JP2016043295A - Ceramic filter manufacturing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a technique for improving the corrosion resistance and strength of a seal portion to be applied to the substrate end portion of a ceramic filter.SOLUTION: A ceramic filter comprises: a substrate formed with a fluid passage by a partition wall made of a ceramic porous body; a membrane film formed on the surface of said partition wall; and a seal layer formed on the end part of said substrate. Said seal layer is formed by injecting ceramic particles by an aerosol deposition method.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a method for manufacturing a ceramic filter.

  As shown in FIG. 4, the structure of the ceramic filter 1 is a substrate 4 in which a fluid flow path 3 is formed by a partition wall 2 made of a ceramic porous body, and a filtration membrane 5 is formed on the surface of the partition wall 2. And the structure which gave the glass seal 6 to the edge part of the base material 4 is disclosed (patent document 1).

  The ceramic filter 1 is used by being housed in a housing 8 via an O-ring 7, and the O-ring 7 hermetically isolates the outer peripheral surface and the end of the ceramic filter 1. It has become. Here, as described above, since the end portion of the base material 4 is covered with the glass seal 6, the fluid to be treated is always the flow path 3, as shown by the solid line (F) in FIG. 4. It passes through the filtration membrane 5 formed on the surface of the flow path 3 and flows out from the outer peripheral surface of the base material. According to the structure, as shown by a broken line (F ′) in FIG. 4, the fluid to be treated that has entered the inside of the base material from the end portion of the base material does not pass through the filtration membrane 5, The phenomenon of flowing out from the outer peripheral surface can be avoided and the intended filtration can be reliably performed.

  In addition, since the ceramic filter accumulates on the surface of the filtration membrane 5 with repeated use and the processing capacity as the filter decreases, the ceramic filter is periodically cleaned with a chemical solution such as caustic soda ( Hereinafter, it is referred to as “medicine wash”.

  However, as in Patent Document 1, in the ceramic filter in which the end of the base material 4 is covered with the glass seal 6, the interface between the glass seal and the base material tends to be eroded by repeated chemical washing, and its corrosion resistance. There was a problem that was not enough.

  In addition, after impregnating a ceramic having the same composition as that of the base material or the filtration membrane at the end of the base material of the ceramic filter, an impregnation zone having an average pore diameter of 1 μm or less is formed through each step of drying and firing. A technique for sealing the portion is also disclosed (Patent Document 2).

  However, since the above impregnation zone is composed of a porous material (a material having a large number of pores), there is a problem in that the strength is inferior and the seal surface tends to be chipped.

  In the technique of Patent Document 1, sealing is performed by applying a glass frit slurry to the edge of the base material, drying it, and firing at a high temperature. The end is impregnated with a ceramic having the same composition as the base material or separation membrane, dried, and then sealed by a method of firing at high temperature. there were.

JP 2006-263498 A Japanese Patent Laid-Open No. 61-8106

  The object of the present invention is to solve the above-mentioned problem, and to form a seal at the substrate end portion of the ceramic fill with a simple process and at a low cost. Further, the corrosion resistance and strength of the seal portion to be applied are improved. It is to provide technology that can be improved.

  In the present invention, in order to solve the above problems, a base material in which a fluid flow path is formed by a partition made of a ceramic porous body, a filtration membrane formed on the surface of the partition, and an end of the base material are formed. In the method of manufacturing a ceramic filter for manufacturing a ceramic filter composed of the sealed layer, a configuration is adopted in which the sealing layer is formed by spraying ceramic particles by an aerosol deposition method. The ceramic particles to be ejected preferably have a volume average particle diameter of 0.1 to 3 μm in a volume reference distribution by a laser diffraction / scattering method. Further, the ceramic particles to be ejected are twice the volume average particle diameter. It is preferable to have a sharp particle size distribution such that the volume ratio of the above particle sizes is 10% or less.

  The aerosol deposition method is a known method for forming a dense structure of a brittle material on the surface of a substrate without a heating step. An aerosol in which fine particles of a brittle material or the like are dispersed in a gas is discharged from a nozzle. Injected toward a base material such as metal, glass, ceramics, or plastic, the fine particles collide with the base material, the brittle material fine particles are deformed or crushed by the impact of the collision, and these are joined together. In this method, a structure made of a constituent material of fine particles is directly formed. According to the aerosol deposition method, a structure can be formed at room temperature, and a dense structure having mechanical strength equivalent to that of a fired body can be obtained.

