WO2019216592A1 - Method for manufacturing superabsorbent polymer sheet - Google Patents

Abstract

The present invention relates to a method for manufacturing a superabsorbent polymer sheet. According to the method for manufacturing a superabsorbent polymer sheet, of the present invention, a porous and flexible superabsorbent polymer sheet having an excellent initial absorption rate can be manufactured.

Description

 [Name of invention]

 Manufacturing Method of Super Absorbent Polymer Sheet [Technical Field]

 Cross Citation with Related Application (s)

 This application claims the benefit of priority based on Korean Patent Application No. 10-2018-0054365 dated May 11, 2018 and Korean Patent Application No. 10-2019-0049878 dated April 29, 2019. All content disclosed in the literature is included as part of this specification.

 The present invention relates to a method for producing a superabsorbent polymer sheet.

Background Art

 Super Absorbent Polymer (SAP) is a synthetic polymer material that has the ability to absorb about 500 to 1,000 times the weight of the body itself.Samsung (Super Absorbency Material), AGM (Absorbent Gel) They are named differently. Such superabsorbent resins have been put into practical use as sanitary instruments, and are currently used in sanitary products such as paper diapers and sanitary napkins for children, horticultural soil repair agents, civil engineering, building index materials, seedling sheets, food fresheners in food distribution. It is widely used as a material for, and for steaming.

In general, various sanitary articles such as diapers, sanitary napkins, or incontinence pads include absorbents including superabsorbent resin particles. The absorbents mainly contain the superabsorbent resin particles and the superabsorbent resin particles, while appropriately fixing the absorbent and sanitary agents. It was common to use fluff pulp to maintain the shape of the article. _,

However, due to the presence of the fluff pulp, it was difficult to slim and thin the absorber and the hygiene products, and there was a problem in that the wear feeling such as sweat between the user's skin and the hygiene products fell. Moreover, due to the necessity of using a large amount of the fluff pulp obtained mainly from wood, there has been a contradiction to recent environmental protection currents, and has become one of the main reasons for increasing the manufacturing cost of the absorbent layer and sanitary ware. For this reason, many attempts have been made to reduce the amount of fluff pulp used in the absorbent layer and the sanitary article, or to provide a sanitary article such as a so-called pulpless diaper that does not use fluff pulp.

 Meanwhile, the current super absorbent polymers are mostly manufactured in powder form and used. Such superabsorbent polymers in powder form may be scattered or leaked in the manufacture of hygiene materials or in actual use, and there is a limitation in the range of use because they must be used with a specific type of substrate.

 Recently, a method of manufacturing a super absorbent polymer in the form of fibers or fibers is proposed. However, there is no deterioration in absorption performance and can be used as a pulpless absorber, and a method for securing a superabsorbent polymer showing sufficient flexibility is still insufficient.

Detailed Description of the Invention

 [Technical problem]

 In order to solve the above problems, the present invention provides a method for producing a super absorbent polymer sheet exhibiting high flexibility and fast absorption rate.

Technical Solution

 One aspect of the present invention to solve the above problems,

 Comonomers having an acidic group and containing at least partly weighted acrylic acid monomers, polyethylene glycol (methyl ether) (meth) acrylates, internal crosslinkers, encapsulated Preparing a monomer composition by mixing a blowing agent, an inorganic blowing agent having an average particle diameter of 1 to 100 nm, and a polymerization initiator;

 Thermally polymerizing or photopolymerizing the monomer composition to form a hydrogel polymer; And

 Drying the hydrogel polymer to form a superabsorbent polymer sheet; As a method of manufacturing a super absorbent polymer sheet comprising a,

The encapsulated blowing agent and the inorganic blowing agent are provided in a weight ratio of 3: 1 to 1: 1, to provide a method for producing a super absorbent polymer sheet. 2019/216592 1 »（： 1 ^ 1 {2019/005223

glyco\ ^6^1 !161·） （111 11）묘（ 4 6）는 상기 아크릴산계 단량체 100 중량부에 대하여 5 내지 40중량부로 포함될 수 있다. Polyethylene glycol (methyl ether) (meth) acrylate

glyco \ ^ 6 ^ 1! 161 ·) (111 11) The seedlings (4 6) may be included in an amount of 5 to 40 parts by weight based on 100 parts by weight of the acrylic acid monomer.

 The encapsulated blowing agent may have an average particle diameter of 2 to 50 Sa! And an expansion ratio in air of 3 to 15 times.

In addition, the encapsulated blowing agent may have a structure including a core including a hydrocarbon and a shell surrounding the core and formed of a thermoplastic resin. In this case, the hydrocarbon is 11-propane, II-butane, -butane, cyclobutane, 11-pentane, 0-pentane, cyclopentane, II-nucleic acid, 0-nucleic acid, cyclonucleic acid, II-heptane, 0-heptane, cyclo Heptane, 1 ₁ -octane, 0 -octane and cyclooctane; and at least one member selected from the group consisting of (meth) acrylate, (meth) acrylonitrile, aromatic vinyl, vinyl acetate, vinyl halide and It may be a polymer formed from one or more monomers selected from the group consisting of vinylidene halides.

및 탄산나트륨어¾（：0₃） 중 선택되는 1종 이상일 수 있다. The inorganic blowing agent is calcium carbonate _& (： 0 ₃ ), sodium bicarbonate fish (： 0 ₃ ), ammonium bicarbonate fish ¾ seedlings, 4/4, ammonium carbonate (fish) ₂ (： 0 ₃ ), ammonium nitrite fish¾> ^ 0 ₂ ), sodium hydrogen borohydride

And sodium carbonate fish ¾ (： 0 ₃ ).

