KR101507299B1 - Preparation method of super absorbent polymer - Google Patents

Abstract

The present invention relates to a method for producing a superabsorbent resin capable of reducing the variation in physical properties by controlling the temperature elevation temperature in two stages at the time of surface crosslinking. More specifically, the present invention relates to a method of manufacturing a superabsorbent resin which can shorten the temperature rise time at the time of manufacturing a superabsorbent resin and can easily control the depth of penetration of the surface crosslinked material, thereby improving physical properties.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to a method for producing a superabsorbent resin,

The present invention relates to a method for producing a superabsorbent resin having improved physical properties.

Super Absorbent Polymer (SAP) is a synthetic polymer material capable of absorbing moisture of about 500 to 1,000 times its own weight. As a result, it is possible to develop a super absorbent polymer (SAM), an absorbent gel Material), and so on. Such a superabsorbent resin has started to be put into practical use as a sanitary article, and nowadays, in addition to sanitary articles such as diapers for children, there are currently used soil repair agents for horticultural use, index materials for civil engineering and construction, sheets for seedling growing, freshness- And it is widely used as a material for fomentation and the like.

As a method of producing such a superabsorbent resin, there are known methods such as reversed-phase suspension polymerization or aqueous solution polymerization. The reversed-phase suspension polymerization is disclosed in, for example, Japanese Unexamined Patent Publication No. 56-161408, Unexamined Japanese Patent Application No. 57-158209, and Japanese Unexamined Patent Publication No. 57-198714. Examples of the method by aqueous solution polymerization include a thermal polymerization method in which the polymerization gel is polymerized while being cooled in a kneader equipped with a shaft, and a photopolymerization method in which a high concentration aqueous solution is irradiated with ultraviolet rays or the like on a belt to perform polymerization and drying simultaneously .

However, the superabsorbent resin needs a process of crosslinking the surface of the absorbent resin for excellent absorption capacity and pressure absorption ability. Conventional surface cross-linking techniques have been studied on the type of cross-linking agent, the composition ratio for controlling the penetration depth of the cross-linking agent, and the process conditions depending on the type of cross-linking agent.

In the conventional process, the hydrogel polymer is generally prepared, the primary drying process, the pulverization and classification process, the surface cross-linking solution is added, and the temperature is raised to 170-200 ° C. to prepare a superabsorbent resin.

However, in the surface cross-linking treatment step, the above method has a disadvantage in that the reaction temperature is high and the reaction time reaches a relatively long time, resulting in a relatively low efficiency. In particular, there is a problem that the physical properties of the superabsorbent resin are deteriorated.

In order to solve this problem, the surface treatment process and the type and composition of the cross-linking agent have been studied. However, there is a problem that the physical properties of the superabsorbent resin are so large that the performance thereof is insufficient.

Accordingly, the present inventors have completed the present invention while repeatedly studying a method for efficiently producing a superabsorbent resin without impairing physical properties of the final superabsorbent resin.

Accordingly, the present invention provides a method for manufacturing a superabsorbent resin which can shorten the time to reach a reaction temperature during surface cross-linking so that the penetration depth of the surface cross-linking agent can be easily controlled, thereby reducing the physical property deviation of the water absorbent resin and ultimately improving the physical properties .

The present invention relates to a process for preparing a monomer composition comprising: forming a monomer composition comprising a water-soluble ethylenically unsaturated monomer and a polymerization initiator;

Polymerizing the monomer composition in a polymerization reactor to produce a hydrogel polymer;

Drying and pulverizing the hydrogel polymer;

Subjecting the pulverized co-gel polymer to a first temperature elevation to 70-100 ° C; And

Adding a surface treatment solution containing a surface cross-linking agent and a solvent to the first heated gelatinized functional polymer, and advancing the surface cross-linking reaction of the hydrogel polymer by secondary heating at 160 to 200 ° C,

In the surface treatment solution,

Water and an alcohol or glycol compound having 3 or more carbon atoms and a boiling point of 90 ° C or higher.

The solvent in the surface treatment solution may include water and an alcohol or glycol compound having a boiling point of not lower than 90 ° C. and having 3 or more carbon atoms.

The alcohol or glycol compound may be at least one selected from the group consisting of n-propanol, butanol, propylene glycol and propanediol.

