Clay dispersion, composition for preparing a superabsorbent polymer containing the same, and method for preparing a superabsorbent polymer using the same in an absorbent article.

Abstract

The present invention provides a clay dispersion having excellent dispersion stability, a composition for preparing a superabsorbent polymer containing the dispersion and incorporated into an absorbent article, and a method for preparing a superabsorbent polymer using the clay dispersion and incorporated into an absorbent article. The clay dispersion of the present invention exhibits a low settling rate of clay and excellent dispersion stability even during long-term storage, and in particular, it exhibits excellent dispersion stability over long periods even in compositions for preparing superabsorbent polymers containing alkali metal salts or basic materials.

Description

Technical Field

[0001] The present invention relates to a clay dispersion liquid having excellent dispersion stability for use in the production of superabsorbent polymers incorporated into absorbent articles, a composition for preparing a superabsorbent polymer for use in absorbent articles containing the clay dispersion liquid, and a method for preparing a superabsorbent polymer using the clay dispersion liquid, wherein the superabsorbent polymer is incorporated into the absorbent article.

Background Art

[0002] A superabsorbent polymer (SAP) is a synthetic polymer material that can absorb 500 to 1000 times its own weight of water. Since the superabsorbent polymer began to be put into practical use in absorbent articles, it is now widely used not only in sanitary products such as disposable diapers for children and menstrual materials for menstrual napkins, but also in horticultural water-retaining soil products, water-stopping materials for civil engineering and construction, seedling-raising sheets, freshness-keeping agents in the food distribution field, and wet compress materials.

[0003] For superabsorbent polymers, water-soluble ethylenically unsaturated monomers are used, and one or more monomers selected from the group consisting of anionic monomers and their salts, nonionic hydrophilic monomers, amino group-containing unsaturated monomers, and quaternized products thereof can be used. The water-soluble ethylenically unsaturated monomer may be neutralized with an alkali metal salt such as sodium salt or a basic compound such as caustic soda, and then polymerized by containing a crosslinking agent and a polymerization initiator. This solution is called a neutralization solution or composition for preparing a superabsorbent polymer. Thermal polymerization or photopolymerization is carried out on this neutralization solution to prepare a water-containing gel polymer, which is then dried, pulverized, and classified to prepare a powdery superabsorbent polymer.

[0004] Studies have been conducted to improve the basic physical properties of superabsorbent polymers, such as centrifuge retention capacity (CRC) and absorption under pressure (AUP), by introducing clay as an additive. However, when clay is introduced into compositions for preparing superabsorbent polymers, there is a problem in ensuring dispersion stability because the clay particles tend to aggregate due to the high ion concentration of alkali metal salts or basic compounds added for neutralization. As a result, the aggregated clay is unevenly distributed in the polymer in the form of particles, and consequently, the effect of improving the physical properties of the polymer may not be obtained.

[0005] Therefore, there is a need to develop a clay dispersion that exhibits excellent dispersibility in compositions for preparing superabsorbent polymers and can improve the physical properties of the superabsorbent polymers. [Overview of the Initiative] [Problems that the invention aims to solve]

[0006] A clay dispersion is provided for application in the production of superabsorbent polymers incorporated into absorbent articles, which exhibits excellent dispersion stability.

[0007] Furthermore, a composition for preparing a superabsorbent polymer for use in absorbent articles is also provided, which comprises a clay dispersion.

[0008] The present invention also provides a method for preparing a superabsorbent polymer using a clay dispersion, wherein the superabsorbent polymer is subsequently incorporated into an absorbent article. [Means for solving the problem]

[0009] According to one embodiment of the present invention, a clay dispersion for application to the production of a superabsorbent polymer is provided, wherein the superabsorbent polymer is subsequently incorporated into an absorbent article, and the clay dispersion comprises a solvent, clay, and a polymer dispersant having two or more functional groups selected from the group consisting of amine groups, carbonyl groups, and hydroxyl groups, wherein the polymer dispersant is present in an amount of more than 20 parts by weight and up to 200 parts by weight per 100 parts by weight of clay.

[0010] According to another embodiment of the present invention, a composition is provided for preparing a superabsorbent polymer for use in absorbent articles, the composition comprising a clay dispersion, a water-soluble ethylenically unsaturated monomer, an alkali metal salt or alkali compound capable of neutralizing the water-soluble ethylenically unsaturated monomer, and a polymerization initiator.

[0011] Absorbent articles containing superabsorbent polymers, manufactured by using a clay dispersion and / or a composition, may be diapers or pants.

[0012] The superabsorbent polymer may be incorporated into an absorbent core, which is contained within an absorbent article.

[0013] The absorbent core can be manufactured by providing two nonwoven webs and incorporating a surface-crosslinked granular water-absorbent resin between the two nonwoven webs.

[0014] The absorbent core between the two nonwoven webs may contain less than 20% by weight of cellulose fibers, preferably less than 10% by weight of cellulose fibers, and more preferably less than 5% by weight of cellulose fibers.

[0015] Within the absorbent core, a superabsorbent polymer can be bonded and fixed between two nonwoven webs.

[0016] The absorbent article may include a top sheet, a back sheet, and an absorbent core between the top sheet and the back sheet.

[0017] A method for preparing a superabsorbent polymer is provided, comprising the steps of: preparing a water-containing gel polymer by heating and / or light-irradiating a composition for preparing a superabsorbent polymer to perform a polymerization reaction; preparing a base polymer by drying and pulverizing the water-containing gel polymer; and forming a surface-crosslinked layer by further crosslinking the surface of the base polymer in the presence of a surface crosslinking agent, wherein the method further comprises the step of incorporating the obtained superabsorbent polymer into a water-absorbing article. [Effects of the Invention]

[0018] The clay dispersion of the present invention exhibits a low settling velocity of clay particles and excellent dispersion stability even during long-term storage. In particular, it shows excellent dispersion stability over long periods even in compositions for preparing superabsorbent polymers containing alkali metal salts or basic materials. Therefore, the clay dispersion can be usefully used as an additive to improve the physical properties of superabsorbent polymers, such as centrifugal retention and pressurized absorption. In addition, there is no concern about discoloration of superabsorbent polymers prepared using the clay dispersion. [Brief explanation of the drawing]

[0019] [Figure 1] These are photographs taken 48 hours after the composition was prepared, showing the compositions for preparing the superabsorbent polymers of Examples 1-1 to 1-3, Comparative Examples 1-3 and 1-4. [Modes for carrying out the invention]

[0020] The language and terms used in this specification are for illustrative embodiments only and are not intended to limit the present invention. Singular expressions may include plural expressions unless the context clearly has a different meaning. In this specification, terms such as "comprising," "including," or "having" are used to specify the presence of features, steps, components, or combinations thereof that exert effects, and it should not be understood as excluding the presence or possibility of addition of one or more different features, steps, components, or combinations thereof.