 Preferably, the particle size of the inorganic blowing agent may be from 2 to 90 ^.

 Also preferably, the encapsulated blowing agent and the inorganic blowing agent may be included in a weight ratio of 2: 1 to 1: 1.

 Meanwhile, the encapsulated blowing agent may be included in an amount of 0.1 to 20 parts by weight based on 100 parts by weight of the acrylic acid monomer, and the inorganic blowing agent may be included in an amount of 0.1 parts by weight or more based on 100 parts by weight of the acrylic acid monomer.

 In addition, the encapsulated blowing agent and the inorganic blowing agent may be included in an amount of 0.4 to 20 parts by weight based on 100 parts by weight of the acrylic acid monomer.

【Effects of the Invention】

The superabsorbent polymer sheet obtained by the manufacturing method of the present invention is obtained in the form of a sheet or a film, unlike a general superabsorbent polymer in a powder state, and can be directly applied as a product, there is no fear of scattering or leaking, and exhibits flexibility. Can be. In addition, the superabsorbent polymer sheet obtained by the method for producing a superabsorbent polymer sheet of the present invention has an open pore channel structure in which pores are connected to each other, thereby capturing water by capillary pressure. Since absorption is possible, absorption rate and permeability can be improved.

 As such, it exhibits a fast absorption rate due to the inherent physical properties of the superabsorbent polymer while having flexibility and flexibility, and can be applied to various products requiring flexibility and high absorbency.

 In addition, the superabsorbent polymer sheet can be used as a pulseless absorber. 【Brief Description of Drawings】

 1 is a scanning electron microscope (SEM) photograph of the cross section of the superabsorbent polymer sheet prepared according to an embodiment of the present invention.

[Form for implementation of the invention]

 The present invention may be modified in various ways and may have various forms, and specific embodiments will be illustrated and described in detail below. However, this is not intended to limit the present invention to a specific disclosed form, it should be understood to include all modifications, equivalents, and substitutes included in the spirit and scope of the present invention.

In the present specification, the particle size Dn of the particle means a particle diameter at an n volume% point of the cumulative particle number distribution according to the particle size. That is, D50 is the particle size at 50% of the particle number cumulative distribution when the particle diameters of particles are accumulated in ascending order, D90 is the particle size at the 90% point of the particle number cumulative distribution according to the particle size, and D10 is Particle size at 10% of particle number cumulative distribution. In the present invention, the average particle diameter refers to the D50 particle size. In the present invention, the particle diameter of the particles may be measured by a laser diffraction method or a scanning electron microscope (SEM) as described below. Hereinafter, a method of manufacturing a super absorbent polymer sheet according to one embodiment of the present invention will be described. According to an embodiment of the present invention, an acrylic acid monomer having an acidic group and at least a portion of the acidic group is neutralized, polyethylene glycol (methyl ether)

A monomer composition is prepared by mixing a comonomer comprising (meth) acrylate (polyethylene glycol (methyl ether) (meth) acrylate), an internal crosslinking agent, an encapsulated blowing agent, an inorganic blowing agent having an average particle diameter of 1 to 100 rnn, and a polymerization initiator. Making; Thermally polymerizing or photopolymerizing the monomer composition to form a hydrogel polymer; And drying the hydrogel polymer to form a highly water repellent resin sheet.

 In the production method of the present invention, the monomer composition, which is a raw material of the superabsorbent polymer, has an acidic group, an acrylic acid monomer in which at least a part of the acidic group is neutralized, polyethylene glycol (methyl ether) (meth) acrylate (Polyethylene glycol ( comonomers containing methyl ether) (meth) acrylate), internal crosslinking agents, encapsulated blowing agents, inorganic blowing agents with an average particle diameter of 1 to 100 nm, and polymerization initiators.

 First, the acrylic acid monomer is a compound represented by the following formula (1):

[Formula 1]

R'-COOM ¹

 In Chemical Formula 1,

An alkyl group having 2 to 5 carbon atoms containing a silver unsaturated bond, and M ¹ is a hydrogen atom, a monovalent or divalent metal, an ammonium group or an organic amine salt.

 Preferably, the acrylic acid monomer includes at least one member selected from the group consisting of acrylic acid, methacrylic acid and monovalent metal salts thereof, divalent metal salts, ammonium salts and organic amine salts.

Here, the acrylic acid monomer may have an acidic group and at least a part of the acidic group may be neutralized. Preferably, those which have been partially neutralized with an alkali substance such as sodium hydroxide, potassium hydroxide, ammonium hydroxide and the like can be used. In this case, the degree of neutralization of the acrylic acid monomer may be 40 to 95 mol%, or 40 to 80 mol%, or 45 to 75 mol%. The range of neutralization can be adjusted according to the final physical properties. However, if the degree of neutralization is too high, the neutralized monomer may be precipitated and polymerization may be difficult to proceed smoothly. If the degree of neutralization is too low, the absorbency of the polymer may not only be greatly reduced, but may exhibit properties such as elastic rubber, which is difficult to handle.

