Biodegradable super absorbent polymer and preparation method thereof

Abstract

The present invention provides: a biodegradable super absorbent polymer exhibiting the excellent absorption performance and liquid permeability of a super absorbent polymer; and a preparation method thereof.

Description

Biodegradable superabsorbent resin and method for manufacturing the same

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

[0002] This application claims the benefit of priority based on Korean Patent Application No. 10-2024-0159145 filed November 11, 2024 and Korean Patent Application No. 10-2025-0163511 filed November 3, 2025, and all contents disclosed in the documents of said Korean patent applications are incorporated herein as part of this specification.

[0003]

[0004] The present invention relates to a biodegradable superabsorbent resin with excellent absorption performance and liquid permeability, and a method for manufacturing the same.

[0005]

[0006] Super Absorbent Polymer (SAP) is a synthetic polymer material capable of absorbing 500 to 1,000 times its own weight in moisture, and developers name it by different names such as SAM (Super Absorbency Material) and AGM (Absorbent Gel Material). The above-mentioned super absorbent polymer began to be commercialized for sanitary devices, and is now widely used in various fields, including sanitary products such as children's disposable diapers, soil conditioners for horticulture, waterproofing materials for civil engineering and construction, seedling sheets, freshness preservation agents in the food distribution sector, materials for compresses, and even in the field of electrical insulation.

[0007]

[0008] These superabsorbent polymers are typically manufactured by obtaining a cross-linked polymer through bulk polymerization or suspension polymerization of acrylic acid-based monomers with a crosslinking agent in the presence of an initiator. Consequently, most conventional superabsorbent polymers lack biodegradability, which causes environmental problems when disposed of as waste. Specifically, when various products containing superabsorbent polymers are landfilled, the polymers are not decomposed by bacteria or microorganisms in the soil, potentially leading to environmental pollution.

[0009]

[0010] Accordingly, attempts have been made to develop superabsorbent resins exhibiting excellent biodegradability using biomass-derived materials; however, it has not been easy to manufacture biodegradable superabsorbent resins that are economically feasible while exhibiting general physical properties similar to those of conventional superabsorbent resins.

[0011]

[0012] Accordingly, there is a continuous demand for the development of technologies related to biodegradable superabsorbent resins that have excellent absorption performance, a fundamental physical property of superabsorbent resins, while also improving liquid permeability.

[0013]

[0014] Accordingly, the present invention aims to provide a biodegradable superabsorbent resin with excellent absorption performance and liquid permeability, and a method for manufacturing the same.

[0015]

[0016] According to one embodiment of the present invention,

[0017] A superabsorbent resin particle comprising (a crosslinked polymer of a carboxyalkylated polysaccharide and a first crosslinking agent) and a second crosslinked layer in which the crosslinked polymer is further crosslinked via a second crosslinking agent; and

[0018] Contains silica,

[0019] The degree of substitution (DS) of the carboxyalkyl group in the above carboxyalkylated polysaccharide is 0.6 to 0.9, and

[0020] The above silica is included in an amount of 0.1 to 1 weight part per 100 weight parts of the above superabsorbent resin particles,

[0021] A biodegradable superabsorbent resin is provided.

[0022]

[0023] According to another embodiment of the present invention, a step of preparing a first crosslinking solution comprising a carboxyalkylated polysaccharide and a first crosslinking agent (step 1);

[0024] Step 2: Drying the first crosslinking solution to produce a crosslinked polymer and then grinding it;

[0025] A step of producing superabsorbent resin particles comprising a second crosslinked layer by further crosslinking a pulverized crosslinked polymer in the presence of a second crosslinking agent (Step 3); and

[0026] It includes a step of mixing silica (step 4), and

[0027] The degree of substitution (DS) of the carboxyalkyl group in the above carboxyalkylated polysaccharide is 0.6 to 0.9, and

[0028] The above silica is used in an amount of 0.1 to 1 weight part per 100 weight parts of the above superabsorbent resin particles,

[0029] A method for manufacturing a biodegradable superabsorbent resin is provided.

[0030]

[0031] Furthermore, according to another embodiment of the present invention, a sanitary product comprising the biodegradable superabsorbent resin is provided.

[0032]

[0033] The biodegradable superabsorbent resin of the present invention exhibits excellent biodegradability by using a carboxyalkylated polysaccharide, which is one of the chemically modified polysaccharides. Furthermore, the biodegradable superabsorbent resin comprises a carboxyalkylated polysaccharide having a certain degree of substitution (DS) of carboxyalkyl groups and a specific amount of silica, thereby not only exhibiting excellent absorption performance but also improving liquid permeability. Accordingly, the biodegradable superabsorbent resin can be applied to various sanitary products without causing environmental pollution problems upon disposal.

[0034]

[0035] The terms used herein are merely for describing exemplary embodiments and are not intended to limit the invention. Singular expressions include plural expressions unless the context clearly indicates otherwise. In this specification, terms such as “comprising,” “comprising,” or “having” are intended to indicate the presence of the implemented features, steps, components, or combinations thereof, and should be understood as not precluding the existence or addition of one or more other features, steps, components, or combinations thereof.

[0036]

[0037] Furthermore, in the present invention, when each layer or element is referred to as being formed "on" or "above" each layer or element, it means that each layer or element is formed directly on each layer or element, or that another layer or element may be additionally formed between each layer, on an object, or on a substrate.

[0038]

[0039] The present invention is capable of various modifications and may take various forms, and specific embodiments are illustrated and described in detail below. However, this is not intended to limit the invention to the specific disclosed forms, and it should be understood that the invention includes all modifications, equivalents, and substitutions that fall within the spirit and scope of the invention.

[0040]

[0041] Furthermore, the technical terms used in this specification are intended merely to refer to specific embodiments and are not intended to limit the invention. Also, the singular forms used herein include plural forms unless the phrases clearly indicate otherwise.

[0042]

[0043] Meanwhile, the term "(meth)acrylate" as used in this specification includes both acrylate and methacrylate.

[0044]

[0045] The terms "polymer" or "polymer" used in the specification of the present invention refer to a state in which monomers having unsaturated substituents are polymerized, and may encompass all moisture content ranges or particle size ranges. Among the polymers, a polymer having a moisture content (water content) of about 40 weight% or more in the state before drying after polymerization may be referred to as a cross-linked polymer, and particles obtained by grinding and drying such a cross-linked polymer may be referred to as a cross-linked polymer.

[0046]

[0047] Furthermore, depending on the context, the term "superabsorbent resin" refers to a cross-linked polymer of a carboxyalkylated polysaccharide and a first cross-linking agent, or a cross-linked polymer in the form of a powder consisting of superabsorbent resin particles formed by grinding said cross-linked polymer, or is used to encompass all products made suitable for commercialization by undergoing additional processes, such as surface crosslinking, fine powder reassembly, drying, grinding, classification, etc. Additionally, surface crosslinking here refers to the surface of said cross-linked polymer being additionally crosslinked via a second cross-linking agent.

[0048]

[0049] Conventional superabsorbent polymers are manufactured by polymerizing acrylic acid-based monomers with a crosslinking agent in the presence of an initiator; however, superabsorbent polymers produced in this way do not possess biodegradability, causing environmental problems.

[0050]

[0051] Accordingly, development of superabsorbent polymers capable of exhibiting biodegradability has been underway. While materials such as polysaccharides, polyaspartic acid, and polyglutamic acid have been discussed as biodegradable materials for manufacturing such polymers, there have been difficulties in replacing superabsorbent polymers manufactured from acrylic acid monomers because these materials reduce the absorption capacity, which is a key physical property of superabsorbent polymers.

[0052]

[0053] Accordingly, the inventors completed the present invention by confirming that it is possible to manufacture a superabsorbent resin having excellent absorption performance as well as excellent liquid permeability by using a carboxyalkylated polysaccharide having a specific range of degree of substitution (DS) of carboxyalkyl groups as a monomer and then adding silica thereto.

