Superabsorbent resin composition and method for producing the same

Abstract

The superabsorbent resin composition and its production method according to the present invention are characterized by having excellent deodorizing power while minimizing the deterioration of the physical properties of the superabsorbent resin by mixing a diester-based compound with the superabsorbent resin.

Description

Technical Field

[0001] [Cross-reference to Related Applications] This application claims the benefit of priority based on Korean Patent Application No. 10-2023-0020907, filed on February 16, 2023, and all the contents disclosed in the literature of the Korean patent application are incorporated herein by reference.

[0002] The present invention relates to a superabsorbent resin composition and a method for producing the same. Specifically, the present invention relates to a superabsorbent resin composition having deodorizing power and a method for producing the same.

Background Art

[0003] A superabsorbent polymer (SAP) is a synthetic polymer material having a function of absorbing water in an amount of about 500 to 1000 times its own weight, and is named differently such as SAM (Super Absorbency Material) and AGM (Absorbent Gel Material) for each developing company. Such superabsorbent resins have begun to be put into practical use as sanitary products, and currently, in addition to sanitary products such as children's disposable diapers, they are widely used as water retention materials for horticultural soils, water stop materials for civil engineering and construction, seedling raising sheets, freshness retainers in the food distribution field, and materials for compresses.

[0004] Most frequently, such superabsorbent resins are widely used in the field of sanitary materials such as diapers and sanitary napkins. In such sanitary materials, the superabsorbent resin is generally contained in a state of being diffused in pulp. However, recently, efforts have continued to provide sanitary materials such as thinner diapers, and as part of this, the development of so-called pulpless diapers in which the pulp content is reduced or even no pulp is used at all has been actively carried out.

[0005] Thus, in the case of a sanitary material in which the pulp content decreases or pulp is not used, a relatively high proportion of superabsorbent resin is contained, and such superabsorbent resin particles are inevitably contained in multiple layers within the sanitary material. In order for the overall superabsorbent resin particles contained in multiple layers in this way to absorb liquid such as urine more efficiently, the superabsorbent resin basically needs to have high water absorption performance and water absorption speed. Not only that, the absorbed liquid must not leak out under external pressure. In addition, permeability is also required to maintain the original form well even when the liquid is absorbed and the material swells.

[0006] Therefore, many studies have been conducted, such as surface cross-linking, to improve the basic water absorption and water retention capacity of superabsorbent resins.

[0007] However, superabsorbent resins can be used in sanitary materials, in which case there may be a problem of reduced usability due to the bad odor of the absorbed liquid such as human and pet excrement. In particular, it is necessary to suppress the bad odor generated from the absorbed liquid.

[0008] Therefore, it has been considered to add an organic acid or an antibacterial substance as a deodorant to endow the superabsorbent resin with deodorant performance. However, the bad odor generated from the actually absorbed liquid is not limited to ammonia, but is generated from various substances. Therefore, it was difficult to suppress the bad odor by using only one substance such as an organic acid or an antibacterial substance.

[0009] Therefore, the need for suppressing bad odor is gradually increasing, not only for the basic physical properties of superabsorbent resins, namely water absorption and water retention capacity. Therefore, the actual situation is that it is necessary to produce superabsorbent resins having excellent deodorant power. Summary of the Invention Problems to be Solved by the Invention

[0010] An object of the present invention is to provide a superabsorbent resin composition having deodorant power and a method for producing the same.

[0011] More specifically, an object of the present invention is to provide a superabsorbent resin composition having excellent deodorizing power while minimizing deterioration of physical properties of the superabsorbent resin, and a method for producing the same.

Means for Solving the Problems

[0012] To solve the above problems, the present invention provides the following superabsorbent resin composition.

[0013] A base resin containing a crosslinked polymer obtained by crosslinking and polymerizing an acrylic acid-based monomer having an acidic group at least partially neutralized with an internal crosslinking agent, and a surface crosslinked layer formed on the surface of the base resin, wherein the crosslinked polymer is additionally crosslinked through a surface crosslinking agent; and a superabsorbent resin containing a diester compound represented by Chemical Formula 1, The diester compound is contained separately from or both within the surface crosslinked layer of the superabsorbent resin.

[0014]

Chemical Formula

[0015] In Chemical Formula 1, n is an integer of 1 to 10, R is C 1-20 linear or branched alkyl.

[0016] Further, the present invention provides a method for producing the following superabsorbent resin composition.

[0017] Crosslinking and polymerizing an acrylic acid-based monomer having an acidic group at least partially neutralized in the presence of an internal crosslinking agent and a polymerization initiator to form a water-containing gel polymer (Step 1); Producing a base resin containing a crosslinked polymer obtained by drying and pulverizing the water-containing gel polymer (Step 2); Mixing a surface crosslinking agent with the base resin to produce a mixture (Step 3); and A step of heat-treating the mixture to produce a superabsorbent resin having a surface crosslinked layer formed on the surface of the base resin (Step 4); is included. During the reaction of the surface crosslinking, after the surface crosslinking, or both, a diester compound represented by Chemical Formula 1 is mixed.

[0018]

Chemical Formula

[0019] (In Chemical Formula 1, n is an integer from 1 to 10, R is a C 1-20 linear or branched alkyl.)

Advantages of the Invention

[0020] As described above, the present invention is characterized by providing a superabsorbent resin composition and a production method that have excellent water absorption ability while having excellent deodorizing power by applying a diester compound to the superabsorbent resin.

Embodiments for Carrying Out the Invention

[0021] The terms used in this specification are used only for explaining exemplary embodiments and are not intended to limit the present invention. Singular expressions include plural expressions unless the context clearly indicates otherwise. In this specification, terms such as "including", "comprising", or "having" are intended to specify the presence of implemented features, steps, components, or combinations thereof, and should not be understood as precluding the presence or addition possibility of one or more other features, steps, components, or combinations thereof.

[0022] The present invention can be subjected to various modifications and can have various forms, and specific examples will be illustrated and described in detail below. However, this is not intended to limit the present invention to specific disclosed forms, and it should be understood to include all modifications, equivalents, and alternatives included in the spirit and technical scope of the present invention.

[0023] Hereinafter, the superabsorbent resin composition and its manufacturing method will be described in more detail according to specific embodiments of the invention.

[0024] Prior to that, the technical terms used in this specification are merely for referring to specific embodiments and are not intended to limit the present invention. And the singular forms used herein include plural forms as well, unless the context clearly indicates the contrary meaning.

[0025] For reference, in this specification, "superabsorbent resin" can be used to mean the superabsorbent resin polymer itself depending on the context, or all of the products that have been made suitable for commercialization through additional processes for the polymer, such as surface crosslinking, micronized regranulation, drying, pulverization, classification, etc.

[0026] Also, in the specification of the present invention, "base resin" or "base resin powder" is a polymer obtained by drying and pulverizing a polymer in which an acrylic acid-based monomer has been polymerized to form particles or powder, and means a polymer in a state where the surface modification or surface crosslinking steps described later have not been performed.

[0027] (Superabsorbent Resin Composition) According to an embodiment of the present invention, a superabsorbent resin composition is provided.

[0028] The superabsorbent resin composition includes a base resin containing a crosslinked polymer obtained by crosslinking and polymerizing an acrylic acid-based monomer having an acidic group at least partially neutralized with an internal crosslinking agent, and a surface crosslinked layer formed on the surface of the base resin, wherein the crosslinked polymer is additionally crosslinked through a surface crosslinking agent; and a diester-based compound, The diester-based compound is contained separately from or both within the surface crosslinked layer of the superabsorbent resin.

[0029] The acrylic acid-based monomer can be any monomer commonly used in the production of superabsorbent resins. Specifically, the acrylic acid-based monomer can be a compound represented by the following Chemical Formula 2.

[0030] [Chemical Formula 2] R 1 -COOM 1

[0031] In Chemical Formula 2, R 1 is an alkyl group having 2 to 5 carbon atoms containing an unsaturated bond, M 1 is a hydrogen atom, a monovalent or divalent metal, an ammonium group or an organic amine salt.

[0032] Preferably, the acrylic acid-based monomer includes one or more selected from the group consisting of acrylic acid, methacrylic acid, and their monovalent metal salts, divalent metal salts, ammonium salts, and organic amine salts.

[0033] The acrylic acid-based monomer has an acidic group, and at least a part of the acidic group can be neutralized. Preferably, the monomer partially neutralized with an alkaline substance such as sodium hydroxide, potassium hydroxide, ammonium hydroxide, etc. can be used.

[0034] At this time, the degree of neutralization of the monomer can be 40 to 95 mol%, or 40 to 80 mol%, or 45 to 75 mol%. The range of the degree of neutralization can vary depending on the final physical properties. If the degree of neutralization is excessively high, the neutralized monomer may precipitate and it may be difficult to carry out polymerization smoothly. On the contrary, if the degree of neutralization is excessively low, not only does the water absorption of the polymer decrease significantly, but it may also exhibit properties similar to those of an elastic rubber that is difficult to handle.

[0035] On the other hand, in order to improve the physical properties of the resin by polymerization of the acrylic acid-based monomer, it is carried out in the presence of a crosslinking agent (an "internal crosslinking agent"). The crosslinking agent is for internally crosslinking the hydrogel polymer and can be used separately from the "surface crosslinking agent" described later.

[0036] As the internal crosslinking agent, any compound can be used as long as it enables the introduction of crosslinking bonds during the polymerization of the acrylic acid-based monomer. As non-limiting examples, the internal crosslinking agent can be N,N'-methylenebisacrylamide, trimethylolpropane tri(meth)acrylate, ethylene glycol di(meth)acrylate, polyethylene glycol di(meth)acrylate, propylene glycol di(meth)acrylate, polypropylene glycol di(meth)acrylate, butanediol di(meth)acrylate, butylene glycol di(meth)acrylate, diethylene glycol di(meth)acrylate, hexanediol di(meth)acrylate, triethylene glycol di(meth)acrylate, tripropylene glycol di(meth)acrylate, tetraethylene glycol di(meth)acrylate, dipentaerythritol pentaacrylate, glycerin tri(meth)acrylate, pentaerythritol tetraacrylate, triallylamine, allyl (meth)acrylate, ethylene glycol diglycidyl ether, propylene glycol, glycerin, or a polyfunctional crosslinking agent such as ethylene carbonate, etc., can be used alone or in combination of two or more.

[0037] Such an internal crosslinking agent can be added to the monomer composition at a concentration of 0.001 to 1% by weight, or 0.01 to 0.8% by weight, or 0.1 to 0.7% by weight. That is, when the concentration of the internal crosslinking agent is excessively low, the water absorption rate of the resin may decrease and the gel strength may become weak, which is not preferable. On the contrary, when the concentration of the internal crosslinking agent is excessively high, the water absorption capacity of the resin may decrease and it may not be preferable as a water-absorbing body.

[0038] In addition to this, the base resin can further contain additives such as a plasticizer, a storage stabilizer, and an antioxidant, if necessary.

[0039] The surface crosslinked layer is formed by additional crosslinking of a crosslinked polymer through a surface crosslinking agent. At this time, the surface crosslinking agent is a surface crosslinking agent generally used for surface crosslinking of the superabsorbent resin, and any compound that can react with the functional groups of the polymer may be used, without any special restrictions.

[0040] Preferably, in order to improve the properties of the resulting superabsorbent resin, 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; polyvalent metal salts; and alkylene carbonate compounds can be used as the surface crosslinking agent.