 The acrylic acid monomer concentration may be about 20 to about 60% by weight, preferably about 40 to about 50% by weight, based on the monomer composition including the raw material and the solvent of the superabsorbent polymer. The concentration may be appropriate in consideration of reaction conditions and the like. However, when the concentration of the monomer is too low, the yield of the superabsorbent polymer may be low and there may be a problem in economics. On the contrary, when the concentration is too high, a part of the monomer may precipitate or the grinding efficiency of the polymerized hydrogel polymer may be low. Etc. may cause problems in the process and may decrease the physical properties of the super absorbent polymer.

 The monomer composition of this invention contains polyethylene glycol (methyl ether) (meth) acrylate as a comonomer.

 The polyethylene glycol (methyl ether) (meth) acrylate is copolymerized with the acrylic acid monomer in the polymerization process to enable polymerization of a super absorbent polymer having a flexible polymer structure.

 In order to form an optimized polymer structure, the number of ethylene glycol repeat units in the polyethylene glycol (methyl ether) (meth) acrylate may be 3 to 100, or 3 to 80, or 3 to 50. The content of the polyethylene glycol (methyl ether) (meth) acrylate may be 5 to 40 parts by weight, preferably 5 to 30 parts by weight, more preferably 10 to 30 parts by weight based on 100 parts by weight of the acrylic acid monomer. . If the content of the comonomer is too small, there may be no effect of improving the flexibility, if it is included too much, there may be a decrease in the absorption rate, and the absorption capacity may be preferable in this respect the content range.

In the present invention, as the internal crosslinking agent, for example, a poly (meth) acrylate compound of a polyol, for example, a poly (meth) acrylate compound of a polyol having 2 to 10 carbon atoms can be used. More specific examples include trimethylolpropane tri (meth) acrylate, ethylene glycol di (meth) acrylate, polyethylene glycol di (meth) acrylate, propylene glycol di (meth) acrylate and polypropylene glycol di (meth) acrylic. Butanediol di (meth) acrylate, Butylene glycol di (meth) acrylate, diethylene glycol di (meth) acrylate, nucleic acid diol di (meth) acrylate, triethylene glycol di (meth) acrylate, tripropylene glycol di (meth) acrylate, tetra Ethylene glycol di (meth) acrylate, dipentaerythritol pentaacrylate, glycerin tri (meth) acrylate or pentaerythritol tetraacrylate can be used, and preferably, polyethylene glycol diacrylate can be used.

 The internal crosslinking agent may be included in a concentration of about 0.01 wt% to about 2 wt%, or 0.1 wt% to 0.5 wt% based on the monomer composition to crosslink the polymerized polymer. The monomer composition of the present invention comprises a blowing agent, wherein the encapsulating blowing agent and the inorganic blowing agent having an average particle diameter of 1 to 100 nm are simultaneously included. As such, when two kinds of blowing agents are mixed, there is an effect of obtaining high porosity and open pores of the superabsorbent polymer sheet. That is, in the case of using the encapsulated blowing agent and the inorganic blowing agent at the same time as the present invention, the main pores of a suitable size to ensure a high porosity in the inside of the superabsorbent polymer sheet is formed by the encapsulated blowing agent, between the main pores As the micro pore channel is formed by the nano-sized inorganic blowing agent, it is possible to secure an open pore channel structure in which the main pores are connected to each other. Therefore, the fine pore channel structure enables rapid quenching of water due to capillary pressure, and excellent centrifugal water retention and initial absorption rate of the superabsorbent polymer sheet produced compared to the case of using each blowing agent alone. Appears.

 The encapsulated blowing agent is present in the encapsulated state during polymerization of the monomer composition and expands by heat, and expands by high temperature heat applied during a drying process described later, and thus, an appropriate size between polymer structures of the superabsorbent polymer. By forming pores, the superabsorbent polymer sheet can exhibit appropriate porosity and open pore channel structure.

The encapsulated blowing agent may have a structure including a core comprising a hydrocarbon and a shell surrounding the core and formed of a thermoplastic resin. The encapsulated foaming agent varies in expansion characteristics according to the components constituting the core and the shell, the weight of each component, and the average particle diameter, and can be expanded to a desired size by controlling the porosity of the superabsorbent polymer sheet. 2019/216592 1 »（： 1 ^ 1 {2019/005223

Meanwhile, in order to determine whether pores of a desired size are formed, it is necessary to first understand the expansion characteristics of the encapsulated blowing agent. However, the form in which the foaming agent encapsulated in the superabsorbent resin is foamed may vary according to the manufacturing conditions of the superabsorbent resin, so it is difficult to define it as one form. Thus, by first encapsulating the encapsulated blowing agent in the air to check the expansion ratio and size, it can be confirmed that it is suitable for forming the desired pores.

의 열을 5 분 동안 가하여 캡슐화된 발포제를 팽창시킨다. 이때, 캡슐화된 발포제가 3 내지 15 배, 5 내지 15 배 혹은 8.5 내지 10 배의 공기 중에서의 최대 팽창 비율을 나타낼 때， 본 발명 고흡수성 수지 시트의 제조방법에 있어 적절한 열린 기공 구조를 형성하기에 적합한 것으로 판단할 수 있다. Specifically, the encapsulating blowing agent was applied onto a glass Petri dish and then

Heat is applied for 5 minutes to expand the encapsulated blowing agent. At this time, when the encapsulated blowing agent exhibits a maximum expansion ratio in air of 3 to 15 times, 5 to 15 times, or 8.5 to 10 times, it is necessary to form an open pore structure suitable for the method of preparing the superabsorbent polymer sheet of the present invention. It may be judged as suitable.

