Cellular filter

Abstract

The present invention provides a honeycomb filter which has excellent trapping performance and can suppress an increase in pressure loss. The thickness of the partition wall (1) is 0.217 mm or less, the porosity of the partition wall (1) is 57 to 63%, the average pore diameter of the partition wall (1) is 6 to 14 μm, and the number of pores having an equivalent circle diameter of more than 3 μm per unit area present on the surface of the partition wall (1) is 800 to 1500 / mm 2 The average opening equivalent circle diameter of the pores having an equivalent circle diameter of more than 3 μm present on the surface of the partition wall (1) is 6.7 to 12.5 μm, and in the pore diameter distribution of the partition wall (1), when the pore diameters (μm) at which the cumulative pore volume reaches 10%, 50%, and 90% of the total pore volume are respectively set as D10, D50, and D90, D10 is 3.0 to 7.0 μm, D90 is 13.0 to 27.0 μm, and (Log(D90) - Log(D10)) / Log(D50) is 0.75 or less.

Description

Technical Field

[0001] This invention relates to cellular filters. More specifically, it relates to cellular filters with excellent capture performance and the ability to suppress pressure loss increases. Background Technology

[0002] Conventionally, honeycomb filters employing a honeycomb structure have been known as filters for capturing particulate matter in exhaust gases emitted from internal combustion engines such as automobile engines, and devices 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 exhaust gas into multiple compartments. The honeycomb filter is constructed by alternately sealing the openings on the inflow end face and the openings on the outflow end face of the multiple compartments relative to the aforementioned honeycomb structure. That is, the honeycomb filter is structured such that inflow compartments with an open inflow end face and a sealed outflow end face, and outflow compartments with a sealed inflow end face and an open outflow end face, are alternately arranged with partitions. Furthermore, in the honeycomb filter, the porous partitions perform a filtering function by capturing particulate matter in the exhaust gas. Hereinafter, particulate matter contained in the exhaust gas is sometimes referred to as "PM". "PM" is short for "particulate matter".

[0003] Currently, emissions restrictions on large diesel vehicles are becoming increasingly stringent, particularly regarding the emission standards for particulate matter (PM) such as soot (PN limits). Therefore, diesel vehicles must be equipped with exhaust filters, such as diesel particulate filters (DPFs).

[0004] Existing technical documents

[0005] Patent documents

[0006] Patent Document 1: Japanese Patent Application Publication No. 2019-171318 Summary of the Invention

[0007] To improve the trapping performance of honeycomb filters like DPFs, it is considered to reduce the average pore size of the septa that form the filter element. However, as a counterproductive characteristic, there is a tendency for pressure loss to increase. On the other hand, fuel consumption regulations for diesel vehicles and the like are becoming increasingly stringent each year. Therefore, from a fuel efficiency perspective, the increased pressure loss of honeycomb filters is undesirable.

[0008] This invention was implemented in view of the problems existing in the prior art described above. According to the invention, a honeycomb filter with excellent trapping performance and the ability to effectively suppress pressure loss rise is provided. In particular, according to the invention, a honeycomb filter that effectively copes with thinning of the partition walls and high porosity, exhibits excellent trapping performance, and is able to suppress pressure loss rise is provided.

[0009] According to the present invention, a cellular filter is provided as follows.

[0010] [1] A honeycomb filter, characterized in that it comprises:

[0011] 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

[0012] 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.

[0013] The thickness of the partition wall is less than 0.217 mm.

[0014] The porosity of the partition wall is 57-63%.

[0015] The average pore size of the partition wall is 6–14 μm.

[0016] The number of pores with an equivalent circular diameter exceeding 3 μm on the surface of the partition wall is 800–1500 per unit area / mm. 2 ,

[0017] The average opening equivalent circle diameter of the fine pores with an equivalent circle diameter exceeding 3 μm present on the surface of the partition wall is 6.7–12.5 μm.

[0018] In the pore size distribution of the partition wall, the pore size (μm) that accumulates to 10% of the total pore volume is defined as D10, the pore size (μm) that accumulates to 50% of the total pore volume is defined as D50, and the pore size (μm) that accumulates to 90% of the total pore volume is defined as D90.

[0019] D10 is 3.0–7.0 μm.

[0020] D90 ranges from 13.0 to 27.0 μm.

[0021] (Log(D90)-Log(D10)) / Log(D50) is below 0.75.

