JPH05208127A - Fine particle coating method and apparatus therefor and spray nozzle - Google Patents

Abstract

PURPOSE:To uniformly coat matrix particles with fine particles by a method wherein fine particles are dispersed in a dispersing medium to prepare a slurry which is, in turn, applied to a dispersing machine to further disperse the fine particles and subsequently added to matrix particles to be sufficiently mixed therewith and the resulting mixture is immediately sprayed. CONSTITUTION:At first, fine particles being coating particles are dispersed in a dispersing medium to prepare a fine particle slurry 16 which is, in turn, sent to a dispersing machine 18 to be highly dispersed. Thereafter, this fine particle slurry 16 is sent to a mixing tank 20 to be mixed with the matrix particles 25 from a particle feeder 23 to prepare a mixed slurry 12 having matrix particles and fine particles dispersed therein. This slurry 12 is immediately sent to a sprayer 14 by a liquid feed pump 22 to be sprayed to a drying chamber 24. By this method, the matrix particles can be uniformly coated with the fine particles.

Description

Detailed Description of the Invention

[0001]

INDUSTRIAL APPLICABILITY According to the present invention, base particles and fine particles smaller than the base particles are uniformly dispersed in a dispersion medium, and the slurry is spray-dried to coat the base particles with the fine particles. Particulate coating method,
Further, the present invention relates to a spray nozzle applied to such fine particle coating by spray drying, and a fine particle coating method and a fine particle coating apparatus to which the spray nozzle is applied.

[0002]

2. Description of the Related Art In the production of toners, cosmetic powders, paints, etc., fine particles (coating particles) are coated on the surface of a powder or granular material which is a base material (coated particles) in order to impart various characteristics. There is. For example, in order to impart fluidity to toner particles having poor fluidity in toner, a fine particle coating having good fluidity is applied to the surface of toner particles, and in the case of cosmetic powder, it is applied to the surface of cosmetic powder in order to make it an anti-UV cosmetic. Ultraviolet-ray-imparting fine particles are coated, and in addition, coating materials are coated with inexpensive pigment fine particles to produce inexpensive pigment raw materials.

[0003] Such coating of fine particles on the base particles is carried out by various methods. Particularly, coating using particles having a small particle size, for example, base particles having an average particle size of about 3 µm to 1 mm is performed. As a method for coating fine particles, a method is used in which a slurry in which each raw material particle is dispersed is prepared and the slurry is spray-dried to coat the surface of the base particles with the fine particles.

In the coating method by spray drying, an evaporable solvent such as an organic solvent such as alcohol or water is used as a dispersion medium, and a predetermined amount of base particles and fine particles to be coating particles are mixed and dispersed in the dispersion medium. To produce a slurry. Next, this slurry is sprayed into the drying chamber by a sprayer using a one-fluid nozzle, a two-fluid nozzle or the like. In the sprayed state, a slurry containing fine particles is present on the surface of the base particles. Therefore, by evaporating the dispersion medium with hot air or the like in the drying chamber, the powder in which the base particles are coated with the fine particles is granulated.

[0005]

When the base particles are coated with the fine particles by such spray-drying, the base particles and the coating particles are uniformly dispersed in the dispersion medium in order to obtain a uniform and good coating. Need to be spray dried.

However, in the coating of fine particles by spray drying, since the particles having a relatively small particle size are targeted, the fine particles aggregate in the dispersion medium and cannot be reliably and satisfactorily dispersed. In particular, as described above, the fine particles easily aggregate in the dispersion medium, and it is difficult to disperse them properly. If the coating (spray drying) is performed in the state where the fine particles are aggregated, not only the coating of the fine particles on the base particles is not uniform, but also an aggregate of fine particles different from the target is granulated.