[0054]

[0055] Hereinafter, a biodegradable superabsorbent resin and a method for manufacturing the same will be described in more detail according to specific embodiments of the invention.

[0056]

[0057] Biodegradable superabsorbent resin

[0058] Specifically, a biodegradable superabsorbent resin according to one embodiment of the invention comprises: superabsorbent resin particles comprising (a crosslinked polymer of a carboxyalkylated polysaccharide and a first crosslinking agent) and a second crosslinked layer in which the crosslinked polymer is further crosslinked via a second crosslinking agent; and silica.

[0059] The degree of substitution (DS) of the carboxyalkyl group in the above carboxyalkylated polysaccharide is 0.6 to 0.9, and

[0060] The above silica is included in an amount of 0.1 to 1 weight part per 100 weight parts of the above superabsorbent resin particles.

[0061]

[0062] Here, the cross-linked polymer has a structure formed by polymerizing monomers containing carboxyalkylated polysaccharides. In this case, as the cross-linked polymer simultaneously includes a main chain formed by polymerizing polysaccharides and a structure formed by polymerizing functional groups called carboxyalkyl groups, the overall physical properties of the superabsorbent resin can be improved.

[0063]

[0064] In addition, the crosslinked polymer may comprise only carboxyalkylated polysaccharides as monomers and not include other unsaturated monomers. A crosslinked polymer composed solely of carboxyalkylated polysaccharides in this manner may exhibit higher biodegradability compared to a crosslinked polymer prepared by including other unsaturated monomers.

[0065]

[0066] The term "polysaccharide" above refers to a polymeric carbohydrate molecule composed of glucose repeating units. In this case, it also includes polymeric molecules composed of a glucosamine repeating unit in which an amino group is introduced to a hydroxyl group attached to the 2nd carbon atom within the glucose repeating unit, and / or an N-acetylglucosamine repeating unit in which an N-acetylamino group is introduced to a hydroxyl group attached to the 2nd carbon atom within the glucose repeating unit. Such polysaccharides can be classified into storage polysaccharides used as general energy sources, structural polysaccharides that form structural components of plants and animals, such as plant cell walls or the exoskeletons of arthropods, or capsular polysaccharides that form the capsules of bacteria. Examples of the above storage polysaccharides include starch, dextrin, glycogen, inulin, etc. Examples of the above structural polysaccharides include cellulose, chitin, chitosan, pectin, arabinoxylan, carrageenan, agar, etc. Examples of the above capsular polysaccharides include alginate, xanthan gum, guar gum, gellan gum, dextran, welan gum, etc. Among these, those capable of gelatinization are suitable for the method of preparing the above carboxyalkylated polysaccharides. More specifically, the above polysaccharides may be starch, dextrin, glucose, inulin, cellulose, chitosan, pectin, agar, carrageenan, alginate, xanthan gum, guar gum, gellan gum, or a combination thereof.

[0067]

[0068] For example, the above polysaccharides may be one or more selected from the group consisting of cellulose, starch, chitosan, dextrin, glucose, pectin, inulin, agar, and guar gum. These polysaccharides are easily carboxylated, which may be advantageous for forming cross-linked polymers, and accordingly, it may be possible to manufacture a superabsorbent resin with improved water permeability.

[0069]

[0070] In addition, the above-mentioned carboxyalkylated polysaccharide is one of the modified polysaccharides that are distinguished from unmodified noncarboxyalkylated polysaccharides typically obtained naturally or synthetically, and means that at least one of the hydroxyl groups (-OH) within the glucose repeating units constituting the carboxyalkylated polysaccharide is substituted with a carboxyalkyl group by chemical treatment and / or heat treatment.

[0071]

[0072] Specifically, the polysaccharide comprises an anhydroglucose repeating unit (AGU) represented by the following chemical formula 1, and the molecular weight of the anhydroglucose unit (AGU) is 162.14.

[0073] [Chemical Formula 1]

[0074]

[0075]

[0076] In this case, the numbering in Chemical Formula 1 refers to the position of each carbon, and carboxyalkylation may occur at the hydroxyl group of carbon number 2 (C2), carbon number 3 (C3), or carbon number 6 (C6) within the anhydrous glucose unit (AGU).

[0077]

[0078] Here, the degree of substitution (DS) of the carboxyalkyl group refers to the average number of hydroxyl groups (-OH) substituted with carboxyalkyl groups per anhydrous glucose repeating unit. That is, since there are 3 hydroxyl groups per glucose repeating unit, the theoretical maximum degree of substitution is 3, and a degree of substitution of 0.1 means that 3 hydroxyl groups are substituted per 10 glucose repeating units. Furthermore, this degree of substitution of the acidic group of the finally prepared carboxyalkylated polysaccharide 1 It can be calculated through H NMR analysis.

[0079]

[0080] The degree of substitution (DS) of the carboxyalkyl group in the above carboxyalkylated polysaccharide is 0.6 to 0.9. If the degree of substitution (DS) of the carboxyalkyl group is less than 0.6, it is difficult to proceed with three-dimensional crosslinking, and there is a concern that the absorption performance of the manufactured superabsorbent resin may be significantly low. If the degree of substitution (DS) of the carboxyalkyl group exceeds 0.9, the formation of a gel with a shape is reduced due to a decrease in crosslinking points, and it is difficult to secure gel strength under pressure, so it may be difficult to improve the permeability of the superabsorbent resin due to the problem of the gel collapsing when in contact with salt water.

[0081]

[0082] More specifically, the degree of substitution (DS) of the carboxyalkyl group in the carboxyalkylated polysaccharide may be 0.6 or more, 0.65 or more, 0.7 or more, 0.75 or more, 0.76 or more, 0.77 or more, 0.78 or more, 0.79 or more, 0.80 or more, or 0.81 or more, and may be 0.9 or less, 0.89 or less, 0.88 or less, 0.87 or less, 0.86 or less, 0.85 or less, or 0.84 or less.

[0083]

[0084] In this case, the carboxyalkylated polysaccharide may be carboxymethylated. Accordingly, the degree of substitution (DS) of the carboxyalkyl group in the carboxyalkylated polysaccharide described above can be interpreted as the degree of substitution of the carboxymethyl group in the carboxymethylated polysaccharide.

[0085]

[0086] These carboxyalkylated polysaccharides can be carboxyalkylated using a metal salt of a haloalkylcarboxylic acid. The metal salt of the haloalkylcarboxylic acid refers to a metal salt of an alkylcarboxylic acid (alkylcarboxylic acid, alkanoic acid, where R is alkyl in R-COOH) having at least one halogen substituent, that is, a compound in which an anion of an alkylcarboxylic acid having at least one halogen substituent and a metal cation are ionically bonded. Here, the metal salt may be an alkali metal salt, an alkaline earth metal salt, or a divalent transition metal salt. Additionally, the halogen substituent may preferably be chloro or bromo. Furthermore, the alkyl group may be straight or branched, and the number of carbon atoms is not particularly limited but may be 1 to 20 or 1 to 10. Specific examples of the above alkyl groups include methyl, ethyl, propyl, n-propyl, isopropyl, butyl, n-butyl, isobutyl, tert-butyl, sec-butyl, 1-methyl-butyl, 1-ethylbutyl, pentyl, n-pentyl, isopentyl, neopentyl, tert-pentyl, 1-ethyl-propyl, 1,1-dimethylpropyl, hexyl, n-hexyl, 1-methylpentyl, 2-methylpentyl, 4-methyl-2-pentyl, 3,3-dimethylbutyl, 2-ethylbutyl, heptyl, n-heptyl, isohexyl, 1-methylhexyl, 2-methylhexyl, 3-methylhexyl, 4-methylhexyl, 5-methylhexyl, cyclopentylmethyl, cyclohexylmethyl, octyl, n-octyl, tert-octyl, 1-methylheptyl, 2-ethylhexyl, Examples include 2,4,4-trimethyl-1-pentyl, 2,4,4-trimethyl-2-pentyl, 2-propylpentyl, n-nonyl, 2,2-dimethylheptyl, but are not limited thereto.

