KR101797391B1 - Super Absorption Polymer and Manufacturing Thereof - Google Patents

Abstract

Disclosed are a super absorbent resin manufactured by polymerizing a monomer composition comprising an acrylic acid monomer and a lactone-based monomer, grinding and drying the same and performing surface cross-linking; and a manufacturing method thereof. To this end, provided is a cross-linking polymer which polymerizes and internally cross-links a composition comprising an acrylic acid monomer which has an acid group and in which at least part of the acid group is polymerized, and a monomer represented by chemical formula 1 or 2, and a super absorbent resin comprising a surface cross-linking layer formed on the surface of the cross-linking polymer.

Description

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

The present invention relates to a superabsorbent resin, and more particularly to a superabsorbent resin which is obtained by polymerizing a monomer composition comprising a monomer composition comprising an acrylic acid monomer and a lactone monomer, And a manufacturing method thereof.

Super absorbent polymer (SAP) is a synthetic polymer material capable of absorbing a level of about 500 to 1,000 times its own weight. As a result, a super absorbent material (SAM), an absorbent gel material) and so on. Such a superabsorbent resin has begun to be put to practical use as a sanitary article and is currently being used in various fields such as a sanitary article for children's paper diapers and the like, a soil repair agent for horticultural use, a soil index material for civil engineering, It is widely used as a material.

Such a method of producing a superabsorbent resin includes a thermal polymerization method in which a hydrogel polymer is polymerized while being broken and cooled in a kneader-type reactor provided with several shafts, a polymerization method in which ultraviolet rays are irradiated onto a high- And a method of producing a superabsorbent resin by suspension polymerization are known.

Such a superabsorbent resin can be produced through polymerization, drying, pulverization, classification, and surface cross-linking processes. In order to improve the absorption ability, it was tried to improve the absorption ability by studying the crosslinking agent in the polymerization process, studying the surface area improvement in crushing and classification, and studying the improvement of the surface crosslinking. However, despite these studies, there has been a limit to improving the absorption ability of the acrylic-based superabsorbent resin.

Korean Patent Laid-Open Publication No. 2015-0082098 (2015.07.15) Korean Patent Laid-Open Publication No. 2015-0088219 (Jul. 31, 2015) International Patent Publication No. WO2015-047029 (2014.09.30)

Disclosure of Invention Technical Problem [8] Accordingly, the present invention has been made to solve the above-mentioned problems, and it is an object of the present invention to provide a method for producing a superabsorbent resin by polymerizing a monomer composition comprising a mixture of an acrylic acid monomer and a lactone monomer, And to provide a superabsorbent resin having an excellent absorption rate without lowering the water solubility and pressure absorption ability.

In order to solve the above-mentioned problems, a first aspect of the present invention is a crosslinked polymer obtained by polymerizing and cross-linking a composition comprising an acrylic acid-based monomer having an acidic group and at least a part of the acidic groups neutralized and a monomer represented by the formula And a surface crosslinked layer formed on the surface of the crosslinked polymer.

[Chemical Formula 1]

(n is an integer of 1 to 10, and M is hydrogen or a monovalent metal or a nonmetal ion)

(2)

(n is an integer of 1 to 10)

Further, the superabsorbent resin has a water absorbency (CRC) of 25 g / g or more and a pressure absorption capacity (AUL) of 15 g / g or more.

(Meth) acrylate, propylene glycol di (meth) acrylate, polypropylene glycol (meth) acrylate, butanediol di (meth) acrylate, butylenedioldi (Meth) acrylate, triethylene glycol di (meth) acrylate, triethylene glycol di (meth) acrylate, tetraethylene glycol di Ethylene glycol di (meth) acrylate, dipentaerythritol pentaacrylate, glycerin tri (meth) acrylate, pentaerythritol tetraacrylate, triarylamine, ethylene glycol diglycidyl ether, propylene glycol, glycerin, and ethylene Carbonate, and the like, by at least one crosslinking agent selected from the group consisting of Wherein the crosslinked polymer is crosslinked.

Also, the surface cross-linked layer may be formed of at least one of ethylene glycol diglycidyl ether, polyethylene glycol diglycidyl ether, glycerol polyglycidyl ether, propylene glycol diglycidyl ether, polypropylene glycol diglycidyl ether, ethylene glycol, But are not limited to, ethylene glycol, propylene glycol, triethylene glycol, tetraethylene glycol, propanediol, dipropylene glycol, polypropylene glycol, glycerin, polyglycerin, butanediol, heptanediol, hexanediol trimethylolpropane, Wherein the cross-linking agent is surface-crosslinked with at least one cross-linking agent selected from the group consisting of sorbitol and sorbitol.

