JP6139250B2 - Ceramic filter element manufacturing method and photocatalytic filter - Google Patents

Description

  The present invention relates to a method for manufacturing a ceramic filter element and a photocatalytic filter, and more particularly, to a method for manufacturing a ceramic filter element having improved strength with light and fluid permeability and a photocatalytic filter using the element.

  In recent years, as a ceramic filter element, porous silicon (Si) and silicon carbide (SiC) are obtained by impregnating a sponge-like organic resin into a slurry containing a carbon source resin and silicon powder, followed by drying and sintering. An Si / SiC structure made of a composite of the above has been proposed (Patent Document 1). Elements composed of such structures have high porosity, light weight, and excellent heat resistance, and can be applied to various purification filters used for purification in contaminated environments such as contaminated air and contaminated water. Expected.

  However, it has been pointed out that such a ceramic filter element is fragile and easily breaks the ceramic linear body constituting the element. For this reason, for example, there is a concern that a part of the linear body may be broken to generate a foreign substance when the purification filter is replaced or cleaned, or when the purification filter is used for a long time or when a large amount of fluid is filtered. Such foreign matters can cause serious losses such as product defects in various manufacturing fields such as semiconductor-related fields, precision parts manufacturing fields, pharmaceutical manufacturing fields, and food manufacturing fields. Therefore, a further improvement in strength is desired for the ceramic filter element.

  On the other hand, in a ceramic filter element different from the Si / SiC structure, in order to increase its strength, an example of filling, adhering or applying a reinforcing frame to the outer periphery of the element (Patent Document 2), In addition, an example (Patent Document 3) in which a frame body made of a sealing portion and a filtration surface made of a porous plate are integrally manufactured using clay is proposed. However, the technology used for these elements is a practical problem in that it is difficult to apply to the Si / SiC structure as it is due to the difference in material, or a complicated manufacturing process is required. It has not yet been resolved.

Japanese Patent Laid-Open No. 2003-119085 JP 2006-122829 A Japanese Patent Laid-Open No. 10-118432

  An object of the present invention is to solve the above-mentioned problems. For example, the object of the present invention is to have excellent strength while maintaining the lightness of a conventional ceramic filter element, and to improve manufacturing efficiency. An object of the present invention is to provide a method for producing an excellent ceramic filter element and a photocatalytic filter.

The present invention is a method of manufacturing a ceramic filter element,
(A) Applying the first ceramic-forming slurry substantially uniformly to the entire porous structure having two opposing fluid passage surfaces and side portions surrounding the fluid passage surface and containing a carbon source. And (b) applying a second slurry to the side surface of the porous structure;
A method comprising

  In one embodiment, the first ceramic-forming slurry contains a mixture of a resin having a carbon source and silicon powder, silicon carbide, alumina, zirconia, or a mixture of calcium hydroxide and phosphoric acid.

  In one embodiment, the second slurry is a ceramic-forming slurry.

  In one embodiment, the second slurry contains a mixture of a resin having a carbon source and silicon powder, silicon carbide, alumina, zirconia, or a mixture of calcium hydroxide and phosphoric acid.

  In one embodiment, after the step (b), the method includes (c) a step of carbonizing the porous structure.

  In a further embodiment, the method includes (a ′) carbonizing the porous structure after the step (a) and before the step (b).

  The present invention also provides a photocatalytic filter in which a photocatalyst is supported on a ceramic filter element obtained by the above method.

  According to the present invention, a ceramic filter element with improved strength can be obtained. The element manufactured according to the present invention is excellent in light and fluid permeability because pressure loss as a filter is reduced. Moreover, the sealing performance in directions other than the fluid flow direction of the element can be kept high. Furthermore, according to the element manufacturing method of the present invention, when manufacturing a purification filter for separating and adsorbing contaminants, it is flexible to manufacture filter materials for small lots and small productions without being restricted by size and shape. It can correspond to. Furthermore, according to the present invention, it is possible to minimize the type of slurry required for manufacturing the element, and it is possible to reduce the environmental load required for waste liquid treatment.

