JPS61227813A - Production of plurally layered ceramic filter - Google Patents

Abstract

PURPOSE:To release a molded body from a gypsum mold without causing damage to the molded body and to obtain the titled filter by forming a mold release layer consisting of three layers, casting a ceramic slurry therein to form the molded body and calcining it after drying and mold release. CONSTITUTION:The fine grains of talc or sericite having about 1mum are used as the flaked mineral grains in the first layer of a casting surface of a gypsum mold. The ceramic fine grains such as TiO2, Al2O3, SiO2, SiC, ZrO2, Si3N4 and sialon are used in the second layer. A water-permeable organic film of sodium alginate and sodium stearate is used in the third layer. These are used in such a state that water is added thereto. The casting method is performed by allowing a ceramic slurry having the small average grain size to stand for the prescribed time, thereafter discharging the nonadhered slurry and forming the titled filter layer.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to an improvement in the method of manufacturing a multilayer ceramic filter by casting a ceramic powder slurry into a plaster mold.

C. Prior Art Conventionally, in the field of fermentation technology that uses yeast and enzymes, organic filters have been used to separate yeast and enzymes from products such as alcohol.

However, organic filters have problems in terms of heat resistance, chemical stability, and durability, and there is a strong desire to replace them with ceramic filters.

Ceramic filters used in this field require very small mesh sizes of several microns in order to separate yeast and enzymes. Moreover, the pore size is the largest so that yeast and enzymes cannot pass through.

That is, it is important how many microns the maximum permeation pore diameter is. In other words, the filter must not have even one pinhole or crack and the maximum permeation pore diameter must not be larger than a predetermined pore diameter.

Furthermore, although ceramic filters must be thicker than organic filters, they must be made as thin as possible in order to reduce the pressure loss associated with one sip. If it is made thinner, the strength will be weakened, so it is necessary to make a multi-layered filter that is an integral combination of one filter layer and a layer for reinforcing the filter layer, that is, a support layer.

One filter layer constituting the multilayer filter is thin, about 10-odd microns thick, and is made of ceramic particles of several microns in size, and the support layer is made of ceramic particles of several tens of microns in thickness. It is about 1 to several thick pieces thick. The support layer is thus much thicker than the single filter layer, but since it is made of large ceramic particles, the mesh size is large and does not reduce the filtering ability of the single filter layer. .

One of the conventional manufacturing methods for multi-layer ceramic filters as described above is to first knead ceramic powder of several tens of microns with water and other additives, then extrude the mixture, dry and fire it, and support it. A known method is to create a body layer and then apply a ceramic powder slurry of several microns to the vaginal support layer, or to soak the support layer in the slurry to adhere the ceramic powder slurry and then dry and fire it. It is being

Another method is that the applicant of the present invention has already filed an application (Japanese Patent Application No. 60
-15847) After casting the slurry into a plaster mold, the mold is removed, dried and fired. In this method, a ceramic slurry to form a filter layer is cast into a plaster mold, and after allowing it to stand for a certain period of time, the excess slurry that did not adhere to the plaster mold is discharged. Next, a ceramic slurry for forming a support layer is cast, the support layer is formed in the same manner as the filter layer, dried, removed from the plaster mold, and then fired.

[Problem that the invention seeks to solve]

However, in the former manufacturing method, the support layer is fired in advance,
Since one layer of the filter is applied or soaked in the support layer later, it is difficult to uniformly adhere the ceramic slurry to the support layer, which makes pinholes and cracks more likely to occur, and the maximum permeation pore diameter is vastly different. They tended to be large, making them unusable.

Furthermore, the latter method, in which ceramic slurry is cast into a mold, uses talc as a mold release agent to make it easier to release the molded body from the plaster mold.

When the mold is removed, a considerable amount of this talc adheres to the surface of the filter. This talc has a low melting point.

It needs to be removed before firing the molded product.

Since the molded body itself is very fragile at this point, it takes a lot of effort to remove the talc, and in the past, the filter has been further damaged, resulting in a high defect rate. In addition, since the thickness of the talc layer used as a mold release agent is thin, the unevenness of the plaster type is transferred directly to the filter layer, making the layer thickness inconsistent, resulting in pinholes and cracks, and the maximum permeation pore diameter does not reach the specified level. It had the disadvantage that it had a higher rate of becoming abnormally thick compared to the conventional method.

[Means for solving problems]

The inventors of the present invention have conducted various studies on a method of manufacturing a multilayer ceramic filter by casting ceramic slurry into a plaster mold.

It was discovered that the above-mentioned drawbacks could be solved by forming a release layer consisting of three layers using eight types of release agents instead of simply attaching one type of release agent as in the previous application.1 We have arrived at the present invention.

