JP2003088552A - Absorber and absorptive article using it - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an absorber valued from multifaceted viewpoints according to actual using state and hardly causing a problem such as flowback in the actual use. SOLUTION: This absorber comprises a water absorptive resin in which the total sum of deformation repelling forces of gels swollen 10 times, 20 times and 30 times the dead weight with physiological saline is 100 kPa or more, and a hydrophilic fiber. The deformation repelling forces of the gels swollen 10 times, 20 times and 30 times the dead weight with physiological saline of the water absorptive resin are 40, 30 and 20 kPa or more, respectively. The water absorptive resin is preferably subjected to surface crosslinking. In this absorber, the ratio of the water absorptive resin is set to 30 wt.% or more and less than 100 wt.% of the total weight of the absorber. The absorber is retained between a liquid permeable sheet and a liquid impermeable sheet to constitute the absorptive article.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to an absorbent body used for sanitary materials such as disposable diapers, incontinence pads and sanitary napkins, and absorbent articles using the same.

[0002]

2. Description of the Related Art In recent years, water-absorbent resins have been used for various purposes such as sanitary materials such as paper diapers, water retention materials, agricultural and horticultural materials such as soil conditioners, water-stopping materials and dew condensation prevention materials. Useful for. Among these, water absorbent resins are widely used as sanitary materials.

Absorbent articles used for disposable hygienic materials such as disposable diapers and sanitary napkins generally have hydrophilic fibers and an absorbent body made of a water-absorbent resin. In the absorbent article (absorbent body), hydrophilic fibers,
They have different roles from the water absorbent resin.

First, the hydrophilic fiber has a very high water absorption rate and excellent liquid diffusivity, but has a characteristic that the water absorption amount per unit amount is low and the contained water is easily released when a pressure is applied. is doing. Therefore, the hydrophilic fibers have a role of retaining the liquid and diffusing the liquid until the water absorbent resin absorbs the liquid.

On the other hand, the water-absorbent resin has a feature that it absorbs a large amount of water per unit amount and does not easily release water even when a certain amount of pressure is applied. Therefore, the water absorbent resin has a role of absorbing and holding the liquid held and diffused by the hydrophilic fibers.

[0006]

In recent years, hygienic materials such as disposable paper diapers have been taken into consideration in terms of convenience of carrying, wearing comfort when worn, and fashionability (design) when used as an adult. Since the thickness of the water absorbent resin is becoming thinner and the proportion of the water absorbent resin contained in the absorbent body tends to be higher, the performance of the water absorbent resin has a great influence on the water absorbent performance of the diaper.

That is, when a large amount of the water-absorbent resin is present in the absorbent body, the swollen water-absorbent resin is deformed to close the gaps between the particles, and gel blocking which hinders the flow of the liquid through the gaps between the particles is likely to occur. However, this is a cause of deterioration in performance as a disposable diaper.

Therefore, conventionally, various water-absorbing properties such as water-absorbing ability, water-absorbing speed, gel strength, etc. are used as an index of a water-absorbing resin used for producing an absorbent body or absorbent article having excellent water-absorbing performance. Invented However, even if the water-absorbent resin excellent in these properties is used, the absorbent body in a state of being actually worn does not have sufficiently satisfactory water-absorbing performance.

For example, when the amount of the water-absorbent resin used increases as the absorbent body becomes thinner, the swollen gel is deformed and gel blocking easily occurs.
As one of the improvement methods, improvement of gel strength is considered. The gel strength is often evaluated by measuring the strength of the gel under load with some index, but conventionally, when evaluating the properties of the water absorbent resin under load, the water absorbent resin is treated under a single load or at a swelling ratio. Was evaluated by.

However, in the actual wearing condition of the disposable diaper, the swelling ratio of the water absorbent resin inside the absorbent body varies depending on the absorption amount and the degree of diffusion of human urine, and the diaper is worn in a stationary state. The load applied to the water-absorbent resin and its swelling gel varies depending on the posture and movement of the wearer. The difference in posture and movement of the wearer changes the load applied to the diaper to cause gel blocking, and affects the water absorption performance of the diaper such as the permeation rate of human urine, the degree of diffusion, and the reversion. Therefore, even with a water-absorbent resin that has obtained good results in the conventional evaluation method,
When it was actually used in a disposable diaper, problems such as backward movement could occur. That is, the conventional evaluation method evaluates the water-absorbent resin only by looking at a specific surface deviated from the actual usage state. Therefore, there is a demand for a water absorbent resin that evaluates the water absorbent resin from a multifaceted point of view in accordance with the actual use state and does not cause a problem such as a reversion when actually used.

Therefore, the present invention is evaluated from a multifaceted viewpoint according to the actual use condition, and an absorbent body using a water-absorbent resin which hardly causes problems such as leakage and reversion during actual use, and the absorbent body are used. It is an object to provide an absorbent article.

[0012]

Means for Solving the Problems As a result of intensive studies to solve the above problems, the present inventors evaluated the deformation repulsive force of the swelling gel described later, and this value was constant at a plurality of swelling ratios. With respect to the water-absorbent resin satisfying the condition (3), it has been found that the above-mentioned problems can be solved, and the present invention has been completed.

That is, the present invention includes a water-absorbent resin and a hydrophilic fiber in which the total repulsive force of deformation of the gel swollen with physiological saline 10 times, 20 times and 30 times its own weight is 100 kPa or more. An absorber is provided.

The sum of the deformation repulsive force at each swelling ratio of the water absorbent resin used in the present invention is preferably 200 kPa or more.

Furthermore, the deformation resilience of the gel obtained by swelling the water-absorbent resin used in the present invention with physiological saline 10 times, 20 times and 30 times its own weight is 40 and 30, respectively.
And preferably 20 kPa or more.

