KR20230147430A - Super absorbent polymer film and preparation method thereof - Google Patents

Abstract

The present invention relates to a superabsorbent polymer film and a manufacturing method thereof. Specifically, the present invention relates to the method for manufacturing the superabsorbent polymer film that is thin but exhibits excellent water absorption performance, contains few water-soluble components, and has improved absorbency under pressure.

Description

Superabsorbent polymer film and manufacturing method thereof {SUPER ABSORBENT POLYMER FILM AND PREPARATION METHOD THEREOF}

The present invention relates to a superabsorbent polymer film and a method of manufacturing the same.

Super Absorbent Polymer (SAP) is a synthetic polymer material that has the ability to absorb moisture 500 to 1,000 times its own weight. Each developer produces SAM (Super Absorbency Material) and AGM (Absorbent Gel). They are named with different names, such as Material). The above-mentioned superabsorbent resins have begun to be commercialized as sanitary products, and currently, in addition to sanitary products such as children's paper diapers and sanitary pads, they are used as soil reservatives for horticulture, water-blocking materials for civil engineering and construction, sheets for seedlings, and freshness maintainers in the food distribution field. It is widely used as a material for poultices, etc.

In general, sanitary products such as various diapers, sanitary napkins, or incontinence pads include absorbents containing superabsorbent resin particles. These absorbents mainly contain superabsorbent resin particles, and properly fix the superabsorbent resin particles while properly fixing the absorbents and sanitary products. It was common to use fluff pulp to maintain its shape.

However, due to the presence of such fluff pulp, it was difficult to slim and thin the absorber and sanitary product, and there was a problem of poor wearing comfort, such as sweat accumulating between the user's skin and the sanitary product. Moreover, since fluff pulp is mainly obtained from wood, it runs counter to the recent environmental protection trend, and the use of fluff pulp is also one of the main reasons for increasing the manufacturing cost of sanitary products.

In addition, most of the current superabsorbent resins are manufactured and used in powder form. These powdered superabsorbent resins have parts that can scatter or leak when manufacturing sanitary materials or during actual use, and are used as substrates of certain types. Because it must be used together with a substrate, there are limits to its range of use and thinning. In addition, because the absorption performance of the absorbent may vary depending on the content distribution of the superabsorbent polymer particles, it was difficult to uniformly control the absorption characteristics.

Accordingly, in order to solve the above problem, Korean Patent Publication No. 2021-0118762 proposed a film-type superabsorbent polymer. Superabsorbent resin film is a superabsorbent resin in the form of an ultra-thin transparent or translucent film with a thickness of about 0.5 mm or less. It has excellent absorption properties, high elasticity and flexibility, and can be used as an absorber by itself without auxiliaries such as fluff pulp. There are advantages to this. However, due to the morphological characteristics of the superabsorbent polymer film, if uniform curing does not occur during the process of curing the monomer composition into a film, the content of water-soluble components (EC) may increase, and due to the nature of the flexible and continuous phase, the absorbency under pressure may be reduced. It is inferior to existing powdery superabsorbent polymers and has the problem of low initial absorption rate.

Korean Public Patent No. 2021-0118762

In order to solve the above problems, the present invention provides a superabsorbent polymer film with fewer water-soluble components, excellent gel strength and absorbency under pressure, and improved absorption rate, and a method for manufacturing the same.

According to one embodiment of the present invention,

An acrylic acid-based monomer having an acidic group and at least a portion of the acidic group neutralized; crosslinking agent; Cellulose-based thickener; moisturizer; blowing agent; succinic acid salts and/or succinic acid esters; polymerization initiator; and mixing solvents to prepare a monomer composition,

Casting the monomer composition onto a substrate to form a monomer composition film,

Forming a water-containing gel polymer film by irradiating heat and/or light while stretching the monomer composition film, and

A method for producing a superabsorbent polymer film is provided, including the step of drying the water-containing gel polymer film.

According to another embodiment of the present invention, an acrylic acid-based monomer having an acidic group and at least a portion of the acidic group is neutralized, an internal crosslinking agent, a cellulose-based thickener, a humectant, a foaming agent, a succinic acid salt and/or a succinic acid ester, and an initiator. Provided is a porous superabsorbent resin film containing a polymer polymerized in the presence of a water-soluble component of 10% by weight or less as measured according to the method of EDANA WSP 270.2.

According to the present invention, it is possible to manufacture a high-absorbent resin film that is thin but exhibits excellent absorption performance, especially improved absorbency under pressure and absorption speed, and has low water-soluble components.

The superabsorbent polymer film manufactured according to the present invention has no risk of scattering or leaking from the product during manufacturing, and does not require auxiliary agents such as fluff pulp, allowing the product to be thinner and reducing the manufacturing process and cost.

The terminology used herein is for the purpose of describing exemplary embodiments only and is not intended to limit the invention. Singular expressions include plural expressions unless the context clearly dictates otherwise. In this specification, terms such as “comprise,” “comprise,” or “have” are intended to designate the presence of implemented features, steps, components, or a combination thereof, and are intended to indicate the presence of one or more other features or steps, It should be understood that the existence or addition possibility of components or combinations thereof is not excluded in advance.

Since the present invention can be subject to various changes and can take various forms, 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, and should be understood to include all changes, equivalents, and substitutes included in the spirit and technical scope of the present invention.

Hereinafter, the present invention will be described in detail.

According to one embodiment of the present invention,

An acrylic acid-based monomer having an acidic group and at least a portion of the acidic group neutralized; crosslinking agent; Cellulose-based thickener; moisturizer; blowing agent; succinic acid salts and/or succinic acid esters; polymerization initiator; and mixing solvents to prepare a monomer composition,

Casting the monomer composition onto a substrate to form a monomer composition film,

Forming a water-containing gel polymer film by irradiating heat and/or light while stretching the monomer composition film, and

A method for producing a superabsorbent polymer film is provided, including the step of drying the water-containing gel polymer film.

The superabsorbent polymer film manufactured according to the present invention has the form of a thin film rather than a powder, so there is no risk of scattering or leaking from the product when handled, and it can be used without additional auxiliaries such as fluff pulp, and has excellent absorption properties on its own. indicates. In particular, the superabsorbent polymer film manufactured according to the present invention contains fewer water-soluble components compared to existing superabsorbent polymer films, and exhibits excellent physical properties with improved gel strength, absorbency under pressure, and absorption speed.

