Honeycomb structure

Abstract

Provided is a honeycomb structure that satisfies all excellent PM collection performance, low pressure loss, excellent catalyst coating properties when a catalyst is loaded, less susceptibility to soot clogging, and excellent mechanical strength. The honeycomb structure is a columnar honeycomb structure provided with a plurality of introduction cells and a plurality of discharge cells adjacent to at least one introduction cell with a partition wall therebetween, the ratio of the opening area Cin of each of the plurality of introduction cells to the opening area Cout of each of the plurality of discharge cells; the thickness WT of the partition wall; the cell density CD based on the total number of the plurality of introduction cells and the plurality of discharge cells; 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 across which the line segment crosses satisfies a predetermined condition, and satisfies 2 < = OF * CD / (WT * PD) < = 7.

Description

Technical Field

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

[0002] The exhaust gas emitted from internal combustion engines such as diesel engines contains a large amount of particulate matter (PM) such as soot, which is mainly composed of carbon and is a cause of environmental pollution, and soot (ash) produced as combustion residues of calcium (Ca). This particulate matter has been confirmed to be carcinogenic, so it is necessary to prevent its release into the atmosphere. At present, in addition to the previous weight-based quantity restrictions centered on Europe, strict restrictions are also imposed to limit the number of PM. Therefore, a filter for capturing particulates (Diesel Particulate Filter: DPF, diesel particulate filter) is usually installed in the exhaust system of diesel engines, etc. In addition, in recent years, particulates emitted from gasoline engines have also been regarded as a problem, and filters (Gasoline Particulate Filter: GPF, gasoline particulate filter) are also installed in gasoline engines.

[0003] Wall-flow filters designed to allow exhaust gas to pass through porous partitions are effective as filters. Specifically, wall-flow filters have multiple inlet cells and multiple outlet cells adjacent to each other, separated by porous partitions. They can be constructed from a honeycomb structure that captures PM as exhaust gas passes through the partitions. Catalysts tailored to the intended purpose can also be supported on the surface of the partitions.

[0004] Wall-flow filters composed of a honeycomb structure are required to have various properties, including excellent PM trapping performance, low pressure loss, excellent catalytic performance when the catalyst is supported, resistance to soot clogging, and excellent mechanical strength.

[0005] It is recorded in Japanese Patent Gazette No. 2023-147536 (Patent Document 1) 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 sealing portion, the porosity of the partition wall, etc. within a predetermined range, a honeycomb filter with low pressure loss, excellent erosion resistance of the sealing portion, and excellent heat shock resistance can be obtained.

[0006] Japanese Patent Gazette No. 7353217 (Patent Document 2) states that by controlling the porosity of the partition walls, the average pore size of the partition walls, the pore size distribution of the partition walls, the thickness of the partition walls, etc. within a predetermined range, a honeycomb filter having excellent collection performance and reduced pressure loss can be obtained.

[0007] Prior art literature

[0008] Patent Literature

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

[0010] Patent Document 2: Japanese Patent No. 7353217 Summary of the Invention

[0011] Problems to be solved by the invention

[0012] However, previous honeycomb structures have not been able to fully meet the requirements of excellent PM capture performance, low pressure loss, excellent catalytic performance when catalyst is loaded, low soot clogging, and excellent mechanical strength. Patent Document 1 describes a honeycomb filter with excellent erosion resistance and thermal shock resistance in the sealed portion, but there is still room for improvement in terms of catalyst coating properties. Patent Document 2 describes a honeycomb filter that achieves excellent capture performance and reduces pressure loss by controlling the porosity of the partition walls, the average pore diameter of the partition walls, the pore diameter distribution of the partition walls, and the thickness of the partition walls within a predetermined range. However, there is still room for improvement in terms of catalyst coating properties.

[0013] The present invention is completed in view of the above situation. In one embodiment, its object is to provide a honeycomb structure that meets all the requirements of excellent PM capture performance, low pressure loss, excellent catalyst coating properties during catalyst loading, low soot clogging, and excellent mechanical strength.

[0014] Solutions to Problems

[0015] Means for Solving the Problems The present inventors have conducted intensive studies to solve the above-mentioned problems and have completed the present invention exemplified below.

[0016] [Scheme 1]

[0017] A columnar honeycomb structure, comprising: an outer peripheral side wall; a plurality of inlet cells, which are arranged on the inner peripheral side of the outer peripheral side wall, extend from the inlet end face to the outlet end face, have an opening at the inlet end face, and have a sealing portion at the outlet end face; and a plurality of discharge cells, which are arranged on the inner peripheral side of the outer peripheral side wall, extend from the inlet end face to the outlet end face, have a sealing portion at the inlet end face, have an opening at the outlet end face, and are adjacent to at least one of the plurality of inlet cells across the partition wall, wherein:

[0018] 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 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 inlet cells and the plurality of outlet cells is 49 to 70 cells / cm 2 ,

[0021] The depth PD of the 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 inlet cells and the plurality of outlet cells extend, a distance OF between a midpoint of a line segment connecting the centers of gravity of the adjacent inlet cells and the outlet cells across the partition wall and a center of the partition wall through which the line segment passes is 0.075 to 0.110 mm.