Further, although atomization is performed by an atomizer, a one-fluid nozzle, a two-fluid nozzle, etc., the conventional atomizer cannot sufficiently reduce the diameter of one droplet,
Particularly when the particle size of the base particles is as small as 3 μm to 1 mm, a large number of base particles are included in one droplet, so that a granulated product in which a large number of base particles are collected is formed. Further, since the droplet diameter is not uniform in the sprayed state, there is a problem that the thickness of the coating film (the thickness of the layer formed by the fine particles on the base particles) becomes uneven. On the other hand, in the case of the one-fluid nozzle and the two-fluid nozzle, it is necessary to reduce the nozzle diameter in order to reduce the droplet diameter, but if the nozzle diameter is reduced, agglomerates are likely to be clogged in the nozzle, which causes troubles. It tends to occur.

An object of the present invention is to solve the above-mentioned problems of the prior art, and when coating fine particles on the base particles, even if the particle size is small, the fine particles or the agglomerates of the base material, etc. It is possible to satisfactorily prepare an object in which fine particles are uniformly coated on a single base particle without granulating, a fine particle coating method and apparatus by spray drying, and used for coating fine particles by spray drying, It is an object of the present invention to provide a spraying nozzle capable of forming a fine slurry containing a matrix particle and a coating particle into a fine and uniform droplet diameter.

[0009]

In order to achieve the above object, a method of coating fine particles of the present invention is a method in which base particles and fine particles finer than the base particles are dispersed in a dispersion medium, and the dispersion solution is spray-dried. By coating the fine particles on the surface of the base particles, a slurry in which the fine particles are dispersed in a dispersion medium is prepared, and then,
The present invention provides a method for coating fine particles, which comprises subjecting the slurry to a dispersing machine to further disperse the fine particles, adding the base particles to the slurry, thoroughly mixing them, and immediately performing spray drying.

Further, the fine particle coating apparatus of the present invention is an apparatus for coating the surface of the base particles with fine particles finer than the base particles by spray drying.
Means for producing a slurry in which the fine particles are dispersed in a dispersion medium, a disperser for further increasing the dispersion of the fine particles in the slurry, and means for adding and dispersing base particles to the slurry solution dispersed by the disperser. , The mother particles are added, liquid feeding means for feeding the dispersed slurry, spraying the slurry sent by the liquid feeding means, a nozzle body, a flow path of the slurry formed in the nozzle body, An atomizer using a spray nozzle having a first nozzle that ejects gas in the middle of the flow path, and a second nozzle that ejects gas toward the center from the outer peripheral portion of the flow path in the vicinity of the outlet of the flow path; And means for drying the slurry sprayed by the sprayer.

In the fine particle coating apparatus of the present invention, the disperser comprises an inlet and an outlet for the slurry produced by the means for producing the slurry,
And a disperser main body having a flow path that communicates the inflow port and the outflow port, an orifice formed in the middle of the flow path, and an ultrasonic wave provided on the downstream side and in the vicinity of the orifice in the middle of the flow path. It is preferably a wet disperser having a generating means.

Further, the spray nozzle of the present invention sprays a slurry in which base particles and fine particles smaller than the base particles are dispersed by spray drying to coat the surfaces of the base particles with the fine particles. Of the nozzle, a nozzle main body, a flow path of the slurry formed in the nozzle main body, a first nozzle for ejecting gas in the flow direction of the slurry in the middle of the flow path, and A second nozzle for ejecting gas from the outer peripheral portion of the flow path toward the center in the vicinity of the outlet is provided.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The fine particle coating method and spray nozzle of the present invention, and the fine particle coating apparatus of the present invention using them will be described in detail below with reference to the preferred embodiments shown in the accompanying drawings.

FIG. 1 conceptually shows the fine particle coating apparatus of the present invention using the fine particle coating method and spray nozzle of the present invention.

