KR20200051564A - Super absorbent polymer - Google Patents

Abstract

The present invention relates to a super absorbent polymer exhibiting excellent thermal stability and, more specifically, to a super absorbent polymer comprising: base resin powder; and a surface cross-linking layer.

Description

Super absorbent polymer {SUPER ABSORBENT POLYMER}

The present invention relates to a super absorbent polymer exhibiting excellent thermal stability.

Super Absorbent Polymer (SAP) is a synthetic polymer material that has the ability to absorb about 500 to 1,000 times its own weight, and SAM (Super Absorbency Material), AGM (Absorbent Gel) for each developer Material). The superabsorbent polymer as described above began to be put into practical use as a sanitary tool, and now, in addition to sanitary products such as children's paper diapers and sanitary napkins, soil repair agents for horticulture, civil engineering, construction materials, nursery sheets, and freshness retention agents in the food distribution field And materials for poultice.

In most cases, these superabsorbent polymers are widely used in the field of sanitary materials such as diapers and sanitary napkins. For this purpose, it is necessary to exhibit high absorbency for moisture, etc., and the absorbed moisture should not escape even under external pressure. In addition to this, it is necessary to show good permeability by absorbing water and maintaining the shape well even in a volume expanded (swelled) state.

However, it is known that the water retention capacity (CRC), which is a property that shows the basic water absorption and water retention capacity of the super absorbent polymer, and the pressure absorption capacity (AUL), which exhibits the property of retaining moisture absorbed by external pressure, are difficult to improve together. . 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 crosslinking structure becomes coarse and the gel strength is lowered, so that the absorption capacity under pressure may be lowered. Conversely, when the absorption capacity under pressure is improved by controlling the crosslinking density to be high, water absorption between the dense crosslinked structures becomes difficult, and thus the basic water retention capacity may be reduced.

For the above-mentioned reasons, there was a limit in providing a super absorbent polymer with improved water retention capacity and absorbency under pressure. To solve this, various attempts have been made to improve these properties together by adjusting the type or amount of the internal crosslinking agent or the surface crosslinking agent, but these attempts have encountered limitations.

In addition, in the process of producing hygiene materials such as diapers and sanitary napkins, the superabsorbent polymer cannot be avoided from being exposed to high temperatures. Accordingly, the superabsorbent polymer applied to the hygiene material exhibits reduced absorption characteristics compared to the superabsorbent polymer immediately after synthesis. The deterioration of the absorbent properties of the superabsorbent polymer is directly related to the deterioration of the physical properties of the hygiene material, and the development of a technology that enables the production of a superabsorbent polymer having excellent thermal stability is continuously required.

Accordingly, the present invention provides a super absorbent polymer exhibiting excellent thermal stability.

According to an embodiment of the present invention, in the presence of an internal crosslinking agent and an inorganic substance, the water-soluble ethylenically unsaturated monomer having an acidic group in which at least a part is neutralized contains 80% by weight or more of the compound represented by the following general formula 1 A base resin powder comprising a crosslinked polymerized crosslinked polymer; And the cross-linked polymer is further cross-linked, including a surface cross-linked layer formed on the base resin powder, the high water absorption at a high temperature calculated by the following equation 1, the change rate (Y) of the superabsorbent 3% to 4% Resin is provided.

[Formula 1]

In Chemical Formula 1, R ¹ is propane-1,3-diyl or propane-1,2-diyl, and R ² is hydrogen or a methyl group.

[Calculation formula 1]

Y = {[P ₁ -P ₂ ] / P ₁ } * 100

In the above formula 1,

Y is the rate of change in absorption characteristics at high temperatures,

P ₁ is the sum of centrifugal water retention capacity (CRC) for physiological saline of a superabsorbent polymer measured before exposure to high temperature and pressure absorption capacity (AUL) of 0.7 psi for physiological saline,

P ₂ is the sum of CRC and AUL of the superabsorbent polymer measured after leaving the superabsorbent polymer in an oven at 185 ° C. for 60 minutes.

P ₁ calculated according to Formula 1 of the superabsorbent polymer may be 68 to 85 g / g. In addition, P ₂ calculated according to Formula 1 of the superabsorbent polymer may be 65 to 85 g / g.

The base resin powder is crosslinked polymerized in the presence of an internal crosslinking agent and an inorganic substance, wherein at least a portion of the water-soluble ethylenically unsaturated monomer having a neutralized acidic group contains at least 80% by weight based on the total weight of the internal crosslinking agent. Crosslinked polymers.

The minerals are montmorillonite, saponite, nontronite, laponite, beidelite, hectorite, soconite, stevensite ), Vermiculite, volkonskoite, magadite, medmontite, kenyaite, kaolin mineral, serpentine mineral, mica ) Minerals, chlorite minerals, sepolite, palygorskite, bauxite silica, alumina, titania or mixtures thereof.

According to one embodiment of the present invention, unlike the conventional common sense that the water retention capacity and the pressure absorption capacity are inversely related to each other, the physical properties such as the water retention capacity and the pressure absorption capacity are improved together to provide a super absorbent polymer that exhibits excellent properties. can do. In addition, the super absorbent polymer can maintain excellent absorbing properties even when exposed to high temperatures due to its excellent thermal stability. Accordingly, when the superabsorbent polymer is used, it is possible to fundamentally solve the problems and technical demands of the existing superabsorbent polymer, and provide various hygiene products and the like having superior properties.

Hereinafter, a super absorbent polymer according to a specific embodiment of the present invention and a method of manufacturing the same will be described.

According to an embodiment of the present invention, in the presence of an internal crosslinking agent and an inorganic substance, the water-soluble ethylenically unsaturated monomer having an acidic group in which at least a part is neutralized contains 80% by weight or more of the compound represented by the following general formula 1 A base resin powder comprising a crosslinked polymerized crosslinked polymer; And the cross-linked polymer is further cross-linked, including a surface cross-linked layer formed on the base resin powder, the high water absorption at a high temperature calculated by the following equation 1, the change rate (Y) of the superabsorbent 3% to 4% Resin is provided.