In the present invention, the superabsorbent polymer film refers to a superabsorbent polymer that has a moisture content of 15% by weight or less, or 14% by weight or less, preferably 13% by weight or less, and takes the form of a flexible, thin layer or film. Preferably, the water content of the superabsorbent polymer film is 15% by weight or less, or 14% by weight or less, or 13% by weight or less, or 12% by weight or less, and 1% by weight or more, or 2% by weight or more, or 4% by weight. % or more, or may be 6 weight % or more.

Meanwhile, throughout this specification, “moisture content” is expressed as a percentage of the amount of moisture contained in the sample relative to the weight of the sample before drying. In other words, the water content can be calculated by subtracting the weight after drying the sample from the weight before drying the sample, dividing it by the weight before drying the sample, and then multiplying by 100. At this time, the drying conditions are to increase the temperature from room temperature to about 150 ℃ and then maintain it at 150 ℃, and the total drying time is set to 20 minutes, including 5 minutes for the temperature increase step.

The superabsorbent polymer film manufactured according to one embodiment of the present invention may have a moisture content of 15% or less, be elastic, and be in the form of a film with excellent flexibility.

In addition, the superabsorbent polymer film of the present invention may have a yellow index of 2.6 or less, 2.5 or less, 2.4 or less, 2.3 or less, 1.9 or less, 1.6 or less, or 1.5 or less according to the ASTM D1925 standard in the thickness range of 0.001 to 0.5 mm. there is.

In the production method of the present invention, the monomer composition, which is the raw material of the superabsorbent polymer film, includes an acrylic acid-based monomer having an acidic group and at least a portion of the acidic group neutralized; Cellulose-based thickener; moisturizer; succinic acid salts and/or succinic acid esters; polymerization initiator; and solvents.

The acrylic acid-based monomer is a compound represented by the following formula (1):

[Formula 1]

R ¹ -COOM ¹

In Formula 1,

R ¹ is an alkyl group having 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-based monomer includes at least one selected from the group consisting of acrylic acid, methacrylic acid, and monovalent metal salts, divalent metal salts, ammonium salts, and organic amine salts thereof.

Here, the acrylic acid-based monomer may have an acidic group and at least a portion of the acidic group may be neutralized. Preferably, the monomer partially neutralized with an alkaline substance such as sodium hydroxide, potassium hydroxide, ammonium hydroxide, etc. may be used. At this time, the degree of neutralization of the acrylic acid-based monomer may be 40 to 95 mol%, or 40 to 80 mol%, or 45 to 75 mol%. The range of the degree of neutralization can be adjusted depending on the final physical properties. If the degree of neutralization is too high, neutralized monomers may precipitate, making it difficult for polymerization to proceed smoothly. Conversely, if the degree of neutralization is too low, the absorption capacity of the polymer may be greatly reduced.

In a preferred embodiment, the alkaline material may be sodium hydroxide (NaOH), potassium hydroxide (KOH), or a combination thereof. In particular, when potassium hydroxide is included as an alkaline material, a superabsorbent polymer film with better flexibility and dimensional stability can be manufactured.

The concentration of the acrylic acid-based monomer 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 of the superabsorbent polymer and the solvent, and polymerization time and The concentration can be adjusted to an appropriate level considering reaction conditions, etc. However, if the concentration of the monomer is too low, the yield of the superabsorbent polymer may be low and problems may arise in economic feasibility. Conversely, if the concentration is too high, problems may occur in the process such as part of the monomer being precipitated, and the physical properties of the superabsorbent polymer may occur. This may deteriorate.

Meanwhile, in the present invention, a thickener and a moisturizer are included in the monomer composition so that the monomer composition can be applied in film form through a solution casting method.

By simultaneously containing a thickener and a humectant, the monomer composition of the present invention exhibits a viscosity suitable for casting into a film, can maintain an appropriate moisture content during the polymerization process after film casting, and the produced superabsorbent resin film has high flexibility. can indicate.

In the present invention, a cellulose-based thickener is used as a thickener, and specifically, it is selected from the group consisting of nanocellulose, hydroxyethylcellulose, hydroxypropylcellulose, hydroxyethylmethylcellulose, hydroxypropylmethylcellulose, and sodium carboxymethylcellulose. One or more types may be used. Preferably, nanocellulose, hydroxyethylcellulose, sodium carboxymethylcellulose, or a combination thereof may be used.

The cellulose-based thickener is present in an amount of 0.01 parts by weight or more, 0.1 parts by weight, 0.2 parts by weight, or 0.4 parts by weight or less, and 5 parts by weight or less, 3 parts by weight or less, and 1 part by weight or less, based on 100 parts by weight of solid content in the monomer composition. , or may be included in an amount of 0.9 parts by weight or less.

At this time, solid content in the monomer composition refers to all components of the composition excluding the solvent. That is, the solid content is a total of acrylic acid-based monomer, an alkali substance for neutralizing acrylic acid-based monomer, cellulose-based thickener, moisturizer, cross-linking agent, thermal initiator, photoinitiator, foaming agent, succinic acid salt and/or succinic acid ester, and other additives. It means content.

If the content of the cellulose-based thickener is less than 0.01 parts by weight based on 100 parts by weight of solid content in the monomer composition, sufficient thickening effect cannot be secured, making it difficult to manufacture a monomer composition film. Conversely, if it exceeds 5 parts by weight, the viscosity of the monomer composition may be excessive. The higher the film thickness, the thicker it becomes, and it may be difficult to control the film thickness uniformly.

The moisturizer may be any substance commonly used as a moisturizing ingredient in pharmaceuticals, cosmetics, chemical products, etc., without limitation. Examples of such humectants include at least one selected from the group consisting of polyhydric alcohols containing two or more hydroxy groups in the molecule, citric acid, and citrate salts.

Specifically, the polyhydric alcohol may be a polyhydric alcohol having 3 to 30 carbon atoms and containing 3 to 12 hydroxy groups in the molecule. In one example, the polyhydric alcohol is glycerin; diglycerin; ethylene glycol; propylene glycol; butylene glycol; sorbitol; polyethylene glycol; polyglycerin-3; polyglycerin-6; polyglycerin-10; and a group consisting of ester compounds of polyglycerin-10 and saturated fatty acids having 3 to 18 carbon atoms (e.g., polyglyceryl-10 distearate, polyglyceryl-10 oleate, polyglyceryl-10 laurate, etc.) There may be one or more types selected from the group consisting of glycerin, diglycerin, propylene glycol, and sorbitol, and one or more types selected from the group may be preferably used.

Additionally, citric acid and/or citric acid salts can be used as moisturizers. Examples of citric acid salts include triethyl citrate, methyl citrate, sodium citrate, and trisodium 2-methyl citrate.

