TW201700501A - Method of preparing super absorbent polymer - Google Patents

Abstract

Provided is a method of preparing super absorbent polymer. The method comprising the steps of, preparing a base resin by adding at least one of compounds represented by Formula (1) below to the hydrogel crosslinked polymer; and drying the base resin. X-(R)n-Y.

Description

Method for preparing superabsorbent polymer

In this case, the priority of the Korean Patent Application No. 10-2015-0037502, the date of March 18, 2015, and all the rights accumulated therein are claimed. The disclosure of the present application is hereby incorporated by reference in its entirety.

Field of invention

This invention relates to a process for preparing superabsorbent polymers.

Background of the invention

Superabsorbent polymer (SAP) is a synthetic polymer material having a function of absorbing 500 to 1000 times its own weight of water. Depending on its developer, it has been distinguished as superabsorbent material (SAM) and absorbent gelling material ( AGM) and so on. Since the beginning of their practical application, these superabsorbent polymers have been widely used as materials in the following fields: soil water retention agents, water-blocking agents for civil engineering and construction, seeding sheets, food distribution products, and sanitary products. Such as baby diapers.

As a method of preparing a superabsorbent polymer, reverse phase suspension polymerization or aqueous solution polymerization is known. For example, the reversed-phase suspension polymerization is disclosed in JP-A-56-161408, JP-A-57-158209, and JP-A-57-198714. to In the aqueous solution polymerization, thermal polymerization in which polymerization is carried out by heating an aqueous solution, photopolymerization in which polymerization is carried out by irradiation of an aqueous solution with ultraviolet light, and the like are known.

Summary of invention

In the process for preparing a superabsorbent polymer, a water soluble component is produced which is a non-crosslinked polymer, and a residual monomer. The content of the water-soluble component and the residual monomer varies depending on the content of the polymerization initiator, the polymerization temperature, the content of the internal crosslinking agent, the surface crosslinking conditions, and the like.

When the content of the water-soluble component and the residual monomer is high, the surface of the diaper becomes sticky, or the liquid permeability thereof is lowered, which may cause skin diseases and cause bad odor.

The present invention is directed to a method for preparing a superabsorbent polymer, whereby the method can improve the processability by removing the surface cross-linking treatment, and obtain a comparative surface cross-linked superabsorbent polymer containing a small amount of water-soluble components. Superabsorbent polymer.

However, the scope of the invention is not limited by the statements herein. The above-mentioned and other aspects of the present invention will become more apparent from the detailed description of the invention.

In accordance with an embodiment of the present invention, a method of making a superabsorbent polymer is presented. The method is a method for preparing a bare superabsorbent resin, and comprises the steps of: preparing a hydrogel crosslinked polymer by polymerizing a monomer composition comprising a hydrophilic monomer, a crosslinking agent, and a polymerization initiator; Preparing a base resin by adding at least one of the compounds represented by the formula (1) to the hydrogel crosslinked polymer; drying the base resin; and pulverizing the dried basic Resin. The bare superabsorbent resin may have an extractable content (EC) of greater than 0% to less than 15% and a residual monomer (RM) concentration of more than 0 ppm of at least 1000 ppm, preferably, may have greater than 0% to less than 15%. An extractable content (EC) and a residual monomer (RM) concentration of more than 0 ppm of at least 600 ppm.

In a specific embodiment, the method may further comprise: preparing a monomer composition, and the monomer composition may include a hydrophilic monomer, a crosslinking agent, a polymerization initiator, a neutralizing agent, and a solvent. For example, preparing the monomer composition may include: preparing a first composition including a neutralizing agent and a solvent; preparing a second composition including a hydrophilic monomer, a crosslinking agent, and a polymerization initiator; and mixing the The first composition and the second composition.

In one embodiment, preparing the hydrogel crosslinked polymer can include: polymerizing the monomer composition; and pulverizing the hydrogel crosslinked polymer.

In one embodiment, the polymerization initiator includes a photopolymerization initiator or a complex polymerization initiator, and, for example, the composite polymerization initiator includes a photopolymerization initiator and a thermal polymerization initiator.

X-(R) _n -Y...(1)

In a specific embodiment, in the formula (1), X may be an unsaturated hydrocarbon group or a group derived therefrom, for example, X may be a monovalent atom group of at least one of the following: C _2-5 ( Methyl)vinyl (CH ₂ =CR _a -, R _a is a hydrogen atom, or a C _1-3 hydrocarbyl group or a group derived therefrom), C _3-5 (meth)allyl (CH ₂ =CR _b -CH ₂ -, R _b is a hydrogen atom, or a C _1-2 hydrocarbyl group or a group derived therefrom), a C _1-5 fluorenyl group (R _c C(=O)-, R _c is a hydrogen atom, or C _{1 -4} hydrocarbon or a group derived therefrom), C _3-5 of (meth) Bing Xixi group _{(CH 2 = CR d -C (} = O) -, R d is a hydrogen atom, or a C _1-2 hydrocarbon radical, or a derivative group), and a (meth) propylene fluorenyloxy group of C _3-5 (CH ₂ =CR _e -C(=O)-O-, R _e is a hydrogen atom, or a C _1-2 hydrocarbon group or Derived group). In one embodiment, X may be a C _3-5 (meth) acryl fluorenyl group (CH ₂ =CR _d -C(=O)-, R _d is a hydrogen atom, or a C _1-2 hydrocarbyl group or a derivative thereof Group).

