Honeycomb structure

Abstract

The invention provides a honeycomb structure, which can maintain the maintenance cost at a low level and can easily detect the maintenance time based on the PM accumulation amount by using a pressure sensor. A honeycomb structure is a cylindrical honeycomb structure provided with an outer peripheral side wall, a plurality of introduction cells, and a plurality of discharge cells, at least some of the plurality of introduction cells being adjacent to at least some of the plurality of discharge cells with a partition wall therebetween, the cell density based on the total number of the plurality of introduction cells and the plurality of discharge cells is 35-47 cells / cm2, and the average value of the opening diameters of the discharge cells other than the discharge cells adjacent to the outer peripheral side wall among the plurality of discharge cells is Dout. When the average value of the opening diameters of the introduction cells other than the introduction cells adjacent to the outer peripheral side wall among the plurality of introduction cells is defined as Din, 0.78 < = Din / Dout < = 0.94 is satisfied.

Description

Technical Field

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

[0002] Diesel engines offer superior thermal efficiency compared to gasoline engines, but their diffusion combustion produces particulate matter (PM), such as soot and ash. These particulate matter are known to be carcinogenic, and their release into the atmosphere must be prevented. Consequently, strict regulations are now in place, primarily in Europe, in addition to existing weight-based regulations.

[0003] However, there are limits to reducing PM emissions through combustion improvements, and the only effective method currently is to insert a filter called a diesel particulate filter (DPF) into the exhaust gas. Wall-flow filters, designed to allow exhaust gas to pass through porous partitions, are effective. 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 the exhaust gas passes through the partitions.

[0004] Wall-flow filters made of honeycomb structures have the problem of increasing pressure loss due to PM accumulation in the filter as the operating time increases. Therefore, such filters inject additional fuel every time a certain amount of PM accumulates, causing the exhaust gas temperature to rise and the soot to burn (regenerate the filter), thereby reducing the pressure loss. In addition, since ash does not burn even at high temperatures, trucks and off-road vehicles that travel longer distances than passenger cars (i.e., the filter has a longer operating time) need to regularly remove the ash accumulated in the filter by cleaning the honeycomb structure to reduce the pressure loss. If the pressure loss increases immediately when PM accumulates, the frequency of filter regeneration and cleaning becomes higher, resulting in increased fuel consumption and maintenance costs. Therefore, research has been conducted to reduce the pressure loss caused by PM accumulation by studying the arrangement and size of the inlet and outlet cells (Patent Documents 1 and 2).

[0005] Prior art literature

[0006] Patent Literature

[0007] Patent Document 1: International Publication No. 2019 / 104057

[0008] Patent Document 2: International Publication No. 2013 / 187444 Summary of the Invention

[0009] Problems to be solved by the invention

[0010] Conventionally, the timing for filter regeneration and cleaning was determined by measuring the pressure loss between the filter's inlet and outlet using a pressure sensor. However, if the pressure loss remains low after a large amount of PM accumulates in the filter, predicting the amount of PM accumulation based on the pressure loss becomes difficult when using a pressure sensor for filter regeneration control, leading to excessive PM accumulation and potentially damaging the filter. Therefore, it is desirable to reduce maintenance costs by minimizing the excessive increase in pressure loss after PM accumulation, thereby reducing the frequency of filter regeneration and cleaning. Furthermore, by increasing the change in pressure loss relative to the amount of PM accumulation (pressure loss gradient), it is easier to detect the amount of PM accumulation suitable for filter regeneration and cleaning using a pressure sensor. Furthermore, filters are required to have a practical heat capacity that does not cause an excessive temperature rise during filter regeneration.

[0011] The present invention has been completed in view of the above situation. In one embodiment, its object is to provide a honeycomb structure that can meet the required characteristics of practical heat capacity without excessive temperature rise during filter regeneration, maintaining low maintenance costs, and easily using a pressure sensor to detect the period when maintenance is required based on the PM accumulation amount.

[0012] Solutions to Problems

[0013] 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.

