Method for preparing super absorbent polymer

Abstract

The present invention relates to a method for manufacturing a superabsorbent resin, and more specifically, to a method for manufacturing a superabsorbent resin that can more productively produce a superabsorbent resin capable of simultaneously achieving excellent absorption performance and appropriate gel stability by using a combination of specific additives in the crosslinking polymerization step and the surface crosslinking step, respectively.

Description

Technology Field

[0001] The present invention relates to a method for manufacturing a superabsorbent resin, and more specifically, to a method for manufacturing a superabsorbent resin that can more productively produce a superabsorbent resin capable of simultaneously achieving excellent absorption performance and appropriate gel stability by using a combination of specific additives in the crosslinking polymerization step and the surface crosslinking step, respectively. Background Technology

[0003] Super Absorbent Polymer (SAP) is a synthetic polymer material capable of absorbing 500 to 1,000 times its own weight in moisture, and developers name it by different names such as SAM (Super Absorbency Material) and AGM (Absorbent Gel Material). The above-mentioned super absorbent polymer began to be commercialized for sanitary devices, and is now widely used as a material for horticultural soil conditioners, waterproofing materials for civil engineering and construction, seedling sheets, freshness preservation agents in the food distribution sector, and for compresses, in addition to sanitary products such as children's disposable diapers.

[0004] In most cases, these superabsorbent polymers are widely used in the field of hygiene products, such as diapers and sanitary pads. For these applications, it is necessary to exhibit high absorption capacity for moisture, excellent pressure-resistant absorption performance that prevents absorbed moisture from escaping even under external pressure, and excellent permeability that maintains its shape well even when swollen after absorbing water.

[0005] In addition, when the aforementioned superabsorbent polymer is incorporated into hygiene materials such as diapers, it is necessary to diffuse urine and other fluids as widely as possible even in an environment where they are pressurized by the user's body weight. Through this, the absorption performance and absorption speed of the hygiene material can be further improved by fully utilizing the superabsorbent polymer particles contained across the entire surface area of ​​the absorbent layer of the hygiene material. Furthermore, due to these diffusion characteristics under pressure, the rewetting properties of the diaper, which prevent urine and other fluids that have been absorbed by the superabsorbent polymer from leaking out again, can be further enhanced, and the leakage prevention properties of the diaper can also be improved.

[0006] Previously, attempts were made to improve the properties of widely dispersing urine and other fluids by modifying the design of hygiene products, such as diapers. For instance, methods to improve the diffusion characteristics of urine and fluids have been attempted, such as introducing an Acquisition Distribution Layer (ADL) into the hygiene product or utilizing absorption channels. However, the improvement in diffusion characteristics resulting from such design changes to the hygiene product itself was insufficient.

[0007] Meanwhile, when used in actual hygiene products, the polymer chains within the superabsorbent resin are destroyed by components such as ascorbic acid present in urine. Consequently, as the wearing time increases, the mechanical properties of the resin, specifically gel stability, significantly deteriorate, leading to a problem where other properties also deteriorate. Therefore, considering the actual usage conditions of the product, research is needed to manufacture a superabsorbent resin capable of achieving appropriate gel stability while maintaining excellent existing absorption properties. The problem to be solved

[0009] Accordingly, the present invention aims to provide a method for manufacturing a superabsorbent resin that can more productively produce a superabsorbent resin capable of simultaneously achieving excellent absorption performance and appropriate gel stability by using a combination of specific additives in the crosslinking polymerization step and the surface crosslinking step. means of solving the problem

[0011] In order to solve the above problem, the present invention,

[0012] A step of obtaining a hydrogel polymer by crosslinking a water-soluble ethylene-based unsaturated monomer having at least some neutralized acidic groups and a chelating agent in the presence of an internal crosslinking agent;

[0013] A step of drying, grinding, and classifying the above-mentioned hydrogel polymer to form a base resin powder; and

[0014] A method for manufacturing a superabsorbent resin is provided, comprising the step of crosslinking the surface of a base resin powder by mixing a surface crosslinking solution containing water-dispersible silica and a surface crosslinking agent with the base resin powder. Effects of the invention

[0016] According to the method for manufacturing a superabsorbent resin of the present invention, a superabsorbent resin can be manufactured that has excellent absorption performance and, when actually applied to sanitary materials, etc., can achieve excellent gel stability even after being left in sanitary water such as urine for a long time. Specific details for implementing the invention

[0018] The terms used in this specification are used merely to describe exemplary embodiments and are not intended to limit the invention.

[0019] The singular expression includes the plural expression unless the context clearly indicates otherwise. In this specification, terms such as “comprising,” “comprising,” or “having” are intended to specify the existence of the implemented features, steps, components, or combinations thereof, and should be understood as not precluding the existence or addition of one or more other features, steps, components, or combinations thereof.

[0020] Terms such as first, second, third, etc. are used to describe various components, and these terms are used solely for the purpose of distinguishing one component from another.

[0021] The present invention is capable of various modifications and may take various forms, and specific embodiments are illustrated and described in detail below. However, this is not intended to limit the invention to the specific disclosed forms, and it should be understood that the invention includes all modifications, equivalents, and substitutions that fall within the spirit and scope of the invention.

[0022] The terms "polymer" or "polymer" used in this specification refer to a state in which water-soluble ethylene-based unsaturated monomers are polymerized, and may encompass all ranges of moisture content or particle size. Among the polymers, a polymer having a moisture content (water content) of about 40 weight% or more in the state before drying after polymerization may be referred to as a hydrogel polymer, and particles obtained by grinding and drying such hydrogel polymers may be referred to as a cross-linked polymer.

[0023] In addition, the term "superabsorbent resin powder" refers to a particulate material comprising a cross-linked polymer in which a water-soluble ethylene-based unsaturated monomer containing an acidic group and at least some of the acidic group is neutralized is polymerized and cross-linked by an internal cross-linking agent.

[0024] Additionally, depending on the context, the term "superabsorbent resin" is used to encompass a cross-linked polymer in which a water-soluble ethylene-based unsaturated monomer containing acidic groups and at least some of the acidic groups are neutralized, or a base resin in the form of a powder made of superabsorbent resin particles formed by grinding the cross-linked polymer, or a cross-linked polymer or base resin made into a state suitable for commercialization through additional processes, such as surface crosslinking, fine powder reassembly, drying, grinding, classification, etc.

