Biodegradable highly absorbent resin and its manufacturing method

Abstract

The present invention provides a superabsorbent resin that exhibits excellent biodegradability without reducing the physical properties of the superabsorbent resin, and a method for producing the same.

Description

[Technical Field]

[0001] Cross-Citation of Related Applications This application claims the benefit of priority based on Korean Patent Application No. 10-2022-0078925, filed June 28, 2022, and Korean Patent Application No. 10-2023-0076830, filed June 15, 2023, and all contents disclosed in the documents of said Korean patent applications are incorporated herein by reference.

[0002] The present invention relates to a biodegradable superabsorbent polymer that exhibits excellent biodegradability without reducing the physical properties of the superabsorbent polymer, and a method for producing the same. [Background technology]

[0003] Super absorbent polymers (SAPs) are synthetic polymers capable of absorbing 500 to 1,000 times their own weight in water, and different developers have given them different names, such as SAM (Super Absorbency Material) or AGM (Absorbent Gel Material). These super absorbent polymers first came into practical use as sanitary products, and are now widely used in a variety of applications, including sanitary products such as baby diapers, soil water retention agents in gardening, water-stopping materials in civil engineering and construction, seedling sheets, freshness-preserving agents in the food distribution industry, and materials for poultices, as well as electrical insulation.

[0004] Such superabsorbent resins are typically produced by bulk polymerization or suspension polymerization of acrylic acid-based monomers with a crosslinker in the presence of a polymerization initiator to obtain a hydrogel polymer. Therefore, conventional superabsorbent resins are rarely biodegradable, causing environmental problems when they are disposed of as waste. Specifically, when various products containing superabsorbent resins are disposed of in landfills, the superabsorbent polymers are not decomposed by bacteria or microorganisms in the soil, which can cause environmental pollution.

[0005] Therefore, although attempts have been made to develop superabsorbent resins that exhibit excellent biodegradability using biomass-derived materials, it has not been very easy to produce economically producible biodegradable superabsorbent resins that exhibit similar levels of physical properties to conventional superabsorbent resins.

[0006] As a result, there is a continuous demand for the development of technologies related to superabsorbent polymers that can exhibit biodegradability without reducing the basic physical properties of the superabsorbent polymers. Summary of the Invention [Problem to be solved by the invention]

[0007] Therefore, the present invention provides a superabsorbent resin that exhibits excellent biodegradability without reducing the physical properties of the superabsorbent resin, and a method for producing the same. [Means for solving the problem]

[0008] According to one embodiment of the present invention, The cross-linked polymer comprises a monomer containing a modified polysaccharide containing at least one of a maleic acid group (-OCOCH=CHCOOH) and a carboxymethyl group (-CH2-COOH), At least a portion of the maleic acid groups and carboxymethyl groups are neutralized; The crosslinked polymer contains 60 parts by weight or more of a repeating unit derived from a modified polysaccharide, The molecular weight of the modified polysaccharide is 190,000 g / mol or more; A biodegradable superabsorbent polymer is provided.

[0009] According to yet another embodiment of the present invention, preparing a monomer composition containing a modified polysaccharide containing at least one of a maleic acid group (-OCOCH=CHCOOH) and a carboxymethyl group (-CH-COOH) in the presence of a polymerization initiator; cross-linking the monomer composition to prepare a hydrogel polymer; and drying, pulverizing and classifying the hydrogel polymer; In a method for producing a biodegradable highly water-absorbent resin, At least a portion of the maleic acid groups and carboxymethyl groups of the modified polysaccharide are neutralized; The crosslinked polymer contains 60 parts by weight or more of a repeating unit derived from a modified polysaccharide, The molecular weight of the modified polysaccharide is 190,000 g / mol or more; A method for producing a biodegradable superabsorbent polymer is provided.

[0010] Furthermore, according to yet another embodiment of the present invention, there is provided a sanitary product comprising the biodegradable highly absorbent polymer. [Effects of the Invention]

[0011] The biodegradable superabsorbent polymer of the present invention exhibits excellent biodegradability by using a chemically modified polysaccharide. Furthermore, the biodegradable superabsorbent polymer of the present invention uses a modified polysaccharide having a weight-average molecular weight above a certain level, allowing for polymerization and crosslinking without unreacted modified polysaccharide, thereby preventing the deterioration of various physical properties of conventional superabsorbent polymers. Therefore, even when the biodegradable superabsorbent polymer is used in various sanitary products, it does not cause environmental pollution problems when disposed of. [Brief explanation of the drawings]

[0012] [Figure 1] 1 shows the 1H NMR spectrum of the maleated chitosan prepared in Preparation Example 1. [Figure 2] 1 shows the 1H NMR spectrum of the maleated modified starch produced in Preparation Example 2. [Figure 3] 1 shows the 1H NMR spectrum of the carboxymethylated modified starch produced in Preparation Example 3. [Figure 4]1 shows the 1H NMR spectrum of the carboxymethylated modified starch produced in Preparation Example 4. [Figure 5] 1 shows the 1H NMR spectrum of the carboxymethylated modified starch produced in Preparation Example 5. [Figure 6] 1 shows the 1H NMR spectrum of the carboxymethylated modified starch produced in Preparation Example 6. DETAILED DESCRIPTION OF THE INVENTION

[0013] The terms used in this specification are merely used to describe exemplary embodiments and are not intended to limit the invention. The singular expressions include the plural expressions unless the context clearly dictates otherwise. In this specification, the terms "comprise," "include," "comprise," or "have" are intended to specify the presence of embodied features, steps, components, or combinations thereof, and should be understood as not precluding the presence or additional possibility of one or more other features, steps, components, or combinations thereof.

[0014] Furthermore, in the present invention, when it is said that each layer or element is formed "on" another layer or element, it means that each layer or element is formed directly on the other layer or element, or that other layers or elements can be additionally formed between each layer, on the object, or on the substrate.

[0015] The present invention can be modified in various ways and can have various forms, and therefore, the following detailed description will be given by way of example of a specific embodiment, but it should be understood that this is not intended to limit the present invention to the specific disclosed form, and that the present invention encompasses all modifications, equivalents, and alternatives within the spirit and technical scope of the present invention.

[0016] Furthermore, the terminology used herein is for the purpose of referring to particular embodiments only and is not intended to limit the present invention, and the singular forms used herein also include the plural forms unless the context clearly dictates otherwise.

[0017] On the other hand, the term "(meth)acrylate" as used herein includes both acrylate and methacrylate.

[0018] The term "polymer" or "macromolecule" as used in the present specification refers to a state in which a water-soluble ethylenically unsaturated monomer is polymerized, and can encompass any range of water content or particle size. Among the polymers, a polymer having a water content (water content) of about 40% by weight or more in the state after polymerization and before drying can be called a hydrogel polymer, and particles obtained by pulverizing and drying such a hydrogel polymer can be called a crosslinked polymer.

[0019] The term "superabsorbent resin particles" refers to a particulate material containing a crosslinked polymer obtained by polymerizing a modified polysaccharide that contains acidic groups and at least a portion of the acidic groups have been neutralized.

