KR102518937B1 - Method for Preparing Super Absorbent Polymer - Google Patents

Abstract

The present invention relates to a superabsorbent polymer and a manufacturing method thereof. More specifically, it is possible to reduce energy during drying by reducing the amount of reassembly of fine powders, reduce the load on the dryer by using a drying process dedicated to reassembly of fine powders, and minimize the deterioration of physical properties by preventing overdrying of the reassembly of fine powders. . In addition, the amount of non-pulverized generation can be minimized by using a grinding machine dedicated to reassembly of fine powders, and the amount of circulation of fine powders in the entire process can be reduced through a process dedicated to reassembly of fine powders.

Description

Method for preparing super absorbent polymer {Method for Preparing Super Absorbent Polymer}

The present invention relates to a method for manufacturing a superabsorbent polymer, and more particularly, to improve the drying efficiency by increasing the drying speed of the stem-shaped reassembly of fine powder, thereby reducing the physical properties of the fine powder reassembly, the decrease in particle strength, and the resulting amount of non-powder generation. It relates to a method for producing a superabsorbent polymer that can prevent the increase.

Super Absorbent Polymer (SAP) is a synthetic high-molecular substance capable of absorbing 500 to 1,000 times its own weight in water. In addition to sanitary products, it is widely used as a soil retainer for horticulture, a waterstop material for civil engineering and construction, a sheet for raising seedlings, a freshness maintainer in the field of food distribution, and a material for steaming.

The absorption mechanism of these superabsorbent polymers is the interaction of osmotic pressure due to the difference in electric attraction of the polymer electrolyte, affinity between water and the polymer electrolyte, molecular expansion due to the repulsive force between the polymer electrolyte ions, and swelling inhibition due to crosslinking. is dominated by That is, the absorbability of the absorbent polymer depends on the above-mentioned affinity and molecular expansion, and the absorption rate is largely dependent on the osmotic pressure of the absorbent polymer itself.

A lot of research is being conducted to improve the absorption rate of these superabsorbent polymers. For example, Korean Patent Publication No. 2014-0063457 discloses a method for manufacturing a superabsorbent polymer including preparing a reassembly of fine powder using only fine powder and a base resin without additives, but the physical properties of the reassembly of fine powder are based on the base resin. There was a problem that the efficiency was lowered than the resin and the process was complicated. In addition, the fine powder inevitably generated in the manufacturing process of the superabsorbent polymer is a factor in deteriorating the physical properties of the product. In order to solve this problem, there is a method of adding fine powder during polymerization, but this method induces non-uniform polymerization or scatters light. There was a problem of hindering polymerization and causing a decrease in physical properties.

Accordingly, a method of reassembling the fine powder using a separate re-granulator has been developed, which is a method of mixing the fine powder and water in a certain ratio to make large particles. As an example, FIG. 1 is a process diagram schematically illustrating a method of preparing a superabsorbent polymer by preparing a fine powder reassembly using a conventional fine powder regranulator and then mixing it with normal particles. Referring to FIG. 1, in the conventional method for producing a superabsorbent polymer using fine powder reassembly, the water-containing gel polymer prepared by polymerization of a monomer composition containing a water-soluble ethylenically unsaturated monomer and a polymerization initiator is pulverized and classified. The fine powder was mixed with water and reassembled to prepare a fine powder reassembly, mixed with a water-containing gel polymer or a coarsely pulverized product thereof, and then dried, pulverized, classified, and surface crosslinked to prepare a superabsorbent polymer. When using the above technology, when water is used at a certain level or higher, the fine particles are sufficiently swollen in water and combined with other fine particles, and when dried, a fine powder assembly usable as a product is formed. However, if water is used below a certain level, fine powder and water cannot be mixed uniformly, resulting in non-uniform particles having different water content. and the particle strength is weaker than that of the fine powder reassembly or the base resin having a high moisture content. This increases the non-powder generation rate in the process, causing a decrease in process stability and physical properties, and an increase in the fine powder generation rate in the final product, which causes the problem of scattering of fine powder in the final product and an increase in the amount of product fine powder with greatly deteriorated physical properties. cause problems

Thus, when reassembling by reducing the amount of water used for granular assembly to a certain level or less, the particle strength is improved through a compression process to solve the problem caused by the decrease in particle strength. As the outer surface was hardened by the heat of compression, the stem-shaped fine powder reassembly, which was not easily dried inside the fine powder reassembly, was discharged.

Republic of Korea Patent Publication No. 2014-0063457

The present invention is to solve the problems of the prior art as described above, by increasing the drying speed of the stem-type fine powder reassembly to improve the drying efficiency, thereby reducing the physical properties of the fine powder reassembly, the particle strength decrease and the resulting amount of re-pulverization It is to provide a method for preparing a superabsorbent polymer capable of preventing an increase in water absorption.

In order to achieve the above object, the present invention,

preparing a water-containing gel polymer by subjecting a monomer composition containing a water-soluble ethylenically unsaturated monomer and a polymerization initiator to thermal polymerization or photopolymerization;

drying and pulverizing the water-containing gel polymer to classify into fine powder having a particle size of 150 μm or less and normal particles having a particle size of more than 150 μm and less than 850 μm;

mixing the fine powder with water and reassembling it to prepare a reassembled fine powder;

preparing a compressed fine powder reassembly by pressing and cutting the fine powder reassembly;

Drying and pulverizing the compressed fine powder reassembly to classify into regranulated fine powder having a particle size of 150 μm or less and regranulated normal particles having a particle size of more than 150 μm and 850 μm or less; and

mixing the reassembly normal particles with the normal particles;

It provides a method for producing a superabsorbent polymer comprising a.

The manufacturing method of the superabsorbent polymer according to the present invention can reduce energy during drying by reducing the amount of water used when reassembling the fine powder.

In addition, the strength of the fine powder reassembly can be improved by using the fine powder reassembly pressing process.

In addition, the load of the basic resin dryer can be reduced by using a drying process dedicated to reassembly of the fine powder.

In addition, by using a drying process dedicated to reassembly of fine powders, overdrying of the reassembled fine powders can be prevented, thereby minimizing deterioration in physical properties.

In addition, the amount of non-pulverized generation can be minimized by using a grinding machine dedicated to reassembly of fine powders, and the amount of circulation of fine powders in the entire process can be reduced through a process dedicated to reassembly of fine powders.

1 is a process diagram schematically showing a manufacturing process of a conventional superabsorbent polymer.
2 is a process diagram schematically illustrating a manufacturing process of a superabsorbent polymer according to an embodiment of the present invention.
FIG. 3 is a photograph of observing the compressed reassembly of fine powder discharged through the discharge port after being compressed and cut by a chopper equipped with a blade during the manufacture of the reassembly of fine powder according to Example 1-1.
FIG. 4 is a photograph of observing the compressed reassembled powder discharged through the discharge port after being compressed by a meat chopper not provided with a blade during the manufacture of the reassembled powder according to Comparative Example 1-1.
5 is a graph showing temperature changes at each dryer location during drying of the compressed fine powder reassembly in Example 1-1 and Comparative Example 1-1.
6 is a graph observing changes in moisture content (M/C) for each dryer position during drying of the compressed fine powder reassembly in Example 1-1 and Comparative Example 1-1.
7 is a photograph of the reassembled compressed fine powder obtained according to Example 1-2 observed with a scanning electron microscope.
8 is a photograph of the reassembled compressed fine powder obtained according to Comparative Example 1-2 observed with a scanning electron microscope.
9 is a photograph of the reassembled compressed fine powder obtained according to Comparative Examples 1-3 observed with a scanning electron microscope.

