WO2019216591A1

WO2019216591A1 - Preparation method for super absorbent polymer sheet

Info

Publication number: WO2019216591A1
Application number: PCT/KR2019/005222
Authority: WO
Inventors: 윤기열; 김기철; 최현; 강성균; 김주은
Original assignee: 주식회사 엘지화학
Priority date: 2018-05-11
Filing date: 2019-04-30
Publication date: 2019-11-14

Abstract

The present invention relates to a preparation method for a super absorbent polymer sheet. According to the preparation method for a super absorbent polymer sheet of the present invention, a porous flexible super absorbent polymer sheet can be produced.

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. 10-2018-0054364 dated May 11, 2018 and Korean Patent Application No. 10-2019-0049877 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 capable of absorbing water of 500 to 1,000 times its own weight. Each developer has a super absorbent material (AMG) and an absorbent gel (AGM). They are named differently. Such superabsorbent resins have been put into practical use as sanitary instruments, and are currently maintained in the fields of gardening soil repair agents, civil engineering, building index materials, seedling sheets, food distribution, as well as sanitary products such as paper diapers and sanitary napkins for children. It is widely used as a material for agent, and poultice.

In general, various sanitary articles such as diapers, sanitary napkins, or incontinence pads include absorbents including superabsorbent polymer particles. The absorbents mainly contain the superabsorbent resin particles and the superabsorbent resin particles, while appropriately fixing the absorbent body and hygiene. 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 absorbent body and the hygiene article, and there was a problem in that the user's skin and the hygiene article had sweating between the user's skin and the sanitary article. Moreover, due to the necessity of using a large amount of the fluff pulp mainly obtained 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 in the absorbent layer and the sanitary article to reduce the amount of fluff pulp used or to provide sanitary articles such as so-called pulpless diapers which do 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 during the manufacture of hygiene materials or in actual use, and are limited in the range of use because they must be used together 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 exhibiting 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 superabsorbent polymer sheet excellent in high flexibility and absorption performance. Technical Solution

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

Comonomers having an acidic group, at least a portion of which is neutralized, an acrylic acid monomer, a copolymer containing polyethylene glycol (methyl ether) (meth) acrylate, an internal crosslinker, encapsulated Preparing a monomer composition by mixing a blowing agent, an inorganic blowing agent having an average particle diameter of 1 to 100, 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 included in a weight ratio of 3: 1 to 1: 1, to provide a method for producing a super absorbent polymer sheet.

The polyethylene glycol (methyl ether) (meth) acrylate 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 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 n-propane, n-butane, iso-butane, cyclobutane, _n -pentane, iso-pentane, cyclopentane, n-nucleic acid, iso-nucleic acid, cyclonucleic acid, n-heptane, iso-heptane, At least one selected from the group consisting of cycloheptane, n-octane, iso-octane and cyclooctane, wherein the thermoplastic resin is (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.

The inorganic blowing agent is calcium carbonate (CaC0 ₃ ), sodium bicarbonate (NaHC0 ₃ ), ammonium bicarbonate (NH ₄ HC0 ₃ ), ammonium carbonate ((NH ₄ ) ₂ C0 ₃ ), ammonium nitrite (NH ₄ NO ₂ ), hydrogen boride It may be at least one selected from sodium (NaBH ₄ ) and sodium carbonate (Na ₂ CO ₃ ).

Preferably, the average particle diameter of the inorganic blowing agent may be 5 to 20 / pa. 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 is based on 100 parts by weight of the acrylic acid monomer.

0.3 to 20 parts by weight may be included, 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, whereby water of 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 is applicable to various products requiring flexibility and high absorbency.

In addition, the superabsorbent polymer sheet can be used as a pulse fleece 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 invention]

As the invention allows for various changes and numerous modifications, particular 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 diameter refers to the particle diameter at the n-vol% 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 cumulative particle number 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. The Dn is a laser diffraction method (Laser Diffraction method), can be used immediately. Specifically, the particle diameter Dn is immediately dispersed in a dispersion medium in a dispersion medium, and then introduced into a commercially available laser diffraction particle size measuring apparatus (for example, the Mastersizer 3000) to determine the difference in diffraction pattern according to the particle size as the particles pass through the laser beam. Can be measured by calculating the particle size distribution.