In other words, the gist of the present invention is to form a plaster-shaped structure with flat mineral fine particles in the first layer, ceramic fine particles in the second layer,
A water-permeable organic film is sequentially attached to the eighth layer to form a release layer, and then a slurry of particles with a smaller average particle size among the slurries of at least two types of ceramic particles with different average particle sizes is applied. , it is poured into the mold and left to stand, a part of it is attached to the inside of the mold via the mold release layer, the remaining slurry that is not attached is discharged, and the second part is made into particles with a large average particle size. A multi-layered ceramic characterized in that a molded body is made by casting the slurry into a pattern using a similar operation, and the molded body is dried, and after molding, the mold release agent adhering to the molded body is removed and then fired. This is a method for manufacturing filters.

The flat mineral fine particles used in the first layer of the casting surface of the plaster mold of the present invention are fine particles of about 1 μm of talc or sericite, or a mixture of both. The ceramic fine particles used in the second layer are TiO2, Al2O3, 8i0
+, 5iOy, ZrO2, Si3N4. It is one type or a mixture of two or more types of sialon. The water-permeable organic membrane used in the third layer is sodium alginate or stearate.

Each mold release agent used for forming the mold release layer is either made into a slurry by adding water or made into an aqueous solution. The slurry used to form the first layer is 5,000 parts by weight of water and 100 parts by weight of release agent.
o, 000 parts by weight, preferably 10,000 to 100,
000 parts by weight. If the water content is less than 5.000 parts by weight, it will be too thick and the thickness of the first layer will not be constant;
If it exceeds 0 parts by weight, the layer thickness will be so thin that it will be difficult to release it from the plaster mold. In addition to water, a dispersant may be added to the slurry used to form the second layer in order to improve the dispersion of the release agent. As the dispersing agent, conventional ones such as hydrochloric acid and sodium pyrophosphate may be used. The slurry contains 80 to 500 parts by weight of water, preferably 30 to 100 parts by weight of release agent.
Mix parts by weight. If the amount of water is less than 30 parts by weight, the fluidity of the slurry will be poor and the thickness of one layer will be constant. The dispersant is preferably hydrochloric acid, and the pH of the slurry after addition may be about 8.Third.
The concentration of the aqueous solution of the mold release agent used to form the layer is 1.0% by weight or less, preferably 0.1 to 0.5% by weight. When the concentration exceeds 1.0% by weight, the viscosity of the solution becomes too high, causing sag in the film and making the film thickness non-uniform.

Next, the manufacturing method of the present invention will be explained using a pipe-shaped ceramic filter as an example. However, the present invention is not limited to pipe-shaped filters, but can also be applied to plate-shaped filters.

A regular plaster mold used as a casting mold is provided with the required holes, for example, 12 mm, and the mold is dried at 45° C. until it reaches a constant weight. Next, in order to adjust the moisture content of the dried plaster mold and at the same time form a release layer, water is first added to talc or sericite or a mixture thereof to form a slurry, and this slurry is then applied to the dried plaster mold. Weigh out 10% of the weight and apply the entire amount to the inner surface of the hole or pour it into the hole to absorb water and adhere to it (
(approximately IOμm). This forms the first layer.

Next, a slurry containing fine ceramic particles is cast into the hole, and after allowing it to stand for a period of time necessary to obtain a predetermined thickness, the slurry that has not adhered is discharged to form a second layer.

followed by sodium alginate or stearic acid)
An aqueous solution of IJum was poured into the hole and allowed to stand for a certain period of time to form an adhesion of about 10 μm, after which the excess aqueous solution was drained and the third
Form a layer.

The thickness of the release layer formed by the above operation is several tens to several thousand micrometers, and particularly the thickness of the second layer is 80 micrometers or more, preferably 500 to 700 micrometers.

After forming a release layer on the inner surface of the hole of the plaster mold, a slurry of ceramic particles having a finer average particle size is cast into the hole through the release layer and left to stand for a predetermined period of time to form the slurry. After adhering approximately 15 μm of slurry, the unadhered slurry is discharged to form a single filter layer. A slurry of ceramic particles with a coarser average particle size is then cast into the holes,
A molded body is obtained by performing the same operation as for one layer of the filter to form a support layer having a thickness of about 1 to 2 lines.

Note that the above description has been made regarding the case of two layers consisting of one filter layer and one support layer.

If the single filter layer itself is to be multilayered, or if the support layer is to be multilayered, or if both are to be multilayered, the above-mentioned operations may be repeated.

Next, the plaster mold that is integrated with the molded body is dried.

