Honeycomb structure

Abstract

To provide a honeycomb structure capable of suppressing peeling of a plugging portion when a film is peeled off.SOLUTION: A honeycomb structure comprises: an outer peripheral sidewall; a plurality of first cells disposed on the inner peripheral side of the outer peripheral sidewall, extending from a first bottom face to a second bottom face, having openings on the first bottom face, and having plugging portions on the second bottom face; and a plurality of second cells disposed on the inner peripheral side of the outer peripheral sidewall, extending from a first bottom face to a second bottom face, having plugging portions on the first bottom face, and having openings on the second bottom face. The plurality of first cells and the plurality of second cells are alternately disposed adjacent to each other with a partition wall interposed therebetween. The plugging portions are formed of ceramics containing 9.0-13.4 mass% of MgO, 29.8-35.0 mass% of Al2O3, and 49.8-57.2 mass% of SiO2, and arithmetic average heights Sa of the plugging portions on the first bottom face and the second bottom face each are 18.0 μm or less.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a honeycomb structure. [Background technology]

[0002] Exhaust gases emitted from internal combustion engines such as diesel engines contain large amounts of particulate matter (particulate matter), which is primarily composed of carbon and causes environmental pollution. For this reason, the exhaust systems of diesel engines and other engines are generally equipped with a filter (Diesel Particulate Filter: DPF) to capture the particulate matter. In recent years, particulate matter emitted from gasoline engines has also become a problem, and gasoline engines are now also being equipped with filters (Gasoline Particulate Filter: GPF).

[0003] A known filter is a wall-flow honeycomb structure having an outer peripheral side wall, a plurality of first cells arranged on the inner peripheral side of the outer peripheral side wall, extending from a first bottom surface to a second bottom surface, with the first bottom surface being open and the second bottom surface being plugged, and a plurality of second cells arranged on the inner peripheral side of the outer peripheral side wall, extending from the first bottom surface to the second bottom surface, with the first bottom surface being open and the second bottom surface being plugged, and the second cells arranged adjacent to each other with partition walls sandwiched between them.

[0004] In a wall-flow honeycomb structure, the plugging parts serve to prevent trapped particulate matter from leaking out of the filter (erosion). For this reason, it is important to ensure filter performance that the plugging parts are formed at the specified positions and to the specified depth without peeling off.

[0005] Patent Document 1 describes a honeycomb filter in which the plugging material is made of a pulverized ceramic material of the same material as the ceramic substrate, with the objective of providing a honeycomb filter in which cracks do not occur in the plugging portions and the substrate, and the plugging portions do not peel off or fall off from the substrate.

[0006] Patent Document 2 describes a honeycomb filter made of a material containing cordierite as the main crystal, with the objective of obtaining a ceramic honeycomb filter with excellent thermal shock resistance, in which at least a portion of the plugging portion is composed of an amorphous oxide matrix formed from ceramic particles and colloidal oxides present between the ceramic particles.

[0007] Patent Document 3 describes a honeycomb structure in which the average porosity of the plugging portions is controlled to 4% or less, with the objective of providing a honeycomb structure that can suppress defects such as plugging peeling during canning and can effectively prevent erosion. [Prior art documents] [Patent documents]

[0008] [Patent Document 1] Japanese Patent Application Laid-Open No. 2002-136817 [Patent Document 2] Japanese Patent Application Laid-Open No. 2005-125318 [Patent Document 3] Patent Publication No. 2021-159868 Summary of the Invention [Problem to be solved by the invention]

[0009] When forming plugging portions, a masking film is temporarily attached to the bottom surface of the honeycomb structure to distinguish between cells to be plugged and other cells. The film is eventually peeled off, but localized plugging peeling occurs during this process, requiring considerable time for repair and, in some cases, resulting in a defective product. Conventional technologies have not provided sufficient countermeasures against plugging peeling during film peeling, and there is still room for improvement.

[0010] The present invention has been made in view of the above circumstances, and an object of one embodiment is to provide a honeycomb structure capable of suppressing peeling of plugged portions when a film is peeled off. [Means for solving the problem]

[0011] The present inventors have conducted extensive research to solve the above problems and have found that controlling the composition and surface roughness of the plugging portions is important for solving the above problems. The present invention has been completed based on this finding and is exemplified below.

[0012] [Aspect 1] A honeycomb structure comprising: an outer peripheral side wall; a plurality of first cells arranged on an inner peripheral side of the outer peripheral side wall, extending from a first bottom surface to a second bottom surface, having openings on the first bottom surface and plugging portions on the second bottom surface; and a plurality of second cells arranged on the inner peripheral side of the outer peripheral side wall, extending from the first bottom surface to the second bottom surface, having plugging portions on the first bottom surface and having openings on the second bottom surface, wherein the plurality of first cells and the plurality of second cells are alternately arranged adjacent to each other with partition walls interposed therebetween, the plugging portion is made of ceramics containing 9.0 to 13.4 mass% of MgO, 29.0 to 35.5 mass% of Al2O3, and 50.0 to 58.0 mass% of SiO2, The arithmetic average height Sa of the plugging portions on the first bottom surface and the second bottom surface is 18.0 μm or less, Honeycomb structure. [Aspect 2] 2. The honeycomb structure according to embodiment 1, wherein the plugging portions are made of ceramics containing 9.0 to 12.0 mass % of MgO, 29.8 to 32.0 mass % of Al2O3, and 54.0 to 57.2 mass % of SiO2. [Aspect 3] 3. The honeycomb structure according to aspect 1 or 2, wherein the arithmetic mean height Sa of the plugging portions on the first bottom surface and the second bottom surface is 5.0 to 17.5 μm. [Aspect 4] 3. The honeycomb structure according to aspect 1 or 2, wherein the arithmetic mean height Sa of the plugging portions on the first bottom surface and the second bottom surface is 5.0 to 12.0 μm. [Aspect 5] 5. The honeycomb structure according to any one of aspects 1 to 4, wherein the plugging portions are in an unfired state. [Aspect 6] 6. The honeycomb structure according to claim 5, wherein the ceramic forming the plugging portions contains cordierite particles and colloidal silica binding the particles together. [Aspect 7] 5. The honeycomb structure according to any one of aspects 1 to 4, wherein the plugging portions are fired. [Aspect 8] 8. The honeycomb structure according to embodiment 7, wherein the ceramic forming the plugging portions is a sintered body of cordierite. [Aspect 9] 9. The honeycomb structure according to any one of aspects 1 to 8, wherein the ceramic constituting the plugging portions has a median diameter of 5 to 25 μm. [Aspect 10] 10. The honeycomb structure according to any one of aspects 1 to 9, wherein the plugging portions in the first bottom surface and the second bottom surface each have an average porosity of 30 to 70%. [Aspect 11] 11. The honeycomb structure according to any one of aspects 1 to 10, wherein the partition walls are made of ceramics containing cordierite as a main component. [Aspect 12] 12. The honeycomb structure according to any one of aspects 1 to 11, wherein the average depth of the plugging portions in the first bottom surface and the second bottom surface is 3 to 7 mm. [Effects of the Invention]

[0013] According to one embodiment of the present invention, there is provided a honeycomb structure capable of suppressing peeling of plugging portions when a film is peeled off. By suppressing peeling of plugging portions, the expected performance required of the plugging portions, such as preventing erosion of trapped particulate matter, can be stably exhibited. Therefore, the honeycomb structure can be suitably used as a honeycomb filter or the like with excellent quality stability. [Brief explanation of the drawings]

