JPH0523807B2 - - Google Patents

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 ceramic powder slurry into a plaster mold. [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 maximum pore diameter, that is, the maximum permeable pore diameter, is important in microns so that yeast and enzymes do not pass through. 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. Ceramic filters must be thicker than organic filters, but they must be made as thin as possible to reduce pressure loss due to filtration. If it is made thin, the strength will be weakened, so it is necessary to make a multi-layered filter by integrally combining a filter layer and a layer for reinforcing the filter layer, that is, a support layer. The filter layer constituting the multilayer filter is thin, about 10 microns thick, made of ceramic particles of several microns, and the support layer is made of ceramic particles of several tens of microns, about 1 to several mm thick.
belongs to. The support layer is thus much thicker than the filter layer, but since it is made of ceramic particles with a large particle size, the mesh size is large and does not reduce the filtration ability of the filter layer. . One of the conventional manufacturing methods for multi-layered 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 bake it, and then support it. A known method is to form a body layer, then apply a ceramic powder slurry of several microns to the support layer, or dip the support layer in the slurry to adhere the ceramic powder slurry, and then dry and fire it. It is being Another method, as already filed by the applicant of the present invention (Japanese Patent Application No. 60-15347), is to cast the slurry into a plaster mold, then remove it from the mold and dry and fire it.
In this method, 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 has not adhered 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. [Problems to be solved by the invention] However, in the former manufacturing method, the support layer is fired in advance, and the filter layer is applied or soaked on the support layer afterwards, so the ceramic slurry is not applied to the support layer. It was difficult to uniformly adhere the material, and as a result, pinholes and cracks were likely to occur, and the maximum permeation pore diameter was often an order of magnitude larger, making it unusable. In addition, in the method after ceramic slurry is cast into a plaster mold, talc is used as a mold release agent to make it easier to release the molded body from the plaster mold, but when the mold is removed, this talc corresponds to the surface of the filter layer. Amount adheres. Since this talc has a low melting point, it needs to be removed before firing the molded product, but the molded product itself is extremely fragile at this point, so removing the talc requires a lot of effort and This has the disadvantage that it damages the filter layer and increases the defective rate. In addition, since the thickness of the talc layer used as a mold release agent is thin, the unevenness of the plaster mold is transferred directly to the filter layer, making the layer thickness inconsistent, resulting in pinholes and cracks, and the maximum permeable pore diameter does not reach the specified level. The disadvantage was that the probability of the product becoming abnormally large compared to the original size was also high. [Means for Solving the Problems] The present inventors have conducted various studies on the method of manufacturing a multi-layer ceramic filter by casting ceramic slurry into a plaster mold, and as a result, the inventors have developed a simple method as in the previous application. We have discovered that the above drawbacks can be solved by forming a release layer consisting of three layers using three types of release agents instead of attaching different types of release agents, and have arrived at the present invention. That is, the gist of the present invention is to sequentially attach 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 plaster mold, and then release the mold. A layer is formed, and 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 separated. The slurry is adhered to the inside of the mold through the mold layer, the remaining unattached slurry is discharged, and the slurry with particles having a large average particle size is then cast into the mold in the same manner to form a molded body. This is a method for producing a multilayer ceramic filter, which is characterized in that the molded product is prepared, dried, removed from the mold, the mold release agent adhering to the molded product is removed, and then fired. 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
It is one or a mixture of two or more of TiO ₂ , Al ₂ O ₃ , SiO ₂ , SiC ₂ , ZrO ₂ , Si ₃ N ₄ , and Sialon. The water-permeable organic membrane used for the third layer is sodium alginate or sodium 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 to 200,000 parts by weight of water, preferably 10,000 to 100,000 parts by weight of water per 100 parts by weight of the release agent.
It is 100000 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 the amount exceeds 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 layer. As the dispersant, conventional ones such as hydrochloric acid and sodium pyrophosphate may be used. The slurry is 30 to 500 parts water per 100 parts by weight of mold release agent.
Parts by weight, preferably 30 to 100 parts by weight, are mixed. If the amount of water is less than 30 parts by weight, the fluidity of the slurry will be poor;
It is difficult to keep the layer thickness constant, and if it exceeds 500 parts by weight, the concentration is too thin and it takes too much time to form the second layer, which is not practical. The dispersant is preferably hydrochloric acid, and the pH of the slurry after addition may be about 3. The concentration of the release layer aqueous solution used to form the third layer is 1.0% by weight or less, preferably 0.1 to 0.5% by weight.
It is. 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 a required hole, for example, a hole of 12 mm in diameter, 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 10 μm). This forms the first layer. Next, a slurry containing fine ceramic particles is cast into the hole and allowed to stand for a period of time necessary to obtain a predetermined thickness, and then the non-adhering slurry is discharged to form a second layer. Subsequently, an aqueous solution of sodium alginate or sodium stearate is poured into the holes and allowed to stand for a certain period of time to form an adhesion of about 10 μm, after which the excess aqueous solution is drained to form a third layer. The thickness of the release layer formed by the above operation is several times
The thickness of the second layer is 10 to several thousand μm.
It is 30 μm or more, preferably 500 to 700 μm. After forming a mold 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 mold release layer, and
After leaving it to stand for a predetermined period of time so that about 15 μm of slurry adheres, the unattached slurry is discharged to form a filter layer. Subsequently, a slurry of ceramic particles having a coarser average particle size is cast into the holes, and the same operation as for the filter layer is performed to form a support layer with a thickness of about 1 to 2 mm, thereby obtaining a molded body. In addition, the case where the filter layer is one layer and the support layer is two layers has been described above, but when the filter layer itself is multilayered, the support layer is multilayered, or both. When creating multiple layers, repeat the above operations for each layer. Next, the plaster mold 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 extracted molded body is sufficiently dried at about 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 molded body, but in the case of alumina, the firing conditions are about 1500°C for about 2 hours. By firing, the filter layer and the support layer are sintered integrally, and a multilayer ceramic filter is obtained. [Function] In the method of the present invention, the roles and functions of each of the first layer, second layer and third layer formed as a mold release layer are as follows. The first layer is made of talc and/or sericite 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 of them is when only the first layer is used as a mold release layer, since the thickness of the mold release layer is thin, the plaster-like irregularities are directly transferred to the molded product, resulting in an uneven thickness of the filter layer. However, the second layer is a relatively thick layer, and since the plaster-like irregularities 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 the filter layer 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 low water absorption ability, so it is possible to prevent the cast slurry for the filter layer from adhering rapidly. Therefore, it is easy to control the deposited thickness of the filter layer, and the thickness can be made uniform. Since the third 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 an outer diameter of 5.5 cm and a height of 50 cm has a diameter of 1.2 cm in the center.
Prepare 40 plaster molds with 45 holes, and
It was dried at ℃ 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-Al ₂ O ₃ (average particle size 1 μm, manufactured by Showa Light Metal), ZrO ₂ (average particle size 1 μm, manufactured by Shin Nippon Metal Chemical Co., Ltd.), and SiC (average particle size 1 μm, manufactured by Fujimi Abrasives Industry Co., Ltd.) were used. ) was prepared. For the third layer, sodium alginate, a first class reagent, and sodium stearate, a first class 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. The slurry for the second layer was adjusted to pH 3 by adding hydrochloric acid. Next, after sealing the bottom of the hole in the plaster mold with a rubber stopper, apply the slurry for the first layer at 10% of the weight of the dry plaster mold.
It was poured into the weighing hole and the entire amount was absorbed into the meat. After that, after pouring the slurry for the second layer and leaving it for 5 minutes,
The rubber stopper was removed and the slurry that did not adhere to the plaster mold was discharged. A rubber plug was again placed at the bottom of the plaster-shaped hole, and the third layer aqueous solution was injected. After standing for 2 minutes, the rubber plug was removed and the excess aqueous solution was drained.

