WO2019117541A1

WO2019117541A1 - Superabsorbent polymer and preparation method therefor

Info

Publication number: WO2019117541A1
Application number: PCT/KR2018/015468
Authority: WO
Inventors: 정선정; 남대우; 성보현; 윤형기
Original assignee: 주식회사 엘지화학
Priority date: 2017-12-11
Filing date: 2018-12-07
Publication date: 2019-06-20

Abstract

The present invention relates to a superabsorbent polymer and a preparation method therefor. The present invention can provide a superabsorbent polymer in which a hydrophobic material having an HLB of 0-6 and a surface cross-linking agent are mixed into a base resin prepared in the presence of water dispersible silica, thereby having improved rewetting characteristics and permeability through surface-modification of the base resin.

Description

2019/117541 1 »(: 1 ^ {2018/015468

Title of the Invention

Superabsorbent resin and method for producing the same

TECHNICAL FIELD

Cross-reference with related application (s)

This application is related to Korean Patent Application No. 10-2017-0169490, dated December 11, 2017,

Claims priority to Korean Patent Application No. 10-2018-0155292, filed on December 5, 2018, the entire contents of which are incorporated herein by reference.

The present invention relates to a superabsorbent resin and a method for producing the same. More particularly, the present invention relates to a superabsorbent resin having improved rewet characteristics and absorption rates and a method for producing the same.

TECHNICAL BACKGROUND OF THE INVENTION

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 use SAM (Super Absorbent Material), AGM Material), and so on. Such a superabsorbent resin has started to be put into practical use as a sanitary article and is currently being used for diapers and sanitary napkins for children, as well as soil repair agents for horticultural use, exponents for civil engineering and construction, sheet for seedling growing, , And as a material for fomentation and the like.

In most cases, such superabsorbent resins are widely used in diapers and sanitary napkins. In order to use such superabsorbent resins, it is necessary to exhibit a high absorption capacity for moisture and the like, In addition, there is a need to exhibit excellent permeability by absorbing water to keep its shape even in the state of volume expansion (swelling).

It has been known that it is difficult to improve both the water repellency (CRC), which is the physical property showing the basic absorption power and the water holding capacity of the superabsorbent resin, and the absorptive capacity under pressure (AUP), which shows the property of holding the moisture absorbed even to the external pressure well . This is because, when the overall cross-linking density of the superabsorbent resin is controlled to be low, the crosslinking density can be relatively high, but the cross-linking structure becomes difficult and the gel strength becomes low, So 2019/117541 1 »(: 1 ^ {2018/015468

When the absorption capacity under pressure is improved, moisture is hardly absorbed between the dense crosslinked structures, and basic storage ability may be lowered. For the above reasons, there is a limit to providing a superabsorbent resin having both a water-repellent ability and an ability to absorb under pressure.

In recent years, however, it has become increasingly important to improve the water absorbing ability and the pressure absorbing ability, which are opposite physical properties, and the improvement of the liquid permeability. It is being installed in the lobby.

In addition, pressure may be applied to sanitary materials such as diapers and sanitary napkins by the weight of the user. Particularly, when a superabsorbent resin applied to a sanitary material such as a diaper or sanitary napkin absorbs a liquid, if a pressure due to the weight of the user is applied to the absorbent resin, a re-wetting phenomenon , Urine

A phenomenon may occur.

Therefore, various attempts have been made to suppress such re-wetting phenomenon. However, there is no concrete method to effectively inhibit the re-wetting phenomenon.

DISCLOSURE OF THE INVENTION

[Problem to be solved]

In order to solve the problems of the prior art as described above, it is an object of the present invention to provide a superabsorbent resin in which rewetting and leakage of urine are suppressed, and a method of manufacturing the same.

MEANS FOR SOLVING THE PROBLEMS

To achieve the above object, according to one aspect of the present invention, there is provided a method for producing an acrylic resin composition, which comprises, in the presence of water-dispersed silica, a base having an acidic group and at least a part of the acidic group neutralized with an acrylic acid-based monomer and an internal cross-

(Step 2) of a hydrophobic substance and a surface cross-linking agent,

Performing the surface modification on the bead resin by raising the mixture of step 2 (step 3); 2019/117541 1 »(: 1 ^ {2018/015468

And a method of producing the superabsorbent resin.

According to another aspect of the present invention,

A base resin comprising a cross-linked polymer obtained by cross-linking an acrylic acid-based monomer in which at least a part of an acidic group is neutralized; and

A surface modification layer formed on the particle surface of the base resin, wherein the cross-linking polymer is additionally crosslinked via a surface cross-linking agent,

Wherein the surface modification layer comprises a hydrophobic material having an HLB of not less than 0 and not more than 6, and a vortex time of not more than 35 seconds.

【Effects of the Invention】

INDUSTRIAL APPLICABILITY According to the present invention and the superabsorbent resin and the method for producing the same, it is possible to provide a superabsorbent resin exhibiting excellent physical properties of absorption and inhibiting porcelain wetting phenomenon and urine leakage phenomenon.

DETAILED DESCRIPTION OF THE INVENTION

The present invention can be variously modified and may take various forms, and specific embodiments will be illustrated and described in detail below. It should be understood, however, that the invention is not intended to be limited to the particular forms disclosed, but includes all modifications, equivalents, and alternatives falling within the spirit and scope of the invention.

Hereinafter, a superabsorbent resin according to one embodiment of the present invention and a method for producing the same will be described in detail. A method of manufacturing a superabsorbent resin according to an embodiment of the present invention includes:

(Step 1) of preparing a base resin crosslinked with an acrylic acid-based monomer and an internal cross-linking agent having an acidic group and neutralizing at least a part of the acidic group in the presence of the water-dispersed silica;

Mixing the base resin with a hydrophobic substance having an HLB of not less than 0 and not more than 6, and a surface cross-linking agent (step 2); and

And performing the surface modification to the base resin by raising the mixture of the step 2 (step 3). 2019/117541 1 »(: 1 ^ {2018/015468

In the specification of the present invention, the term "base resin" or "base resin powder" means a polymer obtained by drying and pulverizing a polymer obtained by polymerizing a water-soluble ethylenically unsaturated monomer,

Means a polymer in a state where the surface modification or surface cross-linking step described later is not performed.

The hydrogel polymer obtained by the polymerization reaction of the acrylic acid-based monomer is subjected to a process such as drying, crushing, classification, surface crosslinking and the like, and is marketed as a superabsorbent resin which is powdery product.

In recent years, not only the absorption properties such as absorption ability and liquid permeability in the super absorbency resin, but also the properties of the surface

How long the condition can be maintained is an important measure of diaper characteristics.

The superabsorbent resin obtained by the production method according to one embodiment of the present invention is excellent in physical properties such as water repellency, pressure absorbing ability and liquid permeability and exhibits excellent absorption performance and remains dry even after being swollen with salt water It is possible to effectively prevent the re-wetting 0 and the urine leakage (1-year) phenomenon in which the urine absorbed in the superabsorbent resin is re-exuded, leading to the present invention.

In the method for producing a superabsorbent resin of the present invention, the monomer composition, which is a raw material of the superabsorbent resin, is prepared by first mixing an acrylic acid-based monomer having an acidic group and at least a part of the acidic groups neutralized, an internal crosslinking agent, Polymerized to obtain a hydrogel polymer, which is dried, pulverized and classified to obtain a base

(Step 1).

This will be described in more detail below.