[0014] [Figure 1] FIG. 1 is a perspective view schematically showing a wall-flow type honeycomb structure. [Figure 2]FIG. 2 is a schematic cross-sectional view of a wall-flow type honeycomb structure when observed in a cross section parallel to the cell extension direction. [Figure 3] FIG. 3 is a schematic partial enlarged view of a partition wall of a honeycomb structure when observed in a cross section perpendicular to the cell extension direction. [Figure 4] FIG. 10 is a schematic partial cross-sectional view for explaining a method for measuring the depth of plugging portions. [Figure 5] FIG. 10 is an explanatory diagram schematically illustrating an example of a method for forming plugging portions by a squeegee method. DETAILED DESCRIPTION OF THE INVENTION

[0015] Next, embodiments of the present invention will be described in detail with reference to the drawings. It should be understood that the present invention is not limited to the following embodiments, and that appropriate design changes and improvements may be made based on the ordinary knowledge of those skilled in the art without departing from the spirit of the present invention.

[0016] (1. Honeycomb structure) 1 and 2 are a schematic perspective view and a cross-sectional view, respectively, of a honeycomb structure 100 applicable as a wall-flow type automotive exhaust gas filter and / or catalyst carrier. The honeycomb structure 100 includes an outer peripheral sidewall 102, a plurality of first cells 108 arranged on the inner peripheral side of the outer peripheral sidewall 102, extending parallel to each other from a first bottom surface 104 to a second bottom surface 106, having openings on the first bottom surface 104 and plugging portions 109 on the second bottom surface 106, and a plurality of second cells 110 arranged on the inner peripheral side of the outer peripheral sidewall 102, extending parallel to each other from the first bottom surface 104 to the second bottom surface 106, having plugging portions 109 on the first bottom surface 104 and having openings on the second bottom surface 106. In this honeycomb structure 100, the first cells 108 and the second cells 110 are arranged alternately adjacent to each other with partition walls 112 interposed therebetween.

[0017] For example, when exhaust gas containing particulate matter such as soot is supplied to the first bottom surface 104 on the upstream side of the honeycomb structure 100, the exhaust gas is introduced into the first cells 108 and travels downstream within the first cells 108. Because the second bottom surfaces 106 on the downstream side of the first cells 108 are plugged, the exhaust gas passes through the porous partition walls 112 that separate the first cells 108 from the second cells 110 and flows into the second cells 110. Since the particulate matter cannot pass through the partition walls 112, it is captured and deposited within the first cells 108. After the particulate matter is removed, the clean exhaust gas that has flowed into the second cells 110 travels downstream within the second cells 110 and flows out from the second bottom surface 106 on the downstream side.

[0018] The bottom shape of the honeycomb structure 100 is not limited, and may be, for example, a circular shape, an elliptical shape, a round shape such as a racetrack shape or an oval shape, a polygonal shape such as a triangular shape or a square shape, or any other irregular shape. The honeycomb structure 100 may have a cylindrical outer shape. The honeycomb structure 100 shown in the figure has a circular bottom shape and is cylindrical as a whole.

[0019] There is no particular limitation on the height of the honeycomb structure (the length from the first bottom surface to the second bottom surface) and it may be set appropriately depending on the application and required performance. The height of the honeycomb structure may be, for example, 40 mm to 450 mm. There is also no particular limitation on the relationship between the height of the honeycomb structure and the maximum diameter of each bottom surface (the maximum length of the diameters passing through the center of gravity of each bottom surface of the honeycomb structure). Therefore, the height of the honeycomb structure may be longer than the maximum diameter of each bottom surface, or the height of the honeycomb structure may be shorter than the maximum diameter of each bottom surface.

[0020] Although there are no limitations on the opening shape of the cells in a cross section perpendicular to the cell extension direction, a square, a hexagon, an octagon, or a combination thereof is preferred. Among these, a square and a hexagon are preferred. By using such a cell shape, the pressure loss when a fluid is passed through the honeycomb structure is reduced, resulting in excellent purification performance.

[0021] There is no particular restriction on the cell density (the number of cells per unit cross-sectional area), and it can be, for example, 6 to 2000 cells / square inch (0.9 to 311 cells / cm 2 ), more preferably 50 to 1000 cells / square inch (7.8 to 155 cells / cm 2 ), and particularly preferably 100 to 600 cells / square inch (15.5 to 92.0 cells / cm 2 Here, the cell density is calculated by dividing the total number of cells (including plugged cells) by one of the bottom areas excluding the outer peripheral side wall of the honeycomb structure.

[0022] The average thickness of the partition walls is preferably 150 μm or more, more preferably 170 μm or more, and even more preferably 190 μm or more, from the viewpoint of increasing the strength of the honeycomb structure and the collection efficiency when used as a filter. Furthermore, the average thickness of the partition walls is preferably 260 μm or less, more preferably 240 μm or less, and even more preferably 220 μm or less, from the viewpoint of suppressing pressure loss. Therefore, the average thickness of the partition walls is, for example, preferably 150 to 260 μm, more preferably 170 to 240 μm, and even more preferably 190 to 220 μm.

[0023] 3 shows a schematic enlarged partial view of the partition walls 112 of the honeycomb structure 100 when observed in a cross section perpendicular to the cell extension direction. The thickness of the partition walls refers to the length of a line segment N that crosses the partition walls when the line segment N connects the centers of gravity O of adjacent cells in a cross section perpendicular to the cell extension direction (height direction of the honeycomb structure). The thickness direction D of the partition walls refers to the direction parallel to the line segment N. The average thickness of the partition walls refers to the average value of the thicknesses of all the partition walls.

[0024] The partition walls can be porous. The average porosity of the partition walls can be adjusted appropriately depending on the application, but from the viewpoint of keeping fluid pressure loss low, it is preferably 40% or more, more preferably 50% or more, and even more preferably 60% or more. Furthermore, from the viewpoint of ensuring the strength of the honeycomb structure, the average porosity of the partition walls is preferably 80% or less, more preferably 75% or less, and even more preferably 70% or less. Therefore, the average porosity of the partition walls is, for example, preferably 40 to 80%, more preferably 50 to 75%, and even more preferably 60 to 70%. The porosity of the partition walls is measured by mercury porosimetry in accordance with JIS R1655:2003. Twenty partition wall test pieces are collected evenly from the center and outer periphery of the honeycomb structure, and the porosity of each is measured, and the average value is taken as the average porosity.

[0025] The material constituting the partition walls and the outer peripheral side wall is not particularly limited, but is preferably ceramic from the viewpoint of strength and heat resistance. The ceramic is preferably, for example, a ceramic containing at least one selected from the group consisting of cordierite, mullite, zircon, aluminum titanate, silicon carbide, silicon-silicon carbide composite, silicon nitride, zirconia, spinel, indialite, sapphirine, corundum, and titania. These ceramics may contain one type alone or two or more types simultaneously. The partition walls and the outer peripheral side wall are preferably formed from a material containing a total of 50 mass% or more of these ceramics, and more preferably 80 mass% or more.