In the present invention, considering the influence of various loads on the water-absorbent resin and its swelling gel, the evaluation method of the water-absorbent resin is improved to make evaluation from a multifaceted viewpoint closer to the actual use condition. By using the water-absorbent resin specified in the evaluation, the problems such as reversion are solved.

The water-absorbent resin used in the present invention has a total gel deformation repulsion force at a plurality of swelling ratios of a specific value or more, or a deformation repulsion force at a plurality of swelling ratios of a specific value or more. . If the repulsive force of deformation of the gel is measured at a plurality of swelling ratios that are assumed in the actual use state, it becomes possible to evaluate from a multifaceted viewpoint closer to the actual use state. As a result, if a water-absorbent resin whose gel repulsion force measured at a plurality of swelling ratios satisfies a specific condition is used, problems such as reversion are less likely to occur.

In order to surely reduce the amount of reversion and to enjoy the above-mentioned effect more reliably, it is preferable that the saturated water absorption amount of the water absorbent resin with respect to the physiological saline is 30 g / g or more.

The weight average particle diameter of the water absorbent resin used in the present invention is preferably 200 to 600 μm.

The water absorbent resin used in the present invention is preferably surface-crosslinked.

The absorbent body of the present invention is characterized by containing a water-absorbent resin having the above-mentioned characteristics and hydrophilic fibers. In this absorber, the proportion of the water absorbent resin is preferably in the range of 30% by weight or more and less than 100% by weight of the total weight of the absorber. On the other hand, the absorbent article of the present invention is characterized in that the absorbent body described above is held between the liquid permeable sheet and the liquid impermeable sheet.

In such an absorbent article (absorbent body), since the water-absorbent resin having the above-mentioned characteristics is used, in the actual use condition, the amount of reversion is suppressed and the repeated urine under pressure is applied. It is possible to absorb water,
Further, it becomes possible to achieve a thin absorbent article (absorbent body) while avoiding the conventional problems.

[0023]

BEST MODE FOR CARRYING OUT THE INVENTION The absorbent body of the present invention and the absorbent article using the same will be described in detail below. Note that examples of the absorbent article include a paper diaper, an incontinence pad, a sanitary napkin, and the like.
It is not limited to these.

The absorbent article is generally composed of a liquid permeable sheet (top sheet), a liquid impermeable sheet (back sheet), and an absorber held between these sheets. The liquid permeable sheet is arranged on the side that contacts the body, and the liquid impermeable sheet is arranged on the side that does not contact the body.

Examples of the liquid permeable sheet include, but are not limited to, porous synthetic resin films or nonwoven fabrics made of polyethylene, polypropylene, polyester, polyamide.

Examples of the liquid impermeable sheet include, but are not limited to, synthetic resin films made of polyethylene, polypropylene, polyvinyl chloride, etc., and films made of a composite material of these synthetic resins and nonwoven fabric. is not.

The absorbent body of the present invention comprises hydrophilic fibers and a water-absorbent resin. Examples of the structure of the absorbent body include, for example, a mixing structure in which a water absorbent resin and hydrophilic fibers are uniformly blended, a sandwich structure in which a water absorbent resin is held between layered hydrophilic fibers, and a water absorbent resin and hydrophilic fibers. There is a structure in which a tissue is wrapped. The structure of the absorber is not limited to these, but a structure including a mixture of the water absorbent resin and the hydrophilic fiber more uniformly is preferable in order to sufficiently exert the effects of the present invention.

The proportion of the water-absorbent resin in the absorbent body of the present invention is, for example, 30% by weight or more, preferably 40% by weight or more, and more preferably, based on the total weight of the absorbent body, in order to achieve a thin absorbent article. Is 50% by weight or more, more preferably 60% by weight or more and less than 100% by weight. The absorbent body of the present invention may contain a small amount of synthetic fiber as an auxiliary material.

Known hydrophilic fibers include cellulose fibers such as mechanical pulp, chemical pulp, and semi-chemical pulp obtained from wood, polyolefin fibers, polyamide fibers, polyester fibers, and artificial cellulose fibers such as rayon and acetate. However, the present invention is not limited to this.

The water-absorbent resin used in the present invention is one in which the sum of the deformation repulsive forces of the gel swollen with physiological saline 10 times, 20 times and 30 times its own weight is 100 kPa or more. The total deformation repulsive force is preferably 200 kPa or more, more preferably 300 to 800 kPa, and most preferably 400 to 700 kP.
a.

Here, the deformation repulsive force means a state (actual volume) in which the gap between gels is almost eliminated when a load is applied to a fixed amount of water-absorbent resin (swollen gel) that has absorbed water and swelled to a specific magnification. This is the load required for this. Therefore, the deformation repulsive force means that when the value is large, the resistance to the load is large (it is difficult to deform). Therefore, with a water-absorbent resin with a large deformation repulsion force, even if a load is applied when urine is absorbed, gaps are secured between particles, and the extent to which diffusion of urine, etc. is hindered is reduced, resulting in reversion. Is less likely to occur. In addition, the value of the deformation repulsive force in the present invention refers to the value measured by the method described later.

As the water-absorbent resin, the gels swollen with physiological saline 10 times, 20 times and 30 times their own weight have deformation repulsive forces of 40, 30 and 20 kPa or more, preferably 50 respectively. ~ 350, 40 ~ 30
0 and 30 to 200 kPa, more preferably 60 to 300, 50 to 250 and 40 to 150, respectively.
You may use what is kPa.

The saturated water absorption of the water absorbent resin used in the present invention with respect to physiological saline is 30 g / g or more, preferably 30 to 70 g / g, more preferably 40 to 50 g / g.
It is good to say When the saturated water absorption is less than 30 g / g,
It is not economical because it cannot absorb human urine sufficiently and requires the use of a large amount of water absorbent resin.

