KR101257410B1 - Drying apparatus for preparation of super adsorbent polymer and preparation method thereof using the same - Google Patents

Abstract

The present invention relates to a dryer for producing a super absorbent polymer and a method for producing a super absorbent polymer using the same. Specifically, the dryer includes two or more rotating shafts; A conveyor belt installed between the rotation shafts and formed to be able to progress in a predetermined direction by the rotation of the rotation shafts; An outer wall sealing a predetermined drying area on the belt; And a plurality of movable partitions formed on the belt such that the widths of the drying zones are variable along the advancing direction of the belt while dividing the drying zone into a plurality of drying zones.

As the dryer includes an outer wall and a plurality of movable partitions that seal a certain drying area on the belt, drying conditions of the polymer for preparing a super absorbent polymer may be efficiently changed. In addition, it is excellent in the physical properties of the super absorbent polymer to be finally provided using the dryer, it can be usefully used in the industrial field for the production of superabsorbent polymer.

Super Absorbent Polymer, Dryer, Airtight, Outer Wall, Mobile Bulkhead, Hot Air, Acrylic Acid

Description

DRYING APPARATUS FOR PREPARATION OF SUPER ADSORBENT POLYMER AND PREPARATION METHOD THEREOF USING THE SAME}

The present invention relates to a dryer for producing a super absorbent polymer and a method for producing a super absorbent polymer using the same.

Super Absorbent Polymer (SAP) is a synthetic polymer material capable of absorbing moisture of about 500 to 1,000 times its own weight. As a result, it is possible to develop a super absorbent polymer (SAM), an absorbent gel Material), and so on. Such a superabsorbent resin has started to be put into practical use as a sanitary article, and nowadays, in addition to sanitary articles such as diapers for children, there are currently used soil repair agents for horticultural use, index materials for civil engineering and construction, sheets for seedling growing, freshness- And it is widely used as a material for fomentation and the like.

As a method of producing such a superabsorbent resin, there are known methods such as reversed-phase suspension polymerization or aqueous solution polymerization. Reverse phase suspension polymerization is disclosed in, for example, Japanese Patent Laid-Open Nos. 56-161408, 57-158209, and 57-198714. Methods of aqueous solution polymerization include a thermal polymerization method in which the hydrogel polymer is polymerized while being broken and cooled in a kneader having several shafts and a method in which a high concentration aqueous solution is irradiated with ultraviolet rays or the like on a belt to perform polymerization and drying simultaneously And the like are known.

The hydrogel polymer obtained through polymerization reaction as described above is generally marketed as a powdery product after being pulverized through a drying process.

On the other hand, the physical properties of commercially available super absorbent polymer powders generally depend on the polymerization method and the like. That is, the physical properties of the final superabsorbent polymer powder to be produced vary depending on the type and concentration of the monomer during polymerization, the method of the polymerization reaction, the polymerization initiator used, and the like. However, even in the drying step that proceeds after the polymerization reaction, the polymerization reaction proceeds in addition, and depending on the drying time, drying method, drying temperature, etc., the amount of fines generated in the grinding step that proceeds after drying, included in the superabsorbent polymer powder after drying The physical properties of the resin powder to be finally prepared, such as the content of water-soluble components and water holding capacity, are also expected to vary.

Therefore, attention has been paid to research for improving the properties of the superabsorbent polymer powder by increasing the efficiency of the drying step and changing the operating conditions of the drying step. The inventors of the present invention, while preparing a super absorbent polymer having excellent physical properties, while studying the drying device that can achieve the optimum drying conditions and the optimum drying conditions when drying the hydrogel polymer, Completed.

Accordingly, the present invention provides a dryer for preparing a superabsorbent polymer and a method for preparing a superabsorbent polymer using the same, while improving the drying efficiency of the hydrogel polymer when drying, while exhibiting excellent physical properties of the final superabsorbent polymer.

The invention the two or more rotation axis; A conveyor belt installed between the rotation shafts and formed to be able to progress in a predetermined direction by the rotation of the rotation shafts; An outer wall sealing a predetermined drying area on the belt; And a plurality of movable partitions formed on the belt such that the widths of the drying zones are variable along the advancing direction of the belt while dividing the drying zone into a plurality of drying zones. .

In addition, the present invention comprises the steps of thermally polymerizing or polymerizing a monomer composition comprising an ethylenically unsaturated monomer and a polymerization initiator to form a hydrogel polymer; It provides a method for producing a super absorbent polymer comprising the step of drying the hydrogel polymer using the dryer for producing a super absorbent polymer.

Hereinafter, a dryer for preparing a super absorbent polymer according to a specific embodiment of the present invention and a method for preparing the superabsorbent polymer using the same will be described.

Dryer for producing a super absorbent polymer according to an embodiment of the present invention,

Two or more rotation shafts 2;

A conveyor belt 4 disposed between the rotation shafts and formed to be able to progress in a predetermined direction by the rotation of the rotation shafts;

An outer wall (6) for sealing a certain drying area on the belt;

A plurality of movable partitions 8 are formed on the belt so that the width of the drying zones is variable along the advancing direction of the belt while dividing the drying zone into a plurality of drying zones 10.

