WO2015156570A1

WO2015156570A1 - Method for producing super-absorbent polymer

Info

Publication number: WO2015156570A1
Application number: PCT/KR2015/003450
Authority: WO
Inventors: 심유진; 백충훈; 김의덕; 오석헌
Original assignee: 한화케미칼 주식회사
Priority date: 2014-04-08
Filing date: 2015-04-07
Publication date: 2015-10-15

Abstract

The present invention relates to a method for producing a super-absorbent polymer. The method for producing a super-absorbent polymer according to the present invention comprises the steps of: polymerizing a monomer composition into a super-absorbent polymer in a polymerization reactor; pulverizing the polymerized super-absorbent polymer; and milling the pulverized polymer particles.

Description

Superabsorbent Resin Manufacturing Method

The present invention relates to a method for producing a super absorbent polymer.

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

As a method for producing such a super absorbent polymer, a method by reverse phase suspension polymerization or a method by aqueous solution polymerization is known. Reverse phase suspension polymerization is disclosed in, for example, Japanese Patent Laid-Open Nos. 56-161408, 57-158209, and 57-198714. As the method by aqueous solution polymerization, a thermal polymerization method for applying polymerization to an aqueous solution and polymerizing it again, and a photopolymerization method for irradiating and polymerizing ultraviolet rays or the like are known.

The superabsorbent polymer is pulverized after polymerization to be used as particles. If the edges have sharp shapes, gel blocking occurs and the fluidity of the fluid decreases.

The problem to be solved by the present invention is to provide a superabsorbent polymer manufacturing method that can smooth the flow and gel permeability (Gel Bed Permeability) by reducing the gel blocking phenomenon by removing the surface edge of the superabsorbent polymer particles.

The objects of the present invention are not limited to the above-mentioned technical problem, and other technical problems not mentioned will be clearly understood by those skilled in the art from the following description.

Method for producing a super absorbent polymer according to an embodiment of the present invention for solving the above problems is a step of polymerizing a monomer composition into a super absorbent polymer in a polymerization reactor, the step of pulverizing the polymerized superabsorbent resin, and the pulverized Milling the resin particles.

The milling step may be performed by mixing the pulverized resin particles and beads.

The beads may have a higher hardness than the resin particles.

The bead may be a ceramic material.

The beads may have an average diameter in the range of 1 mm to 10 mm.

The beads and the resin particles may be mixed in a weight ratio of 1: 0.1 to 1: 1.2.

The milling step may be performed using a planetary mill (rotary mill) in which the rotation and the revolution is performed at the same time.

The idle speed / process radius ratio of the milling step may range from 7 to 30 rpm / cm.

The ratio of the rotating speed to the rotating speed of the milling step may range from 0.1: 1 to 10: 1.

After the milling step may further comprise the step of separating the beads and the resin particles.

The milling step may be made by dry milling.

It may further comprise a surface crosslinking step of crosslinking the surface of the resin particles.

The surface crosslinking step may be performed before the milling step, after the milling step, or before or after the milling step.

Superabsorbent polymer according to an embodiment of the present invention for solving the above problems can be prepared by the above method.

Specific details of other embodiments are included in the detailed description and the drawings.

According to embodiments of the present invention has at least the following effects.

The superabsorbent polymer prepared by the manufacturing method of the present invention may improve the flowability and gel permeability by reducing the edge of the gel by removing sharp edges.

The effects according to the present invention are not limited by the contents exemplified above, and more various effects are included in the present specification.

1 is a schematic diagram of superabsorbent polymer particles before the milling step of the superabsorbent polymer production method according to an embodiment of the present invention.

Figure 2 is a schematic diagram of the super absorbent polymer particles after the milling step of the superabsorbent polymer production method according to an embodiment of the present invention.

3 is a SEM photograph of the super absorbent polymer particles according to the comparative example.

Figure 4 is a SEM photograph of the super absorbent polymer particles according to Example 1.

5 to 7 are schematic diagrams showing an apparatus for measuring gel permeability according to an embodiment of the present invention.