The moisturizer is used in an amount of 5 parts by weight or more, 10 parts by weight, 20 parts by weight, or 30 parts by weight, and 70 parts by weight or less, 60 parts by weight, or 50 parts by weight or less, based on 100 parts by weight of acrylic acid-based monomer. It is desirable to be

If the content of the humectant is less than 5 parts by weight based on 100 parts by weight of acrylic acid-based monomer, the moisture content of the monomer composition film is insufficient, and the film may dry out or break during the subsequent polymerization and drying process, and the flexibility of the produced superabsorbent resin film may decrease. There is a problem that cannot be secured. Conversely, if the content of polyhydric alcohol exceeds 70 parts by weight based on 100 parts by weight of acrylic acid-based monomer, there may be a problem of lowering the absorption capacity of the superabsorbent polymer film. Therefore, it is desirable that the content of the humectant satisfies the above range.

The monomer composition includes a crosslinking agent for crosslinking the polymer. The crosslinking agent may be one used in the production of conventional superabsorbent polymers. More specifically, the crosslinking agent includes a crosslinking agent having at least one functional group capable of reacting with the water-soluble substituent of the acrylic acid-based monomer and at least one ethylenically unsaturated group; Alternatively, a crosslinking agent having two or more functional groups that can react with the water-soluble substituent of the monomer and/or the water-soluble substituent formed by hydrolysis of the monomer may be used.

Specific examples of the cross-linking agent include bisacrylamide, bismethacrylamide, poly(meth)acrylate of polyol with 2 to 10 carbon atoms, or poly(meth)allyl ether of polyol with 2 to 10 carbon atoms, etc. Can be mentioned, more specifically, N, N'-methylenebis(meth)acrylate, ethyleneoxy(meth)acrylate, polyethyleneoxy(meth)acrylate, propyleneoxy(meth)acrylate, glycerin diacrylate. , glycerin triacrylate, trimethylene triacrylate, polyethylene glycol diacrylate, triallylamine, triallyl cyanurate, triallyl isocyanate, polyethylene glycol, diethylene glycol, and propylene glycol. You can use it. In one embodiment, polyethylene glycol diacrylate may be used as the crosslinking agent.

The cross-linking agent may be included in a concentration of 3000 ppm or less relative to the monomer composition to cross-link the polymerized polymer. In one embodiment, the cross-linking agent may be included in an amount of 10 ppm or more, 50 ppm or more, or 100 ppm or more, and 3000 ppm or less, 2500 ppm or less, or 2000 ppm or less.

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

Specifically, the polymerization initiator may be a thermal polymerization initiator or a photopolymerization initiator based on UV irradiation depending on the polymerization method. However, even with the photopolymerization method, a certain amount of heat is generated by irradiation such as ultraviolet ray irradiation, and a certain amount of heat is also generated as the polymerization reaction, which is an exothermic reaction, progresses, so a thermal polymerization initiator may be additionally included. According to a preferred embodiment, a photopolymerization initiator and a thermal polymerization initiator may be used simultaneously as the polymerization initiator.

The photopolymerization initiator can be used without limitation in composition as long as it is a compound that can form 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, and alpha-aminoketone (α-aminoketone) can be used. Meanwhile, specific examples of acylphosphine include commercially available lucirin TPO (2,4,6-Trimethylbenzoyldiphenylphosphine oxide) and Irgacure 819 (Phenylbis(2,4,6-trimethylbenzoyl)phosphine oxide). For more information on photoinitiators, see Reinhold Schwalm's book "UV Coatings: Basics, Recent Developments and New Applications (Elsevier 2007)" p. 115, and is not limited to the examples described above.

The photopolymerization initiator may be included in an amount of 10 ppm or more, 20 ppm or more, or 40 ppm or more, and 2000 ppm or less, 1000 ppm or less, 500 ppm or less, or 100 ppm or less with respect to the monomer composition. If the concentration of the photopolymerization initiator is too low, the polymerization rate may be slow, and if the concentration of the photopolymerization initiator is too high, the molecular weight of the superabsorbent polymer may be small and the physical properties may become non-uniform.

Additionally, the thermal polymerization initiator may be one or more selected from the group of initiators consisting of persulfate-based initiator, azo-based 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 O ₈ ), etc., and examples of azo-based initiators include 2,2-azobis(2-amidinopropane) dihydrochloride, 2 ,2-azobis-(N,N-dimethylene)isobutyramidine dihydrochloride (2,2-azobis-(N,N-dimethylene)isobutyramidine dihydrochloride), 2-(carbamoylazo)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-azobis-(4-cyanovaleric acid), etc. For more information on various thermal polymerization initiators, see Odian's book 'Principle of Polymerization (Wiley, 1981)', p. 203, and is not limited to the examples described above.

The thermal polymerization initiator may be included in the monomer composition in an amount of 10 ppm or more, 100 ppm or more, or 500 ppm or more, and 2000 ppm or less, 1500 ppm or less, or 1000 ppm or less. If the concentration of the thermal polymerization initiator is too low, no additional thermal polymerization occurs, so the effect of adding the thermal polymerization initiator may be minimal. 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 become non-uniform. there is.

The foaming agent is a material that can foam upon polymerization and/or drying, for example, thermally expandable microspheres, expanded microspheres, azo compounds, and inorganic substances. One or more types selected from the group consisting of foaming agents may be used. These foaming agents form a large number of pores in the superabsorbent polymer film, and thus the initial absorption capacity of the superabsorbent polymer film can be greatly improved.

In particular, according to the manufacturing method of the present invention, the absorption rate of the produced superabsorbent polymer film can be maximized by including succinic acid salt and/or succinic acid ester as an additive along with the foaming agent, and the absorbency characteristics under pressure are also improved. Excellent physical properties can be achieved.

The thermally expandable microspheres may have a structure including a core containing hydrocarbon and a thermoplastic resin shell surrounding the core.

Hydrocarbons constituting the core of the thermally expandable microsphere include n-propane, n-butane, iso-butane, cyclobutane, n-pentane, iso-pentane, cyclopentane, n-hexane, iso-hexane, cyclohexane, n -It may be one or more selected from the group consisting of heptane, iso-heptane, cycloheptane, n-octane, iso-octane, and cyclooctane. Among these, hydrocarbons having 3 to 5 carbon atoms (n-propane, n-butane, iso-butane, cyclobutane, n-pentane, iso-pentane, cyclopentane) may be suitable.

