JP2018143957A - Manufacturing method of honeycomb filter - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a manufacturing method of a honeycomb filter having a wall part which is suitable for collecting fine particles.SOLUTION: A manufacturing method of a honeycomb filter 10, which has a plurality of cells S partitioned by a wall part 13 and extending from one end side to the other end side and is used to collect fine particles, includes: a molding process of preparing a honeycomb molding having the wall part 13 by molding a mixture containing ceria-zirconia compound oxide particles and an inorganic binder; a sealing process of sealing an end part on one side of the cell; a firing process of preparing a honeycomb fired body 10A by firing the honeycomb molding; and a pore forming process of forming a pore passing through the wall part 13 by piercing a needle 22 to the wall part 13 of the honeycomb molding or the honeycomb fired body 10A.SELECTED DRAWING: Figure 3

Description

  The present invention relates to a method for manufacturing a honeycomb filter used for collecting fine particles.

  Patent Document 1 discloses a honeycomb filter made of silicon carbide as a honeycomb filter used for collecting fine particles. Patent Document 2 discloses an exhaust gas purification catalyst in which a noble metal is supported on a monolith substrate containing ceria-zirconia composite oxide particles. It is described that the base material is composed of ceria-zirconia composite oxide particles to reduce the heat capacity, to easily raise the temperature of the monolith base material, and to improve the warm-up performance of the catalyst.

International Publication No. 2006/041174 Japanese Patent Laying-Open No. 2015-85241

  By the way, in order to improve the warm-up performance of the honeycomb filter disclosed in Patent Document 1, a substrate containing ceria-zirconia composite oxide particles disclosed in Patent Document 2 is adopted as the wall portion of the honeycomb filter. Can be considered. However, since the base material containing the ceria-zirconia composite oxide particles disclosed in Patent Document 2 cannot pass a gas containing fine particles almost as a wall portion of a honeycomb filter that collects fine particles. Is unsuitable. The silicon carbide particles are recrystallized to form pores between the particles. However, since the ceria-zirconia composite oxide particles are bonded with an inorganic binder, the gas has an appropriate size for the gas to pass between the particles. This is because pores are not formed. In addition, a configuration in which a wall portion made of a substrate such as silicon carbide is covered with a ceria-zirconia composite oxide is also conceivable, but the amount of ceria-zirconia composite oxide supported is limited to a range that can be covered on the wall portion. The effect of improving exhaust gas purification performance is small. The present invention has been made in view of such circumstances, and an object thereof is to provide a method for manufacturing a honeycomb filter having a wall portion that is excellent in warm-up performance, has low pressure loss, and is suitable for collecting fine particles. It is in.

  A method for manufacturing a honeycomb filter according to the present invention for solving the above-described problem has a plurality of cells that are partitioned by a wall portion and extend from one end side to the other end side. A forming step of forming a honeycomb formed body having the wall portion by forming a mixture containing ceria-zirconia composite oxide particles and an inorganic binder, and a sealing step for sealing one end portion of the cell. A firing step in which the honeycomb formed body is fired to produce a honeycomb fired body, and a needle is pierced into the wall portion of the honeycomb formed body or the honeycomb fired body to form pores penetrating the wall portion. And a pore forming step.

  According to this configuration, the ceria-zirconia composite oxide particles are included as a constituent by having a pore forming step of piercing the needle into the wall portion of the honeycomb formed body or the honeycomb fired body to form pores penetrating the wall portion. The gas permeability of the wall part which consists of a base material to perform can be improved. As a result, a honeycomb filter having excellent wall warm-up performance and low pressure loss and having a wall portion suitable for collecting fine particles can be manufactured.

  In the method for manufacturing a honeycomb filter of the present invention, it is preferable that the diameter of the needle is 50 to 200 μm. According to this configuration, pores suitable for collecting fine particles can be formed based on the diameter of the needle.

In the method for manufacturing a honeycomb filter of the present invention, it is preferable that one pore is formed per area 0.25 to 10 mm ^{2 of the} wall portion. According to this structure, since the volume of the pores penetrating the wall portion is sufficient, it is possible to satisfy a reduction in pressure loss and high collection performance.

  Regarding the method for manufacturing a honeycomb filter of the present invention, the mixture preferably contains alumina particles. According to this configuration, the supported catalyst can be highly dispersed, the gas purification performance can be improved, and a honeycomb filter having high mechanical strength in a high temperature state can be manufactured.