[0025] The term "internal crosslinking agent" used in this specification is used to distinguish it from "surface crosslinking agent" used to crosslink the surface of the base resin, and it serves to polymerize by crosslinking the unsaturated bonds of the water-soluble ethylene-based unsaturated monomers described above. Although the crosslinking in the above step proceeds without distinction between the surface and the interior, through the surface crosslinking process of the base resin described later, the surface of the particles of the finally manufactured superabsorbent resin is formed with a structure crosslinked by the surface crosslinking agent, and the interior is formed with a structure crosslinked by the internal crosslinking agent.

[0026] The term "crosslinked polymer" as used in this specification means that the water-soluble ethylene-based unsaturated monomer is crosslinked polymerized in the presence of an internal crosslinking agent, and the term "base resin powder" means a material containing such a crosslinked polymer.

[0028] When superabsorbent polymers are actually used as hygiene materials, they may remain in a swollen state for a long time in urine, body fluids, etc. In this case, the ascorbic acid component in urine or body fluids promotes the action of residual radicals within the polymer, causing the polymer chains to break down. Consequently, there was a problem in that the gel stability of the resin significantly decreased as the wearing time in the swollen state increased. As a result, various absorption properties also deteriorated due to changes in the internal structure.

[0029] Accordingly, the inventors confirmed that when manufacturing a superabsorbent resin using specific additives in the cross-linking polymerization step and the surface cross-linking step, respectively, in order to maximize the interaction effects of the superabsorbent resin particles along with their respective physical properties, while considering the actual product usage conditions, it is possible to achieve excellent gel stability while maintaining the existing absorption properties, and thus completed the present invention.

[0030] Specifically, a chelating agent is used during the cross-linking polymerization stage to suppress the decrease in frictional force caused by water-soluble components released due to the breakdown of polymer chains, and at the same time, water-dispersible silica is used during the surface cross-linking stage to re-adsorb the released water-soluble components onto the surface, thereby improving the frictional force between particles. Accordingly, excellent gel stability is achieved while maintaining excellent absorption properties such as centrifugal retention capacity, absorption capacity under pressure, permeability, and absorption rate.

[0032] Hereinafter, a method for manufacturing a superabsorbent resin according to a specific embodiment of the invention will be described in more detail step by step.

[0034] First, a method for manufacturing a superabsorbent resin according to one embodiment of the invention comprises the step of crosslinking a water-soluble ethylene-based unsaturated monomer having at least some neutralized acidic groups and a chelating agent in the presence of an internal crosslinking agent to obtain a hydrogel polymer.

[0035] The above cross-linking polymerization step may be performed by cross-linking polymerization of a monomer composition containing, in addition to the aforementioned components, components generally used in the manufacture of superabsorbent resins.

[0037] First, a chelating agent is used in the cross-linking polymerization step, and the chelating agent introduces a novel cross-linking structure into the polymer during the polymerization process. Accordingly, the increase in the content of water-soluble components under actual urine or body fluid conditions of the superabsorbent resin produced can be suppressed, thereby enabling the simultaneous realization of excellent absorption properties and high gel strength. In particular, together with water-dispersible silica included in the surface cross-linking step, it is possible to effectively control the problem of reduced frictional force due to the increase in the content of water-soluble components.

[0038] Specifically, the chelating agent may be one or more selected from the group consisting of ethylenediaminetetraacetic acid, diethylenetriaminepentaacetic acid, diethylenetriaminepentaethylenephosphonic acid, oxalic acid, citric acid, and salts thereof, and preferably, ethylenediaminetetraacetic acid, diethylenetriaminepentaacetic acid, citric acid, and salts thereof may be used.

[0039] The content of the above chelating agent is not particularly limited, but, for example, is included in an amount of 100 ppmw to 10,000 ppmw with respect to the weight of the water-soluble ethylene-based unsaturated monomer, and preferably, is included in an amount of 500 ppmw to 5,000 ppmw or 500 ppmw to 2,000 ppmw. When included within the above content range, it is suitable for realizing the aforementioned effect.

[0041] The above-mentioned water-soluble ethylene-based unsaturated monomer may be any monomer commonly used in the manufacture of superabsorbent resins. As a non-limiting example, the above-mentioned water-soluble ethylene-based unsaturated monomer may be a compound represented by the following chemical formula 1:

[0042] [Chemical Formula 1]

[0043] R1-COOM 1

[0044] In the above chemical formula 1,

[0045] R1 is an alkyl group having 2 to 5 carbon atoms containing unsaturated bonds, and

[0046] M 1 is a hydrogen atom, a monovalent or divalent metal, an ammonium group, or an organic amine salt.

[0047] Preferably, the monomer may be one or more selected from the group consisting of acrylic acid, methacrylic acid, and monovalent metal salts, divalent metal salts, ammonium salts, and organic amine salts of these acids. It is advantageous to use acrylic acid or its salts as water-soluble ethylene-based unsaturated monomers in this way, as it is possible to obtain a superabsorbent resin with improved absorbency. In addition, the monomer may be anionic monomers of 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 salts thereof; One or more selected from the group consisting of (meth)acrylamide, N-substituted (meth)acrylate, 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, methoxypolyethylene glycol (meth)acrylate, or polyethylene glycol (meth)acrylate; nonionic hydrophilic containing monomers of (meth)acrylate; and amino group containing unsaturated monomers of (N,N)-dimethylaminoethyl (meth)acrylate or (N,N)-dimethylaminopropyl (meth)acrylamide and their quaternaries may be used.

[0048] Here, the water-soluble ethylene-based unsaturated monomer has an acidic group, and at least a portion of the acidic group is neutralized. Preferably, the monomer may be used after being partially neutralized with an alkaline substance such as sodium hydroxide, potassium hydroxide, ammonium hydroxide, etc.

[0049] At this time, the degree of neutralization of the monomer may be 40 to 95 mol%, or 40 to 80 mol%, or 45 to 75 mol%. The range of the degree of neutralization may vary depending on the final physical properties, but if the degree of neutralization is excessively high, the neutralized monomer may precipitate, making it difficult for polymerization to proceed smoothly; conversely, if the degree of neutralization is excessively low, not only is the absorbency of the polymer significantly reduced, but it may also exhibit properties such as elastic rubber that are difficult to handle.