The second aspect of the present invention also relates to a method for producing a thermoplastic resin composition, comprising the steps of: (a) heating a monomer composition comprising an acrylic acid-based monomer having an acidic group and at least a part of the acidic groups neutralized and a monomer composition represented by the general formula (1) Polymerizing to form a hydrogel polymer; (b) pulverizing the hydrogel polymer; (c) drying the pulverized polymer at 150 to 250 占 폚; (d) pulverizing the dried polymer; And (e) subjecting the pulverized polymer to a surface cross-linking reaction.

And the step (d) comprises pulverizing the dried polymer to a particle size of 150 μm to 850 μm.

And the surface cross-linking reaction is carried out at a temperature of 100 to 250 ° C.

According to the present invention, it is possible to produce a superabsorbent resin having excellent water retention ability and pressure absorption ability and excellent absorption rate by preparing a superabsorbent resin using a monomer composition comprising an acrylic acid monomer and a lactone monomer, And various kinds of industrial fields such as gardening articles, seedling-use sheets, food absorbing sheets, and the like.

Hereinafter, preferred embodiments of the present invention will be described in detail. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described in detail with reference to the accompanying drawings. Throughout the specification, when an element is referred to as "including " an element, it means that it can include other elements, not excluding other elements, unless specifically stated otherwise.

The inventors of the present invention have observed that the existing acrylic-based superabsorbent resins have lower absorption performance than other absorbent materials and have conducted intensive studies in order to solve the problems. As a result, they have found that when acrylic monomers and lactone monomers are mixed, The present inventors have found that the absorbability is greatly improved as compared with the conventional absorbent resin, and the present invention has been completed.

Hereinafter, the present invention will be described in detail.

A first aspect of the present invention relates to a crosslinked polymer obtained by polymerizing and cross-linking a composition having an acidic group and at least a part of the acidic group neutralized with an acrylic acid-based monomer and a monomer represented by the formula And a surface cross-linked layer formed on the surface.

[Chemical Formula 1]

(n is an integer of 1 to 10, and M is hydrogen or a monovalent metal or a nonmetal ion)

(2)

(n is an integer of 1 to 10)

The second aspect of the present invention also relates to a process for producing a polymer composition comprising (a) a step of polymerizing a monomer composition comprising an acrylic acid monomer having an acid group and at least a part of the acid groups neutralized and a monomer composition represented by the formula Thereby forming a hydrogel polymer; (b) pulverizing the hydrogel polymer; (c) drying the pulverized polymer at 150 to 250 占 폚; (d) pulverizing the dried polymer; And (e) subjecting the pulverized polymer to a surface cross-linking reaction.

Hereinafter, the present invention will be described in detail.

Hydrogel  The step of forming the polymer (step 1)

The method for producing the superabsorbent resin includes a step of thermally or photopolymerizing a monomer composition comprising a water-soluble acrylic monomer, a lactone monomer and a polymerization initiator to form a hydrogel polymer.

The water-soluble acrylic monomer contained in the monomer composition may be any monomer conventionally used in the production of a superabsorbent resin. As a non-limiting example, the water-soluble acrylic monomer may be a compound represented by the following general formula (3).

(3)

(Wherein each R is independently hydrogen or an alkyl group having 1 to 10 carbon atoms, M is hydrogen or a monovalent metal or a nonmetal ion)

The monomer may be at least one selected from the group consisting of acrylic acid, methacrylic acid, monovalent metal salts of these acids, divalent metal salts, ammonium salts and organic amine salts. When acrylic acid or a salt thereof is used as the water-soluble acrylic unsaturated monomer, it is advantageous to obtain a highly water-absorbent resin having improved water absorption. Examples of the monomer include (meth) acrylamide, N-substituted (meth) acrylate, 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, methoxypolyethylene glycol (N, N) -dimethylaminoethyl (meth) acrylate, (N, N) -dimethylaminopropyl (meth) acrylamide and the like can be used.