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)

Monomer by mixing a comonomer containing (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 (D50) of 1 to 100 μm, and a polymerization initiator Preparing a composition; thermally polymerizing or photopolymerizing the monomer composition to form a hydrogel polymer; And drying the hydrogel polymer to form a superabsorbent polymer sheet, wherein the encapsulated and inorganic foam agents are included in a weight ratio of 3: 1 to 1: 1, and a method of preparing a superabsorbent polymer sheet is provided. .

In the production method of the present invention, the monomer composition which is a raw material of the super absorbent polymer has an acidic group, an acrylic acid monomer having at least a portion of the acidic group neutralized, polyethylene glycol (methyl ether) (meth) acrylate (polyethylene glycol).

Comonomer containing (methyl ether) (meth) acrylate), internal crosslinking agent, encapsulated blowing agent, average particle diameter (D50) l to 100

Inorganic blowing agents, 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,

R ¹ is an alkyl group of 2 to 5 carbon atoms containing an unsaturated bond,

M ^{1 is a} hydrogen atom, a monovalent or divalent metal, an ammonium group or an organic amine salt. Preferably, the acrylic acid monomer is composed of acrylic acid, methacrylic acid and monovalent metal salts thereof, divalent metal salts, ammonium salts and organic amine salts. It includes one or more selected from the group.

Here, the acrylic acid monomer may have an acid group and at least a part of the acid group may be neutralized. Preferably, those which have been partially neutralized with an alkali substance such as sodium hydroxide, potassium hydroxide, ammonium hydroxide or the like may 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 precipitate and polymerization may be difficult to proceed smoothly. On the contrary, if the degree of neutralization is too low, the absorbency of the polymer may be greatly degraded, and properties such as elastic rubber, which are difficult to handle, may be exhibited. have.

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 considering the reaction conditions. 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 repeating 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, too In the case where it is included in a large amount, there may be a decrease in the absorption rate and the absorption capacity, so the content range may be preferable in this respect.

In the present invention, as the internal crosslinking agent, for example, a poly (meth) acrylate-based compound of polyol, for example, a poly (meth) acrylate-based compound of 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, polypropylene glycol di (meth) acryl 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, tri Propylene glycol di (meth) acrylate, tetraethylene glycol di (meth) acrylate, dipentaerythritol pentaacrylate, glycerin tri (meth) acrylate or pentaerythol 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 an inorganic blowing agent having an average particle diameter (D50) of 1 to 100 u m are simultaneously included. As such, when the two types of blowing agents are mixed, there is an effect of obtaining high porosity and open pores of the superabsorbent polymer sheet. That is, when simultaneously using the encapsulated foaming agent and the inorganic foaming agent as in the present invention, the main pores of the large size suitable for securing a high porosity inside the superabsorbent polymer sheet is formed by the encapsulated foaming agent, such main pores As the fine pore channel is formed between the inorganic blowing agents, it is possible to secure an open pore channel structure in which the main pores are connected to each other. Therefore, due to the microporous channel structure, it is possible to quickly drop water by capillary pressure, and the centrifugal water-retaining ability and the pressure-absorbing ability of the superabsorbent polymer produced are superior to that of each foaming agent alone.

The encapsulated blowing agent is in an encapsulated state upon polymerization of the monomer composition. 2019/216591 1 »（： 1 ^ 1 {2019/005222

Pore channel (opening of the superabsorbent resin sheet is formed by forming a pore of appropriate size between the polymer structure of the superabsorbent polymer, and then expands by heat, and is foamed by high temperature heat applied during the drying process described later. ¥} 30 Refers to the structure of mountain 111½1）.

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 blowing agent varies in expansion characteristics depending on the components constituting the core and the shell, the weight of each component, and the average particle diameter, and the foaming agent can expand to a desired size and control the porosity of the superabsorbent polymer sheet.

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, since the foamed encapsulating agent in the superabsorbent resin is foamed may vary depending on the manufacturing conditions of the superabsorbent resin, 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.

Specifically, after applying the encapsulant blowing agent on a glass Petri dish, 180

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 manufacturing the superabsorbent polymer sheet of the present invention. It may be judged as suitable.

