JPH0733548A - Production of ceramic filter - Google Patents

Abstract

PURPOSE:To obtain a ceramic filter having large strength and excellent in filtering ability by drying a slurry obtained by subjecting ceramic powder to wet mixing with a dispersing medium, a dispersant, a primary binder and carbon to form granules, subjecting the granules to pressure forming and baking the formed body. CONSTITUTION:A dispersing medium, a dispersant and a primary binder are added to ceramic powder and these components are subjected to wet mixing by a ball mill. Then, carbon is added to this mixture and these components are subjected to wet mixing under reducing ball amount in the ball mill to form slurry. Then, the slurry is spray-dried to form granules and the granules are subjected to pressure-forming into desired shape and the formed product is baked at 1200-1350 deg.C under blowing air.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a ceramic filter suitable for liquid filtration, gas rectification and the like.

[0002]

2. Description of the Related Art Ceramic filters are widely used for liquid filtration and gas rectification. Examples of the ceramic material for producing the ceramic filter include silica, alumina, aluminosilicate, magnesia, zirconia, and a ceramic mixture thereof. For example, taking alumina as an example, use a granule that has been added with a dispersant and a binder and molded into granules. 1-2 t / cm lower than the ² 200 to 400
It is possible to fabricate a ceramic filter by lightly molding it at kg / cm ² and then firing it at a firing temperature of 1000 to 1250 ° C., which is lower than the firing temperature of 1500 to 1620 ° C. of a normal product. However, since the alumina filter thus obtained has a low molding pressure and low temperature firing, it is 1 kg / cm in the filtration capacity measuring device shown in FIG.
⁽²⁾ The filtration rate of the pressurized water is about 0.01 L / min, and the filtration capacity is low, and the higher the pressure is from ² to 4 kg / cm ² , the more it breaks, and the mechanical strength is weak.

[0003]

DISCLOSURE OF INVENTION Problems to be Solved by the Invention The inventors have examined the requirements for obtaining a ceramic filter having a high strength and an excellent filtering ability. The present inventors have come to the conclusion that they need to be uniformly distributed in the substrate and have been heat-tightened, and have conducted various test studies to complete the present invention.

[0004]

According to the present invention, a dispersion medium, a dispersant and a binder are added to ceramic powder and wet mixed by a ball mill, and then carbon is further added to the mixture to adjust the amount of balls in the ball mill. Reduced to wet mix to form a slurry, the slurry is spray-dried into granules, and the granules are pressure-molded into a desired shape, and the molded product is air-conditioned at a temperature of 1,200-1,350 ° C. A method for producing a ceramic filter is provided, which comprises firing while blowing. Next, the method of the present invention will be described step by step using alumina as an example. A necessary amount of water, a dispersant, and a binder are added to alumina as a dispersion medium, and the mixture is wet-mixed by, for example, a ball mill charged with zirconia balls. As the dispersant, for example, a polyacrylic acid type is used, and as the binder, those commonly used for ceramic materials such as polyvinyl alcohol and carboxymethyl cellulose are used. To the above mixture, a predetermined amount of carbon adjusted to a single particle having a predetermined single particle diameter is added in order to burn out and leave uniform passage holes during firing. The particle size of carbon is preferably in the range of 3 to 100 μm, and is selected in the above range depending on the filtering ability. 15-40% of the dry standard mixture is suitable for the compounding amount, and 15%
If it is less than 4, the porosity is insufficient and the filter performance is reduced, which is 4
If it exceeds 0%, the filter cannot retain sufficient strength. The above mixture is subjected to ball mill mixing by reducing the amount of balls in the mill and shortening the operation time so as not to destroy carbon having a single particle size as much as possible. The homogeneously mixed slurry obtained as described above is spray-dried with a spray dryer to form granules. The particle size of the granules is preferably about 70 μm from the viewpoint of spray dryer operation. Using the above granules, a green mold is formed by molding by means such as a press or CIP. Molding pressure is 300 kg / cm ² ~
It is performed in the range of 2 ton / cm ² . After the green mold is dried, it is baked while blowing in air. The firing temperature is in the range of 1200 to 1350 ° C., and at 1200 ° C. or lower, the tightening is insufficient and the strength is low, and at a temperature of 1350 ° C. or higher, the shrinkage of the substrate becomes severe and the filtration ability is lowered. When the filter has a cylindrical shape, primary processing may be performed, calcination may be performed, and then main firing may be performed.

[0005]

In a usual slurry preparation method, a ceramic raw material granule and carbon are mixed with a dispersant and a binder and wet mixed. In this method, however, the ceramic raw material granule is not slipped by the carbon and is not crushed. In addition, carbon irregularly remains and becomes firing holes, and the ventilation holes after firing are irregularly distributed due to aggregation of carbon. In the method of the present invention, since the ceramic raw material granules are in a state of excluding carbon, they are crushed at the same time as mixing by a ball mill,
A homogeneous slurry results. Carbon is further added to this slurry to reduce the amount of balls, and the operation time of the ball mill is shortened so that carbon is not subjected to pulverization as much as possible and dispersion is mainly performed. Therefore, carbon maintains a distribution state in which the particle size distribution consists of single particles with few fine particles,
And it is uniformly dispersed in the mixed slurry. By spray-drying this homogeneous slurry, homogeneous granules of uniformly dispersed single carbon particles having uniform particle diameters can be obtained. The one molded and fired by using this is a ceramic filter having uniform through-hole diameters and uniformly dispersed.