In addition, the thermoplastic resin constituting the shell of the heat-expandable microsphere is selected from one or more monomers selected from the group consisting of (meth)acrylate, (meth)acrylonitrile, aromatic vinyl, vinyl acetate, vinyl halide, and vinylidene halide. It may be a polymer that is formed. Among these, a copolymer of (meth)acrylate and (meth)acrylonitrile, or a (meth)acrylate homopolymer is most suitable for realizing the initial absorption capacity in the above-mentioned range.

The thermally expandable microspheres are a type of foaming agent that expands by heat supply, and expand under high temperature conditions during the polymerization and/or drying stage of monomers and may form pores in the superabsorbent polymer film. These thermally expandable microspheres have different expansion characteristics depending on the components that make up the core and shell, the weight of each component, and the average particle diameter, and by adjusting these, they can be expanded to a desired size, thereby controlling the pore structure of the superabsorbent polymer film.

The thermally expandable microspheres may have an average particle diameter (D50) before expansion of 2 μm or more, 5 μm or more, 7 μm or more, or 10 μm or more, and may be 50 μm or less, 40 μm or less, or 35 μm or less. When the thermally expandable microspheres exhibit the above average particle diameter, they can be judged to be suitable for achieving appropriate porosity.

At this time, the average particle diameter (D50) of the thermally expandable microspheres is determined by dispersing the powder to be measured in a dispersion medium and then introducing it into a commercially available laser diffraction particle size measurement device (for example, Mastersizer 3000) when the particles pass through the laser beam. It can be measured by measuring the difference in diffraction patterns according to particle size and calculating the particle size distribution.

Whether the heat-expandable microspheres can form pores of an appropriate size in the superabsorbent polymer film can be confirmed by foaming the capsules in air and checking the expansion rate and size.

The pore size of the superabsorbent polymer film manufactured according to the present invention is preferably about 10 to 500 μm. Accordingly, it is necessary to determine the expansion characteristics of thermally expandable microspheres in order to form pores of appropriate size in the superabsorbent polymer film.

Specifically, thermally expandable microspheres are applied on a glass Petri dish and then heat is applied in the air for 10 minutes to expand the thermally expandable microspheres. At this time, if the thermally expandable microspheres exhibit a maximum expansion ratio in air of 3 to 15 times, 2 to 12 times, or 1 to 7 times, it is suitable for producing a superabsorbent polymer film with pores of an appropriate size.

Additionally, pores of an appropriate size can be formed when thermally expandable microspheres exhibit a maximum expansion size in air of 150 μm or less. Specifically, if the thermally expandable microspheres exhibit a maximum expansion size in air of 10 to 500 μm, 50 to 300 μm, 70 to 150 μm, or 75 to 150 μm, a superabsorbent resin film with pores of an appropriate size can be prepared. suitable for

The thermally expandable microspheres may have a starting temperature of 60 to 200°C, 70 to 170°C, or 80 to 165°C, and a maximum expansion temperature of 100 to 240°C, 120 to 200°C. , or 130 to 190 ° C.

Examples of such thermally expandable microspheres include the Expancel DU series from Nouryon, including Expancel 461 DU 40, Expancel 461 DU 20, Expancel 031 DU 40, Expancel 053 DU 40, Expancel 551 DU 40; and/or Matsunomo's Microsphere F series, including Microsphere F-AC170D, Microsphere F-36, Microsphere F-36LV, Microsphere F-48, Microsphere F-80GS, and Microsphere F-50. Preferably, Expancel 031 DU 40 containing a hydrocarbon core and a shell of acrylate and acrylonitrile copolymer and/or Microsphere F-AC170D containing a hydrocarbon core and a shell of acrylate copolymer may be used, but are limited thereto. It doesn't work.

The expanded microspheres are a foaming agent that is already expanded before use, and may be coated with an inorganic material such as talc and/or calcium carbonate on the surface of thermoplastic resin hollow particles.

The thermoplastic resin may be a polymer formed from one or more monomers selected from the group consisting of (meth)acrylate, (meth)acrylonitrile, aromatic vinyl, vinyl acetate, vinyl halide, and vinylidene halide.

Preferably, the expanded microspheres may be (meth)acrylate and/or (meth)acrylonitrile copolymer hollow particles coated with calcium carbonate on the surface.

The thermoplastic hollow particles of expanded microspheres no longer expand and contract when heated, but the inorganic material on the surface exhibits foaming properties. Accordingly, pores of a size similar to the particle size of the expanded microspheres can be formed, and the pore size formed in the superabsorbent polymer film can be controlled by appropriately selecting the particle size of the expanded microspheres.

Accordingly, the average particle diameter (D50) of the expanded microspheres is 10 μm or more, 20 μm or more, or 30 μm or more, and is in the range of 150 μm or less, 130 μm or less, or 120 μm or less, as described above. It is suitable for producing a superabsorbent polymer film with pores. At this time, the average particle diameter can be measured using the particle size measurement method of the thermally expandable microspheres.

Meanwhile, the foaming temperature of the expanded microspheres may be 130°C or higher, 140°C or higher, or 150°C or higher, and may be 200°C or lower and 180°C or higher.

Examples of the expanded capsules include Matsunomo's Microsphere MFL series, MFL-110CAL, MFL-100MCA, MFA HD60CA, MFL HD30CA, MFL-SEVEN, etc., preferably hollow ones made of acrylate and acrylonitrile copolymers. MFL-110CAL, which has calcium carbonate powder coated on the particle surface, may be used, but is not limited thereto.

The azo-based compounds include 2,2'-azobis(2-methylpropionamidine)dihydrochloride and 2,2-azobis[N-(2-carboxyethyl)-2-methylpropionamidine]tetrahydrate. Azoamidine-based compounds such as can be used, and preferably, 2,2'-azobis(2-methylpropionamidine)dihydrochloride can be used.

The inorganic foaming agent includes calcium carbonate (CaCO ₃ ), sodium bicarbonate (NaHCO ₃ ), ammonium bicarbonate (NH ₄ HCO ₃ ), ammonium carbonate ((NH ₄ ) ₂ CO ₃ ), ammonium nitrite (NH ₄ NO ₂ ), and boron. At least one selected from sodium hydrogen fluoride (NaBH ₄ ) and sodium carbonate (Na ₂ CO ₃ ) may be used, and preferably, calcium carbonate may be used.

The inorganic foaming agent can be any micro- or nano-sized particle with a particle diameter ranging from 1 nm to 100 μm, and an appropriate type can be selected depending on the physical properties of the desired superabsorbent polymer sheet. At this time, the particle size of the inorganic foaming agent may be measured by the laser diffraction method described above, or may be measured through a scanning electron microscope (SEM).

