WO2017155173A1 - Method for preparing highly absorbent resin, and highly absorbent resin - Google Patents

Abstract

The present invention relates to a highly absorbent resin and a method for preparing same. More particularly, the present invention relates to a method for preparing a highly absorbent resin capable of producing reassembled fine particles that maintain excellent physical properties.

Description

 【Specification】

 [Name of invention]

 Method for producing superabsorbent polymer, and superabsorbent polymer

 Reciprocal Citation with Related Application (s)

 This application claims the benefit of priority based on Korean Patent Application No. 10-2016-0029840 dated March 11, 2016 and Korean Patent Application No. 10-2016-0101900 dated August 10, 2016. All content disclosed in the literature is included as part of this specification.

 The present invention relates to a super absorbent polymer and a method for preparing the same. More specifically, the present invention relates to a superabsorbent polymer and a method for preparing the finely divided powder assembly having improved granular strength and exhibiting excellent absorption properties.

[Technique to become background of invention]

 Super Absorbent Polymer (SAP) is from 500 to 500

It is a synthetic polymer material capable of absorbing water up to 1,000 times. It has been put into practical use as a sanitary appliance, and is currently used for gardening, soil repair, civil engineering, building index, and seedling. It is widely used as a material for sheets, freshness retainers in food distribution, and for steaming. The absorption mechanism of the superabsorbent polymer is an interaction between the penetration pressure due to the difference in electrical attraction force of the charge of the polymer electrolyte, the affinity between water and the polymer electrolyte, the expansion of the molecule due to the repulsive force between the polymer electrolyte ions, and the expansion inhibition due to crosslinking. Is ruled by That is, the absorbency of the absorbent polymer depends on the affinity and molecular expansion described above, and the rate of absorption depends largely on the penetration pressure of the absorbent polymer itself.

In order to improve the absorption rate of such superabsorbent polymers, many studies have been conducted. For example, Korean Patent Publication No. 2014-0063457 discloses a step of preparing a fine powder reassembly using only fine powder and base resin without additives. Although a method of preparing a superabsorbent polymer including the polymer is disclosed, there is a problem in that the physical properties of the finely divided reassembly are lower than that of the base resin and the process is complicated and the efficiency is lowered.

 In addition, the fine powder that is inevitably generated in the manufacturing process of the super absorbent polymer has a method of adding a fine powder during the polymerization in order to solve this as a factor of lowering the physical properties of the product, but this method induces non-uniform polymerization or by scattering light There is a problem that interferes with the physical properties. Therefore, a method of reassembling fine powder using a separate reassembler has been developed. This method is a method of mixing fine powder and water at a predetermined ratio to make large particles. The problem with this technique is that due to the small particle size of the fine powder, the absorption rate is increased and the water is unevenly mixed, resulting in non-uniformity of the entire reassembly, thereby producing a non-uniform size and strength reassembly, while incomplete drying of hard particles. Due to the damage to the device during the crushing and the weakly reassembled particles had a problem of reducing the performance of the reassembly because it is easily crushed and returned to the fine powder.

[Content of invention]

 Problem to be solved

 The present invention is to solve the problems of the prior art as described above, the superabsorbent polymer comprising a fine powder reassembly having excellent assembly strength but does not cause a drop in physical properties such as water retention capacity (CRC) or pressure absorption capacity (AUP) And to provide a method for producing the same.

[Measures of problem]

 The present invention to achieve the above object,

 Thermally polymerizing or photopolymerizing a monomer composition comprising a water-soluble ethylenically unsaturated monomer and a polymerization initiator to obtain a hydrogel polymer; Coarsely pulverizing the hydrogel polymer;

Drying and grinding the coarsely pulverized hydrogel polymer to classify it into fine powder having a particle size of less than 150 and normal particles having a particle size of 150 to 850; Preparing a fine powder aqueous solution by mixing the fine powder, water, and additives; And

 It provides a method for producing a super absorbent polymer comprising the step of mixing the fine powder aqueous solution and the coarsely pulverized hydrogel polymer to prepare a fine powder reassembly.

 In addition, the present invention,

Superabsorbent polymer comprising surface-crosslinked finely divided powder reassembled by mixing sodium hydroxide with respect to fine powder having an acidic group and polymerizing a water-soluble ethylenically unsaturated monomer in which at least part of the acidic group is neutralized and having a particle size of less than 150. to ^'

 The water holding capacity (CRC) measured according to the EDANA method WSP 241.3 is 33.0 to 39.0 g / g;

 0.7 psi Pressurized Absorption Capacity (AUP), measured according to EDANA method WSP 241.3, is from 20.0 to 25.0 g / g;

 A superabsorbent polymer having a water absorption rate of 100 seconds or less by Vortex is provided.

【Effects of the Invention】

 According to the superabsorbent polymer according to the present invention and a method for manufacturing the same, compared to the fine powder reassembly by the conventional fine powder reassembly process, the fine powder content is regrinded by using an additive during fine powder reassembly to improve the assembly strength. Can be reduced.

