KR101477226B1 - Monomer composition for preparing super absorbent polymer, its preparation method and preparation method of super absorbent polymer using the same - Google Patents

Abstract

The present invention relates to a monomer composition for preparing a superabsorbent resin, a method for producing the same, and a method for producing a superabsorbent resin using the same. The monomer composition comprises a monomer of a water-soluble ethylenically unsaturated compound containing acrylic acid, an alkali salt thereof, or a mixture thereof; And an aqueous solvent, and satisfies predetermined characteristics at a temperature of 25 占 폚 or more.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a monomer composition for preparing a superabsorbent resin, a method for producing the same, and a method for producing a superabsorbent resin using the same. BACKGROUND ART [0002]

The present invention relates to a monomer composition for preparing a superabsorbent resin, a method for producing the same, and a method for producing a superabsorbent resin using the same. More specifically, the present invention relates to a monomer composition for preparing a superabsorbent resin, which enables production of a superabsorbent resin having excellent physical properties with high productivity, a method for producing the same, and a method for producing a superabsorbent resin using the same.

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.

Such a superabsorbent resin is generally prepared by dissolving an unsaturated compound such as acrylic acid and an alkaline compound in a water solvent to form an aqueous liquid monomer composition containing the unsaturated compound or an alkali salt thereof and proceeding polymerization thereon.

Therefore, in order to obtain a superabsorbent resin having superior physical properties, the composition of the monomer composition is important. In particular, the monomer composition should be able to dissolve the unsaturated compound to stably maintain such a dissolution state to obtain a superabsorbent resin having excellent physical properties, and in particular, such a stable dissolution state is required from the preparation of the monomer composition to the polymerization Be maintained.

However, the specific composition of the monomer composition in which such a stable dissolution state can be maintained previously has not been found. For this reason, a large number of cases in which the unsaturated compounds in the monomer composition are previously precipitated or precipitated before or during the polymerization have caused a considerable amount of monomer components (for example, unsaturated compounds) to remain in the superabsorbent resin after polymerization, This is one of the main factors for lowering the physical properties of the superabsorbent resin.

In order to reduce such disadvantages, a method of reducing the amount of the unsaturated compound added to the monomer composition or dissolving the unsaturated compound at a relatively high temperature has been considered.

However, when the amount of the unsaturated compound is decreased, the productivity of the superabsorbent resin is lowered. Further, when the unsaturated compound or the like is dissolved at a relatively high temperature, the polymerization of the unsaturated compound by the heat of the monomer composition itself may proceed from the start of the actual polymerization process, and the polymerized superabsorbent resin exhibits sufficient polymerization degree and physical properties It is difficult to bet. In addition, heat accumulation of the superabsorbent resin may occur due to heat applied to dissolve the polyunsaturated compounds and the like, which may also be a factor for lowering the physical properties of the superabsorbent resin.

Accordingly, the present invention provides a monomer composition for producing a superabsorbent resin, which enables production of a superabsorbent resin having high physical properties and high productivity.

The present invention is also intended to provide a process for preparing the above monomer composition.

The present invention also provides a process for producing a superabsorbent resin using the monomer composition.

The present invention relates to a water-soluble ethylenically unsaturated compound containing acrylic acid, an alkali salt thereof or a monomer mixture thereof; And an aqueous solvent, and satisfying the following formula (1) at a temperature of 25 占 폚 or higher:

[Equation 1]

y (% by weight)? 52.386 * x ³ - 88.271 * x ² - 24.381 * x + 98.695

X is a real number of 0.40? X? 1.00 as a weight fraction of the alkali salt of the unsaturated compound among the total weight of the monomers contained in the composition, and y represents a mass percentage of the monomer contained in the composition .

Also, the present invention includes first to n-th steps of mixing an aqueous solution of an alkaline compound with a water-soluble ethylenically unsaturated compound containing acrylic acid, wherein the aqueous solution of the alkali compound used in the n-th stage is an n- Wherein the alkali compound has a lower alkaline compound concentration than the aqueous solution of the alkali compound used in < RTI ID = 0.0 >

and n is a natural number of 2 to 10.

The present invention also relates to a process for preparing a polymer composition comprising the steps of: forming the monomer composition; And polymerizing the monomer composition to form a hydrogel polymer.

Hereinafter, a monomer composition for preparing a superabsorbent resin according to embodiments of the present invention, a method for producing the same, and a method for producing a superabsorbent resin using the same will be described in detail.

