WO2015088200A1 - 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 method for preparing a super-absorbent resin, a super-absorbent resin which has an improved absorption rate and solution permeability, no deterioration in water retaining capacity or pressurized absorptive capacity, and improved physical properties can be provided.

Description

 【Specification】

 [Name of invention]

 Manufacturing method of super absorbent polymer

 [Detailed Description of the Invention]

 Technical Field

 The present invention relates to a method for producing a super absorbent polymer. More specifically, it is related with the manufacturing method of a super absorbent polymer which can obtain the superabsorbent polymer which shows not only a high water holding capacity but also a fast absorption rate and liquid permeability.

 This application is subject to the Korean Patent Application No. 10-2013-0153325 filed with the Korean Patent Office on December 10, 2013 and the Korean Patent Application No. 10-2014-0172998 filed with the Korean Patent Office on December 4, 2014. Claiming benefit, the entire contents of which are incorporated herein by reference.

 Background Art

 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, a super absorbent material (SAM) and an absorbent gel (AGM) They are named differently. Such super absorbent polymers have been put into practical use as physiological tools, 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-retaining agents 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, for example, in Japanese Patent Laid-Open Nos. 56-161408, 57-158209, and 57-198714.

 As a method of aqueous solution polymerization, a thermal polymerization method in which a polymer gel is broken and kneaded in a kneader having several shafts, and a photopolymerization method in which polymerization and drying are simultaneously performed by irradiating ultraviolet rays or the like on a belt with a high concentration of aqueous solution Etc. are known.

The hydrous gel polymer obtained through the polymerization reaction as described above is generally pulverized through a drying process and marketed as a powder product. Permeability in products using superabsorbent polymers is a measure of the fluidity of the liquid to be absorbed. Permeability may vary depending on the particle size distribution of the crosslinked resin, the shape of the particles and the connectivity of the openings between the particles, the surface modification of the swollen gel, etc. 통과 Pass through the swollen particles according to the permeation of the superabsorbent resin composition The fluidity of the liquid varies. When the transmittance is low, the liquid cannot easily flow through the super absorbent polymer composition.

 One method of increasing the transmittance in a super absorbent polymer is to perform surface crosslinking reaction after the resin is evaporated. In this case, a method of adding silica or clay together with the surface crosslinking agent has been used. For example, US Pat. Nos. 5,140,076 and 4,734,478 disclose the addition of silica during surface crosslinking of dry superabsorbent resin powders.

 However, as the silica or clay is added, the transmittance is improved. However, there is a problem in that water-repellency or pressure-absorbing capacity is decreased in proportion to the silica and clay, and it is easy to be separated from the super absorbent polymer by an external physical impact during movement.

 In addition, according to the trend of slimming of hygiene products, there is a high demand for fast absorption rate and liquid permeability as well as high water-retaining ability. However, the physical properties are not easy to achieve at the same time.

 [Content of invention]

 [Problem to solve]

 In order to solve the problems of the prior art as described above, the present invention provides a method for producing a superabsorbent polymer that can satisfy the demand for slimming of the thickness of the sanitary article by exhibiting a high water absorption capacity as well as fast absorption rate and solution permeability. It is aimed at

 [Solution of problem].

 In order to achieve the above object, the present invention,

 Thermally polymerizing or photopolymerizing the monomer composition including a water-soluble ethylenically unsaturated monomer, an internal crosslinking agent, and a polymerization initiator to form a hydrogel polymer having a gel strength of 10,000 to 13,000 Pa;

 Coarsely pulverizing the hydrogel polymer;

Drying the coarsely pulverized 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 the surface crosslinking agent.

 【Effects of the Invention】

 According to the manufacturing method of the superabsorbent polymer of the present invention, it is possible to provide a superabsorbent polymer having improved physical properties without having a deterioration in water-retaining capacity or pressure-absorbing capacity while having an improved absorption rate and permeability. Accordingly, it is possible to reduce the ratio of the fiber material of the sanitary article and to implement a thin thickness, to meet the trend of slimming of the sanitary article and to improve the satisfaction for convenience.

 [Specific contents for carrying 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 that is practiced, and that one or more other features or steps, It should be understood that it does not exclude in advance the possibility of the presence or the addition of components, or combinations 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 particular disclosed form, it should be understood to include all modifications, equivalents, and substitutes included in the spirit and scope of the present invention.

 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 of preparing a super absorbent polymer according to a specific embodiment of the present invention will be described in more detail. In the method for preparing a super absorbent polymer according to an embodiment of the present invention, a gel strength is 10,000 to 10,000 by thermal polymerization or photopolymerization of a monomer composition including a water-soluble ethylenically unsaturated monomer, an internal crosslinking agent, and a polymerization initiator. Forming a hydrous gel phase polymer of 13,000 Pa;

 Coarsely pulverizing the hydrogel polymer;

 Drying the coarsely pulverized hydrogel polymer;

 Pulverizing the dried polymer; And

 Mixing the ground polymer with the surface crosslinking agent to perform a surface crosslinking reaction.

The inventors of the present invention continue to study the superabsorbent polymer having high water-retaining ability and high absorption rate and liquid permeability, and the gel strength of the hydrogel polymer which becomes the base resin of the superabsorbent polymer. When (Gd Strength) satisfies a predetermined range and further optimizes the process conditions in the step of coarsely pulverizing the hydrogel polymer, it is possible to improve the physical properties of the final superabsorbent polymer, thereby making the hygiene to which ultra-thin technology is applied. It was confirmed that the article can be produced to complete the present invention. ^'

 In the method for producing a super absorbent polymer of the present invention, the monomer composition which is a raw material of the super absorbent polymer includes a water-soluble ethylenically unsaturated monomer, an internal crosslinking agent and a polymerization initiator.