[0051] In the superabsorbent resin of the above embodiment, the hydrogel polymer may be a polymer in which the monomer is cross-linked in the presence of one or more internal cross-linking agents selected from the group consisting of bis(meth)acrylamide having 8 to 12 carbon atoms, poly(meth)acrylate of a polyol having 2 to 10 carbon atoms, and poly(meth)allyl ether of a polyol having 2 to 10 carbon atoms.

[0052] Any compound that enables the introduction of crosslinking bonds during the polymerization of the above-mentioned water-soluble ethylene-based unsaturated monomer can be used as the above-mentioned internal crosslinking agent. As a non-limiting example, the internal crosslinking agent is N,N'-methylenebisacrylamide, trimethylolpropane tri(meth)acrylate, ethylene glycol di(meth)acrylate, polyethylene glycol (meth)acrylate, polyethylene glycol di(meth)acrylate, propylene 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, triarylamine, ethylene glycol diglycidyl ether, propylene Polyfunctional crosslinking agents such as glycol, glycerin, or ethylene carbonate may be used alone or in combination of two or more, but are not limited thereto. Preferably, among these, ethylene glycol diglycidyl ether may be used.

[0053] In the above monomer composition, such an internal crosslinking agent may be used in an amount of 0.0001 to 5 parts by weight per 100 parts by weight of the water-soluble ethylene-based unsaturated monomer. For example, the internal crosslinking agent may be used in an amount of 0.001 parts by weight or more, 0.005 parts by weight or more, 0.01 parts by weight or more, or 0.45 parts by weight or more, and 5 parts by weight or less, 3 parts by weight or less, 2 parts by weight or less, 1 part by weight or less, or 0.7 parts by weight or less, relative to 100 parts by weight of the water-soluble ethylene-based unsaturated monomer. By doing so, the degree of internal crosslinking of the hydrogel polymer and the base resin powder is controlled, thereby optimizing the absorption performance and permeability of the superabsorbent resin. However, if the content of the internal crosslinking agent becomes excessively large, the basic absorption performance of the superabsorbent resin may be reduced.

[0055] In the above cross-linking polymerization step, a polymerization initiator commonly used in the manufacture of superabsorbent resins may be included. As a non-limiting example, depending on the polymerization method, a thermal polymerization initiator or a photopolymerization initiator may be used as the polymerization initiator, and in particular, a thermal polymerization initiator may be used. However, even in the photopolymerization method, a certain amount of heat is generated by ultraviolet irradiation, and since a certain amount of heat is also generated as the polymerization reaction, which is an exothermic reaction, proceeds, a thermal polymerization initiator may be additionally included.

[0056] As the above thermal polymerization initiator, one or more compounds selected from the group consisting of persulfate-based initiators, azo-based initiators, hydrogen peroxide, and ascorbic acid may be used. Specifically, examples of persulfate-based initiators include sodium persulfate (Na2S2O8), potassium persulfate (K2S2O8), and ammonium persulfate ((NH4)2S2O8). In addition, azo-based initiators include 2,2-azobis-(2-amidinopropane) dihydrochloride, 2,2-azobis-(N,N-dimethylene)isobutyramidine dihydrochloride, 2-(carbamoylazo)isobutylonitril, 2,2-azobis[2-(2-imidazolin-2-yl)propane] dihydrochloride, and 4,4-azobis-(4-cyanovaleric Examples include acid (4,4-azobis-(4-cyanovaleric acid)). A wider variety of thermal polymerization initiators are disclosed on page 203 of Odian's book "Principles of Polymerization" (Wiley, 1981), which can be referenced.

[0057] As the above photopolymerization initiator, for example, one or more compounds selected from the group consisting of benzoin ether, dialkyl acetophenone, hydroxyl alkyl ketone, phenyl glyoxylate, benzyl dimethyl ketal, acyl phosphine, and α-aminoketone may be used. Among these, specific examples of acyl phosphine include diphenyl(2,4,6-trimethylbenzoyl)phosphine oxide, phenylbis(2,4,6-trimethylbenzoyl)phosphine oxide, ethyl(2,4,6-trimethylbenzoyl)phenylphosphineate, etc. A wider variety of photoinitiators is well described in Reinhold Schwalm's book "UV Coatings: Basics, Recent Developments and New Applications" (Elsevier 2007), p. 115, and is not limited to the examples described above.

[0058] Such a polymerization initiator may be added to a monomer composition containing the above-mentioned water-soluble ethylene-based unsaturated monomer at a concentration of about 0.001 to 1 weight%. That is, if the concentration of the polymerization initiator is excessively low, the polymerization rate may be slowed down and a large amount of residual monomer may be extracted into the final product, which is undesirable. Conversely, if the concentration of the polymerization initiator is higher than the above range, the polymer chains forming the network become shorter, which may lead to a higher content of water-soluble components and a lower pressurized absorption capacity, and thus the physical properties of the resin may deteriorate, which is undesirable.

[0060] In addition, the above monomer composition may further include additives such as foaming agents, surfactants, thickeners, plasticizers, preservative stabilizers, and antioxidants as needed.

[0062] The above foaming agent plays a role in increasing the surface area by forming pores within the hydrogel polymer through foaming during polymerization. The above foaming agent may be a carbonate, and for example, sodium bicarbonate, sodium carbonate, potassium bicarbonate, potassium carbonate, calcium bicarbonate, calcium bicarbonate, magnesium bicarbonate, or magnesium carbonate may be used.

[0063] In addition, it is preferable to use the blowing agent at a concentration of 1,500 ppmw or less relative to the weight of the water-soluble ethylene-based unsaturated monomer. If the amount of the blowing agent used exceeds 1,500 ppmw, the pores become too numerous, which may cause the gel strength of the superabsorbent resin to decrease and the density to decrease, potentially leading to problems with distribution and storage. Furthermore, it is preferable to use the blowing agent at a concentration of 500 ppmw or more, or 1,000 ppmw or more, relative to the weight of the water-soluble ethylene-based unsaturated monomer.

[0065] In addition, the surfactant induces uniform dispersion of the foaming agent, thereby preventing a decrease in gel strength or density due to uniform foaming during foaming. It is preferable to use an anionic surfactant as the surfactant. Specifically, the surfactant is SO3 - Compounds containing anions and represented by the following chemical formula 2 may be used.

[0066] [Chemical Formula 2]

[0067] R-SO3Na

[0068] In the above chemical formula 2,

[0069] R is an alkyl having 8 to 16 carbon atoms.

