JP6012369B2 - Plugged honeycomb structure - Google Patents

Description

  The present invention relates to a plugged honeycomb structure used as a filter for collecting particulate matter such as soot contained in exhaust gas discharged from an internal combustion engine such as a diesel engine or various combustion apparatuses. About.

  Exhaust gas discharged from an internal combustion engine such as a diesel engine or various combustion apparatuses contains a large amount of particulate matter (particulate matter (PM)) mainly composed of soot. When this PM is released into the atmosphere as it is, environmental pollution is caused. Therefore, an exhaust system such as an internal combustion engine or a combustion apparatus is equipped with a filter (for example, a diesel particulate filter) for collecting PM. ing.

  In general, a plugged honeycomb structure including a honeycomb structure made of a ceramic material or the like and a plugging portion is used for such a filter. The honeycomb structure is a main part of the plugged honeycomb structure, and is a porous structure that partitions and forms a plurality of cells extending from an inlet end surface that is a fluid (exhaust gas) inlet side to an outlet end surface that is a fluid outlet side. Has a quality partition. Then, the plugged honeycomb structure is configured by plugging the opening end portion on the inlet end face side of the predetermined cell of this honeycomb structure and the opening end portion on the outlet end face side of the remaining cells with the plugging portion. Is done.

  When exhaust gas containing PM is allowed to flow into the remaining cells from the inlet end face of such a plugged honeycomb structure, the exhaust gas passes through the porous partition walls and flows into the adjacent predetermined cells, and then exits. It is discharged from the end face. And PM is collected on a partition, when exhaust gas passes a porous partition.

  Conventionally, in the honeycomb structure that forms the main part of the plugged honeycomb structure, the cell shape in a cross section perpendicular to the cell length direction (hereinafter sometimes simply referred to as “cell shape”) is square. The thing and the hexagonal thing are mainly used (for example, refer patent document 1).

Japanese Patent No. 4944057

  When the plugged honeycomb structure is used as a filter for collecting PM, the important characteristics required for the honeycomb structure forming the main part of the plugged honeycomb structure are as follows. Strength. That is, when the plugged honeycomb structure is used as a filter for collecting PM, the clogging of the partition walls progresses as the collected PM accumulates on the partition walls, and the filter performance decreases. Therefore, it is necessary to periodically perform a regeneration process for burning and removing the accumulated PM. Here, in order to burn and remove PM, it is necessary to raise the temperature of the filter to the combustion temperature of PM, and the temperature rise performance of the honeycomb structure is an important characteristic for rapidly raising the temperature. Further, the heat retaining property is an important characteristic from the viewpoint of maintaining the combustion temperature after the filter has been heated to the combustion temperature of PM. In addition, the filter is usually mounted in an exhaust system such as an internal combustion engine or a combustion device in a state where it is stored (canned) in a cylindrical can body, and the pressure applied to the outer peripheral surface of the honeycomb structure during the storage Therefore, strength is also an important characteristic in order to prevent the honeycomb structure from being damaged.

  However, there is a trade-off relationship between the temperature rise property, the heat retention property, and the strength of the honeycomb structure. That is, in the honeycomb structure 30 having a square cell shape as shown in FIG. 6 and the honeycomb structure 40 having a hexagonal cell shape as shown in FIG. It is necessary to reduce the heat capacity, for example, by reducing the thickness. In this case, although the temperature rise performance of the honeycomb structure is increased, the heat retention is lowered due to the reduction of the heat capacity. In addition, when the partition wall thickness is reduced, the strength of the honeycomb structure naturally decreases. On the other hand, in the honeycomb structure 30 and the honeycomb structure 40, if the heat retention and the strength are to be increased, the heat capacity is increased by increasing the thickness of the partition wall 14 and the strength of the partition wall 14 itself is improved. There is a need. In this case, although the heat retaining property and strength of the honeycomb structure are increased, the temperature rise property is decreased due to the increase of the heat capacity.

  Therefore, in a plugged honeycomb structure in which the conventional cell shape is a rectangular or hexagonal honeycomb structure as a main part, both the temperature rise property, the heat retention property and the strength are used as a filter for collecting PM. It has been difficult to raise the level to a satisfactory level.

  The present invention has been made in view of such a problem, and is capable of achieving both high temperature and heat retention and strength at a high level that can be sufficiently satisfied as a filter for collecting PM. An object is to provide a stationary honeycomb structure.

  In order to achieve the above object, according to the present invention, the following plugged honeycomb structure is provided.

[1] A honeycomb structure having a porous partition wall defining a plurality of cells extending from an inlet end surface serving as a fluid inlet side to an outlet end surface serving as a fluid outlet side, and an opening on the inlet end surface side of a predetermined cell A plugging portion for plugging an opening and an opening end on the outlet end face side of the remaining cells, and the shape of the cell in a cross section perpendicular to the cell extending direction is a hexagon, The six corners of the regular hexagon have three square vertices that exist every other in the circumferential direction of the regular hexagon, and “the other three are parallel to each diagonal line connecting the three vertices and the other three ends. A shape having six new vertices formed by cutting corners including the remaining three vertices by line segments on the sides forming the vertices, and between adjacent cells. And the new vertex and As sides each other connecting the vertices other than the serial new vertex is opposed in parallel with, the plugged honeycomb structure in which the plurality of cells are arranged.

