Esters: unsaturated polyesters [obtained by reacting the above polyols with unsaturated acids such as maleic acid] and di- or tri- (meth) acrylic esters [obtained by reacting polyepoxide with (meth) acrylic acid] ]Such. Carbamyl ester: polyisocyanate [tolylene diisocyanate, hexamethylene diisocyanate,
4,4'-diphenylmethane diisocyanate and N
A carbamyl ester obtained by reacting a CO group-containing prepolymer (obtained by reacting the above polyisocyanate with an active hydrogen atom-containing compound) and hydroxyethyl (meth) acrylate; Di or polyvinyl compounds: divinyl benzene, divinyl toluene, divinyl xylene, divinyl ether,
Divinyl ketone, trivinyl benzene, etc. Di- or poly- (meth) allyl ethers of polyols: di- or poly- (meth) allyl ethers of polyols [alkylene glycols, glycerin, polyalkylene glycols, polyalkylene polyols, carbohydrates, etc.] such as polyethylene glycol diallyl ether and Allylated starch, allylated cellulose and the like. Di- or poly-allyl esters of polycarboxylic acids:
Diallyl phthalate, diallyl adipate and the like. Esters of unsaturated mono- or poly-carboxylic acids with mono (meth) allyl ethers of polyols: (meth) acrylates of polyethylene glycol monoallyl ether and the like. Polyallyloxyalkanes: diallyloxyethane, triaryloxyethane, tetraallyloxyethane, neopentyl glycol triallyl ether, neopentyl glycol tetraallyl ether and the like. Among these, preferred crosslinking agent (a) is bis (meth)
Acrylamide, di- or poly-esters of polyols with unsaturated monocarboxylic or polycarboxylic acids, polyallyloxyalkanes, more preferred crosslinking agents are N, N'-methylenebisacrylamide, ethylene glycol diacrylate, Trimethylolpropane triacrylate, tetraallyloxyethane and neopentyl glycol triallyl ether. Particularly preferred cross-linking agents are that they do not contain a readily hydrolyzable bonding mode such as an amide group or an ester group in the molecule.
Tetraallyloxyethane and neopentyl glycol triallyl ether.

The amount of the crosslinking agent (a) is usually 0.01 to 5% by weight, preferably 0.1% by weight, based on the total weight of the polymerizable monomer.
It is from 0.5 to 3% by weight, more preferably from 0.1 to 1% by weight. If the amount of (a) is less than 0.01% by weight, the elasticity of the resulting water-absorbent resin after shearing of the gel of the resulting water-absorbent resin becomes insufficient even if the crosslinking is further carried out with the second crosslinking agent (b). 5
On the other hand, if the content is more than 10% by weight, the initial elastic modulus becomes too large and becomes brittle, the elastic modulus after shearing of the gel decreases, and the absorption under pressure also decreases.

In the present invention, the water-absorbing resin is further cross-linked by a second cross-linking agent (b) having at least two functional groups capable of covalently bonding to a carboxylic acid group. Examples of the crosslinking agent (b) include polyglycidyl ether compounds (ethylene glycol diglycidyl ether, glycerin-
1,3-diglycidyl ether, glycerin triglycidyl ether, polyethylene glycol diglycidyl ether, etc.); polyol compounds (glycerin, ethylene glycol, polyethylene glycol, etc.); polyamine compounds (ethylene diamine, diethylene triamine, polyamide polyamine epichlorohydrin resin, polyamide epichlorohydrin resin, etc.) ). Among these, preferred crosslinking agents (b) are polyglycidyl ether compounds, polyol compounds and polyamine compounds. Particularly preferred crosslinking agent (b) forms a strong covalent bond with a carboxylic acid group to obtain a water-absorbent resin having excellent elastic modulus after shearing, and allows the crosslinking reaction to be carried out at a relatively low temperature, thereby being economical. And ethylene glycol diglycidyl ether, glycerin-1,3-diglycidyl ether, polyamide polyamine epichlorohydrin resin, and polyamide epichlorohydrin resin. The crosslinking agent (b) which forms an ionic bond with a carboxylic acid group (for example, zinc acetate, calcium acetate, barium acetate, strontium acetate, aluminum hydroxide, zirconium lactate, titanium lactate, etc.) is used in the present invention. Not included. When the above ionic polyvalent metal salt is used as the cross-linking agent (b), a cation may be dissociated when urine is absorbed, so that a good elastic modulus after shearing of the gel cannot be obtained.

The amount of the crosslinking agent (b) is usually 0.001 to 3% by weight, preferably 0.001% by weight, based on the total weight of the monomers.
The content is 5 to 2% by weight, more preferably 0.01 to 1% by weight. When the amount of (b) is less than 0.001% by weight, the initial elastic modulus of the obtained water-absorbent resin is small, and the elastic modulus after shearing of the gel is also low. On the other hand, if it exceeds 3% by weight, the gel becomes too hard and brittle, and the elastic modulus after shearing of the gel decreases, the absorption under pressure decreases, and the absorption rate decreases.

If necessary, other hydrophilic monomers can be used in combination with the monomer comprising acrylate and / or acrylic acid. For example, unsaturated mono- or polycarboxylic acids [methacrylic acid, crotonic acid, maleic acid Acid, itaconic acid, maleic anhydride, etc.], a monomer containing a sulfonic acid group [aliphatic or aromatic vinyl sulfonic acid such as vinyl sulfonic acid, allyl sulfonic acid, vinyl toluene sulfonic acid, styrene sulfonic acid; ) Sulfoethyl acrylate, (meth) acrylsulfonic acid such as sulfopropyl (meth) acrylate, (meth) acrylamidesulfonic acid such as 2-acrylamido-2-methylpropanesulfonic acid, etc.] Monomer [2-hydroxyethyl (meth) acryloyl phosphate, -2-acryloyloxyethyl phosphate, etc.], (meth) acrylamide and its derivatives, and vinyl acetate. The amount of other hydrophilic monomers based on all monomers is usually 0 to 3 based on weight.
0% by weight, preferably 0 to 10% by weight. When the amount of the other hydrophilic monomer exceeds 30%, the absorption of the resulting water-absorbent resin under pressure decreases.

