WO2012157421A1

WO2012157421A1 - Honeycomb filter

Info

Publication number: WO2012157421A1
Application number: PCT/JP2012/061125
Authority: WO
Inventors: 照夫小森; 健太郎岩崎; 明欣根本
Original assignee: 住友化学株式会社
Priority date: 2011-05-17
Filing date: 2012-04-25
Publication date: 2012-11-22
Also published as: JP2012254441A

Abstract

A honeycomb filter (100) has flow paths (110) separated by partition walls (120); the flow paths (110) have a plurality of flow paths (110a) and a plurality of flow paths (110b); of the plurality of flow paths (110b), one flow path (110b) and another flow path (110b) are adjacent to each other; the cross section of flow paths (110b) has long sides (150a) and short sides (150b); each of the sides (140) of flow paths (110a) faces a long side (150a) of a flow path (110b); each of the short sides (150b) of flow paths (110b) faces a short side (150b) of an adjacent flow path (110b); and when the sum of the products of the length of each side forming the cross section of a flow path (110b) and the length in the axial direction of flow paths (110b) is taken to be S, the total sum of S of all the flow paths (110b) contained in the honeycomb filter (100) is at least a predetermined value.

Description

Honeycomb filter

The present invention relates to a honeycomb filter.

The honeycomb filter is used as a ceramic filter for removing the collected matter from the fluid containing the collected matter, for example, for purifying exhaust gas exhausted from an internal combustion engine such as a diesel engine or a gasoline engine. Used as an exhaust gas filter. Such a honeycomb filter has a plurality of parallel flow paths partitioned by porous partition walls (see, for example, Patent Document 1 below).

JP 2009-537741 A

By the way, as the fluid containing the collected matter is supplied into the honeycomb filter, the collected matter is deposited on the surface of the partition wall or inside the partition wall in the honeycomb filter. In this case, if the collected material is excessively accumulated in the honeycomb filter, the movement of the fluid in the honeycomb filter is hindered and the purification performance of the honeycomb filter is deteriorated. Therefore, after depositing a certain amount of collected matter in the honeycomb filter, the honeycomb filter is subjected to combustion regeneration in order to burn and remove the collected matter.

Here, if excessive thermal stress is applied to the honeycomb filter during combustion regeneration, the honeycomb filter may be thermally damaged or melted. Therefore, it is required for the honeycomb filter to reduce the thermal stress generated in the combustion regeneration.

Also, for the honeycomb filter, it is required to sufficiently suppress an increase in pressure loss as the collected object is collected in the honeycomb filter. Therefore, the honeycomb filter is required to reduce the thermal stress generated in the combustion regeneration while reducing the pressure loss.

The present invention has been made in view of such circumstances, and an object of the present invention is to provide a honeycomb filter capable of reducing thermal stress generated in combustion regeneration while reducing pressure loss.

A honeycomb filter according to the present invention is a honeycomb filter having a plurality of parallel flow paths partitioned by a porous partition wall, wherein the plurality of flow paths includes a first flow path and the first flow path. A plurality of second flow paths adjacent to each other, one second flow path and the other second flow paths in the plurality of second flow paths being adjacent to each other, the first The end of one end of the honeycomb filter in the channel is sealed, and the end of the other end of the honeycomb filter in the second channel is sealed, and is perpendicular to the axial direction of the second channel. The cross section of the second channel has a first side and second sides respectively disposed on both sides of the first side, and the second channel is perpendicular to the axial direction of the first channel. Each of the sides forming the cross section of the first channel is opposed to the first side of the second channel, and each of the second sides of the second channel is Opposite to the second side of the adjacent second flow path, a plurality of first flow paths are arranged, and each of the second flow paths has a side that forms a cross section of the second flow path. When the sum of the product of each length and the length of the second flow path in the axial direction of the second flow path is S, S in all the second flow paths included per liter of the honeycomb filter. Is a total of 1.1 m ² or more.

The honeycomb filter according to the present invention can reduce thermal stress generated in the honeycomb filter during combustion regeneration while reducing pressure loss. The reason why the above effect is obtained in the present invention is unknown in detail, but the present inventor presumes as follows. However, the cause is not limited to the following contents.

That is, in the honeycomb filter according to the present invention, the plurality of flow paths include a first flow path and a plurality of second flow paths adjacent to the first flow path. In the first flow path, one second flow path and the other second flow path are adjacent to each other, and an end portion on one end side of the honeycomb filter in the first flow path is sealed, The end portion of the other end side of the honeycomb filter in the flow path is sealed, and the cross section of the second flow path perpendicular to the axial direction of the second flow path is the first side and the first side. Each of the sides forming a cross section of the first flow path perpendicular to the axial direction of the first flow path is formed on each side of the second flow path. Each of the second sides of the second flow channel is opposed to the second side of the adjacent second flow channel. In the present invention having such a configuration, for example, when a fluid containing a trapped substance flows into the second flow path from one end side of the honeycomb filter, the trapped substance is It accumulates on the inner wall and deposits on each of the first side and the second side in the cross section of the second channel perpendicular to the axial direction of the second channel. When combustion recovery of the honeycomb filter is performed in a state where the collected matter is accumulated in this way, a combustion-supporting gas such as oxygen gas that has flowed into the honeycomb filter is supplied to a portion where the collected matter is accumulated. Then, the collected material burns in the presence of the combustion-supporting gas, thereby generating carbon dioxide gas, carbon monoxide gas or the like (hereinafter simply referred to as “carbon dioxide gas or the like”).

Here, in the present invention, the burning rate of the collected matter tends to depend on the ease of diffusion to the flow path on the gas outflow side such as carbon dioxide gas generated by the burning of the collected matter. Guessed. That is, in the present invention, the pressure difference between the first flow path and the second flow path adjacent to each other tends to be larger than the pressure difference between the second flow paths adjacent to each other. Thereby, the carbon dioxide gas etc. which generate | occur | produced by combustion of the to-be-collected substance in one 2nd flow path are easy to flow into the adjacent 1st flow path compared with the 2nd adjacent 2nd flow path. .

And in this invention, the carbon dioxide gas etc. which generate | occur | produced by the combustion of the to-be-collected material deposited on the 1st edge | side have the 1st partition which has a cross section which shares the cross section of a 2nd flow path, and a 1st edge | side. The carbon dioxide gas, etc. generated by the combustion of the collected matter deposited on the second side tends to reach the first flow path through the inside of the second flow path. There is a tendency to move along the partition wall in the second partition wall having a cross section sharing the same to reach the first flow path. In this case, since the path passing through the first partition is shorter than the path passing through the second partition, the carbon dioxide gas generated by the combustion of the trapped material deposited on the first side However, it is easier to diffuse into the flow path on the gas outflow side than carbon dioxide gas or the like generated by the combustion of the collected matter deposited on the second side.

Due to the pressure difference between the flow paths and the difference in the length of the flow path in the partition wall, in the present invention, the carbon dioxide gas generated by the combustion of the collected matter accumulated on the first side, etc. However, it is easier to diffuse to the flow path on the gas outflow side than the carbon dioxide gas generated by the combustion of the collected matter accumulated on the second side. Therefore, the collected matter deposited on the first side becomes easier to burn than the collected matter deposited on the second side, and the collected matter deposited on the first side and the second The burning speed differs depending on the collected matter deposited on the side.

In the present invention described above, since the burning rate of the collected matter differs depending on the portion where the collected matter is accumulated, the burning of the collected matter is abruptly generated in many portions during the combustion regeneration. A sudden change in the temperature in the honeycomb filter is suppressed. Such a phenomenon is presumably caused by the fact that the total sum S of the products in all the second flow paths included in 1 liter of honeycomb filter is 1.1 m ² or more. The Thereby, the thermal stress which arises in a honeycomb filter in combustion regeneration can be reduced.

Further, in the honeycomb filter according to the present invention, the total sum of the products S in all the second flow paths included per liter of the honeycomb filter is 1.1 m ² or more, so that the collected matter is included. It is possible to reduce the thermal stress generated in the honeycomb filter during combustion regeneration while reducing the pressure loss when the fluid is supplied into the honeycomb filter. The reason why such an effect can be obtained is unknown in detail, but the present inventor will ensure that the filtration area is sufficiently secured, and that the collected substances will accumulate locally and block the flow path. It is speculated that the pressure loss is reduced due to the suppression of the pressure. However, the cause is not limited to the content.

The partition preferably contains aluminum titanate. In this case, it is easy to reduce the thermal stress generated in the honeycomb filter during combustion regeneration while reducing the pressure loss.

The cross section of the first flow path and the cross section of the second flow path may be hexagonal.

As a first aspect, a configuration in which one second flow path is disposed between adjacent first flow paths may be employed. In this case, the thermal stress generated in the honeycomb filter during combustion regeneration can be further reduced.

In the first aspect, the lengths of the sides facing each other in the cross section of the second flow path may be equal to each other. Further, the cross section of the second flow path may have two long sides having the same length and four short sides having the same length.

As a second aspect, the two second flow paths are disposed between the first flow paths adjacent to each other and are adjacent to each other in a direction orthogonal to the arrangement direction of the first flow paths. An aspect may be sufficient. In this case, the thermal stress generated in the honeycomb filter during combustion regeneration can be further reduced, and the pressure loss can be easily reduced because the area for filtering the collected matter (effective filtration area) increases.

In the second aspect, the cross section of the second flow path has three long sides having the same length and three short sides having the same length, and the long side and the short side are mutually different. You may face each other.