[2] Each of the line segments, the distance to the nearest line segment on each of the remaining three vertices of said segments from each of the remaining three vertices is a, the remaining three eyes according to the distance from each vertex to the nearest diagonal to each of the remaining three vertices among the diagonal lines when the p, satisfies the relation of the following formula (1) [1] Sealed honeycomb structure.
0.2p ≦ a ≦ 0.7p (1)

[3] The plugged honeycomb structure according to [1] or [2], wherein the partition wall has a thickness of 203 to 508 μm.

[4] The plugged honeycomb structure according to any one of [1] to [3], which is used as a diesel particulate filter.

  The plugged honeycomb structure of the present invention can achieve both high temperature rise and high heat retention and strength. Therefore, when the plugged honeycomb structure of the present invention is used as a filter for collecting PM, the temperature can be quickly raised to the combustion temperature of PM during the regeneration process, and the combustion temperature of the PM can be increased. It is easy to maintain and exhibits high regeneration efficiency. Also, damage during canning hardly occurs.

1 is a partial cross-sectional view showing a part of a cross section perpendicular to a cell extending direction of a honeycomb structure used in an embodiment of a plugged honeycomb structure of the present invention. 1 is a cross-sectional view showing a cross section parallel to a cell extending direction of one embodiment of a plugged honeycomb structure of the present invention. It is a partial top view which shows a part of end surface of one Embodiment of the plugged honeycomb structure of this invention. It is a schematic diagram for demonstrating the cell shape of the plugged honeycomb structure of this invention. It is a graph for demonstrating the evaluation method of the temperature rising property and heat retention in an Example. FIG. 6 is a partial cross-sectional view showing a part of a cross section perpendicular to a cell extending direction of a honeycomb structure having a square cell shape used in a conventional plugged honeycomb structure. FIG. 10 is a partial cross-sectional view showing a part of a cross section perpendicular to the cell extending direction of a hexagonal honeycomb structure used in a conventional plugged honeycomb structure. 4 is a partial plan view showing a part of an end face of a plugged honeycomb structure of Comparative Examples 1, 3, 5, and 7. FIG. 4 is a partial plan view showing a part of an end surface of a plugged honeycomb structure of Comparative Examples 2, 4, 6, and 8. FIG.

  Hereinafter, embodiments of the present invention will be specifically described. However, the present invention is not limited to the following embodiments, and is based on ordinary knowledge of those skilled in the art without departing from the spirit of the present invention. In addition, it should be understood that modifications, improvements, and the like appropriately added to the following embodiments also fall within the scope of the present invention.

(1) Plugged honeycomb structure:
FIG. 1 is a partial cross-sectional view showing a part of a cross section perpendicular to a cell extending direction of a honeycomb structure used in an embodiment of a plugged honeycomb structure of the present invention. FIG. 2 is a cross-sectional view showing a cross section parallel to the cell extending direction of one embodiment of the plugged honeycomb structure of the present invention. FIG. 3 is a partial plan view showing a part of the end face of one embodiment of the plugged honeycomb structure of the present invention. FIG. 4 is a schematic view for explaining the cell shape of the plugged honeycomb structure of the present invention.

  As shown in FIG. 2, the plugged honeycomb structure 20 of the present invention partitions and forms a plurality of cells 13 that extend from an inlet end surface 11 that is a fluid (exhaust gas) inlet side to an outlet end surface 12 that is a fluid outlet side. A honeycomb structure 10 having porous partition walls 14 is provided. The honeycomb structure 10 further includes a plugging portion 21 that plugs the opening end portion of the predetermined cell on the inlet end face 11 side and the opening end portion of the remaining cell on the outlet end face 12 side. In the cell 13, only one of the opening end on the inlet end face 11 side and the opening end on the outlet end face 12 side is plugged. That is, in the predetermined cell, only the opening end on the inlet end surface 11 side is plugged with the plugging portion 21, and the opening end on the outlet end surface 12 side is not plugged. On the other hand, in the remaining cells, only the opening end portion on the outlet end surface 12 side is plugged by the plugging portion 21, and the opening end portion on the inlet end surface 11 side is not plugged.

  When exhaust gas containing PM flows from the inlet end surface 11 of such a plugged honeycomb structure 20 into the remaining cells, the exhaust gas flows through the porous partition walls 14 and flows into the predetermined cells adjacent thereto, Then, it discharges | emits from an exit end surface. PM is collected on the partition wall 14 when the exhaust gas passes through the porous partition wall 14.

  The arrangement of the plugging portions 21 is not particularly limited, but as shown in FIG. 3, in a certain direction (in the direction of the arrow in FIG. 3) on each end face (inlet end face and outlet end face) of the honeycomb structure. It is preferable that every other open end of the cells 13 is plugged with plugging portions 21.