[0070] In addition, it is preferable to use the surfactant at a concentration of 300 ppmw or less relative to the weight of the water-soluble ethylene-based unsaturated monomer. If the amount of the surfactant used exceeds 300 ppmw, the surfactant content in the superabsorbent resin becomes excessive, which is undesirable. Furthermore, it is preferable to use the surfactant at a concentration of 100 ppmw or more, or 150 ppmw or more, relative to the weight of the water-soluble ethylene-based unsaturated monomer.

[0072] In addition, such a monomer composition can be prepared in the form of a solution in which raw materials such as the aforementioned monomer, polymerization initiator, and internal crosslinking agent are dissolved in a solvent.

[0073] As for the solvent that can be used at this time, any solvent capable of dissolving the aforementioned raw materials may be used without limitation in its composition. For example, the solvent may be 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, N,N-dimethylacetamide, or a mixture thereof.

[0075] Furthermore, the formation of a hydrogel-like polymer through the polymerization of the above monomer composition can be carried out by conventional polymerization methods, and the process is not particularly limited. As a non-limiting example, the polymerization method is broadly divided into thermal polymerization and photopolymerization depending on the type of polymerization energy source; when thermal polymerization is carried out, it can be performed in a reactor equipped with a stirring shaft such as a kneader, and when photopolymerization is carried out, it can be carried out in a reactor equipped with a movable conveyor belt.

[0076] For example, a hydrated gel polymer can be obtained by introducing the monomer composition into a reactor, such as a kneader equipped with a stirring shaft, and then supplying hot air or heating the reactor to perform thermal polymerization. At this time, depending on the shape of the stirring shaft equipped in the reactor, the hydrated gel polymer discharged through the reactor outlet can be obtained as particles ranging from several millimeters to several centimeters. Specifically, the obtained hydrated gel polymer can be obtained in various forms depending on the concentration and injection speed of the injected monomer composition, and typically, a hydrated gel polymer with a (weight average) particle size of 2 to 50 mm can be obtained.

[0077] In addition, as another example, when photopolymerization of the monomer composition is carried out in a reactor equipped with a movable conveyor belt, a sheet-shaped hydrogel polymer can be obtained. In this case, the thickness of the sheet may vary depending on the concentration and injection speed of the injected monomer composition, but in order to ensure that the entire sheet is polymerized evenly while also securing the production speed, it is generally preferable to control the thickness to 0.5 to 5 cm.

[0079] According to one embodiment of the invention, the crosslinking polymerization step may be performed at a temperature of 10°C to 140°C, and preferably at a temperature of 70°C to 130°C or 70°C to 120°C. When performed within the above temperature range, it is suitable for achieving an appropriate crosslinking density achieved by the chelating agent of the present invention.

[0081] The moisture content of the hydrogel polymer obtained by the above method may typically be 30 to 80 weight%. Meanwhile, "moisture content" refers to the amount of water contained in the total weight of the hydrogel polymer, calculated by subtracting the weight of the polymer in a dry state from the weight of the hydrogel polymer. Specifically, it is defined as a value calculated by measuring the weight loss due to the evaporation of water within the polymer during the drying process, in which the temperature of the polymer is raised by infrared heating. At this time, the moisture content is measured by maintaining the drying conditions at approximately 180°C for about 40 minutes at room temperature.

[0083] Next, a method for manufacturing a superabsorbent resin according to one embodiment of the invention comprises the step of drying, grinding, and classifying a manufactured hydrogel polymer to form a base resin powder.

[0085] Specifically, a step of drying the obtained hydrogel polymer is performed. If necessary, to increase the efficiency of the drying step, an additional step of coarsely grinding the hydrogel polymer before drying may be performed.

[0086] The grinder used is not limited in its configuration, but specifically, it may include any one selected from the group of grinding machines consisting of a vertical pulverizer, a turbo cutter, a turbo grinder, a rotary cutter mill, a cutter mill, a disc mill, a shred crusher, a crusher, a chopper, and a disc cutter, but is not limited to the examples described above.

[0087] At this time, the coarse grinding step can be performed to grind the water gel polymer to a particle size of 2 to 10 mm. Grinding to a particle size of less than 2 mm is not technically easy due to the high water content of the water gel polymer, and aggregation may occur between the ground particles. On the other hand, if the particle size is ground to more than 10 mm, the effect of increasing the efficiency of the subsequent drying step may be negligible.

[0089] Drying is performed on the hydrogel polymer immediately after polymerization, which has been coarsely ground as described above or has not undergone a coarse grinding step. At this time, the drying temperature of the drying step may be 150°C to 250°C. If the drying temperature is below 150°C, the drying time becomes excessively long, and there is a risk that the physical properties of the finally formed superabsorbent resin will deteriorate. If the drying temperature exceeds 250°C, only the surface of the polymer is dried excessively, which may result in the generation of fine powder during the subsequent grinding process and a risk that the physical properties of the finally formed superabsorbent resin will deteriorate. Therefore, preferably, the drying may be carried out at a temperature of 150°C to 200°C, and more preferably at a temperature of 170°C to 195°C. The drying may be performed in multiple stages by varying the temperature within the above temperature range.

[0090] Meanwhile, regarding the drying time, it may be carried out for 20 to 90 minutes, taking into account process efficiency, but is not limited to this.

[0091] The drying method of the above drying step can also be selected and used without limitation on its composition, as long as it is a method commonly used for drying hydrogel polymers. Specifically, the drying step can be carried out by methods such as hot air supply, infrared irradiation, microwave irradiation, or ultraviolet irradiation. The moisture content of the polymer after such a drying step may be about 0.1 weight% to about 10 weight%.

[0093] Next, a step of grinding the dried polymer obtained through such a drying step is performed.

[0094] The polymer powder obtained after the grinding step may have a particle size of 150 μm to 850 μm. Specifically, the grinder used to grind to such a particle size may be a rotary cutter mill, a pin mill, a hammer mill, a screw mill, a roll mill, a disc mill, or a jog mill, but is not limited to the examples described above.

[0095] In addition, to manage the physical properties of the superabsorbent resin powder that is finalized after such a grinding step, a separate process may be performed to classify the polymer powder obtained after grinding according to particle size. Preferably, polymers with particle sizes of 150 μm to 850 μm may be classified, and only polymer powders with such particle sizes may undergo a surface crosslinking reaction step to be produced. More specifically, the base resin powder that has undergone the classification may have a particle size of 150 μm to 850 μm, may contain 50 weight% or more of particles with a particle size of 300 μm to 600 μm, and may contain less than 3 weight% of fine powder with a particle size of less than 150 μm.

