KR20170119803A - Method for preparing super absorbent polymer - Google Patents

Abstract

A method of producing a superabsorbent resin having an improved absorption rate, comprising the steps of: preparing a second composition by contacting a first composition comprising a hydrophilic monomer, a crosslinking agent, and a polymerization initiator with a foamable material; And then polymerizing the polymer on the polymer.

Description

METHOD FOR PREPARING SUPER ABSORBENT POLYMER [0002]

The present invention relates to a method for producing a superabsorbent resin.

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. In particular, if the absorption rate is insufficient, the surface of the diaper or the like becomes sticky and the feeling of use lowers, which may cause skin diseases and odors.

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

At the same time, it is intended to provide a method for producing a superabsorbent resin having a sufficient water retention capacity and an ability to absorb under pressure.

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 an aspect of the present invention, there is provided a method of preparing a superabsorbent resin, comprising: preparing a second composition by contacting a foamable material with a first composition comprising a hydrophilic monomer, a crosslinking agent, and a polymerization initiator; And polymerizing the second composition in a belt-shaped reactor.

According to another aspect of the present invention, there is provided a method of manufacturing a superabsorbent resin, comprising the steps of: preparing a second composition by contacting the first composition with a foamable material, And providing the first composition to the belt surface provided with the blowing agent powder.

In the method of manufacturing a superabsorbent resin according to one embodiment for solving the above problems, the step of preparing the second composition by contacting the first composition with the foamable material may include the steps of providing the first composition to the mixing tank , And providing the mixing tank with an aqueous foaming agent solution.

In the method for producing a superabsorbent resin according to one embodiment for solving the above problems, the step of preparing the second composition and the step of polymerizing the second composition, The method may further comprise providing the composition.

In the method of manufacturing a superabsorbent resin according to an embodiment of the present invention, the mixing tank is a stirrer, and the step of preparing the second composition comprises mixing the first composition and the aqueous solution of the foaming agent in 250 lt; RTI ID = 0.0 > rpm < / RTI >

In the method of manufacturing a superabsorbent resin according to one embodiment for solving the above problems, the mixing tank may be an in-line homogenizer.

In the method of manufacturing a superabsorbent resin according to one embodiment for solving the above problems, the foaming agent content of the foaming agent aqueous solution may be 1 wt% to 10 wt%.

In the method of manufacturing a superabsorbent resin according to one embodiment for solving the above problems, the second composition is a mixture containing bubbles, and the step of polymerizing the second composition in a belt- And polymerizing the mixture to form a polymer having a pore structure.

In the method for producing a superabsorbent resin according to one embodiment for solving the above problems, after the step of forming the polymer having the pore structure, the step of drying the polymer, and the step of pulverizing the polymer .

In the method of manufacturing a superabsorbent resin according to one embodiment for solving the above problems, the foamable material may include sodium hydrogencarbonate (NaHCO ₃ ) and / or sodium carbonate (NaCO ₃ ).

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

According to the method for producing a superabsorbent resin according to an embodiment of the present invention, the process of forming bubbles in the monomer composition using the belt-shaped continuous reactor, the process of polymerizing the monomer composition, and the subsequent process are successively performed The fairness can be improved.

In addition, a foamable material can form a bubble in the monomer composition, and thus a pore structure can be imparted to the polymer, and a superabsorbent resin having an improved absorption rate can be produced.

Further, the absorption rate may be further improved by providing the foamable material to the belt surface of the belt-shaped reactor and then providing the monomer composition, or vigorously stirring the foamable material and the monomer composition, and then providing the mixture to the belt surface of the belt- .

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, "C _1-5 alkyl group" is an alkyl group having 1 to 5 carbon atoms. "And / or" include each and every combination of one or more of the mentioned items. 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.

Referring to FIGS. 1 and 2, a method of preparing a superabsorbent resin according to an exemplary embodiment of the present invention includes preparing a monomer composition (S110), preparing a foamable material (S120) (S140) of preparing a foamed monomer composition by contacting the foamable material (S130), polymerizing the foamed monomer composition (S140), and drying and pulverizing the polymer (S150).

