KR102069831B1 - Manufacturing Method For Recombine Products Of Super Absorbent Polymer Fines - Google Patents

Abstract

The present invention relates to a method for producing a superabsorbent fine powder reassembly, and more particularly to a manufacturing method for producing a high-strength reassemble by selectively decomposing crosslinking after the surface treatment process. According to the present invention, a superabsorbent fine powder reassembly having a high fine powder cohesive strength and a superabsorbent polymer including the same may be prepared through an easy reassembly process.

Description

Manufacturing Method For Recombine Products Of Super Absorbent Polymer Fines

The present invention relates to a method for preparing a superabsorbent fine powder reassembly, and more particularly, to a method for producing a reassembled product having excellent densities and cohesive strength by selectively decomposing crosslinking only after a surface treatment process. .

Super Absorbent Polymer (SAP) is a synthetic polymer material capable of absorbing water of 500 to 1,000 times its own weight.Samsung (Super Absorbency Material) and AGM (Absorbent Gel) are developed for each developer. They are named differently. Such superabsorbent resins have been put into practical use as physiological tools, and are currently used in sanitary products such as paper diapers for children, horticultural soil repair agents, civil engineering, building index materials, seedling sheets, freshness-retaining agents and poultices in food distribution. It is widely used for materials such as dragons.

The absorption mechanism of the superabsorbent resin is based on the interaction between the expansion pressure due to the molecular expansion and crosslinking due to the penetration pressure due to the difference of the electrical attraction force represented by the charge of the polymer electrolyte, the affinity between water and the polymer electrolyte and the repulsive force between the polymer electrolyte ions. Is governed by That is, the absorbency of the superabsorbent resin depends on the affinity and molecular expansion described above, and the rate of absorption is largely dependent on the penetration pressure of the absorbent polymer itself.

As a method for producing such a superabsorbent polymer, a method by reverse phase suspension polymerization or a method by aqueous solution polymerization is known. Reverse phase suspension polymerization is disclosed, for example, in Japanese Patent Laid-Open No. 56-161408, Japanese Patent Laid-Open No. 57-158209, Japanese Patent Laid-Open No. 57-198714, and the like. Background Art A thermal polymerization method for breaking down and cooling a hydrogel polymer while cooling and a photopolymerization method for simultaneously performing polymerization and drying by irradiating ultraviolet rays or the like on a conveyor belt with a high concentration aqueous solution are known.

In addition, Japanese Patent Laid-Open No. 2004-250689 discloses a method for producing an absorbent molded article which polymerizes by irradiating light intermittently to an aqueous solution containing a photopolymerization initiator and a water-soluble ethylenically unsaturated monomer. In addition, Korean Patent No. 0330127 discloses a method for preparing a superabsorbent polymer in which a water-soluble ethylenically unsaturated monomer having a crosslinking agent is polymerized by irradiating ultraviolet rays in the presence of a radical-based photopolymerization initiator having a benzoyl group and a peroxide.

The hydrogel polymer obtained through the polymerization reaction as described above is made into powder through drying and grinding processes, and the superabsorbent polymer is prepared by surface treatment. The surface treatment process is usually performed by a surface crosslinking reaction in which a solution containing a surface crosslinking agent is sprayed onto the powder. At this time, due to the difference in the surface area due to the particle size distribution of the powder, unevenness of the surface treatment liquid distribution may be caused. Therefore, in order to minimize such non-uniformity, before the surface treatment step, the pulverized powder is subjected to a process of classifying according to the particle size, among which the super absorbent resin by selecting and surface-treated normal particles having a particle size of 150 to 850㎛ It will be prepared.

However, in the manufacturing process of the superabsorbent resin, fine powder having a particle size of less than 150 μm is inevitably generated, and in particular, the fine powder formed in the grinding process (hereinafter referred to as 'base resin fine powder') may be used during the polymerization of the hydrogel polymer. Although there is a method of recycling by addition, this method induces non-uniform polymerization or scatters light, thereby preventing polymerization and acting as a factor of deterioration of product properties.

In order to solve this problem, a method of mixing granules and water using a separate reassembler at a predetermined ratio and then drying them to reassemble them into normal particles having a particle size of 150 to 850 μm has been developed. Due to this is easily broken during the grinding process of the hydrogel polymer, the amount of fine powder is increased compared to the normal polymer.

