Honeycomb structure

Abstract

The utility model provides a honeycomb structural body which meets all excellent PM (particulate matter) trapping performance, low pressure loss, excellent catalyst coating performance during catalyst loading, difficulty in soot blockage and excellent mechanical strength. A columnar honeycomb structure is provided with: an outer peripheral side wall; a plurality of introduction compartments; and a plurality of discharge compartments, characterized in that: the ratio of the opening area Cin of each of the plurality of introduction compartments to the opening area Cout of each of the plurality of discharge compartments satisfies 1 lt; cin / Cout < = 2.5, the thickness WT of the partition wall is 0.18-0.25 mm, the cell density CD based on the total number of the plurality of introduction cells and the plurality of discharge cells is 49-70 cells / cm < 2 >, the depth PD of the hole sealing part is 4-7 mm, and in a cross section perpendicular to the direction in which the plurality of introduction cells and the plurality of discharge cells extend of the honeycomb structure, the thickness WT of the partition wall is 0.18-0.25 mm. The distance OF between the midpoint of a line segment connecting the center of gravity of the introduction compartment and the center of gravity of the discharge compartment adjacent to each other with the partition wall therebetween and the center of the partition wall crossing the line segment is 0.075-0.110 mm, and 2 < = OF * CD / (WT * PD) < = 7 is satisfied.

Description

TECHNICAL FIELD

[0001] The utility model relates to a honeycomb structure. BACKGROUND

[0002] In the exhaust gas discharged from an internal combustion engine such as a diesel engine, a large amount of particulate matter (PM) such as soot mainly composed of carbon, which is a cause of environmental pollution, and soot (ashes) generated as a result of combustion residue of calcium (Ca) or the like. This particulate matter is confirmed to have carcinogenicity, and therefore must be prevented from being released into the atmosphere. Now, in addition to the conventional weight-based quantity restriction centered on Europe, a strict restriction on the number of PM is imposed. Therefore, a filter (Diesel Particulate Filter: DPF) for trapping particulates is generally mounted in the exhaust system of a diesel engine or the like. In recent years, particulates discharged from gasoline engines are also considered to be a problem, and filters (Gasoline Particulate Filter: GPF) are also mounted in gasoline engines.

[0003] As a filter, a wall flow type filter designed in such a manner that exhaust gas passes through a porous partition wall is effective. Specifically, the wall flow type filter has a plurality of inlet cells and a plurality of outlet cells adjacent to each other with a porous partition wall therebetween, and can be composed of a honeycomb structure that traps PM during passage of exhaust gas through the partition wall. A catalyst corresponding to the purpose can also be supported on the surface of the partition wall.

[0004] For the wall flow type filter composed of a honeycomb structure, various characteristics such as excellent PM trapping performance, low pressure loss, excellent catalytic performance at the time of catalyst support, less likelihood of soot clogging, and excellent mechanical strength are required.

[0005] In Japanese Patent Application Publication No. 2023-147536 (Patent Literature 1), it is described that by controlling the cross-sectional shape of the inflow cell, the ratio of the cross-sectional area of the outflow cell to the cross-sectional area of the inflow cell, the thickness of the partition wall, the cell density, the shape of the plugged portion, the porosity of the partition wall, and the like within predetermined ranges, a honeycomb filter can be obtained that has low pressure loss, excellent erosion resistance of the plugged portion, and further excellent thermal shock resistance.

[0006] In Japanese Patent No. 7353217 (Patent Literature 2), it is described that by controlling the porosity of the partition wall, the average fine pore diameter of the partition wall, the fine pore diameter distribution of the partition wall, the thickness of the partition wall, and the like within predetermined ranges, a honeycomb filter can be obtained that has excellent trapping performance and can reduce pressure loss.

[0007] PRIOR ART DOCUMENTS

[0008] PATENT LITERATURE

[0009] Patent Document 1: Japanese Patent Application Publication No. 2023-147536

[0010] Patent Document 2: Japanese Patent No. 7353217 Utility Model Content

[0011] The problem to be solved by the utility model

[0012] However, conventional honeycomb structures cannot fully satisfy the requirements of excellent PM capture performance, low pressure loss, excellent catalytic performance when the catalyst is supported, resistance to soot clogging, and excellent mechanical strength. While Patent Document 1 describes a honeycomb filter with excellent corrosion resistance and thermal shock resistance in the sealing section, there is still room for improvement in catalyst coating properties. Patent Document 2 describes a honeycomb filter that achieves excellent capture performance and reduced pressure loss by controlling the porosity, average pore size, pore size distribution, and thickness of the partition walls within predetermined ranges; however, there is still room for improvement in catalyst coating properties.

[0013] This invention was made in view of the above circumstances. In one embodiment, the objective is to provide a honeycomb structure that satisfies all the requirements of excellent PM capture performance, low pressure loss, excellent catalyst coating properties when catalyst is supported, resistance to soot clogging, and excellent mechanical strength.

[0014] Solution for solving the problem

[0015] In order to solve the above-mentioned problems, the inventors of this utility model have conducted in-depth research and completed the following example of this utility model.

[0016] [Option 1]

[0017] A honeycomb structure, a columnar honeycomb structure, comprising: an outer peripheral sidewall; a plurality of inlet chambers disposed on the inner peripheral side of the outer peripheral sidewall, extending from an inlet end face to an outlet end face, having an opening at the inlet end face and a sealing portion at the outlet end face; and a plurality of outlet chambers disposed on the inner peripheral side of the outer peripheral sidewall, extending from an inlet end face to an outlet end face, having a sealing portion at the inlet end face and an opening at the outlet end face, and being adjacent to at least one of the plurality of inlet chambers through a partition wall, characterized in that...

