KR20170119805A - Method for preparing super absorbent polymer - Google Patents

Abstract

There is provided a method of manufacturing a superabsorbent resin capable of improving the absorption rate, minimizing the residual monomer content, and preventing the deterioration of the water retention ability. The method for producing a superabsorbent resin includes the steps of preparing a crosslinked polymer of a monomer composition comprising a hydrophilic monomer, a crosslinking agent, and a polymerization initiator, contacting the crosslinked polymer with a foamable aqueous solution, and drying the crosslinked polymer .

Description

METHOD FOR PREPARING SUPER ABSORBENT POLYMER [0002]

The present invention relates to a method for producing a superabsorbent resin and a superabsorbent resin prepared by the method.

Super Absorbent Polymer (SAP) is a synthetic polymer material capable of absorbing 500 to 1,000 times its own weight of water. As a result, it is possible to develop a super absorbent polymer (SAM), an absorbent gel material ), And so on. The above-mentioned 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 now various kinds of sanitary articles such as soil repair agents for horticultural use, index materials for civil engineering and construction, sheets for seedling, It is widely used as a material for articles 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. As a method of aqueous solution polymerization, there are known a thermal polymerization method in which heat is applied to an aqueous solution and a photopolymerization method in which ultraviolet light is irradiated to perform polymerization.

On the other hand, as the use of the superabsorbent resin is diversified, the absorption capacity, the centrifugal retention capacity (CRC), the absorption under pressure (AUP), the free swelling rate (FSR) , And filling properties.

On the other hand, during the production of the superabsorbent resin, a part of the un polymerized monomer may remain on the surface and / or the interior of the superabsorbent resin. Such residual monomers (RM) reduce the liquid permeability of diapers and the like and cause skin diseases.

In addition, when the absorption rate of the diaper or the like is insufficient, the absorbent surface becomes sticky, which is a cause of bad smell and may cause a feeling of use. Further, development of a superabsorbent resin having a further improved absorption rate as the diaper or the like is thinned is required It is true.

Accordingly, a problem to be solved by the present invention is to provide a superabsorbent resin having an improved absorption rate and a low residual monomer content, and a method for producing the same.

Further, it is intended to provide a superabsorbent resin having a pore structure inside the superabsorbent resin without deteriorating the water retention ability and a method for producing the same.

The present invention has been made in view of the above problems, and it is an object of the present invention to provide a method of manufacturing the same.

According to one aspect of the present invention, there is provided a method for producing a superabsorbent resin, comprising the steps of: preparing a crosslinked polymer of a monomer composition comprising a hydrophilic monomer, a crosslinking agent, and a polymerization initiator; contacting the crosslinked polymer with a foamable aqueous solution And drying the cross-linked polymer.

Further, before the step of bringing the crosslinked polymer into contact with the foamable aqueous solution, it may further include the step of cutting the crosslinked polymer into a crosslinked polymer having a first average size.

Further, the step of drying the crosslinked polymer may be carried out after the step of contacting the crosslinked polymer and the foamable aqueous solution.

It is also possible to cut the crosslinked polymer having the first average size into a crosslinked polymer having a second average size smaller than the first average size between the step of contacting the crosslinked polymer with the foamable aqueous solution and the step of drying the crosslinked polymer The method comprising the steps of:

In addition, the average size of the crosslinked polymer in the step of contacting the crosslinked polymer with the aqueous foamable solution may be the same as the average size of the crosslinked polymer in the step of drying the crosslinked polymer.

Further, the step of drying the cross-linking polymer may be carried out after the step of contacting the cross-linking polymer with the foamable aqueous solution, and after the step of drying the cross-linking polymer, the step of crushing the cross-linking polymer may be further included.

The step of contacting the crosslinkable polymer with the foamable aqueous solution may be carried out by mixing the crosslinked polymer and 2 to 10 parts by weight of the water to 100 parts by weight of the crosslinked polymer, Or the like.

The step of bringing the crosslinked polymer into contact with the foamable solution may include contacting the crosslinked polymer with 0.1 to 2 parts by weight of the component with respect to 100 parts by weight of the crosslinked polymer.

In addition, the step of drying the crosslinked polymer may be performed at 150 ° C or higher.

In addition, the monomer composition may further include 0 to 3 parts by weight of a foamable substance based on 100 parts by weight of the hydrophilic monomer.

The foamable aqueous solution is an aqueous solution containing urea, and the foamable material is selected from the group consisting of sodium carbonate (NaCO ₃ ), sodium hydrogencarbonate (NaHCO ₃ ), potassium hydrogencarbonate (KHCO ₃ ), ammonium carbonate ((NH ₄ ) ₂ CO ₃ H ₂ O), ammonium hydrogencarbonate (NH ₄ HCO ₃ ), magnesium carbonate (MgCO ₃ ), calcium carbonate (CaCO ₃ ), barium carbonate (BaCO ₃ ) and / or hydrates thereof.

Also, the step of preparing the crosslinked polymer of the monomer composition includes the step of preparing the monomer composition, the step of providing the monomer composition to the belt surface of the belt-shaped reactor, and the step of polymerizing the monomer composition on the belt can do.

According to another aspect of the present invention, there is provided a method for producing a superabsorbent resin comprising the steps of preparing a hydrogel crosslinked polymer, preparing an aqueous urea solution, and mixing the urea aqueous solution And thermally decomposing the internal elements.

The step of thermally decomposing the urea in the urea aqueous solution within the gel of the hydrogel cross-linked polymer may be carried out by injecting the urea aqueous solution onto the surface of the hydrogel cross-linked polymer, Permeating the element, and thermally decomposing the element within an atmosphere of 95 DEG C to 155 DEG C to produce an ammonia gas and / or a carbon dioxide gas, wherein the ammonia gas and / or the carbon dioxide gas is generated The pore structure may be imparted to the inside of the hydrogel crosslinked polymer.

