Cellular filter

Abstract

The present application provides a honeycomb filter with excellent trapping performance and reduced pressure loss. The honeycomb filter has a columnar honeycomb structure portion (4) having porous partition walls (1) arranged to surround a plurality of cells (2) extending from a first end surface (11) to a second end surface (12), and a plugged portion (5) provided at any opening portion of each cell (2), wherein, in a pore size distribution of the partition walls (1) obtained by structure analysis, when a pore size (μm) at which a cumulative pore volume reaches 10%, 50%, and 90% of a total pore volume is set as D10, D50, and D90, respectively, the following formulas (1) to (6) are all satisfied, 8.4 μm < D10 ··· (1) 17.5 μm < D50 < 24.0 μm ··· (2) D90 < 55.2 μm ··· (3) (logD90 - logD10) / logD50 < 0.60 ··· (4) logD90 / logD50 < 1.30 ··· (5) logD50 / logD10 < 1.38 ··· (6).

Description

Technical Field

[0001] This invention relates to cellular filters. More specifically, it relates to cellular filters with excellent trapping performance and reduced pressure loss. Background Technology

[0002] Conventionally, honeycomb filters using a honeycomb structure have been known as devices for capturing particulate matter in exhaust gases from internal combustion engines such as automobile engines, or for purifying toxic gas components such as CO, HC, and NOx (see Patent Document 1). The honeycomb structure has partitions made of porous ceramics such as cordierite, which divide the space into multiple compartments. In the honeycomb filter, the honeycomb structure is provided with sealing portions arranged such that the openings on the inflow end face and the openings on the outflow end face of the multiple compartments are alternately sealed. That is, the honeycomb filter has a structure in which inflow compartments with open inflow end face and sealed outflow end face and outflow compartments with sealed inflow end face and open outflow end face are alternately arranged, sandwiched between partitions. Furthermore, in the honeycomb filter, the porous partitions function as filters for capturing particulate matter in the exhaust gases. Hereinafter, the particulate matter contained in the exhaust gases is sometimes referred to as "PM". "PM" is short for "particulate matter".

[0003] The honeycomb filter purifies exhaust gas as follows: First, the honeycomb filter is configured such that its inlet end face is upstream of the exhaust system from which the exhaust gas is discharged. Exhaust gas flows into the inlet compartment from the inlet end face of the honeycomb filter. Then, the exhaust gas flowing into the inlet compartment passes through the porous partition wall, flows to the outlet compartment, and is discharged from the outlet end face of the honeycomb filter. During passage through the porous partition wall, particulate matter (PM) and other contaminants in the exhaust gas are captured and removed.

[0004] Existing technical documents

[0005] Patent documents

[0006] Patent Document 1: Japanese Patent Application Publication No. 2018-149510 Summary of the Invention

[0007] Honeycomb filters used to purify exhaust gases from automobile engines employ highly porous materials as porous partitions. In recent years, due to stricter restrictions on automobile exhaust emissions, there has been a demand for further improvements in the collection efficiency of honeycomb filters.

[0008] One method to improve the collection efficiency of a honeycomb filter is to reduce the average pore size of the porous septum. However, the average pore size of the septum also significantly affects the pressure loss of the honeycomb filter; reducing the average pore size leads to an increase in pressure loss. Alternatively, increasing the porosity of the septum can be considered to suppress the increase in pressure loss, but further increasing the porosity reduces the strength of the honeycomb filter.

[0009] Furthermore, the average pore size of the partition wall, as described above, has traditionally been managed using measurements obtained via mercury intrusion porosimetry. Within the pores of a porous material like the partition wall, there exists a portion where the pore diameter expands and a constricted portion (hereinafter also referred to as a "neck") between these expanded portions. However, the conventional values ​​for pore size measured by mercury intrusion porosimetry (hereinafter also referred to as "mercury intrusion pore size") depend on the diameter of the neck on the pore inlet side, and sometimes it is impossible to accurately measure the pore size further inward than this neck. Therefore, the conventional mercury intrusion pore size presents a problem in evaluating the quality of the honeycomb filter.

[0010] This invention was made in view of the problems inherent in the prior art. According to the invention, a cellular filter with excellent trapping performance and reduced pressure loss can be provided.

[0011] According to the present invention, a cellular filter as shown below can be provided.

[0012] [1] A honeycomb filter, comprising:

[0013] A columnar honeycomb structure having porous partitions configured to surround multiple compartments forming a fluid flow path extending from a first end face to a second end face; and

[0014] A sealing portion, which is disposed at the opening on the first end face side or the second end face side of each of the compartments.

[0015] In the pore size distribution of the partition wall obtained by structural analysis, if the pore size (μm) that accumulates to 10% of the total pore volume is set as D10, the pore size (μm) that accumulates to 50% of the total pore volume is set as D50, and the pore size (μm) that accumulates to 90% of the total pore volume is set as D90, then all of the following equations (1) to (6) are satisfied.

