KR20110137082A - Preparation method of super absorbent polymer - Google Patents

Abstract

PURPOSE: A producing method of a super absorbent resin is provided to reduce the gel cohesive property of a hydrogel polymer for easily cutting and crushing. CONSTITUTION: A producing method of a super absorbent resin comprises the following steps: producing a monomer composition containing a water-soluble ethylene-based unsaturated monomer and a polymerization initiator; producing a hydrogel polymer by inserting the monomer composition in a polymerization reactor(30) and polymerizing; cooling the surface of the hydrogel polymer to the temperature lower than the dew point using a cooler(50); and cutting and crushing the hydrogel polymer.

Description

Production method of superabsorbent polymer {PREPARATION METHOD OF SUPER ABSORBENT POLYMER}

The present invention relates to a method for preparing a super absorbent polymer, and more particularly, to a high absorbency which can save time and energy of a drying step with a minimum drying process by lowering gel adhesion of a hydrogel polymer formed after polymerization of a monomer composition. It is related with the manufacturing method of resin.

Super Absorbent Polymer (SAP) is a synthetic polymer material capable of absorbing water of 500 to 1,000 times its own weight.As a developer, super absorbent material (SAM) and absorbent gel (AGM) They are named differently. Such super absorbent polymers have been put into practical use as physiological tools, and are currently used in gardening soil repair agents, civil engineering, building index materials, seedling sheets, food fresheners in addition to hygiene products such as paper diapers for children, and It is widely used as a material for steaming.

As a method for producing such a super absorbent polymer, a method by reverse phase suspension polymerization or a method by aqueous solution polymerization is known. Reverse phase suspension polymerization is disclosed in, for example, Japanese Patent Laid-Open Nos. 56-161408, 57-158209, and 57-198714. As a method by aqueous solution polymerization, the thermal polymerization method which breaks | polymerizes a polymer gel while breaking and cooling in a kneading machine with a shaft, and the photopolymerization method which perform superposition | polymerization and drying simultaneously by irradiating an ultraviolet-ray etc. with a high concentration aqueous solution on a belt 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 Registration No. 0330127 discloses a method for preparing an absorbent resin 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 generally prepared in the form of a powdery superabsorbent polymer by cutting, drying, grinding, and surface treatment.

However, since the water content is high in the range of about 35 to 60% by weight due to the nature of the water-containing gel polymer, the adhesion phenomenon of the gel is severe and polymerization at the time of cleavage of the polymerization reactor or the polymer for efficient drying. There is a problem that is entangled in the inner wall of the reactor, cutter and grinder.

That is, the gel particles having a high water content as described above still contains excess moisture, so that the high water-containing gel polymer is entangled or stuck to the inner wall of the cutting device or the grinding device, the grinding blade, the grinding shaft, or the like during the cutting or grinding process. It is not possible to cut or crush the polymer to one size. Therefore, the pulverized particles are agglomerated, resulting in a non-uniform particle shape and a large particle shape, so that the drying efficiency is also very poor. In addition, if the temperature is increased during the drying process to lower the water content, the temperature of the hydrogel polymer and the super absorbent polymer is higher, which may adversely affect the physical properties. Even if the diarrhea temperature is not increased, the drying process is performed for a long time to obtain a desired level. Since it is necessary, efficient drying cannot proceed.

Furthermore, in the conventional method, in order to obtain a super absorbent polymer having small particles, the process of drying and drying the polymer having a large particle size requires an additional grinding and drying process, and thus, the overall process becomes cumbersome and complicated. Can also reduce the physical properties.

Therefore, a technique for preventing the adhesion of such a gel has been developed, and now a technique for preventing adhesion by adding water, steam, surfactant, etc. to the hydrous gel polymer is known (Japanese Patent Laid-Open No. 59-30826, Japanese Patent 59-119172).

However, when the surfactant is added, the additive may remain in the finally produced polymer, which may adversely affect the performance of the superabsorbent polymer product. In addition, when water and the like are added, the amount of moisture to be removed in the final drying step increases, so that the consumption of the drying time and the amount of energy required for drying is high, which may hinder the efficiency of the primary dryer. Accordingly, it is not possible to ensure the efficiency of the process for producing a super absorbent polymer.

As such, when the water, steam, and the surfactant are added, secondary pollution and uneconomical problems of the polymer are caused, and thus, a new process needs to be developed.

The present inventors completed the present invention while repeatedly studying a method for efficiently producing a super absorbent polymer without inhibiting the physical properties of the final superabsorbent polymer.

Therefore, the present invention is to provide a method for producing a super absorbent polymer which can lower the adhesion of the hydrogel polymer by the temperature difference between the polymer and the cutter by controlling the temperature of the polymerization reactor or the cutter when preparing the superabsorbent polymer.