[0041] Specifically, examples of polyhydric alcohol compounds include one or more 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.

[0042] In addition, as the epoxy compound, ethylene glycol diglycidyl ether, glycidol, etc. can be used, and as the polyamine compounds, one or more selected from the group consisting of ethylenediamine, diethylenetriamine, triethylenetetramine, tetraethylenepentamine, pentaethylenehexamine, polyethyleneimine, and polyamide polyamine can be used.

[0043] And as the haloepoxy compound, epichlorohydrin, epibromohydrin, and α-methyl epichlorohydrin can be used. On the other hand, as the mono-, di-, or polyoxazolidinone compound, for example, 2-oxazolidinone, etc. can be used.

[0044] And as the alkylene carbonate compound, ethylene carbonate, etc. can be used. These can be used alone or in combination with each other. On the other hand, in order to improve the efficiency of the surface crosslinking step, one or more polyhydric alcohol compounds having 2 to 10 carbon atoms can be included and used from among these surface crosslinking agents.

[0045] The content of the added surface crosslinking agent can be appropriately selected depending on the type of the specifically added surface crosslinking agent and the reaction conditions. Usually, about 0.001 to about 5 parts by weight, preferably about 0.01 to about 3 parts by weight, more preferably about 0.05 to about 2 parts by weight can be used with respect to 100 parts by weight of the polymer.

[0046] If the content of the surface crosslinking agent is excessively small, the surface crosslinking reaction hardly occurs. When it exceeds 5 parts by weight with respect to 100 parts by weight of the polymer, a decrease in water absorption capacity and physical properties may occur due to the progress of the excessive surface crosslinking reaction.

[0047] On the one hand, the surface crosslinking agent can additionally contain inorganic substances. As such inorganic substances, one or more inorganic substances selected from the group consisting of silica, clay, alumina, silica-alumina composite, titania, zinc oxide, and aluminum sulfate can be used. The inorganic substances can be used in powder form or liquid form, and in particular, alumina powder, silica-alumina powder, titania powder, or nano-silica solution can be used. Further, the inorganic substances can be used in a content of about 0.001 to about 1 part by weight based on 100 parts by weight of the base resin.

[0048] The superabsorbent resin composition according to an embodiment of the present invention can contain a diester-based compound as a deodorant substance. Since the ester and hydrophobic functional groups of the diester-based compound have an affinity for malodorous substances, when a superabsorbent resin composition containing a diester-based compound is applied to a sanitary product, it has the effect of removing the malodor of the liquid absorbed by the sanitary product. The diester-based compound according to an embodiment of the present invention can be represented by the following Chemical Formula 1.

[0049] [Chemical Formula]

[0050] In Chemical Formula 1, n can be an integer from 1 to 10, specifically an integer from 2 to 4.

[0051] R is C 1-20 It can be a linear or branched alkyl group. Specifically, R is C 3-4 It can be a linear or branched alkyl group. As an example, R can be isopropyl or isobutyl.

[0052] The above-mentioned diester compound can be contained separately from the superabsorbent resin or in both within the surface crosslinked layer of the superabsorbent resin. The fact that the diester compound is contained separately from the superabsorbent resin may mean that the diester compound is mixed with the superabsorbent resin having a surface crosslinked layer and exists not inside the surface crosslinked layer of the superabsorbent resin but on the outer surface of the surface crosslinked layer.

[0053] The above-mentioned diester compound can contain one or more selected from the group consisting of diisopropyl adipate, diisobutyl succinate, diisobutyl glutarate, and diisobutyl adipate. Specifically, the diester compound can contain one or more selected from the group consisting of diisopropyl adipate, diisobutyl succinate, and diisobutyl adipate.

[0054] The above-mentioned diester compound can be contained in an amount of 0.1 to 5.0 parts by weight based on 100 parts by weight of the base resin. Specifically, the diester compound can be contained in an amount of 0.1 part by weight or more, 0.2 part by weight or more, 0.3 part by weight or more, or 0.4 part by weight or more to 5.0 parts by weight or less, 4.0 parts by weight or less, 3.0 parts by weight or less, 2.0 parts by weight or less, 1.0 part by weight or less, or 0.5 part by weight or less based on 100 parts by weight of the base resin.

[0055] In order to exhibit the level of deodorizing ability to be achieved in the present invention while maintaining the inherent water absorption properties of the superabsorbent resin, it is preferable that the diester compound as the deodorizing substance is contained within the above content range.

[0056] The above-mentioned superabsorbent resin composition can further contain one or more additives selected from the group consisting of a chelating agent, an iodine-based compound, and an organic acid.

[0057] The superabsorbent resin composition can contain a chelating agent. In the case of a sanitary product containing the superabsorbent resin composition, bacteria derived from the skin or the like may meet with the absorbed liquid, and additional malodor may be generated due to the growth of bacteria. The chelating agent can suppress the growth of such bacteria.

[0058] The chelating agent can contain an aminoacetate-based chelating agent. Specifically, the aminoacetate-based chelating agent can contain one or more selected from the group consisting of ethylenediaminetetraacetic acid (EDTA), L-glutamic acid diacetic acid (GLDA), methylglycine diacetic acid (MGDA), hydroxyethylethylenediaminetriacetic acid (HEDTA), ethanol diglycine acid (EDG), diethylenetriaminepentaacetic acid (DTPA), and their salts. More specifically, the chelating agent can be ethylenediaminetetraacetic acid (EDTA).

[0059] In particular, the aminoacetate-based chelating agent is a component that can effectively suppress the growth of bacteria such as Escherichia coli generated by malodor-generating substances. As the wearing time of the product passes, the growth of bacteria is accelerated by substances that generate malodor remaining in the product, and additional malodor is generated as a result. However, the aminoacetate-based chelating agent can suppress the growth of such bacteria and effectively reduce the generation of additional malodor.

[0060] In particular, the aminoacetate-based chelating agent can effectively suppress the growth of bacteria by collecting polyvalent metal components necessary for the growth of cell membranes.

[0061] The chelating agent can be contained in an amount of 0.1 to 2.0 parts by weight based on 100 parts by weight of the base resin. Specifically, the chelating agent can be 0.1 part by weight or more, 0.2 part by weight or more, 0.4 part by weight or more, or 0.6 part by weight or more to 2.0 parts by weight or less, 1.5 parts by weight or less, or 1.0 part by weight or less based on 100 parts by weight of the base resin.

[0062] When used within the above content range, it is possible to significantly improve the deodorizing power of the water-absorbing resin by embodying the property of effectively suppressing bacteria without degrading the water-absorbing physical properties, which are the inherent physical properties of the superabsorbent resin.

[0063] The chelating agent can be used by being mixed into an aqueous solution in the form of a salt, and the above content range is based on the solid content.

[0064] The superabsorbent resin composition can contain an iodine-based compound. The iodine-based compound can be a metal iodide salt. The metal iodide salt can be added to the manufacturing process in a form in which one or more selected from the group consisting of CuI, NaI, and KI and I2 are both dissolved in water or in the form of a powder obtained by drying an aqueous solution. The metal iodide salt can also be added to the superabsorbent resin, similar to the diester-based compound, to impart deodorizing properties. The metal iodide salt acts on most of the malodorous substances in a manner of oxidizing the malodorous substances to remove the malodor and is generally effective.

[0065] The iodine-based compound can be contained in an amount of 0.1 to 5.0 parts by weight based on 100 parts by weight of the base resin. Specifically, the chelating agent can be 0.1 part by weight or more, 0.2 part by weight or more, 0.4 part by weight or more, or 0.6 part by weight or more to 5.0 parts by weight or less, 4.0 parts by weight or less, 3.0 parts by weight or less, 2.0 parts by weight or less, or 1.0 part by weight or less based on 100 parts by weight of the base resin.

[0066] The superabsorbent resin composition can contain an organic acid. The organic acid can be one or more selected from the group consisting of citric acid, acetic acid, formic acid, fumaric acid, lactic acid, and propionic acid. Specifically, the organic acid can be citric acid. The organic acid can exhibit a deodorizing effect like the diester-based compound in the superabsorbent resin.

[0067] The organic acid may be contained in an amount of 0.1 to 5.0 parts by weight based on 100 parts by weight of the base resin. Specifically, the chelating agent may be 0.1 part by weight or more, 0.2 part by weight or more, 0.4 part by weight or more, or 0.6 part by weight or more to 5.0 parts by weight or less, 4.0 parts by weight or less, 3.0 parts by weight or less, 2.0 parts by weight or less, or 1.0 part by weight or less based on 100 parts by weight of the base resin.

[0068] (Method for producing superabsorbent resin composition) According to one embodiment of the present invention, a method for producing a superabsorbent resin composition is provided.

[0069] The method for producing the superabsorbent resin composition is as follows. Crosslinking and polymerizing an acrylic acid-based monomer having an acidic group at least partially neutralized in the presence of an internal crosslinking agent and a polymerization initiator to form a water-containing gel polymer (Step 1); producing a base resin containing a crosslinked polymer obtained by pulverizing and drying the water-containing gel polymer (Step 2); mixing a surface crosslinking agent with the base resin to produce a mixture (Step 3); and heat-treating the mixture to produce a superabsorbent resin having a surface crosslinked layer formed on the surface of the base resin (Step 4). During the reaction of the surface crosslinking, after the surface crosslinking, or both, a diester-based compound can be mixed.

[0070] The method for producing a superabsorbent resin generally includes polymerizing an acrylic acid-based monomer to produce a water-containing gel polymer and pulverizing the same. In addition, in order to improve various physical properties of the superabsorbent resin, a method of crosslinking the surface of the produced superabsorbent resin is used.

[0071] The present invention provides a superabsorbent resin composition having deodorizing properties by mixing a diester-based compound with the surface-crosslinked superabsorbent resin.

[0072] On the one hand, "mixed in Stage A" in the present invention means that it is additionally mixed into the target mixture during the execution of Stage A, and may mean that it is divided and mixed one or more times so as to meet the target content ratio at this stage. On the other hand, "mixed before and after Stage A" means that it is additionally mixed before Stage A is carried out or after Stage A is completed.

[0073] Hereinafter, the present invention will be described in detail for each stage.

[0074] (Stage 1) The said Stage 1 is a stage of manufacturing a hydrogel polymer. Specifically, it is a stage of forming a hydrogel polymer by crosslinking and polymerizing a monomer composition containing an acrylic acid-based monomer having an acidic group at least partially neutralized.

[0075] The said acrylic acid-based monomer may be any monomer usually used in the manufacture of superabsorbent resins. Specifically, the said acrylic acid-based monomer may be a compound represented by the following Chemical Formula 2.

[0076] [Chemical Formula 2] R 1 -COOM 1

[0077] In the said Chemical Formula 2, R 1 is an alkyl group having 2 to 5 carbon atoms containing an unsaturated bond, M 1 is a hydrogen atom, a monovalent or divalent metal, an ammonium group or an organic amine salt.

[0078] Preferably, the said acrylic acid-based monomer contains one or more selected from the group consisting of acrylic acid, methacrylic acid and their monovalent metal salts, divalent metal salts, ammonium salts and organic amine salts.

[0079] The acrylic monomer has an acidic group, and at least a part of the acidic group may be neutralized. Preferably, a monomer partially neutralized with an alkaline substance such as sodium hydroxide, potassium hydroxide, or ammonium hydroxide can be used.