The honeycomb filter according to the present invention can reduce thermal stress generated in the honeycomb filter during combustion regeneration while reducing pressure loss. By reducing the thermal stress, it is possible to prevent the honeycomb filter from being damaged or melted during combustion regeneration.

FIG. 1 is a drawing schematically showing a honeycomb filter according to a first embodiment of the present invention. FIG. 2 is a view taken along the line II-II in FIG. FIG. 3 is a drawing schematically showing a honeycomb filter according to a second embodiment of the present invention. 4 is a view taken in the direction of arrows IV-IV in FIG. FIG. 5 is a drawing schematically showing a honeycomb filter according to another embodiment of the present invention. FIG. 6 is a drawing schematically showing the covering portion disposed in the flow path. FIG. 7 is a drawing schematically showing the covering portion disposed in the flow path. FIG. 8 is a drawing schematically showing the shape of the wall surface of the partition wall. FIG. 9 is a drawing schematically showing the filter used in the comparative example. FIG. 10 is a drawing schematically showing a pressure loss measuring apparatus. FIG. 11 is a drawing showing the measurement results of pressure loss.

Hereinafter, embodiments for carrying out the present invention will be described in detail with reference to the drawings as necessary. However, the present invention is not limited to the following embodiments. In the drawings, the same elements are denoted by the same reference numerals, and redundant description is omitted. Further, the dimensional ratios in the drawings are not limited to the illustrated ratios.

<Honeycomb filter>
(First embodiment)
FIG. 1 is a drawing schematically showing the honeycomb filter according to the first embodiment, and FIG. 1 (b) is an enlarged view of a region A1 in FIG. 1 (a). FIG. 2 is a view taken along the line II-II in FIG. As shown in FIGS. 1 and 2, the honeycomb filter 100 is a cylindrical body having a plurality of flow paths 110 arranged substantially parallel to each other. The plurality of flow paths 110 are partitioned by partition walls 120 that extend substantially parallel to the central axis of the honeycomb filter 100. The plurality of channels 110 have a plurality of channels (first channels) 110a and a plurality of channels (second channels) 110b adjacent to the channels 110a. The flow path 110 a and the flow path 110 b extend substantially perpendicular to both end faces of the honeycomb filter 100.

One end of the flow path 110a constituting a part of the flow path 110 is sealed by the sealing portion 130 on the one end face 100a of the honeycomb filter 100, and the other end of the flow path 110a is the other end face 100b of the honeycomb filter 100. Is open. On the other hand, one end of the flow path 110b that constitutes the remaining part of the plurality of flow paths 110 is open at the one end face 100a, and the other end of the flow path 110b is sealed by the sealing portion 130 at the other end face 100b. . In the honeycomb filter 100, for example, the end on the one end face 100a side of the flow path 110b is opened as a gas inlet, and the end on the other end face 100b side of the flow path 110a is opened as a gas outlet.

The cross section substantially perpendicular to the axial direction (longitudinal direction) of the flow path 110a and the flow path 110b has a hexagonal shape. The cross section of the flow path 110a is easy to reduce the pressure loss at the time of deposition of the collected substances by allowing the fluid containing the collected substances to easily flow from the flow path on the gas inflow side to the flow path on the gas outflow side. From this point of view, a regular hexagonal shape in which the lengths of the sides 140 forming the cross section are substantially equal to each other is preferable, but a flat hexagonal shape may be used. The cross section of the channel 110b is, for example, a flat hexagonal shape, but may be a regular hexagonal shape. The lengths of the sides facing each other in the cross section of the channel 110b are substantially equal to each other. The cross section of the channel 110b has two long sides (first side) 150a having approximately the same length as the side 150 forming the cross section, and four (two pairs) having substantially the same length. ) Short side (second side) 150b. The short side 150b is disposed on each side of the long side 150a. The long sides 150a face each other substantially in parallel, and the short sides 150b face each other substantially in parallel. The length of the long side 150a is adjusted to be longer than the length of the short side 150b.

The partition 120 has the partition 120a as a part which partitions off the flow path 110a and the flow path 110b. That is, the channel 110a and the channel 110b are adjacent to each other through the partition wall 120a. By disposing one flow path 110b between adjacent flow paths 110a, the flow paths 110a are alternately arranged with the flow paths 110b in the arrangement direction of the flow paths 110a (a direction substantially orthogonal to the side 140). Yes.

Each of the sides 140 of the flow channel 110a faces the long side 150a of any one of the plurality of flow channels 110b substantially in parallel. That is, each of the wall surfaces that form the flow channel 110a is opposed substantially parallel to the one wall surface that forms the flow channel 110b in the partition wall 120a located between the flow channel 110a and the flow channel 110b. Further, the flow path 110 has a structural unit including one flow path 110a and six flow paths 110b surrounding the flow path 110a, and in the structural unit, all the sides 140 of the flow path 110a are included. It faces the long side 150a of the flow path 110b. In the honeycomb filter 100, from the viewpoint of further improving the collection efficiency of the collected object, it is preferable that at least one length of the side 140 of the flow path 110a is substantially equal to the length of the opposing long side 150a. It is more preferable that the length of each of these is substantially equal to the length of the opposing long side 150a.

The partition 120 has the partition 120b as a part which partitions the mutually adjacent flow paths 110b. That is, the flow paths 110b surrounding the flow path 110a are adjacent to each other through the partition wall 120b.

Each of the short sides 150b of the flow path 110b is opposed substantially parallel to the short side 150b of the adjacent flow path 110b. That is, the wall surfaces forming the flow path 110b face each other substantially in parallel in the partition wall 120b located between the adjacent flow paths 110b. In the honeycomb filter 100, from the viewpoint of further improving the collection efficiency of the collected object, at least one length of the short side 150b of the flow path 110b is between the adjacent short sides 150b between the adjacent flow paths 110b. It is preferable that the length is approximately equal to the length, and it is more preferable that each length of the short side 150b is approximately equal to the length of the opposing short side 150b.

The length of the honeycomb filter 100 in the longitudinal direction of the

flow paths

110a and 110b is, for example, 50 to 300 mm. The outer diameter of the honeycomb filter 100 is, for example, 50 to 250 mm. The density (cell density) of the

channels

110a and 110b is, for example, 50 to 400 cpsi (cell per square inch). “Cpsi” represents the number of flow paths (cells) per square inch. In the cross section of the honeycomb filter 100 substantially perpendicular to the axial direction of the

flow paths

110a and 110b, the total area of the gas inflow side flow paths is preferably larger than the total area of the gas outflow side flow paths, that is, the total of the flow paths 110b. The area is preferably larger than the total area of the flow paths 110a.

In the structural unit including one flow path 110a and the flow path 110b surrounding the flow path 110a, the length of the side 140 is 0.2 mm or more from the viewpoint of further reducing the thermal stress generated in the honeycomb filter during combustion regeneration. Preferably, 0.4 mm or more is more preferable, and 0.6 mm or more is still more preferable. The length of the side 140 is preferably 2.0 mm or less, and more preferably 1.6 mm or less, from the viewpoint of further reducing the thermal stress generated in the honeycomb filter during combustion regeneration. The length of the long side 150a of the flow path 110b in the structural unit is preferably 0.4 mm or more, and more preferably 0.6 mm or more from the viewpoint of further reducing the thermal stress generated in the honeycomb filter during combustion regeneration. The length of the long side 150a of the channel 110b is preferably 2.0 mm or less, and more preferably 1.6 mm or less, from the viewpoint of further reducing the thermal stress generated in the honeycomb filter during combustion regeneration. The length of the short side 150b of the flow path 110b in the structural unit is preferably 0.3 mm or more, and more preferably 0.5 mm or more from the viewpoint of further reducing the thermal stress generated in the honeycomb filter during combustion regeneration. From the viewpoint of further reducing the pressure loss, the length of the short side 150b of the channel 110b is preferably 2.0 mm or less, and more preferably 1.0 mm or less.

The thickness (cell wall thickness) of the partition wall 120 in the structural unit is preferably 0.8 mm or less, more preferably 0.5 mm or less, from the viewpoint of further reducing the pressure loss. The thickness of the partition 120 is preferably 0.1 mm or more, and more preferably 0.2 mm or more, from the viewpoint of maintaining the collection efficiency of the collected object and the strength of the honeycomb filter 100 at a high level.

The porosity of the partition wall 120 in the above structural unit is preferably 20% by volume or more, more preferably 30% by volume or more, and still more preferably 40% by volume or more from the viewpoint of further reducing pressure loss. The porosity of the partition walls 120 is preferably 60% by volume or less, and more preferably 50% by volume or less, from the viewpoint of further reducing the thermal stress generated in the honeycomb filter during combustion regeneration. The porosity of the partition wall 120 can be adjusted by the particle diameter of the raw material, the amount of the pore-forming agent added, the kind of the pore-forming agent, and the firing conditions, and can be measured by a mercury intrusion method.

The pore diameter (pore diameter) of the partition wall 120 in the above structural unit is preferably 5 μm or more, more preferably 10 μm or more, from the viewpoint of further reducing the pressure loss. From the viewpoint of improving the soot collection performance, the pore diameter of the partition wall 120 is preferably 30 μm or less, and more preferably 20 μm or less. The pore diameter of the partition wall 120 can be adjusted by the particle diameter of the raw material, the added amount of the pore forming agent, the kind of the pore forming agent, and the firing conditions, and can be measured by a mercury intrusion method.

