Clay dispersion, composition for preparing superabsorbent polymer comprising same, and method for preparing superabsorbent polymer in absorbent article using same

Abstract

The present invention provides a clay dispersion having excellent dispersion stability, a composition for preparing a superabsorbent polymer incorporated into an absorbent article comprising the clay dispersion, and a method for preparing a superabsorbent polymer incorporated into an absorbent article using the clay dispersion. The clay dispersion of the present invention has a low settling rate of clay, and exhibits excellent dispersion stability even during long-term storage, in particular, exhibits long-term excellent dispersion stability even in a composition for preparing a superabsorbent polymer, the composition comprising an alkali metal salt or a basic material.

Description

Technical Field

[0001] The present invention relates to a clay dispersion for use in preparing a superabsorbent polymer to be incorporated into an absorbent article, the dispersion having excellent dispersion stability; a composition for preparing a superabsorbent polymer for use in an absorbent article, the composition comprising the clay dispersion; and a method for preparing a superabsorbent polymer using the clay dispersion, wherein the superabsorbent polymer is incorporated into an absorbent article. Background Art

[0002] Superabsorbent polymers (SAPs) are synthetic polymer materials capable of absorbing 500 to 1,000 times their own weight in water. Since their initial practical application in absorbent products, SAPs have expanded beyond sanitary products (such as disposable diapers and sanitary napkins) to include water-retaining soil products for gardening, waterproofing materials for civil engineering and construction, seedling cultivation sheets, food preservatives, and plasters.

[0003] A water-soluble ethylenically unsaturated monomer is used in superabsorbent polymers. One or more monomers selected from the group consisting of anionic monomers and their salts, nonionic hydrophilic monomers, and amino-group-containing unsaturated monomers and their quaternary compounds can be used. The water-soluble ethylenically unsaturated monomer is neutralized with an alkali metal salt (such as sodium salt) or a basic compound (such as caustic soda). A polymerization reaction is then carried out in the presence of a crosslinking agent and a polymerization initiator. This solution is referred to as a neutralized solution or a composition for preparing a superabsorbent polymer. This neutralized solution is thermally or photopolymerized to produce a hydrogel polymer. This is then dried, pulverized, and classified to produce a powdered superabsorbent polymer.

[0004] Research has been conducted to incorporate clay as an additive to improve basic physical properties of superabsorbent polymers, such as centrifuge retention capacity (CRC) and absorbency under load (AUP). However, when clay is incorporated into compositions used to produce superabsorbent polymers, ensuring dispersion stability is difficult because the clay particles tend to agglomerate due to the high ion concentration of the alkali metal salt or basic compound added during the neutralization reaction. This agglomerated clay forms particles that are unevenly distributed throughout the polymer, potentially preventing the improvement of the polymer's physical properties.

[0005] Therefore, there is a need to develop a clay dispersion that can exhibit excellent dispersibility in a composition for preparing a superabsorbent polymer and can improve the physical properties of the superabsorbent polymer.

[0006] Technical issues

[0007] A clay dispersion useful in preparing superabsorbent polymers to be incorporated into absorbent articles is provided, the clay dispersion exhibiting excellent dispersion stability.

[0008] Also provided is a composition for preparing a superabsorbent polymer for use in an absorbent article, the composition comprising the clay dispersion.

[0009] Also provided is a method of making a superabsorbent polymer using the clay dispersion, wherein the superabsorbent polymer is subsequently incorporated into an absorbent article.

[0010] Technical Solution

[0011] According to one embodiment of the present invention, there is provided a clay dispersion for use in making a superabsorbent polymer, which is subsequently incorporated into an absorbent article. The clay dispersion comprises a solvent, clay, and a polymer dispersant, wherein the polymer dispersant comprises two or more functional groups selected from the group consisting of an amine group, a carbonyl group, and a hydroxyl group. The polymer dispersant is added in an amount of more than 20 parts by weight to 200 parts by weight or less relative to 100 parts by weight of the clay.

[0012] According to another embodiment of the present invention, there is provided a composition for preparing a superabsorbent polymer used in absorbent articles, the composition comprising the clay dispersion, a water-soluble ethylenically unsaturated monomer, an alkali metal salt or a basic compound capable of neutralizing the water-soluble ethylenically unsaturated monomer, and a polymerization initiator.

[0013] The absorbent article comprising the superabsorbent polymer produced by using the clay dispersion and / or by using the composition may be a diaper or a pant.

[0014] Superabsorbent polymers may be incorporated into an absorbent core comprised by the absorbent article.

[0015] The absorbent core can be made by providing two layers of nonwoven webs and incorporating the surface-crosslinked particulate water-absorbent resin between the two layers of nonwoven webs.

[0016] The absorbent core may comprise 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 between the two layers of nonwoven web.

[0017] In the absorbent core, the superabsorbent polymer can be adhesively secured between the two layers of nonwoven web.

[0018] The absorbent article may include a topsheet, a backsheet, and an absorbent core positioned between the topsheet and the backsheet.

[0019] According to yet another embodiment of the present invention, there is provided a method for preparing a superabsorbent polymer, comprising the steps of: preparing an aqueous gel polymer by subjecting a composition for preparing a superabsorbent polymer to polymerization by heating and / or light irradiation; preparing a base polymer by drying and pulverizing the aqueous 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 comprises the further step of incorporating the obtained superabsorbent polymer into an absorbent article.

[0020] Effects of the Invention

[0021] The clay dispersion of the present invention has a low sedimentation rate of the clay particles and maintains excellent dispersion stability even during long-term storage. In particular, the clay dispersion exhibits excellent long-term dispersion stability even in a composition for preparing a superabsorbent polymer containing an alkali metal salt or alkaline material. Therefore, the clay dispersion can be used as an effective additive to improve the physical properties of superabsorbent polymers, such as centrifuge retention capacity and pressurized absorption capacity. Furthermore, superabsorbent polymers prepared using the clay dispersion do not suffer from discoloration. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 The photographs are taken 48 hours after the preparation of the compositions of Examples 1-1 to 1-3, Comparative Example 1-3, and Comparative Example 1-4 for preparing super absorbent polymers. DETAILED DESCRIPTION

[0023] The language and terms used in this specification are intended only to explain exemplary embodiments and are not intended to limit the present invention. Unless the context indicates otherwise, singular expressions may include plural expressions. It must be understood that the terms "comprising," "equipped with," or "having" in this specification are used only to indicate the presence of an effective feature, step, component, or combination thereof, and do not exclude the pre-existence of one or more different features, steps, components, or combinations thereof, nor do they exclude the possibility of adding one or more different features, steps, components, or combinations thereof.

