JP4748730B2 - Ceramic filter and end face sealing method thereof - Google Patents

Description

  The present invention relates to a ceramic filter used for the purpose of filtration in a technical field such as water treatment, and an end face sealing method thereof.

  Ceramic filters are superior to organic membrane filters in physical strength, chemical strength, durability, and so on. For filtering various fluids in various technical fields including sewage treatment and clean water treatment. Widely used. In order to achieve both the filtration accuracy and the filtration flow rate, this ceramic filter has a dense structure in which relatively small-diameter ceramic particles are sintered on the surface of a porous ceramic substrate obtained by sintering relatively large-diameter ceramic particles. A filter membrane made of a porous ceramic material is formed. In particular, a monolith type or honeycomb type ceramic filter in which a large number of cells penetrating from one end surface to the opposite end surface are formed in the base material and a filtration membrane is formed on the inner wall surface of each cell is per unit volume. There is an advantage that a large film area can be obtained.

  Such a ceramic filter has the inner wall surface of the cell as a filtration surface, feeds raw water into each cell from one end surface and filters it, and passes the filtered water through the inside of the base material from the side surface of the filter to the outside. It is usually used to take out. However, if at least the end surface on the raw water side of the base material is not securely sealed, the raw water may enter the base material from that portion and mix with the filtered water to reduce the filtration performance.

  Therefore, as shown in Patent Document 1, a slurry of a sealing material is applied to an end face of a base material on which an inner wall surface of a cell has been formed in advance by spraying, dried and baked to form an inorganic, water-impermeable sealing layer. A method of forming has been developed. This Patent Document 1 discloses a method of spraying a sealing material from an oblique direction toward an end face while rotating a base material around an axis in the longitudinal direction of the cell. According to this method, as shown in the upper stage of FIG. 1 (the shape after drying), the slurry layer 3 having a large thickness can be formed on the end surface 2 of the rib 1, and the portion of the rib corner 4 is also formed in the slurry layer 3. Can be covered.

  However, the slurry of the sealing material sprayed from the oblique direction toward the end face 2 so as to cover the rib corner 4 hardly enters the inside of the cell 5, and in particular, the depth of entry into the cell inner surface on the side close to the spray gun is Nearly zero. For this reason, the cross-sectional shape of the seal layer 6 formed by melting and solidifying the slurry layer 3 by firing is as shown in the lower part of FIG. 1 (post-fired shape), and the seal layer 6 is interrupted and sealed inside the cell 5. Defects sometimes occurred. In particular, the end of the filtration membrane 7 formed on the inner surface of the cell 5 has a drop-off portion of the membrane by cutting the base material after forming the filtration membrane. Therefore, if the depth of penetration of the seal layer 6 is insufficient, the above seal defect occurs. It becomes easy to do. In addition, although the penetration depth to the cell inner surface can be increased by increasing the spray angle toward the end surface 2, another problem that the sealing material adheres as a droplet from the end surface to the deep cell inner surface. Had occurred.

  Thus, the end face seal of the ceramic filter needs to cover not only the end face 2 of the rib 1 but also the entire region including the end of the filtration membrane 7 with the seal layer 6. Therefore, as shown in Patent Document 2, a stamping method has been developed in which a slurry of a sealing material is impregnated into a sponge-like elastic body and pressed against the end surface 2 of the base material. According to this stamp method, the slurry of the sealing material can be uniformly pushed deeply into the inner surface of the cell 5 to about 3 mm.

  However, as shown in the upper part of FIG. 2, according to the stamp method, the thickness of the slurry layer 3 on the end face 2 is reduced to less than 0.2 mm. For this reason, when this is fired, the slurry layer 3 is melted and the cross section is spheroidized by surface tension. As a result, the rib corner 4 is exposed from the seal layer 6 as shown in the lower part of FIG. Another problem was that it was easier. In the stamping method, it is possible to make the thickness of the slurry layer 3 on the end face 2 0.2 mm or more by repeating coating and drying several times or more, but there is a problem that the production efficiency deteriorates. .

As described above, it is not easy to completely seal the end face of the ceramic filter, and depending on the rib shape and the particle diameter / particle shape of the base material, a sealing defect may occur in the melting process at the time of firing, and the filtration performance will deteriorate. Sometimes. In order to solve this problem, conventionally, it has been necessary to apply a sealant for correcting a seal defect to the seal defect portion and fire it on the fired ceramic filter, which requires a lot of man-hours.
JP 2003-230808 A JP-A-2005-219015

  Therefore, the object of the present invention is to eliminate the additional steps of applying a sealing material, applying a sealing material to a fired ceramic filter, and firing the ceramic filter. It is an object of the present invention to provide a ceramic filter and an end face sealing method in which all parts including the sealing member are securely sealed.

