WO2013094518A1

WO2013094518A1 - Honeycomb filter

Info

Publication number: WO2013094518A1
Application number: PCT/JP2012/082370
Authority: WO
Inventors: 健太郎岩崎; 山田　陽一; 照夫小森
Original assignee: 住友化学株式会社
Priority date: 2011-12-22
Filing date: 2012-12-13
Publication date: 2013-06-27
Also published as: JP2013128913A

Abstract

A honeycomb filter (100) has conduits (110) extending parallel to each other and has end surfaces (100a, 100b). The conduits (110) comprise: conduits (110a), the end surface (100b)-side ends of which are sealed; and conduits (110b), the end surface (100a)-side ends of which are sealed. The sum of the areas of openings of the conduits (110a), the openings being open at the end surface (100a), is greater than the sum of the areas of openings of the conduits (110b), the openings being open at the end surface (100b), and the hydraulic diameter of the conduits (110a) is 1.4 mm or less.

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 partition walls, and one end of a part of the plurality of flow paths and the other end of the remaining part of the plurality of flow paths are sealed. (For example, refer to 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 and / 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 combustion regeneration is performed in a state where an excessive amount of collected matter is accumulated in the honeycomb filter, an excessive thermal stress is applied to the honeycomb filter, and the honeycomb filter may be thermally damaged or melted. . From this point of view, it is desirable to perform regenerative combustion before an excessive amount of collected matter is deposited.

The amount of collected matter in the honeycomb filter may be estimated based on the pressure loss that increases with the amount of collected matter. In this case, it is effective to use a honeycomb filter in which the pressure loss is easily changed according to the amount of collected material as one of the methods for performing regeneration combustion before the excessive amount of collected material is deposited. .

The present invention has been made in view of such a situation, and an object of the present invention is to provide a honeycomb filter in which the pressure loss is easily changed according to the amount of collected substances.

That is, the honeycomb filter according to the present invention is a honeycomb filter having a plurality of flow paths parallel to each other, and the honeycomb filter has a first end face and a second end face located on the opposite side of the first end face. A plurality of flow paths, a plurality of first flow paths whose end portions on the second end face side are sealed, and a plurality of second flow paths whose end portions on the first end face side are sealed. A sum of opening areas of the plurality of first passages on the first end face is larger than a sum of opening areas of the plurality of second passages on the second end face, The hydraulic diameter (hydraulic equivalent diameter) of the channel is 1.4 mm or less. In the present specification, the “hydraulic diameter of the flow channel” means a cross-sectional area equivalent to a cross-sectional area obtained by cutting the target flow channel perpendicularly to the axial direction (longitudinal direction) of the flow channel. The diameter of a perfect circle having an area.

When collecting the collected material contained in the fluid, from the viewpoint of improving the collection efficiency of the collected material, the fluid containing the collected material from the end face side where the total of the opening area of the flow path is large. It may be supplied into the honeycomb filter. In the honeycomb filter according to the present invention, when the fluid containing the collected substance is supplied into the honeycomb filter from the first end face side, the pressure loss can be easily changed according to the accumulation amount of the collected substance. it can. As a result, it becomes easy to perform regenerative combustion before an excessive amount of collected matter accumulates, and excessive thermal stress is applied to the honeycomb filter during regenerative combustion, causing thermal damage and melting damage of the honeycomb filter. Can be suppressed.

As described above, the present inventor presumes the factors that cause the pressure loss to easily change as follows. However, the factors are not limited to the following. That is, according to the knowledge of the present inventor, when the hydraulic diameter of the first flow path is large, the amount of the trapped material flowing into each first flow path increases, so that It is presumed that the collected matter is likely to be deposited on the end face side of 2, and the pressure loss is less likely to change depending on the amount of collected matter. On the other hand, in the present invention, when the hydraulic diameter of the first flow path is 1.4 mm or less, the amount of collected matter flowing into each first flow path can be reduced. Thereby, compared with the case where the hydraulic diameter of the first flow path exceeds 1.4 mm, it is possible to suppress the collection of the collected matter on the second end face side in the first flow path, The pressure loss is likely to change depending on the amount of deposits.