[0024] The present invention can be modified in various ways and in various forms, and specific exemplary embodiments are exemplified and described in detail in the following description. However, the present invention is not intended to be limited to the specific exemplary embodiments, and it must be understood that the present invention includes every modification, equivalent, or alternative encompassed within its essence and technical scope.

[0025] As used herein, "clay" refers to particles of a layered silicate mineral, or an aggregate of a plurality of such particles, and "clay dispersion" refers to a dispersion of clay in a solvent.

[0026] As used herein, "(meth)acrylate" is used to mean a term encompassing acrylate and methacrylate.

[0027] As used herein, "base polymer" or "base polymer powder" (ie, in the form of particles or powders prepared by drying or pulverizing a polymer obtained by polymerizing a water-soluble ethylenically unsaturated monomer) refers to a polymer that has not been surface-modified or surface-crosslinked.

[0028] Hereinafter, the present invention will be described in detail.

[0029] The clay dispersion is characterized by comprising a solvent, clay, and a polymer dispersant comprising two or more functional groups selected from the group consisting of an amine group, a carbonyl group, and a hydroxyl group, wherein the polymer dispersant is added in an amount of more than 20 parts by weight to 70 parts by weight or less relative to 100 parts by weight of the clay.

[0030] Because the polymeric dispersant contains two or more functional groups selected from the group consisting of amine groups, carbonyl groups, and hydroxyl groups, the clay dispersion can significantly improve the dispersion stability of the clay. Clay has a layered structure in which small silicate platelets, approximately 1 nm thick, are stacked on top of each other due to strong van der Waals attraction. The polymeric dispersant binds to the clay surface and exfoliates the silicate layers (i.e., by spreading them out to a distance between them exceeding 1 nm). Because chemically exfoliated clay exhibits significantly improved dispersion stability, even when the clay dispersion is included in a composition for preparing a superabsorbent polymer (the composition contains an alkali metal salt or a basic compound), the clay particles can be uniformly dispersed in the composition without agglomeration or sedimentation.

[0031] Therefore, the absorption properties (such as centrifuge retention capacity and pressurized absorption capacity) of superabsorbent polymers prepared using this clay dispersion can be further improved. In addition, since this clay dispersion does not cause discoloration of the superabsorbent polymer, it can be used to manufacture high-quality products.

[0032] As the clay, either swelling clay or non-swelling clay can be used. Swelling clay is a layered organic material with water absorption, and examples thereof include montmorillonite, saponite, nontronite, laponite, beidellite, hectorite, vermiculite, magadiite, and bentonite. As non-swelling clay, examples thereof include kaolin, serpentine, and mica. Clay can be used alone or as a mixture of two or more clays.

[0033] Clay having an average particle size of 0.025µm or greater, 0.05µm or greater, 0.1µm or greater, or 1µm, and 10µm or less, 8µm or less, or 5µm or less can be used. When the average particle size of the clay is less than 0.025µm, the effect of improving the gel strength of the superabsorbent polymer may not be fully achieved. When the average particle size of the clay exceeds 10µm, due to the strong interlayer attraction of the clay, it is difficult to achieve uniform dispersion in the aqueous system and it is difficult to uniformly modify the clay surface, resulting in the problem of not ensuring transparency 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.

[0034] The polymer dispersant includes two or more functional groups selected from the group consisting of an amine group, a carbonyl group, and a hydroxyl group, and is used in an amount of more than 20 parts by weight to 200 parts by weight or less relative to 100 parts by weight of clay.

[0035] As used herein, the term "two or more functional groups selected from the group consisting of an amine group, a carbonyl group, and a hydroxyl group" means a combination of two or more functional groups selected from the group consisting of an amine group, a carbonyl group, and a hydroxyl group, such as an amide group containing both an amine group and a carbonyl group, a carboxyl group containing both a carbonyl group and a hydroxyl group, and the like. For example, a "polymer dispersant containing an amine group and a carbonyl group" may contain an amine group and a carbonyl group, respectively, in the molecule, or may contain an amide group formed by combining an amine group and a carbonyl group.

[0036] Polymer dispersants containing these functional groups can bind to clay surfaces due to the unshared electrons of nitrogen and oxygen atoms. Furthermore, in compositions used to prepare high-ion-concentration superabsorbent polymers, they can induce charges in the polymer due to resonance. These properties can improve the dispersibility of clay by exfoliating its layered structure. Furthermore, these polymer dispersants do not discolor the superabsorbent polymer or degrade its physical properties, making them suitable for use in the preparation of superabsorbent polymers.

[0037] From this perspective, 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.

[0038] Specific examples of the polymer dispersant may include one or more substances selected from the group consisting of polyvinyl pyrrolidone, polyacrylamide, and polyacrylic acid. Preferably, polyvinyl pyrrolidone may be used as the polymer dispersant.

[0039] The molecular weight of the polymer dispersant is not particularly limited. However, for example, a polymer dispersant having a weight average molecular weight of 2,500 g / mol or greater, 5,000 g / mol or greater, or 10,000 g / mol or greater, and 200,000 g / mol or less, 100,000 g / mol or less, or 40,000 g / mol can be used. When the weight average molecular weight of the polymer dispersant is less than 2,500 g / mol, there may be problems in ensuring dispersibility and long-term stability because it is difficult to maintain a sufficiently large distance between the silicate layers of the clay when the polymer dispersant binds to the clay surface. When the weight average molecular weight exceeds 200,000 g / mol, there are process difficulties and the surface modification of the clay is ineffective, so it is preferably within the above range.

[0040] To ensure the dispersibility of the clay, the amount of the polymer dispersant is more than 20 parts by weight to 200 parts by weight or less relative to 100 parts by weight of the clay; preferably, the amount is 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.

