TW201700552A - 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 hydrogel crosslinked polymer by polymerizing a monomer composition including hydrophilic monomers, a crosslinking agent and a polymerization initiator; pulverizing the hydrogel crosslinked polymer; drying the pulverized hydrogel crosslinked polymer; preparing a base resin by pulverizing the dried hydrogel crosslinked polymer; and mixing the base resin with at least one of compounds represented by Formula (1) below and a surface-crosslinking agent to surface-crosslink the base resin: X-(Ra)p(Rb)q-Y ---- (1).

Description

Method for preparing superabsorbent polymer

The priority of the Korean Patent Application No. 10-2015-0044165 filed on March 30, 2015, and the Korean Patent Application No. 10-2016-0025114 filed on March 2, 2016 And all benefits arising therefrom, the disclosure of which is hereby incorporated by reference in its entirety.

background Field

This invention relates to a process for preparing superabsorbent polymers.

2. Related technical description

Superabsorbent polymers (SAPs) are synthetic polymeric materials having a function of absorbing 500 to 1000 times their own weight, and are named as superabsorbent materials (SAM) and absorbent gelling materials by different developers. AGM) and so on. These superabsorbent polymers have been widely used as water retaining agents for soils, waterstops for civil engineering and construction, sheets for sowing, and articles for food circulation, such as for baby paper. The material of the field of sanitary articles for diapers, as they begin to enter practical use.

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

summary

In the process for preparing a superabsorbent polymer, a water soluble component is produced which is an uncrosslinked polymer and residual monomers. 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 its liquid permeability is lowered, and skin diseases and odors are caused.

Aspects of the present invention provide a method of preparing a superabsorbent polymer whereby a superabsorbent polymer containing a small amount of residual monomer can be obtained.

However, aspects of the invention are not limited to those described herein. The above and other aspects of the present invention will become more apparent to those skilled in the <RTIgt;

In accordance with an illustrative embodiment of the invention, a method for making a superabsorbent polymer is provided. The method 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; crosslinking the hydrogel The polymer is pulverized; the pulverized hydrogel crosslinked polymer is dried; a base resin is prepared by pulverizing the dried hydrogel crosslinked polymer; and the base resin is represented by the following chemical formula (1) At least one of the compounds and a surface The binder is mixed to crosslink the surface of the base resin.

In an exemplary embodiment, the polymerization initiator may be at least one of a photopolymerization initiator, a thermal polymerization initiator, and a redox initiator.

In an exemplary embodiment, the method may further comprise preparing the monomer composition, and preparing the monomer composition may comprise preparing a first composition comprising a hydrophilic monomer and a neutralizing agent; A second composition is prepared by mixing with a crosslinking agent and a polymerization initiator.

In an exemplary embodiment, crosslinking the surface of the base resin can further comprise drying the surface treated base resin.

X-(Ra) _p (Rb) _q -Y----(1)

In the formula (1), an X-unsaturated hydrocarbon group or a derivative thereof; each of Ra and Rb is independently a C _1-5 alkyl group (-(CH ₂ ) _m -, m system 1 Up to 5 integers, C _{1-4 one} alkoxy group (-(CH ₂ ) _m -O-, m is an integer of 1 to 4), one of C _2-6 an alkenyl group (-(CH) =CH) _m -, m is an integer from 1 to 3), a C _2-6 alkane (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 each of R _f and R' _f is independently a hydrocarbon group of C _1-5 , or a derivative thereof) 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 hydrocarbon group of C _1-4 , Or a derivative thereof, and one of C _2-6 cyclic carbonyloxy groups (-(CH ₂ ) _s -(C=O)-O-(CH ₂ ) _t -, s and t each Independently an integer of 0 to 3, and a divalent atomic group of at least one of s and t totals 1 to 5).

In the formula (1), p may be an integer of 2 to 10, q may be an integer of 0 to 10, and Y is a hydrogen atom or a hydrophilic group. The hydrophilic group may be a monohydroxy group (-OH), a carboxyl group (-COOH), and an amine group ((-NHR _h , -NH ₂ , or -NR _h2 , _Rh system C ₁ Any of _-5 one of the hydrocarbon groups. In particular, Y may be a hydrogen atom or a hydroxyl group.

X may be a C _2-5 one (methyl)vinyl group (CH ₂ =CR _a -, R _a is a hydrogen atom, or a C _1-3 hydrocarbon group, or a derivative thereof), C _{a 3-5} (meth)allyl group (CH ₂ =CR _b -CH ₂ -, R _b is a hydrogen atom, or a hydrocarbon group of C _1-2 , or a derivative thereof), C One of _1-5 fluorenyl groups (R _c C(=O)-, R _c is a hydrogen atom, or one of C _1-4 hydrocarbon groups, or a derivative thereof), one of C _3-5 ( a methyl) acrylonitrile group (CH ₂ =CR _d -C(=O)-, R _d is a hydrogen atom, or a hydrocarbon group of C _1-2 , or a derivative thereof), and C _{3 - 5 a} (meth) propylene oxirane group (CH ₂ =CR _e -C(=O)-O-, R _e is a hydrogen atom, or a hydrocarbon group of C _1-2 , or a derivative thereof One of at least one of the monovalent atomic groups.