The hydraulic diameter of the second flow path is preferably larger than the hydraulic diameter of the first flow path. In this case, the pressure loss can be further easily changed according to the accumulation amount of the collected object.

According to the present invention, it is possible to provide a honeycomb filter in which the pressure loss is easily changed according to the amount of collected matter.

It is a figure showing typically a honeycomb filter concerning a 1st embodiment of the present invention. FIG. 2 is a view taken in the direction of arrows II-II in FIG. It is a figure which shows typically the honey-comb filter which concerns on 2nd Embodiment of this invention. FIG. 4 is a view taken along arrow IV-IV in FIG. 3. It is a figure which shows typically the measuring apparatus of a pressure loss. It is a figure which shows the measurement result of a 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.

<Honeycomb filter>
FIG. 1 is a diagram schematically showing the honeycomb filter according to the first embodiment, and FIG. 1B is an enlarged view of a region R1 in FIG. FIG. 2 is a view taken along the line II-II in FIG. The honeycomb filter 100 has one end face (first end face) 100a and the other end face (second end face) 100b located on the opposite side of the end face 100a. The end surface 100a and the end surface 100b face each other in parallel.

The honeycomb filter 100 is a cylindrical body having a plurality of flow paths 110 extending in parallel to each other. The plurality of flow paths 110 are partitioned by partition walls 120 extending in 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 110a and the flow path 110b extend from the end face 100a to the end face 100b perpendicular to the end faces 100a and 100b.

One end of the flow path 110a constituting a part of the flow path 110 is opened at the end face 100a, and the other end of the flow path 110a is sealed by the sealing portion 130 at the end face 100b. One end of the flow path 110b constituting the remaining part of the flow path 110 is sealed by the sealing portion 130 at the end face 100a, and the other end of the flow path 110b is opened at the end face 100b. In the honeycomb filter 100, for example, an end portion on the end surface 100a side of the flow path 110a is opened as a gas inlet, and an end portion on the end face 100b side of the flow path 110b is opened as a gas outlet.

The cross section perpendicular to the axial direction of the flow path 110a and the flow path 110b has a hexagonal shape. The cross section of the flow path 110b is, for example, a regular hexagonal shape in which the lengths of the sides 140 forming the cross section are substantially equal to each other, but may be a flat hexagonal shape. The cross section of the flow path 110a has, for example, a flat hexagonal shape, but may have a regular hexagonal shape. The lengths of the sides facing each other in the cross section of the channel 110a are substantially equal to each other. The cross section of the flow path 110a includes two long sides 150a having substantially the same length as the sides 150 forming the cross section, and four (two pairs) short sides 150b having substantially the same length. ,have. The short side 150b is disposed on each side of the long side 150a. The long sides 150a face each other in parallel, and the short sides 150b face each other in parallel.

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 channel 110a between adjacent channels 110b, the channels 110b are alternately arranged with the channels 110a in the arrangement direction of the channels 110b (a direction substantially perpendicular to the side 140). Yes.

Each of the sides 140 of the flow channel 110b faces the long side 150a of any one of the plurality of flow channels 110a in parallel. That is, each of the wall surfaces forming the flow channel 110b faces the one wall surface forming the flow channel 110a in parallel 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 110b and six flow paths 110a surrounding the flow path 110b. In the structural unit, all the sides 140 of the flow path 110b are included. Opposite the long side 150a of the channel 110a. In the honeycomb filter 100, at least one length of the side 140 of the flow path 110b may be substantially equal to the length of the opposed long side 150a, and each length of the side 140 is equal to the length of the opposed long side 150a. It may be substantially equal.

The partition wall 120 has a partition wall 120b as a part for partitioning the adjacent flow paths 110a. That is, the flow paths 110a surrounding the flow path 110b are adjacent to each other via the partition wall 120b.

