Honeycomb Filter

Abstract

To provide a honeycomb filter excellent in collection performance and capable of suppressing an increase in pressure loss.SOLUTION: The thickness of a partition wall 1 is 0.257 mm or less, the porosity of the partition wall 1 is 52-57%, the average pore diameter of the partition wall 1 is 6-13 μm, the number of pores with an equivalent circle diameter of more than 3 μm per unit area present on the surface of the partition wall 1 is 800-1500 / mm2, and the average opening equivalent circle diameter of pores with an equivalent circle diameter of more than 3 μm present on the surface of the partition wall 1 is 8.0-12.0 μm. In a pore size distribution of the partition wall 1, when the pore diameters (μm) at which the cumulative pore volumes account for 10%, 50% and 90% of the total pore volume are defined as D10, D50 and D90 respectively, D10 is 2.0-5.5 μm, D90 is 13.0-25.5 μm, and (Log(D90)-Log(D10)) / Log(D50) is 0.84 or less.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a honeycomb filter, and more particularly to a honeycomb filter that has excellent collection performance and is capable of suppressing an increase in pressure loss. [Background technology]

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

[0003] Currently, exhaust gas regulations for large diesel vehicles are becoming stricter every year, and in particular, emission standards for PM such as soot in exhaust gas (PN regulations: particle matter number regulations) are becoming stricter. For this reason, diesel vehicles are required to be equipped with exhaust gas purification filters, such as diesel particulate filters (DPFs). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 2019-171318 Summary of the Invention [Problem to be solved by the invention]

[0005] One way to improve the collection performance of honeycomb filters such as DPFs is to reduce the average pore size of the partition walls that form the filter body, but this comes at the cost of increasing pressure loss. On the other hand, for diesel vehicles and other vehicles, fuel efficiency regulations are becoming stricter every year, so an increase in pressure loss in honeycomb filters is undesirable from the perspective of fuel efficiency.

[0006] The present invention has been made in view of the problems associated with the prior art. According to the present invention, a honeycomb filter is provided that has excellent filtering performance and can effectively suppress an increase in pressure loss. In particular, according to the present invention, a honeycomb filter is provided that has excellent filtering performance and can suppress an increase in pressure loss while favorably accommodating thinner partition walls and higher porosity. [Means for solving the problem]

[0007] According to the present invention, there is provided the following honeycomb filter.

[0008] [1] A columnar honeycomb structure portion having porous partition walls arranged to surround a plurality of cells that serve as fluid flow paths extending from a first end surface to a second end surface; a plugging portion disposed at an opening on the first end face side or the second end face side of each of the cells, The thickness of the partition wall is 0.257 mm or less, the porosity of the partition walls is 52 to 57%, the partition walls have an average pore size of 6 to 13 μm, The number of pores having a circle equivalent diameter of more than 3 μm present on the surface of the partition wall per unit area is 800 to 1500 pores / mm 2 and the average equivalent circle diameter of pores having an equivalent circle diameter of more than 3 μm present in the surface of the partition wall is 8.0 to 12.0 μm, In the pore size distribution of the partition walls, when a pore size (μm) at which the cumulative pore volume becomes 10% of the total pore volume is defined as D10, a pore size (μm) at which the cumulative pore volume becomes 50% of the total pore volume is defined as D50, and a pore size (μm) at which the cumulative pore volume becomes 90% of the total pore volume is defined as D90, D10 is 2.0 to 5.5 μm, D90 is 13.0 to 25.5 μm, A honeycomb filter in which (Log(D90)-Log(D10)) / Log(D50) is 0.84 or less.

[0009] [2] The thickness of the partition wall is 0.252 mm or less, the porosity of the partition walls is 52.6 to 56.2%, the partition walls have an average pore size of 7 to 12 μm, The number of pores having a circle equivalent diameter of more than 3 μm present on the surface of the partition wall per unit area is 850 to 1260 pores / mm 2 and the average equivalent circle diameter of pores having an equivalent circle diameter of more than 3 μm present in the surface of the partition wall is 8.8 to 11.2 μm, D10 is 2.8 to 5.0 μm, D90 is 16.5 to 24.0 μm, The honeycomb filter according to [1] above, wherein (Log(D90)-Log(D10)) / Log(D50) is 0.77 or less.