In an exemplary embodiment, at least one of the compounds represented by the chemical formula (1) may be at least one of the compounds represented by the following chemical formula (2):

In the formula (2), R ₁ may be any one of a C _1-2 alkyl group and a C _1-2 one alkoxy group; and R ₂ may be a C _1-5 alkyl group. a group (-(CH ₂ ) _m -, m is 1 to 5), a C _1-5 alkoxy group (-(CH ₂ ) _m -O-, m is an integer of 1 to 5), and C _2-6 one of the cyclic carbonyloxy groups (-(CH ₂ ) _s -(C=O)-O-(CH ₂ ) _t -, s and t are each independently an integer from 0 to 3, And a combination of s and t, any one of 1 to 5); Y may be any one of a hydrogen atom and a hydroxyl group (-OH); and n may be an integer of 1 to 10.

In an exemplary embodiment, at least one of the compounds represented by the chemical formula (2) may be at least one of the compounds represented by the chemical formulas (3) to (22):

According to the method for preparing a superabsorbent polymer of the present invention, it is possible to obtain a small amount of a water-soluble component (extractable amount: EC) and residual monomer (RM) and exhibit an improved centrifugal retention capacity (CRC). Absorbing polymer.

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

P1‧‧‧ Preparation of monomer composition

P11‧‧ Preparation of a first composition comprising a hydrophilic monomer and a neutralizing agent

P12‧‧‧ Preparation of the second composition by mixing the first composition with a crosslinking agent and a polymerization initiator

P2‧‧‧ Preparation of hydrogel crosslinked polymer

P3‧‧‧Crushing hydrogel crosslinked polymer

P4‧‧‧Dry the pulverized hydrogel crosslinked polymer

P5‧‧‧ Preparation of base resin by pulverizing the dried hydrogel crosslinked polymer

P6‧‧‧ cross-linking the surface of the base resin

P61‧‧‧ Mixing the base resin with at least one of the compounds represented by the following chemical formula (1) and the surface crosslinking agent X-(Ra) _p (Rb) _q -Y----(1)

P62‧‧‧Dry the surface treated base resin

Brief description of the schema

The above and other aspects and features of the present invention will become more apparent from the detailed description of the exemplary embodiments illustrated in the accompanying drawings in which: FIG. 1 is a schematic illustration of a method of making a superabsorbent polymer in accordance with an embodiment of the present invention. flow chart.

Detailed description of the embodiment

The advantages and features of the present invention and the method of accomplishing the same are more readily understood by reference to the detailed description of the embodiments illustrated herein. However, the invention may be embodied in many different embodiments and should not be construed as limited to the embodiments described herein. Rather, the embodiments are provided so that this disclosure will be thorough and complete, and the invention will be <RTIgt;

Although the terms "first, second, etc." are used to describe different constituent elements, such constituent elements are not limited by this term. This term is only used to distinguish one constituent element from another constituent element. Therefore, in the following description, A first constituent element can be a second constituent element.

In the present specification, "C _AB " means that the number of carbon atoms is A to B. For example, a "C _1-5 alkyl group" is an alkyl group having one 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 and F or less.

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

In the present specification, the "alkyl group" includes a linear or branched alkyl group, and examples thereof may include a n-butyl group and a third butyl group. In the present specification, the "(meth)vinyl group" has a monovalent atomic group having a double bond at its end, and is represented by CH ₂ =CR _a -. In the vinyl group, R _a is a hydrogen atom, and in the methylvinyl group, R _a is a monoalkyl group. In the present specification, the "(meth)allyl group" is a monovalent atomic group having a double bond at its end, 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 a monoalkyl group.

In the present specification, the "G derivative" is defined as an unsaturated hydrocarbon group of G or some or all of the hydrogen atoms of the alkyl group to exclude other atoms of carbon atoms and hydrogen atoms, or to exclude carbon atoms and hydrogen. An atomic group of another atom of an atom, such as oxygen (O), nitrogen (N), a carbonyl group (-(C=O)-), a fluorenyl group (R _c C(=O)-) And a (meth)acrylinyl group (CH ₂ =CR _d -C(=O)-), replacing one of the derivatives.

In the present specification, "alkoxy group" is a monovalent atomic group in which a monoalkyl group is bonded to an oxygen atom and is a derivative of an alkyl group. The alkyl group can be a linear or branched alkyl group. In the present specification, "mercapto group" 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 hydrocarbon group of C _1-5 and a derivative thereof. In the present specification, "(meth)acrylinyl group" is one in which a (meth)vinyl group is bonded to a carbonyl group and is CH ₂ =CR _d -C(=O) - represents one of the monovalent atomic groups. 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 the like. In the present specification, "(meth)acryloxy group" is one in which a (meth) acryloyl group is bonded to an oxygen atom and is CH ₂ =CR _e -C(=O ) -O- represents a monovalent atomic group. In the propylene methoxy group, R _e may be a hydrogen atom, and in the methacryloxy group, R _d may be an alkyl group or the like.