The polymerization method for producing the water-absorbent resin may be a conventionally known method, for example, a method of polymerizing a polymerizable monomer and a crosslinking agent (a) with an aqueous solution, a method of reverse phase suspension polymerization, A method of irradiating radiation, an electron beam, ultraviolet light, or the like to perform polymerization, and the like can be given. The polymerization conditions (polymerization concentration, polymerization solvent, type and amount of polymerization initiator, polymerization temperature, etc.) may be conventionally known conditions.

[0015] The water-absorbent resin in the present invention, after polymerization,
It must be further crosslinked with a second crosslinking agent (b) having at least two functional groups capable of covalently bonding to a carboxylic acid group. There is no particular limitation on this crosslinking method,
To illustrate the case of using acrylic acid as a monomer,
(1) A monomer mixture of acrylic acid and an acrylate is polymerized with a crosslinking agent (a), and then the crosslinking agent (b) is added to the resulting hydrogel polymer in an aqueous solution if necessary. A method of substantially uniform crosslinking by kneading and heating reaction (a crosslinking reaction may be performed simultaneously with drying of the water-containing polymer), (2) polymerization of acrylic acid and crosslinking agent (a),
A method of partially neutralizing the carboxylic acid groups in the obtained hydrogel polymer with an alkali metal salt, further adding and kneading a crosslinking agent (b), and performing a heating reaction to crosslink substantially uniformly; (3) A method in which a crosslinking agent (b) is added or sprayed to the powdery granular polymer obtained in the above (1), mixed, and heat-treated to further surface-crosslink the vicinity of the surface of the powdery granular polymer. (4) A method of adding or spraying and mixing a crosslinking agent (b) to the granular polymer obtained in the above (2), and heat-treating to further crosslink the vicinity of the surface of the granular polymer. And the like. Preferred methods are (2) and
This is the method (5), and the diaper performance when applied to a disposable diaper is improved.

The temperature at which the hydrated gel polymer or the mixture of the granular materials to which the crosslinking agent (b) has been added and kneaded as described above is heated and cross-linked varies depending on the type of (b), but is usually 80.
-220 ° C, preferably 100-190 ° C. 10
If the temperature is lower than 0 ° C., it takes a long time for heating, so that it is not economical, and depending on the type and the amount of (b), the crosslinking reaction may not proceed to an extent sufficient to exhibit the effects of the present invention. is there. On the other hand, when the temperature exceeds 220 ° C., the absorption of the water-absorbent resin under pressure is reduced due to coloring of the water-absorbent resin and thermal crosslinking.

The device for crosslinking is not particularly limited, and a conventionally known device can be used. In the case of crosslinking by the method (1) or (2), as a device for kneading the crosslinking agent (b) into the hydrogel polymer, for example, a kneader,
Examples include a universal mixer, a single-screw or twin-screw kneading extruder, and a meat chopper. In addition, as a device for heat crosslinking and drying, hot air dryer, drum dryer,
A belt type drier, a reduced pressure drier, etc. are mentioned. the above
When the surface is crosslinked by the method (3) or (4) , a device for adding or spraying and mixing the crosslinking agent (b) includes:
For example, a screw-type mixer, a turbulizer, a Nauter-type mixer, a V-type mixer, a ribbon mixer, a double-arm kneader, a flow-type mixer, a gas-flow-type mixer, and the like can be given. Examples of an apparatus for heat-treating this mixture include a hot-air dryer, a flash dryer, a fluidized-bed dryer, a belt-type dryer, a Nauter-type heater, a paddle dryer, and an infrared dryer.

The shape of the water-absorbent resin particles (A) of the present invention is not particularly limited as long as they are powdery and granular.
Any shape such as a granulated shape, a scale shape, a lump shape, and a pearl shape may be used.

The hydrophilic silicon dioxide fine powder (B) used in the present invention is a dry silica produced by hydrolyzing silicon tetrachloride in a flame obtained by burning oxygen and hydrogen at a high temperature, and is usually "Fumed Silica". It is called "". Therefore, (B) used in the present invention is usually non-porous having no internal surface area. Specifically, it is a hydrophilic silicon dioxide having a specific surface area of 50 to 450 m ² / g and a hydrophilicity of 70% or more. Preferably, it is a hydrophilic silicon dioxide having a specific surface area of 100 to 400 m ² / g and a hydrophilicity of 75% or more. Specific surface area is 5
If it is less than 0 m ² / g, the proper absorption rate as the object of the present invention is not achieved, and the initial absorption under pressure (absorption under pressure after 5 minutes) also decreases. Furthermore, the elastic modulus after shearing of the gel does not increase. On the other hand, even if the specific surface area exceeds 450 m ² / g, no change is observed in the performance of the absorbent composition, which is uneconomical because the production cost of the hydrophilic silicon dioxide fine powder increases. When the hydrophilicity is less than 70%, the hydrophobicity of silicon dioxide becomes strong. Therefore, when mixed with a water-absorbing resin having a small fine powder content and a narrow particle size distribution as in the present invention, the resulting absorbent composition can be obtained. , The absorption rate under pressure decreases. Further, hydrophobic silica has poor affinity with hydrophilic water-absorbing resin, and may not be sufficiently adhered to the particle surface of (A). If (B) is not sufficiently adhered to the surface of (A), dust may be generated. 7 hydrophilicity
Less than 0% of silicon dioxide fine powder is usually called hydrophobic silica, and the silanol groups on the surface of the hydrophilic silicon dioxide fine powder in the present invention are further reacted with monomethyltrichlorosilane, dimethyldichlorosilane, trimethylchlorosilane, etc. Hydrophobic by introducing an alkyl group,
For the above reasons, it is not suitable for the present invention. However, hydrophobic silica may be used in such an amount that the degree of hydrophilicity falls within the range of the present invention. The specific surface area here is Brunauer-Emmett
This is a value measured by the Taylor method. The degree of hydrophilicity is the proportion of silicon dioxide suspended colloidally in a mixture of water / methanol = 70/30. The smaller this value, the stronger the hydrophobicity. Incidentally, the particle size of the silicon dioxide fine powder is not particularly limited as long as the specific surface area and the degree of hydrophilicity satisfy the range of the present invention, but is generally said to have a primary particle diameter of 5 to 50 mμ. ing. However, in a normal state, the primary particles are present in an agglomerated form, and are usually in the form of fine powder having a particle size of 0.07-1 μm, preferably 0.1-0.8 μm.