[Formula 1]

In Chemical Formula 1, R ¹ is propane-1,3-diyl or propane-1,2-diyl, R ² is hydrogen or a methyl group,

[Calculation formula 1]

Y = {[P ₁ -P ₂ ] / P ₁ } * 100

In the above formula 1,

Y is the rate of change in absorption characteristics at high temperatures,

P ₁ is the centrifuge retention capacity for physiological saline (CRC, unit: g / g) of the superabsorbent polymer measured before exposure to high temperature, and the pressure absorption capacity of 0.7 psi for physiological saline (AUL, unit: g / g). Is the sum of

P ₂ is the sum of CRC and AUL of the superabsorbent polymer measured after leaving the superabsorbent polymer in an oven at 185 ° C. for 60 minutes.

In general, when the super absorbent polymer is exposed to high temperatures, the absorption characteristics are deteriorated due to heat deformation. As a result of the experiment, the present inventors have confirmed that if a superabsorbent polymer is prepared in the presence of a specific amount of a thermally decomposable internal crosslinking agent, the absorbent properties can be maintained at an excellent level even when the superabsorbent polymer is exposed to high temperatures. The superabsorbent polymer exhibiting such excellent thermal stability has a rate of change in absorption characteristics at a high temperature calculated by Equation 1 above-3% to 4%.

For a more specific method for measuring the rate of change in absorption characteristics at high temperature, reference may be made to the contents described in Test Examples to be described later.

In contrast to the conventional common knowledge that the water absorption capacity and the pressure absorption capacity are inversely related to each other, the superabsorbent polymer having an absorption characteristic conversion rate at -3% to 4% at a high temperature calculated by the calculation formula 1 according to an embodiment is different from the water retention capacity. And the physical properties such as the pressure absorption capacity can be improved together, all exhibit excellent properties. Accordingly, P ₁ in Formula 1 may be 68 to 85 g / g or 70 to 85 g / g, and P ₂ may be 65 to 85 g / g or 70 to 85 g / g.

The superabsorbent polymer according to an embodiment is the presence of an internal crosslinking agent and an inorganic substance containing at least 80% by weight of the compound represented by Chemical Formula 1, wherein the water-soluble ethylenically unsaturated monomer having an acidic group in which at least a part is neutralized, based on the total weight of the internal crosslinking agent A base resin powder comprising a crosslinked polymer crosslinked under polymerization; And a surface crosslinking layer formed on the base resin powder by further crosslinking the crosslinked polymer.

[Formula 1]

In Chemical Formula 1, R ¹ is propane-1,3-diyl or propane-1,2-diyl, and R ² is hydrogen or a methyl group.

The compound represented by Formula 1 is a thermally decomposable internal crosslinking agent, and the internal crosslinked structure derived from the compound of Formula 1 can be decomposed by heat. Accordingly, crosslinking polymerization of the water-soluble ethylenically unsaturated monomer in the presence of the compound of Chemical Formula 1 can provide a crosslinked polymer into which a thermally decomposable internal crosslinking structure is introduced. Then, when such a crosslinked polymer is introduced into a subsequent process at a high temperature, at least a portion of the crosslinked structure derived from the compound of Formula 1 in the crosslinked polymer is decomposed. Accordingly, the internal crosslinking density in the crosslinked polymer is reduced. On the other hand, the crosslinked polymer surface is additionally crosslinked by a surface crosslinking agent, thereby increasing the external crosslinking density. Therefore, when crosslinking polymerization is performed using the compound represented by Chemical Formula 1 and after a subsequent process, the internal crosslinking structure in the crosslinked polymer is decomposed, and the surface of the crosslinked polymer is further crosslinked so that the crosslinking density increases from the inside of the resin to the outside. Increasingly superabsorbent resins can be obtained.

The superabsorbent polymer thus prepared may have a reduced internal crosslinking density than the base resin of the existing superabsorbent polymer. Accordingly, the superabsorbent polymer can exhibit relatively improved water retention capacity compared to the existing superabsorbent polymer. In addition, the superabsorbent polymer may have a surface crosslinking layer thicker than that of the existing superabsorbent polymer because surface crosslinking proceeds after the internal crosslinking is decomposed or decomposed. Accordingly, the superabsorbent polymer can exhibit excellent absorbency under pressure. Therefore, as the crosslinking density of the superabsorbent polymer of one embodiment increases from the inside to the outside, unlike the conventional common sense that water retention capacity and pressure absorption capacity are inversely related to each other, properties such as water retention capacity and pressure absorption capacity are together. It can be improved to show all excellent properties.

In addition, the superabsorbent polymer can maintain excellent absorbent properties even when the superabsorbent polymer is exposed to high temperatures due to the thermally decomposable internal crosslinking structure remaining in the resin. Accordingly, the superabsorbent polymer has a value at which the rate of change in absorption characteristics at high temperatures calculated by Equation 1 is very small. After all, the superabsorbent polymer of one embodiment can fundamentally solve the problems and technical demands of the existing superabsorbent polymer, and can exhibit more excellent absorbent properties and thermal stability.

Hereinafter, a method for manufacturing a super absorbent polymer of one embodiment, and the like will be described in more detail.

The superabsorbent polymer according to the above embodiment includes an internal crosslinking agent and an inorganic substance containing at least a portion of a water-soluble ethylenically unsaturated monomer having a neutralized acidic group in an amount of 80% by weight or more based on the total weight of the internal crosslinking agent. Crosslinking polymerization in the presence to form a hydrogel polymer; Drying the hydrogel polymer to form a base resin powder; And forming a surface crosslinking layer by further crosslinking the surface of the base resin powder in the presence of a surface crosslinking agent.

[Formula 1]

In Chemical Formula 1, R ¹ is propane-1,3-diyl or propane-1,2-diyl, and R ² is hydrogen or a methyl group.

In the step of forming the hydrogel polymer, a hydrogel polymer is formed by crosslinking and polymerizing a monomer mixture including a water-soluble ethylenically unsaturated monomer having an acidic group at least partially neutralized and an internal crosslinking agent.

