WO2016089005A1 - Super-absorbent resin and method for preparing same - Google Patents

Abstract

According to a super-absorbent resin and a method for preparing the same, of the present invention, the super-absorbent resin does not only have excellent solution permeability but can also exhibit high water retention capacity and absorbency under pressure, by controlling the surface cross-linkage degree of a base resin.

Description

 【Specification】

 [Name of invention]

 Super Absorbent Resin and Method for Making the Same

 [Cross Citation with Related Application (s)]

 This application claims the benefit of priority based on Korean Patent Application No. 10-2014-0172999 dated December 14, 2014 and Korean Patent Application No. 10-2015-0145613 dated October 19, 2015. All content disclosed in these references is included as part of this specification.

 Technical Field

The present invention relates to a _super absorbent polymer having excellent solution permeability and a method of preparing the same.

 Background Art

A super absorbent polymer (SAP) is a synthetic polymer material that can absorb about 500 to 1000 times its own weight. It is a SAM (Super Absorbency Material), AGM (Asorbent Gel Material), etc. It is also blowing. Super absorbent resins have been put into practical use as sanitary devices and are now widely used in various materials such as hygiene products such as paper diapers for children, horticultural soil repair agents, civil engineering materials, seedling sheets, and freshness retainers in food distribution. It is used. As a method for producing such a super absorbent polymer, a method by reverse phase suspension polymerization or a solution polymerization is known. Among them, the production of superabsorbent polymers through reverse phase suspension polymerization is disclosed, for example, in Japanese Patent Laid-Open Nos. 56-161408, 5,158, JP, 158,209, and the like. In addition, the production of superabsorbent polymers through polymerization of aqueous solution is a thermal polymerization method for polymerizing a hydrogel polymer in a kneader equipped with several shafts while breaking and angled, and polymerizing and drying by irradiating UV light to a high concentration of aqueous solution on a belt. The photopolymerization method etc. which perform simultaneously are known. On the other hand, absorption rate, which is one of the important physical properties of super absorbent polymer, Similarly, the surface dryness of the product in contact with the skin. In general, this absorption rate can be improved by increasing the surface area of the superabsorbent polymer. For example, a method of forming a porous structure on the particle surface of the super absorbent polymer by using a blowing agent has been applied. However, there is a disadvantage in that the general foaming agent cannot form a sufficient amount of porous structure, so that the increase in absorption rate is not large. As another example, there is a method of increasing the surface area by reassembling the fine powder obtained in the manufacturing process of the super absorbent polymer to form porous particles of irregular shape. However, although the absorption rate of the superabsorbent polymer can be improved through this method, there is a limit that the resin's centrifugal water retention capacity (CRC) and the pressure absorption capacity (AUL) are relatively lowered. As such, the physical properties such as absorption rate, water holding capacity, and pressure absorbing capacity of the super absorbent polymer are in a trade-off relationship, and a manufacturing method capable of improving these properties at the same time is urgently required.

 [Content of invention]

 [Problem to solve]

 The present invention is to provide a superabsorbent polymer and a method for preparing the same, which have a high water permeability and pressure absorbing ability as well as excellent solution permeability by controlling the degree of surface crosslinking of the base resin.

 [Measures of problem]

 In order to solve the above problems, the present invention provides a super absorbent polymer comprising a crosslinked polymer comprising an acidic group and surface-crosslinked a base resin polymerized with a water-soluble ethylenically unsaturated monomer in which at least part of the acidic group is neutralized,

 The gel strength of the base resin is 4000 to 5000 Pa, the gel strength of the crosslinked polymer is 1.4 times or more of the gel strength of the base resin,

The pressure absorption of 0.7 psi of the crosslinked polymer ^ (AUP, g / g) is at least 22 And centrifuged beam SAT (CRC, g / g) of the crosslinked polymer is 28 or more, the transmittance of the solution of cross-linked polymer ^{(SFC, 10- 7 cm 1 ·} sec / g) is more than 30,

 It provides a super absorbent water, characterized in that the centrifugal water retention (CRC) and solution permeability (SFC) of the crosslinked polymer satisfies the following formula 1.

 [Calculation 1]

 CRC + (SFC / 10)> 34. As described above, the superabsorbent polymer according to the present invention controls the degree of surface crosslinking of a base resin having a gel strength in the above range, such that the gel strength of the crosslinked polymer is compared with that of the base resin. By adjusting to the above range, not only has excellent solution permeability, but also has a feature of exhibiting high water holding capacity and pressure absorbing ability. The water-soluble ethylenically unsaturated monomer included in the monomer composition may be any monomer conventionally used for preparing a super absorbent polymer. As a non-limiting example, the water-soluble ethylenically unsaturated monomer may be a compound represented by Formula 1:

 [Formula 1]

 In Chemical Formula 1,

Ri is an alkyl group having 2 to 5 carbon atoms containing an unsaturated bond, and M ¹ is a hydrogen atom, a monovalent or divalent metal, an ammonium group or an organic amine salt. Preferably, the monomer is acrylic acid, methacrylic acid, and