  The honeycomb structure 10 used in the plugged honeycomb structure 20 of the present invention is characterized in that the cell shape is a specific nine-sided polygon. The specific shape of this hexagon is specified as follows. First, as shown in FIG. 4, a diagonal line 4 (4A, 4B) connecting three vertices 1 (1A, 1B, 1C) that exist every other in the circumferential direction of the regular hexagon among the six vertices of the regular hexagon. , 4C). Then, the remaining 3 by the line segment 5 (5A, 5B, 5C) which is parallel to each diagonal line 4 and whose both ends are on the sides forming the remaining three vertices 2 (2A, 2B, 2C), respectively. The corners 6 (6A, 6B, 6C) each including the two apexes 2 are cut. Here, the “corner” is a part of the side forming the remaining three vertices 2 and the remaining three vertices 2 (dotted line portion in FIG. 4).

  By cutting the corner portion 6 in this way, six new vertices 3 (3A, 3B, 3C, 3D, 3E, 3F) are formed. As a result, a honeycomb structure having a nine-sided shape having the three vertices 1 (1A, 1B, 1C) and the six new vertices 3 (3A, 3B, 3C, 3D, 3E, 3F) Ten cell shapes are obtained. The new vertex 3 is formed by a part of the side that formed the remaining three vertices 2 after cutting the corner portion 6 (the portion remaining after cutting the corner portion 6) and the line segment 5. Is done. That is, three of the nine sides of the nine-sided polygon obtained as described above are the line segment 5.

  In the honeycomb structure 10, as shown in FIG. 1, between the adjacent cells 13 and 13, the sides connecting the new vertex 3 of the nine-sided shape and the vertex 1 other than the new vertex are parallel to each other. A plurality of cells 13 are arranged so as to face each other. Note that the portion between the opposing sides becomes the partition wall 14 of the honeycomb structure 10. By arranging the plurality of cells 13 having the above-mentioned hexagonal cell shape in this way, in the direction of the arrow in FIG. It will be in the formed state. In other words, the honeycomb structure of the present invention has both the intersection 16 of the small partition and the intersection 17 of the large partition.

  On the other hand, as shown in FIG. 6, a honeycomb structure 30 having a square cell shape used in a conventional plugged honeycomb structure has only small partitioning intersections 36 having a constant size. Similarly, the honeycomb structure 40 having a hexagonal cell shape used in the conventional plugged honeycomb structure as shown in FIG. 7 is also only an intersection 46 of small partition walls having a constant size. do not have.

  Therefore, when the material, volume (the entire volume including the cell portion), cell density, partition wall thickness, and the like are the same, the honeycomb structure 10 having the large partition wall intersection has only the small partition wall intersection. The heat capacity is larger than that of the honeycomb structure 30 or the honeycomb structure 40. Further, the honeycomb structure 10 has a thick portion (intersection portion 17 of a large partition wall) that does not exist in the honeycomb structure 30 or the honeycomb structure 40. Therefore, the honeycomb structure 10 exhibits higher heat retention and strength than the honeycomb structure 30 and the honeycomb structure 40.

  In the honeycomb structure 10, the number of intersections 17 of the large partition walls is approximately half of the number of intersections of all the partition walls of the honeycomb structure 10, and the remaining approximately half is the intersection part 16 of the small partition walls. is there. In the honeycomb structure 10, the thick portion is only the intersection 17 of the large partition wall, and the partition wall 14 itself is not thick. For this reason, the honeycomb structure 10 does not have an excessively large heat capacity. Therefore, the honeycomb structure 10 exhibits a high heat retaining property and strength while the temperature rise performance is greatly inferior to the honeycomb structure 30 having a rectangular cell shape and the honeycomb structure 40 having a hexagonal cell shape. There is no. That is, when the material, volume (total volume including the cell portion), cell density, partition wall thickness, and the like are the same, the honeycomb structure 10 has a temperature rise property of the honeycomb structure 30 having a square cell shape or the cell shape. Is equivalent to or slightly inferior to the temperature rise property of the hexagonal honeycomb structure 40.

  From the above, the honeycomb structure 10 can achieve both high temperature rising property and high heat retaining property and strength. Therefore, when the plugged honeycomb structure 20 of the present invention is used as a filter for collecting PM, the filter can be quickly used during the regeneration process due to the high temperature rise property of the honeycomb structure 10 that forms the main part thereof. The temperature can be raised to the combustion temperature of PM. Further, due to the high heat retention of the honeycomb structure 10, it is easy to maintain the combustion temperature after the filter is heated to the combustion temperature of PM. Further, due to the high strength of the honeycomb structure 10, damage during canning hardly occurs.