On the other hand, the fine powder generated in the process of surface treatment of the normal particles having a normal particle size distribution (150 to 850㎛) (hereinafter referred to as 'product fine powder') because the cross-linking is strongly formed on the surface, the base resin described above In the case of reassembling by mixing with the fine powder, there is still a problem that the physical properties of the fine powder reassembly are deteriorated due to the weak cohesion between the base resin fine powder, the product fine powder, and the water that mediates them.

In order to solve this problem, a technique of treating with a predetermined amount of basic solution in the process of reassembling and mixing the base resin fine powder and the product fine powder is disclosed in Korean Patent Publication No. 2015-0032045, but the fine powder reassembly having improved physical properties is still present. It is a required situation.

Republic of Korea Patent Application Publication No. 2015-0032045 "Method for producing superabsorbent polymer"

Accordingly, the inventors of the present invention, after performing various studies, decompose the crosslinked bonds in the surface treatment process by basic treatment of only the product fine powder, thereby enhancing the cohesion between the base resin fine powder and the product fine powder and the water that mediates them. It was confirmed that this improved superabsorbent fine powder reassembly can be prepared to complete the present invention.

Accordingly, an object of the present invention is to reassemble a base resin fine powder and a product fine powder, but to provide a method for preparing a superabsorbent fine powder reassembly having improved physical properties of the fine powder reassembly.

Another object of the present invention is to provide a method for preparing a superabsorbent polymer by mixing the superabsorbent fine powder reassembled with enhanced physical properties with the hydrogel polymer in the drying and grinding steps after the polymerization process.

In order to achieve the above object, the present invention comprises the steps of: i) drying and pulverizing a hydrous gel polymer which is a water-soluble ethylenically unsaturated polymer; Ii) classifying the pulverized particles into a base resin fine powder having a particle size of less than 150 μm, normal particles of 150 μm or more and 850 μm or less, and large particles of more than 850 μm; Iii) surface-treating normal particles having a particle size of 150 µm or more and 850 µm or less; Iii) sorting the product fine powder having a particle size of less than 150㎛ generated during the surface treatment and treating it with a basic solution; And iii) mixing the basic processed product fine powder with the base resin fine powder of step ii) and reassembling the fine powder to prepare the superabsorbent fine powder reassembly.

The present invention also provides a method for preparing a superabsorbent polymer by mixing the fine powder reassembly prepared by the above method with the hydrogel polymer of the drying and grinding step after the polymerization process.

According to the present invention, a superabsorbent fine powder reassembly having a high fine powder cohesive strength and a superabsorbent polymer including the same may be prepared through an easy reassembly process.

1 is a Scanning Electron Microscope (SEM) image of a superabsorbent fine powder reassembly according to Example 1 of the present invention.
2 is a scanning electron microscope (SEM) image of the superabsorbent fine powder reassembly according to Comparative Example 1 of the present invention.
3 is a scanning electron microscope (SEM) image of the superabsorbent fine powder reassembly according to Comparative Example 2 of the present invention.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings so that those skilled in the art may easily implement the present invention. As those skilled in the art would realize, the described embodiments may be modified in various different ways, all without departing from the spirit or scope of the present invention.

In the method for preparing superabsorbent fine powder reassembly according to the present invention, the fine powder (base resin fine powder) and the fine powder (product fine powder) which have undergone the surface treatment process are reassembled by mixing with each other, but only the fine powder which has undergone the surface treatment process is selected. To a method of treating with an additive.

Looking more specifically at this,

Iii) drying and grinding the hydrogel polymer which is a water soluble ethylenically unsaturated polymer;

Ii) classifying the pulverized particles into a base resin fine powder having a particle size of less than 150 μm, normal particles of 150 μm or more and 850 μm or less, and large particles of more than 850 μm;

Iii) surface-treating normal particles having a particle size of 150 µm or more and 850 µm or less;

Iii) sorting the product fine powder having a particle size of less than 150㎛ generated during the surface treatment and treating it with a basic solution; And

V) mixing and reassembling the basic treated product fine powder with the base resin fine powder of step ii);

Characterized in that it comprises a.

