Honeycomb filter

Abstract

To provide a honeycomb filter excellent in capture performance.SOLUTION: The honeycomb filter comprising a columnar honeycomb structure part 4 having a porous partition wall 1 so arranged as to enclose a plurality of cells 2 extending from a first end face 11 to a second end face 12, and an opening sealing part 5 arranged at either one opening of each cell 2, has a pore size (m) of D90 (m), a cumulative pore volume of which is 90% of a total pore volume, and in a pore size distribution of the partition wall 1 obtained by a structure analysis, has an average value (m) of an average neck diameter (m) for an equivalent circle diameter of a neck part where a flow passage area of a communication pore in the porous structure is minimum, and in a porous structure of the partition wall 1 obtained by the structure analysis, has a product of the D90 (m) with the average neck diameter (m) of 1.0x10-10 m2 or more and 9.0×101-0 m2 or less.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. [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 Documents 1 to 5). 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 obtained by providing plugging portions in the above-described honeycomb structure 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] Patent No. 5507575 [Patent Document 2] Patent No. 5469335 [Patent Document 3] Patent No. 5518327 [Patent Document 4] Patent No. 5372494 [Patent Document 5] Patent No. 6004150 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 performance of honeycomb filters.

[0006] Conventionally, in order to improve the collection performance of honeycomb filters, for example, the average pore size and pore size distribution of the porous partition walls have been controlled. For example, attempts have been made to control the pore size distribution by adjusting the above-mentioned average pore size or the value of the pore size D90 at which the cumulative pore volume is 90% of the total pore volume, thereby improving the collection performance of honeycomb filters.

[0007] PM such as soot in exhaust gases is captured by the pores of the porous partition walls that make up honeycomb filters. However, the neck portions, where the flow area of ​​the partition wall pores is narrow, can particularly affect the capture performance. Conventionally, the average pore size and pore size distribution of partition walls have been measured by mercury intrusion porosimetry using a mercury porosimeter or the like. However, measurements using conventional mercury porosimetry or the like have not been able to obtain information on the diameter of the neck portions of the pores in the partition walls (hereinafter also referred to as "neck diameter"). For this reason, simply controlling parameters such as the average pore size and pore size distribution, as defined in conventional technology, does not necessarily achieve sufficient improvement in capture performance, and there has been a demand for the development of new technologies to improve the capture performance 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 with excellent collection performance. [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, In the pore size distribution of the partition walls obtained by structural analysis, the pore size (m) at which the cumulative pore volume is 90% of the total pore volume is defined as D90(m), an average value (m) of equivalent-circle diameters of neck portions at which the flow path area of ​​the communicating pores in the porous structure of the partition walls obtained by the structural analysis is the smallest is defined as an average neck diameter (m); The product of the D90 (m) and the average neck diameter (m) is 1.0 × 10 -10 m 2 That's it, 9.0 x 10 -10 m 2 Below is a honeycomb filter.

[0011] [2] The D90(m) is 1.0 x 10 -5 m or more, 8.0×10 -5 The honeycomb filter according to [1], wherein the thickness is 1 / 2 m or less.

[0012] [3] The average neck diameter (m) is 5.0 × 10 -6 m or more, 1.7×10 -5 The honeycomb filter according to [1] or [2], wherein the thickness is 1 / 2 m or less.

[0013] [4] In the pore size distribution of the partition walls obtained by the structural analysis, the pore size (m) at which the cumulative pore volume is 10% of the total pore volume is defined as D10(m), The D10(m) is 5.0 x 10 -6 m or more, 2.5×10 -5 The honeycomb filter according to any one of [1] to [3] above, wherein the thickness is 100 μm or less.

[0014] [5] In the pore size distribution of the partition walls obtained by the structural analysis, the pore size (m) at which the cumulative pore volume is 50% of the total pore volume is defined as D50(m), The D50 (m) is 1.7 x 10 -5 m or more, 4.1×10 -5 The honeycomb filter according to any one of [1] to [4], wherein the thickness is 100 μm or less.

