JPH06277486A - Production of superfine particle - Google Patents

Abstract

PURPOSE:To stably and continuously produce monodisperse superfine particles at a low cost wherein the same are utilized as various functional powder and both a particle shape and a particle diameter are uniform by using an ink-jet or a bubble-jet for an nozzle type atomizer, forming fine droplets, drying and/or burning the fine droplets. CONSTITUTION:A manufacturing device is constituted of the hopper 1 of a raw material, a feeder 2 of the raw material, a nozzle type atomizer 3 being an ink-jet or a bubble-jet, an air introduction port 4, a quartz pipe 5, a heating furnace 6 and a recovery part 7 or the like. Fine droplets are formed by the nozzle type atomizer 3. Superfine particles are produced by drying and/or burning the fine droplets. As a result, the monodispersed superfine particles are produced stably and continuously at a low cost and utilized as the raw material of ceramics and various functional powder and both a particle shape and particle diameter are uniform.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing ultrafine particles, and more particularly to a ceramic material, a catalyst carrier, an adsorbent, an abrasive, a lubricant, a cosmetic, a drug, a magnetic material, an electronic material. The present invention relates to a method for producing ultrafine particles used in materials, optical materials, paints, photographic emulsions, etc., whose particle size and composition can be strictly controlled.

[0002]

2. Description of the Related Art Ultrafine particles include various materials such as ceramic raw materials, catalyst carriers, adsorbents, abrasives, lubricants, cosmetics, chemicals, magnetic materials, electronic materials, optical materials, paints, photographic emulsions, etc. It is a functional powder that is expected to be used in a wide range of fields, and many practical studies have been made.

[0003]

There are various methods such as a solid phase reaction method, a sol-gel method, and a coprecipitation method for producing such ultrafine particles. However, these production methods are generally batch processes. However, there are problems such as low productivity and difficulty in manufacturing on an industrial scale.

For such a batch process, a method for continuously producing ultrafine particles called a spray pyrolysis method has been proposed. For example, in Japanese Patent Application Laid-Open No. 58-34002, ultrafine particles are produced by ultrasonically dropping a solution or suspension of a sample into the high temperature air stream from the upper end of a drying cylinder and instantaneously drying it. The so-called ultrasonic spray drying method has been proposed. Further, Japanese Patent Laid-Open No. 3-33011 proposes a method for producing ultrafine particles using ultrasonic waves as described above as a method for producing spherical alumina particles. These production methods are solid phase reaction methods and sol-gel methods, in that ultrafine particles can be produced by a continuous process.
Higher productivity compared to batch processes such as coprecipitation
Industrial value is high. However, these spray-type manufacturing methods have a problem that the particle size distribution is wider than that of the powder obtained by the liquid phase method. As above,
The ultrafine particles obtained by these production methods are expected to be used as raw materials for ceramics and various functional powders.
The purpose of ultra-fine particles in such applications is, for example, when the material is used as a ceramics material, the structure of the sintered body is made uniform, or in the case of porous ceramics, high accuracy such as pore diameter and pore distribution is obtained. For example, in the case of an abrasive, the polishing accuracy is improved, and in the case of a paint, the fluidity and filling property are improved. It is needless to say that powder is ultrafine particles as one of the factors that support these actions expected of ultrafine particles, but the uniformity of the particle size is also an important factor to exert these actions.

The methods for producing ultrafine particles that have been developed so far have the above-mentioned problems, and still have many technical problems in connection with industrialization.
Moreover, the demand for ultrafine particles that are uniform in particle shape and particle size and are monodispersed is extremely high.

Therefore, the object of the present invention is to solve the above-mentioned conventional technical problems, and as is clear from the above-mentioned purpose, as a raw material powder of ceramics, abrasives, cosmetics, and electronic materials. It is an object of the present invention to provide a method for producing ultrafine particles, which can be used as, for example, particles having a uniform particle shape and particle diameter, and which are capable of producing monodispersed ultrafine particles stably and continuously at low cost.

[0007]

In order to achieve the above object, the method for producing ultrafine particles according to the present invention produces fine droplets by a nozzle type spraying device, and dry and / or calcinate the fine droplets. When the ultrafine particles are produced by doing so, the nozzle type spraying device is an inkjet or a bubble jet.