Terms used in this specification are only used to describe exemplary embodiments, and are not intended to limit the present invention. Singular expressions include plural expressions unless the context clearly dictates otherwise. In this specification, terms such as "comprise", "comprise" or "having" are intended to indicate that there is an embodied feature, step, component, or combination thereof, but one or more other features or steps; It should be understood that the presence or addition of components, or combinations thereof, is not previously excluded.

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

Hereinafter, a method for preparing a superabsorbent polymer according to specific embodiments of the present invention will be described in more detail.

A method for producing a superabsorbent polymer according to an embodiment of the present invention,

preparing a water-containing gel polymer by subjecting a monomer composition containing a water-soluble ethylenically unsaturated monomer and a polymerization initiator to thermal polymerization or photopolymerization (step 1);

Drying and pulverizing the water-containing gel polymer to classify into fine powder having a particle size of 150 μm or less and normal particles having a particle size of more than 150 μm and less than 850 μm (step 2);

Mixing the fine powder with water and reassembling it to prepare a reassembled fine powder (step 3);

preparing a compressed fine powder reassembly by pressing and cutting the fine powder reassembly (step 4);

Drying and pulverizing the compressed fine powder re-granulated body to classify into re-granulated fine powder having a particle size of 150 μm or less and re-granulated normal particles having a particle size of more than 150 μm and 850 μm or less (step 5); and

and mixing the reassembled normal particles with the normal particles (step 6).

For reference, in the specification of the present invention, "polymer" or "polymer" means a state in which water-soluble ethylenically unsaturated monomers are polymerized, and may cover all water content ranges, all particle diameter ranges, and all surface crosslinking states or processing states. can Among the polymers, a polymer having a water content (moisture content) of about 40% by weight or more in a state after polymerization and before drying may be referred to as a water-containing gel polymer. In addition, among the polymers, a polymer having a particle size of 150 μm or less, more specifically, less than 150 μm may be referred to as “fine powder”.

In addition, "superabsorbent polymer" means the polymer itself, depending on the context, or a condition suitable for commercialization through additional processes such as surface crosslinking, fine powder reassembly, drying, pulverization, classification, etc. It is used to cover everything.

2 is a process diagram schematically illustrating a manufacturing process of a superabsorbent polymer according to an embodiment of the present invention. 2 is only an example for explaining the present invention, but the present invention is not limited thereto. Referring to FIG. 2 , each manufacturing step of the superabsorbent polymer will be described in detail below.

Step 1 in the manufacturing method of the superabsorbent polymer of the present invention is a step of preparing a water-containing gel polymer.

The water-containing gel polymer may be prepared by subjecting a monomer composition containing a water-soluble ethylenically unsaturated monomer and a polymerization initiator to thermal polymerization or photopolymerization.

The monomer composition, which is a raw material of the superabsorbent 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 preparation of the superabsorbent polymer may be used without particular limitation. Any one or more monomers selected from the group consisting of anionic monomers and their salts, nonionic hydrophilic monomers, amino group-containing unsaturated monomers, and quaternary products thereof may 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- (meth)acrylamide-2-methyl propane sulfonic acid anionic monomers and salts thereof; (meth)acrylamide, N-substituted (meth)acrylate, 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, methoxypolyethylene glycol (meth)acrylate or polyethylene glycol ( meth) acrylate monomer containing nonionic hydrophilicity; And at least one selected from the group consisting of (N, N) -dimethylaminoethyl (meth) acrylate or (N, N) -dimethylaminopropyl (meth) acrylamide amino group-containing unsaturated monomers and quaternaries thereof. can

More preferably, acrylic acid or a salt thereof, for example, an alkali metal salt such as acrylic acid or a sodium salt thereof, may be used. By using such a monomer, it is possible to manufacture a superabsorbent polymer having more excellent physical properties. When the alkali metal salt of acrylic acid is used as a monomer, acrylic acid may be neutralized 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, based on the monomer composition including the raw material of the superabsorbent polymer and the solvent. An appropriate concentration may be obtained in consideration of time, reaction conditions, and the like. However, if the concentration of the monomer is too low, the yield of the superabsorbent polymer is low and economic problems may arise. Conversely, if the concentration is too high, a part of the monomer is precipitated or the pulverization efficiency of the polymerized water-containing gel polymer is low. Process problems may occur, and physical properties of the superabsorbent polymer may be deteriorated.

The polymerization initiator used during polymerization in the method for preparing the super absorbent polymer of the present invention is not particularly limited as long as it is generally used in the preparation of the super absorbent polymer.

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

As the photopolymerization initiator, any compound capable of forming radicals by light such as ultraviolet light may be used without limitation in its composition.

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) may be used at least one selected from the group consisting of. On the other hand, as a specific example of acylphosphine, 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. . More various photoinitiators are well described in "UV Coatings: Basics, Recent Developments and New Application (Elsevier 2007)" p115, a book by Reinhold Schwalm, and are not limited to the above examples.

The photopolymerization initiator may be included in a concentration of about 0.01 to about 1.0% by weight based on the monomer composition. If the concentration of the photopolymerization initiator is too low, the polymerization rate may be slowed down, and if the concentration of the photopolymerization initiator is too high, the molecular weight of the superabsorbent polymer may be small and physical properties may be non-uniform.

In addition, as the thermal polymerization initiator, at least one selected from the 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 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 ), and examples of the azo-based initiator include 2, 2-azobis (2-amidinopropane) dihydrochloride, 2 , 2-azobis- (N, N-dimethylene) isobutyramidine dihydrochloride (2,2-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), and the like. More various thermal polymerization initiators are well described in Odian's 'Principle of Polymerization (Wiley, 1981)', p203, and are not limited to the above examples.

The thermal polymerization initiator may be included in a concentration of 0.001 to 0.5% by weight based on the monomer composition. If the concentration of the thermal polymerization initiator is too low, additional thermal polymerization hardly occurs, and the effect of adding the thermal polymerization initiator may be insignificant. there is.