By including a plurality of movable partitions as described above, it is easy to change the residence time for each drying zone of the polymer in the drying step, it is possible to efficiently dry, and excellent physical properties of the resulting superabsorbent polymer. In addition, by using an outer wall that seals a certain drying area on the belt, it is possible to control the humidity conditions in the plurality of drying areas by adjusting the amount of hot air and / or temperature of the supplied hot air, thereby providing excellent drying properties. The superabsorbent polymer which represents can be manufactured. For reference, Figure 1 briefly shows a dryer for producing a super absorbent polymer according to an embodiment of the present invention.

 On the other hand, 'closing a certain drying area on the belt' means that from the drying start area of one side of the conveyor belt to which the hydrogel polymer 20 is supplied for the progress of the drying step from the drying start area of one side of the conveyor belt to the other end of the conveyor belt to dry It means a state that can be different from the outside conditions such as humidity and temperature by blocking from the outside. In addition, the movable bulkhead 8 may be installed to seal each of the plurality of drying zones 10 as shown in FIG. 1, wherein at least the belt top and the movable bulkhead are perpendicular to each other so that the polymer located on the belt can move. You need to leave some space between the bottoms. Finally, a rail or the like is provided at a portion where the movable bulkhead and the outer wall contact each other, and are designed to freely adjust the movable bulkhead according to dry driving conditions.

On the other hand, the dryer as described above may be in the form of additionally comprising a hot air supply unit 22 and hot air discharge unit 24. The hot air for drying may be supplied through the hot air supply unit, and the laying position is not limited, but preferably, the bottom of the conveyor belt, the ceiling of the outer wall which seals a certain drying area of the upper belt, or the predetermined drying area of the upper belt is sealed. It may be the side of the outer wall. In addition, it may be designed so that hot air can be supplied in different directions or in the same direction in each drying zone according to the drying step, that is, the longitudinal direction of the conveyor belt.

For reference, FIG. 1 briefly illustrates a dryer installed on a ceiling of an outer wall in which a hot air supply unit 22 is installed at a lower end of a conveyor belt, and a hot air discharge unit 24 seals a predetermined drying area of the upper belt. It is. When the hot air supply port is installed at the bottom of the belt as described above, the conveyor belt is provided with two or more holes having a diameter of 0.1 to 10 mm on the surface at regular intervals so that the hot air can be delivered to each drying zone located inside the outer wall where the hot air is sealed. It may be in the form. At this time, the size of the hole can be adjusted within the above-described numerical range in consideration of the particle size of the polymer to be supplied, and the spacing between the holes laid on the surface of the conveyor belt, in consideration of the drying efficiency and the particle size of the polymer to be supplied. , May be arbitrarily selected in the range of 0.1 to 10mm. On the other hand, the shape of the hole is not limited to the shape, such as round, oval, rectangular, square.

FIG. 2 is a simplified illustration of a top surface of a conveyor belt in which at least two circular holes of a particular size are placed at regular intervals on a belt surface according to the embodiment described above. In addition to the conveyor belt in which holes are formed at regular intervals as described above, a conveyor belt having a mesh surface may be used for more efficient drying. 3 is a simplified illustration of a top surface of a conveyor belt in which the belt surface is in mesh form, according to the embodiment described above.

On the other hand, the position of the hot air supply unit supplied for drying is not limited in the configuration as described above, but preferably, in the initial stage of drying (drying zone in which the hydrogel polymer is supplied and drying starts), hot air is formed at the bottom of the conveyor belt. The hot air supply can be designed at the bottom of the belt to be fed upwards, and in the drying zone at the end of the drying step, hot air is supplied from the top of the conveyor belt to the bottom to prevent the dried polymer from being blown by hot air. The hot air supply can be designed on the ceiling of the outer wall.

The supplied hot air circulates inside each closed drying zone and, if necessary, may be partially discharged through the hot air discharge unit during the drying step. In this case, the dryer may further include a hot air temperature and air flow control unit to adjust the temperature and the air flow rate of the hot air supplied. At this time, the discharge control of the hot air discharge unit may be designed to be freely controlled through a simple device such as a valve for the operation of the appropriate drying conditions.

Meanwhile, the hot air supply unit and the hot air discharge unit may be preferably installed in pairs in each of the drying zones, but may be designed in one or more pairs in each drying zone in some cases.

In addition, the dryer for manufacturing the super absorbent polymer according to the embodiment may further include a hydrogel polymer supply part 32 attached to one end of the conveyor belt and a polymer outlet 34 attached to the other end. . Through the hydrogel polymer supply unit as described above, the hydrogel polymer to be dried may be introduced, and the dried polymer may be discharged through the polymer outlet. In particular, in the case of the supply portion of the hydrogel polymer may be in the form of additionally including a polymer feed rate control unit, in order to control the feed rate of the polymer to be supplied.

