Honeycomb structure

Abstract

The present invention provides a honeycomb structure capable of suppressing peeling of a sealing portion when a film is peeled off. A honeycomb structure is provided with an outer peripheral side wall, a plurality of first cells, and a plurality of second cells. A plurality of first cells disposed on the inner peripheral side of the outer peripheral side wall, extending from the first bottom surface to the second bottom surface, having an opening in the first bottom surface, and having a sealing portion in the second bottom surface; a plurality of second cells disposed on the inner peripheral side of the outer peripheral side wall, extending from the first bottom surface to the second bottom surface, having a hole sealing portion in the first bottom surface, and having an opening portion in the second bottom surface; the plurality of first cells and the plurality of second cells are alternately arranged adjacent to each other with partition walls therebetween. The hole sealing part is composed of a ceramic containing 9.0 to 13.4 mass% of MgO, 29.8 to 35.0 mass% of Al2O3, and 49.8 to 57.2 mass% of SiO2, and the arithmetic average heights Sa of the hole sealing parts of the first bottom surface and the second bottom surface are respectively 18.0 [mu] m or less.

Description

Technical Field

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

[0002] Exhaust gas from internal combustion engines, such as diesel engines, contains large amounts of particulate matter (particles) primarily composed of carbon, a cause of environmental pollution. Therefore, diesel engines and other similar engines are typically equipped with a filter (Diesel Particulate Filter: DPF) to capture particulate matter. Furthermore, particulate matter emitted from gasoline engines has also been recognized as a problem in recent years, leading to the increasing adoption of filters (Gasoline Particulate Filter: GPF) in gasoline engines.

[0003] As a filter, there is known a wall-flow honeycomb structure, which is formed by arranging an outer peripheral side wall, a plurality of first cells and a plurality of second cells alternately adjacent to each other via a partition wall, wherein the plurality of first cells are arranged on the inner peripheral side of the outer peripheral side wall, extend from the first bottom surface to the second bottom surface, the first bottom surface is open, and a sealed portion is provided on the second bottom surface, and the plurality of second cells are arranged on the inner peripheral side of the outer peripheral side wall, extend from the first bottom surface to the second bottom surface, have a sealed portion on the first bottom surface, and are open on the second bottom surface.

[0004] In a wall-flow honeycomb structure, the plugging portion prevents trapped particulate matter from leaking out of the filter (erosion). Therefore, it is important to ensure filter performance that the plugging portion is formed at a predetermined depth and without peeling.

[0005] Patent Document 1 aims to provide a honeycomb filter in which cracks do not occur in the sealing portion and the substrate, or in which the sealing portion does not peel or fall off from the substrate. Patent Document 1 describes a honeycomb filter characterized in that the sealing material is composed of a ceramic crushed product of the same material as the ceramic substrate.

[0006] Patent document 2 aims to obtain a ceramic honeycomb filter with excellent heat shock resistance, and describes a honeycomb filter composed of a material with cordierite as the main crystal, at least a part of the sealing part is composed of an amorphous oxide matrix, and the amorphous oxide matrix is ​​formed by ceramic particles and colloidal oxides existing between them.

[0007] Patent Document 3 aims to provide a honeycomb structure capable of suppressing defects such as sealing peeling during canning and effectively preventing corrosion, and describes a honeycomb structure in which the average porosity of sealed portions is controlled to 4% or less.

[0008] Prior art literature

[0009] Patent Literature

[0010] Patent Document 1: Japanese Patent Application Laid-Open No. 2002-136817

[0011] Patent Document 2: Japanese Patent Application Laid-Open No. 2005-125318

[0012] Patent Document 3: Japanese Patent Application Laid-Open No. 2021-159868 Summary of the Invention

[0013] Problems to be solved by the invention

[0014] During the formation of sealed cells, a masking film is temporarily attached to the bottom surface of the honeycomb structure to distinguish the cells to be sealed from the remaining cells. The film is eventually peeled off, but this process can cause localized peeling of the sealed cells, requiring considerable time to correct and sometimes resulting in defective products. Existing technologies cannot adequately address peeling of the sealed cells during film peeling, and there is room for improvement.

[0015] The present invention has been made in view of the above circumstances, and in one embodiment, an object of the present invention is to provide a honeycomb structure capable of suppressing peeling of a plugged portion during film peeling.

[0016] Methods for solving problems

[0017] The present inventors have conducted intensive research to solve the above-mentioned problems and have found that controlling the composition and surface roughness of the plugged portion is important for solving the above-mentioned problems. The present invention has been completed based on this finding and is exemplified below.

[0018] [Method 1] A honeycomb structure comprising an outer peripheral side wall, a plurality of first cells, and a plurality of second cells; the plurality of first cells are arranged on the inner peripheral side of the outer peripheral side wall, extend from the first bottom surface to the second bottom surface, have an opening portion on the first bottom surface, and have a sealed portion on the second bottom surface; the plurality of second cells are arranged on the inner peripheral side of the outer peripheral side wall, extend from the first bottom surface to the second bottom surface, have a sealed portion on the first bottom surface, and have an opening portion on the second bottom surface; the plurality of first cells and the plurality of second cells are alternately arranged adjacent to each other via a partition wall; the sealed portion is composed of a ceramic containing MgO: 9.0 to 13.4 mass%, Al2O3: 29.0 to 35.5 mass%, and SiO2: 50.0 to 58.0 mass%, and the arithmetic mean height Sa of the sealed portion on the first bottom surface and the second bottom surface is respectively less than 18.0 μm.

[0019] [Mode 2] The honeycomb structure according to Mode 1, wherein the plugging portion is made of ceramic 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.

[0020] [Aspect 3] The honeycomb structure according to aspect 1 or 2, wherein an arithmetic mean height Sa of the plugged portions of the first bottom surface and the second bottom surface is 5.0 to 17.5 μm, respectively.

[0021] [Aspect 4] The honeycomb structure according to aspect 1 or 2, wherein an arithmetic mean height Sa of the plugged portions of the first bottom surface and the second bottom surface is 5.0 to 12.0 μm, respectively.

[0022] [Aspect 5] The honeycomb structure according to any one of aspects 1 to 4, wherein the plugged portion is in an unfired state.

[0023] [Aspect 6] The honeycomb structure according to aspect 5, wherein the ceramic constituting the plugging portion contains cordierite particles and silica gel bonding the particles together.

[0024] [Aspect 7] The honeycomb structure according to any one of aspects 1 to 4, wherein the plugged portion is fired.

[0025] [Mode 8] The honeycomb structure according to Mode 7, wherein the ceramic constituting the plugging portion is a sintered body of cordierite.

[0026] [Aspect 9] The honeycomb structure according to any one of aspects 1 to 8, wherein the median particle size of the ceramic constituting the plugging portion is 5 to 25 μm.

[0027] [Aspect 10] The honeycomb structure according to any one of aspects 1 to 9, wherein the average porosity of the plugged portions of the first bottom surface and the second bottom surface is 30 to 70%, respectively.

[0028] [Aspect 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.