 In addition, by mixing and reassembling the fine powder with the hydrogel polymer, it is possible to obtain a fine powder reassembly having a water retention (CRC) or pressure-absorbing capacity (AUP) properties similar to the hydrogel polymer. Accordingly, even when the fine powder reassembly prepared according to the present invention is mixed with the superabsorbent polymer having a normal particle size and recycled, the physical properties of the entire resin are not lowered, thereby providing a high quality superabsorbent resin.

In addition, the reassembly process is carried out by mixing fine powder in the hydrous gel phase polymer, so the process step is relatively simple, so the efficiency is high, and the absorption rate is High reassembly can be obtained.

[Specific contents to carry out invention]

 The terminology used herein is for the purpose of describing exemplary 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, that includes one or more other features or steps, It is to be understood that the present invention does not exclude the possibility of adding or presenting elements, or a combination thereof.

 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 super absorbent polymer and a method for preparing the same according to specific embodiments of the present invention will be described in detail. Method for producing a super absorbent polymer according to an embodiment of the present invention, the step of thermally polymerizing or photopolymerizing a monomer composition comprising a water-soluble ethylenically unsaturated monomer and a polymerization initiator to obtain a hydrogel polymer; Coarsely pulverizing the hydrogel polymer; Drying and grinding the coarsely pulverized hydrogel polymer to classify it into fine powder having a particle size of less than 150 and normal particles having a particle size of 150 to 850; Preparing a fine powder aqueous solution by mixing the fine powder, water, and additives; And mixing the finely divided aqueous solution with the coarsely pulverized hydrogel polymer to produce a finely divided reassembly.

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, all particle size ranges, all surface crosslinking states, or processing states. Number have. Of the polymer, the water content (moisture content) of about 40 parts by weight ⁰ / I to the drying condition after the polymerization. May refer to one polymer functions as a gel-like polymer. In addition, among the said polymers, the polymer whose particle diameter is less than 150 can be called "fine powder". "Superabsorbent polymer" also means, according to the context, the polymer itself »or in a state suitable for commercialization by further processing such as surface crosslinking, fine powder reassembly, drying, grinding, classification, etc., for the polymer. It is used to encompass everything.

 In the method for preparing a super absorbent polymer of the present invention, first, a hydrogel or photopolymerization is performed on a monomer composition including a water-soluble ethylenically unsaturated monomer and a polymerization initiator to form a hydrogel polymer.

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

 The water-soluble ethylene-based unsaturated monomer can be used without any limitation any monomers commonly used in the production of superabsorbent polymer. Any one or more monomers selected from the group consisting of anionic monomers and salts thereof, nonionic hydrophilic-containing monomers and amino group-containing unsaturated monomers and quaternized compounds thereof can be used.

 Specifically, (meth) acrylic acid, maleic anhydride, fumaric acid, crotonic acid, itaconic acid, 2-acryloylethane sulfonic acid, 2-methacryloylethanesulfonic acid, 2- (meth) acryloylpropanesulfonic acid or 2- Anionic monomers of (meth) acrylamide-2-methyl propane sulfonic acid and salts thereof; (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 amino group-containing unsaturated monomers of (Ν, Ν) -dimethylaminoethyl (meth) acrylate or (Ν, Ν) -dimethylaminopropyl (meth) acrylamide and quaternized compounds thereof. Can be. More preferably, an alkali metal salt such as acrylic acid or a salt thereof, for example acrylic acid or a sodium salt thereof, may be used. It is possible to produce 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).

The concentration of the water-soluble ethylenically unsaturated monomers, said high from about 20 to about 60 weight _^0/0, preferably for a monomer composition containing a source material and a solvent of the water-absorbent resin is about 40 to about 50 weight _^0/0 It may be made to an appropriate concentration in consideration of the polymerization time and reaction conditions. 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, some 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.

Examples of the photopolymerization initiator include benzoin ether, dialkyl acetophenone, hydroxyl alkylketone, phenyl glyoxylate, and benzyl dimethyl ketal. ketal), 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. . For more photoinitiators, see Rein old Schwalm, "UV Coatings: Basics, Recent Developments and New." Application (Elsevier 2007) "pi 15, and is not limited to the above example.

 The photopolymerization initiator may be included in a concentration of about 0.01 to about 1.0 wt% based on the monomer composition. If the concentration of the photopolymerization initiator is too low, the polymerization rate may be slow. If the concentration of the photopolymerization initiator is too high, the molecular weight of the superabsorbent polymer may be low and the physical properties may be uneven.

In addition, the thermal polymerization initiator may be used at least one selected from the group consisting of persulfate initiator, azo initiator, hydrogen peroxide and ascorbic acid. Specifically, examples of persulfate-based initiators include sodium persulfate (Na ₂ S ₂ O _s ), potassium persulfate (K ₂ S ₂ 0 ₈ ), and ammonium persulfate (NH ₄ ). ₂ S ₂ 0 ₈ ), and examples of the azo (Azo) initiator include 2, 2-azobis- (2-amidinopropane) dihydrochloride (2, 2- azobis (2-amidinopropane) dihydrochloride), 2 2,2-azobis- (N, N-dimethylene) isobutyramidine dihydrochloride), 2-azobis- (N, N-dimethylene) isobutyramidine dihydrochloride

(Carbamoyl azo) isobutyronitrile ( ^2- (carbamoylazo) isobutylonitril), 2, 2- azobis [2- (2-imidazoline-2-yl) propane] dihydrochloride (2,2-azobis [ 2- (2-imidazolin-2-yl) propane] dihydrochloride), 4,4-azobis- (4-cyanovaleric acid) (4,4- azobis- (4-cyanovaleric acid)), and the like. More various thermal polymerization initiators are well specified in Odian's Principle of Polymerization (Wiley, 1981), p ² 03, and are not limited to the examples described above.

