JPH0582244B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Field of Application] The present invention relates to an improvement in the method of manufacturing ceramic filters by slurry casting. [Prior Art] Conventionally, in the field of fermentation technology using yeast, organic filters have been used to separate yeast and products. However, organic filters have problems in terms of heat resistance, chemical stability, and durability.
There is a strong demand for a replacement with a ceramic filter. A method of manufacturing ceramic filters used in this field is a method using slurry casting. The outline of this method is as follows. A mold release agent, such as talc powder, is attached to the plaster mold, but after an organic mold release agent such as alginate is attached to form a release layer, water and other substances are added to ceramic fine powder such as alumina fine powder. This slurry is cast into the plaster mold and held for a certain period of time, and a part of the slurry is adhered to the plaster mold through a release layer. A cast body is obtained by discharging the unattached slurry. Furthermore, a slurry may be made from fine ceramic powder having different particle sizes, and the above casting operation may be repeated to form a cast body having two or more layers. Dry the plaster mold, mold release layer, and casting body that are integrated. Since a gap is created between the plaster mold and the mold release layer by drying, the mold release layer and the cast body can be removed from the plaster mold, and a molded body can be obtained. A mold release layer remains on the surface of the cast body, so after removing this, it is fired at a specified temperature (approximately 1500°C if the formed body is alumina-based) and slowly cooled to obtain a ceramic filter. It will be done. [Problems to be solved by the invention] However, when talc is used as a mold release material as in the past, talc has a relatively low melting temperature, so if the molded body is fired without removing the talc, talc will form on the surface of the molded body. Since it melts and sticks, the filter becomes clogged and useless. The talc must therefore be completely removed before firing the compact. However, the compact before firing is fragile;
Moreover, since the work is done manually with a brush, etc., even if you are very careful, it may break during the work.
Talc often causes damage, and it is extremely difficult to completely remove talc without any damage. Furthermore, even if the talc can be removed without damage, handling before the next step, the firing step, is extremely troublesome. That is, as mentioned above, the compact before firing is fragile and must be handled with care to avoid damage when inserted into the firing furnace and set. Furthermore, during firing, it is necessary to avoid sudden temperature rises in order to avoid spalling, and cooling after firing must be done gradually for the same reason.There are various disadvantages in handling. It was hot. [Means for Solving the Problems] As a result of various studies in order to solve the above-mentioned drawbacks, the present inventors formed a specific mold release layer instead of the conventional mold release layer, and this mold release layer was molded into a mold. It was discovered that the object could be achieved by firing the powder while it was attached to the composite, and the present invention was achieved based on this discovery. The gist is to form a release layer by sequentially attaching flat mineral fine particles to the first layer, inorganic fine particles to the second layer, and a water-permeable organic film to the third layer on a plaster mold. Then, the slurry of ceramic particles is cast into a plaster mold and left to stand, allowing a part of it to adhere to the inside of the mold via the mold release layer, and the remaining slurry that is not attached is discharged. After forming the cast body, the cast body, mold release layer and plaster mold are dried,
A method for manufacturing a ceramic filter, which comprises removing a molded body consisting of a cast body and a mold release layer from a plaster mold, and then firing the molded body. Here, examples of the flat mineral fine particles used in the first layer include talc and ceritite. Examples of the inorganic fine particles used in the second layer include alumina or a mixture of alumina and silica. Third
Examples of the water-permeable organic membrane used for the layer include sodium alginate or sodium stearate. Next, an example of the manufacturing method of the present invention will be described for a ceramic filter consisting of two layers: a pipe-shaped support layer and a filter layer. The method of the present invention is not limited to pipe-like filters or two-layer filters, but also plate-like filters, single-layer filters, or three-layer filters.
It can also be applied to filters with more than one layer. A regular plaster mold used as a mold is provided with a required hole, for example, a hole of 12 mm in diameter, and the plaster mold is dried at 45° C. until it reaches a constant weight. Next, adjust the moisture content of the dried plaster mold, and at the same time,
To form the first layer of the mold release layer, water is added to talc or sericite, or a mixture thereof to form a slurry, and this slurry is mixed with 10% of the weight of the dry plaster mold.
%, pour it into the hole, and almost all of it absorbs water and sticks to the meat. This forms a first layer approximately 10 μm thick. Next, about 10% colloidal silica is added to alumina alone or a mixture of alumina and silica to make a slurry, which is cast into the hole and left to stand for the time required to reach the desired thickness. is discharged to form a second layer. The thickness of the second layer is 30~
It is 1500 μm, preferably 500 to 700 μm. 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 adhere to a thickness of about 10 μm, and then the excess aqueous solution is drained to form a third layer. By the above operations, a release layer consisting of three layers is formed on the inner surface of the hole of the plaster mold. After forming the mold release layer, a slurry of ceramic particles having a finer average particle size is cast into the hole through the mold release layer on the inner surface, and left to stand for a predetermined period of time to allow the slurry to adhere at least several tens of μm. , 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 cast body. . In addition, although the case of a two-layer ceramic filter consisting of one filter layer and one support layer has been described above, the filter layer itself can be multi-layered,
Alternatively, when the support layer is made into a multilayer, or when both layers are made into a multilayer, the above operation may be repeated. Next, the plaster mold that is integrated with the cast body is 45
Dry at °C. Due to drying, the plaster mold and the molded body are separated from the first layer of the mold release layer, so the molded body in which the cast body and mold release layer are integrated is pulled out from the hole of the plaster mold. . The extracted molded body is fired in an electric furnace or the like with the release layer still attached. The firing temperature varies depending on the type of ceramic particles used in the cast body, but in the case of alumina-based ceramic particles, it is 1300 to 1600°C. Cooling after firing can be done by slow cooling to room temperature in 12 to 24 hours as in the conventional method, but if the mold release layer is alumina or
If it is a silica mixture, the furnace temperature is 1000-200
When the molded body is taken out of the furnace when the temperature reaches .degree. C., cracks occur only in the fired mold release layer in the substantially circumferential direction, making it easy to remove the mold release layer. Even if there are no cracks in the mold release layer, a gap will be created between the cast body and the mold release layer during the cooling process after firing, so it will not be impossible to remove the mold release layer. However, depending on the type and mixing ratio of the inorganic fine particles used for the second layer of the mold release layer, they may become fused to the cast body at the tip of the pipe, so in this case, a few millimeters of the tip should be cut off. If you do this, the release layer can be removed. As described above, it is possible to sinter the molded body with the mold release layer still attached, so that a ceramic filter can be manufactured without causing damage. [Example] The present invention will be specifically explained with reference to Examples below. Example Example 1 shown in Table 1 is a plaster mold having a hole with a diameter of 1.2 cm in the center of a cylinder with an outer diameter of 5.5 cm and a height of 50 cm.
Prepare 10 pieces each for 2nd and 3rd use, 30 pieces in total.
This was dried at 45°C for 3 days. Talc (average particle size
1 μm, Nippon Talc Co., Ltd.), α-Al ₂ as the second layer
O ₃ (average particle size 4 μm, manufactured by Showa Light Metal Co., Ltd.) and silicic anhydride (average particle size 40 μm, manufactured by Kokusan Kagaku Co., Ltd., reagent grade 1)
And sodium alginate (manufactured by Kanto Kagaku Co., Ltd., reagent grade 1) was used as the third layer. The weight ratio of α-Al ₂ O ₃ and silicic anhydride used in the second layer was silicic anhydride/α-Al ₂ O ₃ = 0/100,
Three types are mixed to give a ratio of 10/100 and 30/100,
To each of these, 10 parts by weight of colloidal silica (manufactured by Nissan Chemical Co., Ltd., SiO ₂ 30% by weight) was added as SiO ₂ solid content per 100 parts by weight of α-Al ₂ O ₃ , and hydrochloric acid was added as a peptizer to adjust the pH to 3. It was adjusted to make a slurry. Table 1 shows the first and second layers for forming a release layer.
The blending ratios of each layer and third layer are shown.