The monomer composition which is a raw material of the superabsorbent resin includes an acrylic acid-based monomer having an acidic group and at least a part of the acidic groups neutralized and a polymerization initiator.

The acrylic acid-based monomer is a compound represented by the following Formula 1:

[Chemical Formula 1]

- on

In Formula 1,

II < ¹ > is an alkyl group having 2 to 5 carbon atoms containing an unsaturated bond, 2019/117541 1 (1) (2018/015468) 1 is an azole, monovalent or divalent metal, an ammonium group or an organic amine salt. Preferably, the acrylic acid-based monomer includes at least one selected from the group consisting of acrylic acid, methacrylic acid, monovalent metal salts thereof, bivalent metal salts, ammonium salts and organic amine salts thereof.

Here, the acrylic acid-based monomer may have an acidic group and at least a part of the acidic group may be neutralized. Preferably, the monomer is partially neutralized with an alkylene material such as sodium hydroxide, potassium hydroxide, ammonium hydroxide and the like. At this time, the neutralization degree of the acrylic acid monomer may be 40 to 95 mol%, or 40 to 80 mol%, or 45 to 75 mol%. The range of the degree of neutralization can be adjusted according to the final properties. However, if the degree of neutralization is too high, neutralized monomers may precipitate and polymerization may be difficult to proceed smoothly. On the other hand, if the degree of neutralization is too low, the absorption capacity of the polymer is greatly decreased, .

The concentration of the acrylic acid monomer may be about 20 to about 60 wt%, preferably about 40 to about 50 wt%, based on the monomer composition including the raw material of the superabsorbent resin and the solvent, The concentration may be appropriate considering the conditions and the like. 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 And the like, may cause problems in the process, 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 upon 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 may form a radical by light such as ultraviolet light 2019/117541 1 »(: 1/10/0/0 018/015468

Can be used without limitation of the constitution.

Examples of the photopolymerization initiator include benzoin ether, dialkyl acetophenone, hydroxyl alkylketone, phenyl glyoxylate, benzyl dimethyl ketal Ketal, acyl phosphine, and a-aminoketone may be used. On the other hand, Specific examples of the acylphosphine commercial lucirin TPO, that is, ^2, ^4, 6, which - may be trimethyl phosphine oxide ^(2, ^4, ^{-trimethyl-6-trimethyl} benzoyl phosphine oxide) - trimethyl-benzoyl For more diverse photoinitiators, see Reinhold Schwalm, TJV Coatings: Basics, Recent Developments and New

Application (Elsevier 2007) 'pi 15, and is not limited to the above example.

The photopolymerization initiator may be included in the monomer composition at a concentration of about 0.01 to about 1.0 wt%. If the concentration of such a photopolymerization initiator is too low, the polymerization rate may be slow. If the concentration of the photopolymerization initiator is too high, the molecular weight of the high absorption 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 () 8)} , potassium sulphate (K ₂ S ₂ O _8), ammonium persulfate NH _{2) 2} S ₂ C) 8). Examples of azo initiators include 2, 2-azobis- (2-amidinopropane)

2-azobis (2-amidinopropane) dihydrochloride), 2, 2-azobis- (N,

N-dimethylene isobutyramidine dihydrochloride, 2,2-azobis- (N, N-dimethylene) isobutyramidine dihydrochloride,

2- (carbamoyl azo) isobutylonitrile, 2,

2-azobis [2- (2-imidazolin-2-yl) propane]

Azobis [2- (2-imida: zolin-2-yl) propane] dihydrochloride), 4,4-azobis- (4-cyanovaleric acid) (4,4-azobis - (4-cyanovaleric acid), etc. For a variety of thermal polymerization initiators, see the Odian book Principle of Polymerization (Wiley, 0 2019/117541 1 »(: 1 ^ 1 {2018/015468

1981) '203, and is not limited to the above-mentioned examples.

According to one embodiment of the present invention, the monomer composition includes an internal cross-linking agent as a raw material for a superabsorbent resin. Examples of the internal crosslinking agent include a crosslinking agent having at least one functional group capable of reacting with the acrylic acid-based monomer and having at least one ethylenic unsaturated group; Or a crosslinking agent having two or more functional groups capable of reacting with a substituent formed by hydrolysis of a substituent and / or a monomer of the acrylic acid-based monomer may be used.

Specific examples of the internal cross-linking agent include '-methylenebisacrylamide, trimethylolpropane tri (meth) acrylate, ethylene glycol di (meth) acrylate, polyethylene glycol (meth) acrylate, propylene glycol di (Meth) acrylate, butylene diol di (meth) acrylate, butylene glycol di (meth) acrylate, diethylene glycol di (meth) acrylate, (Meth) acrylate such as triethylene glycol di (meth) acrylate, tripropylene glycol di (meth) acrylate, tetraethylene glycol di (meth) acrylate, dipentaerythritol pentaacrylate, glycerin tri Triarylamine, ethylene Recall diglycidyl may be used at least one member selected from ether, propylene glycol, the group consisting of glycerin, and ethylene carbonate.

Such an internal cross-linking agent may be present in the monomer composition at a level of from about 0.01 to about

0.5% by weight, so that the polymerized polymer can be crosslinked.

In the production method of the present invention, the monomer composition includes water-dispersed silica.

The dispersion of silica (¥ 11 ₀比句is, means silica in a state where stable dispersion of the silica particles in water without precipitation or flocculation, and, means silica which at least is partly ionized in the silica particle surface. The The method for producing the water-dispersed silica is not particularly limited, and those produced by known methods such as electrodialysis, sol-gel method, ion exchange method, and acid-neutralization method may be used.

Particle size of the dispersion of silica is not more than _11111, yet about 5, or at least about 10 _11111, preferably about ₁₁₀₁ to 100, or up to about 50 _11111, or no more than about 30 wave _11. 2019/117541 1 »(: 1 ^ {2018/015468

If the particle diameter of the water-dispersed silica is too small, the cost is high and the manufacturing cost is increased.

The water-dispersed silica may be added in an amount of about 0.01 to about 1.0 part by weight, or about 0.02 to about 0.5 part by weight based on 100 parts by weight of the acrylic acid monomer. When the amount of the water-dispersed silica exceeds 1.0 part by weight , The water retention ability of the superabsorbent resin may be deteriorated. If the amount is less than 0.01 part by weight, rewetting may not be improved.

Also, since the water-dispersed silica can not obtain the effect of improving the rewetting property when the colloid is not retained in the monomer composition, it is preferable that the water-dispersed silica maintains a stable colloid state in the monomer composition . In this respect, powdery or hydrophobic silica that is not in a colloidal state does not have an effect of improving rewetting, so that the intended effect of the present invention can not be achieved.

As the water-dispersed silica satisfying these conditions, ST-O of Nissan Chemical Co.,

ST-AK, etc., but the present invention is not limited thereto.

According to the production method of the present invention, the above-mentioned water-dispersed silica is added at the time of polymerization, and polymerization is carried out in the presence of the water-dispersed silica to form a gel of the superabsorbent resin particle by hydrogen bonding between the superabsorbent resin and the water- The strength can be improved, and the rewet property can be improved.

In the production process of the present invention, the monomer composition may further include a foaming agent, and / or a foam stabilizer.

