JPH078902A - Powder coating method - Google Patents

Abstract

PURPOSE:To enable stable coating by adding an org. solvent vapor to the spraying gas supplied from the gas jet part of a spray nozzle of an org. solvent soln. CONSTITUTION:A coating soln. is supplied into a coating device 100 from a coating soln. supply pipe 102 and sprayed on a powder from a spray nozzle 7 to be bonded thereto. As the spray nozzle 7, a nozzle constituted so that gas jet parts 7b are arranged around a coating soln. discharge part 7a is used. By using the spray nozzle 7 having this structure, the coating soln. is efficiently formed into liquid droplets by the spraying gas introduced from a spraying gas supply pipe 109 through a gas introducing part 7c. By this constitution, the film of a polymeric substance (coating soln.) can be formed on the surface of the powder in uniform thickness.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for coating powder or granules, and more particularly, to a powder improved so that a film of a polymeric substance can be formed on the surface of the powder or granules with a uniform thickness. The present invention relates to a method for coating granules.

[0002]

2. Description of the Related Art Conventionally, a coated fertilizer whose surface is coated with a polymer has been proposed. Such a coated fertilizer intends to control the elution rate of the fertilizing component depending on the properties of the polymer coating, and therefore the coating formed on the surface is required to have a uniform thickness throughout.

As a method for coating powder or granular material, an organic solvent solution (hereinafter referred to as "coating liquid") in which a polymer substance is dissolved in powder or granular material dispersed in a gas stream for drying.
It is known how to spray. Specifically, in a predetermined coating device, a drying gas is supplied from the lower side to an upper side to form an air flow of the drying gas, and the granular material is dropped into the air stream, and the coating liquid is applied to the granular material. Spray and attach. The coating liquid is usually 30
It is sprayed as fine droplets of 0 μm or less. According to such a coating method, the organic solvent adhered to the surface of the granular material (hereinafter abbreviated as “solvent”) evaporates during the fall of the granular material, so that mutual adhesion of the granular material after falling is prevented. Avoided.

[0004]

However, in the conventional coating method as described above, since the coating liquid which has been formed into fine liquid droplets by spraying evaporates before reaching the granular material, the concentration of the coating liquid is increased. And the fluidity of the coating liquid decreases due to the temperature decrease due to the latent heat of vaporization, and it is difficult to form a film having a uniform thickness over the entire surface of the powder or granules.

In order to deal with the above problems, in actual industrial operation, the concentration of the coating liquid, the installation position of the spray nozzle, the spray amount of the coating liquid, the flow rate of the drying gas, the dropping time of the powder and granules, etc. are set. The optimum conditions are selected by adjusting. However, for example, regarding the spray amount of the coating liquid, there are restrictions such as the need to evaporate the solvent adhering to the surface of the powder or granular material before the powder or granular material falls, and the entire surface of the powder or granular material is limited. It is difficult to select the optimum conditions for forming a film having a uniform thickness. Further, even if the optimum conditions can be selected, the range is inevitably narrow, and stable coating cannot be expected.

[0006]

As a result of various studies in view of the above-mentioned circumstances, the present invention has revealed that if the concentration of solvent vapor is positively increased by including solvent vapor in the drying gas, fine particles can be obtained by spraying. It has been found that the evaporation rate of the coating liquid that becomes a large droplet can be slowed down.

The present invention has been completed on the basis of the above findings, and the gist thereof is to spray an organic solvent solution in which a polymer substance is dissolved into powder particles dispersed in a gas stream for drying. According to the method of coating a granular material for forming a film of a polymer substance on the surface of a granular material, a nozzle equipped with a gas ejection portion around the discharge portion of the organic solvent solution is used as a spray nozzle for the organic solvent solution. And a method for coating a powder or granular material, characterized in that an organic solvent vapor is contained in a spray gas supplied from a gas ejection portion of the nozzle.