As used herein, the term "superabsorbent polymer particles" is a dried and pulverized hydrous gel polymer. More specifically, the hydrogel polymer is a material having a size of 1 cm or more in the form of a hard jelly that has been polymerized and contains a large amount of moisture (50% or more). The hydrogel polymer is dried, cut and pulverized into powder. Superabsorbent polymer particles. The hydrogel polymer thus corresponds to the intermediate state of the process.

However, fines having a particle size of less than about 150 μm are inevitably generated in the powdering process of cutting and pulverizing the hydrogel polymer, and fine powder having a particle size of less than 150 μm is generated even after the surface treatment process. The application of superabsorbent polymer particles prepared in the presence of such fines to a product is undesirable in absorbent hygiene articles because it can deteriorate physical properties.

Therefore, it is important to have a high cohesive strength so as not to include the fine powder in the final resin product or to reassemble the fine powder to agglomerated to a normal particle size, so as not to be broken back into fine powder after reassembly.

Therefore, the present invention selects only the fine powder (product fine powder) that has undergone the surface treatment process and decomposes the crosslink through the basic additive treatment, and then performs the regrinding process with the untreated fine powder (base resin fine powder). To produce the assembly.

Prior to describing the preparation method of the superabsorbent fine powder reassembly according to the present invention, the steps of polymerization, drying, pulverization, classification, surface treatment, basic treatment and fine powder reassembly for preparing the superabsorbent polymer will be described in detail. Shall be.

Gel gel  Drying and Grinding of Polymers

The hydrogel polymer according to the present invention may be a product of a polymerization reaction of a monomer composition including a water-soluble ethylenically unsaturated monomer and a polymerization initiator, and may be represented by the following Chemical Formula 1.

[Formula 1]

R ¹ -COOM ¹

In Formula 1, R 1 is an alkyl group having 2 to 5 carbon atoms including an unsaturated bond, and M 1 is a hydrogen atom, a monovalent metal, an ammonium group, or an organic amine salt.

For example, the water-soluble ethylenically unsaturated monomer is not particularly limited as long as it is a monomer commonly used in the preparation of superabsorbent polymers. Preferably, the anionic monomer and its salt, the nonionic hydrophilic-containing monomer and the amino group-containing unsaturated monomer and its quaternary Any one or more selected from the group consisting of cargoes may be used. Specifically, acrylic acid, methacrylic 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, methoxy polyethylene glycol (meth) acrylate or polyethylene glycol ( Nonionic hydrophilic-containing monomers of meta) acrylate; Amino group-containing unsaturated monomers of (N, N) -dimethylaminoethyl (meth) acrylate or (N, N) -dimethylaminopropyl (meth) acrylamide and their quaternized compounds; And it may be one selected from the group consisting of a combination thereof. More preferably, acrylic acid or a salt thereof may be used. In the case of using acrylic acid or a salt thereof as a monomer, there is an advantage in that a superabsorbent polymer having improved water absorption can be obtained.

In addition, the polymerization initiator may be used a thermal polymerization initiator or a photo polymerization initiator and the like depending on the polymerization method. However, even with the photopolymerization method, since a certain amount of heat is generated by ultraviolet irradiation or the like and a certain amount of heat is generated in accordance with the progress of the polymerization reaction, which is an exothermic reaction, a thermal polymerization initiator is additionally used. May be included.

Here, as the thermal polymerization initiator, one or more selected from the group consisting of persulfate initiator, azo initiator, hydrogen peroxide and ascorbic acid may be used. Specifically, examples of the persulfate-based initiator include sodium persulfate, potassium persulfate, ammonium persulfate, and the like. Moreover, as an azo initiator, 2, 2- azobis- (2- amidino propane) dihydrochloric acid, 2, 2- azobis- (N, N- dimethylene) isobutyramidine dihydrochloride, 2- ( Carbamoylazo) isobutyronitrile, 2,2-azobis [2- (2-imidazolin-2-yl) propane] dihydrochloride, 4,4-azobis- (4-cyanovaleric acid ) May be used.

Meanwhile, as the photopolymerization initiator, one or more selected from the group consisting of benzoin ether, dialkylacetophenone, hydroxyl alkyl ketone, phenylglyoxylate, benzyldimethyl ketal, acylphosphine and alpha-aminoketone may be used. . As an example of the acylphosphine, commercially available lucirin TPO, that is, 2,4,6-trimethyl-benzoyl-trimethyl phosphine oxide may be used.