Advantages and features of the present invention and methods for achieving them will be apparent with reference to the embodiments described below in detail with the accompanying drawings. However, the present invention is not limited to the embodiments disclosed below, but will be implemented in various forms, and only the present embodiments are intended to complete the disclosure of the present invention, and the general knowledge in the art to which the present invention pertains. It is provided to fully convey the scope of the invention to those skilled in the art, and the present invention is defined only by the scope of the claims. Like reference numerals refer to like elements throughout. In the drawings, the sizes and relative sizes of layers and regions may be exaggerated for clarity.

Manufacturing method of super absorbent polymer

According to one or more exemplary embodiments, a method of preparing a super absorbent polymer includes polymerizing a monomer composition into a super absorbent polymer in a polymerization reactor, pulverizing the polymerized super absorbent polymer, and milling the pulverized resin particles. It includes.

Although the step of polymerizing the super absorbent polymer is not particularly limited, the monomer composition may be injected into the polymerizer and polymerized. For efficient processing, the polymerization can be carried out continuously using a continuous polymerization reactor. In this case, in order to form superabsorbent resin, although the said monomer composition can be inject | poured and superposed | polymerized on a belt, it is not limited only to this.

As the monomer contained in the monomer composition, the water-soluble ethylenically unsaturated monomer can be used without limitation as long as it is a monomer generally used in the production of superabsorbent polymers. The monomer can be used at least one selected from the group consisting of anionic monomers and salts thereof, nonionic hydrophilic containing monomers, amino group-containing unsaturated monomers and quaternized compounds thereof.

In an exemplary embodiment, acrylic acid, methacrylic acid, maleic anhydride, fumaric acid, crotonic acid, itaconic acid, 2-acryloylethane sulfonic acid, 2-methacryloylethanesulfonic acid, 2- (meth) acryloylpropanesulfonic acid And 2- (meth) acrylamide-2-methylpropanesulfonic acid; at least one anionic monomer or salt thereof; (Meth) acrylamide, N-substituted (meth) acrylate, 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, methoxy polyethylene glycol (meth) acrylate and polyethylene glycol ( One or more nonionic hydrophilic-containing monomers selected from the group consisting of meth) acrylates; Or one or more amino group-containing unsaturated monomers selected from the group consisting of (N, N) -dimethylaminoethyl (meth) acrylate and (N, N) -dimethylaminopropyl (meth) acrylamide, or quaternized products thereof. can do.

The concentration of the water-soluble ethylenically unsaturated monomer in the monomer composition depends on the polymerization time and reaction conditions (feed rate of the monomer composition, irradiation time of heat and / or light, irradiation range, and irradiation strength, belt width, length and moving speed, etc.). Although appropriately selected and used in consideration, in an exemplary embodiment, it may range from 40 to 60% by weight. In this case, it may be efficient in terms of solubility and economics of the monomer.

The monomer composition may further include one or more additives selected from the group consisting of a photopolymerization initiator, a thermal polymerization initiator and a crosslinking agent. A polymerization initiator can be used, selecting the kind appropriately according to whether thermal polymerization, photopolymerization, or thermal polymerization and photopolymerization are selected in a process process.

The photopolymerization initiator is not particularly limited, but for example, diethoxy acetophenone, 2-hydroxy-2-methyl-1-phenylpropan-1-one, 4- (2-hydroxy ethoxy) phenyl- (2 Acetophenone derivatives such as -hydroxy) -2-propyl ketone and 1-hydroxycyclohexylphenyl ketone; Benzoin alkyl ether compounds such as benzoin methyl ether, benzoin ethyl ether, benzoin isopropyl ether, and benzoin isobutyl ether; benzophenone derivatives such as methyl o-benzoyl benzoate, 4-phenyl benzophenone, 4-benzoyl-4'-methyl-diphenyl sulfide, and (4-benzoyl benzyl) trimethylammonium chloride; Thioxanthone compounds; Acyl phosphine oxide derivatives such as bis (2,4,6-trimethylbenzoyl) -phenyl phosphine oxide and diphenyl (2,4,6-trimethylbenzoyl) -phosphine oxide; Or azo systems such as 2-hydroxy methyl propionitrile and 2,2 '-(azobis (2-methyl-N- (1,1'-bis (hydroxymethyl) -2-hydroxyethyl) propion amide) Although a compound etc. can be used 1 type or in mixture of 2 or more types, It is not limited to these.