[0041] When the polymer dispersant content is 20 parts by weight or less per 100 parts by weight of the clay, the clay surface modification is insufficient, and thus the interlayer spacing of the clay may not be sufficiently expanded. Consequently, the clay dispersion stability is insufficient, and clay particles may easily agglomerate. Furthermore, when the polymer dispersant content is excessively high, exceeding 200 parts by weight per 100 parts by weight of the clay, the polymer dispersant reduces the effect of the clay on improving physical properties, thereby degrading the physical properties of the superabsorbent polymer.

[0042] The type of solvent used for the clay dispersion is not particularly limited, and any solvent can be used without limitation as long as it is used in the composition for preparing the superabsorbent polymer. For example, as the solvent, 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.

[0043] The amount of the solvent used to prepare the clay dispersion is not limited and can be appropriately adjusted according to the types and amounts of the clay and polymer dispersant, as well as the intended use of the clay dispersion.

[0044] 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, 10% by weight or less, or 8% by weight or less. When the clay content satisfies the requirement, the clay particles can maintain excellent dispersibility even during long-term storage without agglomerating or settling.

[0045] Meanwhile, a composition for preparing a super absorbent polymer is provided, which comprises the clay dispersion, a water-soluble ethylenically unsaturated monomer, an alkali metal salt or a basic compound capable of neutralizing the water-soluble ethylenically unsaturated monomer, and a polymerization initiator.

[0046] The description of the clay dispersion is the same as above.

[0047] The clay dispersion may be used in an amount such that the clay content is 0.1 parts by weight or more, 0.2 parts by weight or more, or 0.25 parts by weight or more, and 1 part by weight or less, 0.7 parts by weight or less, or 0.5 parts by weight or less, based on 100 parts by weight of the 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, 0.2 parts by weight or more, or 0.25 parts by weight or more, and 1 part by weight or less, 0.7 parts by weight or less, or 0.5 parts by weight or less, based on 100 parts by weight of the ethylenically unsaturated monomer.

[0048] As the water-soluble ethylenically unsaturated monomer, any monomer can be used without particular limitation as long as it is commonly used for preparing superabsorbent polymers. Preferably, any one or more selected from the group consisting of anionic monomers and salts thereof, nonionic hydrophilic monomers, amino group-containing unsaturated monomers and quaternary compounds thereof can be used. Specific examples of water-soluble ethylenically unsaturated monomers may include one or more substances selected from the group consisting of: 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)acrylamide-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 unsaturated monomers containing amino groups such as (N,N)-dimethylaminoethyl (meth)acrylate or (N,N)-dimethylaminopropyl (meth)acrylamide and their quaternary compounds.

[0049] The concentration of the water-soluble ethylenically unsaturated monomer can be approximately 20 to 60 parts by weight, preferably 40 to 60 parts by weight, relative to 100 parts by weight of the composition for preparing the superabsorbent polymer. This concentration can be appropriately adjusted based on the polymerization reaction time and reaction conditions. If the monomer concentration is too low, the yield of the superabsorbent polymer may be low, and economic feasibility issues may arise. If the concentration is too high, a portion of the monomer may precipitate, or process problems may arise (such as low pulverization efficiency during pulverization of the hydrogel polymer after polymerization), and the physical properties of the superabsorbent polymer may deteriorate.

[0050] In addition, the degree of neutralization of the water-soluble ethylenically unsaturated monomer is 50% to 95%, preferably 70% to 85%. When the degree of neutralization of the monomer is low, the water absorbency of the superabsorbent polymer to be prepared may be reduced, while when the degree of neutralization is high, the monomer may precipitate and it may be difficult to prepare the superabsorbent polymer.

[0051] As the alkali metal salt or basic compound capable of neutralizing the water-soluble ethylenically unsaturated monomer, an alkali metal salt such as sodium acrylate or a basic compound such as caustic soda (NaOH) can be used.

[0052] As the polymerization initiator, depending on the polymerization method, a photopolymerization initiator can be used for photopolymerization, and a thermal polymerization initiator can be used for thermal polymerization.

[0053] However, even if photopolymerization is performed, ultraviolet irradiation or the like may generate a certain amount of heat, and heat is generated along with the polymerization reaction which is an exothermic reaction. Therefore, a thermal polymerization initiator may be further used.

[0054] The thermal polymerization initiator is not particularly limited, but one or more initiators selected from the group consisting of persulfate initiators, azo initiators, hydrogen peroxide, and ascorbic acid can be preferably 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)isobutyramidine dihydrochloride, 2-(carbamoyl azo)isobutyronitrile, 2,2-azobis[2-(2-imidazolin-2-yl)propane] dihydrochloride, and 4,4-azobis-(4-cyanovaleric acid).

[0055] The photopolymerization initiator is not particularly limited, but one or more initiators selected from the group consisting of benzoin ether, dialkyl acetophenone, hydroxyalkyl ketone, phenylglyoxylate, benzyl dimethyl ketal, acylphosphine and α-aminoketone can be preferably used. Meanwhile, specific examples of the acylphosphine can include diphenyl (2,4,6-trimethylbenzoyl) phosphine oxide.

[0056] At the same time, the neutralization solution may further include a cross-linking agent. As the cross-linking agent, a cross-linking agent having one or more functional groups capable of reacting with the water-soluble substituent of the water-soluble ethylenically unsaturated monomer and one or more ethylenically unsaturated groups may be used; or a cross-linking agent having two or more functional groups capable of reacting with the water-soluble substituent of the monomer and / or the water-soluble substituent formed by hydrolysis of the monomer may be used.

[0057] Specific examples of the cross-linking agent may include one or more compounds 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, butene 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, glycerol tri(meth)acrylate, pentaerythritol tetraacrylate, triallylamine, ethylene glycol diglycidyl ether, propylene glycol, glycerol and ethylene carbonate.

[0058] The amount of the crosslinking agent added is 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, relative to 100 parts by weight of the water-soluble ethylenically unsaturated monomer, thereby achieving crosslinking of the product after polymerization.

