JP2008100408A - Ceramic honeycomb structure - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a ceramic honeycomb structure which can be produced with ease. <P>SOLUTION: In the ceramic honeycomb structure 1 having a bulkhead part 2 which is made of a porous ceramic material and partitions a large number of cells penetrating in the axial direction and a sealing part 3 having a part sealing one end and a part sealing the other end, a sealing material 3 contains at least 70 wt.% of a ceramic material constituting the bulkhead part 2, the pore diameters of the part sealing one end and the part sealing the other end of the sealing part are smaller than the pore diameters of the bulkhead part, the ratio (P<SB>1</SB>/P<SB>0</SB>) of the porosity (P<SB>1</SB>) of the part sealing one end and the part sealing the other end of the sealing part to the porosity (P<SB>0</SB>) of the bulkhead part is at least 0.80 and below 1.00, and the length in the axial direction of the part sealing one end and the part sealing the other end of the sealing part is at least 0.5 mm. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a ceramic honeycomb structure that can be easily manufactured.

  Catalytic carrier utilizing catalytic action of internal combustion engine, boiler, chemical reaction device, fuel cell reformer, etc., filter for collecting particulate matter in exhaust gas (particularly particulate matter (PM) in exhaust gas from diesel engine) A ceramic honeycomb structure is used for (hereinafter referred to as DPF).

  A honeycomb structure made of ceramic is generally made of porous ceramics, and partition walls that divide a plurality of cells that serve as fluid flow paths by partition walls, and adjacent cells are opposite to each other so that the end faces form a checkered pattern. And a sealing portion made of ceramics that seals the end portion on the side.

  And after manufacturing the honeycomb structure made of ceramics with an outer peripheral shape larger than a desired outer peripheral shape such as a prismatic shape, the outer peripheral surface in the circumferential direction or the like is formed by means such as cutting into a predetermined shape.

  However, the molding by cutting has a problem that the workability is low due to the denseness of the sealing part itself. Specifically, since the honeycomb structure is used for DPF or the like, the sealing portion is required to have no air permeability. And in order not to give air permeability to a sealing part, the sealing part is formed with precise | minute ceramics.

  The ceramic honeycomb structure is formed in a state where a sealing portion is formed in the cell. And due to the denseness of the sealing part itself, there was a problem that the sealing part provided at the end of the cell peeled off during molding, and the outer peripheral surface in the circumferential direction of the molded body became uneven .

  In addition, the fact that the sealing portion is formed of dense ceramics has a problem that the sealing portion itself is not easily manufactured. In general, the sealing portion is formed by injecting slurry into an end portion of a predetermined cell of the partition wall portion and firing the slurry. In order to obtain a dense sealing portion, a slurry having a high viscosity (low fluidity) is used. For this reason, it has been difficult to inject slurry into the cell.

  That is, the conventional ceramic honeycomb structure has various difficulties in its manufacture.

  This invention is made | formed in view of the said actual condition, and makes it a subject to provide the ceramic honeycomb structure which can be manufactured easily.

  In order to solve the above-mentioned problems, the present inventors have focused on a sealing portion for sealing a cell and have come to make the present invention.

The ceramic honeycomb structure of the present invention is made of porous ceramics, partition walls partitioning a large number of cells penetrating in the axial direction, and a sealing material filled in one end of a predetermined cell among the large number of cells And a sealing portion having a sealing portion filled with the other end portion of the remaining cells of the plurality of cells, and a sealing portion having a sealing portion having a sealing portion filled with the other end portion of the remaining cells. The sealing material contains 70 wt% or more of ceramics constituting the partition wall, and the pore diameters of the one end sealing portion and the other end sealing portion of the sealing portion are smaller than the pore diameter of the partition wall, The ratio (P ₁ / P ₀ ) of the porosity (P ₁ ) of the one-end sealing portion and the multi-end sealing portion to the porosity (P ₀ ) of the partition wall portion is 0.80 or more and less than 1.00, The one-end sealing part and the other-end sealing part of the stopper part are 0.5 mm or more in the axial length of the cell. It is characterized in.