[0022] [2] The honeycomb filter according to [1] above is characterized in that,

[0023] The thickness of the partition wall is less than 0.204 mm.

[0024] The porosity of the partition wall is 58-62%.

[0025] The average pore size of the partition wall is 8–12 μm.

[0026] The number of pores with an equivalent circular diameter exceeding 3 μm on the surface of the partition wall is 900–1250 per unit area / mm. 2 ,

[0027] The average opening equivalent circle diameter of the fine pores with an equivalent circle diameter exceeding 3 μm present on the surface of the partition wall is 8.9–11.7 μm.

[0028] D10 is 3.7–5.9 μm.

[0029] D90 is 15.0–26.0 μm.

[0030] (Log(D90)-Log(D10)) / Log(D50) is below 0.67.

[0031] [3] The cellular filter according to [1] or [2] above is characterized in that,

[0032] The cell density of the honeycomb structure is 43–56 cells / cm². 2 .

[0033] [4] The cellular filter according to any one of [1] to [3] above is characterized in that,

[0034] The partition is made of a material containing cordierite as the main component.

[0035] Invention Effects

[0036] The honeycomb filter of the present invention exhibits excellent collection performance and the ability to suppress the increase in pressure loss. Specifically, in the honeycomb filter of the present invention, excellent collection performance is achieved by setting the thickness, porosity, and average pore size of the partition walls within the aforementioned numerical range. In particular, extremely excellent collection performance is achieved by reducing the average pore size of the partition walls. On the other hand, by increasing the number of pores opening on the surface of the partition walls, the exhaust gas flow permeating through the partition walls is homogenized, thereby avoiding and suppressing the increase in pressure loss caused by reducing the average pore size of the partition walls.

[0037] The honeycomb filter of the present invention, for example, can effectively cope with the thinning of the partition walls and the increase of the porosity, achieving excellent capture performance, and can effectively suppress the increase of pressure loss. Attached Figure Description

[0038] 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.

[0039] Figure 2 yes Figure 1 The diagram shows a plan view of the cellular filter as seen from the inflow end face.

[0040] Figure 3 It is a schematic representation Figure 2 A cross-sectional view of section A-A'.

[0041] Symbol Explanation

[0042] 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

[0043] The embodiments of the present invention will be described below; however, the present invention is not limited to the following embodiments. Therefore, it should be understood that, without departing from the spirit of the present invention, appropriate modifications and improvements to the following embodiments based on the common knowledge of those skilled in the art also fall within the scope of the present invention.

[0044] (1) Honeycomb filter:

[0045] like Figures 1-3 As 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 a columnar honeycomb structure portion having 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 its outer peripheral side also has an outer peripheral wall 3. That is, the outer peripheral wall 3 is configured to surround the partitions 1 which are arranged in a grid pattern.

[0046] 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 yes Figure 1 The diagram shows a plan view of the cellular filter as seen from the inflow end face. Figure 3 It is a schematic representation Figure 2 A cross-sectional view of section A-A'.

[0047] In the honeycomb filter 100, the partition 1 constituting the honeycomb structure part 4 is configured as follows.

[0048] In the honeycomb filter 100, the porosity of the partition 1 is 57-63%. The porosity of the partition 1 is a value obtained by mercury porosimetry. For example, the porosity of the partition 1 can be measured using an Autopore 9500 (trade name) manufactured by Micromeritics. A portion of the partition 1 can be cut from the honeycomb filter 100 to make a test piece, and the porosity of the test piece obtained in this way can be measured. The porosity of the partition 1 is preferably 58-62%, more preferably 59-61%.

[0049] By making the porosity of the partition 1 57-63%, pressure loss can be reduced. If the porosity of the partition 1 is less than 57%, the effect of reducing the pressure loss of the honeycomb filter 100 cannot be fully achieved. On the other hand, if the porosity of the partition 1 exceeds 63%, the mechanical strength of the honeycomb filter 100 decreases.

[0050] In the honeycomb filter 100, the average pore size of the partition wall 1 is 6–14 μm. The average pore size of the partition wall 1 is a value obtained by mercury porosimetry. For example, the Autopore 9500 (trade name) manufactured by Micromeritics can be used to measure the average pore size of the partition wall 1. The aforementioned test piece used for measuring porosity can be used to measure the average pore size. The average pore size of the partition wall 1 is preferably 8–12 μm. The average pore size of the partition wall 1 is a value calculated using mercury porosimetry, defined as the pore size providing half the total pore volume. The average pore size of the partition wall 1 corresponds to the value of "D50 (μm)" in the pore size distribution of the partition wall 1 described later.