According to one embodiment of the invention, monomers of a water-soluble ethylenically unsaturated compound containing acrylic acid, an alkali salt thereof or a mixture thereof; And an aqueous solvent, wherein a monomer composition for producing a superabsorbent resin is provided which satisfies the following formula (1) at a temperature of 25 占 폚 or higher:

[Equation 1]

y (% by weight)? 52.386 * x ³ - 88.271 * x ² - 24.381 * x + 98.695

X is a real number of 0.40? X? 1.00 as a weight fraction of the alkali salt of the unsaturated compound among the total weight of the monomers contained in the composition, and y represents a mass percentage of the monomer contained in the composition .

The formula (1) represents the relationship between the weight fraction x of the alkali salt of the unsaturated compound in the total amount of the monomers contained in the monomer composition and the mass percentage y of the monomer contained in the monomer composition.

In this formula 1, x = (weight of alkali salt of unsaturated compound contained in monomer composition / amount of unsaturated compound contained in monomer composition and alkali salt thereof), and y (% by weight) = { (Weight of unsaturated compound and its alkali salt contained in the monomer composition ÷ total weight of solvent, unsaturated compound and its alkali salt) X 100}.

As a result of experiments conducted by the present inventors, the monomer composition in which the weight fraction x of the alkali salt of the unsaturated compound in the monomer and the mass percentage y of the monomer in the monomer composition satisfy the relation of the formula (1) The above-mentioned unsaturated compound and its alkali salt) can be substantially dissolved, and it has been found that this dissolution state can be stably maintained. Particularly, since such a monomer composition can maintain a stable dissolved state of the monomer in an arbitrary state from its production to the polymerization for the production of a superabsorbent resin, it is possible to manufacture a superabsorbent resin exhibiting excellent physical properties It becomes.

In addition, within the range satisfying the relationship of the above-mentioned formula (1), as many monomers as possible can be contained in the monomer composition to stably dissolve the monomer composition, and it is not necessary to unnecessarily increase the temperature of the monomer composition for such stable dissolution , A superabsorbent resin having superior physical properties can be produced with high productivity by using the above-described monomer composition.

Particularly, since the monomer composition can stably dissolve a relatively large amount of monomers, the content of the water solvent is lower than that of the monomers, so that the polymerization process using such a monomer composition can produce a highly water- In addition, even in the step of drying a water solvent after polymerization of such a monomer composition, the amount of water solvent to be dried or evaporated is relatively reduced, thereby making it possible to efficiently manufacture a highly water absorbent resin. In addition, unnecessary heating of the drying process and the like can be suppressed, contributing greatly to maintenance of excellent physical properties of the superabsorbent resin.

The monomer composition according to one embodiment of the present invention will be described in more detail as follows.

The monomer composition basically comprises a water-soluble ethylenic unsaturated compound containing acrylic acid or an alkali salt which is a neutralized form of such an unsaturated compound as a monomer, and includes an aqueous solvent for dissolving such a monomer.

At this time, as the water-soluble ethylenic unsaturated compound containing acrylic acid, any unsaturated compound which is contained in addition to acrylic acid and which is acidic and can be used as a monomer in the production of a superabsorbent resin, can be used without any limitation. Examples of such unsaturated compounds include anionic unsaturated compounds, and more specifically, methacrylic acid, maleic anhydride, fumaric acid, crotonic acid, itaconic acid, 2-acryloylethanesulfonic acid, 2- methacryloylethane At least one selected from the group consisting of sulfonic acid, 2- (meth) acryloylpropanesulfonic acid and 2- (meth) acrylamide-2-methylpropanesulfonic acid can be used.

The alkali salt of the unsaturated compound may be an alkali metal salt, an alkaline earth metal salt, or an ammonium salt of the above-mentioned unsaturated compound in a form in which the above-mentioned unsaturated compound is neutralized by reaction with an alkali compound. More specifically, Lithium salts, sodium salts, potassium salts, ammonium salts, and the like.

However, it is preferable that the unsaturated compound is acrylic acid, and the alkali salt of the unsaturated compound is sodium acrylate, taking into account physical properties or economy of the ultrafine water-absorbent resin to be finally produced.

Water can also be used as a water solvent for dissolving such unsaturated compounds and their alkali salts, that is, monomers.