[0016] 8.4μm<D10···(1)

[0017] 17.5μm<D50<24.0μm···(2)

[0018] D90 < 55.2 μm ···(3)

[0019] (logD90-logD10) / logD50<0.60···(4)

[0020] logD90 / logD50<1.30···(5)

[0021] logD50 / logD10 < 1.38···(6)

[0022] [2] According to the honeycomb filter described in [1] above, the porosity of the partition wall determined by structural analysis is greater than 60.0% and less than 63.5%.

[0023] [3] According to the honeycomb filter described in [1] or [2] above, the thickness of the partition is greater than 177.8 μm and less than 254.0 μm.

[0024] [4] In any one of the preceding [1] to [3], the cell density of the honeycomb structure exceeds 31.0 cells / cm². 2 And less than 62.0 per cm 2 .

[0025] [5] In the honeycomb filter according to any one of [1] to [4] above, the compartment with the opening on the first end face side of the honeycomb structure portion sealed by the sealing portion is used as the outflow compartment, and the compartment with the opening on the second end face side of the honeycomb structure portion sealed by the sealing portion is used as the inflow compartment.

[0026] In a cross section of the honeycomb structure that is orthogonal to the direction in which the compartment extends, the shape of the outflow compartment is different from the shape of the inflow compartment.

[0027] [6] According to the aforementioned [5] cellular filter, the outflow compartment is either a quadrilateral or an octagon, and the inflow compartment is either a quadrilateral or an octagon.

[0028] Invention Effects

[0029] The honeycomb filter of the present invention exhibits the following effects: excellent collection performance and reduced pressure loss. Specifically, the honeycomb filter of the present invention is configured such that, in the pore size distribution of the partition wall obtained through structural analysis, the values ​​of D10, D50, and D90 satisfy all of the above equations (1) to (6).

[0030] In particular, as in equation (1) above, setting D10 in the pore size distribution to a higher value reduces small pores, thereby lowering the permeation resistance of the partition and effectively suppressing the increase in pressure loss of the honeycomb filter. Furthermore, as in equation (3) above, setting D90 in the pore size distribution to a lower value reduces large pores, thereby suppressing the local increase in the flow velocity of the fluid permeating through the partition and improving the collection efficiency of the honeycomb filter. For the honeycomb filter of the present invention, for example, when a catalyst for exhaust gas purification is supported on the porous partition, the catalyst is supported in a manner that allows it to be uniformly coated inside the pores of the partition. By supporting the catalyst in this way, the collection performance of the catalyst-supported honeycomb filter can be significantly improved, and the pressure loss can be reduced. Attached Figure Description

[0031] Figure 1 This is a perspective view, schematically illustrating one embodiment of the honeycomb filter of the present invention, viewed from the inflow end face.

[0032] Figure 2 From Figure 1 A top view of the inflow end face of the shown cellular filter.

[0033] Figure 3 It is a schematic representation Figure 2 A cross-sectional view of section A-A'.

[0034] Figure 4 This is an example of a gray value graph used to represent the number of connecting holes in a partition.

[0035] Explanation of reference numerals in the attached figures

[0036] 1: partition wall, 2: compartment, 2a: inflow compartment, 2b: outflow compartment, 3: outer peripheral wall, 4: honeycomb structure part, 5: sealing part, 11: first end face, 12: second end face, 100: honeycomb filter. Detailed Implementation

[0037] The embodiments of the present invention will be described below, but the present invention is not limited to the following embodiments. Therefore, it should be understood that solutions obtained by making appropriate changes or improvements to the following embodiments based on ordinary knowledge of those skilled in the art without departing from the spirit of the present invention also fall within the scope of the present invention.

[0038] (1) Honeycomb filter:

[0039] like Figures 1-3As shown, a first embodiment of the honeycomb filter of the present invention is a honeycomb filter 100 having a honeycomb structure portion 4 and a sealing portion 5. The honeycomb structure portion 4 is columnar and has porous partitions 1, which are configured to surround a plurality of compartments 2, which form a fluid flow path 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 also has an outer peripheral wall 3 on its outer peripheral side. That is, the outer peripheral wall 3 is arranged to surround the partitions 1 arranged in a grid pattern.

[0040] The sealing part 5 is provided on the opening on the first end face 11 or the second end face 12 of each compartment 2. Figures 1-3 In the shown honeycomb filter 100, sealing portions 5 are respectively provided at the openings on the first end face 11 side of the designated compartment 2 and at the openings on the second end face 12 side of the remaining compartment 2. Here, when the first end face 11 is designated as the inflow end face and the second end face 12 as the outflow end face, the compartment 2 with the sealing portions 5 provided at the openings on the outflow end face side and the inflow end face side being open is designated as the inflow compartment 2a. In addition, the compartment 2 with the sealing portions 5 provided at the openings on the inflow end face side and the outflow end face side being open is designated as the outflow compartment 2b. The inflow compartment 2a and the outflow compartment 2b are preferably arranged alternately with partition walls 1 in between. Furthermore, it is preferable that a checkerboard pattern is formed on the two end faces of the honeycomb filter 100 by the sealing portions 5 and the "openings of the compartment 2".