[0026] In a preferred embodiment, the outer peripheral side wall, partition walls, and plugging portions of the honeycomb structure each contain cordierite as a main component. This means that the total mass ratio of cordierite (2MgO 2Al2O3 5SiO2) in 100% by mass of the materials constituting the outer peripheral side wall, partition walls, and plugging portions is 50% by mass or more. The mass ratio of cordierite in 100% by mass of the materials constituting the outer peripheral side wall, partition walls, and plugging portions is preferably 70% by mass or more, and more preferably 80% by mass or more.

[0027] The cordierite content can be measured by X-ray diffraction. Specifically, an X-ray diffraction apparatus using Cu Kα rays (e.g., an X'pert PRO apparatus manufactured by PANalytical) is used to perform X-ray analysis measurement in the range of 2θ = 8 to 100° on a sample of the outer peripheral side wall, partition wall, or plugging portion by X-ray diffraction, and the cordierite crystalline phase ratio is measured by analyzing the result using the Rietveld analysis program RIETAN, which is defined as the cordierite content.

[0028] Fine-tuning the chemical composition of the plugging portions is advantageous in suppressing peeling of the plugging portions when the film is peeled off. Specifically, the plugging portions are preferably composed of ceramics containing 9.0 to 13.4 mass% MgO, 29.0 to 35.5 mass% Al2O3, and 50.0 to 58.0 mass% SiO2, more preferably 9.0 to 12.0 mass% MgO, 29.8 to 32.0 mass% Al2O3, and 54.0 to 57.2 mass% SiO2, and even more preferably 10.2 to 11.5 mass% MgO, 30.5 to 32.0 mass% Al2O3, and 54.5 to 56.2 mass% SiO2. This composition contains slightly less MgO and slightly more SiO2 than common cordierite, which has the effect of making the outer surface of the plugging portions easier to smooth. In addition, an effect of improving the mechanical strength of the plugging portion itself can be obtained.

[0029] It is desirable to measure the chemical composition of the plugged portion by cutting out the plugged portion from the honeycomb structure to prepare a measurement sample, and then measure the measurement sample. However, if it is difficult to obtain 10.0 g of a measurement sample from the honeycomb structure, prepare the measurement sample using the following method. The same plugging portion forming slurry as that used to prepare the plugged portions is prepared and poured into a stainless steel mold with a diameter of 60 mm and a length of 15 mm. It is then dried under the same conditions as the actual plugged portions and removed from the stainless steel mold. If the actual plugged portions have been fired, they are then fired under the same conditions. The obtained bulk body is pulverized to prepare a measurement sample. If it is possible to prepare a measurement sample by cutting out plugged portions from the honeycomb structure, the cut-out plugged portions are pulverized to prepare a measurement sample. Pulverization is performed under the following conditions: pestle rotation speed: 100 / 120 rpm, mortar rotation speed: 6 / 7 rpm, and pulverization time: 5 minutes. 10.0 g of the measurement sample is placed in an alloy crucible, 6.0 g of lithium tetraborate is added, and the mixture is mixed with a platinum rod. The alloy crucible is placed in a vitrification device (e.g., HERZOG automatic bead sampler HA-HF16) and vitrified at 1200°C for 15 minutes (glass bead method). Qualitative analysis of the glass beads of each sample is performed by fluorescent X-ray analysis using Si Kα radiation, Al Kα radiation, and Mg Kα radiation, and SiO 2、 AlO 3、 Calculate the mass percentage of MgO.

[0030] The smoothness of the outer surface of the plugged portion can be expressed as an index using the arithmetic mean height Sa. The arithmetic mean height Sa is a type of surface roughness parameter defined in ISO 25178 and represents the average of the absolute values ​​of the height differences at each point relative to the average plane of the surface. Specifically, the arithmetic mean height Sa of the plugged portions on the first and second bottom surfaces is preferably 18.0 μm or less, more preferably 17.5 μm or less, and even more preferably 12.0 μm or less. There is no particular lower limit set for the arithmetic mean height Sa of the plugged portions, but in terms of a balance with manufacturing costs, the arithmetic mean height Sa of the plugged portions on the first and second bottom surfaces is preferably 5.0 μm or more, more preferably 8.0 μm or more, and even more preferably 10.5 μm or more. Therefore, the arithmetic mean height Sa of the plugged portions on the first bottom surface and the second bottom surface is, for example, preferably 5.0 to 18.0 μm, more preferably 5.0 to 17.5 μm, still more preferably 8.0 to 17.5 μm, and even more preferably 5.0 to 12.0 μm.

[0031] In this specification, the arithmetic mean height Sa of the plugged portions on the first bottom face and the second bottom face is the measured value, which is the average value when the arithmetic mean heights Sa of the plugged portions are measured at five positions without bias using a laser microscope. For one plugged portion, measurement can be performed under the following conditions. Measurement equipment name: Shape analysis laser microscope (KEYENCE VK-X250 / 260) or a microscope with equivalent performance Analysis software: Multi-file analysis application (VK-1HXM) or software with equivalent performance Objective lens magnification: 10x Sample size: 20mm x 20mm x 10mm (depth direction of plugged area) Measurement mode: Surface profile Measurement size per field of view: Standard (1024 pixels x 768 pixels) Measurement quality: high precision Measurement time: 1 minute Plane processing: A 750 μm x 750 μm square area is specified and processing is performed to determine the plane (reference plane) that will be used as the reference for measurement. The entire height data is rotated so that the set reference plane is horizontal, and is offset in the height direction so that the reference plane height becomes 0. Reference plane position: -3 μm (offset so that the position at a depth of 3 μm is the height 0.) Ignore minute areas: Ignore (Number of pixels in minute areas: ≥ 6 pixels (surface irregularities of less than 6 pixels will not be recognized as holes.))

[0032] In one embodiment, the plugging portions may be fired. The ceramics constituting the fired plugging portions can be provided as, for example, a cordierite sintered body. The cordierite sintered body can be obtained by firing a plugging portion-forming slurry containing a cordierite-forming raw material. In another embodiment, the plugging portions may be in an unfired state. In this case, the ceramic constituting the plugging portions preferably contains, for example, cordierite particles and an inorganic binder that binds the particles together. Colloidal silica is suitable as the inorganic binder.

[0033] Regardless of whether the plugging portions are fired or not, it is preferable that the median diameter of the ceramics constituting the plugging portions is small. This has the effect of making it easier to smooth the outer surfaces of the plugging portions. Specifically, the upper limit of the median diameter of the ceramics constituting the plugging portions is preferably 25 μm or less, more preferably 20 μm or less, and even more preferably 15 μm or less. Furthermore, from the viewpoint of suppressing sink marks in the plugging portions, the lower limit of the ceramics constituting the plugging portions is preferably 5 μm or more, more preferably 10 μm or more, and even more preferably 12 μm or more. Therefore, the median diameter of the ceramics constituting the plugging portions is preferably, for example, 5 to 25 μm, more preferably 10 to 20 μm, and even more preferably 12 to 15 μm.

