WO2019117511A1 - Superabsorbent polymer and preparation method therefor - Google Patents

Abstract

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

Description

 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. 10-2017-0169492, filed December 11, 2017,

U.S. Patent Application No. 10-2018-0148009, filed on Nov. 27, 2018, all of which are incorporated herein by reference in their entirety.

 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 the weight of lanzai, and each developer can use SAM (Super Absorbent Material), AGM The above-mentioned superabsorbent resin has been put into practical use as a sanitary article, and nowadays, in addition to the diapers and sanitary napkin products for children, it is now used as a soil remover for gardening, an index material for civil engineering and construction, Sheet, a freshness-retaining agent in the field of food distribution, and a material for fomentation.

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 ₎ .

However, it is known that the CRC which is the physical property showing the basic absorption power and the water holding capacity of the superabsorbent resin, and the lower absorption ability (AUP) showing the property of holding the moisture absorbed even to the external pressure are difficult to improve together. 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 2019/117511 1 »(: 1 ^ 1 {2018/014840

When the absorption capacity under pressure is increased, the water absorption is difficult to be absorbed through the superficial crosslinked structure, and the basic water-holding ability may be lowered. For the reasons described above, it is possible to provide a superabsorbent resin having improved water- There is a limit.

 In recent years, however, a higher performance is required for a high-water-based resin due to the thinning of sanitary materials such as diapers and sanitary napkins. Among these, an important task is to improve the water retention ability and the pressure absorption ability, Is emerging.

In addition, pressure may be applied to sanitary materials such as diapers and sanitary napkins by the weight of the user. In particular, 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, a part of the liquid absorbed in the superabsorbent resin is re- , 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

The steps to order to achieve the above object, according to one aspect of the invention, having an acidic group prepared the acrylic acid monomer and internal crosslinking agent are crosslinked polymeric base resin 0 ₃₆切) at least partially neutralizing the acid groups ( Step 1);

To the base resin,

(Step 2) of a hydrophobic substance and an epoxy-based surface cross-linking agent; and

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

 Wherein the surface modification layer is formed on the particle surface of the base resin and the cross-linking polymer is additionally crosslinked via an epoxy-based surface cross-linking agent, and the surface modification layer comprises a hydrophobic substance having a B- Thereby providing a superabsorbent resin.

 【Effects of the Invention】

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

 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 method for producing a superabsorbent resin according to an embodiment of the present invention 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 having an acidic group and at least a part of which is neutralized, and a base resin crosslinked and polymerized with an acrylic acid-based monomer and an internal cross-linking agent;

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

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

. 2019/117511 1 »(: 1 ^ 1 {2018/014840

In the specification of the present invention, the term "base resin" or "base resin powder" refers to a product obtained by drying and pulverizing a polymer obtained by polymerizing a water-soluble ethylenically unsaturated monomer to form particles or powder knowledge (1) Quot; means a polymer that has not undergone surface modification or surface cross-linking steps.

 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, the absorbency and liquid permeability of superabsorbent resins, as well as the degree of absorption of the surface (^> ₁₆₃₃ ) in actual diapers, have become 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 Reabsorption of urine absorbed in the superabsorbent resin again) and urine

And thus the present invention has been accomplished.

In the method for producing a superabsorbent resin according to the present invention, the monomer composition, which is a raw material of the superabsorbent resin, is a monomer composition comprising an acrylic acid-based monomer having an acidic group and at least a part of the acidic groups neutralized, an internal crosslinking agent and a polymerization initiator Polymerized to obtain a hydrogel polymer, which is then 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]

In Formula 1, 2019/117511 1 »(: 1 ^ 1 {2018/014840

II < ¹ > is an alkyl group having 2 to 5 carbon atoms containing an unsaturated bond,

 1 is an avalanche, a 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, divalent metal salts, ammonium salts and organic amine salts.

Here, the acrylic acid-based monomer may have an acidic group and at least a part of the acidic group may be neutralized _. Preferably sodium hydroxide, to the above _monomers, potassium _hydroxide, may be used that was partially neutralized with an alkali substance such as ammonium hydroxide. 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 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.

 The photopolymerization initiator includes, for example, benzoin ether, dialkyl acetophenone, hydroxyl alkylketone, phenyl glyoxylate, benzyl dimethyl ketal

Dimethyl Ketal, acyl phosphine, and a-aminoketone may be used. On the other hand, Specific examples of the acylphosphine commercial liicirin TPO, that is, ^{2, 4, 6,} which-trimethyl-benzoyl-trimethyl phosphine oxide ^{(2, 4 ·, 6-} trimethyl-benzoyl-trimethyl phosphine oxide) available A variety of photoinitiators are well described in Reinhold Schwalm, UV Coatings: Basics, Recent Developments and New Applications (Elsevier 2007), p. 15, and are not limited to the above examples.