In the present specification, the "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 a methyl group (-CH ₂ -), an ethyl group (-CH ₂ CH ₂ -), and the like. In the present specification, an "alkoxy 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 alkoxy group may include a methoxy group (-CH ₂ O-, -OCH ₂ -), an ethoxy group (-CH ₂ CH ₂ O-, -OCH ₂ CH ₂ - )Wait. In the present specification, an "alkylene (oxy)carbonyl group" is a divalent atom group in which an alkylene (oxy) group is bonded to a carbonyl group, and is -(R _f ). _o -(C=O)-(R' _f ) _p - indicates. Examples of the alkane (oxy)carbonyl group may include a methylcarbonyl group (-CH ₂ -(C=O)-) and a methylcarbonyloxy group (-CH ₂ -(C=O)). -CH ₂ -), a methoxycarbonyl group (-CH ₂ -O-(C=O)-), a di-methoxycarbonyl group (-CH ₂ -O-(C=O)- OCH ₂ -, -OCH ₂ -(C=O)-CH ₂ -O-), and the like. In the present specification, a "carbonyloxy group" is a divalent atom group in which a carbonyl group is bonded to an oxygen atom, and is -(R _g ) _r -(C=O)-O - indicated. Examples of the carbonyloxy group may include a carbonyloxy group (-(C=O)-O-), a methylcarbonyloxy group (-CH ₂ -(C=O)-O-), and the like. . In the present specification, a "cyclic carbonyloxy group" is obtained by removing two hydrogen atoms from a cyclic ester to obtain a residue which is a divalent atom group and is -CH ₂ ) _s -(C=O)-O-(CH ₂ ) _t -. Examples of the cyclic carbonyloxy group may include a divalent atom group such as caprolactone.

In the present specification, an "amino 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 case of an amine group, _Rh can be an alkyl group or the like.

1 is a schematic flow diagram of a method of making a superabsorbent polymer in accordance with an 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) preparing a hydrogel. The crosslinked polymer is pulverized; (P4) the pulverized hydrogel crosslinked polymer is dried; (P5) the dried hydrogel crosslinked polymer is pulverized into a base resin; and (P6) the base resin surface is pulverized Cross-linking.

The step (P1) of preparing the monomer composition may include the step of: (P11) Preparing a first composition comprising a hydrophilic monomer and a neutralizing agent; and (P12) mixing the first composition with an internal crosslinking agent and a polymerization initiator to prepare a second composition. a step (P11) for preparing a first composition comprising a hydrophilic monomer and a neutralizing agent, the first composition may include all of the predetermined hydrophilic monomers, and may also include some of the predetermined hydrophilic monomers . In the latter case, the other predetermined hydrophilic monomers may be prepared by mixing the first composition with an internal crosslinking agent and a polymerization initiator to prepare a second composition (P12), and internal A crosslinking agent and a polymerization initiator are added together to the first composition.

The hydrophilic monomer can be used without limitation as long as it is generally used to prepare one of the superabsorbent polymers. The hydrophilic single system has one monomer of a hydrophilic group, and examples of the hydrophilic group may include a monohydroxy group (-OH), a carboxyl group (-COOH), and an amine group ( -NHR _h , -NH ₂ , or -NR _h2 , where R _h may be a C _1-5 alkyl group, etc.).

The hydrophilic monomer may be a water-soluble monomer mainly composed of unsaturated ethylene. The water-soluble monomer mainly composed of unsaturated ethylene may be an anionic monomer and a salt thereof, a nonionic hydrophilic monomer, an unsaturated group containing an amino group, and the like. At least one of the ammonium salts.

Examples of the anionic monomer and salts thereof may include acrylic acid, methacrylic acid, anhydrous maleic acid, fumaric acid, crotonic acid, itaconic acid, 2-propenylsulfonylsulfonic acid, 2-methylpropenylsulfonyl group. Ethane sulfonic acid, 2-(meth) propylene decyl propane sulfonic acid, and 2-(methyl) propylene decylamine-2-methylpropane sulfonic acid.

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

Examples of the amino group-containing unsaturated monomer and the quaternary ammonium salt thereof and the like may include (N,N)-dimethylaminoethyl (meth) acrylate, and (N, N)- Dimethylaminopropyl (meth) acrylamide.

The concentration of the water-soluble monomer which is mainly unsaturated in the monomer composition can be considered in the polymerization reaction and the reaction conditions (the feed rate of the monomer composition, and the irradiation time and irradiation range of heat and/or light) And the irradiation intensity, etc.) are appropriately selected and used. In the illustrated embodiment, the concentration of the water-soluble monomer mainly composed of unsaturated ethylene may range from 30% by weight to 60% by weight.

A neutralizing agent is used to neutralize the hydrophilic monomer. Typical examples thereof include, without limitation, sodium hydroxide and sodium hydrogencarbonate. A neutralizing agent can be used such that the degree of neutralization of the monomer composition is in the range of from 65 mol% to 75 mol%. However, the invention is not limited thereto.