  In the method for manufacturing a honeycomb filter of the present invention, the pore forming step is preferably a step of piercing the heated needle into the honeycomb formed body to form the pores. According to this configuration, it is possible to pierce the needle while vaporizing volatile components such as organic components contained in the honeycomb formed body, and therefore it is possible to reduce resistance when the needle is pierced. In addition, since the voids are not formed between the ceria-zirconia particles in the wall portion in the honeycomb formed body, the strength as a base material is high, and when the needle is stuck, the pores are maintained while maintaining the shape of the wall portion suitably. Can be formed.

  In the method for manufacturing a honeycomb filter of the present invention, it is preferable to use a jig having a base and a plurality of needles protruding from the base in the pore forming step. According to this configuration, since a plurality of needles can be pierced simultaneously by using a jig, a plurality of pores can be efficiently formed.

  In the method for manufacturing a honeycomb filter of the present invention, the sealing step is preferably performed after the pore forming step. According to this configuration, it is possible to easily remove the dust generated in the pore forming step from the end of the cell.

  According to the present invention, it is possible to manufacture a honeycomb filter having excellent wall warm-up performance and low pressure loss and having a wall portion suitable for collecting fine particles.

The perspective view of a honey-comb filter. FIG. 2 is a sectional view taken along line 2-2 in FIG. 1. (A) is a perspective view of a jig for forming pores in the honeycomb filter, (b) is a front view of the jig for forming pores in the honeycomb filter, and (c) is formed in the honeycomb filter by the jig. Explanatory drawing which shows a pore. (A), (b) is a schematic diagram which shows the direction which penetrates a needle.

Hereinafter, an embodiment of the present invention will be described.
First, the honeycomb filter manufactured by the manufacturing method of the present invention will be described.
As shown in FIG. 1, the honeycomb filter 10 of the present embodiment has a cylindrical peripheral wall 11 and a cross section that divides the inside of the peripheral wall 11 into a plurality of cells S extending from one end side to the other end side in the axial direction of the peripheral wall 11. And a partition wall 12 having a honeycomb shape. A wall portion 13 is constituted by the peripheral wall 11 and the partition wall 12. Although the cell structure of the honeycomb filter 10 is not particularly limited, for example, the wall thickness of the partition walls 12 is 0.1 to 0.7 mm, a cell density of 1 cm ² per 15.5 to 124 cells cells It can be a structure. The above “0.1 to 0.7 mm” means “0.1 mm to 0.7 mm”, and “A to B” means “A to B”.

  The wall 13 is formed of a base material containing ceria-zirconia composite oxide (hereinafter also referred to as “CZ composite oxide”), an inorganic binder, and alumina as constituent components. That is, the base material constituting the wall portion 13 contains a CZ composite oxide, an inorganic binder, and alumina. And the catalyst of noble metals etc. is carry | supported on the surface of the particle | grains which comprise a base material.

  Examples of the catalyst supported on the base material include noble metals, alkali metals (element periodic table group 1), alkaline earth metals (element periodic table group 2), rare earth elements (element periodic table group 3), and transition metal elements. Is preferably a noble metal. Examples of the noble metal include platinum group metals such as platinum, palladium, and rhodium. The amount of the noble metal supported is not particularly limited, but is preferably 0.1 to 20 g / L, more preferably 0.5 to 15 g / L with respect to the apparent volume (L) of the honeycomb filter 10. .

  As shown in FIG. 2, the end of a predetermined cell S among the plurality of cells S is sealed with a sealing portion 14. That is, the honeycomb filter 10 includes, as the cell S, a first cell S1 in which an end portion on one end side is opened and an end portion on the other end side is sealed, and an end portion on one end side adjacent to the first cell S1. Is sealed and the second cell S2 is opened at the other end. Since the first cell S1 and the second cell S2 are sealed at different ends, the gas flowing into the first cell S1 from one end side, as shown by the arrows, is separated from the first cell S1 and the second cell S2. It passes through the inside of the wall portion 13 between the cells S2 and flows out from the other end side of the second cell S2. At this time, fine particles are collected on the surface of the wall portion 13 on the first cell S1 side.