The use amount of the polymerization initiator is preferably about 0.001 to about 0.5 parts by weight based on 100 parts by weight of the water-soluble ethylenically unsaturated monomer. If the content of the polymerization initiator is less than 0.001 parts by weight, the conversion rate is low, so that the remaining monomers can be extracted in a large amount in the final product, which is not preferable. If the content is more than 0.5 parts by weight, the polymer chain constituting the network is shortened and the molecular weight of the superabsorbent resin is small. It is not preferable because the physical properties may be uneven.

The method for forming a hydrogel polymer by polymerizing and crosslinking the monomer composition including the water-soluble ethylenically unsaturated monomer and the polymerization initiator described above can be applied without any limitation as long as it is a conventional polymerization method in the art. For example, the polymerization method is largely divided into thermal polymerization and photopolymerization according to the type of polymerization energy source. When the thermal polymerization is performed, the polymerization may be performed in a reactor having a stirring shaft such as a kneader. In the case of proceeding, it may proceed in a reactor equipped with a movable conveyor belt.

According to one embodiment of the present invention, the hydrogel polymer may be obtained by adding the monomer composition to a reactor such as a kneader equipped with a stirring shaft and supplying hot air thereto or by heating the reactor to thermally polymerize it. At this time, the hydrous gel polymer discharged to the reactor outlet according to the shape of the stirring shaft provided in the reactor may be obtained in the particles of several millimeters to several centimeters. For example, the hydrous gel polymer obtained may be obtained in various forms depending on the concentration and injection speed of the monomer composition to be injected, and a hydrogel polymer having a particle size of 2 to 50 mm may be obtained.

According to another embodiment of the present invention, when the photopolymerization of the monomer composition is carried out in a reactor equipped with a movable conveyor belt, a hydrous gel polymer on a sheet (hereinafter referred to as 'polymer sheet') may be obtained. At this time, the thickness of the polymer sheet may vary depending on the concentration and the injection speed of the monomer composition to be injected, in order to ensure the production rate, while the entire sheet is evenly polymerized, a polymer sheet having a thickness of typically 0.5 to 5cm It is desirable to adjust so as to obtain.

At this time, the water content of the hydrogel polymer may be progressed to 30 to 80% by weight, preferably 40 to 60% by weight. It is preferable that the moisture content of the polymer thus formed is included in the above range in order to optimize the efficiency in the drying step described later.

The hydrogel polymer immediately after the polymerization is subjected to a drying step, and the drying step may be performed at a temperature of 150 to 250 ° C. If the drying temperature is less than 150 ℃, the drying time may be longer and the physical properties of the final superabsorbent resin may be lowered. If the drying temperature is higher than 250 ℃, only the surface of the hydrous gel polymer is dried to generate fine powder in the grinding process to be described later It can be a lot. Therefore, the drying temperature may be carried out at a temperature of 150 to 250 ℃, more preferably 160 to 200 ℃. At this time, the drying time is not particularly limited, but may be performed for 20 to 90 minutes under the drying temperature in consideration of process efficiency and the like.

In addition, if the drying method of the drying step can also be commonly used as a drying step of the hydrogel polymer, its configuration is applicable without limitation. Specifically, the drying step may be a method such as hot air supply, infrared irradiation, microwave irradiation or ultraviolet irradiation.

This drying step may be performed so that the water content of the dried polymer (hereinafter referred to as 'base resin') is 0.05 to 5 parts by weight. That is, when the water content of the base resin is less than 0.05 parts by weight, it is not advantageous because the production cost increases due to excessive drying and decomposition of the crosslinked polymer may occur. In addition, when the water content of the base resin exceeds 5 parts by weight, in consideration of the fact that a defect may occur in the subsequent process, it is preferable to make the water content of the base resin to fall within the above range.

Following the drying step, the step of grinding the base resin may be performed, and this grinding process is a step for optimizing the surface area of the base resin, and the particle size of the ground base resin is performed to be 150 or more and 850 μm or less. It is preferable.