[0080] At this time, the degree of neutralization of the monomer can be 40 to 95 mol%, or 40 to 80 mol%, or 45 to 75 mol%. The range of the degree of neutralization can vary depending on the final physical properties. If the degree of neutralization is too high, the neutralized monomer may precipitate and it may be difficult to carry out polymerization smoothly. On the contrary, if the degree of neutralization is too low, not only will the water absorption capacity of the polymer decrease significantly, but it may also exhibit properties similar to those of an elastic rubber that is difficult to handle.

[0081] The monomer composition may contain a polymerization initiator generally used in the production of superabsorbent resins.

[0082] As the polymerization initiator, a thermal polymerization initiator or a photo-polymerization initiator can be used depending on the polymerization method. However, even in the case of the photo-polymerization method, a certain amount of heat is generated by ultraviolet irradiation or the like, and a certain amount of heat is also generated due to the progress of the polymerization reaction, which is an exothermic reaction. Therefore, an additional thermal polymerization initiator may be included.

[0083] 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 can be used. As a specific example of the acyl phosphine among them, commercial lucirin TPO, that is, 2,4,6-trimethyl-benzoyl-trimethyl phosphine oxide can be used. Regarding more diverse photopolymerization initiators, they are disclosed on page 115 of the book "UV Coatings: Basics, Recent Developments and New Application (Elsevier, 2007)" by Reinhold Schwalm, and this can be referred to.

[0084] As the thermal polymerization initiator, one or more compounds selected from the group of initiators consisting of persulfate-based initiators, azo-based initiators, hydrogen peroxide, and ascorbic acid can be used. Specifically, examples of persulfate-based initiators include sodium persulfate (Na2S2O8), potassium persulfate (K2S2O8), ammonium persulfate ((NH4)2S2O8), etc. Examples of azo-based initiators include 2,2-azobis-(2-amidinopropane) dihydrochloride, 2,2-azobis-(N,N-dimethylene)isobutyramidine dihydrochloride, 2-(carbamoylazo)isobutylonitrile, 2,2-azobis[2-(2-imidazolin-2-yl)propane] dihydrochloride, 4,4-azobis-(4-cyanovaleric acid), etc. More diverse thermal polymerization initiators are disclosed on page 203 of the book "Principle of Polymerization (Wiley, 1981)" by Odian, and this can be referred to.

[0085] Such a polymerization initiator can be added at a concentration of 0.001 to 1% by weight, or 0.005 to 0.1% by weight, based on the monomer composition. That is, when the concentration of the polymerization initiator is excessively low, the polymerization rate may become slow, and a large amount of residual monomer may be extracted in the final product, which is not preferable. On the contrary, when the concentration of the polymerization initiator is excessively high, the polymer chains forming the network become short, the content of water-soluble components increases, and the physical properties of the resin may deteriorate, such as a decrease in the pressure absorption capacity, which is not preferable.

[0086] On the other hand, the polymerization of the monomer composition is carried out in the presence of a crosslinking agent ("internal crosslinking agent") in order to improve the physical properties of the resin by the polymerization of the acrylic acid-based monomer. The crosslinking agent is for internally crosslinking the hydrogel polymer and can be used separately from the "surface crosslinking agent" described later.

[0087] As the internal crosslinking agent, any compound can be used as long as it enables the introduction of crosslinking bonds during the polymerization of the acrylic acid-based monomer. As non-limiting examples, the internal crosslinking agent may be N,N'-methylenebisacrylamide, trimethylolpropane tri(meth)acrylate, ethylene glycol di(meth)acrylate, polyethylene glycol di(meth)acrylate, propylene glycol di(meth)acrylate, polypropylene glycol di(meth)acrylate, butanediol di(meth)acrylate, butylene glycol di(meth)acrylate, diethylene glycol di(meth)acrylate, hexanediol di(meth)acrylate, triethylene glycol di(meth)acrylate, tripropylene glycol di(meth)acrylate, tetraethylene glycol di(meth)acrylate, dipentaerythritol pentaacrylate, glycerin tri(meth)acrylate, pentaerythritol tetraacrylate, triallylamine, allyl (meth)acrylate, ethylene glycol diglycidyl ether, propylene glycol, glycerin, or a polyfunctional crosslinking agent such as ethylene carbonate, which can be used alone or in combination of two or more.

[0088] Such internal crosslinking agents can be added at a concentration of 0.001 to 1% by weight, or 0.01 to 0.8% by weight, or 0.1 to 0.7% by weight with respect to the monomer composition. That is, when the concentration of the internal crosslinking agent is excessively low, the water absorption rate of the resin may decrease and the gel strength may become weak, which is not preferable. On the contrary, when the concentration of the internal crosslinking agent is excessively high, the water absorption capacity of the resin may decrease and it may not be preferable as a water-absorbing body.

[0089] In addition, the crosslinking polymerization of the monomer composition can be carried out in the presence of a foaming agent depending on the necessity and degree of improvement of the water absorption rate. Such a foaming agent is decomposed during the crosslinking polymerization reaction process to generate a gas, and thus pores can be formed in the water-containing gel polymer. As a result, when such a foaming agent is additionally used, a more developed porous structure can be formed in the superabsorbent resin, and the water absorption rate of the superabsorbent resin can be further improved.

[0090] As a non-limiting example, the blowing agent can include one or more compounds selected from the group consisting of sodium bicarbonate, sodium carbonate, potassium bicarbonate, potassium carbonate, calcium bicarbonate, calcium carbonate, magnesium bicarbonate, magnesium carbonate, azodicarbonamide (ADCA), dinitroso pentamethylene tetramine (DPT), p,p’-oxybis(benzenesulfonyl hydrazide) (OBSH), p-toluenesulfonyl hydrazide (TSH), sucrose stearate, sucrose palmitate, and sucrose laurate.

[0091] The blowing agent can be present in the monomer composition at a content of 1000 to 4000 ppmw. More specifically, it can be present at a content of 1000 ppm or more, or 1100 ppmw or more, or 1200 ppmw or more; and 4000 ppmw or less, or 3500 ppmw or less, or 3000 ppmw or less.

[0092] In addition, the monomer composition can further include additives such as plasticizers, storage stabilizers, and antioxidants as needed.

[0093] And such a monomer composition can be prepared in the form of a solution in which raw material substances such as the aforementioned acrylic acid-based monomer, polymerization initiator, internal crosslinking agent, foaming agent, etc. are dissolved in a solvent.

[0094] At this time, as the solvent that can be used, any solvent that can dissolve the aforementioned raw material substances can be used without limitation on its composition. For example, as the solvent, 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, etc. can be used.

[0095] The formation of the hydrogel polymer through the polymerization of the monomer composition can be carried out by a normal polymerization method, and the process is not particularly limited.

[0096] As a non-limiting example, the polymerization method is roughly classified into thermal polymerization and photopolymerization according to the type of polymerization energy source. When performing the thermal polymerization, it is carried out in a reactor having a stirring shaft such as a kneader, and when performing the photopolymerization, it can be carried out in a reactor equipped with a movable conveyor belt.

[0097] As an example, the monomer composition can be introduced into a reactor such as a kneader equipped with a stirring shaft, and hot air can be supplied thereto or the reactor can be heated for thermal polymerization to obtain a hydrogel polymer. At this time, depending on the form of the stirring shaft provided in the reactor, the hydrogel polymer discharged from the reactor outlet can be obtained in the form of particles of several millimeters to several centimeters. Specifically, the resulting hydrogel polymer can be obtained in various forms depending on the concentration and injection rate of the monomer composition to be injected, etc., but a hydrogel polymer having a (weight average) particle size of usually 2 to 50 mm can be obtained.

[0098] And as another example, when photopolymerization of the monomer composition is carried out in a reactor equipped with a movable conveyor belt, a hydrogel 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 rate of the monomer composition to be injected, but in order to ensure the production rate etc. while allowing the whole sheet to be uniformly polymerized, it is preferably adjusted to a thickness of usually 0.5 to 10 cm.

[0099] The hydrogel polymer formed by such a method can exhibit a water content of 40 to 80% by weight. Here, the water content is the weight occupied by water in the entire weight of the hydrogel polymer, and can be the value obtained by subtracting the weight of the polymer in the dry state from the weight of the hydrogel polymer. Specifically, it can be defined as the value calculated by measuring the weight loss due to evaporation of water in the polymer during the process of drying by raising the temperature of the polymer through infrared heating. At this time, the drying conditions are such that the temperature is raised from room temperature to about 180 °C and then maintained at 180 °C, and the total drying time can be set to 20 minutes including 5 minutes for the temperature rising stage.

[0100] (Step 2) Step 2 of the present invention is the step of drying, pulverizing and classifying the hydrogel polymer produced in the previous Step 1 to form a base resin powder.

[0101] Specifically, not only can the drying efficiency of the hydrogel polymer be increased, but it can also affect the morphology of the superabsorbent resin and various physical properties of the superabsorbent resin including the water absorption rate. In particular, in order to improve the water absorption rate of the superabsorbent resin, the present invention can further include a step of coarsely pulverizing the hydrogel polymer before drying. Hereinafter, for the purpose of distinguishing from the pulverization after drying, the term "coarse pulverization" is used herein for convenience for the pre-drying pulverization.

[0102] The pulverizer used for the pulverization is not limited in configuration. Specifically, it can include any one selected from the group of pulverizing equipment 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 above-described examples.

[0103] At this time, in the coarse pulverization step, the hydrogel polymer can be pulverized so that the particle size of the hydrogel polymer becomes about 2 mm to about 10 mm. Pulverizing the particle size to less than 2 mm is not technically easy due to the high water content of the hydrogel polymer, and there may also be a phenomenon of aggregation between the pulverized particles. On the other hand, when the particle size is pulverized to exceed 10 mm, the effect of increasing the efficiency of the subsequent drying step may be negligible.

[0104] The drying can be carried out at a temperature of 120 to 250 °C, 140 to 200 °C, or 150 to 190 °C. At this time, the drying temperature can be defined as the temperature of the heat medium supplied for drying or the temperature inside the drying reactor containing the heat medium and the polymer in the drying process. When the drying temperature is low and the drying time is long, the process efficiency decreases. Therefore, in order to prevent this, the drying temperature is preferably 120 °C or higher. Also, when the drying temperature is higher than necessary, the surface of the water-containing gel polymer may be excessively dried, resulting in an increase in the generation of fine powder in the subsequent grinding step, and the physical properties of the final resin may deteriorate. Therefore, in order to prevent this, the drying temperature is preferably 250 °C or lower.

[0105] At this time, the drying time in the drying stage is not particularly limited, but in consideration of process efficiency and the physical properties of the resin, etc., it can be adjusted to 20 minutes to 90 minutes under the drying temperature.

[0106] The drying can be carried out using a normal medium. For example, it can be carried out through methods such as hot air supply to the ground water-containing gel polymer, infrared irradiation, extremely high frequency irradiation, or ultraviolet irradiation.

[0107] And such drying is preferably carried out so that the dried polymer has a water content of 0.1 to 10% by weight. That is, when the water content of the dried polymer is less than 0.1% by weight, it is not preferable because an increase in manufacturing cost due to excessive drying and degradation of the crosslinked polymer may occur. And when the water content of the dried polymer exceeds 10% by weight, defects may occur in the subsequent process, so it is not preferable.

[0108] Next, the dried water-containing gel polymer can be ground. This is a step for optimizing the surface area of the base resin powder and the superabsorbent resin. The grinding can be carried out so that the particle size of the ground polymer becomes 150 to 850 μm.