The inventors of the present invention have conducted various studies with the aim of developing a method for producing ultrafine particles satisfying the above-mentioned requirements, and as a result, produced fine droplets by a nozzle type spraying device and dried these fine droplets. When producing ultrafine particles by firing and / or firing, by using an inkjet or bubble jet in the nozzle type spraying device, the particle shape and the particle size are uniform, and the monodispersed ultrafine particles are stably and continuously. Moreover, they have found that they can be obtained at low cost and have completed the present invention.

[0009]

That is, an inkjet device or a bubble jet must be used as a spraying device for obtaining fine droplets used for carrying out the method for producing ultrafine particles of the present invention. This ink jet or bubble jet is known as a printer nozzle, and is an ink generating device for printing. This ink generator is
Since the purpose is high-precision printing, the generation of ink is highly controlled as shown below. This highly controlled ink generation mechanism is essential in producing the ultrafine particles of the present invention. That is, it is important and indispensable in that the diameter of the generated droplet can be strictly controlled. The generation of droplets when using these nozzles is as follows in the bubble jet method, for example. First, the heater in the nozzle instantaneously heats the aqueous solution to about 300 ° C. to foam the aqueous solution. Further, while the bubble is growing in the nozzle, the discharging operation is repeated at the same time. A mist having the same diameter can be generated by these series of operations.

As described above, either the ink jet or the bubble jet is used for the spraying device used for carrying out the method for producing ultrafine particles of the present invention. The target ultrafine particles can be obtained by using any nozzle, but the ink jet type nozzle has a characteristic that it is relatively inexpensive, while the bubble jet type nozzle is stable and does not clog the solution. This has the advantage that droplets of the same size can be discharged. Therefore, the inkjet or bubble jet may be selected in consideration of these advantages and characteristics. Since the size of the droplet size depends on the size of the nozzle, the size of the nozzle may be selected according to the target droplet size.

After the droplets are generated by the above method,
In order to obtain these as ultrafine particles, drying or firing is performed, and an example of a series of methods for producing these ultrafine particles will be described with reference to the accompanying drawings.

FIG. 1 shows an example of an apparatus for producing ultrafine particles according to the present invention. As shown in the figure, the apparatus for carrying out the method for producing ultrafine particles according to the present invention comprises a raw material hopper 1 and It mainly comprises a raw material supply device 2, a spraying device (inkjet or bubble jet) 3, an air inlet 4, a quartz tube 5, a heating furnace 6 and a recovery part 7. A series of flow in such a manufacturing apparatus is shown below. First, the raw material liquid drawn from the raw material supply device 2 is generated as a mist by the spraying device 3. The mist generated from the spraying device 3 is sent into the heating furnace 6 by an ascending airflow, and is instantly pyrolyzed to generate spherical particles of submicron order. The spherical particles are collected and collected by the collecting unit 7. Regarding the amount of raw material supplied, if a large amount of raw material is supplied, it is easy for the nozzle to become clogged. On the other hand, if only a small amount of raw material is supplied, productivity will drop. Needs to be tightly controlled. Further, the electric furnace used for drying and firing the mist is preferably an infrared concentrated heating type furnace in order to uniformly heat the mist and enhance the generation efficiency of the powder. As the ultrafine particles to be generated, when a hollow body is desired, rapid heating at high temperature is suitable for drying or firing, and conversely, when it is desired to obtain a solid body, the length of the quartz tube is increased. It is better to extend the length of the heating furnace and extend the residence time of mist in the drying and firing zone. Then, although the collection of the powder is not particularly limited, the simplest method is to place a filter paper or the like in the vicinity of the quartz tube outlet while sucking the quartz tube outlet with an aspirator or the like, and collect the ultrafine particles with this filter paper. There is a way to do it.
There is also a method of collecting with a dust collector.

[0013]

EXAMPLES The method for producing ultrafine particles of the present invention will be further described below with reference to Examples, but the following Examples are not intended to limit the present invention in any way, and design changes may be made without departing from the spirit of the invention. Both are included in the technical scope of the present invention.