On the other hand, in the dryer for producing a super absorbent polymer according to the above-described embodiment, one or more movable partitions may be installed without limiting the configuration. The number of drying zones is determined according to the number of movable partitions, and the residence time of the polymer in each drying zone can be controlled during the drying step according to the position of the movable partitions.

On the other hand, in the case of using a dryer equipped with a fixed bulkhead, in order to change the residence time in a specific drying zone, the moving speed of the conveyor belt or the feeding speed of the hydrogel polymer should be changed during the operation of the drying step. The lamination thickness of the polymer supplied for drying on the phases varies from section to section along the entire conveyor belt length direction, so that drying cannot be performed efficiently, resulting in poor physical properties of the resin powder to be dried and finally prepared. In addition, in order to evenly stack the polymer, the feed rate of the hydrogel polymer may be controlled together with the moving speed of the belt, but the operation process is cumbersome, and the above two parameters are controlled by lamination. It is also difficult to make constant the thickness of the hydrogel polymer.

On the other hand, if the number of the movable barrier ribs is one or more, there is no limitation in the configuration, but preferably 3 to 6 laying to be used as a dryer for producing a super absorbent polymer, it can be designed to be divided into 4 to 7 drying zones. As the number of movable bulkheads is laid and operated, it is theoretically possible to create optimized drying conditions. However, since the drying process may be complicated in actual operation, three to six partition walls may be installed.

As will be described in detail in the manufacturing method of the superabsorbent polymer to be described later, the dryer is preferably sequentially along the longitudinal direction from one side of the drying region to which the hydrous gel phase polymer is supplied to start drying, to the other side of the drying region where the drying is terminated. The width of the plurality of drying zones formed may be in a form in which the movable bulkhead is adjusted not to be longer than the width of the preceding drying zone. As described above, when the mobile partition is dried through a controlled drier, drying starts at relatively mild conditions in the initial stage of drying, so that the water content decreases slowly, and thus a superabsorbent polymer having superior physical properties can be manufactured.

In this case, the width of the drying zone in which the drying of the dryer starts may be in a form in which the movable partition wall is adjusted to be 1/7 to 1/2 of the width of the total closed drying area. Most preferably the three movable bulkheads are adjusted at intervals of 1/4 to 1/2, 5/24 to 11/24, and 1/24 to 7/24, respectively, from one side of the drying region where drying starts. Furnace, the drying zone can be designed to be divided into four.

On the other hand, the material of the outer wall and the movable partition wall sealing a certain drying area on the belt can be selected and designed without limiting its configuration as long as it is a material that can make each drying area sealed, and can withstand high temperature hot air. Preferably, steel coated with polytetrafluoroethylene (PTFE), carbon, stainless steel, or polytetrafluoroethylene (PTEF) may be used.

On the other hand, the following provides a method for producing a super absorbent polymer according to another embodiment of the present invention. The preparation method comprises the steps of thermally polymerizing or polymerizing a monomer composition comprising an ethylenically unsaturated monomer and a polymerization initiator to form a hydrogel polymer; And drying the hydrogel polymer using a dryer for preparing a super absorbent polymer according to the above-described embodiment.

In the drying step, the width of the plurality of drying zones sequentially formed along the length direction from one side of the drying region where the hydrogel polymer is supplied to start drying to the other side of the drying region where drying ends is greater than the width of the preceding drying region. The drying step may be performed by adjusting the movable bulkhead not to be long. The inventors of the present invention show that when the moisture content of the polymer decreases slowly at the beginning of the drying step, and when the moisture content is dried relatively steeply by the desired value at the end of the drying step, the physical properties of the final superabsorbent polymer are excellent. It was found that the present invention was completed. In particular, the inventors of the present invention found that the water-absorbing content of the superabsorbent polymer powder prepared according to the above-mentioned method is equal to or higher than that of commercially available products, while the content of the water-soluble component is less than 15.5% by weight of the total superabsorbent polymer powder, and also unreacted. It was confirmed that the amount of the residual monomer also became less than 550 ppm of the total superabsorbent polymer powder. Preferably, the absorbency of the superabsorbent polymer powder prepared according to the above-described method is equal to or higher than that of commercially available, but the content of the water-soluble component is less than 15% by weight of the total superabsorbent polymer powder, and the amount of unreacted residual monomer is also high. It may be less than 500 ppm of the absorbent resin powder. For reference, Figure 4 is a graph briefly showing the water content reduction form according to the drying time of the hydrogel polymer having a drying process using a dryer according to an embodiment of the present invention. As shown in the graph, when the drying process using the dryer according to an embodiment of the present invention, it was found that the change in moisture content occurs slowly with drying time. In addition, as will be described in more detail in the following description of the Examples and Comparative Examples, even if the moisture content of the final superabsorbent polymer powder obtained is the same, as in the embodiment of the present invention when the change in moisture content by drying time is made to the final It turned out that the physical property of the superabsorbent polymer powder obtained is excellent.