The present invention will be described in detail below with reference to the accompanying drawings. 1 and 2 are explanatory views of a coating method for powder particles according to the present invention, FIG. 3 is an explanatory view of an example of a spray nozzle used in the method of the present invention, and FIG. 4 is a coating apparatus preferably used in the method of the present invention. FIG. 5 is a sectional side view showing a configuration example, FIG. 5 is a sectional view taken along line II-II in FIG. 4, and FIG.
FIG. 7 is a perspective view showing a configuration example of a lift provided on the inner peripheral surface of the drum of the coating apparatus shown in FIG. 7, FIGS. 7, 8 and 9 are explanatory views showing an operating method of the coating apparatus shown in FIG. 4, and FIG. 4 is a side sectional view showing another configuration example of the transfer pipe in the coating apparatus shown in FIG. 4, and FIG. 11 is a partial sectional view showing the pneumatic transfer mechanism of the transfer pipe in FIG.

In the coating method of the present invention, the target powder or granule is not particularly limited, and examples thereof include various powders and granules having an average particle diameter of about 2.5 to 3.5 mm. Is used for granular fertilizers and pesticides. On the other hand, the polymer substance as the coating material is arbitrarily selected depending on the coating purpose, and examples thereof include polyethylene and ethylene copolymers.

As the solvent, a solvent having a high boiling point and a low boiling point is selected, and examples thereof include halogenated hydrocarbons such as perchloroethylene, dichlorobenzene and trichloroethylene, benzene, toluene and xylene. An aromatic hydrocarbon etc. are mentioned. As a drying gas,
Usually, an inert gas such as air or nitrogen gas is used.

The coating liquid is prepared by dissolving a polymer substance in a solvent. The concentration of the polymer substance in the coating liquid is usually 1 to 7% by weight, preferably 3 to 5% by weight.
It is better to set the range. Further, the coating liquid may contain a surfactant, inorganic fine particles, and other additives, if necessary.

The coating method of the present invention is carried out as follows in the process shown in FIG. 1 or 2. First,
A drying gas supply pipe (1
01) is supplied with a drying gas, and the coating device (1
The granules in (00) are dispersed in a gas stream for drying.
Next, the coating liquid is supplied from the coating liquid supply pipe (102) into the coating device (100), and
The coating liquid is sprayed and adhered to the powdery particles by the spray nozzle (7). As a result, the solvent is dried and removed from the coating liquid adhering to the surface of the granular material, and a film of the polymer substance is formed on the surface of the granular material.

The flow rate of the drying gas is selected from an appropriate range corresponding to the throughput of the powder or granular material, but is usually 150 to 1,
Is in the range of 500 nm ^3, also linear velocity of the drying gas is usually 1~7m / sec, preferably from 3 to 5 m / se
It is preferable that the range is c. The temperature of the drying gas is
It is usually in the range of 10 to 100 ° C, preferably 60 to 90 ° C. The spray amount of the coating liquid is appropriately selected in consideration of the type of the target powder and granules and the intended coating thickness, but it is usually preferable to set it in the range of 150 to 250 wt% with respect to the powder and granules. . The coating thickness of the polymer substance is usually in the range of 50 to 100 μm.

In the coating method of the present invention, as the spray nozzle (7), as shown in FIG. 3, a nozzle having a gas ejection portion (7b) around a coating liquid ejection portion (7a) is used. According to the spray nozzle (7) having such a structure, the coating gas is efficiently made into droplets by the spray gas introduced from the spray gas supply pipe (109) through the gas introduction part (7c). As the spraying gas, the same inert gas as the above-mentioned drying gas is used. Then, the spray gas is usually discharged at a linear velocity of 15 to 40 m / sec from the gas ejection portion (7b), and the temperature of the spray gas is usually 10 to 10.
The temperature is 80 ° C., preferably 20 to 50 ° C.

Further, in the coating method of the present invention, it is necessary that the spray gas contains solvent vapor. The content of the solvent vapor is preferably adjusted so that the concentration in the gas in the coating device is in the range of 1 to 20% by volume. Such a solvent vapor concentration represents the concentration of the gas in the coating apparatus (100) at the temperature, and when the solvent vapor concentration is less than 1% by volume, the evaporation rate of the coating liquid that has become fine droplets by spraying is sufficient. If the solvent vapor concentration exceeds 20% by volume, the powder or granular material to which the coating liquid is attached cannot be dried sufficiently. The solvent vapor concentration is
It is preferably 1 to 15% by volume, more preferably 1 to 10% by volume, and further preferably 5 to 8% by volume.