The fine particle coating apparatus 10 for carrying out the present invention prepares a mixed slurry 12 containing base particles (particles to be coated) and fine particles which are coating particles (hereinafter referred to as fine particles), which are sprayed by a sprayer 14. Fine particle coating apparatus 10 by spraying and then drying, so-called spray drying (hereinafter, coating apparatus 10
First, fine particles that are coating particles are dispersed in a dispersion medium to obtain fine particle slurry 16. The method of producing the fine particle slurry 16 is not particularly limited, and any known method such as a method using a stirring tank and a method using an ultrasonic tank can be applied.

The dispersion medium to be applied is not particularly limited, and an evaporable dispersion medium such as an organic solvent such as various alcohols, water or the like may be appropriately selected according to the base particles and fine particles. The mixing ratio of the fine particles and the dispersion medium may be set according to the particle diameters of the base particles and the fine particles, the amount of the fine particles adhering to the surfaces of the base particles, the type of spray nozzle, the viscosity at the time of spraying, and the like.

In the present invention, the produced fine particle slurry 16 is sent to the disperser 18 and is further highly dispersed. As described above, when coating the base particles with fine particles by spray drying, if particles with a small particle size are used as the fine particles (coating particles), in the conventional method, the fine particles aggregate and disperse well in the slurry. However, there is a problem that it is difficult to obtain a high-quality product because the coating of the fine particles on the base particles is not uniform, or agglomerates of the fine particles are granulated. there were.

On the other hand, in the fine particle coating method of the present invention, after the fine particle slurry 16 is prepared, it is further highly dispersed by the disperser 18 to make the dispersed state of the fine particles in the mixed slurry 12 uniform and agglomerated. It is possible to manufacture a high-quality product in which base particles are uniformly coated with fine particles, which is a good product without any defects.

The disperser 18 applied to the present invention is not particularly limited, and various known dispersers such as a ball mill, a homogenizer and an ultrasonic disperser can be applied. Preferably, a wet disperser using ultrasonic waves and an orifice together is applied.

FIG. 2 shows a schematic sectional view of such a wet disperser 100. Wet disperser 100 is slurry 1
6, a disperser main body 116 forming the flow path of No. 6, a needle valve 118 having an orifice 128 provided in the middle of the flow path of the fine particle slurry 16, and a superposition in the middle of the flow path of the slurry arranged downstream of the orifice 128. It has an ultrasonic wave generator 120 that generates a sound wave and a micrometer 122 that adjusts the flow rate of the needle valve 118.

In the illustrated example, the fine particle slurry 16 from the inflow port 124 to the outflow port 126 is provided in the disperser body 116.
Of the mixing tank 20, the fine particle slurry 16 flows into the inflow port 124 and flows out from the outflow port 126.
Is flowed into.

The fine particle slurry 16 that has flowed in through the inflow port 124 formed on the side surface of the disperser body 116 first passes through the space portion 129 having a large flow passage diameter, and the flow passage is significantly narrowed as compared with the space portion 129. It passes through an orifice 128 (a gap formed by the orifice 128 and the needle 130 in the illustrated example). As a result, the flow velocity of the fine particle slurry 16 is rapidly increased, and a force for stretching the fine particles (aggregated particles) in the fine particle slurry 16 is applied to the downstream side to cause fragmentation and fracture, and the fine particles in the fine particle slurry 16 are highly advanced. Distributed.

In the wet disperser 100, the material for forming the orifice 128 is not particularly limited, but since the fine particle slurry 16 in which fine particles are dispersed flows at a high speed through the orifice 128, a material having excellent wear resistance is used. Preference is given to applying, in particular ceramic materials.

The wet disperser 100 of the illustrated example has a needle 130 for adjusting the opening area of the orifice 128 as a preferred embodiment, and constitutes a needle valve 118. The needle 130 is held by a bearing 132 that holds the needle 130 in a liquid-tight manner and a fixing member 134, and is engaged with a micrometer 122 that finely adjusts the opening area of the orifice 128.

The wet disperser 100 is not limited to one having a means for adjusting the opening area of the orifice 128 such as the needle 130, and may have a structure having only an orifice in which the flow passage is significantly narrowed. Good.