[0029] [Aspect 12] The honeycomb structure according to any one of aspects 1 to 11, wherein an average depth of the plugged portions of the first bottom surface and the second bottom surface is 3 to 7 mm, respectively.

[0030] Effects of the Invention

[0031] According to one embodiment of the present invention, a honeycomb structure is provided that can suppress peeling of the sealing portion during membrane peeling. By suppressing peeling of the sealing portion, the desired performance required of the sealing portion, such as preventing erosion by trapped particulate matter, can be stably achieved. Therefore, this honeycomb structure is suitable for use as a honeycomb filter, for example, with excellent quality stability. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1It is a perspective view schematically showing a wall-flow type honeycomb structure.

[0033] Figure 2 This is a schematic cross-sectional view of a wall-flow type honeycomb structure observed in a cross section parallel to the direction in which cells extend.

[0034] Figure 3 This is a schematic partial enlarged view of a partition wall of a honeycomb structure observed in a cross section perpendicular to the direction in which cells extend.

[0035] Figure 4 This is a schematic partial cross-sectional view for explaining a method for measuring the depth of a plugged portion.

[0036] Figure 5 This is an explanatory diagram schematically showing an example of a method for forming a plugged portion using a squeegee method.

[0037] Description of Reference Numerals

[0038] 100: Honeycomb structure, 102: Outer peripheral side wall, 104: First bottom surface, 106: Second bottom surface, 108: First cell, 109: Sealing portion, 110: Second cell, 112: Partition wall, 120: Chuck, 121: Membrane, 122: Scraper, 124: Slurry for forming the sealing portion, 125: Cell, 126: Hole, 500: Honeycomb formed body. DETAILED DESCRIPTION

[0039] Next, refer to the attached Figure 1 It should be understood that the present invention is not limited to the following embodiments, and that design changes and improvements can be appropriately made based on the common knowledge of those skilled in the art without departing from the scope of the present invention.

[0040] (1. Honeycomb structure)

[0041] exist Figure 1 and Figure 22 shows a schematic perspective view and a cross-sectional view of a honeycomb structure 100 that can be used as a wall-flow exhaust gas filter and / or catalyst carrier for automobiles. The honeycomb structure 100 includes an outer peripheral sidewall 102, a plurality of first cells 108, and a plurality of second cells 110. The plurality of first cells 108 are arranged on the inner peripheral side of the outer peripheral sidewall 102, extending parallel to a first bottom surface 104 to a second bottom surface 106, having openings on the first bottom surface 104 and sealed portions 109 on the second bottom surface 106. The plurality of second cells 110 are arranged on the inner peripheral side of the outer peripheral sidewall 102, extending parallel to the first bottom surface 104 to the second bottom surface 106, having sealed portions 109 on the first bottom surface 104 and openings on the second bottom surface 106. In this honeycomb structure 100, the first cells 108 and the second cells 110 are alternately arranged adjacent to each other with partition walls 112 interposed therebetween.

[0042] 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. Since the second bottom surface 106 on the downstream side of the first cells 108 is sealed, 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 trapped and accumulates 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 downstream second bottom surface 106.

[0043] The bottom shape of the honeycomb structure 100 is not limited and can be, for example, circular, elliptical, racetrack-shaped, oblong, polygonal, triangular, quadrilateral, or other irregular shapes. The honeycomb structure 100 can have a cylindrical shape. The bottom shape of the illustrated honeycomb structure 100 is circular, and the overall shape is cylindrical.

[0044] The height of the honeycomb structure (the length from the first bottom surface to the second bottom surface) is not particularly limited and can be appropriately set according to the application and required performance. The height of the honeycomb structure can be set to 40 mm to 450 mm, for example. There is no particular limitation on the relationship between the height of the honeycomb structure and the maximum diameter of each bottom surface (referring to the maximum length of the diameter passing through the center of gravity of each bottom surface of the honeycomb structure). Therefore, the height of the honeycomb structure can be longer than the maximum diameter of each bottom surface, or the height of the honeycomb structure can be shorter than the maximum diameter of each bottom surface.

[0045] The shape of the cell openings in a cross section perpendicular to the cell extension direction is not limited, but is preferably a quadrilateral, hexagon, octagon, or a combination thereof. Square and hexagonal shapes are preferred. This cell shape minimizes pressure loss when fluid flows through the honeycomb structure, resulting in excellent purification performance.

[0046] There is no particular limitation on the cell density (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 ), particularly preferably 100 to 600 cells / square inch (15.5 to 92.0 cells / cm 2 Here, the cell density can be calculated by dividing the total number of cells (including sealed cells) by the area of ​​one bottom portion of the honeycomb structure excluding the peripheral sidewalls.

[0047] From the perspective of improving the strength of the honeycomb structure and the collection efficiency in the case of filter use, the average thickness of the partition wall is preferably 150 μm or more, more preferably 170 μm or more, and even more preferably 190 μm or more. In addition, from the perspective of suppressing pressure loss, the average thickness of the partition wall is preferably 260 μm or less, more preferably 240 μm or less, and even more preferably 220 μm or less. Therefore, the average thickness of the partition wall is, for example, preferably 150 to 260 μm, more preferably 170 to 240 μm, and even more preferably 190 to 220 μm.

[0048] Figure 3 is a schematic partial enlarged view of a partition wall 112 of a honeycomb structure 100 viewed in a cross section perpendicular to the cell extension direction. The thickness of a partition wall refers to the length of a line segment N that connects the centers of gravity O of adjacent cells in a cross section perpendicular to the cell extension direction (the height direction of the honeycomb structure) and passes through the partition wall. The thickness direction D of the partition wall refers to a direction parallel to the line segment N. The average thickness of the partition wall refers to the average thickness of all the partition walls.

[0049] The partition walls can be made porous. The average porosity of the partition walls can be adjusted appropriately according to the application, but from the perspective of suppressing the pressure loss of the fluid to a low level, it is preferably 40% or more, more preferably 50% or more, and even more preferably 60% or more. In addition, from the perspective 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 can be measured by mercury intrusion according to JIS R1655:2003. 20 test pieces of the partition walls are evenly collected including the center and periphery of the honeycomb structure, the porosity of each piece is measured, and the average value thereof is taken as the average porosity.

[0050] About the material constituting next door and peripheral sidewall, there is no particular restriction, from the viewpoint of strength, heat resistance, preferably ceramics.As ceramics, for example, preferably containing at least one ceramic selected from the group consisting of cordierite, mullite, zircon, aluminum titanate, silicon carbide, silicon-silicon carbide composite material, silicon nitride, zirconium oxide, spinel, India stone, pseudo sapphire, corundum, titanium dioxide.And, these ceramics can contain 1 kind alone, and can also contain more than 2 kinds simultaneously.Next door and peripheral sidewall are preferably formed by the material containing these ceramics more than 50 mass % in total, more preferably formed by the material containing these ceramics more than 80 mass %.

