KR20230037444A - Preparation method for super absorbent polymer - Google Patents

Abstract

The present invention relates to a method for preparing a super absorbent polymer. According to the method for preparing a super absorbent polymer of the present invention, a super absorbent polymer exhibiting improved absorption rate and anti-caking while maintaining excellent absorbent properties can be provided. The method for preparing a super absorbent polymer comprises the steps of forming a hydrogel polymer; mixing and coarsely pulverizing colloidal silica with the hydrogel polymer; forming a base resin by drying, pulverizing, and classifying the coarsely pulverized hydrogel polymer; and forming a surface cross-linking layer by further cross-linking the surface of the base resin in the presence of any one of colloidal silica and fumed silica and a surface cross-linking agent.

Description

Manufacturing method of super absorbent polymer {PREPARATION METHOD FOR SUPER ABSORBENT POLYMER}

The present invention relates to a method for preparing a superabsorbent polymer. More specifically, it relates to a method for preparing a superabsorbent polymer capable of exhibiting improved absorption rate and anti-caking.

Super Absorbent Polymer (SAP) is a synthetic high-molecular substance that has the ability to absorb moisture 500 to 1,000 times its own weight. Material), etc., are named by different names. The superabsorbent polymer as described above has begun to be put into practical use as a sanitary tool, and now, in addition to sanitary products such as paper diapers and sanitary napkins for children, soil retaining agents for gardening, water retention materials for civil engineering and construction, sheets for raising seedlings, and freshness retainers in the food distribution field It is widely used as a material for steaming, steaming, etc.

In most cases, these superabsorbent polymers are widely used in the field of sanitary materials such as diapers and sanitary napkins. In addition, it is necessary to exhibit excellent permeability by maintaining its shape well even in a volume expansion (swelling) state by absorbing water.

However, it is known that it is difficult to improve both the water retention capacity (CRC), which is a physical property representing the basic absorption and water retention capacity of the superabsorbent polymer, and the absorbency under pressure (AUP), which represents the property of retaining moisture absorbed even under external pressure. . This is because when the overall crosslinking density of the superabsorbent polymer is controlled to be low, the water retention capacity may be relatively high, but the crosslinked structure becomes sparse and the gel strength is lowered, thereby reducing the absorbency under pressure. Conversely, when the absorbency under pressure is improved by controlling the crosslinking density to a high level, water is difficult to be absorbed between the dense crosslinked structures, and the basic water retention capacity may be deteriorated. For the above reasons, there is a limit to providing a superabsorbent polymer with improved water retention capacity and absorbency under pressure.

However, with the recent thinning of sanitary materials such as diapers and sanitary napkins, higher absorption performance is required for superabsorbent polymers. Among these, the simultaneous improvement of the water retention capacity and the pressure absorption capacity, which are opposite physical properties, and the improvement of the liquid permeability, etc. are emerging as important tasks.

On the other hand, since the superabsorbent polymer is included in sanitary materials such as diapers, it is often exposed to high temperature/high humidity conditions. However, when the superabsorbent polymer is exposed to high temperature/high humidity conditions, aggregation and/or caking between particles often occurs. When such aggregation and/or caking occurs, processability such as an increase in load during manufacturing and use processes may be reduced, and difficulties may arise in the use of the superabsorbent polymer.

In the past, attempts have been made to reduce caking between the particles by treating the surface of the superabsorbent polymer with inorganic particles such as silica, but the technical requirements for this have not been sufficiently met.

In order to solve the problems of the prior art as described above, the present invention provides a method for manufacturing a super absorbent polymer that enables the manufacture of a super absorbent polymer exhibiting excellent absorption performance, improved absorption rate, and anti-caking. aims to do

In order to achieve the above object, according to one aspect of the present invention,

forming a water-containing gel polymer by performing photopolymerization or thermal polymerization on a monomer composition including an acrylic acid-based monomer having an acidic group and at least partially neutralizing the acidic group, an internal crosslinking agent, and a polymerization initiator;

mixing and coarsely pulverizing colloidal silica with the water-containing gel polymer;

forming a base resin by drying, pulverizing, and classifying the coarsely pulverized hydrogel polymer; and

Forming a surface crosslinking layer by further crosslinking the surface of the base resin in the presence of either colloidal silica or fumed silica and a surface crosslinking agent,

A method for preparing a superabsorbent polymer is provided.

According to the manufacturing method of the super absorbent polymer of the present invention, it is possible to provide a super absorbent polymer exhibiting improved absorption rate and anti-caking while maintaining excellent absorbent properties.

Since the present invention can have various changes and various forms, specific embodiments will be exemplified and described in detail below. However, it should be understood that this is not intended to limit the present invention to the specific disclosed form, and includes all modifications, equivalents, and substitutes included in the spirit and scope of the present invention.

Hereinafter, a method for preparing a superabsorbent polymer according to an embodiment of the present invention will be described in detail.

A method for producing a superabsorbent polymer according to an embodiment of the present invention,

forming a water-containing gel polymer by performing photopolymerization or thermal polymerization on a monomer composition including an acrylic acid-based monomer having an acidic group and at least partially neutralizing the acidic group, an internal crosslinking agent, and a polymerization initiator;

mixing and coarsely pulverizing colloidal silica with the water-containing gel polymer;

forming a base resin by drying, pulverizing, and classifying the coarsely pulverized hydrogel polymer; and

Forming a surface crosslinking layer by further crosslinking the surface of the base resin in the presence of any one of colloidal silica and fumed silica and a surface crosslinking agent.

In the specification of the present invention, "base resin" or "base resin powder" is a polymer obtained by drying and pulverizing acrylic acid-based monomers into particles or powder form, which will be described later by surface modification or surface crosslinking. It means a polymer in a state in which a step has not been performed.

The water-containing gel polymer obtained by polymerization of acrylic acid-based monomers is commercially available as a superabsorbent polymer in powder form after going through processes such as drying, pulverization, classification, and surface crosslinking.

On the other hand, in recent years, not only various absorption properties such as absorbency and liquid permeability in superabsorbent polymers, but also how much dryness can be maintained on the surface of the swollen superabsorbent polymer in actual use of diapers is an important factor in determining diaper characteristics. becoming a measure. In addition, there are several factors that affect the drying state, but the most important cause among them is the deterioration of the gel by ascorbic acid in urine. That is, ascorbic acid contained in urine reacts with the polymer structure of the super absorbent polymer and decomposes the polymer structure, the water-soluble component increases, which is one of the main causes of deterioration of the super absorbent polymer or diaper, which becomes sticky.

