Novel crosslinking compound and biodegradable super absorbent polymer using the saem

Abstract

The present invention relates to a novel crosslinking agent compound capable of producing a superabsorbent resin exhibiting excellent biodegradability, and a biodegradable superabsorbent resin produced using the same.

Description

Technology Field

[0001] The present invention relates to a novel crosslinking agent compound capable of producing a superabsorbent resin exhibiting excellent biodegradability, and a biodegradable superabsorbent resin produced using the same. Background Technology

[0003] 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.

[0005] 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 a polymerization 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, which can lead to environmental pollution.

[0007] 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.

[0008] Furthermore, the polymerization method is an important factor to consider when developing biodegradable superabsorbent resins. For industrial-scale production, it is necessary to synthesize superabsorbent resins using radical polymerization, which is currently a widely used industrial method, rather than step polymerization.

[0010] Accordingly, while possessing the basic absorbent properties of a superabsorbent resin, There is a continuous demand for the development of technologies related to superabsorbent resins that can exhibit biodegradability and be manufactured by radical polymerization. The problem to be solved

[0012] Accordingly, the present invention aims to provide a crosslinking agent compound capable of producing a superabsorbent resin that possesses basic absorption properties such as water retention capacity and pressure absorption capacity while exhibiting excellent biodegradability, and a biodegradable superabsorbent resin produced using said crosslinking agent. means of solving the problem

[0014] According to one embodiment of the present invention,

[0015] A crosslinking agent compound is provided that comprises the peptide sequence of Chemical Formula 1 below, wherein both ends are modified with polymerizable functional groups:

[0016] [Chemical Formula 1]

[0017] Gly-Gly-Arg-Ser-Lys

[0018] In the above chemical formula 1, Gly is glycine, Arg is arginine, Ser is serine, and Lys is lysine.

[0020] According to another embodiment of the present invention,

[0021] A biodegradable superabsorbent resin is provided, comprising: a crosslinking agent compound having a peptide sequence of Chemical Formula 1 below, wherein both ends are modified into polymerizable functional groups; and a crosslinked polymer formed by crosslinking an acrylic acid-based monomer.

[0022] [Chemical Formula 1]

[0023] Gly-Gly-Arg-Ser-Lys

[0025] Furthermore, according to another embodiment of the present invention, an article comprising the biodegradable superabsorbent resin is provided. Effects of the invention

[0027] The biodegradable superabsorbent resin of the present invention comprises a cross-linked polymer in which an acrylic acid-based monomer is cross-linked by a peptide-derived cross-linking agent, and is capable of natural degradation by an enzyme-substrate reaction by human urine enzymes, thereby exhibiting excellent biodegradability while also exhibiting general physical properties of superabsorbent resins, such as water retention capacity and pressure absorption capacity.

[0028] Accordingly, the above-mentioned biodegradable superabsorbent resin and articles containing it can be applied to various sanitary products and may not cause environmental pollution problems upon disposal. Brief explanation of the drawing

[0030] FIG. 1 is a schematic diagram showing the structure and degradation mechanism of a biodegradable superabsorbent resin according to one embodiment of the present invention. Figure 2(a) is a 1H-NMR showing the chemical structure of a crosslinking agent compound according to one embodiment of the present invention, and (b) is an FT-IR spectroscopic spectrum. Figure 3 is a graph showing the chemical structure of a crosslinking agent compound according to one embodiment of the present invention using an electron spray ionization mass spectrometer (ESI-MS). FIG. 4 is a graph showing the equilibrium swelling ratio Q of superabsorbent resins according to Examples 1 to 4 and Comparative Examples 1 to 4 of the present invention. FIG. 5 shows the volume ratio (V) of the superabsorbent resin according to the culture time in uPA of Examples 1 to 4 of the present invention. fold It is a graph representing ). Specific details for implementing the invention

[0031] 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.

[0032] 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.

[0033] 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.

[0034] 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.

[0035] Meanwhile, the term "(meth)acrylate" as used in this specification includes both acrylate and methacrylate.

[0036] The term "crosslinked polymer" as used in the specification of the present invention refers to a state in which acrylic acid-based monomers are crosslinked by a crosslinking agent compound and polymerized, and may encompass all moisture content ranges or particle size ranges.

[0037] Furthermore, depending on the context, the term "superabsorbent resin" is used to encompass a cross-linked polymer formed by polymerizing acrylic acid-based monomers cross-linked by a cross-linking agent compound, a base resin in powder form consisting of superabsorbent resin particles formed by grinding said cross-linked polymer, or a state suitable for commercialization obtained by subjecting said cross-linked polymer or said base resin to additional processes, such as additional cross-linking, fine powder reassembly, drying, grinding, classification, etc.

[0038] In addition, the term "superabsorbent resin particles" refers to particulate material in which superabsorbent resin has been crushed.

