JPH0762073B2 - Continuous granulation method and apparatus for highly water-absorbent resin powder - Google Patents

Description

Detailed Description of the Invention [Technical Field] The present invention relates to a method and apparatus for continuously granulating highly water-absorbent resin powder, in which fine powder contained in the highly water-absorbent resin powder is granulated to set the particle size of the resin powder within a certain range.

BACKGROUND ART In recent years, superabsorbent resin powders have come to be used in a variety of fields, including hygiene products such as sanitary cotton and disposable diapers, and water retention agents. Such superabsorbent resins are generally produced by polymerizing a resin material, drying the polymer, and then pulverizing the polymer in a pulverizer. As a result, the pulverized superabsorbent resin powder contains fine particles having a particle size smaller than the desired size. If such fine particles are present, the problem of scattering of the fine particles occurs when the superabsorbent resin powder is used.

Therefore, in the past, in order to improve the dry flowability of resin powder, as shown in Japanese Patent Application Laid-Open No. 52-121658, a scattering prevention agent was mixed into the resin powder, or as shown in Japanese Patent Application Laid-Open No. 63-1988,
As shown in Publication No. 39934, in order to suppress scattering of fine powder contained in the resin powder, a dust-preventing agent is mixed into the resin powder.

Other methods have been considered, such as using a sieve to remove fine particles contained in the resin powder or granulating the fine particles using a binder. However, the former method is economically disadvantageous and therefore undesirable. In addition, the latter method generally uses an organic solvent-based binder, which not only poses a risk of fire during the drying process after granulation, but also poses a biological safety problem due to residual organic solvents.
If an aqueous solution is used as a binder, the problems of the latter method described above do not occur, but since the superabsorbent resin powder to be sintered and granulated has the property of rapidly absorbing the aqueous solution, it is difficult to uniformly disperse and mix the aqueous solution, and large, high-density lumps tend to form. Therefore, when these lumps are crushed and granulated, fine powder is generated, making it difficult to obtain uniform granules.

As a method for solving this problem, as shown in Japanese Patent Application Laid-Open Nos. 61-97333 and 61-101536, a method has been attempted in which a high water absorbent resin powder and an aqueous liquid are uniformly mixed and granulated using a specific mixer such as a high speed rotating paddle mixer or an air flow mixer, and then the granulated product is crushed and granulated.

However, it has been found that the basic particle size becomes small when the superabsorbent resin powder and the aqueous liquid are mixed by shear mixing using a high-speed rotating mixer as described above. This is thought to be because, when the resin powder is mixed in the mixer, the particles repeatedly collide with each other and are subjected to mechanical shear, causing particle breakage.
If such particle damage occurs in the resin powder, deterioration of quality due to the damage to the particle surface can become a problem, particularly when a resin whose particle surface has been treated for quality improvement is mixed.

When the above-mentioned air flow type mixer is used, continuous mixing cannot be performed, which is problematic in that it is not suitable for industrial production of highly water-absorbent resin powder. In addition, it is necessary to add the aqueous liquid little by little over a long period of time while heating the resin powder, which makes it difficult to maintain and manage the equipment in practice.

On the other hand, Japanese Patent Application Laid-Open No. 1-236,932 proposes a spray granulation apparatus for continuously granulating powder, and discloses a spray granulation apparatus having a drying chamber, a powder supply device having a powder discharge outlet at the top of the drying chamber, and spray nozzles provided on both sides of the powder discharge outlet and below the outlet for spraying droplet streams that intersect with each other.

This apparatus is effective for continuously granulating powders such as dextrin and melamine resin. However, when used to granulate superabsorbent resin powder with an aqueous liquid, the sintered granules of superabsorbent resin, which have absorbed water and become more adhesive, adhere to the wall, and the amount of the resulting adhesion increases over time, making it impossible to achieve the original purpose of continuous granulation. Furthermore, when the superabsorbent resin powder and the aqueous liquid come into contact at a position where the aqueous liquids intersect, the adhesiveness of the superabsorbent resin powder makes it difficult to disperse the particles with the impact force of the ejected droplets, resulting in an uneven contact state. As a result, the resulting granules contain a large amount of fine powder that is not granulated at all and "mamako" (particles that have absorbed too much water).

In view of the current state of the art, the present inventors have conducted extensive research into a granulation method and apparatus for continuously granulating superabsorbent resin powder and removing fine powder contained in the resin powder. As a result, the present inventors have completed the present invention, which enables high-quality superabsorbent resin powder having a particle size within a desired range to be obtained by causing the resin powder dispersed by the air current and the aqueous liquid to flow downward from the top to the bottom of the cylinder in a parallel flow state to avoid collisions between the superabsorbent resin powder and the aqueous liquid, thereby caking the superabsorbent resin powder containing the fine powder, and crushing and granulating the caking granules thus formed, as necessary.

