Super absorbent polymer and preparation method thereof

Abstract

The present invention relates to a super absorbent polymer and a preparation method thereof. More specifically, the present invention relates to: a super absorbent polymer in which a specific chelate compound is included inside base polymer particles and a modified silicone compound is included in a surface cross-linked layer of the base polymer particles, thereby simultaneously improving the absorbency under pressure, liquid permeability, and gel strength of the absorbent polymer; and a preparation method thereof.

Description

Superabsorbent resin and method for producing the same

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

[0002] This application claims the benefit of priority to Korean Patent Application No. 10-2023-0131047, filed September 27, 2023, and Korean Patent Application No. 10-2024-0123329, filed September 10, 2024, the entire contents of which are incorporated herein by reference.

[0003] The present invention relates to a superabsorbent resin and a method for producing the same. More specifically, the present invention relates to a superabsorbent resin and a method for producing the same, wherein the superabsorbent resin comprises a specific chelate compound in the S portion of the base resin particle and a modified silicone compound in the surface cross-linking layer of the base resin, thereby simultaneously improving the absorbency under pressure, liquid permeability, and gel strength of the absorbent resin.

[0004]

[0005] 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.

[0006] 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.

[0007] 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.

[0008] In addition, when the superabsorbent resin is included in sanitary materials such as diapers, it is necessary to spread urine and the like as widely as possible even in an environment where it is pressurized by the user's body weight. This allows the superabsorbent resin particles included throughout the entire surface area of ​​the sanitary material absorbent layer to be fully utilized, thereby further improving the absorption performance and absorption speed of the sanitary material. Furthermore, due to this pressure-sensitive diffusion characteristic, the rewet characteristic of the diaper, which suppresses urine and the like that have been absorbed by the superabsorbent resin from seeping out again, can be further improved, thereby improving the leakage-prevention characteristic of the diaper.

[0009] Previously, attempts were made to improve the diffusion characteristics of sanitary products, such as diapers, by modifying their design. For example, methods such as introducing Acquisition Distribution Layers (ADLs) into sanitary products or utilizing absorption channels have been attempted to improve the diffusion characteristics of sanitary products.

[0010] However, improvements in diffusion characteristics due to changes in the design of these sanitary materials themselves have not been sufficient. Furthermore, as sanitary materials have become thinner and the content of superabsorbent polymers within them has increased, improvements in diffusion characteristics through design changes in the sanitary materials themselves have reached their limits, and the need to improve the pressurized diffusion characteristics of the superabsorbent polymer itself has become increasingly urgent.

[0011] Due to these technical demands, there is an increasing need for the development of superabsorbent resins that can further improve the pressurized liquid permeability, which is directly related to the pressurized diffusion characteristics, and thereby further improve the rewet properties and leakage prevention properties of sanitary materials such as diapers.

[0012]

[0013] Accordingly, the present invention provides a superabsorbent resin and a method for producing the same, which simultaneously improves the pressurized absorption capacity, liquid permeability, and gel strength of the absorbent resin by including a specific chelate compound inside the base resin particle and including a modified silicone compound in the surface cross-linking layer of the base resin.

[0014]

[0015] In order to solve the above problem, the present invention,

[0016] Base resin particles comprising a crosslinked polymer in which a water-soluble ethylenically unsaturated monomer having at least a portion of an acidic group neutralized in the presence of an aminocarboxylic acid metal chelating agent is crosslinked; and

[0017] A surface crosslinking layer is formed by additional crosslinking of the crosslinked polymer through a surface crosslinking agent on a portion of the surface of the base resin particle,

[0018] Containing a modified silicone compound on at least one of the inside or the surface of the surface cross-linking layer,

[0019] The above modified silicone compound has a polysiloxane main chain,

[0020] Containing at least one carboxylic acid group or polyether group at at least one of the side chains or terminals of the polysiloxane,

[0021] Provides superabsorbent resin.

[0022]

[0023] In addition, according to another embodiment of the invention, in the method for producing the above-described superabsorbent resin,

[0024] A step (step 1) 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 aminocarboxylic acid metal chelating agent;

[0025] A step of drying, crushing and classifying the above functional gel polymer to form base resin particles (step 2);

[0026] A step (step 3) of preparing a surface cross-linking mixture by mixing a surface cross-linking composition into the above base resin particles; and

[0027] A step (step 4) of heat-treating the above surface cross-linking mixture to form a surface cross-linking layer on a portion of the surface of the base resin particles;

[0028] Adding a modified silicone compound in at least one of step 3, step 4 or after step 4,

[0029] The above modified silicone compound has a polysiloxane main chain,

[0030] Containing at least one carboxylic acid group or polyether group at at least one of the side chains or terminals of the polysiloxane,

[0031] A method for producing a superabsorbent resin is provided.

[0032]

[0033] The superabsorbent resin of the present invention includes a specific chelate compound inside the base resin particle and a modified silicone compound in the surface cross-linking layer of the base resin, thereby providing a superabsorbent resin and a method for producing the same, which simultaneously improve the pressurized absorption capacity, liquid permeability, and gel strength of the absorbent resin.

[0034]

[0035] The terminology used herein is for the purpose of describing exemplary embodiments only and is not intended to limit the invention.

[0036] Singular expressions include plural expressions unless the context clearly dictates otherwise. In this specification, terms such as "comprise," "include," or "have" are intended to indicate the presence of a feature, step, component, or combination thereof, but should be understood not to preclude the possibility of the presence or addition of one or more other features, steps, components, or combinations thereof.

[0037] The terms first, second, third, etc. are used to describe various components and are used only for the purpose of distinguishing one component from another.

[0038] 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.

[0039] The term "polymer" or "high molecular weight polymer" as used herein refers to a polymerized state of a water-soluble ethylenically unsaturated monomer, and may encompass any moisture content range or particle size range. Among the polymers, a polymer having a moisture content (moisture content) of about 40 wt% or more before polymerization and drying may be referred to as a hydrogel polymer, and particles of such hydrogel polymer that are pulverized and dried may be referred to as a crosslinked polymer.

[0040] In addition, the term "crosslinked polymer" means a polymer that is crosslinked in the presence of the water-soluble ethylenically unsaturated monomer and an internal crosslinking agent, and the term "base resin particle" means a material containing such a crosslinked polymer.

[0041] In addition, the term "superabsorbent resin" is used to encompass all of a crosslinked polymer obtained by polymerizing a water-soluble ethylenically unsaturated monomer containing an acidic group and at least a portion of the acidic group being neutralized, depending on the context, or a dried base resin particle of the crosslinked polymer, or a particle of the crosslinked polymer or the base resin that has been rendered into a state suitable for commercialization through an additional process, such as surface crosslinking, fine re-assembly, drying, grinding, classification, etc.

[0042] Additionally, the term "superabsorbent resin particles" refers to a particulate material comprising a crosslinked polymer obtained by polymerizing a water-soluble ethylenically unsaturated monomer containing acidic groups and at least a portion of which is neutralized, and crosslinking by an internal crosslinking agent.