[0021] The present invention can be variously modified and have various forms, but specific exemplary embodiments are illustrated and will be described in detail in the following description. However, this is not intended to limit the present invention to specific exemplary embodiments, and it should be understood that the present invention includes all modifications, equivalents, or alternatives included in the spirit and technical scope of the present invention.

[0022] As used in this specification, "clay" refers to particles of phyllosilicate minerals or aggregates of a plurality of such particles, and "clay dispersion" refers to a dispersion in which clay is dispersed in a solvent.

[0023] As used in this specification, (meth)acrylate is used in the sense of including both acrylate and methacrylate.

[0024] As used in this specification, "base polymer" or "base polymer powder" is in the form of particles or powder prepared by drying or pulverizing a polymer obtained by polymerizing a water-soluble ethylenically unsaturated monomer, and refers to a polymer that is not surface-modified or surface-crosslinked.

[0025] Hereinafter, the present invention will be described in detail.

[0026] The clay dispersion contains a solvent, clay, and a polymer dispersant containing two or more functional groups selected from the group consisting of an amine group, a carbonyl group, and a hydroxyl group, and the polymer dispersant is contained in an amount exceeding 20 parts by weight and up to 70 parts by weight based on 100 parts by weight of the clay.

[0027] Due to the polymer dispersant containing two or more functional groups selected from the group consisting of an amine group, a carbonyl group, and a hydroxyl group, the clay dispersion can significantly improve the dispersion stability of the clay. The clay has a layered structure in which small plates of silicate with a thickness of about 1 nm are stacked on top of each other due to strong van der Waals forces. The polymer dispersant binds to the surface of the clay and exfoliates the silicate layers (i.e., expands the silicate layers so that the interlayer distance exceeds 1 nm). Chemically exfoliated clay exhibits significantly improved dispersion stability. As a result, even when the clay dispersion is included in a composition for preparing a superabsorbent polymer containing an alkali metal salt or a basic compound, the clay particles can be uniformly dispersed in the composition without aggregating or sedimenting.

[0028] Therefore, the superabsorbent polymer prepared using the clay dispersion can further have improved absorption properties such as centrifugal retention capacity and pressure absorbency. In addition, the clay dispersion does not cause discoloration of the superabsorbent polymer, so it can be suitably used for manufacturing high-quality products.

[0029] As the clay, swelling or non-swelling clay can be used. The swelling clay is a layered organic material having water absorption properties, and montmorillonite, saponite, nontronite, laponite, beidellite, hectorite, vermiculite, magadite, bentonite, etc. can be used. As the non-swelling clay, kaolin, serpentine, mica, etc. can be used. These clays can be used alone or as a mixture of two or more of them.

[0030] Clay having an average particle size of 0.025 μm or less, or 0.05 μm or less, or 0.1 μm or less, or 1 μm, and 10 μm or less, or 8 μm or less, or 5 μm or less may be used. If the average particle size of the clay is less than 0.025 μm, the effect of improving the gel strength of the superabsorbent polymer may not be sufficiently obtained. If the average particle size of the clay is greater than 10 μm, due to the strong interlayer attraction of the clay, it may be difficult to achieve uniform dispersion in the aqueous system, and it may be difficult to uniformly modify the surface of the clay, and therefore, transparency may not be ensured after dispersion. The average particle size of the clay can be measured by laser diffraction and dynamic light scattering methods using a particle size analyzer.

[0031] The polymer dispersant contains two or more functional groups selected from the group consisting of amine groups, carbonyl groups, and hydroxyl groups, and is used in an amount ranging from more than 20 parts by weight to 200 parts by weight per 100 parts by weight of clay.

[0032] As used herein, "two or more functional groups selected from the group consisting of amine groups, carbonyl groups, and hydroxyl groups" means a combination of two or more functional groups of amine groups, carbonyl groups, and hydroxyl groups, such as an amide group containing both an amine group and a carbonyl group, or a carboxyl group containing both a carbonyl group and a hydroxyl group. For example, a "polymer dispersant containing an amine group and a carbonyl group" may contain an amine group and a carbonyl group respectively in its molecule, or it may contain an amide group in combination with an amine group and a carbonyl group.

[0033] Polymer dispersants containing functional groups can bond to the surface of clay due to the non-bonding electrons of nitrogen and oxygen atoms, and charges can be induced in the polymer due to resonance phenomena in compositions for preparing superabsorbent polymers with high ionic concentrations. Due to these properties, polymer dispersants can improve the dispersibility of clay by exfoliating their layered structure. Furthermore, polymer dispersants do not cause discoloration of superabsorbent polymers or degrade their physical properties, and therefore can be suitably used in the preparation of superabsorbent polymers.

[0034] From this viewpoint, the polymer dispersant may preferably contain an amine group and a carbonyl group, or a carbonyl group and a hydroxyl group. More preferably, the polymer dispersant may contain an amide group and / or a carboxyl group.

[0035] Specific examples of polymer dispersants include one or more selected from the group consisting of polyvinylpyrrolidone, polyacrylamide, and polyacrylic acid. Preferably, polyvinylpyrrolidone can be used as the polymer dispersant.

[0036] The molecular weight of the polymer dispersant is not particularly limited. However, for example, polymer dispersants having a weight-average molecular weight of 2,500 g / mol or more, or 5,000 g / mol or more, or 10,000 g / mol or more, and 200,000 g / mol or less, or 100,000 g / mol or less, or 40,000 g / mol may be used. If the weight-average molecular weight of the polymer dispersant is less than 2,500 g / mol, it may be difficult to ensure sufficient distance between the silicate layers of the clay when bonding the polymer dispersant to the clay surface, which may cause problems in ensuring dispersibility and long-term stability. If the weight-average molecular weight is greater than 200,000 g / mol, there are process difficulties and it is not effective in surface modification of the clay; therefore, it is preferable to satisfy the above range.

[0037] To ensure the dispersibility of the clay, the polymer dispersant is used in an amount ranging from more than 20 parts by weight to 200 parts by weight per 100 parts by weight of clay, preferably 23 parts by weight or more, or 25 parts by weight or more and 150 parts by weight or less, or 100 parts by weight or less.

[0038] If the polymer dispersant content is 20 parts by weight or less per 100 parts by weight of clay, the degree of surface modification of the clay may be insufficient, and therefore the interlayer spacing of the clay may not widen sufficiently. Consequently, the dispersion stability of the clay may be insufficient, and therefore the clay particles may be prone to aggregation. In addition, if the polymer dispersant content is excessively high, exceeding 200 parts by weight per 100 parts by weight of clay, the polymer dispersant reduces the effect of improving the physical properties that can be provided by the clay and causes a decrease in the physical properties of the superabsorbent polymer.