In the present invention, the mixing ratio of (A) and (B) is 0.05- (B) per 100 parts by weight of (A).
5 parts by weight, preferably 0.1 to 2 parts by weight. (B)
If the amount is less than 0.05 part by weight, a sufficient elastic modulus after shearing of the gel cannot be obtained. On the other hand, if the amount of (B) exceeds 5 parts by weight, the effect corresponding to the added amount cannot be obtained, so that it is uneconomical. Furthermore, (A), which is not sufficiently adhered to the particle surface of (A), causes dust generation and increases frictional resistance. Causes deterioration.

The apparatus for mixing (A) and (B) may be an ordinary powder mixing apparatus, for example, a conical blender, a Nauter mixer, a V-type mixer, an air-flow type mixer, a turbulizer, a screw type. Line blending equipment,
And a static mixer. In addition, in the presence of the water-absorbent resin and the inorganic powder, absorb the crosslinking agent and water,
Next, a method for producing a water-absorbing resin in which a crosslinking reaction and water distillation are performed by heating under stirring (Japanese Patent Application Laid-Open No. 60-163956).
The purpose of using the inorganic powder in this proposal is to improve the blocking property when water is absorbed by the water-absorbent resin, and therefore, the water-absorbent resin particles having a specific crosslinked structure and a specific particle size distribution are used. This is essentially different from the present invention in which the hydrophilic silicon dioxide fine powder (B) having a specific property is mixed with (A) and the performance of the absorbent composition is positively modified so that it can be suitably used for disposable diapers. Things. Further, in the present invention, a heating operation after mixing (B) is unnecessary.

In the present invention, the particle size distribution of the absorbent composition is such that the content of particles having a particle size of more than 850μ is 10% by weight or less and the content of particles having a particle size of less than 150μ is 10% by weight or less. Preferably, the content of the particle size larger than 850μ is 5% by weight or less and the content of the particle size smaller than 150μ is 5% by weight or less, more preferably the content of the particle size larger than 710μ is 5% by weight or less than 150μ. The content of small particle size is less than 5% by weight, most preferably 600%
The particle size distribution is such that the content of the particle size larger than μ is 5% by weight or less and the content of the particle size smaller than 150μ is 5% by weight or less. If the amount of particles having a particle size larger than 850 μ exceeds 10% by weight, the absorption rate of the obtained absorbent composition becomes too slow, and when applied to a disposable diaper, leakage may occur. On the other hand, if the particle size of less than 150 μ exceeds 10% by weight, gel blocking is likely to occur when contacted with urine, and leakage may occur due to a decrease in the elastic modulus of the gel after shearing. Furthermore, fine powder may cause dust,
Agglomeration or removal from the fibrous base material is likely to occur due to moisture absorption, so that the workability when applied to a disposable diaper deteriorates. Therefore, by setting the particle size distribution to a specific narrow range, gel blocking does not occur when urine is absorbed,
An appropriate absorption rate for diffusing urine throughout the disposable diaper is obtained, and as a result, a disposable diaper having good surface dryness and no leakage is realized. Note that 850 μ corresponds to 18 mesh in JIS (Japanese Industrial Standard), 710 μ corresponds to 22 mesh, 500 μ corresponds to 28 mesh, and 150 μ corresponds to 100 mesh.

The particle size distribution can be adjusted by a conventionally known method. For example, a method of passing an absorbent composition through a sieve to control the content of particles larger than 850 μm and particles smaller than 150 μm is simple. It is. Others
A method of granulating fine particles (a binder may be used if necessary) to obtain a target particle size distribution, a method of obtaining a target particle size distribution without sieving by optimizing grinding conditions, and the like. . Further, when the inverse suspension polymerization method is employed as the polymerization method, as conventionally known,
It is also possible to obtain a target particle size distribution by selecting the type and amount of the dispersion stabilizer used in the polymerization, optimizing the structure of the reaction tank and the stirring conditions, and the like. The adjustment of the particle size distribution can also be performed at the stage (A). In this case, depending on the device for mixing (A) and (B), some fine powder may be generated due to mechanical shearing force. Therefore, it is preferable that particles smaller than 150 μm be smaller than the above range.