Therefore, the inventors of the present invention can increase the strength of the superabsorbent polymer by mixing colloidal silica in the coarsely pulverizing step of the polymer and perform coarse pulverization, thereby effectively preventing deterioration caused by ascorbic acid. In view of this, the present invention has been reached.

In addition, in the surface crosslinking step, surface crosslinking is performed in the presence of colloidal silica or fumed silica, thereby confirming that the caking phenomenon in which superabsorbent polymer particles coagulate with each other under a high temperature and high humidity environment can be effectively prevented. did

As a result, the superabsorbent polymer obtained by the manufacturing method according to an embodiment of the present invention has excellent physical properties such as water retention capacity, absorbency under pressure, liquid permeability, and absorption speed, and can exhibit an anti-caking effect. there is.

This will be described in more detail below.

In the method for preparing the superabsorbent polymer of the present invention, first, photopolymerization or thermal polymerization is performed on a monomer composition including an acrylic acid-based monomer having an acidic group and at least partially neutralizing the acidic group, an internal crosslinking agent, and a polymerization initiator to form a water-containing gel. The step of forming a polymer is carried out.

The monomer composition, which is a raw material of the superabsorbent polymer, includes an acrylic acid-based monomer internal crosslinking agent having an acidic group at least partially neutralized, and a polymerization initiator.

The acrylic acid-based monomer is a compound represented by Formula 1 below:

[Formula 1]

R ¹ -COOM ¹

In Formula 1,

R ¹ is an alkyl group having 2 to 5 carbon atoms including an unsaturated bond;

M ¹ is a hydrogen atom, a monovalent or divalent metal, an ammonium group, or an organic amine salt.

Preferably, the acrylic acid-based monomer includes at least one selected from the group consisting of acrylic acid, methacrylic acid, and monovalent metal salts, divalent metal salts, ammonium salts, and organic amine salts thereof.

Here, the acrylic acid-based monomer may have an acidic group and at least a portion of the acidic group may be neutralized. Preferably, those obtained by partially neutralizing the monomers with an alkali material such as sodium hydroxide, potassium hydroxide, or ammonium hydroxide may be used. In this case, the degree of neutralization of the acrylic acid-based monomer may be 40 to 95 mol%, or 40 to 80 mol%, or 45 to 75 mol%. The range of the degree of neutralization may be adjusted according to final physical properties. However, if the degree of neutralization is too high, neutralized monomers may precipitate out, making it difficult for the polymerization to proceed smoothly. Conversely, if the degree of neutralization is too low, the absorbency of the polymer is greatly reduced, and it may exhibit properties such as elastic rubber that are difficult to handle. there is.

The concentration of the acrylic acid-based monomer may be about 20 to about 60% by weight, preferably about 40 to about 50% by weight, based on the monomer composition including the raw material of the superabsorbent polymer and the solvent, and the polymerization time and The concentration may be appropriate in consideration of the reaction conditions and the like. However, if the concentration of the monomer is too low, the yield of the superabsorbent polymer is low and economic problems may arise. Conversely, if the concentration is too high, a part of the monomer is precipitated or the pulverization efficiency of the polymerized water-containing gel polymer is low. Process problems may occur, and physical properties of the superabsorbent polymer may be deteriorated.

The polymerization initiator used during polymerization in the method for preparing the super absorbent polymer of the present invention is not particularly limited as long as it is generally used in the preparation of the super absorbent polymer.

Specifically, the polymerization initiator may be a thermal polymerization initiator or a photopolymerization initiator according to UV irradiation according to a polymerization method. However, even with the photopolymerization method, since a certain amount of heat is generated by irradiation such as ultraviolet light irradiation and a certain amount of heat is generated according to the progress of the polymerization reaction, which is an exothermic reaction, a thermal polymerization initiator may be additionally included.

As the photopolymerization initiator, any compound capable of forming radicals by light such as ultraviolet light may be used without limitation in its configuration.

Examples of the photopolymerization initiator include benzoin ether, dialkyl acetophenone, hydroxyl alkylketone, phenyl glyoxylate, and benzyl dimethyl ketal. Ketal), acyl phosphine, and alpha-aminoketone (α-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. . More various photoinitiators are well described in 'UV Coatings: Basics, Recent Developments and New Applications (Elsevier 2007)' p115, a book by Reinhold Schwalm, and are not limited to the above examples.

The photopolymerization initiator may be included in a concentration of about 0.01 to about 1.0% by weight based on the monomer composition. If the concentration of the photopolymerization initiator is too low, the polymerization rate may be slowed down, and if the concentration of the photopolymerization initiator is too high, the molecular weight of the superabsorbent polymer may be small and physical properties may be non-uniform.

In addition, as the thermal polymerization initiator, at least one selected from the group consisting of a persulfate-based initiator, an azo-based initiator, hydrogen peroxide, and ascorbic acid may be used. Specifically, examples of the persulfate-based initiator include sodium persulfate (Na ₂ S ₂ O ₈ ), potassium persulfate (K ₂ S ₂ O ₈ ), and ammonium persulfate ((NH ₄ ) ₂ S ₂ O ₈ ), and examples of the azo-based initiator include 2, 2-azobis (2-amidinopropane) dihydrochloride, 2 , 2-azobis- (N, N-dimethylene) isobutyramidine dihydrochloride (2,2-azobis- (N, N-dimethylene) isobutyramidine dihydrochloride), 2- (carbamoyl azo) isobutyronitrile (2-(carbamoylazo)isobutylonitril), 2, 2-azobis[2-(2-imidazolin-2-yl)propane] dihydrochloride (2,2-azobis[2-(2-imidazolin-2- yl)propane] dihydrochloride), 4,4-azobis-(4-cyanovaleric acid), and the like. More various thermal polymerization initiators are well described in Odian's 'Principle of Polymerization (Wiley, 1981)', p203, and are not limited to the above examples.