[0020] Furthermore, depending on the context, the term "superabsorbent polymer" refers to a crosslinked polymer obtained by polymerizing a modified polysaccharide having acidic groups and at least a portion of the acidic groups being neutralized, or a powder-form base resin consisting of superabsorbent polymer particles obtained by pulverizing the crosslinked polymer, or it is used to encompass all of the crosslinked polymers or base resins that have been subjected to additional processes, such as surface crosslinking, pulverization into fine powder, drying, pulverization, classification, etc., to be in a state suitable for commercialization.

[0021] Conventionally used superabsorbent resins are produced by polymerizing an acrylic acid monomer with a crosslinking agent in the presence of a polymerization initiator, and the superabsorbent resins produced in this manner are not biodegradable, causing environmental problems.

[0022] Therefore, development of biodegradable superabsorbent polymers has been underway. Materials such as polysaccharide, polyaspartic acid, and polyglutamic acid have been considered as biodegradable materials from which such biodegradable polymers can be manufactured. However, it has been difficult to replace superabsorbent polymers manufactured from acrylic acid monomers because they have a reduced water absorption capacity, which is an important physical property of superabsorbent polymers.

[0023] Therefore, the present inventors have confirmed that when a superabsorbent polymer is produced using a modified polysaccharide containing at least one of a maleic acid group (-OCOCH=CHCOOH) and a carboxymethyl group (-CH2-COOH) as a monomer, not only is the polymer excellent in biodegradability but also all of its physical properties are superior to those of previously known biodegradable materials, thereby completing the present invention.

[0024] Hereinafter, the biodegradable highly water-absorbent polymer and the method for producing the same will be described in more detail with reference to specific embodiments of the invention.

[0025] Biodegradable super absorbent resin Specifically, a biodegradable superabsorbent polymer according to one embodiment of the invention comprises a cross-linked polymer of monomers containing a modified polysaccharide containing at least one of a maleic acid group (-OCOCH=CHCOOH) and a carboxymethyl group (-CH2-COOH).

[0026] The crosslinked polymer has a structure formed by polymerizing a monomer containing a modified polysaccharide having at least a partially neutralized maleic acid group (-OCOCH=CHCOOH) and a carboxymethyl group (-CH2-COOH). At this time, as the modified polysaccharide is polymerized and grows into a main chain, the functional groups within the structure are polymerized to form a crosslinked polymerized structure. This crosslinked polymerized structure significantly improves the overall physical properties of the superabsorbent resin.

[0027] The crosslinked polymer also contains 60 parts by weight or more of the modified polysaccharide-derived repeating unit. That is, the crosslinked polymer contains a higher content of the modified polysaccharide than other unsaturated monomers, and the main chain composed of the modified polysaccharide is crosslinked, resulting in superior biodegradability compared to other superabsorbent resins with a high unsaturated monomer content. Preferably, the crosslinked polymer contains 80 parts by weight or more, 85 parts by weight or more, 90 parts by weight or more, or 95 parts by weight or more of the modified polysaccharide-derived repeating unit.

[0028] Furthermore, the modified polysaccharide of the present invention has a molecular weight of 190,000 g / mol or more, and it has been confirmed that a superabsorbent resin cross-linked from a modified polysaccharide in this range is advantageous in forming a cross-linked structure and has excellent overall water absorption properties compared to a superabsorbent resin polymerized from a modified polysaccharide in a lower range.

[0029] Meanwhile, the term "polysaccharide" refers to a polymeric carbohydrate molecule composed of glucose repeating units. This term also includes polymeric molecules composed of glucosamine repeating units, in which an amino group has been introduced to the hydroxyl group attached to the carbon atom 2 of the glucose repeating unit, and / or N-acetylglucosamine repeating units, in which an N-acetylamino group has been introduced to the hydroxyl group attached to the carbon atom 2 of the glucose repeating unit. Therefore, the polysaccharide may be any compound commonly known as a polysaccharide. Examples include, but are not limited to, starch, which is composed of glucose repeating units, and chitosan, which is composed of glucosamine repeating units and N-acetylglucosamine repeating units.

[0030] The modified polysaccharide used in the biodegradable superabsorbent polymer is a concept distinct from unmodified polysaccharides, which are typically obtained naturally or synthetically, and refers to polysaccharides in which the hydroxyl groups (-OH) in the glucose repeating units constituting the polysaccharide have been replaced with other functional groups through chemical and / or heat treatment. Such modified polysaccharides can exhibit physical properties different from unmodified polysaccharides due to the functional groups introduced in place of the hydroxyl groups (-OH).

[0031] For example, the modified polysaccharide is modified starch, modified cellulose, or modified chitosan.

[0032] Meanwhile, the modified polysaccharide is substituted with one or more of maleic acid groups (-OCOCH=CHCOOH) and carboxymethyl groups (-CH2-COOH), and at least a portion of the maleic acid groups (-OCOCH=CHCOOH) and carboxymethyl groups (-CH2-COOH) are neutralized.

[0033] The maleic acid group (-OCOCH=CHCOOH) in the polysaccharide may be introduced by maleic acid or maleic acid anhydride. For example, maleic acid anhydride can replace the hydroxyl group (-OH) present in the unmodified polysaccharide molecule with a maleic acid group (-OCOCH=CHCOOH).

[0034] The carboxymethyl group (-CH2-COOH) in the polysaccharide may be introduced by glycolic acid, monochloroacetic acid, or a salt thereof, such as glycolic acid, monochloroacetic acid, sodium monochloroacetate, sodium glycolate, potassium monochloroacetate, or potassium glycolate. For example, glycolic acid can replace a hydroxyl group (-OH) in the unmodified polysaccharide molecule with a carboxymethyl group (-CH2-COOH).

[0035] On the other hand, the degree of substitution (DS) of the maleic acid group (-OCOCH=CHCOOH) of the modified polysaccharide is defined as "DS" below. M " and is 0.15 to 1.5. If the degree of substitution of the maleic acid group is less than 0.15, a large amount of modified polysaccharide that does not participate in cross-linking polymerization may remain, and if the degree of substitution of the maleic acid group is more than 1.5, the large amount of maleic anhydride used for introducing the maleic acid group may not be completely removed, which may affect the physical properties of the final superabsorbent resin. Preferably, the degree of substitution of maleic acid groups is 0.20 or more, 0.25 or more, 0.30 or more, 0.35 or more, 0.40 or more, 0.45 or more, 0.50 or more, 0.55 or more, 0.60 or more, 0.65 or more, 0.70 or more, 0.75 or more, 0.80 or more, or 0.85 or more; or 1.45 or less, 1.40 or less, 1.35 or less, 1.30 or less, 1.25 or less, 1.20 or less, 1.15 or less, 1.10 or less, 1.05 or less, 1.00 or less, or 0.95 or less.