It may be at least one selected from the group consisting of monovalent metal salts, divalent metal salts, ammonium salts and organic amine salts. As such, when acrylic acid or its salt is used as the water-soluble ethylene-based unsaturated monomer, it is advantageous to obtain a superabsorbent polymer having improved water absorption. In addition, the monomers include maleic anhydride, fumaric acid, crotonic acid, itaconic acid, 2-acryloylethane sulfonic acid, 2- Methacryloylethanesulfonic acid, 2- (meth) acryloylpropanesulfonic acid or 2- (meth) acrylamide-2-methyl propane sulfonic acid, (meth) acrylamide, N-substituted (meth) acrylate, 2-hydrate Hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, methoxypolyethylene glycol

(Meth) acrylate, polyethylene glycol (meth) acrylate, (Ν, Ν) -dimethylaminoethyl (meth) acrylate, (Ν, Ν) -dimethylaminopropyl

(Meth) acrylamide and the like can be used. Here, the water-soluble ethylenically unsaturated monomer has an acidic group, at least a portion of the acidic group may be neutralized. Preferably, those which have been partially neutralized with an alkali substance such as sodium hydroxide, potassium hydroxide, ammonium hydroxide or the like may be used. In this case, the degree of neutralization of the monomer may be 40 to 95 mol%, or 40 to 80 mol% or 45 to 75 mol%. The range of the degree of neutralization may vary depending on the final physical properties, but if the degree of neutralization is too high, the neutralized monomer may precipitate and polymerization may be difficult to proceed smoothly. On the contrary, if the degree of neutralization is too low, the absorbency of the polymer is not only greatly reduced. It can exhibit the same properties as elastic rubber, which is difficult to handle. In addition, the concentration of the water-soluble ethylenically unsaturated monomer in the monomer composition may be appropriately adjusted in consideration of the polymerization time and reaction conditions, preferably 20 to 90% by weight, or 40 to 65% by weight. This concentration range may be advantageous to control the grinding efficiency during the grinding of the polymer to be described later, while eliminating the need for removing the unbanung monomer after the polymerization by using the gel effect phenomenon appearing in the polymerization reaction of the high concentration aqueous solution. However, when the concentration of the monomer is too low, the yield of the super absorbent polymer may be lowered. On the contrary, if the concentration of the monomer is too high, some of the monomers may precipitate or process problems may occur such as when the pulverization efficiency of the polymerized hydrogel polymer is reduced, and the physical properties of the super absorbent polymer may be reduced. The surface crosslinking is a method of increasing the crosslinking density of the surface of the base resin particles, and in particular, in the present invention, the physical properties of the crosslinked polymer are improved by controlling the degree of surface crosslinking of the base resin. Let's do it. On the other hand, the gel strength means the horizontal gel strength of the superabsorbent polymer measured after swelling by absorbing physiological saline solution (0.9% by weight aqueous sodium chloride solution) in the base resin or crosslinked polymer for 1 hour, using a rheometer Can be measured. In addition, the pressure absorption capacity (AUP) of 0.7 psi may be represented by the following formula 2:

 [Calculation 2]

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

 In the formula 2,

W ₀ (g) is the weight of superabsorbent polymer (g) ，

W ₃ (g) is the sum of the weight of the superabsorbent polymer and the weight of the device capable of applying a load to the superabsorbent polymer,

W ₄ (g) is the sum of the weight of the water absorbed superabsorbent resin after supplying water to the superabsorbent polymer for one hour under a load (0.7 psi) and the weight of the device capable of loading the superabsorbent polymer. to be. In addition, the centrifugal water retention capacity (CRC) for the physiological saline can be expressed according to the following equation 3:

 [Calculation 3]

CRC (g / g) = {[W ₂ (g)-Wi (g)] / W ₀ (g)}-1

 In the above formula 3,

W ₀ (g) is the weight of superabsorbent polymer (g) ，

Kg) does not use a super absorbent polymer, but uses a centrifuge Device weight measured after dehydration at 250G for 3 minutes,

W ₂ (g) is the weight of the device, including the superabsorbent polymer, after submerging the superabsorbent polymer for 30 minutes in 0.9 mass% of physiological saline to the silver, followed by dehydration at 250 G for 3 minutes using a centrifuge. Preferably, the centrifugal water holding capacity (CRC, .g / g) of the crosslinked polymer is 29 or more, more preferably 30 or more. In addition, the solution permeability (SFC) is determined by Darcy's law and steady flow method (e.g., "Absorbency", edited by PK Chatter jee, Elsevier 1985, pp. 42-43 and Chemical Engineering, Vol. II, 3rd edit ion, JM Coulson and JF Ri char son, Pergamon Press, 1978, pp. 125-127) and can be measured according to the methods described in columns 54 to 59 of US Pat. No. 5,562,646. Can be. Manufacturing method of super absorbent polymer

 The super absorbent polymer according to the present invention may be prepared by a manufacturing method comprising the following steps.