In one specific embodiment, in Formula (1), R is at least one of the following divalent group of atoms: The C _1-5 alkylene _{(- (CH 2) m -} , m is 1 to An integer of 5), a C _1-4 alkyloxy group (-(CH ₂ ) _m -O-, m is an integer from 1 to 4), a C _2-6 alkyl (oxy)carbonyl group (- (R _f ) _o -(C=O)-(R' _f ) _p -, o and p are each independently an integer from 0 to 2 and not simultaneously 0, and R _f and R' _f are each independently C _a hydrocarbyl group of _1-5 or a derivative thereof), and a carbonyloxy group of C _2-5 (-(R _g ) _r -(C=O)-O-, r is an integer of 0 to 2, and R _g is C _1-4 hydrocarbyl group or a group derived therefrom).

In one embodiment, n can be an integer from 2 to 20; and Y can be a hydrophilic group. The hydrophilic group may be any one of a hydroxyl group (-OH), a carboxyl group (-COOH), and an amine group (-NHR _h , -NH ₂ , or -NR _h2 , and _Rh is a C _1-5 hydrocarbon group). In one embodiment, the hydrophilic group can be a hydroxyl group.

In a specific embodiment, at least one of the compounds represented by the formula (1) is at least one of the compounds represented by the following formula (2):

In a specific embodiment, in the formula (2), R ₁ is any one of a C _1-2 alkyl group and a C _1-2 alkoxy group; and R ₂ is a C _1-5 alkylene group (- (CH ₂ ) _m -, m is an integer of 1 to 5) and a C _1-5 alkyloxy group (-(CH ₂ ) _m -O-, m is an integer of 1 to 5) Y is any one of a hydroxyl group (-OH), a carboxyl group (-COOH), and an amine group (-NHR _h , -NH ₂ , or -NR _h2 ).

In a specific embodiment, in the formula (2), n may be an integer of 2 to 20.

In a specific embodiment, at least one of the compounds represented by the formula (2) may be at least one of the compounds represented by the formulas (3) to (14):

As will be described later, embodiments in accordance with the present invention have the following effects.

The method for producing a superabsorbent polymer according to the present invention can be removed by surface cross-linking treatment, so that workability can be improved.

Further, according to the method for producing a superabsorbent polymer of the present invention, a superabsorbent polymer having a centrifugal retention capacity (CRC) and a pressure absorption (AUP) equal to surface cross-linking can be obtained, and superabsorbent polymerization which compares surface cross-linking can be obtained. The material contains a small amount of water soluble component (EC) and residual monomer (RM).

The effects of the present invention are not limited to the foregoing, and various other kinds are contemplated. effect.

P1-6, P11-13, P21, P22‧‧‧ steps

The above and other aspects of the present invention will become more apparent from the detailed description of the embodiments illustrated in

BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 is a schematic flow diagram of a process for preparing a superabsorbent polymer in accordance with one embodiment of the present invention.

Detailed description of the preferred embodiment

The advantages and features of the present invention and the method for accomplishing the same are more readily understood by reference to the detailed description and the accompanying drawings. However, the invention may be embodied in many different embodiments and should not be construed as being limited to the embodiments set forth herein. Instead, the present invention is intended to be more complete and complete, and the concept of the present invention will be fully conveyed by those skilled in the art, and the invention will be limited only by the scope of the accompanying claims.

Although the terms "first, second, etc." are used to describe a variety of constituent elements, such constituent metasystems are not limited by such terms. These terms are only used to distinguish one constituent element from another constituent element. Accordingly, in the following description, the first constituent element may be the second constituent element.

In the present specification, "surface-crosslinked superabsorbent polymer" is defined as a superabsorbent polymer having a core-shell structure in which a base resin is used as a core, and a surface crosslinked layer is formed on the surface of the core.

In the present specification, "naked superabsorbent polymer" is defined as a superabsorbent polymer in which no surface crosslinked layer is formed on the surface of the base resin.

In the present specification, "hydrogel crosslinked polymer" means any one of a flaky hydrogel crosslinked polymer and a particulate hydrogel crosslinked polymer.

In the present specification, "C _AB " indicates that the number of carbon atoms is A to B. For example, "C _1-5 alkyl" is an alkyl group of 1 to 5 carbon atoms. In the present specification, "C and/or D" is defined as C, D, or C and D. In the present specification, "E to F" is defined as E or more to F or below.

In the present specification, the "unsaturated hydrocarbon group" is defined as a monovalent atom group which is a residue obtained by removing one hydrogen atom from a hydrocarbon having an unsaturated bond. Examples of the unsaturated hydrocarbon group may include a (meth)vinyl group and a (meth)allyl group.

In the present specification, "alkyl" includes linear or branched alkyl groups, and examples thereof include n-butyl and tert-butyl. In the present specification, "(meth)vinyl group" is a monovalent atom group having a double bond at its terminal, and is represented by CH ₂ =CR _a -. Vinyl group in R _a is a hydrogen atom, methyl group and vinyl group in R _a is an alkyl group. In the present specification, "(meth)allyl" is a monovalent atomic group having a double bond at its terminal, and is represented by CH ₂ =CR _b -CH ₂ -. In the allyl group, R _b is a hydrogen atom, and in the methallyl group, R _b is an alkyl group.

In the present specification, a "G derivative" is defined as a derivative in which a part or all of hydrogen atoms of an unsaturated hydrocarbon group or an alkyl group of G are substituted by other atoms excluding carbon atoms and hydrogen atoms, or are included Substitution of atomic groups of other atoms other than carbon atoms and hydrogen atoms, such as oxygen (O), nitrogen (N), carbonyl (-(C=O)-), fluorenyl (R _c C(=O)-), And (meth)acrylonitrile (CH ₂ =CR _d -C(=O)-).