[0014] [Scheme 1]

[0015] A columnar honeycomb structure comprises: an outer peripheral sidewall; a plurality of inlet cells arranged 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 cells arranged on the inner peripheral side of the outer peripheral sidewall, 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, wherein:

[0016] At least some of the plurality of inlet cells are adjacent to at least some of the plurality of outlet cells via a partition wall.

[0017] The compartment density based on the total number of the plurality of inlet compartments and the plurality of outlet compartments is 35 to 47 compartments / cm 2 ,

[0018] If the average opening diameter of the discharge cells other than the discharge cells adjacent to the outer peripheral side wall among the plurality of discharge cells is set as D out The average opening diameter of the plurality of introduction compartments except the introduction compartments adjacent to the outer peripheral side wall is set as Din , then 0.78≤D in / D out ≤0.94.

[0019] [Scheme 2]

[0020] The honeycomb structure according to claim 1, wherein

[0021] The average value D of the opening diameters of the plurality of introduction compartments, excluding the introduction compartment adjacent to the peripheral side wall, is in is 1.07 mm or more and 1.29 mm or less,

[0022] The average value D of the opening diameters of the plurality of discharge compartments, excluding the discharge compartments adjacent to the outer peripheral side wall, is out It is 1.27 mm or more and 1.61 mm or less.

[0023] [Scheme 3]

[0024] The honeycomb structure according to claim 1 or 2, wherein

[0025] The average thickness of the partition walls is 0.19 mm or more and 0.26 mm or less.

[0026] [Scheme 4]

[0027] The honeycomb structure according to any one of aspects 1 to 3, wherein

[0028] The average porosity of the partition walls is 52 to 60%.

[0029] [Scheme 5]

[0030] The honeycomb structure according to any one of aspects 1 to 4, wherein

[0031] The ratio of the number of the plurality of inlet compartments excluding the inlet compartments adjacent to the outer peripheral sidewall to the number of the plurality of outlet compartments excluding the outlet compartments adjacent to the outer peripheral sidewall is 0.9 to 1.1.

[0032] [Scheme 6]

[0033] The honeycomb structure according to any one of aspects 1 to 5, wherein

[0034] If the bulk mass of particulate matter including soot per unit volume of the honeycomb structure is 1 g / L, the pressure loss when the exhaust gas at a temperature of 250° C. and a flow rate of 480 kg / hr passes from the inlet end face to the outlet end face is defined as P1,

[0035] When the bulk mass of the particulate matter including soot per unit volume of the honeycomb structure is 3 g / L, the pressure loss when the exhaust gas at a temperature of 250° C. and a flow rate of 480 kg / hr passes from the inlet end face to the outlet end face is defined as P2.

[0036] Then 54%<(P2-P1) / P1 is satisfied.

[0037] [Scheme 7]

[0038] The honeycomb structure according to any one of aspects 1 to 6, wherein

[0039] The partition walls contain cordierite.

[0040] [Scheme 8]

[0041] The honeycomb structure according to any one of aspects 1 to 7, wherein

[0042] A catalyst is supported in the introduction compartment.

[0043] Effects of the Invention

[0044] By using the honeycomb structure according to one embodiment of the present invention as an exhaust gas filter, the pressure loss after PM accumulation does not increase excessively, thereby reducing the frequency of filter regeneration and cleaning. At the same time, by increasing the change in pressure loss based on the amount of PM accumulation (pressure loss gradient), it is easy to detect the amount of PM accumulation suitable for filter regeneration and cleaning using a pressure sensor. In addition, no excessive temperature rise occurs during filter regeneration, thereby reducing the risk of filter damage. As a result, a filter can be obtained that can maintain low maintenance costs and easily detect the period when maintenance is required based on the amount of PM accumulation using a pressure sensor. Therefore, the possibility of filter damage due to excessive PM accumulation can be reduced. In this way, according to one embodiment of the present invention, it can be said that a honeycomb structure that is extremely excellent in practicality can be provided. BRIEF DESCRIPTION OF THE DRAWINGS

[0045] Figure 1 It is a perspective view schematically showing a wall-flow type honeycomb structure.