[0051] In a preferred embodiment, the outer peripheral sidewalls, partition walls, and plugging portions of the honeycomb structure each contain cordierite as a primary component. This means that the total mass proportion of cordierite (2MgO·2Al2O3·5SiO2) in 100% by mass of the materials comprising the outer peripheral sidewalls, partition walls, and plugging portions is 50% by mass or greater. The mass proportion of cordierite in 100% by mass of the materials comprising the outer peripheral sidewalls, partition walls, and plugging portions is preferably 70% by mass or greater, and more preferably 80% by mass or greater.

[0052] The cordierite content can be measured by X-ray diffraction. Specifically, using an X-ray diffractometer utilizing Cu Kα radiation (e.g., X'pert PRO manufactured by PANalytical), X-ray analysis is performed on samples of the peripheral sidewalls, partition walls, or sealed portions within a range of 2θ = 8 to 100°. Analysis is performed using the Rietveld analysis program RIETAN to determine the cordierite crystal phase ratio, which is used as the cordierite content.

[0053] Fine-tuning the chemical composition of the sealing portion is beneficial in preventing it from flaking during membrane peeling. Specifically, the sealing portion is preferably composed of a ceramic containing 9.0-13.4% by mass of MgO, 29.0-35.5% by mass of Al2O3, and 50.0-58.0% by mass of SiO2. More preferably, it is composed of a ceramic containing 9.0-12.0% by mass of MgO, 29.8-32.0% by mass of Al2O3, and 54.0-57.2% by mass of SiO2. Even more preferably, it is composed of a ceramic containing 10.2-11.5% by mass of MgO, 30.5-32.0% by mass of Al2O3, and 54.5-56.2% by mass of SiO2. This composition, which contains less MgO and more SiO2 than typical cordierite, facilitates smoothing of the outer surface of the sealing portion. It also improves the mechanical strength of the sealing portion itself.

[0054] The chemical composition of the plugged portion is preferably measured by cutting out the plugged portion from the honeycomb structure to prepare a measurement sample. However, when it is difficult to collect 10.0 g of the measurement sample from the honeycomb structure, the measurement sample is prepared by the following method.

[0055] Prepare the same slurry for forming the sealing portion as that used in the production of the sealing portion and flow it into a stainless steel mold with a diameter of 60 mm and a length of 15 mm. Then, dry it under the same conditions as the actual sealing portion and remove it from the stainless steel mold. After that, sinter it under the same conditions as when the actual sealing portion was sintered. Crush the obtained block to make a measurement sample. In the case where the sealing portion can be cut out from the honeycomb structure and the measurement sample is prepared, the cut sealing portion is crushed to make a measurement sample. The crushing is carried out under the conditions of pestle speed: 100 / 120 rpm, mortar speed: 6 / 7 rpm, and crushing time: 5 minutes.

[0056] Place 10.0 g of the sample in an alloy crucible, add 6.0 g of lithium tetraborate, and mix with a platinum rod. Place the alloy crucible in a vitrification apparatus (e.g., HERZOG Automatic Bead Sampler HA-HF16) and vitrify at 1200°C for 15 minutes (glass bead method). Qualitative analysis of the glass beads in each sample is performed using fluorescent X-ray analysis using Si Kα radiation, Al Kα radiation, and Mg Kα radiation to determine the mass percentages of SiO₂, Al₂O₃, and MgO.

[0057] The smoothness of the outer surface of the sealing portion can be represented by the arithmetic mean height Sa as an indicator. The arithmetic mean height Sa is a parameter of surface roughness specified in ISO 25178, which represents the average of the absolute value of the difference in height between each point and the average surface. The arithmetic mean height Sa of the sealing portion of the specific first bottom surface and the second bottom surface is preferably 18.0 μm or less, more preferably 17.5 μm or less, and further preferably 12.0 μm or less. The lower limit of the arithmetic mean height Sa of the sealing portion is not particularly set, but from the perspective of balancing the manufacturing cost, the arithmetic mean height Sa of the sealing portion of the first bottom surface and the second bottom surface is preferably 5.0 μm or more, more preferably 8.0 μm or more, and further preferably 10.5 μm or more. Therefore, the arithmetic mean height Sa of the plugged portions of the first and second bottom surfaces is preferably, for example, 5.0 to 18.0 μm, more preferably 5.0 to 17.5 μm, further preferably 8.0 to 17.5 μm, and even more preferably 5.0 to 12.0 μm.

[0058] In this specification, the arithmetic mean height Sa of the plugged portions of each of the first bottom surface and the second bottom surface is the average value obtained by uniformly measuring the arithmetic mean height Sa of the plugged portions at five locations using a laser microscope.

[0059] One sealed portion can be measured under the following conditions.

[0060] Measurement equipment: Shape analysis laser microscope (KEYENCE VK-X250 / 260) or microscope with equivalent performance

[0061] Parsing software: Multi-file parsing application (VK-1HXM) or equivalent software

[0062] Objective lens magnification: 10x

[0063] Sample size: 20mm×20mm×10mm (depth direction of the sealing part)

[0064] Measurement mode: Surface shape

[0065] Measurement size per field of view: Standard (1024 pixels × 768 pixels)

[0066] Measurement quality: high precision

[0067] Measurement time: 1 minute

[0068] Plane processing: A 750μm x 750μm square area is specified to determine the plane (reference plane) used as the measurement basis. The entire height data is rotated so that the set reference plane becomes horizontal, and the height is offset in the height direction so that the reference plane height becomes zero.

[0069] Reference surface position: -3 μm (offset so that the position with a depth of 3 μm becomes a height of 0.)

[0070] Ignore tiny areas: Ignore (Number of pixels in tiny areas: ≥6 pixels (surface irregularities smaller than 6 pixels are not recognized as holes)).

[0071] In one embodiment, the plugging portion may be fired. The ceramic constituting the fired plugging portion may be provided as a sintered body of cordierite, for example. The sintered body of cordierite may be obtained by firing a slurry for forming the plugging portion containing a cordierite-forming raw material.

[0072] In another embodiment, the sealing portion may be in an unfired state. In this case, the ceramic constituting the sealing portion preferably contains, for example, cordierite particles and an inorganic binder for bonding the particles together. Silica gel is preferably used as the inorganic binder.

[0073] Regardless of whether the sealing portion is fired or not, the median particle size of the ceramic constituting the sealing portion is preferably fine. As a result, the effect of easily smoothing the outer surface of the sealing portion can be obtained. Specifically, the upper limit of the median particle size of the ceramic constituting the sealing portion is preferably 25 μm or less, more preferably 20 μm or less, and further preferably 15 μm or less. In addition, from the viewpoint of suppressing the indentation of the sealing portion, the lower limit of the ceramic constituting the sealing portion is preferably 5 μm or more, more preferably 10 μm or more, and further preferably 12 μm or more. Therefore, the median particle size of the ceramic constituting the sealing portion is, for example, preferably 5 to 25 μm, more preferably 10 to 20 μm, and further preferably 12 to 15 μm.

[0074] The median particle size of the ceramic constituting the plugging portion is preferably measured by cutting out the plugging portion from the honeycomb structure to prepare a measurement sample. However, when it is difficult to prepare a 2.0 g measurement sample from the honeycomb structure, a measurement sample is prepared by the following method.