The surface cross-linking agent may be a diol or a glycol compound having 2 to 8 carbon atoms, preferably 1,3-propanediol, 2,3,4-trimethyl-1,3-pentanediol, 1,3-butanediol, 1,5-pentanediol, 1,6-hexanediol, 1,2-cyclohexanedimethanol, monoethyleneglycol, diethyleneglycol, triethyleneglycol, Polyethylene glycol, propylene glycol, dipropylene glycol, polypropylene glycol, glycerol, and polyglycerol. [0033] The term " a "

Also, the surface treatment solution may contain 0.1 to 20% by weight of a surface cross-linking agent, 10 to 70% by weight of an alcohol or a glycol-based solvent, and a residual amount of water, based on the total weight of the surface treatment solution.

Hereinafter, a method for producing a superabsorbent resin according to a specific embodiment of the present invention will be described in detail.

The present invention can shorten the temperature rise time by raising the temperature of the superabsorbent resin in two steps during crosslinking of the surface, thereby more effectively carrying out superabsorbent resin surface crosslinking. Further, the present invention provides a method for producing a superabsorbent resin which can easily control the depth of penetration of the cross-linked surface of the superabsorbent resin by shortening the temperature rise time at the surface cross-linking of the superabsorbent resin. Thus, the superabsorbent resin of the present invention can be expected to improve the physical properties. According to the present invention, fine particles having a uniform particle size distribution of a desired size can be obtained with ease of process, surface cross-linking can be easily performed, and the variation in physical properties can be reduced.

According to one embodiment of the present invention, there is provided a method for producing a toner, comprising: forming a monomer composition comprising a water-soluble ethylenically unsaturated monomer and a polymerization initiator; Polymerizing the monomer composition in a polymerization reactor to produce a hydrogel polymer; Drying and pulverizing the hydrogel polymer; Subjecting the pulverized co-gel polymer to a first temperature elevation to 70-100 ° C; And a step of adding a surface treatment solution containing a surface cross-linking agent and a solvent to the first heated gelatinized functional polymer and then raising the temperature to 160 to 200 ° C to progress the surface cross-linking reaction of the hydrogel polymer, The solvent in the solution is water, and a method for producing a superabsorbent resin comprising an alcohol or a glycol compound having 3 or more carbon atoms with a boiling point of 90 ° C or higher.

Conventionally, in the process of preparing a superabsorbent resin, when the surface crosslinking of the hydrogel polymer is proceeded, the temperature is raised at one time, so that it takes a long time to reach the reaction temperature for surface cross-linking of the hydrogel polymer, There is a problem that the obtained superabsorbent resin has poor physical properties.

In addition, in the process of producing a super absorbency resin, the temperature of the water absorbent resin before and after the pulverization and classification of the hydrogel polymer is usually about 50 캜. In the past, the surface crosslinking solution was immediately added to the water absorbent resin , The temperature was raised at the surface cross-linking temperature (about 180 캜), and the surface cross-linking proceeded to deteriorate the physical properties of the superabsorbent resin.

On the other hand, in the present invention, after the hydrosugar polymer is pulverized and classified, the surface cross-linking solution is added after the first temperature elevation to about 70 to 100 ° C, and then the surface cross-linking is progressed by the secondary cross- Accordingly, in the present invention, the temperature rise time in the surface cross-linking step can be raised by adjusting the temperature in two steps, so that the reaction time reaching time can be shortened, thereby minimizing the physical property deviation of the final superabsorbent resin.

In addition, the alcohol-based solvent is usually used for preparing a water absorbent resin having excellent physical properties by controlling the penetration depth of the surface cross-linking agent. When only water is used, the penetration depth of the surface cross-linking agent becomes too deep and the physical properties are lowered.

Conventionally, low boiling point solvents such as methanol and ethanol are used for the surface cross-linking solution. However, when a low boiling point solvent such as methanol or ethanol is used according to the prior art, the alcoholic solvent is excessively flushed during surface cross- And the physical properties are deteriorated.

On the other hand, when an alcohol-based solvent having a boiling point similar to that of water is used, water and solvent are maintained in the surface cross-linking process so that the penetration depth is more reliably controlled, and the surface cross-linking agent mainly reacts only on the surface of the water- So that an absorbent resin having better physical properties can be produced.