The fine particle slurry 16 (fine particles therein) dispersed by the orifice 128 is further highly dispersed by the ultrasonic waves generated by the ultrasonic generator 120 while rising in the flow path, and then the space 146. Through the outlet 126. The ultrasonic wave generator 120 includes an ultrasonic wave transmitter 138 and an ultrasonic horn 140 arranged in the flow path of the fine particle slurry 16. Further, the ultrasonic wave transmission unit 138 is connected to a controller (not shown) that controls the generated ultrasonic wave.

The wet disperser 100 includes an ultrasonic wave transmitter 138.
The ultrasonic horn 140 generates an ultrasonic wave, and the ultrasonic waves disperse the fine particles in the fine particle slurry 16 to a higher degree. The orifice 128 and the ultrasonic wave are combined to form an ultrasonic wave. After the dispersion, the ultrasonic waves are continuously dispersed to disperse the fine particles in the fine particle slurry 16, so that a synergistic effect of both having different dispersion mechanisms (the orifice is considered to be split dispersion and the ultrasonic wave is considered to be erosion dispersion) Can be done in a short time, which is impossible with individual dispersion,
A higher degree of fine particle dispersion can be performed. Further, the wet disperser 100 in the illustrated example has a configuration in which the dispersion by the ultrasonic waves is performed after the dispersion by the orifices 128, so that high-level dispersion can be performed in a shorter time.

There is no particular limitation on the frequency or output of the ultrasonic waves used for dispersion, and it is appropriately determined according to the particle size of the particles contained in the particle slurry 16, the concentration of the particle slurry 16, and the desired degree of dispersion. However, normally, the frequency is about 5 kHz to 100 Hz, and the output is 10 W to 1
It is about 0 kW.

The dispersion state of the fine particles in the fine particle slurry 16 by the disperser 18 (wet disperser 100) is, of course, such that the separation of the fine particles is more reliable, but the apparent appearance of the fine particles is preferable. Dispersion is performed until the average particle diameter becomes 1/3 or less of the base particles, and more preferably 1/10. By setting the dispersion state in the fine particle slurry 16 in this way, it is possible to granulate a high-quality product in which fine particles are not uniformly coated on the surface of the base particle, which does not include a granulated body of fine particles.

The fine particle slurry 16 is dispersed by the disperser 18 (wet disperser 100).
May be continuously supplied to a disperser 18 and the fine particle slurry 16 in a highly dispersed state may be sequentially supplied to a mixing tank 20 described later, or the fine particle slurry may be supplied until the fine particles are dispersed in a predetermined state. 16 in a highly dispersed state by circulating 16 through a path including a disperser 18.
May be supplied to the mixing tank 20 batchwise.

The fine particle slurry 16 in which fine particles are more highly dispersed by the disperser 18 is then sent to the mixing tank 20 and the base particles 25 supplied from the powder / particle supply device 23.
To form a mixed slurry 12 in which base particles and fine particles are dispersed.

The method for mixing (dispersing) the mixed slurry 12 and the base particles in the mixing tank 20 is not particularly limited, and a known method such as a stirring method or an ultrasonic method may be used. The amount of the base particles supplied to the mixing tank 20 is the same as the amount of the fine particles described above, the particle diameters of the base particles and the fine particles, the amount of the fine particles attached to the surface of the base particles, the type of the spray nozzle and the viscosity at the time of spraying. It may be set according to the above.

If necessary, starch, ethyl cellulose, various polymers, etc. may be added to the mixing tank 20 as a binder for strengthening the adhesion between the base particles and the fine particles. In addition, in the mixing tank 20, it goes without saying that the concentration (content of base particles and fine particles), viscosity and the like of the mixed slurry 12 may be adjusted by adding a dispersion medium.