The ceramic filter end face sealing method of the present invention made to solve the above problems is formed on a base material made of a ceramic porous body in which a large number of cells partitioned by ribs are formed, and on the inner wall surface of each cell. A method for sealing an end face of a ceramic filter provided with a filtered membrane, wherein a slurry of a sealing material is applied to an end face of a substrate in two stages: application by a stamp and application by a spray. The thickness is set as described above, and a part thereof is made to enter the inner wall surface of each cell adjacent to the end face at a depth of 0.5 to 3 mm and then fired. In addition, it is preferable to perform application | coating by the spray of a slurry by the method of spraying slurry toward two or more places of the end surface of a base material from a spray gun, rotating a base material around an axis line.

The ceramic filter of the present invention is a ceramic filter whose end face is sealed by the method according to claim 1 or 2, wherein the substrate is made of a porous ceramic body in which a large number of cells partitioned by ribs are formed, A filtration membrane formed on the inner wall surface of the cell, the end surface side thickness after firing is 0.2 mm or more on the end surface of the base material, and the depth of penetration into the inner wall surface of the cell is 0.5 to By forming a 3 mm sealing layer, the rib angle and the sealing defect generated inside the cell are prevented.

In addition, it is preferable to chamfer the rib angle of the base material by buffing to make the rib angle a curved surface having a curvature radius of 0.2 mm or more.

  ADVANTAGE OF THE INVENTION According to this invention, the end face side thickness after baking is 0.2 mm or more, and the ceramic filter in which the sealing layer whose penetration depth to the inner wall face of a cell is 0.5-3 mm was formed is provided. Thus, by setting the end face side thickness to 0.2 mm or more, not only the end face side but also the thickness of the rib corner seal layer can be ensured, and the rib corner seal defect can be prevented. If the depth of penetration exceeds 3 mm, the thickness peak position of the slurry layer spheroidized at the time of melting enters from the end face to the back, and it is not preferable because a rib corner seal defect is likely to occur.

  In particular, when the rib angle of the base material is a curved surface having a curvature radius of 0.2 mm or more as in claim 2, seal defects can be prevented more reliably. Such rib corner chamfering can be easily performed by means such as buffing.

  Moreover, according to the ceramic filter end face sealing method of the present invention, the ceramic filter having the above-described configuration can be manufactured. In addition, as described above, the seal layer having an end face side thickness of 0.2 mm or more and a depth of entry to the inner wall surface of the cell of 0.5 to 3 mm can be formed at a time by either the stamp method or the spray method. It is not easy to form. For this reason, it is preferable that a slurry layer is made to enter the inner surface of the cell to a depth of 0.5 to 3 mm by the stamp method, and after drying, a slurry layer of 0.2 mm or more is formed on the end surface side by the spray method.

  Further, when a single spray gun is used, even if spraying is performed while rotating the base material around the axis, it is difficult for the slurry to enter the cell inner surface near the spray gun. Therefore, if the method of spraying slurry from the spray gun toward two or more locations on the end face of the base material while rotating the base material around the axis as in claim 5, the slurry layer is uniformly applied to the inner surface of the cell. It becomes easy to form.

Hereinafter, preferred embodiments of the present invention will be described.
FIG. 3 is an external view of the ceramic filter of the present invention, and FIG. 4 is a partially enlarged sectional view thereof. In these figures, reference numeral 10 denotes a base material made of a ceramic porous body, and a large number of cells 5 partitioned by ribs 1 are formed therein. The base material 1 is obtained by sintering ceramic particles such as alumina, mullite, cordierite, and silicon carbide, and has an average pore diameter of 1 to several hundred μm.

  The cell 5 penetrates from one end surface 2 of the base material 10 to the other end surface, and a filtration membrane 7 is formed on the inner wall surface of each cell 5. The filtration membrane 7 is made of ceramic particles having an average particle size smaller than that of the ceramic particles constituting the substrate 10, and a membrane for forming a filtration membrane is attached to the inner surface of each cell 5 of the substrate 10 to form a film. It can be formed by a method of drying and baking. The average particle diameter varies depending on the use of the ceramic filter, but is about 0.01 to 1 μm. In FIG. 4, the filtration membrane 7 is shown as an example. However, in practice, it is preferable to form an intermediate membrane between the substrate 10 and the filtration membrane 7. As shown in FIG. 4, the end of the filtration membrane 7 (including the intermediate membrane) has a membrane drop-off portion by cutting the substrate after forming the filtration membrane. As described above, it is preferable that the rib corner 4 of the base material 10 is formed into a curved surface having a curvature radius of 0.2 mm or more by buffing or the like in advance after cutting the base material and before applying the slurry of the sealing material.