[0043]

[0044] (superabsorbent resin)

[0045] According to one embodiment of the invention, a superabsorbent resin comprises: a base resin particle comprising a crosslinked polymer obtained by crosslinking a water-soluble ethylenically unsaturated monomer having an acidic group at least partially neutralized in the presence of an aminocarboxylic acid-based metal chelating agent; and a surface crosslinked layer formed on a portion of a surface of the base resin particle by further crosslinking the crosslinked polymer via a surface crosslinking agent, and comprising a modified silicone compound on at least one of the inside or the surface of the surface crosslinked layer, wherein the modified silicone compound has a polysiloxane main chain and includes at least one carboxylic acid group or polyether group on at least one of a side chain or a terminal of the polysiloxane.

[0046]

[0047] Recently, in the field of superabsorbent polymers, not only the basic absorption properties but also the improvement of rewet properties, which prevent the re-leakage of absorbed urine and other substances in sanitary products such as diapers, has become an important criterion for assessing product quality. To improve these rewet properties, properties such as absorbency under pressure, liquid permeability, and gel strength must all meet appropriate levels. However, due to trade-offs among these properties, it has been difficult to simultaneously improve all three properties.

[0048] Accordingly, the inventors of the present invention have made it possible to prevent gel deterioration by introducing the chelating agent into the base resin particles in the step of forming a functional gel polymer, thereby maintaining gel strength, and by using a modified silicone compound in the step of forming a surface cross-linking layer, by introducing the modified silicone compound into at least one of the inside or the surface of the surface cross-linking layer, thereby improving permeability without using a large amount of a permeability-enhancing compound, thereby realizing the effect of improving permeability without reducing the effect of the chelating agent, and thereby simultaneously improving the pressurized absorbency, permeability, and gel strength of an absorbent resin, thereby completing the present invention.

[0049]

[0050] Hereinafter, each component of the superabsorbent resin according to one embodiment of the invention will be described in detail.

[0051]

[0052] A superabsorbent resin according to one embodiment of the invention comprises base resin particles comprising a crosslinked polymer obtained by crosslinking a water-soluble ethylenically unsaturated monomer having acidic groups at least partially neutralized in the presence of an aminocarboxylic acid-based metal chelating agent. The base resin particles may refer to a particle-shaped material comprising a crosslinked polymer of the water-soluble ethylenically unsaturated monomer.

[0053] The above aminocarboxylic acid-based metal chelating agent is contained within the base resin and entraps metal ions that cause gel deterioration, thereby preventing gel deterioration and improving gel strength. In particular, when used together with a modified silicone compound contained in a surface cross-linking layer, it enables the use of a minimal amount of metal compounds typically used to improve liquid permeability, thereby achieving the effect of simultaneously improving liquid permeability without lowering gel strength. Ultimately, the pressurized absorbency, liquid permeability, and gel strength of the absorbent resin can be improved simultaneously, and the rewetting characteristics are improved, thereby further enhancing the quality of products to which the resin is applied.

[0054] The above aminocarboxylic acid-based metal chelating agent may be, for example, at least one selected from the group consisting of ethylenediaminetetraacetic acid, diethylenetriaminepentaacetic acid, hydroxyethylenediaminetriacetic acid, triethylenetetraminehexaacetic acid, trans-1,2-diaminocyclohexanetetraacetic acid, and metal salts thereof. Preferably, it may be ethylenediaminetetraacetic acid (EDTA), diethylenetriaminepentaacetic acid (DTPA), and alkali metal salts thereof.

[0055] The above aminocarboxylic acid metal chelating agent may be included in an amount of 50 ppmw to 5,000 ppmw relative to the water-soluble ethylenically unsaturated monomer, and is suitable for implementing the aforementioned effects within the above content range. Preferably, it may be included in an amount of 100 ppmw to 2,000 ppmw, 200 ppmw to 1,500 ppmw, or 300 ppmw to 1,000 ppmw.

[0056]

[0057] The above crosslinked polymer is a hydrogel polymer formed by crosslinking and polymerizing a water-soluble ethylenically unsaturated monomer having at least a portion of a neutralized acidic group in the presence of an aminocarboxylic acid-based metal chelating agent, and the polymerization method thereof will be described in more detail in the section on the method for producing a superabsorbent resin.

[0058] 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:

[0059] [Chemical Formula 1]

[0060] R1-COOM 1

[0061] In the above chemical formula 1,

[0062] R1 is an alkyl group having 2 to 5 carbon atoms containing an unsaturated bond,

[0063] M 1 is a hydrogen atom, a monovalent or divalent metal, an ammonium group, or an organic amine salt.

[0064] Preferably, the monomer may be at least one selected from the group consisting of acrylic acid, methacrylic acid, and monovalent metal salts, divalent metal salts, ammonium salts, and organic amine salts of these acids. In this way, when acrylic acid or a salt thereof is used as a water-soluble ethylenically unsaturated monomer, a superabsorbent resin with improved absorbency can be obtained, which is advantageous. In addition, examples of the monomer include anionic monomers of 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 and salts thereof; Nonionic hydrophilic monomers containing (meth)acrylamide, N-substituted (meth)acrylate, 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, methoxypolyethylene glycol (meth)acrylate or polyethylene glycol (meth)acrylate; and amino group-containing unsaturated monomers containing (N,N)-dimethylaminoethyl (meth)acrylate or (N,N)-dimethylaminopropyl (meth)acrylamide and quaternary compounds thereof may be used.

[0065] Here, the water-soluble ethylenically unsaturated monomer has an acidic group, and at least a portion of the acidic group can be partially neutralized using a neutralizing agent. The type of neutralizing agent is not particularly limited, and any basic component commonly used in the art can be used.

[0066] At this time, the degree of neutralization of the monomer may be 40 to 95 mol%, or 40 to 80 mol%, or 45 to 75 mol%. The range of the degree of neutralization may vary depending on the final physical properties, but if the degree of neutralization is excessively high, the neutralized monomer may precipitate, making it difficult for polymerization to proceed smoothly, and conversely, if the degree of neutralization is excessively low, not only will the absorbency of the polymer be significantly reduced, but it may also exhibit properties like elastic rubber that are difficult to handle.

[0067]

[0068] Next, a superabsorbent resin according to one embodiment of the invention includes a surface cross-linking layer formed by additionally cross-linking the cross-linked polymer via a surface cross-linking agent on a portion of the surface of the base resin particle. Here, at least one of the interior or surface of the surface cross-linking layer includes a modified silicone compound.

[0069] The above-mentioned modified silicone compound is incorporated into the surface cross-linking layer, thereby enabling the use of a minimal amount of metal compounds typically used to improve permeability, thereby improving permeability without reducing gel strength. In particular, in addition to the effect of improving gel strength through the chelating agent incorporated into the base resin, it simultaneously improves the pressurized absorption capacity, permeability, and gel strength of the absorbent resin, ultimately improving the rewetting characteristics, thereby further enhancing the quality of products to which the resin is applied.

[0070] The above-mentioned modified silicone compound has a polysiloxane main chain and includes at least one carboxylic acid group or polyether group on at least one of the side chains or terminals of the polysiloxane. That is, the modified silicone compound refers to a carboxyl-modified silicone compound or a polyether-modified silicone compound.

[0071] The above polysiloxane main chain may generally refer to a polymer having a bond between silicon and oxygen as the main chain, and the water solubility of the compound may be imparted by a carboxylic acid group or polyether group at the side chain or terminal of the polysiloxane.