The foaming agent acts to increase the surface area by foaming during polymerization to form pores in the hydrogel polymer. Examples of the foaming agent include carbonates such as sodium bicarbonate, sodium carbonate, potassium bicarbonate, potassium carbonate, calcium bicarbonate, calcium bicarbonate, Calcium carbonate, calcium bicarbonate, magnesium bicarbonate or magnesium carbonate can be used. 2019/117541 1 »(: 1 ^ {2018/015468

The blowing agent may be added at a concentration of about 0.005 to about 1 part by weight, or about 0.01 to about 0.3 part by weight based on 100 parts by weight of the acrylic acid monomer. If the amount of the foaming agent is more than 1 part by weight, the pores become too large, the gel strength of the superabsorbent resin decreases, and the density becomes low, which may cause problems in distribution and storage. When the amount is less than 0.005 parts by weight, the role as the blowing agent may be insignificant.

The bubble stabilizer serves to uniformly distribute the bubbles in the entire region of the polymer while maintaining the shape of the bubble formed by the foaming agent, thereby increasing the surface area of the polymer.

Examples of the anionic surfactant that can be used include anionic surfactants such as sodium dodecyl sulfate, sodium stearate, ammonium lauryl sulfate, ), Sodium lauryl ether sulfate, sodium myreth sulfate, or alkylether sulfate compounds similar thereto. The anionic surfactant that can be used is not limited thereto, but preferably sodium dodecyl sulfate or sodium stearate can be used.

The anionic surfactant may be added in a concentration of about 0.001 to about 1 part by weight, or about 0.005 to about 0.05 part by weight based on 100 parts by weight of the acrylic acid monomer. If the concentration of the anionic surfactant is excessively low, it is difficult to achieve an improvement in absorption rate due to its insufficient function as a foam stabilizer. On the other hand, if the concentration is excessively high, surface tension after polymerization may become too low to adversely affect the physical properties of the diaper.

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

Raw materials such as acrylic acid-based monomer, photopolymerization initiator, thermal polymerization initiator, internal cross-linking agent and additive having the above-mentioned acid group and at least part of which is neutralized can be prepared in the form of a monomer composition solution dissolved in a solvent. 2019/117541 1 »(: 1 ^ {2018/015468

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, 1,4- Examples of the organic solvent include glycol, ethylene glycol monobutyl ether, propylene glycol monomethyl ether, propylene glycol monomethyl ether acetate, methyl ethyl ketone, acetone, methyl amyl ketone, cyclohexanone, cyclopentanone, diethylene glycol monomethyl ether, diethylene glycol ethyl One or more selected from ether, toluene, xylenes, butylolactone, carbitol, methylcellosolve acetate and benz-dimethylacetamide can be used in combination.

The solvent may be included in the balance of the total amount of the monomer composition excluding the components described above.

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 divided into thermal polymerization and photopolymerization largely depending on the polymerization energy source. In general, when thermal polymerization is carried out, the polymerization can proceed in a reactor having agitation such as kneader, The polymerization method described above is only one example, and the present invention is not limited to the polymerization method described above.

For example, the function gelled polymer obtained in the reactor such as a kneader (10 ₍₁₎ 1 having an axis stirred, by the thermal polymerization by supplying hot air or heating of the reactor as described above in accordance with the form of a stirring shaft provided in the reactor, The hydrogel polymer discharged into the reactor outlet 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 gel polymer having a weight average particle diameter of 2 to 50 111111 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 and the injection rate of the monomer composition to be injected, 2019/117541 1 »(: 1 ^ {2018/015468

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%. The term "water content" as used throughout the present specification means a value obtained by subtracting the weight of the hydrogel polymer from the weight of the hydrogel polymer in terms of the content of water with respect to the weight of the total functional gel polymer. Specifically, The temperature is increased from room temperature to about 180 ^° C, and then maintained at 180 ^° C. In this case, , And the total drying time is set to 20 minutes including the temperature rising step of 5 minutes, and the 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. The present invention is not limited to the above-described example.

Wherein the milling step may be milled so that the hydrous gel polymer has a particle size of 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 is insignificant. 2019/117541 1 »(: 1 ^ {2018/015468

The drying is carried out on the hydrogel polymer immediately after the polymerization, which has not been pulverized or pulverized as described above, wherein the drying temperature of the drying step may be about 150 to about 25 C. When the drying temperature is lower than 150 ^° C, There is a possibility that the drying time is too long and the physical properties of the superabsorbent resin to be finally formed are lowered. When the drying temperature exceeds 250 ° C, only the polymer surface is dried excessively, There is a possibility that the physical properties of the superabsorbent resin finally formed are lowered. Thus, preferably, the drying can proceed at a temperature of from about 150 to about 200 ° C, more preferably from about 160 to about 180 ° C.

On the other hand, in the case of drying time, in consideration of process efficiency and the like, about 20 to about

But it is not limited thereto.

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. After such a drying step, the water content of the polymer may be about 0.1 to about 10 wt%.

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

The polymer powder obtained after the pulverization step may have a particle size of about 150 to about 850 m. The pulverizer used for pulverizing with such a particle size is specifically a pin mill, a hammer mill, a screw a roll mill, a disc mill, or a jog mill may be used. However, the present invention is not limited to the above-described examples.

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 the pulverization according to the particle size may be carried out. .

Next, a hydrophobic substance having an HLB of 0 or more and 6 or less and a surface cross-linking agent are mixed in the base resin (Step 2).

In a general method for producing a superabsorbent resin, a dried and pulverized polymer, that is, 2019/117541 1 »(: 1 ^ {2018/015468

A surface cross-linking solution containing a surface cross-linking agent is mixed with a base resin, and then the surface cross-linking reaction is performed on the ground polymer by heating the mixture by heating.

The surface crosslinking step is a step of inducing a crosslinking reaction on the surface of the pulverized polymer in the presence of a surface crosslinking agent to form a superabsorbent resin having improved physical properties. Through such surface crosslinking, a surface crosslinked layer (surface modifying layer) is formed on the surface of the pulverized polymer particles.

Generally, the surface cross-linking agent is applied to the surface of the superabsorbent resin particles, so that the surface cross-linking reaction occurs on the surface of the superabsorbent resin particles, which improves the crosslinkability on the surface of the particles without substantially affecting the inside 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.

However, the pressure absorption ability and the permeability can be improved by the surface cross-linking reaction, but the rewetting and maintenance ability can be weakened. However, according to the production method of the present invention, it is possible to improve the re-wetting property by mixing the base resin with a surface crosslinking agent to mix the hydrophobic substance with the base resin before the surface crosslinking reaction is carried out. In addition, the surface crosslinking efficiency is improved, so that the absorption rate and the liquid permeability can be further improved as compared with the resin not using a hydrophobic substance.

The hydrophobic substance may be a material that satisfies 0 or more, or 1 or more, or 2 or more, and 6 or less, or 5 or less, or 5.5 or less as the lower limit of HLB. In addition, since the hydrophobic structure is to be dissolved in the surface modification layer of the base resin by melting in the surface cross-linking reaction, a material having a melting point lower than the surface cross-linking reaction temperature may be used.

A usable hydrophobic substances include, for example, glyceryl stearate (glyceryl stearate), glycol stearate (glycol stearate), magnesium stearyl ^6-rate (magnesium stearate), glyceryl monolaurate (glyceryl laurate), sorbitan stearate Sorbitan stearate, sorbitan trioleate, or PEG-4 dilaurate. Preferably, glyceryl stearate can be used, but it is not limited thereto. It is not. 2019/117541 1 »(: 1 ^ {2018/015468

The hydrophobic substance is distributed in the surface modified layer of the surface of the base resin so that the swollen resin particles in the process of absorbing and swelling the liquid of the super absorbency resin are prevented from aggregating or aggregating according to the increased pressure, It is possible to more easily transmit and diffuse the liquid, thereby contributing to improvement of the re-wetting property of the superabsorbent resin.