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

〔Effect of the invention〕

In manufacturing a multi-layer ceramic filter for separation, the present invention forms a release layer consisting of three layers, a first layer, a second layer, and a third layer, on a plaster mold, thereby achieving a desired maximum permeation pore diameter. It is designed so that you can obtain In other words, in the past, even if ceramic fine particle materials for the filter layer and the support layer were prepared to obtain the desired maximum permeation pore diameter, there was no suitable release agent, so plaster-type irregularities were transferred, This caused pinholes and cracks, and damaged the molded product when removing the mold release agent talc, but the present invention has been able to eliminate all of these problems.

Claims (1)

[Scope of Claims] 1 A plaster-shaped structure, in which flat mineral particles are adhered to the first layer, ceramic particles are attached to the second layer, and a water-permeable organic film is attached to the third layer in order, and then separated. After forming a mold layer, a slurry of at least two types of ceramic particles having different average particle diameters, a slurry of particles with a smaller average particle size, is poured into the mold and kept stationary, and a part of the slurry is separated. The slurry is adhered to the inside of the mold through the mold layer, the remaining unattached slurry is discharged, and the slurry with particles having a large average particle size is then cast into the mold in the same manner to form a molded body. 1. A method for producing a multilayer ceramic filter, which comprises preparing a molded product, drying it, demolding it, removing a mold release agent attached to the molded product, and then firing it. 2. Claim 1, wherein the flat mineral fine particles are fine particles of talc and/or sericite.
Manufacturing method described in section. 3 The ceramic fine particles used in the second layer are TiO ₂ ,
The manufacturing method according to claim 1, wherein one or more of Al ₂ O ₃ , SiO ₂ , SiC, ZrO ₂ , Si ₃ N ₄ , and Sialon is used. 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.