WO2020122471A1 - Method for producing super absorbent polymer, and super absorbent polymer - Google Patents

Abstract

The present invention relates to a super absorbent polymer, and a method for producing same. More specifically, the present invention relates to a super absorbent polymer which exhibits excellent absorption performance and an excellent absorption rate, and includes a fine powder-reassembled body; and a method for producing the super absorbent polymer.

Description

Manufacturing method of super absorbent polymer, and super absorbent polymer

Cross-citation with relevant application(s)

This application claims the benefit of priority based on Korean Patent Application No. 10-2018-0158920 issued on December 11, 2018 and Korean Patent Application No. 10-2019-0152657 issued on November 25, 2019. All content disclosed in the literature is incorporated as part of this specification.

The present invention relates to a super absorbent polymer and a method for manufacturing the same. More particularly, the present invention relates to a superabsorbent polymer comprising fine powder re-assembled material having excellent absorbent properties and a method for manufacturing the same.

Super Absorbent Polymer (SAP) is a synthetic polymer material that has the ability to absorb about 500 to 1,000 times its own weight, and has started to be put into practical use as a physiological tool. In addition to sanitary products such as gardening, it has been widely used as a material for soil repair agents for gardening, civil engineering, construction water supply materials, sheets for raising seedlings, freshness preservatives in the food distribution field, and poultices.

The absorption mechanism of these superabsorbent polymers is the interaction between the penetration pressure due to the difference in the electrical suction power indicated by the charge of the polymer electrolyte, the affinity between water and the polymer electrolyte, the molecular expansion due to the repulsive force between the polymer electrolyte ions, and the expansion inhibition due to crosslinking. Is dominated by. That is, the absorbency of the absorbent resin depends on the above-described affinity and molecular expansion, and the rate of absorption is largely dependent on the penetration pressure of the absorbent polymer itself.

Many studies have been conducted to improve the absorption rate of the super absorbent polymer. For example, Korean Patent Publication No. 2014-0063457 discloses a method of manufacturing a superabsorbent polymer comprising the steps of preparing a fine powder reassembly using only fine powder and a base resin without additives, but the physical properties of the fine powder reassembled base There was a problem that the efficiency was lowered because it was lower than resin and the process was complicated.

[Advanced technical literature]

Patent Document 1: Republic of Korea Patent Publication No. 2014-0063457

The present invention is to solve the problems of the prior art as described above, the superabsorbent polymer comprising a fine powder re-assembly that does not cause a decrease in physical properties such as water retention capacity (CRC) or pressurized water absorption capacity (AUP) while having excellent absorption rate And to provide a method for manufacturing the same.

The present invention to achieve the above object,

Preparing a hydrogel polymer by thermal polymerization or photopolymerization of a monomer composition comprising a water-soluble ethylenically unsaturated monomer and a polymerization initiator;

Drying, grinding and classifying the hydrogel polymer to classify fine powders having a particle diameter of less than 150 μm and normal particles having a particle diameter of 150 to 850 μm;

Preparing an aqueous solution of fine powder by mixing one or more fibers of fluff pulp and synthetic polymer fibers with the fine powder and water; And

It provides a method for producing a super absorbent polymer comprising the step of preparing a fine powder re-assembled by stirring the aqueous powder solution.

The fine powder aqueous solution may include fibers in an amount of 1 part by weight to 20 parts by weight based on 100 parts by weight of the fine powder.

The length of the fiber may be 1 to 20 mm.

The width of the fiber may be 1 to 100 ㎛.

The synthetic polymer fiber may be at least one selected from the group consisting of nylon, polypropylene, polyethylene, polyester, polyacrylonitrile, polyvinyl chloride, polyvinyl alcohol, polyacrylate, and acetate.

The fine aqueous solution may include water in an amount of 50 to 150 parts by weight based on 100 parts by weight of the fine powder.

The manufacturing method of the present invention may further include drying, grinding, and classifying the fine powder re-assembly. In addition, it may further include the step of surface-crosslinking the pulverized and classified fine powder re-assembly.

In addition, the present invention provides a super absorbent polymer prepared by the above manufacturing method.

Specifically, the present invention is a fine particle having a particle size of less than 150 μm among polymers containing an acidic group and polymerizing a water-soluble ethylenically unsaturated monomer in which at least a portion of the acidic group is neutralized; And it provides a superabsorbent polymer comprising a fine powder re-assembly reassembled by mixing one or more fibers of the fluff pulp and synthetic polymer fibers.

At least a portion of the fibers may be mixed through the fine particles of the reassembled particles.

The fine powder re-assembly may include more than 1 part by weight to less than 20 parts by weight of the fiber with respect to 100 parts by weight of the fine powder.

The superabsorbent polymer may have a centrifugal water retention capacity (CRC) of 30 to 45 g/g measured according to EDANA method WSP 241.3.

The super absorbent polymer may have a pressure absorption capacity (AUL) of 0.3 to psi of 25 to 40 g/g measured according to EDANA method WSP 242.3.

The superabsorbent polymer may have a vortex time of 60 seconds or less.

According to the superabsorbent polymer according to the present invention and a method for manufacturing the same, it is possible to provide a high quality superabsorbent polymer having an excellent basic absorption ability and an improved absorption rate.