In the present specification, "alkoxy" is a derivative in which a monovalent atom group is bonded to an oxygen atom and an alkyl group. The alkyl group can be a linear or branched alkyl group. In the present specification, "mercapto" is a monovalent atomic group in which a carbonyl group is bonded to a hydrocarbon group or a derivative thereof, and is represented by R _c C(=O)-. In the fluorenyl group, R _c is a hydrogen atom or a C _1-5 hydrocarbon group and a derivative thereof. In the present specification, "(meth)acrylinyl" is a monovalent atomic group in which a (meth)vinyl group is bonded to a carbonyl group and is represented by CH ₂ =CR _d -C(=O)-. In the propylene fluorenyl group, R _d may be a hydrogen atom, and in the methacryl fluorenyl group, R _d may be an alkyl group or a like. In the present specification, "(meth)acrylenyloxy" is a monovalent atomic group in which a (meth)acryloyl group is bonded to an oxygen atom, and CH ₂ =CR _e -C(=O ) -O- indicates. R _e may be a hydrogen atom in the propylene fluorenyloxy group, and R _d may be an alkyl group or the like in the methacryloyloxy group.

In the present specification, "alkylene group" is a divalent atom group composed of a carbon atom and a hydrogen atom, and is represented by -(CH ₂ ) _m -. Examples of the alkylene group may include methylene (-CH ₂ -), ethylidene (-CH ₂ CH ₂ -), and the like. In the present specification, "alkyleneoxy group" is a divalent atom group in which an alkyl group is bonded to an oxygen atom and is represented by -(CH ₂ ) _m -O-. Examples of the alkyleneoxy group may include a methyleneoxy group (-CH ₂ O-, -OCH ₂ -), an extended ethyloxy group (-CH ₂ CH ₂ O-, -OCH ₂ CH ₂ -), and Its class. In the present specification, "alkyl(oxy)carbonyl" is a divalent atom group in which an alkyl (oxy) group is bonded to a carbonyl group, and -(R _f ) _o -(C=O) -(R' _f ) _p - indicates. Examples of (oxy) alkylene carbonyl group of the carbonyl group may include methylene _{(-CH 2 - (C = O} ) -), carbonyloxy methylene _{(-CH 2 - (C = O} ) -CH 2 -) , methyleneoxycarbonyl (-CH ₂ -O-(C=O)-), dimethyleneoxycarbonyl (-CH ₂ -O-(C=O)-OCH ₂ -, -OCH ₂ - (C=O)-CH ₂ -O-), and its class. In the present specification, "carbonyloxy group" is a divalent atom group in which a carbonyl group is bonded to an oxygen atom, and is represented by -(R _g ) _r -(C=O)-O-. Examples of the carbonyloxy group may include a carbonyloxy group (-(C=O)-O-), a methylenecarbonyloxy group (-CH ₂ -(C=O)-O-), and the like.

In the present specification, the "amine group" is a residue obtained by removing one hydrogen atom from ammonia, and may be represented by -NHR _h , -NH ₂ , or -NR _h2 . In the amine group, _Rh can be an alkyl group or a like.

BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 is a schematic flow diagram of a process for preparing a superabsorbent polymer in accordance with one embodiment of the present invention.

Referring to Figure 1, a method of preparing a superabsorbent polymer according to an embodiment of the present invention comprises the steps of: (P1) preparing a monomer composition; (P2) preparing a hydrogel crosslinked polymer; (P3) by the following formula (1) at least one of the indicated compounds is added to the hydrogel crosslinked polymer to prepare a base resin; (P4) a powdered base resin; (P5) a dried powdered base resin (hereinafter referred to as " The powdered product "); and (P6) pulverize the dried base resin (hereinafter referred to as "dry product").

The step (P2) of preparing the hydrogel crosslinked polymer may further comprise the step of pulverizing the hydrogel crosslinked polymer (P21), and the step of pulverizing the hydrogel crosslinked polymer (P21) to prepare water The step of gel cross-linking the polymer (P2) is carried out.

The step (P1) of preparing the monomer composition may include the following steps: (P11) preparing a first composition including a neutralizing agent and a solvent; (P12) preparing comprising a hydrophilic monomer, a crosslinking agent, and a polymerization initiator a second composition; and (P13) mixing the first composition with the second composition. The monomer composition can include A hydrophilic monomer, a crosslinking agent, a polymerization initiator, and a neutralizing agent and a solvent.

The hydrophilic monomer to be used is not limited as long as it is generally used for preparing a superabsorbent polymer. The hydrophilic monomer is a monomer having a hydrophilic group, and examples of the hydrophilic group may include a hydroxyl group (-OH), a carboxyl group (-COOH), and an amine group (-NHR _h , -NH ₂ , or -NR _h2 , here, R _h may be a C _1-5 alkyl group or a class thereof.

The hydrophilic monomer may be a water-soluble unsaturated ethylene-based monomer. The water-soluble unsaturated ethylene-based monomer may be at least one of an anionic monomer and a salt thereof, a nonionic hydrophilic monomer, and an amine-containing unsaturated monomer and a fourth salt thereof. .