In the honeycomb structure 10 used for the plugged honeycomb structure 20 of the present invention, it is preferable that the line segment 5 when the above-described cell shape is specified satisfies a predetermined condition. As shown in FIG. 4, when the distance from the remaining three vertices 2 to the line segment 5 is a and the distance from the remaining three vertices 2 to the diagonal line 4 is p, as shown in FIG. The conditions satisfy the relationship of the following formula (1).
0.2p ≦ a ≦ 0.7p (1)

  When the nine-sided shape obtained by cutting the corner portion 6 with the line segment 5 satisfying such a condition is the cell shape of the honeycomb structure 10, the temperature rise property, the heat retaining property and the strength of the honeycomb structure 10 Can be balanced at a high level. If a is less than 0.2p, the superiority of heat retention and strength over the honeycomb structure having a square or hexagonal cell shape may not be sufficiently exhibited. Moreover, when a is larger than 0.7 p, the temperature rise property may be insufficient.

  In the present invention, the thickness of the partition wall 14 of the honeycomb structure 10 is preferably 203 to 508 μm, and more preferably 254 to 432 μm. By setting the thickness of the partition wall 14 to such a range, it becomes easy to achieve a good balance between the temperature rise property, the heat retention property, and the strength. Moreover, the excessive raise of the pressure loss at the time of using the plugged honeycomb structure 20 of this invention as a filter for collecting PM can be suppressed. If the partition wall 14 is thinner than 203 μm, the heat retention and strength of the honeycomb structure 10 may be insufficient. Further, if the partition wall 14 is thicker than 508 μm, the temperature rise of the honeycomb structure 10 becomes insufficient, or the plugged honeycomb structure 20 of the present invention is used as a filter for collecting PM. The pressure loss may become too large.

Cell density of the honeycomb structure 10 is preferably from 140 to 543 cells / cm ^2, more preferably 155 to 465 cells / cm ^2. By setting the cell density in such a range, high filter performance is achieved while suppressing an excessive increase in pressure loss when the plugged honeycomb structure 20 of the present invention is used as a filter for collecting PM. Can be demonstrated. When the cell density is lower than 140 cells / cm ² , the area of the partition wall for collecting PM may be too small. On the other hand, if the cell density is higher than 543 cells / cm ² , the pressure loss may become too large when the plugged honeycomb structure 20 of the present invention is used as a filter for collecting PM.

  The aperture ratio of the honeycomb structure 10 is preferably 20 to 55%, and more preferably 25 to 50%. When the aperture ratio is lower than 20%, the pressure loss may be excessive when the plugged honeycomb structure 20 of the present invention is used as a filter for collecting PM. Further, if the aperture ratio is higher than 55%, the heat retention and strength of the honeycomb structure 10 may be insufficient. The “aperture ratio” here refers to the ratio of the cell cross-sectional area to the total area of the cross section perpendicular to the longitudinal direction of the honeycomb structure (the area including the cell cross-sectional area).

  The shape of the honeycomb structure 10 is not particularly limited. For example, the cylindrical shape of the bottom surface (cylindrical shape), the cylindrical shape of the oval shape of the bottom surface, and the polygonal shape of the bottom surface (square, pentagon, hexagon, heptagon, octagon) Etc.). Further, the size of the honeycomb structure 10 is not particularly limited, and when used as a catalyst carrier of an exhaust gas purification catalyst, a size capable of satisfying the required purification performance can be appropriately selected.

  As a material which comprises the honeycomb structure 10, the material which has ceramics as a main component, or a sintered metal can be mentioned as a suitable example. When the honeycomb structure is made of a material mainly composed of ceramics, the ceramics include silicon carbide, cordierite, alumina titanate, sialon, mullite, silicon nitride, zirconium phosphate, zirconia, titania. Preferred examples include alumina, silica, zeolite and the like, or combinations thereof.

  It is preferable to use the same material as the material constituting the honeycomb structure 10 as the material constituting the plugged portion 21. By doing so, the difference in thermal expansion between the honeycomb structure 10 and the plugging portion 21 can be reduced, and the thermal stress generated between the honeycomb structure 10 and the plugging portion 21 can be reduced. .

  The plugged honeycomb structure of the present invention is used as a filter or the like for collecting PM such as soot contained in exhaust gas discharged from an internal combustion engine such as a diesel engine or various combustion devices. be able to. In particular, it can be suitably used as a diesel particulate filter (DPF) for collecting PM contained in exhaust gas discharged from a diesel engine.

(2) Manufacturing method of plugged honeycomb structure:
In the plugged honeycomb structure of the present invention, first, a honeycomb structure (honeycomb structure without a plugging portion) is produced, and one open end (inlet end face side or outlet) of each cell of the honeycomb structure. It can be manufactured by forming a plugging portion at the opening end on the end face side.

  The honeycomb structure can be basically manufactured by a manufacturing method similar to a conventionally known manufacturing method of a honeycomb structure. That is, except that a forming die having a shape corresponding to the hexagonal cell shape as described above is used, in the same manner as a conventionally known method for manufacturing a honeycomb structure, a honeycomb-shaped formed body ( Honeycomb formed body) is obtained, and this can be produced by drying and firing.

  A forming raw material of the honeycomb formed body is prepared by adding a binder, a surfactant, a pore former, water, or the like to a powder such as ceramics as a main component.