[0010] [3] The cell density of the honeycomb structure part is 43 to 56 cells / cm 2 The honeycomb filter according to the above [1] or [2],

[0011] [4] The honeycomb filter according to any one of the above [1] to [3], wherein the partition walls are made of a material containing cordierite as a main component. [Effects of the Invention]

[0012] The honeycomb filter of the present invention has the effect of exhibiting excellent filtering performance and suppressing an increase in pressure loss. That is, the honeycomb filter of the present invention achieves excellent filtering performance by setting the partition wall thickness, porosity, and average pore diameter within the above-mentioned numerical ranges. In particular, extremely excellent filtering performance is achieved by reducing the average pore diameter of the partition walls. Meanwhile, by increasing the number of pores opening to the surface of the partition walls, the flow of exhaust gas passing through the partition walls is made uniform, thereby avoiding or suppressing an increase in pressure loss that occurs when the average pore diameter of the partition walls is reduced.

[0013] The honeycomb filter of the present invention can, for example, satisfactorily accommodate thinner partition walls with higher porosity, while realizing excellent collection performance and effectively suppressing an increase in pressure loss. [Brief explanation of the drawings]

[0014] [Figure 1] 1 is a perspective view seen from the inlet end face side, schematically showing one embodiment of a honeycomb filter of the present invention. [Figure 2] FIG. 2 is a plan view of the honeycomb filter shown in FIG. 1 as viewed from the inlet end face side. [Figure 3] FIG. 3 is a cross-sectional view schematically showing the AA' cross section of FIG. DETAILED DESCRIPTION OF THE INVENTION

[0015] While the present invention will be described below with reference to exemplary embodiments, it should be understood that the present invention is not limited to the following exemplary embodiments. Therefore, it should be understood that modifications and improvements to the following exemplary embodiments, based on the ordinary knowledge of those skilled in the art, are also within the scope of the present invention, provided that they do not deviate from the spirit of the present invention.

[0016] (1) Honeycomb filter: As shown in Figs. 1 to 3, a first embodiment of the honeycomb filter of the present invention is a honeycomb filter 100 including a honeycomb structure portion 4 and plugging portions 5. The honeycomb structure portion 4 is columnar and has porous partition walls 1 arranged so as to surround a plurality of cells 2 that serve as fluid flow paths extending from a first end face 11 to a second end face 12. In the honeycomb filter 100, the honeycomb structure portion 4 is columnar and further has an outer peripheral wall 3 on its outer peripheral side surface. That is, the outer peripheral wall 3 is arranged so as to surround the partition walls 1 arranged in a lattice pattern.

[0017] Fig. 1 is a perspective view seen from the inflow end face side, schematically showing one embodiment of a honeycomb filter of the present invention. Fig. 2 is a plan view seen from the inflow end face side of the honeycomb filter shown in Fig. 1. Fig. 3 is a cross-sectional view schematically showing the A-A' cross section of Fig. 2.

[0018] In the honeycomb filter 100, the partition walls 1 that constitute the honeycomb structure portion 4 are configured as follows.

[0019] In the honeycomb filter 100, the porosity of the partition walls 1 is 52 to 57%. The porosity of the partition walls 1 is a value measured by mercury intrusion porosimetry. The porosity of the partition walls 1 can be measured using, for example, an Autopore 9500 (product name) manufactured by Micromeritics. The porosity can be measured using a test piece obtained by cutting out a part of the partition walls 1 from the honeycomb filter 100. The porosity of the partition walls 1 is preferably 52.6 to 56.2%, and more preferably 53.0 to 55.0%.

[0020] The pressure loss can be reduced by setting the porosity of the partition walls 1 to 52 to 57%. If the porosity of the partition walls 1 is less than 52%, the effect of reducing the pressure loss of the honeycomb filter 100 cannot be sufficiently obtained. On the other hand, if the porosity of the partition walls 1 exceeds 57%, the mechanical strength of the honeycomb filter 100 decreases.

[0021] In the honeycomb filter 100, the average pore diameter of the partition walls 1 is 6 to 13 μm. The average pore diameter of the partition walls 1 is a value measured by mercury intrusion porosimetry. The average pore diameter of the partition walls 1 can be measured using, for example, Autopore 9500 (trade name) manufactured by Micromeritics. The average pore diameter can be measured using the above-mentioned test piece for measuring porosity. The average pore diameter of the partition walls 1 is preferably 7 to 12 μm. The average pore diameter of the partition walls 1 is a value calculated by defining it as the pore diameter that gives half the total pore volume by mercury intrusion porosimetry. The average pore diameter of the partition walls 1 corresponds to the value of "D50 (μm)" in the pore size distribution of the partition walls 1 described below.

[0022] By setting the average pore diameter of the partition walls 1 to 6 to 13 μm, it is possible to improve the filtering performance while reducing the pressure loss. If the average pore diameter of the partition walls 1 is less than 6 μm, the permeation resistance increases, which is undesirable in terms of increasing the pressure loss. On the other hand, if the average pore diameter of the partition walls 1 exceeds 13 μm, the effect of improving the filtering efficiency of the honeycomb filter 100 cannot be sufficiently obtained.