The thermal polymerization initiator is not particularly limited, but for example, an azo initiator, a peroxide initiator, a redox initiator or an organic halide initiator may be used alone or in combination of two or more thereof. . In addition, sodium persulfate (Na ₂ S ₂ O ₈ ) or potassium persulfate (Potassium persulfate, K ₂ S ₂ O ₈ ) among the thermal polymerization initiators may be mentioned, but is not limited thereto.

In the monomer composition, the content of the photopolymerization initiator and the thermal polymerization initiator can be selected as long as it can exhibit the polymerization initiation effect. In an exemplary embodiment, the photopolymerization initiator may be included in the range of 0.005 to 0.1 parts by weight based on 100 parts by weight of the monomer, and the thermal polymerization initiator may be included in the range of 0.01 to 0.5 parts by weight based on 100 parts by weight of the monomer, but is not limited thereto. no.

The crosslinking agent includes at least one functional group capable of reacting with the substituent of the monomer and at least one ethylenically unsaturated group, or two or more functional groups capable of reacting with the substituent of the monomer and / or with the substituent formed by hydrolyzing the monomer. Crosslinking agents can be used.

In an exemplary embodiment, the crosslinking agent is a poly (meth) acrylate of a polyol having 8 to 12 carbon atoms, a bismethacrylamide having 8 to 12 carbon atoms, a polyol having 2 to 10 carbon atoms or a poly (poly) having a polyol having 2 to 10 carbon atoms. Meta) allyl ether, and the like, and more specific examples thereof include N, N'-methylenebis (meth) acrylate, ethyleneoxy (meth) acrylate, polyethyleneoxy (meth) acrylate, and propyleneoxy (meth) acryl. Glycerol diacrylate, glycerin triacrylate, trimethol triacrylate, triallylamine, triarylcyanurate, triallyl isocyanate, polyethylene glycol, diethylene glycol, propylene glycol, or mixtures of two or more thereof Although these are mentioned, It is not limited only to these.

In the monomer composition, if the crosslinking agent can exhibit a crosslinking effect, its content can be selected and used. In an exemplary embodiment, the crosslinking agent may be included in the range of 0.01 to 0.5 parts by weight based on 100 parts by weight of the monomer, but is not limited thereto.

Each of the at least two polymerization reactors may differ from each other in the composition of the monomer composition. In an exemplary embodiment, each of the at least two polymerization reactors may differ in type, content, or type and content of crosslinking agent in the monomer composition.

The superabsorbent polymer having completed polymerization may be introduced into a cutting device, and the superabsorbent polymer may be cut by a cutter.

In this case, the cutter can cut the superabsorbent resin into patterned pieces.

The cleaved superabsorbent polymer may further comprise the step of further grinding the ground, dried and dried polymer. In some cases, before the milling step, a temporary drying step may be further included to prevent agglomeration and the like in the milling step.

Although it does not specifically limit as a grinding | pulverization method, For example, the apparatus which cuts and extrudes a rubbery elastic body can be used. In an exemplary embodiment, cutter type cutters, chopper type cutters, kneader type cutters, vibratory grinders, impact grinders, friction grinders, and the like can be cited, but not limited thereto.

As a drying method, a dryer and a heating furnace can be used normally. In an exemplary embodiment, hot air dryers, fluidized bed dryers, airflow dryers, infrared dryers, dielectric heating dryers, and the like may be mentioned, but are not limited thereto. The drying temperature is not particularly limited, but may be in the range of 100 to 200 ° C. for preventing thermal degradation and for efficient drying.

The superabsorbent polymer particles pulverized as described above may be pulverized by physical force to include sharp edges on the surface, and the surface may be trimmed through the milling step.

The milling step may be performed by mixing the pulverized resin particles and beads to apply a frictional force to process the surface of the resin particles.

The beads can be used as long as the hardness is higher than that of the resin particles. For example, it may be a ceramic material, but is not limited thereto. Zirconia etc. are mentioned as an example of the said ceramic material, However, It is not limited to this, Any material can be used as long as it is a substance whose hardness is higher than resin particle.

The beads may have a spherical shape for surface edge processing, and the average diameter may be selected according to the size of the resin particles, but may be, for example, in the range of 1 mm to 10 mm, but is not limited thereto.