The weight average particle diameter of the water-absorbent resin used in the present invention is determined in consideration of handleability at the time of making an absorbent body, feeling of use when the water-absorbent resin is adopted in an absorbent article, and the like.
For example, 200 to 600 μm, preferably 300 to 50
The range is 0 μm. If the weight average particle size is less than 200 μm, it becomes difficult to achieve the object of the present invention because not only the handling property of the powder is deteriorated due to powder standing but also gel blocking easily occurs, and the weight average particle size is more than 600 μm. And when the water-absorbent resin is used in an absorbent article, the feeling of use deteriorates.

The water absorbent resin used in the present invention includes:
Acrylate polymer cross-linked product, vinyl alcohol-acrylic acid salt copolymer cross-linked product, maleic anhydride grafted polyvinyl alcohol cross-linked product, cross-linked isobutylene-maleic anhydride copolymer, carboxymethyl cellulose alkali salt cross-linked product, starch- Examples thereof include a hydrolyzate of an acrylonitrile graft copolymer. Preferably,
Acrylate polymer crosslinks are used.

Such a water-absorbent resin is usually obtained by polymerizing or copolymerizing a water-soluble ethylenically unsaturated monomer and crosslinking it. The water-soluble ethylenically unsaturated monomer is not particularly limited and is usually used for polymerization.

Specifically, (meth) acrylic acid, 2-
(Meth) acrylamide-2-methylpropanesulfonic acid and alkali salts thereof, (meth) acrylamide, N, N-dimethylacrylamide, 2-hydroxyethyl (meth) acrylate, N-methylol (meth)
Nonionic monomers such as acrylamide, amino group-containing unsaturated monomers such as diethylaminoethyl (meth) acrylate, diethylaminopropyl (meth) acrylate, diethylaminopropyl (meth) acrylamide, and their quaternized products (Note that in the present specification, “acrylic” and “methacrylic” are combined and expressed as “(meth) acrylic”). Two or more kinds of such water-soluble ethylenically unsaturated monomers may be mixed and used.

Among the water-soluble ethylenically unsaturated monomers exemplified above, acrylic acid, methacrylic acid and alkali salts thereof are preferably used because they are industrially easily available.

The water-soluble ethylenically unsaturated monomer is usually used in the state of an aqueous solution. In such a water-soluble ethylenically unsaturated monomer aqueous solution, it is preferable to set the concentration of the water-soluble ethylenically unsaturated monomer to 25% by weight to a saturated concentration.

The degree of neutralization of the water-absorbent resin used in the present invention is 20 to 1 based on the number of moles of acid groups in the water-absorbent resin.
It is preferably in the range of 00 mol%. More preferably, it is 30 to 90 mol%. The water-absorbent resin may be neutralized with a monomer, or during or after the polymerization.

Examples of salts for neutralizing the water-absorbent resin include alkali metal salts, alkaline earth metal salts, ammonium salts and the like, but alkali metal salts such as sodium and potassium are particularly preferably used.

The method for polymerizing the water-absorbent resin in the present invention is not particularly limited, but includes an aqueous solution polymerization method, a reverse phase suspension polymerization method, a bulk polymerization method, a precipitation polymerization method and the like. Among these, the aqueous solution polymerization method and the reverse phase suspension polymerization method are preferable from the viewpoint of water absorption performance and easy control of polymerization. Hereinafter, the reverse phase suspension polymerization method will be described as an example of the method of polymerizing or copolymerizing the aqueous monomer solution, but the polymerization method is not limited thereto.

In the reverse phase suspension polymerization method, for example, by using a polymerization initiator in the presence of at least one of a surfactant and a dispersion aid, a monomer aqueous solution is dispersed in an organic solvent. Polymerization takes place.

When the water-absorbent resin used in the present invention is obtained by the reverse phase suspension polymerization method, an organic solvent is used when dispersing the aqueous monomer solution. The organic solvent used here is an aliphatic hydrocarbon solvent, an alicyclic hydrocarbon solvent or an aromatic hydrocarbon solvent. Examples of the aliphatic hydrocarbon solvent include n-hexane, n-heptane and ligroin. Examples of the alicyclic hydrocarbon solvent include cyclopentane, methylcyclopentane, cyclohexane and methylcyclohexane. As the aromatic hydrocarbon solvent, benzene,
Examples include toluene and xylene.

Among these organic solvents, n-hexane and n, which have industrially constant quality, are easily available and inexpensive
Preference is given to using heptane, cyclohexane, toluene and xylene. Two or more kinds of these hydrocarbon solvents may be mixed and used.

Examples of the surfactant include nonionic surfactants such as sorbitan fatty acid ester, polyglycerin fatty acid ester, sucrose fatty acid ester, sorbitol fatty acid ester and polyoxyethylene alkylphenyl ether. Two or more kinds of such nonionic surfactants may be mixed and used.

Examples of the dispersion aid include ethyl cellulose, ethyl hydroxyethyl cellulose, oxidation-modified polyethylene, maleic anhydride-modified polyethylene, maleic anhydride-modified polybutadiene, maleic anhydride-modified EP.
DM (Ethylene / Propylene / Diene / Terpolymer)
Are used.

Surfactants and dispersion aids include fatty acid salts,
It can also be used in combination with an anionic surfactant such as an alkylbenzene sulfonate, an alkylmethyl taurate, a polyoxyethylene alkylphenyl ether sulfate, a polyoxyethylene alkyl ether sulfonate.

The amount of the surfactant and / or dispersion aid used is usually 0.1 to 5% by weight, preferably 0.2 to 3% by weight, based on the aqueous monomer solution. If the amount used is less than 0.1% by weight, the dispersion stability will be insufficient. On the contrary, if it exceeds 5% by weight, the economical effect corresponding to it cannot be obtained.