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

According to the method of producing a superabsorbent resin according to an embodiment of the present invention, the foamed aqueous solution is permeated into the hydrogel crosslinked polymer having a sufficient degree of polymerization to give a pore structure, thereby improving the absorption rate and minimizing the residual monomer content .

In addition, since the pore structure is imparted to the hydrogel crosslinked polymer in which polymerization has been completed, the monomer composition can contain no surfactant, and therefore, the decrease in the insulating ability can be suppressed.

Further, by spraying the foamable aqueous solution onto the hydrogel crosslinked polymer subjected to one or more cutting steps, the surface area of the foamed aqueous solution can be increased into the gel of the hydrogel crosslinked polymer, thereby forming a sufficient amount of pore structure .

In addition, the step of drying the hydrogel crosslinked polymer without adding any additional processing step can be used to control the reaction rate and the reaction rate of the foamable material.

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

1 is a flowchart showing a method for producing a superabsorbent resin according to an embodiment of the present invention.
Fig. 2 is a schematic view showing a method for producing the superabsorbent resin of Fig. 1; Fig.
3 is a flowchart showing a method for producing a superabsorbent resin according to another embodiment of the present invention.
Fig. 4 is a schematic view showing a method for producing the superabsorbent resin of Fig. 3; Fig.

BRIEF DESCRIPTION OF THE DRAWINGS The advantages and features of the present invention and the manner of achieving them will become apparent with reference to the embodiments described in detail below with reference to the accompanying drawings. The present invention will now be described more fully hereinafter with reference to the accompanying drawings, in which preferred embodiments of the invention are shown. However, it will be understood by those of ordinary skill in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention. To fully disclose the scope of the invention to a person skilled in the art, and the invention is only defined by the scope of the claims.

In the present specification, "C _AB " is defined as having a carbon number of A or more and B or less. For example, a C _1-5 alkyl group means an alkyl group having 1 to 5 carbon atoms. &Quot; and / or " include each and any combination of one or more of the mentioned items. The numerical ranges indicated by using " to " indicate numerical ranges including the lower and upper limits of the values described before and after, respectively, unless otherwise specified. Like reference numerals refer to like elements throughout the specification.

Although the first, second, etc. are used to describe various components, it goes without saying that these components are not limited by these terms. These terms are used only to distinguish one component from another.

Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.

1 is a flowchart showing a method for producing a superabsorbent resin according to an embodiment of the present invention. Fig. 2 is a schematic view showing a method for producing the superabsorbent resin of Fig. 1; Fig.

1 and 2, a method of manufacturing a superabsorbent resin according to an embodiment of the present invention includes a step (S110) of preparing a crosslinked polymer of a monomer composition comprising a hydrophilic monomer, a crosslinking agent and a polymerization initiator (S110) (S120), preparing a foamable solution (S130), and thermally decomposing the foamable material (S140).

The step (S110) of preparing a crosslinked polymer of a monomer composition comprising a hydrophilic monomer, a crosslinking agent and a polymerization initiator includes a step (S111) of preparing a monomer composition comprising a hydrophilic monomer, a crosslinking agent and a polymerization initiator, Step S112, and polymerizing the monomer composition in a reactor (S113).

First, a monomer composition 100 comprising a hydrophilic monomer, a crosslinking agent and a polymerization initiator is prepared (S111).

The hydrophilic monomer may be a monomer including a hydrophilic group such as a hydroxyl group (-OH), a carboxyl group (-COOH), an amide group (-NH ₂ ) and the like. The hydrophilic monomer is not limited as long as it is generally used in the production of a superabsorbent resin, but may be, for example, a water-soluble ethylenically unsaturated monomer. The water-soluble ethylenically unsaturated monomer may be any one of an anionic monomer and its salt, a nonionic hydrophilic-containing monomer, and an amino group-containing unsaturated monomer, a quaternary product thereof, or a mixture thereof.

Specific examples of the anionic monomer and its salt include acrylic acid, methacrylic acid, maleic anhydride, fumaric acid, crotonic acid, itaconic acid, 2-acryloylethanesulfonic acid, 2- methacryloylethanesulfonic acid, 2- (Meth) acryloylpropanesulfonic acid and 2- (meth) acrylamide-2-methylpropanesulfonic acid.

Examples of the nonionic hydrophilic-containing monomer include (meth) acrylamide, N-substituted (meth) acrylate, 2-hydroxyethyl (meth) acrylate, 2- Methoxypolyethylene glycol (meth) acrylate, and polyethylene glycol (meth) acrylate.

Examples of the amino group-containing unsaturated monomer and its quaternary compound include (N, N) -dimethylaminoethyl (meth) acrylate and (N, N) -dimethylaminopropyl (meth) acrylamide .

The concentration of the water-soluble ethylenically unsaturated monomer in the monomer composition (100) may be appropriately selected in consideration of the type of the reactor and the polymerization conditions, but may be in the range of, for example, 30 wt% or more and 60 wt% or less.

The crosslinking agent includes at least one atomic group capable of reacting with the functional group of the hydrophilic monomer and at least one ethylenic unsaturated group, or an atomic group capable of reacting with a functional group formed by hydrolyzing the hydrophilic monomer and the hydrophilic monomer Or more may be used. The cross-linking agent may be included in the range of about 0.01 to about 0.5 parts by weight based on 100 parts by weight of the hydrophilic monomer.

The crosslinking agent is bisacrylamide C _8-12, C _8-12 bismethacrylate acrylamide, C _2-12 poly (meth) poly (meth) allyl ether, or mixtures thereof acrylates, C _2-10 polyols of the polyol . ≪ / RTI >

Specifically, examples of the crosslinking agent include (poly) ethylene glycol (meth) acrylate, (poly) propylene glycol di (meth) acrylate, trimethylolpropane tri (meth) acrylate, ethoxyl Trimethylolpropane tri (meth) acrylate, ethoxyl (6) -trimethylol propane tri (meth) acrylate, ethoxyl (9) (Meth) acrylate glycerin tri (meth) acrylate, glycerin acrylate methacrylate, 2,2-bis [acryloylmethyl] butyl acrylate (3EO), N, N'- (Meth) acrylate, propyleneoxy (meth) acrylate, glycerin, glycerin diacrylate, glycerin triacrylate, trimethylol triacrylate, triallyl But are not limited to, polyoxyethylene, polyoxyethylene, polyoxyethylene, polyoxyethylene, polyoxyethylene, polyoxyethylene, polyoxyethylene, polyoxyethylene, polyoxyethylene, polyoxyethylene, triaryl isocyanurate, triallyl isocyanate, pentaethyleneimine, ethylene glycol, polyethylene glycol diethylene glycol, It is not.