On the other hand, when the superabsorbent resin prepared from the monomer composition is used in applications such as sanitary articles that are likely to come into contact with a human body, it is necessary to neutralize the superabsorbent resin in order for the superabsorbent resin to exhibit excellent physical properties suitable for such use . From this point of view, the monomer composition for the preparation of the superabsorbent resin preferably contains an unsaturated compound in the form of a neutralized alkali salt as a monomer, rather than an unsaturated compound itself containing acrylic acid or other acid groups in an unneutral form Is more preferable.

Therefore, among the monomers (unsaturated compounds and alkali salts thereof) contained in the monomer composition, x representing the weight fraction of the alkali salt of the unsaturated compound may be 0.4 or more, preferably 0.6 or more, 0.65 to 1.00, and most preferably 0.65 to 0.85. In the monomer composition, the degree of neutralization of the unsaturated compound may be 40 mol% or more, preferably 50 mol% or more, and more preferably 60 to 80 mol%. This makes it possible to produce a superabsorbent resin having excellent physical properties suitable for use in a human body so that the necessity of separate neutralization after polymerization is not so great.

The content of each constituent component such as an unsaturated compound, an alkali salt thereof and a water solvent in the monomer composition can be determined in consideration of the amount of the unsaturated compound used for the production amount of the superabsorbent resin and the formula (1). Once the amount of the unsaturated compound used for preparing the preparation of the superabsorbent resin is determined, the amount of the other constituent components may be determined so as to satisfy the expression (1), and as a result, the content of each constituent component in the monomer composition Can be determined.

As described above, the content of the respective components is determined so that the monomers contained in the monomer composition, that is, the unsaturated compound and the alkali salt thereof can be all dissolved to maintain a stable dissolved state.

At this time, if the content of each component is determined within the range where x = 0.4 or more, the stable state of the monomer is maintained in the monomer composition, and the necessity of separate neutralization after polymerization is not large enough, A highly water-absorbent resin having more excellent physical properties can be efficiently obtained.

The monomer composition according to one embodiment of the present invention is (52.386 * x ³ 88.271 * x ² - 24.381 * x + 98.695) - 5 ≤ y (wt%) ≤ 52.386 * x ³ - 88.271 * x ² - 24.381 * x + 98.695). < / RTI > Here, x and y are as defined in the above formula (1). As the monomer composition satisfies these properties, it is possible to incorporate a larger amount of the monomer into the monomer composition while maintaining a stable dissolution state of the monomer, that is, the unsaturated compound and its alkali salt, Productivity and efficiency can be improved.

On the other hand, the above-mentioned monomer composition may further contain a polymerization initiator, a crosslinking agent, or a mixture thereof in addition to the constituent components of the unsaturated compound, its alkali salt and water solvent.

That is, in order to produce a superabsorbent resin, polymerization can be carried out by irradiating ultraviolet (UV) light or supplying heat to the monomer composition. For this purpose, a polymerization initiator can be used. Such a polymerization initiator may be varied in kind depending on the kind of polymerization method such as thermal polymerization or UV polymerization. As the thermal polymerization initiator, an azo-based initiator, a peroxide-based initiator, a redox-based initiator or an organic halide initiator may be used have. As the photopolymerization initiator used in the UV polymerization, acetophenone; Benzoin; Benzophenone; 2-methyl-1-phenylpropan-1-one, benzyldimethyltartarboxylate, 4- (2-hydroxyethoxy) phenyl- (2- hydroxy) Acetophenone derivatives such as 2-propyl ketone and 1-hydroxycyclohexyl phenyl ketone; Benzoin alkyl ethers such as benzoin methyl ether, benzoin ethyl ether, benzoin isopropyl ether and benzoin isobutyl ether; benzophenone derivatives such as methyl o-benzoylbenzoate, 4-phenylbenzophenone, 4-benzoyl-4'-methyl-diphenyl sulfide and (4-benzoylbenzyl) trimethylammonium chloride; Thioxanthone compounds; Acylphosphine oxide derivatives such as bis (2,4,6-trimethylbenzoyl) phenylphosphine oxide and diphenyl (2,4,6-trimethylbenzoyl) -phosphine oxide; Or azo compounds such as 2-hydroxymethylpropionitrile and 2,2 '- {azobis (2-methyl-N- [1,1'-bis (hydroxymethyl) -2- hydroxyethyl] propionamide) Compounds and the like can be used.

