JPH1025181A - Production of coated granular fertilizer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a coated layer free from defects of coating film and agglomerate by using a coating apparatus of a fluidized bed type equipped with a rotary disk partially having an air-permeable part and revolving in the horizontal direction and with a stirring blade above the rotary disk in a barrel part. SOLUTION: A granular fertilizer is fed to a cylindrical column 1 and a fluidizing gas having 0.2 to 10 times the minimum fluidizing rate of the granular fertilizer at 10-150 deg.C is introduced through an inlet 17 at 0.2 to 10m/sec superficial velocity per cross section area of a rotary disk 2 from a gap 11 between the outer periphery of the rotary disk 2 and the inner wall of the column 1 and from the air permeable part of the rotary disk 2 into the column 1. Then, the rotary disk 2 is revolved from a variable motor 5 through a belt 6 and a hollow revolving shaft 4, a revolving shaft 8 inserted through a bearing 7 of the revolving shaft 4 is revolved by a variable motor 9 and a stirring blade 3 is rotated through a belt 10. A coating solution containing a polymer compound at 50-100 deg.C is sprayed from spray nozzles attached to upper wall faces 15 and 16 of the rotary disk 2 to coat the surface of a granular fertilizer with a 3-20wt.% of a polymer compound coating film.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to a method for producing a coated granular fertilizer in which the surface of a granular fertilizer is coated with a film of a polymer compound to control the dissolution rate.

[0002]

2. Description of the Related Art In recent years, with the declining agricultural population and the exacerbation of environmental problems due to the loss of fertilizer, sustainability such as continuous supply of fertilizer components over the entire growing period of crops with only one application of fertilizer. The development of fertilizer is desired. Various types of such persistent fertilizers have been developed in the past, and among them, a coated fertilizer in which the surface of the fertilizer is coated with a thin film of a polymer substance has recently attracted attention.
Further, from the fertilizer component elution pattern, especially for rice, the so-called time capsule type or sigmoid type (hereinafter referred to as S), the elution of the fertilizer component starts after a certain period (elution prevention period) of about 30 to 70 days. (Abbreviated as type)
There is an increasing demand for a type called. Conventionally, thermoplastic resins have been used as such S-type coating materials,
Above all, polyolefin resins and polyvinylidene chloride resins having low water permeability are known.

[0003]

The technical problem of the coated fertilizer is to form a film as thin as possible and with few defects such as pinholes. Reduction of grain formation). With regard to, when the film has a defect, water infiltrates therefrom, so that the fertilizer component elutes faster. This is particularly important for S-type coated fertilizers, where leakage of fertilizer components during the elution prevention period must be minimized.
Conventionally, a method of increasing the film thickness (covering rate) to reduce film defects has been adopted, and a film of 14% by weight or more based on the weight of fertilizer particles has been applied. This is not preferable because it increases the cost of fertilizer. With regard to, with the spread of mechanical fertilization in recent years, the presence of aggregates causes blockage of the fertilizer. For this reason, the aggregates are usually removed by sieving after the production, but if the aggregates are large, the product yield is naturally lowered, which is not preferable. In addition, when there are many aggregates, there are also many particles that have separated from the aggregates, and such separated particles often have film defects, and it is necessary to suppress the formation of aggregates from the viewpoint of . To solve the above problems, methods for selecting a coating material and changing the film thickness as described above have been proposed as solutions. However, there have been few solutions that devised a coating method and a coating apparatus. 2. Description of the Related Art Conventionally, as a method of coating a coated fertilizer, generally, spray coating in which a solution in which a coating material is dissolved in a solvent or a melt of the coating material is sprayed on raw material fertilizer particles is used. On the other hand, the coating apparatus is a pan coating apparatus shown in FIG. 3 (see JP-A-7-133179) and a fluidized bed coating apparatus shown in FIG. 4 or FIG.
No. 0, JP-A-60-5559), spouted bed coating shown in FIG. 6 (see JP-A-7-133179), a Wurster type coating apparatus shown in FIG. 7 (see JP-A-7-172969), etc. However, in each case, the above-mentioned problems have not been overcome.

