CN218166340U

CN218166340U - Honeycomb filter

Info

Publication number: CN218166340U
Application number: CN202221536771.9U
Authority: CN
Inventors: 伊藤匡人; 井爪将
Original assignee: NGK Insulators Ltd
Current assignee: NGK Insulators Ltd
Priority date: 2022-06-20
Filing date: 2022-06-20
Publication date: 2022-12-30
Anticipated expiration: 2032-06-20

Abstract

The utility model provides a can alleviate the honeycomb filter of the thermal stress that produces in hole sealing portion. The honeycomb filter is provided with: columnA honeycomb structure (4) having porous partition walls (1) arranged so as to surround a plurality of cells (2), the plurality of cells (2) forming fluid flow paths extending from an inlet end surface (11) to an outlet end surface (12); and a porous sealing portion (5) disposed at either one of an end portion on the inflow end face (11) side or an end portion on the outflow end face (12) side of the cell (2), wherein the sealing portion (5) is composed of a plurality of particles and has a size of 0.25 [ mu ] m in a processed image obtained by binarizing an electron microscope image of a field region of 480 [ mu ] m × 640 [ mu ] m of the sealing portion (5) ² The number of particles having the area of 1000 or more is 3500 or less.

Description

Honeycomb filter

Technical Field

The utility model relates to a honeycomb filter. More specifically, the present invention relates to a honeycomb filter capable of relaxing thermal stress generated at a sealing portion for sealing openings of cells.

Background

Conventionally, as a filter for trapping particulate matter in exhaust gas discharged from an internal combustion engine such as an engine of an automobile or a device for purifying toxic gas components such as CO, HC, and NOx, a honeycomb filter using a honeycomb structure is known (see patent document 1). The honeycomb structure has partition walls made of porous ceramic such as cordierite, and a plurality of cells are partitioned by the partition walls. The honeycomb filter is obtained by disposing plugging portions in the honeycomb structure so that the openings of the plurality of cells on the inflow end surface side and the openings of the plurality of cells on the outflow end surface side are alternately plugged. That is, the honeycomb filter has a structure in which inflow cells having an open inflow end surface side and a closed outflow end surface side are alternately arranged with partition walls interposed therebetween, and outflow cells having a closed inflow end surface side and an open outflow end surface side are alternately arranged. In the honeycomb filter, the porous partition walls function as a filter for collecting particulate matter in the exhaust gas. Hereinafter, the particulate matter contained in the exhaust gas may be referred to as "PM". "PM" is an abbreviation for "particulate matter".

The purification of exhaust gas by the honeycomb filter is performed as follows. First, the honeycomb filter is configured to: the inflow end surface side thereof is located on the upstream side of the exhaust system from which exhaust gas is discharged. The exhaust gas flows into the inflow cells from the inflow end surface side of the honeycomb filter. The exhaust gas flowing into the inflow cells flows through the porous partition walls, flows into the outflow cells, and is discharged from the outflow end surface of the honeycomb filter. When passing through the porous partition walls, PM and the like in the exhaust gas are collected and removed. In addition, an oxidation catalyst for promoting PM oxidation (combustion), an exhaust gas purification catalyst for purifying harmful components such as NOx, and the like are sometimes carried on such a honeycomb filter.

Documents of the prior art

Patent document

Patent document 1: japanese patent laid-open publication No. 2017-145171

SUMMERY OF THE UTILITY MODEL

In recent years, exhaust gas regulations for gasoline-powered vehicles have become more stringent year by year. Therefore, there is a need to improve the performance of honeycomb filters for gasoline-powered vehicles. Further, a honeycomb filter is used by carrying an exhaust gas purifying catalyst, but as the amount of the catalyst carried increases, a demand for a honeycomb filter having a high porosity increases. Thin-walled honeycomb filters aimed at reducing pressure loss have also been developed as honeycomb filters for diesel engines.