 1) thermally polymerizing or photopolymerizing a monomer composition comprising a water-soluble ethylenically unsaturated monomer and a polymerization initiator to form a hydrogel polymer;

 2) drying the pulverized hydrogel polymer;

 3) pulverizing the dried polymer; and

 4) surface crosslinking the pulverized polymer; Hereinafter, the present invention will be described in detail for each step. Formation of hydrogel polymer (step 1)

First, the method for preparing the superabsorbent polymer includes thermally polymerizing or photopolymerizing a monomer composition including a water-soluble ethylenically unsaturated monomer and a polymerization initiator. Polymerizing to form a hydrogel polymer. The water-soluble ethylenically unsaturated monomer included in the monomer composition is as described above. In addition, the monomer composition may include a polymerization initiator generally used in the production of superabsorbent polymers. As a non-limiting example, a thermal polymerization initiator or a photopolymerization initiator may be used as the polymerization initiator, depending on the polymerization method. However, even by the photopolymerization method, since a certain amount of heat is generated by ultraviolet irradiation or the like, and a certain amount of heat is generated in accordance with the progress of the polymerization reaction, which is an exothermic reaction, a thermal polymerization initiator may be further included. Here, as the photoinitiator, for example, benzoin ether, dialkyl acetophenone, hydroxyl alkylketone, phenylglyoxylate, benzyldimethyl One or more compounds selected from the group consisting of benzyl dimethyl ketal, acyl phosphine and a -aminoketone can be used. As specific examples of the acylphosphine, commercially available lucirin TP0, that is, 2,4,6-trimethyl-benzoyl-trimethyl phosphine oxide (2,4,6-trimethyl benzoyl one trimethyl phosphine oxide) may be used. . A wider variety of photopolymerization initiators are disclosed on page 115 of Reinhold Schwalm, "UV Coatings: Basics, Recent Developments and New Application (Elsevier 2007)", and can be referred to this. As the thermal polymerization initiator, one or more compounds selected from the group consisting of persulfate-based initiators, azo-based initiators, hydrogen peroxide, and ascorbic acid may be used. Specifically, as the persulfate-based initiator, sodium persulfate (Na ₂ S ₂ 0 ₈ ), potassium persulfate (Potassium persulfate; K ₂ S ₂ 0 ₈ ), ammonium persulfate (NH ₄ ) ₂ S ₂ 0 ₈ ) For example. In addition, azo (Azo) -based initiators are 2,2-azobis- (2-amidinopropane) dihydrochloride (2,2-azobis (2— amidinopropane) dihydrochloride), 2,2-azobis- (Ν , Ν—dimethylene) isobutyramimidine dihydrochloride (2,2- azobis- (N, N-dimethyl ene) is obut yr am idi ne dihydrochloride), 2- (carbamoyl azo) isobutyronitrile ( 2- (carbamoylazo) isobutylonitril), 2,2- azobis [2- (2-imidazolin-2-yl) propane] dihydrochloride (2, 2- azobis [2- (2-imidazol in-2- yl) propane] dihydrochlor ide), 4,4—azobis -1- (4-cyanovaleric acid) (4,4-320 5- (4 ^ £ 1110 31 ^^; acid)) . More various thermal polymerization initiators are disclosed on page 203 of Odian's book "Principle of Polymerization (Wiley, 1981)", which can be referred to as about 0.001 to 1 weight based on the monomer composition. In other words, when the concentration of the polymerization initiator is too low, the polymerization rate may be slowed down and a large amount of remaining monomer may be extracted in the final product. Too high is not preferable because the polymer chain forming the network is shortened, so that the content of the water-soluble component and the pressure absorption capacity is lowered, such that the physical properties of the resin may be lowered. Crosslinking agent ("internal crosslinking agent") for improving the physical properties of the resin The crosslinking agent may be used to internally crosslink the hydrogel polymer, and may be used separately from a crosslinking agent (“surface crosslinking agent”) for crosslinking the surface of the hydrogel polymer. Any compound may be used as long as it enables the introduction of crosslinks in the polymerization of the unsaturated monomers, and non-limiting examples of the internal crosslinking agent include Ν, Ν'—methylenebisacrylamide, trimethyl propane tri (meth) acrylate, ethylene glycol Di (meth) acrylate, polyethylene glycol (meth) acrylate, propylene glycol di (meth) acrylate, polypropylene glycol (meth) acrylate, butanediol di (meth) acrylate, butylene glycol die (meth Acrylate, diethylene glycol di (meth) acrylate, nucleic acid die di (meth) acrylate, triethylene glycol di (meth) acrylate, tripropylene glycol di (meth) acrylate, tetraethylene glycol di (meth) Polyacrylates such as acrylates, dipentaerythrates, pentaacrylates, glycerin tri (meth) acrylates, pentaeris, tetraacrylates, triarylamines, ethylene glycol diglycidyl ethers, propylene glycols, glycerin, or ethylene carbonates The functional crosslinking agent may be used alone or in combination of two or more. It is not limited thereto. Such internal crosslinking agent may be added at a concentration of about 0.001 to 1% by weight relative to the monomer composition. That is, when the concentration of the internal crosslinking agent is too low, the absorption rate of the resin may be low and the gel strength may be weakened, which is not preferable. On the contrary, when the concentration of the internal crosslinking agent is too high, the absorbing power of the resin may be low, which may be undesirable as an absorber. In addition, the monomer composition may further include additives such as thickeners, plasticizers, storage stabilizers, and antioxidants as necessary. In addition, the monomer composition may be prepared in the form of a solution in which raw materials such as the aforementioned monomer, polymerization initiator, internal crosslinking agent, and the like are dissolved in a solvent. In this case, any solvent that can be used may be used without limitation as long as it can dissolve the above-described raw materials. For example, the solvent includes water, ethanol, ethylene glycol, diethylene glycol, triethylene glycol, 1,4-butanedi, propylene glycol, ethylene glycol monobutyl ether, propylene glycol monomethyl ether, propylene glycol monomethyl ether. acetate, Methyl ethyl ketone, acetone, methyl amyl ketone, cyclonucleanone, cyclopentanone, diethylene glycol monomethyl ether, diethylene glycol ethyl ether, toluene, xylene, butyrolactone, carbyl, methyl cellosolve acetate , Ν, Ν-dimethylacetamide, or a combination thereof may be used. In addition, the formation of the hydrogel polymer through the polymerization of the monomer composition may be performed by a conventional polymerization method, and the process is not particularly limited. As a non-limiting example, the polymerization method is largely divided into thermal polymerization and photopolymerization according to the type of polymerization energy source. When the thermal polymerization is performed, the polymerization method may be performed in a reactor having a stirring shaft such as a kneader. When the polymerization proceeds, it can be carried out in a semi-unggi equipped with a movable conveyor belt. For example, the monomer composition may be added to a reactor such as a kneader equipped with a stirring shaft, and hot water may be supplied thereto or thermally polymerized by heating the reactor to obtain a hydrogel polymer. At this time, the hydrous gel phase polymer discharged to the semi-unggi outlet according to the shape of the stirring shaft provided in the reactor may be obtained in the particles of several millimeters to several centimeters. Specifically, the resulting hydrogel polymer may be obtained in various forms depending on the concentration and injection rate of the monomer composition to be injected, and a hydrogel polymer having a particle size of 2 to 50 mm 3 can be obtained. And, as another example, when the photopolymerization of the monomer composition in a semi-unggi equipped with a movable conveyor belt may be a hydrous gel polymer in the form of a sheet. At this time, the thickness of the sheet may vary depending on the concentration and the injection rate of the monomer composition to be injected, in order to ensure the production rate while the entire sheet is evenly polymerized, it is usually adjusted to a thickness of 0.5 to 5 cm desirable. Water-containing gel polymer formed by this method is about 40 to 80 Moisture content in weight percent. Herein, the moisture content is a weight of water in the total weight of the hydrogel polymer, and may be a value obtained by subtracting the weight of the dried polymer from the weight of the hydrogel polymer. Specifically, it may be defined as a value calculated by measuring the weight loss due to evaporation of water in the polymer in the process of drying the temperature of the polymer through infrared heating. At this time, the drying conditions may be set to 20 minutes, including 5 minutes of the temperature rise step in such a way that the temperature is raised to about 180 ^° C and then maintained at 180 ^° C. Drying the hydrogel polymer (step 2)

