KR20220160747A - 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 surface-crosslinked superabsorbent resin including: a base resin; and a surface crosslinking layer formed from the surface of the base resin to the inside by surface crosslinking treatment of the base resin with a surface crosslinking agent, wherein the base resin contains a poly(itaconic acid) graft copolymer produced through the polymerization and internal crosslinking of a raw material mixture including at least one of starch and oxidized starch, itaconic acid, acrylic acid derivative, anionic acrylamide derivative, and an internal crosslinking agent. Regarding the surface-crosslinked superabsorbent resin with excellent absorbency under pressure and a manufacturing method thereof according to the present invention, the resin, which is a biodegradable polymer with excellent absorbency, is water-soluble and biodegradable, thereby reducing the environmental burden due to disposal. Also, the resin is manufactured using eco-friendly materials as the main ingredients. Therefore, when applied to sanitary products, the resin is harmless to the human body and can reduce skin irritation. Moreover, using lower-cost materials helps reduce manufacturing costs and develop products with competitive pricing.

Description

Biodegradable superabsorbent polymer with excellent pressurized absorbency and manufacturing method thereof

The present invention relates to a superabsorbent polymer having excellent pressurized absorbency after surface crosslinking and a method for preparing the same, and more particularly, to a biodegradable superabsorbent polymer based on a biodegradable monomer such as itaconic acid and its preparation. It's about how.

Superabsorbent polymers have high absorbency and water retention, 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, recently, research is underway to use absorbent polymers with appropriate gel properties and adhesiveness as part materials for various electronic devices.

In the synthesis of superabsorbent polymers, acrylic acid-based resins, such as sodium polyacrylate crosslinked product, which are generally purified from crude oil, are used as raw materials. It is becoming. Therefore, recently, attempts have been made to use a cellulose derivative as a material having biodegradability and excellent absorbency, and in particular, the use of carboxymethyl cellulose containing a carboxylate in its structure has been studied. For example, a method of chemically crosslinking carboxymethylcellulose and a method of crosslinking using radiation crosslinking are known. However, in the above technology, when only a cellulose derivative is used as a starting material, there is a problem in that the production cost is high, and since the bond between the cross-linked portion and carboxymethyl cellulose is an ether bond, it is chemically stable and thus has a problem in terms of biodegradability.

On the other hand, a method for synthesizing superabsorbent polymers using cellulose, chitin, chitosan, etc. as raw materials and having biodegradability, absorption capacity and absorption rate comparable to existing acrylic acid-based resins has been introduced. Due to its extremely low solubility, it was effective only for some natural materials such as carboxylmethylcellulose (CMC). However, this also had a problem in that the solubility of the solvent was low, so that a high temperature and a long time for dissolution and dispersion were required, and the yield of the produced resin was also low. In addition, a method using succinic anhydride has been announced as a method of crosslinking cellulose-based materials with ester bonds that exhibit high biodegradability rather than ether bonds, but since the content of sodium carboxylic acid salt contained in the absorbent material obtained is small, the absorption rate There was a problem that could not be obtained except for a cross-linked product with a slow. Therefore, it is required to develop a material that can replace crosslinked sodium polyacrylate as a material that can be applied to sanitary products, and to develop a polymer having high absorbability and absorption rate while satisfying biodegradability and environmental friendliness.

On the other hand, IA (Itaconic Acid) is a water-soluble monomer that has two carboxylic acid groups in its molecule. It is a bio-mass-derived material produced through fermentation, and its chemical properties and safety have been proven. IA and IA derivatives are used in the chemical industry and medical fields. is an expanding trend. In particular, recently, through radical polymerization and crosslinking reaction based on IA

Manufactured PIA (Poly Itaconic Acid) Hydro-gel resin has excellent absorbency and decomposability, so it is expected to expand its use in various fields such as improvement materials that increase soil water retention. However, these PIA Hydrogel resins have disadvantages such as weak mechanical strength, especially compressive strength in a state where moisture is absorbed and expanded, that is, gel strength, and poor absorption capacity under pressure, so improvement is required.