As an internal crosslinking agent, having at least one functional group capable of reacting with one of the substituents of the monomer and one crosslinking agent of at least one unsaturated vinyl group, having two or more substituents replaceable with one of the monomers A crosslinking agent which is one of the functional groups which form a substituent reaction by hydrolyzing the monomer can be used.

In the exemplified examples, examples of the internal crosslinking agent may include a poly(methyl) group of a C _8-12 bis acrylamide, a C _8-12 bis methacrylamide, and a C _2-12 polyol. Acrylate, and poly(methyl)allyl ether of one of C _2-10 polyols.

Specific examples of the internal crosslinking agent include, without limitation, (poly)ethylene glycol (meth) acrylate, (poly) propylene glycol di (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 A Acrylate, 2,2-bis[(propyleneoxy)methyl]butyl acrylate (3EO), N,N'-extended methyl bis(meth) acrylate, ethoxylated (methyl) Acrylate, poly(ethoxy)(meth)acrylate, propoxy(meth)acrylate, glycerol diacrylate, glycerol triacrylate, trimethylol triacrylate, triene Propylamine, triaryl cyanurate, triallyl isocyanate, polyethylene glycol, diethylene glycol, propylene glycol, and mixtures of two or more thereof.

In the illustrated embodiment, the internal crosslinking agent may be included in an amount of 0.01 to 0.5 parts by weight based on 100 parts by weight of the hydrophilic monomer, but is not limited thereto.

The polymerization initiator may be at least one of a photopolymerization initiator, a thermal polymerization initiator, and a redox initiator. For example, as a polymerization initiator, both a photopolymerization initiator and a thermal polymerization initiator can be used. Further, for example, as a polymerization initiator, both a thermal polymerization initiator and a redox initiator may be used.

The photopolymerization initiator starts the polymerization of the monomer composition by irradiating ultraviolet rays, and the thermal polymerization initiator starts the polymerization of the monomer composition by heating, and the redox initiator By oxidation The polymerization of the starting monomer composition of the reduction reaction is carried out. When 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, which is used for the heat generated during the photopolymerization reaction. When a redox initiator and a thermal polymerization initiator are used, the polymerization of the monomer composition can be carried out by using a thermal polymerization initiator, which is used for the heat generated during the redox reaction.

Examples of the polymerization initiator may include, without limitation, an acetophenone derivative such as diethoxyacetophenone, 2-hydroxy-2-methyl-1-phenylpropan-1-one, 4-( 2-hydroxyethoxy)phenyl-(2-hydroxy)-2-propanone, and 1-hydroxycyclohexyl benzophenone; benzoin alkyl ethers, such as benzoin methyl ether, benzoin ethyl ether, benzoin isopropyl ether, and Benzoin isobutyl ether; benzophenone derivative, such as methyl o-benzhydryl benzoate, 4-phenyl benzophenone, 4-benzylidene-4'-methyl-di Phenyl sulfide, and (4-benzylidene-benzyl)trimethylammonium chloride; 9-oxosulfur a predominantly compound; a mercaptophosphine oxide derivative such as bis(2,4,6-trimethylbenzylidene)-phenylphosphine oxide, and diphenyl (2,4,6-tri Methyl benzhydryl)-phosphine oxide; azo compounds such as 2-hydroxy-methyl-propionitrile, and 2,2'-(azo-bis(2-methyl-N-(1, 1'-bis(hydroxymethyl)-2-hydroxyethyl)propanamide); and mixtures thereof. Here, the thermal polymerization initiator is not particularly limited, but examples thereof include an azo The main initiator, a peroxide-based initiator, a redox-based initiator, and an organic halide-based initiator. They may be used alone or in the like. A mixture of two or more of them may be used. Specific examples of the thermal polymerization initiator may include, without limitation, sodium persulfate (Na ₂ S ₂ O ₈ ) and potassium persulfate (K ₂ S ₂ O ₈ ).

If the initial reaction efficiency of the polymerization can be exhibited, the content of the polymerization initiator can be appropriately selected. For example, the photopolymerization initiator may be included in the monomer composition in an amount of 0.005 to 0.5 parts by weight based on 100 parts by weight of the hydrophilic monomer, and based on 100 parts by weight of the hydrophilic monomer, heat The polymerization initiator may be contained in the monomer composition in an amount of 0.01 to 0.5 parts by weight.

In the step (P2) of polymerizing the monomer composition, a photopolymerization reaction and/or a thermal polymerization reaction is carried out by applying light and/or heat to the monomer composition, or a redox polymerization reaction is carried out. For example, when the monomer composition is irradiated with ultraviolet rays, a photopolymerization reaction is initiated by a photopolymerization initiator. In the case where the monomer composition includes a photopolymerization initiator and a thermal polymerization initiator, the thermal polymerization initiator can initiate a thermal polymerization reaction for the heat generated during the photopolymerization reaction. The polymerization can be carried out using a belt type polymerization reactor, and the sheet-like hydrogel crosslinked polymer can be obtained by the polymerization.