The absorbent composition of the present invention has an absorbency against artificial urine under pressure of 20 to 50 g / g, an elastic modulus of the artificial urine absorbent gel after shearing of 40,000 dynes / cm ² or more, and an absorption rate of 10 or more. ~ 90 seconds. Preferably, the absorbency under pressure is 25 to 50 g / g, and the elastic modulus after shearing of the gel is 45.0 g / g.
00 dynes / cm 2 or more, and the absorption rate is 15 to 75 seconds. By using an absorbent that satisfies such physical properties, a paper diaper that has a good dry feeling and does not leak even when worn for a long time is realized as described above. In particular, it is useful for a thinned paper diaper in which the ratio of the absorbent to the fibrous base material is large (for example, when the weight ratio of the absorbent / fibrous base material exceeds 30/70).

In the present invention, examples of the fibrous base material include cellulosic fibers, modified cellulose fibers, organic synthetic fibers, and mixtures thereof. As the cellulosic fiber, for example, floc pulp (fluff pulp)
And natural cellulose fibers such as viscose rayon and acetate. Examples of the organic synthetic fibers include polypropylene fibers, polyethylene fibers, polyamide fibers, polyacrylonitrile fibers, polyester fibers, polyvinyl alcohol fibers, and heat-fusible conjugate fibers (for example, at least one of the above fibers).
Fibers whose seeds are compounded into sheath-core type, eccentric type, parallel type, etc.
Fibers in which at least two kinds of the above fibers are blended, fibers in which the surface layer of the above fibers is modified, and the like). Preferred among these fibrous base materials are cellulosic natural fibers, polypropylene fibers, polyethylene fibers,
Polyester-based fibers, heat-fusible conjugate fibers and fibers in which these are mixed, more preferably fluff pulp, sheath-core type, eccentric type, in terms of excellent shape retention after urine absorption of disposable diapers, A heat-fusible conjugate fiber compounded into a parallel type or the like and a mixture thereof. In addition, the above-mentioned organic synthetic fibers are usually subjected to a hydrophilizing treatment with a hydrophilizing agent such as a surfactant and used for a disposable diaper, which is also suitable for the present invention.

The length and thickness of the above-mentioned fibrous base material are not particularly limited, and may be suitably used as long as the length is usually 1 to 200 mm and the thickness is 0.1 to 100 denier. it can. 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 of the absorbent composition of the present invention is usually 20 to 8 based on the total weight of the fibrous base material and the absorbent composition.
0% by weight, preferably 30 to 70% by weight, more preferably 35 to 65% by weight. When the amount of the absorbent composition used is less than 20% by weight, the conventional water-absorbent resin is sufficient, and the effect of using the absorbent composition of the present invention is poor. On the other hand, when it exceeds 80% by weight, it becomes difficult to immobilize the absorbent composition in the fibrous base material.

In the present invention, the method of using the absorbent composition may be a conventionally known method, for example, a method of mixing with a fibrous base material, a method of sandwiching between two layers of fibrous base materials, or a method of mixing three or more layers. A method of spraying between each of the laminated fibrous base materials and the like can be mentioned. Further, the absorbent composition of the present invention and a conventional water-absorbing resin can be used in combination or in combination at different sites.

The absorbent in which the absorbent composition is applied to the fibrous base material by the above-mentioned method may be obtained by further laminating an absorbent paper or a fibrous base material as necessary, and forming a liquid permeable top sheet and a lower part on the upper part thereof. Usually, a liquid-impermeable backsheet is disposed on the diaper, and leg garments, waist gathers, mounting tape and the like are provided to finish the disposable diaper.

As long as the objects and effects of the present invention are not impaired, organic powders (eg, pulp powder, cellulose derivatives, natural polysaccharides and the like), inorganic fillers and the like are added to the absorbent composition of the present invention. A powder (eg, zeolite, ultrafine hydrophobic silica, activated carbon, etc.), a preservative, a bactericide, a coloring agent, a fragrance, a surfactant and the like can be added as necessary.

[0031]

The present invention will be further described with reference to the following examples and comparative examples, but the present invention is not limited to these examples. The absorption amount under normal pressure, the absorption amount under pressure, the initial elastic modulus, the elastic modulus after shearing of the gel, the absorption rate and the performance of the disposable diaper of the absorbent composition were measured by the following methods. Hereinafter, unless otherwise specified,% indicates% by weight.

Absorbing amount under normal pressure: 1 g of the absorbent composition was placed in a tea bag made of a 250 mesh nylon mesh,
Excess artificial urine (0.8% sodium chloride, 2% urea, 0.08% magnesium sulfate, 0.03% calcium chloride
) For 30 minutes, and then lifted up for 15 minutes.
After draining for a minute, the increased weight was measured, and this value was taken as the absorption under normal pressure.

Absorbency under pressure: cylindrical plastic tube (inner diameter 3
(0 mm, height 60 mm), 0.1 g of the absorbent composition is put therein, spread uniformly, and a weight having an outer diameter of 30 mm is placed thereon so as to give a load of 20 g / cm ² . The tube containing the absorbent composition is immersed in a Petri dish (diameter: 12 cm) containing 60 ml of artificial urine for 30 minutes with the nylon mesh side facing downward. The value of 10 times the weight gained after 30 minutes was taken as the absorption under pressure. The above-mentioned initial amount of absorption under pressure is a value measured after 5 minutes in the same manner.