On the other hand, the manufacturing method of the super absorbent polymer includes the step of drying the hydrogel-like laminate formed through the above-described steps. Here, if necessary, in order to increase the efficiency of the drying step, the step of pulverizing (coarse grinding) the hydrogel polymer before the drying may be more rough. As a non-limiting example, the grinders available for the coarse grinding include a vertical pulverizer, a turbo cutter, a turbo grinder, a rotary cutter mill, a cutting type Examples include a cutter mill, a disc mill, a shred crusher, a crusher, a chopper, a disc cutter, and the like. At this time, the coarse grinding may be performed so that the particle size of the hydrogel polymer is 2 to 10 내지. That is, in order to increase the drying efficiency, the hydrous gel polymer is preferably pulverized into particles of 10 mm or less. However, since excessive aggregation may cause intergranular phenomena, the hydrous gel phase polymer is preferably pulverized into particles of 2 mm or more. In this case, when the coarse grinding step is performed before the drying step of the hydrogel polymer, the polymer may stick to the surface of the grinder because the polymer has a high water content. In order to minimize this phenomenon, the coarsely pulverizing step includes, as necessary, steam, water, surfactants, anti-aggregation agents such as clay or Si ica; Thermal sulfate initiators such as persulfate initiators, azo initiators, hydrogen peroxide, and ascorbic acid, epoxy crosslinkers, diol crosslinkers, crosslinkers comprising acrylates of difunctional or trifunctional or more than trifunctional groups, and hydroxyl groups. Crosslinking agents, such as a compound of monofunctional groups, may be added. On the other hand, as described above, the drying of the hydrous gel phase polymer immediately after coarse grinding or polymerization may be performed at a temperature of 120 to 250 ^° C., or 150 to 200 ^° C., or 160 to 180 ^° C. It may be defined as the temperature of the heat medium supplied for drying or the temperature inside the drying reactor comprising the heat medium and the polymer in the drying process. That is, when the drying temperature is low and the drying time is long, the physical properties of the final resin may be lowered. In order to prevent this, the drying temperature is preferably 120 ° C or more. In addition, there is a drying temperature may be a fine powder generated more in the milling process to be described later is dry only the surface of the function, the gel polymer is higher than necessary, the physical properties of the final resin can be lowered, a drying temperature in order to prevent this, is 250 ^° It is preferable that it is C or less. At this time, the drying time in the drying step is not particularly limited, but may be adjusted to 20 to 90 minutes under the drying temperature in consideration of process efficiency and the like. And, if the drying method of the drying step can also be commonly used as a drying step of the hydrous gel phase polymer is applicable to the configuration without limitation. Specifically, the drying step may be a method such as hot air supply, infrared irradiation, microwave irradiation, or ultraviolet irradiation. The polymer dried in this manner may exhibit a water content of about 0.1 to 10% by weight. In other words, if the water content of the polymer is less than 0.1% by weight, it is not advantageous because an increase in the manufacturing cost and degradation of the crosslinked polymer may occur due to excessive drying. In addition, when the water content of the polymer exceeds 10% by weight, defects may occur in subsequent processes, which is not preferable. Grinding the dried polymer (step 3)