  As described above, in the present invention, a base material in which a fluid flow path is formed by a partition made of a ceramic porous body, a filtration membrane formed on the surface of the partition, and an end of the base material are formed. In the manufacturing method of a ceramic filter for manufacturing a ceramic filter composed of a sealing layer, the sealing layer is formed by spraying ceramic particles by an aerosol deposition method. "Is unnecessary, and the sealing layer can be formed by a simple process while suppressing cost.

  In addition, according to the configuration of the present invention “formed by spraying ceramic particles by the aerosol deposition method”, a sealing layer made of dense ceramics is formed, so the end of the substrate is sealed with a glass seal. Compared with the prior art (the prior art described in Patent Document 1), the corrosion resistance of the seal portion can be improved. Moreover, compared with the prior art (prior art described in Patent Document 2) in which the end of the base material is sealed with a ceramic porous body having the same composition as that of the base material or the filtration membrane, the strength of the sealed portion can be improved.

It is a conceptual diagram which shows the state which filled and used the ceramic filter of this embodiment in the housing, and is the schematic sectional drawing which looked at the cut surface which cut | disconnected the ceramic filter along the central axis from the side. It is the schematic of the aerosol deposition apparatus used for formation of a seal layer. It is the schematic sectional drawing which looked at the cut surface which cut the ceramic filter of Examples 1-12 and comparative examples 1-2 along the central axis from the side. It is explanatory drawing of a prior art.

  Preferred embodiments of the present invention are shown below.

  As shown in FIG. 1, the ceramic filter includes a base material 9 in which a fluid flow path is formed by a partition made of a ceramic porous body, a filtration membrane 10 formed on the surface of the partition wall, and an end of the base material. The seal layer 11 is made of a dense ceramic having a porosity of 10% or less and a crystal mass of the seal layer of 80% or more. In this specification, the “end portion of the base material” means a portion including at least the end surface 32 of the base material and including the side surface 33 of the base material in the vicinity thereof as necessary.

  The base material 9 is a porous body having an average pore diameter of 1 to 30 μm, and a preferable shape thereof is a tube shape having a single flow passage, a honeycomb shape having a large number of parallel flow passages, or a monolith shape. In the present specification, the “average pore diameter of the substrate” means an average pore diameter measured by a mercury intrusion method. The base material 9 is formed by sintering at least the aggregate and the sintering aid (I). For example, the aggregate and the sintering aid (I) are formed into a molding aid such as an organic binder and, if necessary, surface active. A clay made by adding an agent or the like and kneaded is extruded into a double cam shape, dried, and then fired. The firing temperature is preferably 1200 to 1550 ° C., and the firing time at the maximum temperature is preferably 1 to 2 hours. Aggregates are ceramic particles that constitute the main component of the substrate. For example, particles such as alumina, mullite, cordierite, silicon carbide, silicon nitride, aluminum nitride, and ceramic scraps are preferable, so that they are suitable for the purpose of filtration. Is appropriately selected. The average particle diameter of the aggregate is preferably about 5 to 200 μm. The aggregate is preferably contained in an amount of 65 to 90% by mass based on the total of the aggregate and the sintering aid (I), and the sintering aid (I) is preferably contained in an amount of 10 to 35% by mass.

The filtration membrane 10 is a member for ensuring the filtration function of the ceramic filter, and is a ceramic porous body formed on the base material 9 and has an average pore diameter smaller than the average pore diameter of the base material 9. In addition, the “average pore diameter of the filtration membrane” in the present specification means an average pore diameter measured by an air flow method described in ASTM F316.
The filter membrane 10 is formed by applying a raw material containing ceramic particles and preferably a sintering aid (II) onto the base material 9 and firing it. For example, the ceramic particles and the sintering aid (II) are formed. A film-forming slurry dispersed in a dispersion medium such as water and added with an organic binder, a pH adjuster, a surfactant, an antifoaming agent, etc. as necessary is formed on the substrate 9, preferably the fluid to be treated. After being applied to the inner surface of the flow passage and dried, it is fired and formed. Firing is performed at a temperature lower than that of the substrate. The ceramic particles used to form the filtration membrane 10 can be made of the same material as the above-mentioned aggregate, and the particle size is appropriately selected so as to have an appropriate pore size according to the purpose of filtration. . The ceramic particles are preferably contained in an amount of 85 to 95% by mass based on the total of the ceramic particles and the sintering aid, and the sintering aid is preferably contained in an amount of 5 to 15% by mass.

  The seal layer 11 is a member for preventing the fluid to be processed from entering the inside of the base material 9 from the end portion of the base material 9, and is formed so as to cover both end portions of the base material 9. The seal layer 11 can also be formed so as to cover a part of the filtration membrane 10 in the vicinity of both ends of the substrate 9.