[0072] The above modified silicone compound may be included in an amount of 0.001 to 0.1 parts by weight relative to the base resin particles, and is suitable for implementing the aforementioned effects within the above content range. Preferably, it may be included in an amount of 0.0015 to 0.07 parts by weight, or 0.003 to 0.005 parts by weight.

[0073]

[0074] The term "surface cross-linking agent" used in this specification is a term used to distinguish it from the "internal cross-linking agent" used in the polymerization step of the base resin, and refers to the content described in the manufacturing method of the polymer described below, and the cross-linking proceeds without distinction between the surface and the interior, but by the surface cross-linking process of the base resin, the particle surface of the finally manufactured superabsorbent resin is formed into a structure cross-linked by the surface cross-linking agent, and the interior is formed into a structure cross-linked by the internal cross-linking agent.

[0075] As the surface cross-linking agent, one or more selected from the group consisting of polyhydric alcohol compounds; epoxy compounds; polyamine compounds; haloepoxy compounds; condensation products of haloepoxy compounds; oxazoline compounds; mono-, di- or polyoxazolidinone compounds; cyclic urea compounds; polyhydric metal salts; and alkylene carbonate compounds may be used.

[0076] Specifically, examples of the polyhydric alcohol compound include at least one selected from the group consisting of mono-, di-, tri-, tetra- or polyethylene glycol, monopropylene glycol, 1,3-propanediol, dipropylene glycol, 2,3,4-trimethyl-1,3-pentanediol, polypropylene glycol, glycerol, polyglycerol, 2-butene-1,4-diol, 1,4-butanediol, 1,3-butanediol, 1,5-pentanediol, 1,6-hexanediol, and 1,2-cyclohexanedimethanol.

[0077] In addition, as the epoxy compound, ethylene glycol diglycidyl ether and glycidol can be used, and as the polyamine compound, at least one selected from the group consisting of ethylenediamine, diethylenetriamine, triethylenetetramine, tetraethylenepentamine, pentaethylenehexamine, polyethyleneimine, and polyamidepolyamine can be used.

[0078] And as haloepoxy compounds, epichlorohydrin, epibromohydrin, and α-methylepichlorohydrin can be used. Meanwhile, as mono-, di-, or polyoxazolidinone compounds, for example, 2-oxazolidinone can be used.

[0079] Additionally, ethylene carbonate and the like can be used as alkylene carbonate compounds. These can be used alone or in combination. Meanwhile, to enhance the efficiency of the surface crosslinking process, one or more polyhydric alcohol compounds having 2 to 10 carbon atoms can be included among these surface crosslinking agents.

[0080] The content of the surface cross-linking agent may be appropriately selected depending on the type of surface cross-linking agent specifically added or the reaction conditions, but typically, about 0.001 to about 5 parts by weight, preferably about 0.01 to about 3 parts by weight, and more preferably about 0.05 to about 2 parts by weight may be used with respect to 100 parts by weight of the base resin particles.

[0081] If the content of the surface cross-linking agent is too small, the surface cross-linking reaction hardly occurs, and if it exceeds 5 parts by weight per 100 parts by weight of the base resin particles, excessive surface cross-linking reaction may occur, resulting in a decrease in absorption capacity and physical properties.

[0082]

[0083] According to one embodiment of the invention, a superabsorbent resin can simultaneously improve the pressurized absorption capacity, liquid permeability, and gel strength of the resin by using an aminocarboxylic acid-based metal chelating agent in the base resin and a modified silicone compound in the surface cross-linking layer.

[0084]

[0085] The superabsorbent resin may have an absorbency under pressure (AUP) of 13.0 g / g or more at 0.7 psi centrifugal separation according to EDANA WSP 242.3-10. Preferably, it may be 13.1 g / g or more, 13.3 g / g or more, 13.5 g / g or more, 14 g / g or more, 14.2 g / g or more, 30 g / g or less, 27 g / g or less, or 24 g / g or less, and may be from 13.0 g / g to 30 g / g, from 13.5 g / g to 27 g / g, or from 14.0 g / g to 24 g / g.

[0086] A more specific measurement method will be explained in the experimental example described below.

[0087]

[0088] The superabsorbent resin may have a permeability measured according to the following mathematical formula 1 of 180 seconds or less. Preferably, it may be 150 seconds or less, or 130 seconds or less. The lower limit of the permeability may be 0 seconds or more, 50 seconds or more, or 80 seconds or more.

[0089] [Mathematical Formula 1]

[0090] Permeability (sec) = T1 - B

[0091] In the above mathematical formula 1,

[0092] T1 is the time taken for the liquid level to decrease from 40 ml to 20 ml by placing 0.2±0.0005 g of superabsorbent resin sample in a chromatography tube equipped with a glass filter, adding brine to make the brine volume 50 ml, leaving it for 30 minutes, then adding an additional piston (0.3 psi), leaving it for 1 minute, and then opening the lower valve.

[0093] B is the time taken for the liquid level to decrease from 40 ml to 20 ml after adding an additional piston (0.3 psi) to a chromatography tube filled with brine.

[0094] Here, brine refers to a 0.9 wt% sodium chloride (NaCl) aqueous solution, and a more specific measurement method will be described in the experimental example described below.

[0095]

[0096] In addition, the superabsorbent resin may have a gel strength of 0.70 N or more, as measured using a tensile compression tester, by immersing 2.5 g of the superabsorbent resin sample in 50 g of ascorbic acid brine and swelling it in a 40°C oven for 24 hours. Preferably, it may be 0.75 N or more, 0.80 N or more, or 0.70 N to 2.0 N, 0.75 N to 1.8 N, or 0.80 N to 1.5 N.

[0097] Here, ascorbic acid saline means a 0.9 wt% sodium chloride (NaCl) and 0.005 wt% ascorbic acid aqueous solution, and a more specific measurement method will be described in the experimental example described below.

[0098]

[0099] In addition, the superabsorbent resin may have a particle size of 150 to 850 μm. More specifically, at least 95 wt% or more of the superabsorbent resin may have a particle size of 150 to 850 μm, may contain 50 wt% or more of particles having a particle size of 300 to 600 μm, and may contain less than 3 wt% of fine powder having a particle size of less than 150 μm.

[0100]

[0101] (Method for producing superabsorbent resin)

[0102] According to one embodiment of the invention, a method for producing a superabsorbent resin comprises the steps of: forming a hydrogel polymer by crosslinking a water-soluble ethylenically unsaturated monomer having at least a partially neutralized acidic group in the presence of an aminocarboxylic acid-based metal chelating agent (step 1); forming base resin particles by drying, pulverizing, and classifying the hydrogel polymer (step 2); preparing a surface crosslinking mixture by mixing a surface crosslinking composition into the base resin particles (step 3); and forming a surface crosslinking layer on a portion of the surface of the base resin particles by heat-treating the surface crosslinking mixture (step 4); wherein a modified silicone compound is added in at least one of steps 3, 4, or after step 4. Here, the modified silicone compound has a polysiloxane main chain and includes at least one carboxylic acid group or polyether group at at least one of a side chain or a terminal of the polysiloxane.