  Further, the honeycomb filter 10 has a cell S as a third cell S3 adjacent to at least one of the first cell S1 and the second cell S2 and having both one end and the other end opened. May be further provided. The gas flowing in from the end portion on the one end side of the third cell S3 can pass through the surface of the wall portion 13 and flow out from the end portion on the other end side of the same third cell S3. When the third cell S3 is adjacent to the first cell S1, the gas flowing into the first cell S1 from one end side passes through the inside of the wall portion 13 between the first cell S1 and the third cell S3. It can also flow out from the other end side of the third cell S3. By providing the third cell, the pressure loss of the honeycomb filter 10 can be reduced.

  The arrangement position of the third cell S3 is appropriately selected in a range adjacent to at least one of the first cell S1 and the second cell S2. For example, as shown in FIG. 2, a cell S having a small cross-sectional area on the outer peripheral side of the honeycomb filter 10 can be set as the third cell S3. Further, the ratio of the third cells S3 to all the cells S is not particularly limited, but is preferably 1/3 or less.

  As shown in FIG. 2, the length T of the sealing portion 14 is not particularly limited, but is preferably thicker than the wall thickness of the partition wall 12. Moreover, when the wall thickness of the partition wall 12 is 0.1-0.7 mm, it is preferable that the length T of the sealing part 14 is 1-10 mm.

  The honeycomb filter 10 of the present embodiment is used for collecting fine particles contained in a gas discharged from an internal combustion engine such as a vehicle or a construction machine. Therefore, the partition wall 12 has pores for allowing the gas to be processed to pass therethrough. The partition wall 12 having pores for passing the gas to be processed is, for example, a wall portion that satisfies a specific gas permeability coefficient described below.

The specific gas permeability coefficient is, for example, 1.0 μm ² or more and 3.0 μm ² or less.
The gas permeability coefficient can be measured by, for example, the following method using a known mass flow meter.

  First, the honeycomb filter 10 is disposed in an airtight state in a metal pipe, and air is circulated through the honeycomb filter 10 through the metal pipe. Then, an air pressure difference ΔP before and after the honeycomb filter 10 is measured. The measurement of the pressure difference ΔP is performed with respect to the air flow rate at 20 points by changing the air flow rate Q flowing into the honeycomb filter 10 in a range of 0 to 80 L / min using a known mass flow meter. The obtained 20 points of data are plotted on a graph with Q as the horizontal axis and ΔP / Q as the vertical axis, and the gas permeation coefficient is obtained from the intercept of the line connecting the plots.

  The porosity of the partition wall 12 is not particularly limited, but is preferably 50 to 80%, and more preferably 55 to 75%. Although the porosity of the sealing part 14 is not specifically limited, It is preferable that it is 40 to 80%, and it is more preferable that it is 40 to 75%. The porosity of the partition wall 12 can be measured by a mercury intrusion method with a contact angle of 130 ° and a surface tension of 485 mN / m.

  Next, a method for manufacturing the honeycomb filter 10 will be described. The manufacturing method of this embodiment has a mixing process, a molding process, a sealing process, a firing process, a pore forming process, and a supporting process described below.

(Mixing process)
The mixing step is a step of preparing a mixture by mixing a raw material composition having CZ composite oxide particles, an inorganic binder, and alumina particles. As the CZ composite oxide particles, it is preferable to use a solid solution of ceria and zirconia. The solid solution of ceria and zirconia is, for example, by adding ammonia water to an aqueous solution in which a cerium salt such as cerium nitrate and a zirconium salt such as zirconium oxynitrate is dissolved to form a coprecipitate, and the resulting precipitate is dried. And then calcining at 400 to 500 ° C. for about 5 hours.

  The CZ composite oxide particles of the present invention preferably contain 10% by mass or more of ceria, more preferably 20% by mass or more. Moreover, it is preferable to contain 70 mass% or less of ceria, and it is more preferable to contain 60 mass% or less. By containing 10% by mass or more of ceria, the ability to occlude and release oxygen in the gas to be processed is increased, and by setting it to 70% by mass or less, thermal durability is increased.

  The CZ composite oxide particles may further contain an element selected from rare earth elements other than cerium. As rare earth elements, scandium (Sc), yttrium (Y), lanthanum (La), praseodymium (Pr), neodymium (Nd), samarium (Sm), gadolinium (Gd), terbium (Tb), dysprosium (Dy), Examples thereof include ytterbium (Yb) and lutetium (Lu).