The polymerization initiator may include at least one of a photopolymerization initiator, a thermal polymerization initiator, and an oxidation-reduction polymerization initiator. For example, the monomer composition (100) may include a photopolymerization initiator and a thermal polymerization initiator as a polymerization initiator.

The photopolymerization initiator may be selected from the group consisting of diethoxyacetophenone, 2-hydroxy-2-methyl-1-phenylpropan-1-one, 4- (2-hydroxyethoxy) phenyl- Acetophenone derivatives such as ketone and 1-hydroxycyclohexyl phenyl ketone; Benzoin alkyl ether compounds such as benzoin methyl ether, benzoin ethyl ether, benzoin isopropyl ether and benzoin isobutyl ether; benzophenone derivatives such as methyl o-benzoylbenzoate, 4-phenylbenzophenone, 4-benzoyl-4'-methyl-diphenyl sulfide and (4-benzoylbenzyl) trimethylammonium chloride; Thioxanthone-based compounds; Bis (2,4,6-trimethylbenzoyl) -phenylphosphine oxide, diphenyl (2,4,6-trimethylbenzoyl) -phosphine oxide, diphenyl (2,4,5-trimethylbenzoyl) An acylphosphine oxide derivative such as a seed; Or an azo group such as 2-hydroxymethylpropionitrile and 2,2 '- (azobis (2-methyl-N- (1,1'-bis (hydroxymethyl) -2- hydroxyethyl) propionamide) (Sodium persulfate, Na2S2O8), Potassium persulfate (K2S2O8), or a mixture thereof, in the presence of an initiator, an azo initiator, a peroxide initiator, a redox initiator, an organic halide initiator, Examples of the thermal polymerization initiator include azo initiators, peroxide initiators, redox initiators, and organic halide initiators, which may be used alone or in combination of two or more. .

The content of the polymerization initiator in the monomer composition (100) may be appropriately selected so as to exhibit polymerization initiating effect. For example, in the case of the photopolymerization initiator, about 0.005 to 0.1 part by weight And in the case of the thermal polymerization initiator, about 0.01 to 0.5 part by weight based on 100 parts by weight of the hydrophilic monomer may be included.

In another embodiment, the monomer composition 100 may further comprise a first foamable material. The first foamable material may impart a pore structure to the crosslinked polymer together with the foamable solution 300 to be described later. The first foamable material is not particularly limited as long as it is a material capable of reacting with an acid to form bubbles. Examples of the foamable material include sodium hydrogencarbonate (NaHCO ₃ ), sodium carbonate (NaCO ₃ ), potassium hydrogencarbonate (KHCO ₃ ) (NH ₄ ) ₂ CO ₃ H ₂ O), ammonium hydrogencarbonate (NH ₄ HCO ₃ ), magnesium carbonate (MgCO ₃ ), calcium carbonate (CaCO ₃ ), barium carbonate (BaCO ₃ ), and / or And hydrates thereof. The first foamable material may be contained in an amount of more than 0 to 3 parts by weight based on 100 parts by weight of the hydrophilic monomer.

The monomer composition is then provided to the reactor (S112). In an exemplary embodiment, the reactor may be a belt-like continuous reactor. That is, the step (S112) of providing the monomer composition to the reactor may be a step of supplying the monomer composition 100 to the surface of the belt 3 of the belt-shaped reactor.

The belt type reactor is arranged so as to form a closed curve between two conveying rolls 2 and 2 'and two conveying rolls 2 and 2' and is rotated in a predetermined direction And a belt 3 extending from the belt 3 to the belt 3. Two or more transfer rolls 2 and 2 'may be provided depending on the length or arrangement of the belt 3 and a power source such as a motor may be connected so that one side of the belt 3 forms a horizontal plane, . The monomer composition 100 is loaded on one side of the belt 3 and transferred, and the reaction can proceed continuously. In some embodiments, the plurality of transport rolls are disposed at different heights with respect to the horizontal plane so that one side of the belt may form a slope. In embodiments where the monomer composition further comprises the first foamable material, the monomer composition loaded and transported on one side of the belt may contain a large amount of bubbles.

Then, the monomer composition is polymerized (S113). In an exemplary embodiment, step (S113) of polymerizing the monomer composition may be a step of photopolymerizing the monomer composition 100 on the belt 3 of a belt-type reactor to form a sheet-like hydrogel crosslinked polymer.

The light irradiation unit 4 may be located behind the monomer composition supply unit 1 with respect to the traveling direction of the belt 3. The light irradiation unit 4 may be a light source such as a Xe lamp, a mercury lamp, or a metal halide lamp. The light may be ultraviolet light having a wavelength in the range of about 200 nm to 400 nm. For example, the light may be irradiated for about 10 seconds to 5 minutes at an exposure amount ranging from about 0.5 mW / cm ² to 500 mW / cm ² , or about 10 seconds to 5 minutes, And can be irradiated at a time ranging from 20 seconds to 3 minutes. An effective photopolymerization reaction can be performed within the wavelength, the exposure amount, and the irradiation time range, and the crosslinking point of the polymer due to the irradiation with excess light can be prevented from being broken. The crosslinked polymer sheet 200 formed by polymerizing the monomer composition 100 can be loaded on one side of the belt 3 and continuously conveyed.