[0041] Figure 1 This is a perspective view, schematically illustrating one embodiment of the honeycomb filter of the present invention, viewed from the inflow end face. Figure 2 From Figure 1 A top view of the inflow end face of the shown cellular filter. Figure 3 It is a schematic representation Figure 2 A cross-sectional view of section A-A'.

[0042] The honeycomb filter 100 has a particularly important configuration in terms of the pore size distribution of the partitions 1 constituting the honeycomb structure 4. That is, the honeycomb filter 100 satisfies all of the following equations (1) to (6) in terms of the pore size distribution of the partitions 1 obtained through structural analysis. Here, in the following equations (1) to (6), D10 represents the pore size (μm) that reaches 10% of the total pore size of the aforementioned pore size distribution. D50 represents the pore size (μm) that reaches 50% of the total pore size of the aforementioned pore size distribution. D90 represents the pore size (μm) that reaches 90% of the total pore size of the aforementioned pore size distribution. The cumulative pore size relative to the total pore size is the cumulative value of the pore size starting from the minimum value of the pore size (e.g., 0 μm).

[0043] 8.4μm<D10···(1)

[0044] 17.5μm<D50<24.0μm···(2)

[0045] D90 < 55.2 μm ···(3)

[0046] (logD90-logD10) / logD50<0.60···(4)

[0047] logD90 / logD50<1.30···(5)

[0048] logD50 / logD10 < 1.38···(6)

[0049] The honeycomb filter 100 of this embodiment exhibits excellent collection performance and reduces pressure loss. In particular, by setting a higher D10 in the pore size distribution as described in equation (1) above, the number of small pores is reduced, thereby lowering the permeation resistance of the partition wall 1 and effectively suppressing the increase in pressure loss of the honeycomb filter 100. Specifically, for the honeycomb filter 100 of this embodiment, when the porous partition wall 1 is loaded with a catalyst for exhaust gas purification, the catalyst is loaded in a manner that it is uniformly coated inside the pores of the partition wall 1. By loading the catalyst in this way, the collection performance of the catalyst-loaded honeycomb filter 100 can be effectively improved and the pressure loss reduced. For example, if the value of D10 is 8.4 μm or less, it is difficult to suppress the 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 values ​​of equations (4) and (6) above.

[0050] The value of D10 can be configured in a manner that satisfies the above formula (1), formula (4), and formula (6), without any particular limitation. The value of D10 is preferably greater than 8.4 μm, and more preferably greater than 8.5 μm.

[0051] Furthermore, as in equation (3) above, by setting D90 in the pore size distribution to a lower value, large and small pores can be reduced, thereby suppressing the local increase in the flow velocity of the fluid permeating through the partition wall 1 and improving the collection efficiency of the honeycomb filter 100. For example, there is no particular restriction on the lower limit value of D90, as long as it satisfies the values ​​in equations (4) to (6) above. On the other hand, if the value of D90 is 55.2 μm or higher, the collection efficiency of the honeycomb filter may sometimes decrease.

[0052] The value of D90 can be configured in a manner that satisfies the above formula (3) and formulas (4) to (6), without any particular limitation. The value of D90 is preferably less than 55.2 μm, and more preferably less than 53.0 μm.

[0053] Furthermore, by setting the D50 in the pore size distribution to a specified range as in equation (2) above, it is expected that the collection efficiency of the cellular filter 100 will be improved and the increase in pressure loss will be suppressed. For example, if the value of D50 is 17.5 μm or less, it is not ideal in terms of pressure loss. On the other hand, if the value of D50 is 24.0 μm or more, it is not ideal in terms of reduced collection efficiency.

[0054] The value of D50 can be configured in a manner that satisfies the above formula (2), formula (4), and formula (5), without any particular restrictions. The value of D50 is preferably greater than 18.7 μm and less than 22.4 μm.

[0055] Furthermore, by constructing the cell filter 100 as described in equations (4) to (6) above, it is expected that the collection efficiency of the cell filter 100 will be improved and the pressure loss will be suppressed. It should be noted that “logD10”, “logD50” and “logD90” in equations (4) to (6) are the base-10 logarithms of D10, D50 and D90.

[0056] For example, if the value of "(logD90-logD10) / logD50" in equation (4) is 0.60 or higher, an improvement in the collection efficiency of the honeycomb filter 100 and a suppression of the increase in pressure loss can be expected. If the value of "logD90 / logD50" in equation (5) is 1.30 or lower, an improvement in the collection efficiency of the honeycomb filter 100 can be expected. If the value of "logD50 / logD10" in equation (6) is 1.38 or lower, a suppression of the increase in pressure loss of the honeycomb filter 100 can be expected.