[0018] The opening area C of each of the multiple inlet compartments in The opening area C of each of the plurality of discharge compartments out The ratio satisfies 1 <C in / C out ≤2.5,

[0019] The thickness WT of the partition wall is 0.18 to 0.25 mm,

[0020] The cell density CD based on the total number of the plurality of introduction cells and the plurality of discharge cells is 49 to 70 cells / cm 2 ,

[0021] The depth PD of the hole sealing portion is 4 to 7 mm,

[0022] In a cross section of the honeycomb structure perpendicular to the direction in which the plurality of introduction cells and the plurality of discharge cells extend, the distance OF between the midpoint of the segment linking the centers of gravity of the introduction cell and the discharge cell adjacent across the partition wall to each other and the center of the partition wall across which the segment passes is 0.075 to 0.110 mm,

[0023] 2 ≤ OF x CD / (WT x PD) ≤ 7 is satisfied.

[0024] [Solution 2]

[0025] The honeycomb structure according to Solution 1, characterized in that

[0026] The porosity of the partition wall is 52 to 61%.

[0027] [Solution 3]

[0028] The honeycomb structure according to Solution 1 or 2, characterized in that

[0029] The average fine pore diameter of the partition wall is 6 to 10 μm.

[0030] [Solution 4]

[0031] The honeycomb structure according to Solution 1 or 2, characterized in that

[0032] The opening shape of each of the plurality of introduction cells is hexagonal or octagonal except for the introduction cell adjacent to the outer peripheral wall.

[0033] [Solution 5]

[0034] The honeycomb structure according to Solution 1 or 2, characterized in that

[0035] The partition wall contains one selected from the group consisting of cordierite, silicon carbide, silicon-silicon carbide composite, silicon nitride, mullite, alumina, and aluminum titanate.

[0036] [Solution 6]

[0037] The honeycomb structure according to Solution 1 or 2, characterized in that

[0038] A catalyst is supported on the partition wall.

[0039] Practical effects

[0040] The honeycomb structure according to one embodiment of the present application satisfies all of excellent PM trapping performance, low pressure loss, excellent catalyst coating property at the time of catalyst support, less occurrence of soot clogging, and excellent mechanical strength. Therefore, according to one embodiment of the present application, it can be said that a honeycomb structure extremely excellent in practicality can be provided, which is suitable for use as a filter for exhaust gas discharged from an internal combustion engine such as a diesel engine. BRIEF DESCRIPTION OF DRAWINGS

[0041] Figure 1 is a perspective view schematically showing a wall flow type honeycomb structure.

[0042] Figure 2 is a schematic cross-sectional view when a wall flow type honeycomb structure is observed from a cross section parallel to the direction in which the cells extend.

[0043] Figure 3 is a schematic enlarged partial view when a partition wall of a honeycomb structure is observed from a cross section orthogonal to the direction in which the cells extend.

[0044] Figure 4 is an explanatory view schematically showing an example of a method of forming a plugging portion based on a scraper method. DETAILED DESCRIPTION

[0045] Next, embodiments of the present application will be described in detail with reference to the drawings. It should be understood that the present application is not limited to the following embodiments, and that design changes, improvements, and the like are appropriately made based on general knowledge of those skilled in the art without departing from the spirit of the present application.

[0046] (1. Honeycomb structure)

[0047] In Figure 1 and Figure 2 , schematic perspective views and cross-sectional views of a columnar honeycomb structure 100 that can be applied as a wall flow type exhaust gas filter for an automobile are respectively illustrated. The honeycomb structure 100 has an outer peripheral side wall 102, a plurality of inlet cells 108 disposed on the inner peripheral side of the outer peripheral side wall 102, extending parallel to an inlet end surface 104 to an outlet end surface 106, having an opening portion 107 at the inlet end surface 104, and having a plugging portion 109 at the outlet end surface 106, and a plurality of outlet cells 110 disposed on the inner peripheral side of the outer peripheral side wall 102, extending parallel to the inlet end surface 104 to the outlet end surface 106, having the plugging portion 109 at the inlet end surface 104, and having the opening portion 107 at the outlet end surface 106, adjacent to at least any one of the plurality of inlet cells across a partition wall 112.

[0048] For example, if the exhaust gas containing particulate matter such as soot is supplied to the inlet end surface 104 on the upstream side of the honeycomb structure 100, the exhaust gas is introduced into the introduction cells 108 and advances within the introduction cells 108 toward the downstream. The outlet end surface 106 on the downstream side of the introduction cells 108 is plugged, and thus the exhaust gas flows into the discharge cells 110 through the partition walls between the adjacent introduction cells 108 and discharge cells 110. The particulate matter cannot pass through the partition walls, and thus is trapped and accumulated within the introduction cells 108. After the particulate matter is removed, the clean exhaust gas flowing into the discharge cells 110 advances within the discharge cells 110 toward the downstream, and flows out from the outlet end surface 106 on the downstream side.

[0049] The honeycomb structure 100 satisfies the following conditions (1) to (6). Thereby, all of the excellent PM trapping performance, low pressure loss, excellent catalyst coating property at the time of catalyst support, less occurrence of soot clogging, and excellent mechanical strength can be satisfied.

[0050] (1) The ratio (C in / C out ) of the opening area (C in ) of each of the plurality of introduction cells 108 to the opening area (C out ) of each of the plurality of discharge cells 110;

[0051] (2) The thickness (WT) (unit: mm) of the partition wall 112;

[0052] (3) The cell density (CD) (unit: pieces / cm 2 ) based on the total number of the plurality of introduction cells 108 and the plurality of discharge cells 110;

[0053] (4) The depth (PD) (unit: mm) of the plugged portion 109;

[0054] (5) In the cross section of the honeycomb structure 100 perpendicular to the direction in which the plurality of introduction cells 108 and the plurality of discharge cells 110 extend, the distance (OF) (hereinafter, also referred to as "offset") (unit: mm) from the midpoint M of the line segment connecting the centers of gravity O of the introduction cells 108 and the discharge cells 110 adjacent to each other with the partition wall 112 sandwiched therebetween to the center C of the partition wall 112 intersected by the line segment;

[0055] (6) OF x CD / (WT x PD).