In some embodiments, the step of polymerizing the monomer composition may be a step of thermally polymerizing the monomer composition on the belt 3 of the belt-type reactor to form a cross-linked polymer. When the monomer composition includes a thermal polymerization initiator, heat may be applied from a heat source or a thermal polymerization reaction may proceed due to heat generated during the photopolymerization reaction. In this case, the heat source may be positioned behind the monomer composition supply unit Can be located.

Next, the prepared sheet-like cross-linked polymer is cut (S120). The step (S120) of cutting the cross-linked polymer may be performed more than once. Step S120 of cutting the cross-linked polymer is a step of transferring the sheet-like cross-linked polymer 200 obtained by the completion of the polymerization reaction to the first cutter 5 and performing primary cutting with the particulate cross-linked polymer 401 having the first average size As a step, for example, the particulate crosslinked polymer 401 having a first average size may have an average size of about 2 cm x 2 cm to about 4 cm x 4 cm, or an average size of about 3 cm x 3 cm. The step (S120) of cutting the cross-linked polymer can be performed using a chopper type cutter, a kneader type cutter, or a cutter type cutter, but is not limited thereto.

In some embodiments, however, the cutting step before step S141 of spraying the foaming solution to be described later may be omitted.

Meanwhile, a foamable solution is prepared (S130). The foamable solution 300 may be an aqueous solution containing a second foamable material and water. In an exemplary embodiment, the second foamable material may comprise a urea. The content of the second foamable material and water is not particularly limited as long as it is capable of forming an aqueous solution. For example, when the second foamable material includes urea, the second foamable material and water may be used in a ratio of about 1: 1 to 1: Can be mixed in a weight ratio of about 1: 6 to 1:10.

Next, the foamable material is thermally decomposed in the primary cut particulate crosslinked polymer (S140). Specifically, the step (S140) of thermally decomposing the foamable material in the cross-linked polymer (401) includes a step (S141) of spraying the foamable solution onto the surface of the cross-linked polymer, a step (S142) of cutting the cross- And drying the polymer (S143).

The step S141 of spraying the foamable solution onto the surface of the crosslinked polymer is a step for uniformly contacting the crosslinked polymer 401 and the foamable solution 300 by spraying the foamable solution 300 onto the surface of the particulate crosslinked polymer 401 . The foamable solution supply part 6a is disposed adjacent to or spaced apart from the first cutter 5 and specifically to the cross-linked polymer 401 cut into granular particles having a first average size through the first cutter 5, (Not shown). The injected foamy solution 300 can be absorbed or penetrated into the gel of the crosslinked polymer 401.

The amount of the foamable solution 300 to be sprayed is not particularly limited. For example, when the foamable solution 300 includes the second foamable material and water, about 2 parts by weight or more, 2 to 10 parts by weight, or about 3 to 5 parts by weight of water. When the water is in contact with 2 parts by weight or more of the crosslinked polymer, a sufficient amount of mobile phase can be secured so that the foamable solution can penetrate into the gel of the crosslinked polymer. In addition, the amount of contact of the second foamable material with the crosslinked polymer 401 may affect the amount of the pore structure and the size of the pore structure. Therefore, the contact ratio of the second foamable material with the cross-linking polymer may be appropriately selected in consideration of this, but may be about 0.1 parts by weight or more, for example, about 0.1 to 2.0 parts by weight, or about 0.1 to 2.0 parts by weight, 0.4 to 1.5 parts by weight, or about 0.5 to 1.0 part by weight of the second foamable material is contacted. When the second foamable material is contacted by 0.1 part by weight or more, the second foamable material penetrates into the gel of the cross-linked polymer to form a pore structure, thereby improving the absorption rate of the superabsorbent resin.

Subsequently, the cross-linked polymer is cut again (S142). Step S142 of re-cutting the cross-linked polymer may be performed more than once. The step (S142) of re-cutting the cross-linked polymer further comprises using the second cutter (7a) to apply the particulate cross-linked polymer (401) having a first average size to the particulate cross-linked polymer having a second average size smaller than the first average size 402, wherein the particulate crosslinked polymer 402 having a second average size, for example, has an average size of about 0.2 cm x 0.2 cm to about 1 cm x 1 cm, or an average size of about 0.5 cm x 0.5 cm Lt; / RTI > The step (S142) of cutting the cross-linked polymer again may be performed using a kneader-type cutter, a cutter-type cutter, or a chopper-type cutter, but the present invention is not limited thereto.

The step (S142) of cutting the cross-linked polymer again can not only cut the cross-linked polymer into a more easily processed size to facilitate post-treatment but also increase the surface area of the cross-linked polymer, 300) is more uniformly in contact with the crosslinked polymer and improves the permeability into the gel, thereby effectively forming the pore structure in the crosslinked polymer.

Subsequently, the cross-linked polymer is dried (S143). The step (S143) of drying the crosslinked polymer is a step of drying the residual solvent of the polymer and the like and simultaneously heating the particulate crosslinked polymer 402 in order to accelerate the thermal decomposition reaction of the second foamed material that has penetrated into the crosslinked polymer . The drying unit 8 may be a hot air drier, a fluidized bed drier, an air stream drier, an infrared drier, or a dielectric heating drier. The drying step may also be performed at a temperature of about 100 ° C or higher, or about 150 ° C or higher, such as about 100 ° C to 200 ° C, or about 120 ° C to 190 ° C, or about 150 ° C to 180 ° C, Min, or from about 30 minutes to about 70 minutes, or from about 40 minutes to about 60 minutes. The cross-linking polymer can be prevented from deteriorating in the range of the temperature and the drying time and can be efficiently dried. In addition, when the second foamable substance includes the urea, the drying process is performed at a temperature at which the thermal decomposition reaction of the urea is effective, for example, at a temperature of at least 95 캜 or at least 155 캜 to dry the residual solvent or the like in the crosslinked polymer The crosslinked polymer 402 can be heated to such an extent that a reaction for forming a pore structure by the elements is performed inside the crosslinked polymer.