In the step (P3) of pulverizing the hydrogel crosslinked polymer, the sheet-like hydrogel crosslinked polymer obtained after the completion of the polymerization is transferred to a cutter and finely or roughly pulverized into a predetermined size. The sheet-like hydrogel crosslinked polymer can be finely or roughly pulverized into a particulate hydrogel crosslinked polymer having a particle size of from 1 cm to 3 cm. The step of pulverizing the hydrogel crosslinked polymer (P3) may use a blade cutter, a chopping cutter, a kneading cutter, a vibrating pulverizer, an impact pulverizer, or a rubbing Pulverizer implementation. The water content of the particulate hydrogel crosslinked polymer may be, for example, from about 40% by weight to about 60% by weight.

The pulverized hydrogel crosslinked polymer is dried at a temperature of from about 150 ° C to about 200 ° C for about 20 minutes to about 60 minutes in the step (P4) of drying the pulverized hydrogel crosslinked polymer. For example, the comminuted hydrogel crosslinked polymer can be dried by a hot air dryer, a fluid bed dryer, an air flow dryer, an infrared dryer, or a dielectric heated dryer.

The step (P5) of preparing the base resin by pulverizing the dried hydrogel crosslinked polymer may comprise finely pulverizing the dried hydrogel crosslinked polymer into a particle size having a micrometer (μm), for example, 150 μm to 850 μm. The step of granules of average particle size. The step of preparing the base resin by pulverizing the dried hydrogel crosslinked polymer (P5) may use a blade cutter, a chopping cutter, a kneading cutter, a vibrating pulverizer, and an impact type. A pulverizer, or a friction pulverizer.

The step (P6) of crosslinking the surface of the base resin may include a step of mixing the base resin with at least one of the compound represented by the chemical formula (1) and a surface crosslinking agent (P61); and subjecting the surface treated substrate The step of drying the resin (P62).

a step of mixing the base resin with at least one of the compound represented by the chemical formula (1) and a surface crosslinking agent (P61) to form a layer having a higher crosslink density than the base resin and having a surface cross-linking, whereby A base resin having a core-core structure surface-crosslinked is provided, wherein the base resin is formed as a core and a surface crosslinked layer is formed on the surface of the base resin. The step (P61) of mixing the base resin with at least one of the compounds represented by the chemical formula (1) and the surface crosslinking agent (if necessary) may be carried out several times.

Examples of the surface crosslinking agent may include, without limitation, alkyl diols, alkylene glycols, alkyl diglycidyl ethers, polyvalent metals, ethylene glycol diglycidyl ethers, alkylene groups. Carbonates such as ethyl carbonate, water, and ethanol.

At least one of the compounds represented by the following chemical formula (1) can reduce the extractable amount (EC) of the superabsorbent polymer by reacting with the uncrosslinked linear polymer chain, and can be reacted by unreacted The monomer reaction reduces the value of the concentration of residual monomer (RM) of the superabsorbent polymer. At the same time, the centrifugal retention capacity (CRC) of superabsorption can be improved by a hydrophilic alkylene group.

<Chemical Formula (1)>X-(Ra) _p (Rb) _q -Y

In the formula (1), an X-unsaturated hydrocarbon group or a derivative thereof; and each of Ra and Rb is independently a C _1-5 alkyl group (-(CH ₂ ) _m -, m system An integer from 1 to 5), a C _1-4 alkoxy group (-(CH ₂ ) _m -O-, m is an integer from 1 to 4), a C ₂ - ₆ alkylene group (- (CH=CH) _m -, m is an integer from 1 to 3), a C _2-6 alkane (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 each of R _f and R' _f is independently a hydrocarbon group of C _1-5 or a derivative thereof 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 hydrocarbon group of C _1-4 a group or a derivative thereof, and one of C _2-6 cyclic carbonyloxy groups (-(CH ₂ ) _s -(C=O)-O-(CH ₂ ) _t -, s and t each The ones are independently an integer from 0 to 3, and a divalent atomic group of at least one of s and t is a total of 1 to 5).

At least one of the compounds represented by the chemical formula (1) and having hydrophilicity in the range of the number of carbon atoms of each of Ra and Rb and the p value and the q value of each of Ra and Rb The hydrogel crosslinked polymer has improved reactivity. Conversely, as the number of carbon atoms in each of Ra and Rb increases or the p and n values increase, the hydrophobicity increases, and thus the depth of penetration of the compound into the hydrophilic hydrogel crosslinked polymer changes. Since at least one of the compounds represented by the chemical formula (1) reacts at a depth at which the compound penetrates into the hydrogel crosslinked polymer, when at least one of the compounds represented by the chemical formula (1) increases in hydrophobicity, the reaction substance is substantially The upper portion only occurs on the surface of the hydrogel crosslinked polymer, and the extractable amount (EC) and residual monomer (RM) of the superabsorbent polymer are not effectively reduced. Therefore, the number of carbon atoms of Ra, the number of carbon atoms of Rb, and the p value and the q value are preferably within the above range.

In the formula (1), p is an integer of 2 to 10, q is an integer of 0 to 10, and Y is a hydrogen atom or a hydrophilic group. The hydrophilic group can form a hydrogen bond by reacting with the unreacted monomer and the linear polymer chain, and can be, for example, a monohydroxy group (-OH), a carboxyl group (-COOH), and an amine group. Any of a group (-NHR _h , -NH ₂ , or -NR _h2 , R _h is a hydrocarbon group of C _1-5 ). In particular, Y is a hydrogen or a hydroxyl group.