The average particle size of the CZ composite oxide particles used as the raw material composition is not particularly limited, but is preferably 1 to 10 μm, and more preferably 1 to 5 μm.
Examples of the inorganic binder include alumina sol, silica sol, titania sol, water glass, sepiolite, attapulgyro, bentonite, and boehmite. Although the ratio of the inorganic binder in the mixture is not particularly limited, it is preferably 10 to 30% by mass.

  Examples of the alumina particles include θ-phase alumina particles (hereinafter also referred to as “θ-alumina particles”) and γ-phase alumina particles (hereinafter also referred to as “γ-alumina particles”). The θ-alumina particles are suppressed in phase transition even when exposed to a high temperature of about 1000 ° C. Therefore, by using the θ-alumina particles as a constituent component of the base material of the wall portion 13, the honeycomb filter 10 in a high temperature state is used. Mechanical strength is improved. The γ-alumina particles have a high specific surface area and can highly disperse a noble metal used as a catalyst. The ratio of the alumina particles in the mixture is not particularly limited, but is preferably 10 to 50% by mass. The average particle diameter of the alumina particles is not particularly limited, but the secondary particles are preferably 1 to 10 μm, and more preferably 1 to 5 μm. The average particle diameter can be measured with a laser diffraction particle size distribution analyzer.

  As needed, other inorganic particles other than CZ composite oxide particles and alumina particles, inorganic fibers, organic fibers, organic binders, pore formers, molding aids, and dispersion media are added to the raw material composition.

  As other inorganic particles, it is preferable to use particles having a smaller thermal expansion coefficient than CZ composite oxide particles and alumina particles (hereinafter also referred to as “low thermal expansion coefficient particles”). When the low thermal expansion coefficient particles are contained, the thermal expansion coefficient of the base material of the wall portion 13 can be reduced, so that the thermal shock resistance of the honeycomb filter 10 is improved. As the low thermal expansion coefficient particles, cordierite, aluminum titanate, lithium aluminosilicate-based material can be used. Examples of lithium aluminosilicate materials include β-spodumene and β-eucryptite.

Examples of the material constituting the inorganic fiber include alumina, silica, silica alumina, and glass.
Examples of the material constituting the organic fiber include acrylic fiber and polyester fiber. Although the dimension of an organic fiber is not specifically limited, It is preferable that a diameter is 1-50 micrometers, and it is more preferable that it is 3-40 micrometers. Moreover, it is preferable that length is 0.1-30 mm, and it is more preferable that it is 0.1-10 mm.

  Examples of the organic binder include methyl cellulose, carboxymethyl cellulose, hydroxyethyl cellulose, polyethylene glycol, phenol resin, and epoxy resin.

Examples of the pore-forming agent include acrylic resin, coke, and starch.
Examples of the molding aid include ethylene glycol, dextrin, fatty acid, fatty acid soap, polyalcohol, and surfactant.

Examples of the dispersion medium include water, organic solvents such as benzene, and alcohols such as methanol.
The raw material composition may be mixed using a known mixer or attritor, and may be further kneaded with a kneader.

(Molding process)
The forming step is a step of forming a honeycomb formed body by forming the mixture obtained in the mixing step. The honeycomb formed body is produced by, for example, extruding a mixture using an extrusion die and cutting it into a predetermined length so as to have the same shape as the honeycomb filter 10 through firing contraction in a subsequent firing step. That is, it is manufactured by extruding the base material constituting the peripheral wall 11 and the partition wall 12 of the honeycomb filter 10 at a time.

(Sealing process)
The sealing step is a step of forming the sealing portion 14 by filling the end portion of the cell S of the honeycomb formed body obtained by the forming step with a sealing material paste. As the sealing material paste, the same paste as the above mixture can be used. The honeycomb formed body in which the sealing portion 14 is formed by the sealing process is dried as necessary. The first cell S1, the second cell S2, and the third cell S3 can be formed by appropriately selecting the cell S filled with the sealing material paste.