[0109] At this time, as the crusher that can be used, ordinary ones such as a pin mill, a hammer mill, a screw mill, a roll mill, a disc mill or a jog mill can be used.

[0110] Also, in order to control the physical properties of the superabsorbent resin to be finally commercialized, a step of selectively classifying particles having a particle size of 150 to 850 μm from the polymer particles obtained through the pulverization step is performed.

[0111] The base resin powder can be obtained through the above classification step. Such a base resin powder can have a particle size of 150 to 850 μm and can contain fine powder having a particle size of less than 150 μm at 2% by weight or less, or 1% by weight or less.

[0112] Also, after drying and pulverizing to obtain a base resin powder, a step of mixing zirconium phosphate can be further included. At this time, zirconium phosphate can be mixed in a dry manner first. That is, zirconium phosphate can be mixed with the base resin in a dry physical manner as a solid content before surface crosslinking. Zirconium phosphate is a substance that can physically adsorb malodorous substances. Therefore, by further mixing zirconium phosphate with the base resin powder, an additional deodorizing effect can be obtained.

[0113] At this time, zirconium phosphate may be contained in an amount of 5.0 parts by weight or less based on 100 parts by weight of the base resin. Zirconium phosphate is for increasing additional deodorizing power and may not be contained, but when it is contained, specifically, it may be contained in an amount of 0.5 parts by weight or more, 0.8 parts by weight or more, 1.0 parts by weight or more, 1.3 parts by weight or more, 1.5 parts by weight or more, or 1.8 parts by weight or more and 5.0 parts by weight or less, 4.0 parts by weight or less, 3.0 parts by weight or less or 2.0 parts by weight or less. When zirconium phosphate is mixed in an excessively small amount, there is a problem that the deodorizing effect thereof is negligible, and when it is contained in an excessively large amount, surface crosslinking may not be performed well, and there may be a problem that the absorption ability under pressure decreases.

[0114] (Step 3) Step 3 of the present invention is a step of mixing a surface crosslinking agent with the base resin powder produced in Step 2.

[0115] The surface crosslinking agent used in Step 3 contains a surface crosslinking agent, and the surface crosslinking agent is a surface crosslinking agent generally used for surface crosslinking of a superabsorbent resin, and any compound that can react with a functional group of the polymer may be used, and there is no particular limitation.

[0116] Preferably, in order to improve the properties of the produced superabsorbent resin, 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; polyvalent metal salts; and alkylene carbonate compounds can be used as the surface crosslinking agent.

[0117] Specifically, as examples of the polyhydric alcohol compound, one or more 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 can be used.

[0118] Also, as the epoxy compound, ethylene glycol diglycidyl ether, glycidol, etc. can be used, and as the polyamine compounds, one or more selected from the group consisting of ethylenediamine, diethylenetriamine, triethylenetetramine, tetraethylenepentamine, pentaethylenehexamine, polyethyleneimine, and polyamide polyamine can be used.

[0119] And as the haloepoxy compound, epichlorohydrin, epibromohydrin, and α-methylepichlorohydrin can be used. On the other hand, as the mono-, di- or polyoxazolidinone compound, for example, 2-oxazolidinone, etc. can be used.

[0120] And as the alkylene carbonate compound, ethylene carbonate, etc. can be used. These can be used alone or in combination with each other. On the other hand, in order to improve the efficiency of the surface crosslinking step, one or more polyhydric alcohol compounds having 2 to 10 carbon atoms can be included and used from among these surface crosslinking agents.

[0121] The content of the surface crosslinking agent to be added can be appropriately selected specifically according to the type of the surface crosslinking agent to be added and the reaction conditions. Usually, it can be about 0.001 to about 5 parts by weight, preferably about 0.01 to about 3 parts by weight, more preferably about 0.05 to about 2 parts by weight, based on 100 parts by weight of the polymer.

[0122] If the content of the surface crosslinking agent is excessively small, the surface crosslinking reaction hardly occurs. When it exceeds 5 parts by weight based on 100 parts by weight of the polymer, a decrease in water absorption capacity and physical properties may occur due to the progress of excessive surface crosslinking reaction.

[0123] On the other hand, the surface crosslinking agent can also be used in the step of forming a surface crosslinking layer by additionally containing an inorganic substance. As such an inorganic substance, one or more inorganic substances selected from the group consisting of silica, clay, alumina, silica-alumina composite, titania, zinc oxide, and aluminum sulfate can be used. The inorganic substance can be used in powder form or liquid form, and particularly can be used in the form of alumina powder, silica-alumina powder, titania powder, or nanosilica solution. Also, the inorganic substance can be used in a content of about 0.001 to about 1 part by weight based on 100 parts by weight of the base resin.

[0124] In addition, a diester-based compound can be mixed with the base resin together with the surface crosslinking agent. The diester-based compound can suppress the bad odor of the substance to be absorbed with water and impart deodorizing power to the superabsorbent resin.

[0125] The diester-based compound of an embodiment of the present invention can be represented by the following Chemical Formula 1.

[0126]

Chemical Formula

[0127] In Chemical Formula 1, n is an integer from 1 to 10, specifically, it can be an integer from 2 to 4.

[0128] R is C 1-20 and can be a linear or branched alkyl group. Specifically, R is C 3-4 and can be a linear or branched alkyl group. As an example, R can be isopropyl or isobutyl.

[0129] The diester compound can include one or more selected from the group consisting of diisopropyl adipate, diisobutyl succinate, diisobutyl glutarate, and diisobutyl adipate. Specifically, the diester compound can include one or more selected from the group consisting of diisopropyl adipate, diisobutyl succinate, and diisobutyl adipate.

[0130] The diester compound can be contained in an amount of 0.1 to 5.0 parts by weight based on 100 parts by weight of the base resin. Specifically, the diester compound can be contained in an amount of 0.1 part by weight or more, 0.2 part by weight or more, 0.3 part by weight or more, or 0.4 part by weight or more to 5.0 parts by weight or less, 4.0 parts by weight or less, 3.0 parts by weight or less, 2.0 parts by weight or less, 1.0 part by weight or less, or 0.5 part by weight or less based on 100 parts by weight of the base resin.

[0131] In order to exhibit the deodorizing ability at the level to be achieved in the present invention while maintaining the inherent water absorption properties of the superabsorbent resin, it is preferable that the diester compound as the deodorizing substance is contained within the above content range.

[0132] The diester compound can be mixed with the base resin together with the surface crosslinking agent in a solution or emulsion state. Alternatively, after the surface crosslinking agent is added, the diester compound in a solution or emulsion state can then be injected and mixed with the base resin. When the diester compound is used in an emulsion state, the emulsifier can be a surfactant, particularly a naturally derived surfactant, such as lecithin. In this case, the diester compound can be present within the surface crosslinked layer.

[0133] On the other hand, the method of mixing the surface crosslinking agent with the base resin is not particularly limited as long as it can uniformly mix these in the base resin, and can be appropriately selected and used.

[0134] For example, methods such as putting the surface crosslinking agent and the base resin into a reaction tank and mixing them, spraying the surface crosslinking agent onto the base resin, and continuously supplying and mixing the base resin and the surface crosslinking agent to a continuously operating mixer can be utilized.

[0135] At this time, the surface crosslinking agent can be an aqueous solution. When the solid content in the solution is 1 wt% or more, 3 wt% or more, 5 wt% or more, 10 wt% or more, or 50 wt% or less, 30 wt% or less, or 20 wt% or less, it is suitable for uniform dispersion in the base resin, and at the same time, the agglomeration phenomenon of the base resin can be prevented.

[0136] (Step 4) Step 4 is a step for reacting the base resin with the surface crosslinking agent to form an interpenetrating polymer network on the surface of the crosslinked polymer contained in the base resin to further improve the physical properties of the superabsorbent resin. Through such surface modification, a surface crosslinked layer is formed on the surface of the pulverized base resin particles.

[0137] The formation of the surface crosslinked layer can be carried out by a normal method of increasing the crosslinking bond density on the surface of the polymer particles. For example, it can be carried out by a method of mixing the surface crosslinking agent containing the surface crosslinking agent with the pulverized polymer and performing a heat treatment to cause a crosslinking reaction.

[0138] Step 4 can be carried out at a temperature of about 80°C to about 250°C. More specifically, the surface cross-linking step can be carried out at a temperature of about 100°C to about 220°C, or about 110°C to about 200°C, or about 120°C to about 190°C, for about 10 minutes to about 2 hours, or about 20 minutes to about 60 minutes. If the cross-linking reaction temperature is less than 160°C or the reaction time is excessively short, the surface cross-linking reaction may not occur well and the transmittance may be low. If the temperature exceeds 200°C or the reaction time is excessively long, there may be a problem that the water retention capacity is reduced.

[0139] The means for raising the temperature for the surface cross-linking reaction is not particularly limited. A heat medium can be supplied or a heat source can be directly supplied for heating. At this time, as the type of heat medium that can be used, heated fluids such as steam, hot air, and hot oil can be used, but the present invention is not limited to these, and the temperature of the supplied heat medium can be appropriately selected in consideration of the means of the heat medium, the heating rate, and the target heating temperature. On the other hand, examples of the heat source directly supplied include heating by electricity and heating by gas, but it is not limited to the examples described above.

[0140] In addition, a diester compound can be mixed with the superabsorbent resin having the surface cross-linked layer formed thereon. The description of the type, mixing amount, and form of mixing of the diester compound is as described in Step 3. When mixed in this way, the diester compound can exist separately from the superabsorbent resin. In this case, the diester compound exists on the surface of the surface cross-linked layer formed in the surface cross-linking step, and there may be an advantage that the contact area with the malodor increases and the deodorizing power is improved.

[0141] Also, after using the diester compound together with the surface cross-linking agent and allowing it to exist in the surface cross-linked layer, the diester compound can be mixed again with the superabsorbent resin having the surface cross-linked layer formed thereon. In this case, it can exist in both the surface cross-linked layer and separately from the superabsorbent resin.

[0142] In addition, one or more additives selected from the group consisting of a chelating agent, an iodine-based compound, and an organic acid can be further mixed with the superabsorbent resin having the surface crosslinked layer formed thereon. Similarly, the additive is present on the surface of the surface crosslinked layer formed at the surface crosslinking stage, and there may be an advantage that the contact area with the malodor increases and the deodorizing power is improved.

[0143] A chelating agent can be mixed with the superabsorbent resin having the surface crosslinked layer formed thereon. In the case of a sanitary product containing a superabsorbent resin composition, bacteria derived from the skin or the like may meet with the absorbed liquid, and malodor may be additionally generated due to the growth of the bacteria. The mixed chelating agent can suppress the growth of such bacteria.

[0144] The chelating agent can include an aminoacetate-based chelating agent. Specifically, the aminoacetate-based chelating agent can include one or more selected from the group consisting of ethylenediaminetetraacetic acid (EDTA), L-glutamic acid diacetic acid (GLDA), methylglycine diacetic acid (MGDA), hydroxyethylethylenediaminetriacetic acid (HEDTA), ethanol diglycine acid (EDG), diethylenetriaminepentaacetic acid (DTPA), and salts thereof. More specifically, the chelating agent can be ethylenediaminetetraacetic acid (EDTA).

[0145] In particular, the aminoacetate-based chelating agent is a component that can effectively suppress the growth of bacteria such as Escherichia coli generated by malodorous substances. As the wearing time of the product passes, the growth of bacteria is accelerated by substances that generate malodor remaining in the product, and additional malodor is generated as a result. However, the aminoacetate-based chelating agent can suppress the growth of such bacteria and effectively reduce the generation of additional malodor.