On the other hand, in order to control the moisture content of the polymer during the drying step as described above, it is preferable to design the drying zone at the time of starting drying preferably to lengthen the residence time of the polymer, more preferably drying at the time of starting drying Within the zone, water in the form of a spray may be supplied to control humidity as necessary. In addition, by controlling the temperature and air volume of the hot air supplied in each drying zone, it is also possible to adjust the degree of water content decrease according to the drying time. However, since the temperature of the polymer itself also increases considerably according to the drying time by the energy of the accumulated hot wind supplied from the time when the drying starts to the end time, the change of the residence time using the movable bulkhead is also explained. The purpose can be achieved.

At this time, the drying zone in which the hydrogel polymer is supplied to start drying may be dried by adjusting the movable partition wall to be 1/7 to 1/2 of the width of the entire drying area sealed by the outer wall. Further, in a preferred form, when three movable partitions are installed to generate four divided drying zones, the partitions are each 1/4 to 1/2, 5/24 to 11 from one side of the drying zone where drying starts. / 24, and 1/24 to 7/24 can be adjusted to proceed with drying the polymer. However, the above-described width interval of the drying zone is only one example for operating the drying step, and drying starts in consideration of the feed rate of the polymer supplied for drying, the moisture content of the supplied polymer, and the moving speed of the conveyor belt. The width of the plurality of drying zones sequentially formed along the length direction from one side of the zone to the other side of the drying zone where the drying is finished is controlled by controlling the movable partition so that the width of the drying zone is not longer than the width of the preceding drying zone. There is no

On the other hand, the temperature of the hot air supplied to the drying step can also be controlled to an appropriate temperature in consideration of the feed rate of the polymer supplied for drying, the water content of the polymer supplied, the moving speed of the conveyor belt, etc., preferably 80 It is possible to adjust the temperature of the hot air supplied to a temperature of to 250 ℃, more preferably at a temperature of 150 to 170 ℃. If the temperature of the hot air is less than 80 ° C., the time until drying at a desired water content becomes too long. If the temperature of the hot air exceeds 250 ° C., only the surface of the polymer is rapidly dried, and there is a fear that fine powder may occur.

On the other hand, the hot air supply temperature for each drying zone separated by the movable partition wall may be set equally for each section within the temperature within the above-described preferred range, it may be supplied differently for each section. Preferably, the hot air supply temperature for each drying section may be operated in the same manner for the convenience of the process, or 80 to 250 ° C. as described above in each of the preceding drying zones along the drying zone where drying ends from the drying zone where drying starts. It can be operated by setting high within the range of.

As described above, when the hot air supply temperature was slightly increased for each section from the drying start area, the physical properties of the superabsorbent polymer to be finally formed were more excellent, and the concentration of the unreacted monomer was also significantly reduced.

Within the temperature range of the above-mentioned numerical value, in some cases, it may operate by changing the temperature for each drying zone. However, due to the adjustment of the residence time of the drying step, it is possible to adjust the degree of moisture content reduction according to the drying time, it is preferable to operate the temperature similar to each section for easy operation during the drying step.

And, the supply direction of the hot air in the drying step is not limited in its configuration, the hot air supply of the drying zone in which the hydrogel polymer is supplied and drying starts, the drying direction of the polymer in the direction from the bottom of the conveyor belt toward the top of the belt The hot air supply of the drying zone to be terminated may be performed downward from the top of the belt. As described above, the moisture content of the polymer is relatively low in the last drying zone where the drying is completed, and when the hot air is supplied from the lower part of the conveyor belt to the upper part, the lighter polymer may be scattered, which is not preferable.

On the other hand, the air supplied to the hot air is circulated in the drying zone, the circulation speed is not limited in its configuration, but is preferably 1 to 3 m ³ / s. In addition, hot air circulated for a certain time may be discharged through the hot air discharge part at the same time as the drying of the polymer. And, in order to adjust the volume of the hot air discharged through the hot air discharge unit, it is possible to further install a valve or the like.

On the other hand, the ethylenically unsaturated monomer and polymerization initiator used in the polymerization of the hydrogel polymer in the superabsorbent polymer production method according to the above-described embodiment is not limited in its configuration as long as it is generally used in the production of superabsorbent polymer.

Specifically, the polymerization initiator may use a thermal polymerization initiator or a photopolymerization initiator according to UV irradiation depending on the polymerization method. As the thermal polymerization initiator, one or more selected from the group consisting of persulfate initiators, azo initiators, hydrogen peroxide, and ascorbic acid may be used. Specifically, examples of persulfate-based initiators include sodium persulfate (Na ₂ S ₂ O ₈ ), potassium persulfate (K ₂ S ₂ O ₈ ), and ammonium persulfate (NH ₄ ). ₂ S ₂ O ₈ ), and examples of azo initiators include 2, 2-azobis- (2-amidinopropane) dihydrochloride, 2 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) and 4,4-azobis- (4-cyanovaleric acid). More various thermal initiators are well described in Odian's Principle of Polymerization (Wiley, 1981), p203, and are not limited to the examples described above.

