WO2017099423A1 - Method for preparing super-absorbent resin - Google Patents

Abstract

The present invention relates to a method for preparing a super-absorbent resin. According to the preparation method of the present invention, the hydrophilicity of the super-absorbent resin is maintained and the crosslinking density thereof is appropriately controlled to lead uniform surface crosslinkage, thereby producing a super-absorbent resin having excellent physical properties. Therefore, an absorbent resin having an improved absorption rate without a deterioration in absorbency under pressure can be provided.

Description

 【Specification】

 [Name of invention]

 Manufacturing method of super absorbent polymer

 Technical Field

 Cross Citation with Related Application (s)

 This application claims the benefit of priority based on Korean Patent Application No. 10-2015-0175001 filed on December 9, 2015 and Korean Patent Application No. 10-2016-0162032 filed on November 30, 2016. All content disclosed in the literature is included as part of this specification.

 The present invention relates to a method for producing a super absorbent polymer. More specifically, the present invention relates to a method for producing a super absorbent polymer having improved water absorption characteristics without deterioration in water holding capacity and pressure absorbing capacity.

 [Technique to become background of invention]

 Super Absorbent Polymer (SAP) is a synthetic polymer material capable of absorbing water of 500 to 1,000 times its own weight.As a developer, super absorbent material (AMG) and absorbent gel (AGM) They are named differently. Such super absorbent polymers have been put into practical use as physiological devices, and are currently used in sanitary products such as paper diapers for children, horticultural soil repair agents, civil engineering, building index materials, seedling sheets, freshness retainers in food distribution, and It is widely used as a material for steaming.

 As a method for producing such a super absorbent polymer, a method by reverse phase suspension polymerization or a method by aqueous solution polymerization is known. Reverse phase suspension polymerization is disclosed in, for example, Japanese Patent Laid-Open Nos. 56-161408, 57-158209, and 57-198714. As the method of aqueous solution polymerization, a thermal polymerization method for breaking and perturbing the hydrogel polymer in a kneader having several shafts, and photopolymerization for simultaneously adding and drying a high concentration aqueous solution by irradiating ultraviolet rays or the like on a belt Method is known 등

On the other hand, the hydrous gel polymer obtained through the polymerization reaction as described above is generally pulverized through a drying process, and then the desired absorption capacity and pressure absorption capacity To selectively crosslink the surface of the polymer. In such surface crosslinking, it is necessary to control the penetration depth of the surface crosslinking agent. For this purpose, it is common to control the penetration depth of the surface crosslinking agent by using alcohol and water. However, when alcohol is used to control the penetration depth of the crosslinking agent, a large amount of alcohol is consumed, which is disadvantageous in terms of cost _{: an} additional drying treatment is required.

 Therefore, in order to solve the above method, conventionally, methods of minimizing the amount of alcohol or using no alcohol have been presented. However, when the amount of alcohol used is excessively lowered, water is excessively absorbed into the polymer and there is a problem that efficient crosslinking is difficult due to agglomeration of the gel.

 [Content of invention]

 Problem to be solved

 According to the present invention, the surface crosslinking reaction is performed by using a surface crosslinking agent that satisfies specific conditions, thereby maintaining the hydrophilicity of the superabsorbent polymer and appropriately adjusting the crosslinking density to further improve the physical properties of the final product. Without absorption rate. It is to provide a method for producing an improved superabsorbent polymer.

 [Solution of problem]

 According to an aspect of the present invention for solving the above problems, the step of thermally polymerizing or photopolymerizing the monomer composition comprising a water-soluble ethylenically unsaturated monomer and a polymerization initiator to form a hydrogel polymer; Drying the hydrogel polymer;

 Pulverizing the dried polymer; And

 It provides a method for producing a super absorbent polymer, comprising the step of performing a surface crosslinking reaction by mixing the ground polymer and a surface crosslinking agent comprising a compound represented by the following formula (1):

[Formula 1]

 In Chemical Formula 1,

 R is selected from the group consisting of hydroxy, carboxyl, amino, and halogen;

 n is an integer of 1-5.

 【Effects of the Invention】

 In the method for preparing a super absorbent polymer according to the present invention, by using a compound modified with a hydrophilic group as the surface crosslinker, the hydrophilicity of the surface of the superabsorbent polymer can be maintained while appropriately adjusting the surface penetration depth of the surface crosslinker. Through the superabsorbent polymer having excellent physical properties can be prepared.