According to one embodiment of the present invention, the monomer composition may further include an internal crosslinking agent as a raw material of the superabsorbent polymer. The internal crosslinking agent may include a crosslinking agent having at least one ethylenically unsaturated group while having at least one functional group capable of reacting with the water-soluble substituent of the water-soluble ethylenically unsaturated monomer; 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 carbon atoms, bismethacrylamide, poly(meth)acrylate of a polyol having 2 to 10 carbon atoms, or poly(meth)allyl ether of a polyol having 2 to 10 carbon atoms, etc. and, more specifically, N,N'-methylenebis(meth)acrylate, ethyleneoxy(meth)acrylate, polyethyleneoxy(meth)acrylate, propyleneoxy(meth)acrylate, glycerin diacrylate , At least one selected from the group consisting of glycerin triacrylate, trimethylol triacrylate, triallylamine, triaryl cyanurate, triallyl isocyanate, polyethylene glycol, diethylene glycol and propylene glycol may be used.

The internal crosslinking agent may be included in a concentration of 0.01 to 0.5% by weight based on the monomer composition to crosslink the polymerized polymer.

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

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

The solvent that can be used at this time can be used without limitation in 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 At least one selected from ether, toluene, xylene, butyrolactone, carbitol, methylcellosolveacetate, and N,N-dimethylacetamide may be used in combination.

The solvent may be included in a residual amount excluding the components described above with respect to the total content of the monomer composition.

On the other hand, the method of forming a water-containing gel polymer by thermal polymerization or photopolymerization of such a monomer composition is also not particularly limited as long as it is a commonly used polymerization method.

Specifically, the polymerization method is largely divided into thermal polymerization and photopolymerization according to the polymerization energy source. In the case of normal thermal polymerization, it can be carried out in a reactor having an agitation shaft such as a kneader, and in the case of photopolymerization, a movable Although it may proceed in a reactor equipped with a conveyor belt, the above polymerization method is an example, and the present invention is not limited to the above polymerization method.

For example, as described above, the water-containing gel polymer obtained by thermal polymerization by supplying hot air to a reactor such as a kneader equipped with an agitation shaft or heating the reactor is directed to the outlet of the reactor according to the shape of the agitation shaft provided in the reactor. The discharged water-containing gel polymer may be in the form of several centimeters to several millimeters. Specifically, the size of the obtained water-containing gel polymer may vary depending on the concentration and injection speed of the monomer composition to be injected, and a water-containing gel polymer having a weight average particle diameter of 2 to 50 mm can usually be obtained.

In addition, as described above, when photopolymerization is performed in a reactor equipped with a movable conveyor belt, the form of a water-containing gel polymer usually obtained may be a sheet-like water-containing gel polymer having the width of a belt. At this time, the thickness of the polymer sheet varies depending on the concentration and injection rate of the monomer composition to be injected, but it is preferable to supply the monomer composition so that a polymer 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, production efficiency is low, which is undesirable. When the thickness of the polymer on the sheet exceeds 5 cm, the polymerization reaction does not occur evenly over the entire thickness due to the excessively thick thickness. may not be

At this time, the water-containing gel polymer obtained in this way may have a normal moisture content of 40 to 80% by weight. Meanwhile, throughout the present specification, "moisture content" refers to a value obtained by subtracting the weight of the dry polymer from the weight of the hydrogel polymer as the content of moisture with respect to the total weight of the hydrogel polymer. Specifically, it is defined as a value calculated by measuring the weight loss due to moisture evaporation in the polymer during drying 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 180 ° C and then maintaining it at 180 ° C. The total drying time is set to 20 minutes including 5 minutes of the temperature raising step, and the moisture content is measured.

According to one embodiment of the invention, a coarse grinding process may be selectively further performed on the hydrogel polymer obtained above.

At this time, the grinder used in the coarse grinding process is not limited in configuration, but specifically, a vertical pulverizer, a turbo cutter, a turbo grinder, a rotary cutter mill), cutter mill, disc mill, shred crusher, crusher, chopper and disc cutter It may include any one, but is not limited to the above-described examples.

At this time, in the coarsely pulverizing step, the hydrogel polymer may be pulverized to have a particle diameter of about 2 to about 20 mm.

Coarsely pulverizing to a particle size of less than 2 mm is not technically easy due to the high water content of the hydrogel polymer, and also may cause aggregation between the pulverized particles. On the other hand, when coarsely pulverized with a particle diameter greater than 20 mm, the effect of increasing the efficiency of the subsequent drying step may be insignificant.

Next, in the method for producing a superabsorbent polymer according to an embodiment of the present invention, step 2 is a step of drying and pulverizing the hydrogel polymer prepared in step 1 to classify into fine powder and normal particles.

The drying process is performed on the water-containing gel polymer that was coarsely pulverized in step 1 or immediately after polymerization that was not subjected to the coarse 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 risk of deterioration in the physical properties of the finally formed super absorbent polymer, and when the drying temperature exceeds 250 ° C, only the surface of the polymer is excessively dried, resulting in a subsequent pulverization process There is a concern that fine powder may be generated in the water, and physical properties of the finally formed superabsorbent polymer may be deteriorated. 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, the drying time may be about 20 to about 90 minutes in consideration of process efficiency, but is not limited thereto.

As long as the drying method of the drying step is also commonly used as a drying process for hydrogel polymers, the composition may be selected and used without limitation. Specifically, the drying step may be performed by a method such as hot air supply, infrared ray irradiation, microwave irradiation, or ultraviolet ray irradiation. The water content of the polymer after the drying step may be about 0.1 to about 10% by weight.

Next, a pulverization process is performed on the dried polymer obtained through such a drying step.

The polymer powder obtained after the grinding step may have a particle size of about 150 to about 850 μm. The grinder used for grinding 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 mill. A jog mill or the like may be used, but the present invention is not limited to the above examples.

In order to manage the physical properties of the superabsorbent polymer powder produced as a final product after such a pulverization step, the polymer powder obtained after pulverization is generally classified according to the particle size. Preferably, a step of classifying into particles having a particle diameter of 150 μm or less and particles having a diameter of more than about 150 μm and less than or equal to 850 μm is performed.

In the specification of the present invention, fine particles having a particle size of less than a certain particle size, that is, about 150 μm or less, are referred to as superabsorbent polymer fine powder, SAP fine powder, or fines (fine powder), and the particle size is more than 150 μm and 850 μm or less. Particles are referred to as normal particles. The fine powder may be generated during the polymerization process, the drying process, or the pulverization step of the dried polymer. When the fine powder is included in the final product, it is difficult to handle and deteriorates physical properties such as exhibiting a gel blocking phenomenon, so it is not included in the final resin product. It is preferable to exclude it so that it is not included or to reuse it so that it becomes normal particles.

For example, a reassembly process of aggregating the fine particles to a normal particle size may be performed. In the reassembly process, a reassembly process in which fine particles are aggregated in a wet state is generally performed to increase cohesive strength. At this time, the higher the moisture content of the fine powder, the higher the cohesive strength of the fine powder, but too large a lump of reassembly may occur during the reassembly process, resulting in problems during process operation. After that, it is often crushed again into fine powder. In addition, physical properties such as water retention capacity (CRC) and absorbency under pressure (AUP) of the finely reassembled product obtained in this way are lower than those of normal particles, resulting in a decrease in the quality of the superabsorbent polymer.