It is a figure for demonstrating an example of the manufacturing method of the ceramics filter element of this invention, Comprising: On the side part of the square pillar (cuboid) -shaped porous structure to which the 1st ceramic forming slurry was provided substantially uniformly It is a figure which shows typically the procedure which impregnates a 2nd slurry and forms a skin layer. It is a figure for demonstrating the other example of the manufacturing method of the ceramics filter element of this invention, Comprising: It is 2nd to the side part of the cylindrical porous structure to which the 1st ceramic forming slurry was provided substantially uniformly. It is a figure which shows typically a mode that a slurry layer is impregnated and a skin layer is formed. It is a figure for demonstrating an example of the ceramics filter element which can be manufactured by this invention, Comprising: It is the perspective view which represented the said element typically. It is a figure for demonstrating an example of the ceramics filter element which can be manufactured by this invention, Comprising: It is sectional drawing in the AA direction of the element shown in FIG. It is a figure for demonstrating an example of the photocatalyst filter which made the ceramic filter element obtained by this invention carry | support a photocatalyst, Comprising: It is the figure which represented the said photocatalyst filter typically. It is a figure for demonstrating the other example of the photocatalyst filter which made the ceramic filter element obtained by this invention carry | support a photocatalyst, Comprising: It is the perspective view which represented the said photocatalyst filter typically. It is a figure for demonstrating an example of the light purification apparatus using the photocatalyst filter of this invention shown in FIG. 6, Comprising: It is a partially cutaway perspective sectional view of the said apparatus.

  Hereinafter, the present invention will be described in detail.

  In the method for manufacturing a ceramic filter element of the present invention, first, (a) the first ceramic-forming slurry is applied substantially uniformly to the entire porous structure.

  The porous structure used in the present invention is composed of a material containing a porous carbon source.

  Examples of the material containing a porous carbon source include an organic resin and / or organic rubber having a sponge structure, and a fabric composed of organic fibers. Examples of organic resins include, but are not limited to, urethane resins such as polyurethane; polyolefin resins such as polyethylene and polypropylene; styrene resins such as polystyrene and ABS (acrylonitrile-butadiene-styrene) resins; polyesters such as polyethylene terephthalate. Resin; polyamide resin such as polyamide; and combinations thereof. Examples of organic rubbers include, but are not limited to, natural rubber, synthetic rubber (for example, chloropyrene rubber, ethylene propylene rubber, acrylic rubber, isoprene rubber, urethane rubber, epichlorohydrin rubber, styrene / butadiene rubber, or butyl rubber. Or a combination thereof) or a combination thereof. Examples of organic fibers include natural organic fibers (eg, plant fibers such as cotton, hemp or linen, animal fibers such as wool, silk or cashmere, or combinations thereof), synthetic organic fibers (eg, Polyester fiber, acrylic fiber, polyamide fiber, polyvinyl alcohol fiber, or a combination thereof) or a combination thereof. Furthermore, a specific example of the synthetic organic fiber includes Gore-Tex (registered trademark). Moreover, as an example of the fabric comprised with organic fiber, the nonwoven fabric, woven fabric, knitted fabric, paper, and these laminated bodies comprised with such an organic fiber are mentioned.

  The porous structure used in the present invention also includes two opposing fluid passage surfaces and a side surface surrounding the fluid passage surface. Examples of such a structure include a rectangular parallelepiped, a cube, a hexagonal column, a pentagonal column, a polygonal column such as a triangular column, a cylinder, and an elliptical column.

  The first ceramic-forming slurry used in the present invention is a colloidal solution slurried using a material capable of forming ceramics by means known to those skilled in the art such as sintering.

  The component constituting the first ceramic-forming slurry is not necessarily limited.For example, (1) a mixture of a resin having a carbon source and silicon powder, (2) silicon carbide, (3) alumina, (4) Zirconia, or (4) a mixture of calcium hydroxide and phosphoric acid. (1) It is preferable to use a mixture of a resin having a carbon source and silicon powder.

  (1) In the mixture of the resin having a carbon source and the silicon powder, the resin that can constitute the mixture includes phenol resin, furan resin, organometallic polymer (for example, polycarbosilane) and sucrose, and these Combinations are mentioned. Silicon powder constituting the mixture includes silicon powder itself and silicon alloy (as metal elements, magnesium, aluminum, titanium, chromium, manganese, iron, cobalt, nickel, copper, zinc, zirconium, niobium, molybdenum, and Tungsten, as well as combinations thereof), and combinations thereof. In the present invention, it is preferable to use fine silicon powder. In particular, it is more preferable to use fine silicon powder having an average particle size adjusted to 30 μm or less from the viewpoint that a more uniform Si / SiC ceramic can be formed.