[0056] (1) C in / C out

[0057] The opening area (C in) to the opening area (C out ) of each of the plurality of discharge cells 110 in out ) is preferably 1 < C in out ≤ 2.5, more preferably 1.5 ≤ C in out ≤ 2.5, and further preferably 1.5 ≤ C in out ≤ 2.2.

[0058] The opening area (C in ) of each of the plurality of intake cells 108 is defined as the average of the opening areas of the intake cells as a whole excluding the cells adjacent to the peripheral side wall 102.

[0059] The opening area (C out ) of each of the plurality of discharge cells 110 is defined as the average of the opening areas of the discharge cells as a whole excluding the cells adjacent to the peripheral side wall 102.

[0060] The opening area (C in ) of each of the plurality of intake cells 108 is preferably, for example, 0.70 to 1.10 mm 2 , more preferably 0.70 to 1.00 mm 2 , and further preferably 0.75 to 0.90 mm 2 .

[0061] (2) WT

[0062] The thickness (WT) of the partition wall 112 is preferably 0.18 to 0.25 mm, more preferably 0.18 to 0.24 mm, and further preferably 0.18 to 0.23 mm. The thickness (WT) of the partition wall 112 refers to the average of the thicknesses (WT) of all the partition walls 112. Figure 3 A schematic partial enlarged view of the partition wall 112 of the honeycomb structure 100 in which the opening shape of the intake cell 108 is octagonal and the opening shape of the discharge cell 110 is quadrangular, as viewed in a cross section orthogonal to the direction in which the cells extend, is shown in FIG. 2. The thickness (WT) of the partition wall 112 refers to the length D of the line segment that, in a cross section orthogonal to the direction in which the cells extend (the height direction of the honeycomb structure 100), connects the centers of gravity O of the adjacent cells to each other, when the centers of gravity O of the adjacent cells are connected to each other by a line segment.

[0063] Further, two cells adjacent with a partition wall therebetween refers to, when the partition wall of the honeycomb structure is viewed in a cross section orthogonal to the direction in which the cells extend, the two cells being adjacent with the opposing walls (the sides of the polygon that divides the cells) of one partition wall therebetween, and does not include the case in which the two cells are adjacent with the vertices of the polygon that divides the two cells therebetween.​​​​

[0064] (3) CD

[0065] The cell density (CD) based on the total number of the plurality of introduction cells 108 and the plurality of discharge cells 110 is preferably 49 to 70 pieces / cm 2 , more preferably 49 to 68 pieces / cm 2 , further preferably 50 to 66 pieces / cm 2 . The cell density indicates the total number of cells (including the cells with the plugged holes, the discharge cells 110 adjacent to the outer peripheral wall 102, and the introduction cells 108 adjacent to the outer peripheral wall 102) divided by the area of one end surface of the honeycomb structure excluding the outer peripheral wall.

[0066] (4) PD

[0067] The depth of the plugged hole portion 109 (PD) is preferably 4 to 7 mm, more preferably 4 to 6.5 mm, further preferably 5 to 6.5 mm. The depth of the plugged hole portion 109 (PD) indicates the average value of the depths (PD) of all the plugged hole portions 109. The depth (PD) of each plugged hole portion 109 is measured by cutting the cross section of the plugged hole portion with a cutting plane parallel to the height direction (the direction in which the cells extend) of the honeycomb structure. In the cross section, the length in the direction in which the cells extend from the position of the inlet end surface or the outlet end surface at which the plugged hole portion is formed to the deepest position at which the plugged hole portion exists is measured as the depth of the plugged hole portion 109.

[0068] (5) OF (offset)

[0069] Referring to Figure 3 , in the cross section of the honeycomb structure 100 perpendicular to the direction in which the plurality of introduction cells 108 and the plurality of discharge cells 110 extend, the distance between the midpoint M of the line segment connecting the centers of gravity O of the introduction cells 108 and the discharge cells 110 adjacent to each other with the cell wall 112 interposed therebetween and the center C of the cell wall 112 across which the line segment passes is referred to as OF (offset). The OF is preferably 0.075 to 0.110 mm, more preferably 0.075 to 0.105 mm, further preferably 0.080 to 0.105 mm. The OF indicates the average value of all the OFs that can be calculated.

[0070] (6) OF x CD / (WT x PD)

[0071] The thickness (WT) of the partition wall 112, the cell density (CD), the depth (PD) of the plugged portion 109, and the OF (offset) preferably satisfy a condition prescribed by OF x CD / (WT x PD) in addition to the conditions described above being satisfied individually. Specifically, it is preferable to satisfy 2 ≤ OF x CD / (WT x PD) ≤ 7, more preferably 2.2 ≤ OF x CD / (WT x PD) ≤ 6.9, further preferably 2.4 ≤ OF x CD / (WT x PD) ≤ 6.9, further more preferably 3.0 ≤ OF x CD / (WT x PD) ≤ 6.9, further more preferably 4.0 ≤ OF x CD / (WT x PD) ≤ 6.5, and further more preferably 5.0 ≤ OF x CD / (WT x PD) ≤ 6.0.

[0072] From the viewpoint of further reducing the pressure loss, the lower limit of the porosity of the partition wall 112 is preferably 52% or more, and more preferably 53% or more. In addition, from the viewpoint of further improving the mechanical strength of the honeycomb structure, the upper limit of the porosity of the partition wall is preferably 61% or less, and more preferably 60% or less. Therefore, for example, the average porosity of the partition wall is preferably 52 to 61%, and more preferably 53 to 60%. In the present specification, the porosity is measured by the mercury intrusion method prescribed by JIS R1655:2003 (Japanese Industrial Standards). In addition, with respect to the porosity, the average value when the porosities of samples (0.3 g each) of the partition wall collected from six sites of the honeycomb structure without bias are found is taken as the measurement value.