The lactone monomer contained in the monomer composition may be a compound represented by the general formula (2). The monomer may be at least one selected from the group of methylene lactone (alpha-methylene-gamma-lactone) derivatives. Methylene-γ-butyrolactone, methylene-γ-valerolactone, methylene caprolactone (α-methylene-γ-butyrolactone) -methylene-y-caproolactone) and derivatives thereof, and the like.

Further, the compound represented by the general formula (1) may be used as a monomer after opening the lactone monomer. For example, sodium 4-hydroxy-2-methylenepropanoate sodium 4-hydroxy-2-methylenebutanoate, sodium 4- hydroxy-2-methylenepentanoate, sodium 4-hydroxy-2-methylenehexanoate, and the like.

The lactone monomer may be partially ring-opened with an alkyl group such as sodium hydroxide, potassium hydroxide, ammonium hydroxide, etc., and the ring-opened monomer may be 70 to 100 mol%. If the ring opening ratio is too low, the absorption capacity of the polymer is greatly decreased.

The acrylic acid-based monomer may have an acidic group and at least a part of the acidic group may be neutralized. Preferably, the monomer is partially neutralized with an alkylene material such as sodium hydroxide, potassium hydroxide, ammonium hydroxide or the like. At this time, the degree of neutralization of the acrylic acid monomer may be 40 to 95 mol%, preferably 40 to 80 mol%, and more preferably 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 not be smoothly proceeded. On the other hand, if the degree of neutralization is too low, the absorption capacity of the polymer is greatly lowered, have.

The concentration of the acrylic acid monomer in the monomer composition may be appropriately controlled in consideration of the polymerization time and the reaction conditions, preferably 20 to 95% by weight, more preferably 40 to 90% by weight have. Such a concentration range may be advantageous in controlling the grinding efficiency of the subsequent process polymer, while eliminating the need to remove unreacted monomers after polymerization using the gel phenomenon that occurs in the polymerization of high concentration aqueous solutions. However, if the concentration of the monomer is excessively low, the yield of the superabsorbent resin may be lowered. On the other hand, if the concentration of the monomer is excessively high, a part of the monomer may precipitate or the pulverization efficiency may be lowered during the pulverization of the polymer gel, and the physical properties of the superabsorbent resin may be deteriorated.

The monomer composition may include a polymerization initiator generally used in the production of a superabsorbent resin. As a non-limiting example, as the polymerization initiator, a thermal polymerization initiator or a photopolymerization initiator may be used depending on the polymerization method. However, even with the photopolymerization method, a certain amount of heat is generated by ultraviolet irradiation or the like, and a certain amount of heat is generated as the polymerization reaction, which is an exothermic reaction, proceeds, so that a thermal polymerization initiator may further be included.

Examples of the photopolymerization initiator include benzoin ether, dialkyl acetophenone, hydroxyl alkylketone, phenyl glyoxylate, benzyldimethyl ketal At least one compound selected from the group consisting of benzyl dimethyl ketal, acyl phosphine and alpha-aminoketone may be used.

As the thermal polymerization initiator, at least one compound selected from the group consisting of a persulfate-based initiator, an azo-based initiator, hydrogen peroxide, and ascorbic acid may be used. Specifically, examples of the persulfate-based initiator include sodium persulfate (Na2S2O8), potassium persulfate (K2S2O8), and ammonium persulfate (NH4) 2S2O8. Azo-based initiators include 2,2-azobis (2-amidinopropane) dihydrochloride, 2,2-azobis- (N, N-dimethylene isobutyramidine dihydrochloride, 2- (carbamoylazo) isobutylonitrile, 2,2-azobis- (N, N-dimethylene) isobutyramidine dihydrochloride, Azobis [2- (2-imidazolin-2-yl) propane] dihydrochloride), 4,2-diazabicyclo [ 4-azobis- (4-cyanovaleric acid), and the like.

Such a polymerization initiator may be added at a concentration of about 0.001 to 1% by weight based on the monomer composition. That is, if the concentration of the polymerization initiator is too low, the polymerization rate may be slowed and the remaining monomer may be extracted in the final product in a large amount, which is not preferable. On the contrary, when the concentration of the polymerization initiator is too high, the chain of the polymer forming the network is shortened, and the physical properties of the resin may be lowered, such that the content of the water-soluble component is increased and the pressure absorption capacity is lowered.