 Accordingly, product properties can be further improved, and in particular, a superabsorbent polymer having an improved absorption rate can be provided without deteriorating the pressure absorption capacity. [Brief Description of Drawings]

1 is for the compound of formula 1 according to an embodiment of the present invention ^! H NMR graph.

 2 is a heteronuclear single quantum correlation spectroscopy (HSQC) graph of the compound of Formula 1 according to an embodiment of the present invention.

FIG. 3 is a ¹³ C NMR graph of the compound of Chemistry 1 in accordance with an embodiment of the present invention. FIG.

 [Specific contents to carry out invention]

The terminology used herein is for the purpose of describing particular example embodiments only and is not intended to be limiting of the invention. Singular expressions include plural expressions unless the context clearly indicates otherwise. As used herein, the terms "comprise", "comprise" or "have" are intended to indicate that there is a feature, step, component, or combination thereof, and one or more other features or steps. , Components, or a combination of these It should be understood that they do not preclude the presence or the possibility of adding them.

 As the invention allows for various changes and numerous modifications, particular embodiments will be illustrated and described in detail below. However, this is not intended to limit the present invention to a specific disclosed form, it should be understood to include all modifications, equivalents, and substitutes included in the spirit and scope of the present invention.

 Hereinafter, a method for preparing a super absorbent polymer according to specific embodiments of the present invention will be described in detail. The method for preparing a super absorbent polymer of the present invention comprises the steps of thermally polymerizing or photopolymerizing a monomer composition including a water-soluble ethylenically unsaturated monomer and a polymerization initiator to form a hydrogel polymer; Drying the hydrogel polymer; Pulverizing the dried polymer; And performing a surface crosslinking reaction by mixing the ground polymer with a surface crosslinking agent comprising a compound represented by the following Chemical Formula 1.

 In Chemical Formula 1,

 R is selected from the group consisting of hydroxy, carboxyl, amino, and halogen;

 n is an integer of 1-5.

For reference, in the specification of the present invention, "polymer" or "polymer" means that the water-soluble ethylenically unsaturated monomer is in a polymerized state, and may cover all water content ranges or particle size ranges. After polymerization of the polymer, it may refer to a water content (water content) is at least about 40 weight _^0/0 of the polymer to be dried before the gel state as a function polymer. In addition, "base resin" or "base resin powder" means that the polymer is dried and ground to form a powder.

 "Superabsorbent resin" also means the polymer or the base resin itself depending on the context, or further processes for the polymer or the base resin, for example surface crosslinking, fine powder reassembly, drying, grinding, classification, etc. It is used to cover everything that has been made suitable for commercialization through.

 In the manufacturing method of the present invention according to the embodiment described above, the step of forming a hydrogel polymer, the drying of the hydrogel polymer, and the step of pulverizing the dried polymer is in the art for preparing a super absorbent polymer It can be carried out by the steps and methods commonly used in the art.

 First, specifically, the monomer composition which is a raw material of the super absorbent polymer includes a water-soluble ethylenically unsaturated monomer and a polymerization initiator.

As the water-soluble ethylenically unsaturated monomer, any monomer commonly used in the preparation of a super absorbent polymer may be used without limitation in the constitution. In general, any one or more selected from the group consisting of anionic monomers and salts thereof, nonionic hydrophilic-containing monomers, amino group-containing unsaturated monomers and quaternized compounds thereof can be used. ^'

 Specifically, acrylic acid, methacrylic acid, maleic anhydride, fumaric acid, crotonic acid, itaconic acid, 2-acryloylethane sulfonic acid, 2-methacryloylethanesulfonic acid, 2- (meth) acryloylpropanesulfonic acid, or 2 Anionic monomers and salts of (meth) acrylamide-2-methyl propane sulfonic acid; (Meth) acrylamide, N-substituted (meth) acrylate, 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate,

Nonionic hydrophilic-containing monomers of methoxy polyethylene glycol (meth) acrylate or polyethylene glycol (meth) acrylate; And an amino group-containing unsaturated monomer of (N, N) -dimethylaminoethyl (meth) acrylate or (N, N) -dimethylaminopropyl (meth) acrylamide and a quaternized product thereof. Can be used.

More preferably acrylic acid or a salt thereof, for example acrylic acid or Alkali metal salts, such as the sodium salt, can be used, but by using such a monomer, it becomes possible to manufacture a super absorbent polymer having better physical properties. When the alkali metal salt of acrylic acid is used as a monomer, acrylic acid may be neutralized with a basic compound such as caustic soda (NaOH). In this case, the degree of neutralization of the water-soluble ethylene unsaturated monomers may be adjusted to about 50 to about 95% or about 70 to about 85%, and within this range, the superabsorbent polymer having excellent water-retaining ability without any fear of precipitation during neutralization Can provide.