[0103]

[0104] (Step 1: Polymerization stage)

[0105] First, a step (step 1) is included in which a water-soluble ethylenically unsaturated monomer having at least a portion of neutralized acidic groups is crosslinked and polymerized in the presence of an aminocarboxylic acid-based metal chelating agent to form a hydrogel polymer.

[0106]

[0107] In the above polymerization step, an internal crosslinking agent and a polymerization initiator may be used together with an aminocarboxylic acid-based metal chelating agent. Specifically, this is a step of forming a hydrogel polymer by thermally or photopolymerizing a monomer composition including a chelating agent, an internal crosslinking agent, a polymerization initiator, and a monomer mixture. The description of the chelating agent and monomer may be applied in the same manner as described above.

[0108]

[0109] The term "internal cross-linking agent" used in this specification is a term used to distinguish it from a "surface cross-linking agent" that cross-links the surface of base resin particles, and plays a role in polymerizing by cross-linking the unsaturated bonds of the above-described water-soluble ethylenically unsaturated monomers. The cross-linking in the above step proceeds without distinction between the surface and the interior, but through the surface cross-linking process of the base resin described below, the surface of the particles of the finally manufactured superabsorbent resin is formed into a structure cross-linked by the surface cross-linking agent, and the interior is formed into a structure cross-linked by the internal cross-linking agent.

[0110] The internal crosslinking agent may be a multifunctional component, for example, N,N'-methylenebisacrylamide, trimethylolpropane tri(meth)acrylate, ethylene glycol di(meth)acrylate, polyethylene glycol(meth)acrylate, propylene glycol di(meth)acrylate, polypropylene glycol(meth)acrylate, butanediol di(meth)acrylate, butylene glycol di(meth)acrylate, diethylene glycol di(meth)acrylate, hexanediol di(meth)acrylate, triethylene glycol di(meth)acrylate, tripropylene glycol di(meth)acrylate, tetraethylene glycol di(meth)acrylate, dipentaerythritol pentaacrylate, glycerin tri(meth)acrylate, pentaerythritol tetraacrylate, triarylamine, ethylene glycol diglycidyl ether, propylene At least one selected from the group consisting of glycol, glycerin, and ethylene carbonate may be used. Preferably, ethylene glycol diglycidyl ether may be used.

[0111] The internal cross-linking agent may be used in an amount of 50 ppmw to 1,000 ppmw based on the weight of the water-soluble ethylenically unsaturated monomer. By being included in the above content range, sufficient cross-linking can be achieved to achieve strength above an appropriate level, and sufficient water retention capacity can be achieved by introducing an appropriate cross-linking structure. Preferably, the amount is 100 ppmw or more, 200 ppmw or more, 300 ppmw or more, or 600 ppmw or more, and 1,000 ppmw or less or 800 ppmw or less, and 200 ppmw to 1,000 ppmw, 200 ppmw to 800 ppmw, or 600 ppmw to 800 ppmw. If the content of the internal cross-linking agent is too low, cross-linking may not occur sufficiently, making it difficult to achieve strength above an appropriate level, and drying efficiency may be significantly reduced. If the content of the internal cross-linking agent is too high, the internal cross-linking density may increase, making it difficult to achieve the desired water retention capacity.

[0112]

[0113] The above polymerization initiator may be a thermal polymerization initiator and / or a photopolymerization initiator.

[0114] As the above thermal polymerization initiator, one or more compounds selected from the group consisting of a persulfate-based initiator, an azo-based initiator, hydrogen peroxide, and ascorbic acid may be used. Specifically, examples of the persulfate-based initiator include sodium persulfate (Na2S2O8), potassium persulfate (K2S2O8), and ammonium persulfate ((NH4)2S2O8). In addition, as azo initiators, 2,2-azobis-(2-amidinopropane) dihydrochloride, 2,2-azobis-(N,N-dimethylene)isobutyramidine dihydrochloride, 2-(carbamoylazo)isobutylonitril, 2,2-azobis[2-(2-imidazolin-2-yl)propane] dihydrochloride, 4,4-azobis-(4-cyanovaleric acid) Examples include 4,4-azobis-(4-cyanovaleric acid)). For more information on various thermal polymerization initiators, please refer to page 203 of Odian's book, "Principle of Polymerization (Wiley, 1981)".

[0115] In addition, as the polymerization initiator, a photopolymerization initiator, etc., in addition to the thermal polymerization initiator described above, may be used.

[0116] As the photopolymerization initiator, for example, one or more compounds selected from the group consisting of benzoin ether, dialkyl acetophenone, hydroxyl alkylketone, phenyl glyoxylate, benzyl dimethyl ketal, acyl phosphine, and α-aminoketone may be used. Among them, specific examples of the acyl phosphine include diphenyl (2,4,6-trimethylbenzoyl) phosphine oxide, phenylbis (2,4,6-trimethylbenzoyl) phosphine oxide, and ethyl (2,4,6-trimethylbenzoyl) phenylphosphinate. A more detailed description of various photoinitiators is given in Reinhold Schwalm's book "UV Coatings: Basics, Recent Developments and New Applications (Elsevier 2007)" p115, and is not limited to the examples described above.

[0117] The polymerization initiator may be included in an amount of 500 ppmw to 10,000 ppmw based on the weight of the water-soluble ethylenically unsaturated monomer, preferably 500 ppmw or more, 750 ppmw or more, 800 ppmw or more or 1,000 ppmw or more, 10,000 ppmw or less, 8,000 ppmw or less, 7,000 ppmw or less, 5,000 ppmw or less, 3,000 ppmw or less, 1,500 ppmw or less or 1,000 ppmw or less, and 500 ppmw to 8,000 ppmw, 500 ppmw to 5,000 ppmw, 750 ppmw to 3,000 ppmw or 800 ppmw to 1,500 ppmw, and within the above range, The effect can be further improved. The content of the polymerization initiator refers to the mixed content of a thermal polymerization initiator and a photopolymerization initiator when they are used together.

[0118]

[0119] In addition, the monomer composition may further include additives commonly used in the field, such as a foaming agent, thickener, plasticizer, preservation stabilizer, antioxidant, and surfactant, as needed.

[0120] The above-mentioned foaming agent plays a role in increasing the surface area by forming pores in the hydrogel polymer by foaming during polymerization. The foaming agent may be a carbonate, and examples thereof include sodium bicarbonate, sodium carbonate, potassium bicarbonate, potassium carbonate, calcium bicarbonate, calcium bicarbonate, magnesium bicarbonate, or magnesium carbonate. As a commercially available foaming agent, an encapsulated foaming agent, F-36D, may be used, but is not limited thereto.

[0121] In addition, it is preferable that the foaming agent be used in an amount of 1,500 ppmw or less relative to the weight of the water-soluble ethylenically unsaturated monomer. If the amount of the foaming agent used exceeds 1,500 ppmw, the pores may become too large, resulting in a decrease in the gel strength and density of the superabsorbent resin, which may cause problems in distribution and storage. In addition, it is preferable that the foaming agent be used in an amount of 500 ppmw or more, or 1,000 ppmw or more relative to the weight of the water-soluble ethylenically unsaturated monomer.

[0122]

[0123] And, such monomer composition can be prepared in the form of a solution in which raw materials such as the aforementioned internal crosslinking agent, water-soluble ethylenically unsaturated monomer, and polymerization initiator are dissolved in a solvent.