Accordingly, in the present invention, it is possible to provide a superabsorbent resin having significantly improved physical properties compared to the conventional method by controlling the temperature raising process in two steps at the time of surface cross-linking of the hydrogel polymer, and simultaneously changing the composition of the surface crosslinking solution.

Preferably, the surface cross-linking step of the superabsorbent resin of the present invention is carried out by: 1) raising the temperature of the water absorbent resin to 70 to 100 DEG C, 2) adding a solvent having a boiling point of 90 DEG C or higher, preferably 100 DEG C or higher, A surface cross-linking solution containing a surface cross-linking component such as a cross-linking agent, and 3) progressing the surface cross-linking reaction at 160 to 200 ° C.

That is, according to the present invention, the temperature of the temperature rise up to the reaction temperature can be shortened to 5 to 10 minutes by first raising the superabsorbent resin after the pulverization to 70 to 100 ° C and then mixing the surface cross-linking solution. In addition, since the surface cross-linking reaction proceeds by secondarily elevating the temperature to about 160 to 200 ° C after the surface cross-linking, the present invention can perform a quick and even cross-linking reaction.

Therefore, according to the present invention, it is easy to control the depth of penetration of the surface cross-linking agent due to the shortening of the temperature rise time, so that the improvement of the physical properties is expected and there is an advantage that the physical property deviation according to the surface cross-linking reaction time can be reduced.

More preferably, the primary temperature elevation temperature range is 80 to 90 占 폚. Further, it is more preferable that the secondary heating temperature range is 170 to 190 占 폚.

If the primary heating temperature is lower than 70 캜, there is a problem that the shortening of the heating time is insignificant. If the primary heating temperature exceeds 100 캜, the solvent may evaporate before the surface crosslinking agent penetrates to a predetermined depth. If the secondary temperature elevation temperature is lower than 160 캜, the surface cross-linking reaction can not proceed smoothly. If the temperature is higher than 200 캜, the internal crosslinking of the superabsorbent resin is broken or the surface of the particle is worsened, Occurs.

In the present invention, the surface treatment solution means a surface cross-linking solution and has the following characteristics.

The surface cross-linking solution of the present invention includes a solvent and a surface cross-linking agent. The solvent includes alcohols or glycol-based compounds having a specific boiling point with water.

Specifically, alcohols are mainly used together with water in the surface cross-linking solution, and low boiling point solvents such as methanol and ethanol are conventionally used. In this case, the present invention is basically similar to the previous one in that water and alcohols are used as a mixed solvent. However, the surface crosslinking agent solution suitable for the process of the present invention is characterized in that it contains a solvent having a boiling point of 90 ° C or higher, more preferably 100 ° C or higher. Since the alcohol or glycol compound having a boiling point of 90 ° C or higher is used as a solvent, excessive evaporation of the solvent in the surface cross-linking process can be prevented, and the penetration depth of the surface cross-linking agent can be easily controlled.

The alcohol or glycol solvent having a boiling point of 90 ° C or higher is similar to water and may be an alcohol-based or glycol-based compound having 3 or more carbon atoms. Preferable examples of the alcohol or glycol compound include at least one of n-propanol, butanol, propylene glycol, and propanediol.

In the present invention, the alcohol or glycol solvent may be the same as the surface cross-linking agent.

The above surface cross-linking agent may be the same as the alcohol solvent as mentioned above, and a diol or glycol compound having 2 to 8 carbon atoms may be used. Examples of the surface cross-linking agent include diol compounds such as 1,3-propanediol, 2,3,4-trimethyl-1,3-pentanediol, 2-butene-1,4-diol, 1,4- 1,3-butanediol, 1,5-pentanediol, 1,6-hexanediol, and 1,2-cyclohexanedimethanol. The glycol compound may be at least one selected from the group consisting of monoethylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, polyethylene glycol, propylene glycol, dipropylene glycol, polypropylene glycol, glycerol and polyglycerol .

Also, in the present invention, it is preferable that the surface treatment solution contains 0.1 to 20% by weight of the surface cross-linking agent, 10 to 70% by weight of the alcohol or glycol solvent, and the remaining amount of water, based on the total weight of the surface treatment solution.

Meanwhile, the superabsorbent resin according to one embodiment of the present invention may be prepared by a method well known in the art, except for the surface cross-linking step, the step of preparing the hydrogel polymer, the drying step, and the classification and pulverization step.