1 is a scanning electron microscope (SEM) photograph of the super absorbent polymer prepared in Example 3.

The terminology used herein is only used to describe exemplary embodiments, and is not intended to limit the present invention. Singular expressions include plural expressions unless the context clearly indicates otherwise. In this specification, the terms "include", "have" or "have" are intended to indicate that an implemented feature, step, component or combination thereof exists, one or more other features or steps, It should be understood that the possibility of the presence or addition of components, or combinations thereof, is not excluded in advance.

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

Hereinafter, a super absorbent polymer and a method of manufacturing the same according to specific embodiments of the present invention will be described in more detail.

A method for preparing a super absorbent polymer according to an embodiment of the present invention includes: preparing a hydrogel polymer by thermal polymerization or photopolymerization of a monomer composition comprising a water-soluble ethylenically unsaturated monomer and a polymerization initiator; Drying, grinding and classifying the hydrogel polymer to classify fine powders having a particle diameter of less than 150 μm and normal particles having a particle diameter of 150 to 850 μm; Preparing an aqueous solution of fine powder by mixing one or more fibers of fluff pulp and synthetic polymer fibers with the fine powder and water; And preparing the fine powder reassembly by stirring the fine powder aqueous solution.

For reference, in the specification of the present invention, "polymer", or "polymer" means that the water-soluble ethylenically unsaturated monomer is in a polymerized state, and covers all water content ranges, all particle size ranges, all surface crosslinking states, or processing states. Can be. Among the polymers, a polymer having a water content (moisture content) of about 40% by weight or more as a state after drying after polymerization may be referred to as a hydrogel polymer.

In addition, among the polymers, polymers having a particle diameter of less than 150 μm may be referred to as “fine powder”. The fine powder may encompass all of the processes of the superabsorbent polymer manufacturing process, for example, polymerization, drying, pulverization of the dried polymer, or surface crosslinking.

In addition, "fine powder reassembled" may mean a particle in which the fine powder is aggregated, a particle size of 150 μm or more, or a cluster in which a plurality of the particles are gathered.

In addition, "superabsorbent polymer" means the polymer itself depending on the context, or the polymer has been subjected to further processes, for example, surface crosslinking, fine powder reassembly, drying, grinding, classification, etc., to make it suitable for commercialization. It is used to cover everything.

In the method for preparing the superabsorbent polymer of the present invention, first, a water-soluble ethylenically unsaturated monomer and a monomer composition containing a polymerization initiator are subjected to thermal polymerization or photopolymerization to form a hydrogel polymer.

The monomer composition, which is a raw material of the super absorbent polymer, includes a water-soluble ethylenically unsaturated monomer and a polymerization initiator.

As the water-soluble ethylenically unsaturated monomer, any monomer commonly used in the production of superabsorbent polymers can be used without particular limitation. Any one or more monomers selected from the group consisting of anionic monomers and salts thereof, nonionic hydrophilic-containing monomers and amino group-containing unsaturated monomers and quaternaries thereof can be used.

Specifically, (meth)acrylic acid, maleic anhydride, fumaric acid, crotonic acid, itaconic acid, 2-acryloylethanesulfonic acid, 2-methacryloylethanesulfonic acid, 2-(meth)acryloylpropanesulfonic acid or 2- Anionic monomers of (meth)acrylamide-2-methyl propane sulfonic acid and salts thereof; (Meth)acrylamide, N-substituted (meth)acrylate, 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, methoxypolyethylene glycol (meth)acrylate or polyethylene glycol ( Nonionic hydrophilic monomers of meth)acrylate; And an amino group-containing unsaturated monomer of (N,N)-dimethylaminoethyl (meth) acrylate or (N,N)-dimethylaminopropyl (meth)acrylamide, and quaternaries thereof. Can be.

More preferably, an acrylic acid or a salt thereof, for example, an alkali metal salt such as acrylic acid or a sodium salt thereof may be used, and the use of such a monomer makes it possible to manufacture a super absorbent polymer having better physical properties. When the alkali metal salt of acrylic acid is used as a monomer, it can be used by neutralizing acrylic acid with a basic compound such as caustic soda (NaOH).

The concentration of the water-soluble ethylenically unsaturated monomer may be about 20 to about 60% by weight, preferably about 40 to about 50% by weight, with respect to the monomer composition containing the raw material and solvent of the superabsorbent polymer, and polymerization It may be an appropriate concentration in consideration of time and reaction conditions. However, if the concentration of the monomer is too low, the yield of the superabsorbent polymer may be low and economic problems may occur. Conversely, if the concentration is too high, a part of the monomer precipitates or the grinding efficiency of the polymerized hydrogel polymer is low. Such problems may occur in the process and physical properties of the super absorbent polymer may be deteriorated.

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

Specifically, the polymerization initiator may be a thermal polymerization initiator or a photopolymerization initiator according to UV irradiation depending on the polymerization method. However, even by the photopolymerization method, since a certain amount of heat is generated by irradiation with ultraviolet rays or the like and a certain amount of heat is generated as the polymerization reaction that is an exothermic reaction proceeds, a thermal polymerization initiator may be additionally included.