[0023] Satisfies 2≤OF×CD / (Wt×PD)≤7.

[0024] [Scheme 2]

[0025] The honeycomb structure according to claim 1, wherein

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

[0027] [Scheme 3]

[0028] The honeycomb structure according to claim 1 or 2, wherein

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

[0030] [Scheme 4]

[0031] The honeycomb structure according to any one of aspects 1 to 3, wherein

[0032] Except for the introduction compartment adjacent to the outer peripheral side wall, the opening shapes of the plurality of introduction compartments are all hexagonal or octagonal.

[0033] [Scheme 5]

[0034] The honeycomb structure according to any one of aspects 1 to 4, wherein

[0035] The partition wall contains one or more materials selected from cordierite, silicon carbide, silicon-silicon carbide composite material, silicon nitride, mullite, alumina and aluminum titanate.

[0036] [Scheme 6]

[0037] The honeycomb structure according to any one of aspects 1 to 5, wherein

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

[0039] Effects of the Invention

[0040] The honeycomb structure according to one embodiment of the present invention satisfies all of the requirements of excellent PM capture performance, low pressure loss, excellent catalyst coating properties during catalyst loading, low soot clogging, and excellent mechanical strength. Therefore, according to one embodiment of the present invention, it can be said that a practically excellent honeycomb structure can be provided, which is suitable for use as a filter for exhaust gas emitted from internal combustion engines such as diesel engines. BRIEF DESCRIPTION OF THE DRAWINGS

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

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

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

[0044] Figure 4 This is an explanatory diagram schematically showing an example of a method for forming a plugged portion using a squeegee method. DETAILED DESCRIPTION

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

[0046] (1. Honeycomb structure)

[0047] exist Figure 1 as well as Figure 2 , a schematic perspective view and a cross-sectional view of a columnar honeycomb structure 100 that can be used as a wall-flow exhaust gas filter for automobiles are shown. The honeycomb structure 100 includes: an outer peripheral sidewall 102; a plurality of inlet cells 108 arranged on the inner peripheral side of the outer peripheral sidewall 102, extending parallel to each other from an inlet end face 104 to an outlet end face 106, having an opening 107 at the inlet end face 104 and a plugging portion 109 at the outlet end face 106; and a plurality of outlet cells 110 arranged on the inner peripheral side of the outer peripheral sidewall 102, extending parallel to each other from the inlet end face 104 to the outlet end face 106, having a plugging portion 109 at the inlet end face 104 and an opening 107 at the outlet end face 106, and adjacent to at least one of the plurality of inlet cells via a partition wall 112.

[0048] For example, when exhaust gas containing particulate matter such as soot is supplied to the upstream inlet end face 104 of the honeycomb structure 100, the exhaust gas is introduced into the inlet cell 108 and flows downstream within the inlet cell 108. Since the outlet end face 106 on the downstream side of the inlet cell 108 is sealed, the exhaust gas passes through the partition wall between the adjacent inlet cell 108 and the outlet cell 110 and flows into the outlet cell 110. The particulate matter cannot pass through the partition wall and is therefore trapped and accumulated within the inlet cell 108. After the particulate matter is removed, the clean exhaust gas that has flowed into the outlet cell 110 flows downstream within the outlet cell 110 and flows out from the downstream outlet end face 106.

[0049] The honeycomb structure 100 satisfies the following conditions (1) to (6), thereby satisfying all of the requirements of excellent PM trapping performance, low pressure loss, excellent catalyst coating properties during catalyst loading, low soot clogging, and excellent mechanical strength.

[0050] (1) The opening area (C) of each of the plurality of introduction compartments 108 in ) and the opening area (C out ) ratio (C in / C out );

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

[0052] (3) Cell density (CD) based on the total number of the plurality of inlet cells 108 and the plurality of outlet cells 110 (unit: cells / cm 2 );

[0053] (4) Depth of the sealing portion 109 (PD) (unit: mm);

[0054] (5) In a cross section of the honeycomb structure 100 perpendicular to the direction in which the plurality of inlet cells 108 and the plurality of outlet cells 110 extend, a distance (OF) (hereinafter also referred to as “offset”) between a midpoint M of a line segment connecting the centers of gravity O of adjacent inlet cells 108 and outlet cells 110 with the partition wall 112 interposed therebetween and a center C of the partition wall 112 through which the line segment intersects (unit: mm);

[0055] (6)OF×CD / (WT×PD).

[0056] (1)C in / C out

[0057] The opening area (C in ) and the opening area (C out) ratio (C in / C out ) preferably satisfies 1 <C in / C out ≤2.5, more preferably 1.5≤C in / C out ≤2.5, and further preferably satisfies 1.5≤C in / C out ≤2.2.