Examples of the anionic monomer and salts thereof may include acrylic acid, methacrylic acid, anhydrous maleic acid, fumaric acid, crotonic acid, itaconic acid, 2-propenyl mercaptoethanesulfonic acid, 2- Methyl propylene decylethane sulfonic acid, 2-(meth) propylene decyl propane sulfonic acid, and 2-(methyl) acrylamide amide methyl ketone sulfonic acid.

Examples of the nonionic hydrophilic monomer may include (meth) acrylamide, N-substituted (meth) acrylate, 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (A) Acrylate, methoxypolyethylene glycol (meth) acrylate, and polyethylene glycol (meth) acrylate.

Examples of the amino group-containing unsaturated monomer and the fourth salt thereof may include (N,N)-dimethylaminoethyl (meth) acrylate and (N, N)-dimethylaminopropyl Base (meth) acrylamide.

Considering the polymerization time and reaction conditions (feed rate of monomer composition, heat and/or light irradiation time, irradiation range, irradiation intensity, etc.), single The concentration of the water-soluble unsaturated ethylene-based monomer in the bulk composition can be appropriately selected and used. In this particular embodiment, the concentration of the water-soluble unsaturated ethylene-based monomer may range from 40 wt% to 60 wt%.

As the crosslinking agent, a crosslinking agent having at least one functional group and at least one unsaturated olefinic group which can react with a substituent of the monomer, or having two or more functional groups which can be substituted with the monomer can be used. a crosslinking agent which reacts with a substituent formed by hydrolysis of the monomer.

Poly (meth) in this particular embodiment, examples of the crosslinking agent may include C _8-12 II of acrylamide, methyl acrylamide II of C _8-12, C _2-12 polyhydric alcohols of acrylic acid Poly(meth)allyl ether of ester, and C _2-10 polyol.

Specific examples of the crosslinking agent may include, but are not limited to, (poly)ethylene glycol (meth) acrylate, (poly) propylene glycol (meth) acrylate, trimethylolpropane tri (meth) acrylate , ethoxylated (3)-trimethylolpropane tri(meth) acrylate, ethoxylated (6)-trimethylolpropane tri(meth) acrylate, ethoxylated (9) - Trimethylolpropane tri(meth)acrylate, ethoxylated (15)-trimethylolpropane tri(meth)acrylate, glycerol tri(meth)acrylate, glycerol acrylate methacrylate Ester, 2,2-indole [(propenyloxy)methyl]butyl acrylate (3EO), N, N'-methylene hydrazine (meth) acrylate, ethyl ethoxy (methyl) Acrylate, polyethyloxy (meth) acrylate, propyl oxy (meth) acrylate, glycerin diacrylate, triglyceride, trimethylolpropane triacrylate, triene Alkylamine, triaryl cyanurate, triallyl isocyanate, polyethylene glycol, diethylene glycol, propylene glycol, and mixtures of two or more thereof.

In this particular embodiment, the hydrophilic monomer is 100 parts by weight. For the purpose of the reference, the content of the crosslinking agent may be from 0.01 to 0.5 part by weight, but is not limited thereto.

The polymerization initiator may be at least one of a photopolymerization initiator, a thermal polymerization initiator, and an oxidation-reduction initiator. The polymerization initiator may be a complex polymerization initiator including two or more polymerization initiators. For example, the complex polymerization initiator may include a photopolymerization initiator and a thermal polymerization initiator. Further, for example, the composite polymerization initiator may include a thermal polymerization initiator and an oxidation-reduction initiator.

The photopolymerization initiator can start the polymerization of the monomer composition by irradiating ultraviolet rays, the thermal polymerization initiator can start the polymerization of the monomer composition by heating, and the oxidation-reduction initiator can be oxidized-reduced by the oxidation-reduction reaction. The polymerization of the starting monomer composition. When both a photopolymerization initiator and a thermal polymerization initiator are used, the polymerization of the monomer composition can be carried out by using a thermal polymerization initiator using heat generated during photopolymerization. When both the oxidation-reduction initiator and the thermal polymerization initiator are used, the polymerization of the monomer composition can be carried out by using a heat polymerization initiator using heat generated during the oxidation-reduction reaction.

Examples of the polymerization initiator may include, but are not limited to, an acetophenone derivative such as diethoxyacetophenone, 2-hydroxy-2-methyl-1-phenylpropan-1-one, 4- (2-hydroxyethoxy)phenyl-(2-hydroxy)-2-propylmethanone, and 1-hydroxycyclohexyl phenyl ketone; benzoin alkyl ethers such as benzoin methyl ether, benzoin ethyl Ether, benzoin isopropyl ether, and benzoin isobutyl ether; benzophenone derivatives such as methyl o-benzhydryl benzoate, 4-phenyl benzophenone, 4-benzhydrazide -4'-methyl-diphenyl sulfide, and (4-benzylidene-benzyl)trimethylammonium chloride; 9-oxosulfur (thioxanthone)-based compound; mercaptophosphine oxide derivatives such as ruthenium (2,4,6-trimethylbenzylidene)-phenylphosphine oxide and diphenyl (2,4,6- Trimethyl benzhydryl)-phosphine oxide; azo compounds such as 2-hydroxy-methyl-propionitrile and 2,2'-(azo-indole (2-methyl-N-(1,1) '-贰(hydroxymethyl)-2-hydroxyethyl)propanamide); and mixtures thereof. Here, the thermal polymerization initiator is not particularly limited, but examples thereof include an azo-based initiator a peroxide-based initiator, a redox-based initiator, and an organic halide-based initiator. They may be used singly or as a mixture of two or more of them. Specific examples of the polymerization initiator may include, but are not limited to, sodium persulfate (Na ₂ S ₂ O ₈ ) and potassium persulfate (K ₂ S ₂ O ₈ ).