In the process shown in FIG. 1, the method of incorporating the solvent vapor in the spray gas is as follows. The spray gas supplied to the spray gas supply pipe (109) is supplied with a predetermined amount from the solvent supply pipe (106). This is done by adding a solvent. In the process shown in FIG. 1, the gas discharged from the coating apparatus (100) after the coating is finished is supplied to an adsorption tower (104) filled with an organic material adsorbent such as activated carbon through an exhaust gas pipe (103). Treated as an exhaust gas and then pipe (105)
Is discharged from the system. When the solvent is added to the spray gas supplied to the spray gas supply pipe (109), the solvent is usually added in droplets using a nozzle.

In the process shown in FIG. 2, the method of incorporating the solvent vapor in the spray gas includes a heat exchanger (10
Use 7) as follows. By supplying the gas discharged from the exhaust gas pipe (103) to the heat exchanger (107) and cooling it, the solvent vapor contained in the gas is condensed,
The solvent thus obtained is supplied to the solvent supply pipe (106).

The gas discharged from the exhaust gas pipe (103) contains a solvent for drying the coating liquid. Therefore, the condensed and recovered solvent is supplied to the solvent supply pipe (106), and the exhaust gas discharged from the heat exchanger (107) is supplied from the pipe (108) to the drying gas supply pipe (101). By operation, the concentration in the gas in the coating device can be controlled. The process shown in FIG. 2 is economically more advantageous than the process shown in FIG. 1 in that the solvent in the gas discharged from the exhaust gas pipe (103) is recovered and circulated.

The solvent supplied into the spray gas does not necessarily have to be the same as the solvent used to prepare the coating liquid, but the same solvent is usually used. Further, in the coating apparatus (100), the powder or granules are circulated to be coated with a predetermined coating thickness, but the average number of circulations of the powder or granules is usually about 100 to 400 times.

In the coating method of the present invention, the coating device (100) may be of any structure as long as it is a device capable of spraying the coating liquid onto the powder or granules dispersed in the air flow of the drying gas. May be. Therefore, for example, starting with a fluidized bed dryer type coating device, the drying gas is supplied from the lower side to the upper side to form an air flow of the drying gas, and the granular material is dropped into the air stream. Various conventionally known coating devices for spraying the coating liquid onto the can be used.

In the coating method of the present invention, a particularly recommended coating apparatus is the coating apparatus shown in FIGS. Such a coating apparatus is a coating apparatus that coats the surface of the granular material with a coating agent while dropping the granular material therein, and has a drying gas introduction port (1A) and an exhaust port (near the bottom and the top). 1B) is provided with a housing (1), and a rotatable drum (2) arranged in the housing with its axis being substantially horizontal and having a peripheral surface formed of a breathable member. A lift (3) protruding from the inner peripheral surface of the drum for scraping the powder particles upward with the rotation of the drum, and a coating provided for a falling path of the scraped powder particles. And a liquid spray nozzle (7).

The powder or granular material contained in the drum (2) is scraped upward by the lift (3) as the drum (2) rotates and falls. Then, during the fall, the coating liquid is sprayed and dried by the spray nozzle (7). The coating liquid is sprayed from the discharge part (7a) of the spray nozzle (7), but is efficiently atomized and sprayed by the spray gas introduced from the gas ejection part (7b) and containing the solvent. It
Therefore, it is possible to efficiently perform a uniform coating treatment on the surface of the granular material.

The casing (1) is an airtight casing for accommodating the cylindrical drum (2),
If the drum (2) is long-axis, then such housing (1)
For example, it is formed in a substantially rectangular parallelepiped and is arranged horizontally in the longitudinal direction. The introduction port (1A) and the discharge port (1B) are arranged so that the supplied drying gas can pass through the drum (2) substantially linearly from the lower side to the upper side. It is provided below and above the side surface. The inner wall of the casing (1) near the inlet (1A) and the outlet (1B) is configured to reliably introduce the supplied drying gas into the drum (2) and allow it to pass therethrough. (1e), (1
c) and (1f) are projected to a position close to the outer peripheral surface of the drum (2) to form an introduction path (A) and a discharge path (B).