[0036] The degree of substitution (DS) of the carboxymethyl group (-CH2-COOH) of the modified polysaccharide is referred to as "DS" below. C " and is 0.20 to 1.2. If the degree of substitution of the carboxymethyl group is less than 0.20, a large amount of modified polysaccharide that does not participate in cross-linking polymerization may remain, and if the degree of substitution of the carboxymethyl group is more than 1.2, glycolic acid, etc., used in large amounts for the introduction of the carboxymethyl group, may not be completely removed, which may affect the physical properties of the final superabsorbent resin. Preferably, the degree of substitution of the carboxymethyl group is 0.21 or more, 0.22 or more, 0.23 or more, 0.24 or more, or 0.25 or more; or 1.15 or less, 1.1 or less, 1.05 or less, or 1.0 or less.

[0037] Here, the degree of substitution of maleic acid groups or carboxymethyl groups refers to the average number of hydroxyl groups (-OH) substituted with maleic acid groups or carboxymethyl groups per glucose repeating unit. That is, since there are three hydroxyl groups per glucose repeating unit, the theoretical maximum degree of substitution is 3, and a degree of substitution of 0.1 means that one hydroxyl group is substituted per 10 glucose repeating units. The degree of substitution of maleic acid groups and carboxymethyl groups is determined by the average number of hydroxyl groups (-OH) substituted with maleic acid groups or carboxymethyl groups per glucose repeating unit. 1 It can be calculated through H NMR analysis, and for more specific details, see the production examples described below.

[0038] Meanwhile, at least a portion of the maleic acid groups and carboxymethyl groups of the modified polysaccharide are neutralized, and the degree of neutralization can be adjusted depending on the type of modified polysaccharide and the desired properties of the final superabsorbent resin. For example, modified starch has a high molecular weight and is water-insoluble, but by increasing the degree of neutralization, the carboxyl groups (COOH) are neutralized to the carboxylate (COO-) form, thereby increasing its water solubility. Specifically, the degree of neutralization of the modified polysaccharide may be 40 to 95 mol%, 40 to 80 mol%, or 45 to 75 mol%.

[0039] In one embodiment, the modified polysaccharide may include at least one of repeating units represented by the following formulas 1 to 4.

[0040] [ka]

[0041] In the above chemical formulas 1 to 4, Each M is independently hydrogen or an alkali metal.

[0042] Specifically, in the above chemical formulas 1 to 4, M + are each independently H + , Na + , or K + is.

[0043] For example, when the modified polysaccharide is a modified starch or a modified dextrin, it may contain repeating units represented by Chemical Formula 1 and Chemical Formula 3, and when the modified polysaccharide is a modified chitosan, it may contain repeating units represented by Chemical Formula 2 and Chemical Formula 4.

[0044] The modified polysaccharide has a weight-average molecular weight of 190,000 g / mol or more. However, if the weight-average molecular weight of the modified starch is too low, crosslinking may not be sufficient, resulting in a large amount of unreacted modified starch remaining. If the weight-average molecular weight is too high, entanglement of the polymer chains of the high-molecular-weight modified polysaccharide may make acid treatment and functionalization difficult, making the preparation of the modified polysaccharide difficult. Preferably, the weight-average molecular weight of the modified polysaccharide is 200,000 g / mol or more, 250,000 g / mol or more, or 300,000 g / mol or more, and 1,000,000,000 g / mol or less, 500,000,000 g / mol or less, 100,000,000 g / mol or less, or 50,000,000 g / mol or less.

[0045] The molecular weight of the modified polysaccharide may vary depending on the type of substance. Specifically, the molecular weight of the modified starch is 400,000 g / mol to 1,000,000,000 g / mol, and preferably 1,000,000 g / mol or more, 5,000,000 g / mol or more, 10,000,000 g / mol or more, or 20,000,000 g / mol or more, but may be 500,000,000 g / mol or less, 100,000,000 g / mol or less, or 50,000,000 g / mol or less.

[0046] Specifically, the molecular weight of the modified cellulose or modified chitosan is 190,000 g / mol to 10,000,000 g / mol, preferably 200,000 g / mol or more, 250,000 g / mol or more, or 300,000 g / mol or more, but may be 5,000,000 g / mol or less, 2,000,000 g / mol or less, 1,000,000 g / mol or less, or 700,000 g / mol or less.

[0047] Here, the weight average molecular weight (Mw) can be measured using gel permeation chromatography (GPC / MALLS). A specific method for measuring the weight average molecular weight will be described in the examples below.

[0048] Alternatively, the modified polysaccharide may be modified starch. The modified starch may contain amylose and amylopectin in a weight ratio of 1:99 to 50:50 based on the total weight. The modification in which the hydroxyl group attached to the 6th carbon of the glucose repeating unit is replaced with another substituent can occur in both amylose and amylopectin, but in terms of processability and solubility, it is advantageous for the amylopectin content to be equal to or greater than the amylose content.

[0049] The modified starch may have a gelatinization temperature of 50 to 90° C. and a peak viscosity (BU) of 50 to 1,000.

[0050] The modified starch may be one or more starches modified from potato starch, corn starch, rice starch, wheat starch, tapioca starch, and sweet potato starch. In particular, potato starch, which has a high amylopectin content, is preferred in terms of processability and solubility.

[0051] Meanwhile, the monomer may further include an acrylic acid-based compound having at least a partially neutralized acid group.

[0052] The acrylic acid monomer is a compound represented by the following formula 3:

[0053] [Chemical formula 3] R-COOM'

[0054] In the above chemical formula 2, R is an alkyl group having 2 to 5 carbon atoms and containing an unsaturated bond, M' is a hydrogen atom, a monovalent or divalent metal, an ammonium group, or an organic amine salt.

[0055] Preferably, the monomer may be one or more selected from the group consisting of (meth)acrylic acid, and monovalent (alkali) metal salts, divalent metal salts, ammonium salts and organic amine salts of these acids.

[0056] When (meth)acrylic acid and / or a salt thereof is used as the acrylic acid monomer in this way, a highly water-absorbent resin with improved water absorption properties can be obtained.

[0057] The acrylic acid-based monomer may have acidic groups, at least some of which have been neutralized. Preferably, the monomer may be partially neutralized with an alkaline substance such as sodium hydroxide, potassium hydroxide, or ammonium hydroxide. The degree of neutralization of the acrylic acid-based monomer may be 40 to 95 mol%, 40 to 80 mol%, or 45 to 75 mol%. The range of the degree of neutralization can be adjusted depending on the final physical properties. However, if the degree of neutralization is too high, the neutralized monomer may precipitate, hindering smooth polymerization. Conversely, if the degree of neutralization is too low, the polymer may exhibit significantly reduced water absorption and rubber-like properties that are difficult to handle.

[0058] In addition, crosslinked polymers of monomers containing modified polysaccharides can be crosslinked via an internal crosslinking agent. The term "internal crosslinking agent" used herein is used to distinguish it from surface crosslinking agents that are commonly used to crosslink the surface of superabsorbent resin particles, and serves to crosslink and polymerize the modified polysaccharide. The crosslinking in this step is carried out regardless of whether it is on the surface or inside. However, when a surface crosslinking process of superabsorbent resin particles is carried out, the surface of the superabsorbent resin particles produced ultimately has a crosslinked structure via the surface crosslinking agent, and the inside has a crosslinked structure via the internal crosslinking agent.

