KR101527585B1 - Preparation method for super absorbent polymer - Google Patents

Abstract

The present invention relates to a method for producing a superabsorbent resin. In the method for producing a superabsorbent resin according to the present invention, a surface crosslinking reaction is carried out using a specific compound as a surface crosslinking agent. According to the production method of the present invention, a superabsorbent resin having improved physical properties can be obtained.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to a method of manufacturing a super absorbent polymer,

The present invention relates to a method for producing a superabsorbent resin. More particularly, the present invention relates to a method for producing a superabsorbent resin having improved solution permeability.

Super Absorbent Polymer (SAP) is a synthetic polymer material capable of absorbing moisture of about 500 to 1,000 times its own weight. As a result, it is possible to develop a super absorbent polymer (SAM), an absorbent gel Material), and so on. Such a superabsorbent resin has started to be put into practical use as a sanitary article, and nowadays, in addition to sanitary articles such as diapers for children, there are currently used soil repair agents for horticultural use, index materials for civil engineering and construction, sheets for seedling growing, freshness- And it is widely used as a material for fomentation and the like.

As a method of producing such a superabsorbent resin, there are known methods such as reversed-phase suspension polymerization or aqueous solution polymerization. The reversed-phase suspension polymerization is disclosed in, for example, Japanese Unexamined Patent Publication No. 56-161408, Unexamined Japanese Patent Application No. 57-158209, and Japanese Unexamined Patent Publication No. 57-198714.

Methods of aqueous solution polymerization include a thermal polymerization method in which a polymerization gel is polymerized while being broken and cooled in a kneading machine having a plurality of shafts and a photopolymerization method in which a high concentration aqueous solution is irradiated with ultraviolet rays or the like on a belt to simultaneously perform polymerization and drying Are known.

The hydrogel polymer obtained through polymerization reaction as described above is generally marketed as a powdery product after being pulverized through a drying process.

In a product using a superabsorbent resin, the permeability is a measure for measuring the fluidity of a liquid to be absorbed. The transmittance may vary depending on the particle size distribution of the cross-linked resin, the shape of the particles and the connectivity of the openings between the particles, and the surface modification of the swollen gel. The fluidity of the liquid passing through the swollen particles varies depending on the transmittance of the superabsorbent resin composition. If the transmittance is low, the liquid can not easily flow through the superabsorbent resin composition.

As a method of increasing the transmittance in a superabsorbent resin, there is a method of carrying out a surface cross-linking reaction after resin polymerization and a method of adding silica or clay together with a surface cross-linking agent has been used. For example, U.S. Pat. Nos. 5,140,076 and 4,734,478 disclose the addition of silica during surface cross-linking of dry superabsorbent resin powders.

However, when the silica or clay is added, the transmittance is improved, but there is a problem that the water repellency or the pressure absorbing ability is decreased in proportion thereto, and the water is easily separated from the superabsorbent resin due to external physical impact during transportation.

In order to solve the problems of the prior art as described above, it is an object of the present invention to provide a method for producing a superabsorbent resin having improved physical properties by performing a surface crosslinking reaction using a specific compound as a surface crosslinking agent.

In order to accomplish the above object, the present invention provides a process for producing a water-soluble ethylenically unsaturated monomer, which comprises thermally polymerizing or photopolymerizing a monomer composition comprising a water-soluble ethylenically unsaturated monomer and a polymerization initiator to form a hydrogel polymer;

Drying the hydrogel polymer;

Pulverizing the dried polymer; And

The δ _tot it defined by the Hansen solubility parameters _{δ tot> 31 (J / cm} 3) 1/2 a polyol satisfying the (polyol) compound, and δ _H defined by the Hansen solubility parameter is 4 <δ _H <6 ( J / cm &lt; ³ &gt;) ^1/2 , and at least one surface cross-linking agent selected from the group consisting of compounds represented by the following formula (1), and a pulverized polymer are mixed to perform a surface cross- Wherein the water-soluble resin is a water-soluble resin.

[Chemical Formula 1]

In Formula 1, R is hydrogen or an alkyl group having 1 to 3 carbon atoms.

INDUSTRIAL APPLICABILITY According to the method for producing a superabsorbent resin of the present invention, it is possible to produce a superabsorbent resin having improved water permeability without deterioration in absorbability or pressure absorption ability.

Hereinafter, a method for producing a superabsorbent resin according to an embodiment of the present invention will be described in detail.

The method for producing a superabsorbent resin according to the present invention comprises the steps of: thermally polymerizing or photopolymerizing a monomer composition comprising a water-soluble ethylenically unsaturated monomer and a polymerization initiator to form a hydrogel polymer; Drying the hydrogel polymer; Pulverizing the dried polymer; And the δ _tot defined by the Hansen solubility parameter is δ _tot > Meets the 31 (J / cm ³⁾ polyol (polyol) compounds satisfying the ^1/2, and δ _H defined by the Hansen solubility parameter is _{4 <δ H <6 (J} / cm 3) 1/2, And a surface cross-linking solution containing at least one surface cross-linking agent selected from the group consisting of a compound represented by the following formula (1) and a ground polymer to perform a surface cross-linking reaction.

[Chemical Formula 1]

In Formula 1, R is hydrogen or an alkyl group having 1 to 3 carbon atoms.

In the method for producing a superabsorbent resin of the present invention, the monomer composition which is a raw material of the superabsorbent resin includes a water-soluble ethylenically unsaturated monomer and a polymerization initiator.

