JPH068199B2 - Method and apparatus for manufacturing ceramic powder - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and an apparatus for manufacturing a ceramic powder used for manufacturing a ceramic part.

Structure of conventional example and its problems Normally, the manufacturing process of ceramic electronic parts is a compounding process in which the main raw material and a small amount of additive raw material are weighed in the optimum composition distribution, and the main raw material and the additive raw material are simultaneously pulverized into fine powder. There is a crushing and mixing step for mixing well. Usually, the crushing and mixing step is performed by using a pot, adding the raw material, water, an organic binder and cobblestone, and rotating the pot. Next, the raw material that has finished the crushing and mixing step is in a slurry state,
There is a granulation step in which this is dried using a spray dryer and at the same time, a spherical granulated powder suitable for molding is formed. next,
Filling the mold with the granulated powder, applying a pressure to form a desired shape, and firing the molded product to cause a chemical reaction at the same time to cause a chemical reaction to obtain a sintered product having desired electrical performance, Further, there is a step of attaching electrodes for drawing out electrical performance.

As described above, the manufacturing process of the ceramic electronic component roughly includes a mixing process, a pulverizing and mixing process, a granulating process, a molding process, a firing process, and an electrode attaching process. Of these processes, the most important step to achieve the desired electrical performance is the compounding process and firing process, but the desired shape is created and the structure is strong, which improves quality and ensures long-term reliability. The important steps in this process are the granulation and molding steps. And
The property of the granulated powder has a great influence on the moldability, and especially when the water content of the granulated powder is not appropriate, the shrinkage rate of the sintered product obtained by firing the molded product varies, and the molded product during molding Internal defects such as voids are generated inside the sintered product due to the pressure distribution and the like generated inside. This has had a major adverse effect on the quality and long-term reliability of ceramic electronic components. As mentioned above, a spray dryer is usually used in the granulation step. This is because a slurry-like mixture is sprayed into hot air through a nozzle and blown up, and the atomized mixture is dried and spherically granulated in the process of ascending and descending. However, the spray dryer is originally used for producing the final product of the granulated powder itself such as detergent and seasoning, and the water content of the granulated powder is usually 0.1% or less. . However, when making a ceramic electronic component, the granulated powder is filled in a mold, pressure is applied to form a molded product, and then a molded product is created, which is then fired in a firing process to cause a chemical reaction at the same time to achieve desired electrical performance. Finish the sintered product. In this case, the molded product has an appropriate strength, and unless the pressure distribution inside the molded product is made small, variations in shrinkage in the firing process and internal defects such as voids occur inside the sintered product. The particle size distribution and the water content of the granulated powder play important roles in producing such an excellent molded product, but the water content is particularly important. This is because the water content in the granulated powder is considered to fulfill the function of transmitting the pressure applied during molding to the center of the molded product. For this reason, when the water content is low, the pressure does not reach the center of the molded product and concentrates only on the surface of the molded product, resulting in a large pressure distribution, which causes a difference in shrinkage ratio between each part of the molded product during firing. Which causes internal defects such as voids. On the other hand, when the water content is high, there is a problem that water oozes out from the molded product during molding, and a drying step of the molded product is required after molding, leading to a problem of a long lead time. From this, the optimum water content of the granulated powder is 0.5 to 1.0%.

As described above, the granulated powder using the spray dryer has a water content of about 0.1%, which is 0.5 to 1.0%.
Water must be added to adjust the water content. Conventionally, in order to adjust the water content, the V blender is used to add an appropriate amount of water to the granulated powder, and the V blender is rotated to adjust the water content of the granulated powder. However, with this method, the mixing of water in the granulated powder is inevitably non-uniform, and a part with a large amount of water (agglomerated) and a part with a small amount of water are formed in the granulated powder. In the above, it is necessary to make the particle size distribution uniform by sieving again, and in the case of mass production, the lead time becomes long, which is a major factor in cost increase.

SUMMARY OF THE INVENTION In view of the above drawbacks, an object of the present invention is to provide a method of manufacturing a ceramic powder and a method for manufacturing the ceramic powder that facilitates the adjustment of the water content of the granulated powder of the ceramic powder.

To achieve this object, in the method for producing a ceramic powder granule of the present invention, liquid fine particles generated from an ultrasonic atomizer are attached to ceramic granulated powder granulated by a spray dryer. The water content is adjusted by means of this, and as its manufacturing device, it consists of a hollow container that has a through hole in the side wall and is opened up and down, and a supersonic atomization device that has an outlet for liquid particles. The device has a structure in which is inserted into the hole of the hollow container.