In the step (S143) of drying the cross-linked polymer, the second foamable material penetrating into the gel of the particulate cross-linked polymer (402) having the second average size thermally decomposes to form a gas, thereby forming a particulate cross- (410). When the second foamable material is urea, the reaction is performed at about 95 ° C to 155 ° C, or about 100 ° C to 150 ° C, and the generated gas may be ammonia gas and / or carbon dioxide gas.

The method for producing a superabsorbent resin according to this embodiment can produce a superabsorbent resin having an improved absorption rate by absorbing or penetrating the foamable solution into the hydrogel crosslinked polymer to give a pore structure inside the gel of the crosslinked polymer. In addition, since the pore structure is formed in the crosslinked polymer after the polymerization of the monomer is sufficiently performed, the content of the residual monomer can be reduced. In addition, it is preferable to add a surfactant in the monomer composition in order to suppress the collapse of the pore structure when pores are formed before the completion of the polymerization, The surfactant is not added to the monomer composition, or even if the surfactant is added, the content thereof can be minimized, and the deterioration of the water retention capacity can be prevented.

On the other hand, although not shown in the drawings, the step of drying the crosslinked polymer may further include a step of pulverizing the dried crosslinked polymer. The step of pulverizing the crosslinked polymer is a step of pulverizing or crushing the particulate crosslinked polymer to a predetermined size, and the step of pulverizing the crosslinked polymer may be carried out by a cutter type cutter, a chopper type cutter, a kneader type cutter, a vibration type pulverizer, A friction type crusher, or the like, but the present invention is not limited thereto. In some embodiments, the step of pulverizing the crosslinked polymer may further comprise drying the pulverized crosslinked polymer again, wherein the step of pulverizing the crosslinked polymer and the step of drying the crosslinked polymer are alternately repeated a plurality of times .

Hereinafter, a method for producing a superabsorbent resin according to another embodiment of the present invention will be described. However, in order not to obscure the essence of the present invention, a description of substantially the same or similar constitution as the method of manufacturing the superabsorbent resin according to the above-described embodiment is omitted, and it will be apparent to those skilled in the art from the accompanying drawings It can be understood.

3 is a flowchart showing a method for producing a superabsorbent resin according to another embodiment of the present invention. Fig. 4 is a schematic view showing a method for producing the superabsorbent resin of Fig. 3; Fig.

3 and 4, a method for preparing a superabsorbent resin according to another embodiment of the present invention includes preparing a crosslinked polymer of a monomer composition comprising a hydrophilic monomer, a crosslinking agent and a polymerization initiator (S210) A cutting step S220, preparing a foamable solution S230, and thermally decomposing the foamable material S240.

(S210) of preparing a crosslinked polymer of a monomer composition comprising a hydrophilic monomer, a crosslinking agent and a polymerization initiator includes a step (S211) of preparing a monomer composition comprising a hydrophilic monomer, a crosslinking agent and a polymerization initiator, Step S212, and polymerizing the monomer composition in a reactor (S213). In an exemplary embodiment, the polymer 200 may be a sheet-like hydrogel crosslinked polymer. The step of preparing the polymer (S210) may be substantially the same as the embodiment according to Fig. 1, and a detailed description thereof will be omitted.

Next, the prepared sheet-like cross-linked polymer is cut (S220). Cutting the cross-linked polymer (S220) may include one or more cutting steps. The step (S220) of cutting the cross-linked polymer can cut the cross-linked polymer into a size that facilitates the processing, thereby facilitating post-processing. In an exemplary embodiment, cutting the cross-linked polymer (S220) comprises first cutting (S221) the sheet-like cross-linked polymer to a cross-linked polymer having a first average size, and forming a cross- RTI ID = 0.0 > S222 < / RTI > with a cross-linked polymer having a second average size that is less than one average size.

Specifically, in the first cutting step S221, the sheet-like crosslinked polymer 200 obtained by completing the polymerization reaction is transferred to the first cutter 5 and is cut into the particulate crosslinked polymer 501 having the first average size Step S222 of cutting the particulate crosslinked polymer 501 having the first average size by using the second cutter 7b with the particulate crosslinked polymer having the second average size smaller than the first average size, (502). ≪ / RTI > For example, the particulate crosslinked polymer may have an average size of about 0.2 cm x 0.2 cm to about 1 cm x 1 cm, or an average size of about 0.5 cm x 0.5 cm. When a plurality of cutting processes are required to obtain a particulate crosslinked polymer of a desired size, the first cutting process and the second cutting process are successively performed, thereby shortening the process path and improving the processability. In addition, it is possible to increase the surface area for contacting the foamable solution by cutting the cross-linked polymer into sufficiently small particles before step (S241) of spraying the foamable solution to be described later.

In some embodiments, however, the step of cutting the cross-linked polymer may be performed only once.

Meanwhile, a foamable solution is prepared (S230). The foamable solution 300 may be an aqueous solution containing a second foamable material and water. In an exemplary embodiment, the second foamable material may comprise an element. Step S230 of preparing the foaming solution may be substantially the same as the embodiment according to Fig. 1, and a detailed description thereof will be omitted.

Next, the foamable material is thermally decomposed in the second cut particulate crosslinked polymer (S240). Specifically, step (S240) of thermally decomposing the foamable material within the cross-linked polymer (502) may include step (S241) of spraying the foamable solution onto the surface of the cross-linked polymer and drying step (S242) of the particulate cross- have.