The water-soluble ethylenically unsaturated monomers include (meth) acrylic acid, maleic acid, maleic anhydride, fumaric acid, crotonic acid, itaconic acid, sorbic acid, vinylphosphonic acid, vinylsulfonic acid, allylsulfonic acid, 2- (meth) acryloylethane Anionic monomers and salts thereof of sulfonic acid, 2- (meth) acryloyloxyethanesulfonic acid, 2- (meth) acryloylpropanesulfonic acid or 2- (meth) acrylamido-2-methylpropanesulfonic acid; (Meth) acrylamide, N-substituted (meth) acrylamide, 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, methoxypolyethylene glycol (meth) acrylate or polyethylene glycol ( Nonionic hydrophilic monomers of meth) acrylate; And an amino group-containing unsaturated monomer of (N, N) -dimethylaminoethyl (meth) acrylate or (N, N) -dimethylaminopropyl (meth) acrylamide and a quaternary product thereof. It can contain.

In the present specification, the term 'water-soluble ethylenically unsaturated monomer having at least a partially neutralized acid group' includes a monomer having an acidic group in the water-soluble ethylenically unsaturated monomer, and at least some of the acidic groups of the monomer having the acidic group are neutralized. Means

In particular, the water-soluble ethylenically unsaturated monomer may be composed of a monomer (a salt of an anionic monomer) that neutralizes at least a portion of an acidic group included in the anionic monomer.

More specifically, as the water-soluble ethylenically unsaturated monomer, acrylic acid or a salt thereof may be used, and when acrylic acid is used, at least a part of it may be neutralized and used. The use of these monomers makes it possible to produce superabsorbent polymers with better physical properties. For example, when the alkali metal salt of acrylic acid is used as the water-soluble ethylenically unsaturated monomer, acrylic acid may be used by neutralizing with a neutralizing agent such as caustic soda (NaOH). At this time, the degree of neutralization of the acrylic acid can be adjusted to about 50 to 95 mol% or about 60 to 85 mol%, and within this range, it is possible to provide a super absorbent polymer having excellent water retention capacity without fear of precipitation during neutralization.

In the monomer mixture containing the water-soluble ethylenically unsaturated monomer, the concentration of the water-soluble ethylenically unsaturated monomer is about 20 to about 60% by weight relative to the total monomer mixture containing each raw material, a polymerization initiator, and a solvent to be described later, or It may be about 25 to about 50% by weight, it may be a suitable concentration in consideration of polymerization time and reaction conditions. However, if the concentration of the monomer is too low, the yield of the super absorbent polymer is lowered, and economic problems may occur. Conversely, when the concentration is too high, a part of the monomer precipitates or the grinding efficiency of the polymerized hydrogel polymer is low. Such problems may occur in the process and physical properties of the super absorbent polymer may be deteriorated.

As the internal crosslinking agent, a compound represented by the formula (1) is used to introduce an internal crosslinking structure that can be decomposed by heat to the crosslinking polymer of the water-soluble ethylenically unsaturated monomer.

R ¹ of Formula 1 may be propane-1,3-diyl or propane-1,2-diyl.

R ¹ is the listed divalent organic group the compound of formula (I) can provide an internal cross-linked structure that facilitates the resolution controlled by the thermal energy, the by-product or a number of components for changing the overall physical properties of the superabsorbent resin after decomposition May not generate.

The internal crosslinking agent may include the compound represented by Formula 1 in 80% by weight to 100% by weight, 85 to 100% by weight, 90 to 100% by weight, 95 to 100% by weight, or 100% by weight relative to the total weight of the internal crosslinking agent. Can be. Within this range, the superabsorbent polymer according to one embodiment of the present invention may have a desired level of crosslink density gradient and thermal stability. For example, the internal crosslinking agent may be made of a compound represented by Chemical Formula 1, that is, when the total amount of internal crosslinking agent is a compound represented by Chemical Formula 1, excellent thermal stability can be secured together with excellent absorption characteristics.

When the compound represented by Chemical Formula 1 is used in an amount of less than 80% by weight and less than 100% by weight based on the total weight of the internal crosslinking agent, the internal crosslinking agent may include the existing internal crosslinking agent in the remaining content. As such an existing internal crosslinking agent, a compound containing two or more crosslinkable functional groups in a molecule can be used. The existing internal crosslinking agent may include a double bond between carbons as a crosslinkable functional group for a smooth crosslinking polymerization reaction of the aforementioned water-soluble ethylenically unsaturated monomer. Specifically, existing internal crosslinking agents include polyethylene glycol diacrylate (PEGDA), glycerin diacrylate, glycerin triacrylate, unmodified or ethoxylated trimethylolpropane triacrylate (TMPTA), hexanediol diacrylate, One or more selected from the group consisting of allyl (meth) acrylate and triethylene glycol diacrylate may be used.

The internal crosslinking agent may be used in an amount of 0.01 to 5 parts by weight, 0.01 to 3 parts by weight, 0.1 to 3 parts by weight, or 0.2 to 1.5 parts by weight based on 100 parts by weight of the water-soluble ethylenically unsaturated monomer. At this time, the content of the water-soluble ethylenically unsaturated monomer is based on the weight of the water-soluble ethylenically unsaturated monomer before the acidic group of the monomer having an acidic group included in the water-soluble ethylenically unsaturated monomer is neutralized. For example, when the water-soluble ethylenically unsaturated monomer contains acrylic acid, the content of the internal crosslinking agent may be adjusted based on the weight of the monomer before neutralizing acrylic acid.

In addition, the internal crosslinking agent may be used in an appropriate concentration with respect to the monomer mixture.

The internal crosslinking agent may be used within the above-described range to provide a superabsorbent polymer having an appropriate crosslinking density gradient, simultaneously improving water retention capacity and pressure absorption capacity, and exhibiting excellent thermal stability.

On the other hand, the monomer mixture may include an inorganic material to prepare a super absorbent polymer exhibiting excellent absorption properties. Accordingly, the superabsorbent polymer is a water-soluble ethylenically unsaturated monomer having an acidic group in which at least a part is neutralized, in the presence of an internal crosslinking agent and an inorganic substance containing 80% by weight or more based on the total weight of the internal crosslinking agent. And a base resin powder comprising a crosslinked polymerized crosslinked polymer.

Examples of the inorganic material include montmorillonite, saponite, nontronite, laponite, beidelite, hectorite, and soconite. ), Stevensite, vermiculite, volkonskoite, magadite, medmontite, kenyaite, kaolin minerals (kaolinite, dick Kite and nacrite), serpentine minerals, mica minerals (including illite), chlorite minerals, sepolite, palygorskite, baux Bauxite silica, alumina, titania or mixtures thereof and the like can be used.