[0023] In addition, the partition walls 1 constituting the honeycomb structure portion 4 have a unit area (1 mm 2 ) of pores having a circle-equivalent diameter of more than 3 μm present on the surface of the partition walls 1. 2 ) is 800 to 1500 pieces / mm 2 Hereinafter, the number of pores present on the surface of the partition wall 1 per unit area (pores / mm 2 ) is simply expressed as the number of pores on the partition wall surface (number / mm 2 The number of pores on the partition wall surface is 800 / mm 2 If the number of pores on the surface of the partition wall 1 is less than 1500 / mm, a sufficient effect of suppressing an increase in pressure loss cannot be obtained. 2 If the thickness exceeds this value, the mechanical strength of the honeycomb filter 100 will decrease.

[0024] Number of pores on the partition wall surface (pcs / mm 2 ) is not particularly limited, but is preferably 850 to 1260 pieces / mm 2 It is preferable that the number of particles is 980 to 1250 / mm 2By configuring in this manner, the above-mentioned effects can be further improved.

[0025] In the partition walls 1 constituting the honeycomb structure portion 4, the pores present on the surface of the partition walls 1 and having an equivalent circle diameter of more than 3 μm have an average equivalent circle diameter of 8.0 to 12.0 μm. Hereinafter, the average equivalent circle diameter (μm) of the pores present on the surface of the partition walls 1 may be simply referred to as "the average equivalent circle diameter (μm) of the pores on the surface of the partition walls 1" or "the average opening diameter (μm) of the pores on the surface of the partition walls 1." If the average opening diameter of the pores on the surface of the partition walls 1 is less than 8.0 μm, this is not preferable in terms of a decrease in isostatic strength. If the average opening diameter of the pores on the surface of the partition walls 1 exceeds 12.0 μm, the effect of improving the collection efficiency of the honeycomb filter 100 cannot be sufficiently obtained.

[0026] The average opening diameter (μm) on the surface of the partition walls 1 is not particularly limited, but is preferably 8.8 to 11.2 μm, and more preferably 9.2 to 10.2 μm. By configuring in this way, the above-mentioned effects can be further improved.

[0027] Number of pores on the partition wall surface (pcs / mm 2 ) and the average opening diameter (μm) of the pores can be measured by the following method. First, a measurement sample is cut out from the honeycomb structure section 4 so that the partition wall 1 surface of the honeycomb structure section 4 can be observed. Then, the partition wall 1 surface of the measurement sample is photographed with a laser microscope. As the laser microscope, for example, a shape analysis laser microscope "VK X250 / 260 (product name)" manufactured by Keyence Corporation can be used. When photographing the partition wall 1 surface, the magnification is set to 480 times, and arbitrary locations in 10 fields of view are photographed. The photographed image is subjected to image processing to determine the number of pores (number / mm 2) and the average opening diameter (μm) of the pores are calculated. Note that, in the image processing, an area is selected so that the area for image processing does not include any partition 1 portion other than the partition 1 surface, and the inclination of the partition 1 surface is corrected to be horizontal. After that, the upper limit of the height recognized as a pore is changed to -3.0 μm from the reference plane. Under the condition that pores with a circular equivalent diameter of 3 μm or less are ignored, the number of pores (pieces) in the captured image and the circular equivalent diameter (μm) of each pore are calculated using image processing software. The circular equivalent diameter (μm) of the pores on the partition 1 surface can be calculated by measuring the opening area S of each pore and using the measured area S as the circular equivalent diameter = √{4 × (area S) / π}. The number of pores on the partition 1 surface (pieces / mm 2 The values ​​of ) are the measurement results of 10 visual fields (i.e., the number of pores (number / mm 2 )) is taken as the average value of the measurement results of 10 visual fields (i.e., the average opening diameter (μm) of each captured image of 10 visual fields). As the image processing software, for example, "VK-X (product name)" attached to the shape analysis laser microscope "VK X250 / 260 (product name)" manufactured by Keyence Corporation can be used. Measurement of the circle equivalent diameter of each pore and image analysis ignoring pores with a predetermined circle equivalent diameter can be performed using the image processing software described above.

[0028] Furthermore, the honeycomb filter 100 has a cumulative pore volume of the partition walls 1 measured by mercury porosimetry, with the horizontal axis representing the pore diameter (μm) and the vertical axis representing the log differential pore volume (cm 3 It is preferable that the pore size distribution expressed as Log(D90)-Log(D10) / g is configured as follows. Here, in the pore size distribution of the partition walls 1 described above, the pore size (μm) at which the cumulative pore volume is 10% of the total pore volume is defined as D10. Similarly, the pore size (μm) at which the cumulative pore volume is 50% of the total pore volume is defined as D50, and the pore size (μm) at which the cumulative pore volume is 90% of the total pore volume is defined as D90. In the pore size distribution of the partition walls 1 of the honeycomb filter 100, D10 is 2.0 to 5.5 μm, D90 is 13.0 to 25.5 μm, and (Log(D90)-Log(D10)) / Log(D50) is 0.84 or less.