[0058] The opening area (C in ) is defined as the average value of the opening area of ​​the entire inlet compartment excluding the compartment adjacent to the outer peripheral side wall 102.

[0059] The opening area (C out ) is defined as the average value of the opening area of ​​the entire discharge compartment excluding the compartment adjacent to the outer peripheral side wall 102.

[0060] The opening area (C in ) is preferably, for example, 0.70 to 1.10 mm 2 , more preferably 0.70 to 1.00 mm 2 , more preferably 0.75 to 0.90 mm 2 .

[0061] (2)WT

[0062] The thickness (WT) of the partition walls 112 is preferably 0.18 to 0.25 mm, more preferably 0.18 to 0.24 mm, and even more preferably 0.18 to 0.23 mm. The thickness (WT) of the partition walls 112 refers to the average value of the thickness (WT) of all the partition walls 112 . Figure 3 1 shows a schematic partial enlarged view of a honeycomb structure 100 in which the opening shape of the inlet cell 108 is octagonal and the opening shape of the outlet cell 110 is quadrilateral, as viewed from a cross section perpendicular to the cell extension direction. The thickness (WT) of the partition wall 112 refers to the length D of the line segment passing through the partition wall when the center of gravity O of adjacent cells is connected by a line segment in the cross section perpendicular to the cell extension direction (the height direction of the honeycomb structure 100).

[0063] In addition, two compartments are adjacent to each other with a partition wall sandwiched between them means that when the partition wall of the honeycomb structure is observed from a cross section perpendicular to the direction in which the compartments extend, the two compartments are adjacent to each other with the opposite wall surfaces of a partition wall sandwiched between them (the sides of the polygon dividing the compartments), and does not include the situation where the two compartments are adjacent to each other with the vertices of the polygon dividing the two compartments sandwiched between them.

[0064] (3)CD

[0065] The cell density (CD) based on the total number of the plurality of inlet cells 108 and the plurality of outlet cells 110 is preferably 49 to 70 cells / cm 2 , more preferably 49 to 68 pieces / cm 2 , more preferably 50 to 66 pieces / cm 2 The cell density is calculated by dividing the total number of cells (including sealed cells, discharge cells 110 adjacent to the outer peripheral side wall 102, and inlet cells 108 adjacent to the outer peripheral side wall 102) by the area of ​​one end face of the honeycomb structure other than the outer peripheral side wall.

[0066] (4)PD

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

[0068] (5)OF (offset)

[0069] Reference Figure 3 In a cross section of the honeycomb structure 100 perpendicular to the direction in which the plurality of inlet cells 108 and the plurality of outlet cells 110 extend, the distance between the midpoint M of a line segment connecting the centers of gravity O of adjacent inlet cells 108 and outlet cells 110 sandwiching a partition wall 112 and the center C of the partition wall 112 through which the line segment intersects is referred to as OF (offset). OF is preferably 0.075 to 0.110 mm, more preferably 0.075 to 0.105 mm, and even more preferably 0.080 to 0.105 mm. OF refers to the average value of all calculable OFs.

[0070] (6)OF×CD / (WT×PD)

[0071] In addition to satisfying the above-mentioned conditions, the thickness (WT) of the partition walls 112, the cell density (CD), the depth (PD) of the sealing portion 109, and the OF (offset) preferably also satisfy the condition defined by OF×CD / (WT×PD). Specifically, 2≤OF×CD / (WT×PD)≤7 is preferred, 2.2≤OF×CD / (WT×PD)≤6.9 is more preferred, 2.4≤OF×CD / (WT×PD)≤6.9 is even more preferred, 3.0≤OF×CD / (WT×PD)≤6.9 is even more preferred, 4.0≤OF×CD / (WT×PD)≤6.5 is even more preferred, and 5.0≤OF×CD / (WT×PD)≤6.0 ​​is even more preferred.

[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, 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, more preferably 60% or less. Therefore, for example, the average porosity of the partition wall is preferably 52 to 61%, more preferably 53 to 60%. In this specification, the porosity is measured by the mercury intrusion method specified in JIS R1655:2003 (Japanese Industrial Standards). In addition, regarding the porosity, samples of the partition wall (0.3 g each) are collected without deviation from 6 locations of the honeycomb structure and the average value of the porosity of each is calculated as the measured value.

[0073] From the viewpoint of further improving the efficiency of collecting particulate matter, the average pore diameter of the partition wall 112 is preferably 10 μm or less, 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, more preferably 7 μm or more. Therefore, the average pore diameter of the partition wall 112 is preferably, for example, 6 to 10 μm, more preferably 7 to 9 μm. The average pore diameter of the partition wall is measured by the mercury intrusion method in accordance with JIS R1655:2003. 20 test pieces of the partition wall are uniformly collected including the center and the outer periphery of the columnar honeycomb structure, and the average pore diameter of each is measured, and the average value thereof is taken as the average pore diameter of the entire columnar honeycomb structure.