[0059] The composition for preparing the superabsorbent polymer may further contain additives such as a foaming agent, a thickener, a plasticizer, a storage stabilizer, an antioxidant, etc., as needed.

[0060] For example, in the composition for preparing superabsorbent polymer, the foaming agent may include 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.

[0061] The foaming agent may be added in an amount of 0.01 parts by weight or more, 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 relative to 100 parts by weight of the monomer.

[0062] The composition for preparing the superabsorbent polymer may contain a solvent. Suitable solvents can be used without limitation in terms of their composition, as long as they can dissolve the above components. For example, the solvent used to prepare the clay dispersion can be used as a solvent for the composition for preparing the superabsorbent polymer.

[0063] Alternatively, the composition for preparing a superabsorbent polymer can be prepared by mixing clay, a polymer dispersant, a water-soluble ethylenically unsaturated monomer, an alkali metal salt or a basic compound capable of neutralizing the water-soluble ethylenically unsaturated monomer, and a polymerization initiator in a single step in the presence of a solvent. Even in this case, the effect of improving the dispersion stability of the clay can be obtained by the polymer dispersant.

[0064] By including the clay dispersion, the composition for preparing a super absorbent polymer maintains excellent dispersion stability in the composition, thereby preventing the clay particles from agglomerating with each other or precipitating.

[0065] Specifically, the clay in the composition for preparing the superabsorbent polymer may have a sedimentation rate of 100 µm / s or less, preferably 50 µm / s or less, 30 µm / s or less, or 10 µm / s or less, and 1 µm / s or greater, or 5 µm / s or greater. The method for measuring the sedimentation rate is described in detail in the "Experimental Examples" below.

[0066] A composition for preparing a superabsorbent polymer includes clay, wherein the clay maintains excellent dispersion stability due to the use of a polymer dispersant including two or more functional groups selected from the group consisting of an amine group, a carbonyl group, and a hydroxyl group, and thus the composition can be suitably used to prepare a superabsorbent polymer having excellent absorption performance without worrying about discoloration.

[0067] Therefore, a method for preparing a super absorbent polymer using the composition for preparing the super absorbent polymer is provided.

[0068] Specifically, the method for preparing a superabsorbent polymer includes the following steps: preparing a hydrogel polymer by polymerizing a composition for preparing a superabsorbent polymer by heating and / or light irradiation; preparing a base polymer by drying and pulverizing the hydrogel polymer; and forming a surface crosslinked layer by further crosslinking the surface of the base polymer in the presence of a surface crosslinking agent.

[0069] The method further comprises the step of incorporating the superabsorbent polymer obtained (eg in the form of particles) into an absorbent article.

[0070] Polymerization methods are primarily categorized into thermal polymerization and photopolymerization, depending on the source of polymerization energy. Thermal polymerization is typically 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. The above polymerization methods are merely examples and the present invention is not limited thereto.

[0071] For example, the hydrogel polymer obtained by thermally polymerizing while introducing hot air into a reactor such as a kneader equipped with a stirring shaft, or by heating the reactor, can have a size on the order of centimeters or millimeters when discharged from the reactor outlet, depending on the type of stirring shaft equipped in the reactor. Specifically, the size of the hydrogel polymer obtained can vary depending on factors such as the concentration of the monomer composition fed to the reactor and the feed rate, but typically, a hydrogel polymer having a weight-average particle size of about 2 mm to about 50 mm can be obtained.

[0072] In addition, as described above, when photopolymerization is carried out in a reactor equipped with a movable conveyor, the obtained hydrogel polymer can generally be a sheet-like hydrogel polymer having a width consistent with the width of the conveyor. In this case, the thickness of the polymer sheet can vary depending on the concentration of the monomer composition fed to the reactor and the feed rate. Generally, it is preferred to supply the monomer composition so that a sheet-like polymer having a thickness of about 0.5 cm to about 5 cm can be obtained. When the amount of monomer composition supplied causes the sheet-like polymer to become too thin, it is disadvantageous due to low production efficiency; and when the sheet-like polymer thickness exceeds 5 cm, due to the excessive thickness, the polymerization reaction may not occur uniformly across the entire thickness range.

[0073] The hydrogel polymer obtained by the above-mentioned method can have a water content of approximately 40% to 80% by weight. As used herein, "water content" refers to the weight ratio of water to the total weight of the hydrogel polymer, which can be obtained by subtracting the dry polymer weight from the weight of the hydrogel polymer. Specifically, the water content can be defined as the value calculated by increasing the polymer temperature via infrared heating and measuring the weight loss due to evaporation of water from the polymer during the drying process. The water content is measured under the following drying conditions: the drying temperature is increased from room temperature to approximately 180°C and then maintained at a constant temperature of 180°C; the total drying time is set to 20 minutes, including a 5-minute temperature increase phase.

[0074] After cross-linking and polymerization of the monomers, base polymer powder can be obtained through processes such as drying, pulverization, and classification. Such pulverization and classification processes are preferably used to prepare and provide base polymer powders having particle sizes ranging from 150 µm to 850 µm and superabsorbent polymers obtained therefrom. More specifically, at least about 95% by weight or more of the base polymer powders and superabsorbent polymers obtained therefrom may have particle sizes ranging from about 150 µm to about 850 µm, and the content of fine particles having a particle size of less than 150 µm may be less than about 3% by weight.

[0075] As described above, when the particle size distributions of the base polymer powder and the super absorbent polymer are adjusted to a desired range, the finally prepared super absorbent polymer can exhibit the above-mentioned physical properties and excellent liquid permeability.

[0076] On the other hand, methods of performing drying, pulverization and classification will be described in more detail below.

[0077] First, regarding the drying of the hydrogel polymer, a coarse pulverization step may be added before drying as needed to improve the efficiency of the drying step.

[0078] In this regard, the configuration of the pulverizer used herein is not limited, and specifically, may include any one selected from the group consisting of a vertical pulverizer, a turbine cutter, a turbine grinder, a rotary cutter mill, a cutter mill, a disc grinder, a shredder, a crusher, a shredder, and a disc shredder, but is not limited to the above examples.

[0079] In this regard, the coarse pulverization step may be performed so that the particle size of the hydrogel polymer reaches about 2 mm to about 10 mm.