[0040] Conventional superabsorbent polymers widely used are cross-linked polymers of poly(acrylic acid) (PAA), which are manufactured by polymerizing acrylic acid monomers with a crosslinking agent in the presence of a polymerization initiator; however, these polyacrylic acid superabsorbent polymers do not possess biodegradability, causing environmental problems.

[0041] Accordingly, in order to develop superabsorbent resins capable of exhibiting biodegradability, attempts were made to synthesize biodegradable superabsorbent resins by incorporating a degradable portion into the superabsorbent resin polymer network. However, these attempts did not achieve sufficient success due to complex synthesis pathways, low production yields, and / or insufficient water absorption and mechanical properties.

[0042] As another alternative, there have been attempts to create superabsorbent resins by crosslinking various charged and biodegradable polymers instead of acrylic acid-based monomer polymers. For example, a crosslinked network of biodegradable poly(aspartic acid) produced through the condensation polymerization of L-aspartic acid has been reported. However, its use in the superabsorbent resin industry has been limited due to its weak mechanical strength and high production cost.

[0043] Furthermore, most conventionally synthesized biodegradable superabsorbent polymers contain ester groups for hydrolytic degradation; however, since this method involves a high-temperature heating step to accelerate hydrolytic degradation, it is difficult to apply to current industrial manufacturing processes for superabsorbent polymers. Therefore, there is a need for a new biodegradable superabsorbent polymer that ensures industrial applicability while improving long-term storage stability.

[0045] Accordingly, considering that the most widely used end product for superabsorbent resins is diapers, the inventors completed the present invention by confirming that when a superabsorbent resin is manufactured using an enzyme-substrate reaction that is degraded by human urinary enzymes, it exhibits not only excellent biodegradability but also a superior balance with water retention capacity and pressure absorption capacity compared to previously known biodegradable materials.

[0046] The most commonly used superabsorbent polymer in the industry today is a polyacrylic acid cross-linked polymer in which polyacrylic acid (PAA) chains are cross-linked with a cross-linking agent. Polyacrylic acid chains with a molecular weight of less than 1 kg / mol are known to be degradable in sewage by soil microorganisms. Therefore, to produce a biodegradable superabsorbent polymer, it is necessary to first decompose and cut the cross-linked sites of the cross-linked superabsorbent polymer into linear superabsorbent polymer chains, and then fragment the linear superabsorbent polymer chains into smaller pieces so that they can be degraded later by soil microorganisms.

[0048] A crosslinking agent compound according to one embodiment of the present invention is a peptide-derived compound that is degradable by an enzyme-substrate reaction using an enzyme found in human urine, and has both ends modified into polymerizable functional groups so that it can react with an acrylic acid monomer to form a crosslinked polymer.

[0049] In addition, it was confirmed that a biodegradable superabsorbent resin according to one embodiment of the present invention, comprising a crosslinked polymer of the crosslinking agent compound and an acrylic acid monomer, gradually decomposes over several days in an aqueous solution containing an enzyme at a physiological concentration found in human urine, and loses its form within 30 days.

[0051] Hereinafter, a novel crosslinking agent compound and a biodegradable superabsorbent resin manufactured using the same will be described in more detail according to specific embodiments of the invention.

[0053] Crosslinking agent compounds for manufacturing superabsorbent resins

[0054] A crosslinking agent compound for manufacturing a superabsorbent resin according to one embodiment is a compound comprising the peptide sequence of Chemical Formula 1 below, wherein both ends are modified into polymerizable functional groups.

[0055] [Chemical Formula 1]

[0056] Gly-Gly-Arg-Ser-Lys

[0057] In the above chemical formula 1, Gly is glycine, Arg is arginine, Ser is serine, and Lys is lysine.

[0059] According to one embodiment of the present invention, the polymerizable functional group may be an acrylamide group.

[0061] More specifically, the crosslinking agent compound may be a compound represented by the following chemical formula 1a:

[0062] [Chemical Formula 1a]

[0063]

[0065] The compound of the above chemical formula 1a is a compound (Ac-GGRSK-Ac) in which both ends of the peptide sequence of Gly-Gly-Arg-Ser-Lys (GGRSK) are modified into polymerizable acrylamide groups.

[0066] The above compound can be prepared by generating a peptide compound linked by peptide bonds in the order of glycine-glycine-arginine-serine-lysine through a known dehydration condensation reaction, and then modifying the primary amine groups of the amino acids at both ends, namely glycine and lysine, into acrylamide groups, which are polymerizable functional groups.

[0068] More specifically, for a peptide compound of Gly-Gly-Arg-Ser-Lys (GGRSK) as shown in Reaction Scheme 1 below, both ends of GGRSK can be modified into polymerizable acrylamide groups by reacting the N-terminus of glycine and the ε-amino group of lysine with an acrylic acid N-hydroxy succinimide ester (Ac-NHS ester).

