JP5694033B2 - Manufacturing method of honeycomb structure - Google Patents

Description

  The present invention relates to a method for manufacturing a honeycomb structure. More specifically, the present invention relates to a method for manufacturing a honeycomb structure capable of firmly fixing a collection layer of a honeycomb structure to the surface of a partition wall and forming such a collection layer at a relatively low temperature. .

  Particulate matter mainly composed of soot (graphite) (hereinafter referred to as “particulate matter” as appropriate) is used as exhaust gas discharged from internal combustion engines such as diesel engines or various combustion devices (hereinafter referred to as “internal combustion engines”). , “Particulate” or “PM”). When this particulate is released into the atmosphere as it is, environmental pollution is caused. Therefore, a filter for collecting particulates (for example, a diesel particulate filter: DPF; hereinafter referred to as an exhaust gas flow path from an internal combustion engine or the like) In general, it is also referred to as “DPF”.

  As a filter used for such a purpose, for example, it has a honeycomb structure substrate in which a plurality of cells serving as exhaust gas flow paths are partitioned by partition walls made of porous ceramics having a large number of pores, A honeycomb in which one open end (open end on the exhaust gas inflow side) and the other open end (open end on the exhaust gas outflow side) of the plurality of cells are alternately plugged by plugging portions. Examples include structures (hereinafter also referred to as “honeycomb filters”) (see, for example, Patent Documents 1 to 3).

  For example, the honeycomb structure (honeycomb filter 101) shown in FIG. 7 has a honeycomb structure 101 (honeycomb substrate) in which a plurality of cells 111 are defined by partition walls 112 made of porous ceramics having a large number of pores. The opening end on the exhaust gas inflow side of a predetermined cell 111b and the opening end on the exhaust gas outflow side of the remaining cell 111a are plugged with plugging portions 113a and 113b. In such a honeycomb filter 101, when exhaust gas flows in from a cell 111a having one end 115a opened (hereinafter sometimes referred to as an “inflow cell”), the partition 112 is separated from the surface of the partition 112 forming the cell 111a. The exhaust gas (purified gas) flows out from the cell 111b that has passed through and the other end 115b is opened. That is, the exhaust gas flowing into the cell 111 a flows out to the cell 111 b through the pores formed in the partition 112, and is discharged from the other end 115 b of the honeycomb filter 101. As described above, when the exhaust gas passes through the partition wall, the particulates in the exhaust gas are collected by the partition wall, and the exhaust gas is purified.

  However, since the DPF has the structure as described above, when PM collection starts from a clean state, PM accumulates in pores inside the partition wall (depth filtration), and suddenly pressure loss (hereinafter referred to as “pressure loss”). May increase). Such a sudden increase in pressure loss is a factor that reduces engine performance. In order to suppress such a sudden increase in pressure loss and to improve the PM collection efficiency, a trapping layer is formed on the inflow side surface of the partition wall to prevent the PM from entering the partition wall. A DPF is disclosed (for example, see Patent Document 4).

  In addition, in order to fix the collection layer to the partition wall, not only the collection layer is applied to the inflow side surface of the partition wall (film formation) but also a binder having a lower melting point than the material constituting the collection layer forming particles and the partition wall (Glue) is used to melt the binding material by firing at a temperature lower than the melting point of the material constituting the collection layer forming particles and the partition walls and higher than the melting point of the binding material. And a collecting layer forming method for fixing them (see, for example, Patent Document 5).

JP 2006-255539 A JP 2005-248726 A JP 2008-188511 A Utility Model Registration No. 2607898 Japanese Patent Laid-Open No. 9-48679

  However, in the collection layer forming method described in Patent Document 5, the binder used has a high melting point, and in order to melt the binder and fix the collection layer constituting particles to the partition walls, the temperature is high (1300 to 1350 ° C.). It was necessary to carry out firing. Therefore, when manufacturing a large amount of DPF having such a collection layer on an industrial scale, there is a problem that it takes a long time to manufacture each DPF and it is difficult to increase the manufacturing efficiency.

  The present invention has been made in view of such problems of the prior art, and the problem is that the trapping layer of the honeycomb structure can be firmly fixed to the surface of the partition wall, and Another object of the present invention is to provide a method for manufacturing a honeycomb structure capable of forming such a trapping layer at a relatively low temperature.

  As a result of intensive studies to achieve the above-mentioned problems, the present inventors have found that the particles constituting the collection layer and the collection layer are formed by heat treatment at a relatively low temperature, for example, 700 to 1000 ° C. A substance capable of forming a bonding part that firmly fixes the layer-constituting particles and the partition walls, for example, a Lewis acid component that forms a salt by reacting with an acid-base reaction with a Lewis base component in ceramics constituting the aggregate particle. It has been found that the above problem can be achieved by using a substance that can be generated or a substance having a relatively low melting point or softening point, and has completed the present invention.

  That is, according to the present invention, the following method for manufacturing a honeycomb structure is provided.

[1] By heating the surface of the partition walls of the honeycomb base material in which a plurality of cells serving as exhaust gas flow paths are defined by porous partition walls, ceramic particles and Lewis base components are heated. The collection layer precursor is formed by coating a collection layer forming raw material including a bond forming raw material capable of producing a Lewis acid component that generates a salt by reacting with the Lewis base component to form a salt, and forming the collection layer precursor, A raw material supplying step for obtaining a honeycomb substrate on which the precursor is formed , and heat treating the obtained honeycomb substrate on which the collection layer precursor is formed at 700 to 1000 ° C. The Lewis acid component in the bond forming raw material is subjected to an acid-base reaction, and the aggregate particles and the aggregate particles and the partition walls are fixed to each other by a bond containing phosphate generated by the acid-base reaction. Caught And a heat treatment step for forming a layered structure. The method for manufacturing a honeycomb structure includes using ammonium dihydrogen phosphate as the bonding portion forming raw material, and using fine particles of cordierite as the aggregate particles. A method for manufacturing a honeycomb structure using a honeycomb substrate made of cordierite.

[ 2 ] In the raw material supplying step, the collection layer precursor is applied to 100 parts by mass of the aggregate particles, and the collection layer forming raw material containing 50 to 250 parts by mass of the binding part forming raw material is applied. The method for manufacturing a honeycomb structure according to the above [1] , wherein the structure is formed.

[ 3 ] On the surface of the partition wall of the honeycomb base material in which a plurality of cells serving as exhaust gas flow paths are defined by porous partition walls, aggregate particles made of cordierite and a melting point or softening point of 500 to 1000 ° C. A collecting layer forming raw material including a bonding portion forming raw material is formed to form a collecting layer precursor, and a raw material supplying step for obtaining a honeycomb substrate on which the collecting layer precursor is formed; By heat-treating the honeycomb base material on which the layered precursor is formed, the joint part forming raw material is melted or softened, and the aggregate particles are formed by the joint part formed from the joint part forming raw material that has been melted or softened. a What was and method for manufacturing a honeycomb structure and a heat treatment step of the said aggregate particles and the partition wall to form a trapping layer secured, as the coupling portion forming raw material, with a glass powder, the honeycomb Method for manufacturing a honeycomb structure used those made of cordierite as a base material.

[ 4 ] The method for manufacturing a honeycomb structured body according to [ 3], wherein the heat treatment is performed at a temperature higher by 0 to 100 ° C. than a melting point or a softening point of a substance used as the bonding portion forming raw material.

[ 5 ] The collection layer from the exhaust gas inflow side end face side of the honeycomb base material in which the open end of the predetermined cell on the exhaust gas inflow side and the open end of the remaining cell on the exhaust gas outflow side are plugged. The forming raw material is conveyed through an air flow, and the trapping layer forming raw material is caused to flow from the opening of the remaining cell having an open end surface on the exhaust gas inflow side, and the trapping material is supplied to the surface of the partition wall in the remaining cell. The method for manufacturing a honeycomb structured body according to any one of [1] to [ 4 ], wherein a layer-forming material is attached.

  According to the method for manufacturing a honeycomb structure of the present invention, it is possible to produce a collection layer that is firmly fixed to the partition walls at a relatively low temperature. Examples of raw materials for forming the bond portion include aggregate particles made of ceramics, a Lewis base component, and a substance capable of generating a Lewis acid component that generates a salt by heating and reacting with the Lewis base component upon heating (bond portion formation). By using a material having a melting point or softening point of 500 to 1000 ° C., it is possible to produce a collection layer firmly fixed to the partition even at a relatively low temperature.

  That is, according to the method for manufacturing a honeycomb structure of the present invention, since the joint portion is formed in the trapping layer, the aggregate particles and the aggregate particles and the partition wall are fixed to each other by the joint portion, so that the partition wall is strong. It is possible to produce a collection layer fixed to the substrate.

  And in the manufacturing method of the honeycomb structure of the present invention, the aggregate particles made of ceramics, the Lewis base component, and the Lewis base component react with the Lewis base component by heating to produce a salt as the bonding part forming raw material. By using a substance capable of producing a Lewis acid component (a raw material for forming a bonding portion) or a substance having a relatively low melting point or softening point, the aggregate particles and the aggregate particles can be fixed to each other even at a relatively low temperature. Possible joints can be formed.