[0074] The opening shape of the inlet compartment 108 is not particularly limited. For example, in the cross section of the honeycomb structure 100 that is perpendicular to the direction in which the compartment extends, it can be set to a polygon (quadrilateral (rectangle, square), pentagon, hexagon, heptagon, octagon, etc.), a circular shape (circle, ellipse, oblong, oval, oblong, etc.), etc. These shapes can be single, or two or more can be combined. Among them, based on the reason of reducing pressure loss, except for the compartment adjacent to the outer peripheral side wall 102, the opening shape of each of the multiple inlet compartments 108 is preferably all hexagonal or octagonal, more preferably octagonal. In the case where the opening shape of the inlet compartment 108 and the discharge compartment 110 is polygonal, the corners can be R-chamfered. In addition, in this specification, even if R-chamfering is performed, it is treated as a polygon.

[0075] The opening shape of the discharge cell 110 is not particularly limited and may be set according to the opening shape of the introduction cell 108. For example, when the opening shape of the introduction cell 108 is octagonal, it is preferably a quadrangle.

[0076] There is no limitation on the shape of the end face of the honeycomb structure 100. For example, it can be a circular shape, an ellipse, a racetrack shape, an oval shape, a polygonal shape such as a triangle and a quadrilateral, or other irregular shapes. The end face of the honeycomb structure 100 shown in the figure is circular, and the entire structure is cylindrical.

[0077] The height of the honeycomb structure (the length from the inlet end face to the outlet end face) 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, for example, 40 to 450 mm, preferably 60 to 400 mm, and more preferably 100 to 330 mm. There is no particular limitation on the relationship between the height of the honeycomb structure and the maximum diameter of each end face (referring to the maximum length of the diameter passing through the center of gravity of each end face of the honeycomb structure). Therefore, the height of the honeycomb structure can be longer than the maximum diameter of each end face, or the height of the honeycomb structure can be shorter than the maximum diameter of each end face.

[0078] From the perspective of obtaining excellent heat shock resistance, at least the partition walls, preferably the peripheral side walls and the partition walls, and more preferably the peripheral side walls, the partition walls and the sealing parts of the honeycomb structure contain one or more selected from cordierite, silicon carbide, silicon-silicon carbide composite materials, silicon nitride, mullite, alumina and aluminum titanate.

[0079] The outer peripheral sidewalls, partition walls, and plugging portions of the honeycomb structure may also contain ceramics other than those mentioned above. Examples of other ceramics include zirconium phosphate, cordierite-silicon carbide composites, zirconium oxide, spinel, India stone, sapphire, corundum, titanium dioxide, and cerium oxide. Furthermore, these other ceramics may be contained alone or in combination of 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 catalysts, there are no limitations, and examples include oxidation catalysts (DOCs) for oxidizing and burning hydrocarbons (HC) and carbon monoxide (CO) to increase the exhaust gas temperature, PM combustion catalysts that assist in the combustion of PM such as soot, SCR catalysts and NSR catalysts for removing nitrogen oxides (NOx), and three-way catalysts that can simultaneously remove hydrocarbons (HC), carbon monoxide (CO), and nitrogen oxides (NOx). The catalyst can appropriately contain, for example, precious 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.), etc.

[0081] The honeycomb structure may be a honeycomb bonded body having a plurality of honeycomb sheets and a bonding layer for bonding the outer peripheral surfaces of the plurality of honeycomb sheets to each other. By using a honeycomb bonded body, the total cross-sectional area of ​​the compartments, which is important for ensuring the flow of air, can be increased while suppressing the generation of cracks. The bonding layer can be formed using a bonding material. The bonding material is not particularly limited, and a material prepared by adding a solvent such as water to a ceramic material to form a paste can be used. The bonding material may also contain the same material as the partition wall. In addition to having the function of bonding the honeycomb sheets to each other, the bonding material can also be used as a peripheral coating material after the honeycomb sheets are bonded.

[0082] (2. Manufacturing Method)

[0083] Hereinafter, the manufacturing method of the columnar honeycomb structure body involved in one embodiment of the present invention will be illustrated. First, after the raw material composition containing cordierite raw material, pore-forming material, dispersion medium and adhesive is mixed and formed into adobe, the adobe is extruded to obtain a columnar honeycomb formed body with an outer peripheral side wall and a plurality of compartments, the plurality of compartments being arranged on the inner peripheral side of the outer peripheral side wall, extending from the inlet end face to the outlet end face, and the inlet end face and the outlet end face both have openings. Additives such as dispersants and other ceramic raw materials can be added as needed in the raw material composition. During extrusion molding, a mold with desired overall shape, compartment shape, compartment arrangement, wall thickness, compartment density, etc. can be used.

[0084] The so-called cordierite-forming raw material is a raw material that becomes cordierite by calcination and can be provided in the form of a powder, for example. The cordierite-forming raw material preferably has a chemical composition of 30-45% by mass of aluminum oxide (Al2O3) (including aluminum hydroxide converted to aluminum oxide), 11-17% by mass of magnesium oxide (MgO), and 42-57% by mass of silicon dioxide (SiO2).