Each of the short side 150b of the flow path 110a is facing in parallel with the short side 150b of the adjacent flow path 110a. That is, the wall surfaces forming the flow path 110a face each other in parallel in the partition wall 120b located between the adjacent flow paths 110a. In the honey-comb filter 100, between the adjacent flow paths 110a, at least one length of the short side 150b of the flow path 110a may be substantially equal to the length of the opposing short side 150b. May be substantially equal to the length of the opposing short side 150b.

Fig. 3 is a diagram schematically showing a honeycomb filter according to the second embodiment, and Fig. 3 (b) is an enlarged view of a region R2 in Fig. 3 (a). 4 is a view taken in the direction of arrows IV-IV in FIG. The honeycomb filter 200 has one end face (first end face) 200a and the other end face (second end face) 200b located on the opposite side of the end face 200a. The end surface 200a and the end surface 200b face each other in parallel.

The honeycomb filter 200 is a cylindrical body having a plurality of flow paths 210 extending in parallel to each other. The plurality of flow paths 210 are partitioned by partition walls 220 extending in parallel with 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 channel 210a and the channel 210b extend from the end surface 200a to the end surface 200b perpendicular to the

end surfaces

200a and 200b.

One end of the flow path 210a constituting a part of the flow path 210 is opened at the end face 200a, and the other end of the flow path 210a is sealed by the sealing portion 230 at the end face 200b. One end of the flow path 210b constituting the remaining part of the flow path 210 is sealed by the sealing portion 230 at the end face 200a, and the other end of the flow path 210b is opened at the end face 200b. In the honeycomb filter 200, for example, an end portion on the end surface 200a side of the flow path 210a is opened as a gas inlet, and an end portion of the flow path 210b on the end surface 200b side is opened as a gas outlet.

The cross section perpendicular to the axial direction of the flow path 210a and the flow path 210b has a hexagonal shape. The cross section of the flow path 210b is, for example, a regular hexagonal shape in which the lengths of the sides 240 forming the cross section are substantially equal to each other, but may be a flat hexagonal shape. The cross section of the flow path 210a 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 210a are different from each other. The cross section of the channel 210a has three long sides 250a having substantially the same length and three short sides 250b having substantially the same length as the sides 250 forming the cross section. The long side 250a and the short side 250b face each other in parallel, and the short side 250b is disposed on each side of the long side 250a.

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 210b, two flow paths 210a adjacent to each other in a direction substantially orthogonal to the arrangement direction of the flow paths 210b are arranged, and the two adjacent flow paths 210a are adjacent to each other. They are arranged symmetrically across a line connecting the centers of the sections of 210b.

Each of the sides 240 of the flow path 210b faces the long side 250a of any one of the plurality of flow paths 210a in parallel. That is, each of the wall surfaces forming the flow path 210b faces the one wall surface forming the flow path 210a in parallel in the partition wall 220a positioned between the flow path 210a and the flow path 210b. The flow path 210 includes a structural unit including one flow path 210b and six flow paths 210a surrounding the flow path 210b. In the structural unit, all the sides 240 of the flow path 210b are included. It faces the long side 250a of the flow path 210a. Each vertex of the cross section of the flow path 210b is opposed to the apex of the adjacent flow path 210b in the arrangement direction of the flow paths 210b. In the honeycomb filter 200, at least one length of the side 240 of the flow path 210b may be substantially equal to the length of the opposed long side 250a, and each length of the side 240 is equal to the length of the opposed long side 250a. It may be substantially equal.

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

Each of the short side 250b of the flow path 210a is facing in parallel with the short side 250b of the adjacent flow path 210a. That is, the wall surfaces forming the flow path 210a face each other in parallel in the partition 220b located between the adjacent flow paths 210a. One flow path 210a is surrounded by three flow paths 210b. In the honey-comb filter 200, between the adjacent flow paths 210a, at least one length of the short side 250b of the flow path 210a may be substantially equal to the length of the opposing short side 250b. May be substantially equal to the length of the opposing short side 250b.