The drum (2) is usually 0.5 to 3.0 m.
The diameter is about 0.5m and the axial length is about 0.5-3.0m.
Such a volume can be appropriately set according to the throughput. Both end surfaces of the drum (2) are, as shown in FIG. 5, respectively, a small diameter donut plate (22) arranged on the axial center side.
a) and a large diameter donut plate (22) arranged on the peripheral surface side.
b). These donut plates (22
The a) and (22b) are coupled via a bearing (24), and the small diameter donut plate (22a) is fixed to the housing (1) side. That is, in the housing (1), the drum (2) has the donut plate (22a).
Is supported by the housing (1) by the casing, and the peripheral wall (21) is configured to be rotatable together with the donut plate (22b) in the outer peripheral portion. The portion corresponding to the donut plate (22a) may be formed integrally with the housing (1), and the portion corresponding to the bearing (24) may be made of a resin material to improve airtightness. You may use the bush formed by the.

A roller (25) is in contact with the peripheral wall (21) forming the peripheral surface of the drum (2). Such rollers (25) are fitted with sprockets (2
7), the chain (29) and the sprocket (28) drive the geared motor (26) to rotate the drum (2) at a peripheral speed of about 0.1 to 0.7 m / min. There is. Further, the peripheral wall (21) is made of a gas permeable member such as a metal mesh that allows the drying gas to sufficiently pass through without leaking the powder or granules contained therein.

The lift (3) scrapes the powdery particles up into the drum (2) as the drum (2) rotates.
It is formed in the shape of a strip plate and is arranged in parallel with the axis of the drum (2) over substantially the entire axial length of the drum (2), and is provided in a state in which its board surface is substantially orthogonal to the peripheral wall (21). The lift (3) is fixed to the donut plate (22b) and the peripheral wall (21), and the drum (2).
6 to 36 sheets, usually about 8 to 24 sheets are evenly arranged in the circumferential direction.

As the spray nozzle (7), various conventionally known spray nozzles are used, and are appropriately selected depending on the viscosity of the coating liquid and the treatment amount. The coating liquid is supplied to the spray nozzle (7) by a coating liquid supply mechanism (not shown) provided separately.

In a preferred embodiment, as shown in FIG. 4, the spray nozzle (7) is provided on the inner wall of the draft (6) which is erected in the dropping path of the granular material. The draft (6) is provided to prevent unnecessary scattering when the powder or granular material scraped up by the lift (3) falls and to efficiently perform the coating process. The draft (6) is formed in a tubular shape having a rectangular cross section, and is opened along the axial length of the drum (2). And the transfer pipe (9) above
It is attached to the outer peripheral surface of and is configured to rotate together with the transfer tube (9). Also, spray nozzle (7)
Are provided on the inner wall of the draft (6) along the axial direction of the drum (2) at appropriate intervals, and are usually arranged in multiple stages on both inner walls facing each other parallel to the axis. It

On the other hand, inside the drum (2), as a preferred embodiment, as shown in FIG. 4, the inside of a substantially half-circumferential portion of the drum (2) from the substantially lowest point to the highest point on the rotational direction side. A guide plate (20) is arranged along the above. That is,
The guide plate (20) is curved along the peripheral wall (21). The guide plate (20) is provided to more efficiently scrape the powder or granular material contained in the drum (2) using the lift (3), and is fixed to the inner wall of the housing (1). It is attached to a donut plate (22a) forming the end surface of the drum (2) and is always in a predetermined position. The position of the guide plate (20) is somewhat on the inner peripheral side of the drum (2) with respect to the peripheral wall (21) rather than the edge of the lift (3).

Further, in a preferred embodiment, the lift (3) is, as shown in FIG. 6, a flat plate (31) which is fixed to the side of the peripheral wall (21) and substantially holds the granular material,
It comprises a scraper (33) which appropriately abuts on the outer peripheral surface of the guide plate (20) and prevents the held granular material from overflowing when scraping. The scraper (33) is swingably attached to the edge of the fixed plate (31) on the axial side of the drum (2) by a hinge (32), and the guide plate (20) described above.
It comes into contact with the outer peripheral surface of the.