 The manufacturing method of the super absorbent polymer includes the step of pulverizing the polymer dried through the above-described steps. The grinding step may be performed to optimize the surface area of the dried polymer, and may be performed to have a particle diameter of 150 to 850. Mills that can be used to grind to these particle sizes include pin mills, hammer mills, screw mills, roll mills, disc mills and jogs. A jog mill etc. are mentioned, for example. The polymer produced by grinding as described above is referred to as 'base resin' in the present invention, which is distinguished from the 'crosslinked polymer' prepared by crosslinking reaction to be described below. And, in order to manage the physical properties of the superabsorbent polymer to be finalized, the step of selectively classifying particles having a particle size of 150 to 850 in the polymer powder obtained through the grinding step may be further performed. Surface crosslinking reaction of the ground polymer (step 4)

The manufacturing method of the super absorbent polymer includes the step of surface crosslinking the polymer pulverized through the above-described steps. Surface crosslinking is a method of increasing the crosslinking density of the surface of a resin particle, and the solution comprising a crosslinking agent (surface crosslinking agent) and the pulverized polymer It can be carried out by a method of mixing and crosslinking reaction. By the surface crosslinking, the gel strength of the base resin having a gel strength of 4000 to 5000 Pa may be increased by 1.4 times or more, and thus solution permeability (SFC), water retention, and pressure absorption may be improved. When the gel strength of the base resin is less than 4000 Pa, the solution permeability (SFC) of the crosslinked polymer is lowered. When the gel strength of the base resin is more than 5000 Pa, the centrifugal water retention capacity (CRC) is lowered. there is a problem. Here, (to surface cross-linking), a cross-linking agent contained in the surface cross-linking solution roneun by surface cross-linking as described above comprising a cross-linking agent to increase the gel strength of at least 1.4 times, in particular (C ₂ - ₄₎ alkylene carbonates, preferably For example, ethylene carbonate or propylene carbonate can be used. At this time, the content of the surface crosslinking agent may be appropriately adjusted according to the type or reaction conditions of the crosslinking agent, and preferably may be adjusted to 0.001 to 5 parts by weight based on 100 parts by weight of the pulverized polymer. When the content of the surface crosslinking agent is too low, surface crosslinking may not be properly introduced, and the physical properties of the final resin may be reduced. On the contrary, when the surface crosslinking agent is used in an excessively high content, the absorption of the resin may be lowered due to excessive surface crosslinking reaction, which is not preferable. Meanwhile, in order to perform the surface crosslinking reaction step, the surface crosslinking solution and the pulverized polymer are mixed in a semi-permanent mixture, a method of spraying the surface crosslinking solution on the pulverized polymer, a pulverized polymer and The method of supplying and mixing the surface crosslinking solution continuously can be used. Further, when the surface crosslinking solution is added, additional water may be added. Can be. As such water is added together, more even dispersion of the crosslinking agent may be induced, aggregation of the polymer powder may be prevented, and the penetration depth of the surface crosslinking agent into the polymer powder may be further optimized. In view of these objects and effects, the amount of water added may be adjusted to 0.5 to 10 parts by weight based on 100 parts by weight of the pulverized polymer. And, the surface crosslinking reaction step may be performed under a temperature of 100 to 250 ^° C, it may be made continuously after the drying and grinding step proceeds to a relatively high temperature. At this time. The surface crosslinking reaction may be performed for 1 to 120 minutes, or 1 to 100 minutes, or 10 to 60 minutes. In other words, in order to induce a minimum surface crosslinking reaction, the polymer particles may be damaged during excessive reaction, thereby preventing the physical properties from deteriorating.