On the other hand, as a photopolymerization initiator, benzoin ether, benzoin ether, dialkyl acetophenone, hydroxyl alkylketone, phenyl glyoxylate, benzyl dimethyl ketal, One or more selected from the group consisting of acyl phosphine and alpha-aminoketone may be used. A wider variety of photoinitiators are well described in Reinhold Schwalm's book UV Coatings: Basics, Recent Developments and New Application (Elsevier 2007), p115, and are not limited to the examples described above.

In addition, as the monomer of the polymerization reaction, the water-soluble ethylenically unsaturated monomer may be used as long as it is a monomer commonly used in the production of superabsorbent polymers, without limiting its configuration. 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, acrylic acid, methacrylic acid, maleic anhydride, fumaric acid, crotonic acid, itaconic acid, 2-acryloylethane sulfonic acid, 2-methacryloylethanesulfonic acid, 2- (meth) acryloylpropanesulfonic acid, or 2 Anionic monomers of-(meth) acrylamide-2-methyl propane sulfonic acid and salts thereof; (Meth) acrylamide, N-substituted (meth) acrylate, 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, methoxypolyethylene glycol (meth) acrylate or polyethylene glycol Non-ionic hydrophilic-containing monomer of (meth) acrylate; And an amino group-containing unsaturated monomer of (N, N) -dimethylaminoethyl (meth) acrylate or (N, N) -dimethylaminopropyl (meth) acrylamide and a quaternized product thereof. Can be used.

More preferably, acrylic acid or a salt thereof can be used. When acrylic acid or a salt thereof is used as a monomer, a super absorbent polymer having improved water absorption can be obtained.

On the other hand, the concentration of the water-soluble ethylenically unsaturated monomer in the monomer composition may be appropriately selected and used in consideration of the polymerization time, reaction conditions, etc., preferably 40 to 55% by weight. When the concentration of the water-soluble ethylenically unsaturated monomer is less than 40% by weight, it is disadvantageous in terms of economy, and when it exceeds 55% by weight, the grinding efficiency of the polymerized hydrous gel phase polymer is low.

On the other hand, the hydrous gel polymer obtained by the above methods usually has a water content of 30 to 60% by weight. The polymer having the water content as described above is fed onto the conveyor belt through the hydrogel polymer supply for the progress of the drying step. In addition, the hydrous gel phase polymer supplied for the drying step may be ground to a weight average particle diameter of 2 to 50mm as needed, and then supplied to the dryer for the progress of the drying step.

On the other hand, in the above-described embodiments, the water content of the hydrogel polymer polymerized through thermal polymerization or UV polymerization is the weight of the polymer in the dry state at the weight of the water-containing gel polymer in the content of water to occupy the total weight of the hydrogel polymer Means minus Specifically, as described in Test Example 1 of the present specification, it is defined as a value calculated by measuring the weight loss due to moisture evaporation in the polymer during the process of raising the temperature of the polymer through infrared heating and drying. As described in Test Example 1, the drying condition was set to 20 minutes, including 5 minutes of the temperature rise step, by increasing the temperature from room temperature to 180 ° C. and maintaining the temperature at 180 ° C., thereby measuring the moisture content.

On the other hand, after the drying step as described above, the moisture content of the polymer is preferably dried to 1 to 5% by weight. Drying should be carried out so as to have a numerical range as described above, so that it is easy to handle to prepare a product of the superabsorbent polymer powder later, and the physical properties of the resin powder are also good.

In addition, the hydrogel polymer after the drying step is provided in the form of a super absorbent polymer powder having a weight average particle diameter of 150 to 850 μm after the grinding step. The grinding device mainly used for the preparation of the super absorbent polymer powder is not limited as long as the polymer can be ground in the form of a resin powder. Specifically, a pin mill, a hammer mill, a screw mill, a roll mill, a disc mill, a jog mill, or the like may be used.

The superabsorbent polymer powder prepared in this manner easily controlled the rate of decrease of the moisture content contained in the polymer in the drying step for each drying section, thereby exhibiting excellent physical properties of the resin powder formed into the final product. In addition, the moisture content reduction rate as described above can be easily controlled by using a dryer provided with a movable partition wall, thereby improving the efficiency of the drying process.

Therefore, it is possible to manufacture the superabsorbent polymer more efficiently by the dryer for preparing the superabsorbent polymer and the method for producing the superabsorbent polymer using the same, and can greatly contribute to the industrial field related to the superabsorbent polymer manufacturing.

As described above, according to the present invention, the hydrogel polymer for preparing the superabsorbent polymer can be dried more efficiently, and the physical properties of the superabsorbent polymer thus prepared are also excellent.

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.