[0057] In this invention, "the pore size distribution of the partition wall 1 obtained by structural analysis" refers to the pore size distribution obtained by structural analysis using the following analytical method: Specifically, it refers to the pore size distribution obtained by analysis using the "particle size measurement function" of one of the interface modules of "GeoDict" (trade name, hereinafter the same)), a microstructure simulation software developed by Math2Market GmbH, Germany. Hereinafter, "the analytical method using the particle size measurement function" will sometimes be referred to as the "particle size measurement analytical method." Therefore, the "pore size distribution of the partition wall 1" in the honeycomb filter 100 of this embodiment refers to the pore size distribution of the partition wall 1 obtained by the particle size measurement analytical method. The pore size distribution of the partition wall 1 obtained by the particle size measurement analytical method can more accurately analyze the pore size inside the partition wall 1. That is, even in the case where there are parts of the pores that expand in diameter and parts that constrict in diameter (i.e., necks) inside the partition wall 1, their pore diameters can be properly determined. Therefore, the pore diameters inside the partition wall 1, which are difficult to accurately measure using conventional mercury intrusion porosimetry, can be obtained more accurately, especially the pore diameters that are further inside than the necks of the pores.

[0058] Here, the "particle size determination analytical method" used to determine the pore size distribution of partition 1 will be explained. Hereinafter, the "particle size determination analytical method" will sometimes be referred to as "this analytical method". This analytical method is as follows: For partition 1 of the honeycomb filter 100, tomographic images are obtained using an X-ray CT device, and the pore size distribution of partition 1 is determined from the partition structure model obtained by three-dimensionalizing the obtained tomographic images.

[0059] Specifically, firstly, a portion of the partition wall 1 is cut from the honeycomb filter 100 to prepare a partition wall sample for analysis. However, the portion containing the sealing pores 5 is removed from the partition wall sample. It should be noted that the partition wall sample is collected at a position centered 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 "axial X") and the direction orthogonal to axial X. The partition wall sample is a cuboid with a length of approximately 1 cm in axial X, a width of approximately 0.5 cm in the direction of the surface of the partition wall 1 orthogonal to axial X, and a thickness of the partition wall 1 orthogonal to both the length and width.

[0060] Next, the prepared septum sample was degassed under vacuum and embedded in resin to obtain an X-ray CT imaging sample. Here, "CT" is short for Computed Tomography. For this sample, continuous tomographic images were obtained using an X-ray CT device at imaging conditions of 60 kV, 0.1° stride, and 1.2 μm / pixel resolution. The continuous tomographic images were in TIFF (Tagged Image File Format) format. The obtained TIFF continuous tomographic images were read using the "Particle Size Measurement Function" within the "PoroDict" module of "GeoDict," a microstructure simulation software developed by Math2Market GmbH, at a resolution of 1.2 μm / pixel.

[0061] Next, in order to separate the skeleton and spatial parts of the read image, it will be separated into... Figure 4 The intersection of the two peaks in the grayscale image shown is used as a threshold to model the three-dimensional sample of the adjacent wall.

[0062] Next, noise from the 3D model is removed by eliminating unwanted portions in a manner that reaches 400 voxels × 400 voxels × partition thickness voxels. Then, the particle size determination function within the "PoroDict function," one of the modules of GeoDict, is used to derive the pore sizes in the 3D partition structure model M. The calculation method using the particle size determination function in GeoDict involves fitting spheres of corresponding sizes to each pore.

[0063] By analyzing the partition wall structure model M using the aforementioned particle size distribution function, the fine pore size distribution and the values ​​of D10, D50, and D90 can be determined. It should be noted that the "particle size distribution function" used is the "Particle Size Distribution Function (2020 Version)" from the aforementioned module of "GeoDict". "Particle Size Distribution Function (2020 Version)" indicates the year (Gregorian calendar) in which this particle size distribution function is provided. Therefore, this analytical method is based on the analysis results using the particle size distribution function provided in 2020 (Gregorian calendar). Here, "2020 Version" indicates the year (Gregorian calendar) provided in Japan, but it is not limited to this if the same analytical results can be clearly obtained. Furthermore, particle size distribution functions provided outside of 2020 (e.g., before or after 2020) can also be used for analysis if the same analytical results as the aforementioned "Particle Size Distribution Function (2020 Version)" can be clearly obtained.

[0064] For the honeycomb filter 100 of this embodiment, the values ​​of D10, D50, and D90 in the pore size distribution of the partition wall 1 obtained by the analytical method described above satisfy the above equations (1) to (6). Here, the pore size distribution of the partition wall 1 is conventionally known as the pore size distribution measured by mercury intrusion porosimetry. However, the pore size distribution measured by mercury intrusion porosimetry or the pore size obtained from such pore size distribution depends on the diameter of the neck of the inlet, and the internal pore size cannot be accurately measured, so the honeycomb filter 100 is sometimes not well evaluated. On the other hand, the honeycomb filter 100 of this embodiment is based on the insight that the neck diameter, etc., greatly contribute to the improvement of collection efficiency and the suppression of pressure loss. As mentioned above, the neck diameter cannot be accurately measured by mercury intrusion porosimetry, so the pore size distribution of the partition wall 1 is determined by the analytical method described above. Therefore, as with the cellular filter 100 of this embodiment, by managing the values ​​of D10, D50 and D90 of the pore size distribution of the partition 1 obtained by this analytical method, particularly superior characteristics can be obtained in terms of improving collection efficiency and suppressing pressure loss increase compared with conventional cellular filters.