On the other hand, PVA resin is a water-soluble resin commonly used in various fields such as film adhesives, and has biocompatibility and biodegradability. In particular, it has excellent mechanical properties, so various studies are underway as a gel material for absorbent resin. However, these PVA-based gel resins have limited absorption capacity, which is an obstacle to their use.

An object of the present invention is to solve the above problems, and to provide a polyitaconic acid-based biodegradable superabsorbent polymer containing starch, which has water solubility and biodegradability and thus reduces environmental burden due to disposal.

In addition, the present invention is to provide a surface cross-linked super absorbent polymer having excellent water absorbency, absorption rate, and absorbency under pressure by preparing a super absorbent polymer based on a water-soluble monomer and a biodegradable monomer.

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

In addition, by using low-cost raw materials, it is possible to provide materials useful for developing absorbent products that are advantageous in terms of price competitiveness by reducing manufacturing costs.

According to one aspect of the invention, the base resin; and a surface cross-linking layer formed from the surface of the base resin to the inside by surface cross-linking treatment of the base resin with a surface cross-linking agent, wherein the base resin is at least one of starch and oxidized starch, itaconic acid, an acrylic acid derivative, and an anionic acid. Provided is a surface cross-linking superabsorbent polymer comprising a polyitaconic acid graft copolymer prepared by polymerization and internal cross-linking of a raw material mixture including an acrylamide derivative and an internal cross-linking agent.

In addition, the polymerization reaction includes a radical reaction and a condensation reaction, the radical reaction is carried out by a radical reaction of at least one vinyl group selected from the group consisting of itaconic acid, acrylic acid derivatives and anionic acrylamide derivatives, and the condensation reaction The reaction may be performed 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 and acrylic acid derivatives.

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

In addition, 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 the structural formulas 1 to 3,

R ₁ and R ₂ are the same as or different from each other, and each independently represents 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.

In addition, 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.

In addition, the acrylic acid derivative may include at least one selected from the group consisting of acrylic acid, methacrylic acid and methyl methacrylic acid.

In addition, the polyitaconic acid graft copolymer is at least one vinyl polymer selected from the group consisting of itaconic acid, acrylic acid derivatives and anionic acrylamide derivatives; at least one of starch and oxidized starch grafted to the vinyl polymer; Polyitaconic acid grafted on at least one of the starch and oxidized starch, polyacrylic acid derivative grafted on at least one of the starch and oxidized starch, polyanionic acrylamide derivative grafted on at least one of the starch and oxidized starch , and at least one selected from the group consisting of an itaconic acid-acrylic acid derivative-anionic acrylamide derivative copolymer grafted onto at least one of the starch and oxidized starch; and an internal crosslinking agent for crosslinking 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.

In addition, the graft of the polyitaconic acid graft copolymer may be by at least one selected from the group consisting of an ester bond, an ionic bond, and a hydrogen bond.

In addition, 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 di 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'-Ethylenebis At least one selected from the group consisting of acrylamide (N,N'-Ethylenebisacrylamide) and N,N'-propylenebisacrylamide (N,N'-Propylenebisacrylamide) may be included.

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 metal cation.

Also, in Structural Formula 5, X is a sulfurous acid group (-SO ₃ ^- ), a sulfuric acid group (-SO ₄ ^- ), or a phosphoric acid group (-PO ₄ ^2- ), and Y is a hydrogen ion, Li ⁺ , Na ⁺ , K ⁺ , 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 be 2-ethylbutane sulfonic acid or a salt thereof.

The surface crosslinking agent may include at least one selected from the group consisting of a polyvalent cationic salt, an epoxy compound, and a polyhydric alcohol compound.

Among the multivalent cation salts, the 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 ^- ), a meta It may include at least one member 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 at least one selected from the group consisting of cyclohexanedimethanol.

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

According to another aspect of the present invention, (a) preparing a mixed solution containing at least one of starch and oxidized starch, itaconic acid, an acrylic acid derivative, an anionic acrylamide derivative, an internal crosslinking 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 treatment of 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 superabsorbent polymer. A method for producing a water absorbent polymer is provided.