On the other hand, the manufacturing method of the superabsorbent polymer according to the present invention may be further subjected to a simple grinding step before the drying step, if necessary, in order to increase the efficiency of the drying step. The simple grinding step before the drying step may be pulverized such that the polymer of the superabsorbent polymer particles has a particle size of 1 to 15 mm. The pulverization of the polymer having a particle size of less than 1 mm may be performed due to the high water content of the superabsorbent polymer particles. It is difficult, and may also appear to agglomerate the pulverized particles with each other, when the particle size is pulverized to exceed 15mm, the effect of increasing efficiency in the subsequent drying step is insignificant.

The pulverizer used here is not limited in configuration, but specifically, a vertical pulverizer, a turbo cutter, a turbo grinder, a rotary cutter mill, a cutting type It may include any one selected from the group of crushing machines consisting of a cutter mill, a disc mill, a shred crusher, a crusher, a chopper, and a disc cutter. It may be, but is not limited to the above-described example.

Subsequently, in the method of preparing the superabsorbent polymer according to the present invention, after the drying step, the base resin is pulverized to obtain superabsorbent polymer particles. The particle size of the superabsorbent polymer particles obtained after the grinding step is 150 to 850 μm. In the manufacturing method of the superabsorbent polymer according to the present invention, the pulverizer used to grind to such a particle size is specifically, a pin mill, a hammer mill, a screw mill, a roll mill A roll mill, a disc mill, a jog mill, or the like may be used, but is not limited thereto.

Classification

According to the present invention, a step of classifying the polymer powder obtained through the above process into fine powders of less than 150 μm, normal particles of 150 to 850 μm, and larger particles of more than 850 μm based on particle size. This step can be further performed to manage the physical properties of the superabsorbent polymer powder to be finalized, it can be used to classify the base resin having a particle size in the above range.

It is possible to apply the conventional methods in the art to classify by size, for example, a sieve having a scale of the mesh size, in particular 850㎛ (20 mesh) and 150㎛ (100 mesh) ) Can be classified as above.

Looking specifically at the manufacturing process of the classification step, the superabsorbent resin particles supplied from the polymer feeder is pulverized in a polymer mill to a particle size of 150 to 850㎛, and then classified through a classifier according to each particle size. At this time, the fine powder having a particle size of less than 150 μm is not classified separately, and the particles having a particle size of more than 850 μm can be separately classified and sent back to the grinder.

At this time, the large particles having a particle size exceeding 850㎛ is regrinded, and again, as in step ii), according to the particle size (base resin fineness of less than 150㎛, normal particles less than 150㎛ and 850㎛ and 850㎛) Larger particles exceeding) may be carried out. This regrinding process is preferably repeated until large particles having a particle size exceeding 850 μm disappear to secure normal particles.

Surface treatment

Meanwhile, in the step of surface treatment in the present invention, the surface crosslinking reaction may be performed by using a surface crosslinking solution containing certain components.

Surface crosslinking is the step of increasing the crosslink density near the surface of the superabsorbent polymer particles with respect to the crosslink density inside the particles. Generally, the surface crosslinking agent is applied to the surface of the superabsorbent resin particles. Thus, this reaction occurs on the surface of the superabsorbent resin particles, which improves crosslinkability on the surface of the particles without substantially affecting the interior of the particles. The surface crosslinked superabsorbent resin particles thus have a higher degree of crosslinking in the vicinity of the surface than in the interior. In this case, the surface crosslinking agent is not limited as long as it is a compound capable of reacting with the functional group of the polymer.

According to one preferred embodiment, the surface crosslinking solution of the present invention comprises a surface crosslinking agent and a solvent, and more particularly, the surface crosslinking solution is a surface crosslinking agent which is a C2 to C8 diol or glycol-based compound; The solvent includes water and an alcohol or a glycol-based organic solvent. It is possible to treat the base resin surface of the normal particle size of the particle size 150 to 850㎛ with the surface crosslinking solution having the composition. At this time, the surface crosslinking solution preferably contains 0.1 to 20% by weight of the surface crosslinking agent, 10 to 70% by weight of the organic solvent and the remaining amount of water.

The surface crosslinking agent is, for example, 1,3-propanediol, 2,3,4-trimethyl-1,3-pentanediol, 2-butene-1,4-diol, 1,4-butanediol, 1,3-butanediol, 1,5-pentanediol, 1,6-hexanediol, 1,2-cyclohexanedimethanol, monoethylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, polyethylene glycol, propylene glycol, dipropylene glycol, poly It is possible to be one selected from propylene glycol, glycerol, polyglycerol and combinations thereof. More preferably, 1,3-propanediol may be used as the surface crosslinking agent, and propylene glycol may also be used. In addition, when using two or more types of surface crosslinking agents in the present invention, the mixing weight ratio may be 2: 8 to 8: 2 based on the weight of the entire surface crosslinking agent.