The step (S241) of injecting the foamable solution onto the surface of the crosslinked polymer may be a step for uniformly contacting the crosslinked polymer 502 and the foamable solution 300. [ The foamable solution supply portion 6b may be configured to spray the foamable solution 300 to the cross-linked polymer 502 cut into a particulate particle having a second average size through the second cutter 7b. The injected foamy solution 300 can absorb or penetrate into the gel of the crosslinked polymer 502. The injection amount of the foamable solution 300 is not particularly limited, but may be about 2 parts by weight or more, for example, about 100 parts by weight of the crosslinked polymer 502 when the foamable solution 300 includes the second foamable substance and water, 2 to 10 parts by weight, or about 3 to 5 parts by weight of water. The foamable solution 300 may be added so that about 0.1 part by weight or more, or about 0.1 to 2 parts by weight, or about 0.4 to 0.6 part by weight, or about 0.5 part by weight, of the second foamable material is contacted with 100 parts by weight of the crosslinked polymer (502) . ≪ / RTI >

Subsequently, the cross-linked polymer is dried (S242). The step (S242) of drying the cross-linked polymer is a step of drying the residual solvent of the polymer and the like and simultaneously heating the particulate cross-linked polymer (502) in order to accelerate the thermal decomposition reaction of the second foamable material penetrated into the cross- .

In step (S242) of drying the cross-linked polymer, the second foamable material penetrating into the gel of the particulate cross-linked polymer (502) having the second average size thermally decomposes to form a gas, thereby forming a pore- (510). When the second foamable material is urea, the reaction is performed at about 95 ° C to 155 ° C, or about 100 ° C to 150 ° C, and the generated gas may be ammonia gas and / or carbon dioxide gas.

In the method for producing a superabsorbent resin according to this embodiment, the average size of the crosslinked polymer in the step (S241) of spraying the foamable solution and the average size of the crosslinked polymer in the step (S242) of drying the crosslinked polymer may be substantially the same . That is, the step (S241) of spraying the foamable solution and the step (S242) of drying the crosslinked polymer do not include a step of deforming the size of the crosslinked polymer such as a cutting step or a pulverizing step. This makes it possible to minimize the loss of the foamable aqueous solution 300 during the transfer of the crosslinked polymer and further to impart a sufficient amount of the pore structure in the crosslinked polymer.

Hereinafter, a method for producing a superabsorbent resin according to the present invention will be described in more detail with reference to Production Examples, Comparative Examples and Experimental Examples.

< Manufacturing example  1>

77.778 g of a 50% aqueous caustic soda solution (NaOH) and 88.84 g of water were mixed and 100 g of acrylic acid was added. 0.23 g of 2,2-bis [acryloylmethyl] butyl acrylate (3EO) 0.033 g of zeol diphenyl (2,4,6-trimethylbenzoyl) -phosphine oxide was further added to prepare a water-soluble unsaturated monomer composition (neutralization degree of acrylic acid monomer was 70 mol%). Then, 1.25 g (urea content: 14.3%) of urea was added to 7.5 g of distilled water (DW) to prepare a foamable aqueous solution. Next, the water-soluble unsaturated monomer composition prepared on the surface of the conveyor belt of the belt-type continuous reactor was supplied, and the polymerization proceeded to prepare a crosslinked polymer sheet. The prepared sheet-like cross-linked polymer was cut (primary cut) into a granular cross-linked polymer having an average size of 3 cm x 3 cm using a cutter-type cutter. Then, the prepared foamable aqueous solution was sprayed onto the cut particulate crosslinked polymer. At this time, the injection amount of the foamable aqueous solution was adjusted so that 3 parts by weight of distilled water and 0.5 parts by weight of urea were mixed with 100 parts by weight of the crosslinked polymer. Thereafter, the resultant was again cut (second cut) with a particulate crosslinked polymer having an average size of 1 cm x 1 cm using Meat Chopper, and dried in a hot-air drier for spraying hot air at 170 ° C for 45 minutes. The dried particulate crosslinked polymer was pulverized using a cutting mill and then sieved to obtain a base polymer in powder form having an average particle diameter of 150 μm to 850 μm. The obtained base polymer was sprayed with a 20% aqueous solution of ethylene carbonate in a surface cross-linking mixer at a rate of 5 phr, and dried again in a hot-air dryer at 180 캜 for 30 minutes. The dried base polymer was classified into a standard mesh of ASTM standard to prepare a water-absorbent resin having an average particle size of 150 mu m to 850 mu m in particle size.

< Manufacturing example  2>

The sheet-form crosslinked polymer thus prepared was cut (primary cut) into a particulate crosslinked polymer having an average size of 3 cm x 3 cm using a cutter-type cutter, and then again with a particulate crosslinked polymer having an average size of 1 cm x 1 cm using Meat Chopper A crosslinked polymer was prepared in the same manner as in Preparation Example 1, except that the foamed aqueous solution prepared above was sprayed onto the cut particulate crosslinked polymer after the single cutting (secondary cutting), to obtain a water absorbent resin in powder form.

< Manufacturing example  3>

A crosslinked polymer was prepared and a resin was obtained in the same manner as in Preparation Example 1, except that 1 g of sodium hydrogencarbonate (NaHCO ₃ ) was further added to the water-soluble unsaturated monomer composition.

< Manufacturing example  4>

A crosslinked polymer was prepared and a resin was obtained in the same manner as in Preparation Example 3, except that the amount of the foamable aqueous solution injected was adjusted so that 5 parts by weight of distilled water was mixed with 100 parts by weight of the crosslinked polymer.

< Manufacturing example  5>

A crosslinked polymer was prepared and a resin was obtained in the same manner as in Production Example 2, except that 1 g of sodium hydrogencarbonate (NaHCO ₃ ) was further added to the water-soluble unsaturated monomer composition.

< Manufacturing example  6>

A crosslinked polymer was prepared and a resin was obtained in the same manner as in Production Example 5, except that the amount of the foamable aqueous solution injected was adjusted so that 5 parts by weight of distilled water could be mixed with 100 parts by weight of the crosslinked polymer.

< Manufacturing example  7>

A crosslinked polymer was prepared and a resin was obtained in the same manner as in Production Example 5, except that the injection amount of the foamable aqueous solution was adjusted so that 1 part by weight of the urea was mixed with 100 parts by weight of the crosslinked polymer.

< Manufacturing example  8>

A crosslinked polymer was prepared and a resin was obtained in the same manner as in Production Example 6, except that the injection amount of the foamable aqueous solution was adjusted so that 1 part by weight of the urea was mixed with 100 parts by weight of the crosslinked polymer.