 The water-soluble ethylenically unsaturated monomer may be used without any limitation any monomers commonly used in the production of superabsorbent polymers. 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-

Anionic monomers and salts thereof of (meth) acryloylpropanesulfonic acid or 2- (meth) acrylamide-2-methyl propane sulfonic acid; (Meth) acrylamide, N-substituted (meth) acrylate, 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, methoxypolyethylene glycol (meth) acrylate or polyethylene Nonionic ^" hydrophilic containing monomers of glycol (meth) acrylate; and amino group-containing ball saturations of (Ν, Ν) -dimethylaminoethyl (meth) acrylate or (Ν, Ν) -dimethylaminopropyl (meth) acrylamide Any one or more selected from the group consisting of monomers and quaternized compounds thereof can be used.

 More preferably, an alkali metal salt such as acrylic acid or a salt thereof, for example acrylic acid or a sodium salt thereof can be used, and it is possible to prepare a super absorbent polymer having better physical properties by using such a monomer. When the alkali metal salt of acrylic acid is used as a monomer, at least a part of the acrylic acid may be neutralized with a basic compound such as caustic soda (NaOH). More specifically, the acrylic acid may be at least about 50 mol%, black at least about 60 mol%, black at least about 70 mol%, and through this, it is possible to more effectively achieve the overall physical properties of the superabsorbent polymer of the present invention. Can be. In other words, the water-soluble ethylenically unsaturated monomer is an acidic group. The degree of neutralization may be about 50 mol% or more.

The concentration of the water-soluble ethylenically unsaturated monomer, in which the 20 against the total weight of monomer composition including a source material and a solvent of the water-absorbent resin to about 60 parts by weight _^0/0, preferably from about 40 to about 50 weight ⁰ / It may be。, and may be 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, 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.

 As the internal crosslinking agent used during polymerization in the method of preparing a super absorbent polymer, the curing amount of the water-soluble ethylenically unsaturated monomer is 100% in terms of the uniformity of the internal crosslinking. To a compound having a curing amount of about 200%. Preferably, the internal crosslinking agent has a curing amount of about 90% to about 180%, more preferably about 95% to about 170%, based on 100% of the curing amount of the water-soluble ethylenically unsaturated monomer Compound.

For example, when acrylic acid (acrylic acid, AA) is used as the water-soluble ethylenically unsaturated monomer, the curing amount of acrylic acid is about 200 mJ / cm ^2, so that the internal crosslinking agent It may have a cure dose of about 160 to about 400 mJ / cm ² , preferably about 180 to about 360 mJ / cm ² , more preferably about 190 to about 340 mJ / cm ² . Here, the cure dose means the amount of energy required for cure. That is, the larger the number indicating the amount of curing, the more energy is required for curing. Values expressed by the amount of curing may be measured using a photometer. For example, the illuminance of a lamp is set to a predetermined hardening machine accessory, and a sample can be sent on the belt of a hardening machine, and can be evaluated through a UV hardening machine. At this time, it can be measured by evaluating how many times the curing machine has passed based on the speed of the conveyor of the curing machine and the amount of light, and calculating the total energy after the surface has been cured. Thus, the ^"curing amounts extra amount of sample during measurement is not limited. In addition, as a more specific example, the measurement may be carried out by rolling a solution of about 0.5 cm thick in 100 mm saale and putting it on a conveyor belt to operate the belt.

 The amount of hardening for some of the arc ¾ate-based hydrocarbon compounds is shown in Table 1 below.

 Table 1

PETTA: Pentaerythritol Triacrylate

 NPG (PO) 2DA: 2mol% propoxylated Neopentylglycol Diacrylate

 TMP (EO) 9TA: 9mol% ethoxylated Trimethylolpropane triacrylate (TMPTA)

* Curing amount of acrylic acid: 200 mJ / cm ²

 * Curing Amount Information: Miwon Specialty Chemical

With reference to the amount of curing according to the material of Table 1, an acrylate-based hydrocarbon compound suitable for the production method of the super absorbent polymer of the present invention can be selected and used as the internal crosslinking agent. However, the internal crosslinking agent usable in the production method of the present invention is not limited to the materials exemplified in Table 1 above, and as described above, it satisfies the relative curing amount range with respect to the curing amount of the single-group water-soluble ethylenically unsaturated monomer. Any material can be used without limitation.

 According to an embodiment of the present invention, the internal crosslinking agent, the curing amount of the various acrylate-based hydrocarbon compounds, based on 100% of the cure dose of the water-soluble ethylenically unsaturated monomer, from about 80% to about 200%, preferably Preferably, the curing amount of about 90% to about 180%, more preferably about 95% to about 170% is used, and more preferably, two or more kinds of compounds having such curing amount range are mixed and used. It is possible to obtain a hydrous gel polymer having a Gel Strength in the range of about 10,000 to about 13,000 Pa.

 In addition, according to one embodiment of the present invention, the internal crosslinking agent is about 4,000 to about 7,500 ppm, preferably about 4,500 to 7,000 ppm, more preferably based on the total weight of the water-soluble ethylenically unsaturated monomer included in the monomer composition. Preferably in a concentration of about 5,000 to 6,500 ppm. When the concentration of the internal crosslinking agent satisfies the above-mentioned range, it is possible to obtain a super optimized superabsorbent polymer having a more optimized physical property while satisfying the gel strength of about 10,000 to about 13,000 Pa. In the case where a mixture of two or more species is used in combination, the concentration of each of the internal crosslinking agents can be adjusted according to the amount of curing of the internal crosslinking agents used in a mixed manner within the range in which the concentration of the entire internal crosslinking agent is satisfied.