[0004]

Means for Solving the Problems In view of the above facts, the present inventors have studied to solve the above-mentioned problems by a coating apparatus. As a coating method that does not generate film defects, the present inventors have (a) sharpened the distribution of the coverage between particles, that is, the thinner the film, the more the defects are likely to occur. Do not produce particles with a significantly lower coverage compared to (a) Do not cause agglomeration between particles, that is, when the agglomerated or adhered particle mass separates or splits, the peeled surface becomes defective. We thought that it was necessary not to form aggregates. These are also preferable from the viewpoint of suppressing aggregation. On the other hand, considering this in terms of the characteristics of the coating apparatus, regarding (A), an apparatus having a high mixing property of the particles so that the spray liquid is uniformly applied to all the particles is suitable. As for (a), there is little contact between particles,
It can be said that an apparatus having a high particle dispersing power and a high drying rate (in the case of melt spraying, a high cooling rate) is suitable. On the other hand, in the case of a coating apparatus that has been conventionally used, in a pan coating apparatus, particles are always in contact with each other, and drying is poor. Fluidized bed and spouted bed coating equipment dry well but have poor mixing and dispersing power. The Wurster type has drawbacks such as having a stationary stagnation portion of particles. The present inventors have studied a coating apparatus having a function of stirring and tumbling particles based on a fluidized bed having excellent drying properties based on the characteristics of the desirable coating apparatus described above and the disadvantages of the conventional apparatus. The present inventors have found that a coated fertilizer which is a thin film and has few defects and aggregates can be easily produced, and the present invention has been accomplished. That is, the gist of the present invention is a fluidized bed type apparatus for producing a coated granular fertilizer having a film containing a polymer compound as a main component on the surface, and has a partially ventilated portion in a body portion and has a horizontal direction. A method for producing a coated granular fertilizer, comprising using a coating apparatus having a structure including a rotating rotating plate and a stirring blade independently rotating above the rotating plate.

[0005]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in detail. (1) Description of Apparatus FIG. 1 is an overall schematic sectional view showing one embodiment of a coating apparatus used in the present invention. The coating apparatus in this embodiment has a fluidized bed type structure, and is provided in a vertical state, and has a cylindrical tube 1 for coating particles charged therein. The flowing gas enters at inlet 17 and exits at outlet 18. At the bottom of the cylinder 1, the cylinder 1
There is provided a rotating disk 2 which rotates in a substantially horizontal direction to roll the particles. Also, on this rotating disk 2,
The stirring blade 3 for stirring the particles is provided so as to be able to rotate substantially horizontally.

The rotary disk 2 is rotated by rotating a hollow rotary shaft 4 provided vertically at the center of the body of the cylinder 1 in a desired direction from a variable speed motor 5 via a belt 6. . On the other hand, the stirring blade 3 is configured such that a rotating shaft 8 coaxially inserted into the hollow rotating shaft 4 via a bearing 7 is connected to a belt 1 by a variable speed motor 9 separate from the motor 5.
By rotating through the rotating disk 0, the rotating disk 2 is rotated in a rotating direction and a rotating speed independent of the rotating disk 2. The effects of such a stirring mechanism include the following. Due to the rotation of the rotating disk, the flowing gas does not flow through and the particles flow evenly, so that the drying efficiency increases. In addition, the rotation of the stirring blade causes the particles to be sufficiently mixed, thereby reducing the variation in the film thickness between the particles. In particular, it is possible to reduce the influence of classification due to the particle size seen in the fluidized bed. Further, since the particles are dispersed by the shearing force of the blade, aggregation between the particles is suppressed.

The gas for causing the particles to flow is supplied to the gap (slit) 11 between the outer periphery of the rotating disk 2 and the inner wall of the cylinder 1,
From both the ventilation portions 12 (see FIG. 2) made of the perforated plate. The flowing gas does not necessarily need to flow from both places, but by controlling the flow rate of each gas by the degree of opening of the dampers 13 and 14, the flow of particles can be delicately controlled and an excellent coating film can be formed.
In addition, the ventilation part 12 of the rotating disk 2 can be made of a sintered plate or a wire mesh having pores to such an extent that particles do not leak, other than the perforated plate.

Nozzles for spraying the coating liquid are provided on the upper wall surfaces 15 and 16 of the rotating disk 2. The nozzle position is preferably in the bed of flowing particles. Although the number of nozzles is not limited, usually there is an upper limit of the spray flow rate per nozzle, so it is necessary to increase or decrease according to the charged amount of particles and the size of the apparatus. As the type of nozzle, either one fluid or two fluids can be used, but a two fluid nozzle capable of changing the droplet diameter is suitable.