[0087]

[0088] These metal salts of haloalkylcarboxylic acids may be alkyl metal salts of haloalkylcarboxylic acids.

[0089]

[0090] In one embodiment, when the carboxyalkylated polysaccharide is carboxymethylated, the metal salt of the haloalkylcarboxylic acid may be an alkali metal salt of the haloacetic acid.

[0091]

[0092] In another embodiment, the metal salt of the haloalkylcarboxylic acid may be an alkali metal salt of an alkylcarboxylic acid substituted with at least one chloro.

[0093]

[0094] In another embodiment, the metal salt of the haloalkylcarboxylic acid may be an alkali metal salt of acetic acid substituted with at least one chloro.

[0095]

[0096] Preferably, considering reactivity, the metal salt of the haloalkylcarboxylic acid may be an alkali metal salt of chloroacetic acid.

[0097]

[0098] The above alkali metal salt of chloroacetate may be one or more selected from the group consisting of sodium monochloroacetate (SMCA), potassium monochloroacetate, and lithium monochloroacetate. Preferably, sodium monochloroacetate (SMCA) is used considering its ease of availability and reactivity.

[0099]

[0100] For example, a carboxymethylated polysaccharide modified using an alkali metal salt of a haloacetic acid contains a carboxymethylated glucose unit represented by the following chemical formula 2:

[0101] [Chemical Formula 2]

[0102]

[0103] In the above chemical formula 2,

[0104] R is independently hydrogen, CH2COO - M + , or CH2COOH, and

[0105] However, at least one of R is CH2COO - M + , or CH2COOH, and

[0106] Here, M means alkali metal.

[0107]

[0108] Meanwhile, the above-mentioned carboxyalkylated polysaccharide may have a viscosity of 4,000 to 13,000 cP when measured with a Brookfield viscometer in a 1 wt% aqueous solution. Specifically, the above-mentioned carboxyalkylated polysaccharide may have a viscosity of 4,000 to 13,000 cP when measured after 1 minute at 30 rpm with spindle #V-74 at 25 ℃ using a Brookfield viscometer (instrument name: Brookfield DV2T LV TJ0, manufacturer: Brookfield) in a 1 wt% aqueous solution. If the viscosity of the above-mentioned carboxyalkylated polysaccharide is excessively low, the gel strength does not increase, so there may be a problem where the gel collapses in the brine and water permeability is not ensured. If the viscosity of the above-mentioned carboxyalkylated polysaccharide is excessively high, uneven mixing occurs due to the high load during the stirring process, and crosslinking does not occur uniformly.

[0109]

[0110] More specifically, the above-mentioned carboxyalkylated polysaccharide may have a viscosity (cP) measured by a Brookfield viscometer in a 1 wt% aqueous solution of 4,000 or more, 4,500 or more, 5,000 or more, 5,500 or more, 6,000 or more, 6,500 or more, 7,000 or more, 7,500 or more, 8,000 or more, 8,500 or more, 9,000 or more, 9,500 or more, or 10,000 or more, and 13,000 or less, or 12,900 or less.

[0111]

[0112] In addition, the carboxyalkylated polysaccharide is 1.0 x 10 6 Up to 1.5 x 10 7 The carboxyalkylated polysaccharides have a weight-average molecular weight (Mw) of g / mol. If the weight-average molecular weight of the carboxyalkylated polysaccharides is excessively low, there is a problem in that sufficient crosslinking does not occur, leaving a large amount of unreacted polysaccharides. If it is excessively high, there is a problem in that acid treatment and the introduction of functional groups may be difficult due to the entanglement of the polymer chains of the high molecular weight polysaccharides, making it difficult to manufacture the carboxyalkylated polysaccharides. Here, the weight-average molecular weight (Mw) can be measured using gel permeation chromatography (GPC / MALLS).

[0113]

[0114] More specifically, the weight-average molecular weight (Mw, g / mol) of the carboxyalkylated polysaccharide is 1.0 x 10⁻⁶ 6 Above, 1.5 x 10 6 That is, 2.0 x 10 6 That is, 3.0 x 10 6 More than, or 4.0 x 10 6 While being more than, 1.5 x 10 7 Below, 1.0 x 10 7 Below, 9.0 x 10 6 Below, 8.0 x 10 6 Less than or equal to, or 7.0 x 10 6 It may be less than.

[0115]

[0116] Meanwhile, the term 'first crosslinking agent' used in this specification is used to distinguish it from the second crosslinking agent, which is typically used to crosslink the surface of superabsorbent resin particles, and serves to connect the hydroxyl groups of multiple polysaccharides to each other. Although the crosslinking in the above step proceeds without distinction between the surface and the interior, when an additional crosslinking process of the superabsorbent resin particles is performed, the surface of the finally manufactured superabsorbent resin particles is composed of a structure mainly crosslinked by the second crosslinking agent, and the interior is composed of a structure mainly crosslinked by the first crosslinking agent. Therefore, the second crosslinking agent can be considered to function as a surface crosslinking agent since it primarily crosslinks the surface of the superabsorbent resin, and the first crosslinking agent can be considered to function as a first crosslinking agent, distinguished from the second crosslinking agent.

[0117]

[0118] This first crosslinking agent may be a polyvalent metal salt or a polyvalent epoxy compound.

[0119]

[0120] Specifically, the polyvalent metal salt is a salt compound containing polyvalent cations of metal within the molecule, and may be one or more selected from the group consisting of aluminum chloride, polyaluminum chloride, aluminum sulfate, aluminum lactate, aluminum acetate, potassium aluminum bissulfate, sodium aluminum bissulfate, calcium chloride, calcium acetate, magnesium chloride, magnesium sulfate, magnesium acetate, zinc chloride, zinc sulfate, zinc acetate, zirconium chloride, zirconium sulfate, and zirconium acetate.

[0121]

[0122] In addition, the above-mentioned polyvalent epoxy compound is a compound containing two or more epoxy groups within the molecule, such as ethylene glycol diglycidyl ether, diethylene glycol diglycidyl ether, polyethylene glycol diglycidyl ether, propylene glycol diglycidyl ether, tripropylene glycol diglycidyl ether, polypropylene glycol diglycidyl ether, neopentyl glycol diglycidyl ether, 1,4-butanediol diglycidyl ether, 1,6-hexanediol diglycidyl ether, polytetramethylene glycol diglycidyl ether, glycerol diglycidyl ether, glycerol triglycidyl ether, diglycerol polyglycidyl ether, polyglycerol polyglycidyl ether, resorcin diglycidyl ether, 2,2-dibromoneopentyl glycol diglycidyl ether, trimethylolpropane triglycidyl ether, pentaerythritol polyglycidyl ether, It may be one or more selected from the group consisting of sorbitol polyglycidyl ether, adipic acid diglycidyl ester, and phthalate diglycidyl ester.

[0123]

[0124] Meanwhile, the superabsorbent resin particles further comprise a second crosslinked layer in which at least a portion of the surface of the crosslinked polymer of the carboxyalkylated polysaccharide and the first crosslinking agent is additionally crosslinked via a second crosslinking agent. Here, the second crosslinked layer is mainly formed on at least a portion of the surface of each particle of the base resin and has a structure in which the crosslinked polymer within the base resin is crosslinked by the second crosslinking agent. This is intended to increase the crosslinking density on the surface of the superabsorbent resin particles, and when the superabsorbent resin particles further comprise a structure in which at least a portion is crosslinked by the second crosslinking agent as described above, they have a structure in which the crosslinking density is higher on the outside than on the inside.