If the polymerization initiation effect can be exerted, the content of the polymerization initiator can be appropriately selected. For example, the photopolymerization initiator may be contained in the monomer composition in an amount of 0.005 to 0.5 part by weight based on 100 parts by weight of the hydrophilic monomer, and based on 100 parts by weight of the hydrophilic monomer. The thermal polymerization initiator may be contained in the monomer composition in an amount of from 0.01 to 0.5 part by weight.

A neutralizing agent is used to neutralize the hydrophilic monomer. Typical examples thereof may include, but are not limited to, sodium hydroxide and sodium hydrogencarbonate. The amount of the neutralizing agent may be such that the degree of neutralization of the monomer composition falls within the range of from 65 mol% to 75 mol%. However, the invention is not limited thereto.

The solvent can be water and water can be used as a polymerization medium.

The step (P2) of preparing a hydrogel crosslinked polymer may include a step (P21) of polymerizing a monomer composition, and a step (P22) of pulverizing a sheet-like hydrogel crosslinked polymer.

Photopolymerization in the step (P21) of polymerizing the monomer composition And/or thermal polymerization is carried out by applying light and/or heat to the monomer composition. For example, when the monomer composition is irradiated with ultraviolet light, photopolymerization is initiated by photopolymerization initiator. As an example, the monomer composition includes both a photopolymerization initiator and a thermal polymerization initiator, and the thermal polymerization initiator can initiate thermal polymerization by using heat generated during the photopolymerization reaction. The polymerization can be carried out using a belt type polymerization reactor, and a sheet-like hydrogel crosslinked polymer can be obtained by the polymerization.

In the step (P22) of pulverizing the sheet-like hydrogel crosslinked polymer, the sheet-like hydrogel crosslinked polymer is pulverized into a granular hydrogel having a particle size of 1 cm (cm) to 3 cm. Copolymer. The water content of the particulate hydrogel crosslinked polymer may be, for example, from about 40% by weight (wt%) to about 60% by weight.

After the step (P2) of preparing the hydrogel crosslinked polymer, a step of preparing a base resin by adding at least one of the compounds represented by the following formula (1) to the hydrogel crosslinked polymer (P3) ).

At least one of the compounds represented by the following formula (1) can reduce the value of the extractable content (EC) by reacting with the non-crosslinked linear polymer chain, and can reduce the residue by reacting with the unreacted monomer The value of the monomer (RM) concentration.

<Formula(1)>X-(R) _n -Y

In the formula (1), X is an unsaturated hydrocarbon group or a group derived therefrom.

In the formula (1), R is a divalent atom group of at least one of the following: a C _1-5 alkyl group (-(CH ₂ ) _m -, m is an integer of 1 to 5), C _{1 -4} alkyleneoxy (-(CH ₂ ) _m -O-, m is an integer from 1 to 4), C _2-6 alkyl (oxy) carbonyl (-(R _f ) _o - ( C=O)-(R' _f ) _p -, o and p are each independently an integer from 0 to 2 and not simultaneously 0, and R _f and R' _f are each independently a C _1-5 hydrocarbon group or a derivatizing group), and a C _2-5 carbonyloxy group (-(R _g ) _r —(C=O)-O-, r is an integer of 0 to 2, and R _g is a C _1-4 hydrocarbon group or Derived group).

In the formula (1), n is an integer of 2 to 20, and Y is a hydrophilic group. The hydrophilic group can form a hydrogen bond by reacting with an unreacted monomer and reacting with a linear polymer chain.

X is a monovalent atomic group of at least one of: C _2-5 (meth)vinyl group (CH ₂ =CR _a -, R _a is a hydrogen atom, or a C _1-3 hydrocarbon group or a derivative thereof group), C _3-5 of (meth) allyl _{(CH 2 = CR b -CH 2} -, R b is a hydrogen atom, or a C _1-2 hydrocarbon or a group derived therefrom), C _1-5 of Sulfhydryl (R _c C(=O)-, R _c is a hydrogen atom, or a C _1-4 hydrocarbyl group or a group derived therefrom), a C _3-5 (meth) propylene fluorenyl group (CH ₂ =CR _d - C(=O)-, R _d is a hydrogen atom, or a C _1-2 hydrocarbyl group or a group derived therefrom, and a C _3-5 (meth) acryloyloxy group (CH ₂ =CR _e -C ( =O)-O-, R _e is a hydrogen atom, or a C _1-2 hydrocarbyl group or a group derived therefrom. In particular, X may be a (meth)acryloyl group of C _3-5 (CH ₂ =CR _d -C(=O)-, R _d is a hydrogen atom, or a C _1-2 hydrocarbon group or a group derived therefrom).

Y may be any of a hydroxyl group (-OH), a carboxyl group (-COOH), and an amine group (-NHR _h , -NH ₂ , or -NR _h2 , and _Rh is a C _1-5 hydrocarbon group). In particular, the hydrophilic group may be a hydroxyl group.

At least one of the compounds represented by the formula (1) has improved reactivity with a hydrogel crosslinked polymer having a hydrophilicity in the range of the number of carbon atoms of R and an n value of R. Conversely, when the number of carbon atoms or n of R increases, the water repellency increases, and thus crosslinks with the hydrogel having hydrophilicity. The reactivity of the polymer may be reduced.