[0075] The same slurry for forming the sealing portion as that used in the production of the sealing portion is prepared and is flowed into a stainless steel mold with a diameter of 60 mm and a length of 15 mm. Then, it is dried under the same conditions as the actual sealing portion and removed from the stainless steel mold. Afterwards, it is fired under the same conditions as the actual sealing portion after firing. The obtained block is crushed with an automatic mortar to prepare a measurement sample. In the case where the sealing portion can be cut out from the honeycomb structure and the measurement sample is prepared, the cut sealing portion is crushed to prepare the measurement sample. The crushing is carried out under the conditions of pestle speed: 100 / 120 rpm, mortar speed: 6 / 7 rpm, and crushing time: 5 minutes. 2.0 g of the measurement sample is set in a laser diffraction / scattering particle size distribution measuring device (Partica LA-960 manufactured by HORIBA is used in the embodiment), and the median particle size (D50) in the cumulative particle size distribution based on volume is measured by laser diffraction / scattering method.

[0076] In one embodiment, the average depth of the sealing portion of the first bottom surface and the second bottom surface is 3 to 7 mm, preferably 4.2 to 6 mm. By setting the lower limit of the average depth of the sealing portion to 3 mm or more, the strength of the sealing portion can be ensured. The average depth of the sealing portion is preferably 4.2 mm or more. In addition, by setting the upper limit of the average depth of the sealing portion to 7 mm or less, the area of ​​the partition wall for capturing particulate matter in the pores can be prevented from becoming smaller. The upper limit of the average depth of the sealing portion is preferably 6 mm or less. The depth of the sealing portion at 20 locations on each bottom surface is measured without deviation, and the average value is used as the average depth of the sealing portion of each bottom surface.

[0077] In this specification, the depth of each sealing portion is measured according to the following steps. First, the sealing portion to be measured in depth is cut in half with a cutting plane parallel to the height direction of the honeycomb structure (the direction in which the cells extend), and a cross section of the sealing portion is cut out. Use a laser microscope (for example: shape analysis laser microscope VKX250 / 260 manufactured by KEYENCE) to photograph the entire cross section of one location of the obtained sealing portion to generate a cross-sectional image of the sealing portion. Measure the length in the cell extension direction from the end of the outer surface side on the central axis M (a straight line with equal distances to a pair of opposing partition walls 112) of the cell where the sealing portion is formed as observed in the cross-sectional image to the deepest position where the sealing portion 109 exists, and use it as the depth E of the sealing portion (refer to Figure 4 ).

[0078] In one embodiment, the average porosity of the sealing portion 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 sealing portion to 30% or more is beneficial to alleviating thermal stress and improving thermal shock resistance. The lower limit of the average porosity of the sealing portion is preferably 35% or more, and more preferably 40% or more. In addition, setting the upper limit of the average porosity of the sealing portion to 70% or less is beneficial in preventing erosion. The upper limit of the average porosity of the sealing portion is preferably 60% or less, and more preferably 50% or less.

[0079] Since it is difficult to directly measure the porosity of the sealed portion by sampling only the sealed portion, it can be measured by the mercury intrusion method specified in JIS 1655:2003 according to the following procedure.

[0080] A test piece of the partition wall portion where no plugging portion was formed was collected, and the porosity P1 (porosity of the partition wall portion) of the test piece was measured.

[0081] A test piece including the partition wall portion of the plugged portion was collected, and the porosity P (porosity of the partition wall portion + the plugged portion) of the test piece was measured.

[0082] In the test piece including the partition wall portion of the plugged portion, the volume V1 of the partition wall portion including pores was measured.

[0083] In the test piece including the partition wall portion of the plugged portion, the volume V2 including the pores of the plugged portion was measured.

[0084] If the porosity of the sealed portion is defined as P2, P, P1, P2, V1, and V2 satisfy the relationship of formula (1).

[0085] P=P1×V1 / (V1+V2)+P2×V2 / (V1+V2)···(1)

[0086] Therefore, P2 can be obtained by formula (2).

[0087] P2=P×(V1+V2) / V2-P1×V1 / V2···(2)

[0088] The porosity P2 of the plugged portions at 20 random locations on each bottom surface was measured, and the average value thereof was taken as the average porosity of the plugged portions on each bottom surface.

[0089] In the test piece including the partition wall portion of the plugged portion, P2 can be obtained by formula (3) when the volume ratio of the volume V1 of the partition wall portion including the pores is defined as v1 and the volume ratio of the volume V2 of the plugged portion including the pores is defined as v2.

[0090] P2=P×(v1+v2) / v2-P1×v1 / v2···(3)

[0091] When a honeycomb structure is used as a catalyst carrier, a catalyst suitable for the purpose can be coated on the surface of the partition walls. Examples of catalysts include, but are not limited to, oxidation catalysts (DOCs) for oxidative combustion of hydrocarbons (HC) and carbon monoxide (CO) to increase exhaust gas temperature, PM combustion catalysts for assisting in the combustion of PM such as soot, SCR 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). Catalysts may include, for example, precious metals (such as Pt, Pd, and Rh), alkali metals (such as Li, Na, K, and Cs), alkaline earth metals (such as Mg, Ca, Ba, and Sr), rare earth metals (such as Ce, Sm, Gd, Nd, Y, La, and Pr), and transition metals (such as Mn, Fe, Co, Ni, Cu, Zn, Sc, Ti, Zr, V, and Cr).

[0092] (2. Manufacturing Method)

[0093] The honeycomb structure with sealing portion can be manufactured by known manufacturing methods except the formation method of sealing portion, and is illustrated below illustratively. First, after the raw material composition containing ceramic raw material, dispersion medium, pore-forming material and adhesive is mixed and formed into green clay, the green clay is extruded and formed into the desired honeycomb formed body. Additives such as dispersants can be coordinated as needed in the raw material composition. During extrusion molding, a metal mold with desired overall shape, cell shape, wall thickness, cell density, etc. can be used.

[0094] Ceramic raw materials remain after the firing of metal oxides and metals, and are part of the raw materials that constitute the honeycomb sintered body skeleton in the form of ceramics. Ceramic raw materials can be provided in the form of powder, for example. As ceramic raw materials, cordierite, mullite, zircon, aluminum titanate, silicon carbide, silicon-silicon carbide composite materials, silicon nitride, zirconium oxide, spinel, India stone, sapphire, corundum, titanium dioxide, etc. can be mentioned as raw materials for obtaining ceramics. Specifically, without limitation, silicon dioxide, talc, aluminum oxide, kaolin, serpentine, pyrophyllite, brucite, boehmite, mullite, magnesite, aluminum hydroxide, etc. can be mentioned. Ceramic raw materials can be used alone or in combination of two or more.

[0095] In the case of filters such as DPFs and GPFs, cordierite can be preferably used as a ceramic. In this case, a cordierite-forming raw material can be used as the ceramic raw material. A cordierite-forming raw material refers to a raw material that becomes cordierite by firing. The cordierite-forming raw material preferably has a chemical composition of 30-45% by mass of aluminum oxide (Al2O3) (including aluminum hydroxide that can be converted into aluminum oxide), 11-17% by mass of magnesium oxide (MgO), and 42-57% by mass of silicon dioxide (SiO2).