  Further, as a bond forming raw material, when a Lewis acid component generated from the bond forming raw material and a Lewis base component undergo an acid-base reaction, a substance that can generate a salt having a melting point higher than that of aggregate particles is used. When the bonding portion containing a salt having a high melting point is formed, the collecting layer is not damaged or peeled off even under a high temperature condition, and a collecting layer having excellent heat resistance can be formed.

[Fig. 3] Fig. 3 is a cross-sectional view schematically showing a honeycomb substrate used in an embodiment of a method for manufacturing a honeycomb structure of the first invention. FIG. 3 is a cross-sectional view schematically showing a state after a collection layer precursor is formed in a raw material supply step of an embodiment of a method for manufacturing a honeycomb structure of the first invention. It is an enlarged view of _{P 2} parts in Figure 2A. 1 is a cross-sectional view schematically showing a honeycomb structure manufactured in an embodiment of a method for manufacturing a honeycomb structure of the first invention. It is an enlarged view of _{P 3} parts in Figure 3A. 1 is a perspective view schematically showing a honeycomb structure manufactured in an embodiment of a method for manufacturing a honeycomb structure of the first invention. FIG. FIG. 4B is a plan view schematically showing one end face of the honeycomb structure shown in FIG. 4A. It is sectional drawing which shows the A-A 'cross section in FIG. 4B typically. It is a spectrum which shows the result of the measurement by a X ray diffraction method. In an Example, it is a schematic diagram which shows the structure of the collection layer preparation apparatus used for film production of a collection layer. It is sectional drawing which shows the structure of the conventional honeycomb filter typically.

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

[1] Manufacturing method (1) of honeycomb structure:
The method for manufacturing a honeycomb structure according to the present invention (first invention) includes a bone made of ceramics on the surface of the partition wall of the honeycomb substrate in which a plurality of cells serving as exhaust gas flow paths are defined by porous partition walls. A collection layer forming raw material is coated that includes material particles, a Lewis base component, and a bond forming raw material capable of producing a “Lewis acid component that generates a salt by acid-base reaction with the Lewis base component” upon heating. Then, a raw material supply step for forming a collection layer precursor and obtaining a “honeycomb substrate on which the collection layer precursor is formed”, and an obtained “honeycomb substrate on which the collection layer precursor is formed” By subjecting the Lewis base component and the Lewis acid component in the bond portion forming raw material to an acid-base reaction by heat treatment, the aggregate particles and the aggregate are joined by a bond portion containing a salt generated by the acid-base reaction. Particles and partition walls were fixed A method and a heat treatment step of forming a collector layer.

  According to the method for manufacturing a honeycomb structure of the present embodiment, since the coupling portion 32 is formed in the collection layer 30, the coupling portion 32 fixes the aggregate particles 21 to each other, and the aggregate particles 21 and the partition walls 12. As a result, the collection layer 30 firmly fixed to the partition wall 12 can be formed.

  And in the manufacturing method of the honeycomb structure of the present embodiment, the Lewis base component and “a substance capable of generating a Lewis acid component that generates a salt by reacting with the Lewis base component by acid-base reaction” as the bonding portion forming raw material 22 Use. By using such a substance as a reactant, an acid-base reaction proceeds even at a relatively low temperature, for example, 700 to 1000 ° C., and a salt having a melting point higher than that of the reactant is generated as a product. The joint part 32 can firmly fix the aggregate particles 21 and the aggregate particles 21 to the partition wall 12 by containing such a salt.

  A collection layer comprising aggregate particles made of ceramics, a Lewis base component, and a bond forming raw material that can generate a “Lewis acid component that generates a salt by acid-base reaction with the Lewis base component” by heating. The Lewis base component in the forming raw material is not particularly limited as long as it forms a salt by an acid-base reaction with the Lewis acid component generated by the bond forming raw material, and examples thereof include magnesia and alumina. Can do.

  In the method for manufacturing a honeycomb structured body according to the first aspect of the present invention, in the raw material supplying step, as the collection layer forming raw material, “aggregate particles made of ceramics containing a Lewis base component” and “ In the heat treatment step, in the aggregate particles, a material that includes a Lewis acid component that reacts with a Lewis base component in ceramics to form a salt by reacting with an acid base to generate a salt ” It is preferable to carry out an acid-base reaction between this Lewis base component and the Lewis acid component in the bond forming raw material. Thus, there is an advantage that a more firmly fixed collection layer can be obtained by using “aggregate particles made of ceramics containing a Lewis base component” without adding a Lewis base component separately. There is an advantage that it does not take time to add a Lewis base component.

One embodiment of a method for manufacturing a honeycomb structure of the present invention (first invention) will be described with reference to FIGS. 1 to 3B. FIG. 1 is a cross-sectional view schematically showing a honeycomb substrate used in an embodiment of a method for manufacturing a honeycomb structure of the first invention. FIG. 2A is a cross-sectional view schematically showing a state after the collection layer precursor is formed in the raw material supply step of the embodiment of the manufacturing method of the honeycomb structure of the first invention. Figure 2B is an enlarged view of _{P 2} parts in Figure 2A. FIG. 3A is a cross-sectional view schematically showing a honeycomb structure 10c manufactured in an embodiment of the method for manufacturing a honeycomb structure of the first invention. Figure 3B is an enlarged view of _{P 3} parts in Figure 3A. The cross-sectional views of FIGS. 1 to 3B are views showing a cross section parallel to the extending direction of the cells 11 of the honeycomb structure 1 (see FIG. 4A). 3A and 4C, the trapping layer 20 is drawn only on the surface of the partition wall 12. However, in terms of the function of the honeycomb structure, in addition to the surface of the partition wall, the inside of the plugging portion (the plugging portion It may be formed on the cell side surface).

  In the method for manufacturing a honeycomb structure of the present embodiment, as shown in FIGS. 1 to 3B, a plurality of cells 11 serving as exhaust gas flow paths are partitioned by porous partition walls 12, and predetermined cells 11b are formed. A honeycomb base material (plugged honeycomb base) in which an open end (one open end) on the exhaust gas inflow side and an open end (one open end) on the exhaust gas outflow side of the remaining cells 11a are plugged. On the surface of the remaining cell 11a side of the partition wall 12 defining the remaining cells 11a of the material 10a) (see FIG. 1), aggregate particles 21 made of ceramics containing a Lewis base component, and “aggregate particles 21. A collecting layer forming raw material including a bond portion forming raw material 22 that can be generated by heating a Lewis acid component that generates a salt by acid-base reaction with the Lewis base component in the ceramics to be formed; , Forming the collection layer precursor 20 A raw material supply step (see FIGS. 2A and 2B) for obtaining a honeycomb substrate (collection layer precursor-forming honeycomb substrate 10b) on which the collection layer precursor 20 is formed, and a collection layer precursor-forming honeycomb substrate 10b is heat-treated to cause acid-base reaction between the Lewis base component in the aggregate particle 21 and the Lewis acid component in the bond portion forming raw material 22 to contain the salt generated by the acid-base reaction The trapping layer 30 in which the aggregate particles 21 and the aggregate particles 21 and the partition walls 12 are fixed is formed by the connecting portion 32 (the honeycomb in which the trapping layer 30 is formed and the trapping layer 30 is formed). And a heat treatment step (see FIGS. 3A and 3B) for obtaining the structure 10c. Thus, the honeycomb structure 10c in which the collection layer 30 is formed on the surface of the partition wall 12 can be manufactured.

  In the method for manufacturing a honeycomb structure according to the first aspect of the present invention, when the Lewis acid component generated from the bond forming raw material and the Lewis base component undergo an acid-base reaction, the salt having a melting point higher than that of the aggregate particles by the acid-base reaction. It is preferable to use a substance capable of producing. Specifically, in the present embodiment, as the bonding portion forming raw material 22, “a salt whose melting point is higher than the melting point of the aggregate particle 21 by the acid-base reaction with the Lewis base component in the ceramics constituting the aggregate particle 21. It is preferable to use a substance capable of producing a Lewis acid component that generates As the bond forming raw material 22, “a substance capable of producing a Lewis acid component that generates a salt having a melting point higher than the melting point of the aggregate particle 21 by an acid-base reaction with a Lewis base component in the ceramics constituting the aggregate particle 21”. When is used, the collection layer 30 is not damaged or peeled off even under high temperature conditions, and a collection layer having excellent heat resistance can be formed. Here, the “high temperature condition” refers to a high temperature within a range not exceeding the melting point of the aggregate particles made of ceramics, that is, the melting point of ceramics.

  In the present specification, “salt” refers to a salt produced by an acid-base reaction between a Lewis acid and a Lewis base in the definition of Lewis.

  In the present specification, the “bonding portion” refers to a bridging portion that bonds the aggregate particles in the collection layer and further bonds the aggregate particles in the collection layer and the partition walls of the honeycomb substrate. That is. The collection layer adheres the aggregate particles and between the aggregate particles and the partition walls by these bonds, and expresses peeling resistance and heat resistance as the collection layer.

  Hereinafter, the manufacturing method of the honeycomb structure of the present embodiment will be described in order.