[0051] By making the average pore size of the partition wall 1 6 to 14 μm, pressure loss can be reduced and collection performance can be improved. If the average pore size of the partition wall 1 is less than 6 μm, the permeation resistance increases, which is undesirable in terms of increased pressure loss. On the other hand, if the average pore size of the partition wall 1 exceeds 14 μm, the effect of improving the collection efficiency of the honeycomb filter 100 cannot be fully obtained.

[0052] Furthermore, for the partition 1 constituting the honeycomb structure portion 4, the number of fine pores with an equivalent circular diameter exceeding 3 μm on the surface of the partition 1 per unit area (1 mm²) 2 The number of elements is 800-1500 per mm. 2 The following is sometimes given as the number of the aforementioned pores per unit area (pores / mm) present on the surface of partition 1. 2 This is abbreviated as "the number of pores on the surface of partition 1 (number / mm)". 2 If the number of pores on the surface of the partition 1 is less than 800 / mm. 2 If the number of pores on the surface of partition 1 exceeds 1500 per mm, the effect of suppressing the increase in pressure loss cannot be fully achieved.2 If this happens, the mechanical strength of the honeycomb filter 100 will decrease.

[0053] Number of pores on the surface of partition 1 (pores / mm) 2 There are no particular limitations, but 900–1250 pieces / mm is preferred. 2 More preferably, it is 980–1100 pieces / mm 2 By constructing it in this way, the above-mentioned effects can be made even better.

[0054] For the partition 1 constituting the honeycomb structure 4, the average opening equivalent circle diameter of the pores on the surface of the partition 1 that have an equivalent circle diameter exceeding 3 μm is 6.7 to 12.5 μm. Hereinafter, the average opening equivalent circle diameter (μm) of the aforementioned pores on the surface of the partition 1 will sometimes be simply referred to as "average opening equivalent circle diameter (μm) of the pores on the surface of the partition 1" or "average opening diameter (μm) of the pores on the surface of the partition 1". If the average opening diameter of the pores on the surface of the partition 1 is less than 6.7 μm, it is not ideal in terms of reducing the isostatic compressive strength. If the average opening diameter of the pores on the surface of the partition 1 exceeds 12.5 μm, the effect of improving the collection efficiency of the honeycomb filter 100 cannot be sufficiently obtained.

[0055] The average opening diameter (μm) of the surface of partition 1 is not particularly limited, but is preferably 8.9 to 11.7 μm, more preferably 9.6 to 11.2 μm. By configuring it in this way, the above-mentioned effects can be improved.

[0056] Number of pores on the surface of partition 1 (pores / mm) 2 The number of pores and the average opening diameter (μm) of the pores can be determined by the following method. First, a sample for measurement is cut from the honeycomb structure 4 so that the surface of the septum 1 of the honeycomb structure 4 can be observed. Then, the surface of the septum 1 of the sample for measurement is photographed using a laser microscope. For example, a shape-resolving laser microscope “VK X250 / 260 (trade name)” manufactured by Keyence Corporation can be used. During the photographing of the septum 1 surface, the magnification is set to 480x, and images are taken of any part of 10 fields of view. The photographed images are processed to calculate the number of pores (pores / mm) on the surface of the septum 1. 2The average opening diameter (μm) of the pores. It should be noted that, regarding image processing, the area being processed is selected such that it excludes portions of septum 1 other than the surface of septum 1, and the tilt of the surface of septum 1 is corrected to be horizontal. Then, the upper limit of the height identified as a pore is changed to -3.0 μm relative to the reference plane. Ignoring pores with an equivalent circle diameter of 3 μm or less, the number of pores in the captured image and the equivalent circle diameter (μm) of each pore are calculated using image processing software. The equivalent circle diameter (μm) of the pores on the surface of septum 1 is calculated as follows: the opening area S of each pore is measured, and the equivalent circle diameter is calculated using the formula: equivalent circle diameter = √{4 × (area S) / π}. The number of pores on the surface of septum 1 (pores / mm) 2 The value is set to the measurement results of 10 fields of view (i.e., the number of pinholes (in mm) in each of the 10 captured images). 2 The average opening diameter (μm) of the pores on the surface of partition 1 is set as the average of the measurement results of 10 fields of view (i.e., the average opening diameter (μm) of each image captured in 10 fields of view). As image processing software, for example, the "VK-X (trade name)" included with the Keyence shape-resolving laser microscope "VK X250 / 260 (trade name)" can be used. The equivalent circle diameter of each pore and image analysis of pores ignoring the specified equivalent circle diameter can be performed using the aforementioned image processing software.