[0029] When D10 is 2.0 to 5.5 μm, an excellent effect in terms of suppressing pressure loss is achieved. For example, when D10 is less than 2.0 μm, it is not preferable in terms of increasing pressure loss. Conversely, when D10 exceeds 5.5 μm, it is not preferable in terms of decreasing collection performance. D10 is preferably 2.8 to 5.0 μm.

[0030] Furthermore, when D90 is 13.0 to 25.5 μm, an excellent effect is exhibited in terms of improving collection performance. For example, when D90 is less than 13.0 μm, it is not preferable in terms of increasing pressure loss. Conversely, when D90 exceeds 25.5 μm, it is not preferable in terms of decreasing collection performance. D90 is preferably 16.5 to 24.0 μm.

[0031] When (Log(D90) - Log(D10)) / Log(D50) is 0.84 or less, an excellent effect is achieved in terms of suppressing pressure loss. (Log(D90) - Log(D10)) / Log(D50) is preferably 0.77 or less. There is no particular restriction on the lower limit of (Log(D90) - Log(D10)) / Log(D50), but the practical lower limit is 0.55.

[0032] The cumulative pore volume of the partition walls 1 is a value measured by mercury intrusion porosimetry. The cumulative pore volume of the partition walls 1 can be measured using, for example, an Autopore 9500 (trade name) manufactured by Micromeritics. The cumulative pore volume of the partition walls 1 can be measured by the following method. First, a test piece for measuring the cumulative pore volume is prepared by cutting out a portion of the partition walls 1 from the honeycomb filter 100. There are no particular restrictions on the size of the test piece, but it is preferably a rectangular parallelepiped with lengths of approximately 10 mm, approximately 10 mm, and approximately 20 mm in height, for example. There are no particular restrictions on the part of the partition walls 1 from which the test piece is cut out, but it is preferably prepared by cutting out the test piece from near the center in the axial direction of the honeycomb structure part. The obtained test piece is placed in a measurement cell of a measurement device, and the pressure inside the measurement cell is reduced. Next, mercury is introduced into the measurement cell. Next, the mercury introduced into the measurement cell is pressurized, and the volume of mercury forced into the pores present in the test piece is measured. As the pressure applied to the mercury increases, the mercury is forced from the larger pores to the smaller pores. Therefore, the relationship between the "pore size of the pores formed in the test piece" and the "cumulative pore volume" can be determined from the relationship between the "pressure applied to the mercury" and the "volume of mercury forced into the pores." As described above, when pressure is gradually applied to force mercury into the pores of a sample (test piece) in a sealed vacuum container using the mercury intrusion method, the applied pressure causes the mercury to penetrate the pores in the sample, from the larger pores to the smaller pores. The pore size and pore volume of the pores formed in the sample can be calculated from the pressure and the amount of mercury injected. Hereinafter, when pore diameters are designated as D1, D2, D3, etc., they are assumed to satisfy the relationship D1>D2>D3. Here, the average pore diameter D between each measurement point (for example, from D1 to D2) can be shown on the horizontal axis as "average pore diameter D = (D1 + D2) / 2." Furthermore, the log differential pore volume on the vertical axis can be calculated by dividing the increase in pore volume dV between each measurement point by the logarithmic difference in pore diameter (i.e., "log(D1) - log(D2)").

[0033] The thickness of the partition wall 1 is 0.257 mm or less. The thickness of the partition wall 1 can be measured using, for example, a scanning electron microscope or a microscope. If the thickness of the partition wall 1 exceeds 0.257 mm, a sufficient effect of suppressing an increase in pressure loss cannot be obtained. The thickness of the partition wall 1 is preferably 0.252 mm or less. There is no particular restriction on the lower limit of the thickness of the partition wall 1; however, for example, if the thickness of the partition wall 1 is extremely thin, it may affect the collection performance and mechanical strength. Therefore, although there is no particular restriction, the lower limit of the thickness of the partition wall 1 can be 0.152 mm.