[0065] In the honeycomb filter 100, the porosity of the partition 1 is preferably greater than 60.0% and less than 63.5%. In this invention, the porosity of the partition 1 is a value obtained through structural analysis. Specifically, the porosity of the partition 1 is a value measured using the open and closed porosity method in one of the modules of "GeoDict" described above, namely the "PoroDict function". By making the porosity of the partition 1 greater than 60.0% and less than 63.5%, a reduction in pressure loss can be achieved. If the porosity of the partition 1 is less than 60.0%, 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 1 is greater than 63.5%, the mechanical strength of the honeycomb filter 100 may sometimes decrease. The porosity of the partition 1 is more preferably greater than 60.0% and less than 63.5%, and particularly preferably greater than 62.4% and less than 63.3%. It should be noted that the partition wall structure model M for determining the porosity of partition wall 1 can be obtained by the same method as the "particle size determination analytical method" previously described for determining the pore size distribution of partition wall 1.

[0066] The thickness of the partition wall 1 is not particularly limited, but preferably it is greater than 177.8 μm and less than 254.0 μm, more preferably greater than 190.4 μm and less than 254.0 μm, and particularly preferably greater than 190.4 μm and less than 216.0 μm. The thickness of the partition wall 1 can be measured, for example, using a scanning electron microscope or a microscope. If the thickness of the partition wall 1 is too thin, the trapping performance will decrease, which is undesirable. On the other hand, if the thickness of the partition wall 1 is too thick, the pressure loss will increase, which is also undesirable.

[0067] The compartment density of compartment 2 formed by partition 1 is preferably greater than 31.0 compartments / cm². 2 And less than 62.0 per cm 2 More preferably, more than 31.0 cells / cm 2 And less than 55.0 pieces / cm 2 With this configuration, the honeycomb filter 100 can be suitably used as a filter for purifying exhaust gases emitted from the engine of a car.

[0068] The shape of the compartment 2 formed in the honeycomb structure portion 4 is not particularly limited. For example, the shape of the compartment 2 in a cross-section orthogonal to the extending direction of the compartment 2 can be polygonal, circular, elliptical, etc. As a polygon, it can be triangular, quadrilateral, pentagonal, hexagonal, octagonal, etc. It should be noted that the shape of the compartment 2 is preferably triangular, quadrilateral, pentagonal, hexagonal, or octagonal. It should be noted that in this invention, the compartment 2 refers to the space surrounded by the partition wall 1.

[0069] Regarding the shape of the compartments 2 formed in the honeycomb structure portion 4, all compartments 2 can have the same shape or different shapes. For example, although not shown in the figure, quadrilateral compartments and octagonal compartments can coexist. For example, it can be configured such that in a cross section of the honeycomb structure portion orthogonal to the direction in which the compartments extend, the shapes of the outflowing compartments and the inflowing compartments are different. In such an arrangement, for example, it is preferable that the shape of the outflowing compartments is either quadrilateral or octagonal, and the shape of the inflowing compartments is either quadrilateral or octagonal.

[0070] Furthermore, regarding the size of the compartments 2 formed in the honeycomb structure portion 4, all compartments 2 can be the same size or different sizes. For example, although the illustration is omitted, among the multiple compartments, the size of some compartments can be increased while the size of other compartments can be relatively decreased.

[0071] The outer peripheral wall 3 of the honeycomb structure 4 can be integrally formed with the partition wall 1, or it can be an outer peripheral coating formed by applying an outer peripheral coating material to the outer peripheral side of the partition wall 1. For example, although the figure is omitted, the partition wall and the outer peripheral wall can be integrally formed during manufacturing, and the outer peripheral wall can be removed by known methods such as grinding, and then the outer peripheral coating can be applied to the outer peripheral side of the partition wall.

[0072] There are no particular limitations on the shape of the honeycomb structure section 4. Examples of the shape of the honeycomb structure section 4 include the first end face 11 (e.g., the inflow end face) and the second end face 12 (e.g., the outflow end face) being cylindrical, circular, elliptical, polygonal, etc.

[0073] There are no particular limitations on the size of the honeycomb structure section 4, such as its length from the first end face 11 to the second end face 12, or the size of the cross section of the honeycomb structure section 4 that is orthogonal to the direction in which the compartment 2 extends. When using the honeycomb filter 100 as a filter for exhaust gas purification, each size can be appropriately selected in order to obtain the best purification performance.