 If the concentration of the photopolymerization initiator is too low, the polymerization rate may be slowed. If the concentration of the photopolymerization initiator is excessively high, the concentration of the photopolymerization initiator may be lowered The molecular weight may be small and the physical properties may be 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 C> _8), potassium persulfate (K ₂ S ₂ O _8), ammonium persulfate (NH 2 _{4) 2} S ₂ 0 g). Examples of azo initiators include 2, 2-azobis- (2-amidinopropane) dihydrochloride ( ² ,

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

N-dimethylene) isobutyramidine dihydrochloride),

2- (carbamoyl azo) isobutylonitrile, 2,

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

Azobis [2- (2-imidazolin-2-yl) propane] dihydrochloride), 4,4-azobis- (4-cyanovaleric acid) 4-cyanovaleric acid)). Various thermal polymerization initiators are well described in the Odim book, Principle of Polynization (Wiley, 1981), p. 203, and are not limited to the above 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.

 The internal cross-linking agent is for crosslinking the interior of the polymerized polymer of the acrylic acid-based monomer, and is distinguished from the surface cross-linking agent for cross-linking the surface of the polymer.

 Specific examples of the internal crosslinking agent include N, N'-methylenebisacrylamide, trimethylolpropane tri (meth) acrylate, ethylene glycol di (meth) acrylate, polyethylene glycol (meth) acrylate, propylene glycol di Butylene diol di (meth) acrylate, butylene glycol di (meth) acrylate, diethylene glycol di (meth) acrylate, nucleic acid diol di (meth) acrylate, Acrylate, triethylene glycol di (meth) acrylate, tripropylene glycol di (meth) acrylate, tetraethylene glycol di (meth) acrylate, dipentaerythritol pentaacrylate, glycerin tri Styrene tetraacrylate, triallyl amine, Ethylene glycol diglycidyl may be used at least one member selected from ether, propylene glycol, the group consisting of glycerin, and ethylene carbonate.

 Such an internal crosslinking agent may be included at a concentration of about 0.01 to about 1.0 wt% based on the monomer composition to crosslink the polymerized polymer.

 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.

The above-mentioned acrylic acid-based monomer having an acidic group and at least part of the acidic group being neutralized, a photopolymerization initiator, a thermal polymerization initiator, an internal cross- 2019/117511 1 »(: 1 ^ 1 {2018/014840

The same raw materials 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, 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 N, N-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 largely divided into thermal polymerization and photopolymerization depending on the polymerization energy source. In general, when thermal polymerization is carried out, the polymerization can proceed in a reactor having a stirring die such as a kneader (1 _½ seeds (1) , 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 hydrogel polymer obtained by supplying hot air or heating the reactor to a reactor such as the kneader 10 _< 1 > (1) having an agitating shaft as described above, 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 resulting hydrogel polymer may vary depending on the concentration of the monomer composition to be injected, the rate of injection, etc. Usually, a gel polymer having a weight average particle diameter of from 2 to 50 μm can be obtained.

Further, when the photopolymerization proceeds in the reactor having the movable conveyor belt as described above, the form of the hydrogel polymer which is usually obtained is Gel-like polymer on the sheet having the width of the belt. At this time, the thickness of the polymer sheet depends on the concentration and the injection rate of the monomer composition to be injected, 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 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 water content of the hydrogel polymer, The phenomenon may also appear. 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.

The drying is carried out on the hydrogel polymer immediately after polymerization, which has not been pulverized or pulverized as described above, wherein the drying temperature of the drying step may be from about 150 to about 250 ° C. When the drying temperature is lower than 150 ^° C. The drying time is too long and the physical properties of the superabsorbent resin to be finally formed may be deteriorated. If the drying temperature exceeds 250 ° C, only the polymer surface is excessively dried, and a fine powder may be generated in a subsequent pulverizing step 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 the drying time, it may proceed for about 20 to about 90 minutes in consideration of the process efficiency and the like, but 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. The water content of the polymer after such a drying step may be from about 0.1 to about 10% by weight.

_Next, the steps of crushing the dried polymer obtained through this drying steps.

The polymer powder obtained after the pulverization step may have a particle diameter of about 150 to about 850 _{1. The} pulverizer used for pulverizing with such a particle size is specifically a pin mill, a hammer mill, a screw mill a screw mill, a roll mill, a disc mill or a jog mill may be used. However, the present invention is not limited to the above 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 Epoxy-based surface cross-linking agent is mixed (step 2).

 In a general method of producing a superabsorbent resin, a surface cross-linking solution containing a surface cross-linking agent is mixed with a dried and ground polymer, that is, a base resin, and then the surface cross-linking reaction .

 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.

 On the other hand, as the surface cross-linking agent, a compound capable of reacting with a functional group contained in the polymer is used, and examples thereof include polyvalent alcohol compounds, epoxy compounds, polyamine compounds, haloepoxy compounds, condensation products of haloepoxy compounds, oxazoline compounds, Or an alkylene carbonate compound can be used.

 On the other hand, according to the production method of the present invention, it has been confirmed that an epoxy-based surface cross-linking agent is used, and the absorption capacity can be further improved without lowering the rewetting property of the superabsorbent resin by using a specific epoxy surface cross-linking agent.

 Examples of the epoxy-based surface cross-linking agent satisfying these conditions include ethyleneglycol diglycidyl ether, diethyleneglycol diglycidyl ether, triethyleneglycol diglycidyl ether, ether, tetraethyleneglycol diglycidyl ether, glycerin polyglycidyl ether, sorbitol polyglycidyl ether, and the like.