Mixed slurry 1 thus prepared
2 is immediately sent to the sprayer 14 by the liquid feed pump 22 and sprayed in the drying chamber 24. The liquid feed pump 22 is not particularly limited, and any known liquid feed means such as various slurry pumps may be used as long as it has a discharge pressure (transport pressure) that allows the mixed slurry 12 to be sprayed by the sprayer 14. Both are applicable.

Further, in the present invention, the mixed slurry 12
After the adjustment, "immediately" means within about one hour.

The sprayer 14 sprays the mixed slurry 12 transported from the liquid feed pump 22 by the spray nozzle into the drying chamber 24. As the spray nozzle applied to the present invention, any of various known spray nozzles such as an atomizer, a one-fluid nozzle, and a two-fluid nozzle can be applied, but preferably, the spray nozzle of the present invention described below. Is applied.

FIG. 3 shows an example of the spray nozzle of the present invention. The spraying nozzle of the present invention basically comprises a nozzle body, a flow path for the mixed slurry 12 formed in the nozzle main body, and a gas jet in the flow direction of the mixed slurry 12 in the middle of the flow path. It has one nozzle and a second nozzle that ejects gas in the central direction from the outer peripheral portion of the flow path in the vicinity of the outlet of the flow path.
A slurry flow path 34 having a circular cross section that penetrates from the slurry input port 30 to the spray port 32 in the cylindrical nozzle body 28, and a gas that jets gas in the middle of the slurry flow path 34
In the nozzle 36 and the slurry flow path 34 near the spray port 32,
The second nozzle 38 for ejecting gas is formed.

The first nozzle 36 is formed in the middle of the slurry flow path 34 so as to surround the slurry flow path 34, that is, in a ring shape, and is formed concentrically and annularly with the first nozzle 36. The compressed gas A is supplied from the gas introduction port 42 through the gas flow path 40, and the gas is ejected into the slurry flow path 34 in the flow direction of the mixed slurry 12. The second nozzle 38 is formed in the vicinity of the spray port 32 so as to surround the slurry flow path 34, that is, in a ring shape, and like the first nozzle 36 described above, the second nozzle 3 is formed.
8 is supplied with the compressed gas A from the gas introduction port 46 through the gas flow passage 44 formed concentrically with the slurry flow passage 34.
A gas is jetted into the slurry flow path 34 from the outer peripheral portion toward the center. In addition, the slurry flow path 34 is the first nozzle 3
The diameter gradually increases from slightly below 6 toward the spray port 32.

In the spray nozzle 26, the mixed slurry 12 is supplied from the slurry inlet 30 into the slurry flow path 34, and the gas is first jetted from the first nozzle 36 so that the jetted gas is mixed by the pulverizing force of the jetted gas. Slurry 1
2 is atomized to form a spray. The finely mixed slurry 12 is more reliably dispersed by the second nozzle 38. Here, some of the droplets adhere to the inner wall of the slurry flow path 34 and fall along the wall as large droplets, but these droplets are crushed by the gas ejected from the second nozzle 38. Atomized. Therefore, according to the spray nozzle 26, the entire mixed slurry 12 to be supplied can be suitably made into fine particles, and no large droplets or the like are generated.
Good spraying with a uniform droplet diameter can be realized.

The first nozzle 36 and the second nozzle 3
8 is not limited to a ring shape surrounding the slurry flow path 34,
A gas may be jetted from four sides, eight sides, etc. surrounding the slurry flow path 34.

In the spray nozzle 26, the first nozzle 3
There is no particular limitation on the gas injection angle from 6 to the slurry flow path 34, that is, the angle θ ₁ of the first nozzle 36, but an effective shearing force is applied to the mixed slurry 12 to make the droplet diameter uniform. From the viewpoint that good spraying can be performed, it is preferable to set between 5 ° and 20 °. Further, in the spraying nozzle 26 of the illustrated example, the slurry flow path 34 has the first nozzle 3
6 has a configuration in which the diameter gradually increases from slightly below 6 toward the spray port 32, but there is no turbulence in the air flow (if the air flow is turbulent,
The diameter is expanded (θ _{2 in} FIG. 3) to 1 ° to 15 ° with respect to the axial direction of the slurry flow path 34 in that the droplets coalesce into a large droplet) and good spraying can be performed. Preferably.