  In the ceramic honeycomb structure of the present invention, the sealing material that forms the sealing portion is formed of ceramics that are substantially the same quality as the ceramic that forms the partition wall. This sealing material has sufficient air permeability as a sealing part. And since the sealing material which comprises this sealing part can perform processes, such as cutting, by the workability | operativity equivalent to a partition part, the ceramic honeycomb structure of this invention is the ceramic honeycomb structure excellent in manufacturability It became.

  The ceramic honeycomb structure of the present invention is made of porous ceramics, partition walls partitioning a large number of cells penetrating in the axial direction, and a sealing material filled in one end of a predetermined cell among the large number of cells The sealing part which has the one end sealing part which consists of, and the other end sealing part which consists of the sealing material with which the other edge part of the remaining cell was filled among many cells is provided. That is, the ceramic honeycomb structure of the present invention has a structure in which a large number of cells are provided, and either one end or the other end of each cell is sealed with the sealing material.

  In the ceramic honeycomb structure of the present invention, the sealing material is preferably made of a ceramic having substantially the same characteristics as the ceramic constituting the partition wall.

  In the ceramic honeycomb structure of the present invention, the sealing material contains 70 wt% or more of ceramics constituting the partition wall. When the sealing material contains 70 wt% or more of ceramics constituting the partition wall and the characteristics of the porosity and the pore diameter are made closer, the sealing part becomes as dense as the partition wall. That is, since the sealing part itself does not become excessively dense, the formability (cutting property) is improved particularly during cutting. In addition, since the sealing material is substantially the same quality as the partition wall, the bondability between the partition wall and the sealing portion is improved. Furthermore, since the difference in coefficient of thermal expansion between the partition wall and the sealing portion is reduced, the thermal shock resistance of the ceramic honeycomb structure is improved. If the ratio of the ceramics constituting the partition wall is less than 70 wt%, it may cause cracks at the time of regenerating soot due to thermal expansion difference with the partition wall, or the bondability with the partition wall may be lowered and cause plugging. Become.

  In the ceramic honeycomb structure of the present invention, the pore diameters of the one end sealing portion and the other end sealing portion of the sealing portion are smaller than the pore diameter of the partition wall portion. The sealing part (one end sealing part and the other end sealing part) is formed with ceramics as a main component, so that the sealing part has pores similarly to the partition part. And the air permeability of a sealing part becomes lower than the air permeability of a partition part because the pore diameter (average pore diameter) of the pore of this sealing part becomes smaller than that of a partition part. That is, it becomes difficult for gas to pass through the sealing portion. As a result, when the ceramic honeycomb structure of the present invention is used for a DPF or the like, gas does not pass through the sealing portion.

In the honeycomb structure of the present invention, the ratio (P ₁ / P ₀ ) between the porosity (P ₁ ) of the one end sealing portion and the multi-end sealing portion of the sealing portion and the porosity (P ₀ ) of the partition wall portion is 0. 80 or more and less than 1.00. Ceramics have a high correlation between porosity and hardness. That is, as the porosity increases, the hardness decreases (workability and machinability improve). In the present invention, the air permeability of the sealing portion is smaller than that of the partition wall because the porosity of the sealing portion due to the pores is slightly smaller than the porosity of the partition wall. In addition, since the sealing part has a porosity as high as that of the partition wall part, the workability and machinability of the sealing part are greatly improved. A more preferable porosity ratio (P ₁ / P ₀ ) is 0.90 or more and less than 1.00.

  In the ceramic honeycomb structure of the present invention, the one end sealing portion and the other end sealing portion of the sealing portion have a length in the axial direction of the cell of 0.5 mm or more. The cell wall partitioning the cell in the partition wall has a thickness of 0.2 to 0.4 mm, and the axial length of the sealing portion is thicker than the cell wall. For this reason, even if at least the partition wall portion and the sealing portion are formed of the same air-permeable material, the length of the sealing portion becomes thicker than the cell wall, so that the air flow in the axial direction of the sealing portion The permeability is lower than the air permeability in the thickness direction of the cell wall that partitions the cells of the partition wall, and the gas does not pass through the sealing part. In the present invention, since the sealing portion is made of a material having a lower air permeability than the partition wall portion, the axial length of the sealing portion is 0.5 mm or more. The air permeability is significantly lower than the air permeability in the thickness direction of the cell wall that partitions the cells of the partition wall portion, and gas does not pass through the sealing portion. The longer the axial length of the sealing portion, the lower the air permeability. A preferable axial length of the sealing portion is 0.5 to 5.0 mm.