More specifically, the curing amount of each internal crosslinking agent (unit: J / cm ² ) * the corresponding internal The sum of the concentrations of the crosslinkers (concentration relative to the total weight of the water-soluble ethylenically unsaturated monomer, in ppm) ranges from about 800 to about 1,800, preferably from about 800 to about 1,600, more preferably from about 1,000 to about 1,500. The concentration of each internal crosslinking agent may be adjusted to be used.

 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, a thermal polymerization initiator may be additionally included.

 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 at least one selected from the group consisting of. On the other hand, as a specific example of acylphosphine, commercially available lucirin TPO, that is, 2,4,6-trimethyl-benzoyl-trimethyl phosphine oxide (2,4,6-trimethyl-benzoyl-trimethyl phosphine oxide) can be used. . A wider variety of photoinitiators are well described in Rein old Schwalm's book, "UV Coatings: Basics, Recent Developments and New Application (Elsevier 2007)" pi 15, and are not limited to the examples described above.

The photopolymerization initiator may be included in a concentration of about 0.01 to about 1.0 weight ⁰ /. When the concentration of the photopolymerization initiator is too low, the polymerization rate may be slow. When 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 (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 ), and the like. Examples are 2, 2-azobis (2-amidinopropane) dihydrochloride, 2, 2-azobis- (N, N-dimethylene) isobutyra Mydine dihydrochloride (2,2-azobis- (N, N-dimethylene) isobutyramidine dihydrochloride), 2- (carbamoyl azo) isobutyronitrile (2- (carbamoylazo) is 3utylonitril), 2, 2-azo bis [2- (2-imidazolin-2-yl) propane] dihydrochloride (2,2-azobis [2- (2-imidazolin-2-yl) propane] dihydrochloride), 4, ^4-azobis- and the like - ^{(4-cyano-ballet} rigs ^{acid) (4, 4 -azobis- (4-} cyanovaleric acid)). More various thermal polymerization initiators are well specified in Odian's 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 0.001 to about 5% by weight based on the total amount of 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.

 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-mentioned 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 cyclonuxanone, cyclopentanone, diethylene glycol monomethyl ether diethylene glycol ethyl ether, toluene , Xylene, butyrolactone, carbyl at least one selected from methyl cellosolve acetate and N, N-dimethylacetamide It 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, can be generally carried out in a reactor having a stirring shaft, such as kneader, in the case of performing the thermal polymerization, and, when the photopolymerization proceeds, 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, the photo-polymerization and the polymerization step is the polymerization temperature is irradiated with about 35 ^° C or higher, or light of from about 35 to, and from about 9CTC performing a heat polymerization step, the same time about 100 to ultraviolet (UV) region of about 400 nm Can be done.

 In addition, as described above, the hydrogel polymer obtained by supplying hot air to the reactor such as a kneader having a stirring shaft or by heating and heating the reactor may be a semi-ungunggi outlet according to the shape of the stirring shaft provided in the reactor. 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, a water-containing gel polymer having a weight average particle diameter of 2 to 50 mm can be obtained.

In addition, when the 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-like 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. When the monomer composition is supplied 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 thickness of the polymer on the sheet exceeds 5 cm, the polymerization reaction does not occur evenly over the entire thickness. You may not. In the manufacturing method of the superabsorbent polymer of the present invention, preferably, the hydrogel polymer can be formed by photopolymerization.

In this case, the water content of the hydrogel polymer obtained by the above method may be about 40 to about 80% by weight. On the other hand, the term "water content" as used throughout the specification refers to the value of the moisture content of the total hydrogel polymer weight minus the weight of the polymer in the dry state. Specifically, it is defined as a value calculated by measuring the weight loss due to moisture evaporation in the polymer in the process of 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 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.

 The polymerization proceeds in the manner described above to obtain a hydrous gel polymer having a gel strength in the range of about 10,000 to about 13,000 Pa, or about 10,500 to about 12,800 Pa, or about 10,500 to about 12,600 Pa. Gel strength is a measure for evaluating the degree of crosslinking of the polymer. The higher the gel strength, the higher the crosslinking density of the polymerized hydrogel polymer. On the other hand, if the gel strength of the hydrous gel phase polymer is too low or too high out of the above range, excessive water solubility occurs in the subsequent coarse grinding step or damage of the hydrogel polymer occurs, thereby achieving sufficient water retention and absorption rate. There is a problem that is difficult to do.

 According to the manufacturing method of the superabsorbent polymer of the present invention, the water-retaining capacity is controlled by adjusting the polymerization conditions so that the gel strength of the hydrogel polymer before coarse grinding is satisfied in the above range, and further optimizing the process conditions in the coarse grinding step described below. It is possible to produce a superabsorbent polymer having excellent harmonized physical properties, which exhibits synergistic effects to the extent that (CRC), pressure absorption capacity (AUP), solution permeability (SFC) and absorption rate (FSR) are excellent at the same time. Next, the step of coarsely crushing the obtained hydrogel polymer is performed.