The water-soluble ethylenically unsaturated monomer may be any monomer conventionally used in the production of a superabsorbent resin without any particular limitations. Here, at least one monomer selected from the group consisting of an anionic monomer and its salt, a nonionic hydrophilic-containing monomer and an amino group-containing unsaturated monomer and a quaternary car- bon thereof may be used.

Specific examples include (meth) acrylic acid, maleic anhydride, fumaric acid, crotonic acid, itaconic acid, 2- acryloylethanesulfonic acid, 2- methacryloylethanesulfonic acid, 2- (meth) acryloylpropanesulfonic acid, 2- Anionic monomers of (meth) acrylamido-2-methylpropanesulfonic acid and salts thereof; (Meth) acrylamide, N-substituted (meth) acrylate, 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, methoxypolyethylene glycol (meth) acrylate or polyethylene glycol Non-ionic hydrophilic-containing monomer of (meth) acrylate; And at least one selected from the group consisting of unsaturated monomers containing an amino group of (N, N) -dimethylaminoethyl (meth) acrylate or (N, N) -dimethylaminopropyl (meth) .

More preferably, acrylic acid or a salt thereof, for example, an alkali metal salt such as acrylic acid or sodium salt thereof can be used. By using such a monomer, it becomes possible to produce a superabsorbent resin having superior physical properties. When the alkali metal salt of acrylic acid is used as a monomer, acrylic acid may be neutralized with a basic compound such as sodium hydroxide (NaOH).

The concentration of the water-soluble ethylenically unsaturated monomer may be about 20 to about 60 wt%, and more preferably about 40 to about 50 wt%, based on the monomer composition including the raw material and the solvent of the superabsorbent resin, The polymerization time and the reaction conditions. However, if the concentration of the monomer is excessively low, the yield of the superabsorbent resin may be low and economical efficiency may be deteriorated. On the other hand, if the concentration is excessively high, a part of the monomer may precipitate or the pulverization efficiency may be low Problems such as the like may occur and the physical properties of the superabsorbent resin may be deteriorated.

In the method for producing a superabsorbent resin of the present invention, the polymerization initiator used in polymerization is not particularly limited as long as it is generally used in the production of a superabsorbent resin.

Specifically, as the polymerization initiator, a thermal polymerization initiator or a photopolymerization initiator based on UV irradiation may be used depending on the polymerization method. However, even when the photopolymerization method is employed, a certain amount of heat is generated by irradiation of ultraviolet light or the like, and a certain amount of heat is generated as the polymerization reaction, which is an exothermic reaction, proceeds.

The photopolymerization initiator can be used without limitation in the constitution as long as it is a compound capable of forming a radical by light such as ultraviolet rays.

Examples of the photopolymerization initiator include benzoin ether, dialkyl acetophenone, hydroxyl alkylketone, phenyl glyoxylate, benzyl dimethyl ketal Ketal, acyl phosphine, and alpha-aminoketone may be used. On the other hand, as a specific example of the acylphosphine, a commonly used lucyrin TPO, i.e., 2,4,6-trimethyl-benzoyl-trimethyl phosphine oxide can be used . More photoinitiators are well described in Reinhold Schwalm, "UV Coatings: Basics, Recent Developments and New Applications (Elsevier 2007) &quot; p. 115, and are not limited to the above examples.

The photopolymerization initiator may be included at a concentration of about 0.01 to about 1.0 wt% based on the monomer composition. If the concentration of such a photopolymerization initiator is too low, the polymerization rate may be slowed. If the concentration of the photopolymerization initiator is too high, the molecular weight of the superabsorbent resin may be small and the physical properties may become uneven.

As the thermal polymerization initiator, at least one selected from persulfate-based initiators, azo-based initiators, initiators consisting of hydrogen peroxide and ascorbic acid can be used. Specifically, examples of the persulfate-based initiator include sodium persulfate (Na ₂ S ₂ O ₈ ), potassium persulfate (K ₂ S ₂ O ₈ ), ammonium persulfate (NH ₄ ) ₂ S ₂ O ₈ Examples of the azo initiator include 2, 2-azobis (2-amidinopropane) dihydrochloride, 2, 2-azobis (N, N-dimethylene) isobutyramidine dihydrochloride, 2- (carbamoyl azo) isobutyronitrile (2- (carbamoylazo) azobis [2- (2-imidazolin-2-yl) propane] dihydrochloride (2-azobisisobutyronitrile) 4,4-azobis- (4-cyanovaleric acid), and the like. A variety of thermal polymerization initiators are well described in the Odian book, Principle of Polymerization (Wiley, 1981), p. 203, and are not limited to the above examples.

The thermal polymerization initiator may be included at a concentration of about 0.001 to about 0.5% by weight based on the monomer composition. If the concentration of the thermal polymerization initiator is too low, additional thermal polymerization hardly occurs, and the effect of addition of the thermal polymerization initiator may be insignificant. If the concentration of the thermal polymerization initiator is excessively high, the molecular weight of the superabsorbent resin may be small and the physical properties may be uneven have.

According to one embodiment of the present invention, the monomer composition composition may further include an internal cross-linking agent as a raw material of the superabsorbent resin. As the internal crosslinking agent, a crosslinking agent having at least one functional group capable of reacting with the water-soluble substituent of the water-soluble ethylenically unsaturated monomer and having at least one ethylenic unsaturated group; Or a crosslinking agent having two or more functional groups capable of reacting with water-soluble substituents formed by hydrolysis of the water-soluble substituents and / or monomers of the monomers.