One. Manufacturing example : Hydrogel  Preparation of Polymer

Into a 20L glass reactor surrounded by a jacket through which a heat medium was circulated at 60 ° C., a solution (A solution) in which 450 g of acrylic acid was mixed with 9.0 g of 10% tetraethyleneglycol diacrylate (TEGDA) diluted in acrylic acid was injected. 750 g of 25% caustic soda solution (B solution) was slowly added dropwise and mixed.

 When the two solutions were mixed, the temperature of the mixed solution rose to 80 ° C. or more due to the heat of neutralization. After the temperature of the mixed solution was cooled to 80 ° C., when the reaction temperature reached 80 ° C., 22.5 g of a 10% sodium persulfate solution diluted in water was injected.

Sodium persulfate was injected, stirred for a few seconds, and then immediately confirmed that polymerization started. Initially it was a clear liquid, but the solution gradually became opaque, and finally, when a gel was formed in the reactor, the stirring was stopped and the polymer polymerization accompanied with foaming was actively performed. The volume expansion rate at the time of foaming was confirmed to be at least 30 times the volume of the initially injected monomer solution.

After 3 minutes had elapsed, foaming gradually disappeared and a hydrous gel polymer was obtained. The finally obtained hydrous gel polymer had a total water content of 49.2% as measured in the form of a gel with a slightly sticky surface. This polymer was ground to a weight average particle diameter of 3 mm using a primary mill (hardening mill).

2. Example : Hydrogel  Drying of polymer

Example  One

The hydrogel polymer obtained in the above production example was dried using a dryer provided with a movable partition.

Specifically, in order to grasp the characteristics according to the drying of the polymer, a dryer having a movable partition on the belt was manufactured and evaluated. The movable inner bulkhead is composed of three, and the drying zone divided by the movable inner bulkhead is named Zone 1, 2, 3, and 4 sequentially from the beginning of drying for convenience. The polymer was transported on a steel belt with a 0.5 mm round bottom, mounted on a tray (20 cm wide and 10 cm wide) with a net made of stainless steel (SUS) on the floor. This attempted to simulate the actual dryer. The feed rate of the polymer and the moving speed of the conveyor were adjusted so that the stack height of the polymer was 5 cm. The air volume and temperature were adjusted by installing a hot air fan that can supply hot air in each zone. The total length of the belt was 1.2 m and the width was 30 cm. In Zones 1 and 2, the hot air supply was installed at the bottom of the belt so that the hot air was supplied from the bottom up, and in the zones 3 and 4, the hot air supply was installed at the top of the belt to supply the hot air from the top to the bottom.

On the other hand, the belt moving speed was evaluated by fixing the total time required for drying at 40 cm / 3 cm / min.

Example 1 is a case in which the residence time for each zone is different, and in this case, Zone 1 and 2 are extended to 15 minutes and 12 minutes, and detailed conditions are shown in Table 1.

Example  2

Example 2 is a case where there is a movable partition and the total residence time is set to 60 minutes and evaluated. As shown in Table 2, drying was performed by adjusting the position of each movable partition wall to have a residence time. The belt movement speed was fixed at 2cm / min, and residence time and hot air supply temperature conditions for each section are shown in Table 1.

Example  3

In Example 3, the belt movement speed, the polymer feed rate, and the movable spacing of the movable partitions were adjusted so that the residence time in each section was the same as in Example 1. However, as in Example 1, the drying was performed by setting the temperature conditions for each drying section a little higher. The residence time and temperature conditions for each section are shown in Table 1.

3. Comparative example : Hydrogel  Drying of polymer

Comparative example  One

As a fixed partition, the intervals between partitions were the same so that the residence time of each zone was constant, and other drying conditions were the same as in Example 1. Detailed conditions are shown in Table 1.

Comparative example  2

As a fixed bulkhead, the intervals between the bulkheads were the same so that the residence time of each zone was constant, and the other conditions were the same as in Example 2. Detailed conditions are shown in Table 1.

Comparative example  3

As the fixed partition, the intervals between the partitions were the same so that the residence time of each zone was constant, and the other conditions were the same as in Example 3. Detailed conditions are shown in Table 1.

Comparative example  4

As the fixed bulkheads, the intervals between the bulkheads were the same so that the residence time of each zone was constant, and the remaining conditions were the same as in Example 3 except that the hot air supply temperature for each zone was also set equal to 155 ° C. . Detailed conditions are shown in Table 1.