[0015] [6] The honeycomb filter according to any one of [1] to [5], wherein the porosity (%) of the partition walls determined by the structural analysis is 33% or more and 65% or less. [Effects of the Invention]

[0016] The honeycomb filter of the present invention has the effect of having excellent filtering performance. That is, the honeycomb filter of the present invention combines the D90 value in the pore size distribution of the partition walls determined by structural analysis with the average neck diameter value in the porous structure of the partition walls, thereby realizing a porous structure that is extremely suitable for filtering performance based on parameters that are highly correlated with filtering performance. The neck diameter in the porous structure of the partition walls is an effective parameter for improving filtering performance, and in the present invention, a structural analysis method is adopted to directly measure such a neck diameter. [Brief explanation of the drawings]

[0017] [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. [Figure 4] FIG. 1 is a diagram showing an example of a gray value diagram used when determining the pore size distribution of partition walls. DETAILED DESCRIPTION OF THE INVENTION

[0018] 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.

[0019] (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.

[0020] 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."

[0021] 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.

[0022] The honeycomb filter 100 has a characteristic structure with respect to the porous structure of the partition walls 1 that constitute the honeycomb structure portion 4. Here, in the pore size distribution of the partition walls 1 obtained by structural analysis of the honeycomb filter 100, the pore diameter (m) at which the cumulative pore volume is 90% of the total pore volume is defined as D90(m). Furthermore, in the porous structure of the partition walls 1 obtained by the structural analysis, the average value (m) of the circle-equivalent diameters of the neck portions at which the flow path area of ​​the communicating pores in the porous structure is the smallest is defined as the average neck diameter (m). In the honeycomb filter 100, the product of the above-mentioned D90(m) and the average neck diameter (m) is 1.0×10 -10 m 2 That's it, 9.0 x 10 -10 m 2 The main configuration is as follows. Hereinafter, in this specification, unless otherwise specified, "pore size distribution of the partition walls 1" means "pore size distribution of the partition walls 1" determined by structural analysis of the honeycomb filter 100 described above. Similarly, unless otherwise specified, "porous structure of the partition walls 1" means "porous structure of the partition walls 1" determined by structural analysis of the honeycomb filter 100 described above. Furthermore, the circle-equivalent diameter of the neck portion at which the flow path area of ​​the communicating pores in the porous structure of the partition walls 1 is smallest is sometimes referred to as "neck diameter (m)." In this specification, fine pores in the porous structure are referred to as "pores" or "pores," and in particular, pores (pores) that communicate two adjacent cells 2, 2 separated by the partition wall 1 are referred to as "communicating pores."

[0023] The honeycomb filter 100 has an effect of excellent filtering performance. That is, the honeycomb filter 100 realizes a porous structure that is extremely suitable for filtering performance based on a parameter highly correlated with filtering performance by combining the value of D90(m) in the pore size distribution of the partition walls 1 and the value of the average neck diameter (m) in the porous structure of the partition walls 1. The neck diameter (m) in the porous structure of the partition walls 1 is an effective parameter for improving filtering performance, and in order to directly measure such a neck diameter, a specific structural analysis method is adopted in the honeycomb filter 100 of this embodiment. Furthermore, as described above, the honeycomb filter 100 of this embodiment adopts the product of D90(m) and the average neck diameter (m) as a parameter highly correlated with filtering performance. For example, not all particulate matter (PM) contained in exhaust gases or the like is captured in the neck portion, and therefore, the narrower the space behind the neck portion, the easier it is for PM to be captured. Therefore, the average neck diameter alone did not show a high correlation with the collection performance.

