JP5438342B2 - Honeycomb filter manufacturing method and honeycomb filter - Google Patents

Description

  The present invention relates to a method for manufacturing a honeycomb filter for collecting particulate matter in exhaust gas, and a honeycomb filter manufactured by the manufacturing method.

  In consideration of the impact on the environment, particulate matter contained in exhaust gas emitted from internal combustion engines such as automobile engines, construction machinery engines, stationary engines for industrial machinery, and other combustion equipment, is removed from the exhaust gas. There is a growing need for removal. In particular, regulations regarding the removal of particulate matter (particulate matter, also referred to as PM) discharged from diesel engines tend to be strengthened globally. Under such circumstances, DPF (diesel particulate filter) for collecting and removing PM has been attracting attention.

  As one aspect of the DPF, a predetermined cell having a porous partition wall that partitions and forms a plurality of cells that serve as fluid flow paths, one end of which is open and the other end is plugged, The remaining cells whose end portions are plugged and the other end portions are opened alternately are arranged, and fluid (exhaust gas) flowing in from one end portion where predetermined cells open is separated by the partition walls. And a honeycomb filter in which PM in exhaust gas is collected and removed by flowing out from the other end where the remaining cells open. I can do it. A filter (wall flow type filter) having a structure in which exhaust gas permeates through porous partition walls, such as this honeycomb filter, can reduce the filtration flow rate (partition wall permeation flow rate) because the filtration area can be increased. The pressure loss is small, and the particulate matter collection efficiency is relatively good.

  However, the DPF to which the honeycomb filter as described above is applied has the following problems to be improved.

  (A) When the DPF starts to collect PM from a clean state, first, the PM enters the pores of the porous partition wall, and the depth of the filtration is collected inside the partition wall, and the surface of the partition wall When PM is deposited on the surface of the partition wall, PM will form a layer and the layer itself will move to cake filtration that acts as a filter. To do. In the progress of such filtering action, PM accumulates inside the partition walls (pores) in the initial depth filtration process. Therefore, immediately after the start of PM collection, the substantial porosity of the partition walls may decrease, the flow rate of exhaust gas passing through the partition walls may increase, and the pressure loss may increase rapidly. Such a sudden increase in pressure loss immediately after the start of PM collection becomes a factor of deteriorating engine performance, which is not preferable.

  (B) In DPF, when a certain amount of PM is collected and deposited, it is necessary to burn and remove the PM and regenerate it. In this case, generally, the amount of accumulated PM is estimated from the pressure loss. However, in the DPF having the conventional partition wall pore structure, PM deposited on the surface of the partition wall at the time of regeneration is easily combusted, and the PM trapped inside the partition wall remains unburned, and the pressure loss returns to the initial value. Therefore, it has a hysteresis with respect to the total accumulation amount of PM, and the amount of PM cannot be accurately estimated from the pressure loss, which is not preferable.

  (C) DPF can collect PM more efficiently as the pore diameter of the partition wall is smaller and the partition wall thickness is larger. In order to prevent PM from entering the interior (pores) of the partition walls and to shift to cake filtration at an early stage, it is preferable to reduce the pore diameter of the partition walls. However, reducing the pore diameter of the partition walls and increasing the thickness of the partition walls is not desirable because it causes an increase in pressure loss of the partition walls before PM deposition and causes engine performance to deteriorate.

  As a method for solving such a problem, a honeycomb filter having a multilayer structure in which a surface layer is formed on a porous partition wall has been proposed.

  The following Patent Documents 1 to 3 are examples of filters having such a multi-layer structure.

  In Patent Document 1, a backwashable filter having a microporous coating having an average pore size smaller than the average pore size of a monolith material, wherein the average pore size of the coating is 0.1 to 5 μm, A filtration device comprising a filter bonded with a reactive inorganic binder is disclosed. In the filtration apparatus provided with this filter, the structure which the above-mentioned film substantially blocks | prevents that the fine particle of a raw material penetrate | invades in the hole of a porous material is employ | adopted.

  Patent Document 2 discloses a catalytic filtration device and method for separating a feed material into a filter cake containing a filtrate and a particulate matter by providing a microporous membrane on the surface. Further, the document 2 discloses a sealing structure, feed gas, and catalyst coating, and further, the pore diameter of the fine membrane is 0.1 to 0.5 μm (the average pore diameter is that of the porous material). Smaller than that).

  In Patent Document 3, a mixture of a refractory particle and a thermally reactive inorganic binder that reacts at a first temperature lower than a second temperature at which the refractory particle sinters is coated on a porous support, A method of forming an inorganic separation membrane by reacting an orientation binder at a temperature is disclosed. It is also disclosed that the refractory particles are ceramic and the inorganic binder is glass frit, fine reactive particles, inorganic colloid.

JP-T 6-506138 Japanese National Patent Publication No. 7-505083 Japanese Examined Patent Publication No. 6-67460

  However, Patent Documents 1 and 2 disclose nothing about how to form a film or a microporous film when forming a film or a microporous film. In particular, the process of forming the PM trapping layer is an important problem that leads not only to its strength, but also to pressure loss control, engine performance improvement, and manufacturing cost reduction. It cannot be said that the filtration apparatus provided with the filter of Patent Document 2 that does not describe various points is insufficient to solve the above-described problems. Further, in Patent Document 3, since the firing is performed many times when forming the inorganic separation membrane, the cost burden is increased and the feasibility is low, and it is not possible to solve the above-mentioned problems. It must be said that it is enough.

  The present invention has been made in order to solve such problems, and has been made by a method for manufacturing a honeycomb filter having a treatment step of binding a trapping layer to the partition wall simultaneously with heat treatment of the outer peripheral coat. The heat treatment of the outer peripheral coat and the heat treatment of the PM trapping layer can be performed simultaneously, the manufacturing cost can be reduced, the PM trapping layer has sufficient strength, the PM initial trapping efficiency is high, and the initial pressure loss increase rate is high. The present invention provides a method for manufacturing a honeycomb filter that is low, has low pressure loss during PM deposition, has low hysteresis characteristics, has sufficient regeneration characteristics, and has performance, manufacturing cost, and durability. In particular, it is possible not only to suppress the PM accumulation in the partition walls in the honeycomb filter but also to avoid the pressure loss hysteresis, and further to reduce the pressure loss, and improve the accuracy of predicting the accumulated PM amount from the pressure loss from the pressure loss linear.

  Furthermore, a catalyst filter manufacturing method having an excellent purification performance is provided by carrying a catalyst.

  In addition, the honeycomb filter manufactured by the above-described manufacturing method can reduce the manufacturing cost, and is sufficiently equipped with the strength of the PM collection layer, has high PM initial collection efficiency, and has a low initial pressure loss increase rate, It is possible to provide a honeycomb filter having a small pressure loss during PM deposition, a small hysteresis characteristic, sufficient regeneration characteristics, and further having performance, manufacturing cost, and durability. In addition, a catalyst-carrying filter having a further excellent catalyst purification function is provided by the catalyst-carrying filter produced by the above-described production method.

[1] A forming raw material containing a ceramic raw material is formed to produce a plurality of honeycomb segments having porous partition walls that partition and form a plurality of cells serving as fluid flow paths. Manufacturing a honeycomb filter as an aggregate formed by joining and integrating through an assembly, wherein the honeycomb segments are joined and integrated to form an aggregate, and then the outer periphery of the aggregate is ground to obtain an outer periphery processed body And forming a precursor of a collection layer for collecting particulate matter on the partition wall of the outer periphery processed body, and drying the precursor of the collection layer to obtain a dried body, which was obtained. A processing step of applying a peripheral coat to the outer periphery of the dry body, and further forming a trapping layer by bonding a precursor of the trapping layer to the entire partition wall on the inflow side simultaneously with the heat treatment of the peripheral coat. Have A method for manufacturing a honeycomb filter, wherein the trapping layer has a peak pore diameter of 2 μm or more and less than 8 μm.

[2] A forming raw material containing a ceramic raw material is formed to produce a plurality of honeycomb segments having porous partition walls that define a plurality of cells that serve as fluid flow paths, and the honeycomb segments are bonded to the bonding material. before integrally bonding via said to form a precursor of the trapping layer for trapping particulate matter on a honeycomb segment of the partition wall, to obtain a dried segment body by drying the precursor of the collecting layer After the obtained dried segment bodies are joined and integrated into an aggregate, the outer periphery of the aggregate is ground to form an outer periphery processed body, and then an outer periphery coat is formed on the outer periphery of the obtained outer periphery processed body. Applying the heat treatment of the outer peripheral coat, and having a treatment step of forming a collection layer by bonding the precursor of the collection layer to the entire partition wall on the inflow side, the peak of the collection layer Pore diameter of 2μm or more and 8μ The method for manufacturing a honeycomb filter is less than.

[3] The method for manufacturing a honeycomb filter according to [1] or [2], wherein a heat treatment temperature of the outer peripheral coat is 400 to 800 ° C.

[4] The method for manufacturing the honeycomb filter according to any one of [1] to [3], wherein the ceramic raw material is made of silicon carbide.

[5] A method for manufacturing a catalyst-carrying filter, in which a honeycomb filter is manufactured by the method for manufacturing a honeycomb filter according to any one of [1] to [4], and then the catalyst is supported on the obtained honeycomb filter.

  The honeycomb filter according to the present invention has the following effects when applied as a DPF.

  Simultaneously with the heat treatment of the outer peripheral coat, by the honeycomb filter manufacturing method having a treatment step of binding the trapping layer to the partition wall, the heat treatment of the outer peripheral coat and the heat treatment of the PM trapping layer can be performed simultaneously, and the manufacturing cost can be reduced, and The PM trapping layer has sufficient strength, the PM initial trapping efficiency is high, the initial pressure loss increase rate is low, the pressure loss during PM deposition is small, the hysteresis characteristics are small, and the regeneration characteristics are sufficient, It is possible to provide an excellent effect that a method for manufacturing a honeycomb filter having performance, manufacturing cost, and durability can be provided. In particular, it is possible not only to suppress the PM accumulation in the partition walls in the honeycomb filter but also to avoid the pressure loss hysteresis, and further to reduce the pressure loss, and improve the accuracy of predicting the accumulated PM amount from the pressure loss from the pressure loss linear.

  Furthermore, a catalyst filter manufacturing method having an excellent purification performance is provided by carrying a catalyst.

  In addition, the honeycomb filter manufactured by the above-described manufacturing method can reduce the manufacturing cost, and is sufficiently equipped with the strength of the PM collection layer, has high PM initial collection efficiency, and has a low initial pressure loss increase rate, It is possible to provide a honeycomb filter having a small pressure loss during PM deposition, a small hysteresis characteristic, sufficient regeneration characteristics, and further having performance, manufacturing cost, and durability. In addition, a catalyst-carrying filter having a further excellent catalyst purification function is provided by the catalyst-carrying filter produced by the above-described production method.