〔Effect of the invention〕

In the method of the present invention, when the cast body is in a fragile state, it is always covered with a mold release layer, which acts as a protective layer, so that it can be handled as before after being removed from the plaster mold. There is no need to pay close attention to this method, and there is an advantage that there is no need to remove the mold release layer when the cast body is in a fragile state. Further, during firing, no matter how many layers the molded bodies are stacked, as long as they do not deform under load, the cast bodies themselves will not come into direct contact with each other, and their surfaces will not be damaged. Furthermore, since the cast body itself is susceptible to thermal shock, when firing it, the temperature must generally be gradually raised from around room temperature, and when cooling after firing, it must be slowly cooled, but in the method of the present invention, the mold release layer is Since it also acts as a heat insulator, the cast body will not crack even if it is subjected to considerable thermal shock from the outside. Therefore, for example, the temperature of an electric furnace can always be kept above a certain temperature (for example, 1000℃),
It is no longer necessary to wait for the temperature of the electric furnace to drop before inserting the molded body, which also improves productivity.

Claims (1)

[Scope of Claims] 1 A plaster-shaped structure, in which flat mineral fine particles are attached to the first layer, inorganic fine particles are attached to the second layer, and a water-permeable organic film is attached to the third layer, and then separated. A mold layer is formed, and then a slurry of ceramic particles is cast into a plaster mold and left to stand, allowing a part of it to adhere to the inside of the mold via the release layer, and the remaining slurry that is not attached is removed. After discharging the cast body to form a cast body, the cast body, mold release layer and plaster mold were dried, and the molded body consisting of the cast body and mold release layer was demolded from the plaster mold. A method for producing a ceramic filter, which comprises subsequently firing the molded body. 2. The manufacturing method according to claim 1, wherein the flat mineral fine particles are talc and/or sericite. 3. The manufacturing method according to claim 1, wherein the inorganic fine particles are alumina and/or an alumina-silica mixture.