[0024] The product of the above D90 (m) and the average neck diameter (m) is 1.0 x 10 -10 m 2 If the diameter is less than 9.0×10, the pressure drop performance will be poor and the catalyst will be prone to clogging at the neck. -10 m 2 If the value exceeds this, the collection performance will deteriorate. The product of D90 (m) and the average neck diameter (m) is 1.0 x 10 -10 m 2 That's it, 9.0 x 10 -10 m 2 It is fine if it is less than 3.0×10 -10 m 2 That's it, 7.0 x 10 -10 m 2 It is preferable that:

[0025] There are no particular restrictions on the value of D90(m), but for example, 1.0 x 10 -5 m or more, 8.0×10 -5 m or less, and 3.0 × 10-5 m or more, 7.0×10 -5 m or less. Such a configuration can further improve the collection performance of the honeycomb filter 100. For example, by reducing the number of large pores by setting a low D90(m) in the pore size distribution, it is possible to prevent the flow velocity of the fluid passing through the partition walls 1 from increasing locally, and thus the collection efficiency of the honeycomb filter 100 can be improved favorably.

[0026] The average neck diameter (m) of the porous structure of the partition wall 1 is not particularly limited, but is preferably 5.0 × 10 -6 m or more, 1.7×10 -5 m or less, and 1.0 × 10 -5 m or more, 1.6×10 -5 It is more preferable that the average neck diameter (m) is equal to or less than D90 (m). By configuring in this way, it is possible to further improve the collection performance of the honeycomb filter 100. As with D90 (m), a smaller average neck diameter (m) is also effective in improving the collection performance.

[0027] 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 "Identify Pores 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 Identify Pores function" may be referred to as the "Identify Pores 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 Identify Pores analysis method. The pore size distribution of the partition walls 1 obtained by the Identify Pores 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 portion) inside, 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 method, can be obtained more accurately, particularly the pore diameter inside the neck portion of the pore.

[0028] Here, an "Identify Pores analysis method" for determining the pore size distribution of the partition walls 1 will be described. Hereinafter, the "Identify Pores analysis method" may be simply referred to as "this analysis method." This analysis method obtains a tomographic image of the partition walls 1 of the honeycomb filter 100 using an X-ray CT device, and determines the pore size distribution of the partition walls 1 from a partition wall structure model obtained by three-dimensionally converting the obtained tomographic image.

[0029] 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.

[0030] Next, the prepared septum specimen is used as an X-ray CT imaging sample. Here, "CT" stands for Computed Tomography. Sequential tomographic images of this sample are acquired using an X-ray CT scanner under the following imaging conditions: voltage: 60 kV, lens: 4x, filter: LE1, and resolution: 1.2 μm / pixel. As an X-ray CT scanner, for example, the Xradia 520 Versa (trade name) manufactured by Zeiss can be used. The image file format of the sequential tomographic images is not particularly limited as long as it is an image file format that can be used in this analysis method. For example, the acquired sequential tomographic images may be in TIFF (Tagged Image File Format) format or BMP (Bitmap) format. Below, an example of acquiring sequential tomographic images in TIFF format is described. The acquired sequential tomographic images in TIFF format are loaded at 1.2 μm / voxel using the "ImportGeo" function, one of the modules in "GeoDict," a microstructure simulation software developed by Math2Market GmbH.

[0031] Next, to separate the skeleton and the space in 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.

[0032] Next, noise is removed from the three-dimensional model, and unnecessary parts are removed so that the model 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 "Identify Pores" function in the "PoroDict" function, one of the modules in GeoDict. The calculation method used by the Identify Pores function in GeoDict is a method of dividing pores into WaterSheds.

[0033] By analyzing the partition structure model M using the above-mentioned Identify Pores function, the pore size distribution and the above-mentioned D10(m), D50(m), and D90(m) values ​​can be determined. The "Identify Pores function" refers to the "Identify Pores function (2020 version)" in the above-mentioned module of "GeoDict." The "Identify Pores function (2020 version)" refers to the year (Gregorian calendar) in which this Identify Pores function was provided. Therefore, this analysis method is based on the analysis results using the Identify Pores 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 an Identify Pores function provided in a year other than 2020 (e.g., before or after 2020) can provide the same analysis results as the above-mentioned Identify Pores function (2020 version), it may be used for analysis.