If the removal of PM in the exhaust gas is continued by the honeycomb filter, PM accumulates inside the honeycomb filter, so that the pressure loss of the honeycomb filter increases. Therefore, in the purification apparatus using the honeycomb filter, the PM accumulated in the honeycomb filter is burned by an automatic or manual operation, thereby preventing an excessive pressure loss of the honeycomb filter. Hereinafter, the operation of burning the PM accumulated inside the honeycomb filter is sometimes referred to as "regeneration operation" of the honeycomb filter. In the regeneration operation of the honeycomb filter, since the PM accumulated in the interior of the honeycomb filter is forcibly burned, the interior of the honeycomb filter is brought into a high-temperature state. Therefore, the honeycomb filter may be damaged by heat generation during the regeneration operation, and particularly, for a honeycomb filter having a high porosity, it is desired to develop a honeycomb filter capable of relaxing thermal stress generated at the plugged portions during the regeneration operation. For example, patent document 1 discloses a technique of preventing the end portions of the cells from cracking and suppressing the plugging portions from falling off from the cells by specifying the young's modulus and the porosity of the plugging portions. In the technique described in patent document 1, it is desired to further improve the thermal shock resistance of the plugged portion.

The present invention has been made in view of the above problems of the prior art. According to the utility model discloses, provide the honeycomb filter that can alleviate the thermal stress that produces in hole sealing portion when regeneration operation.

According to the utility model discloses, the honeycomb filter who provides below is provided.

[1] A honeycomb filter is provided with:

a columnar honeycomb structure having porous partition walls arranged so as to surround a plurality of cells forming fluid flow paths extending from an inflow end surface to an outflow end surface; and

a porous sealing portion disposed at either one of an end portion on the inflow end surface side or an end portion on the outflow end surface side of the cell,

the hole sealing part is composed of a plurality of particles and has a diameter of 0.25 μm in a processed image obtained by binarizing an electron microscope image of a 480 μm × 640 μm field region of the hole sealing part ² The number of particles having the area of 1000 or more is 3500 or less.

[2] The honeycomb filter according to [1], wherein,

in the processed image, has a thickness of 0.25 μm ² The average area of the particles of the above area is 20 μm ² Above 90 μm ² The following.

[3] The honeycomb filter according to [1] or [2], wherein,

in the processed image, the porosity of the plugged portion is 40% or more and 75% or less.

[4] The honeycomb filter according to [1] or [2], wherein,

the processed image has a size of 0.25 μm ² In the particle size distribution based on the number of the particles having the above area, the area of the particles having a particle diameter d90 at a cumulative value of 90% is 5 μm ² Above 62.5 μm ² The following.

[5] The honeycomb filter according to [1] or [2], wherein,

the porosity of the cell walls constituting the honeycomb structure is 45% to 75%.

Effect of the utility model

The utility model discloses a honeycomb filter can alleviate the thermal stress that produces in hole sealing portion when regeneration operation.

Drawings

Fig. 1 is a perspective view schematically showing an embodiment of a honeycomb filter according to the present invention.

Fig. 2 is a plan view showing the inflow end face side of the honeycomb filter shown in fig. 1.

Fig. 3 isbase:Sub>A sectional view schematically showingbase:Sub>A sectionbase:Sub>A-base:Sub>A' of fig. 2.

Description of the symbols

1: partition wall, 2: compartment, 2a: inflow compartment, 2b: outflow compartment, 3: outer peripheral wall, 4: honeycomb structure, 5: plugging portion, 11: inflow end face, 12: outflow end face, 100: a honeycomb filter.

Detailed Description

The following description will explain embodiments of the present invention, but the present invention is not limited to the following embodiments. Thus, it should be understood that: the present invention is not limited to the above embodiments, and various modifications, improvements, and the like can be made to the embodiments without departing from the scope of the present invention.

(1) A honeycomb filter:

one embodiment of the honeycomb filter of the present invention is a honeycomb filter 100 shown in fig. 1 to 3. Here, fig. 1 is a perspective view schematically showing an embodiment of a honeycomb filter of the present invention. Fig. 2 is a plan view showing the inflow end face side of the honeycomb filter shown in fig. 1. Fig. 3 isbase:Sub>A sectional view schematically showingbase:Sub>A sectionbase:Sub>A-base:Sub>A' of fig. 2.