Therefore, an object of the present invention is to provide a continuous granulation method and apparatus which uses an aqueous liquid as a binder to caking and granulate resin powder while avoiding collisions between particles of highly water-absorbent resin powder, and if necessary, crushes and granulates the resulting powder, thereby making it possible to remove fine powder contained in the highly water-absorbent resin powder.

DISCLOSURE OF THE INVENTION The object of the present invention is to provide a method for producing a water-absorbent resin powder by introducing a highly water-absorbent resin powder into a cylindrical body having an open bottom end by an airflow from a dispersing member disposed at the top of the cylindrical body, and spraying fine droplets of an aqueous liquid downward from a nozzle disposed inside the dispersing member, so that the highly water-absorbent resin powder dispersed by the airflow flowing downward toward the bottom of the cylindrical body and the droplets flowing downward while diffusing in the radial direction toward the bottom of the cylindrical body come into contact with each other in a parallel flow state,
This is achieved by a method for continuous granulation of a highly water-absorbent resin powder, characterized in that a granulated mass in which a plurality of the highly water-absorbent resin powder particles are bound together by the droplets is removed from the lower part of the cylinder, and the removed granulated mass is crushed and granulated as necessary.

The above object can also be achieved by a continuous granulation device for high water absorbent resin powder, which comprises a cylinder provided with temperature control means and with an open lower end, high water absorbent resin powder dispersing means which is provided at the upper part of the cylinder and is a hopper-like object equipped with airflow generating means, means for spraying fine droplets of an aqueous liquid in a cocurrent flow with the falling direction of the resin powder, which is provided inside the high water absorbent resin powder dispersing means, and means for removing a coagulated granule formed by bonding a plurality of the high water absorbent resin powder together via the droplets, which is provided near the lower opening of the cylinder.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a cross-sectional view showing an apparatus embodying a method for continuously granulating highly water-absorbent resin powder according to one embodiment of the present invention; FIG. 2 is a cross-sectional view showing an apparatus according to another specific example; FIG. 3 is a cross-sectional view showing an apparatus according to a comparative example; and FIG. 4 is a cross-sectional view showing an apparatus for measuring water absorption capacity against pressure.

According to the present invention, a plurality of superabsorbent resin powder particles are bound together in a cylindrical container using droplets of an aqueous liquid as a binder to form a sintered granule. This converts fine powder particles of a predetermined particle size or smaller into resin powder particles of a predetermined particle size or larger, resulting in the removal of the fine powder particles. In the process of forming the sintered granules, the superabsorbent resin powder particles, dispersed by an airflow including the fine powder particles, are introduced downward from a dispersing member installed at the top of the cylindrical container. At the same time, droplets of the aqueous liquid are sprayed from a nozzle installed inside the dispersing member. This creates a region within the cylindrical container where the resin powder particles and the droplets flow in a parallel flow, avoiding frequent collisions between the resin powder particles. In this state, the resin powder particles come into contact with each other through the droplets, sintering, and forming the sintered granules. Because the superabsorbent resin powder is easily granulated, there is no need for strong collisions between the resin powder particles and the droplets, or between the resin powder particles with droplets attached before forming the sintered granules. This prevents the resin powder itself from being damaged or destroyed, and prevents damage to the surface, and allows highly water-absorbent resin powder of a desired particle size or larger to be obtained.

The sintered granules may be used as they are for applications such as sanitary goods and water retention agents, but in order to improve handling and workability, it is preferable to further crush and granulate the sintered granules after making them by the above procedure.
Moreover, since the coarse particles are crushed, the resulting highly water-absorbent resin powder has a desired particle size or larger and does not contain any coarse particles.

In addition, if a large amount of aqueous liquid is used in the continuous granulation process,
The surface of the resulting sintered granules may be sticky. In such cases, it is preferable to leave the sintered granules for a certain period of time or heat them to reduce the stickiness before crushing and granulating. In this case, drying is not necessarily required. When heating, the conditions are a temperature of 50 to 150°C.
The temperature is preferably 200°C for 3 minutes to 12 hours, and more preferably 70 to 120°C for 10 minutes to 2 hours.

The highly water-absorbent resin powder used in the present invention is substantially insoluble in water, absorbs water, and swells, and has a water absorption capacity of 10 times or more, preferably 50 times or more. The method of the present invention is particularly effective for granulating highly water-absorbent resin powder with a high water absorption capacity.