도입하여 입자들이 레이저 빔을 통과할 때 입자 크기에 따른 회절패턴 차이를 측정하여 입도 분포를 산출함으로써 측정될 수 있다. The encapsulated blowing agent may have an average particle diameter, that is, a 050 particle diameter of 5 to 50, or 5 to 30 m, or 5 to 20 / L, or 7 to 17 ,. It can be determined that the encapsulated blowing agent is suitable to achieve an appropriate porosity when exhibiting such an average particle diameter. At this time, the average particle diameter of the encapsulated blowing agent is 50), after dispersing the powder to be measured in the dispersion medium, a commercially available laser diffraction particle size measuring device (for example,

It can be measured by calculating the particle size distribution by measuring the diffraction pattern difference according to the particle size when the particles pass through the laser beam.

또는 50 내지 190 또는 70 내지 190

또는 75 내지 190 _의 최대 팽창 직경을 나타낼 때 본 발명 고흡수성 수지 시트의 제조방법에 있어 적절한 열린 기공 구조를 형성하기에 적합한 것으로 판단할수 있다. In addition, the encapsulated blowing agent is 20 to 190 in air.

Alternatively 50 to 190 or 70 to 190

Or it can be determined to be suitable for forming a suitable open pore structure in the method for producing a superabsorbent polymer sheet of the present invention when exhibiting a maximum expansion diameter of 75 to 190 _.

 In addition, the maximum expansion ratio and the maximum expansion diameter of the encapsulated blowing agent may be measured by a method of analyzing the shape of the pores formed in the manufactured superabsorbent resin sheet by scanning electron microscope (SEM).

The hydrocarbons constituting the core of the encapsulated blowing agent are 11-propane, 11-butane, 0-butane, cyclobutane, 11-pentane, 0-pentane, cyclopentane, II-nucleic acid, 0-nucleic acid, cyclonucleic acid, 11- Consisting of heptane, -heptane, cycloheptane, 11-octane, -octane and cyclooctane 2019/216592 1 »（： 1 ^ 1 {2019/005223

탄）가 상술한 크기의 기공을 형성하기에 적합하고, -부탄이 가장 적합할 수 있다. It may be one or more selected from the group. Among these, hydrocarbons having 3 to 5 carbon atoms-propane, 11 butane, 0-butane, cyclobutane,

Tan) is suitable for forming pores of the size described above, and -butane may be most suitable.

 The thermoplastic resin constituting the shell of the encapsulated blowing agent is selected from at least one monomer selected from the group consisting of 5 (meth) acrylate, (meth) acrylonitrile, aromatic vinyl, vinyl acetate, vinyl halide and vinylidene halide. It may be a polymer formed. Among these, (meth) acrylate and

Copolymers of (meth) acrylonitrile may be most suitable for forming pores of the sizes described above.

 10 The encapsulated blowing agent is based on the total weight of encapsulating blowing agent / hydrocarbon.

It may comprise 10 to 30% by weight. It may be most suitable for forming an open pore structure within this range.

 The encapsulated blowing agent may be prepared and used, or a blowing agent commercialized by satisfying the above conditions may be used.

 15 The amount of the encapsulated blowing agent may be used in an amount of 0.1 to 20 parts by weight, preferably 0.2 to 10 parts by weight, more preferably 0.5 to 2 parts by weight, based on 100 parts by weight of the acrylic acid monomer. If the content of the encapsulated blowing agent is too small, the open pore structure may not be properly formed, and there is a problem in that proper porosity cannot be secured. On the other hand, excessively high content of encapsulated blowing agent

In the case of 20, the encapsulated blowing agent may be precipitated from the monomer composition due to the low solubility and low density of the encapsulating blowing agent, and thus an open pore structure may not be properly formed. Alternatively, the porosity may be excessively high due to a large amount of encapsulated blowing agent, and the strength of the superabsorbent polymer sheet may be weakened.

 ? 5 The inorganic blowing agent preferably has a particle diameter of 1 to 100 11111, 2 to 90

바람직할 수 있다. 이와 같이 나노 크기의 무기 발포제를 사용함으로써 다수의 핵점（미1（^없;1011 이 에서의 발포 반응을 통하여 보다 많은 열린 기공을 얻을 수 있다. 즉, 나노 크기의 무기 발포제는 미세 기공 채널을 형성함으로써 상기 캡슐화된 발포제에 의하여 생성된 기공 사이의 경계를1 ^ 11, or from 20

It may be desirable. By using the nano-sized inorganic blowing agent in this way, more open pores can be obtained through the foaming reaction at a large number of nuclei (not 1 (^ 10). That is, the nano-sized inorganic blowing agent forms a fine pore channel to form a boundary between the pores produced by the encapsulated blowing agent.

30 can act as a decay, thereby reducing the absorbency of the superabsorbent polymer sheet. 2019/216592 1 »（： 1 ^ 1 {2019/005223

It can greatly improve. The particle size of the inorganic foaming agent can be measured using a scanning electron microscope (SEM).

 If the particle size of the inorganic foaming agent is too small, less than 1 11111, pores of too small size are formed due to low foaming force and too many nuclei, and thus, the above-described effects cannot be collapsed because the boundary between pores generated by the encapsulated foaming agent is not collapsed. Cannot be achieved. On the contrary, if the particle size of the inorganic foaming agent is too large in excess of 100, the size of the pores may be excessively large, or the ratio of the closed pores may increase due to the foaming due to the small nucleus point. Therefore, it is preferable to use particles within the above range.