[0034] In the honeycomb filter 100 of this embodiment, in the pore size distribution of the partition walls 1 obtained by the above-described analysis method, the pore size (m) at which the cumulative pore volume is 90% of the total pore volume is defined as D90(m). Furthermore, hereinafter, in the pore size distribution of the partition walls 1 obtained by the analysis method, the pore size (m) at which the cumulative pore volume is 10% of the total pore volume is defined as D10(m), and the pore size (m) at which the cumulative pore volume is 50% of the total pore volume is defined as D50(m).

[0035] The average neck diameter (m) in the porous structure of partition wall 1 can be calculated using the following method based on the analysis method described above. First, the partition wall structure model M is analyzed using the Identify Pores function described above to WaterShed-separate the pores in the partition wall structure model M. In this process, pores at the edge of the region are removed, and the minimum pore size detected is set to 2 voxels. Furthermore, if the interface between two contacting pores accounts for 30% or more of the surface area of ​​the pores themselves, the two pores are merged into a single pore. Next, starting with the smallest pore ID, the two voxels surrounding the pore are replaced with a different material using the Dilate function in the ProcessGeo module (2020 version) to obtain the contact surface of the divided pores. WaterShed-separation is then performed again at the contact surfaces between the divided pores, and the average neck diameter (average neck diameter) is obtained by performing a number average. Note that WaterShed-separation refers to the division of a region using the WaterShed algorithm.

[0036] In the pore size distribution of the partition wall 1 obtained by this analysis method, although there are no particular limitations, D10(m) is 5.0 × 10 -6 m or more, 2.5×10 -5 m or less, and 1.0 × 10 -5 m or more, 2.3×10 -5 It is more preferable that D10(m) is 5.0×10 or less. By setting D10(m) in the above-mentioned range, there are advantages in improving the collection efficiency, improving the catalyst coating property, and suppressing an increase in pressure loss. For example, when D10(m) is 5.0×10 -6 By setting D10(m) to 2.5×10 or more, it is preferable in that the pressure drop performance is improved and the catalyst can easily enter the inside of the barrier. -5 It is preferable to set the particle diameter to m or less in that the collection performance is improved.

[0037] In addition, in the pore size distribution of partition wall 1 obtained by this analysis method, D50 (m) was 1.7 × 10 -5 m or more, 4.1×10 -5 m or less, and 1.9 × 10-5 m or more, 3.9×10 -5 It is more preferable that D50(m) is 1.7×10 or less. By setting D50(m) in the above-mentioned range, there are advantages in improving the collection efficiency and suppressing an increase in pressure loss. For example, when D50(m) is 1.7×10 -5 m or more is preferable in that the pressure loss performance improves. -5 It is preferable to set the particle diameter to m or less in that the collection performance is improved.

[0038] In the honeycomb filter 100, the porosity of the partition walls 1 is preferably 33% or more and 65% or less. 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 33% or more and 65% or less, it is possible to reduce pressure loss. By setting the porosity of the partition walls 1 to 33% or more, the effect of reducing the pressure loss of the honeycomb filter 100 can be sufficiently obtained. On the other hand, by setting the porosity of the partition walls 1 to 65% or less, it is possible to sufficiently maintain the mechanical strength of the honeycomb filter 100. It is more preferable that the porosity of the partition walls 1 is 35% or more and 60% or less. The partition wall structure model M for determining the porosity of the partition walls 1 can be obtained by the same method as the "Identify Pores analysis method" for determining the pore size distribution of the partition walls 1 described above.

[0039] The thickness of the partition walls 1 is not particularly limited, but is preferably, for example, 178 μm or more and 254 μm or less, and particularly preferably 191 μm or more and 241 μm or less. 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 may decrease. On the other hand, if the thickness of the partition walls 1 is too thick, this is not preferred because the pressure loss increases.