[0034] The honeycomb filter 100 of this embodiment has excellent filtering performance and exhibits the effect of being able to suppress an increase in pressure loss. For example, the honeycomb filter 100 of this embodiment achieves excellent filtering performance by setting the thickness, porosity, and average pore diameter of the partition walls 1 within the numerical ranges described above. In particular, extremely excellent filtering performance is achieved by reducing the value of the average pore diameter of the partition walls 1. On the other hand, by increasing the number of pores opening on the surface of the partition walls 1, the flow of exhaust gas passing through the partition walls 1 is made uniform, thereby avoiding or suppressing an increase in pressure loss that occurs when the average pore diameter of the partition walls 1 is reduced. The honeycomb filter 100 of this embodiment can achieve excellent filtering performance and effectively suppress an increase in pressure loss, while, for example, favorably accommodating thinner and higher porosity partition walls 1.

[0035] There is no particular limitation on the material of the partition wall 1, and the pore size distribution of the partition wall 1 and the number of pores on the surface of the partition wall 1 (number / mm 2) and the average opening diameter (μm) of the pores may be any porous material that satisfies the configuration described above. For example, the material for the partition walls 1 preferably includes at least one selected from the group consisting of cordierite, silicon carbide, a silicon-silicon carbide composite material, a cordierite-silicon carbide composite material, silicon nitride, mullite, alumina, and aluminum titanate. The material for the partition walls 1 preferably contains 90 mass% or more of the materials listed in the above group, more preferably 92 mass% or more, and particularly preferably 95 mass% or more. The silicon-silicon carbide composite material is a composite material formed using silicon carbide as an aggregate and silicon as a binder. The cordierite-silicon carbide composite material is a composite material formed using silicon carbide as an aggregate and cordierite as a binder. In the honeycomb filter 100 of the present embodiment, the material for the partition walls 1 is preferably a material containing cordierite as a main component.

[0036] The shape of the cells 2 formed in the honeycomb structure section 4 is not particularly limited. For example, examples of the shape of the cells 2 in a cross section perpendicular to the extension direction of the cells 2 include polygons, circles, ellipses, etc. Examples of polygons include triangles, rectangles, pentagons, hexagons, and octagons. Note that the shape of the cells 2 is preferably triangles, rectangles, pentagons, hexagons, or octagons. Furthermore, with regard to the shape of the cells 2, all the cells 2 may have the same shape or different shapes. For example, although not shown in the drawings, a mixture of rectangles and octagons may be used. Furthermore, with regard to the size of the cells 2, all the cells 2 may have the same size or different sizes. For example, although not shown in the drawings, among a plurality of cells, the size of some cells may be large and the size of the other cells may be relatively small. Note that in the present invention, the cell 2 refers to a space surrounded by the partition walls 1.

[0037] The cell density of the cells 2 partitioned by the partition walls 1 is 43 to 56 cells / cm 2 It is preferable that the density is 48 to 51 particles / cm 2With this configuration, the honeycomb filter 100 can be suitably used as a filter for purifying exhaust gas emitted from an automobile engine.

[0038] The outer peripheral wall 3 of the honeycomb structure portion 4 may be configured integrally with the partition walls 1, or may be an outer peripheral coating layer formed by applying an outer peripheral coating material to the outer peripheral side of the partition walls 1. For example, although not shown in the drawings, the outer peripheral coating layer can be provided on the outer peripheral side of the partition walls after the partition walls and the outer peripheral wall are integrally formed during production and then the formed outer peripheral wall is removed by a known method such as grinding.

[0039] There is no particular limitation on the shape of the honeycomb structure part 4. Examples of the shape of the honeycomb structure part 4 include a columnar shape such as a circle, an ellipse, or a polygon, in which the first end face 11 (for example, an inflow end face) and the second end face 12 (for example, an outflow end face) have a circular, elliptical, or polygonal shape.

[0040] There are no particular limitations on the size of the honeycomb structure part 4, for example, the length from the first end face 11 to the second end face 12 and the size of the cross section perpendicular to the extension direction of the cells 2 of the honeycomb structure part 4. When the honeycomb filter 100 is used as a filter for purifying exhaust gases, each size may be selected appropriately so as to obtain optimal purification performance.

[0041] In the honeycomb filter 100, plugging portions 5 are arranged at openings on the first end face 11 side of predetermined cells 2 and at openings on the second end face 12 side of the remaining cells 2. Here, when the first end face 11 is the inflow end face and the second end face 12 is the outflow end face, the plugging portions 5 are arranged at the openings on the outflow end face side, and the cells 2 that are open on the inflow end face side are referred to as inflow cells 2a. Furthermore, the plugging portions 5 are arranged at the openings on the inflow end face side, and the cells 2 that are open on the outflow end face side are referred to as outflow cells 2b. The inflow cells 2a and the outflow cells 2b are preferably arranged alternately with the partition wall 1 between them. As a result, it is preferable that a checkerboard pattern is formed on both end faces of the honeycomb filter 100 by the plugging portions 5 and the "openings of the cells 2."