[0059] When a monomer containing a modified polysaccharide is crosslinked in the presence of an internal crosslinking agent, the main chain formed by the polymerization of the polysaccharide is further crosslinked by the internal crosslinking agent to form a three-dimensional network structure. In this way, when a three-dimensional network structure is formed by crosslinking with an internal crosslinking agent, the water retention capacity and pressure water absorption capacity, which are various physical properties of the superabsorbent polymer, can be significantly improved compared to when no additional crosslinking is performed by an internal crosslinking agent.

[0060] The internal cross-linking agent can be any compound that allows the introduction of cross-linking bonds during polymerization of the modified polysaccharide. Non-limiting examples of the internal cross-linking agent include N,N'-methylenebisacrylamide, trimethylolpropane tri(meth)acrylate, ethylene glycol di(meth)acrylate, polyethylene glycol (meth)acrylate, polyethylene glycol di(meth)acrylate, propylene glycol di(meth)acrylate, polypropylene glycol (meth)acrylate, butanediol di(meth)acrylate, butylene glycol di(meth)acrylate, diethylene glycol di(meth)acrylate, hexanediol di(meth)acrylate, Polyfunctional crosslinkers such as (meth)acrylate, triethylene glycol di(meth)acrylate, tripropylene glycol di(meth)acrylate, tetraethylene glycol di(meth)acrylate, dipentaerythritol pentaacrylate, glycerin tri(meth)acrylate, pentaerythritol tetraacrylate, triarylamine, ethylene glycol diglycidyl ether, propylene glycol, glycerin, or ethylene carbonate can be used alone or in combination, but are not limited to these. Of these, N,N'-methylenebisacrylamide or polyethylene glycol diacrylate is preferred.

[0061] The cross-linking polymerization of the modified starch in the presence of such an internal cross-linking agent can be carried out by thermal polymerization, photopolymerization or hybrid polymerization in the presence of a polymerization initiator and, if necessary, a thickener, a plasticizer, a storage stabilizer, an antioxidant, etc., the details of which will be described later.

[0062] The superabsorbent polymer may also be in the form of particles having an average particle size of 150 to 850 μm. This particle size can be measured according to the EDANA WSP 220.3 method of the European Disposables and Nonwovens Association (EDANA). More specifically, the superabsorbent polymer composition may contain superabsorbent polymer particles having a particle size of about 150 to 850 μm, with about 90% by weight, preferably 95% by weight or more, based on the total weight, being comprised of superabsorbent polymer particles, and less than 10% by weight, more specifically less than 5% by weight, being comprised of fine powder having a particle size of less than 150 μm. If the superabsorbent polymer contains a large amount of fine powder having a particle size of less than 150 μm, this is undesirable because it can degrade various physical properties of the superabsorbent polymer.

[0063] The biodegradable highly water-absorbent resin may have a water retention capacity (CRC) of 20 to 50 g / g as measured by EDANA method WSP241.3.

[0064] Manufacturing method of biodegradable superabsorbent resin Meanwhile, the biodegradable highly water-absorbent polymer can be produced by the following production method: preparing a monomer composition containing a modified polysaccharide containing at least one of a maleic acid group (-OCOCH=CHCOOH) and a carboxymethyl group (-CH-COOH) in the presence of a polymerization initiator; cross-linking the monomer composition to prepare a hydrogel polymer; and drying, pulverizing and classifying the hydrogel polymer; In a method for producing a biodegradable highly water-absorbent resin, At least a portion of the maleic acid groups and carboxymethyl groups of the modified polysaccharide are neutralized; The crosslinked polymer contains 60 parts by weight or more of a repeating unit derived from a modified polysaccharide, The molecular weight of the modified polysaccharide is 190,000 g / mol or more; A method for producing biodegradable superabsorbent resin.

[0065] Meanwhile, the modified polysaccharide can be prepared by reacting a polysaccharide with one or more of maleic acid, maleic acid anhydride, glycolic acid, monochloroacetic acid, and salts thereof.

[0066] Specifically, the modified polysaccharide can be prepared by reacting a polysaccharide with one or more of maleic acid, maleic anhydride, glycolic acid, monochloroacetic acid, and salts thereof to prepare a polysaccharide having one or more maleic acid groups and carboxymethyl groups introduced therein. The reaction of the polysaccharide with one or more of maleic acid, maleic anhydride, glycolic acid, monochloroacetic acid, and salts thereof can be carried out at a temperature of 50 to 100°C for 4 to 12 hours.

[0067] For example, the acid-treated polysaccharide can be maleated using maleic anhydride to produce a polysaccharide substituted with maleic acid groups.

[0068] Furthermore, before producing the modified polysaccharide, the unmodified polysaccharide can be acid-treated. Such acid treatment is carried out to destroy the rigid structure of starch due to hydrogen bonds and increase the production efficiency for the above-mentioned polysaccharide modifications such as maleation and carboxylmethylation. Specifically, the acid treatment can be carried out using an acidic solution such as hydrochloric acid at a temperature of 25 to 50°C for 6 to 48 hours.

[0069] Next, the modified starch thus prepared may be cross-linked in the presence of a polymerization initiator to form a hydrogel polymer.

[0070] The steps may include preparing a monomer composition by mixing the modified starch and a polymerization initiator, and thermally or photopolymerizing the monomer composition to form a hydrogel polymer.

[0071] Additionally, the monomer composition may further include an acrylic acid-based compound having at least a partially neutralized acid group. The modified polysaccharide and the acrylic acid-based compound may be included in the monomer composition in a weight ratio of 99:1 to 60:40. When the above range is satisfied, the biodegradable superabsorbent polymer can exhibit excellent biodegradability while simultaneously improving its water absorption and retention capabilities.

[0072] The monomer composition may further include an internal cross-linking agent. For details regarding the internal cross-linking agent, please refer to the above section. In the monomer composition, the internal cross-linking agent may be used in an amount of 0.1 to 5 parts by weight per 100 parts by weight of the modified polysaccharide. For example, the internal cross-linking agent may be used in an amount of 0.1 part by weight or more, or 0.2 parts by weight or more, or 5 parts by weight or less, 3 parts by weight or less, 2 parts by weight or less, 1 part by weight or less, or 0.5 parts by weight or less per 100 parts by weight of the modified polysaccharide. If the content of the upper internal cross-linking agent is too low, cross-linking may not occur sufficiently, making it difficult to achieve an appropriate level of strength. If the content of the upper internal cross-linking agent is too high, the internal cross-link density may increase, making it difficult to achieve the desired water retention capacity.

[0073] In addition, the polymerization initiator can be appropriately selected depending on the polymerization method, and a thermal polymerization initiator can be used when a thermal polymerization method is used, a photopolymerization initiator can be used when a photopolymerization method is used, and both a thermal polymerization initiator and a photopolymerization initiator can be used when a hybrid polymerization method (a method using both heat and light) is used. However, even in the photopolymerization method, a certain amount of heat is generated by light irradiation such as ultraviolet irradiation, and a certain amount of heat is also generated by the progress of the polymerization reaction, which is an exothermic reaction, so a thermal polymerization initiator can also be used.