The encapsulated blowing agent has an average particle diameter, that is, a D50 particle diameter of 5 to 50 m, or 5 to 30

Or 5-20 / pe, or 7-17 _. It can be judged that the encapsulated blowing agent is suitable to achieve an appropriate porosity when exhibiting such an average particle diameter.

In addition, the encapsulated blowing agent is 20 to 190 in air.

To 190 /, or 70 to 190

When exhibiting a maximum expansion diameter of 190 쎈 1, it can be judged to be suitable for forming a suitable open pore structure in the method for producing the superabsorbent polymer sheet of the present invention.

In addition, the maximum expansion ratio and the maximum expansion diameter of the encapsulated blowing agent, 2019/216591 1 »（： 1 ^ 1 {2019/005222

The shape of the pores formed in the superabsorbent polymer sheet may be measured by a method of analyzing with a scanning electron microscope (SEM).

The hydrocarbons constituting the core of the encapsulated blowing agent are 11-propane, 11-butane,

0-pentane, cyclopentane, 11-nucleic acid, 0-nucleic acid,

Cycloheptane, 11-octane,

And cyclooctane may be one or more selected from the group consisting of. Among these, hydrocarbons having 3 to 5 carbon atoms (propane, 11-butane, 0-butane, cyclobutane, 11-pentane, 0-pentane, cyclopentane) are suitable for forming pores of the above-mentioned sizes,

Butane may be most suitable.

And, the thermoplastic resin constituting the shell of the encapsulated blowing agent is

It may be a polymer formed from at least one monomer selected from the group consisting of (meth) acrylate, (meth) acrylonitrile, aromatic vinyl, vinyl acetate, vinyl halide and vinylidene halide. Among these, copolymers of (meth) acrylate and (meth) acrylonitrile may be most suitable for forming pores of the above-described sizes.

The encapsulated blowing agent may comprise from 10 to 30% by weight hydrocarbon based on the total weight of the encapsulating blowing agent. 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.

In addition, the content of the encapsulated blowing agent may be used in an amount of 0.3 to 20 parts by weight, preferably 0.5 to 10 parts by weight, and more preferably 1 to 10 parts by weight, based on 100 parts by weight of the acrylic acid monomer. When the content of the encapsulated foaming agent is too small, the open pore structure may not be properly formed, and adequate porosity may not be secured, and when it is included too much, the porosity may be too high to weaken the strength of the super absorbent polymer. In this regard, the above content range may be preferable.

The inorganic blowing agent preferably has an average particle diameter, that is, a 050 particle diameter of 1 to 100 or 111, and more preferably 3 to 50！, or 5 to 20 / L. This micro-sized inorganic blowing agent acts as a blowing agent and is applied to the superabsorbent polymer sheet. 2019/216591 1 »（： 1 ^ 1 {2019/005222

It can serve simultaneously as an inorganic support imparting mechanical strength. If the average particle diameter of the inorganic foaming agent is less than 1 m, it is possible to form open pores due to the formation of high porosity due to many nucleus points, but it is difficult to secure the strength of the superabsorbent polymer sheet due to its weak role as an inorganic support. Too large in excess of _ may not function properly as a blowing agent for forming micropores, but may function only as an inorganic support. Therefore, in order to produce a superabsorbent sheet having open pores and having an appropriate strength, it is preferable to use particles within the above range.

The inorganic blowing agent can be used without limitation, a substance commonly known as a blowing agent, specifically, calcium carbonate (0 trillion (： 0 ₃ ), sodium bicarbonate 0 »0¾), ammonium bicarbonate ¾11 (： 0 ₃ ), ammonium carbonate At least one selected from the group consisting of (fish ¾) ₂ (： 0 ₃ ), ammonium nitrite fish ¾ 0 ₂ ), sodium hydrogen borohydride fish _and seedlings ¾ and sodium carbonate _¾ (： 0 ₃ ) can be used. Of these, calcium carbonate and / or sodium carbonate may be preferably used in consideration of stability characteristics in the neutralized liquid.

The content of the inorganic blowing agent is based on 100 parts by weight of the acrylic acid monomer.