[0034] It is desirable to measure the median diameter of the ceramics constituting the plugging portion by cutting out the plugging portion from the honeycomb structure to prepare a measurement sample, but if it is difficult to prepare 2.0 g of a measurement sample from the honeycomb structure, prepare the measurement sample by the following method. The same plugging slurry used to prepare the plugged portions was prepared and poured into a stainless steel mold with a diameter of 60 mm and a length of 15 mm. It was then dried under the same conditions as the actual plugged portions and removed from the stainless steel mold. If the actual plugged portions were fired, they were fired under the same conditions. The resulting bulk was pulverized in an automatic mortar to prepare a measurement sample. If a measurement sample can be prepared by cutting plugged portions from the honeycomb structure, the cut-out plugged portions were pulverized to prepare a measurement sample. The pulverization was performed under the following conditions: pestle rotation speed: 100 / 120 rpm, mortar rotation speed: 6 / 7 rpm, and pulverization time: 5 minutes. A 2.0 g sample was placed in a laser diffraction / scattering particle size distribution analyzer (HORIBA Partica LA-960 was used in this example), and the median diameter (D50) of the volume-based cumulative particle size distribution was measured using the laser diffraction / scattering method.

[0035] In one embodiment, the plugging portions of both the first bottom surface and the second bottom surface have an average depth of 3 to 7 mm, preferably 4.2 to 6 mm. When the lower limit of the average depth of the plugging portions is 3 mm or more, the strength of the plugging portions can be ensured. The average depth of the plugging portions is preferably 4.2 mm or more. When the upper limit of the average depth of the plugging portions is 7 mm or less, the area of ​​the partition walls that capture particulate matter in the cells can be prevented from becoming smaller. The upper limit of the average depth of the plugging portions is preferably 6 mm or less. The depth of the plugging portions is measured at 20 locations on each bottom surface without bias, and the average value is taken as the average depth of the plugging portions on each bottom surface.

[0036] In this specification, the depth of each plugging portion is measured by the following procedure. First, the plugging portion for which the depth is to be measured is cut in half along a cross section parallel to the height direction (cell extension direction) of the honeycomb structure, and a cross section of the plugging portion is cut out. One entire cross section of one of the obtained plugging portions is photographed with a laser microscope (e.g., Keyence Corporation's shape analysis laser microscope VK X250 / 260) to generate a cross-sectional image of the plugging portion. The length in the cell extension direction from the outer end of the central axis M of the cell in which the plugging portion is formed (a straight line having an equal distance to a pair of opposing partition walls 112) to the deepest position where the plugging portion 109 exists, observed in the cross-sectional image, is measured, and this is defined as the depth E of the plugging portion (see FIG. 4).

[0037] In one embodiment, the average porosity of the plugging portions of the first bottom surface and the second bottom surface is 30% to 70%, preferably 35 to 60%, and more preferably 40 to 50%. Setting the lower limit of the average porosity of the plugging portions to 30% or more is advantageous for alleviating thermal stress and improving thermal shock resistance. The lower limit of the average porosity of the plugging portions is preferably 35% or more, and more preferably 40% or more. Setting the upper limit of the average porosity of the plugging portions to 70% or less is advantageous for preventing erosion. The upper limit of the average porosity of the plugging portions is preferably 60% or less, and more preferably 50% or less.

[0038] Since it is difficult to directly measure the porosity of the plugged portions by sampling only the plugged portions, the porosity can be measured by the mercury intrusion method specified in JIS 1655:2003 according to the following procedure. A test piece of the partition wall portion where no plugging portion is formed is taken, and the porosity P1 of the test piece (porosity of the partition wall portion) is measured. A test piece of the partition wall portion including the plugged portion is taken, and the porosity P (porosity of the partition wall portion + plugged portion) of the test piece is measured. For the test piece of the partition wall portion including the plugged portion, measure the volume V1 including the pores of the partition wall portion. For the test piece of the partition wall including the plugged portion, measure the volume V2 including the pores of the plugged portion. When the porosity of the plugged portion is P2, P, P1, P2, V1 and V2 satisfy the relationship of formula (1). P=P1×V1 / (V1+V2)+P2×V2 / (V1+V2) ···(1) Therefore, P2 can be calculated using equation (2). P2=P×(V1+V2) / V2-P1×V1 / V2 (2) The porosity P2 of the plugged portion is measured at any 20 points on each bottom surface, and the average value is taken as the average porosity of the plugged portion on each bottom surface. In addition, in a test piece of a partition wall portion including plugged portions, when the volume ratio of the volume V1 including the pores of the partition wall portion is v1 and the volume ratio of the volume V2 including the pores of the plugged portion is v2, P2 may be calculated by the formula (3). P2=P×(v1+v2) / v2-P1×v1 / v2...(3)

[0039] When a honeycomb structure is used as a catalyst carrier, the surface of the partition wall can be coated with a catalyst according to the purpose. Examples of catalysts include, but are not limited to, oxidation catalysts (DOCs) for oxidatively burning hydrocarbons (HC) and carbon monoxide (CO) to increase the exhaust gas temperature, PM combustion catalysts for assisting the combustion of PM such as soot, SCR catalysts and NSR catalysts for removing nitrogen oxides (NOx), and three-way catalysts capable of simultaneously removing hydrocarbons (HC), carbon monoxide (CO), and nitrogen oxides (NOx). The catalyst can appropriately contain, for example, noble metals (e.g., Pt, Pd, Rh), alkali metals (e.g., Li, Na, K, Cs), alkaline earth metals (e.g., Mg, Ca, Ba, Sr), rare earth elements (e.g., Ce, Sm, Gd, Nd, Y, La, Pr), transition metals (e.g., Mn, Fe, Co, Ni, Cu, Zn, Sc, Ti, Zr, V, Cr), etc.

[0040] (2. Manufacturing method) A honeycomb structure having plugged portions can be manufactured by a known manufacturing method, excluding the method for forming the plugged portions, but this will be described below as an example. First, a raw material composition containing ceramic raw materials, a dispersion medium, a pore-forming material, and a binder is kneaded to form a clay, and then the clay is extruded to form a desired honeycomb molded body. Additives such as a dispersant can be blended into the raw material composition as needed. During extrusion molding, a die having the desired overall shape, cell shape, partition wall thickness, cell density, etc. can be used.

[0041] Ceramic raw materials are raw materials that remain after firing of metal oxides, metals, etc., and form the skeleton of the honeycomb fired body as ceramics. The ceramic raw materials can be provided, for example, in the form of powder. Examples of ceramic raw materials include raw materials for obtaining ceramics such as cordierite, mullite, zircon, aluminum titanate, silicon carbide, silicon-silicon carbide composites, silicon nitride, zirconia, spinel, indialite, sapphirine, corundum, and titania. Specific examples include, but are not limited to, silica, talc, alumina, kaolin, serpentine, pyroferrite, brucite, boehmite, mullite, magnesite, and aluminum hydroxide. The ceramic raw materials may be used singly or in combination of two or more.

[0042] In the case of filter applications such as DPF and GPF, cordierite can be suitably used as the ceramic. In this case, a cordierite-forming raw material can be used as the ceramic raw material. The cordierite-forming raw material is a raw material that becomes cordierite when fired. The cordierite-forming raw material preferably has a chemical composition of 30 to 45 mass% alumina (Al2O3) (including aluminum hydroxide converted to alumina), 11 to 17 mass% magnesia (MgO), and 42 to 57 mass% silica (SiO2).

