JPS61122151A - Manufacture of ceramic grain and apparatus therefor - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a method and apparatus for producing ceramic powder used for producing ceramic parts.

Structure of conventional examples and their problems Normally, the manufacturing process of ceramic electronic components involves a blending process in which the main raw material and minor additive raw materials are weighed in an optimal composition distribution, and the blended raw materials are ground into fine powder and the main raw materials and additive raw materials are simultaneously weighed. There is a grinding and mixing process that mixes the ingredients well. Usually, the grinding and mixing step is carried out using a pot, adding raw materials, water, an organic binder and cobblestones, and rotating the pot. Next, the raw materials after the grinding and mixing process are in a slurry state.
There is a granulation process in which this is dried using a spray dryer and simultaneously turned into spherical granulated powder suitable for molding. next,
A molding process in which granulated powder is filled into a mold and pressed into a desired shape, and a firing process in which a chemical reaction is caused at the same time as the molded product is baked and solidified to obtain a sintered product with the desired electrical performance. Furthermore, there is a process for attaching electrodes to bring out the electrical performance.

As mentioned above, the manufacturing process for ceramic electronic components generally includes a blending process, a crushing and mixing process, and a granulation process.

It consists of a molding process, a firing process, and an electrode attachment process. Among these processes, the compounding process and firing process are the most important in achieving the desired electrical performance, creating the desired shape and making the structure strong, which improves quality and ensures long-term reliability. The important processes to ensure this are the granulation process and the molding process. The properties of the granulated powder have a great influence on the moldability, and especially if the moisture content of the granulated powder is not appropriate, the shrinkage rate of the sintered product obtained by firing the molded product will vary, and furthermore, during molding. Internal defects such as voids occur inside the sintered product due to the pressure distribution generated within the molded product.

This had a major negative impact on the quality and long-term reliability of ceramic electronic components.

As mentioned above, a spray dryer is usually used in the granulation process. This passes the slurry-like mixture through a nozzle,
The mixture is blown up into hot air in the form of a spray, and as it rises and falls, it is dried and granulated into spheres. However, spray dryers originally used detergent,
Granulated powder itself is used to manufacture final products such as seasonings, and the moisture content of granulated powder is usually 0.1% or less. However, when making ceramic electronic components, granulated powder is filled into a mold and molded under pressure to create a molded product.The next firing process is to harden and cause a chemical reaction at the same time to achieve the desired electrical performance. Finished into a sintered product with In this case, unless the molded product has appropriate strength and the pressure distribution inside the molded product is kept small, variations in shrinkage rate and internal defects such as voids will occur in the sintered product during the firing process. In producing such an excellent molded product, the particle size distribution, moisture content, etc. of the granulated powder play an important role, and the moisture content is particularly important. This is because the moisture in the granulated powder is thought to function to transmit the pressure applied during molding to the center of the molded product. For this reason, when the moisture content is low, the pressure is not transmitted to the center of the molded product, and the gauze concentrates on the surface of the molded product, creating a large pressure distribution, which causes differences in the shrinkage rate in each part of the molded product during firing. This causes internal defects such as voids. On the other hand, if the water content is high, there will be problems such as water oozing out of the molded product during molding, and a drying process for the molded product will be required after molding, leading to problems such as a longer lead time. For this reason, the optimum moisture content of granulated powder is 0.5 to 1.0%.
It becomes.

As mentioned above, the granulated powder using a spray dryer has a moisture content of about 0.1%, and this is reduced to 0.5 to i, o%.
Water must be added to adjust the moisture content. Conventionally, the moisture content of the granulated powder was adjusted by (1) adding an appropriate amount of water to the granulated powder using a blender, and (2) rotating the blender. However, with this method, the water in the granulated powder inevitably mixes unevenly, resulting in areas with high moisture (clumps) and areas with low moisture in the granulated powder, making it difficult to use in actual use. In the case of mass production, the lead time becomes long, which is a major factor in increasing costs.

OBJECTS OF THE INVENTION In view of the above-mentioned drawbacks, an object of the present invention is to provide a method for manufacturing ceramic powder and an apparatus for manufacturing the same, which facilitates adjustment of the moisture content of granulated powder of ceramic powder.

Structure of the Invention In order to achieve this object, the method for producing ceramic powder and granules of the present invention reduces the moisture content by attaching liquid particles generated from an ultrasonic atomizer to granulated powder of ceramic powder and granules. The manufacturing equipment consists of a vertically open hollow container with a penetrating hole in the side wall, and an ultrasonic atomizer with a tL particle outlet. It is a device that is inserted into a hole.

First, granulated powder granulated by a spray dryer passes through a hollow container, and at this time, liquid particles are blown out from the side wall surface of the hollow container, and the liquid particles adhere to the surface of the granulated powder that is passing through. Usually, granulated powder granulated with a spray dryer has an average particle size of 100 to 160 μm and 69. On the other hand, the average particle size of liquid particles generated by an ultrasonic atomizer is 5 to 10 tons.
tm, it adheres evenly to the granulated powder, and does not produce clay-like lumps with high moisture content as in the humidification method using the V-blender described above. Therefore, there is no need for sieving, and there is no fear of prolonging lead time.