Among these, laponite can effectively improve thermal stability, water retention capacity, and pressure absorption capacity.

The inorganic material may be added in an amount of about 0.001 to 1.0% by weight relative to the monomer mixture to realize excellent absorption properties.

In addition, the monomer mixture may further include a polymerization initiator commonly used in the production of super absorbent polymers.

Specifically, the polymerization initiator may be appropriately selected according to the polymerization method, a thermal polymerization initiator is used when using the thermal polymerization method, a photopolymerization initiator is used when using the photopolymerization method, and hybrid polymerization methods (heat and In the case of using a method using all of the light), both a thermal polymerization initiator and a photo polymerization initiator can be used. However, even with the photopolymerization method, since a certain amount of heat is generated by light irradiation such as ultraviolet irradiation, and a certain amount of heat is generated as the polymerization reaction that is an exothermic reaction proceeds, a thermal polymerization initiator may be additionally used.

If the photopolymerization initiator is a compound capable of forming radicals by light such as ultraviolet rays, the composition may be used without limitation.

The photopolymerization initiator includes, for example, benzoin ether, dialkyl acetophenone, hydroxyl alkylketone, phenyl glyoxylate, and benzyl dimethyl ketal. Ketal), acyl phosphine and one or more selected from the group consisting of alpha-aminoketone. Meanwhile, specific examples of acylphosphine are diphenyl (2,4,6-trimethylbenzoyl) phosphine oxide, phenylbis (2,4,6-trimethylbenzoyl) phosphine oxide, and ethyl (2,4,6- And trimethylbenzoyl) phenylphosphine. For a wider variety of photoinitiators, it is well documented in Reinhold Schwalm's book "UV Coatings: Basics, Recent Developments and New Application (Elsevier 2007)" p115, and is not limited to the examples described above.

The photopolymerization initiator may be included in a concentration of about 0.0001 to about 2.0% by weight relative to the monomer mixture. If the concentration of the photopolymerization initiator is too low, the polymerization rate may be slow, and if the concentration of the photopolymerization initiator is too high, the molecular weight of the super absorbent polymer may be small and the properties may be uneven.

In addition, as the thermal polymerization initiator, one or more selected from the initiator 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 are sodium persulfate (Na ₂ S ₂ O ₈ ), potassium persulfate (K ₂ S ₂ O ₈ ), ammonium persulfate (Ammonium persulfate; (NH ₄ ) ₂ S ₂ O ₈ ), and examples of the azo-based initiator are 2,2-azobis- (2-amidinopropane) dihydrochloride (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) (4,4-azobis- (4-cyanovaleric acid)). More various thermal polymerization initiators are well specified in the Odian book 'Principle of Polymerization (Wiley, 1981)', p203, and are not limited to the above-described examples.

The thermal polymerization initiator may be included in a concentration of about 0.001 to about 2.0% by weight relative to the monomer mixture. If the concentration of the thermal polymerization initiator is too low, the additional thermal polymerization hardly occurs, so the effect of adding the thermal polymerization initiator may be negligible. If the concentration of the thermal polymerization initiator is too high, the molecular weight of the super absorbent polymer may be small and the properties may be uneven. have.

The monomer mixture may further include additives such as a thickener, a plasticizer, a preservative stabilizer, and an antioxidant, if necessary.

Raw materials such as the above-mentioned water-soluble ethylenically unsaturated monomer, internal crosslinking agent, inorganic substance, polymerization initiator, and additive may be prepared in a form dissolved in a solvent.

The solvent that can be used at this time can be used without limitation of its 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, cyclohexanone, cyclopentanone, diethylene glycol monomethyl ether, diethylene glycol Ethyl ether, toluene, xylene, butyrolactone, carbitol, methyl cellosolve acetate and N, N-dimethylacetamide can be used in combination.

The solvent may be included in the remaining amount excluding the above-mentioned components with respect to the total content of the monomer mixture.

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

Specifically, the polymerization method can be largely divided into thermal polymerization and photo polymerization depending on the polymerization energy source. In general, when performing thermal polymerization, it may be carried out in a reactor having a stirring shaft such as a kneader. In addition, when performing thermal polymerization, the compound represented by Chemical Formula 1 may be processed at a temperature of about 80 ° C. or higher and less than about 110 ° C. so as not to be decomposed by heat. Means for achieving the polymerization temperature in the above range is not particularly limited, and may be heated by supplying a heat medium to the reactor or directly supplying a heat source. As the type of heat medium that can be used, heated fluid such as steam, hot air, and hot oil may be used, but the present invention is not limited thereto, and the temperature of the supplied heat medium is considered in consideration of the means of the heat medium, the rate of temperature increase, and the target temperature of temperature increase. You can choose appropriately. On the other hand, the heat source supplied directly may include a heating method through electricity and a gas, but is not limited to the above-described example.

On the other hand, when the photopolymerization is performed, it may be performed in a reactor equipped with a movable conveyor belt, but the polymerization method described above is an example, and the present invention is not limited to the polymerization method described above.

For example, when the thermal polymerization is performed by supplying a heating medium or heating the reactor to a reactor such as a kneader having a stirring shaft as described above, a hydrogel polymer discharged to a reactor outlet may be obtained. The hydrogel polymer thus obtained may be obtained in a size of several centimeters to several millimeters, depending on the shape of the stirring shaft provided in the reactor. Specifically, the size of the hydrogel polymer obtained may vary depending on the concentration and the injection rate of the monomer mixture to be injected.

In addition, when the photopolymerization is performed in a reactor equipped with a movable conveyor belt as described above, the shape of the hydrogel polymer usually obtained may be a hydrogel polymer on a sheet having a belt width. At this time, the thickness of the polymer sheet varies depending on the concentration and the injection rate of the monomer mixture to be injected, but it is usually preferable to supply the monomer mixture so that a polymer on the sheet having a thickness of about 0.5 to about 10 cm can be obtained. When the monomer mixture is supplied to such an extent that the thickness of the polymer on the sheet is too thin, the production efficiency is low, which is undesirable, and when the polymer thickness on the sheet exceeds 10 cm, due to the excessively thick thickness, the polymerization reaction is evenly spread over the entire thickness. It may not happen.