[0057] Furthermore, the honeycomb filter 100 is preferably configured such that the horizontal axis is set to the pore size (μm) and the vertical axis is set to the log differential pore volume (cm³). 3 The pore size distribution of the septum 1, measured by mercury porosimetry, is expressed as follows: Here, in the aforementioned pore size distribution of the septum 1, the pore size (μm) that represents 10% of the total pore volume is defined as D10. Similarly, the pore size (μm) that represents 50% of the total pore volume is defined as D50, and the pore size (μm) that represents 90% of the total pore volume is defined as D90. For the honeycomb filter 100, in the pore size distribution of the septum 1, D10 is 3.0–7.0 μm, D90 is 13.0–27.0 μm, and (Log(D90)-Log(D10)) / Log(D50) is 0.75 or less.

[0058] If D10 is between 3.0 and 7.0 μm, it exhibits excellent performance in suppressing pressure loss. For example, if D10 is less than 3.0 μm, it is undesirable in terms of reducing pressure loss. Conversely, if D10 exceeds 7.0 μm, it is undesirable in terms of reduced trapping performance. D10 is preferably between 3.7 and 5.9 μm.

[0059] Furthermore, a D90 range of 13.0–27.0 μm exhibits excellent performance in terms of improved collection efficiency. For example, a D90 less than 13.0 μm is undesirable due to increased pressure loss. Conversely, a D90 greater than 27.0 μm is undesirable due to decreased collection efficiency. A D90 range of 15.0–26.0 μm is preferred.

[0060] If (Log(D90)-Log(D10)) / Log(D50) is 0.75 or less, it exhibits excellent performance in suppressing pressure loss. (Log(D90)-Log(D10)) / Log(D50) is preferably 0.67 or less. There is no particular limitation on the lower limit of (Log(D90)-Log(D10)) / Log(D50), but a practical lower limit is 0.45.

[0061] The cumulative pore volume of partition 1 is a value obtained by mercury intrusion porosimetry. For example, the Autopore 9500 (trade name) manufactured by Micromeritics can be used to measure the cumulative pore volume of partition 1. The cumulative pore volume of partition 1 can be measured by the following method: First, a portion of partition 1 is cut from the honeycomb filter 100 to prepare a test piece for measuring the cumulative pore volume. The size of the test piece is not particularly limited; for example, a cuboid with length, width, and height of approximately 10 mm, 10 mm, and 20 mm respectively is preferred. The location from which the test piece is cut is not particularly limited; it is preferable to cut a portion of partition 1 near the center of the honeycomb structure in the axial direction to prepare the test piece. The obtained test piece is placed in the measuring unit of the measuring device, and the measuring unit is depressurized. Next, mercury is introduced into the measuring unit. Next, the mercury introduced into the measuring unit is pressurized, and the volume of mercury in the pores present in the test piece is measured during pressurization. At this point, as the pressure applied to the mercury increases, the mercury is sequentially injected into the pores from the larger pores to the smaller pores. Therefore, based on the relationship between the "pressure applied to the mercury" and the "volume of mercury injected into the pores," the relationship between the "pore diameter of the pores formed in the test piece" and the "cumulative pore volume" can be determined. More specifically, as described above, by using mercury intrusion porosimetry, the pressure is gradually increased to allow mercury to penetrate into the pores of the sample (test piece) within a vacuum-sealed container. The pressurized mercury penetrates sequentially from the larger pores to the smaller pores of the sample. Based on the pressure and the amount of mercury injected, the pore diameter and pore volume of the pores formed in the sample can be calculated. Hereinafter, when the pore diameters are set as D1, D2, D3…, the relationship D1 > D2 > D3… is satisfied. Here, the average pore diameter D between each measurement point (e.g., D1 to D2) can be expressed on the horizontal axis as "average pore diameter D = (D1 + D2) / 2". In addition, the Log differential pore volume on the vertical axis can be set as the value obtained by dividing the increase in pore volume dV between each measurement point by the difference between the logarithm of the pore diameter (i.e., "log(D1) - log(D2)").