Another object of the present invention is to reduce the gel adhesion and to facilitate the cutting and grinding process, and to facilitate the progress of the uniform size of the fine particles, as well as to improve productivity and prevent secondary contamination of the polymer. It is to provide a method for producing a super absorbent polymer that can be.

Another object of the present invention is to provide a method for preparing a super absorbent polymer which enables the production of small particles after grinding to expect an energy saving effect in the drying process with minimal drying conditions.

Another object of the present invention is to provide a method for producing a super absorbent polymer which does not inhibit the physical properties of the finally obtained super absorbent polymer.

The present invention comprises the steps of forming a monomer composition comprising a water-soluble ethylenically unsaturated monomer and a polymerization initiator; Introducing the monomer composition into a polymerization reactor and preparing a hydrogel polymer; Cooling the surface temperature of the hydrogel polymer below a dew point of air in the polymerization reactor by using a cooling device provided at an end of the polymerization reactor; And cutting and pulverizing the cooled hydrogel polymer.

In another aspect, the present invention comprises the steps of forming a monomer composition comprising a water-soluble ethylenically unsaturated monomer and a polymerization initiator; Introducing the monomer composition into a polymerization reactor and preparing a hydrogel polymer; Transferring the hydrogel polymer into a cutter equipped with a cooling device; Cutting the hydrogel polymer by cooling the surface temperature of the hydrogel polymer below the dew point of air inside the cutter using the cooling device; And it provides a method for producing a super absorbent polymer comprising the step of grinding the cut hydrogel polymer.

Hereinafter, a method of preparing a super absorbent polymer according to a specific embodiment of the present invention will be described.

The present invention can not only optimize the drying process by lowering the adhesive force of the hydrogel polymer formed during the polymerization of the monomer composition to facilitate cutting and grinding, but also can produce a super absorbent polymer having uniform and fine particles and exhibiting excellent physical properties. have.

In particular, according to the present invention, by controlling the temperature of the polymerization reactor or the cutter to a certain range with respect to the hydrogel polymer formed by the polymerization reaction, dew is formed outside the polymer according to the temperature difference between the hydrogel polymer and the polymerizer or the cutter. Gel adhesion phenomenon can be prevented.

Therefore, the present invention can improve the processability by significantly lowering the adhesion of the hydrogel polymer to the polymerizer, the cutter and the pulverizing machine as in the prior art. Thus, in the subsequent grinding step, the hydrogel polymer can be efficiently pulverized to a uniform size without sticking the hydrogel polymer to the grinding blades, grinding shafts, inner walls of the machine or the like of the cutter or the grinding machine.

Therefore, the present invention can obtain fine particles having a uniform particle size distribution of a desired size due to the ease of cutting and grinding processes, and can easily obtain a super absorbent polymer economically by a drying process. In particular, the present invention does not need to use a surfactant added to improve the adhesion as in the prior art to prevent the problem of secondary contamination of the polymer, the physical properties of the superabsorbent resin to be formed is reduced, or the superabsorbent resin There is no concern of skin irritation that may occur when used as a final product.

Then, according to an embodiment of the present invention, forming a monomer composition comprising a water-soluble ethylenically unsaturated monomer and a polymerization initiator; Preparing a hydrogel polymer by adding the monomer composition to a polymerization reactor and polymerizing the same; Cooling the surface temperature of the hydrous gel polymer below the dew point of the air in the polymerization reactor using a cooling device provided at the end of the polymerization reactor; And cutting and pulverizing the cooled hydrogel polymer is provided.

In addition, according to another embodiment of the present invention, forming a monomer composition comprising a water-soluble ethylenically unsaturated monomer and a polymerization initiator; Adding the monomer composition to a polymerization reactor and polymerizing to prepare a hydrogel polymer; Transferring the hydrogel polymer into a cutter equipped with a cooling device; Cutting the hydrogel polymer using the cooling device while cooling the surface temperature of the hydrogel polymer below the dew point of air inside the cutter; And pulverizing the cut hydrogel polymer is provided.

As described in the above embodiments, the process of the present invention is characterized by cooling the hydrogel polymer obtained after polymerization by providing a cooling device at the end or cutter of the polymerization reactor.

When the monomer composition is introduced into the polymerization reactor through the monomer composition supply unit, an initiation reaction proceeds at the front end of the polymerization reactor and polymerization is performed at the stop part to form a hydrogel polymer, and a gel sizing process of the hydrogel polymer is performed at the terminal part. Can be.