If the photopolymerization initiator is a compound capable of forming radicals by light such as ultraviolet rays, the composition may be used without limitation.

The photopolymerization initiator includes, for example, benzoin ether, dialkyl acetophenone, hydroxyl alkylketone, phenyl glyoxylate, and benzyl dimethyl ketal. ketal), acyl phosphine, and alpha-aminoketone (α-aminoketone). Meanwhile, as a specific 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. . For a wider variety of photoinitiators, it is well documented in Reinhold Schwalm's book "UV Coatings: Basics, Recent Developments and New Application (Elsevier 2007)" p115, and is not limited to the examples described above.

The photopolymerization initiator may be included in a concentration of about 0.01 to about 1.0% by weight relative 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 super absorbent polymer may be small and the properties may be uneven.

In addition, as the thermal polymerization initiator, one or more selected from the initiator group consisting of a persulfate-based initiator, an azo-based initiator, hydrogen peroxide, and ascorbic acid may be used. Specifically, examples of the persulfate-based initiator are sodium persulfate (Na ₂ S ₂ O ₈ ), potassium persulfate (K ₂ S ₂ O ₈ ), ammonium persulfate (Ammonium persulfate; (NH ₄ ) ₂ S ₂ O ₈ ), and examples of the azo-based initiator are 2, 2-azobis-(2-amidinopropane) dihydrochloride (2, 2-azobis (2-amidinopropane) dihydrochloride), 2 , 2-azobis-(N, N-dimethylene)isobutyramidine dihydrochloride (2-azobis-(N,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-azobis-(4-cyanovaleric acid) (4,4-azobis-(4-cyanovaleric acid)). More various thermal polymerization initiators are well specified in the Odian book'Principle of Polymerization (Wiley, 1981)', p203, and are not limited to the above-described examples.

The thermal polymerization initiator may be included in a concentration of about 0.001 to about 0.5% by weight relative to the monomer composition. If the concentration of the thermal polymerization initiator is too low, the additional thermal polymerization hardly occurs, so the effect of the addition of the thermal polymerization initiator may be negligible. If the concentration of the thermal polymerization initiator is too high, the molecular weight of the super absorbent polymer is small and the physical properties may be uneven. have.

According to an embodiment of the present invention, the monomer composition may further include an internal crosslinking agent as a raw material of the super absorbent polymer. As the internal crosslinking agent, while having at least one functional group capable of reacting with the water-soluble substituent of the water-soluble ethylenically unsaturated monomer, a crosslinking agent having at least one ethylenically unsaturated group; Alternatively, a crosslinking agent having two or more functional groups capable of reacting 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 internal crosslinking agent include bisacrylamide having 8 to 12 carbons, bismethacrylamide, poly(meth)acrylate of polyols having 2 to 10 carbons, or poly(meth)allyl ether of polyols having 2 to 10 carbons, etc. And more specifically, N,N'-methylenebis(meth)acrylate, ethyleneoxy(meth)acrylate, polyethyleneoxy(meth)acrylate, propyleneoxy(meth)acrylate, glycerin diacrylate , Glycerin triacrylate, trimethyrol triacrylate, triallylamine, triaryl cyanurate, triallyl isocyanate, polyethylene glycol, diethylene glycol and propylene glycol.

Such an internal crosslinking agent may be included in a concentration of about 0.01 to about 0.5% by weight relative to the monomer composition, thereby crosslinking the polymerized polymer.

In the production method of the present invention, the monomer composition of the super absorbent polymer may further include additives such as a thickener, a plasticizer, a storage stabilizer, and an antioxidant, if necessary.

Raw materials such as the water-soluble ethylenically unsaturated monomer, photopolymerization initiator, thermal polymerization initiator, internal crosslinking agent, and additives described above may be prepared in the form of a solution of a monomer composition dissolved in a solvent.

The solvent that can be used at this time can be used without limitation of its composition 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.

The solvent may be included in the remaining amount excluding the above-mentioned components with respect to the total content of the monomer composition.

On the other hand, if the method for forming a hydrogel polymer by thermal polymerization or photopolymerization of such a monomer composition is also a commonly used polymerization method, there is no particular limitation on the configuration.

Specifically, the polymerization method is largely divided into thermal polymerization and photopolymerization according to the polymerization energy source, and in general, when performing thermal polymerization, it can be carried out in a reactor having a stirring axis such as a kneader, and when performing photopolymerization, it is movable Although it may be carried out in a reactor equipped with a conveyor belt, the polymerization method described above is an example, and the present invention is not limited to the polymerization method described above.

For example, as described above, a hydrogel polymer obtained by thermal polymerization by supplying hot air or heating a reactor to a reactor such as a kneader having a stirring shaft is used as a reactor outlet, depending on the type of the stirring shaft provided in the reactor. The discharged hydrogel polymer may be in the form of several centimeters to several millimeters. Specifically, the size of the hydrogel polymer obtained may vary depending on the concentration and injection speed of the monomer composition to be injected, and a hydrogel polymer having a weight average particle diameter of 2 to 50 mm can be usually obtained.