The amount of the epoxy-based surface cross-linking agent to be added is not particularly limited, About 0.005 parts by weight or more, or about 0.01 parts by weight or more, or about 0.02 parts by weight or more, about 0.2 parts by weight or less, or about 0.1 parts by weight or less, or 0.05 parts by weight or less, based on the weight of the composition.

 If the content of the epoxy-based surface cross-linking agent is too small, the cross-linking density of the surface cross-linked layer becomes too low to lower the absorption characteristics such as absorbency under pressure and liquid permeability. If too much is used, The re-wetting property may be deteriorated.

 When the epoxy-based surface cross-linking agent is added, water may 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 cross-linking 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. 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.

 On the other hand, the pressure absorption ability and the permeability can be improved by the surface cross-linking reaction, but the re-wetting property needs to be further supplemented.

 According to the production method of the present invention, the hydrophilic material can be mixed with the base resin to improve the re-wetting property before the surface cross-linking reaction is performed by mixing the surface cross-linking agent with the base resin. The absorption rate and the liquid permeability can be further improved as compared with a resin not using a hydrophobic substance.

The hydrophobic substance has a HLB lower limit value of 0 or more, or 1 or more, or 2 Or less, and 6 or less, or 5 or less, or 5.5 or less in the upper limit value. In addition, since the hydrophobic substance melts in the surface cross-linking reaction and is located in the surface modification layer of the base resin, a material having a melting point lower than the surface cross-linking reaction temperature may be used.

 Hydrophobic materials that can be used include, for example, glyceryl stearate, glycol stearate, magnesium stearate, glyceryl laurate, sorbitan stearate, stearate, sorbitan trioleate, or PEG-4 dilaurate. Of these, glyceryl stearate or glyceryl laurate may be preferably used. However, The present invention is not limited thereto.

 The hydrophobic substance is distributed in the surface-modified layer of the surface of the base resin to prevent the swollen resin particles from agglomerating or agglomerating due to the increased pressure during the swelling of the high- 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 based on 100 parts by weight of the base resin,

0.5 part by weight or less, or about 0.3 part by weight or less, or about 0.1 part by weight or less. If the content of the hydrophobic substance is less than 0.02 part by weight, the rewet property may be insufficient, If the amount is more than the weight part, the base resin and the hydrophobic substance may be separated from each other, and there may be a problem that the rewetting is not improved or impurities may be present.

 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 with the base resin by dry mixing before mixing the surface cross-linking solution containing the epoxy surface cross-linking agent, or by dispersing the surface cross-linking agent together with the surface cross- 2019/117511 1 »(: 1 ^ 1 {2018/014840

Alternatively, in addition to the surface cross-linking solution, the hydrophobic substance may be heated to a melting point or higher and mixed in a solution state.

 Next, a surface modification step is performed on the base resin by heating the mixture of the base resin and the epoxy surface cross-linking agent (step 3).

 The surface modification step may be performed at a temperature of from about 120 to about 190 (preferably, from about 130 to about 1801: about 10 to about 90 minutes, preferably from about 20 to about

Lt; / RTI > for 70 minutes. When the crosslinking reaction temperature is less than 1201: or the reaction time is too short, the surface cross-linking reaction does not occur in the order of passage and the permeability may be lowered. If the reaction time exceeds 1901: or the reaction time is too long,

 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. By the surface modification step as described above, a surface cross-linking structure formed by reacting with the functional groups of the epoxy-based surface cross-linking agent and the base resin is formed on the surface of the base resin, and the surface cross- A reforming layer can be formed.

 Therefore, the superabsorbent resin produced by the production method of the present invention can have improved rewet characteristics and initial absorption rate without deteriorating physical properties such as water solubility and pressure absorption ability as the surface modifying layer.

According to another embodiment of the present invention, there is provided a resin composition comprising: a base resin comprising a cross-linked polymer wherein at least a part of an acidic group is neutralized with an acrylic acid-based monomer; 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,

By weight or more and not more than 6% by weight, to provide.

 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 28 g / g, or at least about 29 g / g, or at least about 30 g / g, and at least about 40 g / g of CRC measured according to EDANA method WSP 241.3 , Or about 38 g / g or less, or about 35 g / g or less.

 The superabsorbent resin preferably has a pressure absorption capacity (AUP) of about 0.3 g / g or more, about 23 g / g or about 25 g / g or more, and about 0.3 g / 37 g / g or less, or about 35 g / g or less, or about 32 g / g or less.

 Also, the aqueous resin may have a yortex time of 40 seconds or less, or 35 seconds or less, or about 30 seconds or less, or about 28 seconds or less. The lower the absorbing rate, the better the lowering of the absorbing rate is theoretically 0 seconds, for example about 5 seconds or more, about 10 seconds or more, or about 12 seconds or more.

 The absorption rate refers to a time (unit: second) in which the vortex of the liquid disappears due to the rapid top water when the superabsorbent resin is added to the physiological saline solution and stirred. When the time is short, Can be seen to have a fast initial absorption rate.