[0039] The type of solvent used in the clay dispersion is not particularly limited, and any solvent can be used without restriction as long as it is used in the composition for preparing the superabsorbent polymer. For example, one or more solvents selected from the group consisting of water, ethanol, ethylene glycol, diethylene glycol, triethylene glycol, 1,4-butanediol, propylene glycol, ethylene glycol monobutyl ether, propylene glycol monomethyl ether, propylene glycol monomethyl ether acetate, methyl ethyl ketone, acetone, methyl amyl ketone, cyclohexanone, cyclopentanone, diethylene glycol monomethyl ether, diethylene glycol ethyl ether, toluene, xylene, butyrolactone, carbitol, methyl cellosolve acetate, and N,N-dimethylacetamide can be used as solvents.

[0040] The amount of solvent used in the preparation of the clay dispersion is not limited and can be appropriately adjusted considering the type and amount of clay and polymer dispersant, as well as the intended use of the clay dispersion.

[0041] The clay content in the clay dispersion may be 1% by weight or more, or 3% by weight or more and 20% by weight or less, or 10% by weight or less, or 8% by weight or less. When the clay content is met, the clay particles can maintain excellent dispersibility without agglomerating or settling together, even during long-term storage.

[0042] On the other hand, a composition for preparing a superabsorbent polymer is provided, the composition comprising a clay dispersion, a water-soluble ethylenically unsaturated monomer, an alkali metal salt or alkali compound capable of neutralizing the water-soluble ethylenically unsaturated monomer, and a polymerization initiator.

[0043] The description of the clay dispersion is the same as above.

[0044] The clay dispersion may be used such that the clay content is 0.1 parts by weight or more, or 0.2 parts by weight or more, or 0.25 parts by weight or more and 1 part by weight or less, or 0.7 parts by weight or less, or 0.5 parts by weight or less, based on 100 parts by weight of water-soluble ethylenically unsaturated monomer contained in the composition for preparing the superabsorbent polymer. In other words, the clay content in the composition for preparing the superabsorbent polymer may be 0.1 parts by weight or more, or 0.2 parts by weight or more, or 0.25 parts by weight or more and 1 part by weight or less, or 0.7 parts by weight or less, or 0.5 parts by weight or less, based on 100 parts by weight of ethylenically unsaturated monomer.

[0045] As the water-soluble ethylenically unsaturated monomer, there are no particular limitations, but any monomer can be used as long as it is commonly used to prepare superabsorbent polymers. Preferably, one or more of any monomers selected from the group consisting of anionic monomers and their salts, nonionic hydrophilic monomers, and amino group-containing unsaturated monomers and quaternary compounds thereof can be used. Specific examples of water-soluble ethylenically unsaturated monomers include anionic monomers such as acrylic acid, methacrylic acid, maleic anhydride, fumaric acid, crotonic acid, itaconic acid, 2-acryloylethanesulfonic acid, 2-methacryloylethanesulfonic acid, 2-(meth)acryloylpropanesulfonic acid, or 2-(meth)acrylamido-2-methylpropanesulfonic acid, and their salts; nonionic hydrophilic monomers such as (meth)acrylamide, N-substituted (meth)acrylate, 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, methoxypolyethylene glycol (meth)acrylate, or polyethylene glycol (meth)acrylate; and amino group-containing unsaturated monomers such as (N,N)-dimethylaminoethyl (meth)acrylate or (N,N)-dimethylaminopropyl (meth)acrylamide; and one or more selected from the group consisting of these quaternary compounds.

[0046] The concentration of the water-soluble ethylenically unsaturated monomer may be about 20 to 60 parts by weight, preferably 40 to 60 parts by weight, per 100 parts by weight of the composition for preparing the superabsorbent polymer, and may be an appropriate concentration considering the polymerization time and reaction conditions. If the monomer concentration is too low, the yield of the superabsorbent polymer may be low, which may cause problems with economic feasibility. If the concentration is too high, some of it may precipitate, or process problems may occur, such as low grinding efficiency during the grinding of the polymerized water-containing gel polymer, and the physical properties of the superabsorbent polymer may be reduced.

[0047] In addition, the degree of neutralization of the water-soluble ethylenically unsaturated monomer is 50% to 95%, preferably 70% to 85%. If the degree of neutralization of the monomer is low, the water absorption of the superabsorbent polymer prepared may decrease, and if the degree of neutralization is high, the monomer may precipitate, making it difficult to prepare the superabsorbent polymer.

[0048] As alkali metal salts or alkali compounds that can neutralize water-soluble ethylenically unsaturated monomers, alkali metal salts such as sodium acrylate or alkali compounds such as caustic soda (NaOH) can be used.

[0049] As a polymerization initiator, depending on the polymerization method, a photopolymerization initiator may be used for photopolymerization, and a thermal polymerization initiator may be used for thermal polymerization.

[0050] However, even with photopolymerization, a certain amount of heat may be generated due to UV irradiation, and heat may also be generated by the polymerization reaction, which is an exothermic reaction. Therefore, a thermal polymerization initiator may be used in addition.

[0051] The thermal polymerization initiator is not particularly limited, but one or more selected from the group consisting of persulfate initiators, azo initiators, hydrogen peroxide, and ascorbic acid can preferably be used. Specifically, examples of persulfate initiators include sodium persulfate (Na2S2O8), potassium persulfate (K2S2O8), and ammonium persulfate ((NH4)2S2O8). Examples of azo initiators include 2,2-azobis(2-amidinopropane) dihydrochloride, 2,2-azobis-(N,N-dimethylene)isobutylamidine dihydrochloride, 2-(carbamoylazo)isobutyronitrile, 2,2-azobis[2-(2-imidazolin-2-yl)propane] dihydrochloride, and 4,4-azobis-(4-cyanovaleric acid).

[0052] The photopolymerization initiator is not particularly limited, but one or more selected from the group consisting of benzoin ether, dialkylacetophenone, hydroxylalkyl ketone, phenylglyoxylate, benzyldimethyl ketal, acylphosphine, and α-aminoketone may be preferably used. On the other hand, a specific example of acylphosphine is diphenyl(2,4,6-trimethylbenzoyl)phosphine oxide.

[0053] On the other hand, the neutralization solution may further contain a crosslinking agent. As the crosslinking agent, a crosslinking agent having one or more ethylenically unsaturated groups and one or more functional groups that can react with water-soluble substituents of a water-soluble ethylenically unsaturated monomer, or a crosslinking agent having two or more functional groups that can react with water-soluble substituents of the monomer and / or water-soluble substituents formed by hydrolysis of the monomer may be used.

[0054] Specific examples of crosslinking agents include one or more selected from the group consisting of N,N'-methylenebisacrylamide, trimethylolpropane tri(meth)acrylate, ethylene glycol di(meth)acrylate, (meth)acrylate, propylene glycol di(meth)acrylate, polyethylene glycol di(meth)acrylate, polypropylene glycol (meth)acrylate, butanediol di(meth)acrylate, butylene glycol di(meth)acrylate, diethylene glycol di(meth)acrylate, hexanediol di(meth)acrylate, triethylene glycol di(meth)acrylate, tripropylene glycol di(meth)acrylate, tetraethylene glycol di(meth)acrylate, dipentaerythritol pentaacrylate, glycerin tri(meth)acrylate, pentaerythritol tetraacrylate, triallylamine, ethylene glycol diglycidyl ether, propylene glycol, glycerin, and ethylene carbonate.