In the present invention, the thermally expandable microspheres, expanded microspheres, azo compounds, and inorganic foaming agents may each be used as foaming agents, or one or more foaming agents may be used in combination. For example, one or more types of heat-expandable microspheres and expanded microspheres may be used as a first foaming agent, and one or more types of an azo-based compound and an inorganic foaming agent may be used as a second foaming agent.

On the other hand, when one or more types of heat-expandable microspheres and expanded microspheres are used as a first foaming agent, and one or more types of an azo compound and an inorganic foaming agent are mixed and used as a second foaming agent, the first foaming agent and the second foaming agent The weight ratio may range from 1:0.3 to 1:3, or may range from 1:0.5 to 1:2. When this weight ratio is satisfied, an improved initial absorption rate can be achieved as described above.

Meanwhile, the foaming agent is included in an amount of 0.1 to 10 parts by weight, more preferably 0.5 to 7 parts by weight, or 1 to 5 parts by weight, based on 100 parts by weight of acrylic acid-based monomer.

If the content of the foaming agent is less than 0.1 parts by weight based on 100 parts by weight of acrylic acid-based monomer, the porous structure of the superabsorbent polymer film due to foaming cannot be secured, and thus the effect of improving the initial absorption rate cannot be obtained.

Additionally, if the content of the foaming agent exceeds 10 parts by weight based on 100 parts by weight of the acrylic acid-based monomer, there may be a problem in that the degree of crosslinking of the polymer is lowered due to the foaming agent during polymerization. Since heat-expandable microspheres and expanded microsphere foaming agents have low solubility in solvents (e.g., water) and low density, if their content exceeds 10 parts by weight based on 100 parts by weight of acrylic acid-based monomer, they are removed from the monomer composition. Precipitation of the foaming agent may occur, which may result in poor foaming.

Most of the above foaming agents actively foam at temperatures above 80°C or above 100°C. Accordingly, foaming of the foaming agent may occur mainly during the drying step of the water-containing gel polymer film.

Meanwhile, in one embodiment of the present invention, the monomer composition includes succinic acid salt and/or succinic acid ester as an additive. For example, the succinic acid salt and/or succinic acid ester include mono-2-(Acryloyloxy)ethyl succinate, Sodium succinate dibasic, or Succinic acid. At least one selected from the group consisting of acid disodium salt, diethyl succinate and dimethyl succinate may be used, preferably mono-2- ( Acryloyloxy)ethyl succinate can be used alone. Mono-2-(acryloyloxy)ethyl succinate contains double bonds and can further improve the degree of crosslinking of the polymer.

[Formula 1]

The succinic acid salt and/or succinic acid ester serves to further improve the degree of crosslinking of the polymer in the polymerization step. In particular, when succinic acid salts and/or succinic acid esters are added to the production of porous superabsorbent resin films using foaming agents, the gel strength is improved due to an increase in the degree of cross-linking, and thus the absorbency under pressure is improved, and the absorption rate can also be further improved. . Therefore, a superabsorbent polymer film prepared from a monomer composition containing succinic acid salt and/or succinic acid ester together with a foaming agent can exhibit a significantly improved absorption rate compared to a superabsorbent polymer film produced using only a foaming agent.

In addition, the superabsorbent polymer film has a high degree of cross-linking, has fewer water-soluble components, and exhibits improved absorbency under pressure, so it can realize better physical properties compared to existing superabsorbent polymer films.

The succinic acid salt and/or succinic acid ester is contained in an amount of more than 1 part by weight, 2 parts by weight or more, or 3 parts by weight, but less than 15 parts by weight, 13 parts by weight or less, or 10 parts by weight, based on 100 parts by weight of acrylic acid monomer. It can be used in the following amounts.

If the content of succinic acid salt and/or succinic acid ester is less than 1 part by weight based on 100 parts by weight of acrylic acid monomer, the effect of reducing water-soluble components and improving absorption rate, absorbency under pressure, and gel strength cannot be obtained. In addition, when succinic acid salt and/or succinic acid ester are used in an amount of 15 parts by weight or more per 100 parts by weight of acrylic acid monomer, the centrifugal water retention capacity may be greatly reduced, and the water-soluble component reduction effect, pressure absorption capacity, and gel strength may be reduced. Since the improving effect does not increase further and may rather decrease as the amount of succinic acid salt and/or succinic acid ester used increases, it is preferable to satisfy the above range.

In the production method of the present invention, the monomer composition may further include additives such as surfactants, plasticizers, storage stabilizers, and antioxidants, if necessary.

The surfactant may be added to further facilitate casting of the monomer composition. A polyether-modified siloxane-based surfactant can be used as the surfactant. When it is included, the monomer composition can be cast with a more uniform thickness, and even when applied to a continuous process such as a roll-to-roll process, it can be used at high speed without a separate process. A high-absorbent polymer film of uniform quality can be manufactured.

The polyether-modified siloxane-based surfactant is a surfactant containing a polyether chain at the end and/or side chain of the polysiloxane main chain. For example, the polyether-modified siloxane-based surfactant may include a polyethylene oxide group and/or a polypropylene oxide group.

These polyether-modified siloxane-based surfactants can be commercially available, for example, BYK-345, BYK-346, BYK-347, BYK-348, BYK-349, BYK-3450, BYK-3455, BYK- One or more types selected from the group consisting of 3456, BYK-3560, BYK-3565, and BYK-3760 can be used.

The content of the polyether-modified siloxane-based surfactant is 0.05 to 0.5 parts by weight based on 100 parts by weight of the monomer composition, or 0.1 part by weight or more, 0.15 parts by weight or more, or 0.2 parts by weight or more, and 0.45 parts by weight or less, 0.4 parts by weight or more. It may be more preferable that it is less than or equal to 0.35 parts by weight.

If the content of the polyether-modified siloxane-based surfactant is less than 0.05 parts by weight based on 100 parts by weight of the monomer composition, the effect of improving the coating properties of the monomer composition described above cannot be secured, and if it exceeds 0.5 parts by weight, the basic effect of the superabsorbent resin film produced Absorption capacity (initial absorption capacity, normal pressure absorption capacity, etc.) physical properties may be impaired. Accordingly, it is preferable that the polyether-modified siloxane-based surfactant is included in the above-mentioned range so as to exhibit excellent coating properties suitable for application to the roll-to-roll process, etc., while not damaging the physical properties of the final manufactured superabsorbent resin film.

