JP3345656B2 - Granule coating apparatus and granule coating method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an apparatus and a method for coating granules. More specifically, the present invention relates to a granule coating device having a throttle at a lowermost portion in a tank for jetting a gas, the throttle having a cooling function, and a coating method for granules in which a coating operation is performed while cooling the throttle.

[0002]

2. Description of the Related Art A coating method using a jet method is disclosed in, for example, Japanese Patent Publication No. 38-13896.
In the cylindrical tank, the lower part is inverted conical, the tip is cut in the horizontal direction to form a throttle for gas ejection, and gas fluid faster than the orifice is ejected vertically into the tank. Is a coating method in which particles to be coated are blown up and a coating liquid is sprayed at the same time. In Japanese Patent Publication No. 38-2294,
A method is disclosed in which the granules are blown up through a guide tube provided in a central jet portion, and a coating liquid is added from a spray nozzle provided in the tube. All of these coating methods are intended for coating pharmaceuticals, and are preferable in the case of small-scale and careful coating. Hard to say. In order to cover a large amount of particles, it is necessary to use a jet tower having a large diameter. However, when the diameter of the jet tower is large, the whole particles are in a flowing state and a jet cannot be formed. To deal with this problem, Japanese Patent Publication No. 2-31039 discloses a coating apparatus in which a guide tube through which particles pass through a jet apparatus is provided vertically above an orifice, and an inert gas is fed into the apparatus from the orifice. The flow rate of the gas at the orifice is 20 m
It is disclosed that if the coating method is performed by adjusting the flow velocity in the guide tube to 20 m / sec or less from 70 m / sec to 70 m / sec, the jet state can be obtained even if the jet tower is enlarged. As described above, various improvements have been made to the coating method using the jet flow method, and improvement in quality and enlargement of the apparatus have been achieved. The formation of a film on the surface of the granule is based on cooling of a melt adhered to the surface of the granule or drying of a solution such as a resin. In film formation by drying, a large amount of heat is required to instantaneously evaporate the solvent. The coating method using the jet flow method is very high in thermal efficiency because the resin solution attached to the particle surface can be instantaneously dried with the calorific value of the gas that forms the jet flow. I can say

[0003]

The jet-forming gas and the coating liquid themselves are high in temperature, but the temperature of the particles themselves to be coated becomes equilibrium at a certain temperature due to the heat of vaporization of the solvent. Therefore, even if a thermoplastic resin such as polyethylene or polypropylene having a relatively low melting point is used for the coating material, there is no damage to the coating due to heat during the coating, and urea having a relatively low melting point as the coated particles. Even with the use of particles, it was believed that there was no melting and associated deformation. However, in practice, taking a coated granular fertilizer as an example, the coated film may have a coating content of several percent to 30%.
% Pinholes were observed, which contributed to the variation of the elution of the coated fertilizer. When the coating was performed under the condition that the temperature of the jet forming gas exceeded the melting point of urea, deformation of urea particles was observed in some of the particles. It is considered that the deformation of the particles also contributes to the variation in elution. In view of the above-mentioned problems of the prior art, the present inventors have sought to determine where the cause is, and in the coating apparatus main body in contact with the portion where particles flow from the stationary phase into the jet section, a throttle for jetting the jet forming gas. It was found that the temperature at and near the portion had risen to about the same temperature as the jet forming gas temperature. When the function of cooling the constricted portion was given to the conventional jet coating apparatus, surprisingly, the inventors found that damage to the coating and deformation of the particles were significantly reduced, and reached the present invention. That is, the present invention uses a jet coating device provided with a throttle at the bottom of a cylindrical jet tank for ejecting gas into the tank, and a spray nozzle provided near the center of the throttle, using a thermoplastic resin as a solvent. A coating apparatus for forming a coating on the granules while spraying the dissolved resin solution from the nozzle, wherein the restrictor has a cooling function; and A throttle for ejecting gas into the tank is provided at the bottom, and a resin solution obtained by dissolving a thermoplastic resin in a solvent is sprayed from the nozzle using a jet coating device provided with a spray nozzle near the center of the throttle. This is a coating method for forming a film on the granules while coating the granules while cooling the aperture. The purpose is to use a thermoplastic resin such as polyethylene or polypropylene, which has a relatively low melting point, as the coating material, and even to use particles such as urea having a relatively low melting point as the particles to be coated. It is an object of the present invention to provide a granule coating apparatus and a granule coating method capable of producing a coated granular material having a significantly low rate of damage to a coating due to heat during a process, melting and deformation associated therewith, and having a stable elution function. is there.