[0006]

EXAMPLES The present invention will be specifically described below with reference to examples and comparative examples. Example 1 Alumina granules (Al ₂ O ₃ 92%, balance CaO, MgO,
SiO2, dispersant and binder treated product, trade name CH-92A, Marusu Glaze Co., Ltd.) 2,125 g, water 2.1
L, polyacrylic acid-based deoxidizer (trade name: Kaya Disper,
8L of 20g of Nippon Kayaku Co., Ltd. and 40g of acrylic binder (Brand Serum, trade name, manufactured by Mitsui Toatsu Chemicals, Inc.)
Put in a pot mill, add 6 kg of zirconia balls, and
Grind and mix at 0 rpm for 12 hours, then reduce balls to 350 g, add 375 g of artificial graphite fine powder (trade name: UFG10-10 μm, Showa Denko KK) as carbon, mix at 40 rpm for 30 minutes, and mix at 15%. An alumina slurry containing carbon was made. The above slurry is dried with a spray dryer at a drying tower inlet temperature of about 250 ° C and an outlet temperature of about 1
00 ° C, exhaust air volume 50m ³ / min, atomizer 7500r
Granules containing 15% carbon were produced under the conditions of pm and a charging amount of 3 L / hour. The average particle size of the granules was about 70 μm.
Using the above granules, a rubber mold with a core is used to make a cylindrical green mold by 2 ton / cm ² CIP, and primary processing is performed to burn the outer diameter 65 mm,
A cylindrical filter with an inner diameter of 50 mm and a length of 250 mm,
The temperature was raised to 1,250 ° C. over 24 hours in an electric furnace, and the mixture was held and fired at 1,250 ° C. for 2 hours while blowing air to obtain a ceramic filter. As shown in FIG. 1, the filtration capacity measuring device 1
Attach the ceramic filter 2 to the bottom of the, fill the stainless steel cylinder 3 with tap water, pressurize with the air hose 4,
The filtration capacity was represented by the filtrate flow rate L / min. The filtration flow rate is 0.14 L / under a pressure of 1.0 kg / cm ²
It was good with minutes. It should be noted that even if a pressure of 6.5 kg / cm ² was applied, no breakage occurred, and there was sufficient strength.

Example 2 The same procedure as in Example 1 was carried out except that 2,100 g of alumina granules and 2.5 L of water were used.
A cylindrical filter having a diameter of 50 mm, an inner diameter of 50 mm and a length of 250 mm was obtained. This is 1,30 in an electric furnace for 24 hours
The temperature was raised to 0 ° C., and the mixture was held and fired at 1,300 ° C. for 2 hours while blowing air to obtain a ceramic filter. This is attached to the lower surface of the filtration capacity measuring device shown in FIG.
Was filled with tap water and pressurized by the air hose 4, and the filtration capacity was expressed by the filtrate flow rate L / min. Pressurized pressure 1.0kg / c
It was as good as 0.5 L / min under m ² . Also,
Even at a pressure of 6.5 kg / cm ² , it did not break and showed excellent strength. It was also found that uniform pores were formed by observation with an electron microscope at 200 times and 2000 times.

Comparative Example A kneaded material was prepared by wet-mixing the same aluminum granules used in Example 1 with the same carbon mixture as in Example 1 from the beginning to prepare a kneaded material.
CIP molding is performed at g / cm ² , and a cylindrical green mold having an outer diameter of 65 mm, an inner diameter of 50 mm, and a length of 250 mm after firing is made by primary processing, and this is heated to 850 ° C. over 10 hours, and at the same temperature for 2 hours. It was calcined for holding and fired at 1,000 ° C. for 1 hour to prepare a ceramic filter. According to the measurement of 1 kg / cm ² pressure applied by the filtration capacity measuring device shown in FIG. 1, the flow rate was 0.01 L / min, which was extremely low, and the strength was broken at 6.5 kg / cm ² pressure, which was not sufficient. It was

[0009]

According to the method of the present invention, it is possible to obtain a ceramic filter having uniform pores and having excellent filtering ability and strength, and it is very useful for filtering a liquid, rectifying a gas and the like.

[Brief description of drawings]

FIG. 1 is an explanatory diagram showing a configuration of a filtration capacity measuring device for a ceramic filter.

[Explanation of symbols]

 1 Filtering capacity measuring device 2 Ceramic filter 3 Stainless steel cylinder 4 Air hose

Claims (1)

[Claims] 1. A dispersion medium, a dispersant and a primary binder are added to ceramic powder and wet mixed by a ball mill,
Next, carbon is further added to the mixture, the amount of balls in the ball mill is reduced, and the mixture is wet-mixed to form a slurry. The slurry is spray-dried into granules, and the granules are pressure-molded into a desired shape. Molded products from 1,200
A method for producing a ceramic filter, which comprises firing while blowing air at a temperature of 1,350 ° C.