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

Specific examples of the internal crosslinking agent include N, N'-methylenebisacrylamide, trimethylolpropane tri (meth) acrylate, ethylene glycol di (meth) acrylate, polyethylene glycol (meth) acrylate, and propylene glycol di (meth) acrylate. )Acrylate, polypropylene glycol (meth)acrylate, butanedioldi(meth)acrylate, butylene glycol di(meth)acrylate, diethylene glycol di(meth)acrylate, hexanedioldi(meth)acrylate Acrylate, triethylene glycol di(meth)acrylate, tripropylene glycol di(meth)acrylate, tetraethylene glycol di(meth)acrylate, dipentaerythritol pentaacrylate, glycerin tri(meth)acrylate, pentaerythyl At least one selected from the group consisting of stall tetraacrylate, triarylamine, ethylene glycol diglycidyl ether, propylene glycol, glycerin, and ethylene carbonate may be used.

The internal crosslinking agent may be included in a concentration of about 0.01 to about 0.5% by weight based on the monomer composition to crosslink the polymerized polymer.

In the production method of the present invention, the monomer composition may further include additives such as a thickener, a plasticizer, a storage stabilizer, and an antioxidant, if necessary.

Raw materials such as an acrylic acid-based monomer having an acidic group and neutralizing at least a portion of the acidic group, a photopolymerization initiator, a thermal polymerization initiator, an internal crosslinking agent, 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 composition as long as it can dissolve the above-mentioned components, and 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, cyclohexanone, cyclopentanone, diethylene glycol monomethyl ether, diethylene glycol At least one selected from ethyl ether, toluene, xylene, butyrolactone, carbitol, methyl cellosolve acetate, and N,N-dimethylacetamide may be used in combination.

The solvent may be included in a residual amount excluding the components described above with respect to the total content of the monomer composition.

On the other hand, the method of forming a hydrogel polymer by thermal polymerization or photopolymerization of such a monomer composition is also not particularly limited as long as it is a commonly used polymerization method.

Specifically, the polymerization method is largely divided into thermal polymerization and photopolymerization according to the polymerization energy source. In the case of normal thermal polymerization, it can be carried out in a reactor having an agitation shaft such as a kneader, and in the case of photopolymerization, a movable Although it may proceed in a reactor equipped with a conveyor belt, the above polymerization method is an example, and the present invention is not limited to the above polymerization method.

For example, as described above, the water-containing gel polymer obtained by thermal polymerization by supplying hot air to a reactor such as a kneader equipped with an agitation shaft or heating the reactor is directed to the outlet of the reactor according to the shape of the agitation shaft provided in the reactor. The discharged water-containing gel polymer may be in the form of several centimeters to several millimeters. Specifically, the size of the obtained water-containing gel polymer may vary depending on the concentration and injection speed of the monomer composition to be injected, and a water-containing gel polymer having a weight average particle diameter of 2 to 50 mm may be obtained.

In addition, as described above, when photopolymerization is performed in a reactor equipped with a movable conveyor belt, the form of a water-containing gel polymer usually obtained may be a sheet-like water-containing gel polymer having the width of a belt. At this time, the thickness of the polymer sheet varies depending on the concentration and injection rate of the monomer composition to be injected, but it is preferable to supply the monomer composition so that a polymer 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, production efficiency is low, which is undesirable. When the thickness of the polymer on the sheet exceeds 5 cm, the polymerization reaction does not occur evenly over the entire thickness due to the excessively thick thickness. may not be

At this time, the water-containing gel polymer obtained in this way may have a normal water content of about 40 to about 80% by weight. Meanwhile, throughout the present specification, "moisture content" refers to a value obtained by subtracting the weight of the dry polymer from the weight of the hydrogel polymer as the content of moisture with respect to the total weight of the hydrogel polymer. Specifically, it is defined as a value calculated by measuring the weight loss due to moisture evaporation in the polymer during drying by raising the temperature of the polymer through infrared heating. At this time, the drying condition is a method of raising the temperature from room temperature to about 180 ° C and then maintaining it at 180 ° C. The total drying time is set to 20 minutes including 5 minutes of the temperature raising step, and the moisture content is measured.

Next, a step of coarsely pulverizing by mixing colloidal silica with the water-containing gel polymer is performed.

The colloidal silica refers to silica in which silica particles are stably dispersed in water without precipitation or aggregation, and refers to silica in which at least a part of the surface of the silica particles is ionized. The method for preparing the colloidal silica is not particularly limited, and a known method such as electrodialysis, sol-gel method, ion exchange method, acid-neutralization method, etc. may be used.

The colloidal silica is present in an amount of 0.01 part by weight or more, or 0.02 part by weight or more, or 0.03 part by weight or more, or 0.05 part by weight or more, or 0.08 part by weight or more, or 0.1 part by weight or more with respect to 100 parts by weight of the water-containing gel polymer, It may be added in an amount of 1.0 parts by weight or less, or 0.8 parts by weight or less, or 0.5 parts by weight or less, or 0.2 parts by weight or less. When the content of the colloidal silica is within the above-described range, it is possible to achieve an effect of improving gel strength without deteriorating the water absorption properties of the superabsorbent polymer.

In addition, if the colloidal silica is precipitated without maintaining a colloidal state in the process of being coarsely pulverized together with the water-containing gel polymer, the gel strength improving effect cannot be obtained. It is desirable to do In this respect, the powder state or hydrophobic silica, which is not a colloidal state, does not have an effect of improving gel strength, and thus cannot achieve the effect intended by the present invention.

Colloidal silica that satisfies these conditions may include ST-30, ST-O, ST-N, ST-C or ST-AK manufactured by Nissan Chemical, but the present invention is not limited thereto.

According to the manufacturing method of the present invention, the colloidal silica as described above is added during coarse pulverization, and coarse pulverization is performed in the presence of the colloidal silica, so that the water-containing gel polymer and the colloidal silica are evenly mixed and distributed. The gel strength of the polymer may be improved, and this effect may be maintained in the base resin and the final superabsorbent polymer, and thus the deterioration caused by ascorbic acid may be improved.

The grinder used in the coarse grinding step is not limited in configuration, but specifically, vertical pulverizer, turbo cutter, turbo grinder, rotary cutter mill Any one selected from the group of crushing devices consisting of a cutter mill, a disc mill, a shred crusher, a crusher, a chopper, and a disc cutter. It may include, but is not limited to the above-described examples.

At this time, in the coarsely pulverizing step, the water-containing gel polymer may be pulverized to have a particle diameter of about 2 to about 10 mm.