Accordingly, step 3 in the method for manufacturing a superabsorbent polymer according to an embodiment of the present invention is a step of preparing a reassembly of fine powder using the fine powder classified in step 2 above.

Specifically, the fine powder having a particle size of 150 μm or less, classified in step 2, is mixed with water, and reassembled to prepare a reassembled fine powder.

At this time, the water may be included in an amount such that the fine powder can be reassembled in a wet state, specifically, 10 to 150 parts by weight, preferably 10 to 80 parts by weight, more preferably 100 parts by weight based on 100 parts by weight of the fine powder may be 20 to 60 parts by weight. The water is evaporated in the reassembly process after forming the fine powder reassembly. At this time, if the water content is less than 10 parts by weight, the fine powder and water are mixed with the fine powder due to the fast absorption rate of the fine powder to evenly disperse a small amount of water. Since it is difficult, there is a concern that the uniformity of the fine powder reassembly may be deteriorated. In addition, when the moisture content of the fine powder reassembly is reduced, hard lumps may be formed during the subsequent compression process, resulting in deterioration in operational stability of the compression process. In addition, if the water content exceeds 150 parts by weight, the stickiness of the pulverized material assembly increases during the mixing process, preventing normal mixing, and the amount of water to be evaporated increases during the drying process, which increases the load of the dryer. .

Also, according to one embodiment of the present invention, a water-soluble polymer may be selectively further used as an additive when the fine powder and water are mixed.

Examples of the water-soluble polymer include synthetic polymers such as polyethylene glycol, polyethylene oxide, polyvinylpyrrolidone, polyvinyl alcohol, polyacrylamide, polyacrylic acid, polystyrenesulfonic acid, polysilicic acid, polyphosphoric acid, and polyethylenesulfonic acid. synthetic polymers such as acid, polyvinylphenol, polyvinylphenylsulfonic acid, polyethylenephosphoric acid, polyethyleneamide, polyamine or polyamideamine; or non-synthetic polymers such as starch, rubber, cellulose, etc., any one or a mixture of two or more of these may be used. These water-soluble polymers play a role in improving mixing stability and uniformity by promoting a lubricating action of the fine powder reassembly in the mixing mixer. Among the above-described water-soluble polymers, polyethylene glycol may be more preferable due to chemical stability, harmlessness to the human body, excellent dispersion/lubrication effect, and economical characteristics.

In addition, the polyethylene glycol may have a weight average molecular weight of 2,000 to 200,000 g/mol, more preferably 4,000 to 100,000 g/mol. When the molecular weight of polyethylene glycol is less than 2,000 g/mol, the lubricating action may decrease, and when it exceeds 200,000 g/mol, solubility in water may decrease.

The water-soluble polymer may be used in an amount of 0.01 to 5 parts by weight, more preferably 0.01 to 1 part by weight, based on 100 parts by weight of the fine powder. If the content of the water-soluble polymer is less than 0.01 part by weight, it is difficult to obtain the effect of improving the mixing stability and uniformity of the granulated reassembly according to the use of additives, and if the content of the water-soluble polymer exceeds 1 part by weight, the surface tension and discoloration of the final product are lowered. There is a risk of performance degradation.

When the above additives are further used, according to an embodiment of the present invention, an aqueous additive solution is prepared by mixing water and an additive, and the mixture of the fine powder is mixed with the aqueous additive solution, thereby improving the mixing stability and uniformity of the fine powder reassembly. can be obtained.

Next, in the method for manufacturing a superabsorbent polymer according to an embodiment of the present invention, step 4 is a step of preparing a compressed fine powder reassembly using the fine powder reassembly prepared in step 3 above.

The compressed fine powder reassembly may be prepared in the form of secondary particles in the form of stems by pressing and cutting the fine powder reassembly prepared in step 3.

The pressing process for the reassembly of the fine powder may be performed using a conventional extruder such as a meat chopper, and the cutting process is installed at the end of the pressing process, for example, at a hole plate discharge port. It may be performed by a cutter such as a blade or a scraper.

For example, in the case of using a meat chopper in which a blade having two blades is installed at the hole plate discharge port, first, when the fine powder reassembly is put into the meat chopper, the fine powder reassembly is compressed by the meat chopper, and the compressed fine powder reassembly is formed into a hole. It is cut into particles by the blade located on the side of the plate discharge port. At this time, the reassembled compressed fine powders, which are cut into particles, are recombined due to the adhesiveness at the cut site to become secondary particles in the form of stems. In a conventional manufacturing method of granular powder using only a meat chopper, the compressed granular powder is discharged in the form of a stem. On the other hand, in the case of the present invention, a plurality of primary particles cut into single particles are secondary particles recombined in a stem shape by adhesion on the cut surface. Due to this difference, in the conventional method, drying proceeds on the stem-shaped particle surface during the subsequent drying process, so the drying rate is slow and the drying efficiency is low, whereas in the present invention, the particles constituting the stem-shaped secondary particles during the drying process As the recombination site between them is cut off, it is separated into primary particles on a single particle. Accordingly, the drying speed may be increased and the drying efficiency may be increased.

Next, in the method for manufacturing a superabsorbent polymer according to an embodiment of the present invention, step 5 is to dry and pulverize the compressed fine powder reassembly prepared in step 4, which has been converted into secondary particles in a stem shape, to obtain fine reassembly (hereinafter referred to as 'reassembly'). It is a step of classifying into re-assembly normal particles.

The drying process may be performed using a conventional drying device, but according to an embodiment of the present invention, it may be performed using a paddle type dryer or a forced circulation type dryer. When the drying process is performed in these dryers, when the secondary granulated stem-shaped compressed fine powder reassembly flows, for example, in the case of a paddle-type dryer, recombination is easily broken by the force generated during paddle flow, making it easier It can be primary granulated. As a result, it is possible to further increase the drying rate and drying efficiency of the compressed fine powder reassembly.

In addition, the drying process may be performed at a temperature of 120 to 220 ℃. During the drying process, when the temperature is less than 120° C., the drying time becomes longer, and when the temperature exceeds 220° C., there is a risk of deterioration in physical properties due to deterioration of the reassembly of the fine powder. More preferably, at a temperature of 150 to 200° C., the water content in the fine powder reassembly may be 1% by weight or less.

In addition, it is preferable to increase the temperature in the later part of the drying process compared to the initial part of the drying process within the above temperature range because the drying efficiency can be further increased. Specifically, it is more preferable that the temperature at the beginning of the drying process, specifically, at the inlet of the dryer is 120 to 160 ° C, and at the end of the drying process, specifically, at the outlet at the rear end of the dryer is 150 to 200 ° C, since drying efficiency can be increased.

Also, in the drying step, the temperature raising means for drying is not limited in its configuration. Specifically, a 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. Specific heat sources that can be used include steam, electricity, ultraviolet rays, infrared rays, and the like, and a heated thermal fluid may also be used.

In addition, the drying process may be performed so that the moisture content in the dried compressed fine powder reassembly is 1% by weight or more, more specifically, 1 to 2% by weight. When the moisture content in the dried compressed fine powder reassembly is less than 1% by weight, there is a risk of deterioration in physical properties of the fine powder reassembly.