[0062] The thickness of the partition wall 1 is 0.217 mm or less. For example, the thickness of the partition wall 1 can be measured using a scanning electron microscope or a microscope. If the thickness of the partition wall 1 exceeds 0.217 mm, the effect of suppressing the increase in pressure loss cannot be sufficiently obtained. The thickness of the partition wall 1 is preferably 0.204 mm or less. In addition, there is no particular limitation on the lower limit of the thickness of the partition wall 1. For example, if the thickness of the partition wall 1 is extremely thin, it may sometimes affect the trapping performance and mechanical strength. Therefore, although there is no particular limitation, 0.152 mm can be taken as a lower limit for the thickness of the partition wall 1.

[0063] The honeycomb filter 100 of this embodiment exhibits excellent collection performance and can suppress the increase in pressure loss. For example, for the honeycomb filter 100 of this embodiment, excellent collection performance can be achieved by making the thickness, porosity, and average pore size of the partition wall 1 within the numerical range described above. In particular, extremely excellent collection performance can be achieved by reducing the value of the average pore size of the partition wall 1. On the other hand, by increasing the number of pores that are open on the surface of the partition wall 1, the exhaust gas flow passing through the partition wall 1 is homogenized, thereby avoiding and suppressing the increase in pressure loss caused by reducing the average pore size of the partition wall 1. For example, the honeycomb filter 100 of this embodiment can effectively cope with the thinning of the partition wall 1 and the increase of its porosity, achieving excellent collection performance and effectively suppressing the increase in pressure loss.

[0064] There are no particular restrictions on the material of partition 1, as long as the pore size distribution of partition 1 and the number of pores on the surface of partition 1 (number / mm) are suitable. 2 The porous material whose structure and average pore opening diameter (μm) satisfy the above description is acceptable. For example, the material constituting the partition 1 preferably includes at least one material selected from the group consisting of cordierite, silicon carbide, 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 silicon-silicon carbide composite material refers to a composite material formed by using silicon carbide as aggregate and silicon as binder. In addition, cordierite-silicon carbide composite material refers to 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 as the main component.

[0065] The shape of the compartments 2 formed in the honeycomb structure 4 is not particularly limited. For example, the shape of the compartment 2 as a cross-section orthogonal to the direction in which the compartment 2 extends can be polygonal, circular, elliptical, etc. As a polygon, examples include triangles, quadrilaterals, pentagons, hexagons, octagons, etc. It should be noted that the shape of the compartment 2 is preferably triangular, quadrilateral, pentagonal, hexagonal, or octagonal. Furthermore, regarding the shape of the compartments 2, all compartments 2 can have the same shape or different shapes. For example, although the illustration is omitted, quadrilateral compartments and octagonal compartments can coexist. Furthermore, regarding the size of the compartments 2, all compartments 2 can have the same size or different sizes. For example, although the illustration is omitted, among multiple compartments, some compartments can be larger in size, while the size of other compartments can be relatively smaller. It should be noted that in this invention, compartment 2 refers to the space surrounded by partition walls 1.

[0066] The compartment density of compartment 2 formed by partition 1 is preferably 43 to 56 compartments / cm². 2 More preferably, 48–51 cells / cm 2 By configuring it in this way, the honeycomb filter 100 can be well utilized as a filter for purifying exhaust gases emitted from the engine of a car.

[0067] 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 formed outer peripheral wall can be removed by known methods such as grinding, and then an outer peripheral coating can be provided on the outer peripheral side of the partition wall.

[0068] 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 in shape such as circular, elliptical, or polygonal.

[0069] There are no particular limitations on the size of the honeycomb structure section 4, such as the 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, the sizes can be appropriately selected in a way that obtains the best purification performance.

[0070] In the honeycomb filter 100, sealing portions 5 are 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 is designated as the outflow end face, the compartment 2 with the sealing portions 5 at the openings on the outflow end face side and the openings on the inflow end face side is designated as the inflow compartment 2a. In addition, the compartment 2 with the sealing portions 5 at the openings on the inflow end face side and the openings on the outflow end face side is designated as the outflow compartment 2b. The inflow compartment 2a and the outflow compartment 2b are preferably arranged alternately with the partition wall 1 in between. Furthermore, it is preferable that a checkerboard pattern is formed on the two end faces of the honeycomb filter 100 through the sealing portions 5 and the openings of the compartment 2.

[0071] The material of the sealing portion 5 is preferably the same as the material of the partition 1. The material of the sealing portion 5 and the material of the partition 1 can be the same or different.