[0055] The crosslinking agent is included in an amount of 0.01 parts by weight or more, 0.05 parts by weight or more, 0.1 parts by weight or more, or 0.3 parts by weight or more and 2 parts by weight or less, 1.5 parts by weight or less, or 1 part by weight or less per 100 parts by weight of water-soluble ethylenically unsaturated monomer, thereby crosslinking the polymerized polymer.

[0056] The composition for preparing the superabsorbent polymer may further contain additives such as foaming agents, thickeners, plasticizers, preservatives, and antioxidants, as needed.

[0057] For example, a composition for preparing a superabsorbent polymer may contain, as a foaming agent, one or more foaming agents selected from the group consisting of sodium bicarbonate, sodium carbonate, potassium bicarbonate, potassium carbonate, calcium bicarbonate, calcium carbonate, magnesium bicarbonate, and magnesium carbonate.

[0058] The blowing agent may be added in an amount of 0.01 parts by weight or more, or 0.05 parts by weight or more, or 0.08 parts by weight or more, and 0.5 parts by weight or less, 0.3 parts by weight or less, or 0.2 parts by weight or less, per 100 parts by weight of monomer.

[0059] The composition for preparing the superabsorbent polymer may include a solvent. The applicable solvent can be used without limitation on its composition, as long as it can dissolve the components described above. For example, a solvent used to prepare a clay dispersion can be used as a solvent in the composition for preparing the superabsorbent polymer.

[0060] Alternatively, a composition for preparing a superabsorbent polymer may be prepared in one step by mixing clay, a polymer dispersant, a water-soluble ethylenically unsaturated monomer, an alkali metal salt or alkali compound capable of neutralizing the water-soluble ethylenically unsaturated monomer, and a polymerization initiator in the presence of a solvent. Even in this case, the polymer dispersant can be used to improve the dispersion stability of the clay.

[0061] The composition for preparing the superabsorbent polymer maintains excellent dispersion stability in the composition by including a clay dispersion, without causing aggregation or precipitation among the clay particles.

[0062] Specifically, the settling velocity of the clay in the composition for preparing the superabsorbent polymer may be 100 μm / s or less, preferably 50 μm / s or less, or 30 μm / s or less, or 10 μm / s or less, and 1 μm / s or more, or 5 μm / s or more. The method for measuring the settling velocity will be explained in detail in the following experimental example.

[0063] The composition for preparing a superabsorbent polymer contains clay, which maintains excellent dispersion stability due to a polymer dispersant containing two or more functional groups selected from the group consisting of amine groups, carbonyl groups, and hydroxyl groups. Therefore, the composition can be suitably used to prepare a superabsorbent polymer that is free from discoloration concerns and has excellent absorption performance.

[0064] Therefore, a method for preparing a superabsorbent polymer is provided, which uses a composition for preparing a superabsorbent polymer.

[0065] Specifically, a method for preparing a superabsorbent polymer includes the steps of: preparing a water-containing gel polymer by heating and / or irradiating a composition for preparing a superabsorbent polymer with light to perform a polymerization reaction; preparing a base polymer by drying and pulverizing the water-containing gel polymer; and forming a surface-crosslinked layer by further crosslinking the surface of the base polymer in the presence of a surface crosslinking agent.

[0066] This method further includes the step of incorporating the obtained superabsorbent polymer (for example, in granular form) into an absorbent article.

[0067] Polymerization methods are broadly classified into thermal polymerization and photopolymerization, depending on the polymerization energy source. Thermal polymerization can usually be carried out in a reactor such as a kneader equipped with a stirring shaft. Photopolymerization can be carried out in a reactor equipped with a movable conveyor belt. The polymerization methods described above are merely examples, and the present invention is not limited to the polymerization methods described above.

[0068] For example, a water-containing gel polymer obtained by thermal polymerization while supplying hot air to the aforementioned reactor, such as a kneader equipped with a stirring shaft, or while heating the reactor, may have a size of several centimeters or several millimeters when discharged from the outlet of the reactor, depending on the type of stirring shaft provided in the reactor. Specifically, the size of the obtained water-containing gel polymer may vary depending on the concentration and supply rate of the monomer composition supplied to it, and a water-containing gel polymer having a weight-average particle size of about 2 mm to about 50 mm can generally be obtained.

[0069] Furthermore, as described above, when photopolymerization is carried out in a reactor equipped with a movable conveyor belt, the resulting water-containing gel polymer is usually a sheet-like water-containing gel polymer having the width of the belt. In this case, the thickness of the polymer sheet may vary depending on the concentration and supply rate of the monomer composition supplied to it. It is generally preferable to supply the monomer composition in such a way that a sheet-like polymer having a thickness of about 0.5 cm to about 5 cm can be obtained. Supplying the monomer composition to such an extent that the sheet-like polymer becomes too thin is undesirable because it reduces the production efficiency, and if the thickness of the sheet-like polymer exceeds 5 cm, the polymerization reaction may not occur uniformly across the entire thickness due to the excessive thickness.

[0070] The water-containing gel polymer obtained by the method described above may have a water content of approximately 40% to approximately 80% by weight. On the other hand, as used herein, "water content" means the weight of water relative to the total weight of the water-containing gel polymer, and may be a value obtained by subtracting the weight of the dry polymer from the weight of the water-containing gel polymer. Specifically, the water content may be defined as a value calculated by measuring the weight loss due to the evaporation of water in the polymer during the drying process, which involves raising the temperature of the polymer by infrared heating. In this case, the water content is measured under drying conditions determined as follows: The drying temperature is raised from room temperature to approximately 180°C, and then the temperature is maintained at 180°C, and the total drying time is set to 20 minutes, including a 5-minute heating step.

[0071] After crosslinking polymerization of monomers, a base polymer powder may be obtained by processes such as drying, grinding, and classification. It is appropriate to prepare and provide a base polymer powder having a particle size of 150 μm to 850 μm, and a superabsorbent polymer obtained therefrom, by such grinding and classification processes. More specifically, at least about 95% by weight of the base polymer powder and the superabsorbent polymer obtained therefrom may have a particle size of about 150 μm to about 850 μm, and fine particles with a particle size of less than 150 μm may account for less than about 3% by weight.

[0072] As described above, since the particle size distribution of the base polymer powder and the superabsorbent polymer is adjusted to the desired range, the final prepared superabsorbent polymer can exhibit the aforementioned physical properties and excellent liquid permeability.

[0073] On the other hand, the methods for drying, grinding, and classifying will be described in more detail below.

[0074] First, regarding the drying of the water-containing gel polymer, if necessary, a coarse grinding step may be performed before drying to improve the efficiency of the drying process.