Such a highly water-absorbent resin is, for example, a hydrolyzate of a starch-acrylonitrile graft copolymer (JP-B-2003-100626).
49-43395), neutralized starch-acrylic acid graft polymer (JP-B-53-46199, JP-B-55-210
41), saponified acrylic acid ester-vinyl acetate copolymer (JP-B-53-13495, JP-B-55-19243
No. 1979), modified cross-linked polyvinyl alcohol (JP 54
-20093), partially neutralized polyacrylate crosslinked bodies (JP-A-55-84304, JP-A-56-93716, JP-A-56-161408, JP-A-58-71907), crosslinked isobutylene-maleic anhydride copolymers (JP-A-56-161408, JP-A-58-71907),
36504) and the like.

These highly water-absorbent resins may be those in which the crosslinking is uniform, or those in which the crosslinking is uniform.
As disclosed in the above publication and JP-A-58-42602, any of the materials may be used, including those that have been subjected to a surface crosslinking treatment, and therefore the method of the present invention is not limited to any particular material, but is particularly suitable for those that have been subjected to a surface treatment.

The particle size distribution of the highly water-absorbent resin powder is such that 50% by weight of the powder passes through a 100-mesh standard sieve (0.15 mm or less).
If it exceeds 50% by weight, the proportion that does not cohere and granulate in the cylinder increases, and if it is attempted to granulate it, a large amount of aqueous liquid is required, which causes severe adhesion to the equipment, making continuous granulation impossible.
Furthermore, if the highly absorbent resin contains a large amount of aqueous liquid, the performance of the highly absorbent resin will be reduced.

The aqueous liquid used in the present invention is water alone or a mixture of water and an organic solvent miscible with water. Examples of the organic solvent miscible with water include lower alcohols, tetrahydrofuran, and acetone.
Various compounds or mixtures may be dissolved or dispersed in water alone or in the above-mentioned mixtures. Examples of such compounds or mixtures include the deodorants and plant growth aids described in JP-A-61-97333, as well as slurries of finely divided silica.

The amount of aqueous liquid used in the present invention is not particularly limited and can be within a wide range, but if the amount is too small, it is difficult to obtain a significant granulation effect, and conversely, if the amount is too large, it may cause a decrease in water absorption performance when no drying step is performed after granulation. Therefore, the amount of aqueous liquid is usually 1 to 50 parts by weight, more preferably 3 to 50 parts by weight, per 100 parts by weight of the highly water-absorbent resin powder.
It is recommended to use 35 parts by weight.

The fine droplets of the aqueous liquid used in the present invention preferably have an average diameter of 300 μm or less, more preferably 250 μm or less. Usually, the average diameter is 50 to 200 μm. If the average diameter exceeds 300 μm, it becomes difficult to uniformly spread or disperse the aqueous liquid, and high-density lumps may be formed, or a large amount of fine powder may remain in the cylinder without being granulated, which is undesirable.
Methods for generating fine droplets of less than 1 m include the rotating disk method, the pressure nozzle method, and the two-fluid nozzle method. In the present invention, since the highly water-absorbent resin powder is introduced from above, a two-fluid nozzle capable of preventing granulation and adhesion by ejecting gas into the droplet sprayer is suitable. Examples of such a nozzle include the Lumina (Fuso Seiki Co., Ltd.)
Examples of suitable nozzles include a two-fluid nozzle (manufactured by Kobe Casting Co., Ltd.) and a Spray Vector (manufactured by Kobe Casting Co., Ltd.). When the above-mentioned highly water-absorbent resin powder and droplets of the aqueous liquid are allowed to flow downward from the top of a cylindrical body while being diffused or dispersed, the resin powder particles are coagulated using the droplets as a medium, forming coagulated granules with large particle sizes. These particles are then fed into a crusher for crushing and granulation. As the crusher, the New Speed Mill (manufactured by Okada Seiko Co., Ltd.), Flash Mill (manufactured by Fuji Paudal Co., Ltd.), or Speed Mill (manufactured by Showa Engineering Co., Ltd.) disclosed in Japanese Patent Laid-Open Publication No. 61-97333 can be used. The crushing and granulation using these nozzles may be carried out immediately after coagulation and granulation in the cylindrical body, or after leaving the mixture for a certain period of time.

When the highly water-absorbent resin powder is charged into the cylinder, it is charged from above the cylinder while being diffused or dispersed. In order to charge the highly water-absorbent resin powder uniformly into the cylinder, it is preferable to charge the highly water-absorbent resin powder by dispersing it using an air current.