It is one Embodiment of the manufacturing method of the honey-comb filter which concerns on this invention, Comprising: It is a flowchart which shows the process process. It is another embodiment of the manufacturing method of the honey-comb filter which concerns on this invention, Comprising: It is a flowchart which shows the treatment process. It is a manufacturing method of the conventional honeycomb filter, Comprising: It is a flowchart which shows the treatment process. It is a manufacturing method of the conventional honeycomb filter, Comprising: It is a flowchart which shows the treatment process. 1 is a front view schematically showing one embodiment of a honeycomb filter according to the present invention. 1 is a cross-sectional view schematically showing one embodiment of a honeycomb filter according to the present invention. It is a fragmentary sectional view which expands and shows the P section in FIG. 1 is a diagram showing an embodiment of a honeycomb filter according to the present invention, and is a graph showing a pore distribution determined by a mercury intrusion method. 1 is a diagram illustrating an embodiment of a honeycomb filter according to the present invention, and is a graph illustrating a relationship between a distance from a partition wall surface and a porosity. FIG. It is a figure showing the hysteresis characteristic of the honey-comb filter which concerns on this invention, and is a graph which shows the relationship between a pressure loss and PM deposition amount per volume. It is the figure which showed typically the state which forms a PM collection layer in the honeycomb filter which concerns on this invention, Comprising: The cross section of the honeycomb structure before forming a PM collection layer is shown. FIG. 6 is a diagram schematically showing a state in which a PM trapping layer is formed on the honeycomb filter according to the present invention, wherein a jig is attached to the honeycomb structure, and the slurry for forming the PM trapping layer is placed on the honeycomb filter. It is sectional drawing which showed the state poured in from the end surface. It is the figure which showed typically the state which forms PM collection layer in the honeycomb filter which concerns on this invention, Comprising: The state which attracted | sucked the slurry for PM collection layer formation from the lower end side of a honeycomb filter typically It is sectional drawing shown. FIG. 3 is a diagram schematically showing a state in which a PM trapping layer is formed on the honeycomb filter according to the present invention, in which a slurry for forming the PM trapping layer is formed on the partition walls of the honeycomb filter (on the exhaust gas inflow side). It is sectional drawing which showed the state which carried out.

  Hereinafter, the form for implementing the honeycomb filter of this invention is demonstrated concretely. However, the present invention broadly includes honeycomb filters having the invention-specific matters, and is not limited to the following embodiments.

[1] Honeycomb filter of the present invention:
The method for manufacturing a honeycomb filter according to the present invention includes forming a forming raw material containing a ceramic raw material to produce a plurality of honeycomb segments including porous partition walls that partition and form a plurality of cells serving as fluid flow paths. A method of manufacturing a honeycomb filter as an aggregate formed by bonding and integrating the honeycomb segments via a bonding material, the honeycomb segments being bonded and integrated to form an aggregate, and an outer periphery of the aggregate To form a peripheral processed body, to form a collection layer for collecting particulate matter on the partition wall of the peripheral processed body, and to obtain a dried body by drying the collection layer. In addition, a honeycomb filter having a processing step of applying an outer periphery coat to the outer periphery of the dried body, and further combining a trapping layer with the partition wall simultaneously with the heat treatment of the outer periphery coat. It is configured as a law.

  That is, in the honeycomb filter manufacturing method of the present invention, as shown in FIG. 1, (S1) segment molding, (S2) drying, (S3) plugging, (S4) firing, (S5) bonding, (S6) Drying, (S7) processing, (S8) collection layer coating, (S9) drying, (S10) outer periphery coating, (S11) drying, (S12) (S12) to (S12) until heat treatment is performed It is manufactured through a process.

[1-1] Heat treatment step:
The heat treatment step performed in the method for manufacturing a honeycomb filter of the present invention includes forming a segment, drying, forming a plug, firing, joining the above segments, and drying as an aggregate. After the processing of each step such as processing the outer periphery of the substrate into a desired shape, (S8) coating the collection layer, (S9) drying, and (S10) collecting on the partition simultaneously with the heat treatment of the outer periphery coating It has a processing step for bonding the layers.

  Here, in the conventional manufacturing method, as shown in FIG. 3, (P1) segment forming, (P2) drying, (P3) plugging, (P4) firing, and the resulting honeycomb segment (P5) are joined and dried as an aggregate (P6), the outer periphery of the resulting aggregate is processed into a desired shape (P7), and (P8) an outer peripheral coat is applied. The applied assembly was (P9) dried (P10) heat treated, (P11) coated with a collection layer and then (P12) dried again to produce a DPF (hereinafter referred to as appropriate) "Conventional manufacturing method 1"). As another conventional manufacturing method, as shown in FIG. 4, (Q1) segment forming, (Q2) drying, (Q3) plugging, (Q4) firing, and the resulting honeycomb The segments are (Q5) joined and dried as an aggregate (Q6). Then, the outer periphery of the resulting assembly is processed into a desired shape (Q7), (Q8) the outer periphery coat is applied, (Q9) is dried (Q10) is heat-treated, and (Q11) the collection layer coat Then, (Q12) was further dried, and (Q13) heat treatment was performed again (hereinafter referred to as “conventional production method 2” as appropriate).

  However, in the above-described conventional manufacturing method 1, in short, since the collection layer is coated after the DPF is manufactured, and after the collection layer is coated, the heat treatment is not performed. Although the burden is not increased, the strength of the collection layer is weak, and the hysteresis characteristics and the regeneration characteristics are insufficient, such as separation of the collection layer formed during use. Furthermore, in the above-described conventional manufacturing method 2, in short, after the DPF is manufactured, the outer periphery coat is applied and then dried (Q10), heat treatment is performed, and (Q11) the collection layer is coated, and then (Q12) is dried. (Q13) Since the heat treatment is performed again, the strength of the trapping layer is given by performing the heat treatment process, but the heat treatment process increases in the manufacturing process, resulting in an increase in manufacturing cost and price competition. It was inferior in power.

  In other words, since the honeycomb filter manufactured by the conventional manufacturing method 1 is formed without going through the heat treatment step, the PM trapping layer is formed without going through the heat treatment step. The strength of the PM trapping layer becomes fragile, and the pressure loss is likely to increase, resulting in a decrease in engine performance. Moreover, in the honeycomb filter manufactured by the conventional manufacturing method 2, since the heat treatment is performed again after the DPF is manufactured, the strength of the PM trapping layer can be maintained, but the heat treatment process increases, so that the manufacturing cost is increased. Therefore, it has not reached what can be manufactured at low cost while having sufficient strength of the PM trapping layer.

  Therefore, in the method for manufacturing a honeycomb filter of the present embodiment, with the above-described configuration, in the heat treatment step (S12), the heat treatment for bonding the PM trapping layer to the partition wall is performed at the same time as the heat treatment of the outer peripheral coat. Therefore, a honeycomb filter that reduces the manufacturing cost and improves the price competitiveness while maintaining and improving the strength of the PM trapping layer is manufactured. In particular, (1) since the collection layer is formed after being integrated, man-hours can be reduced as compared with the case where the collection layer is formed on the segments, and (2) the collection after processing into a predetermined shape. Since the layer is formed, it is excellent in that the collection layer material can be used effectively without forming the collection layer in a portion not used by processing or the like.

  Further, as a method for manufacturing a honeycomb filter, before the honeycomb segments are joined and integrated through the joining material, a collecting layer is formed on the partition walls of the honeycomb segment, and the collecting layer is dried to obtain a dry segment body. After the obtained dried segment bodies are joined and integrated into an aggregate, the outer periphery of the aggregate is ground to form an outer periphery processed body, and then an outer periphery coat is applied to the outer periphery of the obtained outer periphery processed body And it is also one of the preferable forms to have the process process which combines a collection layer with the said partition simultaneously with the heat processing of the said outer periphery coat | court. According to such a manufacturing method, as shown in FIG. 2, (T1) segment molding, (T2) drying, (T3) plugging, (T4) firing, (T5) collection layer coating, (T6) Through the steps (T1) to (T12) until drying, (T7) bonding, (T8) drying, (T9) processing, (T10) outer periphery coating, (T11) drying, and (T12) heat treatment. Since it is manufactured, in the heat treatment step (T12), the heat treatment for bonding the PM collection layer to the partition wall can be performed at the same time as the heat treatment of the outer peripheral coat, while maintaining and improving the strength of the PM collection layer, A honeycomb filter that reduces manufacturing costs and improves price competitiveness is manufactured. In particular, since the collecting layer is formed in a segment shape, a film forming jig for forming a collecting layer according to the processing shape is unnecessary, and a preferable manufacturing method in that the film can be formed with the same film forming jig. It is.

  More preferably, the heat treatment temperature of the outer peripheral coat is 400 to 800 ° C. By performing the desired heat treatment in this way, the bonding strength between the honeycomb segment and the bonding material or the honeycomb segment and the outer peripheral coating material can be improved, and the mechanical strength and the thermal shock resistance during regeneration (during PM combustion) can be improved. it can.

  Furthermore, it is also one of preferred embodiments that a honeycomb filter is manufactured by the method for manufacturing a honeycomb filter as described above, and then manufactured by supporting the catalyst on the obtained honeycomb filter. In this way, by supporting the catalyst in the partition walls, the oxidation of the collected PM can be promoted. In addition, exhaust gas contains unburned hydrocarbons, carbon monoxide, nitrogen oxides, etc. in addition to PM, and by carrying a catalyst that purifies these, a catalyst filter having excellent purification performance can be manufactured. it can.

[1-2] Specific forming step of manufacturing method of honeycomb filter according to the present invention:
Next, a method for manufacturing a honeycomb filter according to the present invention will be described. Examples of the method for manufacturing a honeycomb filter according to the present invention include the following method. However, the present invention is not limited to such a method for manufacturing a honeycomb structure, and can be manufactured by appropriately using a known method for manufacturing a honeycomb structure as long as the configuration of the present application is employed and the effects of the present application are achieved. .

[1-2-1] Formation of honeycomb segment:
In the step of forming the honeycomb segment S1 shown in FIG. 1 (or the step of forming the honeycomb segment T1 shown in FIG. 2), first, the raw materials listed above are used as the base material of the honeycomb filter, and the raw materials are mixed. Kneaded to form a clay. The material of the substrate of the honeycomb structure is not particularly limited, but ceramic can be suitably used, and from the viewpoint of strength, heat resistance, corrosion resistance, etc., silicon carbide, silicon-silicon carbide composite material, alumina, mullite, cordierite, It is preferably either aluminum titanate or silicon nitride.

  For example, when a silicon-silicon carbide composite material is used as the material for the partition walls as the honeycomb segment raw material, SiC powder and metal Si powder are mixed at a mass ratio of 80:20, and a dispersion medium such as water or a pore former is used. In addition, an organic binder or the like is further added and kneaded to form a plastic clay. The means for preparing the kneaded material by kneading the SiC powder and the metal Si powder raw material (forming raw material) is not particularly limited, and examples thereof include a method using a kneader, a vacuum kneader or the like.

  Examples of the organic binder added to the molding raw material as described above include hydroxypropoxyl methylcellulose, methylcellulose, hydroxyethylcellulose, carboxymethylcellulose, and polyvinyl alcohol. These may be used alone. You may use it in combination of 2 or more types. Examples of the pore-forming material include graphite, starch, synthetic resin, and the like, as long as they have the property of scattering and disappearing in the firing process. Further, inorganic substances such as coke, polymer compounds such as foamed resin, organic substances such as starch, etc. may be used alone or in combination. Examples of the dispersant include ethylene glycol, dextrin, fatty acid soap, polyalcohol and the like. These may be used individually by 1 type, and may be used in combination of 2 or more type.