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

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

The surface cross-linking treated superabsorbent polymer and the manufacturing method thereof of the present invention have water solubility and biodegradability, and thus have an effect of reducing environmental burden due to disposal.

In addition, according to the present invention, by preparing a superabsorbent polymer based on a water-soluble monomer and a biodegradable monomer, there is an effect of excellent water absorption, absorption rate, and absorbency under pressure.

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

In addition, by using low-cost raw materials, it is possible to develop products that are advantageous in terms of price competitiveness by reducing manufacturing costs.

1a and 1b are SEM analysis graphs of a base resin according to Preparation Example 1 and a superabsorbent polymer having excellent absorbency under pressure that is cross-linked according to Example 1
2 is a FT-IR analysis result of a base resin according to Preparation Example 1 and a superabsorbent polymer having excellent absorbency under pressure that is cross-linked according to Example 1
3 is a FT-IR analysis result of the base resin according to Control Examples 1 to 3 and Preparation Example 1.
4 is a TGA analysis result of the base resin according to Control Examples 1 to 3 and Preparation Example 1.

Since the present invention can apply various transformations and have various embodiments, specific embodiments will be exemplified and described in detail in the detailed description. However, it should be understood that this is not intended to limit the present invention to specific embodiments, and includes all transformations, equivalents, and substitutes included in the spirit and 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.

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

Singular expressions include plural expressions unless the context clearly dictates otherwise. In this application, the terms "include" or "have" are intended to designate that there is a feature, number, step, operation, component, part, or combination thereof described in the specification, but one or more other features It should be understood that the presence or addition of numbers, steps, operations, components, parts, or combinations thereof is not precluded.

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

The present invention base resin; and a surface cross-linking layer formed from the surface of the base resin to the inside by surface cross-linking treatment of the base resin with a surface cross-linking agent, wherein the base resin is at least one of starch and oxidized starch, itaconic acid, an acrylic acid derivative, and an anionic acid. Provided is a surface cross-linking superabsorbent polymer comprising a polyitaconic acid graft copolymer prepared by polymerization and internal cross-linking of a raw material mixture including an acrylamide derivative and an internal cross-linking agent.

The base resin is a raw material mixture including a water-soluble ethylenically unsaturated monomer including itaconic acid and acrylic acid derivatives, at least one of starch and oxidized starch, an anionic acrylamide derivative including vinylsulfonic acid or a salt thereof, and an internal crosslinking agent. It may include a copolymer in which the raw materials including polyitaconic acid prepared by polymerization reaction and internal crosslinking reaction are grafted with each other.

The polymerization reaction includes a radical reaction and a condensation reaction, the radical reaction is carried out by a radical reaction of at least one vinyl group selected from the group consisting of itaconic acid, acrylic acid derivatives and anionic acrylamide derivatives, and the condensation reaction This may be performed 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 and acrylic acid derivatives.

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

The starch may include at least one 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. It may include at least one selected from the group consisting of oxidized starch, acid-treated starch, ester starch, ether starch, phosphoric acid cross-linked starch, and acetyladipic acid starch. In addition, 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 refined corn starch. (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 the structural formulas 1 to 3,

R ₁ and R ₂ are the same as or different from each other, and each independently represents 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 at least one selected from the group consisting of acrylic acid, methacrylic acid, and methyl methacrylic acid.

The polyitaconic acid graft copolymer is at least one vinyl polymer selected from the group consisting of itaconic acid, acrylic acid derivatives and anionic acrylamide derivatives; at least one of starch and oxidized starch grafted to the vinyl polymer; Polyitaconic acid grafted on at least one of the starch and oxidized starch, polyacrylic acid derivative grafted on at least one of the starch and oxidized starch, polyanionic acrylamide derivative grafted on at least one of the starch and oxidized starch , and at least one selected from the group consisting of an itaconic acid-acrylic acid derivative-anionic acrylamide derivative copolymer grafted onto at least one of the starch and oxidized starch; and an internal crosslinking agent for crosslinking 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 by at least one selected from the group consisting of an ester bond, an ionic bond, and a hydrogen bond.