The concentration of the water-soluble ethylenically unsaturated monomer, in which the subject from about 20 to about 60 weight _^0/0, preferably from about 40 to about 50% by weight based on the monomer composition containing a source material and a solvent of the water-absorbent resin, and In consideration of the polymerization time and reaction conditions, the concentration may be appropriate. However, when the concentration of the monomer is too low, the yield of the superabsorbent polymer may be low and there may be a problem in economics. On the contrary, when the concentration is too high, a part of the monomer may be precipitated or the grinding efficiency of the polymerized hydrogel polymer may be low. Etc. may cause problems in the process and may decrease the physical properties of the super absorbent polymer. The polymerization initiator used in the polymerization in the method for producing a super absorbent polymer of the present invention is not particularly limited as long as it is generally used for producing the super absorbent polymer.

 Specifically, the polymerization initiator may use a thermal polymerization initiator or a photopolymerization initiator according to UV irradiation depending on the polymerization method. However, even with the photopolymerization method, since a certain amount of heat is generated by irradiation such as ultraviolet irradiation and a certain amount of heat is generated in accordance with the progress of the polymerization reaction, which is an exothermic reaction, it may further include a thermal polymerization initiator.

 The photopolymerization initiator may be used without any limitation as long as it is a compound capable of forming radicals by light such as ultraviolet rays.

Specifically, at least one selected from the group consisting of persulfate initiators, azo initiators, hydrogen peroxide, and ascorbic acid may be used as the thermal polymerization initiator. Specifically, examples of persulfate-based initiators include sodium persulfate (Na ₂ S ₂ 0 ₈ ), potassium persulfate (K ₂ S ₂ 0 ₈ ), ammonium persulfate (NH ₄ ) ₂ S ₂ 0 ₈ ), Examples of azo-based initiators include 2, 2-azobis- (2-amidinopropane) dihydrochloride, 2, 2-azobis- (N, N - dimethylene) isobutoxy Thira Mai Dean dihydrochloride (2,2-azobis- (N, N- dimethylene) isobutyramidine dihydrochloride), 2- ( acrylonitrile carbamoyl azo) isobutyronitrile ^{(2 - (carbamoylazo) isobutylonitril)} , 2 , 2-azobis [2- (2-imidazolin-2-yl) propane] dihydrochloride (2,2-azobis [2- (2-imidazolin-2-yl) propane] dihydrochloride), ⁴ , ⁴ -azobis- ^{(4-cyano-ballet} rigs acid) and the like ^{(4, 4- azobis- (4-} cyanovaleric acid)). A wider variety of thermal initiators are well specified in the Odian book "Principle of Polymerization (Wiley, 1981)", p203, and are not limited to the examples described above.

 The thermal polymerization initiator may be included in a concentration of about 001 to about 0.5% by weight based on the monomer composition. When the concentration of the thermal polymerization initiator is too low, additional thermal polymerization hardly occurs, and the effect of the addition of the thermal polymerization initiator may be insignificant. When the concentration of the thermal polymerization initiator is too high, the molecular weight of the superabsorbent polymer may be low and the physical properties may be uneven. have.

 Examples of the photopolymerization initiator include benzoin ether, dialkyl acetophenone, hydroxyl alkylketone, phenyl glyoxylate, benzyl dimethyl ketal, and acyl. At least one selected from the group consisting of acyl phosphine and alpha -aminoketone may be used. Meanwhile, as an example of acylphosphine, commercially available lucirin TPO, that is, 2,4,6-trimethyl-benzoyl-trimethyl phosphine oxide can be used. . A wider variety of photoinitiators is well described in Reinhold Schwalm's book, "UV Coatings: Basics, Recent Developments and New Application (Elsevier 2007)", pi 15, but is not limited to the examples described above.

The photopolymerization initiator may be included in a concentration of about 0.005 to about 1.0 wt% based on the monomer composition. When the concentration of the photopolymerization initiator is too low, the polymerization rate may be slow, and the concentration of the photopolymerization initiator may be When too high, the molecular weight of the superabsorbent polymer may be small and the physical properties may be nonuniform.

 According to an embodiment of the present invention, the monomer composition may further include an internal crosslinking agent as a raw material of the super absorbent polymer. The internal crosslinking agent may include at least one functional group capable of reacting with the water-soluble substituent of the water-soluble ethylenically unsaturated monomer and at least one ethylenically unsaturated group; Alternatively, a crosslinking agent having two or more water-soluble substituents and / or functional groups capable of reacting with the water-soluble substituents formed by hydrolysis of the monomers may be used.