The compressed airflow from the airflow generating means is blown onto the highly water-absorbent resin powder fed from the feeding member, and the resin powder is also caused to flow downward by the action of this airflow. Air is usually used as the airflow. In this case, the mixing ratio of the highly water-absorbent resin powder to the airflow is 0.1 to ⁵ kg/Nm3, preferably 0.5
It is preferable that the amount of the superabsorbent resin powder is in the range of 1 to ² kg/Nm3, and it is necessary that the powder is sufficiently dispersed before it comes into contact with the droplets. If the amount of the superabsorbent resin powder exceeds 5 kg/ ^Nm3 , the dispersion or diffusion of the superabsorbent resin powder by the air flow becomes insufficient, and uniform contact with the droplets of the aqueous liquid cannot be achieved, resulting in a large amount of residual fine powder. On the other hand, if the amount of the superabsorbent resin powder exceeds 0.1 kg/Nm3, the powder will not be sufficiently dispersed or diffused by the air flow, and uniform contact with the droplets of the aqueous liquid will not be achieved, resulting in a large amount of residual fine powder.
If the ratio is less than ³ , a huge amount of gas is introduced, which requires excessively large equipment to vent it, making it impractical. Furthermore, if the venting is insufficient, the amount of coke adhering to the inner surface of the cylinder increases, making continuous granulation difficult. The residence time of the airflow in the cylinder is determined by controlling the flow rate of the airflow along with the ratio of the airflow to the superabsorbent resin powder described above. It is preferable to set this residence time at about 0.1 to 30 seconds, and particularly about 5 to 15 seconds.

The inner wall of the cylinder is kept at 50 to 200°C by providing a heat insulating means.
It is preferable to keep the temperature within the above range, preferably 70 to 200°C. For example, the inner wall temperature can be kept within the above range by forming a jacket around the cylindrical body and circulating steam through it. This prevents the adhesion of the caking body to the inner surface of the cylindrical body.

The position at which the highly water-absorbent resin powder is introduced and the position at which the fine droplets of the aqueous liquid are sprayed are as follows: the highly water-absorbent resin powder is introduced downward from a dispersing member installed at the top of the cylinder in a dispersed state by an air current, and the fine droplets of the aqueous liquid are sprayed downward from a nozzle located inside the dispersing member, preferably at approximately the center.

In this case, the highly water-absorbent resin powder introduced into the cylindrical body is
The droplets flow downward due to their own weight, the airflow for dispersion, and the airflow containing the droplets from the nozzle.
At this time, the superabsorbent resin powder only flows downward from the top to the bottom of the cylinder, so collisions between the powder particles that would damage the superabsorbent resin powder particles are avoided. The fine droplets sprayed from the nozzle also flow downward due to the spraying force and their own weight, while spreading as they move downward in the cylinder. As a result, the flowing superabsorbent resin powder flows downward from the top to the bottom, while the droplets of the aqueous liquid flow downward from the top to the bottom while spreading at a predetermined angle in the radial direction within the cylinder. Therefore, the resin powder and the aqueous liquid come into contact in a parallel flow state, and multiple resin powder particles are bonded together using the droplets adhering to the resin powder as a binder to form a bonded granule.

The nozzle for spraying the aqueous liquid is installed inside, preferably approximately at the center of, the dispersion member for the highly water-absorbent resin powder. However, if the nozzle is installed outside the dispersion member, the state of contact between the highly water-absorbent resin powder and the aqueous liquid becomes uneven, and the resulting granules contain a large amount of fine powder that is not granulated at all and "mamako" that has absorbed too much water.

Furthermore, the droplets of the aqueous liquid spread and wet the walls, increasing the amount of sintered granules of the highly water-absorbent resin adhering to the walls, which is undesirable because it makes it impossible to achieve the original purpose of continuous granulation.

The sintered granules thus obtained by granulating a plurality of highly water-absorbent resin powders with an aqueous liquid are transported to the next process by a belt conveyor or the like placed below the cylinder.

The cylinder may be a rectangular cylinder whose cross section is a square or a polygon with a larger angle, or a conical cylinder such as a cone or pyramid, but among these, a cylindrical cylinder is preferred.

Furthermore, particulate silica may be premixed with the superabsorbent resin powder used in the present invention to improve its fluidity, or carbon black and/or activated carbon may be premixed with it to improve light resistance and provide a deodorizing effect. Particulate silica is a material primarily composed of silicon dioxide having an average particle size of 50 μm or less, such as "Aerosil 200" manufactured by Nippon Aerosil Co., Ltd. or "Carplex #80" manufactured by Shionogi Pharmaceutical Co., Ltd.

The amount of the particulate silica used is more than 0 and not more than 20 parts by weight, particularly 0.1 to 5 parts by weight, per 100 parts by weight of the highly water-absorbent resin powder.
The ratio is parts by weight. Even if the amount exceeds 20 parts by weight,
The effect does not correspond to the amount added, and the additive may inhibit the high water absorption of the resin powder, or in some cases make granulation difficult.