As shown in fig. 1 to 3, the honeycomb filter 100 includes a honeycomb structure 4 and a plugged portion 5. The honeycomb structure 4 has a columnar shape and porous partition walls 1 arranged to surround a plurality of cells 2, and the plurality of cells 2 form fluid flow paths extending from an inlet end face 11 to an outlet end face 12. The honeycomb filter 100 has a columnar honeycomb structure 4 and an outer peripheral wall 3 on the outer peripheral surface thereof. That is, the outer peripheral wall 3 is disposed so as to surround the partition walls 1 disposed in a lattice shape.

The plugging portion 5 is disposed in an opening on the inflow end surface 11 side or the outflow end surface 12 side of each cell 2. In the honeycomb filter 100 shown in fig. 1 to 3, the plugging portions 5 are disposed at the openings of the end portions on the inflow end face 11 side of the predetermined cells 2 and the openings of the end portions on the outflow end face 12 side of the remaining cells 2, respectively. The inlet compartment 2a is defined as a compartment 2 in which the plugging portion 5 is disposed at the opening on the outlet end surface 12 side and the inlet end surface 11 side is open. The outlet compartment 2b is a compartment 2 in which the plugging portion 5 is disposed at the opening on the inlet end face 11 side and the outlet end face 12 side is open. The inflow compartments 2a and the outflow compartments 2b are preferably arranged alternately with the partition wall 1 therebetween. In this way, the plugging portions 5 and the "openings of the cells 2" preferably form a checkered pattern on both end faces of the honeycomb filter 100.

The honeycomb filter 100 of the present embodiment has particularly main characteristics in terms of the configuration of the plugging portions 5 arranged to plug the openings of the cells 2. That is, in the honeycomb filter 100, in the processed image obtained by binarizing the electron microscope image of the 480 μm × 640 μm field region of the plugged portion 5, the plugged portion 5 is composed of a plurality of particles and has a size of 0.25 μm ² The number of particles having the area described above is 1000 to 3500. The honeycomb filter 100 configured as described above can alleviate the thermal stress generated in the plugged portions 5 during the regeneration operation.

In addition, the honeycomb filter 100 is also excellent in the performance of trapping Particulate Matter (PM) in the exhaust gas. For example, in order to increase the porosity of the honeycomb filter 100, it is effective to increase the porosity of the plugging portions 5 in order to relax the thermal stress during the regeneration operation. However, as the porosity of the plugged portion 5 increases, the pore diameter of the plugged portion 5 tends to increase in a firing process or the like during the production thereof. Further, if the pore diameter of the plugged portions 5 is excessively increased, PM in the exhaust gas may pass through the plugged portions 5, and the PM after passing through may leak from the outlet end face 12 side of the honeycomb filter 100. In the honeycomb filter 100 of the present embodiment, the visual field region has a thickness of 0.25 μm ² Since the number of particles having the area described above is 1000 to 3500, PM penetration can be effectively suppressed.

For example, when a cordierite raw material is used as a raw material for the conventional plugging portion, the raw material may be cordierite-converted by firing at the time of production, and the pore diameter of the plugging portion may increase. In such a conventional sealed portion, the particles constituting the sealed portion are bonded to each other by sintering, and the apparent number of particles in the visual field region is reduced. The pore diameter of the sealing portion in such a state that the number of particles in the visual field region is reduced is increased, and PM easily passes through.

The hole sealing part 5 has a thickness of 0.25 μm in the above-mentioned visual field region ² The number of particles having the area described above may be 1000 to 3500, and other configurations are not particularly limited. For example, the material of the particles constituting the plugging portion 5 is not particularly limited, and from the viewpoint of strength, heat resistance, durability, and the like, various ceramics of oxide or non-oxide may be cited as the main component. The plugging portion 5 may be formed by bonding a plurality of particles to each other with, for example, a bonding agent (adhesive agent), or may be formed by bonding a plurality of particles to each other by sintering or the like while maintaining the shape of the particles in the visual field region. In short, it is preferable that the area of each particle and the number of the particles can be discriminated in the processed image of the visual field region.