The length of the honeycomb filters 100 and 200 in the axial direction of the flow path is, for example, 50 to 300 mm. The outer diameter of the honeycomb filters 100 and 200 is, for example, 50 to 250 mm. In the honeycomb filter 100, the length of the side 140 is, for example, 0.4 to 2.0 mm. The length of the long side 150a is, for example, 0.4 to 2.0 mm, and the length of the short side 150b is, for example, 0.3 to 2.0 mm. In the honeycomb filter 200, the length of the side 240 is, for example, 0.4 to 2.0 mm. The length of the long side 250a is, for example, 0.4 to 2.0 mm, and the length of the short side 250b is, for example, 0.3 to 2.0 mm. The thickness of the partition walls 120 and 220 (cell wall thickness) is, for example, 0.1 to 0.8 mm. The cell density in the honeycomb filters 100 and 200 (for example, in the honeycomb filter 100, the total density of the flow path 110a and the flow path 110b in the end face 100a) is preferably 50 to 600 cpsi, and more preferably 100 to 500 cpsi.

In the honeycomb filter 100, the total opening area of the plurality of flow paths 110a on the end face 100a is larger than the total opening area of the plurality of flow paths 110b on the end face 100b. In the honeycomb filter 200, the total opening area of the plurality of flow paths 210a on the end face 200a is larger than the total opening area of the plurality of flow paths 210b on the end face 200b.

The hydraulic diameters of the

flow paths

110a and 210a on the end faces 100a and 200a are 1.4 mm or less from the viewpoint that pressure loss is likely to change according to the amount of collected matter. In addition, the hydraulic diameters of the

flow paths

110a and 210a are preferably 1.3 mm or less, and more preferably 1.2 mm or less, from the viewpoint that the pressure loss is more likely to change according to the amount of collected substances. The hydraulic diameters of the

flow paths

110a and 210a are preferably 0.5 mm or more, and more preferably 0.7 mm or more, from the viewpoint of further suppressing accumulation of collected substances in the region on the end face side in the flow path.

The hydraulic diameter of the

flow paths

110b and 210b on the end faces 100b and 200b is preferably larger than the hydraulic diameter of the

flow paths

110a and 210a on the end faces 100a and 200a. The hydraulic diameters of the

flow paths

110b and 210b in the end faces 100b and 200b are preferably 1.7 mm or less, and more preferably 1.6 mm or less, from the viewpoint that the pressure loss is more likely to change depending on the amount of collected matter. . The hydraulic diameters of the

flow paths

110b and 210b are preferably 0.5 mm or more, more preferably 0.7 mm or more, from the viewpoint of further suppressing the accumulation of collected substances in the region on the end face side in the flow path. More preferably, it is 9 mm or more.

The shape of the honeycomb filter is such that the cross section of the first channel perpendicular to the axial direction of the first channel (

channels

110a and 210a) is the first side as in the honeycomb filters 100 and 200 described above. (

Long sides

150a, 250a) and second sides (

short sides

150b, 250b) respectively disposed on both sides of the first side, and a second channel (

channels

110b, 210b). ) Each of the sides (sides 140 and 240) forming a cross section of the second flow path perpendicular to the axial direction of the first flow path are opposed to the first side of the first flow path. Each of the second sides may be in a form facing the second side of the adjacent first flow path, but is not necessarily limited to the shape described above.

Further, the cross section of the channel perpendicular to the axial direction of the channel in the honeycomb filter is not limited to the hexagonal shape, and may be a triangular shape, a rectangular shape, an octagonal shape, a circular shape, an elliptical shape, or the like. . Moreover, in the flow path, those having different diameters may be mixed, or those having different cross-sectional shapes may be mixed. In addition, the arrangement of the flow paths is not particularly limited, and the arrangement of the central axes of the flow paths may be an equilateral triangle arrangement, a staggered arrangement, or the like arranged at the apex of the equilateral triangle. Furthermore, the honeycomb filter is not limited to a cylindrical body, and may be a columnar body such as an elliptical column, a triangular column, a quadrangular column, a hexagonal column, or an octagonal column.