[0069] [Reaction Equation 1]

[0070]

[0071] The method for manufacturing the above Ac-GGRSK-Ac is explained in more detail in the following examples.

[0073] In the above reaction scheme 1, the peptide bond site between arginine and serine, that is, the bonding part (Arg-Ser) indicated by the red arrow, is a cleavable site that can be degraded by human urine enzymes, and accordingly, the superabsorbent resin polymerized using the above compound as a crosslinking agent can have excellent biodegradability, being degraded by human urine enzymes.

[0075] Enzymes found in human urine are diverse, including oxidoreductases, transferases, hydrolases, lyases, isomerases, and ligases. Among these, the crosslinking agent of the present invention is a hydrolase and has the characteristic of being degraded by a leucine urokinase-type plasminogen activator (uPA), which is known to cleave specific chemical bonds.

[0076] uPA is a trypsin-like protease that catalyzes the conversion of plasminogen to plasmin in plasma. uPA catalyzes the cleavage of a peptide bond formed between the C-terminus of an arginine (Arg) residue and the N-terminus of an adjacent amino acid residue, as shown in Reaction Scheme 2 below.

[0077] [Reaction Equation 2]

[0078]

[0080] Meanwhile, in a crosslinking agent compound according to one embodiment of the present invention, a sufficient distance is secured between the polymerizable terminal functional group and the cleavage site (Arg-Ser) by the two glycine residues inserted between the N-terminus and arginine and the long alkyl side chain of lysine. Therefore, even in a crosslinked polymer formed by crosslinking the crosslinking agent compound and an acrylic acid-based monomer, uPA can bind to the cleavage site without steric hindrance caused by the polyacrylic acid chain, and thus exhibit excellent biodegradability.

[0082] Biodegradable superabsorbent resin

[0083] A biodegradable superabsorbent resin according to one embodiment comprises: a crosslinking agent compound having a peptide sequence of Formula 1 below and having both ends modified into polymerizable functional groups; and a crosslinked polymer formed by crosslinking an acrylic acid-based monomer:

[0084] [Chemical Formula 1]

[0085] Gly-Gly-Arg-Ser-Lys

[0086] In the above chemical formula 1, Gly is glycine, Arg is arginine, Ser is serine, and Lys is lysine.

[0088] More specifically, the crosslinking agent compound may be a compound represented by the following chemical formula 1a:

[0089] [Chemical Formula 1a]

[0090]

[0092] A specific description of the above-mentioned crosslinking agent compound is as previously explained in “Crosslinking agent compound for manufacturing superabsorbent resins.”

[0094] The above biodegradable superabsorbent resin comprises a cross-linked polymer that is cross-linked with an acrylic acid monomer using a compound having a peptide sequence of Chemical Formula 1 below and modified at both ends to be polymerizable functional groups as a cross-linking agent.

[0096] That is, the crosslinked polymer has a structure in which polyacrylic acid, which is a polymer of acrylic acid-based monomers, is crosslinked by a novel crosslinking agent compound of the present invention, and has a three-dimensional network structure in which a plurality of polyacrylic acid main chains are crosslinked according to the crosslinking agent. In this way, when the crosslinked polymer has a three-dimensional network structure, the water retention capacity and pressure absorption capacity, which are the general physical properties of the superabsorbent resin, can be significantly improved compared to polyacrylic acid with a two-dimensional linear structure that is not further crosslinked by the crosslinking agent.

[0097] In addition, since the crosslinking agent included in the above-mentioned crosslinking polymer can be degraded by enzymes, the superabsorbent resin containing it can also have excellent biodegradability.

[0099] FIG. 1 is a schematic diagram showing the structure and degradation mechanism of a biodegradable superabsorbent resin according to one embodiment of the present invention.

[0100] Referring to FIG. 1, the crosslinking agent compound of the present invention includes a cleavable site that can be degraded by an enzyme present in human urine, and since both ends are modified into polymerizable functional groups, it can react with an acrylic acid monomer to form a crosslinked polymer. Accordingly, the crosslinked polymer formed by the crosslinking of the crosslinking agent compound and the acrylic acid monomer is degraded over several days by an enzyme at a physiological concentration found in human urine, thereby reducing the crosslinking density of the acrylic acid polymer.

[0102] In one embodiment of the present invention, the acrylic acid monomer is a compound represented by the following chemical formula 2:

[0103] [Chemical Formula 2]

[0104] R 1 -COOM 1

[0105] In the above chemical formula 2,

[0106] R 1It is an alkyl group having 2 to 5 carbon atoms containing unsaturated bonds, and

[0107] M 1 It is a hydrogen atom, a monovalent or divalent metal, an ammonium group, or an organic amine salt.

[0108] Preferably, the acrylic acid monomer comprises one or more selected from the group consisting of acrylic acid, methacrylic acid, and their monovalent metal salts, divalent metal salts, ammonium salts, and organic amine salts.