The mixing ratio of the beads and the resin particles may range from 1: 0.1 to 1: 1.2 by weight ratio of beads: resin particles. If the mixing ratio of the beads and the resin particles is less than 1: 0.1, the surface edge processing efficiency no longer increases, and if the ratio of the beads and the resin particles is greater than 1: 1.2, the frequency of the resin particles contacting the beads may be different from each other to obtain a uniform result. have. For the same reason as above, the mixing ratio of the beads and the resin particles may range from 1: 0.2 to 1: 1.

The milling step can be carried out using a milling apparatus which is generally used. For example, a planetary mill which rotates and rotates at the same time can be used, but is not limited thereto. As described above, when the rotation and the revolution is made at the same time, the beads and the resin particles can be rubbed more smoothly to produce a uniform result.

In an exemplary embodiment, the idle speed / process radius ratio of the milling step may range from 7 to 30 rpm / cm. When the idle speed / process radius ratio is less than 7 rpm / cm, the milling effect due to the idle is insignificant, and when the idle speed is greater than 30 rpm / cm, friction is excessively generated and the amount of fine powder is increased.

In another exemplary embodiment, the ratio of rotational speed to idle speed of the milling step may range from 0.1: 1 to 10: 1. When the ratio of the rotational speed to the idle speed is less than 0.1: 1, the milling effect is insignificant, and when the ratio of the rotational speed is greater than 10: 1, the amount of fines generated increases, which may lower the process efficiency.

In an exemplary embodiment, the method of preparing a super absorbent polymer may further include separating the beads and the resin particles after the milling step.

Separating the beads and the resin particles may be performed using a filter such as a sieve, a mesh, and the like, but is not limited thereto. If two filters are used with different sizes, the beads, the resin particles and the fine powder may be separated at the same time. The size of the filter can be appropriately selected according to the sizes of the beads and the resin particles.

The milling step may consist of liquid milling using liquid media for smooth milling or dry milling without using liquid media. In an exemplary embodiment, it may be performed by dry milling, which may exclude a separate drying process and the like.

In an exemplary embodiment, the method of making the superabsorbent polymer may further comprise crosslinking the surface of the superabsorbent polymer.

Surface crosslinking can be accomplished using, for example, ethylene glycol diglycidyl ether, water and ethanol, but is not limited thereto.

Super Absorbent Resin Particles

EMBODIMENT OF THE INVENTION Hereinafter, the superabsorbent polymer particle of this invention is demonstrated with reference to drawings.

1 is a schematic diagram of superabsorbent polymer particles before the milling step of the superabsorbent polymer production method according to an embodiment of the present invention, Figure 2 is a superabsorbent polymer after the milling step of the superabsorbent polymer production method according to an embodiment of the present invention It is a schematic diagram of a resin particle.

Referring to Figure 1, in the case of the super absorbent polymer particles before the milling step, it can be seen that the cross-linking is vigorously progressed to a specific edge portion in the surface cross-linking process to generate a sharp projecting portion.

On the other hand, referring to FIG. 2, it can be seen that the sharply protruding portion is removed as shown in FIG. 1 through the milling step.

Production Example

After mixing 77.778 g of 50% aqueous sodium hydroxide solution (NaOH) and 88.84 g of water, 100 g of acrylic acid, 0.115 g of polyethylene glycol diacrylate as a crosslinking agent, diphenyl (2,4,6-trimethylbenzoyl) -phosphine jade as a UV initiator 0.033 g of the seeds were mixed to prepare a monomer composition having a concentration of 45% by weight of the hydrophilic monomer.

Thereafter, the monomer composition was added to the polymerizer, and then irradiated with ultraviolet rays through a UV irradiation apparatus, and UV polymerization was performed to prepare a hydrogel polymer.

Thereafter, the hydrogel polymer was transferred to a cutter and then cut. At this time, the water content of the cleaved hydrous gel polymer was 50% by weight.

The cleaved gel polymer was chopped using a meat chopper. The hydrous gel polymer was then dried in a hot air dryer at 180 ° C. for 30 minutes and the dried hydrogel polymer was ground in a pin mill grinder to prepare a base polymer.

Comparative example

The base polymer prepared in Preparation Example was sprayed with a 20% ethylene carbonate aqueous solution at a rate of 5 pph in a surface crosslinking mixer, heat-treated at 180 ° C. for 30 minutes, and then mixed with a surface crosslinked resin at a silica ratio of 0.5 pph to obtain a superabsorbent polymer. Prepared.