[0124] At this time, any solvent that can dissolve the above-mentioned raw materials can be used without limitation in its composition. For example, the solvent may be water, ethanol, ethylene glycol, diethylene glycol, triethylene glycol, 1,4-butanediol, propylene glycol, ethylene glycol monobutyl ether, propylene glycol monomethyl ether, propylene glycol monomethyl ether acetate, methyl ethyl ketone, acetone, methyl amyl ketone, cyclohexanone, cyclopentanone, diethylene glycol monomethyl ether, diethylene glycol ethyl ether, toluene, xylene, butyrolactone, carbitol, methyl cellosolve acetate, N,N-dimethylacetamide, or a mixture thereof.

[0125]

[0126] The step of forming a functional gel polymer through polymerization of the above monomer composition can be performed using a conventional polymerization method, and the process is not particularly limited. As a non-limiting example, the polymerization method is broadly divided into thermal polymerization and photopolymerization depending on the type of polymerization energy source. In the case of thermal polymerization, it can be performed in a reactor having a stirring shaft such as a kneader, and in the case of photopolymerization, it can be performed in a reactor equipped with a movable conveyor belt.

[0127] For example, the monomer composition may be introduced into a reactor, such as a kneader, equipped with a stirring shaft, and a hydrogel polymer may be obtained by thermal polymerization by supplying hot air thereto or heating the reactor. At this time, depending on the shape of the stirring shaft equipped in the reactor, the hydrogel polymer discharged through the reactor outlet may be obtained as particles of several millimeters to several centimeters. Specifically, the obtained hydrogel polymer may be obtained in various forms depending on the concentration and injection speed of the injected monomer composition, and typically, a hydrogel polymer having a (weight average) particle diameter of 2 to 50 mm may be obtained.

[0128] In addition, as another example, when photopolymerization of the monomer composition is performed in a reactor equipped with a movable conveyor belt, a functional gel polymer in the form of a sheet can be obtained. At this time, the thickness of the sheet can vary depending on the concentration and injection speed of the injected monomer composition, but in order to ensure that the entire sheet can be polymerized evenly while also securing production speed, etc., it is generally preferable to adjust the thickness to 0.5 to 10 cm.

[0129] The typical moisture content of the hydrogel polymer obtained by this method may be 40 wt% to 80 wt%. Meanwhile, throughout the present specification, "moisture content" refers to the content of moisture in relation to the total weight of the hydrogel polymer, which is the value obtained by subtracting the weight of the polymer in a dry state from the weight of the hydrogel polymer. Specifically, it is defined as a value calculated by measuring the weight loss due to moisture evaporation in the polymer during the drying process by increasing the temperature of the polymer through infrared heating. At this time, the drying condition is set to increase the temperature from room temperature to 180 ° C and then maintain it at 180 ° C, and the total drying time is set to 20 minutes including 5 minutes of the temperature rising step, and the moisture content is measured.

[0130]

[0131] (Step 2: Drying, grinding and classification stage)

[0132] Next, a method for manufacturing a superabsorbent resin according to one embodiment of the invention includes a step (step 2) of drying, crushing, and classifying the manufactured functional gel polymer to form base resin particles.

[0133]

[0134] Specifically, a step of drying the obtained functional gel polymer is performed. If necessary, a step of coarsely crushing (chopping) the functional gel polymer before drying may be further performed to increase the efficiency of the drying step.

[0135] At this time, the pulverizer used is not limited in configuration, but specifically, may include any one selected from a group of pulverizing devices consisting of a vertical pulverizer, a turbo cutter, a turbo grinder, a rotary cutter mill, a cutter mill, a disc mill, a shred crusher, a crusher, a chopper, and a disc cutter, but is not limited to the examples described above.

[0136] At this time, the coarse grinding step can be performed so that the particle size of the hydrogel polymer is 2 mm to 10 mm. Grinding to a particle size of less than 2 mm is technically difficult due to the high moisture content of the hydrogel polymer, and agglomeration may also occur between the ground particles. On the other hand, if the particle size is greater than 10 mm, the efficiency increase effect of the subsequent drying step may be minimal.

[0137]

[0138] Drying is performed on the hydrogel polymer immediately after polymerization, which has been pulverized as described above or has not gone through the pulverization step. At this time, the drying temperature of the drying step may be 150 to 250°C. If the drying temperature is less than 150°C, the drying time may be excessively long and there is a concern that the properties of the superabsorbent resin ultimately formed may deteriorate. If the drying temperature exceeds 250°C, only the surface of the polymer may be excessively dried, which may cause fine powder to be generated in the subsequent pulverization step and there is a concern that the properties of the superabsorbent resin ultimately formed may deteriorate. Therefore, the drying may preferably be performed at a temperature of 150 to 200°C, and more preferably at a temperature of 150 to 190°C.

[0139] In terms of drying time, it can be carried out for 20 to 90 minutes, taking into account process efficiency, etc., but is not limited thereto.

[0140] Meanwhile, the drying step can be performed as a multi-stage process within the above-mentioned temperature range.

[0141] The drying method of the above-mentioned drying step can be selected and used without limitation in its composition, as long as it is a drying process commonly used for functional gel polymers. Specifically, the drying step can be performed by methods such as hot air supply, infrared irradiation, ultrashort wave irradiation, or ultraviolet irradiation. In the case of hot air supply, it can be performed by using an oven capable of vertical air volume transfer.

[0142] The moisture content of the polymer after such a drying step may be about 0.1 to about 10 wt%.

[0143]

[0144] Next, a step of pulverizing the dried polymer obtained through such a drying step is performed.

[0145] The polymer powder obtained after the grinding step may have a particle size of 150 to 850 μm. The grinder used to grind to such a particle size may specifically be a pin mill, a hammer mill, a screw mill, a roll mill, a disc mill, or a jog mill, but is not limited to the examples described above.

[0146]

[0147] In addition, in order to manage the properties of the superabsorbent resin powder that is finally manufactured after the crushing step, a separate process of classifying the base resin particles obtained after crushing according to particle size may be performed.

[0148] Preferably, base resin particles having a particle size of 150 µm to 850 µm are classified, and only base resin particles having such a particle size can be manufactured through a surface cross-linking reaction step. More specifically, the classified base resin particles have a particle size of 150 µm to 850 µm, and may contain 50 wt% or more of particles having a particle size of 300 µm to 600 µm, and may contain less than 3 wt% of fine powder having a particle size of less than 150 µm.

[0149]

[0150] (Step 3 and Step 4: Surface cross-linking step)

[0151] Next, the method includes a step of preparing a surface cross-linking mixture by mixing a surface cross-linking composition into the base resin particles (step 3); and a step of heat-treating the surface cross-linking mixture to form a surface cross-linking layer on a portion of the surface of the base resin particles (step 4).

[0152] The above surface cross-linking step induces a cross-linking reaction on the surface of the base resin particles in the presence of a surface cross-linking composition including a surface cross-linking agent, so that the unsaturated bonds of the water-soluble ethylenically unsaturated monomer remaining on the surface without being cross-linked are cross-linked by the surface cross-linking agent, thereby forming a superabsorbent resin with a high surface cross-linking density. Specifically, a surface cross-linking layer can be formed by a heat treatment process in the presence of a surface cross-linking agent, and the heat treatment process increases the surface cross-linking density, that is, the external cross-linking density, while the internal cross-linking density does not change, so that the manufactured superabsorbent resin with the surface cross-linking layer formed has a structure in which the external cross-linking density is higher than the internal cross-linking density.