[0072] The honeycomb filter 100 preferably has a catalyst for purifying exhaust gas supported in the partition wall 1 that divides the space into multiple compartments 2. Supporting the catalyst in the partition wall 1 means that the catalyst is coated on the surface of the partition wall 1 and the inner wall of the pores formed in the partition wall 1.

[0073] (2) Manufacturing method of honeycomb filter:

[0074] Figures 1-3 The manufacturing method of the honeycomb filter of this embodiment is not particularly limited, and it can be manufactured by, for example, the following method. First, a plastic blank for making the honeycomb structure is prepared. For example, the blank for making the honeycomb structure can be prepared as follows. As raw material powder, talc, kaolin, alumina, aluminum hydroxide, silicon dioxide, etc. can be used, and the above raw material powder is adjusted to a chemical composition in the range of 42-56% by mass of silicon dioxide, 30-45% by mass of alumina, and 12-16% by mass of magnesium oxide.

[0075] For the honeycomb filter of this embodiment, in the pore size distribution of the partition wall, the values ​​of D10 and D90 are within a specified range and (Log(D90)-Log(D10)) / Log(D50) is 0.75 or less. Furthermore, the number of pores on the partition wall surface (pores / mm) is... 2 The average opening diameter (μm) of the pores is also within a specific range. As a method for manufacturing the aforementioned honeycomb filter, for example, a method is described in which a raw material comprising at least one of fused silica and porous silica is used as the blank, and the ratio of fused silica and porous silica contained in the raw material is adjusted.

[0076] Next, the blank obtained above is extruded and molded to produce a honeycomb molded body with partitions forming multiple compartments and an outer wall arranged around the partition.

[0077] The resulting honeycomb molded body is dried using, for example, microwaves and hot air. The openings of the compartments are sealed using the same material that functions as the honeycomb molded body, thus creating sealed sections. After creating the sealed sections, the honeycomb molded body can be further dried.

[0078] Next, the honeycomb molded body with sealed pores is fired to manufacture a honeycomb filter. 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 chosen materials.

[0079] Example

[0080] The present invention will be described in more detail below through embodiments; however, the present invention is not limited to these embodiments in any way.

[0081] (Example 1)

[0082] To prepare a raw material, 2.0 parts by weight of a pore-forming material, 1.0 part by weight of a dispersion medium, and 6 parts by weight of an organic binder are added to 100 parts by weight of cordierite petrochemical raw material. The mixture is then kneaded and mixed. Methylcellulose is used as the organic binder. Potassium laurate soap is used as the dispersant. A water-absorbing polymer with an average particle size of 20 μm is used as the pore-forming material. Talc, kaolin, alumina, aluminum hydroxide, and porous silica are used as the cordierite petrochemical raw material.

[0083] Next, the obtained preform is shaped using an extrusion molding machine to create a honeycomb structure. The honeycomb structure is then subjected to high-frequency dielectric heating and drying, followed by further drying using a hot air dryer. The cells in the honeycomb structure are designed to be quadrilateral.

[0084] 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. Next, the masked end (the end on the inflow end face side) is immersed in sealing slurry, and the sealing slurry is filled into the openings of the unmasked compartments (outflow compartments). Accordingly, 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.

[0085] 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.

[0086] 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 0.191 mm, and the cell density is 50 cells / cm³. 2 The values ​​of the wall thickness and the compartment density are shown in Table 1.

[0087] For the honeycomb filter of Example 1, the porosity of the partition walls was measured using the following method. Additionally, the cumulative pore volume of the partition walls was measured, and based on the measurement results, a graph was constructed with the horizontal axis representing the pore diameter (μm) and the vertical axis representing the logarithmic differential pore volume (cm²). 3The fine pore size distribution of the fabricated pores ( / g) was calculated, and the values ​​of D10 (μm), D50 (μm), and D90 (μm) were determined. The results are shown in Table 1. It should be noted that D50 (μm) is the average fine pore size (μm) of the partition wall. In addition, based on the values ​​of D10 (μm), D50 (μm), and D90 (μm), the value of (Log(D90)-Log(D10)) / Log(D50) was calculated. The calculated value is recorded in the "Equation (1)" column of Table 1. In Table 1, Equation (1) represents (Log(D90)-Log(D10)) / Log(D50). In addition, D50 (μm) represents the average fine pore size (μm) of the partition wall.