[1-1] Production of honeycomb substrate:
As shown in FIG. 1, the plugged honeycomb substrate 10a has a plurality of cells 11 serving as exhaust gas flow paths defined by porous partition walls 12, and has an opening end on the exhaust gas inflow side of a predetermined cell 11b. It has plugging portions 13a and 13b for plugging the opening end portion on the exhaust gas outflow side of the remaining cell 11a.

  Honeycomb base materials include, for example, ceramic particles, water, organic binders (hydroxypropoxyl methylcellulose, methylcellulose, etc.), pore formers (graphite, starch, synthetic resins, etc.), surfactants (ethylene glycol, fatty acid soap) Etc.) are mixed and kneaded to form a clay, the clay is molded into a desired shape, dried to obtain a molded body, and the molded body can be fired. In addition, it is preferable to use particles having an average particle size larger than the aggregate particles for forming the collection layer as the ceramic particles for the honeycomb substrate described above.

  The raw material for the honeycomb substrate is not particularly limited, and a raw material capable of forming ceramics can be suitably used. From the viewpoint of strength, heat resistance, corrosion resistance, etc., a cordierite forming raw material, a silicon-silicon carbide composite material, Alumina, mullite, aluminum titanate, silicon nitride and the like can be mentioned. Among these raw materials, cordierite-forming raw materials are particularly preferable because they have the same thermal expansion coefficient and the like as cordierite preferable as aggregate particles in the collection layer, as will be described later.

  As the honeycomb base material, for example, the following manufacturing method can be given as an example. However, the manufacturing method of the honeycomb substrate is not limited to the following manufacturing method, and can be performed, for example, according to a conventionally known manufacturing method of a honeycomb substrate (honeycomb structure).

  First, as a raw material for the honeycomb substrate, for example, a cordierite-forming raw material is added with a dispersion medium such as water and a pore former, and further an organic binder and a dispersant are added and kneaded, whereby a plastic soot is obtained. Get the soil. Next, the obtained clay is extruded using a predetermined mold to form a honeycomb molded body having a desired shape. Next, the obtained honeycomb formed body is dried with a microwave dryer, and further completely dried with a hot air dryer.

  Next, as shown in FIG. 1, one opening portion of a predetermined cell 11b is plugged with slurry for forming a plugging portion to form a plugging portion 13b. Next, the other opening of the remaining cell 11a is similarly plugged with the slurry to form a plugged portion 13a. Thereafter, the honeycomb formed body on which the plugging portions 13a and 13b are formed is fired (calcined).

  The calcining described above 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 thereto, and is not limited to this. It is preferably carried out according to organic substances (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 3 to 100 hours.

  Further, firing (main firing) is performed. The “main firing” means an operation for sintering 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, the firing temperature is generally about 1400 ° C. to about 1500 ° C., but is not limited thereto.

  As described above, a honeycomb substrate can be manufactured. In the above manufacturing method, an example is described in which a honeycomb substrate is manufactured by performing calcining and main firing after forming a plugged portion that plugs an opening of a cell. The sealing portion may be formed separately after firing the honeycomb formed body (for example, it may be formed after disposing the collection layer as described later). The plugging portion can be formed by any known method without particular limitation. For example, a mask is provided in one opening of a predetermined cell, and the remaining cell opening is formed. A method of filling the plugging slurry, then disposing a mask in the other opening of the remaining cells, and filling the opening of a predetermined cell with the plugging slurry can be mentioned.

  As the raw material for the plugging portion, it is preferable to use the same raw material as the raw material for the honeycomb base material because the expansion coefficient at the time of firing can be the same as that of the honeycomb base material, leading to improvement in durability.

  In the method for manufacturing a honeycomb structure of the present invention, it is preferable to use a plugged honeycomb substrate 10a shown in FIG. 1 having plugged portions 13a and 13b. You may use the honeycomb base material which does not have.

  For example, using a honeycomb substrate that does not have a plugging portion, a raw material supply step is performed to obtain a honeycomb substrate on which a collection layer precursor is formed, and then a heat treatment step is performed, and the collection layer is An arranged honeycomb structure is obtained. Thereafter, the opening end (one opening) on the exhaust gas inflow side of a predetermined cell and the opening end (the other opening) on the exhaust gas outflow side of the remaining cells are plugged to form a plugging portion. You can also In order to form the plugged portion, a conventionally known method can be appropriately employed. Specifically, first, a mask having a hole formed in a portion corresponding to an opening of a predetermined cell is attached to one end face of the honeycomb structure, and the remaining cell opening is attached to the other end face. A mask with holes formed in the corresponding portions is attached. Next, one end portion and the other end portion are sequentially immersed in the plugging slurry, thereby filling the opening end portions of the predetermined cells and the remaining cells with the plugging slurry. Next, drying and baking are performed under conventionally known conditions. In this way, it is possible to obtain a honeycomb structure in which plugging portions are arranged at predetermined positions.

  In the raw material supply step, when using a honeycomb substrate that does not have a plugging portion, it is preferable that the mask is attached to both end faces in advance. Avoiding the provision of the collection layer on the surface of the cell that does not require the collection layer (for example, the surface of the predetermined cell 11b shown in FIG. 3A), and use the collection layer forming raw material unnecessarily. This is because it can be prevented.

  Further, in the above production method, an example in which the honeycomb substrate is integrally extruded (integrated) is described. For example, the honeycomb substrate is formed of a bonded honeycomb segment structure including a plurality of honeycomb segments. A substrate may be prepared and this honeycomb substrate may be used.

  Further, in the above production method, an example in which a cordierite forming raw material is used as the raw material for the honeycomb base material has been described. For example, when the honeycomb base material is made of a Si-SiC composite material, A SiC powder and a metal Si powder can be mixed at a mass ratio of 80:20, and methyl cellulose, hydroxypropoxyl methyl cellulose, a surfactant and water can be added and kneaded to prepare a clay.

[1-2] Preparation of collection layer:
Next, a method for producing a collection layer in the method for manufacturing a honeycomb structure of the present embodiment will be described with reference to FIGS. 2A to 3B. As shown in FIGS. 2A and 2B, the method for producing the collection layer 30 in the method for manufacturing a honeycomb structure of the present embodiment is the rest of the plugged honeycomb substrate 10 a obtained by the above-described production method. On the remaining cell 11a side surface of the partition wall 12 forming the cell 11a, an aggregate particle 21 made of ceramics containing a Lewis base component, and “an acid-base reaction with a Lewis base component in ceramics constituting the aggregate particle 21” Then, the collection layer precursor 20 is formed by coating the Lewis acid component that forms a salt with the bonding portion formation raw material 22 that can be generated by heating to form the collection layer precursor 20. And a raw material supply step for obtaining a honeycomb substrate (collecting layer precursor forming honeycomb substrate 10b) on which 20 is formed, and heat treating the collecting layer precursor forming honeycomb substrate 10b as shown in FIGS. 3A and 3B. By aggregate grain The Lewis base component in 21 and the Lewis acid component in the bond portion forming raw material 22 are subjected to an acid-base reaction, and the aggregate particles 21 and the aggregate particles 21 are joined by the bond portion 32 containing a salt generated by the acid-base reaction. And a heat treatment step of forming the collection layer 30 to which the partition walls 12 are fixed (by forming the collection layer 30 to obtain the honeycomb structure 10c on which the collection layer 30 is formed).

  That is, the method for producing the collection layer 30 in the method for manufacturing a honeycomb structure of the present embodiment is as follows. As the bonding portion forming raw material 22, an acid-base reaction with a Lewis base component in the ceramic constituting the aggregate particle 21 is performed. Using a substance capable of producing a Lewis acid component that generates a salt ”, the heat treatment causes the Lewis base component in the aggregate particles 21 and the Lewis acid component in the bond portion forming raw material 22 to undergo an acid-base reaction to form a salt. This is a method for forming the collection layer 30 fixed by the contained coupling portion 32.

  In the method for manufacturing a honeycomb structure according to the present embodiment, an acid-base reaction is caused to proceed between the aggregate particles 21 and the bonding portion forming raw material 22 to generate salt in the bonding portions 32 to which the aggregate particles 21 are fixed. Thus, the collection layer 30 is formed. Specifically, by using, as the bonding portion forming raw material 22, a substance capable of generating a Lewis acid component that generates a salt by reacting with a Lewis base component in a ceramic constituting the aggregate particle 21 by an acid-base reaction, Even at a low temperature, for example, 700 to 1000 ° C., the aggregated particles 21 and the joint portion 32 that firmly fixes the aggregated particles 21 and the partition wall 12 can be formed. That is, since the acid-base reaction between the Lewis base component and the Lewis acid component proceeds even at a relatively low temperature, the bonding portion 32 can be formed without requiring high temperature conditions as in the prior art. In addition, the Lewis base component that is one reactant of the acid-base reaction can be present in the ceramics constituting the aggregate particle 21. In that case, the acid-base reaction proceeds particularly well at the interface between the aggregate particles 21 and the coupling portion 32 and a salt is generated, so that the coupling (adhesion) between the aggregate particles 21 and the coupling portion 32 is stronger. It becomes.