Specific examples of the internal crosslinking agent include bisacrylamide having 8 to 12 carbon atoms, bismethacrylamide, poly (meth) acrylate of polyol having 2 to 10 carbon atoms or poly (meth) allyl ether of polyol having 2 to 10 carbon atoms (Meth) acrylate, ethyleneoxy (meth) acrylate, propyleneoxy (meth) acrylate, glycerin diacrylate, At least one selected from the group consisting of glycerin triacrylate, trimethylol triacrylate, triallylamine, triaryl cyanurate, triallyl isocyanate, polyethylene glycol, diethylene glycol and propylene glycol can be used.

Such an internal crosslinking agent may be included at a concentration of about 0.01 to about 0.5% by weight based on the monomer composition to crosslink the polymerized polymer.

In the production process of the present invention, the monomer composition of the superabsorbent resin may further contain additives such as a thickener, a plasticizer, a storage stabilizer, and an antioxidant, if necessary.

The raw materials such as the water-soluble ethylenically unsaturated monomer, the photopolymerization initiator, the thermal polymerization initiator, the internal crosslinking agent and the additives described above can be prepared in the form of a monomer composition solution dissolved in a solvent.

The solvent which can be used at this time can be used without limitation of its constitution as long as it can dissolve the above-mentioned components. Examples thereof include water, ethanol, ethylene glycol, diethylene glycol, triethylene glycol, Propylene glycol monomethyl ether, propylene glycol monomethyl ether acetate, methyl ethyl ketone, acetone, methyl amyl ketone, cyclohexanone, cyclopentanone, diethylene glycol monomethyl ether, diethylene glycol At least one selected from ethyl ether, toluene, xylene, butylolactone, carbitol, methylcellosolve acetate and N, N-dimethylacetamide can be used in combination.

The solvent may be included in the remaining amount excluding the above-described components with respect to the total content of the monomer composition.

On the other hand, the method of forming a hydrogel polymer by thermal polymerization or photopolymerization of such a monomer composition is not particularly limited as long as it is a commonly used polymerization method.

Specifically, the polymerization method is largely divided into thermal polymerization and photopolymerization depending on the polymerization energy source. In general, when thermal polymerization is carried out, it may proceed in a reactor having a stirring axis such as a kneader. In the case where light polymerization is proceeded, The polymerization method described above is merely an example, and the present invention is not limited to the polymerization method described above.

For example, the hydrogel polymer obtained by supplying hot air or heating the reactor to a reactor such as a kneader having an agitating shaft as described above and thermally polymerizing the reactor may be supplied to the reactor outlet The discharged hydrogel polymer may be in the range of a few centimeters to a few millimeters. Specifically, the size of the obtained hydrogel polymer may vary depending on the concentration of the monomer composition to be injected, the injection rate, etc. In general, a hydrogel polymer having a weight average particle diameter of 2 to 50 mm can be obtained.

In addition, when photopolymerization proceeds in a reactor equipped with a movable conveyor belt as described above, the form of the hydrogel polymer that is usually obtained may be a hydrogel polymer on a sheet having a belt width. At this time, the thickness of the polymer sheet varies depending on the concentration of the monomer composition to be injected and the injection rate, but it is preferable to supply the monomer composition so that a polymer in the form of a sheet having a thickness of usually about 0.5 to about 5 cm can be obtained. When the monomer composition is supplied to such an extent that the thickness of the polymer in the sheet is too thin, the production efficiency is low, which is undesirable. When the thickness of the polymer on the sheet exceeds 5 cm, the polymerization reaction occurs evenly over the entire thickness due to the excessively thick thickness I can not.

The normal water content of the hydrogel polymer obtained by this method may be about 40 to about 80 wt%. On the other hand, throughout the present specification, the term "moisture content" means the moisture content of the total functional gelated polymer weight minus the weight of the hydrogel polymer in dry state. Specifically, it is defined as a value calculated by measuring the weight loss due to moisture evaporation in the polymer in the process of raising the temperature of the polymer through infrared heating. At this time, the drying condition is a method of raising the temperature from room temperature to about 180 ° C and then keeping it at 180 ° C, and the total drying time is set to 20 minutes including 5 minutes of the temperature raising step, and water content is measured.

Next, the step of drying the obtained hydrogel polymer is carried out.

At this time, if necessary, the step of coarse grinding may be further carried out before drying in order to increase the efficiency of the drying step.

In this case, the pulverizer to be used is not limited in its constitution, but may be a vertical pulverizer, a turbo cutter, a turbo grinder, a rotary cutter mill, A crusher, a disc mill, a disc mill, a shred crusher, a crusher, a chopper, and a disc cutter. However, the present invention is not limited to the above-described example.

Wherein the coarse grinding step may be comminuted so that the size of the hydrogel polymer is from about 2 to about 10 mm.

It is technically not easy to crush to less than 2 mm in diameter due to the high moisture content of the hydrogel polymer, and there may be a phenomenon that the crushed particles cohere to each other. On the other hand, when the particle size is larger than 10 mm, the effect of increasing the efficiency of the subsequent drying step may be insignificant.