 The superabsorbent resin may have a permeability (unit: second) measured according to the following formula 1: about 35 seconds or less, about 30 seconds or less, or about 27 seconds or less. The liquid permeability is better as the value is smaller, and the theoretical lower limit value may be 0 seconds, for example, 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 to 2019/117511 1 »(: 1 ^ 1 {2018/014840

It is the time it takes for the liquid level to decrease from 40 to 20 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, the superabsorbent resin is immersed in water of 100 _시켜

Defined as the weight of water repelled from the superabsorbent resin to the filter paper after being swollen for 10 minutes and left on the filter paper for 1 hour from the initial point of time when the swollen high viscosity aqueous resin was immersed in the tap water, (Water-repellent water-repellency water-repellency) of 2.0 _§ or less, 1.5 _§ or less, or 1.4 _§ or less, or 1.3 or less. The weight of the water is excellent as the value is small and theoretically the lower limit is ¾, _§ or more, or 0.3 툐 or more, or 0.5 _§ or more.

Or the superabsorbent resin

The swollen superabsorbent resin was immersed in water 20 and swelled for 6 hours _. (Pressure water repellent long-term rewetting) defined as the weight of the water repelled from the superabsorbent resin to the filter paper is 1.2 _§ or less, or 1.1 _§ or less, or _§ 1.0 can be as follows: a theoretical lower limit to the weight of water is superior or the smaller the value is, for example, be in the range of 0.1 ₈ or more, or 0.3 or more _{§, §} 0.5 or more.

 The tap water used in the re-wetting property evaluation has an electrical conductivity of 170 -

180 or 8/0 ₁₁ . 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. 2019/117511 1 »(: 1 ^ 1 {2018/014840

<Examples>

 Preparation of superabsorbent resin

 Example 1

(1>01> 1546116)} 01 (400) (1 071 6) 3.2 and acrylic acid 518 _and polyethyleneglycol diacrylate were added to a three-necked glass vessel equipped with a stirrer, a nitrogen introducer and a thermometer, 6-trimethylbenzoyl) -phosphine oxide 0.04 silver was added and dissolved. Then, 24.5% sodium hydroxide solution 822.2 silver was added and nitrogen was continuously added to prepare an aqueous solution of a water-soluble unsaturated monomer. The water-containing unsaturated monomer aqueous solution was cooled to 40 ° C. 50 (¾) of this aqueous solution was added to a container made of stainless steel having a width of 250 ₁₁₁₁₁₁ , a length of 250, and a height of 30 ₁₁₁₁₁₁ , and irradiated with ultraviolet rays (dose:

10 &lt; ₁₁ &gt; / 0) and polymerized for 11 seconds to obtain a hydrogel polymer. The obtained gel-like polymer functions 21111x1 * 2_ and then ground to a size, followed seuteinreseugwa the resulting gel-like resin having a pore size of 600 _ place expanding 30 _{111 111} thickness on the gauze 1801: and then dried for 30 minutes in a hot-air oven. The dry polymer thus obtained was pulverized using a pulverizer,

Classified into a standard standard network

A base resin having a particle size of 150 to 850_ was obtained.

0.025 part by weight of glyceryl stearate (1 part by 3.8 parts) was mixed with 100 parts by weight of the base resin, and then 0.02 part by weight of ethylene glycol diglycidyl ether, 0.01 part by weight of glycerol polyglycidyl ether, 0.025 part by weight of polyethylene glycol, and 0.2 part by weight of aluminum sulfate was injected into a container made of a stirrer and a double jacket, and the surface cross-linking reaction was carried out at 140 ° C for 40 minutes. Classifying the powder after the surface treatment standard sieve mesh of ASTM standard, and having a particle size of 150 to 850 Thyssen ₁ to obtain a water-absorbent resin powder. Then, 0.1 part by weight of silica was dry-mixed with 100 parts by weight of the surface-treated superabsorbent resin to obtain a final high-water absorbent resin product. Example 2

To a three-necked glass vessel equipped with a stirrer, a nitrogen introducer and a thermometer was added acrylic acid 518 polyethylene glycol diacrylate (1> 01} ¾1; 11) 461½ (: -Trimethylbenzoyl) -phosphine oxide (0.04) was added and dissolved, 2019/117511 1 »(: 1 ^ 1 {2018/014840

24.5% by the addition of sodium hydroxide solution 822.2 _§ while nitrogen is continuously introduced to prepare a water-soluble unsaturated monomer aqueous solution. The water-soluble unsaturated monomer aqueous solution was cooled to 401: This aqueous solution was added to a container made of stainless steel having a width of 250 ₁ X ₁₁₁₁ , a height of 250 _{111111 and a} height of 30 _{1 11} , and irradiated with ultraviolet rays (irradiation amount: 10 _{1 1} 70 70 ₁₁ ² )

Polymerization was carried out to obtain a hydrogel polymer. The resultant gel-like polymer was pulverized to a size of 21111x1 * 2_, and then the resulting gel-like resin was spread on a stainless steel wire gauze having a pore size of 600 g and then dried in a hot air oven for 180 minutes. The dried polymer thus obtained was pulverized using a pulverizer, and classified with a standard mesh of Show 811 to obtain a base resin having a particle size of 150 to 850_.