[0153] Here, the modified silicone compound is added in at least one of step 3 (=before the surface cross-linking step), step 4 (=during the surface cross-linking step), or after step 4 (=after the surface cross-linking step), so that the modified silicone compound is included in at least one of the inside or the surface of the surface cross-linking layer.

[0154] That is, as described above, in the formation step of the functional gel polymer, by using a specific chelating agent, the chelating agent is introduced into the inside of the base resin particles, thereby preventing the gel from deteriorating and maintaining the gel strength, and in the formation step of the surface cross-linking layer, by using a modified silicone compound, the modified silicone compound is introduced into at least one of the inside or the surface of the surface cross-linking layer, thereby improving the permeability without using a large amount of the permeability-improving compound, thereby implementing the effect of improving the permeability without reducing the effect of the chelating agent, and thereby simultaneously improving the pressurized absorbency, permeability, and gel strength of the absorbent resin.

[0155]

[0156] First, in the step (step 3) of preparing a surface crosslinking mixture by mixing a surface crosslinking composition into the base resin particles, the surface crosslinking composition includes a surface crosslinking agent for surface crosslinking, and may additionally include water and / or a hydrophilic organic solvent.

[0157] The components and content of the surface cross-linking agent included in the above surface cross-linking composition may be applied in the same manner as described above.

[0158] The above surface cross-linking composition contains water and / or a hydrophilic organic solvent as a medium, which has the advantage of allowing the surface cross-linking agent and the like to be evenly dispersed on the base resin particles. At this time, the content of water and the hydrophilic organic solvent can be applied by adjusting the addition ratio relative to 100 parts by weight of the base resin particles for the purpose of inducing even dissolution / dispersion of the surface cross-linking agent, preventing agglomeration of the base resin particles, and optimizing the surface penetration depth of the surface cross-linking agent.

[0159] The above surface cross-linking composition is prepared as a surface cross-linking mixture by mixing with base resin particles, and there is no particular limitation on the composition of the mixture. For example, a method of mixing the surface cross-linking composition and base resin particles in a reaction tank, a method of spraying the surface cross-linking agent composition onto the base resin particles, a method of continuously supplying the base resin particles and the surface cross-linking agent composition to a continuously operating mixer, and the like can be used.

[0160]

[0161] Next, a step (step 4) of heat-treating the surface cross-linking mixture to form a surface cross-linking layer on a portion of the surface of the base resin particles is included.

[0162] The step of forming the above surface cross-linking layer can be performed by heat treatment at a temperature of 110°C to 200°C, or 110°C to 150°C, for 30 minutes or more. More specifically, the surface cross-linking can be performed by heat treatment at the above-described temperature as the maximum reaction temperature for 30 to 80 minutes, or 40 to 70 minutes, to perform the surface cross-linking reaction.

[0163] By satisfying these surface crosslinking process conditions (particularly, temperature-elevation conditions and reaction conditions at the highest reaction temperature), a superabsorbent resin that appropriately satisfies physical properties such as superior pressure permeability can be manufactured.

[0164] The means for increasing the temperature for the surface crosslinking reaction is not particularly limited. Heating can be achieved by supplying a heat medium or directly supplying a heat source. Usable 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 considering the means of 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.

[0165]

[0166] According to one embodiment of the invention, in the manufacturing step (step 3) of the surface cross-linking mixture, a modified silicone compound may be additionally included, thereby allowing the modified silicone compound to be included within and / or on the surface of the surface cross-linking layer. The aforementioned contents may be equally applied to the components and contents of the modified silicone compound.

[0167]

[0168] According to one embodiment of the invention, in the step of forming a surface cross-linking layer by heat treatment (step 4), a modified silicone compound may be additionally included, whereby the modified silicone compound is included within and / or on the surface of the surface cross-linking layer. The aforementioned contents may be equally applied to the components and contents of the modified silicone compound.

[0169]

[0170] According to one embodiment of the invention, after the step of forming a surface cross-linking layer by heat treatment (step 4), a modified silicone compound may be additionally included, thereby including the modified silicone compound on the surface of the surface cross-linking layer. The aforementioned contents may be equally applied to the components and contents of the modified silicone compound.

[0171] The process after the step of forming a surface cross-linking layer by the above heat treatment (step 4) is not particularly limited, but may be performed together with a post-treatment process commonly applied in the field, such as a cooling process, a water process, and an additive injection process, but is not limited thereto.

[0172]

[0173] According to one embodiment of the invention, in at least one of the step of preparing the surface cross-linking mixture (step 3), the step of forming a surface cross-linking layer by heat treatment (step 4), or the step after the step of forming a surface cross-linking layer by heat treatment (step 4), a modified silicone compound may be additionally included, whereby the modified silicone compound is included inside and / or on the surface of the surface cross-linking layer. The aforementioned contents may be equally applied to the components and contents of the modified silicone compound.

[0174]

[0175] Hereinafter, the functions and effects of the invention will be described in more detail through specific examples. However, these examples are provided merely as examples of the invention and do not define the scope of the invention.

[0176]

[0177] [Examples and Comparative Examples]

[0178] Example 1

[0179] (Step 1: Polymerization stage)

[0180] In a 3 L glass container equipped with a stirrer and a thermometer, 500 g of acrylic acid, 800 ppmw of ethylene glycol diglycidyl ether as an internal crosslinking agent (relative to 100 parts by weight of acrylic acid), and 80 ppmw of diphenyl(2,4,6-trimethylbenzoyl)-phosphine oxide as a photopolymerization initiator (relative to 100 parts by weight of acrylic acid) were added and dissolved, and then 627 g of a 31.5% caustic soda solution was added to prepare a water-soluble unsaturated monomer solution (degree of neutralization: 70 mol%; solid content: 44.9 wt%). When the temperature of the above water-soluble unsaturated monomer solution rises to 40°C due to the heat of neutralization, the mixture is placed in a square container (60 cm wide, 60 cm high) containing 1,000 ppmw of sodium persulfate (relative to 100 parts by weight of acrylic acid) as a thermal polymerization initiator, 800 ppmw of F36D as a capsule foaming agent (relative to 100 parts by weight of acrylic acid), 800 ppmw of sodium dodecyl sulfate (relative to 100 parts by weight of acrylic acid), and 300 ppmw of DTPA-5Na as a chelating agent (relative to 100 parts by weight of acrylic acid), and then irradiated with ultraviolet light for 1 minute (irradiation dose: 10 mV / cm 2 ) and UV polymerization was performed to obtain a functional gel polymer sheet.

[0181] (Step 2: Drying, grinding and classification stage)

[0182] The obtained functional gel polymer sheet was passed through a chopper with a hole size of 16 mm to produce crumbs.

[0183] Next, the crumb was dried in an oven capable of vertical airflow. The drying was performed in multiple stages, and specifically, an air flow oven was used at 170°C for 30 minutes (up flow 5 minutes - down flow 5 minutes - up flow 5 minutes - down flow 5 minutes - up flow 5 minutes - down flow 5 minutes). The dried polymer obtained through the drying process was pulverized using a pulverizer and classified through a standard mesh sieve of ASTM standards to obtain base resin particles having a particle size of 150 to 850 μm.