 Specific examples of the internal crosslinking agent include bisacrylamide having 8 to 12 carbon atoms, bismethacrylamide, poly (meth) acrylate of polyol having 2 to 10 carbon atoms, poly (meth) allyl ether of polyol having 2 to 10 carbon atoms, and the like. More specifically, Ν, Ν'- methylenebis (meth) acrylate, ethyleneoxy (meth) acrylate, polyethyleneoxy (meth) acrylate, propyleneoxy (meth) acrylate, glycerol diacrylate , Glycerin triacrylate, trimethy triacrylate, triallylamine, triarylcyanurate, triallyl isocyanate, polyethylene glycol, diethylene glycol and propylene glycol may be used. Such an internal crosslinking agent may be included in a concentration of about 0.001 to about 2.0 wt% based on the monomer composition to crosslink the polymerized polymer.

 In the production method of the present invention, the monomer composition of the super absorbent polymer may further include additives such as thickeners, plasticizers, preservative stabilizers, antioxidants and the like as necessary.

 Raw materials such as the above-mentioned water-soluble ethylenically unsaturated monomers, photopolymerization initiators, thermal polymerization initiators, internal crosslinking agents and additives may be prepared in the form of a monomer composition solution dissolved in a solvent.

The solvent that can be used at this time can be used without limitation of the composition as long as it can dissolve the above-described components, for example, 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, cyclonucleanone, ^' cyclopentanone, diethylene glycol monomethyl ether, diethylene Glycol ethyl ether, toluene, xylene, butyrolactone, carby, methyl cellosolve acetate, and one or more selected from N, N-dimethylacetamide and the like can be used in combination.

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

 On the other hand, the method of preparing a hydrogel polymer by thermally polymerizing or photopolymerizing 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 according to the polymerization energy source, when the thermal polymerization is usually carried out, it can be carried out in a semi-unggi with a stirring shaft such as kneader, when the photopolymerization, Although it can proceed in a semi-unggi equipped with a movable conveyor belt, the above-described polymerization method is an example, the present invention is not limited to the above-described polymerization method.

 For example, as described above, the hydrogel polymer obtained by thermal polymerization by supplying hot air or by heating the reaction machine may be a semi-unggi outlet, depending on the shape of the stirring shaft provided in the reaction machine. The hydrogel polymer discharged may be in the form of several centimeters to several millimeters. Specifically, the size of the water-containing gel polymer obtained may vary depending on the concentration and the injection speed of the monomer composition to be injected, the water-containing gel polymer having a particle size of 2 to 50 mm can be obtained.

In addition, when photopolymerization is performed in a reactor equipped with a movable conveyor belt as described above, the form of a generally obtained polymer may be a hydrous gel polymer on a sheet having a 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 usually preferable to supply the monomer composition so that a polymer on the sheet having a thickness of about 0.5 to about 15 cm can be obtained. When supplying the monomer composition to such an extent that the thickness of the polymer on the sheet is too thin, the production efficiency is low, which is not preferable, and when the thickness of the polymer on the sheet exceeds 15 cm Due to the excessively thick thickness, the polymerization reaction may not occur evenly over the entire thickness.

 On the other hand, the water content of the hydrogel or photopolymerized hydrogel polymer is

40 to 80% by weight. Throughout this specification, "water content" means the weight of the water-containing gel polymer subtracted from the weight of the dried polymer by the content of moisture to account for the total weight of the water-containing gel polymer. 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 and drying. At this time, the drying conditions were a total drying time in such a manner as to maintain at 180 ^° C after raising the temperature from room temperature to 180 ^° C by including 5 at a temperature ramping up step is set to 40 minutes to measure the water content.

 Next, the hydrous gel polymer obtained is dried. At this time, if necessary, in order to increase the efficiency of the drying step, the rough grinding step before drying may be further roughened.

 At this time, the pulverizer used is not limited in configuration, specifically, a vertical pulverizer, a turbo cutter, a turbo grinder, a rotary cutter mill, a cutting machine Includes any one selected from the group of grinding machines consisting of cutter mills, disc mills, shred crushers, crushers, choppers and disc cutters Although it is possible, it is not limited to the above-mentioned example. At this time, the grinding step may be pulverized so that the particle size of the hydrogel polymer is about 2 to about 10mm.