Effective filtration area of the honeycomb filter 100, from the viewpoint of reducing pressure loss while reducing the thermal stress generated in the honeycomb filter in the combustion regeneration, and a 1.1 m ² / L or more, preferably at least 1.2 m ² / L, 1.3 m ² / L or more is more preferable. “Effective filtration area of the honeycomb filter” means the total area of the inner wall of the gas inflow channel per honeycomb filter 1L (1 liter = 10 ⁻³ m ³ : for example, 10 cm × 10 cm × 10 cm cube) The gas inflow side flow path in the axial direction of the gas inflow side flow path, and the length of each side forming the cross section of the gas inflow side flow path in each gas inflow side flow path. When the sum of products with the length of S is S, it means the sum of S in all the gas inflow channels included per liter of the honeycomb filter. For example, the total product S in the honeycomb filter 100 is the product of the length of the long side 150a of the flow path 110b and the length in the longitudinal direction of the flow path 110b, and the length of the short side 150b of the flow path 110b and the length of the flow path 110b. It means the sum of the product with the length in the longitudinal direction. In addition, the upper limit of an effective filtration area is 2.0 m < ² > / L, for example.

(Second Embodiment)
Fig. 3 is a drawing schematically showing the honeycomb filter according to the second embodiment, and Fig. 3 (b) is an enlarged view of a region A2 in Fig. 3 (a). 4 is a view taken in the direction of arrows IV-IV in FIG. As shown in FIGS. 3 and 4, the honeycomb filter 200 is a cylindrical body having a plurality of flow paths 210 arranged substantially parallel to each other. The plurality of flow paths 210 are partitioned by partition walls 220 extending substantially parallel to the central axis of the honeycomb filter 200. The plurality of flow paths 210 include a plurality of flow paths (first flow paths) 210a and a plurality of flow paths (second flow paths) 210b adjacent to the flow paths 210a. The flow path 210 a and the flow path 210 b extend substantially perpendicular to both end faces of the honeycomb filter 200.

One end of the flow path 210a that forms a part of the flow path 210 is sealed by the sealing portion 230 at the one end face 200a of the honeycomb filter 200, and the other end of the flow path 210a is the other end face 200b of the honeycomb filter 200. Is open. On the other hand, one end of the flow path 210b forming the remaining part of the plurality of flow paths 210 is open at the one end face 200a, and the other end of the flow path 210b is sealed by the sealing portion 230 at the other end face 200b. . In the honeycomb filter 200, for example, the end on the one end face 200a side of the flow path 210b is opened as a gas inlet, and the end on the other end face 200b side of the flow path 210a is opened as a gas outlet.

The cross section substantially perpendicular to the axial direction (longitudinal direction) of the flow path 210a and the flow path 210b is hexagonal. The cross section of the flow path 210a makes it easy to reduce the pressure loss at the time of deposition of the collected substances by allowing the fluid containing the collected substances to easily flow from the flow path on the gas inflow side to the flow path on the gas outflow side. From the viewpoint, a regular hexagonal shape in which the lengths of the sides 240 forming the cross section are substantially equal to each other is preferable, but a flat hexagonal shape may be used. The cross section of the channel 210b is, for example, a flat hexagonal shape, but may be a regular hexagonal shape. The lengths of the sides facing each other in the cross section of the flow path 210b are different from each other. The cross section of the flow path 210b includes three long sides (first sides) 250a having substantially the same length as the sides 250 forming the cross section, and three short sides (second sides) having the substantially same length. ) 250b. The long side 250a and the short side 250b face each other substantially in parallel, and the short side 250b is disposed on each side of the long side 250a. The length of the long side 250a is adjusted to be longer than the length of the short side 250b.

The partition 220 has the partition 220a as a part which partitions off the flow path 210a and the flow path 210b. That is, the flow path 210a and the flow path 210b are adjacent to each other through the partition wall 220a. Between the adjacent flow paths 210a, two flow paths 210b adjacent to each other in a direction substantially orthogonal to the arrangement direction of the flow paths 210a are arranged, and the two adjacent flow paths 210b are adjacent to each other. They are arranged symmetrically across a line connecting the centers of the sections of 210a.

Each of the sides 240 of the flow path 210a faces the long side 250a of any one of the plurality of flow paths 210b substantially in parallel. That is, each of the wall surfaces forming the flow path 210a is opposed substantially parallel to the one wall surface forming the flow path 210b in the partition wall 220a located between the flow path 210a and the flow path 210b. The flow path 210 has a structural unit including one flow path 210a and six flow paths 210b surrounding the flow path 210a. In the structural unit, all the sides 240 of the flow path 210a are included. It faces the long side 250a of the flow path 210b. Each vertex of the cross section of the flow path 210a is opposed to the apex of the adjacent flow path 210a in the arrangement direction of the flow paths 210a. In the honeycomb filter 200, it is preferable that at least one length of the side 240 of the flow path 210a is substantially equal to the length of the opposing long side 250a, from the viewpoint of further improving the collection efficiency of the collection target. It is preferable that the length of each is substantially equal to the length of the opposing long side 250a.

The partition 220 has the partition 220b as a part which partitions off the mutually adjacent flow paths 210b. That is, the flow paths 210b surrounding the flow path 210a are adjacent to each other through the partition 220b.

Each of the short sides 250b of the flow path 210b is opposed substantially parallel to the short side 250b of the adjacent flow path 210b. That is, the wall surfaces forming the flow path 210b face each other substantially in parallel in the partition 220b located between the adjacent flow paths 210b. One flow path 210b is surrounded by three flow paths 210a. In the honeycomb filter 200, from the viewpoint of further improving the collection efficiency of the collected object, at least one length of the short side 250b of the flow path 210b is between the adjacent short sides 250b between the adjacent flow paths 210b. It is preferable that the length is approximately equal to the length, and it is more preferable that each length of the short side 250b is approximately equal to the length of the opposing short side 250b.

The length of the honeycomb filter 200 in the longitudinal direction of the

flow paths

210a and 210b is, for example, 50 to 300 mm. The outer diameter of the honeycomb filter 200 is, for example, 50 to 250 mm. The density (cell density) of the

flow paths

210a and 210b is, for example, 50 to 400 cpsi. In the cross section of the honeycomb filter 200 substantially perpendicular to the axial direction of the

flow paths

210a and 210b, the total area of the gas inflow side flow paths is preferably larger than the total area of the gas outflow side flow paths, that is, the total of the flow paths 210b. The area is preferably larger than the total area of the channels 210a.

In the structural unit including one flow path 210a and the flow path 210b surrounding the flow path 210a, the length of the side 240 is 0.2 mm or more from the viewpoint of further reducing the thermal stress generated in the honeycomb filter during combustion regeneration. Preferably, 0.4 mm or more is more preferable, and 0.6 mm or more is still more preferable. The length of the side 240 is preferably 2.0 mm or less and more preferably 1.6 mm or less from the viewpoint of further reducing the thermal stress generated in the honeycomb filter during combustion regeneration. The length of the long side 250a of the flow path 210b in the structural unit is preferably 0.4 mm or more, and more preferably 0.6 mm or more from the viewpoint of further reducing the thermal stress generated in the honeycomb filter during combustion regeneration. The length of the long side 250a of the flow path 210b is preferably 2.0 mm or less, and more preferably 1.6 mm or less, from the viewpoint of further reducing the thermal stress generated in the honeycomb filter during combustion regeneration. The length of the short side 250b of the flow path 210b in the structural unit is preferably 0.3 mm or more, and more preferably 0.5 mm or more from the viewpoint of further reducing the thermal stress generated in the honeycomb filter during combustion regeneration. From the viewpoint of further reducing the pressure loss, the length of the short side 250b of the flow path 210b is preferably 2.0 mm or less, and more preferably 1.0 mm or less.

The thickness (cell wall thickness) of the partition wall 220 in the structural unit is preferably 0.8 mm or less, and more preferably 0.5 mm or less, from the viewpoint of further reducing the pressure loss. The thickness of the partition 220 is preferably 0.1 mm or more, and more preferably 0.2 mm or more, from the viewpoint of maintaining the collection efficiency of the object to be collected and the strength of the honeycomb filter 200 at a high level.

The porosity of the partition wall 220 in the above structural unit is preferably 20% by volume or more, more preferably 30% by volume or more, and still more preferably 40% by volume or more from the viewpoint of further reducing pressure loss. The porosity of the partition walls 220 is preferably 60% by volume or less, and more preferably 50% by volume or less, from the viewpoint of further reducing the thermal stress generated in the honeycomb filter during combustion regeneration. The porosity of the partition 220 can be adjusted by the particle diameter of the raw material, the amount of the pore-forming agent added, the type of the pore-forming agent, and the firing conditions, and can be measured by a mercury intrusion method.

The pore diameter (pore diameter) of the partition wall 220 in the above structural unit is preferably 5 μm or more, and more preferably 10 μm or more, from the viewpoint of further reducing the pressure loss. From the viewpoint of improving the soot collection performance, the pore size of the partition 220 is preferably 30 μm or less, and more preferably 20 μm or less. The pore diameter of the partition wall 220 can be adjusted by the particle diameter of the raw material, the amount of the pore-forming agent added, the kind of the pore-forming agent, and the firing conditions, and can be measured by a mercury intrusion method.

Effective filtration area of the honeycomb filter 200, from the viewpoint of reducing pressure loss while reducing the thermal stress generated in the honeycomb filter in the combustion regeneration, and a 1.1 m ² / L or more, preferably at least 1.2 m ² / L, 1.3 m ² / L or more is more preferable. In addition, the upper limit of an effective filtration area is 2.0 m < ² > / L, for example.