[0046] 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.

[0047] Figure 3 This is a schematic partial enlarged view of a partition wall of a honeycomb structure viewed from a cross section perpendicular to the direction in which cells extend.

[0048] Figure 4This is an explanatory diagram schematically showing an example of a method for forming a plugged portion using a squeegee method. DETAILED DESCRIPTION

[0049] 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.

[0050] (1. Honeycomb structure)

[0051] (1) Basic structure

[0052] 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 disposed 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 disposed 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.

[0053] In the honeycomb structure 100, at least a portion of the plurality of inlet cells 108 and at least a portion of the outlet cells 110 are adjacent to each other via a partition wall 112. When the inlet cells 108 and the outlet cells 110 are adjacent to each other via the partition wall 112, the surface of the partition wall 112 facilitates filtration. For example, if exhaust gas containing particulate matter such as soot is supplied to the inlet end face 104 on the upstream side of the honeycomb structure 100, the exhaust gas is introduced into the inlet cell 108 and moves downstream within the inlet cell 108. The outlet end face 106 on the downstream side of the inlet cell 108 is sealed, so the exhaust gas flows into the outlet cell 110 by passing through the partition wall 112 located between the adjacent inlet cells 108 and the outlet cells 110. The particulate matter cannot pass through the partition wall 112 and is therefore captured and accumulated within the inlet cell 108. After the particulate matter is removed, the clean exhaust gas that has flowed into the exhaust compartment 110 advances downstream in the exhaust compartment 110 and flows out from the outlet end surface 106 on the downstream side.

[0054] In a preferred embodiment, at least one of the plurality of discharge compartments 110 is adjacent only to the inlet compartment 108 (i.e., not adjacent to the discharge compartment 110 or the peripheral sidewall 102). This is because the discharge compartment 110 exerts a filtering effect by being adjacent to the inlet compartment 108. Furthermore, it is preferred that none of the plurality of discharge compartments 110 be adjacent to one another.

[0055] There is no limitation on the shape of the end face of the honeycomb structure 100. For example, it can be a circular shape such as a circle, 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.

[0056] 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.

[0057] (2) Compartment density

[0058] The cell density is an indicator showing the number of cells per unit area when the honeycomb structure is viewed from the inlet end face or the outlet end face. The cell density based on the total number of inlet cells and outlet cells is preferably 35 to 47 cells / cm 2 , more preferably 37 to 43 cells / cm 2 , more preferably 40 to 41 cells / cm 2 The cell density is calculated by dividing the total number of multiple inlet cells and multiple outlet cells (including sealed cells, outlet cells adjacent to the outer peripheral side wall, and inlet cells adjacent to the outer peripheral side wall) by the area of ​​one end face of the honeycomb structure other than the outer peripheral side wall.

[0059] (3) Opening diameter ratio (D in / D out )

[0060] In conventional honeycomb structures, the increase in pressure loss during PM accumulation is suppressed by making the opening diameter of the inlet cell larger than the opening diameter of the outlet cell. However, with such a structure, it is known that the pressure loss slope tends to become gentle. On the other hand, in a honeycomb structure according to one embodiment of the present invention, the increase in pressure loss during PM accumulation is promoted by making the opening diameter of the inlet cell appropriately smaller than the opening diameter of the outlet cell. In addition, by making the opening diameter of the inlet cell appropriately smaller than the opening diameter of the outlet cell, the initial pressure loss can be reduced, thereby also contributing to improved fuel economy.

[0061] Specifically, if the average opening diameter of the discharge cells other than the discharge cells adjacent to the outer peripheral side wall among the plurality of discharge cells is set to D out The average opening diameter of the plurality of introduction cells, excluding the introduction cells adjacent to the outer peripheral side wall, is set as D in , then it is preferred to satisfy 0.78≤D in ≤D out ≤0.94, more preferably 0.79≤D in ≤D out ≤0.88, more preferably 0.81≤D in ≤D out ≤0.86.