 The thermal polymerization initiator may be included in a concentration of about 0.001 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.

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. Inside the above Examples of the crosslinking agent include at least one functional group capable of reacting with the water-soluble substituent of the water-soluble ethylenically unsaturated monomer and having at least one ethylenically unsaturated group; Or the crosslinking agent which has 2 or more functional groups which can react with the water-soluble substituent of the said monomer, and / or the water-soluble substituent formed by hydrolysis of the monomer can be used.

Specific examples of the internal crosslinking agent include bisacrylamide having 8 to 12 carbon atoms, bismethacrylamide, poly (meth) acrylates having 2 to 10 carbon atoms, or poly (meth) allyl ether having a polyol having 2 to 10 carbon atoms. These etc. are mentioned, More specifically, Ν, Ν'- methylenebis (meth) acrylate, ethyleneoxy (meth) acrylate, polyethyleneoxy (meth) acrylate, propyleneoxy (meth) acrylate, glycerin diacryl One or more selected from the group consisting of acrylate, glycerin triacrylate, trimethol triacrylate, triallylamine, triarylcyanurate, triallyl isocyanate, polyethylene glycol, diethylene glycol and propylene glycol can be used. Such an internal crosslinking agent may be included at a concentration of about 0.01 to about 0.5 weight ⁰ / ^{° 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, storage 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 in 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 Butyllactone, carby, methyl cellosolve acetate, and one or more selected from Ν, Ν-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, if the method of forming a hydrogel polymer by thermally polymerizing or photopolymerizing such a monomer composition is also the polymerization method normally used, there will be no restriction | limiting in particular in a structure.

 Specifically, the polymerization method is largely divided into thermal polymerization and photopolymerization according to the polymerization energy source, and when the thermal polymerization is usually carried out, the polymerization method may be performed in a reactor having a stirring shaft such as a kneader. Although it can be carried out in a semi-unggi equipped with a 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 have a half-stirrer such as a kneader having a stirring shaft. The hydrogel polymer discharged to the mandrel outlet 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 weight average particle diameter of 2 to 50 mm can be obtained.

 In addition, when photopolymerization is carried out in a semi-unggi equipped with a movable conveyor belt as described above, the form of the hydrogel polymer generally obtained may be a hydrogel 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 speed 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 5 cm can be obtained. In the case of supplying the monomer composition to such an extent that the thickness of the polymer on the sheet is too thin, it is not preferable because the production efficiency is low, and when the polymer thickness on the sheet exceeds 5 cm, the polymerization reaction does not occur evenly over the entire thickness. You may not.

In this case, the normal water content of the hydrogel polymer obtained by the above method is About 40 to about 80 weight percent. On the other hand, "water content" throughout the present specification is the amount of water to account for the total weight of the hydrous gel phase polymer dried at the weight of the hydrogel polymer. It means the value obtained by subtracting the weight of the polymer in the state. Specifically, it is defined as a value calculated by measuring the weight loss due to moisture evaporation in the polymer in the process of drying the temperature of the polymer through infrared heating. At this time, the drying conditions are raised to a temperature of about 180 ^° C at room temperature and then maintained at 180 ^° C. The total drying time is set to 20 minutes, including 5 minutes of temperature rise step, the moisture content is measured.

 Next, the hydrogel polymer is coarsely ground.

 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 coarse grinding step may be pulverized so that the particle size of the hydrogel polymer is about 2 to about 20mm.

 Coarse pulverization of less than 2 mm in particle size is not technically easy due to the high water content of the hydrogel polymer, and may also cause agglomeration of pulverized particles with each other. On the other hand, in the case of coarsely pulverizing more than 20mm, the effect of increasing the efficiency of the subsequent drying step may be insignificant.

 Next, the hydrous gel polymer obtained is dried.

As described above, drying is performed on the hydrous gel polymer immediately after polymerization, which is coarsely pulverized or not subjected to the coarsely pulverized step. At this time, the drying temperature of the drying step may be about 150 to about 250 ^° C. If the drying temperature is less than 150 ^° C., the drying time is too long and there is a risk that the physical properties of the superabsorbent polymer to be formed is lowered, if the drying temperature exceeds 250 ^° C, only the polymer surface is dried too much, 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, therefore, the drying is at a temperature of about 150 to about 200 ° C., Preferably at a temperature of about 160 to about 180 ^° C.

 On the other hand, in the case of drying time, in consideration of the process efficiency, etc., it may proceed for about 20 to about 90 minutes, but is not limited thereto.

 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 a method such as hot air supply, infrared irradiation, microwave irradiation, or ultraviolet irradiation. The water content of the polymer after such a drying step may be about 0.1 to about 10% by weight.