In the honeycomb filters 100 and 200, the partition walls are porous, and include, for example, porous ceramics (porous ceramic sintered body). The partition wall has a structure that allows fluid (for example, exhaust gas containing fine particles such as soot) to pass therethrough. Specifically, a large number of communication holes (flow channels) through which fluid can pass are formed in the partition wall.

The partition preferably contains aluminum titanate, and may further contain magnesium or silicon. The partition walls are made of, for example, porous ceramics mainly made of an aluminum titanate crystal. “Mainly composed of an aluminum titanate-based crystal” means that the main crystal phase constituting the aluminum titanate-based ceramic fired body is an aluminum titanate-based crystal phase. An aluminum titanate crystal phase, an aluminum magnesium titanate crystal phase, or the like may be used.

When the partition wall contains magnesium, the composition formula of the partition wall is, for example, Al _{2 (1-x)} Mg _x Ti _{(1 + x)} O ₅ , and the value of x is preferably 0.03 or more, and 0.03 to 0 20 is more preferable, and 0.03 to 0.18 is still more preferable. The partition walls may contain trace components derived from raw materials or trace components inevitably included in the production process.

When the partition contains silicon, the partition may contain a glass phase derived from a silicon source powder. The glass phase refers to an amorphous phase in which SiO ₂ is the main component. In this case, the glass phase content is preferably 4% by mass or less. When the glass phase content is 4% by mass or less, an aluminum titanate-based ceramic fired body that satisfies the pore characteristics required for a ceramic filter such as a particulate filter is easily obtained. The glass phase content is preferably 2% by mass or more.

The partition may contain a phase (crystal phase) other than the aluminum titanate crystal phase or the glass phase. Examples of the phase other than the aluminum titanate-based crystal phase include a phase derived from a raw material used for producing an aluminum titanate-based ceramic fired body. More specifically, the phase derived from the raw material is a phase derived from an aluminum source powder, a titanium source powder and / or a magnesium source powder that remains without forming an aluminum titanate-based crystal phase during the manufacture of the honeycomb filter. Examples of the phase derived from the raw material include phases such as alumina and titania. The crystal phase forming the partition can be confirmed by an X-ray diffraction spectrum.

The honeycomb filter is suitable, for example, as a particulate filter that collects collected matter such as soot contained in exhaust gas from an internal combustion engine such as a diesel engine or a gasoline engine. For example, in the honeycomb filter 100, as shown in FIG. 2, the gas G supplied from the one end face 100a to the flow path 110b passes through the communication hole in the partition wall 120 and reaches the adjacent flow path 110a, and the other end face 100b. Discharged from. At this time, the collected matter in the gas G is collected on the surface of the partition wall 120 or in the communication hole and removed from the gas G, whereby the honeycomb filter 100 functions as a filter. Similarly, the honeycomb filter 200 functions as a filter.

In the conventional honeycomb filter, once the trapped material is deposited on the surface of the partition wall or inside the partition wall (in the communication hole), a new trapped substance is placed in the same channel as the channel on which the trapped material is deposited. Is likely to accumulate. In this case, in the flow path in which a large amount of collected material is accumulated, when the honeycomb filter is combusted and regenerated, the collected material is easily burned in a short time and the amount of generated heat tends to increase. Stress is applied.

On the other hand, in the honeycomb filters 100 and 200, as described below, thermal stress generated in the honeycomb filter during combustion regeneration can be reduced. For example, in the honeycomb filter 100, the burning rate of the collected matter tends to depend on the ease of diffusion into the channel 110a on the gas outflow side such as carbon dioxide gas generated by the burning of the collected matter. It is guessed. That is, in the honey-comb filter 100, the pressure difference between the mutually

adjacent flow paths

110a and 110b tends to be larger than the pressure difference between the adjacent flow paths 110b. Thereby, the carbon dioxide gas etc. which generate | occur | produced by combustion of the to-be-collected substance in one flow path 110b are easy to flow into the adjacent flow path 110a compared with the other adjacent flow paths 110b.

In the honeycomb filter 100, carbon dioxide gas or the like generated by the combustion of the collected matter accumulated on the long side 150a in the cross section of the flow path 110b perpendicular to the axial direction of the flow path 110b is separated from the cross section of the flow path 110b. There is a tendency to move in the partition wall 120a having a cross section sharing the long side 150a and reach the flow path 110a (path R ₁₁ in FIG. 1B), and by burning the collected matter accumulated on the short side 150b. The generated carbon dioxide gas or the like tends to move along the partition 120b having a section sharing the short side 150b with the section of the flow path 110b and reach the flow path 110a (in FIG. 1B). Route R ₁₂ ). In this case, the route R ₁₁ passing through the partition wall 120a is, since shorter than the path R ₁₂ passing through the partition wall 120b, towards the carbon dioxide gas and the like generated by the combustion of the collected matter accumulated on the long side 150a However, it is easier to diffuse into the flow path 110a on the gas outflow side than the carbon dioxide gas generated by the combustion of the collected matter accumulated on the short side 150b.

Due to the pressure difference between the flow paths and the difference in the length of the flow path in the partition wall, in the honeycomb filter 100, carbon dioxide gas or the like generated by the combustion of the collected matter accumulated on the long side 150a is generated. However, it is easier to diffuse into the flow path 110a than carbon dioxide gas or the like generated by combustion of the collected matter deposited on the short side 150b. Therefore, the collected matter deposited on the long side 150a is more easily combusted than the collected matter deposited on the short side 150b, and deposited on the collected matter deposited on the long side 150a and the short side 150b. The burning speed differs depending on the material to be collected.

Further, in the honeycomb filter 100, the pressure difference between the flow path 110a and the flow path 110b tends to be larger than the pressure difference between the adjacent flow paths 110b. In comparison, the combustion-supporting gas is easily supplied to the long side 150a. Therefore, the collected matter deposited on the long side 150a is more easily combusted than the collected matter deposited on the short side 150b, and deposited on the collected matter deposited on the long side 150a and the short side 150b. The burning rate tends to be further different from that of the object to be collected.

As described above, in the honeycomb filter 100, the burning rate of the collected matter differs depending on the portion (the long side 150a and the short side 150b) where the collected matter is accumulated. It is suppressed that the combustion of the collection occurs suddenly in many parts and the temperature in the honeycomb filter 100 changes rapidly. Such a phenomenon is presumably caused by the fact that the effective filtration area of the honeycomb filter 100 is 1.1 m ² or more per liter of the honeycomb filter. Thereby, the thermal stress which arises in the honey-comb filter 100 in combustion reproduction | regeneration can be reduced. When the effective filtration area of the honeycomb filter 100 is less than 1.1 m ² per liter of the honeycomb filter, the length of the path R ₁₁ passing through the partition wall 120a and the length of the path R ₁₂ passing through the partition wall 120b are sufficiently different. However, it is difficult to sufficiently reduce the thermal stress.

Further, in the honeycomb filter 100, since the effective filtration area of the honeycomb filter 100 is 1.1 m ² or more per liter of the honeycomb filter, the pressure loss when the fluid containing the trapped material is supplied to the inside of the honeycomb filter is reduced. While reducing, the thermal stress which arises in a honeycomb filter in combustion reproduction | regeneration can be reduced. It is presumed that the pressure loss is reduced due to the fact that the filtration area is sufficiently secured and the trapped substances are prevented from being deposited locally and blocking the flow path. The Note that when the effective filtration area of the honeycomb filter 100 is less than 1.1 m ² per liter of the honeycomb filter, it is difficult to sufficiently reduce the pressure loss.

In the honeycomb filter 100 described above, even when the collected matter is burned and regenerated with a large amount of the collected matter accumulated in the honeycomb filter 100, the heat caused by the heat generated at that time is generated. Damage to the honeycomb filter 100 due to stress can be suppressed. Therefore, since it is not necessary to frequently regenerate the honeycomb filter 100, it is possible to use the filter continuously for a long time until a large amount of collected substances accumulates. Therefore, the maintainability can be improved and the collection efficiency of the collected object can be improved.

In addition, this invention is not necessarily limited to embodiment mentioned above, A various change is possible in the range which does not deviate from the summary.

For example, in the honeycomb filter 100, the arrangement configuration and the cross-sectional configuration of the channel 110a and the channel 110b are not limited to the above. In the honeycomb filter 100, the side 140 and the long side 150a face each other, and the short sides 150b face each other in the adjacent flow path 110b, but the side 140 and the short side 150b face each other and are adjacent to each other. In the channel 110b, the long sides 150a may face each other. Further, the number of the

flow paths

110a and 110b is not limited to that shown in FIGS.

Furthermore, the lengths of the side 140 and the long side 150a facing each other may be different from each other, and the lengths of the short sides 150b facing each other may be different from each other. The side 140 and the long side 150a facing each other may not extend substantially parallel to each other but may extend in directions intersecting each other. The short sides 150b facing each other may not extend substantially parallel to each other but may extend in directions intersecting each other. When the cross section of the flow path 110b has a flat hexagonal shape, the lengths of sides facing each other in the cross section of the flow path 110b may be different from each other.

In the honeycomb filter 200, the arrangement configuration and the cross-sectional configuration of the flow path 210a and the flow path 210b are not limited to the above. For example, in the honeycomb filter 200, the side 240 and the long side 250a face each other, and the short sides 250b face each other in the adjacent flow path 210b, but the side 240 and the short side 250b face each other, In the adjacent channel 210b, the long sides 250a may face each other. Further, the number of the

flow paths

210a and 210b is not limited to that shown in FIGS.