On the other hand, the monomer composition may contain a crosslinking agent for improving the physical properties of the hydrogel polymer. The cross-linking agent is used as a first cross-linking agent (internal cross-linking agent) for cross-linking the hydrous gel-like polymer to the inside, and is used separately from a second cross-linking agent (cross-linking agent) for cross- linking the surface of the hydrous gel-like polymer in a subsequent step.

The crosslinked polymer may be at least one selected from the group consisting of N, N'-methylenebisacrylamide, trimethylolpropane tri (meth) acrylate, ethylene glycol di (meth) acrylate, polyethylene glycol (meth) acrylate, propylene glycol di Butylene glycol di (meth) acrylate, diethylene glycol di (meth) acrylate, hexane diol di (meth) acrylate, triethylene glycol di (Meth) acrylates such as ethylene glycol di (meth) acrylate, tripropylene glycol di (meth) acrylate, tetraethylene glycol di (meth) acrylate, dipentaerythritol pentaacrylate, glycerin tri , Triarylamine, ethylene glycol diglycidyl ether, propylene glycol, glycerin, and ethylene And one or more cross-linking agents selected from the group consisting of carbonates

Such an internal cross-linking agent may be added at a concentration of about 0.001 to 1% by weight based on the monomer composition. That is, when the concentration of the internal cross-linking agent is too low, the absorption rate of the resin may be lowered and the gel strength may be weakened. On the contrary, when the concentration of the internal cross-linking agent is too high, the absorption power of the resin is lowered, which may be undesirable as an absorber.

In addition, the monomer composition may further contain additives such as a thickener, a plasticizer, a storage stabilizer, and an antioxidant, if necessary.

At this time, usable solvents may be used without limitation of the constitution as long as they can dissolve the above-mentioned raw materials. Examples of the solvent include water, ethanol, ethylene glycol, diethylene glycol, triethylene glycol, 1,4-butanediol, propylene 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 ether, toluene, xylene, butyrolactone, carbitol, methyl cellosolve acetate, N, N-dimethylacetamide, or a mixture thereof may be used

The formation of the hydrogel polymer through polymerization of the monomer composition can be carried out by a conventional polymerization method, and the process is not particularly limited. As a non-limiting example, the polymerization method is divided into thermal polymerization and photopolymerization depending on the type of polymerization energy source. In the case of conducting the thermal polymerization, the polymerization may proceed in a reactor having a stirring axis such as a kneader, It is possible to proceed in a reactor equipped with a movable conveyor belt.

Hydrogel  The step of pulverizing the polymer (step 2)

The hydrogel polymer obtained through the above-mentioned steps is subjected to a drying process for imparting water absorbency. Also, in order to increase the efficiency of drying, a step of pulverizing the hydrogel polymer may be performed before the drying process is performed.

As a non-limiting example, the pulverizers usable for the above coarse grinding include a vertical pulverizer, a turbo cutter, a turbo grinder, a rotary cutter mill, Examples thereof include a cutter mill, a disc mill, a shred crusher, a crusher, a chopper, and a disc cutter.

At this time, the pulverization can be performed so that the diameter of the hydrogel polymer is 2 mm to 10 mm. That is, in order to increase the drying efficiency, the hydrogel polymer is preferably pulverized into particles of 10 mm or less. However, since excessive aggregation may occur during the pulverization, the hydrogel polymer is preferably pulverized into particles of 2 mm or more.

Since the crude pulverization step is carried out at a high moisture content of the polymer, the polymer may stick to the surface of the pulverizer. In order to minimize such a phenomenon, steam, water, a surfactant, an anti-aggregation agent (for example, clay, silica, etc.) may be added to the coarse grinding step, if necessary. A cross-linking agent containing an acrylate of a bifunctional group or a polyfunctional group having three or more functional groups, a cross-linking agent containing a hydroxyl group, a cross-linking agent containing a hydroxyl group, a cross-linking agent containing a hydroxyl group, Etc. may be added.

Hydrogel  The step of drying the polymer (step 3)

The step of drying the coarse pulverized hydrogel polymer is carried out through the steps described above. As the hydrogel polymer is supplied to the drying step in a state of being pulverized into particles of 2 mm to 10 mm through the above-mentioned steps, drying can be performed with higher efficiency.