Drying is carried out on the hydrogel polymer immediately after the polymerization, which has not been subjected to coarse pulverization or crude pulverization as described above. The drying temperature of the drying step may be about 150 to about 250 ° C. If the drying temperature is lower than 150 ° C, the drying time becomes excessively long and the physical properties of the superabsorbent resin to be finally formed may deteriorate. When the drying temperature exceeds 250 ° C, only the polymer surface is excessively dried, And the physical properties of the finally formed superabsorbent resin may be deteriorated. Thus, preferably, the drying can proceed at a temperature of from about 150 to about 200 &lt; 0 &gt; C, more preferably from about 160 to about 180 &lt; 0 &gt; C.

On the other hand, in the case of drying time, it may proceed for about 20 to about 90 minutes, but is not limited thereto, considering process efficiency and the like.

The drying method in the drying step may be selected and used as long as it is usually used as a drying step of the hydrogel polymer. Specifically, the drying step can be carried out by hot air supply, infrared irradiation, microwave irradiation, ultraviolet irradiation, or the like. The water content of the polymer after such a drying step may be from about 0.1 to about 10% by weight.

Next, a step of pulverizing the dried polymer obtained through such a drying step is carried out.

The polymer powder obtained after the milling step may have a particle diameter of from about 150 to about 850 탆. The pulverizer used for crushing with such a particle size is specifically a pin mill, a hammer mill, a screw mill, a roll mill, a disc mill, A jog mill, or the like may be used, but the present invention is not limited to the above examples.

Further, in order to control the physical properties of the superabsorbent resin powder which is finally produced after the pulverization step, a separate process of classifying the polymer powder obtained after pulverization according to the particle size may be performed. Preferably, the polymer having a particle diameter of about 150 to about 850 탆 is classified, and the polymer powder having such a particle diameter can be produced through the surface cross-linking reaction step.

According to one embodiment of the present invention, the ground polymer as a base resin prior to undergoing the surface cross-linking reaction step has a coverage capacity (CRC) of 37 g / g or less, for example 28 to 37 g / g, At the same time, it can have a shear modulus of 4000 Pa or more, for example 4000 to 5300 Pa. When a polymer having the above physical properties is used as a base resin and the surface cross-linking reaction step of the present invention to be described later is carried out, a highly water-absorbent resin having excellent physical properties can be obtained.

Next, as defined by the pulverized polymer, a Hansen solubility parameter δ _tot the _{δ tot> 31 (J / cm} 3) 1/2 a polyol satisfying the (polyol) compound, and Hansen δ _H is defined by a solubility parameter the _{4 <δ H <6 (J} / cm 3) satisfies a ^half, to a mixture of the surface cross-linking solution containing the surface cross-linking agent at least one member selected from the group consisting of compounds represented by the general formula (1) the surface cross-linking reaction .

[Chemical Formula 1]

In Formula 1, R is hydrogen or an alkyl group having 1 to 3 carbon atoms.

The surface cross-linking is a step of increasing the cross-linking density near the surface of the superabsorbent polymer particle in relation to the cross-linking density inside the particle. Generally, the surface cross-linking agent is applied to the surface of the superabsorbent resin particles. Thus, this reaction takes place on the surface of the superabsorbent resin particles, which improves the crosslinkability on the surface of the particles without substantially affecting the interior of the particles. Thus, the surface cross-linked superabsorbent resin particles have a higher degree of crosslinking in the vicinity of the surface than in the interior.

In the production method of the present invention, when the specific compound is used as a surface cross-linking agent for carrying out the surface cross-linking reaction, the surface cross-linking reaction occurs at an appropriate level and exhibits excellent solution transmittance without deteriorating other physical properties.

According to one embodiment of the present invention, when δ _tot defined by the Hansen solubility parameter as a surface cross-linking agent is δ _tot > 31, and satisfying the (J / cm ³⁾ polyol that satisfies ^1/2 (polyol) compound, and Hansen _H δ which is defined by the solubility parameters of the _{4 <δ H <6 (J} / cm 3) 1/2, A compound selected from the group consisting of the compounds represented by the above-mentioned formula (1) may be used alone or two or more substances may be used in combination.

The Hansen solubility parameter was proposed by Charles Hansen as a method for predicting when a substance is dissolved in another substance to form a solution. For example, "INDUSTRIAL SOLVENTS HANDBOOK" (pp. 35-68, published by Marcel Dekker, Inc., 1996) or "DIRECTORY OF SOLVENTS" (pp.22-29, published by Blackie Academic & Professional, 1996) It is the described parameter.

Generally, to calculate the solubility parameter, the cohesive energy should be obtained. In the Hansen solubility parameter, the cohesive energy affecting the solubility constant is classified into the following three types.

δ _D : Solubility constant due to nonpolar dispersion energy (unit: (J / cm ³ ) ^1/2 )

δ _P : solubility constant due to dipole polar energy (unit: (J / cm ³ ) ^1/2 )

δ _H : Solubility constant due to hydrogen bonding energy (unit: (J / cm ³ ) ^1/2 )

? _tot : ((? _D ) ² + (? _P ) ² + (? _H ) ² ) ^1/2

The similarity of the solubility of the two materials can be calculated from the difference between the Hansen solubility parameters of the two materials by obtaining the above parameters. For example, for both substances A and B, the respective Hansen solubility parameter values are A (δ _D ^A , δ _P ^A, δ _H ^A ), in the case of ^B (δ _D ^B , δ _P ^B , δ _H ^B ), the difference (Ra) of the Hansen solubility parameter values of the two materials can be calculated by the following equation.