  The seal layer 11 is preferably formed of a material having better corrosion resistance than glass, such as alumina, titania, zirconia, etc., and is formed of a ceramic having the same composition as that of the base material 9 or the filter membrane 10 to reduce the difference in thermal expansion. It is more preferable to do so.

  In the present invention, the seal layer 11 is formed using the aerosol deposition apparatus shown in FIG. The aerosol deposition apparatus is roughly composed of an aerosol generating unit 12 that aerosolizes fine particles of a film forming material (solid phase-gas phase state), and a film forming unit 13 that forms a film by injecting aerosol toward a substrate. The film forming unit 13 includes an exhaust system 14 that maintains a reduced-pressure atmosphere.

  The aerosol generator 12 includes an aerosol generator 15, a gas cylinder 16 that supplies a compressed carrier gas to the aerosol generator 15, a mass flow controller 17, and pipes 18, 19, and 20.

  The aerosol generator 15 is connected to a pipe 17 in which ceramic particles 22 are filled in a container 21 and a carrier gas is sent into the container 21 and a pipe 18 that sends out aerosol in which the raised ceramic particles are formed together with the carrier gas. ing. The ceramic particles 22 are preferably filled in the container 21 after sufficiently dehumidifying after adjusting the particle size to about 0.08 to 2 μm. In the present embodiment, the volume average particle diameter is 0.1 to 3 μm in the volume reference distribution by the laser diffraction / scattering method, and the volume ratio of the particle diameter that is twice or more the volume average particle diameter is 10%. The following are used.

  In the aerosol generator 15, since the pipe 17 is inserted into the ceramic particles 22, the ceramic particles 22 rise in the space in the container 21 by the carrier gas supplied from the pipe 17 to form an aerosol. The aerosol is sent to the film forming unit 13 via the pipe 20 via the crusher 23 and the classifier 24 via the pipe 18.

  The gas cylinder 16 is filled with a carrier gas. As the carrier gas, an inert gas such as helium, neon, xenon, krypton, or nitrogen can be used in addition to the argon gas.

  The mass flow controller 17 controls the flow rate of the carrier gas and the flow rate of the aerosol formed by the aerosol generator 15.

  The film forming unit 13 is provided in the film forming chamber 25 with an injection nozzle 26 connected via a pipe 20 and a substrate holding table 28 that faces the injection nozzle 26 and rotatably holds a substrate 27. Further, an XYZθ stage 29 for controlling the position of the base material 27 is connected to the base material holding base 28. The aerosol sprayed from the spray nozzle 26 toward the end portion of the base material 27 collides with the end portion of the base material 27. At the time of this collision, the kinetic energy of the aerosol particles is changed to film formation energy, and a film that is firmly bonded to the substrate is formed. The injection speed is preferably set to 50 m / s to 1000 m / s.

  The spray nozzle 26 is preferably configured to be movable in a three-dimensional direction so that aerosol can be sprayed from all directions toward the substrate. The spray nozzle 26 may be tapered to increase the aerosol flow rate.

  The XYZθ stage 29 may perform a constant speed / repetitive driving operation of the base material holder 28 in a direction perpendicular to the incident direction of the aerosol.

  The exhaust system 14 is connected to the film forming chamber 25 and includes a mechanical booster 30 and a vacuum pump 31 for setting the pressure in the film forming chamber 25 to a reduced pressure atmosphere. It has a function to improve. As the vacuum pump 30, for example, a rotary pump, a diaphragm type vacuum pump, or the like can be used.

  As described above, since the sealing layer is formed by the aerosol deposition method using the aerosol deposition apparatus, firing is not necessary, and thus the sealing layer can be formed by a simple process while suppressing costs. it can.

  If necessary, prior to the formation of the seal layer, a thermal spray coating is formed on the end of the base material by a thermal spraying method for the purpose of smoothing the surface of the base material to be sealed, and the seal layer is formed on the thermal spray coating. In addition, prior to the formation of the seal layer, chamfering treatment can also be performed on the edge portion of the base material passage and the peripheral edge portion of the base material. The formation of the seal layer 11 may be performed after the formation of the filtration membrane 10 or may be performed before the formation of the filtration membrane 10. In addition, after forming the first filtration membrane, a seal layer can be formed, and then a second filtration membrane can be further formed.

  In the present invention, the seal layer 11 is made of a dense ceramic having a porosity of 10% or less and a crystal mass of the seal layer of 80% or more, thereby improving the corrosion resistance and strength of the seal portion. ing. When the porosity exceeds 10%, it is not preferable because the strength is reduced as in the case of sealing with a conventional porous ceramic. When the crystal mass is less than 80%, the amorphous component increases, and the conventional glass As in the case of the seal, the corrosion resistance of the seal portion is lowered, which is not preferable.