At this time, according to an embodiment of the present invention, the cooling in the gel sizing process of the hydrogel polymer using the cooling device provided in the polymerization reactor. Through this process, the surface temperature of the hydrogel polymer maintained at a high temperature according to the sudden temperature difference between the hydrogel polymer and the air in the polymerization reactor is cooled below the dew point of the air in the polymerization reactor. Therefore, the present invention can lower the adhesion when the cooled hydrogel polymer is added to the cutting process and the grinding process.

According to another embodiment when simultaneously cooling and cutting the hydrogel polymer in the cutter, the hot gel sized hydrogel polymer transferred from the polymerization reactor is transferred into the cutter equipped with a cooling device. Then, by using the cooling device while cooling the surface temperature of the hydrogel polymer below the dew point of the air inside the cutter while cutting the hydrogel polymer, the present invention can lower the adhesion in the grinding process.

Meanwhile, in the present invention, “dew point” means a temperature at which dew starts to form when cooling such air, in consideration of the temperature and humidity of the air inside the polymerization reactor end. In other words, the present invention lowers the temperature of the polymerization reactor or the cutter by cooling to saturate the air to a temperature drop on its inner wall, so that vaporization of water vapor occurs, and the vaporized water vapor condenses to form a high temperature inside the polymerization reactor or cutter. A dew point is used which is transferred to the surface of the hydrogel polymer to maintain water droplets.

In this embodiment, in the case where the cooling device is installed in the polymerization reactor, the cooling device may be installed at the end of the polymerization reactor.

"End end of the polymerization reactor" in the present invention is at least part of the end of the polymerization reactor close to the outlet side of the hydrogel polymer, the polymer is present after at least 90% or more of the polymerization of the unsaturated monomer for the preparation of the hydrogel polymer is completed It means an area to say. Preferably, the cooling device may be located 2/3 to 3/3 with respect to the axial length direction of the polymerization reactor.

When the hydrogel polymer is cooled using a cooling device installed at the end of the polymerization reactor or a cutter, the cooling is preferably performed for 3 seconds to 5 minutes at a temperature of -10 ° C to 50 ° C. Through this cooling process, the temperature of the hydrogel polymer is preferably maintained at a temperature of 60 to 80 ℃. At this time, if the cooling temperature of the cooling device is 50 ℃ or more, there is a problem that takes a long time to cool down to the dew point, if less than -10 ℃ low temperature of the hydrogel polymer may cause problems in subsequent processes.

The cooling device may include a cooler installed outside the polymerization reactor or in the form of a jacket surrounding the outside of the polymerization reactor. In addition, the cooling device may be an integral type connected to the polymerization reactor.

In another embodiment of the present invention, when the cooling device is installed in the cutter, the cooling device may be connected to the cutter. The cutter equipped with a cooler may include at least one of a vertical cutting blade, a scraper, a horizontal cutting rotary blade, and a casing for cutting the hydrogel polymer into a predetermined size.

The cooling device may be provided with a temperature control means, a moving means of a coolant or cooling water. Preferably, the cooling device may be provided with a device capable of measuring the temperature or humidity of the air in the end of the polymerization reactor or the inside of the cutter for measuring the dew point.

The refrigerant may be used without any particular type as long as it is used in a cooling means as a material having a normal cooling function. For example, the refrigerant has a high evaporation pressure at low temperature, a low condensation pressure at room temperature, a high critical temperature, a low solidification temperature, low power consumption when the same freezing capacity, chemical stability, and does not decompose under compressed heat. It may not be. The refrigerant may be trichlorofluoromethane, dichlorodifluoromethane, freon such as chlorofluoromethane, ethane, propane, butane, isobutane, and the like, but may be appropriately selected and used. At this time, in consideration of environmental aspects, materials other than Freon are more preferable.

In addition, the cooling means may be carried out in a device provided with a line for supplying liquid nitrogen.

The hydrogel polymer cooled above may have a water content of 30 to 70%.

On the other hand, the polymerization reactor is not particularly limited as long as it is used in the manufacture of a conventional super absorbent polymer, and may include a kneader, a conveyor belt or a container moving continuously or discontinuously. Preferably, the polymerization reactor used in the present invention may be a kneader having a single or a plurality of stirring shafts moving continuously.

In addition, the supply unit of the monomer composition for injecting the monomer composition into the polymerization reactor may be provided with a means for controlling the speed, may be provided with a temperature control means as necessary.