In the honeycomb filter 100 of the present embodiment, the plugged portions 5 are not particularly limited, but are preferably an unfired porous body in which a plurality of particles made of ceramics or the like are bonded to each other by a substance having a binder property (for example, colloidal silica or the like). Hereinafter, the plugging portion 5 formed of a porous body in which a plurality of particles are bonded to each other in an unfired state may be referred to as an "unfired plugging portion 5". For example, by using the unfired plugs 5 made of a plurality of particles, thermal stress generated during a regeneration operation or the like can be more effectively relaxed. Even if the plugged portion 5 is not fired, the number of the particles is set to 1000 or more and 3500 or less, and thus the plugging portion 5 can be effectively prevented from falling out of the opening of the cell 2. That is, by setting the number of particles constituting the plugging portion 5 to the above numerical range, the plugging portion 5 becomes denser, and the same piercing strength as that of the plugging portion 5 composed of a sintered body of particles can be achieved. In addition, the plugged portions 5 that are not fired are less likely to cause a crack defect in the plugged portions 5 than the plugged portions 5 that are formed of a fired body of particles. Note that "crack defect" means: a crack-like defect is generated in a part of the sealing portion 5. If various defects such as PM in the exhaust gas passing through are generated in the unfired plugged portions 5, repair and correction of the plugged portions 5 become easy, and the honeycomb filter 100 is excellent in maintainability.

The processed image for observing the number of particles constituting the plugged portion 5 can be obtained by the following method. First, a cross section of the plugged portion 5 of the honeycomb filter 100 was photographed by a scanning electron microscope (hereinafter, also referred to as "SEM"), and an SEM image with a magnification of 200 times was obtained. "SEM" is short for "Scanning Electron Microscope". The SEM image was a tiff image with an image size of 960 × 1280 pixels. As the scanning electron microscope, for example, a "model of a scanning electron microscope" manufactured by hitachi high and new technology: SU3500".

Next, binarization processing is performed on the specified area of the obtained SEM image by a discriminant analysis method. In the binarization processing, binarization is performed with the exception of 30 pixels at the image end of the SEM image. The pore sealing portions 5 in the predetermined region in the SEM image are separated by the binarization process into solid portions in which particles constituting the pore sealing portions 5 exist and void portions between the particles (solid portions). The binarization processing is performed with 1 pixel of the above image size as the minimum unit. The binarization process can be performed by using an image analysis software device "winrooof 2018 (trade name)" manufactured by sango corporation.

Next, in the processed image obtained by performing the binarization processing as described above, the image having a thickness of 0.25 μm ² The number of particles in the above area was measured. The number of particles was measured using the processed image of the 480. Mu. M.times.640. Mu.m visual field region of the sealing portion 5. The actual measurement of the number of particles can be performed by performing image analysis using the image analysis software device. The number of particles was measured in the measurement field at the site of the plugged portion 5 as shown below. First, bees are used as the plugging portions 5 to be measuredAnd a plugged portion 5 near the center of an end face of the honeycomb filter 100 (honeycomb structure 4). In addition, the cross section of the sealed portion 5 to be measured is set as a measurement target at a portion where no significant dent defect such as a pit or a hole is generated in the sealed portion 5 while avoiding the periphery of the partition wall 1 disposed so as to surround the sealed portion 5. Further, the number of particles is measured for each of the processed images of the continuous 3 fields, and the added average value of the number of particles in the measured 3 fields is used. The consecutive 3 fields refer to: in the SEM image, 3 measurement fields were adjacent.