  Next, a honeycomb segment having a desired shape is formed from the obtained clay with a porous partition wall that defines a plurality of cells serving as fluid flow paths using a predetermined mold. Here, the method for producing the honeycomb segment is not particularly limited, and conventionally known molding methods such as extrusion molding, injection molding, and press molding can be used. Among them, a preferable example is a method in which the clay prepared as described above is extruded using a die having a desired cell shape, partition wall thickness, and cell density. Here, the material of the substrate of the honeycomb structure is not particularly limited, but ceramic can be suitably used, and from the viewpoint of strength, heat resistance, corrosion resistance, etc., silicon carbide, silicon-silicon carbide composite material, alumina, mullite, It is preferably one of cordierite, aluminum titanate or silicon nitride.

[1-2-2] Drying:
In the drying step of S2 shown in FIG. 1 (or the drying step of T2 shown in FIG. 2), the obtained honeycomb segment formed body is dried with a microwave dryer, and further dried completely with a hot air dryer. Create a body. The drying means is not particularly limited, and conventionally known drying methods such as hot air drying, microwave drying, dielectric drying, reduced pressure drying, vacuum drying, freeze drying and the like can be used. Especially, the drying method which combined hot air drying and microwave drying or dielectric drying is preferable at the point which can dry the whole molded object rapidly and uniformly.

[1-2-3] Formation of plugged portion:
In the step of forming the plugged portion of S3 shown in FIG. 1 (or the step of forming the plugged portion of T3 shown in FIG. 2), plugging is formed as follows. First, as a method for forming the plugging portion, the plugging slurry is stored in a storage container. And the edge part by the side which gave the said mask is immersed in a storage container, a plugging slurry is filled into the opening part of the cell which is not giving the mask, and a plugging part is formed. For the other end, a mask is applied to the cells plugged at one end, and the plugged portion is formed in the same manner as the plugged portion is formed at the one end. As a result, the cells not plugged at the one end are plugged at the other end, and the cells are alternately closed in a checkered pattern at the other end. The plugging may be performed after the honeycomb formed body is fired to form the honeycomb fired body.

  As the plugging material, it is preferable to use the same material as the honeycomb segment raw material because the expansion coefficient at the time of firing with the honeycomb segment can be made the same and the durability is improved.

[1-2-4] Firing:
In the firing step of S4 shown in FIG. 1 (or the firing step of T4 shown in FIG. 2), the honeycomb segment in which the plugged portions are formed as described above is first fired (calcined). This calcining is performed for degreasing and includes, for example, one performed in an oxidizing atmosphere at 550 ° C. for about 3 hours, but is not limited to this, and the organic matter in the honeycomb formed body It is preferably carried out according to (organic binder, dispersant, pore former, etc.). Generally, the combustion temperature of the organic binder is about 100 to 300 ° C., and the combustion temperature of the pore former is about 200 to 800 ° C. Therefore, the calcining temperature may be about 200 to 1000 ° C. Although there is no restriction | limiting in particular as a calcination time, Usually, it is about 1 to 10 hours.

  Further, firing (main firing) is performed. The “main firing” means an operation for sintering and densifying the forming raw material in the calcined body to ensure a predetermined strength. Since the firing conditions (temperature and time) vary depending on the type of molding raw material, appropriate conditions may be selected according to the type. For example, in the case of a silicon-silicon carbide composite material, firing is performed at a firing temperature of about 1400 ° C. to 1500 ° C. in an Ar inert atmosphere, but is not limited thereto.

[1-2-5] Joining:
In the joining step of S5 shown in FIG. 1, after obtaining a plurality of honeycomb segments (sintered bodies) having desired dimensions through the respective steps described above, a slurry for joining is applied to the peripheral surface of the honeycomb segments, The required number of honeycomb segments are assembled together and pressure-bonded to obtain a bonded honeycomb segment assembly (before drying). As a material for the joining slurry, a material composed of inorganic fibers, an inorganic binder, an organic binder, and inorganic particles can be cited as a preferred example. Specifically, examples of the inorganic fiber include oxide fibers such as aluminosilicate, magnesium silicate, and alumina, and other fibers (for example, SiC fibers). Examples of the inorganic binder include silica sol, alumina sol, clay and the like. Examples of the organic binder include polyvinyl alcohol, carboxymethyl cellulose, and methyl cellulose. Examples of the inorganic particles include ceramics such as silicon carbide, silicon nitride, cordierite, alumina, and mullite. The bonding slurry made of these materials is further subjected to a heat treatment at 400 to 800 ° C. after drying, thereby improving the bonding strength between the honeycomb segment and the bonding material, and the mechanical strength and thermal shock during regeneration (at PM combustion). Can be improved.

[1-2-6] Drying:
In the drying step of S6 shown in FIG. 1, the above-mentioned honeycomb segment bonded body is cured by heat drying to obtain a honeycomb segment bonded body having a square columnar shape (after drying). The drying means is not particularly limited as described above. For example, a conventionally known drying method such as hot air drying, microwave drying, dielectric drying, vacuum drying, vacuum drying, freeze drying, or the like can be used. I can do it. Among these, hot air drying is preferable as a drying method in that the entire bonded body can be quickly and uniformly dried.

[1-2-7] Processing:
In the processing step of S7 shown in FIG. 1, the dried honeycomb segment bonded body is ground into a cylindrical shape to form a cylindrical honeycomb structure having a segment structure.

[1-2-8] PM trapping layer coat:
In the PM collection layer coating (treatment) step of S8 shown in FIG. 1, the PM collection layer is formed on the exhaust gas inflow side cell (inflow side partition wall surface layer) of the partition wall of the honeycomb structure. The material for the PM trapping layer to be formed is preferably composed of aggregate particles that form the trapping layer, the particles, and a binder that binds the particles and the particles constituting the partition walls. Examples of the particles used as the aggregate include silicon carbide, silicon nitride, cordierite, mullite, alumina, zirconia, zirconium phosphate, spinel, silicon carbide cordierite composite material, silicon-silicon carbide composite material, and lithium aluminum. Ceramics such as silicate, aluminum titanate, titania, ceria, zirconia, inorganic powder such as Fe-Cr-Al metal, nickel metal, or metal Si can be employed. The binder preferably contains a colloidal sol such as silica sol or alumina sol, or a layered clay compound that swells and exhibits binding properties. Specifically, colloidal silica can be cited as the colloidal sol, and montmorillonite can be cited as the layered clay compound. These can be diluted with water to form a slurry for forming the PM trapping layer to form a PM trapping layer precursor on the partition walls of the honeycomb structure. Moreover, in order to control the pore structure of the PM trapping layer, a trapping layer that disappears by heat treatment may be added to form the trapping layer. The pore former is not particularly limited, and those used for the preparation of the honeycomb segment described above can be suitably used.

  For example, in forming a PM trapping layer, first, 100 parts by mass of silicon carbide particles (average particle diameter 12 μm), 40 parts by mass of colloidal silica (solution with a solid content concentration of 40%), CMC (carboxymethylcellulose) solution (2%) (Solid content) 100 parts by mass, 1 part by mass of a dispersing agent, and 800 parts by mass of water are added and stirred well to prepare a slurry for forming a collection layer. Next, as shown in FIG. 11A, the side (inflow side cell) on which the PM trapping layer is to be formed is turned up, and jigs 15a and 15b for storing slurry are set as shown in FIG. 11B. And a predetermined amount of slurry is weighed (so that the film thickness etc. of the trapping layer to be formed can be controlled by the slurry composition (solid content concentration) and weight), and the side on which the PM trapping layer is to be formed (inflow side cell) In the above state, as shown in FIG. 11B, the slurry 17 is poured from the honeycomb end face (upper end face) side, and the slurry is supplied to the inlet cell. (When the slurry flows in, the on-off valve indicated by reference numeral 15c in FIG. 11B is closed so that the slurry does not flow out.) Further, as shown in FIG. 11C, after supplying the slurry 17, The filtrate is discharged by suction from the outlet cell side (on-off valve side of the jig 15b). (Draining the filtrate forms a film as a collection layer precursor on the inlet cell surface layer). Thus, as shown in FIG. 11D, the solid content (so-called membrane aggregate of the PM trapping layer) is deposited on the cell surface, and the PM trapping layer 24 is formed. As another method for forming the PM trapping layer, for example, a supply of the film forming slurry by pumping by a pump or a method of immersing the honeycomb structure in the slurry can be used.

  Further, the thermal expansion coefficient of the honeycomb filter of the present embodiment is a value determined by the material of the honeycomb filter to be used and the material constituting the PM trapping layer and is not particularly preferable, but the difference between the thermal expansion coefficients of the two is small. Is preferred. This is because if the difference in thermal expansion coefficient is large, the generated thermal stress when exposed to high-temperature exhaust gas cannot be suppressed within an allowable range, and there is a possibility that thermal stress failure may occur.

[1-2-9] Drying:
In the drying step of S9 shown in FIG. 1, the honeycomb structure on which the PM trapping layer is formed as described above is similarly dried and cured by the above-described drying means. Specifically, it can be dried under conditions such as hot air drying at 120 ° C. for 3 hours.

[1-2-10] Outer peripheral coat:
Further, in the outer peripheral step of S10 shown in FIG. 1, the peripheral surface of the honeycomb structure after the dried PM trapping layer is formed is coated with the outer peripheral coat slurry, and cured by drying, so that the outer peripheral coat is formed. A cylindrical honeycomb structure having a layer (outer peripheral wall, see outer peripheral coat layer (outer peripheral wall) 20 in FIG. 5) is formed. Further, the same material as that for the joining slurry can be suitably used as the material for the outer periphery coating slurry. The outer periphery coating slurry made of these materials is further subjected to heat treatment at 400 to 800 ° C. after drying, so that the adhesive strength between the honeycomb segment and the outer periphery coating material layer is improved, and mechanical strength and regeneration (at PM combustion) are improved. The thermal shock resistance of can be improved.

[1-2-11] Drying:
Thereafter, in the drying step of S11 shown in FIG. 1, drying is performed by the same drying means as described above.

[1-2-12] Heat treatment:
Furthermore, in the heat treatment step of S12 shown in FIG. 1, the honeycomb structure coated and dried with the outer peripheral coat layer as described above is heat-treated at 700 ° C. for 30 minutes to be cured. By doing in this way, it is possible to perform the process of bonding the trapping layer to the partition wall at the same time as the heat treatment of the outer peripheral coat, and the PM trapping layer does not require an additional heat treatment step, and the PM trapping layer is located on the exhaust gas inflow side partition. A desired honeycomb filter formed (formed) thereon can be obtained.

[2] Manufacturing method of honeycomb filter as another embodiment of the present invention:
According to another aspect of the present invention, there is provided a method for manufacturing a honeycomb filter, in which a collecting layer is formed on partition walls of the honeycomb segment before the honeycomb segment is joined and integrated via a joining material, and the collecting layer is formed. Is dried to obtain a dry segment body, and the resulting dry segment body is joined and integrated into an aggregate, and then the outer periphery of the aggregate is ground to form a peripheral processed body. The honeycomb filter manufacturing method includes a processing step of applying an outer periphery coat to the outer periphery of the outer periphery processed body and simultaneously bonding the trapping layer to the partition walls at the same time as the heat treatment of the outer periphery coat.