Further, in order to more effectively proceed polymerization for the production of the superabsorbent resin, a crosslinking agent having at least one functional group capable of reacting with the water-soluble substituent of the monomer and having at least one ethylenic unsaturated group; Or a crosslinking agent having two or more functional groups capable of reacting with water-soluble substituents formed by hydrolysis of the water-soluble substituents and / or monomers of the monomers. Specific examples of such crosslinking agents include bisacrylamide or bismethacrylamide having 8 to 12 carbon atoms, poly (meth) acrylate of polyol having 2 to 10 carbon atoms, poly (meth) allyl ether of polyol having 2 to 10 carbon atoms, (Meth) acrylate, ethyleneoxy (meth) acrylate, propyleneoxy (meth) acrylate, glycerin diacrylate, glycerin One or two kinds selected from the group consisting of triacrylate, trimethylol triacrylate, triallylamine, triaryl cyanurate, triallyl isocyanate, polyethylene glycol, polyethylene glycol diacrylate, diethylene glycol and propylene glycol The above compounds can be used. In addition, various cross-linking agents or additives known to be usable in the production of the superabsorbent resin may be further included.

The polymerization initiator or the crosslinking agent may be contained in an amount that does not deteriorate the economical efficiency or efficiency of polymerization while effectively assisting the monomer polymerization in the monomer composition. For example, the polymerization initiator may be contained in an amount of 0.005 to 0.1 part by weight, preferably 0.01 to 0.05 part by weight based on 100 parts by weight of the monomer (that is, the unsaturated compound and the alkali salt thereof), and the cross- May be contained in an amount of 0.005 to 1.0 part by weight, more preferably 0.01 to 0.5 part by weight, based on 100 parts by weight of the monomer.

As the monomer composition satisfies the predetermined characteristics expressed by the formula (1), the stable state of the monomer can be maintained during the production process of the superabsorbent resin using the same, particularly during the polymerization process. In addition, it is possible to contain a larger amount of monomers and maintain a high solid concentration of at least 40% by weight while securing such a stable dissolving state. Therefore, by using such a monomer composition, a superabsorbent resin having excellent physical properties can be used for productivity and efficiency So that it becomes possible to manufacture it at a high level. At this time, the solid content concentration of the monomer composition may be defined as the concentration of the remaining components excluding the water solvent, for example, the unsaturated compound and the alkali salt thereof.

On the other hand, according to one embodiment of the invention, a method for producing the above-mentioned monomer composition is provided. Such a method for preparing a monomer composition basically includes a step of neutralizing an aqueous ethylenically unsaturated compound containing acrylic acid with an aqueous solution of an alkaline compound. More preferably, the mixing and neutralization steps may be divided into n steps (where n may be a natural number of 2 to 10), and the first to the n-th steps may be performed, It is preferable that the aqueous solution of the alkali compound used in the step (n-1) has a lower concentration of the alkali compound than that of the aqueous solution used in the (n-1) th step.

As described above, the step of mixing the unsaturated compound and the aqueous alkaline solution is divided into a plurality of steps and the concentration of the aqueous alkaline solution is gradually lowered, thereby preparing a monomer composition satisfying the above-mentioned characteristics, that is, And such a monomer composition can maintain a stable dissolution state of the monomer such as the unsaturated compound or a salt thereof.

In addition, when a monomer composition is prepared by such a method, it becomes possible to provide a monomer composition in which a larger amount of a monomer such as an unsaturated compound or its alkali salt is dissolved while maintaining a stable dissolution state of the monomer, , It has been found that a monomer composition containing a neutralized form of the unsaturated compound, that is, a higher proportion of the alkali salt of the unsaturated compound, can be prepared.

Thus, by using the monomer composition thus produced, a highly water-absorbent resin having superior physical properties, particularly excellent physical properties suitable for application to human body, can be produced with high productivity.

On the other hand, in the above-mentioned method for producing a monomer composition, the kinds of the unsaturated compounds which can be used are as described above. As an aqueous solution of an alkali compound to be mixed for neutralization of such an unsaturated compound, an aqueous solution of an alkali metal, an aqueous solution of an alkaline earth metal, an aqueous solution of an amine or an ammonium compound and the like can be used. More specifically, an aqueous solution of lithium hydroxide, , An aqueous solution of potassium hydroxide, an aqueous solution of calcium hydroxide or an aqueous solution of quaternary ammonium salt. In addition, an aqueous solution of various alkaline compounds exhibiting basicity can be used.