In addition, when the photopolymerization is performed in a reactor equipped with a movable conveyor belt as described above, the shape of the hydrogel polymer usually obtained may be a hydrogel polymer on a sheet having a belt width. At this time, the thickness of the polymer sheet varies depending on the concentration and the injection rate of the monomer composition to be injected, but it is usually preferable to supply the monomer composition so that a polymer on the sheet having a thickness of about 0.5 to about 5 cm can be obtained. When the monomer composition is supplied to such an extent that the thickness of the polymer on the sheet is too thin, the production efficiency is low, which is undesirable, and when the polymer thickness on the sheet exceeds 5 cm, due to the excessively thick thickness, the polymerization reaction is evenly spread over the entire thickness. It may not happen.

At this time, the normal water content of the hydrogel polymer obtained in this way may be about 40 to about 80% by weight. On the other hand, in the present specification, "water content" refers to a value obtained by subtracting the weight of the polymer in a dry state from the weight of the hydrogel polymer as the content of moisture to the total weight of the hydrogel polymer. Specifically, it is defined as a calculated value by measuring the weight loss due to evaporation of water in the polymer during the drying process by raising the temperature of the polymer through infrared heating. At this time, the drying condition is a method of raising the temperature from room temperature to about 180° C. and maintaining it at 180° C. The total drying time is set to 20 minutes including 5 minutes of the temperature rising step, and the water content is measured.

Next, the hydrogel polymer is coarsely pulverized.

At this time, the used grinder is not limited in configuration, but specifically, a vertical cutter (Vertical pulverizer), a turbo cutter (Turbo cutter), a turbo grinder (Turbo grinder), a rotary cutting mill (Rotary cutter mill), cutting Cutter mill, disc mill, shred crusher, crusher, chopper, and disc cutter However, it is not limited to the above-described example.

At this time, the coarse crushing step may be pulverized so that the particle diameter of the hydrogel polymer is about 2 to about 20 mm.

Coarse pulverization with a particle diameter of less than 2 mm is not technically easy due to the high water content of the hydrogel polymer, and may also cause agglomeration between the crushed particles. On the other hand, when the particle size is roughly crushed to more than 20 mm, the effect of increasing the efficiency of the drying step to be performed later may be insignificant.

Next, the obtained hydrogel polymer is dried.

Drying is performed on the hydrogel polymer immediately after polymerization, which is coarsely pulverized as described above or has not been subjected to a co-pulverization step. At this time, the drying temperature of the drying step may be about 150 to about 250 ℃. When the drying temperature is less than 150°C, the drying time is too long and there is a fear that the physical properties of the superabsorbent resin to be formed are lowered. When the drying temperature exceeds 250°C, only the polymer surface is dried excessively, and a subsequent grinding process is performed. In the fine powder may be generated, there is a fear that the physical properties of the superabsorbent polymer to be formed finally decreases. Therefore, preferably, the drying may be performed at a temperature of about 150 to about 200 °C, more preferably at a temperature of about 160 to about 180 °C.

Meanwhile, in the case of a drying time, process efficiency may be considered, and may be performed for about 20 to about 90 minutes, but is not limited thereto.

The drying method of the drying step may also be selected and used without limitation, as long as it is commonly used as a drying process for the hydrogel polymer. 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 polymer after the drying step may be about 0.1 to about 10% by weight.

Next, the dried polymer obtained through such a drying step is pulverized.

The polymer powder obtained after the grinding step may have a particle size of about 150 to about 850 μm. The pulverizer used for pulverizing to such a particle size is specifically, a pin mill, a hammer mill, a screw mill, a roll mill, a disc mill or a jog. A mill may be used, but the present invention is not limited to the examples described above.

In order to manage the physical properties of the superabsorbent polymer powder finally produced after such a pulverization step, the polymer powder obtained after pulverization is generally classified according to particle size. Preferably, a step of classifying particles having a particle diameter of less than about 150 μm, particles having a diameter of about 150 to about 850 μm, and particles having a particle diameter greater than 850 μm.

In the specification of the present invention, fine particles having a particle size of less than a certain particle size, that is, less than about 150 μm, are referred to as superabsorbent polymer fine powder, SAP fine powder or fine powder (fines, fine powder), and have a particle diameter of about 150 to about 850 μm. Phosphorus particles are referred to as normal particles. The fine powder may be generated during a polymerization process, a drying process, or a pulverization step of the dried polymer. When the final product contains fine powder, it is difficult to handle and exhibits a gel blocking phenomenon. It is desirable to exclude it from being included or reuse it to become normal particles.

In the present invention, through the process of agglomeration of the fine powders to a normal particle size, a fine powder reassembly of a super absorbent polymer is formed.

More specifically, the fine powder reassembly process, a mixture of one or more fibers of fluff pulp and synthetic polymer fibers, and the fine powder and water to prepare a fine powder aqueous solution, and then agitate the prepared fine powder aqueous solution to agglomerate the substances It is made by the method of manufacturing the powder re-assembly.

At this time, the water content of the fine powder may be 40 to 60%. The higher the water content of the fine powder, the higher the cohesive strength of the fine powder may be, but during the reassembly process, too large a reassembled mass is formed, or a part of the reassembled mass (jelly ball) in a tightly agglomerated state containing a lot of water is formed and subsequently This can cause problems when operating the grinding process. In addition, if the water content of the fine powder is too low, the reassembly process is easy, but since the cohesive strength is low, it is easy to crush into fine powder again after reassembly, so it is preferable to satisfy the water content range.