Furthermore, the lengths of the side 240 and the long side 250a facing each other may be different from each other, and the lengths of the short sides 250b facing each other may be different from each other. The sides 240 and the long sides 250a facing each other may not extend substantially in parallel but may extend in directions intersecting each other. The short sides 250b facing each other may not extend substantially in parallel but may extend in directions intersecting each other. When the cross section of the flow path 210b has a flat hexagonal shape, the lengths of sides facing each other in the cross section of the flow path 210b may be substantially equal to each other.

Further, the cross section of the flow channel substantially perpendicular to the axial direction (longitudinal direction) of the flow channel is not limited to a hexagonal shape, and may be a rectangular shape, an octagonal shape, a triangular shape, a circular shape, an elliptical shape, or the like. Good. For example, the honeycomb filter 300 shown in FIG. 5 has a plurality of flow paths 310 arranged substantially in parallel with each other. The flow path 310 includes a plurality of flow paths (first flow paths) 310a and a plurality of flow paths (second flow paths) 310b adjacent to the flow paths 310a. One channel 310b and another channel 310b are adjacent to each other. One flow path 310b is disposed between the flow paths 310a adjacent to each other. An end portion on one end side of the honeycomb filter 300 in the flow path 310 a and an end portion on the other end side of the honeycomb filter 300 in the flow path 310 b are respectively sealed by a sealing portion 330. In the honeycomb filter 300, for example, one end of the flow path 310b is opened as a gas inlet, and the other end of the flow path 310a is opened as a gas outlet. The flow path 310 is partitioned by a partition wall 320 that extends substantially parallel to the central axis of the honeycomb filter 300. The partition 320 has the partition 320a as a part which partitions off the flow path 310a and the flow path 310b, and has the partition 320b as a part which partitions off the mutually adjacent flow paths 310b.

The cross section substantially perpendicular to the axial direction of the flow path 310a is a square shape, and the cross section substantially perpendicular to the axial direction of the flow path 310b is a regular octagon. The cross section of the flow path 310b perpendicular to the axial direction of the flow path 310b has a first side 350a and second sides 350b respectively disposed on both sides of the side 350a. In the cross section of the channel 310b, the sides 350a face each other and the sides 350b face each other, and the lengths of the sides facing each other are equal to each other. Each of the sides 340 forming a cross section of the flow channel 310a perpendicular to the axial direction of the flow channel 310a faces the side 350a of any one of the plurality of flow channels 310b. Each of the sides 350b of the channel 310b faces the side 350b of the adjacent channel 310b. The effective filtration area of the honeycomb filter 300 (the total area of the inner walls of the flow path 310) is 1.1 m ² or more per liter of the honeycomb filter. Further, in the cross section of the honeycomb filter 300 substantially perpendicular to the axial direction of the

flow paths

310a and 310b, the total area of the gas inflow side flow paths is preferably larger than the total area of the gas outflow side flow paths. Is preferably larger than the total area of the flow paths 310a.

In the honeycomb filter 300, carbon dioxide gas or the like generated by combustion of the trapped material deposited on the side 350a in the cross section of the flow path 310b passes through the partition 320a having a cross section that shares the cross section of the flow path 310b and the side 350a. There is a tendency to move and reach the flow path 310a (path R _{31 in} FIG. 5), and carbon dioxide gas or the like generated by the combustion of the collected matter accumulated on the side 350b passes through the cross section of the flow path 310b and the side 350b. The partition 320b having a shared cross section tends to move along the partition and reach the flow path 310a (path R _{32 in} FIG. 5). In this case, since the path R ₃₁ passing through the partition wall 320a is shorter than the path R ₃₂ passing through the partition wall 320b, the direction of the carbon dioxide gas and the like generated by the combustion of the collected matter accumulated on the sides 350a, It is easier to diffuse out of the honeycomb filter than carbon dioxide gas or the like generated by combustion of the collected matter accumulated on the side 350b. Therefore, the collected matter deposited on the side 350a is more easily combusted than the collected matter deposited on the side 350b, and the collected matter deposited on the side 350a and the collected matter deposited on the side 350b The combustion speed will be different.

Furthermore, in the honeycomb filter, a covering portion that covers at least a part of the surface of the partition wall may be disposed. The covering portion may be disposed on the surface of the partition wall in the gas inflow side flow path, or may be disposed on the surface of the partition wall in the gas outflow side flow path. The covering portion is disposed on at least one surface of a part that partitions the gas inflow side flow paths in the partition walls, or a part that partitions the gas inflow side flow path and the gas outflow side flow paths in the partition walls. May be. The coating | coated part may cover all the one wall surfaces of a partition. The covering portion may be formed of a material similar to that of the partition wall, for example, may be porous, or may be formed of a material that shields gas diffusion. The covering portion extends, for example, continuously or intermittently substantially parallel to the central axis and the flow path of the honeycomb filter. The covering portion may be formed in the flow path in advance in a molding process described later, or may be formed in the flow path in a process subsequent to the molding process.

As a structure of the coating | coated part arrange | positioned at the honey-comb filter 100, the structure shown in FIG. 6 is mentioned, for example. In FIG. 6, the covering portion 160 is disposed on the surface of the partition wall in the flow channel 110b on the gas inflow side. 6A and 6B, the covering portion 160 is disposed on the surface of the partition wall 120a that partitions the flow path 110a and the flow path 110b. 6C and 6D, the covering portion 160 is disposed on the surface of the partition wall 120b that partitions the flow paths 110b. 6A and 6C, the covering portions 160 are respectively disposed on the surfaces of the opposing partition walls, and a cross section substantially perpendicular to the longitudinal direction of the covering portion 160 is rectangular. The covering portion 160 in FIG. 6B extends from one partition 120a to the other partition 120a between a pair of opposing partitions 120a. 6D extends from one partition wall 120b to the other partition wall 120b between the opposing partition walls 120b, and the covering portions 160 are connected to each other at substantially the center of the flow path 110b. Yes.

As a structure of the coating | coated part arrange | positioned at the honey-comb filter 300, the structure shown in FIG. 7 is mentioned, for example. In FIG. 7, the covering portion 360 is disposed on the surface of the partition wall in the gas inflow channel 310 b. 7A and 7B, the covering portion 360 is disposed on the surface of the partition 320b that partitions the flow paths 310b. 7C and 7D, the covering portion 360 is disposed on the surface of the partition 320a that partitions the flow path 310a and the flow path 310b. 7A and 7C, the covering portions 360 are respectively disposed on the surfaces of the opposing partition walls, and a cross section substantially perpendicular to the longitudinal direction of the covering portions 360 is rectangular. The covering portions 360 in FIGS. 7B and 7D extend from one partition wall to the other partition wall between the opposing partition walls, and the covering portions 360 are connected to each other at substantially the center of the flow path 310b. ing.

When the covering part is disposed on the surface of the partition wall, it is estimated that the following phenomenon occurs. For example, in the configuration of FIG. 6A in the honeycomb filter 100, a diffusion path of carbon dioxide gas or the like generated by the combustion of the collected matter deposited on the covering portion 160 is formed in the partition wall 120a covered by the covering portion 160. The diffusion path in the covering portion 160 tends to be longer than the diffusion path of carbon dioxide gas or the like generated by the combustion of the collected matter deposited on the wall surface. Thereby, the burning rate of the collected matter deposited on the covering portion 160 is different from the burning rate of the collected matter deposited on the wall surface of the partition wall 120a, and the burning rate of the collected matter is changed in the flow path 110b. It becomes easy to adjust to a different thing according to the deposition location. Therefore, it becomes easy to reduce the thermal stress generated in the honeycomb filter 100 during combustion regeneration.

In the configuration of FIG. 6C in the honeycomb filter 100, the burning rate of the collected matter deposited on the covering portion 160 is different from the burning rate of the collected matter deposited on the wall surface of the partition wall 120b. It becomes easy to adjust the burning rate of the collected material to a different one depending on the accumulation location in the flow path 110b. Therefore, it becomes easy to reduce the thermal stress generated in the honeycomb filter 100 during combustion regeneration.

Further, the wall surface (surface) of the partition wall is not limited to a flat surface, and may be an uneven surface. In this case, it is possible to increase the effective filtration area of the partition wall, and the pressure loss can be further reduced. For example, as shown in FIG. 8, the partition 400 includes a partition body 400a and a plurality of protrusions 400b formed on the surface of the partition body 400a. The protrusion 400b has, for example, a cone shape (conical shape, quadrangular pyramid shape, etc.) (FIG. 8A), a spherical shape (FIG. 8B), or a wave shape (FIG. 8C). The partition wall body 400a and the protrusion 400b may be formed as separate bodies or may be formed as a single unit. The partition wall having the concavo-convex surface may be formed in advance in a molding process described later, or may be formed in a process subsequent to the molding process.

<Honeycomb filter manufacturing method>
The manufacturing method of the honeycomb filter includes (a) a raw material preparation step of preparing a raw material mixture containing ceramic powder and a pore-forming agent, and (b) a forming step of forming the raw material mixture to obtain a formed body having a flow path, (C) a firing step of firing the molded body, and (d) a sealing step of sealing one end of each flow path between the molding step and the firing step or after the firing step. Hereinafter, each step will be described.

(Process (a): Raw material preparation process)
In the step (a), the ceramic powder and the hole forming agent are mixed and then kneaded to prepare a raw material mixture. In addition to the ceramic powder and the hole forming agent, various additives are mixed in the raw material mixture. The additive is, for example, a binder, a plasticizer, a dispersant, or a solvent.