Ra = (4 * (? _D ^A -? _D ^B ) ² + ^{_{(δ P A - δ P B}} ) 2 + (δ H A - 隆_H ^B ) ² ) ^1/2

The higher the Ra value, the lower the similarity of the two materials in terms of solubility.

For some substances that can be used as cross-linking agents. The Hansen solubility parameter values calculated according to the HSPP (Hansen Solubility Parameters in Practice, 3 ^rd edition version 3.1 published by Hansen-Solubility.com) program developed by the Hansen group are shown in Table 1 below.

Material name Hansen solubility parameter
(Unit: (J / cm ³ ) ^1/2 ) δ _D δ _P 隆_H δ _tot Ethylene glycol 17 11 26 33 1,3-propanediol 16.8 13.5 23.2 31.7 1,4-butanediol 16.6 11 20.9 28.9 1,6-hexanediol 15.7 8.4 17.8 25.2 Propylene glycol 16.8 10.4 21.3 29.1 1,2-hexanediol 16 7.4 16.7 24.9 1,3-butanediol 16.5 8.1 20.9 27.8 2-methyl-1,3-propanediol 16.3 9.2 22.8 29.5 2,5-hexanediol 16 7.5 23.9 29.7 2-methyl-1,3-pentanediol 15.9 7.1 22.4 28.4 2-methyl-2,4-pentanediol 16 8.3 22.1 28.5 Ethylene carbonate 18 21.7 5.1 28.7 Propylene carbonate 20 18 4.1 27.2 Diethylene glycol 16.6 12 19 27.9 Triethylene glycol 16 12.5 18.6 27.5 Tripropylene glycol 16 6.8 16.3 23.8 Glycerol 17.4 11.3 27.2 34.2

When δ _tot defined by the Hansen solubility parameter is δ _tot > 31 polyol (polyol) compounds satisfying the ^{(J / cm 3) 1/} 2 , may be mentioned, for example, 1,3-propanediol, ethylene glycol, glycerol, and the like.

Also, 隆_H defined by the Hansen solubility parameter satisfies 4 < 隆_H < 6 (J / cm ³ ) ^1/2 , and examples of the compound represented by Formula 1 include ethylene carbonate or propylene carbonate And the like.

According to the production process of the present invention, a superabsorbent resin having an improved solution permeability can be obtained by performing a surface cross-linking reaction on a polymer using a compound selected from the group consisting of the compounds satisfying the above-mentioned specific conditions as a surface cross-linking agent .

According to one embodiment of the present invention, the surface cross-linking solution has a δ _{P value} defined by the Hansen solubility parameter δ _P <may further comprise a ^{12 (J / cm 3) 1} /2 add one or more materials selected from the group consisting of a material that satisfies a.

Examples of the material satisfying the above 隆_P <12 (J / cm ³ ) ^1/2 include 1,4-butanediol, 1,6-hexanediol, propylene glycol, 1,2-hexanediol, Methyl-1,3-propanediol, 2,5-hexanediol, 2-methyl-1,3-pentanediol, tripropylene glycol, or glycerol. However, the present invention is not limited thereto, and it is possible to use a substance which is not listed in Table 1 as long as it satisfies the above parameter range.

The present invention is based on the _assumption that δ _tot defined by the Hansen solubility parameter is δ _tot > Meets the 31 (J / cm ³⁾ polyol (polyol) compounds satisfying the ^1/2, and δ _H defined by the Hansen solubility parameter is _{4 <δ H <6 (J} / cm 3) 1/2, one kind of a material that satisfies the necessary and included in the at least one member selected from the group consisting of a compound represented by the formula (1) with a surface crosslinking agent, optionally in the Hansen parameter _{δ P <12 (J / cm} 3) 1/2 The surface cross-linking reaction can be carried out to a degree suitable for the final product.

In the surface cross-linking reaction of the present invention, when the two surface cross-linking agents are included, the respective weight ratios are not particularly limited and may be, for example, from about 1:10 to about 10: 1, or from about 1: 2 to about 2: 1 &lt; / RTI &gt; by weight.

According to one embodiment of the present invention, when δ _tot defined by the Hansen solubility parameter is δ _tot ^{> 31 (J / cm 3)} 1 / a polyol (polyol) compound that satisfies ² used may be ethylene glycol, 1,3-propanediol or glycerol, a δ _H defined by the Hansen solubility parameter 4 <δ _H < 6 (J / cm < ³ &gt;) ^1/2 , and ethylene carbonate or propylene carbonate may be used as the compound represented by the above formula (1). Propylene glycol may be used as a material satisfying? _P <12 (J / cm ³ ) ^1/2 . However, the present invention is not limited thereto.

The total amount of the surface cross-linking agent contained in the surface cross-linking solution may be appropriately selected depending on the kind of the surface cross-linking agent to be added and the reaction conditions, but is preferably about 0.2 to about 1.0 part by weight, Preferably about 0.25 to about 0.8 part by weight may be used.

When the content of the surface cross-linking agent is too small, the surface cross-linking reaction hardly occurs, and with respect to 100 parts by weight of the polymer, 1.0 If it exceeds the weight part, excessive absorption of the surface cross-linking reaction may result in degradation of the absorption capacity and physical properties.

The superabsorbent resin obtained according to the production method of the present invention has an improved solution permeability.