In addition, the conditions of superposition | polymerization of the said monomer composition are not specifically limited, The method used for manufacture of normal super absorbent polymer can be used. For example, the polymerization may include thermal polymerization or UV polymerization of the monomer composition, and may proceed for 10 seconds to 30 minutes at a temperature of 20 ° C to 99 ° C. Specifically, the thermal polymerization may be divided into a redox polymerization method for polymerization for 2 to 30 minutes at a temperature of 25 ~ 50 ℃, and thermal polymerization for 2 to 30 minutes polymerization at a temperature of 40 ~ 90 ℃. In addition, UV polymerization (photopolymerization) is not much influenced by the temperature, so the temperature can be proceeded by irradiating light for 10 seconds to 5 minutes at a temperature of 25 ~ 99 ℃ wide. In addition, the amount of ultraviolet light during UV irradiation may be 0.1 to 30 mW / cm ² . The light source and wavelength range used for UV irradiation can also be used known in the art.

At this time, the polymerization of the water-soluble ethylenically unsaturated monomer is preferably made in the aqueous solution state.

The water-soluble ethylenically unsaturated monomer used in the present invention can be used without limitation in the configuration as long as it is a monomer commonly used in the production of superabsorbent polymers. In general, any one or more selected from the group consisting of anionic monomers and salts thereof, nonionic hydrophilic-containing monomers, amino group-containing unsaturated monomers and quaternized compounds thereof can be used.

Specifically, the water-soluble ethylenically unsaturated monomer is acrylic acid, methacrylic acid, maleic anhydride, fumaric acid, crotonic acid, itaconic acid, 2-acryloylethane sulfonic acid, 2-methacryloylethanesulfonic acid, 2- (meth) acrylic acid Anionic monomers and salts thereof of loylpropanesulfonic acid and 2- (meth) acrylamide-2-methyl propane sulfonic acid; (Meth) acrylamide, N-substituted (meth) acrylate, 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, methoxy polyethylene glycol (meth) acrylate and polyethylene glycol ( Nonionic hydrophilic-containing monomers of meth) acrylate; And amino group-containing unsaturated monomers of (N, N) -dimethylaminoethyl (meth) acrylate and (N, N) -dimethylaminopropyl (meth) acrylamide and quaternized compounds thereof. It is desirable to. More preferably, the water-soluble ethylenically unsaturated monomer can use acrylic acid and its salt, which is advantageous in terms of excellent physical properties.

The concentration of the water-soluble ethylenically unsaturated monomer in the monomer composition may be appropriately selected and used in consideration of polymerization time and reaction conditions, but may be preferably 30 to 60% by weight. If the concentration of the water-soluble ethylenically unsaturated monomer is less than 30% by weight, the yield is low, there is a problem of low economical efficiency, when more than 60% by weight is disadvantageous in terms of physical properties and monomer solubility.

The polymerization initiator may be used by varying the polymerization initiator depending on whether the polymerization method is thermal polymerization or photopolymerization by UV irradiation. Among the polymerization initiators, one or more selected from the group consisting of azo (azo) initiators, peroxide initiators, redox (redox) initiators and organic halide initiators may be used. Examples of photopolymerization initiators include acetophenone, benzoin, benzophenone, benzyl and derivatives thereof such as diethoxy acetophenone, 2-hydroxy-2-methyl-1-phenylpropan-1-one, benzyl dimethyl tar, 4- (2- Acetofetone derivatives such as hydroxy ethoxy) phenyl- (2-hydroxy) -2-propyl ketone and 1-hydroxycyclohexylphenyl ketone; Benzoin alkyl ethers such as benzoin methyl ether, benzoyl ethyl ether, benzoin isopropyl ether and benzoin isobutyl ether; benzophenone derivatives such as methyl o-benzoyl benzoate, 4-phenyl benzophenone, 4-benzoyl-4'-methyl-diphenyl sulfide, and (4-benzoyl benzyl) trimethyl ammonium chloride; Thioxanthone compounds; Acyl phosphine oxide derivatives such as bis (2,4,6-trimethylbenzoyl) -phenyl phosphine oxide and diphenyl (2,4,6-trimethylbenzoyl) -phosphine oxide; Azo compounds such as 2-hydroxy methyl propionitrile and 2,2 '-{azobis (2-methyl-N- [1,1'-bis (hydroxymethyl) -2-hydroxyethyl) propion amide] It may be used one or more selected from the group consisting of.

The polymerization initiator may be used in an amount of 0.01 to 1.0 wt% based on the total monomer composition.

In addition, the monomer composition according to the present invention may further include a crosslinking agent.