The coarsely pulverizing step may be performed by injecting the hydrogel polymer into a chopper or the like and pushing it to an outlet or perforated panel in which a plurality of holes having a predetermined size are formed. . At this time, the extruder used to push the hydrogel polymer may be used a single or multiple screw type extruder. As described above, when the hydrogel polymer is pushed out to the hole where the hole is formed, coarsely pulverized, a constant pressure is applied to the hydrogel polymer, and the original gel strength and morphology of the hydrogel polymer by this pressure ), And the surface area becomes wider. In this case, the physical properties of the polymer after performing the coarse grinding step may vary according to the diameter of the hole. For example, the smaller the diameter of the hole, the greater the pressure applied to the hydrous gel-like polymer and the higher the surface area, the faster the absorption rate. There is a problem that the possibility of damage of the gel polymer is increased, so that the water-retaining ability is lowered and the residual monomers are increased. Therefore, it is not easy to find an optimized coarse grinding condition for obtaining a superabsorbent polymer having high water retention capacity and fast absorption rate and having harmonized physical properties.

 On the other hand, based on the results of the inventors of the present invention, the gel strength (unit: Pa) of the hydrous gel polymer before coarse grinding, and the hole formed in the outlet or the porous plate for coarsely grinding the hydrogel polymer in the coarse grinding step The diameter of the hole (unit: mm) was confirmed that the final superabsorbent polymer can exhibit the optimized physical properties when in the range satisfying the following formula (1).

 [Equation 1]

 1 140 * x + 730 <y <600 * x + 8400

 In Equation 1, X is the diameter of the hole (unit: mm), and y is the gel strength (unit: Pa) of the hydrous gel polymer before coarse grinding.

 In addition, according to an embodiment of the present invention, within the range satisfying Equation 1, the diameter of the hole may be in the range of about 6.5 to about 10 mm. When the diameter of the hole is smaller than 6.5 mm, the particles may be concaved with each other during the grinding process, or the residual monomers may be increased, and when the diameter is too large, exceeding 10 mm, the surface may be irregularly contracted during the subsequent drying process. There is a problem that the quality of the final resin is uneven. Therefore, when coarsely pulverizing the hydrous gel polymer having the gel strength in the above-described range to the diameter in the above-mentioned range, and performing the drying and pulverizing step, the resulting superabsorbent polymer has moderate unevenness on the surface with little generation of residual monomers. Can increase the absorption rate.

Next, drying is performed on the coarsely pulverized hydrogel polymer as described above. At this time, the drying temperature of the drying step may be about 150 to about 250 ^° C. dry If the temperature is less than 150 ^° C, the drying time may be too long and the physical properties of the final superabsorbent polymer may be lowered. If the drying silver exceeds 250 ^° C, only the surface of the polymer is dried too much, resulting in subsequent grinding Fine powder may generate | occur | produce in a process and there exists a possibility that the physical property of the superabsorbent polymer formed finally may fall. Thus preferably the drying may proceed at a temperature of about 150 to about 200 ^° C, more preferably at a temperature of about 160 to about 180 ^° C.

 Meanwhile, in the case of a drying time, the process may be performed for about 20 to about 90 minutes in consideration of process efficiency and the like, but is not limited thereto.

The drying method of the drying step may be selected and used without limitation in the configuration as long as it is commonly used as a drying process of the hydrous gel polymer. Specifically, the drying step may be performed by a method of 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 weight ⁰ /.

 Next, the step of pulverizing the dried polymer obtained through this drying step is carried out.

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

And, like _this. In order to manage the physical properties of the superabsorbent polymer powder to be finalized after the grinding step, a separate process of classifying the polymer powder obtained after grinding according to the particle size may be performed. Preferably, the polymer having a particle size of about 150 to about 850 may be classified and commercialized only through the surface crosslinking reaction step for the polymer powder having such a particle size.

 Next, the surface crosslinking reaction is performed by mixing the ground polymer with the surface crosslinking agent.

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. Therefore, this reaction is a super absorbent polymer Occurs on the surface of the 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, the surface crosslinking agent may be a polyhydric alcohol compound; 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 one or more selected from the group consisting of alkylene carbonate compounds can be used. 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-di, 1,4-butanedi, 1,3-butanedi, 1,5-pentanedi, ^' 1,6 One or more kinds selected from the group consisting of -nucleic acid diol and 1,2-cyclonucleic acid dimethanol can be used. Ethylene glycol diglycidyl ether and glycidol may be used as the epoxy compound, and polyamine compounds may be ethylenediamine, diethylenetriamine, triethylenetetraamine, tetraethylenepentamine, or pentaethylenenucleoamine. , 1 or more types 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 one or more types of polyhydric alcohols among these surface crosslinking agents, and more preferably, C2-C10 polyhydric alcohol compounds can be used.

There is no limitation in the structure about the method of mixing the said surface crosslinking agent with a polymer. Mix the surface crosslinker and the polymer powder in a semi-permanent mixture, or A method of injecting a surface crosslinking agent into the powder, a method of continuously supplying a polymer and a surface crosslinking agent to a mixer which is continuously operated, and the like can be used.

 In addition to the surface crosslinking agent, water and alcohol may be further mixed together and added in the form of the surface crosslinking solution. When water and alcohol are added, there is an advantage that the surface crosslinker can be evenly dispersed in the polymer. At this time, the content of water and alcohol to be added is not particularly limited, but 100 parts by weight of the polymer for the purpose of inducing even dispersion of the surface crosslinking agent, preventing aggregation of the polymer powder and optimizing the surface penetration depth of the crosslinking agent. For example, it is preferably added at a ratio of about 2 to about 20 parts by weight.