In particular, a base resin having a shear modulus of at least 4000 Pa, for example 4000 to 5300 Pa, with a coverage capacity (CRC) of 37 g / g or less, for example 28 to 37 g / When the surface cross-linking reaction using the surface cross-linking agent of the present invention is carried out, a highly water-swellable resin having an excellent balance of physical properties suitable for the final product can be obtained.

According to one embodiment of the present invention, surface crosslinking reaction can be performed by addition of silica or clay, which is porous in addition to the surface cross-linking agent.

The superabsorbent resin obtained according to the production method of the present invention may have improved physical properties due to surface crosslinking. For example, the superabsorbent resin produced according to the production method of the present invention has a weight average molecular weight of about 30 × 10 ^-7 cm ³ * sec / g or more, preferably about 30 × 10 ^-7 to about 170 × 10 ^-7 cm ³ * sec / g of solution transmittance (SFC).

Also, the superabsorbent resin powder prepared according to the production method of the present invention has a retention capacity (CRC) of at least about 25 g / g, preferably about 25 g / g to about 31 g / g, as measured according to EDANA method WSP 241.2 (AUP) of at least about 22.5 g / g, preferably about 23 g / g to about 26 g / g, as measured according to the method of EDANA method WSP 242.2.

Also, the superabsorbent resin powder prepared according to the production method of the present invention has a PDAUP of about 19 g / g or more, preferably about 19 g / g to about 26 g / g, as measured according to EDANA method WSP 243.1. g.

The constitution of the method of adding the surface cross-linking agent to the polymer is not limited. A method in which a surface cross-linking agent and a polymer powder are mixed in a reaction tank or spraying a surface cross-linking agent onto a polymer powder, a method in which a polymer and a surface cross-linking agent are continuously supplied and mixed in a continuously operated mixer can be used.

The surface cross-linking solution may be added to the surface cross-linking except for the addition of water and alcohol together. When water and alcohol are added, there is an advantage that the surface cross-linking agent can be uniformly dispersed in the polymer. The amount of added water and alcohol is about 5 to about 100 parts by weight per 100 parts by weight of the polymer for the purpose of inducing even dispersion of the surface cross-linking agent and preventing the polymer powder from aggregating and optimizing the surface penetration depth of the cross- 12 parts by weight.

By heating the polymer particles to which the surface crosslinking agent has been added at a temperature of about 150 to about 220 DEG C, preferably about 165 to about 210 DEG C, for about 15 to about 80 minutes, preferably about 20 to about 70 minutes, A coupling reaction can be made. When the crosslinking reaction temperature is lower than 150 ° C, the surface crosslinking reaction may not occur sufficiently, and when the crosslinking reaction temperature exceeds 220 ° C, the surface crosslinking reaction may excessively proceed. When the crosslinking reaction time is less than 15 minutes, the crosslinking reaction can not be performed sufficiently, and when the crosslinking reaction time exceeds 80 minutes, the crosslinking density of the surface of the particles becomes excessively high due to excessive surface crosslinking reaction, .

The temperature raising means for the surface cross-linking reaction is not particularly limited. A heating medium can be supplied, or a heating source can be directly supplied and heated. At this time, as the type of usable heat medium, it is possible to use a heated fluid such as steam, hot air or hot oil. However, the present invention is not limited thereto, and the temperature of the heat medium to be supplied can be controlled by means of heat medium, It can be appropriately selected in consideration of the target temperature. On the other hand, as a heat source to be directly supplied, a heating method using electricity or a heating method using gas may be mentioned, but the present invention is not limited to the above-mentioned examples.

As described above, the superabsorbent resin obtained according to the production method of the present invention can have improved solution permeability without deteriorating physical properties such as water retention capacity and pressure absorption ability.

The invention will be described in more detail in the following examples. However, the following examples are illustrative of the present invention, and the present invention is not limited by the following examples.

< Example >

Produce Example  1: Preparation of polymer

100 g of acrylic acid, 0.1 g of polyethylene glycol diacrylate as a crosslinking agent, 38.9 g of caustic soda (NaOH) and 103.9 g of water were mixed to prepare a monomer composition having a monomer concentration of 50% by weight.

Thereafter, the monomer composition was introduced through a feeding part of a kneader polymerization machine rotating continuously, and 1 g of a 1% hydrogen peroxide solution and 1 g of a 2% ascorbic acid aqueous solution were added as a polymerization initiator to the monomers.

The polymerization initiator was mixed, polymerization was started after 1 minute, and polymerization was continued for 15 minutes. At this time, the internal temperature of the reactor was 99 ° C. The polymerized hydrogel polymer was transferred to a cutter and then cut to 0.2 cm. At this time, the water content of the cut functional gel polymer was 50% by weight.

Thereafter, the polymer discharged from the cutter was dried for 1 hour in a hot-air drier at 180 ° C. Subsequently, the resultant was pulverized with a pin mill, and then classified into a polymer having a particle size of less than 150 μm and a polymer having a particle size of 150 μm to 850 μm using a sieve.

The classified polymer had a coverage (CRC) of 36 g / g and a shear modulus of 4800 Pa.

Example  One

5 g of methanol, 4 g of distilled water, 0.5 g of 1,3-propanediol and 0.01 g of silica powder (trade name IM30S) were mixed, and 100 g of the polymer of Preparation Example 1 was mixed. These mixtures were reacted in a convection oven at 180 캜 for 60 minutes, and then the temperature was lowered to room temperature to obtain a surface cross-linked polymer.

