KR102584470B1 - Biodegradable superabsorbent polymer having the excellent absorption under load performance and method for preparing the same - Google Patents

Abstract

The present invention relates to a base resin; And a surface cross-linking layer formed from the surface of the base resin to the inside by surface cross-linking the base resin with a surface cross-linking agent, wherein the base resin is one or more of starch and oxidized starch, itaconic acid, acrylic acid derivative, and anionic It relates to a surface cross-linking treated superabsorbent resin comprising a polyitaconic acid graft copolymer prepared by polymerizing and internal cross-linking a raw material mixture containing an acrylamide derivative and an internal cross-linking agent. The surface cross-linked superabsorbent polymer with excellent pressure absorbency and its manufacturing method of the present invention are water-soluble and biodegradable, so they are biodegradable polymers with excellent absorbency with less environmental burden due to disposal, and also use environmentally friendly raw materials as main raw materials. Since it is manufactured using sanitary products, it is harmless to the human body and can reduce skin irritation when applied to sanitary products, and by using low-cost raw materials, manufacturing costs can be reduced and products that are advantageous in price competitiveness can be developed.

Description

Biodegradable-based superabsorbent resin with excellent absorbency under pressure and its manufacturing method {BIODEGRADABLE SUPERABSORBENT POLYMER HAVING THE EXCELLENT ABSORPTION UNDER LOAD PERFORMANCE AND METHOD FOR PREPARING THE SAME}

The present invention relates to a surface cross-linked superabsorbent resin with excellent absorbency under pressure and a method for producing the same. More specifically, to a biodegradable superabsorbent resin produced based on biodegradable monomers such as itaconic acid and its production. It's about method.

Highly absorbent polymers have high absorbency and water retention properties, so they are used in a wide range of materials, starting with sanitary products, agriculture, horticulture, distribution materials, civil engineering, construction, medical care, and toys. In particular, research is currently underway on how absorbent polymers that have appropriate gel properties and adhesive properties can also be used as component materials for various electronic devices.

In the synthesis of highly absorbent polymers, acrylic acid-based resins such as cross-linked sodium polyacrylate, which are generally refined from crude oil, are used as raw materials. However, acrylic acid-based resins are difficult to decompose, so there are concerns that they may cause environmental problems when disposed of when used in disposable diapers. It is becoming. Therefore, attempts have recently been made to use cellulose derivatives as materials with biodegradability and excellent absorbency, and in particular, the use of carboxymethyl cellulose, which contains carboxylate in its structure, has been examined. For example, methods for chemically crosslinking carboxymethylcellulose and methods for crosslinking using radiation crosslinking are known. However, in the above technology, there is a problem of high manufacturing cost when only a cellulose derivative is used as a starting material, and the bond between the cross-linked portion and carboxymethylcellulose is an ether bond, so it is chemically stable, so there is a problem in terms of biodegradability.

Meanwhile, a method for synthesizing a highly absorbent polymer using cellulose, chitin, chitosan, etc. as raw materials with biodegradability, absorption capacity, and absorption rate comparable to existing acrylic acid-based resins has been introduced, but the solvents selected to proceed with the ester crosslinking reaction have been introduced. Because it had extremely low solubility, it was effective only on some natural materials such as carboxymethylcellulose (CMC). However, this also had the problem of low solubility of the solvent, requiring high temperature and a long dissolution and dispersion time, and the yield of the produced resin was also low. In addition, a method using succinic anhydride was announced as a method of crosslinking cellulose-based materials with ester bonds, which exhibit high biodegradability, rather than ether bonds, but because the content of sodium carboxylic acid salt contained in the absorbent material obtained is low, the absorption rate is low. There was a problem that only late cross-linked products could be obtained. Therefore, there is a need to develop a material that can replace the cross-linked sodium polyacrylate as a material that can be applied to sanitary products, and to develop a polymer that satisfies biodegradability and environmental friendliness while also having high absorbency and absorption rate.

Meanwhile, IA (Itaconic Acid) is a water-soluble monomer that has two carboxylic acid groups in the molecule. It is a bio-mass derived material produced through fermentation. Its chemical properties and safety have been proven, so IA and IA derivatives are used in the chemical industry and even the medical field. There is a trend of expansion. In particular, recently, through radical polymerization and cross-linking reactions based on IA.

The manufactured PIA (Poly Itaconic Acid) Hydro-gel resin has excellent absorbency and decomposability, and is expected to be used in various fields such as improvement materials that increase water retention in soil. However, this PIA Hydrogel resin has the disadvantage of being weak in mechanical strength, especially compressive strength in the expanded state (i.e., gel strength) when water is absorbed and expanded, and its absorption ability under pressure is also low, so improvements are required.

Meanwhile, PVA resin is a water-soluble resin widely used in various fields such as film adhesives, and has biocompatibility and biodegradability. In particular, it has excellent mechanical properties, so various studies are in progress as a gel material for absorbent resin. However, this PVA-based gel resin has limited absorption capacity, which is an obstacle to its development.

The purpose of the present invention is to solve the above problems and to provide a starch-containing polyitaconic acid-based biodegradable superabsorbent resin that has water solubility and biodegradability and thus has a low environmental burden due to disposal.

In addition, the present invention aims to provide a surface cross-linked superabsorbent resin with excellent absorbency, absorption rate, and absorbency under pressure by manufacturing a superabsorbent resin based on water-soluble monomers and biodegradable monomers.

In addition, when applied to hygiene products, it is possible to provide a surface cross-linked superabsorbent resin that is harmless to the human body and reduces skin irritation.

In addition, by using low-cost raw materials, manufacturing costs can be reduced, providing a useful material for developing absorbent products that are advantageous in price competitiveness.

According to one aspect of the present invention, a base resin; And a surface cross-linking layer formed from the surface of the base resin to the inside by surface cross-linking the base resin with a surface cross-linking agent, wherein the base resin is one or more of starch and oxidized starch, itaconic acid, acrylic acid derivative, and anionic A surface cross-linking treated superabsorbent resin is provided, which includes a polyitaconic acid graft copolymer prepared by polymerizing and internal cross-linking a raw material mixture containing an acrylamide derivative and an internal cross-linking agent.

In addition, the polymerization reaction includes a radical reaction and a condensation reaction, and the radical reaction is performed by a radical reaction of one or more vinyl groups selected from the group consisting of itaconic acid, acrylic acid derivatives, and anionic acrylamide derivatives, and the condensation The reaction may be performed by an esterification reaction between one or more hydroxy groups of the starch and oxidized starch and one or more carboxy groups selected from the group consisting of itaconic acid and acrylic acid derivatives.