By heating the surface cross-linking agent to the polymer particles added to about 150 to about 220 ^° C, preferably from about 165 to about 210 ^° C for about 15 to about 80 minutes, preferably about 20 to about 70 minutes Surface crosslinking reactions can be made. If the crosslinking reaction silver is less than 150 ^° C surface crosslinking reaction may not occur sufficiently, if the crosslinking reaction exceeds 220 ^° C may be excessively surface crosslinking reaction. In addition, when the crosslinking reaction time is too short (less than 15 minutes), sufficient crosslinking reaction cannot be performed, and when the crosslinking reaction time exceeds 80 minutes, the crosslinking density of the particle surface is excessively high due to the excessive surface crosslinking reaction, resulting in deterioration of physical properties. 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. At this time, the type of heat medium that can be used may be a heated fluid such as steam, hot air, hot oil, etc., but the present invention is not limited thereto. The target silver may be selected appropriately. On the other hand, the heat source directly supplied may be a method of heating through electricity-heating, gas, but the present invention is not limited to the above examples.

The total content of the surface crosslinking agent included in the surface crosslinking solution may be appropriately selected according to the kind or reaction conditions of the additional surface crosslinking agent, but, based on 100 parts by weight of the pulverized polymer, about 0.01 to about 10 parts by weight, Preferably from about 0.01 to about 5 parts by weight can be used. When the content of the surface crosslinking agent is too small, the surface crosslinking reaction hardly occurs, and when the content of the surface crosslinking agent is too large, Due to the excessive surface crosslinking reaction, deterioration of absorption capacity and physical properties may occur.

 The superabsorbent polymer obtained according to the production method of the present invention as described above has improved water retention, solution permeability and absorption rate, and exhibits harmonized properties of the above properties. Therefore, it is possible to obtain a super absorbent polymer that exhibits high permeability and absorption rate without deteriorating water holding capacity.

 As described above, the present invention provides a synergistic effect by combining a complex physical property that simultaneously optimizes the centrifugal water retention capacity (CRC), the pressure absorption capacity (AUL), the solution permeability (SFC), and the absorption rate (FSR). By providing the harmonized properties. Therefore, it is possible to obtain a super absorbent polymer exhibiting high permeability and absorption rate without deterioration in water retention capacity, and by using the superabsorbent polymer of the present invention, it is possible to induce excellent physical properties and comfortable fit in the manufacture of hygiene products.

 At this time, the Centrifuge Retention Capacity (CRC) is a value measured according to the ED ANA method WSP 241.2, and the Absorbency Under Load (AUL) is a value measured according to the EDANA method WSP 242.2.

 In addition, the solution permeability (SFC: Saline Flow Conductivity) may be measured according to the method described in US Pat. No. 5,669,894. Absorption rate or free swell rate (FSR) may be a value measured according to WO 2009/016055. In the superabsorbent polymer of the present invention, the centrifugal water retention capacity (CRC) for the physiological saline may be calculated according to the following Equation 1.

 [Calculation 1]

CRC (g / g) = { [W 2 (g) - W t (g)] / Wo (g)} - 1

 In the above formula 1,

W ₀ (g) is the weight of the super absorbent polymer (g), W (g) is the weight of the device measured after dehydration at 250G for 3 minutes using a centrifuge without using the super absorbent polymer, W ₂ ( g) is the weight of the device measured after submerging the superabsorbent polymer in 0.9 mass% of physiological saline for 30 minutes, followed by dehydration at 250 G for 3 minutes using a centrifuge. In particular, the weight W ₀ (g) of the superabsorbent polymer may be measured by the weight of the superabsorbent polymer classified as 300 to 600 micrometers (μιη). The centrifugal water retention capacity (CRC) of physiological saline of the superabsorbent polymer is about 25 g / g or more, preferably about 26 g / g or more, more preferably about 27 g / g or more, for example about 25 to about 34 g / g, or about 25 to about 32 g / g, or from about 26 to about 30 g / g. When the centrifugal water retention capacity (CRC) for the physiological saline is less than 25 g / g, the water repellency of the final product, such as sanitary products is lowered may cause a problem of poor physical properties of the final product.

 In addition, in the superabsorbent polymer of the present invention, a pressurized absorption capacity (AUL) of 0.9 psi with respect to physiological saline may be calculated by the following Equation 2.

 [Calculation 2]

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

 In the formula 2,

W ₀ (g) is the weight (g) of the superabsorbent polymer, W ₃ (g) is the weight and the sum of the high to give a load to the water-absorbent ^resin, the device in the weight of the superabsorbent resin, W ₄ (g ) Is the sum of the weight of the superabsorbent polymer absorbed by water after supplying the superabsorbent polymer for 1 hour under a load (0.9 psi) and the weight of the device capable of applying a load to the superabsorbent polymer.

As an example of the present invention, 0.9 psi of pressure absorbency (AUL) is 300 to 600 micrometers Cam) 0.16 g of classified superabsorbent polymer in a pressure absorption capacity (AUL) measurement kit with a weight of 0.9 psi It can be measured after pressure swelling for 1 hour under 0.9% brine. At this time, after 1 hour, the cell can be weighed to measure the absorbency (AUL) under pressure. In this case, the superabsorbent weight W ₀ (g) may be measured by the weight of the super absorbent polymer classified as 300 to 600 micrometers On). The pressure absorbing capacity (AUL) of 0.9 psi of the superabsorbent polymer may be about 20 g / g or more, preferably about 22 g / g or more, and more preferably about 23 g / g or more, for example About 20 to about 32 g / g, or about 22 to about 30 g / g, or about 23 to about 28 g / g. The higher the pressure absorbing capacity is better, but the pressure absorbing capacity may be lowered when the pressure absorbing capacity is too high due to the physical properties opposite to the water holding capacity. Improving the pressure absorption capacity and water retention capacity at the same time is an important technical factor. In the present invention, W ₀ (g) described in Formulas 1 to 2 corresponds to the weight (g) of the superabsorbent polymer applied to each property value, and may be the same or different. The solution permeability (SFC) in the superabsorbent polymer of the present invention can be measured and calculated according to US Pat. No. 5,669,894.