 Next, the dried polymer obtained through this drying step is pulverized.

 The polymer powder obtained after the grinding step may have a particle diameter of about 150 to about 850! M. Mills used to grind to such particle diameters are specifically pin mills, hammer mills, screw mills, mills, disc mills or jogs. Although a jog mill or the like may be used, the present invention is not limited to the above-described example.

 In order to manage the physical properties of the super absorbent polymer powder to be finalized after such a grinding step, the polymer powder obtained after grinding is generally classified according to the particle size. Preferably, the particles are classified into particles having a particle size of less than about 150, particles of about 150 to about 850, and particles having a particle size of more than 850 mm 3. In the context of the present invention, finely divided particles having a particle size of less than a certain particle size, that is, less than about 150 / m, are referred to as superabsorbent polymer fine powder, SAP fine powder or fine powder (fines, fine powder), having a particle diameter of about 150 to about 850 Particles that are / m are called normal particles. The fine powder may be generated during a polymerization process, a drying process, or a pulverization step of a dried polymer. When the fine product is included in the final product, the fine powder is difficult to handle and exhibits a gel blocking phenomenon. It is desirable to exclude them from inclusion or to reuse them to be normal particles.

As an example, the fine powder may be subjected to a reassembly process in which the fine particles are formed to have a normal particle size. In the reassembly process, generally, a reassembly process is performed in which the fine particles are coarse in a wet state in order to increase the coarse strength. At this time The higher the moisture content of the fine powder, the higher the coarse strength of the fine powder. However, the reassembly process may cause too large reassembly lumps, which may cause problems during the operation of the process. It is often broken into fine powder again. In addition, the fine powder reassembly thus obtained has lower physical properties such as water-retaining capacity (CRC) and pressure-absorbing capacity (AUP) than normal particles, resulting in deterioration of the quality of the super absorbent polymer.

 Thus, according to the production method of the present invention, a fine powder reassembly is prepared by mixing a finely divided hydrogel polymer having a particle size of less than 150 to prepare a fine powder reassembly.

 More specifically, the fine powder, water, and additives are mixed to prepare a fine powder aqueous solution, and thus the fine powder aqueous solution and the coarsely pulverized hydrogel polymer are mixed to prepare a fine powder reassembly.

 At this time, the additives included in the fine powder solution include sodium hydroxide, a crosslinking agent, and a thermal polymerization initiator.

The sodium hydroxide (NaOH) may be included as about 1 to about 10 parts by weight _^0/0, preferably about 2 to about 8 parts by weight _^0/0, preferably about 2 to about 6% by weight relative to the differential solution and the differential member assembly May contribute to the improvement of water retention (CRC).

 The crosslinking agent forms a crosslinked structure between the fine particles and serves to improve granulation strength. Crosslinking agents that can be used include polyethylene glycol diacrylate (PEGDA), nucleic acid-1,6-di diacrylate (hexane-l, 6-diol diacrylate, HDD A), and ethoxylated trimethyl propane. Acrylate (ethoxylated trimethylolpropane triacrylate, ETTA), or ethylene carbonate (EC), and the like, and preferably polyethylene glycol diacrylate.

 The crosslinking agent may be included in an amount of about 1 to about 0.5 parts by weight, preferably about 0.2 to about 0.4 parts by weight, based on 100 parts by weight of the fine powder. When the crosslinking agent is included in the above weight part range, it may exhibit high assembly strength and physical properties.

The thermal polymerization initiator is assembled by inducing further polymerization of the fine powder It serves to improve strength. Examples of thermal polymerization initiators that can be used include sodium persulfate, potassium persulfate, and the like, and preferably sodium persulfate.

 The thermal polymerization initiator may include about 0.1 to about 0.5 parts by weight, preferably about 0.1 to about 0.3 parts by weight, based on 100 parts by weight of the fine powder. When the thermal polymerization initiator is included in the above weight part range, high assembly strength and physical properties may be exhibited.

 The fine powder aqueous solution includes water so that the fine powder can be reassembled in a wet state, wherein the amount of water included is about 100 to about 300 parts by weight, preferably about 100 to about 200 parts by weight based on 100 parts by weight of the fine powder. Can be added.

 According to an embodiment of the present invention, the fine powder aqueous solution may further include porous particles.

The porous particles may be silica particles having a BET specific surface area of about 300 to about 1500 m ² / g and a porosity of about 50% or more, for example, about 50 to about 98%. have. In addition, the porous particles may have a superhydrophobicity with a contact angle with respect to water of 125 ° or more, preferably 140 ° or more, more preferably 145 ° or more.

 The fine powder aqueous solution may further include a porous particle as described above, thereby further performing fine powder reassembly, thereby further improving permeability and pore strength of the fine powder reassembled product.

 The porous particles may include about 0.01 to about 0.4 parts by weight, preferably about 0.05 to about 2 parts by weight, based on 100 parts by weight of the fine powder. When the porous particles are included in the weight part range, it may exhibit high assembly strength and improved permeability.

 The above-mentioned additives and optionally porous particles are added to the fine powder to prepare a fine powder aqueous solution.