Additionally, the internal crosslinking reaction may be performed by a radical reaction between the vinyl group of the internal crosslinking agent and one or more vinyl groups selected from the group consisting of itaconic acid, acrylic acid derivatives, and anionic acrylamide derivatives.

Additionally, the itaconic acid may be one or more compounds selected from the group consisting of structural formulas 1 to 3 below.

[Structural Formula 1]

[Structural Formula 2]

[Structural Formula 3]

In structural formulas 1 to 3,

R ₁ and R ₂ are the same or different from each other, and are each independently a hydrogen atom, a C1 to C18 alkyl group, a C5 to C18 cyclic alkyl group, or a C6 to C18 aryl group,

R ₃ is each independently a valence bond, a C1 to C18 alkylene group, a C5 to C18 cyclic alkylene group, or a C6 to C18 arylene group.

Additionally, the acrylic acid derivative may be a compound represented by structural formula 4 below.

[Structural Formula 4]

In structural formula 4,

R ₄ is a hydrogen atom or a C1 to C3 alkyl group.

Additionally, the acrylic acid derivative may include one or more selected from the group consisting of acrylic acid, methacrylic acid, and methyl methacrylic acid.

In addition, the polyitaconic acid graft copolymer may include at least one vinyl polymer selected from the group consisting of itaconic acid, acrylic acid derivatives, and anionic acrylamide derivatives. At least one type of starch and oxidized starch grafted to the vinyl polymer; Polyitaconic acid grafted to one or more of the starch and oxidized starch, a polyacrylic acid derivative grafted to one or more of the starch and oxidized starch, and a polyanionic acrylamide derivative grafted to one or more of the starch and oxidized starch. , and at least one selected from the group consisting of itaconic acid-acrylic acid derivative-anionic acrylamide derivative copolymer grafted to at least one of the starch and oxidized starch; and an internal crosslinking agent that crosslinks at least one selected from the group consisting of the vinyl polymer, polyitaconic acid, polyacrylic acid derivative, polyanionic acrylamide derivative, and itaconic acid-acrylic acid derivative-anionic acrylamide derivative copolymer. can do.

Additionally, the graft of the polyitaconic acid graft copolymer may be formed by one or more types selected from the group consisting of ester bonds, ionic bonds, and hydrogen bonds.

In addition, the internal cross-linking agent is polyethylene glycol diacrylate (PEGDA), 1,6-hexanediol acrylate (HDDA), ethylene glycol diacrylate, ethylene glycol dimethacrylate, diethylene glycol diacrylate, and diethylene glycol diacrylate. Methacrylate, dipropylene glycol diacrylate, dipropylene glycol dimethacrylate, triethylene glycol diacrylate, triethylene glycol dimethacrylate, tetraethylene glycol diacrylate, tetraethylene glycol dimethacrylate, polyethylene Glycol dimethacrylate, pentaerythritol dimethacrylate, pentaerythritol trimethacrylate, N,N'-methylenebisacrylamide, N,N'-ethylenebisacrylamide It may include one or more types selected from the group consisting of acrylamide (N,N'-Ethylenebisacrylamide) and N,N'-Propylenebisacrylamide.

The anionic acrylamide derivative may be represented by structural formula 5 below.

[Structural Formula 5]

In structural formula 5,

R ₅ is a hydrogen atom or a C1 to C3 alkyl group,

R ₆ is a hydrogen atom or a C1 to C3 alkyl group,

R ₇ is a C1 to C9 linear or branched alkylene group,

X is an anionic functional group,

Y is a hydrogen ion or a metal cation.

^In _addition ^{, in the} _structural ^formula ₅ ^, It may be Ag ⁺ , Au ⁺ , Mg ²⁺ , Ca ²⁺ , Ba ²⁺ , Mn ²⁺ , Ni ²⁺ , or Cu ²⁺ .

The anionic acrylamide derivative is 2-acrylamido 2-methylpropane sulfonic acid or a salt thereof, 2-acrylamido 2-ethylpropane sulfonic acid or a salt thereof, 3-acrylamido 2-methylbutane sulfonic acid or a salt thereof, 3 -Acrylamido may also be 2-ethylbutane sulfonic acid or a salt thereof.

The surface cross-linking agent may include one or more selected from the group consisting of polyvalent cationic salts, epoxy compounds, and polyhydric alcohol compounds.

Among ^the polyvalent cation salts, cations are Al ³⁺ , Zr ⁴⁺ , Sc ³⁺ , Ti ⁴⁺ , V ⁺⁵ , Cr ³⁺ , Mn ²⁺ , Fe ^{3+ , Ni 2+} , Cu ²⁺ , Zn ²⁺ , Ag ⁺ , Pt ⁴⁺ and Au ⁺ , and the anion is a sulfate group (SO ₄ ^2- ), ^a sulfurous acid group (SO ₃ ^2- ), a nitrate group (NO _3- ), and meta. It may include one or more types selected from the group consisting of a phosphoric acid group (PO ₃ ^- ) and a phosphoric acid group (PO ₄ ^{3 -} ).

The epoxy compound may include at least one selected from the group consisting of ethylene glycol diglycidyl ether and glycidol.

The polyhydric alcohol compound is mono-, di-, tri-, tetra- or polyethylene glycol, monopropylene glycol, 1,3-propanediol, dipropylene glycol, 2,3,4-trimethyl-1,3-pentanediol, Polypropylene glycol, glycerol, polyglycerol, 2-butene-1,4-diol, 1,4-butanediol, 1,3-butanediol, 1,5-pentanediol, 1,6-hexanediol, and 1,2- It may include one or more selected from the group consisting of cyclohexanedimethanol.

According to another aspect of the present invention, an absorbent material including the surface cross-linked superabsorbent polymer is provided.

According to another aspect of the present invention, (a) preparing a mixed solution containing at least one type of starch and oxidized starch, itaconic acid, an acrylic acid derivative, an anionic acrylamide derivative, an internal cross-linking agent, and a neutralizing agent; (b) adding an internal initiator to the mixed solution and reacting to prepare a base resin containing a polyitaconic acid graft copolymer; and (c) surface cross-linking the base resin with a surface cross-linking agent to form a surface cross-linking layer formed from the surface of the base resin to the inside to prepare a surface cross-linking treated superabsorbent resin. A method for producing an absorbent resin is provided.

Additionally, in step (c), the surface cross-linking treated superabsorbent polymer may include 1 to 50 parts by weight of the surface cross-linking agent based on 100 parts by weight of the base resin.

Additionally, in step (c), the surface crosslinking treatment may be performed at a temperature of 100°C to 200°C for 10 to 200 minutes.