[0096] As a pore-forming material, as long as it becomes pores after firing, there is no particular limitation, for example, wheat flour, starch, foaming resin, water-absorbing resin, silica gel, carbon (for example: graphite), ceramic beads, polyethylene, polystyrene, polypropylene, nylon, polyester, acrylic resin, phenol, etc. can be mentioned. One pore-forming material can be used alone, or two or more can be used in combination. From the viewpoint of improving the porosity of the fired honeycomb structure, the content of the pore-forming material is preferably 0.5 mass parts or more relative to 100 mass parts of ceramic raw materials, more preferably 2 mass parts or more, and further preferably 3 mass parts or more. From the viewpoint of ensuring the strength of the fired honeycomb structure, the content of the pore-forming material is preferably 30 mass parts or less relative to 100 mass parts of ceramic raw materials, more preferably 27 mass parts or less, and further preferably 24 mass parts or less.

[0097] As adhesive, organic adhesives such as methylcellulose, hydroxypropoxymethylcellulose, hydroxypropyl methylcellulose, hydroxyethyl cellulose, carboxymethyl cellulose, polyvinyl alcohol can be exemplified. In addition, from the viewpoint of improving the intensity of the honeycomb formed body, relative to 100 parts by mass of ceramic raw materials, the content of adhesive is preferably more than 4 parts by mass, more preferably more than 5 parts by mass, and further preferably more than 6 parts by mass. From the viewpoint of suppressing the cracking caused by the abnormal heating in the firing process, the content of adhesive is preferably less than 9 parts by mass, more preferably less than 8 parts by mass, and further preferably less than 7 parts by mass relative to 100 parts by mass of ceramic raw materials. One adhesive can be used alone or in combination with two or more.

[0098] Dispersants that can be used include ethylene glycol, dextrin, fatty acid soap, and polyether polyol. These dispersants can be used alone or 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.

[0099] Examples of the dispersion medium include water and a mixed solvent of water and an organic solvent such as alcohol, and water is particularly preferably used.

[0100] 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 relative to 100 parts by mass of the ceramic raw material. By setting the water content of the honeycomb formed body to 20 parts by mass or more relative to 100 parts by mass of the ceramic raw material, the advantage of easily stabilizing the quality of the honeycomb structure can be easily obtained. By setting the water content of the honeycomb formed body to 90 parts by mass or less relative to 100 parts by mass of the ceramic raw material, the shrinkage during drying is reduced, and deformation can be suppressed. In this specification, the water content of the honeycomb formed body refers to the value measured by the loss on drying method.

[0101] The honeycomb formed body can be dried by conventionally known drying methods such as hot air drying, microwave drying, dielectric drying, reduced pressure drying, vacuum drying, and freeze drying. Among these, a drying method combining hot air drying with microwave drying or dielectric drying is preferred because it can rapidly and uniformly dry the entire honeycomb formed body.

[0102] The subsequent steps differ depending on whether the honeycomb structure as a product has fired plugged portions or unfired plugged portions, and therefore each case will be described.

[0103] (1) When the honeycomb structure has a fired plugged portion

[0104] The case where the honeycomb structure has fired plugging portions will be described. After the honeycomb formed body is dried, 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, followed by drying. Subsequently, the unfired plugging portions are fired together with the honeycomb formed body. Thus, fired plugging portions are formed.

[0105] In one embodiment, the slurry for forming the sealing portion contains a cordierite-forming raw material, a dispersion medium, a pore-forming material, and a binder. For example, the slurry for forming the sealing portion contains 30-60 parts by mass of the dispersion medium, 5-20 parts by mass of the pore-forming material, and 0.2-2.0 parts by mass of the binder per 100 parts by mass of the cordierite-forming raw material. In a preferred embodiment, the slurry for forming the sealing portion contains 35-50 parts by mass of the dispersion medium, 8-16 parts by mass of the pore-forming material, and 0.2-1.5 parts by mass of the binder per 100 parts by mass of the cordierite-forming raw material.

[0106] Examples of cordierite-forming raw materials used in the plugging portion forming slurry include silica, talc, alumina, kaolin, serpentine, pyrophyllite, brucite, boehmite, mullite, magnesite, and aluminum hydroxide. The blending ratio of these raw materials is selected so that the plugging portion obtained after firing has the above-described chemical composition.

[0107] To improve the smoothness of the outer surface of the plugged portion, the cordierite-forming raw material is preferably as fine as possible. For example, the median diameter (D50) in the volume-based cumulative particle size distribution determined by laser diffraction / scattering 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.

[0108] Examples of the dispersion medium include water and a mixed solvent of water and an organic solvent such as alcohol, and water is particularly preferably used.

[0109] 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 beads, polyethylene, polystyrene, polypropylene, nylon, polyester, acrylic resin, phenol, etc. The pore-forming material may be used alone or in combination of two or more. The median particle size (D50) of the pore-forming material in the volume-based cumulative particle size distribution determined by a laser diffraction / scattering method is preferably 35 to 55 μm.

[0110] Examples of the binder include organic binders such as methylcellulose, hydroxypropoxymethylcellulose, hydroxypropylmethylcellulose, hydroxyethylcellulose, hydroxyethylmethylcellulose, carboxymethylcellulose, and polyvinyl alcohol. The binder may be used alone or in combination of two or more.

[0111] The slurry for forming the sealing portion may contain a thickener as appropriate. For example, the thickener may contain 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 raw material. As thickeners used in the slurry for forming the sealing portion, pectin, guar gum, xanthan gum, propylene glycol, and polyethylene oxide can be mentioned. Among them, the solution preferably shows high viscosity even at low concentrations and has a fluidity-improving effect of polyethylene oxide. One type of thickener may be used alone, or two or more types may be used in combination.

[0112] The sealing portion forming slurry may contain a dispersant as appropriate. For example, the dispersant may be contained in an amount of 0.1 to 3 parts by mass, preferably 0.2 to 2 parts by mass, per 100 parts by mass of the cordierite forming raw material. Examples of dispersants include ethylene glycol, dextrin, fatty acid soaps, and polyols. One dispersant may be used alone, or two or more may be used in combination.

[0113] The filling of the slurry for forming the sealing portion into the opening of the cell can be carried out, for example, by the following "scraper method". Figure 5 As shown, a film 121 is pasted on the bottom surface (here, the second bottom surface 106 in the figure) of the upper side of the dried honeycomb formed body 500 fixed by a chuck 120, and a laser is irradiated at a position of the film 121 corresponding to the arrangement conditions of the sealing portion (for example, a "checkerboard pattern", etc.), and a plurality of holes 126 are provided through the film 121.

[0114] Then, the slurry 124 for forming the sealing portion is placed on the film 121, and the scraper 122 is moved along the film 121 to form the sealing portion. Figure 5 Thus, a certain amount of the plugging portion forming slurry 124 is filled into the cells 125 opened at positions corresponding to the holes 126 of the film 121 .

