Preparation method of super absorbent polymer and super absorbent polymer

Abstract

The present disclosure relates to a method for preparing a super absorbent polymer . More specifically, according to the preparation method of a super absorbent polymer of the present disclosure, it is possible to effectively control the init iation and inhibition of polymerization reactions, thereby reducing the content of unreacted monomers in the final product.

Description

Method for producing superabsorbent resin and superabsorbent resin

[0001] Cross-citation with related application(s)

[0002] This application claims the benefit of priority to Korean Patent Application No. 10-2021-0079644, filed June 18, 2021, Korean Patent Application No. 10-2021-0080231, filed June 21, 2021, and Korean Patent Application No. 10-2022-0074941, filed June 20, 2022, the entire contents of which are incorporated herein by reference.

[0003]

[0004] The present invention relates to a method for producing a superabsorbent resin. More specifically, it relates to a method for producing a superabsorbent resin capable of significantly reducing the generation of unreacted monomers within the product.

[0005]

[0006] Super absorbent polymer (SAP) is a synthetic polymer material that can absorb 500 to 1,000 times its own weight in water. Different developers call it by different names, such as SAM (Super Absorbency Material) and AGM (Absorbent Gel Material). The above super absorbent polymer began to be put to practical use as a sanitary product, and is currently widely used as a soil conditioner for horticulture, a water-stopping material for civil engineering and construction, a sheet for nursery cultivation, a freshness-preserving agent in the food distribution industry, and a material for steaming.

[0007] These superabsorbent polymers are widely used in sanitary products, such as diapers and sanitary napkins. Within these sanitary products, the superabsorbent polymers are typically dispersed within pulp. However, recent efforts to provide thinner sanitary products, such as diapers, are ongoing. As part of this effort, the development of so-called pulpless diapers, which contain reduced pulp content or even eliminate pulp altogether, is actively underway.

[0008] Thus, in sanitary materials with reduced pulp content or no pulp, a relatively high proportion of superabsorbent resin is included, and superabsorbent resin particles are inevitably embedded in multiple layers within the sanitary material. In order for the superabsorbent resin particles embedded in multiple layers to efficiently absorb large amounts of liquids such as urine, the superabsorbent resin must fundamentally exhibit not only high absorption performance but also a rapid absorption rate.

[0009] These superabsorbent resins are produced by drying, grinding and classifying a hydrogel polymer produced by crosslinking polymerization of a monomer containing a water-soluble ethylenically unsaturated carboxylic acid or its salt, or by surface crosslinking the same.

[0010] When crosslinking and polymerizing the above-mentioned monomers, an appropriate type of polymerization initiator or polymerization inhibitor is used, and the progress of the polymerization reaction is controlled through the reaction process conditions, etc. In particular, for polymerization activation, a method is known in which dissolved oxygen present in the monomer mixture is removed before being introduced into the polymerization reactor.

[0011] In addition, in order to obtain excellent properties of the finally manufactured superabsorbent resin, it is necessary to precisely control the initiation or inhibition of the reaction, but this is very difficult due to the nature of the radical reaction, and there is a problem that the properties of the superabsorbent resin deteriorate depending on the amount of polymerization initiator or polymerization inhibitor used.

[0012] In particular, when the initiator and monomer come into contact, the polymerization reaction begins immediately, so the polymerization begins in the transport line such as a pipe rather than in the polymerization reactor, making continuous operation difficult, and rather, the problem of increasing the content of unreacted monomer in the final product may arise.

[0013] Therefore, research is needed to efficiently control the initiation and inhibition of polymerization reactions.

[0014]

[0015] The present specification provides a method for producing a superabsorbent resin, which can efficiently control the initiation and inhibition of a polymerization reaction when polymerization is carried out.

[0016]

[0017] The present invention relates to a method for producing a polymer, comprising: performing polymerization on a monomer composition comprising a water-soluble ethylenically unsaturated monomer having an acidic group, an internal crosslinking agent, and a polymerization initiator, thereby forming a polymer in which the water-soluble ethylenically unsaturated monomer having an acidic group and the internal crosslinking agent are crosslinked; (Step 1) forming a hydrogel polymer by neutralizing at least a portion of the acidic groups of the polymer; (Step 2) forming a micronized hydrogel polymer in the presence of a surfactant; And a step (step 4) of drying the neutralized and micronized polymer to produce dry superabsorbent resin particles, and in the step of forming the polymer, the first monomer composition including the monomer and the internal crosslinking agent is transported through a monomer transport line, and the polymerization initiator is transported through an initiator transport line, respectively, and immediately before being introduced into a polymerization reactor, the monomer transport line and the initiator transport line are combined, and the first monomer composition and the initiator are mixed to form a second monomer composition.

[0018]

[0019] In addition, the present specification provides a superabsorbent resin manufactured by the method for manufacturing the superabsorbent resin.

[0020]

[0021] According to the method for producing a superabsorbent resin of the present invention, the initiation and inhibition of a polymerization reaction can be efficiently controlled, thereby reducing the content of unreacted monomer in the final product.

[0022]

[0023] The terminology used herein is for the purpose of describing exemplary embodiments only and is not intended to limit the present invention. The singular expression includes the plural expression unless the context clearly indicates otherwise. In this specification, it should be understood that the terms "comprise," "include," or "have" indicate the presence of a feature, step, component, or combination thereof, but do not preclude the possibility of the presence or addition of one or more other features, steps, components, or combinations thereof.

[0024] The present invention is susceptible to various modifications and takes various forms. Specific embodiments are illustrated and described in detail below. However, this is not intended to limit the present invention to specific disclosed forms, but rather to encompass all modifications, equivalents, and alternatives falling within the spirit and technical scope of the present invention.

[0025] The present invention is susceptible to various modifications and takes various forms. Specific embodiments are illustrated and described in detail below. However, this is not intended to limit the present invention to specific disclosed forms, but rather to encompass all modifications, equivalents, and alternatives falling within the spirit and technical scope of the present invention.

[0026] Hereinafter, a method for manufacturing a superabsorbent resin and a superabsorbent resin will be described in more detail according to specific embodiments of the invention.

[0027] Before proceeding, it should be noted that the technical terminology used herein is solely for the purpose of describing specific embodiments and is not intended to limit the present invention. Furthermore, the singular forms used herein also include the plural forms, unless the context clearly dictates otherwise.

[0028]

[0029] According to one embodiment of the invention, a method for producing a polymer comprises: performing polymerization on a monomer composition comprising a water-soluble ethylenically unsaturated monomer having an acidic group, an internal crosslinking agent, and a polymerization initiator, thereby forming a polymer in which the water-soluble ethylenically unsaturated monomer having an acidic group and the internal crosslinking agent are crosslinked; (Step 1) neutralizing at least a portion of the acidic groups of the polymer to form a hydrogel polymer; (Step 3) atomizing the hydrogel polymer in the presence of a surfactant; And a step (step 4) of drying the neutralized and atomized polymer to produce dry superabsorbent resin particles, wherein in the step of forming the polymer, the first monomer composition including the monomer and the internal crosslinking agent is transported through a monomer transport line, and the polymerization initiator is transported through an initiator transport line, respectively, and immediately before being introduced into a polymerization reactor, the monomer transport line and the initiator transport line are combined, and the first monomer composition and the initiator are mixed to form a second monomer composition.

[0030]

[0031] The term "polymer" or "high molecular weight polymer" as used in the specification of the present invention means a polymerized state of a water-soluble ethylenically unsaturated monomer, and may encompass any moisture content range or particle size range.

[0032] In addition, the term "superabsorbent resin" is used to mean, depending on the context, a base resin in powder form made of a crosslinked polymer or superabsorbent resin particles obtained by pulverizing the crosslinked polymer, or to encompass all of the crosslinked polymer or the base resin that have been subjected to additional processes, such as drying, pulverization, classification, surface crosslinking, etc., to make them suitable for commercialization.

[0033] Additionally, the term "fine particles" refers to particles having a particle size of less than 150 μm among superabsorbent resin particles. The particle size of such resin particles can be measured according to the European Disposables and Nonwovens Association (EDANA) standard EDANA WSP 220.3 method.

[0034] Additionally, the term "chopping" is used to refer to cutting the hydrogel polymer into small pieces on the order of millimeters to increase drying efficiency, as distinguished from grinding to a normal particle size.

[0035] Additionally, the term “micronizing” refers to grinding a hydrogel polymer into particle sizes of tens to hundreds of micrometers, and is used to distinguish it from “chopping.”

[0036]

[0037] Conventionally, superabsorbent resins have been manufactured by including the following steps.

[0038] (Polymerization) A step of forming a hydrogel polymer by crosslinking and polymerizing a water-soluble ethylenically unsaturated monomer having at least a portion of neutralized acidic groups in the presence of an internal crosslinking agent and a polymerization initiator;

[0039] (Chopping) A step of chopping the above functional gel polymer;

[0040] (drying) a step of drying the chopped functional gel polymer; and

[0041] (Crushing / classification) A step of crushing the above dried polymer and then classifying it into normal particles and fine powder.

[0042] During the above-described series of manufacturing processes, in the polymerization step, a polymerization reaction can proceed immediately upon contact between the monomer and initiator. For example, if the monomer and initiator components meet in the transfer line used to supply each reactant to the reactor, the polymerization reaction may proceed within the transfer line, potentially causing the transfer line to become clogged.

[0043] Accordingly, the inventors of the present invention have completed the present invention by noting that when batch polymerization is performed in the polymerization step, the first monomer composition including the monomer and the internal cross-linking agent is transported through a monomer transport line, and the polymerization initiator is transported through an initiator transport line, respectively, and immediately before being introduced into a polymerization reactor, the monomer transport line and the initiator transport line are combined to mix the first monomer composition and the initiator to form a second monomer composition, thereby solving the problem of clogging of the transport lines.