The surface cross-linked superabsorbent polymer of the present invention and its manufacturing method have water solubility and biodegradability, thereby reducing the environmental burden due to disposal.

In addition, the present invention produces a superabsorbent resin based on water-soluble monomers and biodegradable monomers, thereby providing excellent absorbency, absorption speed, and absorbency under pressure.

In addition, since the present invention is manufactured using non-toxic materials as the main raw material, when applied to sanitary products, it is friendly to the human body and can reduce skin irritation.

Additionally, by using low-cost raw materials, manufacturing costs can be reduced and products that are advantageous in price competitiveness can be developed.

1A and 1B are SEM analysis graphs of the base resin according to Preparation Example 1 and the surface cross-linked superabsorbent polymer with excellent absorbency under pressure according to Example 1.
Figure 2 shows the FT-IR analysis results of the base resin according to Preparation Example 1 and the surface cross-linked superabsorbent polymer with excellent absorbency under pressure according to Example 1.
Figure 3 shows the results of FT-IR analysis of the base resin according to Control Examples 1 to 3 and Preparation Example 1.
Figure 4 shows the TGA analysis results of the base resin according to Control Examples 1 to 3 and Preparation Example 1.

Since the present invention can be modified in various ways and can have various embodiments, specific embodiments will be illustrated and described in detail in the detailed description. However, this is not intended to limit the present invention to specific embodiments, and should be understood to include all transformations, equivalents, and substitutes included in the spirit and technical scope of the present invention. In describing the present invention, if it is determined that a detailed description of related known technologies may obscure the gist of the present invention, the detailed description will be omitted.

Additionally, when a component is referred to as “on another component,” “formed on another component,” or “stacked on another component,” it means that it is directly on the front or one side of the surface of that other component. It may be formed by being attached or laminated, but it should be understood that other components may additionally exist in the middle.

Singular expressions include plural expressions unless the context clearly dictates otherwise. In this application, terms such as “comprise” or “have” are intended to designate the presence of features, numbers, steps, operations, components, parts, or combinations thereof described in the specification, but are not intended to indicate the presence of one or more other features. It should be understood that this does not exclude in advance the possibility of the existence or addition of elements, numbers, steps, operations, components, parts, or combinations thereof.

Hereinafter, the surface cross-linking treated superabsorbent polymer of the present invention will be described.

The present invention relates to a base resin; And a surface cross-linking layer formed from the surface of the base resin to the inside by surface cross-linking the base resin with a surface cross-linking agent, wherein the base resin is one or more of starch and oxidized starch, itaconic acid, acrylic acid derivative, and anionic A surface cross-linking treated superabsorbent resin is provided, which includes a polyitaconic acid graft copolymer prepared by polymerizing and internal cross-linking a raw material mixture containing an acrylamide derivative and an internal cross-linking agent.

The base resin is a raw material mixture containing water-soluble ethylenically unsaturated monomers containing itaconic acid and acrylic acid derivatives, at least one type of starch and oxidized starch, an anionic acrylamide derivative containing vinyl sulfonic acid or a salt thereof, and an internal crosslinking agent. The raw materials including polyitaconic acid prepared through polymerization reaction and internal cross-linking reaction may include a copolymer grafted to each other.

The polymerization reaction includes a radical reaction and a condensation reaction, and the radical reaction is performed by a radical reaction of one or more vinyl groups selected from the group consisting of itaconic acid, acrylic acid derivatives, and anionic acrylamide derivatives, and the condensation reaction This can be performed by an esterification reaction between one or more hydroxy groups of the starch and oxidized starch and one or more carboxy groups selected from the group consisting of itaconic acid and acrylic acid derivatives.

The internal crosslinking reaction may be performed by a radical reaction between the vinyl group of the internal crosslinking agent and one or more vinyl groups selected from the group consisting of itaconic acid, acrylic acid derivatives, and anionic acrylamide derivatives.

The starch may include one or more selected from the group consisting of corn starch, waxy corn starch, tapioca starch, potato starch, sweet potato starch, wheat starch, rice starch, sago starch, and modified starches thereof, and the modified starch is It may include one or more selected from the group consisting of oxidized starch, acid-treated starch, ester starch, ether starch, phosphoric acid cross-linked starch, and acetyladipic acid starch. Additionally, the starch may be modified corn starch, and the modified corn starch may include oxidized corn starch, hydroxyethylated dent corn starch, hydroxypropylated crosslinked dent corn starch, and hydroxypropylated crosslinked tablets. (waxy) may include one or more selected from the group consisting of corn starch.

The itaconic acid may be one or more compounds selected from the group consisting of structural formulas 1 to 3 below.

[Structural Formula 1]

[Structural Formula 2]

[Structural Formula 3]

In structural formulas 1 to 3,

R ₁ and R ₂ are the same or different from each other, and are each independently a hydrogen atom, a C1 to C18 alkyl group, a C5 to C18 cyclic alkyl group, or a C6 to C18 aryl group,

R ₃ is each independently a valence bond, a C1 to C18 alkylene group, a C5 to C18 cyclic alkylene group, or a C6 to C18 arylene group.

The acrylic acid derivative may be a compound represented by structural formula 4 below.

[Structural Formula 4]

In structural formula 4,

R ₄ is a hydrogen atom or a C1 to C3 alkyl group.

The acrylic acid derivative may include one or more selected from the group consisting of acrylic acid, methacrylic acid, and methyl methacrylic acid.

The polyitaconic acid graft copolymer is one or more vinyl polymers selected from the group consisting of itaconic acid, acrylic acid derivatives, and anionic acrylamide derivatives; At least one type of starch and oxidized starch grafted to the vinyl polymer; Polyitaconic acid grafted to one or more of the starch and oxidized starch, a polyacrylic acid derivative grafted to one or more of the starch and oxidized starch, and a polyanionic acrylamide derivative grafted to one or more of the starch and oxidized starch. , and at least one selected from the group consisting of itaconic acid-acrylic acid derivative-anionic acrylamide derivative copolymer grafted to at least one of the starch and oxidized starch; and an internal crosslinking agent that crosslinks at least one selected from the group consisting of the vinyl polymer, polyitaconic acid, polyacrylic acid derivative, polyanionic acrylamide derivative, and itaconic acid-acrylic acid derivative-anionic acrylamide derivative copolymer. can do.

The graft of the polyitaconic acid graft copolymer may be formed by one or more types selected from the group consisting of ester bonds, ionic bonds, and hydrogen bonds.