FIG. 4 shows a schematic sectional view of another example of the spray nozzle of the present invention. The spray nozzle 26 shown in FIG.
The first nozzle 36 and the second nozzle 38 both inject gas toward the center from the outer periphery of the slurry flow path 34. However, the atomizing nozzle 48 shown in FIG.
The nozzle is configured to inject gas outward from the center of the slurry flow channel. Generally, the spray nozzle 26 shown in FIG. 3 is preferably used when the viscosity of the mixed slurry 12 is low, while the spray nozzle 48 shown in FIG. 4 is preferably used when the viscosity of the mixed slurry 12 is high. Be done.

The spray nozzle 48 shown in FIG. 4 uses a cylindrical nozzle body 50 whose upper surface is closed, forms a path for supplying the mixed slurry 12 from the side, and sprays from the slurry charging port 52. Slurry flow path 56 to the mouth 54
Make up. A cylindrical first nozzle 58 for injecting a gas is arranged in the middle of the slurry flow path 56 in the center of the cross-sectional direction of the slurry flow path 56, and a straight tubular gas flow path formed from the upper surface of the nozzle body 50. Compressed air A is supplied from 60. Here, the first nozzle 58 has a configuration in which the diameter gradually increases at an angle of θ _{3 in} the gas ejection direction. Also,
In the vicinity of the spray port 54, so as to surround the slurry flow path 56,
That is, the second nozzle 62 is formed in a ring shape, the compressed gas A is supplied from the gas introduction port 66 through the gas flow path 64 formed concentrically, and is directed toward the center from the outer peripheral portion of the slurry flow path 56. Eject gas.

A spraying nozzle 48 having such a structure
In the above, the mixed slurry 12 is supplied from the slurry input port 52 and is sent through the slurry flow path 56. Here, since the first nozzle 58 is arranged in the center of the slurry flow path 56 and has an enlarged diameter at an angle of θ ₃ as described above, the mixed slurry 12 is slurried by the gas injected from here. It is pressed against the inner wall of the flow path 56 to form a thin film. The thinned mixed slurry 12 is then atomized by the ring-shaped second nozzle 62 by the gas jetted from the outer periphery of the slurry flow path 56 toward the center, and sprayed from the spray port 54.

In the spray nozzle 48 of the illustrated example, the first
The diameter expansion angle θ ₃ of the nozzle 58 is not particularly limited, but it is preferably set to 5 ° to 30 ° from the viewpoint that the thin film formed on the inner wall of the slurry channel 56 can be made more suitable.

The second nozzle 62 has a slurry flow path 56.
The shape is not limited to the ring shape that surrounds the slurry flow path, and the gas may be jetted from four directions, eight directions, etc. surrounding the slurry flow path 34.

In the atomizing nozzles 26 and 48 of the present invention, the pressure and the supply amount of the compressed gas A supplied to each gas inlet are not particularly limited, but the amount of gas injected from the first and second nozzles is not limited. It is preferable to adjust the flow velocity to 50 m / s or more. By setting the flow velocity of the gas ejected from both nozzles to 50 m / s or more, it is possible to more reliably perform better spraying with a uniform droplet diameter. As the gas applied to the spray nozzle 26, any of those applied to a normal two-fluid nozzle, such as air or an inert gas such as nitrogen gas, can be applied.

According to such a spraying nozzle of the present invention, not only is it possible to perform fine spraying which is sufficiently fine and has a uniform droplet diameter, but it is also sufficient without reducing the diameter of the slurry flow path. Since it is possible to spray finely divided droplets, it is possible to perform stable fine particle coating without causing trouble such as nozzle clogging. Also,
Since the droplet diameter that can be generated can be adjusted by adjusting the flow velocity of the gas ejected from each of the first and second nozzles, and the adjustment range is wide, it can be applied over a wide range of base particle diameters. is there.