[0088] Table 1

[0089]

[0090] Porosity

[0091] The porosity of the septum was determined using an Autopore 9500 (trade name) manufactured by Micromeritics. For the porosity determination, a portion of the septum was cut from the honeycomb filter to create a test piece, which was then used to measure its porosity. The test piece was a cuboid with lengths of approximately 10 mm, widths of approximately 10 mm, and heights of approximately 20 mm. The test piece was taken from near the axial center of the honeycomb structure.

[0092] [Cumulative pore volume (D10, D50, D90, and formula (1))]

[0093] The cumulative pore volume of the partition wall was determined using an Autopore 9500 (trade name) manufactured by Micromeritics. The cumulative pore volume was measured using a porosity test piece.

[0094] For the cellular filter of Example 1, pressure loss performance, trapping performance, and isostatic strength were evaluated using the following methods. The results are shown in Table 2.

[0095] [Pressure Loss Performance Evaluation]

[0096] Exhaust gas from a 6.7L diesel engine was fed into the honeycomb filter of each embodiment and comparative example. The septa of the honeycomb filter were used to collect soot from the exhaust gas. 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 subjected to a flow rate of 12Nm. 3The pressure at the inflow and outflow sides of the honeycomb filter was measured at an inflow rate of / min. Then, the pressure difference between the inflow and outflow sides was calculated, thereby determining the pressure loss (kPa) of the honeycomb filter. The honeycomb filters of each embodiment and comparative example were evaluated based on the following evaluation criteria. First, the pressure loss value of the honeycomb filter of Comparative Example 1 was set as P0, and the pressure loss value of each honeycomb filter was set as P... x Calculate (P) x The value of -P0) / P0. Set the calculated value as "pressure loss ratio (%)", and set the case where the pressure loss ratio (%) is negative (less than 0%) as qualified, and the case where the pressure loss ratio (%) is greater than 0% as unqualified.

[0097] [Capture Performance Evaluation]

[0098] Exhaust gas from a 6.7L diesel engine was fed into the honeycomb filters of each embodiment and comparative example. The honeycomb filter septa were used to collect the number of soot particles in the exhaust gas. In determining the number of soot particles, the cumulative number of soot particles emitted after driving in WHTC (World Harmonized Transient Cycle) mode was set as the number of soot particles in the honeycomb filter to be evaluated. The honeycomb filters of each embodiment and comparative example were evaluated based on the following evaluation criteria. First, the number of soot particles emitted from the honeycomb filter of Comparative Example 1 was set as N0, and the number of soot particles emitted from each honeycomb filter was set as N... x Calculate (N) x The value of -N0) / N0. Set the calculated value as "the percentage of soot emissions (%)", and set the case where the percentage of soot emissions (%) is negative (less than 0%) as qualified, and the case where the percentage of soot emissions (%) is greater than 0% as unqualified.

[0099] [Isostatic Strength Evaluation]

[0100] The isostatic pressure breaking strength of the honeycomb filters in each embodiment and comparative example was measured according to the method for determining isostatic pressure breaking strength as specified in the JASO standard M505-87 issued by the China Automotive Technology and Research Center. In the isostatic pressure strength evaluation, an isostatic pressure strength of 0.7 MPa or higher was considered acceptable, while an isostatic pressure strength less than 0.7 MPa was considered unacceptable.

[0101] Table 2

[0102]

[0103] (Examples 2-14)

[0104] In Examples 2-14, for the preparation of the blanks used to make the honeycomb molded body, the raw materials shown below were used to manufacture honeycomb filters with the wall thickness and cell density shown in Table 1. For the obtained honeycomb filters, the porosity of the wall was measured using the same method as in Example 1. In addition, the cumulative pore volume of the wall was measured, and D10 (μm), D50 (μm), and D90 (μm) were calculated based on the pore size distribution obtained from the measurement results. The results are shown in Table 1. It should be noted that in Examples 2-14, the average particle size, blending ratio, and amount of added water of the water-absorbing polymer, etc., in the raw materials were changed.

[0105] (Comparative Examples 1-8)

[0106] In Comparative Examples 1-8, the raw materials shown below were used to prepare the blanks for making the honeycomb molded bodies, and honeycomb filters with the wall thickness and cell density shown in Table 1 were manufactured. The porosity of the wall was measured for the obtained honeycomb filters using the same method as in Example 1. Furthermore, the cumulative pore volume of the wall was measured, and D10 (μm), D50 (μm), and D90 (μm) were calculated based on the pore size distribution obtained from the measurement results. The results are shown in Table 1. It should be noted that in Comparative Examples 1-8, the average particle size, blending ratio, and amount of added water of the water-absorbing polymer, etc., in the raw materials were changed. In addition, in some comparative examples, a pore-forming resin was added to the pore-forming material.

