Honeycomb Filter

Abstract

To provide a honeycomb filter which is excellent in capturing performance and has pressure loss reduced.SOLUTION: The honeycomb filter comprises columnar honeycomb structure parts 4 having porous bulkheads 1 arranged to surround a plurality of cells 2 extending from a first end face 11 to a second end face 12, and sealing parts 5 arranged at opening parts at one side of the cells. When pore sizes (μm) at which cumulative pore volumes are equal to 10%, 50% and 90% of total pore volumes are defined as D10, D50 and D90 respectively in a pore size distribution of the bulkheads determined by structural analysis, all of the following formulas are satisfied: 8.4 μm<D10, 17.5 μm<D50<24.0 μm, D90<55.2 μm, (logD90-logD10) / logD50<0.60, logD90 / logD50<1.30, and logD50 / logD10<1.38.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a honeycomb filter, and more particularly to a honeycomb filter having excellent collection performance and reduced pressure loss. [Background technology]

[0002] Conventionally, honeycomb filters using a honeycomb structure have been known as filters for capturing particulate matter in exhaust gases emitted from internal combustion engines such as automobile engines, or as devices for purifying toxic gas components such as CO, HC, and NOx (see Patent Document 1). The honeycomb structure has partition walls made of porous ceramics such as cordierite, and these partition walls define a plurality of cells. A honeycomb filter is a honeycomb structure in which plugging portions are provided so that openings on the inflow end faces and openings on the outflow end faces of a plurality of cells are alternately plugged. That is, the honeycomb filter has a structure in which inflow cells that are open on the inflow end face and plugged on the outflow end face, and outflow cells that are plugged on the inflow end face and open on the outflow end face are alternately arranged with the partition walls sandwiched between them. In the honeycomb filter, the porous partition walls function as a filter for capturing particulate matter in exhaust gases. Hereinafter, particulate matter contained in exhaust gases may be referred to as "PM." "PM" stands for "particulate matter."

[0003] Exhaust gas purification using a honeycomb filter is performed as follows. First, the honeycomb filter is positioned so that its inlet end face is located upstream of the exhaust system from which the exhaust gas is discharged. The exhaust gas flows into the inlet cells from the inlet end face of the honeycomb filter. The exhaust gas that flows into the inlet cells then passes through the porous partition walls, flows into the outlet cells, and is discharged from the outlet end face of the honeycomb filter. As the exhaust gas passes through the porous partition walls, PM and other substances in the exhaust gas are captured and removed. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 2018-149510 Summary of the Invention [Problem to be solved by the invention]

[0005] Honeycomb filters used to purify exhaust gases emitted from automobile engines have traditionally used highly porous bodies as their porous partition walls. In recent years, tightening automobile exhaust gas regulations and other factors have created a demand for further improvements in the collection efficiency of honeycomb filters.

[0006] One way to improve the collection efficiency of a honeycomb filter is to reduce the average pore size of the porous partition walls. However, the average pore size of the partition walls also has a significant effect on the pressure loss of the honeycomb filter, and reducing the average pore size of the partition walls increases the pressure loss of the honeycomb filter. Increasing the porosity of the partition walls is also considered as a measure to suppress the increase in pressure loss, but further increasing the porosity of the partition walls reduces the strength of the honeycomb filter.

[0007] Furthermore, conventionally, the average pore diameter of the partition walls described above has generally been controlled by measurements obtained by mercury porosimetry. The pores of porous bodies such as partition walls have portions where the pore diameter is expanded and constricted portions (hereinafter also referred to as "necks") between such expanded portions. However, values ​​such as pore diameters measured by conventional mercury porosimetry (hereinafter also referred to as "mercury porosimetry pore diameters") depend on the diameter of the necks on the pore inlet side, and the pore diameters inside such necks are sometimes not measured accurately. For this reason, there has been a problem in that the conventional mercury porosimetry pore diameters cannot provide good characterization of honeycomb filters.

[0008] The present invention has been made in view of the above problems of the prior art, and provides a honeycomb filter having excellent collection performance and reduced pressure loss. [Means for solving the problem]

[0009] According to the present invention, there is provided the following honeycomb filter.

[0010] [1] A columnar honeycomb structure portion having porous partition walls arranged to surround a plurality of cells that serve as fluid flow paths extending from a first end surface to a second end surface; a plugging portion disposed at an opening on the first end face side or the second end face side of each of the cells, A honeycomb filter that satisfies all of the following formulas (1) to (6), where D10 is the pore diameter (μm) at which the cumulative pore volume becomes 10% of the total pore volume, D50 is the pore diameter (μm) at which the cumulative pore volume becomes 50% of the total pore volume, and D90 is the pore diameter (μm) at which the cumulative pore volume becomes 90% of the total pore volume, in the pore diameter distribution of the partition walls obtained by structural analysis.

[0011] 8.4 μm <D10 ··· (1) 17.5 μm <D50<24.0μm ··· (2) D90<55.2μm (3) (logD90-logD10) / logD50<0.60 ···(4) logD90 / logD50<1.30 (5) logD50 / logD10<1.38 (6)

[0012] [2] The honeycomb filter according to [1] above, wherein the porosity of the partition walls determined by structural analysis is greater than 60.0% and less than 63.5%.