In addition, in the above production method, the mixing step of the unsaturated compound and the aqueous alkaline solution may be performed twice or three times in consideration of the efficiency of the production process, the solubility of the monomers, and the neutralization degree of the unsaturated compound. If the mixing step is carried out in one step, there is a limit in obtaining a monomer composition containing a large amount of monomers to maintain a stable dissolution state. If the mixing step is divided into four or more times, the amount of the monomer soluble in the monomer composition The effect of further increasing the ratio of the alkaline salt of the neutralized form of the unsaturated compound is not large and the efficiency of the process may be lowered.

In the above production method, the mixing of the first to the n-th steps is preferably carried out at a temperature of 25 to 99 ° C, preferably 30 to 90 ° C for 1 to 30 minutes, preferably 2 to 20 minutes Do. Under such conditions, as the mixing step is progressed, the composition of the monomer composition in each step can maintain a stable dissolution state while satisfying the above-described formula (1), and as a result, A monomer composition capable of maintaining a stable dissolution state can be suitably prepared and the efficiency of the monomer composition manufacturing process can be improved.

On the other hand, according to another embodiment of the present invention, a method for producing a superabsorbent resin using the above-described monomer composition is provided. The method for producing such a superabsorbent resin includes the steps of forming the above-mentioned monomer composition; And polymerizing the monomer composition to form a hydrogel polymer.

According to this production method, the above-mentioned monomer composition is polymerized to obtain a hydrogel polymer, from which a superabsorbent resin is produced. Therefore, the stable dissolved state of the monomer is maintained during polymerization, and there is substantially no possibility of precipitation or precipitation of the monomer. Thus, the hydrogel polymer and the superabsorbent resin having excellent physical properties can be obtained, in which the amount of the residual monomer is greatly reduced.

In addition, since the monomer concentration in the monomer composition is relatively high and the water solvent content is relatively low, the solid content concentration of the hydrogel polymer obtained therefrom can be as high as 45 to 70% by weight. Therefore, in the process of producing a superabsorbent resin by drying and pulverizing such a hydrogel polymer, the drying process and the like are efficiently performed, and the physical properties of the superabsorbent resin can be reduced by heat during such a drying process. Here, the solid content concentration may be defined as the concentration of the remaining polymer dissolved in the aqueous solution obtained after completion of the polymerization except for the aqueous solvent as the medium. In addition, from the monomer composition having a relatively high solubility concentration of the monomer, the hydrogel polymer and the superabsorbent resin can be obtained with higher productivity.

In the method for producing the superabsorbent resin, the polymerization step of the monomer composition may be carried out at a temperature of 25 to 99 캜 for 1 to 30 minutes. Under such conditions, the polymerization can be appropriately proceeded while maintaining the stable state of the monomer during the polymerization, and the hydrogel polymer formed by the polymerization can be inhibited from being thermally damaged or deteriorated in physical properties due to the high temperature.

In the method for producing a superabsorbent resin, the maximum temperature of the hydrogel polymer formed by the polymerization may be maintained at a temperature of 50 to 150 ° C, preferably 80 to 130 ° C. The monomer composition used in the above production method is not required to raise the temperature before the polymerization in order to maintain the stable dissolution state of the monomer contained therein. Thus, the hydrogel polymer obtained from such a monomer composition can maintain a relatively low temperature, which is not significantly higher than the polymerization conditions. Therefore, deterioration of physical properties of the hydrogel polymer and the superabsorbent resin due to thermal damage can be minimized, and it becomes possible to manufacture a superabsorbent resin having superior physical properties.

Meanwhile, in the above production process, the polymerization step of the monomer composition may be carried out under ultraviolet irradiation or heat supply in accordance with the conventional preparation process of a superabsorbent resin. In this case, the monomer composition may further contain a photopolymerization initiator or a thermal polymerization initiator Is already described above. In these cases, specific polymerization methods, ultraviolet irradiation or heat supply conditions and the like are known to those skilled in the art.

Also, during the polymerization process, as the irradiation with ultraviolet rays or the heat supply is performed, a certain degree of drying with respect to the hydrogel polymer can be performed together.

After the polymerization, the functional gel polymer is pulverized; And further drying the hydrogel polymer, from which a superabsorbent resin in powder form can be obtained. More specifically, after the polymerization, the first step of drying the hydrogel polymer, the step of pulverizing the polymer, the step of second-order pulverization and surface cross-linking of the pulverized polymer, Can be obtained.