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 dimetha 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 At least one selected from the group consisting of amide (N,N'-Ethylenebisacrylamide) and N,N'-propylenebisacrylamide (N,N'-Propylenebisacrylamide) may be included.

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 metal cation.

In Structural Formula 5, X is a sulfurous acid group (-SO ₃ ^- ), a sulfuric acid group (-SO ₄ ^- ), or a phosphoric acid group (-PO ₄ ^2- ), and Y is a hydrogen ion, Li ⁺ , Na ⁺ , K ⁺ , 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 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 vinylsulfonate.

The surface crosslinking agent may include at least one selected from the group consisting of a polyvalent cationic salt, an epoxy compound, and a polyvalent al compound.

Among the multivalent cation salts, the 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 ^- ), a meta It may include at least one member 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 at least one selected from the group consisting of cyclohexanedimethanol.

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

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

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

Referring to Scheme 1 below, the bonding structure of the base resin can be grasped. A raw material mixture including water-soluble ethylenically unsaturated monomers including itaconic acid and acrylic acid derivatives, at least one of starch and oxidized starch, an anionic acrylamide derivative including vinylsulfonic acid or its salt, and an internal crosslinking agent is subjected to polymerization reaction and internal The base resin prepared by the crosslinking reaction is a four-component copolymer resin in which IA (itaconic acid) / AA (acrylic acid) / oxidized starch / AMPS (sodium vinylsulfonate) are mutually grafted.

[Scheme 1]

The present invention provides an absorbent material including a superabsorbent polymer having excellent absorbency under pressure, which has been surface-crosslinked.

The present invention provides sanitary products including the absorbent material.

Hereinafter, a method for producing a superabsorbent polymer having excellent absorbency under pressure after surface crosslinking treatment of 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 crosslinking 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 dimetha 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 At least one selected from the group consisting of amide (N,N'-Ethylenebisacrylamide) and N,N'-propylenebisacrylamide (N,N'-Propylenebisacrylamide) may be included.

The neutralizing agent may include at least one selected from the group consisting of a non-metal hydroxide, ammonium hydroxide, an organic base compound including an alkyl amine, and an organic compound including a hydroxyl group.

It is preferable to neutralize the itaconic acid with the neutralizing agent before polymerizing the itaconic acid. The neutralizing agent converts an 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 x is a neutralizing salt has a value provided) can be used for neutralization. In addition, non-metal hydroxides such as ammonium hydroxide, as well as organic amines, including primary amines (eg alkyl amines such as monomethyl amine, dimethylamine, trimethylamine, monoethylamine, diethylamine, triethylamine) A base compound and/or an organic compound containing a hydroxyl (OH) functional group (eg ethylene glycol) may be used.

The amount of neutralization can be adjusted to provide less than complete neutralization of the acidic groups present in the polyitaconic acids of the present disclosure. For example, for the representative monomer itaconic acid, it can be appreciated that complete neutralization would 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. If a divalent base is used to neutralize itaconic acid, the amount of divalent base selected to completely neutralize itaconic acid will be 1.0 moles of divalent base for each mole of itaconic acid, and for partial neutralization, less than 1 mole of divalent base will be applied. Itaconic acid monomers can be partially neutralized.

The neutralizing agent may be an organic base compound containing an amine group and an organic compound containing a hydroxyl 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 including a polyitaconic acid graft copolymer (step b).

The internal initiator may include at least one selected from the group consisting of a free radical initiator, a water-soluble radical initiator, and a water-soluble initiator. For example, peroxides and azo compounds such as azobisisobutyronitrile (AIBN) can be used for radical initiation, preferably a water-soluble radical initiator can be used, wherein the selected initiator is selected from 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. In addition, as the water-soluble initiator, hydrogen peroxide (H ₂ O ₂ ), tertiobutyl hydroperoxide, and a water-soluble azo initiator may also be included.

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

The surface crosslinking agent may include at least one selected from the group consisting of a polyvalent cationic salt, an epoxy compound, and a polyhydric alcohol compound.

Among the multivalent cation salts, the 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 ^- ), a meta It may include at least one member 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 at least one selected from the group consisting of cyclohexanedimethanol.