X system C _2-5 one (meth) vinyl group (CH ₂ =CR _a -, R _a is a hydrogen atom, or one of C _1-3 hydrocarbon groups, or a derivative thereof), C _{3 -5 a} (meth)allyl group (CH ₂ =CR _b -CH ₂ -, R _b is a hydrogen atom, or a hydrocarbon group of C _1-2 , or a derivative thereof), C _{1 -5} one fluorenyl group (R _c C(=O)-, R _c is a hydrogen atom, or one of C _1-4 hydrocarbon groups, or a derivative thereof), one of C _3-5 (A a propylene group (CH ₂ =CR _d -C(=O)-, R _d is a hydrogen atom, or a hydrocarbon group of C _1-2 , or a derivative thereof), and C _3-5 a (meth) propylene oxirane group (CH ₂ =CR _e -C(=O)-O-, R _e is a hydrogen atom, or a hydrocarbon group of C _1-2 , or a derivative thereof a monovalent atomic group of at least one of. In particular, X may be a C _3-5 one (meth) acryl fluorenyl group (CH ₂ =CR _d -C(=O)-, R _d is a hydrogen atom, or a C _1-2 hydrocarbon group Group, or a derivative thereof).

The content of at least one of the compounds represented by the chemical formula (1) may be in the range of more than 0.1% by weight to less than 10% by weight based on the total amount of the superabsorbent polymer. When the content is in the above range, the physical properties of the superabsorbent polymer can be improved. For example, the centrifugal retention capacity (CRC) reduction of superabsorbent polymers can be minimized.

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

In the formula (2), R ₁ may be any one of a C _1-2 alkyl group and a C _1-2 one alkoxy group; and R ₂ may be a C _1-5 alkyl group. a group (-(CH ₂ ) _m -, m is an integer from 1 to 5), a C _1-5 alkoxy group (-(CH ₂ ) _m -O-, m is an integer from 1 to 5), And one of C _2-6 cyclic carbonyloxy groups (-(CH ₂ ) _s -(C=O)-O-(CH ₂ ) _t -, s and t are each independently 0 to 3 An integer, and any one of s and t, any one of 1 to 5); Y may be any one of a hydrogen and a hydroxyl group (-OH); and n is an integer from 1 to 10.

At least one of the compounds represented by the chemical formula (2) may be at least one of the compounds represented by the chemical formulas (3) to (22).

<Chemical Formula (9)>

<Chemical Formula (12)>

<Chemical Formula (15)>

<Chemical Formula (19)>

a step of drying the surface-treated base resin (P62), The surface treated base resin may be heat treated at a temperature of from about 150 ° C to about 200 ° C for from about 20 minutes to about 60 minutes.

Hereinafter, a method for preparing a superabsorbent polymer according to the present invention will be described with reference to the following examples and experimental examples to provide a superabsorbent having a small amount of water-soluble components and residual monomers and having improved centrifugal retention ability. polymer.

<Comparative Example 1>

500 g of acrylic acid was mixed with 971.4 g of a 20% aqueous sodium hydroxide solution, and then 1.5 g of ethoxy-trimethylolpropane triacrylate as an internal crosslinking agent and 0.165 g of a photopolymerization initiator were added. Diphenyl (2,4,5-trimethylbenzylidene)-phosphine oxide to prepare a water-soluble unsaturated monomer solution (polymerization degree of acrylic acid-based monomer: 70 mol% ).

The photopolymerization of a monomer mixture is carried out by ultraviolet irradiation to prepare a fine hydrogel polymer.

The prepared hydrogel polymer was made into a hydrogel polymer pellet through a meat grinder and then dried at 170 ° C for 40 minutes by means of a hot air belt drier. The dried hydrogel polymer is pulverized by a cutting and grinding pulverizer and then sieved to obtain a base polymer having an average particle size of from about 150 μm to about 850 μm.

Thereafter, 100 g of the obtained base polymer was mixed with a surface crosslinking solution containing 1 g of ethyl acetonate, 3 g of water, and 3 g of ethanol, and then, one reaction was carried out in a hot oven at 180 ° C. minute. The reaction product is sieved to prepare a particle size having a particle size of from about 150 μm to about 850 μm. A surface treated polymer.

<Example 1>

In addition to 0.5 g of polyethylene glycol monomethacrylate (Bisomer PEM 6LD, 6 EO units, manufacturer: Cognis) having 6 moles of ethylene oxide units added to the surface crosslinking solution, once surface treated The superabsorbent polymer was prepared in the same manner as in Comparative Example 1.

<Example 2>

In addition to 1 gram of polyethylene glycol monomethacrylate (Bisomer PEM 6LD, 6 EO units, manufacturer: Cognis) having 6 moles of ethylene oxide units added to the surface crosslinking solution, once surface treated The superabsorbent polymer was prepared in the same manner as in Comparative Example 1.