중탄산암모늄어¾11（：0₃）, 탄산암모늄（어¾）₂（：0₃）, 아질산암모늄어11 0₂）, 붕소화수소나트륨어_&8¾） 및 탄산나트륨어¾（：0₃） 중 선택되는 1종 이상이 사용 가능하다. 이 중, 중화액 내에서의 안정성 특성을 고려할 때, 탄산칼슘이 바람직하게 사용될 수 있다. The inorganic blowing agent can be used without limitation a substance known as a conventional blowing agent, specifically, calcium carbonate 3 (： 0 ₃ ), sodium bicarbonate

Ammonium bicarbonate fish ¾11 （： 0 ₃ ）, ammonium carbonate （fish ¾） ₂ （： 0 ₃ ）, ammonium nitrite fish 11 0 ₂ ）, sodium hydrogen borohydride _& 8¾） and sodium carbonate fish ¾ （： 0 ₃ ） 1 or more types can be used. Among these, calcium carbonate can be preferably used in consideration of stability characteristics in the neutralizing liquid.

 The inorganic foaming agent may be used in an amount of 0.1 parts by weight or more based on 100 parts by weight of the acrylic acid monomer, preferably 0.2 to 10 parts by weight, more preferably 0.3 to 5 parts by weight. If the content of the inorganic blowing agent is too small, there may be a problem that the closed pores are formed, if too much may include a problem that the mechanical strength is lowered.

The mixing ratio of the encapsulated blowing agent and the inorganic blowing agent is preferably 3: 1 to 1: 1 weight ratio, and more preferably in the range of 2: 1 to 1: 1. When satisfying the above range, the superabsorbent polymer sheet to be produced has open pores, so that the absorption rate is improved, thereby improving the centrifugal water retention capacity and the initial absorption rate at the same time. If the mixed use ratio of the encapsulated blowing agent and the inorganic blowing agent is higher than 3: 1, and the ratio of the encapsulating blowing agent is too high, the fine pore channel structure by the inorganic blowing agent connecting the main pores generated by the encapsulating blowing agent is Since it is difficult to form, the open pore structure may not be properly generated, and thus the initial absorption rate may be lowered. On the contrary, if the mixed use ratio of the encapsulated foaming agent and the inorganic foaming agent is less than 1: 1, and the ratio of the encapsulating foaming agent is too small, the pore formation by the encapsulated foaming agent is not properly performed to secure porosity of the superabsorbent resin sheet. Do not have there is a problem.

 In addition, the encapsulated blowing agent and the inorganic blowing agent are included in an amount of 20 parts by weight or less based on 100 parts by weight of the acrylic acid monomer, and more preferably 0.4 to 20 parts by weight, or 0.7 to 10 parts by weight, or 1 to 5 parts by weight. desirable. When the total content of the blowing agent is too large, the degree of foaming is too high, the strength of the superabsorbent polymer may be lowered, and if it is included too little, the porosity is lowered and it is difficult to form an open pore structure.

 The polymerization initiator used in the polymerization in the method for producing a superabsorbent polymer sheet of the present invention is not particularly limited as long as it is generally used for the production of a superabsorbent polymer.

 Specifically, the polymerization initiator may be a thermal polymerization initiator or

The photoinitiator according to UV irradiation can be used. However, even with the photopolymerization method, since a certain amount of heat is generated by irradiation such as ultraviolet irradiation, and a certain amount of heat is generated in accordance with the progress of the polymerization reaction, which is an exothermic reaction, a thermal polymerization initiator may be additionally included.

 The photopolymerization initiator may be used without any limitation as long as it is a compound capable of forming radicals by light such as ultraviolet rays.

 Examples of the photopolymerization initiator include benzoin ether, dialkyl acetophenone, hydroxyl alkylketone, phenyl glyoxylate, and benzyl dimethyl ketal. Ketal), acyl phosphine (acyl phosphine) and alpha-aminoketone (a-aminoketone) may be used at least one selected from the group consisting of. Meanwhile, as an example of acylphosphine, a commercially available lucirin TPO, that is, 2,4,6-trimethyl-benzoyl-trimethyl phosphine oxide may be used. . For more photoinitiators, see Reinhold Schwalm, "UV Coatings: Basics, Recent."

Developments and New Application (Elsevier 2007) "pi 15, and is not limited to the above example.

The photopolymerization initiator may be included in a concentration of about 0.01 to about 1.0 wt% based on the monomer composition. If the concentration of the photopolymerization initiator is too low, the polymerization rate may be slow. If the concentration of the photopolymerization initiator is too high, The molecular weight of the super absorbent polymer may be small and the physical properties may be nonuniform.

In addition, the thermal polymerization initiator may be used at least one selected from the group consisting of persulfate initiator, azo initiator, hydrogen peroxide and ascorbic acid. Specifically, examples of persulfate-based initiators include sodium persulfate (Na ₂ S ₂ O ₈ ), potassium persulfate (K ₂ S ₂ O ₈ ), and ammonium persulfate (NH ₄ ). ₂ S ₂ 0 ₈ ), and examples of azo initiators include 2,2-azobis- (2-amidinopropane) dihydrochloride, 2 , 2-azobis- (N, N-dimethylene) isobutyramidine dihydrochloride (2,2-azobis- (N, N-dimethylene) isobutyTamidine dihydrochloride), 2- (carbamoylazo) isobutyronitrile (2- (carbamoylazo) isobutylonitril), 2,2-azobis [2- (2-imidazoline-2-yl) propane] dihydrochloride (2,2-azobis [2- (2-imidazolin-2- yl) propane] dihydrochloride) and 4,4-azobis- (4-cyanovaleric acid). More various thermal polymerization initiators are well specified in Odian's Principle of Polymerization (Wiley, 1981), p203, and are not limited to the examples described above.