[0184] (Steps 3 and 4: Surface cross-linking step)

[0185] First, a surface cross-linking composition containing 6 parts by weight of water, 3 parts by weight of methanol, 0.1 parts by weight of aluminum sulfate, and 0.05 parts by weight of ethylene glycol diglycidyl ether (EGDGE) was prepared (based on 100 parts by weight of base resin particles).

[0186] Thereafter, a surface crosslinking mixture was prepared by evenly mixing 100 parts by weight of base resin particles, 9.15 parts by weight of the surface crosslinking composition prepared above, and 0.005 parts by weight of a carboxyl-modified silicone compound (based on 100 parts by weight of base resin particles).

[0187] The above surface cross-linking mixture was supplied to a surface cross-linking reactor, and a surface cross-linking reaction of the base resin particles was performed at 130°C for 40 minutes. Thereafter, 0.05 parts by weight of fumed silica was mixed to obtain a superabsorbent resin.

[0188]

[0189] Example 2

[0190] A superabsorbent resin was manufactured in the same manner as in Example 1, except that in the polymerization step of Step 1 of Example 1, the content of the chelating agent DTPA-5Na was used at 800 ppmw (relative to 100 parts by weight of acrylic acid).

[0191]

[0192] Example 3

[0193] A superabsorbent resin was manufactured in the same manner as in Example 1, except that in the polymerization step of Step 1 of Example 1, EDTA was used as a chelating agent in an amount of 1,000 ppmw (relative to 100 parts by weight of acrylic acid) instead of DTPA-5Na.

[0194]

[0195] Example 4

[0196] A superabsorbent resin was manufactured in the same manner as in Example 1, except that in the surface cross-linking steps of steps 3 and 4 of Example 1, a carboxyl-modified silicone compound was used in an amount of 0.01 parts by weight (relative to 100 parts by weight of the base resin particles).

[0197]

[0198] Example 5

[0199] A superabsorbent resin was manufactured in the same manner as in Example 1, except that in the surface crosslinking steps of steps 3 and 4 of Example 1, a polyether-modified silicone compound was used in place of a carboxyl-modified silicone compound in an amount of 0.005 parts by weight (relative to 100 parts by weight of base resin particles).

[0200]

[0201] Comparative Example 1

[0202] A superabsorbent resin was prepared in the same manner as in Example 1, except that no modified silicone compound was used in the surface cross-linking steps of steps 3 and 4 of Example 1.

[0203]

[0204] Comparative Example 2

[0205] A superabsorbent resin was manufactured in the same manner as in Example 1, except that a chelating agent was not used in the polymerization step of Step 1 of Example 1, and a modified silicone compound was not used in the surface cross-linking steps of Steps 3 and 4.

[0206]

[0207] Comparative Example 3

[0208] A superabsorbent resin was manufactured in the same manner as in Example 1, except that no chelating agent was used in the polymerization step of Step 1 of Example 1.

[0209]

[0210] Comparative Example 4

[0211] A superabsorbent resin was manufactured in the same manner as in Example 1, except that no chelating agent was used in the polymerization step of Step 1 of Example 1, and 0.03 parts by weight (relative to 100 parts by weight of base resin particles) of DTPA-5Na was additionally used in the surface crosslinking steps of Steps 3 and 4.

[0212]

[0213] Comparative Example 5

[0214] A superabsorbent resin was manufactured in the same manner as in Example 1, except that no chelating agent was used in the polymerization step of Step 1 of Example 1, and 0.03 parts by weight (relative to 100 parts by weight of base resin particles) of EDTMP-5Na was additionally used in the surface crosslinking steps of Steps 3 and 4.

[0215]

[0216] Comparative Example 6

[0217] A superabsorbent resin was manufactured in the same manner as in Example 1, except that in the surface cross-linking steps of steps 3 and 4 of Example 1, 0.005 parts by weight (based on 100 parts by weight of base resin particles) of an epoxy-modified silicone compound (KF 101, Shin-Etsu Corporation) was used instead of a carboxyl-modified silicone compound.

[0218]

[0219] Comparative Example 7

[0220] A superabsorbent resin was manufactured in the same manner as in Example 1, except that in the surface cross-linking steps of steps 3 and 4 of Example 1, 0.005 parts by weight (based on 100 parts by weight of base resin particles) of an amino-modified silicone compound (KF 808, Shin-Etsu Corporation) was used instead of a carboxyl-modified silicone compound.

[0221]

[0222] [Experimental Example]

[0223] The properties of the superabsorbent resin including the base resin manufactured in the above examples and comparative examples were evaluated using the following method, and the results are shown in Table 1.

[0224] Unless otherwise specified, all of the following property evaluations were conducted at room temperature (25±1°C), and saline solution or saline refers to a 0.9 wt% sodium chloride (NaCl) aqueous solution, and ascorbic acid saline refers to a 0.9 wt% sodium chloride (NaCl) and 0.005 wt% ascorbic acid aqueous solution.

[0225]

[0226] (1) Centrifuge Retention Capacity (CRC)

[0227] For the superabsorbent resins manufactured in the above examples and comparative examples, particles having a particle size of 150 ㎛ to 850 ㎛ were taken, and the centrifugal retention capacity (CRC) by the no-load absorption rate was measured according to the European Disposables and Nonwovens Association (EDANA) standard EDANA WSP 241.2.

[0228] Specifically, the absorbent resin samples W0 (g) (approximately 0.2 g) obtained through the examples and comparative examples were uniformly placed in non-woven bags, sealed, and then immersed in physiological saline solution (0.9 wt%) at room temperature. After 30 minutes, water was removed from the bags for 3 minutes using a centrifuge at 250 G, and the mass W2 (g) of the bags was measured. In addition, the same operation was performed without using the resin, and the mass W1 (g) at that time was measured. Using each obtained mass, CRC (g / g) was calculated according to the following mathematical formula 2.

[0229] [Equation 2]

[0230] CRC (g / g) = {[W2(g) - W1(g)] / W0(g)} - 1

[0231]

[0232] (2) Voterx absorption rate (seconds)

[0233] For the superabsorbent resins manufactured in the above examples and comparative examples, particles having a particle size of 150 µm to 850 µm were taken, 2 g of the superabsorbent resin sample was added to 50 mL of physiological saline solution, stirred at 600 rpm, and the time until the vortex disappeared was measured in seconds.

[0234]

[0235] (3) Absorbing under pressure (AUP)

[0236] For the superabsorbent resins manufactured in the above examples and comparative examples, particles having a particle size of 150 ㎛ to 850 ㎛ were taken, and the 0.7 psi absorbency under pressure (AUP) was measured according to the method of the European Disposables and Nonwovens Association (EDANA) standard EDANA method WSP 242.3-10.

[0237] First, a 400-mesh stainless steel wire mesh was installed on the bottom of a plastic cylinder with an inner diameter of 60 mm. Under conditions of room temperature and 50% humidity, a superabsorbent resin W0 (g) was uniformly sprayed on the wire mesh, and a piston capable of uniformly applying a load of 0.7 psi was installed on top of it. The piston had an outer diameter slightly smaller than 60 mm, had no gap with the inner wall of the cylinder, and was designed to move up and down without obstruction. At this time, the weight W3 (g) of the device was measured.