[0146] In particular, the aminoacetate-based chelating agent is a divalent cation that forms an ionic bond between the components constituting the cell membrane, and can effectively suppress the growth of bacteria by destroying the bacterial cell membrane.

[0147] The chelating agent can be mixed in an amount of 0.1 to 2.0 parts by weight based on 100 parts by weight of the base resin. Specifically, the chelating agent can be 0.1 part by weight or more, 0.2 part by weight or more, 0.4 part by weight or more, or 0.6 part by weight or more to 2.0 parts by weight or less, 1.5 parts by weight or less, or 1.0 part by weight or less based on 100 parts by weight of the base resin.

[0148] When mixed within the above content range, it is possible to effectively suppress bacteria without degrading the water absorption physical properties, which are the inherent physical properties of the superabsorbent resin, and to significantly improve the deodorizing power of the water-absorbent resin by embodying the property of suppressing bacteria.

[0149] The chelating agent can be mixed and used in an aqueous solution in the form of a salt, and the above content range is based on the solid content.

[0150] An iodine-based compound can be mixed into the superabsorbent resin having the surface crosslinked layer formed thereon. The iodine-based compound can be a metal iodide salt. The metal iodide salt can be added to the manufacturing process in a form in which one or more selected from the group consisting of CuI, NaI, and KI and I2 are dissolved in water together or in the form of a powder obtained by drying an aqueous solution. The metal iodide salt can also be added to the superabsorbent resin in the same manner as the diester-based compound to impart deodorizing characteristics. The metal iodide salt acts on most of the malodorous substances in a manner of oxidizing the malodorous substances to remove the malodor, and is generally effective.

[0151] The iodine-based compound can be mixed in an amount of 0.1 to 5.0 parts by weight based on 100 parts by weight of the base resin. Specifically, the chelating agent can be 0.1 part by weight or more, 0.2 part by weight or more, 0.4 part by weight or more, or 0.6 part by weight or more to 5.0 parts by weight or less, 4.0 parts by weight or less, 3.0 parts by weight or less, 2.0 parts by weight or less, or 1.0 part by weight or less based on 100 parts by weight of the base resin.

[0152] An organic acid can be mixed with the superabsorbent resin having the surface crosslinked layer formed thereon. The organic acid can be one or more selected from the group consisting of citric acid, acetic acid, formic acid, fumaric acid, lactic acid, and propionic acid. Specifically, the organic acid can be citric acid. The organic acid can exhibit a deodorizing effect like a diester compound in the superabsorbent resin.

[0153] The organic acid can be mixed in an amount of 0.1 to 5.0 parts by weight based on 100 parts by weight of the base resin. Specifically, the chelating agent can be 0.1 part by weight or more, 0.2 part by weight or more, 0.4 part by weight or more, or 0.6 part by weight or more to 5.0 parts by weight or less, 4.0 parts by weight or less, 3.0 parts by weight or less, 2.0 parts by weight or less, or 1.0 part by weight or less based on 100 parts by weight of the base resin.

[0154] When a deodorizing substance and, if necessary, additives or the like are added to the superabsorbent resin having the surface crosslinked layer formed thereon after being added with water in an aqueous solution, a drying step can be additionally performed later.

[0155] Hereinafter, preferred embodiments are presented for the understanding of the invention. However, the following embodiments are merely for exemplifying the present invention and do not limit the present invention only thereto.

[0156] Comparative Example 1 100 g of acrylic acid, 0.37 g of N,N'-methylenebisacrylamide as a crosslinking agent, 0.15 g of sodium persulfate (SPS) as a thermal initiator, 0.008 g of benzoin ether as a UV initiator, 40 g of caustic soda (NaOH), and 127 g of water were mixed to produce a monomer aqueous solution composition having a monomer concentration of 45.8% by weight. After the monomer aqueous solution composition was charged into the supply section of a polymerizer equipped with a conveyor belt that continuously moves, the polymerization atmosphere temperature was maintained at 80°C and irradiated with ultraviolet rays by a UV irradiation device (irradiation dose: 10 mW / cm 2 ), and UV polymerization was carried out for 2 minutes to produce a water-containing gel polymer.

[0157] The aqueous gel polymer was transferred to a meat chopper and cut into pieces of 2 mm to 10 mm. At this time, the water content of the cut aqueous gel polymer was 47% by weight. Next, the aqueous gel polymer was dried in a hot air dryer at a temperature of 170 °C for 30 minutes, and the dried aqueous gel polymer was pulverized with a pin mill. Next, the polymer with a size of 150 μm to 850 μm was classified with a sieve to produce a base resin.

[0158] Thereafter, 2.5 parts by weight of water, 0.1 part by weight of ethylene glycol diglycidyl ether (EX-810), 0.1 part by weight of aluminum sulfate 18 hydrate (Al-S), and 0.1 part by weight of silica (Aerosil A200) as a surface crosslinking agent were uniformly mixed with 100 parts by weight of the produced base resin, and then a surface crosslinking reaction was carried out at 140 °C for 30 minutes. After completion of the surface treatment, a superabsorbent resin with a particle size of 150 to 850 μm was obtained using a sieve.

[0159] Comparative Example 2 100 g of acrylic acid, 0.37 g of N,N'-methylenebisacrylamide as a crosslinking agent, 0.15 g of sodium persulfate (SPS) as a thermal initiator, 0.008 g of benzoin ether as a UV initiator, 40 g of caustic soda (NaOH), and 127 g of water were mixed to produce a monomer aqueous solution composition with a monomer concentration of 45.8% by weight. After the monomer aqueous solution composition was charged into the supply section of a polymerizer equipped with a conveyor belt that continuously moves, the polymerization atmosphere temperature was maintained at 80 °C and irradiated with ultraviolet rays using a UV irradiation device (irradiation dose: 10 mW / cm 2 ), and UV polymerization was carried out for 2 minutes to produce an aqueous gel polymer.

[0160] The manufactured water-containing gel polymer was in the form of a sheet, and this sheet was transferred to a meat chopper and cut into pieces 2 mm to 10 mm in size. At this time, the water content rate of the cut water-containing gel polymer was 47% by weight. Next, the water-containing gel polymer was dried in a hot air dryer at a temperature of 170 °C for 30 minutes, and the dried water-containing gel polymer was pulverized using a pin mill. Next, the polymer having a size of 150 μm to 850 μm was classified using a sieve to produce a base resin.

[0161] Thereafter, to 100 parts by weight of the manufactured base resin, a surface crosslinking agent (2.5 parts by weight of water, 0.1 part by weight of ethylene glycol diglycidyl ether (EX-810), 0.1 part by weight of aluminum sulfate 18 hydrate (Al-S), and 0.1 part by weight of silica (Aerosil A200)) was uniformly mixed, and then a surface crosslinking reaction was carried out at 140 °C for 30 minutes. After completion of the surface treatment, a superabsorbent resin having a particle size of 150 to 850 μm was obtained using a sieve.

[0162] Thereafter, while spraying an EDTA aqueous solution (EDTA concentration: 40%) onto the surface crosslinked superabsorbent resin, chopping (hole size: 16 mm) was carried out and mixed. At this time, the mixture was carried out so that EDTA became 0.6 part by weight based on 100 parts by weight of the base resin. Thereafter, a drying step was carried out at 80 °C for 25 minutes.

[0163] Comparative Example 3 100 g of acrylic acid, 0.37 g of N,N'-methylenebisacrylamide as a crosslinking agent, 0.15 g of sodium persulfate (SPS) as a thermal initiator, 0.008 g of benzoin ether as a UV initiator, 40 g of caustic soda (NaOH), and 127 g of water were mixed to produce a monomer aqueous solution composition having a monomer concentration of 45.8% by weight. After the monomer aqueous solution composition was charged into the supply section of a polymerizer equipped with a conveyor belt that continuously moves, the polymerization atmosphere temperature was maintained at 80 °C and irradiated with ultraviolet rays using a UV irradiation device (irradiation dose: 10 mW / cm 2) A hydrogel polymer was produced by performing UV polymerization for 2 minutes.

[0164] The produced hydrogel polymer was in the form of a sheet. This sheet was transferred to a meat chopper and cut into pieces with a size of 2 mm to 10 mm. At this time, the water content rate of the cut hydrogel polymer was 47% by weight. Next, the hydrogel polymer was dried in a hot air dryer at a temperature of 170 °C for 30 minutes, and the dried hydrogel polymer was pulverized with a pin mill. Next, the polymer with a size of 150 μm to 850 μm was classified with a sieve to produce a base resin.

[0165] Thereafter, 100 parts by weight of the produced base resin was uniformly mixed with a surface crosslinking agent (2.5 parts by weight of water, 0.1 part by weight of ethylene glycol diglycidyl ether (EX-810), 0.1 part by weight of aluminum sulfate 18 hydrate (Al-S), and 0.1 part by weight of silica (Aerosil A200)), and then a surface crosslinking reaction was carried out at 140 °C for 30 minutes. After the completion of the surface treatment, a superabsorbent resin with a particle size of 150 to 850 μm was obtained using a sieve.

[0166] Thereafter, while spraying an EDTA aqueous solution (EDTA concentration 40%) onto the surface-crosslinked superabsorbent resin, chopping (hole size 16 mm) was performed and mixed. At this time, the mixture was adjusted so that the amount of EDTA was 1.0 part by weight based on 100 parts by weight of the base resin. Thereafter, a drying step was carried out at 80 °C for 25 minutes.

[0167] Comparative Example 4 100 g of acrylic acid, 0.37 g of N,N'-methylenebisacrylamide as a crosslinking agent, 0.15 g of sodium persulfate (SPS) as a thermal initiator, 0.008 g of benzoin ether as a UV initiator, 40 g of caustic soda (NaOH) and 127 g of water were mixed to produce a monomer aqueous solution composition with a monomer concentration of 45.8% by weight. After charging the monomer aqueous solution composition into the feeding section of a polymerizer equipped with a conveyor belt that continuously moves, the polymerization atmosphere temperature was maintained at 80 °C and irradiated with ultraviolet rays by a UV irradiation device (irradiation dose: 10 mW / cm 2 ), and UV polymerization was carried out for 2 minutes to produce a hydrogel polymer.

[0168] The produced hydrogel polymer was in the form of a sheet, and this sheet was transferred to a meat chopper and cut into 2 mm to 10 mm. At this time, the water content rate of the cut hydrogel polymer was 47% by weight. Next, the hydrogel polymer was dried in a hot air dryer at a temperature of 170 °C for 30 minutes, and the dried hydrogel polymer was pulverized by a pin mill. Next, the polymer with a size of 150 μm to 850 μm was classified by a sieve to produce a base resin.

[0169] Thereafter, to 100 parts by weight of the produced base resin, a surface crosslinking agent (2.5 parts by weight of water, 0.1 part by weight of ethylene glycol diglycidyl ether (EX-810), 0.1 part by weight of aluminum sulfate 18 hydrate (Al-S), and 0.1 part by weight of silica (Aerosil A200)) was uniformly mixed, and then a surface crosslinking reaction was carried out at 140 °C for 30 minutes. After completion of the surface treatment, a superabsorbent resin with a particle size of 150 to 850 μm was obtained using a sieve.