[0062] The opening diameter of each of the plurality of introduction compartments is defined as an equivalent circle diameter calculated based on the opening area of ​​the introduction compartment. in The diameter of the opening of each of the plurality of introduction cells is calculated based on the opening diameters of all the introduction cells except the introduction cells adjacent to the outer peripheral side wall.

[0063] The opening diameter of each of the plurality of discharge compartments is defined as an equivalent circle diameter calculated based on the opening area of ​​the discharge compartment. out It is calculated based on the opening diameters of all the discharge compartments except the discharge compartments adjacent to the outer peripheral side wall among the plurality of discharge compartments.

[0064] (4) Opening diameter

[0065] From the viewpoint of suppressing the initial pressure loss and preventing the pressure loss after PM accumulation from becoming excessive, the average opening diameter D of the plurality of inlet cells, excluding the inlet cell adjacent to the outer peripheral side wall, is in It is preferably 1.07 mm or more and 1.29 mm or less, more preferably 1.13 to 1.21 mm, and even more preferably 1.15 to 1.19. In addition, the average opening diameter D of the plurality of discharge cells, excluding the discharge cells adjacent to the outer peripheral side wall, is outIt is preferably 1.27 mm or more and 1.61 mm or less, more preferably 1.31 to 1.53 mm, and even more preferably 1.45 to 1.53 mm.

[0066] (5) Average thickness of partition walls

[0067] From the perspective of satisfying the above-mentioned cell density and ensuring practical heat capacity and strength of the honeycomb structure, the average thickness of the partition wall 112 is preferably greater than 0.19 mm and less than 0.26 mm, more preferably greater than 0.20 mm and less than 0.24 mm, and further preferably greater than 0.21 mm and less than 0.23 mm. Figure 3 is a schematic partial enlarged view of a honeycomb structure 100 in which the opening of the inlet cell 108 is a quadrilateral and the opening of the outlet cell 110 is an octagon, as viewed from a cross section perpendicular to the cell extension direction. The thickness of the partition wall 112 refers to the length D of the line segment that passes through the partition wall when connecting the centers of gravity O of adjacent cells in the cross section perpendicular to the cell extension direction (the height direction of the honeycomb structure). The average thickness of the partition wall 112 is calculated based on the thickness of all the partition walls 112.

[0068] 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.

[0069] (6) Average porosity of the partition wall

[0070] From the viewpoint of reducing pressure loss, the lower limit of the average porosity of the partition wall 112 is preferably 52% or more, more preferably 53% or more. In addition, from the viewpoint of improving the heat capacity and mechanical strength of the honeycomb structure, the upper limit of the average porosity of the partition wall is preferably 60% or less, more preferably 58% or less. Therefore, the average porosity of the partition wall is preferably, for example, 52 to 60%, more preferably 53 to 58%. In this specification, the porosity of the partition wall is measured by the mercury intrusion method specified in JIS R1655:2003 (Japanese Industrial Standards). In addition, regarding the average 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.

[0071] (7) Ratio of the number of inlet compartments to the number of outlet compartments

[0072] From the viewpoint of suppressing the increase in pressure loss and increasing the pressure loss inclination, the ratio of the number of the plurality of inlet cells to the number of the plurality of outlet cells is preferably 0.9 to 1.1, more preferably 0.95 to 1.05, further preferably 0.99 to 1.01, and most preferably 1. Furthermore, when calculating the ratio of the number of inlet cells to the number of outlet cells, the outlet cells adjacent to the outer peripheral side wall and the inlet cells adjacent to the outer peripheral side wall are not counted.