The drying of the coarse hydrogel polymer may be carried out at a temperature of 120 to 250 ° C, preferably 130 to 200 ° C. The drying temperature may be defined as the temperature of the heat medium supplied for drying or the temperature inside the drying reactor including the heat medium and the polymer in the drying process. If the drying temperature is low and the drying time is long, the process efficiency is lowered. To prevent this, the drying temperature is preferably 120 ° C or more. In addition, when the drying temperature is higher than necessary, the surface of the hydrogel polymer is excessively dried, so that the generation of fine powder may be increased in the subsequent grinding step and the physical properties of the final resin may be lowered. To prevent this, It is preferable that the temperature is 250 DEG 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.

The drying method of the drying step may be applied to the drying method of the hydrogel polymer as long as it can be used normally. Specifically, the drying step may be performed by hot air supply, infrared irradiation, microwave irradiation, ultraviolet irradiation, or the like.

The polymer dried in this way may exhibit a water content of about 0.1 to 10% by weight. That is, when the water content of the polymer is less than 0.1% by weight, an increase in the manufacturing cost due to excessive drying and degradation of the cross-linking polymer may occur, which is not advantageous. If the water content of the polymer exceeds 10% by weight, defects may occur in the subsequent step, which is not preferable.

Hydrogel  Crushing the polymer (step 4)

The pulverization step is a step for optimizing the surface area of the dried polymer, and may be carried out such that the particle diameter of the pulverized polymer is 150 to 850 mu m. The pulverizer usable for crushing with such a particle size may be a pin mill, a hammer mill, a screw mill, a roll mill, a disc mill, a jog mill jog mill) and the like.

Further, in order to manage the physical properties of the superabsorbent resin to be finally produced, the step of selectively classifying particles having a particle diameter of 150 to 850 mu m in the polymer powder obtained through the pulverization step may be further performed.

Step (5) of surface-crosslinking the pulverized polymer,

The surface cross-linking can be carried out by a method of increasing the cross-linking density of the surface of the resin particle by mixing the solution containing the cross-linking agent (surface cross-linking agent) with the ground polymer and performing a cross-linking reaction.

Here, the type of the cross-linking agent (surface cross-linking agent) contained in the surface cross-linking solution is not particularly limited. Non-limiting examples of the surface cross-linking agent include ethylene glycol diglycidyl ether, polyethylene glycol diglycidyl ether, glycerol polyglycidyl ether, propylene glycol diglycidyl ether, polypropylene glycol diglycidyl ether, ethylene The organic solvent may be selected from the group consisting of a carbonate, an ethylene glycol, a diethylene glycol, a propylene glycol, a triethylene glycol, a tetraethylene glycol, a propanediol, a dipropylene glycol, a polypropylene glycol, a glycerin, a polyglycerin, a butanediol, At least one compound selected from the group consisting of propane, pentaerythritol, sorbitol, calcium hydroxide, magnesium hydroxide, aluminum hydroxide, iron oxide, calcium chloride, magnesium chloride, aluminum chloride and iron chloride.

At this time, the content of the surface cross-linking agent may be appropriately adjusted according to the type of cross-linking agent, reaction conditions, etc., and preferably 0.001 to 5 parts by weight based on 100 parts by weight of the ground polymer. If the content of the surface cross-linking agent is too low, the surface cross-linking may not be properly introduced, and the physical properties of the final resin may be deteriorated. On the contrary, if the surface cross-linking agent is used in an excessive amount, the absorption force of the resin may be lowered due to excessive surface cross-linking reaction, which is not preferable.

On the other hand, in order to carry out the surface cross-linking reaction step, a method of mixing the surface cross-linking solution and the pulverized polymer into a reaction tank and mixing them, a method of spraying a surface cross-linking solution on the pulverized polymer, A method in which the surface cross-linking solution is continuously supplied and mixed, or the like can be used.

Further, water and alcohol may be added when the surface cross-linking solution is added. As such, the addition of water and alcohol together can induce a more even dispersion of the crosslinking agent, prevent the aggregation of the polymer powder, and further optimize the penetration depth of the surface crosslinking agent to the polymer powder. In view of these objects and effects, the content of water to be added can be adjusted to 0.5 to 10 parts by weight based on 100 parts by weight of the ground polymer.

The surface cross-linking reaction step may be carried out at a temperature of 100 to 250 ° C and continuously after the drying and crushing step which proceeds at relatively high temperatures. At this time. The surface cross-linking reaction may be conducted for 1 to 120 minutes, or for 1 to 100 minutes. That is, the surface cross-linking reaction may be carried out in order to prevent the polymer particles from being damaged due to excessive reaction while lowering the surface cross-linking reaction to a minimum.