  That is, in the method for manufacturing a honeycomb filter as another embodiment of the present invention, as shown in FIG. 2, (T1) segment molding, (T2) drying, (T3) plugging, (T4) firing, (T5 ) Collecting layer coat, (T6) drying, (T7) bonding, (T8) drying, (T9) processing, (T10) outer periphery coating, (T11) drying, and (T12) heat treatment. It is. By manufacturing a honeycomb filter by such a method, it is possible to give strength to the collection layer by performing heat treatment after the collection layer coating on the honeycomb segment, and by performing a heat treatment step after the outer periphery coating. This reduces the cost burden without increasing the number of new heat treatment steps.

  Hereinafter, a method for manufacturing a honeycomb filter according to another embodiment of the present invention will be specifically described, but the description of the same processing steps as those of the method for manufacturing a honeycomb filter according to an embodiment of the present invention will be omitted as much as possible. The point where the difference occurs will be explained. Therefore, for the omitted processing steps, refer to the above-described method for manufacturing a honeycomb filter as an embodiment of the present invention.

  In the method for manufacturing a honeycomb filter as another embodiment of the present invention, the processing steps up to (T1) segment forming, (T2) drying, (T3) sealing, and (T4) firing are as described above. In addition, since it is the same as the manufacturing method 1 of the honeycomb filter as the embodiment of the present invention, here, (T5) PM trapping layer coating and subsequent processing steps will be described, and from (T1) to (T4) For each processing step, refer to the honeycomb filter manufacturing method 1 as an embodiment of the present invention.

[2-1] PM trapping layer coat:
After obtaining a plurality of honeycomb segments (sintered bodies) having desired dimensions through the respective steps (T1) to (T4) described above, the coating process step of the PM collection layer of (T5) shown in FIG. Then, a PM collection layer is formed. This is different from the manufacturing method 1 of the honeycomb filter according to the embodiment of the present invention in which the PM trapping layer is formed after joining the honeycomb segments, and also from the conventional manufacturing method. Specifically, a PM trapping layer is formed on the exhaust gas inflow side cell (inflow side partition wall surface layer) of the partition walls of the honeycomb segment (sintered body) before being joined. In addition, adjustment of the slurry for PM collection layer formation is performed similarly to the manufacturing method 1 of the honey-comb filter of this invention embodiment. Although not shown, when the PM trapping layer is formed on the honeycomb segment, a jig suitable for the size of the honeycomb segment is used instead of the above-mentioned jig for the joined body (see FIG. 11B). Thus, the PM trapping layer may be formed on the honeycomb segment in the same manner as the PM trapping layer is formed on the joined body.

[2-2] Drying:
In the drying step (T6) shown in FIG. 2, the honeycomb segment formed body on which the PM trapping layer has been formed is dried with a dryer to produce a dried body. The drying means is not particularly limited, and conventionally known drying methods such as hot air drying, microwave drying, dielectric drying, reduced pressure drying, vacuum drying, freeze drying and the like can be used. Among these, hot air drying is preferable as a drying method in that the entire honeycomb segment formed with the PM trapping layer can be quickly and uniformly dried.

[2-3] Joining:
In the joining step (T7) shown in FIG. 2, the honeycomb segments dried in the drying step (T6) are coated on the peripheral surfaces of the honeycomb segments, and the required number of honeycomb segments are assembled together. To obtain a bonded honeycomb segment assembly (before drying). As a material for the joining slurry, a material composed of inorganic fibers, an inorganic binder, an organic binder, and inorganic particles can be cited as a preferred example. Specifically, examples of the inorganic fiber include oxide fibers such as aluminosilicate, magnesium silicate, and alumina, and other fibers (for example, SiC fibers). Examples of the inorganic binder include silica sol, alumina sol, clay and the like. Examples of the organic binder include polyvinyl alcohol, carboxymethyl cellulose, and methyl cellulose. Examples of the inorganic particles include ceramics such as silicon carbide, silicon nitride, cordierite, alumina, and mullite. The bonding slurry made of these materials is further subjected to a heat treatment at 400 to 800 ° C. after drying, thereby improving the bonding strength between the honeycomb segment and the bonding material, and the mechanical strength and thermal shock during regeneration (at PM combustion). Can be improved.

[2-4] Drying:
In the joining step (T8) shown in FIG. 2, the above-mentioned honeycomb segment joined body (before drying) is cured by the drying means as described above, and the overall shape is a square pillar-shaped (after drying) honeycomb segment. Obtain a zygote.

[2-5] Processing:
In the processing step (T9) shown in FIG. 2, the dried bonded honeycomb segment assembly is further ground into a columnar shape to form a columnar honeycomb structure having a segment structure.

[2-6] Outer peripheral coat:
Further, in the outer periphery coating step (T10) shown in FIG. 2, the outer peripheral coating layer (outer peripheral wall, FIG. 2) is formed by coating the peripheral surface of the cylindrical honeycomb structure with the outer peripheral coating slurry and curing it by drying. A cylindrical honeycomb structure having 5 outer peripheral coat layers (outer peripheral walls) 20) is formed. Further, the same material as that for the joining slurry can be suitably used as the material for the outer periphery coating slurry. The outer periphery coating slurry made of these materials is further subjected to heat treatment at 400 to 800 ° C. after drying, so that the adhesive strength between the honeycomb segment and the outer periphery coating material layer is improved, and mechanical strength and regeneration (at PM combustion) are improved. The thermal shock resistance of can be improved.

[2-7] Drying:
Thereafter, in the drying step (T11) shown in FIG. 2, drying is performed by the same drying means as described above.

[2-8] Heat treatment:
Further, in the heat treatment step (T12) shown in FIG. 2, the dried honeycomb structure is cured by heat treatment at 700 ° C. for 30 minutes. By doing so, it is possible to perform a treatment for binding the trapping layer to the partition wall simultaneously with the heat treatment of the outer peripheral coat, and it is possible to obtain a honeycomb filter without requiring an additional new heat treatment step.

[3] Catalyst loading method:
Furthermore, when a catalyst is supported on a honeycomb filter formed by the above-described honeycomb filter manufacturing method to form a catalyst filter, for example, the following forming method can be exemplified.

  The method for supporting the catalyst component is not particularly limited, but it can be supported by a known method. For example, a method such as dipping or suction may be used. Furthermore, for example, a catalyst liquid containing a catalyst component is washed on the partition walls of the honeycomb structure, and then dried and heat-treated, so that the catalyst is supported on the surface of the particles constituting the partition walls or in the pores of the partition walls. can do. Although the drying method of the honeycomb structure carrying the catalyst is not particularly limited, it can be dried by a known method. For example, after removing excess catalyst slurry by air blow, the honeycomb structure carrying the catalyst may be put in a hot air dryer and dried, or the hot air obtained by the hot air generator is supplied to each cell of the honeycomb structure. You may let it pass and dry. As a drying temperature, it is preferable to perform drying at a temperature of about 80 to 200 ° C. Furthermore, by carrying out the heat treatment of the honeycomb segment on which the catalyst is supported and dried, the supported catalyst component can be firmly fixed on the partition wall surface of the honeycomb segment or in the pores of the partition wall. The temperature for the heat treatment is preferably 400 ° C to 600 ° C. The amount of catalyst to be supported and its shape can be adjusted to desired values by controlling the concentration of the catalyst solution, the coating time, and the like. In order to support the catalyst component in a highly dispersed state, it is preferable that the catalyst component is once supported in advance on a heat-resistant inorganic oxide having a large specific surface area such as alumina and then supported on the partition walls of the honeycomb structure.

[4] Honeycomb filter:
It is preferable that the honeycomb filter is manufactured by the method for manufacturing a honeycomb filter described so far. It is preferable that the honeycomb filter is manufactured by the above-described honeycomb filter manufacturing method because the honeycomb filter can achieve the effects of the present invention while reducing the cost burden. Specifically, a honeycomb filter having the following characteristics can be manufactured.

[4-1] Honeycomb filter of the present invention:
As shown in FIGS. 5, 6, and 7, the honeycomb filter 1 of the present invention includes a plurality of cells that are defined by partition walls 4 made of porous ceramic having a large number of pores and that serve as exhaust gas flow paths. 3, in which the opening portions 2 a and the other opening end portions 2 b of the plurality of cells 3 are formed with alternately plugged portions 10, and the partition walls 4 is configured as a honeycomb filter 1 in which a PM trapping layer 24 having a small average pore diameter is formed.

[4-1] PM collection layer:
In the honeycomb filter of the present embodiment, a PM trapping layer having an average pore diameter smaller than that of the partition walls is formed as a surface layer on the partition walls made of porous ceramic having a large number of pores. That is, by forming a layer having a small average pore diameter on the partition wall as a PM trapping layer, particulate matter (PM) mainly composed of exhaust gas soot (graphite) is trapped in the PM trapping layer. It plays a role of blocking the passage of the inside of the pores. In other words, the PM trapping layer plays a role of preventing the soot from passing into the pores of the partition walls when the soot passes into the pores of the partition walls. This is to obtain a high soot burning rate while suppressing an increase in the pressure loss because the soot accumulates on the surface and the risk of pressure loss during the deposition increases.

  Further, in the honeycomb filter of the present embodiment, a predetermined cell in which one end is opened and the other end is plugged, and one end is plugged and the other end is opened. The remaining cells are alternately arranged, for example, a fluid (exhaust gas) flowing in from one end where a predetermined cell opens, and a partition wall from the side provided with a surface layer on which a PM trapping layer is formed Is a wall flow type filter that collects and removes PM in the exhaust gas by flowing out from the other end where the remaining cells open. is there.

  In the preferred embodiment of the honeycomb filter of the present embodiment, the surface layer formed as the PM trapping layer has a peak pore diameter of 2 μm or more and less than 8 μm, and a porosity of 40% or more and less than 80%. preferable. By being formed in this way, it is possible to maintain good PM collection efficiency, prevent a sudden increase in pressure loss immediately after the start of PM collection, reduce pressure loss during PM deposition, and durability of the collection layer. On the other hand, if the peak pore diameter is less than 2 μm, the initial pressure loss where PM is not deposited may be excessive, and if it exceeds 8 μm, the collection efficiency may deteriorate or the collection layer may pass through the inside of the pores. There may be an increase in soot reaching, and the pressure loss reduction effect during PM deposition may be reduced. Also, if the porosity is less than 40%, the initial pressure loss where PM is not deposited may be excessive, and if it is 80% or more, the surface layer as a durable PM collection layer is manufactured. Difficult to do.

  As shown in FIG. 6, in the honeycomb filter 1 of the present embodiment, when used, the exhaust gas (fluid) flows from one end face 2a side (one end (end face where a predetermined cell 3 opens)). From the side where the PM trapping layer 24 is provided, and from the side where the PM trapping layer 24 is provided, the cell 3 (residual residual surface 2b) is opened as the permeated fluid. It flows out to the cell 3) and flows out from the other end surface 2b side (the other end of the remaining cell 3 (end on the end surface 2b side)) to the outside. When passing through the partition walls 4, most of the PM contained in the exhaust gas is collected by the PM collection layer 24 formed on the surface layer of the partition walls 4. By collecting PM contained in the exhaust gas by the PM trapping layer 24, PM is prevented from passing into the pores of the partition walls 4, and an increase in pressure loss during PM deposition is suppressed.

  FIG. 6 is a schematic view when exhaust gas is allowed to flow into the honeycomb filter of the present embodiment, and shows a state in which the honeycomb filter is sectioned in the length direction (axial direction).