At this time, in the pulverization step, the hydrogel polymer can be cut or extruded by pulverizing according to a conventional process of manufacturing a superabsorbent resin. For this purpose, a cutting means such as a cutter type cutter, a chopper type cutter or a kneader type cutter is used Or an extrusion grinding means such as a vibration type pulverizer, an impact type pulverizer or a friction type pulverizer may be used.

In the drying step, usually, a dryer and a heating furnace can be used. For example, a hot air drier, a fluidized bed drier, an air drier, an infrared drier or a dielectric heating drier can be used. The drying temperature is not particularly limited, but is usually 100-200 占 폚. Drying can be carried out within such a range, drying efficiency can be promoted, and deterioration of physical properties of the superabsorbent resin due to heat can be reduced.

Other secondary pulverization and surface cross-linking steps can also be carried out according to the conventional production process of superabsorbent resin.

As described above, according to the present invention, it is possible to provide a monomer composition capable of maintaining a stable dissolved state of a monomer until polymerization and capable of producing a superabsorbent resin having excellent physical properties and a method for producing the same.

In addition, such a monomer composition can maintain the above-described stable dissolved state while containing a larger amount of monomers, so that the productivity of the superabsorbent resin can be greatly improved.

Therefore, the present invention can greatly contribute to the production of a superabsorbent resin having better physical properties.

Hereinafter, various embodiments of the present invention will be described. However, this is an example of the invention, and the scope of the invention is not limited thereby.

Examples 1 to 5: Preparation of monomer composition

Sodium hydroxide was added to water to form a first aqueous solution of sodium hydroxide and an aqueous solution of sodium hydroxide and another amount of sodium hydroxide were added to an equal amount of water to form a second aqueous solution of sodium hydroxide.

Then, neutralization was carried out by mixing the aqueous solution of sodium hydroxide and acrylic acid and stirring at 25 ° C for 5 minutes. The mixture was mixed with a second aqueous sodium hydroxide solution and stirred at 80 ° C for 5 minutes for neutralization. Thus, all the acrylic acid was dissolved to form the monomer composition for producing super absorbent polymer of Examples 1 to 5 in which acrylic acid or sodium acrylate was dissolved.

In these Examples 1 to 5, the amounts of acrylic acid, sodium hydroxide and water used are summarized in Table 1 below. Further, the temperature of each monomer composition was maintained, and the degree of neutralization of x, y, f (x) and acrylic acid with respect to these monomer compositions was calculated according to the following formula, and the results are summarized in Table 1 below.

x = (weight of sodium acrylate contained in the monomer composition / weight sum of acrylic acid and sodium acrylate contained in the monomer composition)

y (wt.%) = {(weight of acrylic acid and sodium acrylate contained in the monomer composition ÷ total weight of monomer composition) X 100}

f (x) = 52.386 * x ³ - 88.271 * x ² - 24.381 * x + 98.695

Neutralization degree (mol%) = {(weight of sodium acrylate contained in monomer composition / molecular weight of sodium acrylate) / (total weight of acrylic acid charged into monomer composition divided by molecular weight of acrylic acid)} X 100

Acrylic acid
(g) Sodium hydroxide
(g) water
(g) x y (% by weight) f (x) Neutralization degree
(mole%) Example 1 448 166 385 0.72 54.0 55.0 66.6 Example 2 441 162 427 0.76 50.0 52.2 70.8 Example 3 408 168 424 0.79 50.0 50.1 74.2 Example 4 383 157 459 0.79 47.0 49.8 73.9 Example 5 341 162 497 0.88 43.0 44.1 85.3

Comparative Examples 1 to 3: Preparation of monomer composition

Sodium hydroxide was added to water to form an aqueous sodium hydroxide solution. This sodium hydroxide aqueous solution and acrylic acid were mixed and stirred at 25 캜 for 5 minutes to neutralize. As a result, the monomer composition for preparing super absorbent polymer of Comparative Examples 1 to 3 in which acrylic acid or sodium acrylate was dissolved was formed.

In these Comparative Examples 1 to 3, the amounts of acrylic acid, sodium hydroxide, and water used are summarized in Table 2 below. The degrees of neutralization of x, y, f (x) and acrylic acid for these monomer compositions were calculated in the same manner as in Examples, and are summarized in Table 2 below.