[0080] Due to the high water content of hydrogel polymers, pulverizing them to a particle size of less than 2 mm is technically difficult, and the pulverized particles may agglomerate. Furthermore, pulverizing the polymer to a particle size greater than 10 mm may not significantly improve the efficiency of the subsequent drying step.

[0081] The hydrogel polymer that has been coarsely pulverized as described above, or the hydrogel polymer obtained directly after polymerization without undergoing a coarse pulverization step, must be dried. In this regard, the drying temperature in the drying step may be from about 150°C to about 250°C. If the drying temperature is lower than 150°C, there is a risk that the drying time will become too long, and the physical properties of the resulting superabsorbent polymer may deteriorate. If the drying temperature is higher than 250°C, there is a risk that the polymer surface will be over-dried, resulting in the generation of fine particles during the subsequent pulverization process, and the physical properties of the resulting superabsorbent polymer may deteriorate. Therefore, drying can be preferably performed at a temperature of from about 150°C to about 200°C, and more preferably at a temperature of from about 160°C to about 180°C.

[0082] Meanwhile, based on process efficiency considerations, the drying step may be performed for about 20 minutes to about 90 minutes, but is not limited thereto.

[0083] In the drying step, any drying method can be selected and used without limitation, as long as it is commonly used in drying processes for hydrogel polymers. Specifically, the drying step can be performed using methods such as hot air supply, infrared radiation, microwave radiation, or ultraviolet radiation. Upon completion of the drying step, the water content of the polymer can be between approximately 0.1% and approximately 10% by weight.

[0084] Next, the dried polymer obtained in the drying step is subjected to a pulverization step.

[0085] The polymer powder obtained by the pulverization step can have a particle size of about 150 µm to about 850 µm. Specific examples of pulverizers that can be used to achieve the above particle size requirements include, but are not limited to, pin mills, hammer mills, spiral mills, roller mills, disc mills, or vibration mills.

[0086] To tailor the physical properties of the final commercial superabsorbent polymer powder after the pulverization step, the resulting polymer powder can be subjected to a particle size classification process. Preferably, polymer powder with a particle size of approximately 150µm to approximately 850µm is separated, and only the polymer powder with this particle size is subjected to the surface crosslinking reaction and subsequently commercialized.

[0087] Meanwhile, after performing the process of forming the above-mentioned base polymer powder, a surface crosslinked layer may be formed by additionally crosslinking the surface of the base polymer powder in the presence of a surface crosslinking agent, thereby preparing a super absorbent polymer.

[0088] As the surface crosslinking agent, a compound capable of reacting with a polymer functional group is used, and for example, a polyol compound, a polyepoxy compound, a polyamine compound, a halogenated epoxy compound, a condensate of a halogenated epoxy compound, an oxazoline compound, or an alkylene carbonate compound can be used.

[0089] Specifically, examples of the polyol compound may include one or more compounds selected from the group consisting of diethylene glycol, triethylene glycol, tetraethylene glycol or polyethylene glycol, 1,3-propylene glycol, 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.

[0090] In addition, as the polyepoxide, ethylene glycol diglycidyl ether, polyethylene glycol diglycidyl ether, glycidol, etc. can be used. As the polyamine compound, one or more compounds selected from the group consisting of ethylenediamine, diethylenetriamine, triethylenetetramine, tetraethylenepentamine, pentaethylenehexamine, polyethyleneimine, and polyamidepolyamine can be used.

[0091] As the halogenated epoxy compound, epichlorohydrin, epibromohydrin, and α-methylepichlorohydrin may be used. Meanwhile, examples of the monooxazolidinone, bisoxazolidinone, or polyoxazolidinone compound may include 2-oxazolidinone and the like.

[0092] As the alkylene carbonate compound, ethylene carbonate or the like can be used.

[0093] These compounds can be used alone or in combination.

[0094] The content of the surface crosslinking agent to be added can be appropriately and specifically selected according to the type of the surface crosslinking agent added or the reaction conditions, but the amount of the surface crosslinking agent used can generally be 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, relative to 100 parts by weight of the base polymer.

[0095] The method of adding the surface crosslinking agent to the base polymer powder is not limited in embodiment. For example, the surface crosslinking agent and the base polymer powder may be mixed in a reactor; the surface crosslinking agent may be sprayed onto the base polymer powder; or the base polymer powder and the surface crosslinking agent may be continuously supplied and mixed in a continuously operated mixer.

[0096] After adding the surface crosslinker, water and methanol can be further added after mixing. This has the advantage of uniformly dispersing the surface crosslinker throughout the base polymer powder. To achieve uniform dispersion of the surface crosslinker, prevent agglomeration of the base polymer powder, and optimize the surface penetration depth of the surface crosslinker, the amount of water and methanol added can be preferably controlled relative to 100 parts by weight of the base polymer powder.

[0097] The surface crosslinking reaction can be carried out by heating the base polymer powder to which a surface crosslinking agent has been added at a temperature of approximately 160°C or higher for approximately 20 minutes or longer. Specifically, to produce a superabsorbent polymer that more appropriately meets the physical properties of 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 longer at the maximum reaction temperature, or approximately 20 minutes or longer and 1 hour or shorter. Furthermore, the heating time required to raise the temperature 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 longer, or approximately 10 minutes or longer and approximately 1 hour or shorter. It has been confirmed that by meeting the surface crosslinking process conditions mentioned above, a superabsorbent polymer that appropriately meets the physical property requirements of one embodiment can be produced.

[0098] The means for raising the surface crosslinking reaction temperature are not particularly limited. Heating can be performed by providing a heating medium or directly providing a heat source. In this regard, suitable heating media may include steam, hot air, or a thermal fluid (such as hot oil), but the present invention is not limited thereto. The temperature of the heating medium to be provided can be appropriately selected based on the method of providing the heating medium, the heating rate, and the target temperature. Furthermore, as a directly provided heat source, an electric heater or a gas heater can be used, but the present invention is not limited to these examples.

[0099] The superabsorbent polymer obtained according to the above preparation method can exhibit very excellent properties, and its overall physical properties (such as water retention capacity and pressure absorption capacity, etc.) are also improved, which makes the superabsorbent polymer particularly suitable for subsequent incorporation into absorbent products.