According to one embodiment of the present invention, after mixing the water and the additive to prepare an aqueous solution of the additive, and after heating the aqueous solution of the additive to a temperature of about 40 to about 80 ° C, preferably about 60 to about 80 ^° C, The heated additive A fine powder aqueous solution can be manufactured by mixing fine powder with aqueous solution. By mixing the fine powder in the heated additive aqueous solution as described above it can exhibit a more improved foam strength.

 Next, a fine powder reassembly is prepared by mixing the prepared fine powder aqueous solution and the coarsely pulverized hydrogel polymer.

The coarsely pulverized hydrogel polymer means that the hydrous gel polymer obtained by thermal polymerization or photopolymerization of the monomer composition described above is first ground in a form of lumps having a large particle size before drying. At this time, the particle size of the milled crude function polymer gel is from about 2 to may be about 20mm, before drying because the water content is from about 40 to about 80 weight _^0/0 of the hydrogel state.

 According to the present invention, a finely divided aqueous solution is mixed with the coarsely pulverized hydrogel polymer to form a fine powder reassembly, and thus the finely divided reassembly is maintained at a similar level with the high physical strength of the original hydrogel polymer. High quality fine powder reassembly can be obtained.

According to an embodiment of the present invention, the coarsely pulverized hydrogel polymer may be mixed in an amount of about 50 to about 500 parts by weight, preferably about ₅₀ to about ₃₀₀ parts by weight, based on 100 parts by weight of fine powder contained in the fine powder solution. have. When the coarsely pulverized hydrogel polymer is included in the weight range, it may exhibit high assembly strength and improved physical properties.

 The method for adding the finely divided aqueous solution to the coarsely pulverized hydrogel polymer is not limited in its configuration. For example, the finely divided aqueous solution and the coarsely pulverized hydrous gel polymer are mixed in a semi-aperture, or the finely divided aqueous solution and the coarsely pulverized hydrous gel polymer are mixed in a semi-permanent mixture such as a mixer. The method of supplying continuously and mixing etc. can be used.

 According to one embodiment of the present invention, the obtained fine powder reassembly may further comprise the step of drying, grinding and classifying.

Drying the fine powder reassembly may be performed for 20 to 90 minutes at a temperature of 150 to 250 ^° C. In addition, as a temperature raising means for drying in the above, there is no limitation in the structure. Specifically, supply the heat medium or electricity Although it can heat directly by means, etc., this invention is not limited to the above-mentioned example. Specific heat sources that may be used include steam, electricity, ultraviolet rays, infrared rays, and the like, and a heated thermal fluid may be used.

 Next, the dried fine powder reassembly may be ground to have a particle size of about 150 to about 850. Mills used to grind to such particle diameters are specifically pin mills, hammer mills, screw mills, mills, disc mills or jogs. Although a jog mill or the like may be used, the present invention is not limited to the above-described example.

 The fine powder reassembly obtained according to the production method of the present invention has a high foaming strength with a low ratio of re-crushing into fine powder after the reassembly and drying and grinding step as described above.

 The reassembled polymer obtained according to the preparation method of the present invention has a weight ratio of fine powder having a particle size of 150 m or less after grinding, for example, less than about 15% by weight of the total fine powder reassembly, preferably about 10 Less than%, more preferably less than about 7%.

 In addition, the finely divided reassembly obtained after grinding may be classified into particles having a particle size of less than about 150, particles of about 150 to about 850 Λπ, and particles having a particle size of more than 850 depending on the particle size.

 The classified fine powder reassembly may be performed alone or in combination with other normal particles to perform a surface crosslinking process.

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

 In this case, the surface crosslinking agent is not limited as long as it is a compound capable of reacting with the functional group of the polymer.

Preferably in order to improve the properties of the resulting super absorbent polymer, Polyhydric alcohol compounds as the surface crosslinking agent; Epoxy compounds; Polyamine compounds; Haloepoxy compound; Condensation products of haloepoxy compounds; Oxazoline compounds; Mono-, di- or polyoxazolidinone compounds; Cyclic urea compounds; Polyvalent metal salts; And it may be used one or more selected from the group consisting of alkylene carbonate compounds.

 Specifically, examples of the polyhydric alcohol compound include mono-, di-, tri-, tetra- or polyethylene glycol, monopropylene glycol, 1,3-propanediol, dipropylene glycol, 2,3,4-trimethyl-1,3 -Pentanediol, polypropylene glycol, glycerol, polyglycerol, 2-butene-1,4-diol, 1,4-butanediol, 1,3-butanediol, 1,5-pentanediol, 1,6- nucleic acid diol And 1, 1 or more selected from the group consisting of 1,2-cyclonucleodimethane can be used.

 In addition, ethylene glycol diglycidyl ether and glycidol may be used as the epoxy compound, and as polyamine compounds, ethylene diamine, diethylene triamine, triethylene tetraamine, tetraethylenepentamine, pentaethylene nucleoamine , At least one selected from the group consisting of polyethyleneimine and polyamide polyamine can be used.

As the haloepoxy compound, epichlorohydrin, epibromohydrin and _α -methyl epichlorohydrin can be used. In addition, as a mono-, di-, or a polyoxazolidinone compound, 2-oxazolidinone etc. can be used, for example.