Specifically, the flat plate (31) drum (2)
A stopper (34) is provided adjacent to the hinge (32) on the board surface on the rotation direction side of the scraper (3).
It is configured to restrict the bending range of 3) in the rotation direction to a predetermined angle. That is, the scraper (33)
By controlling the swing range of the scraper (3
3) the fixed plate (3
1) It is designed to prevent the superposition. The bending range of the scraper (33) is up to about 90 °, preferably up to about 60 ° with respect to the surface of the fixed plate (31) on the rotational direction side.

Further, in a preferred embodiment, as shown in FIG. 5, a transfer pipe (9) for the granular material is inserted through the axis of the drum (2), and the transfer pipe (9) is provided. Has a bearing (23) interposed in a portion of the end surface of the drum (2) through which the donut plate (22a) is inserted, and is rotatable. Airtightness is maintained by the shielding member (11) at the portion inserted into the housing (1). And the transfer pipe (9) is shown in FIG.
As shown in FIG. 3, the motor is configured to rotate by a forward and reverse rotatable motor (96) via a sprocket (98), a chain (98) and a sprocket (97) fitted to the transfer pipe.

Further, as shown in FIG. 4, a slit (9c) is opened in the transfer pipe (9) along the longitudinal direction thereof, and a hopper for introducing powder particles is provided above the slit. (9H) is projected. The opening of the hopper (9H) is formed along with the slit (9c) over substantially the axial length of the drum (2), and is scraped up by the lift (3) and dropped from the upper end of the guide plate (20). It is configured to collect the treated powder particles.

As a preferred embodiment of the transfer pipe (9), the transfer pipe (9) is equipped with a screw conveyor (82) as shown in FIG. 5, and is used as a supply pipe and a discharge pipe for the granular material. . A supply pipe (8) for supplying a powder or granular material is inserted into one end of the transfer pipe (9), and the powder or granular material is introduced into the supply pipe (8). A supply port (8A) is provided. The other end of the supply pipe (8) serves as an outlet (9B).
It is inserted into a storage tank (87) for storing the processed powder and granules.

The screw conveyor (82) is continuously inserted through the transfer pipe (9) and the supply pipe (8), and the motor (86) via the sprocket (88), the chain (89) and the sprocket (87). ) Is rotated by. The transfer pipe (9) and the supply pipe (8) are kept airtight by the shielding member (91), and the upstream end of the supply pipe (8) and the drive shaft of the screw conveyor (82) are shielded from each other. Airtightness is maintained by (81).

Next, a method of treating powdery or granular material by the above coating apparatus will be described. [Loading of Raw Material Granules] In the above coating apparatus, batch-type processing is performed, and a single processing amount is supplied to the drum (2). First, the transfer pipe (9) is rotated so that the slit (9c) (the hopper (9
H)) is turned downward. Next, the screw conveyor (82) is activated to supply the raw material powder or granular material to the supply pipe (8).
To the supply port (8A). The charged granular material is sequentially transferred in the supply pipe (8) and the transfer pipe (9) by the screw conveyor (82), and, as shown by reference numeral (W) in FIG. It falls into the drum (2) through 9c).

[Coating treatment] The powder (W) is placed on the drum (2).
Then, the transfer pipe (9) is rotated again to position the opening of the draft (6) below the upper end of the guide plate (20) (state of FIG. 4). Then, drive motor (2
6) is activated to rotate the drum (2). On the other hand, after supplying the granular material (W), the inlet (1A) of the housing (1)
Supply drying gas to the spray nozzle (7)
The coating liquid is supplied to and sprayed into the draft (6). Note that the drum (2) may be activated when the powder or granular material (W) is supplied.

With the rotation of the drum (2), the peripheral wall (21)
As shown in FIG. 8, the lift (3) protruding from the
The granular material (W) staying below the drum (2) is appropriately scraped and sequentially conveyed upward. When scraping up the granular material (W), the swingable scraper (33) of the lift (3) is restricted in the bending range of the drum (2) in the rotation direction, and the uppermost part of the drum (2) is regulated. As it moves upward from the lower point position, it leans toward the axis of the drum (2) by its own weight,
Guide plate (20) located approximately half around the drum (2)
Abut on the outer peripheral side. Therefore, even when the flat plate (31) holding the granular material (W) moves further upward from the position where it is approximately horizontal, the scraper (33) and the guide (20)
By the above, it is possible to prevent the granular material (W) from overflowing from the lift (3) and efficiently scrape it.