 Grinding to a particle diameter of less than 2 mm is not technically easy due to the high water content of the hydrogel polymer, and may also cause a phenomenon in which the crushed particles cross each other. On the other hand, when the particle size is pulverized more than 10mm, the effect of increasing the efficiency of the subsequent drying step is insignificant.

As described above, the hydrogel polymer after being pulverized or immediately after the polymerization is subjected to a drying step. Preferably, the drying temperature of the drying step may be 150 ^° C to 250 ^° C. Throughout this specification, "drying temperature" refers to the drying of the heating medium including the heating medium and the polymer at the temperature or drying process of the heating medium supplied for drying. It can be defined as the temperature of the reaction.

If the drying temperature is less than 150 ^° C., the drying time is too long and there is a fear that the physical properties of the superabsorbent polymer to be finally formed is lowered, if the drying silver exceeds 250 ^° C, only the polymer surface is too dry, Fine powder may occur in the grinding process, and there is a fear that the physical properties of the superabsorbent polymer to be finally formed decrease. Preferably the drying may be carried out ^at a temperature of 150 ^° C to 200 ^° C, more preferably at a temperature of 160 ^° C to 180 ^° C. On the other hand, in the case of the drying time is not limited to the configuration, in consideration of the process efficiency, etc., it may proceed for 20 to 90 minutes.

 In addition, if the drying method of the drying step is also commonly used as a drying step of the hydrogel polymer, it can be selected and used without limitation of the configuration. Specifically, the drying step may be performed by hot air supply, infrared irradiation, microwave irradiation, or ultraviolet irradiation. The water content of the polymer after the drying step may be 0.1 to 10% by weight.

 The dried polymer obtained through this drying step is subjected to a grinding step.

 The polymer powder obtained after the final milling step may have a weight average particle diameter of 150 to 850 / in. The grinder used to grind to such a weight average particle diameter is specifically a pin mill, a hammer mill, a screw mill, a roll mill, a disc mill. Or a jog mill (jog mill) and the like can be used, but the present invention is not limited to the above examples.

 In addition, in order to manage the physical properties of the super absorbent polymer powder to be finalized after such a grinding step, a separate process of classifying the polymer powder obtained after grinding according to the particle diameter may be performed. Preferably, the polymer having a particle size of about 150 to about 850 mm 3 is classified, and the surface crosslinking reaction step may be performed only for the polymer powder having such a particle size.

 Next, a surface crosslinking agent is added to the ground polymer to proceed with a surface crosslinking reaction.

Surface crosslinking is the step of increasing the crosslink density near the polymer particle surface with respect to the crosslink density inside the particles. Generally, the surface The crosslinking agent is applied to the surface of the polymer particles. Thus, this reaction occurs on the surface of the polymer particles, which improves the crosslinkability on the surface of the particles without substantially affecting the interior of the particles. The surface crosslinked polymer particles thus have a higher degree of crosslinking near the surface than inside.

 In the method for preparing a super absorbent polymer of the present invention, surface crosslinking reaction is performed using a surface crosslinking agent containing a compound represented by the following Chemical Formula 1.

 In Chemical Formula 1

 R is selected from the group consisting of hydroxy, carboxyl, amino, and halogen;

 n is an integer of 1-5.

 In the compound represented by Formula 1, preferably R may be a hydroxyl group.

In the method for producing a super absorbent polymer, conventionally used surface crosslinking agents include polyhydric alcohol compounds, epoxy compounds, amine compounds, polyvalent metal salts, and the like. However, in the case of the surface crosslinking agent conventionally used as described above, as the reaction time increases, the degree of penetration of the surface crosslinking agent is too deep and crosslinking tends to proceed to the inside of the polymer. The crosslinking reaction in the polymer also increases the crosslinking density to reduce the water-retaining capacity (CRC), and also decreases the hydrophilicity of the surface of the superabsorbent polymer, resulting in deterioration of physical properties of the final product. On the other hand, in order to prevent this, the surface crosslinking reaction time may be shortened or the reaction temperature may be lowered, but in this case, surface crosslinking may not occur sufficiently. In other words, it is difficult to control the penetration depth of the surface crosslinking agent. On the other hand, in the method of preparing a super absorbent polymer of the present invention, as shown in Formula 1, a compound of a specific formula modified with a hydrophilic group as a surface crosslinking agent This solved this problem. When the surface crosslinking reaction is performed by adding the compound of Formula 1 to the polymer, crosslinking reaction time does not increase even when the crosslinking reaction time increases, forming a crosslinking region only on the polymer surface, and at the same time, due to the hydrophilic modifier (R), The hydrophilicity of the resin surface can be maintained. Therefore, it is possible to obtain a superabsorbent polymer having an improved absorption rate while maintaining the water-retaining capacity and pressure-absorbing capacity of the base resin.