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

When the surface crosslinking agent is evenly sprayed onto the base resin and then exposed to a high temperature, crosslinking (condensation polymerization) proceeds on the surface of the base resin to increase the crosslinking density of the surface compared to the inside, thereby increasing the absorbency under load (AUL). ) and liquid permeability (SPT).

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

[Preparation of base resin]

Preparation Example 1

Itaconic acid (IA) 40% by weight, acrylic acid (Acrylic Acid AA) 50% by weight, 2-acrylamido-2-methyl-1-propanesulfonic acid sodium salt (2-Acrylamide-2-methylpropanesulfonic acid) 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). In the monomer composition solution, 0.08% by weight of Poly(ethyleneglycol) diacrylate (PEGDA), 0.08% by weight of 1,6-hexanediol diacrylate (HDODA) as an internal crosslinking agent, 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 (NaOH) was slowly introduced into the reactor to neutralize the monomer composition solution. While maintaining the internal temperature of the reactor at 60 ° C., nitrogen was introduced for 1 hour to remove oxygen inside the reactor. Polymerization was initiated by adding 0.5% by weight of sodium persulfate as an internal initiator. The polymerization process was carried out for 2 hours at an internal temperature of 60 °C. The polymerized water-containing gel polymer was transferred to a polypropylene container and dried for 24 hours in a hot air circulation type dryer preheated to 60 ° C. The dried water-containing gel polymer was placed in a freezer at minus 40°C and frozen for 4 hours. The frozen water-containing gel polymer was coarsely pulverized using a grinder. It was completely dried for 24 hours in a 60 ℃ hot air circulation dryer. The dried material was pulverized with a pulverizer, and a quaternary copolymer-based base resin (super absorbent polymer before surface crosslinking treatment) having a particle size of 300 to 600 μm was prepared using an ASTM standard classifier.

[Preparation of superabsorbent polymer treated with surface cross-linking]

Example 1

Aluminum sulfate 1.2 wt%, distilled water 38.5 wt%, ethylene glycol diglycidyl ether 4 wt%, 1,3-propanediol 4 wt%, 1,4-butanediol 4 wt%, propylene glycol A surface crosslinking agent was prepared by mixing 6.8% by weight of methanol, 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 evenly stirred at a stirring speed of 400 rpm, and 12.5% by weight of the surface crosslinking agent was evenly sprayed onto the base resin. Stirring was stopped and swelling was performed for 10 minutes to allow the surface crosslinking agent to penetrate into the base resin. The base resin into which the surface crosslinking agent swelled was placed in a self-made stainless cylinder and installed in a rotary oven. The surface cross-linking treatment was prepared by setting the temperature of the rotary oven to 170° C. as a surface cross-linking temperature and performing surface cross-linking for 60 minutes.

Example 2

A surface cross-linked superabsorbent polymer was prepared in the same manner as in Example 1, except that 10.0 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.

Example 3

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

Example 4

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

Example 5

Example 1 except for spraying 12.5% by weight of the surface crosslinking agent on the base resin and surface crosslinking for 60 minutes in Example 1, spraying 10.0% by weight of the surface crosslinking agent on the base resin and surface crosslinking for 90 minutes. A surface crosslinked superabsorbent polymer was prepared in the same manner.

Example 6

Example 1 except that 12.5% by weight of the surface crosslinking agent in Example 1 was sprayed on the base resin and surface crosslinked for 60 minutes instead of spraying 15.0% by weight of the surface crosslinking agent on the base resin and surface crosslinked for 90 minutes. A surface crosslinked superabsorbent polymer was prepared in the same manner.

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 diglycidyl 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 crosslinking 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, 61% by weight of methanol and konasil (K-200) in a composition of 0.3% by weight to prepare a surface cross-linking agent, except that the surface cross-linking superabsorbent polymer was prepared in the same manner as in Example 1.

Comparative Example 2

A surface crosslinked superabsorbent polymer was prepared in the same manner as in Comparative Example 1, except that 10.0% by weight of the surface crosslinking agent was sprayed on the base resin instead of spraying 12.5% by weight of the surface crosslinking agent on the base resin in Comparative Example 1.