[0040] The cell density of the cells 2 separated by the partition walls 1 is 43 cells / cm 2 More than 57 pieces / cm 2 Preferably, the number is 47 or less per cm 2 More than 54 pieces / cm 2 It is more preferable that the following is true: By configuring the honeycomb filter 100 in this way, it can be suitably used as a filter for purifying exhaust gas emitted from an automobile engine.

[0041] 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.

[0042] 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.

[0043] 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.

[0044] 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.

[0045] 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.

[0046] 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.

[0047] The material of the partition walls 1 is not particularly limited, and may be any porous material that satisfies the porous structure of the partition walls 1 described above. 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.

[0048] 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.

[0049] 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.

[0050] 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.

[0051] (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-absorbent polymer, binder, 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 D90 (m) and average neck diameter (m) of the porous structure described above.

[0052] 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.

[0053] 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.

[0054] 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.

[0055] By the above-described manufacturing method, it is possible to manufacture a honeycomb filter having partition walls that realize the porous structure (that is, D90 and average neck diameter) described above. [Example]

[0056] 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.

[0057] Example 1 Talc, kaolin, alumina, aluminum hydroxide, a water-absorbent polymer, and porous silica were prepared as molding raw materials for preparing the clay. In Example 1, the molding raw materials were prepared so that the compounding ratio of each raw material was in the range of 42 to 56 mass% silica, 30 to 45 mass% alumina, and 12 to 16 mass% magnesia to obtain a chemical composition.

[0058] Next, 2 parts by mass of water-absorbent polymer as a pore-forming material, 6 parts by mass of binder, and 1 part by mass of dispersant were added to 100 parts by mass of the molding raw material excluding the water-absorbent polymer to prepare a clay. The water-absorbent polymer used as the pore-forming material had an average particle size of 20 μm. Methylcellulose was used as the binder. Potassium laurate soap was used as the dispersant.

[0059] 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.

[0060] 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.

[0061] 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.

[0062] The honeycomb filter of Example 1 had an end face diameter of 304 mm, a length in the cell extension direction of 100 mm, a partition wall thickness of 243 μm, and a cell density of 54 cells / cm 2 It was.

[0063] The porosity of the partition walls was measured by the following method for the honeycomb filter of Example 1. The porosity of the partition walls was 53.2%.

[0064] (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 "Identify Pores analysis method" for determining the pore size distribution described in this embodiment.

[0065] The pore size distribution of the partition walls in the honeycomb filter of Example 1 was determined by the Identify Pores analysis method, and the values ​​of D10(m), D50(m), and D90(m) were determined based on the obtained pore size distribution (analysis value). D10(m) indicates the pore size (m) at which the cumulative pore volume is 10% of the total pore volume. D50(m) indicates the pore size (m) at which the cumulative pore volume is 50% of the total pore volume. D90(m) indicates the pore size (m) at which the cumulative pore volume is 90% of the total pore volume. A series of analyses using the Identify Pores analysis method were performed using the methods described above, and the microstructure simulation software "GeoDict (product name)" developed by Math2Market GmbH was used for the analyses. The average neck diameter of the partition walls was also determined by the above-mentioned analysis method. The obtained values ​​of D10 (m), D50 (m), D90 (m), and average neck diameter (m) are shown in Table 1. In addition, the "product of D90 (m) and average neck diameter (m)" was calculated from the values ​​of D90 (m) and average neck diameter (m). The results are shown in Table 1 as "D90 × average neck diameter (m)" 2 ) column.

[0066] [Table 1]

[0067] The honeycomb filter of Example 1 was evaluated for collection performance by the following method. The results are shown in Table 1.

[0068] (Collection performance) Soot emissions (kg / m) were measured using the "FilterDict" function of GeoDict. 3 The three-dimensional data of the porous body was obtained by the "Identify Pores analysis method" for determining the pore size distribution described in this embodiment.