[0073] (8) Opening shape of compartment

[0074] The opening shape of the inlet compartment is not particularly limited. For example, in the cross section of the honeycomb structure perpendicular to the direction in which the compartment extends, it can be set to a polygon (quadrilateral (rectangle, square), pentagon, hexagon, heptagon, octagon, etc.), 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 inlet compartment adjacent to the outer peripheral side wall, the opening shape of each of the multiple inlet compartments is preferably all quadrilateral, and square is more preferred. In the case where the opening shape of the inlet compartment and the discharge compartment 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 is not particularly limited and may be set according to the opening shape of the introduction cell. For example, when the opening shape of the introduction cell is a quadrangle, it is preferably an octagon.

[0076] (9) Pressure loss tilt

[0077] If the change in pressure loss (pressure loss gradient) based on the amount of PM accumulated in the honeycomb structure is large, it is easy to detect the PM accumulation amount suitable for filter regeneration and cleaning using the pressure sensor.

[0078] Specifically, when the bulk mass of particulate matter including soot per unit volume of the honeycomb structure is 1 g / L, the pressure loss when exhaust gas at a temperature of 250°C and a flow rate of 480 kg / hr passes from the inlet end face to the outlet end face is defined as P1.

[0079] When the bulk mass of particulate matter including soot per unit volume of the honeycomb structure is 3 g / L, the pressure loss when the exhaust gas at a temperature of 250° C. and a flow rate of 480 kg / hr passes from the inlet end face to the outlet end face is defined as P2.

[0080] It is preferable to satisfy 54%<(P2-P1) / P1, more preferably to satisfy 57%≤(P2-P1) / P1, and even more preferably to satisfy 61%≤(P2-P1) / P1.

[0081] In addition, from the perspective of suppressing excessive pressure loss increase and ensuring practicality as a filter, it is preferred to satisfy (P2-P1) / P1≤76%, more preferably to satisfy (P2-P1) / P1≤72%, and even more preferably to satisfy (P2-P1) / P1≤69%.

[0082] Therefore, for example, the pressure loss gradient of the honeycomb structure preferably satisfies 54%<(P2-P1) / P1≤76%6, more preferably satisfies 57%≤(P2-P1) / P1≤72%, and further preferably satisfies 61%≤(P2-P1) / P1≤69%.

[0083] From the perspective of suppressing excessive pressure loss increase and ensuring practicality as a filter, the upper limit of P2 is preferably 5.00 kPa or less, more preferably 4.94 kPa or less, and even more preferably 4.93 kPa or less. From the perspective of improving the pressure loss slope, the lower limit of P2 is preferably 4.14 kPa or more, more preferably 4.38 kPa or more, and even more preferably 4.91 kPa or more.

[0084] (10) Material

[0085] 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.

[0086] 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.

[0087] In the case where the honeycomb structure is mainly composed of cordierite, the lower limit of the cordierite content of the partition walls, preferably the outer side walls and the partition walls, more preferably the outer side walls, the partition walls and the plugging parts of the honeycomb structure is preferably 90% by mass or more, more preferably 91% by mass or more, and further preferably 92% by mass or more. The lower limit is not particularly set, but from the perspective of changing the characteristics of the honeycomb structure by adding other ceramics, the upper limit of the cordierite content of the partition walls, preferably the outer side walls and the partition walls, more preferably the outer side walls, the partition walls and the plugging parts of the honeycomb structure is preferably 96% by mass or less, more preferably 95% by mass or less, and further preferably 94% by mass or less. Therefore, in the case where the honeycomb structure is mainly composed of cordierite, the cordierite content of the partition walls, preferably the outer side walls and the partition walls, more preferably the outer side walls, the partition walls and the plugging parts of the honeycomb structure is, for example, preferably 90 to 96% by mass, more preferably 91 to 95% by mass, and further preferably 92 to 94% by mass.

[0088] The cordierite content can be measured by X-ray diffraction. Specifically, using an X-ray diffractometer utilizing Cu Kα radiation (e.g., X'pert PRO manufactured by Malvern Panalytica), X-ray analysis is performed within the range of 2θ = 8 to 100° on samples of the peripheral sidewalls, partition walls, or sealed portions. Analysis is performed using the Rietveld analysis program RIEETAN to measure the cordierite crystal phase ratio, which is used as the cordierite content.