When initiating the polymerization, a polymerization initiator can be used. As the polymerization initiator, it is preferable to use a commonly used water-soluble radical polymerization initiator such as potassium persulfate, ammonium persulfate and sodium persulfate. Such a water-soluble radical polymerization initiator,
It can also be used as a redox type initiator in combination with sulfite or the like.

An oil-soluble radical polymerization initiator can also be used as the polymerization initiator. However, when an oil-soluble radical polymerization initiator is used, the polymer produced is generally water-soluble, and therefore the above-mentioned crosslinking agent must be used in order to obtain a water-absorbent resin. As the oil-soluble radical polymerization initiator, it is preferable to use benzoyl peroxide, azobisisobutyronitrile or the like.

The amount of the polymerization initiator used is usually 0.005 to 1.0 mol% based on the total amount of the monomers. If the amount used is less than 0.005 mol%, the polymerization reaction will take a long time. If the amount used exceeds 1.0 mol%, a rapid polymerization reaction will occur, making it difficult to control the polymerization. .

The polymerization temperature for carrying out the polymerization reaction varies depending on the polymerization initiator used, but is usually 20 to 110 ° C, preferably 40 to 80 ° C. When the polymerization temperature is lower than 20 ° C., the polymerization rate decreases and the polymerization time becomes long, which is not economical. On the contrary, when the temperature is higher than 110 ° C, it becomes difficult to remove the heat of polymerization, and it becomes difficult to carry out a smooth polymerization reaction.

The water-absorbent resin used in the present invention is preferably crosslinked inside by reacting or copolymerizing with a crosslinking agent.

The cross-linking agent which can be used here has two or more polymerizable unsaturated groups or reactive functional groups. Examples of the cross-linking agent having two or more polymerizable unsaturated groups include ethylene glycol, propylene glycol, trimethylolpropane, glycerin polyoxyethylene glycol, polyoxypropylene glycol, polyglycerin, and other polyols such as di- or tri (meth) acryl. Acid esters; the above-mentioned polyols and maleic acid,
Unsaturated polyesters obtained by reacting with unsaturated acids such as fumaric acid; Bisacrylamides such as N, N'-methylenebisacrylamide; Di or tris obtained by reacting polyepoxide with (meth) acrylic acid (Meth) acrylic acid esters; di (meth) acrylic acid carbamyl esters obtained by reacting polyisocyanates such as tolylene diisocyanate and hexamethylene diisocyanate with hydroxyethyl (meth) acrylate; allylated starch, allyl Cellulose,
Examples include diallyl phthalate, N, N ′, N ″ -triallyl isocyanurate, and divinylbenzene.

Among the cross-linking agents having two or more polymerizable unsaturated groups exemplified, ethylene glycol diacrylate, ethylene glycol dimethacrylate, diethylene glycol diacrylate, diethylene glycol dimethacrylate, propylene glycol diacrylate, propylene glycol dimethacrylate, polyethylene glycol. Preference is given to using diacrylate, polyethylene glycol dimethacrylate, diallyl phthalate, N, N'-methylenebisacrylamide.

On the other hand, as the cross-linking agent having two or more reactive functional groups, for example, a diglycidyl ether compound, a haloepoxy compound, an isocyanate compound or the like can be used, and among them, the diglycidyl ether compound is preferable. Specific examples of the diglycidyl ether compound include ethylene glycol diglycidyl ether, polyethylene glycol diglycidyl ether, propylene glycol diglycidyl ether, polypropylene glycol diglycidyl ether, glycerin diglycidyl ether, and polyglycerin diglycidyl ether. Of these, particularly preferred is ethylene glycol diglycidyl ether.

Examples of haloepoxy compounds include epichlorohydrin, epibromhydrin, α-methylepichlorohydrin and the like. Furthermore, examples of the isocyanate compound include 2,4-tolylene diisocyanate and hexamethylene diisocyanate.

The crosslinking agent may have two or more polymerizable unsaturated groups and two or more reactive functional groups at the same time.

The amount of the cross-linking agent that cross-links the inside of the water absorbent resin is usually set to 0.001 to 3% by weight based on the total amount of the monomers. When the amount used is less than 0.001% by weight, the resulting resin becomes water-soluble. On the contrary, if it exceeds 3% by weight, satisfactory water absorption performance cannot be obtained.

Further, in order to obtain a water absorbent resin having physical properties for achieving the object of the present invention, it is more preferable to add a crosslinking agent after polymerization of the water absorbent resin to crosslink the surface of the water absorbent resin. preferable. By surface-crosslinking, the surface strength of the swollen gel is increased, and the deformation of the water absorbent resin due to the external pressure can be prevented. That is, the pressure applied to the outside by the swelling of the water absorbent resin can be kept high.

Here, the surface cross-linking means cross-linking the surface layer of the water-absorbent resin to increase the degree of cross-linking of the surface layer as compared with the inner layer. Therefore, the surface-crosslinked resin has a higher surface layer strength than the surface-uncrosslinked resin,
Even when the liquid is taken into the resin, it is difficult to be deformed, gel blocking is less likely to occur, and the diffusivity at the time of absorbing water becomes good.