[0042] The material of the plugging portions 5 is preferably a material that is considered to be preferable as the material of the partition walls 1. The material of the plugging portions 5 and the material of the partition walls 1 may be the same material or different materials.

[0043] In the honeycomb filter 100, a catalyst for purifying exhaust gases is preferably supported on the partition walls 1 that define the plurality of cells 2. Supporting a catalyst on the partition walls 1 means that the surfaces of the partition walls 1 and the inner walls of the pores formed in the partition walls 1 are coated with the catalyst.

[0044] (2) Honeycomb filter manufacturing method: The honeycomb filter of this embodiment shown in Figs. 1 to 3 can be manufactured by any method, for example, as follows. First, a plastic clay for manufacturing the honeycomb structure is prepared. The clay for manufacturing the honeycomb structure can be prepared, for example, as follows. Talc, kaolin, alumina, aluminum hydroxide, silica, etc. are used as raw material powders, and these raw material powders can be prepared so as to have a chemical composition in the range of 42 to 56 mass % silica, 30 to 45 mass % alumina, and 12 to 16 mass % magnesia.

[0045] The honeycomb filter of the present embodiment has a pore size distribution of the partition walls of D10 、D The value of D90 falls within a predetermined range, and (Log(D90)-Log(D10)) / Log(D50) is 0.84 or less. 2 The average opening diameter (μm) of the pores also falls within a specific range. As a method for producing such a honeycomb filter, for example, a method can be mentioned in which a raw material containing at least one of fused silica and porous silica is used as a raw material for the clay, and the ratio of the fused silica and the porous silica contained in such a raw material is adjusted.

[0046] Next, the clay thus obtained is extrusion-molded to produce a honeycomb formed body having partition walls that define a plurality of cells and outer walls disposed so as to surround the partition walls.

[0047] The obtained honeycomb formed body is dried, for example, by microwaves and hot air, and the openings of the cells are plugged with the same material as that used to produce the honeycomb formed body, thereby producing plugging portions. After producing the plugging portions, the honeycomb formed body may be further dried.

[0048] Next, the honeycomb formed body with the plugged portions is fired to manufacture a honeycomb filter. The firing temperature and firing atmosphere vary depending on the raw materials, and a person skilled in the art can select the optimum firing temperature and firing atmosphere for the selected materials. [Example]

[0049] The present invention will be explained in more detail below with reference to examples, but the present invention is not limited to these examples in any way.

[0050] Example 1 To 100 parts by mass of the cordierite raw material, 0.5 parts by mass of a pore-forming material, 1.0 part by mass of a dispersion medium, and 6 parts by mass of an organic binder were added, mixed, and kneaded to prepare a clay. Methylcellulose was used as the organic binder. Potassium laurate soap was used as the dispersant. A water-absorbing polymer with an average particle size of 20 μm was used as the pore-forming material. Talc, kaolin, alumina, aluminum hydroxide, and porous silica were used as the cordierite raw materials.

[0051] The resulting clay was then molded using an extrusion molding machine to produce a honeycomb molded body. The resulting honeycomb molded body was then dried using high-frequency dielectric heating and then further dried using a hot-air dryer. The cell shape of the honeycomb molded body was rectangular.

[0052] Next, plugging portions were formed on the dried honeycomb formed body. First, a mask was applied to the inflow end face of the honeycomb formed body. Next, the masked end (the end on the inflow end face side) was immersed in plugging slurry, and the plugging slurry was filled into the openings of the unmasked cells (outflow cells). In this way, plugging portions were formed on the inflow end face side of the honeycomb formed body. Then, plugging portions were also formed on the inflow cells on the outflow end face of the dried honeycomb formed body in the same manner.

[0053] Next, the honeycomb formed body with the plugged portions formed thereon was dried in a microwave dryer, and further completely dried in a hot air dryer, after which both end faces of the honeycomb formed body were cut and adjusted to a predetermined size. Next, the dried honeycomb formed body was degreased and fired to produce the honeycomb filter of Example 1.

[0054] The honeycomb filter of Example 1 had an end face diameter of 228.6 mm, a length in the cell extension direction of 184.2 mm, a partition wall thickness of 0.241 mm, and a cell density of 51 cells / cm. 2 The partition wall thickness and cell density values ​​are shown in Table 1.

[0055] For the honeycomb filter of Example 1, the porosity of the partition walls was measured by the following method. In addition, the cumulative pore volume of the partition walls was also measured, and based on the measurement results, the horizontal axis represents the pore diameter (μm) and the vertical axis represents the log differential pore volume (cm 3 A pore size distribution expressed as (μm / g) was created, and D10 (μm), D50 (μm), and D90 (μm) of the created pore size distribution were determined. The results are shown in Table 1. D50 (μm) is the average pore size (μm) of the partition walls. From the values ​​of D10 (μm), D50 (μm), and D90 (μm), the value of (Log(D90)-Log(D10)) / Log(D50) was calculated. The calculated values ​​are shown in the column of "Formula (1)" in Table 1. In Table 1, Formula (1) represents (Log(D90)-Log(D10)) / Log(D50). D50 (μm) represents the average pore size (μm) of the partition walls.