  Further, as shown in FIG. 5, in the honeycomb filter 1 of the present embodiment, the plurality of honeycomb segments 40 are joined through the joining material layer 21, and the outer peripheral portion of the obtained joined body is ground into a predetermined shape. The outer peripheral coat layer 20 is formed by coating the outer peripheral portion of the processed honeycomb segment bonded body 30 with the outer peripheral coat slurry. Further, in the honeycomb filter 1, the plugging portions 10 are arranged so as to plug the cells 3 at the end faces 2a and 2b.

The cell density (cell density) of the honeycomb filter of the present embodiment is preferably 15 / cm ² or more and less than 65 / cm ² , and the thickness of the partition wall 4 is 200 μm or more and less than 600 μm. Preferably there is. Since the pressure loss during PM deposition decreases as the filtration area increases, the pressure loss during PM deposition decreases as the cell density increases. On the other hand, the initial pressure loss is increased by reducing the hydraulic diameter of the cell. Therefore, the cell density is preferably large from the viewpoint of reducing the pressure loss during PM deposition, but the cell density is preferably small from the viewpoint of reducing the initial pressure loss. If the thickness of the partition wall 4 is increased, the collection efficiency is improved, but the initial pressure loss is increased. In consideration of the trade-off between the initial pressure loss, the pressure loss during PM deposition, and the collection efficiency, the range of the cell density and the partition wall thickness satisfying all of them is the above-described range.

  In the honeycomb filter of the present embodiment, it is preferable that the peak pore diameter in the PM collection layer formed as the PM collection layer is equal to or smaller than the average pore diameter of the partition walls 4. Here, the peak pore diameter means the pore diameter constituting the peak of the pore distribution. In the present specification, the pore size distribution of the partition walls is represented by a value measured by a mercury intrusion method. The pore size distribution and the average pore size described later can be measured using, for example, a product name: Porosimeter Model 9810 manufactured by Shimadzu Corporation. FIG. 8 is a graph showing the pore size distribution obtained by the mercury intrusion method, and shows the relationship between the pore volume and the pore size. In this specification, the peak pore diameter of the PM collection layer is the result of measuring the pore size distribution of the partition wall (with the PM collection layer (with the PM collection layer)) and the transition layer (PM collection layer). The difference between the pore size distribution of the PM trapping layer and the measurement result of the pore size distribution in the PM trapping layer that does not include the PM trapping layer (equivalent to the partition wall, without the PM trapping layer) It is defined by its peak (see FIG. 8).

  Further, in the honeycomb filter of the present embodiment, the thickness of the PM trapping layer 24 needs to be set to a suitable thickness depending on the porosity and pore diameter of the PM trapping layer 24. When the pore diameter of the PM trapping layer 24 is large or when the porosity is large, PM becomes easy to pass through the PM trapping layer 24, so the thickness of the trapping layer needs to be increased. Further, when the pore diameter of the PM trapping layer 24 is small or the porosity is small, it becomes difficult for the PM to pass through the PM trapping layer 24. Therefore, even if the trapping layer has a small thickness, Sufficient PM can be collected. In either case, excessively increasing the PM trapping layer thickness increases the permeation resistance of the trapping layer itself, which may increase the pressure loss of the honeycomb structure. It is necessary to determine the required film thickness as appropriate.

  The thickness of the surface layer formed as the PM trapping layer can be determined, for example, by using an image analyzer (trade name “NEXIV, VMR-1515” manufactured by Nikon Corporation), and the honeycomb segment after the PM trapping layer is formed. Measure the cross section of, calculate the diameter of the cell in which the PM trapping layer is formed, and ½ the difference from the cell diameter of the honeycomb segment before forming the PM trapping layer as the thickness of the PM trapping layer Can be sought. Moreover, it can also obtain | require by performing the image analysis through SEM (scanning electron microscope) of the cross section of a partition. For example, FIG. 9 is a graph showing the relationship between the distance from the surface of the partition wall of the honeycomb filter and the porosity. When determining the thickness of the surface layer formed as the PM trapping layer, first, 1000 or more in the thickness direction for a region having a thickness half the thickness of the partition including the side on which the PM trapping layer is formed. Dividing into the above, the porosity in the square in each divided area is measured as the space / solid area ratio on the image from the area close to the surface, and plotted against the distance from the surface. In addition, the average value of 20 visual fields shall be plotted at each distance. Then, an average of three points close to the surface excluding one point closest to the surface is obtained, and this is used as the porosity of the PM trapping layer (referred to as porosity x). On the other hand, at a position sufficiently away from the surface (the central part in the partition wall thickness direction), an average space / solid area ratio of 20 square fields (one side of the square is 1/1000 of the partition wall thickness) is measured. This is defined as the porosity of the partition wall (referred to as porosity y). Then, the position (distance from the surface) where the straight line obtained by the arithmetic mean of the porosity x and the porosity y and the straight line connecting the plots intersect (distance from the surface) is obtained as the thickness (depth) of the PM trapping layer. it can.

  In the honeycomb filter of the present embodiment, the average pore diameter of the partition walls is preferably 10 μm or more and less than 60 μm. The average pore diameter of the partition wall is a value measured by a mercury intrusion method. The average pore diameter of the partition wall can be obtained by cutting out one partition wall, removing the PM trapping layer by grinding, and measuring the remaining part (corresponding to the partition wall). The pore diameter may be measured by cutting out partition walls from the honeycomb segment before forming the PM trapping layer.

  In the honeycomb filter of the present embodiment, it is preferable that the porosity of the PM collection layer 24 is larger than the porosity of the partition walls 4 as shown in FIG. In this specification, the porosity is a value measured by performing image analysis through a SEM (scanning electron microscope) of the cross section of the partition wall. Measure the space / solid area ratio of 20 square fields (one square piece is 1/1000 of the partition wall thickness) in the obtained image for both the PM collection layer and partition wall, and calculate the average value. And the porosity.

  The PM collection layer being formed “on the partition wall” means that it is formed on the partition wall formed on the gas inflow side. That is, it is a partition wall on the gas inflow side provided in the honeycomb filter, and a region as a PM trapping layer having a small average pore diameter is formed on the partition wall in order to prevent soot from entering. In other words, this PM trapping layer is formed as an inlet on the gas inflow side. Specifically, as shown in FIGS. 6 and 7, a PM trapping layer 24 is formed on the partition wall 4 of the cell 3 as an inlet of a gas inflow passage.

(Other configurations of the honeycomb filter of the present embodiment)
As shown in FIGS. 5 and 6, the honeycomb filter according to the present embodiment includes a plurality of cells 3 that are partitioned by partition walls 4 made of porous ceramic having a large number of pores and serve as exhaust gas flow paths. Yes. Plugged portions 10 are alternately formed at one open end 2a and the other open end 2b of the plurality of cells 3. However, the overall shape of the honeycomb structure is not particularly limited. For example, in addition to a cylindrical shape as shown in FIG. 5, an elliptical column shape, a long column shape, a quadrangular column shape, a triangular column shape, other polygonal column shapes, etc. The shape can be mentioned.

  In addition, the cell shape (cell shape in a cross section perpendicular to the cell formation direction) included in the honeycomb filter is not particularly limited. For example, in addition to the square cells as shown in FIG. Examples include a polygon such as a hexagon, a combination of an octagon and a rectangle, a circle, an ellipse, a racing track, or a shape obtained by partially deforming them. However, it is not limited to such a shape, and can widely include known cell shapes. From the viewpoint of easy production, the cross-sectional shape of the cell is preferably a triangle, a rectangle, a hexagon, or a combination of an octagon and a rectangle. In particular, when octagons and squares are combined, by making octagonal cells on the fluid inlet side, it is possible to increase the surface area on the fluid inlet side and increase the amount of particulate matter to be collected. I can do it. In addition, since the PM trapping layer is formed on the surface layer of the cell on the fluid inlet side, a sufficient hydraulic diameter can be maintained even after the PM trapping layer is formed by increasing the surface area on the fluid inlet side. This is advantageous in terms of reducing pressure loss. Further, a circular cell or a polygonal cell having a square shape or more is preferable in that the thickness of the PM trapping layer at the corner portion can be reduced and the thickness of the PM trapping layer can be made uniform in the cell section.

[5] Catalyst-supporting honeycomb filter:
A catalyst-carrying filter produced by the method for producing a catalyst-carrying filter described so far or by the method for producing a honeycomb filter explained so far is preferable. It is preferable to manufacture by the above-described honeycomb filter manufacturing method or catalyst-carrying filter manufacturing method because the catalyst-carrying filter can achieve the effects of the present application while reducing the cost burden. Specifically, a catalyst filter having the following characteristics can be manufactured.

  As in this embodiment, the PM trapping layer is formed on the partition wall, and the partition wall is coated with a catalyst, so that even if the engine is rotated at a high load and high speed, the PM trapping layer is reduced while reducing the pressure loss. It is preferable because the soot and Ash can be reliably collected and the soot can be reliably combusted by the purification action of the supported catalyst. Furthermore, because soot and Ash are collected in this PM collection layer, it is possible to prevent poisoning of the catalyst supported on the partition walls and improve durability, improve low temperature combustibility and reduce the amount of catalyst supported Can do.

[5-1] Catalyst:
Examples of the catalyst for coating the partition walls include an oxidation catalyst. However, the present invention is not limited to this, and the effects of the present application can be obtained. Any known one can be applied to the present embodiment.

[5-1-1] Oxidation catalyst:
As the oxidation catalyst, a noble metal such as platinum (Pt), palladium (Pd), rhodium (Rh) is preferably used.

In the catalyst-carrying filter of the present invention, another catalyst or a purification material may be carried. For example, NO _x storage catalyst, three-way catalyst, cerium (Ce) and / or zirconium (Zr) made of alkali metals (Li, Na, K, Cs, etc.) and alkaline earth metals (Ca, Ba, Sr, etc.) A co-catalyst typified by an oxide, an HC (Hydro Carbon) adsorbent, or the like may be supported.

  For example, the catalyst may include Ce and at least one other rare earth metal, alkaline earth metal, or transition metal.

  Here, the rare earth metal can be selected from, for example, Sm, Gd, Nd, Y, La, Pr and the like.

  The alkaline earth metal contained in the catalyst can be selected from, for example, Mg, Ca, Sr, Ba and the like.

  The transition metal contained in the catalyst can be selected from, for example, Mn, Fe, Co, Ni, Cu, Zn, Sc, Ti, V, and Cr.

Further, the oxidation catalyst, carrying a catalyst component such as _the NO _X storage catalyst is not particularly limited, for example, the barrier ribs of the honeycomb structure, the catalyst solution containing the catalyst component was washcoat, was heat-treated at a high temperature The method of baking etc. are mentioned. Further, for example, a catalyst supporting layer may be formed by a method in which a ceramic slurry is attached to a partition wall of a substrate having a honeycomb structure, dried, and fired using a conventionally known ceramic film forming method such as a dipping method. . At this time, the thickness of the catalyst support layer can be adjusted to a desired value by controlling the concentration of the catalyst coat slurry, the time required for catalyst support, and the like.

Since catalyst components such as an oxidation catalyst and NO _X storage catalyst are supported in a highly dispersed state, the catalyst components are first supported on a heat-resistant inorganic oxide having a large specific surface area, such as alumina, and then the partition walls of the honeycomb structure. You may make it carry on.

  Further, the catalyst is formed by, for example, a method in which a catalyst slurry is supported in the partition walls and / or the pores of the PM collection layer by applying a conventionally known catalyst supporting method such as a suction method, and is dried and calcined. May be.