The raw materials such as the above-described acrylic acid monomer, cellulose thickener, moisturizer, crosslinking agent, polymerization initiator, foaming agent, succinic acid salt and/or succinic acid ester, and optionally included additives are in the form of a monomer composition solution dissolved in a solvent. Ready.

The solvent that can be used can be used without limitation as long as it can dissolve the above-mentioned 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, cyclohexanone, cyclopentanone, diethylene glycol monomethyl ether, diethylene glycol ethyl ether. , toluene, xylene, butyrolactone, carbitol, methyl cellosolve acetate, and N,N-dimethylacetamide can be used in combination. For example, water can be used as the solvent.

In the present invention, the monomer composition includes a cellulose-based thickener and a humectant and exhibits a viscosity suitable for solution casting. Specifically, the viscosity of the monomer composition at 25°C is 100 mPa·s or more, 150 mPa·s or more, 200 mPa·s or more, or 300 mPa·s or more, and is 12,000 mPa·s or less, 5,000 mPa·s or less, It may be 3,000 mPa·s or less, 2,000 mPa·s or less, or 1,600 mPa·s or less. The viscosity of the monomer composition can be measured with a viscometer (for example, TV-22 from TOKI) under the conditions of spindle #1 and rotation speed of 1 rpm.

If the viscosity of the monomer composition is less than 100 mPa·s, it may be difficult to cast the monomer composition to a uniform thickness and polymerize it while stretching it. Conversely, if the viscosity of the monomer composition exceeds 12,000 mPa·s, it is difficult to manufacture a uniform monomer composition, the flowability of the monomer composition is low, resulting in poor processability, and it is difficult to defoame, which is not preferable.

After preparing the monomer composition, it is cast on a substrate to prepare a monomer composition film, which is stretched and polymerized to form a water-containing gel polymer film. The casting and polymerization process of this monomer composition can be performed continuously through a roll-to-roll process. In particular, when a modified siloxane-based surfactant is included in the monomer composition, the application of the monomer composition can be more smooth, making it more suitable for continuous processes that proceed at high speed.

The material of the substrate is not particularly limited, but it is preferable to use a material that facilitates the application of the monomer composition and allows the hydrogel polymer film to be easily separated after polymerization.

Specifically, the substrate may be a polyethylene terephthalate (PET) film, which is commonly used as a release film, and has at least one surface hydrophobically treated with silicon or fluorine. For example, the substrate may be a PET film surface-treated with a siloxane-based polymer or polytetrafluoroethylene (Teflon ^® ). However, the material of the base material is not limited to this, and a suitable base material can be selected depending on the composition and properties of the monomer composition.

For example, the PET film whose surface is hydrophobically treated may have a contact angle with water of 105° to 110° and a surface energy of 20 to 25 mN/m. Such hydrophobically treated PET film not only facilitates application of the monomer composition film, but also facilitates peeling of the hydrogel polymer film produced after polymerization, thereby improving the convenience of the manufacturing process. In particular, when the monomer composition includes the above-described polyether-modified siloxane-based surfactant, the affinity with the hydrophobically treated PET film having the above-mentioned contact angle and surface energy characteristics is higher, so that casting with a uniform thickness is possible. Even in a roll-to-roll continuous process, a uniform and thin film can be formed, further improving productivity.

Meanwhile, unlike the general solution casting method of polymers in which the solvent is removed after casting the polymer solution, in the present invention, after the monomer composition is applied to the substrate, stretching and polymerization processes are immediately performed to prevent the moisture content from decreasing.

If the water content of the monomer composition film is too low, components constituting the monomer composition may precipitate before polymerization, and there may be a problem of the film breaking up after polymerization. Accordingly, the moisture content of the monomer composition film preferably satisfies the range of 30% by weight to 60% by weight, and preferably satisfies the range of 30% by weight to 50% by weight, or 30% by weight to 45% by weight.

The thickness of the monomer composition film can be appropriately adjusted depending on the thickness of the desired superabsorbent polymer film. The thickness of the monomer composition film changes little during the polymerization stage, but the thickness may decrease by about 10 to 40% or 15 to 35% as the moisture content decreases during the drying process of the hydrogel polymer film after polymerization. Taking this into account, A monomer composition film is prepared to an appropriate thickness.

For example, the thickness of the monomer composition film may be 0.8 mm or less, 0.6 mm or less, or 0.5 mm or less, and may be 0.001 mm or more, or 0.01 mm or more, but is not limited thereto, and may be used in the composition, polymerization, or drying steps of the monomer composition. It can be appropriately adjusted depending on the specific conditions and the desired thickness of the superabsorbent polymer film.

Next, a polymerization reaction is performed by irradiating heat and/or light while stretching the monomer composition film in the machine direction (MD direction) to form a water-containing gel polymer film. In this way, mechanical properties such as flexibility and strength of the hydrogel polymer film produced by stretching the film during polymerization can be adjusted.

At this time, the tension applied to the monomer composition film is 40 N/m or more, or 45 N/m or more, or 50 N/m or more, or 60 N/m or more and 100 N/m or less, or 90 N/m or less, or It may be less than 80 N/m. If stretching is applied with too much tension, the monomer composition film may break or become too thin, and if the tension is too small, mechanical properties such as flexibility and strength may not be secured.

The temperature during polymerization can be appropriately adjusted depending on the composition of the monomer composition, but is preferably above 40°C or 50°C for smooth reaction progress. Additionally, if the temperature is too high, the solvent may evaporate and components constituting the monomer composition may precipitate, so the polymerization temperature is preferably 90°C or lower, or 80°C or lower.

The water content of the hydrogel polymer film prepared through the polymerization step is about 20% by weight or more, preferably 25% by weight or more, and may be 40% by weight or less, or 35% by weight or less. Accordingly, the water-containing gel polymer film is dried to prepare the final superabsorbent polymer film.

The temperature of the drying step may preferably be in the range of 80 to 150 °C, or 90 to 120 °C.

In addition, by drying within the above temperature range for about 5 to 30 minutes, the moisture content is 15% by weight or less, or 12% by weight or less, or 10% by weight or less, or 9% by weight or less, and 1% by weight or more, or 2% by weight or more. , or 4% by weight or more, or 6% by weight or more, a superabsorbent polymer film can be obtained.

The superabsorbent polymer film of the present invention has a thickness of 0.5 mm or less and does not require separate auxiliaries, so it can create a thinner absorber than existing powder-type superabsorbent resins. Preferably, the thickness of the superabsorbent polymer film is 0.5 mm or less, or 0.4 mm or less, or 0.3 mm or less, or 0.2 mm or less, or 0.1 mm or less, and 0.001 mm or more, or 0.005 mm or more, or 0.01 mm or more, or 0.05 mm or less. It may be more than mm.