First, a monomer composition is prepared (S110). The monomer composition (101) may include a hydrophilic monomer, a crosslinking agent, and a polymerization initiator.

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 101 may be appropriately selected in consideration of the polymerization time and the polymerization conditions (feed rate, polymerization time, etc.), but may be, for example, in the range of 30% Lt; / RTI >

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 initiator. For example, the monomer composition 101 may contain a photopolymerization initiator and a thermal polymerization initiator together as a polymerization initiator.

The photopolymerization initiator induces the initiation of the polymerization reaction of the monomer composition 101 when ultraviolet light is irradiated. The heat polymerization initiator induces the initiation of the polymerization reaction of the monomer composition 101 by heating, The reduction initiator can induce the initiation of the polymerization reaction of the monomer composition 101 by an oxidation-reduction reaction.

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, 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 101 may be appropriately selected so as to exhibit polymerization initiating effect. For example, in the case of the photopolymerization initiator, the content of the polymerization initiator is in the range of about 0.005 to 0.1 part by weight relative to 100 parts by weight of the hydrophilic monomer 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.

Subsequently, a foamable material is prepared (S120). The foamable material may be the foaming agent powder 201. [ The foaming agent powder 201 is not particularly limited as long as it is a substance capable of reacting with an acid to form bubbles. Examples of the foaming agent powder 201 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 foaming agent powder 201 may have a particle size of about 1 to 150 mu m. By increasing the contact area between the foam material powder 201 and the monomer composition 101 within the above range, it is possible to form a bubble capable of giving a pore structure of a sufficient amount and size to the polymer to be described later.

Next, the monomer composition and the foaming agent powder are contacted with each other on the reactor to prepare a foamed monomer composition (S130). In an exemplary embodiment, the reactor may be a continuous reactor, such as a belt-type reactor. The belt-shaped reactor is arranged to form a closed curve between two transfer rolls 4, 4 'and two transfer rolls 4, 4' and is moved in a certain direction by the rotation of the transfer rolls 4, 4 ' And a belt 5 which is made of a metal. Specifically, two or more conveying rolls 4, 4 'may be provided depending on the length or arrangement of the belt 5, and a power source such as a motor is connected to form a horizontal surface of the belt 5, . The reactant is loaded on one side of the belt 5 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 this case, the step (S 130) of preparing the monomer composition (301) in which bubbles are formed by bringing the monomer composition and the foaming agent powder into contact with each other on a belt-shaped reactor includes the step (S 131) of providing a foaming agent powder And a step (S132) of providing the monomer composition 101 to the belt type reactor to bring the monomer composition 101 into contact with the foaming agent powder 201.

The step S131 of providing the foaming agent powder 201 to the belt type reactor may be a step of applying the foaming agent powder 201 to the surface of the belt 5 of the belt type reactor. The foaming agent powder 201 may be loaded on one surface of the belt 5 and then transferred. The step S132 of bringing the foaming agent powder 201 into contact with the monomer composition 101 may be a step of supplying the monomer composition 101 to the surface of the belt 5 to which the foaming agent powder 201 is applied. The monomer composition feeding part 1 may be located behind the foaming agent powder feeding part 2 with respect to the advancing direction of the belt 5. [ The foaming agent powder 201 and the monomer composition 101 are uniformly contacted and mixed by supplying the monomer composition 101 onto the foaming agent powder 201 already applied to the surface of the belt 5, The bubbles 301a can be formed by reacting with the acid in the composition 101. [ The bubble-formed monomer composition 301 can be loaded on one surface of the belt 5 and transported.

Subsequently, the bubble-formed monomer composition 301 is polymerized on a belt-shaped reactor (S140). Specifically, the foamed monomer composition 301 is conveyed by the belt 5 and a continuous polymerization reaction can be performed to form a sheet-like polymer 401 having a pore structure 401a.