  The mixing ratio of the resin having a carbon source and the silicon powder in the mixture of (1) above is not necessarily limited and may be either Si-rich or C-rich. It is preferable that the atomic ratio (Si / C) between silicon and carbon contained in the slurry is 0.05 to 4.

  In addition to the above components, the first ceramic-forming slurry may contain an organic medium such as ethanol, methanol, propanol, acetonitrile, and diethyl ether, or a medium such as water. Further, the slurry is added with carbon powder, graphite powder, carbon black, or as an aggregate or antioxidant, silicon carbide, silicon nitride, zirconia, zircon, alumina, silica, mullite, molybdenum disilicide, boron carbide. , And may contain additives such as boron powder. The content of the additive is not particularly limited. Any content can be selected by a person skilled in the art within a range that does not impair the effects of the above components contained in the first ceramic-forming slurry.

  The substantially uniform application of the first ceramic-forming slurry to the entire porous structure can be achieved, for example, by a person skilled in the art wholly or part of the porous structure is contained in the first ceramic-forming slurry. The first ceramic-forming slurry is substantially uniformly dispersed throughout the porous structure by being impregnated using a well-known means and then appropriately squeezed using a means well known to those skilled in the art. Alternatively, the first ceramic-forming slurry is sprayed over the entire porous structure, and appropriately squeezed using means well known to those skilled in the art as needed, so that the entire porous structure is One ceramic-forming slurry is applied substantially uniformly. After the slurry is applied to the structure, the porous structure may be dried as necessary.

  In the present invention, after the first ceramic-forming slurry is applied to the porous structure (a), before the following step (b), (a ′) the porous structure is carbonized. Also good. Specifically, the porous structure is exposed to a temperature of, for example, 900 ° C. to 1350 ° C. under an inert atmosphere such as vacuum or argon. By applying such a temperature, among the materials constituting the porous structure, the material containing the porous carbon source is thermally decomposed, while the material contained in the first ceramic-forming slurry. The ceramic structure is formed while the components substantially maintain the original porous skeleton. Thereby, a carbonized porous structure can be obtained.

  In the present invention, after the step (a), (b) the second slurry is applied to the side surface of the porous structure.

  The second slurry used in the present invention may be a slurry similar to the first ceramic-forming slurry, that is, as a constituent, for example, (1) a mixture of a resin having a carbon source and silicon powder (2) silicon carbide, (3) alumina, (4) zirconia, or (4) a mixture of calcium hydroxide and phosphoric acid. (1) Any of a mixture of a resin having a carbon source and silicon powder may be contained.

  Alternatively, as the second slurry, for example, when the carbonization step (a ′) is performed in the present invention, a slurry other than the above can be used. Examples of components constituting the slurry that can be used in such a case include thermoplastic resins, thermosetting resins, natural or synthetic rubbers, and combinations thereof. Examples of thermoplastic resins include polyethylene, polypropylene, polyvinyl chloride, polystyrene, polyvinyl acetate, polytetrafluoroethylene, polyethylene terephthalate, polybutylene terephthalate, polyamide, polycarbonate, ABS (acrylonitrile-butadiene-styrene) resin, AS ( Acrylonitrile styrene) resin, and poly (meth) acrylate and combinations thereof. Examples of thermosetting resins include phenolic resins, epoxy resins, melamine resins, urea resins, and alkyd resins, and combinations thereof. Examples of synthetic rubber include polybutadiene rubber, nitrile rubber, chloroprene rubber, and more specific examples include urethane rubber, butadiene rubber, butyl rubber, styrene-butadiene rubber, isoprene rubber, nitrile rubber, Acrylic rubber, ethylene propylene rubber, epichlorohydrin rubber, chloroprene rubber, silicone rubber, fluorine rubber and the like can be mentioned. The content of these components in the second slurry is not particularly limited. Any content can be selected by one skilled in the art.