[0074] The photopolymerization initiator can be any compound that can form radicals when exposed to light such as ultraviolet light, and is not limited in its composition.

[0075] The photopolymerization initiator may be at least one selected from the group consisting of benzoin ether, dialkyl acetophenone, hydroxyl alkyl ketone, phenyl glyoxylate, benzyl dimethyl ketal, acyl phosphine, and α-aminoketone. Specific examples of acyl phosphines include diphenyl(2,4,6-trimethylbenzoyl)phosphine oxide, phenylbis(2,4,6-trimethylbenzoyl)phosphine oxide, and ethyl(2,4,6-trimethylbenzoyl)phenylphosphinate. A wide variety of photoinitiators are described in detail in Reinhold Schwalm's "UV Coatings: Basics, Recent Developments and New Applications" (Elsevier, 2007), p. 115, and are not limited to the above examples.

[0076] The thermal polymerization initiator may be at least one selected from the group consisting of persulfate initiators, azo initiators, hydrogen peroxide, and ascorbic acid. Specific examples of persulfate initiators include sodium persulfate (NaSO), potassium persulfate (KSO), and ammonium persulfate ((NHSO). Examples of azo initiators include 2,2-azobis(2-amidinopropane) dihydrochloride and 2,2-azobis(N,N-dimethylene)isobutyramidine dihydrochloride. dihydrochloride, 2-(carbamoylazo)isobutylonitrile, 2,2-azobis[2-(2-imidazolin-2-yl)propane]dihydrochloride, and 4,4-azobis-(4-cyanovaleric acid). A wide variety of thermal polymerization initiators are well documented in Odian's book, "Principle of Polymerization" (Wiley, 1981), p. 203, and are not limited to the examples mentioned above.

[0077] Such a polymerization initiator can be used in an amount of 2 parts by weight or less per 100 parts by weight of the modified polysaccharide. That is, if the concentration of the polymerization initiator is too low, the polymerization rate may be slowed and a large amount of residual monomer may be extracted into the final product, which is undesirable. Conversely, if the concentration of the polymerization initiator is higher than the above range, the polymer chains forming the network may become shorter, the content of water-soluble components may increase, and the physical properties of the resin may be reduced, such as reducing the water absorption capacity under pressure.

[0078] The monomer composition may further contain additives such as a thickener, a plasticizer, a storage stabilizer, and an antioxidant, if necessary.

[0079] The monomer composition containing the monomer may be in the form of a suspension if it is insoluble, such as high-molecular-weight starch, or in the form of a solution dissolved in a solvent such as water, if it is water-soluble, such as low-molecular-weight dextrin. The solid content of the monomer composition, i.e., the concentrations of the monomer, internal crosslinking agent, and polymerization initiator, can be appropriately adjusted taking into account the polymerization time and reaction conditions. For example, the solid content of the monomer composition may be 10 to 80 wt %, 15 to 60 wt %, or 30 to 50 wt %.

[0080] When the monomer composition has a solid content within the above range, it is possible to eliminate the need to remove unreacted monomers after polymerization by utilizing the gel effect phenomenon that occurs in the polymerization reaction of a highly concentrated aqueous solution, and it may also be advantageous for controlling the grinding efficiency when grinding the polymer described below.

[0081] The solvent that can be used in this case is not limited in composition as long as it can dissolve the above-mentioned components. For example, one or more solvents selected from the group consisting of water, ethanol, ethylene glycol, diethylene glycol, triethylene glycol, 1,4-butanediol, propylene glycol, ethylene glycol monobutyl ether, propylene glycol monomethyl ether, propylene glycol monomethyl ether acetate, methyl ethyl ketone, acetone, methyl amyl ketone, cyclohexanone, cyclopentanone, diethylene glycol monomethyl ether, diethylene glycol ethyl ether, toluene, xylene, butyrolactone, carbitol, methyl cellosolve acetate, and N,N-dimethylacetamide can be used in combination.

[0082] On the other hand, the cross-linking polymerization of the modified polysaccharide can be carried out without any particular limitation as long as it can form a hydrogel polymer by thermal polymerization, photopolymerization or hybrid polymerization.

[0083] Specifically, polymerization methods are broadly divided into thermal polymerization and photopolymerization depending on the polymerization energy source. Typically, thermal polymerization can be carried out in a reactor having a stirring shaft such as a kneader, and photopolymerization can be carried out in a reactor equipped with a movable conveyor belt or in a flat-bottomed vessel. However, the above-mentioned polymerization methods are merely examples, and the present invention is not limited to the above-mentioned polymerization methods.

[0084] For example, the hydrogel polymer obtained by thermal polymerization by supplying hot air to a reactor such as a kneader equipped with an agitator shaft or by heating the reactor as described above may be discharged from the reactor outlet in the form of a few centimeters to a few millimeters, depending on the shape of the agitator shaft installed in the reactor. Specifically, the size of the obtained hydrogel polymer varies depending on the concentration of the injected monomer composition and the injection rate, and typically a hydrogel polymer with a weight-average particle size of 2 to 50 mm can be obtained.

[0085] Furthermore, when photopolymerization is performed in a reactor equipped with a movable conveyor belt or a flat-bottomed vessel as described above, the resulting hydrogel polymer typically takes the form of a sheet-like hydrogel polymer having the width of the belt. The thickness of the polymer sheet varies depending on the concentration of the monomer composition injected and the injection rate or amount, but it is generally preferred to supply the monomer composition so as to obtain a sheet-like polymer having a thickness of about 0.5 to about 5 cm. Supplying the monomer composition so that the thickness of the sheet-like polymer is excessively thin is undesirable because it reduces production efficiency, and if the thickness of the sheet-like polymer exceeds 5 cm, the polymerization reaction may not proceed uniformly across the entire thickness due to the excessive thickness.

[0086] The hydrogel polymer obtained by this method may have a water content of 40 to 70 wt %. For example, the water content of the hydrogel polymer may be 40 wt % or more, 45 wt % or more, or 50 wt % or more, or 70 wt % or less, 65 wt % or less, or 60 wt % or less. If the water content of the hydrogel polymer is too low, it may be difficult to secure an adequate surface area in the subsequent pulverization step, reducing the efficiency of drying. If the water content of the hydrogel polymer is too high, the pressure applied in the subsequent pulverization step may increase, reducing the water absorption capacity under pressure, and the drying step after pulverization may require a lot of energy and take a long time.

[0087] Throughout this specification, the term "moisture content" refers to the moisture content relative to the total weight of the hydrogel polymer, calculated by subtracting the weight of the polymer in a dry state from the weight of the hydrogel polymer. Specifically, it is defined as the value calculated by measuring the weight loss due to evaporation of moisture in the polymer during the drying process by raising the temperature of the polymer in a crumb state using infrared heating. Here, the drying for measuring moisture content is performed by raising the temperature to about 50°C at room temperature and then vacuum drying at 50°C for about 6 hours.

[0088] Meanwhile, after preparing the hydrogel polymer, a coarse pulverization process for pulverizing the prepared hydrogel polymer may be optionally carried out prior to the subsequent drying and pulverization processes.