[0013] [3] The honeycomb filter according to the above [1] or [2], wherein the thickness of the partition walls is more than 177.8 μm and less than 254.0 μm.

[0014] [4] The cell density of the honeycomb structure part is 31.0 cells / cm 2 Exceeding 62.0 pieces / cm 2 The honeycomb filter according to any one of the above [1] to [3], wherein the average particle diameter is less than 1 / 2 mm.

[0015] [5] The cells whose openings on the first end face side of the honeycomb structure part are plugged by the plugging portions are defined as outflow cells, and the cells whose openings on the second end face side of the honeycomb structure part are plugged by the plugging portions are defined as inflow cells, The honeycomb filter according to any one of [1] to [4], wherein the shape of the outflow cells and the shape of the inflow cells are different in a cross section of the honeycomb structure portion perpendicular to the cell extension direction.

[0016] [6] The honeycomb filter according to [5], wherein the shape of the outflow cells is either a rectangle or an octagon, and the shape of the inflow cells is the other of a rectangle or an octagon. [Effects of the Invention]

[0017] The honeycomb filter of the present invention has excellent collection performance and is effective in reducing pressure loss. That is, the honeycomb filter of the present invention is configured such that the above-mentioned D10, D50, and D90 values ​​in the pore size distribution of the partition walls determined by structural analysis satisfy all of the above formulas (1) to (6).

[0018] In particular, by setting D10 in the pore size distribution high and reducing the number of small pores as in the above formula (1), the permeation resistance of the partition walls is reduced, and an increase in pressure loss of the honeycomb filter can be effectively suppressed. Furthermore, by setting D90 in the pore size distribution low and reducing the number of large pores as in the above formula (3), a local increase in the flow rate of the fluid passing through the partition walls can be suppressed, and the collection efficiency of the honeycomb filter can be improved. In the honeycomb filter of the present invention, for example, when a catalyst for purifying exhaust gases is loaded on the porous partition walls, the catalyst is loaded so as to be uniformly coated inside the pores of the partition walls. By loading the catalyst in this manner, it is possible to effectively achieve both improved collection performance and reduced pressure loss of the honeycomb filter loaded with the catalyst. [Brief explanation of the drawings]

[0019] [Figure 1] 1 is a perspective view seen from the inlet end face side, schematically showing one embodiment of a honeycomb filter of the present invention. [Figure 2] FIG. 2 is a plan view of the honeycomb filter shown in FIG. 1 as viewed from the inlet end face side. [Figure 3] FIG. 3 is a cross-sectional view schematically showing the AA' cross section of FIG. 2. [Figure 4] FIG. 1 is a diagram showing an example of a gray value diagram used when measuring the number of communicating holes in a partition wall. DETAILED DESCRIPTION OF THE INVENTION

[0020] While the present invention will be described below with reference to exemplary embodiments, it should be understood that the present invention is not limited to the following exemplary embodiments. Therefore, it should be understood that modifications and improvements to the following exemplary embodiments, based on the ordinary knowledge of those skilled in the art, are also within the scope of the present invention, provided that they do not deviate from the spirit of the present invention.

[0021] (1) Honeycomb filter: As shown in Figs. 1 to 3, a first embodiment of the honeycomb filter of the present invention is a honeycomb filter 100 including a honeycomb structure portion 4 and plugging portions 5. The honeycomb structure portion 4 is columnar and has porous partition walls 1 arranged so as to surround a plurality of cells 2 that serve as fluid flow paths extending from a first end face 11 to a second end face 12. In the honeycomb filter 100, the honeycomb structure portion 4 is columnar and further has an outer peripheral wall 3 on its outer peripheral side surface. That is, the outer peripheral wall 3 is arranged so as to surround the partition walls 1 arranged in a lattice pattern.

[0022] The plugging portions 5 are arranged at the openings on the first end face 11 side or the second end face 12 side of each cell 2. In the honeycomb filter 100 shown in FIGS. 1 to 3, the plugging portions 5 are arranged at the openings on the first end face 11 side of predetermined cells 2 and at the openings on the second end face 12 side of the remaining cells 2. Here, when the first end face 11 is the inflow end face and the second end face 12 is the outflow end face, the plugging portions 5 are arranged at the openings on the outflow end face side, and the cells 2 that are open on the inflow end face side are referred to as inflow cells 2a. Furthermore, the plugging portions 5 are arranged at the openings on the inflow end face side, and the cells 2 that are open on the outflow end face side are referred to as outflow cells 2b. The inflow cells 2a and the outflow cells 2b are preferably arranged alternately with the partition wall 1 between them. As a result, it is preferable that a checkerboard pattern is formed on both end faces of the honeycomb filter 100 by the plugging portions 5 and the "openings of the cells 2."

[0023] Fig. 1 is a perspective view seen from the inflow end face side, schematically showing one embodiment of a honeycomb filter of the present invention. Fig. 2 is a plan view seen from the inflow end face side of the honeycomb filter shown in Fig. 1. Fig. 3 is a cross-sectional view schematically showing the A-A' cross section of Fig. 2.