[0075] In this regard, the pulverizers used herein are not limited by their configuration and may include, but are not limited to, any one selected from the group consisting of vertical pulverizers, turbo cutters, turbo grinders, rotary cutter mills, cutter mills, disc mills, shred crushers, crushers, choppers, and disc cutters.

[0076] From this perspective, the coarse grinding process may be carried out so that the particle size of the water-containing gel polymer is approximately 2 mm to approximately 10 mm.

[0077] Grinding to particle sizes smaller than 2 mm is technically difficult due to the high water content of the water-containing gel polymer, and aggregation of the ground particles may occur. On the other hand, grinding the polymer to particle sizes larger than 10 mm may have only a slight effect on improving the efficiency of the subsequent drying process.

[0078] Drying is performed on the water-containing gel polymer that has been roughly ground as described above, or on the water-containing gel polymer immediately after polymerization without the rough grinding step. In this respect, the drying temperature of the drying step may be about 150°C to about 250°C. It is understood that if the drying temperature is lower than 150°C, the drying time will be too long, which may reduce the physical properties of the superabsorbent polymer that is finally formed. It is understood that if the drying temperature is higher than 250°C, only the polymer surface will be excessively dried, and therefore, fine particles may be generated during the subsequent grinding process, which may reduce the physical properties of the superabsorbent polymer that is finally formed. Therefore, drying may be performed preferably at a temperature of about 150°C to about 200°C, more preferably at a temperature of about 160°C to about 180°C.

[0079] On the other hand, the drying process may be carried out for approximately 20 to 90 minutes, taking process efficiency into consideration, but is not limited to this.

[0080] In the drying process, any drying method can be selected and used, without being limited in terms of its composition, as long as it is commonly used in processes for drying water-containing gel polymers. Specifically, the drying process may be carried out by methods such as supplying hot air, infrared irradiation, microwave irradiation, or ultraviolet irradiation. When the above-described drying process is completed, the water content of the polymer may be about 0.1% by weight to about 10% by weight.

[0081] Next, the dried polymer obtained from the drying process is subjected to a grinding step.

[0082] The polymer powder obtained by the grinding process may have a particle size of approximately 150 μm to approximately 850 μm. Specific examples of grinders that can be used to achieve the above particle sizes include, but are not limited to, pin mills, hammer mills, screw mills, roll mills, disc mills, or jog mills.

[0083] To control the physical properties of the superabsorbent polymer powder that is ultimately produced as a product after the grinding process, a separate process may be performed to classify the polymer powder obtained after grinding according to its particle size. Preferably, polymers having a particle size of about 150 μm to about 850 μm are classified, and only polymer powders with such particle sizes are subjected to a surface crosslinking reaction before being produced as a product.

[0084] On the other hand, after performing the process described above to form the base polymer powder, the surface crosslinking layer may be formed by further crosslinking the surface of the base polymer powder in the presence of a surface crosslinking agent, and as a result, a superabsorbent polymer can be prepared.

[0085] As a surface crosslinking agent, a compound that can react with the functional groups of the polymer can be used, such as polyalcohol compounds, polyepoxy compounds, polyamine compounds, haloepoxy compounds, condensates of haloepoxy compounds, oxazoline compounds, or alkylene carbonate compounds.

[0086] Specifically, examples of polyalcohol compounds include one or more selected from the group consisting of di, tri, tetra, or polyethylene glycol, 1,3-propanediol, dipropylene glycol, 2,3,4-trimethyl-1,3-pentanediol, polypropylene glycol, glycerol, polyglycerol, 2-butene-1,4-diol, 1,4-butanediol, 1,3-butanediol, 1,5-pentanediol, 1,6-hexanediol, and 1,2-cyclohexanedimethanol.

[0087] Furthermore, as polyepoxy compounds, ethylene glycol diglycidyl ether, polyethylene glycol diglycidyl ether, and glycidol may be used. As polyamine compounds, one or more selected from the group consisting of ethylenediamine, diethylenetriamine, triethylenetetraamine, tetraethylenepentamine, pentaethylenehexamine, polyethyleneimine, and polyamide polyamine may be used.

[0088] Epichlorohydrin, epibromohydrin, and α-methylepichlorohydrin can be used as halo-epoxy compounds. On the other hand, examples of mono, di, or polyoxazolidinone compounds include 2-oxazolidinone.

[0089] Ethylene carbonate and other similar compounds can be used as alkylene carbonate compounds.

[0090] These compounds can be used individually or in combination.

[0091] The amount of surface crosslinking agent added can be appropriately and specifically selected depending on the type of surface crosslinking agent added or the reaction conditions, but the surface crosslinking agent can generally be used in an amount of 0.001 to 5 parts by weight, preferably 0.01 to 2 parts by weight, and more preferably 0.05 to 3 parts by weight, per 100 parts by weight of the base polymer.

[0092] Furthermore, the method for adding the surface crosslinking agent to the base polymer powder is not limited to the above configuration. For example, methods such as placing the surface crosslinking agent and the base polymer powder in a reactor and mixing them, spraying the surface crosslinking agent onto the base polymer powder, or continuously supplying the base polymer powder and the surface crosslinking agent to a continuously operated mixer and mixing them can be used.

[0093] When a surface crosslinking agent is added, water and ethanol may be added after mixing. Adding water and methanol has the advantage of allowing the surface crosslinking agent to be uniformly dispersed in the base polymer powder. In this case, it is preferable to control the amount of water and methanol added per 100 parts by weight of base polymer powder in order to induce uniform dispersion of the surface crosslinking agent, prevent aggregation of the base polymer powder, and optimize the surface penetration depth of the surface crosslinking agent.

[0094] The surface crosslinking reaction may be carried out by adding a surface crosslinking agent to the base polymer powder and heating it at approximately 160°C or higher for approximately 20 minutes or more. In particular, in order to prepare a superabsorbent polymer that more appropriately satisfies the physical properties according to one embodiment, the surface crosslinking process conditions include a maximum reaction temperature of approximately 180°C to 200°C and a holding time of approximately 20 minutes or more, or approximately 20 minutes or more at the maximum reaction temperature and up to 1 hour. In addition, the heating time from the initial reaction temperature (e.g., approximately 160°C or higher, or approximately 160°C to 170°C) to the maximum reaction temperature can be controlled to approximately 10 minutes or more, or approximately 10 minutes or more and up to approximately 1 hour. It was confirmed that by satisfying the above surface crosslinking process conditions, a superabsorbent polymer that appropriately satisfies the physical properties of one embodiment can be prepared.

[0095] The means for raising the temperature for the surface crosslinking reaction are not particularly limited. Heating can be performed by providing a heating medium or by directly providing a heat source. In this view, the types of heating mediums that can be applied may be steam, hot air, hot oil, or other thermal fluids, but the present invention is not limited thereto. The temperature of the heating medium provided can be appropriately selected considering the means of the heating medium, the heating rate, and the target temperature. On the other hand, electric heaters or gas heaters may be used as the directly provided heat source, but the present invention is not limited thereto.