[0097] Meanwhile, after manufacturing the base resin powder through the classification process described above, a surface crosslinking solution containing water-dispersible silica and a surface crosslinking agent is mixed with the base resin powder to perform a step of crosslinking the surface of the base resin powder.

[0098] The above surface crosslinking step induces a crosslinking reaction on the surface of the base resin powder in the presence of a surface crosslinking solution, so that the unsaturated bonds of the water-soluble ethylene-based unsaturated monomers remaining on the surface without being crosslinked are crosslinked by the surface crosslinking agent, thereby forming a superabsorbent resin with a high surface crosslinking density.

[0099] By using water-dispersible silica in the above surface crosslinking step, the applicability of the surface crosslinking solution to the surface of the base resin powder is improved, allowing for uniform surface crosslinking, and the frictional force between each powder particle can be improved due to the porous structure of the silica. In addition, the water-soluble components leached out under actual usage conditions can be re-adsorbed onto the surface, thereby suppressing the reduction in frictional force caused by the water-soluble components.

[0100] The above water-dispersible silica refers to silica in which silica particles are stably dispersed in water without precipitation or aggregation, and refers to silica in which at least a portion of the surface of the silica particles is ionized. The method of manufacturing the above water-dispersible silica is not particularly limited, and silica prepared by known methods such as electrodialysis, the sol-gel method, the ion exchange method, or the acid neutralization method may be used.

[0101] Furthermore, since the desired effect cannot be obtained if the water-dispersible silica precipitates without maintaining a colloidal state within the monomer composition, it is preferable to use water-dispersible silica that maintains a stable colloidal state within the monomer composition. In this regard, powdered silica or hydrophobic silica that is not in a colloidal state does not provide a rewetting improvement effect, so the effect intended by the present invention cannot be achieved; in particular, if fumed silica is used alone, there is a high risk of coarse particles being generated, making it difficult to realize the effect of increasing friction. However, optionally, fumed silica, etc., may be used together with water-dispersible silica.

[0103] The above water-dispersible silica may be a solution containing 0.1 to 20 parts by weight of silica per 100 parts by weight of solvent, and preferably, a solution containing 0.5 to 20 parts by weight or 5 to 20 parts by weight. By using water-dispersible silica of the above concentration, the frictional force increase effect can be further enhanced, and accordingly, the absorption properties, gel strength, etc. of the superabsorbent resin produced can be improved.

[0104] The content of the above water-dispersible silica is not particularly limited, but is included in an amount of 0.01 to 2 parts by weight per 100 parts by weight of base resin powder, and preferably, may be included in an amount of 0.05 to 0.5 parts by weight or 0.05 to 1 part by weight. By using it within the above content range, the effect of increasing frictional force can be further enhanced, and accordingly, the absorption properties, gel strength, etc. of the superabsorbent resin produced can be improved.

[0105] The above water-dispersible silica comprises silica having an average particle size (D50) of 1 nm to 50 nm, and preferably, silica having an average particle size of 5 nm to 20 nm or 5 nm to 40 nm may be used. By satisfying the above average particle size range, the effect of increasing frictional force can be further enhanced. The above average particle size (D50) refers to the particle size or particle diameter at the 50% point of the cumulative distribution of the number of particles according to particle size.

[0106] In addition, the water-dispersible silica has a BET specific surface area of ​​10 m² 2 / g to 1,000 m 2 Silica with a content of / g can be used, preferably 100 m 2 / g to 1,000 m 2 / g, or 200 m 2 / g to 500 m 2 Silica with a specific surface area of ​​1 / g can be used. By satisfying the above BET specific surface area, the frictional force increase effect can be further enhanced.

[0107] In addition, the above water-dispersible silica may use silica having a contact angle with water of 0° to 90°, and preferably, silica having a contact angle of 0° to 30° or 0° to 60° may be used. By satisfying the above contact angle range, the effect of increasing frictional force can be further enhanced.

[0108] Commercially available water-dispersible silica products satisfying the above conditions include, but are not limited to, Snowtex-O from Nissan Chemical.

[0110] Specifically, a surface crosslinking layer can be formed by a heat treatment process in the presence of a surface crosslinking solution containing a surface crosslinking agent and water-dispersible silica. During the heat treatment process, the surface crosslinking density, i.e., the external crosslinking density, increases, while the internal crosslinking density remains unchanged. Consequently, the superabsorbent resin with the manufactured surface crosslinking layer has a structure in which the external crosslinking density is higher than the internal one.

[0111] In the above surface crosslinking step, a surface crosslinking agent composition comprising an alcohol-based solvent and water in addition to the surface crosslinking agent may be used.

[0112] Meanwhile, as the surface crosslinking agent included in the above surface crosslinking agent composition, any surface crosslinking agent conventionally used in the manufacture of superabsorbent resins may be used without any particular restrictions. For example, the above surface crosslinking agent may be one or more polyols selected from the group consisting of ethylene glycol, propylene glycol, 1,3-propanediol, 1,4-butanediol, 1,6-hexanediol, 1,2-hexanediol, 1,3-hexanediol, 2-methyl-1,3-propanediol, 2,5-hexanediol, 2-methyl-1,3-pentanediol, 2-methyl-2,4-pentanediol, tripropylene glycol, and glycerol; one or more carbonate-based compounds selected from the group consisting of ethylene carbonate and propylene carbonate; epoxy compounds such as ethylene glycol diglycidyl ether; polyamine compounds; oxazoline compounds; It may include mono-, di-, or poly- oxazolidinone compounds; or cyclic urea compounds; etc. Preferably, the same as the internal crosslinking agent described above may be used, and for example, alkylene glycol diglycidyl ether compounds such as ethylene glycol diglycidyl ether may be used.

[0113] Such a surface crosslinking agent may be used in an amount of 0.001 to 2 parts by weight per 100 parts by weight of base resin powder. Preferably, it may be used in an amount of 0.005 parts by weight or more, 0.01 parts by weight or more, or 0.02 parts by weight or more, and in an amount of 0.5 parts by weight or less, or 0.3 parts by weight or less. By adjusting the content range of the surface crosslinking agent to the range described above, a superabsorbent resin exhibiting excellent absorption performance and water permeability and other physical properties can be manufactured.