(Baking process)
The firing step is a step of firing the honeycomb formed body to produce a honeycomb fired body. The mechanical strength of the honeycomb fired body is improved by bonding the particles of CZ composite oxide or the like with an inorganic binder by firing. The firing step can be performed using a known single furnace, a so-called batch furnace, or a continuous furnace. Although a calcination temperature is not specifically limited, 800-1300 degreeC is preferable and it is more preferable that it is 900-1200 degreeC. Although baking time is not specifically limited, It is preferable to hold | maintain for 1 to 20 hours in said baking temperature, and it is more preferable to hold | maintain for 1 to 15 hours. The firing atmosphere is not particularly limited, but the oxygen concentration is preferably 1 to 20%.

  In addition, when the honeycomb formed body contains organic components such as organic fibers and an organic binder, a degreasing process is performed before the firing process. A degreasing process can be performed using a well-known single furnace, what is called a batch furnace, and a continuous furnace. The degreasing temperature is not particularly limited, but is preferably 300 to 800 ° C, and more preferably 400 to 750 ° C. The degreasing time is not particularly limited, but the degreasing temperature is preferably maintained for 1 to 10 hours, more preferably 2 to 5 hours. The degreasing atmosphere is not particularly limited, but the oxygen concentration is preferably 0.1 to 20%. The degreasing step may be performed separately using a furnace different from the firing step, or may be performed continuously using the same furnace as the firing step.

(Pore formation process)
The pore forming step is a step of forming pores penetrating the partition wall 12 in the partition wall 12 of the honeycomb fired body using a needle. As shown in FIGS. 3A and 3B, in this step, a base 21 along a part (half circumference) of the outer peripheral surface of the honeycomb fired body 10A and a plurality of needles 22 protruding from the base 21 are provided. A pair of jigs 20 provided is used. The thickness of the vertical wall 12A when both sides of the honeycomb fired body 10A in the radial direction, specifically, the wall extending in one direction in the partition wall 12 is the vertical wall 12A and the wall intersecting the vertical wall 12A is the horizontal wall 12B. The honeycomb fired body 10A is sandwiched between the pair of jigs 20 from both sides in the vertical direction. And as shown to Fig.4 (a), after piercing the needle 22 so that the needle 22 may penetrate each vertical wall 12A, the jig | tool 20 is removed from 10 A of honeycomb fired bodies. Thereby, pores penetrating through the vertical wall 12A of the partition wall 12 of the honeycomb fired body 10A in the thickness direction are formed.

  Further, as shown in FIG. 4 (b), if necessary, the operation of sandwiching the honeycomb fired body 10A with the pair of jigs 20 is performed in the same manner from both sides of the partition wall 12 in the thickness direction of the lateral wall 12B. The pores penetrating the lateral wall 12B of the partition wall 12 in the thickness direction may be formed.

  The diameter of the needle 22 of the jig 20 is set to 50 to 200 μm. Therefore, the diameter of the pores penetrating the partition wall 12 formed by the needle 22 is also 50 to 200 μm. By selecting the diameter of the needle 22, the diameter of this pore can be adjusted. The diameters of the needles 22 may all be the same, or may be different within the above range. Note that the diameter of the pores penetrating the partition wall 12 can be measured by observing the surface of the partition wall 12 with an electron microscope.

In addition, the number of pores formed in this step is not particularly limited, but for example, it is preferably 1 per 0.25 to 10 mm ^{2 on} the surface of the partition wall 12.
Moreover, you may change suitably the position and the number of the needles 22 with which the jig | tool 20 is equipped. For example, as shown in FIG. 3C, when the distance L between the individual needles 22 is about 1 cm and the direction in which the cells S extend and the direction in which the needles 22 are aligned are aligned, about 1 cm along the direction in which the cells S extend. The pores can be formed at intervals.
A honeycomb filter having a wall portion suitable for collecting fine particles, comprising a base material containing CZ composite oxide as a constituent component through the mixing step, molding step, sealing step, firing step, and pore forming step. 10 can be manufactured.

(Supporting process)
The supporting step is a step of further supporting the catalyst on the honeycomb filter 10 in which the pores are formed by the pore forming step. Examples of the method for supporting the catalyst include a method in which the honeycomb filter 10 is immersed in a solution containing catalyst particles and a complex, and then the honeycomb filter 10 is pulled up and heated. By supporting the catalyst, the wall portion 13 of the honeycomb filter 10 includes a base material containing a CZ composite oxide as a constituent component and a catalyst supported on the base material.