[0109] Here, the acrylic acid monomer may have acidic groups, and at least a portion of the acidic groups may be neutralized. Preferably, the monomer may be partially neutralized with an alkaline substance such as sodium hydroxide, potassium hydroxide, calcium hydroxide, or ammonium hydroxide. In this case, the degree of neutralization of the acrylic acid monomer may be 40 to 95 mol%, or 40 to 80 mol%, or 45 to 75 mol%. The range of the degree of neutralization may be adjusted according to the final physical properties. However, if the degree of neutralization is excessively high, the neutralized monomer may precipitate, making it difficult for polymerization to proceed smoothly; conversely, if the degree of neutralization is excessively low, not only is the absorption capacity of the polymer significantly reduced, but it may also exhibit properties such as elastic rubber, which is difficult to handle.

[0111] According to one embodiment of the present invention, the crosslinking agent compound may be included in an amount of 0.001 to 1 mol% relative to 100 mol% of an acrylic acid-based monomer. If the content of the crosslinking agent compound is excessively low, crosslinking may not occur sufficiently, making it difficult to achieve strength above an appropriate level; if the content of the crosslinking agent compound is excessively high, the internal crosslinking density may increase, making it difficult to achieve the desired water retention capacity. Specifically, the crosslinking agent compound may be included in an amount of 0.001 mol% or more, 0.01 mol% or more, 0.02 mol% or more, or 0.04 mol% or more relative to 100 mol% of the acrylic acid-based monomer, and in an amount of 1 mol% or less, 0.8 mol% or less, 0.6 mol% or less, or 0.5 mol% or less.

[0113] According to one embodiment of the present invention, the superabsorbent resin 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.

[0114] In addition, the above-mentioned biodegradable superabsorbent resin may have an excellent balance of water retention capacity and pressure absorption capacity.

[0115] Specifically, the biodegradable superabsorbent resin may have a water retention capacity (CRC) of 10 to 50 g / g as measured according to the EDANA method WSP 241.3. For example, the biodegradable superabsorbent resin may have a water retention capacity (CRC) of 11 g / g or more, 12 g / g or more, 20 g / g or more, 21 g / g or more, or 24 g / g or more, and may have a CRC of 40 g / g or less, 35 g / g or less, 30 g / g or less, 25.5 g / g or less, or 25 g / g or less.

[0116] In addition, the above-mentioned biodegradable superabsorbent resin may have an applied absorption capacity (AUP) of 5 to 30 g / g at 0.7 psi as measured according to the EDANA method WSP 242.3. For example, the above-mentioned biodegradable superabsorbent resin may have an applied absorption capacity (AUP) of 7 g / g or more, 8 g / g or more, 9 g / g or more, 10 g / g or more, 11 g / g or more, 12 g / g or more, 13 g / g or more, 14 g / g or more, or 15 g / g or more, and may be 25 g / g or less, 23 g / g or less, 20 g / g or less, or 17 g / g or less.

[0118] Furthermore, an article comprising the aforementioned biodegradable superabsorbent resin is provided.

[0119] 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.

[0120] In this case, sanitary products containing the superabsorbent resin may include, for example, children's diapers, adult diapers, or sanitary pads. In particular, the superabsorbent resin may be preferably applied to diapers intended primarily for urine absorption. 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.

[0122] Meanwhile, the above-mentioned biodegradable superabsorbent resin can be prepared by polymerizing a monomer composition comprising a crosslinking agent compound having a peptide sequence of Chemical Formula 1 below and having both ends modified into polymerizable functional groups, an acrylic acid-based monomer, and a polymerization initiator.

[0123] [Chemical Formula 1]

[0124] Gly-Gly-Arg-Ser-Lys

[0126] Hereinafter, the method for manufacturing a superabsorbent resin of one embodiment will be described in more detail step by step.

[0127] The monomer composition, which is the raw material of the superabsorbent resin, comprises an acrylic acid-based monomer, a crosslinking agent compound having a peptide sequence of Chemical Formula 1 and having both ends modified into polymerizable functional groups, and a polymerization initiator.

[0128] The description and specific examples of the above acrylic acid-based monomer and crosslinking agent compounds are as previously explained.

[0129] The polymerization initiator used during polymerization in the method for manufacturing a superabsorbent resin according to the present invention is not particularly limited as long as it is one that is generally used in the manufacture of superabsorbent resins.

[0130] Specifically, the polymerization initiator may be a thermal polymerization initiator or a photopolymerization initiator based on UV irradiation, depending on the polymerization method. However, even in the case of a photopolymerization method, a certain amount of heat is generated by irradiation such as ultraviolet irradiation, and since a certain amount of heat is also generated as the polymerization reaction, which is an exothermic reaction, proceeds, a thermal polymerization initiator may additionally be included.

[0132] The above photopolymerization initiator can be used without limitation on its composition as long as it is a compound capable of forming radicals by light such as ultraviolet light.