Hereinafter, a method for manufacturing a honeycomb filter having partition walls containing aluminum titanate will be described as an example. The ceramic powder includes at least an aluminum source powder and a titanium source powder, and may further include a magnesium source powder and a silicon source powder.

(Aluminum source powder)
The aluminum source powder is a powder of a compound that becomes an aluminum component constituting the partition wall. Examples of the aluminum source powder include alumina (aluminum oxide) powder. Examples of the crystal type of alumina include γ-type, δ-type, θ-type, and α-type, and may be indefinite (amorphous). The crystal type of alumina is preferably α type.

The aluminum source powder may be a powder of a compound that is led to alumina by firing alone in air. Examples of such a compound include an aluminum salt, aluminum alkoxide, aluminum hydroxide, metal aluminum and the like.

The aluminum salt may be an aluminum inorganic salt with an inorganic acid or an aluminum organic salt with an organic acid. Specific examples of the aluminum inorganic salt include aluminum nitrates such as aluminum nitrate and ammonium aluminum nitrate; aluminum carbonates such as ammonium carbonate aluminum and the like. Examples of the aluminum organic salt include aluminum oxalate, aluminum acetate, aluminum stearate, aluminum lactate, and aluminum laurate.

Specific examples of the aluminum alkoxide include, for example, aluminum isopropoxide, aluminum ethoxide, aluminum sec-butoxide, aluminum tert-butoxide and the like.

Examples of the aluminum hydroxide crystal type include a gibbsite type, a bayerite type, a norosotrandite type, a boehmite type, and a pseudo-boehmite type, and may be amorphous (amorphous). Examples of amorphous aluminum hydroxide include an aluminum hydrolyzate obtained by hydrolyzing an aqueous solution of a water-soluble aluminum compound such as an aluminum salt or an aluminum alkoxide.

The aluminum source powder may be one type or two or more types. The aluminum source powder may contain trace components that are derived from the raw materials or inevitably contained in the production process.

The aluminum source powder is preferably alumina powder, more preferably α-type alumina powder.

In the aluminum source powder, the particle size (center particle size, D50) equivalent to a volume-based cumulative percentage of 50% measured by a laser diffraction method is preferably 20 to 60 μm. By adjusting D50 of the aluminum source powder within this range, an aluminum titanate ceramic fired body exhibiting excellent porosity can be obtained, and the firing shrinkage rate can be more effectively reduced. The D50 of the aluminum source powder is more preferably 25 to 60 μm.

(Titanium source powder)
The titanium source powder is a powder of a compound that becomes a titanium component constituting the partition walls, and is, for example, a titanium oxide powder. Titanium oxide is, for example, titanium (IV) oxide, titanium (III) oxide, or titanium (II) oxide, and preferably titanium (IV) oxide. The crystal forms of titanium (IV) oxide are anatase, rutile, and brookite. The titanium oxide may be amorphous (amorphous). The titanium oxide is more preferably anatase type or rutile type titanium (IV) oxide.

The titanium source powder may be a powder of a compound that is led to titania (titanium oxide) by firing alone in the air. For example, titanium salt, titanium alkoxide, titanium hydroxide, titanium nitride, titanium sulfide, titanium It is a metal.

Examples of the titanium salt include titanium trichloride, titanium tetrachloride, titanium (IV) sulfide, titanium sulfide (VI), and titanium sulfate (IV). Titanium alkoxides include, for example, titanium (IV) ethoxide, titanium (IV) methoxide, titanium (IV) t-butoxide, titanium (IV) isobutoxide, titanium (IV) n-propoxide, titanium (IV) tetraisopropoxide, And these chelating products.

The titanium source powder may be one type or two or more types. The titanium source powder may contain a trace component derived from the raw material or unavoidably contained in the production process.

The titanium source powder is preferably a titanium oxide powder, more preferably a titanium (IV) oxide powder.

In the titanium source powder, the volume-based cumulative particle diameter (D50) measured by laser diffraction method is preferably 0.1 to 25 μm. The D50 of the titanium source powder is more preferably 1 to 20 μm in order to achieve a sufficiently low firing shrinkage rate.

The titanium source powder may show a bimodal particle size distribution. When the titanium source powder having such a bimodal particle size distribution is used, the particle size of the particles forming the peak having the larger particle size measured by the laser diffraction method is preferably 20 to 50 μm.

The mode diameter of the titanium source powder measured by the laser diffraction method is usually 0.1 to 60 μm.

The molar ratio of the aluminum source powder in terms of Al ₂ O ₃ (alumina) and the titanium source powder in terms of TiO ₂ (titania) in the raw material mixture (aluminum source powder: titanium source powder) is preferably 35:65 to 45 : 55, more preferably 40:60 to 45:55. Within such a range, by using the titanium source powder excessively with respect to the aluminum source powder, it becomes possible to more effectively reduce the firing shrinkage rate of the molded body of the raw material mixture.

(Magnesium source powder)
The raw material mixture may further contain a magnesium source powder. When the raw material mixture contains a magnesium source powder, the obtained aluminum titanate ceramic fired body is a fired body containing aluminum magnesium titanate crystals. The magnesium source powder is not only magnesia (magnesium oxide) powder but also a powder of a compound introduced into magnesia by firing alone in air. Such compounds are, for example, magnesium salts, magnesium alkoxides, magnesium hydroxide, magnesium nitride, and metallic magnesium.

Magnesium salts include, for example, magnesium chloride, magnesium perchlorate, magnesium phosphate, magnesium pyrophosphate, magnesium oxalate, magnesium nitrate, magnesium carbonate, magnesium acetate, magnesium sulfate, magnesium citrate, magnesium lactate, magnesium stearate, magnesium salicylate , Magnesium myristate, magnesium gluconate, magnesium dimethacrylate, and magnesium benzoate.

Examples of the magnesium alkoxide include magnesium methoxide and magnesium ethoxide.

As the magnesium source powder, a powder of a compound serving both as a magnesium source and an aluminum source can be used. Such a compound is, for example, magnesia spinel (MgAl ₂ O ₄ ).

When using a powder of a compound that serves as both a magnesium source and an aluminum source as the magnesium source powder, it is included in the amount of Al ₂ O ₃ (alumina) equivalent of the aluminum source powder and a compound powder that serves as both the magnesium source and the aluminum source. The molar ratio between the total amount of Al ₂ O ₃ (alumina) equivalent of the Al component and the amount of TiO ₂ (titania) equivalent of the titanium source powder is adjusted to be within the above range in the raw material mixture.

The magnesium source powder may be one type or two or more types. The magnesium source powder may contain trace components that are derived from the raw materials or inevitably contained in the production process.

In the magnesium source powder, the particle size (D50) equivalent to a volume-based cumulative percentage of 50% as measured by a laser diffraction method is preferably 0.5 to 30 μm. The D50 of the magnesium source powder is more preferably 3 to 20 μm from the viewpoint of reducing the firing shrinkage of the molded body.

The content of magnesium source powder in terms of MgO (magnesia) in the raw material mixture is based on the total amount of aluminum source powder in terms of Al ₂ O ₃ (alumina) and titanium source powder in terms of TiO ₂ (titania). The molar ratio is preferably 0.03 to 0.15, more preferably 0.03 to 0.12. By adjusting the content of the magnesium source powder within this range, an aluminum titanate-based ceramic fired body having a large pore diameter and porosity with improved heat resistance can be obtained relatively easily.

(Silicon source powder)
The raw material mixture may further contain a silicon source powder. The silicon source powder is a powder of a compound that becomes a silicon component and is contained in the aluminum titanate ceramic fired body. By using the silicon source powder in combination, a heat-resistant aluminum titanate ceramic fired body is obtained. Is possible. The silicon source powder is, for example, a powder of silicon oxide (silica) such as silicon dioxide or silicon monoxide.

The silicon source powder may be a powder of a compound led to silica by firing alone in air. Such compounds are, for example, silicic acid, silicon carbide, silicon nitride, silicon sulfide, silicon tetrachloride, silicon acetate, sodium silicate, sodium orthosilicate, feldspar, glass frit, preferably feldspar, glass frit, industrial Glass frit is more preferable because it is easily available and has a stable composition. Glass frit refers to flakes or powdery glass obtained by pulverizing glass. It is also preferable to use a powder made of a mixture of feldspar and glass frit as the silicon source powder.

When using a glass frit, it is preferable that the yield point of the glass frit is 600 ° C. or higher from the viewpoint of further improving the thermal decomposition resistance of the obtained aluminum titanate ceramic fired body. In this specification, the yield point of the glass frit is determined by measuring the expansion of the glass frit from a low temperature using a thermomechanical analyzer (TMA: Thermo Mechanical Analysis). It is defined as

As the glass constituting the glass frit, a general silicate glass containing silicate [SiO ₂ ] as a main component (50 mass% or more in all components) can be used. The glass constituting the glass frit includes, as other components, alumina [Al ₂ O ₃ ], sodium oxide [Na ₂ O], potassium oxide [K ₂ O], calcium oxide [ CaO], magnesia [MgO] and the like may be included. The glass constituting the glass frit may contain ZrO ₂ in order to improve the hot water resistance of the glass itself.

The silicon source powder may be one type or two or more types. The silicon source powder may contain a trace component derived from the raw material or inevitably contained in the production process.