By the above drying process, the fine powder reassembly in the form of stems is converted into primary particles in the form of single particles.

The compressed fine powder reassembly obtained after the drying process has a high cohesive strength with a low rate of re-crushing into fine powder after passing through the crushing step.

Specifically, in the compressed fine powder reassembly, the weight ratio of fine powder having a particle size of 150 μm or less after grinding is less than about 15% by weight, preferably less than about 13.5% by weight, more preferably less than about 13.5% by weight, based on the weight of the entire compressed fine powder reassembly body. It may be less than 10% by weight.

In addition, the compressed fine powder reassembly obtained after grinding is classified into particles having a particle size of 150 μm or less, particles having a particle size of more than 150 μm and less than or equal to 300 μm, particles greater than 300 μm and less than or equal to 600 μm, particles greater than 600 μm and less than or equal to 850 μm, and particles having a particle size of greater than 850 μm When classified into particles, the ratio of the particles having a size greater than 600 μm and less than 850 μm may be 30% by weight or more, and more specifically, 33 to 40% by weight.

In addition, the water retention capacity (CRC) measured according to the EDANA method WSP 241.3 of the compressed fine powder reassembly having a particle size of more than 300 μm and less than 600 μm is 33.0 to 39.0 g / g, and the absorption rate by the Vortex method is 40 less than a second In the measurement by the vortex method, 50 ml saline was added to a 100 ml beaker with a magnetic stir bar, and the stirring speed of the magnetic stir bar was set to 600 rpm using a stirrer, and then 2.0 g of the fine powder reassembly was added to the stirred saline solution. At the same time as adding, measure the time and measure the time (unit: seconds) taken until the vortex disappears in the beaker as the vortex time. The lower limit of the absorption rate is not particularly limited, but may be about 20 seconds or more, or about 30 seconds or more.

In addition, the compressed fine powder reassembly has a moisture content of 30% or less, and can exhibit excellent particle strength despite having such a low moisture content.

Next, the dried compressed fine powder reassembly is pulverized and classified.

The pulverization may be performed so that the particle size of the dried compressed fine powder reassembly is greater than 150 μm and less than 850 μm. The grinder used for grinding 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 mill. A jog mill or the like may be used, but the present invention is not limited to the above examples.

In order to manage the physical properties of the superabsorbent polymer powder to be finalized after such a pulverization step, the polymer powder obtained after pulverization is generally classified according to the particle size. Preferably, a step of classifying into unrefined flour having a particle diameter of 150 μm or less and re-granular normal particles having a particle diameter of more than 150 μm and less than 850 μm are performed.

Next, in the method for manufacturing a superabsorbent polymer according to an embodiment of the present invention, step 6 is a step of mixing the reassembled normal particles classified in step 5 with the normal particles prepared in step 2.

Specifically, after the classification in step 5, the re-aggregated normal particles having a particle diameter of 150 μm or less are circulated to the fine powder reassembly process, and the reassembly normal particles having a particle diameter of more than 150 μm and less than 850 μm are previously prepared in step 2 Mix with normal particles. In addition, after the mixing process, the surface crosslinking process may be selectively performed by additionally introducing the reassembled normal particles and the normal particles into a surface crosslinking mixer.

The surface crosslinking is a step of increasing the crosslinking density near the surface of the superabsorbent polymer particle in relation to the crosslinking density inside the particle. Generally, the surface crosslinking agent is applied to the surface of the superabsorbent polymer particles. Accordingly, 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 cross-linked superabsorbent polymer particles have a higher degree of cross-linking in the vicinity of the surface than in the inside.

At this time, as long as the surface crosslinking agent is a compound capable of reacting with a functional group of a polymer, there is no limitation in its configuration.

Preferably, a polyhydric alcohol compound as the surface cross-linking agent in order to improve the properties of the resulting superabsorbent polymer; epoxy compounds; polyamine compounds; haloepoxy compounds; condensation products of haloepoxy compounds; oxazoline compounds; mono-, di- or polyoxazolidinone compounds; cyclic urea compounds; polyvalent metal salts; And at least one selected from the group consisting of alkylene carbonate compounds may be used.

Specifically, examples of polyhydric alcohol compounds 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 At least one selected from the group consisting of 1,2-cyclohexanedimethanol may be used.

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

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

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

The amount of the surface crosslinking agent added may be appropriately selected depending on the type of the surface crosslinking agent added or reaction conditions, but is usually about 0.001 to about 5 parts by weight, preferably about 0.01 to about 5 parts by weight, based on 100 parts by weight of the polymer. 3 parts by weight, more preferably from about 0.05 to about 2 parts by weight may be used.

If the content of the surface crosslinking agent is too small, surface crosslinking reaction hardly occurs, and when it exceeds 5 parts by weight with respect to 100 parts by weight of the polymer, excessive surface crosslinking reaction may cause deterioration in water absorption capacity and physical properties. .

By heating the polymer particles to which the surface crosslinking agent is added, the surface crosslinking reaction and drying can be achieved simultaneously.

The means for raising the temperature for the surface crosslinking reaction is not particularly limited. It can be heated by supplying a heat medium or directly supplying a heat source. At this time, as the type of heat medium that can be used, steam, hot air, heated fluids such as hot oil, etc. can be used, but the present invention is not limited thereto, and the temperature of the heat medium supplied depends on the means of the heat medium, the rate of temperature increase and the temperature rise. It can be selected appropriately in consideration of the target temperature. On the other hand, as the directly supplied heat source, heating through electricity or heating through gas may be mentioned, but the present invention is not limited to the above-described examples.

In addition, after the surface crosslinking, surface crosslinked fine powder having a particle size of 150 μm or less and surface crosslinked normal particles having a particle size of more than 150 μm and less than 850 μm are classified, and the surface crosslinked fine powder having a particle size of 150 μm or less is a fine powder material. It is reintroduced to the process for granulation, and the surface cross-linked normal particles can be commercialized and used.

The superabsorbent polymer prepared by the above method is reassembled by mixing water with respect to fine powder having a particle diameter of 150 μm or less among polymers obtained by polymerizing water-soluble ethylenically unsaturated monomers containing acidic groups and at least partially neutralizing the acidic groups. A superabsorbent polymer obtained by surface cross-linking of compressed fine powder reassembly, and has a water retention capacity (CRC) of 33.0 to 39.0 g/g measured according to EDANA method WSP 241.3; 0.7 psi Pressure Absorption Capacity (AUP) of 20.0 to 25.0 g/g, measured according to EDANA method WSP 241.3; It is characterized in that the absorption rate by the vortex method is 100 seconds or less, and the apparent density (B / D) is 0.6 to 0.7 g / cm ³ .