The superabsorbent polymer film manufactured according to the present invention exhibits excellent absorption performance despite being thin, and exhibits excellent physical properties due to the small amount of water-soluble components.

Specifically, the superabsorbent polymer film satisfies 10% by weight or less, or 5% by weight or less, or 4% by weight or less of water-soluble components measured according to the method of EDANA WSP 270.2. The lower the amount of water-soluble component, the better. The theoretical lower limit is not limited, but may be, for example, 0.5% by weight or more, 1% by weight or more, or 2% by weight or more.

Additionally, the superabsorbent polymer film may have an absorption speed of 25 seconds or less, 23 seconds or less, or 20 seconds or less, and may be 5 seconds or more, or 10 seconds or more.

In addition, the superabsorbent polymer film has an absorbency under pressure (AUP) under 0.7 psi measured according to EDANA method WSP 242.2 of 7.5 g/g or more, or 8.0 g/g or more, or 8.5 g/g or more, and 25 g/g. Below, or below 20 g/g, or below 15 g/g, it exhibits excellent absorption properties compared to existing superabsorbent polymer films.

Methods for measuring water-soluble components, absorption rate, and absorbency under pressure of the superabsorbent polymer film can be specified in the examples below.

As such, the superabsorbent polymer film of the present invention not only has excellent absorbent performance, but also has excellent flexibility and elasticity, such as waterproofing and reinforcing materials such as bars, diapers, wires and cables, electrolyte absorbers, flame retardants, wound protectants, freshness-maintaining materials for food, soil repairing materials, etc. It can be used for a variety of purposes.

The shape of the superabsorbent polymer film is not particularly limited as long as the thickness is 0.5 mm or less. That is, the superabsorbent polymer film may be in the form of a flat film with no irregularities on the surface and a constant thickness, or may have a pattern formed on the surface to improve the flowability of liquid. At this time, the shape of the pattern is not particularly limited, and the pattern can be formed by variously adjusting the length, width, depth, etc. of the recessed portion and the convex portion as needed.

Preferred examples are presented below to aid understanding of the present invention. However, the following examples are merely illustrative of the present invention, and it is clear to those skilled in the art that various changes and modifications can be made within the scope and spirit of the present invention. It is natural that changes and modifications fall within the scope of the attached patent claims.

[Example]

Example 1

A neutralization solution in which 70 mol% of acrylic acid was neutralized was prepared by mixing 55 g of acrylic acid, 66.6 g of a 45% by weight solution of potassium hydroxide (KOH), and 55 g of water.

In the neutralization solution, polyethylene glycol diacrylate (PEGDA, MW=400, Aldrich) as a crosslinking agent, hydroxyethylcellulose (HEC, Natrosol 250HR from Ashland) as a thickener, glycerin as a humectant, and mono-2-(acrylate) as an additive. Royloxy) ethyl succinate, 2,2' Azobis(2-methyl-propionamidine) dihydro chloride as a foaming agent (2,2' Azobis(2-methyl-propionamidine) dihydro chloride, Sigma Aldrich, hereinafter referred to as V -50) and a heat-expandable microsphere, Microsphere F-AC170D (Matsunomo, hereinafter referred to as 170D), sodium persulfate as a thermal polymerization initiator, and Irgacure 819 as a photopolymerization initiator were added, so that the solid content (TSC) was 54 weight. % monomer composition was prepared.

When preparing the monomer composition, HEC was added at 0.45 parts by weight based on 100 parts by weight of solid content of the monomer composition, and mono-2-(acryloyloxy)ethyl succinate was added at 3 parts by weight based on 100 parts by weight of acrylic acid. As for the foaming agent, 0.5 parts by weight of V-50 and 1.0 parts by weight of 170D were added based on 100 parts by weight of acrylic acid. The glycerin was added at 40 parts by weight based on 100 parts by weight of acrylic acid, and the thermal polymerization initiator was added at 1000 ppm, the photopolymerization initiator at 80 ppm, and the crosslinking agent at 1000 ppm based on the total weight of the monomer composition.

The viscosity of the prepared monomer composition at 25°C was measured using a TOKI viscometer (TV-22) at 1 rpm, spindle #1. As a result, the viscosity of the monomer composition was confirmed to be 800 mPa·s.

Next, the monomer composition was cast on one side of a polyethylene terephthalate (PET) release film (Mitsubishi MRL film) whose surface was hydrophobically treated with a siloxane-based polymer to form a 0.1 mm thick monomer composition film (moisture content: 30%). . A comma coater (Gap 500 ㎛) was used for the casting, and the moving speed of the applicator roll was set at 0.3 m/min.

Then, polymerization was performed on the monomer composition film by irradiating ultraviolet rays of 370 mJ/cm ² to form a water-containing gel polymer film. At this time, the polymerization reaction was carried out by stretching the monomer composition film by applying a tension of 60 N/m in the MD direction. The thickness of the prepared hydrogel polymer film was 0.09 mm, and it was confirmed that there was no significant change compared to the monomer composition, and the moisture content was 30% by weight.

Next, the prepared hydrogel polymer film was dried at a temperature of 110°C for 10 minutes to obtain a moisture content of 10% by weight, A rectangular superabsorbent polymer film (SAP film) with a thickness of 0.06 mm, a width of 300 mm, and a height of 400 mm was manufactured.

Examples 2 to 3 and Comparative Examples 1 to 4

When preparing the monomer composition, the superabsorbent resin film was prepared in the same manner as in Example 1, except that the content of mono-2-(acryloyloxy)ethyl succinate and the thickness of the superabsorbent resin film were changed as shown in Table 1 below. Manufactured.

Experiment example

Hereinafter, the physical properties of the superabsorbent polymer films of Examples and Comparative Examples were measured by the following method.

(1) Thickness of superabsorbent polymer film

Using a film thickness gauge from Mitutoyo, the thickness was measured at three different random positions within the superabsorbent polymer film, and the average value was calculated.

(2) Moisture content

The moisture content was calculated from the weight before drying (a) and the weight after drying (b) of the superabsorbent polymer film. At this time, drying of the specimen was performed by raising the temperature from room temperature (25 ℃) to 150 ℃ over 5 minutes and then maintaining it at 150 ℃ for 15 minutes.

Moisture content (%) = (a-b)/a*100

(3) Water-soluble components (EC, weight%)

Water-soluble components (EC) were measured according to the method of EDANA method WSP 270.2.