[0043] The pore-forming material is not particularly limited as long as it forms pores after firing, and examples thereof include wheat flour, starch, foamed resin, water-absorbent resin, silica gel, carbon (e.g., graphite), ceramic balloons, polyethylene, polystyrene, polypropylene, nylon, polyester, acrylic resin, and phenol. One type of pore-forming material may be used alone, or two or more types may be used in combination. From the viewpoint of increasing the porosity of the honeycomb structure after firing, the content of the pore-forming material is preferably 0.5 parts by mass or more, more preferably 2 parts by mass or more, and even more preferably 3 parts by mass or more, relative to 100 parts by mass of the ceramic raw materials. From the viewpoint of ensuring the strength of the honeycomb structure after firing, the content of the pore-forming material is preferably 30 parts by mass or less, more preferably 27 parts by mass or less, and even more preferably 24 parts by mass or less, relative to 100 parts by mass of the ceramic raw materials.

[0044] Examples of binders include organic binders such as methyl cellulose, hydroxypropoxyl methyl cellulose, hydroxypropyl methyl cellulose, hydroxyethyl cellulose, carboxymethyl cellulose, and polyvinyl alcohol. Furthermore, from the viewpoint of increasing the strength of the honeycomb formed body, the binder content is preferably 4 parts by mass or more, more preferably 5 parts by mass or more, and even more preferably 6 parts by mass or more, per 100 parts by mass of the ceramic raw materials. From the viewpoint of suppressing cracks due to abnormal heat generation during the firing process, the binder content is preferably 9 parts by mass or less, more preferably 8 parts by mass or less, and even more preferably 7 parts by mass or less, per 100 parts by mass of the ceramic raw materials. The binder may be used singly or in combination of two or more types.

[0045] The dispersant may be ethylene glycol, dextrin, fatty acid soap, polyether polyol, etc. One type of dispersant may be used alone, or two or more types may be used in combination. The content of the dispersant is preferably 0 to 2 parts by mass per 100 parts by mass of the ceramic raw material.

[0046] Examples of the dispersion medium include water and a mixed solvent of water and an organic solvent such as alcohol, with water being particularly preferred.

[0047] The water content of the honeycomb formed body before the drying process is preferably 20 to 90 parts by mass, more preferably 60 to 85 parts by mass, and even more preferably 70 to 80 parts by mass, per 100 parts by mass of the ceramic raw materials. When the water content of the honeycomb formed body is 20 parts by mass or more per 100 parts by mass of the ceramic raw materials, the advantage of easily stabilizing the quality of the honeycomb structure is easily obtained. When the water content for honeycomb formation is 90 parts by mass or less per 100 parts by mass of the ceramic raw materials, the amount of shrinkage during drying is small, and deformation can be suppressed. In this specification, the water content of the honeycomb formed body refers to a value measured by the loss on drying method.

[0048] The honeycomb formed body can be dried by a conventionally known drying method, such as hot air drying, microwave drying, dielectric drying, reduced pressure drying, vacuum drying, freeze drying, etc. Among these, a drying method that combines hot air drying with microwave drying or dielectric drying is preferred, since it can dry the entire honeycomb formed body quickly and uniformly.

[0049] The subsequent steps differ depending on whether the honeycomb structure as a product has fired plugging portions or unfired plugging portions, and will be explained separately for each case.

[0050] (1) When the honeycomb structure has fired plugging portions A case where a honeycomb structure has fired plugging portions will be described. After drying the honeycomb formed body, unfired plugging portions are formed on both bottom surfaces of the honeycomb formed body. The unfired plugging portions can be formed by filling the openings of the first and second cells where the plugging portions are to be formed with a plugging portion forming slurry, and then drying the slurry. Next, the unfired plugging portions are fired together with the honeycomb formed body. As a result, fired plugging portions are formed.

[0051] In one embodiment, the plugging portion forming slurry contains a cordierite-forming raw material, a dispersion medium, a pore-forming material, and a binder. Illustratively, the plugging portion forming slurry contains 30 to 60 parts by mass of the dispersion medium, 5 to 20 parts by mass of the pore-forming material, and 0.2 to 2.0 parts by mass of the binder, relative to 100 parts by mass of the cordierite-forming raw material. In a preferred embodiment, the plugging portion forming slurry contains 35 to 50 parts by mass of the dispersion medium, 8 to 16 parts by mass of the pore-forming material, and 0.2 to 1.5 parts by mass of the binder, relative to 100 parts by mass of the cordierite-forming raw material.

[0052] Examples of cordierite-forming raw materials used in the slurry for forming plugging portions include silica, talc, alumina, kaolin, serpentine, pyroferrite, brucite, boehmite, mullite, magnesite, aluminum hydroxide, etc. The compounding ratio of these raw materials is selected so that the plugging portions obtained after firing have the above-mentioned chemical composition.

[0053] The cordierite-forming raw material is preferably as fine as possible from the viewpoint of improving the smoothness of the outer surface of the plugged portion. For example, the median diameter (D50) in the cumulative particle size distribution on a volume basis determined by a laser diffraction / scattering method is preferably 9 to 31 μm for talc, 3 to 8 μm for alumina (and aluminum hydroxide), 2 to 9 μm for kaolin, and 2 to 8 μm for silica.

[0054] Examples of the dispersion medium include water and a mixed solvent of water and an organic solvent such as alcohol, with water being particularly preferred.

[0055] The pore-forming material is not particularly limited as long as it forms pores after firing, and examples thereof include wheat flour, starch, foamed resin, water-absorbent resin, silica gel, carbon (e.g., graphite), ceramic balloons, polyethylene, polystyrene, polypropylene, nylon, polyester, acrylic resin, and phenol. One type of pore-forming material may be used alone, or two or more types may be used in combination. The median diameter (D50) of the pore-forming material in the cumulative particle size distribution on a volume basis determined by a laser diffraction / scattering method is preferably 35 to 55 μm.

[0056] Examples of binders include organic binders such as methyl cellulose, hydroxypropoxyl methyl cellulose, hydroxypropyl methyl cellulose, hydroxyethyl cellulose, hydroxyethyl methyl cellulose, carboxymethyl cellulose, polyvinyl alcohol, etc. One type of binder may be used alone, or two or more types may be used in combination.

[0057] The plugging portion forming slurry may contain a thickener as appropriate. For example, the thickener may be contained in an amount of 0.1 to 0.5 parts by mass, preferably 0.2 to 0.4 parts by mass, relative to 100 parts by mass of the cordierite forming raw material. Examples of thickeners used in the plugging portion forming slurry include pectin, guar gum, xanthan gum, propylene glycol, and polyethylene oxide. Among these, polyethylene oxide is preferred because the solution exhibits high viscosity even at a low concentration and has a flowability improving effect. One type of thickener may be used alone, or two or more types may be used in combination.

[0058] The slurry for forming plugged portions may contain a dispersant as appropriate. The dispersant may be contained in an amount of, for example, 0.1 to 3 parts by mass, preferably 0.2 to 2 parts by mass, relative to 100 parts by mass of the cordierite-forming raw material. Examples of the dispersant include ethylene glycol, dextrin, fatty acid soap, and polyalcohol. The dispersant may be used alone or in combination of two or more types.

[0059] The openings of the cells can be filled with the plugging portion forming slurry, for example, by the following "squeegee method." As shown in Fig. 5, a film 121 is attached to the upper bottom surface (here, the second bottom surface 106 in the figure) of the dried honeycomb formed body 500 fixed using a chuck 120, and a laser is irradiated to the film 121 at positions corresponding to the arrangement conditions of the plugging portions (for example, a "checkered pattern" or the like), and a plurality of holes 126 are formed in the film 121.