Grinding to a particle diameter of less than 2 mm is not technically easy due to the high water content of the hydrogel polymer, and also may cause aggregation between the pulverized particles. On the other hand, when grinding with a particle diameter of more than 10 mm, the effect of increasing the efficiency of the subsequent drying step is insignificant.

Next, a step of forming a base resin by drying, pulverizing, and classifying the coarsely pulverized water-containing gel polymer is performed.

A drying temperature in the drying step may be about 150 to about 250 °C. When the drying temperature is less than 150 ° C, the drying time is too long and there is a risk of deterioration in the physical properties of the finally formed super absorbent polymer, and when the drying temperature exceeds 250 ° C, only the surface of the polymer is excessively dried, resulting in a subsequent pulverization process There is a concern that fine powder may be generated in the water, and physical properties of the finally formed superabsorbent polymer may be deteriorated. Therefore, preferably, the drying may be performed at a temperature of about 150 to about 200 °C, more preferably at a temperature of about 160 to about 180 °C.

Meanwhile, the drying time may be about 20 to about 90 minutes in consideration of process efficiency, but is not limited thereto.

As long as the drying method of the drying step is also commonly used as a drying process for hydrogel polymers, the composition may be selected and used without limitation. Specifically, the drying step may be performed by a method such as hot air supply, infrared ray irradiation, microwave irradiation, or ultraviolet ray irradiation. The water content of the polymer after the drying step may be about 0.1 to about 10% by weight.

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

Grinding may be performed so that the particle diameter of the polymer powder obtained after the pulverizing step is 150 to 850 μm. The grinder used to grind to have such a particle size is specifically, a pin mill, a hammer mill, a screw mill, a roll mill, a disc mill, or A jog mill or the like may be used, but the present invention is not limited to the above example.

In addition, in order to manage the physical properties of the superabsorbent polymer powder to be finalized after the pulverization step, the polymer powder obtained after pulverization may be subjected to a process of classifying according to the particle size, and the polymer powder may be prepared in a certain weight ratio according to the particle size range. can be classified.

The classification process may be performed according to a conventional method, such as using a standard sieve according to ASTM regulations, and through this classification process, fine particles having a particle diameter of less than 150 μm and coarse particles greater than 850 μm are separated and removed, and 150 to 850 μm Normal particles of the superabsorbent polymer can be obtained.

A polymer obtained by polymerizing acrylic acid-based monomers in the above-described process is dried and pulverized to form particles or powder, which is referred to as a base resin.

The base resin of the present invention prepared as described above has a water retention capacity (CRC) of 45 g/g or more, or 50 g/g or more, or 51 g/g or more, or 52 g/g or more, measured according to EDANA method WSP 241.3. g or more, but less than or equal to 60 g/g, or less than or equal to 58 g/g, or less than or equal to about 55 g/g.

Although the water retention capacity (CRC) of the base resin is inevitably reduced in the surface crosslinking reaction step described later, according to the present invention, the water retention capacity of the final product can be maintained high as the water retention capacity of the base resin is formed high.

In addition, the base resin of the present invention has a gel strength of 0.1 N or more, or 0.12 N or more, or 0.14 N or more, or 0.15 N or more, and 0.20 N or less, or 0.19 N or less, or a high gel strength range of 0.18 N or less.

Next, a step of forming a surface crosslinking layer by additionally crosslinking the surface of the base resin in the presence of either colloidal silica or fumed silica and a surface crosslinking agent is performed.

In a general method for producing superabsorbent polymers, a surface crosslinking solution containing a surface crosslinking agent is mixed with a dried and pulverized polymer, that is, a base resin, and then heated by heating the mixture to perform a surface crosslinking reaction for the pulverized polymer. carry out

The surface crosslinking step is a step of forming a superabsorbent polymer having more improved physical properties by inducing a crosslinking reaction on the surface of the pulverized polymer in the presence of a surface crosslinking agent. Through this surface crosslinking, a surface crosslinking layer (surface modification layer) is formed on the surface of the pulverized base resin.

In general, since the surface crosslinking agent is applied to the surface of the superabsorbent polymer particle, a surface crosslinking reaction occurs on the surface of the superabsorbent polymer particle, which improves the crosslinkability on the surface of the particle without substantially affecting the inside of the particle. Therefore, the surface cross-linked superabsorbent polymer particles have a higher degree of cross-linking in the vicinity of the surface than in the inside.

According to the manufacturing method of the present invention, in the step of performing the surface crosslinking reaction by mixing the surface crosslinking agent with the base resin, hydrophobic silica, colloidal silica or fumed silica is additionally mixed to perform the surface crosslinking reaction Do it. As a result, colloidal silica or fumed silica is included in the crosslinking structure on the surface crosslinking layer to improve surface crosslinking efficiency, and permeability can be further improved compared to superabsorbent polymers without using colloidal silica or fumed silica. It is possible to effectively prevent a caking phenomenon in which the superabsorbent polymer sites coagulate with each other under the condition of being wet.

More specifically, the colloidal silica or fumed silica is distributed in the surface modification layer on the surface of the base resin, and in the process of swelling by absorbing liquid, the swollen resin particles aggregate or agglomerate with each other according to the increased pressure. It is prevented from falling, and by imparting appropriate hydrophobicity to the surface, it is possible to more easily permeate and spread the liquid. Therefore, it can contribute to improving the absorption rate, liquid permeability, and anti-caking properties of the superabsorbent polymer.

Examples of the colloidal silica include ST-30, ST-O, ST-N, ST-C or ST-AK manufactured by Nissan Chemical, but the present invention is not limited thereto.

Examples of the fumed silica include commercially available silica, for example, silica represented by trade names such as Aerosil, Tixosil, or DM30S, but the present invention is not limited thereto.

The colloidal silica or fumed silica is present in an amount of 0.01 parts by weight or more, or 0.02 parts by weight or more, or 0.03 parts by weight or more, or 0.05 parts by weight or more, or 0.08 parts by weight or more, or 0.1 parts by weight or more, based on 100 parts by weight of the base resin. or more, but may be added in an amount of 1.0 parts by weight or less, or 0.8 parts by weight or less, or 0.5 parts by weight or less, or 0.2 parts by weight or less. When the content of the colloidal silica or fumed silica is within the above-described range, liquid permeability and anti-caking effects can be achieved without deterioration in the absorbent properties of the superabsorbent polymer, and in this respect, the weight part range may be preferable.