Example  And Comparative Example

Example  One

40 g of acrylic acid, 10 g of methylene-gamma-butyrolactone, 50 g of distilled water and 20 g of sodium hydroxide were added to the reaction vessel, and the mixture was stirred and reacted for 30 minutes. The temperature increased due to the neutralizing heat was cooled to about 40 ° C, and then 0.1 parts of an internal crosslinking agent, trimethylolpropane triacrylate, 2 ', 2'-azobismethylpropionamidine dihydrochloride (2', 2 ' -azobis (2-methylpropionamidine) dihydrochloride) and 0.05 g of sodium peroxodisulfate were added. The mixture was stirred for 5 minutes and then subjected to a polymerization reaction at 80 mW / cm ² for 2 minutes using a UV lamp. The gel-state polymer after polymerization was cut through a chopper and then dried in a hot air oven at 180 ° C for 2 hours. Then, the dried and hardened polymer was pulverized through a grinding machine and classified into a size of 150 to 850 mu m to prepare a superabsorbent resin.

Then, 5 g of ethylene glycol diglycidyl ether and 85 g of water and 10 g of ethanol were used to prepare a surface cross-linking liquid, and 0.5 g of surface cross-linking liquid was sprayed on the prepared superabsorbent resin. After crosslinking the surface of the superabsorbent resin, it was reacted in an oven at 140 DEG C for 40 minutes and a superabsorbent resin having a surface size of 150 to 850 mu m was produced using a sheave.

Example  2

40 g of acrylic acid, 10 g of? -Methylene-? -Butyrolactone, 50 g of distilled water and 30 g of sodium hydroxide were added to the reaction vessel, and the mixture was stirred and reacted for 30 minutes. The reaction was carried out in the same manner as in Example 1, except that the pH was adjusted to 5 by using HCl after the reaction.

Example  3

10 g of methylenebutyrolactone (10 g), distilled water (50 g) and sodium hydroxide (20 g) were placed in a reaction vessel, and the mixture was stirred and reacted for 30 minutes. The reaction was carried out in the same manner as in Example 1, except that 40 g of acrylic acid was added and the reaction was further conducted.

Comparative Example  One

Except that 40 g of acrylic acid and 50 g of acrylic acid instead of 10 g of methylenebutyrolactone were used as a reaction vessel in the reaction vessel.

Experimental Example  : Property evaluation

(1) CRC (Centrifuge Retention Capacity)

According to EDANA method WSP 241.2, the insulating performances of the resins of the above Examples and Comparative Examples were measured. That is, the resin W (g) (about 0.2 g) obtained through the examples and the comparative examples was uniformly put in an envelope made of a nonwoven fabric, sealed, and impregnated with physiological saline (0.9 wt%) at room temperature. After about 30 minutes, water was drained from the envelope for 3 minutes under a condition of 250 G using a centrifuge, and the mass W2 (g) of the envelope was measured. Further, after the same operation was performed without using a resin, the mass W1 (g) at that time was measured. Using the obtained masses, CRC (g / g) was calculated according to the following equation.

 [Equation 1]

CRC (g / g) = {(W2 - W1) / W} - 1

(2) Absorption Under Pressure (AUP)

According to EDANA method WSP 242.3, the pressure absorption capacity of the resins of the above Examples and Comparative Examples was measured. That is, a 400 mesh wire mesh made of stainless steel was attached to the bottom of a plastic cylinder having an inner diameter of 60 mm. The piston capable of uniformly spreading the water absorbent resin W (g) (about 0.90 g) on the wire net and uniformly applying a load of 4.83 kPa (0.7 psi) on the wire net under the conditions of room temperature and humidity of 50% mm so that there is no gap between the inner wall of the cylinder and the up and down movement is not interrupted. At this time, the weight Wa (g) of the device was measured.

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

Then, the pressure absorption ability (g / g) was calculated from Wa and Wb according to the following equation.

 &Quot; (2) "

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

(3) Absorption rate (T (20): Time required to reach up to 20 g / g)

The absorption rate was measured according to the method disclosed in U.S. Patent Publication No. 2013-0079740, wherein 2 g of the superabsorbent resin prepared in the Examples and Comparative Examples were respectively used.