Hereinafter, the "0.25 μm" in the processed image obtained by the binarization processing may be set to ² The particles having the above areas are referred to as "specific constituent particles" constituting the plugged portion 5. The "480 μm × 640 μm field of view" in which the number of specific constituent particles is measured in the processed image of the plugged portion 5 may be referred to as a "specific field of view" in which the number of specific constituent particles constituting the plugged portion 5 is measured. Therefore, the honeycomb filter 100 of the present embodiment can be said to have: the image of the specific visual field region of the sealing portion 5 had a thickness of 0.25 μm ² The number of specific constituent particles having the area described above is 1000 to 3500. The number of the specific constituent particles in the honeycomb filter 100 is preferably 1000 to 3500, more preferably 1500 to 3000. An example of the honeycomb filter of the present invention is a honeycomb filter having 2348 specific constituent particles. In addition, as another example, a honeycomb filter having 2833 or 2879 specific constituent particles may be mentioned.

In addition, the processed image of the specific visual field region of the sealing portion 5 described above has a size of 0.25 μm ² The average area of the specific constituent particles having the above area is preferably 20 μm ² Above 90 μm ² Hereinafter, more preferably 20 μm ² Above 50 μm ² The following. The average area of the specific constituent particles is 20 μm ² Above 50 μm ² In the following range, the effect of relaxing the thermal stress generated in the plugged portion 5 is particularly remarkable. The average area of the specific constituent particles can be determined by using the image analysis software described aboveThe apparatus performs image analysis to obtain. When the average area of the specific constituent particles is within the above numerical range, it is preferable from the viewpoint of stress relaxation and strength of the plugged portions 5. As an example of the honeycomb filter of the present invention, there can be mentioned a honeycomb filter in which the average area of the specific constituent particles is 43 μm ² The honeycomb filter of (1). In addition, as another example, the average area of the specific constituent particles is 41 μm ² The honeycomb filter of (1).

In the processed image of the specific visual field region, the porosity of the sealed portion 5 is preferably 40% to 75%, more preferably 50% to 70%. The porosity of the plugged portion 5 can be obtained by performing image analysis using the image analysis software device described above. Specifically, the percentage (%) of the ratio of the area of the void portion to the entire area of the processed image (i.e., the total area of the solid portion and the void portion) is the porosity of the plugged portions 5. An example of the honeycomb filter of the present invention is a honeycomb filter in which the porosity of the plugged portion 5 is 63.64%. Another example is a honeycomb filter having cell holes 5 with porosities of 55.55% and 57.49%.

In the particle size distribution based on the number of the specific constituent particles in the processed image in the specific visual field region, the area of the particles having the particle diameter d90 at the cumulative value of 90% (that is, the cumulative number of the specific constituent particles is 90% of the total number) is preferably 5 μm ² Above 62.5 μm ² Hereinafter, it is more preferably 25 μm ² Above 50 μm ² The following. In the particle size distribution based on the number of specific constituent particles in the processed image, the area of the particles having the particle diameter d90 can be obtained by performing image analysis using the image analysis software device described above. When the area of the particles having the particle diameter d90 is in the above numerical range, the strength of the plugged portion 5 is preferable. For example, even if the porosity of the plugging portion 5 and the number of particles of the specific constituent particles are the same value, and the area of the particles having the particle diameter d90 is small, the area ratio occupied by the large particles having the particle diameter d90 or more increases. Here, from the viewpoint of relaxing the thermal stress generated in the sealing portion 5It is considered that it is important to reduce the number of large particles (i.e., particles that are less likely to relax thermal stress) as compared with the number of small particles, and the larger the value of the particle diameter d90, the more advantageous the thermal stress relaxation. In the honeycomb filter 100 of the present embodiment, the area of particles having a particle diameter d90 of a specific constituent particle is 25 μm ² Above 50 μm ² In the following range, the above effects are particularly remarkable. As an example of the honeycomb filter of the present invention, there is given a honeycomb filter having a particle size d90 of 35 μm in area ² The honeycomb filter of (1). In another example, the area of the particles having a particle diameter d90 is 48 μm ² 、37μm ² The honeycomb filter of (1).

In the honeycomb filter 100, the structure of the honeycomb structure 4 having the porous partition walls 1 is not particularly limited. Among these, the honeycomb structure 4 is preferably as follows.