  The average pore diameter of the PM trapping layer is preferably formed to an appropriate size in order to fulfill the purpose of trapping particulates. That is, if the average pore diameter of the PM trapping layer of the partition wall is too small, when the Ash is trapped in the PM trapping layer, the Ash is located above the pores of the PM trapping layer (in the inlet side or near the inlet of the Ash). ), It becomes a lid so that clogging is likely to occur, and there is a risk of blocking the inflow of gas to the outlet side of the partition wall. If the gas inflow is blocked, the purification treatment of the catalyst supported on the partition wall is hindered, and the catalyst purification performance is reduced, which is not preferable. On the other hand, if the average pore diameter of the PM trapping layer is too large, it becomes difficult to trap PM, and as a result, the cylinder may be pulled out toward the partition wall, and gas purification may not be sufficiently performed. Therefore, the catalyst purification performance is reduced, which is not preferable.

  In other words, it is preferable that an appropriate amount of catalyst is supported (coated) on the partition walls. This is because the catalyst is supported (coated) in an appropriate amount on the partition walls, so that PM can be sufficiently collected and the supported catalyst functions sufficiently.

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

[1-1] Partition wall thickness, cell density, cell size:
It calculated by measuring the cross section of a honeycomb segment using the image analysis apparatus (The Nikon Corporation make, brand name "NEXIV, VMR-1515"). Specifically, the coordinates corresponding to the partition walls of the honeycomb segment were automatically recognized, and the thickness of the partition walls was measured. Furthermore, using the above-mentioned apparatus, the distance between the partition walls was measured, and the cell density and the size of the inlet cell (the size of the outlet cell) were calculated.

[1-2] Average pore diameter of partition walls:
Measurement was performed using a product name: Porosimeter Model 9810, manufactured by Shimadzu Corporation. Specifically, the partition walls were cut out from the honeycomb filter, the PM trapping layer was removed by grinding, and the average pore diameter was measured by mercury porosimetry for the remaining part (corresponding to the partition walls). did.

[1-3] Porosity of partition walls:
Through SEM (scanning electron microscope), an image of the cross section of the honeycomb segment was taken, and the image was analyzed with the image analysis software. The area of the segment portion and the pore portion was measured, and the porosity was calculated. Specifically, the average space / solid area of 20 square fields (one side of the square is 1/1000 of the thickness of the partition wall) at a position sufficiently separated from the surface of the partition wall (center portion in the thickness direction of the partition wall). The ratio was measured and used as the porosity of the partition wall.

[1-4] Thickness of PM trapping layer:
Using an image analysis device (trade name “NEXIV, VMR-1515” manufactured by Nikon Corporation), the cross section of the honeycomb segment after the PM collection layer is formed is measured, and the diameter of the cell in which the PM collection layer is formed And 1/2 of the difference from the cell diameter of the honeycomb segment before forming the PM trapping layer was taken as the thickness of the PM trapping layer.

[1-5] Peak pore diameter of PM trapping layer:
Measurement was performed using a product name: Porosimeter Model 9810, manufactured by Shimadzu Corporation. Specifically, the partition wall is cut out from the honeycomb filter, the pore distribution of the honeycomb segment in which the PM collection layer is formed is measured by the above-described porosimeter, and the pores of the partition wall, which is a substrate other than the PM collection layer, are measured. The difference from the distribution was calculated, and the maximum value of the increased pore diameter was taken as the peak pore diameter of the PM trapping layer.

[1-6] Porosity of PM trapping layer:
Take an image of the cross section of the honeycomb segment through SEM (scanning electron microscope), bipolarize it with image analysis software, measure the area of the PM trapping layer and the pores, and calculate the porosity of the PM trapping layer did. Specifically, the space / solid area ratio of 20 square fields (one side of the square is 1/1000 of the partition wall thickness) is measured in the PM collection layer, and the average of these is calculated as the porosity of the PM collection layer. It was.

[1-7] Weight of PM trapping layer:
Since the weight has a strong correlation with the heat capacity and contributes to the regeneration characteristics, the weight of the finished product was measured with a balance. Since the outer diameters of the segments are the same, if the honeycomb filter has the same shape, the weight of the bonding material and the weight of the coating material are also the same. Therefore, the weight of the finished product can be replaced with the weight of the PM trapping layer.

[2-1] PM trapping layer strength:
The strength of the PM trapping layer in the honeycomb filter before supporting the catalyst was evaluated as follows. First, air was blown from the DPF outlet side with 0.3 MPa air, and the weight of the PM trapping layer material discharged from the inlet side was measured. The weight of the PM trapping layer material separated by the weight difference before and after air blowing was calculated. Further, the weight of the PM trapping layer material was calculated from [DPF weight]-[DPF made of the same honeycomb segment (DPF of reference example)], and the peel weight ratio was calculated by the following formula (A). .
Peel weight ratio = [Weight ratio of peeled PM trapping layer material] / [PM trapping layer material weight] × 100 (A)

  Furthermore, the numerical value calculated by the above-mentioned formula (A) is 10% or less, and the numerical value larger than 10% is ×. In addition, when the peel weight ratio was evaluated based on 10%, if it exceeds 10%, there is a high possibility that the same peel occurs even under actual use conditions, and the PM trapping layer becomes insufficient in strength. This is because the function of the layer is not expressed, and the layer cannot withstand actual use. Similarly, if the strength of the PM trapping layer is insufficient, the PM trapping layer may be peeled off during the catalyst supporting step, and the intended function of the PM trapping layer may not be exhibited.

[2-2] Initial collection efficiency:
The initial state before PM is deposited on the honeycomb filter when exhaust gas from the light oil burner is caused to flow into the honeycomb filter under the conditions that the PM concentration is 1 mg / m ³ , the temperature is 200 ° C., and the flow rate is 2.4 Nm ³ / min. , The number of PM particles upstream (before flowing into the honeycomb filter) and downstream (after flowing out of the honeycomb filter) was measured. Then, the collection efficiency was calculated according to the formula of ((the number of upstream PM particles) − (the number of downstream PM particles)) / (the number of upstream PM particles) × 100. The number of PM particles was measured by counting the PM particles using SMPS (Scanning Mobility Particle Sizer) manufactured by TSI. When the initial collection efficiency was 80% or more, the evaluation was “good”, and when it was less than 80%, the evaluation was “poor”.

[2-3] Initial pressure loss:
Air at normal temperature is flowed into the honeycomb filter on which PM is not deposited at a flow rate of 8 Nm ³ / min. The pressure difference with the honeycomb filter outlet end face side) was measured with a differential pressure gauge to determine the initial pressure loss.

[2-3-1] Initial pressure loss increase rate:
((Initial pressure loss) − (pressure loss of DPF (reference example DPF) manufactured with the same honeycomb segment)) / (pressure loss of DPF (reference example DPF) manufactured with the same honeycomb segment)) × 100 Thus, the increase rate of the initial pressure loss was calculated. The initial pressure loss increase rate was evaluated as ◯ if it was less than 20%, Δ if it was 20% or more but less than 40%, and x if it was 40% or more.

[2-4] Pressure loss during PM deposition:
4 g / L of PM is deposited as a mass per volume on a honeycomb filter on which PM is not deposited, and 200 ° C. air flows at a flow rate of 2.4 Nm ³ / min into the honeycomb filter on which the PM is deposited. The pressure difference between the upstream and downstream of the honeycomb filter was measured with a differential pressure gauge, and the pressure loss during PM deposition (referred to as pressure loss A, see FIG. 10 described later) was obtained.

Further, the PM pressure loss reduction rate (hereinafter referred to as “PM pressure loss reduction rate” as appropriate) was calculated by the following equation using the pressure loss A described above.
PM pressure loss reduction rate = ((PM pressure loss A of DPF (reference example DPF) made of the same honeycomb segment) − (PM pressure loss A)) ÷ (DPF made of the same honeycomb segment (DPF of the reference example)) PM pressure loss A) x 100

  Thus, the value of the PM pressure loss reduction rate was determined, and 20% or more was evaluated as ◯, 10% or more and less than 20% as Δ, and less than 10% as x.

[2-5] Hysteresis characteristics:
FIG. 10 is a graph showing the hysteresis characteristics of the honeycomb filter, and shows the relationship between the pressure loss and the PM deposition amount per volume. In this example, after depositing 6 g / L of PM as mass per volume at a temperature of 200 ° C. on a honeycomb filter, a part of PM is burned at a temperature of 400 ° C., and the PM is reduced to 2 g / L. Pressure loss (referred to as pressure loss C) was obtained. And the pressure loss difference B which is the difference of the said pressure loss A and the pressure loss C was calculated, ratio of the pressure loss difference B with respect to the pressure loss A was displayed in%, and this was evaluated as a hysteresis characteristic. Specifically, 10% or less was evaluated as ◯, 10% or more and less than 20% as Δ, and 20% or more as ×.

[2-6] Reproduction characteristics:
Combustion gas containing soot (soot) generated by combustion of diesel fuel gas oil was introduced into the honeycomb filter, and a PM amount of 8 g / L was collected in the honeycomb filter. Thereafter, the exhaust gas temperature was raised by post-injection, the inlet gas temperature of the honeycomb filter was maintained at 650 ° C. for 10 minutes, and the soot in the honeycomb filter was removed by combustion. The maximum temperature during combustion removal was measured. Specifically, the maximum temperature was evaluated as less than 1250 ° C., and the maximum temperature as 1250 ° C. or more was evaluated as x.

[3] Overall evaluation:
The following performance evaluation, manufacturing cost evaluation, and durability evaluation were performed.

[3-1] Performance:
As a reference example, the DPF performance was evaluated based on the superiority of the honeycomb filter formed. Specifically, the superiority is studied by comprehensively examining each of the above-described PM collection layer strength, initial collection efficiency, initial pressure loss, pressure loss during PM deposition, hysteresis characteristics, and regeneration characteristics. : Evaluation was made from the point of superiority in all items, Δ: superiority in some items, ×: no superiority.

[3-2] Manufacturing cost:
It evaluated by the frequency | count of the heat processing after joining, PM collection layer formation, and outer periphery coating. Specifically, ◯: the number of heat treatments of 700 ° C. or higher was 1 time, and x: the number of heat treatments of 700 ° C. or higher was 2 times. In addition, since the colloidal silica which is a binder does not exhibit sufficient strength, the drying step at 200 ° C. or lower is not included in the number of times.

[3-3] Durability:
Evaluation was made based on whether or not the PM trapping layer was peeled off in the honeycomb filter before supporting the catalyst. Specifically, using the above-described evaluation of the peeling weight ratio, the numerical value calculated by the above-described equation (A) was 10% or less, and the numerical value larger than 10% was taken as x.

[3-4] Overall evaluation:
Comprehensive evaluation: ○: all items of performance evaluation, manufacturing cost evaluation, durability are △, △: performance evaluation, manufacturing cost evaluation, part of durability is Δ, ×: performance evaluation, manufacturing cost evaluation, durability Part of was done as x.