[0004]

The present invention comprises the following constitutions (1) to (6). (1) A thermoplastic resin is dissolved in a solvent using a jet coating device provided with a throttle at the bottom of a cylindrical jet tank for jetting gas into the tank and a spray nozzle provided near the center of the throttle. A coating apparatus that enables a coating to be formed on particles held in a jet state in the tank while spraying the resin solution from the nozzle, wherein the throttle has a cooling function. A granule coating apparatus, characterized in that:

(2) The apparatus for coating a granular material according to the above (1), wherein the throttle is an orifice or a venturi.

(3) The apparatus for coating granules according to the above (1) or (2), wherein a cooling medium path is provided inside the throttle.

(4) The apparatus for coating granules according to (1) or (2) above, wherein a cooling pipe is provided in contact with a lower portion of the throttle.

(5) The apparatus for coating granules according to the first and second aspects, wherein a jacket for a refrigerant is provided around the throttle.

(6) A throttle is provided at the bottom of the cylindrical jet tank for jetting gas into the tank, and a thermoplastic resin is provided using a jet coating apparatus provided with a spray nozzle near the center of the throttle. A coating method for forming a coating on particles held in a jet state in the tank while spraying a resin solution dissolved in a solvent from the nozzle, wherein the particles are subjected to a coating operation while cooling the throttle. Coating method.

The details of the present invention will be described below. The cylindrical jet tank used in the present invention is a tank whose central axis is vertical. The coating apparatus of the present invention is provided with a throttle for ejecting gas at a lower end portion in the tank, and a gas inlet pipe for jet flow is connected to the throttle, and a spray nozzle is provided near the center of the throttle. It is a thing. The shape of the tank is not particularly limited, and may have a circular or polygonal cross section. The lower end of the tank may be flat or inverted conical. However, in the case where the lower end of the tank is flat, when the particles are formed into a jet-like body, it is preferable that the tank has an inverted conical shape because the circulation of the particles deteriorates at a part of the lower end. In terms of surface, it is desirable that the cross section of the tank has a circular shape. In addition, various orifice plates and venturis may be separately inserted into the throttle at the lower end of the tank.

Further, the coating apparatus of the present invention may be provided with a guide tube in a vertical direction above the throttle. Examples of the shape of the guide tube include a pipe, a pipe perforated, a pipe made of a metal mesh, and the like. In the present invention, the shape and material are not particularly limited,
In order to minimize damage to the coating during coating, it is preferable to use a smooth pipe having no holes or protrusions. At this time, the guide tube is fixed or suspended vertically above the throttle.

The position of the spray nozzle may be any position as long as it substantially coincides with the center axis of the throttle, and may be a position higher or lower than the throttle. The position and shape of the nozzle may be appropriately determined depending on the properties of the spray liquid, operating conditions, and the like.

The wind speed at the throttle portion is determined by the amount of gas ejected and the diameter of the throttle, but the wind speed in the guide tube can be converted by the same method. It is preferable that the distance between the guide tube and the constricted portion is selected within a range that does not hinder the circulation of the particles. The diameter of the guide tube is 1.2 to 4.0 times the aperture diameter, preferably 1.5.
It is good to make it 3.0 times. In the present invention, the flow rate of the gas in the throttle portion, and the flow rate of the gas in the guide tube are not particularly limited, but in order to stabilize the quality, when introducing the inert gas from the throttle into the apparatus, The flow velocity of the gas at the throttle is from 20 m / sec to 70 m
/ Sec and the flow rate in the guide tube is adjusted to 20 m / sec or less to perform coating. The gas used in the present invention is not particularly limited as long as it is inert with respect to the properties of the particles and the solvent. The shape of the throttle for ejecting gas in the present invention is not particularly limited. For example, the lower end of the tank may have an inverted pyramid shape, and a part of the shape of the tank may be used as a throttle, such as the joint at the lowermost end of the tank with the jet-forming gas inlet pipe may be narrowed. Alternatively, an orifice plate, a venturi nozzle, or the like may be used. Usually, in a jet tower, the jetting speed varies depending on the particle size and density of the particles to be coated, and the air volume changes depending on the concentration of the coating liquid and the spray amount.Therefore, it is better to use an orifice plate or a venturi nozzle that can change the throttle diameter. desirable. The degree of cooling of the squeeze is not particularly limited as long as it is a temperature below the softening point of the resin component of the coating and below the softening point of the particles.