[0115] Meanwhile, there are no specific limitations on the composition of the method for mixing the surface crosslinking agent solution and the base resin powder. For example, methods such as mixing the surface crosslinking agent solution and the base resin powder by placing them into a reaction vessel, spraying the surface crosslinking agent solution onto the base resin powder, or continuously supplying and mixing the base resin powder and the surface crosslinking agent solution into a continuously operated mixer may be used.

[0116] In addition, the surface crosslinking solution may further include water and / or a hydrophilic organic solvent as a medium. This provides the advantage that the surface crosslinking agent, etc., can be evenly dispersed on the base resin powder. At this time, the content of water and the hydrophilic organic solvent can be applied by adjusting the addition ratio to 100 parts by weight of the base resin powder for the purpose of inducing even dissolution / dispersion of the surface crosslinking agent, preventing clumping of the base resin powder, and optimizing the surface penetration depth of the surface crosslinking agent.

[0118] The above surface crosslinking step can be carried out by heat treating at a temperature of 70°C to 220°C or 70°C to 200°C for at least 30 minutes. If performed outside the above temperature range, it may be difficult to achieve the effect of increasing frictional force by water-dispersible silica.

[0119] More specifically, the surface crosslinking reaction can be carried out by heat treating at the above-mentioned temperature as the maximum reaction temperature for 30 to 80 minutes or 40 to 70 minutes.

[0120] By satisfying these surface crosslinking process conditions (in particular, temperature increase conditions and reaction conditions at the maximum reaction temperature), a superabsorbent resin that appropriately satisfies physical properties such as superior pressurized liquid permeability can be manufactured.

[0122] The means for raising the temperature for the surface crosslinking reaction are not particularly limited. Heating can be achieved by supplying a heat medium or by directly supplying a heat source. In this case, types of heat mediums that can be used include heated fluids such as steam, hot air, and hot oil, but are not limited thereto. Furthermore, the temperature of the supplied heat medium can be appropriately selected considering the medium type, the heating rate, and the target temperature. Meanwhile, directly supplied heat sources include heating via electricity and heating via gas, but are not limited to the examples described above.

[0124] Meanwhile, in order to further improve liquid permeability and other properties, the method for manufacturing a superabsorbent resin according to one embodiment of the invention may further use aluminum salts, such as aluminum sulfate salts, and other various polyvalent metal salts during surface crosslinking. Such polyvalent metal salts may be included on the surface crosslinking layer of the finally manufactured superabsorbent resin.

[0126] The superabsorbent resin produced according to the method for producing a superabsorbent resin of the above-described embodiment can more productively produce a superabsorbent resin having excellent absorption performance and excellent gel stability with an appropriate crosslinking density.

[0128] Specifically, the superabsorbent resin manufactured according to the above manufacturing method may have a centrifugal retention capacity (CRC) of 36.0 g / g or more, as measured according to the EDENA method WSP 241.2, preferably 36.0 g / g to 40.0 g / g, or 36.5 g / g to 38 g / g. The specific method for measuring the centrifugal retention capacity will be explained in more detail in the experimental examples described later.

[0130] The superabsorbent resin manufactured according to the above manufacturing method has an increase in centrifugal retention capacity defined by the following mathematical formula 1 of 25% or less, preferably 23% or less, 1% to 20%, or 10% to 20%:

[0131] [Mathematical Formula 1]

[0132] Increase in centrifugal retention capacity (%) = (CRC2 - CRC1) / (CRC1) * 100

[0133] Among the foods,

[0134] CRC1 is the water-soluble component content measured using brine according to the EDENA method WSP 241.2, and

[0135] CRC2 is the water-soluble component content measured after swelling for 60 minutes using an ascorbic acid solution instead of brine in the EDENA method WSP 241.2 method. Here, the ascorbic acid solution refers to an aqueous solution of 0.9 wt% NaCl and 0.005 wt% ascorbic acid (L-Ascorbic acid).

[0136] The above increase in centrifugal retention capacity is an indicator of resistance to degradation of L-Ascorbic acid components contained in urine, body fluids, etc., and the specific measurement method will be explained in more detail in the experimental examples described later.

[0138] The superabsorbent resin prepared according to the above manufacturing method is prepared by immersing 2.5 g of the superabsorbent resin in 50 g of ascorbic acid brine and swelling it in an oven at 40°C for 24 hours, and then having a gel stability defined by the force (N) measured using a tensile compression tester on the swollen superabsorbent resin, which is 0.70 N or higher, preferably 0.70 N to 1.5 N, 0.75 N to 1.2 N, or 0.78 N to 1.12 N. Here, the ascorbic acid brine refers to an aqueous solution of 0.9 wt% NaCl and 0.005 wt% ascorbic acid (L-Ascorbic acid). The gel stability is an indicator of resistance to degradation of L-Ascorbic acid components contained in urine, body fluids, etc., and the specific method for measuring gel stability will be explained in more detail in the experimental examples described later.

[0140] The operation and effects of the invention will be described in more detail below through specific embodiments. However, these embodiments are merely examples of the invention and do not define the scope of the invention.

[0142] [Example]

[0143] Example 1

[0144] A monomer aqueous solution was prepared by adding 550 g of acrylic acid, 680 g of 31.5% sodium hydroxide aqueous solution, and 180 g of water to a 3L glass reaction vessel equipped with a stirrer and a thermometer. When the temperature of the above aqueous solution of the water-soluble unsaturated monomer rises due to the heat of neutralization and then drops again to 40 ℃, this mixture is placed in a container containing 1,000 ppmw of ethylene glycol diglycidyl ether (relative to weight of acrylic acid) as an internal crosslinking agent, 80 ppmw of diphenyl(2,4,6-trimethylbenzoyl)-phosphine oxide (relative to weight of acrylic acid) as a photoinitiator, 1,500 ppmw of sodium persulfate (SPS) as a thermal initiator (relative to weight of acrylic acid), and 500 ppmw of ethylenediaminetetraacetic acid (A1) as a chelating agent (relative to weight of acrylic acid), and then irradiated with ultraviolet light for 1 minute (irradiation dose: 10 mV / cm² 2 UV polymerization was performed to obtain a hydrogel-type polymer sheet. The obtained hydrogel-type polymer sheet was passed through a chopper with a hole size of 16 mm to produce a crumb.