(2) Granular fertilizer to be coated The fertilizer used in the present invention is not particularly limited. urea,
Ammonium sulfate, salts weaker, potassium chloride, potassium sulfate, in addition to the single fertilizer granular such as phosphoric ammonia, N1, K ₂ O, the Genpi granular fertilizer of the present invention product comprising multiple components such as P ₂ O ₅ used. The particle size and shape of the fertilizer are not particularly limited, but are generally 1-4 mm.
Spherical or nearly spherical particles are preferred over angular or very irregular shapes.

(3) Coating material A polymer compound is used as the coating material.
There is no particular limitation. For example, polyolefin, polyvinylidene chloride resin, polyvinyl chloride resin, polystyrene resin, polycarbonate, polyamide, polymethyl methacrylate, polyurethane, thermoplastic resin such as ethylene-vinyl acetate, alkyd resin, phenol resin, urea resin, Thermosetting resin such as melamine resin, ABS resin, epoxy resin, silicone resin, other natural rubber and SB
Synthetic rubbers such as R and NBR, furthermore, polycaptolactone, polybutyric acid, aliphatic polyester, polyglycot,
Degradable polymers such as polyvinyl alcohol and oxidized polyethylene are mentioned. Among them, thermoplastic resins having a high water-permeable property and having a high elution-preventing effect even in a small amount are preferable, and polyolefin resins such as polyethylene and polypropylene are particularly suitable. . These resins can be used alone or as a mixture of two or more. Further, as long as the purpose of coating is not impaired, the coating may be carried out in the presence of other inorganic or organic substances in addition to the polymer compound. For example, when coated with a resin having high water permeability as described above, for the purpose of adjusting the dissolution property or increasing the amount of the resin, talc, calcium carbonate, clay, diatomaceous earth, syria, metal oxide, sulfur, etc. Organic substances such as surfactants and waxes may be added in addition to inorganic substances.

(4) Solvent When coating the above-mentioned coating material, there are two methods of melting the material and spraying it directly on the granular fertilizer, and dissolving it in a solvent and spraying the solution. The method is particularly limited. Not done. However, polymer compounds suitable for the present invention generally have high melting points and high melt viscosities, so they are industrially unsuitable for spray coating, and a method using a solvent to form a solution is preferred. The type of the solvent is not particularly limited, but is appropriately selected in consideration of various conditions. As the judgment material, the dissolving power, dissolving temperature, handleability, ease of recovery, toxicity, safety, price, and the like of the polymer compound serving as the film material can be cited. For example,
When a polyolefin resin, particularly low-density polyethylene, is used as the coating material, hydrocarbon solvents such as hexane, octane, toluene, xylene and tetralin, and chlorinated hydrocarbon solvents such as trichloroethylene and perchloroethylene are preferred. When coating with a water-soluble polymer, emulsion resin, latex, or the like, water is used as a solvent.

The concentration of the solution is not particularly limited.
For example, it is preferable to increase the concentration because the amount of the solvent used is reduced and the processing time is shortened. On the other hand, when the concentration is lowered, the viscosity of the solution is lowered and the handling property is improved.
However, in the case of spray coating, it is necessary to adjust the concentration so as to have a viscosity that allows an appropriate spray state to be obtained according to the spray nozzle and spray pressure used. As a specific example, when low-density polyethylene is used as the coating material and perchlorethylene is used as the solvent, the concentration of the solution is 1 to 12% by weight, preferably 3 to 10%.
% By weight. In general, when the polymer compound is cold,
Since many solvents are insoluble, heating usually requires stirring for dissolution.