[0056] [Table 1]

[0057] [Porosity] The porosity of the partition walls was measured using an Autopore 9500 (trade name) manufactured by Micromeritics. In measuring the porosity, a part of the partition wall was cut out from the honeycomb filter to form a test piece, and the porosity was measured using the obtained test piece. The test piece was a rectangular parallelepiped with length, width, and height of approximately 10 mm, approximately 10 mm, and approximately 20 mm, respectively. The test piece was taken from near the center of the axial direction of the honeycomb structure part.

[0058] [Cumulative pore volume (D10, D50, D90, and formula (1))] The cumulative pore volume of the partition walls was measured using Autopore 9500 (trade name) manufactured by Micromeritics, Inc. The cumulative pore volume was also measured using the same test piece used in measuring the porosity.

[0059] The honeycomb filter of Example 1 was evaluated for pressure loss performance, collection performance, and isostatic strength by the following methods. Table 2 shows the results.

[0060] [Pressure loss performance evaluation] Exhaust gas emitted from a 6.7 L diesel engine was made to flow into the honeycomb filters of each Example and Comparative Example, and soot in the exhaust gas was collected by the partition walls of the honeycomb filter. The soot collection was continued until the amount of soot deposited per unit volume (1 L) of the honeycomb filter reached 3 g / L. Then, when the amount of soot deposited reached 3 g / L, the engine exhaust gas at 200°C was passed through the filter at a flow rate of 12 Nm. 3 / min, and the pressure at the inlet end face side and the outlet end face side of the honeycomb filter was measured. Then, the pressure difference between the inlet end face side and the outlet end face side was calculated to determine the pressure loss (kPa) of the honeycomb filter. The honeycomb filters of each example 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 designated as P0, and the pressure loss value of each honeycomb filter was designated as P xLet (P x The calculated value was taken as the "pressure loss ratio (%)." The pressure loss ratio (%) was calculated as follows: negative A value of less than 0% was judged as pass, and a value of 0% or more was judged as fail.

[0061] [Collection performance evaluation] Exhaust gas emitted from a 6.7 L diesel engine was made to flow into the honeycomb filters of each Example and Comparative Example, and the number of soot particles in the exhaust gas was collected by the partition walls of the honeycomb filter. In determining the number of soot particles, the cumulative total number of soot particles emitted after running in a WHTC (World Harmonized Transient Cycle) mode was taken as the number of soot particles in the honeycomb filter to be evaluated, and the honeycomb filters of each Example 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 taken as NO, and the number of soot particles emitted from each honeycomb filter N x Let (N x The calculated value was taken as the "soot emission number ratio (%)" and the soot emission number ratio (%) was calculated as follows: negative The value (less than 0%) was judged as pass, and the value (%) of the soot emission number ratio (%) of 0% or more was judged as fail.

[0062] [Isostatic strength evaluation] The isostatic strength (MPa) of the honeycomb filters of each example and comparative example was measured according to the method for measuring isostatic fracture strength specified in JASO standard M505-87, an automotive standard issued by the Society of Automotive Engineers of Japan, Inc. In the isostatic strength evaluation, an isostatic strength of 2.3 MPa or more was considered to be pass, and an isostatic strength of less than 2.3 MPa was considered to be fail.

[0063] [Table 2]

[0064] Examples 2 to 14 In Examples 2 to 14, the raw materials shown below were used in preparing clay for producing a honeycomb formed body, and honeycomb filters having the partition wall thickness and cell density shown in Table 1 were manufactured. For the obtained honeycomb filters, the porosity of the partition walls was measured using the same method as in Example 1. The cumulative pore volume of the partition walls was also measured, and D10 (μm), D50 (μm), and D90 (μm) were calculated from the pore size distribution based on the measurement results. The results are shown in Table 1. In Examples 2 to 14, the average particle size, blending ratio, and amount of water added of the water-absorbing polymer and the like in the raw materials were changed.