 【Effects of the Invention】

 The superabsorbent polymer according to the present invention and a method for preparing the same have the characteristics of having excellent solution permeability by controlling the degree of surface crosslinking of the base resin, and exhibiting high water retention and pressure absorption capability.

 [Brief Description of Drawings]

 1 is a graph showing physical property data of a super absorbent polymer according to an embodiment of the present invention.

 [Specific contents to carry out invention]

 Hereinafter, preferred embodiments are presented to help understand the invention. However, the following examples are only for illustrating the present invention, and the present invention is not limited thereto. Property measurement method

Gel strength, pressure absorption capacity (AUP), centrifugal water retention capacity (CRC), and solution permeability (SFC) measured in the following Production Examples, Examples, and Experimental Examples were measured by the following methods. 1) gel strength

 The resin was sieved through a sieve (30-50 mesh) and weighed 0.5 g, which was then swollen in 50 g of 0.9% NaCl solution for 1 hour. The swollen gel was then spread over a Buchner funnel covered with filter paper to remove the remaining fluids for 3 minutes under vacuum. The gel was stored in a closed container until the test was ready. The gel was sucked into the filter paper so that there was no remaining water between the particles during testing before placing the gel between the rheometer and the parallel plate. Gel strength was measured with a rheometer with 2 g of the swollen gel. At this time, the measurement conditions of the rheometer were as follows. The measured values were taken for 5 minutes and then averaged.

Plate Gap Size: 2 mm 3; Strain amplitude 1%; Osci lat ion frequency 10 readina / sec; ambient temperature: 22 ^° C; plate: 25 mm, TA Instruments-AR series

2) Pressurized Absorption Capacity (AUP)

Pressurized absorption capacity was measured by the following method according to the EDANA method WSP 242.2, the European Disposables and Nonwovens Association (EDANA) standard. A stainless steel 400 mesh wire was mounted on the bottom of a 60 mm diameter plastic cylinder. 0.9 g (W ₀ ) of the resin was uniformly spread on the wire mesh under conditions of 50% of humidity and room temperature, and a piston was formed thereon which could further uniformly apply a load of 0.7 psi. The piston had an outer diameter of slightly less than 60 mm 3, no gap with the inner wall of the cylinder, and the up and down movement was not disturbed. At this time, the weight W ₃ (g) of the apparatus was measured. A 90 mm diameter and 5 mm thick glass filter was placed inside a 150 mm diameter petri dish, and physiological saline consisting of 0.90 wt% sodium chloride was added at the same level as the top surface of the glass filter. One sheet of filter paper having a diameter of 90 mm was placed thereon. The measuring device was placed on filter paper and the solution was allowed to absorb under constant load. After 1 hour, the measuring apparatus was lifted up, and the weight W ₄ (g) was measured. The AUP was measured by the measurement result as shown in Equation 2 below. ^'

 [Calculation 2]

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

3) Centrifugal water retention capacity (CRC)

Beam SAT by Mucha Heavy absorption ratio was determined according to European Nonwoven Industry Association _{(European Disposables and Nonwovens Association,.} EDANA) standard EDANA WSP 241.2. Specifically, 0.2 g (W ₀ ) of the resin was uniformly placed in a bag made of a nonwoven fabric and sealed, and then immersed in 0.9% physiological saline at room temperature. After 30 minutes, the bag was drained at 250 G for 3 minutes using a centrifuge, and then the mass (g) of the bag was measured. In addition, the time of the mass Kg After the same operation without the use of ^resin), was measured. From each mass thus obtained, CRC (g / g) was calculated according to the following formula.

 [Calculation 3]

CRC (g / g) = {[W ₂ (g)-W! (G)] / W ₀ (g)}-1 4) Solution Permeability (SFC)

Darcy's Law and Steady Flow Method (e.g., "Absorbency", edited by PK Chatter jee, Elsevier 1985, pp. 42-43 and Chemical Engineering, Vol. II 3rd edition, JM Coulson and JF Ri char son, Pergamon Press, 1978, Pp. 125-127) and measured according to the methods described in columns 54-59 of US Pat. No. 5,562,646. The weight of the super absorbent polymer used in the measurement was 0.9 g. Example

 Step 1) Preparation of Base Resin

 100 g of acrylic acid, polyethylene glycol diacrylate as crosslinking agent (Mw = 523)