  In addition to the above components, the second slurry may contain an organic medium such as ethanol, methanol, propanol, acetonitrile, and diethyl ether, or a medium such as water. Further, the slurry may contain additives such as low melting point metals such as zinc, tin, lead, indium, gallium and bismuth; solder powder; fluororesin; By containing these additives, the heat resistance, chemical resistance, UV resistance and the like of the obtained ceramic filter element are further improved. In addition, content of an additive is not specifically limited. Any content can be selected by a person skilled in the art within a range that does not impair the effects of the above components contained in the second slurry.

  The application of the second slurry to the side surface portion of the porous structure is, for example, impregnating the side surface portion of the porous structure into the second slurry by means well known to those skilled in the art, Alternatively, the second slurry can be sprayed on the side surface of the porous structure by means well known to those skilled in the art.

  In particular, when the second slurry is impregnated with the side surface portion of the porous structure, for example, it is performed as follows.

  FIG. 1 is a diagram for explaining an example of a method for producing a ceramic filter element according to the present invention, and is a quadrangular prism (cuboid) porous structure to which a first ceramic-forming slurry is applied substantially uniformly. It is a figure which shows typically the procedure which impregnates a 2nd slurry in the side part.

  First, as shown in FIG. 1A, one surface 100a of the side surface portion of the porous structure 100 to which the first ceramic-forming slurry has already been applied is the container 104 in which the second slurry 102 is disposed. Placed on top. Thereafter, the porous structure 100 is gently immersed in the second slurry 102 ((b) in FIG. 1). The degree of immersion (depth) of the porous structure 100 in this immersion, the immersion time, and the temperature set during the immersion can be appropriately selected by those skilled in the art. After the immersion, the porous structure 100 is slowly separated from the container 104 ((c) in FIG. 1). As a result, a layer 106 a impregnated with the second slurry 102 is formed on one side surface of the porous structure 100. Next, the porous structure 100 is rotated and disposed so that the new surface 100b faces the container 104 containing the second slurry 102, and in the same manner as in FIG. 100 is gently immersed in the second slurry 102 (FIG. 1 (d)). Thus, a layer 106b impregnated with the second slurry 102 is formed on the other side surface portion of the porous structure ((e) of FIG. 1). Further, the porous structure 100 is rotated so that the new surface 100c faces the container 104 containing the second slurry 102, and the porous structure 100 is formed in the same manner as in FIG. 100 is gently immersed in the second slurry 102 (FIG. 1 (f)). Thus, a layer 106c impregnated with the second slurry 102 is formed on another side surface portion of the porous structure ((g) in FIG. 1). Furthermore, the porous structure 100 is rotated so that the new surface 100d is disposed on the container 104 containing the second slurry 102 so as to face the porous structure 100. Similarly to FIG. The body 100 is gently immersed in the second slurry 102 (FIG. 1 (h)). In this way, the layer 106d impregnated with the second slurry 102 is formed on the other side surface of the porous structure ((i) in FIG. 1).

  In this manner, the layers 106a, 106b, 106c, and 106d impregnated with the second slurry are formed on all of the side surfaces of the quadrangular columnar porous structure 100.

  FIG. 2 is a view for explaining another example of the method for producing a ceramic filter element of the present invention, and is a side view of a cylindrical porous structure to which a first ceramic-forming slurry is applied substantially uniformly. It is a figure which shows a mode that a 2nd slurry is impregnated to a part typically.

  As shown in FIG. 2, the cylindrical porous structure 120 is immersed in the container 104 containing the second slurry 102 and then gently rotated around the axis to be impregnated with the second slurry. The layer 126 is formed on the side surface constituting the outer periphery of the porous structure 120.

  After the second slurry is applied to the porous structure, the porous structure may be dried as necessary.

  In the present invention, when the ceramic-forming slurry is applied as the second slurry to the side part of the (b) porous structure, after the application, (c) the porous structure is carbonized. Also good. Specifically, the porous structure is exposed to a temperature of, for example, 900 ° C. to 1350 ° C. under an inert atmosphere such as vacuum or argon. By providing such a temperature, when carbonization by the step (a ′) is not performed in advance, a porous carbon source is included among materials constituting the porous structure. While the material is thermally decomposed, on the other hand, the component contained in the first ceramic-forming slurry forms a ceramic structure while substantially maintaining the original porous skeleton, and the portion to which the second slurry is applied Can form a skin layer having a higher density ceramic structure. In addition, when carbonization is previously performed by the step (a ′), a skin layer having a high-density ceramic structure can be formed only in a portion to which the second slurry is applied.