The fluff pulp is a cellulose fluff pulp, but may be wood fluff pulp such as softwood kraft paper, broadleaf kraft pulp, but is not limited thereto, and fluff pulp used for absorbent articles may be used without limitation.

The synthetic polymer fiber may be at least one selected from the group consisting of nylon, polypropylene, polyethylene, polyester, polyacrylonitrile, polyvinyl chloride, polyvinyl alcohol, polyacrylate, and acetate. Such a synthetic polymer fiber is excellent in hygroscopicity, and it is easy to control the width or length of the fiber, so it is possible to easily control the physical properties of the super absorbent polymer.

The fiber may be preferably used having a length of 1 to 20 mm. In addition, the fiber may preferably have a width of 1 to 100 μm. If the length of the fiber is too short or too narrow, the effect of improving the absorption rate of the fine powder reassembled body cannot be secured. Conversely, if the length of the fiber is too long or the width is too wide, it may be difficult to introduce the fiber into the fine powder reassembly.

In this aspect, the length of the fiber is preferably 2 mm or more, or 3 mm or more, and may be 15 mm or less, or 10 mm or less. As an example, while the individual fiber length satisfies 1 to 20 mm, the fiber having an average length of 3 to 10 mm may be preferably used. At this time, the average length of the fibers can be derived by randomly selecting 100 fibers, measuring the length of individual fibers, and calculating the average value thereof.

Further, the width of the fiber may be 5 μm or more, or 10 μm or more, and 80 μm or less, or 50 μm or less.

In the step of forming the fine powder re-assembly, the content of the fibers contained in the fine powder solution is 1 part by weight or more, 2 parts by weight or more, or 5 parts by weight or more, and less than 20 parts by weight, 15 parts by weight or less, Or 10 parts by weight or less. If the fiber is less than 1 part by weight based on 100 parts by weight of the fine powder, it is impossible to secure an effect of improving the absorption rate of the fine powder re-assembly according to the content of the fluff pulp. Basic absorption properties such as absorption capacity may be deteriorated.

Meanwhile, the aqueous solution of fine powder contains water, and the content of water may be 50 to 150 parts by weight, or 70 to 150 parts by weight based on 100 parts by weight of the fine powder. If the water content exceeds 150 parts by weight with respect to 100 parts by weight of the fine powder, the re-assembled mass may be too large or jelly balls may be generated as described above, and if it is less than 50 parts by weight, the cohesive strength of the re-assembled product may be reduced.

In one embodiment, the preparation of the aqueous fine powder solution may be by a method of preparing the aqueous fine powder solution by first mixing the powder and the fiber dryly before adding water, and then adding water and stirring. When dry water is mixed with the fine powder and the fiber and then water is added, it is preferable because the fiber can be more uniformly dispersed in the fine powder re-assembly.

Next, the prepared fine powder aqueous solution is mixed to form a fine powder reassembly. The method of mixing the finely divided aqueous solution is not particularly limited, but for example, at a temperature of 25 to 100° C., it may be achieved by stirring at a speed of 200 to 2000 rpm for 5 to 60 seconds.

According to an embodiment of the present invention, the obtained fine powder re-assembled may further include a step of drying, grinding and classifying.

The step of drying the fine powder reassembly may be performed for 20 minutes to 90 minutes at a temperature of 150 to 250°C. In addition, as the heating means for drying in the above, the configuration is not limited. Specifically, the heating medium may be supplied or directly heated by means such as electricity, but the present invention is not limited to the above-described examples. Examples of heat sources that can be specifically used include steam, electricity, ultraviolet rays, infrared rays, etc., and heated thermal fluids can also be used.

Next, the dried fine powder re-assembly can be pulverized to have a particle size of about 150 to about 850 μm. The pulverizer used for pulverizing to such a particle size is specifically, a pin mill, a hammer mill, a screw mill, a roll mill, a disc mill or a jog. A mill may be used, but the present invention is not limited to the examples described above.

Additionally, the fine powder re-assembly obtained after pulverization may be classified into particles having a particle diameter of less than about 150 μm, particles having a diameter of about 150 to about 850 μm, and particles having a particle diameter greater than 850 μm depending on the particle size.

The classified fine powder reassembly may be performed alone or by mixing with other normal particles (particles having a particle size of 150 to 850 μm) to perform a surface crosslinking process.

Surface crosslinking is a step of increasing the crosslinking density near the surface of the superabsorbent polymer particle with respect to the crosslinking density inside the particle. Generally, the surface crosslinking agent is applied to the surface of the superabsorbent polymer particles. Thus, this reaction takes place on the surface of the superabsorbent polymer particles, which improves the crosslinkability on the surface of the particles without substantially affecting the inside of the particles. Therefore, the surface-crosslinked superabsorbent polymer particles have a higher degree of crosslinking near the surface than from the inside.

At this time, the surface crosslinking agent is not limited in its structure as long as it is a compound capable of reacting with a functional group of the polymer.