The carbon black and/or activated carbon may be in the form of a commercially available powder.

The amount of carbon black and/or activated carbon used is more than 0 to 50 parts by weight, particularly 0.1 to 10 parts by weight, per 100 parts by weight of the highly water-absorbent resin powder. An amount exceeding 50 parts by weight is undesirable because it inhibits the high water absorbency of the resulting granules.

When a superabsorbent resin powder containing particulate silica is used, the ratio of the aqueous liquid to the total amount of the two components (100 parts by weight) is preferably 1 to 50 parts by weight, particularly 3 to 35 parts by weight, as in the case of not containing particulate silica. Similarly, when a superabsorbent resin powder containing carbon black and/or activated carbon is used, the same ratio is preferably used.

The present invention will be described in detail below with reference to examples, but the scope of the present invention is not limited to these examples.

In the following examples, unless otherwise specified, "%" refers to weight percent.
All parts are by weight.

Example 1 A jacketed stainless steel double-arm kneader with an internal volume of 10, an opening of 220 × 260 mm, a depth of 240 mm, and two sigma-type blades with a blade rotation diameter of 120 mm was fitted with a lid. 43% of an aqueous solution of sodium acrylate was poured into the kneader.
5500 g of an aqueous solution of acrylate monomers (monomer concentration 37%) consisting of 80 g of acrylic acid, 414 g of acrylic acid, and 706 g of ion-exchanged water
% by weight, neutralization rate 75 mol%) and 3.4 g of trimethylolpropane triacrylate were added, and nitrogen gas was blown into the reaction system to convert the atmosphere to nitrogen.
The mixture was rotated at a speed of 56 rpm and heated by passing 35° C. hot water through the jacket, while 2.8 g of ammonium sulfate and 0.14 g of 1-ascorbic acid were added as polymerization initiators.
After the addition of the initiator, polymerization started in 5 minutes, the temperature in the reaction system reached 83°C in 20 minutes, and the hydrogel-like material was broken into fine particles with a diameter of about 5 mm. The polymerization was completed in 60 minutes, and the hydrogel-like polymer was taken out.

This hydrous gel polymer was spread to a thickness of 50 mm in a hot air dryer and dried for 90 minutes with hot air at a temperature of 150°C to obtain a highly water-absorbent resin with a water content of 10% by weight or less, which was then pulverized in a hammer-type pulverizer and sieved through a 20-mesh wire screen to obtain water-absorbent resin (1).

A liquid consisting of 0.5 parts by weight of glycerin, 2 parts by weight of water, and 6 parts by weight of methanol was mixed with 100 parts by weight of the obtained water absorbent resin (1), and the mixture was heat-treated and then sieved through a 20-mesh wire screen to obtain a highly water absorbent resin powder (A-1) as the 20-mesh pass-through material.

To 100 parts by weight of the obtained highly water-absorbent resin powder (A-1), 6 parts by weight of water was added, and continuous granulation was carried out by the following method.

That is, as shown in Figure 1, a cylinder 10 having an opening 11 at its lower end was provided facing vertically, and a dispersion member 12, which was a hopper-like object, was installed in the center of the upper part of this cylinder 10 and was formed by a tapered portion 16a whose diameter became smaller as it went downward, and a straight portion 16b extending downward from the lower end of this tapered portion 16a.

Compressed air was blown from an airflow generating means consisting of a nozzle 18a attached to the tip of the pneumatic piping 18 onto the highly absorbent resin powder (A-1) fed from the feeding member 13 onto the upper surface of the tapered portion 16a, and the highly absorbent resin powder (A-1) was dispersed in the radial direction of the cylinder 10 by its own weight and the action of this airflow and flowed downwards of the cylinder 10.