  The portion of the ceramic filter including the end face 2 of the rib 1, the rib corner 4, and the end of the cell 5 is covered with a water-impermeable seal layer 6 as shown in FIG. 4 and supplied from the end face 2 side. The raw water is prevented from entering the inside of the base material 10. The water-impermeable sealing layer 6 is made of glass or other water-impermeable film forming material, and when glass is used, it contains a glass fine powder having an average particle diameter of about 5 to 50 μm and a dispersion medium thereof. The slurry is applied to the end face 2 of the substrate 10 and dried and fired. In this case, the melting point of the glass to be used is preferably in the range of 600 to 1200 ° C. This is because the glass fine powder is melted at a temperature equal to or lower than the sintering temperature of the base material 10 and the filtration membrane 7 to form the seal layer 6 without adversely affecting the base material 10 and the filtration membrane 7.

  In the present invention, the end face side thickness A after firing of the seal layer 6 formed on the end face 2 of the substrate 10 is 0.2 mm or more, and the depth of penetration B into the inner wall surface of the cell 5 is 0.5 to 0.5. By forming such a seal layer 6 as 3 mm, the end face 2 of the rib 1 is completely sealed, and a seal defect occurring inside the rib corner 4 and the cell 5 is prevented.

  The reason why the end face side thickness A is 0.2 mm or more is that if it is thinner than this, the thickness of the seal layer 6 at the rib corner 4 is insufficient, and a seal defect may occur. Further, the depth of penetration B is set to 0.5 to 3 mm. If the depth of penetration is shallower than this, the end of the filtration membrane 7 cannot be reliably covered, and a seal defect may occur inside the cell 5. Because there is. On the contrary, if the penetration depth B exceeds 3 mm, the peak position of the curved surface formed by the surface tension in the molten state is too far from the end face 2, and the thickness of the seal layer 6 at the end of the filtration membrane 7 is insufficient. This is because a seal defect may occur in the interior of 5.

  As described in the section of the prior art, once the sealing layer 6 having the end face side thickness A after firing of 0.2 mm or more and the depth of penetration B into the inner wall surface of the cell 5 of 0.5 to 3 mm is applied once. It is difficult to form by only baking of the conventional method by spray application of the conventional method, the problem that the spray of the sealing material penetrates deep inside the cell, and the problem of the end face side thickness A being 0.2 mm or less by the stamp application. The method for sealing the end face of the ceramic filter according to the present invention that enables this will be described below.

  In the present invention, first, the slurry layer 3a is formed on the end face 2 of the substrate 10 by the stamp method. As shown in Patent Document 2, the stamp method is a method in which a slurry of a sealing material is impregnated in a sponge-like elastic body and pressed against the end surface 2 of the base material. As the slurry for the sealing material, a slurry containing the above-described fine glass powder having an average particle diameter of about 5 to 50 μm and a dispersion medium thereof can be used. It is preferable to use methylcellulose and water as the dispersion medium and adjust the viscosity to be suitable for the stamp method.

  As shown in FIG. 5, the slurry layer 3a formed on the end face 2 of the base material 10 by this stamp method does not reach the end face side thickness of 0.2 mm, and the thickness at the rib corner 4 is insufficient. By selecting an appropriate sponge thickness, slurry viscosity, and pressing force, the penetration depth B into the inner wall surface of the cell 5 can be set to 0.5 to 3 mm. After drying the slurry layer 3a formed by the stamp method in this way, the slurry layer 3b is applied on the slurry layer 3a by spraying.

  As shown in FIG. 6 (plan view), the slurry is applied by spraying the sealing material from the spray gun 20 toward the end face 2 of the base material 10 while rotating the base material 10 that has been erected around the horizontal axis. This is done by spraying the slurry. The illustrated spray angle α is preferably around 45 °, and the distance between the tip of the spray gun 20 and the end face 2 of the substrate 10 is preferably around 200 mm. As described above, according to the spray method, the thick slurry layer 3 b can be formed on the end surface 2 of the rib 1. Further, the slurry layer 3 b can be formed also on the rib corner 4 by spraying from the oblique direction toward the end surface 2 of the substrate 10. In this embodiment, spraying is performed in the horizontal direction, but the spraying direction is not limited to this.

  However, when spraying the end face 2 of the rib 1 at the position D shown in FIG. 7 while rotating the base material 10 around the axis, the slurry layer 3b is formed thick on the outer wall side in the cell 5, as shown in FIG. The slurry layer 3b on the center side becomes thin. When spraying is performed on the end surface 2 of the rib 1 at the position A in FIG. 7, a slurry layer 3b is formed thick on the left wall surface toward the center of the substrate in the cell 5 as shown in FIG. As shown in FIG. 10, a thick slurry layer 3b is formed on the central wall surface in the cell 5, as shown in FIG.