Preferably, in order to improve the properties of the resulting super absorbent polymer, a polyhydric alcohol compound as the surface crosslinking agent; Epoxy compounds; Polyamine compounds; Halo epoxy compounds; Condensation products of haloepoxy compounds; Oxazoline compounds; Mono-, di- or polyoxazolidinone compounds; Cyclic urea compounds; Polyvalent metal salts; And it may use one or more selected from the group consisting of alkylene carbonate compounds.

Specifically, examples of the polyhydric alcohol compound include mono-, di-, tri-, tetra- or polyethylene glycol, monopropylene glycol, 1,3-propanediol, dipropylene glycol, 2,3,4-trimethyl-1,3 -Pentanediol, polypropylene glycol, glycerol, polyglycerol, 2-butene-1,4-diol, 1,4-butanediol, 1,3-butanediol, 1,5-pentanediol, 1,6-hexanediol, and One or more selected from the group consisting of 1,2-cyclohexanedimethanol can be used.

In addition, ethylene glycol diglycidyl ether and glycidol may be used as the epoxy compound, and ethylenediamine, diethylenetriamine, triethylenetetraamine, tetraethylenepentamine, and pentaethylenehexamine may be used as polyamine compounds. , Polyethyleneimine and polyamide polyamine may be used one or more selected from the group consisting of.

In addition, epichlorohydrin, epibromohydrin, and α-methylepichlorohydrin may be used as haloepoxy compounds. Meanwhile, as the mono-, di- or polyoxazolidinone compound, for example, 2-oxazolidinone and the like can be used.

And, as the alkylene carbonate compound, ethylene carbonate or the like can be used. These may be used alone or in combination with each other. Meanwhile, in order to increase the efficiency of the surface crosslinking process, it is preferable to use one or more polyhydric alcohol compounds among these surface crosslinking agents, and more preferably, polyhydric alcohol compounds having 2 to 10 carbon atoms can be used.

The content of the surface crosslinking agent to be added may be appropriately selected depending on the type or reaction conditions of the surface crosslinking agent to be added, but usually, about 100 parts by weight of the polymer, about 0.001 to about 5 parts by weight, preferably about 0.01 to about 3 parts by weight, more preferably from about 0.03 to about 2 parts by weight can be used.

When the content of the surface crosslinking agent is too small, the surface crosslinking reaction hardly occurs, and when it is more than 5 parts by weight with respect to 100 parts by weight of the polymer, a phenomenon of deterioration of absorption capacity and physical properties may occur due to excessive progress of the surface crosslinking reaction .

The surface crosslinking reaction and drying can be simultaneously performed by heating the polymer particles to which the surface crosslinking agent is added.

The heating means for the surface crosslinking reaction is not particularly limited. The heating medium may be supplied or a heat source may be directly supplied to heat. At this time, as the kind of heat medium that can be used, a heated fluid such as steam, hot air, and hot oil may be used, but the present invention is not limited to this, and the temperature of the heat medium supplied is the means of the heat medium, the rate of temperature increase, and the temperature increase. It can be appropriately selected in consideration of the target temperature. On the other hand, the heat source directly supplied may include a heating method through electricity or a gas, but the present invention is not limited to the above-described example.

The fine powder re-assembly produced by the above-described method includes fibers having excellent hygroscopicity, and has excellent basic absorption properties, but also excellent absorption speed. That is, according to the manufacturing method of the present invention, since the hygroscopic fibers are mixed together with the fine powder in the fine powder re-assembly step, at least a part of the fibers are mixed through the fine powder re-assembled particles, and the mixed fibers rapidly absorb the surrounding moisture. Since it can be transferred to the fine powder re-assembled, it can have a significantly improved absorption rate compared to the complex of simply mixing the fine powder re-assembled with hygroscopic fibers.

Thus, according to an embodiment of the present invention, a fine particle having a particle diameter of less than 150 μm among polymers containing an acidic group and polymerizing a water-soluble ethylenically unsaturated monomer in which at least a portion of the acidic group is neutralized; And it is provided a superabsorbent polymer comprising a fine powder re-assembled by mixing one or more fibers of the fluff pulp and synthetic polymer fibers.

In the fine powder reassembly included in the superabsorbent polymer, at least a portion of the fibers may be incorporated through the fine powder reassembled particles. That is, the fibers can be distributed inside and outside the particles of the fine powder re-assembled body, thereby rapidly absorbing surrounding moisture and transferring it to the fine powder re-assembled particles, thereby contributing to the improvement of the absorption rate.

The fine powder re-assembly may contain 1 part by weight or more, 2 parts by weight or more, or 5 parts by weight or more, and less than 20 parts by weight, 15 parts by weight or less, or 10 parts by weight or less based on 100 parts by weight of fine powder. When the content of the fiber satisfies the above range, it is possible to secure an effect of improving the absorption rate while maintaining excellent basic absorption properties such as water retention capacity and pressure absorption capacity.

The super absorbent polymer has a water retention capacity (CRC) measured according to EDANA method WSP 241.3 of about 30 g/g or more, 32 g/g or more, or about 33 g/g or more, and about 45 g/g or less, 40 g/g or less, or about 35 g/g or less.