A method of mixing the colloidal silica or the fumed silica is not particularly limited as long as it can be uniformly mixed with the base resin, and may be appropriately adopted and used.

For example, the colloidal silica or the fumed silica is mixed in a dry manner before mixing the surface crosslinking solution containing the surface crosslinking agent with the base resin, or is first dispersed in the surface crosslinking solution and then added to the base resin together with the surface crosslinking solution. It can be mixed in a mixed way.

When adding the surface crosslinking agent, water may be further mixed together and added in the form of a surface crosslinking solution. When water is added, there is an advantage that the surface crosslinking agent can be evenly dispersed in the polymer. At this time, the amount of water added is from about 1 to about 10 based on 100 parts by weight of the base resin for the purpose of inducing uniform dispersion of the surface crosslinking agent, preventing agglomeration of the polymer powder, and at the same time optimizing the surface penetration depth of the surface crosslinking agent. It is preferably added in a proportion by weight.

In addition, as long as the surface crosslinking agent is a compound capable of reacting with a functional group of a polymer, there is no limitation in its configuration.

Preferably, a polyhydric alcohol compound as the surface cross-linking agent in order to improve the properties of the resulting superabsorbent polymer; epoxy compounds; polyamine compounds; haloepoxy compounds; condensation products of haloepoxy compounds; oxazoline compounds; mono-, di- or polyoxazolidinone compounds; cyclic urea compounds; polyvalent metal salts; And at least one selected from the group consisting of alkylene carbonate compounds may be used.

Specifically, examples of polyhydric alcohol compounds 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-hexanediol, and At least one selected from the group consisting of 1,2-cyclohexanedimethanol may be used.

In addition, as the epoxy compound, ethylene glycol diglycidyl ether and glycidol may be used, and as the polyamine compound, ethylenediamine, diethylenetriamine, triethylenetetraamine, tetraethylenepentamine, and pentaethylenehexamine , At least one selected from the group consisting of polyethyleneimine and polyamide polyamine may be used.

In addition, as the haloepoxy compound, epichlorohydrin, epibromohydrin, and α-methylepichlorohydrin may be used. Meanwhile, as the mono-, di- or polyoxazolidinone compound, for example, 2-oxazolidinone or the like can be used.

In addition, ethylene carbonate or the like can be used as the alkylene carbonate compound. These may be used alone or in combination with each other. On the other hand, in order to increase the efficiency of the surface crosslinking process, one or more kinds of polyhydric alcohol compounds having 2 to 10 carbon atoms may be included and used among these surface crosslinking agents.

The amount of the surface crosslinking agent added may be appropriately selected depending on the type of the surface crosslinking agent added or reaction conditions, but is usually 0.001 to 5 parts by weight, preferably 0.01 to 3 parts by weight, based on 100 parts by weight of the base resin. , more preferably 0.05 to 2 parts by weight.

If the content of the surface crosslinking agent is too small, surface crosslinking reaction hardly occurs, and if it exceeds 5 parts by weight based on 100 parts by weight of the base resin, excessive surface crosslinking reaction may cause deterioration in water absorption capacity and physical properties. .

On the other hand, in addition to the surface crosslinking agent described above, a polyvalent metal salt, for example, an aluminum salt, more specifically, at least one selected from the group consisting of sulfate, potassium salt, ammonium salt, sodium salt and hydrochloride of aluminum may be further included.

As such a polyvalent metal salt is additionally used, the liquid permeability of the superabsorbent polymer prepared by the method of one embodiment may be further improved. The polyvalent metal salt may be added to the surface crosslinking solution together with the surface crosslinking agent, and may be used in an amount of 0.01 to 4 parts by weight based on 100 parts by weight of the base resin.

Forming a surface crosslinking layer by additionally crosslinking the surface of the base resin is performed by raising the temperature by applying heat to a mixture of the colloidal silica or fumed silica, the base resin, and the surface crosslinking agent.

The elevated temperature is about 80 to about 190 ° C, preferably about 100 to about 180 ° C, more preferably about 110 to about 140 ° C for about 10 to about 90 minutes, preferably about 20 to about 70 minutes. This can be done by heating. If the crosslinking reaction temperature is too low or the reaction time is too short, the surface crosslinking reaction does not occur properly and the permeability may decrease.

The means for raising the temperature for the surface crosslinking reaction is not particularly limited. It can be heated by supplying a heat medium or directly supplying a heat source. At this time, as the type of heat medium that can be used, steam, hot air, heated fluids such as hot oil, etc. can be used, but the present invention is not limited thereto, and the temperature of the heat medium supplied depends on the means of the heat medium, the rate of temperature increase and the temperature rise. It can be selected appropriately in consideration of the target temperature. On the other hand, as the directly supplied heat source, heating through electricity or heating through gas may be mentioned, but the present invention is not limited to the above-described examples.

According to the manufacturing method of the present invention, the base resin has excellent gel strength due to the colloidal silica added during coarse grinding, In addition, a surface crosslinking layer in which silica is distributed in the surface crosslinking structure may be formed by colloidal silica or fumed silica added in the surface crosslinking step.

Therefore, the superabsorbent polymer prepared by the manufacturing method of the present invention has an improved absorption rate without deteriorating physical properties such as water retention capacity and absorbency under pressure due to the characteristics of the base resin and the surface crosslinking layer formed on the base resin. , liquid permeability, and anti-caking properties.

Accordingly, the superabsorbent polymer prepared by the manufacturing method of the present invention has a water retention capacity (CRC) of 35 g/g or more, or 36 g/g or more, or 37 g/g or more, measured according to EDANA method WSP 241.3. g or more, but may range from 45 g/g or less, or 43 g/g or less, or 40 g/g or less.

In addition, the superabsorbent polymer prepared by the production method of the present invention has an absorbency under load (AUP) of 0.7 psi of 20 g/g or more, or 21 g/g or more, and 30 g/g, measured according to the EDANA method WSP 242.3 or less, or 28 g/g or less, or 26 g/g or less.

In addition, the superabsorbent polymer prepared by the manufacturing method of the present invention may have a vortex time of 45 seconds or less, or 43 seconds or less, or 42 seconds or less, or 41 seconds or less. The absorption rate is excellent as the value is small, and the lower limit of the absorption rate is 0 seconds in theory, but may be, for example, 5 seconds or more, 10 seconds or more, or 20 seconds or more.