The solution permeability (SFC) of the super absorbent polymer is about 70 * l (T ⁷ cm ³ * sec / g or more, preferably about 80 * 10 ^{" 7} cm ³ * sec / g or more, more preferably about 90 * 10 ^_7 cm ³ * sec / g or more, for example about 70 * 10 ^-7 to about 150 * 10 ^"7 cm ³ * sec / g, or about 80 * 10 ^{" 7} to about 140 * KT ⁷ cni ³ * sec / g, or about 90 * l (r ⁷ to about i30 * UT ⁷ cm ³ * sec / g.) Solution Permeability (SFC) is an evaluation of the flowability of liquids absorbed in superabsorbent resins. If the solution permeability (SFC) is less than 70 * 10 ^"7 cm ³ * sec / g, the pressure absorption capacity is lowered, which may cause a problem of poor physical properties of the final product.

 In the superabsorbent polymer of the present invention, the absorption rate (FSR) is disclosed in WO WO.

May be measured and calculated according to 2009/016055.

 The absorption rate (FSR) of physiological saline of the superabsorbent polymer may be about 0.25 g / g / s or more, preferably about 0.27 g / g / s or more, and more preferably about 0.30 g / g / s or more. And, for example, about 0.25 to about 0.5 g / g / s, or about 0.27 to about 0.5 gg / s, or about 0.27 to about 0.45 g / gs. Absorption rate (FSR) is a value for evaluating the free swelling rate of superabsorbent polymers. When the absorption rate (FSR) is less than 0.25 g / g / s, the absorption rate of the final product is lowered, resulting in poor physical properties of the final product. Problems may arise.

 As described above, the superabsorbent polymer obtained according to the production method of the present invention exhibits fast absorption rate and solution permeability under pressure while maintaining water retention capacity and pressurized absorption capacity above a certain level, and exhibits harmonized properties of the above properties. In general, when the solution permeability is high in the superabsorbent polymer, the water holding capacity and the pressure absorbing capacity tend to be low. In other words, when the crosslinking degree is high and the strength of the superabsorbent polymer is high, the water holding ability is high, but the solution permeability and the absorption rate are low. On the contrary, when the solution permeability and the absorption rate are high, the water holding ability and solution permeability are relatively low. At the same time there is a difficulty in raising.

 However, the superabsorbent polymer obtained according to the manufacturing method of the present invention can provide a superabsorbent polymer having improved physical properties without deterioration in water-retaining capacity or pressure-absorbing capacity while having an improved absorption rate and solution permeability.

Accordingly, the opposite properties of the water holding capacity and the transmission rate are balanced, so It can be suitably used for the filling of ultra-thin hygiene products. Hereinafter, the present invention will be described in more detail in the following 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.

<Example>

 Example 1

25 ^° in a glass reactor of C pre-wrapped around a cooling jacket which heat medium is circulated 2 L capacity in the dilute acid in the acrylic acid 450 g 0.5 wt. _^0/0 IRGACURE 819 traces were combined initiator 8 g, 5 wt diluted acid % polyethylene glycol diacrylate 5 parts by weight ⁰ / implanted a common combined solution (PEGDA, molecular weight 598 g / mol, Cure Dose 200 mJ / cm 2) 50 g , diluted to acrylic acid. the nucleic acid 1,6-diol diacrylate rate was heunhap by injecting (1,6- hexandiol diacrylate, molecular weight 226 g mol, mol, Cure Dose 320 mJ / cm 2) 10 g , and slowly added dropwise to 32 parts by weight _^0/0 sodium hydroxide solution 660 g.

After confirmed that the two solutions The silver rise above 80 ^° C in the heunhap when common hapaek by junghwayeol, and a 2% diluted in water when the temperature reaches the 40 ^° C as to be waited that the reaction temperature 40 ^° C Cooling 50 g of sodium sulfate solution was injected.

 The solution was poured into a Vat-shaped tray (15 cm x 15 cm) mounted in a square polymerizer with a light irradiating device mounted on the top and preheated to 80 t, and irradiated with light to start light. After 25 seconds, the gel was generated from the surface, and after 50 seconds, it was confirmed that the polymerization reaction occurred at the same time as the foaming. After 3 minutes, the polymerized sheet was taken out and the gel strength of the polymerized hydrogel was measured. .

 The cemented sheet was cut into 3 cm x 3 cm and then chopped using a meat chopper having a hole diameter of 8 mm to prepare a powder. .

The powder was dried in an oven capable of transferring air volume up and down. The hot air ^at 180 ^° C. was heated uniformly from 20 minutes to below and 20 minutes from above to below to dry uniformly, and after drying, the moisture content of the dried body was 2% or less. After drying, the resultant was pulverized with a grinder and classified to select a 150 to 850 IM size to prepare a base resin.