As the surface cross-linking agent, one capable of reacting with the carboxyl group in the water absorbent resin is used. For example, (poly) ethylene glycol diglycidyl ether,
Epoxy compounds such as (poly) glycerol polyglycidyl ether, (poly) propylene glycol diglycidyl ether, glycidol; epichlorohydrin,
Halogenated epoxy compounds such as epibromhydrin and α-methylepichlorohydrin; (poly) ethylene glycol, (poly) propylene glycol, 1,3-propanediol, (poly) glycerin, diols, pentanediols, Hexanediols, cyclohexanediols, trimethylolpropane, diethanolamine, triethanolamine, polyoxypropylene,
Polyhydric alcohol compounds such as pentaerythritol and sorbitol; ethylenediamine, diethylenetriamine, triethylenetetramine, tetraethylenepentamine, pentaethylenehexamine, polyethyleneimine,
Polyvalent amine compounds such as polyamide polyamine; 2,4
Polyvalent isocyanate compounds such as tolylene diisocyanate and hexamethylene diisocyanate; polyvalent oxazoline compounds such as 1,2-ethylenebisoxazoline; γ-glycidoxypropyltrimethoxysilane, γ
Silane coupling agents such as aminopropyltrimethoxysilane; hydroxides such as aluminum, magnesium and titanium; and polyvalent metal compounds such as chlorides; however, they are not particularly limited.

Of the above surface cross-linking agents, epoxy compounds and polyhydric alcohol compounds are preferably used. These surface cross-linking agents may be used alone or in combination of two or more.

The amount of the surface cross-linking agent used is 0.01 to 100 parts by weight of the water-absorbent resin, although it depends on the water absorption performance of the water-absorbent resin before surface cross-linking and the type of the surface cross-linking agent used.
It is preferably within the range of 5 parts by weight, more preferably 0.01.
The amount may be in the range of 1 part by weight.

If the amount of the surface cross-linking agent used is less than 0.01 part by weight, the cross-linking density near the surface of the water absorbent resin cannot be sufficiently increased. Further, when the amount of the surface cross-linking agent used is more than 5 parts by weight, the amount of the cross-linking agent becomes excessive, which may leave unreacted cross-linking agent remaining. Difficult to do.

The surface cross-linking agent may be added at any time after completion of the polymerization of the monomers, and is not particularly limited. Since it penetrates to the surface, it is difficult to crosslink the vicinity of the surface with high density. Therefore, it is preferably added all at once in the presence of 1 to 300 parts by weight of water per 100 parts by weight of the water absorbent resin, or more preferably 5 to 200 parts by weight per 100 parts by weight of the water absorbent resin. The first surface cross-linking agent may be added in the presence of water, and after dehydration, the second surface cross-linking agent may be added in the presence of 1 to 130 parts by weight of water with respect to 100 parts by weight of the water absorbent resin. . By doing so, it is assumed that the crosslink density gradually increases from the inside to the outside of the resin particles, and the water absorbent resin having a high deformation repulsive force used in the present invention can be obtained. Alternatively, the surface cross-linking agent dispersed in the stock solution or a small amount of water may be uniformly added to the powdery water-absorbent resin.

[0068]

EXAMPLES Hereinafter, the present invention will be described together with Examples and Comparative Examples. Prior to that, the measurement items and the measuring methods in each Example and each Comparative Example will be described, and each Example and each Comparative Example will be described. The method for producing the water absorbent resin used in the examples will be described.

(1) Saturated water absorption (g / g) : 200 ml of 0.9 wt% saline (physiological saline) was placed in a 300 ml beaker containing a rotor, and a water-absorbent resin was stirred with a magnetic stirrer. 1.0 g was added. After stirring for 1 hour, the amount of swelling resin remaining on the wire net was measured by filtering with a 200 mesh wire net, and the amount of water absorption (g) per 1 g of the water absorbent resin was measured.

Weight average particle size : J
Eight standard sieves corresponding to IS-Z8801-1982 (openings 850 μm, 500 μm, 355 μm, 300 μm,
250 μm, 180 μm, 106 μm, a pan) was placed in a sieve with the largest opening and vibrated for 10 minutes using a low-tap type sieve vibrator. The weight of the water-absorbent resin remaining on each sieve was measured, and based on the result, the weight average particle diameter at which the integrated weight was 50% by weight of the total weight was calculated by the following formula.

[0071]

[Equation 1]

In the formula, A is the weight sequentially accumulated from the coarser particle size distribution, and the accumulated weight is less than 50% by weight, and 5
It is the integrated value (g) when the integrated value of the point closest to 0% by weight was obtained, and B is the opening (μm) of the knot when the integrated value was obtained. Further, D is the integrated value (g) when the integrated weights are sequentially added from the coarser particle size distribution, and the integrated value of the integrated weight of 50% by weight or more and the point closest to 50% by weight is obtained. Yes, and C is a node opening (μm) when the integrated value is obtained.

(2) Deformation repulsion force (Pa) : The deformation repulsion force of the water-absorbent resin is the load per unit area required to deform the actual volume of the swollen gel of the water-absorbent resin in physiological saline to eliminate the gap. It is represented by.

The load required to deform to the actual volume and eliminate the gap means the load applied to the gel when the gel swollen at a predetermined magnification is crushed until the gap is almost eliminated.

A specific method of measuring the deformation repulsion force will be described with reference to the deformation repulsion force measuring device X shown in FIG. The water absorbent resin 1 was classified so that the particle size was less than 32 mesh (pore size: about 500 microns) and 42 mesh (pore size: about 355 microns) or more, and 0.10 g of which was precisely weighed.
The water-absorbent resin was evenly put on the bottom of a cylindrical container 2 having an inner diameter of about 20.5 mm and a height of about 50 mm, which was attached with a nylon sheet 20 of 200 mesh (hole diameter: about 75 μm, thickness: about 0.1 mm) on the bottom surface. .

0.90 g of physiological saline was put in a container 3 having a diameter slightly larger than that of the cylindrical container 2, and the cylindrical container 2 was gently placed thereon to swell the water-absorbent resin 1 to obtain a uniform swollen gel 1. (Swell 10 times). Next, on the pressure-sensitive shaft (load cell) 4 of the precision type Leo robot KA300PV (manufactured by Kyowa Seiko Co., Ltd.), a diameter of about 19.7 mm in the cylinder 2 described above.
The column-shaped shaft 40 is attached to the load cell 4 so that the load cell 4 is adjusted so that the load is not applied.
The load cell 4 is set to descend at a constant speed in min.