[0060] Thereafter, the plugging portion forming slurry 124 is placed on the film 121, and the squeegee 122 is moved along the film 121 in the direction of the arrow in Fig. 5. As a result, a certain amount of the plugging portion forming slurry 124 is filled into the cells 125 that are opened at positions corresponding to the holes 126 of the film 121.

[0061] The depth of the plugging portion can be changed by the number of times the squeegee 122 is moved, the contact angle between the squeegee 122 and the film 121, the pressing pressure of the squeegee 122 against the film 121, and the viscosity of the plugging portion forming slurry 124, etc.

[0062] After filling the plugging portion forming slurry 124, excess plugging portion forming slurry 124 remaining on the surface of the film 121 is wiped off with a squeegee 122, the film 121 is peeled off, and the entire honeycomb formed body 500 is dried. As a result, the plugging portion forming slurry 124 filled in the cells 125 is dried, and plugging portions before firing are formed. Drying can be performed, for example, under conditions of a drying temperature of 100 to 230°C for about 60 to 150 seconds.

[0063] The material of the film is not particularly limited, but polypropylene (PP), polyethylene terephthalate (PET), polyimide, or Teflon (registered trademark) are preferred because they are easy to heat process to form holes in. The film also preferably has an adhesive layer, and the adhesive layer is preferably made of an acrylic resin, a rubber-based material (e.g., a rubber whose main component is natural rubber or synthetic rubber), or a silicone-based resin. The film can preferably be an adhesive film with a thickness of, for example, 20 to 50 μm.

[0064] In addition to the above-mentioned "squeegee method," another method for filling the openings of the cells with the plugging portion forming slurry is the "press-fit method." The "press-fit method" is a method in which the bottom surface of a honeycomb formed body, to which a film has been attached and which has holes drilled, is immersed in a liquid tank containing the plugging portion forming slurry, and the cells are filled with the plugging portion forming slurry. In this case, the depth of the plugging portions can be changed by changing the depth to which the honeycomb formed body is immersed in the plugging portion forming slurry.

[0065] After drying, the plugging portions protrude from the bottom surface of the honeycomb formed body by the thickness of the film, so it is preferable to scrape them off and smooth them (hereinafter also referred to as "smoothing process"). In this case, if the plugging portions have a suitable composition, the outer surfaces of the plugging portions are easily smoothed. The method of smoothing process is not limited, but a preferred method is to press one bottom surface of a fired ceramic honeycomb structure (hereinafter also referred to as "smoothing jig") against the outer surfaces of the plugging portions to be smoothed, while rubbing them. For example, the smoothing jig can be preferably made of the same material as the fired honeycomb formed body to be smoothed, for example, made of cordierite. However, the smoothing jig may or may not have plugging portions.

[0066] The bottom surface of the smoothing jig is preferably smooth. Specifically, the arithmetic mean height Sa of the surface of the partition walls constituting the bottom surface of the smoothing jig is, for example, preferably 1.0 to 5.0 μm, more preferably 2.0 to 4.0 μm, and even more preferably 2.5 to 3.5 μm. The arithmetic mean height Sa of the surface of the partition walls constituting the bottom surface of the smoothing jig can be measured by the same method as the method for measuring the arithmetic mean height Sa of the plugged portions described above.

[0067] Furthermore, during smoothing, it is preferable to move the smoothing jig and the honeycomb formed body relative to each other so that the direction of the sides (partition walls) that define the cell opening shape of the honeycomb formed body being smoothed and the direction of the sides (partition walls) that define the cell opening shape of the smoothing jig are not parallel, for example, so that the angle between the two sides is 30° to 60°. This is because chipping is more likely to occur if the direction of the sides (partition walls) that define the cell opening shape of the honeycomb formed body being smoothed and the direction of the sides (partition walls) that define the cell opening shape of the smoothing jig are parallel.

[0068] The honeycomb formed body filled with the plugging portion forming slurry is then subjected to a degreasing process and a firing process. This produces a honeycomb structure having fired plugging portions. The combustion temperature of the binder is about 200°C, and the combustion temperature of the pore-forming material is about 300 to 1000°C. Therefore, the degreasing process can be carried out by heating the honeycomb formed body to a temperature range of about 200 to 1000°C. The heating time is not particularly limited, but is usually about 10 to 100 hours. The honeycomb formed body after the degreasing process is called a calcined body. The firing process can be carried out by heating the calcined body to 1300 to 1450°C and holding it for 3 to 24 hours, for example, although it depends on the material composition of the honeycomb structure.

[0069] (2) When the honeycomb structure has unfired plugged portions Next, a case where the honeycomb structure has unfired plugging portions will be described. In this case, after drying the honeycomb formed body, the degreasing process and the firing process are carried out without forming plugging portions. The conditions for the degreasing process and the firing process are as described above. This produces a honeycomb structure without plugging portions. Next, unfired plugging portions are formed on both bottom surfaces of the honeycomb structure. The unfired plugging portions can be formed by filling the openings of the first and second cells where the plugging portions are to be formed with a plugging portion forming slurry, and then drying the slurry.

[0070] In one embodiment, the plugging portion forming slurry contains cordierite particles, a dispersion medium, and an inorganic binder. Illustratively, the plugging portion forming slurry contains 10 to 35 parts by mass of the dispersion medium and 10 to 25 parts by mass of the inorganic binder with respect to 100 parts by mass of the cordierite particles. In a preferred embodiment, the plugging portion forming slurry contains 15 to 30 parts by mass of the dispersion medium and 11 to 20 parts by mass of the inorganic binder with respect to 100 parts by mass of the cordierite particles. The compounding ratio of these raw materials is selected so that the plugging portions obtained after drying have the aforementioned chemical composition.

[0071] The cordierite particles contain cordierite as a main component. This means that the total mass ratio of cordierite (2MgO 2Al2O3 5SiO2) in 100 mass% of the cordierite particles is 50 mass% or more. The mass ratio of cordierite in 100 mass% of the cordierite particles is preferably 70 mass% or more, and more preferably 80 mass% or more. The method for measuring the cordierite content is as described above.

[0072] The cordierite particles are preferably fine from the viewpoint of improving the smoothness of the outer surface of the plugged portion. However, if the cordierite particles are too fine, the porosity decreases. Therefore, in order to obtain a desired porosity, it is preferable that the cordierite particles are not too fine. The cordierite particles preferably have a median diameter (D50) of 40 μm or less, more preferably 30 μm or less, in a volume-based cumulative particle size distribution determined by, for example, a laser diffraction / scattering method. There is no particular lower limit set for the median diameter (D50) of the cordierite particles. From the viewpoint of availability, the median diameter (D50) of the cordierite particles is usually 10 μm or more, and typically 20 μm or more. Therefore, the median diameter (D50) of the cordierite particles is preferably, for example, 10 to 40 μm, more preferably 20 to 30 μm.

[0073] Examples of the dispersion medium include water and a mixed solvent of water and an organic solvent such as alcohol, with water being particularly preferred.

[0074] As the inorganic binder, colloidal silica can be suitably used.