[0073] From the viewpoint of further improving the collection efficiency of the particulate matter, the average pore diameter of the partition wall 112 is preferably 10 μm or less, and more preferably 9 μm or less. In addition, from the viewpoint of further reducing the pressure loss, the average pore diameter of the partition wall 112 is preferably 6 μm or more, and more preferably 7 μm or more. Therefore, the average pore diameter of the partition wall 112 is, for example, preferably 6 to 10 μm, and more preferably 7 to 9 μm. The average pore diameter of the partition wall is measured by the mercury intrusion method according to JIS R1655:2003. Test pieces of 20 partition walls are collected uniformly from the center portion and the outer peripheral portion of the honeycomb structure including the columnar shape, the average pore diameters thereof are measured, and the average value thereof is taken as the average pore diameter of the entire honeycomb structure of the columnar shape.

[0074] The shape of the opening of the introduction cell 108 is not particularly limited. For example, in a cross section of the honeycomb structure 100 orthogonal to the direction in which the cells extend, it can be provided as a polygonal shape (quadrilateral (rectangular, square), pentagonal, hexagonal, heptagonal, octagonal, etc.), a circular shape (circular, elliptical, oblong, oval, obround, etc.), or the like. These shapes can be single, or two or more can be combined. Among them, based on the reason of reduction in pressure loss, the shape of the opening of each of the plurality of introduction cells 108 is preferably all hexagonal or octagonal, and more preferably octagonal, except for the cells adjacent to the peripheral side wall 102. In the case where the shape of the opening of the introduction cell 108 and the shape of the opening of the discharge cell 110 are polygonal, the corners can be R-chamfered. In the present specification, even if R-chamfering is performed, it is treated as a polygonal shape.

[0075] The shape of the opening of the discharge cell 110 is also not particularly limited, and can be set in accordance with the shape of the opening of the introduction cell 108. For example, in the case where the shape of the opening of the introduction cell 108 is octagonal, it is preferably quadrangular.

[0076] The shape of the end face of the honeycomb structure 100 is not limited, and can be, for example, a circular shape such as a circular shape, an elliptical shape, a racetrack shape, and an obround shape, a polygonal shape such as a triangular shape and a quadrilateral shape, and other special shapes. The shape of the end face of the illustrated honeycomb structure 100 is circular, and the entire shape is cylindrical.

[0077] The height of the honeycomb structure (length from the inlet end face to the outlet end face) is not particularly limited, and can be appropriately set in accordance with the use and required performance. The height of the honeycomb structure can be, for example, 40 to 450 mm, preferably 60 to 400 mm, and more preferably 100 to 330 mm. The relationship between the height of the honeycomb structure and the maximum diameter of each end face (the maximum length among the diameters passing through the centers of gravity of each end face of the honeycomb structure) is also not particularly limited. Therefore, the height of the honeycomb structure can be longer than the maximum diameter of each end face, and the height of the honeycomb structure can also be shorter than the maximum diameter of each end face.

[0078] From the viewpoint of obtaining excellent thermal shock resistance, at least the partition wall of the honeycomb structure, preferably the peripheral side wall and the partition wall, and more preferably the peripheral side wall, the partition wall, and the plugged portion, contain one or two or more selected from the group consisting of cordierite, silicon carbide, silicon-silicon carbide composite, silicon nitride, mullite, alumina, and aluminum titanate.

[0079] The peripheral side wall, the partition wall, and the plugged portion of the honeycomb structure can also contain ceramics other than the above. As the other ceramics, for example, zirconium phosphate, cordierite-silicon carbide composite, zirconia, spinel, indialite, sapphirine, corundum, titanium dioxide, cerium oxide, and the like can be given. Furthermore, these other ceramics can contain one alone, or two or more.

[0080] The honeycomb structure can also be used as a catalyst carrier. A catalyst corresponding to the purpose can be supported on the surface of the partition wall. As the catalyst, there are no limitations, and examples include an oxidation catalyst (DOC) for oxidatively combusting hydrocarbons (HC) and carbon monoxide (CO) to increase the temperature of exhaust gas, a PM combustion catalyst for assisting the combustion of PM such as soot, an SCR catalyst and an NSR catalyst for removing nitrogen oxides (NOx), and a three-way catalyst capable of simultaneously removing hydrocarbons (HC), carbon monoxide (CO), and nitrogen oxides (NOx). The catalyst can appropriately contain, for example, noble metals (Pt, Pd, Rh, etc.), alkali metals (Li, Na, K, Cs, etc.), alkaline earth metals (Mg, Ca, Ba, Sr, etc.), rare earths (Ce, Sm, Gd, Nd, Y, La, Pr, etc.), transition metals (Mn, Fe, Co, Ni, Cu, Zn, Sc, Ti, Zr, V, Cr, etc.), and the like.

[0081] The honeycomb structure can be a honeycomb joined body having a plurality of honeycomb sheets and a joining layer joining the outer peripheral surfaces of the plurality of honeycomb sheets to each other. By using the honeycomb joined body, it is possible to increase the total cross-sectional area of the cells important for securing the flow rate of air while suppressing the generation of cracks. The joining layer can be formed using a joining material. As the joining material, there are no particular limitations, and a material made into a paste shape by adding a solvent such as water to a ceramic material can be used. The joining material can also contain the same material as the partition wall. The joining material can be used not only as a material for joining the honeycomb sheets to each other but also as an outer peripheral coating material after the honeycomb sheets are joined.

[0082] (2. Manufacturing method)

[0083] Hereinafter, a manufacturing method of a columnar honeycomb structure according to an embodiment of the present application will be described by way of example. First, a raw material composition containing cordierite-forming raw materials, a pore-forming material, a dispersing medium, and a binder is kneaded to form a clay, and the clay is extrusion-molded, whereby a columnar honeycomb formed body having an outer peripheral wall and a plurality of cells is obtained. The plurality of cells are arranged on the inner peripheral side of the outer peripheral wall, extend from an inlet end surface to an outlet end surface, and the inlet end surface and the outlet end surface each have an opening portion. Additives such as a dispersant, other ceramic raw materials, and the like can be added to the raw material composition as needed. At the time of extrusion molding, a mold having a desired overall shape, cell shape, cell arrangement, partition wall thickness, cell density, and the like can be used.