A short time after the measurement was started, the swelling gel 1
Since the load of the load cell 4 is required to keep the drop at a constant speed due to the repulsion of, the height (h) of the swollen gel 1 and the load are recorded with time from that time.

Since the actual volume of the water-absorbent resin refers to the volume of the swollen gel 1 in the state where there is no gap in the swollen gel 1 as described above, the actual volume is the bottom area of the cylinder 2 (about 3.3c).
The value obtained by dividing by m ² ) is the height of the swollen gel 1 in actual volume. The height (h) of the respective swollen gels 1 in the actual volume state in the cylinder 2 is 2.90 mm for the 10 times swollen gel and 5.90 m for the 20 times swollen gel.
In the case of m and 30 times swollen gel, it is 8.90 mm, and the load at these heights is the deformation repulsion force at each swelling ratio.

In the same manner as above, 20 times swollen gel (physiological saline 1.90 g) and 30 times swollen gel (physiological saline 2.
The measurement was also carried out at 90 g).

(3) Permeation rate, amount of reversion and diffusion length
(Water absorption performance of the absorbent body) : 10.0 g of water absorbent resin and 100
After dry-mixing 10.0 g of pulverized pulp having a basis weight of g / m ² with a mixer and holding it between two tissues, a load of 196 kPa was applied to the entire sheet surface and pressed for 30 seconds. A liquid permeable sheet was placed on the upper part to make an absorber. The absorber had a size of 40 cm × 12 cm, a weight of 22 g, and a ratio of the water absorbent resin of 50% by weight.

The permeation rate (time) was measured three times.
The first measurement is to inject 50 ml of artificial urine into the center of the absorber using a 3 cm diameter cylinder and start the stopwatch at the same time, and measure the time until the artificial urine completely penetrates the absorber. went. As artificial urine, 60 g of sodium chloride, 1.8 g of calcium chloride dihydrate and 3.6 g of magnesium chloride hexahydrate were placed in a 10 L container, and distilled water was adjusted to 6000 g.
The one colored with No. was used.

In the second measurement, the cylinder was removed after the first measurement, and after 30 minutes, 50 ml of artificial urine was poured again from the same position in the same manner, and the artificial urine was completely absorbed by the stopwatch in the same manner. It was carried out by measuring the time until penetration. The third measurement was also performed by repeating the same operation 30 minutes after the second measurement.

The amount of reversion was measured 60 minutes after the third measurement. Specifically, first, filter paper folded into 10 cm × 10 cm is piled up to make about 80 g, and the weight Wa (g)
Was measured in advance. Then, the folded filter paper is placed in the center of the absorber, and a 5 kg weight (bottom 10
(cm × 10 cm) was put on and a load was applied for 5 minutes. After that,
The weight Wb (g) of the filter paper was measured after removing the weight, and the amount of reversion was obtained by subtracting the weight of the dry filter paper Wa (g) from this weight Wb (g).

The diffusion length was measured by measuring the longitudinal spread (cm) of the artificial urine in the absorbent body after measuring the amount of reversion.

(4) Monitor test : (Preparation of disposable diaper) A disposable diaper is sealed by inserting the absorber prepared as follows between a top sheet (liquid permeable sheet) and a back sheet (liquid impermeable sheet). It was created by doing. The absorbent body was obtained by cutting three pulp sheets (4.1 g) cut into a size of 41 cm × 11 cm between two adjacent pulp sheets to obtain a water absorbent resin (4.5 g).
It was prepared by stacking g) in a uniformly dispersed state, holding it between two tissues, and then pressing it by applying a load of 196 kPa to the entire surface of the pulp sheet.

(Monitor test method) For five infants, 10 or more samples of each of a plurality of types of water-absorbent resins produced by different production methods were distributed, and the samples were distributed overnight (7 to 11 hours). It was collected the next morning after being worn.

(Leak Rate) The leak rate was obtained as a ratio of the leaked sheets out of all the evaluated sheets using the same type of water absorbent resin. The leakage rate was evaluated only for a disposable diaper having a human urine absorption amount of 150 ml or more in order to reduce wearing error.

(Average Absorption Amount) The average absorption amount was obtained by summing the absorption amounts of urine of all the samples using the same type of water absorbent resin and dividing this by the number of samples.

Production Example 1 : 1000 ml equipped with a stirrer, a reflux condenser, a dropping funnel, a thermometer and a nitrogen gas introducing pipe
N-heptane 500m in a 5-necked cylindrical round bottom flask
1 was added. To this, HLB as a surfactant is 3.0
0.92 g of sucrose ester (surfactant: S-370 manufactured by Mitsubishi Chemical Foods Co., Ltd.) was added and dispersed.
After the temperature was raised to 0 ° C. to dissolve the surfactant, it was cooled to 30 ° C.

On the other hand, 75 g of acrylic acid was added to a 500 ml Erlenmeyer flask. While cooling from the outside,
172 g of an 18 wt% sodium hydroxide aqueous solution was added dropwise to neutralize 75 mol% to prepare a partially neutralized acrylic acid aqueous solution. Furthermore, 0.11 g of potassium persulfate as a polymerization initiator and 9.2 mg of ethylene glycol diglycidyl ether as an internal cross-linking agent were added, and this was added to 1
The monomer aqueous solution (a) was used for the step polymerization. Next, 96 g of acrylic acid was added to another 500 ml Erlenmeyer flask, and 184.6 g of a 21.6 wt% sodium hydroxide aqueous solution was added dropwise while cooling as described above to perform neutralization of 75 mol%. 0.14 g of potassium persulfate and 35.7 mg of ethylene glycol diglycidyl ether were added to obtain an aqueous monomer solution (b) for the second stage polymerization.