0.5 g, a mixture of diphenyl (2,4,6-trimethylbenzoin) -phosphine oxide 0.033 g, 50% aqueous sodium hydroxide solution (NaOH) and 89.8 g of water as a UV initiator, monomer concentration is 45.7% by weight A phosphorus monomer aqueous solution composition was prepared. The monomer aqueous solution composition was continuously fed into the supply section of the polymerized polymer conveyor belt, and then irradiated with UV light using a UV irradiation apparatus (irradiation amount: 20 mW / ciif), followed by UV polymerization for 2 minutes to form a hydrogel polymer. Was prepared. The hydrogel polymer was transferred to a cutter and cut into 0.2 cm. At this time, the water content of the hydrogel polymer was 47% by weight. Subsequently, the hydrogel polymer was dried at a temperature of 160 ^° C. in a hot air dryer for 30 minutes, and the dried hydrogel polymer was pulverized with a pin mill grinder. Subsequently, sieves were used to classify polymers having a particle size (average particle diameter size) of 150 µη to 850 to prepare a base resin. CRC of the prepared base resin was 33 ~ 35 g / g, the gel strength was 4500-5000 Pa. Step 2) Preparation of Super Absorbent Resin

100 g of the base resin prepared in step 1 was mixed with a solution of 3 g of distilled water and 0.4 g of ethylene carbonate (EC), followed by crosslinking reaction at a temperature of 194 ^° C. in a convection oven at intervals of 10 minutes. The physical properties were taken and measured as shown in FIG. 1 (total 40 minutes). After completion of the surface crosslinking reaction, the mixture was cooled to room temperature and dried, and then the sieve size (average particle size) was 150. The polymers from 850 to 850 were classified to prepare surface-crosslinked superabsorbent polymers. Comparative Example 1

 Prepared in the same manner as in Example 1, but instead of ethylene carbonate

Resin was prepared using 1,3-propanedi (1, 3-P). Samples were taken at 10 minute intervals during the crosslinking reaction as in Example 1, and the physical properties thereof were shown in FIG. 1 (total 40 minutes). Comparative Example 2

 In Step 2 of Example 1, except that a solution containing 3 g of distilled water, 0.3 g of 4-butanediol and 100 g of base resin was mixed, a superabsorbent polymer was prepared in the same manner as in Example 1. It was. Comparative Example 3

 In Step 2 of Example 1, a superabsorbent polymer was prepared in the same manner as in Example 1, except that 100 g of the base resin was mixed with 3 g of distilled water and 0.3 g of ethylene glycol. Comparative Example 4

A base resin was prepared in the same manner as in Step 1 of Example 1, except that 0.3 g of polyethylene glycol diacrylate (Mw = 523) was used. The CRC of the prepared base resin was 43 g / g, and the gel strength was 3120 Pa. 100 g of the base resin prepared above was mixed with a solution of 3 g of distilled water and 0.4 g of ethylene carbonate, followed by crosslinking reaction at a temperature of 194 ^° C. for 40 minutes in a convection oven. After the completion of the surface crosslinking reaction, the phase was cooled with silver and dried, and then sieve was used to classify a polymer having a particle size (average particle diameter size) of 150 urn to 850 to prepare a surface-crosslinked superabsorbent polymer. Comparative Example 5

A base resin was prepared in the same manner as in Step 1 of Example 1, except that 0.1 g of polyethylene glycol diacrylate (Mw = 523) was used. The CRC of the prepared base resin was 52 g / g, and the gel strength was 1980 Pa. 100 g of the base resin prepared above was mixed with a solution of 3 g of distilled water and 0.4 g of ethylene carbonate, followed by a crosslinking reaction for 40 minutes at a temperature of 194 ^° C. in a convection oven. After completion of the surface crosslinking reaction, it was cooled to room temperature and dried, and then sieve was used to classify a polymer having a particle size (average particle diameter size) of 150 pm to 850 to prepare a surface-crosslinked superabsorbent polymer. Experimental Example: Property Comparison

As shown in FIG. 1, the physical properties of the Example (red) and Comparative Example (black) were different. In particular, as shown in Figure 1 (b), the solution permeability of the Example was higher than the comparative example of similar gel strength. In addition, as shown in Figure 1 (c), the centrifugal water holding capacity of the Example was higher than the comparative example of similar solution permeability, the sum of the centrifugal water holding capacity and the solution permeability of the embodiment (CRC + SFC / 10) It was higher than this comparative example (FIG. 1 (d)). Therefore, it was confirmed that the super absorbent polymer according to the present invention can simultaneously achieve high centrifugal water-retaining ability and solution permeability. In addition, the measurement results of the physical properties of Comparative Examples 2 to 5 are shown in Table 1, and as shown in Table 1 below, in Examples 2 and 3, the values of CRC + (SFC / 10) were different from those of the surface crosslinking agent. In the case of Comparative Examples 4 and 5 where the gel strength of the base resin was less than 34 and the gel strength was less than 4000 Pa, the SFC value was Did not reach Table 1

Claims

Claims 1. The superabsorbent polymer comprising a crosslinked polymer comprising an acidic group and surface-crosslinked with a base resin polymerized with a water-soluble ethylene-unsaturated monomer in which at least a part of the acidic group is neutralized. The gel strength of the base resin is 4000 to 5000 Pa, the gel strength of the crosslinked polymer is 1.4 times or more the gel strength of the base resin, and the pressure absorption capacity (AUP, g / g) of 0.7 psi of the crosslinked polymer is 22 or more. And the centrifugal water retention capacity (CRC, g / g) of the crosslinked polymer is 28 or more, the solution permeability (SFC, 10 " 7 cm3-sec / g) of the crosslinked polymer is 30 or more, and the centrifugation of the crosslinked polymer A super absorbent polymer, characterized in that the water holding capacity (CRC) and the solution permeability (src) satisfy the following formula 1.