In the present invention, the cooling method is not particularly limited as long as the throttle portion can be cooled. However, as a device, a shape for cooling the throttle unit while maintaining high cooling efficiency, specifically, providing a refrigerant path inside the throttle, installing a cooling pipe under the throttle so as to be in contact with the throttle, , A method of providing a jacket for the refrigerant around the periphery. Although not particularly limited, the method is effective when the throttle portion is an orifice plate, and the method is effective when the throttle portion is a venturi nozzle. The above cooling methods may be used alone or in combination.

Taking the case of coated fertilizers as an example, conventional products have a coating after coating of a few percent, in some cases 30%.
% Pinholes were observed, which contributed to the variation of the elution of the coated fertilizer. When the coating was performed under the condition that the temperature of the jet forming gas exceeded the melting point of urea, deformation of urea particles was observed in some of the particles. The deformation of the particles also contributes to the fluctuation of the elution. The inventors of the present invention have found that, in the coating apparatus body in contact with the portion where particles flow from the stationary phase into the jet portion, the temperature of the throttle portion for jetting the jet forming gas and the temperature around its poles are almost the same as the jet forming gas temperature. This was attributed to the rise in temperature.

The jet forming gas and the coating liquid themselves are at a high temperature, but the particles to be coated reach equilibrium at a certain temperature due to heat of vaporization when the solvent is vaporized. Therefore, even if a thermoplastic resin such as polyethylene or polypropylene having a relatively low melting point is used for the coating material, there is no damage to the coating due to heat during coating, and urea particles having a relatively low melting point are used as particles to be coated. Even if used, it was believed that there would be no melting and associated deformation. Actually, in the production of coated granular urea containing polyethylene as a main component, the temperature of particles of the stationary phase immediately after receiving the coating and the temperature of the stationary phase particles reach equilibrium below the softening point of polyethylene. On the other hand, the throttle portion in the jet tower has no cooling effect due to evaporation of the solvent, etc., and the only cooling effect of the device is heat radiation from the surface of the device to the atmosphere. The temperature has risen to almost the same temperature as the jet forming gas temperature. Under these circumstances, the present inventors have no speculation, but damage to the coating and deformation of the particles occur when some of the stationary phase particles come into contact with the high-temperature constricted portion immediately before the jet. Think it's happening. Therefore, the present invention is effective when the coating is performed under the condition that the temperature of the jet forming gas greatly exceeds the softening point and melting point of the thermoplastic resin used for the coating.

In the present invention, a resin solution obtained by dissolving a thermoplastic resin in a solvent is used as the coating solution. Examples of the thermoplastic resin include polyolefin and its copolymer, and polyvinylidene chloride and its copolymer. Preferred polyolefins and copolymers thereof are polyethylene,
Polypropylene, ethylene / propylene copolymer, ethylene / vinyl acetate copolymer, ethylene / carbon monoxide copolymer, ethylene / vinyl acetate / carbon monoxide copolymer, ethylene / acrylate copolymer, ethylene / methacrylic acid copolymer Polymers, rubber resins, polystyrene, polymethyl methacrylate, and the like, and preferred polyvinylidene chloride and copolymers thereof include polyvinylidene chloride,
And vinylidene chloride-vinyl chloride copolymer.
Further, biodegradable polyesters represented by poly-2-hydroxy-2-alkylacetic acid, poly-3-hydroxy-3-alkylpropionic acid and the like can also be mentioned.

These coating materials are dissolved in an organic solvent and sprayed onto particles in a jet state to perform coating. The present invention is particularly effective in a film forming method in which a film is formed by flash drying using a poor solvent solution of the above resin. In the case of instantaneous drying using a poor solvent for the resin, in the combination of the resin and the organic solvent, those having a property of melting well when hot, and having a property of forming a jelly-like resin upon cooling,
The coating by this method forms a very dense coating and is particularly preferable. As a coating material other than the above, an inorganic filler represented by talc, a surfactant, or the like can also be used.
These coating materials are dissolved and dispersed in a solvent, sent to a spray nozzle and co-coated with the coating.