Specifically, the superabsorbent polymer film was cut to weigh 1.0 g. 200 g was placed in a 0.9 wt% NaCl solution and soaked for 16 hours while stirring at 500 rpm, and then the aqueous solution was filtered through filter paper. The filtered solution was first titrated to pH 10.0 with a 0.1 N caustic soda solution, then back-titrated to pH 2.7 with a 0.1 N hydrogen chloride solution, and the uncrosslinked polymer material was calculated as a water-soluble component from the amount required for neutralization. Measured.

(4) Absorbency under pressure (AUP, g/g)

The absorbency under pressure (AUP) under 0.7 psi was measured according to the EDANA method WSP 242.2. The water content of the superabsorbent polymer films of each Example and Comparative Example to be measured is as shown in Table 1 below, and the absorbency under pressure was measured without separate moisture content adjustment.

Specifically, a stainless steel 400 mesh wire mesh was mounted on the bottom of a plastic cylinder with an inner diameter of 25 mm. Under the conditions of room temperature and 50% humidity, the absorbent resin film is cut and placed on a wire mesh to a weight (W3) of 0.6 g, and the piston, which can evenly apply a load of 0.7 psi, has an outer diameter of slightly less than 25 mm. It is small and has no gaps with the inner wall of the cylinder, and the up and down movement is not hindered. At this time, the weight W4 (g) of the device was measured.

A glass filter with a diameter of 90 mm and a thickness of 5 mm was placed inside a petro dish with a diameter of 150 mm, and a physiological saline solution consisting of 0.9 wt% sodium chloride was placed at the same level as the upper surface of the glass filter. A sheet of filter paper with a diameter of 90 mm was placed on top of it. The measuring device was placed on filter paper, and the liquid was absorbed for 1 hour under load. After 1 hour, the measuring device was lifted and the weight W5 (g) was measured.

Using each obtained mass, the absorbency under pressure (g/g) was calculated according to the following equation.

AUP(g/g) = [W5(g) - W4(g)]/W3(g)

(5) Absorption rate

The superabsorbent polymer film was cut to a size of 15 cm * 10 cm and sandwiched between two sheets of 30 gsm nonwoven fabric of 18 cm * 10 cm. The nonwoven fabric does not affect the absorption rate and was used to confirm the direction of diffusion of salt water.

A cylinder tube with diameter ID 30mm, OD 40mm, height 50mm, and weight 30g was placed on the nonwoven fabric, 10ml of 0.9% NaCl solution was added into the cylinder tube, and the time taken to absorb all of it was measured.

The moisture content of the superabsorbent polymer films of each Example and Comparative Example, which were the subject of measurement, was as described in each table below, and the initial absorption rate was measured without separate moisture content adjustment.

Additive content* SAP film thickness (mm) SAP film moisture content (%) EC (%) AUP(g/g) Absorption speed (seconds) Comparative Example 1 0 0.06 10% 17.65 7.8 14.66 Comparative Example 2 0 0.09 10% 11.7 9.1 28.62 Example 1 5 0.06 10% 3.44 8.6 12.82 Example 2 5 0.09 10% 3.32 10.2 21.34 Example 3 10 0.06 10% 2.35 8.9 11.40 Example 4 10 0.09 10% 2.41 10.9 15.00

* Parts by weight of mono-2-(acryloyloxy)ethyl succinate compared to 100 parts by weight of acrylic acid

Referring to Table 1, when the thickness of the superabsorbent polymer film is the same, the Example including succinic acid salt and/or succinic acid ester has significantly fewer water-soluble components and has an absorbency under pressure improved by more than 10% compared to the comparative example. It can be seen that the absorption rate is improved by more than 10%, up to 47.6%.

From these results, it can be seen that by using succinic acid salt and/or succinic acid ester as an additive, the absorption rate of the foamed superabsorbent polymer film can be further improved and the amount of water-soluble components can be reduced by promoting internal crosslinking. .

Claims (10)

An acrylic acid-based monomer having an acidic group and at least a portion of the acidic group neutralized; crosslinking agent; Cellulose-based thickener; moisturizer; blowing agent; succinic acid salts and/or succinic acid esters; polymerization initiator; and mixing solvents to prepare a monomer composition,
Casting the monomer composition onto a substrate to form a monomer composition film,
Forming a water-containing gel polymer film by irradiating heat and/or light while stretching the monomer composition film, and
A method for producing a superabsorbent polymer film comprising drying the water-containing gel polymer film.
According to paragraph 1,
A method for producing a superabsorbent polymer film, wherein the succinic acid salt and/or succinic acid ester is contained in an amount of more than 1 part by weight and less than 15 parts by weight based on 100 parts by weight of acrylic acid monomer.
According to paragraph 1,
The succinic acid salt and/or succinic acid ester is a superabsorbent polymer selected from the group consisting of mono-2-(acryloyloxy)ethyl succinate, disodium succinate, diethyl succinate, and dimethyl succinate. Film manufacturing method.
According to paragraph 1,
A method of producing a superabsorbent polymer film, wherein the foaming agent is one or more selected from the group consisting of heat-expandable microspheres, expanded microspheres, azo compounds, and inorganic foaming agents.
According to paragraph 1,
A method of producing a superabsorbent polymer film wherein the foaming agent is included in an amount of 0.1 to 10 parts by weight based on 100 parts by weight of acrylic acid-based monomer.
According to paragraph 1,
A method for producing a superabsorbent resin film, wherein the cellulose-based thickener is included in an amount of 0.01 to 5 parts by weight based on 100 parts by weight of solid content in the monomer composition.
According to paragraph 1,
A method for producing a superabsorbent resin film, wherein the moisturizing agent is included in an amount of 5 to 70 parts by weight based on 100 parts by weight of acrylic acid-based monomer.
According to paragraph 1,
In the step of forming the hydrogel polymer film, the tension applied to the monomer composition film is 40 to 100 N/m.
According to paragraph 1,
A method of producing a superabsorbent polymer film wherein the temperature of the step of forming the hydrogel polymer film is 40 to 90 ℃, and the temperature of the drying step is 80 to 150 ℃.
A porous polymer comprising an acrylic acid-based monomer having an acidic group and at least a portion of the acidic group neutralized, polymerized in the presence of an internal crosslinking agent, a cellulose-based thickener, a humectant, a foaming agent, a succinic acid salt and/or a succinic acid ester, and an initiator. As a superabsorbent resin film,
A superabsorbent polymer film containing 10% by weight or less of water-soluble components as measured according to the EDANA method WSP 270.2.