[0170] Thereafter, while spraying an aqueous solution of cyclodextrin (cyclodextrin concentration 10%) onto the surface-crosslinked superabsorbent resin, chopping (hole size 16 mm) was performed and they were mixed. At this time, they were mixed so that cyclodextrin became 0.5 parts by weight based on 100 parts by weight of the base resin. Thereafter, a drying step was carried out at 80°C for 25 minutes.

[0171] Comparative Example 5 100 g of acrylic acid, 0.37 g of N,N'-methylenebisacrylamide as a crosslinking agent, 0.15 g of sodium persulfate (SPS) as a thermal initiator, 0.008 g of benzoin ether as a UV initiator, 40 g of caustic soda (NaOH) and 127 g of water were mixed to produce a monomer aqueous solution composition with a monomer concentration of 45.8% by weight. After the monomer aqueous solution composition was charged into the supply section of a polymerization reactor equipped with a conveyor belt that continuously moves, the polymerization atmosphere temperature was maintained at 80°C and irradiated with ultraviolet rays by a UV irradiation device (irradiation dose: 10 mW / cm 2 ), and UV polymerization was carried out for 2 minutes to produce a hydrogel polymer.

[0172] The produced hydrogel polymer was in the shape of a sheet. This sheet was transferred to a meat chopper and cut into pieces of 2 mm to 10 mm. At this time, the water content rate of the cut hydrogel polymer was 47% by weight. Next, the hydrogel polymer was dried in a hot air dryer at a temperature of 170°C for 30 minutes, and the dried hydrogel polymer was pulverized with a pin mill. Next, the polymer with a size of 150 μm to 850 μm was classified with a sieve to produce a base resin.

[0173] Subsequently, 2.5 parts by weight of water, 0.1 part by weight of ethylene glycol diglycidyl ether (EX-810), 0.1 part by weight of aluminum sulfate 18 hydrate (Al-S), and 0.1 part by weight of silica (Aerosil A200) as a surface crosslinking agent were uniformly mixed with 100 parts by weight of the produced base resin, and then a surface crosslinking reaction was carried out at 140°C for 30 minutes. After completion of the surface treatment, a superabsorbent resin having a particle size of 150 to 850 μm was obtained using a sieve.

[0174] Subsequently, while injecting an aqueous citric acid solution (citric acid concentration: 20%) into the surface-crosslinked superabsorbent resin, chopping (hole size: 16 mm) was performed and mixed. At this time, mixing was carried out so that the amount of citric acid became 1.0 part by weight based on 100 parts by weight of the base resin. Subsequently, a drying step was carried out at 80°C for 25 minutes.

[0175] Comparative Example 6 100 g of acrylic acid, 0.37 g of N,N'-methylenebisacrylamide as a crosslinking agent, 0.15 g of sodium persulfate (SPS) as a thermal initiator, 0.008 g of benzoin ether as a UV initiator, 40 g of caustic soda (NaOH), and 127 g of water were mixed to produce a monomer aqueous solution composition having a monomer concentration of 45.8% by weight. After the monomer aqueous solution composition was charged into the supply section of a polymerizer equipped with a conveyor belt that continuously moves, the polymerization atmosphere temperature was maintained at 80°C and irradiated with ultraviolet rays using a UV irradiation device (irradiation dose: 10 mW / cm 2 ), and UV polymerization was carried out for 2 minutes to produce a hydrogel polymer.

[0176] The produced hydrogel polymer was in the form of a sheet, and this sheet was transferred to a meat chopper and cut into pieces 2 mm to 10 mm in size. At this time, the water content of the cut hydrogel polymer was 47% by weight. Next, the hydrogel polymer was dried in a hot air dryer at a temperature of 170°C for 30 minutes, and the dried hydrogel polymer was pulverized using a pin mill. Next, the polymer with a size of 150 μm to 850 μm was classified using a sieve to produce a base resin.

[0177] Thereafter, 100 parts by weight of the produced base resin was uniformly mixed with a surface crosslinking agent (2.5 parts by weight of water, 0.1 part by weight of ethylene glycol diglycidyl ether (EX-810), 0.1 part by weight of aluminum sulfate 18 hydrate (Al-S), and 0.1 part by weight of silica (Aerosil A200)), and then a surface crosslinking reaction was carried out at 140°C for 30 minutes. After completion of the surface treatment, a superabsorbent resin with a particle size of 150 to 850 μm was obtained using a sieve.

[0178] Thereafter, while spraying an aqueous citric acid solution (citric acid concentration: 20%) onto the surface-crosslinked superabsorbent resin, chopping (hole size: 16 mm) was carried out and mixed. At this time, mixing was carried out so that the amount of citric acid became 5.0 parts by weight based on 100 parts by weight of the base resin. Thereafter, a drying step was carried out at 80°C for 25 minutes.

[0179] Example 1 100 g of acrylic acid, 0.37 g of N,N'-methylenebisacrylamide as a crosslinking agent, 0.15 g of sodium persulfate (SPS) as a thermal initiator, 0.008 g of benzoin ether as a UV initiator, 40 g of caustic soda (NaOH), and 127 g of water were mixed to produce a monomer aqueous solution composition with a monomer concentration of 45.8% by weight. After the monomer aqueous solution composition was charged into the supply section of a polymerizer equipped with a continuously moving conveyor belt, the polymerization atmosphere temperature was maintained at 80°C and irradiated with ultraviolet rays using a UV irradiation device (irradiation dose: 10 mW / cm 2) The aqueous gel polymer was produced by performing UV polymerization for 2 minutes.

[0180] The produced aqueous gel polymer was in the form of a sheet. This sheet was transferred to a meat chopper and cut into pieces 2 mm to 10 mm in size. At this time, the water content rate of the cut aqueous gel polymer was 47% by weight. Next, the aqueous gel polymer was dried in a hot air dryer at a temperature of 170 °C for 30 minutes, and the dried aqueous gel polymer was pulverized with a pin mill. Next, the polymer with a size of 150 μm to 850 μm was classified using a sieve to produce a base resin.

[0181] Thereafter, 100 parts by weight of the base resin produced above was uniformly mixed with a surface crosslinking agent (2.5 parts by weight of water, 0.1 part by weight of ethylene glycol diglycidyl ether (EX - 810), 0.1 part by weight of aluminum sulfate 18 hydrate (Al - S), and 0.1 part by weight of silica (Aerosil A200)), and then a surface crosslinking reaction was carried out at 140 °C for 30 minutes. After completion of the surface treatment, a superabsorbent resin with a particle size of 150 to 850 μm was obtained using a sieve.

[0182] Thereafter, while spraying diisopropyl adipate emulsion (diisopropyl adipate concentration 20%) and an EDTA aqueous solution (EDTA concentration 40%) using lecithin as an emulsifier onto the surface - crosslinked superabsorbent resin, chopping (hole size 16 mm) was carried out and mixed. At this time, diisopropyl adipate was adjusted to 0.5 part by weight based on 100 parts by weight of the base resin, and EDTA was mixed to be 0.6 part by weight based on 100 parts by weight of the base resin.

[0183] Example 2 100 g of acrylic acid, 0.37 g of N,N'-methylenebisacrylamide as a crosslinking agent, 0.15 g of sodium persulfate (SPS) as a thermal initiator, 0.008 g of benzoin ether as a UV initiator, 40 g of caustic soda (NaOH), and 127 g of water were mixed to produce a monomer aqueous solution composition with a monomer concentration of 45.8% by weight. After the monomer aqueous solution composition was charged into the supply section of a polymerization reactor equipped with a conveyor belt that continuously moves, the polymerization atmosphere temperature was maintained at 80°C and irradiated with ultraviolet rays using a UV irradiation device (irradiation dose: 10 mW / cm 2 ), and UV polymerization was carried out for 2 minutes to produce a hydrogel polymer.

[0184] The produced hydrogel polymer was in the form of a sheet, and this sheet was transferred to a meat chopper and cut into 2 mm to 10 mm. At this time, the water content rate of the cut hydrogel polymer was 47% by weight. Next, the hydrogel polymer was dried in a hot air dryer at a temperature of 170°C for 30 minutes, and the dried hydrogel polymer was pulverized with a pin mill. Next, the polymer with a particle size of 150 μm to 850 μm was classified using a sieve to produce a base resin.

[0185] Thereafter, to 100 parts by weight of the produced base resin, a surface crosslinking agent (2.5 parts by weight of water, 0.1 part by weight of ethylene glycol diglycidyl ether (EX-810), 0.1 part by weight of aluminum sulfate 18 hydrate (Al-S), and 0.1 part by weight of silica (Aerosil A200)) was uniformly mixed, and then a surface crosslinking reaction was carried out at 140°C for 30 minutes. After completion of the surface treatment, a superabsorbent resin with a particle size of 150 to 850 μm was obtained using a sieve.

[0186] Subsequently, while spraying a Diisopropyl adipate emulsion (Diisopropyl adipate concentration: 20%) and an aqueous citric acid solution (citric acid concentration: 20%) using lecithin as an emulsifier onto the surface-crosslinked superabsorbent resin, chopping (hole size: 16 mm) was performed and the mixture was mixed. At this time, the amount of Diisopropyl adipate was adjusted to 0.5 parts by weight based on 100 parts by weight of the base resin, and citric acid was mixed to be 0.6 parts by weight based on 100 parts by weight of the base resin.

[0187] Example 3 100 g of acrylic acid, 0.37 g of N,N'-methylenebisacrylamide as a crosslinking agent, 0.15 g of sodium persulfate (SPS) as a thermal initiator, 0.008 g of benzoin ether as a UV initiator, 40 g of caustic soda (NaOH), and 127 g of water were mixed to produce a monomer aqueous solution composition with a monomer concentration of 45.8% by weight. After the monomer aqueous solution composition was introduced into the supply section of a polymerization reactor equipped with a continuously moving conveyor belt, the polymerization atmosphere temperature was maintained at 80°C and ultraviolet rays were irradiated with a UV irradiation device (irradiation dose: 10 mW / cm 2 ), and UV polymerization was carried out for 2 minutes to produce a hydrogel polymer.

[0188] The produced hydrogel polymer was in the form of a sheet. This sheet was transferred to a meat chopper and cut into pieces with a size of 2 mm to 10 mm. At this time, the water content rate of the cut hydrogel polymer was 47% by weight. Next, the hydrogel polymer was dried in a hot air dryer at a temperature of 170°C for 30 minutes, and the dried hydrogel polymer was pulverized with a pin mill. Next, the polymer with a size of 150 μm to 850 μm was classified with a sieve to produce a base resin.

[0189] Thereafter, to 100 parts by weight of the produced base resin, a surface crosslinking agent (2.5 parts by weight of water, 0.1 part by weight of ethylene glycol diglycidyl ether (EX-810), 0.1 part by weight of aluminum sulfate 18 hydrate (Al-S), and 0.1 part by weight of silica (Aerosil A200)) was uniformly mixed, and then a surface crosslinking reaction was carried out at 140°C for 30 minutes. After completion of the surface treatment, a superabsorbent resin having a particle size of 150 to 850 μm was obtained using a sieve.

[0190] Thereafter, while injecting a diisopropyl adipate emulsion (diisopropyl adipate concentration 20%) using lecithin as an emulsifier into the surface crosslinked superabsorbent resin, chopping (hole size 16 mm) was carried out and mixed. At this time, mixing was carried out so that the diisopropyl adipate became 0.5 part by weight based on 100 parts by weight of the base resin.