A pipe 14 was attached to the center of the dispersion member 12, and a nozzle 15 was attached to the tip of this pipe, positioned below the dispersion member 12. Air and water were simultaneously ejected from this nozzle 15, and the water was sprayed downward inside the cylinder 10 in the form of fine droplets. The sprayed water droplets flowed downward inside the cylinder 10 while diffusing in the radial direction of the cylinder 10, but by adjusting the nozzle and the absorption of the highly water-absorbent resin powder, the water droplets could be dispersed at any position in the height direction of the cylinder 10.
The droplets were absorbed into the superabsorbent resin powder during the downward flow of the cylinder 10, and the droplets were hardly observed at the bottom of the cylinder 10. At this time, the mixing ratio of the superabsorbent resin powder (A-1) to the airflow was 2kJ.
The average water droplet diameter was about 100 ^μm . The residence time of the highly water-absorbent resin powder in the cylindrical body 10 was
The time was 10 seconds. The inner wall temperature of the cylinder 10 was maintained at 90°C by external heating. The cohesive granules obtained in this way were transported to a crusher 17 (flash mill, manufactured by Fuji Paudal Co., Ltd.) by a bucket conveyor 20. Hot air at about 90°C was blown into the bucket conveyor 20, and the stickiness of the cohesive granules was reduced during the residence time of about 20 minutes. Crusher
The solidified material introduced into 17 was crushed and granulated, and then classified by sieve 19 to obtain granulated material (1) passing through a 20 mesh. The obtained granulated material was measured for (a) absorption capacity, (b)
The absorption capacity under pressure, (c) suction force, and (d) viscosity distribution were evaluated as follows.

(a) Absorption Capacity: 0.2 g of the obtained highly water-absorbent resin powder (A-1) or granulated product (1) was placed in a nonwoven tea bag (40 mm x 150 mm).
The granules were placed evenly in a tea bag (100 ml), immersed in 0.9% saline, and weighed after 30 minutes. The absorbed weight of the tea bag alone was used as a blank, and the water absorption capacity of the granules (1) was calculated according to the following formula.

(b) Absorbency under pressure The absorbency under pressure is measured using the apparatus shown in FIG.
A stopper 23 is placed on the upper opening 22 of the burette 21, and a measuring table 24 and an air vent
The measuring table 24 is set at the same height. A filter paper, 0.2 g of the highly absorbent resin powder (A-1) or granulated material (1), and a filter paper 27 are placed on a 70 mm diameter glass filter (No. 1) 26 in the measuring table 24, and a weight 28 of 20 g/ ^cm2 is placed on top. After that, the artificial urine (composition: urea 1.9%, NaCl 0.8%) that has been absorbed for 30 minutes is poured into the filter paper.
%, CaCl ₂ 0.1% and MgSO ₄ 0.1%) were expressed as (ml/g).

(c) Suction force: 20 ml of artificial urine was added to a tissue paper (55 mm x 75 mm) to prepare a substrate containing the artificial urine, and 1.0 g of the superabsorbent resin powder (A-1) or granules (1) was placed on the substrate. After 10 minutes, the swollen gel was collected and its weight was measured to determine the suction force of the tissue paper.

(d) Particle size distribution mesh size 20 mesh, 50 mesh, 100 mesh diameter 70m
1m standard sieve and a classification tray are placed on top of each other, and 30 g of the highly water-absorbent resin powder (A-1) or granulated material (1) is placed on top of them.
The mixture was shaken in a classifier for 10 minutes, and the classified product was weighed and expressed in weight %.

FIG. 2 shows a coil through which a heat transfer medium such as steam flows.
1 except that it is provided with a temperature control means 33 consisting of a heat insulating material 32 such as glass wool, phenolic resin wool, asbestos, or the like in which a heat insulating material 31 is embedded.
Other symbols are the same as in FIG.

Comparative Example 1 100 parts by weight of the superabsorbent resin powder (A-1) obtained in Example 1 and 6 parts of water were mixed in a Turbulizer (a high-speed rotating paddle mixer, manufactured by Hosokawa Micron Corporation), and the resulting sintered granules were treated in the same manner as in Example 1 to obtain comparative granules (1) that passed through a 20 mesh sieve. The obtained comparative granules (1) were evaluated in the same manner as in Example 1.

Examples 2 to 5 Granules (2) to (5) were obtained by repeating the same procedure as in Example 1, except that the conditions of the inner wall temperature of the cylinder, the mixing ratio of the superabsorbent resin powder (A-1) to the airflow, the residence time of the airflow in the cylinder, and the average droplet size of the water were changed as shown in Table 2. The evaluation results of these granules are shown in Table 2.

Example 6 50 parts by weight of corn starch, 200 parts by weight of water, and 1,000 parts by weight of methanol were charged into a reactor equipped with a stirrer, a nitrogen inlet tube, and a thermometer, and heated at 50°C for 1 hour under a nitrogen stream.
After stirring for 1 hour, the mixture was cooled to 30°C, and 25 parts by weight of acrylic acid,
75 parts by weight of sodium acrylate, 0.5 parts by weight of methylenebisacrylamide, 0.1 parts by weight of ammonium persulfate as a polymerization catalyst, and 0.1 parts by weight of sodium hydrogen sulfite as an accelerator were added, and the mixture was reacted at 60°C for 4 hours, yielding a white suspension.