 And as an alkylene carbonate compound, ethylene carbonate etc. can be used. These may be used alone or in combination with each other. On the other hand, in order to improve the efficiency of a surface crosslinking process, it is preferable to use at least 1 type of polyhydric alcohol among these surface crosslinking agents, and more preferably, C2-C10 polyhydric alcohol compounds can be used.

The amount of the surface crosslinking agent to be added may be appropriately selected depending on the kind of the surface crosslinking agent to be added or the reaction conditions, but it is usually from about αοοι to about 5 parts by weight, preferably about 0.01 to about 1 part by weight of the polymer loo. 3 parts by weight, more preferably from about 0.05 to about 2 parts by weight can be used have.

 When the content of the surface crosslinking agent is too small, the surface crosslinking reaction hardly occurs, and when 100 parts by weight of the polymer is more than 5 parts by weight, the excessive absorption of the surface crosslinking reaction may result in deterioration of absorbing ability and physical properties. .

 The surface crosslinking reaction and drying can occur simultaneously by heating the polymer particles to which the surface crosslinking agent is added.

 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, and 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, the heat source directly supplied may be 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 prepared by the above-described method is prepared by mixing sodium hydroxide with respect to fine powder having a particle size of less than 150 in a polymer including an acidic group and polymerizing a water-soluble ethylenically unsaturated monomer in which at least a part of the acidic group is neutralized. A superabsorbent polymer having surface-crosslinked finely divided reassembly, the water-retaining capacity (CRC) measured according to EDANA method WSP 241.3 is 33.0 to 39.0 g / g; EDANA Law WSP

0.7 psi Pressurized Absorption Capacity (AUP), measured according to 241.3, is between 20.0 and 25.0 g / g; The absorption rate by the vortex method is 100 seconds or less. In one embodiment of the superabsorbent polymer, the polymer comprises an acidic group and polymerized a water-soluble ethylene-based unsaturated monomer in which at least a portion of the acidic group is neutralized. The same as exemplarily described in the method for preparing a gel polymer.

In addition, in the super absorbent polymer of one embodiment of the present invention, the fine powder refers to particles having a particle diameter of less than 150 / zm in the polymer, regardless of the step or surface crosslinking occurs the fine powder, all of the superabsorbent resin The process, for example, a polymerization process, a drying process, the pulverization process of the dried polymer, the surface crosslinking process, etc. can include all.

 The fine powder reassembly may be reassembled by mixing sodium hydroxide with respect to fine powder, or may be reassembled by adding more crosslinking agent, thermal polymerization initiation, or porous particles in addition to sodium hydroxide. More detailed description of the crosslinking agent, thermal polymerization initiation, or porous particles is as described above in the method for preparing a super absorbent polymer.

 The sodium hydroxide may be included in an amount of about 0.1 to about 20 parts by weight, or about 1 to about 15 parts by weight, or about 1 to 10 parts by weight, based on 100 parts by weight of the fine powder. When the sodium hydroxide is included in the weight range, it may contribute to high assembly strength, improved permeability and water retention.

 In addition, the fine powder may be reassembled by mixing the coarsely pulverized hydrogel polymer. More detailed description of the mixing with the coarsely pulverized hydrogel polymer is as described above in the preparation method of the super absorbent polymer.

 The superabsorbent polymer surface-crosslinked with the reassembled finely divided granules has a water retention (CRC) of about 33.0 to about 39.0 g / g, or about 34.0 to about 38.0 g / g, measured according to EDANA WSP 241.3. Can be. In addition, the 0.7 psi pressurized absorbent capacity (AUP) measured according to the EDANA method WSP 241.3 may be from about 20.0 to about 25.0 g / g, or from about 21.0 to about 25.0 g / g.

 In addition, the superabsorbent polymer may have an absorption rate of about 100 seconds or less, or about 95 seconds or less based on a vortex method. In the vortex method, 50 ml saline was added to a 100 ml beaker with a magnetic stir bar, the stirring speed of the magnetic stir bar was set at 600 rpm using a stirrer, and 2.0 g of superabsorbent polymer was added to the stirred saline. At the same time, measure the time and measure the time (in seconds) until the vortex disappears from the beaker as the vortex time. The lower limit of the absorption rate is not particularly limited but may be about 20 seconds or more, or about 30 seconds or more.

Hereinafter, the present invention will be described in more detail with reference to Examples. However, the following examples are merely to illustrate the invention, but the content of the present invention is not limited by the following examples. Further, in the following examples and comparative examples "%" And "part" which represent content are mass references | standards unless there is particular notice. <Example>

 Preparation of Super Absorbent Resin Particles

 Preparation Example 1

 100 g of acrylic acid, 0.3 g of polyethylene glycol diacrylate as crosslinking agent, 0.033 g of diphenyl (2,4,6-trimethylbenzoyl) -phosphine oxide as initiator, 38.9 g of caustic soda (NaOH), and 103.9 g of water To prepare a monomer mixture having a monomer concentration of 50% by weight.

Thereafter, the monomer mixture was placed on a continuously moving conveyor belt, and irradiated with ultraviolet light (irradiation amount: 2 mW / cm ² ) to undergo UV polymerization for 2 minutes to obtain a hydrous gel polymer.