To 100 parts by weight of the base resin, glyceryl stearate

And 0.075 part by weight of a surfactant were dry mixed, and then 0.02 part by weight of ethylene glycol diglycidyl ether, 0.01 part by weight of glycerol polyglycidyl ether, 8 parts by weight of water, 0.025 part by weight of polyethylene glycol and 0.2 part by weight of aluminum sulfate, The solution was sprayed, mixed and placed in a container made of a stirrer and a double jacket, and the surface cross-linking reaction was carried out at 1401: for 40 minutes. Then, the surface-treated powder

To obtain a superabsorbent resin powder having a particle size of 150 to 850_. Then, 0.1 part by weight of silica was dry-mixed with 100 parts by weight of the surface-treated superabsorbent resin to obtain a final high-water absorbent resin product. Example 3

A stirrer, a nitrogen injector, acrylate, 518 the third glass container equipped with a thermometer _¾ polyethylene glycol diacrylate ^{(1> 01 61; 11>} 46116} ^ 01 (400)) 3.¾ and diphenyl (2,4, 6- Trimethylbenzoyl) -phosphine oxide was added and dissolved. Then, a solution of 24.5% sodium hydroxide solution (822.2) was added, and nitrogen was continuously added to prepare an aqueous solution of a water-soluble unsaturated monomer. The water-soluble unsaturated monomer aqueous solution was cooled to 40 ° C. This aqueous solution (50/4) was applied to a container made of stainless steel having a width of 250 ₁₁₁₁₁₁ , a length of 250_, a height of 3

Polymerization was carried out to obtain a hydrogel polymer. The resultant hydrogel polymer was pulverized to a size of 2 * 2111111, 2019/117511 1 »(: 1 ^ 1 {2018/014840

600 mesh, stainless steel wire gauze having a hole size of about 30 &lt; RTI ID = 0.0 &gt; l &lt; / RTI &gt; The dry polymer thus obtained was pulverized using a pulverizer and classified with a standard mesh of ASTM standard to obtain a base resin having a particle size of 150 to 850 !.

 After 0.3 parts by weight of glyceryl stearate 13 3.8 parts by weight was added to 100 parts by weight of the base resin, 0.02 part by weight of ethylene glycol diglycidyl ether, 0.01 part by weight of glycerol polyglycidyl ether, 8 parts by weight of water, 0.025 part by weight of glycol, and 0.2 part by weight of aluminum sulfate was injected into a container made of a stirrer and a double jacket, and the surface crosslinking reaction was carried out at 140X for 40 minutes. Then, the surface-treated powder was classified into a standard mesh of ASTM standard to obtain a superabsorbent resin powder having a particle size of 150 to 850_. Then, 0.1 part by weight of silica was dry-mixed with 100 parts by weight of the surface-treated superabsorbent resin to obtain a final high-water absorbent resin product. Example 4

Acrylic acid 518 _and aminoethyleneglycol diacrylate (1 * 01): 117 1 ^ 1> 400 (400) (1 071 6) 3.2 were added to 3 glass containers equipped with a stirrer, a nitrogen introducer and a thermometer, 4,6, was prepared phosphine oxide was dissolved by the addition of 0.04 _§, 24.5% sodium hydroxide aqueous solution and 822.2 water-soluble unsaturated monomer was added to the _§ input of nitrogen in a row-trimethylbenzoyl). The water-soluble unsaturated monomer aqueous solution was cooled to 40.. This aqueous solution 50 was applied to a container made of stainless steel having a width of 250111111, a length of 250_, and a height of 30_ _. Irradiated with ultraviolet rays (dose: 10111 \ 7011 ² )

Polymerization was carried out to obtain a hydrogel polymer. The resultant hydrogel polymer was pulverized to a size of 2 * 2111111, and then the resulting gel resin was spread on a stainless wire gauze having a pore size of 600 mm to a thickness of about 30 占 and dried in a 180 hot air oven for 30 minutes. The dried polymer thus obtained was pulverized using a pulverizer and classified with a standard mesh of ASTM standard to obtain a base resin having a particle size of 150 to 850_.

To 100 parts by weight of the base resin, 0.025 part by weight of glyceryl stearate (3.8), 0.02 part by weight of ethylene glycol diglycidyl ether, 0.025 part by weight of glycerol polyglycidyl 2019/117511 1 »(: 1 ^ 1 {2018/014840

A surface cross-linking solution containing 0.01 part by weight of ether, 8 parts by weight of water, 0.025 part by weight of polyethylene glycol and 0.2 part by weight of aluminum sulfate was mixed and sprayed in a container made of a stirrer and a double jacket, The reaction proceeded. Thereafter, the surface-treated powder was classified into a standard mesh of Show Standard to obtain a superabsorbent resin powder having a particle size of 150 to 850 _/ L. Then, 0.1 part by weight of silica was dry-mixed with 100 parts by weight of the surface-treated superabsorbent resin to obtain a final high-water absorbent resin product. Example 5

Acrylic acid 518 and polyethyleneglycol diacrylate 3.2 out of diphenyl (2, 4, 6-trimethylbenzoyl) - (meth) acrylate were added to three glass containers equipped with a stirrer, a nitrogen introducer and a thermometer. phosphine oxide was dissolved by the addition of 0.04 _§, 24.5% sodium hydroxide solution, 822.2 is a water-soluble unsaturated monomer aqueous solution with added nitrogen is continuously added was prepared. The water-soluble unsaturated monomer aqueous solution was cooled to 40 ° C. The aqueous solution 500 has a width 250 _{111 111,} 250 _{111 111 vertically,} the height 30Inm was added to the container of the stacking Nu-less material is irradiated with ultraviolet rays (dose: wave /! ² )

Polymerization was carried out to obtain a hydrogel polymer. After the resulting hydrogel polymer was pulverized to a size of 2 _{111111 *} 2111111, the obtained gel resin was spread on a stainless steel wire gauze having a pore size of 600 g and then dried in a hot air oven for 180 minutes. The dry polymer thus obtained was pulverized using a pulverizer and classified with a standard mesh of ASTM standard to obtain a base resin having a particle size of 150 to 850 _/ L.