[0084] The so-called cordierite-forming raw material is a raw material that becomes cordierite by calcination, and is, for example, provided in the form of a powder. The cordierite-forming raw material preferably has a chemical composition of 30 to 45 mass% of alumina (AI2O3) (including a component of aluminum hydroxide converted into alumina), 11 to 17 mass% of magnesia (MgO), and 42 to 57 mass% of silica (SiO2).

[0085] As the dispersion medium, water, or a mixed solvent of water and an organic solvent such as alcohol, and the like can be given, and water is particularly preferable.

[0086] The content of the dispersion medium of the honeycomb-shaped body before the drying step is preferably 20 to 110 parts by weight, more preferably 25 to 100 parts by weight, and further preferably 30 to 90 parts by weight, with respect to 100 parts by weight of the cordierite-forming raw material. By making the content of the dispersion medium of the honeycomb-shaped body 20 parts by weight or more with respect to 100 parts by weight of the cordierite-forming raw material, the quality of the honeycomb structure is easily stabilized. By making the content of the dispersion medium of the honeycomb-shaped body 110 parts by weight or less with respect to 100 parts by weight of the cordierite-forming raw material, the shrinkage amount at the time of drying is small, and deformation can be suppressed. In the present specification, the content of the dispersion medium of the honeycomb-shaped body refers to a value measured by the drying loss method.

[0087] As the pore-forming material, there is no particular limitation as long as it is a material that becomes a pore after calcination, and, for example, wheat flour, starch, foamed resin, water-absorbing resin, silica gel, carbon (for example, graphite), ceramic ball, polyethylene, polystyrene, polypropylene, nylon, polyester, acrylic resin, phenol, and the like can be given. The pore-forming material can be used alone or in combination with two or more. From the viewpoint of improving the porosity of the honeycomb structure after calcination, the content of the pore-forming material is preferably 1 part by weight or more, more preferably 6 parts by weight or more, and further preferably 9 parts by weight or more, with respect to 100 parts by weight of the cordierite-forming raw material. From the viewpoint of ensuring the strength of the honeycomb structure after calcination, the content of the pore-forming material is preferably 30 parts by weight or less, more preferably 27 parts by weight or less, and further preferably 24 parts by weight or less, with respect to 100 parts by weight of the cordierite-forming raw material.

[0088] As the binder, organic binders such as methylcellulose, hydroxypropoxymethylcellulose, hydroxypropylmethylcellulose, hydroxyethylcellulose, hydroxyethylmethylcellulose, carboxymethylcellulose, and polyvinyl alcohol can be exemplified. In view of improving the strength of the honeycomb-shaped body before calcination, the content of the binder is preferably 4 parts by weight or more, more preferably 4.5 parts by weight or more, and further preferably 5 parts by weight or more, relative to 100 parts by weight of the cordieritizing raw material. In view of suppressing the occurrence of cracking due to abnormal heat generation in the calcination step, the content of the binder is preferably 9 parts by weight or less, more preferably 8 parts by weight or less, and further preferably 7 parts by weight or less, relative to 100 parts by weight of the cordieritizing raw material. The binder can be used alone or in combination with two or more kinds.

[0089] As the dispersant, ethylene glycol, dextrin, fatty acid soap, polyether polyol, and the like can be used. The dispersant can be used alone or in combination with two or more kinds. The content of the dispersant is preferably 0 to 2 parts by weight relative to 100 parts by weight of the cordieritizing raw material.

[0090] The drying of the honeycomb-shaped body can be performed by, for example, a publicly known drying method such as hot air drying, microwave drying, dielectric drying, reduced pressure drying, vacuum drying, and freeze drying. Among them, a drying method in which hot air drying is combined with microwave drying or dielectric drying is preferable in terms of being able to rapidly and uniformly dry the entire honeycomb-shaped body.

[0091] After the honeycomb-shaped body is dried, a plugging portion is formed on both end surfaces of the honeycomb-shaped body. Each plugging portion can be formed by filling a slurry for plugging portion formation into an opening portion of the inlet cell and the outlet cell, which should be plugged, and then drying and calcining the filled slurry. The slurry for plugging portion formation can use the same material as the honeycomb-shaped body. Although not limited, for example, in the case where the honeycomb-shaped body contains the cordieritizing raw material, the pore-forming material, the dispersing medium, and the binder, the slurry for plugging portion formation can contain the cordieritizing raw material, the pore-forming material, the dispersing medium, and the binder.

[0092] Exemplarily, the slurry for plugging portion formation contains the dispersing medium at 30 to 60 parts by weight, the pore-forming material at 5 to 20 parts by weight, and the binder at 0.2 to 2.0 parts by weight, relative to 100 parts by weight of the cordieritizing raw material. In the preferable embodiment, the slurry for plugging portion formation contains the dispersing medium at 35 to 50 parts by weight, the pore-forming material at 8 to 16 parts by weight, and the binder at 0.2 to 1.5 parts by weight, relative to 100 parts by weight of the cordieritizing raw material.

[0093] As the dispersing medium, water, or a mixed solvent of water and an organic solvent such as alcohol, and the like can be given, and water is particularly preferable.

[0094] As a pore-forming material, there are no particular limitations as long as the material becomes porous after calcination. Examples include wheat flour, starch, foaming resin, water-absorbing resin, silica gel, carbon (e.g., graphite), ceramic balls, polyethylene, polystyrene, polypropylene, nylon, polyester, acrylic resin, phenol, etc. A single pore-forming material can be used, or two or more can be used in combination.

[0095] Examples of adhesives include organic adhesives such as methylcellulose, hydroxypropoxymethylcellulose, hydroxypropylmethylcellulose, hydroxyethylcellulose, hydroxyethylmethylcellulose, carboxymethylcellulose, and polyvinyl alcohol. An adhesive can be used alone or in combination with two or more other types.