The white suspension was filtered, and the obtained powder was washed with a water-methanol mixed solution (water to methanol in a weight ratio of 2:10), dried under reduced pressure at 60°C for 3 hours, pulverized, and further sieved through a 20 mesh wire screen to obtain a 20 mesh pass-through product (water absorbent resin (2)).

A liquid consisting of 1 part by weight of glycerin and 8 parts by weight of methanol was mixed with 100 parts by weight of the obtained water-absorbent resin (2), and after heat treatment, the same operation as in Example 1 was repeated to obtain a 20
A highly water-absorbent resin powder (A-2) was obtained as a product that passed through the mesh.

100 parts by weight of the obtained highly water-absorbent resin powder (A-2) was mixed with 20 parts by weight of water.
The same procedure as in Example 1 was carried out except that 1 part by weight of granules was added, thereby obtaining granules (6) passing through a 20 mesh sieve. Granules (6) were left to stand and dry at 105°C for 3 hours, and then evaluated.

Example 7 A mixture of 60 parts by weight of vinyl acetate and 40 parts by weight of methyl acrylate was added with 0.5 parts by weight of benzoyl peroxide as an initiator.
The resulting mixture was dispersed in 300 parts by weight of water containing 3 parts by weight of partially saponified polyvinyl alcohol and 10 parts by weight of salt, and subjected to suspension polymerization at 65°C for 6 hours, followed by filtration and drying to obtain a copolymer. The resulting copolymer was saponified, washed, dried, pulverized, and classified to obtain a 20-mesh pass-through product (water absorbent resin (3)).

The obtained water-absorbent resin (3) was heat-treated in the same manner as in Example 6 to obtain a highly water-absorbent resin powder (A-3). The same procedure as in Example 1 was carried out except that 35 parts by weight of water was added to 100 parts by weight of the obtained highly water-absorbent resin powder (A-3), and a granulated product (7) passing through a 20 mesh was obtained. The granulated product (7) was sieved at 105°C.
The sample was left to dry at room temperature for 3 hours and then evaluated.

Example 8 A superabsorbent resin powder (A-1) was granulated in the same manner as in Example 1 to obtain a granulated product (8), except that the water in Example 1 was replaced with the same amount of a 15% aqueous solution of Camellia family plant leaf extract (product name N1 Fresca 800MO, manufactured by Shirai Matsuyaku Co., Ltd.) as a deodorant.

Example 9 The highly water-absorbent resin powder (A-1) obtained in Example 1 was mixed with finely divided silica particles ("Aerosil 20" manufactured by Nippon Aerosil Co., Ltd.).
0") was added to 100 parts by weight of the highly water-absorbent resin powder (A-1) in a ratio of 1 part by weight of finely divided silica, and the mixture was thoroughly mixed to obtain a mixed powder P.

The mixed powder P was granulated in the same manner as in Example 1, except that 10 parts by weight of water was added to 100 parts by weight of the obtained mixed powder P, to obtain granules (9).

Example 10 Carbon black (Mitsubishi Carbon Black #600 manufactured by Mitsubishi Chemical Industries, Ltd.) was added to the highly water-absorbent resin powder (A-1) obtained in Example 1 in a ratio of 4 parts by weight of carbon black to 100 parts by weight of highly water-absorbent resin powder (A-1), and the mixture was thoroughly mixed to obtain a mixed powder Q.

The mixed powder Q was granulated in the same manner as in Example 1, except that 10 parts by weight of water was added to 100 parts by weight of the obtained mixed powder Q.
Granules (10) were obtained.

Comparative Example 2 100 parts by weight of the highly water-absorbent resin powder (A-1) obtained in Example 1 and 6 parts by weight of water were granulated by the method shown in Fig. 3. Fig. 3 shows the air and water ejection nozzle 15 inserted into the dispersion member 12.
This shows another apparatus similar to that shown in Fig. 1, except that the two granules are installed at two locations on the outside of the apparatus so that they face diagonally downward. Other symbols are the same as in Fig. 1. With this apparatus, a large amount of deposits 34 formed on the wall, and continuous granulation could not be achieved. The obtained granules were subjected to the same procedure as in Example 1.
Comparative granules (2) were obtained which passed through a 20 mesh sieve. The evaluation of the comparative granules (2) obtained is shown in Table 3.

According to the present invention, a superabsorbent resin powder dispersed by an airflow from above and droplets of an aqueous liquid are allowed to flow downward into a vertically positioned cylinder, and the resin powder and the droplets are brought into contact with each other in a parallel flow toward the bottom of the cylinder, thereby avoiding collisions between the resin powder particles and allowing the droplets to caking and granulate a plurality of the resin powder particles without using mechanical shearing force. This prevents the resin powder from being pulverized or the surface of the resin powder from being damaged during the process of forming caking granules, and the resulting superabsorbent resin powder is of high quality and does not contain fine powder. Furthermore, by simply allowing the caking granules to flow continuously down the cylinder, caking granules can be obtained, and crushing and granulation can be carried out directly without a drying process, thereby enabling continuous granulation of superabsorbent resin powder with high productivity.