Due to drying, the plaster mold and the molded body are separated from the first layer of the mold release layer, so that the molded body is pulled out from the hole of the plaster mold. After the molded body that was extracted was sufficiently dried at approximately 100°C.

The release layer is removed and fired in a heating furnace such as an electric furnace.

The firing conditions vary depending on the type of ceramic particles used in the compact, but in the case of alumina, the firing conditions are approximately 1,50%.
It takes about 2 hours at 0°C.

By firing, the filter layer and the support layer are integrally sintered, and a multilayer ceramic filter is obtained.

[For production]

In the method of the present invention, the respective roles and functions of the first layer, second layer and third layer formed as a mold release layer are as follows.

The first layer is talc and/or cerizite fine particles, and is used to improve the separation between the plaster mold and the molded body, as in the conventional method.

The second layer is a relatively thick layer of ceramic particles that serves two purposes.

One is that when only the first layer is used as a mold release layer, the thickness of the mold release layer is thin, so the plaster-like unevenness is directly transferred to the molded product, and the thickness of one filter layer becomes 4 uniform. . However, the second layer is a relatively thick layer, and since the plaster-like unevenness can be absorbed by the second layer, the thickness of the filter layer does not become non-uniform.

Part 2 is that when the slurry to form one layer of the filter is cast into a plaster mold, if there is no second layer, the plaster mold will absorb water so intensely that the slurry will absorb water and stick to the mold in a very short time. Therefore, it is difficult to form a uniform thin filter layer. However, unlike plaster, the second layer has a small water-absorbing power, so it is possible to prevent the single-layer slurry from adhering to the cast filter from occurring suddenly. Therefore, it is easy to control the adhesion thickness of one layer of the filter.
Moreover, the thickness can be made uniform.

Since the eighth layer is a water-permeable organic film, it prevents the ceramic fine particles used in the second layer from adhering to the filter layer.

〔Example〕

Examples 1 to 4 A cylinder with a diameter of 1 in the center of a cylinder with an outer diameter of 5.5 ffi and a height of 50 m.
．． Forty plaster molds with holes of 2 crfL were prepared and dried at 45° C. for 3 days.

As mold release agents for forming the mold release layer, talc (average particle size 1 μm, manufactured by Nippon Talc Co., Ltd.) and sericite (average particle size 3 μm, manufactured by Sanshin Koko Co., Ltd.) were prepared for the first layer.

As the second layer, α-AI203 (average particle size 1 μm, manufactured by Showa Light Metal Co., Ltd.), Zr(h (average particle size 1 μm, manufactured by Shin Nippon Metal Chemical Co., Ltd.) and SiC (average particle size 1 μm, manufactured by Fujimi Abrasive Industries Co., Ltd.), R) was prepared.

For the 8th layer, sodium alkinate of first grade reagent and sodium stearate of first grade reagent were prepared.

These mold release agents were mixed with water in the proportions shown in Table 1 to form a slurry or an aqueous solution.

Note that the slurry for the second layer was adjusted to pH 8 by adding hydrochloric acid.

Next, the bottom of the hole in the plaster mold was plugged with a rubber stopper, and the slurry for the first layer was measured in IO% of the weight of the dry plaster mold and poured into the hole, and the entire amount was allowed to absorb water and adhere to the meat. Thereafter, the slurry for the second layer was injected and left to stand for 5 minutes, and then the rubber stopper was removed and the slurry that did not adhere to the plaster mold was discharged. After putting a rubber stopper at the bottom of the plaster-shaped hole again, the aqueous solution for the 8th layer was injected.

After standing for 2 minutes, the rubber stopper was removed and excess aqueous solution was drained.

Table 1 Table 2 shows the combinations of mold release agents used above.

Table 2 Into the plaster mold thus produced with a release layer formed, a filter monolayer phase and a slurry for a support layer were cast for the purpose of manufacturing a ceramic filter pipe having a pore size of 1-211 m. .

α-A with an average particle size of 1 μm as a filter single layer phase, 120
3 (manufactured by Showa Light Metal Co., Ltd.) and 5i (h
(manufactured by Shin Nippon Metal Chemical Co., Ltd.) 5i02/α-Al2O2=
O, 1, 2 (weight ratio), mix 1
00 parts by weight and 60 parts by weight of water were mixed and purified with 3N hydrochloric acid.
The mixture was mixed for 100 minutes while adjusting the temperature to H8.

α-AI203 (with an average particle size of 20 μm) was used for the support layer.
(manufactured by Naigai Fireproof Industry) and 5i02 (manufactured by Naigai Fireproof Industry Co., Ltd.) and 5i02 (manufactured by Naigai Fireproof Industry Co., Ltd.) and 5i02 (manufactured by
(Manufactured by Shin Nippon Metal Chemical Industry Co., Ltd.) 5iOv/a-AI203
= o, 15 (weight ratio), 100 parts by weight of the mixture was mixed with 55 parts by weight of water, and the mixture was left for 10 days while adjusting the pH to 8 with 3N hydrochloric acid.