< Manufacturing example  9>

A crosslinked polymer was prepared and a resin was obtained in the same manner as in Production Example 6, except that the injection amount of the foamable aqueous solution was adjusted so that 2 parts by weight of urea was mixed with 100 parts by weight of the crosslinked polymer.

< Comparative Example  1>

77.778 g of a 50% aqueous caustic soda solution (NaOH) and 88.84 g of water were mixed and 100 g of acrylic acid was added. 0.23 g of 2,2-bis [acryloylmethyl] butyl acrylate (3EO) 0.033 g of zeol diphenyl (2,4,6-trimethylbenzoyl) -phosphine oxide was further added to prepare a water-soluble unsaturated monomer composition (neutralization degree of acrylic acid monomer was 70 mol%). Next, the water-soluble unsaturated monomer composition prepared on the surface of the conveyor belt of the belt-type continuous reactor was supplied, and the polymerization proceeded to prepare a crosslinked polymer sheet. The prepared sheet-like cross-linked polymer was cut (primary cut) into a granular cross-linked polymer having an average size of 3 cm x 3 cm using a cutter-type cutter. Thereafter, the resultant was again cut (second cut) with a particulate crosslinked polymer having an average size of 1 cm x 1 cm using Meat Chopper, and dried in a hot-air drier for spraying hot air at 170 ° C for 45 minutes. The dried particulate crosslinked polymer was pulverized using a cutting mill and then sieved to obtain a base polymer in powder form having an average particle diameter of 150 μm to 850 μm. The resulting base polymer was sprayed with a 20% aqueous solution of ethylene carbonate in a surface cross-linking mixer at a rate of 5 pph and dried again in a hot-air dryer at 180 캜 for 30 minutes. The dried base polymer was classified into a standard mesh of ASTM standard to prepare a water-absorbent resin having an average particle size of 150 mu m to 850 mu m in particle size.

< Comparative Example  2>

A crosslinked polymer was prepared and a resin was obtained in the same manner as in Comparative Example 1 except that 1 g of sodium hydrogencarbonate (NaHCO ₃ ) was further added to the water-soluble unsaturated monomer composition.

The timing of injection of the foamable solution used in the production of the crosslinked polymer in Production Examples 1 to 9 and Comparative Examples 1 and 2, the content of sodium hydrogencarbonate in the water-soluble unsaturated monomer composition, the content of urea mixed with the crosslinked polymer, and the content of distilled water are summarized in Table 1 . In the present specification, phr (part per hundred resin) means the mass percentage for the crosslinked polymer, and phm (part per hundred monomer) means the mass percentage for the hydrophilic monomer.

Process order Sodium bicarbonate content (phm) Element content (phr) Distilled water content (phr) Production Example 1 Spraying of foaming solution before second cutting - 0.5 3 Production Example 2 Spraying foaming solution after 2nd cutting - 0.5 3 Production Example 3 Spraying of foaming solution before second cutting One 0.5 3 Production Example 4 Spraying of foaming solution before second cutting One 0.5 5 Production Example 5 Spraying foaming solution after 2nd cutting One 0.5 3 Production Example 6 Spraying foaming solution after 2nd cutting One 0.5 5 Production Example 7 Spraying foaming solution after 2nd cutting One 1.0 3 Production Example 8 Spraying foaming solution after 2nd cutting One 1.0 5 Production Example 9 Spraying foaming solution after 2nd cutting One 2.0 5 Comparative Example 1 Foamable solution fine powder - - - Comparative Example 2 Foamable solution fine powder One - -

<Experimental Example>

Centrifuge Retention Capacity (CRC), Free Swelling Rate (FSR), and Residual Monomer (RM) of the resins prepared and obtained according to Production Examples 1 to 9 and Comparative Examples 1 to 2 were measured. And the results are shown in Table 2 below.

The analysis of the abilities was carried out according to EDANA (European Disposables and Nonwovens Association) WSP 241.2 method. Specifically, 0.2 g of the absorbent resin sample was sealed in a teabag, immersed in a 0.9% saline solution for 30 minutes, removed in a centrifuge set at 250 G for 3 minutes, and then weighed to determine the amount of brine , And the results were analyzed.

The absorption rate was analyzed by vortex time measurement. Specifically, 1.000 parts by weight of 0.90 wt% sodium chloride aqueous solution (physiological saline solution) which had been adjusted in advance was adjusted to a liquid temperature of 25 캜. 50 ml of physiological saline was quantitatively measured and stirred into a 100 ml beaker having a body diameter of 55 mm and a height of 72 mm by a magnetic stirrer made of a cylindrical Teflon (registered trademark) having a length of 29 mm and a thickness of 8 mm at 600 rpm. 2.0 g of the water absorbent resin sample was introduced and the absorption rate (sec) was measured. The point of time and the end point were measured by measuring the disappearance time of the vortex and the absorption rate (g / gs) analysis was carried out by the following equation. ** Absorption rate (g / gs) = 25 / Absorption rate (sec)

The content of residual monomer was analyzed according to EDANA WSP 210.2 method. Specifically, 184.3 g of a 0.90 wt% aqueous solution of sodium chloride and 1.00 g of a water absorbent resin sample were placed in a plastic container having a capacity of 250 ml and stirred for 16 hours. The filtrate obtained by extracting water in the sample was analyzed by high performance liquid chromatography, Were analyzed.

Performance (g / g) Absorption rate (g / gs) Residual monomer content (ppm) Production Example 1 39 0.57 291 Production Example 2 38 0.55 194 Production Example 3 36 0.69 296 Production Example 4 39 0.74 223 Production Example 5 40 0.64 397 Production Example 6 37 0.77 394 Production Example 7 39 0.70 360 Production Example 8 38 0.81 303 Production Example 9 41 0.71 285 Comparative Example 1 37 0.40 425 Comparative Example 2 35 0.6 542

Referring to Table 2, it was confirmed that resins of Production Examples 1 to 9 in which a foamable aqueous solution was sprayed had substantially the same level of storage ability as the resins of Comparative Examples 1 and 2 in which the foamable aqueous solution was not sprayed .