The content of at least one of the compounds represented by the formula (1) may range from 1% by weight to 10% by weight based on the total weight of the bare superabsorbent polymer. When the content of at least one of the compounds represented by the formula (1) falls within the foregoing range, the extractable content (EC) of the superabsorbent polymer of the present invention and the residual monomer (RM) concentration thereof The value can be reduced to a lesser extent than the value of a conventional surface crosslinked superabsorbent polymer, and its centrifuge retention capacity (CRC) can have a level equal to the CRC of a conventional surface crosslinked superabsorbent polymer.

At least one of the compounds represented by the formula (1) may be at least one of the compounds represented by the following formula (2).

In formula (2), R ₁ is C _1-2 alkyl and C _1-2 alkoxy any one of; R & lt extension ₂ is the C _1-5 alkyl _{(- (CH 2) m -} , m is an integer of 1 to 5) and a C _1-5 alkyloxy group (-(CH ₂ ) _m -O-, m is an integer of 1 to 5); and Y is a hydroxyl group (- Any of OH), a carboxyl group (-COOH), and an amine group (-NHR _h , -NH ₂ , or -NR _h2 ). In the formula (2), n is an integer of 2 to 20. Within the number of carbon atoms of R ₁ , the carbon-carbon double bond (C=C) in the (meth) acrylonitrile group can be chemically bonded to the unreacted monomer and the linear polymer chain without steric blocking.

At least one of the compounds represented by the formula (2) may be at least one of the compounds represented by the formulae (3) to (14).

In the step (P4) of pulverizing the base resin, the base resin is roughly pulverized into particles having a particle size of a millimeter (mm). The step of pulverizing the base resin (P4) can be carried out using a blade cutter, a mashing cutter, a kneading cutter, a vibration pulverizer, an impact pulverizer, or a friction pulverizer.

The drying step (P5) of the pulverized base resin can be carried out at a temperature of from about 150 ° C to about 200 ° C for about 20 minutes to 40 minutes. The drying step (P5) of the pulverized base resin can be carried out using a hot air dryer, a fluid bed dryer, a quick dryer, an infrared dryer, or a dielectric heating dryer.

In the step (P6) of pulverizing the dried base resin, the dried product is finely pulverized into particles having a particle size of micrometer (μm). The step (P6) of pulverizing the dried base resin may include the step of classifying particles having an average particle size of 150 μm to 850 μm.

A method of preparing a superabsorbent polymer can provide a bare superabsorbent polymer. The bare superabsorbent polymer may have a degree of centrifuge retention (CRC) and pressure absorption (AUP) to the extent that the surface cross-linked superabsorbent polymer, and may have a superabsorbent polymer having a lower level than surface cross-linking. The level of extractable content (EC) and residual monomer (RM) concentration.

The invention will be described in detail below with reference to the following examples and experimental examples.

<Preparation Example 1>

77.778 grams of a 50% aqueous caustic soda (NaOH) solution and 88.84 grams of water were mixed to form a mixed solution. Then, 100 g of acrylic acid, 0.115 g of 2,2-indole [(propenyloxy)methyl]butyl acrylate (3EO), 0.115 g of polyethylene glycol diacrylate (Mw=400) was added as a crosslinking agent. And 0.033 g of diphenyl(2,4,6-trimethylbenzylidene)-phosphine oxide as a photopolymerization initiator added to the mixed solution, thereby preparing a monomer having a hydrophilic monomer concentration of 45 wt% Composition.

1.33 g of potassium persulfate as a thermal polymerization initiator was dissolved in 8.67 g of water to obtain a solution, and 3.008 g of a solution was mixed with a monomer composition.

Then, the obtained monomer composition was placed in a polymerization reactor continuously moving on a conveyor belt at a temperature of 40 ° C, irradiated with ultraviolet light by a UV irradiation device (light dose: 9 Mw/cm ² ), and then UV-polymerized for 3 minutes, thereby preparing a tablet. Hydrogel crosslinked polymer.

The sheet-like hydrogel crosslinked polymer was transferred to a cutter and then cut into a size of 2 cm to obtain a particulate hydrogel crosslinked polymer. In these cases, the obtained granular hydrogel crosslinked polymer had a water content ratio of 50% by weight.

<Preparation Example 2>

The granulated hydrogel crosslinked polymer was prepared in the same manner as in Preparation Example 1, except that 0.033 g of diphenyl(2,4,6-trimethylbenzylidene)-phosphine oxide and 2.256 g of water were used. The monomer composition of the potassium persulfate solution was supplied to a polymerization reactor continuously moving on a conveyor belt at a temperature of 30 ° C, and then irradiated with ultraviolet light for 2 minutes.

<Preparation Example 3>

The granulated hydrogel crosslinked polymer was prepared in the same manner as in Preparation Example 1, except that 0.033 g of diphenyl(2,4,6-trimethylbenzylidene)-phosphine oxide and 2.256 g of water were used. The monomer composition of the potassium persulfate solution was supplied to a polymerization reactor continuously moving on a conveyor belt at a temperature of 20 ° C, and then irradiated with ultraviolet light for 2 minutes.

<Example 1>

100 g of the granulated hydrogel crosslinked polymer of Preparation Example 1 was uniformly mixed with 2 g of an ethoxylated (6) methacrylate compound (Bisomer PEM6LD), and then mashed by a mincer. Subsequently, the pulverized granulated hydrogel crosslinked polymer was dried by a hot air dryer at a temperature of 180 ° C for 30 minutes, and the dried granulated hydrogel crosslinked polymer was pulverized by a corner pulverizer. Thereafter, a bare superabsorbent polymer having an average particle size of 150 to 850 μm was prepared by sieving.