The internal crosslinking agent is polyethylene glycol diacrylate (PEGDA), 1,6-hexanediol acrylate (HDDA), ethylene glycol diacrylate, ethylene glycol dimethacrylate, diethylene glycol diacrylate, diethylene glycol dimethacrylate. Acrylate, dipropylene glycol diacrylate, dipropylene glycol dimethacrylate, triethylene glycol diacrylate, triethylene glycol dimethacrylate, tetraethylene glycol diacrylate, tetraethylene glycol dimethacrylate, polyethylene glycol Dimethacrylate, pentaerythritol dimethacrylate, pentaerythritol trimethacrylate, N,N'-Methylenebisacrylamide, N,N'-ethylenebisacrylamide It may include one or more selected from the group consisting of amides (N,N'-Ethylenebisacrylamide) and N,N'-Propylenebisacrylamide.

The anionic acrylamide derivative may be represented by structural formula 5 below.

[Structural Formula 5]

In structural formula 5,

R ₅ is a hydrogen atom or a C1 to C3 alkyl group,

R ₆ is a hydrogen atom or a C1 to C3 alkyl group,

R ₇ is a C1 to C9 linear or branched alkylene group,

X is an anionic functional group,

Y is a hydrogen ion or a metal cation.

_{In structural formula} ^{5 , _ _ _ _ +} , Au ⁺ , Mg ²⁺ , Ca ²⁺ , Ba ²⁺ , Mn ²⁺ , Ni ²⁺ , or Cu ²⁺ .

The anionic acrylamide derivative is 2-acrylamido 2-methylpropane sulfonic acid or a salt thereof, 2-acrylamido 2-ethylpropane sulfonic acid or a salt thereof, 3-acrylamido 2-methylbutane sulfonic acid or a salt thereof, 3 -Acrylamido may be 2-ethylbutane sulfonic acid or a salt thereof, preferably 2-acrylamido-2-methylpropane sulfonic acid sodium salt.

The anionic acrylamide derivative may be sodium vinyl sulfonic acid.

The surface cross-linking agent may include one or more selected from the group consisting of polyvalent cationic salts, epoxy compounds, and polyvalent al compounds.

Among the polyvalent cation salts, cations are Al ³⁺ , Zr ⁴⁺ , Sc ³⁺ , Ti ⁴⁺ , V ⁺⁵ , Cr ^{3+ ,} Mn ²⁺ , Fe ^{3+ , Ni 2+} , Cu ²⁺ , Zn ²⁺ , Ag ⁺ , Pt ⁴⁺ and Au ⁺ , and the anion is a sulfate group (SO ₄ ^2- ), ^a sulfurous acid group (SO ₃ ^2- ), a nitrate group (NO _3- ), and meta. It may include one or more types selected from the group consisting of a phosphoric acid group (PO ₃ ^- ) and a phosphoric acid group (PO ₄ ^{3 -} ).

The epoxy compound may include at least one selected from the group consisting of ethylene glycol diglycidyl ether and glycidol. The polyhydric alcohol compound is mono-, di-, tri-, tetra- or polyethylene glycol, monopropylene glycol, 1,3-propanediol, dipropylene glycol, 2,3,4-trimethyl-1,3-pentanediol, Polypropylene glycol, glycerol, polyglycerol, 2-butene-1,4-diol, 1,4-butanediol, 1,3-butanediol, 1,5-pentanediol, 1,6-hexanediol, and 1,2- It may include one or more selected from the group consisting of cyclohexanedimethanol.

The surface cross-linking agent may further include an inorganic compound, and the inorganic compound may include silica, fumed silica, clay, alumina, silica-alumina composite, titania, zinc oxide, aluminum sulfate, and It may include one or more types selected from the group consisting of mixtures thereof.

The surface cross-linked resin may be a highly absorbent resin with excellent absorbency under pressure.

The surface cross-linked superabsorbent resin having excellent absorbency under pressure may be a biodegradable resin.

The bonding structure of the base resin can be determined by referring to Scheme 1 below. A raw material mixture containing a water-soluble ethylenically unsaturated monomer containing itaconic acid and acrylic acid derivatives, one or more types of starch and oxidized starch, an anionic acrylamide derivative containing vinyl sulfonic acid or a salt thereof, and an internal cross-linking agent is subjected to polymerization and internal processing. The base resin produced by crosslinking reaction is a four-component copolymer resin in which IA (itaconic acid)/AA (acrylic acid)/oxidized starch/AMPS (sodium vinyl sulfonate) are mutually grafted.

[Scheme 1]

The present invention provides an absorbent material comprising a surface cross-linked superabsorbent polymer with excellent absorbency under pressure.

The present invention provides a hygiene product comprising the above absorbent material.

Hereinafter, the method for producing the surface cross-linked superabsorbent polymer with excellent pressure absorbency according to the present invention will be described.

First, a mixed solution containing at least one of starch and oxidized starch, itaconic acid, an acrylic acid derivative, an anionic acrylamide derivative, an internal cross-linking agent, and a neutralizing agent is prepared (step a).

The internal crosslinking agent is polyethylene glycol diacrylate (PEGDA), 1,6-hexanediol acrylate (HDDA), ethylene glycol diacrylate, ethylene glycol dimethacrylate, diethylene glycol diacrylate, diethylene glycol dimethacrylate. Acrylate, dipropylene glycol diacrylate, dipropylene glycol dimethacrylate, triethylene glycol diacrylate, triethylene glycol dimethacrylate, tetraethylene glycol diacrylate, tetraethylene glycol dimethacrylate, polyethylene glycol Dimethacrylate, pentaerythritol dimethacrylate, pentaerythritol trimethacrylate, N,N'-Methylenebisacrylamide, N,N'-ethylenebisacrylamide It may include one or more selected from the group consisting of amides (N,N'-Ethylenebisacrylamide) and N,N'-Propylenebisacrylamide.

The neutralizing agent may include one or more selected from the group consisting of non-metal hydroxides, ammonium hydroxide, organic base compounds containing alkyl amines, and organic compounds containing hydroxy groups.

Before polymerizing the itaconic acid, it is preferable to neutralize the itaconic acid with the neutralizing agent. The neutralizing agent can be used to bind the acidic monomer to any base, such as a monovalent inorganic base, for example M ⁺ [OH ^- ] _x (where M represents a cationic moiety selected from sodium, potassium, lithium and It can be neutralized using (has the value provided). Additionally, organic amines include primary amines (e.g. alkyl amines such as monomethyl amine, dimethylamine, trimethylamine, monoethylamine, diethylamine, triethylamine) as well as non-metal hydroxides such as ammonium hydroxide. Basic compounds and/or organic compounds containing a hydroxyl (OH) group functional group (e.g. ethylene glycol) can be used.