<Example 3>

In addition to 2 grams of polyethylene glycol monomethacrylate (Bisomer PEM 6LD, 6 EO units, manufacturer: Cognis) with 6 moles of ethylene oxide units added to the surface crosslinking solution, once surface treated The superabsorbent polymer was prepared in the same manner as in Comparative Example 1.

<Example 4>

A surface treated superabsorbent polymer was prepared in the same manner as in Comparative Example 1, except that 0.5 g of poly(ethylene glycol) methacrylate (average Mn 500, manufacturer: aldrich) was added to the surface crosslinking solution. .

<Example 5>

A surface treated superabsorbent polymer was prepared in the same manner as in Comparative Example 1, except that 1 gram of poly(ethylene glycol) methacrylate (average Mn 500, manufacturer: aldrich) was added to the surface crosslinking solution. .

<Example 6>

A surface treated superabsorbent polymer was prepared in the same manner as in Comparative Example 1, except that 2 g of poly(ethylene glycol) methacrylate (average Mn 500, manufacturer: aldrich) was added to the surface crosslinking solution. .

<Example 7>

A surface-treated superabsorbent polymer was prepared in the same manner as in Comparative Example 1, except that 0.5 g of 2-hydroxyethyl acrylate (manufacturer: aldrich) was added to the surface crosslinking solution.

<Example 8>

A surface-treated superabsorbent polymer was prepared in the same manner as in Comparative Example 1, except that 1 g of 2-hydroxyethyl acrylate (manufacturer: aldrich) was added to the surface crosslinking solution.

<Example 9>

A surface-treated superabsorbent polymer was prepared in the same manner as in Comparative Example 1, except that 2 g of 2-hydroxyethyl acrylate (manufacturer: aldrich) was added to the surface crosslinking solution.

<Example 10>

A surface-treated superabsorbent polymer was prepared in the same manner as in Comparative Example 1, except that 0.5 g of hydroxypropyl acrylate (isomer mixture, manufacturer: aldrich) was added to the surface crosslinking solution.

<Example 11>

A surface-treated superabsorbent polymer was prepared in the same manner as in Comparative Example 1, except that 1 g of hydroxypropyl acrylate (isomer mixture, manufacturer: aldrich) was added to the surface crosslinking solution.

<Example 12>

A surface-treated superabsorbent polymer was prepared in the same manner as in Comparative Example 1, except that 2 g of hydroxypropyl acrylate (isomer mixture, manufacturer: aldrich) was added to the surface crosslinking solution.

<Example 13>

A surface-treated superabsorbent polymer was prepared in the same manner as in Comparative Example 1, except that 0.5 g of 2-hydroxyethyl methacrylate (manufacturer: aldrich) was added to the surface crosslinking solution.

<Example 14>

A surface-treated superabsorbent polymer was prepared in the same manner as in Comparative Example 1, except that 1 g of 2-hydroxyethyl methacrylate (manufacturer: aldrich) was added to the surface crosslinking solution.

<Example 15>

A surface-treated superabsorbent polymer was prepared in the same manner as in Comparative Example 1, except that 2 g of 2-hydroxyethyl methacrylate (manufacturer: aldrich) was added to the surface crosslinking solution.

<Experimental Example 1>

The centrifugal retention capacity (CRC), the extractable amount (EC), the absorbency under pressure (AUP), and the residual monomer of each of the superabsorbent polymers obtained in Comparative Example 1 and Examples 1 to 15 (RM) was measured individually and the results are summarized in Table 1 of the table. The analysis of the centrifugal retention capacity (CRC), the absorption rate under pressure (AUP), the extractable amount (EC), and the residual monomer (RM) is based on EDANA (European disposables and non-woven fabrics). Association (European Disposables and Nonwovens Association)) WSP241.2.R3, EDANA WSP242.2.R3, EDANA WSP270.2.R3, and EDANA WSP 210.2.R3 are implemented individually.

With reference to Table 1, the extractable amount of each of the superabsorbent polymers of Examples 1 and 2, which were prepared by adding the compound represented by the above chemical formula (1) to a surface crosslinking solution, was confirmed ( The EC) and residual monomer (RM) concentrations were lower than those of the superabsorbent polymer of Comparative Example 1 to which no such compound was added. Further, it was confirmed that the effect of lowering the extractable amount (EC) and the residual monomer (RM) concentration was increased in accordance with the increase in the content of the compound.

In the course of the detailed description, those skilled in the art will appreciate that many variations and modifications can be made to the preferred embodiments without departing from the principles of the invention. Row. Accordingly, the preferred embodiments of the present invention are intended to be used only as a general and descriptive and non-limiting purpose.