[0024] The honeycomb filter 100 has a particularly important configuration with regard to the pore size distribution of the partition walls 1 that constitute the honeycomb structure section 4. That is, the honeycomb filter 100 satisfies all of the following formulas (1) to (6) in the pore size distribution of the partition walls 1 determined by structural analysis. In the following formulas (1) to (6), D10 indicates the pore size (μm) at which the cumulative pore volume in the pore size distribution is 10% of the total pore volume. D50 indicates the pore size (μm) at which the cumulative pore volume in the pore size distribution is 50% of the total pore volume. D90 indicates the pore size (μm) at which the cumulative pore volume in the pore size distribution is 90% of the total pore volume. The cumulative pore volume relative to the total pore volume is the integrated value of the pore volume starting from the minimum pore size (for example, 0 μm).

[0025] 8.4 μm <D10 ··· (1) 17.5 μm <D50<24.0μm ··· (2) D90<55.2μm (3) (logD90-logD10) / logD50<0.60 ···(4) logD90 / logD50<1.30 (5) logD50 / logD10<1.38 (6)

[0026] The honeycomb filter 100 of this embodiment has excellent filtering performance and can reduce pressure loss. In particular, by reducing the number of small pores by setting a high D10 in the pore size distribution as in the above formula (1), the permeation resistance of the partition walls 1 is reduced, and an increase in pressure loss of the honeycomb filter 100 can be effectively suppressed. In particular, in the honeycomb filter 100 of this embodiment, when an exhaust gas purification catalyst is loaded on the porous partition walls 1, the catalyst is loaded so as to be uniformly coated inside the pores of the partition walls 1. By loading the catalyst in this manner, it is possible to effectively achieve both improved filtering performance and reduced pressure loss of the honeycomb filter 100 loaded with the catalyst. For example, if the D10 value is 8.4 μm or less, it becomes difficult to suppress an increase in pressure loss of the honeycomb filter 100. There is no particular limitation on the upper limit of D10, as long as it satisfies the above formulas (4) and (6).

[0027] The value of D10 is not particularly limited as long as it satisfies the above formula (1) and also satisfies the above formulas (4) and (6), but the value of D10 is preferably greater than 8.4 μm, and more preferably greater than 8.5 μm.

[0028] Furthermore, by reducing the number of large pores by setting a low D90 in the pore size distribution as in the above formula (3), it is possible to suppress a local increase in the flow velocity of the fluid passing through the partition walls 1, thereby improving the collection efficiency of the honeycomb filter 100. For example, there is no particular restriction on the lower limit of D90, as long as it satisfies the above formulas (4) to (6). On the other hand, if the value of D90 is 55.2 μm or more, the collection efficiency of the honeycomb filter may decrease.

[0029] The D90 value is not particularly limited as long as it satisfies the above formula (3) and also satisfies the above formulas (4) to (6), but the D90 value is preferably less than 55.2 μm, and more preferably less than 53.0 μm.

[0030] Furthermore, by setting D50 in the pore size distribution within a predetermined range as in the above formula (2), it is possible to expect an improvement in the collection efficiency and suppression of an increase in pressure loss of the honeycomb filter 100. For example, if the D50 value is 17.5 μm or less, it is not preferable in terms of an increase in pressure loss. On the other hand, if the D50 value is 24.0 μm or more, it is not preferable in terms of a decrease in collection efficiency.

[0031] The D50 value is not particularly limited as long as it satisfies the above formula (2) and also satisfies the above formulas (4) and (5), but it is preferable that the D50 value is greater than 18.7 μm and less than 22.4 μm.

[0032] Furthermore, by configuring as in the above formulas (4) to (6), it is expected that the collection efficiency of the honeycomb filter 100 will be improved and an increase in pressure loss will be suppressed. Note that "logD10", "logD50", and "logD90" in formulas (4) to (6) are logarithms of D10, D50, and D90 to the base 10.

[0033] For example, if the value of "(logD90-logD10) / logD50" in formula (4) is 0.60, less than When the value of "logD90 / logD50" in the formula (5) is 1.30, it is possible to expect an improvement in the collection efficiency of the honeycomb filter 100 and an effect of suppressing an increase in pressure loss. less than If this is the case, it is possible to expect an improvement in the collection efficiency of the honeycomb filter 100. When the value of "logD50 / logD10" in the formula (6) is 1.38 less than In this case, it can be expected that an increase in pressure loss of the honeycomb filter 100 can be suppressed.

[0034] In the present invention, the "pore size distribution of the partition walls 1 obtained by structural analysis" refers to a pore size distribution obtained by structural analysis using the following analytical method. That is, it refers to a pore size distribution obtained by analysis using the "Granulometry function," which is one of the interface modules of "GeoDict (product name (hereinafter the same))," a microstructure simulation software developed by Math2Market GmbH in Germany. Hereinafter, the "analysis method using the Granulometry function" may be referred to as the "Granulometry analysis method." Therefore, the "pore size distribution of the partition walls 1" in the honeycomb filter 100 of the present embodiment refers to the pore size distribution of the partition walls 1 obtained by the Granulometry analysis method. The pore size distribution of the partition walls 1 obtained by the Granulometry analysis method enables more accurate analysis of the pore sizes inside the partition walls 1. That is, even when the partition wall 1 has a portion where the diameter of the pore is expanded or a portion where the diameter of the pore is narrowed (i.e., a neck), the diameter of those pores can be determined appropriately. Therefore, the pore diameter inside the partition wall 1, which was difficult to measure accurately by the conventional mercury intrusion porosimetry, can be obtained more accurately, particularly the pore diameter inside the neck of the pore.