Next, the total amount of the monomer aqueous solution (a) for the first-stage polymerization was added to and dispersed in a round bottom flask under stirring, the system was sufficiently replaced with nitrogen, and the temperature was raised to 70 ° C. A polymerization reaction was carried out. Then, the polymerization slurry was cooled to 40 ° C., and the monomer aqueous solution (b) for the second stage polymerization was added. After adding all
The inside of the system was sufficiently replaced with nitrogen again, and the temperature was raised to 70 ° C. to carry out the second stage polymerization reaction. After the completion of the second-stage polymerization, 42.2 mg of ethylene glycol diglycidyl ether dissolved in 2 g of water was added as a surface-crosslinking agent for the first time, and about 70% by weight (about 245 g) of water was added from the hydrogel. Azeotropic distillation with heptane to distill only water out of the system. As a second surface cross-linking agent for the dehydrated hydrous gel, 10
211.1 mg of ethylene glycol diglycidyl ether dissolved in g of water was added and heated and dried to obtain 230.1 g of water-absorbent resin (A) (weight average particle diameter of 377 μm). The water-absorbent resin (A) was used in Example 1 and Example 7.
Used in.

Production Example 2 : In Production Example 1, as the first surface crosslinking agent, ethylene glycol diglycidyl ether 84 dissolved in 4 g of water was used instead of 42.2 mg of ethylene glycol diglycidyl ether dissolved in 2 g of water. Manufactured except that ethylene glycol diglycidyl ether 168.9 mg dissolved in 8 g of water was used in place of ethylene glycol diglycidyl ether 211.1 mg dissolved in 10 g of water as the second surface crosslinking agent. The same reaction as in Example 1 was carried out to obtain 229.5 g (weight average particle diameter of 386 μm) of the water absorbent resin (B). The water-absorbent resin (B) was used in Example 2 and Example 8.
Used in.

Production Example 3 : In Production Example 1, 10 g was used as the second surface crosslinking agent without using the first surface crosslinking agent.
The same reaction as in Production Example 1 was carried out except that 253.3 mg of ethylene glycol diglycidyl ether dissolved in 12 g of water was used instead of 211.1 mg of ethylene glycol diglycidyl ether dissolved in water, and a water absorbent resin ( C) 231.7 g (weight average particle diameter 369 μm) was obtained. The water-absorbent resin (C) is used in Examples 3 and 9
Used in.

Production Example 4 : In Production Example 1, N, N'-methylene was used in place of 9.2 mg of ethylene glycol diglycidyl ether as the internal crosslinking agent in the aqueous monomer solution (a) for the first-stage polymerization. Bisacrylamide 18.4m
g as an internal cross-linking agent in the aqueous monomer solution (b) for the second stage polymerization, ethylene glycol diglycidyl ether 3
Instead of 5.7 mg, 23.8 mg of N, N′-methylenebisacrylamide was further reacted in the same manner as in Production Example 1 except that the first surface crosslinking agent was not used, and the water absorbent resin (D) 227 was used. 0.5 g (weight average particle diameter 391 μm) was obtained. The water absorbent resin (D) was used in Examples 4 and 10.

Production Example 5 : In Production Example 1, as the second surface cross-linking agent, 61.1 was used instead of 211.1 mg of ethylene glycol diglycidyl ether dissolved in 10 g of water.
The same reaction as in Production Example 1 was performed except that 126.7 mg of ethylene glycol diglycidyl ether dissolved in g of water was added to obtain 231.5 g of a water absorbent resin (E) (weight average particle diameter of 390 μm). This water absorbent resin (E) is
Used in Example 5 and Example 11.

Production Example 6 : In Production Example 1, the amount of the internal cross-linking agent in the aqueous monomer solution (b) for the second stage polymerization was changed to 35.7 mg of ethylene glycol diglycidyl ether, and the first surface cross-linking was performed. As a second surface cross-linking agent without using any agent, instead of 211.1 mg of ethylene glycol diglycidyl ether dissolved in 10 g of water, ethylene glycol diglycidyl ether 16 dissolved in 8 g of water was used.
The same reaction as in Production Example 1 was performed except that 8.9 mg was used, and 225.7 g of the water absorbent resin (F) (weight average particle diameter 3
96 μm) was obtained. This water absorbent resin (F) was used in Example 6
And used in Example 12.

Production Example 7 : In Production Example 1, the amount of the internal cross-linking agent in the monomer aqueous solution (a) for the first stage polymerization was changed to 18.4 mg of ethylene glycol diglycidyl ether, and the second stage polymerization was conducted. Ethylene glycol diglycidyl ether 3 as an internal crosslinking agent in the aqueous monomer solution (b)
Instead of 5.7 mg, 35.7 mg of N, N′-methylenebisacrylamide was used without using the first surface cross-linking agent.
Production Example 1 except that 210.6 mg of ethylene glycol diglycidyl ether dissolved in 10 g of water was used as the second surface-crosslinking agent, and 10.6 mg of ethylene glycol diglycidyl ether dissolved in 0.5 g of water was used. Water-absorbent resin (G) 229.5 g
(Weight average particle diameter of 370 μm) was obtained. This water absorbent resin (G) was used in Comparative Examples 1 and 3.