P1‧‧‧ Preparation of monomer composition

P11‧‧ Preparation of a first composition comprising a hydrophilic monomer and a neutralizing agent

P12‧‧‧ Preparation of the second composition by mixing the first composition with a crosslinking agent and a polymerization initiator

P2‧‧‧ Preparation of hydrogel crosslinked polymer

P3‧‧‧Crushing hydrogel crosslinked polymer

P4‧‧‧Dry the pulverized hydrogel crosslinked polymer

P5‧‧‧ Preparation of base resin by pulverizing the dried hydrogel crosslinked polymer

P6‧‧‧ cross-linking the surface of the base resin

P61‧‧‧ Mixing the base resin with at least one of the compounds represented by the following chemical formula (1) and the surface crosslinking agent X-(Ra) _p (Rb) _q -Y----(1)

P62‧‧‧Dry the surface treated base resin

Claims (9)

A method for preparing a 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; The hydrogel crosslinked polymer is pulverized; the pulverized hydrogel crosslinked polymer is dried; a base resin is prepared by pulverizing the dried hydrogel crosslinked polymer; and the base resin is made Surface-crosslinking the base resin by mixing with at least one of the compounds represented by the following chemical formula (1) and a surface crosslinking agent: X-(Ra) _p (Rb) _q -Y---(1) Chemical formula (1), an X-unsaturated hydrocarbon group or a derivative thereof; each of Ra and Rb is independently a C _1-5 alkyl group (-(CH ₂ ) _m -, m system 1 to 5 integer), C _{1-4 one} alkoxy group (-(CH ₂ ) _m -O-, m is an integer of 1 to 4), one of C _2-6 an alkenyl group (-(CH= CH) _m -, m is an integer from 1 to 3), a C _2-6 alkane (oxy)carbonyl group (-(R _f ) _o -(C=O)-(R' _f ) _p -, Each of o and p is independently an integer from 0 to 2 and not simultaneously 0, and each of R _f and R' _f is independently a hydrocarbon group of C _1-5 , or a derivative thereof, a C _2-5 carbonyloxy group (-(R _g ) _r -(C=O)-O-, r is an integer from 0 to 2, and R _g is C _{1 -4} one of a hydrocarbon group, or a derivative thereof), and one of C _2-6 cyclic carbonyloxy groups (-(CH ₂ ) _s -(C=O)-O-(CH ₂ ) _t - , s and t are each independently an integer from 0 to 3, and a divalent atomic group of at least one of s and t is a total of 1 to 5); p is an integer from 2 to 10; An integer from 0 to 10; and Y is a hydrogen atom or a hydrophilic group. The method of the requested item 1, wherein, X one system C _2-5 (meth) vinyl group _{(CH 2 = CR a -,} R a line a hydrogen atom, or one C _1-3 hydrocarbon radical, Or a derivative thereof, a C ( _3-5 ) allyl group of C _3-5 (CH ₂ =CR _b -CH ₂ -, R _b is a hydrogen atom, or a hydrocarbon group of C _1-2 , Or a derivative thereof, a C _1-5 fluorenyl group (R _c C(=O)-, R _c is a hydrogen atom, or a C _1-4 hydrocarbon group, or a derivative thereof) And one of C _3-5 (meth) propylene fluorenyl groups (CH ₂ =CR _d -C(=O)-, R _d is a hydrogen atom, or one of C _1-2 hydrocarbon groups, or one of them a derivative), and one of C _3-5 (meth) propylene oxirane groups (CH ₂ =CR _e -C(=O)-O-, R _e is a hydrogen atom, or C _1-2 One of at least one of a hydrocarbon group, or a derivative thereof, is a monovalent atomic group. The method of claim 1, wherein the hydrophilic group is a monohydroxy group (-OH), a carboxyl group (-COOH), and an amine group (-NHR _h , -NH ₂ , or - NR _h2 , R _h is any one of C _1-5 hydrocarbon groups). The method of claim 1, wherein the X system C _{3-5 is a} (meth) propylene group (CH ₂ = CR _d - C (= O) -, R _d is a hydrogen atom, or C _{1 - 2 a} hydrocarbon group, or a derivative thereof), and Y is a hydrogen atom or a hydroxyl group. The method of claim 1, wherein at least one of the compounds represented by the chemical formula (1) is at least one of the compounds represented by the following chemical formula (2): In the formula (2), R ₁ is a C _1-2 alkyl group and a C _{1-2 a} alkoxy group; R ₂ is a C _1-5 alkyl group (-(CH ₂ ) _m -, m is 1 to 5), C _{1-5 an} alkoxy group (-(CH ₂ ) _m -O-, m is an integer of 1 to 5), and C _{2 -6} one of the cyclic carbonyloxy groups (-(CH ₂ ) _s -(C=O)-O-(CH ₂ ) _t -, s and t are each independently an integer from 0 to 3, and Any one of s and t totals 1 to 5); Y is any one of a hydrogen atom and a monohydroxy group (-OH); and n is an integer from 1 to 10. The method of claim 5, wherein at least one of the compounds represented by the chemical formula (2) is at least one of the compounds represented by the chemical formulas (3) to (22): The method of claim 1, further comprising: preparing the monomer composition, wherein the preparing the monomer composition comprises: preparing a first composition comprising the hydrophilic monomer and a neutralizing agent; The first composition is mixed with the crosslinking agent and the polymerization initiator to prepare a second composition. The method of claim 1, wherein the polymerization initiator is at least one of a photopolymerization initiator, a thermal polymerization initiator, and a redox initiator. The method of claim 1, wherein the cross-linking the surface of the base resin further comprises: drying the surface-treated base resin.