In the superabsorbent polymer of one embodiment, the polymer is obtained by polymerizing a water-soluble ethylenically unsaturated monomer containing an acidic group and at least a portion of the acidic group is neutralized. is the same as described in

In addition, in the super absorbent polymer of one embodiment of the present invention, the fine powder refers to particles having a particle size of 150 μm or less among the polymers, and regardless of the step of generating the fine powder or surface crosslinking, all processes of the super absorbent polymer, For example, it may cover all of those generated in a polymerization process, a drying process, a pulverization process of a dried polymer, or a surface crosslinking process.

The compressed fine powder reassembly may be reassembled by mixing the fine powder with water, or may be reassembled by further mixing a water-soluble polymer in addition to water. A more detailed description of the water-soluble polymer is the same as described above in the method for preparing the superabsorbent polymer.

The superabsorbent polymer obtained by surface crosslinking the reassembled compressed fine powder reassembly as described above has a water retention capacity (CRC) of about 33.0 to about 39.0 g/g, or about 34.0 to about 38.0 g/g, measured according to EDANA method WSP 241.3. can be Further, the 0.7 psi Pressure Absorption Capacity (AUP) measured according to EDANA method WSP 241.3 may be from about 20.0 to about 25.0 g/g, or from about 21.0 to about 25.0 g/g.

In addition, the superabsorbent polymer may have an absorption rate of about 100 seconds or less or about 95 seconds or less by a vortex method. The measurement by the vortex method is the same as described above except that the superabsorbent polymer is used instead of the fine powder reassembly.

Hereinafter, the present invention will be described in more detail based on examples. However, the following examples are merely illustrative of the present invention, and the contents of the present invention are not limited by the following examples. In the following Examples and Comparative Examples, "%" and "parts" indicating content are based on weight unless otherwise specified.

<Example>

Preparation of superabsorbent polymer particles

Preparation Example 1

A monomer mixture having a monomer concentration of 50% by weight was prepared by mixing 100 g of acrylic acid, 0.3 g of polyethylene glycol diacrylate as a crosslinking agent, 0.033 g of sodium persulfate as an initiator, 38.9 g of caustic soda (NaOH), and 103.9 g of water. did

Thereafter, the monomer mixture was put on a continuously moving conveyor belt, and ultraviolet light was irradiated (irradiation amount: 2mW/cm ² ) to perform UV polymerization for 2 minutes to obtain a water-containing gel polymer.

The hydrogel polymer was pulverized with a meat chopper (hole size: 10 mm) to obtain a coarsely pulverized hydrogel polymer. It is dried for 1 hour in a hot air dryer at 170 ° C., pulverized with a pin mill grinder, and then classified with a standard ASTM sieve to form normal particles having a particle size of more than 150 μm and less than 850 μm, and having a particle size of less than 150 μm. Finely divided particles were obtained.

Manufacturing examples of finely ground reassembly

Example 1-1

Of the superabsorbent polymer prepared in Preparation Example 1, 12 kg/h of fine powder having a particle size of 150 μm or less and 0.5% by weight of PEG (polyethylene gylcol, MW=6,000 g/mol) were dissolved in water at a flow rate of 4.8 kg/h While supplying to a continuous mixing mixer, it was operated at a stirring speed of 1,500 rpm to prepare a fine powder reassembly. The pulverized ash assembly was put into a meat chopper equipped with a blade having two cutting edges at a hole plate discharge port, and compression was performed. The compressed fine powder reassembly was cut into particles by the blade, and some of the particles were recombined due to the adhesiveness of the cut portion and discharged in the form of a stem. This was put into a forced circulation dryer and dried at a temperature of 180 ° C. for 60 minutes to recover the compressed fine powder reassembly.

Comparative Example 1-1

Of the superabsorbent polymer prepared in Preparation Example 1, 12 kg/h of fine powder having a particle size of 150 μm or less and 0.5% by weight of PEG (polyethylene gylcol, MW=6,000 g/mol) were dissolved in water at a flow rate of 4.8 kg/h While supplying to a continuous mixing mixer, it was operated at a stirring speed of 1,500 rpm to prepare a fine powder reassembly. The reassembly of the fine powder was put into a forced circulation dryer without pressing, and dried at 180° C. for 60 minutes to recover the reassembly of the fine powder.

Comparative Example 1-2

Of the superabsorbent polymer prepared in Preparation Example 1, 12 kg/h of fine powder having a particle size of 150 μm or less and water were supplied to the continuous mixing mixer at a flow rate of 14.4 kg/h while operating at a stirring speed of 1,500 rpm to reassemble the fine powder. manufactured. The reassembly of the fine powder was put into a forced circulation dryer without pressing, and dried at 180° C. for 60 minutes to recover the reassembly of the fine powder.

Example 2

Of the superabsorbent polymer prepared in Preparation Example 1, 12 kg/h of fine powder having a particle size of 150 μm or less and 0.5% by weight of PEG (polyethylene gylcol, MW=6,000 g/mol) were dissolved in water at a flow rate of 4.8 kg/h While supplying to a continuous mixing mixer, it was operated at a stirring speed of 1,500 rpm to prepare a fine powder reassembly.

The reassembly of the fine powder was put into a meat chopper equipped with a blade having two cutting edges at the outlet of the hole plate, and compression was performed. The compressed fine powder reassembly was cut into particles by the blade, and some of the particles were recombined due to the adhesiveness of the cut portion and discharged in the form of a stem. This was continuously put into a paddle-type dryer having an internal volume of 77 L, a total length of 180 cm, and a paddle diameter of 16 cm, and drying was performed at a temperature of 180 ° C. As the drying process proceeded inside the dryer, the stem-shaped compressed fine powder reassembly was pulverized into particles by the paddle flow. On the other hand, the temperature inside the dryer at the initial stage of inputting the stem-type fine powder reassembly into the dryer was 120 ° C, and the temperature at the outlet at the rear end of the dryer was 173 ° C. In addition, the moisture content of the compressed fine powder reassembly at the initial stage of drying was 27.5% by weight, the moisture content of the final dried product was 1.4% by weight, and the position of the dryer showing a moisture content of 5% by weight or less was found to be within 80 to 120 cm. The residence time of the compressed fine powder reassembly in the above section was found to be 0.92 hours.

Comparative Example 2

Mixing, pressing, and drying of the fine powder reassembly were performed in the same manner as in Example 1, except that the fine powder reassembly was pressed under the condition that there was no blade at the hole plate discharge port of the meat chopper. In the condition without the blade, the compressed fine powder reassembly was discharged in the form of a stem. This was continuously put into a paddle-type dryer having an internal volume of 77 L, a total length of 180 cm, and a paddle diameter of 16 cm, and drying was performed at a temperature of 180 ° C. As the stem-type compressed fine powder reassembly was dried inside the dryer, the stems were crushed and pulverized into particles. The moisture content of the dried initially compressed fine powder reassembly was 29.6% by weight, and the moisture content of the final dry product was 3.5% by weight. The position of the dryer showing a moisture content of less than 5% by weight was found to be within 120 to 150 cm. The residence time of the compressed fine powder reassembly in the section was found to be 1.42 hours.