In addition, the superabsorbent polymer has a pressure absorption capacity (AUL) of 0.3 psi measured according to EDANA method WSP 242.3 of 25 g/g or more, or 27 g/g or more, and 40 g/g or less, or 30 g/g or less. Can be.

In addition, the superabsorbent polymer is added to 2 g of superabsorbent polymer in 50 mL of physiological saline at 23 °C to 24 °C, and the magnetic bar (8 mm in diameter and 31.8 mm in length) is stirred at 600 rpm to vortex. ) May be less than or equal to 60 seconds, or less than or equal to 50 seconds. The lower the absorption rate, the better, and the lower limit is not limited, but may be, for example, 10 seconds or more, or 20 seconds or more.

Hereinafter, the present invention will be described in more detail based on examples. However, the following examples are only illustrative of the present invention, and the contents of the present invention are not limited by the following examples. In addition, "%" and "part" showing content in the following Examples and Comparative Examples are based on mass unless otherwise specified.

<Example>

Preparation Example 1

100 g of acrylic acid, 3.0 g of polyethylene glycol diacrylate (PEGDA, Mw = 523) as a crosslinking agent, 0.008 g of phenylbis(2,4,6-trimethylbenzoyl)phosphine oxide as a photoinitiator, sodium persulfate (SPS) as a thermal initiator 0.08 g, caustic soda (NaOH) 128 g, and 63.5 g water were mixed. Here, 5 parts by weight of each fiber in Table 1 based on 100 parts by weight of the monomer composition was added to prepare a monomer composition.

Thereafter, the monomer composition was put on a continuously moving conveyor belt and irradiated with ultraviolet rays (irradiation amount: 2 mW/cm ² ) to undergo UV polymerization for 2 minutes to obtain a hydrogel polymer sheet.

After cutting the hydrogel polymer sheet to a size of 3 cm x 3 cm, minced with a meat chopper (hole size 16 mm, speed 60 Hz) to prepare a crumb. The crumb was dried in an oven capable of transferring air volume up and down. Specifically, hot air at 185°C was uniformly dried by flowing from bottom to top for 15 minutes and from top to bottom for 15 minutes, and after drying, the water content of the dried body was 2% or less.

The dried polymer was pulverized with a grinder, and then classified for 10 minutes at an amplitude of 1.5 mm (mesh combination, #20 / #30 / #50 / #100), with normal particles having a particle size of 150 μm to 850 μm, Fine particles having a particle diameter of less than 150 mu m were obtained.

Examples 1 to 9

(1) Preparation of fine powder reassembly

With respect to 100 parts by weight of the fine powder having a particle diameter of less than 150 μm obtained in Preparation Example 1, each fiber of Table 1 below was added to the weight of Table 1 and mixed for 1 minute, and then 150 parts by weight of water was added and further mixed for 10 seconds. A fine powder reassembly was prepared.

(2) Preparation of superabsorbent polymer containing fine powder reassembled

In Preparation Example 1, the hydrogel polymer pulverized with a meat chopper (hole size 16 mm) and the fine powder re-assembled were mixed at a weight ratio of 75:25 to obtain a coarsely pulverized hydrogel polymer. Subsequently, the base resin was prepared through drying, grinding, and classification steps in the same manner as in Production Example 1.

Then, 100 parts by weight of the prepared base resin, surface crosslinking solution (6.2 parts by weight of water, 6.2 parts by weight of methanol, 0.03 parts by weight of ethylene glycol diglycidyl ether, 0.01 parts by weight of silica Aerosil200), and evenly mixed, 140 The surface crosslinking reaction was performed at 30°C for 30 minutes. After the surface treatment was completed, a super absorbent polymer having an average particle diameter of 850 μm or less was obtained using a sieve.

Comparative Example 1

A superabsorbent polymer comprising a fine powder reassembled was prepared in the same manner as in Example 1, except that no fiber was added when the fine powder reassembled.

Comparative Example 2

A superabsorbent polymer containing the finely divided re-assembled was prepared in the same manner as in Example 1, except that the fluff pulp was used in 20 parts by weight based on 100 parts by weight of fine powder when the fine powder was reassembled.

Comparative Example 3

To 100 parts by weight of the super absorbent polymer of Comparative Example 1, 5 parts by weight of fluff pulp used in Example 1 was added and mixed to prepare a super absorbent polymer.

<Experimental Example>

The physical properties of the superabsorbent polymer prepared in each of the Examples and Comparative Examples were measured by the following method, and the results are shown in Table 1.

(1) Centrifugal Retention Capacity (CRC)

The water retention capacity of each resin by the load-free absorption magnification was measured according to EDANA WSP 241.3.

Specifically, from the resins obtained through the examples and comparative examples, resins classified by a sieve of #40-50 were obtained. After the resin W0(g) (about 0.2g) was uniformly put in a nonwoven fabric bag and sealed, it was immersed in physiological saline (0.9% by weight) at room temperature. After 30 minutes, the bag was drained for 3 minutes under the condition of 250G using a centrifuge, and the mass W2 (g) of the envelope was measured. Moreover, the mass W1 (g) at that time was measured after performing the same operation without using a resin. CRC (g/g) was calculated according to the following equation using each obtained mass.