[0096] The superabsorbent polymer obtained according to the preparation method described above exhibits excellent properties, with overall physical properties such as water retention capacity and pressure absorption simultaneously improved. This makes the superabsorbent polymer particularly suitable for subsequent incorporation into absorbent articles.

[0097] Absorbent articles The superabsorbent polymers of this disclosure are incorporated into absorbent articles, such as absorbent cores contained within absorbent articles.

[0098] "Absorbent articles" refer to devices that absorb and contain bodily excrement, specifically urine and other water-containing liquids, and more specifically, devices that are placed in contact with or near the wearer's body to absorb and contain various types of excrement released from the body. Absorbent articles may include diapers (for infants and toddlers, and for adult incontinence) and pants (for infants and toddlers, and for adult incontinence). As used herein, the term "excrement" is not limited to but includes urine, blood, vaginal discharge, sweat, and fecal matter. Preferred absorbent articles of the present invention are disposable absorbent articles, more preferably disposable diapers, disposable pants, and disposable absorbent inserts.

[0099] The term "absorbent core" is used herein to refer to a structure positioned between the top sheet and back sheet of an absorbent article, intended to absorb and contain the liquid that the absorbent article receives.

[0100] "Disposable" is used in its ordinary sense to mean an item that is disposed of or discarded after a limited number of uses over various periods, for example, fewer than 10 times, fewer than 5 times, or fewer than 2 times. When disposable absorbent items are diapers, pants, absorbent inserts, sanitary napkins, sanitary pads, or wet wipes for personal hygiene purposes, disposable absorbent items are, in most cases, intended to be disposed of after a single use. Used and disposed of absorbent items may or may not be recycled thereafter. As used herein, the terms "absorbent item," "pants," and "diaper" always also refer to disposable absorbent item, disposable pants (and disposable absorbent pants), and disposable diaper.

[0101] "Diapers" and "pants" refer to absorbent articles generally worn by infants, toddlers and incontinent persons around the lower torso so as to surround the wearer's waist and legs, and in particular, adapted to receive and contain urine and feces. In pants, as used herein, the longitudinal edges of a first waist region and the longitudinal edges of a second waist region are attached to each other to pre-form waist and leg openings. Pants are positioned on the wearer by inserting the wearer's legs into the leg openings and sliding the absorbent article of the pants into place around the wearer's lower torso. Pants may be pre-formed by any preferred method, including, but not limited to, reattachable and / or non-reattachable fastenings (e.g., sews, welds, adhesives, tacks, fasteners, etc.) to connect parts of the absorbent article to each other. Pants may be pre-formed at any position along the outer circumference of the article (e.g., side fastening, front waist fastening). In a diaper, the waist opening and leg openings are formed only when the diaper is applied to the wearer by attaching the longitudinal edges of the first waist region and the second waist region to each other (removably) on both sides by a suitable fastening system.

[0102] Each absorbent article may include a top sheet, a back sheet, an absorbent core, and optionally a gain / distribution system. The absorbent core is placed between the back sheet and the top sheet, and the optional gain / distribution system is typically placed between the absorbent core and the top sheet.

[0103] The superabsorbent polymers of this disclosure may be incorporated into an absorbent core of an absorbent article. The absorbent core may or may not contain other absorbent materials, such as non-crosslinked cellulose fibers (pulp fibers), in addition to the superabsorbent polymer. The absorbent core may contain at least 60% by mass, at least 75% by mass, at least 85% by mass, at least 95% by mass, or at least 98% by mass, or 100% by mass of the superabsorbent polymers disclosed herein.

[0104] Diapers or pants may also include elastic leg cuffs and barrier leg cuffs, which provide improved containment of liquids and other bodily waste, particularly within the leg opening area. Typically, each of the leg cuffs and barrier cuffs includes one or more elastic strings.

[0105] "Female care absorbent products" are personal care products used by women during menstruation to absorb and retain substances from menstruation, vaginal discharge, and other bodily functions related to the vulva. Examples of female care absorbent products include panty liners and sanitary napkins.

[0106] The following are preferred exemplary embodiments to aid in understanding the present invention. However, these exemplary embodiments are merely illustrative of the present invention, and it will be apparent to those skilled in the art that various changes and modifications are possible without departing from the spirit and scope of the invention, as disclosed in the appended claims. [Examples]

[0107] <Preparation of compositions for preparing superabsorbent polymers> Example 1-1 An acrylic acid monomer composition was prepared by mixing 450 g of acrylic acid, 3 g of polyethylene glycol diacrylate 400, and 0.04 g of diphenyl (2,4,6-trimethylbenzoyl)phosphine oxide, and then adding 580 g of a 31.5% aqueous sodium hydroxide solution.

[0108] Separately, 5 g of ZrO2 beads were weighed out as a grinding medium and placed in a 10 mL vial. 12 mg of polyvinylpyrrolidone (PVP, Aldrich's PVP10, average molecular weight 10,000) was added as a dispersant, followed by 24 mg of clay powder (bentonite, BYK's OPTIGEL CK, particle size range 1-5 μm, average particle size 3 μm). 4.7 g of the acrylic acid monomer composition was added to this mixture and mixed by shaking at 300 rpm for 4 minutes using a shaker (JEIO TECH, SK-600) to prepare a composition for producing a superabsorbent polymer.

[0109] Examples 1-2 to 1-3 and Comparative Examples 1-1 to 1-4 Except for changing the type and amount of dispersant used as shown in Table 1 below, compositions for preparing the superabsorbent polymers of Examples 1-2 to 1-3 and Comparative Examples 1-1 to 1-4 were prepared in the same manner as in Example 1-1.

[0110] The DISPERBYK-102 (BYK) used in Comparative Examples 1-2 is a phosphate ester polymer, while the Sokalan HP-20 (BASF) used in Comparative Examples 1-3 is a polyethyleneimine polymer dispersant.

[0111] [Table 1]

[0112] Experimental Example 1: Evaluation of the physical properties of a composition for preparing a superabsorbent polymer. The physical properties of the compositions for preparing the superabsorbent polymers in Examples 1-1 to 1-3 and Comparative Examples 1-1 to 1-4 were evaluated by the following methods, and the results are shown in Table 2.

[0113] (1) Settlement velocity The settling velocity of clay particles in each composition of Examples 2-1 to 2-3 and Comparative Examples 2-1 to 2-4 was measured using a LUMiSizer Dispersion & Particle Size Analyzer.

[0114] In detail, 1.6 mL of the composition for preparing the superabsorbent polymer was taken, placed in a 10 mm PC cell, and then mounted on a LUMiSizer. At a temperature of 25°C and 1,500 rpm (approximately 280 G), 400 transmittance profiles were measured at 10-second intervals. In the measured transmittance profiles, the threshold was set to 21%, and the sedimentation velocity was calculated.