The absorption rate refers to the time (time, unit: seconds) at which the vortex of the liquid disappears due to rapid absorption when the superabsorbent polymer is added to physiological saline and stirred, and the shorter the time, the higher the superabsorbent polymer can be seen as having a fast initial absorption rate.

In addition, the superabsorbent polymer prepared by the manufacturing method of the present invention may have permeability (unit: seconds) of 50 seconds or less, or 48 seconds or less, or 46 seconds or less, or 45 seconds or less. The liquid permeability is excellent as the value is small, and the lower limit in theory is 0 seconds, but may be, for example, 10 or more, 20 seconds or more, or 30 seconds or more.

The liquid permeability measurement method will be described in more detail in Examples to be described later.

In addition, the superabsorbent polymer prepared by the production method of the present invention has an anti-caking efficiency of 88.0% or more, or 88.5% or more, or 89.0% or more, or 89.5% or more, and 95.0% or less, or 94.0% or less, or 93.0% or less, or 92.0% or less.

The anti-caking efficiency measurement method will be described in more detail in the Examples to be described later.

In addition, the superabsorbent polymer prepared by the manufacturing method of the present invention has a gel strength of 0.70 N or more, or 0.72 N or more, or 0.74 N or more, or 0.75 N or more, and 0.90 N or less, measured according to a tensile/compression test method. , or a high gel strength range of 0.85 N or less, or 0.80 N or less.

The gel strength measurement method will be described in more detail in the Examples to be described later.

In addition, the superabsorbent polymer prepared by the manufacturing method of the present invention has the aforementioned water retention capacity (CRC), absorbency under load (AUP) of 0.7 psi, vortex time, permeability, and anti-caking efficiency. , and at least one or more, preferably two or more, of the range of physical properties of gel strength, and more preferably all of the physical property ranges may be satisfied simultaneously.

As described above, the superabsorbent polymer of the present invention has excellent absorption capacity and can exhibit improved absorption rate, liquid permeability, and anti-caking properties.

The present invention is explained in more detail in the following examples. However, the following examples are merely illustrative of the present invention, and the contents of the present invention are not limited by the following examples.

<Example>

Manufacture of superabsorbent polymer

Example 1

In a 2L glass container equipped with a stirrer and thermometer, 507.8 g of acrylic acid, 0.3 g of ethylene glycol diglycidyl ether (EGDGE) as an internal crosslinking agent, 0.04 g of bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide as a photoinitiator, and heat A water-soluble unsaturated monomer aqueous solution was prepared by mixing 0.76 g of initiator sodium persulfate (SPS), 627.1 g of 31.5% sodium hydroxide solution, 0.51 g of surfactant sodium dodecyl sulfate (SDS), and 238.7 g of distilled water. (degree of neutralization: 70% by mole; solid content: 41% by weight).

Thereafter, when the temperature of the aqueous monomer solution reached 43° C., UV polymerization was performed by irradiating UV light for 1 minute (irradiation amount: 10 mW/cm ² ), and maintained in a polymerization reactor for 2 minutes to obtain a hydrogel polymer. 0.1 part by weight of colloidal silica was added to 100 parts by weight of the obtained hydrogel polymer, and pulverized to a size of 2 mm * 2 mm, and the moisture content (drying at 180 degrees for 40 minutes) was measured and found to be 53%.

The obtained water-containing gel polymer was spread on a stainless wire gauze having a pore size of 600 μm to a thickness of about 30 mm and dried in a hot air oven at 180° C. for 30 minutes. The thus-obtained dry polymer was pulverized using a grinder, and classified using an ASTM standard mesh sieve to obtain a base resin having a particle size of 150 to 850 μm.

Then, based on 100 parts by weight of the prepared base resin, 5.8 parts by weight of water, 3 parts by weight of methanol, 0.5 parts by weight of propylene glycol, 0.1 parts by weight of ethylene glycol diglycidyl ether (EGDGE), and 0.05 parts by weight of colloidal silica After uniformly mixing the surface treatment solution, it was supplied to one surface crosslinking reactor, and a surface crosslinking reaction of the base resin was performed at 130° C. for 40 minutes.

After the surface treatment was completed, a surface-treated superabsorbent polymer having an average particle diameter of 150 to 850 μm was obtained using a sieve.

Example 2

In Example 1, a super absorbent polymer was prepared in the same manner as in Example 1, except that 0.05 part by weight of fumed silica was added instead of adding colloidal silica during surface crosslinking.

Example 3

In Example 1, a superabsorbent polymer was prepared in the same manner as in Example 1, except that 0.03 part by weight of colloidal silica was added during surface crosslinking.

Example 4

In Example 1, a superabsorbent polymer was prepared in the same manner as in Example 1, except that 0.1 part by weight of colloidal silica was added during surface crosslinking.

Example 5

In Example 2, a superabsorbent polymer was prepared in the same manner as in Example 2, except that 0.03 part by weight of fumed silica was added during surface crosslinking.

Example 6

In Example 2, a superabsorbent polymer was prepared in the same manner as in Example 2, except that 0.1 part by weight of fumed silica was added during surface crosslinking.

Comparative Example 1

In Example 1, a superabsorbent polymer was prepared in the same manner as in Example 1, except that colloidal silica was not added during coarse grinding.

Comparative Example 2

In Example 2, a superabsorbent polymer was prepared in the same manner as in Example 2, except that colloidal silica was not added during coarse grinding.

Comparative Example 3

In Example 1, instead of adding colloidal silica during coarse grinding, polymerization was performed by adding 0.1 part by weight of colloidal silica to the monomer composition based on 100 parts by weight of neutralized acrylic acid, and colloidal silica was not added during surface crosslinking. A superabsorbent polymer was prepared in the same manner as in Example 1, except that it was not.

Comparative Example 4

In Example 1, instead of adding colloidal silica during coarse grinding, polymerization was performed by adding 0.1 part by weight of fumed silica to the monomer composition based on 100 parts by weight of neutralized acrylic acid, and colloidal silica was not added during surface crosslinking. A superabsorbent polymer was prepared in the same manner as in Example 1 except for the above.

Comparative Example 5

In Example 1, a superabsorbent polymer was prepared in the same manner as in Example 1, except that colloidal silica was not added during surface crosslinking.