The crosslinking agent may be a crosslinking agent having at least one functional group capable of reacting with a water-soluble substituent of an ethylenically unsaturated monomer, a water-soluble substituent of an ethylenically unsaturated monomer, and having at least one ethylenically unsaturated group or a mixture thereof; And a water-soluble substituent of an ethylenically unsaturated monomer, a crosslinking agent having at least two or more functional groups capable of reacting with a water-soluble substituent produced by hydrolysis of the vinyl monomer, and a mixture thereof. . Examples of the crosslinking agent having two or more ethylenically unsaturated groups include bisacrylamide having 8 to 12 carbon atoms, bismethacrylamide, poly (meth) acrylate of polyol having 2 to 10 carbon atoms, and poly (meth) of polyol having 2 to 10 carbon atoms. ) Allyl ether is used, and N, N'-methylenebis (meth) acrylate, ethyleneoxy (meth) acrylate, polyethyleneoxy (meth) acrylate, propyleneoxy (meth) acrylate, glycerin diacrylate, glycerin Any one or more selected from the group consisting of triacrylate, trimetholpropane triacrylate, triallyl amine, triarylcyanurate, triallyl isocyanate, polyethylene glycol, diethylene glycol and propylene glycol can be used.

The crosslinking agent may be used in an amount of 0.01 to 0.5 wt% based on the total monomer composition.

Meanwhile, in one embodiment of the present invention, the hydrogel polymer obtained through cooling is subjected to the steps of cutting and pulverizing.

The cutting may include cutting the hydrogel polymer into a predetermined size (0.1 cm to 5 cm). The configuration of the device used in the cutting step can be used for all that is used in the usual super absorbent polymer. For example, the cutting process may be performed through a cutter having at least one of a longitudinal cutting blade, a scraper, a horizontal cutting rotary blade, and a casing.

When pulverizing the hydrogel polymer, the pulverization may be selected without any limitation as long as it is a method used for pulverization of the resin. Preferably, any one grinder selected from the group consisting of a pin mill, a hammer mill, a screw mill, a roll mill, and the like may be selected and pulverized. At this time, it is preferable that the average particle diameter of the final superabsorbent polymer particles after the grinding step is 150 to 850 µm.

In addition, the hydrogel polymer according to an embodiment of the present invention may further include a step of drying before the cutting process.

The drying temperature and time may be appropriately selected according to the water content of the polymer polymerized through thermal polymerization or UV polymerization, preferably 10 minutes to 60 minutes at a temperature condition of 110 to 200 ℃. At the time of drying, when temperature is less than 110 degreeC, a drying effect is insignificant, drying time becomes too long, and it is difficult to reduce water content by 30 weight% or less. In addition, when the drying temperature exceeds 200 ° C., only the surface of the hydrogel polymer is locally excessively dried, and a large amount of fine powder may occur in a subsequent grinding step.

The configuration of the apparatus in the drying step is not particularly limited, and for example, drying may be performed through infrared irradiation, hot air, microwave irradiation, or ultraviolet irradiation. In addition, the drying temperature and time may be appropriately selected according to the water content of the polymer polymerized through thermal polymerization or UV polymerization, preferably 20 to 120 minutes at a temperature condition of 80 to 200 ℃. At the time of drying, when the temperature is less than 80 ° C., there is a problem that the drying effect is insignificant and the drying time is too long. When drying at a temperature exceeding 200 ° C., there is a problem that the super absorbent polymer is thermally decomposed.

In addition, according to another embodiment of the present invention, when cooling is simultaneously performed in the cutter, the cut hydrogel polymer may be subjected to a grinding step.

The grinding step can be carried out in the same manner as the method according to the embodiment and the conditions are not particularly limited.

In the above embodiments, the polymer that has undergone the grinding process may be subjected to a surface treatment process to obtain a uniform, superabsorbent polymer having fine particles.

In addition, in the above embodiments, the water content after drying of the hydrogel polymer polymerized through thermal polymerization or UV polymerization may be 0.5 to 10% by weight. At this time, the water content of the hydrogel polymer means the value of the water content of the total gel gel subtracted from the weight of the water-containing gel polymer minus the weight of the dry polymer.

Meanwhile, FIGS. 1 to 5 briefly illustrate a method of preparing a super absorbent polymer according to various embodiments of the present disclosure.

As shown in FIG. 1, according to the first embodiment of the present invention, the monomer composition is formed by mixing the water-soluble ethylenically unsaturated monomer and the polymerization initiator in the mixer 10. In this case, the supply unit and the solvent supply unit of the raw material such as the monomer and the polymerization initiator may be connected to the mixer.

Then, the present invention transfers the monomer composition to the monomer composition supply port 20 through a transfer line connected to the mixer 10.

Then, the monomer composition is supplied to the polymerization reactor 30 including the belt 36 formed to rotate about the rotation shafts 32 and 34 and move in a predetermined direction. Subsequently, polymerization is performed in the belt-like polymerization reactor 30 to form a sheet-like hydrogel polymer 40. In addition, the hydrogel polymer is cooled by a cooling device 50 that is integrally installed at the distal end of the belt-shaped polymerization reactor (30). Thereafter, the hydrogel polymer having the dew point formed by the temperature difference is transferred to the cutter 60 and then cut through the cutting means 70 to obtain the hydrogel polymer 42 having low adhesion. Thereafter, the cut hydrogel polymer may be transferred to a grinder, pulverized into fine particles, and then dried and surface treated to be made of a uniform and finely absorbent polymer having fine particles. At this time, the drying step may be further performed before the grinding step.