[0035] Here, a description will be given of the "Granulometry analysis method" for determining the pore size distribution of the partition walls 1. Hereinafter, the "Granulometry analysis method" may be simply referred to as "this analysis method." This analysis method involves obtaining a tomographic image of the partition walls 1 of the honeycomb filter 100 using an X-ray CT device, and determining the pore size distribution of the partition walls 1 from a partition wall structure model obtained by three-dimensionally converting the obtained tomographic image.

[0036] Specifically, first, a portion of the partition wall 1 is cut out from the honeycomb filter 100 to prepare a partition wall sample piece for analysis. However, the portion where the plugging portions 5 exist is excluded from the partition wall sample piece. The partition wall sample piece is collected from the center position in both the direction extending from the first end face 11 to the second end face 12 of the honeycomb filter 100 (hereinafter also referred to as the "axial direction X") and the direction perpendicular to the axial direction X. The partition wall sample piece has a rectangular parallelepiped shape with a length of about 1 cm in the axial direction X, a width of about 0.5 cm in the surface direction of the partition wall 1 perpendicular to the axial direction X, and a thickness perpendicular to both the length and width that is the thickness of the partition wall 1.

[0037] Next, the prepared septum sample piece is embedded in resin while being vacuum degassed to obtain an X-ray CT imaging sample. Here, "CT" stands for Computed Tomography. Sequential tomographic images of this sample are obtained using an X-ray CT scanner under the following imaging conditions: voltage: 60 kV, step: 0.1°, and resolution: 1.2 μm / pixel. The sequential tomographic images are in TIFF (Tagged Image File Format) format. The obtained sequential tomographic images in TIFF format are read using the "Granulometry function" of the "PoroDict function," one of the modules of "GeoDict," a microstructure simulation software developed by Math2Market GmbH, under the condition of 1.2 μm / voxel.

[0038] Next, to separate the skeleton and spatial regions of the imported image, the intersection of the two peaks in the gray value diagram shown in Figure 4 is used as a threshold value to create a three-dimensional model of the partition wall sample piece.

[0039] Next, noise is removed from the three-dimensional model, and unnecessary parts are removed so that the size is 400 voxels x 400 voxels x partition thickness voxels. Next, the size of the pores in this three-dimensional partition structure model M is derived using the "Granulometry function" in the "PoroDict function," one of the modules of GeoDict. The calculation method using the Granulometry function in GeoDict is to fit a sphere that corresponds to the size of each pore to each pore.

[0040] By analyzing the partition structure model M using the above-mentioned Granulometry function, the pore size distribution and the above-mentioned D10, D50, and D90 values ​​can be obtained. The "Granulometry function" refers to the "Granulometry function (2020 version)" in the above-mentioned module of "GeoDict." The "Granulometry function (2020 version)" refers to the year (Gregorian calendar) in which this Granulometry function was provided. Therefore, this analysis method is based on the analysis results using the Granulometry function provided in 2020. Here, the "2020 version" refers to the year (Gregorian calendar) in which it was provided in Japan, but this does not apply if it is clear that the same analysis results can be obtained. Furthermore, if it is clear that a Granulometry function provided in a year other than 2020 (e.g., before or after 2020) can obtain the same analysis results as the above-mentioned Granulometry function (2020 version), it may be used for analysis.

[0041] In the honeycomb filter 100 of the present embodiment, the values ​​of D10, D50, and D90 in the pore size distribution of the partition walls 1 obtained by the present analytical method described above satisfy the above formulas (1) to (6). Here, conventionally, as the pore size distribution of the partition walls 1, a pore size distribution measured by mercury porosimetry has been widely known. However, the pore size distribution measured by mercury porosimetry and the values ​​of the pore sizes obtained from the pore size distribution depend on the diameter of the inlet neck, and the internal pore sizes cannot be accurately measured, so that the honeycomb filter 100 cannot be properly characterized. On the other hand, the honeycomb filter 100 of the present embodiment is based on the finding that the neck diameter and the like contribute greatly to improving the collection efficiency and suppressing the pressure loss. Because the neck diameter cannot be accurately measured by the mercury porosimetry as described above, the pore size distribution of the partition walls 1 is specified by the present analytical method described above. Therefore, by controlling the values ​​of D10, D50, and D90 based on the pore size distribution of the partition walls 1 obtained by this analysis method, as in the honeycomb filter 100 of this embodiment, it is possible to obtain particularly excellent properties in terms of improved collection efficiency and suppression of an increase in pressure loss compared to conventional honeycomb filters.