The hydrophobic material may be present in an amount of at least about 0.02 part by weight, or at least about 0.025 part by weight, or at least about 0.05 part by weight, and up to about 0.5 part by weight, or up to about 0.3 part by weight, or up to about 0.1 part by weight, If the content of the hydrophobic substance is less than 0.02 part by weight, the rewet property may not be improved. If the content of the hydrophobic substance is more than 0.5 part by weight, the base resin and the hydrophobic substance may be separated from each other There may be a problem that the rewetting improving effect does not exist or may act as an impurity, so the weight range may be preferable from this point of view.

The method of mixing the hydrophobic substance is not particularly limited as long as it can mix the base resin uniformly and can be suitably employed.

For example, the hydrophobic substance may be mixed by dry mixing before mixing the surface cross-linking solution containing the surface cross-linking agent into the base resin, or by first dispersing the surface cross-linking solution in the base cross- Alternatively, separately from the surface cross-linking solution, the hydrophobic substance may be heated to a melting temperature or higher to be mixed in a solution state.

When the above-mentioned surface cross-linking agent is added, water can be further mixed together and added in the form of a surface cross-linking solution. When water is added, there is an advantage that the surface crosslinking agent can be uniformly dispersed in the polymer. At this time, the added water content is preferably from about 1 to about 10 wt. Parts per 100 parts by weight of the polymer for the purpose of inducing uniform dispersion of the surface cross-linking agent and preventing the polymer powder from aggregating and optimizing the surface penetration depth of the surface cross- By weight.

The surface cross-linking agent is not limited in its constitution as long as it is a compound capable of reacting with a functional group contained in the polymer.

Preferably, in order to improve the properties of the resulting superabsorbent resin, 2019/117541 1 »(: 1 ^ {2018/015468

A surface crosslinking agent, a polyhydric alcohol compound, an epoxy compound, a polyamine compound, a haloepoxy compound, A condensation product of a haloepoxy compound; Oxazoline compounds; Mono-, di- or polyoxazolidinone compounds; Cyclic urea compounds; Polyvalent metal salts; And an alkylene carbonate compound can be used. Specific examples of the polyhydric alcohol compound include mono-, di-, tri-, tetra- or polyethylene glycol, monopropylene glycol, 1,3-propanediol, dipropylene glycol, 2,3,4- - pentanediol, polypropylene glycol, glycerol, polyglycerol, 2-butene-1,4-diol, 1,4-butanediol, 1,3-butanediol, 1,5-pentanediol, 1,2-cyclic nucleic acid dimethanol, and the like.

Examples of the epoxy compounds include ethylene glycol diglycidyl ether and glycidol. Examples of the polyamine compounds include ethylene diamine, diethylenetriamine, triethylenetetramine, tetraethylenepentamine, pentaethylene nucleus amine, Polyethyleneimine and polyamidepolyamines can be used.

As the haloepoxy compound, epichlorohydrin, epibromohydrin, and (X-methyl epichlorohydrin can be used. As the mono-, di- or polyoxazolidinone compounds, for example, 2-oxazolidinone Dinonone, etc. As the alkylene carbonate compounds, ethylene carbonate and the like can be used. These can be used alone or in combination with each other. [0112] On the other hand, in order to increase the efficiency of the surface cross- One or more polyhydric alcohol compounds having 2 to 10 carbon atoms may be used.

The amount of the surface crosslinking agent to be added may be appropriately selected depending on the kind of the surface crosslinking agent to be added and the reaction conditions, but is usually about 0.001 to about 5 parts by weight, preferably about 0.01 to about 5 parts by weight, About 3 parts by weight, more preferably about 0.05 to about 2 parts by weight may be used.

If the content of the surface cross-linking agent is too small, the surface cross-linking reaction hardly occurs, and when the amount is more than 5 parts by weight based on 100 parts by weight of the polymer, 2019/117541 1 »(: 1 ^ {2018/015468

The progress of the surface cross-linking reaction may cause a decrease in the absorption capacity and physical properties.

On the other hand, in addition to the surface-crosslinking agent described above, it may further include at least one selected from the group consisting of polyvalent metal salts such as aluminum salts, more specifically, aluminum sulfate, potassium salt, ammonium salt, sodium salt and hydrochloride.

As the polyvalent metal salt is further used, the liquid permeability and the like of the superabsorbent resin produced by the method of one embodiment can be further improved. The multivalent metal salt may be added to the surface cross-linking solution together with the surface cross-linking agent, and may be used in an amount of 0.01 to 4 parts by weight based on 100 parts by weight of the base resin.

Next, the base resin, the surface cross-linking agent, and the mixture of the hydrophobic substances are heated to raise the temperature, thereby performing the surface modification step (step 3).

The surface modification step may be carried out by heating at a temperature of from about 80 to about 190 (preferably from about 100 to about 180 (preferably from about 10 to about 90 minutes, preferably from about 20 to about 70 minutes) . The crosslinking reaction temperature

Or the reaction time is too short, the surface cross-linking reaction does not occur properly and the permeability may be lowered. If the reaction time exceeds 1901: or the reaction time is too long, the water retention ability may decrease.

The temperature raising means for the surface reforming 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 heat medium that can be used, steam, hot air, hot fluid, or the like can be used, but the present invention is not limited thereto, and the temperature of the heat medium to be supplied is controlled by means of heating medium, It can be selected appropriately considering the 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. According to the production method of the present invention, the base resin has excellent gel strength due to the water-dispersed silica added at the time of polymerization, and further, by the surface modification step, the surface cross-linking agent and the base resin A surface crosslinked structure formed by reaction with a functional group is formed, and the surface crosslinked structure 2019/117541 1 »(: 1 ^ {2018/015468

A surface modification layer in which the aforementioned hydrophobic substance is evenly distributed can be formed. Therefore, the superabsorbent resin produced by the production method of the present invention is superior in the properties of such a base resin and the surface reforming layer formed on the base resin to improve the rewetting properties without deteriorating properties such as water retention capacity and pressure absorption capacity Properties and initial absorption rates.

According to another embodiment of the present invention, there is provided a base resin comprising a base resin comprising a cross-linked polymer obtained by crosslinking at least part of an acidic group with an acrylic acid-based monomer, and a base resin formed on the surface of the base resin, Wherein the surface modifying layer comprises a hydrophobic substance having an HLB of not less than 0 and not more than 6, and has a vortex time of 35 seconds or less.

Details of the specific production method and physical properties of the superabsorbent resin are the same as those described above in the production method of the superabsorbent resin.

The superabsorbent resin has a CRC of at least about 30 g / g, or at least about 31 g / g, or at least about 32 g / g, and at least about 40 g / g, as measured according to EDANA method WSP 241.3 , Or about 38 g / g or less, or about 35 g / g or less.

Further, the superabsorbent resin preferably has a pressure absorption capacity (AUP) of about 0.7 g / g or more, about 22 g / g or more, or about 23 g / g or more, measured according to EDANA method WSP 242.3 35 g / g or less, or about 33 g / g or less, or about 32 g / g or less.