<Example 2>

A bare superabsorbent polymer was prepared in the same manner as in Example 1, except that 100 g of the particulate hydrogel crosslinked polymer of Preparation Example 2 and 1 g of an ethoxylated (6) methacrylate compound (Bissomo PEM6LD) Mix evenly.

<Example 3>

A bare superabsorbent polymer was prepared in the same manner as in Example 1, except that 100 g of the granulated hydrogel crosslinked polymer of Preparation Example 2 and 2 g of the ethoxylated (6) methacrylate compound (Bissomo PEM6LD) Mix evenly.

<Example 4>

A bare superabsorbent polymer was prepared in the same manner as in Example 1, but 100 g of the granular hydrogel crosslinked polymer of Preparation Example 3 and 2 g of ethoxylated (6) The methacrylate compound (Bissomo PEM6LD) was uniformly mixed.

<Comparative Example 1>

The granular hydrogel crosslinked polymer of Preparation Example 1 was mashed by a mincer. Subsequently, the pulverized granulated hydrogel crosslinked polymer was dried by a hot air dryer at a temperature of 180 ° C for 30 minutes, and the dried granulated hydrogel crosslinked polymer was pulverized by a corner pulverizer. Thereafter, a bare superabsorbent polymer having an average particle size of 150 to 850 μm was obtained by sieving. The bare superabsorbent polymer obtained in this manner was sprayed with a 20% aqueous ethyl carbonate solution in a surface cross-linking mixer at a ratio of 5 pph, and then dried again at a temperature of 180 ° C for 30 minutes. The dried bare superabsorbent polymer is classified by a standard sieve of the ASTM standard, thereby preparing a surface crosslinked superabsorbent polymer having an average particle size of from 150 micrometers to 850 micrometers.

<Comparative Example 2>

The surface crosslinked superabsorbent polymer was prepared in the same manner as in Comparative Example 1, except that the particulate hydrogel crosslinked polymer of Preparation Example 2 was used instead of the particulate hydrogel crosslinked polymer of Preparation Example 1.

<Comparative Example 3>

The surface crosslinked superabsorbent polymer was prepared in the same manner as in Comparative Example 1, except that the particulate hydrogel crosslinked polymer of Preparation Example 3 was used instead of the particulate hydrogel crosslinked polymer of Preparation Example 1.

<Comparative Example 4>

77.778 grams of a 50% aqueous caustic soda (NaOH) solution and 88.84 grams of water were mixed to form a mixed solution. Then, 100 grams of acrylic acid, 0.115 grams of 2,2-indole [(propenyloxy)methyl]butyl acrylate (3EO), 0.115 grams of polyethylene Alcohol diacrylate (Mw=400) as crosslinker, 0.033 g of diphenyl(2,4,6-trimethylbenzylidene)-phosphine oxide as photopolymerization initiator, and 2 g of ethoxylated A acrylate compound (Bissomo PEM6LD) was added as a comonomer to the mixed solution, thereby preparing a monomer composition having a hydrophilic monomer concentration of 45 wt%.

1.33 g of potassium persulfate as a thermal polymerization initiator was dissolved in 8.67 g of water to obtain a solution, and 3.008 g of a solution was mixed with a monomer composition.

Then, the obtained monomer composition was placed in a polymerization reactor continuously moving on a conveyor belt at a temperature of 40 ° C, irradiated with ultraviolet light by a UV irradiation device (light dose: 9 Mw/cm ² ), and then UV-polymerized for 3 minutes, thereby preparing a tablet. Hydrogel crosslinked polymer.

The sheet-like hydrogel crosslinked polymer was transferred to a cutter and then cut into a size of 2 cm to obtain a particulate hydrogel crosslinked polymer. In these cases, the obtained granular hydrogel crosslinked polymer had a water content ratio of 50% by weight.

Subsequently, the granulated hydrogel crosslinked polymer was dried by a hot air dryer at a temperature of 180 ° C for 30 minutes, and the dried granulated hydrogel crosslinked polymer was pulverized by a corner pulverizer. Thereafter, a bare superabsorbent polymer having an average particle size of 150 to 850 μm was obtained by sieving.

<Experimental Example 1>

The unreacted monomer concentrations of the particulate hydrogel crosslinked polymers prepared in Preparation Examples 1 to 3 were measured, and the results thereof are shown in Table 1 below.

<Experimental Example 2>

Centrifugal retention capacity (CRC), extractable content (EC), pressure absorption of the bare superabsorbent polymer obtained in Examples 1 to 4 and the surface crosslinked superabsorbent polymer obtained in Comparative Examples 1 to 3. (AUP) and residual monomer (RM) were measured, respectively, and the results are summarized in Table 2 below. Centrifuge Retention Capacity (CRC) is based on the European Disposable and Nonwovens Association (EDANA) WSP 241.2.R3 standard. The extractable content (EC) is measured based on the EDANA WSP 270.2.R3 standard. Pressure Absorption (AUP) is measured based on the EDANA WSP 242.2.R3 standard. Residual monomer (RM) concentrations were measured based on the EDANA WSP 210.2.R3 standard.

Referring to Table 2, the extractable contents (EC) and residual monomer (RM) concentration systems of each of the bare superabsorbent polymers obtained in the examples can be determined. It is lower than the value of each of the surface crosslinked superabsorbent polymers obtained in the comparative examples.