[0115] (2) Dispersion stability after 48 hours The compositions for preparing the superabsorbent polymers in Examples 2-1 to 2-3 and Comparative Examples 2-1 to 2-4 were each placed in 10 mL vials, placed in a vial rack, and left at 25°C for 48 hours. Next, the presence or absence of layer separation in the supernatant was visually observed. If layer separation occurred, it was evaluated as having no dispersion stability (X), and if layer separation did not occur, it was evaluated as having dispersion stability (O).

[0116] [Table 2]

[0117] Referring to Table 2, in the compositions for preparing superabsorbent polymers of Examples 1-1 to 1-3, in which a clay dispersion containing 25 to 50 parts by weight of PVP dispersant was added to 100 parts by weight of clay, little clay sedimentation occurred. Excellent dispersion stability was confirmed even after 48 hours.

[0118] <Preparation of clay dispersion and superabsorbent polymer using the same> Example 2-1 (1) Preparation of a 4% by weight clay dispersion In a flask, 2 g of clay (bentonite, BYK's OPTIGEL CK, particle size range 1-5 μm, average particle size 3 μm) and 1 g (50 parts by weight per 100 parts by weight of clay) of polyvinylpyrrolidone (Aldrich's PVP10, average molecular weight 10,000) were placed as a polymer dispersant, and water was added until the total weight of the mixture reached 50 g. This mixture was stirred using a magnetic stirrer at 500 rpm for 12 hours to prepare a 4% by weight clay dispersion.

[0119] (2) Preparation of superabsorbent polymers In a 3L glass container, 450g of acrylic acid (AA), 3g of polyethylene glycol diacrylate 400 (PEGDA 400), and 0.04g of diphenyl (2,4,6-tribenzoyl)-phosphine oxide were added and dissolved. Then, 580g of a 31.5% aqueous sodium hydroxide solution was added to prepare an acrylic acid monomer composition.

[0120] A 4% by weight clay dispersion prepared in (1) was added to the monomer composition so that the clay content was 0.5 parts by weight per 100 parts by weight of acrylic acid. Sodium bicarbonate (SBC), a carbonate-based blowing agent, was added in an amount of 0.1 parts by weight per 100 parts by weight of acrylic acid, thereby preparing a composition for producing a superabsorbent polymer.

[0121] 1000g of the composition for preparing the superabsorbent polymer is poured into a stainless steel container measuring 250mm wide, 250mm long, and 30mm high, and irradiated with ultraviolet light (irradiation dose 10mV / cm²). 2 By performing UV polymerization for 90 seconds, a water-containing gel polymer was obtained.

[0122] Subsequently, the sheet-like water-containing gel polymer obtained in this manner was placed in a meat chopper to obtain water-containing gel particle powder, which was then dried in a dryer. As a result, the water content of the dried product was less than 1%. The dried particles were pulverized in a pulverizer and classified to prepare base polymers having a size of 150 μm to 850 μm.

[0123] 100 g of base polymer powder was sprayed with 6 g of an aqueous surface crosslinking agent solution containing 3 g of ethylene carbonate, and the mixture was stirred at room temperature to uniformly distribute the surface crosslinking solution over the base polymer powder. Next, the base polymer powder mixed with the surface crosslinking solution was placed in a surface crosslinking reactor and heated to 190°C for 30 minutes, and the surface crosslinking reaction was carried out at the same temperature for 15 minutes.

[0124] After the surface crosslinking process, the powder was classified using a standard ASTM mesh sieve to prepare superabsorbent polymers with particle sizes ranging from 150 μm to 850 μm.

[0125] Examples 2-2 to 2-3 and Comparative Examples 2-1 to 2-3 When preparing the clay dispersions, each clay dispersion was prepared in the same manner as in Example 2-1 (1), except that the types and contents of clay and dispersion were adjusted as shown in Table 3 below. Then, the superabsorbent polymers of Examples 2-2 to 2-3 and Comparative Examples 2-1 to 2-3 were prepared in the same manner as in Example 2-1 (2).

[0126] [Table 3]

[0127] Experimental Example 2: Evaluation of the physical properties of superabsorbent polymers The physical properties of the superabsorbent polymers in Examples 2-1 to 2-3 and Comparative Examples 2-1 to 2-3 were evaluated by the following methods, and the results are shown in Table 4.

[0128] (1) Effective Absorption Capacity (EFFC) The EFFC value was calculated according to the following formula. EFFC = 1 / 2(CRC + AUP) In the formula, CRC and AUP were measured by the following method. a) Measurement of centrifugal retention capacity (CRC) The CRC of superabsorbent polymers was measured according to the EDANA method WSP 241.2.

[0129] In detail, polymers were obtained from the polymers obtained in the examples and comparative examples, classified using sieves of size 30 to 50. This superabsorbent polymer W0 (g) (approximately 0.2g) was uniformly placed in a nonwoven fabric bag, sealed, and then immersed in physiological saline (0.9 wt%) at room temperature. After 30 minutes, water was removed from the bag using a centrifuge at 250G for 3 minutes, and the weight of the bag W2 (g) was measured. In addition, the same procedure was performed without using the polymer, and W1 (g) at that point was measured.

[0130] Using the obtained weight, the CRC (g / g) was calculated according to the following formula. CRC(g / g)={[W2(g)-W1(g)] / W0(g)}-1

[0131] b) Measurement of pressure absorption capacity (AUP) The AUP of 0.7 psi of the superabsorbent polymer was measured according to the EDANA method WSP 242.2.

[0132] First, when measuring pressure absorption, the same classified polymer used for CRC measurement was used.

[0133] In detail, a 400-mesh stainless steel net was placed at the bottom of a plastic cylinder with an inner diameter of 60 mm. Under room temperature and 50% humidity conditions, superabsorbent polymer W0 (g) (0.90 g) was uniformly scattered on the stainless steel net. A piston capable of uniformly applying a load of 0.7 psi was placed on top of it, but the outer diameter of the piston was slightly smaller than 60 mm, there was no gap between the inner wall of the cylinder and the piston, and the up-and-down motion (jig-jog) of the cylinder was not interrupted. At this point, the weight of the apparatus W4 (g) was measured.

[0134] A glass filter with a diameter of 90 mm and a thickness of 5 mm was placed in a Petri dish with a diameter of 150 mm. Physiological saline solution consisting of 0.9 wt% sodium chloride was then poured in until the surface level of the saline solution was level with the upper surface of the glass filter. A sheet of filter paper with a diameter of 90 mm was placed on top of the glass filter. The measuring device was placed on the filter paper, and the liquid was absorbed by its load for 1 hour. After 1 hour, the measuring device was lifted, and its weight W5 (g) was measured.

[0135] From the obtained weight, AUP(g / g)(g / g) was calculated according to the following formula. AUP(g / g)=[W5(g)-W4(g)] / W3(g)

[0136] (2) Color b The color b value of the superabsorbent polymer was measured according to the ASTM D2985 standard.