[4-1] Preparation of honeycomb segment:
As a honeycomb segment raw material, a mixed powder of SiC powder 80% by mass and metal Si powder 20% by mass is used. To this mixed powder 100 parts by mass, a pore former is 13 parts by mass, a dispersion medium 35 parts by mass, and an organic binder. 6 parts by mass and 0.5 parts by mass of a dispersant were added, mixed and kneaded to prepare a clay. Water is used as a dispersion medium, a mixture of starch and acrylic acid polymer resin having an average particle size of 10 μm is used as a pore former, hydroxypropylmethylcellulose is used as an organic binder, and ethylene glycol is used as a dispersant. used. Next, the clay is extruded using a mold having a predetermined slit width in which the cell shape is octagonal cells-rectangular cells are alternately formed, and the honeycomb shape of the desired size of the octagonal cells-rectangular cells is obtained. Obtained.

[4-2] Production of plugged honeycomb segment:
After the honeycomb segment is dried with a microwave dryer and further completely dried with a hot air dryer, the cell openings on one end face of the honeycomb segment are alternately masked in a checkered pattern (staggered pattern), The end portion on the masked side was immersed in the plugging slurry containing the honeycomb segment raw material described above to form plugged portions alternately arranged in a checkered pattern. Thereafter, the honeycomb formed body on which the plugged portions were formed was dried with a hot air dryer, and further fired (calcined) at about 550 ° C. for about 3 hours in an oxidizing atmosphere. Further, firing was performed for 2 hours at a firing temperature of 1450 ° C. in an Ar inert atmosphere. Thus, the cell density is 46.5 (cells / cm ³ ), the partition wall thickness is 0.25 mm, the shape of the inlet cell is octagonal, the size is 1.41 mm, the shape of the outlet cell is square, A rectangular columnar honeycomb segment A having a size of 1.01 mm, an average pore diameter of 14 μm, a length of 152 mm consisting of a porosity of 41%, and a side of 36 mm was prepared. The segment characteristics are shown in Table 1.

Similarly, the cell density is 46.5 (cells / cm ³ ), the partition wall thickness is 0.31 mm, the shape of the inlet cell is an octagon, the size is 1.36 mm, the shape of the outlet cell is a square, Honeycomb segment B having a size of 0.96 mm, an average pore diameter of 14 μm, a porosity of 41%, a cell density of 46.5 (pieces / cm ³ ), a partition wall thickness of 0.25 mm, and an inlet cell shape of 8 Honeycomb segment C having a square shape, a size of 1.41 mm, an outlet cell shape of a square, a size of 1.01 mm, an average pore diameter of 23 μm, and a porosity of 58%, a cell density of 46.5 (pieces) / Cm ³ ), the partition wall thickness is 0.31 mm, the shape of the inlet cell is octagonal, the size is 1.36 mm, the shape of the outlet cell is square, the size is 0.96 mm, and the average pore diameter is 23μm, porosity 58% The two cam segments D were prepared respectively in advance. The cell shape of the honeycomb segment can be changed by changing the mold at the time of extrusion, and the porosity and pore diameter can be adjusted by appropriately adjusting the size of the SiC particles to be used, the size of the pore former to be added, and the addition amount. Of honeycomb segments were obtained. These honeycomb segment characteristics are shown in Table 1.

  For the above-mentioned “cell density”, “inlet cell size”, and “exit cell size”, the honeycomb segment cross section was measured with an image analyzer (trade name “NEXIV VMR1515” manufactured by Nikon Corporation). Calculated by measuring.

[5] Preparation of slurry for PM collection layer:
The slurry for forming the PM trapping layer was adjusted. First, add 0.65% by mass of SiC (average particle size: 12 μm) as an aggregate and 4.5% by mass of colloidal silica (solution with a solid concentration of 40%) as a binder in a predetermined amount of water, and stir well. The slurry I for collecting layer formation is adjusted. Similarly, for collecting layer formation prepared by adding SiC (average particle diameter of 12 μm) as an aggregate to 1.30% by mass and colloidal silica (solution having a solid content of 40%) as a binder by adding 4.5% by mass. For forming a collection layer prepared by adding 2.60% by mass of SiC (average particle size 12 μm) as an aggregate, and 4.5% by mass of colloidal silica (solution having a solid concentration of 40%) as a binder. For forming a collection layer prepared by adding Slurry III, 1.30% by mass of SiC (average particle size 15 μm) as an aggregate, and 5.1% by mass of colloidal silica (solution with a solid content of 40%) as a binder Slurry IV, SiC (average particle size 15 μm) as an aggregate, 1.30% by mass, colloidal silica (solution with a solid content of 40%) as a binder, 6.2% by mass, and polymethyl methacrylate particles PMMA, average particle size 5 [mu] m) the slurry IV for trapping layer formed was adjusted by adding 0.5 wt% were respectively prepared. Table 2 shows the mixing ratio of the slurries I to V used to form these PM trapping layers.

  Next, using the honeycomb segments A to D that have been facilitated in advance as described above and the slurries I to V for forming the PM trapping layer, Examples 1 to 12, Comparative Examples 1 to 4, and Honeycomb filters of Reference Examples 1 to 4 were produced.

Example 1
First, 4 × 4 honeycomb segments A (after firing) were used, and a slurry for joining was applied to the peripheral surface of the honeycomb segments, assembled to each other, and pressure-bonded. A joined body was obtained, dried with a hot air dryer, and the joined honeycomb segment joined body was cured to obtain a joined honeycomb segment joined body having a square pillar shape (after drying). The bonding slurry is composed of SiC powder as inorganic particles, aluminosilicate fiber as oxide fibers, silica sol aqueous solution and clay as colloidal oxides, water added and mixed for 30 minutes with a mixer. A slurry was prepared. Further, the dried bonded honeycomb segment assembly was ground into a desired columnar shape to form a columnar honeycomb structure having a segment structure. Thereafter, using the slurry II prepared in advance as described above for the exhaust gas inflow side cell (inflow side partition wall surface) of the partition walls of the honeycomb structure described above, the precursor of the PM collection layer on the surface layer of the inlet cell. A film was formed. Thereafter, the honeycomb structure on which the PM trapping layer was formed was similarly cured by drying using the drying means described above. Furthermore, the peripheral surface of the honeycomb structure after the dried PM trapping layer is formed is coated with a slurry for outer periphery coating, cured by drying, and a cylindrical honeycomb structure of φ144 mm × 152 mm provided with the outer periphery coating layer And dried at 120 ° C. for 2 hours by the same drying means as described above. The outer periphery coating slurry was the same as the bonding material layer slurry.

  Then, the dried honeycomb structure was cured by heat treatment at 700 ° C. for 30 minutes to obtain a cylindrical honeycomb filter with a diameter of 144 mm × 152 mm.

The catalyst was supported on the obtained honeycomb filter. The catalyst slurry was prepared by adding Al ₂ O ₃ sol and water to a Pt-supported γ-Al ₂ O ₃ catalyst and CeO ₂ powder (co-catalyst). Next, the catalyst slurry was supported by wash coating so that the platinum component was 1.06 g / L and the total catalyst component was 30 g / L with respect to the honeycomb filter. The catalyst was loaded by allowing the catalyst slurry to flow into the cell (cell on the exhaust gas outflow side) from the end face on the exhaust gas outflow side of the honeycomb filter so that a large amount of catalyst was present in the partition walls. And after drying at the temperature of 120 degreeC, the honeycomb filter of Example 1 which carry | supported the catalyst was obtained by further heat-processing for 3 hours at 500 degreeC. The obtained honeycomb filter had a PM trapping layer thickness of 49 μm, a PM trapping layer peak pore size of 3.1 μm, a PM trapping layer porosity of 48%, and a DPF mass of 1905 g. It was shown to.

(Example 2)
First, using the slurry II prepared in advance as described above for the exhaust gas inflow side cell (inflow side partition wall surface layer) of the honeycomb segment A described above (after firing), a PM trapping layer is formed on the surface of the inlet cell. A precursor film was formed. Thereafter, the honeycomb structure on which the PM trapping layer was formed was similarly cured by drying using the drying means described above. Furthermore, 4 × 4 honeycomb segments after forming the dried PM trapping layer were used, and the joining slurry was applied to the peripheral surface of the honeycomb segments, assembled together, and pressure-bonded (before drying). The honeycomb segment joined body is obtained by drying with a hot air dryer and cured to obtain a honeycomb segment joined body having a square columnar shape (after drying). A honeycomb filter was obtained.

  The obtained honeycomb filter had a PM trapping layer thickness of 50 μm, a PM trapping layer peak pore diameter of 3.1 μm, a PM trapping layer porosity of 48%, and a DPF mass of 1910 g. It was shown to.

(Example 3)
A honeycomb filter of Example 3 was obtained in the same manner as in Example 1 except that the amount of slurry for forming the PM trapping layer was 1.5 times that of Example 1. The obtained honeycomb filter has a PM trapping layer thickness of 74 μm, a PM trapping layer peak pore size of 3.1 μm, a PM trapping layer porosity of 48%, and a DPF mass of 1970 g. It was shown to.

Example 4
A honeycomb filter of Example 4 was obtained in the same manner as in Example 1 except that Slurry I was used as the slurry for forming the PM trapping layer. The obtained honeycomb filter has a PM trapping layer thickness of 25 μm, a PM trapping layer peak pore size of 3.1 μm, a PM trapping layer porosity of 48%, and a DPF mass of 1850 g. It was shown to.

(Example 5)
A honeycomb filter of Example 5 was obtained by the same method as Example 1 except that slurry III was used as the slurry for forming the PM trapping layer. The obtained honeycomb filter has a PM trapping layer thickness of 75 μm, a PM trapping layer peak pore diameter of 3.1 μm, a PM trapping layer porosity of 48%, and a DPF mass of 1970 g. It was shown to.

(Example 6)
A honeycomb filter of Example 6 was obtained in the same manner as in Example 1 except that slurry IV was used as the slurry for forming the PM trapping layer. The obtained honeycomb filter has a PM trapping layer thickness of 50 μm, a PM trapping layer peak pore diameter of 4.5 μm, a PM trapping layer porosity of 60%, and a DPF mass of 1900 g. It was shown to.

(Example 7)
A honeycomb filter of Example 7 was obtained in the same manner as in Example 1 except that the above-mentioned (after firing) honeycomb segment B was used. The obtained honeycomb filter had a PM trapping layer thickness of 50 μm, a PM trapping layer peak pore diameter of 3.1 μm, a PM trapping layer porosity of 48%, and a DPF mass of 1910 g. It was shown to.

(Example 8)
A honeycomb filter of Example 8 was obtained in the same manner as in Example 6, except that the above-described honeycomb segment C (after firing) was used. The obtained honeycomb filter had a PM trapping layer thickness of 49 μm, a PM trapping layer peak pore diameter of 4.6 μm, a PM trapping layer porosity of 61%, and a DPF mass of 1625 g. It was shown to.

Example 9
A honeycomb filter of Example 9 was obtained in the same manner as in Example 2 except that the above-described honeycomb segment C (after firing) was used and the slurry IV was used as the slurry for forming the PM trapping layer. It was. The obtained honeycomb filter had a PM trapping layer thickness of 50 μm, a PM trapping layer peak pore diameter of 4.6 μm, a PM trapping layer porosity of 61%, and a DPF mass of 1630 g. It was shown to.

(Example 10)
A honeycomb filter of Example 10 was obtained in the same manner as in Example 8, except that the amount of slurry for forming the PM trapping layer was 1.5 times that of Example 8. The obtained honeycomb filter had a PM trapping layer thickness of 75 μm, a PM trapping layer peak pore diameter of 4.6 μm, a PM trapping layer porosity of 61%, and a DPF mass of 1675 g. It was shown to.