[0145] The above crumb was dried in an air flow oven capable of vertical airflow transfer. The drying was performed in multiple stages at 150°C for 7 minutes, 130°C for 7 minutes, 155°C for 7 minutes, 170°C for 7 minutes, 180°C for 7 minutes, and 160°C for 7 minutes. Next, the dried material was ground into particles using a rotary cutter mill to produce a base resin powder.

[0146] Next, a surface crosslinking solution was prepared by stirring 3 g of water, 4 g of methanol, 0.1 g of ethylene glycol diglycidyl ether, and 0.1 g of water-dispersible silica (B1), and 6.5 g of the surface crosslinking solution was mixed with 100 g of base resin powder using a stirrer and surface crosslinked for 40 minutes at 130°C to prepare a superabsorbent resin.

[0148] Comparative Examples 1 to 3

[0149] Comparative Example 1 prepared a superabsorbent resin in the same manner as Example 1, except that the chelating agent and water-dispersible silica of the present invention were not used.

[0150] Comparative Examples 2 and 3 prepared superabsorbent resins in the same manner as Comparative Example 1, except that ethylene glycol diglycidyl ether, an internal crosslinking agent, was used at 1,200 ppmw and 1,500 ppmw, respectively.

[0152] Examples 2 to 8 and Comparative Examples 4 to 7

[0153] A superabsorbent resin was prepared in the same manner as in Example 1, except that the components used in the polymerization step and the surface crosslinking step were used as shown in Table 1 below.

[0154] division Cross-linking polymerization step Surface cross-linking stage (Ingredients / ppmw*) (Ingredients / Parts by weight**) Example 1 A1 / 500 B1 / 0.1 Example 2 A1 / 750 B1 / 0.1 Example 3 A1 / 1,500 B1 / 0.1 Example 4 A2 / 750 B1 / 0.1 Example 5 A3 / 750 B1 / 0.1 Example 6 A1 / 750 B1 / 0.05 Example 7 A1 / 750 B1 / 0.2 Example 8 A1 / 750 B1 / 0.1, B'1 / 0.1 Comparative Example 1 - - Comparative Example 2 - - Comparative Example 3 - - Comparative Example 4 A1 / 750 - Comparative Example 5 - B1 / 0.1 Comparative Example 6 - B'1 / 0.1 Comparative Example 7 A1 / 750 B'1 / 10 *ppmw: relative to the total weight of water-soluble ethylene-based unsaturated monomers **parts by weight: relative to the total weight of base resin powder (100) A1: Ethylenediaminetetraacetic acid (EDTA) A2: Diethylenetriaminepentaacetic acid (DTPA) A3: Citric acid B1: Snowtex-O (particle size 10-20 nm, water-dispersible silica (silica content 20 wt%)) B'1: Aerosil 200 (specific surface area (BET) 200 m² 2 / g, dry silica)

[0155] [Experimental Example]

[0156] The physical properties of the superabsorbent resin compositions prepared in the above examples and comparative examples were evaluated in the following manner, and the results are shown in Table 2.

[0157] Unless otherwise indicated, all of the following physical property evaluations were performed at room temperature (24±1℃), and physiological saline or brine refers to a 0.9 wt% sodium chloride (NaCl) aqueous solution. Ascorbic acid brine refers to a 0.9 wt% sodium chloride (NaCl) and 0.005 wt% ascorbic acid aqueous solution.

[0159] (1) Measurement of increase in centrifuge retention capacity (CRC, g / g)

[0160] (1-1). Centrifugation retention capacity under saline conditions (CRC) 1 Measurement of )

[0161] Among the superabsorbent resin powders prepared in the above examples and comparative examples, samples having a particle size of 150 to 850 μm were taken, and the centrifugal retention capacity (CRC1) based on the absorption ratio under no load was measured according to the European Disposables and Nonwovens Association (EDANA) standard EDANA WSP 241.2.

[0162] Specifically, the above sample W0 (g) (approx. 0.2g) was uniformly placed into a nonwoven bag and sealed, then immersed in brine at room temperature (24±1℃). After 30 minutes, the water was drained from the bag for 3 minutes under conditions of 250g using a centrifuge, and the mass W2 (g) of the bag was measured. In addition, the same operation was performed without using the sample, and the mass W1 (g) was measured. Using each obtained mass, CRC1 (g / g) was calculated according to the following mathematical formula 1-1.

[0163] [Mathematical Formula 1-1]

[0164] CRC1(g / g) = {[W2(g) - W1(g)] / W0(g)} - 1

[0166] (1-2). Centrifugation retention capacity (CRC) under ascorbic acid saline conditions 2 Measurement of )

[0167] Among the superabsorbent resin powders prepared in the above examples and comparative examples, samples having a particle size of 150 to 850 μm were taken, and the centrifugal retention capacity (CRC) was measured. The procedure was performed in the same manner except that the solution swollen according to the European Disposables and Nonwovens Association (EDANA) standard EDANA WSP 241.2 was swollen for 60 minutes using ascorbic acid solution instead of brine.

[0168] Specifically, the above sample W'0(g) (approx. 0.2g) was uniformly placed into a nonwoven fabric bag and sealed, then immersed in an ascorbic acid brine at 40°C. After 60 minutes, the water was drained from the bag for 3 minutes under conditions of 250g using a centrifuge, and the mass W'2(g) of the bag was measured. In addition, the same operation was performed without using the sample, and the mass W'1(g) was measured. Using each obtained mass, CRC2(g / g) was calculated according to the following Equation 1-2.

[0169] [Mathematical Formula 1-2]

[0170] CRC2(g / g) = {[W'2(g) - W'1(g)] / W'0(g)} - 1

[0172] (1-3). Increase in centrifugation water retention capacity

[0173] For the CRC1 and CRC2 measured above, the increase in centrifugal retention capacity was measured according to the following mathematical formula 1.

[0174] [Mathematical Formula 1]

[0175] Increase in centrifugal retention capacity (%) = (CRC2 - CRC1) / (CRC1) * 100

[0177] (3) Gel stability (N)

[0178] Among the superabsorbent resins, those having a particle size of 150 to 850 μm were selected, 2.5 g of the superabsorbent resin was immersed in 50 g of ascorbic acid brine, and then swollen in an oven at 40°C for 24 hours. Afterward, the force (N) of the swollen superabsorbent resin was measured using a tensile compression tester.