[0042] In the honeycomb filter 100, the porosity of the partition walls 1 is preferably more than 60.0% and less than 63.5%. In the present invention, the porosity of the partition walls 1 is a value determined by structural analysis. Specifically, the porosity of the partition walls 1 is a value measured by the Open and Closed Porosity method of the "PoroDict function," which is one of the modules of the "GeoDict" described above. By setting the porosity of the partition walls 1 to more than 60.0% and less than 63.5%, it is possible to reduce pressure loss. If the porosity of the partition walls 1 is 60.0% or less, the effect of reducing the pressure loss of the honeycomb filter 100 may not be sufficiently obtained. On the other hand, if the porosity of the partition walls 1 is 63.5% or more, the mechanical strength of the honeycomb filter 100 may be reduced. The porosity of the partition walls 1 is more preferably more than 60.0% and less than 63.5%, and particularly preferably more than 62.4% and less than 63.3%. The partition wall structure model M for determining the porosity of the partition walls 1 can be obtained by the same method as the "Granulometry analysis method" for determining the pore size distribution of the partition walls 1 described above.

[0043] The thickness of the partition walls 1 is not particularly limited, but is, for example, preferably more than 177.8 μm and less than 254.0 μm, more preferably more than 190.4 μm and less than 254.0 μm, and particularly preferably more than 190.4 μm and less than 216.0 μm. The thickness of the partition walls 1 can be measured, for example, using a scanning electron microscope or a microscope. If the thickness of the partition walls 1 is too thin, this is not preferred because the collection performance decreases. On the other hand, if the thickness of the partition walls 1 is too thick, this is not preferred because the pressure loss increases.

[0044] The cell density of the cells 2 separated by the partition walls 1 is 31.0 cells / cm 2 Exceeding 62.0 pieces / cm 2 It is preferable that the density is less than 31.0 particles / cm 2 Exceeding 55.0 pieces / cm 2With this configuration, the honeycomb filter 100 can be suitably used as a filter for purifying exhaust gas emitted from an automobile engine.

[0045] There are no particular restrictions on the shape of the cells 2 formed in the honeycomb structure section 4. For example, examples of the shape of the cells 2 in a cross section perpendicular to the extension direction of the cells 2 include polygonal, circular, and elliptical shapes. Examples of polygonal shapes include triangular, rectangular, pentagonal, hexagonal, and octagonal shapes. The shape of the cells 2 is preferably triangular, rectangular, pentagonal, hexagonal, or octagonal. In the present invention, the cell 2 refers to a space surrounded by partition walls 1.

[0046] Regarding the shape of the cells 2 formed in the honeycomb structure section 4, all the cells 2 may have the same shape or different shapes. For example, although not shown in the drawings, the honeycomb structure section may have a mixture of rectangular cells and octagonal cells. For example, the honeycomb structure section may be configured such that the shape of the outflow cells and the shape of the inflow cells are different in a cross section perpendicular to the cell extension direction. In such an embodiment, it is preferable that the shape of the outflow cells is either rectangular or octagonal, and the shape of the inflow cells is the other shape of rectangular or octagonal.

[0047] Furthermore, the size of the cells 2 formed in the honeycomb structure section 4 may be the same for all the cells 2 or may be different for all the cells 2. For example, although not shown in the drawings, among the multiple cells, the size of some cells may be made large and the size of other cells may be made relatively small.

[0048] The outer peripheral wall 3 of the honeycomb structure portion 4 may be configured integrally with the partition walls 1, or may be an outer peripheral coating layer formed by applying an outer peripheral coating material to the outer peripheral side of the partition walls 1. For example, although not shown in the drawings, the outer peripheral coating layer can be provided on the outer peripheral side of the partition walls after the partition walls and the outer peripheral wall are integrally formed during production and then the formed outer peripheral wall is removed by a known method such as grinding.

[0049] There is no particular limitation on the shape of the honeycomb structure part 4. Examples of the shape of the honeycomb structure part 4 include a columnar shape such as a circle, an ellipse, or a polygon, in which the first end face 11 (for example, an inflow end face) and the second end face 12 (for example, an outflow end face) have a circular, elliptical, or polygonal shape.

[0050] There are no particular limitations on the size of the honeycomb structure part 4, for example, the length from the first end face 11 to the second end face 12 and the size of the cross section perpendicular to the extension direction of the cells 2 of the honeycomb structure part 4. When the honeycomb filter 100 is used as a filter for purifying exhaust gases, each size may be selected appropriately so as to obtain optimal purification performance.

[0051] The material of the partition walls 1 is not particularly limited, and may be a porous material having a pore size distribution that satisfies the above formulas (1) to (6). For example, the material of the partition walls 1 preferably includes at least one selected from the group consisting of silicon carbide, cordierite, a silicon-silicon carbide composite material, a cordierite-silicon carbide composite material, silicon nitride, mullite, alumina, and aluminum titanate. The material constituting the partition walls 1 is preferably a material containing 90 mass% or more of the materials listed in the above group, more preferably a material containing 92 mass% or more, and particularly preferably a material containing 95 mass% or more. The silicon-silicon carbide composite material is a composite material formed using silicon carbide as an aggregate and silicon as a binder. The cordierite-silicon carbide composite material is a composite material formed using silicon carbide as an aggregate and cordierite as a binder. In the honeycomb filter 100 of the present embodiment, the material constituting the partition walls 1 is particularly preferably cordierite.