Dryer operating conditions Zone 1
(Stay time / temperature) Zone 2
(Stay time / temperature) Zone 3
(Stay time / temperature) Zone 4
(Stay time / temperature) Example 1 15 minutes / 150 ℃ 12 minutes / 155 ℃ 8 minutes / 160 ℃ 5 minutes / 165 ℃ Example 2 20 minutes / 150 ℃ 20 minutes / 155 ℃ 10 minutes / 160 ℃ 10 minutes / 165 ℃ Example 3 15 minutes / 155 ℃ 12 minutes / 160 ℃ 8 minutes / 165 ℃ 5 minutes / 170 ℃ Comparative Example 1 10 minutes / 150 ℃ 10 minutes / 155 ℃ 10 minutes / 160 ℃ 10 minutes / 165 ℃ Comparative Example 2 15 minutes / 150 ℃ 15 minutes / 155 ℃ 15 minutes / 160 ℃ 15 minutes / 165 ℃ Comparative Example 3 10 minutes / 155 ℃ 10 minutes / 160 ℃ 10 minutes / 165 ℃ 10 minutes / 170 degrees Celsius Comparative Example 4 10 minutes / 155 ℃ 10 minutes / 155 ℃ 10 minutes / 155 ℃ 10 minutes / 155 ℃

4. Example  And In a comparative example  After drying, crushing

The polymer particles dried according to the above Examples and Comparative Examples were ground in a food mixer (Hanil Electric, model name FM681) for 30 seconds, and then classified into a resin powder having a particle size of 300 to 600 µm using a 30 to 50 mesh network. After that, the physical properties were evaluated. On the other hand, the fine powder content (% by weight) after the final grinding step as described above is shown in Table 1.

5. Test Example : Comparative example  And Example  Evaluation of Physical Properties of Superabsorbent Polymer Powders Prepared accordingly

Test Example  One: Hydrogel  Moisture Content Evaluation of Polymers

The water content of the hydrogel polymer according to the above Examples and Comparative Examples was measured by the following method.

The moisture content of the polymer was measured by measuring the weight loss due to moisture evaporation in the polymer during the process of raising the temperature of the polymer through infrared heating. Drying conditions were raised to 180 ℃ at room temperature and maintained at 180 ℃ total drying time was set to 20 minutes, including 5 minutes in the temperature rise step to measure the water content.

On the other hand, in order to evaluate the physical properties of the super absorbent polymer powder according to the Examples and Comparative Examples was carried out the following test

Test Example  2: Function  Measure

The water holding capacity was measured with respect to the particle classified by the method mentioned above. Conservative performance was measured according to the EDANA method WSP 241.2. Put 0.2g of sample classified into 30-50 mesh into a tea bag, soak in 0.9% saline solution for 30 minutes, remove water for 3 minutes in a centrifuge set at 250G and weigh it to measure the amount of water in superabsorbent resin. The water holding capacity was measured in the manner.

Test Example  3: Soluble  Ingredient amount measurement

The water-soluble component was measured about the particle classified by the above-mentioned method. Soluble ingredients were measured according to the EDANA method WSP 270.2. 1.0 g of the sample classified into 30-50 mesh was placed in 200 g 0.9% saline solution and stirred for 16 hours while stirring at 500 rpm, followed by filtering the aqueous solution with filter paper. The filtered solution was first titrated with a caustic soda solution of pH 10.0, and then subjected to reverse staticity with a hydrogen chloride solution of pH 2.7 to calculate the uncrosslinked polymer material as an aqueous component from the amount necessary for neutralization.

Test Example  4: unreacted Monomeric  Concentration measurement

The unreacted monomer component was measured for the particles classified by the above-described method. Unreacted monomer component was measured according to the EDANA method WSP 210.2. 1.0 g of the sample classified into 30-50 mesh was placed in 200 g 0.9% saline solution, and stirred for 16 hours while stirring at 500 rpm, followed by filtration of the aqueous solution with filter paper. The solution was analyzed by liquid chromatography, and the concentration of unreacted monomer was calculated from the calibration curve according to the area ratio of chromatogram to AA acid according to a predetermined procedure. The amounts of unreacted monomers according to the examples and the comparative examples are shown in Table 2 below.

Moisture content Function
(g / g) Soluble
ingredient
(wt%) Amount of unreacted monomer
(ppm) Immediately after polymerization (% by weight) After drying step (% by weight) Example 1 49.2 2.7 38.6 13.8 420 Example 2 Homology 2.4 40.2 14.5 380 Example 3 Homology 1.8 43.3 15.1 520 Comparative Example 1 Homology 3.8 37.2 18.4 680 Comparative Example 2 Homology 3.0 38.3 17.2 590 Comparative Example 3 Homology 2.3 46.4 23.2 780 Comparative Example 4 Homology 4.5 36.3 16.2 720

From the above test results, when the drying is performed by adjusting the residence time for each section by using a dryer provided with a movable partition, as shown in Table 2, the width of the drying zone of the dryer is not fixed, rather than being fixed. The amount of the monomer was small, and the polymerization product showing high water-retaining ability while having low water-soluble components was secured.

Therefore, the dryer of the present invention, which can easily control the residence time for each section, and a method of preparing a super absorbent polymer using the same can be usefully used for the preparation of a polymer having excellent physical properties.

1 is a view briefly showing a dryer for preparing a super absorbent polymer according to one embodiment of the present invention.