[Equation 1]

(2) Absorbency under Load (AUL)

The pressure absorption capacity of 0.3 psi of each resin was measured according to EDANA method WSP 242.3. In the measurement of the pressure absorption capacity, the resin classifier for the CRC measurement was used.

Specifically, a 400 mesh wire mesh made of stainless steel was mounted on a cylindrical bottom of a plastic having an inner diameter of 25 mm. A piston capable of uniformly spreading the absorbent resin W3(g) (0.16 g) on a wire mesh under conditions of normal temperature and humidity of 50%, and giving a load of 0.3 psi evenly thereon, the piston is slightly smaller than the outer diameter of 25 mm and a cylinder. There was no gap with the inner wall of the and the vertical movement was not disturbed. At this time, the weight W4(g) of the device was measured.

A glass filter having a diameter of 90 mm and a thickness of 5 mm was placed inside the petri dish of 150 mm in diameter, and the physiological saline composed of 0.9 wt% sodium chloride was brought to the same level as the top surface of the glass filter. A sheet of filter paper having a diameter of 90 mm was placed thereon. The measuring device was mounted on a filter paper, and the liquid was absorbed for 1 hour under a load. After 1 hour, the measuring device was lifted, and the weight W5 (g) was measured.

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

[Equation 2]

(3) Absorption rate (vortex)

The absorption rate of each resin was measured in seconds according to the method described in International Patent Publication No. 1987-003208.

Specifically, the absorption rate (or vortex time) of 23 °C to 24 °C 50 g of physiological saline, 2 g of superabsorbent polymer is added, and a magnetic bar (diameter 8 mm, length 31.8 mm) is stirred at 600 rpm. It was calculated by measuring the time until the vortex disappears in seconds.

*The average length of the fiber is the average value of the length derived by randomly selecting 100 fibers.

Referring to Table 1, the superabsorbent polymer prepared according to the present invention has excellent basic properties such as CRC and AUL, but is significantly improved compared to Comparative Example 1 without fibers and Comparative Example 3 with simple mixing of fibers. It can be confirmed that the absorption rate is shown. However, when the fluff pulp content is too high, the absorption rate may be improved, but it can be confirmed through Comparative Example 2 that basic absorption properties such as CRC and AUL are deteriorated.

Claims (15)

1. Preparing a hydrogel polymer by thermal polymerization or photopolymerization of a monomer composition comprising a water-soluble ethylenically unsaturated monomer and a polymerization initiator;

   Drying, grinding and classifying the hydrogel polymer to classify fine powders having a particle diameter of less than 150 μm and normal particles having a particle diameter of 150 to 850 μm;

   Preparing an aqueous solution of fine powder by mixing one or more fibers of fluff pulp and synthetic polymer fibers with the fine powder and water; And

   A method for producing a super absorbent polymer comprising the step of preparing a fine powder re-assembled by stirring the fine aqueous solution.
2. According to claim 1,

   The fine aqueous solution is a method for producing a super absorbent polymer containing 1 part by weight or more and less than 20 parts by weight of fibers with respect to 100 parts by weight of fine powder.
3. According to claim 1,

   Method of manufacturing a super absorbent polymer having a length of 1 to 20 mm.
4. According to claim 1,

   Method of manufacturing a super absorbent polymer having a width of 1 to 100 μm.
5. According to claim 1,

   The synthetic polymer fiber is nylon, polypropylene, polyethylene, polyester, polyacrylonitrile, polyvinyl chloride, polyvinyl alcohol, polyacrylate, and one or more selected from the group consisting of acetate, a method for producing a super absorbent polymer .
6. According to claim 1,

   The fine aqueous solution contains 50 to 150 parts by weight of water with respect to 100 parts by weight of the fine powder, a method for producing a super absorbent polymer.
7. According to claim 1,

   Further comprising the step of drying, pulverizing and classifying the fine powder re-assembly, a method for producing a super absorbent polymer.
8. The method of claim 7,

   A method for producing a super absorbent polymer, further comprising the step of surface crosslinking the pulverized and classified fine powder re-assembly.
9. A super absorbent polymer prepared by the method of claim 1.
10. A fine particle having a particle size of less than 150 μm among polymers containing an acidic group and polymerizing a water-soluble ethylenically unsaturated monomer in which at least a portion of the acidic group is neutralized; And a fine powder re-assembled by remixing one or more fibers of fluff pulp and synthetic polymer fibers.
11. The method of claim 10,

    At least a portion of the fibers are mixed through the fine particles of the re-assembled particles, the super absorbent polymer.
12. The method of claim 10,

    The fine powder re-assembly, the superabsorbent polymer containing less than 20 parts by weight of the fiber with respect to 100 parts by weight of the fine powder.
13. The method of claim 10,

    A superabsorbent polymer having a centrifugal water retention capacity (CRC) of 30 to 45 g/g measured according to EDANA method WSP 241.3.
14. The method of claim 10,

    A super absorbent polymer having a pressure absorption capacity (AUL) of 0.3 to psi of 25 to 40 g/g measured according to EDANA method WSP 242.3.
15. The method of claim 10,

    A super absorbent polymer having a vortex time of 60 seconds or less.

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