[0085] 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.

[0086] The content of the dispersion medium of the honeycomb formed body before the drying process is preferably 20 to 110 parts by weight, more preferably 25 to 100 parts by weight, and even more preferably 30 to 90 parts by weight relative to 100 parts by weight of the cordierite-forming raw material. By setting the content of the dispersion medium of the honeycomb formed body to 20 parts by weight or more relative to 100 parts by weight of the cordierite-forming raw material, the advantage of easily stabilizing the quality of the honeycomb structure can be easily obtained. By setting the content of the dispersion medium of the honeycomb formed body to 110 parts by weight or less relative to 100 parts by weight of the cordierite-forming raw material, the shrinkage during drying is reduced, and deformation can be suppressed. In this specification, the content of the dispersion medium of the honeycomb formed body refers to the value measured by the loss on drying method.

[0087] As a pore-forming material, there is no particular limitation as long as it is a material that becomes pores after calcination, and examples thereof 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. One pore-forming material can be used alone, or two or more can be used in combination. From the viewpoint of increasing the porosity of the honeycomb structure after calcination, the content of the pore-forming material is preferably 1 part by weight or more relative to 100 parts by weight of the cordierite raw material, more preferably 6 parts by weight or more, and further preferably 9 parts by weight or more. 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 relative to 100 parts by weight of the cordierite raw material, more preferably 27 parts by weight or less, and further preferably 24 parts by weight or less.

[0088] As the binder, organic binders such as methylcellulose, hydroxypropoxymethylcellulose, hydroxypropylmethylcellulose, hydroxyethylcellulose, hydroxyethylmethylcellulose, carboxymethylcellulose, and polyvinyl alcohol can be exemplified. In addition, from the viewpoint of improving the strength of the honeycomb formed 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 cordierite raw material. From the viewpoint of suppressing the occurrence of cracking caused by abnormal heat in the calcination process, 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 cordierite raw material. One type of binder can be used alone, or two or more types can be used in combination.

[0089] Dispersants that can be used include ethylene glycol, dextrin, fatty acid soap, and polyether polyol. A single dispersant or a combination of two or more may be used. The content of the dispersant is preferably 0 to 2 parts by weight per 100 parts by weight of the cordierite-forming raw material.

[0090] 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 quickly and uniformly dry the entire honeycomb formed body.

[0091] After the honeycomb formed body is dried, sealing portions are formed on both end surfaces of the honeycomb formed body. Each sealing portion can be formed by filling the openings of the inlet compartment and the outlet compartment where the sealing portion is to be formed with a slurry for forming the sealing portion, and then drying and calcining the filled slurry. The slurry for forming the sealing portion can use the material of the honeycomb formed body. Although not limited, for example, when the honeycomb formed body contains a cordierite-forming raw material, a pore-forming material, a dispersion medium, and a binder, the slurry for forming the sealing portion can contain a cordierite-forming raw material, a pore-forming material, a dispersion medium, and a binder.

[0092] Illustratively, the slurry for forming the plugging portion contains 30-60 parts by weight of the dispersion medium, 5-20 parts by weight of the pore-forming material, and 0.2-2.0 parts by weight of the binder per 100 parts by weight of the cordierite-forming raw material. In a preferred embodiment, the slurry for forming the plugging portion contains 35-50 parts by weight of the dispersion medium, 8-16 parts by weight of the pore-forming material, and 0.2-1.5 parts by weight of the binder per 100 parts by weight of the cordierite-forming raw material.

[0093] 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.

[0094] The pore-forming material is not particularly limited as long as it forms pores after calcination. Examples thereof include wheat flour, starch, foamed resin, water-absorbent resin, silica gel, carbon (e.g., graphite), ceramic balls, polyethylene, polystyrene, polypropylene, nylon, polyester, acrylic resin, and phenol. The pore-forming material may be used alone or in combination of two or more.

[0095] 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.

[0096] The slurry for forming the sealing portion may contain a dispersant as appropriate. Examples of the dispersant include ethylene glycol, dextrin, fatty acid soap, and polyols. The dispersant may be used alone or in combination of two or more.

[0097] The filling of the sealing portion forming slurry into the opening of the cell can be carried out, for example, by the following "scraper method". Figure 4 As shown, a film 121 is pasted on the upper end face (here, the outlet end face 106 in the figure) of the dried honeycomb formed body 400 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, and a plurality of holes 126 are drilled in the film 121.

[0098] 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 4 Thus, a constant amount of the plugging portion forming slurry 124 is filled into the cells 125 opened at positions corresponding to the holes 126 of the membrane 121 .

[0099] The depth of the plugging portion can be changed depending on 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 .