  Examples of the binder include methyl cellulose, hydroxypropyl methyl cellulose, hydroxypropoxyl cellulose, hydroxyethyl cellulose, carboxymethyl cellulose, and polyvinyl alcohol. The content of the binder is preferably 2.0 to 10.0 parts by mass when the mass of powder such as ceramics as a main component is 100 parts by mass.

  The water content is preferably 20 to 60 parts by mass when the mass of the powder such as ceramics as the main component is 100 parts by mass.

  As the surfactant, ethylene glycol, dextrin, fatty acid soap, polyalcohol and the like can be used. The content of the surfactant is preferably 0.1 to 2.0 parts by mass when the mass of the powder such as ceramic as the main component is 100 parts by mass.

  As the pore former, graphite, starch, foamed resin, water absorbent resin, silica gel or the like can be used. The content of the pore former is preferably 0.5 to 10.0 parts by mass when the mass of the ceramics as a main component is 100 parts by mass.

  The forming raw material is kneaded by a kneader, a vacuum kneader, or the like, and a honeycomb formed body is formed by extrusion molding or the like using this kneaded material.

  The drying method of the honeycomb formed body is not particularly limited. For example, an electromagnetic heating method drying method such as microwave heating drying or high frequency dielectric heating drying, or an external heating method drying method such as hot air drying or superheated steam drying is used. Can do. After a certain amount of moisture is dried by the electromagnetic heating method drying method, the remaining moisture may be dried by the external heating method drying method.

  Firing of the dried honeycomb formed body (honeycomb dry body) is performed using an electric furnace, a gas furnace, or the like. Firing conditions such as a firing atmosphere, a firing temperature, and a firing time can be appropriately determined according to the constituent material of the honeycomb dried body. The firing may be performed together with the firing of the plugged portion after the plugged portion is formed at the opening end of the cell.

  A conventionally known method can also be used as a method of forming the plugging portion at the opening end of the cell. As an example of a specific method, first, a sheet is attached to the end face of the honeycomb structure manufactured by the above method. Next, a hole is made in the sheet at a position corresponding to the cell in which the plugging portion is to be formed. Next, with the sheet attached, the end face of the honeycomb structure is immersed in a plugging slurry in which the constituent material of the plugging portion is slurried, and the plugging is made through the holes formed in the sheet. The plugging slurry is filled into the open end of the cell to be stopped. The plugging slurry thus filled is dried and then fired and cured to form a plugging portion.

  EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples, but the present invention is not limited to these examples.

(Examples 1-9)
For 100 parts by mass of the cordierite forming material, 5.0 parts by mass of foamed resin as a pore-forming agent, 5.0 parts by mass of methylcellulose as a binder, 1.0 part by mass of ethylene glycol as a surfactant, and water as a dispersion medium 40 parts by mass was added and kneaded to prepare a clay. Here, “cordierite raw material” means a raw material that becomes cordierite by firing. In this example, as a cordierite forming raw material, a mixture of 41% by mass of talc, 19% by mass of kaolin, 25% by mass of aluminum oxide, and 15% by mass of silica was used. The thus prepared kneaded material was vacuum degassed and then extrusion molded using a molding die capable of obtaining a hexagonal cell shape as shown in FIG. 1 to obtain a honeycomb formed body. Next, the obtained honeycomb formed body was dried with a microwave dryer and further completely dried with a hot air dryer to obtain a honeycomb dried body.

  Next, plugged portions were formed at one open end of each cell of the dried honeycomb body. As shown in FIG. 3, the plugging portion is formed in such a way that the open end portion of the cell 13 is in the fixed direction (arrow direction in FIG. 3) on each end face (inlet end face and outlet end face) of the honeycomb structure. Every other plugging was performed by the sealing portion 21. As a method for forming the plugged portions, first, a sheet was attached to the end face of the dried honeycomb body, and holes were formed in the sheet at positions corresponding to the cells where the plugged portions were to be formed. Subsequently, with the sheet attached, the end face of the honeycomb dried body is immersed in a plugging slurry in which the constituent material of the plugging portion is slurried, and the plug is sealed through the holes formed in the sheet. The plugging slurry was filled into the open end of the cell to be stopped. In addition, the cordierite-forming raw material was used for the constituent material of the plugging portion.

  Thus, after drying the plugging slurry filled in the open ends of the cells, this honeycomb dried body is fired at a maximum temperature range of 1400 to 1430 ° C., so that the cell shape is a hexagonal shape. The plugged honeycomb structures of Examples 1 to 9 were obtained in which the values of the distance a shown in FIG. As shown in Table 1, the volume (the entire volume including the cell portion), the partition wall thickness, and the cell density are the same in any of the honeycomb structures of Examples 1-9.

(Comparative Example 1)
Except for using a die for forming a square cell shape as shown in FIG. 6, in the same manner as in Examples 1 to 9, the cell shape is a square, and the volume, partition wall thickness, and cell density were measured. A plugged honeycomb structure of Comparative Example 1 which is the same as the plugged honeycomb structure of Examples 1 to 9 was obtained. As shown in FIG. 8, the plugged portions are formed in a cell 13 in which the plugged portion 21 is formed at the opening end and a cell 13 in which the plugged portion 21 is not formed in the opened end. Thus, each end face (inlet end face and outlet end face) of the honeycomb structure was made to have a checkered pattern.