[0075] The plugging portion forming slurry may contain an organic binder in addition to the inorganic binder. For example, the organic binder may be contained in an amount of 0.2 to 2.0 parts by mass, preferably 0.2 to 1.5 parts by mass, per 100 parts by mass of cordierite particles. Examples of the organic binder include methyl cellulose, hydroxypropoxyl methyl cellulose, hydroxypropyl methyl cellulose, hydroxyethyl cellulose, hydroxyethyl methyl cellulose, carboxymethyl cellulose, polyvinyl alcohol, diutan gum, welan gum, xanthan gum, and guar gum. The organic binder may be used alone or in combination of two or more types.

[0076] The slurry for forming plugged portions may contain a dispersant as appropriate. The dispersant may be contained in an amount of, for example, 0.1 to 3 parts by mass, preferably 0.2 to 2 parts by mass, per 100 parts by mass of cordierite particles. Examples of the dispersant include ethylene glycol, dextrin, fatty acid soap, and polyalcohol. The dispersant may be used alone or in combination of two or more types.

[0077] The openings of the cells can be filled with the slurry for forming plugging portions by a known filling method such as the "squeegee method" or "pressure-fitting method" described above. The subsequent film peeling and drying conditions are also as described above.

[0078] After drying, it is preferable to carry out the smoothing process described above. At this time, if the plugging portions have a suitable composition, the outer surfaces of the plugging portions are easily smoothed. The conditions for the smoothing process are as described above. [Example]

[0079] <Comparative Examples 1 and 2, Example 1> (1) Preparation of honeycomb molded body A raw material composition was prepared by adding 25 parts by mass of a pore-forming material, 80 parts by mass of a dispersion medium, 5 parts by mass of a binder, and 1 part by mass of a dispersant to 100 parts by mass of the cordierite-forming raw material, and kneading the resulting composition to prepare a clay. The cordierite-forming raw materials used were talc, alumina, aluminum hydroxide, kaolin, and silica. Water was used as the dispersion medium, a water-absorbent resin and silica gel were used as the pore-forming material, methylcellulose was used as the binder, and ethylene glycol was used as the dispersant.

[0080] This clay was placed in an extrusion molding machine and extruded through a die of a predetermined shape to obtain a cylindrical honeycomb molded body. The obtained honeycomb molded body was subjected to dielectric drying and hot air drying, after which both bottom surfaces were cut to the predetermined dimensions and further dried with hot air at 70°C for 2 hours.

[0081] (2) Formation of plugging parts A pore-forming material, a dispersion medium, an organic binder, and a dispersant were added to a total of 100 parts by mass of a cordierite-forming raw material containing each raw material in the mass blending ratios shown in Table 1, and the mixture was kneaded to prepare a slurry for forming plugged portions. Talc, alumina, aluminum hydroxide, kaolin, and silica were used as the cordierite-forming raw materials. The median diameters (D50) of these raw materials are as shown in Table 1. A foamed resin was used as the pore-forming material, water as the dispersion medium, methylcellulose as the organic binder, and ethylene glycol as the dispersant. Using the "squeegee method" described above, this slurry for forming plugged portions was filled on both bottom surfaces so that the first and second cells were alternately arranged adjacent to each other. After that, excess slurry for forming plugged portions adhering to the film was wiped off with a squeegee, and the film was peeled off. The film was then dried in an air atmosphere at 180°C for 200 seconds.

[0082] For each honeycomb formed body, the state of the outer surface of the plugging portion immediately after peeling the film was observed with an optical microscope (magnification 100x), and the peeling depth at five randomly selected peeled locations was measured with a scale, and peeling of the plugging portion was evaluated according to the following criteria. The results are shown in Table 1. ○:≦1.0mm △: 1.1~1.5mm ×:≧1.6mm

[0083] (3) Smoothing processing A honeycomb structure made of fired cordierite was prepared as a smoothing jig. The specifications of this honeycomb structure were as follows: Overall shape: Cylinder with a diameter of 118 mm and a height of 20 mm Cell shape in cross section perpendicular to the flow direction: square Cell density (number of cells per unit cross-sectional area): 750 cells / in² (118 cells / cm²) 2 ) Average thickness of the partition wall: 2.5 mil (64 μm) (nominal value based on the specifications of the base) Arithmetic mean height Sa of the partition wall surface that constitutes the bottom surface of the smoothing jig: 3.3 μm

[0084] Next, the plugged portions of each dried honeycomb formed body were manually smoothed. During the smoothing process, the honeycomb formed body to be smoothed and the smoothing jig were moved relative to each other so that the angle formed by the sides (partition walls) defining the cell opening shape of the honeycomb formed body and the sides (partition walls) defining the cell opening shape of the smoothing jig was 45°.

[0085] (4) Firing Next, the honeycomb structure was degreased by heating at about 200°C in an air atmosphere, and then fired at 1400°C for 10 hours in an air atmosphere to obtain a cylindrical honeycomb structure having fired plugged portions. The honeycomb structures were prepared in the number required to investigate the following properties.

[0086] (5) Honeycomb structure specifications The specifications of the obtained honeycomb structure are as follows: Overall shape: cylindrical, diameter 132mm x height 152mm Cell shape in cross section perpendicular to the flow direction: square Cell density (number of cells per unit cross-sectional area): 300 cells / in² (47 cells / cm²) 2 ) Average partition wall thickness: 8.5 mil (216 μm) (nominal value based on the base specifications) Average porosity of partition wall: 63% Average depth of plugging area: 5mm The outer side walls, partition walls and plugged portions of the columnar honeycomb structure were subjected to X-ray analysis measurement in the range of 2θ=8 to 100° by X-ray diffraction using an X'pert PRO device manufactured by PANalytical using Cu Kα rays, and the cordierite crystalline phase ratio was determined using the Rietveld analysis program RIETAN, which was found to be 75 to 94 mass%.

[0087] (6) Chemical composition of plugging part Since it was difficult to collect measurement samples from the honeycomb structure, the same slurry for forming plugging portions as that used for producing the plugging portions was prepared, and measurement samples were prepared by the procedure described above, and the chemical composition was measured by the method described above. The results are shown in Table 1.

[0088] (7) Median diameter of plugged area Since it was difficult to collect measurement samples from the honeycomb structure, the same slurry for forming plugging portions as that used to prepare the plugging portions was prepared, and measurement samples were prepared using the procedure described above. The median diameter of the ceramics constituting the plugging portions was measured using the method described above. The results are shown in Table 1.

[0089] (8) Arithmetic mean height Sa of plugged area The arithmetic mean height Sa of the plugged portions on one bottom surface of the obtained honeycomb structure was measured by the method described above using a shape analysis laser microscope VK X250 / 260 manufactured by Keyence Corporation. The results are shown in Table 1. Although Table 1 does not show the arithmetic mean height Sa of the plugged portions on the other bottom surface, it was approximately the same as that on one bottom surface.

[0090] (9) Average porosity of plugged area The average porosity of the plugged portions on one bottom surface of the obtained honeycomb structure was measured by the method described above. The results are shown in Table 1. Although Table 1 does not show the average porosity of the plugged portions on the other bottom surface, it was approximately the same as that of the one bottom surface.