(Embodiment 1) Using the manufacturing apparatus shown in FIG. 1, yttrium aluminum garnet (hereinafter referred to as YA)
G) was synthesized. First, aluminum nitrate and yttrium nitrate were mixed at a metal molar ratio of 5: 3 and dissolved in water to prepare a 0.1 mol / l aqueous solution. This was fed into the inkjet nozzle with a metering pump. At this time, the applied voltage of the nozzle was 10 to 20 V, the applied current was 0.2 A, and the frequency was 50 KHz. Droplets generated from the inkjet nozzle were sent to an air-infrared intensive heating furnace together with air and thermally decomposed at 800 ° C. The YAG powder produced by thermal decomposition was collected by adhering it to the filter paper of the glass filter provided at the quartz tube outlet. Recovered YAG
The powder was spherical particles monodispersed as shown in FIG. 2, and as shown in FIG. 3, the average particle diameter was 0.537 μm.
It was a monodisperse particle having an extremely sharp particle size distribution with m and σg = 1.15.

(Example 2) Under the same conditions as in Example 1, only the spray nozzle was replaced with a bubble jet nozzle to synthesize YAG ultrafine particles. Here, as in Example 1, monodisperse ultrafine particles having an extremely sharp particle size distribution with an average particle size of 0.586 μm and σg = 1.14 were produced.

(Comparative Example 1) Using the apparatus of Example 1, YAG was synthesized by changing the spray generator from an ink jet type nozzle to an ultrasonic generator. First, aluminum nitrate and yttrium nitrate were mixed at a metal molar ratio of 5: 3 and dissolved in water to prepare a 0.1 mol / l aqueous solution. This was fed into the ultrasonic generator with a metering pump.
The vibration frequency at this time was set to 1.6 MHz. Droplets generated from the ultrasonic generator were sent to an air-infrared intensive heating furnace together with air and thermally decomposed at 800 ° C. The YAG powder produced by thermal decomposition was collected by adhering it to the filter paper of the glass filter provided at the quartz tube outlet. The recovered YAG powder was spherical particles monodispersed as shown in FIG. 4, but as shown in FIG. 5, the average particle diameter was 0.464 μm,
With σg = 1.26, a broader particle size distribution was given compared to Examples 1 and 2.

[0017]

EFFECTS OF THE INVENTION According to the method for producing ultrafine particles of the present invention, by adopting the above-mentioned constitution, it can be utilized as a raw material for ceramics and various functional powders, and the particle shape and particle diameter are uniform and monodispersed. The ultrafine particles can be stably and continuously provided at low cost.

[Brief description of drawings]

FIG. 1 is a schematic view showing an example of a manufacturing apparatus for carrying out the method for manufacturing ultrafine particles of the present invention.

2 is an electron micrograph of the YAG powder obtained in Example 1. FIG.

FIG. 3 is a particle size distribution diagram of the YAG powder obtained in Example 1.

FIG. 4 is an electron micrograph of the YAG powder obtained in Comparative Example 1.

5 is a particle size distribution chart of the YAG powder obtained in Comparative Example 1. FIG.

[Explanation of symbols]

1 Raw material hopper 2 Raw material supply device (quantitative pump) 3 Spraying device (inkjet or bubble jet) 4 Air inlet port 5 Quartz tube 6 Heating furnace 7 Recovery section

Front Page Continuation (72) Inventor Kenji Ogawa 2-4-2 Daisaku, Sakura-shi, Chiba Central Research Laboratory, Onoda Cement Co., Ltd. (72) Kenji Nagata 2-4-2 Daisaku, Sakura-shi, Chiba Onoda Cement Co., Ltd. In-house Central Research Laboratory (72) Inventor Shinji Iguchi 2-4-2 Daisaku Sakura City, Chiba Prefecture Onoda Cement Co., Ltd. Central Research Laboratory

Claims (1)

[Claims] 1. A method for producing ultrafine particles by producing fine droplets by a nozzle type spraying device and drying and / or firing the fine droplets, wherein the nozzle type spraying device is an inkjet or bubble jet. And a method for producing ultrafine particles.