In the silicon source powder, the particle size (D50) equivalent to a 50% cumulative percentage on a volume basis measured by a laser diffraction method is preferably 0.5 to 30 μm. The D50 of the silicon source powder is more preferably 1 to 20 μm in order to obtain a fired body having higher mechanical strength by further improving the filling factor of the molded body.

When the raw material mixture includes a silicon source powder, the content of the silicon source powder in the raw material mixture is the sum of the aluminum source powder in terms of Al ₂ O ₃ (alumina) and the titanium source powder in terms of TiO ₂ (titania). The amount is usually 0.1 to 10 parts by mass, preferably 0.1 to 5 parts by mass in terms of SiO ₂ (silica) with respect to 100 parts by mass.

In the manufacture of a honeycomb filter, a compound containing two or more metal elements among titanium, aluminum, silicon and magnesium as a raw material powder, such as a composite oxide such as magnesia spinel (MgAl ₂ O ₄ ), is used. be able to. In this case, the compound can be considered to be the same as the raw material in which the respective metal source compounds are mixed. Based on such an idea, the content of the aluminum source, the titanium source, the magnesium source and the silicon source in the raw material mixture is adjusted within the above range.

The raw material mixture may contain aluminum titanate or aluminum magnesium titanate. For example, when aluminum magnesium titanate is used as a constituent of the raw material mixture, the aluminum magnesium titanate corresponds to a raw material mixture having a titanium source, an aluminum source, and a magnesium source.

Aluminum titanate or aluminum magnesium titanate may be prepared from a honeycomb filter obtained by this production method. For example, when the honeycomb filter obtained by the present manufacturing method is damaged, the damaged honeycomb filter or its fragments can be pulverized and used. The powder obtained by pulverization can be aluminum magnesium titanate powder.

(Pore forming agent)
As the pore-forming agent, those formed by a material that disappears at or below the firing temperature at which the molded body is fired in step (c) can be used. In degreasing and firing, when a molded body containing a hole forming agent is heated, the hole forming agent disappears due to combustion or the like. As a result, a space is created at the location where the pore-forming agent was present, and the ceramic powder located between the spaces shrinks during firing, so that the communication holes through which the fluid can flow are formed in the honeycomb filter. It can be formed in the partition wall.

In the method for manufacturing a honeycomb filter, a hole forming agent can be used to form a predetermined communication hole. Examples of the pore-forming agent include corn starch, barley starch, wheat starch, tapioca starch, bean starch, rice starch, pea starch, coral starch, canna starch, and potato starch (potato starch). The average particle diameter of the pore forming agent is preferably 5 to 25 μm.

The content of the pore-forming agent in the raw material mixture is preferably 1 to 25 parts by mass with respect to 100 parts by mass of the ceramic powder. When the content of the pore-forming agent is within this range, it becomes easy to prevent the leakage of the collected material while keeping the initial pressure loss low. When the content of the pore forming agent is less than 1 part by mass with respect to 100 parts by mass of the ceramic powder, the pressure loss tends to increase because the number of pores formed in the partition walls decreases. On the other hand, when the content of the pore-forming agent is more than 25 parts by mass with respect to 100 parts by mass of the ceramic powder, the proportion of pores formed in the partition walls becomes too large, and the collected material tends to leak.

In manufacturing a honeycomb filter, an organic component (additive) such as a binder, a plasticizer, a dispersant, and a solvent may be blended in the raw material mixture in addition to the ceramic powder and the hole forming agent described above.

The binder is, for example, celluloses such as methyl cellulose, carboxymethyl cellulose, sodium carboxymethyl cellulose; alcohols such as polyvinyl alcohol; salts such as lignin sulfonate; waxes such as paraffin wax and microcrystalline wax. The content of the binder in the raw material mixture is usually 20 parts by mass or less, preferably 15 parts by mass or less with respect to 100 parts by mass of the total amount of the aluminum source powder, titanium source powder, magnesium source powder and silicon source powder. .

Examples of the plasticizer include alcohols such as glycerin; higher fatty acids such as caprylic acid, lauric acid, palmitic acid, alginic acid, oleic acid and stearic acid; stearic acid metal salts such as Al stearate; polyoxyalkylene alkyl ethers . The content of the plasticizer in the raw material mixture is usually 0 to 10 parts by mass, preferably 1 to 5 parts by mass with respect to 100 parts by mass of the total amount of the aluminum source powder, titanium source powder, magnesium source powder and silicon source powder. Part.

Examples of the dispersant include inorganic acids such as nitric acid, hydrochloric acid, and sulfuric acid; organic acids such as oxalic acid, citric acid, acetic acid, malic acid, and lactic acid; alcohols such as methanol, ethanol, and propanol; interfaces such as ammonium polycarboxylate It is an activator. The content of the dispersant in the raw material mixture is usually 0 to 20 parts by mass, preferably 2 to 8 parts by mass with respect to 100 parts by mass of the total amount of the aluminum source powder, titanium source powder, magnesium source powder and silicon source powder. Part.

The solvent is usually water, and is preferably ion-exchanged water from the viewpoint of few impurities. The content of the solvent in the raw material mixture is usually 10 to 100 parts by mass, preferably 20 to 80 parts by mass with respect to 100 parts by mass of the total amount of the aluminum source powder, titanium source powder, magnesium source powder and silicon source powder. .

(Process (b): Molding process)
In the step (b), a honeycomb structure having a plurality of flow paths is obtained as a ceramic molded body. In the step (b), for example, a so-called extrusion molding method in which the raw material mixture is extruded from a die while being kneaded by a single screw extruder can be employed.

When a plasticizer is added to the raw material mixture as an additive, most of the plasticizers can function as a lubricant for reducing friction between the raw material mixture and the die when the raw material mixture is extruded from the die. For example, each plasticizer described above can function as a lubricant.

(Process (c): Firing process)
In the step (c), degreasing (calcination) for removing a hole forming agent or the like contained in the molded body (in the raw material mixture) may be performed before firing the molded body. Degreasing is performed in an atmosphere having an oxygen concentration of 0.1% or less.

In this specification, “%” used as a unit of oxygen concentration means “volume%”. By controlling the oxygen concentration in the degreasing step (at the time of temperature rise) to a concentration of 0.1% or less, heat generation of the organic matter can be suppressed and cracking after degreasing can be suppressed. In degreasing, degreasing is performed in an atmosphere having an oxygen concentration of 0.1% or less, whereby a part of organic components such as a pore-forming agent is removed, and the remainder is carbonized and remains in the ceramic molded body. preferable. Thus, the trace amount of carbon remains in the ceramic molded body, so that the strength of the molded body is improved and the ceramic molded body can be easily charged into the firing step. Examples of such an atmosphere include an inert gas atmosphere such as nitrogen gas and argon gas, a reducing gas atmosphere such as carbon monoxide gas and hydrogen gas, and a vacuum. In addition, firing may be performed in an atmosphere with a low water vapor partial pressure, or steaming with charcoal may reduce the oxygen concentration.

The maximum temperature for degreasing is preferably 700 to 1100 ° C, more preferably 800 to 1000 ° C. By increasing the maximum degreasing temperature from about 600 to 700 ° C to 700 to 1100 ° C, the strength of the ceramic body after degreasing is improved by grain growth. It becomes easy. In addition, degreasing preferably suppresses the rate of temperature rise until reaching the maximum temperature as much as possible in order to prevent cracking of the ceramic molded body.

Degreasing is used for normal firing of tubular electric furnace, box-type electric furnace, tunnel furnace, far-infrared furnace, microwave heating furnace, shaft furnace, reflection furnace, rotary furnace, roller hearth furnace, gas combustion furnace, etc. A similar furnace is used. Degreasing may be performed batchwise or continuously. Moreover, degreasing may be performed by a stationary method or a fluid method.

The time required for degreasing may be a time sufficient for a part of the organic component contained in the ceramic molded body to disappear, and preferably 90 to 99% by mass of the organic component contained in the ceramic molded body. It is time to disappear. Specifically, although it varies depending on the amount of the raw material mixture, the type of furnace used for degreasing, temperature conditions, atmosphere, etc., the time for keeping at the maximum temperature is usually 1 minute to 10 hours, preferably 1 to 7 hours. is there.

The ceramic molded body is fired after the above degreasing. The firing temperature is usually 1300 ° C. or higher, preferably 1400 ° C. or higher. Moreover, a calcination temperature is 1650 degrees C or less normally, Preferably it is 1550 degrees C or less. The rate of temperature increase up to the firing temperature is not particularly limited, but is usually 1 to 500 ° C./hour. When the silicon source powder is used, it is preferable to provide a step of holding at a temperature range of 1100 to 1300 ° C. for 3 hours or more before the firing step. Thereby, melting and diffusion of the silicon source powder can be promoted.

Calcination is preferably performed in an atmosphere having an oxygen concentration of 1 to 6%. By setting the oxygen concentration to 6% or less, combustion of residual carbides generated by degreasing can be suppressed, so that the ceramic molded body is less likely to crack during firing. Moreover, since moderate oxygen exists, the organic component of the finally obtained aluminum titanate ceramic molded body can be completely removed. The oxygen concentration is preferably 1% or more because carbide (soot) derived from organic components does not remain in the obtained aluminum titanate-based ceramic fired body. Depending on the type and usage ratio of the raw material mixture, that is, the aluminum source powder, titanium source powder, magnesium source powder and silicon source powder, it may be fired in an inert gas such as nitrogen gas or argon gas, or carbon monoxide You may bake in reducing gas, such as gas and hydrogen gas. Further, the firing may be performed in an atmosphere in which the water vapor partial pressure is lowered.