The polymerization time of the monomer mixture is not particularly limited, and may be adjusted to about 30 seconds to 60 minutes.

The normal water content of the hydrogel polymer obtained in this way may be about 30 to about 80% by weight. Meanwhile, in the present specification, “water content” refers to a content of moisture occupied with respect to the total weight of the hydrogel polymer, which means the weight of the hydrogel polymer minus the dry polymer weight. Specifically, it is defined as a calculated value by measuring the weight loss due to evaporation of water in the polymer during the drying process 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 40 minutes, including 5 minutes of temperature rise, to measure the water content.

In the step of forming the base resin powder, the hydrogel polymer obtained through the step of forming the hydrogel polymer is dried to provide a base resin powder.

The step of forming the base resin powder may include a step of co-pulverizing the hydrogel polymer before drying in order to increase drying efficiency.

At this time, the grinder used is not limited in configuration, specifically, a vertical cutter (Vertical pulverizer), a turbo cutter (Turbo cutter), a turbo grinder (Turbo grinder), a rotary cutting mill (Rotary cutter mill), cutting Includes any one selected from the group of crushers consisting of a cutter mill, disc mill, shred crusher, crusher, chopper and disc cutter However, it is not limited to the above-described example.

Through this coarse grinding process, the particle diameter of the hydrogel polymer can be adjusted to about 0.1 to about 10 mm. Grinding such that the particle diameter is less than 0.1 mm is not technically easy due to the high water content of the hydrogel polymer, and there may also be a phenomenon in which agglomerated particles are aggregated with each other. On the other hand, if the particle size is pulverized to exceed 10 mm, the effect of increasing the efficiency of the subsequent drying step may be insignificant.

Drying is performed on the hydrogel polymer immediately after polymerization, which has been subjected to the coarse grinding process or without the coarse grinding process. At this time, the drying temperature may be about 20 ℃ to about 250 ℃. When the drying temperature is less than about 20 ° C, the drying time is too long and there is a fear that the physical properties of the superabsorbent polymer to be formed are lowered, and when the drying temperature exceeds about 250 ° C, only the polymer surface is dried excessively, which is to be achieved later. Fine powder may be generated in the pulverization process, and there is a fear that the physical properties of the superabsorbent polymer finally formed may be deteriorated. Therefore, preferably, the drying may be performed at a temperature of about 40 ° C to about 200 ° C, more preferably at a temperature of about 110 ° C to about 200 ° C.

In particular, when the drying temperature of the hydrogel polymer is from about 110 ° C to about 200 ° C, at least a part of the crosslinked structure derived from the compound represented by Chemical Formula 1 may be thermally decomposed. As a result, the internal crosslinking density of the crosslinked polymer in the drying step can be reduced. The crosslinked polymer in which the internal crosslinking density is reduced may provide a superabsorbent polymer with significantly improved water retention capacity compared to the crosslinked polymer in which the internal crosslinking density is not reduced.

Meanwhile, in the case of the drying time, it may be performed for about 20 minutes to about 12 hours in consideration of process efficiency and the like. For example, the hydrogel polymer may be dried for about 20 minutes to 100 minutes or about 30 minutes to about 50 minutes so that the internal crosslinked structure of the hydrogel polymer is sufficiently decomposed.

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

The step of forming the base resin powder may further include a step of pulverizing the dried polymer obtained through the drying step.

The polymer powder obtained after the grinding step may have a particle size of about 150 to about 850 μm. The pulverizer used for pulverizing to such a particle size is specifically, a pin mill, a hammer mill, a screw mill, a roll mill, a disc mill or a jog. It may be a mill (jog mill), but is not limited to the above-described example.

And, the step of forming the base resin powder may further include classifying the pulverized polymer obtained through the pulverizing step. That is, the step of forming the base resin powder may provide the base resin powder by drying, grinding, and classifying the hydrogel polymer.

Through the step of classifying the polymer powder obtained after the crushing step according to the particle size, it is possible to manage the physical properties of the superabsorbent polymer powder that is finally commercialized. Through such processes such as pulverization and classification, it is appropriate that the base resin powder and the superabsorbent resin obtained therefrom are manufactured and provided to have a particle diameter of about 150 to 850 μm. More specifically, at least about 95% by weight or more of the base resin powder and the superabsorbent polymer obtained therefrom will have a particle diameter of about 150 to 850 μm, and a fine powder having a particle diameter of less than about 150 μm will be less than about 3% by weight. Can be.

As described above, as the particle size distribution of the base resin powder and the superabsorbent polymer is adjusted to a desired range, the final superabsorbent polymer can exhibit excellent absorbent properties. Therefore, in the classification step, a polymer having a particle diameter of about 150 to about 850 μm can be classified, and only a polymer powder having such a particle diameter can be commercialized through a surface crosslinking reaction step.

On the other hand, after forming the base resin powder described above, in the presence of a surface crosslinking agent, the surface of the base resin powder can be further crosslinked to form a surface crosslinking layer, whereby a super absorbent polymer can be produced.

As the surface crosslinking agent, any surface crosslinking agent that has been used in the manufacture of super absorbent polymers can be used without any limitation. More specific examples thereof, ethylene glycol, propylene glycol, 1,3-propanediol, 1,4-butanediol, 1,6-hexanediol, 1,2-hexanediol, 1,3-hexanediol, 2-methyl- One or more polyols selected from the group consisting of 1,3-propanediol, 2,5-hexanediol, 2-methyl-1,3-pentanediol, 2-methyl-2,4-pentanediol, tripropylene glycol and glycerol ; At least one carbonate-based compound selected from the group consisting of ethylene carbonate and propylene carbonate; Epoxy compounds such as ethylene glycol diglycidyl ether; Oxazoline compounds such as oxazolidinone; Polyamine compounds; Oxazoline compounds; Mono-, di- or polyoxazolidinone compounds; Or cyclic urea compounds; And the like.

The surface crosslinking agent may be used in an amount of about 0.01 to 3 parts by weight based on 100 parts by weight of the base resin powder. By adjusting the content range of the surface crosslinking agent to the above-described range, it is possible to provide a super absorbent polymer exhibiting excellent water absorption properties.