  In this way, a ceramic filter element can be manufactured.

  As shown in FIG. 3, a ceramic filter element 200 manufactured by the method of the present invention includes a porous ceramic portion 202 formed from a first ceramic-forming slurry, and a first surrounding the outer edge of the ceramic portion 202. Skin layers 206a, 206b, 206c, and 206d sealed with a second slurry.

  FIG. 4 is a view for explaining an example of the ceramic filter element that can be manufactured according to the present invention, and is a cross-sectional view in the AA direction of the ceramic filter element 200 shown in FIG.

  As shown in FIG. 4, the ceramic filter element 200 has a porous ceramic structure 202 in the central portion, and therefore allows fluid to pass through the filter from the top to the bottom or from the bottom to the top of FIG. 4. Can do. On the other hand, at the outer edge of the element 200, the side surface of the element 200 is blocked from the outside by skin layers (206b and 206d in FIG. 4). In other words, since the outer periphery of the element 200 has a structure reinforced by the skin layers 206a, 206b, 206c and 206d, the element 200 has strength in both the lateral direction and the fluid passing direction. Has been enhanced.

  According to the method of the present invention, when the porous structure is applied to the second slurry, the skin layers 206a, 206b, 206c, and 206d are formed by changing the depth immersed in the second slurry, for example. It can be changed to any thickness. As a result, when higher strength is required, the thickness of the skin layer may be increased. Further, when it is desired to increase the strength of only a part of the side surface portion of the porous structure, the skin layer corresponds. What is necessary is just to set so that the thickness of only one part may become large.

In the ceramic filter element thus obtained, the pore diameter is, for example, 500 μm to 600 μm, the open porosity is, for example, 85% or more, preferably 90% or more, more preferably 95% or more, and / or the density. There is, for example ^{0.15g / cm 3 ~0.3g / cm 3} .

  The ceramic filter element obtained by the method of the present invention can be applied to filters for various fluids, for example, purification filters for use in purification under contaminated environments such as contaminated air and contaminated water. In obtaining such a purification filter, various functions can be imparted to the element.

  In particular, when Si / SiC ceramics is selected from the respective components of the first ceramic-forming slurry and the second slurry, the ceramic is excellent in workability and good light if used as a porous structure substrate. Since it has permeability, it is also useful as a support for photocatalysts.

  Here, an example of producing a photocatalytic filter by applying a photocatalyst to the ceramic filter element obtained by the method of the present invention will be described.

  The ceramic filter element obtained by the method of the present invention is provided with, for example, a colloid solution (hereinafter also referred to as “treatment solution”) in which anatase-type titanium oxide is dispersed.

  The anatase-type titanium oxide contained in the treatment liquid is conventionally known titanium oxide as a photocatalyst and can be distinguished from rutile-type titanium oxide. However, in the present invention, as long as it contains anatase-type titanium oxide, the inclusion of such rutile-type titanium oxide is not excluded. As the anatase-type titanium oxide, one having an arbitrary particle size (for example, a primary particle size of 5 nm to 30 nm) can be used. Anatase titanium oxide may be either untreated or partially coated with porous silica or the like.

  Although content of the anatase titanium oxide contained in the said processing solution is not specifically limited, For example, it becomes a density | concentration of 5 weight%-25 weight% with respect to the weight of the whole processing solution, Preferably it is 10 weight%-20 weight%. Can be prepared as follows. If the content of anatase titanium oxide contained in the treatment solution is less than 5% by weight, even if the treatment solution is applied to the ceramic filter element, a sufficient photocatalytic film cannot be formed on the element, There is a possibility that the performance of separating and adsorbing contaminants as a photocatalytic filter may be reduced. If the content of the anatase titanium oxide contained in the treatment solution exceeds 25% by weight, there is little change in the separation / adsorption performance of the contaminants of the photocatalyst filter obtained compared to the amount of photocatalyst used. Only the production cost may be increased.

  Although the kind of solvent contained in the said processing solution is not specifically limited, For example, water (tap water, ion-exchange water, pure water, etc.) and alcohol (Methanol, ethanol, etc.) are mentioned.