[0100] absorbent products

[0101] The superabsorbent polymers of the present disclosure are incorporated into absorbent articles, such as absorbent cores contained within absorbent articles.

[0102] "Absorbent article" refers to devices that absorb and contain body exudates, especially urine and other aqueous liquids, and more specifically refers to devices that are placed against or adjacent to the wearer's body to absorb and contain the various exudates discharged from the body. Absorbent articles may include diapers (for infants and young children, as well as for incontinent adults), pants (for infants and young children, as well as for incontinent adults). As used herein, the term "exudates" includes, but is not limited to, urine, blood, vaginal discharge, sweat, and feces. Preferred absorbent articles of the present invention are disposable absorbent articles, more preferably disposable diapers, disposable pants, and disposable absorbent inserts.

[0103] As used herein, "absorbent core" refers to a structure intended to be positioned between the topsheet and the backsheet of an absorbent article for absorbing and storing liquids received by the absorbent article.

[0104] "Disposable" is used in its ordinary sense to refer to an article that is disposed of or discarded after a limited number of use events (e.g., less than 10 events, less than 5 events, or less than 2 events) over varying lengths of time. If the disposable absorbent article is a diaper, pants, absorbent insert, sanitary napkin, catamenial pad, or wet wipe for personal hygiene, the disposable absorbent article is generally intended to be discarded after a single use. The used and discarded absorbent article may or may not be subsequently recycled. As used herein, "absorbent article," "pants," and "diaper" also refer to disposable absorbent articles, disposable pants (and disposable absorbent pants), and disposable diapers.

[0105] "Diapers" and "pants" refer to absorbent articles typically worn by infants and incontinent individuals around the lower torso so as to encircle the wearer's waist and legs and are specifically adapted to receive and contain urine and feces. In pants, as used herein, the longitudinal edges of the first and second waist regions are attached to each other to pre-form a waist opening and leg openings. The pants are applied to the wearer by inserting the wearer's legs into the leg openings and pulling the pants absorbent article into position near the wearer's lower torso. Pants can be pre-formed using any suitable method, including but not limited to joining the various parts of the absorbent article together using refastenable and / or non-refastenable bonding (e.g., seams, welding, adhesives, cohesive bonds, fasteners, etc.). Pants can be pre-formed at any location along the periphery of the article (e.g., side fastening, front waist region fastening). In a diaper, the waist opening and leg openings are formed only when the diaper is applied to the wearer by (releasably) attaching the longitudinal edges of the first and second waist regions to each other on both sides using a suitable fastening system.

[0106] The absorbent articles may each comprise a top sheet, a back sheet, an absorbent core and an optional acquisition-distribution system. The absorbent core is placed between the back sheet and the top sheet, and the optional acquisition-distribution system is typically placed between the absorbent core and the top sheet.

[0107] The superabsorbent polymers disclosed herein can be incorporated into the absorbent core of an absorbent article. In addition to the superabsorbent polymer, the absorbent core may or may not contain other absorbent materials, such as non-crosslinked cellulose fibers (pulp fibers). The absorbent core may contain at least 60%, at least 75%, at least 85%, at least 95%, at least 98%, or 100% by mass of the superabsorbent polymer disclosed herein.

[0108] Diapers or pants may also include elasticized leg cuffs and barrier leg cuffs that improve the containment of liquids and other body exudates, particularly in the leg opening areas. Typically, the leg cuffs and barrier cuffs each include one or more elastic threads.

[0109] "Feminine care absorbent articles" are personal care products used by women to absorb and retain menstrual fluids, vaginal discharge, and substances from other bodily functions related to the vulva during menstruation. Feminine care absorbent articles include panty liners and sanitary napkins.

[0110] Hereinafter, preferred exemplary embodiments are provided for a better understanding of the present invention. However, the following exemplary embodiments are only used to illustrate the present invention, and it is obvious to those skilled in the art that various changes and modifications may be made without departing from the scope and spirit of the present invention as disclosed in the appended claims.

[0111] Example

[0112] <Preparation of Composition for Preparing Superabsorbent Polymer>

[0113] Example 1-1

[0114] 450 g of acrylic acid, 3 g of polyethylene glycol diacrylate 400, and 0.04 g of diphenyl(2,4,6-trimethylbenzoyl)phosphine oxide were mixed, and then 580 g of a 31.5% sodium hydroxide aqueous solution was added thereto to prepare an acrylic monomer composition.

[0115] 5g of ZrO2 beads were weighed as a grinding medium and placed in a 10mL vial. 12mg of polyvinylpyrrolidone (PVP, Aldrich PVP10, average molecular weight 10,000) was added as a dispersant, followed by 24mg of clay powder (bentonite, BYK OPTIGEL CK, particle size range 1µm to 5µm, average particle size 3µm). 4.7g of the acrylic monomer composition was added to the mixture and mixed using an oscillator (JEIO TECH SK-600) at 300 rpm for 4 hours to prepare a composition for preparing a superabsorbent polymer.

[0116] Examples 1-2 to 1-3 and Comparative Examples 1-1 to 1-4

[0117] The compositions for preparing superabsorbent polymers of Examples 1-2 to 1-3 and Comparative Examples 1-1 to 1-4 were prepared in the same manner as Example 1-1, except that the type of dispersant and the amount thereof were as shown in Table 1 below.

[0118] DISPERBYK-102 (BYK) used in Comparative Example 1-2 is a phosphate ester polymer, and Sokalan HP-20 (BASF) used in Comparative Example 1-3 is a polyethyleneimine polymer dispersant.

[0119] Table 1

[0120]

[0121] Experimental Example 1: Evaluation of physical properties of compositions for preparing superabsorbent polymers

[0122] The physical properties of the compositions for preparing super absorbent polymers of Examples 1-1 to 1-3 and Comparative Examples 1-1 to 1-4 were evaluated by the following methods, respectively. The results are shown in Table 2.

[0123] (1) Sedimentation rate

[0124] The sedimentation rate of the 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 and particle size analyzer.