[0044]

[0045] Meanwhile, a method has been proposed for incorporating surfactants into the chopping process to reduce the adhesiveness of hydrogel polymers. However, when surfactants are added during the chopping process, the high water content of hydrogel polymers causes the surfactants to penetrate into the hydrogel polymer rather than remaining at the interface, preventing the surfactants from properly performing their function.

[0046] This means that although the surface area may increase to some extent since the chopped particles are formed into particles of several mm or several cm in size compared to the polymer before chopping, it is difficult to expect an effect that can effectively improve the absorption rate. Therefore, a method of increasing the surface area by mixing with increased mechanical force during the chopping step to improve the absorption rate can be considered, but in this case, excessive agglomeration occurs due to the unique stickiness of the polymer, so that after chopping, drying, and pulverization, only amorphous single particles with an uneven particle surface are formed, and the water-soluble component may rather increase due to excessive mixing or crushing.

[0047]

[0048] To solve this problem, as a result of repeated research, it was confirmed that, instead of performing polymerization in a state where the acidic groups of a water-soluble ethylenically unsaturated monomer are neutralized, as in the conventional method for producing superabsorbent resins, polymerization is first performed in a state where the acidic groups are not neutralized to form a polymer, and then the hydrogel polymer is micronized in the presence of a surfactant and then the acidic groups of the polymer are neutralized, or the hydrogel polymer is formed by neutralizing the acidic groups of the polymer and then the hydrogel polymer is micronized in the presence of a surfactant, or the acidic groups present in the polymer are neutralized simultaneously with the micronization, so that the surfactant is present in a large amount on the surface of the polymer and can sufficiently play a role in lowering the high adhesiveness of the polymer, preventing the polymer from excessively agglomerating, and controlling the agglomeration state to a desired level.

[0049] Accordingly, the amount of fine particles generated during the process can be significantly reduced by manufacturing the polymer as secondary particles in the form of aggregated primary particles and then performing the crushing and drying process under milder conditions.

[0050]

[0051] In addition, when the polymer is micronized in the presence of the surfactant, the hydrophobic functional group contained in the surfactant imparts hydrophobicity to the surface of the pulverized superabsorbent resin particles, thereby alleviating the friction between particles and increasing the apparent density of the superabsorbent resin. At the same time, the hydrophilic functional group contained in the surfactant can also be bonded to the superabsorbent resin particles, thereby preventing the surface tension of the resin from decreasing. Accordingly, the superabsorbent resin manufactured according to the above-described manufacturing method can exhibit a higher apparent density value while exhibiting the same level of surface tension as a resin that does not use a surfactant.

[0052]

[0053] In addition, by first performing polymerization in an uncrosslinked state to form a polymer and then neutralizing the acidic groups present in the polymer, it is possible to form a polymer with a longer chain, and thus achieve the effect of reducing the content of water-soluble components that exist in an uncrosslinked state due to incomplete crosslinking.

[0054] Since the above-mentioned water-soluble component has the property of easily dissolving when the superabsorbent resin comes into contact with a liquid, when the content of the water-soluble component is high, most of the dissolved water-soluble component remains on the surface of the superabsorbent resin, making the superabsorbent resin sticky and causing a decrease in liquid permeability. Therefore, from the perspective of liquid permeability, it is important to keep the content of the water-soluble component low.

[0055] According to one embodiment of the present invention, by performing polymerization in an unsaturated state, the content of water-soluble components is reduced, and thus the permeability of the superabsorbent resin can be improved.

[0056] In addition, the superabsorbent resin manufactured according to one embodiment of the present invention can have a uniform particle size distribution, and thus can provide a superabsorbent resin having excellent overall absorption properties such as water retention capacity, pressure absorption capacity, rewet characteristics, and absorption speed.

[0057]

[0058] Hereinafter, each step of the method for manufacturing a superabsorbent resin according to an embodiment will be described in more detail.

[0059]

[0060] Step 1: Polymerization Step

[0061] First, polymerization is performed on a monomer composition including a water-soluble ethylenically unsaturated monomer having an acidic group, an internal crosslinking agent, and a polymerization initiator, thereby forming a polymer in which the water-soluble ethylenically unsaturated monomer having an acidic group and the internal crosslinking agent are crosslinked.

[0062] The above step may be comprised of a step of preparing a monomer composition by mixing the water-soluble ethylenically unsaturated monomer having the acidic group, an internal crosslinking agent, and a polymerization initiator, and a step of polymerizing the monomer composition to form a polymer.

[0063] And, the step of forming the polymer is carried out by continuous batch polymerization.

[0064]

[0065] The water-soluble ethylenically unsaturated monomer may be any monomer commonly used in the production of superabsorbent resins. As a non-limiting example, the water-soluble ethylenically unsaturated monomer may be a compound represented by the following chemical formula 1:

[0066] [Chemical Formula 1]

[0067] R-COOM'

[0068] In the above chemical formula 1,

[0069] R is an alkyl group having 2 to 5 carbon atoms containing an unsaturated bond,

[0070] M' is a hydrogen atom, a monovalent or divalent metal, an ammonium group, or an organic amine salt.

[0071] Preferably, the monomer may be at least one selected from the group consisting of (meth)acrylic acid, and monovalent (alkali) metal salts, divalent metal salts, ammonium salts, and organic amine salts of these acids.

[0072] In this way, when (meth)acrylic acid and / or its salt is used as a water-soluble ethylenically unsaturated monomer, a superabsorbent resin with improved absorbency can be obtained, which is advantageous. In addition, as the monomers, maleic anhydride, fumaric acid, crotonic acid, itaconic acid, 2-acryloylethane sulfonic acid, 2-methacryloylethane sulfonic acid, 2-(meth)acryloylpropanesulfonic acid or 2-(meth)acrylamide-2-methyl propane sulfonic acid, (meth)acrylamide, N-substituted (meth)acrylate, 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, methoxypolyethylene glycol (meth)acrylate, polyethylene glycol (meth)acrylate, (N,N)-dimethylaminoethyl (meth)acrylate, (N,N)-dimethylaminopropyl (meth)acrylamide, etc. can be used.

[0073] Here, the water-soluble ethylenically unsaturated monomer has an acidic group. As explained above, in the production of conventional superabsorbent resins, a monomer in which at least a portion of the acidic groups are neutralized by a neutralizing agent is crosslinked and polymerized to form a hydrogel polymer. Specifically, in the step of mixing the water-soluble ethylenically unsaturated monomer having the acidic group, an internal crosslinking agent, a polymerization initiator, and a neutralizing agent, at least a portion of the acidic groups of the water-soluble ethylenically unsaturated monomer are neutralized.

[0074]

[0075] However, according to one embodiment of the present invention, polymerization is first performed in a state where the acidic group of the water-soluble ethylenically unsaturated monomer is not neutralized to form a polymer.

[0076] Water-soluble ethylenically unsaturated monomers (e.g., acrylic acid) whose acid groups are not neutralized are liquid at room temperature and have high miscibility with the solvent (water), so they exist as a mixed solution in the monomer composition. However, water-soluble ethylenically unsaturated monomers whose acid groups are neutralized are solid at room temperature and have different solubility depending on the temperature of the solvent (water), with the solubility decreasing at lower temperatures.

[0077] In this way, a water-soluble ethylenically unsaturated monomer in which the acidic groups are not neutralized has a higher solubility or miscibility in a solvent (water) than a monomer in which the acidic groups are neutralized, and thus does not precipitate even at low temperatures, and is therefore advantageous for long-term polymerization at low temperatures. Accordingly, a water-soluble ethylenically unsaturated monomer in which the acidic groups are not neutralized can be used for long-term polymerization to stably form a polymer having a higher molecular weight and a uniform molecular weight distribution.

[0078] In addition, it is possible to form polymers of longer chains, and thus achieve the effect of reducing the content of water-soluble components that exist in an uncrosslinked state due to incomplete polymerization or crosslinking.

[0079] In addition, if polymerization is first performed in a state where the acidic groups of the monomer are not neutralized to form a polymer, and then the polymer is micronized in the presence of a surfactant after neutralization, or the polymer is micronized in the presence of a surfactant and then neutralized, or the acidic groups present in the polymer are neutralized simultaneously with the micronization, the surfactant can sufficiently play a role in reducing the adhesiveness of the polymer by being present in large quantities on the surface of the polymer.

[0080] The concentration of the water-soluble ethylenically unsaturated monomer in the monomer composition may be appropriately adjusted in consideration of polymerization time, reaction conditions, etc., and may be about 20 to about 60 wt%, or about 20 to about 40 wt%.

[0081]

[0082] The term 'internal crosslinking agent' used in this specification is a term used to distinguish it from a surface crosslinking agent for crosslinking the surface of superabsorbent resin particles described later, and it plays a role in forming a polymer including a crosslinked structure by introducing crosslinking bonds between unsaturated bonds of the water-soluble ethylenically unsaturated monomers described above.

[0083] The crosslinking in the above step is carried out without distinction between the surface and the interior, but when the surface crosslinking process of the superabsorbent resin particles described later is carried out, the surface of the finally manufactured superabsorbent resin particles may include a structure newly crosslinked by the surface crosslinking agent, and the interior of the superabsorbent resin particles may maintain the structure crosslinked by the internal crosslinking agent.

[0084] According to one embodiment of the present invention, the internal crosslinking agent may include at least one of a multifunctional acrylate compound, a multifunctional allyl compound, or a multifunctional vinyl compound.