Example 1

55 g of the base polymer obtained in the above example and 55 g of the zirconia 5 mm beads were filled in a container, and the planetary bead mill was used for 30 minutes of milling at a rotational speed of 5: 1 and 20 rpm / cm. The beads were filtered by classifying at 0.15 mm.

The filtered base polymer was sprayed onto the powder at a rate of 5 pph in an aqueous 20% ethylene carbonate solution in a surface crosslinking mixer, and heat-treated at 180 ° C. for 30 minutes. The heat-treated powder was mixed with the resin cross-linked at a Silica 0.5 pph ratio and then classified into a standard mesh of ASTM standards to prepare a super absorbent polymer having a particle size of 150 to 850 μm.

Example 2

The base polymer obtained in Preparation Example was sprayed onto the powder at a rate of 5 pph in a 20% aqueous solution of ethylene carbonate in a surface crosslinking mixer, and heat-treated at 180 ° C. for 30 minutes. The heat-treated powder was subjected to the same milling operation as in Example 1. The beads were filtered by classifying 0.85 mm and 0.15 mm meshes, mixed with a resin cross-linked at a Silica 0.5 pph ratio, and classified into a standard mesh of ASTM standard to obtain a superabsorbent polymer having a particle size of 150 to 850 μm.

Experimental Example 1

The SEM image of the base polymer prepared in Comparative Example was measured and shown in FIG. 3, and the SEM image of the base polymer prepared in Example 1 was measured and shown in FIG. 4.

3 and 4, it can be seen that the particles of the base polymer of FIG. On the contrary, it can be seen that the particles of the base polymer of FIG. 4 have rounded corners and are not relatively sharp.

Experimental Example 2

The Centrifuge Retention Capacity (CRC), Absorbency Under Pressure (AUP), gel permeability, flowability, and bulk density of each of the base polymers prepared in Comparative Examples, Examples 1 and 2 were measured, and the results are shown in Table 1 below. Same as CRC and AUP are EDANA WSP 241.2. R3, EDANA WSP 242.2. It was measured according to the R3 standard, flowability and bulk density was measured according to the ASTM D 1895-96 standard.

In addition, gel permeability can be measured using the apparatus of FIG. More specifically, FIG. 6 is an enlarged cross-sectional view of the piston 200 in the apparatus for measuring permeability of FIG. 5, and FIG. 7 is a plan view of a portion projected on the bottom of the piston 200 in FIGS. 5 and 6.

As shown in FIG. 5, the piston 200 is positioned in the vessel 300, and the plurality of perforations 10 are formed in the piston lower portion 100 as shown in FIGS. 6 and 7.

Referring back to FIG. 5, the tank 500 and the vessel 300 are connected to each other, and the amount of the liquid introduced into the vessel 300 by the coke 600 is adjusted, and the lower portion of the vessel 300 is provided. The mesh network 400 is formed, the lower portion of the mesh network 400 is spaced at a predetermined interval, the collection container 700 is located on the scale 800, the inflow through the mesh network 400 from the container 300 The flow rate may be measured using the scale 800 of the weight of the liquid.

Meanwhile, 2.0 g of the base polymer prepared in Comparative Examples, Example 1 and Example 2 was extracted to prepare a sample, and the sample was uniformly spread on the bottom of the cylindrical cell 50. After placing the sampled cylindrical cell 50 on the mesh network 400 of the vessel 300, using the piston 200 to measure the gal height (H1) of the sample before swelling.

Subsequently, the piston 200 is removed, and the sample-folded cylindrical cell 50 is placed on the mesh network 400 of the container 300 and swollen for 60 minutes while pouring 0.9% saline. After 60 minutes, the piston 200 is placed in the container 300, the piston height H2 after swelling is measured, and the height H1 of the piston 200 before swelling and the height H2 of the piston 200 after swelling. The difference between the s) is measured to determine the height of the swollen gel layer (H = H2-H1).