[0089] The coarse pulverization process is a process for increasing the drying efficiency in the subsequent drying process and controlling the particle size of the final superabsorbent polymer powder. The pulverizer used here is not limited in terms of its configuration, and specifically may include any one selected from the group of pulverizing devices consisting of a vertical pulverizer, a turbo cutter, a turbo grinder, a rotary cutter mill, a cutter mill, a disc mill, a shred crusher, a crusher, a meat chopper, and a disc cutter, but is not limited to the above examples.

[0090] The coarse pulverization step can be carried out, for example, so that the particle size of the hydrogel polymer is about 2 to about 10 mm. Pulverizing the hydrogel polymer to a particle size of less than 2 mm is technically difficult due to the high water content of the hydrogel polymer, and the pulverized particles may aggregate together. On the other hand, pulverizing the hydrogel polymer to a particle size of more than 10 mm results in little increase in the efficiency of the subsequent drying step.

[0091] Next, the hydrogel polymer prepared in the previous step is dried, crushed, and classified to prepare a base resin.

[0092] The drying method may be selected from any method commonly used in the drying process of hydrogel polymers, without limitation on its structure. Specifically, the drying step may be carried out by a method such as hot air supply, infrared radiation, microwave radiation, or ultraviolet radiation.

[0093] Specifically, the drying can be carried out under vacuum conditions at a temperature of less than 100° C., specifically, at a temperature of about 30° C. to about 80° C. Drying temperatures of 100° C. or higher are not suitable because the modified polysaccharide may be decomposed, and drying temperatures of less than 30° C. may require an excessively long drying time.

[0094] On the other hand, the drying time can be about 20 to about 90 minutes, taking into consideration process efficiency, but is not limited to this.

[0095] The water content of the polymer after such a drying step may be about 5 to about 10% by weight.

[0096] After the drying step, a pulverization step is carried out.

[0097] The pulverization process can be carried out so that the particle size of the polymer powder, i.e., the base resin, is about 150 to about 850 μm. Specific examples of the pulverizer used to pulverize to such a particle size include a pin mill, hammer mill, screw mill, roll mill, disc mill, and jog mill, but the present invention is not limited to these examples.

[0098] After the pulverization step, the pulverized polymer powder may be further classified according to particle size in order to control the physical properties of the superabsorbent resin to be manufactured as a final product.

[0099] Preferably, polymers having particle sizes of about 150 to about 850 μm are classified, and only polymers having such particle sizes are used as the base resin, which can be subjected to a surface cross-linking reaction step to produce a product.

[0100] The base resin obtained as a result of the above process may be in the form of a powder containing a crosslinked polymer obtained by crosslinking an acrylic acid-based monomer and an internal crosslinking agent. Specifically, the base resin may be in the form of a powder having a particle size of 150 to 850 μm.

[0101] On the other hand, there is also provided a sanitary product containing the above-mentioned biodegradable highly water-absorbent polymer.

[0102] Preferred examples are presented below to aid in understanding the invention, but the following examples are merely for the purpose of illustrating the invention and are not intended to limit the invention thereto. [Example]

[0103] Production Example 1: Production of modified chitosan (M / S) 20g of chitosan (200-600mPa.s, 0.5% in 0.5% acetic acid at 20°C, manufactured by TCI) and 100g of maleic anhydride were added to a 500ml three-neck flask containing 200ml of water and stirred at 70°C for 6 hours. After the reaction, the mixture was precipitated in acetone and filtered to remove excess maleic anhydride. After drying at 50°C for 24 hours or more, maleated chitosan was obtained.

[0104] The weight average molecular weight of the produced chitosan was 3.3×10 5 g / mol, and the degree of substitution (DS M ) was 0.94. At this time, the degree of substitution of the substituent 1 It was calculated based on the integral ratio of the peaks corresponding to the vinyl (CH=CH, 6.3 ppm, 5.8 ppm) of the maleic acid group in H NMR, and the specific calculation method is as follows.

[0105] First, the maleated chitosan was 1The H NMR spectrum was obtained and is shown in Figure 1. Referring to Figure 1, the peaks at 6.3 ppm and 5.8 ppm corresponding to the vinyl groups of the maleic acid groups were observed, confirming that maleic acid groups had been introduced into chitosan. The integral ratio of these peaks indicated the degree of substitution of maleic acid groups (-OCOCH=CHCOOH) in the maleated chitosan.

[0106] Production Example 2: Production of Modified Starch 1 (M / S-1) 20g of starch (from potato, manufactured by Aldrich) and 100g of maleic anhydride were added to a three-neck flask containing 250ml of water and 200ml of water, and then stirred at 70°C for 6 hours. After the reaction, the mixture was precipitated in acetone and filtered to remove excess maleic anhydride. After drying at 50°C for at least 24 hours, maleated modified starch was obtained.

[0107] The modified starch produced has a weight average molecular weight of 3.4×10 7 g / mol, and the degree of substitution (DS M ) was 0.88.

[0108] At this time, the substitution degree of the substituent is determined based on the maleated modified starch produced. 1 After obtaining the H NMR spectrum, the integral ratio of the peaks corresponding to the vinyl of the maleic acid group (CH=CH, 6.45 ppm, 6.28 ppm) in the spectrum was calculated, and the ratio of the maleated modified starch was calculated. 1 The 1 H NMR spectrum is shown in Figure 2. The specific calculation method was the same as that for the modified chitosan (M / S) in Preparation Example 1, and calculations were also performed in the remaining Preparation Examples.

[0109] Production Example 3: Production of Modified Starch 2 (M / S-2) Starch (from poatato, manufactured by Aldrich), isopropyl alcohol (IPA), and an aqueous NaOH solution (concentration: approximately 40%) were mixed in a 500 mL RBF (Round Bottom Flask) and stirred at room temperature for approximately 20 minutes. The weight ratio of the mixture was 1:4:0.8 (starch:IPA:NaOH aqueous solution). Approximately 80 parts by weight of sodium monochloroacetate was then added to 100 parts by weight of the starch, heated to 60°C, stirred for approximately 1 hour, and cooled to room temperature. After cooling to room temperature, the solvent was removed, the reactant was dissolved in water, and precipitated in methanol to remove water-soluble impurities. The starch was recovered by filtration and dried in a vacuum oven at 40°C for approximately 12 hours to obtain a solid target product.

[0110] 50 mg of the obtained solid target product was mixed with 200 mg of a 30% DSO in D0 solution, and the mixture was stirred at 50°C for about 1 hour to induce a hydrolysis reaction. 1 H NMR analysis was performed on the carboxymethylated modified starch produced. 1 The 1 H NMR spectrum is shown in Figure 3.

[0111] The modified starch produced has a weight average molecular weight of 1.2×10 7 g / mol, and the degree of substitution of the carboxymethyl group (DSc) was 0.6.