Gel elasticity after shearing: 1 g of the absorbent composition was placed in a 50-ml glass bottle with a stopper, and artificial urine 40 was added thereto.
Then, add 40 ml to make a 40-fold absorption gel and seal it tightly. This is put in a 40 ° C. constant temperature bath and kept warm for 5 hours. Next, 0.1 g of the gel kept warm for 5 hours is placed on the center of a support table of a creep meter (manufactured by Yamaden Corporation). The upper cylinder is then lowered to compress the gel to a thickness of 0.3 mm. By moving the cylinder up and down, compression is repeated a total of 20 times, the stress at the 20th compression and the cross-sectional area of the compressed gel are measured, and the stress per unit area after shearing is calculated by the following equation. The post-shear modulus of the gel was taken as the modulus. The modulus of elasticity of the gel after shearing (dyne / cm ² ) = (F × 98)
0) / S where F: stress at the 20th compression (g) 980: acceleration of gravity S: cross-sectional area of gel after 20 compressions (cm ² )

Absorption rate: 50cc in a 100ml beaker
Artificial urine (liquid temperature 25 ± 2 ℃) and magnetic stirrer (diameter 8m)
m; length 30 mm) and stirred with a magnetic stirrer at 600 rpm. 2 g of absorbent composition in vortex
, And the time from when the absorbent composition absorbs artificial urine until the vortex disappears and the liquid level becomes horizontal was measured, and this value was taken as the absorption rate.

Evaluation of dryness using a disposable diaper: Preparation of a model disposable diaper: A tissue paper of the same size and fluff pulp having a basis weight of 200 g / m ² are overlaid on a polyethylene sheet cut into a rectangle of 14 cm × 36 cm. Next, 7.5 g of a water-absorbent resin is evenly spread on the fluff pulp, and fluff pulp having a basis weight of 100 g / m ² , tissue paper and nonwoven fabric are laminated in this order. This laminate was pressed at a pressure of 5 kg / cm ² for 90 seconds to produce a model paper diaper.・ Measurement of dryness: artificial urine (colored with blue ink) 80m
1 is poured into the center of the model diaper, and after 30 minutes, the surface of the diaper is rolled 10 times with a 1 kg roller to apply a shearing force. Next, another 80 ml of artificial urine is poured into the center of the model paper diaper, and a shearing force is similarly applied 30 minutes later. This operation is repeated once more. After the three operations, the dryness of the surface of the disposable diaper was judged by 10 panelists for finger touch and evaluated on the following four scales. This average was defined as dryness. ◎: Good dry feeling ○: Slightly wet, but satisfactory level of dry feeling △: Poor dry feeling, moist state ×: No dry feeling, completely wet state ・ Diffusion area measurement: artificial after evaluating dryness The area where urine was absorbed and spread (colored blue) was measured and defined as the diffusion area.

Production Example 1 of Water Absorbent Resin Particles 77 g of sodium acrylate, 23 g of acrylic acid, 0.4 g of N, N'-methylenebisacrylamide and 296 g of deionized water were charged into a 1 liter glass reaction vessel, and stirred. The temperature of the contents was maintained at 5 ° C. while mixing. After flowing nitrogen into the contents to reduce the amount of dissolved oxygen to 1 ppm or less, 1 g of a 1% aqueous solution of hydrogen peroxide, 1.2 g of a 0.2% aqueous solution of ascorbic acid and 2,2′-azobisamidinopropane dihydro The polymerization was started by adding 2.5 g of a 2% aqueous solution of chloride, and the polymerization was carried out for about 5 hours to obtain a hydrogel polymer (I). While kneading the hydrogel polymer with a kneader, 6 g of a 5% aqueous solution of ethylene glycol diglycidyl ether was added and kneaded uniformly. The hydrogel is dried with hot air at 130 to 150 ° C. and pulverized, and then the particle size is adjusted so that the particle size of 850 to 150 μ (particle size larger than 850 μ is 4%; particle size smaller than 150 μ is 2%) is 94%. This was adjusted to obtain water-absorbent resin particles (a).

Production Example 2 of Water Absorbent Resin Particles The hydrogel polymer (I) obtained in Production Example 1 was treated with
After drying with hot air at 150 ° C and crushing, 850-150μ
(Particle size larger than 850μ was 4%; particle size smaller than 150μ was contained 2%) The particle size was adjusted so that the particle size became 94% to obtain crosslinked polymer particles (II). While 100 g of the crosslinked polymer particles (II) are stirred at a high speed, 3 g of a 10% aqueous solution of ethylene glycol diglycidyl ether is sprayed uniformly and heat-treated at about 140 ° C. for 30 minutes to obtain the water absorbent resin particles (b). Obtained. Incidentally, the particle size distribution of (b) was almost the same as (II).

Production Example 3 of Water Absorbent Resin Particles Acrylic acid 100 was placed in a 1-liter glass reaction vessel.
g, neopentyl glycol triallyl ether 0.5
g and 330 g of deionized water, and the temperature of the contents was kept at 5 ° C. while stirring. After flowing nitrogen into the contents to reduce the amount of dissolved oxygen to 1 ppm or less, 1 g of a 1% aqueous solution of hydrogen peroxide, 1.2 g of a 0.2% aqueous solution of ascorbic acid and 2,2′-azobisamidinopropane dihydro The polymerization was started by adding 2.5 g of a 2% aqueous solution of chloride, and the polymerization was carried out for about 5 hours to obtain a hydrogel polymer. While kneading the hydrogel polymer with an extruder equipped with a perforated plate, a 35% aqueous sodium hydroxide solution 11 was added.
By adding 6 g and uniformly kneading, a gel polymer (III) in which 73 mol% of acrylic acid was neutralized was obtained. To this gel polymer (III), 6 g of a 5% aqueous solution of ethylene glycol diglycidyl ether was added and uniformly kneaded. The hydrogel was dried with a drum dryer having a surface temperature of 180 ° C. and crushed.
(Particle size larger than 850μ is 2%; particle size smaller than 150μ is contained 4%) The particle size is adjusted so that the particle size becomes 94% to obtain water-absorbent resin particles (C).