Comparative Example 3

A surface crosslinked superabsorbent polymer was prepared in the same manner as in Comparative Example 1, except that 15.0% by weight of the surface crosslinking agent was sprayed on the base resin instead of spraying 12.5% by weight of the surface crosslinking agent on the base resin in Comparative Example 1.

Comparative Example 4

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

Comparative Example 5

In Comparative Example 1, except for spraying 12.5% by weight of the surface crosslinking agent on the base resin and surface crosslinking for 60 minutes, instead of spraying 10.0% by weight of the surface crosslinking agent on the base resin and surface crosslinking for 90 minutes, Comparative Example 1 and A surface crosslinked superabsorbent polymer was prepared in the same manner.

Comparative Example 6

In Comparative Example 1, except that 12.5% by weight of the surface crosslinking agent was sprayed on the base resin and surface crosslinked for 60 minutes, 15.0% by weight of the surface crosslinking agent was sprayed on the base resin and surface crosslinked for 90 minutes. A surface crosslinked superabsorbent polymer was prepared in the same manner.

[Test Example]

Test Example 1: SEM analysis before and after surface crosslinking

1a and 1b are SEM analysis images of a base resin according to Preparation Example 1 and a surface-crosslinked superabsorbent polymer according to Example 1. The analysis was taken using a SEM instrument (manufacturers: VEGA3, TESCAN, CZECH).

In order to increase the absorbency under pressure, it is possible to increase the content of the internal crosslinking agent, but the absorbency is relatively lowered. Therefore, in the core-cell structure, the proper degree of crosslinking inside the resin and the degree of surface crosslinking must be harmonized. Morphology should be formed, which can be confirmed through Figures 1a and 1b.

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

2 is a result of FT-IR analysis of a base resin according to Preparation Example 1 and a surface crosslinked superabsorbent polymer according to Example 1. Analysis was performed using KBr in a scan range of 400 to 4000 cm ^-1 .

According to FIG. 2, the peak appearing at about 1728 cm ^-1 is an ester C=O band (ester carbonyl band) in which a crosslinking reaction between the -OH functional group of oxidized starch and -COOH functional group of polyitaconic acid (PIA) or polyacrylic acid (PAA) has occurred. ), and it can be seen that the sensitivity of the peaks is changed by surface cross-linking treatment. In particular, the 1580 cm ^-1 , 1408 cm ^-1 and 1030 cm ^-1 peaks are each aliphatic related to the grafting structure of the polymer according to Example 1. It can be seen that the sensitivity is greatly changed by the surface crosslinking 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 with acrylic acid/itaconic acid/oxidized starch (AA /IA/OS) was used as Control Example 3, and FIG. 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 instrument (manufacturer: Nicolet Thermo Scientific, Nicolet 380, USA).

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

In particular, the resin (AA/IA/OS/AMPS) containing acrylic acid/itaconic acid/oxidized starch/AMPS (sodium vinylsulfonate) prepared according to Preparation Example 1 obtained the following analysis results. A carbonyl group peak was observed around 1700 cm ^-1 , and wide bands were formed around 3000 cm ^-1 and 3800 cm ^-1 due to the -OH group of oxidized starch. In addition, the peaks at about 2918 cm ^-1 , 1599 cm ^-1 , 1404 cm ^-1 and 1025 cm ^-1 are respectively attributed to aliphatic CH, COO- (asymmetric), COO- (symmetric) and CO functional groups of oxidized starch. In addition, about 2903 cm ^-1 , 1580 cm ^-1 , 1408 cm ^-1 and 1030 cm ^-1 peaks are respectively aliphatic CH, COO- (asymmetric), COO- (symmetric) and related to the grafting structure of the polymer according to Example 1 It is due to the CO functional group. And the peak appearing at about 1728 cm ^-1 is due to the ester C = O band (ester carbonyl band) in which a crosslinking reaction occurred between the -OH functional group of oxidized starch and -COOH functional group of polyitaconic acid (PIA) or polyacrylic acid (PAA) it did Based on the above analysis results, it can be predicted that a copolymer grafted between the base monomers injected in Preparation Example 1 is 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 with acrylic acid/itaconic acid/oxidized starch (AA /IA/OS) was used as Control Example 3, and FIG. 4 shows the TGA analysis results of Control Examples 1 to 3 and Preparation Example 1. The analysis was performed using a thermogravimetric analysis (TGA) instrument (manufacturer: METTLER TOLEDO, TGA 2, USA).