In an exemplary embodiment, the step (S140) of polymerizing the foamed monomer composition 301 may be a step of irradiating light to perform the photo polymerization reaction. The light irradiating unit 6 is a light source such as a Xe lamp, a mercury lamp, or a metal halide lamp, and the light irradiating unit 6 may be positioned behind the monomer composition supplying unit 1 with respect to the traveling direction of the belt 5. The light may be ultraviolet light having a wavelength in the range of about 200 nm to 400 nm. And may be irradiated at an exposure dose of about 0.5 mw / cm ² to 500 mw / cm ² . In addition, the exposure time, that is, the time during which the monomer composition 301 on the surface of the belt 5 is irradiated with the light irradiation portion 6 may be in the range of about 10 seconds to 5 minutes, or about 20 seconds to 3 minutes. An effective photopolymerization reaction can be performed within the wavelength, exposure amount, and exposure time range, and the crosslinking point of the polymer due to irradiation with excess light can be prevented from being broken.

In another embodiment, the step of polymerizing the foamed monomer composition may be a step of performing heat polymerization reaction by applying heat. For example, when the monomer composition includes a thermal polymerization initiator, heat may be applied, or thermal polymerization may proceed due to heat generated during the photopolymerization reaction. In this case, the heat supply portion may be located behind the monomer composition supply portion with respect to the advancing direction of the belt.

Then, the polymer is dried and pulverized (S150). The step of drying and crushing the polymer (S150) can be performed by passing the sheet-like polymer 401 on the surface of the belt 5 through a dryer (not shown) and a crusher (not shown) and drying and crushing.

The step of drying the polymer may be a step of drying the residual solvent or the like of the polymer. The polymer 401 may be dried using a hot air drier, a fluidized bed drier, an air dryer, an infrared drier, a dielectric heating drier, or the like. In order to prevent deterioration of the polymer 401 and efficiently dry, Deg.] C for about 20 minutes to about 80 minutes, or about 40 minutes to about 60 minutes. The step of pulverizing the polymer is a step of transferring the sheet-like polymer 401 obtained after the completion of the polymerization reaction to a cutter to crush or crush to a predetermined size. For example, the sheet-like polymer 401 has a particle size of about 1 cm RTI ID = 0.0 > 3 cm. ≪ / RTI > The step of pulverizing the polymer may be carried out by using a cutter-type cutter, a chopper-type cutter, a kneader-type cutter, a vibration type crusher, an impact type crusher, a friction type crusher and the like.

In some embodiments, however, the step of drying the polymer and the step of pulverizing the polymer may be alternately performed a plurality of times, or a part thereof may be omitted.

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 monomer composition (S210), preparing a foamable material (S220), and mixing the monomer composition and the foamable material (S230) a mixture of the monomer composition and the foamable material (S240), and drying and pulverizing the polymer (S250).

First, a monomer composition is prepared (S210). The monomer composition (101) may include a hydrophilic monomer, a crosslinking agent, and a polymerization initiator. The monomer composition 101 may be substantially the same composition as the monomer composition of the embodiment according to Fig. 1, and a detailed description thereof will be omitted.

Subsequently, a foamable material is prepared (S220). The foamable material may be the blowing agent aqueous solution 202. The foaming agent aqueous solution 202 can be prepared by dissolving the foaming agent in a solvent, for example, water. The foaming agent is not particularly limited as long as it is a substance capable of reacting with an acid to form bubbles. Examples of the foaming agent 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 ) . ≪ / RTI > The foaming agent content of the foaming agent aqueous solution 202 may be about 1 wt% to 10 wt%. When the blowing agent content is 10% by weight or more, bubbles capable of imparting a sufficient amount and size of pores to the polymer can be formed. When the amount is 10% by weight or less, the shape of the sheet-like polymer can be maintained.

A mixture of the monomer composition and the aqueous foaming agent solution is then provided to the reactor (S230). The reactor may be a continuous reactor, such as a belt-type reactor.

In this case, the step (S230) of providing a mixture (302) of the monomer composition and the aqueous foaming agent solution to the belt type reactor (S230) may include providing the monomer composition 101 to the mixing tank (S231) A step S233 of contacting the monomer composition 101 with the aqueous foaming agent solution 202 and a step S233 of providing a mixture 302 of the monomer composition 101 and the foaming agent aqueous solution 202 to the belt- (Step S234).