 The thermal polymerization initiator may be included in a concentration of about 0.001 to about 0.5% by weight based on the monomer composition. When the concentration of the thermal polymerization initiator is too low, additional thermal polymerization hardly occurs, so that the effect of the addition of the thermal polymerization initiator may be insignificant. When the concentration of the thermal polymerization initiator is too high, the molecular weight of the superabsorbent polymer may be small and the physical properties may be uneven. have.

 In the production method of the present invention, the monomer composition may further include additives such as thickeners, plasticizers, preservative stabilizers, antioxidants and the like as necessary.

 Raw materials such as the acrylic acid unsaturated monomers, comonomers, internal crosslinking agents, polymerization initiators, and additives described above may be prepared in the form of a monomer composition solution dissolved in a solvent. The solvent may be included in the remaining amount except for the above-described components with respect to the total content of the monomer composition.

The solvent that can be used can be used without limitation as long as it can dissolve the above-described components, for example, water, ethanol, ethylene glycol, diethylene glycol, triethylene glycol, 1,4-butanediol, propylene glycol , 2019/216592 1 »（： 1 ^ 1 {2019/005223

-디메틸아세트아미드 등에서 선택된 1종 이상을 조합하여 사용할수 있다. Ethylene glycol monobutyl ether, propylene glycol monomethyl ether, propylene glycol monomethyl ether acetate, methyl ethyl ketone, acetone, methyl amyl ketone, cyclonucleanone, cyclopentanone, diethylene glycol monomethyl ether, diethylene glycol ethyl ether, Toluene, xylten, butyrolactone, carbitol, methylcellosolve acetate and

It may be used in combination of one or more selected from -dimethylacetamide and the like.

 Next, the monomer composition is thermally polymerized or photopolymerized to form a hydrogel polymer.

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

 Specifically, the polymerization method can be largely divided into thermal polymerization and photopolymerization according to the polymerization energy source. In general, when the thermal polymerization proceeds, it may proceed in a reactor having a stirring shaft such as a kneader (10½3 (under 1)). On the other hand, when the photopolymerization is carried out, but may be carried out in a reactor having a movable conveyor belt, the above-described polymerization method is an example, the present invention is not limited to the above-described polymerization method.

 Thermal polymerization or photopolymerization reaction temperature of the monomer composition is not particularly limited, but may be, for example, 80 to 120 V, preferably 90 to 110 kPa.

 In this case, the water content of the hydrogel polymer obtained by the above method may be about 40 to about 80% by weight. On the other hand, the term "water content" throughout the present specification means the amount of water occupied by the total weight of the water-containing gel polymer minus the weight of the polymer in the dry state, specifically, the polymer through infrared heating It is defined as a value calculated by measuring the weight loss according to the water evaporation in the polymer during drying by raising the temperature of drying, wherein the drying conditions are the total drying by raising the temperature from room temperature to about 1801: and maintaining at 180. The time is set to 20 minutes, including 5 minutes of temperature rise, to measure the moisture content.

 Next, the hydrogel polymer is molded into a sheet and dried to form a superabsorbent polymer sheet.

At this time, the drying temperature of the drying step may be about 120 to about 2501 :. If the drying temperature is less than about 1201: the drying time becomes too long and the final There is a fear that the physical properties of the superabsorbent polymer to be formed is lowered, when the drying temperature exceeds about 250 ^° C, only the polymer surface is too dry, there is a fear that the physical properties of the final superabsorbent resin is formed. Thus, preferably, the drying may proceed at a temperature of about 120 to about 250 ^° C, more preferably at a temperature of about 140 to about 200 ^° C. In this drying step, the fine pore channel is formed between the main pores by the foaming of the blowing agent, so that an open pore channel structure can be obtained.

 On the other hand, in the case of the drying time, in consideration of the process efficiency, etc., it may proceed for about 20 to about 90 minutes, but is not limited thereto.

 If the drying method of the drying step is also commonly used as a drying step of the hydrogel polymer, it can be selected and used without limitation of the configuration. Specifically, the drying step may be performed by hot wind supply, infrared irradiation, microwave irradiation, or ultraviolet irradiation.

 Water content of the superabsorbent polymer sheet after the drying step is about 10% by weight or more, for example, about 10 to about 40% by weight, or about 15 to about 30% by weight. When the water content of the superabsorbent polymer sheet is in the above range, the flexibility of the sheet can be ensured.

 According to one embodiment of the present invention, the thickness of the superabsorbent polymer sheet obtained by the above process is about 100_ or more, or 1,000_, or 5,000 // m and about 10 cm or less, or about 5 cm or less, or about lcm It may be: If the thickness of the superabsorbent polymer sheet is too thin, the sheet may be torn due to its low strength, and if it is too thick, drying and processing may be difficult. It may be desirable to have the above-described thickness range in this respect.

 According to the manufacturing method of the superabsorbent polymer sheet of the present invention as described above, in the superabsorbent polymer sheet, at least a portion of the pores is a sheet of an open pore channel structure in which the pores are connected to each other. As water absorption is possible due to capillary pressure, absorption rate and permeability can be improved, and the pulse free absorber can be provided as a log.