In addition, in the surface crosslinking process, one or more inorganic materials selected from the group consisting of silica, clay, alumina, silica-alumina composite, titania, zinc oxide, and aluminum sulfate are additionally added to the surface crosslinking agent. It can be added to carry out a surface crosslinking reaction. The inorganic material may be used in a powder form or in a liquid form, and in particular, it may be used as alumina powder, silica-alumina powder, titania powder, or nano silica solution. In addition, the inorganic material may be used in an amount of about 0.001 to about 2 parts by weight based on 100 parts by weight of the base resin powder.

In addition, in the surface crosslinking process, the surface crosslinking structure of the superabsorbent polymer can be further optimized as surface crosslinking is performed by adding polyvalent metal cations instead of or together with the inorganic material. This is expected because such metal cations can further reduce the crosslinking distance by forming a chelate with the carboxyl group (COOH) of the super absorbent polymer.

In addition, the method of adding the surface crosslinking agent to the base resin powder is not limited in its configuration. For example, a method of mixing the surface crosslinking agent and the base resin powder in a reaction tank, or spraying the surface crosslinking agent on the base resin powder, a method of continuously supplying and mixing the base resin powder and the surface crosslinking agent to a continuously operated mixer, etc. Can be used.

When the surface crosslinking agent is added, water and methanol may be mixed and added together. When water and methanol are added, there is an advantage that the surface crosslinking agent can be evenly dispersed in the base resin powder. At this time, the content of water and methanol to be added can be appropriately adjusted to induce even dispersion of the surface crosslinking agent and to prevent the agglomeration of the base resin powder while optimizing the surface penetration depth of the crosslinking agent.

The surface crosslinking reaction may be achieved by heating the base resin powder to which the surface crosslinking agent is added to a predetermined temperature or higher. In this surface crosslinking step, an internal crosslinking decomposition reaction may be simultaneously performed with the surface crosslinking reaction. Accordingly, in the surface crosslinking step, at least a part of the crosslinked structure derived from the compound of Formula 1 may be thermally decomposed in the base resin powder to lower the internal crosslinking density. And, due to the above reactions, a superabsorbent polymer having a crosslinking density gradient in a form in which crosslinking density is increased from the inside to the outside can be produced.

In particular, in order to prepare a super absorbent polymer having both improved water retention capacity and absorbency under pressure, the surface crosslinking process conditions may be performed at a temperature of about 110 to 200 ° C.

More specifically, the surface crosslinking process conditions may be a maximum reaction temperature of about 160 ° C or more, or about 180 to 200 ° C, a retention time at a maximum reaction temperature of about 20 minutes or more, or about 20 minutes or more and 2 hours or less. have. In addition, at a temperature at the beginning of the initial reaction, for example, at a temperature of about 110 ° C. or higher, or about 160 to 170 ° C., a temperature increase time from the temperature to the maximum reaction temperature is about 10 minutes or more, or about 10 minutes or more 1 It can be controlled in less than a time, and it was confirmed that a superabsorbent polymer excellent in both water retention capacity and pressure absorption capacity can be produced by satisfying the above-mentioned surface crosslinking process conditions.

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

The superabsorbent polymer obtained according to the above-described manufacturing method has a shape in which a part of the thermally decomposable internal crosslinking structure is partially decomposed in a subsequent process at a high temperature after the polymerization process, and thus has a form in which the crosslinking density increases from the inside to the outside. It can exhibit very excellent properties with improved physical properties such as absorption capacity. In addition, even when exposed to high temperatures, the superabsorbent polymer can maintain excellent absorbent characteristics of the superabsorbent polymer. Accordingly, the superabsorbent polymer may provide hygiene products such as diapers that exhibit excellent absorbent properties even after a high-temperature production process.

Hereinafter, the operation and effect of the invention will be described in more detail through specific examples of the invention. However, this is provided as an example of the invention, and the scope of the invention is not limited in any way.

Example 1: Preparation of super absorbent polymer

100 g of acrylic acid in a glass reactor, 0.6 g of 4-methylpentane-1,4-diyl diacrylate as an internal crosslinking agent, 0.008 g of Irgacure TPO (diphenyl (2,4,6-trimethylbenzoyl) phosphine oxide), laponite 0.18 g and 55 g water were injected. Then, 123.5 g of a 32% by weight caustic soda solution was slowly added dropwise to the glass reactor and mixed.

When the caustic soda solution was added dropwise, the temperature of the mixed solution increased due to the heat of neutralization, and the mixed solution was waited for cooling. When the temperature of the mixed solution was cooled to about 45 ° C., 0.2 g of sodium persulfate was added to the mixed solution to prepare a monomer mixture.

The monomer mixture was fed at a rate of 500 to 2000 mL / min on a conveyor belt in which a belt 10 cm wide and 2 m long rotated at a rate of 50 cm / min. Then, the polymerization reaction was performed for 60 seconds by irradiating ultraviolet rays having an intensity of 10 mW / cm ² at the same time as the supply of the monomer mixture.

Then, the polymer obtained through the polymerization reaction was manufactured into a crump by passing through a hole having a diameter of 10 mm using a meat chopper. Subsequently, using an oven capable of transferring air volume up and down, hot air at 185 ° C was flowed from the bottom to the top for 20 minutes, and then again flowed from the top to the bottom for 20 minutes to uniformly dry the crump. . The dried powder was pulverized by a grinder and then classified to obtain base resins having a size of 150 to 850 μm.

To the 100 g of the base resin powder prepared above, a solution of 3.2 g of ultrapure water, 4.0 g of methanol, 0.088 g of ethylene carbonate, and 0.01 g of silica (trade name: REOLOSIL DM30S, manufactured by Tokuyama Corporation) is administered, mixed for 1 minute, and then 185 The surface was crosslinked at 90 ° C for 90 minutes.

Then, the obtained product was pulverized and classified to obtain a super absorbent polymer having a particle size of 150 to 850 μm.

Example 2: Preparation of super absorbent polymer

Same as Example 1, except that 0.6 g of 2-methylpentane-2,4-diyl diacrylate was used instead of 0.6 g of 4-methylpentane-1,4-diyl diacrylate as the internal crosslinking agent in Example 1 above. A super absorbent polymer was prepared by the method.