(5) Manufacturing method The raw material granular fertilizer is charged into the coating device of (1),
A flowing gas is introduced. Usually, air is used as the type of flowing gas. However, when a flammable solvent is used, an inert gas such as nitrogen or carbon dioxide can be used to prevent explosion.
The flow rate of the flowing gas is 0.2 min of the minimum fluidization rate of the raw material fertilizer.
To 10 times, preferably 0.5 to 5 times. This is usually 0.2 to 10 m / sec, and preferably 0.5 to 5 m / sec, in terms of superficial velocity per sectional area of the rotating disk in the coating apparatus. The temperature of the gas is between 10 and 150 ° C., preferably between 50 and 100 ° C. at the entrance of the coating device. After introducing the flowing gas, the rotating disk and the stirring blade are rotated. The rotating speed of the rotating disk is 0.1 to 6 m / sec, preferably 1 to 3 m / sec at the peripheral speed.
On the other hand, the rotation speed of the stirring blade is 0.5 to 5 of the rotating disk.
2 times, preferably 1 to 3 times. The rotation speed of both
If the speed is too slow, the mixing of the particles will naturally deteriorate, but if the speed is too fast, the coating will be damaged, so an appropriate range must be selected.
Next, the coating liquid is sprayed from a spray nozzle. The temperature of the coating solution is usually from 50 to 100 ° C, preferably from 70 to 90 ° C. The spray flow rate is appropriately determined from the flowing gas flow rate and the drying speed of the solvent. The amount of the coating material to be applied depends on the target elution characteristics of the coated fertilizer.
It is 20% by weight, preferably 5 to 15% by weight. After the spraying is completed, a drying time and a cooling time are appropriately set, and then the particles are extracted from the apparatus. By the operation as described above, it is possible to produce a coated fertilizer with few film defects and aggregates.

Next, the present invention will be described in detail with reference to examples, but the present invention is not limited to the following examples unless it exceeds the gist.

[0015]

【Example】

(Example 1-4 and Comparative Example 1-5) Granular urea having a particle size of 2.0 to 3.4 mm was used as a raw material fertilizer, polyethylene was used as a film material, and perchlorethylene was used as a solvent for the material. Coated ureas were produced and their quality was compared.

[0016]

Example 1 A coated fertilizer was manufactured by the methods (1) to (3) shown in <Coating>, and the coated fertilizer obtained by the methods (a) to (e) shown in <Quality evaluation> Checked the quality. The results are summarized in Table 1. <Coating>

(1) Coating Apparatus In FIG. 1, a coating apparatus having a rotating disk diameter of 260 mm and a diameter of 400 mm at the straight body of the cylinder was used. (2) Preparation of coating solution 1.5 kg of low-density polyethylene having a melting point of 106 ° C. (“Mitsubishi Polyethylene LJ805” manufactured by Mitsubishi Chemical Corporation) as a coating material,
121.5 g of polyoxyethylene nonylphenol ether ("Emulgen 909" manufactured by Kao) as an elution modifier
Was weighed and added to 28.5 kg of perchlorethylene as a solvent, and both materials were dissolved at 80 ° C. to prepare a coating solution.

(3) Coating 3.2 kg of granular urea is charged into the above coating apparatus, and air at 70 ° C. is supplied at a flow rate of 600 Nm ³ / h (rotating disk) while rotating at a rotating disk rotation speed of 100 rpm and a stirring blade rotation speed of 170 rpm. Air was blown into the apparatus at a superficial velocity of 3.9 m / sec per section. After 5 minutes, the above coating solution was added at 150 g / min.
(Using a two-fluid nozzle). The coating solution was sprayed for 25 minutes.

<Evaluation of Quality> (a) Measurement of Coverage 10 g of the coated fertilizer is weighed, pulverized by a small pulverizer, water is added to dissolve urea, and only the film is recovered by filtration. The coating was dried and weighed to calculate the coverage from the following equation.

[0020]

(Equation 1)

(B) Measurement of the number of particles having a film defect 10 g of the coated fertilizer is weighed into a test tube, and 10 cc of the ink is applied.
, And left for 1 hour in constant temperature water at 40 ° C, and then the coated fertilizer is collected by filtration. When the adhered ink is washed with water, the color of the ink remains at the defective portion of the film, so that defective particles can be distinguished. Count the three types of particles that are partially colored in this way, the particles that are entirely colored due to the large defect area, and the shell particles that have already eluted urea and become a film only. I do. The total number of particles of 10 g of the coated urea in the example was about 700.

(C) Measurement of the initial dissolution rate When the dissolution amount of the fertilizer component in water is measured, the dissolution rate of the particles having film defects increases. Here, the number of film defect particles is compared by measuring the urea elution rate at 25 ° C. and two weeks. The measuring method is as follows. Weigh 7 g of coated fertilizer, add 200 g of water, close the container and seal at 25 ° C.
Put in a constant temperature bath. The urea eluted in water is measured at the second week, and the urea eluted in water is measured with a total nitrogen analyzer, and the elution rate is calculated by the following equation.