[0133] For example, one or more selected from the group consisting of benzoin ether, dialkyl acetophenone, hydroxyl alkylketone, phenyl glyoxylate, benzyl dimethyl ketal, acyl phosphine, and α-aminoketone may be used as the photopolymerization initiator. Meanwhile, as a specific example of acyl phosphine, commercially available lucirin TPO, i.e., 2,4,6-trimethyl-benzoyl-trimethyl phosphine oxide, may be used. A wider variety of photoinitiators is well described in Reinhold Schwalm's book 'UV Coatings: Basics, Recent Developments and New Applications (Elsevier 2007)' p. 115, and is not limited to the examples described above.

[0134] The above photopolymerization initiator may be included in the monomer composition at a concentration of about 0.01 to about 1.0 weight%. If the concentration of the photopolymerization initiator is excessively low, the polymerization rate may be slowed down, and if the concentration of the photopolymerization initiator is excessively high, the molecular weight of the superabsorbent resin may be small and the physical properties may become non-uniform.

[0136] In addition, one or more initiators selected from the group consisting of persulfate-based initiators, azo-based initiators, hydrogen peroxide, and ascorbic acid may be used as the thermal polymerization initiator. Specifically, examples of persulfate-based initiators include sodium persulfate (Na2S2O8), potassium persulfate (K2S2O8), and ammonium persulfate ((NH4)2S2O8), while examples of azo-based initiators include 2,2-azobis-(2-amidinopropane) dihydrochloride, 2,2-azobis-(N,N-dimethylene)isobutyramidine dihydrochloride, 2-(carbamoylazo)isobutylonitril, 2, Examples include 2-azobis[2-(2-imidazolin-2-yl)propane] dihydrochloride and 4,4-azobis-(4-cyanovaleric acid). A wider variety of thermal polymerization initiators are well described in Odian's book 'Principles of Polymerization' (Wiley, 1981), p. 203, and are not limited to the examples mentioned above.

[0138] In the manufacturing method of the present invention, the monomer composition of the superabsorbent resin may further include additives such as a thickener, a plasticizer, a preservative stabilizer, and an antioxidant, as needed.

[0139] Raw materials such as acrylic acid-based monomers having the aforementioned acidic groups and at least some of the acidic groups neutralized, photopolymerization initiators, thermal polymerization initiators, crosslinking agents, and additives can be prepared in the form of a monomer composition solution dissolved in a solvent.

[0140] The solvent that can be used at this time may be used without limitation in composition as long as it can dissolve the components described above, and for example, one or more selected from water, ethanol, ethylene glycol, diethylene glycol, triethylene glycol, 1,4-butanediol, propylene glycol, ethylene glycol monobutyl ether, propylene glycol monomethyl ether, propylene glycol monomethyl ether acetate, methyl ethyl ketone, acetone, methyl amyl ketone, cyclohexanone, cyclopentanone, diethylene glycol monomethyl ether, diethylene glycol ethyl ether, toluene, xylene, butyloractone, carbitol, methyl cellosolve acetate, and N,N-dimethylacetamide may be used in combination.

[0141] The above solvent may be included as the remainder excluding the above-described component with respect to the total content of the monomer composition.

[0143] Meanwhile, the method of forming a hydrogel-like polymer by thermal polymerization or photopolymerization of such a monomer composition is also not limited in composition, as long as it is a commonly used polymerization method.

[0144] Specifically, polymerization methods are broadly classified into thermal polymerization and photopolymerization depending on the polymerization energy source. Typically, thermal polymerization can be carried out in a reactor equipped with 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 aforementioned polymerization methods are merely examples, and the present invention is not limited to the aforementioned polymerization methods.

[0145] At this time, the typical moisture content of the hydrogel polymer obtained by such a method may be about 40 to about 80 weight%. Meanwhile, throughout this specification, "moisture content" refers to the amount of water contained in the total weight of the hydrogel polymer, which is the value obtained by subtracting the weight of the polymer in a dry state from the weight of the hydrogel polymer. Specifically, it is defined as a value calculated by measuring the weight loss due to water evaporation in the polymer during the process of drying by raising the temperature of the polymer through infrared heating.

[0146] At this time, the drying conditions are set such that the temperature is raised from room temperature to about 180°C and then maintained at 180°C, and the total drying time is set to 20 minutes, including a 5-minute temperature raising step, to measure the moisture content.

[0148] Subsequently, the steps of drying the above-mentioned gel-like polymer, grinding the dried polymer, and classifying the ground polymer may be further performed.

[0150] Next, a drying step is performed on the obtained hydrogel-like polymer.

[0151] At this time, if necessary, a coarse grinding step may be added before drying to increase the efficiency of the above drying step.

[0152] At this time, the grinder used is not limited in its configuration, but specifically, it may include any one selected from the group of grinding machines consisting of a vertical pulverizer, a turbo cutter, a turbo grinder, a rotary cutter mill, a cutter mill, a disc mill, a shred crusher, a crusher, a chopper, and a disc cutter, but is not limited to the examples described above.