0.1 parts by weight or more may be used, 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 is included, due to the high porosity, there may be 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. Within this range, high porosity and mechanical strength improving effect can be obtained, and thus the centrifugal water-retaining capacity and the pressure-absorbing capacity of the superabsorbent polymer sheet can be improved. 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 in the range of 0.4 to 20 parts by weight, 0.7 to 10 parts by weight, or 1 to 5 parts by weight. . 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 too small, the open pore structure is less likely to be formed, thus satisfying the above range. The polymerization initiator used in the polymerization in the method for producing a super absorbent polymer sheet of the present invention is not particularly limited as long as it is generally used for producing a super absorbent polymer.

Specifically, the polymerization initiator may use a thermal polymerization initiator or a photopolymerization initiator according to UV irradiation depending on the polymerization method. However, even with the photopolymerization method, since a certain amount of heat is generated by irradiation of ultraviolet rays or the like, 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 limitation in the composition 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.

One or more selected from the group consisting of dimethyl ketal, acyl phosphine and alpha-aminoketone can be used. Meanwhile, as an example of acylphosphine, a commercially available lucirin TPO, that is, 2, 4, 6-trimethyl-benzoyl-trimethyl phosphine oxide (2, 4, 6-trimethyl -benzoyl-trimethyl phosphine oxide) can be used. . A wider variety of photoinitiators are well described in Reinhold Schwalm's book, "UV Coatings: Basics, Recent Developments and New Application (Elsevier 2007)" pi 15, but are not limited to the examples described above.

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 superabsorbent polymer may be low and the physical properties may be uneven.

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 0 g), potassium persulfate (K ₂ S ₂ O ₈ ), ammonium persulfate (NH ₄ ) ₂ SiOg), etc. An example of this, and azo (azo) based initiators include ^2, ^2-azobis- (2-amidinopropane) dihydrochloride (2,2-azobis (2- amidinopropane) dihydrochloride), 2,2-azobis- (N, N-dimethylene) isobutyramimidine dihydrochloride (2,2-azobis- (N, dimethylene) isobutyramidine dihydrochloride), 2- (carbamoyl) azo) isobutyronitrile (2- (carbamoylazo) isobutylonitril), 2,2-azobis [2- ^{^{(2-imidazolin-2-yl)}} propane] dihydrochloride ^(2, ² -azobis ^[2- ( ^{^{2 -imidazolin_ 2 - yl) propane]}} dihydrochloride), 4,4 - include cyano ballet rigs acid) (4,4-azobis- (4- cyanovaleric acid)) - azobis- (4. 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. If the concentration of the thermal polymerization initiator is too low, additional thermal polymerization hardly occurs, and the effect of adding the thermal polymerization initiator may be insignificant. If 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 above-described acrylic acid unsaturated monomers, comonomers, internal crosslinking agents, polymerization initiators, and additives 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 may 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 , 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 It may be used in combination of one or more selected from toluene, xylene, butyrolactone, carbitol, methyl cellosolve acetate and N, N-dimethylacetamide.

Next, the monomer composition is thermally polymerized or photopolymerized to form a hydrogel polymer. 2019/216591 1 »（： 1 ^ 1 {2019/005222

Form.

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 the case of usually thermal polymerization,

It can proceed in a reactor with a stirring shaft. On the other hand, in the case of the photopolymerization, it can 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, for example, 80 to 120

Preferably from 90 to 110 I: It can be.

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 refers to the amount of water to the total weight of the hydrogel gel polymer minus the weight of the polymer in the dry state, specifically, the polymer by infrared heating In the process of drying by increasing the temperature, the weight loss according to the water evaporation in the polymer is defined as a value calculated immediately, wherein the drying conditions are increased by increasing the temperature from room temperature to about 1801: and then maintained at 1801: The drying time is set to 20 minutes including the temperature rise step 5 minutes, and the moisture content is measured.

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 120 ^° 0, the drying time may be too long and the physical properties of the final superabsorbent polymer may be lowered. If the drying temperature is higher than about 250 ^° ：, only the polymer surface may be excessively dried. There is a fear that the physical properties of the superabsorbent polymer to be finally formed decrease. Thus preferably the drying may proceed at a temperature of about 120 to about 250, more preferably at a temperature of about 140 to about 2001 :. In this drying step, the main pores by the foaming of the blowing agent A fine pore channel is formed in between, so that an open pore channel structure can be obtained. On the other hand, in the case of drying time, in consideration of process efficiency and the like, from about 20 to about

It may proceed for 90 minutes, but is not limited thereto.