Comparative Example 6

In Example 1, 0.1 part by weight of fumed silica was added to 100 parts by weight of the water-containing gel polymer instead of colloidal silica when coarsely pulverized, and colloidal silica was not added when surface crosslinking was performed in the same manner as in Example 1. A superabsorbent polymer was prepared.

Comparative Example 7

In Example 1, a superabsorbent polymer was prepared in the same manner as in Example 1, except that 0.1 part by weight of fumed silica was added to 100 parts by weight of the hydrogel polymer instead of colloidal silica during coarse grinding.

Comparative Example 8

In Example 1, 0.1 part by weight of fumed silica was added to 100 parts by weight of hydrogel polymer instead of colloidal silica when coarsely pulverized, and 0.05 part by weight of fumed silica was added to 100 parts by weight of base resin during surface crosslinking. A superabsorbent polymer was prepared in the same manner as in Example 1.

The silica input conditions of the Examples and Comparative Examples are summarized in Table 1 below.

polymerization step coarse grinding step surface cross-linking step Example 1 not input colloidal silica, 0.1 part by weight colloidal silica, 0.05 parts by weight Example 2 not input colloidal silica, 0.1 part by weight Fumed silica, 0.05 part by weight Example 3 not input colloidal silica, 0.1 part by weight colloidal silica, 0.03 part by weight Example 4 not input colloidal silica, 0.1 part by weight colloidal silica, 0.1 part by weight Example 5 not input colloidal silica, 0.1 part by weight Fumed silica, 0.03 parts by weight Example 6 not input colloidal silica, 0.1 part by weight Fumed silica, 0.1 part by weight Comparative Example 1 not input not input colloidal silica, 0.05 parts by weight Comparative Example 2 not input not input Fumed silica, 0.05 parts by weight Comparative Example 3 colloidal silica, 0.1 part by weight not input not input Comparative Example 4 Fumed silica, 0.1 part by weight not input not input Comparative Example 5 not input colloidal silica, 0.1 part by weight not input Comparative Example 6 not input Fumed silica, 0.1 part by weight not input Comparative Example 7 not input Fumed silica, 0.1 part by weight colloidal silica, 0.05 part by weight Comparative Example 8 not input Fumed silica, 0.1 part by weight fumed silica,
0.05 parts by weight

<Experimental example>

The physical properties of the superabsorbent polymers prepared in Examples and Comparative Examples were evaluated in the following manner.

Unless otherwise indicated, the following physical property evaluations were all conducted at constant temperature and humidity (23 ± 1 ° C, relative humidity 50 ± 10%), and physiological saline or saline means 0.9 wt% sodium chloride (NaCl) aqueous solution.

In addition, unless otherwise indicated, evaluation of the physical properties of the base resin before surface crosslinking was performed on resins having a particle diameter of 300 μm to 600 μm classified by an ASTM standard sieve, and evaluation of physical properties of the final superabsorbent polymer surface crosslinked was performed. It was performed on resins having a particle diameter of 150 μm to 850 μm classified through an ASTM standard sieve.

(1) Centrifuge Retention Capacity (CRC)

The water retention capacity by water absorption capacity under no load of each resin was measured according to EDANA WSP 241.3.

Specifically, the superabsorbent polymer W ₀ (g) (about 0.2 g) was uniformly put into a bag made of nonwoven fabric, sealed, and immersed in physiological saline (0.9% by weight) at room temperature. After 30 minutes, water was drained from the bag for 3 minutes under the condition of 250 G using a centrifuge, and the mass W ₂ (g) of the bag was measured. Moreover, after carrying out the same operation without using resin, the mass _W1 (g) at that time was measured. Using each obtained mass, CRC (g/g) was calculated according to the following equation.

[Equation 1]

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

(2) Absorbency under Pressure (AUP)

The absorbency under pressure of 0.7 psi of each resin was measured according to the EDANA method WSP 242.3.

Specifically, a stainless steel 400 mesh wire mesh was attached to the bottom of a plastic cylinder having an inner diameter of 60 mm. Under conditions of room temperature and 50% humidity, superabsorbent polymer W ₀ (g) (0.9 g) is uniformly sprayed on a wire mesh, and a piston capable of uniformly applying a load of 0.7 psi thereon is slightly larger than the outer diameter of 60 mm. It is small and has no gaps with the inner wall of the cylinder, so that up and down movement is not hindered. At this time, the weight W ₃ (g) of the device was measured.

A glass filter having a diameter of 90 mm and a thickness of 5 mm was placed inside a petro dish having a diameter of 150 mm, and physiological saline solution composed of 0.9% by weight sodium chloride was leveled with the top surface of the glass filter. One sheet of filter paper having a diameter of 90 mm was placed thereon. The measuring device was placed on a filter paper, and the liquid was absorbed for 1 hour under a load. After 1 hour, the measuring device was lifted up and its weight W ₄ (g) was measured.

Using each obtained mass, the absorbency under load (g/g) was calculated according to the following formula.

[Equation 2]

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

(3) Permeability

Permeability was measured according to the method described in Patent No. US9656242 B2.

The device for measuring liquid permeability is a chromatography tube with an inner diameter of 20 mm and a glass filter installed at the bottom. Lines were marked on the liquid levels of 20 ml and 40 ml of liquid in the state where the piston was inserted into the chromatography tube. Thereafter, water was added in reverse to prevent bubbles from forming between the glass filter at the bottom of the chromatography tube and the cock, and about 10 ml was filled, washed 2 to 3 times with saline, and 0.9% saline was filled up to 40 ml or more. The time (B) for the liquid level to decrease from 40 ml to the 20 ml mark was recorded by inserting the piston into the chromatography tube and opening the lower valve.

Leaving 10 ml of saline in the chromatography tube, 0.2 ± 0.0005 g of the superabsorbent polymer sample classified (300 μm to 600 μm) was added and saline was added to make the volume of the saline solution to 50 ml, and then allowed to stand for 30 minutes. After that, put a piston (0.3psi=106.26g) with a weight in the chromatography tube, leave it for 1 minute, open the bottom valve of the chromatography tube, record the time (T1) for the liquid level to decrease from 40ml to the 20ml mark, and record T1 - The time of B (unit: seconds) was calculated.

(4) Absorption rate (Vortex time)

The absorption rate (vortex time) was measured in seconds according to the method described in International Publication No. 1987-003208.