[1-2-1] Raw material supply process:
The material of the aggregate particles constituting the collection layer is not particularly limited as long as it includes a Lewis base component that reacts as a Lewis base in an acid-base reaction with a Lewis acid component in the bond forming raw material. Cordierite, silicon carbide, alumina, mullite, aluminum titanate, calcia, and boron nitride are preferable. Among these aggregate particles, those that undergo acid-base reaction with the Lewis base contained in the bond forming raw material, such as cordierite, alumina, mullite, and calcia are more preferred, and cordierite, alumina, and mullite are preferred. Particularly preferred. Those having an acid-base reaction with a Lewis base contained in such a bond forming raw material can produce a salt having a higher melting point. The Lewis base component is a component (compound) that reacts as a Lewis base in an acid-base reaction.

  The average particle diameter of the aggregate particles is not particularly limited as long as it can form a porous collection layer having pores having an average pore diameter smaller than the pores of the partition walls of the honeycomb substrate. However, it is preferable to use particles having an average particle diameter of 0.5 to 15 μm, more preferably 1 to 10 μm, and particularly preferably 2 to 5 μm. If the average particle diameter of the aggregate particles is less than 0.5 μm, the aggregate particles may enter the pores of the honeycomb substrate and deteriorate the pressure loss characteristics. On the other hand, if the average particle diameter exceeds 15 μm, The pore size may increase, and the collection efficiency and pressure loss characteristics may deteriorate.

  In the present embodiment, as the bonding part forming raw material, a “substance that can generate a Lewis acid component that generates a salt by an acid-base reaction with a Lewis base component in ceramics constituting the aggregate particles” during the heat treatment described below. Use. That is, the bond forming raw material is a substance that generates a Lewis acid component by heat treatment (when heat is applied). Such a bond-forming material is preferably at least one selected from the group consisting of a phosphoric acid compound, a sulfuric acid compound, a nitric acid compound, a carbonic acid compound, a chloric acid compound, an oxalic acid compound, and an iodic acid compound. It is more preferable to contain at least one selected from the group consisting of a sulfuric acid compound and a carbonate compound, and it is particularly preferable to contain at least one selected from the group consisting of a phosphoric acid compound and a sulfuric acid compound. preferable.

  More specifically, the bond forming raw material is preferably ammonium dihydrogen phosphate, sodium hydrogen phosphate, ammonium hydrogen sulfate, or sodium hydrogen sulfate, more preferably ammonium dihydrogen phosphate, sodium hydrogen phosphate, or ammonium hydrogen sulfate. Particularly preferred are ammonium dihydrogen phosphate and ammonium hydrogen sulfate. By using such a bond forming raw material, a salt having a higher melting point can be generated by an acid-base reaction with a Lewis base component in the aggregate particles during the heat treatment described later. The Lewis acid component is a component (compound) that reacts as a Lewis acid in an acid-base reaction.

  In the collection layer forming raw material, the blending ratio of the aggregate particles and the joint forming raw material is preferably 15 to 250 parts by weight of the joint forming raw material with respect to 100 parts by weight of the aggregate particles. More preferably, it is part. By making the blending ratio of the aggregate particles and the bond forming raw material within the above-mentioned numerical range, the acid-base reaction is efficiently advanced, and a bond having a high content of salt generated by the acid-base reaction is formed. And aggregate particles can be more firmly fixed. In addition, when the bonding part forming raw material is less than 50 parts by mass with respect to 100 parts by mass of the aggregate particles, the progress of the acid-base reaction may be insufficient, and it may be difficult to form the bonding part. That is, the collection layer may be easily peeled off. On the other hand, if the bonding part forming raw material is more than 250 parts by mass with respect to 100 parts by mass of the aggregate particles, the gaps of the aggregate particles are filled with the coupling parts, and the pores of the collection layer are blocked. is there. That is, the porosity of the collection layer may be reduced.

  In the raw material supply step in the method for producing the collection layer, the method for applying the collection layer forming raw material is not particularly limited, and conventionally known methods such as an air flow method and a slurry method can be appropriately used. In the present embodiment, the airflow method is particularly preferable because a thin and uniform collection layer precursor can be formed, and even a water-soluble bond forming material can be used.

  Here, the air flow method refers to capturing from the end surface side of the exhaust gas inflow side of the honeycomb substrate in which the opening end portion on the exhaust gas inflow side of a predetermined cell and the opening end portion on the exhaust gas outflow side of the remaining cells are plugged. Condensation layer forming raw material is conveyed through an air flow, and the collection layer forming raw material is introduced from the opening of the remaining cell where the end surface on the exhaust gas inflow side is opened, and the collecting layer is formed on the surface of the partition wall in the remaining cell. This is a method of attaching a raw material.

  In addition, the slurry method is a method in which a slurry containing aggregate particles and a bonding portion forming raw material is press-fitted from one end face side of a honeycomb substrate to adhere the slurry to the partition wall surface, and then the slurry is discharged to the partition wall surface. In this method, the remaining slurry is dried to form a film. There is no restriction | limiting in particular as a dispersion medium of a slurry, For example, water etc. can be used and water is preferable among these.

[1-2-2] Heat treatment step:
In the heat treatment step in the method for producing the collection layer, the honeycomb substrate on which the collection layer precursor is formed in the above-described raw material supply step is heat treated at, for example, 700 to 1000 ° C. In this step, an acid-base reaction between the base component and the Lewis acid component in the bond forming raw material proceeds to form a collection layer in which the aggregate particles and the aggregate particles and the partition walls are fixed by the bond.

  In the heat treatment step, the Lewis base component and the Lewis acid component in the bond portion forming raw material undergo an acid-base reaction, and a salt as a reaction product is contained in the bond portion. The particles and the partition walls of the honeycomb substrate are firmly bonded. If the melting point of the salt contained in the joint is higher than the melting point of the aggregate particles, the joint does not melt or soften even under high temperature conditions. In addition, the trapping layer having excellent heat resistance can be formed without being peeled off from the partition walls. In the heat treatment step, a Lewis acid component is generated from the bond forming raw material, and an acid-base reaction occurs between the Lewis acid component generated from the bond forming raw material and the Lewis base component in the aggregate particles. In the heat treatment step, when the acid-base reaction is completed depending on the set temperature (that is, when all of the ammonium dihydrogen phosphate is converted to aluminum phosphate), the acid-base reaction is not completed, and the ammonium dihydrogen phosphate. May be left unreacted (ie, aluminum phosphate and ammonium dihydrogen phosphate coexist). In the present invention, the acid-base reaction may or may not be completed, but it is preferable to set the temperature so that the acid-base reaction is completed.

  The heat treatment temperature in the heat treatment step is preferably 700 to 1000 ° C, more preferably 800 to 1000 ° C, and particularly preferably 900 to 1000 ° C. If the heat treatment temperature is less than 700 ° C., the Lewis base component in the aggregate particles and the Lewis acid component in the bond forming raw material cannot sufficiently react, and the aggregate particles can be firmly bonded together. There are cases where it is impossible. On the other hand, when the heat treatment temperature is higher than 1000 ° C., the formed bonded portion and the honeycomb substrate itself may be melted and the pores of the collection layer may be blocked.

  The time for the heat treatment is not particularly limited, but the heat treatment is preferably 0.5 to 72 hours, more preferably 1 to 48 hours, and more preferably 3 to 24 hours. Is particularly preferred. If the heat treatment time is less than 0.5 hours, the acid-base reaction may not sufficiently proceed. On the other hand, if the heat treatment time exceeds 72 hours, further acid-base reaction is difficult to proceed, and the energy cost in the heat treatment tends to increase.

[2] Honeycomb structure (1):
A honeycomb structure 1 (10c) manufactured in an embodiment of the method for manufacturing a honeycomb structure of the present invention (first invention) will be described with reference to FIGS. 4A to 4C. Here, FIG. 4A is a perspective view of the honeycomb structure 1 manufactured in an embodiment of the manufacturing method of the honeycomb structure of the present invention, and FIG. 4B is one end face of the honeycomb structure 1 shown in FIG. 4A. 4C is a cross-sectional view schematically showing an AA ′ cross section in FIG. 4B.

  As shown in FIGS. 4A to 4C, the honeycomb structure 1 manufactured in the present embodiment partitions and forms a plurality of cells 11 extending from one end 15a to the other end 15b serving as an exhaust gas flow path. Look at the porous partition wall 12 and the opening end (one opening end) on the exhaust gas inflow side of a predetermined cell 11b and the opening end (the other opening end) on the exhaust gas outflow side of the remaining cell 11a. A honeycomb substrate (plugged honeycomb substrate 10a (see FIG. 1)) having plugged portions 13a and 13b to be sealed and an inflow cell (remaining cell) 11a having an open end on the inflow side are partitioned. A honeycomb structure provided with a porous collection layer 30 having a pore having an average pore diameter smaller than the average pore diameter of the partition wall 12 disposed in a film shape on the surface of the partition wall 12 on the side to be formed. is there. An outer peripheral wall 14 is formed on the outer periphery of the honeycomb base material.

  The honeycomb structure manufactured in the present embodiment is configured as described above, so that the particulate matter in the exhaust gas can be collected well. That is, since a porous collection layer having pores having an average pore diameter smaller than the pores of the partition walls is disposed on the surfaces of the partition walls constituting the honeycomb substrate, the partition walls of the particulate matter in the exhaust gas are disposed. Intrusion into the pores can be effectively prevented.