 0.025 part by weight of glyceryl laurate (1 part by weight, 5.2 parts by weight) was added to 100 parts by weight of the base resin. Then, 0.02 part by weight of ethylene glycol diglycidyl ether, 0.01 part by weight of glycerol polyglycidyl ether, , Polyethylene glycol

0.025 part by weight of aluminum sulfate and 0.2 part by weight of aluminum sulfate was injected and mixed in a container made of a stirrer and a double jacket, and the surface cross-linking reaction was carried out at 140 ^{° C} for 40 minutes. Thereafter, the surface-treated powder was classified into a standard mesh of Show Standard to obtain a superabsorbent resin powder having a particle size of 150 to 850 _/ L. Then, 100 parts by weight of the surface-treated superabsorbent resin was mixed with 100 parts by weight of silica 0.1 2019/117511 1 »(: 1 ^ 1 {2018/014840

Weight parts were dry mixed to obtain a final hard dope aqueous resin product. Example 6

 A superabsorbent resin was prepared in the same manner as in Example 1, except that the content of glyceryl stearate was changed to 0.15 parts by weight in Example 1. Example 7

 A superabsorbent resin was prepared in the same manner as in Example 1, except that the content of glyceryl stearate was changed to 0.5 parts by weight. Comparative Example 1

Acrylic acid 518 _and polyethylene glycol diacrylate (1 ⁵ ₀₁ > ½ _{1 1 6116} } ^ ₀₁ (400)) were added to a 31 ᅴ glass vessel equipped with a stirrer, a nitrogen introducer and a thermometer. 3.2. trimethyl benzoyl) phosphine oxide was dissolved by the addition of 0.04 _§, 24.5% sodium hydroxide solution, 822.2 aqueous unsaturated monomer solution was added to the _§ input of nitrogen was continuously prepared. The water-soluble unsaturated monomer aqueous solution was cooled to 40 ° C. 50 (¾) of this aqueous solution was added to a container made of stainless steel having a width of 250 _{111111, a} length of 250 _{111111 and a} height of 30 _{占 하고} and irradiated with ultraviolet rays (dose:

Polymerization was carried out for 11 seconds at 11, to obtain a hydrogel polymer. The resultant gel-like polymer was pulverized to a size of 2 * 2 * ₁₁₁₁₁₁ , and then the resulting gel-like resin was spread on a stainless steel wire gauze having a pore size of 600 mm to a thickness of about 30 占 and dried in a 1801: hot air oven for 30 minutes. The dry polymer thus obtained was pulverized using a pulverizer and classified with a standard mesh of ASTM standard to obtain a base resin having a particle size of 150 to 850.

0.1 part by weight of silica was mixed with 100 parts by weight of the base resin, and then 0.02 part by weight of ethylene glycol diglycidyl ether, 8 parts by weight of water and 0.2 part by weight of aluminum sulfate was injected and mixed, and a 140 ° double put in a jacket made of a container (: from 40 minutes to proceed with the surface cross-linking reaction and the water-absorbent resin powder to a subsequent surface-treated powder having the particle size of the classified to 150 to 850 Thyssen _first body standard web of ASTM standards &Lt; / RTI &gt; Then the surface 2019/117511 1 »(: 1 ^ 1 {2018/014840

0.1 part by weight of silica was dry-mixed with 100 parts by weight of the treated superabsorbent resin to obtain a final superabsorbent resin product. Comparative Example 2

(400) of acrylic acid 518 _and polyethylene glycol diacrylate (1 * _{01761; 1161 § 3} ) (400) in three glass containers equipped with a stirrer, a nitrogen introducer and a thermometer. ) - phosphine oxide _§ 0.04 with the solution obtained, 24.5% of sodium hydroxide was dissolved was added 822.2 aqueous unsaturated monomer solution was added to the _§ input of nitrogen was continuously prepared. The water-soluble unsaturated monomer aqueous solution was cooled to 40 ° C. The solution of 50 (250 to ₁₁₁₁₁₁ ¾ horizontal, vertical 250 _{111 111,} was added to a stainless steel container of a height 3 (切wave ₁ is irradiated with ultraviolet rays (dose: 10 to _{111 \} ^ / 0 ₁₁ ²⁾

Polymerization was carried out to obtain a hydrogel polymer. The resultant gel-like polymer was pulverized to a size of 2 mm, and then the obtained gel-like resin was spread on a stainless steel wire gauze having a pore size of 600 mm and a thickness of about 30 mm and dried in a 180 l hot air oven for 30 minutes. The dry polymer thus obtained was pulverized using a pulverizer, and classified with a standard mesh of Show Standard to obtain a base resin having a particle size of 150 to 850_.