[0153] At this time, the grinding step can be performed so that the particle size of the hydrogel polymer is about 2 to about 10 mm.

[0154] Grinding to a particle size of less than 2 mm is not technically easy due to the high water content of the gel-like polymer, and aggregation may occur between the ground particles. On the other hand, if the particle size is ground to more than 10 mm, the effect of increasing the efficiency of the subsequent drying step is negligible.

[0156] Drying is performed on the hydrogel-like polymer immediately after polymerization, which has been ground as described above or has not undergone a grinding step. At this time, the drying temperature of the drying step may be about 150 to about 250°C. If the drying temperature is below 150°C, the drying time becomes excessively long and there is a risk that the physical properties of the finally formed superabsorbent resin will deteriorate; if the drying temperature exceeds 250°C, only the surface of the polymer is dried excessively, which may result in fine powder being generated during the subsequent grinding process and there is a risk that the physical properties of the finally formed superabsorbent resin will deteriorate. Therefore, preferably, the drying may be carried out at a temperature of about 150 to about 200°C, and more preferably at a temperature of about 160 to about 180°C.

[0157] Meanwhile, regarding the drying time, it may be carried out for about 20 to about 90 minutes, taking into account process efficiency, but is not limited thereto.

[0158] The drying method of the above drying step can also be selected and used without limitation on its composition, as long as it is a method commonly used for drying gel-like polymers. Specifically, the drying step can be carried out by methods such as hot air supply, infrared irradiation, microwave irradiation, or ultraviolet irradiation. The moisture content of the polymer after such a drying step may be about 0.1 to about 10 weight%.

[0160] Next, a step of grinding the dried polymer obtained through such a drying step is performed.

[0161] The polymer powder obtained after the grinding step may have a particle size of about 150 to about 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.

[0162] In addition, to manage the physical properties of the superabsorbent resin powder that is finalized after such a grinding step, a separate process may be performed to classify the polymer powder obtained after grinding according to particle size, and the polymer powder may be classified into a certain weight ratio according to the particle size range.

[0163] A polymer in which acrylic acid monomers are polymerized through the process described above is dried and ground to form a particle or powder, which is called a base resin.

[0165] Next, a surface crosslinking reaction for the base resin in the presence of a surface crosslinking agent may be further performed to form a surface crosslinking layer on the surface of the base resin in which the crosslinking polymer is additionally crosslinked via the surface crosslinking agent.

[0166] In a general method for manufacturing a superabsorbent resin, a surface crosslinking solution containing a surface crosslinking agent is mixed with a dried and ground polymer, i.e., a base resin, and then a surface crosslinking reaction is performed on the ground polymer by applying heat to the mixture to raise the temperature.

[0167] The above surface crosslinking step is a step of forming a superabsorbent resin having improved physical properties, particularly an improved absorption rate, by inducing a crosslinking reaction on the surface of the pulverized polymer in the presence of a surface crosslinking agent. Through this surface crosslinking, a surface crosslinking layer is formed on the surface of the pulverized polymer particles.

[0168] Generally, since a surface crosslinking agent is applied to the surface of superabsorbent resin particles, the surface crosslinking reaction occurs on the surface of the superabsorbent resin particles, which improves the crosslinking bonding on the surface of the particles without substantially affecting the interior of the particles. Therefore, surface-crosslinked superabsorbent resin particles have a higher degree of crosslinking near the surface than in the interior.

[0170] Meanwhile, when adding the surface crosslinking agent, water may be additionally mixed together to form a surface crosslinking solution. Meanwhile, the surface crosslinking step described above may be carried out by using one or more polyvalent metal salts in addition to the surface crosslinking agent, for example, aluminum salts, more specifically, aluminum sulfates, potassium salts, ammonium salts, sodium salts, and hydrochloride salts.

[0171] By applying heat to the mixture of the base resin and the surface crosslinking agent to raise the temperature, a surface crosslinking layer is formed on the surface of the base resin in which the crosslinking polymer is additionally crosslinked via the surface crosslinking agent.

[0173] The present invention is described in more detail in the following examples. However, the following examples are merely illustrative of the present invention, and the scope of the present invention is not limited by the following examples.

[0175] <Example>

[0176] Preparation Example 1: Synthesis of Acrylamide Terminal Modifying Crosslinking Agent Compound (Ac-GGRSK-Ac)

[0177]

[0178] GGRSK peptide (synthesized by Cosmogenetech (Korea) by forming peptide bonds in the order of glycine-glycine-arginine-serine-lysine via a dehydration condensation reaction) and Ac-NHS ester (purchased from Sigma Aldrich) were dissolved in anhydrous DMSO containing 30 µl of triethylamine (purchased from Sigma Aldrich) at a molar ratio of 1:2. The reaction mixture was stirred overnight at room temperature.