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

The porosity of the partition walls is preferably 20% by volume or more, and more preferably 30% by volume or more, from the viewpoint of further improving the collection efficiency and pressure loss of the honeycomb filter. The porosity of the partition walls is preferably 70% by volume or less, and more preferably 60% by volume or less. The average pore diameter of the partition walls is preferably 5 μm or more, and more preferably 8 μm or more from the viewpoint of further improving the collection efficiency and pressure loss of the honeycomb filter. The average pore diameter of the partition walls is preferably 30 μm or less, and more preferably 25 μm or less. The porosity and average pore diameter of the partition walls can be adjusted by the particle diameter of the raw material, the amount of pore former added, the kind of pore former, and the firing conditions, and can be measured by mercury porosimetry.

Examples of the material constituting the partition include oxides such as alumina, silica, mullite, cordierite, glass, and aluminum titanate ceramics; silicon carbide; silicon nitride. Among these, aluminum titanate ceramics are preferable. Aluminum titanate or aluminum magnesium titanate is more preferable.

When the partition contains an aluminum titanate ceramic, the molar ratio of aluminum converted to Al ₂ O ₃ and titanium converted to TiO ₂ (aluminum: titanium) is preferably 35:65 to 45:55, and 40 : 60 to 45:55 is more preferable. When the partition wall contains aluminum magnesium titanate, the composition formula of aluminum magnesium titanate 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. 0.03-0.20 is more preferable, and 0.03-0.18 is still more preferable.

The partition wall containing the aluminum titanate-based ceramics is formed of, for example, porous ceramics mainly made of aluminum titanate-based crystals. “Mainly composed of an aluminum titanate crystal” means that the main crystal phase constituting the ceramic fired body is an aluminum titanate crystal phase. The aluminum titanate crystal phase is, for example, aluminum titanate. Crystal phase, aluminum magnesium titanate crystal phase.

The partition containing the aluminum titanate ceramic may contain a glass phase derived from silicon source powder. The glass phase refers to an amorphous phase in which SiO ₂ is the main component. Moreover, the partition containing an aluminum titanate ceramic may contain crystal phases other than an aluminum titanate crystal phase and a glass phase. Examples of such a crystal phase include a phase derived from a raw material used for producing a ceramic fired body. The phase derived from the raw material is, for example, a phase derived from an aluminum source powder, a titanium source powder, a magnesium source powder, or the like remaining without forming an aluminum titanate-based crystal phase during the manufacture of the honeycomb filter, such as alumina, titania, magnesia. And the like. The crystal phase forming the partition can be confirmed by an X-ray diffraction spectrum.

Honeycomb filters 100 and 200 are suitable as particulate filters that collect collected materials such as soot contained in exhaust gas from internal combustion engines such as diesel engines and gasoline engines. For example, in the honeycomb filter 100, as shown in FIG. 2, the gas G supplied from the end face 100a to the flow path 110a passes through the communication hole in the partition wall 120 and reaches the adjacent flow path 110b, and from the end face 100b. Discharged. At this time, the collected matter in the gas G is collected on the surface of the partition wall 120 and / 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.

<Honeycomb filter manufacturing method>
Next, a method for manufacturing a honeycomb filter will be described. A method for manufacturing a honeycomb filter includes, for example, a raw material preparation step for preparing a raw material mixture containing an inorganic compound powder and an additive, a forming step for forming a raw material mixture to obtain a formed body having a flow path, and firing the formed body. A sealing step of sealing one end of each flow path between the molding step and the baking step or after the baking step. Hereinafter, a method for manufacturing a honeycomb filter will be described by taking as an example a case where the partition walls include an aluminum titanate ceramic.