The mixing tank may be the stirrer 3 in the step S231 of providing the monomer composition 101 to the mixing tank and the step S232 of providing the mixing tank with the aqueous foaming agent solution 202. [ In this case, step S231 of providing the monomer composition 101 to the stirrer 3 may be performed before or after the step S232 of providing the aqueous foaming agent solution 202 to the stirrer 3, . In some embodiments, the mixing tank may use an in-line homogenizer.

Step S233 of contacting the monomer composition 101 with the aqueous foaming agent solution 202 may be a step of preparing the mixture 302 by mixing and stirring the monomer composition 101 and the foaming agent aqueous solution 202. [ The agitation speed of the agitator 3 may be about 250 rpm or more, but is not limited thereto. Within this range, a pore structure of sufficient amount and size can be imparted to the polymer to be described later. The foaming agent component of the foaming agent aqueous solution 202 may react with an acid in the monomer composition 101 in the presence of stirring to form a large amount of bubbles (not shown) in the mixture 302.

Next, the step (S234) of providing the belt-shaped reactor with the mixture 302 'of the monomer composition 101 and the aqueous foaming agent solution 202 is carried out in such a manner that the monomer composition 101 and the aqueous foaming agent solution 0.0 > 202 < / RTI > The mixture 302 'of the monomer composition 101 and the foaming agent aqueous solution 202 may be loaded and transported on one side of the belt 5 and the mixture 302' (302'a).

Subsequently, the foamed monomer composition 302 'is polymerized on the belt-shaped reactor (S240). Specifically, the bubbled mixture 302 'is conveyed by the belt 5 and a continuous polymerization reaction can take place to form a sheet-like polymer 402 having a pore structure 402a. In an exemplary embodiment, the step (S240) of polymerizing the bubbled mixture 302 'may be a step of performing a photopolymerization reaction by irradiating light or a thermal polymerization reaction by applying heat, 6) or the heat supply portion may be located behind the mixture supply portion 3 'with respect to the traveling direction of the belt 5. [

Then, the polymer is dried and pulverized (S250). The steps of drying and pulverizing the polymer have been described above in conjunction with the embodiment according to Fig. 1, so a detailed description thereof will be omitted.

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>

7.2 kg of a 20% sodium hydroxide aqueous solution was added to 3.7 kg of acrylic acid, and then 11 g of ethoxyl-trimethylolpropane triacrylate as an internal cross-linking agent and 0.1 g of diphenyl (2,4,5-trimethylbenzoyl) -phosphine 1.2 g of pin oxide was added to prepare a water-soluble unsaturated monomer composition (neutralization degree of acrylic acid monomer: 70 mol%). Then, a sodium hydrogen carbonate powder having an average particle diameter of 100 mu m was prepared. Subsequently, sodium bicarbonate was first applied to the belt surface of a belt-type continuous reactor having a width of 30 cm and a conveyance speed of 33 cm / min. After 10 seconds, a water-soluble unsaturated monomer composition was fed onto a belt coated with sodium hydrogencarbonate, Photopolymerization proceeded after 20 seconds to prepare a sheet polymer. At this time, the content ratio of the sodium hydrogencarbonate powder and the water-soluble unsaturated monomer composition is 1 part by weight of sodium hydrogencarbonate powder relative to 100 parts by weight of the water-soluble unsaturated monomer composition. The sheet polymer thus prepared was pulverized in particulate form on a belt via a mitochondrator, and then dried in a hot-air dryer at 170 DEG C for 40 minutes. The dried particulate polymer was pulverized again using a cutting mill and then sieved to obtain a resin having an average particle diameter of 150 μm to 850 μm.