As shown in FIG. 8, the granular material (W) scraped up along the guide (20) is transferred to the guide plate (2).
It falls from the upper end of 0) to the draft (6) provided in the fall path. The spray nozzle (7) provided in the draft (6) sprays the coating liquid onto the powder or granules (W) passing through the inside of the cylinder of the draft (6). that time,
The draft (6) prevents scattering of the falling particles (W), and thus enables efficient and uniform spraying of the individual particles (W).

On the other hand, the drying gas supplied from the inlet (1A) of the housing (1) is introduced from the inlet (A) to the drum (2).
Through the peripheral wall (21) of the draft, through the inside of the cylinder of the draft (6) to reach the discharge path (B). Then, the drying gas passing through the draft (6) flows in the direction opposite to the falling direction of the granular material (W), so that the contact efficiency with the granular material (W) is enhanced. As a result, the granular material (W) with the coating liquid attached
Is quickly dried while falling. Furthermore, when the drying gas is heated, the coating liquid applied to the powder or granular material (W) can be dried more quickly.

When the coating liquid is sprayed, the peripheral wall (2
1) The granular material (W) that has dropped onto the drum (2) is scraped up again in the drum (2) by the rotating drum (2) and dropped into the draft (6). Then, while repeating rolling and dropping in the drum (2), the uniform coating treatment is performed on each of the granular materials (W). Moreover, the powdery particles (W) scraped up by the lift (3), even when rolling on the peripheral wall (21) of the drum (2), are mixed with the drying gas while the coating liquid on the surface is falling. Since it has been dried in advance by contact, it does not adhere to the agglomerate shape, and therefore the surface of the powdery or granular material (W) can be efficiently subjected to a uniform coating treatment. Such repetitive processing is performed for a predetermined time based on the amount of powder (W) to be processed and the film thickness to be formed.

[Discharge of Product Granules] After performing the coating treatment, the spraying of the coating liquid and the supply of the drying gas are stopped, and as shown in FIG. 9, the transfer pipe (9) is again attached. It is rotated to position the hopper (9H) (slit (9c)) below the upper end of the guide plate (20). The rotating drum (2) and lift (3) scrape up and drop the granular material (W) with respect to the hopper (9H) in a substantially vertical state. When the granular material (W) is supplied from the hopper (9H) to the screw conveyor (82), the screw conveyor (82) conveys inside the transfer pipe (9) and from the discharge port (9B) to the storage tank (87). Discharge as a product.

Next, in the above coating apparatus,
Another aspect regarding supply and discharge of the granular material will be described.
As shown in FIG. 10, another aspect of the coating apparatus is that in the above-mentioned configuration, the transfer pipe (9) is equipped with a pneumatic transfer mechanism, and is used as a discharge pipe for powder or granular material. In this case, the transfer pipe (9) is vertically divided by the perforated plate (83), and the end portion (9A) opposite to the discharge port (9B) is inert to pressurized air, nitrogen or the like. It is connected to an air supply mechanism (not shown) that supplies gas.

As shown in FIG. 11, the perforated plate (83) is provided with a large number of holes (83c) having a diameter smaller than the particle diameter of the granular material and not allowing the granular material to pass through. ,
These holes (83c) are usually inclined toward the discharge port (9B) side of the transfer pipe (8). On the other hand, as a mechanism for supplying the granular material to the drum (2), for example, one end on the upstream side is connected to the supply hopper (85), and the other end on the downstream side is one donut plate (on the end surface of the drum (2) ( 22a) and a supply pipe (86) inserted through the housing (1).