 0.025 part by weight of polyethylene glycol glyceryl stearate 1 part 15), 0.02 part by weight of ethylene glycol diglycidyl ether, 0.01 part by weight of glycerol polyglycidyl ether, 8 parts by weight of water, polyethylene glycol 0.025 part by weight And 0.2 part by weight of aluminum sulfate were sprayed and mixed, and the mixture was placed in a container made of a stirrer and a double jacket to carry out surface cross-linking reaction at 140 40 for 40 minutes. Then, the surface-treated powder was classified into a standard mesh of ASTM standard to obtain a superabsorbent resin powder having a particle size of 150 to 850. Then, 0.1 part by weight of silica was dry-mixed with 100 parts by weight of the surface-treated superabsorbent resin to obtain a final high-water-soluble resin product. Comparative Example 3

In a three-necked glass vessel equipped with a stirrer, a nitrogen introducer and a thermometer, acrylic acid 518 _& Polyethylene glycol diacrylate (1>01> 1 61 1) Example (400) <1 071) 3.2 was prepared by dissolving 0.04 _§ of diphenyl (2,4,6-trimethylbenzoyl) after that, by the addition of 24.5% sodium hydroxide solution 822.2 ₈ while nitrogen is continuously introduced to prepare an aqueous solution of water-soluble unsaturated monomer. The water-soluble unsaturated monomer aqueous solution was cooled to 40 ° C. It was added to the aqueous solution in a vessel of stainless steel in the transverse 50¾ 250 ^ ₁₁ 250 _1X1111 vertical, height 30rnm irradiated with ultraviolet rays (dose:

Polymerization was carried out to obtain a hydrogel polymer. The resultant gel-like polymer was pulverized into 2-by-2 mm size, and then the obtained gel-type resin was spread on a stainless wire gauze having a pore size of 600 mm to a thickness of about 30 占 and dried in a hot air oven for 180 minutes. The dried polymer thus obtained was pulverized using a pulverizer and classified with a standard mesh of ASTM standard to obtain a base resin having a particle size of 150 to 850_.

To 100 parts by weight of the base resin, glyceryl stearate

0.025 part by weight was dry mixed, and then a surface cross-linking solution containing 0.03 part by weight of ethylene carbonate, 8 parts by weight of water, 0.025 part by weight of polyethylene glycol and 0.2 part by weight of aluminum sulfate was injected and mixed. The surface cross - linking reaction was carried out at 1401: for 40 minutes. Then, the surface-treated powder was classified into a standard mesh having a standard of show standard to obtain a superabsorbent resin powder having a particle size of 150 to 850 sun !. Thereafter, 0.1 part by weight of silica was dry-mixed with 100 parts by weight of the surface-treated superabsorbent resin to obtain a final highly hydrous resin product.

<Experimental Example>

 The physical properties of the aqueous 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.

In addition, the tap water used in the re-wetting property evaluation described below has an electrical conductivity of from 170 to 180, as measured by Orion Star A222 (company: Thermo Scientific) pS / cm was used.

(1) Centrifugal Retention Capacity (CRC)

 The retention capacity of each resin by the zero-load capacity was measured according to EDANA WSP 241.3.

Specifically, the superabsorbent resin W _{0 (} g) (about 0. 3) was uniformly put in an envelope made of a nonwoven fabric and sealed, and then immersed 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 WJg 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 1 (g)] AV 0 (g)} - 1 (2) gaapreul SAT (AUP: Absorption Under Pressure)

 The pressure absorption capacity of each resin of 0.3 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. Piston that is under conditions of normal temperature and humidity of 50%, and on the wire evenly spraying the water-absorbing resin W _{0 (g) (0.90,} even more give a load of 0.3 psi on it is slightly smaller cylinder than an outer diameter 60 mm And the upper and lower movements were not disturbed at this time, the weight W _{3 (} g) of the device was immediately given.

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 1 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 formula. &Quot; (2) &quot;

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

(3) Permeability

 The permeability measurement method was imposed in accordance with the method described in Patent No. US 9656242 B2.

 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 sample (300-600 _/ L) 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. After that, add a piston (0.3 psi = 106.26g) in the chromatograph tube and leave it for 1 minute. Open the bottom of the chromatograph tube and time it decreases from 40m to 20ml mark The time (unit: second) was calculated.

(4) Top procedure (Vortex time)

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

Specifically, 2 g of superabsorbent resin was put into 50 mL of physiological saline at 23 ^° C, and the magnetic bar (diameter: 8 mm, length: 30 mm) was stirred at 600 rpm to measure the time until the vortex disappeared. .

(5) Waterless seawater Short-term rewet (lhr)

① 1 g of a superabsorbent resin was put into a cup (upper diameter 7 cm, lower diameter 5 cm, height 8 cm, height 192 ml), 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-based resin swollen on the filter paper (Whatman, catalog No. 1004-110, pore size 20-25 μm, 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.

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

 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) Place 20 sheets of filter paper (manufacturer whatman, catalog No. 1004-110, pore size 20-25 ₍ xm, diameter: 1 cm) with a diameter of 11 cm and swell for 6 hours from the time when water was poured. And pressed for 1 minute with 1 kg of 5 kg weight (0.75 psi).