  And the collection layer of the honeycomb structure manufactured in this embodiment has the aggregate particle | grains which consist of ceramics, and the coupling | bond part which couple | bonds aggregate particle | grains and aggregate particle | grains and a partition.

  Further, the bond part contains a salt produced by an acid-base reaction between the Lewis base component of the aggregate particles and the Lewis acid component in the bond part forming raw material, and the melting point of the salt is the aggregate. It is preferably higher than the melting point of the particles. Since the honeycomb structure manufactured in the present embodiment has such a configuration, the aggregate particles are firmly fixed to each other even though the honeycomb structure is formed at a relatively low temperature. The particulate matter can be efficiently removed, and the trapping layer is not damaged or peeled off even under high temperature conditions.

[2-1] Honeycomb substrate:
As described above, the honeycomb base material constituting the honeycomb structure manufactured in the present embodiment may be provided with a plugged portion or may not be provided with a plugged portion. There may be. As shown in FIGS. 4A to 4C, the honeycomb substrate has porous partition walls 12 that partition and form a plurality of cells 11 extending from one end portion 15a to the other end portion 15b serving as an exhaust gas flow path. It is. In the honeycomb structure 1 manufactured in the present embodiment, the predetermined cells 11b and the remaining cells 11a are alternately arranged adjacent to each other, and the plugging portions 13a and 13b are shown in FIGS. 4A to 4C. As shown, the opening end of the predetermined cell 11b on the exhaust gas inflow side and the opening end of the remaining cell 11a on the exhaust gas outflow side may be alternately plugged. That is, the cell opening on one end face of the plugged honeycomb substrate 10a may be plugged in a checkered pattern.

  There is no restriction | limiting in particular about the whole shape of a honeycomb base material, For example, shapes, such as elliptical shape, quadratic prism shape, triangular prism shape other than cylindrical shape as shown to FIG. 4A, can be mentioned. As such a honeycomb substrate, a honeycomb substrate used in a conventionally known honeycomb structure can be preferably used.

  In addition, as the shape of the cells formed on the honeycomb substrate (cell shape in a cross section perpendicular to the cell penetration direction), for example, a rectangular cell as shown in FIG. 4B, a hexagonal cell, an octagonal cell, etc. And a shape such as a triangular cell. However, the shape of the cells formed on the honeycomb substrate is not limited to such a shape, and can widely include known cell shapes.

  In the honeycomb substrate, different cell shapes can be combined. By making the cell on one side of adjacent cells octagonal and making the other side square, the one side cell (that is, octagonal cell) can be made larger than the other side cell (that is, square cell). In particular, when used in an engine having a large amount of ash generated, an increase in pressure loss during ash deposition can be suppressed by increasing the cell (inflow cell) on the gas inflow side.

The cell density of the honeycomb substrate is not particularly limited, but when used as a honeycomb structure as in the present embodiment, it is preferably in the range of 0.9 to 233 cells / cm ² , and 15.5 to 62. more preferably in the range of 2.0 cells / cm ^2, particularly preferably in the range of 23.3 to 45.0 cells / cm ^2. By setting it as such a range, the area | region which accumulates a particulate matter in an inflow cell can be ensured favorably.

  The thickness of the partition walls constituting the honeycomb substrate is preferably in the range of 20 to 2000 μm, more preferably in the range of 100 to 635 μm, and in the range of 200 to 500 μm from the balance between strength and pressure loss. Is particularly preferred.

  There is no particular limitation on the material of the honeycomb substrate, but ceramics can be suitably used. From the viewpoint of strength, heat resistance, corrosion resistance, etc., cordierite, silicon carbide, alumina, mullite, aluminum titanate, silicon nitride, and It is preferably one of silicon-silicon carbide based composite materials formed using silicon carbide as an aggregate and metal silicon as a bond forming material. Among these materials, cordierite is particularly preferable because it has the same thermal expansion coefficient as cordierite preferable as aggregate particles in the collection layer, as will be described later.

  The plugged portions used in the honeycomb structure manufactured in the present embodiment are plugged portions disposed in a conventional plugged honeycomb structure (honeycomb structure having a plugged portion). Those similarly configured can be used.

  As the average pore diameter of the pores of the partition walls constituting the honeycomb substrate, if the average pore diameter of the partition wall pores is large, it is difficult to form a trapping layer, whereas if the average pore diameter is small, for example, a honeycomb structure When supporting a catalyst (for example, an oxidation catalyst) for removing particulate matter collected in the body, it becomes difficult to support the catalyst. For this reason, the average pore diameter of the pores of the partition walls is preferably 0.3 to 150 μm, more preferably 1 to 60 μm, and particularly preferably 3 to 30 μm.

  Further, the porosity of the partition walls is preferably 30 to 70%, more preferably 35 to 60%. When the porosity of the partition wall is less than 30%, the pressure loss may increase. Moreover, when the porosity exceeds 70%, the strength of the partition walls is insufficient, which is not preferable. The porosity of the partition walls indicates the original porosity of the partition walls of the honeycomb substrate excluding the trapping layer. In the present invention, “average pore diameter” and “porosity” of the partition walls (before forming the trapping layer) constituting the honeycomb substrate mean the average pore diameter and porosity measured by the mercury intrusion method. It shall be.

[2-2] Collection layer:
The honeycomb structure manufactured in the present embodiment has an average finer than the pores of the partition walls arranged in the form of a film on the surface of the partition walls on the side that forms the inflow cells where the open ends on the exhaust gas inflow side are open. A porous collection layer having pores with small pore diameters is provided. And the collection layer of the honeycomb structure manufactured in this embodiment has the aggregate particle | grains which consist of ceramics, and the coupling | bond part which couple | bonds aggregate particle | grains and aggregate particle | grains and a partition.

  The collection layer may be a multilayer (that is, a layer in which two or more collection layers are stacked). Moreover, the pore diameter or particle diameter of the collection layer may be inclined. In that case, it is preferable that the pore diameter or particle diameter is smaller as it is closer to the surface because PM deposition in the pores of the partition walls can be prevented and an increase in pressure loss can be reduced.

  Further, when the average pore diameter of the pores of the partition wall and the average pore diameter of the pores of the collection layer are compared, the average pore diameter of the pores of the collection layer is 1 / (average pore diameter of the partition wall pores). It is preferably 1000 to 9/10 times, more preferably 1/100 to 1/2 times the average pore diameter of the pores of the partition walls, and particularly preferably 1/20 to 1/5 times. . When the average pore size of the pores of the collection layer is less than 1/1000 times the average pore size of the pores of the partition walls, the pores of the collection layer and the like are too small and the pressure loss of the honeycomb structure increases. There is. On the other hand, if the average pore diameter of the collection layer or the like exceeds 9/10 times the average pore diameter of the pores of the partition walls, the pores of the collection layer are too large and are substantially different from the pores of the partition walls. May disappear, and particulate matter may enter the pores of the collection layer, increasing pressure loss.

  The average pore diameter of the pores of the collection layer in the honeycomb structure manufactured in the present embodiment is preferably 0.1 to 30 μm, more preferably 0.1 to 15 μm, and 0.9 to It is still more preferable that it is 11 micrometers, and it is especially preferable that it is 1.5-6 micrometers. By configuring in this way, it is possible to effectively collect particulate matter on the surface of the collection layer (that is, collect in a cake layer) while effectively suppressing an increase in pressure loss due to the collection layer. it can. If the average pore diameter is less than 0.1 μm, the gas permeability becomes small and the permeation resistance of the pores tends to increase rapidly, which is not preferable. If it is larger than 30 μm, the collection performance decreases, and the PM emission is a European regulation Euro. 5 It is not preferable because the regulation value is easily exceeded.

  The average pore diameter of the pores of the trapping layer of the honeycomb structure of the present embodiment is a value measured by the following method from an image obtained by SEM (scanning electron microscope) of the partition wall cross section of the honeycomb structure. First, a desired region of a cross section perpendicular to the axial direction of the partition walls of the honeycomb structure is resin-filled and polished, and observed with a scanning electron microscope (SEM) at a magnification of 1000 times, and an image of the cross section (SEM image) ) This SEM image is an image in which one pixel is 0.261 μm long × 0.261 μm wide. Next, the obtained SEM image is binarized. By the binarization process, the SEM image is separated into the actual part of the captured aggregate particles and the gaps between the aggregate particles. The binarization process is performed with 1 pixel as a minimum unit.

  Next, in this binarized image, in the region recognized as the void gap of the aggregate particle (hereinafter sometimes referred to as “void area”), a “circle” of a size that fits in the void area, Draw in order from circles with larger diameters so that the circles do not overlap. Specifically, first, a circle having the largest diameter (hereinafter, also referred to as “inscribed circle”) is drawn in the void area. Next, the area where the inscribed circle is drawn is excluded from the “gap area”. The inscribed circle having the largest diameter in this state is again drawn in the “void region excluding the region where the inscribed circle is drawn” thus obtained, and then this inscribed circle (the second inscribed circle) The area where the inscribed circle is drawn is further removed from the “gap area”. Hereinafter, the inscribed circle is drawn according to the above method until it becomes impossible to draw the inscribed circle in the “void area (specifically, the void area from which the inscribed circle is drawn)”. That is, the inscribed circle is continuously drawn in the void area up to 1 pixel which is the minimum unit of the image. Commercial image analysis software (for example, trade name “Halcon” manufactured by MVtec Software GmbH) can be used for binarization of the SEM image and image processing for drawing an inscribed circle in the void area.