Production Example 8 : In Production Example 1, the amount of the internal cross-linking agent in the aqueous monomer solution (a) for the first stage polymerization was changed to 27.6 mg of ethylene glycol diglycidyl ether for the second stage polymerization. As an internal cross-linking agent in the monomer aqueous solution (b), N, N′-in place of 211.1 mg of ethylene glycol diglycidyl ether dissolved in 10 g of water.
Methylenebisacrylamide 35.7 mg, the first time,
The same reaction as in Production Example 1 was carried out except that the surface cross-linking agent was not used in the second time to obtain 231.1 g of the water absorbent resin (H) (weight average particle diameter of 395 μm). This water absorbent resin (H) was used in Comparative Examples 2 and 4.

[Examples 1 to 6 and Comparative Examples 1 and 2] In these Examples and Comparative Examples, the water-absorbing resins (A) to (H) obtained in Production Examples 1 to 8 were subjected to the above-mentioned methods. The amount of water absorption and the repulsive force of deformation were measured by means of to determine the permeation rate, the amount of reversion and the diffusion length of the absorbent body using those water absorbent resins. The results are shown in Table 1.

[0100]

[Table 1]

From the results in Table 1, 10 times, 20 times and 3 times
Absorber using water absorbent resins (A) to (F) having a relatively large sum of deformation repulsive forces of the water absorbent resin swollen by 0 times or relatively large deformation repulsive forces at each swelling rate (Example 1) ~ 6)
Is a water-absorbent resin ((G) to (H)) whose total sum is relatively small or whose deformation repulsion force at each swelling ratio is relatively small.
As a result, the permeation rate was faster, the amount of reversion was smaller, and the diffusion length was longer than those of the absorbers (Comparative Examples 1 and 2) using the above.

Therefore, when a water absorbent resin having a high deformation repulsive force of the swollen gel is used in a paper diaper, it is presumed that human urine is quickly permeated and diffused into a wider range, resulting in a smaller amount of reversion. .

[Examples 7 to 12 and Comparative Examples 3 to 4] The paper diapers using the water-absorbent resins (A) to (H) obtained in Production Examples 1 to 8 leaked by a monitor test according to the method described above. The rate and the average absorption amount were measured. The results are shown in Table 2.

[0104]

[Table 2]

From the results of Table 2, the diapers using the water-absorbent resins (A) to (F) having a relatively large sum of deformation repulsion force or deformation repulsion force at each swelling ratio (Examples 7 to 12).
Is a paper diaper using the water-absorbent resins (G) to (H) having a relatively small total amount of deformation repulsion force or relatively small deformation repulsion force at each swelling ratio (comparative example). Three
~ 4) leaked to the outside.

As is clear from the comparison of the results in Tables 1 and 2, the sum of the deformation repulsion force at each swelling ratio is relatively large, or the deformation repulsion force at each swelling ratio is large. Even when the paper diaper prepared by using the resins (A) to (F) was actually used, a problem such as leakage (reversion) did not occur. On the other hand, the sum total of the deformation repulsion force at each swelling ratio is relatively small, or the deformation repulsion force at each swelling ratio is small respectively.
If you actually use a paper diaper made using (H),
Problems such as leakage (return) occurred.

Therefore, in the method of measuring the deformation repulsion force by a plurality of swelling factors and judging whether or not it satisfies a certain condition, the result at the laboratory level and the result at the actual use state are Therefore, if the evaluation method adopted in the present invention is adopted, it is possible to provide an absorbent body and an absorbent article that are less likely to cause a problem in actual use.

[0108]

As described above, according to the present invention, an absorber that is evaluated from a multifaceted viewpoint according to the actual use state and is less likely to cause a problem such as reversion during actual use, and an absorber using the same. Sex goods are provided.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram of an apparatus for measuring a deformation repulsive force of a swollen gel.

[Explanation of symbols]

X deformation repulsive force measuring device 1 Water-absorbent resin (swelling gel) 2 cylinder 20 nylon sheet 3 containers 4 load cell 40 axes

Continuation of front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) // A61F 5/44 A61F 13/18 307F C08L 101: 00 (72) Inventor Masato Fujikake Irifune-cho, Shikima-ku, Himeji-shi, Hyogo No. 1 Sumitomo Seika Chemicals Co., Ltd. Functional Resin Research Laboratory F-term (reference) 3B029 BA17 4C003 AA27 4C098 AA09 CC03 DD06 DD24 DD26 DD28 4F070 AA03 AA26 AA29 AB03 AB08 AB13 AC87 AC89 AE08 BA02 GA06 GC01 4F072 AA08 AB03 AB01 AD08 AD05 AB06 AB06 AB09 AD53 AG04 AH05 AL01

Claims (8)

[Claims] 1. A total sum of deformation repulsive forces of a gel swollen with physiological saline 10 times, 20 times and 30 times its own weight is 100.
An absorber containing a water absorbent resin having a kPa or more and hydrophilic fibers. 2. The absorbent body according to claim 1, wherein the sum of deformation repulsive forces of the gel of the water-absorbent resin is 200 kPa or more. 3. The physiological saline of the water-absorbent resin has a weight of 1
The absorbent body according to claim 1 or 2, wherein the gels that have been swollen 0 times, 20 times, and 30 times have deformation repulsive forces of 40, 30 and 20 kPa or more, respectively. 4. The absorbent body according to claim 1, wherein the saturated water absorption of the water-absorbent resin with respect to physiological saline is 30 g / g or more. 5. The weight average particle diameter of the water absorbent resin is 2
The absorber according to any one of claims 1 to 4, which has a size of 00 to 600 µm. 6. The water-absorbent resin is surface-crosslinked.
The absorber according to any one of claims 1 to 5. 7. The absorbent body according to claim 1, wherein a proportion of the water absorbent resin is 30% by weight or more and less than 100% by weight based on a total weight of the absorbent body. 8. An absorbent article, wherein the absorbent body according to any one of claims 1 to 7 is held between a liquid permeable sheet and a liquid impermeable sheet.