[0191] Example 4 100 g of acrylic acid, 0.37 g of N,N'-methylenebisacrylamide as a crosslinking agent, 0.15 g of sodium persulfate (SPS) as a thermal initiator, 0.008 g of benzoin ether as a UV initiator, 40 g of caustic soda (NaOH), and 127 g of water were mixed to produce a monomer aqueous solution composition having a monomer concentration of 45.8% by weight. After the monomer aqueous solution composition was charged into the supply section of a polymerizer equipped with a conveyor belt that continuously moves, the polymerization atmosphere temperature was maintained at 80°C and irradiated with ultraviolet rays using a UV irradiation device (irradiation dose: 10 mW / cm 2 ), and UV polymerization was carried out for 2 minutes to produce a water-containing gel polymer.

[0192] The produced hydrogel polymer was in the form of a sheet, and this sheet was transferred to a meat chopper and cut into pieces 2 mm to 10 mm in size. At this time, the water content of the cut hydrogel polymer was 47% by weight. Next, the hydrogel polymer was dried in a hot air dryer at a temperature of 170 °C for 30 minutes, and the dried hydrogel polymer was pulverized using a pin mill. Next, the polymer with a size of 150 μm to 850 μm was classified using a sieve to produce a base resin.

[0193] Thereafter, 100 parts by weight of the produced base resin was uniformly mixed with a surface crosslinking agent (2.5 parts by weight of water, 0.1 part by weight of ethylene glycol diglycidyl ether (EX-810), 0.1 part by weight of aluminum sulfate 18 hydrate (Al-S), and 0.1 part by weight of silica (Aerosil A200)), and then a surface crosslinking reaction was carried out at 140 °C for 30 minutes. After completion of the surface treatment, a superabsorbent resin with a particle size of 150 to 850 μm was obtained using a sieve.

[0194] Thereafter, while spraying a diisopropyl adipate emulsion (diisopropyl adipate concentration 20%) using lecithin as an emulsifier onto the surface-crosslinked superabsorbent resin, chopping (hole size 16 mm) was carried out and mixed. At this time, the mixture was adjusted so that the amount of diisopropyl adipate was 1.0 part by weight based on 100 parts by weight of the base resin.

[0195] Example 5 100 g of acrylic acid, 0.37 g of N,N'-methylenebisacrylamide as a crosslinking agent, 0.15 g of sodium persulfate (SPS) as a thermal initiator, 0.008 g of benzoin ether as a UV initiator, 40 g of caustic soda (NaOH) and 127 g of water were mixed to produce a monomer aqueous solution composition with a monomer concentration of 45.8% by weight. After the monomer aqueous solution composition was charged into the supply section of a polymerizer equipped with a conveyor belt that continuously moves, the polymerization atmosphere temperature was maintained at 80 °C and irradiated with ultraviolet rays using a UV irradiation device (irradiation dose: 10 mW / cm 2 ), and UV polymerization was carried out for 2 minutes to produce a hydrogel polymer.

[0196] The produced hydrogel polymer was in the form of a sheet, and this sheet was transferred to a meat chopper and cut into 2 mm to 10 mm. At this time, the water content rate of the cut hydrogel polymer was 47% by weight. Next, the hydrogel polymer was dried in a hot air dryer at a temperature of 170 °C for 30 minutes, and the dried hydrogel polymer was pulverized with a pin mill. Next, the polymer with a particle size of 150 μm to 850 μm was classified using a sieve to produce a base resin.

[0197] Thereafter, to 100 parts by weight of the produced base resin, a surface crosslinking agent (2.5 parts by weight of water, 0.1 part by weight of ethylene glycol diglycidyl ether (EX-810), 0.1 part by weight of aluminum sulfate 18 hydrate (Al-S), and 0.1 part by weight of silica (Aerosil A200)) was uniformly mixed, and then a surface crosslinking reaction was carried out at 140 °C for 30 minutes. After completion of the surface treatment, a superabsorbent resin with a particle size of 150 to 850 μm was obtained using a sieve.

[0198] Subsequently, while spraying a diisobutyl succinate emulsion (diisobutyl succinate concentration: 20%) using lecithin as an emulsifier onto the surface-crosslinked superabsorbent resin, chopping (hole size: 16 mm) was performed and they were mixed. At this time, they were mixed so that the amount of diisobutyl succinate became 0.5 parts by weight based on 100 parts by weight of the base resin.

[0199] Example 6 100 g of acrylic acid, 0.37 g of N,N'-methylenebisacrylamide as a crosslinking agent, 0.15 g of sodium persulfate (SPS) as a thermal initiator, 0.008 g of benzoin ether as a UV initiator, 40 g of caustic soda (NaOH), and 127 g of water were mixed to produce a monomer aqueous solution composition with a monomer concentration of 45.8% by weight. After the monomer aqueous solution composition was charged into the supply section of a polymerization reactor equipped with a continuously moving conveyor belt, the polymerization atmosphere temperature was maintained at 80°C and irradiated with ultraviolet rays using a UV irradiation device (irradiation dose: 10 mW / cm 2 ), and UV polymerization was carried out for 2 minutes to produce a water-containing gel polymer.

[0200] The produced water-containing gel polymer was in the form of a sheet. This sheet was transferred to a meat chopper and cut into pieces 2 mm to 10 mm in size. At this time, the water content rate of the cut water-containing gel polymer was 47% by weight. Next, the water-containing gel polymer was dried in a hot air dryer at a temperature of 170°C for 30 minutes, and the dried water-containing gel polymer was pulverized using a pin mill. Next, the polymer with a size of 150 μm to 850 μm was classified using a sieve to produce a base resin.

[0201] Thereafter, 2.5 parts by weight of water, 0.1 part by weight of ethylene glycol diglycidyl ether (EX-810), 0.1 part by weight of aluminum sulfate 18 hydrate (Al-S), and 0.1 part by weight of silica (Aerosil A200) as a surface crosslinking agent were uniformly mixed with 100 parts by weight of the produced base resin, and then a surface crosslinking reaction was carried out at 140°C for 30 minutes. After completion of the surface treatment, a superabsorbent resin having a particle size of 150 to 850 μm was obtained using a sieve.

[0202] Thereafter, while injecting a diisobutyl succinate emulsion (diisobutyl succinate concentration: 20%) using lecithin as an emulsifier into the surface crosslinked superabsorbent resin, chopping (hole size: 16 mm) was performed and mixed. At this time, mixing was carried out so that the amount of diisobutyl succinate became 1.0 part by weight based on 100 parts by weight of the base resin.

[0203] Example 7 100 g of acrylic acid, 0.37 g of N,N'-methylenebisacrylamide as a crosslinking agent, 0.15 g of sodium persulfate (SPS) as a thermal initiator, 0.008 g of benzoin ether as a UV initiator, 40 g of caustic soda (NaOH), and 127 g of water were mixed to produce a monomer aqueous solution composition having a monomer concentration of 45.8% by weight. After the monomer aqueous solution composition was charged into the supply section of a polymerizer equipped with a continuously moving conveyor belt, the polymerization atmosphere temperature was maintained at 80°C and irradiated with ultraviolet rays by a UV irradiation device (irradiation dose: 10 mW / cm 2 ), and UV polymerization was carried out for 2 minutes to produce a hydrogel polymer.

[0204] The manufactured water-containing gel polymer was in the form of a sheet. This sheet was transferred to a meat chopper and cut into pieces with a size of 2 mm to 10 mm. At this time, the water content of the cut water-containing gel polymer was 47% by weight. Next, the water-containing gel polymer was dried in a hot air dryer at a temperature of 170°C for 30 minutes, and the dried water-containing gel polymer was pulverized using a pin mill. Next, the polymer with a size of 150 μm to 850 μm was classified using a sieve to produce a base resin.

[0205] Thereafter, 100 parts by weight of the manufactured base resin was uniformly mixed with a surface crosslinking agent (2.5 parts by weight of water, 0.1 part by weight of ethylene glycol diglycidyl ether (EX-810), 0.1 part by weight of aluminum sulfate 18 hydrate (Al-S), and 0.1 part by weight of silica (Aerosil A200)), and then a surface crosslinking reaction was carried out at 140°C for 30 minutes. After completion of the surface treatment, a superabsorbent resin with a particle size of 150 to 850 μm was obtained using a sieve.

[0206] Thereafter, while spraying a diisobutyl adipate emulsion (diisobutyl adipate concentration 20%) using lecithin as an emulsifier onto the surface-crosslinked superabsorbent resin, chopping (hole size 16 mm) was performed and mixed. At this time, the mixture was made such that the diisobutyl adipate was 0.5 part by weight based on 100 parts by weight of the base resin.

[0207] Example 8 100 g of acrylic acid, 0.37 g of N,N'-methylenebisacrylamide as a crosslinking agent, 0.15 g of sodium persulfate (SPS) as a thermal initiator, 0.008 g of benzoin ether as a UV initiator, 40 g of caustic soda (NaOH) and 127 g of water were mixed to produce a monomer aqueous solution composition with a monomer concentration of 45.8% by weight. After the monomer aqueous solution composition was charged into the supply section of a polymerizer equipped with a conveyor belt that continuously moves, the polymerization atmosphere temperature was maintained at 80 °C and irradiated with ultraviolet rays by a UV irradiation device (irradiation dose: 10 mW / cm 2 ), and UV polymerization was carried out for 2 minutes to produce a hydrogel polymer.

[0208] The produced hydrogel polymer was in the form of a sheet, and this sheet was transferred to a meat chopper and cut into 2 mm to 10 mm. At this time, the water content rate of the cut hydrogel polymer was 47% by weight. Next, the hydrogel polymer was dried in a hot air dryer at a temperature of 170 °C for 30 minutes, and the dried hydrogel polymer was pulverized by a pin mill. Next, the polymer with a particle size of 150 μm to 850 μm was classified by a sieve to produce a base resin.

[0209] Thereafter, to 100 parts by weight of the produced base resin, a surface crosslinking agent (2.5 parts by weight of water, 0.1 part by weight of ethylene glycol diglycidyl ether (EX-810), 0.1 part by weight of aluminum sulfate 18 hydrate (Al-S), and 0.1 part by weight of silica (Aerosil A200)) was uniformly mixed, and then a surface crosslinking reaction was carried out at 140 °C for 30 minutes. After the completion of the surface treatment, a superabsorbent resin with a particle size of 150 to 850 μm was obtained using a sieve.

[0210] Thereafter, while spraying lecithin as an emulsifier, diisopropyl adipate emulsion (diisopropyl adipate concentration: 20%) and aqueous citric acid solution (citric acid concentration: 20%) onto the surface-crosslinked superabsorbent resin, chopping (hole size: 16 mm) was performed and mixing was carried out. At this time, the amount of diisopropyl adipate was adjusted to 0.5 parts by weight based on 100 parts by weight of the base resin, and citric acid was mixed to be 5.0 parts by weight based on 100 parts by weight of the base resin.

[0211] Example 9 100 g of acrylic acid, 0.37 g of N,N'-methylenebisacrylamide as a crosslinking agent, 0.15 g of sodium persulfate (SPS) as a thermal initiator, 0.008 g of benzoin ether as a UV initiator, 40 g of caustic soda (NaOH), and 127 g of water were mixed to produce a monomer aqueous solution composition with a monomer concentration of 45.8% by weight. After the monomer aqueous solution composition was charged into the supply section of a polymerization reactor equipped with a continuously moving conveyor belt, the polymerization atmosphere temperature was maintained at 80°C and ultraviolet rays were irradiated with a UV irradiation device (irradiation dose: 10 mW / cm 2 ), and UV polymerization was carried out for 2 minutes to produce a hydrogel polymer.