[0085] Non-limiting examples of multifunctional acrylate compounds include ethylene glycol di(meth)acrylate, diethylene glycol di(meth)acrylate, triethylene glycol di(meth)acrylate, tetraethylene glycol di(meth)acrylate, polyethylene glycol di(meth)acrylate, propylene glycol di(meth)acrylate, tripropylene glycol di(meth)acrylate, polypropylene glycol di(meth)acrylate, butanediol di(meth)acrylate, butylene glycol di(meth)acrylate, hexanediol di(meth)acrylate, pentaerythritol di(meth)acrylate, pentaerythritol tri(meth)acrylate, pentaerythritol tetra(meth)acrylate, dipentaerythritol di(meth)acrylate, dipentaerythritol tri(meth)acrylate, dipentaerythritol Examples thereof include tetra(meth)acrylate, dipentaerythritol penta(meth)acrylate, trimethylolpropane di(meth)acrylate, trimethylolpropane tri(meth)acrylate, glycerin di(meth)acrylate, and glycerin tri(meth)acrylate, and these may be used alone or in combination of two or more.

[0086] Non-limiting examples of polyfunctional allyl compounds include ethylene glycol diallyl ether, diethylene glycol diallyl ether, triethylene glycol diallyl ether, tetraethylene glycol diallyl ether, polyethylene glycol diallyl ether, propylene glycol diallyl ether, tripropylene glycol diallyl ether, polypropylene glycol diallyl ether, butanediol diallyl ether, butylene glycol diallyl ether, hexanediol diallyl ether, pentaerythritol diallyl ether, pentaerythritol triallyl ether, pentaerythritol tetraallyl ether, dipentaerythritol diallyl ether, dipentaerythritol triallyl ether, dipentaerythritol tetraallyl ether, dipentaerythritol pentaallyl ether, trimethylolpropane diallyl ether, Examples include trimethylolpropane triallyl ether, glycerin diallyl ether, and glycerin triallyl ether, and they can be used alone or in combination of two or more.

[0087] Non-limiting examples of polyfunctional vinyl compounds include ethylene glycol divinyl ether, diethylene glycol divinyl ether, triethylene glycol divinyl ether, tetraethylene glycol divinyl ether, polyethylene glycol divinyl ether, propylene glycol divinyl ether, tripropylene glycol divinyl ether, polypropylene glycol divinyl ether, butanediol divinyl ether, butylene glycol divinyl ether, hexanediol divinyl ether, pentaerythritol divinyl ether, pentaerythritol trivinyl ether, pentaerythritol tetravinyl ether, dipentaerythritol divinyl ether, dipentaerythritol trivinyl ether, dipentaerythritol tetravinyl ether, dipentaerythritol pentavinyl ether, trimethylolpropane divinyl ether, trimethylolpropane Examples thereof include trivinyl ether, glycerin divinyl ether, and glycerin trivinyl ether, and these may be used singly or in combination of two or more. Preferably, pentaerythritol triallyl ether may be used.

[0088] The above-mentioned multifunctional allyl compound or multifunctional vinyl compound can form a cross-linked structure during the polymerization process by having two or more unsaturated groups included in the molecule bond with the unsaturated bonds of water-soluble ethylenically unsaturated monomers or the unsaturated bonds of other internal cross-linking agents, and unlike the acrylate compound including an ester bond (-(C=O)O-) in the molecule, the cross-linked bond can be more stably maintained even during the neutralization process after the above-mentioned polymerization reaction.

[0089] Accordingly, the gel strength of the superabsorbent resin being manufactured can be increased, process stability can be improved during the discharging process after polymerization, and the amount of water-soluble components can be minimized.

[0090] Crosslinking polymerization of the water-soluble ethylenically unsaturated monomer in the presence of such an internal crosslinking agent can be carried out in the presence of a polymerization initiator, a thickener if necessary, a plasticizer, a preservative stabilizer, an antioxidant, etc.

[0091] In the above monomer composition, such internal cross-linking agent may be used in an amount of 0.01 to 5 parts by weight based on 100 parts by weight of the water-soluble ethylenically unsaturated monomer. For example, the internal cross-linking agent may be used in an amount of 0.01 parts by weight or more, or 0.05 parts by weight or more, or 0.1 parts by weight or more, and 5 parts by weight or less, or 3 parts by weight or less, or 2 parts by weight or less, or 1 part by weight or less, or 0.7 parts by weight or less, based on 100 parts by weight of the water-soluble ethylenically unsaturated monomer. If the content of the upper internal cross-linking agent is too low, cross-linking may not occur sufficiently, making it difficult to achieve a strength higher than an appropriate level, and if the content of the upper internal cross-linking agent is too high, the internal cross-linking density may increase, making it difficult to achieve a desired water retention capacity.

[0092]

[0093] The polymer formed using such an internal cross-linking agent has a three-dimensional network structure in which the main chains formed by polymerization of the water-soluble ethylenically unsaturated monomers are cross-linked by the internal cross-linking agent. In this way, when the polymer has a three-dimensional network structure, the overall physical properties of the superabsorbent resin, such as water retention capacity and absorbency under pressure, can be significantly improved compared to a two-dimensional linear structure that is not further cross-linked by the internal cross-linking agent.

[0094]

[0095] According to one embodiment of the present invention, the step of performing polymerization on the monomer composition to form a polymer can be performed in a batch type reactor.

[0096] In the manufacturing method of a typical superabsorbent resin, the polymerization method is largely divided into thermal polymerization and photopolymerization depending on the polymerization energy source. When thermal polymerization is performed, it can be performed in a reactor with a stirring shaft such as a kneader, and when photopolymerization is performed, it can be performed in a reactor equipped with a movable conveyor belt or in a flat-bottomed container.

[0097] Meanwhile, the polymerization method as described above generally proceeds with a short polymerization reaction time, about 1 hour or less, so that a polymer having a small molecular weight and a wide molecular weight distribution is formed.

[0098]

[0099] Meanwhile, when photopolymerization is performed in a reactor equipped with a movable conveyor belt or a flat-bottomed vessel, the form of the functional gel polymer obtained is usually a polymer in the form of a functional gel in the form of a sheet having the width of the belt, and the thickness of the polymer sheet varies depending on the concentration of the injected monomer composition and the injection speed or injection amount, but is usually obtained to have a thickness of about 0.5 to about 5 cm.

[0100] However, if the monomer composition is supplied so that the thickness of the polymer on the sheet is excessively thin, the production efficiency is low, which is not desirable, and if the thickness of the polymer on the sheet is thickened for productivity, the polymerization reaction does not occur evenly across the entire thickness, making it difficult to form a high-quality polymer.

[0101] In addition, polymerization in a reactor having a reactor stirring shaft equipped with the conveyor belt is continuously performed by supplying a new monomer composition to the reactor while the polymerization product moves, so polymers with different polymerization rates are mixed, and accordingly, it is difficult to achieve even polymerization throughout the entire monomer composition, which may result in a deterioration of the overall physical properties.

[0102] However, according to one embodiment of the present invention, since polymerization is carried out in a fixed-bed type in a batch reactor, there is less concern that polymers with different polymerization rates will be mixed, and thus a polymer with consistent quality can be obtained.

[0103] In addition, the polymerization step is performed in a batch reactor having a predetermined volume, and the polymerization reaction is performed for a longer period of time, for example, 6 hours or more, than when polymerization is performed continuously in a reactor equipped with a conveyor belt. Despite the long polymerization reaction time as described above, since the polymerization is performed on a water-soluble ethylenically unsaturated monomer in an unneutralized state, the monomer does not precipitate easily even when polymerization is performed for a long period of time, and therefore, it is advantageous for long-term polymerization.

[0104]

[0105] Meanwhile, since polymerization in the batch reactor of the present invention utilizes a thermal polymerization method, the polymerization initiator uses a thermal polymerization initiator.

[0106] As the above thermal polymerization initiator, one or more selected from the group of initiators consisting of persulfate initiators, azo initiators, hydrogen peroxide, and ascorbic acid can be used. Specifically, examples of persulfate initiators include sodium persulfate (Na2S2O8), potassium persulfate (K2S2O8), and ammonium persulfate ((NH4)2S2O8), and examples of azo initiators include 2,2-azobis-(2-amidinopropane) dihydrochloride, 2,2-azobis-(N,N-dimethylene)isobutyramidine dihydrochloride, 2-(carbamoylazo)isobutylonitril, Examples include 2,2-azobis[2-(2-imidazolin-2-yl)propane] dihydrochloride, 4,4-azobis-(4-cyanovaleric acid), etc. A more diverse range of thermal polymerization initiators is well described in Odian's book, 'Principle of Polymerization (Wiley, 1981), p203, and is not limited to the examples described above.

[0107] An excessively low concentration of polymerization initiator can slow the polymerization rate and result in a large amount of residual monomer being extracted into the final product, which is undesirable. Conversely, an excessively high concentration of polymerization initiator can shorten the polymer chains forming the network, leading to a higher content of water-soluble components and lower pressure absorption capacity, which can deteriorate the physical properties of the resin, which is undesirable.

[0108] The amount of the thermal polymerization initiator used can affect the properties of the base resin manufactured through the subsequent process, particularly the content of the water-soluble component of the base resin. As the content of the water-soluble component increases, the properties of the final superabsorbent resin deteriorate, particularly the absorbency under pressure (AUP) and permeability. Furthermore, if too little of the thermal polymerization initiator is used, the efficiency of hydrogel polymerization may decrease, resulting in deterioration of various properties of the final superabsorbent resin.

[0109] In general, the polymerization initiators described above are used in a form that is initially included in a first monomer composition (mixture) containing a water-soluble ethylenically unsaturated monomer and an internal crosslinking agent, but according to one aspect of the present invention, the initiator is prepared separately from the first monomer composition described above.