Thereafter, 5 g of water, 2 g of ethylene carbonate (ethylene carbonate), 0.5 g of aluminum sulfate (A1 ₂ S0 ₄ ) were mixed with 100 g of base resin, and then surface crosslinked at 190 ^° C. for 50 minutes, followed by grinding. Using a sieve to obtain a surface-treated superabsorbent polymer having a particle size of 150 to 850. Example 2

The amount of the increase of 5% 1, 6-hexanediol diacrylate dieul diluted usage in the first embodiment, ^"the 5% by weight of polyethylene glycol diacrylate dilution in the acid, and acrylic acid with 50 g instead of 55 g 10 Superabsorbent polymer was prepared in the same manner as in Example 1, except that 1 g was used instead of g. Example 3

In Example 1, the amount of the acrylic acid in the dilution increment of 5 _^0/0 pulley glycol diacrylate with 50 g instead of 46 g, and the dilution to the weight of acrylic acid 5 _^0/0 1,6 nucleic diacrylate A super absorbent polymer was prepared in the same manner as in Example 1, except that 9 g was used instead of 10 g. . Example 4

 In Example 1, the same method as in Example 1 was used except that a meat chopper having a diameter of 6.5 mm was used instead of a meat chopper having a diameter of 8 mm. An absorbent resin was prepared. Example 5

In Example 1, the superabsorbency is the same as in Example 1 except that a meat chopper having a diameter of 10 mm is used instead of a meat chopper having a diameter of 8 mm. Resin was prepared. Comparative Example 1 In Example 1, the amount of 5% by weight of polyethylene glycol diacrylate as the usage rate of 62 g instead of 50 g, and the acrylic acid 5 parts by dilution _^0/0 1,6 nucleic diacrylate diluted acid A super absorbent polymer was prepared in the same manner as in Example 1, except that 21 g was used instead of 10 g. Comparative Example 2

 In Example 1, the amount of 5% by weight of polyethylene glycol diacrylate diluted in acrylic acid is 31 g instead of 50 g, and 5% by weight of 1,6-nucleic acid diol diacrylate diluted in acrylic acid is not used. Super absorbent polymer was prepared in the same manner as in Example 1. . Comparative Example 3

 In Example 1, the amount of 5% by weight polyethylene glycol diacrylate diluted in acrylic acid is 62 g instead of 50 g, and the amount of 5% by weight 1,6-nucleodiol diacrylate diluted in acrylic acid is 10 g. Instead, it is 21 g, and the superabsorbency is the same as in Example 1 except that a meat hopper having a hole diameter of 16 mm is used instead of a meat chopper having a hole diameter of 8 mm. Resin was prepared. Comparative Example 4

In Example 1, the amount of 5% by weight of polyethylene glycol diacrylate diluted in acrylic acid is 31 g instead of 50 g, and 5% by weight ⁰ /. 1,6-nucleic acid diacrylate diluted in acrylic acid is not used. The superabsorbent polymer was prepared in the same manner as in Example 1, except that the meat chopper having a diameter of 16 mm was used instead of the meat chopper having a diameter of 8 mm. . Comparative Example 5

In Example 1, a meat chopper having a diameter of 16 mm is used instead of a meat chopper having a diameter of 8 mm. Superabsorbent polymer was prepared in the same manner as in Example 1, except that. In Examples 1 to 5 and Comparative Examples 1 to 5, main process conditions are shown in Table 2 below.

 Table 2

In Table 1, PEGDA is polyethyleneglycol diacrylate, and HDDA is 1,6-hexanediol diacrylate (1,6-hexanediol diacrylate).

 * The density | concentration of each internal crosslinking agent was made into the density | concentration (ppm) with respect to the total weight of acrylic acid contained in a monomer composition.

Experimental Example

 Evaluation of physical properties of the superabsorbent polymers prepared according to Examples 1 to 5 and Comparative Examples 1 to 5 was carried out in the following manner, and the measured physical properties are shown in Table 3 below.

 (1) Gel Strength

In the production method of the super absorbent polymers of Examples 1 to 5 and Comparative Examples 1 to 5 About the obtained hydrogel polymer, the gel strength was measured by the following method.

 First, 30 g of the hydrogel polymer samples obtained after polymerization were weighed. The weighed sample was sufficiently swollen in 300 g of 0.9% NaCl solution for 1 hour. The hydrogel was cut to a size of 5 mm 5 mm x 5 mm and kept in a closed container until the test was ready.

 The hydrogel was sucked into a filter paper so that no water remained between the particles during testing before placing between the rheometer and the parallel plate.

 The swollen hydrous gel was measured with a rheometer with 2 g. At this time, the test conditions of the rheometer, Plate Gap Size 2 mm; Strain amplitude 1%; Oscilation frequency 10 radian / sec; ambient tempeature 22 ° C; plate 25mm, measured by TA Instruments-AR Series. The measured value was taken for 5 minutes and then averaged. (2) Centrifuge Retention Capacity (CRC)

 According to the European Disposables and Nonwovens Association (ED ANA) standard EDANA WSP 241.2, the water-absorbing capacity by the unloaded absorption ratio of the superabsorbent polymers of Examples 1 to 5 and Comparative Examples 1 to 5 was measured.

That is, the resultant super-absorbent resin W ₀ (g, about 0.2g) after the sealing (seal) placed uniformly on the envelope of the nonwoven fabric was immersed in saline solution of 0.9% by weight at room temperature. After 30 minutes, the envelope was centrifuged and drained at 250 G for 3 minutes, and then the mass W ₂ (g) of the envelope was measured. Moreover, the mass W and (g) at that time were measured after carrying out the same operation without using the super absorbent polymer.

 Using each mass thus obtained, CRC (g / g) was calculated according to the following equation 1 to confirm the water holding capacity.