 The content of the compound represented by Formula 1 may be about 0.02 to about 0.5 parts by weight, preferably about 0.02 to about 0.3 parts by weight, and more preferably about 0.02 to about 0.2 parts by weight, based on 100 parts by weight of the polymer. .

 When the content of the compound represented by the formula (1) is too small, the surface crosslinking reaction hardly occurs, and if it contains too much, deterioration of absorption capacity and physical properties may occur due to the excessive surface crosslinking reaction.

 The compound represented by Chemical Formula 1 is not limited thereto, for example, epichlorohydrin and monoethylene glycol may be prepared according to a known organic synthesis method using starting materials, and NMR analysis. Its structure can be confirmed by applying such as a surface crosslinking agent.

 According to an embodiment of the present invention, in addition to the compound represented by Formula 1, it may further include a porous silica (silica) or clay (clay) as a surface crosslinking agent. Since silica or clay has porosity, the transmittance of the superabsorbent polymer may be improved by adding them as a surface crosslinking agent.

 There is no limitation in the structure about the method of adding the said surface crosslinking agent to a polymer. The surface crosslinking agent and the polymer powder may be mixed in a semi-permanent mixture, or a method of spraying the surface crosslinking agent on the polymer powder, a method of continuously supplying the polymer and the surface crosslinking agent to the mixer to be operated continuously, and the like may be used.

Upon addition of the surface crosslinker, water, low alcohol (methanol or Ethanol) or these can be mixed together and added. When the solvent is added, there is an advantage that the surface crosslinker can be evenly dispersed in the polymer. At this time, the content of the solvent is about 1 to about 10 parts by weight relative to 100 parts by weight of the polymer for the purpose of inducing even dispersion of the surface crosslinking agent and preventing aggregation of the polymer powder and optimizing the surface penetration depth of the crosslinking agent. Is preferably added.

The surface cross-linking agent is about 160 with respect to the polymer particles was added to about 220 ^° C, preferably from about 20 to about 120 minutes at a temperature of from about 180 to about 200 ^° _C: preferably heated for about 30 to 110 minutes by the surface cross-linking banung and drying can be done ^at the same time. If the crosslinking reaction temperature is less than 160 ^° C, surface crosslinking reaction may not occur, and if it exceeds 220 ^° C, foreign substances and odors may be generated due to carbonization, or property degradation and stable process operating conditions may be secured due to excessive reaction. Missing problems can occur. Also cause crosslinking banung If the time is over in less than 20 minutes is short, it can not be sufficient crosslinking banung, if the cross-linking banung time exceeds 120 minutes, due to excessive surface cross-linking banung, ^"Physical Properties of the damage of the polymer particle decreases Can be. The temperature raising means for surface crosslinking reaction is not specifically limited. It can be heated by supplying a heat medium or by directly supplying a heat source. In this case, as the type of heat medium that can be used, a heated fluid such as steam, hot air, or hot oil may be used, but the present invention is not limited thereto, and the temperature of the heat medium to be supplied is a means of heating medium, a temperature increase rate, and a temperature increase. It may be appropriately selected in consideration of the target temperature. On the other hand, as a heat source directly supplied, a heating method through electricity, a heating method through a gas, but the present invention is not limited to the above examples.

 The superabsorbent polymer obtained according to the production method of the present invention as described above has improved water retention, pressure absorption capacity and transmittance.

As described above, the super absorbent polymer prepared according to the preparation method of the present invention has a water retention capacity (CRC) of about 30 g / g to 40 g / g, preferably about 35 g / g, measured according to the EDANA method WSP 241.2. To about 40 g / g, with a pressurized absorption capacity (AUP) measured according to EDANA method WSP 242.2, from about 15 g / g to about 27 g / g, preferably about 20 g / g to about 26 g / g, more preferably about 24 g / g to about 26 g / g, it can exhibit excellent water retention and pressure absorption. In addition, the absorption rate measured by the Vortex test may be in the range of about 10 seconds to about 65 seconds, preferably about 30 seconds to about 65 seconds or less.

 Hereinafter, the operation and effects of the invention will be described in more detail with reference to specific embodiments of the invention. However, these embodiments are only presented as an example of the invention, whereby the scope of the invention is not determined.