[0110] Specifically, in the step of forming the polymer, the first monomer composition including the monomer and the internal crosslinking agent is transported through a monomer transport line, and the polymerization initiator is transported through an initiator transport line, respectively, and immediately before being introduced into the polymerization reactor, the monomer transport line and the initiator transport line are combined, and the first monomer composition and the initiator are mixed to form a second monomer composition.

[0111] In the above method, the problem of the polymerization reaction being initiated in the transport line through which the polymerization reactant is supplied and the polymerization line being closed can be prevented.

[0112] And, in the step of combining the monomer transfer line and the initiator transfer line, it may be preferable that the ratio (speed ratio) of the supply speed (m / s) of the initiator supplied from the initiator transfer line to the supply speed (m / s) of the first monomer mixture supplied from the monomer transfer line be about 3.6 or more, or about 4.0 or more, or about 5.0 or more, or about 7.0 or more. The upper limit thereof is not particularly significant, but may be about 20 or less, or about 17 or less, or about 15 or less.

[0113] The above supply speed, i.e. the linear speed supplied from the transfer line, is the mass and density supplied per unit time (kg / hr; kg / m 3 ) or volume (m 3 / hr) can be measured and calculated using the cross-sectional area of ​​the transport line.

[0114] That is, it should be noted that the above speed ratio is a ratio to the linear speed in each transport line, rather than the speed related to the supply amount at the time of supply.

[0115] When two fluids are adjacent and mixed, the pressure of the fluid with a relatively slow velocity (e.g., the monomer transport line) increases, and the pressure of the fluid with a relatively fast velocity (e.g., the initiator transport line) decreases, according to Bernoulli's principle. The pressure difference between the two causes the substances contained in each fluid to diffuse, resulting in mixing. When the speed range described above is satisfied, rapid diffusion occurs instantaneously, allowing the monomer and initiator components to be mixed quickly and evenly.

[0116] Accordingly, the polymerization reaction can be prevented from starting in the transfer line, and at the same time, the monomer component and the initiator component are uniformly mixed, so that the polymerization reaction inside the reactor can also proceed uniformly throughout, and accordingly, the unreacted monomer component (Residual monomer) in the polymer produced can be significantly reduced.

[0117] And, in the step of combining the monomer transfer line and the initiator transfer line, the ratio of the supply flow rate (kg / hr) of the initiator supplied from the initiator transfer line to the supply flow rate (kg / hr) of the first monomer mixture supplied from the monomer transfer line (flow rate ratio) may be about 0.01 to about 0.1.

[0118]

[0119] Meanwhile, in one embodiment of the present invention, polymerization can be initiated by introducing a reducing agent that forms a redox couple with the initiator.

[0120] Specifically, the initiator and reducing agent react with each other to form radicals when introduced into a polymer solution.

[0121] The formed radicals react with the monomer, and since the oxidation-reduction reaction between the initiator and reducing agent is highly reactive, polymerization is initiated even when only a small amount of initiator and reducing agent is added, so there is no need to increase the process temperature, low-temperature polymerization is possible, and changes in the physical properties of the polymer solution can be minimized.

[0122] The polymerization reaction utilizing the above oxidation-reduction reaction can occur smoothly even at temperatures near room temperature (25°C) or lower. For example, the polymerization reaction can be performed at a temperature of 5°C or higher and 25°C or lower, or 5°C or higher and 20°C or lower.

[0123] In one embodiment of the present invention, when a persulfate-based initiator is used as the initiator, the reducing agent may be at least one selected from the group consisting of sodium metabisulfite (Na2S2O5); tetramethyl ethylenediamine (TMEDA); a mixture of iron (II) sulfate and EDTA (FeSO4 / EDTA); sodium formaldehyde sulfoxylate; and disodium 2-hydroxy-2-sulfinoacetate.

[0124] For example, potassium persulfate may be used as the initiator and disodium 2-hydroxy-2-sulfinoacetate may be used as the reducing agent; ammonium persulfate may be used as the initiator and tetramethylethylenediamine may be used as the reducing agent; or sodium persulfate may be used as the initiator and sodium formaldehyde sulfoxylate may be used as the reducing agent.

[0125] In another embodiment of the present invention, when a hydrogen peroxide-based initiator is used as the initiator, the reducing agent may be at least one selected from the group consisting of ascorbic acid; sucrose; sodium sulfite (Na2SO3), sodium metabisulfite (Na2S2O5); tetramethyl ethylenediamine (TMEDA); a mixture of iron (II) sulfate and EDTA (FeSO4 / EDTA); sodium formaldehyde sulfoxylate; disodium 2-hydroxy-2-sulfinoacteate; and disodium 2-hydroxy-2-sulfoacteate.

[0126] That is, the second monomer composition further includes a reducing agent, and the reducing agent may be supplied together with the initiator through the initiator transport line or may be supplied through a separate reducing agent transport line.

[0127] And, the ratio (speed ratio) of the supply speed (m / s) of the reducing agent to the supply speed (m / s) of the first monomer mixture supplied from the monomer transfer line may also be about 3.5 or more, or about 4.0 or more, or about 5.0 or more, or about 6.0 or more, or about 6.5 or more, and the upper limit thereof may not have a significant meaning, but may be about 20 or less, or about 17 or less, or about 15 or less.

[0128] The technical significance of the above reducing agent supply rate ratio is replaced by an explanation of the initiator supply rate ratio.

[0129] The above monomer composition may further include additives such as a thickener, a plasticizer, a preservative stabilizer, and an antioxidant, as needed.

[0130] And, the monomer composition including the monomer may be in a solution state dissolved in a solvent such as water, for example, and the solid content in the monomer composition in the solution state, i.e., the concentration of the monomer, internal crosslinking agent, and polymerization initiator, may be appropriately adjusted in consideration of the polymerization time, reaction conditions, etc. For example, the solid content in the monomer composition may be 10 to 80 wt%, or 15 to 60 wt%, or 30 to 50 wt%.

[0131] The solvent that can be used at this time can be used without limitation in its composition as long as it can dissolve the above-mentioned components, and for example, one or more selected from 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 in combination.

[0132]

[0133] The polymer obtained in this way can form a polymer having a high molecular weight and a uniform molecular weight distribution as described above by polymerizing using an ethylenically unsaturated monomer in an unsaturated state, and the content of the water-soluble component can be reduced.

[0134] The polymer obtained in this way is in a state of a functional gel polymer, and may have a moisture content of 30 to 80 wt%. For example, the moisture content of the polymer may be 30 wt% or more, or 45 wt% or more, or 50 wt% or more, and 80 wt% or less, or 70 wt% or less, or 60 wt% or less.

[0135] If the moisture content of the polymer is too low, it may be difficult to secure an appropriate surface area in the subsequent grinding step, and thus the polymer may not be effectively ground. If the moisture content of the polymer is too high, the pressure applied in the subsequent grinding step may increase, making it difficult to grind to the desired particle size.

[0136] Meanwhile, throughout this specification, "moisture content" refers to the moisture content in relation to the total polymer weight, which is the value obtained by subtracting the weight of the polymer in a dry state from the weight of the polymer. Specifically, it is defined as a value calculated by measuring the weight loss due to moisture evaporation in the polymer during the drying process by increasing the temperature of the polymer in a crumbly state through infrared heating. At this time, the drying conditions are such that the temperature is increased from room temperature to about 180°C and then maintained at 180°C, and the total drying time is set to 40 minutes, including 5 minutes for the temperature increase step, to measure the moisture content.

[0137]

[0138] When a reducing agent is used, the reducing agent may be supplied together with the initiator through the initiator transfer line, and at the stage where the monomer transfer line and the initiator transfer line are combined, the ratio of the supply speed of the reducing agent supplied from the initiator transfer line to the supply speed of the first monomer mixture supplied from the monomer transfer line (speed ratio) may be 4.0 or more.

[0139] In the step of combining the monomer transfer line and the initiator transfer line, the ratio of the supply flow rate of the initiator supplied from the initiator transfer line to the supply flow rate of the first monomer mixture supplied from the monomer transfer line (flow rate ratio) may be about 0.01 to about 0.1.

[0140]

[0141] And, the monomer composition including the monomer may be in a solution state dissolved in a solvent such as water, for example, and the solid content in the monomer composition in the solution state, i.e., the concentration of the monomer, internal crosslinking agent, and polymerization initiator, may be appropriately adjusted in consideration of the polymerization time, reaction conditions, etc. For example, the solid content in the monomer composition may be 10 to 80 wt%, or 15 to 60 wt%, or 30 to 50 wt%.

[0142] The solvent that can be used at this time can be used without limitation in its composition as long as it can dissolve the above-mentioned components, and for example, one or more selected from 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 in combination.

[0143] The above monomer composition may further include additives such as a thickener, a reducing agent, a plasticizer, a preservative stabilizer, and an antioxidant, as needed.

[0144]

[0145] Step 2: Neutralization Step and Step 3: Atomization Step

[0146] Next, a step (step 2) of neutralizing at least a portion of the acidic groups of the polymer is performed.

[0147] At this time, a basic substance such as sodium hydroxide, potassium hydroxide, or ammonium hydroxide that can neutralize acid groups can be used as a neutralizing agent.

[0148] In addition, the degree of neutralization, which refers to the degree to which the acidic groups contained in the polymer are neutralized by the neutralizing agent, may be 50 to 90 mol%, or 60 to 85 mol%, or 65 to 85 mol%, or 65 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 too high, the absorption capacity of the superabsorbent resin may decrease, and if the concentration of carboxyl groups on the particle surface is too low, it is difficult to properly perform surface crosslinking in a subsequent process, which may decrease the absorption characteristics under pressure or the permeability. On the other hand, if the degree of neutralization is too low, not only the absorption capacity of the polymer is greatly reduced, but it may also exhibit properties like elastic rubber that are difficult to handle.