Manufacturing Example of Super Absorbent Polymer

Example 3

After pulverizing the compressed fine powder reassembly prepared in Example 1-1 with a roll mill, it is classified with an ASTM standard standard mesh sieve to obtain reassembly fine powder having a particle size of 150 μm or less and normal particles of the reassembly having a particle diameter of more than 150 μm and less than 850 μm. classified as

0.2 g of poly(ethylene glycol) diglycidyl ether, 5 g of methanol, 4 g of water, and silica airgel in 100 g of a mixture of the classified normal particles of the reassembly and the normal particles prepared in Preparation Example 1 at a weight ratio of 20:80 After mixing with a surface crosslinking solution containing 0.01 g of (AeroZelTM, JIOS), a surface crosslinking reaction was performed at a temperature of 180° C. for 60 minutes to obtain a final superabsorbent polymer.

Comparative Example 3-1

A superabsorbent polymer was obtained in the same manner as in Example 3, except that the fine powder reassembly prepared in Comparative Example 1-1 was used instead of the fine powder reassembly prepared in Example 1-1.

Comparative Example 3-2

A superabsorbent polymer was obtained in the same manner as in Example 3, except that the fine powder reassembly prepared in Comparative Example 1-2 was used instead of the fine powder reassembly prepared in Example 1-1.

<Experimental Example 1>

Table 1 shows the results of the particle size distribution after crushing and classification by a roll mill in order to determine the crushing strength of the reassembly of the fine powder according to Example 1-1 and Comparative Examples 1-1 and 1-2. .

particle size distribution Example 1 Comparative Example 1-1 Comparative Example 1-2 weight% weight% weight% >850 μm 2.2 0.6 0.7 Below 850㎛ - above 600㎛ 33.7 24.8 32 Below 600㎛ - above 300㎛ 41.3 36.1 44.5 Below 300㎛ - above 150㎛ 13.3 18 15 ≤150 μm 9.5 20.5 7.9

As a result of the experiment, the fine powder reassembly of Comparative Example 1-2 with relatively high water consumption had a non-flour generation rate of 7.9% by weight, but the fine powder reassembly of Comparative Example 1-1 with reduced water consumption had a non-flour generation rate. It showed a tendency to increase 2.6 times to 20.5% by weight. However, the pulverized reassembly of Example 1 subjected to meat chopper compression showed a crushing strength similar to that of the pulverized reassembly of Comparative Example 1-2 with a non-flour generation rate of 9.5% by weight.

<Experimental Example 2>

In the manufacture of the reassembled pressed fine powder according to Example 1-1 and Comparative Example 1-1, the compressed fine powder discharged through the discharge port of the meat chopper was observed. The results are shown in Figures 3 and 4.

As a result of observation, the reassembly of the fine powder of Comparative Example 1-1 compressed through the meat chopper without blades was discharged in a continuous stem shape, whereas the compressed powder reassembly of Example 1-1 compressed through the meat chopper equipped with blades The fine powder reassembly was discharged in the form of secondary particles in the form of stems through recombination of the fine powder reassembly of the cut primary particles.

<Experimental Example 3>

In the manufacture of the fine powder reassembly according to Example 2 and Comparative Example 2, the dryer temperature and the moisture content of the dried material were measured according to the distance from the dryer raw material inlet, and the results are shown in Table 2 and FIGS. 5 and 6 below.

Distance from dryer raw material inlet (cm) 0 20 50 80 120 150 180 Example 2 with chopper blade dryer temperature
(℃) - 120 145 158 171 173 - Dry matter moisture content (% by weight) 27.5 16.34 10.48 7.93 3.48 2.64 1.37 Comparative Example 2 no chopper blade dryer temperature
(℃) - 121 140 147 159 170 - Dry matter moisture content (% by weight) 29.58 15.98 14.51 11.42 7.74 3.78 3.48

As a result of the experiment, at the beginning of drying, the drying speed of the compressed fine powder reassembly of Example 2 and Comparative Example 2 was similar regardless of the presence or absence of the chopper blade, but Example 2 using the chopper blade from 20 cm from the dryer raw material inlet was a comparative example. Compared to 2, the drying rate was faster and the moisture content was significantly reduced. As a result, in the case of Example 2, the compressed fine powder reassembly is cut into particles by the blade provided in the chopper, and the cut particles are discharged in the form of recombined stems due to the adhesiveness at the cut site. This is because the grinding speed into granules was increased by the paddle flow during the drying process. On the other hand, in the case of Comparative Example 2, the crushing speed of the stem into particles was slower than that of Example 2 because the reassembly of the compressed fine powder was introduced into the dryer without being cut by the meat chopper.

<Experimental Example 4>

In addition, in order to evaluate the physical properties of the compressed fine powder reassembly, after classifying the compressed fine powder reassembly prepared in Example 1 and Comparative Examples 1-1 and 1-2, a compressed fine powder material having a particle diameter of more than 300 μm and less than 600 μm The physical properties of the assembly were measured by the following method, and the results are shown in Table 3.

(1) Shape of the compressed fine powder reassembly: The particle shape was observed with the naked eye.

(2) CRC (Centrifugal Retention Capacity)

The water holding capacity of the compressed fine powder reassembly prepared in Example 1 and Comparative Examples 1-1 and 1-2 was measured. The measurement of water retention capacity was based on the EDANA method WSP 241.3. 0.2 g of a sample having a particle diameter of more than 300 μm and less than 600 μm among the prepared re-granulated powders is placed in a tea bag and precipitated in a 0.9% saline solution for 30 minutes. Then, after dehydration for 3 minutes with a centrifugal force of 250 G (gravity), the amount W ₂ (g) absorbed by the saline solution was measured. In addition, the mass W ₁ (g) at that time was measured after the same operation was performed without using the compressed fine powder re-granulated body.

Using each mass thus obtained, CRC (g/g) was calculated according to Equation 1 below to confirm the water retention capacity.

[Equation 1]

CRC(g/g) = {[W ₂ (g) - W ₁ (g)]/W ₀ (g)} - 1

In the above calculation formula 1,

W ₀ (g) is the initial weight (g) of the compressed fine powder reassembly,

W ₁ (g) is the weight of the device measured after dehydration at 250 G for 3 minutes using a centrifuge without using the compressed fine powder reassembly,

W ₂ (g) was measured including the compressed fine powder reassembly after immersing and absorbing the compressed fine powder reassembly in 0.9 wt% physiological saline solution at room temperature for 30 minutes, dehydrating at 250 G for 3 minutes using a centrifuge, is the weight of the device.

(3) Absorption rate (Vortex)

Absorption rate was measured for the compressed fine powder reassembly prepared in Example 1 and Comparative Examples 1-1 and 1-2. To measure the absorption rate, 50 ml saline was added to a 100 ml beaker with a magnetic bar. The stirring speed was set to 600 rpm using a stirrer. The time was measured at the same time that 2.0 g of the compressed fine powder reassembly was added to the saline solution being stirred. The time measurement was terminated when the vortex disappeared in the beaker.