 [Calculation 1]

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

 In Formula 1,

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

W ^ g) does not use superabsorbent polymer, but 250G using a centrifuge. Device weight measured after dehydration for 3 minutes,

W ₂ (g) is a device weight including the superabsorbent polymer after submerging the superabsorbent polymer in 0.9 mass% physiological saline at room temperature for 30 minutes, followed by dehydration at 250 G for 3 minutes using a centrifuge.

(3) Absorbency under Load (AUL)

 For the superabsorbent resins of Examples 1 to 5 and Comparative Examples 1 to 5, Absorbency under Load (AUL) of 0.9 psi, according to European Disposables and Nonwovens Association (ED ANA) standard EDANA WSP 242.2 ) Was measured.

First, a stainless steel 400 mesh wire was mounted on the bottom of a plastic cylinder having an inner diameter of 25 mm. The superabsorbent polymers W ₀ (g, 0.16 g) of Examples 1 to 5 and Comparative Examples 1 to 5 were evenly sprayed on the wire mesh under conditions of a room temperature and a humidity of 50%, and a load of 5.1 kPa (0.9 psi) was applied thereon. The even more uniform piston has a smaller outer diameter than 25 mm, no cylindrical inner wall, and no up and down movement. At this time, the weight W ₃ (g) of the apparatus was measured.

A glass filter of 90 mm diameter and a thickness of 5 mm was placed inside a petri dish having a diameter of 150 mm, and a physiological saline composed of 0.90 wt% sodium chloride was made at the same level as the upper surface of the glass filter. One sheet of filter paper 90 mm in diameter was loaded thereon. The measuring device was placed on the filter paper and the liquid was absorbed for 1 hour under load. After 1 hour, the measuring device was lifted up and the weight W ₄ (g) was measured.

 Using each mass thus obtained, AUL (g / g) was calculated according to the following equation 2 to confirm the pressure absorbing ability.

 "[Equation 2]

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

 In the formula 2,

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

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

W ₄ (g) moisturizes the superabsorbent polymer for 1 hour under load (0.9 psi). It is the sum total of the weight of the superabsorbent polymer absorbed by the water after supply and the weight of the device capable of applying a load to the superabsorbent polymer.

(4) Free Swell Rate (FSR)

 For the super absorbent polymers of Examples 1 to 5 and Comparative Examples 1 to 5, the absorption rate (FSR) was measured according to the method described in WO 2009/016055.

(5) Saline Flow Conductivity (SFC)

 For the superabsorbent polymers of Examples 1 to 5 and Comparative Examples 1 to 5, solution permeability (SFC) was measured according to the method described in US Pat. No. 5,669,894.

Table 3

As shown in Table 2, the super absorbent polymers of Examples 1 to 5 according to the present invention have a water-retaining capacity (CRC), pressure-absorbing capacity (AUP), solution permeability (SFC) and absorption rate ( It is possible to provide an excellent superabsorbent polymer having a harmonized physical property that exhibits a synergistic effect to a high degree at the same time.

Claims

【Patent Claims】

【Claim 1】

Forming a hydrous gel polymer having a gel strength of 10,000 to 13,000 Pa by performing thermal or photo polymerization on a monomer composition containing a water-soluble ethylenically unsaturated monomer, an internal crosslinking agent, and a polymerization initiator;

Crudely pulverizing the water-containing gel polymer;

^A step of drying the coarsely ground hydrogel polymer;

pulverizing the dried polymer; and

A method for producing a superabsorbent polymer, comprising the step of performing a surface crosslinking reaction by mixing the pulverized polymer with a surface crosslinking agent.

【Claim 2】

According to claim 1,

The step of coarsely pulverizing the water-containing gel polymer is performed by pushing the water-containing gel polymer through an outlet where a hole is formed.

[Claim 3]

According to clause 2,

The hole diameter and the gel strength of the hydrogel polymer satisfy the following equation 1:

[Equation 1]

1140*x + 730 < y < 600*x + 8400

In equation 1 above,

X is the diameter of the hole (unit: mm), and y is the gel strength of the hydrogel polymer before coarse grinding (unit: Pa).

【Claim 4】

According to clause 1,

The internal crosslinking agent has a cure amount of the water-soluble ethylenically unsaturated monomer. A method of producing a superabsorbent polymer, which is a compound having a curing amount of 80% to 200% compared to dose.

【Claim 5】

In clause 1,

The internal crosslinking agent is a compound having a curing amount of 160 to 400 mJ/cni ² , a method of producing a superabsorbent polymer.

【Claim 6】

According to clause 1,

The internal crosslinking agent is 2 selected from the group consisting of polyethyleneglycol diacrylate, hexanediol diacrylate, and ethoxylated trimethylolpropane triacrylate (TMPTA). Method for producing more than one species of superabsorbent polymer.

【Claim 7】

According to clause 1,

The internal crosslinking agent is included in an amount of 4,000 to 7,500 ppm based on the total weight of the water-soluble ethylenically unsaturated monomer contained in the monomer composition.

【Claim 8】

According to clause 1,

A method for producing a superabsorbent polymer, characterized in that it further comprises the step of classifying polymers having a particle size of 150 to 850 μπι before performing a surface cross-linking reaction on the pulverized polymer.

【Claim 9】

According to clause 1,

The centrifugal retention capacity (CRC) of the superabsorbent polymer is 25 gg or more, and A superabsorbent polymer with an absorption capacity (AUL) of 20 g/g or more, an absorption rate (FSR) of 0.2 ⁵ g/g/s or more, and a solution permeability (SFC) of 70* ^10-7 cm ³ *sec/g or more. Manufacturing method.