[0115] The depth of the plugging portion can be changed by the number of movement operations of the squeegee 122 , the contact angle between the squeegee 122 and the film 121 , the pressing pressure of the squeegee 122 on the film 121 , and the viscosity of the plugging portion forming slurry 124 .

[0116] After filling the plugging portion forming slurry 124, the excess plugging portion forming slurry 124 remaining on the surface of the membrane 121 is wiped off with a scraper 122. The membrane 121 is then peeled off, and the entire honeycomb formed body 500 is dried. In this manner, the plugging portion forming slurry 124 filled in the cells 125 is dried, forming the plugging portions before firing. Drying can be performed, for example, at a drying temperature of 100 to 230°C for approximately 60 to 150 seconds.

[0117] The material of the membrane is not particularly limited, but in order to facilitate thermal processing for forming holes, polypropylene (PP), polyethylene terephthalate (PET), polyimide, or Teflon (registered trademark) is preferred. In addition, the membrane preferably has an adhesive layer, and the material of the adhesive layer is preferably an acrylic resin, a rubber-based resin (e.g., a rubber mainly composed of natural rubber or synthetic rubber), or a silicone resin. For example, an adhesive film with a thickness of 20 to 50 μm can be suitably used.

[0118] In addition to the "scraper method" described above, a "press-in method" can be used as a method for filling the cell openings with the plugging portion forming slurry. The "press-in method" is a method in which the bottom portion of a honeycomb formed body, to which a membrane has been attached and perforated, is immersed in a tank containing the plugging portion forming slurry, thereby filling the cells with the plugging portion forming slurry. In this case, the depth of the plugging portion can be varied depending on the depth of immersion of the honeycomb formed body in the plugging portion forming slurry.

[0119] After drying, the sealing portion protrudes from the bottom surface of the honeycomb formed body in an amount equivalent to the thickness of the film, so it is preferably scraped off and smoothed (hereinafter also referred to as "smoothing processing"). At this time, if the sealing portion has a suitable composition, the outer surface of the sealing portion is easily smoothed. The method of smoothing processing is not limited, and it is preferred to press a bottom surface of a fired ceramic honeycomb structure (hereinafter also referred to as a "smoothing fixture") on the outer surface of the sealing portion as the smoothing processing object and rub it. The smoothing fixture can, for example, preferably use the same material as the fired material of the honeycomb formed body that is the smoothing processing object, such as a material made of cordierite. Among them, the smoothing fixture may have a sealing portion or may not have a sealing portion.

[0120] The bottom surface of the smoothing jig is preferably smooth. Specifically, the arithmetic mean surface height Sa of the partition walls constituting the bottom surface of the smoothing jig is preferably, for example, 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 surface height Sa of the partition walls constituting the bottom surface of the smoothing jig can be measured using the same method as that for measuring the arithmetic mean height Sa of the sealed portion described above.

[0121] Furthermore, during the smoothing process, it is preferred that the sides (partition walls) defining the opening shape of the cells of the honeycomb formed body to be smoothed and the sides (partition walls) defining the opening shape of the cells of the smoothing jig are not parallel to each other, for example, the sides are relatively moved so that the angle formed by the two sides is 30° to 60°. This is because if the sides (partition walls) defining the opening shape of the cells of the honeycomb formed body to be smoothed and the sides (partition walls) defining the opening shape of the cells of the smoothing jig are parallel to each other, notches are likely to be generated.

[0122] The honeycomb formed body filled with the slurry for forming the sealing portion is then subjected to a degreasing process and a firing process. A honeycomb structure having fired sealing portions is thus manufactured. The combustion temperature of the adhesive is about 200°C, and the combustion temperature of the pore-forming material is about 300-1000°C. Therefore, the degreasing process can be carried out by heating the honeycomb formed body to a temperature in the range of about 200-1000°C. The heating time is not particularly limited and is generally about 10-100 hours. The honeycomb formed body after the degreasing process is called a calcined body. The firing process also depends on the material composition of the honeycomb structure. For example, it can be carried out by heating the calcined body to 1300-1450°C and maintaining it for 3-24 hours.

[0123] (2) When the honeycomb structure has unfired plugged portions

[0124] Next, the case where the honeycomb structure has unfired sealing portions will be described. In this case, after the honeycomb formed body is dried, the degreasing process and the firing process are performed without forming the sealing portions. The conditions of the degreasing process and the firing process are as described above. In this way, a honeycomb structure without sealing portions is manufactured. Next, unfired sealing portions are formed on both bottom surfaces of the honeycomb structure. The unfired sealing portions can be formed by filling the openings of the first and second cells, where the sealing portions are to be formed, with a slurry for forming the sealing portions, and then drying them.

[0125] In one embodiment, the slurry for forming the sealing portion contains cordierite particles, a dispersion medium, and an inorganic binder. For example, the slurry for forming the sealing portion contains 10 to 35 parts by mass of the dispersion medium and 10 to 25 parts by mass of the inorganic binder relative to 100 parts by mass of the cordierite particles. In a preferred embodiment, the slurry for forming the sealing portion contains 15 to 30 parts by mass of the dispersion medium and 11 to 20 parts by mass of the inorganic binder relative to 100 parts by mass of the cordierite particles. The mixing ratio of these raw materials is selected so that the sealing portion obtained after drying has the above-mentioned chemical composition.

[0126] The cordierite particles contain cordierite as a main component. This means that the total mass proportion of cordierite (2MgO·2Al2O3·5SiO2) in 100% by mass of the cordierite particles is 50% by mass or greater. The mass proportion of cordierite in 100% by mass of the cordierite particles is preferably 70% by mass or greater, and more preferably 80% by mass or greater. The method for measuring the cordierite content is as described above.

[0127] From the viewpoint of improving the smoothness of the outer surface of the sealing portion, the cordierite particles are preferably fine. However, if the cordierite particles are too fine, the porosity decreases. Therefore, in order to obtain the desired porosity, the cordierite particles are preferably not too fine. For cordierite particles, the median particle size (D50) in the cumulative particle size distribution based on volume obtained, for example, by a laser diffraction / scattering method is preferably 40 μm or less, more preferably 30 μm or less. The lower limit of the median particle size (D50) of the cordierite particles is not particularly set. From the viewpoint of ease of acquisition, the median particle size (D50) of the cordierite particles is generally 10 μm or more, typically 20 μm or more. Therefore, the median particle size (D50) of the cordierite particles is, for example, preferably 10 to 40 μm, more preferably 20 to 30 μm.

[0128] Examples of the dispersion medium include water and a mixed solvent of water and an organic solvent such as alcohol, and water can be used particularly preferably.

[0129] As the inorganic binder, silica gel can be preferably used.

[0130] The slurry for forming the sealing portion may also contain an organic binder in addition to an inorganic binder. For example, it may contain 0.2 to 2.0 parts by mass, preferably 0.2 to 1.5 parts by mass, relative to 100 parts by mass of cordierite particles. As the organic binder, methylcellulose, hydroxypropoxymethylcellulose, hydroxypropylmethylcellulose, hydroxyethylcellulose, hydroxyethylmethylcellulose, carboxymethylcellulose, polyvinyl alcohol, diutan gum, wellan gum, xanthan gum, guar gum and other organic binders may be exemplified. One organic binder may be used alone or in combination of two or more.