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

[Table 1]

2019/117511 1 »(: 1 ^ 1 {2018/014840

Referring to Table 1, it was confirmed that Examples 1 to 7 of the present invention all exhibited excellent rewet characteristics and fluidity.

On the other hand, when the hydrophobic substance is not used,

It can be seen that Comparative Examples 1 and 2 to which a substance exceeding 6 were added had poor rewet characteristics than the Examples.

 In addition, Comparative Example 3 in which a non-epoxy surface cross-linking agent was used did not have satisfactory transparency and remanence characteristics.

Claims

Claims:

 [Claim 1]

 (Step 1) of preparing a base resin having an acidic group and at least a part of which is neutralized, and a base resin crosslinked and polymerized with an acrylic acid-based monomer and an internal cross-linking agent;

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

 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 hydrophobic substance is first dry-mixed with the base resin, and then the epoxy-based surface cross-linking agent is dissolved in water and mixed in the state of surface cross-linking solution.

[Claim 3]

 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 4

 The method according to claim 1,

The hydrophobic material may be selected from the group consisting of glyceryl stearate, glycol stearate, magnesium stearate, glyceryl laurate, sorbitan stearate, sorbitan trioleate, Sorbitan trioleate, and PEG-4 dilaurate. The method for producing a superabsorbent resin according to claim 1,

[Claim 5]

 The method according to claim 1,

 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.

[Claim 6]

 The method according to claim 1,

The epoxy-based surface cross-linking agent may be ethylene glycol diglycidyl

ether), diethylene glycol diglycidyl ether (出_11> ½ _116> Example ¾1} 1 ether), triethylene glycol diglycidyl ether (1 11 _{11 6116} min _{01 (% 1> 1 ether)} , At least one member selected from the group consisting of tetraethylene glycol diglycidyl ether, glycerin polyglycidyl ether, and sorbitol polyglycidyl ether, By weight.

_*

[7]

 The method according to claim 1,

 The epoxy-based surface cross-linking agent is preferably used in an amount of

0.005 to 0.2 part by weight.

8.

 The method according to claim 1,

 Wherein step 3 is carried out at a temperature of from 120 to 1901 &lt; RTI ID = 0.0 &gt;:. &Lt; / RTI &gt;

[Claim 9]

 The method according to claim 1,

In the step 1, Polymerizing a monomer composition comprising an acrylic acid-based monomer having an acidic group and at least a part of the acidic groups neutralized, an internal cross-linking agent, and a polymerization initiator to form a hydrogel-like polymer;

 Drying the hydrogel polymer;

 Pulverizing the dried polymer; and

 And a step of classifying the pulverized polymer.

Claim 10

 The method according to claim 1,

 Wherein the superabsorbent resin has a vortex time of 40 seconds or less.

Claim 11

 The method according to claim 1,

 Wherein the superabsorbent resin has a permeability (unit: sec) measured according to the following formula (1) is 35 seconds or less:

 [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, leaving it for 30 minutes, ml, 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 12

 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

Is formed on the particle surface of the base resin, and the cross-linked polymer Wherein the surface modifying layer comprises a hydrophobic substance having an HLB of not less than 0 and not more than 6, wherein the surface modifying layer is additionally crosslinked via an epoxy-based surface crosslinking agent.

Claim 13

 13. The method of claim 12,

 A high water-based resin having a permeability (unit: second) imposed in accordance with the following formula (1) is 35 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 #) classified into a chromatographic tube was added and the brine volume was adjusted to 50 ml by adding brine. After standing for 30 minutes, ml, 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.

14.

 13. The method of claim 12,

 The hydrophobic material may be selected from the group consisting of glyceryl stearate, glycol stearate, magnesium stearate, glyceryl laurate, sorbitan stearate, sorbitan trioleate, Sorbitan trioleate, PEG-4 dilaurate, and PEG-4 dilaurate.

15.

 13. The method of claim 12,

The epoxy-based surface cross-linking agent is selected from the group consisting of ethyleneglycol diglycidyl ether, diethylene glycol diglycidyl But are not limited to, diethyleneglycol diglycidyl ether, triethyleneglycol diglycidyl ether, tetraethyleneglycol diglycidyl ether, glycerin polyglycidyl ether, And sorbitol polyglycidyl ether. &Lt; RTI ID = 0.0 &gt; 11. &lt; / RTI &gt;

Claim 16

 13. The method of claim 12,

 Wherein the superabsorbent resin has a vortex time of 40 seconds or less.

17.

 13. The method of claim 12,

 The high-sheath water-based resin is prepared by immersing 1 g of the high-shear water-based resin in 100 g of water and allowing it to swell for 10 minutes, then allowing the swollen super-absorbent resin to stand on the filter paper for 1 hour from the initial point of immersion in water, Wherein the re-wetting property (unreacted water repellency, short-term re-wetting) defined by the weight of the water repelled from the superabsorbent resin to the filter paper is 2.0 g or less. Claim 18

 13. The method of claim 12,

The high-sheath water-based resin is obtained by immersing 4 g of the high-water-based resin in 200 g of tap water and swelling for 6 hours, then placing the swollen superabsorbent resin on a filter paper under a pressure of 0.75 psi for 1 minute, from

Water-repellent long-term rewetting) of 1.2 g or less.