According to Figure 4, the decomposition temperature of PAA according to Control Example 1 is 450 ℃, PIA according to Control Example 2 is 360 ℃, terpolymer containing AA / IA / OS according to Control Example 3 is 220 ℃, Production Example The decomposition temperature of the quaternary copolymer including AA/IA/OS/AMPS according to No. 1 was displayed around 223° C., and it was confirmed that each resin had a different decomposition temperature.

Test Example 5: Performance Analysis of Super Absorbent Polymer

In Table 1 below, 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 were respectively described.

Retentive capacity (CRC) measurement

After adding 200 ml of distilled water to a beaker, quantifying and dissolving NaCl to form a 0.9 wt.% NaCl aqueous solution, 0.2 g of the superabsorbent polymer according to Examples 1 to 6 and Comparative Examples 1 to 6 of the present invention was added to a dried tea bag. After quantitative input, it is immersed in a beaker containing NaCl aqueous solution for 30 minutes, centrifuged at 300 gravity for 3 minutes to completely remove moisture simply attached to the surface, and then accurately weighed the swollen tea bag to obtain the following results. Swelling ratio was calculated by 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 added

Pressure absorption capacity (AUL) measurement

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

[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 polymers according to Examples 1 to 6 and Comparative Examples 1 to 6 of the present invention were swollen for 30 minutes by adding a sufficient amount of 0.9 wt% NaCl aqueous solution to a liquid permeability meter. The time until 20 ml of saline passed through the saline was measured while the load of 0.3 psi (= 106.26 g) was applied to the measuring cylinder.

Item Surface cross-linking agent 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 load were observed under most of the experimental conditions, but Examples 1 to 6 showed better absorbency, absorbency under load and liquid permeability than Comparative Examples 1 to 6, and in particular, Example 1 was the best case.