[0125]

[0126] As the above second crosslinking agent, any second crosslinking agent that has been conventionally used in the manufacture of superabsorbent resins can be used without any particular restrictions.

[0127] For example, the second crosslinking agent may be one or more selected from the group consisting of polycarboxylic acids, polyols, carbonate compounds, epoxy compounds, oxazoline compounds, polyamine compounds, and cyclic urea compounds.

[0128]

[0129] More specifically, the second crosslinking agent comprises: one or more polycarboxylic acids selected from the group consisting of succinic acid, citric acid, and their anhydrides; one or more polyols selected from the group consisting of ethylene glycol, propylene glycol, 1,3-propanediol, 1,4-butanediol, 1,6-hexanediol, 1,2-hexanediol, 1,3-hexanediol, 2-methyl-1,3-propanediol, 2,5-hexanediol, 2-methyl-1,3-pentanediol, 2-methyl-2,4-pentanediol, tripropylene glycol, and glycerol; one or more carbonate compounds selected from the group consisting of ethylene carbonate, propylene carbonate, and glycerol carbonate; and one or more epoxy compounds selected from the group consisting of mono-epoxy compounds, poly-epoxy compounds, and epihalohydrin compounds. It may include oxazolidinone, mono-, di-, or polyoxazolidinone compounds, oxazolidinone compounds, polyamine compounds, or cyclic urea compounds.

[0130] For example, the above polyvalent epoxy compound is as described above, and the above epihalohydrin compound may be one or more selected from the group consisting of epichlorohydrin, epiiodohydrin, epibromohydrin, and 2-(chloromethyl)-2-methyloxirane.

[0131]

[0132] In addition, the second crosslinking agent described above may be used as one type of the second crosslinking agent, or one or more types, or two or more types together.

[0133]

[0134] Meanwhile, the above-degradable superabsorbent resin contains silica in an amount of 0.1 to 1 part by weight per 100 parts by weight of the superabsorbent resin particles. If the silica is contained in the superabsorbent resin in an amount of less than 0.1 part by weight per 100 parts by weight of the superabsorbent resin particles, there may be a problem in that liquid permeability is not ensured, and if it is contained in an amount exceeding 1 part by weight per 100 parts by weight of the superabsorbent resin particles, there may be a problem in that the physical properties of the superabsorbent resin are degraded. More specifically, the silica may be included in the superabsorbent resin in an amount of 0.1 parts by weight or more, 0.15 parts by weight or more, 0.2 parts by weight or more, 0.21 parts by weight or more, 0.22 parts by weight or more, 0.23 parts by weight or more, 0.24 parts by weight or more, 0.25 parts by weight or more, 0.26 parts by weight or more, 0.27 parts by weight or more, 0.28 parts by weight or more, or 0.29 parts by weight or more, relative to 100 parts by weight of superabsorbent resin particles.

[0135]

[0136] In addition, the silica may be fumed silica or wet silica.

[0137]

[0138] In addition, the silica may be unsurface-treated silica having silanol (-SiOH) on its surface.

[0139] Alternatively, the silica may be silica that has been surface-modified by a surface treatment agent as needed. The surface treatment agent may be selected from the group consisting of dimethyldichlorosilane (DDS), polydimethylsiloxane (PDMS), and hexamethyldisilazane (HMDS). That is, the surface-modified silica may exhibit hydrophobicity by introducing an organic group, such as a methyl group, to the silanol (-SiOH) groups on the surface.

[0140]

[0141] More specifically, the silica may be untreated fumed silica.

[0142]

[0143] In addition, the silica has a specific surface area of ​​100 to 300 m² 2 It may be / g. If the specific surface area of ​​the silica is excessively low, there may be a problem of reduced adsorption with the resin, and if the specific surface area of ​​the silica is excessively high, there may be a problem of increased bonding between silica particles. The specific surface area of ​​the silica was measured by the BET method, specifically using a Micrometrics ASAP 2010 instrument to measure the partial pressure (0.11 <p / po<1)에 따른 질소의 흡 / 탈착량으로 분석할 수 있다.

[0144]

[0145] In addition, the silica may have an average particle size of primary particles of 5 to 50 nm. In this case, primary particles refer to particles that are not aggregated with each other and are distinguished from aggregates / agglomerates.

[0146]

[0147] In addition, the above-mentioned biodegradable superabsorbent resin may have a free swelling gel bed permeability (GBP) of 10 darcy or more. Here, GBP can be measured by swelling a sample in a 0.9% saline solution for 60 minutes under no pressure and then passing the saline solution through it under pressure. Here, darcy is a CGS unit for permeability; for example, 1 darcy is the permeability of 1 cm of a fluid with a viscosity of 1 cps when the pressure difference between the two cross-sections of a solid is 1 atm. 2 This cross-sectional thickness is 1cm and the cross-sectional area is 1cm 2It is the transmittance of a solid flowing within one second. Since there is no SI unit for transmittance, it has the same unit as area, m 2 This is used. 1 Darcy is approximately 0.98692 × 10⁻⁶ -12 m 2 or approximately 0.98692 × 10⁻⁶ -8 cm 2 It is identical to the above. A method for measuring such gelbed permeability is described in the specification of Korean Patent Application No. 2014-7018005.

[0148]

[0149] Furthermore, the gel bed permeability (GBP) described above is a measurement of the permeability of a swollen bed of gel particles (e.g., surface-treated absorbent material or superabsorbent material before surface treatment) under a condition specifically referred to as a "free swelling" state. A high gel bed permeability under such load implies high gel strength, which can serve as an indicator simulating permeability under pressure from a baby's body weight after urinating.

[0150]

[0151] More specifically, the above-mentioned biodegradable superabsorbent resin may have a free swelling gel bed permeability (GBP,darcy) of 10 or more, 11 or more, 12 or more, 13 or more, 14 or more, 15 or more, 16 or more, 17 or more, 18 or more, 19 or more, 20 or more, 21 or more, 22 or more, 23 or more, 24 or more, or 25 or more. Additionally, since a higher GBP value indicates higher permeability, there is no upper limit thereto, but the free swelling gel bed permeability (GBP,darcy) may be 50 or less, 49 or less, 48 ​​or less, 47 or less, 46 or less, 45 or less, 44 or less, 43 or less, 42 or less, 41 or less, 40 or less, or 39 or less.

[0152]

[0153] In addition, the above-mentioned biodegradable superabsorbent resin may have a non-pressurized GBP value of at least twice that of the above-mentioned silica-free resin. More specifically, the above-mentioned biodegradable superabsorbent resin may have a non-pressurized GBP value of at least twice, at least 2.5 times, or at least three times that of the above-mentioned silica-free resin. In this case, there is no upper limit, but for example, the above-mentioned biodegradable superabsorbent resin may have a non-pressurized GBP value of at least seven times, at least six times, or at least five times that of the above-mentioned silica-free resin. This can be confirmed through the examples and comparative examples described later, and accordingly, it can be seen that the presence or absence of silica affects liquid permeability.

[0154]

[0155] In addition, the above-mentioned biodegradable superabsorbent resin may have a centrifugal retention capacity (CRC) of 19 g / g or more and an absorption capacity (0.9 AUP) under 0.9 psi pressure of 10 g / g or more.

[0156]

[0157] More specifically, the biodegradable superabsorbent resin may have a water retention capacity (CRC) measured according to the EDANA method WSP 241.3 of 19 g / g or more, 20 g / g or more, 21 g / g or more, 22 g / g or more, 23 g / g or more, or 24 g / g or more, and may have a range of 40 g / g or less, 35 g / g or less, or 30 g / g or less.

[0158] In addition, the above-mentioned biodegradable superabsorbent resin may have an applied absorption capacity (AUP) at 0.9 psi measured according to the EDANA method WSP 242.3 of 10 g / g or more, 11 g / g or more, 12 g / g or more, 12.5 g / g or more, 13 g / g or more, 13.5 g / g or more, 14 g / g or more, 14.5 g / g or more, or 15 g / g or more, and may be 30 g / g or less, 25 g / g or less, or 20 g / g or less.