The superabsorbent polymer sheet produced according to the present invention has an open pore channel structure in which at least a portion of the pores are connected to each other, whereby water can be knotted by capillary pressure. Accordingly Absorption rate and permeability may be improved over conventional superabsorbent polymers in powder form. In addition, the superabsorbent polymer sheet may have a pore volume of 40% to 80%, or 54% to 74% of the total volume.

 The superabsorbent polymer sheet has a centrifugal water-retaining capacity (1 (:)) of about 10 to about 45, preferably about 15 to about 45, and more preferably about 20 to about 20 centrifugal water capacity measured according to the method of EDANA ᄊ 241.2. It can range from about 45 ^.

 In addition, the superabsorbent polymer sheet has an initial absorption rate of about 5 to about 50 seconds, preferably about 5 to about 30 seconds, more preferably about 5 to about 10, which is the time taken for the NaCl (0.9%) solution to be absorbed. It can have a range of seconds. As described above, the superabsorbent polymer sheet of the present invention has excellent absorption characteristics and permeability, and can be used as a pul free absorber.

 Hereinafter, the operation and effects of the invention will be described in more detail with reference to specific examples of the invention. However, this is presented as an example of the invention, whereby the scope of the invention is not limited to any meaning.

<Example>

 In the following examples, the particle size of the encapsulated blowing agent was immediately determined by using a laser diffraction method. Specifically, after immediately dispersing lmg of the target powder in 30g of distilled water, it was introduced into a laser diffraction particle size measuring apparatus (Mastersizer 3000) to calculate the particle size distribution by measuring the diffraction pattern difference according to the particle size as the particles pass through the laser beam. . D50 was calculated by calculating the particle diameter at the point where 50% of the cumulative particle number distribution according to the particle diameter in the measuring apparatus was obtained. In addition, the particle diameter of the inorganic foaming agent was measured and analyzed using the scanning electron microscope (SEM). Preparation of High Top Water Resin Sheet

 Example 1

27.5 g of acrylic acid, 35.7 g of caustic soda (NaOH, 30% by weight solution) and 5.7 ml of water were mixed to prepare about 70% by weight of the neutralized neutralized liquid (solid content: 50% by weight) of acrylic acid. Ready.

 Polyethylene glycol (methyl ether) as a comonomer to the neutralizing solution

(Meth) acrylate (Polyethylene glycol (methyl ether) (meth) acrylate) (trade name: FA-401, manufacturer: Han Thickening agent) 5.5 g, polyethylene glycol diacrylate (MW = 330 manufacturer:

5 aldrich) 0.08 g, sodium persulfate 0.06 g, encapsulated blowing agent (Akzonobel, Expancel 031 DU 40, average particle diameter (D50) 16 / m) 0.41 g, calcium carbonate (CaC0 ₃ ) (as inorganic blowing agent) A monomer composition was prepared by adding 0.41 g of a particle diameter of 20 nm to 60 ran).

 The monomer composition was high shear mixed for about 10 minutes at a speed of 500 10 rpm using a mechanical mixer.

Thereafter, the mixture was introduced through a feeder of the polymerizer to perform polymerization to form a hydrogel polymer. The temperature of the polymerization reactor was maintained at 100 ^° C, the maximum temperature of the polymerization was 110 ^° C, polymerization time was 10 minutes.

Subsequently, the hydrogel polymer was dried at a temperature of 180 ^° C. for 5 minutes, and 15 were cut into sheet form (thickness: around 2_) using a cutting machine. Example 2

 In Example 1, 20 was prepared in the same manner as in Example 1, except that 0.5% of the inorganic blowing agent was used relative to 100% by weight of acrylic acid. Comparative Example 1

 In Example 1, a superabsorbent polymer sheet was manufactured in the same manner as in Example 1, except that the calcium carbonate blowing agent was not used.

 25

 Comparative Example 2

 In Example 1, a superabsorbent polymer sheet was prepared in the same manner as in Example 1 except that the encapsulated blowing agent was not used.

B0 Comparative Example 3 2019/216592 1 »（： 1 ^ 1 {2019/005223

In Example 1, a superabsorbent polymer sheet was prepared in the same manner as in Example 1 except that the encapsulated blowing agent and the calcium carbonate blowing agent were not used. Comparative Example 4

 In Example 1, a superabsorbent polymer sheet was prepared in the same manner as in Example 1, except that 4.5 wt% of the encapsulating foaming agent and 1.5 wt% of the inorganic foaming agent were used. Comparative Example 5

 In Example 1, a superabsorbent polymer sheet was prepared in the same manner as in Example 1, except that 0.5 wt% of the encapsulating foaming agent and 1.0 wt% of the inorganic foaming agent were used.

<Experimental Example>

 Characterization of Super Absorbent Resin Sheet

 (1) cross section of superabsorbent polymer sheet

 A scanning electron microscope (SEM) photograph of the cross section of the superabsorbent polymer sheet according to Example 1 of the present invention is shown in FIG. 1. Referring to Figure 1, it can be seen that the open pore channel structure is formed on the surface of the superabsorbent polymer sheet according to the first embodiment of the present invention.

(2) Centrifugal water holding capacity (1 (：))

241.2의 방법에 따라 원심분리 보수능 ( 1(：)을 측정하였다. EDANA method for the superabsorbent polymer sheet of each example and comparative example

The centrifugal water holding capacity (1 (：)) was measured according to the method of 241.2.