For example, the present invention relates to a polymerization reactor for polymerizing a monomer composition in which a monomer and a polymerization initiator are mixed, which is connected to a supply portion of a monomer and a polymerization initiator for supplying a monomer and a polymerization initiator, The superabsorbent resin can be manufactured through the apparatus constitution including At this time, after the monomers and the cross-linking agent are mixed into the polymerization initiator supply unit, the conventional initiator system can be administered as needed.

In one embodiment of the present invention, a step of polymerizing the monomer composition using the apparatus to produce a hydrogel polymer and drying the hydrogel polymer is performed. After the pulverization and classification process, the surface treatment step of the two-step heating process described above can be made into a highly absorbent resin having uniform and fine particles.

The polymerization reactor for producing the hydrogel polymer may be a conventional one used for producing a super absorbent resin, for example, a continuously moving conveyor belt may be used. Also, the conveyor belt may be used by circulating a belt made of rubber, cloth, wire netting, steel plate, plastic resin or the like to which some hydrophilicity is imparted.

In addition, the polymerization reactor may be equipped with a temperature control means for internal or external thermal polymerization, and it is preferable that the internal temperature is maintained at 60 to 100 ° C, preferably 90 ° C.

Also, in the present invention, the surface treatment solution used in the surface cross-linking may be supplied by spraying on the hydrogel polymer, but the method is not particularly limited.

The polymerization of the monomer composition is not particularly limited, and a method used in the production of a conventional superabsorbent resin can be used. For example, the polymerization of the monomer composition may be carried out by a redox polymerization method in which polymerization is carried out at a temperature of 30 to 100 ° C for 2 to 50 minutes or a thermal polymerization is carried out at a temperature of 40 to 90 ° C for 2 to 30 minutes.

In the present invention, the polymerization may be carried out by using an injection device in the polymerization of the monomer composition, and in such a case, the monomer mixture may be polymerized in the form of fine particles. Therefore, in the present invention, it is also possible to obtain a superabsorbent resin of fine particles only by a drying process, and a desired product can be obtained through further pulverization if ultrafine particles are desired.

The drying temperature and time of the polymer may be appropriately selected according to the water content of the hydrogel polymer, and preferably 20 to 40 minutes at 160 to 180 ° C. When the drying temperature is less than 160 ° C, the drying effect is insignificant, so that the drying time becomes too long and it is difficult to lower the water content by 30% or less. In addition, when the drying temperature exceeds 180 DEG C, only the surface of the hydrogel polymer is locally excessively dried, and a large amount of fine powder may be generated in the subsequent pulverization step.

The constitution of the apparatus in the drying step is not particularly limited, and drying can be performed by, for example, infrared irradiation, hot air, microwave irradiation, or ultraviolet irradiation. The drying temperature and time may be appropriately selected according to the water content of the polymer polymerized through thermal polymerization or thermal polymerization. Preferably, the drying temperature and time are preferably 20 to 120 minutes at a temperature of 80 to 200 ° C. When the drying temperature is lower than 80 ° C., the drying effect is insignificant and the drying time is excessively long. When the drying is performed at a temperature exceeding 200 ° C., there is a problem that the superabsorbent resin is thermally decomposed.

In the case of carrying out further pulverization on the dried polymer, pulverization can be selected without limitation of the constitution as long as it is the method used for pulverizing the resin. Preferably, any one of the grinding apparatuses selected from the group consisting of a pin mill, a hammer mill, a screw mill, and a roll mill may be selected and pulverized. At this time, the particle size of the final superabsorbent resin particles after the pulverization step is preferably 150 to 850 탆.

In the present invention, the polymer subjected to the drying step and the additional pulverization step as necessary can be obtained in the form of a superabsorbent resin having uniform and fine particles by performing a surface treatment process or the like.

Here, the water content of the hydrogel polymer polymerized through the thermal polymerization may be 2 to 10% by weight after drying. Here, the water content of the hydrogel polymer means the amount of moisture occupied by the weight of the whole polymer gel minus the weight of the hydrogel polymer and the weight of the polymer in the dry state.

On the other hand, the constitution of each monomer for forming the monomer composition will be described.

In the present invention, the polymerization of the water-soluble ethylenically unsaturated monomer is preferably carried out in an aqueous solution.