(Comparative Example 2)
Except for using a die for forming a hexagonal cell shape as shown in FIG. 7, the cell shape is hexagonal, and the volume, partition wall thickness, and cell density are the same as in Examples 1-9. A plugged honeycomb structure of Comparative Example 2 that was the same as the plugged honeycomb structures of Examples 1 to 9 was obtained. In addition, as shown in FIG. 9, the plugging portions are formed in such a way that the open end portions of the cells 13 are in a certain direction (arrow direction in FIG. 9) on each end face (inlet end face and outlet end face) of the honeycomb structure. Then, every other plugging portion was plugged by the plugging portion 21.

(Evaluation)
With respect to the plugged honeycomb structures of Examples 1 to 9 and Comparative Examples 1 and 2, the temperature rise property, heat retention property and strength were evaluated by the following methods, and the results are shown in Table 1.

[Method for evaluating temperature rise and heat retention]
A method for evaluating temperature rise and heat retention will be described with reference to FIG. First, exhaust gas containing soot generated by the combustion of diesel fuel is introduced from the inlet end face of the plugged honeycomb structure and out of the outlet end face, whereby 10 g / L (plugged) is plugged into the plugged honeycomb structure. 10 g) of soot was deposited per liter volume of the stationary honeycomb structure. Next, heated air was allowed to flow at a constant flow rate to the plugged honeycomb structure that had been cooled to room temperature (25 ° C.) to raise the temperature of the plugged honeycomb structure. In this way, the temperature of the plugged honeycomb structure is increased, and after the temperature of the plugged honeycomb structure reaches 550 ° C., the temperature is kept for 30 minutes, and then air at room temperature (25 ° C.) is kept constant. The honeycomb structure was cooled to room temperature by flowing at a flow rate. The time T when the plugged honeycomb structure reached 550 ° C. during the temperature rise was measured, and the soot regeneration efficiency after the temperature drop of the plugged honeycomb structure was determined. T is a time measured from the time when heated air starts to flow through the plugged honeycomb structure. It can be said that the shorter the T, the higher the temperature rise property. Further, the regeneration efficiency is determined by the amount of soot (A) deposited in the plugged honeycomb structure before the temperature rise of the plugged honeycomb structure and the plugged honeycomb structure after the temperature of the plugged honeycomb structure is lowered. It is a value obtained by the following equation (2) from the amount of soot remaining in the body (B). This regeneration efficiency increases as the temperature-decreasing rate of the plugged honeycomb structure decreases, and the temperature above the soot combustion temperature (530 ° C.) is kept longer. Therefore, it can be said that the higher the regeneration efficiency, the higher the heat retention.
Reproduction efficiency (%) = {(A−B) / A} × 100 (2)

[Strength evaluation method]
The plugged honeycomb structure was inserted into the flexible tube, a uniform pressure was applied by water pressure, and the pressure at which partial fracture occurred was measured. This was defined as the isostatic strength of the plugged honeycomb structure. In addition, the measurement result was displayed relative to the measurement value of the plugged honeycomb structure of Comparative Example 2 as 1.0.

(Discussion)
As shown in Table 1, among Examples 1 to 9 in which the cell shape is a specific hexagon, Examples 2 to 9 are Comparative Example 1 in which the cell shape is a square and Comparative Example 2 in which the cell shape is a hexagon. Higher regeneration efficiency (heat retention) was obtained. Example 1 has higher regeneration efficiency than Comparative Example 2 in which the cell shape is hexagonal, and has higher temperature rise performance and slightly lower regeneration efficiency than Comparative Example 1 in which the cell shape is square. It was almost the same. Moreover, from the results shown in Table 1, the temperature rise performance of Examples 2 to 7 in which the value of distance a satisfies the following formula (1) among Examples 1 to 9 is a comparison in which the cell shape is a quadrangle. It can be seen that there is no significant difference (T difference is within 10 seconds) as compared with the temperature rise performance of Example 1 and Comparative Example 2 in which the cell shape is hexagonal. Moreover, it turns out that the heat retention of these Examples 2-7 is higher than the heat retention of the comparative example 1 whose cell shape is a square, and the comparative example 2 whose cell shape is a hexagon. Furthermore, it turns out that the intensity | strength of these Examples 2-7 is equivalent or more compared with the intensity | strength of the comparative example 2 whose cell shape is a hexagon.

(Example 10)
As in Examples 1 to 9, the cell shape is a hexagon, the value of the distance a shown in FIG. 4 is 0.5 p, and the volume, the partition wall thickness, and the cell density are the values shown in Table 2. A plugged honeycomb structure of Example 10 was obtained. As shown in FIG. 3, the plugging portions are formed in such a way that the open end portions of the cells 13 are in a certain direction (arrow direction in FIG. 3) on each end face (inlet end face and outlet end face) of the honeycomb structure. Then, every other plugging portion was plugged by the plugging portion 21.