[0089] 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.

[0090] In one embodiment, with respect to the sealing portions of the inlet end face and the outlet end face, the average depth of the sealing portions is 2 to 8 mm. By having an average depth of the sealing portions of 2 mm or more, the strength of the sealing portions can be ensured. The average depth of the sealing portions is preferably 3 mm or more. In addition, by making the average depth of the sealing portions 8 mm or less, the area of ​​the partition wall for capturing particulate matter in the compartment can be prevented from becoming smaller. The average depth of the sealing portions is preferably 7 mm or less. The depth of the sealing portion in the direction in which the compartment extends is measured at any 20 locations on each end face, and the average value is taken as the average depth of the sealing portion of each end face. The depth of each sealing portion refers to the length in the direction in which the compartment extends 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.

[0091] 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. The catalyst is preferably supported in the inlet compartment. The catalyst is not limited, and examples include an oxidation catalyst (DOC) for oxidizing and burning hydrocarbons (HC) and carbon monoxide (CO) to increase the exhaust gas temperature, 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 that can simultaneously remove hydrocarbons (HC), carbon monoxide (CO) and nitrogen oxides (NOx). The catalyst may 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.

[0092] (11) Density

[0093] From the perspective of ensuring practical heat capacity, the honeycomb structure preferably has a high mass per unit volume, that is, a high density. The density referred to here is a value calculated based on the volume measured by the external dimensions of the honeycomb structure, without considering the internal cell structure and pores. Specifically, the lower limit of the density of the honeycomb structure is preferably 0.36 g / cm 3 More than 0.37 g / cm 3 More preferably, 0.38 g / cm 3 The upper limit of the density of the honeycomb structure is not particularly limited, but is preferably 0.41 g / cm 3 from the perspective of the cell structure and ease of manufacturing of the material. 3 Below, more preferably 0.40g / cm 3 Below, more preferably 0.39 g / cm 3 Therefore, for example, the density of the honeycomb structure is preferably 0.36 to 0.41 g / cm3 , more preferably 0.37 to 0.40 g / cm 3 , more preferably 0.38 to 0.39 g / cm 3 .

[0094] (2. Method for Manufacturing Honeycomb Structure)

[0095] 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.

[0096] 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).

[0097] 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.

[0098] 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 90 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.

[0099] 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 improving the porosity of the honeycomb structure after calcination, the content of the pore-forming material is preferably 3 parts by weight or more, more preferably 6 parts by weight or more, and further preferably 9 parts by weight or more relative to 100 parts by weight of the cordierite 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 relative to 100 parts by weight of the cordierite raw material.

[0100] 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.

[0101] 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.

[0102] 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.

[0103] 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.

[0104] Illustratively, the slurry for forming the sealing 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 sealing 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.

[0105] 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.

[0106] 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.

[0107] 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.

[0108] 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.

[0109] 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.

[0110] 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 .

[0111] 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 .

[0112] 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 filler, and therefore can be trimmed off as needed.

[0113] 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 29 to 50 μm, can be suitably used.

[0114] 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.

[0115] 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.

[0116] 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.

[0117] [Example]

[0118] Hereinafter, examples are described for better understanding of the present invention and its advantages, but the present invention is not limited to the examples.

[0119] (1. Production of honeycomb structure).

[0120] [Honeycomb structures made of cordierite: Examples 1 to 10, Comparative Examples 1 to 4]

[0121] To 100 parts by weight of a cordierite-forming raw material, 5 parts by weight of a pore-forming material, 60 parts by weight of a dispersion medium, and 4 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. Methylcellulose 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. 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%.

[0122] 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.

[0123] 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.

[0124] 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.