[0065] (Comparative Examples 1 to 8) In Comparative Examples 1 to 8, the raw materials shown below were used in preparing clay for producing a honeycomb formed body, and honeycomb filters with the partition wall thickness and cell density shown in Table 1 were manufactured. For the obtained honeycomb filters, the porosity of the partition walls was measured using the same method as in Example 1. In addition, the cumulative pore volume of the partition walls was also measured, and D10 (μm), D50 (μm), and D90 (μm) were calculated from the pore size distribution based on the measurement results. The results are shown in Table 1. In Comparative Examples 1 to 8, the average particle size, blending ratio, and amount of water added of the water-absorbing polymer and the like in the raw materials were changed. In addition, in some Comparative Examples, a pore-forming resin was added to the pore-forming material.

[0066] The honeycomb filters of Examples 2 to 14 and Comparative Examples 1 to 8 were evaluated for pressure loss performance, collection performance, and isostatic strength in the same manner as in Example 1. Table 2 shows the results.

[0067] (result) It was confirmed that the honeycomb filters of Examples 1 to 14 exceeded the performance of the benchmark honeycomb filter of Comparative Example 1 in all evaluations of pressure drop performance, collection performance, and isostatic strength. Therefore, the honeycomb filters of Examples 1 to 14 were excellent in collection performance and were able to effectively suppress an increase in pressure drop compared to conventional honeycomb filters such as Comparative Example 1.

[0068] On the other hand, the honeycomb filters of Comparative Examples 2 to 8 were inferior in performance to the honeycomb filter of Comparative Example 1, which was used as the benchmark, in any of the evaluations of pressure loss performance, collection performance, and isostatic strength. The honeycomb filter of Comparative Example 2 had a partition wall surface with pores of 760 / mm 2 The pressure loss performance was poor. The honeycomb filter of Comparative Example 3 had a pore count of 1570 pores / mm 2 Many of them had low isostatic strength. The honeycomb filter of Comparative Example 4 has a partition wall Porosity The pressure loss was low at 51.6%, which was poor. The honeycomb filter of Comparative Example 5 has a partition wall Porosity The strength was high at 57.5% and the isostatic strength was low. The honeycomb filter of Comparative Example 6 had D10, D50 and D90 values ​​below the predetermined ranges, and had poor pressure loss performance. The honeycomb filter of Comparative Example 7 had D10, D50 and D90 values ​​that exceeded the predetermined numerical ranges, and had poor collection performance. The honeycomb filter of Comparative Example 8 had a thick partition wall thickness of 0.262 mm, and the D50 and D90 values ​​and the average opening diameter of the pores on the partition wall surface were outside the specified numerical ranges, resulting in poor pressure loss performance. [Industrial Applicability]

[0069] The honeycomb filter of the present invention can be used as a collection filter for removing particulates and the like contained in exhaust gases. [Explanation of symbols]

[0070] 1: partition wall, 2: cell, 2a: inlet cell, 2b: outlet cell, 3: outer wall, 4: honeycomb structure portion, 5: plugging portion, 11: first end face, 12: second end face, 100: honeycomb filter.

Claims

1. a columnar honeycomb structure portion having porous partition walls arranged to surround a plurality of cells that serve as fluid flow paths extending from a first end face to a second end face; a plugging portion disposed at an opening on the first end face side or the second end face side of each of the cells, The thickness of the partition wall is 0.257 mm or less, the porosity of the partition walls is 52 to 56.9%, the partition walls have an average pore diameter of 7 to 12 μm, The number of pores having a circle equivalent diameter of more than 3 μm present on the surface of the partition wall per unit area is 800 to 1500 pores / mm ２ and the average equivalent circle diameter of pores having an equivalent circle diameter of more than 3 μm present in the surface of the partition walls is 9.2 to 10.2 μm, In the pore size distribution of the partition walls, when a pore size (μm) at which the cumulative pore volume becomes 10% of the total pore volume is defined as D10, a pore size (μm) at which the cumulative pore volume becomes 50% of the total pore volume is defined as D50, and a pore size (μm) at which the cumulative pore volume becomes 90% of the total pore volume is defined as D90, D10 is 2.0 to 5.5 μm, D90 is 13.0 to 25.5 μm, A honeycomb filter, wherein (Log(D90)-Log(D10)) / Log(D50) is 0.84 or less.

2. The thickness of the partition wall is 0.252 mm or less, the porosity of the partition walls is 52.6 to 56.2%, The number of pores having a circle equivalent diameter of more than 3 μm present on the surface of the partition wall per unit area is 850 to 1260 pores / mm ２ and D10 is 2.8 to 5.0 μm, D90 is 16.5 to 24.0 μm, The honeycomb filter according to claim 1, wherein (Log(D90)-Log(D10)) / Log(D50) is 0.77 or less.

3. The cell density of the honeycomb structure part is 43 to 56 cells / cm ２ The honeycomb filter according to claim 1 or 2, wherein

4. The honeycomb filter according to any one of claims 1 to 3, wherein the partition walls are made of a material containing cordierite as a main component.

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