[0052] The material of the plugging portions 5 is preferably a material that is considered to be preferable as the material of the partition walls 1. The material of the plugging portions 5 and the material of the partition walls 1 may be the same material or different materials.

[0053] In the honeycomb filter 100, a catalyst for purifying exhaust gas is preferably supported on the partition walls 1 that define the plurality of cells 2. Supporting a catalyst on the partition walls 1 means that the catalyst is coated on the surfaces of the partition walls 1 and the inner walls of the pores formed in the partition walls 1. This configuration makes it possible to convert CO, NOx, HC, and other substances in the exhaust gas into harmless substances through a catalytic reaction. It also promotes the oxidation of PM, such as collected soot. In the honeycomb filter 100 of this embodiment, it is particularly preferable that the catalyst is supported inside the pores of the porous partition walls 1. This configuration makes it possible to achieve both improved collection performance and reduced pressure loss after catalyst loading when a low catalyst amount is used. Furthermore, since the gas flow becomes uniform after catalyst loading, improved purification performance can also be expected.

[0054] There is no particular limitation on the catalyst supported on the partition walls 1. For example, a catalyst containing a platinum group element, which contains an oxide of at least one element selected from aluminum, zirconium, and cerium, can be used.

[0055] (2) Honeycomb filter manufacturing method: Next, a method for manufacturing the honeycomb filter of this embodiment will be described. The honeycomb filter of this embodiment can be manufactured, for example, by the following method. First, a plastic clay for manufacturing the honeycomb structure part is prepared. The clay for manufacturing the honeycomb structure part can be prepared, for example, as follows. Talc, kaolin, alumina, aluminum hydroxide, and porous silica are prepared as raw material powders, and a water-absorbing polymer, a binder, a surfactant, and water are added as organic pore-forming materials to prepare the plastic clay. In particular, by adjusting the compounding ratio of the raw material powders and the organic pore-forming material in the preparation of the clay, the resulting partition walls can have a pore size distribution that satisfies the above formulas (1) to (6).

[0056] Next, the clay thus obtained is extrusion-molded to produce a honeycomb formed body having partition walls that define a plurality of cells and outer walls disposed so as to surround the partition walls.

[0057] The obtained honeycomb formed body is dried, for example, by microwaves and hot air, and the openings of the cells are plugged with the same material as that used to produce the honeycomb formed body, thereby producing plugging portions. After producing the plugging portions, the honeycomb formed body may be further dried.

[0058] Next, the honeycomb formed body with the plugged portions is fired to manufacture a honeycomb filter. The firing temperature and firing atmosphere vary depending on the raw materials, and a person skilled in the art can select the optimum firing temperature and firing atmosphere for the selected materials.

[0059] By the above-described manufacturing method, a honeycomb filter having partition walls realizing a pore size distribution that satisfies the above formulas (1) to (6) can be manufactured. [Example]

[0060] The present invention will be explained in more detail below with reference to examples, but the present invention is not limited to these examples in any way.

[0061] Example 1 Talc, kaolin, alumina, aluminum hydroxide, and porous silica were prepared as molding raw materials for preparing the clay. The cumulative particle size distribution of each raw material was measured using a laser diffraction / scattering particle size distribution analyzer (product name: LA-960) manufactured by HORIBA. In Example 1, the raw materials were blended so that the blending ratio (parts by mass) of each raw material was the value shown in Table 1 to prepare a cordierite-forming raw material. In Table 1, the horizontal row of "particle size D50 (μm)" indicates the particle size of 50% by volume of each raw material (i.e., the median diameter).

[0062] Next, 3.0 parts by mass of a water-absorbent polymer as a pore-forming material, 6 parts by mass of a binder, 1 part by mass of a surfactant, and 80 parts by mass of water were added to 100 parts by mass of the forming raw material to prepare a clay. The water-absorbent polymer used as the pore-forming material had a particle diameter of 30 μm. Methylcellulose was used as the binder. Potassium laurate soap was used as the dispersant. Table 2 shows the blending ratios (parts by mass) of the pore-forming material (organic pore-forming material) and other raw materials. In Table 2, the horizontal row of "particle size D50 (μm)" indicates the particle diameter of 50% by volume of the organic pore-forming material (i.e., the median diameter). The blending ratios (parts by mass) shown in Table 2 indicate the ratios to 100 parts by mass of the cordierite-forming raw material.

[0063] The resulting clay was then molded using an extrusion molding machine to produce a honeycomb molded body. The resulting honeycomb molded body was then dried using high-frequency dielectric heating and then further dried using a hot-air dryer. The cell shape of the honeycomb molded body was rectangular.

[0064] Next, plugging portions were formed on the dried honeycomb formed body. First, a mask was applied to the inflow end face of the honeycomb formed body. Next, the masked end (the end on the inflow end face side) was immersed in plugging slurry, and the plugging slurry was filled into the openings of the unmasked cells (outflow cells). In this way, plugging portions were formed on the inflow end face side of the honeycomb formed body. Then, plugging portions were also formed on the inflow cells on the outflow end face of the dried honeycomb formed body in the same manner.