[0107] For the honeycomb filters of Examples 2-14 and Comparative Examples 1-8, pressure loss performance, trapping performance, and isostatic strength were evaluated using the same method as in Example 1. The results are shown in Table 2.

[0108] (result)

[0109] It was confirmed that the honeycomb filters of Examples 1-14 outperformed the honeycomb filter of Comparative Example 1, which served as the benchmark, in all evaluations of pressure loss performance, collection performance, and isostatic strength. Therefore, the honeycomb filters of Examples 1-14 exhibit excellent collection performance and, compared with conventional honeycomb filters such as Comparative Example 1, can effectively suppress the increase in pressure loss.

[0110] On the other hand, the honeycomb filters of Comparative Examples 2 to 8 performed worse than the honeycomb filter of Comparative Example 1, which served as the benchmark, in any evaluation of pressure loss performance, trapping performance, and isostatic strength.

[0111] In the honeycomb filter of Comparative Example 2, the number of pores on the partition surface is as low as 780 per mm. 2 It has poor pressure loss performance.

[0112] In the honeycomb filter of Comparative Example 3, the number of pores on the partition surface is as high as 1550 per mm. 2 It has low isostatic strength.

[0113] In the honeycomb filter of Comparative Example 4, the porosity of the partition wall was as low as 56.5%, resulting in poor pressure loss performance.

[0114] In the honeycomb filter of Comparative Example 5, the porosity of the partition wall is as high as 63.4%, and the isostatic strength is low.

[0115] In the honeycomb filter of Comparative Example 6, the values ​​of D10, D50 and D90 are lower than the specified range, indicating poor pressure loss performance.

[0116] In the cellular filter of Comparative Example 7, the values ​​of D10, D50 and D90 exceeded the specified range, resulting in poor collection performance.

[0117] In the honeycomb filter of Comparative Example 8, the thickness of the partition wall reached 0.229 mm. In addition, the values ​​of D10 and D90 deviated from the specified range, resulting in poor pressure loss performance.

[0118] Industrial availability

[0119] The honeycomb filter of the present invention can be used as a trap filter for removing particles and the like contained in exhaust gas.

Claims

1. A honeycomb filter, characterized in that, have: A columnar honeycomb structure having porous partitions configured to surround a plurality of compartments forming a fluid flow path extending from a first end face to a second end face; as well as 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. The thickness of the partition wall is less than 0.217 mm. The porosity of the partition wall is 57%–63%. The average pore size of the partition wall is 6μm to 14μm. The number of pores with an equivalent circular diameter exceeding 3 μm on the surface of the partition wall is 800 per unit area / mm. 2 ~1250 pieces / mm 2 , The average opening equivalent circle diameter of the pores with an equivalent circle diameter exceeding 3 μm present on the surface of the partition wall is 6.7 μm to 9.6 μm. In the pore size distribution of the partition wall, 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. Here, the unit of pore size is μm. D10 ranges from 3.0 μm to 7.0 μm. D90 ranges from 13.0 μm to 27.0 μm. (Log(D90) - Log(D10)) / Log(D50) is below 0.

75.

2. The honeycomb filter according to claim 1, characterized in that, The thickness of the partition wall is less than 0.204 mm. The porosity of the partition wall is 58%–62%. The average pore size of the partition wall is 8μm to 12μm. The number of pores with an equivalent circular diameter exceeding 3 μm on the surface of the partition wall is 900 per unit area / mm. 2 ~1250 pieces / mm 2 , The average opening equivalent circle diameter of the fine pores with an equivalent circle diameter exceeding 3 μm present on the surface of the partition wall is 8.9 μm to 9.6 μm. D10 ranges from 3.7 μm to 5.9 μm. D90 ranges from 15.0 μm to 26.0 μm. (Log(D90) - Log(D10)) / Log(D50) is below 0.

67.

3. The honeycomb filter according to claim 1 or 2, characterized in that, The cell density of the honeycomb structure is 43 cells / cm². 2 ~56 pieces / cm 2 .

4. The honeycomb filter according to claim 1 or 2, characterized in that, The partition is made of a material containing cordierite as the main component.

5. The honeycomb filter according to claim 3, characterized in that, The partition is made of a material containing cordierite as the main component.

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