[0159]

[0160] In addition, the biodegradable superabsorbent resin particles may be in the form of particles having an average particle size of 150 to 850 μm. In this case, such particle size may be measured according to the European Disposables and Nonwovens Association (EDANA) standard EDANA WSP 220.3 method. More specifically, the superabsorbent resin composition may consist of superabsorbent resin particles having a particle size of approximately 150 to 850 μm, comprising about 90 wt%, preferably 95 wt% or more, based on the total weight, and fine powder having a particle size of approximately 150 μm or less, comprising about 10 wt%, more specifically about 5 wt% or less. It is undesirable for the superabsorbent resin to contain a large amount of fine powder having a particle size of less than 150 μm, as this may degrade the overall physical properties of the superabsorbent resin.

[0161]

[0162] Method for manufacturing biodegradable superabsorbent resin

[0163] Meanwhile, the above-described biodegradable superabsorbent resin is manufactured by including the following steps:

[0164] A step of preparing a first crosslinking solution comprising a carboxyalkylated polysaccharide and a first crosslinking agent (Step 1);

[0165] Step 2: Drying the first crosslinking solution to produce a crosslinked polymer and then grinding it;

[0166] A step of producing superabsorbent resin particles comprising a second crosslinked layer by further crosslinking a pulverized crosslinked polymer in the presence of a second crosslinking agent (Step 3); and

[0167] Step of mixing silica (Step 4).

[0168] At this time, the degree of substitution (DS) of the carboxyalkyl group in the carboxyalkylated polysaccharide is 0.6 to 0.9, and the silica is used in an amount of 0.1 to 1 weight part per 100 weight parts of the superabsorbent resin particles.

[0169]

[0170] (Step 1)

[0171] First, Step 1 is performed to prepare a first crosslinking solution comprising a carboxyalkylated polysaccharide and a first crosslinking agent.

[0172]

[0173] The above-described carboxyalkylated polysaccharide is prepared by carboxyalkylation of an unmodified polysaccharide using a metal salt of a haloalkylcarboxylic acid as described above, and such carboxyalkylation reaction can be carried out in a solvent of water and / or alcohol in the presence of a hydroxide. Specifically, the carboxyalkylation reaction can be carried out at a temperature of 50 to 100 °C for 4 to 12 hours. In addition, the degree of substitution of the carboxyalkylated polysaccharide can be controlled by varying the number of moles of the metal salt of the haloalkylcarboxylic acid relative to the polysaccharide.

[0174]

[0175] In addition, in the first crosslinking solution, the first crosslinking agent may be used in an amount of 0.01 to 1 part by weight relative to 100 parts by weight of the carboxyalkylated polysaccharide. For example, the first crosslinking agent may be used in an amount of 0.01 parts by weight or more, 0.02 parts by weight or more, or 0.03 parts by weight or more relative to 100 parts by weight of the carboxyalkylated polysaccharide, and in an amount of 1 part by weight or less, 0.7 parts by weight or less, 0.5 parts by weight or less, 0.3 parts by weight or less, or 0.1 parts by weight or less. If the content of the first crosslinking agent is excessively low, crosslinking may not occur sufficiently, making it difficult to achieve strength above an appropriate level; if the content of the first crosslinking agent is excessively high, the internal crosslinking density may increase, making it difficult to achieve the desired water retention capacity. In this case, the first crosslinking agent may be used after being dissolved in the solvent in advance.

[0176]

[0177] At this time, the first crosslinking solution may include a solvent. For example, one or more solvents selected from water, ethanol, ethylene glycol, diethylene glycol, triethylene glycol, 1,4-butanediol, propylene glycol, ethylene glycol monobutyl ether, propylene glycol monomethyl ether, propylene glycol monomethyl ether acetate, methyl ethyl ketone, acetone, methyl amyl ketone, cyclohexanone, cyclopentanone, diethylene glycol monomethyl ether, diethylene glycol ethyl ether, toluene, xylene, butyrolactone, carbitol, methyl cellosolve acetate, and N,N-dimethylacetamide may be used in combination.

[0178]

[0179] In addition, the solid content of the first crosslinking solution may be 30% by weight or less. If the carboxyalkylated polysaccharide has a high molecular weight, the first crosslinking solution may be in a suspension state or in a mixed state in which the polysaccharide exists in a crumb state, and if the carboxyalkylated polysaccharide has a low molecular weight, the first crosslinking solution may be in a solution state. Furthermore, if the solid content of the first crosslinking solution exceeds 30% by weight based on the total weight of the first crosslinking solution, there is a risk that the problem of insufficient liquid permeability may arise.

[0180]

[0181] More specifically, the solid content of the first crosslinking liquid may be 1% to 30% by weight. For example, the solid content of the first crosslinking liquid may be 1 wt% or more, 2 wt% or more, 3 wt% or more, 4 wt% or more, 5 wt% or more, 6 wt% or more, 7 wt% or more, 8 wt% or more, 9 wt% or more, 10 wt% or more, 11 wt% or more, 12 wt% or more, 13 wt% or more, 14 wt% or more, 15 wt% or more, and 30 wt% or less, 29 wt% or less, 28 wt% or less, 27 wt% or less, 26 wt% or less, 25 wt% or less, 24 wt% or less, 23 wt% or less, 22 wt% or less, 21 wt% or less, 20 wt% or less, 19 wt% or less, 18 wt% or less, 17 wt% or less, or 16 wt% or less.

[0182]

[0183] The first crosslinking solution may further include additives such as a thickener, a plasticizer, a preservative stabilizer, and an antioxidant, as needed.

[0184]

[0185] (Step 2)

[0186] Next, a step of drying the first crosslinking solution to prepare a crosslinked polymer and then grinding it is performed. At this time, during the drying process, the carboxyalkylated polysaccharide is crosslinked in the presence of the first crosslinking agent, so that a crosslinked polymer of the carboxyalkylated polysaccharide and the first crosslinking agent can be prepared.

[0187]

[0188] The above drying can be performed at a temperature of 130 to 150 ℃. More preferably, it can be performed at a temperature of 130 to 150 ℃ for 20 minutes to 1 hour.

[0189]

[0190] The above drying method can be selected and used without limitation on its composition, as long as it is commonly used as a drying process for polymers. Specifically, the drying step can be carried out by methods such as hot air supply, infrared irradiation, microwave irradiation, or ultraviolet irradiation. After drying, the moisture content of the cross-linked polymer may be 10% or less.

[0191]

[0192] After the above drying process, a grinding process is performed.

[0193] The above grinding process can be performed so that the particle size of the polymer powder is approximately 150 to approximately 850 μm. Specifically, the grinder used to grind to such a particle size may be a pin mill, a hammer mill, a screw mill, a roll mill, a disc mill, or a jog mill, but the present invention is not limited to the examples described above.

[0194] In addition, after the grinding step described above, in order to control the physical properties of the superabsorbent resin produced as a final product, the ground polymer powder may be further classified according to particle size.

[0195]

[0196] The crosslinked polymer obtained as a result of the above-described process may have a powder form. Specifically, the crosslinked polymer may have a powder form having a particle size of 150 to 850 μm.

[0197]

[0198] (Step 3)

[0199] Next, a step is performed to produce superabsorbent resin particles comprising a second cross-linked layer by further cross-linking the pulverized cross-linked polymer prepared in step 2 above in the presence of a second cross-linking agent.

[0200]

[0201] In the above step, a cross-linked layer may be formed in which the cross-linked polymer is additionally cross-linked via a second cross-linking agent. That is, a superabsorbent resin particle in which a second cross-linked layer is formed on at least a portion of the surface of the cross-linked polymer particle can be obtained.