The hydrogel polymer was pulverized with a meat chopper (hole size 8 mm) to obtain a coarsely pulverized hydrogel polymer. It was dried for 2 hours in a hot air dryer at 170 ^° C, crushed by a pin mill grinder and classified into a standard mesh of ASTM standard.

Normal particles having a particle size of 150 ai to 850 and fine particles having a particle size of less than 150 / mi were obtained. Preparation Example of Fine Powder Reassembly

 Example 1

 An additive aqueous solution comprising 1,500 ppm of sodium persulfate (SPS), 3,000 ppm of polyethylene glycol diacrylate (PEGDA), 1,000 ppm of silica aerogel (Silica Aerogel, AeroZelTM, JIOS) and 3% by weight of sodium hydroxide was prepared. The additive aqueous solution was heated to 8 (rc.

 750 g of the heated additive aqueous solution and 500 g of fine powder having a particle size of less than 150 obtained in Preparation Example 1 were mixed for 1 minute using a planetary mixer. 500 g of the coarsely pulverized hydrogel polymer obtained in Preparation Example 1 was added to the mixture and further mixed for 1 minute to prepare a fine powder reassembled product.

The reassembled thus was ground through a meat chopper. After drying for 30 minutes in a hot air dryer at a temperature of 180 ^° C, the rotary mixer The particles were regrind and classified into a standard mesh of ASTM standard, and classified into particles having a particle size of less than 150 zm and particles having a particle size of 150 Pa or more and 850 or less. 100 g of particles having a particle size of 150 or more and less than 850 were mixed with a surface crosslinking solution containing 0.2 g of poly (ethylene glycol) diglycidyl ether, 3 g of methanol, 5 g of water, and silica aerogel (AeroZelTM, JIOS) O.Olg. The surface crosslinking reaction was performed for 50 minutes at a temperature of 180 ^° C to obtain a final superabsorbent resin. Example 2

 A super absorbent polymer was prepared in the same manner as in Example 1, except that 250 g of fine powder and 750 g of a coarsely pulverized hydrogel polymer were used. Comparative Example 1

1,000 g of coarsely pulverized hydrogel polymer obtained in Preparation Example 1 was dried in a hot air dryer for 30 minutes at a temperature of 180 ^° C. The particles were classified into particles having a particle diameter of 150 Pa or more and 850 or less.

Surface crosslinking comprising 100 g of particles having a classified particle diameter of 150 η or more and less than 850 // m, containing 0.2 g of poly (ethylene glycol) diglycidyl ether, 3 g of methane, 5 g of water, and silica aerogel (AeroZelTM, JIOS) O.Olg After mixing with the solution, a surface crosslinking reaction was performed for 50 minutes at a temperature of 180 ^° C to obtain a final superabsorbent polymer.

Experimental Example

 In order to evaluate the physical properties of the fine powder reassembly, the physical properties of the superabsorbent polymers (resin before surface crosslinking and resin after surface crosslinking) prepared by the method according to Comparative Example 1 and Examples 1 to 2 were measured by the following method. The results are shown in Table 1.

(1) Centrifugal Retention Capacity (CRC) For each of the superabsorbent polymers prepared in Examples 1 and 2 and Comparative Example 1, the water holding capacity was measured before and after the surface crosslinking reaction. The measurement of water retention capacity was based on the EDANA method WSP 241.3. 0.2 g of a 300 to 600 m particle size sample was put into a tea bag and precipitated in a 0.9% saline solution for 30 minutes. After dehydration for 3 minutes with a centrifugal force of 250G (gravity) was measured the amount of saline solution absorbed.

(2) Absorption Under Pressure (AUP)

 The absorbency under pressure was measured for each of the superabsorbent polymers prepared in Examples 1 to 2 and Comparative Example 1. The measurement of the absorbency under pressure was based on the EDANA method WSP 241.3. 0.9 g of the particle size 300 to 600 / ΛΙΙ sample of the prepared superabsorbent polymer was put in a cylinder defined by EDANA, and a pressure of 0.7 psi was applied to the piston and weight. After that, the amount of 0.9% saline solution absorbed for 60 minutes was measured.

(3) Absorption Rate (Vortex)

Absorption rates were measured for each of the superabsorbent polymers prepared in Examples 1 and 2 and Comparative Example 1. Measurement of absorption rate ₅₀ ml ^ saline

Placed in a 100 ml beaker with a magnetic bar. The stirring speed was specified at 600 rpm using a stirrer. The time was measured while putting 2.0 g of superabsorbent polymer in the stirred brine. The time measurement was terminated when the swirl disappeared in the beaker.

(4) Permeability

 Permeability was measured for each of the superabsorbent polymers prepared in Examples 1 and 2 and Comparative Example 1.

In order to prevent bubbles from forming between the glass tube and the bottom of the chromatography tube, water was added in the reverse direction, filled with about 10 mL, washed 2-3 times with brine, and filled with 9% brine to 40mL or more. Insert the piston into the chromatography tube, open the lower valve, and the liquid level is 20 mL at the 40 mL mark. Blank experiment was performed by recording the time until the display line (B: sec). Prepared super absorbency. 0.2 g of a particle size of 300 to 600 i / m of the resin was added thereto, and then brine was added so that the total amount of saline was 50 mL. The superabsorbent polymer was allowed to stand for 30 minutes to sufficiently swell. An additional piston (0.3 psi) was placed in the chromatography tube and allowed to stand for 1 minute. Open the stopper at the bottom of the chromatography tube and record the time (T1: sec) from the 40 mL mark to the 20 mL mark. The transmittance is represented by the following equation.