[0074] The material of the partition 1 is not particularly limited, as long as it is a porous material that can satisfy the fine pore size distribution of the above formulas (1) to (6). For example, as the material of the partition 1, it is preferable to include at least one material selected from the group consisting of silicon carbide, cordierite, silicon-silicon carbide composite material, cordierite-silicon carbide composite material, silicon nitride, andalusite, alumina, and aluminum titanate. The material constituting the partition 1 is preferably a material with a content of 90% by mass or more of the materials listed in the above group, more preferably a material with a content of 92% by mass or more, and particularly preferably a material with a content of 95% by mass or more. It should be noted that the silicon-silicon carbide composite material is a composite material formed by using silicon carbide as aggregate and silicon as binder. In addition, the cordierite-silicon carbide composite material is a composite material formed by using silicon carbide as aggregate and cordierite as binder. In the honeycomb filter 100 of this embodiment, the material constituting the partition 1 is particularly preferably cordierite.

[0075] The material of the sealing portion 5 is preferably the same as the material of the partition wall 1. The material of the sealing portion 5 and the material of the partition wall 1 can be the same or different.

[0076] The honeycomb filter 100 preferably has a catalyst for purifying exhaust gas supported on the partition walls 1, which are divided into multiple compartments 2. Supporting the catalyst on the partition walls 1 means that the catalyst is coated on the surface of the partition walls 1 and on the inner walls of the pores formed in the partition walls 1. With this configuration, CO, NOx, or HC in the exhaust gas can be converted into harmless substances through a catalytic reaction. Furthermore, it can promote the oxidation of PM such as soot collected in the filter. In the honeycomb filter 100 of this embodiment, it is particularly preferable to support the catalyst inside the pores of the porous partition walls 1. With this configuration, improved collection performance and reduced pressure loss can be achieved after supporting the catalyst with a low catalyst amount. Furthermore, after supporting the catalyst, the airflow becomes more uniform, thereby also promising improved purification performance.

[0077] There are no particular limitations on the catalyst supported on partition 1. For example, catalysts containing oxides of platinum group elements and including at least one of aluminum, zirconium, and cerium can be cited.

[0078] (2) Manufacturing method of honeycomb filter:

[0079] Next, the manufacturing method of the honeycomb filter according to this embodiment will be described. The honeycomb filter according to this embodiment can be manufactured, for example, by the following method. First, a plastic blank for making the honeycomb structure is prepared. The blank for making the honeycomb structure can be prepared, for example, as follows. Talc powder, kaolin, alumina, aluminum hydroxide and porous silica are prepared as raw material powders, and a water-absorbing polymer, an adhesive, a surfactant and water are added as organic pore-forming materials to prepare a plastic blank. In particular, in the preparation of the blank, by adjusting the mixing ratio of raw material powder and organic pore-forming material, the resulting partition wall can satisfy the pore size distribution of the above formulas (1) to (6).

[0080] Next, by extruding the blank thus obtained, a honeycomb molded body is made having partitions that divide into multiple compartments and an outer wall arranged around the partitions.

[0081] The obtained honeycomb molded body is dried using, for example, microwave and hot air. The openings of the compartments are then sealed using the same material that acts on the honeycomb molded body, thereby creating sealed sections. After creating the sealed sections, the honeycomb molded body can be further dried.

[0082] Next, a honeycomb filter is manufactured by firing the honeycomb molded body with the sealed pores. The firing temperature and firing atmosphere vary depending on the raw materials, and those skilled in the art can select the optimal firing temperature and firing atmosphere for the selected materials.

[0083] By using the manufacturing method described above, a honeycomb filter with a pore size distribution that satisfies the above formulas (1) to (6) can be manufactured.

[0084] Example

[0085] The present invention will be further described in detail below through embodiments, but the present invention is not limited to these embodiments in any way.

[0086] (Example 1)

[0087] Talc, kaolin, alumina, aluminum hydroxide, and porous silica were prepared as molding raw materials for preparing the billet. The cumulative particle size distribution of each raw material was measured using a HORIBA laser diffraction / scattering particle size distribution measuring device (trade name: LA-960). In Example 1, cordierite raw materials were prepared by mixing the raw materials in the proportions (parts by mass) shown in Table 1. In Table 1, the horizontal rows of "Particle Size D50 (μm)" represent the 50% by volume particle size (i.e., median particle size) of each raw material.

[0088] Next, relative to 100 parts by weight of the molding raw material, 3.0 parts by weight of a water-absorbing polymer as a pore-forming material, 6 parts by weight of a binder, 1 part by weight of a surfactant, and 80 parts by weight of water were added to prepare a blank. The water-absorbing polymer used as the pore-forming material had a particle size of 30 μm. Methylcellulose was used as the binder. Potassium lauryl soap was used as the dispersant. Table 2 shows the proportions (parts by weight) of the pore-forming material (organic pore-forming material) and other raw materials. In Table 2, the horizontal row of "Particle Size D50 (μm)" shows the 50% by volume particle size (i.e., median particle size) of the organic pore-forming material. Furthermore, the proportions (parts by weight) shown in Table 2 represent the proportions relative to 100 parts by weight of the cordierite raw material.

[0089] Next, the obtained preform is shaped using an extrusion molding machine to create a honeycomb molded body. Then, the honeycomb molded body is dried using high-frequency induction heating, followed by further drying using a hot air dryer. The compartments in the honeycomb molded body are quadrilateral in shape.