[0091] (10) Plugging strength Nine plugging portions (excluding those located within 5 mm from the outer periphery of one bottom surface of the obtained honeycomb structure) were inserted from the other bottom surface of the honeycomb structure, and were pushed with a stainless steel push rod (cylindrical, 1.1 mm in diameter x 40 mm in length) from the other bottom surface, with two plugging portions at equal intervals in the ± directions of the X axis and the ± directions of the Y axis, with the center of gravity being the origin O of the XY coordinate system. The applied force was gradually increased. As the applied force increased, the push rod eventually penetrated the plugging portions. The maximum load (plugging portion strength) until penetration was achieved was measured with a load cell. The same measurement was performed for the plugging portions on the other bottom surface. In this way, the strength of a total of 18 plugging portions was measured for one honeycomb structure, and the average value was calculated. Table 1 shows the relative values, with the average value of Comparative Example 1 set to 1.0.

[0092] <Examples 2 to 4> (1) Fabrication of a cylindrical honeycomb structure without plugging portions A cylindrical honeycomb formed body was produced under the same conditions as in Example 1. The obtained honeycomb formed body was then subjected to dielectric drying and hot air drying, after which both bottom surfaces were cut to a predetermined size and further hot air dried at 70°C for 2 hours. Next, it was heated and degreased at about 200°C in an air atmosphere, and further fired at 1400°C for 10 hours in an air atmosphere to obtain a cylindrical honeycomb structure without plugging portions.

[0093] (2) Formation of plugging parts A dispersion medium, an organic binder, colloidal silica (inorganic binder), and a dispersant were added to a total of 100 parts by mass of cordierite particles A (cordierite content = 90 mass%) and cordierite particles B (cordierite content = 90 mass%) blended at the blending ratio by mass shown in Table 1, and kneaded to prepare a slurry for forming plugging portions. The chemical compositions of cordierite particles A and cordierite particles B were measured by quantitative analysis using fluorescent X-ray analysis. The cordierite particles A contained 53.0 mass% SiO, 32.1 mass% AlO, and 11.1 mass% MgO. The cordierite particles B contained 54.5 mass% SiO, 30.9 mass% AlO, and 12.4 mass% MgO. The median diameters (D50) of these particles are as shown in Table 1. Water was used as the dispersion medium, diutan gum as the organic binder, and ethylene glycol as the dispersant. Using the "squeegee method" described above, this plugging portion forming slurry was filled onto both bottom surfaces so that the first cells and second cells were alternately arranged adjacent to each other. After that, excess plugging portion forming slurry adhering to the film was wiped off with a squeegee, and the film was peeled off and dried in an air atmosphere at 180°C for 200 seconds.

[0094] Each honeycomb structure was evaluated for peeling of plugging portions in the same manner as in Example 1. The results are shown in Table 1.

[0095] (3) Smoothing processing A honeycomb structure made of fired cordierite was prepared as a smoothing jig. The specifications of this honeycomb structure were the same as those of the smoothing jig used in Example 1.

[0096] Next, for each honeycomb structure after the plugging portions had been dried, smoothing processing of the plugging portions was performed manually. During the smoothing processing, the smoothing jig and the honeycomb formed body to be smoothed were moved relative to each other so that the angle formed between the sides (partition walls) defining the cell opening shape of the honeycomb formed body and the sides (partition walls) defining the cell opening shape of the smoothing jig was 45°. In this way, honeycomb structures having unfired plugging portions were manufactured. The number of honeycomb structures required to investigate the following properties was prepared.

[0097] (4) Honeycomb structure specifications The specifications of the obtained honeycomb structure are as follows: Overall shape: cylindrical, diameter 132mm x height 152mm Cell shape in cross section perpendicular to the flow direction: square Cell density (number of cells per unit cross-sectional area): 300 cells / in² (49 cells / cm²) 2 ) Average partition wall thickness: 8.5 mil (216 μm) (nominal value based on the base specifications) Average depth of plugging area: 5mm Average porosity of partition wall: 63% The outer side walls, partition walls and plugged portions of the columnar honeycomb structure were subjected to X-ray analysis measurement in the range of 2θ=8 to 100° by X-ray diffraction using an X'pert PRO device manufactured by PANalytical using Cu Kα rays, and the cordierite crystalline phase ratio was determined using the Rietveld analysis program RIETAN, which was found to be 75 to 94 mass%.

[0098] (5) Characteristics of plugging parts The chemical composition, median diameter, arithmetic mean height Sa, mean porosity, and strength of the plugged portions were measured in the same manner as in Example 1. The results are shown in Table 1.

[0099] [Table 1] [Explanation of symbols]

[0100] 100: Honeycomb structure 102: Outer wall 104: First bottom surface 106: Second bottom surface 108: First cell 109: Plugging part 110: Second cell 112: Bulkhead 120: Zipper 121: Film 122: Squeegee 124: Plugging slurry 125: Cell 126: Hole 500: Honeycomb molded body

Claims

1. A honeycomb structure comprising: an outer peripheral side wall; a plurality of first cells arranged on an inner peripheral side of the outer peripheral side wall, extending from a first bottom surface to a second bottom surface, having openings on the first bottom surface and plugging portions on the second bottom surface; and a plurality of second cells arranged on the inner peripheral side of the outer peripheral side wall, extending from the first bottom surface to the second bottom surface, having plugging portions on the first bottom surface and openings on the second bottom surface, wherein the plurality of first cells and the plurality of second cells are alternately arranged adjacent to each other with partition walls interposed therebetween, The plugging portion contains MgO: 9.0 to 13.4 mass %, Al 2 O 3 :29.0 to 35.5% by mass, SiO 2 : It is composed of ceramics containing 50.0 to 58.0 mass% The arithmetic mean height Sa of the plugging portions on the first bottom surface and the second bottom surface is 18.0 μm or less, Honeycomb structure.

2. The plugging portion contains MgO: 9.0 to 12.0 mass %, Al 2 O 3 :29.8 to 32.0% by mass, SiO 2 2. The honeycomb structure according to claim 1, which is made of ceramics containing 54.0 to 57.2 mass % of arsenic.

3. 2. The honeycomb structure according to claim 1, wherein the arithmetic mean height Sa of the plugging portions on the first bottom surface and the second bottom surface is 5.0 to 17.5 μm.

4. 2. The honeycomb structure according to claim 1, wherein the arithmetic mean height Sa of the plugging portions on the first bottom surface and the second bottom surface is 5.0 to 12.0 μm.

5. 2. The honeycomb structure according to claim 1, wherein the plugging portions are in an unfired state.

6. 6. The honeycomb structure according to claim 5, wherein the ceramics constituting the plugging portions contain cordierite particles and colloidal silica that binds the particles together.

7. The honeycomb structure according to claim 1, wherein the plugging portions are fired.

8. 8. The honeycomb structure according to claim 7, wherein the ceramics constituting the plugging portions is a sintered body of cordierite.

9. 2. The honeycomb structure according to claim 1, wherein the ceramics constituting the plugging portions have a median diameter of 5 to 25 μm.

10. 2. The honeycomb structure according to claim 1, wherein the average porosity of the plugging portions in the first bottom surface and the second bottom surface is 30 to 70%, respectively.

11. 2. The honeycomb structure according to claim 1, wherein the partition walls are made of ceramics containing cordierite as a main component.

12. 2. The honeycomb structure according to claim 1, wherein the average depth of the plugging portions on the first bottom surface and the second bottom surface is 3 to 7 mm.

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