The amount of neutralization can be adjusted to provide less than complete neutralization of the acidic groups present in the polyitaconic acid of the present application. For example, in the case of itaconic acid, a representative monomer, it can be understood that complete neutralization will require 2 moles of neutralizing agent for each mole of itaconic acid. That is, 2 moles of sodium hydroxide will provide complete neutralization of 1 mole of itaconic acid, and any amount of sodium hydroxide less than 2 moles will provide the desired result of partial neutralization. When neutralizing itaconic acid using a divalent base, the amount of divalent base selected to completely neutralize itaconic acid will be 1.0 mole of divalent base for each mole of itaconic acid, and for partial neutralization, less than 1 mole of divalent base should be applied. Itaconic acid monomer can be partially neutralized.

The neutralizing agent may be an organic base compound containing an amine group or an organic compound containing a hydroxy group, and preferably may be a sodium hydroxide solution.

Next, an internal initiator is added to the mixed solution and reacted to prepare a base resin containing a polyitaconic acid graft copolymer (step b).

The internal initiator may include one or more selected from the group consisting of a free radical initiator, a water-soluble radical initiator, and a water-soluble initiator. For example, radical initiation can be performed using peroxides and azo compounds, such as azobisisobutyronitrile (AIBN). Preferably, a water-soluble radical initiator can be used, wherein the selected initiator is dissolved in deionized water or a combination of water-miscible polar solvents. It can be prepared in solution by dissolving in . Water-soluble initiators may include persulfates such as ammonium persulfate, sodium persulfate, and potassium persulfate, including mixtures thereof. Additionally, the water-soluble initiator may include hydrogen peroxide (H ₂ O ₂ ), tertiobutylhydroperoxide, and a water-soluble azo initiator.

The internal initiator is peroxide, azo compound, azobisisobutyronitrile (AIBN), persulfate, ammonium persulfate, sodium persulfate, potassium persulfate, hydrogen peroxide (H ₂ O ₂ ), and tertiobutylhydroperoxide. It may include one or more types selected from the group consisting of.

Finally, the base resin is surface cross-linked with a surface cross-linking agent, and a surface cross-linked layer is formed from the surface of the base resin to the inside to prepare a surface cross-linked superabsorbent polymer (step c).

In step (c), the surface crosslinking treatment may be performed at 100°C to 200°C, preferably at 160°C to 180°C.

In step (c), the surface crosslinking treatment may be performed for 10 minutes to 200 minutes, preferably for 30 minutes to 120 minutes, and more preferably for 50 minutes to 100 minutes. .

In step (c), based on 100 parts by weight of the base resin, 1 to 50 parts by weight of the surface crosslinking agent may be included, preferably 10 to 30 parts by weight, and more preferably 10 to 15 parts by weight. It can be included.

The surface cross-linking agent may include one or more selected from the group consisting of polyvalent cationic salts, epoxy compounds, and polyhydric alcohol compounds.

Among the polyvalent cation salts, cations are Al ³⁺ , Zr ⁴⁺ , Sc ³⁺ , Ti ⁴⁺ , V ⁺⁵ , Cr ^{3+ ,} Mn ²⁺ , Fe ^{3+ , Ni 2+} , Cu ²⁺ , Zn ²⁺ , Ag ⁺ , Pt ⁴⁺ and Au ⁺ , and the anion is a sulfate group (SO ₄ ^2- ), ^a sulfurous acid group (SO ₃ ^2- ), a nitrate group (NO _3- ), and meta. It may include one or more types selected from the group consisting of a phosphoric acid group (PO ₃ ^- ) and a phosphoric acid group (PO ₄ ^{3 -} ).

The epoxy compound may include at least one selected from the group consisting of ethylene glycol diglycidyl ether and glycidol.

The polyhydric alcohol compound is mono-, di-, tri-, tetra- or polyethylene glycol, monopropylene glycol, 1,3-propanediol, dipropylene glycol, 2,3,4-trimethyl-1,3-pentanediol, Polypropylene glycol, glycerol, polyglycerol, 2-butene-1,4-diol, 1,4-butanediol, 1,3-butanediol, 1,5-pentanediol, 1,6-hexanediol, and 1,2- It may include one or more selected from the group consisting of cyclohexanedimethanol.

The surface cross-linking agent may further include an inorganic compound, and the inorganic compound may include silica, fumed silica, clay, alumina, silica-alumina composite, titania, zinc oxide, aluminum sulfate, and It may include one or more types selected from the group consisting of mixtures thereof.

When the surface cross-linking agent is evenly sprayed onto the base resin and then exposed to high temperature, cross-linking (condensation polymerization) progresses on the surface of the base resin, causing the cross-linking density on the surface to increase compared to the inside, resulting in the absorbency under pressure (AUL). ) and improve liquid permeability (SPT).

Hereinafter, the present invention will be described in more detail through examples. However, this is for illustrative purposes and does not limit the scope of the present invention.

[Manufacture of base resin]

Manufacturing Example 1

40% by weight of polymerized monomer Itaconic acid (IA), 50% by weight of Acrylic Acid AA, 2-Acrylamide-2-methylpropanesulfonic acid sodium salt A monomer composition solution was prepared by mixing 7.5% by weight of acid sodium salt (AMPS) and 2.5% by weight of oxidized starch (OS). The monomer composition solution contains 0.08% by weight of poly(ethyleneglycol) diacrylate (PEGDA), 0.08% by weight of 1,6-hexanediol diacrylate (HDODA), which are internal crosslinking agents, and distilled water. 80% by weight was added and mixed by constant stirring at a stirring speed of 300 rpm. 80% by weight of 50% aqueous caustic soda solution (NaOH) was slowly added to the reactor to neutralize the monomer composition solution. The internal temperature of the reactor was maintained at 60°C and nitrogen was introduced for 1 hour to remove oxygen inside the reactor. Polymerization was initiated by adding 0.5% by weight of the internal initiator sodium persulfate. The polymerization process was carried out for 2 hours at an internal temperature of 60°C. The polymerized hydrogel polymer was transferred to a polypropylene container and dried in a hot air circulation dryer preheated to 60°C for 24 hours. The dried hydrogel polymer was placed in a freezer at -40°C and frozen for 4 hours. The frozen hydrogel polymer was coarsely ground using a grinder. It was completely dried in a hot air circulation dryer at 60°C for 24 hours. The dried product was pulverized with a grinder, and a quaternary copolymer-based base resin (superabsorbent resin before surface cross-linking treatment) with a particle size of 300-600㎛ was prepared using an ASTM standard classifier.