[0149]

[0150] Simultaneously with the above step 2, or before or after performing the above step 2, a step of micronizing the polymer is performed in the presence of a surfactant (step 3).

[0151] The above step is a step for micronizing the polymer in the presence of a surfactant. Rather than chopping the polymer into millimeter-sized pieces, it is a step in which both cutting and agglomeration into pieces of tens to hundreds of micrometers in size occur simultaneously. In other words, this is a step for producing secondary aggregated particles in the form of aggregated primary particles cut into pieces of tens to hundreds of micrometers in size by imparting appropriate adhesiveness to the polymer. The secondary aggregated particles, which are hydrophilic superabsorbent resin particles, produced through this step have a normal particle size distribution while significantly increasing their surface area, thereby significantly improving their absorption rate.

[0152]

[0153] After mixing the polymer and the surfactant in this way, the polymer can be micronized in the presence of the surfactant to produce secondary coagulated particles that are finely divided and coagulated in a state where the superabsorbent resin particles and the surfactant are mixed.

[0154] Here, the “functional superabsorbent resin particles” are particles having a moisture content (moisture content) of about 30 wt% or more, and since the polymer is cut and aggregated into particle form without a drying process, it can have a moisture content of 30 to 80 wt% like the polymer.

[0155]

[0156] According to one embodiment of the present invention, the surfactant may be a compound represented by the following chemical formula 2 or a salt thereof, but the present invention is not limited thereto:

[0157] [Chemical Formula 2]

[0158]

[0159] In the above chemical formula 2,

[0160] A is alkyl having 5 to 21 carbon atoms,

[0161] B1 is -OCO-, -COO-, or -COOCH(R1)COO-,

[0162] B2 is -CH2-, -CH2CH2-, -CH(R2)-, -CH=CH-, or -C≡C-,

[0163] Here, R1 and R2 are each independently alkyl having 1 to 4 carbon atoms,

[0164] n is an integer from 1 to 3,

[0165] C is a carboxyl group.

[0166] At this time, the surfactant is at least one selected from the group consisting of a carboxylic acid represented by the chemical formula 2 and a metal salt thereof. Specifically, the surfactant is at least one selected from the group consisting of a carboxylic acid represented by the chemical formula 2, an alkali metal salt of the carboxylic acid represented by the chemical formula 2, and an alkaline earth metal salt of the carboxylic acid represented by the chemical formula 2. More specifically, the surfactant is one of the carboxylic acid represented by the chemical formula 2, an alkali metal salt of the carboxylic acid represented by the chemical formula 2, and an alkaline earth metal salt of the carboxylic acid represented by the chemical formula 2.

[0167]

[0168] In the above chemical formula 2, A is a hydrophobic moiety and may be a linear or branched alkyl group having 5 to 21 carbon atoms. However, it is more advantageous when A is a linear alkyl group in terms of suppressing agglomeration of pulverized particles and improving dispersibility. When A is an alkyl group having less than 5 carbon atoms, there is a problem that the chain length is short and agglomeration control of pulverized particles is not effectively achieved, and when A is an alkyl group having more than 21 carbon atoms, the mobility of the surfactant may be reduced, so that it may not be effectively mixed into the polymer, or there may be a problem that the unit price of the composition may increase due to an increase in the cost of the surfactant.

[0169] Specifically, in the above chemical formula 2, A may be a linear alkyl having 5 to 21 carbon atoms, i.e., n-pentyl, n-hexyl, n-heptyl, n-octyl, n-nonyl, n-decanyl, n-undecanyl, n-dodecanyl, n-tridecanyl, n-tetradecanyl, n-pentadecanyl, n-hexadecanyl, n-heptadecanyl, n-octadecanyl, n-nonadecanyl, n-icosanyl, or n-heticosanyl.

[0170] More specifically, A may be a linear alkyl having 6 to 18 carbon atoms. For example, A may be -C6H 13 , -C11 H 23 , -C 12 H 25 , -C 17 H 35 , or -C 18 H 37 It could be.

[0171]

[0172] In addition, in the above chemical formula 2, the (B1-B2) portion is a portion that plays a role in improving the adsorption performance for the polymer surface that may be insufficient with only the C portion. When the number of carbon atoms in B2 is 3 or more, the distance between the B1 portion and the C portion increases, and the adsorption performance for the polymer may decrease.

[0173] At this time, R1 and R2 can each independently be a linear or branched alkyl having 1 to 4 carbon atoms, and more specifically, R1 and R2 can each independently be methyl, ethyl, propyl, isopropyl, butyl, isobutyl, sec-butyl, or tert-butyl, but since it is advantageous for the surfactant molecular structure to not be bulky in terms of the surfactant being adsorbed to the superabsorbent resin particles, both R1 and R2 can be methyl.

[0174] In addition, in the above chemical formula 2, n may be 1, 2, or 3. More specifically, n, which means the number of (B1-B2), is preferably 1, considering that the (B1-B2) portion is for reinforcing the adsorption performance for the C portion and the molecular length for the surfactant to be effectively adsorbed to the polymer.

[0175]

[0176] Specifically, in the above chemical formula 2, B1 is , , or It can be, where * is a bonding site with a neighboring atom.

[0177] For example, B1 , or It could be.

[0178]

[0179] Also, in the above chemical formula 2, B2 is , , , , , or It can be, and here, * is a bonding site with a neighboring atom. At this time, B2 is used in terms of improving the adsorption performance of the surfactant for the crosslinked polymer together with the C moiety. , , or It is desirable that.

[0180]

[0181] In addition, in the above chemical formula 2, the C part is a part that exhibits hydrophilicity and is a carboxyl group (COOH), but if the surfactant is a salt, it is a carboxylate group (COO - )am.

[0182]

[0183] In other words, the surfactant may be a compound represented by the following chemical formula 2a:

[0184] [Chemical Formula 2a]

[0185]

[0186] In the above chemical formula 2a,

[0187] M is H + , a monovalent cation of an alkali metal, or a divalent cation of an alkaline earth metal,

[0188] k is M is H + Or, if it is a monovalent cation of an alkali metal, it is 1, and if it is a divalent cation of an alkaline earth metal, it is 2.

[0189] Descriptions of A, B1, B2 and n are as defined in the chemical formula 2 above.

[0190]

[0191] More specifically, when the surfactant is an alkali metal salt of a carboxylic acid represented by the above chemical formula 2, the surfactant may be represented by the following chemical formula 2':

[0192] [Chemical Formula 2']

[0193]

[0194] In the above chemical formula 2',

[0195] M1 is an alkali metal, for example, sodium or potassium,

[0196] Descriptions of A, B1, B2 and n are as defined in the chemical formula 2 above.

[0197]

[0198] In addition, when the surfactant is an alkaline earth metal salt of a carboxylic acid represented by the chemical formula 2, the surfactant may be represented by the following chemical formula 2":

[0199] [Chemical Formula 2"]

[0200]

[0201] In the above chemical formula 2", M2 is an alkaline earth metal, for example, calcium,

[0202] Descriptions of A, B1, B2 and n are as defined in the chemical formula 2 above.

[0203]

[0204] For example, the surfactant may be any one carboxylic acid selected from the group consisting of:

[0205]

[0206] .

[0207]

[0208] Alternatively, the surfactant may be any one alkali metal salt selected from the group consisting of:

[0209]

[0210]

[0211] In the above,

[0212] M1 is independently an alkali metal.

[0213]

[0214] Alternatively, the surfactant may be any one alkaline earth metal salt selected from the group consisting of:

[0215]

[0216]

[0217] In the above,

[0218] M2 is independently an alkaline earth metal.

[0219]

[0220] For example, the surfactant may be any one of the compounds represented by the following chemical formulas 2-1 to 1-7, but is not limited thereto:

[0221] .

[0222]

[0223] According to another embodiment of the present invention, the surfactant may be a compound represented by the following chemical formula 3 or a salt thereof, but the present invention is not limited thereto:

[0224] [Chemical Formula 3]

[0225]

[0226] In the above chemical formula 3,

[0227] A1, A2 and A3 are each independently a single bond, carbonyl, , or and, provided that at least one of these is carbonyl or , wherein, m1, m2 and m3 are each independently an integer from 1 to 8, are each connected to an adjacent oxygen atom, are connected to adjacent R1, R2 and R3 respectively,

[0228] R1, R2 and R3 are each independently hydrogen, straight or branched chain alkyl having 6 to 18 carbon atoms or straight or branched chain alkenyl having 6 to 18 carbon atoms,

[0229] n is an integer from 1 to 9.

[0230]

[0231] The above surfactant is added so that the atomization step can be easily achieved without agglomeration by mixing with the polymer.

[0232] The surfactant represented by the above chemical formula 3 is a nonionic surfactant, and has excellent surface adsorption performance by hydrogen bonding even with an unneutralized polymer, and is therefore suitable for implementing the desired coagulation control effect. On the other hand, in the case of anionic surfactants, rather than nonionic surfactants, when mixed with a polymer neutralized with a neutralizing agent such as NaOH or Na2SO4, adsorption occurs via Na+ ions ionized at the carboxyl group substituents of the polymer, and when mixed with an unneutralized polymer, there is a problem that the adsorption efficiency for the polymer is relatively lowered due to competition with the anion of the carboxyl group substituents of the polymer.