In addition, the high viscosity aqueous resin may have a vortex time of 35 seconds or less, or about 32 seconds or less, or about 30 seconds, or 28 seconds or less. The lower limit of the absorption rate is theoretically 0 seconds, but may be, for example, about 5 seconds or more, or about 10 seconds or more, or about 12 seconds or more.

The regeneration speed means a time (unit: second) during which the vortex of the liquid disappears due to the rapid top water when high-viscosity aqueous resin is added to the physiological saline solution and the time is short, Can be seen to have a fast initial absorption rate.

Further, the superabsorbent resin is preferably a resin which is measured according to the following formula 1 2019/117541 1 »(1 ^ 1 {2018/015468

The permeability (unit: sec) may be about 20 seconds or less, or about 18 hours or less, or about 16 seconds or less. The liquid permeability is better as the value is smaller, About 5 seconds or more, or about 10 seconds or more, or about 12 seconds or more.

[Formula 1]

Liquid permeability (sec) = Tl - B

In Equation (1)

0.2 ± 0.0005 g of a superabsorbent resin sample (30 # - 50 #) in a chromatographic tube was added and the brine volume was adjusted to 50 ml by adding brine. The mixture was allowed to stand for 30 minutes, , And B is the time it takes for the liquid level to decrease from 40 ml to 20 ml in a chromatographic tube filled with salt water.

In addition, the superabsorbent resin can exhibit excellent absorption characteristics while exhibiting improved rewet characteristics.

More specifically, 1 g of the high viscosity aqueous resin is immersed in 100 g of tap water

Defined as the weight of water repelled from the superabsorbent resin to the filter paper after being allowed to stand on the filter paper for 3 hours from the initial time when the swollen superabsorbent resin is immersed in the tap water after swelling for 10 minutes, (Non-pressurized water supply water or long-term rewet) may be 3.0 g or less, or 2.5 g or less, or 2.0 g or less. The lower the weight of the water is, the better the lower theoretical value may be 0 g, for example, 0.1 g or more, or 0.5 g or more, or 1.0 g or more.

Or 1 g of the superabsorbent resin is immersed in 100 g of tap water and swelled for 10 minutes and then allowed to stand on the filter paper for 1 hour from the initial point of immersing the swollen superabsorbent resin in tap water, The rewet property defined as the weight of water reabsorbed to the filter paper (unpressurized water short-term rehydrated) may be less than 1.0 g, or not more than 0.9 g, or not more than 0.8 g. The lower the weight of the water is, the better the lower theoretical value may be 0 g, for example, 0.1 g or more, or 0.2 g or more, or 0.3 g or more. 2019/117541 1 »(: 1 ^ {2018/015468

The tap water used in the re-wetting property evaluation has an electrical conductivity of 170 to ISOtiS / cm. Since the electrical conductivity of the tap water greatly affects the physical properties of the tap water, it is necessary to measure the physical properties such as rewet using tap water having an equivalent level of electrical conductivity.

As described above, the superabsorbent resin of the present invention has excellent absorption ability, and excellent rewetting and leakage of urine can be suppressed even when a large amount of urine is absorbed.

The present 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.

Preparation of superabsorbent resin

Example 1

100 g of acrylic acid, 20 g of polyethylene glycol diacrylate (PEGDA,

Sodium bicarbonate (SBC) as a blowing agent, 0.6 g of sodium persulfate (SPS) as a photoinitiator, 0.008 g of bis (2,4,6-trimethylbenzoyl) -phenylphosphine oxide, 0.15 g of sodium persulfate 0.08 g of a surfactant, 0.035 g of sodium dodecylsulfate (SDS), 0.4 g of water-dispersed silica (ST-O), 123.3 g of 31.5% caustic soda (NaOH) and 38.53 g of water to prepare a monomer aqueous solution composition . After the monomer aqueous solution composition was received in a tray, ultraviolet light was irradiated (irradiated amount: 10 mW / cm ² ) with a UV irradiator for 1 minute while maintaining the polymerization atmosphere temperature at 80 ^° C, aging for 2 minutes, A polymer sheet was prepared.

The polymerized sheet was taken out and cut into a size of 3 cm x 3 cm, followed by chopping using a meat chopper to prepare a crumb. The crumb was dried in an oven capable of airflow transfer up and down. The hot air of 185 ° C was flowed from the lower side to the upper side for 15 minutes and the lower side was flowed from the upper side to the lower side for 15 minutes. After drying, the water content of the dried body was made to be 2% or less. , Followed by addition of Amplitute 2019/117541 1 »(: 1 ^ {2018/015468

(Classification mesh combination # 20-30 / # 30-50 / # 50-100) of 1.5 mm and collecting each class (10% / 75% / 15% , And a base resin powder was obtained in this way.

Thereafter, 0.02 part by weight of glyceryl stearate, and 7.6 parts by weight of a surface cross-linking agent (7.6 parts by weight of water,

, 0.075 part of ethylene glycol diglycidyl ether (EX-810), 0.03 part of sodium metabisulfite, 0.1 part of aluminum sulfate 18 hydrate (Al-S) And 0.03 parts by weight of aluminum oxide (Alu 130)) were uniformly mixed, and surface cross-linking reaction was carried out at 140 ° C for .35 minutes. After completion of the surface treatment, a water absorbent resin having an average particle size of 150 to 850 _ was obtained using a sieve.

Thereafter, 0.05 parts by weight of aluminum oxide (Alu 130) was dry-mixed with the above superabsorbent resin. Example 2

100 g of acrylic acid, 0.6 g of polyethylene glycol diacrylate (PEGDA, Mw = 523) as a crosslinking agent, 0.008 g of bis (2,4,6-trimethylbenzoyl) -phenylphosphine oxide as a photoinitiator, 0.08 g of sodium persulfate 0.08 g of sodium bicarbonate (SBC) as a foaming agent, 0.035 g of sodium dodecylsulfate (SDS) as a surfactant, 0.4 g of water-dispersed silica (ST-AK)

123.3 g of 31.5% caustic soda (NaOH), and 38.53 g of water were mixed to prepare a monomer aqueous solution composition. After the monomer aqueous solution composition was received in a tray, ultraviolet light was irradiated (irradiated amount: 10 mW / cm ² ) with a UV irradiator for 1 minute while maintaining the polymerization atmosphere temperature at 80 ^° C, aging for 2 minutes, A polymer sheet was prepared.

The polymerized sheet was taken out and chopped using a meatchopper cut to a size of 3 cm x 3 cm to prepare a crumb. The crumb was dried in an oven capable of airflow transfer up and down. 185 ° C hot air was uniformly dried by flowing from below to upward for 15 minutes and from downward to upward for 15 minutes. After drying, 2019/117541 1 »(: 1 ^ {2018/015468

The water content was adjusted to 2% or less. After drying, the mixture was pulverized by a pulverizer, and then Amplitute

(Classification mesh combination # 20-30 / # 30-50 / # 50-100) of 1.5 mm and collecting each class (10% / 75% / 15% ______________________________________ A base resin powder was obtained in this way.

, 0.075 part of ethylene glycol diglycidyl ether (EX-810), 0.03 part of sodium metabisulfite, 0.1 part of aluminum sulfate 18 hydrate (Al-S) And 0.03 part by weight of aluminum oxide (Alu 130)) were uniformly mixed, and the surface cross-linking reaction was carried out at 140 ° C for 35 minutes. After completion of the surface treatment, a superabsorbent resin having an average particle size of 150 to 850 _/ D was obtained using a sieve.