  Next, the area of all inscribed circles drawn in the void area is accumulated sequentially from the inscribed circle with the largest diameter, and the accumulated area is calculated by adding the areas of all inscribed circles drawn in the void area. To do. At the time of integration, the diameter of the inscribed circle added when reaching 50% of the total integrated area is set as the average pore diameter of the pores of the collection layer. For example, “the diameter of the inscribed circle to be added when reaching 50% of the total accumulated area” is the inscribed circle diameter and the accumulated area, the horizontal axis is the diameter of the inscribed circle, and the vertical axis Can be obtained by calculating a diameter of the inscribed circle corresponding to 50% of the total integrated area.

  Further, when measuring the average particle diameter of the fine particles forming the collection layer, etc., a cross section obtained by resin filling and polishing a desired region of a cross section perpendicular to the axial direction of the partition wall, or a fractured surface is multiplied by 100 times. SEM (scanning electron microscope) observation is performed in a field of view of up to 1000 times, and the particle diameter (maximum diameter) of the fine particles forming the collection layer is measured. The average of all particle diameters measured within one field of view is defined as the average particle diameter.

  Further, the thickness of the collection layer is preferably 3/500 to 1/2 of the thickness of the partition wall, more preferably 1/150 to 1/5, and 1/100 to 1/10. It is particularly preferred. If the thickness of the trapping layer is less than 3/500 of the thickness of the partition wall, the trapping layer is too thin to sufficiently collect the particulate matter. Part of the particulate matter may easily pass through the collecting layer. Moreover, when the thickness of the collection layer exceeds 1/2 of the partition wall thickness, the influence of an increase in pressure loss due to the collection layer is increased, and the initial pressure loss of the honeycomb structure may be increased.

  In the present invention, “thickness of the collection layer” means a thickness measured by the following method.

(Method for measuring the thickness of the collection layer)
First, the partition in which the collection layer is formed is cut perpendicular to the cell penetration direction. Next, a desired region in the cross section of the obtained partition wall is resin-filled and polished. Next, the cross section polished and filled with resin is imaged at a magnification of 500 times with a scanning electron microscope (SEM). Draw a straight line that divides the taken SEM picture into 100, and observe the straight line from the top of the SEM picture in order, and the top straight line that touches the surface of the partition wall and the particles that form the collection layer The top straight line among the straight lines touching is determined. The determined width between the two straight lines is the film thickness of the field of view (ie, in the SEM photograph), and the average of 20 fields of view (ie, in the 20 SEM photographs obtained by imaging different parts at the same magnification) The value is the thickness of the collection layer.

  In addition, as a more specific thickness of a collection layer, it is preferable that it is 1-100 micrometers, and it is still more preferable that it is 5-60 micrometers. By comprising in this way, a particulate matter can be collected favorably and the increase in an initial pressure loss can be suppressed effectively.

  The aggregate particles constituting the collection layer are preferably, for example, any one of cordierite, silicon carbide, alumina, mullite, aluminum titanate, and silicon nitride.

  Among the above-mentioned materials, the aggregate particles constituting the collection layer are more preferably materials containing at least one selected from the group consisting of aluminum, magnesium, calcium, sodium, potassium, strontium, and barium. A material containing at least one selected from the group consisting of aluminum, magnesium, calcium, and potassium is more preferable. More specifically, any one of cordierite, alumina, mullite, and aluminum titanate is more preferable, and any one of cordierite, alumina, and mullite is still more preferable. The aggregate particles constituting the trapping layer are composed of the above-described materials, so that the acid-base reaction with the Lewis acid component supplied from the bond forming raw material results in a strong bond containing a salt. In addition, it is possible to form a bonding portion having excellent heat resistance.

  These aggregate particles are also preferably the same material as the partition walls constituting the honeycomb substrate. For example, when the partition walls are made of cordierite material, the collection layer is preferably formed using aggregate particles made of the same cordierite material as the partition walls. By configuring in this way, the thermal expansion coefficients of the partition walls and the trapping layer are the same, and damage or the like can be made difficult to occur due to a temperature change during forced regeneration of the honeycomb structure.

  The melting point of the bonding part constituting the collection layer is preferably 700 to 3000 ° C, more preferably 1000 to 2500 ° C, and particularly preferably 1200 to 2300 ° C. If the melting point of the bonding part is lower than 700 ° C., a part of the bonding part may be melted, and the pores of the collection layer may be blocked. If the melting point of the bonding portion exceeds 3000 ° C., the raw materials that can be used as the collection layer are limited, and there are cases where there is less time to adjust various characteristics such as thermal expansion of the collection layer. .

  The binding portion preferably contains a salt formed by a reaction between a Lewis base component in the aggregate particle and a Lewis acid component contained in the binding portion forming raw material.

  The salt contained in the bonding part is preferably at least one selected from the group consisting of phosphate, sulfate, nitrate, carbonate, chlorate, oxalate, and iodate. More preferably, it is at least one selected from the group consisting of acid salts, sulfates, and carbonates, and particularly preferably at least one selected from the group consisting of phosphates and sulfates. And it is preferable that the salt contained in the binding part constituting the collection layer is a salt containing at least one selected from the group consisting of aluminum, magnesium, calcium, potassium, sodium, strontium, and barium, More preferred is a salt containing at least one selected from the group consisting of magnesium, calcium and potassium, and particularly preferred is a salt containing at least one selected from the group consisting of aluminum, magnesium and calcium. .

  Specifically, as the salt as described above, aluminum phosphate, calcium phosphate, calcium sulfate and barium sulfate are preferable, aluminum phosphate, calcium phosphate and calcium sulfate are more preferable, and aluminum phosphate and calcium phosphate are particularly preferable. When the salt contained in the bonding portion is a salt having a low generation temperature and a high melting point as described above, the heat resistance of the collection layer can be improved.

  The porosity of the collection layer is preferably 40 to 90%, and more preferably 50 to 80%. If the porosity of the trapping layer is less than 40%, there is a risk that the pressure loss will increase, and if it exceeds 90%, the strength of the trapping layer will be insufficient, so that the trapping surface will be trapped. This is not preferable because there is a possibility that a problem occurs in that the layer is peeled off.

  Note that it is preferable to form the trapping layer with a porosity of 5% or more larger than the porosity of the partition wall because there is an advantage that the pressure loss (permeation pressure loss) in the trapping layer can be reduced.

  Here, the porosity of the collection layer is obtained by polishing and embedding a desired region of a cross section perpendicular to the axial direction of the partition wall, and performing SEM (scanning electron microscope) observation with a field of view of magnification 100 to 1000 times. The obtained image can be binarized and measured by the area ratio of the voids and particles in one field of view.

  In addition, the collection layer in the honeycomb structure manufactured in the present embodiment prevents intrusion of the particulate matter into the pores of the partition walls described so far, and plays a role of collecting the particulate matter in advance ( In addition to (function), the collection layer may be provided with a role (function) for oxidizing the collected PM.

  That is, an oxidation catalyst may be supported on the collection layer. By comprising in this way, the function as a collection layer which collects PM and the function which oxidizes PM are combined, and PM is satisfactorily obtained by the collection layer formed on the inflow side of the partition wall. While collecting, the collected PM can be oxidized.

  As such an oxidation catalyst, noble metals such as platinum (Pt), palladium (Pd), rhodium (Rh) and silver (Ag) are preferably used.

  In addition, in the honeycomb structure manufactured in the present embodiment, in addition to the oxidation catalyst, another catalyst or a purification material may be further supported. For example, a promoter represented by an oxide of cerium (Ce) or zirconium (Zr) may be supported.

  Such an oxidation catalyst may be further supported on at least a part of the pores of the partition walls. By configuring in this way, even if a part of the PM in the exhaust gas is not collected by the collection layer and penetrates the collection layer and enters the pores of the partition wall, PM can be removed by combustion using an oxidation catalyst.

  In addition, there is no restriction | limiting in particular about the load per 1 L of volumes of the honeycomb structure of such an oxidation catalyst, However, It is preferable that it is 1-34 g / L, and it is still more preferable that it is 5-30 g / L. For example, if the supported amount of the oxidation catalyst is less than 1 g / L, sufficient combustion performance of the particulate matter by the catalyst may not be obtained. On the other hand, if it exceeds 34 g / L, the pores of the collection layer may be reduced. The pressure loss may be high even if the soot is not blocked and soot is deposited. Since the particulate matter is almost deposited on the portion of the collection layer, it is not necessary to carry the particulate matter inside the partition pores, and the amount of particulate matter can be reduced from the conventional carrying amount.

[3] Honeycomb structure manufacturing method (2):
Next, an embodiment of a method for manufacturing a honeycomb structure of the present invention (second invention) will be described with reference to FIGS. 1 to 3B.