In addition, in the second embodiment, a separate cooling device 60 is installed on the upper part of the outside of the end of the belt-type polymerization reactor (30). Thereafter, cooling may be performed by applying a predetermined temperature to the hydrogel polymer that has been polymerized, and dew may be formed due to a temperature difference, and the cooled hydrogel polymer may be transferred to a cutter to perform cutting (FIG. 2).

In the third embodiment, the hydrogel polymer, which has undergone polymerization, may be transferred to the cutter 60 to perform cutting, and at the same time, cooling may be performed using the cooling device 50 provided in the cutter (FIG. 3). At this time, the cooling device shown in the drawing is located in the upper portion of the inside of the cutter, the configuration of the cutter is shown for simplicity for convenience.

4 and 5 show an example using a kneader-type polymerization reactor in the embodiment of the present invention.

In FIG. 4, the present invention proceeds polymerization in a kneader 80 having a single or plural rotary shafts and rotary blades moving in one direction, and installs a cooling device 52 on the upper end of the kneader 80. After the cooling is performed, the cooled hydrogel polymer may be transferred to the cutter 60 to be cut.

In addition, as shown in FIG. 5, the present invention proceeds polymerization in a kneader 80 having a single or plural rotary shafts and rotary blades moving in one direction, and is integrally installed at the distal end of the kneader 80. After the cooling is performed, the cooled hydrogel polymer may be transported to the cutter 60 and cut.

The cut hydrogel polymer may then be transferred to a grinder to be pulverized into fine particles, followed by a drying and surface treatment process to produce a uniform and finely absorbent polymer having fine particles. At this time, the drying step may be further performed before the grinding step.

At this time, in the manufacturing apparatus of the super absorbent polymer of FIGS. 4 and 5 using the kneader, cooling may be performed by installing a cooling device in the cutter instead of cooling the kneader.

As described above, in the above embodiments, according to the present invention, the hydrogel polymer may be cooled in a polymerization reactor or a cutting machine to reduce adhesion due to a dew point due to a temperature difference between the polymer and the polymerization reactor or the cutting machine. Therefore, the present invention can effectively cut or pulverize the hydrogel polymer without sticking to the inner wall of the device in the subsequent cutting or pulverization process, thereby obtaining a hydrogel polymer having a uniform particle size distribution, and greatly improving its drying efficiency. You can.

Therefore, the superabsorbent polymer of the present invention can not only effectively remove the water after polymerization, but also reduce the physical properties of the superabsorbent polymer to be finally prepared, and thus require only a minimum additional drying process, thereby improving the efficiency of the entire process. have.

According to the present invention, the water content of the hydrogel polymer is greatly lowered, thereby reducing the adhesion of the gel polymer to the cutter or the grinder during the cutting or pulverization. In addition, it is possible to grind into uniform and fine particles according to the easy grinding, thereby excellent drying efficiency and productivity can be improved, thereby contributing to the energy saving effect by improving the overall process. Furthermore, the present invention does not require the addition of water, steam, surfactants, etc., thereby preventing secondary contamination of the hydrogel polymer. Therefore, according to the present invention, since the superabsorbent polymer having excellent physical properties can be produced more efficiently by the method for preparing the superabsorbent polymer, the present invention can greatly contribute to the industrial field related to the superabsorbent polymer production.

Figure 1 is a schematic diagram showing the process of the manufacturing method of the super absorbent polymer according to the first embodiment of the present invention.
2 is a schematic diagram briefly showing the process of the manufacturing method of the super absorbent polymer according to the second embodiment of the present invention.
3 is a schematic diagram briefly showing the process of the manufacturing method of the super absorbent polymer according to the third embodiment of the present invention.
4 is a schematic diagram briefly showing the process of the manufacturing method of the super absorbent polymer according to the fourth embodiment of the present invention.
5 is a schematic diagram briefly showing the process of the manufacturing method of the super absorbent polymer according to the fifth embodiment of the present invention.

Hereinafter, the operation and effects of the invention will be described in more detail with reference to specific examples of the invention. However, these embodiments are only presented as an example of the invention, whereby the scope of the invention is not determined.

Example  One

A super absorbent polymer was prepared according to the method shown in FIG. 1.