[0065] Next, the honeycomb formed body with the plugged portions formed thereon was dried in a microwave dryer, and further completely dried in a hot air dryer, after which both end faces of the honeycomb formed body were cut and adjusted to a predetermined size. Next, the dried honeycomb formed body was degreased and fired to produce the honeycomb filter of Example 1.

[0066] The honeycomb filter of Example 1 had an end face diameter of 228.6 mm, a length in the cell extension direction of 184.2 mm, a partition wall thickness of 190.5 μm, and a cell density of 54.3 cells / cm 2 The partition wall thickness and cell density values ​​are shown in Table 3.

[0067] The porosity of the partition walls of the honeycomb filter of Example 1 was measured by the following method. The porosity of the partition walls was 63.2%. The measurement results are shown in Table 3.

[0068] (Porosity) The porosity of the partition walls was measured using the Open and Closed Porosity function of the PoroDict function, which is one of the modules of GeoDict. Specific analysis methods are the same as those described in this embodiment. The three-dimensional model and the partition wall structure model M were obtained by the same method as the "Granulometry analysis method" for determining the pore size distribution described in this embodiment.

[0069] The pore size distribution of the partition walls in the honeycomb filter of Example 1 was determined by granulometry analysis, and the D10, D50, and D90 values ​​were determined based on the obtained pore size distribution (analysis value). D10 indicates the pore size (μm) at which the cumulative pore volume is 10% of the total pore volume, D50 indicates the pore size (μm) at which the cumulative pore volume is 50% of the total pore volume, and D90 indicates the pore size (μm) at which the cumulative pore volume is 90% of the total pore volume. A series of analyses using the granulometry analysis method were performed using the method described above, and the microstructure simulation software "GeoDict (product name)" developed by Math2Market GmbH was used for the analyses. The determined D10, D50, and D90 values ​​are shown in Table 3. Furthermore, the values ​​of "(logD90-logD10) / logD50," "logD90 / logD50," and "logD50 / logD10" were calculated from the values ​​of D10, D50, and D90. These values ​​are shown in the "Formula (4)," "Formula (5)," and "Formula (6)" columns of Table 3.

[0070] [Table 1]

[0071] [Table 2]

[0072] [Table 3]

[0073] [Table 4]

[0074] The honeycomb filter of Example 1 was evaluated for pressure loss and collection efficiency by the following methods. The results are shown in Table 4.

[0075] (pressure loss) Exhaust gas emitted from a 6.7 L diesel engine was introduced into the honeycomb filters of each Example and Comparative Example, and soot in the exhaust gas was collected by the partition walls of the honeycomb filter. Soot collection was continued until the amount of soot deposited per unit volume (1 L) of the honeycomb filter reached 3 g / L. When the amount of soot deposited reached 3 g / L, engine exhaust gas at 200°C was introduced at a flow rate of 12 m / min, and the pressure at the inlet end and outlet end of the honeycomb filter was measured. The pressure difference between the inlet end and outlet end was calculated to determine the pressure loss (kPa) of the honeycomb filter. The pressure loss ratio (%) of each honeycomb filter was calculated, assuming that the pressure loss value of the honeycomb filter of Comparative Example 1 was 100%, and the honeycomb filters of each Example and Comparative Example were evaluated based on the following evaluation criteria. In the following evaluation criteria, "pressure loss ratio (%)" refers to the ratio (%) of the pressure loss of each honeycomb filter when the pressure loss value of the honeycomb filter of Comparative Example 1 is taken as 100%. Evaluation "Excellent": A pressure loss ratio (%) of 96% or less is considered "Excellent." Evaluation "Good": A pressure loss ratio (%) exceeding 96% and not exceeding 98% is evaluated as "Good". Evaluation: "Acceptable": The pressure loss ratio (%) is rated as "acceptable" if it is greater than 98% and less than or equal to 100%. Evaluation: "Fail": If the pressure loss ratio (%) exceeds 100%, it is rated as "Fail."

[0076] (Collection efficiency) First, exhaust gas purification devices were fabricated using the honeycomb filters of each Example and Comparative Example as an exhaust gas purification filter. Next, the fabricated exhaust gas purification devices were connected to the outlet side of the exhaust manifold of a 6.7L diesel engine, and the number of soot particles contained in the gas discharged from the outlet of the exhaust gas purification device was measured using the PN measurement method. In determining the number of soot particles, the cumulative number of soot particles discharged after driving in a WHTC (World Harmonized Transient Cycle) mode was used as the number of soot particles in the exhaust gas purification device to be evaluated. The soot number ratio (%) of each honeycomb filter was calculated when the number of soot particles in the exhaust gas purification device using the honeycomb filter of Comparative Example 1 was set to 100%, and the honeycomb filters of each Example and Comparative Example were evaluated based on the following evaluation criteria. The "Evaluation" column of "Collection Efficiency (Soot Number Ratio (%))" in Table 4 shows the evaluation results based on the following evaluation criteria. Evaluation "Excellent": A soot count ratio (%) of 50% or less is considered "Excellent." Evaluation "Good": The soot count ratio (%) is greater than 50% and less than 80%. Evaluation: "Fair": The soot count ratio (%) is greater than 80% and less than 100%. Evaluation: "Fail": When the soot count ratio (%) exceeds 100%, it is rated as "Fail."