(Comparative Example 3)
Except for using a die for forming a square cell shape as shown in FIG. 6, in the same manner as in Examples 1 to 9, the cell shape is a square, and the volume, partition wall thickness, and cell density were measured. A plugged honeycomb structure of Comparative Example 3 which is the same as the plugged honeycomb structure of Example 10 was obtained. As shown in FIG. 8, the plugged portions are formed in a cell 13 in which the plugged portion 21 is formed at the opening end and a cell 13 in which the plugged portion 21 is not formed in the opened end. Thus, each end face (inlet end face and outlet end face) of the honeycomb structure was made to have a checkered pattern.

(Comparative Example 4)
Except for using a die for forming a hexagonal cell shape as shown in FIG. 7, the cell shape is hexagonal, and the volume, partition wall thickness, and cell density are the same as in Examples 1-9. Thus, a plugged honeycomb structure of Comparative Example 2 which is the same as the plugged honeycomb structure of Example 10 was obtained. In addition, as shown in FIG. 9, the plugging portions are formed in such a way that the open end portions of the cells 13 are in a certain direction (arrow direction in FIG. 9) on each end face (inlet end face and outlet end face) of the honeycomb structure. Then, every other plugging portion was plugged by the plugging portion 21.

(Evaluation)
With respect to the plugged honeycomb structures of Example 10 and Comparative Examples 3 and 4, the temperature rise property, the heat retaining property and the strength were evaluated by the above-described methods. The results are shown in Table 2. However, the measurement result of the isostatic strength was displayed relative to the measurement value of the plugged honeycomb structure of Comparative Example 4 as 1.0.

(Discussion)
From the results shown in Table 2, the temperature rise performance of Example 10 is not significantly different from the temperature rise performance of Comparative Example 3 in which the cell shape is a square and Comparative Example 4 in which the cell shape is a hexagon (T It can be seen that the difference is within 10 seconds). Moreover, it turns out that the heat retention of Example 10 is higher than the heat retention of the comparative example 3 whose cell shape is a rectangle, and the comparative example 4 whose cell shape is a hexagon. Furthermore, it turns out that the intensity | strength of Example 10 is higher than the intensity | strength of the comparative example 3 whose cell shape is a square, and the comparative example 4 whose cell shape is a hexagon.

(Example 11)
As in Examples 1 to 9, the cell shape is a hexagon, the value of distance a shown in FIG. 4 is 0.5 p, and the volume, partition wall thickness, and cell density are the values shown in Table 3. A plugged honeycomb structure of Example 11 was obtained. As shown in FIG. 3, the plugging portions are formed in such a way that the open end portions of the cells 13 are in a certain direction (arrow direction in FIG. 3) on each end face (inlet end face and outlet end face) of the honeycomb structure. Then, every other plugging portion was plugged by the plugging portion 21.

(Comparative Example 5)
Except for using a die for forming a square cell shape as shown in FIG. 6, in the same manner as in Examples 1 to 9, the cell shape is a square, and the volume, partition wall thickness, and cell density were measured. A plugged honeycomb structure of Comparative Example 5 which is the same as the plugged honeycomb structure of Example 11 was obtained. As shown in FIG. 8, the plugged portions are formed in a cell 13 in which the plugged portion 21 is formed at the opening end and a cell 13 in which the plugged portion 21 is not formed in the opened end. Thus, each end face (inlet end face and outlet end face) of the honeycomb structure was made to have a checkered pattern.

(Comparative Example 6)
Except for using a die for forming a hexagonal cell shape as shown in FIG. 7, the cell shape is hexagonal, and the volume, partition wall thickness, and cell density are the same as in Examples 1-9. A plugged honeycomb structure of Comparative Example 6 that is the same as the plugged honeycomb structure of Example 11 was obtained. In addition, as shown in FIG. 9, the plugging portions are formed in such a way that the open end portions of the cells 13 are in a certain direction (arrow direction in FIG. 9) on each end face (inlet end face and outlet end face) of the honeycomb structure. Then, every other plugging portion was plugged by the plugging portion 21.

(Evaluation)
With respect to the plugged honeycomb structures of Example 11 and Comparative Examples 5 and 6, the temperature rise property, the heat retaining property and the strength were evaluated by the above-described methods, and the results are shown in Table 3. However, the measurement result of the isostatic strength was displayed relative to the measurement value of the plugged honeycomb structure of Comparative Example 6 as 1.0.

(Discussion)
From the results shown in Table 3, the temperature rise performance of Example 11 is not significantly different from the temperature rise performance of Comparative Example 5 in which the cell shape is a square and Comparative Example 6 in which the cell shape is a hexagon (T It can be seen that the difference is within 10 seconds). Moreover, it turns out that the heat retention of Example 11 is higher than the heat retention of the comparative example 5 whose cell shape is a rectangle, and the comparative example 6 whose cell shape is a hexagon. Furthermore, it turns out that the intensity | strength of Example 11 is higher than the intensity | strength of the comparative example 5 whose cell shape is a square, and the comparative example 6 whose cell shape is a hexagon.