[0202]

[0203] At this time, the second crosslinking agent used may be any crosslinking agent that has been conventionally used in the manufacture of superabsorbent resins without any particular restrictions, with reference to the above description. More preferably, in terms of crosslinking efficiency, a polycarboxylic acid or an anhydride thereof may be used as the second crosslinking agent.

[0204]

[0205] In addition, the second crosslinking agent may be used in an amount of 0.01 to 5 parts by weight relative to 100 parts by weight of the crosslinked polymer. If the content of the second crosslinking agent is excessively low relative to the crosslinked polymer, surface modification may not be properly performed, which may lead to a decrease in the pressurized absorption capacity of the final superabsorbent resin; conversely, if an excessive amount of the second crosslinking agent is used, the basic water retention capacity of the resin may actually decrease due to an excessive crosslinking reaction, which is undesirable. More specifically, the second crosslinking agent may be used in an amount of 0.02 parts by weight or more, 0.05 parts by weight or more, 0.1 parts by weight or more, 0.2 parts by weight or more, 0.3 parts by weight or more, or 0.4 parts by weight or more relative to 100 parts by weight of the crosslinked polymer, and in an amount of 4 parts by weight or less, 3 parts by weight or less, 2 parts by weight or less, 1 part by weight or less, or 0.7 parts by weight or less.

[0206]

[0207] There are no limitations on the composition of the method for mixing the second crosslinking agent into the crosslinked polymer. Methods such as mixing the second crosslinking agent and the crosslinked polymer powder by placing them into a reaction vessel, spraying the second crosslinking agent onto the crosslinked polymer powder, or continuously supplying the crosslinked polymer and the second crosslinking agent to a continuously operated mixer for mixing may be used.

[0208]

[0209] More preferably, the second crosslinking agent may be introduced in the form of a second crosslinking liquid mixed in a solvent containing water. When water is added, there is an advantage that the second crosslinking agent can be evenly dispersed in the polymer.

[0210]

[0211] At this time, for the purpose of inducing even dispersion of the second crosslinking agent, preventing clumping of the polymer powder, and optimizing the surface penetration depth of the second crosslinking agent, it is preferable to use the water in an amount of 1 to 20 parts by weight relative to 100 parts by weight of the crosslinking polymer. For example, the water may be used in an amount of 0.5 parts by weight or more, 1 part by weight or more, 1.5 parts by weight or more, or 2 parts by weight or more relative to 100 parts by weight of the crosslinking polymer, and 10 parts by weight or less, 9 parts by weight or less, 8 parts by weight or less, 7 parts by weight or less, 6 parts by weight or less, or 5 parts by weight or less.

[0212]

[0213] In addition, the second crosslinking solution may further include methanol. In particular, water and methanol may be included in the second crosslinking solution in a weight ratio of 20:80 to 80:20. Preferably, water and methanol may be used in a weight ratio of 25:75.

[0214]

[0215] In addition, the additional crosslinking in step 3 above may be performed at a temperature of 80 to 140°C. More specifically, the crosslinking in step 3 above may be performed at a temperature of 120 to 140°C for 5 to 60 minutes or 20 to 40 minutes.

[0216]

[0217] By satisfying the crosslinking process conditions in step 3, a superabsorbent resin that appropriately satisfies the physical properties of one embodiment can be manufactured more effectively.

[0218]

[0219] The means for raising the temperature for the crosslinking in Step 3 above is not particularly limited. Heating can be achieved by supplying a heat medium or by directly supplying a heat source. In this case, the types of heat mediums that can be used include heated fluids such as steam, hot air, and hot oil, but are not limited thereto. Additionally, the temperature of the supplied heat medium can be appropriately selected by considering the means of the heat medium, the rate of heating, and the target temperature. Meanwhile, the heat source supplied directly may include heating via electricity or heating via gas, but is not limited to the examples described above.

[0220]

[0221] The superabsorbent resin obtained according to the above-described manufacturing method maintains excellent absorption performance, such as water retention capacity and pressurized absorption capacity, and satisfies the improved absorption rate, thereby satisfying all physical properties of one embodiment.

[0222]

[0223] (Step 4)

[0224] Next, the method includes a step of mixing silica with the superabsorbent resin particles prepared in step 3 above. At this time, the silica is used in an amount of 0.1 to 1 part by weight per 100 parts by weight of the superabsorbent resin particles, and the silica used in the above step is described in reference to the above.

[0225]

[0226] In step 4 above, the mixing of the silica can be performed at a temperature of 20 to 30°C, for example, at room temperature. Satisfying the above-described temperature conditions is preferable in that it allows the physical properties of the resin to be maintained.

[0227]

[0228] At this time, the mixing of the silica may be performed for 3 to 10 minutes, more preferably for 3 to 5 minutes. Satisfying the above-described time conditions is desirable in terms of the uniformity of the mixing.

[0229]

[0230] In addition, the method of mixing the silica with the superabsorbent resin particles is not particularly limited and can be appropriately adopted as long as it is a method capable of evenly mixing the superabsorbent resin particles. For example, the silica may be mixed in an unmixed state in a solvent, specifically in a solution dissolved in water. Specifically, the superabsorbent resin and silica may be placed in a reaction vessel or a mixer and physically mixed.

[0231]

[0232] hygiene products

[0233] Meanwhile, furthermore, a sanitary product comprising the aforementioned biodegradable superabsorbent resin is provided.

[0234]

[0235] The above-mentioned articles may be one or more selected from absorbent articles, sanitary products, soil repair agents, waterproofing materials for civil engineering, waterproofing materials for construction, seedling sheets, freshness preservatives, materials for compresses, electrical insulators, articles for oral care, articles for teeth, articles for cosmetics, and articles for skin.

[0236] At this time, sanitary products containing the superabsorbent resin may include, for example, children's paper diapers, adult diapers, or sanitary pads. In particular, the superabsorbent resin can be preferably applied to adult diapers where secondary odors caused by proliferation are a particular problem. Such sanitary products may have the composition of conventional sanitary products, except that the superabsorbent resin of the above-described embodiment is included in the absorbent body.

[0237]

[0238] Preferred embodiments are presented below to aid in understanding the invention. However, the following embodiments are intended only to illustrate the invention and do not limit the invention to these embodiments.

[0239]

[0240] [Example] Preparation of superabsorbent resin

[0241] Example 1

[0242] (Step 1) Polysaccharide component DS 0.81, viscosity 10060 cP, and Mw 4.2 x 10 6 600 g of carboxymethylated cellulose CMC-1 (manufactured by Eagle Chemicals) at g / mol, 0.3 g of the first crosslinking agent AlCl3, and 3400 mL of distilled water were stirred at 30 rpm for 30 minutes at room temperature to prepare a first crosslinking solution in which the CMC-1 well mixed with water existed in a crumb state. At this time, the first crosslinking agent AlCl3 was dissolved in distilled water and added, and the solid content of the first crosslinking solution was 15 wt%.

[0243] (Step 2) Next, the CMC-1 crumb was uniformly ground into particles smaller than 1 cm using a mixer, and then crosslinking was carried out by uniformly drying with high-temperature air using a hot air dryer capable of vertical airflow transfer at 130°C for 12 minutes from bottom to top and for 18 minutes from top to bottom. After drying, the LOD was maintained at 10% or less. After drying, the mixture was ground with a grinder and then classified to select particles with a size of 150 to 850 μm, thereby preparing a base resin which is a dried, ground, and classified crosslinked polymer.

[0244] (Step 3) A second crosslinking solution comprising 0.5 parts by weight of succinic acid, 2.5 parts by weight of water, and 7.5 parts by weight of methanol, based on 100 parts by weight of the base resin, was sprayed onto the prepared base resin powder and stirred at room temperature to mix the two so that the second crosslinking solution was evenly distributed on the base resin powder. Subsequently, the base resin powder mixed with the second crosslinking solution was placed in a crosslinking reactor and the crosslinking reaction was carried out at 130 degrees for 30 to 40 minutes to obtain a superabsorbent resin in powder form.