[0179] The extent of the reaction was investigated using TLC (mobile phase BuOH:Acetic acid:D2O=3:1:1, containing ninhydrin, Rf of product=0.63). The reaction mixture was concentrated by evaporating DMSO using a centrifugal evaporator at room temperature for 12 hours, and then the mixture was precipitated in THF and EA, respectively, to obtain Ac-GGRSK-Ac (yield: 92%) with both ends modified to acrylamide. To remove low molecular weight impurities, the product was purified using a demineralized spin column (89870, Thermo, USA, 50% acetonitrile solution containing 0.1% trifluoroacetic acid).

[0181] The chemical structure of Ac-GGRSK-Ac was confirmed using 1H-NMR (Fig. 2(a)), FT-IR spectroscopy (Fig. 2(b)), and electron spray ionization mass spectrometry (ESI-MS) (Varian 500-Ms, Agilent, USA) (Fig. 3). Referring to Fig. 3, the molecular weight measured at a maximum intensity of 612.3 g / mol was consistent with the calculated value for Ac-GGRSK-Ac (1 g / mol for ionization).

[0183] Example: Preparation of biodegradable superabsorbent resin

[0184] Example 1

[0185] An aqueous polymerization solution was prepared comprising 100 mol% acrylic acid, 0.041 mol% Ac-GGRSK-Ac of Preparation Example 1, 70 mol% NaOH, 523 mol% water, and 0.065 mol% photoinitiator (Darocur 1173). Cover glasses were placed over and under a glass spacer with a thickness of 1 mm, and the aqueous polymerization solution was rapidly injected into the empty space. UV (365 nm (30.8 mW / cm²) 2 Examining ), for 30 seconds, a rectangular size of 3 mm in width, 4 mm in height, and 1 mm in thickness A superabsorbent resin in the form of a hydrogel was prepared. The unreacted solution remaining in the prepared hydrogel was removed with primary distilled water.

[0187] Example 2

[0188] In Example 1, a hydrogel was prepared in the same manner as in Example 1, except that Ac-GGRSK-Ac was used at 5 times (0.205 mol%).

[0190] Example 3

[0191] In Example 1, a hydrogel was prepared in the same manner as in Example 1, except that Ac-GGRSK-Ac was used at 10 times (0.41 mol%).

[0193] Example 4

[0194] In Example 3, a hydrogel was prepared in the same manner as in Example 3, except that UV was irradiated for 30 seconds.

[0196] Comparative Example 1

[0197] In Example 1, a hydrogel was prepared in the same manner as in Example 1, except that bisacrylamide was used at 0.041 mol% instead of Ac-GGRSK-Ac.

[0199] Comparative Example 2

[0200] In Example 2, a hydrogel was prepared in the same manner as in Example 2, except that bisacrylamide was used at 0.205 mol% instead of Ac-GGRSK-Ac.

[0202] Comparative Example 3

[0203] In Example 3, a hydrogel was prepared in the same manner as in Example 3, except that bisacrylamide was used at 0.41 mol% instead of Ac-GGRSK-Ac.

[0205] Comparative Example 4

[0206] In Comparative Example 3, a hydrogel was prepared in the same manner as in Comparative Example 3, except that UV was irradiated for 30 seconds.

[0208] <Experimental Example>

[0209] Experimental Example 1: Evaluation of Swelling Degree

[0210] To measure the degree of swelling of the superabsorbent resins of Examples 1 to 4 and Comparative Examples 1 to 4, the equilibrium swelling ratio Q, defined as the weight ratio of the superabsorbent resin in an equilibrium swelling state relative to the dry state, was measured and is shown in FIG. 4 and Table 1 below.

[0211] All processes were carried out in a constant temperature and humidity room (23±0.5℃, relative humidity 45±0.5%), and the average of three measurements was used as the measurement data to prevent measurement errors.

[0212] In addition, primary distilled water was used in the following physical property evaluation. The prepared hydrogel was first sufficiently dehydrated using Kim Wypall to achieve an initial dry state, and its weight was measured. The superabsorbent polymer in this initial dry state was immersed in a Petri dish containing primary distilled water for 10 minutes to observe free swelling. When the superabsorbent polymer reached an equilibrium state where it no longer swelled, the weight of the hydrogel swollen by the primary distilled water was measured to calculate the equilibrium swelling ratio.

[0213] The equilibrium swelling ratio (Q, g / g) is calculated by the following Equation 1, and since the water absorption capacity decreases due to the rigid network structure as the crosslinking network structure increases, the above equilibrium swelling ratio is interpreted as being inversely proportional to the degree of crosslinking.

[0214] [Equation 1]

[0215] Q (g / g) = Weight of superabsorbent resin in equilibrium state free-swelled by primary distilled water (g) / Weight of superabsorbent resin in initial dry state (g)

[0217] Referring to Figure 4 and Table 1, the Q measured for the superabsorbent resin of Example 1 was approximately 760, the Q of Example 2 was 336, and the Q of Example 3 was reduced to 15.