[0112] Production Example 4: Production of Modified Starch 3 (M / S-3) Starch (from corn, manufactured by Samyang), isopropyl alcohol (IPA), and an aqueous NaOH solution (concentration: approximately 40%) were mixed in a 500 mL round bottom flask (RBF) and stirred at room temperature for approximately 20 minutes. The weight ratio of the mixture was 1:4:0.8 (starch:IPA:NaOH solution). Approximately 80 parts by weight of sodium monochloroacetate was then added to 100 parts by weight of the starch, heated to 60°C, stirred for approximately 1 hour, and cooled to room temperature. After cooling to room temperature, the solvent was removed, the reactant was dissolved in water, and precipitated in methanol to remove water-soluble impurities. The starch was recovered by filtration and dried in a vacuum oven at 40°C for approximately 12 hours to obtain a solid target product.

[0113] 50 mg of the obtained solid target product was mixed with 200 mg of a 30% DSO in D0 solution, and the mixture was stirred at 50°C for about 1 hour to induce a hydrolysis reaction. 1 H NMR analysis was performed on the carboxymethylated modified starch produced. 1 The 1 H NMR spectrum is shown in Figure 4.

[0114] The modified starch produced has a weight average molecular weight of 3×10 7 g / mol, and the degree of substitution of the carboxymethyl group (DSc) was 0.6.

[0115] Production Example 5: Production of Modified Starch 4 (M / S-4) Starch (from poatato, manufactured by Daesang), isopropyl alcohol (IPA), and an aqueous NaOH solution (concentration: approximately 40%) were mixed in a 500 mL round bottom flask (RBF) and stirred at room temperature for approximately 20 minutes. The weight ratio of the mixture was 1:4:0.8 (starch:IPA:NaOH aqueous solution). Approximately 80 parts by weight of sodium monochloroacetate was then added to 100 parts by weight of the starch, heated to 60°C, stirred for approximately 1 hour, and cooled to room temperature. After cooling to room temperature, the solvent was removed, the reactant was dissolved in water, and precipitated in methanol to remove water-soluble impurities. The starch was recovered by filtration and dried in a vacuum oven at 40°C for approximately 12 hours to obtain a solid target product.

[0116] 50 mg of the obtained solid target product was mixed with 200 mg of a 30% DSO in D0 solution, and the mixture was stirred at 50°C for about 1 hour to induce a hydrolysis reaction. 1 H NMR analysis was performed on the carboxymethylated modified starch produced. 1 The 1 H NMR spectrum is shown in Figure 5.

[0117] The modified starch produced has a weight average molecular weight of 1.9×10 7 g / mol, and the degree of substitution of the carboxymethyl group (DSc) was 0.6.

[0118] Production Example 6: Production of Modified Starch 5 (M / S-5) Starch (from corn, manufactured by Daesang), isopropyl alcohol (IPA), and an aqueous NaOH solution (concentration: approximately 40%) were mixed in a 500 mL round bottom flask (RBF) and stirred at room temperature for approximately 20 minutes. The weight ratio of the mixture was 1:4:0.8 (starch:IPA:NaOH solution). Approximately 80 parts by weight of sodium monochloroacetate was then added to 100 parts by weight of the starch, heated to 60°C, stirred for approximately 1 hour, and cooled to room temperature. After cooling to room temperature, the solvent was removed, the reactant was dissolved in water, and precipitated in methanol to remove water-soluble impurities. The starch was recovered by filtration and dried in a vacuum oven at 40°C for approximately 12 hours to obtain a solid target product.

[0119] 50 mg of the obtained solid target product was mixed with 200 mg of a 30% DSO in D0 solution, and the mixture was stirred at 50°C for about 1 hour to induce a hydrolysis reaction. 1 H NMR analysis was performed on the carboxymethylated modified starch produced. 1 The 1 H NMR spectrum is shown in Figure 6.

[0120] The modified starch produced has a weight average molecular weight of 2.4×10 7 g / mol, and the degree of substitution of the carboxymethyl group (DSc) was 0.8.

[0121] Comparative Production Example 1: Production of modified starch (M) 20g of starch (soluble, manufactured by Mita Chemicals) and 60g of maleic anhydride were added to a 500ml three-neck flask containing 200ml of water and stirred at 70°C for 6 hours. After the reaction, the mixture was precipitated in acetone and filtered to remove excess maleic anhydride. After drying at 50°C for at least 24 hours, maleated modified starch (M) was obtained.

[0122] The final modified starch (M) had a weight-average molecular weight of 1.5 x 10 5 g / mol, and the degree of substitution (DS M ) was 0.81.

[0123] Comparative Production Example 2: Production of modified chitosan (M-1) 20 g of chitosan (5-20 mPa.s, 0.5% in 0.5% acetic acid at 20°C, manufactured by TCI) and 100 g of maleic anhydride were added to a 500 ml three-neck flask containing 200 ml of water and stirred at 70°C for 6 hours. After the reaction, the mixture was precipitated in acetone and filtered to remove excess maleic anhydride. After drying at 50°C for at least 24 hours, maleated modified starch (M) was obtained.

[0124] The final modified chitosan (M-1) had a weight-average molecular weight of 5 × 10 4 g / mol, and the degree of substitution (DS M ) was 1.11.

[0125] Comparative Production Example 3: Production of modified starch (M-2) Starch (soluble, manufactured by Tokuyama Pharmaceutical Co., Ltd.), isopropyl alcohol (IPA), and an aqueous NaOH solution (concentration: approximately 40%) were mixed in a 500 mL round bottom flask (RBF) and stirred at room temperature for approximately 20 minutes. The weight ratio of the mixture was 1:4:0.8 (starch:IPA:NaOH aqueous solution). Approximately 80 parts by weight of sodium monochloroacetate was then added to 100 parts by weight of the starch, heated to 60°C, stirred for approximately 1 hour, and cooled to room temperature. After cooling to room temperature, the solvent was removed, the reactant was dissolved in water, and precipitated in methanol to remove water-soluble impurities. The starch was recovered by filtration and dried in a vacuum oven at 40°C for approximately 12 hours to obtain the target solid.

[0126] The final modified starch (M-2) had a weight average molecular weight of 9.2 × 10 4 g / mol, and the degree of substitution of carboxymethyl (DS M(c?) ) was 0.68.

[0127] Example 1 50 mL of distilled water and 3 g of the modified chitosan (M / S) from Preparation Example 1 were added to a 250 mL RBF (Round Bottom Flask). The mixture was stirred in a 35°C oil bath for at least 30 minutes to fully dissolve the modified chitosan in the distilled water. An initiator (approximately 0.03 g of ammonium persulfate) was then added. After adding the initiator, the mixture was stirred for approximately 4 hours at approximately 70°C to allow crosslinking. After crosslinking, ethanol was added to precipitate a polymer material containing the crosslinked polymer. The precipitate was then filtered and dried overnight in a vacuum oven at 40°C to obtain the target polymer material. The dried polymer was then pulverized using a pulverizer and classified using an ASTM standard mesh sieve to obtain a base resin with a particle size of 300-600 μm, which was used as a superabsorbent resin.

[0128] Example 2 A superabsorbent polymer was prepared in the same manner as in Example 1, except that the modified starch (M / S-1) of Preparation Example 2 was used instead of the modified chitosan (M / S) in Example 1.

[0129] Example 3 A superabsorbent polymer was prepared in the same manner as in Example 1, except that the modified starch (M / S-2) of Preparation Example 3 was used instead of the modified chitosan (M / S) in Example 1.