[0077] (Examples 2 and 3) In Examples 2 and 3, the compounding ratio (parts by mass) of each raw material used in the cordierite-forming raw material was changed as shown in Table 1. The compounding ratio (parts by mass) of the organic pore-forming material and other raw materials was also changed as shown in Table 2. A honeycomb filter was produced in the same manner as in Example 1, except that the clay was prepared using such raw materials.

[0078] (Comparative Examples 1 and 2) In Comparative Examples 1 and 2, the compounding ratios (parts by mass) of the raw materials used in the cordierite-forming raw material were changed as shown in Table 1. The compounding ratios (parts by mass) of the organic pore-forming material and other raw materials were also changed as shown in Table 2. A honeycomb filter was produced in the same manner as in Example 1, except that the clay was prepared using such raw materials.

[0079] For the honeycomb filters of Examples 2 and 3 and Comparative Examples 1 and 2, the porosity of the partition walls was measured by the same method as in Example 1. Furthermore, for the honeycomb filters of Examples 2 and 3 and Comparative Examples 1 and 2, the pore size distribution of the partition walls was determined by granulometry analysis, and the values ​​of D10, D50 and D90 were calculated based on the obtained pore size distribution (analysis value). The results are shown in Table 3.

[0080] The honeycomb filters of Examples 2 and 3 and Comparative Examples 1 and 2 were evaluated for pressure loss and collection efficiency in the same manner as in Example 1. Table 4 shows the results.

[0081] (result) It was confirmed that the honeycomb filters of Examples 1 to 3 exceeded the performance of the honeycomb filter of Comparative Example 1, which served as the benchmark, in all evaluations of pressure loss and collection efficiency. The honeycomb filter of Comparative Example 1 does not satisfy the relational expressions (2) to (3) and (5) to (6) described above. It was found that the honeycomb filters of Examples 1 to 3 have excellent collection performance and can suppress an increase in pressure loss compared to a conventional honeycomb filter such as Comparative Example 1. On the other hand, the honeycomb filter of Comparative Example 2 does not satisfy the relational expressions (2) to (6) described above. The honeycomb filter of Comparative Example 2 exhibited a significant deterioration in pressure loss. [Industrial Applicability]

[0082] The honeycomb filter of the present invention can be used as a collection filter for removing particulates and the like contained in exhaust gases. [Explanation of symbols]

[0083] 1: partition wall, 2: cell, 2a: inlet cell, 2b: outlet cell, 3: outer wall, 4: honeycomb structure portion, 5: plugging portion, 11: first end face, 12: second end face, 100: honeycomb filter.

Claims

1. a columnar honeycomb structure portion having porous partition walls arranged to surround a plurality of cells that serve as fluid flow paths extending from a first end face to a second end face; a plugging portion disposed at an opening on the first end face side or the second end face side of each of the cells, In the pore size distribution of the partition walls obtained by a granulometry analysis method, which is a structural analysis method for obtaining a pore size distribution of partition walls from a partition wall structure model obtained by three-dimensionally converting a tomographic image obtained by an X-ray CT scanner, all of the following formulas (1) to (6) are satisfied, when the pore size distribution is defined as D10, the pore size (μm) at which the cumulative pore volume is 10% of the total pore volume is D50, and the pore size (μm) at which the cumulative pore volume is 50% of the total pore volume is D90, the porosity of the partition walls determined by structural analysis is greater than 62.4% and less than 63.3%, A honeycomb filter, wherein the partition walls have a thickness of more than 190.4 μm and less than 216.0 μm. 8.5μm≦D10≦10.5μm...(1) 18.8μm≦D50≦22.3μm...(2) 43.5μm≦D90≦52.9μm...(3) 0.52≦(log(D90)-log(D10)) / log(D50)≦0.56...(4) 1.27≦log(D90) / log(D50)≦1.29...(5) 1.32≦log(D50) / log(D10)≦1.37...(6)

2. The cell density of the honeycomb structure part is 31.0 cells / cm ２ exceeding 62.0 counts / cm ２ The honeycomb filter according to claim 1 , wherein the thickness of the honeycomb filter is less than 1 / 2 mm.

3. the cells whose openings on the first end face side of the honeycomb structure part are plugged by the plugging portions are defined as outflow cells, and the cells whose openings on the second end face side of the honeycomb structure part are plugged by the plugging portions are defined as inflow cells, 3. The honeycomb filter according to claim 1, wherein the shape of the outflow cells and the shape of the inflow cells are different in a cross section of the honeycomb structure section perpendicular to the cell extension direction.

4. 4. The honeycomb filter according to claim 3, wherein the shape of the outflow cells is either a rectangle or an octagon, and the shape of the inflow cells is the other of a rectangle or an octagon.

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