[Raw material preparation process]
In the raw material preparation step, the inorganic compound powder and the additive are mixed and then kneaded to prepare a raw material mixture. The inorganic compound powder includes, for example, an aluminum source powder such as α-alumina powder and a titanium source powder (titanium source powder) such as anatase type or rutile type titania powder, and magnesia powder or magnesia spinel as necessary. A magnesium source powder such as a powder and / or a silicon source powder such as a silicon oxide powder or a glass frit can be further included. Each raw material powder may be one type or two or more types. Each raw material powder may contain a trace component derived from the raw material or inevitably contained in the production process.

For each raw material powder, a volume-based cumulative particle size equivalent to 50% (center particle size, D50) measured by a laser diffraction method is preferably in the following range. D50 of the aluminum source powder is, for example, 20 to 60 μm. D50 of the titanium source powder is, for example, 0.1 to 25 μm. The D50 of the magnesium source powder is, for example, 0.5 to 30 μm. D50 of the silicon source powder is, for example, 0.5 to 30 μm.

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 an aluminum source, a titanium source, and a magnesium source.

Examples of additives include a pore-forming agent (pore-forming agent), a binder, a plasticizer, a dispersant, and a solvent.

As the pore-forming agent, one formed by a material that disappears at a temperature lower than the temperature at which the molded body is degreased and fired in the firing process can be used. In degreasing or firing, when a molded body containing a pore forming agent is heated, the pore 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 communication hole through which the fluid can flow is formed in the partition wall by shrinking the inorganic compound powder located between the spaces during firing. Can be formed.

The pore-forming agent is, for example, corn starch, barley starch, wheat starch, tapioca starch, bean starch, rice starch, pea starch, coral starch, canna starch, potato starch (potato starch). In the pore-forming agent, the volume-based cumulative particle size (D50) measured by the laser diffraction method is 50 to 50 μm, for example. When the raw material mixture contains a pore-forming agent, the content of the pore-forming agent is, for example, 1 to 25 parts by mass with respect to 100 parts by mass of the inorganic compound powder.

The binder is, for example, celluloses such as methyl cellulose, hydroxypropyl 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. Content of the binder in a raw material mixture is 20 mass parts or less with respect to 100 mass parts of inorganic compound powder, for example.

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 aluminum stearate, polyoxyalkylene alkyl ethers (for example, Polyoxyethylene polyoxypropylene butyl ether). Content of the plasticizer in a raw material mixture is 10 mass parts or less with respect to 100 mass parts of inorganic compound powder, for example.

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; ammonium polycarboxylate. Content of the dispersing agent in a raw material mixture is 20 mass parts or less with respect to 100 mass parts of inorganic compound powder, for example.

The solvent is, for example, water, and ion-exchanged water is preferable in terms of few impurities. When the raw material mixture contains a solvent, the content of the solvent is, for example, 10 to 100 parts by mass with respect to 100 parts by mass of the inorganic compound powder.

[Molding process]
In the forming step, a green honeycomb formed body having a honeycomb structure is obtained. In the molding step, 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.

[Baking process]
In the firing step, the green honeycomb formed body having a honeycomb structure obtained in the forming step is fired to obtain a honeycomb fired body. In the firing step, calcination (degreasing) for removing a binder or the like contained in the molded body (in the raw material mixture) may be performed before the molded body is fired. In the firing of the molded body, 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 temperature raising rate is not particularly limited, but is usually 1 to 500 ° C./hour. The firing time may be a time sufficient for the inorganic compound powder 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.