Comparing Comparative Example 1 with Comparative Example 2, it can be seen that the residual monomer content of the resin of Comparative Example 2 in which sodium bicarbonate was added to the monomer aqueous solution was increased.

In addition, it can be confirmed that the absorption rate of the resins of Production Example 1 and Production Example 2 in which the foamable aqueous solution is sprayed is lower than that of the resin of Comparative Example 1 in which the foamable aqueous solution is not sprayed, while the content of the residual monomers is decreased.

In addition, in the case of the resins of Preparative Examples 3 to 9 in which the foamable aqueous solution was sprayed, the absorption rate was improved, but the content of the residual monomers was decreased compared to the resin of Comparative Example 2 in which the foamable aqueous solution was not sprayed.

In addition, it can be confirmed that the absorption rate is further improved as the distilled water content is increased, as compared with the case of Production Example 3, Production Example 4, Production Example 5 and Production Example 6, and Production Example 7 and Production Example 8, respectively.

Further, when the urea content was increased from 0.5 phr to 1.0 phr, it was confirmed that the absorption rate was improved as compared with that of Preparation Example 5 and Production Example 7.

On the other hand, when the urea content was increased from 0.5 phr to 1.0 phr, the absorption rate was improved, but it was confirmed that the absorption rate was lowered as the urea content was increased to 2.0 phr .

While the present invention has been described with reference to exemplary embodiments, it is to be understood that the invention is not limited to the disclosed exemplary embodiments, but many variations and modifications may be made without departing from the spirit and scope of the invention. It will be appreciated that many variations and applications not illustrated above are possible. For example, each component specifically shown in the embodiments of the present invention can be modified and implemented. It is to be understood that all changes and modifications that come within the meaning and range of equivalency of the claims are therefore intended to be embraced therein.

1: Monomer composition supply part
2, 2 ': Feed roll
3: Belt
4:
5: First cutter
6a, 6b: foamable solution supply part
7a and 7b: a second cutter
8: Dryer
100: monomer composition
200: Sheet-like crosslinked polymer
300: foamable solution

Claims (14)

Preparing a crosslinked polymer of a monomer composition comprising a hydrophilic monomer, a crosslinking agent, and a polymerization initiator;
Contacting the crosslinked polymer with a foamable aqueous solution; And
And drying the cross-linked polymer. The method according to claim 1,
Before the step of contacting the crosslinkable polymer and the foamable aqueous solution,
And cutting the cross-linked polymer into a cross-linked polymer having a first average size. 3. The method of claim 2,
The step of drying the crosslinked polymer is carried out after the step of contacting the crosslinked polymer and the foamable aqueous solution. The method of claim 3,
Between the step of bringing the crosslinked polymer into contact with the foamable aqueous solution and the step of drying the crosslinked polymer,
Further comprising cutting the cross-linked polymer having the first average size into a cross-linked polymer having a second average size smaller than the first average size. The method of claim 3,
Wherein the average size of the cross-linking polymer in the step of contacting the cross-linking polymer with the aqueous foamable solution is the same as the average size of the cross-linking polymer in the step of drying the cross-linking polymer. The method according to claim 1,
The step of drying the crosslinked polymer is carried out after the step of contacting the crosslinked polymer and the foamable aqueous solution,
Further comprising a step of pulverizing the cross-linked polymer after the step of drying the cross-linked polymer. The method according to claim 1,
The foaming aqueous solution is a solution containing urea and water,
Wherein the step of contacting the crosslinkable polymer with the foamable aqueous solution comprises:
And contacting the cross-linked polymer with 2 to 10 parts by weight of the water to 100 parts by weight of the cross-linked polymer. 8. The method of claim 7,
Wherein the step of contacting the crosslinked polymer with the foamable solution comprises:
Contacting the cross-linked polymer with 0.1 to 2 parts by weight of the urea with respect to 100 parts by weight of the cross-linking polymer. The method according to claim 1,
Wherein the step of drying the crosslinked polymer is carried out at 150 ° C or higher. The method according to claim 1,
Wherein the monomer composition further comprises 0 to 3 parts by weight of a foamable material based on 100 parts by weight of the hydrophilic monomer. 11. The method of claim 10,
Wherein the effervescent aqueous solution is an aqueous solution containing urea,
The foamed material is sodium carbonate (NaCO _3), sodium bicarbonate (NaHCO _3), potassium bicarbonate (KHCO _3), ammonium carbonate _{((NH 4) 2 CO 3} H 2 O), ammonium bicarbonate (NH ₄ HCO ₃₎ , magnesium carbonate (MgCO _3), calcium carbonate (CaCO _3), barium carbonate (BaCO ₃₎ and / or the method for producing a superabsorbent resin containing a hydrate of the foregoing. The method according to claim 1,
The step of preparing the crosslinked polymer of the monomer composition comprises:
Preparing the monomer composition,
Providing said monomer composition to the belt surface of a belt-type reactor, and
And polymerizing the monomer composition on the belt. Preparing a hydrogel crosslinked polymer;
Preparing an aqueous urea solution; And
And thermally decomposing the urea in the urea aqueous solution within the gel of the hydrogel crosslinked polymer. 14. The method of claim 13,
Thermally decomposing the urea in the urea aqueous solution within the gel of the hydrogel crosslinked polymer,
Injecting the urea aqueous solution onto the surface of the hydrogel crosslinked polymer to penetrate the element in the urea aqueous solution into the gel of the hydrogel crosslinked polymer; and
And thermally decomposing the element in an atmosphere of 95 ° C to 155 ° C in the gel to produce an ammonia gas and / or a carbon dioxide gas,
Wherein the pore structure is imparted to the inside of the hydrogel crosslinked polymer by the step of producing the ammonia gas and / or the carbon dioxide gas.

Images