The particles used in the coating apparatus of the present invention are not particularly limited. However, the coating by the coating apparatus of the present invention is not suitable for those in which the active ingredient contained in the particles needs to control the dissolution rate. Especially effective. The active ingredients include urea, ammonium sulfate, ammonium salt, ammonium nitrate, chloride potassium, sulfate potassium, nitrate potassium, sodium nitrate, ammonium phosphate, phosphate potassium, phosphate lime, chelate iron, iron oxide, iron chloride, boric acid. , Borax, manganese sulfate, manganese chloride, zinc sulfate,
Copper sulfate, sodium molybdate, ammonium molybdate, OMUP (clotilidene diurea), IBDU
Fertilizers such as (isobutylidene diurea) and oxamide
Examples include pesticides such as insecticides, fungicides, herbicides, and the like, but are not limited thereto. The particles may be in the form of granules of one or more active ingredients, or may be granules of one or more active ingredients and an inert carrier such as bentonite, zeolite, talc, clay, diatomaceous earth and the like. . Further, the above-mentioned active ingredient particles may be coated with a resin or an inorganic substance.

[0020]

According to the present invention, a thermoplastic resin is dissolved in a solvent by using a jet coating device provided with a throttle at the bottom of the tank for jetting gas into the tank and a spray nozzle provided near the center of the throttle. A coating apparatus for forming a coating on the granules while spraying the resin solution from the nozzle, wherein the throttle has a cooling function, and a coating apparatus for the granules,
A throttle is provided at the bottom of the tank for ejecting gas into the tank, and a spray coating device provided with a spray nozzle near the center of the throttle is used to supply a resin solution obtained by dissolving a thermoplastic resin in a solvent from the nozzle. This is a coating method for forming a coating on the granules while spraying, and is a coating method for the granules in which the coating operation is performed while cooling the throttle. And a thermoplastic resin such as polyethylene or polypropylene with a relatively low melting point is used for the covering material,
Furthermore, even if particles such as urea having a relatively low melting point are used as particles to be coated, damage to the film due to heat during coating,
Melting and accompanying deformation are remarkably low, and a remarkable effect is obtained in that a coated granular material having a stable elution function can be produced. This is particularly effective when the coating is performed under the condition that the temperature of the jet forming gas greatly exceeds the softening point and melting point of the thermoplastic resin used for the coating.

[0021]

Embodiments of the present invention will be described below with reference to embodiments, but the present invention is not limited to the embodiments described below.

1. 1. Coating apparatus FIG. 1 shows a coating apparatus which is a comparative example of the present invention and is a basic structure of an example. In FIG. 1, 1 is a jet tower, 2 is an inlet for the granules to be coated, 3 is a granule inlet valve, 4 is a throttle for jetting air jets, 5 is a spray nozzle, 6 is an outlet for coated granules, 7 is a discharge pipe of air used for jetting and drying, 8 is an air heater, 9 is a flow meter, 10 is a blower, 11 is a coating liquid adjusting tank, 12 is a jacket for steam heating, 13 is a coating liquid supply pump, 14 Is a guide tube. Tower diameter is 450m
m, the diameter of the guide tube is 120 mm. FIGS. 2 to 7 exemplify a throttle having a cooling function used in the present invention. Fifteen
Denotes a coolant path, 16 denotes an orifice plate, 17 denotes a cooling jacket, and 18 denotes a venturi nozzle. FIGS. 2 to 5 are views of the diaphragm usable in the present invention viewed from directly above and from the side.

FIG. 2 shows a state in which a refrigerant passage is provided inside the orifice plate, and FIG. 3 shows a state in which the refrigerant passage is in contact with the lower part of the orifice plate. 2 and 3, the passage of the refrigerant is a round tube, but the shape, arrangement method, density and the like of the passage are not particularly limited. Further, as shown in FIG. 4, the orifice plate may be hollow so as to fill and pass the refrigerant. FIG. 5 shows a Venturi nozzle with a cooling jacket attached to the outer periphery thereof, and FIG. 6 shows a Venturi nozzle in which a coolant passage is spirally provided inside the Venturi nozzle as in FIG. FIG. 7 is similar to FIG. 4 except that the inside of the Venturi nozzle is hollow. Needless to say,
The shape of the diaphragm according to the present invention is not limited to the above description. In the embodiment of the present invention, the throttle shown in FIG. 2 or FIG. 5 was used, and in the comparative example, an orifice having no cooling function was used.