FIG. 2 is a schematic view illustrating a top surface of a conveyor belt in which a fine hole is disposed at a predetermined interval on a surface of the dryer for preparing a super absorbent polymer according to an embodiment of the present invention.

Figure 3 in the dryer for producing a super absorbent polymer according to an embodiment of the present invention, it shows a brief view of the upper surface of the conveyor belt having a mesh structure.

4 is a graph showing a water content reduction form according to the drying time of the hydrogel polymer having a drying process using a dryer according to an embodiment of the present application.

<Description of Drawing>

100: dryer for manufacturing superabsorbent polymer

2: rotary shaft 4: conveyor belt

6: outer wall 8: movable bulkhead

10: drying zone

20: hydrogel polymer

22: hot air supply unit 24: hot air discharge unit

32: hydrogel polymer supply 34: polymer outlet

Claims (19)

Two or more axes of rotation; A conveyor belt installed between the rotation shafts and formed to be able to progress in a predetermined direction by the rotation of the rotation shafts; An outer wall sealing a predetermined drying area on the belt; And And a plurality of movable partitions formed on the belt such that the widths of the drying zones are variable along the advancing direction of the belt while dividing the drying zone into a plurality of drying zones. The method of claim 1, Dryer for producing a super absorbent polymer further comprising a hot air supply and hot air discharge. The method of claim 1, Dryer for manufacturing a super absorbent polymer further comprising a hydrogel polymer supply portion attached to one end of the conveyor belt and a polymer outlet attached to the other end. The method of claim 1, Dryer for manufacturing a super absorbent polymer having three to six movable partitions. The method of claim 1, The widths of the plurality of drying zones sequentially formed along the length direction from one side of the drying zone where the hydrogel polymer is supplied and drying to the other side of the drying zone where drying ends are not longer than the width of the preceding drying zone. Dryer for manufacturing superabsorbent polymer resin with controlled bulkheads. 6. The method of claim 5, A dryer for preparing a super absorbent polymer, wherein the movable partition is adjusted such that the width of the first drying zone where the hydrogel polymer is supplied to start drying is 1/7 to 1/2 the width of the total drying area closed by the outer wall. 6. The method of claim 5, Dryer for manufacturing a super absorbent polymer in which three movable bulkheads are adjusted at intervals of 1/4 to 1/2, 5/24 to 11/24, and 1/24 to 7/24, respectively, from one side of the drying zone where drying starts. . The method of claim 1, The outer wall and the movable partition wall is made of polytetrafluoroethylene (PTFE), carbon, stainless steel, or polytetrafluoroethylene (polytetrafluoroethylene, PTEF) is a dryer for manufacturing a super absorbent polymer. The method of claim 1, Dryer for producing a super absorbent polymer further comprises a hot air supply unit and hot air discharge portion attached to each of the plurality of drying zones. The method of claim 1, The conveyor belt is a dryer for producing a super absorbent polymer in which at least two holes having a diameter of 0.1 to 10 mm on the surface is laid at regular intervals. 11. The method of claim 10, The gap between the holes is 0.1 to 10 mm dryer for manufacturing a super absorbent polymer. Thermally polymerizing or polymerizing a monomer composition including an ethylenically unsaturated monomer and a polymerization initiator to form a hydrogel polymer; Method for producing a super absorbent polymer comprising the step of drying the hydrogel polymer using a dryer according to any one of claims 1 to 11. 13. The method of claim 12, The widths of the plurality of drying zones sequentially formed along the length direction from one side of the drying zone where the hydrogel polymer is supplied and drying to the other side of the drying zone where drying ends are not longer than the width of the preceding drying zone. The manufacturing method of the super absorbent polymer which adjusts and isolates a partition. 13. The method of claim 12, A method of producing a super absorbent polymer, wherein the movable partition is dried such that the width of the first drying zone where the hydrous gel polymer is supplied to start drying is 1/7 to 1/2 of the width of the entire drying area closed by the outer wall. 13. The method of claim 12, Superabsorbent polymer which is dried by adjusting three movable partition walls at intervals of 1/4 to 1/2, 5/24 to 11/24, and 1/24 to 7/24, respectively, from one side of the drying region where drying starts. Method of preparation. 13. The method of claim 12, Method for producing a super absorbent polymer to dry by supplying hot air of 80 to 250 ℃ in the drying step. 13. The method of claim 12, Hot air supply in the drying zone where the hydrogel polymer is supplied and drying starts is directed from the bottom of the conveyor belt toward the top of the belt, and hot air supply in the drying zone where the drying of the polymer is finished is directed from the top of the belt toward the bottom of the belt. Method of producing a super absorbent polymer by drying the step. 13. The method of claim 12, The water content of the polymer after the drying step is a method for producing a super absorbent polymer of 1 to 5% by weight. 13. The method of claim 12, After the drying step further proceeds to the grinding step to prepare a super absorbent polymer for preparing a resin in the form of a powder having a weight average particle diameter of 150 to 850 ㎛.

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