[Manufacture of surface cross-linked superabsorbent polymer]

Example 1

Aluminum sulfate 1.2% by weight, distilled water 38.5% by weight, ethylene glycol diglycidyl ether 4% by weight, 1,3-propanediol 4% by weight, 1,4-butanediol 4% by weight, propylene glycol A surface cross-linking agent was prepared by mixing 6.8% by weight, 80% by weight of methanol, and 2% by weight of konasil (K-200).

Next, 100% by weight of the base resin according to Preparation Example 1 was added and stirred evenly at a stirring speed of 400 rpm, and 12.5% by weight of the surface cross-linking agent was evenly sprayed on the base resin. Stirring was stopped and swelling was performed for 10 minutes to allow the surface cross-linking agent to penetrate into the base resin. The base resin into which the swollen surface cross-linking agent had penetrated was placed in a self-made stainless steel cylinder and placed in a rotary oven. The temperature of the rotary oven was set to 170°C as the surface crosslinking temperature, and the surface crosslinked for 60 minutes to prepare a surface crosslinked superabsorbent polymer.

Example 2

A surface cross-linked superabsorbent polymer was prepared in the same manner as in Example 1, except that instead of spraying 12.5 wt% of the surface cross-linking agent on the base resin, 10.0 wt% of the surface cross-linking agent was sprayed on the base resin.

Example 3

A surface cross-linked superabsorbent polymer was prepared in the same manner as in Example 1, except that instead of spraying 12.5 wt% of the surface cross-linking agent on the base resin, 15.0 wt% of the surface cross-linking agent was sprayed on the base resin.

Example 4

A surface cross-linked superabsorbent polymer was prepared in the same manner as Example 1, except that surface cross-linking was performed for 90 minutes instead of surface cross-linking for 60 minutes in Example 1.

Example 5

Example 1 and Example 1, except that instead of spraying 12.5% by weight of the surface crosslinking agent on the base resin and surface crosslinking for 60 minutes, 10.0% by weight of the surface crosslinking agent was sprayed on the base resin and surface crosslinking for 90 minutes. Surface cross-linked superabsorbent polymer was prepared using the same method.

Example 6

Example 1 and Example 1, except that instead of spraying 12.5% by weight of the surface crosslinking agent on the base resin and surface crosslinking for 60 minutes, 15.0% by weight of the surface crosslinking agent was sprayed on the base resin and surface crosslinking for 90 minutes. Surface cross-linked superabsorbent polymer was prepared using the same method.

Comparative Example 1

In Example 1, 1.2% by weight of aluminum sulfate, 38.5% by weight of distilled water, 4% by weight of ethylene glycol digricidyl ether, 4% by weight of 1,3-propanediol, 4% by weight of 1,4-butanediol, 6.8% by weight of propylene glycol, Instead of preparing a surface cross-linking agent by mixing 80% by weight of methanol and 2% by weight of konasil (K-200), 0.2% by weight of aluminum sulfate, 29% by weight of distilled water, 10% by weight of 1,4-butanediol, and 61% by weight of methanol. A surface cross-linked superabsorbent polymer was prepared in the same manner as in Example 1, except that a surface cross-linking agent was prepared by mixing 0.3% by weight of konasil (K-200).

Comparative Example 2

A surface cross-linked superabsorbent polymer was prepared in the same manner as Comparative Example 1, except that instead of spraying 12.5 wt% of the surface cross-linking agent on the base resin, 10.0 wt% of the surface cross-linking agent was sprayed on the base resin.

Comparative Example 3

A surface cross-linked superabsorbent polymer was prepared in the same manner as Comparative Example 1, except that 15.0 wt% of the surface cross-linking agent was sprayed on the base resin instead of spraying 12.5 wt% of the surface cross-linking agent on the base resin.

Comparative Example 4

A surface cross-linked superabsorbent polymer was prepared in the same manner as Comparative Example 1, except that surface cross-linking was performed for 90 minutes instead of surface cross-linking for 60 minutes in Comparative Example 1.

Comparative Example 5

Comparative Example 1 and Comparative Example 1, except that instead of spraying 12.5% by weight of the surface crosslinking agent on the base resin and surface crosslinking for 60 minutes, 10.0% by weight of the surface crosslinking agent was sprayed on the base resin and surface crosslinking for 90 minutes. Surface cross-linked superabsorbent polymer was prepared using the same method.

Comparative Example 6

Comparative Example 1 and Comparative Example 1, except that instead of spraying 12.5% by weight of the surface crosslinking agent on the base resin and surface crosslinking for 60 minutes, 15.0% by weight of the surface crosslinking agent was sprayed on the base resin and surface crosslinking for 90 minutes. Surface cross-linked superabsorbent polymer was prepared using the same method.

[Test example]

Test Example 1: SEM analysis before and after surface crosslinking

1A and 1B are SEM analysis images of the base resin according to Preparation Example 1 and the surface cross-linked superabsorbent polymer according to Example 1. The analysis was imaged using a SEM device (manufacturer: VEGA3, TESCAN, CZECH).

In order to increase the absorbency under pressure, it is possible to increase the content of the internal cross-linking agent, but because the absorbency is relatively lowered, the appropriate degree of internal cross-linking and surface cross-linking must be balanced in the core-cell structure. To achieve this, the surface of the resin particle must have an appropriate bonding density. Morphology must be formed, which can be confirmed through Figures 1a and 1b.

Test Example 2: FT-IR analysis before and after surface cross-linking

Figure 2 is the FT-IR analysis result of the base resin according to Preparation Example 1 and the surface cross-linked superabsorbent polymer according to Example 1. The analysis was performed using an FT-IR device (manufacturer: Nicolet Thermo Scientific, Nicolet 380, USA). Analysis was performed using KBr in a scanning range of 400 to 4000 cm ^-1 .

According to Figure 2, the peak appearing at about 1728 cm ^-1 is an ester C=O band (ester carbonyl band) in which a crosslinking reaction occurred between the -OH functional group of oxidized starch and the -COOH functional group of polyitaconic acid (PIA) or polyacrylic acid (PAA). ), it can be seen that the sensitivity of the peak changes with surface cross-linking treatment, and in particular, the 1580 cm ^-1 , 1408 cm ^-1, and 1030 cm ^-1 peaks are aliphatic related to the grafting structure of the polymer according to Example 1, respectively. It can be seen that the sensitivity changes significantly by surface cross-linking treatment, which is due to the CH, COO- (asymmetric), COO- (symmetric), and CO functional groups.