[0100] After filling with the plugging portion forming slurry 124, the film 121 is peeled off, and the entire honeycomb formed body 400 is dried. The plugging portion forming slurry 124 filled in the cells 125 is thereby 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. After drying, the plugging portions protrude from the end faces of the honeycomb formed body by an amount corresponding to the thickness of the film, and therefore can be shaved off as needed.

[0101] The material of the membrane is not particularly limited, but polypropylene (PP), polyethylene terephthalate (PET), polyimide, or Teflon (registered trademark) are preferred for ease of thermal processing for hole formation. Furthermore, the membrane preferably includes an adhesive layer, preferably made of an acrylic resin, a rubber-based resin (e.g., a rubber primarily composed of natural rubber or synthetic rubber), or a silicone resin. Thin films, for example, with a thickness of 20 to 50 μm, can be suitably used.

[0102] 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 slurry for forming the plugging portion. The "press-in method" is a method in which a film is applied and the end surface of the honeycomb formed body having holes therein is immersed in a tank containing the slurry for forming the plugging portion, thereby filling the cells with the slurry for forming the plugging portion. In this case, the depth of the plugging portion can be varied depending on the depth of the honeycomb formed body immersed in the slurry for forming the plugging portion.

[0103] The honeycomb formed body filled with the slurry for forming the sealing portion is then subjected to a degreasing process and a calcining 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 degreasing process can be carried out by heating the honeycomb formed body to a temperature in the range of about 200 to 1000°C. The heating time is not particularly limited and is generally about 10 to 100 hours. The honeycomb formed body after the degreasing process is called a calcined body. The calcining 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 to 1450°C and maintaining it for 3 to 24 hours.

[0104] The catalyst can be loaded onto the partition walls of the honeycomb structure thus manufactured. As an exemplary method for loading the catalyst onto the partition walls, a catalyst slurry can be introduced into the partition walls by a conventionally known suction method, etc., and then adhered to the surface and pores of the partition walls. The catalyst slurry is then subjected to a high-temperature treatment to sinter the catalyst onto the partition walls. The types of catalysts are described above.

[0105] [Example]

[0106] Hereinafter, examples are described for better understanding of the present invention and its advantages, but the present invention is not limited to the examples.

[0107] (1. Manufacturing of Honeycomb Structure)

[0108] [Honeycomb structures made of cordierite: Comparative Examples 1 to 7, Examples 1 to 5]

[0109] To 100 parts by weight of a cordierite-forming raw material, 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 were added, mixed, and kneaded to prepare an adobe. The cordierite-forming raw materials used were alumina, aluminum hydroxide, kaolin, talc, and silica. Water was used as the dispersion medium. Methyl cellulose was used as the organic binder. A water-absorbent resin with a median particle size of 20 μm was used as the pore-forming material. In this example, the median particle size of the raw material refers to the particle size (D50) at which the cumulative value of the particle size distribution, as determined by laser diffraction scattering, reaches 50%.

[0110] Next, the adobe was extruded and molded using a die used for a honeycomb forming body to obtain a honeycomb formed body having an overall cylindrical shape. The structure of the die varied depending on the test number.

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

[0112] Next, a slurry for forming the plugging portions is prepared using the same material as that used for the honeycomb formed body. This slurry is then used to form plugging portions at the openings of the predetermined cells on the inlet end face side of the dried honeycomb formed body and at the openings of the remaining cells on the outlet end face side, such that the inlet cells and the outlet cells are alternately adjacent to each other.

[0113] Next, the honeycomb formed bodies with each sealed portion formed therein were degreased and calcined to produce the honeycomb structures corresponding to the respective test numbers. The inlet and outlet end faces of the honeycomb structures thus obtained were circular cylindrical in shape. The diameters of the inlet and outlet end faces were 330 mm. Furthermore, the length of the honeycomb structures in the direction in which the cells extended was 254 mm. The number of honeycomb structures required to determine the following characteristics was prepared.

[0114] (2. Structural characteristics of honeycomb structure)

[0115] Table 1 shows the following structural characteristics of the honeycomb structures according to the test numbers manufactured above.

[0116] ·Thickness of partition wall (WT)

[0117] Compartment density (CD) based on the total number of inlet compartments and outlet compartments

[0118] The opening area of ​​each of the multiple introduction compartments (C in ) and the opening area of ​​each of the multiple discharge compartments (C out ) ratio (C in / C out )

[0119] The opening area of ​​each of the multiple introduction compartments (C in )

[0120] Offset (OF)

[0121] Depth of sealing part (PD)

[0122] OF×CD / (WT×PD)

[0123] Porosity of the partition wall

[0124] Average pore size of partition walls

[0125] The shape of the opening of the inlet compartment

[0126] ·Opening shape of the discharge compartment

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

[0128] The compartment density (CD) refers to the compartment density based on the total number of inlet compartments and outlet compartments, and is measured according to the above method.

[0129] C in / C out and C in Observation was performed using a scanning electron microscope (SEM) or calculation was performed using a microscope.

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

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

[0132] The porosity and average pore diameter of the cell walls were measured by the aforementioned mercury intrusion method using Autopore 9500 (trade name) manufactured by Micromeritics.