  The ceramic forming the partition wall is not particularly limited, and a conventionally known ceramic can be used. The ceramic is preferably mainly composed of one kind selected from aluminum titanate, silicon carbide, silicon nitride, and cordierite. Of these ceramics, it is more preferable to be made of a ceramic mainly composed of aluminum titanate. Ceramics made of aluminum titanate have microcracks inside. And even if the ceramic honeycomb structure undergoes thermal expansion by having this micro crack, the stress caused by the thermal expansion is relaxed by opening and closing the opening of this micro crack, and the shape change and damage do not occur.

  In the ceramic honeycomb structure of the present invention, the partition wall may have a structure in which a plurality of parts are joined with a joining material, as in a conventionally known honeycomb structure. Such a structure can change the characteristic for every partition part, and can give desired performance to the whole partition part. When the partition wall is composed of a plurality of parts, the material of each part may be the same or different. That is, the partition wall portion is preferably formed by bonding a plurality of ceramic fractions via an adhesive layer.

  A conventionally known bonding material can also be used as the bonding material for bonding the ceramic body. As this bonding material, for example, a SiC-based bonding material can be used. The bonding material layer formed between the ceramic bodies when the ceramic bodies are bonded with a bonding material is preferably formed with a thickness of 0.5 to 5 mm.

  Further, when the partition wall is formed by bonding a plurality of ceramic segments through an adhesive layer, the size (cell shape) of the cells formed in each ceramic segment is the same or different. Or any of them. The size (cell shape) of each ceramic segment cell is preferably the same.

  The cell forming the outer peripheral surface in the circumferential direction preferably has one end sealing portion and the other end sealing portion. Since the cells forming the outer peripheral surface in the circumferential direction have the one end sealing portion and the other end sealing portion, the strength of the end portion of the cell wall defining the cell is increased. Due to the increase in strength, the cell wall is prevented from being damaged, and the workability during the molding operation is improved.

  The ceramic honeycomb structure of the present invention preferably has an outer peripheral material layer having a thickness of 0.5 mm or more on the outer peripheral surface in the circumferential direction. By having the outer peripheral material layer, the shape change that occurs when the ceramic honeycomb structure is used for a DPF or the like can be suppressed. Specifically, when the ceramic honeycomb structure is used for applications such as DPF, the ceramic honeycomb structure is exposed to high heat. The ceramic honeycomb structure undergoes thermal expansion. This thermal expansion can be suppressed by having the outer peripheral material layer. A conventionally known material can be used as the material constituting the outer peripheral material layer. For example, SiC, silica compounds, alumina compounds such as aluminum titanate, and the like can be used.

  Further, since the thickness of the outer peripheral material layer varies depending on the shape of the ceramic honeycomb structure, the thickness thereof cannot be generally determined, but for example, it is preferably formed with a thickness of 0.5 mm or more. More preferably, it is 0.5-5.0 mm.

  The ceramic honeycomb structure of the present invention is preferably used for a DPF. The ceramic honeycomb structure of the present invention includes a partition wall and a sealing portion, so that the ceramic honeycomb structure can be used as a wall flow type filter catalyst through which exhaust gas (gas) passes through a cell wall partitioning a cell of the partition wall. Among these filter catalysts, it is particularly preferable to use as a DPF.

  When the ceramic honeycomb structure of the present invention is used as a DPF, it is preferable that at least one of a porous oxide made of alumina or the like, or a catalytic metal such as Pt, Pd, or Rh is supported on at least the pore surfaces of the partition walls. . By carrying these substances, purification performance such as particulates as DPF is improved.

  The outer peripheral shape of the ceramic honeycomb structure of the present invention is not particularly limited, and can be a conventionally known shape. For example, the cross section may be a substantially circular or elliptical cylinder, and the cross section may be a square or polygonal prism, and more preferably a cylinder.

  Although the manufacturing method of the ceramic honeycomb structure of the present invention is not particularly limited, for example, it can be manufactured by the following manufacturing method.