[0233]

[0234] Specifically, in the surfactant represented by the above chemical formula 3, the hydrophobic functional group is the terminal functional group R1, R2, R3 portion (if not hydrogen), and the hydrophilic functional group further includes a glycerol-derived portion within the chain and a terminal hydroxyl group (if An is a single bond and Rn is hydrogen at the same time, n=1 to 3). The glycerol-derived portion and the terminal hydroxyl group are hydrophilic functional groups that serve to improve the adsorption performance on the polymer surface. Accordingly, the aggregation of superabsorbent resin particles can be effectively suppressed.

[0235] In the above chemical formula 3, the hydrophobic functional groups R1, R2, and R3 (if not hydrogen) are each independently a straight-chain or branched alkyl having 6 to 18 carbon atoms or a straight-chain or branched alkenyl having 6 to 18 carbon atoms. In this case, if the R1, R2, and R3 portions (if not hydrogen) are alkyl or alkenyl having less than 6 carbon atoms, there is a problem that the agglomeration control of the pulverized particles is not effectively performed due to the short chain length, and if the R1, R2, and R3 portions (if not hydrogen) are alkyl or alkenyl having more than 18 carbon atoms, the mobility of the surfactant may be reduced so that it may not be effectively mixed with the polymer, and there may be a problem that the unit price of the composition increases due to the increase in the cost of the surfactant.

[0236] Preferably, R1, R2, R3 may be hydrogen, or, if it is a straight-chain or branched alkyl having 6 to 18 carbon atoms, 2-methylhexyl, n-heptyl, 2-methylheptyl, n-octyl, n-nonyl, n-decanyl, n-undecanyl, n-dodecanyl, n-tridecanyl, n-tetradecanyl, n-pentadecanyl, n-hexadecanyl, n-heptadecanyl, or n-octadecanyl, or, if it is a straight-chain or branched alkenyl having 6 to 18 carbon atoms, 2-hexenyl, 2-heptenyl, 2-octenyl, 2-nonenyl, n-dekenyl, 2-undekenyl, 2-dodekenyl, 2-tridekenyl, 2-tetradekenyl, 2-pentadekenyl, 2-hexadekenyl, It can be 2-heptadekenyl or 2-octadekenyl.

[0237]

[0238] The above surfactant may be selected from compounds represented by the following chemical formulas 3-1 to 3-14:

[0239] [Chemical Formula 3-1]

[0240]

[0241] [Chemical Formula 3-2]

[0242]

[0243] [Chemical Formula 3-3]

[0244]

[0245] [Chemical Formula 3-4]

[0246]

[0247] [Chemical Formula 3-5]

[0248]

[0249] [Chemical Formula 3-6]

[0250]

[0251] [Chemical Formula 3-7]

[0252]

[0253] [Chemical Formula 3-8]

[0254]

[0255] [Chemical Formula 3-9]

[0256]

[0257] [Chemical Formula 3-10]

[0258]

[0259] [Chemical Formula 3-11]

[0260]

[0261] [Chemical Formula 3-12]

[0262]

[0263] [Chemical Formula 3-13]

[0264]

[0265] [Chemical Formula 3-14]

[0266] .

[0267]

[0268] Meanwhile, the surfactant may be used in an amount of 0.01 to 10 parts by weight relative to 100 parts by weight of the polymer. If the surfactant is used in an excessively small amount, the surfactant may not be evenly adsorbed on the surface of the polymer, which may cause re-agglomeration of particles after pulverization. In addition, if the surfactant is used in an excessive amount, the overall physical properties of the finally manufactured superabsorbent resin may deteriorate. For example, the surfactant may be used in an amount of 0.01 parts by weight or more, 0.015 parts by weight or more, or 0.1 parts by weight or more, but 5 parts by weight or less, 3 parts by weight or less, 2 parts by weight or less, or 1 part by weight or less relative to 100 parts by weight of the polymer.

[0269] The method for mixing these surfactants into the polymer is not particularly limited, and any method capable of evenly mixing them into the polymer may be appropriately employed. Specifically, the surfactants may be mixed dry, dissolved in a solvent and then mixed in a solution state, or melted and then mixed.

[0270] For example, the surfactant may be mixed in a solution state dissolved in a solvent. Any type of solvent, whether inorganic or organic, may be used, but water is most suitable considering the ease of drying and the cost of the solvent recovery system. Furthermore, the solution may be prepared by mixing the surfactant and polymer in a reactor, placing the polymer in a mixer and spraying the solution, or continuously supplying the polymer and solution to a continuously operating mixer for mixing.

[0271]

[0272] Meanwhile, according to one embodiment of the present invention, the step of neutralizing at least a portion of the acidic groups of the polymer (step 2) and the step of micronizing the polymer in the presence of a surfactant (step 3) may be performed sequentially, alternately, or simultaneously.

[0273] That is, a neutralizing agent may be added to the polymer to first neutralize the acidic groups, and then a surfactant may be added to the neutralized polymer to micronize the polymer mixed with the surfactant (performed in the order of Step 2->Step 3), or the neutralizing agent and the surfactant may be added to the polymer simultaneously to neutralize and micronize the polymer (perform Steps 2 and 3 simultaneously). Alternatively, the surfactant may be added first and the neutralizing agent may be added later (performed in the order of Step 3->Step 2). Alternatively, the neutralizing agent and the surfactant may be added alternately in a cross-sectional manner. Alternatively, the surfactant may be added first to micronize, the neutralizing agent may be added to neutralize, and then an additional surfactant may be added to the neutralized hydrogel polymer to further perform the micronization process.

[0274] Meanwhile, it may be desirable to leave a certain time gap between the introduction of the neutralizing agent and the atomization process to ensure even neutralization of the entire polymer.

[0275] At least some or a significant amount of the above surfactant may be present on the surface of the functional superabsorbent resin particles.

[0276] Here, the meaning of the surfactant being present on the surface of the hydrophilic superabsorbent resin particle means that at least a part or a significant amount of the surfactant is adsorbed or bound to the surface of the hydrophilic superabsorbent resin particle. Specifically, the surfactant may be physically or chemically adsorbed to the surface of the superabsorbent resin. More specifically, the hydrophilic functional group of the surfactant may be physically adsorbed to the hydrophilic portion of the surface of the superabsorbent resin by an intermolecular force such as a dipole-dipole interaction. In this way, the hydrophilic portion of the surfactant is physically adsorbed to the surface of the superabsorbent resin particle to surround the surface, and the hydrophobic portion of the surfactant is not adsorbed to the surface of the resin particle, so that the resin particle may be coated with the surfactant in the form of a kind of micelle structure. This is because the surfactant is not introduced during the polymerization process of the water-soluble ethylenically unsaturated monomer, but is introduced at the micronization stage after polymer formation. Therefore, the surfactant can faithfully perform its role as a surfactant compared to the case where the surfactant is introduced during the polymerization process and exists inside the polymer, and pulverization and coagulation occur simultaneously, so that particles with a large surface area can be obtained in the form of fine particles being coagulated.

[0277]

[0278] According to one embodiment of the present invention, the step of micronizing the polymer to produce a functional superabsorbent resin particle may be performed two or more times.

[0279] According to one embodiment of the present invention, the atomization step is performed by an atomization device, and the atomization device may include a body part including a transport space into which a polymer is transported; a screw member rotatably installed inside the transport space to move the polymer; a driving motor providing a rotational driving force to the screw member; a cutter member installed in the body part to pulverize the polymer; and a porous plate having a plurality of holes formed therein, which discharges the polymer pulverized by the cutter member to the outside of the body part. At this time, the hole size provided in the porous plate of the atomization device may be 1 mm to 20 mm, or 5 mm to 15 mm, or 5 mm to 12 mm.

[0280] According to one embodiment of the present invention, the first and second atomization steps are performed by first and second atomization devices, respectively, and the first and second atomization devices may include a body part including a transport space into which a polymer is transported; a screw member rotatably installed inside the transport space to move the polymer; a driving motor providing a rotational driving force to the screw member; a cutter member installed in the body part to pulverize the polymer; and a porous plate having a plurality of holes formed therein, which discharges the polymer pulverized by the cutter member to the outside of the body part.

[0281]

[0282] The hole sizes of the perforated plates provided in each of the first and second atomization devices may be the same or different.

[0283] Meanwhile, according to one embodiment of the present invention, for ease of pulverization, it is preferable that the hole size of the porous plate of the secondary atomizer be smaller than the hole size of the porous plate of the primary atomizer. For example, the hole size of the porous plate of the primary atomizer may be 1 mm to 6 mm, and the hole size of the porous plate of the secondary atomizer may be 0.5 mm to 6 mm.

[0284] In this way, when the polymer mixed with the surfactant is pulverized using a micronizer, a smaller particle size distribution is realized, so that the subsequent drying and pulverization processes can be performed under milder conditions, thereby preventing the generation of fine particles and improving the properties of the superabsorbent resin.

[0285]

[0286] Step 4: Drying

[0287] Next, a step (step 4) is performed to dry the neutralized and micronized polymer to produce dry superabsorbent resin particles.

[0288] The above step is a step of drying the moisture in the water-absorbent polymer particles obtained by neutralizing at least a portion of the acidic groups of the polymer and micronizing the polymer in the presence of a surfactant.

[0289]

[0290] In a typical method for producing a superabsorbent resin, the drying step is generally performed until the moisture content of the superabsorbent resin becomes less than 10 wt%. However, according to one embodiment of the present invention, the superabsorbent resin is dried so that the moisture content becomes 10 wt% or more, for example, about 10 to about 20 wt%, or about 10 to about 15 wt%. However, the present invention is not limited thereto.

[0291]

[0292] For this purpose, the temperature within the dryer used in the drying step may be about 150°C or lower, for example, about 80°C to about 150°C, and may be performed at a relatively low temperature. If the temperature within the dryer is excessively low, the drying time may be excessively long, and if the drying temperature is excessively high, a superabsorbent resin having a moisture content lower than the desired moisture content may be obtained.