Next, as shown in FIG. 5, the piston 200 is positioned above the cylindrical cell 50, and the coke 600 of the tank 500 containing 0.9% physiological saline is opened to maintain a constant water height of 7.95 cm. do. While applying pressure to the piston 200 corresponding to a 0.3 psi weight, the amount of liquid passing through the gel layer through the computer and the balance 800 is measured at 1 second intervals for 1 minute as a function of time. The velocity Q of the liquid passing through the swollen sample can be found in units of g / s by the linear least-squares method of weight (g) versus time (seconds).

Permeability (cm 2) is obtained by the following equation:

K = [Q * H * μ / [A * ρ * P]

Where K = permeability (cm 2), Q = flow rate (g / sec), H = height of the swollen sample (cm), μ = liquid viscosity (P) (approximately 1 cP for the test solution used in this test), A = cross-sectional area for the liquid flow (28.27 cm 2 for the sample vessel used for this test), ρ = liquid density (g / cm 3) (approximately 1 g / cm 3 for the test solution used for this test), P = hydrostatic pressure ( dynes / cm 2) (typically approximately 7,797 dynes / cm 2). The hydrostatic pressure is calculated from P = ρ * g * h, where ρ = liquid density (g / cm 3), g = gravity acceleration, typically 981 cm / sec ² , h = fluid height, 7.95 cm.

Table 1

	CRC (g / g)	0.7 psi AUP (g / g)	Gel Permeability (x 10 ^-8 cm ² )	Flowability (g / sec)	Bulk density (g / ml)
Comparative Example 1	33	22	8	10	0.68
Example 1	33	24	14	11	0.66
Example 2	33	21	10	11	0.66

As shown in Table 1, Comparative Examples and Examples 1 and 2 can be seen that the CRC and AUP value are similar. In the case of Example 1, the surface edge was removed by milling, followed by the surface cross-linking process to achieve uniform surface crosslinking, and the superabsorbent polymers were placed at even intervals and expanded in a uniform form, thus causing gel blocking. To reduce the gel bed permeability. In addition, through the milling operation, the overall size of the super absorbent polymer is reduced in size, and the angular portion is reduced, thereby reducing the bulk density and improving flowability.

Although the embodiments of the present invention have been described above, the present invention is not limited to the above embodiments and can be manufactured in various forms, and a person of ordinary skill in the art to which the present invention pertains has the technical idea of the present invention. However, it will be understood that other specific forms may be practiced without changing the essential features. Therefore, it should be understood that the embodiments described above are exemplary in all respects and not restrictive.

Claims

Polymerizing the monomer composition into a super absorbent polymer in a polymerization reactor;

Pulverizing the polymerized superabsorbent polymer; And

Method for producing a super absorbent polymer comprising the step of milling the pulverized resin particles.
The method of claim 1,

The milling step is a method of producing a super absorbent polymer is performed by mixing the pulverized resin particles and beads (bead).
The method of claim 2,

The beads are a method of producing a super absorbent polymer having a higher hardness than the resin particles.
The method of claim 2,

The bead is a ceramic manufacturing method of a super absorbent polymer.
The method of claim 2,

The beads are a method of producing a super absorbent polymer having an average diameter in the range of 1 mm to 10 mm.
The method of claim 2,

The beads and the resin particles are mixed in a weight ratio of 1: 0.1 to 1: 1.2 method for producing a super absorbent polymer.
The method of claim 1,

The milling step is a method of producing a super absorbent polymer is carried out using a planetary mill (planetary mill) is the rotation and revolving at the same time.
The method of claim 7, wherein

Revolving speed / process radius ratio of the milling step is a method for producing a super absorbent polymer in the range of 7 to 30 rpm / cm.
The method of claim 7, wherein

Method of producing a super absorbent polymer in the ratio of the rotational speed: the revolution speed of the milling step is in the range of 0.1: 1 to 10: 1.
The method of claim 2,

After the milling step further comprising the step of separating the beads and the resin particles super absorbent polymer production method.
The method of claim 1,

The milling step is a method of producing a super absorbent polymer consisting of dry milling.
The method of claim 1,

Method for producing a super absorbent polymer further comprising a surface crosslinking step of crosslinking the surface of the resin particles.
The method of claim 12,

The surface crosslinking step is carried out before the milling step, after the milling step, or before and after the milling step of producing a super absorbent polymer.
Superabsorbent polymer prepared by the method according to any one of claims 1 to 13.