Specifically, 2 g of superabsorbent polymer was added to 50 mL of physiological saline at 23 ° C to 24 ° C, and the magnetic bar (diameter 8 mm, length 30 mm) was stirred at 600 rpm, until the vortex disappeared. was calculated by measuring in seconds.

(5) anti-caking efficiency

The weight of a Petri-dish with a diameter of 9 cm was accurately weighed and recorded (W1). 2 ± 0.01 g of the superabsorbent polymer sample was precisely weighed and evenly sprayed on the Petri-dish, placed in a constant temperature and humidity chamber set at a temperature of 40 ° C and a humidity of 80% RH, and left for 10 minutes. After 10 minutes, the Petri-dish was taken out and turned over on A4 paper and left for 5 minutes. After 5 minutes, the weight of the sample dropped on the floor (S1) and the weight of the Petri-dish (S2) were accurately recorded. Anti-caking efficiency (A/C efficiency) was calculated according to Equation 3 below using the measured values.

[Equation 3]

Anti-caking efficiency (%) = [S1/(S2-W1) + S1] x 100

(6) Gel strength

2.5 ± 0.01 g of the super absorbent polymer sample was precisely weighed and evenly sprinkled in a 100 ml capacity beaker, and 50 ml of a mixture solution in which ascorbic acid was dissolved at a concentration of 0.005 wt % in physiological saline (0.9 wt % saline) was added. After wrapping the beaker containing the swollen superabsorbent polymer with plastic wrap, it was placed in an oven set at 40° C. and degraded for 24 hours. After 24 hours, take out the beaker, put it on a stand for measuring gel strength (FGS-50E-H, SHIMPO Co., Japan), and use a tensile/compression tester (FGP-2, SHIMPO Co., Japan) attached to the stand. Swelling in the beaker Pressure was applied to the superabsorbent polymer. At this time, the value indicated on the tensile/compression tester was recorded as gel strength.

The physical property values of the Examples and Comparative Examples are listed in Table 2 below.

Base resin before surface crosslinking Superabsorbent polymer after surface crosslinking division CRC gel strength CRC 0.7psi AUP Anti-caking gel strength Permeability Vortex unit g/g N g/g g/g % N candle candle Example 1 53.8 0.16 36.4 22.5 88.7 0.78 43 41 Example 2 53.8 0.16 38.3 21.0 89.9 0.76 45 40 Example 3 53.8 0.16 36.3 22.4 88.5 0.77 44 41 Example 4 53.8 0.16 37.1 22.2 89.0 0.82 38 40 Example 5 53.8 0.16 38.2 21.1 89.7 0.75 45 41 Example 6 53.8 0.16 38.3 21.3 90.1 0.79 41 40 Comparative Example 1 52.9 0.08 36.2 21.8 72.1 0.52 80 43 Comparative Example 2 52.9 0.08 37.4 19.8 78.1 0.42 85 45 Comparative Example 3 52.5 0.1 37.7 22.1 80.9 0.48 141 44 Comparative Example 4 51.6 0.1 37.7 18.1 83.1 0.45 94 44 Comparative Example 5 53.8 0.16 37.8 25.3 83.1 0.77 48 42 Comparative Example 6 50.4 0.15 37.6 26.5 92.3 0.71 59 45 Comparative Example 7 50.4 0.15 36.9 19.6 90.8 0.73 53 48 Comparative Example 8 50.4 0.15 37.8 19.1 92.8 0.69 64 40

Referring to Table 2, it was confirmed that Examples 1 to 6 of the present invention all exhibited high gel strength, excellent absorption properties, absorption rate, liquid permeability, and anti-caking efficiency.

On the other hand, Comparative Examples 1 to 4 in which colloidal silica was not added during coarse grinding showed low gel strength and anti-caking efficiency, and in addition, it can be seen that the liquid permeability is not better than that of Examples.

In Comparative Example 5, silica was not added during surface crosslinking, and liquid permeability and anti-caking efficiency were low. In Comparative Examples 6 to 8, fumed silica was added instead of colloidal silica during coarse grinding, so gel strength and liquid permeability were low. .

Claims (11)

forming a water-containing gel polymer by performing photopolymerization or thermal polymerization on a monomer composition including an acrylic acid-based monomer having an acidic group and at least partially neutralizing the acidic group, an internal crosslinking agent, and a polymerization initiator;
mixing and coarsely pulverizing colloidal silica with the water-containing gel polymer;
forming a base resin by drying, pulverizing, and classifying the coarsely pulverized hydrogel polymer; and
Forming a surface crosslinking layer by further crosslinking the surface of the base resin in the presence of either colloidal silica or fumed silica and a surface crosslinking agent,
A method for producing a superabsorbent polymer.
According to claim 1,
In the step of mixing and coarsely pulverizing the colloidal silica with the water-containing gel polymer, the colloidal silica is included in an amount of 0.01 to 1.0 parts by weight based on 100 parts by weight of the water-containing gel polymer.
According to claim 1,
In the step of additionally crosslinking the surface of the base resin to form a surface crosslinking layer, the colloidal silica or fumed silica is included in 0.01 to 1.0 parts by weight based on 100 parts by weight of the base resin.
According to claim 1,
The base resin has a gel strength of 0.1 N or more, measured according to a tensile/compression test method.
Manufacturing method of superabsorbent polymer.
According to claim 1,
The base resin has a water retention capacity (CRC) of 45 g / g or more, measured according to EDANA method WSP 241.3,
A method for producing a superabsorbent polymer.
According to claim 1,
The super absorbent polymer has a water retention capacity (CRC) of 35 g/g or more, measured according to EDANA method WSP 241.3,
A method for producing a superabsorbent polymer.
According to claim 1,
The superabsorbent polymer has an absorbency under load (AUP) of 0.7 psi of 20 g/g or more, measured according to EDANA method WSP 242.3.
A method for producing a superabsorbent polymer.
According to claim 1,
The super absorbent polymer has a permeability (unit: second) of 50 seconds or less, a method for producing a super absorbent polymer.
According to claim 1,
The superabsorbent polymer has a vortex time of 45 seconds or less by the vortex method,
A method for producing a superabsorbent polymer.
According to claim 1,
The superabsorbent polymer has an anti-caking efficiency of 88.0% or more,
A method for producing a superabsorbent polymer.
According to claim 1,
The superabsorbent polymer has a gel strength of 0.70 N or more, measured according to a tensile/compression test method.
A method for producing a superabsorbent polymer.