[0293] At this time, drying can be performed in a moving type. This moving type drying is distinguished from static drying by the presence or absence of movement of the material during drying.

[0294] The above-mentioned moving-type drying method refers to a method of drying by mechanically stirring the drying material. The direction in which the hot air passes through the material may be the same as or different from the material's circulation direction. Alternatively, the material may be dried by circulating within the dryer and passing the heat-generating fluid (heat-generating oil) through a separate pipe outside the dryer.

[0295] On the other hand, static drying refers to a method of drying in which the material to be dried is placed on a perforated iron plate or other permeable floor, and hot air passes through the material from bottom to top.

[0296] Therefore, it is preferable to dry the water-absorbent resin using a fluid drying method in order to complete even drying within a short period of time as desired in the above step.

[0297] Devices that can be used for drying using this fluid drying method include a horizontal-type mixer, a rotary kiln, a paddle dryer, a steam tube dryer, or a generally used fluid dryer.

[0298]

[0299] Step 5: Grinding Stage

[0300] Next, a step of producing superabsorbent resin particles by crushing the above-described dry superabsorbent resin particles is performed.

[0301] Specifically, the above-described grinding step can be performed to grind the dry superabsorbent resin particles to have a particle size at the level of normal particles, i.e., a particle size of 150 μm to 850 μm.

[0302] The pulverizer used for this purpose may be, specifically, 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, or a disc cutter, but is not limited to the examples described above.

[0303] Alternatively, a grinder such as a pin mill, hammer mill, screw mill, roll mill, disc mill or jog mill may be used, but is not limited to the examples described above.

[0304] Meanwhile, in the manufacturing method of the present invention, superabsorbent resin particles having a smaller particle size distribution can be realized in the micronization step than in the conventional chopping step, and when moving type drying is performed, the moisture content after drying is maintained relatively high at 10 wt% or more, so that even if grinding is performed under mild conditions with less grinding force, a superabsorbent resin having a very high content of normal particle size of 150 ㎛ to 850 ㎛ can be formed, and the fine powder generation rate can be greatly reduced.

[0305]

[0306] The superabsorbent resin particles manufactured as described above may contain superabsorbent resin particles having a particle size of 150 ㎛ to 850 ㎛, i.e., normal particles, in an amount of 80 wt% or more, 85 wt% or more, 89 wt% or more, 90 wt% or more, 92 wt% or more, 93 wt% or more, 94 wt% or more, or 95 wt% or more, based on the total weight. The particle size of these resin particles may be measured according to the European Disposables and Nonwovens Association (EDANA) standard EDANA WSP 220.3 method.

[0307] In addition, the superabsorbent resin particles may contain fine particles having a particle size of less than 150 μm in an amount of about 20 wt% or less, or about 18 wt% or less, or about 15 wt% or less, or about 13 wt% or less, or about 12 wt% or less, or about 111 wt% or less, or about 10 wt% or less, or about 9 wt% or less, or about 8 wt% or less, or about 5 wt% or less, relative to the total weight. This is in contrast to having fine particles in an amount of more than about 20 wt% to about 30 wt% when producing a superabsorbent resin according to a conventional production method.

[0308]

[0309] Additional steps

[0310] After the step of crushing the superabsorbent resin particles, a step of classifying the crushed superabsorbent resin particles according to particle size may be further included.

[0311]

[0312] In addition, a step of forming a surface cross-linking layer on at least a portion of the surface of the superabsorbent resin particles in the presence of a surface cross-linking agent after the superabsorbent resin particles have been pulverized and / or classified may be further included. By this step, the cross-linked polymer contained in the superabsorbent resin particles may be further cross-linked via the surface cross-linking agent, thereby forming a surface cross-linking layer on at least a portion of the surface of the superabsorbent resin particles.

[0313] As the surface cross-linking agent, any surface cross-linking agent that has been conventionally used in the production of superabsorbent resins can be used without particular limitation. For example, the surface cross-linking agent may be at least one polyol 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; at least one carbonate compound selected from the group consisting of ethylene carbonate, propylene carbonate, and glycerol carbonate; an epoxy compound such as ethylene glycol diglycidyl ether; an oxazoline compound such as oxazolidinone; a polyamine compound; It may include oxazoline compounds; mono-, di- or polyoxazolidinone compounds; or cyclic urea compounds; etc.

[0314] Specifically, one or more, two or more, or three or more of the surface cross-linking agents described above may be used as the surface cross-linking agent, for example, ethylene carbonate-propylene carbonate (ECPC), propylene glycol, and / or glycerol carbonate may be used.

[0315] Such surface cross-linking agent may be used in an amount of about 0.001 to about 5 parts by weight per 100 parts by weight of the superabsorbent resin particles. For example, the surface cross-linking agent may be used in an amount of 0.005 parts by weight or more, or 0.01 parts by weight or more, or 0.05 parts by weight or more, or 5 parts by weight or less, or 4 parts by weight or less, or 3 parts by weight or less, per 100 parts by weight of the superabsorbent resin particles. By adjusting the content range of the surface cross-linking agent within the above-described range, a superabsorbent resin exhibiting excellent overall absorption properties can be manufactured.

[0316] In addition, the step of forming the surface cross-linking layer can be performed by adding an inorganic substance to the surface cross-linking agent. That is, in the presence of the surface cross-linking agent and the inorganic substance, the step of additionally cross-linking the surface of the superabsorbent resin particles to form a surface cross-linking layer can be performed.

[0317] As such inorganic materials, one or more inorganic materials selected from the group consisting of silica, clay, alumina, silica-alumina composites, titania, zinc oxide, and aluminum sulfate can be used. The inorganic material can be used in powder or liquid form, and in particular, can be used as alumina powder, silica-alumina powder, titania powder, or nano silica solution. In addition, the inorganic material can be used in an amount of about 0.001 to about 1 part by weight based on 100 parts by weight of superabsorbent resin particles.

[0318] In addition, there is no limitation on the composition of the method for mixing the surface cross-linking agent into the superabsorbent resin composition. For example, a method of mixing the surface cross-linking agent and the superabsorbent resin composition in a reaction tank, a method of spraying the surface cross-linking agent onto the superabsorbent resin composition, a method of continuously supplying the superabsorbent resin composition and the surface cross-linking agent to a continuously operating mixer, and the like can be used.

[0319] When mixing the surface cross-linking agent and the superabsorbent resin composition, water and methanol may be additionally mixed and added. Adding water and methanol has the advantage of allowing the surface cross-linking agent to be evenly dispersed throughout the superabsorbent resin composition. The amount of water and methanol added can be appropriately adjusted to ensure even dispersion of the surface cross-linking agent, prevent clumping of the superabsorbent resin composition, and optimize the depth of surface penetration of the cross-linking agent.

[0320] The above surface cross-linking process may be performed at a temperature of about 80°C to about 250°C. More specifically, the surface cross-linking process may be performed at a temperature of about 100°C to about 220°C, or about 120°C to about 200°C, for about 20 minutes to about 2 hours, or about 40 minutes to about 80 minutes. When the above-described surface cross-linking process conditions are met, the surface of the superabsorbent resin particles may be sufficiently cross-linked, thereby increasing the absorbency under pressure.

[0321] The means for increasing the temperature for the above surface crosslinking reaction is not particularly limited. Heating can be achieved by supplying a heat medium or directly supplying a heat source. At this time, available heat mediums include, but are not limited to, heated fluids such as steam, hot air, and hot oil. Furthermore, the temperature of the supplied heat medium can be appropriately selected in consideration of the means for the heat medium, the heating rate, and the target temperature. Meanwhile, directly supplied heat sources include, but are not limited to, heating via electricity or gas.

[0322]

[0323] According to one embodiment of the present invention, after the step of forming a surface cross-linking layer on at least a portion of the surface of the superabsorbent resin particles, the method may further include at least one of a cooling step of cooling the superabsorbent resin particles on which the surface cross-linking layer has been formed, a watering step of adding water to the superabsorbent resin particles on which the surface cross-linking layer has been formed, and a post-treatment step of adding an additive to the superabsorbent resin particles on which the surface cross-linking layer has been formed. In this case, the cooling step, the watering step, and the post-treatment step may be performed sequentially or simultaneously.

[0324] The additives added in the above post-processing step may include a permeability improver, an anti-caking agent, a fluidity improver, and an antioxidant, but the present invention is not limited thereto.

[0325] By selectively performing the above cooling step, water step, and post-treatment step, the moisture content of the final superabsorbent resin can be improved, and a higher quality superabsorbent resin product can be manufactured.

[0326]

[0327] According to another embodiment of the present invention, a superabsorbent resin manufactured by the above manufacturing method is provided.

[0328] The superabsorbent resin manufactured by the above manufacturing method has a fast absorption rate and a low fine particle content, and its overall absorption properties, such as water retention capacity (CRC) and absorbency under load (AUP), can be at an equivalent level or higher than those of the superabsorbent resin manufactured by the conventional method.

[0329] In addition, the particle size distribution is narrowed to provide a uniform particle size distribution, and the water-soluble component (EC) content is reduced to provide a superabsorbent resin with excellent liquid permeability and rewet properties.

[0330]

[0331] Hereinafter, preferred examples are presented to aid in understanding the present invention. However, the following examples are intended only to illustrate the present invention, and the scope of the present invention is not limited by the following examples.

[0332]

[0333] <Example>

[0334] As a monomer component, an aqueous solution of acrylic acid (AA) was used.

[0335] To remove dissolved oxygen within the above monomer solution, nitrogen gas was used for purging at 1 L / min under temperature conditions of 5°C for approximately 1 hour.