  Thus, since the thickness distribution of the slurry layer 3b in the cell 5 differs depending on the position where the spray is applied, the slurry can be sprayed from the spray gun 20 toward two or more locations on the end surface 2 of the base material 10. preferable. In this embodiment, spraying was performed at a total of four positions A, B, C, and D. The spray angle α at each position was constant. The spray amount was also constant. Thereby, as shown in FIG. 5, the slurry layer 3 b having a substantially uniform thickness can be formed over the entire circumference in the cell 5.

  Thus, if the slurry layer 3a by the stamp method and the slurry layer 3b by the spray method are formed on the end face 2 of the rib 1 and fired, the seal layer 6 having a sufficient thickness as shown in the lower part of FIG. Is formed. The sealing layer 6 has an end face side thickness A of 0.2 mm or more after firing, and an entry depth B to the inner wall surface of the cell 5 of 0.5 to 3 mm. A ceramic filter in which all portions including the inner surface of the end portion of the cell 5 are reliably sealed can be obtained.

  An end face seal was applied to a cylindrical honeycomb ceramic filter in which a filtration membrane having an average pore diameter of 1 μm was formed on the inner surface of a cell formed on an alumina substrate. In addition, the end surface of the base material was buffed to chamfer the rib corner with a radius of curvature of about 0.2 mm. The used sealing material is a slurry obtained by adding 2 parts by mass of methylcellulose to 100 parts by mass of glass powder having an average particle diameter of 10 μm and further adding water. First, this sealant slurry was impregnated into a sponge having a thickness of 5 mm, and applied to the end face of the substrate so as to be stamped. This was dried to form a slurry layer.

  Next, the slurry of the same sealant is prepared using a spray gun set horizontally and supported on the end surface of the substrate in a horizontal plane while slowly rotating around its central axis. Sprayed to the end face of the material. The spray angle α was 45 °, and the distance to the end face was 200 mm. Spraying was performed at positions A, B, C, and D shown in FIG. The discharge amount per unit time at each position was 10 g per minute, and the spray time was the same as 10 seconds.

  Thereafter, the ceramic filter was fired, and the slurry layer was melted and solidified to form a seal layer. When the thickness of the sealing layer was observed using an optical microscope and the thickness was measured, the average thickness on the end face side was 0.3 mm, the average penetration depth to the inner wall surface of the cell was 2 mm, the end face of the rib, and the rib angle It was confirmed that the ceramic filter was surely sealed at all portions including the inner surface of the end portion of the cell.

It is sectional drawing which shows the slurry layer formed by the spray method. It is sectional drawing which shows the slurry layer formed by the stamp method. It is a perspective view which shows the external appearance of the ceramic filter of this invention. It is a partial expanded sectional view of the ceramic filter of this invention. It is sectional drawing which shows the slurry layer formed by this invention method. It is a top view which shows a spray state. It is a perspective view which shows a spray position. It is a schematic diagram which shows the slurry adhesion state in the cell at the time of spraying in A position of FIG. It is a schematic diagram which shows the slurry adhesion state in the cell at the time of spraying in the B position of FIG. It is a schematic diagram which shows the slurry adhesion state in the cell at the time of spraying in the C position of FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Rib 2 End surface 3 Slurry layer 3a Slurry layer 3b by stamp method Slurry layer by spray method 4 Rib angle 5 Cell 6 Seal layer 7 Filtration membrane 10 Base material 20 Spray gun

Claims (4)

A sealing method for an end face of a ceramic filter comprising a base material made of a ceramic porous body in which a large number of cells partitioned by ribs are formed, and a filtration membrane formed on the inner wall surface of each cell, the sealing material The slurry is applied to the end face of the base material in two stages of application by stamp and application by spraying to a thickness of 0.2 mm or more, and a part of the slurry is added to the inner wall surface of each cell adjacent to the end face. A method for sealing an end face of a ceramics filter, which is fired after entering at a depth of 5 to 3 mm. 2. The ceramic according to claim 1 , wherein the application of the slurry by spraying is performed by a method of spraying the slurry toward two or more locations on the end face of the substrate while rotating the substrate around the axis. Filter end face sealing method. A ceramic filter having an end face sealed by the method according to claim 1 or 2, wherein the filter is formed on a base material made of a ceramic porous body in which a large number of cells partitioned by ribs are formed, and an inner wall surface of each cell. A sealing membrane having a thickness of 0.2 mm or more after firing and a depth of entry to the inner wall surface of the cell of 0.5 to 3 mm is formed on the end surface of the base material. A ceramic filter characterized by preventing rib defects and seal defects occurring inside the cell. 4. The ceramic filter according to claim 3 , wherein the rib angle of the substrate is chamfered by buffing, and the rib angle is a curved surface having a curvature radius of 0.2 mm or more.

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