[0090] Next, sealing portions are formed on the dried honeycomb molded body. First, a mask is applied to the inflow end face of the honeycomb molded body. Then, the masked end (the end on the inflow end face side) is immersed in sealing slurry, and the openings of the unmasked compartments (outflow compartments) are filled with sealing slurry. In this way, sealing portions are formed on the inflow end face side of the honeycomb molded body. Then, sealing portions are also formed on the inflow compartments on the outflow end face of the dried honeycomb molded body in the same way.

[0091] Next, the honeycomb molded body with sealed pores is dried using a microwave dryer, and then completely dried using a hot air dryer. The two end faces of the honeycomb molded body are then cut off and adjusted to the specified dimensions. Next, the dried honeycomb molded body is degreased and fired to manufacture the honeycomb filter of Example 1.

[0092] In the honeycomb filter of Example 1, the diameter of the end face is 228.6 mm, and the length of the cell in the extending direction is 184.2 mm. Additionally, the thickness of the partition wall is 190.5 μm, and the cell density is 54.3 cells / cm². 2 The thickness of the partition walls and the density of the compartments are shown in Table 3.

[0093] For the honeycomb filter of Example 1, the porosity of the partition walls was determined using the following method. The porosity of the partition walls was 63.2%. The measurement results are shown in Table 3.

[0094] (porosity)

[0095] The porosity of the partition wall was measured using the open / closed porosity measurement function within the GeoDict module, specifically the PoroDict function. The specific analytical method was performed as described in this embodiment. Furthermore, the three-dimensional model and the partition wall structure model M were obtained using the same method as the "particle size determination analytical method" described in this embodiment for determining the fine pore size distribution.

[0096] Furthermore, the pore size distribution of the septa in the honeycomb filter of Example 1 was determined using particle size analysis. Based on the obtained pore size distribution (analytical values), the values ​​of D10, D50, and D90 were calculated. It should be noted that D10 represents the pore size (μm) at which the cumulative pore volume reaches 10% of the total pore volume, D50 represents the pore size (μm) at which the cumulative pore volume reaches 50% of the total pore volume, and D90 represents the pore size (μm) at which the cumulative pore volume reaches 90% of the total pore volume. The series of analyses performed using particle size analysis were conducted according to the methods described above, using the microstructure simulation software "GeoDict" (trade name) developed by Math2Market GmbH. The calculated values ​​of D10, D50, and D90 are shown in Table 3. In addition, based on the values ​​of D10, D50, and D90, the values ​​of "(logD90-logD10) / logD50", "logD90 / logD50", and "logD50 / logD10" are calculated. These values ​​are shown in the "Equation (4)", "Equation (5)" and "Equation (6)" columns of Table 3.

[0097] [Table 1]

[0098]

[0099] [Table 2]

[0100]

[0101] [Table 3]

[0102]

[0103] [Table 4]

[0104]

[0105] For the cellular filter of Example 1, pressure loss and collection efficiency were evaluated using the following methods. The results are shown in Table 4.

[0106] (Pressure loss)

[0107] Exhaust gas from a 6.7L diesel engine was fed into the honeycomb filter of each embodiment and comparative example, and soot was captured in the exhaust gas using the septa of the honeycomb filter. Soot collection continued until the soot accumulation per unit volume (1L) of the honeycomb filter reached 3g / L. Then, with the soot accumulation reaching 3g / L, the engine exhaust gas at 200°C was passed through a 12m³ / min flow. 3 The pressure at the inflow and outflow sides of the honeycomb filter was measured at a flow rate of / min. The pressure difference between the inflow and outflow sides was then calculated to determine the pressure loss (kPa) of the honeycomb filter. Furthermore, the pressure loss ratio (%) of each honeycomb filter was calculated when the pressure loss value of the honeycomb filter in Comparative Example 1 was set to 100%. The honeycomb filters of each embodiment and comparative example were evaluated based on the following evaluation criteria. It should be noted that in the following evaluation criteria, "pressure loss ratio (%)" refers to the pressure loss ratio (%) of each honeycomb filter when the pressure loss value of the honeycomb filter in Comparative Example 1 was set to 100%.

[0108] Evaluation "Excellent": Cases with a pressure loss ratio (%) below 96% are rated as "Excellent".

[0109] The rating is "Good": a situation where the pressure loss ratio (%) exceeds 96% but is below 98% is defined as "Good".

[0110] Evaluation "Acceptable": Cases where the pressure loss ratio (%) exceeds 98% but is below 100% are rated as "Acceptable".

[0111] Evaluation "Poor": Cases where the pressure loss ratio (%) exceeds 100% are rated as "Poor".

[0112] (Capture efficiency)

[0113] First, an exhaust gas purification device was fabricated, using the honeycomb filters of each embodiment and the comparative example as filters for exhaust gas purification. Next, the fabricated exhaust gas purification device was 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 WHTC (World Harmonized Transient Cycle) mode was used as the determination object, i.e., the number of soot particles in the exhaust gas purification device. The soot particle count 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%. Based on the following evaluation criteria, the honeycomb filters of each embodiment and the comparative example were evaluated. The "Determination" column of "Collection Efficiency (Soot Count Ratio (%)" in Table 4 shows the determination results based on the following evaluation criteria.