Production Example 4 of Water Absorbent Resin Particles The gel polymer (III) obtained in Production Example 3 was dried with a drum dryer having a surface temperature of 180 ° C. and pulverized.
850-150μ (particle size larger than 850μ is 2%; 1
The particle size was adjusted so that the particle size (containing 4% of a particle size smaller than 50 μm) was 94% to obtain crosslinked polymer particles (IV).
While stirring 100 g of the crosslinked polymer particles (IV) at a high speed, the polyamide polyamine epichlorohydrin resin
% Aqueous solution was uniformly sprayed and heat-treated at about 140 ° C. for 30 minutes to obtain water-absorbent resin particles (d).
Incidentally, the particle size distribution of (d) was almost the same as that of (IV).

Preparation Example 5 of Water Absorbent Resin Particles In a 200 ml flask, 65.4 g of acrylic acid and 78.6 g of deionized water were charged, and while cooling to 20 to 30 ° C., 56.0 g of a 48% aqueous sodium hydroxide solution was added. 74 mol% of acrylic acid was neutralized by drop-wise dropping with stirring.
0.15 g of N, N′-methylenebisacrylamide is dissolved in the aqueous monomer solution, and then 0.1% of potassium persulfate is dissolved.
g was added and dissolved at room temperature, and then nitrogen gas was introduced to reduce the amount of dissolved oxygen in the solution to 1 ppm or less. A 1-liter flask equipped with a reflux condenser was charged with 400 g of n-hexane and 3 g of sorbitan monostearate.
After dissolving, the dissolved oxygen amount in the solution was reduced to 1 ppm or less by flowing nitrogen gas. Then, while maintaining the temperature at about 60 ° C. with a warm bath, while stirring, the above-mentioned aqueous solution of the monomer containing potassium persulfate is added dropwise, polymerization is carried out for about 3 hours, and further aging is carried out under reflux conditions for 2 hours. As a result, a dispersion liquid of the pearl-like hydropolymer was obtained.
Then ethylene glycol diglycidyl ether 10
A 3% aqueous solution was added, and a crosslinking reaction was carried out for 1 hour under reflux conditions. The hydropolymer was separated from the polymerization dispersion by filtration and centrifugally dehydrated to obtain a pearl-like hydropolymer. The water-containing polymer is dried under reduced pressure at 90 to 95 ° C.,
(Particle size larger than 850μ is 1%; particle size smaller than 150μ is contained 8%) The particle size is adjusted so that the particle size becomes 91% to obtain water-absorbent resin particles (e).

Production Example 6 of Water Absorbent Resin Particles 3 g of a 5% aqueous solution of ethylene glycol diglycidyl ether was added to the gel polymer (III) obtained in Production Example 3 and uniformly kneaded. The surface temperature of this hydrogel is 180 ° C.
After drying with a drum dryer and pulverizing,
Water-absorbent resin particles (f) were obtained by adjusting the particle size so that the particle size of 50μ (8% of the particle size larger than 850μ; 6% of the particle size smaller than 150μ) was 86%.

Production Examples 1-2 of Comparative Water Absorbent Resin Particles The crosslinked polymer particles (II) containing only the crosslinking agent (a) obtained in Production Example 2 were used as comparative water absorbent resin particles (g), Production Example 4 The crosslinked polymer particles (IV) containing only the crosslinking agent (a) obtained in the above were used as comparative water-absorbent resin particles (H).

Production Example 3 of Comparative Water Absorbent Resin Particles In Production Example 3, the particle size of 850 to 150 μ (particle size larger than 850 μ is 15%; particle size smaller than 150 μ is 1%) is 84%. Comparative water-absorbing resin particles (R) were obtained in the same manner as in Production Example 3 except that the particle size was adjusted.

Production Example 4 of Comparative Water Absorbent Resin Particles In Production Example 3, the particle size of 850 to 150 μm (containing 1% of a particle size larger than 850 μm; containing 15% of a particle size smaller than 150 μm) was 84%. Comparative water-absorbing resin particles (N) were obtained in the same manner as in Production Example 3 except that the particle size was adjusted.

Examples 1, 3, 5, 6 Water-absorbent resin particles (a), (c), (e), (f) 10
0 g, specific surface area 200 ± 20 m2 / g, degree of hydrophilicity 10
0% hydrophilic silicon dioxide fine powder (“Relosil QS
-102 "; manufactured by Tokuyama Soda Co., Ltd.).
The mixture was sufficiently mixed with a mold mixer to obtain the absorbent composition of the present invention.
The addition of the hydrophilic silicon dioxide fine powder hardly changed the particle size distribution. Reference Examples 2 and 4 Performed using 100 g of each of the water absorbent resin particles (b) and (d).
Reference Examples 2 and 4 were obtained in the same manner as in Example 1.

Examples 7 to 8 To 100 g of the water-absorbing resin particles (c), 0.8 g of the following fine powder of hydrophilic silicon dioxide was added, and the mixture was thoroughly mixed with a V-type mixer. An absorbent composition of the invention was obtained. The addition of the hydrophilic silicon dioxide fine powder hardly changed the particle size distribution. Hydrophilic silicon dioxide fine powder having a specific surface area of 380 ± 30 m ² / g and hydrophilicity of 100% (“Aerosil 380”; manufactured by Nippon Aerosil Co., Ltd.) Specific surface area of 140 ± 20 m ² / g, hydrophilicity of 98% Functional silicon dioxide fine powder ("Reloseal QS-1
0 "(manufactured by Tokuyama Soda Co., Ltd.) Table 1 shows the performance measurement results of these absorbent compositions.

Examples 9 and 10 100 g of the water-absorbent resin particles (c) was added with "Reolosil QS-
102 "in 0.3 g (Example 9) or 2 g (Example 1).
0) was added and thoroughly mixed with a V-type mixer to obtain an absorbent composition of the present invention. The addition of the hydrophilic silicon dioxide fine powder hardly changed the particle size distribution. Table 1 shows the performance measurement results of these absorbent compositions.