In the above, the preferred embodiment of the present invention has been described in detail, but the present invention is not limited to the above embodiment, and various modifications may be made by those skilled in the art within the scope of the technical idea of the present invention. It is 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 treatment of the base resin with a surface cross-linking agent;
The base resin includes a polyitaconic acid graft copolymer prepared by polymerization and internal crosslinking of a raw material mixture including at least one of starch and oxidized starch, itaconic acid, an acrylic acid derivative, an anionic acrylamide derivative, and an internal crosslinking agent. to do,
Superabsorbent polymer with surface cross-linking treatment. According to claim 1,
The polymerization reaction includes a radical reaction and a condensation reaction,
The radical reaction is carried out by a radical reaction of at least one vinyl group selected from the group consisting of itaconic acid, acrylic acid derivatives and anionic acrylamide derivatives,
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 carboxy group selected from the group consisting of itaconic acid and acrylic acid derivatives. Suzy. According to claim 1,
Surface cross-linking treatment characterized in that the internal cross-linking reaction is carried out by a radical reaction of at least one vinyl group selected from the group consisting of itaconic acid, acrylic acid derivatives and anionic acrylamide derivatives and the vinyl group of the internal cross-linking agent Suzy. According to claim 1,
The surface crosslinking-treated superabsorbent polymer, characterized in that the itaconic acid is 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 the structural formulas 1 to 3,
R ₁ and R ₂ are the same as or different from each other, and each independently represents 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 claim 1,
The surface cross-linking treated super absorbent polymer, 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 claim 1,
The surface cross-linking treated superabsorbent polymer, characterized in that the acrylic acid derivative contains at least one selected from the group consisting of acrylic acid, methacrylic acid and methyl methacrylic acid. According to claim 1,
The polyitaconic acid graft copolymer
at least one vinyl polymer selected from the group consisting of itaconic acid, acrylic acid derivatives and anionic acrylamide derivatives;
at least one of starch and oxidized starch grafted to the vinyl polymer;
Polyitaconic acid grafted on at least one of the starch and oxidized starch, polyacrylic acid derivative grafted on at least one of the starch and oxidized starch, polyanionic acrylamide derivative grafted on at least one of the starch and oxidized starch , and at least one selected from the group consisting of an itaconic acid-acrylic acid derivative-anionic acrylamide derivative copolymer grafted onto at least one of the starch and oxidized starch; and
An internal crosslinking agent for crosslinking at least one member selected from the group consisting of the vinyl polymer, polyitaconic acid, polyacrylic acid derivative, polyanionic acrylamide derivative, and the itaconic acid-acrylic acid derivative-anionic acrylamide derivative copolymer. Characterized in that the surface cross-linking treated super absorbent polymer. According to claim 7,
Surface cross-linking treated superabsorbent polymer, characterized in that the graft of the polyitaconic acid graft copolymer is by at least one selected from the group consisting of ester bonds, ionic bonds, and hydrogen bonds. According to claim 1,
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 dimetha 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 A surface cross-linked superabsorbent polymer comprising at least one selected from the group consisting of amide (N,N'-Ethylenebisacrylamide) and N,N'-propylenebisacrylamide (N,N'-Propylenebisacrylamide). According to claim 1,
The surface cross-linking treated superabsorbent polymer, characterized in that the anionic acrylamide derivative is represented by the following structural formula (5).
[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 metal cation. According to claim 10,
In Structural Formula 5,
X is a sulfurous acid group (-SO ₃ ^- ), a sulfuric acid group (-SO ₄ ^- ), or a phosphoric acid group (-PO ₄ ^2- );
Y is a hydrogen ion, Li ⁺ , Na ⁺ , K ⁺ , Ag ⁺ , Au ⁺ , Mg ²⁺ , Ca ²⁺ , Ba ²⁺ , Mn ²⁺ , Ni ²⁺ , or Cu ²⁺ Cross-linked superabsorbent polymer. According to claim 10,
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 2-ethylbutane sulfonic acid or a salt thereof, characterized in that the surface cross-linking treated superabsorbent polymer. According to claim 1,
The surface crosslinking-treated superabsorbent polymer, characterized in that the surface crosslinking agent comprises at least one selected from the group consisting of a polyvalent cationic salt, an epoxy compound, and a polyhydric alcohol compound. According to claim 13,
Among the multivalent cation salts, the 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 ^- ), a meta A surface cross-linked superabsorbent polymer comprising at least one member selected from the group consisting of a phosphoric acid group (PO ₃ ^- ) and a phosphoric acid group (PO ₄ ^{3 -} ). According to claim 13,
The surface crosslinking-treated superabsorbent polymer, characterized in that the epoxy compound comprises at least one selected from the group consisting of ethylene glycol diglycidyl ether and glycidol. According to claim 13,
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- A surface crosslinking-treated superabsorbent polymer comprising at least one selected from the group consisting of cyclohexanedimethanol. An absorbent material comprising the superabsorbent polymer subjected to surface cross-linking of claim 1. (a) preparing a mixed solution containing at least one of starch and oxidized starch, itaconic acid, an acrylic acid derivative, an anionic acrylamide derivative, an internal crosslinking agent and a neutralizing agent;
(b) preparing a base resin containing a polyitaconic acid graft copolymer by adding an initiator to the mixed solution and reacting; and
(c) preparing a surface cross-linked superabsorbent polymer by surface cross-linking treatment of the base resin with a surface cross-linking agent to form a surface cross-linking layer formed from the surface to the inside of the base resin;
A method for producing a superabsorbent polymer comprising surface cross-linking treatment. According to claim 18,
In step (c),
The surface cross-linking treated superabsorbent polymer,
Method for producing a surface cross-linked super absorbent polymer 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 claim 18,
In step (c),
The method for producing a surface cross-linked super absorbent polymer, characterized in that the surface cross-linking treatment is performed at a temperature of 100 ℃ to 200 ℃ for 10 minutes to 200 minutes.

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