The bottom of the plaster-shaped hole forming the release layer was plugged with a comb plug, and the slurry for a single layer of filter was cast. Thereafter, the mold was allowed to stand for 1 minute, and the slurry that did not adhere to the plaster mold was discharged. After the gypsum mold was left to stand for about 3 minutes, the bottom of the hole was again plugged with a comb plug and the slurry for the support layer was cast. After standing for 20 minutes, the slurry that did not adhere to the gypsum mold was discharged from the bottom of the hole.

After casting, the plaster mold was left as it was for about 30 minutes, and then dried at 45° C. for 72 hours.

As a result of drying, a gap was formed between the first layer of the mold release layer and the inner surface of the plaster mold, and the molded product could be easily removed from the plaster mold.

The molded body was further dried at 100°C for 2 hours.

Peel off the mold release layer adhering to the surface of the molded product and heat at 1500°C.
It was baked for 2 hours. These operations were repeated 10 times to obtain 10 multilayer ceramic filter pipes each.

In order to confirm the quality of each ceramic filter pipe obtained, the maximum permeation pore diameter was measured using the pneumatic method.
The results are also listed in Table 2.

Here we will explain how to determine the maximum permeation pore diameter using the pneumatic method.

After sealing the bottom of the ceramic filter pipe with a comb stopper, submerge the entire pipe in water and connect the rubber port connected to the vacuum pump to the open side of the pipe. Run the vacuum pump to fill the pipe with water.

Then air is pumped into the pipe in reverse. As the pressure of the air being fed is gradually increased, bubbles will eventually form on the surface of the pipe. The maximum permeation pore diameter is calculated from the air pressure at that point using the following formula.

D: Maximum permeation pore diameter (μm) p: Air pressure when bubbles are generated (mmHz) h Distance between the position where bubbles are generated and the water surface (mm) σ: Surface tension of water (
dyne/cwL) ρ: Water density comparative example A gypsum mold of the same size and with the same holes as in the example was prepared.

Add mold release agent and only talc in the same manner as in the example.
was applied to the inner surface of the hole. Thereafter, a single filter layer and a support layer were formed using the same materials and methods as in the example, and the drying and demolding operations were repeated 10 times to obtain 34,710 ceramic filters.

Since talc powder was attached to the surface of the pipe, it was carefully removed using a brush.

After firing the pipe at 1500° C. for 2 hours, the maximum permeation pore diameter was measured in the same manner as in the example. The results are also listed in Table 2.

The maximum permeation hole diameter of each of the 10 pipes in the example was 1. Z
While it is well controlled at ~1.5 μm,
Five of the pipes in the comparative example had pinholes, cracks, or damage, so the maximum permeation pore diameter was abnormally large.

〔Effect of the invention〕

In the present invention, in manufacturing a composite non-ceramic filter that applies separation p, the first layer is formed on a plaster type.

By forming a release layer consisting of three layers, the second layer and the eighth layer, a desired maximum permeation pore diameter can be obtained. In other words, in the past, even if a filter single-layer phase and a support layer ceramic fine powder material were prepared to obtain the desired maximum permeation pore size, there was no suitable mold release agent, and plaster-type irregularities were transferred. However, the present invention has been able to eliminate all of these problems.

Claims (4)

[Claims] (1) Form a release layer by sequentially attaching flat mineral fine particles to the first layer, ceramic fine particles to the second layer, and water-permeable organic film to the third layer to a gypsum mold. Then, among the slurry of at least two types of ceramic particles having different average particle diameters, the slurry of particles with a smaller average particle diameter is cast into the mold, left to stand, and a part of the slurry is applied to the mold release layer. The remaining slurry that has not adhered is discharged, and then the slurry with particles having a large average particle size is cast into the mold in the same manner to produce a molded body, A method for manufacturing a multilayer ceramic filter, which comprises drying and demolding, removing the mold release agent attached to the molded body, and then firing it. (2) The manufacturing method according to claim (1), wherein the flat mineral fine particles are fine particles of talc and/or sericite. (3) The ceramic fine particles used in the second layer are TiO_2,
Al_2O_3, SiO_2, SiC, ZrO_2, S
The manufacturing method according to claim (1), which is one or more of i_3N_4 and Sialon. (4) The manufacturing method according to claim (1), wherein the water-permeable organic membrane is formed from an aqueous solution of sodium alginate or sodium stearate.