Thereafter, 0.05 parts by weight of aluminum oxide (Alu 130) was dry-mixed with the above superabsorbent resin. Example 3

100 g of acrylic acid, 0.75 g of polyethylene glycol diacrylate (PEGDA, Mw = 523) as a crosslinking agent, 0.008 g of bis (2,4,6-trimethylbenzoyl) -phenylphosphineoxide as a photoinitiator, 0.08 g of sodium persulfate 0.2 g of sodium bicarbonate (SBC) as a foaming agent, 0.025 g of sodium dodecylsulfate (SDS) as a surfactant, 0.1 g of water-dispersed silica (ST-O), 31.5% of caustic soda NaOH) and 38.53 g of water to prepare a monomer aqueous solution composition. After the monomer aqueous solution composition was received in a tray, ultraviolet light was irradiated (irradiated amount: 10 mW / cm ² ) with a UV irradiator for 1 minute while maintaining the polymerization atmosphere temperature at 80 ^° C, aging for 2 minutes, A polymer sheet was prepared.

The polymerized sheet was taken out and cut into a size of 3 cm x 3 cm, followed by chopping using a meat chopper to prepare a crumb. The crumb was dried in an oven capable of airflow transfer up and down. The hot air at 185 ° C was turned upside down for 15 minutes, 2019/117541 1 »(: 1 ^ {2018/015468

After drying, it was pulverized by a pulverizer, and then Amplitute

(5% / 75% / 20%) were collected and classified to a particle diameter of about 150 to 850 , And a base resin powder was obtained in this way.

Thereafter, 0.025 part by weight of glyceryl stearate, and a surface cross-linking solution (7.7 parts by weight of water,

, 0.05 parts by weight of sodium metabisulfite, 0.1 part by weight of aluminum sulfate 18 hydrate (Al-S) And 0.03 part by weight of aluminum oxide (Alu 130)) were uniformly mixed, and the surface cross-linking reaction was carried out at 140 ^° C for 35 minutes. After completion of the surface treatment, a water absorbent resin having an average particle size of 150 to 850 _ was obtained using a sieve.

Thereafter, 0.05 parts by weight of aluminum oxide (Alu 130) was dry-mixed with the above superabsorbent resin. Example 4

100 g of acrylic acid, 0.75 g of polyethylene glycol diacrylate (PEGDA, Mw = 523) as a crosslinking agent, 0.008 g of bis (2,4,6-trimethylbenzoyl) -phenylphosphineoxide as a photoinitiator, 0.08 g of sodium persulfate 0.28 g of sodium bicarbonate (SBC) as a blowing agent, 0.025 g of sodium dodecylsulfate (SDS) as a surfactant, 0.1 g of an aqueous dispersion silica (ST-AK), 31.5% of caustic soda NaOH) and 38.53 g of water to prepare a monomer aqueous solution composition. After the monomer aqueous solution composition was received in a tray, ultraviolet light was irradiated (irradiated amount: 10 mW / cm ² ) with a UV irradiator for 1 minute while maintaining the polymerization atmosphere temperature at 80 ^° C, aging for 2 minutes, A polymer sheet was prepared.

The polymerized sheet was taken out and cut into a size of 3 cm x 3 cm, followed by chopping using a meat chopper to prepare a crumb. The crumb is placed in an oven capable of airflow transfer up and down 2019/117541 1 »(: 1 ^ {2018/015468

And dried. The hot air of 185 ^° C was flowed from the lower side to the upper side for 15 minutes and the lower side was flowed from the upper side to the lower side for 15 minutes. After drying, the water content of the dried body was made to be 2% or less. , Followed by addition of Amplitute

(5% / 75% / 20%) were collected and classified to a particle diameter of about 150 to 850 ______________________________________ A base resin powder was obtained in this way.

Thereafter, 0.05 parts by weight of aluminum oxide (Alu 130) was dry-mixed with the above superabsorbent resin. Example 5

The polymerized sheet was taken out, cut into a size of 3 cm x 3 cm, and chopped using a meat chopper to obtain a crumb 2019/117541 1 »(: 1 ^ {2018/015468

. The crumb was dried in an oven capable of airflow transfer up and down. The hot air of 185 ^° C was flowed from the lower side to the upper side for 15 minutes and the lower side was flowed from the upper side to the lower side for 15 minutes. After drying, the water content of the dried body was made to be 2% or less. (5% / 75% / 20%) were collected from each sample, and then classified for 10 minutes in an Amplitute 1.5 mm (classification mesh combination: # 20-30 / # 30-50 / # 50-100) A polymer having a particle diameter of about 150 to 850 _{/ was} obtained by classification, and a base resin powder was obtained in this way.

Thereafter, 0.2 part by weight of glyceryl stearate, 7.7 parts by weight of water, 5.5 parts by weight of methanol, ethylene glycol diglycidyl ether (EX-810), and 0.1 part by weight of glyceryl stearate were added to 100 parts by weight of the base resin, 0.05 parts by weight of sodium metabisulfite, 0.1 part by weight of aluminum sulfate 18 hydrate (Al-S), and 0.03 parts by weight of aluminum oxide (Alu 130) were uniformly mixed , And the surface cross-linking reaction was carried out at 140 ^° C for 35 minutes. After completion of the surface treatment, a water absorbent resin having an average particle size of 150 to 850 g was obtained using a sieve.

Thereafter, 0.05 parts by weight of aluminum oxide (Alu 130) was dry-mixed with the above superabsorbent resin. Comparative Example 1

100 g of acrylic acid, 20 g of polyethylene glycol diacrylate (PEGDA,

Sodium bicarbonate (SBC) as a blowing agent, 0.6 g of sodium persulfate (SPS) as a photoinitiator, 0.008 g of bis (2,4,6-trimethylbenzoyl) -phenylphosphine oxide, 0.15 g of sodium persulfate 0.038 g of a surfactant, 0.035 g of sodium dodecylsulfate (SDS) as a surfactant, 123.3 g of 31.5% caustic soda (NaOH) and 38.53 g of water were mixed to prepare a monomer aqueous solution composition. Then, UV polymerization was carried out by irradiating ultraviolet ray (irradiation amount: 10 mW / cm ² ) with a UV irradiator for 1 minute while maintaining the polymerization atmosphere temperature at 80 ^° C and aging for 2 minutes to prepare a hydrogel polymer sheet.

The polymerized sheet was taken out, cut into a size of 3 cm x 3 cm, chopped using a meat chopper to obtain a crumb 2019/117541 1 »(: 1 ^ {2018/015468

. The crumb was dried in an oven capable of airflow transfer up and down. The hot air of 185 ^° C was flowed from the lower side to the upper side for 15 minutes and the lower side was flowed from the upper side to the lower side for 15 minutes. After drying, the water content of the dried body was made to be 2% or less. (10% / 75% / 15%) were collected from each sample, and then classified by Amplitute 1.5 mm for 10 minutes (classification mesh combination: # 20-30 / # 30-50 / # 50-100) A polymer having a particle diameter of about 150 m to 850 was obtained by classification, and a base resin powder was obtained in this manner.