The organic solvent is selected from the group consisting of ethanol, methanol, isopropyl alcohol, ethylene glycol, propylene glycol, polyethylene glycol, ethylene glycol diglycidyl ether, polypropylene glycol, normal-propanol, butanol, propanediol and combinations thereof 1 or more types can be used.

The surface crosslinking solution can be treated by spraying through a pipe or nozzle, but is preferably sprayed on the surface of the normal particles through the nozzle, for 10 to 120 minutes, preferably 20 to 90 minutes at a temperature of 120 to 300 ℃ It is preferable to carry out the crosslinking reaction of the said normal particle surface.

After the surface cross-linking reaction and before the classification step described later, it may further include a conventional drying process, the conditions are not limited.

When the surface crosslinking reaction is completed, the product is further processed through the process of classifying the product fine powder having a particle size of less than 150 μm and the normal particles of 150 μm or more and 850 μm or less, or, in some cases, the large particles having a particle size exceeding 850 μm. . Particles with a particle size of less than 150㎛ generated at this time is then sorted and stored for treatment with a basic solution.

Basic treatment

In the surface treatment step, product fine powder having a particle size of less than 150 μm is generated, and this is selected and treated with a basic solution to decompose the crosslinking formed during the surface treatment of the product fine powder. That is, as a basic solution capable of reacting with the carboxylic acid formed from Formula 1, at least one solution selected from the group consisting of NaOH, KOH, Na ₂ CO ₃ , NaHCO ₃ and combinations thereof in a concentration of 1 to 10% by weight Can be used. At this time, it is preferable to proceed by a method of spraying or dipping the basic solution in the product fine powder for 30 seconds to 10 minutes at a temperature of 60 to 200 ℃.

Differential Reassembly

In the process of reassembling the fine powder according to the present invention, the reassembly process may be performed in a wet state having a water content of about 30 to 60% to increase the cohesive strength. For example, the finely divided polymer may be sprayed with moisture or added in bulk to mix the finely divided water with stirring. At this time, the higher the moisture content of the fine powder, the higher the cohesive strength of the fine powder, but during the reassembly process, too large reassembly lumps or partly water-containing reassembly lumps (jelly balls) are formed. If not easy to handle, while the water content is low, the reassembly process is easy, but the cohesive strength is often lowered again to fine powder after reassembly.

The weight ratio of the product fine powder and the base resin fine powder is preferably 1: 9 to 9: 1 mixed and reassembled, and the water content is 50 to 100 parts by weight based on the total weight of the total weight of the base resin fine powder and the product fine powder. 200 parts by weight of water can be mixed and wetted.

At this time, the moisture may be supplied in the form of a mist or spray for more uniform mixing. For example, the wetting process is to supply fine powder to at least one powder feeder or hopper while uniformly injecting a predetermined amount of water into the fine powder using at least one spray nozzle. By feeding in form.

Thereafter, a step of drying the reassembled fine powder may be performed, wherein the drying temperature of the drying step may be about 150 to 250 ° C. If the drying temperature is less than 150 ° C., the drying time may be too long and the physical properties of the final superabsorbent resin may be lowered. If the drying temperature exceeds 250 ° C., only the surface of the polymer is dried too much, and a subsequent grinding step Fine powder may occur, and there is a fear that the physical properties of the superabsorbent polymer to be finally formed decrease. Therefore, preferably, the drying may be performed at a temperature of about 150 to 250 ℃, more preferably at a temperature of about 160 to 200 ℃. Meanwhile, in the case of a drying time, the process may be performed for about 20 to about 90 minutes in consideration of process efficiency and the like, but is not limited thereto. The water content of the reassembled fine powder after the drying step may be about 0.05 to about 10% by weight.