[Sealing process]
The sealing step is performed between the molding step and the firing step or after the firing step. When a sealing step is performed between the forming step and the firing step, one end of each flow path of the green honeycomb molded body obtained in the forming step is sealed with a sealing material, and then green honeycomb forming is performed in the firing step. By firing the sealing material together with the body, a honeycomb filter having a sealing portion that seals one end of the flow path is obtained. When performing the sealing step after the firing step, after sealing one end of each flow path of the honeycomb fired body obtained in the firing step with the sealing material, the flow path is obtained by firing the sealing material together with the honeycomb fired body. A honeycomb filter provided with a sealing portion that seals one end of the above is obtained. As the sealing material, a mixture similar to the raw material mixture for obtaining the green honeycomb molded body can be used.

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

<Production of honeycomb filter>
Example 1
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: 41.4 Al ₂ O ₃ -49 .9TiO ₂ -5.4MgO-3.3SiO ₂ (the numerical values in the formula represent molar ratios), a pore mixture, an organic binder, a plasticizer, and water. The content of main components 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 Porogen: D50 Potato starch having a particle size of 25 μm, 12.0 parts by mass Organic binder 1: methylcellulose (manufactured by Samsung Seimitsu Chemical Co., Ltd .: MC-40H), 5.5 parts by mass ) 2.4 parts by mass Plasticizer 1: Glycerin, 0.4 parts by mass Plasticizer 2: Polyoxyethylene polyoxypropylene butyl ether, 4.6 parts by mass Water: 28.4 parts by mass

The raw material mixture was kneaded and then extrusion molded to obtain a green honeycomb molded body. Next, the green honeycomb molded body was sealed and fired to produce a cylindrical honeycomb filter having a structure shown in FIGS. The firing temperature was 1500 ° C. The honeycomb titanate ratio (AT ratio) of the honeycomb filter was measured and found to be 100%. The AT conversion rate is the integral of the peak (titania / rutile phase (110) plane) appearing at 2θ = 27.4 ° in the powder X-ray diffraction spectrum of the powder obtained by crushing the honeycomb filter with a mortar. From the intensity (I _T ) and the integrated intensity (I _AT ) of the peak (aluminum magnesium titanate phase (230) plane) appearing at 2θ = 33.7 °, the calculation was performed according to the following formula.
AT conversion rate (%) = I _AT / (I _T + I _AT ) × 100

The length of the honeycomb filter in the axial direction of the flow path was 152 mm (6.00 inches). The outer diameter of the honeycomb filter was 144 mm (5.66 inches). The density of the flow path (cell density) was 350 cpsi. The length of one side of the regular hexagonal channel was 1.2 mm. The length of the long side in the flat hexagonal flow path was 1.2 mm, and the length of the short side was 1.1 mm. The partition wall thickness between the channels was 0.31 mm (12.3 mil). The porosity of the partition walls was 45% by volume, and the average pore diameter of the partition walls was 15 μm.

The total opening area of the flat hexagonal channel on one end face of the honeycomb filter was larger than the total opening area of the regular hexagonal channel on the other end face of the honeycomb filter. The hydraulic diameter of each flat hexagonal flow path on one end face of the honeycomb filter was 1.1 mm. The hydraulic diameter of each regular hexagonal flow path on the other end face of the honeycomb filter was 1.2 mm.

(Comparative Example 1)
A cylindrical body having a plurality of parallel flow paths partitioned by partition walls made of SiC was prepared as a honeycomb filter. A plurality of flow paths includes a plurality of flow paths A _1, hydraulic diameter and a plurality of flow passages B ₁ which is different from the flow path A _1, the flow path A ₁ and the flow path B ₁ represents arranged alternately It was. The flow path A ₁ was open at _one end face F ₁₁ of the honeycomb filter, and the flow path A ₁ was sealed at the other end face F ₁₂ of the honeycomb filter. Flow path _{B 1} at the end face _{F 11} is sealed, a flow path _{B 1} at the end face _{F 12} was opened.

The length of the honeycomb filter in the axial direction of the flow path was 152 mm (6.00 inches). The outer diameter of the honeycomb filter was 144 mm (5.66 inches). The density of the flow path (cell density) was 160 cpsi. The partition wall thickness between the channels was 0.38 mm (15 mil).