The water-soluble ethylenic unsaturated monomer can be used without limitation in the constitution as long as it is a monomer usually used in the production of a superabsorbent resin. At least one selected from the group consisting of anionic monomers and salts thereof, nonionic hydrophilic-containing monomers, and amino group-containing unsaturated monomers and quaternary amines thereof can be used.

Specifically, the water-soluble ethylenic unsaturated monomer is at least one monomer selected from the group consisting of acrylic acid, methacrylic acid, maleic anhydride, fumaric acid, crotonic acid, itaconic acid, 2- acryloylethanesulfonic acid, 2- methacryloylethanesulfonic acid, 2- Anionic monomers of 2- (meth) acrylamide-2-methylpropanesulfonic acid and its salts; (Meth) acrylamide, N-substituted (meth) acrylate, 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, methoxypolyethylene glycol Non-ionic hydrophilic-containing monomer of (meth) acrylate; And at least one selected from the group consisting of unsaturated monomers containing an amino group of (N, N) -dimethylaminoethyl (meth) acrylate and (N, N) -dimethylaminopropyl (meth) . More preferably, the water-soluble ethylenically unsaturated monomer can use acrylic acid and a salt thereof, which is advantageous in that it has excellent physical properties.

The concentration of the water-soluble ethylenically unsaturated monomer in the monomer composition may be appropriately selected in consideration of the polymerization time and the reaction conditions, and preferably 0.01 to 1.0% by weight. When the concentration of the water-soluble ethylenically unsaturated monomer is less than 0.01% by weight, the crosslinking concentration is low and high extractable contents values can be obtained. When the concentration is more than 1.0% by weight, desired properties can not be obtained due to high crosslinking concentration.

The thermal polymerization initiator may use at least one selected from the group consisting of an azo initiator, a peroxide initiator, a redox initiator, a persulfate series and an organic halide initiator. The polymerization initiator may be used in an amount of 0.01 to 1.0% by weight based on the total monomer composition.

The monomer composition according to the present invention may further comprise a polymerization crosslinking agent.

The type of the polymerization crosslinking agent is preferably a water-soluble substituent of the ethylenically unsaturated monomer, a crosslinking agent having at least one functional group capable of reacting with the water-soluble substituent of the ethylenically unsaturated monomer and having at least one ethylenic unsaturated group, or a mixture thereof; And a water-soluble substituent of the ethylenically unsaturated monomer, a cross-linking agent having at least two functional groups capable of reacting with a water-soluble substituent formed by hydrolysis of the vinyl monomer, and a mixture thereof. . Examples of the crosslinking agent having two or more ethylenic unsaturated groups include bisacrylamide having 8 to 12 carbon atoms, bismethacrylamide, poly (meth) acrylate of polyol having 2 to 10 carbon atoms, and poly (meth) acrylate having 2 to 10 carbon atoms (Meth) acrylate, ethyleneoxy (meth) acrylate, propyleneoxy (meth) acrylate, glycerin diacrylate, glycerin At least one selected from the group consisting of triacrylate, trimethylolpropane triacrylate, triallylamine, triaryl cyanurate, triallyl isocyanate, polyethylene glycol, diethylene glycol and propylene glycol can be used.

The crosslinking agent used in the production of the hydrogel polymer may be used in an amount of 0.01 to 0.5% by weight based on the total monomer composition.

According to the present invention, it is possible to shorten the time for reaching the reaction temperature at the time of surface cross-linking to 5 to 10 minutes or less by controlling the temperature elevation condition during surface cross-linking of the hydrogel polymer, It is possible to prevent the problem of deterioration of the physical properties due to the elongation.

Best Mode for Carrying Out the Invention Hereinafter, the function and effect of the present invention will be described in more detail through specific examples of the present invention. It is to be understood, however, that these embodiments are merely illustrative of the invention and are not intended to limit the scope of the invention.

Example  One

0.5 g of polyethylene glycol diacrylate (Mw = 523) as a crosslinking agent, 0.033 g of diphenyl (2,4,6-trimethylbenzoyl) -phosphine oxide as a UV initiator, 83.3 g of 50% caustic soda (NaOH) And 89.8 g of water were mixed to prepare a monomer aqueous solution composition having a monomer concentration of 45% by weight.