Acrylic acid
(g) Sodium hydroxide
(g) water
(g) x y (% by weight) f (x) Neutralization degree
(mole%) Comparative Example 1 429 183 388 0.81 53.0 49.8 76.7 Comparative Example 2 387 187 426 0.90 49.0 44.1 87.1 Comparative Example 3 386 170 443 0.83 48.0 47.5 79.3

Examples 6 to 10: Preparation of superabsorbent resin

0.033 parts by weight of diphenyl (2,4,6-trimethylbenzoyl) -phosphine oxide (photopolymerization initiator) and 0.033 part by weight of sodium persulfate (thermal polymerization initiator) were added to 100 parts by weight of acrylic acid in the monomer compositions of Examples 1 to 5 ) And 0.1 part by weight of polyethylene glycol diacrylate (crosslinking agent) were added and mixed.

This monomer composition was placed on a continuously moving conveyor belt, irradiated with ultraviolet light (irradiation amount: ² Mw / cm ² ), and subjected to UV polymerization at 80 캜 for 3 minutes.

The maximum temperature (占 폚), the solid content concentration (% by weight) and the residual monomer content (% by weight) during or after the polymerization of the hydrogel polymer thus obtained were measured and summarized in Table 3 below.

On the other hand, the hydrogel polymer was obtained through the above polymerization, and the polymer was transferred to a pulverizer, pulverized to a size of 1 × 1 mm, dried in a hot air drier at 150 ° C. for 5 hours, pulverized with a pin mill and then sieved A superabsorbent resin having a particle diameter of 150 to 850 탆 was obtained.

Thereafter, the superabsorbent resin was surface-crosslinked at 120 ° C for 1 hour by using a 3% solution of ethylene glycol diglycidyl ether, and then surface crosslinked Example 6 having a particle diameter of 150 to 850 μm was formed using a sieve To 10 of super absorbent resin.

The absorption capacity (CRC), water component, and residual monomer of the superabsorbent resin were measured and are summarized in Table 3 below.

Comparative Examples 4 to 6: Preparation of superabsorbent resin

The hydrogel polymers and the superabsorbent resins of Comparative Examples 4 to 6 were prepared in the same manner as in Examples 6 to 10 except that the monomer compositions of Comparative Examples 1 to 3 were used.

The maximum temperature (占 폚), the solid concentration (% by weight) and the residual monomer content (% by weight) of the hydrogel polymer in the polymerization process or immediately after polymerization were measured in the same manner as in Examples 6 to 10, . In the same manner as in Examples 6 to 10, the absorption coefficient (CRC), water content and residual monomer of the finally obtained superabsorbent resin were measured and summarized together in Table 3 below.

Test Example: Evaluation of Solid Content and Properties of Superabsorbent Resin

The physical properties of the superabsorbent resins of Examples and Comparative Examples were evaluated by the following methods. This method of measuring the physical properties was conducted in a manner recommended by EDANA.

1. Solid concentration: 1 g of the superabsorbent resin powder before surface cross-linking was dried in an infrared drier at 180 캜 for 40 minutes, and the water content was measured to calculate the solid content concentration.

2. Water retention capacity: 0.2 g of the superabsorbent resin powder before surface cross-linking was put into a tea bag, sedimented and absorbed in 0.9 wt% saline solution for 30 minutes, dehydrated for 3 minutes with 250 g of centrifugal force, (This was measured by the weight change of the sample).

3. Water component: 1 g of the superabsorbent resin powder before surface cross-linking was placed in a 250 ml Erlenmeyer flask, and 200 ml of a 0.9% by weight saline solution was added thereto, followed by elution with stirring at 500 rpm for 18 hours. Thereafter, the gel portion of the superabsorbent resin was filtered with a filter paper (No. 4), and only the portion dissolved in the 0.9 wt% saline solution was analyzed to determine the weight ratio of the superabsorbent resin eluted to the weight of the superabsorbent resin before the elution And the water content of the water was measured (see EDANA 270.2 method).

The physical properties of the hydrogel polymer and the superabsorbent resin sample (powder) of Examples 1 to 10 and Comparative Examples 1 to 6, which were measured by the above-described method, are summarized in Table 3 below.