  Furthermore, the processing solution may contain any additive such as a dispersant. The content of such additives in the processing solution can be arbitrarily set by those skilled in the art.

  Application of the treatment solution to the ceramic filter element can be performed using means / methods known to those skilled in the art, and means / methods such as spraying, brushing, and dipping can be selected. It is preferable to employ spraying or brushing because it can be selected regardless of the size or shape of the ceramic substrate and because it does not require large equipment such as an immersion bath.

  The base material to which the treatment solution is applied is dried as necessary, and then fired for firmly supporting titanium oxide on the ceramic filter element. Calcination can be performed by heating at a temperature at which titanium oxide does not transfer to the rutile structure, for example, 500 ° C. to 600 ° C. for 1 to 2 hours.

  In this manner, a photocatalytic filter in which the photocatalyst is supported on the ceramic filter element is manufactured.

  In the above description, the case where the photocatalyst is supported after the ceramic filter element is once manufactured by the method of the present invention has been described. However, in the present invention, after the step (a) and before the step (b) (A ′) adopting a step of carbonizing the porous structure, and as a second slurry in the step (b), components such as the thermoplastic resin, thermosetting resin, natural or synthetic rubber are added. When the contained slurry is used, the photocatalyst may be supported after the step (a ′) and before the step (b).

  An example of the photocatalytic filter that can be manufactured as described above is shown in FIG.

  A photocatalytic filter 300 shown in FIG. 5 has a filter portion 310 on which a photocatalyst is supported in addition to the ceramic filter element skin layers 206a, 206b, 206c, and 206d. The filter portion 310 has a porous structure, and a photocatalyst is supported also in the interior (not shown).

  FIG. 6 is a view for explaining another example of the photocatalytic filter in which the photocatalyst is supported on the ceramic filter element obtained by the present invention, and is a perspective view schematically showing the photocatalytic filter.

  A photocatalytic filter 400 shown in FIG. 6 is manufactured using a ceramic filter element using a cylindrical porous structure and having a skin layer on the outer peripheral side surface of the cylinder. A skin layer 406 is provided on the outer periphery of the filter 400 with a substantially constant thickness, and has a filter portion 410 inside the skin layer 406.

  FIG. 7 is a view for explaining an example of a light purification device using the photocatalytic filter 400 of the present invention shown in FIG. 6, and is a partially cutaway perspective sectional view of the device.

  In the light purification device 500 shown in FIG. 7, a columnar ultraviolet lamp 502 is inserted inside the photocatalytic filter 400. By passing a fluid containing contaminants such as contaminated air and contaminated water through the filter portion 410 and turning on the ultraviolet lamp 502, decomposition of the contaminants is promoted in the filter portion 410 by a photocatalytic reaction, and the fluid is purified. On the other hand, since the decomposition of the contaminants and the passage of the fluid take place in the filter portion 410 covered by the skin layer 406, the possibility of leakage from the outside of the apparatus 500, including the light of the ultraviolet lamp 502, is also eliminated.

  In this way, purification of the fluid containing the contaminant can be performed more efficiently and safely.

  EXAMPLES Hereinafter, although an Example demonstrates this invention more concretely, this invention is not limited by these Examples.

Example 1
The phenol resin and silicon powder are mixed in a ratio of 5: 3 by the carbonization of the phenol resin and added to ethyl alcohol to dissolve the phenol resin. In order to reduce the size, a slurry was obtained by mixing with a ball mill for 1 day. Next, 260 mm × 260 mm × (thickness) 20 mm polyurethane sponge was impregnated with this slurry for 1 minute and squeezed by hand with a force that does not block the pores of the sponge.

  Then, the outer peripheral part (four sides) of this sponge was immersed in the said slurry for 1 minute to the width of about 5 mm for every surface. Drawing was not performed after immersion of each surface of the outer periphery.

  The sponge was then dried at 110 ° C. for 3 hours in a drying oven. After drying, this sponge was baked and carbonized at 800 ° C. for 10 minutes under an argon atmosphere, and further melted and impregnated with silicon to obtain a ceramic porous body in which the original sponge was carbonized.

A skin layer filled with Si / SiC is formed on the outer periphery of the obtained porous body over a width of about 5 mm, and the inside is a porous ceramic portion made of Si / SiC in which the sponge skeleton is substantially held. It was confirmed that it was formed. The pore size of the ceramic portion of the obtained porous body was 500 to 600 μm, the open porosity was 97%, and the density was 0.07 g / cm ³ . The density of the skin layer of the obtained porous body was 2.5 g / cm ³ .