Furthermore, according to the method of the present invention, the superabsorbent resin powder does not contain fine powder, so that when the resin powder is used, there is no generation of dust, no deterioration of the working environment, etc. In particular, when the surfaces of the resin powder particles are crosslinked to improve the quality of the resin powder, the resin powder is not damaged by mutual collisions or mechanical shear forces during the caking and granulation process inside the cylinder, so the crosslinked layer is not destroyed and high-quality superabsorbent resin powder can be granulated.

The thus obtained granulated superabsorbent resin powder can be used in a wide range of applications, including hygiene products such as sanitary cotton and disposable diapers, and agricultural water retention agents and desiccants.

Claims (18)

[Claims] [Claim 1] A method for continuous granulation of superabsorbent resin powder, characterized in that: superabsorbent resin powder is introduced into a cylindrical body with an open lower end by an airflow from a dispersion member installed at the top of the cylindrical body; fine droplets of an aqueous liquid are sprayed toward the bottom from a nozzle installed inside the dispersion member; the superabsorbent resin powder dispersed by the airflow flowing down toward the bottom of the cylindrical body and the droplets flowing down while diffusing radially toward the bottom of the cylindrical body are brought into contact with each other in a parallel flow state; and a coagulated granule in which a plurality of the superabsorbent resin powder is coagulated by the droplets is removed from the bottom of the cylindrical body. 2. The method according to claim 1, wherein the sintered granules removed from the lower part of the cylindrical body are crushed and granulated. 3. The method according to claim 1 or 2, wherein the temperature of the inner wall of the cylindrical body is maintained at 50 to 200° C. by a temperature control means provided in the cylindrical body. 4. The method according to claim 1, wherein the cylindrical body is formed into a cylindrical shape. 5. The method according to claim 1, wherein the nozzle for spraying the droplets is disposed approximately at the center of the dispersion member. 6. The method according to claim 1, wherein the mixing ratio of the highly water-absorbent resin powder to the airflow is 0.1 to 5 kg/Nm ³ . 7. The residence time of the airflow in the cylindrical body is 0.1
7. The method according to claim 6, wherein the time is between 10 seconds and 30 seconds. 8. The method according to any one of claims 1 to 7, wherein the droplets of the aqueous liquid have an average diameter of 300 μm or less. 9. The method according to claim 1, wherein the ratio of the aqueous liquid to 100 parts by weight of the highly water-absorbent resin powder is 1 to 50 parts by weight. Claim 10: Highly water-absorbent resin powder contained therein
10. The method according to any one of claims 1 to 9, wherein the amount of fine powder passing through a standard sieve of 0 mesh is 50% by weight or less. 11. The method according to any one of claims 1 to 10, wherein a deodorant is dissolved in the aqueous liquid. 12. The method according to any one of claims 1 to 11, wherein a plant growth aid is dissolved in the aqueous liquid. [Claim 13] A method according to any one of claims 1 to 12, wherein the ratio of the aqueous liquid is 1 to 50 parts by weight per 100 parts by weight of the total amount of the highly absorbent resin powder containing particulate silica. [Claim 14] A method described in any one of claims 1 to 13, in which the aqueous liquid is used in an amount of 1 to 50 parts by weight per 100 parts by weight of a total amount of highly absorbent resin powder containing at least one member selected from the group consisting of carbon black and activated carbon. [Claim 15] A continuous granulation device for high water absorbent resin powder, comprising: a cylinder equipped with temperature control means and having an open lower end; high water absorbent resin powder dispersing means which is a hopper-like object equipped with airflow generating means and is provided at the upper part of the cylinder; means for spraying fine droplets of an aqueous liquid in a parallel flow with the falling direction of the resin powder, provided inside the high water absorbent resin powder dispersing means; and means for removing a plurality of coagulated granules formed by coagulating the high water absorbent resin powder via the droplets, provided near the lower opening of the cylinder. 16. The method according to claim 1, wherein a crushing and granulating means for said granules is further provided below said granule removing means.
16. The device according to clause 15. 17. The apparatus according to claim 15 or 16, wherein the droplet spraying means is installed approximately at the center of the highly water-absorbent resin powder dispersing means. 18. The apparatus according to claim 17, wherein droplet spraying means is provided near the outlet of said hopper-like object.