[0131] The sealing portion forming slurry may contain a dispersant as appropriate. For example, the dispersant may be contained in an amount of 0.1 to 3 parts by mass, preferably 0.2 to 2 parts by mass, per 100 parts by mass of the cordierite particles. Examples of dispersants include ethylene glycol, dextrin, fatty acid soaps, and polyols. One dispersant may be used alone, or two or more may be used in combination.

[0132] The plugging portion forming slurry can be filled into the openings of the cells by known filling methods such as the "squeegee method" and "press-in method." The subsequent film peeling and drying conditions are also as described above.

[0133] After drying, the above-mentioned smoothing process is preferably performed. At this time, if the sealing portion has an appropriate composition, the outer surface of the sealing portion can be easily smoothed. The conditions for the smoothing process are as described above.

[0134] Example

[0135] <Comparative Examples 1 and 2, Example 1>

[0136] (1) Preparation of honeycomb molded body

[0137] To 100 parts by mass of a cordierite-forming raw material, 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 were added and kneaded to prepare a clay. Talc, alumina, aluminum hydroxide, kaolin, and silica were used as the cordierite-forming raw materials. Water was used as the dispersion medium, a water-absorbing resin and silica gel were used as the pore-forming materials, methylcellulose was used as the binder, and ethylene glycol was used as the dispersant.

[0138] The molded clay is fed into an extruder and extruded through a metal die of a predetermined shape to obtain a cylindrical honeycomb molded body. The obtained honeycomb molded body is subjected to dielectric drying and hot air drying, and then cut on both bottom surfaces to a predetermined size and further hot air drying at 70°C for 2 hours.

[0139] (2) Formation of the sealing portion

[0140] In a total of 100 parts by mass of a cordierite-forming raw material containing each raw material in the mass proportions described in Table 1, a pore-forming material, a dispersion medium, an organic binder and a dispersant are added in the mass proportions described in Table 1, mixed, and a slurry for forming a sealing portion is prepared. As cordierite-forming raw materials, talc, alumina, aluminum hydroxide, kaolin and silica are used. The median particle size (D50) of these raw materials is as described in Table 1. A foaming resin is used as a pore-forming material, water is used as a dispersion medium, methyl cellulose is used as an organic binder, and ethylene glycol is used as a dispersant. Using the above-mentioned "scraper method", the slurry for forming a sealing portion is filled on both bottom surfaces in a manner such that the first cells and the second cells are alternately arranged adjacent to each other. Then, after wiping off the excess slurry for forming a sealing portion attached to the membrane with a scraper, the membrane is peeled off and dried under the conditions of 180°C × 200 seconds in an atmospheric atmosphere.

[0141] For each honeycomb formed article, the state of the outer surface of the plugged portion immediately after the film was peeled off was observed using an optical microscope (100x magnification), and the peeling depths of five peeled locations were randomly measured using a ruler. The peeling of the plugged portion was evaluated according to the following criteria. The results are shown in Table 1.

[0142] ○: ≤1.0mm

[0143] △: 1.1~1.5mm

[0144] ×: ≥1.6mm

[0145] (3) Smoothing

[0146] A honeycomb structure made of fired cordierite was prepared as a smoothing jig. The specifications of the honeycomb structure were as follows.

[0147] Overall shape: cylindrical with a diameter of 118mm and a height of 20mm

[0148] Cell shape in a cross section perpendicular to the cell flow direction: Square

[0149] Cell density (cells per unit cross-sectional area): 750 cells / square inch (118 cells / cm 2 ) Average thickness of partition wall: 2.5 mil (64 μm) (nominal value based on metal mold specifications)

[0150] Surface arithmetic mean height Sa of the partition walls constituting the bottom surface of the smoothing jig: 3.3 μm

[0151] Next, each honeycomb formed body after drying was manually smoothed at the sealed portion. During the smoothing process, the sides (partition walls) defining the cell opening shape of the honeycomb formed body to be smoothed and the sides (partition walls) defining the cell opening shape of the smoothing jig were moved relative to each other so that the angle formed between the sides (partition walls) was 45°.

[0152] (4) Firing

[0153] Next, degreasing was performed by heating at about 200°C in air atmosphere, and further sintering was performed at 1400°C in air atmosphere for 10 hours to obtain a cylindrical honeycomb structure having sintered plugged portions.

[0154] (5) Specifications of honeycomb structure

[0155] The specifications of the obtained honeycomb structure are as follows.

[0156] Overall shape: cylindrical with a diameter of 132mm and a height of 152mm

[0157] Cell shape in a cross section perpendicular to the cell flow direction: Square

[0158] Cell density (number of cells per unit cross-sectional area): 300 cells / square inch (47 cells / cm 2 ) Average thickness of partition wall: 8.5 mil (216 μm) (nominal value based on metal mold specifications)

[0159] Average porosity of the partition wall: 63%

[0160] Average depth of sealing part: 5mm

[0161] The outer peripheral side walls, partition walls, and sealed portions of the cylindrical honeycomb structure were analyzed by X-ray diffraction in the range of 2θ = 8 to 100° using an X'pert PRO apparatus manufactured by PANalytical using Cu Kα rays. The cordierite crystal phase ratio, determined by analysis using the Rietveld analysis program RIETAN, was analyzed to be 75 to 94% by mass.

[0162] (6) Chemical composition of the sealing part

[0163] Since it was difficult to collect measurement samples from the honeycomb structure, the same plugging portion forming slurry as that used for the plugging portion was prepared, and the measurement samples were prepared according to the above-mentioned procedure. The chemical composition was measured by the above-mentioned method. The results are shown in Table 1.

[0164] (7) Median particle size of the sealed portion

[0165] Because it is difficult to collect measurement samples from honeycomb structures, we prepared the same plugging slurry used for plugging, followed the aforementioned procedure to create measurement samples, and measured the median particle size of the ceramic constituting the plugging using the aforementioned method. The results are shown in Table 1.

[0166] (8) Arithmetic mean height Sa of the sealing part

[0167] The arithmetic mean height Sa of the plugged portions on one bottom surface of the resulting honeycomb structure was measured using the above method using a KEYENCE VK X250 / 260 shape analysis laser microscope. The results are shown in Table 1. It should be noted that, although the arithmetic mean height Sa of the plugged portions on the other bottom surface is not listed in Table 1, it is approximately the same as that on the one bottom surface.

[0168] (9) Average porosity of the sealed portion

[0169] The average porosity of the plugged portion on one bottom surface of the obtained honeycomb structure was measured by the above method. The results are shown in Table 1. It should be noted that although the average porosity of the plugged portion on the other bottom surface is not shown in Table 1, it is approximately the same as that on the one bottom surface.