[0023]

(Equation 2)

(D) Measurement of Distribution Distribution between Particles Forty coated fertilizers are taken and the weight of each particle is measured. Next, the film is torn with a cutter knife, immersed in water to dissolve and remove urea, and only the film is separated. This is dried and weighed to obtain one film weight. The coverage of one grain based on the calculation formula (a) is calculated, a histogram of the coverage is created for 40 grains, and the standard deviation σ thereof is obtained. This σ
Is used as an index of the coverage distribution. The closer the σ is to 0, the sharper the distribution of the coverage, and the less the dispersion of the coverage between particles.

(E) Measurement of Aggregation Rate 20 g of the coated fertilizer is taken, and the aggregation contained therein is picked up visually. The weight is measured and the weight% in 20 g is calculated.

[0026]

Example 2 In Example 1, the flow rate of the blown gas was set to 5
Coating was carried out under the same conditions except that the speed was 00 Nm ³ / h (superficial velocity 3.2 m / sec). Table 1 shows the quality of the obtained coated urea.

[0027]

Example 3 In Example 3, the temperature of the blown gas was set to 8
Coating was carried out under the same conditions except at 0 ° C. Table 1 shows the quality of the obtained coated urea.

[0028]

Comparative Example 1 Coating was performed under the same conditions as in Example 1 except that the rotating disk and the stirring blade were not rotated. This is the usual fluidized bed coating. Table 1 shows the quality of the obtained coated urea.

[0029]

Comparative Example 2 1 kg of urea as in Example 1 was charged into a Wurster type coating apparatus shown in FIG. 8, and air at a temperature of 90 ° C. was blown at 80 Nm ³ / h to form a jet state of urea particles. Thereafter, the same coating solution as in Example 1 was sprayed at a flow rate of 65 g / min for 33 minutes to perform urea coating. Table 1 shows the quality of the obtained coated urea.

[0030]

[Table 1]

[Brief description of the drawings]

FIG. 1 is a sectional view showing one embodiment of a coating apparatus used in the present invention.

FIG. 2 is an enlarged view of a rotating disk 2 of the coating apparatus of FIG.

FIG. 3 is a view showing a pan coating apparatus.

FIG. 4 is a view showing a fluidized bed coating apparatus.

FIG. 5 is a view showing a fluidized bed coating apparatus.

FIG. 6 is a view showing a spouted bed coating apparatus.

FIG. 7 is a diagram showing a Wurster-type coating apparatus.

FIG. 8 is a view showing a Wurster-type coating apparatus used in Comparative Example 2.

[Explanation of symbols]

 Reference Signs List 1 cylinder 2 rotating disk 3 stirring blade 4 rotating shaft 5 motor 6 belt 7 bearing 8 rotating shaft 9 variable speed motor 10 belt 11 gap 12 ventilation section 13,14 damper 15,16 wall surface 17 inlet 18 outlet

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Toyohiko Yokka 1000 Kamoshida-cho, Aoba-ku, Yokohama-shi, Kanagawa Prefecture Inside Mitsubishi Chemical Corporation Yokohama Research Laboratory

Claims (6)

[Claims] When producing a coated granular fertilizer having a film containing a polymer compound as a main component on a surface thereof, it is a fluidized bed type device, which has a partially ventilated portion in a body portion and rotates horizontally. A method for producing a coated granular fertilizer, comprising using a coating apparatus having a structure including a rotating plate that rotates and a stirring blade that rotates independently above the rotating plate. 2. The method for producing a coated granular fertilizer according to claim 1, wherein a coating apparatus having a slit for ventilation between the rotating plate and the body is used. 3. The method for producing a coated granular fertilizer according to claim 1, wherein the rotating plate uses a coating device having pores for ventilation. 4. The method for producing a coated granular fertilizer according to claim 1, wherein the method for forming the film is spray coating. 5. The method for producing a coated granular fertilizer according to claim 1, wherein the mounting position of the spray nozzle is on a side surface of the rotating plate. 6. The method for producing a coated granular material according to claim 1, wherein the polymer compound is a thermoplastic resin.