  In addition, according to the separation performance required for the ceramic filter, the ceramic filter is subjected to grinding at a position where it comes into contact with the O-ring when used in the housing via the O-ring. You can also.

  EXAMPLES Hereinafter, although an Example demonstrates this invention further in detail, this invention is not limited by a following example. In Examples 1 to 12 and Comparative Examples 1 and 2, as shown in FIG. 3, a base material 9 having a fluid flow path formed by a partition made of a ceramic porous body, and an intermediate film formed on the surface of the partition 34, a filter membrane 10 formed on top of the intermediate membrane 34, and a ceramic filter comprising a seal layer 11 formed so as to cover the end portion of the substrate 9 and a part of the filter membrane 10 in the vicinity thereof. It was created.

  In the examples and comparative examples, the following materials were used. Each of the following “average particle diameters” was measured using a laser diffraction particle size measuring apparatus.

Aggregate: Alumina abrasive with an average particle size of 80 μm Ceramic particle 1: Fine alumina with an average particle size of 3.0 μm (for interlayer film)
Ceramic particles 2: Fine titania with an average particle size of 0.5 μm (for filtration membrane)
Material 1: Material obtained by finely pulverizing and mixing potassium feldspar and kaolin Average particle size 0.8μm
Material 2: Frit obtained by melting and homogenizing glass raw materials shown in Table 1 at 1600 ° C., and pulverizing to 1.0 μm after cooling

(Manufacture of ceramic filters of Examples 1 to 12)
Based on the total mass of the aggregate and the sintering aid, 85 mass% of the aggregate, 15 mass% of the material 1 as the sintering aid, and 4.5 parts by mass with respect to the total of 100 parts by mass. Methylsemellose and 1.0 part by mass of a surfactant were mixed, and a honeycomb-shaped formed body having a plurality of flow paths was obtained by extrusion molding. The molded body was dried and then fired at 1500 ° C. for 2 hours to obtain a substrate 9 having an average pore diameter of 10 μm.

  Next, 14 parts by weight of the frit of the material 2 is added to 100 parts by mass of the ceramic particles 1, and further, water, a dispersant and a thickener are added and mixed, and the slurry is used. A film having a film thickness of 200 μm was formed on the inner peripheral surface of the base material by the filtration film forming method described in Japanese Patent Publication No. 63-66565, and then baked at 950 ° C. for 1 hour in an air atmosphere to form an intermediate film 34. Furthermore, after that, the slurry is adjusted by adding water, a dispersant and a thickener to the ceramic particles 2 and mixing them, and a film is formed on the intermediate film 34 to a film thickness of 20 μm by a filtration film formation method. The filtration membrane 10 was formed by baking at 950 degreeC for 1 hour in air | atmosphere atmosphere.

  Finally, a seal layer was formed under the conditions shown in Table 3 below so as to cover the end portion of the base material 9 and the filtration membrane 10 portion in the vicinity of the end portion.

  Specifically, the AD method (carrier gas is argon, controlled at an injection speed of aerosol particles of 100 to 500 m / s) was used for forming the seal layers of Examples 1 to 12. In Examples 9 and 10, prior to the formation of the seal layer, alumina particles were sprayed onto the end portions of the base material by a spraying method to form a sprayed coating. At this time, the part covering the end surface 32 of the base material 9 is sprayed at a spraying angle of 90 ° with respect to the base material end face, and the part covering the side surface 33 of the base material 9 is spraying angle with respect to the base material end face. Thermal spraying was performed at 0 °. In Example 10, prior to the formation of the seal layer, the chamfering treatment was performed on the edge portion of the base material flow passage and the peripheral edge portion of the base material.

(Manufacture of ceramic filters of Comparative Examples 1 and 2)
In the same manner as in “Examples 1 to 12”, the base material 9, the intermediate membrane 34 and the filtration membrane 10 are formed, and the end portion of the base material 9 and a part of the filtration membrane 10 in the vicinity thereof are covered. Then, a slurry for glass sealing was applied and fired at 950 ° C. for 1 hour to obtain ceramic filters of Comparative Examples 1 and 2.

  Specifically, the glass seal was formed as follows. First, as a frit, a glass raw material shown in Table 2 was melted and homogenized at 1600 ° C., cooled, and then ground to an average particle size of 15 μm. A slurry was prepared by adding water and an organic binder to the frit and mixing them. The slurry was applied to both ends of the ceramic filter, dried, and then fired at 950 ° C. for 1 hour to obtain a ceramic filter with a glass seal.