Then, 100 parts by weight of the base resin thus prepared was mixed with 7.6 parts by weight of water, 7.6 parts by weight of methanol, 0.075 part by weight of ethylene glycol diglycidyl ether (EX-810), sodium metabisulfite, 0.03 part by weight of aluminum sulfate, 0.1 part by weight of aluminum sulfate 18 hydrate (Al-S) and 0.03 part by weight of aluminum oxide (Alu 130) were uniformly mixed and subjected to surface cross-linking reaction at 14 CTC for 35 minutes After completion of the surface treatment, an absorbent resin having an average particle size of 150 to 850 was obtained using a sieve.

Thereafter, 0.05 parts by weight of aluminum oxide (Alu 130) was dry-mixed with the above superabsorbent resin. Comparative Example 2

100 g of acrylic acid, 0.6 g of polyethylene glycol diacrylate (PEGDA, Mw = 523) as a crosslinking agent, 0.008 g of bis (2,4,6-trimethylbenzoyl) -phenylphosphine oxide as a photoinitiator, 0.08 g of sodium persulfate 0.08 g of sodium bicarbonate (SBC) as a foaming agent, 0.035 g of sodium dodecylsulfate (SDS) as a surfactant, 0.4 g of silica (Aerosil 200), 31.5% of caustic soda (NaOH) And 38.53 g of water were mixed to prepare a monomer aqueous solution composition. After the monomer aqueous solution composition was received in a tray, ultraviolet light was irradiated (irradiated amount: 10 mW / cm ² ) with a UV irradiator for 1 minute while maintaining the polymerization atmosphere temperature at 80 ^° C, aging for 2 minutes, A polymer sheet was prepared.

The polymerized sheet was taken out and chopped using a meat chopper cut into a size of 3 cm x 3 cm to prepare a crumb. 2019/117541 1 »(: 1 ^ {2018/015468

. The crumb was dried in an oven capable of airflow transfer up and down. The hot air of 185 ^° C was flowed from the lower side to the upper side for 15 minutes and the lower side was flowed from the upper side to the lower side for 15 minutes. After drying, the water content of the dried body was made to be 2% or less. and then, 10 minutes classified as Amplitute 1.5 mm pulverized to (classification mesh combination: # ^{^20-30} / 0 # ³ 50 / # ^50-100) were each classified min (10% / 75% / 15 %) Was collected and classified to obtain a polymer having a particle diameter of about 150 pm to 850. The base resin powder was obtained in this manner.

Then, 100 parts by weight of the base resin thus prepared was mixed with 7.6 parts by weight of water, 7.6 parts by weight of methanol, 0.075 part by weight of ethylene glycol diglycidyl ether (EX-810), sodium metabisulfite, 0.03 part by weight of aluminum sulfate 18, 0.1 part by weight of aluminum sulfate 18 hydrate (Al-S) and 0.03 part by weight of aluminum oxide (Alu 130) were uniformly mixed and then subjected to surface crosslinking reaction at 140 ^° C for 35 minutes After the completion of the surface treatment, a sieve was used to average

Thereafter, 0.05 parts by weight of aluminum oxide (Alu 130) was dry-mixed with the above superabsorbent resin.

The physical properties of the high water absorbent resin prepared in the above Examples and Comparative Examples were evaluated by the following methods.

Unless otherwise indicated, the following physical properties were evaluated at constant temperature and humidity (23 ± 1 ° C, relative humidity: 50%, 10%), and saline or brine means 0.9% sodium chloride (NaCl) aqueous solution.

Further, to be also used in rewet properties evaluation are Orion Star A222: as determined by the (company Thermo Scientific), the electrical conductivity 170 to 180 _| was used as the _i S / cm.

(1) Centrifugal Retention Capacity (CRC)

The retention capacity of each resin by the zero-load capacity was measured according to EDANA WSP 241.3. 2019/117541 1 »(: 1 ^ {2018/015468

Specifically, the superabsorbent resin W _{0 (} g) (about 0.2 g) was uniformly put in an envelope made of a nonwoven fabric and sealed, followed by immersion in physiological saline (0.9 wt%) at room temperature. After 30 minutes, water was drained from the envelope for 3 minutes under a condition of 250 G using a centrifuge, and the mass W _{2 (} g) of the envelope was measured. Also, after the same operation was performed without using a resin, the mass Wg at that time was measured. Using the obtained masses, CRC (g / g) was calculated according to the following equation.

[Equation 1]

CRC (g / g) = {[W _{2 (} g) - W, (g)] AV _{0 (} g)} - 1 (2) Absorbency under pressure

The pressure absorption capacity of each resin of 0.7 psi was measured according to EDANA method WSP 242.3.

Specifically, a 400 mesh wire mesh made of stainless steel was mounted on a cylindrical bottom of a plastic having an inner diameter of 60 mm. The piston capable of uniformly applying a load of 0.7 psi uniformly over the superabsorbent resin W _{0 (} g) (0.9 grains) on the wire net under conditions of room temperature and humidity of 50% is slightly smaller than the outer diameter of 60 mm The inner wall of the cylinder was free from cracks and the up and down movement was not disturbed, and the weight W _{3 (} 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 0.9% 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 a filter paper, and the solution was absorbed under a load for 1 hour. After one hour, the measuring device was lifted and its weight W _{4 (} g) was measured. The pressure absorption capacity (g / g) was calculated by using the obtained masses according to the following equation. .

&Quot; (2) "

AUP (g / g) = [ W 4 (g) - W 3 (g)] / W 0 (g)

(3) Permeability

The method for measuring the permeability is disclosed in Patent No. US 9656242 B2 2019/117541 1 »(: 1 ^ {2018/015468

The measurement was carried out in accordance with the described method.

The liquid permeability measuring device is a chromatography tube having an inner diameter of 20 mm and a glass filter at the lower end. Lines were indicated on the liquid surface of 20 ml and 40 ml with the piston in the chromatographic tube. Thereafter, water was added in an amount of about 10 ml to prevent air bubbles between the lower glass filter and the cock of the chromatography tube, and the mixture was washed 2-3 times with brine and filled with 0.9% brine to a volume of 40 ml or more. Put the piston into the chromatography tube and open the lower valve to record the time (in millimeters) of reducing the liquid level from 40 ml to the 20 ml marking line.

0.2 ± 0.0005 g of a superabsorbent resin (30 # - 50 #) was placed in a chromatographic tube, leaving 10 ml of brine. Brine was added to make a brine volume of 50 ml and left for 30 minutes. Thereafter, a piston (0.3 psi = 106.26 g) added to the chromatographic tube was placed and allowed to stand for 1 minute, and the time (T1) during which the liquid level was reduced from 40 ml to 20 ml marking line by opening the bottom of the chromatography tube was recorded, (Unit: second) was calculated.

(4) Vortex time

The vortex time was measured in the first place according to the method described in International Patent Application No. 1987-003208.

More specifically to the, 23 ^° C to insert a superabsorbent resin 2g of the physiological saline 50 mL of 24 ^° C, the magnetic bars (diameter: 8 mm, length 30 mm) for the mixture was stirred at 600 rpm vortex (vortex) lyrics la eases Of the total time.

(5) Confiscated water for long-term re-wetting (3hrs)

1 g of a superabsorbent resin having a particle size of # 30- # 50 was placed in a cup (diameter of 7 cm above the cup, diameter of 5 cm, height of 8 cm, volume of 192 ml), and 100 g of tap water was swollen at 500 rpm and swelled.

② Stirring was stopped at the point when the water-absorbent resin became water level and the water surface became flat and water flow did not flow.