The droplets of the mixed slurry 12 sprayed from the sprayer 14 (spraying nozzle) into the drying chamber 24 have one base particle as a core and a slurry containing fine particles attached to the surface thereof. ing. Therefore, by being dried by the gas heated by the heater 68 in the drying chamber 24, the dispersion medium of the slurry evaporates and the base particles become particles coated with fine particles.

The coating apparatus 10 shown in FIG.
Although the spraying of the mixed slurry 12 into the drying chamber 24 is performed in the downward direction, which is so-called downward spraying, the present invention is not limited to this, and the spraying is performed upward as shown in FIG. Needless to say, it may be performed by so-called top spraying. Note that the example shown in FIG. 5 has exactly the same configuration as the example shown in FIG. 1 except that the spraying method in the drying chamber 24 is different. Is omitted.

Normally, the downward blowing as shown in FIG. 1 is used when the weight of the sprayed droplets is small (the droplet diameter is small, the specific gravity of the base particles and fine particles is small, etc.), and FIG. Top blowing as shown is used when the weight of the sprayed droplets is high.

The particles dried by the drying chamber 24 are collected by the cyclone 70 to be product particles. In addition, the particles that could not be recovered by the cyclone 70
It is sucked by the blower 72 and collected by the filter 74. When the adhesive force between the base particles and the fine particles is weak, the product particles may of course be collected by the filter 74 instead of the cyclone.

Although the fine particle coating method and spray nozzle of the present invention and the fine particle coating apparatus of the present invention using them have been described above, the present invention is not limited to the above-mentioned embodiments, and the gist of the present invention is not limited thereto. Needless to say, various improvements and changes may be made without departing from the above.

[0054]

EXAMPLES The present invention will be described in more detail with reference to specific examples of the present invention.

Fine particle coating apparatus 1 shown in FIG.
0 was used as the base particles of alumina having an average particle size of 10 μm and fine particles (coating particles) of latex (particles) having an average particle size of 0.1 μm to coat the alumina surface with latex.

First, 50 g of latex was put into 1000 g of water and mixed and dispersed to prepare a fine particle slurry 16. The fine particle slurry 16 was circulated in a system including the wet disperser 100 shown in FIG. 2 and was dispersed to a higher degree by the wet disperser 100. The circulation was performed by adjusting the needle valve 118 so that the flow rate by the circulation pump was 100 kg / h and the discharge pressure from the wet disperser 100 was 30 kg / cm ² . Further, the ultrasonic generator 120 has an oscillation frequency of 15 kHz and a maximum output of 37 W.

After circulating the fine particle slurry 16 for 30 minutes in such a circulation system, the highly dispersed fine particle slurry 16 is sent to the mixing tank 20 to add alumina as the base particles, and the mixture is dispersed. The mixed slurry 12 was obtained. The amount of alumina added was 300 g.

The mixed slurry 12 thus prepared
Was sent to the sprayer 14 by the liquid feed pump 22, sprayed in the drying chamber 24 by the spraying nozzle 26 shown in FIG. 3, and collected by the cyclone 70. The flow rate by the liquid feed pump 22 is 0.2 kg / h and the discharge pressure is 3 k.
g / cm ² , and the gas velocity of compressed air is 150 m / s
And The obtained product had good product quality in which the latex was uniformly dispersed on the surface of the alumina, which was the base particle. From the above results, the effect of the present invention is clear.