[0096] The slurry used to form the sealing portion may contain a dispersant. Examples of dispersants include ethylene glycol, dextrin, fatty acid soaps, and polyols. A single dispersant may be used, or two or more may be used in combination.

[0097] The filling of the opening of the compartment with slurry to form the sealing section can be achieved, for example, by the following "scraper method". Figure 4 As shown, a membrane 121 is attached to the upper end face (exit end face 106 in the figure) of the dried honeycomb molded body 400 fixed by a chuck 120. A laser is irradiated at the position of the membrane 121 corresponding to the arrangement conditions of the sealing part, and multiple holes 126 are made in the membrane 121.

[0098] Then, a slurry 124 for forming the sealing portion is placed on the membrane 121, and the scraper 122 is moved along the membrane 121 towards... Figure 4 The operation moves in the direction of the arrow in the image. As a result, a constant amount of sealing slurry 124 is filled into the compartment 125, which opens at the position corresponding to the hole 126 in the membrane 121.

[0099] The depth of the sealing section can vary depending on the number of times the scraper 122 moves, the contact angle between the scraper 122 and the membrane 121, the pressing pressure of the scraper 122 on the membrane 121, and the viscosity of the slurry 124 used to form the sealing section.

[0100] After filling the sealing portion forming slurry 124, the membrane 121 is peeled off, and the honeycomb molded body 400 is dried as a whole. Thus, the sealing portion forming slurry 124 filled in the compartment 125 is dried, forming the sealing portion before calcination. Drying can be carried out at a drying temperature of, for example, 100~230°C, for approximately 60~150 seconds. After drying, the sealing portion protrudes from the end face of the honeycomb molded body by an amount corresponding to the thickness of the membrane; therefore, it is trimmed off as needed.

[0101] The material of the film is not particularly limited, but in order to easily perform heat processing for forming the holes, polypropylene (PP), polyethylene terephthalate (PET), polyimide, or Teflon (registered trademark) is preferred. In addition, the film preferably has an adhesive layer, and the material of the adhesive layer is preferably an acrylic resin, a rubber-based (for example, rubber in which natural rubber or synthetic rubber is the main component), or a silicone-based resin. An adhesive film having a thickness of 20 to 50 μm can be appropriately used, for example.

[0102] In addition to the above-described "squeegee method", as a method of filling the opening of the cell with the seal portion forming slurry, a "press-in method" can be given. The "press-in method" is a method in which the film is adhered, the end face of the honeycomb-shaped body in which the hole is provided is dipped in a tank in which the seal portion forming slurry is stored, and the seal portion forming slurry is filled into the cell. In this case, the depth of the seal portion can be changed depending on the depth at which the honeycomb-shaped body is dipped in the seal portion forming slurry.

[0103] The honeycomb-shaped body filled with the seal portion forming slurry is then subjected to a debinding process and a calcination process, thereby manufacturing a honeycomb structure. 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 debinding process can be performed by heating the honeycomb-shaped body to a range of about 200 to 1000°C. The heating time is not particularly limited, and is usually about 10 to 100 hours. The honeycomb-shaped body after the debinding process is referred to as a pre-fired body. The calcination process also depends on the material composition of the honeycomb structure, and can be performed by heating the pre-fired body to about 1300 to 1450°C and maintaining it for about 3 to 24 hours, for example.

[0104] The catalyst can be supported on the cell walls of the honeycomb structure thus manufactured. As a method of supporting the catalyst on the cell walls, exemplarily, a method can be given in which the catalyst slurry is introduced into the cell by a conventionally known suction method or the like, is allowed to adhere to the surface and pores of the cell walls, and then high-temperature treatment is performed to sinter and support the catalyst contained in the catalyst slurry on the cell walls. The type of the catalyst is as described above.

[0105] [Examples]

[0106] Hereinafter, examples for better understanding the present application and advantages thereof will be illustrated, but the present application is not limited to the examples.

[0107] (1. Manufacture of honeycomb structure)

[0108] [Manufacture of cordierite honeycomb structure: Comparative Examples 1 to 7 and Examples 1 to 5]

[0109] A clay blank was prepared by adding 2 parts by weight of a pore-forming material, 20 parts by weight of a dispersion medium, and 7 parts by weight of an organic binder to 100 parts by weight of cordierite-forming raw material, and mixing and kneading them. As the cordierite-forming raw material, alumina, aluminum hydroxide, kaolin, talc, and silica were used. As the dispersion medium, water was used. As the organic binder, methyl cellulose was used. As the pore-forming material, a water-absorbing resin having a median particle diameter of 20 μm was used. In this example, the median particle diameter of the raw material refers to the particle diameter (D50) at which the cumulative value in the particle size distribution obtained by the laser diffraction scattering method is 50%.

[0110] Next, the clay blank was extrusion-molded using a mold for forming a honeycomb molded body, and a honeycomb molded body having a cylindrical shape as a whole was obtained. The structure of the mold was changed depending on the test number.

[0111] Next, the honeycomb molded body was dried using a microwave dryer, and further dried using a hot air dryer, and then both end surfaces of the honeycomb molded body were cut and adjusted to predetermined sizes.

[0112] Next, a slurry for forming a plugging portion was prepared using the same material as the honeycomb molded body. Then, using the slurry, the plugging portion was formed at the opening of the predetermined cells on the inlet end surface side of the dried honeycomb molded body and at the openings of the remaining cells on the outlet end surface side, so that the inlet cells and the outlet cells were alternately adjacent to each other.

[0113] Next, the honeycomb molded body on which the plugging portions were formed was subjected to debinding and calcination, and a honeycomb structure body relating to each test number was manufactured. The shapes of the inlet end surface and the outlet end surface of the honeycomb structure body thus obtained were circular cylindrical shapes. The diameters of the inlet end surface and the outlet end surface were 330 mm. In addition, the length of the direction in which the cells of the honeycomb structure body extended was 254 mm. The number of honeycomb structure bodies required to determine the following properties was prepared for each test number.