[0130] Example 4 A superabsorbent polymer was prepared in the same manner as in Example 1, except that the modified starch (M / S-3) of Preparation Example 4 was used instead of the modified chitosan (M / S) in Example 1.

[0131] Example 5 A superabsorbent polymer was prepared in the same manner as in Example 1, except that the modified starch (M / S-4) of Preparation Example 5 was used instead of the modified chitosan (M / S) in Example 1.

[0132] Example 6 A superabsorbent polymer was prepared in the same manner as in Example 1, except that the modified starch (M / S-5) of Preparation Example 6 was used instead of the modified chitosan (M / S) in Example 1.

[0133] Comparative Example 1 A superabsorbent polymer was prepared in the same manner as in Example 1, except that the modified starch (M) of Comparative Preparation Example 1 was used instead of the modified chitosan (M / S) in Example 1.

[0134] Comparative Example 2 A superabsorbent resin was prepared in the same manner as in Example 1, except that the modified chitosan (M-1) of Comparative Preparation Example 2 was used instead of the modified chitosan (M / S) in Example 1.

[0135] Comparative Example 3 A superabsorbent polymer was prepared in the same manner as in Example 1, except that the modified starch (M-2) of Comparative Preparation Example 3 was used instead of the modified chitosan (M / S) in Example 1.

[0136] Experimental example The properties of the superabsorbent resins produced in the above Examples and Comparative Examples were evaluated by the following methods, and the results are shown in Table 1 below.

[0137] Unless otherwise specified, all of the following physical property evaluations were performed at constant temperature and humidity (23±1°C, relative humidity 50±10%), and saline or salt water refers to a 0.9 wt% aqueous sodium chloride (NaCl) solution.

[0138] (1) Weight average molecular weight The weight average molecular weight is measured by GPC / MALLS, and the detailed measurement method is as follows.

[0139] 1) Preparation of mobile phase 1000 mL of 100 mM NaNO3 aqueous solution containing 0.02% NaN3 was filtered using a solvent clarification system.

[0140] 2) Preparation of sample solution 5 mL of 100 mM NaNO3 aqueous solution containing 0.02% NaN3 was added to 25 mg of sample, heated at 110°C for 1 hour, filtered through a 0.45 micrometer nylon syringe filter, and applied to analysis.

[0141] 3)GPC / MALLS conditions Stationary phase: Shodex OH-Pak 804 column, Shodex OH-Pak 80 column Mobile phase: 100 mM NaNO3 aqueous solution containing 0.02% NaN3 Flow rate: 0.4mL / min Stationary phase temperature: 25℃ Injection volume: 100 microliters Analysis time: 120 minutes

[0142] (2)Centrifuge Retention Capacity (CRC) The water retention capacity of each resin was measured by the absorbency under no load using EDANA WSP 241.3.

[0143] Specifically, a superabsorbent resin W0 (g) (approximately 0.2 g) was evenly placed in a nonwoven fabric envelope, sealed, and then immersed in physiological saline (0.9 wt%) at room temperature. After 30 minutes, the envelope was centrifuged at 250 G for 3 minutes to remove water, and the mass of the envelope W2 (g) was measured. The same procedure was repeated without the resin, and the mass W1 (g) was then measured. The CRC (g / g) was calculated using the obtained masses using the following formula.

[0144] [Formula 1] CRC(g / g)={[W2(g)-W1(g)] / W0(g)}-1

[0145] (3) Biodegradability test Measurements were made based on the KS M ISO 14851 standard.

[0146] [Table 1]

[0147] As can be seen from Table 1 above, it was confirmed that the biodegradable highly water-absorbent resin containing the high molecular weight modified polysaccharide according to the present invention has excellent water absorption properties and also excellent biodegradability.

Claims

1. Maleic acid group (-OCOCH=CHCOOH) and carboxymethyl group (-CH ２ -COOH) (a crosslinked polymer of a monomer containing a modified polysaccharide containing at least one of the following: At least a portion of the maleic acid groups and carboxymethyl groups are neutralized; The crosslinked polymer contains 60 parts by weight or more of a repeating unit derived from a modified polysaccharide, the modified polysaccharide is modified starch or modified chitosan; The molecular weight of the modified polysaccharide is 190,000 g / mol or more; The molecular weight of the modified starch is 10,000,000 g / mol to 1,000,000,000 g / mol; Biodegradable super absorbent resin.

2. 2. The biodegradable highly water-absorbent resin according to claim 1, wherein the degree of substitution of maleic acid groups in the modified polysaccharide is 0.15 to 1.

5.

3. 2. The biodegradable highly water-absorbent resin according to claim 1, wherein the degree of substitution of carboxymethyl groups in the modified polysaccharide is 0.2 to 1.

2.

4. 2. The biodegradable superabsorbent polymer according to claim 1, wherein the maleic acid group is introduced by maleic acid or maleic acid anhydride.

5. 2. The biodegradable superabsorbent polymer according to claim 1, wherein the carboxymethyl group is introduced by any one of glycolic acid, monochloroacetic acid, and salts thereof.

6. The biodegradable highly absorbent resin according to claim 1, wherein the modified polysaccharide contains at least one repeating unit represented by the following chemical formulas 1 to 4: 【Chemistry 1】 In the above chemical formulas 1 to 4, Each M is independently hydrogen or an alkali metal.

7. 2. The biodegradable highly absorbent resin according to claim 1, wherein the crosslinked polymer contains 80 parts by weight or more of repeating units derived from a modified polysaccharide.

8. 2. The biodegradable highly absorbent resin according to claim 1, wherein the molecular weight of the modified polysaccharide is 300,000 g / mol to 1,000,000,000 g / mol.

9. 2. The biodegradable highly absorbent resin according to claim 1, wherein the molecular weight of the modified polysaccharide is 300,000 g / mol to 50,000,000 g / mol.

10. 2. The biodegradable highly absorbent resin according to claim 1, wherein the molecular weight of the modified chitosan is 190,000 g / mol to 10,000,000 g / mol.

11. In the presence of a polymerization initiator, maleic acid groups (-OCOCH=CHCOOH) and carboxymethyl groups (-CH ２ preparing a monomer composition containing a modified polysaccharide containing one or more of the following: cross-linking the monomer composition to prepare a hydrogel polymer; and drying, pulverizing and classifying the hydrogel polymer; In a method for producing a biodegradable highly water-absorbent resin, At least a portion of the maleic acid groups and carboxymethyl groups of the modified polysaccharide are neutralized; The hydrogel polymer contains 60 parts by weight or more of a repeating unit derived from a modified polysaccharide, The molecular weight of the modified polysaccharide is 190,000 g / mol or more; A method for producing biodegradable superabsorbent resin.

12. 12. The method for producing a biodegradable superabsorbent resin according to claim 11, wherein the modified polysaccharide is produced by reacting a polysaccharide with at least one of maleic acid, maleic acid anhydride, glycolic acid, monochloroacetic acid, and salts thereof.

13. A sanitary product comprising the biodegradable highly absorbent resin according to any one of claims 1 to 10.

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