[0125] Next, the honeycomb formed body with each sealed portion formed thereon was degreased and calcined to produce the honeycomb structure corresponding to each test number. The inlet end face and the outlet end face of the honeycomb structure thus obtained were in the shape of a circular cylinder. The diameter of the inlet end face and the outlet end face was 228.6 mm. The length of the cell extension direction of the honeycomb structure was 184.2 mm. With respect to Comparative Example 1, except for the inlet cell adjacent to the outer peripheral side wall, the opening shape of the inlet cell was an octagon, and except for the outlet cell adjacent to the outer peripheral side wall, the opening shape of the outlet cell was a square. With respect to Examples 1 to 10, Comparative Examples 3 and 4, except for the inlet cell adjacent to the outer peripheral side wall, the opening shape of the inlet cell was a square, and except for the outlet cell adjacent to the outer peripheral side wall, the opening shape of the outlet cell was an octagon. With respect to Comparative Example 2, the opening shape of both the inlet cell and the outlet cell was a square. The average depth of the sealed portion of the inlet end face and the outlet end face was approximately 7 mm. The honeycomb structures were prepared in the number required to determine the following characteristics.

[0126] (2. Structural characteristics of honeycomb structure)

[0127] Table 1 shows the following structural characteristics of the honeycomb structures according to the test numbers manufactured above.

[0128] Compartment density

[0129] Average thickness of the partition wall

[0130] The average value D of the opening diameters of the plurality of inlet compartments, excluding the inlet compartment adjacent to the peripheral side wall in

[0131] The average value D of the opening diameters of the plurality of discharge compartments, excluding the discharge compartments adjacent to the peripheral side wall out

[0132] ·Opening diameter ratio (D in / D out )

[0133] Average porosity of the partition wall

[0134] The ratio of the number of inlet compartments to the number of outlet compartments

[0135] Density (mass of honeycomb structure divided by overall dimensions)

[0136] The cell density refers to the cell density based on the total number of inlet cells and outlet cells, and is measured according to the above method.

[0137] The average thickness of the partition walls is measured by observation with a scanning electron microscope (SEM) or using a microscope.

[0138] The opening diameter of each of the introduction cell and the discharge cell is observed using a scanning electron microscope (SEM) or calculated using a microscope.

[0139] Based on the opening diameters of all the discharge compartments except the discharge compartments adjacent to the outer peripheral side wall among the plurality of discharge compartments, an average value D is calculated. out .

[0140] Based on the opening diameters of all the introduction cells except the introduction cells adjacent to the outer peripheral side wall among the plurality of introduction cells, the average value D is calculated. in .

[0141] The porosity of the cell walls was measured by the above-mentioned mercury intrusion method using Autopore 9500 (trade name) manufactured by Micromeritics.

[0142] The ratio of the number of inlet cells to the number of outlet cells was calculated by visually counting the number of outlet cells and the number of inlet cells, excluding cells adjacent to the outer peripheral side wall.

[0143] (3. Functional characteristics of honeycomb structure)

[0144] The honeycomb structures corresponding to the test numbers prepared above were used as exhaust gas filters, and the following characteristics were evaluated.

[0145] [Pressure loss characteristics]

[0146] An exhaust filter was installed in the exhaust system of a diesel engine with a 13-liter exhaust volume, and a test was conducted to cause soot to accumulate on the filter. Furthermore, when soot accumulated, the fuel injection pressure was reduced to facilitate soot generation, and the engine was operated at a low exhaust temperature of less than 280°C at the filter inlet to prevent soot combustion. The pressure loss at the start of the test (before soot accumulation) (initial pressure loss), the pressure loss when the soot accumulation amount (g) per liter of filter volume was 1g / L (P1), and the pressure loss when the soot accumulation amount (g) per liter of filter volume was 3g / L (P2) were measured. To measure the pressure loss, the engine output was increased, and the pressure loss was measured when exhaust gas at a temperature of 250°C at the filter inlet and a flow rate of 480kg / hr passed from the inlet end face to the outlet end face. The results are shown in Table 1.

[0147] Taking Comparative Example 2, which is a representative example of a conventional honeycomb structure, as a benchmark, all the acceptance criteria for pressure loss characteristics satisfy the following conditions: The acceptance criteria for pressure loss characteristics are determined in consideration of the influence on fuel consumption.