The porosity of the partition walls 1 constituting the honeycomb structure 4 is preferably 45% to 75%, more preferably 50% to 70%. The porosity of the partition wall 1 is a value measured by a mercury intrusion method. For example, the porosity of the partition wall 1 can be measured by using Autopore 9500 (trade name) manufactured by Micromeritics. A part of the cell wall 1 may be cut out from the honeycomb structure 4 to prepare a sample piece, and the porosity of the cell wall 1 may be measured using the sample piece thus obtained. The porosity of the partition walls 1 is preferably a constant value over the entire area of the honeycomb structure 4. If the porosity of the partition walls 1 is less than 45%, the pressure loss of the honeycomb filter 100 may increase. If the porosity of the partition walls 1 exceeds 75%, the mechanical strength (for example, isostatic strength) of the honeycomb filter 100 may be reduced. In the honeycomb filter 100 of the present embodiment, the above-described effect is particularly remarkable when the porosity of the cell walls 1 is in the range of 50% to 70%. An example of the honeycomb filter of the present invention is a honeycomb filter in which the porosity of the partition walls 1 is 65%. Another example is a honeycomb filter in which the cell walls 1 have porosities of 63.4% and 64.2%.

The thickness of the partition wall 1 is not particularly limited, and for example, the thickness of the partition wall 1 is preferably 0.152 to 0.305mm, and more preferably 0.203 to 0.254mm. For example, the thickness of the partition wall 1 may be measured using a scanning electron microscope or a microscope (microscope). If the thickness of the partition wall 1 is less than 0.152mm, sufficient strength may not be obtained. On the other hand, if the thickness of the partition walls 1 exceeds 0.305mm, the pressure loss of the honeycomb filter 100 may increase.

The shape of the compartment 2 delimited by the partition wall 1 is not particularly limited. For example, the shape of the cell 2 in a cross section orthogonal to the direction in which the cell 2 extends may be a polygon, a circle, an ellipse, or the like. Examples of the polygon include a triangle, a quadrangle, a pentagon, a hexagon, and an octagon. The shape of the cells 2 is preferably triangular, quadrangular, pentagonal, hexagonal, octagonal. The shape of the cells 2 may be the same or different for all the cells 2. For example, although illustration is omitted, quadrangular cells and octagonal cells may be mixed. The sizes of the compartments 2 may be the same or different for all the compartments 2. For example, although not shown, some of the plurality of compartments may be made larger in size, and the other compartments may be made relatively smaller in size. Note that, in the present invention, the compartment means: a space surrounded by the partition wall.

The cell density of the honeycomb structure 4 is not particularly limited, and for example, the cell density of the honeycomb structure 4 is preferably 31 to 62 cells/cm ² More preferably 39 to 54 pieces/cm ² . By configuring in this manner, the pressure loss can be suppressed from increasing while maintaining the trapping performance of the honeycomb filter 100.

The shape of the honeycomb structure 4 is not particularly limited. The shape of the honeycomb structure 4 includes a columnar shape such as a circle, an ellipse, or a polygon, as the shapes of the inflow end face 11 and the outflow end face 12.

The size of the honeycomb structure 4, for example, the length from the inflow end face 11 to the outflow end face 12, and the size of the cross section of the honeycomb structure 4 perpendicular to the direction in which the cells 2 extend are not particularly limited. When the honeycomb filter 100 is used as a filter for purifying exhaust gas, the size may be appropriately selected so as to obtain the optimum purification performance.

The material constituting the partition walls 1 of the honeycomb structure 4 is not particularly limited. For example, it is preferable that the material of the partition walls 1 contains at least 1 selected from the group consisting of cordierite, silicon carbide, silicon-silicon carbide composite, cordierite-silicon carbide composite, silicon nitride, mullite, alumina, and aluminum titanate. In the honeycomb filter 100 of the present embodiment, the material of the partition walls 1 includes at least 1 of cordierite, silicon carbide, and aluminum titanate as a preferable example.

The material of the plugging portion 5 is also not particularly limited. For example, the same material as that of the partition wall 1 can be used.