The operation and effect of this embodiment will be described.
(1) A wall portion made of a base material containing ceria-zirconia composite oxide particles as a constituent component by having a pore forming step of piercing a needle into the wall portion of the honeycomb fired body to form pores penetrating the wall portion The gas permeability can be improved. Therefore, it is possible to manufacture a honeycomb filter having excellent wall warm-up performance and low pressure loss and having a wall portion suitable for collecting fine particles.

  In addition, as a method for forming pores in the wall portion, a method using a laser instead of a needle is also conceivable. However, this method is suitable for a ceramic substrate having a relatively high strength. When a substrate made of ceria-zirconia composite oxide particles and an inorganic binder is used as a target, the shape of the wall portion is changed. It is difficult to form pores while keeping it suitable. According to the above method using a needle, the occurrence of such a problem can be suppressed.

(2) The needle has a diameter of 50 to 200 μm. Therefore, pores suitable for collecting fine particles can be formed based on the diameter of the needle.
(3) One pore is formed per 0.25 to 10 mm ^{2 of the} wall area. Therefore, the volume of the pores penetrating the wall becomes sufficient, and the pressure loss can be reduced and the high collection performance can be satisfied.

(4) The mixture includes alumina particles. Therefore, it is possible to produce a honeycomb filter that can disperse the supported catalyst highly and has high mechanical strength in a high temperature state.
(5) A jig having a base and a plurality of needles protruding from the base is used in the pore forming step. Since a plurality of needles can be pierced simultaneously by using a jig, a plurality of pores can be efficiently formed.

The present embodiment can be implemented with the following modifications. Moreover, it is also possible to implement combining the structure of the said embodiment and the structure shown in the following modified examples suitably.
The pore forming step may be performed on the honeycomb formed body before the firing step. Further, the honeycomb formed body may have been subjected to a sealing process. Moreover, when performing a pore formation process with respect to a honeycomb molded object, it is preferable to pierce a honeycomb molded object with the heated needle and to form a pore. In this case, if a needle heated to a temperature higher than the temperature at which volatile components such as organic components contained in the honeycomb molded body are vaporized is used, the needle can be pierced while vaporizing the volatile component, so that resistance when the needle is pierced Can be reduced. In addition, since the voids are not formed between the ceria-zirconia particles in the wall portion in the honeycomb formed body, the strength as a base material is high, and when the needle is stuck, the pores are maintained while maintaining the shape of the wall portion suitably. Can be formed. The heating temperature of the needle is not particularly limited, but is preferably 200 to 500 ° C.

  -You may perform a sealing process after a degreasing process, a baking process, and a pore formation process. In particular, by performing the sealing step after the pore forming step, debris generated in the pore forming step can be easily removed from the end of the cell.

  -It may replace with the aspect which pierces a needle from the both sides of the radial direction of a honeycomb calcination object using a pair of jigs, and may pierce the needle from only one side of the diameter of a honeycomb calcination object.

  -In this embodiment, although the surrounding wall and the partition wall were shape | molded simultaneously in the formation process, you may shape | mold only a partition wall. In this case, for example, an outer peripheral coat layer may be formed on the outer periphery of the partition wall after the firing step.

  -A 3rd cell does not need to be formed in a sealing process. That is, the sealing portion may be formed so that all cells are sealed at either one end or the other end. With this configuration, the collection efficiency of the honeycomb filter can be improved.

  -The mixture produced at the mixing process may not contain alumina particles.

Hereinafter, examples in which the above embodiment is further embodied will be described.
Example 1
The following raw material composition was mixed to prepare a mixture.

CZ composite oxide particles having an average particle diameter of 2 μm: 28.0% by mass
Θ-alumina particles having an average particle diameter of 2 μm: 14.0% by mass
Α-alumina fiber (inorganic fiber) having an average fiber diameter of 3 μm and an average fiber length of 60 μm: 6.0% by mass
Boehmite (inorganic binder): 11.0% by mass
Methyl cellulose (organic binder): 8.0% by mass
Polyoxyethylene oleyl ether (molding aid): 5.0% by mass
Ion exchange water (dispersion medium): 28.0% by mass
Using this mixture, a cylindrical molded body was molded by an extruder. Next, this molded body is cut to a predetermined length to produce a honeycomb molded body, and then the end of a predetermined cell is sealed with a sealing agent to form a sealed portion as shown in FIG. did. The composition of the sealing agent is the same as that of the above mixture. Moreover, the length of the sealing part was about 3 mm. Next, the honeycomb formed body was dried, degreased at 700 ° C. for 3 hours, and fired at 1100 ° C. for 10 hours to prepare a honeycomb fired body. As shown in FIG. 3, the honeycomb fired body was sandwiched from both sides, and needles were pierced into the wall portion. The diameter of the pores formed by the needle was about 100 μm, and the number of pores formed by the needle was 4 / mm ² as the number per unit area on the surface of the partition wall.