  Furthermore, the compressive strength of the porous body obtained in this example was measured according to JIS R 1608. It was confirmed that the compressive strength of the porous body obtained in this example was 1 MPa at the ceramic portion and 10 MPa or more at the skin layer.

(Comparative Example 1)
A ceramic porous body having no skin layer was obtained in the same manner as in Example 1 except that the slurry was not immersed in the outer peripheral portion (four sides) of the sponge.

The obtained porous body (ceramic part) had a pore diameter of 500 to 600 μm, an open porosity of 97%, and a density of 0.07 g / cm ³ .

  Furthermore, the compressive strength of the porous body obtained in this comparative example was measured according to JIS R 1608. The compressive strength of the porous body (ceramic part) obtained in this comparative example was 1 MPa.

  As is clear from the results of Example 1 and Comparative Example 1, the element of Example 1 in which the skin layer was formed had a compressive strength at the outer peripheral portion of 10 times or more of the compressive strength inside (the ceramic portion). Thus, it can be seen that a porous body with improved strength was produced in Example 1.

(Example 2)
A ceramic porous body having no skin layer was obtained in the same manner as in Example 1 except that the slurry was not immersed in the outer peripheral portion (four sides) of the sponge.

  Next, this porous body was immersed in a colloidal solution containing 20% by weight of anatase-type titanium oxide for 5 minutes.

  On the other hand, 60% by weight of alumina powder, 25% by weight of inorganic binder (containing sodium silicate, boron oxide, boric acid, and other glass substances in a predetermined ratio; AEROSIL200 manufactured by Nippon Aerosil Co., Ltd.) and 15% by weight of water are mixed. Then, an alumina slurry was prepared by mixing with a ball mill for 2 hours.

  Then, the outer peripheral part (four sides) of the porous body immersed in the colloidal solution was immersed in the alumina slurry for 1 minute to a width of about 5 mm for each surface and dried at 110 ° C. for 2 hours. Drawing was not performed after immersion of each surface of the outer periphery.

  Subsequently, this porous body was baked for 1 hour at a temperature (500 ° C. to 600 ° C.) at which the anatase-type titanium oxide does not become a rutile type, thereby obtaining a porous body in which alumina was imparted to the skin layer.

The pore size of the ceramic portion other than the skin layer of the obtained porous body was 500 to 600 μm, the open porosity was 97%, and the density was 0.07 g / cm ³ . The density of the skin layer of the obtained porous body was 2.9 g / cm ³ .

  Furthermore, it was confirmed that the compressive strength of the element obtained in this example was 1 MPa in the ceramic portion and 5 MPa or more in the skin layer.

  According to the present invention, a ceramic filter element with improved strength can be obtained. The element obtained by the present invention is useful as an element for a filter such as an air cleaner.

100, 120 Porous structure 102 Second slurry 104 Container 200 Ceramic filter element 202 Ceramic portions 206a, 206b, 206c, 206d, 406 Skin layers 300, 400 Photocatalytic filters 310, 410 Filter surface 500 Light purification device 502 Ultraviolet lamp

Claims (5)

A method for manufacturing a ceramic filter element, comprising:
(A) Applying the first ceramic-forming slurry substantially uniformly to the entire porous structure having two opposing fluid passage surfaces and side portions surrounding the fluid passage surface and containing a carbon source. Process;
(A ′) a step of carbonizing the porous structure; and (b) a step of applying a second slurry to the side surface of the porous structure;
Including in this order .   The method according to claim 1, wherein the first ceramic-forming slurry contains a mixture of a resin having a carbon source and silicon powder, silicon carbide, alumina, zirconia, or a mixture of calcium hydroxide and phosphoric acid. .   The method according to claim 1, wherein the second slurry is a ceramic-forming slurry.   The method according to claim 3, wherein the second slurry contains a mixture of a resin having a carbon source and silicon powder, silicon carbide, alumina, zirconia, or a mixture of calcium hydroxide and phosphoric acid.   The method according to any one of claims 1 to 4, comprising a step of (c) carbonizing the porous structure after the step (b).

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