[0148] Initial pressure loss is less than 1.01kPa;

[0149] The pressure loss (P1) when the accumulation of soot is 1g / L is less than 3.07kPa;

[0150] The pressure loss (P2) is less than 5.00 kPa when the accumulation of soot is 3 g / L;

[0151] (P2-P1) / P1, which is an indicator of the pressure loss inclination, exceeds 54%.

[0152] [Table 1]

[0153]

[0154] [Investigation]

[0155] In Comparative Example 1, the opening diameter of the introduction cell is larger than the opening diameter of the discharge cell, and therefore the pressure loss gradient is small.

[0156] In Comparative Example 2, the opening diameter of the discharge cell is the same as the opening diameter of the introduction cell. Although this is improved compared to Comparative Example 1, the pressure loss inclination is still small.

[0157] In Comparative Example 3, the opening diameter of the introduction cell is smaller than the opening diameter of the discharge cell, so the pressure loss gradient is large. However, since the opening diameter of the introduction cell is too small, the initial pressure loss increases.

[0158] In Comparative Example 4, since the cell density was too low, the pressure loss during soot accumulation increased excessively.

[0159] In contrast, Examples 1 to 10 exhibited appropriate cell density, opening diameter ratios, and other factors, resulting in a lower initial pressure loss than in Comparative Example 2. Meanwhile, the pressure loss during soot accumulation increased moderately, resulting in a larger pressure loss gradient. Furthermore, given the density, the resulting heat capacity was practical.

[0160] Explanation of symbols

[0161] 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 peripheral side of the outer peripheral 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, The honeycomb structure is characterized in that At least some of the plurality of inlet cells are adjacent to at least some of the plurality of outlet cells via a partition wall. The compartment density based on the total number of the plurality of inlet compartments and the plurality of outlet compartments is 35 to 47 compartments / cm 2 , If the average opening diameter of the discharge cells other than the discharge cells adjacent to the outer peripheral side wall among the plurality of discharge cells is set as D out The average opening diameter of the plurality of introduction compartments except the introduction compartments adjacent to the outer peripheral side wall is set as D in , then 0.78≤D in / D out ≤0.

94.

2. The honeycomb structure according to claim 1, wherein The average value D of the opening diameters of the plurality of introduction compartments, excluding the introduction compartment adjacent to the peripheral side wall, is in is 1.07 mm or more and 1.29 mm or less, The average value D of the opening diameters of the plurality of discharge compartments, excluding the discharge compartments adjacent to the outer peripheral side wall, is out It is 1.27 mm or more and 1.61 mm or less.

3. The honeycomb structure according to claim 1, wherein The average thickness of the partition walls is 0.19 mm or more and 0.26 mm or less.

4. The honeycomb structure according to claim 1 or 2, characterized in that The average porosity of the partition walls is 52 to 60%.

5. The honeycomb structure according to claim 1 or 2, characterized in that: The ratio of the number of the plurality of inlet compartments excluding the inlet compartments adjacent to the outer peripheral sidewall to the number of the plurality of outlet compartments excluding the outlet compartments adjacent to the outer peripheral sidewall is 0.9 to 1.

1.

6. The honeycomb structure according to claim 1 or 2, characterized in that: If the bulk mass of particulate matter including soot per unit volume of the honeycomb structure is 1 g / L, the pressure loss when the exhaust gas at a temperature of 250° C. and a flow rate of 480 kg / hr passes from the inlet end face to the outlet end face is defined as P1, When the bulk mass of the particulate matter including soot per unit volume of the honeycomb structure is 3 g / L, the pressure loss when the exhaust gas at a temperature of 250° C. and a flow rate of 480 kg / hr passes from the inlet end face to the outlet end face is defined as P2. Then 54%<(P2-P1) / P1 is satisfied.

7. The honeycomb structure according to claim 1 or 2, characterized in that: The partition walls contain cordierite.

8. The honeycomb structure according to claim 1 or 2, characterized in that: A catalyst is supported in the introduction compartment.

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