Next, dinitrodiammine palladium nitrate solution ([Pd (NH ₃ ) ₂ (NO ₂ ) ₂ ] HNO ₃ , palladium concentration 100 g / L) solution, rhodium nitrate solution ([Rd (NO ₃ ) ₃ ], rhodium concentration 50 g / L) L) was prepared by mixing at a volume ratio of 3: 1 solution. The honeycomb filter manufactured by the above process was immersed in this mixed solution and held for 15 minutes. Then, it dried at 110 degreeC for 2 hours, and baked at 500 degreeC in nitrogen atmosphere for 1 hour, and carry | supported the palladium catalyst and the rhodium catalyst. The amount of catalyst supported was 0.14 g / L per apparent volume of the honeycomb filter in total of palladium and rhodium. The obtained honeycomb filter had a cylindrical shape with a diameter of 117 mm and a length of 80 mm, a cell density of 46 cells / cm ² (300 cpsi), and a wall thickness of 0.254 mm (10 mil).

(Measurement of gas permeability coefficient)
The gas permeability coefficient was measured using the honeycomb filter of Example 1. First, the honeycomb filter was disposed in an airtight state in a metal tube, and air was circulated through the honeycomb tube through the metal tube. The air pressure difference ΔP before and after the honeycomb filter was measured. The measurement of the pressure difference ΔP was performed with respect to the air flow rate at 20 points by changing the air flow rate Q flowing into the honeycomb filter in a range of 0 to 80 L / min using a known mass flow meter. The obtained 20 points of data were plotted on a graph with Q as the horizontal axis and ΔP / Q as the vertical axis, and the gas permeability coefficient k was determined from the intercept of the straight line connecting the plots. As a result, the gas permeation coefficient of the honeycomb filter of Example 1 was 2.8 μm ² . From this result, it was confirmed that the honeycomb filter of Example 1 functions as a filter for collecting fine particles.

  DESCRIPTION OF SYMBOLS 10 ... Honeycomb filter, 11 ... Perimeter wall, 12 ... Partition wall, 13 ... Wall part, 14 ... Sealing part, 22 ... Needle, 10A ... Honeycomb fired body, S ... Cell.

Claims (7)

A method of manufacturing a honeycomb filter having a plurality of cells partitioned from a wall and extending from one end side to the other end side, and used for collecting fine particles,
A molding step of forming a honeycomb molded body having the wall by molding a mixture containing ceria-zirconia composite oxide particles and an inorganic binder,
A sealing step of sealing one end of the cell;
A firing step of firing the honeycomb formed body to produce a honeycomb fired body;
A method for manufacturing a honeycomb filter, comprising: a pore forming step of forming a pore penetrating the wall portion by piercing a needle into the wall portion of the honeycomb formed body or the honeycomb fired body.   The method for manufacturing a honeycomb filter according to claim 1, wherein the needle has a diameter of 50 to 200 µm. The method for manufacturing a honeycomb filter according to claim 1 or 2, wherein one pore is formed per area 0.25 to 10 mm ^{2 of the} wall portion.   The method for manufacturing a honeycomb filter according to any one of claims 1 to 3, wherein the mixture includes alumina particles.   The method for manufacturing a honeycomb filter according to any one of claims 1 to 4, wherein the pore forming step is a step of piercing the heated needle into the honeycomb formed body to form the pores.   In the said pore formation process, the manufacturing method of the honey-comb filter as described in any one of Claims 1-5 using the jig | tool which has a base and the some needle which protrudes from the said base.   The method for manufacturing a honeycomb filter according to any one of claims 1 to 6, wherein the sealing step is performed after the pore forming step.

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