100 g of acrylic acid, 0.1 g of polyethylene glycol diacrylate as a crosslinking agent, 0.033 g of diphenyl (2,4,6-trimethylbenzoyl) -phosphine oxide as an initiator, 38.9 g of caustic soda (NaOH) and 103.9 g of water were mixed, A monomer aqueous solution composition having a monomer concentration of 50% by weight was prepared.

Thereafter, the monomer aqueous solution composition was introduced through a monomer supply unit on a continuously moving conveyor belt, and irradiated with ultraviolet rays (irradiation amount: 2 mW / cm 2) to proceed with UV polymerization for 2 minutes.

The hydrogel polymer was then continuously moved on a conveyor belt and cooled for 3 minutes at a temperature of 10 ° C. in a chiller installed at the end of the polymerization reactor. The end portion of the polymerization reactor was provided with a thermometer and a hygrometer to measure the temperature and humidity of the air inside. At this time, the internal temperature and humidity of the terminal portion of the polymerization reactor before the cooling was 80 ℃ and 70%. In addition, the internal temperature and humidity of the polymerization reactor terminal part after cooling were 72 degreeC and 98%. The surface temperature of the hydrogel polymer after cooling was lowered to 68 ° C., and the surface of the hydrogel polymer was lowered below the dew point of the air inside the polymerization reactor by the cooling, thereby causing dew (drops) on the surface of the polymer. It was confirmed.

The cooled water-containing polymer was transferred to a cutter and then cut into 0.2 cm, and the adhesion and yield were confirmed by measuring the weight of the amount of resin that was not attached and discharged. At this time, the water content was 58%, the yield was 98%.

Thereafter, the discharged resin was dried in a hot air dryer at 180 ° C. for 1 hour. Subsequently, it was pulverized with a pin mill grinder to obtain a super absorbent polymer having an average particle size of 150 to 850 µm using a sieve.

Subsequently, after crosslinking the superabsorbent polymer by using a 3% solution of ethylene glycol diglycidyl ether, the reaction was carried out at 120 ° C. for 1 hour, and the surface treatment having a particle size of 150˜850 μm using a sieve after grinding. Superabsorbent polymer was obtained.

Example  2

A superabsorbent polymer was prepared in the same manner as in Example 1, except that cooling was performed on the hydrogel polymer to be polymerized by installing a cooling device on the belt-shaped polymerization reactor according to the method shown in FIG. 3. At this time, the water content of the super absorbent polymer after cooling was 55%, the yield was 96%.

Example  3

According to the method shown in FIG. 3, the hydrogel polymer, which has completed polymerization in the belt-shaped polymerization reactor, was transferred to a cutter, and then cooling was performed by using a cooling device installed in the cutter while cutting. After the process was carried out in the same manner as in Example 1 to prepare a super absorbent polymer. At this time, the water content of the super absorbent polymer after cooling was 56%, the yield was 96%.

Example  4

According to the method shown in Figure 4, a super absorbent polymer was prepared in the same manner as in Example 1 except that the polymerization was carried out in a kneader equipped with a cooling device instead of the polymerization reactor on the belt. At this time, the water content of the super absorbent polymer after cooling completion was 59%, yield 98%.

Comparative example  One

For 100 g of the hydrogel polymer of Example 1, grinding was performed at room temperature without a cooler. As a result, entanglement occurred and the hydrogel polymer adhered to the inner wall of the mill. At this time, the water content of the super absorbent polymer was 43%, the yield was 91%. As a result, large particles of 0.4 cm in size were obtained in agglomerated state, and dried at a temperature of 180 ° C. for 2 hours. Thereafter, the dried hydrogel polymer was pulverized and surface treated in the same manner as in Example 1 to prepare an absorbent resin having an average particle diameter of 150 to 850 µm.

Test Example : Evaluation of Water Content and Physical Properties of Super Absorbent Polymers

Test Example  1: moisture content evaluation

The water content of the water absorbent resin according to the Examples and Comparative Examples was measured by the following method, the results are shown in Table 1.

1 g of each absorbent resin powder was put in a dryer using IR (infrared ray), dried at 180 ° C. for 40 minutes, and the moisture content was measured.

Test Example  2: particle size evaluation

The particle size of the polymer on the hydrous gel was evaluated as an average after measuring the size of each sample represented by the representative group using a microscope.

Test Example  3: yield evaluation

The yield evaluation of the polymerization water content was evaluated by the following equation (1).

[Equation 1]

Yield (%) = amount of resin discharged (100-water content) / (100 monomer monomer concentration)

Test Example  4: property evaluation

In order to evaluate the physical properties of the super absorbent polymer of Example and the resin of Comparative Example, the following test was conducted.

1) Water retention measurement

The water retention capacity is divided into 300 ~ 600㎛ size of the pulverized powder, put 0.1g into the tea bag, soaked in 0.9% saline solution for 30 minutes, dehydrated in 250G centrifuge for 3 minutes to calculate the absorbed amount It was.