Comparative Example 1: Preparation of super absorbent polymer

Same as Example 1, except that 0.6 g of 2-methylpropane-1,2-diyl diacrylate was used instead of 0.6 g of 4-methylpentane-1,4-diyl diacrylate as the internal crosslinking agent in Example 1 above. A super absorbent polymer was prepared by the method.

Comparative Example 2: Preparation of super absorbent polymer

Same as Example 1, except that 0.6 g of 2-methylbutane-2,4-diyl diacrylate was used instead of 0.6 g of 4-methylpentane-1,4-diyl diacrylate as the internal crosslinking agent in Example 1 above. A super absorbent polymer was prepared by the method.

Comparative Example 3: Preparation of super absorbent polymer

In Example 1, except that 0.4 g of polyethylene glycol diacrylate (PEGDA, weight average molecular weight 598 g / mol) was used instead of 0.6 g of 4-methylpentane-1,4-diyl diacrylate as an internal crosslinking agent, Example A super absorbent polymer was prepared in the same manner as 1.

For reference, when the content of polyethylene glycol diacrylate is adjusted to 0.6 g as in Example 1, a very poorly superabsorbent polymer having absorbency is prepared, and the content of polyethylene glycol diacrylate is adjusted to 0.4 g unlike Example 1 A super absorbent polymer was prepared.

Comparative Example 4: Preparation of super absorbent polymer

Comparative Example 2, except that 0.6 g of 2-methylbutane-2,4-diyl diacrylate and 0.4 g of polyethylene glycol diacrylate (PEGDA, weight average molecular weight 598 g / mol) were used as the internal crosslinking agent. A superabsorbent polymer was prepared in the same manner as 2.

Comparative Example 5: Preparation of super absorbent polymer

Same as Comparative Example 2, except that 0.6 g of 2-methylbutane-2,4-diyl diacrylate and 0.6 g of polyethylene glycol (PEG, number average molecular weight 600 g / mol) were used as the internal crosslinking agent in Comparative Example 2 above. A super absorbent polymer was prepared by the method.

Test Example: Evaluation of physical properties of super absorbent polymer

The properties of the superabsorbent polymer prepared according to Examples and Comparative Examples were evaluated in the following manner, and the results are shown in Table 1 below.

(1) Rate of change in absorption characteristics at high temperatures

After the superabsorbent polymer prepared according to the above Examples and Comparative Examples was exposed to high temperatures, changes in absorption characteristics before and after exposure to high temperatures were measured.

Specifically, samples were taken from the superabsorbent polymer prepared according to Examples and Comparative Examples, and centrifugal water retention capacity (CRC, unit: g / g) for physiological saline and pressure absorption capacity of 0.7 psi for physiological saline (AUL) , Unit: g / g). The CRC and AUL were measured according to the items (2) and (3) below.

On the other hand, after taking a sample from the superabsorbent polymer prepared according to Examples and Comparative Examples, and leaving the sample in an oven at 185 ° C for 60 minutes, CRC and AUL of the sample exposed to high temperature were performed as follows (2) and (3) Measured according to the item. Then, by using the obtained CRC and AUL values, the rate of change in the absorption characteristics at high temperature was confirmed by the following Equation 1.

[Calculation formula 1]

Y = {[P ₁ -P ₂ ] / P ₁ } * 100

In the above formula 1,

Y is the rate of change in absorption characteristics at high temperatures,

P ₁ is the centrifuge retention capacity for physiological saline (CRC, unit: g / g) of the superabsorbent polymer measured before exposure to high temperature, and the pressure absorption capacity of 0.7 psi for physiological saline (AUL, unit: g / g). Is the sum of

P ₂ is the sum of CRC and AUL of the superabsorbent polymer measured after leaving the superabsorbent polymer in an oven at 185 ° C. for 60 minutes.

(2) Centrifuge Retention Capacity (CRC)

The superabsorbent polymer's centrifugal water retention capacity (CRC) for physiological saline was measured according to the method of EDANA method NWSP 241.0.R2.

Specifically, among the superabsorbent polymer to measure centrifugal water retention capacity, a US standard 20 mesh screen was passed through, and a sample having a particle size of 150 to 850 μm maintained on the US standard 100 mesh screen was prepared.

Then, samples W ₀ (g, about 0.2 g) having a particle diameter of 150 to 850 μm were uniformly placed in a nonwoven fabric bag and sealed. Then, the bag was immersed in 0.9% by weight aqueous sodium chloride solution (physiological saline) at room temperature. After 30 minutes, the envelope was dehydrated at 250 G for 3 minutes using a centrifuge, and then the weight W ₂ (g) of the envelope was measured. On the other hand, after performing the same operation using an empty bag without a sample, the weight W ₁ (g) at that time was measured.

Using each weight thus obtained, the centrifugal water retention capacity was confirmed by the following Equation 2.

[Calculation formula 2]

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

In the above equation 2,

W ₀ (g) is an initial weight (g) of a sample having a particle diameter of 150 to 850 μm,

W ₁ (g) is the weight of the non-woven fabric empty bag measured after immersing the non-woven fabric empty bag without samples in physiological saline at room temperature for 30 minutes, followed by dehydration at 250 G for 3 minutes using a centrifuge,

W ₂ (g) was absorbed by immersing the nonwoven fabric bag containing the sample in physiological saline at room temperature for 30 minutes, then dehydrating at 250 G for 3 minutes using a centrifuge, and measuring the nonwoven fabric bag containing the sample. Is the weight.

(3) Absorbency under Load (AUL)

The absorbency under pressure (AUL) of 0.7 psi with respect to the physiological saline of the superabsorbent polymer was measured according to the method of EDANA method NWSP 242.0.R2.

Specifically, a stainless steel 400 mesh screen was mounted on the bottom of a plastic cylinder having an inner diameter of 25 mm. Then, the super absorbent polymer W ₀ (g, about 0.16 g) to measure the pressure absorption capacity was uniformly sprayed on the screen under room temperature and humidity of 50%. Subsequently, a piston capable of uniformly applying a load of 4.8 kPa (0.7 psi) was added to the superabsorbent polymer. At this time, as the piston, the outer diameter was slightly smaller than 25 mm, so that there was no gap with the inner wall of the cylinder, and one manufactured to move freely up and down was used. Then, the weight W ₃ (g) of the device thus prepared was measured.