Example  2

A surface cross-linked polymer was prepared in the same manner as in Example 1, except that 0.58 g of ethylene carbonate was used instead of 0.5 g of 1,3-propanediol.

Example  3

A surface cross-linked polymer was prepared in the same manner as in Example 1, except that 0.17 g of 1,3-propanediol and 0.28 g of ethylene carbonate were used instead of 0.5 g of 1,3-propanediol.

Example  4

A surface cross-linked polymer was prepared in the same manner as in Example 1, except that 0.33 g of 1,3-propanediol and 0.28 g of ethylene carbonate were used instead of 0.5 g of 1,3-propanediol.

Example  5

A surface cross-linked polymer was prepared in the same manner as in Example 1, except that 0.4 g of 1,3-propanediol and 0.10 g of propylene glycol were used instead of 0.5 g of 1,3-propanediol.

Example  6

A surface cross-linked polymer was prepared in the same manner as in Example 1 except that 0.41 g of ethylene glycol was used instead of 0.5 g of 1,3-propanediol.

Comparative Example  One

A surface cross-linked polymer was prepared in the same manner as in Example 1, except that 0.59 g of 1,4-butanediol was used in place of 0.5 g of 1,3-propanediol.

Comparative Example  2

A surface cross-linked polymer was prepared in the same manner as in Example 1, except that 0.91 g of 1,6-hexanediol was used instead of 0.5 g of 1,3-propanediol.

Comparative Example  3

A surface cross-linked polymer was prepared in the same manner as in Example 1 except that 0.5 g of propylene glycol was used instead of 0.5 g of 1,3-propanediol.

< Experimental Example >

Function , Pressure Absorption capacity , Solution permeability and pressure Liquid permeability  Measure

(1) CRC (Centrifuge Retention Capacity)

The maintenance performance was measured according to EDANA method WSP 241.2. More specific methods are as follows.

The highly water-absorbent resin W (g) (about 0.2 g) was uniformly put in an envelope made of nonwoven fabric and sealed, and then immersed in 0.9% by mass of physiological saline at room temperature. After 30 minutes, the envelope was subjected to centrifugal separation at 250G for 3 minutes, and the weight W2 (g) of the envelope was measured. After the same operation was performed without using a resin, the mass W1 (g) at that time was measured. Using the obtained masses, the CRC (g / g) was calculated according to the following formula 1 to confirm the retention capacity.

[Formula 1]

CRC (g / g) = {(W2 (g) - W1 (g)) / W (g)

(2) Absorption under pressure (AUP)

The pressure absorption capacity was measured according to the method of EDANA WSP 242.2. More specific methods are as follows.

A 400 mesh wire mesh made of stainless steel was attached to the bottom of a plastic cylinder having an inner diameter of 60 mm. A piston capable of uniformly spreading the water absorbent resin W (g) (0.90 g) on the iron mesh under the condition of room temperature and humidity of 50% and uniformly applying a load of 4.83 kPa (0.7 psi) Is slightly smaller than 60 mm, and there is no gap between the inner wall of the cylinder and the up and down movement is prevented from being disturbed. At this time, the weight Wa (g) of the device was measured.

A glass filter having a diameter of 90 mm and a thickness of 5 mm was placed inside a Petro dish having a diameter of 150 mm and a physiological saline solution composed of 0.90% by weight sodium chloride was made to have the same level as the upper surface of the glass filter. And a filter paper having a diameter of 90 mm was placed thereon. The measuring device was placed on the filter paper and the liquid was absorbed under load for 1 hour. After one hour, the measuring device was lifted and its weight Wb (g) was measured. AUP (g / g) was calculated according to the following formula 2 to confirm the pressure absorption ability.

[Formula 2]

AUP (g / g) = {Wb (g) - Wa (g)} / W (g)

(3) Saline flow conductivity (SFC)

The solution permeability was measured according to U.S. Publication No. Was measured according to the method described in [0184] to [0189] of column 16 of 2009-0131255.

(4) Gravimetric Determination of Permeability Dependent Absorption Under Pressure (PDAUP)

EDP was measured according to the method of EDANA WSP 243.1. More specific methods are as follows.

A 400 mesh wire mesh made of stainless steel was attached to the bottom of a plastic cylinder having an inner diameter of 60 mm. A piston capable of uniformly spreading the water absorbent resin W (g) (5.0 g) onto the iron mesh under the condition of room temperature and humidity of 50% and uniformly applying a load of 4.83 kPa (0.7 psi) Is slightly smaller than 60 mm, and there is no gap between the inner wall of the cylinder and the up and down movement is prevented from being disturbed. At this time, the weight W3 (g) of the apparatus was measured.

A glass filter having a diameter of 90 mm and a thickness of 5 mm was placed inside a Petro dish having a diameter of 150 mm and a physiological saline solution composed of 0.90% by weight sodium chloride was made to have the same level as the upper surface of the glass filter. And a filter paper having a diameter of 90 mm was placed thereon. The measuring device was placed on the filter paper and the liquid was absorbed under load for 1 hour. After one hour, the measuring device was lifted and its weight W4 (g) was measured. AUP (g / g) was calculated according to the following formula 3 to confirm the pressure absorption ability.