The honeycomb filter 100 preferably carries an exhaust gas purifying catalyst on partition walls 1 partitioning a plurality of cells 2. The catalyst is supported on the partition walls 1: the surface of the partition wall 1 and the inner wall of the pores formed in the partition wall 1 are coated with a catalyst. With such a configuration, CO, NOx, HC, and the like in the exhaust gas can be made harmless by a catalytic reaction. Further, oxidation of the trapped PM such as soot can be promoted.

The catalyst supported on the partition walls 1 is not particularly limited. For example, a catalyst containing a platinum group element and containing an oxide of at least one element selected from aluminum, zirconium and cerium is mentioned.

(2) The manufacturing method of the honeycomb filter comprises the following steps:

the method for producing the honeycomb filter of the present invention is not particularly limited, and the following methods may be mentioned, for example. First, a plastic preform for producing a honeycomb structure is prepared. The material for producing the honeycomb structure can be prepared by adding an additive such as a binder, a pore-forming material, and water to a material selected from the above-described preferable materials for the partition walls as the raw material powder as appropriate.

Next, the thus-obtained preform is extrusion-molded to produce a columnar honeycomb molded body having partition walls partitioning a plurality of cells and an outer peripheral wall arranged to surround the partition walls. In the extrusion molding, as a die for the extrusion molding, a die in which a slit having a reversed shape of a honeycomb molded body to be molded is provided on an extrusion surface of a material can be used.

Next, the dried honeycomb formed body is fired to obtain a honeycomb fired body. The firing temperature and firing atmosphere vary depending on the raw material, and those skilled in the art can select the firing temperature and firing atmosphere most suitable for the selected material.

Next, a plugging portion was disposed at the opening of the cell of the obtained honeycomb fired body. Specifically, first, a plugging material containing a raw material for forming a plugging portion is prepared. Next, a mask is applied to the inflow end face of the honeycomb formed body in such a manner that the inflow cells are covered. Next, the plugging material prepared previously was filled into the openings of the outflow cells on the inflow end face side of the honeycomb formed body to which no mask was applied. Then, the plugging material is filled into the openings of the inflow cells also in the outflow end face of the honeycomb formed body by the same method as described above. The honeycomb filter of the present invention can be manufactured by filling the openings of the inflow cells and the outflow cells with the plugging material and drying the filling, and if necessary, performing heat treatment at a temperature lower than 1300 ℃.

Examples

The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples.

(example 1)

As molding raw materials for preparing a billet, talc, kaolin, alumina, and silica were prepared. In example 1, the mixing ratio (parts by mass) of each raw material was 39:18:14:14, mixing the raw materials to prepare a cordierite raw material.

Next, 4.0 parts by mass of a foaming resin as a pore-forming material, 5.6 parts by mass of a binder, 0.5 part by mass of a surfactant, and 85 parts by mass of water were added to 100 parts by mass of the molding material to prepare a preform. As the water-absorbent polymer as the pore-forming material, a polymer having a particle diameter of 30 μm was used. As the binder, methylcellulose (Methylcellulose) was used. Potassium laurate soap was used as the dispersant.

Next, the obtained material was molded by an extrusion molding machine to produce a honeycomb molded body. Next, the obtained honeycomb formed body was subjected to high-frequency dielectric heating and drying, and then further dried by a hot air dryer. The cells in the honeycomb formed body are quadrilateral in shape. Next, the dried honeycomb formed body was degreased and fired to produce a honeycomb structure.

Next, plugging portions are formed in the honeycomb structure. First, a mask is applied to the inflow end face of the honeycomb structure. Next, the end portion (end portion on the inflow end face side) to which the mask is applied is immersed in the sealing slurry, and the opening portions of the cells (outflow cells) to which the mask is not applied are filled with the sealing slurry. In this way, the plugging portion is formed on the inflow end face side of the honeycomb formed body. Then, the plugging portions are formed in the inflow cells in the same manner as the outflow end face of the dried honeycomb formed body. In the hole sealing slurry, talc, kaolin, alumina and silicon dioxide are used as raw materials.