<Example>

 Preparation Example 1 Preparation of Base Resin

In a 2L-glass glass reactor, surrounded by a jacket in which the heat medium pre-cornered at 25 ^° C is circulated, 20 g of 0.21% IRGACURE 819 initiator diluted in 500 g of acrylic acid and acrylic acid, 10% polyethylene glycol diacrylate (PEGDA, diluted in acrylic acid) 14 g of molecular weight 400) were mixed, and 870 g of a 24% caustic soda solution was slowly added dropwise.

After confirming that the temperature of the mixture rises above 80 ^° C due to the heat of neutralization when mixing the two solutions, wait for the temperature to rise to 40 ^° C, and when the reaction temperature reaches 40 ^° C, 50 g of sodium sulfate solution and 0.54 g of sodium bicarbonate were injected.

The solution was poured into a Vat-shaped tray (15 cm x 15 cm) mounted in a square polymerizer equipped with a light irradiation apparatus on the top and preheated to 80 ^° C. and irradiated with light. After about 25 seconds after the light irradiation, the gel is generated from the surface, and after 50 seconds, the polymerization reaction occurs at the same time as the foaming, and after further reaction until the total reaction time is 3 minutes, the polymerized sheet is taken out and 3x3 cm of After cutting to size, a crumb was prepared by chopping using a meat chopper.

The crumb was dried in an oven capable of transferring air volume up and down. The hot air at 185 ^° C was uniformly dried by flowing 20 minutes from the bottom to the top and 20 minutes from the top to the bottom. After drying, the water content of the dried body was less than 2%. After drying, the resultant was pulverized with a pulverizer and then classified to select a size of 150 to 850 μιη. The base resin was prepared. Preparation Example 2 Preparation of Compound of Formula 1

 Using epichlorohydrin and monoethylene glycol as starting materials and carrying out a reaction using NaOH as a catalyst, a compound of formula 1 (R = OH and a complex form of 0 = 1 to 5) was synthesized. It was.

An NMR (solvent: CDC1 ₃ ) analysis graph of the compound using Aglient 500 MHz NMR is shown in FIG. 1, and a heteronuclear single quantum correlation spectroscopy (HSQC) analysis graph is shown in FIG. 2, and a ¹³ C NMR analysis graph is shown in FIG. 3.

Based on the analysis results, it was confirmed that the CH ₂ OH group was present at 0.08 mol and the CHOH group was 0.52 mol with respect to 1 mol of the epoxy group, and the compound having the formula (I) (weight average molecular weight: about 500 g / mol). Example 1

Into 100 g of the base resin of Preparation Example 1, 3.5 g of water, 4.5 g of methanol, and Compound O.lg and Silica (trade name DM30S) O.Olg of Preparation Example 2 were mixed to perform a surface crosslinking reaction for 60 minutes at a temperature of 185 ^° C. It was.

 After the surface cross-linking reaction, it was classified into a standard network of ASTM standard from 150 / m to

A super absorbent polymer having a particle size of 850 / mi was obtained. Example 2

100 g of the base resin of Preparation Example 1 was mixed with 3.5 g of water, 4.5 g of methanol, and a compound of Formula 1 (R = OH and a form of a mixture of n = l to 5) O.lg for 60 minutes at a temperature of 185 ^° C. Surface crosslinking reaction was performed.

After the surface crosslinking reaction, a superabsorbent polymer having a particle size of 150 to 850 was obtained by classifying with a standard mesh of ASTM specification. Example 3 Into 100 g of the base resin of Preparation Example 1, 3.5 g of water, 4.5 g of methanol, 0.2 g of Compound of Preparation Example 2 and silica (trade name DM30S) O.Olg were mixed to perform a surface crosslinking reaction at a temperature of 185 ^° C. for 60 minutes. .

 After surface crosslinking reaction, a superabsorbent polymer having a particle size of 150 // m to 850 was obtained by classifying to a standard mesh of ASTM specification. Comparative Example 1

To 100 g of the base resin of Preparation Example 1, 3.5 g of water, 4.5 g of methane, PEG (Mw = 200) O.lg and silica (trade name DM30S) O.Olg were mixed and subjected to surface crosslinking reaction at a temperature of 185 ^° C for 60 minutes. Was performed.

 After the surface crosslinking reaction, a superabsorbent polymer having a particle size of 150 / m to 850 was obtained by classifying to a standard network of ASTM standard.

Experimental Example

 For the superabsorbent polymers of Examples and Comparative Examples, physical properties were measured by the following method, and the results are shown in Table 1.