[0114] The rating is "Excellent": The situation where the percentage of ash particles is less than 50% is rated as "Excellent".

[0115] The rating "Good" is defined as a condition where the percentage of ash particles exceeds 50% but is below 80%.

[0116] Evaluation "Acceptable": Cases where the percentage of ash particles exceeds 80% but is below 100% are rated as "Acceptable".

[0117] Evaluation "Poor": Cases where the percentage of ash particles exceeds 100% are classified as "Poor".

[0118] (Examples 2-3)

[0119] In Examples 2 and 3, the proportions (parts by mass) of the raw materials used in the cordierite petrochemical feedstock were changed as shown in Table 1. Additionally, the proportions (parts by mass) of the organic pore-forming material and other raw materials were changed as shown in Table 2. A honeycomb filter was fabricated using the same method as in Example 1, except that the billet was prepared using these raw materials.

[0120] (Comparative Examples 1-2)

[0121] In Comparative Examples 1 and 2, the proportions (parts by mass) of the raw materials used in the cordierite feedstock were changed as shown in Table 1. Furthermore, the proportions (parts by mass) of the organic pore-forming material and other raw materials were changed as shown in Table 2. A honeycomb filter was fabricated using the same method as in Example 1, except that the billet was prepared using these raw materials.

[0122] For the honeycomb filters of Examples 2-3 and Comparative Examples 1-2, the porosity of the partition walls was measured using the same method as in Example 1. Furthermore, for the honeycomb filters of Examples 2-3 and Comparative Examples 1-2, the pore size distribution of the partition walls was determined using a particle size analysis method. Based on the obtained pore size distribution (analytical values), the values ​​of D10, D50, and D90 were calculated. The results are shown in Table 3.

[0123] For the cellular filters of Examples 2-3 and Comparative Examples 1-2, pressure loss and collection efficiency were evaluated using the same method as in Example 1. The results are shown in Table 4.

[0124] (result)

[0125] For the honeycomb filters of Examples 1-3, it can be confirmed that they exceed the performance of the honeycomb filter of Comparative Example 1, which serves as the benchmark, in all evaluations of pressure loss and collection efficiency. The honeycomb filter of Comparative Example 1 does not satisfy the relationships of Equations (2)-(3) and (5)-(6) described above. For the honeycomb filters of Examples 1-3, it is evident that they have excellent collection performance and, compared to existing honeycomb filters like Comparative Example 1, they can suppress the increase in pressure loss. On the other hand, the honeycomb filter of Comparative Example 2 does not satisfy the relationships of Equations (2)-(6) described above. The pressure loss of the honeycomb filter of Comparative Example 2 deteriorates sharply.

[0126] Industrial availability

[0127] The honeycomb filter of the present invention can be used as a trapping filter for removing particulate matter and the like contained in exhaust gas.

Claims

1. A honeycomb filter, comprising: A columnar honeycomb structure having porous partitions configured to surround multiple compartments forming a fluid flow path extending from a first end face to a second end face; and A sealing portion, which is disposed at the opening on the first end face side or the second end face side of each of the compartments. In the pore size distribution of the partition wall determined by particle size analysis, if the pore size that accumulates to 10% of the total pore volume is defined as D10, the pore size that accumulates to 50% of the total pore volume is defined as D50, and the pore size that accumulates to 90% of the total pore volume is defined as D90, then all of the following equations (1) to (6) are satisfied, where the unit of pore size is μm. 8.4µm<D10···(1) 17.5µm<D50<24.0µm···(2) D90 < 55.2µm ···(3) 0.52≤(logD90-logD10) / logD50<0.60···(4) logD90 / logD50<1.30···(5) logD50 / logD10<1.38···(6).

2. The honeycomb filter according to claim 1, characterized in that, The porosity of the partition wall, determined by particle size analysis, is greater than 60.0% and less than 63.5%.

3. The honeycomb filter according to claim 1 or 2, characterized in that, The thickness of the partition is greater than 177.8 μm and less than 254.0 μm.

4. The honeycomb filter according to claim 1 or 2, characterized in that, The cell density of the honeycomb structure exceeds 31.0 cells / cm². 2 And less than 62.0 per cm 2 .

5. The honeycomb filter according to claim 1 or 2, characterized in that, The compartment where the opening on the first end face of the honeycomb structure is sealed by the sealing portion serves as the outflow compartment, and the compartment where the opening on the second end face of the honeycomb structure is sealed by the sealing portion serves as the inflow compartment. In a cross section of the honeycomb structure that is orthogonal to the direction in which the compartment extends, the shape of the outflow compartment is different from the shape of the inflow compartment.

6. The honeycomb filter according to claim 5, characterized in that, The outflow compartment is either a quadrilateral or an octagon, and the inflow compartment is either a quadrilateral or an octagon.

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