Example 1
(Moisture content 28.6% compressed fine powder reassembly) Comparative Example 1-1
(Moisture content 28.6% differential reassembly) Comparative Example 1-2
(Moisture content 54.5% differential reassembly) Form of pressed fine powder reassembly dense particle shape A mixture of dense particles and individual particles dense particle shape CRC (g/g) 38.1 37.3 40.0 Vortex (sec) 40 37 47

Referring to Table 3, in the case of the compressed fine powder reassembly of Example 1 in which the fine powder reassembly process was performed according to the manufacturing method of the present invention, physical properties such as water retention capacity and absorption rate were comparable to those of Comparative Examples 1-1 and 1- Compared to 2, it was improved or showed an equivalent level.

<Experimental Example 5>

In addition, in order to evaluate the physical properties of the super absorbent polymer containing the fine powder reassembly according to the change in the fine powder reassembly process, the physical properties of the super absorbent polymer prepared in Example 3 and Comparative Examples 3-1 and 3-2 were evaluated in the Experimental Example. It was measured in the same way as in 4, and the results are shown in Table 4.

(1) Water retention capacity (CRC) and absorption rate (Vortex): Except for using the superabsorbent polymer prepared in Example 3 and Comparative Examples 3-1 and 3-2 instead of the compressed fine powder reassembly, the above experiment Water retention capacity and absorption rate were measured in the same manner as in Example 4, respectively.

(2) Absorbency under Pressure (AUP)

A stainless steel 400 mesh wire mesh was attached to the bottom of a plastic cylinder with an inner diameter of 60 mm. 0.90 g of the superabsorbent polymer according to Example 1 and Comparative Examples 1-1 and 1-2 was uniformly sprayed on the wire mesh under conditions of room temperature and 50% humidity, respectively, and a load of 4.83 kPa (0.7 psi) was applied thereon. The piston, which can be further imparted uniformly, has an outer diameter slightly smaller than 60 mm, and there is no gap with the inner wall of the cylinder, and the vertical movement is not hindered. At this time, the weight Wa (g) of the device was measured. A glass filter having a diameter of 90 mm and a thickness of 5 mm was placed inside a petro dish having a diameter of 150 mm, and physiological saline solution composed of 0.90% by weight of sodium chloride was leveled with the upper surface of the glass filter. One sheet of filter paper having a diameter of 90 mm was placed thereon. The measuring device was placed on a filter paper, and the liquid was absorbed for 1 hour under a load. After 1 hour, the measuring device was lifted up and its weight Wb (g) was measured. Then, the absorbency under pressure was calculated from Wa and Wb according to the following equation.

[Equation 2]

AUP (g/g) = [Wb (g) - Wa (g)]/mass of absorbent resin (g)

(3) Bulk density (B/D)

100 g of the super absorbent polymer prepared in Example 3 or Comparative Examples 3-1 and 3-2 was flowed through an orifice of a standard fluidity measuring device, received in a container having a volume of 100 ml, and the super absorbent polymer was shaved so that it was horizontal, After adjusting the volume of the super absorbent polymer to 100 ml, the weight of only the super absorbent polymer excluding the container was measured. In addition, the apparent density corresponding to the weight of the super absorbent polymer per unit volume was obtained by dividing the weight of only the super absorbent polymer by the volume of the super absorbent polymer, 100ml.

Example 3 Comparative Example 3-1 Comparative Example 3-2 CRC (g/g) 34.8 35.4 34.6 AUP (0.7 psi) 24.1 23.0 26.4 B/D (g/cm ³ ) 0.63 0.62 0.64 Vortex (sec) 75 55 79

Referring to Table 4, in the case of the superabsorbent polymer of Example 3, which was subjected to the fine powder reassembly process according to the manufacturing method of the present invention, compared to Comparative Examples 3-1 and 3-2, the superabsorbent polymer exhibited an equivalent or higher absorbency. was

Claims (14)

preparing a water-containing gel polymer by subjecting a monomer composition containing a water-soluble ethylenically unsaturated monomer and a polymerization initiator to thermal polymerization or photopolymerization;
drying and pulverizing the water-containing gel polymer to classify into fine powder having a particle size of 150 μm or less and normal particles having a particle size of more than 150 μm and less than 850 μm;
mixing the fine powder with water and reassembling it to prepare a reassembled fine powder;
preparing a compressed fine powder reassembly by pressing and cutting the fine powder reassembly;
Drying and pulverizing the compressed fine powder reassembly to classify into regranulated fine powder having a particle size of 150 μm or less and regranulated normal particles having a particle size of more than 150 μm and 850 μm or less; and
Including; mixing the reassembly normal particles with the normal particles,
The compressed fine powder reassembly is a secondary particle in which a plurality of primary particles cut into single particles are recombined in a stem shape by adhesion on the cut surface,
Drying of the compressed fine powder reassembly is performed using a paddle-type dryer or a forced circulation type dryer, and the compressed fine powder reassembly is recombined into a stem shape by the drying process and converted into secondary particles into primary particles in the form of single particles. A method for preparing a superabsorbent polymer.
According to claim 1,
Wherein the water is used in an amount of 10 to 150 parts by weight based on 100 parts by weight of the fine powder.
According to claim 1,
When the fine powder and water are mixed, a water-soluble polymer is further added, a method for producing a super absorbent polymer.
According to claim 3,
The water-soluble polymer is polyethylene glycol, polyethylene oxide, polyvinylpyrrolidone, polyvinyl alcohol, polyacrylamide, polyacrylic acid, polystyrenesulfonic acid, polysilicic acid, polyphosphoric acid, polyethylenesulfonic acid, polyvinyl A method for preparing a superabsorbent polymer comprising any one or two or more selected from the group consisting of phenol, polyvinylphenylsulfonic acid, polyethylenephosphoric acid, polyethyleneamide, polyamine, polyamideamine, starch, rubber, and cellulose.
According to claim 3,
The water-soluble polymer is polyethylene glycol, a method for producing a super absorbent polymer.
According to claim 3,
Wherein the water-soluble polymer is polyethylene glycol having a weight average molecular weight of 2,000 to 200,000 g/mol.
According to claim 3,
Wherein the water-soluble polymer is added in an amount of 0.01 to 5 parts by weight based on 100 parts by weight of the fine powder.
According to claim 1,
The compression is performed by an extruder, a method for producing a super absorbent polymer.
According to claim 1,
The cutting is performed by a blade or a scraper, a method for producing a super absorbent polymer.
delete According to claim 1,
Drying of the compressed fine powder reassembly is performed at 120 to 220 ° C., a method for producing a super absorbent polymer.
According to claim 1,
The drying of the compressed fine powder reassembly is carried out at a temperature of 120 to 160 ° C in the initial drying period and at a temperature of 150 to 200 ° C in the later drying period,
The manufacturing method of the superabsorbent polymer, wherein the drying temperature is higher in the late drying period than in the initial drying period.
delete According to claim 1,
The method of manufacturing a superabsorbent polymer further comprising the step of surface cross-linking the reassembled normal particles and a mixture of the normal particles.

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