Thereafter, the monomer aqueous solution composition was introduced through a feeder of a polymerization reactor composed of a conveyor belt for continuously moving, and UV polymerization was conducted for 2 minutes by irradiating ultraviolet rays (irradiation amount: 2 mW / cm 2) .

The hydrogel polymer was transferred to a cutter and cut to 0.2 cm. At this time, the water content of the cut hydrogel polymer was 50% by weight.

Then, the hydrogel polymer was dried in a hot-air dryer at 160 ° C. for 30 minutes, and the dried hydrogel polymer was pulverized with a pin mill. Then, a polymer having a particle size (average particle diameter size) of less than 150 μm and a polymer having a particle size of 150 μm to 850 μm were classified using a sieve.

Then, the temperature of the classified hydrogel polymer was first raised to 90 ° C, and a surface cross-linking solution corresponding to 10% by weight of hydrogel polymerization was sprayed thereon. Then, the temperature was raised to 180 ° C, . The surface cross-linking solution was prepared by mixing 5 wt% of 1,3-propanediol as a surface cross-linking agent, 10 wt% of n-butanol as a solvent, and the remaining amount of water, based on the total weight of the surface treatment solution.

When the surface cross-linking is completed, the product is pulverized with a pin mill and then a superabsorbent resin having a particle diameter of 150 to 300 탆 is obtained by using a sieve.

Example  2

A superabsorbent resin was prepared in the same manner as in Example 1, except that the primary temperature elevation temperature was changed to 80 캜.

Example  3

A superabsorbent resin was prepared in the same manner as in Example 1, except that the first temperature elevation temperature was changed to 100 캜.

Example  4

A superabsorbent resin was prepared in the same manner as in Example 1, except that a surface crosslinking solution containing 5% by weight of 1,3-propanediol, 30% by weight of isopropanol and the balance of water was used.

Comparative Example  One

In the surface treatment of the hydrogel polymer, a surface cross-linking solution containing 30 wt% of methanol was used instead of n-butanol, and the surface cross-linking solution was sprayed without a first heating step. , A superabsorbent resin was prepared in the same manner as in Example 1.

Comparative Example  2

A superabsorbent resin was prepared in the same manner as in Example 1 except that 30 wt% of methanol was used instead of n-butanol as a solvent used in the surface cross-linking solution.

Test Example : Evaluation of water content and physical properties of superabsorbent resin

Test Example  1: Moisture content evaluation

The water content of the water absorbent resin according to the above Examples and Comparative Examples was measured by the following method, and the results are shown in Table 1. 1 g of each of the water absorbent resin powders was placed in a drier using infrared ray (IR), dried at 180 ° C for 40 minutes, and water content was measured.

Example 1 Example 2 Example 3 Example 4 Comparative Example 1 Comparative Example 2 Moisture content (%) 0.32 0.28 0.34 0.21 0.25 0.31

As shown in Table 1, the drying state of the water absorbent resin prepared by the method of the present invention is similar to that of the water absorbent resin prepared by the conventional methods of Comparative Examples 1 and 2.

Test Example  2: Property evaluation

In order to evaluate the physical properties of the super absorbent resin of the examples and the resin of the comparative examples, the following tests were conducted.

The physical properties of the water absorbent resin according to Examples and Comparative Examples were measured by the following methods, and the results are shown in Table 2.

(1) No-load capacity (CRC, Centrifuge Retention Capacity)

The resin W (g) (about 0.1 g) obtained in Examples and Comparative Examples was uniformly put in an envelope made of a nonwoven fabric and sealed, and then immersed in 0.9% by mass of physiological saline at room temperature. After 30 minutes, the envelope was subjected to centrifugal separation at 250G for 3 minutes, and the weight W2 (g) of the envelope was measured. After the same operation was performed without using a resin, the mass W1 (g) at that time was measured. Using the obtained masses, CRC (g / g) was calculated according to the following equation.

[Equation 1]

CRC (g / g) = {(W2 (g) - W1 (g)) / W (g)

(2) Extractable content

The water component measurement was performed in the same manner as described in WO 2005/092956. However, it has been modified to use 190 g of saline solution.