Firing is usually performed using conventional equipment such as a tubular electric furnace, box-type electric furnace, tunnel furnace, far-infrared furnace, microwave heating furnace, shaft furnace, reflection furnace, rotary furnace, roller hearth furnace, gas combustion furnace, etc. Done. Firing may be performed batchwise or continuously. Moreover, baking may be performed by a stationary type or may be performed by a fluid type.

The firing time may be a time sufficient for the ceramic molded body to transition to the aluminum titanate-based crystal, and varies depending on the amount of raw material, type of firing furnace, firing temperature, firing atmosphere, etc., but usually 10 minutes to 24 hours.

(Process (d): Sealing process)
Step (d) is performed between step (b) and step (c) or after step (c). When performing step (d) between step (b) and step (c), after sealing one end of each flow path of the unfired ceramic molded body obtained in step (b) with a sealing material In the step (c), the sealing material is fired together with the ceramic molded body to obtain a sealing portion that seals one end of the flow path. When the step (d) is performed after the step (c), one end of each flow path of the ceramic molded body obtained in the step (c) is sealed with a sealing body, and then the sealing body is baked together with the ceramic molded body. By doing so, the sealing part which seals one edge part of a flow path is obtained. As the sealing material, the same mixture as the raw material mixture can be used.

A honeycomb filter can be obtained through the above steps. The honeycomb filter has a shape that substantially maintains the shape of the molded body immediately after the molding in the step (b), but after the step (b), the step (c) or the step (d), a grinding process or the like is performed, It can also be processed into a desired shape.

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

Example 1
<Preparation of raw material mixture>
Raw material powder of aluminum magnesium titanate (Al ₂ O ₃ powder, TiO ₂ powder, MgO powder), SiO ₂ powder, ceramic powder having a composite phase of aluminum magnesium titanate, alumina and aluminosilicate glass (composition formula at the time of preparation) : 41.4Al ₂ O ₃ -49.9TiO ₂ -5.4MgO-3.3SiO ₂ , the numerical values in the formula represent molar ratios), pore formers, organic binders, lubricants, plasticizers, dispersants and A raw material mixture containing water (solvent) was prepared. The content of each component in the raw material mixture was adjusted to the following values.

[Components of raw material mixture]
Al ₂ O ₃ powder: 37.3 parts by mass TiO ₂ powder: 37.0 parts by mass MgO powder: 1.9 parts by mass SiO ₂ powder: 3.0 parts by mass Ceramic powder: 8.8 parts by mass Porous agent: potato 12.0 parts by weight of organic binder 1: methylcellulose (manufactured by Samsung Precision Chemical Co., Ltd .: MC-40H), 5.5 parts by weight of organic binder 2: hydroxypropylmethylcellulose (manufactured by Samsung Precision Chemical Co., Ltd.) : PMB-40H), 2.4 parts by mass

The above raw material mixture was kneaded and extruded. And the cylindrical columnar body (DPF) which has a structure shown in FIG.1, 2 was produced by baking after sealing one edge part of each flow path of a molded object with a sealing material.

The length of the columnar body in the longitudinal direction of the flow path (through hole) was 153 mm. The outer diameter of the end face of the columnar body was 144 mm. The density of the flow path (cell density) was 290 cpsi. The length of one side of the regular hexagonal channel was 0.9 mm. In the flat hexagonal channel, the long side length was 0.9 mm, and the short side length was 0.6 mm. The thickness of the partition between flow paths was 12 mil (milli-inch, 0.30 mm). The porosity of the partition walls was 45% by volume. The pore diameter of the partition wall was 15 μm. The effective filtration area (the area of the inner wall of the gas inflow side channel (flat hexagonal channel) per 1 L of the columnar body) was 1.30 m ² / L.

(Comparative Example 1)
The same raw material mixture as in Example 1 was kneaded and then extruded. And the columnar body (DPF) 500 which has the structure shown in FIG. 9 was produced by baking after sealing one edge part of each flow path of a molded object with a sealing material. In the columnar body 500, in the flow paths P2 and P3 adjacent to the flow path P1, the side of the flow path P2 and the side of the flow path P3 do not face each other.

In the columnar body of Comparative Example 1, each channel (through hole) 510 had a square cross section, and the ends of the adjacent channels 510 were alternately sealed by the sealing portions 530. The length of the columnar body in the longitudinal direction of the flow path was 153 mm. The outer diameter of the end face of the columnar body was 144 mm. The cell density was 290 cpsi. The length of one side of the square channel was 1.1 mm. The partition wall thickness between the channels was 13 mil (0.33 mm). The effective filtration area was 1.07 m ² / L.

<Pressure loss measurement>
(Measurement of pressure loss during soot deposition)
DPF pressure loss measurement was performed as follows. FIG. 10 shows a schematic diagram of a pressure loss measuring apparatus. For the pressure loss measurement, a soot generator (trade name: REXS, manufactured by Matter Engineering Co., Ltd.) 600 and a large compressor device 610 were used. One end face of the DPF was connected to the soot generator 600, and the compressor device 610 was connected to a pipe connecting the DPF and the soot generator 600.

To the soot generator 600, propane gas was supplied at a flow rate of 2 L / min, nitrogen gas was supplied at a flow rate of 2 L / min, and air was supplied at a flow rate of 1000 L / min. The soot generated from the soot generator 600 is artificial soot generated by incomplete combustion of propane gas. In the soot generator 600, the average particle diameter of soot is controlled by the air flow rate, oxygen concentration, and the like. can do. In the measurement, the average particle diameter of the soot was adjusted to about 90 nm. The flow rate of air containing soot was adjusted to 200 Nm ³ h ⁻¹ by the compressor device 610.

In order to grasp the pressure loss behavior during the soot deposition, the pressure difference before and after the DPF (the pressure difference ΔP between the pressure P1 and the pressure P2 in FIG. 10) was recorded while supplying soot inside the DPF. FIG. 11A shows the result of measuring the pressure loss accompanying the increase in the soot deposition amount using the DPFs of Example 1 and Comparative Example 1. FIG. As shown in FIG. 11A, it is confirmed that the pressure loss value is smaller in Example 1 than in Comparative Example 1. Moreover, in Example 1, it is confirmed that the increase amount of the pressure loss accompanying the increase in the amount of soot deposition is small compared with the comparative example 1.

(Measurement of pressure loss after soot deposition)
When the soot accumulation amount reached 8 g per liter of DPF, the soot generator 600 was stopped. Then, the differential pressure before and after the DPF (the differential pressure ΔP in FIG. 10) was recorded while increasing the flow rate of the gas discharged from the compressor device 610 from 200 Nm ³ h ⁻¹ to 600 Nm ³ h ⁻¹ . FIG. 11B shows the result of measuring the pressure loss accompanying the increase in gas flow rate using the DPFs of Example 1 and Comparative Example 1. As shown in FIG. 11B, it is confirmed that the pressure loss value is smaller in Example 1 than in Comparative Example 1. Moreover, in Example 1, it is confirmed that the increase amount of the pressure loss accompanying the increase in gas flow rate is small compared with the comparative example 1.

100, 200, 300 ... Honeycomb filter, 100a, 100b, 200a, 200b ... End of honeycomb filter, 110a, 210a, 310a ... Channel (first channel), 110b, 210b, 310b ... Channel (second) , 120, 220, 320 ... partition walls, 140, 240, 340 ... sides forming the cross section of the flow path (first flow path), 150a, 250a, 350a ... flow paths (second flow path). Sides forming the cross section (first side), 150b, 250b, 350b,..., Sides forming the cross section of the flow path (second flow path) (second side).

Claims

A honeycomb filter having a plurality of parallel flow paths partitioned by a porous partition wall,
The plurality of channels have a first channel and a plurality of second channels adjacent to the first channel,
One second flow path and the other second flow path in the plurality of second flow paths are adjacent to each other,
An end of one end of the honeycomb filter in the first flow path is sealed;
The end of the other end side of the honeycomb filter in the second flow path is sealed,
A cross section of the second flow path perpendicular to the axial direction of the second flow path has a first side and second sides respectively disposed on both sides of the first side. ,
Each of the sides forming the cross section of the first channel perpendicular to the axial direction of the first channel is opposed to the first side of the second channel,
Each of the second sides of the second flow path is opposed to the second side of the adjacent second flow path;
A plurality of the first flow paths are disposed;
The product of the length of each side forming the cross section of the second flow path in each second flow path and the length of the second flow path in the axial direction of the second flow path. A honeycomb filter in which the total sum of S in all the second flow paths included per liter of the honeycomb filter is 1.1 m 2 or more, where S is a total.
The honeycomb filter according to claim 1, wherein the partition wall includes aluminum titanate.
The honeycomb filter according to claim 1 or 2, wherein the cross section of the first flow path and the cross section of the second flow path are hexagonal.
The honeycomb filter according to any one of claims 1 to 3, wherein one of the second flow paths is disposed between the first flow paths adjacent to each other.
The honeycomb filter according to claim 4, wherein lengths of sides facing each other in the cross section of the second flow path are equal to each other.
The honeycomb filter according to claim 5, wherein the cross section of the second flow path has two long sides having the same length and four short sides having the same length.
The two second flow paths are disposed between the first flow paths adjacent to each other and are adjacent to each other in a direction orthogonal to the arrangement direction of the first flow paths. The honeycomb filter according to any one of items 1 to 3.
The cross section of the second flow path has three long sides having the same length and three short sides having the same length, and the long side and the short side face each other. The honeycomb filter according to claim 7.