[0212] The produced hydrogel polymer was in the form of a sheet, and this sheet was transferred to a meat chopper and cut into pieces with a size of 2 mm to 10 mm. At this time, the water content rate of the cut hydrogel polymer was 47% by weight. Next, the hydrogel polymer was dried in a hot air dryer at a temperature of 170°C for 30 minutes, and the dried hydrogel polymer was pulverized with a pin mill. Next, the polymer with a size of 150 μm to 850 μm was classified with a sieve to produce a base resin.

[0213] Subsequently, 2.5 parts by weight of water, 0.1 part by weight of ethylene glycol diglycidyl ether (EX-810), 0.1 part by weight of aluminum sulfate 18 hydrate (Al-S), and 0.1 part by weight of silica (Aerosil A200) as a surface crosslinking agent were uniformly mixed with 100 parts by weight of the manufactured base resin, and then a surface crosslinking reaction was carried out at 140°C for 30 minutes. After completion of the surface treatment, a superabsorbent resin having a particle size of 150 to 850 μm was obtained using a sieve.

[0214] Subsequently, while injecting diisopropyl adipate emulsion (diisopropyl adipate concentration 20%) and an EDTA aqueous solution (EDTA concentration 40%) using lecithin as an emulsifier into the surface crosslinked superabsorbent resin, chopping (hole size 16 mm) was carried out and mixed. At this time, diisopropyl adipate was adjusted to 0.5 part by weight based on 100 parts by weight of the base resin, and EDTA was mixed to be 1.0 part by weight based on 100 parts by weight of the base resin.

[0215] Experimental Example For the superabsorbent resin compositions produced in the above Examples and Comparative Examples, each physical property was measured by the following method.

[0216] 1) Odor evaluation 2 g of the produced superabsorbent resins of Examples 1 to 9 and Comparative Examples 1 to 6 were placed in a 500 mL glass bottle, and then 50 mL of urine was injected. After sealing the glass bottle, aging was carried out in a constant temperature chamber for 3 hours. At this time, the temperature of the constant temperature chamber was 35°C. After completion of aging, the degree of bad odor was evaluated by sensory evaluation. A total of 9 people evaluated, and the degree of bad odor was evaluated on a scale of 1 to 5. The closer the score is to 1, the less the bad odor, and the closer the score is to 5, the stronger the bad odor. Table 1 shows the average of the evaluation results of 9 people.

[0217] 2) Centrifuge Retention Capacity (CRC) The water retention capacity based on the water absorption ratio of each resin under no load was measured according to EDANA WSP 241.3 of the European Disposables and Nonwovens Association (EDANA) standard.

[0218] Specifically, resins classified in the particle size range of 300 to 600 μm were obtained from the resins obtained in the examples and comparative examples, respectively. Such resin W0 (g) (about 0.2 g) was uniformly placed in a non-woven envelope and sealed, and then immersed in physiological saline (0.9 wt%) at room temperature. After 30 minutes, moisture was removed from the envelope for 3 minutes under the condition of 250G using a centrifuge, and the mass W2 (g) of the envelope was measured. In addition, after performing the same operation without using the resin, the mass W1 (g) at that time was measured.

[0219] Using the obtained masses, CRC (g / g) was calculated according to the following calculation formula 1.

[0220] [Calculation formula 1] CRC (g / g) = {[W2 (g) - W1 (g)] / W0 (g)} - 1

[0221] 3) Absorbency under Pressure (AUP) The absorbency under pressure of 0.7 psi of the superabsorbent resins in the examples and comparative examples was measured according to WSP 242.3 of the EDANA method.

[0222] First, when measuring the absorbency under pressure, the resin classified powder at the time of CRC measurement was used.

[0223] Specifically, a 400-mesh stainless steel wire mesh was attached to the bottom of a plastic cylinder with an inner diameter of 25 mm. Under the conditions of room temperature and humidity of 50%, the superabsorbent resin W0 (g) was uniformly sprayed on the wire mesh, and a piston that could further uniformly apply a load of 0.7 psi was slightly smaller than 25 mm in outer diameter, had no gap with the inner wall of the cylinder, and did not prevent vertical movement. At this time, the weight W3 (g) of the device was measured.

[0224] A glass filter with a diameter of 90 mm and a thickness of 5 mm was placed inside a petri dish with a diameter of 150 mm, and physiological saline composed of 0.9 wt% sodium chloride was made to be at the same level as the upper surface of the glass filter. One piece of filter paper with a diameter of 90 mm was placed thereon. The measuring device was placed on the filter paper, and the liquid was absorbed under load for 1 hour. After 1 hour, the measuring device was lifted up, and its weight W4 (g) was measured. Using each of the obtained masses, the pressure absorption capacity (g / g) was calculated according to the following calculation formula 2.

[0225] [Calculation formula 2] AUP (g / g) = [W4 (g) - W3 (g)] / W0 (g)

[0226] 4) Deodorization rate The deodorization rate was measured by the adsorption tube measurement method. As aldehyde-based malodorous substances, 3-methylbutanal was selected, as ketone-based substances, Diacetyl was selected, and as sulfur compound-based malodorous substances, dimethyltrisulfide (DMTS) was selected to test the deodorizing power.

[0227] - Adsorption observation measurement method: After putting 1 g of the superabsorbent resin into a 500 mL glass bottle (Bottle), 25 mL of the malodorous substance was injected. Then, after 3 hours of aging progress in a constant temperature chamber, collection was carried out for 20 minutes. At this time, the temperature of the constant temperature chamber was 35°C, and the N2 flow rate (Flow Rate) was set to 250 mL / min. The extruded malodor was then adsorbed by the connected adsorption tube, and this was repeated 2 times per same sample for collection. The collection results were analyzed by GC to confirm the results.

[0228] - Deodorizing power (%) = (Amount of malodor of the Reference sample (superabsorbent resin of Comparative Example 1) measured by GC - Amount of malodor of the sample measured by GC) / Amount of malodor of the Reference sample (superabsorbent resin of Comparative Example 1) measured by GC × 100 (%)

[0229] The evaluation results of odor evaluation, centrifugal retention capacity (CRC), and absorption under pressure (AUP) are shown in Table 1, and the deodorization rate is shown in Table 2.

[0230]

Table 1

[0231]

Table 2

[0232] According to the results in Table 1 above, in the case of Examples 1 to 9, it was found that while the water absorption capacity was maintained at a similar level compared to Comparative Example 1 without an additive, the deodorizing power was excellent.

[0233] Also, in the case of Comparative Examples 2 and 3 using only a chelating agent without a diester compound, the deodorizing power tended to be lower compared to the Examples. In the case of Comparative Examples 4 and 5 using cyclodextrin or citric acid alone, the deodorizing power also showed a lower result compared to the Examples. In the case of Comparative Example 6 using a large amount of citric acid, although the deodorizing power was somewhat improved compared to other comparative examples, it was still confirmed that the deodorizing power was at a level inferior to that of Example 8 using diisopropyl adipate, which is a diester compound.

[0234] According to the results in Table 2 above, it was confirmed that Comparative Examples 1 to 6 showed a very inferior suppression rate of malodorous substances compared to Examples 1 to 9. In the case of Comparative Example 6 using a large amount of citric acid, it also showed an effect of being inferior at a level similar to other comparative examples in terms of the suppression rate of malodorous substances.

Claims

1. A base resin containing a crosslinked polymer obtained by crosslinking and polymerizing an acrylic acid monomer having an acidic group at least partially neutralized with an internal crosslinking agent, and a surface crosslinked layer formed on the surface of the base resin, wherein the crosslinked polymer is additionally crosslinked through a surface crosslinking agent; and a high water-absorbing resin composition containing a diester compound represented by Chemical Formula 1, wherein the diester compound is contained separately from or both in the high water-absorbing resin within the surface crosslinked layer of the high water-absorbing resin, a high water-absorbing resin composition. 【Chemical Formula 1】 (In Chemical Formula 1, n is an integer from 1 to 10, R is C １－２０ which is linear or branched alkyl.)

2. The diester compound includes one or more selected from the group consisting of diisopropyl adipate, diisobutyl succinate, diisobutyl glutarate, and diisobutyl adipate, The high water-absorbing resin composition according to Claim 1.

3. The diester compound is contained in an amount of 0.1 to 5.0 parts by weight based on 100 parts by weight of the base resin, The high water-absorbing resin composition according to Claim 1.

4. The high water-absorbing resin composition further includes one or more additives selected from the group consisting of a chelating agent, an iodine compound, and an organic acid, The high water-absorbing resin composition according to Claim 1.

5. The chelating agent includes an aminoacetate-based chelating agent, The high water-absorbing resin composition according to Claim 4.

6. The aminoacetate-based chelating agent includes one or more selected from the group consisting of ethylenediaminetetraacetic acid (EDTA), L-glutamic acid diacetic acid (GLDA), methylglycine diacetic acid (MGDA), hydroxyethylethylenediaminetriacetic acid (HEDTA), ethanol diglycine acid (EDG), diethylenetriaminepentaacetic acid (DTPA), and their salts, The high water-absorbing resin composition according to Claim 5.

7. The iodine compound is a metal iodide salt, The high water-absorbing resin composition according to Claim 4.

8. The organic acid is one or more selected from the group consisting of citric acid, acetic acid, formic acid, fumaric acid, lactic acid, and propionic acid, The high water-absorbing resin composition according to Claim 4.

9. In the presence of an internal crosslinking agent and a polymerization initiator, crosslinking polymerization of an acrylic acid-based monomer having at least partially neutralized acidic groups to form a hydrogel polymer (Step 1); Producing a base resin containing the crosslinked polymer obtained by drying and pulverizing the hydrogel polymer (Step 2); Mixing a surface crosslinking agent with the base resin to produce a mixture (Step 3); and Heat-treating the mixture to produce a superabsorbent resin having a surface crosslinked layer formed on the surface of the base resin (Step 4); including During the reaction of the surface crosslinking, after the surface crosslinking, or both, mixing a diester compound represented by Chemical Formula 1, A method for producing a superabsorbent resin composition. 【Chemical Formula 2】 (In the Chemical Formula 1, n is an integer from 1 to 10, R is C １－２０ which is linear or branched alkyl.)

10. The diester compound includes one or more selected from the group consisting of diisopropyl adipate, diisobutyl succinate, diisobutyl glutarate, and diisobutyl adipate, The method for producing a superabsorbent resin composition according to Claim 9.

11. The diester compound is mixed in an amount of 0.1 to 5.0 parts by weight based on 100 parts by weight of the base resin, The method for producing a superabsorbent resin composition according to Claim 9.

12. After Step 4, to the superabsorbent resin having a surface crosslinked layer formed, Further mixing one or more additives selected from the group consisting of a chelating agent, an iodine-based compound, and an organic acid, The method for producing a superabsorbent resin composition according to Claim 9.

13. The chelating agent includes an aminoacetate-based chelating agent, The method for producing a superabsorbent resin composition according to Claim 12.

14. The iodine-based compound is a metal iodide salt, The method for producing a superabsorbent resin composition according to Claim 12.

15. The organic acid is one or more selected from the group consisting of citric acid, acetic acid, formic acid, fumaric acid, lactic acid, and propionic acid, The method for producing a superabsorbent resin composition according to Claim 12.

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