  In the method for manufacturing a honeycomb structure according to the present embodiment, a plurality of cells 11 serving as exhaust gas flow paths are defined by porous partition walls 12, and an opening end portion on the exhaust gas inflow side of a predetermined cell 11b and the remaining portion are left. In the honeycomb substrate body (plugged honeycomb substrate 10a) (see FIG. 1) in which the opening end portion on the exhaust gas outflow side of the cells 11a is plugged, the remaining partition walls 12 forming the remaining cells 11a are partitioned. A raw material supplying step (FIG. 2A) of forming a trapping layer precursor 20 by applying a trapping layer forming raw material including aggregate particles 21 made of ceramics and a bonding portion forming raw material 23 to the surface on the cell 11a side. 2B) and the honeycomb base material on which the collection layer precursor 20 was formed (collection layer precursor formation honeycomb base material 10b) were heat-treated, whereby the aggregate particles 21 were fixed to each other by the coupling portion 33. A collection layer 30 is formed (capture A heat treatment step (see FIG. 3A and FIG. 3B), and a melting point or a softening point of 500 to 500 is used as the bonding portion forming raw material 23. By using a substance having a temperature of 1000 ° C., the bonding portion forming raw material 23 is melted or softened by heat treatment, and the aggregate particles 21 and the aggregate particles 21 and the partition walls 12 are formed by the bonding portion 33 formed from the bonding portion forming raw material 23. This is a method for forming the fixed collection layer 30.

  The method for manufacturing a honeycomb structure of the present embodiment (second invention) replaces the collection layer forming raw material in one embodiment of the method for manufacturing the honeycomb structure of the first invention described above with “bones made of ceramics”. The collecting layer forming raw material including the material particles and the bond forming raw material having a melting point or softening point of 500 to 1000 ° C. is used. The collection layer forming raw materials in both the first and second inventions are raw materials that can form a collection layer (particularly, a bonding portion) even at a relatively low temperature.

  In this embodiment, a material having a melting point or a softening point of 500 to 1000 ° C. is used as the bond forming raw material, and the bond forming raw material is melted or softened by heat treatment and fixed by the bond formed from the bond forming raw material. By forming the trapping layer, it is possible to form a bonded portion that firmly fixes the aggregated particles and the aggregated particles to the partition walls even at a relatively low temperature, for example, 500 to 1000 ° C.

  In the present embodiment, the melting point or softening point of the substance used as the bond forming raw material is 500 to 1000 ° C., preferably 550 to 950 ° C., more preferably 600 to 900 ° C., It is especially preferable that it is 650-850 degreeC. When the melting point or softening point of the bonding portion forming raw material is within the above-described temperature range, the heat treatment temperature in the heat treatment step can be set low, and the time required for producing each honeycomb structure can be shortened. Efficiency can be increased. In addition, when the melting point or softening point of the bonding portion forming raw material is less than 500 ° C., the raw material is easily melted under a temperature environment in an actual use environment. When the melting point or softening point of the bond forming raw material exceeds 1000 ° C., the energy cost in the heat treatment increases.

  As such a bond forming raw material, that is, a substance having a melting point or softening point of 500 to 1000 ° C., glass powder (glass Frit) is preferred.

  In the present embodiment, the heat treatment is preferably performed at a temperature 0 to 100 ° C. higher than the melting point or softening point of the substance used as the bonding portion forming raw material, more preferably 10 to 80 ° C., and more preferably 20 to 50 ° C. It is particularly preferable to carry out at a high temperature. By performing the heat treatment within the above temperature range, the collection layer can be efficiently formed without excessive heating.

  In addition, the description similar to 1st invention can be performed except regarding the coupling | bond part formation raw material etc. which were demonstrated so far about this embodiment. For example, the honeycomb substrate, the aggregate particles constituting the collection layer, and the like can be the same as those described in the first invention.

  EXAMPLES Hereinafter, although this invention is demonstrated concretely based on an Example, this invention is not limited to these Examples.

Example 1
[Preparation of honeycomb substrate]
As the cordierite forming raw material, alumina, aluminum hydroxide, kaolin, talc, and silica are used. The cordierite forming raw material is 100 parts by weight, the pore former is 13 parts by weight, the dispersion medium is 35 parts by weight, and the organic binder is 6 parts. 0.5 parts by mass of a part by mass and a dispersant were added, mixed and kneaded to prepare a clay. Water was used as the dispersion medium, coke having an average particle diameter of 10 μm was used as the pore former, hydroxypropylmethylcellulose was used as the organic binder, and ethylene glycol was used as the dispersant.

  The prepared clay was extruded to obtain a honeycomb formed body. The obtained honeycomb molded body was dried using a microwave dryer and further dried completely using a hot air dryer, and then both ends were cut to obtain a honeycomb dried body having a predetermined length. Obtained. Next, after forming plugged portions at both ends of the cells of the dried honeycomb body so that adjacent cells are alternately plugged, the plugged portions are fired at 1410 to 1440 ° C. for 5 hours. A honeycomb base material (plugged honeycomb base material) on which was formed was obtained.

The obtained plugged honeycomb substrate had a quadrangular cell shape in the cross section perpendicular to the cell penetrating direction and a quadrangular prism shape as a whole. In addition, the length of one side in the cross section perpendicular to the cell penetration direction (the bottom surface of the quadrangular prism) was 36 mm, and the length in the cell penetration direction (the height of the quadrangular prism) was 152.4 mm. The cell density was 46.5 cells / cm ² , the partition wall thickness was 356 μm, the partition wall porosity was 48%, and the average pore diameter was 12 μm.

[Production of collection layer]
Mix 2.0 parts by weight of cordierite powder with an average particle size of 2.1 μm as aggregate particles, 1.5 parts by weight of ammonium dihydrogen phosphate as a raw material for forming a binding part, and mix and collect using a mortar. A layer forming raw material was obtained. The cordierite powder is obtained by pulverizing and classifying the waste material produced when producing a cordierite honeycomb substrate or the like so as to have an average particle diameter of 2.1 μm (cordierite cerbene), and phosphoric acid. As the ammonium dihydrogen, a trade name “ammonium dihydrogen phosphate” manufactured by Wako Pure Chemical Industries, Ltd. was used.

  Next, the collection layer precursor was formed using the obtained collection layer forming raw material (raw material supply step). Specifically, a collection layer was produced (film formation) using a collection layer production apparatus as shown in FIG. First, the collection layer forming raw material 46 is introduced into the raw material supplier 47, and a certain amount of the collection layer forming raw material 46 is introduced from the raw material supplier 47 into the honeycomb substrate 40 (plugged honeycomb substrate 10a). The ejector 48 (vacuum generator) provided on the side 40a is used for scattering. At this time, on the outflow side 40b of the honeycomb substrate 40, suction is performed by the blower 45 at 400 L / min (liter / min) to guide the collection layer forming raw material 46 into the inflow cell. In this manner, the collection layer precursor was prepared by depositing the collection layer forming raw material 46 on the surface of the partition wall forming the inflow cells of the honeycomb substrate 40 on the inflow cell side. The collection layer precursor was produced for 10 seconds (ie, suction by the blower 45 was stopped 10 seconds after the collection layer forming raw material 46 was introduced into the raw material supplier 47).

  Here, FIG. 6 is a schematic diagram showing the configuration of the collection layer preparation apparatus used for preparation of the collection layer precursor in the examples. In addition, in FIG. 6, the code | symbol 43 shows the air introduce | transduced into an ejector.

  Thereafter, heat treatment was performed at 700 ° C. for 1 hour to form a collection layer in which the aggregate particles and the aggregate particles and the partition walls were fixed to each other by a joint portion, thereby obtaining a honeycomb structure (heat treatment step). The formed collection layer had a porosity of 65% and an average pore diameter of 3 μm.

The obtained honeycomb structure was evaluated as follows. As a result, the separation rate of the collection layer of the honeycomb structure of Example 1 was “0 (%)”, and the heat resistance was “good”. As a result of measurement by X-ray diffraction, it was confirmed that aluminum phosphate was generated at the joint in the collection layer of the honeycomb structure of Example 1. As an X-ray diffractometer, a trade name “X'Pert PRO MPD” manufactured by PANalytical was used. FIG. 5 shows the results of measurement by X-ray diffraction. The formation of aluminum phosphate was confirmed by the appearance of the peak (Al (PO ₄ )) indicated by the arrow in FIG. Note that “bonding portion” in Table 1 indicates the main component of the bonding portion measured by X-ray diffraction (that is, components other than aggregate particles among the components constituting the trapping layer of the honeycomb structure). In the present specification, “main component” means 50% or more of all components.

[Peeling resistance evaluation]
From the outflow side of the honeycomb structure, air compressed to 0.4 MPa using an air gun (trade name “Air Gun (AG50)” manufactured by Kurita Seisakusho Co., Ltd., 3 mm in diameter) is discharged from the outflow side of the honeycomb structure. Sprayed over the entire end face. At this time, the air gun outlet was sprayed with the distance from the outflow side end face of the honeycomb structure fixed to 20 mm.