[0245] (Step 4) 100 parts by weight of the obtained superabsorbent resin particles and 0.3 parts by weight of silica Aerosil ® 200 (Manufactured by Evonik, specific surface area 200 ±25 m²) 2 / g, primary particle average diameter 12 nm) was mixed at room temperature for 5 minutes to ensure even mixing, thereby obtaining a final biodegradable superabsorbent resin.

[0246]

[0247] Example 2

[0248] A biodegradable superabsorbent resin was obtained using the same method as in Example 1, except that 0.6 g of 1,4-butanediol diglycidyl ether (BDDE) was added instead of the AlCl3 crosslinking agent in Step 1 of Example 1 above.

[0249]

[0250] Example 3

[0251] In the above Example 1, instead of CMC-1, DS 0.84, viscosity 12830 cP, and Mw 6.1 x 10 6 A biodegradable superabsorbent resin was obtained using the same method as in Example 1, except that g / mol of CMC-2 (manufactured by Weikem Chemical) was used.

[0252]

[0253] Example 4

[0254] In the above Example 1, instead of CMC-1, DS 0.69, viscosity 6109 cP and Mw 1.7 x 10 6 A biodegradable superabsorbent resin was obtained using the same method as in Example 1, except that g / mol of CMC-3 (manufactured by Lamberti. SpA) was used.

[0255]

[0256] Example 5

[0257] Silica Aerosil in Example 1 above ®A biodegradable superabsorbent resin was obtained using the same method as in Example 1, except that 200 was used in an amount of 0.2 parts by weight.

[0258]

[0259] Example 6

[0260] Silica Aerosil in Example 1 above ® A biodegradable superabsorbent resin was obtained using the same method as in Example 1, except that 200 was used in an amount of 0.5 parts by weight.

[0261]

[0262] Example 7

[0263] Silica Aerosil in Example 1 above ® A biodegradable superabsorbent resin was obtained using the same method as in Example 1, except that 200 was used in an amount of 0.8 parts by weight.

[0264]

[0265] Comparative Example 1

[0266] A biodegradable superabsorbent resin was obtained using the same method as in Example 1, except that step 4 was not performed in Example 1.

[0267]

[0268] Comparative Example 2

[0269] A biodegradable superabsorbent resin was obtained using the same method as in Example 1, except that step 4 was not performed in Example 2 above.

[0270]

[0271] Comparative Example 3

[0272] In Example 1 above, DS 1.11 instead of CMC-1, viscosity 4242 cP and Mw 1.3 x 10 6 A biodegradable superabsorbent resin was obtained using the same method as in Example 1, except that g / mol of CMC-X1 (manufactured by Wealthy Chemical Industry) was used.

[0273]

[0274] Comparative Example 4

[0275] In Example 1 above, instead of CMC-1, DS 0.3, viscosity 2496 cP, and Mw 5.1 x 10 5 A biodegradable superabsorbent resin was obtained using the same method as in Example 1, except that g / mol of CMC-X2 (manufactured by LG Chem) was used.

[0276]

[0277] Test Example 1: Measurement of Physical Properties of Carboxymethylated Cellulose (CMC)

[0278] The degree of substitution (DS), viscosity, and weight-average molecular weight (Mw) of the carboxymethylated cellulose CMC-1, CMC-2, CMC-X1, and CMC-X2 used in the examples and comparative examples were measured by the following method.

[0279]

[0280] (1) Measurement of degree of substitution (DS)

[0281] For each, to measure the degree of substitution of carboxymethylated cellulose 1 The H NMR spectrum was obtained. Specifically, 1 A sample for H NMR analysis was prepared by preparing 50 mg of the sample, dissolving the prepared sample in 0.75 mL of D20 and 0.25 mL of D2SO4, which are NMR measurement solvents, stirring at 90°C for 1 hour, and confirming that the sample turned dark yellow.

[0282]

[0283] More specifically, the degree of substitution of the carboxymethylated cellulose prepared in Preparation Example 1 was measured as follows.

[0284] 1) of carboxymethylated cellulose 1After obtaining the H NMR spectrum, the integrals of the peaks at 2.57 ppm, 2.58 ppm, 2.60 ppm, 2.64 ppm, 2.66 ppm, 3.15 ppm, 3.16 ppm, 3.33 ppm, and 3.34 ppm, which are within the range of 2.5 ppm to 3.6 ppm, were set to be 1.

[0285] 2) Next, the degree of substitution at carbon 2 (2-DS) was calculated as the sum of the integrals at the 3.34 ppm, 3.33 ppm (doublet, 0.23) and 2.57 ppm, 2.58 ppm (doublet, 0.20) peaks, the degree of substitution at carbon 3 (3-DS) was calculated by dividing the integral value at the 2.39 ppm, 2.41 ppm (0.20) peaks by 2, and the degree of substitution at carbon 6 (6-DS) was calculated by dividing the integral value at the 2.14 ppm, 2.15 ppm (0.19) peaks by 2. Subsequently, all the above degrees of substitution were summed to obtain the value of 2-DS + 3-DS + 6-DS, which was used as the degree of substitution.

[0286] In the same way, the degree of substitution of the carboxymethyl groups of carboxymethylated cellulose in other manufacturing examples and comparative manufacturing examples was determined, substantially 1 Since a shift in the H NMR spectrum may occur to some extent, the results of measuring the degree of substitution compared with the spectrum of Example 1 are shown in Table 1.

[0287]

[0288] (2) Viscosity measurement

[0289] The viscosity of each carboxymethylated cellulose was measured in a 1 wt% aqueous solution using a Brookfield viscometer (instrument name: Brookfield DV2T LV TJ0, manufacturer: Brookfield) at 25°C with spindle #V-74 at 30 rpm for 1 minute, and the results are shown in Table 1.

[0290]

[0291] (3) Measurement of weight-average molecular weight (Mw)

[0292] The weight-average molecular weight was measured using GPC / MALLS, and the detailed measurement method is as follows.

[0293] 1) Preparation of the mobile phase

[0294] 1000 mL of a 0.01 M NaH2PO4 aqueous solution containing 0.02% NaN3 was filtered using a solvent clarification system.

[0295] 2) Preparation of sample solution

[0296] 5 mL of a 0.01 M NaH2PO4 aqueous solution containing 0.02% NaN3 was added to 25 mg of the sample, and 110 It was heated at ℃ for 1 hour and filtered through a 0.45 micrometer nylon syringe filter for analysis.

[0297] 3) GPC / MALLS conditions

[0298] Stationary phase: Shodex SB 804 column, Shodex SB 806 column

[0299] Mobile phase: 0.01 M aqueous NaH2PO4 containing 0.02% NaN3

[0300] Flow rate: 1 mL / min

[0301] Stationary bed temperature: 25 ℃

[0302] Injection volume: 100 microliters

[0303] Analysis time: 120 minutes

[0304]

[0305] Test Example 2: Measurement of Physical Properties of Superabsorbent Resin

[0306] (1) Measurement of GBP

[0307] The gel bed permeability (GBP) of the superabsorbent resins of the examples and comparative examples in physiological saline solution under no pressure was measured using the apparatus shown in Figures 1 to 3 of Patent Application No. 2014-7018005 according to the method described in the specification of Patent Application No. 2014-7018005, and the results are shown in Table 1 below.

[0308]

[0309] (2) Measurement of Centrifuge Retention Capacity (CRC)

[0310] The water retention capacity of the superabsorbent resins prepared in the examples and comparative examples was measured according to the European Disposables and Nonwovens Association (EDANA) standard EDANA WSP 241.3, and the results are shown in Table 1 below.