In this case, in order to increase the efficiency of the drying step, a simple grinding step before drying may be more rough. At this time, the pulverizer used is not limited in configuration, but specifically, a vertical pulverizer, a turbo cutter, a turbo grinder, a rotary cutter mill, a cutting machine Any one selected from the group of crushing machines consisting of cutter mills, disc mills, shred crushers, crushers, choppers and disc cutters Although it is possible, it is not limited to the above-mentioned example. At this time, the grinding step may be crude grinding so that the particle size of the reassembled fine powder is about 1 to about 15mm.

The reassembled fine powder may be further ground or classified to have a particle size of about 150 to 850 μm. At this time, the pulverizer used to grind the reassembled fine powder is specifically, a pin mill, a hammer mill, a screw mill, a roll mill, a disc mill ) Or a jog mill may be used, but the present invention is not limited to the above-described example.

Superabsorbent  Resin manufacturing

The superabsorbent polymer particles containing the fine powder reassembly preferably include the fine powder reassembly within 50% by weight based on the total weight.

Hereinafter, the present invention will be described in detail with reference to Examples. However, embodiments according to the present invention can be modified in many different forms, the scope of the present invention should not be construed as limited to the embodiments described below. The embodiments of the present invention are provided to more completely explain the present invention to those skilled in the art.

Preparation Example 1 Preparation of Super Absorbent Polymer Fine Powder

A monomer composition having a monomer concentration of 50% by weight was prepared by mixing 100 g of acrylic acid, 0.5 g of polyethylene glycol diacrylate, 38.9 g of caustic soda (NaOH), and 103.9 g of water as a crosslinking agent. Thereafter, 0.01 g of Irgacure 651 (2,2-dimethoxy-1,2-di (phenyl) ethanon) and 0.3 g of sodium persulfate were mixed with the monomer composition, and then introduced through a supply unit of a rotating belt polymerizer and irradiated with ultraviolet rays. . The polymerization was initiated within 1 minute by irradiation of ultraviolet rays, and the polymerization was continued for 5 minutes, at which time the internal temperature of the reactor was adjusted to be 80 to 99 ° C.

The polymerized superabsorbent polymer was transferred and cut with a cutter. Thereafter, the polymer discharged from the cutter was dried in a hot air dryer at 180 ° C. for 1 hour. Subsequently, the resultant was pulverized with a pin mill grinder, and then classified into a base resin fine powder, which was a particle classified into a particle size of less than 150 µm, a normal particle size of 150 µm or more and 850 µm or less, and large particles exceeding 850 µm. . At this time, the large particles exceeding 850㎛ was recycled to the grinder, and the base resin fine powder of less than 150㎛ was discharged separately and stored.

Superabsorbent by spraying a surface crosslinking solution containing 5% by weight of 1,3-propanediol, 5% by weight of propylene glycol, and the balance of water to a base resin having a particle size of 150 µm or more and 850 µm or less classified as normal particle size. The surface of the resin was treated. In addition, in the step of treating the surface, the classified hydrous gel polymer was supplied to one surface crosslinking reactor, and the surface crosslinking reaction of the hydrogel polymer was performed for 20 to 50 minutes at a temperature of 190 ° C. or higher.

After the surface treatment, Sieve was further used to classify product fine powder, particles having a particle size classified as less than 150 μm, products having a size of 150 μm or more and 850 μm or less, and large particles larger than 850 μm. Large particles larger than 850 μm were regrind in this process, and product fine powder less than 150 μm was stored separately in the reservoir.

<Example 1>

600 g of the product fine powder produced during the production of the superabsorbent polymer was introduced into a 40L planetary mixer. At this time, the chopper of the mixer was set to 1500 rpm and the impeller (Impeller) to 60 rpm, and an aqueous solution in which 5 wt% of sodium hydroxide (NaOH) was added to the same amount of water heated to 80 ° C. was stirred for 30 seconds. After stirring, 1400 g of base resin fine powder was added to the planetary mixer. At this time, the chopper of the mixer was set to 1500rpm, the impeller was set to 60rpm and the same amount of water was added and stirred for 60 seconds to prepare a superabsorbent fine powder reassembly.

Comparative Example 1

2000 g of a powder mixture of a product powder and a base resin powder produced in the process of preparing a super absorbent polymer was added to a 40L capacity planetary mixer. At this time, the chopper of the mixer was set to 1500rpm, the impeller was set to 60rpm and the same amount of water heated to 80 ℃ was added to the mixture for 60 seconds to prepare a fine powder reassembly.