(Example 12)
As in Examples 1 to 9, the cell shape is a hexagon, the value of distance a shown in FIG. 4 is 0.5 p, and the volume, partition wall thickness, and cell density are the values shown in Table 4. A plugged honeycomb structure of Example 12 was obtained. As shown in FIG. 3, the plugging portions are formed in such a way that the open end portions of the cells 13 are in a certain direction (arrow direction in FIG. 3) on each end face (inlet end face and outlet end face) of the honeycomb structure. Then, every other plugging portion was plugged by the plugging portion 21.

(Comparative Example 7)
Except for using a die for forming a square cell shape as shown in FIG. 6, in the same manner as in Examples 1 to 9, the cell shape is a square, and the volume, partition wall thickness, and cell density were measured. A plugged honeycomb structure of Comparative Example 7 which is the same as the plugged honeycomb structure of Example 12 was obtained. As shown in FIG. 8, the plugged portions are formed in a cell 13 in which the plugged portion 21 is formed at the opening end and a cell 13 in which the plugged portion 21 is not formed in the opened end. Thus, each end face (inlet end face and outlet end face) of the honeycomb structure was made to have a checkered pattern.

(Comparative Example 8)
Except for using a die for forming a hexagonal cell shape as shown in FIG. 7, the cell shape is hexagonal, and the volume, partition wall thickness, and cell density are the same as in Examples 1-9. A plugged honeycomb structure of Comparative Example 8 that is the same as the plugged honeycomb structure of Example 12 was obtained. In addition, as shown in FIG. 9, the plugging portions are formed in such a way that the open end portions of the cells 13 are in a certain direction (arrow direction in FIG. 9) on each end face (inlet end face and outlet end face) of the honeycomb structure. Then, every other plugging portion was plugged by the plugging portion 21.

(Evaluation)
With respect to the plugged honeycomb structures of Example 12 and Comparative Examples 7 and 8, the temperature rise property, the heat retaining property and the strength were evaluated by the above-described methods. The results are shown in Table 4. However, the measurement result of the isostatic strength was displayed relative to the measurement value of the plugged honeycomb structure of Comparative Example 8 as 1.0.

(Discussion)
From the results shown in Table 4, the temperature rise performance of Example 12 is not significantly different from the temperature rise performance of Comparative Example 7 in which the cell shape is a square and Comparative Example 8 in which the cell shape is a hexagon (T It can be seen that the difference is within 10 seconds). Moreover, it turns out that the heat retention of Example 12 is higher than the heat retention of the comparative example 7 whose cell shape is a rectangle, and the comparative example 8 whose cell shape is a hexagon. Furthermore, it turns out that the intensity | strength of Example 12 is higher than the intensity | strength of the comparative example 7 whose cell shape is a square, and the comparative example 8 whose cell shape is a hexagon.

  INDUSTRIAL APPLICABILITY The present invention can be suitably used as an exhaust gas purifying catalyst used for purifying exhaust gas from automobiles or the like or a catalyst carrier thereof.

1 (1A, 1B, 1C): Vertex 2 (2A, 2B, 2C): Vertex 3 (3A, 3B, 3C, 3D, 3E, 3F): Vertex 4 (4A, 4B, 4C): Diagonal line, 5 (5A, 5B, 5C): line segment, 6 (6A, 6B, 6C): corner, 10: honeycomb structure, 11: inlet end surface, 12: outlet end surface, 13: cell, 14: partition wall, 16: Intersection portion, 17: intersection portion, 20: plugged honeycomb structure, 21: plugged portion, 30: honeycomb structure, 36: intersection portion, 40: honeycomb structure, 46: intersection portion.

Claims (4)

A honeycomb structure having a porous partition wall defining a plurality of cells extending from an inlet end surface serving as a fluid inlet side to an outlet end surface serving as a fluid outlet side; an opening end portion of the predetermined cell on the inlet end surface side; A plugging portion that plugs the opening end portion on the outlet end face side of the remaining cells;
The shape of the cell in a cross section perpendicular to the cell extending direction is a hexagon,
Of the six vertices of the regular hexagon, the nine-sided hexagon is parallel to the three vertices that exist every other in the circumferential direction of the regular hexagon, and the diagonal lines connecting the three vertices, and both ends are the remaining three. A shape having six new vertices formed by cutting corners including the remaining three vertices by line segments on the sides forming the respective vertices;
A plugged honeycomb structure in which the plurality of cells are arranged so that sides connecting the new vertex and a vertex other than the new vertex face each other in parallel between adjacent cells. Each of said line segment, wherein the remainder of the distance from each of the three vertices of the nearest line segment on each of the remaining three vertices of said segments is a, each of the remaining three vertices 2. The plugged honeycomb according to claim 1, wherein p is a distance from the first to the diagonal line closest to each of the remaining three vertices in the diagonal line. Structure.
0.2p ≦ a ≦ 0.7p (1)   The plugged honeycomb structure according to claim 1 or 2, wherein the partition wall has a thickness of 203 to 508 µm.   The plugged honeycomb structure according to any one of claims 1 to 3, which is used as a diesel particulate filter.

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