[0125] Specifically, 1.6 mL of the composition used to prepare a superabsorbent polymer was placed in a 10 mm PC cuvette, then mounted on a LUMiSizer instrument. Transmittance data was measured at 400 points every 10 seconds at 25°C and 1,500 rpm (approximately 280 G). A threshold of 21% was set for the measured transmittance data, and the sedimentation rate was calculated.

[0126] (2) Dispersion stability after 48 hours

[0127] 4 g of each of the compositions for preparing superabsorbent polymers from Examples 2-1 to 2-3 and Comparative Examples 2-1 to 2-4 were placed in 10 ml vials. The vials were placed in a vial rack and left at 25°C for 48 hours. The supernatant was then visually inspected for separation. If separation occurred, the dispersion stability was evaluated as absent (X); if no separation occurred, the dispersion stability was evaluated as present (O).

[0128] Table 2

[0129]

[0130] As shown in Table 2, 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 a PVP dispersant per 100 parts by weight of clay was added, did not result in satisfactory clay sedimentation. However, excellent dispersion stability was confirmed even after 48 hours.

[0131] <Preparation of Clay Dispersion and Superabsorbent Polymer Using Clay Dispersion>

[0132] Example 2-1

[0133] (1) Preparation of 4 wt% clay dispersion

[0134] To a flask, add 2g of clay (bentonite, BYK OPTIGEL CK, particle size range 1µm to 5µm, average particle size 3µm) and 1g (50 parts by weight per 100 parts by weight of clay) of polyvinylpyrrolidone (Aldrich PVP10, average molecular weight 10,000) as a polymer dispersant. Water is then added to bring the total weight of the mixture to 50g. This mixture is stirred at 500 rpm with a magnetic stirrer for 12 hours to produce a 4% by weight clay dispersion.

[0135] (2) Preparation of superabsorbent polymer

[0136] In a 3 L glass container, 450 g of acrylic acid (AA), 3 g of polyethylene glycol diacrylate 400 (PEGDA 400), and 0.04 g of diphenyl (2,4,6-tribenzoyl) phosphine oxide were placed and dissolved, and then 580 g of a 31.5% sodium hydroxide aqueous solution was added to prepare an acrylic monomer composition.

[0137] 4 wt% of the clay dispersion prepared in (1) was added to a monomer composition so that the clay content was 0.5 parts by weight relative to 100 parts by weight of acrylic acid, and 0.1 parts by weight of sodium bicarbonate (SBC) as a carbonate-based foaming agent was added relative to 100 parts by weight of acrylic acid to prepare a composition for preparing a superabsorbent polymer.

[0138] 1000 g of the composition for preparing superabsorbent polymer was poured into a stainless steel container with a width of 250 mm, a length of 250 mm and a height of 30 mm, and the container was irradiated with ultraviolet light (radiation dose of 10 mV / cm 2 ) was subjected to UV polymerization for 90 seconds to obtain a hydrogel polymer.

[0139] The resulting sheet-shaped hydrogel polymer was then fed into a meat grinder to obtain a hydrogel particle powder. This powder was then dried in an oven, resulting in a dry product with a moisture content of 1% or less. The dried particles were then pulverized and classified in a pulverizer to produce a base polymer having a particle size of 150 to 850 μm.

[0140] 6 g of an aqueous surface crosslinking agent solution containing 3 g of ethylene carbonate was sprayed onto 100 g of base polymer powder and stirred at room temperature to evenly distribute the surface crosslinking solution throughout the base polymer powder. The base polymer powder mixed with the surface crosslinking solution was then placed in a surface crosslinking reactor. The reactor was heated to 190°C and maintained for 30 minutes, followed by a surface crosslinking reaction at the same temperature for 15 minutes.

[0141] After the surface cross-linking process is completed, the powder is classified using a standard sieve that meets ASTM standards to produce a superabsorbent polymer with a particle size of 150µm to 850µm.

[0142] Examples 2-2 to 2-3 and Comparative Examples 2-1 to 2-3

[0143] Each clay dispersion was prepared in the same manner as in Example 2-1 (1), except that the types and contents of clay and dispersant were adjusted when preparing the clay dispersion (as shown in Table 3 below). Subsequently, 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).

[0144] Table 3

[0145]

[0146] Experimental Example 2: Evaluation of physical properties of superabsorbent polymers

[0147] The physical properties of the superabsorbent polymers of Examples 2-1 to 2-3 and Comparative Examples 2-1 to 2-3 were evaluated by the following methods, respectively. The results are shown in Table 4.

[0148] (1) Effective absorption capacity (EFFC)

[0149] The EFFC value is calculated according to the following formula.

[0150] EFFC = 1 / 2 (CRC+AUP)

[0151] In this formula, CRC and AUP are measured by the following method.

[0152] a) Measure centrifuge retention capacity (CRC)

[0153] The CRC of superabsorbent polymers is measured according to EDANA method WSP 241.2.

[0154] Specifically, from the polymers obtained in the Examples and Comparative Examples, polymers fractionated with a #30-50 sieve were obtained. Approximately 0.2 g of this superabsorbent polymer (W0 (g)) was evenly placed in a nonwoven bag, which was then sealed and immersed in physiological saline (0.9% by weight) at room temperature. After 30 minutes, the bag was drained using a centrifuge at 250 g for 3 minutes, and the bag's weight (W2 (g)) was measured. Furthermore, the same procedure was repeated without the polymer, and the weight (W1 (g)) was measured.

[0155] CRC (g / g) was calculated using the obtained weight according to the following formula.

[0156] CRC (g / g) = {[W2(g) - W1(g)] / W0(g)} – 1

[0157] b) Measurement of Absorption Under Pressure (AUP)

[0158] The AUP of superabsorbent polymer at 0.7 psi is measured according to EDANA method WSP 242.2.

[0159] First, when measuring the pressure absorption capacity, the same fractionated polymers used when measuring the CRC were used.

[0160] Specifically, a 400-mesh stainless steel mesh was attached to the bottom of a plastic cylinder with an inner diameter of 60 mm. At room temperature and 50% humidity, 0.90 g of superabsorbent polymer (W0) was evenly spread over the mesh. A piston with an outer diameter slightly smaller than 60 mm, capable of applying a uniform load of 0.7 psi, was placed on the cylinder. There was no gap between the piston and the inner wall of the cylinder, and the cylinder was able to move without any binding. The weight of the device, W4 (g), was then measured.