(Example 11)
A honeycomb filter of Example 11 was obtained in the same manner as in Example 8, except that Slurry II was used as the slurry for forming the PM trapping layer. The obtained honeycomb filter had a PM trapping layer thickness of 49 μm, a PM trapping layer peak pore size of 3.1 μm, a PM trapping layer porosity of 48%, and a DPF mass of 1595 g. It was shown to.

(Example 12)
A honeycomb filter of Example 12 was obtained in the same manner as in Example 8, except that slurry V was used as the slurry for forming the PM trapping layer. The obtained honeycomb filter had a PM trapping layer thickness of 49 μm, a PM trapping layer peak pore size of 5.1 μm, a PM trapping layer porosity of 68%, and a DPF mass of 1615 g. It was shown to.

(Comparative Example 1)
In the same manner as in Example 1, 4 × 4 honeycomb segments A (after firing) were used, and the joining slurry was applied to the peripheral surface of the honeycomb segments, assembled to each other, and pressure-bonded (dried). A previous honeycomb segment bonded body was obtained, dried with a hot air dryer, and the honeycomb segment bonded body was cured to obtain a honeycomb segment bonded body having a square pillar shape (after drying). The bonding slurry is composed of SiC powder as inorganic particles, aluminosilicate fiber as oxide fibers, silica sol aqueous solution and clay as colloidal oxides, water added and mixed for 30 minutes with a mixer. A slurry was prepared. Further, the dried bonded honeycomb segment assembly was ground into a desired columnar shape to form a columnar honeycomb structure having a segment structure. Next, the peripheral surface of the honeycomb structure after processing is coated with a slurry for outer periphery coating and cured by drying to form a cylindrical honeycomb structure having a diameter of 144 mm × 152 mm provided with an outer periphery coating layer. Then, the dried honeycomb structure was dried at 120 ° C. for 2 hours, and the dried honeycomb structure was cured by heat treatment at 700 ° C. for 30 minutes. Thereafter, using the slurry II prepared in advance as described above for the exhaust gas inflow side cell (inflow side partition wall surface) of the partition walls of the honeycomb structure described above, the precursor of the PM collection layer on the surface layer of the inlet cell. A film having a cylindrical shape of φ144 mm × 152 mm was obtained by drying at 120 ° C. for 2 hours by the same drying means as described above. Then, the catalyst was supported on the obtained honeycomb filter in the same manner as in Example 1 to obtain a honeycomb filter of Comparative Example 1. The obtained honeycomb filter had a PM trapping layer thickness of 49 μm, a PM trapping layer peak pore size of 5.1 μm, a PM trapping layer porosity of 48%, and a DPF mass of 1905 g. It was shown to.

(Comparative Example 2)
Comparative Example 1 was obtained in the same manner as Comparative Example 1 except that a cylindrical honeycomb filter having a diameter of 144 mm × 152 mm formed with a PM trapping layer was obtained, and the PM trapping layer was cured by heat treatment at 700 ° C. for 30 minutes. 2 honeycomb filters were obtained. The obtained honeycomb filter had a PM trapping layer thickness of 48 μm, a PM trapping layer peak pore size of 3.1 μm, a PM trapping layer porosity of 48%, and a DPF mass of 1910 g. It was shown to.

(Comparative Example 3)
A honeycomb filter of Comparative Example 3 was obtained in the same manner as in Comparative Example 1 except that the above-described honeycomb segment C (after firing) was used and the slurry IV was used as the slurry for forming the PM trapping layer. It was. The obtained honeycomb filter had a PM trapping layer thickness of 51 μm, a PM trapping layer peak pore diameter of 4.6 μm, a PM trapping layer porosity of 61%, and a DPF mass of 1630 g. It was shown to.

(Comparative Example 4)
Comparative Example 3 was obtained in the same manner as in Comparative Example 3, except that a cylindrical honeycomb filter having a φ 144 mm × 152 mm formed with a PM trapping layer was obtained, and the PM trapping layer was cured by heat treatment at 700 ° C. for 30 minutes. 4 honeycomb filters were obtained. The obtained honeycomb filter had a PM trapping layer thickness of 48 μm, a PM trapping layer peak pore diameter of 4.5 μm, a PM trapping layer porosity of 60%, and a DPF mass of 1625 g. It was shown to.

(Reference Example 1)
In the same manner as in Example 1, 4 × 4 honeycomb segments B (after firing) were used, and the joining slurry was applied to the peripheral surfaces of the honeycomb segments, assembled to each other, and pressure-bonded (dried). A previous honeycomb segment bonded body was obtained, dried with a hot air dryer, and the honeycomb segment bonded body was cured to obtain a honeycomb segment bonded body having a square pillar shape (after drying). The bonding slurry is composed of SiC powder as inorganic particles, aluminosilicate fiber as oxide fibers, silica sol aqueous solution and clay as colloidal oxides, water added and mixed for 30 minutes with a mixer. A slurry was prepared. Further, the dried bonded honeycomb segment assembly was ground into a desired columnar shape to form a columnar honeycomb structure having a segment structure. Next, the peripheral surface of the honeycomb structure after processing is coated with a slurry for outer periphery coating and cured by drying to form a cylindrical honeycomb structure having a diameter of 144 mm × 152 mm provided with an outer periphery coating layer. The dried honeycomb structure was cured by heat treatment at 700 ° C. for 30 minutes to obtain a cylindrical honeycomb filter having a diameter of 144 mm × 152 mm. In this way, a honeycomb filter of Reference Example 1 having a DPF mass of 1910 g was obtained without forming a PM trapping layer.

(Reference Example 2)
A honeycomb filter of Reference Example 2 was obtained in the same manner as in Reference Example 1, except that the above-described (after firing) honeycomb segment A was used. The obtained honeycomb filter had a DPF mass of 1625 g.

(Reference Example 3)
A honeycomb filter of Reference Example 3 was obtained in the same manner as in Reference Example 1, except that the above-described honeycomb segment D (after firing) was used. The obtained honeycomb filter had a DPF mass of 1630 g.

(Reference Example 4)
A honeycomb filter of Reference Example 4 was obtained in the same manner as in Reference Example 1 except that the above-mentioned (after firing) honeycomb segment C was used. The obtained honeycomb filter had a DPF mass of 1540 g.

  Table 3 shows the characteristics of the honeycomb filters of Examples 1 to 12, Comparative Examples 1 to 4, and Reference Examples 1 to 4 manufactured by the process as described above, and the results of the evaluation test described above are shown in Table 3. 3 shows.

(Discussion)
From the results shown in Table 3, the honeycomb filters of Examples 1 to 10 have sufficient collection layer strength, high initial PM collection efficiency, low initial pressure loss increase rate, and low pressure loss during PM deposition. A honeycomb filter having a small size, a small hysteresis characteristic, and sufficient regeneration characteristics can be realized. Also, as a comprehensive evaluation, a honeycomb filter having performance, manufacturing cost, and durability can be realized, which is superior. Further, in Example 11, the rate of increase in the initial pressure loss is slightly high, and although it is inferior in performance compared with Examples 1 to 10, the manufacturing cost is reduced while sufficiently providing the strength of the PM trapping layer. It was possible to realize a honeycomb filter capable of achieving the above. Furthermore, in Example 12, the PM pressure loss reduction rate in the pressure loss at the time of PM deposition is low, and although it is inferior in terms of performance as compared with Examples 1 to 10, the strength of the PM trapping layer is sufficient. It was possible to realize a honeycomb filter capable of reducing the manufacturing cost while being prepared, and it was excellent.

  On the other hand, in Comparative Examples 1 and 3, since the PM collection layer was formed and then heat treatment was not performed only in the drying process, the PM collection layer was insufficient in strength, and both the hysteresis characteristics and the regeneration characteristics were poor. It was. Furthermore, the performance and durability were not sufficient, and it was proved that practicality was difficult. Moreover, in Comparative Examples 2 and 4, since the PM collection layer was formed and dried, and then the heat treatment process was performed again, it was confirmed that the manufacturing cost increased and the practicality was poor in terms of price competitiveness. It was.

  Furthermore, in Reference Examples 1 to 4, since the PM trapping layer was not formed, it was confirmed that the initial trapping efficiency, the pressure loss during PM deposition, the hysteresis characteristics, and the regeneration characteristics were poor and the performance was poor.

  The method for manufacturing a honeycomb filter according to the present invention can be used as a means for manufacturing the honeycomb filter according to the present invention.

  The honeycomb filter according to the present invention removes particulate matter in exhaust gas discharged from internal combustion engines such as automobile engines, construction machine engines, and stationary engines for industrial machines, and other combustion devices, from the exhaust gas. Can be used for

1: honeycomb filter, 2a, 2b: end face, 3: cell, 4: partition, 10: plugging portion, 15a, 15b: jig, 15c: on-off valve, 17: (for PM trapping layer) slurry, 20 : Outer peripheral coating layer (outer peripheral wall), 21: bonding material layer, 24: PM collection layer (surface layer), 30: honeycomb segment bonding material (after processing), 40: honeycomb segment.

Claims (5)

A forming raw material containing a ceramic raw material is formed to produce a plurality of honeycomb segments having porous partition walls that define a plurality of cells that serve as fluid flow paths, and the honeycomb segments are further bonded via a bonding material. A method of manufacturing a honeycomb filter as an aggregate formed by joining and integrating,
After the honeycomb segments are joined and integrated to form an aggregate, the outer periphery of the aggregate is ground to form a peripheral processed body,
Forming a collection layer precursor for collecting particulate matter on the partition wall of the outer periphery processed body;
Drying the collection layer precursor to obtain a dried product,
Apply an outer periphery coat on the outer periphery of the dried body obtained
Furthermore, simultaneously with the heat treatment of the outer peripheral coat, it has a processing step of forming a trapping layer by bonding a precursor of the trapping layer to the entire partition on the inflow side,
A method for manufacturing a honeycomb filter, wherein the trapping layer has a peak pore diameter of 2 μm or more and less than 8 μm. Forming a forming raw material containing a ceramic raw material to produce a plurality of honeycomb segments including porous partition walls that define a plurality of cells that serve as fluid flow paths,
The honeycomb segments, prior to joining integrated via the bonding material, wherein the precursor of the collection layer is formed for collecting the particulate matter on the honeycomb segments of the septum, the precursor of the collecting layer After drying to obtain a dry segment body, the obtained dry segment body is joined and integrated into an aggregate, and then the outer periphery of the aggregate is ground to form a peripheral processed body, and then the outer periphery obtained and the outer periphery to the outer periphery coating processing body is applied, have the outer peripheral heat treatment coat and simultaneously, the whole on the partition wall on the inflow side, is bound precursor of the trapping layer to film a collection layer processing step And the manufacturing method of the honeycomb filter whose peak pore diameter of the said collection layer is 2 micrometers or more and less than 8 micrometers.   The method for manufacturing a honeycomb filter according to claim 1 or 2, wherein a heat treatment temperature of the outer peripheral coat is 400 to 800 ° C. The method for manufacturing the honeycomb filter according to any one of claims 1 to 3, wherein the ceramic raw material is made of silicon carbide.   A method for producing a catalyst-carrying filter, comprising producing a honeycomb filter by the method for producing a honeycomb filter according to any one of claims 1 to 4 and then carrying the catalyst on the obtained honeycomb filter.

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