Functional gel polymer Superabsorbent resin Monomer composition Maximum temperature (℃) Solid concentration
(weight%) Remaining
Monomer
content
(weight%) Function
(g / g) Water component
(weight%) Remaining monomer
(weight%) Example 6 Example 1 124 68 0.2 42 13 0.09 Example 7 Example 2 118 64 0.4 43 14 0.08 Example 8 Example 3 115 61 0.9 45 15 0.09 Example 9 Example 4 109 55 1.3 44 13 0.10 Example 10 Example 5 105 52 1.2 45 14 0.12 Comparative Example 4 Comparative Example 1 129 58 2.4 38 15 0.5 Comparative Example 5 Comparative Example 2 125 53 3.1 42 18 0.4 Comparative Example 6 Comparative Example 3 125 50 4.5 42 18 1.4

Referring to Table 3, the hydrogel polymer and the superabsorbent resin of Examples 1 to 10 were superior in physical properties such as water content and water retention capacity and water content as compared with Comparative Examples 1 to 6, It was confirmed that the residual monomer content was low. This is because the hydrogel polymers of Examples 1 to 10 are made of a monomer composition satisfying the physical properties of the formula (1), while those of the comparative examples 1 to 6 are made of a monomer composition which does not satisfy them.

Claims (17)

Monomers of a water-soluble ethylenically unsaturated compound containing acrylic acid, an alkali salt thereof or a mixture thereof; And an aqueous solvent, and satisfying the following formula (1) at a temperature of 25 占 폚 or higher:
[Equation 1]
y (% by weight)? 52.386 * x ³ - 88.271 * x ² - 24.381 * x + 98.695
X is a real number of 0.40? X? 1.00 as a weight fraction of the alkali salt of the unsaturated compound among the total weight of the monomers contained in the composition, and y represents a mass percentage of the monomer contained in the composition .
The method of claim 1, wherein the unsaturated compound is 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- (Meth) acrylamide-2-methylpropanesulfonic acid, and 2- (meth) acrylamide-2-methylpropanesulfonic acid.
The monomer composition according to claim 1, wherein the unsaturated compound is acrylic acid, and the alkali salt of the unsaturated compound is sodium acrylate.
The monomer composition for producing a superabsorbent resin according to claim 1, wherein the weight fraction x of the alkali salt of the unsaturated compound is 0.6 to 1.00.
The method of claim 1, wherein (52.386 * x ³ - 88.271 * x ² - 24.381 * x + 98.695) - 5 ≤ y (wt%) ≤ 52.386 x ³ - 88.271 * x ² - 24.381 * x + 98.695 By weight based on the total weight of the composition.
The composition according to claim 1, wherein the degree of neutralization of the unsaturated compound is at least 40 mol%.
The monomer composition according to claim 1, further comprising a polymerization initiator, a crosslinking agent, or a mixture thereof.
A first step of mixing an aqueous solution of an alkaline compound with a water-soluble ethylenically unsaturated compound containing acrylic acid; And
And second to n-th steps of adding and mixing an aqueous solution of an alkaline compound to the mixed solution formed in the first step,
Wherein the aqueous solution of the alkali compound used in the n-th stage has a lower alkaline compound concentration than the aqueous solution of the alkali compound used in the (n-1)
n is a natural number of 2 or 3.
The method for producing a monomer composition according to claim 8, wherein the aqueous solution of the alkaline compound is an aqueous solution of an alkali metal, an aqueous solution of an alkaline earth metal, or an aqueous solution of an amine or an ammonium compound.
delete The method according to claim 8, wherein in the first to n-th steps, the aqueous solution of the alkaline compound is mixed with the unsaturated compound at a temperature of 25 to 99 ° C for 2 to 20 minutes.
Forming a monomer composition according to any one of claims 1 to 7;
Polymerizing the monomer composition to form a hydrogel polymer;
Pulverizing the hydrogel polymer;
Drying the hydrogel polymer; And
And a step of subjecting the hydrogel polymer to secondary pulverization and surface cross-linking.
13. The method of producing a superabsorbent resin according to claim 12, wherein the polymerization step is conducted at a temperature of 25 to 99 DEG C for 1 to 30 minutes.
The method of producing a superabsorbent resin according to claim 12, wherein the maximum temperature of the hydrogel polymer is from 80 to 130 캜.
The method of producing a superabsorbent resin according to claim 12, wherein the hydrogel polymer has a solid concentration of 45 to 70% by weight.
The method of producing a superabsorbent resin according to claim 12, wherein the polymerization step is conducted under ultraviolet irradiation or heat supply.
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