(3) initial absorption rate measurement

 The time taken to absorb NaCl (0.9%) solution 27 after cutting the superabsorbent polymer sheets of each of Examples and Comparative Examples to 12011 * 12011 size was measured.

Table 1 2019/216592 1 »（： 1 ^ 1 {2019/005223

 1) Weight% of blowing agent to 100% by weight of acrylic acid Referring to Table 1 above, in the case of a super absorbent polymer sheet manufactured by simultaneously using an encapsulated blowing agent and an inorganic blowing agent in a 3: 1 to 1: 1 weight ratio, It can be seen that it exhibits excellent centrifugal water-retaining capacity and initial absorption rate compared to the superabsorbent polymer sheet which is used alone or without a blowing agent. In Comparative Example 4, the encapsulated blowing agent and the inorganic blowing agent were used simultaneously, but the weight ratio exceeded 3: 1, and it was confirmed that the initial absorption rate was remarkably decreased. In addition, when the weight ratio of the encapsulated foaming agent and the inorganic foaming agent as in Comparative Example 5 is less than 1: 1, sufficient porosity was not secured, and it can be seen that the initial absorption rate was also low. From this, it can be seen that in order to obtain excellent physical properties due to the open pore structure of the superabsorbent polymer sheet, the weight ratio of the encapsulated blowing agent and the inorganic blowing agent of the present invention must be satisfied.

Claims

[Range of request]  [Claim 1]  Comonomers having an acidic group and containing at least partially weighted acrylic acid monomers, polyethylene glycol (methyl ether) (meth) acrylates, internal crosslinking agents, encapsulated Preparing a monomer composition by mixing a blowing agent, an inorganic blowing agent having an average particle diameter of 1 to 100 nm, and a polymerization initiator;  Thermally polymerizing or photopolymerizing the monomer composition to form a hydrogel polymer; And  Drying the hydrogel polymer to form a superabsorbent polymer sheet; As a manufacturing method of a super absorbent polymer sheet comprising a,  The encapsulated foaming agent and the inorganic foaming agent is included in a weight ratio of 3: 1 to 1: 1, a method for producing a super absorbent polymer sheet. [Claim 2]  The method of claim 1,  The polyethylene glycol (methyl ether) (meth) acrylate (polyethylene glycol (methyl ether) (meth) acrylate) is contained in 5 to 40 parts by weight based on 100 parts by weight of the acrylic acid monomer, the manufacturing method of the super absorbent polymer sheet. [Claim 3]  The method of claim 1,  The encapsulated blowing agent has an average particle diameter of 2 to 50!, The method of producing a super absorbent polymer sheet. [Claim 4]  The method of claim 1, The encapsulated blowing agent has an expansion ratio of 3 to 15 times in air, the method for producing a super absorbent polymer sheet. 2019/216592 1 »（： 1 ^ 1 {2019/005223 [Claim 5]  According to claim 1,  The encapsulating blowing agent has a structure comprising a core comprising a hydrocarbon and a shell surrounding the core and formed of a thermoplastic resin. [Claim 6]  The method of claim 5, The hydrocarbon is 11-propane, 11-butane, 0-butane, cyclobutane, 11-phenlan,

Preparation of a superabsorbent polymer sheet, which is at least one member selected from the group consisting of cyclopentane,! -Nucleic acid, -nucleic acid, cyclonucleic acid, 11-heptane, 0-heptane, cycloheptane, 11-octane, 0-octane and cyclooctane Way. [Claim 7]  The method of claim 5,  The thermoplastic resin is a polymer prepared from at least one monomer selected from the group consisting of (meth) acrylate, (meth) acrylonitrile, aromatic vinyl, vinyl acetate, vinyl halide and vinylidene halide. Way. [Claim 8]  The method of claim 1, The inorganic blowing agent is calcium carbonate (0 _& 0¾), sodium bicarbonate fish tank 1 祀 0 ₃ ), ammonium bicarbonate fish ¾: »0) ₃ ), ammonium carbonate (¾) ₂ (： 0 ₃ ), ammonium nitrite (> 0 ₂ ), A method for producing a super absorbent polymer sheet, which is at least one selected from sodium hydrogen borohydride _& 8¾) and sodium carbonate fish ¾ (0 ₃ ). [Claim 9]  The method of claim 1, The particle size of the inorganic blowing agent is 2 to 90 111x1, the manufacturing method of the super absorbent polymer sheet. 2019/216592 1 »（： 1 ^ 1 {2019/005223 [Claim 10]  The method of claim 1,  The encapsulated blowing agent and the inorganic blowing agent is included in a weight ratio of 2: 1 to 1: 1, a method for producing a super absorbent polymer sheet.  [Claim 1 11]  The method of claim 1,  The encapsulated blowing agent is included in an amount of 0.1 to 20 parts by weight based on 100 parts by weight of the acrylic acid monomer, a method for producing a super absorbent polymer sheet. [Claim 12]  The method of claim 1,  The inorganic blowing agent is contained 0.1 parts by weight or more based on 100 parts by weight of the acrylic acid monomer, a method for producing a super absorbent polymer sheet. [Claim 13]  The method of claim 1,  The encapsulated blowing agent and the inorganic blowing agent are contained in an amount of 0.4 to 20 parts by weight based on 100 parts by weight of the acrylic acid monomer, a method for producing a super absorbent polymer sheet.