Comparative Example 2

The fine powder reassembly was obtained in the same manner as in Comparative Example 1, except that 6% by weight of sodium hydroxide was used instead of the charged water to prepare the fine powder reassembly.

Table 1 below shows the NaOH treatment concentrations of Example 1 and Comparative Examples 1 and 2 described above and whether sequential reassembly (two-step reassembly) was performed, and FIGS. 1 to 3 are Comparative Examples 1 and 3 of the present invention. Scanning Electron Microscope (SEM) images of superabsorbent fine powder reassembly according to 1 and 2.

division NaOH concentration (wt%) 2-step reassembly Example 1 5 O Comparative Example 1 0 X Comparative Example 2 6 X

In Example 1, only the product fine powder was selectively treated with NaOH to decompose the surface crosslinking, and then a reassembly with the base resin fine powder was formed (two stage reassembly), and the fine powder reassembled therefrom is shown in FIG. As a result, it was visually confirmed that the porous structure was densely aggregated to improve the cohesive strength and the density.

On the contrary, in Comparative Example 1, the product fine powder and the base resin fine powder were reassembled without NaOH treatment, and the comparative example 2 was reassembled by NaOH treatment after mixing the product fine powder and the base resin fine powder. As shown in FIG. 3, the cohesive strength and the density were found to be weaker than those of Example 1 in the form of the porous structure as it is.

Claims (9)

In the superabsorbent fine powder reassembly manufacturing method,
Iii) drying and milling the hydrogel polymer which is a water soluble ethylenically unsaturated polymer;
Ii) classifying the pulverized particles into a base resin fine powder having a particle size of less than 150 μm, normal particles of 150 μm or more and 850 μm or less, and large particles of more than 850 μm;
Iii) surface-treating normal particles having a particle size of 150 µm or more and 850 µm or less;
Iii) selecting a product fine powder having a particle size of less than 150㎛ generated during the surface treatment and treating it with a basic solution; And
V) mixing and reassembling the basic treated product fine powder with the base resin fine powder of step ii);
In the superabsorbent fine powder reassembly manufacturing method comprising a,
The basic solution of step iii) is an aqueous NaOH solution at a concentration of 5% by weight,
The reassembly of step iii) is a method for producing superabsorbent fine powder reassembly, characterized in that the basic treated product fine powder, the base resin fine powder of step ii) and water are added to the mixer and stirred.
The method of claim 1,
The surface treatment of step iii) is a method for producing superabsorbent fine powder reassembly, characterized in that the surface of the normal particle is treated with a surface crosslinking solution containing a diol or glycol-based compound of C2 to C8, an organic solvent and water. .
The method of claim 2,
The surface cross-linking solution is 0.1 to 20% by weight of the surface cross-linking agent, 10 to 70% by weight of an organic solvent and a residual amount of superabsorbent fine powder reassembling method characterized in that it comprises a residual amount of water.
The method of claim 2,
The organic solvent is selected from the group consisting of ethanol, methanol, isopropyl alcohol, ethylene glycol, propylene glycol, polyethylene glycol, ethylene glycol diglycidyl ether, polypropylene glycol, normal-propanol, butanol, propanediol and combinations thereof Superabsorbent fine powder reassembly manufacturing method characterized in that one.
The method of claim 1,
The surface treatment of step iii) comprises the step of crosslinking the surface of the normal particles for 20 to 90 minutes at a temperature of 120 to 300 ℃ superabsorbent fine powder reassembly manufacturing method.
The method of claim 1,
The water input to the mixer of step iii) is added to 50 to 200 parts by weight based on 100 parts by weight of the total weight of the base resin fine powder and product fine powder, characterized in that the superabsorbent fine powder reassembly manufacturing method.
The method of claim 1,
The weight ratio of the product fine powder and the base resin fine powder of the step iii) is 1: 9 to 9: 1 is mixed and reassembled, characterized in that the superabsorbent fine powder reassembly manufacturing method.
A method for producing a superabsorbent polymer, characterized in that the fine powder reassembly prepared by the method of any one of claims 1 to 7 is mixed with the hydrous gel polymer of step (iii).
The method of claim 8,
The superabsorbent polymer manufacturing method of the superabsorbent polymer, characterized in that containing the fine powder reassembly within 50% by weight.

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