Test Example 3: FT-IR analysis of base resin

For comparison, polyacrylic acid (PAA: acrylic acid monomer homopolymer) was used in Control Example 1, polyitaconic acid (PIA: itaconic acid monomer homopolymer) was used in Control Example 2, and a copolymer produced from acrylic acid/itaconic acid/oxidized starch (AA). /IA/OS) was used as Control Example 3, and Figure 3 shows the FT-IR analysis results of Control Examples 1 to 3 and Preparation Example 1. The analysis was performed using an FT-IR device (Manufacturer: Nicolet Thermo Scientific, Nicolet 380, USA).

According to Figure 3, peaks and sensitivities at different positions were observed for each polymer with different components.

In particular, the following analysis results were obtained for the resin (AA/IA/OS/AMPS) containing acrylic acid/itaconic acid/oxidized starch/AMPS (sodium vinyl sulfonate) prepared according to Preparation Example 1. A carbonyl group peak was observed around 1700 cm ^-1 , and a wide band was formed around 3000 cm ^-1 and 3800 cm ^-1 due to the -OH group of oxidized starch. Additionally, the peaks at about 2918 cm ^-1 , 1599 cm ^-1 , 1404 cm ^-1 and 1025 cm ^-1 are attributed to the aliphatic CH, COO- (asymmetric), COO- (symmetric) and CO functional groups of oxidized starch, respectively. Additionally, the peaks at about 2903 cm ^-1 , 1580 cm ^-1 , 1408 cm ^-1 and 1030 cm ^-1 are aliphatic CH, COO- (asymmetric), COO- (symmetric) and It is due to the CO functional group. And the peak that appears at about 1728 cm ^-1 is due to the ester C=O band (ester carbonyl band) where a crosslinking reaction occurred between the -OH functional group of oxidized starch and the -COOH functional group of polyitaconic acid (PIA) or polyacrylic acid (PAA). It was done. Based on the above analysis results, it can be predicted that a copolymer grafted to the base monomers injected in Preparation Example 1 was formed.

Test Example 4: TGA analysis

For comparison, polyacrylic acid (PAA: acrylic acid monomer homopolymer) was used in Control Example 1, polyitaconic acid (PIA: itaconic acid monomer homopolymer) was used in Control Example 2, and a copolymer produced from acrylic acid/itaconic acid/oxidized starch (AA). /IA/OS) was used as Control Example 3, and Figure 4 shows the TGA analysis results of Control Examples 1 to 3 and Preparation Example 1. The analysis was measured using a thermogravimetric analysis (TGA) device (manufacturer: METTLER TOLEDO, TGA 2, USA).

According to Figure 4, the decomposition temperature of PAA according to Control Example 1 is 450°C, PIA according to Control Example 2 is 360°C, and the terpolymer containing AA/IA/OS according to Control Example 3 is 220°C, Preparation Example The quaternary copolymer containing AA/IA/OS/AMPS according to 1 showed a decomposition temperature around 223°C, and it was confirmed that each resin had a different decomposition temperature.

Test Example 5: Performance analysis of superabsorbent polymer

Table 1 below shows the water retention capacity (CRC), absorbency under pressure (AUL, @0.3psi), and liquid permeability (SPT) of the superabsorbent polymers according to Examples 1 to 6 and Comparative Examples 1 to 6, respectively.

Water retention capacity (CRC) measurement

Put 200 ml of distilled water in a beaker, add NaCl in a metered amount to make a 0.9 wt.% NaCl aqueous solution, and dissolve it. Then, 0.2 g of the superabsorbent resin according to Examples 1 to 6 and Comparative Examples 1 to 6 of the present invention was added to the dried tea bag. After adding a fixed amount, it was immersed in a beaker containing NaCl aqueous solution for 30 minutes, then centrifuged at 300 gravity for 3 minutes to completely remove the moisture simply attached to the surface, and then the weight of the swollen tea bag was accurately measured and measured as follows. Swelling ratio was calculated using Equation 1, and the average value was calculated after measuring three times for each sample.

[Equation 1]

CRC (g/g) = (W _t - W ₀ ) / W ₀

W _t = weight of SAP swollen in 0.9 wt.% NaCl aqueous solution for 30 minutes

W ₀ = weight of SAP initially introduced

Absorbency under pressure (AUL) measurement

Equipment containing a macro-porous sintered glass filter plate (porosity # 0, d = 80mm, h = 7mm) was used in a self-made petri dish (d = 118mm, h = 12mm). The superabsorbent polymer (0.9 ± 0.01g) according to Examples 1 to 6 and Comparative Examples 1 to 6 of the present invention was placed on a petri dish lined with polyester gauze, and a glass cylinder (SAP) was placed around the superabsorbent polymer (SAP). d = 60 mm, h = 50 mm). Afterwards, a cylindrical piston (Teflon d = 60mm) was placed on the dry SAP, and a load of 0.3 psi was applied to the SAP, while 0.9% saline was placed in a petri dish and absorbed into the SAP through a glass filter. The entire equipment was sealed and tested to prevent surface evaporation and changes in salt water concentration. After 60 minutes, the weight of the swollen SAP was measured and the Absorption Under Load (AUL) was calculated.

[Equation 2]

AUL (g/g) = (W1 - W0) / W0

W0 = weight of dried SAP

W1 = weight of swollen SAP

Liquid permeability (SPT) measurement

0.5 g of the superabsorbent polymer according to Examples 1 to 6 and Comparative Examples 1 to 6 of the present invention was swelled for 30 minutes by adding sufficient 0.9 wt% NaCl aqueous solution to a liquid permeability meter. Salt water was passed through the measuring cylinder while a load of 0.3 psi (= 106.26 g) was pressurized, and the time until 20 ml of salt water passed was measured.

item Surface cross-linker content
(weight%) surface crosslinking time
(min.) CRC
(g/g) AUL
(g/g) SPT
(sec) Example 1 12.5 60 36 29 40 Example 2 10 60 34 28 45 Example 3 15 60 35 27 48 Example 4 12.5 90 35 28 50 Example 5 10 90 34 27 49 Example 6 15 90 33 26 52 Comparative Example 1 12.5 60 30 25 95 Comparative Example 2 10 60 32 23 106 Comparative Example 3 15 60 28 25 86 Comparative Example 4 12.5 90 28 22 124 Comparative Example 5 10 90 30 21 97 Comparative Example 6 15 90 27 23 132

According to Table 1, excellent absorbency and absorbency under pressure were observed under most experimental conditions, but overall better absorbency, absorbency under pressure, and liquid permeability were observed in Examples 1 to 6 than Comparative Examples 1 to 6, especially Example 1. The case was the best.