  The above spraying was performed until the powder (peeled collection layer) was not discharged from the inflow side end of the honeycomb structure. Whether or not the powder was discharged was determined by measuring the mass of the honeycomb structure and determining whether or not the powder was discharged based on whether or not the mass changed before and after spraying.

After confirming that the powder is no longer discharged, that is, no change in the mass of the honeycomb structure before and after spraying, the mass of the honeycomb structure before starting spraying and the powder is no longer discharged. The difference in the mass of the honeycomb structure after this was taken as the amount of peeling. And the ratio (percentage) of the peeling amount with respect to the film forming amount as represented by the following formula (1) was defined as the peeling rate (%). As the amount of film formation, the difference between the mass of the honeycomb structure after film formation (after film formation) and the mass of the honeycomb substrate (before film formation) was used in the raw material supply step. The obtained peel rate (%) is shown in Table 1.
Peeling rate (%) = peeling amount (g) / film forming amount (g) × 100 (1)

[Heat resistance evaluation]
Heating was performed for 1 minute in an electronic furnace in which the furnace temperature was set to 1000 ° C. Thereafter, the microstructure of the collection layer was observed using a scanning electron microscope (SEM) (trade name “S-3200N” manufactured by Hitachi, Ltd.), and the collection layer was maintained before and after the thermal cycle test. The trapping layer is evaluated as “good” and the binding layer is melted and the pores of the trapping layer are clogged or penetrated into the pores of the partition walls of the honeycomb substrate. Those that were not maintained were evaluated as “bad”. The evaluation results are shown in Table 2. In Example 3, although slight alteration was confirmed, it was evaluated as “good (slightly altered)” because the collection layer was maintained.

(Examples 2-9, Comparative Examples 1-5)
The same as the honeycomb structure of Example 1, except that the collection layer forming raw material used was the aggregate particles shown in Table 1 and the joint portion forming raw material used in the blending amounts (parts by mass) shown in Table 1. Thus, a honeycomb structure was produced and evaluated. The evaluation results are also shown in Table 1. In addition, the coupling | bond part formation raw material (coupling | bond part formation raw material in Table 1) used in Examples 2-9 and Comparative Examples 1-5 is a substance shown below.

Glass powder (SiO ₂ · B ₂ O ₃ · ZnO): trade name “ASF1620B” manufactured by Asahi Glass Co., Ltd. (average particle size: 4.5 μm)
Glass powder (SiO ₂ · B ₂ O ₃ · R ₂ O): trade name “ASF102M” (average particle size 3.5 μm) manufactured by Asahi Glass Co., Ltd.
Talc: Trade name “Hytron A” (average particle size: 3.0 μm) manufactured by Takehara Chemical Industry Co., Ltd.
Montmorillonite: Product name “Benger HVP” manufactured by Hojun Co., Ltd.
Kaolin: Trade name “Satinton W” manufactured by Takehara Chemical Co., Ltd.
Highly basic aluminum chloride: trade name “Takibine # 3000” manufactured by Taki Chemical Co., Ltd.

  In Table 1, “No bond part formed (substance name)” described in “Main component” in the column of bond part is a substance used as a bond part forming raw material because the temperature of heat treatment is low. Means that no joint is formed. That is, for example, in Comparative Example 1, “no bond portion is formed (talc)” means that “talc” used as a bond portion forming raw material does not form a bond portion because the temperature of the heat treatment is low. means. In addition, “(numerical value)” described in “melting point” in the column of the bond portion indicates the melting point of the substance used as the bond portion forming raw material. That is, for example, “(1500)” in Comparative Example 1 indicates the melting point of “talc” used as the bond forming raw material. In Example 4, the evaluation result of heat resistance and porosity being “−” means that the evaluation is not performed because the peeling rate is 20% or more.

(Discussion)
As is clear from the results in Table 1, the trapping layer fixed by the salt-containing bond portion by the acid-base reaction of the Lewis base component in the aggregate particles and the Lewis acid component in the bond portion forming raw material. Has a low peeling rate even when heat treatment is performed at a low temperature (about 700 ° C.) and firmly adheres to the partition walls. Furthermore, when the high melting-point salt was contained in the joint part, the collection layer was also excellent in heat resistance (Examples 1 and 2).

  In addition, the trapping layer using a substance having a melting point or softening point of 500 to 800 ° C. as a bonding part forming raw material has a low peeling rate even when heat-treated at a low temperature (about 700 ° C.) and is firmly fixed to the partition. (Examples 3 and 4).

  Among Examples 1, 2, and 5 to 8, Examples 1 and 5 to 7 were preferable because the peeling rate was 0% and the heat resistance was good.

  On the other hand, the honeycomb structures of Comparative Examples 1 to 4 were not melted or reacted with the components contained in the aggregate particles at a low temperature (about 700 ° C.), and the bonded portion was not formed. (The peel rate is high). The honeycomb structure of Comparative Example 5 does not use the bonding portion forming raw material, and therefore, the aggregate particles made of cordierite did not melt at low temperatures (about 700 ° C.), and the bonding portion was not formed. It peeled.

  The honeycomb structure manufactured by the method for manufacturing a honeycomb structure of the present invention includes diesel engines, ordinary automobile engines, internal combustion engines including engines for large vehicles such as trucks and buses, and exhaust gas discharged from various combustion apparatuses. It can be suitably used as a filter for collecting particulates contained therein.

1, 10c: Honeycomb structure, 10a: Plugged honeycomb substrate, 10b: Collection layer precursor-formed honeycomb substrate, 11: Cell, 11a: Inflow cell (remaining cell), 11b: Outflow cell (predetermined Cell), 12: partition wall, 13a, 13b: plugging portion, 14: outer peripheral wall, 15a: one end portion, 15b: the other end portion, 20: collection layer precursor, 21: aggregate particle, 22 , 23: raw material for forming a joint part, 30: collection layer, 32, 33: joint part, 40: honeycomb substrate, 40a: inflow side (inflow side of honeycomb base material), 40b: outflow side (outflow of honeycomb base material) Side), 43: air, 45: blower, 46: collection layer forming raw material, 47: raw material feeder, 48: ejector, 101: honeycomb structure, 111: cell, 111a: inflow cell, 111b: outflow cell, 112 : Partition wall, 113a, 113b: plugging portion, 1 15a: one open end, 115b: the other open end.

Claims (5)

On the surface of the partition wall of the honeycomb substrate in which a plurality of cells serving as exhaust gas flow paths are formed by porous partition walls, aggregate particles made of ceramics, a Lewis base component, and the Lewis base are heated. A collecting layer forming raw material comprising a bond forming raw material that can generate a Lewis acid component that generates a salt by reacting with an acid base to form a collecting layer precursor, and the collecting layer precursor is A raw material supply step for obtaining a formed honeycomb substrate; and
The resulting honeycomb base material on which the collection layer precursor is formed is heat-treated at 700 to 1000 ° C. to cause the Lewis base component to react with the Lewis acid component in the bond forming raw material. And a heat treatment step for forming a collection layer in which the aggregate particles and the aggregate particles and the partition walls are fixed to each other by a bonding portion containing a phosphate produced by the acid-base reaction. Is a manufacturing method of
As the bonding part forming raw material, using ammonium dihydrogen phosphate,
As the aggregate particles, fine particles made of cordierite are used,
A method for manufacturing a honeycomb structure, wherein the honeycomb substrate is made of cordierite.   In the raw material supply step, the collecting layer precursor is formed by applying the collecting layer forming raw material containing 50 to 250 parts by mass of the joint forming raw material to 100 parts by mass of the aggregate particles. The method for manufacturing a honeycomb structured body according to claim 1. Bonded with aggregate particles made of cordierite and a melting point or softening point of 500-1000 ° C. on the surface of the partition walls of the honeycomb substrate in which a plurality of cells serving as exhaust gas flow paths are defined by porous partition walls A raw material supplying step of applying a collecting layer forming raw material containing a part forming raw material to form a collecting layer precursor, and obtaining a honeycomb substrate on which the collecting layer precursor is formed;
The honeycomb base material on which the collection layer precursor is formed is heat-treated to melt or soften the joint portion forming raw material, and the bone is formed by the joint portion formed from the melted or softened joint portion forming raw material. And a heat treatment step of forming a trapping layer in which the aggregated particles and the aggregate particles and the partition walls are fixed, and a manufacturing method of a honeycomb structure,
While using glass powder as the bonding part forming raw material,
A method for manufacturing a honeycomb structure, wherein the honeycomb substrate is made of cordierite.   The method for manufacturing a honeycomb structured body according to claim 3, wherein the heat treatment is performed at a temperature 0 to 100 ° C higher than a melting point or a softening point of a substance used as the bonding part forming raw material.   The collection layer forming raw material is formed from the end surface of the honeycomb base material on which the exhaust gas inflow side of the predetermined cell is plugged with the open end of the remaining cell on the exhaust gas outflow side. The trapping layer is formed on the surface of the partition walls in the remaining cells by transporting it through an air flow, allowing the trapping layer forming raw material to flow from the opening of the remaining cells having an open end face on the exhaust gas inflow side. The manufacturing method of the honeycomb structure as described in any one of Claims 1-4 to which a raw material is made to adhere.

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