[0137] [Table 4]

[0138] Referring to Table 4, in Comparative Example 2-1, no dispersant was included, and therefore the dispersion stability of the clay decreased, resulting in a significant decrease in the EFFC value.

[0139] On the other hand, when comparing Examples 2-1 to 2-3, which use clay dispersions containing a dispersant along with clay, with Comparative Examples 2-2 and 2-3, it was found that Comparative Examples 2-2 and 2-3, which use Sokalan HP-20 as a dispersant, exhibited higher color b values ​​than Examples 2-1 to 2-3, which use PVP.

[0140] From the above results, it was confirmed that the clay dispersion of the present invention can improve the absorption properties of the prepared superabsorbent polymer due to the excellent dispersion stability of the clay in the composition for preparing the superabsorbent polymer. Furthermore, it was confirmed that the clay dispersion of the present invention does not cause discoloration of the superabsorbent polymer when used with it, and is therefore suitable for producing high-quality products.

[0141] The dimensions and values ​​disclosed herein should not be understood as being strictly limited to the exact numerical values ​​listed. Instead, unless otherwise specified, each such dimension is intended to mean both the listed value and the functionally equivalent range encompassing that value. For example, a dimension disclosed as "40 mm" is intended to mean "approximately 40 mm."

[0142] All documents cited herein, including cross-referenced or related patents or applications, are incorporated herein in their entirety by reference unless expressly excluded or otherwise limited. No citation of any document shall be deemed prior art to any invention disclosed or claimed herein, nor shall it be deemed to teach, suggest or disclose any such invention, either alone or in combination with any one or more other references. Furthermore, to the extent that any meaning or definition of a term in this document conflicts with any meaning or definition of the same term in any document incorporated by reference, the meaning or definition given to that term in this document shall prevail.

[0143] While specific embodiments of the present invention have been illustrated and described, it will be apparent to those skilled in the art that various other changes and modifications can be made without departing from the spirit and scope of the invention. Therefore, it is intended that all such changes and modifications within the scope of the invention be covered in the appended claims.

Claims

1. A method for producing an absorbent article containing a superabsorbent polymer, wherein the superabsorbent polymer is prepared by using a clay dispersion, and the clay dispersion is Solvent and, Clay and A polymer dispersant comprising two or more functional groups selected from the group consisting of amine groups, carbonyl groups, and hydroxyl groups, A method wherein the polymer dispersant is contained in an amount ranging from more than 20 parts by weight to 200 parts by weight or less, per 100 parts by weight of clay.

2. The method according to claim 1, wherein the polymer dispersant is contained in the clay dispersion in an amount of 25 to 100 parts by weight per 100 parts by weight of clay.

3. The method according to claim 1 or 2, wherein the clay is one or more selected from the group consisting of montmorillonite, saponite, nontronite, laponite, beiderite, hectorite, vermiculite, magadite, bentonite, kaolin, serpentine, and mica.

4. The method according to any one of claims 1 to 3, wherein the average particle size of the clay is 0.025 μm to 10 μm.

5. The method according to any one of claims 1 to 4, wherein the polymer dispersant in the clay composition comprises an amine group and a carbonyl group.

6. The method according to any one of claims 1 to 5, wherein the polymer dispersant in the clay composition is one or more selected from the group consisting of polyvinylpyrrolidone, polyacrylamide, N-acetylpolyimine, and polyaminoacrylate.

7. The method according to any one of claims 1 to 6, wherein the method further includes a step of incorporating the superabsorbent polymer into the absorbent article.

8. A method for producing an absorbent article containing a superabsorbent polymer, wherein the superabsorbent polymer is prepared by using a composition, the composition comprising a clay dispersion, a water-soluble ethylenically unsaturated monomer, an alkali metal salt or alkali compound capable of neutralizing the water-soluble ethylenically unsaturated monomer, and a polymerization initiator. The clay dispersion said above, Solvent and, Clay and A polymer dispersant comprising two or more functional groups selected from the group consisting of amine groups, carbonyl groups, and hydroxyl groups, A method wherein the polymer dispersant is contained in an amount ranging from more than 20 parts by weight to 200 parts by weight or less, per 100 parts by weight of clay.

9. The method according to claim 8, wherein the clay in the composition has a settling velocity of 100 μm / s or less.

10. In the composition, the water-soluble ethylenically unsaturated monomer is anionic monomer such as acrylic acid, methacrylic acid, maleic anhydride, fumaric acid, crotonic acid, itaconic acid, 2-acryloylethanesulfonic acid, 2-methacryloylethanesulfonic acid, 2-(meth)acryloylpropanesulfonic acid, or 2-(meth)acrylamido-2-methylpropanesulfonic acid, and salts thereof. Nonionic hydrophilic monomers such as (meth)acrylamide, N-substituted (meth)acrylate, 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, methoxypolyethylene glycol (meth)acrylate, or polyethylene glycol (meth)acrylate, and The method according to claim 8 or 9, wherein the amino group-containing unsaturated monomer is selected from the group consisting of (N,N)-dimethylaminoethyl (meth)acrylate or (N,N)-dimethylaminopropyl (meth)acrylamide, and quaternary compounds thereof.

11. The method according to any one of claims 8 to 10, wherein the clay content in the composition is 0.1 to 1 part by weight per 100 parts by weight of the ethylenically unsaturated monomer.

12. The method according to any one of claims 8 to 11, further comprising the step of incorporating the superabsorbent polymer into the absorbent article.

13. A method for producing an absorbent article containing a superabsorbent polymer, wherein the method is A step of preparing a water-containing gel polymer by performing a polymerization reaction by heating and / or light irradiation of a composition for preparing the superabsorbent polymer described in claim 7, The process involves drying and pulverizing the water-containing gel polymer to prepare a base polymer. The process involves forming a surface-crosslinked layer by further crosslinking the surface of the base polymer in the presence of a surface crosslinking agent. Includes, A method further comprising the step of incorporating the superabsorbent polymer into the absorbent article.

14. The method according to claim 13, wherein the absorbent article is a diaper or pants.

15. The method according to claim 13 or 14, wherein the superabsorbent polymer is incorporated into an absorbent core, and the absorbent core is contained by the absorbent article.

16. The method according to claim 15, wherein the absorbent core is manufactured by providing two nonwoven webs and incorporating a surface-crosslinked granular water-absorbent resin between the two nonwoven webs.

17. The method according to claim 15 or 16, wherein the absorbent core between the two nonwoven webs comprises less than 20% by weight of cellulose fibers, preferably less than 10% by weight of cellulose fibers, and more preferably less than 5% by weight of cellulose fibers.

18. The method described above is The method according to claim 16 or 17, further comprising the step of adhering and fixing the superabsorbent polymer between the two nonwoven webs.

19. The method described above is - Further processes for providing the top sheet, - Further processes to provide the backsheet, - The method according to any one of claims 15 to 18, further comprising the step of providing the absorbent core between the top sheet and the back sheet.

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