  Table 3 shows the results obtained by calculating the crystal mass and the porosity of the ceramic filter provided with each seal layer obtained as described above, and evaluating the corrosion resistance and strength. The crystal mass was calculated by a calibration curve method using a standard by X-ray diffraction, and the porosity was calculated by binarization by electron microscope image analysis. Corrosion resistance and strength were evaluated by the following methods.

(Corrosion resistance evaluation method)
As cleaning chemicals, a 2% by mass aqueous citric acid solution and an aqueous sodium hypochlorite solution having an effective chlorine content of 5000 ppm were prepared. After adjusting the liquid temperature of these chemical solutions to 30 ° C., this cycle was repeated a plurality of times, with one cycle consisting of alternately dipping the ceramic filter in each chemical solution for 6 hours. Every 10 soaking operations, the foaming pressure of the glass seal portion was measured according to the bubble point method test described in JIS K3832, and the corrosion resistance of the ceramic filter was evaluated from the change in the value. Specifically, if the foaming pressure of the glass seal portion was 100 kPa or more, it was judged that there was no deterioration of the ceramic filter, and the superiority or inferiority of the corrosion resistance was evaluated based on the number of times until it fell below 100 kPa.

(Strength evaluation method)
A load of 1 kg was applied to an iron pin having a tip R of 0.5 mm, and the seal layer was scratched by moving at a rate of 30 mm / sec.

As shown in Table 3, it was confirmed that all of Examples 1 to 12 in which the seal layer was formed by the AD method showed good corrosion resistance and strength. Among these, in Examples 1 to 11, a “seal layer made of a dense ceramic having a porosity of 10% or less and a crystal mass of the seal layer of 80% or more” is formed, and exhibits particularly good corrosion resistance. confirmed. On the other hand, it was confirmed that in Comparative Example 1 in which the sealing layer was formed through the steps of applying, drying, and firing the glass frit slurry, the corrosion resistance was inferior compared to Examples 1-12. Further, in Comparative Example 2 in which the seal layer was formed through the steps of impregnation, drying and firing of the slurry using alumina particles as a raw material, the porosity was as high as 35%, and cracks were also generated by firing. Therefore, compared with Examples 1-12, it was confirmed that intensity | strength is inferior.

DESCRIPTION OF SYMBOLS 1 Ceramic filter 2 Partition 3 Flow path 4 Base material 5 Filtration membrane 6 Glass seal 7 O-ring 8 Housing 9 Base material 10 Filtration membrane 11 Sealing layer 12 Aerosol generating part 13 Film part 14 Gas system 15 Aerosol generator 16 Sbomb 17 Mass flow Controllers 18, 19, and 20 Piping 21 Container 22 Ceramic particles 23 Crusher 24 Classifier 25 Film forming chamber 26 Injection nozzle 27 Base material 28 Base material holder 29 XYZθ stage 30 Mechanical booster 31 Vacuum pump 32 End face 33 Side face 34 Intermediate film

Claims (7)

A ceramic filter comprising a base material in which a fluid flow path is formed by a partition made of a ceramic porous body, a filtration membrane formed on the surface of the partition, and a seal layer formed on an end of the base is manufactured. A method for producing a ceramic filter, comprising:
A method for producing a ceramic filter, wherein the sealing layer is formed by spraying ceramic particles by an aerosol deposition method.   2. The method for producing a ceramic filter according to claim 1, wherein the ceramic particles have a volume average particle diameter of 0.1 to 3 [mu] m in a volume reference distribution by a laser diffraction / scattering method.   3. The method for producing a ceramic filter according to claim 2, wherein the ceramic particles are those having a volume ratio of 10% or less of a particle size of at least twice the volume average particle size.   The method for producing a ceramic filter according to any one of claims 1 to 3, wherein the seal layer is made of a dense ceramic having a porosity of 10% or less.   The method for producing a ceramic filter according to any one of claims 1 to 4, wherein the seal layer is made of a dense ceramic having a crystal mass of 80% or more.   Prior to the formation of the seal layer, a thermal spray coating is formed on an end portion of the base material by a thermal spraying method, and the seal layer is laminated on the thermal spray coating. Ceramic filter manufacturing method.   The ceramic according to any one of claims 1 to 5, wherein, prior to the formation of the sealing layer, a chamfering process is performed on an edge portion of a flow path entrance / exit of the base material and an outer peripheral edge portion of the base material. A method for manufacturing a filter.