 [Calculation 1]

 C C + (SFC / 10)> 34.

[Claim 2]

 The method of claim 1,

 The water-soluble ethylenically unsaturated monomer is characterized in that the compound represented by the formula (1),

 Super Absorbent Resin:

 [Formula 1] In Formula 1,

 ¾ is an alkyl group having 2 to 5 carbon atoms containing an unsaturated bond,

M ¹ is a hydrogen atom, a monovalent or divalent metal, an ammonium group or an organic amine salt.

[Claim 3]

According to claim 1 The water-soluble ethylenically unsaturated monomers are acrylic acid, methacrylic acid, maleic anhydride, fumaric acid, crotonic acid, itaconic acid, 2-acryloylethane sulfonic acid, 2-methacryloylethanesulfonic acid, 2- (meth) acryloylpropane Anionic monomers of sulfonic acid or 2- (meth) acrylamide-2-methyl propane sulfonic acid and salts thereof; (Meth) acrylamide, N-substituted (meth) acrylate, 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, mesopolyethylene glycol (meth) acrylate or polyethylene glycol ( Nonionic hydrophilic-containing monomers of meth) acrylate; And an amino group-containing unsaturated monomer of (Ν, Ν) -dimethylaminoethyl (meth) acrylate or (Ν, Ν) -dimethylaminopropyl (meth) acrylamide and its quaternized product; Characterized by including

 Superabsorbent polymer.

[Claim 4]

 The method of claim 1,

The surface crosslinking of the base resin, and - characterized in that the carbonate is carried out by reacting (C _{2 4} alkylene),

 Superabsorbent polymer.

[Claim 5]

 The method of claim 4,

The (C ₂ - ₄ alkylene) carbonate, characterized in that the ethylene carbonate or propylene carbonate,

 Superabsorbent polymer.

[Claim 6]

 The method of claim 1,

^'Absorption capacity under pressure (AUP) of the 0.7 psi is characterized in that represented by the following formula 2, Super Absorbent Resin:

 [Calculation 2]

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

 In the formula 2,

W ₀ (g) is the weight of superabsorbent polymer (g) ，

W ₃ (g) is the sum of the weight of the superabsorbent polymer and the weight of the device capable of applying a load to the superabsorbent polymer,

W ₄ (g) is the weight of the water absorbed superabsorbent resin after supplying water to the superabsorbent polymer for 1 hour under a load (0.7 ps i) and the weight of the device capable of applying a load to the superabsorbent polymer. Total.

[Claim 7]

 The method of claim 1,

 The centrifugal water retention capacity (CRC) for the physiological saline is characterized in that shown in accordance with the following formula 3,

 Super Absorbent Polymer ：

 [Calculation 3]

CRC (g / g) = {[W ₂ (g)-Wi (g)] / W ₀ (g)} ᅳ 1

 In the above formula 3,

W ₀ (g) is the weight of superabsorbent polymer (g) ，

 Kg) is the weight of the device measured after dehydration at 250G for 3 minutes without using a super absorbent polymer, using a centrifuge,

W ₂ (g) is the weight of the device including superabsorbent polymer after 30 minutes of superabsorbent polymer was immersed in physiologically saline solution of 0.9 mass ¾> at room temperature for 30 minutes and then dehydrated at 250G for 3 minutes using a centrifuge. to be.

[Claim 8]

 The method of claim 1,

The super absorbent polymer is characterized in that it is produced by a manufacturing method comprising the following steps, Super Absorbent Resin:

 1) thermally polymerizing or photopolymerizing a monomer composition comprising a water-soluble ethylenically unsaturated monomer and a polymerization initiator to form a hydrogel polymer;

 2) drying the hydrogel polymer;

 3) pulverizing the dried polymer; and

 4) surface crosslinking the pulverized polymer;

[Claim 9]

 The method of claim 8,

 Between the step 1 and step 2, characterized in that it further comprises the step of grinding the hydrogel polymer to a particle diameter of 2 to 10 mm 3,

 Superabsorbent polymer.

[Claim 10]

 The method of claim 8,

The drying of step 2, characterized in that carried out at a temperature of 120 to 250 ^° C,

 Superabsorbent polymer.

[Claim 11]

 According to claim 8,

 The pulverization of the step 3 is characterized in that to be carried out so that the particle diameter of the pulverized polymer is 150 to 850,

 Superabsorbent polymer.

[Claim 12]

 According to claim 8

The surface crosslinking reaction of step 4 is characterized in that it is carried out under a temperature of 100 to 250 ^° C, Superabsorbent polymer