Further, it was confirmed that each of the bare superabsorbent polymers obtained in Examples 2 to 4, in which a hydrogel crosslinked polymer containing a plurality of unreacted monomers, was used, the centrifuge retention ability (CRC) and addition The pressure absorption (AUP) is approximately equal to the value of the surface crosslinked superabsorbent polymer obtained in Comparative Examples 1 to 3, even if these bare superabsorbent polymers are not surface crosslinked.

Meanwhile, it was confirmed that each of the bare superabsorbent polymers obtained in the examples had excellent centrifugal retention ability (CRC) and low residual singles compared to the surface crosslinked superabsorbent polymer obtained in Comparative Example 4. Body (RM) concentration.

A detailed description of the preferred embodiments will be apparent to those skilled in the art, and many variations and modifications can be made to the preferred embodiments without departing from the principles of the invention. Accordingly, the preferred embodiments of the invention disclosed are intended to be

P1-6, P11-13, P21, P22‧‧‧ steps

Claims (11)

A method for preparing a bare superabsorbent polymer, comprising the steps of: preparing a hydrogel crosslinked polymer by polymerizing a monomer composition comprising a hydrophilic monomer, a crosslinking agent, and a polymerization initiator; 1) at least one of the indicated compounds is added to the hydrogel crosslinked polymer to prepare a base resin; drying the base resin; and pulverizing the dried base resin: X-(R) _n -Y.. (1) In the formula (1), X is an unsaturated hydrocarbon group or a group derived therefrom; R is a divalent atom group of at least one of the following: a C _1-5 alkyl group (-(CH) ₂ ) _m -, m is an integer from 1 to 5), a C _1-4 alkyloxy group (-(CH ₂ ) _m -O-, m is an integer from 1 to 4), and a C _2-6 extension Alkyl(oxy)carbonyl (-(R _f ) _o -(C=O)-(R' _f ) _p -, o and p are each independently an integer from 0 to 2 and not simultaneously 0, and R _f and R _'f are each independently C _1-5 hydrocarbon or a group derived therefrom), and the C _2-5 carbonyloxy group _{(- (R g) r -} (C = O) -O-, r is 0 An integer of up to 2, and R _g is a C _1-4 hydrocarbyl group or a group derived therefrom; n is an integer from 2 to 20; and Y is a hydrophilic group. The method of claim 1, wherein X is a monovalent atomic group of at least one of: a C _2-5 (meth)vinyl group (CH ₂ =CR _a -, R _a is a hydrogen atom, or C _1-3 hydrocarbyl group or a derivative thereof), C _3-5 (meth)allyl (CH ₂ =CR _b -CH ₂ -, R _b is a hydrogen atom, or a C _1-2 hydrocarbyl group or a derivative thereof a group of C _1-5 , R _c C(=O)-, R _c is a hydrogen atom, or a C _1-4 hydrocarbon group or a derivative thereof, and a C _3-5 (meth) propylene hydride a group (CH ₂ =CR _d -C(=O)-, R _d is a hydrogen atom, or a C _1-2 hydrocarbon group or a group derived therefrom), and a (meth)acryl decyloxy group of C _3-5 ( CH ₂ =CR _e -C(=O)-O-, R _e is a hydrogen atom, or a C _1-2 hydrocarbon group or a group derived therefrom. The method of claim 1, wherein Y is a hydroxyl group (-OH), a carboxyl group (-COOH), and an amine group (-NHR _h , -NH ₂ , or -NR _h2 , and _Rh is a C _1-5 hydrocarbon group) Either. The method of claim 1, wherein X is a (meth)acryloyl group of C _3-5 (CH ₂ =CR _d -C(=O)-, R _d is a hydrogen atom, or a C _1-2 hydrocarbyl group or Derived group). The method of claim 1, wherein at least one of the compounds represented by the formula (1) is at least one of the compounds represented by the following formula (2): In the formula (2), R ₁ is any one of a C _1-2 alkyl group and a C _1-2 alkoxy group; and R ₂ is a C _1-5 alkylene group (-(CH ₂ ) _m -, m is an integer of 1 to 5) and a C _1-5 alkyloxy group (-(CH ₂ ) _m -O-, m is an integer of 1 to 5); Y is a hydroxyl group (-OH Any one of a carboxyl group (-COOH), and an amine group (-NHR _h , -NH ₂ , or -NR _h2 ); and n is an integer of 2 to 20. The method of claim 5, wherein at least one of the compounds represented by the formula (2) is at least one of the compounds represented by the formulas (3) to (14): The method of claim 1, further comprising: preparing the monomer composition, wherein the preparing the monomer composition comprises: preparing a first composition comprising a neutralizing agent and a solvent; preparing the hydrophilic monomer, the a crosslinking agent, and a second composition of the polymerization initiator; and mixing the first composition and the second composition. The method of claim 1, wherein the polymerization initiator comprises a photopolymerization initiator or a complex polymerization The initiator, and the composite polymerization initiator include the photopolymerization initiator and a thermal polymerization initiator. The method of claim 1, wherein the preparing the hydrogel crosslinked polymer comprises: polymerizing the monomer composition; and pulverizing the hydrogel crosslinked polymer. The method of claim 1, wherein the bare superabsorbent resin has greater than 0% and less than 15% extractable content (EC) and a residual monomer (RM) concentration of more than 0 ppm and less than 1000 ppm. The method of claim 10, wherein the bare superabsorbent resin has greater than 0% and less than 15% extractable content (EC) and a residual monomer (RM) concentration of more than 0 ppm and less than 600 ppm.