[0238] A glass filter with a diameter of 90 mm and a thickness of 5 mm was placed inside a 150 mm diameter petroleum dish, and a saline solution consisting of 0.9 wt% sodium chloride was placed so that it was level with the upper surface of the glass filter. A sheet of filter paper with a diameter of 90 mm was placed on top of it. The measuring device was placed on the filter paper, and the liquid was absorbed under a load for 1 hour. After 1 hour, the measuring device was lifted, and its weight W4 (g) was measured. Using each mass obtained, the absorbency under pressure (g / g) was calculated according to the following mathematical equation 3.

[0239] [Equation 3]

[0240] AUP(g / g) = [W4(g) - W3(g)] / W0(g)

[0241]

[0242] (4) Permeability (seconds)

[0243] For the superabsorbent resins manufactured in the above examples and comparative examples, particles of the resin classified through a #30-#50 sieve were taken, and the permeability was measured according to the method of the following mathematical formula 1.

[0244] [Mathematical Formula 1]

[0245] Permeability (sec) = T1 - B

[0246] In the above mathematical formula 1,

[0247] T1 is the time taken for 0.2 g of superabsorbent resin sample to be placed in a chromatography tube equipped with a glass filter, brine is added to make the brine volume 50 ml, left for 30 minutes, an additional 0.3 psi piston is added, left for 1 minute, and the lower valve is opened for the liquid level to decrease from 40 ml to 20 ml.

[0248] B is the time taken for the liquid level to decrease from 40 ml to 20 ml when an additional 0.3 psi piston (0.3 psi) is added to a chromatography tube filled with brine.

[0249]

[0250] (5) Gel strength (N)

[0251] For the superabsorbent resins manufactured in the above examples and comparative examples, particles having a particle size of 150 μm to 850 μm were taken, 2.5 g of the superabsorbent resin sample was immersed in 50 g of ascorbic acid saline solution, and swelled in an oven at 40°C for 24 hours. Then, the gel strength of the swollen base resin powder was measured using a tensile compression tester.

[0252] Specifically, the above-mentioned swollen base resin powder is measured using a digital force gauge FGP-2, which is a tensile compression tester, and the peak value of the force (N) applied to the tip as the tip penetrates is measured three times under the following conditions, and the arithmetic average value thereof is taken as the gel strength (unit: N).

[0253] Tip size: terminal diameter 10±0.1 mm

[0254] Beaker size: 50±0.1 mm

[0255] Penetration speed: 500±0.5 mm / min

[0256]

[0257] Classification CRC (g / g) Vortex (sec) AUP (g / g) Liquid permeability (sec) Gel strength (N) Example 139.8 37 14.21 230.79 Example 239.0 38 14.41 190.85 Example 339.3 37 14.51 300.75 Example 439.7 37 14.71 020.80 Example 539.9 38 14.51 300.78 Comparative Example 139.7 35 12.42 800.76 Comparative Example 239.5 37 13.11 800.31 Comparative Example 339.5 38 14.01 800.34 Comparative Example 439.4 37 13.22 600.45 Comparative Example 539.63713.32700.48Comparative example 640.83611.73400.50Comparative example 740.93610.94500.45

[0258] As can be confirmed from the results in Table 1 above, it was confirmed that the superabsorbent resin according to the embodiment of the present invention can simultaneously improve the pressurized absorbency, liquid permeability, and gel strength required for improving the rewetting characteristics by including a specific chelate compound therein and including a modified silicone compound in the surface cross-linking layer of the base resin.

[0259] In the case of comparative examples that did not include one or more of the two components of the present invention or had different injection stages, it was confirmed that it was difficult to simultaneously improve pressurized absorbency, liquid permeability, and gel strength.

Claims

1. Base resin particles comprising a crosslinked polymer obtained by crosslinking a water-soluble ethylenically unsaturated monomer having at least a portion of an acidic group neutralized in the presence of an aminocarboxylic acid metal chelating agent; and A surface crosslinking layer is formed by additional crosslinking of the crosslinked polymer through a surface crosslinking agent on a portion of the surface of the base resin particle, Containing a modified silicone compound on at least one of the inside or the surface of the surface cross-linking layer, The above modified silicone compound has a polysiloxane main chain, Containing at least one carboxylic acid group or polyether group at at least one of the side chains or terminals of the polysiloxane, Superabsorbent resin.

2. In paragraph 1, The above aminocarboxylic acid metal chelating agent comprises at least one selected from the group consisting of ethylenediaminetetraacetic acid, diethylenetriaminepentaacetic acid, hydroxyethylenediaminetriacetic acid, triethylenetetraminehexaacetic acid, trans-1,2-diaminocyclohexanetetraacetic acid, and metal salts thereof. Superabsorbent resin.

3. In paragraph 1, The above aminocarboxylic acid metal chelating agent is contained in an amount of 50 ppmw to 5,000 ppmw with respect to a water-soluble ethylenically unsaturated monomer. Superabsorbent resin.

4. In paragraph 1, The above modified silicone compound is included in an amount of 0.001 to 0.1 parts by weight relative to the base resin particles. Superabsorbent resin.

5. In paragraph 1, The above superabsorbent resin has an absorbency under pressure (AUP) of 13.0 g / g or more at 0.7 psi centrifugal separation according to EDANA method WSP 242.3-10. Superabsorbent resin.

6. In paragraph 1, The above superabsorbent resin has a permeability of 180 seconds or less as measured by the following mathematical formula 1. Superabsorbent resin: [Mathematical Formula 1] Permeability (sec) = T1 - B In the above mathematical formula 1, T1 is the time taken for the liquid level to decrease from 40 ml to 20 ml by placing 0.2±0.0005 g of superabsorbent resin sample in a chromatography tube equipped with a glass filter, adding brine to make the brine volume 50 ml, leaving it for 30 minutes, then inserting an additional 0.3 psi piston, leaving it for 1 minute, and then opening the lower valve. B is the time taken for the liquid level to decrease from 40 ml to 20 ml when an additional 0.3 psi piston (0.3 psi) is added to a chromatography tube filled with brine.

7. In paragraph 1, The above superabsorbent resin is a superabsorbent resin sample 2.5 g immersed in 50 g of ascorbic acid saline solution, swelled in a 40°C oven for 24 hours, and then the swollen superabsorbent resin has a gel strength of 0.70 N or more measured using a tensile compression tester. Superabsorbent resin.

8. A method for manufacturing a superabsorbent resin according to Article 1, A step (step 1) 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 aminocarboxylic acid metal chelating agent; A step of drying, crushing and classifying the above functional gel polymer to form base resin particles (step 2); A step (step 3) of preparing a surface cross-linking mixture by mixing a surface cross-linking composition into the above base resin particles; and A step (step 4) of heat-treating the above surface cross-linking mixture to form a surface cross-linking layer on a portion of the surface of the base resin particles; Adding a modified silicone compound in at least one of step 3, step 4 or after step 4, The above modified silicone compound has a polysiloxane main chain, Containing at least one carboxylic acid group or polyether group at at least one of the side chains or terminals of the polysiloxane, Method for producing superabsorbent resin.