Above, the present invention has been described in detail with preferred embodiments, but the present invention is not limited to the above embodiments, and various modifications can be made by those skilled in the art within the scope of the technical idea of the present invention. possible.

Claims (20)

base resin; and
A surface cross-linking layer formed from the surface of the base resin to the inside by surface cross-linking the base resin with a surface cross-linking agent,
The base resin is a polyitaconic acid graft copolymer prepared by polymerizing and internal cross-linking a raw material mixture containing at least one type of starch and oxidized starch, an itaconic acid derivative, an acrylic acid derivative, an anionic acrylamide derivative, and an internal cross-linking agent. It includes,
The surface cross-linking agent includes aluminum sulfate, ethylene glycol digricidyl ether, 1,3-propanediol, 1,4-butanediol, and propylene glycol,
The anionic acrylamide derivative includes 2-Acrylamide-2-methylpropanesulfonic acid sodium salt (AMPS),
Super absorbent polymer with surface cross-linking. According to paragraph 1,
The polymerization reaction includes a radical reaction and a condensation reaction,
The radical reaction is carried out by a radical reaction of one or more vinyl groups selected from the group consisting of itaconic acid derivatives, acrylic acid derivatives, and anionic acrylamide derivatives,
A surface cross-linked polymer, characterized in that the condensation reaction is carried out by an esterification reaction between at least one hydroxyl group of the starch and oxidized starch and at least one carboxyl group selected from the group consisting of itaconic acid derivatives and acrylic acid derivatives. Absorbent resin. According to paragraph 1,
A surface cross-linked product, characterized in that the internal cross-linking reaction is carried out by a radical reaction between the vinyl group of the internal cross-linking agent and one or more vinyl groups selected from the group consisting of itaconic acid derivatives, acrylic acid derivatives, and anionic acrylamide derivatives. Absorbent resin. According to paragraph 1,
A surface cross-linked superabsorbent resin, characterized in that the itaconic acid derivative is one or more compounds selected from the group consisting of the following structural formulas 1 to 3.
[Structural Formula 1]

[Structural Formula 2]

[Structural Formula 3]

In structural formulas 1 to 3,
R ₁ and R ₂ are the same or different from each other, and are each independently a hydrogen atom, a C1 to C18 alkyl group, a C5 to C18 cyclic alkyl group, or a C6 to C18 aryl group,
R ₃ is each independently a valence bond, a C1 to C18 alkylene group, a C5 to C18 cyclic alkylene group, or a C6 to C18 arylene group. According to paragraph 1,
A surface cross-linked superabsorbent resin, characterized in that the acrylic acid derivative is a compound represented by the following structural formula 4.
[Structural Formula 4]

In structural formula 4,
R ₄ is a hydrogen atom or a C1 to C3 alkyl group. According to paragraph 1,
A surface cross-linked superabsorbent resin, wherein the acrylic acid derivative includes at least one selected from the group consisting of acrylic acid, methacrylic acid, and methyl methacrylic acid. According to paragraph 1,
The polyitaconic acid graft copolymer
At least one vinyl polymer selected from the group consisting of itaconic acid derivatives, acrylic acid derivatives, and anionic acrylamide derivatives;
At least one type of starch and oxidized starch grafted to the vinyl polymer;
Polyitaconic acid grafted to one or more of the starch and oxidized starch, a polyacrylic acid derivative grafted to one or more of the starch and oxidized starch, and a polyanionic acrylamide derivative grafted to one or more of the starch and oxidized starch. , and at least one selected from the group consisting of an itaconic acid derivative-acrylic acid derivative-anionic acrylamide derivative copolymer grafted onto one or more of the starch and oxidized starch; and
An internal crosslinking agent that crosslinks at least one selected from the group consisting of the vinyl polymer, polyitaconic acid, polyacrylic acid derivative, polyanionic acrylamide derivative, and the itaconic acid derivative-acrylic acid derivative-anionic acrylamide derivative copolymer. A surface cross-linked superabsorbent resin characterized in that. In clause 7,
A surface cross-linked superabsorbent resin, characterized in that the graft of the polyitaconic acid graft copolymer is formed by at least one selected from the group consisting of ester bond, ionic bond, and hydrogen bond. According to paragraph 1,
The internal crosslinking agent is polyethylene glycol diacrylate (PEGDA), 1,6-hexanediol diacrylate (HDDA), ethylene glycol diacrylate, ethylene glycol dimethacrylate, diethylene glycol diacrylate, diethylene glycol diacrylate. Methacrylate, dipropylene glycol diacrylate, dipropylene glycol dimethacrylate, triethylene glycol diacrylate, triethylene glycol dimethacrylate, tetraethylene glycol diacrylate, tetraethylene glycol dimethacrylate, polyethylene Glycol dimethacrylate, pentaerythritol dimethacrylate, pentaerythritol trimethacrylate, N,N'-methylenebisacrylamide, N,N'-ethylenebisacrylamide A surface cross-linked superabsorbent resin comprising at least one selected from the group consisting of acrylamide (N,N'-Ethylenebisacrylamide) and N,N'-Propylenebisacrylamide (N,N'-Propylenebisacrylamide) . delete delete delete delete delete delete delete An absorbent material comprising the surface cross-linked superabsorbent polymer of claim 1. (a) preparing a mixed solution containing at least one of starch and oxidized starch, an itaconic acid derivative, an acrylic acid derivative, an anionic acrylamide derivative, an internal cross-linking agent, and a neutralizing agent;
(b) adding an initiator to the mixed solution and reacting to prepare a base resin containing a polyitaconic acid graft copolymer; and
(c) surface cross-linking the base resin with a surface cross-linking agent to form a surface cross-linking layer formed from the surface of the base resin to the inside, thereby producing a surface cross-linking treated superabsorbent resin;
The surface cross-linking agent includes aluminum sulfate, ethylene glycol digricidyl ether, 1,3-propanediol, 1,4-butanediol, and propylene glycol,
The anionic acrylamide derivative includes 2-Acrylamide-2-methylpropanesulfonic acid sodium salt (AMPS),
A method for producing a surface cross-linked superabsorbent polymer according to claim 1. According to clause 18,
In step (c),
The surface cross-linked superabsorbent polymer,
A method for producing a surface cross-linked superabsorbent resin, comprising 1 to 50 parts by weight of the surface cross-linking agent based on 100 parts by weight of the base resin. According to clause 18,
In step (c),
A method for producing a surface cross-linked superabsorbent polymer, characterized in that the surface cross-linking treatment is performed at a temperature of 100 ° C. to 200 ° C. for 10 minutes to 200 minutes.