Production Example 7 of Water Absorbent Resin Particles To the gel polymer (I) obtained in Production Example 1, 1.5 g of a 5% aqueous solution of ethylene glycol diglycidyl ether was added and uniformly kneaded. The hydrogel was dried with hot air at 130 to 150 ° C. and pulverized, and then 850 to 150 μm (850 μm).
1% larger particle size; 4% smaller than 150μ
(Containing) was adjusted to a particle size of 95% to obtain crosslinked polymer particles. While rapidly stirring 100 g of the crosslinked polymer particles, 3 g of a 10% aqueous solution of ethylene glycol diglycidyl ether was sprayed at 30 ° C. at about 140 ° C.
The mixture was subjected to a heat treatment for 1 minute to obtain water-absorbent resin particles (R).

Production Example 8 of Water Absorbent Resin Particles To the gel polymer (III) obtained in Production Example 3, 1.5 g of a 5% aqueous solution of ethylene glycol diglycidyl ether was added and uniformly kneaded. 130-150 of this hydrogel
After drying with hot air at ℃ and pulverizing, 850-150μ (85
Crosslinked polymer particles were obtained by adjusting the particle size so that the particle size larger than 0μ was 1%; and the particle size smaller than 150μ was 4%). While 100 g of the crosslinked polymer particles are stirred at high speed, 3 g of a 10% aqueous solution of ethylene glycol diglycidyl ether is sprayed uniformly and heat-treated at about 140 ° C. for 30 minutes to obtain water-absorbent resin particles (e).
I got

Production Example 9 of Water Absorbent Resin Particles
%; A water-absorbent resin particle (W) was obtained in the same manner as in Production Example 8 except that the particle size was smaller than 150 μm.

Production Example 10 of Water Absorbent Resin Particles
%; A water-absorbing resin particle (f) was obtained in the same manner as in Production Example 8 except that the particle size was smaller than 150 µm.

Examples 11 to 14 Each 100 g of the water-absorbing resin particles (L) to (F) was coated with a hydrophilic silicon dioxide fine powder having a specific surface area of 200 ± 20 m ² / g and a hydrophilicity of 100% (“Reloseal QS-102”). "; Manufactured by Tokuyama Soda Co., Ltd.) and sufficiently mixed with a V-type mixer to obtain an absorbent composition of the present invention. The addition of the hydrophilic silicon dioxide fine powder hardly changed the particle size distribution. Table 1 shows the performance measurement results of these absorbent compositions.

Comparative Examples 1 to 6 Table 2 shows the performance measurement results of the water-absorbent resin particles (a) to (f) to which no hydrophilic silicon dioxide fine powder was added.

Comparative Examples 7 to 10 Comparative water-absorbent resin particles (g) to (g)
0.8 g of "Reolosil QS-102" was added, and the mixture was sufficiently mixed with a V-type mixer to obtain a comparative absorbent composition. still,
The addition of the hydrophilic silicon dioxide fine powder hardly changed the particle size distribution. Table 2 shows the results of these performance measurements.

COMPARATIVE EXAMPLE 11 100 g of the water-absorbent resin particles (c) was added with "Reolosil QS-
102 "was added and sufficiently mixed with a V-type mixer to obtain a comparative absorbent composition. The addition of the hydrophilic silicon dioxide fine powder hardly changed the particle size distribution. Table 2 shows the performance measurement results.

Comparative Example 12 A specific surface area of 120 ± 10 was added to 100 g of the water absorbent resin particles (c).
0.8 m ² / g of silicon dioxide fine powder having a degree of hydrophilicity of 58% (“Reolosil MT-10”; manufactured by Tokuyama Soda Co., Ltd.)
g was added and sufficiently mixed with a V-type mixer to obtain a comparative absorbent composition. The addition of this fine powder of silicon dioxide hardly changed the particle size distribution. Table 2 shows the performance measurement results.

[0058]

[Table 1]

[0059]

[Table 2]

As can be seen from Tables 1 and 2, Examples 1 to 14
The composition of the present invention containing the hydrophilic silicon dioxide fine powder of the present invention is far superior in the performance of the absorbent composition and the disposable diaper as compared with the compositions of Comparative Examples 1 to 6 not containing the fine powder. . Moreover, the composition using only the first crosslinking agent (Comparative Examples 7 and 8), the composition having a large amount of coarse particles (Comparative Example 9), the composition having a large amount of fine powder (Comparative Example 10), and the amount of the hydrophilic silicon dioxide It can be seen that the composition of the present invention and the performance of the disposable diaper are superior even when compared with a composition having a small amount (Comparative Example 11) and a composition using hydrophobic silicon dioxide (Comparative Example 12).

[0061]

The absorbent composition of the present invention has the following features and effects. It has a high absorption under pressure for artificial urine. Further, the initial absorption under pressure is excellent. Therefore, when used in a disposable diaper, it has a high initial elasticity that absorbs urine well even under a load of a wearer. Therefore, when used for a disposable diaper, the absorbent gel does not deform or break due to the load of the wearer. Excellent elastic modulus after shearing of artificial urine absorbing gel. Therefore, when used for a disposable diaper, even when a shearing force due to the movement of the wearer (crawls, shifts the buttocks, rolls over, etc.) is exerted, a stable absorbing power is exhibited, and urine can be repeatedly absorbed. Has a moderate absorption rate. Therefore, urine is diffused widely in the disposable diaper. The gel has a good dry feeling after water absorption and shows a slaty feel. It has a low fines content and a narrow particle size distribution. Therefore, gel blocking does not occur when urine is absorbed by being applied to a disposable diaper, and urine is widely diffused into the disposable diaper. When applied to a disposable diaper, dust is not generated and the fluidity of the powder is good, so that the workability is improved. There is no phenomenon that the absorbent composition comes off from the fibrous base material. Therefore, the productivity in manufacturing the disposable diaper is improved (the loss rate is reduced). It can be manufactured by a simple operation of mixing (A) and (B).