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

The moisture content of the superabsorbent polymer sheet after the drying step may be about 10 wt% or more, for example, about 10 wt% to about 40 wt%, or about 15 wt% to about 30 wt%. When it is in the above-mentioned 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 / year, or 5,000 / zm and about 10 cm or less, or about 5 cm or less, or about lcm or less. Can 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 part of the pores is in a sheet state of an open pore channel structure in which the pores are connected to each other. Since the absorption of water by capillary pressure is possible, the absorption rate and permeability can be improved and can be provided as it is as a pulseless absorber.

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, the absorption rate and permeability may be improved than the conventional superabsorbent polymer in powder form. In addition, the superabsorbent polymer sheet has a centrifugal water retention (CRC) of about 10 to about 40 g / g, preferably about 15 to about 40 g / g, more preferably measured according to the method of EDANA WSP 241.2. May range from about 25 to about 40 g / g. In addition, the superabsorbent polymer sheet was measured according to the method of 242.2 by EDANA method \ 8.

About 5 to about 20 dung, preferably about 7 to about 15 _§ /, more preferably about 10 to about

It can have a range.

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. However, this is presented as an example of the invention, whereby the scope of the invention is not limited to any meaning.

In the following examples, the particle diameters of the encapsulated blowing agent and the inorganic blowing agent were 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 the laser diffraction particle size measuring apparatus (Mastersizer 3000) to measure the particle size distribution by measuring the diffraction pattern difference according to the particle size as the particles pass through the laser beam. . The particle diameter at the point which becomes 50% of the cumulative particle number distribution according to the particle diameter in a measuring apparatus was calculated, and D50 was calculated | required. Preparation of Super Absorbent Resin Sheet

Example 1

27.5 g of acrylic acid, 35.7 g of caustic soda (NaOH, 30 wt% solution) and 5.7 g of water were mixed to prepare a neutralizing solution (solid content: 50 wt%) in which about 70 mol% of the acrylic acid was neutralized.

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

(Meth) acrylate (Polye ethylene glycol (methyl ether) (meth) acrylate) (trade name: FA-401, manufacturer: Han Thickening agent) 5.5 g, polyethylene glycol diacrylate (MW = 330 manufacturer: 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 (average particle size (E> ⁵ 0 ) 12 pm) Add 041 g of monomer The composition was prepared.

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

Thereafter, the mixture was introduced through a feeder of the polymerization reactor 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 was cut into sheet form (thickness: around 2_) using a cutting machine. Example 2

In Example 1, a superabsorbent polymer sheet was manufactured in the same manner as in Example 1, except that 0.75 wt% of the encapsulating foaming agent and the calcium carbonate foaming agent were used, respectively, relative to 100 wt% of acrylic acid. Example 3

In Example 1, a superabsorbent polymer sheet was prepared in the same manner as in Example 1, except that 1.5 wt% and 0.75 wt% of the encapsulating and calcium carbonate blowing agents were used, respectively, relative to 100 wt% of acrylic acid. Example 4

In the first embodiment, acrylic acid 100 The foaming agent, and sodium carbonate word ¾ encapsulated percent by weight (0 ₃₎ a blowing agent (average particle diameter: 50) 12, the same procedure as in Example 1 except for using 0.75 wt.%), Respectively A superabsorbent polymer sheet was prepared. Comparative Example 1

In Example 1, a superabsorbent polymer sheet was prepared in the same manner as in Example 1 except that no calcium carbonate blowing agent was used. Comparative Example 2 2019/216591 1 »（： 1 ^ 1 {2019/005222

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. Comparative Example 3

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 manufactured in the same manner as in Example 1, except that 4.5 wt% of encapsulated blowing agent and 1.5 wt% of calcium carbonate blowing agent were used relative to 100 wt% of acrylic acid. Comparative Example 5

In Example 1, a superabsorbent polymer sheet was prepared in the same manner as in Example 1, except that 1.5 wt% of encapsulated blowing agent and 3.0 wt% of calcium carbonate blowing agent were used relative to 100 wt% of acrylic acid.

Characterization of High Top Water 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 FIG. 1, it can be seen that an open pore channel structure is formed on the surface of the superabsorbent polymer sheet according to Example 1 of the present invention.