(3) Absorption under pressure (AUP)

A 400 mesh wire mesh made of stainless steel was attached to the bottom of a plastic cylinder having an inner diameter of 60 mm. A piston capable of evenly spraying 0.90 g of water absorbent resin on an iron mesh under uniform temperature and humidity of 50% and uniformly applying a load of 4.83 kPa (0.7 psi) on it, has an outer diameter of 60 mm or more It was a little small and had no inner wall of the cylinder and no gap, so that the up and down movements were not disturbed. At this time, the weight Wa (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 a physiological saline solution composed of 0.90% by weight sodium chloride was made to have the same level as the upper surface of the glass filter. And a filter paper having a diameter of 90 mm was placed thereon. The measuring device was placed on the filter paper and the liquid was absorbed under load for 1 hour. After one hour, the measuring device was lifted and its weight Wb (g) was measured.

Then, the pressure absorption ability was calculated from Wa and Wb according to the following equation.

&Quot; (2) "

AUP (g / g) = [Wb (g) - Wa (g)] /

Weightless absorption capacity (g / g) Water content (%) 0.7 psi
Pressure absorption capacity (g / g) Example 1 35.5 13.5 24.8 Example 2 35.7 13.1 24.8 Example 3 36.1 12.8 22.8 Example 4 35.8 13.4 25.1 Comparative Example 1 33.2 13.8 22.1 Comparative Example 2 31.4 13.4 21.7

It can be seen from Table 2 that Examples 1 to 4 of the present invention provide a superabsorbent resin having excellent physical properties as compared with Comparative Examples 1 and 2.

Claims (9)

Forming a monomer composition comprising a water-soluble ethylenically unsaturated monomer and a polymerization initiator;
Polymerizing the monomer composition in a polymerization reactor to produce a hydrogel polymer;
Drying and pulverizing the hydrogel polymer;
Subjecting the pulverized co-gel polymer to a first temperature elevation to 70-100 ° C; And
Adding a surface treatment solution containing a surface cross-linking agent and a solvent to the first heated gelatinized functional polymer, and advancing the surface cross-linking reaction of the hydrogel polymer by secondary heating at 160 to 200 ° C,
In the surface treatment solution,
Water, and an alcohol or glycol compound having 3 or more carbon atoms and a boiling point of 90 占 폚 or more. The method according to claim 1, wherein the alcohol or glycol compound is at least one selected from the group consisting of n-propanol, butanol, propylene glycol and propanediol. The method of producing a superabsorbent resin according to claim 1, wherein the surface crosslinking agent is a diol or a glycol compound having 2 to 8 carbon atoms. The surface cross-linking agent according to claim 1, wherein the surface cross-linking agent is 1,3-propanediol, 2,3,4-trimethyl-1,3-pentanediol, Diethylene glycol, triethylene glycol, tetraethylene glycol, polyethylene glycol, propylene glycol, diethylene glycol, diethylene glycol, diethylene glycol, triethylene glycol, Propylene glycol, polypropylene glycol, glycerol, and polyglycerol. The surface treatment solution according to claim 1, wherein the surface treatment solution contains 0.1 to 20% by weight of a surface cross-linking agent based on the total weight of the surface treatment solution, 10 to 70% by weight of an alcohol or a glycol- Gt; The method of producing a superabsorbent resin according to claim 1, wherein the polymerization is carried out by UV polymerization or thermal polymerization. The water-soluble ethylenically unsaturated monomer according to claim 1, wherein the water-
(Meth) acrylic acid, methacrylic acid, maleic anhydride, fumaric acid, crotonic acid, itaconic acid, 2-acryloylethanesulfonic acid, 2- methacryloylethanesulfonic acid, 2- ) Anionic monomers of acrylamido-2-methylpropanesulfonic acid and its salts; (Meth) acrylamide, N-substituted (meth) acrylate, 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, methoxypolyethylene glycol (meth) acrylate or polyethylene glycol Non-ionic hydrophilic-containing monomer of (meth) acrylate; And at least one selected from the group consisting of an unsaturated monomer containing an amino group of (N, N) -dimethylaminoethyl (meth) acrylate or (N, N) -dimethylaminopropyl (meth) By weight. The method according to claim 1, wherein the polymerization initiator is any one selected from the group consisting of an azo initiator, a peroxide initiator, a redox initiator, a persulfate series and an organic halide initiator A method for producing an absorbent resin. The method of producing a superabsorbent resin according to claim 1, wherein the monomer composition further comprises a polymerization crosslinking agent.