[0311]

[0312] Specifically, the superabsorbent resins prepared in the examples and comparative examples were classified through a #30-50 sieve to obtain only superabsorbent resins having a particle size of 300 to 600 μm. This superabsorbent resin W0 (g) (about 0.17 g) was uniformly placed into a nonwoven fabric bag and sealed, then immersed in physiological saline solution (0.9 wt%) at room temperature. After 30 minutes, the water was drained from the bag for 3 minutes under conditions of 250 G using a centrifuge, and the mass W2 (g) of the bag was measured. In addition, the same operation was performed without using the resin, and the mass W1 (g) at that time was measured.

[0313] Using each obtained mass, the CRC(g / g) was calculated according to the following mathematical formula 1.

[0314] [Mathematical Formula 1]

[0315] CRC (g / g) = {[W2(g) - W1(g)] / W0(g)} - 1

[0316]

[0317] (3) Absorbency under Pressure (AUP)

[0318] The pressurized absorption capacity of the superabsorbent resins of the above examples and comparative examples at 0.9 psi was measured according to the standard EDANA WSP 242.3, and the results are shown in Table 1 below.

[0319] First, when measuring pressurized absorption capacity, the resin classifier from the above CRC measurement was used.

[0320] Specifically, a stainless steel 400 mesh wire mesh was mounted on the bottom of a plastic cylinder with an inner diameter of 25 mm. Under conditions of room temperature and 50% humidity, an absorbent resin composition W0 (g) (0.16 g) was uniformly spread over the wire mesh, and a piston capable of uniformly applying a load of 0.9 psi was positioned so that its outer diameter was slightly smaller than 25 mm, there was no gap with the inner wall of the cylinder, and its vertical movement was not obstructed. At this time, the weight W3 (g) of the device was measured.

[0321] A glass filter with a diameter of 90 mm and a thickness of 5 mm was placed on the inside of a petroleum dish with a diameter of 150 mm, and physiological saline solution composed of 0.9 wt% sodium chloride was placed at the same level as the top surface of the glass filter. A sheet of filter paper with a diameter of 90 mm was placed on top of it. The measuring device was placed on the filter paper, and the liquid was absorbed under load for 1 hour. After 1 hour, the measuring device was lifted, and its weight W4 (g) was measured.

[0322] Using each mass obtained, the pressurized absorption capacity (g / g) was calculated according to the following mathematical formula 2.

[0323] [Mathematical Formula 2]

[0324] AUP(g / g) = [W4(g) - W3(g)] / W0(g)

[0325]

[0326] CMC 1st Crosslinking Agent Silica Content (parts by weight) Superabsorbent Resin Type Degree of Substitution Viscosity (cP) CRC (g / g) AUP (g / g) GBP (darcy) Example 1 CMC - 10.8 1100 60 AlCl3 0.3 25.3 15.3 25.8 Example 2 CMC - 10.8 1100 60 BDDE 0.3 24.1 16.6 38.2 Example 3CMC-20.8412830AlCl30.325.117.035.5 Example 4CMC-30.696109AlCl30.321.416.636.3 Example 5CMC-10.8110060AlCl30.226.616.521.3 Example 6CMC-10.8110060AlCl30.524.714.739 Example 7CMC-10.8110060AlCl30.823.814.238 Comparative Example 1CMC-10.8110060AlCl3-25.614.48.0 Comparative Example 2CMC-10.8110060BDDE-24.615.19.5 Comparative Example 3CMC-X11.114242AlCl30.326.99.90.2 Comparative Example 4CMC-X20.32496AlCl30.35.74.70.1

[0327]

[0328] Referring to Table 1 above, it can be seen that a superabsorbent resin particle comprising a carboxyalkylated polysaccharide having a degree of substitution (DS) of a specific range of carboxyalkyl groups, a crosslinked polymer of a first crosslinking agent, and a second crosslinking layer, and a superabsorbent resin comprising a specific amount of silica, exhibits excellent absorption performance and water permeability. On the other hand, it is confirmed that the superabsorbent resins of comparative examples that do not contain silica and comparative examples in which the degree of substitution (DS) of a carboxyalkyl group in the polysaccharide is less than 0.6 or exceeds 0.9 exhibit significantly reduced water permeability compared to the examples.

Claims

1. A superabsorbent resin particle comprising (a crosslinked polymer of a carboxyalkylated polysaccharide and a first crosslinking agent) and a second crosslinked layer in which the crosslinked polymer is further crosslinked via a second crosslinking agent; and Contains silica, The degree of substitution (DS) of the carboxyalkyl group in the above carboxyalkylated polysaccharide is 0.6 to 0.9, and The above silica is included in an amount of 0.1 to 1 weight part per 100 weight parts of the above superabsorbent resin particles, Biodegradable superabsorbent resin.

2. In Paragraph 1, The above polysaccharides are one or more selected from the group consisting of cellulose, starch, chitosan, dextrin, glucose, pectin, inulin, agar, and guar gum, Biodegradable superabsorbent resin.

3. In Paragraph 1, The above-mentioned carboxyalkylated polysaccharide is a carboxymethylated one, Biodegradable superabsorbent resin.

4. In Paragraph 1, The above carboxyalkylated polysaccharide has a viscosity of 4,000 to 13,000 cP as measured by a Brookfield viscometer in a 1 wt% aqueous solution, Biodegradable superabsorbent resin.

5. In Paragraph 1, The above silica is unsurface-treated fumed silica, Biodegradable superabsorbent resin.

6. In Paragraph 1, The above silica has a specific surface area of ​​100 to 300 m² 2 / g person, Biodegradable superabsorbent resin.

7. In Paragraph 1, The first crosslinking agent is a polyvalent metal salt or a polyvalent epoxy compound. Biodegradable superabsorbent resin.

8. In Paragraph 1, The second crosslinking agent is one or more selected from the group consisting of polycarboxylic acids, polyols, carbonate compounds, epoxy compounds, oxazoline compounds, polyamine compounds, and cyclic urea compounds. Biodegradable superabsorbent resin.

9. In Paragraph 1, The above-mentioned biodegradable superabsorbent resin has a free swelling gel bed permeability (GBP) of 10 darcy or more, Biodegradable superabsorbent resin.

10. In Paragraph 1, The above-mentioned biodegradable superabsorbent resin has a non-pressurized GBP value of at least twice that of the above-mentioned silica-free resin, Biodegradable superabsorbent resin.

11. In Paragraph 1, The above-mentioned biodegradable superabsorbent resin has a centrifugal retention capacity (CRC) of 19 g / g or more and an absorption capacity (0.7 AUP) under 0.9 psi pressure of 10 g / g or more, Biodegradable superabsorbent resin.

12. A step of preparing a first crosslinking solution comprising a carboxyalkylated polysaccharide and a first crosslinking agent (Step 1); Step 2: Drying the first crosslinking solution to produce a crosslinked polymer and then grinding it; A step of producing superabsorbent resin particles comprising a second crosslinked layer by further crosslinking a pulverized crosslinked polymer in the presence of a second crosslinking agent (Step 3); and It includes a step of mixing silica (step 4), and The degree of substitution (DS) of the carboxyalkyl group in the above carboxyalkylated polysaccharide is 0.6 to 0.9, and The above silica is used in an amount of 0.1 to 1 weight part per 100 weight parts of the above superabsorbent resin particles, Method for manufacturing a biodegradable superabsorbent resin.

13. In Paragraph 12, The solid content of the first crosslinking liquid is 30 weight% or less, Method for manufacturing a biodegradable superabsorbent resin.

14. In Paragraph 12, In step 2 above, the drying is performed at a temperature of 130 to 150 ℃, Method for manufacturing a biodegradable superabsorbent resin.

15. In Paragraph 12, In step 4 above, the mixing of the silica is performed at a temperature of 20 to 30 ℃, Method for manufacturing a biodegradable superabsorbent resin.

16. A sanitary product comprising a biodegradable superabsorbent resin according to any one of claims 1 to 11.

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