  First, a prismatic ceramic segment having cells partitioned in the axial direction is manufactured by a conventionally known manufacturing method. And the slurry which can form the ceramic which has the ceramics which comprise a ceramic body as a main component when baked is prepared, This slurry is inject | poured into the edge part of the cell of the joined body of a ceramic body. The slurry was injected such that each end face had a checkered pattern. At this time, further, slurry was injected into both ends of the cell defining the outer peripheral surface of the ceramic honeycomb structure. Thereafter, the slurry was heated and fired to form a sealing portion of 0.5 mm or more. Thereafter, a plurality of sealed ceramic bodies are bonded using a bonding material such as SiC, and heated and fired.

  Subsequently, the outer peripheral surface in the circumferential direction of the fired body was formed by means such as cutting. This molding was performed so that the cells having the sealing portions at both ends formed the outer peripheral surface.

  And the slurry which has SiC as a main component is apply | coated to the outer peripheral surface of the circumferential direction, and a peripheral material layer is manufactured by drying and baking. Thereby, the ceramic honeycomb structure of the present invention can be manufactured.

  Hereinafter, the present invention will be described using examples.

  As an example of the present invention, a honeycomb structure for DPF was manufactured.

(Example)
First, a raw material of a ceramic fraction mainly composed of SiC is weighed, and after sufficiently mixing (kneading) this raw material, it is made of columnar SiC of 70 × 70 × 150 mm in which many cells are formed in the axial direction A formed body of ceramic body 2 was manufactured by extrusion molding, which is a conventionally known manufacturing method. The molded body of the ceramic body 2 has cells having a square section. Moreover, the thickness of the cell wall which divides a part of cell and isolates an adjacent cell was 0.3 mm. The compact of the ceramic body 2 is shown in FIG. Here, the outer peripheral shape (apparent shape) of the formed body of the ceramic divided body 2 is not only a prismatic shape as shown in FIG. 1 but also an outer peripheral shape that substantially matches the outer peripheral shape when the honeycomb structure is formed. Can be formed.

  Subsequently, a slurry having a solid content substantially composed of SiC particles was prepared. In addition, this slurry contains additives, such as a viscosity modifier. And this slurry was inject | poured into the predetermined | prescribed cell from the edge part of the both ends of the molded object of the dried ceramic body 2, and it was made to dry at 80 degreeC. Here, the predetermined cell is provided so that the cell into which the slurry is injected has a checkered pattern. In addition, the slurry was injected only into one end or the other end of the cell.

  And when it shape | molded at the subsequent process, the slurry was inject | poured into the cell which divides the outer peripheral surface of the honeycomb structure 1 into the both ends.

  Thereafter, the molded body of the ceramic body 2 in which the slurry is injected into the cell at 2300 ° C. is fired to fire the ceramic body 2, and the slurry is solidified to form the sealing material 3, which is sealed with the sealing material 3. A ceramic body 2 having a cell (sealing part) was formed. The length of the sealing material 3 in the axial direction of the cell was 3 mm. The state in which the sealing part is formed is schematically shown in FIG.

  And the ceramic segments 2 in which the sealing part was formed were joined by the SiC type | system | group joining material. In the bonding with the bonding material, the bonding material was applied to the outer peripheral surface of the ceramic body 2 so as to have a thickness of 1.5 to 2.0 mm, and another honeycomb body 2 was then bonded to the surface. . This joining was repeated, and 16 ceramic parts 2 were joined so that the cross section was a square, and dried at 80 ° C. The joined body of the ceramic body 2 is shown in FIGS. 2 shows an end face showing the structure of the joined body of the ceramic body 2, and FIG. 3 is a view showing the arrangement of the sealing portion in the joined body of the ceramic body 2.

  Then, this joined body was cut using an electric saw to form an outer peripheral shape. The cutting with the electric saw was made into a substantially columnar shape in which the cells having the sealing material formed at both ends thereof formed the outer peripheral surface along the line indicated by the broken line in FIG. During this cutting, no peeling of the sealing material from the cell was observed. The joined body (molded body) after molding is schematically shown in FIG.

  And the slurry which a main component consists of SiC was prepared, and it apply | coated to the outer peripheral surface of a molded object, and after drying at 80 degreeC, it heated at 850 degreeC and solidified the joining material and the slurry. Thereby, the outer peripheral material layer 5 having a thickness of 5 mm was formed on the outer peripheral surface.