[0218] In the case of Example 4, where high-dose UV irradiation was applied to increase the conversion of Ac-GGRSK-Ac, Q was significantly lowered to 7.

[0219] Meanwhile, when the superabsorbent resins of the comparative examples contained a low amount of crosslinking agent (Comparative Examples 1 and 2), the equilibrium swelling ratio was similar to that of Examples 1 and 2, respectively; however, in the case of Examples 3 to 4 containing a high amount of crosslinking agent, the equilibrium swelling ratio was lower than that of Comparative Examples 3 and 4.

[0220] This suggests that the structure of the Ac-GGRSK-Ac crosslinking agent (molecular weight 612 g / mol) used in the example is longer than that of the bisacrylamide (molecular weight 154 g / mol) used in the comparative example, and thus has flexible polymer chain properties when swollen, which may explain the decrease in Q.

[0222] Equilibrium swelling ratio No. 1 No. 2 No. 3 No. 4 Examples Q 758.4 336.0 15.1 7.0 Comparative example Q 741.1 260.7 159.7 131.0

[0224] Experimental Example 2: Evaluation of degradation by urokinase-type plasminogen activator (uPA)

[0226] The superabsorbent resins of Examples 1 to 4 were thoroughly washed with water and immersed in an aqueous solution containing 1 μM uPA (Urokinase (EC 3.4.4.21) type plasminogen activator, purchased from Fortunachem (China)). After incubating at 37°C for various times, they were washed several times with Dulbecco's PBS (pH 7.4) to stop the enzymatic reaction. The biodegradability of the superabsorbent resins is V fold It was measured as the ratio of the volume increasing with culture time relative to the initial volume.

[0227] FIG. 5 shows the volume ratio (V) of the superabsorbent resins of Examples 1 to 4 according to the incubation time in uPA. fold It is a graph representing ).

[0228] Referring to Fig. 5, a superabsorbent resin prepared with a crosslinking agent of a higher molar ratio and irradiated with a higher UV dose V according to incubation time fold It was confirmed that the crosslinking agent was degraded more rapidly by uPA, showing a rapid increase.

[0229] After 30 days, it was confirmed that the superabsorbent resin had swollen too much and practically lost its shape, and that most of the crosslinking agent had been decomposed and cut by uPA.

[0230] Meanwhile, although not shown in the graph, as a control experiment, a superabsorbent resin was prepared using bisacrylamide, a non-cleaving crosslinking agent, in the same manner as in Example 1, and V under the same conditions fold When measuring, even as time elapses, V fold It does not increase It was confirmed that decomposition by uPA did not occur.

[0232] As can be seen from the above, the biodegradable superabsorbent resin according to the present invention exhibits excellent biodegradability while maintaining the absorbent properties of the superabsorbent resin.

Claims

Claim 1 A crosslinking agent compound comprising the peptide sequence of the following chemical formula 1, wherein both ends are modified into polymerizable functional groups: [Chemical Formula 1] Gly-Gly-Arg-Ser-Lys In the above chemical formula 1, Gly is glycine, Arg is arginine, Ser is serine, and Lys is lysine. Claim 2 In claim 1, the crosslinking agent compound is represented by the following chemical formula 1a, crosslinking agent compound: [Chemical Formula 1a] Claim 3 A biodegradable superabsorbent resin comprising: a crosslinking agent compound having a peptide sequence of the following chemical formula 1, wherein both ends are modified into polymerizable functional groups; and a crosslinked polymer formed by crosslinking an acrylic acid monomer: [Chemical Formula 1] Gly-Gly-Arg-Ser-Lys In the above chemical formula 1, Gly is glycine, Arg is arginine, Ser is serine, and Lys is lysine. Claim 4 In paragraph 3, the crosslinking agent compound is a biodegradable superabsorbent resin represented by the following chemical formula 1a: [Chemical Formula 1a] Claim 5 In paragraph 3, the acrylic acid-based monomer is a biodegradable superabsorbent resin represented by the following chemical formula 2: [Chemical Formula 2]R 1 -COOM 1 In the above chemical formula 2, R 1 is an alkyl group having 2 to 5 carbon atoms containing unsaturated bonds, and M 1 It is a hydrogen atom, a monovalent or divalent metal, an ammonium group, or an organic amine salt. Claim 6 A biodegradable superabsorbent resin according to paragraph 3, wherein the acrylic acid monomer has an acidic group and at least a portion of the acidic group is neutralized. Claim 7 In paragraph 3, the biodegradable superabsorbent resin comprising the crosslinking agent compound in an amount of 0.001 to 1 mol% with respect to 100 mol% of acrylic acid-based monomer. Claim 8 An article comprising a biodegradable superabsorbent resin according to any one of paragraphs 3 through 7.

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