< Manufacturing example  2>

7.2 kg of a 20% sodium hydroxide aqueous solution was added to 3.7 kg of acrylic acid, and then 11 g of ethoxyl-trimethylolpropane triacrylate as an internal cross-linking agent and 0.1 g of diphenyl (2,4,5-trimethylbenzoyl) -phosphine 1.2 g of pin oxide was added to prepare a water-soluble unsaturated monomer composition (neutralization degree of acrylic acid monomer: 70 mol%). To 333 g of water was added 37 g of sodium hydrogencarbonate to prepare an aqueous solution of sodium hydrogencarbonate. Then, the water-soluble unsaturated monomer composition and the aqueous sodium hydrogencarbonate solution prepared above were mixed in a stirring tank and stirred at a speed of 250 rpm. Thereafter, a mixture of a water-soluble unsaturated monomer composition and an aqueous sodium hydrogencarbonate solution was supplied to the belt surface of a belt-type continuous reactor having a width of 30 cm and a conveyance speed of 33 cm / min. After 20 seconds, photo- . The sheet polymer thus prepared was pulverized in particulate form on a belt via a mitochondrator, and then dried in a hot-air dryer at 170 DEG C for 40 minutes. The dried particulate polymer was pulverized once again using a cutting mill and then sieved to obtain a resin having an average particle size of 150 μm to 850 μm).

< Comparative Example  1>

7.2 kg of a 20% sodium hydroxide aqueous solution was added to 3.7 kg of acrylic acid, and then 11 g of ethoxyl-trimethylolpropane triacrylate as an internal cross-linking agent and 0.1 g of diphenyl (2,4,5-trimethylbenzoyl) -phosphine 1.2 g of pin oxide was added to prepare a water-soluble unsaturated monomer composition (neutralization degree of acrylic acid monomer: 70 mol%). Next, the water-soluble unsaturated monomer composition was supplied to the surface of the belt of a belt-type continuous reactor having a width of 30 cm and a conveyance speed of 33 cm / min. After 20 seconds, photo polymerization was carried out to prepare a sheet-like polymer. The sheet polymer thus prepared was pulverized in particulate form on a belt via a mitochondrator, and then dried in a hot-air dryer at 170 DEG C for 40 minutes. The dried particulate polymer was pulverized again using a cutting mill and then sieved to obtain a resin having an average particle diameter of 150 μm to 850 μm.

< Comparative Example  2>

The procedure of Example 1 was repeated except that the water-soluble unsaturated monomer composition was first fed to the belt surface of the belt-type continuous reactor, and 10 seconds later, the surface of the unsaturated monomer composition to be conveyed by the belt was coated with sodium bicarbonate powder. And obtained.

< Comparative Example  3>

7.2 kg of a 20% sodium hydroxide aqueous solution was added to 3.7 kg of acrylic acid, and then 11 g of ethoxyl-trimethylolpropane triacrylate as an internal cross-linking agent and 0.1 g of diphenyl (2,4,5-trimethylbenzoyl) -phosphine 1.2 g of pin oxide was added to prepare a water-soluble unsaturated monomer composition (degree of neutralization of acrylic acid-based monomer: 70 mol%). To 333 g of water was added 37 g of sodium hydrogencarbonate to prepare an aqueous solution of sodium hydrogencarbonate. The water-soluble unsaturated monomer composition was then fed through a feed line to a belt-type continuous reactor at a flow rate of 1 kg / min, and an aqueous solution of sodium hydrogencarbonate was directly fed into the unsaturated monomer composition feed line at a flow rate of 0.1 kg / min. Thereafter, a resin was obtained in the same manner as in Example 2, except that a mixture of a water-soluble unsaturated monomer composition and an aqueous sodium hydrogencarbonate solution was supplied to the belt surface of a belt-type continuous reactor having a width of 30 cm and a conveyance speed of 33 cm / And obtained.

< Comparative Example  4>

A resin was prepared and obtained in the same manner as in Example 2 except that the water-soluble unsaturated monomer composition and the aqueous solution of sodium hydrogencarbonate were not stirred in the stirring tank.

< Experimental Example  1: Comparison of the effect of foaming agent powder input>

(CRC), absorption capacity under pressure (AUP) and absorption rate (FSR) of the resin prepared and obtained according to Production Example 1, Comparative Example 1 and Comparative Example 2 were measured and the results are shown in Table 1 . Analysis of water holding capacity and pressure absorption capacity was carried out according to EDANA (European Disposables and Nonwovens Association) WSP241.2.R3, EDANA WSP242.2.R3 method. Analysis of the absorption rate was carried out according to the vortex time measurement.