[0179] Specifically, the above-mentioned swollen superabsorbent resin is measured using a digital force gauge FGP-2, which is a tensile compression tester, and the peak value of the force (N) applied to the tip as the tip penetrates is measured three times according to the following conditions, and the arithmetic mean value thereof is defined as gel stability (unit: N).

[0180] Tip size: terminal diameter 10±0.1 mm

[0181] Beaker size: 50±0.1 mm

[0182] Penetration speed: 500±0.5 mm / min

[0184] division CRC1(g / g) CRC2(g / g) Increase in centrifuge retention capacity (%) Gel stability (N) Example 1 36.9 42.5 15.2 0.95 Example 2 37.3 43.3 16.1 0.92 Example 3 38.2 44.4 16.2 0.88 Example 4 37.5 42.4 13.1 0.90 Example 5 37.0 45.6 23.2 0.78 Example 6 37.6 44.1 17.3 0.83 Example 7 36.5 42.0 15.1 1.12 Example 8 37.2 43.1 15.9 0.98 Comparative Example 1 37.5 52.2 39.2 0.42 Comparative Example 2 36.7 50.2 36.8 0.59 Comparative Example 3 34.2 46.7 36.5 0.68 Comparative Example 4 36.5 44.2 21.1 0.67 Comparative Example 5 35.4 47.2 33.3 0.58 Comparative Example 6 35.5 46.8 31.8 0.49 Comparative Example 7 36.2 45.5 25.7 0.68

[0185] As can be seen in Table 2 above, in the case of the example where a chelating agent was used in the polymerization step and water-dispersible silica was used in the surface crosslinking step, excellent stability was exhibited under ascorbic acid saline conditions similar to actual body fluids, and it was confirmed that the increase in centrifugal retention capacity was small and the gel stability was excellent.

[0186] In the case of comparative examples that did not use the above additives, the increase in centrifugation retention capacity was significantly greater compared to the examples, and in particular, it was confirmed that gel stability was significantly reduced under ascorbic acid saline conditions similar to body fluids.

Claims

Claim 1 A method for manufacturing a superabsorbent resin, comprising the steps of: crosslinking a water-soluble ethylene-based unsaturated monomer having at least some neutralized acidic groups and a chelating agent in the presence of an internal crosslinking agent to obtain a hydrogel polymer; drying, grinding, and classifying the hydrogel polymer to form a base resin powder; and mixing a surface crosslinking solution comprising water-dispersible silica and a surface crosslinking agent with the base resin powder to crosslink the surface of the base resin powder, wherein the water-dispersible silica comprises 0.1 to 20 parts by weight of silica per 100 parts by weight of solvent. Claim 2 A method for manufacturing a superabsorbent resin according to claim 1, wherein the chelating agent is one or more selected from the group consisting of ethylenediaminetetraacetic acid, diethylenetriaminepentaacetic acid, diethylenetriaminepentaethylenephosphonic acid, oxalic acid, citric acid, and salts thereof. Claim 3 A method for manufacturing a superabsorbent resin according to claim 1, wherein the chelating agent is one or more selected from the group consisting of ethylenediaminetetraacetic acid, diethylenetriaminepentaacetic acid, citric acid, and salts thereof. Claim 4 A method for manufacturing a superabsorbent resin according to claim 1, wherein the chelating agent is included in an amount of 100 ppmw to 10,000 ppmw with respect to a water-soluble ethylene-based unsaturated monomer. Claim 5 A method for manufacturing a superabsorbent resin according to claim 1, wherein the chelating agent is included in an amount of 500 ppmw to 5,000 ppmw with respect to a water-soluble ethylene-based unsaturated monomer. Claim 6 In claim 1, the internal crosslinking agent is N,N'-methylenebisacrylamide, trimethylolpropane tri(meth)acrylate, ethylene glycol di(meth)acrylate, polyethylene glycol (meth)acrylate, polyethylene glycol di(meth)acrylate, propylene 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, triarylamine, ethylene glycol diglycidyl ether, propylene A method for manufacturing a superabsorbent resin, comprising one or more selected from the group consisting of glycol, glycerin, and ethylene carbonate. Claim 7 delete Claim 8 A method for manufacturing a superabsorbent resin according to claim 1, wherein the water-dispersible silica comprises silica having an average particle size of 1 nm to 50 nm. Claim 9 A method for manufacturing a superabsorbent resin according to claim 1, wherein the water-dispersible silica is included in an amount of 0.01 to 2 parts by weight per 100 parts by weight of base resin powder. Claim 10 A method for manufacturing a superabsorbent resin according to claim 1, wherein the surface crosslinking agent is one or more selected from the group consisting of ethylene glycol, propylene glycol, 1,3-propanediol, 1,4-butanediol, 1,6-hexanediol, 1,2-hexanediol, 1,3-hexanediol, 2-methyl-1,3-propanediol, 2,5-hexanediol, 2-methyl-1,3-pentanediol, 2-methyl-2,4-pentanediol, tripropylene glycol, glycerol, ethylene carbonate, propylene carbonate, ethylene glycol diglycidyl ether, polyamine compounds, oxazolidin compounds, mono-, di-, or poly-oxazolidinone compounds, and cyclic urea compounds. Claim 11 A method for manufacturing a superabsorbent resin according to claim 1, wherein the superabsorbent resin has a centrifugal retention capacity (CRC) of 36.0 g / g or more as measured according to the EDENA method WSP 241.

2. Claim 12 A method for manufacturing a superabsorbent resin according to claim 1, wherein the superabsorbent resin is prepared by immersing 2.5 g of the superabsorbent resin in 50 g of ascorbic acid brine, swelling it in an oven at 40°C for 24 hours, and then having a gel stability defined by a force (N) measured using a tensile compression tester on the swollen superabsorbent resin of 0.80 N or higher. Claim 13 In claim 1, the superabsorbent resin is a method for manufacturing a superabsorbent resin having an increase in centrifugal water retention capacity of 25% or less, defined by the following mathematical formula 1: [Mathematical Formula 1] Increase in centrifugal water retention capacity (%) = (CRC2 - CRC1) / (CRC1) * 100, wherein CRC1 is the water-soluble component content measured using brine according to the EDENA method WSP 241.2 method, and CRC2 is the water-soluble component content measured after swelling at 40±1℃ for 60 minutes using ascorbic acid brine instead of brine in the EDENA method WSP 241.2 method.

Images