 Permeability = T1-B

 TABLE 1

Referring to Table 1, in the case of the super absorbent polymer which has been subjected to the fine powder reassembly process according to the manufacturing method of the present invention, physical properties such as water retention, pressure absorbing ability, absorption rate, and permeability are improved or equivalent to those before fine powder reassembly. Level was shown.

Claims

[Patent Claims]

 [Claim 1]

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

 Drying and pulverizing the coarsely pulverized hydrogel polymer to classify it into fine particles having a particle size of less than 150 mm 3 and normal particles having a particle size of 150 to 850; Preparing a fine powder aqueous solution by mixing the fine powder, water, and additives; And mixing the finely divided aqueous solution and the coarsely pulverized hydrogel polymer to produce a finely divided reassembled product.

[Claim 2]

 In U,

 The additive includes a sodium hydroxide, a crosslinking agent, and a thermal polymerization initiator, a method for producing a super absorbent polymer.

[Claim 3]

 According to claim 1,

 The fine aqueous solution further comprises a porous particle, a method for producing a super absorbent polymer.

[Claim 4]

 The method of claim 3,

The porous particles are silica particles having a BET specific surface area of 300-1500 m ² / g and a porosity of 50% or more.

[Claim 5]

The method of claim 3, wherein The finely divided aqueous solution comprises 0.01 to 0.4 parts by weight of the porous particles with respect to 100 parts by weight of the fine powder, a method for producing a super absorbent polymer.

[Claim 6]

 The method of claim 2,

The crosslinking agent is polyethylene glycol diacrylate (PEGDA), nucleic acid-1,6-diol diacrylate (hexane-l, ^6- diol diacrylate, HDD A), and an oxylated trimethylolpropane triacrylate. (ethoxylated trimethylolpropane triacrylate, ETTA), and ethylene carbonate (ethylene carbonate, EC) comprising at least one member selected from the group consisting of.

[Claim 7]

 The method of claim 2,

 The fine powder aqueous solution is based on 100 parts by weight of the fine powder, the crosslinking agent

0.1 to 0.5 parts by weight, the method of producing a super absorbent polymer.

[Claim 8]

 The method of claim 2,

 The thermal polymerization initiator comprises sodium persulfate or potassium persulfate, a method for producing a super absorbent polymer.

[Claim 9]

 According to claim 2,

 The said fine powder aqueous solution contains the said thermal-polymerization initiator in 1 thru | or 0.5 weight part with respect to 100 weight part of said fine powders, The manufacturing method of the super absorbent polymer.

[Claim 10]

 The method of claim 1,

The fine powder aqueous solution is water from 100 to 100 parts by weight of the fine powder; It contains 300 weight part, The manufacturing method of a super absorbent polymer.

【Claim 11】

 The method of claim 1,

 A method for producing a super absorbent polymer, comprising mixing 50 to 500 parts by weight of the coarsely pulverized hydrogel polymer with respect to 100 parts by weight of fine powder contained in the fine aqueous solution.

[Claim 12]

 According to claim 1,

 The particle size of the coarsely pulverized hydrogel polymer is 2 to 20 mm, a method for producing a super absorbent polymer.

[Claim 13]

 The method of claim 1,

 Preparing the differential aqueous solution,

 Mixing the water and the additive to prepare an additive aqueous solution;

Heating the additive aqueous solution to 40 to 80 ^° C .; And

 Mixing the fine powder in the heated additive aqueous solution, a method for producing a super absorbent polymer.

[Claim 14]

 According to claim 1,

 Method for producing a super absorbent polymer further comprising the step of drying the fine powder reassembly.

[Claim 15]

 The method of claim 14,

The method of manufacturing a super absorbent polymer further comprising the step of pulverizing and classifying the dried fine powder reassembly.

[Claim 16]

 The method of claim 15,

 The method of producing a super absorbent polymer further comprising the step of surface crosslinking the pulverized and classified fine powder reassembly.

[Claim 17]

 In the superabsorbent polymer containing an acidic group and polymerizing a water-soluble ethylene-based unsaturated monomer in which at least a portion of the acidic group is neutralized, the finely divided finely reassembled finely divided powder reassembled by mixing sodium hydroxide As absorbent resin ，

 The water holding capacity (CRC) measured according to the EDANA method WSP 241.3 is 33.0 to 39.0 g / g;

 0.7 psi Pressurized Absorption Capacity (AUP), measured according to EDANA method WSP 241.3, is from 20.0 to 25.0 g / g;

 The absorption rate by the vortex method is 100 seconds or less ，

 Superabsorbent polymer.

[Claim 18]

 The method of claim 17,

 A super absorbent polymer, wherein the sodium hydroxide is mixed at 0.1 to 20 parts by weight based on 100 parts by weight of the fine powder.