2) Water Availability

The water-soluble component was fractionated to 300 ~ 600㎛ size of the pulverized powder, 1.0g into a Erlenmeyer flask, 200g into 0.9% saline solution, and stirred for 16 hours in a 500rpm stirrer to measure the water-soluble component It was. Then, after soaking in the saline solution for 30 minutes, dehydrated for 3 minutes in a 250G centrifuge to calculate the amount absorbed.

The measurement method was measured based on EDANA WSP 270.2.

3) Absorbency against Pressure (AUP)

In the case of the pressure absorption capacity was measured by the method of EDANA WSP 242.2, the sample was measured the physical properties after the cross-linking treatment in the same way.

Polymer after gelsizing Superabsorbent polymer Moisture content (%) yield(%) Water retention capacity (g / g) Water Availability (%) AUP (g / g) Example 1 58 98 36 11.2 26.2 Example 2 55 96 35.4 11.5 25.6 Example 3 56 96 35.4 12.3 25 Example 4 59 97 35.2 12 24.3 Comparative Example 1 43 91 34.1 12.5 24.3

In the results of Table 1, in the case of Comparative Example 1 it can be seen that the water content is low, the water-retaining capacity of the superabsorbent resin is low, the water-soluble content is high and the pressure absorption capacity is low.

On the other hand, in Examples 1 to 4 of the present invention, since the hydrogel polymer does not adhere to the polymerizer, the cutter, or the pulverizer, the adhesiveness is low, the yield is particularly high while the desired moisture content is high, and the physical properties of the super absorbent polymer are high. All are equally excellent.

100: manufacturing apparatus of super absorbent polymer
10: mixer 20: monomer composition supply unit
30: belt type polymerization reactor
32, 34: rotating shaft 36: belt
40: hydrogel polymer sheet 42: cut hydrogel polymer
50, 52: Chiller 60: Cutter
70: cutting means 80: kneader

Claims (16)

Forming a monomer composition comprising a water-soluble ethylenically unsaturated monomer and a polymerization initiator;
Introducing the monomer composition into a polymerization reactor and preparing a hydrogel polymer;
Cooling the surface temperature of the hydrogel polymer below a dew point of air in the polymerization reactor by using a cooling device provided at an end of the polymerization reactor; And
Cutting and pulverizing the cooled hydrogel polymer
Method for producing a super absorbent polymer comprising a. The method of claim 1, wherein the cooling is performed at a temperature of −10 ° C. to 50 ° C. for 3 seconds to 5 minutes. The method of claim 1, wherein the cooling device is located at 2/3 to 3/3 with respect to the axial length direction of the polymerization reactor. The method of claim 1, wherein the cooled hydrogel polymer has a water content of 30 to 70%. The method of claim 1, wherein the polymerization is performed for 10 seconds to 30 minutes at a temperature of 20 to 90 ℃. The method of claim 1, wherein the polymerization reactor comprises a kneader, a conveyor belt, or a container moving continuously or discontinuously. The method of claim 1, wherein the monomer composition further comprises a crosslinking agent. The method of claim 1, wherein the cutting and pulverization to form a resin in the form of a powder having an average particle diameter of 150 to 850㎛, and a water content of 0.5 to 10% by weight after drying the resin. Forming a monomer composition comprising a water-soluble ethylenically unsaturated monomer and a polymerization initiator;
Introducing the monomer composition into a polymerization reactor and preparing a hydrogel polymer;
Transferring the hydrogel polymer into a cutter equipped with a cooling device;
Cutting the hydrogel polymer by cooling the surface temperature of the hydrogel polymer below the dew point of air inside the cutter using the cooling device; And
Grinding the cut hydrogel polymer
Method for producing a super absorbent polymer comprising a. The method of claim 9, wherein the cooling is performed at a temperature of −10 ° C. to 50 ° C. for 3 seconds to 5 minutes. The method of claim 9, wherein the cut hydrogel polymer has a water content of 30 to 70%. The method of claim 9, wherein the polymerization is performed for 10 seconds to 30 minutes at a temperature of 20 to 99 ℃. 10. The method of claim 9, wherein the polymerization reactor comprises a kneader, a conveyor belt, or a container moving continuously or discontinuously. The method of claim 9, wherein the hydrogel polymer further comprises the step of drying before the cutting process. The method of claim 9, wherein the monomer composition further comprises a crosslinking agent. 10. The method of claim 9, wherein the cutting and pulverization to form a resin in the form of a powder having an average particle diameter of 150 to 850 ㎛, and the water content of the resin after drying of 0.5 to 10% by weight.

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