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

[0134] [Table 1]

[0135]

[0136] (3.Filter performance)

[0137] The honeycomb structures of the test numbers prepared above were used as filters to evaluate the following filter performance.

[0138] [Capture performance]

[0139] First, the honeycomb filters of each Example and Comparative Example were enclosed in a metal housing as exhaust gas purification filters to produce an exhaust gas purification device. The resulting exhaust gas purification device was then connected to the outlet of a 6.7L diesel engine's exhaust manifold, and the number of soot particles contained in the gas discharged from the exhaust gas purification device's outlet was measured using the PN measurement method. To determine the soot particle count, the cumulative number of soot particles emitted after driving in the WHTC (World Harmonized Transient Cycle) mode was used as the soot particle count of the exhaust gas purification device being evaluated. The soot particle count ratio (%) of each honeycomb filter was calculated, with the soot particle count of the exhaust gas purification device using the honeycomb filter of Comparative Example 1 as 100%. The honeycomb filters of each Example and Comparative Example were evaluated based on the following evaluation criteria. The results are shown in Table 2.

[0140] Evaluation "Excellent": When the ratio of soot particles (%) is 80% or less

[0141] Evaluation "Good": When the value of the number ratio (%) of soot exceeds 80% and is 90% or less

[0142] ··Evaluation "Acceptable": When the value of the number ratio (%) of soot exceeds 90% and is 100% or less

[0143] ··Evaluation "Not acceptable": When the value of the number ratio (%) of soot exceeds 100%

[0144] [Pressure loss]

[0145] Exhaust gas from a 6.7L diesel engine was passed through the filters of each embodiment and comparative example, and soot in the exhaust gas was captured in the filters. Soot capture was continued until the soot accumulation per unit volume (1L) of the filter reached 5g / L. Then, with the soot accumulation at 5g / L, the engine exhaust gas at 200°C was passed through the filter at a speed of 12m 3 A flow rate of 1 / min was flowed in, and the pressures at the inlet and outlet ends of the filter were measured. The pressure loss (kPa) of the filter was then determined by calculating the pressure difference between the inlet and outlet ends. The pressure loss of the filter in Comparative Example 1 was set to 100%, and the ratio (%) of the pressure loss of the filters in each example and comparative example was calculated. The pressure loss of the filters was evaluated based on the following evaluation criteria. The results are shown in Table 2.

[0146] ··Evaluation "Excellent": When the pressure loss ratio (%) is 70% or less

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

[0148] ··Evaluation "Acceptable": When the pressure loss ratio (%) exceeds 75% and is 100% or less

[0149] ··Evaluation "Not Acceptable": When the pressure loss ratio (%) exceeds 100%

[0150] [Catalyst coating properties]

[0151] First, an oxidation catalyst is loaded on the partition wall of the honeycomb filter. The loading amount of the catalyst is 10 g / L. Next, 3 g / L of soot is deposited in the honeycomb filter loaded with the catalyst as described above. In this state, another honeycomb structure (catalyst support) loaded with an oxidation catalyst is set in the front section of the honeycomb filter. Then, high-temperature exhaust gas is made to flow from the upstream side of the honeycomb structure of the front section, and the exhaust gas passing through the honeycomb structure of the front section is ventilated from the inlet end face of the honeycomb filter to perform continuous regeneration of the filter. The exhaust gas is discharged from a 6.7L diesel engine. The regeneration conditions are to set the gas temperature at the inlet end face to 350°C and the gas ventilation time to 60 minutes. Then, the honeycomb filter is removed from the device that has been continuously regenerated, and the amount of soot remaining in the honeycomb filter is measured. The percentage (%) of the ratio obtained by dividing the mass of soot reduced by continuous regeneration by the mass of soot initially deposited is calculated as the regeneration efficiency (%) during continuous regeneration. The regeneration efficiency of the filter in Comparative Example 1 was set to 100%, and the regeneration efficiency ratio (%) of the filters in each Example and Comparative Example was calculated. The catalyst performance of the filters was evaluated based on the following evaluation criteria. A higher catalyst coating property indicates a more uniform coating of the catalyst within the filter, resulting in improved regeneration efficiency. The results are shown in Table 2.

[0152] ··Evaluation "Excellent": When the regeneration efficiency ratio (%) exceeds 115%

[0153] Evaluation "Good": When the regeneration efficiency ratio (%) exceeds 110% and is 115% or less

[0154] ··Evaluation "OK": When the regeneration efficiency ratio (%) exceeds 100% and is 110% or less

[0155] ··Evaluation "Not acceptable": When the regeneration efficiency ratio (%) is 100% or less

[0156] [Ash blockage]

[0157] First, exhaust gas was introduced into the honeycomb filter from the inlet end face using a 6.7L diesel engine, allowing a predetermined amount of soot to accumulate within the filter. The soot accumulation was set to 30g / L. Computed tomography (CT) was used to image the honeycomb filter after soot accumulation, confirming the distribution of soot within the filter. A filter with no inlet cells clogged with soot, or with soot accumulated on the outlet end face of the inlet cells, was deemed acceptable. A filter with even one inlet cell clogged with soot was deemed unacceptable.