(4) water content

1 g of the superabsorbent resin prepared in the Examples and Comparative Examples was put in a 250 ml Erlenmeyer flask and swelled in 200 ml of 0.9% NaCl solution at 25 ° C and 500 rpm for 16 hours, . The eluted solution was passed through a filter paper, and 50 mL was taken. The content of water-soluble components was measured using a titrator (Mettler Toledo, Titrator T70).

CRC
(g / g) AUP
(g / g) Absorption rate
20 g / g (sec) Water component
(%) Example 1 31.9 22.3 153 7.7 Example 2 33.6 22.9 147 7.2 Example 3 33.1 23.1 149 7.5 Comparative Example 1 25.6 17.9 196 9.8

As shown in Table 1, it was confirmed that the absorption rates of Examples 1 to 3 polymerized by mixing acrylic acid and lactone were significantly improved as compared with Comparative Example 1 in which acrylic acid alone was polymerized using only acrylic acid. In addition, the water retention capacity and the pressure absorption capacity were remarkably improved, and the water-soluble fraction was decreased, and the polymer eluted upon contact with the liquid was remarkably decreased.

The preferred embodiments of the present invention have been described in detail above. It will be understood by those of ordinary skill in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention as defined by the appended claims.

Accordingly, the scope of the present invention is defined by the appended claims rather than the foregoing detailed description, and all changes or modifications derived from the meaning, range, and equivalence of the claims are included in the scope of the present invention Should be interpreted.

Claims (7)

A cross-linked polymer obtained by polymerizing and cross-linking a composition comprising an acrylic acid-based monomer having an acidic group and at least a part of which is neutralized and a monomer represented by the general formula (1) or (2), and a surface crosslinked layer formed on the surface of the cross- Highly absorbent resin.
[Chemical Formula 1]

(n is an integer of 1 to 10, and M is hydrogen or a monovalent metal or a nonmetal ion)
(2)

(n is an integer of 1 to 10) The method according to claim 1,
Wherein the superabsorbent resin has a retention capacity (CRC) of 25 g / g or more and a pressure absorption capacity (AUL) of 15 g / g or more. The method according to claim 1,
The crosslinked polymer may be at least one selected from the group consisting of N, N'-methylenebisacrylamide, trimethylolpropane tri (meth) acrylate, ethylene glycol di (meth) acrylate, polyethylene glycol (meth) acrylate, propylene glycol di Butylene glycol di (meth) acrylate, diethylene glycol di (meth) acrylate, hexane diol di (meth) acrylate, triethylene glycol di (Meth) acrylates such as ethylene glycol di (meth) acrylate, tripropylene glycol di (meth) acrylate, tetraethylene glycol di (meth) acrylate, dipentaerythritol pentaacrylate, glycerin tri , Triarylamine, ethylene glycol diglycidyl ether, propylene glycol, glycerin, and ethylene Wherein the cross-linking agent is cross-linked by at least one cross-linking agent selected from the group consisting of carbonate and carbonate. The method according to claim 1,
Wherein the surface cross-linked layer is selected from the group consisting of ethylene glycol diglycidyl ether, polyethylene glycol diglycidyl ether, glycerol polyglycidyl ether, propylene glycol diglycidyl ether, polypropylene glycol diglycidyl ether, ethylene glycol, diethylene Butylene glycol, propylene glycol, triethylene glycol, tetraethylene glycol, propanediol, dipropylene glycol, polypropylene glycol, glycerin, polyglycerin, butanediol, heptanediol, hexanediol trimethylolpropane, pentaerythritol, sorbitol ≪ / RTI > wherein the cross-linking agent is surface-crosslinked by at least one crosslinking agent selected from the group consisting of polyolefins. A process for producing a superabsorbent resin according to any one of claims 1 to 4, comprising the steps of:
(a) thermally polymerizing or photopolymerizing a monomer composition comprising an acrylic acid-based monomer having an acidic group and at least a part of the acidic groups neutralized and a monomer composition represented by the formula (1) or (2) and a polymerization initiator to form a hydrogel- ;
(b) pulverizing the hydrogel polymer;
(c) drying the pulverized polymer at 150 to 250 占 폚;
(d) pulverizing the dried polymer; And
(e) cross-linking the ground polymer. 6. The method of claim 5,
Wherein the step (d) comprises pulverizing the dried polymer to a particle diameter of 150 to 850 占 퐉. 6. The method of claim 5,
Wherein the surface cross-linking reaction is carried out at a temperature of 100 to 250 ° C.