Further, a disposable diaper using the absorbent composition obtained by the method of the present invention in a fibrous base material has the following properties. Good dry feeling and salat feeling on the surface of the disposable diaper after urine absorption. Since the water-absorbing resin has an appropriate absorption rate, urine can be easily diffused in the disposable diaper, and urine can be efficiently absorbed by the entire disposable diaper. There is no worry about urine leakage.

Because of the above effects, the absorbent composition obtained by the method of the present invention is suitable for use in disposable diapers (child diapers and adult diapers). Particularly, it is suitable for a thinned paper diaper having a large ratio of absorbent / fibrous base material. Further, other absorbent materials and sanitary materials used in the fibrous base material absorbent composition (for example,
Sanitary napkins, incontinence pads, breast milk pads, surgical underpads, pet sheets, etc.) can also be suitably used.

────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁷ Identification symbol FI B01J 20/26 A61F 13/18 307A C08F 20/06 Examiner Shigeru Chiba (56) References JP-A-4-214736 (JP, A JP-A-3-174414 (JP, A) JP-A-59-62665 (JP, A) WO 92/18171 (WO, A1) WO 91/17200 (WO, A1) US Patent 4,666,983 (US, A) US Pat. No. 4,734,478 (US, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) A61F 13/53 A61F 5/44 A61F 13/49 A61L 15/60 B01J 20/10 B01J 20/26 C08F 20/06

Claims (11)

(57) [Claims] 1. A sorbent composition particulate for use as a disposable diaper with a fibrous substrate, Oyo acrylate
And acrylic acid as a main monomer component of a polymer, a first crosslinking agent (a) having at least two double bonds copolymerizable with the monomer, and a functional group capable of covalently bonding with a carboxylic acid group Water-absorbent resin particles (A) having a structure cross-linked by a second cross-linking agent (b) having at least two (A) , wherein (A) is
Monomer mixture of acrylic acid and acrylate and (a)
Is polymerized, and then the carbohydrate in the obtained hydrogel polymer is obtained.
Reacting the acid groups in (b) to make them substantially uniform
What is obtained by crosslinking , specific surface area 50-450 m2 /
mg of hydrophilic silicon dioxide fine powder (B) having a hydrophilicity of 70% or more, wherein (A) is a mixing ratio of 0.05 to 5 parts by weight with respect to 100 parts by weight, and 8
The content of a particle size larger than 50μ is 10% by weight or less,
An absorbent composition for a disposable diaper having a particle size distribution in which the content of a particle size smaller than 0μ is 10% by weight or less. 2. A powdery and granular absorbent composition for use as a disposable diaper together with a fibrous base material, comprising an acrylate and a powdery absorbent.
And acrylic acid as a main monomer component of a polymer, a first crosslinking agent (a) having at least two double bonds copolymerizable with the monomer, and a functional group capable of covalently bonding with a carboxylic acid group Water-absorbent resin particles (A) having a structure crosslinked by a second crosslinking agent (b) having at least two (A)
Polymerizes acrylic acid and (a), and contains
Carboxylic acid group in water-gel polymer
And neutralize the carboxylic acid groups in the polymer by (b).
To obtain a substantially uniform cross-link.
The a, becomes from a specific surface area 50~450m2 / mg in and hydrophilicity of 70% or more hydrophilic silicon dioxide fine powder (B), (A) with respect to 100 parts by weight of (B) 0.05 to 5 weight The composition according to claim 1, wherein the content of particles having a particle size of more than 850 μm is 10% by weight or less, and the content of particles having a particle size of less than 150 μm is 10% by weight or less. 3. The method of claim 1, wherein (A) is obtained by crosslinking the substantially uniform.
The water-absorbing resin particles obtained by subjecting the surface of the obtained water-absorbing resin particles to surface cross-linking with a cross-linking agent (b).
3. The composition according to 1 or 2 . 4. The amount of (a) is 0.05 to 3% by weight based on the weight of the monomer, and the amount of (b) is 0.01 to 2% by weight based on the weight of the monomer. The composition according to any one of claims 1 to 3 , wherein 5. The composition of claim 1, wherein the ratio of (A) to (B) is 0.1 to 2 parts by weight of (B) per 100 parts by weight of (A) .
5. The composition according to any of 4 . 6. The content of a particle size larger than 850 μm is 5% by weight or less, and the content of a particle size smaller than 150 μm is 5% by weight.
The composition according to any one of claims 1 to 5 , which is: 7. The content of a particle size larger than 710 μm is 5% by weight or less, and the content of a particle size smaller than 150 μm is 5% by weight.
The composition according to any one of claims 1 to 6 , wherein 8. The content of a particle size larger than 600 μm is 5% by weight or less, and the content of a particle size smaller than 150 μm is 5% by weight.
The composition according to claim 1 , wherein: 9. The composition according to claim 1, wherein said composition absorbs artificial urine under pressure in an amount of 20 to 50 g / g, has an elastic modulus after shearing of the artificial urine absorbing gel of 40,000 dynes / cm 2 or more, and has an absorption rate of 10
9. The composition according to any one of claims 1 to 8 , wherein the time is from 90 to 90 seconds. 10. A fibrous substrate, cotton-like pulp, hot-melt-adhesive composite fibers and compositions according to any one of claims 1 to 9 is at least one selected from a mixture thereof. 11. The amount of the composition A composition according to any one of claims 1 to 10 30 to 70% by weight relative to the total weight of the fibrous substrate and the composition.