  Thus, the honeycomb structure 1 of the present example was manufactured. The honeycomb structure of the present example is shown in FIGS. 5 shows an end face of the honeycomb structure 1, and FIG. 6 shows a cross section in the axial direction of the honeycomb structure 1.

  As shown in the figure, the honeycomb structure 1 of the present example includes a partition wall portion in which a plurality of ceramic segments 2 made of porous SiC ceramics are bonded via a bonding material layer 4, and a large number of cells. One end sealing portion made of the sealing material 3 filled in one end portion of a predetermined cell, and the other end made of the sealing material 3 filled in the other end portion of the remaining cells among many cells It has the structure provided with the sealing part which has a sealing part, and the outer peripheral material layer 5 formed on the outer peripheral surface of the circumferential direction of a partition part.

  In this example, the average pore diameter and the porosity of each of the ceramic body 2 and the sealing material 3 were measured. The measurement results are shown in Table 1.

  As shown in Table 1, the average pore diameter and porosity were smaller in the sealing material 3 than in the ceramic fraction 2. Moreover, the axial length of the cell of the sealing material 3 was much longer than the thickness of the partition wall, and the air permeability of the sealing material 3 was smaller than that of the partition wall. That is, the sealing material 3 has lower air permeability than the ceramic body 2 (partition wall). That is, when the honeycomb structure of the present embodiment is used for a DPF or the like, the exhaust gas does not pass through the sealing material 3 but passes through the cell wall.

  At the time of manufacturing the honeycomb structure 1 of the present example, the sealing material 3 was formed of a material substantially the same quality as the ceramic body 2, so that the sealing material 3 was peeled (dropped) during molding with an electric saw. I couldn't. That is, there was no unevenness on the outer peripheral surface after molding due to the sealing material 3 falling off and the cell wall being exposed. In the present embodiment, the sealing material 3 is filled in the cell, and the strength of the cell wall is sufficiently secured, so that the cell wall can be prevented from being damaged due to the protruding cell wall. Safety at the time has improved.

  That is, the honeycomb structure 1 of the present example was a honeycomb structure excellent in workability during manufacturing.

  The honeycomb structure 1 of this example can be used as a DPF.

It is the figure which showed the ceramic fraction used for the honeycomb structure of an Example. It is the figure which showed the end surface of the joined body of ceramic division. It is the figure which showed the state which formed the sealing material in the conjugate | zygote of ceramic division. It is the figure which showed the sintered body after shaping | molding. It is the figure which showed the end surface of the honeycomb structure of an Example. It is sectional drawing of the honeycomb structure of an Example.

Explanation of symbols

1: Honeycomb structure 2: Ceramic fraction 3: Sealing material 4: Bonding material layer 5: Outer material layer

Claims (5)

A partition wall made of porous ceramics and defining a large number of cells penetrating in the axial direction;
One end sealing portion made of a sealing material filled in one end portion of a predetermined cell among many cells, and the sealing filled in the other end portion of the remaining cells among the many cells A sealing portion having the other end sealing portion made of a material,
In a ceramic honeycomb structure having
The sealing material contains 70 wt% or more of the ceramics constituting the partition;
The pore diameter of the one end sealing portion and the other end sealing portion of the sealing portion is smaller than the pore diameter of the partition wall portion,
The ratio (P ₁ / P ₀ ) of the porosity (P ₁ ) of the one-end sealing portion and the multi-end sealing portion of the sealing portion to the porosity (P ₀ ) of the partition wall portion is 0.80 or more, 1 Less than 0.00,
The ceramic honeycomb structure according to claim 1, wherein the one end sealing portion and the other end sealing portion of the sealing portion have a length in the axial direction of the cell of 0.5 mm or more.   The ceramic honeycomb structure according to claim 1, wherein the ceramic is mainly composed of one kind selected from aluminum titanate, silicon carbide, silicon nitride, cordierite, and mullite.   The ceramic honeycomb structure according to claim 1, wherein the partition wall is formed by bonding a plurality of ceramic bodies through an adhesive layer.   The ceramic honeycomb structure according to claim 1, wherein a cell forming an outer peripheral surface in a circumferential direction has the one end sealing portion and the other end sealing portion.   The ceramic honeycomb structure according to claim 1, further comprising an outer peripheral material layer having a thickness of 0.5 mm or more on an outer peripheral surface in a circumferential direction.

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