Performance (g / g) Absorption capacity under pressure (g / g) Absorption rate (g / gs) Production Example 1 37 15 0.52 Comparative Example 1 38 15 0.37 Comparative Example 2 37 16 0.43

As shown in Table 1, it was confirmed that the resins of Preparation Example 1 and Comparative Example 2 prepared by adding the foaming agent powder had the same level of storage ability and absorbency under pressure as the resin of Comparative Example 2 in which the foaming agent powder was not added .

In comparison with the resin of Comparative Example 2 in which a water-soluble unsaturated monomer composition is first supplied to the belt surface and a foaming agent powder is applied to the surface of the belt, the foaming agent powder is first applied to the surface of the belt, It can be confirmed that the absorption rate is further improved in the case of the resin of Production Example 1 in which the water-soluble unsaturated monomer composition is supplied.

< Experimental Example  2: Comparison of the effect of the blowing agent aqueous solution>

The absorbency and the absorption rate under pressure and the absorption rate of the resin prepared and obtained according to Production Example 2, Comparative Example 1, Comparative Example 3 and Comparative Example 4 were measured in the same manner as in Experimental Example 1. The results are shown in Table 2 below Respectively.

Performance (g / g) Absorption capacity under pressure (g / g) Absorption rate (g / gs) Production Example 2 38 15 0.69 Comparative Example 1 38 15 0.37 Comparative Example 3 38 16 0.37 Comparative Example 4 37 16 0.38

In the case of the resins of Production Example 2, Comparative Example 3 and Comparative Example 4 prepared by adding the aqueous solution of the foaming agent to the resin of Comparative Example 2 in which the aqueous foaming agent solution was not added, Absorbing ability.

In addition, in the production method using a belt type continuous reactor, the water-soluble unsaturated monomer composition and the aqueous solution of the foaming agent were stirred vigorously with respect to the resin of Comparative Example 3 and Comparative Example 4 in which the aqueous solution of the foaming agent was not stirred, It can be confirmed that the absorption rate of the resin of Production Example 2 is further improved.

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: blowing agent powder supply part
4, 4 ': Feed roll
5: Belt
6:
101: monomer composition
201: Blowing powder
301: monomer composition in which bubbles are formed
401: polymer

Claims (10)

Preparing a second composition by contacting a foamable material with a first composition comprising a hydrophilic monomer, a crosslinking agent, and a polymerization initiator; And
And polymerizing the second composition in a belt-type reactor. The method according to claim 1,
Wherein the step of preparing the second composition by contacting the first composition with the foamable material comprises:
Providing a foaming agent powder on the belt surface of the belt type reactor; And
And providing the first composition to the surface of the belt provided with the foaming agent powder. The method according to claim 1,
Wherein the step of preparing the second composition by contacting the first composition with the foamable material comprises:
Providing the first composition to a mixing tank; And
And a step of providing an aqueous solution of a foaming agent in the mixing tank. The method of claim 3,
Further comprising providing the second composition on the belt surface of the belt-type reactor between the step of preparing the second composition and the step of polymerizing the second composition. The method of claim 3,
The mixing tank is a stirrer,
Wherein the step of preparing the second composition further comprises stirring the first composition and the aqueous solution of the foaming agent at 250 rpm or higher in the stirrer. The method of claim 3,
Wherein the mixing tank is an in-line homogenizer. The method of claim 3,
Wherein the foaming agent content of the foaming agent aqueous solution is 1 wt% to 10 wt%. The method according to claim 1,
Wherein the second composition is a mixture comprising bubbles,
Wherein the step of polymerizing the second composition in a belt-shaped reactor is a step of polymerizing the mixture containing the bubbles to form a polymer having a pore structure. 9. The method of claim 8,
After the step of forming the polymer having the pore structure,
Drying the polymer; And
Further comprising a step of pulverizing the polymer. The method according to claim 1,
Wherein the foamable material comprises sodium hydrogencarbonate (NaHCO ₃ ) and / or sodium carbonate (NaCO ₃ ).

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