[0069] Examples 2 to 9 In Examples 2 to 9, the blending ratio (parts by mass) of each raw material used in the cordierite-forming raw material was changed as shown below. For the obtained honeycomb filter, the average neck diameter (m) and D90 (m) were determined using the same method as in Example 1. The results are shown in Table 1. In Examples 2 to 9, the average particle diameter, blending ratio, and amount of water added of the water-absorbing polymer or porous silica in the raw material were changed.

[0070] (Comparative Examples 1 to 5) In Comparative Examples 1 to 5, the blending ratio (parts by mass) of each raw material used in the cordierite-forming raw material was changed as shown below. For the obtained honeycomb filter, the average neck diameter (m) and D90 (m) were determined using the same method as in Example 1. The results are shown in Table 1. In Comparative Examples 1 to 3, the average particle diameter, blending ratio, and amount of water added of the water-absorbing polymer or porous silica in the raw material were changed. In addition, in some Comparative Examples, a pore-forming resin was added to the pore-forming material.

[0071] For the honeycomb filters of Examples 2 to 9 and Comparative Examples 1 to 5, the porosity of the partition walls was measured in the same manner as in Example 1. Furthermore, for the honeycomb filters of Examples 2 to 9 and Comparative Examples 1 to 5, the pore size distribution of the partition walls was determined by the Identify Pores analysis method, and the values ​​of D10(m) and D50(m) were calculated based on the obtained pore size distribution (analysis value). The results are shown in Table 1.

[0072] The honeycomb filters of Examples 2 to 9 and Comparative Examples 1 to 5 were evaluated for collection performance in the same manner as in Example 1. The results are shown in Table 1.

[0073] (result) The honeycomb filters of Examples 1 to 9 showed excellent results in the evaluation of collection performance. In particular, the honeycomb filter of Example 1 had small D90 (m) and average neck diameter (m), and thus showed high collection performance.

[0074] On the other hand, the honeycomb filters of Comparative Examples 1 to 5 had inferior collection performance to the honeycomb filters of Examples 1 to 9. For example, the honeycomb filters of Comparative Examples 1 to 3 had smaller D90 values ​​than the honeycomb filter of Example 3, but the collection performance was poor. [Industrial Applicability]

[0075] 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]

[0076] 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 structural analysis, the pore size (m) at which the cumulative pore volume becomes 90% of the total pore volume is defined as D90 (m), an average value (m) of equivalent-circle diameters of neck portions at which the flow path area of ​​the communicating pores in the porous structure of the partition walls obtained by the structural analysis is the smallest is defined as an average neck diameter (m); The product of the D90 (m) and the average neck diameter (m) is 1.0 × 10 －１０ m ２ That's it, 9.0 x 10 －１０ m ２ Below is a honeycomb filter.

2. The D90 (m) is 1.0 x 10 －５ m or more, 8.0×10 －５ The honeycomb filter according to claim 1, wherein the thickness of the honeycomb filter is 1 / 2 m or less.

3. The average neck diameter (m) is 5.0 × 10 －６ m or more, 1.7×10 －５ The honeycomb filter according to claim 1 or 2, wherein the thickness of the honeycomb filter is 1 / 2 m or less.

4. In the pore size distribution of the partition walls obtained by the structural analysis, the pore size (m) at which the cumulative pore volume becomes 10% of the total pore volume is defined as D10 (m), The D10 (m) is 5.0 × 10 －６ m or more, 2.5×10 －５ The honeycomb filter according to claim 1 or 2, wherein the thickness of the honeycomb filter is 1 / 2 m or less.

5. In the pore size distribution of the partition walls obtained by the structural analysis, the pore size (m) at which the cumulative pore volume becomes 50% of the total pore volume is defined as D50 (m), The D50 (m) is 1.7 × 10 －５ m or more, 4.1×10 －５ The honeycomb filter according to claim 1 or 2, wherein the thickness of the honeycomb filter is 1 / 2 m or less.

6. The honeycomb filter according to claim 1 or 2, wherein the porosity (%) of the partition walls determined by the structural analysis is 33% or more and 65% or less.

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