Subsequently, a glass filter having a diameter of 90 mm and a thickness of 5 mm was placed inside a petri dish having a diameter of 150 mm, and 0.9 weight% aqueous sodium chloride solution (physiological saline) was poured into the petri dish. At this time, the saline solution was poured until the water surface of the saline solution was level with the top surface of the glass filter. Then, a sheet of filter paper having a diameter of 90 mm was placed on the glass filter.

Subsequently, the prepared device was placed on a filter paper so that the superabsorbent polymer in the device was swollen by physiological saline under load. After 1 hour, the weight W ₄ (g) of the device containing the swollen superabsorbent polymer was measured.

Using this measured weight, the absorbency under pressure was calculated according to the following Equation 3.

[Calculation formula 3]

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

In the above equation 3,

W ₀ (g) is the initial weight of the super absorbent polymer (g),

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

W ₄ (g) is the sum of the weight of a superabsorbent polymer and the weight of a device capable of applying a load to the superabsorbent polymer after absorbing physiological saline in the superabsorbent polymer for 1 hour under a load (0.7 psi).

Example Comparative example One 2 One 2 3 4 5 Before exposure to high temperatures CRC [g / g] 46.3 44.7 42.3 38.2 35.4 33.7 35.7 AUL [g / g] 26.1 25.3 24.3 26.4 24.1 24.6 23.4 P ₁ = CRC + AUL 72.4 70.0 66.6 64.6 59.5 58.3 59.1 After exposure to high temperatures CRC [g / g] 46.0 45.8 39.6 36.4 31.0 30.5 31.2 AUL [g / g] 24.2 24.7 23.1 24.9 22.1 22.8 21.9 P ₂ = CRC + AUL 70.2 70.5 62.7 61.3 53.1 53.3 53.1 Y = {[P ₁ -P ₂ ] / P ₁ } * 100 3.0 -0.7 5.9 5.1 10.8 8.6 10.2

The pressure absorption capacity (AUL) of 0.9 psi with respect to the physiological saline of the superabsorbent polymers prepared in Examples 1, 2 and Comparative Example 2 was further measured. The pressure absorption capacity of 0.9 psi with respect to the physiological saline of the superabsorbent polymer was measured in the same manner as the pressure absorption capacity measurement method of 0.7 psi described above, except that a piston capable of uniformly imparting a load of 6.3 kPa (0.9 psi) was used. . As a result of the measurement, the absorbency under pressure of 0.9 psi with respect to the physiological saline of the superabsorbent polymer prepared in Example 1 was 19.4 g / g, and the absorbency under 0.9 psi with respect to the physiological saline of the superabsorbent resin prepared in Example 2 was 18.7. g / g, and the absorbency under pressure of 0.9 psi with respect to physiological saline of the superabsorbent polymer prepared in Comparative Example 2 was 25.5 g / g.

Referring to Table 1, the superabsorbent polymers of Examples 1 and 2 in which the superabsorbent polymer was prepared by using the thermally decomposable internal crosslinking agent in an amount of 80% by weight or more based on the total weight of the internal crosslinking agent exhibit excellent absorption characteristics even when exposed to high temperatures. It is confirmed to maintain.

In contrast, the superabsorbent polymers of Comparative Examples 3 without using the thermally decomposable internal crosslinking agent, and the superabsorbent polymers of Comparative Examples 4 and 5 using the thermally decomposable internal crosslinking agent in an amount of less than 80% by weight relative to the total weight of the internal crosslinking agent were all calculated as described above. The rate of change in absorption characteristics at high temperatures calculated as 1 was high. In addition, it is confirmed that the superabsorbent polymers of Comparative Examples 3 to 5 do not exhibit excellent properties in both water retention capacity and pressure absorption capacity.

On the other hand, when comparing Examples 1 and 2 with Comparative Examples 1 and 2, R ¹ is methane-1,1-diyl (Comparative Example 1) among the compounds represented by Formula 1; Propane-1,3-diyl (Example 1); Alternatively, in the case of propane-1,2-diyl (Example 2), excellent water retention performance can be achieved, among which R ¹ is propane-1,3-diyl (Example 1); Or it is confirmed that in the case of propane-1,2-diyl (Example 2), better thermal stability, water retention capacity and pressure absorption capacity can be realized.

Claims (4)

A water-soluble ethylenically unsaturated monomer having at least a partially neutralized acidic group comprising a crosslinked polymer crosslinked in the presence of an internal crosslinking agent and an inorganic substance containing 80% by weight or more of the compound represented by the following general formula 1 Base resin powder; And
The crosslinked polymer is further crosslinked to include a surface crosslinked layer formed on the base resin powder,
Superabsorbent polymer having a change rate (Y) of absorption characteristics at a high temperature of 3% to 4% calculated by the following Equation 1:
[Formula 1]

In Chemical Formula 1, R ¹ is propane-1,3-diyl or propane-1,2-diyl, R ² is hydrogen or a methyl group,
[Calculation formula 1]
Y = {[P ₁ -P ₂ ] / P ₁ } * 100
In the above equation 1,
Y is the rate of change in absorption characteristics at high temperatures,
P ₁ is the sum of centrifugal water retention capacity (CRC) for physiological saline of a superabsorbent polymer measured before exposure to high temperature and pressure absorption capacity (AUL) of 0.7 psi for physiological saline,
P ₂ is the sum of CRC and AUL of the superabsorbent polymer measured after leaving the superabsorbent polymer in an oven at 185 ° C. for 60 minutes.
The superabsorbent polymer according to claim 1, wherein P ₁ is 68 to 85 g / g.
The superabsorbent polymer according to claim 1, wherein P ₂ is 65 to 85 g / g.
The method of claim 1, wherein the inorganic material is montmorillonite, montmorillonite, saponite, nontronite, laponite, beidelite, hectorite, soconite ), Stevensite, vermiculite, volkonskoite, magadite, medmontite, kenyaite, kaolin mineral, serpentine ) Minerals, mica minerals, chlorite minerals, sepolite, palygorskite, bauxite silica, alumina, titania or their A superabsorbent resin that is a mixture.