③ paper filter in 10 minutes from the time the number of swelling may (manufacturer: Whatman, catalog No. 1004-110, pore size 20-25 | am, 11cm diameter) with an aqueous swelling gotop 5 Zhang 2019/117541 1 »(: 1 ^ {2018/015468

I turned the cup with the resin over.

(3) After 3 hours from the time when water was poured, the cup and superabsorbent resin were removed and the amount of water added to the filter paper was measured (unit:). (6)

① 1 g of a high-viscosity water-based resin was put into a cup (diameter of 7 cm, diameter of 5 cm, height of 8 cm, volume of 192 ml), and 100 g of tap water was added and swelled.

② After 10 minutes from the time when the water was poured, the cup containing the swollen water resin swollen on the filter paper (Whatman, catalog No. 1004-110, pore size 20-25 am, diameter 11 cm) was turned upside down.

③ After 1 hour from the time when the water was poured, the cup and the water-absorbent resin were removed, and the amount (unit: g) of water added to the filter paper was measured.

(7) Pressurized water Long term rewet ( ⁶ hrs)

① 4 g of superabsorbent resin was uniformly distributed in a 13 cm diameter petri dish and evenly distributed using a spatula, and 200 g of tap water was swollen and swollen.

② Twelve sheets of filter paper (manufacturer whatman, catalog No. 1004-110, pore size 20-25 μm, diameter 11 cm) with a diameter of 11 cm and a height of 5 kg (0.75 psi ) For 1 minute.

(3) The amount of water added to the filter paper after 1 minute of pressurization was measured. The physical properties of the above Examples and Comparative Examples are shown in Table 1 below.

2019/117541 1 »(: 1 ^ {2018/015468

Referring to Table 1, Examples 1 to 5 of the present invention all exhibited excellent absorption rate and liquid permeability, and it was confirmed that the rewetting amount with respect to the tap water was very small under pressureless pressure and pressure, showing improved rewetting characteristics .

5, whereas Comparative Examples 1 and 2 show that rewetting and absorption rates are not as good as in the Examples.

Claims

2019/117541 1 (: 1 ^ {2018/015468)

[Claim 1]

Performing the surface modification to the base resin by raising the mixture of step 2 (step 3);

Absorbent resin.

[Claim 2]

The method according to claim 1,

Wherein the water-dispersed silica has a particle diameter of 10 to 100 nm.

[Claim 3]

The method according to claim 1,

Wherein the water-dispersed silica is contained in an amount of 0.01 to 1.0 part by weight based on 100 parts by weight of the acrylic acid-based monomer.

[4]

The method according to claim 1,

Wherein the hydrophobic substance has a melting point equal to or lower than the temperature elevating temperature of step (3).

[Claim 5]

The method according to claim 1,

The hydrophobic material may be selected from the group consisting of glyceryl stearate, glycol stearate, magnesium stearate, 2019/117541 1 »(: 1 ^ {2018/015468

At least one selected from the group consisting of glyceryl laurate, sorbitan stearate, sorbitan trioleate, and PEG-4 dilaurate. Absorbent resin.

[Claim 6]

6. The method of claim 5,

Wherein the hydrophobic substance is glyceryl stearate.

[7]

In the 11th aspect,

Wherein the hydrophobic substance is mixed in an amount of 0.02 to 0.5 part by weight based on 100 parts by weight of the base resin.

8.

The method according to claim 1,

Wherein in step 2, the hydrophobic substance is first dry-mixed with the base resin, and then the surface cross-linking solution containing the surface cross-linking agent is mixed.

9]

In that U section,

Wherein step 3 is carried out at a temperature of 80 to 190 ° C.

Claim 10

The method according to claim 1,

In the step 1,

An acrylic acid group-containing acrylic acid group having an acidic group and at least a part of the acidic group being neutralized 2019/117541 1 »(: 1 ^ {2018/015468

Polymerizing a monomer composition comprising a monomer, an internal cross-linking agent, an aqueous dispersion silica, and a polymerization initiator to form a hydrogel polymer;

Drying the hydrogel polymer;

Pulverizing the dried polymer; and

And a step of classifying the pulverized polymer.

1.1.

11. The method of claim 10,

Wherein the monomer composition further comprises a foaming agent and a foam stabilizer.

Claim 12

12. The method of claim 11,

The foaming agent may be selected from the group consisting of sodium bicarbonate, sodium carbonate, potassium bicarbonate, potassium carbonate, calcium bicarbonate, calcium bicarbonate, magnesium bicarbonate, Magnesium bicarbonate, and magnesium carbonate. The method for producing a superabsorbent resin according to claim 1,

Claim 13

12. The method of claim 11,

The foam stabilizer may be selected from the group consisting of sodium dodecyl sulfate, sodium stearate, ammonium lauryl sulfate, sodium lauryl ether sulfate (SLES), and sodium lauryl ether sulfate Sodium hypophosphite, and sodium myreth sulfate. &Lt; RTI ID = 0.0 > 11. < / RTI >

14. 2019/117541 1 »(: 1 ^ {2018/015468

The method according to claim 1,

Wherein the high viscosity aqueous resin has a vortex time of 35 seconds or less.

15.

The method according to claim 1,

Wherein the superabsorbent resin has a permeability (unit: second) measured according to the following formula 1: 20 seconds or less.

[Formula 1]

Liquid permeability (sec) = Tl - B

In Equation (1)

0.2 ± 0.0005 g of a superabsorbent resin sample (30 # ~ 50 #) in a chromatographic tube was added and the brine volume was adjusted to 50 ml by adding brine. The mixture was allowed to stand for 30 minutes, , And B is the time it takes for the liquid level to decrease from 40 ml to 20 ml in a chromatographic tube filled with salt water.

Claim 16

Wherein the surface modifying layer comprises a hydrophobic substance having a density of 0 or more and 6 or less and a vortex time of 35 seconds or less.

17.

17. The method of claim 16,

Wherein the base resin is crosslinked in the presence of the water-dispersed silica. 2019/117541 1 »(: 1 ^ {2018/015468

Claim 18

17. The method of claim 16,

Wherein the high-shear water-based resin has a permeability (unit: sec) of at most 20 seconds,

[Formula 1]

Liquid permeability (sec) = Tl - B

In Equation (1)

T1 was obtained by adding 0.2 ± 0.0005 g of a superabsorbent resin sample (30 # - 50 #) classified into a chromatographic tube, adding brine to make the volume of the brine to be 50 ml, allowing to stand for 30 minutes, ml, and the time it takes for the liquid surface height to decrease from 40 ml to 20 ml in a chromatographic tube filled with brine.

Claim 19

17. The method of claim 16,

The above water-soluble resin is obtained by immersing 1 g of the high-water-based resin in 100 g of tap water and swelling for 10 minutes, then allowing the swollen superabsorbent resin to stand on the filter paper for 3 hours from the initial point of immersion in tap water, Wherein the re-wetting property (no-pressure water-repellent water-repellent long-term rewetting) defined by the weight of water repelled from the superabsorbent resin to the filter paper is 3.0 g or less.

Claim 20

17. The method of claim 16,

The super-absorbent resin is immersed in 100 g of tap water and swelled for 10 minutes, then allowed to stand on the filter paper for 1 hour from the initial point of time when the swollen super-absorbent resin is immersed in tap water, Wherein the rewetting property (ungrained water repellency, short-term rewet) defined by the weight of water repelled from the superabsorbent resin to the filter paper is not more than 1.0 g.