[0059]

As described above in detail, according to the method for coating fine particles of the present invention, in the case of fine particle coating by spray-drying, it is possible to use base particles and coating particles (fine particles) having a small particle size. Also, it is possible to suitably granulate the target product in which the base particles are uniformly coated with the microparticles, without granulating the microparticles or the agglomerates of the base material. Further, in the fine particle coating by spray drying, by applying the spraying nozzle of the present invention, it is possible to make the slurry containing the base particles and the coating particles fine and good spray having a uniform droplet diameter. It is possible to granulate quality products.

[Brief description of drawings]

FIG. 1 is a diagram conceptually showing an example of a coating apparatus for carrying out the fine particle coating method of the present invention.

FIG. 2 is a schematic sectional view of an example of a wet disperser applied to the present invention.

FIG. 3 is a schematic perspective view of an example of the spray nozzle of the present invention.

FIG. 4 is a schematic perspective view of another example of the spray nozzle of the present invention.

FIG. 5 is a diagram conceptually showing another example of the coating apparatus for carrying out the fine particle coating method of the present invention.

[Explanation of symbols]

 10 Coating Device 12 Mixed Slurry 14 Sprayer 16 Fine Particle Slurry 18 Disperser 20 Mixing Tank 22 Liquid Delivery Pump 23 Powder and Granules Supply Device 24 Drying Chamber 25 Base Particles 26, 48 Spray Nozzle 28, 50 Nozzle Main Body 30, 52 Slurry Charge Port 32, 54 Spray port 34, 56 Slurry flow channel 36, 58 First nozzle 38, 62 Second nozzle 40, 44, 60, 64 Gas flow channel 42, 46, 66 Gas inlet port 68 Heater 70 Cyclone 72 Blower 74 Filter 100 Wet disperser 114 Circulation pump 116 Disperser main body 118 Needle valve 120 Ultrasonic wave generating means 122 Micrometer 124 Inlet 126 Outlet 128 Orifice 130 Needle 132 Bearings 134, 36, 44 Fixing member 138 Ultrasonic transmitter 140 Ultra Sound wave horn 146,154 Space A Compressed gas

Claims (4)

[Claims] 1. A base material and fine particles finer than the base particles are dispersed in a dispersion medium, and the dispersion solution is spray-dried to coat the surface of the base particles with the fine particles. To prepare a slurry in which the fine particles are dispersed, then further disperse the fine particles by applying the slurry to a disperser, add the base particles to the slurry, mix them sufficiently, and immediately perform spray drying. Characteristic fine particle coating method. 2. An apparatus for coating the surface of base particles with fine particles finer than the base particles by spray drying, and means for producing a slurry in which the fine particles are dispersed in a dispersion medium, and the fine particles in the slurry. A dispersing machine to further enhance the dispersion, means for adding and dispersing mother particles to a slurry solution dispersed by the dispersing machine, and mother particles added, a liquid feeding means for feeding the dispersed slurry, A nozzle body for spraying the slurry sent by the liquid sending means, a flow path for the slurry formed in the nozzle body, a first nozzle for ejecting gas in the middle of the flow path, and an outlet of the flow path A sprayer that uses a spray nozzle having a second nozzle that ejects gas toward the center from the outer peripheral portion of the flow path in the vicinity, and the slurry sprayed by the sprayer is dried. A fine particle coating device comprising: 3. An inflow port and an outflow port for the slurry, wherein the disperser is made by means for making the slurry,
And a disperser main body having a flow path that communicates the inflow port and the outflow port, an orifice formed in the middle of the flow path, and an ultrasonic wave provided on the downstream side and in the vicinity of the orifice in the middle of the flow path. The fine particle coating apparatus according to claim 2, which is a wet disperser having a generating unit. 4. A spraying nozzle for coating the surface of the base particles with the fine particles by spray-drying a slurry in which the base particles and fine particles smaller than the base particles are dispersed. A flow path for the slurry formed in the nozzle body, a first nozzle for ejecting gas in the flow direction of the slurry in the middle of the flow path, and an outer peripheral portion of the flow path near the outlet of the flow path. A second nozzle that ejects gas toward the center of the spray nozzle.