[0336] As an internal cross-linking agent, P-30 (Pentaerythritol diallyl ether) was used by mixing it at approximately 3500 ppmw compared to the acrylic acid.

[0337] As an initiator component, a separate aqueous solution was used in which approximately 600 ppmw (relative to acrylic acid) of VA-086, an azo initiator, and approximately 40 ppmw (relative to acrylic acid) of hydrogen peroxide were mixed to supply the initiator.

[0338] As a reducing agent, it was used in the form of a separate aqueous solution mixed to supply approximately 150 ppmw of ascorbic acid (relative to acrylic acid) and approximately 1.5 ppmw of iron sulfate (FeSO4) (relative to acrylic acid).

[0339] The concentration of solute in each aqueous solution is organized separately as shown in the table below.

[0340] Distinctive Monomer Aqueous Solution (wt%) Initiator *M / U Solution (wt%) Accelerator *M / U Solution (wt%) AAP-30VA-086H2O2Ascorbic acidFeSO4Example 130.830.111.300.090.500.010Example 231.720.110.650.040.250.005Example 333.650.120.330.020.120.002Example 431.720.110.650.040.250.005Example 531.720.110.650.040.250.005

[0341] *Make Up

[0342] The monomer aqueous solution, initiator aqueous solution, and reducing agent aqueous solution are all supplied through separate transfer lines, and the initiator transfer line and reducing agent transfer line are sequentially connected to the monomer transfer line just before reaching the reactor.

[0343] The supply process conditions of the monomer transfer line, initiator transfer line, and reducing agent transfer line are summarized in the following table.

[0344]

[0345] ClassificationMonomerInitiatorAcceleratorMain Diameter*Nozzle Diameter**Flow Rate(kg / hr)Flow Rate(kg / hr)Flow Rate(kg / hr)(m)(m)Example 110701.6152.5149.00.07790.005Example 210403.0302.6297.40.07790.005Example 39805.8602.8594.40.07790.005Example 410403.0302.6297.40.07790.010Example 510403.0302.6297.40.03900.005

[0346] * Monomer transfer line diameter** Initiator transfer line and reducing agent transfer line diameter (circular)

[0347]

[0348] Under the above conditions, a monomer aqueous solution, an initiator, and a reducing agent were supplied (supply amount) to the reactor for 1 hour, and the reaction was initiated, and a polymerization reaction was performed for about 6 hours at a temperature condition of about 90°C to form a crosslinked polymer.

[0349] The obtained cross-linked polymer was dried / pulverized to obtain a powder form, and the content of unreacted monomer in the polymer was analyzed according to the EDANA method, NWSP 210.0.R2 (15) for the sample.

[0350] The above contents are summarized in the table below.

[0351] DistinctionMonomer flow rate (m / s)Initiator flow rate (m / s)Accelerator flow rate (m / s)Rate ratioInitiator / monomerRate ratioAccelerator / monomerUnreacted monomer content (ppmw)Example 10.622.162.113.53.410000Example 20.614.284.217.16.92000Example 30.578.538.4114.914.7800Example 40.611.071.051.81.713000Example 52.434.284.211.81.711000

[0352] Referring to Table 2 above, it can be confirmed that, as in Examples 2 and 3, when a specific speed ratio is satisfied, the content of unreacted monomer is greatly reduced.

[0353] As explained above, this is thought to be due to the fact that, due to Bernoulli's principle, the pressure increases on the side of the fluid with a relatively slow velocity (monomer transport line) and the pressure increases on the side of the fluid with a relatively fast velocity (initiator transport line), resulting in instantaneous rapid diffusion and rapid and uniform mixing of the monomer component and the initiator component.

Claims

1. A step (step 1) of performing polymerization on a monomer composition comprising a water-soluble ethylenically unsaturated monomer having an acidic group, an internal crosslinking agent, and a polymerization initiator to form a polymer in which the water-soluble ethylenically unsaturated monomer having an acidic group and the internal crosslinking agent are crosslinked; A step of neutralizing at least a portion of acidic groups of the polymer to form a functional gel polymer (step 2); A step of micronizing the functional gel polymer in the presence of a surfactant (step 3); and A step (step 4) of drying the neutralized and micronized polymer to produce dry superabsorbent resin particles, In the step of forming the polymer, the first monomer composition including the monomer and the internal crosslinking agent is respectively transported through a monomer transport line and the polymerization initiator through an initiator transport line, and immediately before being introduced into the polymerization reactor, the monomer transport line and the initiator transport line are combined and the first monomer composition and the initiator are mixed to form a second monomer composition. A method for producing a superabsorbent resin.

2. In paragraph 1, The step of forming the above polymer is performed in a batch type reactor. A method for producing a superabsorbent resin.

3. In paragraph 1, The above steps 2 and 3 are performed sequentially, simultaneously, or interleavedly. A method for producing a superabsorbent resin.

4. In paragraph 1, A method for producing a superabsorbent resin, wherein, in a step in which the monomer transfer line and the initiator transfer line are combined, the ratio (speed ratio) of the supply speed (m / s) of the initiator supplied from the initiator transfer line to the supply speed (m / s) of the first monomer mixture supplied from the monomer transfer line is 3.6 or more.

5. In paragraph 1, The second monomer composition further comprises a reducing agent, The above reducing agent is supplied together with the initiator through the initiator transport line or through a separate reducing agent transport line. A method for producing a superabsorbent resin, wherein the ratio of the supply speed (m / s) of the reducing agent to the supply speed (m / s) of the first monomer mixture supplied from the monomer transfer line (speed ratio) is also 3.5 or more.

6. In paragraph 1, A method for producing a superabsorbent resin, wherein, in a step in which the monomer transfer line and the initiator transfer line are combined, the ratio of the supply flow rate (kg / hr) of the initiator supplied from the initiator transfer line to the supply flow rate (kg / hr) of the first monomer mixture supplied from the monomer transfer line is 0.01 to 0.1 (flow rate ratio).

7. In paragraph 1, The step of drying the neutralized and atomized polymer is performed in a moving type. A method for producing a superabsorbent resin.

8. In paragraph 7, The above fluid drying is performed using a horizontal-type mixer, a rotary kiln, a paddle dryer, or a steam tube dryer. A method for producing a superabsorbent resin.

9. In paragraph 1, The step of drying the neutralized and atomized polymer is performed at a temperature of 150°C or less. A method for producing a superabsorbent resin.

10. In paragraph 1, The moisture content of the superabsorbent resin particles obtained by drying the neutralized and micronized polymer is 10 to 30 wt%. A method for producing a superabsorbent resin.

11. In paragraph 1, At least a portion of the surfactant is present on the surface of the functional gel polymer; A method for producing a superabsorbent resin.

12. In paragraph 1, A method for producing a superabsorbent resin, wherein the surfactant comprises at least one selected from the group consisting of a compound represented by the following chemical formula 2, a salt thereof, a compound represented by the following chemical formula 3, and a salt thereof. [Chemical formula 2] In the above chemical formula 2, A is alkyl having 5 to 21 carbon atoms, B 1 Silver -OCO-, -COO-, or -COOCH(R 1 )COO-and, B 2 is -CH 2 -, -CH 2 CH 2 -, -CH(R 2 )-, -CH=CH-, or -C≡C-, Here, R 1 and R 2 are each independently an alkyl having 1 to 4 carbon atoms, n is an integer from 1 to 3, C is a carboxyl group, [Chemical Formula 3] In the above chemical formula 3, A1, A2 and A3 are each independently a single bond, carbonyl, , or and, provided that at least one of these is carbonyl or , wherein, m1, m2 and m3 are each independently an integer from 1 to 8, are each connected to an adjacent oxygen atom, are connected to adjacent R1, R2 and R3 respectively, R1, R2 and R3 are each independently hydrogen, a straight or branched chain alkyl having 6 to 18 carbon atoms or a straight or branched chain alkenyl having 6 to 18 carbon atoms, n is an integer from 1 to 9.

13. In paragraph 1, The above superabsorbent resin particles contain 89 wt% or more of superabsorbent resin particles having a particle size of 150 ㎛ to 850 ㎛ based on the total weight of the superabsorbent resin particles. A method for producing a superabsorbent resin.

14. In paragraph 1, The above superabsorbent resin particles contain 20 wt% or less of superabsorbent resin particles having a particle diameter of less than 150 ㎛ relative to the total weight of the superabsorbent resin particles. A method for producing a superabsorbent resin.

15. In paragraph 1, After the step of drying the neutralized and micronized polymer to produce superabsorbent resin particles, a step of further comprising pulverizing the superabsorbent resin particles is included. A method for producing a superabsorbent resin.

16. In paragraph 15, After the step of further pulverizing the superabsorbent resin particles, a step of classifying the pulverized superabsorbent resin particles according to particle size is further included. A method for producing a superabsorbent resin.

17. In paragraph 1 or paragraph 16, Further comprising a step of forming a surface cross-linking layer on at least a portion of the surface of the superabsorbent resin particles. A method for producing a superabsorbent resin.

18. In paragraph 17, After the step of forming a surface cross-linking layer on at least a portion of the surface of the above superabsorbent resin particles, A method of manufacturing a superabsorbent resin particle having a surface cross-linked layer formed thereon, comprising at least one of a cooling step of cooling the superabsorbent resin particle having the surface cross-linked layer formed thereon; a watering step of adding water to the superabsorbent resin particle having the surface cross-linked layer formed thereon; and a post-treatment step of adding an additive to the superabsorbent resin particle having the surface cross-linked layer formed thereon. A method for producing a superabsorbent resin.

19. In paragraph 18, The above cooling step, water step, and post-processing step are performed simultaneously. A method for producing a superabsorbent resin.

20. Manufactured by the manufacturing method of Article 1, Superabsorbent resin.