[0114] (2. Structure properties of the honeycomb structure body)

[0115] For each of the honeycomb structure bodies relating to the test numbers manufactured as described above, the following structure properties were shown in Table 1.

[0116] • Thickness of the partition wall (WT)

[0117] • Cell density (CD) based on the total number of the plurality of inlet cells and the plurality of outlet cells

[0118] • Ratio of the opening area of the plurality of inlet cells (C in ) to the opening area of the plurality of outlet cells (C out ) (C in / C out )

[0119] • Opening area of each of the plurality of introduction cells (C in )

[0120] • Offset (OF)

[0121] • Depth of the sealing portion (PD)

[0122] • OF x CD / (WT x PD)

[0123] • Porosity of the partition wall

[0124] • Average pore diameter of the partition wall

[0125] • Opening shape of the introduction cell

[0126] • Opening shape of the discharge cell

[0127] The thickness (WT) of the partition wall is measured by scanning electron microscope (SEM) observation or microscope.

[0128] The cell density (CD) is the cell density based on the total number of the introduction cells and the discharge cells, and is measured according to the above method.

[0129] C in / C out and C in are calculated using scanning electron microscope (SEM) observation or microscope.

[0130] The offset (OF) is measured by scanning electron microscope (SEM) observation or microscope.

[0131] The depth of the sealing portion (PD) is measured by scanning electron microscope (SEM) observation or microscope.

[0132] The porosity and the average pore diameter of the partition wall are measured according to the aforementioned mercury intrusion method using Autopore 9500 (trade name) manufactured by Micromeritics Corporation.

[0133] The opening shape of the introduction cell and the opening shape of the discharge cell are determined by scanning electron microscope (SEM) observation or microscope.

[0134] [Table 1]

[0135]

[0136] (3. Filter performance)

[0137] Using the honeycomb structures of each of the test numbers prepared above as filters, the filter performance described below was evaluated.

[0138] [Capturing performance]

[0139] First, the honeycomb filters of each of the examples and the comparative example were packed in a metal case as exhaust gas purification filters, whereby an exhaust gas purification device was produced. Next, the produced exhaust gas purification device was connected to the outlet side of the exhaust manifold of a 6.7L diesel engine, and the number of soot contained in the gas discharged from the outlet of the exhaust gas purification device was measured by the PN measurement method. In the number of soot determination, the cumulative number of soot discharged after the WHTC (World Harmonized Transient Cycle) mode was run was taken as the number of soot of the exhaust gas purification device to be determined, and the ratio (%) of the number of soot of each honeycomb filter was calculated in the case where the number of soot of the exhaust gas purification device using the honeycomb filter of Comparative Example 1 was taken as 100%, and the evaluation of the honeycomb filters of each of the examples and the comparative example was performed based on the following evaluation criteria. The results are shown in Table 2.

[0140] Evaluation "Good": the case where the value of the ratio (%) of the number of soot was more than 80% and was 90% or less

[0141] Evaluation "Good": the case where the value of the ratio (%) of the number of soot was more than 80% and was 90% or less

[0142] Evaluation "Good": the case where the value of the ratio (%) of the number of soot was more than 80% and was 90% or less

[0143] Evaluation "Good": the case where the value of the ratio (%) of the number of soot was more than 80% and was 90% or less

[0144] [Pressure loss]

[0145] The exhaust gas discharged from a 6.7L diesel engine was made to flow into the filters of each of the examples and the comparative example, and soot in the exhaust gas was captured in the filters. The capturing of soot was performed until the amount of accumulation of soot per unit volume (1L) of the filter became 5g / L. Then, while the amount of accumulation of soot was 5g / L, engine exhaust gas at 200°C was made to flow at a flow rate of 12m 3 / min, and the pressures of the inlet end surface side and the outlet end surface side of the filter were measured. Then, by calculating the pressure difference between the inlet end surface side and the outlet end surface side, the pressure loss (kPa) of the filter was found. The value of the pressure loss of the filter of Comparative Example 1 was taken as 100%, the ratio (%) of the pressure loss of the filter of each of the examples and the comparative example was calculated, and the evaluation of the pressure loss of the filter was performed based on the following evaluation criteria. The results are shown in Table 2.

[0146] Evaluation "Good": the case where the value of the ratio (%) of pressure loss exceeds 70% and is 75% or less

[0147] Evaluation "Good": the case where the value of the ratio (%) of pressure loss exceeds 70% and is 75% or less

[0148] Evaluation "Good": the case where the value of the ratio (%) of pressure loss exceeds 70% and is 75% or less

[0149] Evaluation "Good": the case where the value of the ratio (%) of pressure loss exceeds 70% and is 75% or less

[0150] [Catalyst coating property]

[0151] First, an oxidation catalyst was supported on the cell walls of a honeycomb filter. The supported amount of the catalyst was 10 g / L. Next, 3 g / L of soot was stacked in the honeycomb filter in which the catalyst was supported as described above. In this state, another honeycomb structure (catalyst support) in which an oxidation catalyst was supported was provided in the front stage of the honeycomb filter. Then, high-temperature exhaust gas was made to flow from the upstream side of the honeycomb structure of the front stage, and the exhaust gas that passed through the honeycomb structure of the front stage was made to pass through the inlet end surface of the honeycomb filter, and continuous regeneration of the filter was performed. The exhaust gas was discharged from a 6.7 L diesel engine. The conditions of the regeneration were that the gas temperature of the inlet end surface was set to 350°C, and the gas passage time was set to 60 minutes. Then, the honeycomb filter was removed from the device in which the continuous regeneration was performed, and the amount of soot remaining in the honeycomb filter was measured. The percentage (%) of the ratio obtained by dividing the mass of soot reduced by the continuous regeneration by the mass of soot initially stacked was calculated as the regeneration efficiency (%) at the time of the continuous regeneration. The value of the regeneration efficiency of the filter of Comparative Example 1 was set to 100%, the ratio (%) of the regeneration efficiency of the filter of each of the examples and the comparative examples was calculated, and the catalyst evaluation of the filter was performed based on the following evaluation criteria. The higher the catalyst coating property, the more uniformly the catalyst can be coated in the filter, and thus it is considered that the regeneration efficiency is improved. The results are shown in Table 2.