[0158] [strength]

[0159] Strength was measured based on the isostatic breaking strength test specified in M505-87 of the Automotive Standards (JASO Standards) issued by the Japan Association of Automotive Engineers (JASO). The isostatic breaking strength test involves placing a honeycomb filter in a rubber cylindrical container, covering it with an aluminum plate, and isostatically compressing it in water. The isostatic strength measured in this test is expressed as the pressure (MPa) applied when the honeycomb filter breaks. An isostatic strength of 1.0 MPa or higher is considered acceptable, while a strength below 1.0 MPa is considered unacceptable.

[0160] [Table 2]

[0161] Test number Capture performance Pressure loss Catalyst coating properties Ash blockage strength Comparative Example 1 Benchmark Benchmark Benchmark Unqualified qualified Comparative Example 2 No Can No qualified qualified Comparative Example 3 No excellent good Unqualified qualified Comparative Example 4 excellent excellent Can qualified Unqualified Comparative Example 5 Can excellent good Unqualified Unqualified Comparative Example 6 excellent No Can qualified qualified Comparative Example 7 excellent Can No qualified qualified Example 1 excellent good good qualified qualified Example 2 good excellent excellent qualified qualified Example 3 excellent excellent excellent qualified qualified Example 4 good Can Can qualified qualified Example 5 Can good Can qualified qualified

[0162] (4. Inspection)

[0163] According to the test results of the filter performance of the honeycomb structures of the embodiments and comparative examples, it can be seen that in / C out , the thickness of the partition wall (WT), the cell density (CD), the depth of the sealing portion (PD), the offset (OF), and OF×CD / (WT×PD) all appropriately satisfy all the requirements of excellent PM collection performance, low pressure loss, excellent catalyst coating during catalyst loading, low likelihood of soot clogging, and excellent mechanical strength. Furthermore, it can be seen that Examples 2 and 3, in which OF×CD / (WT×PD) are optimal, can satisfy the required characteristics at a high level. On the other hand, in the comparative examples, it can be seen that due to the C in / C out , the thickness of the partition wall (WT), the cell density (CD), the depth of the sealing portion (PD), the offset (OF), and any one or more of OF×CD / (WT×PD) are not appropriate, so it is impossible to meet all the requirements of excellent PM capture performance, low pressure loss, excellent catalyst coating during catalyst loading, low soot clogging, and excellent mechanical strength.

[0164] Explanation of symbols

[0165] 100—honeycomb structure; 102—outer peripheral side wall; 104—inlet end face; 106—outlet end face; 107—opening; 108—introduction compartment; 109—sealing portion; 110—discharge compartment; 112—partition wall; 120—chuck; 121—membrane; 122—scraper; 124—slurry for forming the sealing portion; 125—compartment; 126—hole; 400—honeycomb formed body.

Claims

1. A columnar honeycomb structure comprising: peripheral sidewall; a plurality of inlet compartments arranged on the inner circumference side of the outer circumferential side wall, extending from the inlet end face to the outlet end face, having an opening at the inlet end face and a sealing portion at the outlet end face; and A plurality of discharge compartments are arranged on the inner circumference side of the outer circumferential side wall, extending from the inlet end face to the outlet end face, having a sealing portion at the inlet end face and an opening at the outlet end face, and adjacent to at least one of the plurality of inlet compartments via a partition wall. The honeycomb structure is characterized in that 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 satisfies 1 <C in / C out ≤2.5, The thickness WT of the partition wall is 0.18 to 0.25 mm, The cell density CD based on the total number of the plurality of inlet cells and the plurality of outlet cells is 49 to 70 cells / cm 2 , The depth PD of the sealing portion is 4 to 7 mm. In a cross section of the honeycomb structure perpendicular to the direction in which the plurality of inlet cells and the plurality of outlet cells extend, a distance OF between a midpoint of a line segment connecting the centers of gravity of the adjacent inlet cells and the outlet cells across the partition wall and a center of the partition wall through which the line segment passes is 0.075 to 0.110 mm. Satisfies 2≤OF×CD / (Wt×PD)≤7.

2. The honeycomb structure according to claim 1, wherein The porosity of the partition walls is 52 to 61%.

3. The honeycomb structure according to claim 1 or 2, characterized in that The average pore diameter of the partition walls is 6 to 10 μm.

4. The honeycomb structure according to claim 1 or 2, characterized in that Except for the introduction compartment adjacent to the outer peripheral side wall, the opening shapes of the plurality of introduction compartments are all hexagonal or octagonal.

5. The honeycomb structure according to claim 1 or 2, characterized in that: The partition wall contains one or more materials selected from cordierite, silicon carbide, silicon-silicon carbide composite material, 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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