[0161] A glass filter with a diameter of 90 mm and a thickness of 5 mm was placed in a 150 mm diameter Petri dish. A physiological saline solution containing 0.9 wt% sodium chloride was then poured in until the liquid level reached the top of the glass filter. A piece of filter paper with a diameter of 90 mm was placed on the glass filter. A measuring device was attached to the filter paper, and the liquid was absorbed under load for one hour. After one hour, the measuring device was lifted and the weight (W5 g) was measured.

[0162] AUP (g / g) was calculated using the obtained weight according to the following formula.

[0163] AUP(g / g) = [W5(g) – W4(g)] / W3(g)

[0164] (2) Color b

[0165] The color b value of the superabsorbent polymer was measured according to ASTM D2985 standard.

[0166] Table 4

[0167]

[0168] As shown in Table 4, in Comparative Example 2-1, since no dispersant was added, the dispersion stability of the clay was reduced, resulting in a significant decrease in the EFFC value.

[0169] On the other hand, when comparing Examples 2-1 to 2-3 with Comparative Examples 2-2 and 2-3 (each of which used a combination of a clay dispersion containing a dispersant and clay), it was found that Comparative Examples 2-2 and 2-3 using Sokalan HP-20 as a dispersant had higher color b values ​​than Examples 2-1 to 2-3 using PVP.

[0170] These results confirm that the clay dispersion of the present invention can improve the absorption characteristics of the superabsorbent polymer produced due to the excellent dispersion stability of the clay in the composition used to produce the superabsorbent polymer. It was also confirmed that the clay dispersion of the present invention does not cause discoloration of the superabsorbent polymer when used in the composition, and is therefore suitable for producing high-quality products.

[0171] The dimensions and values ​​disclosed herein should not be understood as being strictly limited to the exact numerical values ​​recited. Instead, unless otherwise indicated, each such dimension is intended to mean both the recited value and a functionally equivalent range encompassing that value. For example, a dimension disclosed as "40 mm" is intended to mean "approximately 40 mm."

[0172] Unless expressly excluded or otherwise limited, each document cited herein, including any cross-referenced or related patent or application, is hereby incorporated by reference in its entirety. The citation of any document is not an admission that it is prior art with respect to any of the present inventions disclosed or claimed herein, or that it, by itself or in combination with any one or more of the references, proposes, suggests, or discloses any such invention. Further, 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 a document incorporated by reference, the meaning or definition assigned to that term in this document shall govern.

[0173] Although 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 may be made without departing from the spirit and scope of the invention. It is therefore intended that all such changes and modifications within the scope of the invention be encompassed in the appended claims.

Claims

1. A method of making an absorbent article comprising a superabsorbent polymer, wherein the superabsorbent polymer is prepared by using a clay dispersion comprising: Solvents, Clay and a polymer dispersant comprising two or more functional groups selected from the group consisting of an amine group, a carbonyl group, and a hydroxyl group, in, The polymer dispersant is added in an amount of more than 20 parts by weight to no more than 200 parts by weight relative to 100 parts by weight of the clay.

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

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

4. A method according to any one of the preceding claims, wherein the clay has an average particle size of 0.025 µm to 10 µm.

5. A method according to any one of the preceding claims, wherein In the clay composition, the polymer dispersant comprises an amine group and a carbonyl group.

6. A method according to any one of the preceding claims, wherein In the clay composition, the polymer dispersant is one or more substances selected from the group consisting of polyvinyl pyrrolidone, polyacrylamide, N-acetyl polyimine and polyaminoacrylate.

7. The method according to any one of the preceding claims, wherein the method comprises the further step of incorporating the superabsorbent polymer into the absorbent article.

8. A method of making an absorbent article comprising a superabsorbent polymer, wherein the superabsorbent polymer is prepared by using a composition comprising a clay dispersion, a water-soluble ethylenically unsaturated monomer, an alkali metal salt or a basic compound capable of neutralizing the water-soluble ethylenically unsaturated monomer, and a polymerization initiator; wherein the clay dispersion comprises Solvents, Clay and a polymer dispersant comprising two or more functional groups selected from the group consisting of an amine group, a carbonyl group, and a hydroxyl group, in, The polymer dispersant is added in an amount of more than 20 parts by weight to no more than 200 parts by weight relative to 100 parts by weight of the clay.

9. The method according to claim 8, wherein In the composition, the clay has a sedimentation rate of 100 μm / s or less.

10. The method according to claim 8 or 9, wherein: In the composition, the water-soluble ethylenically unsaturated monomer is one or more substances selected from the group consisting of 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 salts thereof; Nonionic hydrophilic monomers such as (meth)acrylamide, N-substituted (meth)acrylates, 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, methoxypolyethylene glycol (meth)acrylate, or polyethylene glycol (meth)acrylate; and Unsaturated monomers containing amino groups, such as (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 In the composition, the clay is included in an amount of 0.1 to 1 parts by weight relative to 100 parts by weight of the ethylenically unsaturated monomer.

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

13. A method of making an absorbent article comprising a superabsorbent polymer, the method comprising the steps of: preparing a hydrogel polymer by polymerizing the composition for preparing a superabsorbent polymer according to claim 7 by heating and / or irradiating light; preparing a base polymer by drying and pulverizing the hydrogel polymer; and The surface of the base polymer is further cross-linked in the presence of a surface cross-linking agent to form a surface cross-linked layer. The method further comprises the step of incorporating the superabsorbent polymer into an absorbent article.

14. The method of claim 13, wherein the absorbent article is a diaper or a pant.

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

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

17. The method according to claim 15 or 16, wherein the absorbent core 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 between the two layers of nonwoven web.

18. The method according to claim 16 or 17, wherein the method comprises The additional step of adhesively securing the superabsorbent polymer between the two layers of nonwoven web.

19. The method according to any one of claims 15 to 18, wherein the method comprises the following additional steps: - Top sheet provided - Provide negatives - providing the absorbent core between the topsheet and the backsheet.

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