[0152] Evaluation "Good": the case where the value of the ratio (%) of pressure loss exceeds 70% and is 75% or less

[0153] Evaluation "Good": the case where the value of the ratio (%) of pressure loss exceeds 70% and is 75% or less

[0154] Evaluation "Good": the case where the value of the ratio (%) of pressure loss exceeds 70% and is 75% or less

[0155] Evaluation "Good": the case where the value of the ratio (%) of pressure loss exceeds 70% and is 75% or less

[0156] [Soot clogging]

[0157] First, a 6.7L diesel engine was used to make exhaust gas flow from the inlet end face of the honeycomb filter, and a predetermined amount of soot was accumulated in the honeycomb filter. In addition, the amount of soot accumulation was 30 g / L. The honeycomb filter after soot accumulation was photographed by tomography (CT), and confirmation of the soot distribution inside the honeycomb filter was performed. The case where the introduction cells were not partially clogged by soot at all, and the soot was accumulated on the outlet end face side of the introduction cells, was set as acceptable, and the case where even one introduction cell was partially clogged by soot was set as unacceptable.

[0158] [Strength]

[0159] The measurement of strength was performed based on the isostatic compression strength test prescribed in M505-87 of the automobile standards (JASO standards) issued by the Automotive Technology Council. The isostatic compression strength test is a test in which a honeycomb filter is put in a cylindrical container of rubber and covered with an aluminum plate, and isostatic compression is performed in water. The isostatic compression strength measured by the isostatic compression strength test is represented by the pressurization pressure value (MPa) at the time of destruction of the honeycomb filter. The isostatic compression strength was acceptable when it was 1.0 MPa or more, and was unacceptable when it was less than 1.0 MPa.

[0160] [Table 2]

[0161]

[0162] (4. Investigation)

[0163] From the test results of the filter performance of the honeycomb structures involved in each of the examples and the comparative examples, it was found that in the examples in which all of the C in / C out , the thickness of the partition wall (WT), the cell density (CD), the depth of the plugged portion (PD), the offset (OF), and OF x CD / (WT x PD) were all appropriate, all of the excellent PM capturing performance, low pressure loss, excellent catalyst coating property at the time of catalyst support, ease of occurrence of soot clogging, and excellent mechanical strength could be satisfied. Furthermore, it was found that Examples 2 and 3 in which OF x CD / (WT x PD) was optimal could satisfy the required characteristics at a high level. On the other hand, in the comparative examples, it was found that since any one or more of the C in / C out , the thickness of the partition wall (WT), the cell density (CD), the depth of the plugged portion (PD), the offset (OF), and OF x CD / (WT x PD) were not appropriate, all of the excellent PM capturing performance, low pressure loss, excellent catalyst coating property at the time of catalyst support, ease of occurrence of soot clogging, and excellent mechanical strength could not be satisfied.

[0164] Explanation of symbols

[0165] 100 — honeycomb structure; 102 — peripheral side wall; 104 — inlet end face; 106 — outlet end face; 107 — opening portion; 108 — introduction compartment; 109 — plugging portion; 110 — discharge compartment; 112 — partition wall; 120 — chuck; 121 — film; 122 — doctor blade; 124 — plugging portion-forming slurry; 125 — compartment; 126 — hole; 400 — honeycomb formed body.

Claims

1. A honeycomb structure which is a columnar honeycomb structure, comprising: an outer peripheral wall; a plurality of introduction cells arranged on an inner peripheral side of the outer peripheral wall, extending from an inlet end surface to an outlet end surface, having an opening portion at the inlet end surface, and having a plugged portion at the outlet end surface; and a plurality of discharge cells arranged on the inner peripheral side of the outer peripheral wall, extending from the inlet end surface to the outlet end surface, having the plugged portion at the inlet end surface, and having the opening portion at the outlet end surface, and being adjacent to at least any one of the plurality of introduction cells with a partition wall therebetween, characterized in that: a thickness WT of the partition wall is 0.18 to 0.25 mm, a depth PD of the plugged portion is 4 to 7 mm, a distance OF between a midpoint of a line segment connecting centers of gravity of the introduction cell and the discharge cell adjacent to each other with the partition wall therebetween and a center of the partition wall across which the line segment passes is 0.075 to 0.110 mm in a cross section of the honeycomb structure perpendicular to a direction in which the plurality of introduction cells and the plurality of discharge cells extend, and 2 ≤ OF x CD / (WT x PD) ≤ 7 is satisfied. The opening area C of each of the plurality of introduction compartments in The opening area C of each of the plurality of discharge compartments out The ratio of the opening area C of each of the plurality of introduction compartments to the opening area C of each of the plurality of discharge compartments satisfies 1 < C < 2.5 in / C out ≤2.5, 2. The honeycomb structure according to claim 1, characterized in that: a porosity of the partition wall is 52 to 61%. The cell density CD based on the total number of the plurality of import compartments and the plurality of export compartments is 49 to 70 cells / cm 2 , 3. The honeycomb structure according to claim 1 or 2, characterized in that: an average pore diameter of the partition wall is 6 to 10 μm.

4. The honeycomb structure according to claim 1 or 2, characterized in that: the opening shape of each of the plurality of introduction cells other than the introduction cell adjacent to the outer peripheral wall is a hexagon or an octagon.

5. The honeycomb structure according to claim 1 or 2, characterized in that: the partition wall contains one selected from the group consisting of cordierite, silicon carbide, silicon-silicon carbide composite, silicon nitride, mullite, alumina, and aluminum titanate.

6. The honeycomb structure according to claim 1 or 2, characterized in that: a catalyst is supported on the partition wall. ​ ​ ​ ​ ​ ​ ​ ​ ​

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