(2) Measurement of centrifugal water holding capacity (1 (：) and pressure absorption capacity ^ 111 ^» )

About the superabsorbent polymer sheet of each Example and a comparative example,

According to the method of 241.2, centrifugal water holding capacity (幻 1 (：)) was measured, and the EDANA method \ ¥? 2019/216591 1 »（： 1 ^ 1 {2019/005222

The absorbency under pressure (show 111 ^> ) under 0.7 was measured according to the method of 242.2, and the results are shown in Table 1 below.

Table 1

1) Weight% of blowing agent to 100% by weight of acrylic acid Referring to Table 1, in the case of a super absorbent polymer sheet manufactured by using the encapsulated blowing agent and the inorganic blowing agent in a 3: 1 to 1: 1 weight ratio, each blowing agent was It can be seen that it exhibits excellent centrifugal water-retaining capacity and pressure-absorbing capacity as compared with the superabsorbent polymer sheet which is used alone or without a blowing agent. On the other hand, the weight ratio of the encapsulated blowing agent and the inorganic blowing agent is 3: 1 and Comparative Example 5 in which the weight ratio of less than 1: 1, both the centrifugal water retention capacity and the pressure absorption capacity was significantly lower than the Example. 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]

Comonomer containing an acidic group, at least a portion of which is neutralized, an acrylic acid monomer, a polyethylene glycol (methyl ether) (meth) acrylate (polyethylene glycol (methyl ether) (meth) acrylate), an internal crosslinking agent, encapsulated Preparing a monomer composition by mixing a blowing agent, an inorganic blowing agent having an average particle diameter of 1 to 100, and a polymerization initiator;

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

The encapsulated blowing agent and the inorganic blowing agent is included in a weight ratio of 3: 1 to 1: 1, the manufacturing method of the 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 a method for producing a super absorbent polymer sheet is contained in 5 to 40 parts by weight based on 100 parts by weight of the acrylic acid monomer.

[Claim 3]

The method of claim 1,

The encapsulated foaming agent has an average particle diameter of 2 to 50, method of producing a super absorbent polymer sheet.

[Claim 4]

The method of claim 1,

The encapsulated blowing agent has a expansion ratio of 3 to 15 times in air, a method for producing a super absorbent polymer sheet. 2019/216591 1 »（： 1 ^ 1 {2019/005222

[Claim 5]

The method of claim 1,

The encapsulated 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,

At least one member selected from the group consisting of cyclobutane, 11-pentane, -pentane, cyclopentane, 11nucleic acid, 0-nucleic acid, cyclonucleic acid, 11heptane, 0-heptane, cycloheptane, 11 octane, 0-octane and cyclooctane , Method for producing superabsorbent polymer sheet.

[Claim 7]

The method of claim 5,

The thermoplastic resin is a polymer formed of at least one monomer selected from the group consisting of (meth) acrylate, (meth) acrylonitrile, aromatic vinyl, vinyl acetate, vinyl halide and vinylidene halide, to prepare a superabsorbent polymer sheet. Way.

[Claim 8]

The method of claim 1,

The inorganic blowing agent is calcium carbonate 0 ₃ ), sodium bicarbonate _¾ 1 犯 0 ₃ ), ammonium bicarbonate ¾11 (： 0 ₃ ), ammonium carbonate (a¾) ₂ (： 0 ₃ ), ammonium nitrite ¾ ₃ 0 ₂ ）, Sodium hydrogen borohydride _& 8¾) and sodium carbonate fish ¾ (： 0 ₃ ) is a method of producing a super absorbent polymer sheet.

[Claim 9]

The method of claim 1,

The average particle diameter of the inorganic blowing agent is 5 to 20 i, of the super absorbent polymer sheet 2019/216591 1 »（： 1 ^ 1 {2019/005222

Manufacturing method.

[Claim 10]

The method of claim 1,

The encapsulated blowing agent and the inorganic blowing agent is contained in a weight ratio of 2: 1 to 1: 1, the method of producing a super absorbent water-based water sheet.

[Claim 11]

The method of claim 1,

The encapsulated foaming agent is included in an amount of 0.3 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, 0.4 to 20 parts by weight with respect to 100 parts by weight of the acrylic acid monomer, a method for producing a super absorbent polymer sheet.