Next, the honeycomb formed body having the plugged portions formed thereon was dried by a microwave dryer, and further completely dried by a hot air dryer, thereby producing a honeycomb filter of example 1. In example 1, when the plugging portion was prepared, the plugging portion was prepared by drying the plugging slurry filled in the opening portion of the cell without firing the plugging portion.

For the honeycomb filter of example 1, the diameter of the end face was 191mm, and the length in the direction in which the cells extended was 152mm. In addition, the thickness of the partition wall was 0.229mm, and the cell density was 46.5 cells/cm ² . The porosity of the partition wall was 55.6%. The porosity of the partition wall was measured by using an Autopore 9500 (trade name) manufactured by Micromeritics. The results are shown in table 1.

In addition, with respect to the plugged portions in the honeycomb filter of example 1, "the number (number) of particles in the visual field region of the plugged portions", "the porosity (%) of the plugged portions", and "the average area (μm) of the particles were measured ² ) "and" particle diameter dArea of particles of 90 (. Mu.m) ² ) ". The measurement method of each item is as described in the above embodiment. The results are shown in table 1.

TABLE 1

The honeycomb filter of example 1 was evaluated for stress relaxation of the end face by the following method. The results are shown in table 1.

(evaluation of stress relaxation of end surface)

A burner peeling test was carried out using a burner tester having a standard pilot air flow rate of 50NL/min and a standard pilot gas (LPG) flow rate of 2.5 NL/min. The temperature raising and lowering time was set to 5 minutes, and the number of cycles was set to 10 cycles. The starting temperature was set to 820 ℃ and the up-regulation was repeated at 50 ℃ each time until the occurrence of the end face crack, and the presence or absence of the end face crack was evaluated based on the following evaluation criteria. First, the maximum temperature at which no end face crack occurs was set to the safe temperature (c), and the evaluation value in the stress relaxation evaluation of the end face was obtained by the following formula (1). The evaluation value of 10 or more and less than 12 was evaluated as "acceptable", the evaluation value of 12 or more and less than 15 was evaluated as "good", and the evaluation value of 15 or more was evaluated as "excellent".

Formula (1): evaluation value = safe temperature (° c)/barrier thickness (mm) × 25.4 (inch/mm)] ²

(examples 2 to 5)

In examples 2 to 5, the structures of the honeycomb structure and the plugged portions were changed as shown in table 1. In examples 2 to 5, the plugging portions were prepared by drying the plugging slurry using talc, kaolin, alumina, and silica as raw materials for preparing the plugging portion plugging slurry.

Comparative examples 1 and 2

In comparative examples 1 and 2, the structures of the honeycomb structure and the plugged portions were changed as shown in table 1. In comparative examples 1 to 2, the plugging portions were prepared by firing the plugging slurry using talc, kaolin, alumina, and silica as raw materials for preparing the plugging slurry for the plugging portions.

(results)

The honeycomb filters of examples 1 to 5 were evaluated for stress relaxation at the end face, and the evaluation results were good or excellent. On the other hand, the results of evaluating the stress relaxation of the end faces of the honeycomb filters of comparative examples 1 to 2 were inferior to those of the honeycomb filters of examples 1 to 5.

Industrial applicability

The honeycomb filter of the present invention can be used as a filter for trapping particulate matter in exhaust gas.

Claims

1. A honeycomb filter is provided with:

a columnar honeycomb structure having porous partition walls arranged so as to surround a plurality of cells forming fluid flow paths extending from an inlet end surface to an outlet end surface; and

it is characterized in that the preparation method is characterized in that,

the sealing portion is composed of a plurality of particles and has a size of 0.25 μm in a processed image obtained by binarizing an electron microscope image of a 480 μm × 640 μm field region of the sealing portion ² The number of particles having the area described above is 1000 to 3500.

2. The honeycomb filter of claim 1,

3. The honeycomb filter of claim 1 or 2,

4. The honeycomb filter of claim 1 or 2,

5. The honeycomb filter of claim 1 or 2,