The raw material granules are loaded from the supply hopper (85) into the drum (2) through the supply pipe (86), and the treated product granules are fed to the hopper (9H) (slit (9c)). ) Through the perforated plate (83) of the transfer pipe (9)
It is dropped on the upper surface of. In the transfer pipe (9), the perforated plate (8) is supplied by the pressurized gas fed from the end (9A).
3) Ejecting port (9B) while appropriately floating the granules above
Transfer to. According to such an aerodynamic transfer mechanism, the contact with the member in the transfer pipe (9) is small and the contact between the particles is buffered by the gas, so that the coating formed on the product granules is prevented from being damaged. You can

[0046]

EXAMPLES The present invention will be described in more detail with reference to examples below, but the present invention is not limited to the following examples as long as the gist thereof is not exceeded. 4 to 1 equipped with the spray nozzle shown in FIG. 3 in the following examples.
1 coating device (drum (2) diameter 60
0 mm, axis length 500 mm, number of lifts (3) installed is 12
Sheets) were used.

Example 1 Using the conditions shown in Table 1, perchlorethylene was added to the spray gas to control the concentration of the gas in the coating apparatus to 6% by volume, and fertilizer coating was performed. As a result of evaluating the appearance of the obtained Cotig fertilizer by an electron microscope photograph, it was confirmed that a polyethylene film was formed on the surface of the fertilizer particles with a uniform thickness.

[0048]

[Table 1] Fertilizer average particle size 3.0 mm Treatment amount for 10 times Circulation number for 10 kg treatment 250 times Coating liquid (polyethylene and perchloroethylene) (Polyethylene concentration: 5% by weight) Spray amount of coating liquid 20 Kg Gas for spraying Linear velocity 20 m / sec Spray gas temperature 50 ° C. Drying gas linear velocity (linear velocity in draft (6)) 4.5 m / sec Drying gas temperature 80 ° C. Droplet diameter of coating liquid 150 to 200 μm Target coating thickness 75 μm

Comparative Example 1 A fertilizer was coated in the same manner as in Example 1 except that perchlorethylene was not added to the spray gas. As a result of evaluating the appearance of the obtained coating fertilizer with an electron microscope, the polyethylene coating formed on the surface of the fertilizer particles was not uniform.

[0050]

As described above, according to the coating method of the present invention, it is possible to form a coating film of a polymeric substance on the surface of a granular material with a uniform thickness, and the range of optimum conditions therefor. Can be alleviated.

[Brief description of drawings]

FIG. 1 is an explanatory view of a coating method for powder or granules of the present invention.

FIG. 2 is an explanatory diagram of a coating method for powder or granules of the present invention.

FIG. 3 is an explanatory diagram of an example of a spray nozzle used in the method of the present invention.

FIG. 4 is a side sectional view showing a structural example of a coating apparatus preferably used in the method of the present invention.

5 is a sectional view taken along line II-II in FIG.

6 is a perspective view showing a configuration example of a lift provided on the inner peripheral surface of the drum of the coating apparatus shown in FIG.

FIG. 7 is an explanatory diagram showing an operating method of the coating apparatus shown in FIG.

8 is an explanatory diagram showing an operating method of the coating apparatus shown in FIG.

9 is an explanatory diagram showing a method of operating the coating apparatus shown in FIG.

10 is a side sectional view showing another configuration example of the transfer pipe in the coating apparatus shown in FIG.

11 is a partial cross-sectional view showing the pneumatic transfer mechanism of the transfer pipe in FIG.

[Explanation of symbols]

 100: coating device 101: drying gas supply pipe 102: coating liquid supply pipe 103: exhaust gas pipe 104: adsorption tower 106: solvent supply pipe 107: heat exchanger 109: spray gas supply pipe 1: housing 1A: inlet 1B : Discharge port 2: Drum 20: Guide plate 3: Lift 31: Fixed plate 33: Scraper 6: Draft 7: Spray nozzle 82: Screw conveyor 9: Transfer pipe 9c: Slit 9H: Hopper W: Granules

Claims (1)

[Claims] 1. Powder particles for forming a film of a polymeric substance on the surface of the granular material by spraying an organic solvent solution in which the polymeric material is dissolved on the granular material dispersed in a gas stream for drying. In the body coating method, a nozzle having a gas ejection portion around the ejection portion of the organic solvent solution is used as a spray nozzle for the organic solvent solution, and the organic solvent is added to the spray gas supplied from the gas ejection portion of the nozzle. A method for coating a powder or granular material, which comprises containing steam.