2. Trial Production of Samples of Examples and Comparative Examples of the Present Invention In the coating operation, a predetermined amount of particles is charged while sending air maintained at a predetermined air volume and temperature from a blower 10 to a jet tower.
Next, when the particles in the tower reach a predetermined temperature, the resin solution (coating liquid) is sent from the coating liquid supply pump at a predetermined speed for a predetermined time, and after the coating rate is set to a predetermined value, the blower 10 is stopped to remove the coated particles. The coated granules are extracted from the outlet 6. However, in the examples, the coating operation was performed while cooling the throttle and maintaining the temperature of the tangential portion of the throttle at 70 ° C. Coating solution composition Polyethylene (low-density polyethylene, d = 0.918, MI = 22) 6 parts by weight Ethylene / vinyl acetate copolymer (VAc = 15 wt%, MI = 7.0) 3 タ ル talc (average particle size 10 μm) 11 ト ル エ ン toluene 400 〃

In this production example, coating was performed while maintaining the following basic conditions until a predetermined coating rate reached 10% by weight. One-fluid nozzle: opening 0.8 mm full-con type Hot air volume: 450 Nm ³ / h Hot air temperature: 100 ± 2 ° C. or 130 ± 2 ° C. Table 1 shows which hot air temperature was applied in each test section. Resin melting temperature: 100 ± 2 ° C Fertilizer: urea Fertilizer input: 40 kg Test solvent: toluene Particle temperature of the jet part: 70 ± 3 ° C * The coating liquid is sent from the pump 5 and reaches the nozzle, but 80
Make the pipe a double pipe so that the temperature does not drop below ℃ and let the steam flow.

3. Coating Damage Confirmation Test 10 g of each of the prototype coated fertilizer samples of the present invention was
Immerse in 00 ml of water and leave at 25 ° C. After a predetermined period, it is divided into fertilizer and water, and urea eluted in the water is determined by quantitative analysis. 200 ml of fresh water is added to the fertilizer, and the sample is left to stand at 25 ° C. again. By repeating such an operation, the relationship between the total dissolution of urea eluted in water and the number of days is graphed to form a dissolution rate curve, and the number of days until the 80% dissolution rate can be known. Table 1 shows the results of the dissolution test. The initial elution amount in the table is the elution rate 24 hours after the start of elution. The amount eluted in the past 24 hours (initial elution amount)
From this, the degree of damage to the coating was determined. As is clear from the results in Table 1, in the example of the present invention, the elution start 2
The eluted amount was small after 4 hours, indicating that the coating was slightly damaged. On the other hand, in the comparative example, 2
The elution for 4 hours was as high as 6 to 8%, which clearly impaired the function of controlling the elution of the coating.

[0027]

[Table 1]

[Brief description of the drawings]

FIG. 1 shows a basic structure of an apparatus according to an embodiment of the present invention.

FIG. 2 is a structural explanatory view of an orifice plate according to the present invention.

FIG. 3 is another structural explanatory view of the orifice plate according to the present invention.

FIG. 4 is another structural explanatory view of the orifice plate according to the present invention.

FIG. 5 is another structural explanatory view of the orifice plate according to the present invention.

FIG. 6 is another structural explanatory view of the orifice plate according to the present invention.

FIG. 7 is another structural explanatory view of the orifice plate according to the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Spout tower 2 Granule inlet 3 Granule inlet valve 4 Spout air jet throttle 5 Spray nozzle 6 Coated grain outlet 7 Air exhaust pipe 8 Air heater 9 Flow meter 10 Blower 11 Coating liquid adjustment tank 12 Steam heating Jacket 13 coating liquid supply pump 14 guide tube 15 refrigerant passage 16 orifice plate 17 cooling jacket 18 Venturi nozzle

Continuation of front page (58) Field surveyed (Int. Cl. ⁷ , DB name) B01J 2/00 C05G 3/00

Claims (6)

(57) [Claims] 1. A jet coating apparatus having a throttle provided at a lowermost portion of a cylindrical jet tank for jetting gas into the tank, and a spray coating apparatus provided with a spray nozzle near the center of the throttle. A coating solution on the granules held in a jet state in the tank while spraying a resin solution dissolved in the nozzle from the nozzle, wherein the throttle has a cooling function. An apparatus for coating a granular material. 2. The granule coating apparatus according to claim 1, wherein the throttle is an orifice or a venturi. 3. The granule coating apparatus according to claim 1, further comprising a refrigerant passage inside the throttle. 4. The apparatus for coating granules according to claim 1, wherein a cooling pipe is provided in contact with a lower portion of the throttle. 5. The apparatus for coating particles according to claim 1, wherein a jacket for a refrigerant is provided around the throttle. 6. A spray coating device having a throttle provided at a lowermost portion of a cylindrical jet tank for jetting gas into the tank, and a spray nozzle provided near a center of the throttle, using a thermoplastic resin as a solvent. A coating method for forming a coating on particles held in a jet state in the tank while spraying the resin solution dissolved in the nozzle from the nozzle, wherein the coating is performed while cooling the throttle. Method.