[0170] (10) Sealing strength

[0171] For the 9 sealing parts (the center of gravity of the bottom surface, and 2 equally spaced parts from the center of gravity as the origin O of the XY coordinates along the ± direction of the X axis and the ± direction of the Y axis) of one bottom surface of the obtained honeycomb structure, except for the area within 5 mm from the outer periphery, a stainless steel pressing rod (cylindrical with a diameter of 1.1 mm and a length of 40 mm) inserted from the other bottom surface is used to press and gradually increase the applied force. As the applied force increases, the pressing rod soon penetrates the sealing part. The maximum load (sealing part strength) until penetration is measured using a load sensor. The sealing part of the other bottom surface is also measured in the same way. In this way, the average value of the strength of 18 sealing parts measured for a honeycomb structure is obtained. In addition, the relative value when the average value of Comparative Example 1 is set to 1.0 is shown in Table 1.

[0172] <Examples 2 to 4>

[0173] (1) Preparation of a cylindrical honeycomb structure without a sealed portion

[0174] A cylindrical honeycomb formed body was produced under the same conditions as in Example 1. The resulting honeycomb formed body was then subjected to dielectric drying and hot-air drying, and then cut to predetermined dimensions on both bottom surfaces. The body was then further hot-air dried at 70°C for 2 hours. Subsequently, the body was heated at approximately 200°C in an air atmosphere for degreasing, and then sintered at 1400°C in an air atmosphere for 10 hours to obtain a cylindrical honeycomb structure without plugged portions.

[0175] (2) Formation of the sealing portion

[0176] In a total of 100 parts by mass of cordierite particles A (cordierite content = 90% by mass) and cordierite particles B (cordierite content = 90% by mass) prepared in the mass proportions described in Table 1, a dispersion medium, an organic binder, a silica gel (inorganic binder), and a dispersant were added in the mass proportions described in Table 1, and the mixture was kneaded to prepare a slurry for forming a sealing portion. The chemical composition of cordierite particles A and cordierite particles B was measured using a quantitative analysis method based on fluorescent X-ray analysis. As a result, for cordierite particles A, SiO2 was 53.0% by mass, Al2O3 was 32.1% by mass, and MgO was 11.1% by mass. For cordierite particles B, SiO2 was 54.5% by mass, Al2O3 was 30.9% by mass, and MgO was 12.4% by mass. Their median particle sizes (D50) are as described in Table 1. Water was used as the dispersion medium, diutanol as the organic binder, and ethylene glycol as the dispersant. Using the "squeegee method" described above, the sealing portion-forming slurry was filled onto both bottom surfaces, with the first and second cells alternately arranged adjacent to each other. Excess sealing portion-forming slurry adhered to the membrane was then wiped off with a squeegee. The membrane was then peeled off and dried in an atmosphere at 180°C for 200 seconds.

[0177] Each honeycomb structure was evaluated for peeling of the plugged portion by the same method as in Example 1. The results are shown in Table 1.

[0178] (3) Smoothing

[0179] As a smoothing jig, a honeycomb structure made of fired cordierite was prepared. The specifications of this honeycomb structure were the same as those of the smoothing jig used in Example 1.

[0180] Next, each honeycomb structure, after drying the sealed portions, was manually smoothed. During the smoothing process, the edges (partition walls) defining the opening shape of the cells of the honeycomb formed body to be smoothed and the edges (partition walls) defining the opening shape of the cells of the smoothing jig were moved relative to each other so that the angle between them was 45°. In this way, honeycomb structures with unfired sealed portions were manufactured. The number of honeycomb structures required for investigating the following characteristics was prepared.

[0181] (4) Specifications of honeycomb structure

[0182] The specifications of the obtained honeycomb structure are as follows.

[0183] Overall shape: cylindrical with a diameter of 132mm and a height of 152mm

[0184] Cell shape in a cross section perpendicular to the cell flow direction: Square

[0185] Cell density (cells per unit cross-sectional area): 300 cells / square inch (49 cells / cm 2 ) Average thickness of partition wall: 8.5 mil (216 μm) (nominal value based on metal mold specifications)

[0186] Average depth of sealing part: 5mm

[0187] Average porosity of the partition wall: 63%

[0188] The outer peripheral side walls, partition walls, and sealed portions of the cylindrical honeycomb structure were analyzed by X-ray diffraction in the range of 2θ = 8 to 100° using an X'pert PRO apparatus manufactured by PANalytical using Cu Kα rays. The cordierite crystal phase ratio, determined by analysis using the Rietveld analysis program RIETAN, was analyzed to be 75 to 94% by mass.

[0189] (5) Characteristics of the sealing part

[0190] The chemical composition, median diameter, arithmetic mean height Sa, average porosity, and sealing strength of the plugged portion were measured by the same method as in Example 1. The results are shown in Table 1.

[0191] [Table 1]

[0192]

Claims

1. A honeycomb structure comprising an outer peripheral sidewall, a plurality of first cells, and a plurality of second cells; The plurality of first cells are arranged on the inner peripheral side of the outer peripheral side wall, extending from the first bottom surface to the second bottom surface, having an opening portion on the first bottom surface and a sealing portion on the second bottom surface; The plurality of second cells are arranged on the inner peripheral side of the outer peripheral side wall, extending from the first bottom surface to the second bottom surface, having a sealing portion on the first bottom surface and an opening portion on the second bottom surface; The plurality of first cells and the plurality of second cells are alternately arranged adjacent to each other with partition walls interposed therebetween; The sealing portion is composed of ceramic containing MgO: 9.0-13.4 mass%, Al2O3: 29.0-35.5 mass%, and SiO2: 50.0-58.0 mass%. The arithmetic mean heights Sa of the sealed portions of the first bottom surface and the second bottom surface are both 18.0 μm or less.

2. The honeycomb structure according to claim 1, wherein The sealing portion is made of ceramic containing 9.0 to 12.0 mass % of MgO, 29.8 to 32.0 mass % of Al 2 O 3 , and 54.0 to 57.2 mass % of SiO 2 .

3. The honeycomb structure according to claim 1, wherein The arithmetic mean heights Sa of the sealing portions of the first bottom surface and the second bottom surface are 5.0 to 17.5 μm, respectively. The honeycomb structure according to claim 1 , wherein: The arithmetic mean heights Sa of the sealing portions of the first bottom surface and the second bottom surface are 5.0 to 12.0 μm, respectively. The honeycomb structure according to claim 1 , wherein: The sealing portion is in an unfired state. The honeycomb structure according to claim 5 , wherein: The ceramic constituting the plugging portion includes cordierite particles and colloidal silica bonding the particles together.

7. The honeycomb structure according to claim 1, wherein The sealing portion is fired.

8. The honeycomb structure according to claim 7, wherein The ceramic constituting the sealing portion is a sintered body of cordierite.

9. The honeycomb structure according to claim 1, wherein The ceramic constituting the sealing portion has a median particle size of 5 to 25 μm.

10. The honeycomb structure according to claim 1, wherein The average porosity of the sealing portions of the first bottom surface and the second bottom surface is 30-70%, respectively. The honeycomb structure according to claim 1 , wherein: The partition walls are made of ceramics containing cordierite as a main component.

12. The honeycomb structure according to claim 1, wherein The average depths of the sealing portions of the first bottom surface and the second bottom surface are 3 to 7 mm, respectively.

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