The total opening area of the flow path A ₁ at the end face F ₁₁ were those greater than the sum of the opening area of the flow path B ₁ at the end face F _12. Hydraulic diameter of the channel _{A 1} at the end face _{F 11} was 2.0 mm. Hydraulic diameter of the channel _{B 1} of the end face _{F 12} was 1.2 mm.

(Comparative Example 2)
A cylindrical body having a plurality of parallel flow paths partitioned by partition walls made of SiC was prepared as a honeycomb filter. A plurality of flow paths includes a plurality of flow paths A _2, hydraulic diameter and a plurality of flow paths B ₂ which is different from the flow path A _2, the flow path A ₂ and the flow path B ₂ are arranged alternately It was. The flow path A ₂ was opened at the end face F ₂₁ of the honeycomb filter, and the flow path A ₂ was sealed at the end face F ₂₂ of the honeycomb filter. Flow path _{B 2} in the end face _{F 21} is sealed, the flow path _{B 2} at the end face _{F 22} was opened.

The length of the honeycomb filter in the axial direction of the flow path was 152 mm (6.00 inches). The outer diameter of the honeycomb filter was 144 mm (5.66 inches). The density of the flow path (cell density) was 280 cpsi. The thickness of the partition between the channels was 0.28 mm (10.9 mil).

The total opening area of the flow path A ₂ at the end face F ₂₁ were those greater than the sum of the opening area of the flow path B ₂ at the end face F _22. Hydraulic diameter of the channel _{A 2} of the end face _{F 21} was 1.5 mm. Hydraulic diameter of the channel _{B 2} at the end face _{F 22} was 0.9 mm.

<Pressure loss measurement>
The pressure loss measurement during soot deposition was performed as follows. FIG. 5 is a diagram schematically illustrating a pressure loss measuring apparatus. For the pressure loss measurement, a soot generator (product name: REXS) 400 and a large compressor device 410 were used. The end face having the larger total opening area of the flow paths in the honeycomb filter was connected to the soot generator 400, and the compressor device 410 was connected to a pipe connecting the honeycomb filter (Diesel particulate filter) and the soot generator 400.

To the soot generator 400, 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 400 is artificial soot generated by incomplete combustion of propane gas. In the soot generator 400, the average particle diameter of the soot can be controlled by the air flow rate or the oxygen concentration. 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 410.

In order to grasp the pressure loss behavior during soot deposition, the pressure difference before and after the honeycomb filter (the pressure difference ΔP between the pressure P1 and the pressure P2 in FIG. 5) was recorded while supplying soot inside the honeycomb filter. FIG. 6 shows the result of measuring the pressure loss associated with the increase in the amount of soot deposition using the honeycomb filters of Example 1 and Comparative Examples 1 and 2. As shown in FIG. 6, in Example 1, it was confirmed that the pressure loss was likely to increase in accordance with the amount of collected material compared to Comparative Examples 1 and 2.

DESCRIPTION OF SYMBOLS 100,200 ... Honeycomb filter, 100a, 200a ... One end surface (1st end surface), 100b, 200b ... The other end surface (2nd end surface), 110, 210 ... Channel, 110a, 210a ... Channel (first) 1 channel), 110b, 210b... Channel (second channel), 120, 220.

Claims

A honeycomb filter having a plurality of flow paths parallel to each other,
The honeycomb filter has a first end face and a second end face located on the opposite side of the first end face;
The plurality of flow paths include a plurality of first flow paths whose end portions on the second end face side are sealed, and a plurality of second flow paths whose end portions on the first end face side are sealed. Have
A sum of opening areas of the plurality of first flow paths in the first end face is larger than a sum of opening areas of the plurality of second flow paths in the second end face;
A honeycomb filter having a hydraulic diameter of the first flow path of 1.4 mm or less.
The honeycomb filter according to claim 1, wherein a hydraulic diameter of the second flow path is larger than the hydraulic diameter of the first flow path.