The apparatus of the present invention can be simply installed at the granulated powder outlet of the existing spray dryer, and can be easily constructed.

DESCRIPTION OF EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 shows a schematic diagram of the ceramic powder manufacturing apparatus of the present invention attached to a spray dryer. 1 is a spray dryer, 2 is a granulated powder, 3 is a hollow container that has penetrating holes 4 in the side wall and opens up and down, 5 is an ultrasonic atomizer,
6 is a humidifying part, 7 is a humidified granulated powder, and 8 is a storage container for the granulated powder.

Figure 2 shows the particle size distribution of granulated powder.
C is the particle size distribution of the granulated powder obtained in one example of the present invention.

First, add Bz203 and 0o2 to ZnO powder 2oOKf.
03°MnO□, 5b20. Additive 2o consisting of etc.
Kg, pure water and an organic binder were added, and mixed using a disper mill. Next, the slurry mixture is
Drying and granulation were performed using a spray dryer 1. Here, the hot air temperature of spray dryer 1 is 260℃~3
00°C, and the exhaust air temperature was 140-17Q°C. What is the moisture content of the granulated powder at this time? , 2%. This particle size distribution is shown in Figure 2. Next, this granulated powder was humidified using the moisture content adjusting device of the present invention shown in FIG. Granulated powder 2 is poured from a spray dryer 1 into a hollow container 3 that is open at the top and bottom. Then, insert the opening of the ultrasonic atomizer 5 for blowing out liquid particles into the through hole 4 on the wall of the hollow container 3, inject the atomized liquid particles into the hollow container 3, and apply the liquid particles to the surface of the granulated powder 2. A humidifying section 6 is created to which the water is deposited. Then, the humidified granulated powder 7 was put into the storage container 8. Processing amount is granulated powder 40 ~, atomization amount is 5 oocc
Met. What is the moisture content of the granulated powder thus obtained?

, 8%, and the particle size distribution is G in FIG. 2, which means that the particle size is slightly coarser than when no humidification is performed.

Further, granulation was performed in the same manner as above, and using a V-blader as a humidification method, 50cc of water was first added to the soK granulated powder and mixed for 3 hours. Then, to remove large lumps, I passed it through a 32# sieve. As a result, the moisture content of the obtained granulated powder was 0.8%, and the particle size distribution was as shown in B in FIG. 2, with the particle size moving toward the larger side.

These granulated powders were molded into a diameter of 4 ONJI and a length of 401 ff using a hydraulic molding machine at a pressure of 400 kg/i, and this was baked at 1200° C. for 5 hours. The shape of the sintered body thus obtained was 32N in diameter and 32mm in length.

Next, the sintered body (several pots of 60 samples) was examined using an X-ray fluoroscope.
The incidence of internal defects such as voids was investigated.

This X-ray fluoroscope has the ability to detect a diameter of 1 mm.

As shown in the table below, all the samples humidified by the method of the present invention had no internal defects.

On the other hand, 13 out of 50 cases of items that were not humidified in the conventional manner had internal defects, and 6 out of 50 cases of items that were humidified with a V-blender.
It can be seen that the sintered body obtained using the manufacturing method and manufacturing apparatus of the present invention is excellent with few internal defects.

Effects of the Invention As described in detail, the present invention is capable of uniformly increasing the water content by attaching liquid fine particles to the granulated powder of ceramics using an ultrasonic atomizer, and producing a powder free of internal defects. It is possible to provide a sintered body, which has great practical value in the production of ceramic electronic components in the future.

Although ZnO was used as an example, it goes without saying that the present invention is not affected by the type of raw material.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram of the ceramic powder manufacturing apparatus of the present invention attached to a spray dryer, and FIG. 2 is a diagram showing the particle size distribution of granulated powder. 1... Spray dryer, 2... Granulated powder, 3... Hollow container with penetrating holes and open top and bottom, 4... Hollow container a hole penetrating the side wall of the
5... Ultrasonic atomization device, 6... Humidifying section, 7... Humidified granulated powder, 8... Storage container for granulated powder. . Name of agent: Patent attorney Toshio Nakao and 1 other person No. 1
Figure 21! ! dryness (p town

Claims (2)

[Claims] (1) A method for producing ceramic powder, which comprises attaching liquid particles generated from an ultrasonic atomizer to ceramic powder. (2) Consisting of a vertically open hollow container that has a penetrating hole in the side wall and allows the ceramic granulated powder to pass through, and an ultrasonic atomizer that has a blowout port for liquid particles, and the blowout port is connected to the hollow container. A ceramic powder manufacturing device characterized by being inserted into a hole.