[Formula 3]

PDAUP (g / g) = {W4 (g) - W3 (g)} / W (g)

In Equation (3)

W (g) is the weight of the water absorbent resin,

W3 (g) is the total sum of the weight of the water absorbent resin and the weight of the apparatus for applying the load to the water absorbent resin,

W4 (g) is the total sum of the weight of the water absorbed resin absorbed after supplying water to the water absorbent resin for 1 hour under a load (0.7 psi) and the weight of the apparatus for applying the load to the water absorbent resin.

* The polymers of Examples and Comparative Examples according to the above methods were measured for coverage ability, pressure absorption capacity, solution permeability and pressure permeability, and are shown in Table 2 below.

Support function (CRC)
(Unit: g / g) Pressure Absorption Capacity (AUP)
(Unit: g / g) Solution Transmittance (SFC)
(Unit: cm ³ * sec / g) Pressurized liquid (PDAUP)
(Unit: g / g) Example 1 28.3 24.4 46x10 ^-7 22.5 Example 2 29.3 24.7 69x10 ^-7 23.0 Example 3 30.0 24.5 47x10 ^-7 22.1 Example 4 30.0 24.6 39x10 ^-7 21.7 Example 5 29.5 24.7 34x10 ^-7 19.6 Example 6 30.0 26.7 46x10 ^-7 22.1 Comparative Example 1 29.1 24.2 27x10 ^-7 18.1 Comparative Example 2 30.6 24.5 23x10 ^-7 17.6 Comparative Example 3 29.9 22.7 14x10 ^-7 15.0

Referring to Table 2, the polymer obtained according to the preparation method of the present invention exhibited improved physical properties as compared with Comparative Examples.

Claims (16)

Thermally polymerizing or photopolymerizing a monomer composition comprising a water-soluble ethylenically unsaturated monomer and a polymerization initiator to form a hydrogel polymer;
Drying the hydrogel polymer;
Pulverizing the dried polymer; And
When δ _tot defined by the Hansen solubility parameter is δ _tot > 31, and satisfying the (J / cm ³⁾ polyol that satisfies ^1/2 (polyol) compound, and Hansen _H δ which is defined by the solubility parameters of the _{4 <δ H <6 (J} / cm 3) 1/2, And a surface cross-linking solution containing at least one surface cross-linking agent selected from the group consisting of a compound represented by the following formula (1) and a pulverized polymer to perform a surface cross-linking reaction:
[Chemical Formula 1]

In Formula 1, R is hydrogen or an alkyl group having 1 to 3 carbon atoms.
The method of claim 1, wherein the δ _tot defined by the Hansen solubility parameter is δ _tot > 31. The method of superabsorbent polymer to the polyol (polyol) compounds satisfying the ^{(J / cm 3) 1/} 2 contains one or more selected from 1,3-propanediol, ethylene glycol, and the group consisting of glycerol .
The method according to claim 1, wherein the 隆_H defined by the Hansen solubility parameter satisfies 4 < 隆_H < 6 (J / cm ³ ) ^1/2 and the compound represented by the above formula (1) is ethylene carbonate or propylene carbonate By weight.
The surface cross-linking solution according to claim 1, wherein? _P defined by the Hansen solubility parameter is _{δ P <12 (J / cm} 3) 1/2 The method for producing a superabsorbent polymer which comprises one or more surface cross-linking agent is selected from the group consisting of materials satisfying.
The method of claim 4, wherein the material which satisfies the _{δ P <12 (J / cm} 3) 1/2 is 1,4-butanediol, 1,6-hexanediol, propylene glycol, 1,2-hexanediol, 1, At least one selected from the group consisting of 3-butanediol, 2-methyl-1,3-propanediol, 2,5-hexanediol, 2-methyl-1,3-pentanediol, tripropylene glycol, A method for producing a resin.
The method of producing a superabsorbent resin according to claim 1, wherein the surface crosslinking reaction further comprises silica.
The method according to claim 1, wherein the surface cross-linking agent is added in an amount of 0.2 to 1.0 part by weight based on 100 parts by weight of the pulverized polymer .
The method of producing a superabsorbent resin according to claim 1, wherein the superabsorbent resin has a solution transmittance (SFC) of ³⁰ x 10 ^-7 to 170 x 10 ^-7 cm ³ * sec / g.
The method of producing a superabsorbent resin according to claim 1, wherein the superabsorbent resin has a water retention capacity (CRC) of 25 to 31 g / g.
The method of producing a superabsorbent resin according to claim 1, wherein the superabsorbent resin has a pressure absorption capacity (AUP) of 23 to 26 g / g.
The method of producing a superabsorbent resin according to claim 1, wherein the superabsorbent resin has a pressure-permeability (PDAUP) of 19 to 26 g / g.
The method of claim 1, wherein the ground polymer has a coverage capacity (CRC) of 37 g / g or less and a shear modulus of 4000 Pa or higher.
The method of producing a superabsorbent resin according to claim 1, further comprising a step of pulverizing the hydrogel polymer to a particle size of 2 to 10 mm before the step of drying the hydrogel polymer.
The method of manufacturing a superabsorbent resin according to claim 1, wherein the drying of the hydrogel polymer is carried out at a temperature of 150 to 250 ° C.
The method for producing a superabsorbent resin according to claim 1, wherein the pulverization of the dried polymer proceeds so that the ground polymer has a particle diameter of 150 to 850 탆.
The method for producing a superabsorbent resin according to claim 1, further comprising the step of classifying the polymer into a polymer having a particle diameter of 150 to 850 탆 before performing the surface cross-linking reaction on the ground polymer.