First, the granulated powder granulated by the spray dryer passes through the hollow container, at which time liquid fine particles are blown out from the side wall surface of the hollow container, and the liquid fine particles adhere to the surface of the granulated powder during passage. Usually, the granulated powder granulated with a spray dryer has an average particle size of 100 to 150 μm, while the liquid microparticles generated by the ultrasonic atomizer have an average particle size of 5 to 10 μm.
Since it is m, it is not evenly adhered to the granulated powder and a clay-like lump having a high water content can be formed unlike the humidification method using the V blender described above. Therefore, there is no need for sieving, and there is no fear of increasing the lead time. The apparatus of the present invention is simply installed at the granulated powder outlet of the current spray dryer, and can be simply 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 case where the apparatus for producing ceramic powder particles of the present invention is attached to a spray dryer. 1 is a spray dryer, 2 is a granulated powder, 3 is a hollow container which has a hole 4 penetrating therethrough on the side wall and is opened vertically, 5 is an ultrasonic atomizer, 6
Is a humidifying part, 7 is a humidified granulated powder, and 8 is a container for the granulated powder.

Fig. 2 shows the particle size distribution of granulated powder, where A is not humidified and B is
Is humidified using a V blender, and C is the particle size distribution of the granulated powder obtained in one example of the present invention.

First, 200 kg of ZnO powder was mixed with Bi ₂ O ₃ , Co ₂ O ₃ , MnO ₂ , and Sb ₂ O _3.
Approximately 20 kg of an additive such as the above was added, pure water and an organic binder were added, and mixed using a Dispermill. Next, the slurry-like mixture was dried and granulated using the spray dryer 1. Here, the hot air temperature of the spray dryer 1 is 250 ° C. to 300 ° C., and the exhaust air temperature is 140 to 17
It was 0 ° C. The water content of the granulated powder at this time was 0.2%. This particle size distribution is shown in A of FIG. Next, this granulated powder was humidified by the water content adjusting device of the present invention shown in FIG. That is, the granulated powder 2 is poured from the spray dryer 1 into the hollow container 3 opened up and down. Then, an opening for ejecting the liquid fine particles of the ultrasonic atomizing device 5 is inserted into the through hole 4 on the wall surface of the hollow container 3, the atomized liquid fine particles are injected into the hollow container 3, and the liquid fine particles are formed on the surface of the granulated powder 2. The humidifying part 6 to which is attached is created. And the humidified granulated powder 7
Was placed in the storage container 8. Treated amount is 40kg of granulated powder,
The atomization amount was 500 cc. The water content of the granulated powder thus obtained is 0.8%, and the particle size distribution is C in FIG. 2, and the particle size is slightly coarser than that in the case where it is not humidified.

Further, granulation is performed in the same manner as above, and a V blender is used as a humidifying method.
00 cc of water was added and mixed for 3 hours. Then, through a 32 ^# sieve to remove the big chunks. as a result,
The water content of the obtained granulated powder was 0.8%, the particle size distribution was as shown in FIG. 2B, and the particle size moved to the larger side.

Using a hydraulic molding machine, these granulated powders were molded at a pressure of 400 kg / cm ^{2 into} a diameter of 40 mm and a length of 40 mm.
It was baked at 0 ° C. for 5 hours. The shape of the sintered body thus obtained is 32 mm in diameter and 32 mm in length.

Next, using an X-ray fluoroscope, a sintered body (50 samples each)
The occurrence rate of internal defects such as voids was investigated. This fluoroscope has a detection capability of 1 mm in diameter. As a result, as shown in the table below, the products humidified by the method of the present invention did not generate all internal defects. On the other hand, in the non-humidified ones as in the conventional case, 13 out of 50 had internal defects, and in the one moistened by the V blender, 6 in 50, the manufacturing method and the manufacturing apparatus of the present invention. It can be seen that the sintered body obtained by using is excellent with few internal defects.

Effects of the Invention As described above in detail, according to the present invention, the water content can be easily and evenly made by adhering the liquid fine particles by the ultrasonic atomizer to the ceramic granulated powder granulated by the spray dryer. Therefore, a sintered body having no internal defect can be provided as a result, and its value will be great in the future production of ceramic electronic components.

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 description of drawings]

FIG. 1 is a schematic view of the case where the apparatus for producing ceramic powder particles of the present invention is attached to a spray dryer, and FIG. 2 is a view showing the particle size distribution of granulated powder. 1 ... spray dryer, 2 ... granulated powder, 3 ... hollow container having a through hole opened up and down, 4 ... hole penetrating the side wall of the hollow container, 5 ... ultrasonic atomizer, 6 ... Humidifying part, 7 ... Humidified granulated powder, 8 ... Storage container for granulated powder.

Claims (2)

[Claims] 1. A method for producing a ceramic powder or granular material, characterized in that liquid fine particles generated from an ultrasonic atomizer are adhered to ceramic granulated powder granulated by a spray dryer. 2. An ultrasonic atomizer having a hollow container having a penetrating hole in the side wall thereof, the hollow container opening and closing through which a ceramic granulated powder granulated by a spray dryer passes, and an outlet for ejecting liquid fine particles. The manufacturing apparatus of ceramic powdery particles, wherein the blowout port is inserted into the hole of the hollow container.