1) Concentration Retention Capacity (CRC)

The superabsorbent polymers of the Examples and Comparative Examples were measured for centrifugal water retention (CRC) by unloaded absorption ratio according to EDANA method WSP 241.2. Specifically, the resin obtained in Examples and Comparative Examples was classified into 300 600 micrometer (/ ΛΠ) size and W (g) (about 0.2g) was uniformly placed in a non-woven bag and sealed. ， Impregnated in physiological saline of 0.9 mass ⁰ /. After 30 minutes, the bag was centrifuged and drained at 250 G for 3 minutes, and then the mass W2 (g) of the bag was measured. Moreover, after carrying out the same operation without using resin, the mass W1 (g) at that time was measured. Using each mass obtained, CRC (g / g) was computed according to the following formula.

 [Calculation 1]

 CRC (g / g) = {(W2 (g)-Wl (g) -W (g)}) / W (g)}

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

Wl (g) is a weight measuring device and then after a non-woven fabric bag not loaded the water absorbent resin during the impregnation of 0.9 parts by weight _^0/0 30 minutes in physiological saline at room temperature by using the centrifugal dehydration 3 minutes at 250G,

 W2 (g) is the weight of the device including the absorbent resin after 30 minutes of impregnation with the absorbent resin in a 0.9 wt% physiological saline solution in silver and then dehydrated at 250 G for 3 minutes using a centrifuge. .

2) Absorbency under Load (AUL)

 EDANA method WSP for superabsorbent polymers of Examples and Comparative Examples

Pressurized absorbent capacity (AUL) was measured according to 242.2.

 Specifically, the obtained resin is classified into 300-600 micrometer (m) size, W (g) (approximately 0.16g, A) is evenly sprayed on the AUL cylinder, 0.9psi weight is added and weighed (B) . The petri dish containing 0.9 mass% of saline was swelled and swollen for 60 minutes. After 60 minutes, taken out and weighed (C),

 Using each mass obtained, AUL (g / g) was computed according to the following formula.

 [Calculation 2]

 AUL (g / g) = (C-B) / A

 Where

 A is the weight of absorbent resin (g) ，

 B is the weight of AUL Kit assembly with absorbent resin,

 C is the weight of the AUL Kit assembly after swelling in 0.9 wt% physiological saline for 60 minutes at room temperature.

3) Vortex test

50.0 ± 1.0 mL of 0.9 wt% saline (NaCl) solution was added to a 100 mL beaker. A cylindrical stir bar (30 × 6 mm) was added and the brine solution was stirred on a stir plate at 600 rpm. 2.000 ± 0.010 g of superabsorbent polymer particles are added to the beaker as soon as possible, and the vortex of the liquid Measure the time until disappearance and smooth surface 매끄러운

 Table 1

As can be seen in Table 1, in the case of using the compound of Formula 1 as a surface crosslinking agent, it showed improved water holding capacity, pressure absorption capacity, and absorption rate compared to the comparative example using polyethylene glycol under the same reaction conditions.

Claims

[Patent Claims]

 [Claim 1]

 Thermally polymerizing or photopolymerizing the monomer composition including a water-soluble ethylenically unsaturated monomer and a polymerization initiator to form a hydrogel polymer; Drying the hydrogel polymer;

 Pulverizing the dried polymer; And

 Comprising the step of performing a surface crosslinking reaction by mixing the ground polymer and a surface crosslinking agent comprising a compound represented by the formula (1),

 Manufacturing method of super absorbent polymer:

 In Chemical Formula 1,

 R is selected from the group consisting of hydroxy, carboxyl, amino, and halogen;

 n is an integer of 1-5.

[Claim 2]

 The method of claim 11, wherein in Formula 1, R is a hydroxyl group.

[Claim 3]

 According to claim 1, wherein the compound represented by Formula 1 is the polymer

0.02 to 0.5 parts by weight based on 100 parts by weight, the method of producing a super absorbent polymer.

[Claim 4]

According to claim U, Porous silica (silica) or as the surface crosslinking agent A method for producing a super absorbent polymer, further comprising clay.

[Claim 5]

 The method of claim 1, wherein the water absorbency (CRC) of the super absorbent polymer is 30 g / g to 40 g / g, and the absorbency (AUP) is 15 g / g to 27 g / g. .

[Claim 6]

 The method for producing a super absorbent polymer according to claim U, wherein the water removal rate measured by the Vortex test of the superabsorbent polymer is 10 to 65 seconds.

[Claim 7]

The method of claim 1, wherein the surface crosslinking reaction is performed for 20 to 120 minutes at a temperature of 160 to 220 ^° C.